SLIDING PISTON FOR A HYDRAULIC CONTROL VALVE

摘要

m A sliding piston for a hydraulic control device provided with piston sections, the piston sections being separated from each other by annular grooves. Known similar apparatus do not permit for optimum reduction of reaction forces acting on piston movement over an entire fine control range. This is particularly disadvantageous in the case of sliding pistons having large dimensions and large oil circulation therethrough. The present invention provides an improved hydraulic sliding piston that can be actuated over the entire control displacement with minimum force even with large amounts of high pressure liquid flow around the piston. Accordingly, the sliding piston according to the present invention has diametrically opposed fine control grooves situated on the front side of the piston sections. The annular grooves and the line control grooves are connected to each other. Lateral faces of each fine control groove are open at a semi-circle to a cylindrical surface of the sliding piston and at right angles to a front surface of the annular groove separating the piston sections. A front side of each fine control groove is provided with a milled concave slot. A hydrodynamic body is exposed to the front side of the fine control groove and is provided with a sloped surface forming a throttling location. The hydrodynamic body is eccentrically positioned in the fine control groove and is held therein in such a position that a radial surface of the hydrodynamic body and the cylindrical surface of the piston sections are on the same diameter.