Pneumatic jack with end stops formed by trapped air - uses piston rod lip seals as non-return valves

摘要

The piston(2) of a pneumatic jack is brought to rest by the pressure rise of air trapped when the piston rod extensions(6) engage the lip seals (7, 8). The lip seals are free to slide a limited distance in recesses formed in the end caps and are retained by a shoulder(81). When the jack is actuated the air supply pushes the seal off the seat(82) so that air flows into the cylinder(10) through the holes(90) and immediately acts on the full area of the piston(2) to produce maximum force.