U.S. patent application number 10/913565 was filed with the patent office on 2005-02-10 for surgical device with tack-free gel and method of manufacture.
Invention is credited to Adlparvar, Payam, Ahlberg, Russell E., Brustad, John R., Martinez, Daniel, Taylor, Scott V., Wixey, Matthew A..
Application Number | 20050033246 10/913565 |
Document ID | / |
Family ID | 34119019 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050033246 |
Kind Code |
A1 |
Ahlberg, Russell E. ; et
al. |
February 10, 2005 |
Surgical device with tack-free gel and method of manufacture
Abstract
A process of making a tack-free gel is disclosed comprising the
steps of providing a mold defining a mold cavity, the mold cavity
comprising a plastic material; pouring or injecting a molten gel
having a high molding temperature into the mold cavity; and forming
the tack-free gel as a thin layer of plastic of the mold cavity is
melted over the gel. The forming step further comprises cooling the
gel from the molten state to a solidified state. The melting
temperature of the plastic material is lower than the molding
temperature of the gel; and the higher the temperature
differential, the greater the melting of the plastic material and
the thicker the layer of the plastic material on the surface of the
gel. The mold may be formed of low-density polyethylene (LDPE).
With the process of the invention, the heat of the molten gel at
its molding temperature is transferred to the surface of the LDPE
mold so as to melt a thin layer of the LDPE. The mold may comprise
a mold base having a plurality of mold holes forming a plurality of
mold cavities, each of the mold holes comprising an axial pin to
mold an axial hole through a center of the gel, an LDPE cylinder
providing a predetermined inside diameter for the mold, and an LDPE
disc mounted on the axial pin and disposed at the bottom of each
mold cavity in the mold base. The process may further comprise the
step of dabbing the gel in a low-friction powder such as
polytetrafluoroethylene (PTFE) and a lubricant. The mold may
further comprise a mold top disposed axially of the mold base and
comprises a plurality of holes forming a plurality of cavities,
each of the mold top holes is adapted to receive the LDPE cylinder,
and a second LDPE disc disposed at the top of each mold cavity of
the mold top.
Inventors: |
Ahlberg, Russell E.; (Rancho
Santa Margarita, CA) ; Adlparvar, Payam; (Lake
Forest, CA) ; Taylor, Scott V.; (Mission Viejo,
CA) ; Wixey, Matthew A.; (Dana Point, CA) ;
Martinez, Daniel; (Corona, CA) ; Brustad, John
R.; (Dana Point, CA) |
Correspondence
Address: |
APPLIED MEDICAL RESOUCES CORPORATION
22872 Avenida Empresa
Rancho Santa Margarita
CA
92688
US
|
Family ID: |
34119019 |
Appl. No.: |
10/913565 |
Filed: |
August 5, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10913565 |
Aug 5, 2004 |
|
|
|
10776387 |
Feb 10, 2004 |
|
|
|
60492949 |
Aug 6, 2003 |
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Current U.S.
Class: |
604/264 |
Current CPC
Class: |
B29C 39/123 20130101;
B29C 39/006 20130101; A61B 17/3423 20130101; A61B 2017/22067
20130101; A61B 17/3462 20130101; B29C 39/025 20130101; A61B
2017/00469 20130101; A61M 3/0279 20130101; B29C 37/0067 20130101;
A61B 17/3498 20130101 |
Class at
Publication: |
604/264 |
International
Class: |
A61M 025/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 14, 2002 |
WO |
PCT/US02/15696 |
Claims
1. A method of making a tack-free gel, comprising the steps of:
providing a mold defining a mold cavity, the mold cavity comprising
a plastic material; pouring or injecting a molten gel having a high
molding temperature into the mold cavity; and forming the tack-free
gel as a thin layer of plastic of the mold cavity is melted over
the gel.
2. The method of claim 1, wherein the mold providing step further
comprises the step of injecting or spraying the mold cavity with
the plastic material.
3. The method of claim 1, wherein the forming step further
comprises cooling the gel from the molten state to a solidified
state.
4. The method of claim 1, wherein a melting temperature of the
plastic material is lower than the molding temperature of the
gel.
5. The method of claim 4, wherein the difference in the melting
temperature of the plastic material and the molding temperature of
the gel is in a range of about 20.degree. F. to about 100.degree.
F.
6. The method of claim 4, wherein the higher the temperature
differential, the greater the melting of the plastic material and
the thicker the melted layer of the plastic material on the surface
of the gel.
7. The method of claim 1, wherein the gel molding temperature is
about 450.degree. F.
8. The method of claim 1, wherein the mold is formed of low-density
polyethylene (LDPE) and having a melting temperature of about
240.degree. F.
9. The method of claim 8, wherein the heat of the molten gel at its
molding temperature is transferred to a surface of the LDPE mold so
as to melt a thin layer of the LDPE.
10. The method of claim 9, further comprising the step of cooling
the molten gel and melted LDPE so as to form a non-tacky surface on
the solidified gel.
11. The method of claim 10, wherein the solidified gel has a
cylindrical shape having a first opposing end, a second opposing
end and a cylindrical body.
12. The method of claim 1, wherein the mold comprises a mold base
having: a plurality of mold holes forming a plurality of mold
cavities, each of the mold holes comprising an axial pin to mold an
axial hole through a center of the gel; a low-density polyethylene
(LDPE) cylinder providing a predetermined inside diameter for the
mold; and an LDPE disc mounted on the axial pin and disposed at the
bottom of each mold cavity in the mold base.
13. The method of claim 12, wherein each of the mold cavities
includes a disposable plastic liner.
14. The method of claim 12, wherein the LPDE cylinder is replaced
after each molding process.
15. The method of claim 11, further comprising the step of dabbing
at least one of the opposing ends in a low-friction powder.
16. The method of claim 15, wherein the low-friction powder
includes at least one of polytetrafluoroethylene (PTFE) and a
lubricant.
17. The method of claim 12, wherein the mold further comprises a
mold top disposed axially of the mold base and comprising: a
plurality of holes forming a plurality of cavities, each of the
mold top holes is adapted to receive the LDPE cylinder; and a
second LDPE disc disposed at the top of each mold cavity of the
mold top.
18. The method of claim 1, wherein the plastic is formed from at
least one of PVC, ABS, acrylic, polycarbonate, clear polycarbonate,
Delrin, acetal, polypropylene and high-density polyethylene
(HDPE).
19. The method of claim 1, further comprising the step of tumbling
or coating the gel in a lubricious material.
20. The method of claim 1, further comprising the step of applying
a lubricious coating to the gel in a vacuum deposition process.
21. The method of claim 1, further comprising the step of dipping
the gel in a lubricious material.
22. The method of claim 1, further comprising the step of spraying
the solidified gel with a lubricious material.
23. The method of any one of claims 19-22, wherein the lubricious
material includes Parylene.
24. A method of making a tack-free gel by co-extrusion, comprising
the steps of: extruding an elongate sleeve formed of a plastic
material around a molten gel having a high molding temperature, the
elongate sleeve having an axis and a diameter; pressurizing the
molten gel to control the diameter of the filled elongate sleeve;
and cooling the filled elongate sleeve to form the tack-free
gel.
25. The method of claim 24, wherein the plastic material is
low-density polyethylene (LDPE).
26. The method of claim 24, further comprising the step of radially
cutting the elongate sleeve into individual segments having
predetermined lengths.
27. The method of claim 24, further comprising the step of removing
the gel by squeezing the sleeve and pulling the gel from the
sleeve.
28. The method of claim 27, wherein the gel has a cylindrical shape
having a first opposing end, a second opposing end and a
cylindrical body.
29. The method of claim 28, further comprising the step of dabbing
at least one of the opposing ends in a low-friction powder.
30. The method of claim 29, wherein the low-friction powder
includes at least one of polytetrafluoroethylene (PTFE) and a
lubricant.
31. The method of claim 24, further comprising the step of tumbling
or coating the gel in a lubricious material.
32. The method of claim 24, further comprising the step of applying
a lubricious coating to the gel in a vacuum deposition process.
33. The method of claim 24, further comprising the step of dipping
the gel in a lubricious material.
34. The method of claim 24, further comprising the step of spraying
the gel with a lubricious material.
35. The method of any one of claims 31-34, wherein the lubricious
material includes Parylene.
36. A trocar adapted to provide access for a surgical instrument
through a body wall and into a body cavity, comprising: a cannula
having a proximal end and a distal end; a seal housing
communicating with the cannula to define a working channel; a seal
assembly disposed within the seal housing; at least one roller
included in the seal assembly and having an axle supported by the
seal housing; and the roller having a tack-free surface and
properties for forming a zero seal in the absence of the
instrument, and an instrument seal in the presence of the
instrument.
37. The trocar recited of claim 36, wherein the roller is pivotal
with the axle relative to the seal housing.
38. The trocar recited of claim 36, wherein the tack-free surface
is formed of LDPE.
39. The trocar recited of claim 38, wherein the roller further
comprises a lubricious coating.
40. The trocar recited of claim 39, wherein the lubricious coating
includes at least one of polytetrafluoroethylene (PTFE)
low-friction powder or a lubricant including Parylene.
41. A medical access device, comprising: a tubular member having an
elongate configuration; at least one wall defining with the tubular
member a working channel sized and configured to receive an
instrument; and a gel disposed in the working channel and being
adapted to form a seal with any instrument disposed in the working
channel, wherein the gel includes a non-tacky film to facilitate
movement of any instrument through the working channel.
42. The medical access device of claim 41, wherein the film is
formed by a fluoropolymer including polytetrafluoroethylene
(PTFE).
43. The medical access device of claim 42, wherein the non-tacky
film is applied as a powder or as a tape over the gel.
44. The medical access device of claim 41, wherein the gel and
non-tacky film have properties including an elongation up to about
1500 percent.
45. The medical access device of claim 41, wherein the gel is
coated with a lubricant including Parylene.
46. A surgical handport facilitating a sealing relationship with a
surgeon's arm extending through the handport and into an incision
in an abdominal wall of a patient, comprising: a valve structure
comprising only a single valve disposed relative to the incision in
the abdominal wall, the single valve having a first state in the
absence of the arm of the surgeon extending through the valve
structure, and a second state in the presence of the arm of the
surgeon extending through the valve structure; means for coupling
the valve structure to the abdominal wall in a sealing relationship
with the abdominal wall around the incision; the single valve in
the first state forming a zero seal in the absence of the arm of
the surgeon extending through the valve structure; and the single
valve structure in the second state forming an arm seal with the
arm of the surgeon in the presence of the arm of the surgeon
extending through the handport, wherein the single valve includes a
non-tacky film to facilitate movement of the arm of the surgeon
through the handport.
47. The surgical handport of claim 46, wherein the valve structure
further comprises: a gel; at least portions of the gel partially
define an opening through the valve structure; and the opening
defining portions of the gel having properties in the first state
for sealing the opening in the absence of the arm of the surgeon
extending through the opening.
48. The surgical handport of claim 46, wherein the zero seal and
the arm seal have properties for inhibiting the escape of liquids
and gases through the single seal.
49. The surgical handport of claim 46, wherein the coupling means
includes an adhesive having properties for attaching the valve
structure to the abdominal wall.
Description
[0001] This is a continuation-in-part application claiming the
priority of provisional application Ser. No. 60/492,949, filed on
Aug. 6, 2003, entitled "Surgical Device With Tack-Free Gel and
Method of Manufacture," and of U.S. application Ser. No.
10/776,387, filed on Feb. 10, 2004, entitled "Access Sealing
Apparatus and Method," which claims priority to PCT application
Serial No. PCT/US02/15696, filed on May 14, 2002, entitled "Access
Sealing Apparatus and Method," and to provisional application Ser.
No. 60/312,683, filed on Aug. 14, 2001, entitled "Access Sealing
Apparatus and Method," all of which are fully incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention generally relates to gels having tacky
surfaces and, more specifically, to surface treatments which will
render the gel tack-free.
[0004] 2. Discussion of Related Art
[0005] A "gel" is often defined as a semisolid condition of a
precipitated or coagulated colloid. Within this definition, gels
can differ widely. On one end of the spectrum gels are more fluid
in nature but have some solid properties. An example of such a gel
might be a gel toothpaste. At the opposite end of the spectrum, the
gels are considered solids with some fluid properties.
[0006] It is toward this end of the spectrum that gels are commonly
used to facilitate load distribution. Gels enhance this function by
offering a high degree of compliance which basically increases the
amount of area available to support a load. With an increased area
of support, the load is accommodated at a considerably reduced
pressure. Particularly where the human body is involved, a reduced
pressure is desirable in order to maintain capillary blood flow in
body tissue. It is with this in mind that gels are commonly used
for bicycle seats, wrist pads, insole supports, as well as elbow
and shoulder pads.
[0007] While the advantageous properties of gels have made them
candidates for many applications, one disadvantage has seriously
limited their use. Most gels are extremely tacky. This
characteristic alone makes them difficult to manufacture and
aggravating to use.
[0008] Attempts have been made to produce gels that are naturally
non-tacky. But such attempts unfortunately have resulted in an
intolerable sacrifice of the advantageous properties. Attempts have
been made to enclose the gels in a non-tacky pouch. This has also
tended to mask the advantageous properties and to significantly
increase manufacturing costs. Powders and lubricants have been
applied to the tacky surfaces with results limited in both duration
and effect.
[0009] Gels have also been of particular interest in the formation
of seals where the high compliance and extensive elongation of the
gel are of considerable value. Such is the case with seals used in
trocars and other surgical access devices, where a seal must be
formed both in the presence of a surgical instrument and in the
absence of a surgical instrument.
[0010] In general, a trocar is a surgical device intended to
provide tubular access for surgical instruments across a body wall,
such as the abdominal wall, and into a body cavity, such as the
abdominal cavity. Often, the body cavity is pressurized with a gas,
typically carbon dioxide, to enlarge the operative volume of the
working environment. Under these conditions, the trocar must
include appropriate seals to inhibit loss of the pressurizing gas
through the trocar. Thus, a zero seal must be provided to seal the
working channel of the trocar in the absence of the instrument, and
an instrument seal must be provided to seal the working channel in
the presence of the instrument.
[0011] Most recently, both zero seals and instrument seals have
been provided by a pair of rollers disposed on opposing sides of
the working channel. The rollers have been formed of a gel material
providing a high degree of compliance, significant tear strength
and exceptional elongation. As noted, however, the best gel
materials tend to exhibit surfaces that are very tacky. The use of
a tacky gel can make the processes of manufacturing and using the
gel seals extremely difficult. The disadvantages are increasing in
this application, where a tacky gel also produces significant drag
forces during instrument insertion. Furthermore, the tacky surfaces
tend to draw and retain particulate matter during the manufacturing
and handling processes. For these reasons it has been even more
desirable to render the highly tacky gel surfaces non-tacky in the
case of medical devices such as trocars.
[0012] Many attempts have been made to facilitate handling the
rollers during manufacture and to lower instrument drag forces
during use. For example, use of lubricants such as silicone oil, KY
jelly, and Astroglide, have been applied to the surface to reduce
tackiness. Unfortunately, these lubricants tend to dry out over
time leaving the gel in its natural tacky state. Non-tacky gels
have also been investigated. The non-tacky gels, however, are not
particularly heat tolerant, as low amounts of heat can rapidly
cause the materials to take a set and distort particularly under
compressive loads. This can occur over an extended period of time,
for example, even at normal room temperatures.
SUMMARY OF THE INVENTION
[0013] In accordance with the present invention, a gel material
having all of the advantageous properties previously discussed is
further blessed with a non-tacky surface that can be provided at
the earliest possible opportunity, during the molding step of the
manufacturing process. From the time when the molten gel material
first achieves its solid characteristics, it is provided with a
non-tacky surface. In the case of a trocar seal, significant drag
forces are avoided during the process of instrument insertion.
Moreover, the advantages of high compliance, significant tear
strength, and exceptional elongation are maintained without any of
the disadvantages associated with a tacky device.
[0014] In a first aspect of the invention, a process of making a
tack-free gel is disclosed comprising the steps of providing a mold
defining a mold cavity, the mold cavity comprising a plastic
material; pouring or injecting a molten gel having a high molding
temperature into the mold cavity; and forming the tack-free gel as
a thin layer of plastic of the mold cavity is melted over the gel.
More specifically, the forming step further comprises cooling the
gel from the molten state to a solidified state. The mold providing
step may further comprise the step of injecting or spraying the
mold cavity with the plastic material. It is appreciated that the
melting temperature of the plastic material is lower than the
molding temperature of the gel and, in this aspect, the difference
in the melting temperature of the plastic material and the molding
temperature of the gel is in a range of about 20.degree. F. to
about 100.degree. F. It should be noted that the higher the
temperature differential, the greater the melting of the plastic
material and the thicker the layer of the plastic material on the
surface of the gel.
[0015] The mold may be formed of low-density polyethylene (LDPE)
and has a melting temperature of about 240.degree. F. With the
process of the invention, the heat of the molten gel at its molding
temperature is transferred to the surface of the LDPE mold so as to
melt a thin layer of the LDPE. The solidified gel may be a
cylindrical shape having a first opposing end, a second opposing
end and a cylindrical body. The mold may comprise a mold base
having a plurality of mold holes forming a plurality of mold
cavities, each of the mold holes comprising an axial pin to mold an
axial hole through a center of the gel, an LDPE cylinder providing
a predetermined inside diameter for the mold, and an LDPE disc
mounted on the axial pin and disposed at the bottom of each mold
cavity in the mold base. After each molding process, the LPDE
cylinder may be replaced. The process of the invention may further
comprise the step of dabbing at least one of the opposing ends in a
low-friction powder such as polytetrafluoroethylene (PTFE) and a
lubricant. In another aspect, the mold may further comprise a mold
top disposed axially of the mold base and comprises a plurality of
holes forming a plurality of cavities, each of the mold top holes
is adapted to receive the LDPE cylinder, and a second LDPE disc
disposed at the top of each mold cavity of the mold top.
[0016] In another aspect of the invention, the plastic material may
be formed from at least one of PVC, ABS, acrylic, polycarbonate,
clear polycarbonate, Delrin, acetal, polypropylene and high-density
polyethylene (HDPE). The process of the invention may further
comprise the step of tumbling or coating the gel in a lubricious
material, applying a lubricious coating to the gel in a vacuum
deposition process, dipping the gel in a lubricious material, or
spraying the solidified gel with a lubricious material to further
facilitate the non-tackiness surface of the gel. The lubricious
material includes Parylene.
[0017] In yet another aspect of the invention, a process of making
a tack-free gel by co-extrusion is disclosed comprising the steps
of extruding an elongate sleeve formed of a plastic material around
a molten gel having a high molding temperature, the elongate sleeve
having an axis and a diameter; pressurizing the molten gel to
control the diameter of the filled elongate sleeve; and cooling the
filled elongate sleeve to form the tack-free gel. The plastic
material of the elongate sleeve may be low-density polyethylene
(LDPE). The process may further comprise the step of radially
cutting the elongate sleeve into individual segments having
predetermined lengths, and removing the gel by squeezing the sleeve
and pulling the gel from the sleeve. With this aspect of the
invention, the gel may have a cylindrical shape having a first
opposing end, a second opposing end and a cylindrical body. The
process may further comprise the step of dabbing at least one of
the opposing ends in a low-friction powder, which may include at
least one of polytetrafluoroethylene (PTFE) and a lubricant,
tumbling or coating the gel in a lubricious material, applying a
lubricious coating to the gel in a vacuum deposition process,
dipping the gel in a lubricious material, or spraying the gel with
a lubricious material. The lubricious material includes
Parylene.
[0018] Another aspect of the invention is directed to a trocar
being adapted to provide access for a surgical instrument through a
body wall and into a body cavity, the trocar comprising a cannula
having a proximal end and a distal end, a seal housing
communicating with the cannula to define a working channel, a seal
assembly disposed within the seal housing, at least one roller
included in the seal assembly and having an axle supported by the
seal housing, and the roller having a tack-free surface and
properties for forming a zero seal in the absence of the
instrument, and an instrument seal in the presence of the
instrument. With this aspect, the roller is pivotal with the axle
relative to the seal housing. The tack-free surface may be formed
of LDPE, and the roller may further comprise a lubricious coating
including at least one of polytetrafluoroethylene (PTFE)
low-friction powder or a lubricant including Parylene.
[0019] In a final aspect, a medical access device is disclosed
comprising a tubular member having an elongate configuration, at
least one wall defining with the tubular member a working channel
sized and configured to receive an instrument, and a gel disposed
in the working channel and being adapted to form a seal with any
instrument disposed in the working channel, wherein the gel
includes a non-tacky film to facilitate movement of any instrument
through the working channel. It is appreciated that the film may be
formed by a fluoropolymer including polytetrafluoroethylene (PTFE).
The non-tacky film may be applied as a powder or as a tape over the
gel. It is further appreciated that the gel and non-tacky film may
have properties including an elongation up to about 1500 percent,
and that the gel may be coated with a lubricant including
Parylene.
[0020] These and other features of the invention will become more
apparent with a description of the various embodiments and
reference to the associated drawings.
DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings, which are included in and
constitute a part of this specification, illustrate the embodiments
of the invention and, together with the description, explain the
features and principles of the invention. In the drawings:
[0022] FIG. 1a is a side elevation view partially in cross-section
of a trocar with a roller seal assembly;
[0023] FIG. 1b is a side elevation view of the trocar illustrated
in FIG. 1a;
[0024] FIG. 2a is a perspective view of a plastic mold with
multiple mold cavities;
[0025] FIG. 2b is a perspective view of a gel roller with an outer
layer of mold plastic;
[0026] FIG. 2c is a perspective view of a metal mold and multiple
cylinders and discs each associated with an individual mold
cavity;
[0027] FIG. 2d is a perspective view showing the mold cylinders
disposed in the mold base;
[0028] FIG. 3 is a side elevation view illustrating a step of
dabbing a tacky gel surface into powder;
[0029] FIG. 4 is a side elevation view similar to FIG. 1b and
illustrating a single low friction disc mounted between a tacky
roller surface and the seal housing;
[0030] FIG. 5 is a schematic view illustrating co-extrusion of an
LDPE sleeve and a gel;
[0031] FIG. 6 is a perspective view of base and top molds used in
an injection molding operation;
[0032] FIG. 7 illustrates a method for applying a coating by vacuum
deposition;
[0033] FIG. 8 is a perspective view illustrating application of a
coating in a dipping process;
[0034] FIG. 9 is a perspective view illustrating application of a
coating by spraying;
[0035] FIG. 10 is a perspective view illustrating an application of
a coating by tumbling;
[0036] FIG. 11 is a perspective view of a hand port wherein a gel
seal is overlayed with a fluoropolymer film; and
[0037] FIG. 12 is a cross-section view taken along lines 12-12 of
FIG. 11.
DESCRIPTION OF THE INVENTION
[0038] A trocar is illustrated in FIG. 1 and designated by the
reference numeral 10. The trocar 10 is an access device commonly
used in surgeries to provide a working channel 12 across a body
wall and into a body cavity. The working channel 12 in this case is
defined by a cannula 14 and a seal housing 16. Within the seal
housing, a seal apparatus 18 is formed by a pair of opposing
rollers 21 and 23. These rollers 21 and 23 are typically formed of
a gel material 30 that provides the seal apparatus 18 with a high
degree of compliance, significant tear strength and exceptional
elongation. In this case, the gel rollers 21 and 23 are merely
representative of any gel structure adapted for use in a medical
device, such as the trocar 10.
[0039] The gel materials contemplated for the rollers 21 and 23
typically have a high melting temperature and exhibit a tacky
surface as previously discussed. These two properties, normally
considered disadvantages, become advantages in a method of
manufacture of the invention. In this case, the gel at a high
molding temperature and liquid state, is brought into contact with
a plastic molding material having a melting temperature less than
the molding temperature of the gel 30.
[0040] A roller mold 25 is illustrated in FIG. 2a with a plurality
of mold cavities or holes 27. In this case, the mold 25 is formed
entirely of a plastic material 26 which defines each of the
cylindrical mold cavities 27. The gel 30 in its high temperature
liquid state is poured into each of the mold holes 27 to form one
of the rollers 21, 23. At the high molding temperature, the gel 30
initially melts a thin layer 32 of the mold plastic 26 which cools
onto the gel surface as illustrated in FIG. 2b. In this process, it
is believed that the tacky properties of the gel 30 attract and
hold this thin layer 32 of plastic thereby resulting in a non-tacky
surface on the gel 30.
[0041] With the process of the invention, it is desirable that the
melting temperature of the plastic material 26 be only slightly
lower than the molding temperature of the gel 30. In one aspect,
the differential in temperature is in a range of about 20.degree.
F. to about 100.degree. F. It is anticipated that the higher this
temperature differential, the greater the melting of the plastic
material, thereby resulting in a thicker layer of the plastic
material on the surface of the gel.
[0042] In one example, a gel can be chosen with a gel molding
temperature of about 450.degree. F. A mold 25 formed of a
non-metal, plastic material such as low-density polyethylene (LDPE)
having a melting temperature of about 240.degree. F. is
particularly suited for this process. With the mold at room
temperature, and the liquid gel heated to its molding temperature,
the gel can be poured into the mold cavities. During and after this
molding step, the heat of the liquid gel at its molding temperature
is transferred to the surface of the plastic mold and in fact melts
a thin layer of the LDPE. At this point, the mold 25 and gel 30
rapidly cool and the melted LDPE forms the thin layer 32 on the
outer surface of the solidified gel 30. As the gel solidifies, its
naturally tacky surface attracts and holds the thin LDPE layer 32
to the outer surface. This thin layer 32 of LDPE provides the
resulting gel roller 21 with a non-tacky surface.
[0043] Using the mold formed entirely of the LDPE plastic will
gradually increase the size of the mold cavities 27 as succeeding
interior layers 32 of the LDPE are removed from the mold cavities
27. One way of addressing this problem is to provide a mold base 41
having a plurality of mold holes 43 as illustrated in FIG. 2c. In
this case, the mold holes 43 are formed with an axial pin 45 which
can be used to mold an axial hole through the center of the roller
21. Each of the mold holes 43 in the base 41 can then be lined with
an LDPE cylinder 47 providing a predetermined inside diameter for
the mold. In addition, an LDPE disc 50 can be mounted on the pin 45
and disposed in the bottom of each mold cavity 43 in the base 41.
In this case, the cylinder 47 and disc 50 provide the preferred
mold cavities 27 formed of LDPE and ready to receive the gel
30.
[0044] With this mold base 41 appropriately filled with the LDPE
cylinders 47 and discs 50, the molten gel 30 can be poured into the
top of each cylinder 47 to mold each roller 21 with a cylindrical
outer surface 52 and an axial pin 45. In the manner previously
discussed, the high temperature of the molten gel will melt a layer
off the inside of the LDPE cylinder 47 and disc 50 to provide a
non-tacky surface on each roller 21. One advantage provided by the
method illustrated in FIG. 3 is that the LDPE cylinders 47 can be
discarded after each molding process and replaced with new LDPE
cylinders 47 having the predetermined diameter.
[0045] It will be noted that in the absence of an LDPE disc on the
top of the mold cavity, one end 56 of the roller 21 will maintain
its tacky properties. Although the single tacky end 56 may not be
particularly detrimental in use, there are several methods that can
be implemented to make the tacky end 56 less tacky. For example,
this end 56 can be dabbed in a low friction powder 57, such as
PTFE, as shown in FIG. 3. Also, the tacky end 56 can be lubricated
to make it less tacky. As a third alternative, the tacky end 56 of
the roller 21 can be mounted in the trocar 10 adjacent to a low
friction disc 58 as illustrated in FIG. 4.
[0046] An alternative method for constructing the rollers 21, 23
with a non-tacky surface might involve the use of co-extrusion
techniques. In such a process, illustrated in FIG. 5, an elongate
sleeve 61 of LDPE can be extruded around the molten gel 30. In this
case, the gel 30 can be pressurized to control the diameter of the
filled sleeve 61. After the filled sleeve 61 is permitted to cool,
it can be radially cut into individual segments 62 having a
predetermined length as illustrated in FIG. 5. The gel 30 can be
removed by merely squeezing the sleeve 61 and pulling the gel 30
from the sleeve. Once removed, the gel roller 21 will have an outer
cylindrical surface 63 with an LDPE coating 65, and a pair of
opposing ends 67 and 70. In this process, both of the ends 67 and
70 of the roller 21 will be uncoated and will therefore have tacky
surfaces. These two ends 67, 70 can be addressed in the manner
previously discussed with reference to the roller end 56 in FIG.
3.
[0047] Another process which might be used to eliminate the tacky
ends of the roller 21, might be an injection molding process such
as that illustrated in FIG. 6. In this case both a mold base 72 and
a mold top 74 are provided to receive an LDPE cylinder 74 and a
pair of LDPE discs 76 and 78, one on each end of the cylinder 74.
Rather than pouring the molten gel 30 into the open top of the
cylinder as illustrated in FIG. 2, the molten gel 30 in this
process would be injected into the LDPE mold cavity 43. The
resulting gel roller 21 would have all of its surfaces, including
both ends, coated with a thin layer of LPDE.
[0048] The foregoing processes have been discussed with respect to
a single plastic, namely low density polyethylene. It is apparent
that other types of plastics might be similarly used to provide the
desired non-tacky surface for the gel compounds. Other plastics
which might be of advantage in this process could include for
example, PVC, ABS, acrylic, polycarbonate, clear polycarbonate,
"Delrin" (a trademark of Dupont), acetyl, polypropylene, and high
density polyethylene (HDPE). Of this group of plastics, the HDPE
appears to reduce the tackiness of the gel surface to the greatest
extent.
[0049] Other types of coatings can be applied to either a tacky or
non-tacky surface of the roller 21. One highly lubricious coating
is that manufactured and sold by Para Tech Coating, Inc. under the
trademark "Parylene". It has been found that this material can be
applied to the surface of the roller 21 by processes including
vacuum deposition in a chamber 81 (FIG. 7), dipping on a tray 83
(FIG. 8) and spraying on a shelf 85 (FIG. 9). A highly lubricious
coating, such as Parylene may also be applied in a tumbler 87 as
illustrated in FIG. 10. In this case, the rollers 21, 23 being
tumbled must already have a non-tacky surface in order to remain
separate during the tumbling process.
[0050] Another apparatus and method for addressing the natural
tacky properties of a gel seal is discussed with reference to FIG.
11. In this view, a medical device in the form of a hand port is
adapted to overlay a body wall, such as an abdominal wall 92, and
to provide sealed access to a body cavity, such as an abdominal
cavity 93, for a surgical instrument, such as a surgeon's hand
94.
[0051] In this embodiment, the hand port 90 includes a rigid or
semi-rigid base structure 96 in the form of a ring 98. A gel
material 101, of the types previously discussed, can be molded into
the ring 98 with portions 103 of the gel 101 defining a slit 105.
This slit 105, which is of particular interest in one aspect of the
invention, forms part of a working channel 107 that extends through
the abdominal wall 92 and into the abdominal cavity 93.
[0052] In this embodiment, the ring 98 is similar to the cannula 14
and seal housing 16 discussed with reference to FIG. 1a, in that it
is disposed around the working channel 107 and is adapted to form a
seal 110 with the abdominal wall 92.
[0053] A second seal 112 is formed between the gel material 101 and
the ring 98 so there is no communication between the abdominal
cavity 93 and regions exterior of the abdominal wall 92 as long as
the slit 105 remains closed. In this manner, the hand port 90
functions as a zero seal in the absence of the surgeon's hand 94,
or any other medical instrument.
[0054] The highly advantageous properties of the gel material 101
are particularly beneficial in the hand port 90, where they provide
a high degree of compliance together with elongation or stretch as
great as 1500 percent. Thus, the gel material 101 is ideally suited
to form a zero seal in the absence of the surgeon's hand 94, or an
instrument seal in the presence of the surgeon's hand 94. It can be
seen that the gel material 101 is similar to that previously
discussed with respect to the rollers 21 and 23 in FIG. 1a. In that
regard, the gel material 101 is disposed in the base structure and
forms the second seal 112 with the base structure. The gel material
101 will typically have the tacky properties in its natural state,
as previously discussed.
[0055] In order to address these tacky properties in the hand port
90, and also with respect to the trocar 10 of FIG. 1a, a film 14
can be applied to the surface of the gel material 101. This is
particularly advantageous with respect to the portions 103 where
the film 114 lines the working channel 107 through the hand port
90. When the film 114 is applied to any surface of the gel material
101, it functions to mask the tacky properties of the gel material
101 greatly facilitating handling of the hand port 90 during
manufacture. But in the particular location where the film 114 is
applied to the portions 103 defining the slit 105, the gel not only
masks the tacky properties, but also facilitates movement of the
medical instrument such as the surgeon's hand 94 into and through
the working channel 107. In certain preferred embodiments, the film
114 is formed by a fluoropolymer, such as polytetrafluoroethylene
(PTFE). In one method of manufacture, the film 114 is applied as a
PTFE powder. In other processes, the film 114 can be applied as a
PTFE tape.
[0056] One advantage associated with the PTFE film 114 is the
adhesive properties which this material exhibits with respect to
the gel material 101. Although not fully understood, it is believed
that the mineral oil present in a typical gel 101 is highly
attracted to the PTFE where it facilitates adhesion between the gel
material 101 and the film 114.
[0057] Another advantage associated with the PTFE film 114 is
associated with its stretchability or elasticity. While the film
114 is desirable to mask the tacky properties of the gel 105, it is
important that the elongation properties of the gel be maintained.
It has been found that the elongation of the gel material 101, up
to 1500 percent, is generally matched by the elongation or
stretchability of the PTFE film 114. Thus, the gel 101 and PTFE
film 114 can be stretched about 1000 percent, and perhaps as much
as 1500 percent, from an original state to a stretched state
without breaking the film 114, and returned from the stretched
state to the original state.
[0058] Although the PTFE film 114 masks the tacky properties of the
gel, it is not necessarily lubricious. If this lubricious property
is desired in addition to the non-tacky properties, the film 114
can be coated with a lubricant 116, such as the Parylene and other
lubricants previously discussed.
[0059] It will be understood that many other modifications can be
made to the various disclosed embodiments without departing from
the spirit and scope of the invention. For these reasons, the above
description should not be construed as limiting the invention, but
should be interpreted as merely exemplary of embodiments.
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