Process for the production of plates made of transparent plastic material with non-transparent overinjected parts

Abstract

Described herein is a process for the production of plates made of transparent plastic material with non-transparent overmoulded parts by means of a first direct injection and subsequent compression for the formation of the transparent plate, and a second injection for overmoulding said parts on the transparent plate, covering the indicators or witness marks of the first injection. Each injection can be in spots controlled in sequence, and the second injection can be followed by a respective step of post-compression.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a Continuation of U.S. Ser. No. 11 / 047,498, filed on Jan. 31, 2005, and titled “PROCESS FOR THE PRODUCTION OF PLATES MADE OF TRANSPARENT PLASTIC MATERIAL WITH NON-TRANSPARENT OVERINJECTED PARTS,” which claims priority from Italian application number TO2004A000702, filed on Oct. 11, 2004, the entire disclosures of which are incorporated herein by reference.[0002]This application also relates to U.S. patent application Ser. No. 11 / 047,480, filed on Jan. 31, 2005, and titled “AN APPARATUS AND A METHOD FOR THE INJECTION-COMPRESSION MOULDING OF ARTICLES MADE OF PLASTIC MATERIAL WITH TWO COMPONENTS,” now U.S. Pat. No. 7,462,316, issued on Dec. 9, 2008, the contents of which are incorporated herein by reference.[0003]This application also relates to U.S. patent application Ser. No. 11 / 047,500, filed on Jan. 31, 2005, and titled “A PROCESS FOR THE PRODUCTION OF PLATES MADE OF TRANSPARENT PLASTIC MATERIAL WITH NON-TRANSPARENT A...

AI Technical Summary

Benefits of technology

[0012]The purpose of the invention is to overcome the limitations imposed by film-injection systems and enable an efficient production of articles made of transparent plastic material, particularly but not exclusively plates, with parts of non-transparent material, as a continuous or discontinuous peripheral edge, having optimal aesthetic and optical properties.

[0015]moulding said transparent plastic material by means of injection-compression to limit the stresses on the injection spots generating said transparent plate with indicator of injection or witness mark; and

[0019]The injection of the transparent plastic material can advantageously be performed according to a particular sequential modality, and there is conveniently envisaged a step of compression not only at the end of the step of injection of the transparent plastic material, but also at the end of the step of injection of the non-transparent plastic material so as to reduce sensibly possible residual stresses of the plate.

Problems solved by technology

The transparent material, typically polycarbonate, is much more sensitive than other plastic materials to lines of flow, joints, etc., so much so that, as the dimensions of the products increase, the difficulties of injection are such that it is impossible to eliminate some typical aesthetic and optical defects unless very sophisticated injection systems are provided.

This system enables many of the problems typical of these transparent plastic materials to be solved but, as the dimensions increase, does not enable sufficiently high levels of quality to be achieved.

Furthermore, this type of injection involves cutting of the appendage of the film projecting from the moulded plate, said appendage having a non-negligible mass with respect to that of the product and involving an evident waste of material.

These stresses tend in fact to deform the product, altering its optical properties.

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