Valve arrangement for controlling a reversible hydraulically operated

Abstract

The valve arrangement includes four main control valves connected in a bridge circuit connected, at one end of a first diagonal, to a source of fluid under pressure and, at the other end of the first diagonal, to a fluid reservoir. Opposite ends of a second diagonal of the bridge are connected to inlet and outlet ports of the operated device. The arrangement includes two pressure adjusting valves, each connected to a respective pair of main control valves. In one bridge circuit, the main control valves are pressure limiting valves and each pair of main control valves includes one main control valve in one branch of the bridge circuit and another main control valve in the other branch of the bridge circuit. In a second bridge circuit, the main control valves adjacent the connection to the source of fluid under pressure are pressure reducing valves, and the main control valves adjacent the connection to the reservoir are pressure limiting valves, with each pair of main control valves including a pressure reducing valve and a pressure limiting valve forming a bridge branch. In the second bridge circuit, pilot-controlled check valves are included in the connections to the operated device. The pressure adjusting valves are electrohydraulic valves continuously adjustable between the closed and the fully open position and each associated with a respective potentiometer for adjusting its exciting current.