JPH0157648B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a runnerless injection molding method and a runner chip body that can be used in this method.

[Prior art]

In the past, the inventions developed by the present inventor, such as those disclosed in Japanese Patent Publication No. 48-5093 and Japanese Patent Publication No. 51-38936, have been widely known and have been implemented on a global scale by companies related to the present inventor. There is. As shown in FIG. 3, the basic configuration of this prior art is that a heating element 4 is placed near the gate 2 of the molds 1, 1, that is, on the gate land 3, and the heating element 4 is made to generate heat each time an injection molding operation is performed. The molding resin near the gate 2 is locally heated and melted to open the gate 2 to enable the injection molding operation.After this molding operation, the heat generation of the heating element 4 is stopped and the molding resin near the gate 2 is melted. is locally cooled and solidified, and the gate 2 is closed to complete a series of injection molding operations.

In other words, the resin in the vicinity of the extremely narrow gate 2 is locally heated using an extremely small heating element 4 to instantaneously melt, cool, and solidify the resin. It is extremely effective in preventing poor moldability and deterioration in quality and enabling precision molding equivalent to precision molding with a sprue runner.

In contrast to such conventional technology, the present inventor further replaced the resin near the gate 2 with the above-mentioned heating element 4 and installed another heating means (not shown) in the mold to locally heat the area around the gate 2. A cooling means for electrically heating or forced cooling is provided.
A thin tube is formed around the gate 2 or inside a bullet-shaped runner chip 5 with a heating element 4 at the tip, and air or other refrigerant is supplied to the runner chip 5 to forcibly displace the molten resin at the same time as the heating element 4 stops generating heat. Improvements were made by providing a cooling effect to effectively close gate 2.

In the runnerless injection molding method using a heating means such as the conventional heating element 4, the heating means can be operated extremely effectively by active control, and the solidified resin near the gate 2 can be heated. While it is possible to efficiently melt the gate 2 and open the gate 2, it is necessary to use a cooling means such as heat dissipation from a heating means such as a heating element 4 or a separately provided forced cooling mechanism. The former method of heat dissipation has the problem that the molten resin cannot be forcibly cooled and solidified, while the latter method of forced cooling has the problem of complicating the structure.

[Summary of the invention]

This invention was made by focusing on the above points, and it is arranged in the vicinity of an extremely narrow gate and does not get in the way, and has a simple structure that allows forcible heating and cooling. The object of the present invention is to obtain a new runnerless injection molding method and a runner chip body.

That is, this invention arranges a joint of dissimilar metals near the gate leading to the cavity of the mold,
By changing the direction of current flow through dissimilar metals, forced control of heating and heat absorption based on the Peltier effect is performed at the joint, which melts and solidifies the accumulated resin near the gate, making it possible to open and close the gate with extreme precision. To obtain a runnerless injection molding method and a runner chip body which can efficiently carry out precision molding and high quality molding.

In addition, the present invention allows the dissimilar metal junction exhibiting the Peltier effect to be placed in the vicinity of the gate, facing the gate land portion, or filled in the outer periphery of the gate in the mold forming the gate, or in any desired configuration. An object of the present invention is to provide a runnerless injection molding method in which a molding operation is performed by alternately heating and melting the resin near the gate and cooling and solidifying it.

〔Example〕

Examples of the present invention will be described below with reference to the drawings.

Note that the same reference numerals are given to the same or corresponding parts as in the conventional example, and detailed description thereof will be omitted.

Reference numeral 6 denotes a joint between two types of metals 7 and 8 provided at the conical sharp end of the runner chip body 5, for example,
Dissimilar metals such as bismuth and tellurium, antimony,
It is a joining point between different metals such as bismuth.

Therefore, when a current is passed between metal 7 and metal 8, a Peltier effect occurs that generates or absorbs heat depending on the direction of the current, heating or cooling the resin near the gate 2. The gate 2 can be opened and closed to allow a series of injection molding operations to be performed.

9 is a switching mechanism such as a switch capable of switching the direction of current flow to the metals 7 and 8;
10 is a timer that controls the switching mechanism 9; 11 is a manifold; 12 is a heating cylinder of the injection molding machine; 13
1 and 2 respectively indicate the nozzles, and, in common with FIG. 3, numeral 14 indicates a runner portion and numeral 15 indicates a cavity.

Incidentally, the runner chip body 5 may have a built-in auxiliary heater for keeping the resin of the runner portion 14 in a molten state at all times.

The operation of this invention will be explained based on the above configuration.

First, all conditions necessary for injection molding are provided by known means.

Before the injection molding operation, the timer 10 is activated, and when electricity flows from one metal 7 to the other metal 8 via the switching mechanism 9, the joint 6 generates heat (or absorbs heat) due to the Peltier effect.

When the direction of current flow is reversed by the switching operation of the switching mechanism 9, the joint 6 absorbs heat (or generates heat).

Therefore, the molding resin near the gate where the joint 6 faces is melted when the joint 6 generates heat due to the Peltier effect, the gate 2 is opened, and the resin is melted in advance by the injection operation of the injection molding machine. The resin in the runner section 14 and manifold 11 is injected into the cavity 15 through the gate 2 to complete the injection operation.

When the switching mechanism 9 reverses the direction of current flow to the metals 7 and 8, the joint 6 is endothermically cooled by the Peltier effect and the molten resin near the gate 2 is cooled and solidified, so the gate 2 is closed. After the mold opening operation, the molded product inside the cavity 15 can be taken out.

By continuously performing this series of molding operations, a highly accurate and highly efficient runnerless injection molded product can be obtained.

Although one embodiment of this invention has been described above, the joint 6 of two different metals 7 and 8 can be placed in the vicinity of the gate 2 as well as in the flow path of the molten resin as in this embodiment. 2 (not shown).

〔Effect of the invention〕

According to this invention, not only is the resin accumulated in the vicinity of the gate portion forcibly heated and melted, but also the cooling operation is also forcibly performed, so that the opening and closing operations of the gate can be performed with a crisp operation. , the processing accuracy of molded products can be significantly improved, the molding cycle can be shortened, and highly efficient manufacturing can be expected. Furthermore, since there is no sprue runner, it is possible to eliminate waste of resin raw materials, and has many other effects.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway sectional view of the main parts of an embodiment of the runnerless injection molding method according to the present invention, Fig. 2 is an enlarged explanatory view of the same main parts, and Fig. 3 shows the conventional manufacturing method. FIG. DESCRIPTION OF SYMBOLS 1, 1...Mold, 2...Gate, 4...Heating element, 5...Runner chip body, 6...Joint part of dissimilar metals 7 and 8.

Claims (1)

[Scope of Claims] 1. The thermoplastic resin for molding existing near the gate of the mold is melted and solidified alternately by heating action based on the Pelletier effect and endothermic action each time an injection molding operation is performed to form the gate. A runnerless injection molding method characterized by opening and closing. 2. A runner chip body characterized in that a joint part of different metals is provided at the tip of a runner body vertically mounted on a sprue part, and this joint part is made to face near the gate of a mold.