Conversion of variable delivery pump to fixed delivery pump for a friction welder

Claim 1

An inertia friction welder of the kind in which a flywheel for driving one part and for storing the energy required to produce the weld is accelerated to a selected speed prior to engaging the parts to be welded and comprising, hydraulically actuated loading means for pressing the parts together in rubbing contact under welding pressure at a common interface after the flywheel has reached the selected speed, hydraulic motor means for accelerating the flywheel to the selected speed, a hydraulic pump of the kind in which the displacement of the pump is varied by changing the angular position of a wobble plate, conduit means connecting the pump alternately to the motor means and the loading means, a hydraulic servo motor including a servo piston connected to the wobble plate, servo motor control means responsive to the output pressure of the pump for controlling the servo motor to cause the pump to operate as a variable displacement pump while the pump is connected to the motor means to accelerate the flywheel, and locking means for locking the servo motor in a predetermined position to cause the pump to operate as a fixed displacement pump while the pump is connected to the loading means.