Vehicle windscreen wiper hydraulic drive - has pressure feed from pump to cylinder via control valve with differential dia. pistons

摘要

The windscreen wiper hydraulic drive comprises a pressure medium source, a working cylinder and a control valve which automatically regulates the pressure medium flow to and from the working cylinder. The control valve (3) comprises two interconnected pistons (10, 11) of different dias. arranged at a distance from each other. A spring (8) is fitted between one piston and a fixed stop (20) and the pressure medium feed from the pump (1) to the working cylinder (6) occurs via the space between both pistons (10, 11) of the control valve (3) at least on one throttle (4) and the rear side of the larger piston (11). Between the control valve (3) and the throttles (4, 5) a pressure balance is fitted to maintain the working piston speed constant.