CYLINDER & SEAL GP-BOOM 3731111 - Caterpillar

When the engine is off, spring (17) holds swashplate (13) at the maximum angle. When the engine is started, shaft (14) begins to rotate. Oil is drawn into the bore of pistons (15). Barrel (18) starts to rotate and pistons (15) stroke. This forces hydraulic oil into the hydraulic system.The pump is in low-pressure standby when the following conditions are met:
The machine is operating.
The implements are in the HOLD position.
There is no demand on the steering.As the pump produces flow, the system pressure begins to increase. The system pressure overcomes the spring force of spring (10) and the signal pressure in line (9).Spool (9) moves up and oil flows into passage (6) to piston (12). The oil pressure inside piston (12) overcomes the force of spring (17) and the system pressure inside piston (16). Piston (12) moves the swashplate to the minimum angle. When the swashplate is moved to the minimum angle, the oil flows through the cross-drilled passage to the pump case. The system pressure is now at low-pressure standby.When the pump is at low-pressure standby, the pump produces enough flow in order to compensate for internal leakage. Also, the pump produces enough flow in order to maintain sufficient system pressure. Low-pressure standby is maintained in order to ensure instantaneous response under one of the following conditions:
The steering is activated.
An implement is activated.The pump supply oil moves spool (9) upward. This compresses spring (10). Since spool (9) is moved upward, more of the pump supply oil is allowed to flow through passage (6). The oil will flow through passage (6) and flow out of the cross-drilled passage to the pump case.Upstroke
Illustration 3 g01389054
Typical example of a piston pump during upstroke
(1) Pump control valve
(2) Adjustment screw for the flow compensator
(3) Adjustment screw for the pressure compensator
(4) Spring (pressure compensator)
(5) Oil flow to the pump case
(6) Oil flow to the control piston
(7) Oil flow from the output port of the pump
(8) Spool (pressure compensator)
(9) Spool (flow compensator)
(10) Spring (flow compensator)
(11) Line for signal oil pressure
(12) Control piston
(13) Swashplate
(14) Pump drive shaft
(15) Pistons
(16) Bias piston
(17) Bias spring
(18) BarrelWhen more oil flow is needed, the hydraulic pump upstrokes. Signal oil is sent to the pressure and flow compensator valve when increased oil flow is required by the steering and or implement system. Both signal pressure in line (11) and the force of spring (10) cause spool (9) to block the oil flow into passage (6). With no oil flow to piston (12), spring (17) is now allowed to increase the swashplate angle. The hydraulic pump will produce more oil flow.Constant Flow
Illustration 4 g01389058
Typical example of a piston pump during constant flow
(1) Pump control valve
(2) Adjustment screw for the flow compensator
(3) Adjustment screw for the pressure compensator
(4) Spring (pressure compensator)
(5) Oil flow to the pump case
(6) Oil flow to the control piston
(7) Oil flow from the output port of the pump
(8) Spool (pressure compensator)
(9) Spool (flow compensator)
(10) Spring (flow compensator)
(11) Line for signal oil pressure
(12) Control piston
(13) Swashplate
(14) Pump drive shaft
(15) Pistons
(16) Bias piston
(17)