Compact fluid actuator

Claim 1

A compact air operated piston-type double-acting actuator, for operation with essentially no side thrust, comprising an operating cylinder having a longitudinal cylindrical bore and inlet-exhaust ports; end walls removably secured within said cylindrical bore, near each end thereof, and in fluid-tight engagement therewith, each of said end walls being devoid of air port means for placing said bore in fluid communication with a reservoir of air outside said cylinder, and each end wall having a counterbored central recess in its inner face to provide an annular boss having a circumferential bevel on the outside surface of said boss, said central recess having an area in the range from about 60 percent to about 85 percent of the cross-sectional area of said cylindrical bore; a reciprocable piston disposed in said cylindrical bore, said piston being movable in response to air pressure acting thereon, compressible sealing means disposed between said piston and said cylinder, an operating shaft extending outwardly through one of said end walls; and air cushioning means for decelerating said piston as it approaches the limit at each end of its travel within said cylindrical bore, including a cushion chamber defined by a transverse planar surface of said piston in abutment against said annular boss of each end wall, and a vent passage in said annular boss, said vent passage placing said cushion chamber in directly linear preselectedly restricted fluid communication with an inlet-exhaust port in said operating cylinder, wherein said inlet-exhaust port is disposed adjacent an end wall and is at least partially blocked as said piston moves towards said annular boss.