Fluid operated rotary drive

A fluid operated rotary drive comprising a drive housing and an output shaft able to be driven in relation to it by fluid force to perform a reciprocating rotary movement about its longitudinal axis and furthermore a pivotal abutment kinematically coupled with the output shaft and cooperating with at least one counter abutment extending into its path of pivoting for limiting the angular movement of the output shaft in an adjustable manner, said counter abutment being able to be positioned around the longitudinal axis of the output shaft in different abutment positions and able to be clamped by a clamping means in a releasable manner against a clamping face of the housing, said clamping face extending at least for some distance around the longitudinal axis of the output shaft, wherein the at least one counter abutment has an anchoring structure having at least one anchoring projection wherein opposite to such anchoring structure an anchoring face fixedly connected with the drive housing and extending at least for some distance around the longitudinal axis of the output shaft is present which prior to initial fitting of the at least one counter abutment is smooth and wherein on clamping the counter abutment the anchoring structure is able to bite into such anchoring face with the formation of a permanent recess structure having at least one anchoring recess.