JPH08187751A - Injection mold - Google Patents

Abstract

PURPOSE: To produce a molded product free from a sink and a gate by applying dwell pressure after the injection molding due to an injection molding machine. CONSTITUTION: After the injection molding due to an injection cylinder, dwell pressure is applied to a slide piston 58 to operate a gate cutting piston 70 to perform gate cutting or, after injection molding, dwell pressure is applied and, after a molten resin is solidified, a mold is opened to move a cotter slide 94 to upwardly move a cutter guide 86 and gate cutting is performed by the gate cutter 88 fixed to the cutter guide 86.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin injection molding machine, which is provided with a gate cutting means in a mold so that a molded article does not have a gate after injection molding, and a sink mark does not occur. Regarding the type.

[0002]

2. Description of the Related Art Conventionally, Japanese Laid-Open Patent Publication No. 5-124068 discloses a molding die for cutting a gate when a molded product is taken out from a resin molding mold to form a sink-free molded product. In the publication, the slide block 25 is inserted into an insertion hole 37 provided in the mold plate 23 in the molding die 1, and the other end is held by the slide plate 24.
4 is a hydraulic cylinder 41 mounted on the movable side mounting plate 33
Is fixed to the tip of the piston rod 41a. Therefore, after the injection of the molten resin 50 is completed, the slide plate 24 is moved to the closed position in the initial state of the pressure holding state, and the rear end surface 44a of the slide block 25 closes the injection port 39a and the rear end portion of the closed portion 44. Closes the other end opening of the runner 46. As a result, the molten resin 50 inside the cavity 36 and the molten resin 50 inside the gate 45 are separated.

[0003]

However, this conventional technique has the following problems. That is, when the slide block 25 closes the injection port 39a, the molten resin 5
Since a pressure higher than the injection pressure is applied to 0, the molten resin flows backward and no holding pressure is applied, and the sink mark cannot be eliminated. This point has not been disclosed in the specification and remains unsolved. Therefore, it is an object of the present invention to apply a holding pressure after injection molding to produce a molded product having no sink mark and no gate.

[0004]

In order to achieve this object, an injection molding die according to the first aspect of the present invention is a mold composed of a fixed mold plate and a movable mold plate, wherein an injection cylinder is provided in the movable mold plate. A slide piston that operates by receiving the pressure of the molten resin, a gate cut piston that cuts a gate in conjunction with the slide piston, and a lever that connects the slide piston and the gate cut piston. . The lever also includes a link mechanism. Second
The injection molding die of the invention is a die comprising a fixed die plate and a movable die plate, and a cotter slide that operates in conjunction with the movement of the die when the die is closed to open, and the cotter slide. A cutter guide that operates in the vertical direction at the convex part of
It is characterized by having a gate cutter that divides the gate from the molded product. The convex portion includes a triangular cross section, a hill shape, or an arc shape.

[0005]

In the first aspect of the invention, the injection of the molten resin into the cavity of the die is performed by the injection cylinder via the insertion hole. Since the resin in the mold cavity and the resin in the gate are separated by the gate cut piston that operates by receiving the holding pressure from the injection cylinder, there is no gate in the molded product and no sink mark occurs. Further, unlike the prior art, since a hydraulic cylinder is not used, there is an advantage that the program of the control device does not need to be changed and the control device becomes simple. Second
According to the invention, the holding pressure is applied after injection into the cavity of the mold by the injection cylinder. And when the mold is opened after the molten resin has solidified, the cotter slide moves
Since the cutter guide is moved upward by the convex portion and the tip portion of the gate cutter is inserted into the insertion hole and the gate is cut, there is no gate in the molded product and no sink mark occurs.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the first invention will be described below with reference to the drawings. FIG. 1 shows an overall view of an injection molding device. The screw 5 is fitted in the injection cylinder 3 of the injection molding machine 1. A spline 7 is engraved on the right end of the injection ram 9
It is connected to. The injection ram 9 slides in the injection cylinder 8. A large-diameter gear 10 is fitted to the spline 7, and a small-diameter gear 11 meshing with the gear 10 is fitted to the shaft of the motor 12. The left end of the injection cylinder 3 has a conical shape, an injection nozzle 13 is formed at the tip, and the tip 14 has a spherical shape. Several heaters 15 are wound around the outer circumference of the injection cylinder 3, and the control device 19 heats the injection cylinder 3 to an appropriate temperature.

The injection cylinder 3 is fixed to the main body 20, and the main body 20 is connected to a rod 21a of a moving cylinder 21 fixedly mounted on the bed 2 so that it can slide in the left and right directions. The screw chamber 23 is connected to the hopper 16 provided on the upper portion of the injection cylinder 3. A fixed die plate 17 is fixedly mounted on the bed 2 in the vicinity of the injection nozzle 13. The block 24 is the bed 2 at a predetermined distance from this.
Is fixed to the left end portion of the and is connected by four tie bars 28. The movable plate 18 and the block 25 are fitted into the tie bar 28 so that the tie bar 28 can slide in the left-right direction.
Further, the block 25 and the movable side die plate 18 are connected by a link 27. The connecting pin 29 is connected to an expanding and contracting rod 30 of a cylinder 26 fixed to the block 24.

A fixed mold plate 32 and a movable mold plate 33 are fixedly mounted on the fixed die plate 17 and the movable die plate 18, respectively. A hydraulic cylinder 34 is fixedly mounted on the left end surface of the movable die plate 18 and is connected to the push pin 35. A switching valve 36 is connected to the injection cylinder 8, a switching valve 37 is connected to the hydraulic cylinder 26, a switching valve 38 is connected to the hydraulic cylinder 34, and a switching valve 39 is connected to the moving cylinder 21. The switching valves 36 to 39 are connected in parallel to the hydraulic pump 40. It is connected to the. The fixed mold plate 32 and the movable mold plate 33 are collectively referred to as a mold 31. The injection molding device 1 is controlled by a control device 19 including a microcomputer.
The output end of the controller 19 is a heating element, that is, the heater 15,
Hydraulic pump 40, motor 12, and switching valves 36-3
9 and so on.

FIG. 2 is an enlarged cross-sectional view of the main part of the mold. A sprue 42 is formed in the horizontal direction of the fixed mold plate 32, and the right end of the sprue 42 is open to the spherical recess 44. The spherical concave portion 44 abuts the spherical tip portion 14 of the injection nozzle 13 at the time of injection. The left end of the sprue 42 is connected to a runner 46 formed in the movable template 33, and the lower end of the runner 46 is connected to the gate 48. The gate 48 and the runner 46 are formed on the mating surfaces 41 of the fixed mold plate 32 and the movable mold plate 33, and communicate with the cavity 50 through the insertion holes 52. The cavity 50 formed in the mold 31 is a space between the shape of the concave portion 54 of the fixed mold plate 32 and the outer shape of the core 56 that is fixed to the movable mold plate 33 so as to project therefrom. Runner 46,
The cross-sectional area relationship between the insertion hole 52 and the gate 48 is the runner 46,
The insertion hole 52 is larger than the gate 48.

A slide piston 58 having a step portion is fitted in the cylinders 59 and 61, the right end surface thereof is exposed to the runner 46, and the rod 60 is fixedly mounted on the left end surface thereof. The rod 60 projects outward from the stopper 62. A spring 64 is elastically provided between the stopper 62 and the slide piston 58 to urge the slide piston 58 to the right. One end 65 of the lever 66 is attached to the left end arc surface of the rod 60.
, And the other end 67 is in contact with the circular arc surface of the rod 76 fixed to the gate cut piston 70. A shaft 68 fixed to the movable mold plate 33 is fitted into the fulcrum of the lever 66. The gate cut piston 70 has a cylinder hole 7 with a bottom.
8, the rod 72 is fixed to the left end surface of the gate cut piston 70 and is inserted into the insertion hole 52. A spring 74 is elastically provided between the gate cut piston 70 and the bottom surface 80 of the cylinder 78 of the movable mold plate 33 to bias the gate cut piston 70 to the left.

Extrusion pins 77, 79 are provided with through holes 69, 71 penetrating through the core 56 fixed to the movable mold plate 33.
The right end surface is fixed to the surface of the core 56 and the other end is fixed to the plate 75. Further, a rod 63 of a hydraulic cylinder 34 fixed to the movable die plate 18 fixed to the movable mold plate 33 is fixed to the plate 75. Next, the operation will be described with reference to FIGS. With the mold 31 of FIG. 2 clamped by the moving cylinder 21, the controller 19 first contacts the tip 14 of the injection nozzle 13 with the spherical recess 44 of the fixed mold plate 32, drives the hydraulic pump 40, and switches. The injection pressure acts on the injection ram 9 by opening the valve 36, and the leftward movement and rotation are given to the screw 5 by the rotation of the motor 12. The injection pressure acts on the molten resin, and the molten resin is injected from the injection nozzle 13 toward the sprue 42.

When the molten resin is filled in the cavity 50, the heat of the molten resin is taken by the mold 31 because the gate 48 has a small cross-sectional area, and is immediately cooled and solidified. This is generally called a gate seal. Subsequently, the molten resin in the cavity 50 also begins to solidify. Then, the resin volume in the cavity 50 contracts to reduce the pressure in the cavity, and the holding pressure is applied to the right end surface of the slide piston 58 as shown in FIG.
The slide piston 58 moves to the left against the above, the lever 66 is rotated counterclockwise, and the gate cut piston 70 is pushed, so that the rod 72 applies pressure to the insertion hole 52. However, since the resin in the gate 48 has already been solidified, the molten resin in the insertion hole 52 does not flow backward, and the molded product 51 in the cavity 50 is replenished with the molten resin and the insertion hole 52 is closed to perform gate cutting.

Excluding the holding pressure, at this time, the molten resin is solidified and the slide piston 58 is not returned to its original position by the urging force of the springs 64 and 74, and the gate-cut state is maintained as shown in FIG. It When the mold 31 is opened, that is, when the movable mold plate 33 moves to the left, the gate, runner, and sprue are formed as a unit 81 and a molded product 51, as shown in FIG. Next, as shown in FIG. 5, the hydraulic cylinder 34 is pressurized by the switching valve 38, the push pins 57, 77, 79 are pushed to the right, and the molded product 51 and the integrated body 81 are separated from the core 56. Complete. Second
An embodiment of the invention will be described. FIG. 6 shows an enlarged cross-sectional view of the main part of the mold. The sprue 42 is horizontally provided on the fixed mold plate 32, the right end of which is opened to the spherical recess 44, and the left end of which is opened to the fixed mold plate 32. Fixed mold plate 32 and movable mold plate 33
The runner 82, the gate 84, and the insertion hole 83 are provided on the mating surface 41. Further, the cavity 50 is formed in the space between the concave portion 54 formed in the fixed mold plate 32 and the core portion 56.

A gate cutter 88 is provided so as to face the insertion hole 83, and a tip end 89 thereof is fixed to a cutter guide 86 with a thin blade shape or knife edge shape. The lower end of the cutter guide 86 has a triangular cross section formed by the inclined surfaces 90 and 91 to form a convex portion. A spring 92 is elastically provided on the upper end surface 103 of the cutter guide 86 and the bottom 108 of the hole 109 to urge the cutter guide 86 downward. A cotter slide 94 is provided with respect to the cutter guide 86 with its center line in a direction perpendicular to the cutter guide 86, and the inclined surface 9 is provided on the upper side surface thereof.
6, 97, a triangular cross section is formed to form a convex portion. Its top 95 engages the top 87 of the ramps 90, 91. The inclined surfaces 90, 91, 96, 97 may be arcs instead of straight lines. A spring 98 is elastically provided between the cotter slide 94 and the bottom surface 99 of the hole 110 to urge the cotter slide 94 to the right. Also the cotter slide 9
A groove 100 is provided on the outer peripheral side surface of No. 4 in the axial direction thereof and is guided by a pin 102. Next, the operation will be described with reference to FIGS.

As shown in FIG. 6, an injection pressure is applied to the molten resin from the injection ram 9 by the control device 19 to cause the cavity 5 to move.
It is injected into 0. When the molten resin solidifies after a while, the mold 31 opens as shown in FIG. Cotter slide 94
Is moved to the right by the urging force of the spring 98, the inclined surface 97 of the cotter slide 94 presses the inclined surface 91 of the cutter guide 86 toward the insertion hole 83, and the tip portion 8 of the gate cutter 88.
The resin in the insertion hole 83 is cut by 9. Continued Figure 8
When the mold 31 is further opened, as shown in FIG.
Since the top portion 87 of the blade rides over the top portion 95 of the inclined surfaces 96 and 97, the cutter guide 86 returns to its original position and is integrated with the blade 10.
1 and the molded product 85 are separated. Further, as shown in FIG. 9, when the mold 31 is completely opened, the push-out pins 106, 107 and 112 are pushed rightward by the hydraulic cylinder 34, and the molded product 85, the runner and the sprue 101 are pushed out from the movable mold plate 33. As a result, a molded product 85 having no gate and having no sink mark is completed and drops downward.

[0016]

The present invention has the following effects. First
In the invention, the injection of molten resin into the cavity of the mold is
It is performed by the injection cylinder through the insertion hole, and the molded product in the cavity of the mold and the resin in the insertion hole gate, that is, the integrated body, are cut by the slide piston that receives the holding pressure from the injection cylinder. Since the insertion hole is cut by the gate cut piston while receiving the holding pressure, there is no gate and a molded product without sink marks is completed. Second
In the invention, after the molten resin is injected into the cavity of the mold by the injection cylinder, the molten resin is solidified while applying the holding pressure, and then the mold is opened. At this time, since the gate cutter is moved upward together with the cutter guide by the convex portion of the cotter slide to cut the gate, a molded product having no gate and no sink mark is completed. Further, unlike the prior art, since the hydraulic cylinder is not used, there is an advantage that the program of the control device is not changed and it is simple.

[0017]

[Brief description of drawings]

FIG. 1 is a front view of an injection molding machine according to an embodiment of the first invention.

FIG. 2 is an enlarged sectional view of a main part of the mold of the embodiment of FIG.

FIG. 3 is a diagram showing an operating state of a piston of the mold of FIG.

FIG. 4 is a view showing a state where the mold of FIG. 2 is opened.

5 is a diagram showing an operating state of a push pin of the mold shown in FIG. 2;

FIG. 6 is an enlarged cross-sectional view of a main part of a mold of an embodiment according to the second invention.

FIG. 7 is a diagram showing a state where the mold of the embodiment of FIG. 6 is slightly open.

FIG. 8 is a view showing a state where the mold of FIG. 6 is wide open.

9 is a view showing a state where the push-out pin of the mold shown in FIG. 6 is operated.

[Explanation of symbols]

 48, 84-Gate 52, 83-Insert hole 58-Slide piston 60, 72, 76-Rod 66-Lever 70-Gate cut piston 86-Cutter guide 88-Gate cutter 94-Cotter slide

Claims (2)

[Claims] 1. A mold comprising a fixed mold plate and a movable mold plate, a slide piston which operates by receiving pressure of molten resin from an injection piston in the mold, and a gate which is interlocked with the slide piston to cut a gate. A mold for injection molding, comprising: a gate cut piston, and a lever that connects the slide piston and the gate cut piston. 2. A mold comprising a fixed mold plate and a movable mold plate, wherein a cotter slide which operates in conjunction with movement of the mold when the mold is opened from a closed state, and a protrusion provided on the cotter slide. A mold for injection molding, comprising: a cutter guide that operates in a vertical direction on a curved surface; and a gate cutter that is fixed to the cutter guide that divides between the gate and the cavity.