PISTON AS 3319822 - Caterpillar

Illustration 1 g01348970
Pressure override valve (POR valve) under normal conditions (1) Adjustment screw (2) Locknut (3) Spring (4) Signal oil from the pump stroking actuator (5) Passage to case drain (6) Low pressure oil from the drive loop (7) High pressure oil from the drive loop (8) Spring retainer (9) Spring retainer (10) Piston (11) Piston (12) Passage (13) ResolverOil from the drive loop enters the POR valve through passage (6) and through passage (7) . Since the pressure of the oil in passage (7) is greater than the pressure of the oil in passage (6) , resolver (13) moves to the left. High pressure oil from the drive loop flows through passage (12) . The pressure oil acts against piston (11) . Under normal operating conditions, the pressure of the oil from passage (7) is less than the force of spring (3) . Since the oil pressure is less than the force of spring (3) , piston (10) and piston (11) do not move.
Illustration 2 g00855107
Pressure override valve (POR valve) during a stall (1) Adjustment screw (2) Locknut (3) Spring (4) Signal oil from the pump stroking actuator (5) Passage to case drain (6) Low pressure oil from the drive loop (7) High pressure oil from the drive loop (8) Spring retainer (9) Spring retainer (10) Piston (11) Piston (12) Passage (13) ResolverWhen the drive loop encounters a stall, the pressure oil in passage (12) overcomes the force of spring (3) . The pressure oil moves piston (11) to the left. As a result, piston (11) moves piston (10) to the left. As piston (10) moves to the left, piston (10) opens a path from passage (4) to passage (5) . Signal oil from the pump stroking actuator in passage (4) drains to the case drain through passage (5) and the piston pump destrokes in order to reduce the flow through the drive loop until the drive loop pressure decreases to normal operating conditions.As the drive loop pressure decreases, spring (3) overcomes the pressure that is acting against piston (12) . Spring (3) moves spring retainer (9) to the right. As a result, piston (10) moves to the right and the piston blocks the oil in passage (4) .