In the course of this method, an amount of expansible mixture is poured into a mould, after which the mould is obturated by means of a plug. A vacuum is created in the chamber of the mould by way of the plug so as to cause the foaming of the mixture. The vacuum is maintained for a period after the foamable...http://www.google.com.au/patents/US4285893?utm_source=gb-gplus-sharePatent US4285893 - Method and device for forming plastic cellular material in a mold from a foamable liquid reaction mixture
