JPH0222259Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold for molding plastic or metal.

Conventionally, in order to obtain a molded part as shown in FIG. 1, a mold shown in FIG. 2, for example, is used. 1 is a lower mold that forms the outside of the molded product, and 2 is an upper mold that forms the inside of the molded product.The molding material 3 is injected between the upper mold 2 and the lower mold 1 (a in the same figure). ), a molded product is obtained by pressing the upper mold 2 onto the lower mold 1 from above (see figure b).
However, in this type of mold, if there is a slight gap between the contact portion 4 of the upper mold 2 and the lower mold 1, burrs will occur in the molded product obtained. Therefore, it is important to make the mold contact surface smooth and to accurately align the upper mold 2 and the lower mold 1, and this requires a large amount of work.

The purpose of this invention is to eliminate the above-mentioned conventional drawbacks, and to provide a molding die that has a simple structure, prevents the occurrence of burrs, and reduces the burden on the work. be.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a side sectional view of one embodiment of the molding die of the present invention. The difference from FIG. 2 is that a sealing material 5 made of a shape memory alloy is interposed between the contact portion 4 of the upper mold 2 and the lower mold 1. For shape memory alloys
There are Ti-Ni alloy, Cu-Zu-Al-Ni alloy, etc.
When these alloys are heated above the transformation end temperature (Af point) from the martensitic phase to the parent phase, they exhibit a so-called pseudoelastic effect, which allows them to return to their original shape when the stress is released, even if they undergo large strain deformations due to the application of stress. has. FIG. 4 is a graph of stress-strain characteristics showing the pseudoelastic effect of shape memory alloys.

When the upper mold 2 is pressed against the lower mold 1 in Fig. 3b, the sealing material 5 is at a high temperature (above point Af).
Becomes under high pressure. At that time, the sealing material is deformed and a stress-induced martensitic phase is induced. Since the shape memory alloy becomes extremely soft in the state of stress-induced martensitic phase, it deforms according to the surface irregularities at the abutting portion of the upper mold 2 and the lower mold 1, thereby eliminating the gap. When molded using the above-mentioned molding die, a high-quality product can be produced without burrs. After the molding process, if the upper mold 2 and lower mold 1 are separated, the sealing material 5
Since the stress applied to the sealing material 5 is removed, the sealing material 5 returns to its original shape due to the pseudoelastic effect. In this way, the sealing material 5 repeatedly deforms and recovers each time pressure is applied by the molding die, so that it can be used repeatedly without needing to be replaced.

As explained above, according to the present invention, it is possible to obtain a molding die that is convenient for work and can prevent burrs with a simple structure.

[Brief explanation of drawings]

Figure 1 is an external perspective view of a molded product, Figure 2 is a side sectional view of a conventional mold, Figure 3 is a side sectional view of an embodiment of the mold of the present invention, and Figure 4 is stress in shape memory alloy. A distortion characteristic graph diagram is shown. In the figure, 1: lower mold, 2: upper mold, 3: molding material, 4: contact part, 5: sealing material.

Claims (1)

[Scope of utility model registration request] A molding die characterized in that a sealing material made of a shape memory alloy is interposed at the abutting portion of an upper die and a lower die.