JP2657193B2 - Injection mold equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold apparatus.

[0002]

2. Description of the Related Art In general, an injection molding mold apparatus defines a cavity by a fixed mold and a movable mold under a clamped state, and injects a resin as a molding material into the cavity. After the resin is solidified in the cavity, the mold is opened and cut at the gate position to obtain a molded product separated from the runner. The molded product remaining in the cavity when the mold is opened is discharged by a protruding pin provided on the movable mold.

The protruding pins are inserted into communication holes formed in the movable receiving plate and the movable mold plate so as to communicate with the cavity from the space in the spacer block. When the protruding plate to which the protruding pin is fixed is retracted in the spacer block, its tip is provided so as to substantially coincide with the bottom surface of the cavity.

[0004]

In the above-described injection molding die apparatus, if the difference between the diameter of the protruding pin and the inner diameter of the communication hole is large under the clamped state, a gap formed around the protruding pin. The resin enters the gap, and burrs are formed at the portion. This gap becomes even larger when the projecting pin is biased in the communication hole. The penetration of the resin into the gap often occurs when molding a low-viscosity resin such as polyethylene, which causes deterioration in the quality of the molded product. This can be avoided by minimizing the difference in diameter between the communication hole and the protruding pin, but this makes it difficult to insert the protruding pin into the communication hole in the mold assembling process, which causes a problem that the assembly is troublesome. .

Accordingly, an object of the present invention is to make it easier to insert a projecting pin into a communication hole at the time of assembling a mold, and to reduce a gap between the communication hole and the projecting pin at the time of injection molding. An object of the present invention is to prevent the occurrence of burrs and improve the quality of molded products.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, a feature of the present invention is that a projecting pin is a mold member constituting a mold.
Having a coefficient of thermal expansion greater than that of aluminum
Communication hole through which the protruding pin is inserted
The gap between the protruding pin and the protruding pin
Based on the difference in thermal expansion coefficient from the pin,
When the mold is heated during operation, the molded product does not flash.
Is set to be smaller by

[0007]

When the mold is assembled at room temperature, the diameter of the protruding pin is small and a large gap is formed between the communication hole and the protruding pin, so that the protruding pin can be easily inserted into the communication hole. At the time of injection molding, the cavity is filled with a high-temperature resin and heated by a temperature control mechanism to increase the temperature of the mold. As a result, the temperature of the projecting pin also rises, and the projecting pin thermally expands. Since the coefficient of thermal expansion of the protruding pin is larger than that of the mold material, the ratio of the protruding pin becoming thicker than the expansion of the communication hole is larger, so that the gap in the communication hole becomes smaller, and this gap is Resin does not enter.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. The injection mold apparatus of the present invention includes a fixed mold A fixed to an injection molding machine main body frame (not shown).
And a movable mold B provided so as to advance and retreat with respect to the fixed mold.

The fixed-side mold A includes a fixed-side mounting plate 1, a fixed-side receiving plate 2 that contacts the inside (the right side in FIG. 1), and a fixed-side mold plate 3 that contacts the inside. Guide shafts 4 and 4 are respectively attached to the concave portions provided outside the fixed-side mounting plate 1 and the holes 1a and 1a penetrating from the concave portions in the thickness direction. The fixed-side receiving plate 2 and the fixed-side mold plate 3 can advance and retreat along these guide shafts 4 and 4.

A nozzle bush 5 is attached to the center of the fixed-side mounting plate 1 and the fixed-side receiving plate 2 via a locating ring 6. When the mounting plate 1 and the receiving plate 2 are in contact with each other,
It matches the front surface of the receiving plate 2. At the center of the nozzle bush 5, there is provided a hole 5a into which an injection nozzle (not shown) provided in the main frame of the injection molding machine is fitted.
A sprue portion 5b is provided at a position from the hole to the tip of the nozzle bush. The sprue portion 5b communicates with a runner portion 3a provided on the fixed mold plate 3. The tip of the runner 3a is narrowed down and formed on the gate 3b.

The fixed-side receiving plate 2 and the fixed-side mold plate 3 are made of a precipitation-hardened pre-hardened steel mold, and a cavity is formed near the position where the gate 3b is provided on the front surface of the mold plate 3. Recess 3c is provided.

The structure of the movable mold B is such that the movable mounting plate 1 is connected to a cylinder block (not shown) of the molding machine main body.
A spacer block 12 is fixedly abutted on the inner side (left side in FIG. 1) of the apparatus 1, a movable receiving plate 13 is fixed on the inner side thereof, and a movable mold plate 14 is fixedly fixed on the inner side thereof. Movable receiving plate 1
The mold 3 and the mold plate 14 are made of a precipitation hardened prehardened steel mold material.

A recess 14c forming a cavity is provided on the front surface of the movable mold plate 14. A core pin 15 for forming a recess in the center of the molded product S is provided at the center of the cavity recess. Is protruding.

In a space 12a provided at the center of the spacer block 12, a molded product projecting mechanism D is provided. The protruding mechanism D includes a protruding plate 1 on which two plates abut.
6, a protruding pin 17 fixed to the protruding plate, a protruding rod (not shown) for advancing the protruding plate, and a return spring (not shown) for returning the protruding plate 16.

The protruding pin 17 is made of brass material, and is fixed to two protruding plates 16 via a brim formed at the base end, and the distal end thereof is a movable-side receiving plate 13 and a movable-side mold plate 14. Through the communication holes 13a, 14a provided in the
It slides back and forth in the communication hole, and is disposed so that the tip thereof coincides with the bottom surface of the cavity recessed portion 14c when the protruding plate 16 is retracted.

As shown in FIG. 2, the diameter of the protruding pin 17 is small at normal temperature, as indicated by a two-dot chain line 17a, and its tip is located at a position slightly receded from the bottom of the cavity recess 14c. There are relatively large gaps between the inner diameters of the communication holes 13a and 14a.

In FIG. 1, guide holes 12d, 13d, and 14d are provided in the spacer block 12, the movable-side receiving plate 13, and the movable-side mold plate 14, respectively, and the movable-side mold B is a fixed-side mold. A can move forward and backward along the guide shaft 4 with respect to A.

Next, the operation will be described. When the movable-side mold B is advanced toward the fixed-side mold A by a cylinder block (not shown), the two mold plates 3 and 14 are brought into contact with each other to be in a mold-clamped state, and the concave portions 3c and 14c are connected to each other. A cavity C is defined between the plates. In this state, the projecting plate 16 is urged by the return spring so as to abut the fixed-side mounting plate 11, so that the tip end of the projecting pin 17 has a cavity 14c formed in the movable-side mold plate 14. It almost coincides with the bottom of.

At the time of assembly, since the mold is at room temperature, if the diameter of the protruding pin is about 5 mm, a gap of about 0.03 mm is formed between the protruding pin 17 and the communication holes 13a and 14a. The communication holes 13a, 1
Since the projecting pin 17 is easily inserted into the inside of the mold 4a, assembly of the mold is extremely simple. However, when this mold is heated by a temperature adjusting mechanism (not shown) and the temperature of the protruding pin rises, the diameter of the protruding pin 17 increases as shown by a solid line in FIG. 2 due to thermal expansion. On the other hand, since the diameter of the communication hole does not expand so much because the thermal expansion coefficient of the mold material forming the receiving plate 13 and the mold plate 14 is small, the above-mentioned gap is reduced to about 0.01 mm.

When the mold is closed under such a condition, the sprue 6 is moved from the injection nozzle of the injection molding machine body.
When the resin is filled into the cavity C via the b and the runner 3a, a molded product S integral with the runner is formed. At this time, as described above, the protruding pin 17 and the communication holes 13a, 14a
Since the gap between them is as small as about 0.01 mm, the resin does not enter the gap, and there is no possibility that burrs will occur in the molded product. When the movable mold B is retracted along the guide shaft 4 after a predetermined curing time has elapsed, the molded product S and the runner are cut off at the gate 3b, and both are separated. Although not described in detail, the runner formed in the runner portion 3a and the sprue portion 5b is cut and discharged from an injection nozzle (not shown).

On the other hand, in response to the retreat of the movable-side mold B, a projecting rod (not shown) advances from the through hole 11a of the movable-side mounting plate 11, and the projecting plate 16 is advanced, thereby causing the projecting pin 17 to move forward. The distal end is projected from the front surface of the movable mold plate 14. The tip of the protruding pin 17 is
Because of the contact with the bottom surface of the
And fall out of the cavity.

After the molded product S is obtained by the above steps, if the movable die B is advanced again, the protruding plate 16 returns to the original position, and the fixed mounting plate 1, the receiving plate 2, and the fixed die The mold clamping is completed when the plate 3 and the movable mold plate 14 are in close contact with each other.

In this embodiment, the cavities and the runners have a simple structure. However, the present invention can be applied to all injection mold apparatuses including an injection mold having a complicated structure using protruding pins. . In addition, although the brass rod is used as the material of the protruding pin, the same effect can be obtained by using a material such as phosphor bronze having a larger coefficient of thermal expansion than the mold material, without being limited to this. .

[0024]

As described above, according to the present invention, a metal material having a larger coefficient of thermal expansion than the mold material is used as the material of the projecting pin, so that the projecting pin can be easily inserted into the communication hole when assembling the mold. Since it can be inserted, the assembly of the mold is simplified. And, at the time of injection molding, as the mold temperature is increased, the diameter of the protruding pin becomes larger at a larger ratio than the enlargement of the diameter of the insertion hole, so that the gap between the insertion hole and the protruding pin becomes smaller, Since the entry of the resin into the gap is hindered, there is no possibility that burrs will be formed on the molded product, and the quality of the molded product is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a relationship between a protruding pin and a communication hole.

[Explanation of symbols]

 A, B Mold C Cavity S Molded product 17 Projection pin

Claims (1)

(57) [Claims] 1. An injection molding die having a cavity defined by fixed and movable dies , and having a protruding pin reciprocatingly sliding in a communication hole for discharging a molded product formed in the cavity. in the apparatus, the ejector pin is Thea and a metal material having a thermal expansion coefficient greater than the thermal expansion coefficient of the mold member constituting the mold is, the gap between the communication hole and the ejector pin, and the molding material Up
At room temperature, based on the difference in thermal expansion coefficient
Burrs occur in molded products under the above mold heating during large operation
An injection molding die apparatus characterized in that it is set so as to be small to such an extent that it does not occur .