Surgical needle abstract
A surgical needle has a top edge formed by two pressed faces located
inside or outside of curvature from pressing a material blank made
of austenitic stainless steel having fibrous texture and cutting
edges formed on both sides of a base. The top edge is sharp at a
needle point and the sharp needle point is constituted of fibrous
texture formed at the surface layer of the material blank. Grinding
marks extending crosswise formed on the face of the mold are transferred
to the pressed faces. A mold constitutes plural faces forming projecting
angles (angle between two intersecting faces is 180.degree. or below,
and the line at which the two faces intersect is made as a projecting
line) along edges of the blocks made of two rectangular prisms,
and constitutes a cavity by suitably contacting the edges of the
blocks.
Surgical needle claims
What is claimed is:
1. A method of producing a surgical needle with a substantially
triangular cross section comprising the steps of;
extending austenitic stainless steel by wiredrawing to make a material
blank having fibrous texture at its surface;
forming a needle material blank with a substantially triangular
cross section by pressing said material blank using a mold formed
with a pair of blocks which have oblique faces to form a cavity
so as to make a projecting angle between them less than 180.degree.;
and
forming a pair of cutting edges on both sides of another face of
said needle material opposing an edge which is formed between two
pressed faces formed by said oblique faces of said mold by removing
surface of said another face.
2. A method of producing a surgical needle according to claim 1
wherein ground marks extending crosswise to a longitudinal direction
of said needle material blank is formed on said oblique faces of
said mold so as to transfer fibrous texture onto said pressed faces
of said needle material blank when said pressed faces are pressed.
Surgical needle description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority benefits under 35 U.S.C .sctn.119
of Japanese application Serial No. 6-198333 filed Aug. 23rd, 1994
the entire disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a surgical needle for suture having a
point of a triangle cross section and a mold for manufacturing the
surgical needle.
2. Description of Related Art
A surgical needle for suture whose point has a triangular cross
section, has keen cutting edges of certain length from the point,
on both sides of the base of the triangular cross section and at
a top edge opposing to the base. The surgical needle has a sharp
needle point at which the respective cutting edges are integrated.
The major part of the top edge is however formed in a gently curving
shape without forming such a cutting edge. When an incised portion
is to be sutured, the needle penetrates human's body tissues by
its sharp needle point and incises them by the cutting edges, thereby
passing through the tissues as pushing the incised tissues aside
by the top edge. Such a triangular needle takes one of various thicknesses,
arranges the top edge at either inside or outside, and is formed
to be curving with predetermined curvature. A properly selected
triangular needle is used according to the portions to be sutured.
The inventors of this invention have previously proposed a method
for manufacturing a triangular needle, as disclosed in Japanese
Patent Publication No. 1-26785 in which an intermediate material
is made so that its distal end is formed in a triangular prism shape
by pressing the original material and in which only base face opposing
to the top edge of the intermediate material is ground. With this
method, as shown in FIGS. 5A and 5B, a top edge 52 of the triangular
prism 51 is molded into a blunt shape by pressing. Thus, grinding
of oblique faces 55 located on both sides of the edge 52 is required
to form a sharp needle point 54 in addition to grinding of the base
face 53 of the prism 51.
The size of the original material for surgical needle is extremely
fine as of 0.1 mm through 1.5 mm. A small cavity is formed in a
mold for forming an intermediate material by pressing it. That is,
such a small cavity is formed in a V-shape corresponding to the
cross section of the surgical needle at the mold. The angle portion
of the V-shaped cavity corresponds to the edge of the triangular
prism. If such a V-shaped cavity would have been formed by a single
material, it is impossible to fabricate the bottom of the cavity
corresponding to the angle portion. For example, even if the material
is cut or ground by a milling cutter or hone having a keen edge
formed in association with the designated angle, it is impossible
to form a V-shaped cavity having an accurate edge due to wearing
of the cutter or hone as proceeding fabrications.
To solve this problem, a mold as disclosed in Japanese Unexamined
Patent Publication No. 2-133137 has been used for fabricating the
original material. With the technique of the invention above, in
order to mold a triangular prism corresponding to the cross section
of the predetermined surgical needle, two quadratic prisms are ground
off at their comers so as to respectively form a half of the triangular
prism, or a triangle when viewed to its cross section, divided by
a perpendicular drawn from the top edge to the base.
The mold can be formed by contacting those quadratic prisms with
each other and allows the angle portion of the V-shape which makes
the bottom of the cavity to be fabricated accurately.
Stainless steel is used as a material for such surgical needle.
The surgical needle requires to have proper strength and stiffness
because it will be subject to stress of complex directions when
penetrating through the tissues. Therefore, martensitic stainless
steel is ordinarily used. After formed with cutting edges and an
eye and after curved into a predetermined shape, a surgical needle
is given strength and stiffness by a heat treatment.
However, a problem arises which rust may occur if such martensitic
stainless steel is not used for a long time of period after manufactured.
To avoid this problem, this inventors have proposed and established
a manufacturing technology of a surgical needle in use of austenitic
stainless steel, as disclosed in Japanese Patent Publication No.
1-11084. In this technology, a wire rod made of austenitic stainless
steel is wiredrawn with face reduction rate of 80% or above, and
the drawn wire is fabricated while maintained at 500.degree. C.
or below to manufacture the surgical needle. That is, by cold wiredrawing
of the wire rod of austenitic stainless steel, the needle gains
rigidity and fiber-like, or fibrously, extended texture, and where
the texture is maintained at the temperature of recrystallization
or below, the surgical needle to be manufactured assures its strength
and stiffness.
We found, as a result of proceeding of further research and development
for surgical needle and its manufacturing technology, that the material
cold wiredrawn from an austenitic stainless steel wire rod has the
stiffest layer at its surface and reduces its stiffness as approaches
the material center and that it would be advantageous to manufacture
the surgical needle where such a surface layer is left on the needle.
However, the mold is for molding a triangular prism as an intermediate
material by pressing the original material, so that when a sharp
needle point is formed, two faces between the bottom and the edge
are necessary to be ground. Hence, the needle point of the obtained
surgical needle tends to be formed by grinding off the stiff surface
layer.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a mold capable of forming
a sharp needle point with the hardest surface layer of the material
therefor.
A mold according to the invention is constituted of a pair of rectangularly
shaped blocks having oblique faces extending in a longitudinal direction
of an edge of each block so that the oblique faces form a cavity
for surgical needles when the blocks are contacted with each other
so as to meet the opposing oblique faces to each other. The oblique
face is formed of plural subdivided faces constituting an angle
between them equal to 180.degree. or below.
With the mold, when the blocks are contacted with each other, the
cavity is formed of a cross-sectionally V-shaped groove having a
larger cross section on a side of a needle proximal end than the
cross section of the material blank and a smaller cross section
on a side of a needle distal end than the cross section of the material
blank and sharply intersecting edges at a V-shaped point. Therefore,
when a material blank is inserted into the cavity and is then pressed,
an intermediate material can be fabricated to be blunt on the side
of the needle proximal end and keen on the side of the needle distal
end.
The shape of the intermediate material is a transformed triangular
pyramid whose top edge comes close to the base as approaches the
needle distal end. Therefore, a surgical needle with a sharp point
can be manufactured by grinding the intermediate material so as
to make the base slightly close to the top edge. The needle point
is substantially constituted of two faces located on both side of
the top edge, and is constituted of the hardest surface layer of
the material, which constitutes the two faces. Accordingly, almost
the entire surface including the needle point is made of the surface
layer of the material, so that surgical needles can be manufactured
whose strength and stiffness are so maintained under the best condition.
A surgical needle according to the invention is made from austenitic
stainless steel blank having fibrous texture, and has a top edge
located inside or outside of curvature and made by two pressing
faces, and cutting edges formed at both sides of inside or outside
face of the curvature. The top edge becomes sharp on the needle
distal end of the surgical needle, and a keen needle tip is constituted
by the fibrous texture formed at the surface layer of material.
Such a surgical needle can maintain its strength and stiffness
because the needle becomes sharper, or namely, changes from face
contact to liner contact against the body tissues, as the top edge
approaches the needle tip and because the sharp needle point is
constituted of the hardest material's surface layer.
According to an embodiment of the invention, a surgical needle
has a top edge located inside or outside of curvature and made by
two pressed faces, cutting edges formed at both sides of inside
or outside face of the curvature. A part of the pressed face is
transferred with grinding marks extending in a cross direction formed
on the oblique face.
With such a surgical needle, grinding marks in the cross direction
are transferred from the oblique faces of the mold to at least a
portion of the two pressed faces located on both sides of the top
edge, and the serrate cutting edges can be made by the grinding
marks, thereby reducing penetration resistance when the tissues
are incised.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and features of the invention are apparent
to those skilled in the art from the following preferred embodiments
thereof when considered in conjunction with the accompanied drawings,
in which:
FIG. 1 is a perspective view showing a surgical needle according
to the invention;
FIG. 2A is an enlarged top view of the surgical needle point of
the surgical needle shown in FIG. 1;
FIG. 2B is an enlarged side view of the needle point of the surgical
needle shown in FIG. 1;.
FIG. 2C is an enlarged top view of the needle point of the surgical
needle shown in FIG. 1 showing the oblique faces;
FIG. 2D is an enlarged front view of the needle point of the surgical
needle shown in FIG. 1;
FIG. 3A is a perspective view of one block of the mold B for forming
the surgical needle;
FIG. 3B is an enlarged rear view of the mold B for forming the
surgical needle;
FIG. 3C is an enlarged front view of the mold B for forming the
surgical needle;
FIG. 4(a) is a side view of an intermediate material formed by
pressing the material blank with the mold;
FIG. 4(b) is a top view of an intermediate material formed by pressing
the material blank with the mold; and
FIG. 5A is a side view partially cut away of a conventional surgical
needle;
FIG. 5B is a front view of a conventional surgical needle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings in detail, a surgical needle, as well
as a mold for manufacturing it, according to a preferred embodiment
of the invention is shown.
First, referring to FIGS. 1 and 2A-2D, constitution of a surgical
needle A is described. The surgical needle A uses a material whose
texture is made to be fibrously extended by cold wiredrawing of
liner austenitic stainless steel material at a predetermined face
reduction rate and which is fabricated to have a diameter equivalent
to the diameter of the objective surgical needle A, and is manufactured
using material blanks in which the material is cut at the length
corresponding to the length of the objective surgical needle A.
The material blank has fibrously extended texture from the center
to the surface layer, and the hardness at the surface layer is harder
than that at the center. The surgical needle A is therefore manufactured
using the surface layer of the material blank as much as possible
as the surface of the surgical needle A.
In FIG. 1 a hole 2 as means for connecting a suture is formed
at an end 1a on the proximal end 1 as one end of the surgical needle
A, and a sharp needle point 3 is formed at the other end. Cross
sections between a needle body 4 and the needle point 3 are formed
in a triangle made of a base 5 and oblique faces 6a, 6b, and a
top edge 7 is formed corresponding to the top of the triangle.
The numeral 8 is a portion on a side of the distal end between
the needle point 3 and the needle body 4; the needle tip portion
8 has predetermined length and is constituted corresponding to a
ground face 9 which is ground so as to make the base 5 come close
to the top edge 7 as approaches the needle point 3. Cutting edges
10 are formed on both sides of the ground face 9.
The top edge 7 is formed by the top of the oblique faces 6a, 6b
formed by the mold B; the top edge 7 is made blunt on the side of
the proximal end and keen on the side of the distal end, or namely
changes from a blunt state to a keen state, as approaches to the
needle point 3.
That is, the needle tip portion 8 of the surgical needle A has
the two oblique faces 6a, 6b, as shown in FIG. 2C formed by press
and the ground face 9 is formed with the top edge 7 made from the
oblique faces 6a, 6b to have sharpness so as to function as almost
a cutting edge, and is formed with the cutting edges 10 made from
the oblique faces 6a, 6b and the ground face 9 on both side of the
ground face 9. The needle point 3 is formed at a point at which
the cutting edges 10 and the top edge 7 are integrated.
Therefore, only the base 5 is ground when the needle point 3 is
formed. The oblique faces 6a, 6b are not ground, at which the surface
layer of the blank is left as it is. Accordingly, two faces at the
needle tip portion 8 and three faces at the needle body 4 have the
surface layer of the material blank in the surgical needle A, so
that the surgical needle can maintain high strength and stiffness.
The surgical needle A thus constituted by remaining the surface
layer of the material blank as much as possible, can oppose to large
penetration resistance and large bending force occurring when passing
through body tissues.
It is to be noted that although in this embodiment the surgical
needle is formed as an eyeless needle by forming the hole 2 for
connecting a suture at the end 1a, connecting means for a suture
is not limited to such a structure, and the surgical needle can
be as a matter of course formed as so called an eyed needle with
a hole having elasity at the end 1a. The ground face 9 is not necessary
to mean a face formed by grinding in use of a hone, and includes
a face formed by removing the base 5 by a metal removing method,
for example, such as, an electroerosion machining method when the
cutting edges 10 are formed.
Referring to FIGS. 3A-3C, constitution of a mold B for forming
the surgical needle A is described. In FIGS. 3B-3C, the mold B is
constituted of blocks 11 12 made of two rectangularly shaped prisms.
A half of the cross section of a cavity 13 and a leaking portion
14 in continuation with the cavity 13 are symmetrically formed at
the corresponding edges of the blocks 11 12 respectively, and
the mold B is constituted by facing the blocks 11 12 with each
other and fixing them by means of fixing jigs or whatever not shown
so as to oppose molding force.
The cavity 13 is formed of plural subdivided faces 15 to 17 having
relationship of a projecting angle (the angle between two intersecting
faces is 180.degree. or below, and the line at which the two faces
intersect is made as a projecting line) formed in correspondence
with the needle body 4 and the needle tip portion 8 and is formed
to have a V-shape with various depths in accordance with positions.
The cavity 13 when the material blank is pressed, is constituted
to make the top edge 7 blunt at a portion corresponding to the needle
body 4 and keen at a portion corresponding to the needle point 3
and is constituted so that the top edge 7 is surely formed to be
sharp in accordance with the cross section of the cavity 13 in particular
by rendering the cross section of the cavity smaller than the cross
section of the material blank at a portion corresponding to the
needle tip portion 8.
That is, the face 15 constituting the cavity 13 is formed in continuation
with the leaking portion 14 formed at one end of the mold B, and
is constituted as an area for forming the needle body 4. The face
15 has the same length as the needle body 4 of the surgical needle
A, has depth that the cross section at a connection 18a between
the face 15 and the leaking portion 14 is larger than the cross
section of the material blank, and is formed in a V-shape having
depth that the cross section at a position (connection 18b between
the face 16 and the face 15) remotest from the leaking portion 14
is almost equal to or slightly larger than the cross section of
the material blank.
The faces 16 17 are constituted as areas for forming the needle
tip portion 8 and are formed as to have sufficiently longer length
than the length of the needle tip portion 8. The face 16 is formed
in continuation with the face 15 and the connection 18b between
the face 16 and the face 15 forms the projecting angle to form a
V-shape that becomes shallower as remote from the connection 18b.
The face 17 is formed in a condition that it stacked against the
face 16 with the projecting angle. Changes of depth of the face
17 with respect to the axis direction of the mold B are not restricted.
In this embodiment, the face 17 is formed to be deeper as remote
from the connection 18b. Therefore, the connection 18c between the
faces 16 17 forms a projecting angle thereat.
The cavity 13 composed of faces 15 to 17 described above can be
formed without interference of the grinding machine with the already
processed face at a time that subsequently processed face is to
be ground where the edges of blocks 11 12 are ground at their faces
by a machine such as a plain grinder. For example, when plural faces
are connected with an angle equal to or greater than 180.degree.
between the faces, whatever grinding order of the respective faces
would interfere with the already processed area by the grinding
tool, and it is impossible to form a suitable cavity.
Next, an intermediate material C manufactured by the mold B is
described. The intermediate material C shown in FIGS. 4A and 4B
is obtainable by pressing by the mold B a material blank (not shown)
in which a liner material having diameter corresponding to the diameter
of the objective surgical needle A is cut by a length corresponding
to the length of the surgical needle A.
A portion corresponding to the needle body 4 of the intermediate
material C is formed in a triangle with rounded corners because
the cross section near the end 1 formed by opposing faces 15 is
larger than the cross section of the material blank. At the needle
point 3 and its vicinity, the top edge 7 is made relatively keen
even though not functioning as a cutting edge.
At a portion corresponding to a needle tip portion 8 of the intermediate
material C, the top edge 7 is made relatively keen and so do the
edges on both sides of the base 5 because the cross section formed
by the opposing faces 16 at the connection 18b between the face
15 and the face 16 is nearly equal to that of the material blank.
The top edge 7 is made considerably keen even though not functioning
as a cutting edge because the cross section formed by the opposing
faces 16 17 becomes smaller than that of the material blank as
becoming remote from the connection 18b, and residual materials
are formed on both sides of the base 5 as burrs 19.
A straight needle as a condition prior to bending process of surgical
needle A shown in FIG. 1 can be manufactured by removing the burrs
19 at the needle tip portion 8 by grinding the base 5 of the intermediate
material C, grinding the base 5 in accordance with the length of
the predetermined needle tip portion 8 and with depth from the base
5 of the top edge 7 corresponding to that length to make the base
5 close to the top edge 7 and integrating the ground face 9 at
which the base 5 is ground and two oblique faces 6a, 6b to form
the needle point 3.
It is to be noted that although with the mold B the top edge 7
corresponding to the needle tip portion 8 is entirely made keen,
it can be constituted that only a portion corresponding to the needle
point 3 is made keen.
With surgical needles having cutting edges, it has been known that
their incision characteristics can be improved by grinding, when
the cutting edge is formed, in a direction intersecting the cutting
edge, or preferably, in a perpendicular direction to the edge, and
forming tiny serrate portions on the cutting edge. Therefore, serrate
portions may be formed on the cutting edge by grinding the base
opposing to the top edge and the two oblique faces, respectively,
in a triangular needle. However, if the oblique faces are thus ground
off, the process that the surface layer of the material blank is
left becomes meaningless.
With the mold B according to the invention, the edges of the blocks
11 12 corresponding to the faces 16 17 are ground in a direction
perpendicular to the axis direction of the material blank (a direction
perpendicular to the top face of the mold B in FIG. 3B) by a plain
grinder, and the faces 16 17 remaining grinding marks (cross marks)
formed at the edges are formed.
By molding the material blank using the mold B, the grinding marks
20 on the faces 16 17 are transferred to the oblique faces 6a,
6b of the surgical needle A, and the serrate portions can be formed
on the cutting edges 10 with the grinding marks and the ground face
9. That is, the grinding marks extending in the cross direction
of the face can be formed without grinding the oblique faces 6a,
6b made of the surface layer of the material blank. Particularly,
by grinding only the face 17 of the mold B to form the crosswise
marks, the marks can be transferred to only the vicinity of the
cutting edges 10 as shown in FIGS. 2A-2D.
As described above, with the mold according to the invention, the
cavity is made by the subdivided faces having a relationship that
the angle between the faces is 180.degree. or below so as to project
the connecting line between the faces, so that notwithstanding of
processing order a predetermined cavity can be formed using a machine
such as a plain grinder. Therefore, the mold can be easily manufactured
with high accuracy.
With the surgical needle according to the invention, since the
top edge approaching the needle point is formed to be keen by pressing
the liner material made of austenitic stainless steel having fibrous
texture, and since the sharp needle point is, by grinding the base
opposing to the top edge, formed with the two faces sandwiching
the top edge, the surgical needle can be constituted of the hard
surface layer of the material blank, thereby maintaining the strength
and stiffness of the material.
With the surgical needle according to the invention, since the
top edge approaching the needle point is formed to be keen by pressing
the material blank, since the sharp needle point is, by grinding
the base opposing to the top edge, formed with the two faces sandwiching
the top edge, and since grinding marks of the mold are transferred
to the oblique faces, the surgical needle can be constituted of
the hard surface layer of the material blank and the cutting edges
with serrate portions can be constituted, so that the surgical needle
can maintain the strength and stiffness of the material and reduce
penetration resistance.
It is understood that although the present invention has been described
in detail with respect to preferred embodiments thereof, various
other embodiments and variations are possible to those skilled in
the art which fall within the scope and spirit of the invention,
and such other embodiments and variations are intended to be covered
by the following claims. |