GB671832A - Improvements in or relating to methods of manufacturing articles from sheet material impregnated with low pressure synthetic resin - Google Patents

Abstract

671,832. Moulding synthetic-resin-impregnated laminae. ASHDOWNS, Ltd., and JOSEPH, C. B. May 25, 1950 [April 27, 1949], No. 11231/49. Class 87(ii) [Also in Group VIII] In a method of low-pressure moulding a laminated article from layers of synthetic-resin impregnated sheets, in which the sheets are covered on the side thereof which is opposite to that in contact with the mould by a non-adhering sheet and pressure is applied to the laminae, at least in part, through a mobile or flowing porous body in contiguity with the sheet; the article is moulded in a portable mould 17 and each layer of impregnated sheets 14 is formed of overlapping blanks and the non-adhering sheet 15 is formed of over lapping strips whereby occluded air is driven off between the strips during the early stages of the moulding. As described, the mobile porous body comprises lead shot 16 which is progressively introduced in the mould cavity, and if a pressure higher than that provided by the weight of the shot is required a wedge 23 may be inserted in the shot and weights placed on the wedge, or pressure may be applied to the wedge by clamping means. The application of the process to moulding a fireman's helmet is particularly described, the helmet incorporating lugs and loops formed from resinimpregnated glass cloth placed so that they are moulded integrally with the main body. The resins may be polyester resins, e.g. diallyl-phthalate, or compatible co-polymers of polyester resins with or without the addition of a styrene, such resins being referred to as " low pressure resins." The resin may be pre-polymerized to reduce storing time. Other materials than shot may be used for the pressure aplication, e.g. sand, and pressure may be applied externally and transmitted through the sand.