GB686171A - Improvements in or relating to moulds and moulding - Google Patents

Abstract

686,171. Compound sheet materials. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 6, 1950. [June 9, 1949] No. 15439/49. Class 140. [Also in Group V] A lining 12, 13, Fig. 4, of resin impregnated asbestos has removable pins 35 which support either a templet for shaping the article to be moulded or an insert 36. The mould is formed by coating a lining 12, 13, Fig. 3, with a parting agent (methyl cellulose or silicone grease), while it is on a wood or plaster pattern 11, then moulding layers of uncured resinated fabric on the lining by enclosing the layers in a bag 25 having a heating element 27, and exhausting the bag through a pipe 15. Heating elements 23 are placed between each pair of layers forming the mould, to produce a mould provided with enclosed heating elements. The outer layer is stitched with wire 24 which is cut after moulding and bent outwardly to key with a cementitious surround 28, Fig. 4, for the mould. The pattern 11 may be removed from the mould by disintegrating it or by initially leaving part of the mould free from cementitious material and thus allowing the mould walls to be flexed outwardly. In a moulding operation the lining is removed and provided with threaded holes to receive the pins 35, and the templet or insert fixed to the pins. The lining is charged with layers of uncured material, preferably while out of the mould, and the layers covered with a heating element 39 and a moulding bag 37. A mould may be formed about the lining while it is on its pattern for making replacement linings, Fig. 5 (not shown). The layers of moulding material may be impregnated with partly condensed phenolformaldehyde and one may also be impregnated with resorcinol whilst the other is impregnated with paraformaldehyde as and for the purpose described in Specification 658,269.