U.S. patent number 3,911,766 [Application Number 05/469,967] was granted by the patent office on 1975-10-14 for box lock surgical instrument and method of its manufacture.
This patent grant is currently assigned to Pilling Co.. Invention is credited to John W. Fridolph, Rodney J. Kulp, Robert W. Wilson.
United States Patent |
3,911,766 |
Fridolph , et al. |
October 14, 1975 |
Box lock surgical instrument and method of its manufacture
Abstract
By electrically fusing a pin between the outer elements of a box
hinge, and thereafter performing the hardening step, stresses which
tend to cause instrument failures after a period of use are
eliminated. Even if the pin fractures during use, the fact that it
is fused to the outer elements of the box hinge prevents broken-off
parts of the pin from falling out of the instrument.
Inventors: |
Fridolph; John W. (Berlin,
NJ), Wilson; Robert W. (Dresher, PA), Kulp; Rodney J.
(Harleysville, PA) |
Assignee: |
Pilling Co. (Fort Washington,
PA)
|
Family
ID: |
23865738 |
Appl.
No.: |
05/469,967 |
Filed: |
May 15, 1974 |
Current U.S.
Class: |
76/101.1; 30/266;
81/416; 76/104.1; 606/208 |
Current CPC
Class: |
F16C
11/045 (20130101); B23K 9/007 (20130101); B23P
11/00 (20130101); B25B 7/06 (20130101); A61B
17/2816 (20130101); F16C 2316/10 (20130101); F16C
2226/36 (20130101) |
Current International
Class: |
B23P
11/00 (20060101); A61B 17/28 (20060101); B25B
7/06 (20060101); B23K 9/007 (20060101); B25B
7/00 (20060101); B21K 021/00 (); B25B 007/06 ();
A61B 017/28 () |
Field of
Search: |
;76/101,11A,104,14A
;30/266,267 ;128/321 ;81/416 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hinson; Harrison L.
Attorney, Agent or Firm: Smith, Harding, Earley &
Follmer
Claims
We claim:
1. The method of making a box lock surgical instrument comprising
the steps of:
providing first and second members, the first member having a
bifurcated portion at an intermediate location whereby its ends are
connected by two separate elements having a slot between them;
forming first and second aligned holes respectively in said
separate elements of the first member and a third hole in an
intermediate portion of said second member, the third hole
alignable with the holes in the first member when said intermediate
portion of the second member is positioned in the slot between said
separable elements;
with the intermediate portion of the second member positioned in
said slot, aligning the third hole with the first and second
holes;
inserting a pin through said first, second and third holes;
electrically fusing said pin at one end to one of the separate
elements of the first member for a sufficiently long period of time
to produce a weld having a 75 to 100 percent depth of penetration
in said one of the separate elements;
electrically fusing said pin at its other end to the other of the
separate elements of the first member for a sufficiently long
period of time to produce a weld having a 75 to 100 percent depth
of penetration in said other of the separate elements;
grinding the outside surfaces of the separate elements of the first
member to remove excess material resulting from the fusing steps;
and
hardening said instrument.
2. The method according to claim 1 in which the pin is provided
with a head sufficiently large to prevent its passing through the
holes of said separate elements.
3. The method according to claim 1 in which the instrument is
rotated in a plane transverse to the axis of the aligned holes
during fusion.
4. The method of making a box lock surgical instrument comprising
the steps of:
providing first and second members, the first member having a
bifurcated portion at an intermediate location whereby its ends are
connected by two separate elements having a slot between them;
forming, in a single drilling operation, first and second aligned
holes respectively in said separate elements of the first member
and a third hole in an intermediate portion of said second member,
the third hole being alignable with the holes in the first member
when said intermediate portion of the second member is positioned
in the slot between said separable elements;
with the intermediate portion of the second member positioned in
said slot, aligning the third hole with the first and second
holes;
inserting a pin through said first, second and third holes;
fusing said pin at one end to one of the separate elements of the
first member;
fusing said pin at its other end to the other of the separate
elements of the first member;
grinding the outside surfaces of the separate elements of the first
member to remove excess material resulting from the fusing steps;
and
hardening said instrument.
5. The method of claim 4 in which the drilling and fusion steps are
carried out while the instrument is mounted on a fixture.
6. The method of claim 4 in which the drilling and fusion steps are
carried out while the instrument is mounted on a fixture rotatable
in a plane transverse to the axis of drilling and in which rotation
of said fixture takes place during the fusion steps.
Description
BACKGROUND OF THE INVENTION
This invention relates to surgical instruments, and particularly to
the so-called "box lock" instruments. Instruments such as forceps,
hemostats, and clamps are often provided with box lock joints
particularly where a high degree of reliability and the very
accurate meeting of grasping members is required.
The box lock joint is a special hinge used in instruments of the
type comprising first and second members each having, at one end,
operative means such as a clamping or gripping jaw adapted to
cooperate with the operative means of the other member, and each
having at its opposite end manipulable means, typically a ring
handle, for controlling the movement of the operative means on the
same member. The first member has a bifurcated portion at an
intermediate location whereby its operative means and its
manipulable means are connected by two separate elements having a
slot between them. The second member extends through the slot with
its operative means and its manipulable means on opposite sides of
the bifurcated portion of the first member. A pin, extending across
the slot and through a hole in the portion of the second member
within the slot, completes the hinge and allows the operative means
to be controlled by the manipulable means for clamping, depending
on the nature of the particular instrument. The box lock joint is
generally preferred because of its strength, the low degree of play
which it allows, and its resistance to working loose. These
characteristics are of particular importance in special instruments
wherein the accurate cooperation of opposed operative means is
required. This is the case, for example, with surgical clamping
means having jaws specially designed to clamp tubular vessels of
the body with the avoidance of damage thereto such as those
described in U.S. Pat. No. 3,608,554, issued Sept. 28, 1971.
Heretofore, forceps and other surgical instruments having box lock
joints were typically made by producing aligned holes in the two
members to be joined, inserting a temporary pin, performing the
necessary bending operations as well as grinding and polishing
operations, removing the temporary pin, punching the holes in the
bifurcated portion of the first member to a square or star
configuration, hardening the first and second members, inserting a
second pin, swaging or peening the pin, and finally finishing the
instrument. Swaging of the pin following hardening results in the
setting up of stresses in the instrument which remain unrelieved
when the instrument goes into use. When the instrument is subjected
to the influences of superheated steam (autoclaving), repeated
mechanical loads under surgical conditions, and corrosion caused by
the various elements in the surgical environment, these stresses
eventually, if not in a very short time, manifest themselves as
cracks in and around the box lock joint. Instrument breakage often
occurs at the location of these cracks, and can constitute a
serious safety hazard if it takes place during surgery.
In some cases, the hinge pin is inserted and swaged prior to
hardening. However, peening is sometimes required to tighten the
pin when shrinkage occurs in the hardening process. This peening
results in stresses similar to those which occur when the pin is
swaged following hardening. The danger of breakage therefore exists
in instruments made by this alternative method.
The hinge pin itself is also susceptible to breakage. Although it
is not a common occurence, if a hinge pin in a conventional
instrument breaks, it is possible for a part of the pin to fall out
of the instrument while in use. In surgery, such an occurrence also
represents a serious hazard to the patient's safety.
In accordance with this invention, a pin having a head slightly
larger than the holes in the member having the bifurcated portion
is inserted into the aligned holes in the two members. The pin is
electrically fused in two steps, and thereby secured to the two
separate elements of the bifurcated portion, there being a circular
zone of fusion in each of the two separate elements having a
penetration depth desirable between 75 and 100 percent and
preferably 100 percent. Fusion preferably takes place in an inert
gas environment. The outer surfaces of the two separate elements of
the bifurcated portion are ground and polished, and the pin becomes
invisible. Hardening takes place after electric fusion. The process
produces a substantially stress-free box lock joint which is much
less likely to fail in use than box lock joints made in accordance
with conventional methods. In addition, if the hinge pin fractures,
it is prevented from falling out of the instrument by the fact that
it is fused to the elements of the bifurcated portion of the first
member.
The principal object of the invention, therefore, is to provide a
substantially stress-free box lock joint having greater durability
than conventional box lock joints. A second object of the invention
is to insure against the loss of the hinge pin or parts thereof in
the event of hinge pin breakage. Further objects of the invention
include the simplification of the manufacturing process and the
production of a box lock joint having as little play as possible.
Still other objects will be apparent from the following detailed
description when read in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a box lock clamp in accordance with
the invention;
FIG. 2 is a partially cut away side elevation of a square punched
box lock joint in accordance with the prior art;
FIG. 3 is a bottom plan view of the joint of FIG. 2;
FIG. 4 is a partially cut away side elevation of a star punched box
lock joint in accordance with the prior art;
FIG. 5 is a bottom plan view of the joint of FIG. 4;
FIGS. 6 through 9 are vertical sections taken through a box lock
joint in accordance with the invention, illustrating the successive
steps of manufacture;
FIG. 10 is a perspective view of a fixture used in the manufacture
of a box lock surgical instrument in accordance with the invention;
and
FIG. 11 is a vertical section of the fixture of FIG. 10.
DETAILED DESCRIPTION
In FIG. 1, a box lock surgical clamp generally indicated at 12
comprises a pair of members 14 and 16 joined together by a box lock
joint generally designated 18. A jaw 20 on member 14 is arranged to
cooperate with jaw 22 on member 16. Movement of the jaws toward and
away from each other is controlled by manipulable rings 24 and 26.
Latching means adapted to set the jaws in any desired one of a
number of discrete positions comprise ratchet 28 and cooperating
tooth 30 respectively on members 14 and 16.
Member 14 has a bifurcated portion at the location of the joint
whereby jaw 20 and ring 24 are connected by two separate elements
32 and 34 having between them a slot 36. Internally, slot 26 has
substantially flat, parallel sides. A portion 38 of member 16,
machined to conform with the flat inner surfaces of slot 36 extends
through the slot with jaw 22 and ring 26 on opposite sides of the
bifurcated portion of member 14. A hinge pin (not shown in FIG. 1)
extends across the interior of the slot and through a hole in
element 38. The hinge pin allows the jaws to be controlled by the
manipulation of rings 24 and 26.
As described thus far, the instrument is entirely conventional. In
manufacture in accordance with conventional methods, forged members
corresponding to members 14 and 16 of the finished product are
joined by spreading apart the elements corresponding to elements 32
and 34 of member 14, inserting member 16 between those elements,
and bringing elements 32 and 34 back to their normal relationship.
A hole is drilled through the elements corresponding to elements
34, 38 and 32, and a temporary pin is inserted to keep the parts in
alignment during formation of the jaws and other necessary bending
and machining operations. The temporary pin is then removed, and
the members corresponding to members 32 and 34 are punched to a
square configuration as shown in FIG. 3, or to a multiple-point or
"star" configuration as shown in FIG. 5. The elements of the
instrument are then hardened, and the final hinge pin is inserted
and swaged into place. Following swaging, final finishing of the
instrument takes place. FIGS. 2, 3, 4 and 5 illustrate two box lock
joints in accordance with the prior art. In FIG. 2, it will be
noted that the pin 40 is held in place only by reason of the fact
that the swaging step widens its ends to fill the square
configuration of the holes in the outer elements of the joint. This
is also the case in FIG. 4 in which the ends of pin 42 are swaged
to fill the six-pointed star configuration of the holes in the
outer elements of the joint. In either case, the pin depends on its
own integrity to hold it in place. Should it break by reason of a
material failure transverse to the longitudinal axis, the pin could
fall into the patient during an operation. As previously stated,
the box lock joint, as illustrated in FIGS. 2, 3, 4 and 5 is
subject to breakage by reason of the stresses produced by the
swaging operation.
FIGS. 6, 7, 8 and 9 illustrate successive steps in the production
of the fused box lock joint in accordance with the invention. As
shown in FIG. 6, a pin 44 having a head 46 is inserted into aligned
holes in the elements of the box lock joint, the inner element
being designated 48, and the outer elements being designated 50 and
52. The head 46 is larger in diameter than the hole in element 50,
and the pin is thus retained for the first fusing operation.
FIG. 7 illustrates the result of the first fusing operation. The
head is transformed into a weld 54 which securely fastens pin 44 to
element 50 of the joint. Weld 54 has a 100 percent depth of
penetration in element 50. This is not difficult to achieve, and
optimum fusion time for a given size of instrument can be easily
determined. When a 100 percent depth is reached, there is a
considerably time lag before the current tends to weld element 50
to element 48. Thus, there is considerable leeway in the range of
fusion time which will produce a good weld with 100 percent
penetration depth.
Following the first fusion step, the instrument is turned upside
down, and a second fusion step takes place which fuses the
protruding end of pin 44 to element 52, producing a weld 56, as
shown in FIG. 8, which is similar to weld 54.
Finally, the excess fused material is ground away, and the
instrument is subjected to any necessary final finishing steps and
polishing. The final operations produce smooth surfaces 58 and 60,
as shown in FIG. 9. The pin is invisible. Except for the fact that
the pin is invisible, the instrument made in accordance with the
invention resembles conventional instruments.
Preferably, a special fixture, such as that shown in FIGS. 10 and
11, is used for the drilling and fusion operations in accordance
with the invention. The fixture comprises a base 62 on which are
mounted specially shaped clamps including fixed clamps 64 and 66
and slidable clamps 68 and 70. The clamps hold the elements of the
instrument securely in a fixed position as shown for drilling of
the aligned holes. Base 62, as shown in FIG. 11, is provided with a
depression 72 for drilling and also in order to accommodate the
protruding end of the pin. The base is mounted on gearing including
gear 74 and pinion 76 for rotation of the base during fusion to
insure a uniform weld. An electrode 78 is shown in FIGS. 10 and 11
in position just above the pin.
By way of specific example, a DeBakey ring handle bulldog clamp
having an overall length of about 5 inches and consisting of 410
stainless steel is assembled in accordance with the invention using
a headed 0.075 inch diameter, 0.195 inch long pin, also of 410
stainless. The instrument is drilled to 0.078 inches. Fusion takes
place at 32 amperes for 12 seconds with the electrode centered
above the pin and spaced 0.037 inches from the head of the pin. The
base is rotated at 10 rpm so that it rotates through two complete
revolutions during each fusing step. The foregoing produces a 100
percent weld on each side of the box lock joint without fusing the
elements of the box lock joint together.
A DeBakey angled straight jaw peripheral vascular clamp having an
overall length of 7 inches, a pin length of 0.230 inches and a pin
diameter of 0.090 inches and otherwise similar to the
above-mentioned bulldog clamp is assembled under the same
conditions as listed above, except that the instrument is drilled
to 0.093 inches and a current of 35 amperes is used.
A 10 inch DeBakey tangential occlusion clamp having a pin length of
0.271 inches and a pin diameter of 0.093 inches, and otherwise
similar to the above-mentioned clamps is assembled under the same
conditions as the above-mentioned vascular clamp except that the
fusion current is set at 38 amperes.
Heavier instruments are assembled by the use of a longer fusing
time, or a heavier fusing current, or both, and smaller instruments
are assembled using a shorter time or a lighter fusing current. The
required conditions can be easily determined for any given
instrument. Furthermore, the nature of the process allows for the
production of uniform 100 percent welds with a large margin of
error in fusing conditions.
The process produces an exceptionally strong and reliable box lock
joint. Since no swaging of the pin takes place, the stresses which
resulted in failures of prior art instruments are not set up.
Furthermore, since hardening takes place following fusion, any
stresses which are present as a result of bending or machining or
fusing steps are relieved in the process of hardening the
instrument. In addition, since the hinge pin is secured by fusing
to the outer elements of the box lock joint, it is prevented from
falling out of the instrument even if it is broken in use.
* * * * *