Moulding rubber undercut bellows shapes - by injection moulding preform without undercuts, placing this plus its core tool in final mould, extending core, inflating preform

摘要

Hollow elastomer mouldings, and bellows type sleeving in partic, are produced by injection moulding a preform round a mandrel whose o.d. diminishes lengthwise in steps, placing the preform plus mandrel in a heated mould of the desired external shape, stretching the mandrel axially, inflating the preform by compressed air from the gaps between the sections of the mandrel, and finally curing and demoulding. ADVANTAGE: The process is a simple way of producing such awkward shapes without (in partic) applying stresses on to them when demoulding which could damage them.