Patent ID: 8136574

Claim:
A multi-piece piston to be fastened to a high-pressure side end region of a piston rod displaceable axially in a casting cylinder of a cold chamber casting machine, comprising a piston cover forming a piston end wall on the high-pressure side wherein the piston cover is adapted to bring the piston end wall thereof in direct axial bearing contact with an axial end face of the end region of the piston rod, a piston body, axially adjoining the piston cover on its low-pressure side, in the form of a bush adapted to surround the end region of the piston rod, fastening members for releasable axial fixing of the piston cover and of the piston body in relation to the piston rod, wherein the fastening members comprise a plurality of bayonet locking members provided on the piston cover and adapted to axially fix the piston cover directly to the end region of the piston rod through a plurality of bayonet locking members provided on the end region of the piston rod and being mutually assigned in pairs to the bayonet locking members of the piston cover, wherein the pairs of mutually assigned locking members are offset in the circumferential direction and leave free passages between them, and wherein the piston cover and the piston body are adapted to form a first coolant duct between the piston end wall of the piston cover and the axial end face of the end region of the piston rod and a second coolant duct between an inner circumferential surface of the piston body and an outer circumferential surface of the end region of the piston rod, and wherein the first and second coolant ducts are connected to one another through the passages between the pairs of locking members and are adapted to bring substantially the entire length of the piston body into contact with coolant.