Abstract: A friction clutch including interleaved compressible friction plates or overlapping conical rings and selectively operable structure effecting engagement thereof. One aspect of the invention relates to the structure for utilizing torque generated between the parts to be clutched for providing the compression force to be applied to the plates or the cone rings. Roller and ramp structure is provided between driving and driven parts responding to torque initially applied to the driving member for generating an axial force which is then applied to the clutch pack compressing structure. The roller has an elongated structure which will permit it to first roll about an axis perpendicular to the axis of rotation of the friction clutch and subsequently slide along its axial length. This structure will prevent or at least considerably reduce the power surges following a complete clutching operation.

Abstract: Double-acting hydraulic clutches. In a double-acting hydraulic clutch of the type having a pair of oppositely movable pistons for effecting engagement of clutch plates there is provided a resilient partition separating the chambers occupied by each of said pistons. Such resilient partition yields sufficiently upon the supplying to a given cylinder of energizing fluid whereby without slowing the entry of such fluid the shock of the in-rushing fluid is softened and undesired suddenness, or grab, in clutch engagement is minimized.