ROD-PISTON 4737287 - Caterpillar

Relief And Unloading Valve
All of the pump oil for the elevator motor (three pump sections) goes through the relief and unloading valve to the tank when the control lever for the elevator is in the HOLD position. The relief valve is in the pump oil circuit when the pump oil goes through the valve to the elevator motor.The FAST forward position of the elevator valve stem, in the control valve, stops the oil in the vent lines from openings (2) and (10). Oil from two pumps (sections) goes through opening (6) and out through opening (8) to the elevator motor.
RELIEF AND UNLOADING SCHEMATIC
1. Stem. 2. Vent line opening. 3. Pilot valve (relief valve). 4. Unloading valve. 5. Opening to tank. 6. Opening for pump oil. 7. Unloading valve stem. 8. Opening to elevator motor. 9. Opening for pump oil. 10. Vent line opening.The oil from the other pump (section) goes through opening (9), around unloading valve stem (7) and then goes out through opening (8) with the oil from the other pumps. The oil from the pumps in the relief and unloading valve goes through an orifice in unloading valve (4) and the spring and