Patent ID: 7275583

Claim:
An apparatus for processing molten material into a desired shape, comprising: means for forming a cavity to receive said molten material and to allow solidification of said material within said cavity; a source of vacuum to be connected to said cavity for sucking air out; a hollow after-pressure cylinder in communication with said cavity so as to receive a portion of said material, said after-pressure cylinder having a first end for connection to said cavity, and a second, opposite end, the region of said second end including a connection opening for connecting said vacuum source; after-pressure piston means moveable in said after-pressure cylinder to press said portion of material into said cavity to compensate for any shrinkage of said material; drive means for moving said after-pressure piston in said after-pressure cylinder into three different positions, wherein (a) in a first position, said after-pressure piston is in the region of said second end, leaving said connection opening in communication with said cavity, (b) in the second position, said after-pressure piston has moved over said connection opening to interrupt said communication with said cavity, and (c) in a third position, said after-pressure piston has moved from said second position towards said cavity to press said portion of material into said cavity.