Air cylinder with self-contained pneumatic piston return

Claim 1

Apparatus comprising an air cylinder having a self-contained pneumatic piston return and comprising a pair of fixed end walls, a cylindrical member extending between said end walls and defining therewith a piston chamber, a fluid impermeable piSton head reciprocatable in said piston chamber and having a piston rod passing through a bore provided in one of said end walls, a pressure fluid inlet port provided in the other of said end wall to supply pressure fluid to said piston chamber, a second chamber disposed outside of said cylindrical member and concentrically about said piston chamber, supply means including passage means provided in said other end wall to supply a predetermined amount of said pressure fluid to said second chamber, vent means to vent air from an upper portion of said piston chamber upon movement of said piston head towards said one end wall, means including passage means in said one end wall to automatically supply pressure fluid from said second chamber to the upper portion of said piston chamber to actuate return movement of said piston head upon stopping the supply of pressure fluid through said inlet port, and workpiece clamping means for temporarily holding a workpiece while work is performed thereon, said workpiece clamping means being secured to and reciprocated by said piston rod.