Additional Hydraulics Valve - Fig. WH 211
To prepare control of an optional actuator, remove the sandwich board (Item 17, WH 210) from the basic block and assemble the individual components on the basic block, see Fig. WH 211. These individual components comprise a primary high pressure protection escape (Item 2) integrated with a make-up check valve (Item 1), a double relief valve for Connections A and B, relieving to T1 and integrated into the plate (Item 3), and the high performance solenoid valve (Item 4).
The block being completely assembled, oil from the connected pump will flow through Connection P and the directional control valve to Connection T1. Fan drive on T1 is again as described under "Basic Cooling Block". Now, if a magnet of the directional control valve is energized, the oil flow is directed to the respective Connection A or B. The pump Connection P is protected from high pressure by the relief valve (Item 2). The oil flowing back from Connections A and B is available for fan drive T1. Only if nozzles are mounted to the actuator Connections A and B, the main relief valve (Item 2) opened relief. This relief oil goes to actuator Connection T and is therefore no longer available for fan drive on T1 during this phase. The running down fan can take the oil required for filling through the makeup check valve in the plate (Item 1). This also applies if the electromagnetically controlled actuator is in a mechanical end position and the main relief valve is completely opened relief.
In order to reduce surges on Connections A or B, pressure relief valves (Item 3) are provided on Connections A and B to the reservoir.
Functional Description of the High Performance Solenoid Valve (Item 4)
The solenoid valve is a slave piston controlled, high performance slide valve. The main slide contains a small pilot control piston. In the central position of the directional valve, oil is flowing freely from Connection P to Connection T. When initiating an electromagnetic signal, the small pilot control piston is deviated from its central position, and the pressure applied to P reaches the respective face of the main piston to be actuated through the central nozzle (1). Hereby, not only the magnetic force is available as switching power, but at the same time the face of the main piston is pressurized by the load pressure of P. The same function applies when the magnet is de-energized and the directional valve goes back into its central position. Due to the slave piston control, the pressure is directed to the opposite face until the main piston reaches its central position. This design allows using the same magnets for fan drive as are used for the switching valve. Emergency actuation can also be effected through (2). This applies to both sides.
Functional Description of Pressure Inserts (Item 1)
These pressure inserts are operating exactly as the above described switching valve for fan drive, see topic, Basic Cooling Block WH 210, but the maximum pressure is manually adjustable.
Assembly and Troubleshooting
During assembly, care should be taken not to exceed the tightening torque of 6 N·m for the round-neck nut, Item 5. Equally the tightening torque of the relief valve cartridges should not exceed 25 N·m. If the optional actuator is not moving when initiating the electrical switching signal, it should be checked first whether the electrical current reaches the magnets. In addition, the machine can still be actuated by the described emergency actuating system to run it if necessary. If this is possible, failure of the solenoid valve itself may be excluded. If the system is not building up pressure, the primary relief valve, Item 2, should be checked. For this purpose, the cartridge can be unscrewed to check freedom of action of the piston (3). At the same time, it can be checked whether the nozzle (4) (0.8 mm Dia.) is clogged. If the piston can be freely pushed from front to rear and if it reaches its foremost position again, no failure is likely to exist. This also applies to secondary escape (vent) valves. Furthermore, care should be taken as far as possible not to alter any settings. A defective cartridge can be changed without dismounting the complete unit.
Actuator Connections A and B are only as tight in central position as is usual for slide valves, i.e. there is some oil leakage as is normal for slides. Therefore, the actuator under control can not absolutely be locked in its positions. If this is desired, a sandwich type barrier block can be mounted either immediately on the base plate or between solenoid valve and pressure valve.