| abstract |
The hydraulic control device for a double-acting operating cylinder (17) having two pressure spaces (21, 22) has a control valve (14, 30; 24, 33) assigned to each of these pressure spaces for loading and relieving the relevant pressure space. Extending of the operating cylinder is carried out via a pressure balance (11) which is connected to the pump pressure line (13) and is assigned to the control valves for filling the pressure spaces. In a specific operating state, the so-called biased piston, with pressure medium neither flowing to nor from the operating cylinder, the pressure balance is set via a change-over valve (37) by means of the higher of the two pressures in one of the pressure spaces such that it is only used for pressure regulation and ensures that virtually no higher pressure is produced in the pressure space (22) on the piston-rod side than in the bottom-side pressure space (21). The result is a more reliable operation of the hydraulic system. <IMAGE> |