Pressure valves of type DRG are pilot-operated pressure reducing valves. They are used for reducing a system pressure. The pressure reducing valves from this series mainly consist of a pilot control valve with electric motor as pressure adjustment element, a main valve with main spool insert and an optional check valve. The reduced pressure in A is set by means of a DC motor (6) with speed reduction transmission (7). The output shaft of the speed reduction transmission (7) turns the cam (5) that adjusts the preload of the spring (5) via the spring plate (9) to cause a pressure change. The reduced pressure is present in port A and the inlet pressure in port B. The main flow is from B to A. The cam position (5) is reported back by the actual value potentiometer (8). Optionally, electric limit switches can be installed instead of the actual value potentiometer (8) to limit the min. and max. pressure. For the version with limit switch, the min. adjustment time is 8 seconds for the pressure range pmin to pmax. The adjustment time of 8 seconds facilitates a sensitive start-up of the desired pressure in jog mode. For the version with actual value potentiometer, the min. adjustment time is 3 seconds for the pressure range pmin to pmax. Together with the corresponding amplifier type VT-VRM, program control is possible. With 2 additional pressure switches, the min. and max. pressure can be limited. If the energy supply is interrupted (cable break, fuse defect, short-circuit, etc.), the pressure set at the valve remains unchanged for the version with limit switch.
Type DRG NG8 and 10
The reduced pressure in A is simultaneously applied to the spring-loaded side of the main spool (1) via nozzle (2.1), control line (4), nozzle (2.2) and nozzle (3). The pressure on the spring-loaded side of the main spool (1) is lower than the pressure in A by the pressure drop of the compression spring (10.2). The compression spring (10.2) acts in opening direction on the main spool (1). Depending on the cross-section of the nozzles (2.1; 2.2.) and the pressure drop of the compression spring (10.2), the pilot oil flows via nozzle (2.1), control line (4), nozzle (2.2), poppet (6) into the spring chamber (7) and then back to the tank via Y, with subplate mounting (12.2), with threaded connection (12.1). If the pressure in A exceeds the pressure set at the pilot control valve (11), the main spool (1) reduces the flow cross-section from B to A until the pressure set at the pilot control valve (11) is reached again in port A. Correspondingly, the main spool (1) opens the flow cross-section B to A if the pressure in A is lower than the pressure set at the pilot control valve (11). With standing oil column between A and the actuator, only the pilot oil flows from B to A via the main spool. If a lower pressure is set at the pilot control valve (11) in this position, the main spool (1) interrupts the pilot oil supply from B to A until the oil volume between A and the actuator has expanded to the lower pressure in the pilot control valve (11) via nozzle (2.1), control line (4), nozzle (2.2), poppet (6) and port Y.For the free return flow from A to B, a check valve (14) can optionally be installed.
Type DRG NG16 to 32
In contrast to DRG 8 and DRG 10, the pilot oil is taken from the inlet pressure in channel B with these valves. The flow controller (13) regulates the pilot oil volume to a constant level. If with standing oil column between A and actuator, a lower pressure is set at the pilot control valve (11), the oil column is unloaded via check valve (10.1), control line (4), poppet (6) and port Y.
Type DRG 10-1X/…Y…
Type DRG 20-1X/…Y…