Abstract: A torque-limiting coupling device including a cylindrical sleeve and a cylindrical shaft in radially tensioned frictional engagement for transferring torque up to a torque limit that corresponds to the radial tension and at which the sleeve begins to rotate relative to the shaft. The device also includes at least one pump mechanism which is adapted to be driven to pump liquid to the interface between co-acting surfaces of the sleeve and shaft upon relative rotation between the sleeve and the shaft. The shaft includes a surface layer that defines one of the co-acting surfaces and that is made of a material, e.g. tombak, whose plasticizing limit is lower than the plasticizing limit of the material in the co-acting surface of the sleeve. The surface layer may include cavities which enable the surface layer to take a smaller radial thickness after plasticization thereof.

Abstract: A coupling includes at least one thin-walled sleeve which forms an axially extending defining wall of a substantially annular chamber. The chamber is arranged to be supplied with a pressure medium to elastically deform said sleeve in a radial direction into clamping engagement with a surface on an element which is to be connected to the coupling, the shape and dimension of said surface substantially corresponding to the shape and dimension of a surface on the sleeve remote from said chamber. The chamber has extending therefrom a channel arrangement which is arranged to cooperate with coupling-release means which can be activated by relative movement between said surfaces, or by a given torsional deformation thereof, to a state in which pressure medium can flow through said channel arrangement from said chamber to relieve the chamber of pressure acting therein.