ARM AS 2794353 - Caterpillar

Constant Flow
Illustration 4 g00472660
Operation of the pump and pressure and flow compensator valve (1) Implement hydraulic pump (2) Margin spring (3) Pressure and flow compensator valve (4) Passage from the implement control valves for the load sensing signal (5) Flow compensator spool (6) Actuator piston (7) Bias spring (9) Swashplate (12) Pump outlet (13) Adjustment for the flow compensator spool (AA) Supply oil (BB) Reduced supply oil (DD) Pilot signal oil (EE) Tank oil (LL) Sump oilWhen a constant flow of oil is demanded by an implement hydraulic circuit, the supply oil pressure from pump outlet (12) will increase on the right side of flow compensator spool (5). The pressure on the left side of flow compensator spool (5) is the sum of the following pressures: load sensing signal (4) and margin spring (2). Flow compensator spool (5) will meter the force on both ends of the spool. Once the forces become equal on each end of the spool the system will stabilize.Swashplate (9) is held at a relative constant angle in order to maintain the required flow.The difference between the pressure of load sensing signal (4) and the supply oil pressure is called margin pressure. Margin pressure is the value of margin spring (2) .Margin pressure is 1690 100 kPa (245 15 psi). Margin pressure is adjusted by turning adjustment screw (13) on flow compensator spool (5) .Destroking
Illustration 5 g00473473
Operation of the pump and pressure and flow compensator valve (1) Implement hydraulic pump (2) Margin spring (3) Pressure and flow compensator valve (4) Passage from the implement control valves for the load sensing signal (5) Flow compensator spool (6) Actuator piston (7) Bias spring (9) Swashplate (12) Pump outlet (AA) Supply oil (BB) Reduced supply oil (DD) Pilot signal oil (EE) Tank oil (LL) Sump oilWhen less flow is required, implement hydraulic pump (1) destrokes. Implement hydraulic pump (1) destrokes when the force at the right of flow compensator spool (5) becomes greater than the force at the left.Flow compensator spool (5) moves to the left which allows more oil flow to actuator piston (6). Pressure on actuator piston (6) is now increased.The increased pressure overcomes the force of bias spring (7) which moves swashplate (9) to a reduced angle. When the pressure from pump outlet (12) matches the force at the left of flow compensator spool (5), the spool returns to a metering position. Implement hydraulic pump (1) will return to a constant flow.The following conditions result in destroking the implement hydraulic pump:
When a main control spool for an implement control valve is moved to the HOLD position the implement hydraulic pump will destroke.
If the main control spool for an implement control valve is moved to a position that requires less flow the implement hydraulic pump will destroke.
If multiple implement control valves are being used, the implement hydraulic pump will destroke when there is a reduction in demand from any one of the implement control valves.
If there