Suture needle abstract
There are disclosed a method of and apparatus for grinding an elongated
material for a suture needle. An elongated grinding tape is reciprocally
moved in its longitudinal direction, and simultaneously the material
is pressed against the grinding tape in such a manner that the material
is disposed substantially perpendicular to the longitudinal direction
of the grinding tape and is inclined relative to one face of the
grinding tape, thereby grinding the material to form a cutting edge
on at least one side edge of a grounded surface of the material.
The grinding apparatus includes a mechanism for reciprocally moving
the grinding tape in opposite directions along the longitudinal
direction of the grinding tape, a mechanism for transferring the
grinding tape in a predetermined one of the opposite directions
along the longitudinal direction of the grinding tape, a tape support
member, and a mechanism for supporting the material and for pressing
the material against that portion of the grinding tape positioned
at a support surface of the tape support member. A suture needle
includes at least one ground surface, and a pair of cutting edges
formed respectively on opposite side edges of the ground surface.
The ground surface has grinding traces which extend perpendicular
to an axis of the suture needle, and the pair of cutting edges are
in generally the same condition from a microscopic point of view.
Suture needle claims
What is claimed is:
1. A suture needle including at least one ground surface, and a
pair of cutting edges formed respectively on opposite side edges
of said ground surface, said ground surface having grinding traces
which extend perpendicular to an axis of said suture needle, and
each of said cutting edges in said pair essentially being in the
same condition as the other, from a microscopic point of view.
2. A suture needle according to claim 1 in which burrs formed
on said pair of cutting edges are of generally the same size in
a predetermined range.
3. A suture needle according to claim 1 in which said pair of
cutting edges are rounded to generally the same level in a predetermined
range.
Suture needle description
BACKGROUND OF THE INVENTION
This invention relates to a suture (surgical) needle and a method
of and apparatus for grinding a needle material to form a suture
needle having a cutting edge.
A general method of producing a suture needle having a cutting
edge will now be briefly described.
First, a wire is cut into a predetermined length to provide an
elongated needle material. Then, a mounting hole to which a gut
is to be attached is formed in one end portion of the needle material.
Then, the needle material is pressed into a required cross-sectional
shape. Then, the needle material is ground to form a cutting edge.
Then, the needle material is bent into a required shape. Then, the
needle material is subjected to a heat treatment, and then is subjected
to chemical polishing and/or electropolishing. Finally, a silicone
coating is optionally applied to the needle thus produced.
Japanese Patent Publication No. 35383/88 discloses one method of
grinding a needle material. This method will now be described in
detail with reference to FIG. 14. In this method, there are used
a whetstone 90 with a cylindrical peripheral surface and a chucking
jig 91. A needle material 100 having a mounting hole formed in its
one end portion is chucked or held by the chucking jig 91 and is
pressed against the peripheral surface of the whetstone 90 in such
a manner that the needle material 100 is oriented perpendicular
to an axis 90a of rotation of the whetstone 90. The needle material
100 is ground by the rotation of the whetstone 90 and as a result
a cutting edge is formed at one or each of lateral edges of the
ground surface of the needle material, and at the same time the
end of the needle material remote from the one end portion thereof
chucked by the chucking jig 91 is pointed.
This method has the following disadvantages (1) to (4):
(1) The grinding direction (that is, the direction of movement
of abrasive grains bonded to the peripheral surface of the whetstone)
is generally parallel to the longitudinal direction of the needle
material, and hence is substantially parallel to the cutting edge
produced by the grinding. Therefore, burrs formed on the cutting
edge are considerably large. When these burrs are to be removed
by electropolishing or chemical polishing, it is difficult to determine
a proper time for such polishing treatment. More specifically, if
the treatment time is too short, the burrs fails to be removed to
a satisfactory level, and in contrast if the treatment time is too
long, the cutting edge becomes rounded. In either case, the piercing
properties of the resultant suture needle are adversely affected.
(2) The direction of rotation of the whetstone 90 during the grinding
is so determined that the abrasive grains bonded to the peripheral
surface of the whetstone 90 move in a direction away from the chucked
end of the needle material 100 toward the pointed end thereof. The
reason for this is to prevent the pointed end of the needle material
100 from interfering with the peripheral surface of the whetstone
90. However, with this rotation direction, the heat produced by
the grinding concentrates on the pointed end of the needle material
100 having a small heat capacity, to soften the pointed end of
the needle material 100 so that the piercing properties and strength
of the resultant suture needle are adversely affected.
(3) The condition of the peripheral surface of the whetstone 90
is changed little by little in the course of a long-period use,
and as a result the condition of the cutting edge obtained by the
grinding is changed little by little from one needle material to
another.
(4) As shown in FIG. 14 when the needle material 100 is pressed
against the peripheral surface of the whetstone 90 the chucking
jig 91 must be held apart from the peripheral surface of the whetstone
90. This does not pose any problem when grinding the needle material
for a long suture needle, but poses a problem when grinding the
needle material for a short suture needle used for an operation
on the eye. When the needle material is short, the chucking jig
91 must be located at a position shown in phantom in FIG. 14; however,
at this position, the chucking jig 91 interferes with the whetstone
90. Therefore, actually, the chucking jig 91 is located at the position
shown in a solid line in FIG. 14 and the needle material must be
much longer than the resultant suture needle. This requires an additional
step of cutting the needle material after the grinding step, and
after this cutting step, the step of forming the mounting hole in
the end of the needle material must be carried out. During the cutting
step and the mounting hole-forming step, it is possible that the
cutting edges of a number of the needle materials are contacted
with one another, and are damaged, which adversely affects the piercing
properties of the cutting edges. And besides, because of the additional
cutting step and the waste of the material, the manufacturing cost
of the suture needle is increased.
In another conventional method of grinding a needle material, there
is used an endless abrasive sheet extended around a pair of rollers.
This abrasive sheet comprises a sheet-like substrate made of a cloth,
paper or the like, and abrasive grains bonded to an outer surface
of this substrate. In this method, a chucking jig disposed near
the peripheral surface of the roller chucks the needle material
in such a manner that the needle material is oriented in parallel
relation to the direction of movement of the abrasive sheet, and
the needle material is pressed against that portion of the abrasive
sheet extended around the peripheral surface of the roller. This
method also has the above-mentioned disadvantages (1) to (4).
Japanese Utility Model Publication Nos. 39420/76 41208/80 and
6885/86 and Japanese Laid-Open (Kokai) Utility Model Application
No. 135106/85 disclose suture needles having a number of grinding
traces extending perpendicular to a cutting edge. Although a grinding
method is not clearly described in these prior art publications,
it is clear that abrasive grains move in a direction perpendicular
to the cutting edge to effect the grinding. In such method, the
above disadvantage (2) is overcome, and probably the above disadvantage
(4) may be overcome However, the above disadvantage (3) is not overcome,
and instead of the above disadvantage (1), another disadvantage
is encountered. More specifically, large burrs are formed on one
of the two cutting edges which is disposed at a downstream side
of the direction of movement of the abrasive grains, the two cutting
edges being formed respectively on the lateral edges of the ground
surface of the needle material. Burrs are hardly formed on the other
cutting edge disposed at an upstream side of the direction of movement
of the abrasive grains. Therefore, when the burrs on the downstream-side
cutting edge are removed by electropolishing or chemical polishing
after the grinding operation, the upstream-side cutting edge becomes
rounded. This adversely affects the piercing properties of the resultant
suture needle.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a suture needle and
a method of and apparatus for grinding a needle material for a suture
needle, which overcome the above deficiencies of the prior art.
According to one aspect of the present invention, there is provided
a method of grinding an elongated material for a suture needle,
comprising the step of reciprocally moving an elongated grinding
tape in opposite directions along a longitudinal direction of the
grinding tape, and simultaneously pressing the material against
one face of the grinding tape in such a manner that the material
is disposed substantially perpendicular to the longitudinal direction
of the grinding tape and is inclined relative to the one face of
the grinding tape, thereby grinding the material to form a cutting
edge on at least one side edge of a grounded surface of the material.
According to another aspect of the present invention, there is
provided a grinding apparatus for grinding an elongated material
for a suture needle, comprising:
(a) an elongated grinding tape;
(b) reciprocal movement means for reciprocally moving the grinding
tape in opposite directions along a longitudinal direction of the
grinding tape;
(c) transfer means for transferring the grinding tape in a predetermined
one of the opposite directions along the longitudinal direction
of the grinding tape;
(d) a tape support member having a support surface along which
the grinding tape is moved; and
(e) pressing means for supporting the material in such a manner
that the material is disposed substantially perpendicular to the
longitudinal direction of the grinding tape and is inclined relative
to one face of the grinding tape, and for pressing the material
against that portion of the grinding tape positioned at the support
surface of the tape support member.
According to a further aspect of the present invention, there is
provided a suture needle including at least one ground surface,
and a pair of cutting edges formed respectively on opposite side
edges of the ground surface, the ground surface having grinding
traces which extend perpendicular to an axis of the suture needle,
and the pair of cutting edges being in generally the same condition
from a microscopic point of view.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic front-elevational view of a grinding apparatus
according to the present invention;
FIG. 2 is a plan view of a reciprocal movement mechanism of the
grinding apparatus;
FIG. 3 is an enlarged transverse cross-sectional view of a grinding
tape;
FIG. 4 is a plane view showing pressing mechanisms of the grinding
apparatus arranged adjacent to the lateral sides of the grinding
tape;
FIG. 5 is a side-elevational view of the pressing mechanism of
the grinding apparatus;
FIG. 6 is a side-elevational view of a needle material with its
diameter shown as exaggerated;
FIG. 7 is a side-elevational view of the ground needle material
with its diameter shown as exaggerated;
FIG. 8 is a perspective view of a suture needle obtained by bending
the ground needle material;
FIG. 9 is a cross-sectional view taken along the line IX--IX of
FIG. 8;
FIG. 10 is a fragmentary, enlarged view of the needle material,
showing a cutting edge and grinding traces formed on the needle
material;
FIGS. 11 to 13 are cross-sectional views of modified suture needles,
respectively; and
FIG. 14 is a front-elevational view of a conventional grinding
apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
Before describing a method and apparatus of the present invention,
a suture needle (final product) 200 will be first described in detail
with reference to FIGS. 8 to 10. The suture needle 200 includes
a first portion (proximal end portion) 200a of a circular cross-section,
an intermediate portion 200b of a triangular cross-section generally
uniform in cross-sectional area throughout an entire length of the
intermediate portion 200b, and a third portion (distal end portion)
200c of a triangular cross-section decreasing in cross-sectional
area progressively toward a pointed end 201. The third portion 200c
has three ground surfaces, and each of the three edges of the third
portion 200c defined by intersection between respective two adjacent
ground surfaces serves as a sharp cutting edge 202. The three cutting
edges 202 are generally in the same condition from a microscopic
point of view. Namely, when burrs remain on the three cutting edges
in an allowable range, the burrs on these cutting edges are of generally
the same size. And, when the burrs hardly remain on the three cutting
edges 202 these cutting edges are rounded to generally the same
level. Grinding traces 204 are formed on each of the three ground
surfaces, and extend in a direction perpendicular to the axis of
the suture needle, and intersect the cutting edge 202. A blind hole
is formed in the proximal end face of the suture needle 200 and
extends along the axis of the proximal end portion 200a. This blind
hole serves as a mounting hole 203 to which a gut is to be attached.
The mounting hole may be constituted by a through hole extending
transversely through the proximal end portion 200a perpendicularly
to the axis thereof.
The dimensions of the suture needle 200 are not particularly limited.
For example, the suture needle 200 has a thickness of 0.07 to 1.4
mm and a length of 4 to 65 mm, and particularly the suture needle
200 has a thickness of 0.07 to 0.33 mm and a length of 4 to 13 mm
for use in an operation on the eye.
Next, the method of producing the suture needle 200 will now be
described briefly. A wire of austenite-type stainless steel is cold-drawn
into a required diameter, with its crystals converted into a fiber-like
structure. Then, this wire is cut into a predetermined length to
provide an elongated stock of a circular cross-section. The stock
may be composed of martensite-type stainless steel or precipitation
hardened stainless steel.
The length of the stock is generally equal to the length of the
suture needle (final product) 200. More exactly, the stock is slightly
longer than the suture needle 200 taking into consideration that
amount of the stock to be lost by the grinding. A laser beam or
an electron beam is applied to the proximal end face of the stock
to form the mounting hole 203 (FIG. 6). Then, the stock is shaped
by pressing into a triangular cross-section except for that portion
thereof (proximal end portion) where the mounting hole 203 is formed,
thereby providing a needle material 100 shown in FIG. 6. The pressed
portion of the needle material 100 has a generally uniform triangular
cross-sectional area throughout an entire length thereof. For obtaining
the needle material 100 the stock may be shaped into a triangular
cross-section by grinding, instead of the pressing. Then, the three
side faces of the cross-sectionally triangular portion are ground
according to the procedure of the present invention, thereby forming
the three cutting edges 202 and the pointed end 201. Then, the needle
material 100 thus ground is bent to thereby obtain the suture needle
200 as shown in FIG. 8. Thereafter, the suture needle 200 is subjected
to a heat treatment, and then to chemical polishing and/or electropolishing.
Next, a grinding apparatus for grinding the needle material 100
in the above-mentioned manner will now be described with reference
to FIGS. 1 to 5. As shown in FIG. 1 this grinding apparatus includes
a long grinding tape 10. As shown in FIG. 3 the grinding tape 10
comprises a tape body or substrate 10a made of a synthetic resin
such as polyester. The tape body 10a has a thickness of 0.1 mm,
a width of 12.5 to 25 mm, and a length of 50 to 100 m, and has a
smooth surface. Abrasive grains 10b, such as white alundum (WA),
having a grain size of 1300 to 2000 (4 to 14 micron meter diameter)
are bonded to the smooth surface of the tape body 10a by a binder
resin (not shown). The size of the abrasive grains 10b of the grinding
tape 10 is determined, taking into consideration the grinding of
the needle material 100 for the suture needle 200 of a very small
size. The tape body 10a may be made of metal.
The grinding apparatus comprises a pair of guide rollers 11 and
12 for guiding the grinding tape 10 these guide rollers being spaced
from each other in a horizontal direction. The guide rollers 11
and 12 are disposed at the same height or level, and a back-up plate
13 serving as a tape support member is horizontally provided between
the guide rollers 11 and 12. A flat upper surface of the back-up
plate 13 is disposed at the same height as those of the top points
of the guide rollers 11 and 12 and serves as a support surface
13a. Part of the grinding tape 10 is placed on the back-up plate
13 in such a manner that the surface of that part having the abrasive
grains 10a bonded thereto is directed upwardly.
The grinding apparatus is provided with a transfer mechanism 20
for transferring or moving that portion of the grinding tape 10
which is placed on the back-up plate 13 in a predetermined direction
(that is, in a left-hand direction in FIG. 1) which is the longitudinal
direction of the grinding tape 10. The transfer mechanism 20 comprises
a feed mechanism 21 for feeding a fresh or unused grinding tape
10 to the back-up plate 13 and a take-up mechanism 22 for taking
up or winding up the used grinding tape 10 fed from the back-up
plate 13. More specifically, the feed mechanism 21 is disposed below
the guide roller 11 and comprises a motor 21a with a brake, and
a rotation shaft 21b connected to the motor 21a. The take-up mechanism
22 is disposed below the other guide roller 12 and comprises a
motor 22a with a brake, and a rotation shaft 22b connected to the
motor 22a. A roll 10a of the unused grinding tape 10 is supported
on the rotation shaft 21b of the feed mechanism 21. A roller 10b
of the used grinding tape 10 is supported on the rotation shaft
22b of the tape-up mechanism 22. The grinding tape 10 is fed or
supplied from the roll 10a is passed past the guide roller 11 the
back-up plate 13 and the guide roller 12 and reaches the roll 10b.
The grinding apparatus is provided with a reciprocal movement mechanism
30 for reciprocally moving that portion of the grinding tape 10
which is placed on the back-up plate 13 in opposite directions
(i.e., the right and left directions in FIG. 1) along the longitudinal
direction of the grinding tape 10. The reciprocal movement mechanism
30 comprises four rollers 31 32 33 and 34 rotatable at their respective
fixed positions, two floating rollers 35 and 36 a support plate
(roller support member) 37 and a motor (drive means) 38. The rollers
31 and 32 are disposed between the guide roller 11 and the feed
mechanism 21 and are vertically spaced from each other in opposed
relation to each other. The rollers 33 and 34 are disposed between
the guide roller 12 and the take-up mechanism 22 and are spaced
from each other in opposed relation to each other. The support plate
37 is disposed between the opposed rollers 31 and 32 and the opposed
rollers 33 and 34 and is supported by guide means (not shown) so
as to reciprocally move in the right and left directions in FIG.
1. The support plate 37 is horizontally disposed at a level lower
than the rollers 31 and 33 but higher than the rollers 32 and 34.
A pair of notches 37a are formed respectively in the opposite ends
of the support plate 37 and the floating rollers 35 and 36 are
rotatably received in these notches 37a, respectively. That portion
of the grinding tape 10 extending between the feed mechanism 21
and the guide roller 11 is extended around the roller 32 the floating
roller 35 and the roller 31. That portion of the grinding tape 10
extending between the guide roller 12 and the tape-up mechanism
22 is extended around the roller 33 the floating roller 36 and
the roller 34.
The motor 38 is disposed below the support plate 37. As best shown
in FIG. 2 the motor 38 has an eccentric shaft 38a, and the eccentric
shaft 38a is received in a slot 37b which is formed through the
support plate 37 and extends in the direction of the width of the
support plate 37. When the motor 38 is rotated, the support plate
37 is reciprocally moved in the right and left directions. When
the support plate 37 is moved in the left direction, that portion
of the grinding tape 10 extended around the right floating roller
35 is pulled whereas that portion of the grinding tape 10 extended
around the left floating roller 36 is loosened, so that the grinding
tape 10 on the back-up plate 13 is moved in the right direction.
In contrast, when the support plate 37 is moved in the right direction,
the grinding tape 10 on the back-up plate 13 is moved in the left
direction. Thus, the rotation of the motor 38 causes the grinding
tape 10 to reciprocally move on the back-up plate 13 in the right
and left directions.
The reciprocal movement mechanism may use a cam operatively associated
with the motor so as to reciprocally move the support plate, and
also may use any suitable drive means, such as a pneumatic cylinder,
a hydraulic cylinder and a solenoid, instead of the motor.
The grinding apparatus is provided with a tension mechanism 40.
The tension mechanism 40 comprises a roller 41 rotatable at a fixed
position, a floating roller 42 and a spring 43 urging the floating
roller 42. The spring 43 applies a predetermined tension to the
grinding tape 10 extended around the roller 41 and the floating
roller 42.
As shown in FIG. 4 the grinding apparatus is provided with six
pressing mechanisms 50 for supporting the needle materials 100 and
pressing them against the grinding tape 10. More specifically, three
pressing mechanisms 50 are disposed adjacent to one lateral side
of the back-up plate 13 and are juxtaposed in the longitudinal
direction of the back-up plate 13. Similarly, the other three pressing
mechanism 50 are disposed adjacent to the other lateral side of
the back-up plate 13 and are juxtaposed in the longitudinal direction
of the back-up plate 13.
As shown in FIG. 5 each of the pressing mechanisms 50 includes
a chucking jig 51. The chucking jig 51 has a support rod 52 of a
generally square cross-section extending in the longitudinal direction
of the grinding tape 10 that is, in a direction perpendicular to
the sheet of FIG. 5. The support rod 52 has a through hole 52a extending
in the direction of the width thereof. A first plate 53 is passed
through the through hole 52a of the support rod 52. Fixing screws
54 are threaded into one end face of the support rod 52 and are
held at their distal ends against the side edge of the first plate
53 thereby fixing the first plate 53 relative to the support rod
52. A pair of guide members 55 (only one of which is shown in FIG.
5) are fixedly mounted on the upper surface of the first plate 53
at the rear end portion thereof, the guide members 55 being spaced
from each other in a direction perpendicular to the sheet of FIG.
5. A sliding rod 56 is supported by the pair of guide members 55
so as to be rotated about its axis and also to slide in a direction
perpendicular to the sheet of FIG. 5. A second plate 57 is fixedly
secured at its rear end to the sliding rod 56. A pair of elongated
elastic members 53a and 57a each made of rubber or the like and
extending in a direction perpendicular to the sheet of FIG. 5 are
secured respectively to the opposed surfaces of the first and second
plates 53 and 57 at the distal end portions of these plates 53 and
57. A number of needle materials 100 are held between the elastic
members 53a and 57a in such a manner that the needle materials 100
are disposed perpendicular to the grinding tape 10 and are juxtaposed
in the longitudinal direction of the grinding tape 10. Each of the
needle materials 100 is chucked or clamped by the elastic members
53a and 57a at one end portion thereof having the mounting hole
203.
Means for imparting, to the first and second plates 53 and 57
the force for clamping the needle materials 100 is as follows. A
through hole 53b is formed through the intermediate portion of the
first plate 53 and an elongated through hole 57b extending in a
direction perpendicular to the sheet of FIG. 5 is formed through
the second plate 57. A bolt 58 is passed through the two through
holes 53b and 57b. A nut 58a is threaded on the lower end of the
bolt 58 and a lever 59 is pivotally connected at one end thereof
to the upper end of the bolt 58 through a pin 58b. The lever 59
has a cam surface 59a formed at the one end thereof, and the cam
surface 59a is held in contact with a washer 60 placed on the upper
surface of the second plate 57. When the lever 59 is erected, that
is, moved away from the second plate 57 the force applied by the
first and second plates 53 and 57 to clamp the needle materials
100 is released. When the lever 59 is laid down, that is, moved
toward the second plate 57 the first and second plates 53 and 57
is supplied with the force for clamping the needle materials 100
because of the cam action achieved by the cooperation of the cam
surface 59a with the washer 60.
A pair of blocks 61 (only one of which is shown in FIG. 5) are
mounted on the upper surface of the first plate 53 and are spaced
from each other in a direction perpendicular to the sheet of FIG.
5. A pair of set screws 62 are threaded respectively through the
pair of blocks 61 from the outer sides of the blocks 61 to extend
in a direction perpendicular to the sheet of FIG. 5. The distal
ends of the two set screws 62 are held respectively against the
lateral sides of the second plate 57 thereby positioning the second
plate 57 relative to the first plate 53 in a direction perpendicular
to the sheet of FIG. 5.
The pressing mechanism 50 further comprises a jig support member
65 angularly-movably supporting the chucking jig 51.
The jig support member 65 includes a slider portion 65a supported
by a guide member 70 so as to slide vertically (i.e., upward and
downward), and a support portion 65b extending upwardly from the
upper end face of the slider portion 65a, and is tapered away from
the slider portion 65a. The upper edge of the support portion 65b
serves as a knife grinding tape 10 that is, in a direction perpendicular
to the sheet of FIG. 5. The knife edge 65c is received in a groove
52b of a triangular cross-section formed in the lower surface of
the support rod 52 and extending in a direction perpendicular to
the sheet of FIG. 5. With this arrangement, the chucking jig 51
is supported on the jig support member 65 in such a manner that
the chucking jig 51 is angularly movable about the knife edge 65c
serving as a fulcrum. Due to an angular moment caused by the weight
of the chucking jig 51 the chucking jig 51 urges the needle materials
100 against the grinding tape 10 placed on the back-up plate 13.
By loosening the fixing screws 54 the position of the first plate
53 relative to the support rod 52 can be adjusted. By this adjustment,
the angular moment of the chucking jig 51 and hence the force of
pressing of the needle materials 100 against the grinding tape 10
can be adjusted. In this embodiment, the pressing force is, for
example, 6 g.
The lower end of the slider portion 65a of the jig support member
65 is connected to an eccentric shaft 75a of a motor (drive means)
75 via a link 76. When the motor 75 rotates, the jig support member
65 is moved upward and downward, so that the fulcrum of angular
movement of the chucking jig 51 is moved upward and downward, thereby
changing the angle of inclination of the needle materials 100 relative
to the grinding tape 10 in a predetermined range.
The grinding of the needle materials 100 by the above grinding
apparatus will now be described in detail. As described above, a
number of needle materials 100 are chucked by each chucking jig
51 in such a manner that the needle materials 100 are juxtaposed
in the longitudinal direction of the grinding tape 10. Each of the
thus chucked needle materials 100 is disposed perpendicular to the
grinding tape 10 and is inclined with respect to the surface of
the grinding tape 10 and one side face of the cross-sectionally
triangular portion of the needle material 100 is positioned on the
grinding tape 10. Preferably, that portion of the needle material
100 to be chucked should be about one-third (1/3) of the overall
length thereof. The needle materials 100 are pressed against the
grinding tape 10 due to the weight of the chucking jig 51. At this
time, the force of pressing of the needle materials 100 is received
by the back-up plate 13 and therefore the grinding tape 10 is not
flexed downwardly.
In this condition, the motor 38 of the reciprocal movement mechanism
30 is driven, so that the grinding tape 10 is reciprocally moved
on the back-up plate 13 in the right and left directions (FIG. 1),
thereby grinding the needle materials 100. During this reciprocal
movement of the grinding tape 10 the motors 21a and 22a are stopped
against rotation by their respective brakes. For example, this reciprocal
movement is effected several hundreds to several thousands times
at a speed of 40 m/min. over a distance of 10 mm.
When the needle materials 100 are to be thus ground by reciprocally
moving the grinding tape 10 over the distance of 10 mm, it is preferred
that the needle materials 100 supported by the chucking jig 51 should
be spaced a distance of at least 10 mm from one another. By doing
so, those regions of the grinding tape 10 for grinding the needle
materials 100 respectively, do not overlap one another. However,
this is not imperative, and such grinding regions may overlap one
another.
After the above grinding operation is finished, the motors 21a
and 22a are rotated at the same speed, so that the unused grinding
tape 10 is supplied from the roll 10a, and also the used grinding
tape 10 is wound on the roll 10b, thereby providing an unused portion
of the grinding tape 10 onto the support surface 13a of the back-up
plate 13. The speed of transfer of the grinding tape 10 is, for
example, 5 mm/min. Before or after the transfer of the grinding
tape 10 the lever 59 of the chucking jig 51 is angularly moved
upward to weaken the force of clamping of the needle materials 100
applied by the first and second plates 53 and 57 and then the pair
of set screws 62 are adjusted to move the second plate 57 relative
to the first plate 53 in a direction perpendicular to the sheet
of FIG. 5 thereby rolling the needle materials 100 through 120.degree..
Thereafter, the lever 59 is laid down to again clamp the needle
materials 100.
By repeating the above procedure, the three side faces of the distal
end portion of each needle material 100 are ground to form the three
cutting edges 202. As described above, the needle materials 100
are kept inclined relative to the grinding tape 10 and in this
condition are ground by the grinding tape 10. Therefore, the distal
end of each needle material 100 which is not chucked by the chucking
jig 51 is pointed as at 201 in FIG. 7.
During the above grinding operation, the motor 75 of the pressing
mechanism 50 is rotated to reciprocally move the knife edge 65c
upward and downward once or a plurality of times, so that the angle
of the needle materials 100 relative to the grinding tape 10 is
changed in the predetermined range. As a result, the angle of the
cutting edge 202 relative to the axis of the needle material 100
increases progressively toward the pointed end 201.
Since the needle materials 100 are ground by the grinding tape
10 reciprocally moved several hundreds to several thousands times,
the grinding tape 10 can be used without any waste. And besides,
after this grinding operation, the next unused portion of the grinding
tape 10 is supplied to the back-plate 13 and therefore the grinding
can always be effected under the same condition. The grinding condition
does not vary from one side face of the needle material 100 to another,
and hence the grinding condition does not vary from one needle material
100 to another. Therefore, a required grinding condition can be
obtained stably.
The tape body 10a of the grinding tape 10 is made of a synthetic
resin or metal, and has the smooth surface, and the abrasive grains
10b are very fine. Therefore, even when the grinding tape 10 is
reciprocally moved in the direction perpendicular to the axes of
the needle materials 100 a stable grinding can be carried out.
If an abrasive sheet having a substrate made of cloth or paper,
part of the fibers of the substrate are projected from the surface
of the abrasive sheet, and such projected fibers would tend to interfere
with the needle material 100 during the reciprocal movement of the
abrasive sheet, so that a large bending moment would be applied
to the needle material 100. In this embodiment, however, such disadvantage
is not encountered.
As shown in FIG. 5 since the distal end of the chucking jig 51
can be located close to the lateral edges of the back-up plate 13
and the grinding tape 10 the needle materials 100 can be ground
even if the needle materials 100 are short. Therefore, as described
above, the needle material 100 can be generally equal in length
to the suture needle (final product) 200. Therefore, the needle
material 100 does not need to be cut after the grinding operation,
and damage to the cutting edges caused by the contact between the
cutting edges of the needle materials 100 during such cutting operation
can be prevented. Moreover, the formation of the mounting hole 203
can be made before the grinding operation, which also can reduce
the possibility of damage to the cutting edges.
In this embodiment, the six chucking jigs 51 are arranged on the
lateral sides of the grinding tape 10 and each of these chucking
jigs 51 supports a number of needle materials 100. Therefore, the
grinding operation can be carried out efficiently.
Next, the most important advantages provided by reciprocally moving
the grinding tape 10 in the direction perpendicular to the needle
materials 100 will now be described. Each time each side face of
the needle material 100 is ground, one ground surface is obtained.
Two cutting edges 202 are formed respectively on both side edges
of the ground surface. When the grinding tape 10 is moved in one
direction, one of these two cutting edges 202 is disposed at a downstream
side of this grinding direction, so that burrs are liable to be
formed on the one cutting edge 202; however, subsequently, when
the grinding tape 10 is moved in the opposite direction, the one
cutting edge is disposed at an upstream side of the grinding direction
so that part of the burrs can be removed. Therefore, the burrs formed
on each cutting edge 202 can be reduced in size, and such burrs
can be easily removed when carrying out the chemical polishing or
the electropolishing after the grinding operation. Moreover, the
two cutting edges 202 formed respectively on both side edges of
the ground surface, have respective burrs of generally the same
size, and therefore there is not encountered a disadvantage that
one of the two cutting edges 202 would be excessively rounded when
removing the burrs on the two cutting edges 202 by the chemical
polishing or the electropolishing. As a result, the cutting edges
202 can be sharpened to generally the same level. If the cutting
edges 202 are rounded when the burrs are removed by the electropolishing
or the chemical polishing, such roundness is allowable if it is
in an allowable range. Also, if the burrs still remain after the
electropolishing and the chemical polishing, such burrs are allowable
if it is in an allowable range. In this case, the burrs formed on
the two cutting edges formed respectively on the opposite side edges
of the ground surface are of generally the same size.
Further, since the grinding tape 10 is reciprocally moved in the
direction perpendicular to the needle materials 100 the heat produced
by the grinding is prevented from concentrating on the pointed end
201 of each needle material 100 thus preventing the softening of
the pointed end 201.
The suture needles (hereinafter referred to as "suture needles
of the invention") produced according to the above grinding
method of the invention were compared with suture needles (hereinafter
referred to as "conventional suture needles") produced
according to the conventional grinding method shown in FIG. 14
in order to determine their piercing properties. Results obtained
are as follows. When the compared suture needles had a thickness
of 0.14 mm and a length of 5.5 mm, the conventional suture needle
required a piercing force of 10 to 12 g whereas the suture needle
of the invention only required a piercing force of 6 g. When the
compared suture needles had a thickness of 0.2 mm and a length of
6.5 mm, the conventional suture needle required a piercing force
of 10 to 15 g whereas the suture needle of the invention only required
a piercing force of 8 g.
The present invention is not to be restricted to the above embodiment,
and various modifications can be made. For example, the motors 21a
and 22a may be driven to transfer the grinding tape 10 in one direction
at a low speed as described above, while the grinding tape 10 is
being reciprocally moved at a high speed by the motor 38.
For grinding one side face of each needle material 100 the reciprocal
movement of the grinding tape 10 and the transfer of the grinding
tape 10 in one direction may be alternately repeated several times.
The back-up plate 13 may be so modified that its support surface
13a has a concavely-curved shape as viewed from the end of the back-up
plate 13 in which case the back-up plate 13 has a uniform cross-section
throughout the entire length thereof. In this case, the needle material
100 can have the curved cutting edges corresponding in shape to
the curved support surface 13a of the back-up plate 13 without the
need for reciprocally moving vertically the fulcrum of angular movement
of the chucking jig 51. Where the support surface 13a of the back-up
plate 13 is flat, the cutting edges of the needle material 100 are
straight if the fulcrum of angular movement of the chucking jig
51 is not moved.
A plurality of the back-up plates may be provided depending on
the number of the pressing mechanisms. In this case, a mechanism
for adjusting the orientation of each back-up plate may be provided.
The step of forming the mounting hole in each needle material may
be carried out after the grinding operation.
The present invention is not limited to the case of producing the
suture needles of a triangular cross-section, but can be applied
to the case of producing similar suture needles having any other
suitable cross-section. For example, the suture needle may have
the intermediate portion of a trapezoidal cross-section (FIG. 11),
and the distal end portion of a triangular cross-section. In this
case, the intermediate portion has two cutting edges 202A and 202A
which are continuous respectively with two of the three cutting
edges formed on the distal end portion. Also, the the suture needle
may have a rhombic cross-section (FIG. 12) in which case two acute
edges serve as cutting edges 202B and 202B, respectively. Further,
the suture needle may a flatten hexagonal cross-section (FIG. 13)
in which case two acute edges serve as cutting edges 202C and 202C,
respectively.
|