JPH0712630B2 - Injection mold - 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 molding die having a punching pin for forming a large number of holes in a molded product.

[0002]

2. Description of the Related Art In a mold for injection molding a molded article having a plurality of through holes and the like, a pin for punching is provided in a cavity. This pin is supported by a pressing plate or the like provided in the mold, and its tip is in close contact with the cavity wall surface.

[0003]

If the pin for piercing and the cavity wall surface are not in close contact with each other and a slight gap is generated, burrs are apt to be generated there, and secondary processing for deburring is required after molding. Becomes

For this reason, the drilling pin is required to have processing accuracy and assembling accuracy. Also, if there is only one pin, it is easy to ensure close contact at the tip by using a pressing device such as hydraulic pressure, but if there are multiple pins, a means for protruding and adjusting the length for each pin is required. Incorporating the adjusting means together with the pressing device not only complicates the mold structure, but also invites an increase in cost, and depending on the size of the mold, there is no space for providing it, so the adoption of the pressing device is specific. It was limited to things.

The present invention has been conceived in order to solve the above-mentioned conventional problems, and its purpose is to utilize the elastic deformation recovery force of a shape memory alloy to bring the pin tip for punching into close contact. It is to provide a new injection mold that can be secured under a sufficient pressure.

[0006]

The feature of the present invention according to the above object is that the cavity has a plurality of pins for perforation, the rear end of each pin is supported by a pressing plate, and the front end is the wall surface of the cavity. In the injection molding die that is in close contact with, the pressing plate is formed of a shape memory alloy.

[0007]

In the above structure, the pressing plate made of the shape memory alloy is
The pins are pressed and deformed by the pressure applied to the pin abutting portion when the mold is closed, and each pin is pressed by the elastic deformation recovery force generated thereby, and the tips are brought into close contact with the cavity wall surface. In addition, the close contact is maintained under a pressing force that can oppose the injection pressure, and the occurrence of burrs due to the gap is prevented.

In the figure, reference numeral 1 denotes a movable mold, which is composed of an outer mold 2 and an inner mold 5 which is inside thereof and forms a single cavity 4 by a parting surface of a fixed mold 3.

The cavity 4 is provided with a plurality of punching pins 6 and 6 for forming through holes in the molded product. The pin 6 penetrates the inner mold 5 to reach the cavity wall surface by the parting surface of the fixed mold 3, and the flange 7 integrally formed at the rear end projects a required amount from the rear surface of the inner mold in the mold closed state. It consists of length.

Reference numeral 8 is a pressing plate for the pins 6 and 6, which is formed of a shape memory alloy having a required thickness. As this shape memory alloy, a TiNi alloy manufactured by Kobe Steel, Ltd. having material properties of shape recovery temperature of −10 to 100 ° C., tensile strength of 70 to 110 g / cm ² , and density of 6.4 g / cm ³ is adopted. be able to. This shape memory alloy has a superelastic characteristic in which a large deformation strain of several percent is restored in the shape recovery temperature range, and even if it deforms by 8 percent, it returns to its original shape upon unloading, When recovering the shape, a large recovery force of more than 30 kg / mm ² is generated.

The pressing plate 8 is provided in close contact between the outer die 2 and the inner die 5. By incorporating this pressing plate 8,
The rear end surfaces of the pins 6 and 6 and the rear end surface of the inner mold are aligned on the same plane, and the tip ends of the pins are positioned so as to protrude from the parting surface by an extra length in the mold open state.

In the figure, 9 is a knockout pin, 10 is a knockout plate, and 11 is a fixed type 3 sprue.

In the above embodiment, when the mold is closed, the tip is brought into contact with the cavity surface defined by the parting surface of the fixed mold 3 and pressure is applied. By this pressurization, the pressing plate 8 is compressed and deformed, and the pins 6 and 6 are pushed back to the parting surface by the protruding extra length to maintain contact with the cavity surface. The amount of deformation at that time is different for each pin.

Further, in the pressing plate 8, an elastic deformation recovery force corresponding to the amount of deformation is generated in the compression deformation portion in contact with each of the pins 6 and 6, and this acts as a pressing force of the pin 6,
While making the tip of the pin 6 adhere to the cavity wall surface,
Maintain close contact.

Therefore, even if there is a slight dimensional difference between the pins 6 and 6, the pins 6 and 6 are brought into close contact with the cavity wall surface by the elastic deformation recovery force generated according to the difference. It is possible to easily form the molded product 13 having the plurality of through holes 12 shown in FIG.

[0016]

As described above, the present invention provides the cavity 4
In an injection molding die having a plurality of punching pins 6 and 6 therein, the rear ends of the pins 6 and 6 being supported by a pressing plate 8 and the tips being in close contact with the cavity wall surface, Since the plate 8 is made of the shape memory alloy, the elastic deformation recovery force of the shape memory alloy allows each pin to be individually and surely brought into close contact with the cavity wall surface.

Further, since it is only necessary to form the pressing plate with a shape memory alloy and it is not necessary to perform the pin machining accuracy and the assembling accuracy as strictly as before, it is possible to save labor and apply to a small mold. Therefore, it can be used in a wide range, and the cost of the mold can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an injection molding die according to the present invention. FIG. 2 is a perspective view of a molded product having a plurality of through holes.

[Explanation of symbols]

 1 Movable mold 2 Outer mold 3 Fixed mold 4 Cavity 5 Inner mold 6 Drilling pin 7 Flange 8 Pressing plate

Claims (1)

[Claims] 1. An injection molding die having a plurality of punching pins in a cavity, the rear end of each pin being supported by a pressing plate, and the tip being in close contact with the cavity wall surface.
An injection molding die, characterized in that the pressing plate is formed of a shape memory alloy.