Abstract: In an injection moulding process for forming hollow preforms on a mandrel which is subsequently used as a blowing pin for blowing the preforms to the final shape in a blow mould separation of the preform from the mandrel during cooling of the preform from the injection temperature is prevented by applying a vacuum to the blowing channel in the mandrel before the injection pressure is released.

Abstract: An injection moulding apparatus having an injection mould and a mandrel insertable within the mould is provided with frustoconical co-operating surfaces on the mandrel and mould respectively which are adapted to engage with one another when the mandrel is inserted in the mould. A sliding connection is provided between the mould and its carrier so that the engagement of the conical surfaces can effect alignment of the axis of the mould with the axis of the mandrel. A locking device is provided for locking the mould to the carrier together with a locking control mechanism which releases the locking device as the conical surfaces approach one another and locks the mould to the carrier when the conical surfaces are fully engaged.

Abstract: A manifold for dividing a stream of plasticised material into a plurality of sub-streams as a main channel terminating in an inwardly tapering end wall. A plurality of sub-channels are symmetrically arranged in the inwardly tapering end wall and are provided with transition passages inwardly tapering away from the main channel, adjoining transition passages intersecting to form intersection edges havin knife like edges facing the main channel. The vertex angle of the inwardly tapering end wall and of the transition passages is less than 90.degree. and where there are three or more sub-channels the end wall of the main channel merges substantially tangentially with the intersection edges. A manifold is particularly useful for dividing a main stream of heat sensitive plasticized material such as PVC into a plurality of sub-streams.