Patent ID: 7427190

Claim:
A hydraulic device for pumping molten metal and/or controlling flow thereof, comprising an enclosure that forms internally a cylindrical chamber, for the connection of at least one first duct and one second duct for the passage of molten metal, within which a piston can slide hermetically in order to pump and/or control flow, an insulating cushion of inert gas being interposed between said piston and the molten metal, said piston being associated with piston movement means for actuating movement thereof with a reciprocating rectilinear motion, said piston comprising a substantially disk portion, which forms a seal with said cylindrical chamber, and a substantially cylindrical portion whose diametrical dimension is smaller than that of said cylindrical chamber in order to form an interspace comprising inert gas that forms a cup-shaped insulating cushion, said substantially cylindrical portion comprising an outer shell that is substantially cup-shaped, is made of ceramic material, is filled with insulating putty, and is fixed to said substantially disk portion.