Moulding plastics article by varying cyclically its composition

In a method of molding plastics articles, each said article having at least one predetermined part of different composition from the remainder of the article, the method comprising passing a solid plastics feed material through a melting zone, propelling a quantity of the resultant molten material into a mold, allowing the plastics material to solidify, and removing the article from the mold, wherein the composition of the materials entering the mold is varied cyclically, the improvement comprising monitoring progress of materials through the melting zone and controlling the sequence of feeding of first and second feed materials in response thereto so as to provide in the feed material entering the melting zone, at a position remote from the mold, sequential layers of first and second materials, the size and spacing of the layers being chosen such that the first and second materials form predetermined parts of each molded article.

Apparatus for molding plastics articles, each said article having at least one predetermined part of different composition from the remainder of the article, the apparatus comprising an injection device including screw feed means for propelling a solid plastics material through a melting zone, and for propelling the resultant molten plastics material to shaping means for shaping the molten material, including control means for monitoring the positions of said screw feed means and for controlling the introduction of different feed materials into said screw feed means at a location remote from said shaping means according to the instantaneous monitored position of said screw feed means so as to cyclically vary the composition of the plastics material entering the shaping means, whereby the composition of the material entering the shaping means is controlled to form said at least one predetermined part of the molded article of different composition from the remainder of the article.

Apparatus for molding plastics articles, each said article having at least one predetermined part of different composition from the remainder of the article, the apparatus comprising an injection device for passing a solid plastics material through a melting zone, and for propelling a quantity of the resultant molten material into a mold, including, at a position remote from the mold, means for monitoring progress of materials through the melting zone and for controlling the sequence of feeding of first and second materials in response thereto so as to provide in the material entering the melting zone sequential layers of said first and second materials, the size and spacing of the layers being chosen such that said first and second materials form predetermined parts of each molded article.