PISTON 1575537 - Caterpillar

Illustration 1 g00519890
(1) Signal pressure screw (2) Pump control valve (3) Signal inlet port (4) Case drain passage (5) Signal pressure screw (6) Spring (7) Spool (8) Chamber (9) Spring (10) Spool (11) Spring (12) Pin (13) Swashplate (14) Stop adjustment (15) Spring (16) Actuator piston (17) Chamber (18) Stop adjustment (19) Bias piston (20) Crosshole (21) Spring (22) ChamberPump control valve (2) automatically keeps the pump flow at established rates for the speed of the elevator motor. The signal oil in chamber (8) with spring (9) moves spool (10) to the left. This blocks the discharge oil across the spool which upstrokes the pump. The end of spool (10) rests on spring (11) . When piston pin (12) is upstroked, the piston pin presses against spring (11) .Discharge oil from the pump is allowed into chamber (17) . Then, actuator piston (16) is moved to the left. This works against bias piston (19) and spring (21) . Bias piston (19) and spring (21) try to keep the pump at a minimum angle. As the pump upstrokes, piston pin (12) moves to the left. The forces move spool (10) to the left. This opens the pump discharge pressure to chamber (22) . The pump is destroked. The left force and the right force works on spool (10) . This meters discharge oil from the pump in chamber (22) and out chamber (22) . This action allows the pump to stroke to a given output. Then, the pump is held in that position.Signal pressure screw (1) changes the setting when the pump will start to upstroke. Signal pressure screw (1) should be adjusted so that the pump will begin to upstroke at 600 20 kPa (87 3 psi). The pump discharge pressure should be at 6900 kPa (1000 psi) .Stop adjustment (18) regulates the maximum pressure when the elevator pump operates. The maximum discharge pressure of the elevator pump is 36200 700 kPa (5250 100 psi). When maximum pressure is reached, spool (7) moves left against spring (6) . High pressure oil is metered across spool (7) and into chamber (22) . High pressure shifts bias piston (19) left. This destrokes the pump toward the minimum angle. If the demand for high pressure remains in the system, the discharge oil will meter through spool (7) . This will keep the pump at the angle that is necessary to maintain the pressure setting.Stop adjustment (18) regulates the maximum pump displacement. Stop adjustment (18) regulates the maximum flow output of the elevator pump. Stop adjustment (14) regulates the minimum pump displacement. Crosshole (20) regulates the minimum flow output of the elevator pump.Upstroking
When signal pressure from the pilot valve is sent to signal inlet port (3) , the pump upstrokes. Signal pressure oil flows into chamber (8) . Signal pressure works with spring (9) in