JP3131882B2 - Method and apparatus for injection molding a molded article having a tunnel gate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and an injection molding apparatus in which a spool connected to a tunnel gate and an injection-molded product are molded, and the spool and the injection-molded product are pressed by extrusion pins to release the mold. About.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional injection molding die. This injection molding die comprises a fixed die 1 and a movable die 2 which can be brought into and out of contact with the fixed die 1 by a drive source (not shown). In addition, a cavity 3 for molding the injection molded product W is formed between the fixed mold 1 and the movable mold 2. In addition, a conical spool space 4 whose diameter increases from the fixed mold 1 to the movable mold 2 is connected to the injection mold, and a large diameter portion of the spool space 4 and a peripheral edge of the cavity 3 in the movable mold 2 are connected. A conical tunnel gate space 5 is formed. An extruding plate 7 connected to the cylinder 6 and driven in the opening / closing direction of the movable die 2 is provided inside the movable die 2. A pin 8 and an extrusion pin 9 reaching the large diameter portion of the spool space 4 are implanted. Further, the fixed mold 1 is provided with a molten resin injection nozzle 10 detachably connected to the small diameter portion of the spool space 4.

In such an injection mold, when a molten resin is injected from an injection nozzle 10 in a state where the fixed mold 1 and the movable mold 2 are clamped, the molten resin flows into the cavity 3 via the spool space 4 and the tunnel gate space 5. The injection molding W is filled and molded. After the resin is cooled and solidified, as shown in FIG. 8, when the movable mold 2 is opened from the fixed mold 1 and the cylinder 6 is driven to extend, the extrusion pin 7 projects together with the extrusion plate 7 toward the fixed mold 1 and injection molding is performed. The product W is released from the movable mold 2. Spool S which is formed integrally with the injection-molded article W at this time is pushed to the large diameter portion to the ejector pin 9, the distal end of the tunnel gate S ₁ is to release is disconnected from the injection molded article W.

[0004]

In the above-mentioned conventional injection molding die, the spool S having the tunnel gate is pushed by the push pin 9 so that the opening 4 of the spool space 4 of the movable die 2 is formed.
When extruded from _1, because the tunnel gate S ₁ projecting from the spool S flared is caused to forcibly bent in the opening 4 _1, tunnel gate S ₁ the spool S is curved at the moment away from the movable mold 2 In some cases, the spool S returned to the original shape due to its own elasticity, and the spool S vigorously popped out of the movable mold 2 due to the reaction.

[0005] For this reason, even if a basket or the like is installed under the mold to receive the separated spool S,
Since the spool S may scatter in an indeterminate direction and do not fall into the basket, the scattered spool S
Had to be picked up manually.

The present invention has been made in view of the above circumstances, and has as its object to prevent scattering of a spool separated from a movable die of an injection molding die.

[0007]

In order to achieve the above object, the present invention provides a method for forming a tunnel by injecting molten resin from a spool space through a tunnel gate space into a cavity formed between a fixed mold and a movable mold. In the injection molding method of a molded product having a tunnel gate for molding a spool and an injection molded product connected by a gate and pressing each of the spool and the injection molded product with an extrusion pin to release the mold, an axial direction is applied to an end of the spool. A first method is to hold the spool at the tip of the push pin via a plurality of lock portions formed in the first portion and deform the lock portion by pulling the spool in the axial direction to separate the spool from the push pin. Features.

The present invention is also directed to forming an injection molded article with a spool connected by a tunnel gate by injecting a molten resin from a spool space through a tunnel gate space into a cavity formed between a fixed mold and a movable mold. In an injection molding apparatus for molded articles having a tunnel gate for releasing the mold by pressing the spool and the injection molded article with an extrusion pin, an engagement portion capable of holding the spool at a tip end of the extrusion pin for pushing the spool. Is a second feature.

Further, the present invention provides, in addition to the second feature described above,
A third feature is that the engaging portion comprises a plurality of notches formed axially symmetrically at the tip of the push pin, and the spool has a plurality of legs extending in the axial direction and locked in the notches. And

[0010] The present invention provides, in addition to the third feature described above,
A fourth feature is that a projection that engages with the groove is formed at the tip of the leg by connecting the groove to the notch, and the projection is an undercut portion.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

[0012] As shown in FIG.
It is used for injection molding using BS, PP or the like as a molding material, and includes a fixed mold 1, a movable mold 2, a cylinder 6, an extruded plate 7, an extruded pin 8, and an extruded pin 9 as in the conventional one. The shape of the push-out pin 9 for pressing the spool S is different from the conventional one.

[0013] That is, as apparent from FIGS. 4 and 5, with respect to the four notches 9 ₁ the center axis of the extrusion pin 9 at 90 ° intervals in the circumferential direction on the tip of the ejector pin 9 It is formed in a symmetrical groove 9 ₂ arc-shaped are formed respectively on the inner part of the notches 9 _1. Accordingly, the large diameter portion of the spool S has four legs S ₂ extending in the axial direction and having a semicircular cross section, and a protrusion which projects inward from the tip of the leg portion S ₂ and becomes an undercut portion when the mold is released. S ₃ is formed integrally. Note that two of the four legs S ₁ is provided in particular so as to face each other in a plane including the center axis and the tunnel gate S ₁ of the spool S. Further, the leg S ₂
Maximum radius r of the thickness t and the locking projection S _3, it it 1m of
m and about 1.5 mm are appropriate.

As shown in FIG. 2, a take-out unit 11 which can enter between a movable mold 2 and a fixed mold 1 which are opened by a robot (not shown) has cylinders 14 and 15 and its cylinder 1
4 and 15 are provided with clamp members 16 and 17 for clamping the injection molded product W from above and below. A pair of cylinders 19 and 20 supported by the take-out unit 11 via a U-shaped bracket 18 are provided with wedge-shaped clamp claws 21 and 22 for gripping a small diameter portion of the spool S.

Next, the operation of the above-described embodiment of the present invention will be described.

As shown in FIG. 1, a molten resin is injected from an injection nozzle 10 in a state where the fixed mold 1 and the movable mold 2 are clamped, and an injection molded product W is formed integrally with the spool S. Subsequently, after the movable mold 2 is opened from the fixed mold 1, the extrusion pin 8 is driven by the cylinder 6 as shown in FIG. 2 to release the injection molded article 8 from the movable mold 2. At this time, the pair of upper and lower clamp members 16 and 17 of the take-out unit 11 that has entered between the fixed mold 1 and the movable mold 2 approach each other by the cylinders 14 and 15, and clamp the injection molded product W from above and below.

On the other hand, the spool S pressed by the push pin 9 driven together with the push pin 8 is automatically cut from the injection molded product W at the tip of the tunnel gate S _{1 and} released from the movable mold 2. I do. At this time, it engages the legs S ₂ of the four spool S is the tip of the ejector pin 9, moreover increases the holding force of the spool S projections S ₃ of the leading end of the leg portion S ₂ becomes an undercut portion Therefore, even when a load is applied when the tunnel gate S ₁ passes through the opening of the movable mold 2, the spool S is released while being held at the tip of the push pin 9.

Subsequently, the small diameter portion of the spool S is clamped by driving the pair of cylinders 19 and 20 of the take-out unit 11. At this time, the four legs S of the spool S
_{Since 2} is arranged axially symmetrically, it has a large resistance to lateral force, and the spool S held by the push-out pin 9 is at a fixed position and is reliably gripped by the take-out unit 11. Next, as shown in FIG. 3, the take-out unit 11 is moved in the direction of arrow A to separate the spool S from the push-out pin 9. At this time, even if the spool S is firmly supported by the extrusion pins 9 as described above, if the injection molded product W is formed of a hard resin such as ABS, the leg is actuated by the action of the undercut portion. since the base of a portion of the part S ₂ is broken and deformed, it is possible to easily separate the spool S from the extrusion pin 9. When the injection-molded product W is formed of a soft resin such as PP, the portion a is elastically deformed outward, so that the spool S can be easily separated from the extrusion pin 9. Thus, without being influenced by the shape and molding conditions of a tunnel gate S _1, it can be reliably collected without scattering the spool S.

Thus, the injection molded product W and the spool S clamped by the take-out unit 11 are carried out from between the fixed mold 1 and the movable mold 2 and are respectively discharged to separate places.

FIG. 6 shows a second embodiment of the present invention.
This embodiment is characterized in that projecting from normal loosely tapered truncated cone-shaped projection 9 ₃ than draft to the tip of the ejector pin 9.

According to this embodiment, the protrusion 9 of the push pin 9 is
₃ and the recess S _{4 of the} spool S are engaged with each other, so that the spool S and the push pin 9 are integrated (this is referred to as spool lockability). Is prevented from falling off. The spool S is separated from the push-out pin 9 by being pulled in the axial direction by the take-out unit 11 as in the previous embodiment. However, if the spool lock property is excessive, it becomes difficult to separate the spool S. The spool-locking is affected by molding conditions in addition to the projection 9 ₃ tapered, for example, the type of the molding early low spool-locking becomes large easily.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, and various small designs may be made without departing from the present invention described in the appended claims. It is possible to make changes.

[0023] For example, the shape of the tip of the ejector pin 9 is not limited to the first and second embodiments, the spool S withstood load when the tunnel gate S ₁ passes through the opening of the movable die 2 Any shape can be selected as long as it can be held at the tip of the extrusion pin 9. That change the number and angle of inclination of the notches 9 _1, it is possible to change the shape of the groove 9 ₂ a triangle or a quadrangle other than the arc.

[0024]

As described above, according to the first aspect of the present invention, when a spool having a tunnel gate integrally formed therein is pressed by an extrusion pin and released from the mold, the spool is fixed to the extrusion pin by a locking portion. It is prevented from falling while being held by the tip. Therefore, by pulling the spool in the axial direction and separating from the extrusion pin, the spool can be collected without being scattered on the floor surface.

According to the second feature of the present invention, when the spool having the tunnel gate integrally formed thereon is pressed by the push pin to release the mold, the spool is held by the engaging portion formed at the tip of the push pin. Being prevented from falling. As a result, the spool is not scattered on the floor surface, and can be easily and reliably collected. In addition, the present invention can be implemented by a simple design change in which only the engaging portion is formed at the tip of the extrusion pin of the conventional injection molding apparatus.

According to a third aspect of the present invention, since the spool has a plurality of legs extending in the axial direction thereof and locked in the notches of the push pin, the resistance of the spool to the lateral pressing force is provided. In addition to being able to more effectively prevent the spool from falling off when the mold is released due to the increase in force, the spool can be held in a fixed posture with respect to the extrusion pin, so that the spool is separated from the extrusion pin. Can be easily performed.

According to the fourth aspect of the present invention, the projection formed at the tip of the leg serves as an undercut portion to increase the holding force of the spool, and the projection is formed by pulling the spool in the axial direction. The leg portion can be deformed by the action of and can be easily separated from the extrusion pin.

[Brief description of the drawings]

FIG. 1 is a sectional view of an injection molding apparatus according to a first embodiment.

FIG. 2 is a diagram showing a state of an injection molded product and a spool at the time of mold release.

FIG. 3 is a diagram showing a state when a spool is removed.

FIG. 4 is an enlarged side view of an extrusion pin and a spool.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is a sectional view of an injection molding apparatus according to a second embodiment.

FIG. 7 is a sectional view of a conventional injection mold.

FIG. 8 is a view showing a state at the time of mold release of a conventional injection molded product and a spool.

[Explanation of symbols]

1 ··· fixed type 2 ··· movable type 3 ··· cavity 4 ··· spool space 5 ··· tunnel gate space 8 ··· extrusion pin 9 ··· extrusion pin 9 ₁ ... notch (engaging part) 9 ₂ ... groove (engaging part) 9 ₃ ... projection (engaging part) S ... spool S ₁ ... tunnel gate S ₂ ...・ Leg part (locking part) S ₃・ ・ ・ Projection (locking part) W ・ ・ ・ ・ Injection molded product

Claims (4)

(57) [Claims] A tunnel gate is formed by injecting molten resin from a spool space (4) through a tunnel gate space (5) into a cavity (3) formed between a fixed mold (1) and a movable mold (2). The spool (S) and the injection molded product (W) connected in (S ₁ ) are formed, and the spool (S) and the injection molded product (W) are pressed by the extrusion pins (8, 9) to release the mold. In the injection molding method for a molded article having a tunnel gate to be made, the spool (S) is pushed out through an end portion of the spool (S) through a plurality of locking portions (S ₂ , S ₃ ) formed in the axial direction. (9), and the spool (S) is pulled in the axial direction to thereby stop the locking portion (S).
_2, S ₃₎ is deformed, characterized in that to separate from the extrusion pin (9), injection molding method of a molded article having a tunnel gate. 2. A tunnel gate is formed by injecting molten resin from a spool space (4) through a tunnel gate space (5) into a cavity (3) formed between a fixed mold (1) and a movable mold (2). The spool (S) and the injection molded product (W) connected in (S ₁ ) are formed, and the spool (S) and the injection molded product (W) are pressed by the extrusion pins (8, 9) to release the mold. in the injection molding apparatus of the molded article having a tunnel gate to the tip end portion of the spool (S) extrusion presses the pin (9), engaging portions capable of holding the spool (S) (9 _1, 9 _2, 9 ₃ ) An injection molding apparatus for a molded article having a tunnel gate, wherein the injection molding apparatus is formed. 3. The engaging portion is axially symmetric with the tip of the push pin (9).
Notches (9₁) Consisting of a spool
(S) extends in the axial direction of the notch (9). ₁) Lock
Legs (S_Two),
Injection of a molded article having the tunnel gate according to claim 2.
Shaped device. 4. The notch (9)₁) In the groove (9_Two)
The legs (S _Two) At the end of the groove (9)_Two) Engage
Projection (S_Three), And the protrusions (S_Three) And under
4. The torch according to claim 3, wherein the cut-out portion is formed.
Injection molding equipment for molded products having a tunnel gate.