JP3065422U - Piston for valve gate - Google Patents

Abstract

(57) [Problem] To provide a piston for a valve gate which can use a piston ring made of a heat-resistant resin without changing a valve bushing even when molding a super heat-resistant resin. SOLUTION: This is a valve gate piston in which a piston is slidably disposed in a recess of a valve bushing formed between a mold plate and a manifold, wherein the piston is constituted by a piston main body and an adiabatic piston portion. The heat-insulating piston has a small cross-sectional area and a large heat-dissipating area.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a valve gate piston in a hot runner valve gate device for injection molding.

[0002]

[Prior art]

 FIG. 2 shows a main part of a conventional hot runner valve gate apparatus for injection molding of this kind, in which 1 is a template, 2 is a manifold, and 3 is a valve formed therebetween. 4 is a recess formed in the valve bushing 3, 7 is a resin flow path formed in the manifold 2, 8 is a pneumatic circuit for opening the gate, 9 is a pneumatic circuit for closing the gate, and 10 is a front surface of the piston 5. , A reference numeral 11 denotes a valve stem protruding from the spacer, 15 denotes a piston slidably disposed in the recess 4, and 16 denotes a piston ring mounted on the piston 15.

In such a device, the temperature of the sliding surface in the recess 4 of the bushing 3 on which the piston 15 slides during use is the temperature of the manifold 2 equal to the resin temperature and the temperature of the mold equal to the mold temperature. The temperature is between the temperature of the plate 1 and the temperature of the resin. In general, in the case of molding a general-purpose resin such as polyethylene, the resin temperature is 200 ° C. and the mold temperature is 20 ° C. Therefore, a normal O-ring is used as the piston ring 16.

[0004]

[Problems to be solved by the invention]

 However, when molding a heat-resistant resin, the resin temperature must be 350 ° C or higher and the mold temperature must be 170 ° C or higher.In such a case, it is necessary to use a piston ring consisting of an ordinary O-ring. become unable. Therefore, even if an O-ring made of heat-resistant resin is used as the piston ring, the piston 15 is connected to the piston 15 via the valve bushing 3 and the spacer 10 while the gate (not shown) is closed by the valve stem 11. There is a problem that the heat is transmitted to exceed the limit temperature of the heat-resistant resin, and the piston ring 16 becomes unusable.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional piston for valve gates and to keep the valve bushing unchanged even when molding a super heat resistant resin, and to provide a piston ring made of heat resistant resin. An object of the present invention is to provide a valve gate piston which can be used as it is.

[0006]

[Means for Solving the Problems]

 In order to achieve the object as described above, the invention according to claim 1 is directed to a valve slidably disposed in a recess of a valve bushing formed between a template and a manifold. In the gate piston, the piston comprises a piston base, a heat-insulating piston portion, and a heat-resistant resin piston ring, and the heat-insulating piston portion has a small vertical cross-sectional area and a large heat radiation area. .

According to a second aspect of the present invention, in the first aspect, a concave groove is formed in a front surface of the heat-insulating piston portion.

According to a third aspect of the present invention, in the first or second aspect, the piston ring made of heat-resistant resin is provided on an outer periphery of a joint between the piston body and the heat-insulating piston portion. It is characterized by the following.

[0009]

[Embodiment of the invention]

 In the embodiment of the present invention shown in FIG. 1, the same parts as those in the conventional example are denoted by the same reference numerals, and the description thereof will be omitted. The different parts will be mainly described. The piston 5 is composed of a piston base 12 formed of the same material as in the conventional example, a heat insulating piston portion 13 formed of a heat insulating material, and a heat-resistant resin piston ring 6 used in the conventional example. The overall thickness is not much different from that of the conventional piston 5, so that the heat-insulating piston portion 13 is thin and has a small cross-sectional area. The piston ring 6 is arranged on the outer periphery of the joint between the piston base 12 and the heat-insulating piston portion 13.

In such a structure, a concave groove 14 is formed on the front surface of the heat-insulating piston portion 13. In this embodiment, the concave groove 14 is formed by a plurality of linear grooves. It may have a shape, and the provision of such concave grooves 14 increases the heat radiation area.

When a synthetic resin container is molded by using such a hot runner / valve gate device equipped with the valve gate piston 5, the heat insulating piston portion 12 has a small cross-sectional area, so that heat conduction is prevented. Since the heat dissipation area is small and the cooling area by the compressed air is large due to the large heat radiation area, the valve bushing 3 can be used as it is, and the conventional piston ring 6 made of heat-resistant resin can be used as it is.

[0012]

[Effect of the invention]

 This invention is as described above, and the invention according to claim 1 is a valve gate piston slidably disposed in a recess of a valve bushing formed between a mold plate and a manifold. The piston is composed of a piston base, a heat-insulating piston portion, and a heat-resistant resin piston ring, and the heat-insulating piston portion has a small cross-sectional area and a large heat radiation area. A concave groove is formed on the outer surface of the part, and the invention according to claim 3 is based on the fact that the piston ring made of heat-resistant resin is disposed on the outer periphery of the joint between the piston base and the heat insulating piston part. Even when molding heat-resistant resin, there is an effect that a piston ring made of heat-resistant resin can be used as it is.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a conventional valve gate piston of the same type as the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold plate 2 Manifold 3 Valve bushing 4 Concave part 5 Piston 6 Piston ring 7 Resin channel 8 Compressed air circuit 9 Compressed air circuit 10 Spacer 11 Valve stem 12 Piston base 13 Heat-insulating piston part 14 Concave groove

Claims (3)

[Utility model registration claims] 1. A piston for a valve gate slidably disposed in a recess of a valve bushing formed between a mold plate and a manifold, comprising: a piston base; a heat-insulating piston; The heat-insulating piston section has a small cross-sectional area,
A valve gate piston characterized by a large heat dissipation area. 2. The valve gate piston according to claim 1, wherein a concave groove is formed in a front surface of the heat insulating piston portion. 3. The valve gate piston according to claim 1, wherein the heat-resistant resin-made piston ring is provided on an outer periphery of a joint portion between the piston base and the heat-insulating piston portion.