Control mechanism for thread rolling attachment

摘要

The wedge-shaped operating member of a thread rolling attachment is reciprocated by a piston rod which extends into one end of a fluid pressure cylinder. A rotatable valve stem is mounted intermediate its ends in the opposite end of the cylinder for limited axial movement, and has thereon a valve seat normally closing a port which leads to a reversible valve that directs fluid under pressure selectively to opposite ends of the cylinder to shift the piston rod between retracted and advanced positions. The inner end of the stem is slidably connected to the piston rod so that when the latter reaches its advanced position it momentarily unseats the valve seat from the port to effect reversal of the valve and consequent return of the piston rod. The valve stem is rotatable to adjust the length of the stroke of the piston rod.