JPH0716887A - Inmold gate-out method, mold and apparatus in injection molding - Google Patents

Abstract

PURPOSE:To provide an inmold gate-cut method capable of performing an inmold gate-cut even in gate molded items having a thin wall gate being in parallel with a PL face by employing a resin returning method through a pressure pin as a method contrary to employing of a resin pushing in method through a pressure pin. CONSTITUTION:The stationary part 20 has a sprue-bush 23 that can comes in and out at a stroke L, e.g. of the order of 1-2mm with respect to a stationary side retainer platen 22. The sprue-bush is capable of coming in and out by means of bolts 24 as a guide that are inserted in its flange part 23a and screwed in a stationary side securing plate 21 in their tip ends. Thus, in the tip of the sprue-bush 23, an auxiliary space (expansion space) 25 can be defined in addition to the space of a runner 26 respect to a gate 27 in a side gate method, pressure pins 32a are faced, which can come in and out in the thickness direction. The tip end face of the pressure pins 32a is formed into an inclined lace (one side wedge face) A, and the slope line of the inclined face A is directed to the side of the runner 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-mold gate cutting method applicable to a gate method in which a gate is provided on a side surface of a molded product such as a side gate, a tab gate, a fan gate, and a film gate in an injection molding method. , A mold structure and an injection molding apparatus for realizing the same.

[0002]

2. Description of the Related Art Conventionally, in an in-mold gate cutting method in an injection molding method, a vibrating force having a large amplitude is applied to a pressure pin of a gate portion and a molten resin is pushed into a cavity before the gate portion is solidified. At the same time, the gate portion is separated. For example, in the submarine gate system, FIG.
As shown in (a), in the resin filling step, the molten resin injected from the sprue (not shown) of the fixed-side template 1 passes through the runner 2 and crosses the PL surface (divided surface) to the movable-side template 3 Pressing pin hole 5 passing through the conical hole 4 provided in
In the pressure-holding step, as shown in FIG. 5B, the pressurizing pin 5a is press-fitted in the direction indicated by the arrow (perpendicular to the PL plane). , The connecting portion of the pressure pin hole 5 and the conical hole 4 is shaved to separate the gate portion, and the residual resin in the hole 5 is pushed into the cavity 6 so that the flat surface of the tip of the pressure pin 5a is a mold of the molded product. Try to form part of the surface. 6a is a protruding pin.

[0003]

The in-mold gate cutting method using such a pressure pin is not limited to the above-mentioned submarine gate method, but is effective in the direction perpendicular to the PL surface such as overlap gates and disk gates. Although it is applicable to a gate system having a gate thickness, it is not applicable to a gate system having a thin gate oriented parallel to the PL surface such as a standard gate due to the following reasons.

For example, the thickness of the side gate is usually 30 to 40% of the thickness of the molded product, which is thin, so that the gate seal takes a short time. When the pressure pin is pressed in the thickness direction of the side gate, the inside of the resin cavity is The push pin tends to be incompletely cut, and the resin is wrapped around the pressure pin, resulting in poor finish on the pushing surface. Gate residue may remain.

Since the resin is not directly pushed into the cavity but is pushed in the thickness direction of the gate, a considerable reaction force is generated when the pressure pin is pushed, and the force applied to the pressure pin can be adjusted. difficult. Particularly, in the fan gate and film gate systems having a wide gate width, since the tip area of the pressurizing pin is wide, it is necessary to apply a considerably high pressure, which is difficult to set.

In view of the above problems, the first problem of the present invention is that, contrary to the method of pushing the resin by the pressure pin,
By adopting a resin return method using a pressure pin,
An object of the present invention is to provide an in-mold gate cutting method capable of performing in-mold gate cutting even with a gate-type molded product having a thin gate parallel to the PL surface. And the 2nd subject of this invention is providing the metal mold | die which can implement | achieve the in-mold gate cutting method suitably.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the means taken by the present invention is to shear the gate simultaneously with the process of returning the resin to the runner side in the step of extruding the extruding member in the thickness direction of the gate. It is characterized by having the process of doing it together. In such extrusion process,
Further, it is desirable to include a process of forming an escape reservoir for receiving the escape resin in the resin path upstream of the gate.

As a mold for realizing the above-described in-mold gate cut, the extruding member is capable of protruding in the thickness direction of the gate and has a one-sided wedge surface whose normal line faces the runner side at the tip. Is characterized by. Further, in such a mold, it is desirable to add a resin escape reservoir forming means that forms an expansion space in at least a part of the resin path upstream of the gate in synchronization with the pushing operation of the pushing member. As a concrete resin escape reservoir forming means, a sprue bush capable of projecting and retracting with respect to a fixed die with a predetermined stroke may be used, or a protruding pin that retracts from the runner in conjunction with the protruding operation of the pushing member. May be. Further, another resin escape reservoir forming means may be an escape pin that retracts along the side surface of the runner in conjunction with the pushing operation of the pushing member. In such a case, it is desirable to arrange the escape pin at the corner of the runner facing the gate.

[0009]

According to such in-mold gate cutting, the resin of the gate is not pushed into the cavity but is positively returned to the runner side and cut, so that the resin does not wrap around the extruding member. , Gate cutting is good. Therefore, it is possible to successfully perform in-mold gate cutting even for gate methods such as side gates, tab gates, fan gates, film gates, etc. that have thin gates on the side surfaces, which was not possible in the past. Labor saving can be achieved. In particular, when the process of forming the escape reservoir for receiving the escape resin is included, it is not necessary to increase the ejection force, and the ejection force can be easily set.

As a mold for realizing the in-mold gate cut having such an effect, it is sufficient to provide an extruding member having a one-sided wedge surface whose normal line faces the runner side at the tip. Therefore, most of the conventional structure of the mold can be used as it is without causing a large change. Also, if a sprue bush that can be retracted with a predetermined stroke is used as the resin escape reservoir forming means, it is only necessary to change the sprue bush mounting structure, so a low-cost mold is realized. it can. In such a case, a resin escape reservoir is formed on the tip side of the sprue bush,
When the distance from the gate to the resin escape reservoir is long, it is difficult to return the resin.

Therefore, in order to form a resin escape reservoir at a portion closer to the gate side, a push-out pin for withdrawing from the runner in association with the push-out operation of the push-out member may be provided.

In this case, the escape reservoir is formed on the opening side of the protruding pin hole. Further, it may be a relief pin that retracts along the side surface of the runner in conjunction with the pushing operation of the pushing member. Also in this case, the escape reservoir is formed on the opening side of the escape pin hole. It is sufficient if the relief pin is arranged along the side surface of the runner, but if the relief pin is arranged at the corner of the runner facing the gate, the fluidized bed inside the runner is formed at the corner. Since it hits the skin layer vertically, it is possible to sufficiently receive the return resin.

[0013]

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

[Embodiment 1] FIG. 1 is a vertical sectional view showing a mold according to Embodiment 1 of the present invention. This mold 10 has a fixed part 2
The fixed part 20 includes a fixed side mounting plate 21, a fixed side mold plate 22 attached to the fixed side mount plate 21, and a stroke L of about 1 to 2 mm with respect to the fixed side mold plate 22.
It has a sprue bush 23 that can appear and disappear. The sprue bush 23 can be inserted into and removed from the flange 23a of the sprue bush 23 by using a bolt 24 whose tip is screwed to the fixed side mounting plate 21 as a guide. Therefore, an auxiliary space (expansion space) 25 added to the space of the runner 26 can be formed at the tip of the sprue bush 23. On the other hand, the movable part 30 is
Fixed type mounting 31, pressure pin 32a and return pin 3
A pressure plate 32 having 2b and movable back and forth from a pressure rod 32c.
A receiving plate 33 having a spacer block, a protruding plate 34 having a protruding pin 34a and a sprue lock pin 34b and capable of moving forward and backward by a rod 34c, and a receiving plate 33
It has a movable side mold plate 35 attached to.

The mold 10 is a side gate type,
The runner 26 communicates with the cavity 28 via a thin gate 27. A pressure pin 32a that can move back and forth in the thickness direction faces the gate 27. The tip end surface of the pressure pin 32a is formed as a one-side inclined surface 8 (one-side wedge surface) A, and the normal line of the inclined surface A faces the runner 26 side.

In the mold having such a structure, when the nozzle 50 is brought into contact with the sprue bush 23 after the mold is clamped,
The nozzle touch pressure causes the sprue bush 23 to move forward by the stroke L, the auxiliary space 25 disappears, and the state shown in FIG. In this state, the molten resin is injected from the nozzle 50 with a predetermined injection pressure to the sprue 23a, the runner 26, and the side gate 2.
It is filled into the cavity 28 via 7. After this filling step, the nozzle 50 is retracted, and the sprue bush 23 can be separated from the runner 26. In this state, the pressure pin 32a is projected in the thickness direction of the gate 27 before the resin is solidified. This pressure pin 32a
By pushing out, the resin in the vicinity of the inclined surface A side is pushed back to the runner 26 side by the wedge action (power boosting action), and the gate portion is cut at the other surface (shear surface) B. The resin portion pushed back in this gate causes the runner 23a
The pressure in the sprue bush 23 increases momentarily.
Is retracted by the stroke L, and a resin escaped reservoir corresponding to the auxiliary space (expansion space) 25 is formed at the tip of the sprue bush 23.

Since the gate cut surface is on the shearing surface (non-wedge surface) B side of the pressing pin 32a, the resin is not pushed into the cavity 28 and the winding of the resin does not occur on the pressing pin. A good finish of the gate cut surface can be realized. Moreover, since the resin is returned to the runner 26 side by the wedge action, and at the same time, the recessed portion of the auxiliary space 25 corresponding to the volume of the resin pushed back by the inclined surface A is formed, the pressing pin 3 is formed.
It is difficult to apply a reaction force to 2a, and it is not necessary to increase the ejection force. Also, the shape of the pressure plate 32a and the sprue bush 2 are changed.
It is only necessary to change the mounting structure of 3, and it is possible to provide a low-cost mold.

[Embodiment 2] FIG. 3 is a longitudinal sectional view showing a main part of a mold according to Embodiment 2 of the present invention. Unlike the resin escape reservoir of the auxiliary space 25 formed at the tip of the sprue bush 23 of the first embodiment, the mold 60 of this embodiment allows the resin escape of the opening side space (expansion space) 45 of the protruding pin hole. It is used as a reservoir. That is, the pressure plate 32 of the mold 60 has the fixed pressure pin 32a and the protruding pin 34a that can move forward and backward, and the movable side mounting plate 3
1 has a lever member 46 in which one arm portion 46a abuts the bottom surface of the pressure plate 32 and the other arm portion 46b abuts the base end of the protruding pin 34a. In the resin filling step, as shown in FIG. 3, the tip end inclined surface A of the pressure pin 32a is at a position retracted from the gate 27, and the tip end surface C of the protrusion pin 34a is a part of the cavity 26 adjacent to the surface. Is formed. Pressure rod 34c before solidification of resin
When the pressure plate 32 is pushed out, the pressure plate 32 advances in the direction of the arrow in the figure, and accordingly, the pressure pin 32a is pushed out and the inclined surface thereof advances to the position A ', the gate 27 is cut, and the molten resin in the gate portion runs. It is pushed back to the 26 side. At this time, since the pressure plate 32 moves in the separating direction with respect to the arm portion 46a of the lever member 46, the lever member 46 is rotatable in the direction of the arrow in the figure. Therefore, when the molten resin is pushed back toward the runner 26 side, the return pressure pushes the tip end surface C of the protrusion pin 34a to move it to the retracted position C '. As a result, the opening side space 45 of the protruding pin hole is formed and serves as a resin escape reservoir.

The feedback type resin escape reservoir forming mechanism by the retraction of the ejecting pin 34a in conjunction with the forward movement of the pressure pin 32a generates a return pressure in synchronism with the cutting of the gate, so the timing is set. There are also benefits that can be automated. However, when the resin is filled, the protruding pin 34
Since a high resin pressure is applied to a, the protrusion pin 34a may be retracted and the pressure pin 32a may be advanced. This is because the simple lever member 46 is used as the mechanism for forming the resin escape reservoir.
This can be easily improved by adding a stopper mechanism or a lock mechanism that allows the lever member 46 to rotate when the forward movement of 2 is started.

[Embodiment 3] FIG. 4A is a vertical sectional view showing a mold according to Embodiment 3 of the present invention, and FIG. 4B is a plan view thereof. The mold 70 of this embodiment has a lever member 46 similar to that shown in FIG. 3, but instead of the ejector pin, an escape pin 44a having no ejecting function for the runner is provided. The escape pin 44a is capable of advancing and retracting with respect to the pressing plate 32, and the side surface on the tip end side is in contact with the thickness side surface of the runner 26. The portion where the side surface on the tip end side of the escape pin 44a contacts the runner 26 may be the broken line portions P _{1 to} P ₄ shown in FIG. 4B, but in this example, it is provided at the corner portion P facing the gate 27. is there. As described above, when the side surface on the tip end side of the escape pin 44a is in contact with the thickness side surface of the runner 26, the escape pin 4 is formed in the resin filling step.
The resin pressure is not applied in the axial direction of 4a, and the escape pin 44a does not retract before the forward movement of the pressure plate 32.

In this embodiment, since the side surface of the escape pin 44a on the tip side is located at the corner portion P, the amount of resin returned by the pressing by the pressure pin 32a is the escape portion formed by the retreat of the escape pin 44a. Accepted smoothly by 45. This is because the resin periphery of the runner 26 is a skin layer in a semi-solidified state, but its central part a fluidized bed, the side surface of the distal end side of the relief pin 44a is in the broken line position P ₁ to P _4, flow The return resin of the layer flows in the tangential direction (sliding direction) with respect to the semi-solidified skin layer, and the receptive force is poor, but if the side surface on the tip side of the escape pin 44a is at the corner P, the fluidized layer This is because the return resin abuts on the skin layer in the normal direction, so that the receptive force can be increased.
By thus providing the escape pin 44a exclusively, a resin escape reservoir forming mechanism can be configured by a simple synchronizing mechanism such as the lever member 46.

In the above embodiment, the tip of the pressing pin is a flat inclined surface A, but it may be a curved surface having a wedge action. Further, the inclination angle or the opening angle is set to an optimum value depending on the thickness of the gate, the resin pressure, the resin material and the like. Further, various pin shapes such as round pins and square pins can be adopted. Further, the escape reservoir may be formed near the gate of the runner, or may be the branch runner or the main runner. And the number may be plural. It can also be formed on the side of the sprue lock pin 34b.

[0023]

As described above, the present invention is characterized in that the resin of the gate is not pushed into the cavity but is positively returned to the runner side and cut. The pushing member is characterized in that it has a wedge surface on one side whose normal line faces the runner side. Therefore, the following effects are obtained.

No resin winding occurs on the extruding member, and gate cutting is good. Therefore, it is possible to perform in-mold gate cutting even in a gate method such as side gates, tab gates, fan gates, film gates, etc. that have thin gates on the side surface, which was not possible in the past, and it is a great labor saving. Can be achieved. In addition, it is possible to provide a low-cost mold because there are few modified parts of the mold structure.

In particular, when the process for forming the escape reservoir for receiving the escape resin is included, it is not necessary to increase the ejection force, smooth gate cutting can be performed, and the ejection force can be easily set.

When a sprue bush capable of appearing and retracting with respect to the fixed die at a predetermined stroke is adopted as the resin escape reservoir forming means, it is only necessary to change the attachment structure of the sprue bush, so that a low-cost die is used. realizable.

As the resin escape reservoir forming means, a resin escape reservoir is formed on the tip side of the sprue bush, but it tends to be difficult to return the resin when the distance from the gate to the resin escape reservoir is long. Therefore, in order to form the resin escape reservoir in a portion closer to the gate side, a protrusion pin that retracts from the runner in association with the protrusion operation of the pushing member may be provided. In such a case, an escape reservoir will be formed on the opening side of the protruding pin hole,
Since the distance from the gate is short, the resin return operation can be performed without any problems.

Further, it may be a relief pin that is retracted along the side surface of the runner in conjunction with the pushing operation of the pushing member. Also in this case, the escape reservoir is formed on the opening side of the escape pin hole. It is sufficient if the relief pin is arranged along the side surface of the runner, but if the relief pin is arranged at the corner of the runner facing the gate, the fluidized bed inside the runner is formed at the corner. Since it hits the skin layer vertically, it becomes possible to sufficiently receive the return resin.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a mold according to a first embodiment of the present invention.

FIG. 2A is a sectional view showing a filling step in the same embodiment, and FIG. 2B is a sectional view showing a step of in-mold gate cutting.

FIG. 3 is a vertical sectional view showing a mold according to a second embodiment of the present invention.

4A is a vertical cross-sectional view showing a mold according to a third embodiment of the present invention, and FIG. 4B is a plan view thereof.

5A is a cross-sectional view showing a filling step in a conventional submarine gate type mold, and FIG. 5B is a cross-sectional view showing a step of cutting the gate in the mold.

[Explanation of symbols]

 10, 60, 70 ... Mold 20 ... Fixed part 30 ... Movable part 21 ... Fixed side mounting plate 22 ... Fixed side mold plate 23 ... Sprue bush 23a ... Flange part 24 ... Tightening bolt 25 ... Auxiliary space (expansion space) 31 ... Fixed side mounting plate 32 ... Pressure plate 32a ... Pressure pin 32a ... Return pin 32 ... Pressure rod 33 ... Reception plate 34a ... Projecting pin 34b ... Sprulock pin 34c ... Projecting rod 26 ... Runner 28 ... Cavity 44a ... Escape pin 45 … Opening space (expansion space) 46… Lever member 50… Nozzle A… Inclined surface (wedge surface) L… Stroke P… Corner part

Claims (9)

[Claims] 1. An in-mold gate cutting method in injection molding, wherein an extruding member in a mold is projected from a gate before resin solidification after resin filling to separate a molded product from the gate,
An in-mold gate cutting method in injection molding, characterized in that the extruding member is extruded in the thickness direction of the gate and returned to the runner side on one side to release the resin while shearing the gate on the other side. 2. The in-mold gate cutting method for injection molding according to claim 1, wherein the escape reservoir should receive the escape resin in a resin path upstream of the gate in synchronization with the time when the pushing member is ejected. An in-mold gate cutting method, which comprises forming 3. A mold having an extruding member capable of extruding with respect to a gate in the die, wherein the extruding member is capable of extruding in the thickness direction of the gate and has a one-side wedge surface whose normal line faces the runner side at the tip. A mold characterized by having. 4. The mold according to claim 3, further comprising a resin escape reservoir forming means that forms an expansion space in at least a part of a resin path upstream of the gate in synchronization with a pushing operation of the pushing member. A mold characterized by having. 5. The mold according to claim 4, wherein the resin escape reservoir forming means is a sprue bush capable of appearing and retracting in a fixed stroke with respect to the fixed mold. 6. The mold according to claim 4, wherein the resin escape reservoir forming means is a protrusion pin that retracts from the runner in conjunction with a protrusion operation of the pushing member. . 7. The mold according to claim 4, wherein the resin escape reservoir forming means is an escape pin that retreats along a side surface of the runner in conjunction with a protrusion operation of the pushing member. And the mold. 8. The mold according to claim 7, wherein the escape pin is arranged in a corner portion of the runner facing the gate. 9. An injection molding apparatus comprising the mold defined in any one of claims 3 to 8.