Two-layer foam injection molding machine

Details Two-layer foam injection molding machine Two-layer foam injection molding machine

1996-06-27

1998-06-30

Heitbrink, Tim

Plastic article or earthenware shaping or treating: apparatus

Female mold and charger to supply fluent stock under...

With coupling between charger and mold

264255, 2642972, 2643288, 425574, 425576, B29C 4516

Patent

active

057730490

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a two-layer foam injection molding machine for obtaining, by means of injection molding, composite foam moldings in which a surface member having a skin layer on a surface of a cushiony foam layer is formed in a body on one side of a core member made from a hard resin and more particularly to a machine which provides two-layer foam moldings having a desirable touch and surface continuously and efficiently under control of foaming states of a foaming resin.
2. Description of Related Art
As a foam injection molding method for obtaining two-layer foam moldings of this type, one disclosed in Japanese Patent Publication No. 51-8424 has been known. This method provides two-layer foam moldings having a skin layer cold-set on a surface of a mold and a foam layer formed within molds by injecting a foaming resin containing a foaming agent into a space of the molds held to be openable and then foaming the resin by expanding the space by opening the molds. With regard to this two-layer foam injection molding method, however, although a circuit structure for changing a mold opening speed per injection by providing a flow regulating valve in a mold opening hydraulic circuit is disclosed in the above-mentioned Patent Publication, no means for changing the mold opening speed during injection is disclosed.
In recent years, this two-layer foam injection molding method has come to be applied to mold interior panels of cars because it allows a yield of the resin to be kept high and to be able to mold continuously as compared to methods in which the skin layer is molded separately by a vacuum molding or the like.
The car interior panels are required to have a soft surface having a soft touch. A selection of a proper material is also important to obtain such a touch, and a thermo-plastic elastomer which has a rubber-like elasticity in normal temperature and which is plasticized and can be injection-molded in high temperature has come to be used as a material for forming the skin layer and the foam layer.
When the prior art two-layer foam injection molding method was applied to mold the thermoplastic elastomer, however, no moldings having a desirable touch and surface condition could be obtained because a foam expansion ratio or foam cell size was not adequate.
Due to that, a foam injection molding method which can maintain an adequate foam expansion ratio or foam cell size and can provide foam moldings having a desirable touch has been studied. Then, based on findings obtained through numerous experiments, the applicant of the present application has devised and applied a two-layer foam injection molding method which can provide foam moldings having foam cells in an adequate size and an adequate expansion ratio as well as a soft touch and an excellent surface condition whose crimp or crepe pattern transfer is good by controlling a foaming process by changing a mold opening speed (space expanding rate) during injection (Japanese Patent Application No. Hei. 5-257781).
To obtain such two-layer moldings efficiently, it is preferable to use a two-layer foam injection molding machine which can injection-mold two-layer moldings in which two kinds of different materials or different color resin materials are laminated by one machine as disclosed in Japanese Patent Publication No. Hei. 3-51207.
The two-layer foam injection molding machine in the above-mentioned Patent Publication is provided with a rotary plate between a fixed plate and a movable plate to perform primary molding between the fixed plate and the rotary plate and secondary molding between the rotary plate and the movable plate, respectively. That is, a primary molding is obtained by injecting a resin into primary molds between the fixed plate and the rotary plate and then a two-layer secondary molding is obtained by turning the rotary plate by 180.degree. and by injecting another resin into secondary molds, where the primary molding exist, between the rotary plate and the fixed plate. A

REFERENCES:
patent: 4734023 (1988-03-01), Nesch et al.
patent: 5030406 (1991-07-01), Sorensen

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