Hydraulic actuator for a friction clutch

A motor vehicle clutch assembly comprising a fixed part of a vehicle, a friction type transmission clutch, and means mounting the clutch to said fixed part of the vehicle, the clutch including a cover plate, a first bearing mounted centrally in the cover plate, a declutching means within the cover plate, and an actuating member engaging the declutching means and comprising a second bearing in the form of a rolling bearing having a fixed bearing ring, for acting in traction on the declutching means whereby to disengage the clutch, the clutch assembly further including a fluid operated actuator comprising a hollow tubular cylinder having a leading end portion and a free end, a hollow tubular piston mounted concentrically within the cylinder and capable of axial translation with respect to the cylinder, a central chamber delimited by said cylinder and said piston, and means for preventing relative rotation between the piston and cylinder, the cylinder defining axial thrust means for axial engagement on said first bearing, and the piston having means for engaging the declutching means for acting on the declutching means, wherein said leading end portion of the cylinder is arranged to bear on said first bearing, the actuator further including first rotation stop means carried by the cylinder for preventing rotation of the cylinder with respect to said fixed part, the piston projecting axially beyond said leading end portion of the cylinder for cooperation with said fixed bearing ring of the second bearing.