Bosch Rexroth R900900987

The 4/2 and 4/3 proportional directional valves are designed as direct operated devices in plate design. Operation by means of proportional solenoids with central thread and detachable coil. The solenoids are controlled via integrated electronics. Set-up: The valve basically consists of:

• Housing (1) with connection surface

• Control spool (2) with compression springs (3 and 4)

• Solenoids (5 and 6) with central thread

• Integrated electronics (7)

Function:

• With de-energized solenoids (5 and 6), central position of the control spool (2) due to compression springs (3 and 4)

• Direct actuation of the control spool (2) by energization of one proportional solenoid, e. g. energization of solenoid "b" (6)

• Control spool (2) is moved to the left in proportion to the electrical input signal

• Connection from P to A and B to T via orifice-type cross-sections with progressive flow characteristics

• Switching off of the solenoid (6)

• Control spool (2) is returned to the central position by the compression spring (3)

Valve with two spool positions (type 4WRA...A...): The function of this valve version basically corresponds to the valve with three spool positions. This 2 spool position valve is, however, only equipped with solenoid “a”. Instead of the 2nd proportional solenoid, there is a plug screw (8.1) with NG 6 or a cover (8.2) with NG10. Notice: The tank line must not be allowed to run empty. With corresponding installation conditions, a preload valve (preload pressure approx. 2 bar) must be installed.