Soft-touch pneumatic drive unit

摘要

A soft-touch pneumatic drive unit for welding is provided. The drive unit includes a first section, a second section, and a third section. A piston rod extends substantially throughout these sections and contains a drive piston in the second section and a second drive piston in the third section. Pressurized fluid is supplied through the first section and into the second section to provide a driving force on these pistons. Cushioning fluid is supplied through the first section to the second section to cushion and slow the piston rod as an electrode carried thereby is moved toward a workpiece. A floating piston in the second section then blocks the flow of cushioning fluid from the first section with fluid pressure in the second section then decreasing to atmospheric pressure to enable full welding force to be applied through the drive pistons and the piston rod to the electrode. The cushioning fluid also aids in returning the piston components to the retracted position upon the completion of a weld.