JPH04223120A - Injection mold - Google Patents

Abstract

PURPOSE:To surely abut a hot runner nozzle by proper pressurizing force by a method wherein the characteristics of shape memory alloy are utilized for abutting. CONSTITUTION:In the injection mold concerned having a plurality of cavities 4, against the gate 9 of each of which a hot runner nozzle 8 is abutted, said hot runner nozzle 8 is made of shape memory alloy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold having a plurality of cavities and a hot runner nozzle.

0002

[Prior Art] An injection mold with multiple cavities is equipped with a block with hot runners that guide molten resin from the center of the mold to each cavity. A nozzle is provided to abut the gate of each cavity.

0003

[Problem to be Solved by the Invention] Except in special cases, the hot runner nozzle is brought into contact by inserting a plate between the back of the hot runner block and the mold mounting plate. Problems tend to occur with the contact force of the nozzle, and if the contact force is weak, resin leakage will occur.

[0004] Naturally, there is a slight difference in the protrusion size from the hot runner block among the plurality of nozzles. This difference in protrusion size is corrected before assembly into the mold, but since the difference is extremely small, correction is time-consuming and requires skill, which is a problem that needs to be solved.

[0005] This invention was devised to solve the above-mentioned conventional problems, and its purpose is to utilize the elastic deformation recovery force of shape memory alloys to achieve a structure that is not affected by the difference in the protruding dimensions of the nozzle. Another object of the present invention is to provide a new injection mold that can ensure nozzle contact under moderate pressure.

[0006]

[Means for Solving the Problems] The feature of the present invention according to the above object is to provide an injection mold having a plurality of cavities and a hot runner nozzle in contact with the gate of each cavity. It is made of a shape memory alloy.

[0007]

[Operation] In the above configuration, the nozzle made of shape memory alloy
The pressurizing force at the time of contact compresses and deforms the material to make it come into close contact with the gate of each cavity, and the elastic deformation recovery force maintains this contact under sufficient contact force.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the figure, reference numeral 1 denotes a stationary mold, which has a plurality of cavities 4, 4 of the same shape in its parting portion to be closed with a core mold 3 of a movable mold 2.

Reference numeral 5 designates a hot runner block in the fixed mold, in which the same number of hot runners 7,
7 is perforated.

[0010] At the tip of each hot runner 7, 7,
The hot runner nozzles 8, 8 with flat tips made of a shape memory alloy are used by screwing or other means.
The protrusion dimensions are the same.

[0011] As this shape memory alloy, a Ni (nickel)-Ti (titanium) alloy or the like is used. This shape memory alloy has superelastic properties that allow it to return to its original shape after a large deformation strain of several percent at a given temperature, and even after being deformed by 8 percent, it completely returns to its original shape upon unloading. It sometimes generates a large recovery force exceeding 30 kg/mm2.

[0012] The hot runner nozzles 8, 8 are brought into contact with the cavity gates 9, 9 by inserting a plate 11 of a required thickness between the back surface of the hot runner block 6 and the mold mounting plate 10. Therefore, each hot runner nozzle 8,8
The flat end surface of the nozzle is strongly pressed against the wall surface surrounding the cavity gate, and the nozzle itself is compressively deformed by the pressure within a range that does not prevent injection of the molten resin.

[0013] Due to this compressive deformation, the plurality of hot runner nozzles 8, 8 come into close contact with each other, and since the elastic deformation recovery force acts as a contact force, the close contact is maintained under sufficient pressure. Completely prevents resin leakage during injection.

In the figure, 12 is a knockout pin, 13 is a knockout pin, and 13 is a knockout pin.
is the mold mounting plate on the movable mold side.

[0015]

Effects of the Invention As described above, since the hot runner nozzles 8, 8 are formed of a shape memory alloy, the present invention utilizes the elastic deformation recovery force of the shape memory alloy.
The nozzle can be brought into close contact with the cavity gate with sufficient pressing force, and resin leakage will not occur due to the weak contact force.

Furthermore, even if there is a slight difference in the protruding dimensions of each hot runner nozzle, the difference will be naturally corrected depending on the degree of compressive deformation of each hot runner nozzle. There is no need to align.

Furthermore, since the hot runner nozzle is simply formed of a shape memory alloy and there is no need to take any other special measures, it has the advantage that it can be immediately applied to injection molds of conventional structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal cross-sectional view of an injection mold according to the present invention.

[Explanation of symbols]

1 Fixed mold 2 Movable mold 3 Core type 4 Cavity 5 Hot runner block 6 Sprue bush 7 Hot runner 8 Hot runner nozzle 9 Cavity gate 10 Type mounting plate 11 Plate body 12 Knockout pin 13 Mold mounting plate for movable mold

Claims (1)

[Claims] 1. An injection mold having a plurality of cavities and a hot runner nozzle in contact with the gate of each cavity, characterized in that the hot runner nozzle is made of a shape memory alloy. Mold for injection molding.