Abstract: A deformable sealing member, particularly a sealing tube, which is at least partially elastic is secured at two distant locations to two working members, e.g. to a piston part and a cylinder part respectively to form a leakproof working chamber for pressurizing therein a working fluid or for transferring the power of a pressurized working fluid introduced in the working chamber to said working members, the apparatus thus being able to operate as a pump or motor respectively. The sealing member is supported against the working pressure in said chamber by a support surface, and between said sealing member and said support surface there being a low-friction component which is constituted by a solid material, e.g.

Abstract: A relatively movable piston and cylinder are joined by an elastic sealing element which engages the piston and cylinder at spaced locations and at least partially defines a working chamber. The sealing element bears against a bearing surface via a lubricant space, and means are provided for feeding lubricant between the bearing surface and the sealing element. Part of the bearing surface comprises a transition surface section extending oblique to the axis of the cylinder. The lubricant feed mouth opens to the bearing surface at a predetermined location relative to the transition surface section of the bearing surface.

Abstract: The method and the device for the lubricant feed works by introduction of the lubricant into a clearance volume (3b) between a, for example, tubular flexible sealing element of a cylinder-piston arrangement and a bearing surface within the working stroke at comparatively low working pressure. Consequently a comparatively low lubricant feed pressure is adequate. Return of lubricant into the feed is advantageously excluded by a non-return valve arrangement (8d,15).Preferably a non-return valve member (15) is arranged in the region of the mouth (9) from the lubricant feed, whereby low-inertia operation results with secure maintenance of pressure in the lubricant space (3b).

Abstract: The tubular sealing element consisting of flexible material, between a cylinder and a piston as working members for the formation of a pressure working space is connected by a connection of the substance of the material, in particular by a vulcanized connection (10) to one working member (1) which forms a bearing surface (4) for the sealing element under the action of the working pressure. This connection makes possible secure closure and gentle introduction of the stresses into the flexible material of the seal. Preferably the connection area (11) of the working member (1) is made toroidal with a uniformly curved profile, whereby stress concentrations in the connection region are reduced.

Abstract: An apparatus comprising a cylinder, a piston located in part in the cylinder and movable relative thereto, an elastic tube member sealingly engaging the piston and the cylinder at spaced locations and at least partially defining a working chamber, the tube member stretching and contracting and the working chamber varying in volume upon relative movement of the piston and the cylinder, the tube member having a portion sliding against the inner wall of the cylinder as the volume of the working chamber varies and a ring member encircling the tube member and located between the tube member and the cylinder inner wall in the connection region of the tube member and the piston.