Patent ID: 7718916

Claim:
A weld cylinder comprising: a cylinder supporting a rod providing home, intermediate and work positions, the cylinder including a block separating a pair of barrels each providing a separate cavity; a retract piston assembly arranged in the cylinder within one of the cavities and movable between retract-return and retract-forward positions, the retract piston assembly providing a cushion chamber, the retract piston assembly near the block in the retract-forward position; a weld flange arranged in the retract piston assembly and movable between weld-return and weld-forward positions, the weld flange supporting the rod; a differential pressure valve regulating pressure in the chamber; and an isolator valve cooperating with the differential pressure valve to bias the differential pressure valve to a closed position, the isolator valve movable relative to the block and the differential pressure valve and cooperating with the block in the retract-forward position to move the isolator valve from a closed position to an open position, wherein the differential pressure valve and isolator valve and concentric with one another.