Bosch Rexroth R900912549

General 2-way cartridge valves for pressure functions are pilot-operated valves in seat or spool design. The power section designed as cartridge valve (1) is installed into a receiving hole standardized according to DIN ISO 7368 and closed with a control cover (2). The pilot control valve (4) for manual or electrically proportional pressure adjustment is integrated into the control cover (2) or is installed on the control cover (2) as pilot valve with mounting dimensions according to DIN 24 340. By combination of cartridge valves with the control covers, different pressure functions can be realized. . Pressure relief function The cartridge valve (1) for the pressure relief function (type LC . DB...) is designed as seat valve without area difference (no effective area at port B). The effective pressure at port A is directed via the pilot oil supply orifice (5) to the spring side (6) of the element. Under the pressure set at the pilot control valve (4), the spool (3) is pressure-compensated and closed by the spring force. On reaching the set pressure, the spool (3) is opened and the pressure at port A is limited according to the pressure-flow characteristics. Pressure reducing function Rest position closed For the pressure reducing function with opening characteristic, a pressure limitation cartridge valve (type LC..DB40D...) and a control cover with a pressure reducing pilot control valve (type LFA..DR...) are applied. The pilot oil is directed from port A via the supply orifice and the opened pilot control valve to side B. The main spool is opened and the flow from port A to port B is released. On reaching the set pressure, the spool is closed and the pressure at port B is reduced according to the pressure-flow characteristics. Potential pressure increases on the secondary side are discharged to the tank via the 3rd way of the pilot control valve. Set-up of a directional valve enables realization of an additional blocking function (type LFA..DRW...). Pressure sequencing functions This function enables pressure-dependent connection of a second system. The required switching pressure is set at the pilot control valve integrated into the control cover. The pilot oil supply may either be realized externally (pilot oil port X) or internally (from port A via pilot oil ports X or Z2). The pilot control spring chamber is directed via ports Y or Z1, depressurized to the tank. Circuit examples Example 1: (Circuit for pressure-dependent unloading of the low-pressure system) In the illustrated circuit, the system is supplied via a high-pressure and a low-pressure pump. The system pressure pS acts externally from the high-pressure side via pilot oil port X on the pilot control valve, which sets the low-pressure side to depressurized circulation after the set pressure value is reached. The check valve RV (not included in the scope of delivery) prevents the connection of the high-pressure system with the now depressurized low-pressure system. On reaching the pressure set at the pilot control spring, the pilot control valve is switched and the spring chamber of the main valve to the tank is unloaded. The main spool is opened and the connection A to B is released. With the version LFA..DZW..., the required switching position can be selected besides the hydraulic circuit by means of an electrically operated pilot control valve (not included in the scope of delivery of the control cover LFA..DZ...). Example 2: (Circuit for pressure-dependent connection of a second system) With this circuit, system 2 is not connected before the pressure in system 1 complies with the specified value. Pilot oil discharge is realized internally from port A of the main valve.