U.S. patent application number 16/672800 was filed with the patent office on 2020-04-30 for methods of making a prosthesis with a smooth covering.
This patent application is currently assigned to Cook Medical Technologies LLC. The applicant listed for this patent is Cook Medical Technologies LLC. Invention is credited to Brent A. MAYLE, James C. MERK, Gary NEFF, Ram H. PAUL, JR..
Application Number | 20200129285 16/672800 |
Document ID | / |
Family ID | 57885750 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200129285 |
Kind Code |
A1 |
MERK; James C. ; et
al. |
April 30, 2020 |
METHODS OF MAKING A PROSTHESIS WITH A SMOOTH COVERING
Abstract
The present invention relates to methods of making a prosthesis
or a stent with a smooth covering. The method includes providing an
elastomeric tube including an inner diameter and an outer diameter,
positioning the elastomeric tube in a tube expander including a
vacuum, expanding the inner diameter and the outer diameters of the
elastomeric tube by applying the vacuum, providing a mandrel,
positioning an inner covering over the mandrel, positioning a stent
over the inner covering, positioning an outer covering over the
stent to form a covered stent, positioning the mandrel and the
covered stent in the tube expander, releasing the vacuum, removing
the elastomeric tube, the covered stent, and the mandrel form the
tube expander, applying pressure and heat to the elastomeric tube,
the covered stent, and the mandrel, removing the elastomeric tube,
the covered stent, and the mandrel from the pressure and the heat,
removing the elastomeric tube from the covered stent, and removing
the mandrel from the covered stent.
Inventors: |
MERK; James C.; (Terre
Haute, IN) ; MAYLE; Brent A.; (Spencer, IN) ;
NEFF; Gary; (Bloomington, IN) ; PAUL, JR.; Ram
H.; (Bloomington, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cook Medical Technologies LLC |
Bloomington |
IN |
US |
|
|
Assignee: |
Cook Medical Technologies
LLC
Bloomington
IN
|
Family ID: |
57885750 |
Appl. No.: |
16/672800 |
Filed: |
November 4, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15224101 |
Jul 29, 2016 |
10463470 |
|
|
16672800 |
|
|
|
|
62199764 |
Jul 31, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2240/001 20130101;
A61F 2002/91575 20130101; A61F 2002/072 20130101; A61F 2/915
20130101; A61F 2/07 20130101 |
International
Class: |
A61F 2/07 20060101
A61F002/07 |
Claims
1-20. (canceled)
21. An encapsulated stent graft comprising a substantially tubular
body comprising: a luminal surface; an abluminal surface; a balloon
expandable stent having an inner surface and an outer surface; an
inner cover covering the inner surface of the balloon expandable
stent, the inner covering comprising: a first layer consisting
essentially of a first material having a porous structure and a
melting point and a second material, different from the first
material and parallel to the first porous material, within the
first layer and having a melting point lower than the melting point
of the first porous material of the first layer, and a second layer
over the first layer consisting essentially of a first material
having a porous structure and a melting point and a second
material, different from the first material of the second layer,
parallel to the first porous material within the second layer and
having a melting point lower than the melting point of the first
porous material of the second layer, wherein the first material of
the first layer is the luminal surface of the stent graft, the
first material of the second layer contacts the first material of
the first layer and the second material of the second layer, the
second material of the second layer contacts the stent, and the
second material of the first layer, upon the application of heat
sufficient to melt the second material of the first layer, flows
into the porous structure of the first material of the first layer
and the porous structure of the first material of the second layer
thereby forming a bond between the first material of the first
layer and the first material of the second layer; and an outer
cover covering the outer surface of the balloon expandable stent,
the outer cover comprising; a first layer consisting essentially of
a first material having a porous structure and a melting point and
a second material, different from the first material, parallel to
the first material within the first layer and having a melting
point lower than the melting point of the first material of the
first layer, and, a second layer over the first layer consisting
essentially of a first material having a porous structure and
melting point and a second material, different from the first
material of the second layer, parallel to the first material within
the second layer and having a melting point lower than the melting
point of the first material of the second layer, wherein the second
material of the first layer contacts the stent and the first
material of the first layer, the first material of the second layer
is the abluminal surface of the stent graft, and second material of
the second layer, upon the application of heat sufficient to melt
the second material of the second layer, flows into the porous
structure of the first material of the first layer and the porous
structure of the first material of the second layer thereby forming
a bond between the first material of the first layer and the first
material of the second layer.
22. The stent graft of claim 21, wherein the first material of the
first layer and the second layer of the inner cover and the first
material of the first layer and the second layer of the outer cover
is selected from PTFE, esPTFE and ePTFE.
23. The stent graft of claim 22, wherein the second material of the
first layer and the second layer of the inner cover and the second
material of the first layer and the second layer of the outer cover
is selected from FEP and polyurethane.
24. The stent graft of claim 21, wherein the first material of the
first layer and the second layer of the inner cover is esPTFE and
the second material of the first layer and the second layer of the
outer cover is polyurethane.
25. The stent graft of claim 21, wherein the first material of the
first layer and the second layer of the inner cover is ePTFE and
the second material of the first layer and the second layer of the
outer cover is polyurethane.
26. The stent graft of claim 21, wherein the first material of the
first layer and the second layer of the inner cover is esPTFE and
the second material of the first layer and the second layer of the
outer cover is FEP.
27. The stent graft of claim 21, wherein the first material of the
first layer and the second layer of the inner cover is ePTFE and
the second material of the first layer and the second layer of the
outer cover is FEP.
28. The stent graft of claim 21, wherein each of the inner cover
and the outer cover each further include one or more additional
layers consisting essentially of a first material having a porous
structure and a melting point and a second material, different from
the first material, parallel to the first material having a melting
point greater than the melting point of the second material and
wherein in each of the one or more additional layers the first and
second materials are in an alternating pattern.
29. An encapsulated stent graft comprising a substantially tubular
body comprising: a luminal surface; an abluminal surface; a balloon
expandable stent having an inner surface and an outer surface; an
inner cover covering the inner surface of the balloon expandable
stent, the inner covering comprising: a first layer consisting
essentially of a first material selected from PTFE, ePTFE and
esPTFE, and a second material parallel to the first material
selected from FEP and polyurethane and having a melting point lower
than a melting point of the first material of the first layer, and
a second layer over the first layer consisting essentially of a
first material that is the same as the first material of the first
layer and a second layer parallel to the first material that is the
same as the second material of the first layer and having a melting
point lower than the melting point of the first material of the
second layer, wherein the first material of the first layer is the
luminal surface of the stent graft, the first material of the
second layer contacts the first material of the first layer and the
second material of the second layer, the second material of the
second layer contacts the stent, and the second material of the
first layer, upon the application of heat sufficient to melt the
second material of the first layer, is a bond between the first
material of the first layer and the first material of the second
layer; and an outer cover covering the outer surface of the balloon
expandable stent, the outer cover comprising; a first layer
consisting essentially of a first material selected from PTFE,
ePTFE and esPTFE, and a second material parallel to the first
material selected from FEP and polyurethane and having a melting
point lower than a melting point of the first material of the first
layer, and a second layer over the first layer consisting
essentially of a first material that is the same as the first
material of the first layer and a second layer parallel to the
first material that is the same as the second material of the first
layer and having a melting point lower than the melting point of
the first material of the second layer, wherein the second material
of the first layer contacts the stent and the first material of the
first layer, the first material of the second layer is the
abluminal surface of the stent graft, and second material of the
second layer, upon the application of heat sufficient to melt the
second material of the second layer, is a bond between the first
material of the first layer and the first material of the second
layer; and wherein the luminal and abluminal surfaces of the stent
graft have no visible creases or ridges.
30. The stent graft of claim 29, wherein each of the inner cover
and the outer cover each further include one or more additional
layers consisting essentially of a first material that is the same
as the first material of the first and second layers and a second
material that is the same as the second material of the first and
second layers and each of the one or more additional layers the
first and second materials are in an alternating pattern.
Description
RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 15/224,101, filed on Jul. 29, 2016,
which claims the benefit of the filing date under 35 U.S.C. .sctn.
119(e) of Provisional U.S. Patent Application Ser. No. 62/199,764,
filed on Jul. 31, 2015, the contents of which are hereby
incorporated by reference in their entireties.
BACKGROUND
1. Technical Field
[0002] The present invention relates to methods of making a
prosthesis with a smooth covering.
2. Background Information
[0003] Some medical prostheses, such as stents, include material,
fabric or a graft to cover the prosthesis. Covered stents include a
stent graft that includes fabric or other material that covers and
is supported by a stent. Covered stents are manufactured by
different methods. One method includes placing the stent on a
mandrel between shells of a pressure applicator. The pressure
applicator may include two halves or multiple components that form
a cavity with a circular cross section. Each component of the
pressure applicator may contain one or more layers of material for
application to the stent. When the components of the pressure
applicator are brought together to cover the stent, the resulting
covered stent may have visible creases where the components meet.
The creases create a lack of continuity in the material covering
the stent and may cause premature failure of the material or an
area that may catch on a vessel or collect undesirable
material.
[0004] Other methods of manufacturing covered stents include using
shrink tubes and/or tubing that are off the shelf and readily
available to attach the fabric or graft on the stent. For example,
covered stents have been made using off the shelf silicone tubing
having a high durometer, such as high durometer silicone tubing
including silicone tubing with a durometer of 50-70 Shore A.
Manufacturers identify silicone tubing having a durometer of 50-70
Shore A as soft and silicone tubing having a durometer of 35-45
Shore A as very soft, both of which are readily available from
manufacturers. Silicone tubing with a lower durometer is not
readily available from manufacturers.
[0005] These methods to make covered stents using shrink tubes,
tubing having a high durometer, and/or sheets of material having a
high durometer to attach the fabric or graft on the stent may
create visible creases or ridges that form on the graft of the
stent, which create a lack of continuity on the stent. Previously
used pressure methods also cause the struts of the stent to deform
or distort when the shrink tubes or high durometer tubes are
applied to the fabric and the stent because higher deformation
forces and displacement of the tubes is needed to compress the
fabric or graft around the struts of the stent for bonding. In
addition, when using these methods, the fabric or graft is not able
to conform to the struts of the stent, or otherwise profile the
struts of the stent, to create a smooth covering over the
stent.
BRIEF SUMMARY OF THE INVENTION
[0006] A method of making a stent with a smooth covering is
described. The method includes using a low durometer elastomeric
tube, preferably a low durometer silicone tube, in the method of
making a covered prosthesis.
[0007] One exemplary method includes positioning the elastomeric
tube in a tube expander, and applying a vacuum to the tube expander
to increase both the inner and outer diameters of the elastomeric
tube. In one example, a mandrel is then provided with an inner
covering. A stent is positioned over the inner covering, and then
an outer covering is positioned over the stent to form a covered
stent. In some examples, only an inner covering may be used or only
an outer covering may be used. The mandrel and the covered stent
are placed in the tube while the elastomeric tube is still in the
tube expander, and the vacuum is released. Release of the vacuum
causes the elastomeric tube to return to its previous diameter. The
elastomeric tube, the covered stent, and the mandrel are then
removed from the tube expander. Pressure and heat are applied to
the elastomeric tube, the covered stent, and the mandrel. The
pressure and heat are then removed. The elastomeric tube is removed
from the now covered stent and the covered stent is removed from
the mandrel.
[0008] A variation of the method includes providing a slit cannula
including an inner diameter, an outer diameter, and a plurality of
slits. A first elastomeric tube is positioned over the slit
cannula, and an inner covering is positioned over the first
elastomeric tube. A stent is positioned over the inner covering. A
mandrel is positioned within the slit cannula to expand the first
elastomeric tube and the inner covering. A second covering is
positioned over the stent. A second elastomeric tube is provided
that includes an inner diameter and an outer diameter, and the
second elastomeric tube is positioned in a tube expander including
a vacuum. A vacuum is applied to expand the inner diameter and
outer diameter of the second elastomeric tube. The covered stent,
the first elastomeric tube, the slit cannula, and the mandrel are
then positioned in the second elastomeric tube within the tube
expander, and the vacuum is released. The first and second
elastomeric tubes, the covered stent, the slit cannula, and the
mandrel are removed from the tube expander, and heat and pressure
are applied to the first and second elastomeric tubes, the covered
stent, the slit cannula, and the mandrel. The first and second
elastomeric tubes, the covered stent, the slit cannula, and the
mandrel are removed from the pressure and the heat, and the second
elastomeric tube is removed from the covered stent. The mandrel is
removed from the slit cannula, and the covered stent is removed
from the first elastomeric tube and the slit cannula.
[0009] Another variation includes encapsulating a prosthesis with a
smooth covering. The method includes providing a mandrel and
positioning a first covering over the mandrel. A prosthesis is
positioned over the first covering, and a second covering is
positioned over the prosthesis to form a covered prosthesis. A
first tube is provided that includes an inner diameter and an outer
diameter, and the first tube is positioned in a tube expander
including a vacuum. A vacuum is applied to the tube expander to
expand the inner and outer diameters of the first tube. The covered
prosthesis and the mandrel are positioned in the tube expander, and
the vacuum is released. The first tube, the covered prosthesis, and
the mandrel are removed from the tube expander. A second tube is
provided that includes an inner diameter and an outer diameter. The
inner diameter of the second tube is smaller than the inner
diameter of the first tube. The second tube is positioned over the
first tube, and heat is applied to the first and second tubes, the
covered prosthesis, and the mandrel. The first and second tubes,
the covered prosthesis, and the mandrel are removed from the heat,
and the second tube is removed from the first tube, the covered
prosthesis, and the mandrel. The first tube is removed from the
covered prosthesis and the mandrel, and the mandrel is removed from
the covered prosthesis.
[0010] These methods provide, among others, the advantages of
making a stent or a prosthesis with a covering that conforms to the
struts of the stent or prosthesis, has a smooth covering, has no
visible creases that form within the covering of the stent of
prosthesis, and has a smooth covering that does not distort or
deform the struts of the stent or prosthesis.
[0011] These methods also provide the advantages of making a stent
or other prosthesis with a smooth inner surface and an outer
surface that conforms to the struts of the stent or other
prosthesis, which is not exposed to blood flow in the body.
Therefore, the likelihood of turbulent blood flow and associated
stagnation points is reduced with stents or other prosthesis formed
by these methods.
[0012] At least one unique and important feature of the methods is
that the tube used to apply the covering to the stent has a very
low durometer on the Shore A or Shore 00 scale. Such low durometer
tubes are not standard and not readily or commercially available
from manufacturers. These low durometer tubes allow sufficient
pressure to be applied to the stent or other prosthesis to displace
the tube around the struts of the stent and ensure contact of the
inner and outer coverings for increased surface area for bonding
the inner and outer coverings without distorting or deforming the
stent or other prosthesis.
[0013] The accompanying drawings, which are incorporated herein and
constitute part of this specification, and, together with the
general description give above and the detailed description given
below, serve to explain features of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a perspective view of an example of expanding
an elastomeric tube by positioning the elastomeric tube in a tube
expander to expand the elastomeric tube;
[0015] FIG. 2 shows a cross-sectional view of FIG. 1;
[0016] FIG. 3 shows a perspective view of wrapping the elastomeric
tube around the ends of the tube expander to seal the elastomeric
tube to the tube expander;
[0017] FIG. 4 shows a cross-sectional view of FIG. 3;
[0018] FIG. 5 shows a perspective view of connecting a vacuum
source to a port of the tube expander;
[0019] FIG. 5A shows an example of rings positioned over the
elastomeric tube to seal the elastomeric tube to the tube
expander;
[0020] FIG. 5B shows an example of caps positioned over the
elastomeric tube to seal the elastomeric tube to the tube
expander;
[0021] FIG. 6 shows a perspective view of applying the vacuum
source to the tube expander;
[0022] FIG. 7 shows a cross-sectional view of FIG. 6 after the
vacuum source has been applied;
[0023] FIGS. 8 and 9 show perspective views of positioning a
mandrel with a stent with inner and outer coverings in the
elastomeric tube in the tube expander;
[0024] FIG. 10 shows a cross-sectional view of FIG. 9;
[0025] FIG. 10A shows a partial exploded view of FIG. 10;
[0026] FIG. 11 shows a perspective view of releasing the vacuum
source from the tube expander;
[0027] FIG. 12 shows a cross-sectional view of FIG. 11 after the
vacuum source has been released;
[0028] FIG. 12A shows a partial exploded view of FIG. 12;
[0029] FIG. 13 shows a perspective view of removing the elastomeric
tube, the mandrel, and the stent with inner and outer coverings
from the tube expander;
[0030] FIG. 14 shows a cross-sectional view of FIG. 13;
[0031] FIG. 15 shows a perspective view of positioning the
elastomeric tube, the mandrel, and the stent with inner and outer
coverings in a press fixture;
[0032] FIG. 15A shows a perspective view of an example of sleeves
positioned over the mandrel;
[0033] FIG. 16 shows a perspective view of the elastomeric tube,
the mandrel, and the stent with inner and outer coverings in the
press fixture;
[0034] FIG. 17 shows a cross-sectional view of FIG. 16;
[0035] FIG. 17A shows a partial exploded view of FIG. 17;
[0036] FIG. 18 shows a perspective view of applying heat and
pressure to the press fixture;
[0037] FIG. 19 shows a cross-sectional view of FIG. 18;
[0038] FIG. 19A shows a partial exploded view of FIG. 19;
[0039] FIG. 20 shows a perspective view of the elastomeric tube,
the mandrel, and the stent after removal from the press
fixture;
[0040] FIG. 21 shows a cross-sectional view of FIG. 20;
[0041] FIG. 22 shows an example of removing the elastomeric tube
from the stent by peeling or ripping the elastomeric tube away from
the stent;
[0042] FIG. 23 shows a side view of the stent after removal of the
elastomeric tube;
[0043] FIG. 24 shows a side view of removing the mandrel from the
stent;
[0044] FIG. 25 shows a cross-sectional view of the stent with the
layer of the first material and the second material after removal
of the mandrel;
[0045] FIG. 26 shows a side view of an example of a slit cannula
for use in encapsulating a stent with a stent mandrel assembly;
[0046] FIG. 27 shows a cross-sectional view of FIG. 26 of a first
end of the slit cannula;
[0047] FIG. 28 shows a cross-sectional view of FIG. 26 of a second
end of the slit cannula;
[0048] FIG. 29 shows a perspective view of FIG. 26;
[0049] FIG. 30 shows a perspective view of an example of a first
mandrel and a second mandrel for insertion within the first and
second ends of the slit cannula;
[0050] FIG. 31 shows a perspective view of positioning the first
mandrel within the first end of the slit cannula;
[0051] FIG. 32 shows a perspective view of expanding the slit
cannula with the first mandrel;
[0052] FIG. 33 shows a perspective view of a first elastomeric tube
over a non-expanded portion of the slit cannula;
[0053] FIG. 34 shows a perspective view of an inner covering over
the elastomeric tube;
[0054] FIG. 35 shows a perspective view of a stent over the inner
covering and positioning the second mandrel within the second end
of the slit cannula;
[0055] FIG. 36 shows a perspective view of an outer covering over
the stent;
[0056] FIG. 37 shows an example of removing handles from the first
and second mandrels;
[0057] FIG. 38 shows a perspective view of positioning the first
and second mandrels, the slit cannula, the first elastomeric tube,
and the stent with the inner and outer coverings within a tube
expander with a second elastomeric tube;
[0058] FIG. 39 shows a perspective view of the first and second
mandrels, the slit cannula, the first elastomeric tube, the stent
with the inner and outer coverings, and the second elastomeric tube
after removal from the tube expander;
[0059] FIG. 40 shows a perspective view of FIG. 39 in a press
fixture;
[0060] FIG. 41 shows a perspective view of FIG. 40 within a heat
press;
[0061] FIG. 42 shows a perspective view of positioning the first
and second mandrels, the slit cannula, the first elastomeric tube,
the smooth covered stent, and the second elastomeric tube within a
tube expander after applying heat and pressure;
[0062] FIG. 43 shows a perspective view of removing the first and
second mandrels, the slit cannula, the first elastomeric tube, and
the smooth covered stent from the tube expander;
[0063] FIG. 44 shows a perspective view of an example of
positioning the end caps on the first and second mandrels;
[0064] FIG. 45 shows a perspective view of removing the first and
second mandrels from the slit cannula and removing the smooth
covered stent from the slit cannula;
[0065] FIG. 46 shows a perspective view of the smooth covered stent
with stripes or indentations on the inner surface of the smooth
covered stent;
[0066] FIG. 47 shows a perspective view of a third mandrel to be
inserted into the smooth covered stent;
[0067] FIG. 48 shows a perspective view of the third mandrel with
the smooth covered stent and a first elastomeric tube;
[0068] FIG. 49 shows a perspective view of the third mandrel, the
smooth covered stent, and the first elastomeric tube and a second
elastomeric tube;
[0069] FIG. 50 shows a perspective view of the third mandrel with
the first elastomeric tube and the smooth covered stent with the
second elastomeric tube with a press fixture;
[0070] FIG. 51 shows a perspective view of FIG. 50 within a heat
press;
[0071] FIG. 52 shows a perspective view of removing the second
elastomeric tube from the first elastomeric tube;
[0072] FIG. 53 shows a perspective view of positioning a shrink
tube over the first elastomeric tube;
[0073] FIG. 54 shows a perspective view of applying heat to the
smooth covered stent, the first elastomeric tube, and the shrink
tube;
[0074] FIG. 55 shows a perspective view of removing the shrink tube
form the first elastomeric tube;
[0075] FIG. 56 shows a perspective view of the smooth covered stent
without the stripes or indentations on the inner surface of the
smooth covered stent;
[0076] FIG. 57 shows a perspective view of an example of the slit
cannula and an example of a single mandrel;
[0077] FIG. 58 shows a cross-sectional view of FIG. 57;
[0078] FIG. 59 shows a perspective view of the single mandrel
within the slit cannula;
[0079] FIG. 60 shows a cross-sectional view of FIG. 59;
[0080] FIG. 61 shows a perspective view of the slit cannula of FIG.
57 with a second example of a single mandrel;
[0081] FIG. 62 shows a cross-sectional view of FIG. 61;
[0082] FIG. 63 shows a perspective view of the second example of
the single mandrel within the slit cannula;
[0083] FIG. 64 shows a cross-sectional view of FIG. 63;
[0084] FIG. 65 shows a perspective view of a covered stent
positioned on a mandrel;
[0085] FIG. 66 shows a perspective view of positioning a first tube
in the tube expander;
[0086] FIG. 67 shows a perspective view of applying a vacuum source
to the tube expander;
[0087] FIG. 68 shows a perspective view of positioning the covered
stent and the mandrel in the tube expander;
[0088] FIG. 69 shows a perspective view of releasing the vacuum
source from the tube expander;
[0089] FIG. 70 shows a perspective view of the first tube, the
covered stent, and the mandrel after removal from the tube
expander;
[0090] FIG. 71 shows a perspective view of positioning a second
tube in the tube expander;
[0091] FIG. 72 shows a perspective view of applying a vacuum source
to the tube expander;
[0092] FIG. 73 shows a perspective view of the covered stent and
the mandrel after the first and second tubes are applied to the
covered stent;
[0093] FIG. 74 shows a perspective view of the first and second
tubes, the covered stent, and the mandrel on a rack in a heated
oven;
[0094] FIG. 75 shows a microscopic view of the smooth covered
stent;
[0095] FIG. 76 shows a microscopic view of the smooth covered
stent;
[0096] FIG. 77 shows a perspective view of a tapered rod, a first
hollow mandrel, a second hollow mandrel, and a stent;
[0097] FIG. 78 shows a perspective view of positioning the stent on
the tapered rod of FIG. 77;
[0098] FIG. 79 shows a perspective view of positioning the tapered
end of the tapered rod into the first hollow mandrel of FIG.
77;
[0099] FIG. 80 shows a perspective view of the first hollow mandrel
positioned over the tapered end of the tapered rod of FIG. 77;
[0100] FIG. 81 shows a perspective view of sliding the stent along
the tapered rod onto the first hollow mandrel of FIG. 77;
[0101] FIG. 82 shows a perspective of positioning the second hollow
mandrel over the over an end of the first hollow mandrel of FIG.
77;
[0102] FIG. 83 shows a perspective view of the second hollow
mandrel positioned over the end of the first hollow mandrel of FIG.
77 and sliding the stent along the first hollow mandrel onto the
second hollow mandrel;
[0103] FIG. 84 shows a perspective view of the stent positioned on
the second hollow mandrel of FIG. 77;
[0104] FIG. 85 shows a perspective view of providing a mandrel with
a first layer of elastomeric tube and an inner covering;
[0105] FIG. 86 shows a perspective view of the mandrel with the
first layer of elastomeric tube and inner covering positioned
within the second hollow mandrel of FIG. 77;
[0106] FIG. 87 shows a perspective view of removing the second
hollow mandrel from beneath the stent to allow the stent to
position onto the inner covering, elastomeric tube, and
mandrel;
[0107] FIG. 88 shows a perspective view of removing the mandrel
from beneath the first layer of elastomeric tube;
[0108] FIG. 89 shows a perspective view of positioning a support
mandrel with holes beneath the first layer of elastomeric tube,
positioning the outer covering over the stent to form the covered
stent, and positioning the second layer of elastomeric tube over
the outer covering;
[0109] FIG. 90 shows a transparent perspective view of the support
mandrel with holes, the first and second layers of elastomeric
tube, and the covered stent;
[0110] FIG. 91 shows a transparent perspective view of the support
mandrel with holes, the first and second layers of elastomeric
tube, and the covered stent and a perspective view of connecting a
barb fitting with a cap to first ends of the first and second
layers of elastomeric tubes and a tubing line via a barb fitting to
second ends of the first and second layers of elastomeric
tubes;
[0111] FIG. 92 shows a perspective view of positioning the support
mandrel with holes, the first and second layers of elastomeric
tubes, and the covered stent connected to the tubing line into a
press fixture;
[0112] FIG. 93 shows a perspective view of the press fixture of
FIG. 92 in a closed position; and
[0113] FIG. 94 shows a perspective view of a smooth covered
stent.
DETAILED DESCRIPTION OF THE DRAWINGS AND THE PREFERRED
EMBODIMENTS
[0114] In the following detailed description of the various
embodiments of methods of making a stent with a smooth covering,
like elements and structures are numbered or labeled alike.
[0115] Tube Expander with Press Fixture and Heated Press
[0116] FIGS. 1-25 illustrate an exemplary method of making a stent
100 with a smooth, uninterrupted covering. The stent 100 has a
circular cross-section when expanded with an inner diameter 102, an
outer diameter 104, a first end 106, a second end 108, a
longitudinal length 110, an inner surface 112, an outer surface
114, and a plurality of struts 115.
[0117] The inner and outer diameters 102, 104 of the stent 100 may
vary and are measured in the expanded state of the stent 100. For
example, the expanded inner diameter 102 may range from 5.0 to 14.0
mm, and in some examples may range from 6.0 to 8.0 mm. When the
stent 100 is used in aortic or venous indications, the expanded
inner diameter 102 may range 5.0 to 40 mm. The nominal diameter of
the stent 100 is defined as the unrestrained diameter of a stent
100 in its expanded form. For balloon-expandable stents, the
diameter of the stent 100 is defined by the expanded inner diameter
102 of the stent 100, and the stent 100 in its nominal diameter
state may be expanded into the intended vessel size to resist
compression. For self-expanding stents, the diameter of the stent
100 is defined by the expanded outer diameter 104 of the stent 100,
and the stent 100 will be oversized as compared to the intended
vessel to ensure constant outward force against the vessel. The
longitudinal length 110 of the stent 100 is defined from the first
end 106 to the second end 108 of the stent 100 and will vary
depending on the intended vessel for implantation. In one example,
the longitudinal length 110 of the stent 100 is 120 mm. When the
stent 100 is used in aortic or venous indications, the longitudinal
length 110 of the stent 100 may be up to 300 mm.
[0118] A tube of elastomeric material 116 provides compression to
the stent 100 during an encapsulation process. The elastomeric tube
116 is hollow and includes an inner diameter 118, an outer diameter
120, a first end 122, a second end 124, and a longitudinal length
126. The longitudinal length 126 is defined from the first end 122
to the second end 124 of the elastomeric tube 116. The inner
diameter 118 of the elastomeric tube 116 may range from 2 mm to 15
mm. The outer diameter 120 of the elastomeric tube 116 may range
from 3 mm to 21 mm.
[0119] Suitable materials for the elastomeric material of the tube
116 include silicone, neoprene, latex, butyl rubber, isoprene
rubber, natural rubber, Thoralon.RTM. or other thermosets, or other
known or discovered materials so long as they have the necessary
properties described here.
[0120] Elastomeric materials are used because they have the
capability of resuming their original shape after deformation.
Elastomeric materials that have high temperature stability and thus
can withstand high temperatures without melting are preferred. For
example, silicone has the properties, among others, of high
temperature stability, low volatile content, being capable of
varying its hardness or softness, and chemical inertness that make
it useful. The inventors have discovered that not all elastomeric
tubes may be used in the methods here. The inventors have
discovered that advantageously the tubes they designed having very
low durometer are preferred. In one example, the elastomeric tube
116 includes a specifically designed low durometer silicone, such
as MED-4014, MED-4020, or MED-4025 sold by NuSil Technology or
other low durometer silicone, such as custom blends of raw
silicone, that provide similar mechanical properties. On the shore
hardness scale, the durometer of the silicone may range from 10
Shore 00 to 30 Shore A, preferably approximately 15 to 25 Shore A,
and preferably 20 Shore A. Depending on the type of low durometer
silicone used, the tensile strength may range from approximately
700 psi (4.8 MPa) to 1,400 psi (9.7 MPa), the tear strength is 130
ppi (22.9 kN/m) to 190 ppi (33.5 kN/m), the specific gravity is
1.08 to 1.11, the elongation is 890% to 1,330%, and stress at 200%
strain of 40 psi (0.38 MPa) to 105 psi (0.72 MPa).
[0121] Another important feature the inventors have discovered is
the application of a coating to the inner surface of the
elastomeric tube 116. This reduces or eliminates tackiness of the
elastomer to which the coating is applied. For example, the coating
may include MED-6670 sold by NuSil Technology, MED-6671 sold by
NuSil Technology, or a similar friction reducing coating for
silicone surfaces. The coating helps to remove the stickiness of
the elastomeric tube 116. The coating may include a thickness
ranging from 20 to 100 micrometers (.mu.m), or preferably a range
of 40 to 50 micrometers (.mu.m). In some examples, the coating may
have a higher durometer than the elastomeric tube. In other
examples, the durometers may be close or the same. The coating is
cured after applying it to the elastomeric tube 116.
[0122] In the present method, to radially expand the elastomeric
tube 116, the elastomeric tube 116 is positioned within a tube
expander 128. FIG. 1 shows a perspective view of the tube expander
128 that includes an opening 130 to receive a port 132. As shown in
FIGS. 1, 3 and 4, the port 132 may be positioned within and sealed
to the opening 130 of the tube expander 128. The port 132 is
configured to receive different sources or inputs, including a
vacuum, a syringe, a pressure source, a heat source or other
sources.
[0123] The tube expander 128 is hollow and includes a shape to
conform to the tube and the device. Here it is shown having
circular shape with an inner diameter 134, an outer diameter 136, a
first end 138, a second end 140, and a longitudinal length 142. The
longitudinal length 142 is defined from the first end 138 to the
second end 140 of the tube expander 128. The elastomeric tube 116
is positioned through the first and second ends 138, 140 of the
tube expander 128. In its original state, the elastomeric tube 116
includes an outer diameter 120 smaller than the inner diameter 134
of the tube expander 128. FIG. 2 shows a cross-sectional view of
the elastomeric tube 116 within the tube expander 128.
[0124] After positioning the elastomeric tube 116 in the tube
expander 128, the first and second ends 122, 124 of the elastomeric
tube 116 may be rolled up over the first and second ends 138, 140
of the tube expander 128 to create a seal as shown in FIG. 3. The
sealing of the elastomeric tube 116 to the tube expander 128 helps
to keep the elastomeric tube 116 in position within the tube
expander 128. Other sealing devices or techniques or devices to
maintain the position of the elastomeric tube 116 within the tube
expander 128 may be used. For example, devices such as rings,
sleeves, ties, caps, or other clamping devices may also be
positioned over the first and second ends 122, 124 of the
elastomeric tube 116 and the first and second ends 138, 140 of the
tube expander 128 to maintain the position of the elastomeric tube
116 within the tube expander 128 and to prevent the elastomeric
tube 116 from moving along the longitudinal length 142 of the tube
expander 128.
[0125] FIGS. 5A and 5B show rings 144 and caps 146, respectively,
positioned over the first and second ends 122, 124 of the
elastomeric tube 116 and the first and second ends 138, 140 of the
tube expander 128. FIGS. 2 and 4 show cross-sectional views of the
elastomeric tube 116 within the tube expander 128 before any source
or input is applied to the tube expander 128.
[0126] To radially expand the inner and outer diameters 118, 120 of
the elastomeric tube 116, a vacuum may be applied to the tube
expander 128. FIG. 5 shows a perspective view of connecting a
vacuum source 148 to the port 132 of the tube expander 128. The
vacuum source 148 is applied to the tube expander 128 to uniformly
expand the inner and outer diameters 118, 120 of the elastomeric
tube 116. When the vacuum source 148 is applied, as described
previously, the outer diameter 120 of the elastomeric tube 116
seals to the inner diameter 134 of the tube expander 128. This
sealing of the elastomeric tube 116 to the tube expander 128 helps
to prevent the elastomeric tube 116 from moving along the
longitudinal length 142 of the tube expander 128. As shown in FIGS.
6 and 7, when the vacuum source 148 is applied, the outer diameter
120 of the elastomeric tube 116 is in contact with the inner
diameter 134 of the tube expander 128.
[0127] A mandrel 150 is provided to support the stent 100 or other
prosthesis and maintain the nominal diameter of the stent 100 or
prosthesis during the covering or encapsulation process. FIG. 8
shows a perspective view of the mandrel 150 that includes a
diameter 152, a first end 154, a second end 156, and a longitudinal
length 158, which is defined as the length from the first end 154
to the second end 156. The mandrel 150 may be hollow or solid
depending on the strength of the material of the mandrel 150 and
the heating characteristics or capabilities of the mandrel 150. In
some examples, the mandrel 150 may be hollow with an inner diameter
160. When the mandrel 150 is hollow, it may also include a
plurality of holes 162. When the mandrel 150 is hollow, heat may be
applied internally within the mandrel 150, such as with a cartridge
heater, for allow for faster heating. A hollow mandrel 150 also
allows for faster cooling. The material of the mandrel 150 may
include glass, metal, stainless steel and/or an alloy. When the
mandrel is solid, the diameter 152 of the mandrel 150 is smaller
than the inner diameter 118 of the elastomeric tube 116 in its
expanded state.
[0128] An inner covering 164 is provided that is positioned over
and wrapped around the mandrel 150 as shown in FIG. 10A. In this
example, the inner covering 164 includes a layer 164A of first
material 166 and second material 168 that is used for covering the
inner surface 112 of the stent 100 or a prosthesis. In an
alternative example, the layer 164A of the inner covering 164 only
includes the first material 166.
[0129] The dimensions of the inner covering 164 will vary depending
on the inner diameter 102 and the longitudinal length 110 of the
stent 100. For example, the inner covering 164 includes a
rectangular or square cross section with a width and a length. The
length of the inner covering 64 is the length of the inner covering
164 that wraps around the mandrel 150. The width of the inner
covering 164 is the length of the inner covering 164 that extends
along the longitudinal length 158 of the mandrel 150. In some
examples, the width of the inner covering 164 may range from 1.25
to 6 inches.
[0130] The diameter 152 of the mandrel 150 and the inner and outer
diameters 118, 120 of the elastomeric tube 116 will also vary
depending on the inner and outer diameters 102, 104 of the stent
100. In one example, the diameter 152 of the mandrel 150 is 6.0 mm
and the inner diameter 118 of the elastomeric tube 116 is 6.0 mm.
In particular, the inner diameter 118 of the elastomeric tube 116
in its original state will vary depending on the outer diameter 104
of the stent 100.
[0131] The first material 166 and the second material 168 of the
inner covering 164 are parallel to each other within the layer
164A. The inner covering 164 is positioned and wrapped around the
mandrel 150 such that when the stent 100 is positioned over the
inner covering 164 and the mandrel 150, the inner surface 112 of
the stent 100 is completely covered with the inner covering 164.
The inner covering 164 is positioned over the mandrel 150 such that
the first material 166 is in contact with the mandrel 150 and the
second material 168 is not in contact with the mandrel 150. The
second material 168 of the inner covering 164 contacts the inner
surface 112 of the stent 100 when the stent 100 is positioned over
the inner covering 164.
[0132] The first material 166 preferably is a thermoplastic or a
thermoset material, such as polytetrafluoroethylene (PTFE),
including electrospun PTFE (esPTFE) and expanded PTFE (ePTFE),
electrospun polymers, and other woven or non-woven polymers. The
second material 168 preferably is a thermoplastic material, such as
polyurethane, nylon, polyolefins, elastomers, fluorinate ethylene
propylene (FEP), styrenic block copolymers (TPE-s), incluing SEBS,
SIBS, SEBS, SEPS, SIS, polyolefin blends (TPE-o), elastomeric
alloys (TPE-c or TPV), thermoplastic polyurethanes (TPU),
thermoplastic copolyester, and thermoplastic polyamides.
Electrospun materials and methods are disclosed in the following
patents and patent applications and are incorporated herein by
reference: U.S. Pat. No. 9,060,852; 8,876,849; 8,795,577;
8,637,109; 8,403,979; 8,211,168; 8,100,683; 7,779,261; 7,678,144;
7,641,844; U.S. Pub. No. 2015-0112383; U.S. Pub. No. 2014-0188212;
U.S. Pub. No. 2014-0081386; U.S. Pub. No. 2013-0122248; U.S. Pub.
No. 2013-0018220; U.S. Pub. No. 2012-0259170; U.S. Pub. No.
2012-0141656; U.S. Pub. No. 2011-0054512; U.S. Pub. No.
2010-0323052; U.S. Pub. No. 2009-0142505; U.S. Pub. No.
2008-0157444.
[0133] The inner covering 164 may include a second layer 164B of
both the first material 166 and the second material 168. The inner
covering 164 may include one to ten layers of the first material
166 and the second material 168. When more than one layer is used,
the layers are positioned over the first layer 164A such that the
first and second materials 166, 168 maintain an alternating
pattern. For example, the first material 166 of the second layer
164B contacts the second material 168 of the first layer 164A, and
the second material 168 of the second layer 164B does not contact
either the first material 166 or the second material 168 of the
first layer 164A.
[0134] The inner covering 164 may be rolled in a sterilized liquid,
for example, 70% or 100% isopropanol, ethanol, processed deionized
water, or propylene glycol, to assist the inner covering 164 to lay
flat against the mandrel 150. Other sterilized liquids may also be
used. To keep the inner covering 164 in place, a soldering iron may
be used to tack or otherwise adhere edges of the inner covering 164
to the mandrel 150. Other types of adhesion or soldering devices,
such as soldering guns and tips, may be used to adhere edges of the
inner covering 164. For example, in one example, a soldering
station, such as one sold by Weller, may be used with a blunt
chisel tip.
[0135] The second material 168 may be referred to as a tie layer, a
bonding layer or an adhesive because it helps to bond the first
material 166 in each of the layers of the inner cover 164 together.
The second material 168 may have a lower melting point than the
first material 166 to melt and flow through the porous structure of
the first material 166 to create a bond between the first materials
166 of the layers 164A, 164B of the inner covering 164. After the
inner covering 164 is applied to the mandrel 150, the mandrel 150
and the inner covering 164 include a diameter 170.
[0136] In this example, the stent 100 includes a balloon expandable
stent. A self-expanding stent may also be used, but a
balloon-expanded stent may be preferred in this example. A variety
of biocompatible materials may be used to construct the stent,
including metals, and/or alloys, medically-acceptable polymers
and/or bioabsorbable polymers or materials. For example, the metals
and/or alloys may include stainless steel, tantalum, nitinol,
tungsten, platinum, inconel, cobalt-chromium alloys, iridium,
molybdenum, moly-rhenium, other alloys of nitinol (including
ternary and quaternary alloys), and magnesium or its alloys (as
degradable stents). If a self-expanding stent it used, other steps
may be required to prevent the diameter restriction of the stent
100, including pre-expansion of the stent 100 and cooling of the
stent 100 to allow it to be positioned over the inner covering
164.
[0137] The inner diameter 102 of the stent 100 is greater than the
diameter 170 of the mandrel 150 and the inner covering 164 such
that the stent 100 may slide over the mandrel 150 and the inner
covering 164. As shown in FIG. 10A, the stent 100 is positioned
over the inner covering 164 and the mandrel 150 and is in contact
with the second material 168 of the inner covering 164. A crimper,
such as an iris crimper, or other reducing device may be used to
uniformly secure the stent 100 in place over the inner covering 164
and the mandrel 150. The stent 100 is approximately at its nominal
diameter when positioned over the mandrel 150 and the inner
covering 164, as well as after use of the crimper.
[0138] After the stent 100 is positioned over the inner covering
164 and the mandrel 150, in this example, an outer covering 172 is
provided that includes a layer 172A of the first material 166 and
the second material 168 that are parallel to each other within the
layer 172A. In an alternative example, the layer 172A of the outer
covering 172 only includes the first material 166. The outer
covering 172 may be positioned over and wrapped around the stent
100 such that the second material 168 of the outer covering 172 is
in contact with the stent 100 and the first material 166 is not in
contact with the stent 100. The outer covering 172 is positioned
over and wrapped around the stent 100 such that the outer surface
114 of the stent 100 is completely covered with the outer covering
172.
[0139] As with the inner covering 164, the outer covering 172 may
include a second layer 172B of both the first material 166 and the
second material 168. The outer covering 172 may include one to ten
layers of the first material 166 and the second material 168. When
more than one layer is used, the layers are positioned over the
first layer 172A such that the first and second materials 166, 168
maintain an alternating pattern as described previously with the
inner covering 164. For example, the second material 168 of the
second layer 172B contacts the first material 166 of the first
layer 172A, and the first material 166 of the second layer 172B
does not contact either the first material 166 or the second
material 168 of the first layer 172A.
[0140] As described previously with the inner covering 164, the
outer covering 172 may be rolled in a sterilized liquid, for
example, 70% or 100% isopropanol, ethanol, processed deionized
water, or propylene glycol, to assist the outer covering 172 to lay
flat against the stent 100. Other sterilized liquids may also be
used. Also, other types of adhesion or soldering devices, such as
soldering guns and tips, may be used to adhere edges of the outer
covering 172.
[0141] After the outer covering 172 is applied to the stent 100,
the inner surface 112 of the stent 100 is covered with the inner
covering 164 and the outer surface 114 of the stent 100 is covered
with the outer covering 172, resulting in covered stent 174. The
covered stent 174 and the mandrel 150 include a diameter 176. The
inner diameter 128 of the elastomeric tube 116 is smaller than or
the same as the diameter 176.
[0142] The covered stent 174 and the mandrel 150 are then
positioned within the lumen of the expanded elastomeric tube 116 in
the tube expander 128 such that the elastomeric tube 116 covers the
covered stent 174 as shown in FIGS. 8 and 9. For example, the
longitudinal length 126 of the elastomeric tube 116 is greater than
or the same as the longitudinal length 110 of the stent 100. FIGS.
10 and 10A show cross-sectional views of the elastomeric tube 116,
the covered stent 174, and the mandrel 150 within the tube expander
128 when the elastomeric tube 116 is in its expanded state. Once
the mandrel 150 is in position, as shown in FIG. 11, the vacuum
source 148 may be released so that the elastomeric tube 116
recovers to the covered stent 174 and surrounds the covered stent
174. FIGS. 12 and 12A show cross-sectional views of the elastomeric
tube 116, the covered stent 174, and the mandrel 150 in the tube
expander 128 after the release of the vacuum source 148. After the
release of the vacuum source 148, the outer diameter 120 of the
elastomeric tube 116 is smaller than the inner diameter 134 of the
tube expander 128.
[0143] After the vacuum source is released allowing the elastomeric
tube 116 to recover to the covered stent 174, the elastomeric tube
116, the covered stent 174, and the mandrel 150 are removed from
the tube expander 128 as shown in FIG. 13. The elastomeric tube
116, the covered stent 174, and the mandrel 150 together include a
diameter 178. FIG. 14 shows a cross-sectional view of the mandrel
150, the covered stent 174, and the elastomeric tube 116 after
removal from the tube expander 128. Pressure and heat are then
applied to uniformly encapsulate and compress the inner and outer
coverings 164, 172 and the stent 100 together.
[0144] In one example, after removal of the mandrel 150, the
covered stent 174, and the elastomeric tube 166 from the tube
expander 128 and prior to applying pressure and heat, the mandrel
150, the covered stent 174, and the elastomeric tube 166 may be
placed in a vacuum chamber for a pretreatment vacuum step. The
pretreatment vacuum step may remove any air bubbles from the
elastomeric tube 166. Air bubbles within the elastomeric tube 166
may affect heating and bonding of the inner and outer coverings
164, 172 to the stent 100. The vacuum chamber may be any vacuum
chamber known in the art, and the mandrel 150 may be positioned on
a rack in the vacuum chamber to provide uniform distribution of the
pressure around the elastomeric tube 166. In one example, the
vacuum pressure applied may be approximately 500 to 700 mmHg
(vacuum pressure) may be applied for approximately 15 minutes to
two (2) hours. In another example, the vacuum pressure applied may
be approximately 600 mmHg (absolute vacuum pressure) for
approximately 1 hour. The vacuum pressure applied may vary and may
range from approximately 50 mmHg to 760 mmHg (absolute vacuum
pressure), and as the vacuum pressure applied increases, the time
the vacuum pressure will be applied decreases.
[0145] To apply pressure and heat to uniformly encapsulate and
compress the inner and outer coverings 164,172 and the stent 100
together, in one example, as shown in FIG. 15A, a sleeve or cap 180
that is hollow and includes an inner diameter 182 and an outer
diameter 184 may be positioned on each of the first and second ends
154, 156 of the mandrel 150. The inner diameter 182 of the sleeve
180 is the same or slightly larger than the diameter 152 of the
mandrel 150 such that the sleeves 180 may slide along the mandrel
150 to contact the first and second ends 122, 124 of the
elastomeric tube 116. The sleeves 180 help to prevent or minimize
the longitudinal length 126 of the elastomeric tube 116 from
expanding when pressure, heat and/or compression are applied and
help with heat transfer. The sleeves 180 may include metal and/or
alloys.
[0146] To apply pressure and heat, in one example as shown in FIG.
15, the mandrel 150 with the covered stent 174, and the elastomeric
tube 116 are positioned in a press fixture 186. The press fixture
186 includes a first portion 188 and a second portion 190. The
first and second portions 188, 190 each include a slot 192 for
receiving the mandrel 150 with the covered stent 174, and the
elastomeric tube 116. The slots 192 each include a half circular
cross-section such that when the first and second portions 188, 190
connect, or the press fixture is closed, the slots 192 form a
hollow circle with a diameter 194. The diameter 194 is the same as
or smaller than the diameter 178 of the mandrel 150, the covered
stent 174, and the elastomeric tube 116 together. In other words,
the diameter 178 is the same or slightly larger than the diameter
194 of the press fixture 186. Preferably, the diameter 178 is
slightly larger than the diameter 194 of the press fixture 186 such
that the first and second portions 188, 190 of the press fixture
186 do not contact each other when brought together until
compression is applied to the press fixture 186. The press fixture
186 may include multiple slots 192 with varying diameters 194.
[0147] As shown in FIGS. 16 and 17, after positioning the mandrel
150 with the covered stent 174 and the elastomeric tube 116 in one
of the slots 192 of the press fixture 186, the first and second
portions 188, 190 are brought together. The press fixture 186 is
not completely closed when the first and second portions 188, 190
are brought together because the diameter 178 is larger than the
diameter 194 of the slots 192 of the press fixture 186. Thus, the
first and second portions 188, 190 may not contact each other until
compression is applied to the press fixture 186. FIGS. 17 and 17A
show cross-sectional views of the mandrel 150, the covered stent
174, and the elastomeric tube 116 within the press fixture 186
before compression is applied.
[0148] As shown in FIG. 18, the press fixture 186 with the mandrel
150, the covered stent 174, and the elastomeric tube 116 are then
positioned in a heated press 196, such as those sold by Carver,
Inc., to uniformly apply compression and heat to the elastomeric
tube 116 and the covered stent 174. When pressure is applied to the
heated press 196, the pressure compresses the press fixture 196,
which compresses the elastomeric tube 116 uniformly against the
covered stent 174 and displaces the elastomeric tube 116 to ensure
contact between the inner and outer coverings 164, 172 as shown in
FIG. 19A. Heat is also applied to the press fixture 186 to
uniformly melt the second material 168 of the inner and outer
coverings 164, 172 to bond the first material 166 of the inner and
outer coverings 164, 172 together around the struts 115 of the
stent 100.
[0149] The amount of pressure applied may also vary, and in one
example, is applied until a pressure gauge on the heated press 196
moves slightly or until the first and second portions 188, 190
contact each other. The amount of pressure applied depends on the
size and durometer of the elastomeric tube 116, as more pressure
will need to be applied to thicker and higher durometer elastomeric
tubes 116. For example, rather than measuring the amount of
pressure, the displacement of the thickness of the elastomeric tube
116 may be measured. The displacement of the thickness of the
elastomeric tube 116 allows the elastomeric tube 116 to conform
around struts 115 of the stent 100. The displacement may range from
approximately 0.002 to 0.050 inches, and preferably will range from
approximately 0.005 to 0.010 inches.
[0150] The amount of heat applied may vary depending on the
material of the second material 168. For example, when the second
material 168 is polyurethane, the heat temperature may range from
380.+-.5 to 430.+-.5 degrees Fahrenheit, and preferably is 390.+-.5
degrees Fahrenheit. When the second material 168 is fluorinated
ethylene propylene (FEP), the heat temperature may range from
490.+-.5 to 540.+-.5 degrees Fahrenheit, and preferably is 500.+-.5
degrees Fahrenheit. The amount of heat applied should be sufficient
to melt the second material 168 of the inner and outer coverings
164, 172 and will vary depending on the type of second material 168
used. When the inner and outer coverings 164, 172 only include the
first material 166, the inner and outer coverings 164, 172 are
heated to above the glass transition temperature of the first
material 166.
[0151] The pressure applied minimizes the diameter 178 of the
mandrel 150 with the covered stent 174, and the elastomeric tube
116 together to be the same as the diameter 194 of the slots 192 of
the press fixture 186 and compresses the elastomeric tube 116
against the covered stent 174 in a uniform distribution around the
elastomeric tube 116. The pressure and heat may be applied for a
time of one minute. However, the time that the pressure and heat
are applied may increase or decrease depending on the amount of
pressure and heat necessary to displace the thickness of the
elastomeric tube 116 to conform around the struts 115 of the stent
100 and melt the second material 168 of the inner and outer
coverings 164, 172.
[0152] Alternatively, pressure may be applied to the press fixture
186 by compression molding or an alternative pressure source that
would permit even pressure distribution around the elastomeric tube
116 and the covered stent 174. Also, heat may also be applied
through the mandrel 150, such as described previously with a
cartridge heater, if the mandrel 150 is hollow, to heat the covered
stent 174 to melt the second material 168 of the inner and outer
coverings 164, 172.
[0153] The application of heat and pressure to the covered stent
174 uniformly encapsulates the stent 100 with the inner and outer
coverings 164, 172 to form a smooth covered stent 198. The smooth
covered stent 198 includes no visible creases, and the inner and
outer coverings 164, 172 include no creases or ridges that create
distortions or lack of continuity on the inner and outer coverings
164, 172. The press fixture 196 and the elastomeric tube 116 permit
uniform pressure and heat distribution around the covered stent
174. FIG. 19A shows a cross-sectional view of the mandrel 150, the
smooth covered stent 198, and the elastomeric tube 116 after the
heat and pressure are applied for a specific time. After the heat
and pressure are applied, the press fixture 186 is removed from the
heated press 196 and the elastomeric tube 116, the smooth covered
stent 198, and the mandrel 150 are removed from the press fixture
186. The elastomeric tube 116, the smooth covered stent 198, and
the mandrel 150 may be placed in room temperature water to cool,
blown with compressed air to cool, allowed to cool to room
temperature of the air, or cooled with freeze spray or liquid
nitrogen.
[0154] In one example, the elastomeric tube 116 may be removed from
the smooth covered stent 198 by positioning the elastomeric tube
116, the smooth covered stent 198, and the mandrel 150 through the
tube expander 128. The first and second ends 122, 124 of the
elastomeric tube 116 may be rolled up over the first and second
ends 138, 140 of the tube expander 128 to create a seal. As
discussed above, sealing devices or techniques to maintain the
position of the elastomeric tube 116 within the tube expander 128
may be used.
[0155] The vacuum source 148 is applied to the tube expander 128 to
uniformly expand the inner and outer diameters 118, 120 of the
elastomeric tube 116. The vacuum source 128 causes the inner and
outer diameters 118, 120 of the elastomeric tube 116 to uniformly
expand so that the outer diameter 120 of the elastomeric tube 116
is in contact with the inner diameter 134 of the tube expander 128.
The smooth covered stent 198 and the mandrel 150 are removed from
the tube expander 128, and the vacuum source 148 is released to
allow the elastomeric tube 116 to recover. The mandrel 150 is then
removed from the smooth covered stent 198 as shown in FIGS. 23 and
24. FIGS. 75 and 76 show microscopic views of the smooth covered
stent 198, and the outer covering 172 conforming around struts of
the stent 100.
[0156] During the encapsulation process, the inner and outer
diameters 102, 104 of the stent 100 remain approximately the same
to maintain integrity of the stent 100. Thus, from the beginning of
the encapsulation process, when the stent 100 is positioned over
the inner covering 164, until the end of the encapsulation process,
when the smooth covered stent 198 is formed, the stent 100
maintains its nominal diameter.
[0157] In an alternative example, if a self-expanding stent is
used, a second elastomeric tube may be positioned around the
mandrel 150 via the tube expander 128 including the vacuum 148, as
described previously above, prior to placement of the inner
covering 164 over the mandrel 150. After placement of the second
elastomeric tube around the mandrel 150, tension is applied to the
second elastomeric tube to radially decrease the outer diameter of
the second elastomeric tube to allow the stent 100 to slide or
otherwise be positioned over the second elastomeric tube on the
mandrel 150. Specifically, the tension applied outer diameter of
the second elastomeric tube is less than the inner diameter 102 of
the stent 100. The tension may be applied by using clamps to pull
on the ends of the second elastomeric tube. With the tension
applied to the second elastomeric tube on the mandrel 150, the
inner covering 164 is positioned over and wrapped around the second
elastomeric tube with the first material 166 of the inner covering
164 in contact with the second elastomeric tube, as described
previously. The stent 100 is positioned over the inner covering 164
and in contact with the second material 168 of the inner covering
164. After the stent 100 is positioned over the inner covering 164,
the tension applied to the second elastomeric tube may be released
and the clamps removed. When the tension is released, the second
elastomeric tube radially expands to a non-tension applied state.
After expansion, the inner covering 164 contacts the inner diameter
102 of the stent 100, and the stent 100 maintains its nominal
diameter and is not significantly expanded. The subsequent steps
described above to form the smooth covered stent 198 may then be
applied, including without limitation the application of an outer
covering 172, the application of the elastomeric tube 116, and the
application of heat and pressure using a press fixture 186 and
heated press 196.
[0158] The tables and steps below provide examples of the materials
and steps using the aforementioned method.
EXAMPLE 1
Balloon-Expandable Stent and Inner and Outer Coverings including
First and Second Materials
TABLE-US-00001 [0159] Element Specifications Stent 100 Inner
diameter 102 is 6.0 mm, outer diameter 104 is 6.4 mm, nominal
diameter is 6 mm, longitudinal length 110 is 30 mm,
balloon-expandable Elastomeric tube inner diameter 118 is 6 mm,
outer diameter 120 is 116 8 mm, longitudinal length 126 is 75 mm,
and the material is silicone with a durometer of 20-25 Shore A
Coating MED-6670, thickness is 45 .mu.m Tube expander 128 inner
diameter 134 is 14 mm Inner covering 164 includes first material
166 and second material 168 First material 166 esPTFE Second
material 168 polyurethane Outer covering 172 includes first
material 166 and second material 168 Mandrel 150 diameter is 6 mm,
the material is glass with smooth finish Slot 192 of Press diameter
194 of slot 192 is 8 mm Fixture 186
Steps:
[0160] The coating is applied to the inner diameter 118 of the
elastomeric tube 116 and then cured; [0161] The elastomeric tube
116 is positioned within the tube expander 128 including the port
128 and the vacuum 148; [0162] The mandrel 150 is provided; [0163]
The inner covering 164 is rolled in 70% isopropanol; [0164] The
inner covering 164 is positioned or wrapped around the mandrel 150
with the first material 166 in contact with the mandrel 150; [0165]
The stent 100 is initially slightly over-expanded and then
positioned over the inner covering 164 and in contact with the
second material 168 of the inner covering 164; [0166] An Iris
crimper is used to secure the stent 100 to the inner covering 164;
[0167] The outer covering 172 is rolled in 70% isopropanol; [0168]
The outer covering 172 is positioned or wrapped around the stent
100 with the second material 168 of the outer covering 172 in
contact with the stent 100 to form the covered stent 174; [0169]
The first and second ends 122, 124 of the elastomeric tube 116 are
rolled up and wrapped around the first and second ends 138, 140 of
the tube expander 128; [0170] The vacuum 148 is applied expanding
the inner and outer diameters 118, 120 of the elastomeric tube 116
until the outer diameter 120 of the elastomeric tube 116 contacts
the inner diameter 134 of the tube expander 128; [0171] The covered
stent 174 and the mandrel 150 are positioned in the tube expander
128; [0172] The vacuum 148 is released allowing the inner and outer
diameters 118, 120 of the elastomeric tube 116 to retract to an
unexpanded state and recover to the covered stent 174; [0173] The
elastomeric tube 116, the covered stent 174, and the mandrel 150
are positioned in a vacuum chamber with an applied pressure of 600
mmHg (absolute vacuum pressure) for 1 hour; [0174] The elastomeric
tube 116, the covered stent 174, and the mandrel 150 are removed
from the vacuum chamber and positioned in the slot 192 of the press
fixture 186 and the first and second portions 188, 190 of the press
fixture 186 are brought together; [0175] The press fixture 186 is
positioned in the heated press 196; [0176] Pressure is applied to
the press fixture 186 to displace the thickness of elastomeric tube
116 by 0.005.+-.0.001 inches; [0177] Heat is applied to the press
fixture 186 to 390.+-.5 degrees Fahrenheit and is applied for 1
minute time; [0178] The press fixture 186 is removed from the
heated press 196; [0179] The elastomeric tube 116, the smooth
covered stent 198, and the mandrel 150 are removed from the press
fixture 186 and positioned in room temperature water for cooling;
[0180] The elastomeric tube 116, the smooth covered stent 198, and
the mandrel 150 are positioned in the tube expander 128; [0181] The
first and second ends 122, 124 of the elastomeric tube 116 are
rolled up and wrapped around the first and second ends 138, 140 of
the tube expander 128; [0182] The vacuum 148 is applied allowing
the inner and outer diameters 118, 120 of the elastomeric tube 116
to uniformly expand; [0183] The smooth covered stent 198 and the
mandrel 150 are removed from the tube expander 128; and [0184] The
mandrel 150 is removed from the smooth covered stent 198.
EXAMPLE 2
Balloon-Expandable Stent and Inner and Outer Coverings including
First Material
TABLE-US-00002 [0185] Element Specifications Stent 100 Inner
diameter 102 is 8.0 mm, outer diameter 104 is 8.4 mm, nominal
diameter is 8 mm, longitudinal length 126 is 30 mm,
balloon-expandable Elastomeric tube inner diameter 118 is 8 mm,
outer diameter 120 116 is 10 mm, longitudinal length 126 is 75 mm,
and the material is silicone with a durometer of 20 Shore A Coating
MED-6670, thickness is 45 .mu.m Tube expander 128 inner diameter
134 is 14 mm Inner covering 164 includes first material 166 only
First material 166 esPET Outer covering 172 includes first material
166 only Mandrel 150 diameter is 8 mm, the material is stainless
steel Slot 192 of Press diameter 194 of slot 192 is 10 mm Fixture
186
Steps:
[0186] The coating is applied to the inner diameter 118 of the
elastomeric tube 116 and then cured; [0187] The elastomeric tube
116 is positioned within the tube expander 128 including the vacuum
148; [0188] The mandrel 150 is provided; [0189] The inner covering
164 is rolled in 70% isopropanol; [0190] The inner covering 164 is
positioned or wrapped around the mandrel 150; [0191] The stent 100
is initially slightly over-expanded and then positioned over the
inner covering 164; [0192] An Iris crimper is used to secure the
stent 100 to the inner covering 164; [0193] The outer covering 172
is rolled in 70% isopropanol; [0194] The outer covering 166 is
positioned or wrapped around the stent 100 to form the covered
stent 174; [0195] The first and second ends 122, 124 of the
elastomeric tube 116 are rolled up and wrapped around the first and
second ends 138, 140 of the tube expander 128; [0196] The vacuum
148 is applied expanding the inner and outer diameters 118, 120 of
the elastomeric tube 116 until the outer diameter 120 of the
elastomeric tube 116 contacts the inner diameter 134 of the tube
expander 128; [0197] The covered stent 174 and the mandrel 150 are
positioned in the tube expander 128; [0198] The vacuum 148 is
released allowing the inner and outer diameters 118, 120 of the
elastomeric tube 116 to retract to an unexpanded state and recover
to the covered stent 174; [0199] The elastomeric tube 116, the
covered stent 174, and the mandrel 150 are positioned in a vacuum
chamber with an applied pressure of 600 mmHg (absolute vacuum
pressure) for 1 hour; [0200] The elastomeric tube 116, the covered
stent 174, and the mandrel 150 are removed from the vacuum chamber
and positioned in the slot 192 of the press fixture 186 and the
first and second portions 188, 190 of the press fixture 186 are
brought together; [0201] The press fixture 186 is positioned in the
heated press 196; [0202] Pressure is applied to the press fixture
186 to displace the thickness of elastomeric tube 116 by
0.005.+-.0.001 inches; [0203] Heat is applied to the press fixture
186 to 365.+-.5 degrees Fahrenheit and is applied for 1 minute
time; [0204] The press fixture 186 is removed from the heated press
196; [0205] The elastomeric tube 116, the smooth covered stent 198,
and the mandrel 150 are removed from the press fixture 186 and
positioned in room temperature water for cooling; [0206] The
elastomeric tube 116, the smooth covered stent 198, and the mandrel
150 are positioned in the tube expander 128; [0207] The first and
second ends 122, 124 of the elastomeric tube 116 are rolled up and
wrapped around the first and second ends 138, 140 of the tube
expander 128; [0208] The vacuum 148 is applied allowing the inner
and outer diameters 118, 120 of the elastomeric tube 116 to
uniformly expand; [0209] The smooth covered stent 198 and the
mandrel 150 are removed from the tube expander 128; and [0210] The
mandrel 150 is removed from the smooth covered stent 198.
Manual Removal of the Elastomeric Tube
[0211] In another example, as shown in FIG. 22, the elastomeric
tube 116 may be removed from the smooth covered stent 198 by
ripping or peeling the elastomeric tube 116 away from the smooth
covered stent 198. The elastomeric tube 116 may also be removed by
skiving or pulling the elastomeric tube 116 along a longitudinal
length 200 of the smooth covered stent 198. The mandrel 150 is
removed from the smooth covered stent 198 as shown in FIGS. 23 and
24. FIG. 25 shows a cross-sectional view of the smooth covered
stent 198. If the longitudinal length 200 of the smooth covered
stent 198 exceeds beyond the desired length, any excess on a first
end 202 and second end 204 of the smooth covered stent 198 may be
trimmed, cut, or otherwise removed.
Swelling Agent for Radial Expansion of Elastomeric Tube
[0212] Another example of expanding the inner and outer diameters
118, 120 of the elastomeric tube 116 includes placing the
elastomeric tube 116 in a container including a swelling agent. The
container may include a glass vial or any other container capable
of holding a liquid. The swelling agent may include hexane,
volatile methyl siloxane, Freon.RTM., Swellex.RTM., Swellex.RTM. P,
or other swelling agents.
[0213] The elastomeric tube 116 remains in the container with the
swelling agent until the elastomeric tube 116 is adequately
expanded so that the inner diameter 118 of the elastomeric tube 116
is greater than the diameter 170 of the mandrel 150 and the covered
stent 174. Thus, the time the elastomeric tube 116 remains in the
container with the swelling agent may vary, and may include
approximately ten minutes.
[0214] The elastomeric tube 116 is then removed from the container,
and the mandrel 150 and the covered stent 174 may be positioned
within the elastomeric tube 116 such that the elastomeric tube 116
surrounds the covered stent 174. For example, the longitudinal
length 126 of the elastomeric tube 116 is greater than or the same
as the longitudinal length 110 of the stent 100. The elastomeric
tube 116, the mandrel 150, and the covered stent 174 are allowed to
air dry under a fume hood, exposed to a dryer, such as an electric
dryer, or otherwise permitted to dry to allow the elastomeric tube
116 to recover to the covered stent 174. Heat and pressure are then
applied to the covered stent 174 as described previously including
the press fixture 186 and the heated press 196 to uniformly form
the smooth covered stent 198.
[0215] After the heat and pressure are applied, the press fixture
186 is removed from the heated press 196, and the mandrel 150, the
smooth covered stent 198, and the elastomeric tube 116 are removed
from the press fixture 186. The elastomeric tube 116 may then be
removed from the smooth covered stent 198 by any of the methods
previously described including by ripping or peeling the
elastomeric tube 116 away from the smooth covered stent 198, by
using the tube expander 128 to uniformly expand the inner and outer
diameters 118, 120 of the elastomeric tube 116 away from the smooth
covered stent 198, or by placing elastomeric tube 116, the smooth
covered stent 198, and the mandrel 150 in the container with the
swelling agent to uniformly expand the inner and outer diameters
118, 120 of the elastomeric tube 116 away from the smooth covered
stent 198. After the elastomeric tube 116 is removed from the
smooth covered stent 198, the mandrel 150 is then removed from the
smooth covered stent 198.
Expansion Mandrels and Slit Cannula
[0216] FIGS. 26-64 show another example of a method of making a
stent with a smooth covering. A slit cannula 300 is provided that
is hollow and includes a circular cross section with an inner
diameter 302, an outer diameter 304, a first end 306, a second end
308, and a longitudinal length 310, which is defined from the first
end 306 to the second end 308 as shown in FIG. 26. The material of
the slit cannula 300 is polytetrafluoroethylene (PTFE), including
Teflon.RTM., stainless steel or another material that is capable of
withstanding the pressure and temperature without material
failure.
[0217] In this example, the stent 100 includes a self-expanding
stent. However, a balloon-expandable stent may also be used. A
variety of biocompatible materials may be used to construct the
stent, including metals, and/or alloys, medically-acceptable
polymers and/or bioabsorbable polymers or materials. For example,
the metals and/or alloys may include stainless steel, tantalum,
nitinol, tungsten, platinum, inconel, cobalt-chromium alloys,
iridium, molybdenum, moly-rhenium, other alloys of nitinol
(including ternary and quaternary alloys), and magnesium or its
alloys (as degradable stents).
[0218] The slit cannula 300 also includes a plurality of slits 312.
The slits 312 include a first end 314, a second end 316, and a
longitudinal length 318, which is defined from the first end 314 to
the second end 316. The longitudinal length 318 of the slits 312 is
smaller than the longitudinal length 310 of the slit cannula 300.
The slits 312 allow radial expansion of the slit cannula 300 and
the inner and outer diameters 302, 304 of the slit cannula 300 to
increase.
[0219] In one example, as shown in FIGS. 26-32, the first ends 314
of the slits 312 begin either at the first or second ends 306, 308
of the slit cannula 300. The second ends 316 of the slits 312 do
not interact with either the first or second ends 306, 308 of the
slit cannula 300. The second ends 316 of the slits 312 each include
a circular end 320. The circular ends 320 provide stress relief and
release on the slits 312 during expansion of the slit cannula 300
and prevent the longitudinal length 318 of the slits 312 from
increasing and thereby extending the second ends 316 of the slits
312 to either the first or second ends 306, 308 of the slit cannula
300.
[0220] The slits 312 form an alternating pattern around the outer
diameter 304 of the slit cannula 300 such that if the first end 314
of one of the slits 312 begins at the first end 306 of the slit
cannula 300, the first end 314 of the adjacent slits 312 begins at
the second end 308 of the slit cannula 300. For example, as shown
in FIGS. 26-32, the slit cannula 300 includes twelve slits 312. In
other examples, 8 to 10 slits may be used depending on the outer
diameter 104 of the stent 100. FIG. 27 shows a cross-sectional view
of the first end 306 of the slit cannula 300, and FIG. 28 shows a
cross-sectional view of the second end 308 of the slit cannula 300.
The number of slits 312 will vary depending on the inner and outer
diameters 302, 304 of the slit cannula 300.
[0221] The inner and outer diameters 302, 304 of the slit cannula
300 will vary depending on the nominal diameter of the stent 100.
For example, the nominal diameter of the stent 100 may range from
5-14 mm. When the stent 100 is used in aortic or venous
indications, the expanded outer diameter 104 may range 5.0 to 40
mm. The inner diameter 302 of the slit cannula 300 may range from
2.16.+-.0.13 to 5.33.+-.0.13 mm, and the outer diameter 304 may
range from 3.175.+-.0.13 to 6.35.+-.0.13 mm.
[0222] In one example, as shown in FIGS. 30-32, a first mandrel 322
is provided as a support base for the slit cannula 300. The
material of the first mandrel 322 includes glass, metal, stainless
steel or an alloy, and preferably stainless steel. As shown in FIG.
32, when the first mandrel 322 is fully inserted within the slit
cannula 300, the portion of the slit cannula 300 covering the first
mandrel 322 is expanded. The first mandrel 322 includes a circular
cross-section with a first portion 323 and a second portion 325.
The first portion 323 includes a diameter 324, and the second
portion 325 includes a diameter 327. The diameter 324 of the first
portion 323 is greater than the diameter 327 of the second portion
325. In an alternative example, the first mandrel 322 may be hollow
to allow for faster heating and cooling or alternative methods of
heating and cooling underneath the stent 100.
[0223] The first mandrel 322 includes a first end 326, a second end
328, a tip 330, and a longitudinal length 332, which is defined
from the first end 326 to the second end 328 of the first mandrel
322. The longitudinal length 332 of the first mandrel 322 is
smaller than the longitudinal length 310 of the slit cannula 300.
The tip 330 is located at the first end 326 of the first mandrel
322. In an alternative example, the first mandrel 322 may be
permanently fixed with the slit cannula to provide stability.
[0224] As shown in FIGS. 30-32, in one example, the first mandrel
322 includes a handle 334. The handle 334 has a circular cross
section, a first end 336, a second end 338, and a slot 340 that has
a circular cross section for receiving the second portion 325 of
the first mandrel 322. For example, when the diameter 327 of the
second portion 325 is 0.1250.+-.0.005 inches, the diameter of the
slot 340 of the handle 334 is 0.1260.+-.0.005 inches. The handle
334 slides onto the second portion 325 and is attached to the first
mandrel 322 by a press fit and/or other fastening means that permit
the handle 334 to be easily removed from the first mandrel 322. In
an alternative example, the first mandrel 322 does not include a
handle 334. In another example, the second portion 325 of the first
mandrel 322 is knurled or machined to allow for gripping or
handling of the first mandrel 322. The material of the handle 334
includes glass, metal, stainless steel or an alloy, and preferably
stainless steel.
[0225] A first layer of elastomeric tube 342 is provided and
positioned over a non-expanded portion of the slit cannula 300 as
shown in FIG. 33. As described previously, the elastomeric material
of the tube 342 may include the same material as the elastomeric
tube 116 or, preferably, an elastomeric material with a higher
durometer than the elastomeric tube 116. The elastomeric tube 342
includes an inner diameter 344 , an outer diameter 346, and a
thickness 345, which is defined from the inner diameter 344 to the
outer diameter 346. In its original state, the inner diameter 344
of the elastomeric tube 342 is slightly smaller than the outer
diameter 304 of the slit cannula 300. The inner and outer diameters
344, 346 will vary depending on the nominal diameter of the stent
100. For example, the nominal diameter of the stent 100 may range
from 5 to 14 mm. The outer diameter 346 may range from
0.130.+-.0.005 to 0.524.+-.0.005 inches. The inner diameter 344 may
range from 0.090.+-.0.005 to 0.484.+-.0.005 inches. When the stent
100 is used in aortic or venous indications, the expanded outer
diameter 102 may range 5.0 to 40 mm. The first layer of elastomeric
tube 342 is hollow and includes a first end 348, a second end 350,
and a longitudinal length 352. The longitudinal length 352 is
defined from the first end 348 to the second end 350 of the
elastomeric tube 342 and is the same as or slightly smaller than
the longitudinal length 310 of the slit cannula 300.
[0226] The inner covering 164 including the first material 166 and
the second material 168, as described previously, that is used to
cover the inner surface 112 of the stent 100 or a prosthesis, is
positioned over and wrapped around the first layer of elastomeric
tube 342 as shown in FIG. 34. The first material 166 is in contact
with the first layer of the elastomeric tube 342. The stent 100 is
then positioned over the inner covering 164 and is in contact with
the second material 168 of the inner covering 164.
[0227] As described previously, the inner covering 164 may include
more than one layer such that the first and second materials 166,
168 of the inner covering 164 to maintain an alternating pattern
underneath the stent 100. To keep the layers in place, as
previously described, a soldering iron may be used to tack or
otherwise adhere edges of the inner covering 164. In other
examples, the first mandrel 322 is provided after the first layer
of elastomeric tube 342, the inner covering 164, and the stent 100
are positioned over the slit cannula 300.
[0228] A coating, as previously described, that reduces the
friction on the surface of the first layer of elastomeric tube 342
may be applied to the outer diameter 346 of the first layer
elastomeric tube 342. The coating helps to remove the stickiness or
tackiness of the first layer of elastomeric tube 342, so that the
first layer of elastomeric tube 342 does not stick to the inner
covering 164.
[0229] As shown in FIG. 35, a second mandrel 354 is provided to
expand the slit cannula 300, the first layer of elastomeric tube
342, and the inner covering 164. The material of the second mandrel
354 includes glass, metal, stainless steel or an alloy, and
preferably stainless steel. After expansion, the inner covering 164
contacts the inner diameter 102 of the stent 100, and the stent 100
maintains its nominal diameter and is not significantly
expanded.
[0230] The second mandrel 354 includes a circular cross-section
with a first portion 356 and a second portion 358. The first
portion 356 includes a diameter 360, and the second portion 358
includes a diameter 362. The diameter 360 of the first portion 356
is greater than the diameter 362 of the second portion 358. The
second mandrel 354 includes a first end 364, a second end 366, a
tip 368, and a longitudinal length 370, which is defined from the
first end 364 to the second end 366 of the second mandrel 356. The
longitudinal length 370 of the second mandrel 354 is smaller than
the longitudinal length 310 of the slit cannula 300. The tip 368 is
located at the first end 364 of the second mandrel 354. In an
alternative example, the second mandrel 354 may be permanently
fixed with the slit cannula to provide stability. In an alternative
example, the first mandrel 322 may be hollow to allow for faster
heating and cooling or alternative methods of heating and cooling
underneath the stent 100.
[0231] When the second mandrel 354 is fully inserted within the
slit cannula 300, the portion of the slit cannula 300 that covers
the second mandrel 354 and the stent 100 is expanded, and the tip
368 of the second mandrel 354 is in contact with the tip 330 of the
first mandrel 322. As shown in FIG. 36, the second mandrel 354
extends beneath the longitudinal length 110 of the stent 100 so the
first layer of elastomeric tube 342 and the inner covering 164 are
expanded to contact the inner diameter 102 of the stent 100. The
stent 100 is not expanded and maintains its nominal diameter when
the second mandrel 354 is fully inserted within the slit cannula
300.
[0232] The second mandrel 354 also includes a handle 372. The
handle 372 has a circular cross section, a first end 374, a second
end 376, and a slot 378 that has a circular cross section for
receiving the second portion 358 of the second mandrel 354. For
example, when the diameter 362 of the second portion 358 is
0.1250.+-.0.005 inches, the diameter of the slot 378 of the handle
372 is 0.1260.+-.0.005 inches. The handle 372 slides onto the
second portion 358 of the second mandrel 354 and is attached to the
second mandrel 354 by a press fit and/or other fastening means that
permit the handle 372 to be easily removed from the second mandrel
354. In an alternative example, the second mandrel 354 does not
include a handle 372. In another example, the second portion 358 of
the second mandrel 354 is knurled or machined to allow for gripping
or handling of the second mandrel 354. The material of the handle
373 includes glass, metal, stainless steel or an alloy, and
preferably stainless steel.
[0233] After expanding the slit cannula 300, the outer covering
172, including the first material 166 and the second material 168,
as described previously, that is used for encapsulating the stent
100 or a prosthesis, is positioned over and wrapped around the
stent 100 as shown in FIG. 36. The second material 168 is in
contact with the stent 100, and the first material 166 is not in
contact with the stent 100. As described previously, additional
layers may also be added such that the first and second materials
166, 168 of the layers maintain an alternating pattern over the
stent 100. To keep the layers in place, as previously described, a
soldering iron may be used to tack or otherwise adhere edges of the
layers.
[0234] As shown in FIG. 38, a second layer of elastomeric tube 380
is positioned in the tube expander 128. As described previously,
the elastomeric material of the tube 380 may include the same
material as the elastomeric tube 116. The elastomeric tube 380 is
hollow and includes a circular cross section with an inner diameter
382, an outer diameter 384, a first end 386, a second end 388, and
a longitudinal length 390. The longitudinal length 390 is defined
from the first end 386 to the second end 388 of the elastomeric
tube 380. The second layer of elastomeric tube 380 is positioned
within the tube expander 128, as previously described, to uniformly
expand the inner and outer diameters 382, 384 of the elastomeric
tube 380. As previously described, the first and second ends 386,
388 of the elastomeric tube 380 may be may be rolled up over the
first and second ends 138, 140 of the tube expander 128 to create a
seal. The vacuum source 148 is applied to the tube expander 128 to
uniformly expand the inner and outer diameters 382, 384 of the
elastomeric tube 380.
[0235] A coating, as previously described, that reduces the
friction on the surface of the second layer of elastomeric tube 380
may be applied to the inner diameter 382 of the second layer
elastomeric tube 380. The coating helps to remove the stickiness or
tackiness of the second layer elastomeric tube 380, so that the
second layer elastomeric tube 380 does not stick to the outer
covering 172.
[0236] As shown in FIG. 37, one or both of the handles 334, 372 may
be removed from the second portions 325, 358 of the first and
second mandrels 322, 354 in order to position the slit cannula 300
with the covered stent 174 and the first and second mandrels 322,
354 within the tube expander 128. The slit cannula 300 and the
covered stent 174 are positioned with the tube expander 128 as
shown in FIG. 38, and then the vacuum source 148 is released to
allow the inner and outer diameters 382, 384 of the second layer of
elastomeric tube 380 to return to an unexpanded state and recover
to the covered stent 174. The second layer of elastomeric tube 380
and the covered stent 174 are removed from the tube expander 128 as
shown in FIG. 39, and the handles 334, 372 may then be positioned
back on the first and second mandrels 322, 354.
[0237] In one example, as described previously, after removal from
the tube expander 128 and prior to applying pressure and heat, the
first and second layers of elastomeric tube 342, 380, the covered
stent 174, the slit cannula 300, and the first and second mandrels
322, 354 may be placed in a vacuum chamber for a pretreatment
vacuum step. The pretreatment vacuum step may remove any air
bubbles from the first and second layers of elastomeric tube 342,
380. Air bubbles within the first and second layers of elastomeric
tube 342, 380 may affect heating and bonding of the inner and outer
coverings 164, 172 to the stent 100. The vacuum chamber may be any
vacuum chamber known in the art, and the first and second mandrels
322, 354 may be positioned on a rack in the vacuum chamber to
provide uniform distribution of the pressure around the first and
second layers of elastomeric tube 342, 380. In one example, the
vacuum pressure applied may be approximately 500 to 700 mmHg
(vacuum pressure) may be applied for approximately 15 minutes to
two (2) hours. In another example, the vacuum pressure applied may
be approximately 600 mmHg (absolute vacuum pressure) for
approximately 1 hour. The vacuum pressure applied may vary and may
range from approximately 50 mmHg to 760 mmHg (absolute vacuum
pressure), and as the vacuum pressure applied increases, the time
the vacuum pressure will be applied decreases.
[0238] As shown in FIGS. 40-42, the first and second layers of
elastomeric tube 342, 380, the covered stent 174, the slit cannula
300, and the first and second mandrels 322, 354 are positioned in
the press fixture 186 and then in the heated press 196, where heat
and pressure are applied as previously described to create the
smooth covered stent 198. Alternatively, heat and pressure may be
applied as described in the "First and Second Tubes with Heated
Oven" example, or other heat and pressure applications.
[0239] The first and second layers of elastomeric tube 342, 380,
the smooth covered stent 198, the slit cannula 300, and the first
and second mandrels 322, 354 are cooled, and then the handles 334,
372 may be removed from the first and second mandrels 322, 354 to
position the second layer of elastomeric tube 380 and the smooth
covered stent 198 in the tube expander 128 to remove the second
layer of elastomeric tube 380 as shown in FIGS. 42-43. Other
removal methods as described previously may also be used to remove
the second layer of elastomeric tube 380 from the smooth covered
stent 198. The handles 334, 372 are positioned backed on the first
and second mandrels 322, 354 as shown in FIG. 44. As shown in FIG.
45, the second mandrel 354 is removed from the slit cannula 300,
which decreases the outer diameter 304 of the slit cannula 300, and
then the smooth covered stent 198 is removed from the slit cannula
300.
[0240] As shown in FIG. 46, the smooth covered stent 198 may
include a plurality of stripes or indentations 392 on an inner
surface 394 of the smooth covered stent 198 from compression
against the slits 312 of the slit cannula 300. When the material of
the first layer of elastomeric tube 342 includes an elastomeric
material with a higher durometer than the material of the
elastomeric tube 116, the stripes or indentations 392 may not form
or are reduced in frequency.
[0241] As shown in FIGS. 47-49, to remove the strips 392 and to
smooth the inner surface 394 of the smooth covered stent 198, a
mandrel 396 with a diameter 398 is provided. The mandrel 396
includes a smooth outer surface 400, which may include glass or
other suitable material with a smooth outer surface. The mandrel
396 is positioned within the smooth covered stent 198, and a first
layer of elastomeric tube 402 with an inner diameter 404 and an
outer diameter 406 is positioned over the smooth covered stent 198.
The first layer of elastomeric tube 402 may include the same
material as the elastomeric tube 116 previously described. The tube
expander 128 may be used to uniformly expand the first layer of
elastomeric tube 402 over the smooth covered stent 198. A coating,
as previously described, that reduces the friction on the surface
of the first layer of elastomeric tube 402 may be applied to the
inner diameter 404 of the first layer of elastomeric tube 402 so
that the first layer of elastomeric tube 402 does not stick to the
smooth covered stent 198.
[0242] As shown in FIG. 49, a second layer of elastomeric tube 408
with an inner diameter 410 and an outer diameter 412 is positioned
over the first layer of elastomeric tube 402. The second layer of
elastomeric tube 408 may include the same material as the
elastomeric tube 116 previously described. The inner and outer
diameters 410, 412 of the second layer of elastomeric tube 408 are
smaller than the inner and outer diameters 404, 406 of the first
layer of elastomeric tube 402. To position the second layer of
elastomeric tube 408 over the first layer of elastomeric tube 402,
the tube expander 128 may be used to uniformly expand the second
layer of elastomeric tube 408 over the first layer of elastomeric
tube 402. A coating, as previously described, that reduces the
friction on the surface of the second layer of elastomeric tube 408
may be applied to the inner diameter 410 of the second layer of
elastomeric tube 408 so that the second layer of elastomeric tube
408 does not stick to the first layer of elastomeric tube 402.
[0243] The mandrel 396, the smooth covered stent 198, and the first
and second layers of elastomeric tube 402, 408 are positioned in
the press fixture 186 and then in the heated press 196, where heat
and pressure are applied as previously described and as shown in
FIGS. 40-41. The amount of heat applied and the time of heat
application may vary, and in one example is 420 degrees Fahrenheit
for two minutes. Alternatively, heat and pressure may be applied as
described in the "First and Second Tubes with Heated Oven" example,
or other heat and pressure applications.
[0244] After removal from the heated press 196, cooling, and
removal from the press fixture 186, the second layer of elastomeric
tube 408 is removed from the first layer of elastomeric tube 402,
as shown in FIGS. 52 and 53. Any of the removal methods as
described previously may be used to remove the second layer of
elastomeric tube 408 from the first layer of elastomeric tube 402.
A shrink tube 414 may be positioned over or wrapped around the
first layer of elastomeric tube 402 and smooth covered stent 198.
The material of the shrink tube 414 may include shrink silicone,
polyimide shrink, shrink polyetheretherketone (PEEK), fluorinated
ethylene propylene (FEP), polytetrafluoroethylene (PTFE), or
polyethylene terephthalate (PET), and the shrink tube 414 includes
a diameter 416. The diameter 416 of the shrink tube 414 is
sufficient to be positioned over the first layer of elastomeric
tube 402.
[0245] As shown in FIG. 54, a heating source 418, such as a heating
gun, is applied to the shrink tube 414 to shrink the first layer of
elastomeric tube 402 and apply compression and heat to the smooth
covered stent 198. The amount of heat and the time of heat
application may vary, and in one example, may be 215 degrees
Celsius (or 420 degrees Fahrenheit) for five minutes when a shrink
tube 414 comprising FEP is used. The shrink tube 414 is removed
from the first layer of elastomeric tube 402, and then the first
layer of elastomeric tube 402 is removed from the smooth covered
stent 198 using any of the removal methods as described previously.
The smooth covered stent 198 is then removed from the mandrel 396.
As shown in FIGS. 55 and 56, the inner surface 394 of the smooth
covered stent 198 is smooth and the stripes 392 are removed. In
another example, the strips 392 may be removed from the inner
surface 394 of the smooth covered stent 198 without use of the
press fixture 186 and the heated press 196.
[0246] FIGS. 57-60 show another example of the slit cannula 300
when only a single mandrel 420 is used. The first ends 314 of the
slits 300 all begin at the first end 306 of the slit cannula 300.
FIG. 58 shows a cross sectional view of the first end 306 of the
slit cannula 300.
[0247] The mandrel 420 includes a circular cross-section with a
first portion 422 and a second portion 424. The first portion 422
includes a diameter 426, and the second portion 424 includes a
diameter 428. The diameter 426 of the first portion 422 is greater
than the diameter 428 of the second portion 424. The mandrel 420
includes a first end 430, a second end 432, a tip 434, and a
longitudinal length 436, which is defined from the first end 430 to
the second end 432 of the mandrel 420. The longitudinal length 436
of the mandrel 420 is smaller than the longitudinal length 310 of
the slit cannula 300. In an alternative example, the mandrel 420
may be permanently fixed with the slit cannula to provide
stability.
[0248] FIGS. 59 and 60 show the mandrel 420 within the slit cannula
300. In this example, the mandrel 420 is positioned within the slit
cannula 300 after the first layer of elastomeric tube 342, the
inner covering 164, and the stent 100 are positioned over the slit
cannula 300. The steps as previously described can then be used to
encapsulate the stent 100, including application of the outer
covering 172 and the second layer of elastomeric tube 380 and the
use of the press fixture 186 and the heated press 196 to apply
pressure and heat.
[0249] FIGS. 61-64 show another example of the mandrel 420
including a plurality of splines 438. The number of splines 438 is
the same as the number of slits 312 of the slit cannula 300. The
mandrel 420 with the splines 438 helps to prevent the plurality of
stripes or indentations 392 on the inner surface 394 of the smooth
covered stent 198 from forming during compression. FIG. 64 shows a
cross-sectional view of the mandrel 420 with the splines 438 when
positioned within the slit cannula 300.
[0250] The tables and steps below provide examples of the materials
and steps using the aforementioned method.
EXAMPLE 3
Self-Expandable Stent, Slit Cannula and Two Mandrels with
Handles
TABLE-US-00003 [0251] Element Specifications Stent 100 inner
diameter 102 is 7.6 mm, outer diameter 104 is 8.0 mm, nominal
diameter is 8 mm, longitudinal length 126 is 70 mm, self-expanding
Slit cannula 300 inner diameter 302 is 3.76 mm, outer diameter 304
is 4.76 mm, longitudinal length is 210 mm, material is stainless
steel Slits 312 number slits 312 is 10, longitudinal length 318 of
slits is 208 mm First mandrel 322 longitudinal length 332 is 92 mm,
diameter 324 is first portion 323 is 6.22 mm, diameter 327 of
second portion 325 is 3.175 mm, material is stainless steel, Handle
334 of diameter of slot 340 is 3.20 mm, material is first mandrel
322 stainless steel First layer of material is silicone with a
durometer of 50 elastomeric tube Shore A, longitudinal length 352
is 210 mm, 342 inner diameter 344 is 4.29 mm, outer diameter 346 is
5.31 mm Coating MED-6670, thickness is 45 .mu.m Inner covering 164
includes first material 166 and second material 168 First material
166 ePTFE Second material 168 FEP Second mandrel 354 longitudinal
length 370 is 144 mm, diameter 324 is first portion 356 is 6.22 mm,
diameter 327 of second portion 358 is 3.175 mm, material is
stainless steel, Handle 372 of diameter of slot 378 is 3.20 mm,
material is second mandrel stainless steel 354 Outer covering 172
includes first material 166 and second material 168 Second layer of
material is silicone with a durometer of 20 elastomeric tube Shore
A, longitudinal length 390 is 114 mm, 380 inner diameter 382 is 6
mm, outer diameter 384 is 8 mm Tube expander 128 inner diameter 134
is 14 mm Slot 192 of Press diameter 194 of slot 192 is 9.6 mm
Fixture 186
Steps:
[0252] The first mandrel 322 is positioned within the slit cannula
300; [0253] The coating is applied to the outer diameter 346 of the
first elastomeric tube 342 and then cured; [0254] The first layer
of elastomeric tube 342 is positioned over the slit cannula 300;
[0255] The inner covering 164 is rolled in 70% isopropanol; [0256]
The inner covering 164 is positioned over and wrapped around a
non-expanded portion of the slit cannula 300 with the first
material 166 of the inner covering 164 in contact with the first
elastomeric tube 342; [0257] The stent 100 is positioned over the
inner covering 164 and in contact with the second material 168 of
the inner covering 164; [0258] The second mandrel 354 is positioned
within the slit cannula 300 and radially expands the slit cannula
300, the first layer of elastomeric tube 342, and the inner
covering 164 such that the inner covering 164 is in contact with
the inner diameter 102 of the stent 100; [0259] The outer covering
172 is rolled in 70% isopropanol; [0260] The outer covering 172 is
positioned over and wrapped around the stent 100 with the second
material 168 in contact with the stent 100 to form the covered
stent 174; [0261] The coating is applied to the inner diameter 382
of the second layer of elastomeric tube 380 and then cured; [0262]
The second layer of elastomeric tube 380 is positioned within the
tube expander 128 including the vacuum 148; [0263] The first and
second ends 306, 308 of the second layer of elastomeric tube 380
are rolled up and wrapped around the first and second ends 138, 140
of the tube expander 128; [0264] The vacuum 148 is applied
expanding the inner and outer diameters 382, 384 of second layer of
elastomeric tube 380 until the outer diameter 384 of the second
elastomeric tube 380 contacts the inner diameter 134 of the tube
expander 128; [0265] One of the handles 334, 372 is removed from
either the first or second mandrel 322, 354; [0266] The covered
stent 174, the first layer of elastomeric tube 342, the slit
cannula 300, and the first and second mandrels 322, 354 are
positioned in the tube expander 128; [0267] The vacuum 148 is
released allowing the inner and outer diameters 382, 384 of second
layer of elastomeric tube 380 to retract to an unexpanded state and
recover to the covered stent 174; [0268] The first and second
layers of elastomeric tube 342, 380, the covered stent 174, the
slit cannula 300, and the first and second mandrels 322, 354 are
removed from the tube expander 128; [0269] One of the handles 344,
372 previously removed is positioned back on either the first or
second mandrel 322, 354; [0270] The first and second layers of
elastomeric tube 342, 380, the covered stent 174, the slit cannula
300, and the first and second mandrels 322, 354 are positioned in a
vacuum chamber with an applied pressure of 600 mmHg (absolute
vacuum pressure) for 1 hour; [0271] The first and second layers of
elastomeric tube 342, 380, the covered stent 174, the slit cannula
300, and the first and second mandrels 322, 354 are removed from
the vacuum chamber and positioned in the slot 192 of the press
fixture 186 and the first and second portions 188, 190 of the press
fixture 186 are brought together; [0272] The press fixture 186 is
positioned in the heated press 196; [0273] Pressure is applied to
the press fixture 186 to displace the thickness of second layer of
elastomeric tube 380 by 0.005.+-.0.001 inches; [0274] Heat is
applied to the press fixture 186 to 500.+-.5 degrees Fahrenheit and
is applied for 1 minute time; [0275] The press fixture 186 is
removed from the heated press 196; [0276] The first and second
layers of elastomeric tube 342, 380, the smooth covered stent 198,
the slit cannula 300, and the first and second mandrels 322, 354
are removed from the press fixture 186 and positioned in room
temperature water for cooling; [0277] One of the handles 334, 372
is removed from either the first or second mandrel 322, 354; [0278]
The first and second layers of elastomeric tube 342, 380, the
smooth covered stent 198, the slit cannula 300, and the first and
second mandrels 322, 354 are positioned in the tube expander 128;
[0279] The vacuum 148 is applied allowing the inner and outer
diameters 382, 384 of second layer of elastomeric tube 380 to
uniformly expand; [0280] The smooth covered stent 198, the first
layer of elastomeric tube 342, the slit cannula 300, and the first
and second mandrels 322, 354 are removed from the tube expander
128; [0281] One of the handles 344, 372 previously removed is
positioned back on either the first or second mandrel 322, 354;
[0282] The second mandrel 354 is removed from the slit cannula 300;
and [0283] The smooth covered stent 198 is removed from the slit
cannula 300.
EXAMPLE 4
Self-Expandable Stent, Slit Cannula and Single Mandrel without
Handle
TABLE-US-00004 [0284] Element Specifications Stent 100 inner
diameter 102 is 7.6 mm, outer diameter 104 is 8.0 mm, nominal
diameter is 8 mm, longitudinal length 126 is 70 mm, self-expandable
Slit cannula 300 inner diameter 302 is 3.76 mm, outer diameter 304
is 4.76 mm, longitudinal length is 210 mm, material is stainless
steel Slits 312 number slits 312 is 10, longitudinal length 318 of
slits is 208 mm Mandrel 420 longitudinal length 436 is 236 mm,
diameter 426 of first portion 422 is 6.22 mm, diameter 428 of
second portion 424 is 3.175 mm, material is stainless steel First
layer of material is silicone with a durometer of 50 elastomeric
tube Shore A, longitudinal length 352 is 210 mm, 342 inner diameter
344 is 4.29 mm, outer diameter 346 is 5.31 mm Coating MED-6670,
thickness is 45 .mu.m Inner covering 164 includes first material
166 and second material 168 First material 166 esPTFE Second
material 168 Polyurethane Outer covering 172 includes first
material 166 and second material 168 Second layer of material is
silicone with a durometer of 20 elastomeric tube Shore A,
longitudinal length 390 is 114 mm, 380 inner diameter 382 is 6 mm,
outer diameter 384 is 8 mm Tube expander 128 inner diameter 134 is
14 mm Slot 192 of Press diameter 194 of slot 192 is 9.6 mm Fixture
186
Steps:
[0285] The coating is applied to the outer diameter 346 of the
first elastomeric tube 342 and then cured; [0286] The first layer
of elastomeric tube 342 is positioned over the slit cannula 300;
[0287] The inner covering 164 is rolled in 70% isopropanol; [0288]
The inner covering 164 is positioned over and wrapped around the
slit cannula 300 with the first material 166 of the inner covering
164 in contact with the first elastomeric tube 342; [0289] The
stent 100 is positioned over the inner covering 164 and in contact
with the second material 168 of the inner covering 164; [0290] The
mandrel 420 is positioned within the slit cannula 300 and radially
expands the slit cannula 300, the first layer of elastomeric tube
342, and the inner covering 164 such that the inner covering 164 is
in contact with the inner diameter 102 of the stent 100; [0291] The
outer covering 172 is rolled in 70% isopropanol; [0292] The outer
covering 172 is positioned over and wrapped around the stent 100
with the second material 168 in contact with the stent 100 to form
the covered stent 174; [0293] The coating is applied to the inner
diameter 382 of the second layer of elastomeric tube 380 and then
cured; [0294] The second layer of elastomeric tube 380 is
positioned within the tube expander 128 including the vacuum 148;
[0295] The first and second ends 306, 308 of the second layer of
elastomeric tube 380 are rolled up and wrapped around the first and
second ends 138, 140 of the tube expander 128; [0296] The vacuum
148 is applied expanding the inner and outer diameters 382, 384 of
second layer of elastomeric tube 380 until the outer diameter 384
of the second elastomeric tube 380 contacts the inner diameter 134
of the tube expander 128; [0297] The covered stent 174, the first
layer of elastomeric tube 342, the slit cannula 300, and the
mandrel 420 are positioned in the tube expander 128; [0298] The
vacuum 148 is released allowing the inner and outer diameters 382,
384 of second layer of elastomeric tube 380 to retract to an
unexpanded state and recover to the covered stent 174; [0299] The
first and second layers of elastomeric tube 342, 380, the covered
stent 174, the slit cannula 300, and the mandrel 420 are removed
from the tube expander 128; [0300] The first and second layers of
elastomeric tube 342, 380, the covered stent 174, the slit cannula
300, and the first and second mandrels 322, 354 are positioned in a
vacuum chamber with an applied pressure of 600 mmHg (absolute
vacuum pressure) for 1 hour; [0301] The first and second layers of
elastomeric tube 342, 380, the covered stent 174, the slit cannula
300, and the mandrel 420 are removed from the vacuum chamber and
positioned in the slot 192 of the press fixture 186 and the first
and second portions 188, 190 of the press fixture 186 are brought
together; [0302] The press fixture 186 is positioned in the heated
press 196; [0303] Pressure is applied to the press fixture 186 to
displace the thickness of second layer of elastomeric tube 380 by
0.005.+-.0.001 inches; [0304] Heat is applied to the press fixture
186 to 390.+-.5 degrees Fahrenheit and is applied for 1 minute
time; [0305] The press fixture 186 is removed from the heated press
196; [0306] The first and second layers of elastomeric tube 342,
380, the smooth covered stent 198, the slit cannula 300, and the
mandrel 420 are removed from the press fixture 186 and positioned
in room temperature water for cooling; [0307] The first and second
layers of elastomeric tube 342, 380, the smooth covered stent 198,
the slit cannula 300, and the mandrel 420 are positioned in the
tube expander 128; [0308] The vacuum 148 is applied allowing the
inner and outer diameters 382, 384 of second layer of elastomeric
tube 380 to uniformly expand; [0309] The smooth covered stent 198,
the first layer of elastomeric tube 342, the slit cannula 300, and
the mandrel 420 are removed from the tube expander 128; [0310] The
mandrel 420 is removed from the slit cannula 300; and [0311] The
smooth covered stent 198 is removed from the slit cannula 300.
Applied Tension to Elastomeric Tube
[0312] In an alternative embodiment, when a self-expanding stent is
used, tension may be applied to an elastomeric tube positioned on
the mandrel rather than use of the slit cannula 300. For example,
the first layer of elastomeric tube 342 is positioned within the
tube expander 128 including the vacuum 148, and the first and
second ends 348, 350 are rolled up and wrapped around the first and
second ends 138, 140 of the tube expander 128. The vacuum 148 is
applied expanding the inner and outer diameters 344, 346 of the
first layer of elastomeric tube 342. The mandrel 150 is positioned
in the tube expander 128, and the vacuum 148 is released allowing
the inner and outer diameters 344, 346 of the first layer of
elastomeric tube 342 to retract to an unexpanded state and recover
to the mandrel 150. The outer diameter 346 of the first layer of
elastomeric tube 342 on the mandrel 150 is then reduced by applying
tension to the first layer of elastomeric tube 342 to allow the
stent 100 to slide or otherwise be positioned over the first layer
of elastomeric tube 342. Specifically, the tension applied outer
diameter 346 of the first layer of elastomeric tube 342 is less
than the inner diameter 102 of the stent 100. The tension may be
applied by using clamps to pull on the first and second ends 348,
350 of the first layer of elastomeric tube 342.
[0313] With the tension applied to the first layer of elastomeric
tube 342 on the mandrel 150, the inner covering 164 is positioned
over and wrapped around the first layer of elastomeric tube 342
with the first material 166 of the inner covering 164 in contact
with the first layer of elastomeric tube 342, as described
previously. The stent 100, which in this example is a
self-expanding stent, is positioned over the inner covering 164 and
in contact with the second material 168 of the inner covering 164.
After the stent 100 is positioned over the inner covering 164, the
tension applied to the first layer of elastomeric tube 342 may be
released and the clamps removed. When the tension is released, the
first layer of elastomeric tube 342 expands to a non-tension
applied state. After expansion, the inner covering 164 contacts the
inner diameter 102 of the stent 100, and the stent 100 maintains
its nominal diameter and is not significantly expanded. The
subsequent steps described above to form the smooth covered stent
198 may then be applied, including without limitation the
application of the outer covering 172, the application of the
second layer of elastomeric tube 380, the application of heat and
pressure using the press fixture 186 and heated press 196, may be
used.
First and Second Tubes with Heated Oven
[0314] FIGS. 65-74 show another example of a method of making a
stent with a smooth cover. FIG. 65 shows the covered stent 174
positioned over the mandrel 150 using the process steps as
described previously. A first tube of elastomeric tube 500 is
positioned in the tube expander 128. The first tube of elastomeric
tube 500 may include the same material as the elastomeric tube 116
previously described. The first tube of elastomeric tube 500
includes an inner diameter 502, an outer diameter 504, a first end
506, a second end 508, and a longitudinal length 510, which is
defined from the first end 506 to the second end 508. The
longitudinal length 510 of the first tube 500 is longer than the
longitudinal length of the covered stent 174 to completely cover
the covered stent 174. In this example, the stent 100 is a balloon
expandable stent. The inner diameter 502 of the elastomeric tube
500 may range from 2 mm to 15 mm. The outer diameter 504 of the
elastomeric tube 500 may range from 3 mm to 21 mm.
[0315] A coating, as previously described, that reduces the
friction on the surface of the first tube 500 may be applied to the
inner diameter 502 of the first tube 500. The coating helps to
remove the stickiness or tackiness of the first tube 500, so that
the first tube 500 does not stick to the outer covering 172 of the
covered stent 174.
[0316] As shown in FIG. 67, the first and second ends 506, 508 of
the first tube 500 are wrapped around the first and second ends
138, 140 of the tube expander 128 to seal the first tube 500 to the
tube expander 128, and then the vacuum 148 is applied to uniformly
expand the inner and outer diameters 502, 504 of the first tube
500. The covered stent 174 and the mandrel 150 are then positioned
in the tube expander 128 as shown in FIG. 68, and the vacuum source
148 is released to allow the first tube 500 to recover to the
covered stent 100 as shown in FIG. 69. In its original state, the
inner diameter 502 of the first tube 500 is smaller than the
diameter 176 of the covered stent 100 and the mandrel 150.
[0317] A second tube 512 is provided as shown in FIG. 71. The
second tube 512 may include the same material as the elastomeric
tube 116 previously described, or the second tube 512 may include a
shrink tube as previously described including shrink silicone,
polyimide shrink, shrink polyetheretherketone (PEEK), fluorinated
ethylene propylene (FEP), polytetrafluoroethylene (PTFE), or
polyethylene terephthalate (PET). The material of the second tube
512 has a higher durometer than the material of the first tube 500.
The second tube 512 includes an inner diameter 514, an outer
diameter 516, a first end 518, a second end 520, and a longitudinal
length 522, which is defined from the first end 518 to the second
end 520. The inner diameter 514 of the second tube 512 may range
from 2 mm to 17 mm. The outer diameter 516 of the second tube 512
may range from 3 mm to 23 mm.
[0318] The longitudinal length 522 is the same as or longer than
the longitudinal length 510 of the first tube 500. The inner
diameter 514 of the second tube 510 is smaller than the outer
diameter 504 of the first tube 500 such that when the second tube
510 is applied to the first tube 500, the second tube 510
compresses the first tube 500 to the covered stent 174 and
compresses the inner and outer coverings 164, 172 of the covered
stent 174 sufficiently together to conform the outer covering 174
around the stent 100. When the second tube 512 is a shrink tube,
the inner diameter 514 of the shrink tube 512 is initially larger
than the outer diameter 504 of the first tube 500 to allow the
second tube 512 to position over the first tube 500. The inner
diameter 514 of the shrink tube 512 will decrease when heat is
applied to apply compression.
[0319] When the second tube 512 includes an elastomeric tube, the
second tube 512 is positioned in the tube expander to uniformly
expand the inner and outer diameters 514, 516 of the second tube
512 as shown in FIGS. 71-73. The mandrel 150 with the covered stent
174 and the first tube 500 is then positioned in the tube expander
128, and the vacuum source 148 is released to allow the inner and
outer diameters 514, 516 of the second tube 512 to return to an
unexpanded state and recover to the first tube 500. As described
previously, when the second tube 512 recovers to the first tube
500, the second tube 512 compresses the first tube 500 to the
covered stent 174. FIG. 73 shows the mandrel 150 with the covered
stent 174 and the first and second tubes 500, 512. When the second
tube 512 includes a shrink tube, the second tube 512 is positioned
over and wrapped around the first tube 500 and the tube expander
128 is not used. If the second tube 512 includes shrink tape rather
than a shrink tube, the shrink tape may be wrapped around the first
tube 500.
[0320] In one example, when the second tube 512 includes an
elastomeric tube, prior to applying pressure and heat, the mandrel
150 with the covered stent 174 and the first and second tubes 500,
512 may be placed in a vacuum chamber for a pretreatment vacuum
step. The pretreatment vacuum step may remove any air bubbles from
the first and second tubes 500, 512. Air bubbles within the first
and second tubes 500, 512 may affect heating and bonding of the
inner and outer coverings 164, 172 to the stent 100. The vacuum
chamber may be any vacuum chamber known in the art, and the mandrel
150 may be positioned on a rack in the vacuum chamber to provide
uniform distribution of the pressure around the first and second
tubes 500, 512. In one example, the vacuum pressure applied may be
approximately 500 to 700 mmHg (vacuum pressure) may be applied for
approximately 15 minutes to 2 hours. In another example, the vacuum
pressure applied may be approximately 600 mmHg (absolute vacuum
pressure) for approximately 1 hour. The vacuum pressure applied may
vary and may range from approximately 50 mmHg to 760 mmHg (absolute
vacuum pressure), and as the vacuum pressure applied increases, the
time the vacuum pressure will be applied decreases.
[0321] As shown in FIG. 74, to melt the second material 168 of the
inner and outer coverings 164, 172 of the covered stent 174, the
mandrel 150 with the covered stent 174 and the first and second
tubes 500, 512 are positioned in an oven 524 on an elevated rack
526 to apply uniform heat to the covered stent 174. The temperature
applied may be the same as described previously for approximately 5
minutes. If the second tube 512 is a shrink tube, the temperature
applied is above the recovery temperature of the shrink tube. The
time will vary based on the melting temperature of the second
material 168 or above the glass transition temperature of the first
material 166 if the second material 168 is not used. Thus, the time
period of heat application from range from 2 to 30 minutes.
[0322] After the heat is applied, the mandrel 150 with the smooth
covered stent 198 and the first and second tubes 500, 512 are
removed from the oven 524 and cooled. The first and second tubes
500, 512 may then be removed from the smooth covered stent 198
using any of the removal methods previously described, including
use of the tube expander 128. The mandrel 150 is then removed from
the smooth covered stent 198.
[0323] In another example, the aforementioned method may be used
with a self-expanding stent. When a self-expanding stent is used,
the slit cannula 300 is used with either the first and second
mandrels 322, 354 previously described or the single mandrel 420
rather than the mandrel 150. In this example, the first and second
tubes 500, 512 may be applied, as described above, to the covered
stent 174, the slit cannula 300, and the first and second mandrels
322, 354 or the single mandrel 420. If the second tube 512 is
elastomeric, the first and second mandrels 322, 354 or the single
mandrel 420 and the slit cannula 300 with the covered stent 174 and
the first and second tubes 500, 512 may be placed in a vacuum
chamber for the pretreatment vacuum step. After removal from the
vacuum chamber, heat may be applied as described above using the
oven 524 and the first and second tubes 500, 512 may be removed
from the smooth covered stent 198 using any of the removal methods
previously described, including use of the tube expander 128. After
the removal of the first and second tubes 500, 512, if the first
and second mandrels 322, 354 are used, rather than the single
mandrel 420, the smoother covered stent 198 may include the
plurality of stripes or indentations 392 on the inner surface 394
of the smooth covered stent 198 from compression against the slits
312 of the slit cannula 300. The plurality of stripes or
indentations 392 may be removed using the steps previously
described above.
[0324] In an alternative example, as described previously above, if
a self-expanding stent is used, tension may be applied to an
additional elastomeric tube, or a third tube, positioned on the
mandrel rather than use of the slit cannula 300. Specifically, the
third tube may be positioned around the mandrel 150 via the tube
expander 128 including the vacuum 148, as described previously
above, prior to placement of the inner covering 164 over the
mandrel 150. After placement of the third tube around the mandrel
150, tension is applied to the third tube to radially decrease the
outer diameter of the third tube to allow the stent 100 to slide or
otherwise be positioned over the third tube on the mandrel 150.
Specifically, the tension applied outer diameter of the third tube
is less than the inner diameter 102 of the stent 100. The tension
may be applied by using clamps to pull on the ends of the second
elastomeric tube.
[0325] With the tension applied to the third tube on the mandrel
150, the inner covering 164 is positioned over and wrapped around
the third tube with the first material 166 of the inner covering
164 in contact with the third tube, as described previously. The
stent 100 is positioned over the inner covering 164 and in contact
with the second material 168 of the inner covering 164. After the
stent 100 is positioned over the inner covering 164, the tension
applied to the third tube may be released and the clamps removed.
When the tension is released, the third tube radially expands to a
non-tension applied state. After expansion, the inner covering 164
contacts the inner diameter 102 of the stent 100, and the stent 100
maintains its nominal diameter and is not significantly expanded.
The subsequent steps described above to form the smooth covered
stent 198 may then be applied, including without limitation the
application of an outer covering 172, the application of the first
and second tubes 500, 512, and the application of heat using the
oven 524, may be used.
[0326] The tables and steps below provide examples of the materials
and steps using the aforementioned method.
EXAMPLE 5
Balloon-Expandable Stent, First and Second Tubes, and Inner and
Outer Coverings with First and Second Materials
TABLE-US-00005 [0327] Element Specifications Stent 100 inner
diameter 102 is 8.0 mm, outer diameter 104 is 8.4 mm, nominal
diameter is 8 mm, longitudinal length 126 is 30 mm,
balloon-expandable Mandrel 150 diameter is 8 mm, the material is
stainless steel First tube 500 material is silicone with a
durometer of 20 Shore A, longitudinal length 510 is 75 mm, inner
diameter 502 is 6 mm, outer diameter 504 is 8 mm Coating MED-6670,
thickness is 45 .mu.m Inner covering 164 includes first material
166 and second material 168 First material 166 esPTFE Second
material 168 Polyurethane Outer covering 172 includes first
material 166 and second material 168 Second tube 512 material is
silicone with a durometer of 25 Shore A, longitudinal length 522 is
75 mm, inner diameter 514 is 6 mm, outer diameter 516 is 8 mm Tube
expander 128 inner diameter 134 is 14 mm
Steps:
[0328] The inner covering 164 is rolled in 70% isopropanol; [0329]
The inner covering 164 is positioned over and wrapped around the
mandrel 150 with the first material 166 of the inner covering 164
in contact with the mandrel 150; [0330] The stent 100 is initially
slightly over-expanded and then positioned over the inner covering
164 and in contact with the second material 168 of the inner
covering 164; [0331] An Iris crimper is used to secure the stent
100 to the inner covering 164; [0332] The outer covering 172 is
rolled in 70% isopropanol; [0333] The outer covering 172 is
positioned over and wrapped around the stent 100 with the second
material 168 in contact with the stent 100 to form the covered
stent 174; [0334] The coating is applied to the inner diameter 502
of the first tube 500 and then cured; [0335] The first tube 500 is
positioned within the tube expander 128 including the vacuum 148;
[0336] The first and second ends 506, 508 of the first tube 500 are
rolled up and wrapped around the first and second ends 138, 140 of
the tube expander 128; [0337] The vacuum 148 is applied expanding
the inner and outer diameters 502, 504 of the first tube 500 until
the outer diameter 504 of the first tube 500 contacts the inner
diameter 134 of the tube expander 128; [0338] The covered stent 174
and the mandrel 150 are positioned in the tube expander 128; [0339]
The vacuum 148 is released allowing the inner and outer diameters
502, 504 of the first tube 500 to retract to an unexpanded state
and recover to the covered stent 174; [0340] The first tube 500,
the covered stent 174, and the mandrel 150 are removed from the
tube expander 128; [0341] The coating is applied to the inner
diameter 514 of the second tube 512 and then cured; [0342] The
second tube 512is positioned within the tube expander 128 including
the vacuum 148; [0343] The first and second ends 518, 520 of the
second tube 512 are rolled up and wrapped around the first and
second ends 138, 140 of the tube expander 128; [0344] The vacuum
148 is applied expanding the inner and outer diameters 514, 516 of
the second tube 512 until the outer diameter 516 of the second tube
512 contacts the inner diameter 134 of the tube expander 128;
[0345] The first tube 500, the covered stent 174, and the mandrel
150 are positioned in the tube expander 128; [0346] The vacuum 148
is released allowing inner and outer diameters 514, 516 of the
second tube 512 to retract to an unexpanded state and recover to
the first tube 500 and the covered stent 174; [0347] The first and
second tubes 500, 512 the covered stent 174, and the mandrel 150
are removed from the tube expander 128; [0348] The first and second
tubes 500, 512, the covered stent 174, and the mandrel 150 are
positioned in a vacuum chamber with an applied pressure of 600 mmHg
(absolute vacuum pressure) for 1 hour; [0349] The first and second
tubes 500, 512, the covered stent 174, and the mandrel 150 are
removed from the vacuum chamber and positioned on the rack 526 in
the heated oven 524 and heated to 390.+-.5 degrees Fahrenheit and
is applied for 5 minutes time; [0350] The first and second tubes
500, 512, the smooth covered stent 198, and the mandrel 150 are
removed from the heated oven 524 and then compressed air or freeze
spray is applied for cooling; [0351] The first and second tubes
500, 512, the smooth covered stent 198, and the mandrel 150 are
positioned in the tube expander 128; [0352] The vacuum 148 is
applied allowing the inner and outer diameters 514, 516 of the
second tube 512 to expand away from the first tube 500; [0353] The
first tube 500, the smooth covered stent 198, and the mandrel 150
are removed from the tube expander 128; [0354] The vacuum 148 is
released allowing the inner and outer diameters 514, 516 of the
second tube 512 to retract to an unexpanded state and the second
tube 512 is removed from the tube expander 128; [0355] The first
tube 500, the smooth covered stent 198, and the mandrel 150 are
positioned in the tube expander 128; [0356] The vacuum 148 is
applied allowing the inner and outer diameters 502, 504 of the
first tube 500 to expand away from the smooth covered stent 198;
[0357] The smooth covered stent 198 and the mandrel 150 are removed
from the tube expander 128; and [0358] The mandrel 150 is removed
from the smooth covered stent 198.
EXAMPLE 6
Balloon-Expandable Stent, First and Second Tubes, and Inner and
Outer Coverings with First Material
TABLE-US-00006 [0359] Element Specifications Stent 100 inner
diameter 102 is 8.0 mm, outer diameter 104 is 8.4 mm, nominal
diameter is 8 mm, longitudinal length 126 is 30 mm,
balloon-expandable Mandrel 150 diameter is 8 mm, the material is
stainless steel First tube 500 material is silicone with a
durometer of 20 Shore A, longitudinal length 510 is 75, inner
diameter 502 is 6 mm, outer diameter 504 is 8 mm Coating MED-6670,
thickness is 45 .mu.m Inner covering 164 includes first material
166 First material 166 PET Outer covering 172 includes first
material 166 Second tube 512 material is silicone with a durometer
of 25 Shore A, longitudinal length 522 is 75 mm, inner diameter 514
is 6 mm, outer diameter 516 is 8 mm Tube expander 128 inner
diameter 134 is 14 mm
Steps:
[0360] The inner covering 164 is rolled in 70% isopropanol; [0361]
The inner covering 164 is positioned over and wrapped around the
mandrel 150; [0362] The stent 100 is initially slightly
over-expanded and then positioned over the inner covering 164;
[0363] An Iris crimper is used to secure the stent 100 to the inner
covering 164; [0364] The outer covering 172 is rolled in 70%
isopropanol; [0365] The outer covering 172 is positioned over and
wrapped around the stent 100 to form the covered stent 174; [0366]
The coating is applied to the inner diameter 502 of the first tube
500 and then cured; [0367] The first tube 500 is positioned within
the tube expander 128 including the vacuum 148; [0368] The first
and second ends 506, 508 of the first tube 500 are rolled up and
wrapped around the first and second ends 138, 140 of the tube
expander 128; [0369] The vacuum 148 is applied expanding the inner
and outer diameters 502, 504 of the first tube 500 until the outer
diameter 504 of the first tube 500 contacts the inner diameter 134
of the tube expander 128; [0370] The covered stent 174 and the
mandrel 150 are positioned in the tube expander 128; [0371] The
vacuum 148 is released allowing the inner and outer diameters 502,
504 of the first tube 500 to retract to an unexpanded state and
recover to the covered stent 174; [0372] The first tube 500, the
covered stent 174, and the mandrel 150 are removed from the tube
expander 128; [0373] The coating is applied to the inner diameter
514 of the second tube 512 and then cured; [0374] The second tube
512 is positioned within the tube expander 128 including the vacuum
148; [0375] The first and second ends 518, 520 of the second tube
512 are rolled up and wrapped around the first and second ends 138,
140 of the tube expander 128; [0376] The vacuum 148 is applied
uniformly expanding the inner and outer diameters 514, 516 of the
second tube 512 until the outer diameter 516 of the second tube 512
contacts the inner diameter 134 of the tube expander 128; [0377]
The first tube 500, the covered stent 174, and the mandrel 150 are
positioned in the tube expander 128; [0378] The vacuum 148 is
released allowing inner and outer diameters 514, 516 of the second
tube 512 to retract to an unexpanded state and recover to the first
tube 500 and the covered stent 174; [0379] The first and second
tubes 500, 512 the covered stent 174, and the mandrel 150 are
removed from the tube expander 128; [0380] The first and second
tubes 500, 512, the covered stent 174, and the mandrel 150 are
positioned in a vacuum chamber with an applied pressure of 600 mmHg
(absolute vacuum pressure) for 1 hour; [0381] The first and second
tubes 500, 512, the covered stent 174, and the mandrel 150 are
removed from the vacuum chamber and positioned on the rack 526 in
the heated oven 524 and heated to 365.+-.5 degrees Fahrenheit and
is applied for 5 minutes time; [0382] The first and second tubes
500, 512, the smooth covered stent 198, and the mandrel 150 are
removed from the heated oven 524 and then compressed air or freeze
spray is applied for cooling; [0383] The first and second tubes
500, 512, the smooth covered stent 198, and the mandrel 150 are
positioned in the tube expander 128; [0384] The vacuum 148 is
applied allowing the inner and outer diameters 514, 516 of the
second tube 512 to expand away from the first tube 500; [0385] The
first tube 500, the smooth covered stent 198, and the mandrel 150
are removed from the tube expander 128; [0386] The vacuum 148 is
released allowing the inner and outer diameters 514, 516 of the
second tube 512 to retract to an unexpanded state and the second
tube 512 is removed from the tube expander 128; [0387] The first
tube 500, the smooth covered stent 198, and the mandrel 150 are
positioned in the tube expander 128; [0388] The vacuum 148 is
applied allowing the inner and outer diameters 502, 504 of the
first tube 500 to expand away from the smooth covered stent 198;
[0389] The smooth covered stent 198 and the mandrel 150 are removed
from the tube expander 128; and [0390] The mandrel 150 is removed
from the smooth covered stent 198.
Internal Pressure Application
[0391] FIGS. 77-94 show another example of a method of making a
stent with a smooth cover. FIG. 77 shows a tapered rod 600, a first
hollow mandrel 602, a second hollow mandrel 604, and the stent 100,
described previously above. In this example, the stent 100 is a
self-expanding stent. As described in more detail below, the use of
the tapered rod 600, the first hollow mandrel 602, and the second
hollow mandrel 604 allow for gradual radial expansion of the inner
and outer diameters 102, 104 of the stent 100. The tapered rod 600
includes a first end 606, a second end 608, a length 610 extending
from the first end 606 to the second end 608, and a diameter 612.
The diameter 612 of the tapered rod 610 is less than the inner and
outer diameters 102, 104 of the stent 100. A handle 614 is
positioned over or otherwise connected to the first end 606 of the
tapered rod 600. The second end 608 of the tapered rod is a tapered
end 616. The material of the tapered rod 600 and the handle 614 may
include glass, metal, stainless steel, brass and/or an alloy.
[0392] The first hollow mandrel 602 includes a first end 617, a
second end 618, a length 620 extending from the first end 617 to
the second end 618, an inner diameter 622, and an outer diameter
624. The first end 617 of the first hollow mandrel 602 may include
a tapered portion 619, as shown in FIG. 77. The inner diameter 622
of the first hollow mandrel 602 is greater than the diameter 612 of
the tapered rod 600 such that the tapered rod 600 may be inserted
into the first hollow mandrel 602.
[0393] The second hollow mandrel 604 includes a first end 626, a
second end 628, a length 630 extending from the first end 626 to
the second end 628, an inner diameter 632, and an outer diameter
634. The second end 628 of the second hollow mandrel 604 may
include a tapered portion 629, as shown in FIG. 77. The inner
diameter 632 of the second hollow mandrel 604 is greater than the
outer diameter 624 of the first hollow mandrel 602 such that the
first hollow mandrel 602 may be inserted into the second hollow
mandrel 604. The material of the first hollow mandrel 602 and the
second hollow mandrel 604 may include glass, metal, stainless
steel, brass and/or an alloy. In an alternative embodiment, a
hollow mandrel with a gradually expanding outer diameter along its
length may be used rather than the first hollow mandrel 602 and the
second hollow mandrel 604 to allow for gradual radial expansion of
the stent 100.
[0394] FIG. 78 shows the stent 100 to be positioned over the
tapered end 616 and onto the tapered rod 600. As described
previously, the diameter 612 of the tapered rod 600 is less than
the inner and outer diameters 102, 104 of the stent 100 such that
the stent 100 may slide onto the tapered rod 600 without the inner
and outer diameters 102, 104 of the stent 100 significantly
expanding. The tapered rod 600 with the stent 100 may be inserted
into the first end 617 having the tapered portion 619 of the first
hollow mandrel 602, as shown in FIG. 79. FIG. 80 shows that tapered
end 616 of the tapered rod 600 positioned within the first hollow
mandrel 602. As described previously, the diameter 612 of the
tapered rod 600 is less than the inner diameter 622 of the first
hollow mandrel 602 such that the tapered rod 600 may be inserted
into the first hollow mandrel 602. The stent 100 may then slide
along the tapered rod 600 and onto the first hollow mandrel 602, as
shown in FIG. 81, which allows for gradual radial expansion of the
stent 100. After the stent 100 is positioned over the first hollow
mandrel 602, the tapered rod 600 is removed from the first hollow
mandrel 602.
[0395] The first hollow mandrel 602 with the stent 100 may be
inserted into the second end 628 having the tapered portion 629 of
the second hollow mandrel 604, as shown in FIG. 82. As described
previously, the outer diameter 624 of the first hollow mandrel 602
is less than the inner diameter 632 of the second hollow mandrel
604 such that the first hollow mandrel 602 may be inserted into the
second hollow mandrel 604. The stent 100 may then slide along the
first hollow mandrel 602 and onto the second hollow mandrel 604, as
shown in FIG. 83, which allows for gradual radial expansion of the
stent 100. After the stent 100 is positioned over the second hollow
mandrel 604, the first hollow mandrel 602 may be removed from the
second hollow mandrel 604, as shown in FIG. 84.
[0396] As shown in FIG. 85, the mandrel 150 with the first layer of
elastomeric tube 342 positioned over the mandrel 150 and the inner
covering 164 wrapped around the first layer of elastomeric tube 342
is provided. As described previously, the first layer of
elastomeric tube 342 may include the same material as the
elastomeric tube 116, and the coating may be applied to the outer
diameter 346 of the first layer of elastomeric tube 342 to remove
the stickiness or tackiness of the first layer of elastomeric tube
342 so that the first layer of elastomeric tube 342 does not stick
to the inner covering 164. The first layer of elastomeric tube 342
may be positioned over the mandrel 150 using steps described
previously.
[0397] Also, as previously described, the inner covering 164,
including the first material 166 and the second material 168, is
positioned over and wrapped around the first layer of elastomeric
tube 342 such that the first material 166 is in contact with the
first layer of the elastomeric tube 342. Additional layers may also
be added such that the first and second materials 166, 168 of the
layers maintain an alternating pattern over the stent 100, as
described previously. To keep the layers in place, the soldering
iron, described previously, may be used to tack or otherwise adhere
edges of the inner covering 164. In an alternative embodiment, the
mandrel 150 is not used and the inner covering 164 is wrapped
around the first layer of elastomeric tube 342 without the mandrel
150 beneath the first layer of elastomeric tube.
[0398] The mandrel 150 with the first layer of elastomeric tube 342
and the inner covering 164 is positioned within the second hollow
mandrel 604, as shown in FIG. 86. Once the second hollow mandrel
604 is positioned over the inner covering 164, the second hollow
mandrel 604 is pulled away such that the stent 100 is positioned
over the inner covering 164, as shown in FIG. 87, and the stent 100
recovers to its nominal diameter. When the stent 100 is positioned
over the inner covering 164, the second material 168 of the inner
covering 164 is in contact with the stent 100. The mandrel 150 may
then be removed from the first layer of elastomeric tube 342 by
pulling the mandrel 150 from beneath the first layer of elastomeric
tube 342, as shown in FIG. 88.
[0399] In one example, freeze spray or liquid nitrogen may be
applied to the stent 100 positioned on the second hollow mandrel
604 prior to removing the second hollow mandrel 604 from beneath
the stent 100. The freeze spray or liquid nitrogen freezes the
stent 100 in its expanded state, which facilitates positioning and
placement of the stent 100 over the inner covering 164. When the
stent 100 returns to room temperature, the stent 100 recovers to
its nominal diameter and to the inner covering 164.
[0400] A support mandrel 636 is inserted into the first layer of
elastomeric tube 342, as shown in FIG. 89. The support mandrel 636
includes a first end 638, a second end 640, a length 642 extending
from the first end 638 to the second end 640, and an outer diameter
644 is shown in FIG. 89. The outer diameter 644 of the support
mandrel 636 is less than the inner diameter 344 of the first layer
of elastomeric tube 342 in an unexpanded state such that the
support mandrel 636 may slide into the first layer of elastomeric
tube 342. In this example, the support mandrel 636 is hollow and
includes an inner diameter and a plurality of holes 646 along its
length 642, as shown in FIG. 89. The plurality of holes 646 within
the hollow support mandrel 636 allow for air, gas or hydraulic
pressure to contact the first layer of elastomeric tube 342 and
allow for expansion of the first layer of elastomeric tube 342. The
support mandrel 636 provides support to the stent 100 during the
pressurization and heating process. In alternative examples, the
support mandrel may be solid and/or include supporting rib elements
that extend along its length.
[0401] In another alternative example, the support mandrel 636 may
be used rather than the mandrel 150 such that the first layer of
elastomeric tube 342 is positioned over the support mandrel 636,
the inner covering 164 is wrapped around the first layer of
elastomeric tube 342, and the stent 100 is positioned over the
inner covering 164, as described previously above. In this
alternative example, the support mandrel 636 would not be removed
prior to applying heat and pressure and would remain within the
first layer of elastomeric tube 342 until after heat and pressure
are applied, as described in more detail below.
[0402] The outer covering 172, including the first material 166 and
the second material 168, is positioned over and wrapped around the
stent 100 as described previously and as shown in FIG. 89 to form
the covered stent 174. The second material 168 is in contact with
the stent 100, and the first material 166 of the outer covering 172
is not in contact with the stent 100. As described previously,
additional layers may also be added such that the first and second
materials 166, 168 of the layers maintain an alternating pattern
over the stent 100. To keep the layers in place, the soldering
iron, described previously, may be used to tack or otherwise adhere
edges of the outer covering 172.
[0403] The second layer of elastomeric tube 380, as described
previously, is positioned over the covered stent 174 and the first
layer of elastomeric tube 342 as shown in FIGS. 89-90. The inner
diameter 382 of the second layer of elastomeric tube 380 is greater
than the outer diameter 104 of the stent 100 with the outer
covering 172 applied such that the second layer of elastomeric tube
380 may be positioned over the outer covering 172 and the stent
100. In an alternative embodiment, if the inner diameter 382 of the
second layer of elastomeric tube 380 is smaller than or the same as
the outer diameter 104 of the stent with the outer covering 172
applied, then the tube expander 128 may be used to radially expand
the second layer of elastomeric tube 380 to be positioned over the
outer covering 172 and the stent 100, as described previously. In
one example, prior to applying pressure and heat, the pretreatment
vacuum step may be used, including the vacuum chamber, to remove
any air bubbles from the first and second layers of elastomeric
tube 324, 380, as described previously.
[0404] As described previously, the second layer of elastomeric
tube 380 may include the same material as the elastomeric tube 116,
and the coating may be applied to the inner diameter 382 of the
second layer of elastomeric tube 380 to remove the stickiness or
tackiness of the second layer of elastomeric tube 380 so that the
second layer of elastomeric tube 380 does not stick to the outer
covering 172. In one example, the first layer of elastomeric tube
342 includes a durometer smaller than the durometer of the second
layer of elastomeric tube 380. Specifically, the durometer of the
first layer of elastomeric tube 342 may be 25 Shore A, and the
durometer of the second layer of elastomeric tube 380 may be 30
Shore A. In an alternative example, the durometer of the first
layer of elastomeric tube 342 is greater than the durometer of the
second layer of elastomeric tube 380. Specifically, the durometer
of the first layer of elastomeric tube 342 may be 50 Shore A, and
the durometer of the second layer of elastomeric tube 380 may be 25
Shore A.
[0405] To apply pressure and heat to the first and second layers of
elastomeric tube 324, 380 and the covered stent 174, a pair of barb
fittings 648 are inserted into the first ends 348, 386 and the
second ends 350, 388 of the first and second layers of elastomeric
tube 324, 380, as shown in FIG. 91. The barb fittings 648 are barb
fittings known in the art including hose barb fittings. A cap 650
is attached to the barb fitting 648 that is inserted into the first
ends 348, 386 of the first and second layers of elastomeric tube
324, 380. The cap 650 acts as a plug to seal off the first ends
348, 386 of the second and second layers of elastomeric tube 324,
380. A tubing line 652 is attached to the barb fittings 648 that is
inserted into the second ends 350, 388 of the first and second
layers of elastomeric tube 324, 380, as shown in FIG. 91. The
tubing line 652 allows pressure, such as air, gas or hydraulic
pressure, to enter into the first layer of elastomeric tube 324. A
safety guard (not shown) may be positioned on the barb fittings 648
to secure the position of the barb fittings 648 to the first and
second layers of elastomeric tube 324, 380.
[0406] The first and second layers of elastomeric tube 324, 380,
the covered stent 174, the support mandrel 636, and the barb
fittings 648 may be inserted into the slot 192 of the press fixture
186, as shown in FIG. 92. In this example, the outer diameter of
the first and second layers of elastomeric tube 324, 380 and the
covered stent 174 is less than the diameter 194 of the slot 192
such that there is space for the outer diameter of the first and
second layers of elastomeric tube 324, 380 and the covered stent
174 to radially expand within the slot 192 when pressure is
applied. After the press fixture 186 is closed, as shown in FIG.
93, the press fixture 186 may be positioned in the heated press
196, as described previously. Heat may be applied via the heated
press 196, and pressure is applied via the tubing line 652 to apply
pressure internally to the first layer of elastomeric tube 324. The
internal pressure causes the first layer of elastomeric tube 324 to
expand against the inner covering 164 toward the second layer of
elastomeric tube 380. As described previously, the heat and
pressure uniformly encapsulate and compress the inner and outer
coverings 164, 172 and the stent 100 together to form the smooth
covered stent 198, as shown in FIG. 94.
[0407] After removal from the heated press 196, cooling, and
removal from the press fixture 186, the barb fittings 648,
including the cap 650 and tubing line 652, are also removed from
the first and second layers of elastomeric tube 324, 380 and the
support mandrel 636 is also removed. The first and second layers of
elastomeric tube 324, 380 are removed from the smooth covered stent
198 using any of the removal methods as described previously.
[0408] In an alternative example, when a self-expanding stent is
used, tension may be applied to an elastomeric tube positioned on
the mandrel rather than use of the tapered rod 600, the first
hollow mandrel 602 and the second hollow mandrel 604. For example,
the first layer of elastomeric tube 342 is positioned over the
mandrel 150 via the tube expander 128 including the vacuum 148. The
outer diameter 346 of the first layer of elastomeric tube 342 on
the mandrel 150 is then reduced by applying tension to the first
layer of elastomeric tube 342 to allow the stent 100 to slide or
otherwise be positioned over the first layer of elastomeric tube
342. Specifically, the tension applied outer diameter 346 of the
first layer of elastomeric tube 342 is less than the inner diameter
102 of the stent 100. The tension may be applied by using clamps to
pull on the first and second ends 348, 350 of the first layer of
elastomeric tube 342.
[0409] With the tension applied to the first layer of elastomeric
tube 342 on the mandrel 150, the inner covering 164 is positioned
over and wrapped around the first layer of elastomeric tube 342
with the first material 166 of the inner covering 164 in contact
with the first layer of elastomeric tube 342, as described
previously. The stent 100, which in this example is a
self-expanding stent, is positioned over the inner covering 164 and
in contact with the second material 168 of the inner covering 164.
After the stent 100 is positioned over the inner covering 164, the
tension applied to the first layer of elastomeric tube 342 may be
released and the clamps removed. When the tension is released, the
first layer of elastomeric tube 342 expands to a non-tension
applied state. After expansion, the inner covering 164 contacts the
inner diameter 102 of the stent 100, and the stent 100 maintains
its nominal diameter and is not significantly expanded. The
subsequent steps described above to form the smooth covered stent
198 may then be applied, including without limitation the removal
of the mandrel 150, the positioning of the support mandrel 636
within the first layer of elastomeric tube 342, the positioning of
the second layer of elastomeric tube 380, and the application of
heat and internal pressure using the barb fittings 648, the cap
650, the tubing line 652, the press fixture 186, and the heated
press 196, may be used.
[0410] The tables and steps below provide examples of the materials
and steps using the aforementioned method.
EXAMPLE 7
Self-Expanding Stent, First and Second Tubes, Inner and Outer
Coverings with First and Second Materials, and Internal
Pressurization
TABLE-US-00007 [0411] Element Specifications Stent 100 inner
diameter 102 is 7.6 mm, outer diameter 104 is 8 mm, nominal
diameter is 8 m