Patent ID: 7762177
Filing Date: 2010-07-27
Classification: F15B

Abstract:
1. A hydraulic cylinder unit, comprising: a cylinder tube presenting an inner surface; a piston received within said cylinder tube and which is guided on said inner surface, said piston including an outer surface, each of said inner surface of said cylinder tube and said outer surface of said piston being configured as an axially extended cylinder; a cylinder head and a cylinder floor spaced apart from one another, said cylinder head and said cylinder floor being connected to said cylinder tube; a piston rod joined to said piston, said piston rod including a rod surface, configured as an axially extended cylinder, which is guided in said cylinder head and that together with said piston encloses a piston rod-side cylinder space; at least one rod seal disposed in said cylinder head which presents a rotationally symmetrical inner seal surface operable to seal said piston rod-side cylinder space from an area of said cylinder unit between said rod surface and said cylinder head; and at least one piston seal disposed about said piston that seals said piston-rod side cylinder space and an other cylinder space bounded by the cylinder floor and said piston, said at least one piston seal between said inner surface and said outer surface of said piston by means of a rotationally symmetrical outer seal surface; said at least one rod seal and/or said at least one piston seal each being configured as a hydrodynamic seal having a respective seal surface which includes a shape that deviates from a sealing surface of a respective one said circular cylinder facing said seal surface, so as to form at least one axially converging gap with respect to said sealing surface, said hydrodynamic seal being structurally adapted to lift from contact with the sealing surface when said piston and said piston rod are moved axially relative to said cylinder tube, thereby reducing mechanical frictional forces therebetween.