JP3409802B2 - Mold for injection molding - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a male die having a core pin, a female die having a circular cross-sectional groove, and the core pin having the circular cross-sectional groove. The present invention relates to a mold for injection molding for injection-molding a cylindrical body by being fitted in a center line direction. 2. Description of the Related Art Conventionally, when obtaining a molded article that is a cylindrical body,
The molded product is released from the core pin by protruding with a stripper plate or an ejector sleeve. [0003] On the other hand, some molded products are thin or have an undercut portion. Further, the material of the resin is shifting from sulfide rubber such as NBR to soft material such as thermoplastic elastomer. [0004] However, in such a conventional technique, when the molded product is thin or soft, when the molded product is released from the core pin, it is simply protruded by a stripper plate or the like. However, since the molded product is deformed or buckled due to the release resistance from the core pin and becomes a defective product, it can be released manually or to reduce the release resistance, for example, immediately before injection molding In addition, since a step of spraying a release agent onto the core pin is required, there is a problem that productivity is reduced. The present invention has been made in view of such conventional problems. At the end of injection molding, the tubular body is pulled out from the core pin while blowing compressed air or the like from the core pin side. To provide a mold for injection molding that can significantly reduce the mold release resistance, prevent the molded product from being deformed, eliminate special man-hours for mold release, and increase productivity. The purpose is. SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is as follows: 1 A male pin (20) is provided with a core pin (40), and a female section (30) is provided with a circular cross section. A groove (32) is formed, and the core pin (40) is inserted in the direction of the center line of the groove (32) having a circular cross-section, and is used for injection molding for injection-molding a cylindrical body (W). In the mold, holes (44, 44a) for taking in compressed air are drilled in the central axis of the core pin (40), and the holes (44, 44) for taking in compressed air are formed in the outer periphery of the core pin (40). , 44a) to discharge compressed air for release and to form a fine compressed air discharge hole (58) so that resin material does not flow into the core pin (40).
And an inner core (42) centered on the inner core (4).
2) and an outer core (52) that fits over the outer core (52).
4,44a), and a communication hole (46) communicating with the compressed air intake hole (44,44a) and extending radially around the compressed air intake hole (44,44a). ) Is formed, and the part where the communication hole (46) is formed is lowered by one step from the general outer peripheral surface of the inner core (42), so that the part where the communication hole (46) is formed and the outer core (52) are formed. An outer gap (49a) is formed between the outer core (52) and the inner peripheral wall, and the outer core (52) is divided into a plurality of annular outer pieces (54) in the axial direction. The compressed air ejection hole (58) is formed on at least one of the opposing divided surfaces (56, 56a), and the compressed air is discharged through the communication hole (46) and the annular gap (49a). Air intake It consists in a mold for injection molding, characterized in that a groove (58) of the hole for the compressed air jet which communicate with the (44, 44a) use. The male pin (40) is fitted in the center line direction of the female-shaped groove (32) having a circular cross section, and the core pin (4) is inserted.
A resin material is injected into a gap having an annular cross section between the groove (0) and the groove (32) having a circular cross section. Thereby, a cylindrical body (W) is formed. At this time, since the compressed air ejection hole (58) is so finely formed that the resin material does not flow, the resin material may flow into the core pin (40) through the compressed air ejection hole (58). Absent. When the cylindrical body (W) is formed, compressed air is taken in through compressed air intake holes (44, 44a) formed in the center shaft of the core pin (40), and the core pin (40) is taken in. 40) The compressed air jet holes (5
8) Compressed air is blown outward through. Thereby,
A gap is formed between the outer peripheral portion of the core pin (40) and the inner peripheral wall of the cylindrical body (W), the mold release resistance from the outer peripheral portion of the core pin (40) is reduced, and the cylindrical body (W) is deformed. You can take it out without having to. An inner core (42) centered on the core pin (40) and an outer core (52) fitted to the inner core (42) are provided.
2) The holes (44, 44a) for taking in the compressed air are drilled, and the holes (44, 4) for taking in the compressed air are provided.
4a) and the compressed air intake holes (44, 4).
A communication hole (46) extending radially around the center 4a) is formed, and the outer core (52) is constituted by an annular outer piece (54) overlapping a plurality of pieces in the axial direction, and the outer piece (54) is divided so as to face the outer piece (54). Face (56,56
In at least one of (a), a compressed air ejection groove (58) communicating with the compressed air intake hole (44, 44a) through a communication hole (46) is formed. The outer piece (54) can be easily formed, and the manufacturing cost can be reduced. An embodiment of the present invention will be described below with reference to the drawings. Each drawing shows an embodiment of the present invention. The injection molding die 20a according to the present embodiment is for taking a large number of cylindrical bodies W, and the cylindrical body W is used for a grip shaft of a mechanical pen or a ballpoint pen. ,
A cylindrical body W is connected to a sprue part (not shown) serving as a center through a runner part (not shown) extending from the film gate and a film gate (not shown). As shown in FIGS. 2 and 3, the injection mold 20a has a male mold 20 and a female mold 30, and the male mold 20 and the female mold 30 are closed by guide pins (not shown). It is guided to the open state and the open state. The male mold 20 is provided with a core pin 40,
The female mold 30 is formed with a groove 32 having a circular cross section for fitting the core pin 40 in the center line direction. Core pin 4
A resin material is filled in a gap having an annular cross section between the groove 32 and the groove 32 having a circular cross section. As shown in FIG. 1 to FIG.
Is constituted by an inner core 42 serving as a center, and an outer core 52 which is fitted to the inner core 42. [0015] As shown in FIGS.
2 is a top core 43 on the tip side and a base core 4 on the base side.
3a is screwed. A male thread is formed at the rear end of the top core 43, and a female thread is formed at the front end of the base core 43a. Holes 44 and 44a for taking in compressed air which are continuous in the central axis direction are formed in the top core 43 and the base core 43a, respectively. The top end of the top core 43 has a large diameter portion 47, and the base end of the top core 43 has a small diameter portion 48. A communication hole 46 is formed in the small diameter portion 48 of the top core 43 so as to communicate with the hole 44 for taking in compressed air and extend radially around the hole 44 for taking in compressed air. The portion where the communication hole 46 is formed is a minimum diameter portion 49 having a smaller diameter, and is one step lower than the general outer peripheral surface of the small diameter portion 48. As shown in FIGS. 5, 11 and 12,
The outer core 52 is composed of a plurality of annular outer pieces 54 which are divided in the axial direction and whose front divided surface 56 and rear divided surface 56a overlap each other. An annular gap 49 a is formed between the minimum diameter portion 49 of the top core 43 and the inner peripheral wall 59 of the outer piece 54. On the front divided surface 56 of the outer piece 54, a compressed air ejection groove 58 for ejecting compressed air communicates with the compressed air intake hole 44 through a communication hole 46 and an annular gap 49a. It is formed radially from the center. The groove 58 for jetting compressed air is formed with a fine groove length such that the resin material does not flow. The groove length is 0.1mm ~
It is set to about 0.002 mm. As shown in FIG. 2, a groove for a film gate and a groove for a runner, also not shown, are formed on the front surface of the female mold 30 so as to be continuous with the grooves 32 of each circular cross section. I have. Hole 3 for sprue in groove for runner
7 are provided continuously. Male mold 20 and female mold 30
And a stripper plate 60 is interposed therebetween.
The stripper plate 60 is movably supported by guide pins (not shown) at a separated position away from the male mold 20 toward the female mold 30 and at a close position approaching the male mold 20. The stripper plate 60 is urged away from the male mold 20 by a spring member (not shown). Mold 30 for stripping stripper plate 60 from the separated position
A stopper pin (not shown) for immovably restraining the side is implanted in the male mold 20. A guide bush 6 for guiding the core pin 40 to be relatively movable when the stripper plate 60 moves is provided on the stripper plate 60.
2 are provided. Next, the operation will be described. The molding material is injected through the inlet 68 of the sprue hole 67 by fitting the core pin 40 of the male mold 20 in the center line direction of the groove 32 having the circular cross section of the female mold 30. The molding material flows into the sprue hole 37 through the sprue hole 67, and also flows into each runner groove to each film gate groove (not shown), and finally, the core pin 40 and the circular cross-sectional shape. A resin material is filled in a gap having an annular cross section between the groove 32 and the groove 32. Thereby, the cylindrical body W is formed. At this time, since the compressed air ejection hole 58 is so finely formed that the resin material does not flow, the resin material does not flow into the core pin 40 through the compressed air ejection hole 58. When the cylindrical body W is formed, compressed air is taken in through a compressed air intake hole 44 formed in the center shaft portion of the core pin 40, and is passed through the communication hole 46 and the annular gap 49a. Compressed air ejection hole 58 of outer piece 54
Compressed air is ejected outward through the air. Thereby, a gap is formed between the outer peripheral portion of the outer piece 54 of the core pin 40 and the inner peripheral wall of the cylindrical body W, and the outer piece 5 of the core pin 40 is formed.
The mold release resistance from the outer periphery of 4 is greatly reduced. Next, when the male mold 30 starts to open, the stripper plate 60 is pressed by the urging force of a spring member (not shown).
The state of contact with the female mold 30 is maintained. Thereby,
Since the tubular body W is pressed by the stripper plate 60, the core pin 40 and the tubular body W move relatively. At this time, the compressed air is ejected outward through the compressed air ejection holes 58, and the release resistance of the core pin 40 from the outer peripheral portion of the outer piece 54 of the core pin 40 with respect to the cylindrical body W is greatly reduced. Therefore, the tubular body W can be easily removed from the male mold, and the tubular body W does not deform or buckle. When the male mold 30 is completely opened, the stripper plate 60 returns to the separated position before and after. Next, when a protrusion pin (not shown) projects into the groove 32 having a circular cross section, the cylindrical body W filled in the groove 32 having a circular cross section is pushed and detached from the groove 32 having a circular cross section. In the above embodiment, since the plurality of outer pieces 54 are superimposed to form the compressed air ejection groove 58, the compressed air ejection groove 5 is formed.
8 can be easily provided, and the manufacturing cost can be reduced. Further, through a groove 58 for jetting compressed air,
A release agent may be ejected. According to the injection molding die of the present invention, the cylindrical member is ejected outward through the compressed air ejection hole formed in the outer peripheral portion of the core pin. Since the core is removed from the core pin, the release resistance from the outer peripheral portion of the core pin to the cylindrical body is greatly reduced, the cylindrical body can be easily removed from the core pin, and the cylindrical body is thin, Even if it is soft, it does not deform or buckle when the tubular body is pulled out from the core pin, and it does not become a defective product. No man-hours are required, and productivity can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a core pin showing one embodiment of the present invention. FIG. 2 is a sectional view of a main part of an injection mold according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a main part of a mold for injection molding showing one embodiment of the present invention. FIG. 4 is a perspective view of a core pin showing one embodiment of the present invention. FIG. 5 is a longitudinal sectional view of a core pin showing one embodiment of the present invention. FIG. 6 is a sectional view of a main part of a core pin showing an embodiment of the present invention. FIG. 7 is a rear view of the core pin showing one embodiment of the present invention. FIG. 8 is a sectional view of a main part of a core pin showing one embodiment of the present invention. FIG. 9 is a partial side view of a core pin showing one embodiment of the present invention. FIG. 10 is a partial longitudinal sectional view of a core pin showing one embodiment of the present invention. FIG. 11 is an exploded sectional view of a core pin showing one embodiment of the present invention. FIG. 12 is a sectional view of a main part of a core pin showing one embodiment of the present invention. [Description of Signs] W: Cylindrical body 20: Male mold 30: Female mold 32: Groove 40 having a circular cross-sectional shape ... Core pin 42: Inner cores 44, 44a: Holes 46 for intake of compressed air ... Communication hole 52: Outer core 54 ... Outer piece 56: front divided surface (divided surface) 56a: rear divided surface (divided surface) 58: groove for compressed air ejection 60: stripper plate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/26-45/44 B29C 33/00-33/76 B29C 39/26-39/36 B29C 41 / 38-41/42

Claims (1)

(57) [Claims 1] A male pin is provided with a core pin, a female mold is formed with a groove having a circular cross section, and the core pin is fitted in the center line direction of the groove with the circular cross section. In a mold for injection molding for injection-molding a cylindrical body, a hole for compressed air intake is formed in a central shaft portion of the core pin, and an outer peripheral portion of the core pin is provided with a hole for compressed air intake. A compressed air ejection hole for discharging mold air in communication with the hole, and fine enough to prevent the resin material from flowing into the hole, and an inner core centered on the core pin and an outer fit to the inner core. A communication hole formed with an outer core, wherein the hole for taking in compressed air is formed in the inner core, and the communication hole communicates with the hole for taking in compressed air and extends radially around the hole for taking in compressed air. Drilling the said communication hole is drilled By lowering the part that is one step lower than the general outer peripheral surface of the inner core, an annular gap is formed between the part where the communication hole is drilled and the inner peripheral wall of the outer core, and the outer core is divided in the axial direction. The compressed air ejection hole is formed on at least one of the opposing divided surfaces of the adjacent outer pieces, wherein the compressed air ejection hole is formed by a plurality of annular outer pieces, and the compressed air is injected through the communication hole and the annular gap. A mold for injection molding, wherein a groove for compressed air ejection communicating with a hole for air intake is formed.