Expansible mold for the manufacture of plaster pieces

Claim 1

A mold for the production of plaster parts comprising at least two mold walls normally spaced one from the other in open position by an amount greater than the spaced relation between said walls when defining the mold space, at least two incompressible but deformable components positioned between outer ends of the said walls in sealing engagement therewith, a feed opening communicating with the mold space for the introduction of plaster material to be molded, rigid spacers between outer ends of said walls immediately adjacent the outer ends of the deformable components having a width less than the width of the deformable material and positioned to be engaged by said walls to define the mold space therebetween, a pressure means operative on at least one of said walls for displacement under pressure in the direction towards the other to define the walls of the mold space upon engagement with said spacers whereby the deformable, incompressible components are deformed in the direction towards the said mold walls and expanded in the space between the said mold walls to define the end walls of the mold space therebetween and which, in response to release of pressure return to normal position between said walls by expansion in the direction between the mold walls to displace the mold walls in the direction away from each other to open position while retracting lengthwise between the mold walls to release the article molded in the mold space.