JP2002036306A - Molding method and valve gate type mold device used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a molding defect by preventing generation of center deviation of a valve pin in the case of injecting a resin into a cavity for a product from a gate and to facilitate an alignment work of both a stationary mold side and a movable mold side at a time for manufacturing a mold. SOLUTION: A valve pin 34 is provided in a stationary mold 1 and a pressing pin 71 abutting on the valve pin 34 is provided in a movable mold 2. When the valve pin 34 is moved to the side of the movable mold 2, a gate 16 is opened and in the reverse case, when the pressing pin 71 pushes the valve pin 34 and the same is moved, the gate 16 is closed. A projecting part 37 is formed in the tip face of the valve pin 34 and a recess part 73 engaging with the projecting part 37 is formed in the tip face of the pressing pin 71.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method and a valve gate type mold apparatus used in the molding method, and more particularly to a molding method used for injection molding of a thermoplastic resin.

[0002]

In order to increase productivity in injection molding of a thermoplastic resin as a molding material, a valve gate type mold apparatus heats a resin in a material passage to a gate to a product cavity. In a hot runner type mold apparatus which always keeps a molten state, a gate is mechanically opened and closed by a gate opening and closing member such as a valve pin.

[0003] As this kind of valve gate type mold device,
For example, as described in Japanese Patent No. 2683949, a plunger as a gate opening / closing member that is provided in a fixed mold (fixed mold) and moves in the opening and closing directions of the fixed mold and the movable mold (moving mold) is a movable mold. There is known a configuration in which a gate is opened when moved to a side and closed when moved to an opposite side. The plunger is urged by a spring in a direction to close the gate, and is moved and opened by the pressure of the resin injected into the material passage. Further, the plunger is pushed by a hydraulically driven male cutter provided on the movable mold side to close the gate and to form a through hole of a disk as a product to be molded.

However, in the valve gate type mold apparatus described in the above publication, especially when the gate is opened, the tip of the plunger on the product cavity side merely abuts the tip of the male cutter in a plane. In addition, the plunger is liable to be tilted or misaligned due to the pressure of the resin or the like, and therefore, the flow of the resin from the gate to the product cavity is biased, so that there is a problem that molding failure is apt to occur.

Therefore, it is conceivable that when the gate is opened, a gate opening / closing member such as a plunger is fitted into a fitting hole formed in a movable mold. However, in this case, unless the gate opening / closing member on the fixed mold side and the fitting hole are accurately aligned in advance, the gate opening / closing member does not securely fit into the fitting hole, resulting in malfunction or a gate failure. There is a problem that a gap is formed between the opening / closing member and the fitting hole, and burrs are generated in a molded product. However, since the fixed mold and the movable mold are mutually opened and closed and are separately assembled, it is easy to accurately align the gate opening / closing member on the fixed mold with the fitting hole on the movable mold. Not that.

The present invention is intended to solve such a problem. When a molding material is injected into a product cavity from an opened gate, misalignment of a gate opening / closing member can be prevented, and molding defects can be prevented. It is an object of the present invention to provide a molding method capable of preventing the occurrence of the problem and a valve gate type mold apparatus used in the method. It is another object of the present invention to facilitate the centering operation in mold production.

[0007]

According to a first aspect of the present invention, in order to achieve the above object, a plurality of molds that can be opened and closed with each other are closed, and a product cavity is formed between these molds. In a molding method, a thermoplastic molding material in a material passage provided in a mold body is heated and constantly kept in a molten state, while a gate from the material passage to the product cavity is opened and closed by a gate opening and closing member. As a member, a first gate opening / closing member provided on a mold having the material passage, and a second gate provided on the mold facing the mold having the material passage and abutting on the first gate opening / closing member Opening and closing the mold by closing the mold, moving the first gate opening and closing member toward the second gate opening and closing member, and opening the gate to form a molding material from the gate into the product cavity. After the molding material is filled in the product cavity, the first gate opening / closing member is pushed and moved by the second gate opening / closing member to close the gate, and in the mold closed state, The projection provided on one of the contact surfaces of the first gate opening / closing member and the second gate opening / closing member and the recess provided on the other are fitted to each other.

In this manner, in the mold closed state, the protrusions and recesses of the contact surfaces of the first gate opening and closing member and the second gate opening and closing member provided on the molds that open and close to each other are fitted to each other. With this, even when the gate is open,
The inclination and misalignment of the gate opening / closing member due to the pressure of the molding material and the like are prevented.

According to a second aspect of the present invention, in the molding method of the first aspect, one of the first gate opening and closing member and the second gate opening and closing member is connected to the other gate opening and closing member. The convex portion and the concave portion are fitted in a fitting hole formed in the provided mold so as to be able to be inserted and removed so that the one gate opening / closing member fits in the fitting hole when the mold is closed. Are fitted to each other.

Thus, if only the alignment of the first gate opening / closing member and the second gate opening / closing member is reliably performed in manufacturing the mold, the alignment of the gate opening / closing member and the fitting hole is also reliably performed. be able to.

According to a third aspect of the present invention, there is provided a valve gate type mold apparatus used in the molding method according to the first aspect, wherein the first and second molds are opened and closed to form a product cavity therebetween when the mold is closed.
And a second mold, wherein the first mold has a gate for opening a material passage located inside the first mold to the product cavity, and a thermoplastic resin in the material passage. A heating means for keeping the molding material in a molten state at all times, and a movable first gate opening / closing member, wherein the second mold body has a movable second gate which is in contact with the first gate opening / closing member. These gate opening / closing members open the gate when the first gate opening / closing member moves to the second gate opening / closing member, and conversely, the second gate opening / closing member moves to the first gate opening / closing member.
When the gate opening / closing member is pushed and moved, the gate is closed, and a projection is provided on one of the contact surfaces of the first gate opening / closing member and the second gate opening / closing member, and the projection is provided on the other side. A concave portion is provided so as to be removably fitted.

The molding method according to the first aspect of the present invention can be performed by the valve gate type mold apparatus.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a molding method of the present invention and a valve gate type mold apparatus used in the method will be described with reference to FIGS. First, the configuration of the mold apparatus will be described. 1 is a fixed type which is a first type body,
Reference numeral 2 denotes a movable mold as a second mold body. The fixed mold 1 and the movable mold 2 facing each other move in the vertical direction (mold opening / closing direction) shown in FIGS. Sometimes a product cavity 3 is formed between each other.

The fixed die 1 includes a fixed-side mounting plate 11 mounted on a fixed-side platen of an injection molding machine, and a frame-shaped fixed-side die plate fixed to a surface of the fixed-side mounting plate 11 on the movable mold 2 side. 12 and a cavity block fitted inside the fixed-side mold plate 12 and fixed to the fixed-side mounting plate 11.
13 and has.

The fixed side mounting plate 11 and the cavity block 13 are formed with through holes 14 and 15 which are connected to each other. And the cavity block
The distal end of the through hole 14 of the movable mold 2 on the side of the through hole 14 is a disk-shaped gate 16 opening to the product cavity 3. Further, on the surface of the fixed-side mounting plate 11 opposite to the fixed-side mold plate 12, a locate ring 17 surrounding the through hole 14 is provided.
Has been fixed.

A sprue bush 21 is incorporated in the through holes 14 and 15. This sprue bush 21
The flange 22 formed at the end opposite to the movable mold 2 is fixed by being sandwiched between the fixed-side mounting plate 11 and the locate ring 17, and the outer periphery of the distal end of the movable mold 2 is Is fixed to the inner peripheral surface of the through hole 15 and supported. The sprue bush 21 includes a first bush member 24 and a second bush member 25 joined to each other in the axial direction, that is, the mold opening and closing direction. In addition, a cylindrical sprue bush
The sprue insert 26 is built in the inside 21. The sprue insert 26 includes a first insert member 27 and a second insert member 28 joined to each other in the mold opening / closing direction in the same manner as the sprue bush 21, but these insert members 27, 28 are provided. The flange 29 formed at the joint is formed by the two bush members 24,
25, they are fixed to each other and fixed to the sprue bush 21. The sprue 31, which is a material passage, is formed by a gap between the inner peripheral surface of the sprue bush 21 and the outer peripheral surface of the sprue insert 26. In the flange 29 of the insert members 27, 28, The plurality of through holes 32 formed in the flange portion 29 form a part of the sprue 31. The sprue 31 communicates with the product cavity 3 through the gate 16.
The tip portion 31a on the side of the gate 16 has a cylindrical shape having the same diameter as the gate 16, and is coaxially located with the gate 16.

Further, the inside of the sprue insert 26 has a hollow portion 33, and the sprue insert 26
A valve pin 34 as a first gate opening / closing member is slidably penetrated through the end on the side of the gate 16. The valve pin 34 moves in the mold opening / closing direction to open and close the gate 16, and has a flange-shaped valve portion 35 at an end on the gate 16 side. The valve portion 35 is fitted into the gate 16 or the tip of the sprue 31 on the gate 16 side so as to be freely inserted and removed. The movable mold 2 in the valve section 35
The other surface is a tapered guide surface 36 inclined with respect to the mold opening / closing direction. The inclination direction is a direction from the sprue 31 side to the product cavity 3 side.
Further, a substantially cylindrical guiding convex portion 37 is formed in the center of the distal end surface of the valve portion 35 on the movable mold 2 side. The tip of the projection 37 is a frusto-conical taper 38. Further, the valve pin 34 has a spring receiver 41 fixed to an end opposite to the movable mold 2 and the hollow portion 41.
The spring 33 is urged to the side opposite to the movable mold 2 by a spring 42 as an urging means mounted between the movable mold 2 and the end face on the movable mold 2 side.

Further, a band heater 43 as a heating means is provided on the outer peripheral surface of the sprue bush 21, and a cylindrical heater cover 44 for covering the band heater 43 from the outer peripheral side is provided. By the heating of the band heater 43, the thermoplastic resin as a thermoplastic molding material in the sprue 31 is always kept in a molten state.

The movable die 2 has a frame-shaped movable mounting plate 51 mounted on a movable platen of an injection molding machine, and a frame-shaped second mounting plate 51 fixed to a surface of the movable die mounting plate 51 on the fixed mold 1 side. A first movable-side receiving plate 52, a second movable-side receiving plate 53 fixed to the surface of the first movable-side receiving plate 52 on the fixed mold 1 side, and a fixing at the second movable-side receiving plate 53. A frame-shaped third movable-side receiving plate 54 fixed to the surface of the mold 1 side
And a frame-shaped movable-side mold plate 55 fixed to a surface of the third movable-side receiving plate 54 on the fixed mold 1 side. The movable mold plate 55 abuts against the fixed mold plate 12 when the mold is closed.

A frame-shaped first core block 61 is fixed inside the third movable-side receiving plate 54, and a frame-shaped second core block 61 is mounted inside the movable-side mold plate 55. 62 is fixed. Further, inside the second movable-side receiving plate 53, a movable core block 63 is provided with the first movable-side receiving plate 52 and the first movable-side receiving plate 52.
The core block 61 is provided so as to be movable in a predetermined range in the mold opening and closing direction. The movable core block 63 has a cavity forming convex portion 64 protruding toward the fixed mold 1 side.
The cavity forming protrusion 64 is formed by the first core block 6.
1 slidably penetrates through the inside of the first core block 62, and the front end projects into the product cavity 3 formed inside the second core block 62. That is, the cavity forming protrusion 64
Forms part of the wall surface of the product cavity 3. It should be noted that a slide bearing 65 is provided between the inner peripheral surface of the first core block 61 and the outer peripheral surface of the cavity forming projection 64. A relay plate 66 is provided on a surface of the movable die mounting plate 51 opposite to the fixed die 1 so as to be movable in the die opening and closing direction. A connecting pin 67 fixed to the relay plate 66 slidably passes through the first movable side receiving plate 52 and the second movable side receiving plate 53 and is fixed to the movable core block 63. . A slide bearing 68 is provided between the connecting pin 67 and the first movable-side receiving plate 52 and the second movable-side receiving plate 53.

The movable core block 63 has a second
A cylindrical pressing pin 71 as a gate opening / closing member is supported by a slide bearing 72 so as to be movable in the mold opening / closing direction. The pressing pin 71 protrudes into the product cavity 3 and coaxially contacts the valve pin 34 on the fixed mold 1 side. In addition, a cylindrical pressing pin 71
Has the same diameter as the disc-shaped valve portion 35 of the valve pin 34 so that the gate 16 and the sprue 31 as the fitting holes of the fixed mold 1 can be removably fitted into the tip of the sprue 31 on the gate 16 side. It has become. Further, a guide concave portion 73 into which the convex portion 37 of the valve portion 35 is fitted when the mold is closed is formed on the distal end surface of the pressing pin 71 which comes into contact with the distal end surface of the valve portion 35. On the other hand, the end of the pressing pin 71 opposite to the fixed die 1 forms a piston 74 and is located in the first movable-side receiving plate 52. Hydraulic cylinder consisting of 75
Is configured.

Further, inside the movable side mounting plate 51, a projecting plate 81 is formed on the inner peripheral side of the movable side mounting plate 51 and a receiving surface 82 facing the first movable side receiving plate 52 side and a first surface. The movable side receiving plate 52 is provided so as to be movable in the mold opening and closing direction. 83 is a guide bolt for slidably guiding the projecting plate 81. The projecting plate 81 is wound around the guide bolt 83 and is connected to the third movable-side receiving plate 54 and the projecting plate.
81 is urged to the opposite side to the fixed mold 1 by a return spring 84 mounted between the fixed mold 1 and the fixed mold 1. The protruding plate 81
, Also comes into contact with the relay plate 66 from the fixed mold 1 side. And the protruding plate 81 has a protruding pin 85
Has been fixed. The protruding pin 85 slidably penetrates through the first movable-side receiving plate 52 and the movable core block 63, and a tip thereof is located facing the product cavity 3.

Next, a molding method using the valve gate type mold apparatus will be described. When the fixed mold 1 and the movable mold 2 are opened, as shown in FIG.
The valve pin 34 has been moved to the opposite side to the movable mold 2 by the force of (2), and is fitted to the tip 31a of the sprue 31 on the gate 16 side to close the tip 31a. Therefore, the molten thermoplastic resin as the molding material does not leak from the sprue 31.

Then, the fixed mold 1 and the movable mold 2 are closed. With this mold closing, the convex part of the valve pin 34 on the fixed mold 1 side
37 fits into the concave portion 73 of the pressing pin 71 on the movable mold 2 side, and the tip of the pressing pin 71 fits in the gate 16 of the fixed mold 1 and further in the tip 31a of the sprue 31, and the valve pin 34
Hit.

When the melted resin is injected into the sprue 31 from the nozzle of the injection molding machine (not shown) in the state where the mold is closed, the pressure of the resin is increased to the valve portion 35 of the valve pin 34.
, The pressure of the resin exceeds the force of the spring 42, and the valve pin 34 moves to the movable mold 2 side, that is, the pressing pin 71 side, as shown in FIG. In this state, the valve portion 35 of the valve pin 34 comes out of the gate 16 and is located in the product cavity 3, and the gate 16 is opened. As a result, the resin flows from the sprue 31 through the gate 16 to the product cavity 3.
Injected into.

After the resin is filled in the product cavity 3, the pressing pin 71 is moved toward the fixed mold 1 by driving the fluid pressure cylinder 75 as shown in FIG. Press pin 71
By pushing the valve pin 34, the valve pin 34 also moves. Then, as described above, the valve portion 35 of the valve pin 34
Fits into the tip 31a of the sprue 31 and closes it, and the tip of the pressing pin 71 is the tip of the gate 16 and the tip of the sprue 31.
The gate 16 is closed by fitting into the inside 31a.

Further, when a pressing rod (not shown) provided in the injection molding machine presses the relay plate 66, the movable core block 63 moves to the fixed mold 1 side, and the resin in the product cavity 3 is compressed.

Further, after the resin in the product cavity 3, that is, the product is cooled and solidified, the fixed mold 1 and the movable mold 2 are opened. With the opening of the mold, the molded product is separated from the fixed mold 1 first. Then, when a projecting rod (not shown) provided on the injection molding machine pushes the projecting plate 81, the projecting pin 85 moves to the fixed mold 1 side to release the product from the movable mold 2. Furthermore, after the product is taken out,
The fixed mold 1 and the movable mold 2 are closed again, and the above molding cycle is repeated. And throughout the molding cycle,
The resin in the sprue 31 is always kept in a molten state by the heating of the heater 43.

According to the configuration of the above embodiment, when the mold is closed,
Since the convex portion 37 provided on the distal end surface of the valve pin 34 on the fixed die 1 side is fitted into the concave portion 73 on the distal end surface of the pressing pin 71 on the movable die 2 side, the product cavity 3 is opened from the opened gate 16.
When the resin is injected into the inside, it is possible to prevent the valve pin 34 and the pressing pin 71 from being inclined or misaligned against the pressure of the resin. Therefore, the inflow of the resin from the gate 16 to the product cavity 3 can be made uniform over the entire circumference.
Molding defects can be prevented.

The surface of the valve portion 35 of the valve pin 34 opposite to the movable mold 2 is moved from the sprue 31 side to the product cavity 3.
Since the tapered guide surface 36 is inclined in the direction toward the side, the resin can be smoothly guided from the gate 16 to the product cavity 3, and therefore, better molding can be performed.

Further, when the gate 16 is closed in the mold closed state, the pressing pin 71 on the movable mold 2 side
Since the push pin 71 is fitted into the tip end portion 31a of the sprue 16 and the sprue 31, it is possible to reliably prevent the pressing pin 71 from being inclined or misaligned by the pressure of the resin in this state. Therefore, the pressing pin
With 71, the accuracy of the hole formed in the center of the product can be improved.

Next, a second embodiment of the present invention will be described with reference to FIGS. Reference numeral 101 denotes a fixed mold that is a first mold body, and 102 denotes a movable mold that is a second mold body. The opposed fixed mold 102 and movable mold 102 move in the vertical direction (mold opening and closing direction) in the figure. They are opened and closed with each other, and form a product cavity 103 therebetween when the mold is closed.

As in the first embodiment, the fixed mold 101 is embedded and fixed in a fixed mold plate (not shown) to form the cavity block 1 forming the product cavity 103.
11, a sprue bush 113 having a sprue 112 therein as a material passage, a band heater 114 as a heating means provided on an outer peripheral side of the sprue bush 113, a heater cover 115, a fixing ring 116, and the like. However, in the second embodiment, the sprue bush 113 is incorporated in the gate bush 117 embedded and fixed in the cavity block 111, and the gate 118 for opening the sprue 112 to the product cavity 113 is the gate bush 11
7 is formed. Further, a stamper retainer 119 is provided between the cavity block 111 and the gate bush 117.

A valve pin 121 as a first gate opening / closing member is provided in the sprue 112 of the fixed mold 111 so as to be movable in the mold opening / closing direction. This valve pin
The valve 121 has a configuration similar to that of the valve pin 34 of the first embodiment, and has a disk flange-shaped valve unit 122 at the distal end on the movable mold 102 side. The valve portion 122 is inserted into and detached from the gate 118 having the same shape to open and close the gate 118. The surface of the valve portion 122 opposite to the movable mold 102 is formed as a smoothly curved tapered guide surface 123 inclined from the sprue 112 side to the product cavity 103 side. A substantially cylindrical guiding convex portion 124 is formed at the center of the distal end surface of the valve portion 122 on the movable mold 102 side. The tip of the convex portion 124 is a frusto-conical tapered portion 125.

The movable mold 102 is embedded and fixed in a movable mold plate (not shown), and is fixed to the product cavity.
Core block 131 forming 103, this core block 131
Air blow bush 132 embedded and fixed in
A protruding sleeve 133 slidably fitted in the air opening / closing direction in the air blowing bush 132, and a second gate opening / closing member slidably fitted in the protruding sleeve 133 in the mold opening / closing direction. Cylindrical pressing pin
136 and so on. This pressing pin 136 protrudes into the product cavity 103, and is a valve pin on the fixed mold 101 side.
It coaxially abuts 121. Further, the cylindrical pressing pin 136 is provided with the disc-shaped valve portion 122 of the valve pin 121.
And the same diameter. Further, a guide concave portion 137 into which the convex portion 124 of the valve portion 122 is removably fitted when the mold is closed is formed on the distal end surface of the pressing pin 136 which comes into contact with the distal end surface of the valve portion 122. In addition, 134 is the air blowing bush 1
This is a slide bearing provided between 32 and the protrusion sleeve 133.

Further, the gate 118 is opened when the valve pin 121 moves to the movable mold 102 side. At this time, the valve portion 122 of the valve pin 121 is moved inside the protruding sleeve 133 on the movable mold 102 side. It is adapted to be removably fitted into the fitting hole 133a. The valve pin 121
The fitting length of the convex portion 124 and the concave portion 137 of the pressing pin 136 is such that the convex portion 124 and the concave portion 137 fit before the valve portion 122 of the valve pin 121 fits into the fitting hole 133a with the closing of the mold. Is set to

Next, the molding method will be described. When the fixed mold 101 and the movable mold 102 are opened, as shown in FIG. 5, the valve pin 121 is moved to the opposite side to the movable mold 102, and is fitted to the gate 118 to close the gate 118. are doing. Therefore, the molten thermoplastic resin as the molding material does not leak from the sprue 112.

Then, the fixed mold 101 and the movable mold 102 are closed. With the closing of the mold, the convex portion 124 of the valve pin 121 of the fixed mold 102 is fitted into the concave portion 137 of the pressing pin 136 of the movable mold 102,
Further, the distal end surface of the pressing pin 136 comes into contact with the distal end surface of the valve pin 121.

With the mold closed in this way, as shown in FIG.
The resin is moved to the sixth side to open the gate 118, and the molten resin is injected into the sprue 112 from a nozzle of an injection molding machine (not shown). Then, resin is injected into the product cavity 103 from the sprue 112 through the gate 118.
In this state, when the gate 118 is open, the valve portion 122 of the valve pin 121 moves beyond the product cavity 103,
The movable die 102 is fitted into the fitting hole 133a.

After the resin is filled into the product cavity 103, the pressing pin 136 is moved to the fixed mold 101 as shown in FIG. When the pressing pin 136 pushes the valve pin 121, the valve pin 121 also moves. Then, as described above, the valve portion 122 of the valve pin 121 is fitted into the gate 118 to close the gate 118.

Further, after the resin in the product cavity 103, that is, the product is cooled and solidified, the fixed mold 101 and the movable mold 102 are cooled.
And open the mold. With the opening of the mold, the molded product is separated from the fixed mold 101 first. Next, the protruding sleeve 133 and the like move toward the fixed mold 101 to release the product from the movable mold 102. After the product is removed, the fixed
The mold is closed with the movable mold 102, and the above molding cycle is repeated. Then, throughout the entire molding cycle, sprue 11
The resin in 2 is always kept in a molten state by the heating of the heater 114.

According to the configuration of the above embodiment, when the mold is closed,
Convex part 124 provided on the end face of valve pin 121 on fixed mold 101 side
Into the recess 137 on the distal end surface of the pressing pin 136 on the movable die 102 side, and with the gate 118 opened, the valve portion 122 of the valve pin 121 fits the projecting sleeve 133 on the movable die 102 side. The resin is fitted into the hole 133a, so that when the resin is injected into the product cavity 103 from the opened gate 118, the valve pin is pressed against the pressure of the resin.
It is possible to reliably prevent the tilt and misalignment of the 121 from occurring.
Therefore, the flow of the resin from the gate 118 to the product cavity 103 can be made uniform over the entire circumference, and molding defects can be prevented.

Further, the surface of the valve portion 122 of the valve pin 121 opposite to the movable mold 102 is formed as a guide surface 123 which is smoothly curved and inclined in a direction from the sprue 112 side toward the product cavity 103 side. The resin can be smoothly guided to the product cavity 103, and therefore, better molding can be performed.

As described above, since the valve pins 121 on the fixed mold 101 side are removably fitted into the protruding sleeves 133 on the movable mold 102 side, these valve pins 121 are provided.
If the protruding sleeve 133 is not accurately aligned with the protruding sleeve 133, a gap may be formed between the valve pin 121 and the protruding sleeve 133, and burrs may be formed on the molded product. In order to increase the centering accuracy between the valve pin 121 and the protruding sleeve 133, in terms of mold production, on the fixed mold 101 side, the fixed mold plate, the cavity block 111, the gate bush 117, the valve pin 121, etc., and the movable mold 102 On the side, movable side mold plate, core block 131, bush 13
2. When assembling the members from the outside to the inside with the protruding sleeve 133 and the like, it is necessary to sequentially increase the accuracy by using shrink fitting or the like, but this is a troublesome operation. On the other hand, according to the configuration of the second embodiment, since the convex portion 124 and the concave portion 137 for guiding are respectively formed on the distal end surfaces of the valve pin 121 and the pressing pin 136, the centering of the valve pin 121 and the pressing pin 136 is performed. If only the step is performed reliably, the centering of the valve pin 121 and the protruding sleeve 133 can be performed reliably, so that the mold can be easily manufactured, and further, it is possible to prevent burrs from being formed on the molded product.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the above embodiment, the valve pins 34, 121 on the fixed type 1, 101 side are used.
Are provided with convex portions 37, 124, and pressing pins 71,
Although the concave portions 73 and 137 are provided on the 136, the concave portion may be provided on the valve pin and the concave portion may be provided on the pressing pin. The valve pin may be moved in the opening direction by the pressure of the resin as in the above embodiment, but may be driven in the opening direction and the closing direction by a fluid pressure cylinder such as an air cylinder or a hydraulic cylinder.

[0046]

According to the first aspect of the present invention, the gate opening / closing member is provided on the first gate opening / closing member provided on the mold having the material passage, and on the mold facing the mold having the material passage. And a second gate opening / closing member abutting against the first gate opening / closing member, and moving the first gate opening / closing member to the second gate opening / closing member side after the mold is closed, thereby opening the gate and producing a product from the gate. In a molding method of injecting a molding material into a cavity and filling the molding material into the product cavity, the second gate opening / closing member pushes and moves the first gate opening / closing member to close the gate. In this state, the convex portion provided on one of the contact surfaces of the first gate opening / closing member and the second gate opening / closing member and the concave portion provided on the other are fitted to each other, so that the product is released from the opened gate. Cavite When the molding material is injected into the gate, the misalignment of the gate opening / closing member can be prevented, and therefore,
It is possible to prevent the flow of the molding material from the gate to the product cavity from being deflected, and to prevent molding defects.

According to the molding method of the second aspect, in addition to the effects of the first aspect, one of the first gate opening and closing member and the second gate opening and closing member is connected to the other. The gate opening / closing member is removably fitted into a fitting hole formed in the mold provided with the gate opening / closing member, and when the mold is closed, before the one gate opening / closing member fits into the fitting hole, the protrusion is formed. Since the portion and the concave portion are fitted to each other, a centering operation for fitting the gate opening / closing member into the fitting hole can be easily performed in manufacturing the mold.

According to the third aspect of the present invention, the first gate body having the gate is provided with the first gate opening / closing member.
A second mold body that opens and closes with respect to the first mold body is provided with a second gate opening and closing member that contacts the first gate opening and closing member. 2
The gate is opened when moved to the side of the gate opening / closing member, and conversely, when the second gate opening / closing member pushes and moves the first gate opening / closing member, the gate is closed. Since the convex portion is provided on one of the contact surfaces of the gate opening / closing member 2 and the concave portion on which the convex portion is removably fitted is provided, the molding method of the invention of claim 1 can be carried out.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of a valve gate type mold apparatus according to the present invention, showing a state where a gate is opened.

FIG. 2 is a sectional view showing a state where the gate is closed.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1 and does not show a fixed-side mounting plate.

FIG. 4 is a sectional view showing a second embodiment of the valve gate type mold apparatus according to the present invention, showing a state where a gate is opened.

FIG. 5 is a sectional view showing a state in which the gate is closed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed type (1st type | mold) 2 Movable type | mold (2nd type | mold) 3 Product cavity 16 Gate 31 Sprue (material passage) 34 Valve pin (1st gate opening / closing member) 37 Convex part 43 Band heater (heating means) 71 Pressing pin (second gate opening / closing member) 73 Recess 101 Fixed die (first die) 102 Movable die (second die) 103 Product cavity 112 Sprue (material passage) 114 Band heater (heating means) 118 Gate 121 Valve pin (first gate opening / closing member) 124 Convex portion 133a Fitting hole 136 Pressing pin (second gate opening / closing member) 137 Recess

Claims (3)

[Claims] 1. A plurality of molds that can be opened and closed with each other are closed, a product cavity is formed between the molds, and a thermoplastic molding material in a material passage provided in the molds is heated. In a molding method for opening and closing a gate from the material passage to the product cavity by a gate opening / closing member while always maintaining a molten state, a first gate opening / closing provided on a mold having the material passage as the gate opening / closing member Using a member and a second gate opening / closing member provided on the mold facing the mold having the material passage and abutting against the first gate opening / closing member, and after closing the mold, the first gate opening / closing member is moved to the first gate opening / closing member. After the gate is opened by moving it to the gate opening / closing member side of 2, the molding material is injected into the product cavity from the gate, and after the molding material is filled into the product cavity, The second gate opening / closing member pushes and moves the first gate opening / closing member to close the gate, and in the mold closed state, a contact surface between the first gate opening / closing member and the second gate opening / closing member. Wherein the convex portion provided on one side and the concave portion provided on the other side are fitted to each other. 2. One of the first gate opening and closing member and the second gate opening and closing member is inserted into a fitting hole formed in a mold provided with the other gate opening and closing member. 2. The convex portion and the concave portion are fitted to each other, and the convex portion and the concave portion are fitted to each other before the one gate opening / closing member is fitted in the fitting hole when the mold is closed. Molding method. 3. A valve gate type mold apparatus used in the molding method according to claim 1, wherein the first mold body and the second mold body are opened and closed with each other to form a product cavity therebetween when the mold is closed.
Wherein the first mold body has a gate for opening a material passage located inside the first mold body to the product cavity, and a thermoplastic molding material in the material passage which is constantly melted. A heating means for maintaining the state, and a movable first gate opening / closing member, wherein the second mold body has a movable second gate opening / closing member abutting on the first gate opening / closing member,
These gate opening / closing members open the gate when the first gate opening / closing member moves to the second gate opening / closing member, and conversely cause the second gate opening / closing member to push and move the first gate opening / closing member. The first gate opening / closing member and the second gate opening / closing member are provided with a convex portion on one of the contact surfaces thereof, and the concave portion into which the convex portion is removably fitted. A valve gate type mold apparatus characterized by comprising: