Moulding of multi=layer foamed plastic products and process equipment

摘要

A process for moulding of multi-layer foamed plastic components uses two or more upper tools with different shaped cavities and a corresponding number of lower tools. In a first cycle at a first forming station (a) a first foam layer (5) is moulded, at a second station(b) a first layer (5) is enclosed in a second foam layer (13) and in a third station (c) the completely foamed component is cooled. In a second working cycle the foamed component produced in the first station (a) is transferred to the second station (b), replacing a two layer foamed component (5,13) which is transferred to the third station (c) to replace a demoulded, cooled component. All upper tools (3,12) then return to their initial position to commence another first cycle. Process equipment comprises upper tools (3,12) with different cavity shapes and lower tools, the first two (1,10) being supplied with steam, the third (17) with cool air. Upper tools are mounted on a common traverse (4) permitting horizontal and vertical movement relative to the fixed lower tools. Preferably the upper tools (3,12) move horizontally and vertically relative to the lower tools (1,10,17) between each moulding cycle. Each layer (5,13) of the moulded product is of a different pre-expanded plastic material which is sintered inside the tool with hot air. At the second station (b) steam effects both foaming and sintering of the second layer (13) of pre-foamed material and creates the bond between this material and the first sintered layer (5). Moulded components are held by vacuum in the upper tools (3,12) during transfer between stations (a,b,c).