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Method of operating a two-shot injection-molding machine

  • US 4,444,711 A
  • Filed: 12/21/1981
  • Issued: 04/24/1984
  • Est. Priority Date: 12/21/1981
  • Status: Expired due to Term
First Claim
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1. A method of operating a two-shot injection-molding machine to produce composite articles each having one part of a relatively flexible modified rubber with a tendency to cling to a mold cavity during an extended hardening period and further having another part of a relatively rigid and more rapidly hardening plastic material adjoining said one part, comprising the steps of:

  • (a) injecting said modified rubber into a first cavity formed at one station of the machine between a primary mold portion and a secondary mold portion juxtaposed with each other, thereby producing a first workpiece section;

    (b) retaining said first workpiece section on said primary mold portion while removing said secondary mold portion therefrom to expose a major surface of said first workpiece section while letting same cool;

    (c) juxtaposing a tertiary mold portion at another station of the machine with said primary mold portion to form a second cavity bounded by said major surface of the first workpiece section;

    (d) injecting said relatively rigid plastic material into said second cavity to produce a second workpiece section adhering to said first workpiece section along said major surface;

    (e) allowing said second workpiece section to cool with further cooling of said first workpiece section;

    (f) thereafter separating said tertiary mold portion from said primary mold portion; and

    (g) gradually pulling said second workpiece section away from said primary mold portion at a controlled rate slow enough to maintain the coherence of the entire workpiece.

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