Surgical suture abstract
The invention relates to methods for heating and cutting a suture
tip formed from a length of unfinished surgical suture material.
Surgical suture claims
what is claimed is:
1. A method for heating and cutting a suture tip formed form a
length of unfinished surgical suture material, comprising the steps
of:
(A) positioning said length of unfinished surgical suture material
at a combined heating and cutting location between a first face
of a first heating die and a second face of a second heating die;
(B) after step (A), moving said first heating die from a retracted
to an extended position and moving said second heating die from
a retracted position to an extended position in order to form a
length of suture tip material, said first face of said first heating
die being against said second face of said second heating die when
said first heating die is in its extended position and said second
heating die is in its extended position;
(C) after step (B), exposing said length of suture tip material
positioned at said combined heating and cutting location by moving
said first heating die from its extended to its retracted position
and moving said second heating die from its extended to its retracted
position; and
(D) while said length of suture tip material is positioned at said
combined heating and cutting location, moving a cutting blade across
a cross-section of said length of suture tip material.
2. The method of claim 1 wherein step (D) comprises the steps
of, while said length of suture tip material is positioned at said
combined heating and cutting location:
(i) moving a first cutting die from a retracted to an extended
position and moving a second cutting die from a retracted position
to an extended position, said first cutting die being positioned
against said second cutting die when said first cutting die is in
its extended position and said second cutting die is in its extended
position;
(ii) after step (i), moving said cutting blade across said cross-section
of said length of suture tip material; and
(iii) after step (ii), moving said first cutting die from its extended
to its retracted position and moving said second cutting die from
its extended to its retracted position.
3. The method of claim 2 wherein said first heating die has a
first face with a first heating groove therein, and said second
heating die has a second face with a second heating groove therein,
said first and second heating grooves extending along a common axis,
step (B) further comprising receiving a portion of said length of
said unfinished surgical suture material into said first and second
heating grooves.
4. The method of claim 3 wherein said first and second heating
grooves define a singular heating die opening when said first face
of said first heating die is positioned against said second face
of said second heating die.
5. The method of claim 4 wherein said singular heating die opening
has a constant cross-section perpendicular to said common axis.
6. The method of claim 5 step (C) further comprising the step
of signaling at least one heating die mechanical actuator to move
said first and second heating dies from their respective extended
positions to their respective retracted positions a predetermined
period of time after said first and second heating dies first reach
their respective extended positions in step (B).
7. The method of claim 6 step (A) further comprising aligning
said length of said unfinished surgical suture material along said
common axis.
8. The method of claim 7 wherein said at least one heating die
mechanical actuator is formed from a heating die master cylinder
coupled to said first heating die and a heating die slave cylinder
coupled to said second heating die, step (B) further comprising
moving, with said heating die master cylinder, said first heating
die from its retracted position to its extended position with a
first force, and moving, with said slave cylinder, said second heating
die from its retracted position to its extended position with a
second force that is smaller than said first force.
9. The method of claim 8 step (B) further comprising moving, wit
said heating die master cylinder, said first heating die a distance
which causes said first heating groove to overshoot said combined
heating and cutting location.
10. The method of claim 9 wherein said first heating die has at
least one V-shaped heating die guide affixed thereto for directing
said length of said unfinished surgical suture material into said
first groove as said heating die master cylinder moves said first
heating die from its retracted position to its extended position.
11. The method of claim 10 wherein said first cutting die has
a first face with a cutting groove therein aligned along said common
axis, said second cutting die has a second face, step (D)(i) further
comprising receiving at least a portion of said cross-section of
said length of suture tip material into said cutting groove.
12. The method of claim 11 wherein said first face of said first
cutting die is positioned against said second face of said second
cutting die at the end of step (D)(i), said cutting groove and said
second face of said second cutting die defining a singular cutting
die opening when said first face of said first cutting die is positioned
against said second face of said second cutting die.
13. The method of claim 12 wherein said singular cutting die opening
has a cross-section perpendicular to said common axis that is small
enough to compress said cross-section of said suture tip material
when said first face of said first cutting die is positioned against
said second face of said second cutting die.
14. The method of claim 13 wherein said second face of said second
cutting die includes a notch extending therefrom, said cutting groove
in said first face of said first cutting die being sized to receive
said notch during step (D)(i);
wherein said cutting groove and said notch define said singular
cutting die opening when aid first face of said first cutting die
is positioned against said second face of said second cutting die.
15. The method of claim 14 wherein said cutting groove in said
first face of said first cutting die is sized to receive all of
said cross-section of said suture tip in step (D)(i).
16. The method of claim 15 wherein said cross-section of said
suture tip is circular.
17. The method of claim 16 wherein said cutting groove in said
first face of said first cutting die has a cross-section that is
semi-circular in shape.
18. The method of claim 17 wherein said notch has a rectangular
shape.
19. The method of claim 18 wherein step (D)(ii) further comprises
signaling at least one cutting die mechanical actuator to retract
said first and second cutting dies after said cutting blade has
moved across said cross-section of said length of suture tip material.
20. The method of claim 19 wherein said at least one cutting die
mechanical actuator is formed from a cutting die master cylinder
coupled to said first cutting die and a cutting die slave cylinder
coupled to said second cutting die, step (D)(i) further comprising
moving, with said cutting die master cylinder, said first cutting
die from its retracted to its extended position with a third force
and moving, with said cutting die slave cylinder, said second cutting
die from its retracted to its extended position with a fourth force
that is smaller than said third force.
21. The method of claim 20 step (D)(i) further comprising moving,
with said cutting die master cylinder, said first cutting die a
distance which causes said cutting groove to overshoot said combined
heating and cutting location.
22. The method of claim 1 wherein step (A) further comprises the
step of tensioning said length of unfinished surgical suture material.
Surgical suture description
FIELD OF THE INVENTION
The present invention is directed to systems for processing strings
and yarns. Mowe particularly, the present invention is directed
to automated systems for thermally forming and cutting surgical
sutures.
BACKGROUND OF THE INVENTION
Various automated systems for forming and cutting surgical suture
tips exist or are known in the art. In one such machine, means for
simultaneously advancing in parallel at least six separate strands
of suture material, and six independent tensioners for maintaining
respective parallel portions of each of the six strands at a preset
tension are provided. Once a predetermined length of suture material
had been advanced by the advancing means, a horizontal heater bar
(positioned perpendicular to the six suture strands) is actuated
by an electronically controlled solenoid which moves a planar heater
bar into contact with one side of the suture strands for a predetermined
dwell time. Once the predetermined dwell time has elapsed, the solenoid
retracts the heater bar to its original position, and the heat exposed
(or heat-stiffened) section of suture material is advanced to a
cutting station. At the cutting station, the heat-stiffened section
of suture material is cut at its midpoint, thereby producing a suture
with two stiffened ends. Other mechanisms for forming and cutting
surgical suture tips are shown in U.S. Pat. Nos. 4832025 4806737
and 5226336 to Coates. The system described in the Coates patents
uses convective or non-contact heating to form suture tips.
Known systems for forming and cutting surgical suture tips suffer
from two primary drawbacks. First, such systems typically produce
a suture tip which lacks a substantially uniform cross-section.
Second, such systems typically cut the suture tip in an imprecise
manner, thereby leaving a cut end which may be irregular or distorted
in shape. From a manufacturing standpoint, suture tips having non-uniform
cross-sections and/or irregular or distorted cut ends are undesirable
because, among other things, such sutures are difficult to insert
into needles.
It is therefore an object of the present invention to provide a
surgical suture having a tip with a substantially uniform cross-section
and a precisely cut end which may be easily inserted into a needle.
It is a further object of the present invention to an automated
system and method for manufacturing surgical sutures having tips
with substantially uniform cross-sections.
It is a still further object of the present invention to provide
an automated system and method for making surgical sutures with
tips having precisely cut ends.
These and other objects and advantages of the invention will become
more fully apparent from the description and claims which follow
or may be learned by the practice of the invention.
SUMMARY OF THE INVENTION
The present invention is directed to a combined apparatus for heating
and cutting a suture tip formed from a length of unfinished surgical
suture material. First and second heating dies are provided for
heating the length of unfinished surgical suture material to form
the suture tip, and first and second cutting dies are provided for
cutting the suture tip, At least one heating die mechanical actuator
is provided for moving the first heating die between a retracted
and an extended position and for moving the second heating die between
a retracted and an extended position, the first and second heating
dies occupying a combined heating and cutting space adjacent to
the unfinished surgical suture material only when the first and
second cutting dies are in their retracted positions. At least one
cutting die mechanical actuator is provided for moving the first
cutting die between its retracted and an extended position and for
moving the second cutting die between its retracted and an extended
position, the first and second cutting dies occupying the combined
heating and cutting space only when the first and second heating
dies are in their retracted positions.
In accordance with a still further aspect, the present invention
is directed to a method for heating and cutting a suture tip formed
from a length of unfinished surgical suture material. The length
of unfinished surgical suture material is first positioned at a
combined heating and cutting location between a first face of a
first heating die and a second face of a second heating die. Next,
the first heating die is moved from a retracted to an extended position
and the second heating die is moved from a retracted position to
an extended position, the first face of the first heating die being
against the second face of the second heating die when the first
heating die is in its extended position and the second heating die
is in its extended position. Next, a length of suture tip material
positioned at the combined heating and cutting location is exposed
by moving the first heating die from its extended to its retracted
position and by moving the second heating die from its extended
to its retracted position. While the length of suture tip material
is positioned at the combined heating and cutting location, a cutting
blade is moved across a cross-section of the length of suture tip
material. In a preferred embodiment, first and second cutting dies
are placed in a closed position when the cutting blade is moved
across the cross-section of the length of suture tip material.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the manner in which the above-recited and other advantages
and objects of the invention are obtained and can be appreciated,
a more particular description of the invention briefly described
above will be rendered by reference to a specific embodiment thereof
which is illustrated in the appended drawings. Understanding that
these drawings depict only a typical embodiment of the invention
and are not therefore to be considered limiting of its scope, the
invention and the presently understood best mode thereof will be
described and explained with additional specificity and detail through
the use of the accompanying drawings.
FIG. 1 is a schematic diagram showing a machine for thermally forming
and cutting surgical sutures, in accordance with a preferred embodiment
of the present invention.
FIG. 2 is an isometric view of a suture tipping station formed
from a pair of opposing heating dies both of which are in their
retracted positions, in accordance with a preferred embodiment of
the present invention.
FIG. 3 is an isometric view of the suture tipping station of FIG.
2 wherein one of the heating dies in the station is in its retracted
position and the other heating die in the station is in its extended
position.
FIG. 4 is a further isometric view of the suture tipping station
of FIG. 2 wherein both of the heating dies in the station are in
their extended or closed positions.
FIGS. 5 and 6 show isometric views of the opposing heating dies
illustrated in FIGS. 2-4.
FIG. 7 is a cross-sectional view of an exemplary length of surgical
suture material which has not been contacted by the heating dies
of the heating station shown in FIGS. 2-4.
FIG. 8 is a graph illustrating the statistical distribution of
the varying cross-sectional diameters found in the unfinished suture
material depicted in FIG. 7.
FIG. 9 is a cross-sectional View of an exemplary length of a surgical
suture tip which has been thermally formed by the heating dies of
the heating station shown in FIGS. 2-4 in accordance with a preferred
embodiment of the present invention.
FIG. 10 is a graph illustrating the statistical distribution of
the generally uniform cross-sectional diameters found in tie thermally
formed suture tip depicted in FIG. 9 and the statistical relationship
between these generally uniform tip diameters and the varying cross-sectional
diameters found in the body portion of a suture made in accordance
with a preferred embodiment of the present invention.
FIG. 11 is an isometric view of a suture cutting station formed
from a pair of opposing cutting dies, wherein one of the cutting
dies is in its retracted position and the other cutting die is in
its extended position, in accordance with a preferred embodiment
of the present invention.
FIG. 12 is an isometric view of the suture cutting station of FIG.
11 wherein both of the cutting dies in the station are in their
extended or closed positions, in accordance with a preferred embodiment
of the present invention.
FIG. 13 is an isometric view of the suture cutting station of FIG.
12 illustrating the position of the cutting dies in the station
as a cutting blade moves through a cross-section of thermally formed
surgical suture material positioned in the cutting station, in accordance
with a preferred embodiment of the present invention.
FIG. 14 is a cross-sectional view showing the components of the
suture cutting station of FIGS. 11-13.
FIG. 15 is an exploded isometric view of the opposing cutting dies
shown in FIGS. 12-13.
FIG. 16 is an exploded front elevational view of the opposing cutting
dies shown in FIG. 15.
FIG. 17 is a front elevational view of the opposing cutting dies
of FIGS. 15-16 in accordance with a preferred embodiment of the
present invention.
FIG. 18 is a cross-sectional view of a suture cutting station for
simultaneously cutting a length of thermally formed surgical suture
material at two different locations, in accordance with an alternative
preferred embodiment of the present invention.
FIG. 19 is a side view of the suture cutting station shown in FIG.
18.
FIG. 20 shows the position of optical sensors used for monitoring
the movement of the heating and cutting dies in the combined heating
and cutting station shown in FIGS. 2-4 and 11-13 in accordance
with a preferred embodiment of the present invention.
FIG. 21 is a cross-sectional view of a moving clamp shown in its
closed state for grasping and advancing surgical suture material,
in accordance with a preferred embodiment of the present invention.
FIG. 22 is a cross-sectional view showing the moving clamp of FIG.
21 in its open state, in accordance with a preferred embodiment
of the present invention.
FIG. 23 is a cross-sectional view of a stationary clamp shown in
its closed state for grasping surgical suture material, in accordance
with a preferred embodiment of the present invention.
FIG. 24 is a cross-sectional view showing the stationary clamp
of FIG. 23 in its open state, in accordance with a preferred embodiment
of the present invention.
FIG. 25 is an isometric view of a system for tensioning a length
of surgical suture material, in accordance with a preferred embodiment
of the present invention.
FIG. 26 is an isometric view of an optical detection system for
detecting knots in surgical suture material passing through the
system, in accordance with a preferred embodiment of the present
invention.
FIG. 27 is a further isometric view showing a knot positioned between
the optical source and the optical detector of the knot detection
system of FIG. 26 in accordance with a preferred embodiment of
the present invention.
FIG. 28 is a cross-sectional view of FIG. 27 showing a knot positioned
between the optical source and the optical detector of the knot
detection system of FIG. 26 in accordance with a preferred embodiment
of the present invention.
FIG. 29 is an isometric view of a suture material holding arm which
is used for producing sutures having lengths that exceed the length
of the machine of FIG. 1 in accordance with a preferred embodiment
of the present invention.
FIG. 30 is a cross-sectional view showing the suture material holding
arm of FIG. 29 in its retracted position.
FIG. 31 is a cross-sectional view showing the suture material S
holding arm of FIG. 29 in its extended position.
DETAILED DESCRIPTION OF THE INVENTION
Overall System Operation
Referring now to FIG. 1 there is shown a schematic diagram showing
a machine 10 for thermally forming and cutting surgical sutures,
in accordance with a preferred embodiment of the present invention.
A continuous length of unfinished surgical suture material 110 is
supplied to machine 10 from a supply spool 100 having unfinished
surgical suture material 110 wound thereon. Unfinished surgical
suture material 110 from supply spool 100 is initially advanced
through a tensioning assembly 200 for creating a tension in the
unfinished surgical suture material, and then through a knot detector
system 300 for detecting whether a knot is present in any unfinished
surgical suture material 110 passing through knot detector system
300. After passing through the knot detector system 300 the unfinished
surgical suture material is advanced to a combined heating and cutting
station 400 where (i) a predetermined length of the unfinished
surgical suture material 110 is thermally formed into a length of
surgical suture tip material, and (ii) the thermally formed surgical
suture tip material is cut, thereby yielding a finished surgical
suture 120 having a body portion formed of unfinished surgical suture
material 110 and a thermally formed tip portion terminating with
a cut end.
As explained more fully below, the unfinished surgical suture material
110 from supply spool 100 is advanced through machine 10 by a moving
clamp 500 which is coupled to a linear actuator 550 for driving
the moving clamp 500 between a starting or home position 510 on
one side of the combined heating and cutting station 400 and an
end position 512 on the other side of combined heating and cutting
station 400. Moving clamp 500 has a grasping (or closed) state shown
in FIG. 20 and a non-grasping (or open) state shown in FIG. 21.
In accordance with instructions received from a controller 800
the moving clamp 500 selectively grasps and pulls the unfinished
surgical suture material 110 through machine 10 in order to facilitate
the manufacture of the finished surgical sutures 120. In addition
to advancing unfinished surgical suture material through the machine,
the moving clamp 500 functions to initially position and align the
unfinished surgical suture material 110 within combined heating
and cutting station 400.
During operation of the machine 10 the moving clamp 500 initially
grasps or closes on the unfinished surgical suture material 110
at the home position 510. Next, while the moving clamp 500 remains
in its grasping or closed state, the linear actuator 550 drives
the moving clamp 500 from its home position 510 to the end position
512. As the linear actuator 550 drives moving clamp 500 from its
home position 510 to its position 512 the moving clamp 500 pulls
a length of the unfinished surgical suture material 110 through
the combined heating and cutting station 400 and through a stationary
clamp 600 positioned between the end position 512 and the combined
heating and cutting station 400. Like the moving clamp 500 the
stationary clamp 600 has a grasping (or closed) state which is shown
in FIG. 22 and a non-grasping (or open) state shown in FIG. 23.
As the linear actuator 550 drives the moving clamp 500 from home
position 510 to end position 512 the stationary clamp 600 is in
its open state. After the moving clamp reaches its end position
512 the stationary clamp 600 grasps or closes on the unfinished
surgical suture material 110 positioned within the stationary clamp
600. The position of stationary clamp 600 along the length of machine
10 may be adjusted in order to facilitate the creation of sutures
with different lengths.
As illustrated in FIG. 2 the combined heating and cutting station
400 includes a pair of opposing heating dies 402 404 and a pair
of opposing cutting dies 450 452. The opposing heating dies 402
404 have both an open and a closed state. Similarly, the opposing
cutting dies 450 452 have an open and a closed state. When, as
described above, the linear actuator 550 drives the moving clamp
500 from home position 510 to end position 512 both the opposing
heating dies 402 404 and the opposing cutting dies 450 452 in
the combined heating and cutting station 400 are in their open positions.
After the moving clamp reaches its end position 512 and the stationary
clamp 600 has grasped or closed on the unfinished surgical suture
material 110 positioned within the stationary clamp 600 the heating
dies 402 404 move from their open state to their closed state in
order to thermally form a predetermined length of surgical suture
tip material. The operation of the heating dies 402 404 is described
in greater detail below in connection with FIGS. 2-10. After the
heating dies 402 404 move from their open to their closed state,
the moving clamp 500 releases the unfinished surgical suture material
110 in its grasp and, while the moving clamp is in its open or non-grasping
state, the linear actuator 550 drives the moving clamp 500 from
its end position 512 to its home position 510 where the moving clamp
closes on a next piece of unfinished surgical suture material 110.
After the opposing heating dies 402 404 have been in their closed
state for a predetermined period of time, the heating dies 402
404 move from their closed to their open state, thereby exposing
a predetermined length of surgical suture tip material positioned
between the opposing heating dies 402 404. Next, while the surgical
suture tip material remains positioned between the open heating
dies 402 404 the opposing cutting dies 450 452 move from their
open state to their closed state in order to "pinch" or
firmly grasp the predetermined length of surgical suture tip material,
preferably at a point adjacent to the midsection of the length of
surgical suture tip material formed by the heating dies 402 404.
While the cutting dies 450 452 are in their closed position, a
cutting blade 480 is moved across a cross-section of the surgical
suture tip material at a point adjacent to the cutting dies 450
452 thereby yielding a thermally formed surgical suture tip with
a cut end.
Thereafter, the cutting dies 450 452 move from their closed position
to their open position and the stationary clamp 600 releases the
surgical suture material within its grasp. As the stationary clamp
opens and releases the previously grasped surgical suture material,
a finished surgical suture 120 having a thermally formed and cut
tip falls by gravity onto an arm affixed to the stationary clamp
600. Prior to the time that the cutting dies 450 452 are moved
from their closed to their open position, the moving clamp 500 grasps
or closes on the surgical suture material at home position 510
and the process described above is then preferably repeated in order
to manufacture flier finished surgical sutures 120. Since the tensioning
assembly 200 exerts a tensioning force on the surgical suture material
110 positioned within machine 10 it is important for the moving
clamp 500 to grasp or close on the surgical suture material at home
position 510 prior to the time that the cutting dies 450 452 are
moved from their closed to their open position, in order to prevent
the tensioning assembly 200 from pulling the trailing end of the
surgical suture material cut by blade 480 in a reverse direction
past home position 510 when the cutting dies 450 452 are opened.
The unfinished surgical suture material 110 used in machine 10
for manufacturing the finished sutures 120 may consist of any thermoplastic
braided suture material such as, for example, a polyester braided
suture material, or a polyamide or polyolyfin suture material. In
a preferred embodiment of the present invention described more fully
below, the unfinished surgical suture material 110 used in machine
10 is a braided suture material formed of a polyethylene terephthalate,
such as that sold by Ethicon, Inc. under the trademark Ethibond.RTM.
Excel.RTM.. In a preferred embodiment, a Simatic model TI435 controller
manufactured by Siemens is used to implement controller 800. An
operator interface is preferably coupled to the controller 800.
Operation of Heating Dies
As mentioned above, after the moving clamp 500 has reached its
end position 512 and the stationary clamp 600 has grasped or closed
on the unfinished surgical suture material 110 positioned within
the stationary clamp 600 the heating dies 402 404 in the combined
heating and cutting station 400 operate to thermally form a predetermined
length of surgical suture tip material from the unfinished surgical
suture material 110 positioned within the station 400. During the
operation of the heating dies 402 404 the unfinished surgical
suture material 110 is suspended in an aligned and fixed positioned
within station 400 by the stationary clamp 600 which is positioned
on one side of station 400 and by the pulley 514 which is positioned
on an opposing side of station 400. In addition, during the operation
of the heating dies 402 404 the unfinished surgical suture material
110 suspended within station 400 is maintained with a preset tension
by tensioning system 200.
FIGS. 2-4 show three views of the combined heating and cutting
station 400. Each of the views illustrates the position of the heating
dies 402 404 at a particular point dunning a suture tipping cycle.
Referring now specifically to FIG. 2 there is shown an isometric
view of station 400 wherein the heating dies 402 404 are both
in their retracted or open positions. FIG. 2 shows the position
of heating dies 402 404 when the moving clamp 500 has reached its
end position 512 and the stationary clamp 600 grasps or closes on
the unfinished surgical suture material 110 positioned within the
stationary clamp 600. After the moving clamp 500 has reached its
end position 512 and the stationary clamp 600 has grasped or closed
on the unfinished surgical suture material 110 positioned within
the stationary clamp 600 a master cylinder 406 (controlled by controller
800) drives the heating die 404 from its retracted to its extended
position. FIG. 3 shows the position of the heating dies 402 404
after the master cylinder 406 has moved heating die 404 to its extended
position. As the heating die 404 is moved to its extended position,
a cross-sectional portion of the suture material 110 suspended within
station 400 is received into a groove or channel 405 (shown in FIG.
6) within heating die 404. A pair of V-shaped guides 404a, 404b
are affixed to the ends of the heating die 404 in order to facilitate
the guidance of the unfinished suture material 110 into groove 405
during this step. In a preferred embodiment of the present invention,
the master cylinder 406 causes the groove 405 in the heating die
404 to slightly overshoot (or pass) the centerline of the unfinished
suture material 10 suspended within the station 400 in order to
ensure that at least a cross-sectional portion of the unfinished
suture material 110 is in fact received into the groove 405.
After the master cylinder 406 has moved heating die 404 to its
extended position, a slave cylinder 408 (controlled by controller
800) drives heating die 402 from its retracted to its extended position.
FIG. 4 shows the position of the heating dies 402 404 after the
slave cylinder 408 has moved heating die 402 to its extended position.
As the heating die 402 is moved to its extended position, the cross-sectional
portion of the suture material 110 which was not previously received
into groove 405 is received into a groove or channel 403 (shown
in FIG. 5) within heating die 402. After the slave cylinder 408
has driven heating die 402 to its extended position, the face 405a
of heating die 404 stands adjacent to and abuts the face 403a of
heating die 402. In a preferred embodiment of the present invention,
the force used by slave cylinder 408 to drive heating die 402 to
its extended position is less than the force used by master cylinder
406 to drive heating die 404 to its extended position. The use of
a reduced force by the slave cylinder 406 insures that the position
of the heating die 404 will not be disturbed when the heating die
402 is brought into contact with the heating die 404 as shown in
FIG. 4. After faces 403a and 405a have been brought together and
the heating dies 402 404 have "closed on" the unfinished
surgical suture material 110 as shown in FIG. 4 the heating dies
402 404 remain in their closed or extended positions for a predetermined
dwell time. Thereafter, the cylinders 406 and 408 open the heating
dies 402 404 by bringing them back to their initial retracted positions,
thereby exposing a predetermined length of thermally formed surgical
suture tip material suspended between opposing open heating dies
402 404.
In the preferred embodiment of the present invention, the cross-sections
of grooves 403 and 405 each represent a half circle or semi-circle
such that, when faces 403a and 405a are brought into contact with
each other as shown in FIG. 4 grooves 403 and 405 together form
a singular cylindrical opening with a circular cross section (hereinafter
"the heating die cross-section") running perpendicular
to the axis of the cylindrical opening. The axis of the cylindrical
opening formed by grooves 403 and 405 is aligned in parallel with
the length of the surgical suture material 110 along the "x"
axis (shown in FIGS. 2-4). In the preferred embodiment of the present
invention, the diameter of the heating die cross-section is always
less than the average cross-sectional size of the unfinished surgical
suture material 110 provided from supply spool 100. By making the
diameter of the heating die cross-section less than the average
cross-sectional size of the unfinished surgical suture material
110 the present invention insures that grooves 403 and 405 both
contact and apply pressure to the suture material 110 during the
suture tipping process. The tension maintained in the unfinished
surgical suture material 110 by tensioning assembly 200 functions
to prevent the heating die cross-section from overly pinching or
constricting the suture material during the suture tipping process.
Referring now to FIG. 7 there is shown a cross-sectional view
of an exemplary length of unfinished surgical suture material 110
which has not been contacted by the heating dies 402 404 of station
400. Unfinished suture material 110 (as shown in FIG. 7) is used
to form the untipped body portions of sutures made in accordance
with the present invention. Unfinished suture material 110 is formed
of a plurality of yams 112 each of which is formed from several
strands or filaments 114. Since unfinished suture material 110 is
braided, its cross-section is not uniformly circular. On the contrary,
the diameter of the cross-section of the unfinished suture material
110 varies depending on the position of the diameter measured. Thus,
the three exemplary diameter measurements 117 118 119 of the suture
material 110 shown in FIG. 7 all of which pass through the centroid
116 of the cross-section, each have a different length. FIG. 8 shows
a graph illustrating the statistical distribution of the varying
cross-sectional diameters found in the unfinished suture material
depicted in FIG. 7 and, in particular, the varying cross-sectional
diameters found in unfinished size 0 Ethibond.RTM. Excel.RTM. surgical
suture material. As shown in FIG. 8 for a given length of unfinished
surgical suture material 110 there is an average cross-sectional
diameter (D.sub.avg), a first standard deviation cross-sectional
diameter (D.sub.sd1) representing a cross-sectional diameter length
that is one standard deviation below D.sub.avg, and a second standard
deviation cross-sectional diameter (D.sub.sd2) representing a cross-sectional
diameter length that is two standard deviations below D.sub.avg.
In a first preferred embodiment of the present invention, the diameter
of the heating die cross-section formed by grooves 403 and 405 is
a constant that is less than the D.sub.avg value for the unfinished
suture material 110; in a second preferred embodiment of the present
invention, the diameter of the heating die cross-section formed
by grooves 403 and 405 is a constant that is about equal to the
D.sub.sd1 value for the unfinished suture material 110; and in a
still further preferred embodiment of the present invention, the
diameter of the heating die cross-section formed by grooves 403
and 405 is a constant that is about equal to the D.sub.sd2 value
for the unfinished suture material 110.
Referring now to FIG. 9 there is shown a cross-section 122 of
an exemplary length of a surgical suture tip that has been thermally
formed by the heating dies 402 404 of station 400 as described
above in connection with FIGS. 2-4. The exemplary cross-section
122 shown in FIG. 9 was thermally formed (or finished) using a heating
die cross-section having a constant diameter that was about equal
to the D.sub.sd2 value for the unfinished suture material 110 initially
supplied to station 400. As a result of the fact that the diameter
of the heating die cross-section was less than the D.sub.avg value
for the unfinished suture material 110 the unfinished suture material
110 was contacted by the heating dies 402 404 during the thermal
heat tipping process. The contacting of the heating dies 402 404
with the unfinished suture material 110 during the thermal heat
tipping process, together with the fact that the suture material
110 is under tension during this process, causes the suture material
110 which is contacted by the heating dies 402 404 to be compressed,
thereby resulting in the "rounding" of filaments (such
as filaments 124) positioned about the perimeter of cross-section
122. As a result of this "rounding" of the filaments about
its perimeter, the cross-section 122 is generally uniform in diameter.
In contrast to the varying diameters of the cross-section of the
unfinished suture material 110 shown in FIG. 7 the diameters of
the cross-section 122 are generally constant irrespective of the
position of the diameter measured. Thus, the three exemplary diameter
measurements 126 127 128 of the cross-section 122 shown in FIG.
9 all of which pass through the centroid 129 of the cross-section,
each having the same length. Tables I, II, and III illustrate the
cross-sectional diameters of size 0 2/0 and 3/0 sutures having
body portions formed from unfinished Ethibond.RTM. Excel.RTM. suture
material and tip portions which have been formed by dies 402404
(having a constant cross-sectional diameter about equal to the D.sub.sd2
value of the unfinished suture material), in accordance with the
present invention. As these tables show, the present invention results
in sutures having tip portions (110a) with a cross-section that
is both smaller in diameter and more uniform (i.e., smaller diameter
standard deviation) than the unfinished suture body portions (110b)
adjacent to such tip portions.
TABLE I Size Measurements of Tip and Body Diameters of Size 0 Sutures
SET 1 SET 2 BODY/TIP END TIP END BODY TIP END BODY DIAMETER MILS
MILS MILS MILS SAMPLE # 1 17.44 18.97 17.92 20.85 2 17.64 20.40
17.82 19.41 3 17.29 18.45 18.10 20.08 4 17.52 18.96 17.70 19.56
5 17.59 19.38 17.63 19.43 6 17.82 19.47 17.82 20.70 7 17.90 19.74
17.45 18.57 8 17.57 20.47 18.20 19.31 9 17.43 20.44 17.70 19.83
10 17.61 20.07 17.90 19.27 AVERAGE 17.58 19.63 17.82 19.70 STANDARD
DEV. 0.18 0.71 0.22 0.69
TABLE II Size Measurements of Tip and Body Diameters of Size 2/0
Sutures SET 1 SET 2 BODY/TIP END TIP END BODY TIP END BODY DIAMETER
MILS MILS MILS MILS SAMPLE # 1 14.78 16.66 15.39 17.70 2 14.98 17.74
14.55 15.93 3 15.03 16.84 14.87 15.87 4 15.04 17.44 14.92 16.91
5 15.14 16.54 14.74 17.15 6 15.19 16.71 14.61 16.07 7 14.97 17.05
15.24 20.01 8 14.86 15.41 14.75 17.53 9 15.04 17.17 14.61 16.39
10 14.89 18.57 14.85 17.12 AVERAGE 14.99 17.01 14.85 17.07 STANDARD
DEV. 0.12 0.83 0.27 1.22
TABLE II Size Measurements of Tip and Body Diameters of Size 2/0
Sutures SET 1 SET 2 BODY/TIP END TIP END BODY TIP END BODY DIAMETER
MILS MILS MILS MILS SAMPLE # 1 14.78 16.66 15.39 17.70 2 14.98 17.74
14.55 15.93 3 15.03 16.84 14.87 15.87 4 15.04 17.44 14.92 16.91
5 15.14 16.54 14.74 17.15 6 15.19 16.71 14.61 16.07 7 14.97 17.05
15.24 20.01 8 14.86 15.41 14.75 17.53 9 15.04 17.17 14.61 16.39
10 14.89 18.57 14.85 17.12 AVERAGE 14.99 17.01 14.85 17.07 STANDARD
DEV. 0.12 0.83 0.27 1.22
FIG. 10 shows a graph illustrating the statistical distribution
of the generally uniform cross-sectional diameters found in the
thermally formed suture tip depicted in FIG. 9 and exemplified by
Table I above. As shown in FIG. 10 the suture tip produced by the
heating dies of the present invention has a generally uniform cross-sectional
diameter which centers about the heating die cross-section (in this
case D.sub.sd2), and which is less than the D.sub.avg value corresponding
to the unfinished suture material 110 supplied to station 400 and
forming the untipped body portion of the resulting suture.
Since the heating die cross-section used in the present invention
varies depending upon the D.sub.avg value of the unfinished suture
material 110 being supplied to machine 10 the heating dies 402
404 are secured to heater manifolds 410 412 respectively, by removable
screws 414 which allow an operator to change the heating dies 402
404 being used in station 400 depending on the size of the suture
material 110 being used. A thermocouple 415 for heating the removable
heating dies 402 404 is positioned in each of the manifolds 410
412 and coupled to controller 800. Thus, for larger diameter suture
material 110 the operator will use heating dies 402 404 which
form a greater heating die cross-section than dies used for thermally
forming tips on smaller diameter suture material. Set forth in Table
IV below are the preferred heating die cross-section diameters used
for thermally forming tips on different sizes of an unfinished braided
suture material formed of a polyethylene terephthalate, such as
that sold by Ethicon, Inc. under the trademark Ethibond.RTM. Excel.RTM..
Also set forth in Table IV below are the preferred temperatures
that heating dies 402 404 should be maintained at during the heat
tipping process, the preferred tensions at which the slltulres should
be maintained during the heat tipping process, and the preferred
dwell times during which the heating dies 402 404 should remain
closed on the unfinished suture material 110 during the heat tipping
process.
TABLE IV SIZE OF UN- FINISHED SUTURE MATERIAL 0 2/0 3/0 4/0 5/0
Heating Die 17.70 15.00 11.40 9.00 6.85 Cross- Section Diameter
(in mils) Heating Die 246-250 246-250 246-250 246-250 246-250 Temperature
(in .degree. C.) Heating Die 2.6-3.0 2.6-3.0 2.6-3.0 2.4-2.8 2.0-2.4
Dwell Time (in seconds) Tension (in 100-120 100-120 100-120 40-60
40-60 grams)
In the preferred embodiment of the present invention, heating dies
402 404 are made of steel, and are coated with a non-stick substance
such as Teflon.RTM. or Nedox.RTM., manufactured by General Magnaplate,
in order to facilitate the release of the suture material from the
grooves 403 405 when the heating dies 402 404 are opened. Although
in the preferred embodiment described above, the heating die cross-section
formed by grooves 403 405 was circular in shape, it will be understood
by those skilled in the art that heating die crosssections defining
other geometric shapes may also be used in conjunction with the
present invention.
Operation of Cutting Dies
After the cylinders 406 and 408 open the heating dies 402 404
by bringing them back to their initial retracted positions, thereby
exposing a predetermined length of thermally formed surgical suture
tip material suspended between opposing open heating dies 402 404
the cutting dies 450 452 in the combined heating and cutting station
400 operate to cut the thermally formed length of surgical suture
tip material, When the present invention is used to create finished
suture material for "double-armed" sutures (i.e., sutures
having needles at both ends of each suture), the thermally formed
length of surgical suture tip material is preferably cut at its
midpoint; otherwise the thermally formed length of surgical suture
tip material is preferably cut near one of its ends. During the
initial operation of the cutting dies 450 452 the surgical suture
material suspended in station 400 remains in the same position that
it occupied during the thermal tipping process described above.
Thus, the surgical suture material remains positioned and aligned
along axis "x". In addition, during the initial operation
of the cutting dies 450 452 the surgical suture material suspended
within station 400 is maintained at the Same present tension that
was used during the thermal tipping process described above.
FIGS. 11-13 show three further views of the combined heating and
cutting station 400. Each of the views illustrates the position
of the cutting dies 450 452 and the cutting blade 480 at a particular
point during a suture cutting cycle. During the thermal tipping
cycle described above, both of the cutting dies 450 452 remained
in their open or retracted positions. Following the opening of heating
dies 402 404 at the end of the thermal tipping cycle, a master
cylinder 460 (controlled by controller 800) drives the cutting die
450 from its retracted to its extended position. FIG. 10 shows the
position of the cutting dies 450 452 after the master cylinder
460 has moved cutting die 450 to its extended position. As the cutting
die 450 is moved to its extended position, a cross-section of the
thermally tipped suture material 110a suspended within station 400
is received into a groove or channel 451 (shown in FIGS. 15-16)
within cutting die 450. A pair of V-shaped guides (not shown) may
be affixed to the ends of the cutting die 450 in order to facilitate
the guidance of the thermally tipped suture material 110a into groove
451 during this step. In a preferred embodiment of the present invention,
the master cylinder 460 causes the groove 451 in the cutting die
450 to slightly overshoot the location of the thermally tipped suture
material 110a suspended within the station 400 in order to ensure
that the entirety of a cross-sectional portion of the thermally
tipped suture material 110a is in fact received into the groove
451 (as shown in FIG. 17).
After the master cylinder 460 has moved the cutting die 450 to
its extended position, a slave cylinder 462 (also controlled by
controller 800) drives the cutting die 452 from its retracted to
its extended position. FIG. 12 shows the position of the cutting
dies 450 452 after the slave cylinder 462 has moved cutting die
452 to its extended position. After the slave cylinder 462 has driven
cutting &e 452 to its extended position, the face 451a of cutting
die 450 stands adjacent to and abuts the face 453a of cutting die
452. The cutting die 452 includes a square-shaped notch (or boss)
453 which is received into groove 451 when faces 451a and 453a are
brought together. In a preferred embodiment of the presently oveon,
the force used by slave cylinder 462 to drive cutting die 452 to
its extended position is less than the force used by mimtr Cylinder
460 to drive cutting die 450 to its extended position. The use of
a reduced force by the slave cylinder 462 insures that the position
of the cutting die 450 will not be disturbed when the cutting die
452 is brought into contact with the cutting die 450 as shown in
FIG. 12. After faces 451a and 453a have been brought together and
the cutting dies 450 452 have "closed on" the thermally
tipped suture material 110a as shown in FIG. 17 blade 480 is moved
by slave cylinder 462 across the thermally tipped suture material
110a in a direction perpendicular to the axis "x", thereby
shearing the thermally tipped suture material 110a material 110a
at a point adjacent to the cutting dies 450 452 and creating a
finished suturo 120 having a body portion formed of unfinished surgical
suture material 110 and a thermally fonned tip portion terminating
with a cut end. FIG. 13 illustrates the positions of the cutting
dies 450 452 as the cutting blade 480 slices through the thermally
tipped suture material 110a, and FIG. 14 shows the proximity of
the cutting blade 480 to the cutting dies 450 452 which is maintained
during the cutting process. Following the slicing of the thermally
tipped suture material 110a, cylinders 460 and 462 open the curing
dies 450 452 by bringing them back to their initial retracted positions.
As mentioned above, prior to the opening of the cutting dies 450
452 at the end of the cutting cycle, the moving clamp 500 grasps
or closes on the surgical suture material 110 at home position 510
in order to prevent the tensioning assembly 200 from pulling the
trailing end 110b of the surgical suture material cut by blade 480
in a reverse direction past home position 510 when the cutting dies
450 452 are opened.
In the preferred embodiment of the present invention, the cross-sections
of groove 451 and notch 453 are such that, when faces 451a and 453a
are brought into contact with each other as shown in FIG. 17 groove
451 and notch 453 together form a singular cutting die opening aligned
along the "x" axis with a cross-section (hereinafter "the
cutting die cross-section") running perpendicular to the "x"
axis. Thus, the axis of the cutting die opening formed by groove
450 and notch 452 is aligned in parallel with the length of the
thermally tipped surgical suture material 110a along the "x"
axis. In the preferred embodiment of the present invention, the
diameter "d" (shown in FIG. 17) of the cutting die cross-section
is always less than the diameter of the heating die cross-section
used for thermally forming the tipped suture material 110a. By making
the diameter of the cutting die cross-section less tan the diameter
of the heating die cross-section, the present invention insures
that groove 451 and notch 453 not only contact, but also firmly
hold or pinch the thermally tipped suture material 110a positioned
between the cutting dies 450 452 during the suture cutting process.
By firmly holding or pinching the thermally tipped suture material
110a at a point directly adjacent to the location where blade 480
slices through the suture material 110a, the cutting mechanism of
the present invention yields a suture with an extremely precise
cut end which, among other things, facilitates the later insertion
of the cut end into a needle.
Alternative Preferred Cutting Die Mechanism
The cutting die system described above in conjunction with FIGS.
11-17 is advantageous for creating single-armed sutures which have
a needle attached at only one end. However, for some surgical procedures,
double-armed sutures which have a needle attached at each end are
required. In order to manufacture suture material that can be used
for making double-armed sutures, it is important for both ends of
the suture material to be formed from precise cuts, so that each
end of the suture can be inserted into a needle. An alternative
cutting die system 900 shown in FIGS. 18-19 may be used in place
of the cutting die system shown in FIGS. 11-17 for fabricating finished
sutures 120 having precise cuts at both ends.
System 900 functions substantially the same as the cutting system
described in the section immediately above, except that, in system
900 the master cylinder 460 simultaneously drives a pair of cutting
dies 902 904 between their retracted and extended positions, the
slave cylinder 462 simultaneously drives a pair of cutting dies
906 908 between their retracted and extended positions, and the
slave cylinder simultaneously moves two cutting blades 910 912
across two separate cross-sections of the thermally tipped suture
material 110a. Thus, cutting dies 902 904 are each substantially
identical to cutting die 450 and cutting dies 906 908 are each
substantially identical to cutting die 452. During operation of
system 900 the master cylinder 460 first simultaneously drives
the cutting dies 902 904 from their retracted to their extended
positions. As the cutting dies 902 904 are moved to their extended
positions, a separate cross-section of the thermally tipped suture
material 110a suspended within station 400 is received into a groove
451 within each of the cutting dies 902 904. Next, the slave cylinder
462 simultaneously drives the cutting dies 906 908 from their retracted
to their extended positions. After the slave cylinder 462 has driven
the cutting dies 906 908 to their extended positions, the faces
451a of the cutting dies 902 904 stand adjacent to and abut the
faces 453a of cutting dies 902 904. After both sets of faces 451a
and 453a have been brought together and the cutting dies 902 904
906 and 909 have "closed on" their respective cross-sections
of thermally tipped suture material 110a, blades 910 912 are simultaneously
moved by slave cylinder 462 across two cross-sections of the thermally
tipped suture material 110a in a direction perpendicular to the
axis "x", thereby shearing the thermally tipped suture
material 110a at two points adjacent to the cutting dies 906 908
and creating two precisely cut suture ends. Following the slicing
of the suture material 110a, cylinders 460 and 462 open the cutting
dies 902 904 906 and 908 by bringing them back to their initial
retracted positions.
Optical Sensor Control System
The state/position (i.e., open or closed) of the moving clamp 500
the stationary clamp 600 the heating dies 402 404 and the cutting
dies 450 452 as well as the movement and position of the master
cylinders 406 460 the slave cylinders 408 462 the linear actuator
550 the cutting blade 480 and the tensioning assembly 200 are
monitored and controlled by a controller 800. FIG. 20 shows the
positions of several optical sensors which are coupled to controller
800 and which monitor and verify the positions of the heating dies
402 404 and cutting dies 450 452 during the operation of the combined
heating and cutting station 400. More specifically, optical sensors
801 and 802 are provided for monitoring/verifying whether heating
die 404 is in its extended or retracted position; optical sensors
803 and 804 arc provided for monitoring/verifying whether heating
die 402 is in its extended or retracted position; optical sensor
805 is provided for monitoring/verifying whether cutting die 450
is in its extended or retracted position; and optical sensor 806
is provided for monitoring/verifying whether cutting die 452 is
in its extended or retracted position. In the preferred embodiment
of the present invention, controller 800 will not allow the master
cylinder 406 to drive the heating die 404 to its extended position
unless the sensors 805 806 indicate that the cutting dies 450
452 are in their retracted positions; controller 800 will not allow
the slave cylinder 408 to drive the heating die 402 to its extended
position unless the sensors 805 806 indicate that the cutting dies
450 452 are in their retracted positions and the sensors 801 802
indicate that the heating die 404 is in its extended position, controller
800 will not allow the cylinder 460 to drive the cutting die 450
to its extended position unless the sensors 801 802 803 and 804
indicate that the heating dies 402 404 are in their retracted positions;
and controller 800 will not allow the cylinder 462 to drive the
cutting die 452 to its extended position unless the sensors 801
802 803 804 and 805 indicate that the heating dies 402 404 are
in their retracted positions and that the cutting die 450 is in
its extended position.
FIGS. 21 and 22 show the position of an optical sensor 807 which
is coupled to controller 800 and which monitors and verifies the
state (either open or closed) of moving clamp 500. FIGS. 23 and
24 show the position of an optical sensor 808 which is coupled to
controller 800 and which monitors and verifies the state (either
open or closed) of stationary clamp 600.
Suture Tensioning System
Referring now to FIG. 25 there is shown an isometric view of the
system 200 for tensioning a length of surgical suture material 110
in accordance with a preferred embodiment of the present invention.
System 200 includes a tensioning spool 202 having a width, a weight
and a circular perimeter 204 perpendicular to the width of the spool.
The tensioning spool 202 has a groove 206 in its perimeter 204 for
receiving the surgical suture material 110. Tensioning system 200
also includes a track 208 formed from a pair of slots 208a, 208b
extending in parallel along the length of the track 208. Track 208
and slots 208a, 208b are preferably positioned along a purely vertical
axis, although, in alternate embodiments (not shown), track 208
and slots 208a, 208b may be aligned along an axis that includes
both horizontal and vertical components. The slots 208a, 208b function
to receive and guide the tensioning spool 202 along the length of
track 208 during operation of system 200. The length of the track
208 is preferably aligned perpendicularly to the width of the tensioning
spool 202.
During operation of the system 200 the tensioning spool 202 is
suspended vertically within slots 208a, 208b by the surgical suture
material 110. While the tensioning spool 202 is suspended vertically
within slots 208a, 208b by the surgical suture material 110 the
weight of the tensioning spool 202 exerts a corresponding tensioning
force on the suture material 110 equal to one half the weight of
spool 202. In order to vary the tension exerted on the suture material
110 during operation of system 200 additional weights 210 may be
adAed or removed from a spool arm extending from the center of spool
202.
When the moving clamp 500 described above is in its grasping state
and moves from its home position 510 to its end position 512 suture
material 110 suspended in the track 208 is drawn forwardly through
station 400 and stationary clamp 600 of machine 10. As the suture
material is drawn forwardly through the machine by the moving clamp
500 the tensioning spool 202 is pulled upwardly within track 208.
However, regardless of the vertical position of the spool 202 within
the track 208 the tension exerted on the suture material 110 by
system 200 will be the constant and equal to one half the weight
of spool 202. An optical sensor 212 coupled to controller 800
is provided for determining whether the pulling action of the moving
clamp 500 has caused the spool 202 to be drawn upwardly within the
track 208 past the height of the sensor 212. When optical sensor
212 detects that the tensioning spool 202 ha been pulled upwardly
past the location of the sensor 212 controller 800 causes a motor
(not shown) coupled to the supply spool 100 to unwind unfinished
surgical suture material 110 from the supply spool 100. As flirter
unlined surgical suture material 110 is unwound from the supply
spool 100 the tensioning spool 202 moves downwardly within the
track 208. In the preferred embodiment, controller 900 continues
to unwind unfinished surgical suture material 110 from the supply
spool 100 until the tensioning spool 202 falls below the level of
optical sensor 212.
An optical sensor 214 is provided at the bottom of track 208 for
determining whether there has been a break in the surgical suture
material 110 or a loss of tension in the suture material within
machine 10. Since, during normal operation, the tensioning spool
202 should not fall below the level of optical sensor 212 a break
in suture material 110 or a loss of suture tension within machine
10 will be signaled by sensor 214 if the sensor determines that
the tensioning spool 202 has fallen to the level of the sensor 214.
Although tensioning system 200 has been described in connection
with the tensioning of surgical suture material, it will be understood
by those skilled in the art that tensioning system 200 may be used
for tensioning any type of string or yarn.
Knot Detection System
Referring now to FIGS. 26 and 27 there are shown two isometric
views of an optical detection system 300 for detecting knots in
surgical suture material 110 passing through system 300 in accordance
with a preferred embodiment of the present invention. Knot detector
system 300 includes an optical light source 302 for directing a
plane of light 304 at an optical light detector 106 when surgical
suture material 110 is positioned between the optical light source
302 and the optical light detector 306 (shown in FIG. 28). The optical
light source 302 is preferably formed it of a plurality of optical
fibers 302a having their terminating ends aligned along the optical
plane 304. Controller 800 is coupled to an output of the optical
light detector 306 for processing the signals output by detector
306 and determining whether a knot exists in the suture material
110 positioned between the light source 302 and light detector 306.
More particularly, by comparing a magnitude of a shadow 308 cast
on the optical light detector 306 by the suture material 110 against
a predetermined threshold, controller 800 determines whether or
not a knot exists in the suture material 110 positioned between
the light source 302 and light detector 306. In a preferred embodiment,
the predetermined threshold used in this comparison corresponds
to a magnitude of a shadow 308a cast on the optical light detector
306 by an unknotted cross-section of suture material 110. In a still
further preferred embodiment, controller 800 will determine that
a knot exists in the suture material 110 passing through system
300 only if the magnitude of the shadow cast on light detector 306
by suture material 110 exceeds by at least 30% the magnitude of
a shadow 308a cast on the optical light detector 306 by an unknoted
cross-section of suture material 110.
Although knot detection system 300 has been described in connection
with the detection of knots in surgical suture material, it will
be understood by those skilled in the art that knot detection system
300 may be used for detecting knots in any type of string or yarn.
Extended Length Suture Mode
Although, in the process described above, machine 10 was used to
manufacture a finished surgical suture 120 having a length that
was less than length of the linear actuator 550 machine 10 may
also be used in an extended length suture mode, described below,
in order to make finished surgical sutures which are longer than
linear actuator 550. As shown in FIG. 1 and also in FIGS. 29-31
a suture material holding arm 700 affixed to machine 10 is provided
for holding suture material during the manufacture of extended length
surgical sutures. Suture material holding arm 700 includes an end
portion 704 formed of a cylindrical central portion bounded by sides
702 703. An actuator 705 coupled to controller 800 drives the
end portion 704 between its retracted position (shown in FIGS. 29-30)
and its extended position (shown in FIG. 31). When machine 10 functions
in its extended length suture mode, actuator 705 maintains end portion
704 in its extended position; otherwise, actuator 705 maintains
end portion 704 in its retracted position.
During operation of the machine 10 in the extended length suture
mode, the moving clamp 500 initially grasps or closes on the unfinished
surgical suture material 110 at the home position 510. Next, while
the moving clamp 500 remains in its grasping or closed state, the
linear actuator 550 drives the moving lamp 500 from its home position
510 to the end position 512. As the linear actuator 550 drives moving
clamp 500 from its home position 510 to its position 512 the moving
clamp 500 pulls a length of the unfinished surgical suture material
110 through the combined heating and cutting station 400 and through
the stationary clamp 600. After the moving clamp reaches its end
position 512 the stationary clamp 600 grasps or closes on the unfinished
surgical suture material 110 positioned within the stationary clamp
600. The moving clamp 500 then releases the unfinished surgical
suture material 110 in its grasp, allowing the suture material 110
previously grasped by the moving clamp 500 to fall onto and be held
by the end portion 704. Next, while the moving clamp is in its open
or non-grasping state, the linear actuator 550 drives the moving
clamp 500 from its end position 512 to its home position 510 where
the moving clamp 500 again grasps or closes on the unfinished surgical
suture material 110 at the home position 510. After the moving clamp
500 grasps the unfinished surgical suture material 110 at the home
position 510 for the second time, the stationary clamp 600 opens.
Thereafter, while the moving clamp 500 remains in its grasping or
closed state and the stationary clamp 600 remains in its open state,
the linear actuator 550 again drives the moving clamp 500 from its
home position 510 to the end position 512. After the imoing clamp
500 reaches its end position 512 for the second time, the stationary
clamp 600 again grasps or closes on the unfinished surgical suture
material 110 positioned within the stationary clamp 600.
After the unfinished surgical suture material 10 has been "pulled
twice" by the moving clamp 500 as described in the paragraph
above, the heating dies 402 404 and the cutting dies 450 452 in
the combined heating and cutting station 400 function as described
above to thermally form and cut a length of surgical suture tip
material positioned within the station. After the cutting dies 450
452 move from their closed position to their open position following
the cutting of the suture tip, the stationary clamp 600 releases
the surgical suture material within its grasp. As the stationary
clamp opens and releases the previously grasped surgical suture
material, a finished surgical suture 120 having a thermally formed
and cut tip falls by gravity onto an arm affixed to the stationary
clamp 600. Since the moving clamp 500 pulled the suture material
110 two times consecutively before the combined heating and cutting
station 400 thermally formed and cut the suture tip, the resulting
finished surgical suture, 120 produced by the extended length suture
mode may have a length which is greater than the length of the linear
actuator 550.
Furthermore, it is to be understood that although the present invention
has been described with reference to a preferred embodiment, various
modifications, known to those skilled in the art, may be made to
the structures and process steps presented herein without departing
from the invention as recited in the several claims appended hereto. |