U.S. patent application number 12/276761 was filed with the patent office on 2009-09-24 for reinforced medical tubing.
This patent application is currently assigned to Composite Plastic, Inc.. Invention is credited to Terence M. Fogarty.
Application Number | 20090240236 12/276761 |
Document ID | / |
Family ID | 41088072 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090240236 |
Kind Code |
A1 |
Fogarty; Terence M. |
September 24, 2009 |
REINFORCED MEDICAL TUBING
Abstract
A molded spiral reinforced tubing suitable for use in an
implantable medical device includes a molded inner layer comprised
of an elastomeric material. The molded inner layer includes an
inner surface having an inner diameter that defines a lumen and
further includes an outer surface having an outer diameter. The
outer surface includes one or more recessed pathways formed
therein. A continuous reinforcement element is provided within each
of the one or more recessed pathways. A molded outer layer
comprised of an elastomeric material includes an inner surface
having an inner diameter and an outer surface having an outer
diameter. The inner surface of the outer layer substantially
conforms with the reinforcement element and the outer surface of
the inner layer.
Inventors: |
Fogarty; Terence M.;
(Hudson, WI) |
Correspondence
Address: |
FAEGRE & BENSON LLP;PATENT DOCKETING - INTELLECTUAL PROPERTY
2200 WELLS FARGO CENTER, 90 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402-3901
US
|
Assignee: |
Composite Plastic, Inc.
Hudson
WI
|
Family ID: |
41088072 |
Appl. No.: |
12/276761 |
Filed: |
November 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61038206 |
Mar 20, 2008 |
|
|
|
Current U.S.
Class: |
604/533 ;
138/140 |
Current CPC
Class: |
B29L 2023/007 20130101;
B29C 70/70 20130101; B29C 70/46 20130101; A61M 25/005 20130101;
B29C 70/885 20130101; A61M 25/0012 20130101 |
Class at
Publication: |
604/533 ;
138/140 |
International
Class: |
A61M 39/00 20060101
A61M039/00; F16L 9/14 20060101 F16L009/14 |
Claims
1. A tubing for connecting components in medical devices, the
tubing comprising: a molded inner layer comprised of an elastomeric
material, wherein the inner layer includes an inner surface having
an inner diameter that defines a lumen and further includes an
outer surface having an outer diameter, and wherein the outer
surface includes one or more recessed pathways formed therein; a
continuous reinforcement element within at least one of the one or
more recessed pathways; and a molded outer layer comprised of an
elastomeric material, wherein the outer layer includes an inner
surface having an inner diameter and an outer surface having an
outer diameter, and wherein the inner surface of the outer layer
substantially conforms with the reinforcement element and the outer
surface of the inner layer and is secured to the outer surface of
the inner layer.
2. The tubing of claim 1, wherein the outer layer is chemically
and/or mechanically secured to the inner layer.
3. The tubing of claim 1, wherein the outer layer is not chemically
or mechanically secured to the reinforcement element.
4. The tubing of claim 1, wherein the reinforcement element
comprises a coating to reduce surface tension between the
reinforcement element and the inner and outer layers.
5. The tubing of claim 1, wherein at least one of the inner layer
and the outer layer comprises a thermoplastic elastomer.
6. The tubing of claim 5, wherein the thermoplastic elastomer
comprises a material selected from the group consisting of
polyvinyl chloride (PVC) and polyurethane.
7. The tubing of claim 1, wherein at least one of the inner layer
and the outer layer comprises a thermoset elastomer.
8. The tubing of claim 7, wherein the thermoset elastomer comprises
a material selected from the group consisting of ethylene propylene
diene monomer (EPDM) and silicone.
9. The tubing of claim 8, wherein the outer layer is coated with an
acetoxy cured silicone to enhance abrasion resistance.
10. A tubing of claim 9, wherein the acetoxy cured silicone is
applied as a dispersion.
11. The tubing of claim 1, wherein each recessed pathway includes
an arc having a radius at its base.
12. The tubing of claim 11, wherein the radius of the arc is
between about 2% and about 40% smaller than a radius of the
reinforcement element.
13. The tubing of claim 12, wherein the radius of the arc is
between about 10% and about 20% smaller than a radius of the
reinforcement element.
14. The tubing of claim 1, wherein each recessed pathway includes
transition arcs between the outer surface of the inner layer and
the recessed pathway.
15. The tubing of claim 1, wherein a depth of the one or more
recessed pathway is substantially equal to a diameter of the
reinforcement element.
16. The tubing of claim 1, wherein the reinforcement element is
comprised of a metallic material.
17. The tubing of claim 16, wherein the metallic material is
selected from the group consisting of carbon steel, non-carbon
steel, stainless steel, and MP35N.
18. The tubing of claim 1, wherein the reinforcement element is
comprised of a polymeric material.
19. The tubing of claim 18, wherein the polymeric material is
selected from the group consisting of polypropylene and
polyamide.
20. The tubing of claim 1, wherein the outer surface of the inner
layer includes a plurality of projections configured to contact an
outer layer mold during molding of the outer layer to facilitate
centering of the inner layer with respect to the outer layer.
21. The tubing of claim 1, and further comprising at least one of a
sensor, a fiber optic cable, and an electrical conductor within at
least one of the one or more recessed pathways.
22. The tubing of claim 1, wherein the medical device is selected
from the group consisting of an inflatable penile prosthesis, an
inflatable urinary incontinence device, and inflatable fecal
incontinence device, an inflatable mammary prosthesis, an
inflatable tissue expander, and a medical device with a remote
injection port.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of provisional
application Ser. No. 61/038,206, filed Mar. 20, 2008, entitled
"REINFORCED MEDICAL TUBING AND METHOD TO MANUFACTURE," which is
incorporated by reference in its entirety. This application is
related to co-pending application Ser. No. ______, filed on even
date herewith, entitled "Method for Manufacturing Reinforced
Medical Tubing."
TECHNICAL FIELD
[0002] The present invention relates to medical devices. In
particular, the present invention relates to a reinforced tubing
suitable for use in medical devices.
BACKGROUND
[0003] In certain implantable devices, flexible silicone tubing is
used to provide a fluid conduit between and connect device
components. One such implantable device is a multi-component
inflatable penile prosthesis (IPP). In the early 1980's, spiral
reinforcement was incorporated in silicone tubing for IPP to
provide kink-resistance. Historically, spiral reinforced silicone
tubing is fabricated by first extruding and curing an inner layer
of silicone elastomer over a core material, wrapping the inner
layer of silicone with spiral reinforcement, extruding and curing
an outer layer of silicone elastomer over the spiral reinforced
inner layer, cutting the tubing and core material to desired
lengths, and separating the tubing from the core material.
SUMMARY
[0004] The present invention relates to a molded spiral reinforced
tubing suitable for use in an implantable medical device. In one
embodiment, a molded inner layer comprised of an elastomeric
material includes an inner surface having an inner diameter that
defines a lumen and further includes an outer surface having an
outer diameter. The outer surface includes one or more recessed
pathways formed therein. A continuous reinforcement element is
provided within each of the one or more recessed pathways. A molded
outer layer comprised of an elastomeric material includes an inner
surface having an inner diameter and an outer surface having an
outer diameter. The inner surface of the outer layer substantially
conforms with the reinforcement element and the outer surface of
the inner layer.
[0005] While multiple embodiments are disclosed, still other
embodiments of the present invention will become apparent to those
skilled in the art from the following detailed description, which
shows and describes illustrative embodiments of the invention.
Accordingly, the drawings and detailed description are to be
regarded as illustrative in nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is an isometric view of a molded spiral reinforced
tubing according to embodiments of the present invention.
[0007] FIG. 2 is a cross-sectional view of the molded spiral
reinforced tubing shown in FIG. 1.
[0008] FIG. 3 is a cross-sectional view of a core and inner layer
of the molded spiral reinforced tubing according to the present
invention.
[0009] FIG. 3a is an enlarged cross-sectional view of the core and
inner layer shown in FIG. 3.
[0010] FIG. 4 is a plan view of the core and inner layer of the
molded spiral reinforced tubing with a reinforcement member
according to the present invention.
[0011] FIG. 4a is an enlarged plan view of the core and inner layer
with the reinforcement member shown in FIG. 4.
[0012] FIG. 5 is a cross-sectional view of the core and inner layer
with an outer layer molded over the inner layer and the
reinforcement member according to the present invention.
[0013] FIG. 5a is an enlarged cross-sectional view of the outer
layer molded over the inner layer and the reinforcement member
shown in FIG. 5.
[0014] FIG. 6 is an isometric view of a transfer mold for molding
inner and outer layers of a spiral reinforced tubing according to
the present invention.
[0015] FIG. 7 is an isometric view of a transfer mold in an open
arrangement showing the mold cavity halves and a molded shot with
inner and outer tubing layers.
[0016] FIGS. 7a and 7b are enlarged plan views of portions of the
mold cavity halves shown in FIG. 7.
[0017] FIG. 8 is a cross-sectional view of the molded shot with
inner and outer tubing layers shown in FIG. 7.
[0018] FIGS. 8a and 8b are enlarged cross-sectional views of
portions of the molded shot shown in FIG. 8.
[0019] FIG. 9 is an isometric view of a molded inner layer on the
mold core, with multiple centering projections emanating from the
outer surface of the inner molded layer according to embodiments of
the present invention.
[0020] FIG. 9a is a cross-sectional view of the molded inner layer
on the mold core shown in FIG. 9.
[0021] FIG. 10 is an isometric view of a molded inner layer and
reinforcement on a mold core, with a centering sleeve installed
over the outer surface of the inner molded layer according to
embodiments of the present invention.
[0022] FIG. 11 is an isometric view of molded spiral reinforced
tubing with the centering sleeve on the mold core after molding the
outer layer.
[0023] FIG. 12 is an isometric view of a transfer mold for molding
inner and outer layers of a molded spiral reinforced tubing,
depicting axial orientation of the centering sleeve over inner
layer prior to molding.
[0024] FIG. 13 is an isometric view of a transfer mold for molding
inner and outer layers of a molded spiral reinforced tubing,
depicting axial orientation of the centering sleeve after
molding.
[0025] While the invention is amenable to various modifications and
alternative forms, specific embodiments have been shown by way of
example in the drawings and are described in detail below. The
intention, however, is not to limit the invention to the particular
embodiments described. On the contrary, the invention is intended
to cover all modifications, equivalents, and alternatives falling
within the scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION
[0026] FIG. 1 depicts a reinforced tubing 1 according to
embodiments of the present invention. FIG. 2 depicts a sectional
view of the molded spiral reinforced tubing 1, and FIG. 2a is an
enlarged view of a segment from FIG. 2 depicting a single spiral
reinforcement member 6, an inner molded layer 7, and an outer
molded layer 8. The tubing 1 includes a continuous lumen 2 and an
outer surface 3 between tubing ends 4 and 5. As will be described
in more detail herein, the tubing 1 is molded and includes a spiral
reinforcement. It has utility in a variety of applications where
flexible fluid conduit with spiral reinforcement improves
performance characteristics by enhancing resistance to deformation
from internal or external forces. In some applications, the
reinforced tubing 1 may be used in medical devices, since the
construction conforms with variations in the patient's anatomy. One
example use for tubing 1 in a medical device is as a fluid conduit
between components in the medical device. Examples of medical
devices that might utilize reinforced tubing 1 as a fluid conduit
between components are inflatable penile prostheses, inflatable
mammary prostheses, inflatable urinary or fecal incontinence
devices, inflatable tissue expanders, and devices utilizing
implantable injection ports.
[0027] FIGS. 3-5 illustrate steps in the formation of the spiral
reinforced tubing 1 illustrated in FIGS. 1 and 2. FIG. 3 is a
sectional view of a core 110 and the inner layer 7 of a molded
spiral reinforced tubing 1. FIG. 3a is an enlarged view of the
portion circled in FIG. 3 depicting the inner molded layer 7
including the lumen 2 (defined by the diameter of the core 110) and
an outer surface 9. The outer surface 9 has a major diameter 14 and
includes a recessed pathway 10 for receiving the continuous spiral
reinforcement member 6 (not shown in FIGS. 3 and 3a). The pathway
10 includes arc 11 at its base (i.e., the portion of the pathway
most proximate to the lumen 2). Surfaces 12 and 13 connect the arc
11 to the outer surface 9. A transition arc 15 may extend between
the surface 12 and the outer surface 9, and a transition arc 16 may
extend between the surface 13 and the outer surface 9. In some
embodiments, the radius of the arc 11 is sized between about 2% and
about 40% smaller than the radius of the reinforcement member 6, to
retain the reinforcement member 6 in the pathway 10 between the
surfaces 12 and 13. More preferably, the radius of the arc 11 is
sized between about 10% and about 20% smaller than the radius of
the reinforcement member 6. The depth of the pathway 10 (extending
from the outer surface 9 to the bottom of the arc 11) is preferably
equal to the diameter of the reinforcement member 6.
[0028] FIG. 4 depicts the core 110 and the inner layer 7 of the
spiral reinforced tubing 1 with the reinforcement member 6 secured
to the core 110. FIG. 4a is an enlarged view of the portion circled
in FIG. 4 depicting the inner molded layer 7 and the reinforcement
member 6. The core 110 includes crossholes 111 and 112 formed
proximate the ends of the core 110. The reinforcement member 6 is
spirally wound and deposited into the recessed pathway 10. The ends
of the reinforcement member 6 are inserted through the crossholes
111 and 112 of the core 110. The ends of the reinforcement member 6
are secured to the core 110 by mechanical means such as a knot,
swedging, heading, or a retention cuff, or the reinforcement member
6 may be tucked between the core 110 and the inner layer 7. If the
reinforcement member 6 is metallic in composition, swedging or
heading may be accomplished mechanically. If the reinforcement
member 6 is a thermoplastic composition, swedging or heading may be
accomplished thermally. The core 110 may also have additional
crossholes 113 and 114 to facilitate securement of the
reinforcement member 6 to the core 110. The reinforcement member 6
is secured to the core 110 by first routing the reinforcement
member 6 through the crosshole 111, then through the crosshole 113,
then depositing the reinforcement into the recessed pathway 10,
then routing the reinforcement through the crosshole 112, and
finally through the crosshole 114. The crossholes 111-114 may
penetrate the core 110 in the same or different radial orientations
or may be angled so that the crosshole entry and exit may be at
different elevations along the axis of the core 110 to ease
installation of the reinforcement member 6. The crossholes 111-114
may be tapered to provide a larger opening or entry target to
introduce the reinforcement member 6 and a smaller exit to retain
the reinforcement member 6. The crossholes 111-114 may be
electro-discharge machined (EDM) in the core 110, wherein the shape
of each crosshole 111-114 is not limited to a uniform configuration
as might be the case with twist drilling.
[0029] In some embodiments, the reinforcement member 6 has a
diameter at least 0.002 inch smaller than the diameters of the
crossholes 111 and 112. In one actual implementation, a 0.013-inch
diameter Nylon 6 monofilament was utilized with a single 0.015-inch
diameter crosshole on both ends of core 110.
[0030] The reinforcement member 6 forms a sharp bend as it
transitions from the crosshole entry to overlying the circumference
of the core 110 that provides a means to retain the reinforcement
member 6 in the crosshole. Excess portions of the reinforcement
member 6 may be trimmed flush with the exit side of the crossholes
111, 112.
[0031] FIG. 5 depicts a sectional view of the core 110 with the
outer tubing layer 8 molded over the inner tubing layer 7 and the
reinforcement member 6. FIG. 5a is an enlarged view of the portion
circled from FIG. 5 depicting the outer molded layer 8 over the
inner molded layer 7 and the reinforcement member 6. The outer
molded layer 8 has an outer surface 3 and an inner surface 17. The
inner surface 17 is conformal with the reinforcement member 6 and
the outer surface 9 of the inner molded layer 7. In some
embodiments, the outer molded layer 8 is chemically and
mechanically bonded to inner molded layer 7, but not to the
reinforcement member 6. Bonding of the molded layers 7 and 8
mechanically retains the reinforcement member 6 between the
recessed pathway 10 of the inner layer 7 and the inner surface 17
of the outer layer 8. Materials selected for the outer layer 8 and
the reinforcement member 6 prevent bonding of the outer layer 8 to
the reinforcement member 6. If necessary, the reinforcement member
6 should be coated to prevent adhesion of the molded outer layer 8
to the reinforcement member 6. Additionally, the reinforcement
member 6 may be coated to reduce the surface tension between the
molded layers 7 and 8. The reinforcement member 6 should move
freely in the recessed pathway 10 when the tubing is flexed, to
prevent localized stresses that will reduce fatigue life.
[0032] Components of the spiral reinforced tubing 1 may be molded
from a thermoplastic elastomer (e.g., polyurethane or polyvinyl
chloride (PVC)), a thermoset elastomer (e.g., silicone or ethylene
propylene diene monomer (EPDM)), or a combination of thermoplastic
and thermoset elastomers. In certain implantable medical devices,
such as implantable penile prostheses (IPP), silicone elastomer may
be favored for its biocompatibility and low modulus. In these
embodiments, the inner layer 7 is molded from a gum or
high-consistency elastomer such as Nusil MED 4755, a platinum cured
two-part elastomer. Two-part platinum elastomers have one part
containing a catalyst that is mixed with the another part
containing a crosslinker. Platinum cured two-part liquid injection
molding (LIM) elastomer such as Nusil MED 4850 may also be used for
the inner layer. High-consistency elastomers have good tear
resistance, making them particularly suitable for the inner layer
7. The two parts of high consistency silicone elastomer are usually
combined on a two-roll mill and molded using either compression or
transfer molding methods. Alternatively, the inner layer 7 may be
molded with one-part high-consistency elastomer, such as peroxide
cured silicone elastomer, that may be compression or transfer
molded.
[0033] The outer layer 8 may be molded from a gum or
high-consistency elastomer such as Nusil MED 4755 because it has a
high tear strength. The surface tension between the core 110 and
the inner tubing layer 7 is configured to allow removal of the core
110 after molding, but also to minimize movement of the inner layer
7 on core 110 during overmolding of the outer layer 8. The selected
overmolding parameters, such as mold temperature and transfer
speed, optimize the elastomer flow over the reinforcement member 6
and inner layer 7.
[0034] The outer layer 8 may also be dispersion coated by dipping
or spraying a dispersion grade elastomer. Dispersion grade
elastomers can be formulated from peroxide, platinum or acetoxy
cure silicone elastomers with a range of solids content using
chemical solvents such as xylene, trichloroethane, naptha, hexane
and toluene. Two part elastomers may be converted to dispersions
prior to or after combining the two parts. Molding by dispersion
coating is considerably slower than molding with gum or LIM
elastomers using matched metal molds. The desired thickness of the
outer layer 8 may be achieved with multiple dispersion coatings.
Subsequent to volatilizing the dispersion solvent, the silicone
elastomer is vulcanized. Acetoxy cured elastomers may also be used
to provide improved abrasion resistance.
[0035] The reinforcement member 6 may be comprised of a metallic or
polymeric material. Examples of metallic reinforcement are AISI
316L, a low carbon steel, or MP35N, a chromium, nickel, molybdenum
and cobalt alloy. Metallic reinforcement has significantly higher
tensile modulus than plastic reinforcement and can sustain
permanent deformation if deformed beyond its elastic limit. The
higher modulus metal reinforcement has less fatigue resistance than
lower modulus plastic reinforcement. Metal reinforcements may be
formed using spring winding equipment prior to placement on the
inner layer 7.
[0036] Examples of polymeric materials suitable for reinforcement
member 6 are nylon, polyester or polypropylene. Plastic
reinforcement may be wound directly onto the tubing inner layer 7.
For certain long-term medical applications, such as IPP, plastic
reinforcement may better suited than metal, because it is less
susceptible to permanent deformation, more resistant to fatigue and
provides a more compliant tubing. In some embodiments, polyamide,
commonly referred to as nylon, is favored for the reinforcement
member 6 due its physical properties, biocompatibility, and because
it is less likely to bond with the inner layer 7 during
vulcanization.
[0037] FIG. 6 depicts a family transfer mold 101 with cavity plates
102 and 103 in the closed mode. A sprue 104 is depicted in the
center of the cavity plate 102. The family transfer mold 101
depicted in FIG. 6 is for molding a short length of molded spiral
reinforced tubing 1 for developing test samples and prototypes. It
will be appreciated that the cavity plates 102 and 103 can be sized
to mold tubing 1 having a desired length. A rotary cavity shut off
valve 123 in the cavity plate 102 allows for molding either the
inner or outer layers separately or simultaneously. In actual
implementation, production molds would likely be multi-cavity
versions of either the inner layer 7 or the outer layer 8, since
the inner layer 7 and the outer layer 8 may be molded from
different elastomers or require different molding parameters such
as transfer pressure, transfer speed, mold temperature and
vulcanization or curing cycle times.
[0038] FIG. 7 depicts an isometric view of an opened family
transfer mold 101 with the cavity plates 102 and 103 separated
along their longitudinal axis for molding the inner layer 7 and the
outer tubing layer 8. The cavity plate 102 includes a sprue 104 and
a runner 105 for transferring elastomer to ring gate halves 106 and
108 in the cavity plate 102 and the opposing ring gate halves 107
and 109 located in the cavity plate 103. Ring gating from a single
end of the tubing to introduce elastomer into the mold cavities
substantially eliminates the potential for knit lines. Ring gating
from a single end also minimizes the potential for bending of the
mold core 110 that forms the lumen 2. FIG. 7 also depicts an inner
layer cavity half 115 and an outer layer cavity half 117 in the
cavity plate 103 and an inner layer cavity half 116 and an outer
cavity half 118 in the cavity plate 102.
[0039] FIGS. 7a and 7b are enlarged plan views of the circled
portions on the cavity plate 103 and the cavity plate 102,
respectively, in FIG. 7. FIG. 7a is a plan view of the
reinforcement securement surround half 119 located between the ring
gate half 109 and the outer layer cavity half 117 in the cavity
plate 103. FIG. 7b is a plan view of the reinforcement securement
surround half 120 located between the ring gate half 108 and the
outer layer cavity half 118 in the cavity plate 102. A
reinforcement securement surround half 121 adjacent the outer layer
cavity half 117 in cavity plate 103 and a reinforcement securement
surround half 122 adjacent the outer layer cavity half 118 in
cavity plate 102 are shown in FIG. 7. The reinforcement securement
surrounds provide a segment to accommodate the bulk of the
reinforcement securement means described above. FIG. 7 also shows a
molded shot between separated cavity plates 102 and 103. The molded
shot includes the inner layer 7 over the core 110, the outer tubing
layer 8 over the inner tubing layer 7 and the reinforcement member
6, and a runner 18 connecting the cores 110.
[0040] The mold cavity plates 102 and 103 may be filled with a
thermoset elastomer material using any suitable molding technique,
such as compression, transfer, or LIM molding. With compression
molding, the elastomer is placed in the mold cavities 115-118 and
the elastomer is compressed as the mold is closed to fill out the
part, replicating the mold detail. With transfer molding, the
elastomer is placed in a transfer pot, usually a component of the
press or mold. Transfer molding is accomplished by either closing
the mold, if using a compression molding press, or closing the mold
and activating the transfer plunger if using a transfer press. In
either case, the elastomer is transferred through the sprue 104 in
the mold and subsequently through the ring gate 106-109 to fill the
mold forming the part. The runner 105 may be used to connect the
sprue 104 and the gate 106-109. With LIM molding, multiple
components of liquid elastomer are pumped separately to a mixing
chamber from which they are fed into an injection chamber. The
injection molding press closes the mold cavity plates 102 and 103
and subsequently injects the combined multi-component elastomer
into the mold cavities 115-118, filling out the part. For thermoset
elastomers, the parts may be compression, transfer or injection
molded by introducing uncured elastomer into the mold cavities
115-118, thermally curing the elastomer for a specific time,
opening the mold, and removing the part along with the sprue 104
and runner 105. For any thermoplastic elastomer, the parts may be
injection molded by introducing molten elastomer into the mold
cavities 115-118, thermally cooling the elastomer for a specific
time, opening the mold, and removing the part along with the sprue
104 and runner 105.
[0041] FIG. 8 is a cross-sectional view of a single molded shot
including the molded inner layer 7 on the core 110, the outer layer
8 molded over the inner layer 7 and the reinforcement member 6, and
the runner 18 connecting cores 110. FIG. 8a is an enlarged
cross-sectional view of the portion circled of the inner layer 7 on
the core 110 in FIG. 8 depicting the ring gate 19. FIG. 8b is an
enlarged cross-sectional view of the portion circled of the outer
layer 8 on the core 110 in FIG. 8, depicting the ring gate 20 and
the reinforcement securement surround 21.
[0042] While the present invention has been described with regard
to a reinforced tubing 1 including a single spiral reinforcement
member 6, it will be appreciated that variations on this design are
contemplated. For example, in an alternative embodiment, the tubing
1 may be configured to accommodate a plurality of continuous spiral
reinforcement members 6. Multiple spiral reinforcement members 6
may have advantages in certain applications and may be accomplished
by providing detail for multiple reinforcement pathways 10 in the
inner layer cavity halves 115 and 116, additional crossholes in the
core 110, multiple recessed pathways 10 in the inner layer 7 and
multiple reinforcement members 6 in the molded spiral reinforced
tubing 1. Multiple reinforcement members 6 may be used, for
example, to reduce the reinforcement angle with respect to the
longitudinal axis of the tubing 1. Multiple reinforcement members 6
provide a larger reinforcement angle with respect to the tubing
axis and will facilitate greater radial expansion of the lumen 2
for applications involving insertion of a connector or tubing
insert.
[0043] In alternative embodiments, the reinforced tubing 1 is
assembled with elements that provide additional functional
components in the tubing 1. For example, in embodiments including
multiple recessed pathways 10, a color coding member may be formed
in one of the recessed pathways 10 to color code the tubing 1 for
identification for particular applications. As another example, one
or more of the multiple recessed pathways 10 may have one or more
electrically conductive paths formed therein to communicate
electrical signals between components connected by the tubing 1.
One or more of the multiple recessed pathways 10 may also include a
fiber optic element to facilitate optical communication across the
tubing 1. Furthermore, one or more of the multiple recessed
pathways 10 may have a sensing element formed therein to sense
physiological characteristics (e.g., oxygen or pH levels) around
the tubing 1.
[0044] FIG. 9 depicts inner layer 7 on the core 110 with multiple
centering projections 125 emanating from the outer surface 14 of
the inner layer 7, according to an alternative embodiment of the
present invention. FIG. 9a is an enlarged view of a cross-section
of the inner layer 7 and the core 110 shown in FIG. 9 depicting
multiple centering projections 125 emanating from the major
diameter 14 of the inner layer 7. The embodiment shown in FIGS. 9
and 9a is configured to center the inner layer 7 with respect to
the outer layer mold cavities 117 and 118 during molding of the
outer layer 8. In particular, the centering projections 125 are
configured to contact the outer layer mold cavity halves 117 and
118, during molding of the outer molded layer 8, to facilitate
centering of inner molded tubing layer 7 within outer molded tubing
layer 8. In some embodiments, the centering projections 125 are
positioned at a minimum of 120.degree. apart radially, and a
suitable distance apart axially, to maintain centering with respect
to the mold cavity halves 117 and 118.
[0045] The centering projections 125 is just one example mechanism
that may be used to center the inner layer 7 with respect to the
outer layer mold cavities 117 and 118 during overmolding. For
example, FIG. 10 depicts the inner layer 7 and the reinforcement
member 6 on the core 110 and a centering sleeve 124 positioned over
the outer surface 14 of the inner layer 7 and the reinforcement
member 6, according to another embodiment of the present invention.
The centering sleeve 124 is disposed around the outer surface 14 of
the inner layer 7 and centers the inner layer 7 and the
reinforcement member 6 within outer molded tubing layer 8, during
molding of the outer layer 8. In some embodiments, the diameter of
the bore of centering sleeve 124 is sized 0.001 to 0.002 inch
greater than the diameter of the outer surface 14 of the inner
layer 7 and the outer radius of the centering sleeve 124 is sized
0.001 to 0.002 inch smaller than the radii of the outer layer
cavity halves 117 and 118. The centering sleeve 124 is placed over
the inner layer 7 and the reinforcement member 6 and axially
located proximal to outer layer ring gate halves 108 and 109. As
elastomer is introduced into the mold, it advances the centering
sleeve 124 axially between inner molded tubing layer 7 and cavity
halves 117 and 118 until the elastomer flow is complete and the
centering sleeve 124 is distal to the ring gate 108, 109. The
centering sleeve 124 can be fabricated from a heat resistant
plastic such as polysulfone or metal such as aluminum or stainless
steel. FIG. 11 depicts molded spiral reinforced tubing with the
outer layer 8 and the centering sleeve 124 on the mold core 110
after molding the outer layer 8.
[0046] FIG. 12 is an isometric view of a family transfer mold for
molding the inner layer 7 and the outer layer 8, prior to molding
the device shown in FIGS. 10 and 11. The cavity plates 102 and 103
are separated along their longitudinal axis. The centering sleeve
124 is located proximal to the ring gate half 108 of the cavity
plate 102 and the ring gate half 109 of the cavity plate 103 prior
to molding. The centering sleeve 124 is radially positioned over
the inner layer 7 and the reinforcement member 6 on the core 110.
FIG. 13 is an isometric view of a family transfer mold after
molding the inner layer 7 on the core 110 and the outer layer 8
over the inner layer 7 and the reinforcement member 6. As is shown,
the centering sleeve 124 travels to the end distal to the ring gate
108, 109 during molding of the outer layer 8.
[0047] Molded tubing provides design opportunity because the bore
and major diameter need not have a continuous profile. Molding
multiple layer tubing provides additional design freedom especially
when reinforcement is incorporated in the tubing. For example, the
tubing 1 of the present invention has a non-continuous outer
surface 14 on the inner layer 7 that includes a recessed pathway 10
for accommodating a spiral reinforcement member 6. The recessed
pathway 10 eliminates the need to tension the reinforcement member
6 to stabilize it during subsequent manufacturing operations, which
also provides design opportunity to fabricate tubing 1 with a
continuous lumen 2. A reinforcement member 6 that is not tensioned
is less likely to cause localized stress that could initiate
fatigue failure than a tensioned reinforcement. In addition, the
greatest elongation during bending or flexing of the inner layer of
the tubing 1 is directed to the thinnest cross-section at the
bottom of the recessed pathway 10. The compressive and tensile
stresses from flex of the tubing 1 are minimized by reducing the
thickness. Spiral reinforcement member 6 causes the greatest
abrasive activity at the base of the recessed pathway during flex
of the tubing 1. However, the reduction or elimination of tension
on the reinforcement member 6 as is done in the tubing 1 according
to the present invention can significantly reduce this abrasive
activity. That is, the tubing 1 is provided with the recessed
pathway 10 on the inner layer 7, facilitating spiral reinforcement
with minimal or no tension, so that compressive forces caused by
the reinforcement member 6 on the adjacent inner layer 7 during
flex of tubing 1 are reduced for greater fatigue resistance.
[0048] One or more of the following advantages may be provided in
certain implementations. First, molded spiral reinforced tubing can
be provided that is simple to manufacture. Second, molded spiral
reinforced tubing can be provided that can be manufactured more
consistently than extruded spiral reinforced tubing. Third, molded
tubing provides greater design freedom over extruded tubing because
the tubing profile need not be continuous and enables incorporation
of features for ease of manufacture or improved performance.
Fourth, molded spiral reinforced tubing can be provided with a
constant lumen without undulations from tensioned reinforcement.
Fifth, molded spiral reinforced tubing can be provided with greater
fatigue resistance than extruded spiral reinforced tubing.
[0049] A significant advantage in molded silicone tubing over
extruded silicone tubing is that molded tubing is compressed and
densified during vulcanization or curing. Extruding tubing is
compressed as it is forced through an extrusion die but is not
densified during vulcanization. Physical properties are enhanced as
the interface between the elastomer and reinforcing filler improves
and mechanical densification that occurs during closed molding
improves that interface.
[0050] Various modifications and additions can be made to the
exemplary embodiments discussed without departing from the scope of
the present invention. For example, while the embodiments described
above refer to particular features, the scope of this invention
also includes embodiments having different combinations of features
and embodiments that do not include all of the described features.
Accordingly, the scope of the present invention is intended to
embrace all such alternatives, modifications, and variations as
fall within the scope of the claims, together with all equivalents
thereof.
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