Abstract: An element is to be mounted on a shaft of a non-positive displacement machine and forms a gap for limited passage of a flowing medium. A bush-like part for mounting on a shaft of the machine has an outer periphery provided with a recess for accommodating a ring. During operation of the machine, the ring, which is partially surrounded on its faces by circular ring-shaped walls of the recess, forms an axial gap with the circular, ring-shaped walls of the recess and a radial gap with the bottom of the recess. The ring is held by frictional contact with a rigid wall which surrounds it. To reduce wear on rings made of soft, flowable material, a second recess is formed in the rigid wall and surrounds the faces of the ring that project from the walls of the bush-like part. One of the lateral bounds of the second recess is formed by a tubular part detachably joined to the rigid wall.

Abstract: An element which is to be mounted on a shaft of a non-positive displacement machine and which forms a gap for limited passage of a flowing medium, which includes a bush-like part (2) for mounting on a shaft of the machine having an outer periphery provided with a recess (4) for accommodating a ring (5). During operation of the machine, the ring (5), which is partially surrounded on its faces by circular ring-shaped walls of the recess (4), forms an axial gap with the circular, ring-shaped walls of the recess (4) and a radial gap with the bottom of the recess. Ring (5) is held by frictional contact with a rigid wall (1) which surrounds it. To reduce wear on rings made of soft, flowable material, a second recess is formed in the rigid wall (1) and surrounds the faces of the ring (5) that project from the walls of the bush-like part (2). One of the lateral bounds of the second recess is formed by a tubular part (7) detachably joined to the rigid wall (1).

Abstract: A seal which is arranged between a shaft and a casing opening and separates, from one another, two spaces at different pressures, with the exception of a residual annular gap which permits a slight leakage caused by a gap flow. The seal can replace prior seal types and only permits a very small leakage volume flow while being relatively uncomplicated in terms of components, assembly and maintenance. The seal includes a bush (13) tightly surrounding the shaft (2), having at least one grooves (14) in each of which is arranged, with slight axial clearance, an elastic annular element (15, 18, 20, 21, 23) split by a longitudinally extending gap (16, 17, 19). The pressure difference between axial end surfaces of the annular element(s) (15, 18, 20, 21, 23) urges the annular element(s) (15, 18, 20, 21, 23) into sealing contact with the casing opening (3) in such a way that the gap flow is guided via the annular gap between the groove(s) (14) and the annular element(s) (15, 18, 20, 21, 23).