GB767515A - Improvements in or relating to the manufacture of preforms for moulding - Google Patents

Abstract

A continuous method for the manufacture of glass fibre/plastic preforms for moulding comprises (i) moving a master form stepwise in a closed circuit and subjecting it between successive movements and at predetermined locations in the circuit to the operations (ii) of coating with a mixture of glass fibre and resinous binder, (iii) heating in one or more stages, (iv) removal of the preform from the master. Below stage (iii) the movement may be stopped to allow the preform to be inspected. A convenient apparatus comprises several master forms, e.g. five, each made of wire gauze and mounted on a rotating platform, all these platforms being mounted on a turntable. At the start, the turntable is stationary with the master form rotating in a closed chamber into which glass fibre and powdered resinous binder and/or resin emulsion spray are fed, which may be drawn on the master form by suction applied through a central channel in the platform. Polyester resins are mentioned as suitable. The powder may be a phenolic resin in the B stage. The glass fibre rovings are passed through a feed shoot and between feed rollers and a variable p length cutter, operated so that longer fibres are deposited first so as to avoid blocking the interstices in the wire gauze. The lower part of the side wall is raised to allow the master form with its deposit to leave the chamber. The heating chamber is similarly constructed to allow the form to enter and leave. As the form remains in the heating chamber for the time taken to deposit the material, two heating chambers may be provided so that the time to dry the liquid or partly cure the solid resin is twice the forming time. The hot air may be drawn through the material by suction and recirculated through a heater. Alternatively high frequency or infra-red ray heating may be used.