Abstract: An actuator arrangement for urging a ram against a controlled device. An actuator such as a stack of piezoelectric disks is mounted and moves together with the ram along a line of movement. An end of the ram remote from the controlled device is engaged by re-adjusting elements which urge that end of the ram toward the controlled elements, and is also engaged by a releasable locking actuator which locks the ram end with respect to the controlled device. While the working actuator is energized, release and re-application of the locking actuator enables play in the actuator arrangement to be taken up.