Fluid pressure actuator having position setting means

Claim 1

A fluid pressure actuator comprising: a cylinder (2) having axially disposed end walls (3, 4), at least one side wall, and an inner chamber (2a) bounded longitudinally by said end walls and transversely by said at least one side wall; first and second pistons (5, 6) located in said inner chamber, said pistons being simultaneously movable in opposite directions along the longitudinal axis of said cylinder in response to fluid pressure introduced into said inner chamber, each of said pistons having a toothed rack portion (7, 8) extending longitudinally toward the interior of the inner chamber; a toothed wheel (9) having teeth which mesh with the teeth of said toothed rack portions, said toothed wheel being mounted on an actuating member (10) journaled for rotation in a side wall of said cylinder 2; at least one fluid passage (11) for supplying pressure fluid to said inner chamber (2a) between said two pistons to thereby extend said pistons to their respective outer terminal positions; means for causing said pistons to retract to their fully retracted, zero-position upon release of said pressure fluid from between said two pistons; first adjusting means (16) passing through at least one of said end walls such that it projects past the end wall into the inner chamber while being accessible from the exterior of the cylinder, for adjusting the maximum outer terminal positions of said pistons; second adjusting means (17), passing through one of said pistons such that it projects into the inner chamber between said two pistons and into engagement with the toothed rack portion of the other of said pistons, while being accessible from that portion of the inner chamber between said one piston and its juxtaposed end wall, for adjusting the relative positions of said pistons in their fully retracted, zero-position; and means in the end wall juxtaposed to said one piston for providing access to said second adjusting means without removal of said juxtaposed end wall.