U.S. patent application number 12/899304 was filed with the patent office on 2011-01-27 for molded insulating hinge for bipolar instruments.
Invention is credited to Dennis J. Harvilla, Joe D. Sartor.
Application Number | 20110018164 12/899304 |
Document ID | / |
Family ID | 23079352 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110018164 |
Kind Code |
A1 |
Sartor; Joe D. ; et
al. |
January 27, 2011 |
Molded Insulating Hinge for Bipolar Instruments
Abstract
An electrosurgical instrument includes a pair of first and
second elongated shafts each having an end effector attached to a
distal end thereof and a handle. The handle is movable from a first
position wherein the end effectors are disposed in spaced relation
relative to one another to a second position wherein the end
effectors are closer relative to one another. Each of the elongated
shafts includes a hinge plate which mounts atop a pivot assembly
for effecting movement of the end effectors relative to one
another. The instrument also includes a hinge assembly made from an
overmold composition which encapsulates and secures the hinge
plates and the pivot assembly. The overmold composition is made
from an electrically insulating material which insulates the end
effectors from one another.
Inventors: |
Sartor; Joe D.; (Longmont,
CO) ; Harvilla; Dennis J.; (Lafayette, CO) |
Correspondence
Address: |
TYCO Healthcare Group LP;Attn: IP Legal
5920 Longbow Drive, Mail Stop A36
Boulder
CO
80301-3299
US
|
Family ID: |
23079352 |
Appl. No.: |
12/899304 |
Filed: |
October 6, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11491824 |
Jul 24, 2006 |
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12899304 |
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10473618 |
Sep 29, 2003 |
7103947 |
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PCT/US02/11100 |
Apr 5, 2002 |
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11491824 |
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60281924 |
Apr 6, 2001 |
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Current U.S.
Class: |
264/242 |
Current CPC
Class: |
Y10T 29/4998 20150115;
A61B 18/1445 20130101; A61B 2017/2939 20130101; Y10T 29/24
20150115; Y10T 29/49888 20150115; A61B 2018/126 20130101 |
Class at
Publication: |
264/242 |
International
Class: |
B29C 47/02 20060101
B29C047/02 |
Claims
1. A method of forming a hinge assembly comprising the steps of:
providing a pair of first and second elongated shafts each having
an end effector attached to a distal end thereof, a handle and a
hinge plate, the handle for effecting movement of the end effectors
relative to one another, the hinge plate of the first elongated
shaft and the hinge plate of the second elongated shaft mountable
about a pivot pin having a reinforcing portion; mounting the
elongated shafts to a die block; introducing an overmold
composition into the die block to encapsulate at least a portion of
the hinge plates; extruding an amount of the overmold composition
through the pivot pin to a side of the hinge plate of the second
elongated shaft opposite the hinge plate of the first elongated
shaft around the reinforcing portion of the pivot pin to form a
retention tab; and curing the overmold composition to form a hinge
assembly.
2. A method according to claim 1, wherein after a portion of the
overmold composition is extruded around the reinforcing portion of
the pivot pin, the method further comprises stamping the retention
tab against a side of the hinge plate of the second elongated
shaft.
3. A method according to claim 2, wherein the step of stamping
secures the hinge plates in close abutment relative to one another
about the pivot pin.
4. A method according to claim 2, wherein the step of stamping
secures the hinge assembly by mechanically engaging a portion
thereof to one of the hinge plates.
5. A method according to claim 1, wherein each of the hinge plates
mounts atop the pivot pin for effecting movement of the end
effectors relative to one another and wherein the step of securing
the hinge assembly between the hinge plates and mechanically
engaging a portion of the hinge plate includes biasing the end
effectors in a predetermined open, closed or intermediary
position.
6. A method according to claim 1, wherein an outer surface of the
hinge plate of the second elongated shaft includes at least two
interfaces that mechanically engage the retention tab.
7. A method according to claim 1, wherein the pivot includes a
series of undulations about an outer periphery thereof configured
to strengthen mechanical interfacing of the overmold composition to
the pivot pin.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of, and claims the
benefits of and priority to, U.S. patent application Ser. No.
11/491,824, entitled "MOLDED INSULATING HINGE FOR BIPOLAR
INSTRUMENTS" filed on Jul. 24, 2006, now U.S. Patent Application
Publication No. US2006/0264922 A1, which is a division of U.S.
patent application Ser. No. 10/473,618, filed on Sep. 29, 2003, now
U.S. Pat. No. 7,103,947, filed as a 35 U.S.C. .sctn.371 application
of international application PCT/US02/11100, filed on Apr. 5, 2002,
published as WO2002/080798, "MOLDED INSULATING HINGE FOR BIPOLAR
INSTRUMENTS" on Oct. 17, 2002, which claims the benefits of and
priority to U.S. Provisional Patent Application Ser. No. 60/281,924
entitled: "MOLDED INSULATING HINGE FOR BIPOLAR INSTRUMENT" which
was filed on Apr. 6, 2001 by Sartor et al. The entire contents of
each of the foregoing applications are hereby incorporated by
reference herein.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to joints and hinges which
connect movable components of an electrosurgical instrument and
methods for fabricating hinges for movable components of an
electrosurgical instrument. More particularly, the present
disclosure relates to an easily customizable hinge made from a
plastic overmold composition which connects two end effectors for
relative movement therebetween. The present disclosure also relates
to a method for fabricating the overmolded hinge.
[0004] 2. Background of Related Art
[0005] Typically, joints and hinges for electrosurgical instruments
which connect movable components are formed from an insulating
material to prevent shorting between component parts and/or prevent
the formation of alternate current paths through the instrument. As
such, instrument designers have manufactured electrosurgical
instruments which involve complex rotating hinge configurations to
isolate, insulate and/or control the electrosurgically active areas
of the instrument. For example, traditional metal hinge
configurations typically include multiple independent subassemblies
which are overmolded with plastic material having high bond
strengths. These separately overmolded subassemblies are
mechanically integrated and arranged in a series of manufacturing
steps that often require tightly controlled and time consuming
processes to achieve proper jaw alignment and reliable and
consistent gap separation between electrodes. Moreover, additional
steps are often undertaken to control other parameters associated
with the rotational movement about the hinge, e.g., friction,
torque, etc.
[0006] Thus, a continuing need exists for a simple and effective
insulating hinge that can be readily integrated into the
manufacturing process to electrically isolate the movable
components of an electrosurgical instrument. Further need exists
for the development of a simplified manufacturing process which
effectively fabricates an electrosurgical instrument which includes
an insulated hinge that isolates and integrates the electrically
active components of the instrument and results in the repeated
formation of a reliable and easily customizable instrument which
meets specific tolerance requirements for proper jaw alignment and
gap distances.
SUMMARY
[0007] An electrosurgical instrument includes a pair of first and
second elongated shafts each having an end effector attached to a
distal end thereof and a handle. The handle is movable from a first
position wherein the end effectors are disposed in spaced relation
relative to one another to a second position wherein the end
effectors are closer relative to one another. Each of the elongated
shafts includes a hinge plate which mounts atop a pivot assembly
for effecting movement of the end effectors relative to one
another. The instrument also includes a hinge assembly which is
overmolded to encapsulate and secure the hinge plates and the pivot
assembly. The hinge assembly is made from an electrically
insulating material which insulates the end effectors from one
another.
[0008] Preferably, the hinge assembly is made from a composition of
materials selected from the group consisting of: polyamides, nylon,
arcylanitride-butane nitro styrene acetyl, polyesters,
syndiotactic-polystryrene (SPS), polybutylene terephthalate (PBT),
polycarbonate (PC), acrylonitrile butadiene styrene (ABS),
polyphthalamide (PPA), polymide, polyethylene perephthalate (PET),
polyamide-imide (PAD, acrylic (PMMA), polystyrene-(PS and HIPS),
polyether sulfone (PES), aliphatic polyketone, acetal (POM)
copolymer, polyurethane (PU and TPU), nylon with
polyphenylene-oxide dispersion and acrylonitrile styrene acrylate.
In another embodiment, the hinge assembly is made from a
composition of lubricating materials selected from the group
consisting of: silicon, molybdenum disulfide and light olefins.
[0009] In one embodiment, the pivot assembly includes a pivot pin
integrally associated with a first of the hinge plates and a pivot
hole formed within a second of the hinge plates. Preferably, the
pivot pin is made from an electrically insulating material. In
another embodiment, the overmold composition of the hinge assembly
is disposed between the pivot pin and the pivot hole to
electrically insulate each of the hinge plates from one
another.
[0010] In yet another embodiment, the hinge assembly includes a
retention tab which secures the hinge assembly between the hinge
plates. Preferably, the retention tab is formed during the overmold
process as the overmold composition leaches through the pivot pin
to form a tab on the outer-facing surface of the hinge plate. Once
the retention tab cures, the hinge assembly is securely held
between the hinge plates. In still yet another embodiment, the
hinge assembly includes a stop member for limiting the movement of
the end effectors relative to one another.
[0011] The present disclosure also relates to a method of forming a
hinge assembly and includes the steps of: providing a pair of first
and second elongated shafts each having an end effector attached to
a distal end thereof, a handle and a hinge plate. The handle is
dimensioned to effect movement of the end effectors relative to one
another. The method further includes the step of mounting the
elongated shafts to a die block, introducing an overmold
composition into the die block to encapsulate at least a portion of
the hinge plates and curing the overmold composition to form the
hinge assembly.
[0012] In another embodiment, the method further includes the step
of: selectively positioning at least one spacer between the end
effectors to maintain a gap distance between the end effectors
during the molding and curing step.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Preferred embodiments of the presently disclosed surgical
instrument having a molded insulating hinge assembly are described
herein with reference to the drawings, wherein:
[0014] FIG. 1 is a perspective view of one embodiment of a bipolar
forceps having a molded insulating hinge assembly constructed in
accordance with the present disclosure;
[0015] FIG. 2A is an enlarged, right, side view of an end effector
of the bipolar forceps of FIG. 1 prior to overmolding;
[0016] FIG. 2B is a bottom view of the end effector of FIG. 2A;
[0017] FIG. 2C is a left, side view of the end effector of FIG.
2A;
[0018] FIG. 3A is an enlarged, right, side view of a second end
effector of the bipolar forceps of FIG. 1 prior to overmolding;
[0019] FIG. 3B is a bottom view of the end effector of FIG. 3A;
[0020] FIG. 3C is a left, side view of the end effector of FIG.
3A;
[0021] FIG. 4 is an exploded, perspective view of the bipolar
instrument of FIG. 1; and
[0022] FIG. 5 is a perspective view of the embodiment shown in FIG.
1 shown with a spacer disposed between a pair of jaw members to fix
a specific gap distance during the overmolding process.
DETAILED DESCRIPTION
[0023] Referring now in specific detail to the drawings in which
like reference numerals identify similar or identical elements
throughout the several views, and initially to FIGS. 1-3C, one
particular embodiment of an electrosurgical instrument 10 includes
two elongated shafts 30 and 60 each having a distal end effector
32, 62 and a proximal handle portion 34 and 64, respectively.
Handles 34 and 64 are movable relative to one another about a hinge
assembly 20 from a first position wherein the distal end effectors
32, 62 are positioned in spaced relation relative to one another to
a second position in which the distal end effectors 32, 62
cooperate to grasp tissue therebetween. It is envisioned that
handles 34 and 64 may take any design configuration suitable for
manipulation or control of the surgical instrument 10.
[0024] Each distal end, e.g., 32, has a jaw member 36 disposed at
the distal end thereof which includes a tissue grasping surface 38
dimensioned to cooperate with the other jaw member, e.g., 66, and
other tissue grasping surface, e.g., 68, to grasp tissue and other
luminal structures upon actuation of the handles 34 and 64. The jaw
members 36, 66 each also include a hinge plate 35, 65,
respectively, which cooperate to support opposing sides of the
hinge assembly 20 as explained in more detail below. Hinge plate 35
includes a pivot pin 74 which mechanically engages a corresponding
pivot hole 61 disposed within hinge plate 65 to form pivot assembly
70.
[0025] Hinge assembly 20 as described herein relates to one
particular embodiment for use with a bipolar electrosurgical
forceps 10, however, it is contemplated that the presently
disclosed hinge assembly 20 could be dimensioned for use with other
electrosurgical instruments including vessel sealing instruments,
grasping instruments, ablation instruments, electrosurgical
scissors, etc. Moreover, it is also envisioned that the hinge
assembly 20 may be configured for use with a broad range of other
non-electrical surgical instruments such as pliers, scissors,
shears, crimpers and wire cutters.
[0026] Preferably, hinge assembly 20 is made from a composition 25
of insulating material such as plastic which is overmolded to
encapsulate the hinge plates 35, 65 during the manufacturing
process. As best seen in FIG. 2C, pivot pin 74 includes a
reinforcing portion 72 which allows the mold composition 25 to
extrude through the pivot pin 74 of hinge plate 35 to an opposite
side 63 of hinge plate 65 to form a retention tab 50. More
particularly, after a significant amount of mold composition 25 is
extruded around the reinforcing portion 72 of the pivot pin 74, the
retention tab 50 is stamped against the opposite side 63 of hinge
plate 65 to secure the hinge plates 35 and 65 in close abutment
about the pivot assembly 70. As can be appreciated in this
embodiment of the present disclosure, the mold composition 25 is
contiguous with the exterior of the hinge plate 35 through aperture
31, around reinforcing portion 72 and with the retention tab 50
which securely engages the hinge assembly 20 between the hinge
plates 35, 65.
[0027] As can be appreciated, both the mold composition 25 and the
retention tab 50 are formed during the same molding step resulting
in the formation of the hinge assembly 20. It is envisioned that
once cured, the retention mechanism 50 forms a structural limit
that at least partially controls the alignment of the distal end
effectors 32 and 62 as well as the amount of pivotal movement
between the jaw members 36 and 66. Alternatively, the retention tab
50 may be made from the same or a different mold composition 25 and
is designed to mechanically engage the pivot pin 74 or the hinge
plate 65 to secure the hinge assembly between the hinge plates 35
and 65.
[0028] As best shown in the exploded view of FIG. 4, the formation
of the hinge assembly 20 in this manner electrically isolates the
two end effectors 32 and 62 and the component parts thereof
enabling a user to selectively apply electrosurgical energy through
the tissue and between the jaw members 36 and 66 as needed. More
particularly, during the overmold process, the plastic cures about
the outer periphery 75 of pivot pin 74 which electrically isolates
hinge plate 35 from hinge plate 65. As can be appreciated, the
retention tab 50 which, as mentioned above, is also formed of
plastic which extrudes through pivot pin 74 to the opposite side 63
of hinge plate 65, not only retains the two hinge plates 35 and 65
in secure abutment about the pivot assembly 70 but also
electrically isolates the hinge plates 35 and 65 from one
another.
[0029] Because the presently disclosed hinge assembly 20 is
preferably formed during a single manufacturing step, it can be
easily customized and dimensioned to suit a particular purpose or
to achieve a particular result. For example, the alignment of the
jaw members 36 and 66, e.g., jaw angle or jaw offset, may be easily
customized depending upon a particular purpose. Moreover, the
formation of a gap distance between the jaw members 36, 66 may be
easily customized. For example, the hinge assembly 20 may be molded
or formed during the manufacturing process such that the jaw
members 36 and 66 maintain a consistent and specific gap distance
within the range of about 0.001 inches to about 0.005 inches at
closure. The formation of the gap distance is discussed below with
particular reference to FIG. 5.
[0030] Generally, hinge 20 is formed from an overmold composition
containing a joint-forming base resin material and a lubricating
component. Hinge-forming materials for use herein can be any
commercially available materials known to one skilled in the art
for toughness and strength as well as being capable of injection
molding. Suitable joint-forming base resin materials include, but
are not limited to, polyamides such as nylon, arcylanitride-butane
nitro styrene; acetyl, polyesters, etc. Preferably, the overmold
composition is made from a plastic or plastic-based material having
a Comparative Tracking Index of about 300 volts to about 600 volts
for dielectric isolation. For example, the overmold composition 25
may be made from a group of materials selected from a group which
includes Nylons, Syndiotactic-polystryrene (SPS), Polybutylene
Terephthalate (PBT), Polycarbonate (PC), Acrylonitrile Butadiene
Styrene (ABS), Polyphthalamide (PPA), Polymide, Polyethylene
Terephthalate (PET), Polyamide-imide (PAT), Acrylic (PMMA),
Polystyrene (PS and HIPS), Polyether Sulfone (PES), Aliphatic
Polyketone, Acetal (POM) Copolymer, Polyurethane (PU and TPU),
Nylon with Polyphenylene-oxide dispersion and Acrylonitrile Styrene
Acrylate. Alternatively, it is envisioned that a non-plastic
insulating material, e.g., ceramic, may be used in lieu of or in
combination with one or more of the above-identified materials to
facilitate the manufacturing process and possibly contribute to
more uniform and consistent transfer of electrosurgical energy
across the tissue.
[0031] Suitable lubricating components for use with the base resin
material include a broad range of materials known to compliment the
overmold composition to provide mold having a low bonding strength
with good surface lubricating qualities. Such lubricating
components include, but are not limited to, silicon-like materials,
molybdenum disulfide, light olefins, etc. Depending upon the
overall composition of the base resin material being used, a
lubricating component may not be required.
[0032] It is also anticipated that additional materials may be
employed in combination with the above materials to achieve
suitable levels of toughness and strength in the molded hinge 20.
These additional materials may include, for example, reinforcing
agents such as glass fibers, ground glass, or elongated glass
fibers. For example, in one particular embodiment, hinge assembly
20 is formed from a commercially available nylon material having
about 2.5 wt. % glass fiber reinforcing material and a silicone
lubricating component in the range of about 0.75 wt. % to about 10
wt. %. In another embodiment, hinge assembly 20 may be formed from
a nylon having glass fiber reinforcing material in the range of
about 5 wt. % to about 40 wt. % and silicone in the range of about
2 wt. % to about 8 wt. %.
[0033] While silicone or other lubricating agents are typically
used in injection molding processes, it has been found that the
amount of silicone should be tightly controlled to provide uniform
and consistent curing and operating efficiencies. It is envisioned
that the silicone component of the overmold composition creates a
sustained lubricated surface at the interface between hinge plates
35 and 65. It has also been found that increasing the level of
silicone, e.g., amounts greater than 2 wt. %., in the joint-forming
material of hinge assembly 20, produces an overmold composition
having a low bond strength. As can be appreciate, although the
overmold composition 25 has a low bond strength to the surrounding
metals, i.e., elongated shafts 30, 60 and hinge plates 35, 65, the
low bonding strength is offset by a the mechanical advantages of
the retention tab 50 and aperture 31.
[0034] As mentioned above, the presently disclosed hinge assembly
20 may be formed during a single manufacturing step and may be
easily customized depending upon a particular purpose or to achieve
a particular result. For example, parameters such as self
lubrication of the hinge assembly 20, hinge assembly 20 strength,
jaw member 36, 66 alignment, e.g., jaw angle or jaw offset,
isolation of the jaw members 36 and 66 during electrosurgical
application and the formation of a gap distance between the jaw
members 36 ad 66 (or electrodes or probes attached to the jaw
members 36 and 66) may be easily achieved.
[0035] The present application is not limited to the above
identified materials, but contemplates a broad range of overmold
composition 25 in varying combinations and amounts that provide an
overmold composition suitable for the function of hinge assembly
20. It is envisioned that applications described herein relating to
the injection overmolding of thermoplastic polyamides, for example,
may be translated into other areas including, but not limited to
other engineering plastic materials, engineering metals and
ceramics that may be selectively applied in varying insulative as
well as mechanical applications.
[0036] The overmold composition 25 of the present disclosure is
configured to create a tough and strong hinge assembly 20 by at
least partially encapsulating the hinge plates 35 and 65 and the
pivot assembly 70 (and the various components thereof. The overmold
composition 25 provides suitable strength as a result of its
continuity of encapsulation as well as the ability of the overmold
composition 25 to form surface features which are specifically
dimensioned to improve the strength of the hinge assembly 20 once
cured. For example, features within the pivot pin 74 and features
within the pivot hole 61 may be provided to increase the overall
strength of the instrument and/or hinge assembly 20, e.g. notches,
detents, cavities, overmolded posts, etc. Further, structural
strength for the hinge assembly 20 may be gained by coating or
filling features defined in the surface of the hinge plates 35, 65
to augment the mechanical bonding of the plastic mold with the
hinge plates 35, 65, pivot pins 74 and pivot holes 61. For example,
surface undulations such as lip structures, overhanging shapes,
concave shapes, or cantilevered structures having different
geometric shapes may be employed to mechanically engages the hinge
assembly 20 to the hinge plates 35.
[0037] Preferably, the elongated shafts 30, 60 are made from a
stainless steel material. However, other metal alloys, plastics,
ceramics, or composites are also contemplated including
combinations of one or more plastics, composites, metals, graphite,
carbon-coated plastics and/or any other conductive materials which
are well suited for overmolding purposes. Preferably, the elongated
shafts 30 and 60 are die-cut, stamped, or micro-machined such that
the end effectors 32 and 62 and the hinge plates 35 and 65 from
integral parts thereof. As can be appreciated, making these
elements integral and utilizing the overmold hinge assembly 20 as
presently disclosed herein greatly simplifies the overall
manufacturing and assembly processes.
[0038] Instrument 10 may also include surface treatments (e.g.,
nylon powder coatings, chemical treatments, nickel alloy coatings,
mechanical finish treatments, shrink tubing, etc.) which facilitate
manipulation of the tissue structures, enhance conduction of
electrosurgical energy across the jaw members 36, 66 and/or reduce
the likelihood of inconsistencies across the treatment area which
may lead to collateral tissue damage, flashover, thermal spread,
arcing, etc.
[0039] Preferably, the thickness of the hinge assembly 20 can be
selectively altered depending upon a particular purpose or for use
with a certain instrument. The ultimate thickness and strength of
the overmold composition 25 is also related to the viscosity of the
overmold composition 25 and the duration and temperature of the
curing process. For example, the hinge assembly 20 may include a
range of thickness from about 0.020 to about 0.040 inches in
thickness. The thickness of the overmold composition 25 also
depends on mechanical load bearing and dimensional requirements of
a particular application.
[0040] As best shown in FIG. 4, the outer periphery 75 of pivot pin
74 provides a basis for the formation of additional molded material
around the pivot pin 74 which not only electrically insulates the
jaw members 36 and 66 from one another but also reduces the chances
of the pivot slipping or rotating when torquing, cross-loading, or
shearing forces are applied during the normal use of instrument
10.
[0041] It is envisioned that the hinge assembly may be designed as
a more complex mechanism and/or may be designed to encapsulate a
more complex pivoting mechanism. For example, it is contemplated
that the hinge assembly 20 may include various multiple-link
systems such as a two-bar, three-bar or four-bar linkage or may
include a two-step hinge. The pivot pin 74 and/or the pivot hole 61
may also be dimensioned in a variety of different shapes and sizes
depending upon a particular purpose or to achieve a particular
result, e.g., cam and cam-follower, arcuate, elliptical, etc. It is
also envisioned that the hinge assembly 20 may include one or more
stop members 19 which limit the overall distance that the jaw
members 36, 66 may pivot in either the open or closed positions.
The stops 19 may be configured in steps or as a cantilevered
feature to define more than one gap distance between jaw members 36
and 66.
[0042] In one embodiment, retention tab 50 may be configured to
mechanically engage a portion of the hinge plate 65 and/or pivot
pin 74 which is contemplated to serve two purposes: 1) to
mechanically retain the retention tab 50 against the hinge plate 65
and further secure the instrument 10 as assembled; and 2) to bias
the pivot assembly 70 to a predetermined open, closed, or
intermediary position. For example, the outer-facing surface 63 of
hinge plate 65 may be provided with slots or grooves (not shown)
which mechanically engage the retention tab 50.
[0043] With respect the to particular surgical instrument of FIGS.
1-4, i.e., bipolar forceps 10, first and second conductive wires 41
and 45 are each electrically coupled to a respective distal end
effector 32 and 62 at one end thereof and ultimately connected to
an electrosurgical generator (not shown) at the opposite end
thereof. The first electrical conductor 41 (see FIG. 2A) connects
the first jaw member 36 to a first electrical potential and the
second electrical conductor 45 (see FIG. 3A) connects the second
jaw member 66 to a second electrical potential. Preferably, the
first and second electrical conductors 41 and 45 are disposed
within longitudinally-oriented channels defined within elongated
shafts 30 and 60, respectively. The channels are preferably
oriented and dimensioned to facilitate mechanical engagement of the
electrical conductors 41 and 45 with the respective jaw members 36
and 66 in such a manner to allow free, pivotable movement of the
jaw members 36 and 66 relative to one another. Preferably, the
cable leads are attached to the electrically conductive jaw members
36 and 66 by a crimp-like electrical connection (not shown). As
mentioned above, the hinge assembly 20 includes at least one stop
19 which abuts against elongated shafts 30, 60 to prevent
over-rotation of the jaw members 36 and 66 to avoid straining the
electrical leads.
[0044] Preferably, hinge assembly 20 is manufactured in a single
injection molding or manufacturing process step in which elongated
shafts 30 and 60 are mounted atop a die block within an injection
molding machine. The overmold composition 25 of the hinge assembly
20 is then injected between the jaw members 36 and 66 to
encapsulate the hinge plates 35 and 65 and the pivot assembly 70.
As mentioned above, the hinge assembly 20 is strengthened by the
continuity of the plastic overmold composition 25 which extrudes
through the pivot pin 74 and pivot hole 61 to form the retention
tab 50. Thus, in one particular embodiment, the hinge assembly 20
is completely formed by overmold composition flowing around and
through the various components parts of the hinge assembly 20 and
the pivot assembly 70. As mentioned above, the retention tab may be
a separate component made from the same or a similar composition
which is dimensioned to mechanically engage the pivot pin 74 or the
outer-facing surface 63 of the hinge plate 65.
[0045] As mentioned briefly above and as shown in FIG. 5, a spacer
100 may be positioned between jaw members 36 and 66 prior to the
overmolding process. The spacer 100 sets a fixed gap distance "G"
between jaw members 36 and 66 at closure (i.e., when the jaw
members 36 and 66 are disposed in the closed or tissue grasping
position) by limiting the formation of the stop 19 during the
overmolding process. As can be appreciated, different and/or
customized gap distances "G" between the jaw members 36 and 66 can
be easily formed depending upon a particular purpose or to achieve
a particular result.
[0046] The presently disclosed overmolding process also enables the
manufacturer to customize the precise alignment of the jaw members
36 and 66 relative to one another. Thus, in applications in which
the alignment of jaw members 36 and 66 is critical, such as for
shearing, cutting and sealing, the accuracy, alignment and
configuration of the hinge assembly 20, pivot assembly 70 and jaw
members 36 and 66 can be easily customized. Further, the presently
disclosed process also provides a repeatable and reliable alignment
tool for mass manufacturing of surgical instruments according to
specific tolerances.
[0047] From the foregoing and with reference to the various figure
drawings, those skilled in the art will appreciate that certain
modifications can also be made to the present disclosure without
departing from the scope of the present disclosure. For example, it
is contemplated that hinge assembly 20 can be configured to join a
plurality of different components or subassemblies in the assembly
depending upon a particular purpose. Moreover, the outer periphery
75 of pivot pin 74 could also include features such as a series of
undulations or knurling, or a series of radially aligned cavities
having features within those cavities that strengthen the
mechanical interface of the overmold composition to the pivoting
assembly 70.
[0048] In one embodiment, the instrument includes a conductive
strip (not shown) disposed through one shaft, e.g., shaft 30.
Electrosurgical wires or cables (not shown) from an electrosurgical
generator (not shown) connect the two electrical potentials to the
conductive strip. The opposite end of the conductive strip includes
one electrical connection to end effector 32 and a second
electrical connection to pivot assembly 70 which provides
electrical continuity to the opposite end effector 62. More
particularly, the second electrical connection of the conductive
strip makes contact across the moving junction of the pivot
assembly. It is not necessary that the conductive strip wrap around
the pivot pin 74 between the instrument halves because during the
molding process the conductive strip is forced into intimate
contact with the opposite end effector 62, i.e, the flow of the
uncured hinge material positions the conductive strip into contact
with end effector 62.
[0049] As a result thereof, secondary washers or force loading
devices are not required to initiate contact between the conductive
strip and the opposite end effector 62. The conductive strip my
also include a series of wave-like folds, e.g., accordion folds,
which give the conductive strip a spring-like quality and which
fosters contact with the opposite end effector 62 during and after
curing. As can be appreciated, this arrangement assures that a
moving or sliding contact is maintained between the conductive
strip and the end effector 62 during movement, i.e., pivoting, of
the end effectors relative to one another.
[0050] While several embodiments of the disclosure have been shown
in the drawings, it is not intended that the disclosure be limited
thereto, as it is intended that the disclosure be as broad in scope
as the art will allow and that the specification be read likewise.
Therefore, the above description should not be construed as
limiting, but merely as exemplications of preferred embodiments.
Those skilled in the art will envision other modifications within
the scope and spirit of the claims appended hereto.
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