Patent ID: 6358446
Filing Date: 2002-03-19
Classification: B29C

Abstract:
A method of forming an article via injection of plastics material into a mould, the method consisting of the steps of:providing a mould tool defining in its closed state a mould cavity, the mould tool being adapted to be partially expandable from an injection volume for receiving a load of plastics material to a final, larger volume determining the finish formed shape of the article, the mould tool having at least one movable member, which is adapted to be withdrawn to increase the volume of the mould cavity, the difference in the injection and final volumes being represented by a void exposed in the mould cavity when the movable member is withdrawn. closing the mould tool to delimit the injection volume, injection into the injection volume a plastics material mixture comprising a basic polymer and a foam producing additive, withdrawing the movable member by means of an actuator which pulls back the movable member, in order to allow the plastics material to take up the shape of the final volume, and opening the mould and ejecting the finish formed article; wherein there is a delay between filing of the injection volume and withdrawing the movable member, and wherein the withdrawal is effected with substantially minimal delay on filling of the injection volume, whereby rapid expansion foaming occurs into the void on the withdrawal.