Air cylinder with end position damping

Abstract

An air cylinder has a main piston which is movable backwardly and forwardly under the control of air pressure and it is closed on at least one end with an axially extending damping bore which terminates in a closed end having a stop member adjacent this end. A vent hole connects to the interior of the cylinder to the damping bore and another vent hole connects into the cylinder main space. Each vent hole is advantageously connected to a throttle and check valve which permits inflow of air to the associated spaces and a throttled exit of the air depending on the position of the piston in the cylinder. The piston carries a damping piston in the form of a cylindrical extension thereof which is movable with the piston toward the closed end and has an open end with an axially extending damping bore therein having a check valve which closes the opening. The damping piston moves with the main piston so that adjacent the end position of movement of the main piston, the damping piston enters into the damping bore so as to bring its end into proximity to the stop which opens the check valve. The effect is to cause a slowing motion of the main piston until the stop reaches the check at which the main piston approaches substantially its end position at which time the remainder of the air trapped ahead of the main piston is exhausted through one or more of the vent holes.