Hydraulic system control valve - has sliding sleeve with piston each end and seating for auxiliary valve on lower piston

摘要

The control valve for a hydraulic system, as in the main patent, has a body (16) with ports for a control line (11) a piston and cylinder (10), reservoir vessels (1) and the pump (3). Under the tap cap (17') is a stem carrying a piston (51), and inside the bottom cap (17") is a second piston (52). These two pistons are enclosed in a sliding sleeve (18) with a return spring (35) around one end. The sleeve has a restricted portion about midway between the two pistons. This acts as a seating for an auxiliary valve (33) with its stem (34) fitting inside blind hole (54) inside the lower piston. Between the head of the auxiliary valve and the face of the lower piston is a helical spring (55).