JP2865980B2 - Local pressure injection molding method and local pressure injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local pressurized injection molding method and a local pressurized injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a screw is disposed in a heating cylinder so as to be rotatable and advanceable and retractable. In a measuring step, the screw is rotated and retracted to melt a resin in front of the screw. In the storing and filling (10) step, the screw is advanced to inject the molten resin from the injection nozzle and fill the cavity of the mold.

On the other hand, the mold comprises a fixed mold and a movable mold, and the movable mold can be moved forward and backward by a mold opening / closing device so as to be brought into and out of contact with the fixed mold. Therefore, the movable mold is brought into contact with the fixed mold to close the mold, the movable mold is pressed against the fixed mold, the mold is clamped, then the cavity is filled with resin, and the resin is cooled and molded. Goods. The molded product can be pushed down by moving the movable mold away from the fixed mold to open the mold, and ejecting the ejector pins from the fixed mold.

The resin injected from the injection nozzle enters a runner through a sprue, and is filled from the runner through the gate into the cavity. For example, when the gate is of a submarine type, a portion corresponding to the gate (hereinafter, referred to as a “gate portion”) is automatically folded when the molded product is pushed down, and is separated from the molded product. I have.

[0005] However, after the gate portion is separated, a gate mark remains or flash occurs on the molded product. Therefore, an operation for removing gate marks and burrs is required, which increases costs. Therefore, there has been provided a local pressurized injection molding machine in which a pressurizing pin is provided corresponding to the gate portion, and the pressurizing pin is advanced to cut the gate. In this case, no gate mark remains or burrs occur.

[0006]

However, in the conventional local pressurized injection molding machine, when a pressing pin for gate cutting and another pressing pin are mounted on a pressing plate and simultaneously advanced, the gate cutting is performed. The types of other processing that can be performed besides are limited in type, and the type of other processing cannot be changed.

For example, when a pressing pin for gate cutting and another pressing pin are attached to a pressing plate and simultaneously moved forward, the gate is cut, and at the same time, shrinkage of the resin due to shrinkage of the resin during cooling is prevented. It is possible to make holes, make holes, form thin portions, and perform compression molding when molding optical components. There is also provided a local pressure injection molding machine capable of dispersing the stress distribution of the resin in the cavity by advancing another pressure pin (Japanese Patent Publication No. Hei 4-5912).
No. 8).

However, when another pressing pin is advanced in order to process a molded product, the advance distance (hereinafter referred to as "effective stroke") required for other processing is as follows.
It differs depending on the type of processing. Therefore, if the position of the tip of the pressure pin for performing another processing on the molded product is set, it is not possible to perform another processing using the same pressure pin. When a pressure pin for preventing sink marks is provided, the pressure pin for preventing sink marks cannot be used for punching.

In addition, two or more other processes cannot be applied to a molded product at the same time. Furthermore, when using a submarine type gate, the effective stroke of the pressure pin for gate cutting can be set large,
Other processing becomes easy, but when a side-type gate or overlap-type gate is used, the effective stroke of the pressure pin cannot be set large because of the structure, making other processing difficult. turn into.

The present invention solves the problems of the conventional local pressurized injection molding machine, and does not limit the types of other processing that can be performed in addition to gate cutting. It is an object of the present invention to provide a local pressurized injection molding method and a local pressurized injection molding machine that can change the type and can perform two or more other processes.

[0011]

For this purpose, in the local pressurized injection molding method of the present invention, the setting is made from immediately before the resin injected from the injection nozzle is completely filled into the cavity to immediately after the resin is filled. At this point, the first local pressure pin facing the gate is advanced to cut the gate, and the first
The local pressure pin is advanced to push the resin of the dummy portion in front of the first local pressure pin into the cavity.

After the first local pressure pin is started to advance, the second local pressure pin facing the cavity is advanced to push the resin in front of the second local pressure pin into the cavity. In the local pressurized injection molding machine of the present invention, a fixed mold, a movable mold that is disposed so as to be able to freely contact and separate from the fixed mold and forms a cavity between the two, and penetrates the movable mold. A first local pressure pin extends and has a tip facing the gate, and a second local pressure pin extends through the movable mold and has a tip facing the cavity.

In addition, a pressure plate is provided for supporting rear ends of the first local pressure pin and the second local pressure pin. The pressure plate forms a play at the rear end of the second local pressure pin, and sets the effective stroke of the second local pressure pin shorter than the effective stroke of the first local pressure pin.

[0014]

According to the present invention, as described above, in the local pressurized injection molding method, a set point in time is set immediately before the resin injected from the injection nozzle is completely filled in the cavity until immediately after the resin is filled. Then, the first local pressure pin facing the gate is advanced to cut the gate, and then the first local pressure pin is advanced to push the resin of the dummy portion in front of the first local pressure pin into the cavity.

After the first local pressure pin starts to advance, the second local pressure pin facing the cavity is advanced to push the resin in front of the second local pressure pin into the cavity. In this case, even if the inside of the cavity is cut off with cooling after the inside of the cavity is cut off from the runner by the gate cut and the filling of the resin is cut off, the resin in the waste boss portion can be pushed into the cavity.

In the local pressurized injection molding machine according to the present invention, a fixed mold, a movable mold which is disposed so as to be able to contact and separate from the fixed mold and forms a cavity between the two, and There is a first local pressure pin extending through and having a tip facing the gate, and a second local pressure pin extending through the movable mold and having a tip facing the cavity. Also, a pressure plate is provided for supporting rear ends of the first local pressure pin and the second local pressure pin. The pressure plate is provided with the second
A play is formed at the rear end of the local pressure pin, and the effective stroke of the second local pressure pin is set shorter than the effective stroke of the first local pressure pin.

Therefore, the resin injected from the injection nozzle is filled into the cavity through the gate, and at this time, the resin is also filled in front of the first local pressure pin and the second local pressure pin. You. When the pressure plate starts to move forward, the first local pressure pin also moves forward to cut the gate, so that the inside of the cavity is cut off from the runner. Thereafter, the first local pressure pin continues to advance, and pushes the resin of the dummy portion in front of the first local pressure pin into the cavity.

When the pressure plate advances by the amount of play, the second local pressure pin starts to advance and pushes the resin in front of the second local pressure pin into the cavity. When the local pressure pin advances and stops by the effective stroke, the second local pressure pin also stops, and the pushing of the resin ends.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a local pressurized injection molding machine showing a first embodiment of the present invention, and FIG.
It is X sectional drawing. In the figure, 11 is a fixed mold mounting plate,
Reference numeral 12 denotes a fixed mold. The fixed mold 12 is attached to a fixed platen (not shown) via the fixed mold mounting plate 11. Then, the injection device (not shown) advances in the injection process, and the tip of the injection nozzle (not shown) is
Is contacted with the sprue bush 13.

On the other hand, a movable platen (not shown) is moved forward and backward by a mold opening / closing device (not shown) so that the movable mold 14 is brought into and away from the fixed mold 12. Therefore, the movable mold 14 is fixed to a movable platen via a movable mold mounting plate 15 and a spacer block (not shown). The resin injected from the injection nozzle enters the runner 19 via the sprue 18, passes through the submarine type gate 20 from the runner 19, and forms a cavity 21 formed between the fixed mold 12 and the movable mold 14. Is filled in.

When the injection process is completed, the process enters a pressure-holding process, in which the resin pressure in the cavity 21 is maintained and the cooling of the resin is started.
4 and the two molds 12 and 1 are kept in a state where a molded product (not shown) is left.
4 is opened and the molded product is pushed down by the ejector device. Therefore, a sprue lock pin 25 and an ejector pin 26 are provided. The sprue lock pin 25
Is disposed so as to face the sprue 18 and holds the molded product when the mold is opened to leave it on the movable mold 14 side. The ejector pins 26 are disposed so as to face the cavity 21 and the runner 19, and protrude from the movable mold 14 after the mold is opened, and separate the molded product from the movable mold 14 and push it down.

Heads 25a and 26 formed at the rear ends of the sprue lock pin 25 and the ejector pin 26, respectively.
a is sandwiched and fixed by the ejector plates 31 and 32. The ejector plates 31 and 32 are supported so as to be able to move forward and backward, and advance the sprue lock pin 25 and the ejector pin 26 as they move forward. As shown in FIG. 1, a gap (gap) is formed between the ejector plate 32 and the rear end of the movable mold 14 at the retreat limit of the ejector pin 26. The gap becomes a stroke of the ejector pin 26.

An ejector rod contact member 33 is fixed to the rear end of the ejector plate 32, and an ejector rod of an ejector cylinder (not shown) contacts the ejector rod contact member 33.
Accordingly, the ejector plates 31 and 32 can be advanced and retracted by operating the ejector cylinder.

Incidentally, first and second local pressure pins 34 and 35 are provided in order to perform other processing besides gate cutting on the molded product and to improve the quality.
The first local pressure pin 34 extends forward through the ejector plates 31 and 32 and the movable mold 14, and its front end faces the gate 20. The resin filled in the disposal boss portion 21a as a dummy portion in front of
Push in. The second local pressure pin 35 extends forward through the ejector plates 31, 32 and the movable mold 14, and its front end faces the thick portion of the cavity 21. The resin filled in the disposal boss 21b in front of 35 is pushed into the cavity 21.

The first and second local pressure pins 34 and 35
Are set to have different effective strokes L _D and L _C from each other. The first and second local pressure pins 34,
In addition to 35, other local pressure pins with further different effective strokes can be provided. The head portion 34a formed at the rear end of the first local pressure pin 34 is sandwiched and fixed by the pressure plates 36 and 37 disposed behind the ejector plate 32. The effective stroke L _D of the pin 34 is the pressure plate 3
The same value as the movement stroke L _A of 6,37.

The stepped portion 35 a formed at the rear end of the second local pressure pin 35 is provided with pressure plates 36 and 37.
It is housed in the stepped portion housing chamber 38 formed between them, and
It is arranged movably. A rear pin portion 35b is formed behind the stepped portion 35a to protrude through the pressure plate 37. Here, the stepped portion accommodation room 3
The depth of 8 value greater than the thickness of the stepped portion 35a, play L _B is formed.

Therefore, the effective stroke L _C of the second local pressure pin 35 is L _C = L _D -L _B = L _A -L _B. Thus, the effective stroke L _{D of} the first local pressure pin 34 and the effective stroke L _D of the second local pressure pin 35
_C can be different. When a different effective stroke is required, a play of a different value is formed by the pressure plates 36 and 37 at the rear end of the other local pressure pins.

A pressure rod contact member 39 is fixed to the rear end of the pressure plate 37, and a pressure rod of a pressure cylinder (not shown) comes into contact with the pressure rod contact member 39. I have. Therefore, the pressure plates 36 and 37 can be moved forward and backward by operating the pressure cylinder. Reference numeral 41 denotes a pressure plate guide pin for guiding the pressure plates 36 and 37. The tip of the pressure plate guide pin 41 is connected to the ejector plate 31,
The effective stroke L _D is set by penetrating through the mold 32 and the movable mold 14 and facing the fixed mold 12.

Next, the first and second local pressure pins 34,
The operation of 35 will be described. The resin injected from the injection nozzle enters the runner 19 through the sprue 18, passes through the submarine type gate 20 from the runner 19, and enters the cavity 21 formed between the fixed mold 12 and the movable mold 14. Is filled. At this time, the discarded boss 21
Resins are also filled in a and 21b.

Then, at a set time from immediately before the filling of the resin into the cavity 21 to one second immediately after the completion of the filling, the pressurizing cylinder operates to move the pressurizing rod forward. Then, it is brought into contact with the pressure rod contact member 39. At this time, the pressure plates 36 and 37 start moving forward. It should be noted that it is determined whether or not a set time from immediately before the filling of the resin into the cavity 21 to one second immediately after the filling is completed is determined.
The determination can be easily made by detecting the resin pressure in 1 and the injection pressure of an injection cylinder (not shown).

When the pressure plates 36 and 37 start moving forward, the first local pressure pin 34 also starts moving and cuts the gate, so that the inside of the cavity 21 is cut off from the runner 19. At this time, the resin in the cavity 21 contracts with cooling and the specific volume decreases, but the rib a shown in FIG.
In a thick portion such as a boss portion (not shown) or the like, cooling is most delayed, and sink occurs.

Therefore, the interior of the cavity 21 is cut off from the runner 19, and the first local pressure pin 34 continues to advance even after the filling of the resin is cut off, and the resin of the waste boss 21a is pushed into the cavity 21. The effective stroke L _D is set so as to perform the following. By the way, when the pressure plates 36 and 37 are at the initial position where they come into contact with the movable mold mounting plate 15, the rear pin portions 35b of the second local pressure pins 35
Is moved forward by being pressed by the movable mold mounting plate 15, and the stepped portion 35 a is also at the front position in the stepped portion accommodation chamber 38. When the pressurizing cylinder operates and the pressurizing plates 36 and 37 move forward away from the movable mold mounting plate 15, the second local pressurizing pin 35 becomes a stepped portion 35.
a is maintained in the stopped state until the back by L _B content play a stepped portion accommodating chamber 38.

[0033] Therefore, the stepped portion 35a with the forward movement of the pressure plate 36, 37 is retracted by L _B content play a stepped portion accommodating chamber 38, the second local pressurizing pin 35 begins to move forward. Since the resin of the disposal boss portion 21b is pushed into the cavity 21 with the advance of the second local pressure pin 35, the resin pressure in the cavity 21 can be made uniform, and the sink in the thick portion can be reduced. Can be prevented from occurring.

Then, the second local pressure pin 35 pushes the resin of the waste boss 21b into the cavity 21, and the pressure plates 36 and 37 advance by the effective stroke L _{D of} the first local pressure pin 34. When it stops, the second local pressure pin 35 also stops, and the pushing of the resin ends. In this way, even if the inside of the cavity 21 is blocked from the runner 19 and the resin in the cavity 21 contracts with cooling after the filling of the resin is cut off, the resin in the disposal boss portions 21a and 21b is put into the cavity 21. Since the resin can be pushed in, the resin pressure in the cavity 21 can be made uniform, and the occurrence of sink marks in the thick portion can be prevented.

Further, with respect to the effective stroke L _{D of} the first local pressure pin 34 disposed facing the gate 20, the second local pressure pin 35 disposed at a position distant from the gate 20. effective stroke L _C for shorter only play L _B content of, become overfilled is prevented. The length of the disposal bosses 21a and 21b is changed according to the shape of the molded product, and is set to be long at a place where sink marks are likely to occur and short at a place where sink marks are unlikely to occur. In this case, for example, the adjustment can be made by inserting a washer (not shown) into the base of the second local pressure pin 35.

Then, the second local pressure pin 35 is used for other processing, and a hole is formed, a thin portion is formed, and compression molding for forming an optical component is performed. be able to. In this case, change the value of play L _B which is formed on the rear end portion of the second local pressurizing pins 35, to change the effective stroke L _C of the second local pressurizing pins 35. Further, the disposal boss 21b is unnecessary.

Therefore, the type of other processing that can be performed in addition to the gate cut is not limited, and the type of other processing can be changed. For example, in the present embodiment, in addition to the gate cut by the first local pressure pin 34, the second local pressure pin 35 prevents the sink from occurring, but the second local pressure pin 35 Accordingly, holes can be punched out, thin portions can be formed, and compression molding for molding optical components can be performed.

When performing other processes on the molded product in addition to the gate cut, two or more other processes can be performed on the molded product. For example, in the present embodiment, in addition to the gate cut by the first local pressure pin 34, the second local pressure pin 35 prevents the sink from occurring, but the second local pressure pin 35 Accordingly, at least two other processes of punching, formation of a thin portion, and compression molding can be performed together.

Next, a second embodiment of the present invention will be described. FIG. 3 is a sectional view of a main part of a local pressurized injection molding machine showing a second embodiment of the present invention. (A) of the figure is a vertical sectional view of a main part of the local pressurized injection molding machine, and (b) is a YY sectional view of (a). In the figure, 18 is a sprue, 19 is a runner, 21 is a cavity, 21b is a discard boss, 26 is an ejector pin, and 35 is a second local pressure pin.

In this case, the gate 43 is of a side type, and the first local pressure pin 44 having a sharp cut surface formed at the tip faces the gate 43 and cuts the gate when the gate 43 is advanced. Resin in cavity 21
Push in. Further, the second local pressure pin 35 faces the thick portion of the cavity 21 and is discarded when it is advanced.
1b is pushed into the cavity 21.

L _C is the effective stroke of the second local pressure pin 35, and L _D is the effective stroke of the first local pressure pin 44. In this embodiment, the first local pressure pin 4
Recess 1 to ensure sufficient effective stroke L _D
9a is formed, but when it is difficult to form the concave portion 19a, a sufficient effective stroke L _D cannot be secured for the first local pressure pin 44, and the second local pressure pin 35 Of the effective stroke L _C becomes correspondingly small.

In this case, the play L _B (FIG. 1) of the second local pressure pin 35 is changed to increase the effective stroke L _C. When an overlap type gate (not shown) other than the side type gate 43 is used, for example,
Further, the play L _B is changed. As described above, when other processing is performed on a molded product in addition to the gate cut, other processing can be easily performed regardless of the type of gate used.

Next, a third embodiment of the present invention will be described. FIG. 4 is a sectional view of a local pressurized injection molding machine showing a third embodiment of the present invention. In the figure, reference numeral 11 denotes a fixed mold attaching plate, and 12 denotes a fixed mold. The fixed mold 12 is attached to a fixed platen (not shown) via the fixed mold attaching plate 11. Then, the injection device (not shown) advances in the injection process, and the tip of the injection nozzle (not shown) is brought into contact with the sprue bush 13 of the fixed mold 12.

On the other hand, a movable platen (not shown) is advanced and retracted by a mold opening / closing device (not shown) so that the movable mold 14 comes into contact with and separates from the fixed mold 12. Therefore, the movable mold 14 is fixed to a movable platen via a movable mold mounting plate 15 and a spacer block (not shown). The resin injected from the injection nozzle enters the runner 19 via the sprue 18, passes through the submarine type gate 20 from the runner 19, and forms a cavity 21 formed between the fixed mold 12 and the movable mold 14. Is filled in.

A sprue lock pin 25 and an ejector pin 26 are provided to push down a molded product (not shown) when the molds 12 and 14 are opened. The sprue lock pin 25 is disposed facing the sprue 18 and holds the molded product when the mold is opened, and leaves it on the movable mold 14 side. The ejector pin 26 is provided in the cavity 21.
The mold is opened facing the runner 19 and the like, and is protruded from the movable mold 14 after the mold is opened. The molded product is separated from the movable mold 14 and pushed down.

Head portions 25a, 26 formed at the rear ends of the sprue lock pin 25 and the ejector pin 26
a is sandwiched and fixed by the ejector plates 31 and 32. The ejector plates 31 and 32 are supported so as to be able to move forward and backward, and advance the sprue lock pin 25 and the ejector pin 26 as they move forward. As shown in the figure, a gap is formed between the ejector plate 32 and the rear end of the movable mold 14 at the retreat limit of the ejector pin 26. The gap is the ejector pin 26
Stroke.

Incidentally, first and second local pressure pins 34 and 35 are provided in order to process and improve the quality of the molded product. The first local pressure pin 34
Are the ejector plates 31 and 32 and the movable mold 1
4, the tip extends toward the gate 20, the tip faces the gate 20, the gate is cut when the tip advances, and the resin filled in the disposal boss portion 21 a as a dummy portion in front of the first local pressure pin 34 is filled into the cavity 21. Press The second local pressure pin 35 is connected to the ejector plate 3.
1 and 32 and the movable mold 14, the tip extends forward and the tip faces the thick portion of the cavity 21, and the resin filled in the disposal boss portion 21 b in front of the second local pressure pin 35 when the resin is moved forward is filled with the cavity. Press into 21.

The first and second local pressure pins 34, 35
Are set to have different effective strokes L _D and L _C from each other. The first and second local pressure pins 34,
In addition to 35, other local pressure pins with further different effective strokes can be provided. The head portion 34 a formed at the rear end of the first local pressure pin 34 is sandwiched and fixed by the pressure plates 36 and 37 disposed behind the ejector plate 32, so that the first
The effective stroke L _D of the local pressure pin 34 has the same value as the movement stroke L _A of the pressure plates 36 and 37. Even the same value as the movement stroke L _A of the pressure plate 36, 37 the gap between the ejector plate 32 and the pressure plate 36.

The stepped portion 35 a formed at the rear end of the second local pressure pin 35 is provided with pressure plates 36 and 37.
It is housed in the stepped portion housing chamber 38 formed between them, and
It is arranged movably. A rear pin portion 35b is formed behind the stepped portion 35a to protrude through the pressure plate 37. Here, the stepped portion accommodation room 3
The depth of 8 value greater than the thickness of the stepped portion 35a, play L _B is formed.

Therefore, the effective stroke L _C of the second local pressure pin 35 is L _C = L _D -L _B = L _A -L _B. Thus, the effective stroke L _{D of} the first local pressure pin 34 and the effective stroke L _D of the second local pressure pin 35
_C can be different. When a different effective stroke is required, a play of a different value is formed by the pressure plates 36 and 37 at the rear end of the other local pressure pins.

Further, a rod contact member 46 is fixed to the rear end of the pressure plate 37, and a rod of a hydraulic cylinder (not shown) contacts the rod contact member 46. Therefore, the pressure plates 36 and 37 can be advanced and retracted by operating the hydraulic cylinder. Then, after the pressure plate 36 are in contact are advanced by the movement stroke L _A partial ejector plate 32, pressure plate 36, 37 and the ejector plate 3
1 and 32 are integrated and further advanced by the stroke of the ejector pin 26.

The reference numeral 41 designates the pressure plates 36, 37
Is a pressure plate guide pin for guiding the pressure. The distal end of the pressure plate guide pin 41 penetrates through the ejector plates 31 and 32 and the movable mold 14 to allow the fixed mold 1
2, the effective stroke L _D is set. Next, the operation of the first and second local pressure pins 34 and 35 will be described.

The resin injected from the injection nozzle enters the runner 19 through the sprue 18 and is formed from the runner 19 through the submarine type gate 20 between the fixed mold 12 and the movable mold 14. The cavity 21 is filled. At this time, the waste boss portions 21a and 21b are also filled with resin. Then, at a set point from immediately before the filling of the resin into the cavity 21 to one second immediately after the filling is completed, the hydraulic cylinder is operated to move the rod forward, and the rod contact member 46 is moved. Is abutted. At this time, the pressure plates 36 and 37 start moving forward.

As the pressure plates 36 and 37 advance, the first local pressure pin 34 also advances and cuts the gate, so that the interior of the cavity 21 is cut off from the runner 19. Thereafter, the first local pressure pin 34 continues to advance, and pushes the resin of the disposal boss 21 a into the cavity 21. By the way, the pressurizing plates 36 and 37 are connected to the movable mold mounting plate 15.
Is in the initial position where it contacts the second local pressure pin 35
The rear pin portion 35b is moved forward by being pressed by the movable mold mounting plate 15, and the stepped portion 35a is also at the front position in the stepped portion accommodation chamber 38. When the hydraulic cylinders operate and the pressure plates 36 and 37 move forward away from the movable mold mounting plate 15, the second local pressure pin 35 moves the stepped portion 35 a into the stepped portion accommodation chamber 38. Play L
_The stop state is maintained until the vehicle retreats by _B minutes.

[0055] Therefore, the stepped portion 35a with the forward movement of the pressure plate 36, 37 is retracted by L _B content play a stepped portion accommodating chamber 38, the second local pressurizing pin 35 begins to move forward. Then, the second local pressure pin 35 pushes the resin of the discard boss 21b into the cavity 21, and when the pressure plates 36 and 37 move forward by the effective stroke L _{D of} the first local pressure pin 34 and stop there. Then, the second local pressure pin 35 is also stopped, and the pushing of the resin is terminated. At this time, the pressure plate 36 comes into contact with the ejector plate 32. Further, the tip of the pressure plate guide pin 41 comes into contact with the fixed mold 12.

The first device disposed facing the gate 20
For the effective stroke L _D of the local pressure pin 34, the second local pressure pin 3 disposed at a position away from the gate 20.
Since the effective stroke L _C of No. 5 is shortened by the play L _B , overfilling is prevented. Subsequently, when the hydraulic cylinder is further operated, the pressurizing plates 36 and 37 move forward integrally with the ejector plates 31 and 32, and the sprue lock pin 25 and the ejector pin 26 start moving forward.

In the local pressurized injection molding machine having the above-described structure, it is not necessary to provide another ejector cylinder for operating the ejector device, and the cost can be reduced. It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0058]

As described above in detail, according to the present invention, in the local pressurized injection molding method, the resin injected from the injection nozzle is filled immediately before the resin is completely filled into the cavity. At the set time, the first local pressure pin facing the gate is advanced to cut the gate, and the first local pressure pin is further advanced to remove the resin of the dummy portion in front of the first local pressure pin into the cavity. Press

After the first local pressure pin is started to advance, the second local pressure pin facing the cavity is advanced to push the resin in front of the second local pressure pin into the cavity. In this case, even if the resin in the cavity shrinks with cooling after the inside of the cavity is cut off from the runner by the gate cut and the filling of the resin is cut off, the first,
The resin in front of the second local pressure pin can be pushed into the cavity.

Therefore, the resin pressure in the cavity can be made uniform, and the occurrence of sink marks in the thick portion can be prevented. In the local pressurized injection molding machine of the present invention, a fixed mold, a movable mold that is disposed so as to be able to freely contact and separate from the fixed mold and forms a cavity between the two, and penetrates the movable mold. A first local pressure pin extends and has a tip facing the gate, and a second local pressure pin extends through the movable mold and has a tip facing the cavity.

Further, there is provided a pressure plate for supporting rear ends of the first local pressure pin and the second local pressure pin. The pressure plate forms a play at the rear end of the second local pressure pin, and sets the effective stroke of the second local pressure pin shorter than the effective stroke of the first local pressure pin. In this case, when the pressure plate and the first local pressure pin advance by the amount of play, the second local pressure pin starts to advance, so that the first local pressure pin and the second local pressure pin start to advance. It is possible to very easily adjust the timing of the operation.

Therefore, the type of other processing that can be performed in addition to the gate cut is not limited, and the type of other processing can be changed. In addition, even if any type of gate is used, other processing can be easily performed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a local pressurized injection molding machine showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a sectional view of a main part of a local pressurized injection molding machine showing a second embodiment of the present invention.

FIG. 4 is a sectional view of a local pressurized injection molding machine showing a third embodiment of the present invention.

[Explanation of symbols]

12 fixed mold 14 movable mold 20 gate 21 cavity 34 first local pressurizing pins 35 second local pressurizing pins 36 and 37 the pressure plate 21a, 21b discarded boss L _B play L _C, L _D effective stroke

──────────────────────────────────────────────────続 き Continuation of the front page (72) Nobuhiro Ogura, Inventor No. 731 Naganumaharamachi, Inage-ku, Chiba-shi, Chiba Chiba Works, Sumitomo Heavy Industries, Ltd. (56) Reference JP-A-6-99461 (JP, A) JP-A-5-425 (JP, A) JP-A-60-151013 (JP, A) JP-A-58-131041 (JP, A) JP-A-58-179625 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) B29C 45/56-45 / 57,45 / 37-45/38

Claims (2)

(57) [Claims] (A) A first local pressure pin facing a gate is advanced at a set point in time from immediately before the resin injected from an injection nozzle is completely filled into a cavity to immediately after the resin is filled. (B) further advance the first local pressure pin to push the resin of the dummy portion in front of the first local pressure pin into the cavity, and (c) advance the first local pressure pin. And starting the second local pressure pin facing the cavity to push the resin in front of the second local pressure pin into the cavity. 2. A fixed mold, (b) a movable mold that is disposed so as to be able to contact and separate from the fixed mold and forms a cavity therebetween, and (c) penetrates the movable mold. A first local pressure pin having a front end facing the gate; (d) a second local pressure pin extending through the movable mold and having a front end facing the cavity; A pressure plate for supporting the rear end of the first local pressure pin and the second local pressure pin, and (f) the pressure plate plays with the rear end of the second local pressure pin. A local pressure type injection molding machine, wherein the effective stroke of the second local pressure pin is set shorter than the effective stroke of the first local pressure pin.