JP2007098698A - Resin injection-molded object, injection mold, syringe sleeve and injection mold for syringe sleeve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin injection-molded object free from burrs generated due to a runner near a gate position, and an injection mold for molding the resin injection-molded object. <P>SOLUTION: This injection mold 1 is for the resin injection-molded object with a draft angle formed on the exterior surface and has a cavity 2 which forms at least an exterior shape of the injection-molded object and also assumes the draft angle. The cavity 2 has an undercut formation part 20 with a scarfed area 21 as a back draft to the draft angle. In addition, a molten resin injection gate 5 is formed in the tilted area 21 of the undercut formation part 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin injection molded product, an injection mold, an outer cylinder for a syringe, and an injection mold for an outer cylinder for a syringe.

More resin injection molded products than before are molded using an injection mold. An example of such an injection-molded product is a syringe outer cylinder.
When forming an outer cylinder for syringes, for injection molding comprising an outer mold (cavity) for forming the outer surface shape of the outer cylinder for syringes, and a core for forming the inner surface shape and the proximal end shape of the outer cylinder for syringes This is performed by an injection molding method in which a molten resin is injected between these molds using molds. The cavity is given a draft for drawing the molded product.
As a mold used for such injection molding, Japanese Patent Application Laid-Open No. 7-100862 (Patent Document 1) discloses a fixed mold 22 and a movable mold 23 that can be moved forward and backward with respect to the fixed mold 22. A runner 27 provided in the fixed mold 22 and communicating with the resin injection port 26; a peripheral surface portion 29 provided in the fixed mold 22 and forming the outer peripheral wall of the cylindrical molded product; and an end surface portion 30 forming the bottom wall. And a cavity 28 having a gate (resin injection port) 32 communicating with a runner at the boundary between the peripheral surface portion and the end surface portion, and a tip provided on the movable mold is concentrically inserted into the cavity. In addition, the core 35 is movable forward and backward in the axial direction, the first position where the core 35 is advanced and retracted in the axial direction, and the front end surface thereof is brought into contact with the end surface portion of the cavity 28, and the front end surface is separated from the end surface portion of the cavity. Form the bottom wall space of the molded product Those composed of a hydraulic cylinder 41. switch to the second position is described that. By injection molding using such a mold, it is possible to prevent uneven thickness of a thin and long cylindrical molded product like a syringe, and a high-quality molded product can be obtained.
However, in the injection molded product using the above mold, burrs caused by the runner are generated near the gate position. Such burrs are removed after molding, or are released spontaneously during the die removal operation. For this reason, it is necessary to manage the deburring process or the burrs that are naturally separated, which deteriorates the workability. In particular, the management of burrs that spontaneously separate is complicated, and it is necessary to pay close attention not to be mixed into the syringe outer cylinder.
Further, in the injection molding using the above mold, the flow of the molten resin between the cavity 28 and the core 35 cannot be appropriately controlled, and thus a sufficiently homogeneous resin molded product cannot be obtained.
Japanese Patent Laid-Open No. 7-100822

Accordingly, a first object of the present invention is to provide a resin injection molded product that does not generate burrs due to runners near the gate position, and an injection mold for molding such a resin injection molded product. is there.
In addition, the second object of the present invention is to provide a homogeneous outer cylinder for a syringe having a sufficient strength, a syringe using the outer cylinder for a syringe, and a flow of molten resin injected from a molten resin injection gate. The present invention provides an injection mold for a syringe outer cylinder that can produce a syringe outer cylinder having sufficient strength.

What achieves the above object is as follows.
(1) A resin injection molded article having a draft on the outer surface, the resin injection molded article having an undercut portion having an inclined surface that is opposite to the draft, and further comprising the undercut Injection molded product comprising a molten resin injection gate position on the inclined surface of the portion.
(2) The said undercut part is a resin injection molded product as described in (1) formed in the outer surface which has the said draft of the said injection molded product.
(3) The resin injection molded product according to (1) or (2), wherein the undercut portion is a recess.
(4) The resin according to any one of (1) to (3), wherein the molten resin injection gate position is located at a rear side end portion with respect to a drawing direction of the draft of the inclined surface of the undercut portion. Injection molded product.
(5) The resin injection molded product according to any one of (1) to (4), wherein an inclination of the inclined surface of the undercut portion with respect to a drawing direction of the draft is 2 to 12 °.
(6) The resin injection molded product according to any one of (1) to (5), wherein the resin injection molded product is an outer cylinder for a syringe.
(7) The syringe outer cylinder is provided along the entire circumference of the outer cylinder main body, the liquid discharge port provided at the distal end of the outer cylinder main body, and the base end of the outer cylinder main body. The resin injection molded product according to (6), further including a flange portion, wherein the undercut portion is provided on an outer surface of the flange portion.

(8) The flange portion includes two gripping portions formed so as to be substantially opposed to the central axis of the outer cylinder main body portion, the undercut portion is the flange portion, and the gripping portion The resin injection-molded product according to (7), which is a portion that is not, and is provided in the vicinity of an outer surface of a portion that is close to the proximal end portion of the outer cylinder main body.
(9) An injection mold for a resin injection molded article having a draft angle, the injection mold having at least the outer surface shape of the injection molded article and having a cavity having a draft angle. The cavity has an undercut forming portion having an inclined surface opposite to the draft angle, and further includes a molten resin injection gate on the inclined surface of the undercut forming portion. Type.
(10) The undercut forming portion is a protruding portion protruding from the inner surface of the cavity, and the inclined surface has a lower end of the molten resin injection gate as a top portion and becomes lower in a drawing direction of the draft. The mold for injection molding as described in (9).
(11) The injection mold according to (10), wherein an inclination of the inclined surface of the undercut forming portion with respect to a drawing direction of the draft is 2 to 12 °.
(12) The injection mold according to any one of (9) to (11), wherein the injection mold is an outer cylinder injection mold for a syringe.

(13) The injection mold includes a cavity and a core for forming an outer surface shape and an inner surface shape of the syringe outer cylinder, and the cavity and the core are proximal end portions of the outer cylinder main body forming portion. The mold for injection molding according to (12), further including a flange forming portion provided along the entire circumference, wherein the undercut forming portion is provided on a side surface of the flange forming portion.
(14) The flange forming portion is formed so as to protrude outward from the base end portion of the outer cylinder main body forming portion so as to be opposed to each other, and forms a gripping portion for gripping the syringe outer tube. An injection mold for an outer cylinder for a syringe according to (13), which has a gripping portion forming portion for the purpose.
(15) The mold for injection molding according to (14), wherein the molten resin injection gate is provided on a side surface of a portion that is the flange forming portion and is close to a base end portion of the outer cylinder main body forming portion. .

Moreover, what achieves the said objective is as follows.
(16) By injection molding having an outer cylinder main body, a liquid discharge port provided at the distal end of the outer cylinder main body, and a flange provided along the entire circumference of the base end of the outer cylinder main body An outer cylinder for a syringe, which has an annular rib located on a peripheral edge portion of the flange on a front end side surface or a base end side surface of the flange, and a molten resin on an outer surface of the flange. An outer cylinder for a syringe provided with an injection gate position.
(17) The flange according to (16), wherein the flange is formed so as to protrude from a proximal end portion of the syringe outer cylinder so as to face the flange, and has a grip portion for gripping the syringe outer cylinder. Syringe outer cylinder.
(18) The molten resin injection gate position is a portion that is not the grip portion of the flange and is provided in the vicinity of the outer surface of a portion close to the base end portion of the outer cylinder main body portion (17). The outer cylinder for syringes described.
(19) The syringe outer cylinder according to any one of (16) to (18), wherein the annular rib is formed along the vicinity of an outer edge portion of the flange.
(20) The syringe outer cylinder is a resin injection-molded article having a draft, and includes an undercut portion having an inclined surface that is opposite to the draft, and further, the slope of the undercut portion The syringe outer cylinder according to any one of (16) to (19), wherein the molten resin injection gate position is provided on a surface.

Moreover, what achieves the said objective is as follows.
(21) An outer syringe body having an outer cylinder main body, a liquid discharge port provided at the distal end of the outer cylinder main body, and a flange provided along the entire circumference of the base end of the outer cylinder main body. An injection mold for injection molding of a cylinder, the injection mold including a cavity and a core for forming an outer surface shape and an inner surface shape of the outer cylinder for a syringe, the cavity and the core The core has a flange forming portion provided along the entire circumference of the base end portion of the outer tube main body forming portion, and the flange forming portion is provided on the distal end surface or the base end surface forming portion of the flange forming portion. A molten resin guiding annular groove for guiding the molten resin injected into the gap between the cavity and the core, and the cavity is formed on a side surface of the flange forming portion. To inject molten resin into the gap with the core A mold for injection molding of an outer cylinder for a syringe provided with a molten resin injection gate.
(22) The flange forming portion is formed so as to protrude outward from a proximal end portion of the outer cylinder main body portion forming portion so as to face the flange forming portion, and forms a gripping portion for gripping the syringe outer tube. The mold for injection molding of the outer cylinder for syringes according to (21), which has a gripping part forming part for the purpose.
(23) The syringe outer cylinder according to (22), wherein the molten resin injection gate is provided on a side surface of a portion that is the flange forming portion and is close to a proximal end portion of the outer cylinder main body portion forming portion. Injection mold.
(24) The cavity includes an undercut forming portion having a draft and an inclined surface that is opposite to the draft, and the molten resin is injected into the inclined surface of the undercut forming portion. The injection mold of the outer cylinder for a syringe according to any one of (21) to (23), wherein a gate is disposed.
(25) The injection molding die for an outer cylinder for a syringe according to any one of (21) to (24), wherein the annular groove for guiding a molten resin is provided along the vicinity of an outer edge of the flange forming portion. .

The resin injection-molded article of the present invention is a resin injection-molded article having a draft on the outer surface, and the resin injection-molded article has an undercut portion having an inclined surface that is opposite to the draft. Further, a molten resin injection gate position is provided on the inclined surface of the undercut portion. For this reason, there is no burr caused by the runner in the vicinity of the gate position.
The injection mold of the present invention is an injection mold for a resin injection molded product having a draft, and the injection mold forms at least the outer shape of the injection molded product. And a cavity having a draft angle, the cavity having an undercut forming portion having an inclined surface opposite to the draft angle, and injecting a molten resin into the inclined surface of the undercut forming portion Has a gate.
For this reason, when the resin molded product is pulled out from the cavity, the end portion of the molten resin injection gate on the inclined surface of the undercut forming portion cuts the protruding portion due to the runner, so that no burr due to the runner is formed.
The syringe outer cylinder of the present invention is provided along the outer circumference of the outer cylinder main body, the liquid discharge port provided at the distal end of the outer cylinder main body, and the entire circumference of the base end of the outer cylinder main body. A syringe outer cylinder formed by injection molding having a flange, and having an annular rib positioned at the peripheral edge of the flange, and further provided with a molten resin injection gate position on the outer surface of the flange. ing.
For this reason, the outer cylinder for syringes of the present invention is homogeneous and has sufficient strength.
The syringe of the present invention is a syringe provided with the syringe outer cylinder, a gasket slidably accommodated in the syringe outer cylinder, and a plunger attached to or attachable to the gasket. It is.
For this reason, the syringe outer cylinder which comprises the syringe of this invention is homogeneous and has sufficient intensity | strength.
An injection mold for injection molding the syringe outer cylinder according to the present invention includes an outer cylinder main body, a liquid discharge port provided at a tip of the outer cylinder main body, and a base of the outer cylinder main body. An injection mold for injection molding a syringe outer cylinder having a flange provided along the entire circumference of the end portion, the injection mold having an outer surface shape of the syringe outer cylinder and A cavity and a core for forming an inner surface shape are provided, and the cavity and the core have a flange forming portion provided on the entire circumference of the base end portion of the outer tube main body forming portion, and the distal end side of the flange forming portion A molten resin guiding ring is formed on the surface or the base end side surface forming portion so as to be positioned at the peripheral edge of the flange forming portion, and for guiding the molten resin injected into the gap between the cavity and the core. A groove portion, and the key is formed on a side surface of the flange forming portion. Molten resin injection gate for injecting the molten resin into the gap between the Activity and the core is provided.
For this reason, if it is the injection mold of this invention, since the flow of the molten resin injected from the molten resin injection gate can be controlled, the outer cylinder for syringes which is homogeneous and has sufficient strength can be manufactured. .

Hereinafter, the injection molded product and the injection mold according to the present invention will be described with reference to an example in which the syringe outer cylinder and syringe outer cylinder injection mold shown in the drawings are applied.
FIG. 1 is a cross-sectional view of an embodiment in which the injection mold of the present invention is applied to an injection mold of a syringe outer cylinder, and FIG. 2 is a side cross-sectional view of the injection mold shown in FIG. FIG. 3 is a partially enlarged sectional view of the injection mold shown in FIG. 1, and FIG. 4 is a partially enlarged sectional view of the injection mold shown in FIG. 5 is a cross-sectional view taken along line AA in FIG. 6 is a cross-sectional view taken along line BB in FIG. 7 to 9 are explanatory views for explaining the operation of the injection mold according to the present invention.
The injection mold of the present invention is not limited to the injection mold of the syringe outer cylinder, and may be any injection mold. In particular, it is effective for a cylindrical injection mold. Specifically, it is particularly effective for molds such as a syringe outer tube, a resin blood collection tube, a resin test tube, and a resin cup.

First, the injection mold will be described.
The injection mold 1 of the present invention is an injection mold for a resin injection molded product having a draft on the outer surface. The injection mold 1 is provided with a cavity 2 that forms at least the outer surface shape of an injection-molded product and has a draft, and the cavity 2 has an undercut having an inclined surface 21 that is opposite to the draft. The molten resin injection gate 5 is provided on the inclined surface 21 of the undercut forming portion 20.
In the injection mold 1 of this embodiment, the undercut forming portion 20 is a protruding portion that protrudes from the inner surface of the cavity 2 as shown in FIGS. 4 to 8, and the inclined surface 21 is a molten resin. The lower end of the injection gate 5 is the top and becomes lower in the draft direction. The lower end of the gate 5 is preferably located at the lower end 22 of the inclined surface 21, but the lower end of the gate 5 may be located above the lower end 22 of the inclined surface 21. And inclination (theta) (refer FIG.4, FIG.7 and FIG.8) with respect to the drawing direction of the draft of the inclined surface 21 of the undercut formation part 20 is 2-12 degrees.

An injection mold 1 for an outer cylinder for a syringe according to this embodiment includes an outer cylinder main body 37, a liquid discharge port 38 c provided at the distal end of the outer cylinder main body 37, and a base end of the outer cylinder main body 37. This is an injection mold 1 for a syringe outer cylinder 31 having a flange 39 provided along the entire circumference of the part. The injection mold 1 includes a cavity 2 and cores 3 and 14 for forming an outer surface shape and an inner surface shape of an outer cylinder 31 for a syringe, and the cavity 2 and the cores 3 and 14 include an outer cylinder main body forming part. 4 has a flange forming portion 7 provided along the entire circumference of the base end portion. Further, the injection mold 1 is formed on the front surface side or base surface side surface forming portion of the flange forming portion 7 so as to be positioned at the peripheral edge of the flange forming portion 7, and the cavity 2 and the cores 3, 14. For injecting the molten resin into the gap between the cavity 2 and the cores 3 and 14 on the side surface of the flange forming portion 7. A molten resin injection gate is provided.
In this way, by forming the molten resin guiding annular groove 15 and providing the molten resin injection gate 5 on the side surface of the flange forming portion 7, the flow of the molten resin injected between the cavity 2 and the cores 3 and 14 can be reduced. Since it can control, the outer cylinder 31 for syringes which is homogeneous and has sufficient intensity | strength can be manufactured. Specifically, the molten resin injected into the gap 10 from the molten resin injection gate 5 smoothly flows to the opposite side of the molten resin injection gate 5 along the molten resin guiding annular groove 15 of the flange forming portion 7. An outer cylinder 31 for a syringe can be produced.
As shown in FIGS. 1 and 2, the injection mold 1 includes a cavity 2 and cores 3 and 14. By inserting the core 3 into the cavity 2, a gap 10 is formed between the cavity 2 and the cores 3 and 14 in which a syringe outer cylinder molded product is formed.

As shown in FIGS. 1 and 2, the cavity 2 includes an outer cylinder main body forming portion 4, a nozzle portion forming portion 8, a tip surface side portion forming portion 9 of the flange 39, and a molten resin injection gate 5. ing.
As shown in FIGS. 1 and 2, the core 3 includes an outer cylinder main body forming portion 6 and a nozzle portion forming portion 11. Further, the core 14 includes a proximal end side portion forming portion 12 of the flange 39. The flange forming portion 7 is configured by a distal end surface side portion forming portion 9 of the flange 39 of the cavity 2 and a proximal end surface side portion forming portion 12 of the core 14.
The nozzle portion forming portion 8 of the cavity 2 is a portion that is provided at the distal end portion of the outer cylinder main body portion forming portion 4 and that forms the outer surface shape of the nozzle portion 38 having the liquid discharge port 38c at the distal end. In this embodiment, the nozzle portion forming portion 8 is formed so as to have a tapered diameter toward the distal end side, the forming portion 8c of the liquid discharge port 38c is provided at the distal end portion, and the proximal end portion is provided. A forming portion 8a of the nozzle portion side screwing portion 38a and a forming portion 8b of the nozzle portion side engaging portion 38b are provided in this order from the tip side.
The outer cylinder main body forming portion 4 of the cavity 2 is a portion that forms the outer surface shape of the outer cylinder main body portion 37 of the syringe outer cylinder 31. As shown in FIG. 1, the outer cylinder main body forming portion 4 has a substantially reduced inner diameter portion 4 b and a reduced diameter portion 4 a that decreases in a tapered shape toward the distal end side formed on the distal end side of the substantially identical inner diameter portion 4 b. And. Moreover, it is preferable that the substantially identical inner diameter part 4b of the outer cylinder main body part forming part 4 has a draft angle. The cavity 2 is preferably provided with an air vent (not shown) so that air or gas in the mold can be smoothly discharged.

As shown in FIGS. 1, 2, 3, and 4, the flange forming portion 7 includes a gripping portion forming portion 7 a, a gripping portion connecting portion forming portion 7 b, a gripping portion forming portion 7 a, and a gripping portion connecting portion forming portion. 7b includes a molten resin guiding annular groove 15, a molten resin injection gate 5 formed on the side surface of the flange forming portion 7, and a reinforcing rib forming groove 18 provided on the grip forming portion 7a. ing.
In the embodiment shown in FIG. 1, the flange forming portion 7 is formed so as to protrude from the outside of the base end portion of the outer cylinder main body portion forming portion 4 so as to be opposed, and for holding the syringe outer cylinder 31. A gripping portion forming portion 7a for forming the gripping portion 39a and a gripping portion connecting portion forming portion 7b for forming a gripping portion connecting portion 39b for connecting the opposing gripping portions 39a are provided. The annular groove portion 15 for guiding the molten resin is located at the peripheral edge portion of the front surface forming portion of the flange forming portion 7, and so as to surround the peripheral edge portion of the base end portion of the outer cylinder main body forming portion 4. And the grip portion connecting portion forming portion 7b. Note that the molten resin guiding annular groove may be provided in the base-end-side surface forming portion of the flange forming portion.
Since the molten resin guiding annular groove portion 15 is formed so as to surround the peripheral edge portion of the flange forming portion 7, the molten resin injected from the molten resin injection gate 5 easily spreads over the entire flange forming portion.

The grip portion forming portion 7a and the grip portion connecting portion forming portion 7b of the flange forming portion 7 have shapes for forming the flange 39 as shown in FIGS. The flange forming part 7 is formed so as to protrude vertically along the entire circumference of the base end part of the outer cylinder main body part forming part 4. The shape seen from the upper surface of the flange forming portion 7 of the embodiment of the present invention is an elliptical shape so as to form a flange 39 as shown in FIG. The both longitudinal side portions of the flange forming portion 7 in the longitudinal direction form gripping portion forming portions 7a, and the short side portion forms the gripping portion connecting portion forming portion 7b. As shown in FIGS. 2 and 4, the gripping part connecting part forming part 7 b is formed so as to protrude slightly outward from the base end part of the outer cylinder main body part forming part 4.
Further, the molten resin guiding annular groove 15 is an annular groove for forming an annular rib 55 as shown in FIG. By having the molten resin guiding annular groove 15, the molten resin injected from the molten resin injection gate 5 into the cavity 2 and the cores 3 and 14 can easily reach the entire flange forming portion. The annular groove portion 15 for guiding the molten resin in the embodiment is formed along the outer edge portion shape of the flange forming portion 7 and has an elliptical shape in which both side portions in the longitudinal direction are crushed. Further, the shape of the annular groove for guiding the molten resin may be such that the molten resin injected into the cavity 2 and the cores 3 and 14 is surely guided to the entire flange forming portion along the annular groove for guiding the molten resin. Any shape may be used, and it may be a substantially elliptical shape or a substantially circular shape.

Moreover, it is preferable that the cross-sectional shape of the inner surface of an annular groove part is a substantially semicircle shape, a substantially semi-elliptical shape, a substantially trapezoid shape, etc. The cross-sectional shape of the inner surface of the annular groove portion 15 of the embodiment of the present invention is a substantially semicircular shape. The cross-sectional shape of the inner side surface of the annular groove may be any shape as long as the injected molten resin is reliably guided.
Further, the molten resin guiding annular groove portion 15 is formed along the vicinity of the outer edge portion of the flange forming portion 7 as in the embodiments shown in FIGS. 1, 2, 3, and 4. With such a configuration, the molten resin injected from the molten resin injection gate 5 is easily guided to the molten resin guiding annular groove 15 and spread over the entire flange forming portion.
In this embodiment, the molten resin guiding annular groove portion 15 is formed along the outer edge portion of the flange forming portion 7 in the portion excluding both ends of the grip portion connecting portion forming portion 7b and the grip portion forming portion 7a. At both ends of the part forming part 7a, it is formed slightly inside the outer edge part. In addition, if the injected molten resin is distributed over the entire flange forming portion along the molten resin guiding annular groove portion, the molten resin guiding groove portion is formed along the outer edge portion of the flange forming portion in all portions. In addition, the molten resin guiding annular groove portion may be formed inside the outer edge portion of the flange forming portion in all portions. In addition, a peripheral part contains the part inside said outer edge part and an outer edge part.

Further, as shown in FIGS. 2 and 4, the molten resin injection gate 5 has a side surface (specifically, a flange forming portion 7 formed so as to be close to the base end portion of the outer cylinder main body forming portion 4. Formed on the outer surface). A resin flow path 51 communicating with the molten resin injection gate 5 is formed between the cavity 2 and the core 14.
In the embodiment shown in FIG. 4, the molten resin guiding annular groove portion 15 is formed so as to be close to the base end portion of the outer cylinder main body portion forming portion 4 in the gripping portion connecting portion forming portion 7 b. In 7a, it forms in the position spaced apart to some extent with respect to the base end part of the outer cylinder main-body-part formation part 4. FIG. The molten resin injection gate 5 is formed at a central portion (specifically, a position corresponding to the central axis of the outer cylinder main body forming portion 4) of the side surface of the gripping portion connecting portion forming portion 7b of the flange forming portion 7. ing.
Specifically, the molten resin injection gate 5 is formed on a side surface of the flange forming portion 7 and at a position slightly on the proximal side (lower side in FIG. 4). With such a configuration, the molten resin formed between the cavity 2 and the cores 3 and 14 is easily guided to the molten resin guiding annular groove 15.
Further, since the molten resin injection gate 5 is provided in the flange forming portion 7 as in the present invention, the cold slug stays in the flange forming portion 7 when the molten resin is injected, so that the molten resin injected gate 5 The flow is not disturbed.
Furthermore, the cavity 2 is preferably provided with an undercut forming portion 20 that is a peripheral portion of the molten resin injection gate 5 and is provided at a tip side portion of the outer cylinder main body forming portion. In particular, the mold according to this embodiment includes an undercut forming portion 20 as shown in FIGS. 4 and 5 to 8.

FIG. 4 is a partially enlarged sectional view of the injection mold shown in FIG. 5 is a cross-sectional view taken along line AA in FIG. 4, and FIG. 6 is a cross-sectional view taken along line BB in FIG.
The undercut forming part 20 is a protruding part that protrudes toward the core 6 as shown in FIGS. 4 and 6. The undercut forming part 20 is provided with a molten resin injection gate 5 at the center lower part thereof. The undercut forming portion 20 has an inclined surface 21 that is opposite to the draft of the cavity 2, and extends from the apex 22 of the inclined surface 21 toward the range of the inclined surface 21 and is in the opposite direction to the inclined surface 21. A second inclined surface 23 is provided. And the molten resin injection | pouring gate 5 is arrange | positioned so that the lower end may be located in the vertex 22 of an undercut formation part.
In other words, the inclined portion 21 of the undercut forming portion 20 forms an inclined surface that becomes lower from the apex 22 toward the distal end side of the outer cylinder main body portion forming portion, and the second inclined portion 23 is the outer cylinder main body portion. An inclined surface that decreases toward the base end side of the forming portion is formed.
The undercut forming portion 20 has a function of preventing the generation of burrs caused by the resin in the resin flow path (runner) 51. Without this undercut forming part, the runner part between the injection molded product and the cavity cannot be cut cleanly, and it is torn off as the molded product leaves the cavity, resulting in burrs. This may cause separation from the molded product during handling in the process and contaminate the environment in the process, or a burr itself attached to the molded product may cause a problem in appearance.
Specifically, as shown in FIG. 7, the resin 25 is injected into the injection mold 1. When cooled, the solidified resin 25 slightly shrinks as shown in FIG. And the resin part 23 located in the front-end | tip of a runner (in other words, the inner side of the molten resin injection | pouring gate 5) by this resin contraction is pulled by the molded article side, as shown in FIG. This part is the cause of the generation of burrs. However, in the mold of the present invention, when the injection molded product 25 formed on the outer surface of the core 3 together with the core 3 and the core 14 from the cavity 2 and slightly contracted by cooling is pulled out, the undercut forming portion 20 of the cavity 2 is extracted. The top portion 22 of the knives performs the action of cutting off the protruding portion caused by the runner. For this reason, as shown in FIG. 9, the resin part 23 resulting from a runner is cut off and a burr | flash is not generated.

The inclination θ (FIG. 4) of the inclined portion 21 of the undercut forming portion 20 is preferably 2 to 12 ° with respect to the axial center of the cavity, and particularly preferably 4 to 10 °. If it has such a structure, the gate cut-off property will be better. Moreover, as a length (lateral length) of the circumferential direction of the undercut formation part 20, about 2-6 mm is suitable. Moreover, as length of the vertical direction of the undercut formation part 20, about 0.8-1.8 mm is suitable.
The undercut forming portion 20 includes an inclined portion 23 having a lower end portion 22 of the molten resin injection gate 5 as a top portion and being lowered toward the cavity 14 side of the outer cylinder main body forming portion.
In this embodiment, the undercut forming portion 20 including the molten resin injection gate 5 is a central portion (specifically, outer cylinder main body) of the side surface of the gripping portion connecting portion forming portion 7b of the flange forming portion 7 of the cavity 2. (Position corresponding to the central axis of the part forming part 4). By doing so, the formation surface due to the gate and undercut formation portion becomes inconspicuous, so it is preferable in appearance, and there is no gate portion on the long diameter side forming the grip portion, so that the gate portion is not touched when using the syringe This is preferable because there is no sense of incongruity. The undercut forming part 20 including the molten resin injection gate 5 may be provided in the grip part.

Further, in this embodiment, a reinforcing rib forming groove 18 is formed in the tip surface side forming portion (cavity 2 in the embodiment of the present invention) of the grip portion forming portion 7a. As shown in FIGS. 1 and 3, the reinforcing rib forming groove 18 is provided inside the molten resin guiding annular groove 15. The reinforcing rib forming groove 18 is an arcuate groove. The reinforcing rib forming groove may have any shape as long as it can reinforce the flange. The rib formed by the reinforcing rib forming groove 18 also serves as an anti-slip rib when the syringe 30 (syringe outer cylinder 31) is gripped.
Further, the base end surface side forming portion of the flange forming portion 7 has a convex portion 7 d for forming a concave portion 39 d formed on the base end surface of the flange 39.
As shown in FIGS. 1 to 4, the core 3 includes an outer cylinder main body forming part 6 and a nozzle part forming part 11.
The nozzle portion forming portion 11 is a portion that is formed on the distal end side of the main body portion forming portion 6 and forms the inner surface shape of the nozzle portion 38.
The main body portion forming portion 6 is a portion that forms the inner surface shape of the outer cylinder main body portion 37 of the syringe outer cylinder 31. As shown in FIGS. 1 and 2, the main body portion forming portion 6 includes a reduced diameter portion 6a and a substantially identical outer diameter portion 6b. And the rib 13 is provided in the base end part of the substantially same outer diameter part 6b.
The reduced diameter portion 6 a is a portion that forms the inner surface of the reduced diameter portion 41 provided at the distal end portion of the outer cylinder main body portion 37 of the syringe outer cylinder 31. The reduced diameter portion 6a is tapered in a tapered shape toward the tip side. The same outer diameter portion 6 b is a portion for forming an inner surface excluding the proximal end portion of the cylindrical portion 42 of the outer cylinder main body portion 37 of the outer cylinder 31 for syringe. The same outer diameter part 6b is formed to the vicinity of the base end part continuously with the reduced diameter part 6a. The same outer diameter portion 6b may have a draft angle.
Moreover, it is preferable that the rib 13 provided in the main body part forming part 6 is an annular rib 13 formed on the circumference of the main body part forming part 6. The annular rib 13 has a substantially trapezoidal cross section in the embodiment of the present invention. Further, the annular rib 13 may have a substantially circular or substantially elliptical cross-sectional shape. Further, the base end side portion of the cores 3 and 14 is enlarged in diameter toward the base end side from the annular rib 13. By forming the annular rib 13 on the core 3, an annular groove 59 is formed in the syringe outer cylinder 31.

Next, the manufacturing method of the outer cylinder for syringes of this invention is demonstrated.
The manufacturing method of the syringe outer cylinder 31 of the present invention includes an outer cylinder main body portion 37, a liquid discharge port 38 c provided at the distal end portion of the outer cylinder main body portion 37, and the entire circumference of the base end portion of the outer cylinder main body portion 37. It is a manufacturing method of the outer cylinder 31 for syringes which has the flange 39 provided along, Comprising: The manufacturing method is injection molding which forms the outer cylinder 31 for syringes by injection-molding using the metal mold | die 1 for injection molding. It has a process.
The injection molding process is performed by injecting molten resin from the molten resin injection gate 5 into the gap 10 formed between the cavity 2 and the cores 3 and 14 with the core 3 inserted into the cavity 2. . The injection pressure is preferably 60 to 300 MPa, and particularly preferably 80 to 270 MPa.
As the injection speed is preferably 20~200cm ² / s, particularly preferably is in 30~180cm ² / s.
The mold temperature is preferably 15 to 140 ° C, and particularly preferably 20 to 120 ° C.
The molten resin injected from the molten resin injection gate 5 is filled in the gap 10 while controlling the flow along the molten resin guiding annular groove 15. Therefore, according to the manufacturing method of the present invention, it is possible to manufacture the outer cylinder 31 for a syringe that is sufficiently homogeneous and has sufficient strength.
After injection of the molten resin, after pressure holding and cooling, the syringe outer cylinder 31 which is a resin molded product is taken out from the mold.

Next, the injection molded product of the present invention will be described using an example in which the injection molded product is applied to a syringe outer cylinder.
10 is a front view of the syringe outer cylinder of the present invention, FIG. 11 is a side view of the syringe outer cylinder shown in FIG. 10, and FIG. 12 is a top view of the syringe outer cylinder shown in FIG. 13 is a perspective view of the syringe outer cylinder shown in FIG. 10, FIG. 14 is a partially enlarged view of the vicinity of the flange of the syringe outer cylinder shown in FIG. 13, and FIG. FIG. 16 is a vertical cross-sectional view of the syringe outer cylinder shown in FIG. 11, and FIG. 17 is a portion near the base end of the syringe outer cylinder shown in FIG. It is an expanded sectional view.
The injection molded product of the present invention is not limited to the syringe outer cylinder, and may be any injection molded product. In particular, it is effective for cylindrical injection molded products. Specifically, it is particularly effective for syringe outer cylinders, resin blood collection tubes, resin test tubes, resin cups, and the like.
The resin injection-molded article of the present invention is a resin injection-molded article having a draft on the outer surface, and the resin injection-molded article includes an undercut portion 60 having an inclined surface 56 that is opposite to the draft. Further, the inclined surface 56 of the undercut portion 60 is provided with a molten resin injection gate position.
In the resin injection molded product of this embodiment, the undercut portion 60 is formed on the outer surface (outer surface of the flange) having the draft of the injection molded product. Furthermore, the undercut part 60 is a recessed part (a recessed part with respect to the outer surface of a flange). Further, the molten resin injection gate position is located at the rear side end portion with respect to the drawing direction of the draft of the inclined surface 56 of the undercut portion 60. Moreover, it is preferable that the inclination with respect to the drawing direction of the said draft of the said inclined surface of an undercut part is 2-12 degrees.

The syringe outer cylinder 31 of this embodiment includes an outer cylinder main body 37, a liquid discharge port 38 c provided at the distal end of the outer cylinder main body 37, and the entire circumference of the base end of the outer cylinder main body 37. It is formed by injection molding having a flange 39 provided. The syringe outer cylinder 31 of this embodiment has an annular rib 55 located at the peripheral edge of the front end side surface or the base end side surface of the flange 39, and a molten resin injection gate position on the outer surface of the annular rib 55. 57.
With such a configuration, the syringe outer cylinder 31 is homogeneous and has sufficient strength because the flow of the molten resin injected between the cavity 2 and the cores 3 and 14 is sufficiently controlled during molding. is doing.
In addition, the syringe outer cylinder of this embodiment includes an undercut portion 60 that is formed on the side surface of the flange 39 and is a recess, and a molten resin injection gate position 57 is disposed in the undercut portion 60. .
Specifically, as shown in FIGS. 10 and 11, the syringe outer cylinder 31 of the present invention includes an outer cylinder main body portion 37, a nozzle portion 38 provided at the distal end portion of the outer cylinder main body portion 37, And a flange 39 provided at the base end portion of the tube main body portion 37. The nozzle portion 38 includes a liquid discharge port 38c at the tip thereof. As shown in FIGS. 11 and 12, the nozzle part 38 is a cylindrical part having a smaller diameter than the outer cylinder main body part 37. The nozzle portion 38 is a tapered portion that decreases in diameter toward the tip side. The nozzle portion 38 is provided with an opening for discharging the chemical solution and the like in the outer cylinder 31 and is formed so as to be tapered toward the tip. In the embodiment of the present invention, a nozzle portion side screwing portion 38 a for screwing the seal cap 32 is provided at the base end portion of the nozzle portion 38. Further, a nozzle portion side engaging portion 38b for engaging with the seal cap 32 is provided on the proximal end side of the nozzle portion side screwing portion 38a. Moreover, it is preferable that the nozzle part 38 becomes a shape which can attach an injection needle.

Further, it is preferable that an annular groove 59 is formed on the inner surface of the base end portion of the outer cylinder main body portion 37 as shown in FIGS. 13, 15, and 16. Since the groove portion 59 is formed on the inner surface of the base end portion of the outer cylinder main body portion 37, the gasket can be easily vacuumed.
In the embodiment of the present invention, as shown in FIGS. 10, 11, and 12, the flange 39 includes a gripping portion 39a and a gripping portion connecting portion 39b. The flange 39 includes an annular rib 55 and a reinforcing rib 58.
In the embodiment shown in FIGS. 10 and 11, the flange 39 is a plate-like portion formed so as to protrude in the vertical direction from the entire circumference of the base end portion of the outer cylinder main body portion 37. The shape seen from the upper surface of the flange 39 of the embodiment of the present invention is an elliptical shape in which both side portions in the longitudinal direction are crushed so as to form the flange 39 as shown in FIG. The both longitudinal portions of the flange 39 in the longitudinal direction form gripping portions 39a, and the short-side portions form gripping portion connecting portions 39b. The grip portion 39a protrudes from the base end portion of the outer cylinder main body portion 37 to the extent that it can be gripped, and the grip portion connecting portion 39b is formed to protrude slightly from the base end portion of the outer cylinder main body portion forming portion 4. ing.
Further, since the annular rib 55 is formed on the front end surface side of the flange 39 and the flow of the molten resin injected between the cavity 2 and the core 3 at the time of injection molding is controlled, the outer cylinder 31 for a syringe of the present invention is It is homogeneous and has sufficient strength.
And the annular rib 55 of an Example is formed along the outer edge part vicinity of the flange 39, and becomes the ellipse shape where the both sides part of the longitudinal direction was crushed. Further, the shape of the annular rib 55 may be a substantially elliptical shape or a substantially circular shape. The cross-sectional shape of the inner surface of the annular rib is preferably a substantially semicircular shape, a substantially semielliptical shape, a substantially trapezoidal shape, or the like. The cross-sectional shape of the inner surface of the annular rib 55 according to the embodiment of the present invention is a substantially semicircular shape. In this embodiment, the annular rib 55 is provided on the front end side surface of the flange 39, but may be provided on the base end side surface.

The annular rib 55 is preferably formed along the vicinity of the outer edge portion of the flange 39. With such a configuration, the flow of the molten resin is sufficiently controlled at the time of injection molding. Therefore, the syringe outer cylinder 31 of the present invention has a uniform and sufficient strength. In this embodiment, the annular rib 55 is formed along the outer edge portion of the flange 39 in a portion excluding both end portions of the flange 39. And in the both ends of the flange 39, the cyclic | annular rib 55 is formed in a little inner side from the outer edge part. Note that the annular rib may be formed along the outer edge portion in all portions of the flange. Further, the annular rib may be formed on the inner side of the outer edge portion in all portions of the flange. In addition, a peripheral part contains the part inside said outer edge part and an outer edge part.
Further, since the molten resin injection gate position 57 is formed on the outer surface of the flange 39, the flow of the molten resin is sufficiently controlled at the time of molding. Therefore, the syringe outer cylinder 31 of the present invention is uniform and sufficient. Has strength. In this embodiment, the molten resin injection gate position 57 is formed on the outer surface of the flange 39 and slightly on the base end side (lower side shown in FIG. 17).
The molten resin injection gate position 57 is preferably a portion that is not the grip portion 39 a of the flange 39 and is provided in the vicinity of the outer surface of a portion that is close to the proximal end portion of the outer cylinder main body portion 37. Specifically, as shown in FIGS. 10, 13, and 17, the molten resin injection gate position 57 is located at a position close to the proximal end portion of the outer cylinder main body portion 37 of the annular rib 55 (in other words, the gripping portion connection position). Part) is preferably provided on the outer surface. With such a configuration, since the molten resin injected at the time of molding can be easily controlled, the syringe outer cylinder 31 of the present invention is more homogeneous and has sufficient strength.

In this embodiment, the flange 39 is formed between a gripping portion 39a for gripping the syringe outer tube 31 protruding from the proximal end portion of the syringe outer tube 31 so as to face the gripping portion 39a. A grip portion connecting portion 39b formed so as not to protrude outward from the grip portion 39a, and the annular rib 55 is formed on the grip portion 39a and the grip portion connecting portion 39b so as to surround the base end portion of the outer cylinder main body portion 37. Is provided. Specifically, the molten resin injection gate position 57 is formed on the outer surface of a position that is an intermediate portion of the gripping portion 39a facing the annular rib 55 (in other words, the central portion of the gripping portion connecting portion 39b).
The peripheral portion 56 of the molten resin injection gate position 57 is an undercut portion 60 as shown in FIGS. Due to such a configuration, there is no burr near the gate position. The reason that the burr does not exist is as described in the injection mold described above.
The undercut form in this embodiment is constituted by a recess 55 with respect to the other part of the flange 39. That is, the outer cylinder 31 of this embodiment has an undercut portion 60 that constitutes a recess formed on the side surface of the flange 39. 13, 14, and 17, the recess 60 has the top of the inclined surface 56 (in this embodiment, also the lower end of the molten resin injection gate position 57) 62 as a bottom point, An inclined surface 56 that is thicker toward the tip side is provided. 17 is preferably 2 to 12 ° with respect to the axial direction of the syringe outer cylinder 31. The inclination θ of the inclined surface shown in FIG. The length of the outer cylinder of the undercut portion 60 in the circumferential direction (lateral length) is preferably about 2 to 6 mm. Moreover, as a length of the vertical direction of the undercut part 60, about 0.8-1.8 mm is suitable. In addition, the undercut shape portion 60 includes a second inclined portion 61 having the bottom end of the molten resin injection gate position 57 as a bottom point and increasing in thickness toward the proximal end face side of the flange 39.
The reinforcing rib 58 is provided on the front end surface side of the flange 39. Specifically, the reinforcing rib 58 is provided inside the annular rib 55 of the flange 39. In the embodiment, the reinforcing rib 58 is an arc-shaped rib. The reinforcing rib 58 also serves as a non-slip rib when the syringe 30 (syringe outer cylinder 31) is gripped. The reinforcing rib forming groove portion may have any shape as long as it reliably reinforces the flange.
Further, a recess 39 d is provided on the base end face side of the flange 39.

  As a material for forming the outer cylinder 31, a material having low drug adsorption, oxygen permeability and water vapor permeability, and excellent sterilization resistance such as γ-ray resistance and autoclave resistance are preferable. As a forming material of the outer cylinder 31 for a syringe, polypropylene, polyethylene, polystyrene, polyamide, polycarbonate, polyvinyl chloride, poly- (4-methylpentene-1), acrylic resin, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate Various resins such as polyester and cyclic polyolefin can be used, and among them, resins such as polypropylene and cyclic polyolefin are preferable because they are easy to mold and have heat resistance.

Next, the syringe of the present invention will be described.
FIG. 18 is a front view of the syringe according to the embodiment of the present invention.
The syringe 30 of the present invention includes a syringe outer cylinder 31, a gasket 35 slidably accommodated in the syringe outer cylinder 31, and a plunger 36 attached to or attachable to the gasket 35. .
Since the syringe outer cylinder 31 is as described above, the above description is referred to.
As shown in FIG. 18, the syringe 30 of the present invention includes a syringe outer cylinder 31, a seal cap 32 attached to the distal end portion of the syringe outer cylinder 31, and a syringe outer cylinder 31 in the embodiment of the present invention. A gasket 35 slidable inside in a liquid-tight manner, a plunger 36 attached to the gasket 35, and a chemical solution 40 stored in the syringe outer cylinder 31 are provided.

It is preferable to use a known seal cap 32. The seal cap 32 includes a seal cap body 33 and a seal member 34.
The seal cap body 33 is made in a cap shape, and the tip is open. The cap main body 33 includes a storage portion for storing the nozzle portion 38, a cap-side screwing portion screwed with the nozzle-side screwing portion 38 a provided in the syringe outer tube 31, and a nozzle provided in the outer tube 31. A cap-side engaging portion that engages with the portion-side engaging portion 38b. And the sealing member 34 is arrange | positioned at the front-end | tip opening part. The nozzle portion 38 is liquid-tightly sealed by the tip opening of the nozzle portion 38 coming into contact with the seal member 34. The seal member 34 is formed of an elastic material that can be pierced by a liquid passing needle or the like. Examples of the material for forming the seal member 34 include natural rubber, isoprene rubber, butadiene rubber, fluorine rubber, silicone rubber and other synthetic rubbers, styrene elastomers such as SBS elastomer and SEBS elastomer, and ethylene-α-olefin copolymers. It is preferable to use a thermoplastic elastomer such as a polyolefin-based elastomer. In addition, as a seal cap, it is not limited to the thing which can be pierced by such a liquid passing needle. As a forming material of the seal cap 32, it is preferable to use the same material as the outer cylinder 31 for syringes.

The gasket 35 includes a main body portion 35a extending to substantially the same outer diameter and a plurality of annular ribs 35b provided on the main body portion 35a. The annular rib 35 b is in liquid-tight contact with the inner surface of the outer cylinder 31. Although the number of the annular ribs 35b is two in this embodiment, the number may be appropriately determined as long as the liquid-tightness and the sliding property are satisfied. Further, the front end portion of the gasket 35 has a tapered diameter so that a gap is not formed as much as possible when contacting the inner surface of the front end of the outer cylinder 31.
The gasket 35 is made of rubber having elasticity (for example, butyl rubber, latex rubber, silicone rubber, etc.) or a synthetic resin (for example, SBS elastomer, SEBS elastomer, polyolefin elastomer, etc.).
The gasket 35 is provided with a recess extending inward from the base end. The concave portion is a female screw portion. The concave portion can be screwed with a male screw portion formed at the distal end portion of the plunger 36. The plunger 36 may be removed at the assembly stage and attached at the time of use.
The plunger 36 includes a main body portion 36a and a male screw portion provided at the distal end portion of the main body portion 36a. The main body portion 36a has a cross-shaped cross section and extends in the axial direction. The base end portion includes a pressing disk portion 36b and a rib 36c provided on the main body portion 36a. As a forming material of the plunger 36, it is preferable to use the same material as that of the outer cylinder 31.
The seal cap 32, the gasket 35, and the plunger 36 are preferably manufactured by injection molding using the above-described resin.
As the drug solution 40, physiological saline, high-concentration sodium chloride injection solution, drug solutions such as vitamins, minerals, antibiotics, and powdered or lyophilized drugs are used.
Then, the seal cap 32 is attached to the nozzle portion 38 of the outer cylinder 31. And under pressure reduction conditions, the chemical | medical solution 40 is filled in the outer cylinder for syringes, and the gasket 35 is stoppered from a base end opening part. Then, the plunger 36 is attached to the gasket 35, and the manufacture of the syringe 30 of the present invention is completed.

FIG. 1 is a cross-sectional view of an embodiment in which the injection mold of the present invention is applied to an injection mold of a syringe outer cylinder. 2 is a side sectional view of the injection mold shown in FIG. FIG. 3 is a partially enlarged cross-sectional view of the injection mold shown in FIG. FIG. 4 is a partially enlarged sectional view of the injection mold shown in FIG. 5 is a cross-sectional view taken along line AA in FIG. 6 is a cross-sectional view taken along line BB in FIG. FIG. 7 is an explanatory view for explaining the operation of the injection mold of the present invention. FIG. 8 is an explanatory diagram for explaining the operation of the injection mold according to the present invention. FIG. 9 is an explanatory diagram for explaining the operation of the injection mold according to the present invention. FIG. 10 is a front view of an example in which the injection molded product of the present invention is applied to an outer cylinder for a syringe. FIG. 11 is a side view of the syringe outer cylinder shown in FIG. 10. 12 is a top view of the syringe outer cylinder shown in FIG. FIG. 13 is a perspective view of the syringe outer cylinder shown in FIG. 10. 14 is a partially enlarged view of the vicinity of the flange of the syringe outer cylinder shown in FIG. 15 is a longitudinal sectional view of the syringe outer cylinder shown in FIG. 16 is a longitudinal sectional view of the syringe outer cylinder shown in FIG. FIG. 17 is a partially enlarged cross-sectional view of the vicinity of the proximal end portion of the syringe outer cylinder illustrated in FIG. 15. FIG. 18 is an external view of a syringe using a syringe outer cylinder that is an injection molded product of the present invention.

Explanation of symbols

31 Outer cylinder for syringe 37 Outer cylinder main body 38c Liquid discharge port 39 Flange 55 Annular rib 57 Molten resin injection gate position

Claims (25)

A resin injection molded article having a draft on the outer surface, the resin injection molded article comprising an undercut portion having an inclined surface opposite to the draft, and further comprising the undercut portion A resin injection molded product comprising a molten resin injection gate position on an inclined surface. The resin injection molded product according to claim 1, wherein the undercut portion is formed on an outer surface having the draft of the injection molded product. The resin injection molded product according to claim 1, wherein the undercut portion is a concave portion. The resin injection molded product according to any one of claims 1 to 3, wherein the molten resin injection gate position is located at a rear side end portion with respect to a drawing direction of the draft of the inclined surface of the undercut portion. The resin injection molded product according to any one of claims 1 to 4, wherein an inclination of the inclined surface of the undercut portion with respect to a drawing direction of the draft is 2 to 12 °. The resin injection molded product according to any one of claims 1 to 5, wherein the resin injection molded product is an outer cylinder for a syringe. The syringe outer cylinder includes an outer cylinder main body, a liquid discharge port provided at the distal end of the outer cylinder main body, and a flange provided along the entire circumference of the base end of the outer cylinder main body. The resin injection molded product according to claim 6, wherein the undercut portion is provided on an outer surface of the flange portion. The flange portion includes two gripping portions formed so as to be substantially opposed to the central axis of the outer cylinder main body portion, and the undercut portion is the flange portion and a portion that is not the gripping portion. The resin injection-molded product according to claim 7, wherein the resin injection-molded product is provided near an outer surface of a portion close to a proximal end portion of the outer cylinder main body. An injection mold for a resin injection molded article having a draft, the injection mold comprising at least the outer shape of the injection molded article and a cavity having a draft, the cavity Has an undercut forming portion having an inclined surface opposite to the draft angle, and further includes a molten resin injection gate on the inclined surface of the undercut forming portion. Mold. The undercut forming portion is a protruding portion that protrudes from the inner surface of the cavity, and the inclined surface has a lower end of the molten resin injection gate as a top portion and decreases toward a drawing direction of the draft. 9. A mold for injection molding according to 9. The mold for injection molding according to claim 10, wherein an inclination of the inclined surface of the undercut forming portion with respect to a drawing direction of the draft is 2 to 12 °. The injection mold according to any one of claims 9 to 11, wherein the injection mold is an outer cylinder injection mold for a syringe. The injection mold includes a cavity and a core for forming an outer surface shape and an inner surface shape of the outer cylinder for the syringe, and the cavity and the core are provided around the entire base end portion of the outer cylinder main body forming portion. The mold for injection molding according to claim 12, further comprising a flange forming portion provided along the flange, wherein the undercut forming portion is provided on a side surface of the flange forming portion. The flange forming portion is formed so as to protrude outward from a base end portion of the outer cylinder main body portion forming portion so as to be opposed, and a grip for forming a gripping portion for gripping the syringe outer tube The mold for injection molding of the outer cylinder for syringes according to claim 13, which has a part forming part. The mold for injection molding according to claim 14, wherein the molten resin injection gate is provided on a side surface of a portion that is the flange forming portion and is close to a proximal end portion of the outer cylinder main body forming portion. It was formed by injection molding having an outer cylinder main body, a liquid discharge port provided at the distal end of the outer cylinder main body, and a flange provided along the entire circumference of the base end of the outer cylinder main body. An outer cylinder for a syringe, the front end surface or the base end side surface of the flange has an annular rib positioned at a peripheral edge of the flange, and a molten resin injection gate position is provided on the outer surface of the flange. An outer cylinder for a syringe, characterized in that is provided. The outer periphery for a syringe according to claim 16, wherein the flange has a gripping portion that is formed so as to protrude from a proximal end portion of the outer tube for syringe so as to face the flange, and grips the outer tube for syringe. Tube. 18. The syringe according to claim 17, wherein the molten resin injection gate position is a portion that is not the grip portion of the flange and is provided near an outer surface of a portion that is close to a proximal end portion of the outer cylinder main body portion. Outer cylinder. The syringe outer cylinder according to any one of claims 16 to 18, wherein the annular rib is formed along the vicinity of an outer edge portion of the flange. The outer cylinder for a syringe is a resin injection molded product having a draft angle, and includes an undercut portion having an inclined surface that is opposite to the draft angle, and further on the inclined surface of the undercut portion. The syringe outer cylinder according to any one of claims 16 to 19, which has a molten resin injection gate position. A syringe outer cylinder having an outer cylinder main body, a liquid discharge port provided at the distal end of the outer cylinder main body, and a flange provided along the entire circumference of the base end of the outer cylinder main body is injected. An injection mold for molding, the injection mold including a cavity and a core for forming an outer surface shape and an inner surface shape of the outer cylinder for the syringe, the cavity and the core, It has a flange forming portion provided along the entire circumference of the base end portion of the outer cylinder main body forming portion, and the distal end surface of the flange forming portion or the base end surface forming portion has a peripheral portion of the flange forming portion. A molten resin guiding annular groove for guiding the molten resin injected into the gap between the cavity and the core, and the cavity and the core on the side surface of the flange forming portion. Molten tree for injecting molten resin into the voids Injection mold syringe outer cylinder for characterized in that the injection gate is provided. The flange forming portion is formed so as to protrude outward from a base end portion of the outer cylinder main body portion forming portion so as to be opposed, and a grip for forming a gripping portion for gripping the syringe outer tube The mold for injection molding of the outer cylinder for syringes according to claim 21, which has a part forming part. The injection molding of an outer cylinder for a syringe according to claim 22, wherein the molten resin injection gate is provided on a side surface of a portion that is the flange forming portion and is close to a proximal end portion of the outer cylinder main body forming portion. Mold. The cavity has a draft and an undercut forming portion having an inclined surface opposite to the draft, and the molten resin injection gate is disposed on the inclined surface of the undercut forming portion. 24. A mold for injection molding of an outer cylinder for a syringe according to any one of claims 21 to 23. The injection mold for an outer cylinder for a syringe according to any one of claims 21 to 24, wherein the annular groove portion for guiding a molten resin is provided along the vicinity of an outer edge portion of the flange forming portion.

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