HOSE 3718950 - Caterpillar

Piston Pump
Illustration 1 g01401131
(1) Drive shaft
(2) Cylinder barrel assembly
(3) Case drain passage
(4) Pressure compensator valve
(5) Pressure compensator spool
(6) Orifice
(7) Signal passage to actuator piston
(8) Actuator piston
(9) Swashplate
(10) Bias spring
(11) Pump inlet
(12) Pump outlet
(BB) Cutaway section
(CC) Component surface
(FF) Activated component
(GG) Tank pressure The hydraulic pump has the following characteristics:
variable displacement
compensation for pressureThis piston pump has variable displacement. The displacement is dependent on the system demands that are sensed by pressure compensator valve (4).The hydraulic pump has the following components:Drive shaft (1) - The rotation of the pump is counterclockwise when the pump is viewed from the drive end. The cylinder barrel assembly is splined to the drive shaft.Cylinder barrel assembly (2) - The cylinder barrel contains nine pistons. The cylinder barrel assembly rotates whenever the engine is running. The pistons move oil into the barrel and out of the barrel.Pressure compensator valve (4) - The pressure compensator valve controls the delivery of oil and the return of oil to the actuator piston.Actuator piston (8) - When oil pressure increases behind the actuator piston, the piston will overcome the force of the bias spring which causes the angle of the swashplate to be reduced.Swashplate (9) - The displacement of the pump is controlled by the angle of the swashplate. Angling of the swashplate causes the pistons to move in and out of the rotating barrel.Bias spring (10) - If there is no pressure behind the actuator piston, the bias spring will hold the swashplate at the maximum angle.When the engine is OFF, there is no pressure behind actuator piston (8). Bias spring (10) is able to hold swashplate (9) at the maximum angle.When the engine is started, drive shaft (1) starts to rotate. Oil flows into the piston bore from pump inlet (11). Oil is forced out of pump outlet (12) and into the system as cylinder barrel assembly (2) rotates.Constant Flow
Illustration 2 g03704137
(1) Drive shaft
(2) Cylinder barrel assembly
(3) Case drain passage
(4) Pressure compensator valve
(5) Pressure compensator spool
(6) Orifice
(7) Signal passage to actuator piston
(8) Actuator piston
(9) Swashplate
(10) Bias spring
(11) Pump inlet
(12) Pump outlet
(BB) Cutaway section
(CC) Component surface
(FF) Activated component
(GG) Tank pressure
(KK) High pressure
(LL) First pressure reduction When the engine is running, the supply oil pressure from pump outlet (12) will increase at pressure compensator spool (5). The spool moves against the spring. The pressure moves compensator spool (5) upward. When the spool moves, the passage opens to signal passage (7). The pressure in the signal passage acts against actuator piston (8). The force of bias spring (10) is overcome. The angle of swashplate (9) gets smaller. The pump destrokes.When the pump destrokes, the pressure in pump outlet (12) decreases. The spring in the compensator valve moves the spool downward. Once the forces become equal on each end of the spool, pressure compensator spool (5) will meter oil to actuator piston (8) and the system will stabilize.Swashplate (9) is held at a relative constant angle in order to maintain the required flow.The pressure compensator valve has orifice (6) in the