JPH02136213A - Runnerless injection molding method and apparatus for elastomer - Google Patents

Abstract

PURPOSE:To perform mold opening operation in such a state that a molding is adhered to a movable mold by easily releasing the molding from a fixed mold by releasing the vacuum close adhesion state of the fixed mold and the molding through the fitting part formed to the cavity corresponding place of the fixed mold. CONSTITUTION:A molten resin stock hardly releasable from an elastomer is injected in a cavity 3 having a desired shape from a runner part through a gate 6 by injection molding operation to fill the cavity 3 and, subsequently, the resin stock in the gate 6 is cooled and solidified to close the gate 6. Further, the resin in the cavity 3 is cooled and solidified while a movable mold 5 is retracted to open the cavity 3 and, at this time, vacuum release making the release of a molding from a fixed mold 4 possible is performed through the fitting part 15 formed to the place corresponding to the cavity 3 of the fixed mold 4 to hold the molding to a movable mold 5 and the molding is taken out of the movable mold 5 by the action of a protruding plate 17 in the return process of the mold 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a runnerless injection molding method for elastomers and an apparatus therefor, which are suitable for molding elastic polymeric materials such as elastomers.

[Conventional technology]

Conventionally, a gasket 1a for a syringe has a cap shape as shown in FIGS. 1(a) and 1(b).

When 1b is densely molded using an elastic polymer material called elastomer, the adhesion with the mold is extremely strong, so it is mainly used as an unvulcanized sheet-like raw material, similar to vulcanization molding of rubber products. is housed in a mold with a multi-cavity configuration,
After heating and vulcanization molding and releasing the mold, a single molded product is obtained by punching or the like.

In addition, when molding using injection molding equipment, the molded product has an elastic effect, has strong adhesion to the mold, and is difficult to release, so the sprue runner method is exclusively used, and after release from the mold, In order to obtain a molded product for one piece, a complicated process is performed to cut out the sprue runner.

[Problem to be solved by the invention]

As described above, with conventional technology, there is no method or equipment for efficiently manufacturing elastic polymers such as elastomers that have elastic properties, and even when injection molding is used, which is said to be efficient, there are still residual materials called sprue runners. It was considered impossible to create a so-called runnerless injection molding method or device that eliminates the runner.

That is, even if the gasket 1a is equipped with the undercut 2 protruding from the inner periphery as shown in FIG.
Even if the movable mold is moved and released after the molding operation, there is a problem in that the molded product comes off from the movable mold and remains stuck in the fixed mold, resulting in an abnormal state where it cannot be pushed out.

(Means for Solving the Problems) The present invention has been made by focusing on the above-mentioned points.
The purpose of the present invention is to provide a new runnerless injection molding method and apparatus that can be carried out efficiently by runnerless injection molding, eliminate waste of materials, and enable high-grade molding.

That is, in this invention, a molten resin raw material such as an elastomer is injected and filled into a cavity of a desired shape from a runner part through a gate by an injection molding operation, and then the resin raw material in the gate part is cooled and solidified to close the gate. In addition to cooling and solidifying the resin in the cavity, when the movable mold is retreated to open the cavity, a vacuum is created that allows the mold to be separated from the fixed mold through a fitting part formed in a portion corresponding to the cavity of the fixed mold. A runnerless injection molding method for elastomers, characterized in that the molded product is held in the movable mold by releasing the mold, and the molded product is taken out during the return movement of the movable mold by the action of an ejector plate, and further A runner part that holds a molten resin raw material such as an elastomer in a heated molten state, a narrow gate that leads from the runner part to the cavity, a gate opening/closing means that can open and close the gate by cooling and solidifying the resin raw material in this gate part and heating and melting it. A mold means comprising a fixed mold and a movable mold capable of forming a gate is provided, and a part of the mold means that communicates with the cavity of the fixed mold is provided with mold release for vacuum tight contact between the molded product molded in the cavity and the fixed mold. The present invention relates to a runnerless injection molding apparatus for elastomer, characterized in that it is provided with means for facilitating mold release. The mold release means in this invention uses the space formed along the outer periphery of the gate as a gas reservoir, which can communicate through the fitting part between the cavity and the mold gap, and is used as a gas vent during molding, and during the dawn molding. This is characterized in that the vacuum can be released by supplying gas.

[Effect]

According to a desired injection molding operation, a molten resin such as an elastomer is injected and filled into the cavity from the runner section through the gate.

After the IfB resin in the gate part is cooled and solidified by the gate opening/closing means provided in the gate part, the resin is uncoupled at the gate part, and the resin in the cavity is solidified, the mold opening operation is performed.

In this case, the mold release means is activated by the mold gap leading to the cavity from the fixed mold, and the vacuum tendency that occurs between the molded product and the fixed mold when the mold is opened completely disappears, and the molded product is strongly connected to the fixed mold. The adhesion is released, and the mold is taken out in its normal state with adhesion to the movable mold, and in the process of movement, it is easier to obtain individual molded products than with a fixed mold.

Furthermore, when the S-shaped means is gas supply, the turf effect between the molded product and the fixed mold can be improved more than when a mold gap is simply formed.

After the molded product is removed, the movable mold is moved back so that a cavity can be formed between it and the fixed mold, and the injection molding operation is performed again to perform similar runnerless injection molding.

(Example) Two embodiments of the invention will be described below with reference to the drawings.

3 shows a cavity of a gasket la for a syringe molded from the elastomer material shown in FIG. 1(a), and is formed by a fixed mold 4 and a movable mold 5.

This fixed mold 4 includes a cage 6 that communicates with the cavity 3.
and a gate opening/closing means 7 that can locally melt or solidify the resin of the gate 6.

The gate heating means 7 has either an internal heating method shown in FIGS. 2 to 5 or an external heating method shown in FIGS. 6 to 9. Also,
A runner part 8 is provided next to the gate 6, and a runner heating means 9 for heating the runner part 8 is configured by an internal heating method or an external heating method, similar to the fermentation gate opening/closing means 7. .

Reference numeral 10 denotes a gas reservoir in a conical space arranged along the periphery of the gate 6 in the fixed mold 4, and is arranged around a nozzle-shaped mold piece 11 and the outer periphery of this mold piece 11. A gas inlet pipe 13 and a gas outlet pipe 14 are formed between the concave part 12 and the concave part 12 communicating with the energy saving part 3 . The inlet pipe 13 is connected to a desired compressor, etc., so that the compressor can be operated to supply high-pressure gas in connection with the injection molding operation. Reference numeral 15 denotes a fitting portion between the tip of the mold piece 11 and the cavity 3 of the concave portion 12, which corresponds to a so-called mold gap, and enables gas removal during injection molding and gas supply during mold release.

Although the depth e of this fitting portion 15 does not necessarily need to be specified, it may be approximately 0.01 to 0.02+am, and the structure is such that the resin does not enter.

In the figure, 15 is a sealing part between the mold piece 11 and the fixed mold 4, 16 is a recess made in the movable mold 5 in order to form the undercut 2 of the gasket 1a, and 17 is a part of the molded product from the movable mold 5. The protruding plates for removal are shown respectively.

Here, the gate opening/closing means 7 and the runner heating means 9
In the case of the internal heating method (Figs. 2 to 5), the F! , +4 hot runner probe 20, and in the case of the external heating method (FIGS. 6 to 9), the narrow part 21 forming the gate 6 and the body forming the runner part 8 are used. It is equipped with a cylindrical hot runner body 23 consisting of a tube part 22, and each part 21 and 22 is provided with a nichrome wire 2, for example.
4 etc. can be wound and heated.

The C1 effect will be explained based on the structure of the chart.

Molten elastomer resin injected by a desired known injection mechanism is injected and filled into the cavity 3 in the state shown in FIGS. 2 and 6.

During this injection and filling, the gas in the cavity 3 is pushed out through the fitting part (mold gap) 15 into the gas reservoir lO of the fixed mold 4, so-called degassing is performed, and a complete injection operation is completed.

The elastomer for cavity 3 is obtained as a molded product that conforms to the shape of cooling assimilation tongue and cavity 3, but since the molded product is an elastomer, fixed molds 4 and 6
Close contact with dynamic type 5 is strong.

(See Figures 3 and 7) In addition to cooling and assimilating the molded material in the cavity 3, the gate opening/closing means 7 of the gate 6 melts the molten resin at the gate 6 by heating and changes its action to cooling and solidification. , Tokoro 3i1,
The gate 6 is made of solidified resin and is in a closed state, completing preparations for the next mold opening operation.

Prior to the mold opening operation, if a desired gas is supplied from the gas reservoir 10 to the cavity 3, it will pass through the fitting part 15 and move along the joining line t between the molded product and the inner surface of the cavity 3 of the fixed mold 4 as shown in FIG. , the molded product adhered to the movable mold 5 by working in the state shown in FIG. In addition to being able to take out the molded product to the outside in a state in which the movable mold 5 is moved, it can be obtained by peeling off the molded product that is firmly attached to the movable mold 5 by the ejecting plate 17 during the movement of the movable mold 5.

As described above, one molding operation is completed by taking out the molded product, but the movable mold 5 is moved again to form the cavity 3 with the fixed mold 4 and the mold is in a clamped state, and the gate opening/closing means 7 is used to close the gate part. When the resin that has been cooled and solidified by locally heating is heated and melted, and the so-called gate 6 is opened and an injection operation is performed, the molten resin flows from the runner section 8 through the gate 6 into the cavity 3. is injection filled.

(See FIGS. 2 and 3) Subsequently, continuous injection molding operations can be performed through the same process.

Two embodiments of the present invention have been described above, but in particular, the gas reservoir 10 can be formed by simply forming a space and even if the structures such as the inlet pipe 13 and the outlet pipe 14 communicating with the high pressure gas are omitted, Of course, it can be carried out satisfactorily by softening the adhesion to the object.

(Effect of the invention) In general, when using an elastic polymeric material such as an elastomer as a raw material, when the molten resin injected into the cavity is cooled and solidified, the molded product is divided into a fixed mold, a movable mold, and a strong However, according to the present invention, the molded product remains firmly attached to the fixed mold and detaches from the movable mold when the mold is opened. Since a mold release means is provided which can release the vacuum contact with the fixed mold, the molded product can be released from the mold more easily than the fixed mold and can be opened while attached to the movable mold.

Moreover, the mold release means is extremely simple and efficient because the vacuum between the cavity and the molded product is released through a gas reservoir provided in the fixed mold and a fitting part that communicates with the fixed mold's carrier and tee. It has the effect of

Further, according to the present invention, there is no waste of material compared to conventional manufacturing methods, so resources can be saved, costs can be reduced, and molded products can be provided at low cost.

[Brief explanation of the drawing]

FIGS. 1(a) and 5(b) are partially cutaway side views of two types of syringe gaskets made of elastomer molded products obtained by carrying out the present invention, and FIGS. 2 to 5 are views according to the present invention. An explanatory diagram of a four-stage molding process showing the structure of a main part of a runnerless injection molding apparatus for elastomers in cross section, FIGS. 6 to 9 are main parts of a runnerless injection molding apparatus for elastomers according to other embodiments of the present invention. It is an explanatory diagram of a four-stage molding process showing the structure in cross section. a 1b... Gasket 2 for syringe...
Undercut 3...Cavity 4...Fixed type 5...Movable type 6...Gate 7...Gate opening/closing means 10... ...Gas reservoir 15...Fitting part

Claims (3)

[Claims] (1) The molten resin raw material of the elastomer is injected and filled into the cavity of the desired shape from the runner part through the gate by injection molding operation, and then the resin raw material in the gate part is cooled and solidified to close the gate and the resin in the cavity is filled. At the same time, when the movable mold is retreated to open the cavity, the vacuum is released to enable the mold to be separated from the fixed mold through a fitting part formed at a location corresponding to the cavity of the fixed mold. A runnerless injection molding method for elastomers, characterized in that the molded product is held in a movable mold, and the molded product is taken out during the return movement of the movable mold by the action of an ejector plate. (2) A runner part that holds molten resin raw material such as elastomer in a heated and molten state, a narrow gate that leads from this runner part to the cavity, and a gate that can open and close the gate by cooling and solidifying the resin raw material in this gate part and heating and melting it. means, a mold means consisting of a fixed mold and a movable mold capable of forming the gate, and a part of the mold means communicating with the cavity of the fixed mold for vacuum-adhering the molded product to be molded in the cavity and the fixed mold. A runnerless injection molding apparatus for elastomer, characterized in that it is provided with a mold release means for facilitating mold release. (3) The mold release means uses the space formed along the outer periphery of the gate as a gas reservoir that can be communicated through the fitting part between the cavity and the mold gap, and is used for gas release during molding and gas supply during mold release. 3. The runnerless injection molding apparatus for elastomer according to claim 2, wherein the runnerless injection molding apparatus for elastomer is capable of releasing the vacuum by performing the following steps.