JP2023071257A - Injection molding device - Google Patents

Abstract

To provide an injection molding device for narrow bottomed containers that eliminates a post-process of removing a gate mark and is good in terms of material and work efficiency.SOLUTION: An injection molding device 1a includes: a cavity mold 3 surrounding an outer peripheral surface 4 and an outer bottom surface 5 of a cavity 2a; a core liner 10 having a tip side narrow diameter part 11 entering inside the cavity 2a, a base side thick diameter part 13 connected to a base side thereof and having a recess 15 along a central axis, a runner sprue 14a penetrating axially from a bottom of the recess 15, and cooling means 19; a nozzle 20 having a tip side inserted into the recess 15, having a flow path 24 for molten resin therein, and equipped with heating means 25; a stem 30 that advances and retracts along an axial direction within the nozzle 20 and allows a tip 34 to pass through a tip hole 23 of the flow path 24; a pin 32 concentrically connected to the tip 34 thereof and advancing and retreating in the runner sprue 14a through the core liner 10; and an outward recess 38 formed in the pin 32. The pin 32 does not block a gate G even when it advances to a tip side.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an injection molding apparatus suitable for efficiently injection-molding a small-diameter container with a bottom or a small-diameter lid.

For example, like a lipstick containing lipstick, a cylindrical or prismatic container or lid with a relatively small outer diameter or side of about 15 mm or less and one end closed (hereinafter referred to as a bottomed small diameter container or A lid with a small diameter) is required to have a smooth surface on the outer peripheral surface, the outer surface, or the outer end surface so that no convex or concave gate marks, which are gate marks during injection molding, remain. Moreover, after injection molding, in order to omit the post-process of removing gate traces by polishing, etc., it is necessary to use It is required to arrange a gate for press-fitting the molten resin in.

For example, in order to injection mold a parison (preform) with a small diameter, a concave cavity mold forming a U-shaped cavity with an elongated cross section and a convex core mold are placed in the mold body on the movable side, A relatively large-diameter runner nozzle having a band heater wound around the outer peripheral surface of the runner part on the movable side is arranged concentrically with the cavity, and the tip of the runner nozzle is positioned near the top of the hemispherical part on the outside of the cavity. A hot-runner type injection molding die device has been proposed that allows communication via a provided gate (see, for example, Patent Document 1). However, in the injection molding device of Patent Document 1, a post-process is required to make the sprue portion (gate trace) inconspicuous by excising and removing it before reheating and blow molding after injection molding. .

Japanese Patent Application Laid-Open No. 57-24220 (pages 1 to 4, figures 1 to 3)

On the other hand, in order to omit the post-process for removing gate traces, it is conceivable to provide a gate on the bottom surface of the inside (hollow portion) of the cavity serving as a small-diameter container with a bottom or a small-diameter lid. For example, it is possible to apply a so-called cold runner type injection molding apparatus that uses a small diameter and divisible nozzle (insertion side mold) that can be easily inserted into a narrow hollow portion. However, in the case of the cold runner method, a long resin slug covering the sprue, runner, and gate is generated each time injection molding is performed, and the resin slug must be removed each time the mold is opened. There was a problem with work efficiency.

The present invention solves the above-mentioned problems, eliminates the post-process of removing gate traces from a small-diameter container with a bottom or a small-diameter lid, can be injection molded with good material efficiency and work efficiency, and has a simple mold structure. An object of the present invention is to provide a molding apparatus.

The injection molding apparatus according to the invention comprises:
An apparatus for injection molding a small-diameter container with a bottom or a small-diameter lid by a hot runner method,
a cavity mold surrounding an outer peripheral surface and an outer bottom surface of a cavity for molding the small-diameter container with a bottom or the small-diameter lid;
A tip side small diameter portion entering the inside surrounded by the cavity, a base side large diameter portion continuously provided on the base end side and enclosing a recess along the central axis, and a tip end side from the bottom surface of the recess a core insert having a runner sprue passing through along the axial direction and a cooling means;
a nozzle whose tip side is inserted into the recess of the core insert, has a flow path for molten resin along the central axis, and is equipped with a heating means;
a stem that advances and retreats along the axial direction of the flow path of the molten resin in the nozzle and whose tip portion can pass through a tip hole of the flow path of the molten resin;
a pin that is concentrically connected to the distal end of the stem and moves forward and backward in the runner sprue that penetrates the core insert along its axial direction;
an outward recess formed in the pin;
When the stem moves forward, the tip of the stem comes into surface contact with the inner wall surface of the runner sprue of the core insert, and the tip of the pin is positioned inside the runner sprue of the core insert. ing.

The runner sprue passing through the core insert and the pin have similar shapes to each other such that the diameters of the runner sprues and the pins are gradually or continuously reduced on the tip end side and the diameters are gradually or continuously increased on the base end side. You may present it.

Between the base end face of the cavity mold and the base-side large-diameter portion of the core insert, a stripper ring whose inner peripheral surface abuts against the opening-side end face of the outer peripheral surface of the cavity is provided on the axis of the core insert. You may arrange|position so that advance and retreat are possible along a direction.

A plurality of sets of the hot runner unit consisting of the cavity mold, the core insert, the nozzle, the stem, the pin, and the stripper ring are arranged side by side, and each set of the nozzles has a flow path for the molten resin. may communicate with a single sprue bushing.

The outward concave portion formed in the pin has a single ring-shaped groove or a plurality of ring-shaped grooves formed along the axial direction, or at least one or a point-symmetrical position with respect to the central axis of the pin. may be formed in plural.

A gate located at the tip of the runner sprue penetrating the core insert may open at the center or the periphery of the inner bottom surface of the cavity in the cavity mold.

The stem may have at least one reverse flow groove axially formed from the distal end toward the proximal end.

According to the injection molding apparatus of the present invention, gate traces are formed on the inner bottom surface of the small-diameter container with a bottom or the small-diameter lid molded in the cavity. With a simple hot runner system, it is possible to injection-mold a small-diameter container with a bottom or a small-diameter lid with good material efficiency and work efficiency.

(A) is a cross-sectional view schematically showing an injection molding apparatus according to one embodiment of the present invention, (B) is a partial cross-sectional view taken along line BB in (A), and (C) is , a side view of the same portion as (B). (A) and (B) are schematic diagrams showing the state of use of the injection molding apparatus. (A) and (B) are schematic diagrams showing the state of use following FIG. 2(B). (A1) and (A2) are partial cross-sectional views showing the bottom wall of the molded small-diameter container with bottom, (B1) and (B2) are schematic views showing cross-sections of the pin before and after injection, and (C) is , Schematic which shows the deformation|transformation of the injection molding apparatus of embodiment. (A) is a schematic diagram showing an injection molding apparatus of a different embodiment, (B) is a side view showing its stem and pins, (C1) and (C2) are the CC line in (B). Cross-sectional view along the arrow. (A) and (B) are schematic diagrams showing the operation of the injection molding apparatus of different embodiments.

EMBODIMENT OF THE INVENTION Below, the form (Example) for implementing this invention is demonstrated.
In the present invention, the small-diameter container with a bottom or the small-diameter lid to be molded is, for example, a long and narrow container or lid for cosmetics such as lipstick or mascara, or a resin container for storing writing instruments such as a high-grade fountain pen. A cap having a cylindrical or polygonal prism shape as a whole with a bottom closed at one end, and having a diameter of about 40 mm or less, preferably 30 mm or less in a cross section perpendicular to the axial direction, or a diagonal line in the cross section. The object is about 50 mm or less, preferably 40 mm or less. The axial length of the bottomed small-diameter container or the small-diameter lid is at least 0.5 times or more the diameter or diagonal length.

FIG. 1A is a cross-sectional view schematically showing an injection molding apparatus 1a according to one embodiment (example) of the present invention. In the following similar drawings including this drawing, the lower side of the drawing is referred to as the distal end side, and the upper side of the drawing is referred to as the proximal end side. As shown in FIG. 1(A), the injection molding apparatus 1a includes a cavity mold 3, a stripper ring 8, and a core insert, which are sequentially arranged from the distal end side to the proximal end side and constitute a set of hot runner units. It comprises an element 10, a nozzle 20, a stem 30 and a pin 32. In the injection molding apparatus 1a, the cavity mold 3 is included in the movable mold, and the stripper ring 8, the core insert 10, the nozzle 20, the stem 30, the pin 32, etc. are included in the fixed mold.

The cavity mold 3 is a female mold having a cylindrical outer peripheral surface 4 and an outer bottom surface 5 circular in plan view in an elongated cavity 2a for molding a bottomed small-diameter container 50a later. The ratio of the axial length of the cavity 2a to the diameter along the radial direction is about 2:1 to 2:1 or more. In FIG. 1A, the upper surface of the cavity mold 3 is a mold opening surface 6, and a stripper plate 7 sharing the mold opening surface 6 is disposed above the mold opening surface 6 so as to be movable up and down. The stripper plate 7 has a relatively small-diameter through-hole 7a located on the base end side and a relatively large-diameter through-hole 7b concentrically adjacent to the distal end side thereof. , a stripper ring 8 having a trapezoidal cross section is fixed. Of the lower surface of the stripper ring 8, the inner peripheral surface side facing the upper end surface of the side wall portion of the cavity 2a serves as a ring-shaped contact surface 8a that pushes a bottomed small diameter container 50a described later toward the tip side from the mold opening surface 6. Become. The stripper plate 7 including the stripper ring 8 has a plurality of ends, as illustrated on the right side of FIG. , when the mold is opened, it is slidable to the tip end side as shown in the drawing.

As shown in FIG. 1A, core inserts 10 are arranged in the through holes 7a and 7b of the stripper plate 7 along their axial directions. The core insert 10 extends to the base end side through a tip-side small-diameter portion 11 entering the inside surrounded by the outer peripheral surface 4 of the cavity 2a and a bent portion 12 having an L-shaped cross section located above it. It has a proximal large-diameter portion 13 that includes a cylindrical concave portion 15 that is continuous and extends along the central axis. Between the center of the conical bottom surface of the concave portion 15 and the tip surface of the tip side small diameter portion 11, a two-tiered runner sprue 14a having a small diameter on the tip end side and a large diameter on the base end side is provided in the axial direction. passes through along the A narrowest gate (product gate) G communicating with the inside of the cavity 2a opens at the tip side of the runner sprue 14a. The tip side narrow diameter portion 11 is a male mold that forms the cavity 2a. A channel (cooling means) 19 for circulating cooling water is provided in an annular shape on the outer peripheral surface side of the core insert 10 . The core insert 10 is surrounded and supported by a core plate 16 on the outside.

As shown, a nozzle 20 is concentrically arranged inside the recess 15 in the core insert 10 . The nozzle 20 has a cylindrical nozzle body 21 in which a molten resin flow path 24 is provided along the central axis, a conical tip portion 22 connected to the tip side of the nozzle body 21, and the center of the tip portion 22. and a flange 26 located on the base end side of the nozzle body 21 and for fixing the entire nozzle 20 to the side wall of the manifold 27 on the tip side. integrally prepared. A band heater (heating means) 25 is wound around the outer peripheral surface of the nozzle body 21 .

The base end side of the nozzle body 21 is surrounded by the manifold plate 17 with the space 18 interposed therebetween. The tip side of the molten resin flow path 24 communicates with the runner sprue 14 a of the core insert 10 via the tip hole 23 . On the other hand, the base end side of the flow path 24 for the molten resin communicates with flow paths 28 and 29 that penetrate the inside of the manifold 27 and have an inverted L shape as a whole. A horizontal channel 29 in the drawing communicates with a sprue bushing (not shown) to which molten resin is supplied. That is, the illustrated Holrunner unit, along with other similar units, are of multi-cavity form, converging and communicating with a single sprue bushing.

As shown in FIG. 1(A), a rod-shaped stem 30 is arranged in the central part of the molten resin flow path 24 of the nozzle 20 so as to be able to move back and forth along the axial direction (the direction of the distal end and the proximal end). The proximal end of the stem 30 passes through the corners of the flow paths 28 and 29 in the manifold 27, and is the piston of an air cylinder (fluid pressure cylinder) 40 built in a manifold back plate 44 located on the most proximal side. It is continuous with the rod 43 . The air cylinder 40 includes a piston 42 that reciprocates in a cylinder chamber 41 along the direction of the distal end and the proximal end, and a piston rod 43 that is connected to the piston 42 . In the illustrated state, the piston 42 is located on the proximal side in the cylinder chamber 41, so the stem 30 is also retracted toward the proximal side.

As shown in FIG. 1A, the distal end of the stem 30 includes a large-diameter portion 31 on the proximal end side via a conical distal end portion 34, and a relatively small-diameter portion located on the distal end side. Pins 32 are concentrically connected. A tip portion 33 of the pin 32 is hemispherical. The pin 32 including the large-diameter portion 31 has a substantially similar shape to the runner sprue 14a of the core insert 10 as a whole. Therefore, when the stem 30 is moved forward, the tip 33 of the pin 32 approaches the gate G side. At the same time, the distal end portion 34 of the stem 30 passes through the distal end hole 23 of the nozzle 20 and comes into surface contact with the inner wall surface of the runner sprue 14a so that the inside of the nozzle 20 can be blocked. Note that the tip portion 33 of the pin 32 may be in the form of a flat surface perpendicular to the axial direction or in a conical shape (the same applies to each form described later).

The surface (outer peripheral surface) of the pin 32 including the large-diameter portion 31 has a ring-shaped groove as a whole, and as shown in FIG. A plurality of recessed portions (undercuts) 38 are formed at approximately equal intervals along the axial direction. As will be described later, the recessed portion 38 is for locking the solidified resin cylindrically adhering to the surface of the pin 32 including the large-diameter portion 31 when the injection molding apparatus 1a is used. In addition, as shown in FIG. 1C, a plurality of local recesses 39 having an elliptical or horseshoe shape when viewed from the side are formed on the entire surface of the pin 32, including the tip side, in a scattered manner. can be The horseshoe-shaped recessed portion 39 has a flat surface perpendicular to the axial direction on the distal end side of the elliptical shape. As shown in FIGS. 1(A) and 1(B), the stem 30 has a pair (plurality) of left and right backflow grooves 37 formed along the axial direction from the distal end 34 toward the base end. . The backflow groove 37 has a substantially parallelogram shape when viewed from the side, and its inner corners (inner corners) are smoothly rounded.

A method of using the injection molding apparatus 1a will be described below.
FIG. 2(A) is an enlarged sectional view showing the vicinity of the core insert 10 of the injection molding apparatus 1a. By retracting the piston 42 of the air cylinder 40 to the proximal side, the stem 30 and the pin 32 are retracted to the proximal side as indicated by the thick arrows in the figure. In this state, the molten resin branched from the sprue bushing (not shown) passes through channels 28 and 29 in the manifold 27, and passes through the channel 24 and the tip hole 23 in the nozzle 20 as indicated by thin arrows in the figure. Then, through the runner sprue 14a of the core insert 10 surrounding the pin 32 and the gate G, it is injected into the cavity 2a and filled. The molten resin consists of a thermoplastic resin (eg, polyethylene, polypropylene, etc.). Cooling water is circulated and supplied in advance in the flow path 19 of the core insert 10 .

As shown in FIG. 2(B), when the cavity 2a is entirely filled with molten resin, a cylindrical side wall 51 including an upper end surface 54 surrounding the opening and outer and inner bottom surfaces circular in plan view are formed. A bottomed small-diameter container 50a provided with 52 and 53 is molded. This state is held for a predetermined time. After that, the piston 42 of the air cylinder 40 is advanced to the tip side, the stem 30 and the pin 32 are advanced to the tip side as indicated by the thick arrow in the figure, and the tip portion 33 of the pin 32 is moved to the gate G side. bring close to At the same time, the distal end side outer peripheral surface of the stem 30 comes into surface contact with the large diameter side inner wall surface of the runner sprue 14a. At this time, part of the molten resin flows back from the runner sprue 14a into the flow path 24 of the nozzle 20 through the pair of reverse flow grooves 37, as indicated by the thin dashed arrows in FIG. 2(B). As a result, overfilling (overpacking) of molten resin in the runner sprue 14a is prevented. During this time, the core insert 10 is cooled by the cooling water circulating in the flow path 19 .

As a result, at the center of the inner bottom surface 53 of the bottomed small-diameter container 50a, after the molten resin remaining in the runner sprue 14a solidifies, the pin 32 is retracted to the base end side together with the stem 30, for example, to break. A raised gate trace 55 is formed. At the same time, since the pin 32 including the large-diameter portion 31 is in surface contact with the cooled core insert 10, its specific surface area (surface area per unit volume) is relatively large. Cooled down. Therefore, the molten resin remaining in the runner sprue 14a is not overfilled with the molten resin in the runner sprue 14a, so as shown in FIG. Become. At that time, when the pin 32 including the large-diameter portion 31 together with the stem 30 is retracted toward the base end side by the part 61 of the solidified resin 60 that has entered the recess 38 , the entire solidified resin 60 is axially displaced. A tensile force along the As a result, the solidified resin 60 receives a strong shearing force along the axial direction between itself and the inner wall surface of the runner sprue 14a. , a conical (funnel-shaped) solidified resin 60 as a whole is formed.

When the entire molten resin forming the bottomed small-diameter container 50a has solidified, as shown in FIG. 51 and the outer bottom surface 52 are exposed to the outside. Next, as indicated by the thick arrow in FIG. 3(B), the stripper plate 7 including the stripper ring 8 is advanced to move the piston rod 9 and the like to the tip side by advancing the piston rod 9 and the like. As a result, as shown in the figure, the contact surface 8a of the stripper ring 8 pushes the entire upper end surface 54 of the side wall 51 of the bottomed small diameter container 50a axially toward the tip side. Therefore, it becomes possible to easily take out the bottomed small-diameter container 50a from the injection molding apparatus 1a. At this time, the leading end side of the solidified resin 60 in the runner sprue 14a and the gate mark 55 on the side of the bottomed small-diameter container 50a are broken and separated.

Gate traces formed at the center of the inner bottom surface 53 of the molded small-diameter container 50a with a bottom include gate traces 55 broken into a convex shape as shown in FIG. also includes a recessed gate trace 56 broken near the inner bottom surface 53 . One of the gate traces 55 and 56 is formed depending on the position where the solidified resin 60 solidified in the runner sprue 14a is broken near the gate G. As shown in FIG. Since the gate traces 55 and 56 are located at the center of the inner bottom surface 53 of the bottomed small-diameter container 50a, they cannot be visually observed from the outside, and the visible outer bottom surface 52 has a smooth and safe surface. Become.

Immediately before the first injection, nothing adheres to the surface of the pin 32 including the large-diameter portion 31, as shown in FIG. 4B1. After the second and subsequent injections, as shown in FIG. 4B2, the molten resin spreads along the entire surface of the pin 32 including the large-diameter portion 31 and the tip portion 33 and the tip portion 34 of the stem 30. The solidified solidified resin 60 adheres in a cylindrical shape. In the process of injecting the molten resin into the cavity 2a, the molten resin is in a hot runner state where it is heated and kept warm by the band heater 25 of the heating means when flowing through the flow path 24 in the nozzle 20. FIG. However, when the molten resin leaves the nozzle 20 having the band heater 25 and is pumped through the runner sprue 14a of the core insert 10 along the periphery of the pin 32 including the large diameter portion 31, it is cooled. It is cooled by heat removal by the core insert 10 and begins to solidify. As a result, a cylindrical and funnel-shaped solidified resin 60 is formed on the entire surface of the pin 32 from the large-diameter portion 31 to the tip portion 33 for each injection.

As shown in FIG. 4B2, a portion 61 of the solidified resin 60 is solidified while entering each of a plurality of recesses 38 formed along the axial direction of the pin 32 including the large-diameter portion 31. . Therefore, when the pin 32 is retracted to the base end side together with the stem 30 in preparation for the next injection process, a portion 61 of the solidified resin 60 serves as an anchor portion. This prevents the pin 32 including the diameter portion 31 from slipping out. Therefore, in the injection process from the next time onward, along the gap between the inner wall surface of the runner sprue 14a of the core insert 10 and the solidified resin 60 fixed to the entire surface of the pin 32 including the large diameter portion 31, from the nozzle 20 side By circulating the pumped molten resin to the gate G and the cavity 2a side, it is possible to reliably perform continuous injection molding by a hot runner method with a simple mold structure.

The plurality of recessed portions 38, which are ring-shaped grooves, are arranged at regular intervals along the axial direction of the pin 32 including the large diameter portion 31. It is good also as a form formed in the end side. Alternatively, one or more local recesses 39 may be formed along both the axial direction and the radial direction of the pin 32 including the large diameter portion 31, for example in a scattered pattern.

FIG. 4C is a cross-sectional view showing a main part of an injection molding apparatus 1b, which is a modification (example) of the injection molding apparatus 1a. The injection molding apparatus 1b includes a cavity mold 3, a stripper ring 8, a nozzle 20, a stem 30, etc. similar to the injection molding apparatus 1a. The injection molding apparatus 1b differs from the injection molding apparatus 1a in that it has an elongated conical runner sprue 14b between the recess 15 of the core insert 10 having the same outer shape and the gate G, and the tip 34 of the stem 30. A conical pin 35 having a substantially similar shape to the runner sprue 14b is continuously provided on the side of the runner sprue 14b, and a plurality of recessed portions 38 are arranged in the pin 35 at equal intervals along the axial direction. That is.

A cylindrical linear portion 14d including a stepped portion d is formed on the base end side of the runner sprue 14b so as to come into surface contact with the tip side of the stem 30 including the tip portion . In the injection molding apparatus 1b as well, when the pin 35 is advanced to the gate G side together with the stem 30, the tip portion 33 of the pin 35 approaches the gate G side. At the same time, the distal end side of the stem 30 including the distal end portion 34 and the straight portion 14d of the runner sprue 14b are in surface contact with each other except for the pair of reverse flow grooves 37. As shown in FIG. The injection molding apparatus 1b can also be used in the same manner as the injection molding apparatus 1a.

According to the injection molding apparatuses 1a and 1b described above, gate traces 55 and 56 are not formed on the outer bottom surface 52 of the small-diameter container 50a to be molded, and the gate traces are removed because the surface can be made smooth. In addition, the hot runner method, which has a simple mold structure, can be used to injection-mold the small-diameter container 50a with a resin material with good work efficiency. Incidentally, the bottomed small-diameter container 50a may be a similar small-diameter lid. Any number of localized indentations 39 may be used instead of the plurality or singular indentations 38 for the injection molding apparatus 1a, 1b. In the injection molding apparatuses 1a and 1b, it is sufficient that at least the tip portions 33 of the pins 32 and 35 approach the gate G side when the stem 30 is advanced to the tip side. In the injection molding apparatuses 1 a and 1 b , one or more backflow grooves 37 may be provided at point-symmetrical positions with respect to the central axis of the stem 30 .

5 and 6 relate to an injection molding apparatus 1c of a different embodiment (example), FIG. 5(A) showing a schematic cross section, and FIG. 5(B) showing a stem 30 and 5(C1) and 5(C2), which are side views showing the pin 36, are cross-sectional views taken along line CC in (B). As shown in FIG. 5(A), the injection molding apparatus 1c has a cavity mold 3 which is shorter in the axial direction than the injection molding apparatus 1b and which constitutes the outer peripheral side of the cavity 2b, and a short mold corresponding to the cavity 2b. It includes a core insert 10 having a tip-side small diameter portion 11, a stripper ring 8, a nozzle 20, a stem 30, and the like. Incidentally, in the embodiment shown in FIG. 5A, the ratio of the axial length to the radial diameter of the cavity 2b is approximately 0.75:1.

As shown in FIGS. 5(B), 5(C1) and (C2), the injection molding device 1c is provided with four or three (a plurality of) axially extending portions on the outer peripheral surface of the stem 30 on the distal end portion 34 side. ) is provided, and a pin 36 having a relatively short axial length concentrically connected via the tip portion 34 is provided. The surface of the pin 36 is provided with three (plurality) recesses 38 along the axial direction. A cylindrical linear portion 14d extending to a ring-shaped stepped portion d is attached to the base end side of the runner sprue 14c of the core insert 10 .

As indicated by the thick arrow in FIG. 5(A), which shows the state immediately before the molten resin is injected into the cavity 2b, the pin 36 is moved forward together with the stem 30, and when the pin 36 is advanced to the tip side, the tip portion 33 of the pin 36 becomes the core. It enters the middle of the runner sprue 14c in the insert 10 in the axial direction. As a result, a bottomed small-diameter container having a short axial length is molded in the cavity 2b. During this time, as shown in FIG. 6A, the outer peripheral surface of the stem 30 near the distal end portion 34 enters the straight portion 14d of the runner sprue 14c to close the proximal end side of the runner sprue 14c. As a result, the molten resin pumped between the pin 36 and the gate G may become overfilled (overpacked). At this time, as indicated by thin dashed arrows in the figure, part of the molten resin is circulated in the flow path 24 of the nozzle 20 after flowing through the plurality of backflow grooves 37 to the base end side.

During this time, the pin 36 is concentrated via the stem 30 which is in surface contact with the straight portion 14d of the runner sprue 14c of the core insert 10 due to the cooling water circulating in the flow path 19 of the core insert 10. effectively cooled. As a result, as shown in FIG. 6(B), when the pin 36 is retracted together with the stem 30 after injection, the solidified resin 60 forms a cylindrical and funnel-like shape on the entire surface of the pin 36. A portion 61 of the solidified resin 60 enters each recess 38 while being fixed.

Therefore, as indicated by the thick arrow in FIG. 6(B), when the pin 36 is retracted to the base end side together with the stem 30, a part 61 of the solidified resin 60 entering each recess 38 acts as an anchor. Therefore, it is possible to reliably prevent the front end side of the solidified resin 60 from breaking near the gate G and the solidified resin 60 having a funnel shape as a whole to fall off the pin 36 . According to the injection molding apparatus 1c as described above, it is possible to obtain the same actions and effects as those of the injection molding apparatuses 1a and 1b. Instead of the plurality of recesses 38, a plurality of local recesses 39 may be provided in a scattered manner on the pin 36 of the injection molding apparatus 1c.

The outer bottom surfaces (outer end surfaces) 52 of the bottomed small-diameter containers (including small-diameter lids) 50a and 50b may be curved surfaces or hemispherical surfaces that bulge outward along the axial direction. The side walls 51 of the bottomed small-diameter containers 50a and 50b are not limited to a cylindrical shape, but may have a conical shape that gradually expands in diameter from the outer bottom surface 52 toward the upper end surface 54 surrounding the opening of the hollow portion, or may have a conical shape. The cross section perpendicular to the . is triangular or larger, and the entire shape may be a regular polygonal prism shape, a scalene polygonal prism shape, or a regular polygonal pyramid shape or a scalene polygonal pyramid shape.

Corresponding portions of the cavity mold 3 and the core insert 10 are also made to have a similar shape according to each form of the bottomed small-diameter containers 50a and 50b. The position of the gate G provided in the core insert 10 is not limited to the central portion of the inner bottom surface of the cavities 2a and 2b, and may be provided on the peripheral side. A coolant other than water may be circulated in the flow path 19 of the core insert 10 . The cross section of the recessed portion 38, which is a ring-shaped groove, along the axial direction of the pin 32 may be semicircular, rectangular, trapezoidal with the longer side on the outer peripheral surface side, or triangular. The concave portion may have a form in which a plurality of spiral grooves are arranged in opposite directions so as to intersect with each other. Air cylinder 40 may be a hydraulic cylinder or a hydraulic cylinder.

The injection molding apparatus of the present invention can also be applied to resin products in which molten resin can only be injected by a cold runner method in which the mold on the insert side is of a split type due to the mold structure.

According to the present invention, it is possible to reliably provide an injection molding apparatus that omits the post-process of removing gate traces from a small-diameter container with a bottom or a small-diameter lid, and that can perform injection molding on materials with good work efficiency.

1a to 1c injection molding apparatus 2a, 2b cavity 3 cavity mold 4 outer peripheral surface 5 outer bottom surface 6 mold opening surface 7 stripper plates 7a, 7b through hole 8 stripper ring 8a contact surface 9 piston rod 10 core insert 11 tapered tip Radial portion 12 Bending portion 13 Base side large diameter portion 14a to 14c Runner sprue 14d Straight portion 15 Recessed portion 16 Core plate 17 Manifold plate 18 Space 19 Channel (cooling water channel: cooling means)
20 Nozzle 21 Nozzle main body 22 Tip part 23 Tip hole 24 Flow path (flow path of molten resin)
25 band heater (heating means)
26 Flange 27 Manifold 28, 29 Flow path 30 Stem 31 Large diameter portion 32, 35, 36 Pin 33 Tip of pin 34 Tip of stem 37 Backflow groove 38, 39 Recess (undercut)
40 Air cylinder 41 Cylinder chamber 42 Piston 43 Piston rod 44 Manifold back plate 50a, 50b Small-diameter container with bottom 51 Side wall 52 Outer bottom surface 53 Inner bottom surface 54 Upper end surface 55, 56 Gate mark 60 Solidified resin 61 Part of solidified resin G Gate d multi-layered part

Claims (7)

An apparatus for injection molding a small-diameter container with a bottom or a small-diameter lid by a hot runner method,
a cavity mold surrounding an outer peripheral surface and an outer bottom surface of a cavity for molding the small-diameter container with a bottom or the small-diameter lid;
A tip side small diameter portion entering the inside surrounded by the cavity, a base side large diameter portion continuously provided on the base end side and enclosing a recess along the central axis, and a tip end side from the bottom surface of the recess a core insert having a runner sprue passing through along the axial direction and a cooling means;
a nozzle whose tip side is inserted into the recess of the core insert, has a flow path for molten resin along the central axis, and is equipped with a heating means;
a stem that advances and retreats along the axial direction of the flow path of the molten resin in the nozzle and whose tip portion can pass through a tip hole of the flow path of the molten resin;
a pin that is concentrically connected to the distal end of the stem and moves forward and backward in the runner sprue that penetrates the core insert along its axial direction;
an outward recess formed in the pin;
When the stem moves forward, the tip of the stem comes into surface contact with the inner wall surface of the runner sprue of the core insert, and the tip of the pin is positioned inside the runner sprue of the core insert. ing,
An injection molding apparatus characterized by: The runner sprue passing through the core insert and the pin have similar shapes to each other such that the diameters of the runner sprues and the pins are gradually or continuously reduced on the tip end side and the diameters are gradually or continuously increased on the base end side. present,
The injection molding apparatus according to claim 1. Between the base end face of the cavity mold and the base-side large-diameter portion of the core insert, a stripper ring whose inner peripheral surface abuts against the opening-side end face of the outer peripheral surface of the cavity is provided on the axis of the core insert. It is arranged so that it can advance and retreat along the direction,
3. The injection molding apparatus according to claim 1 or 2. A plurality of sets of the hot runner unit consisting of the cavity mold, the core insert, the nozzle, the stem, the pin, and the stripper ring are arranged side by side, and each set of the nozzles has a flow path for the molten resin. communicates with a single sprue bushing,
The injection molding apparatus according to claim 3. The outward concave portion formed in the pin has a single ring-shaped groove or a plurality of ring-shaped grooves formed along the axial direction, or at least one or a point-symmetrical position with respect to the central axis of the pin. multiple pieces are formed in
Injection molding apparatus according to any one of claims 1 to 4. The gate located at the tip of the runner sprue penetrating the core insert is open at the center or peripheral portion of the inner bottom surface of the cavity in the cavity mold,
Injection molding apparatus according to any one of claims 1 to 5. The stem has at least one reverse flow groove formed along the axial direction from the distal end toward the proximal end.
Injection molding apparatus according to any one of claims 1 to 6.

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