PLATE & FILM GP 4415832 - Caterpillar

Before the engine is started, displacement piston (30) and bias spring forces the swashplate in feeder pump (28) to the maximum angle. As the engine is started, the pump immediately generates flow. The feeder pump draws oil from the hydraulic tank through port "S1".When the engine is started, feeder pump (28) generates flow. The supply oil flow from the feeder pump is sent to port "P" of steering manifold (39). The pump also delivers oil to pressure compensator spool (27) and load sensing spool (26).When pump supply pressure reaches 19000 1000 kPa (2755 145 psi), pressure compensator spool (27) moves against the spring force. This movement opens a passage for pump supply oil to flow into the chamber of displacement piston (30). Pressure in the piston chamber causes the displacement piston to move the swashplate against the force of the bias spring. This movement reduces the angle of the swashplate. The pressure compensator spool maintains pump output at a constant pressure.Resolver valve (32) in steering manifold (39) compares the load signals of main implement manifold (1) to the highest load signal in the steering manifold. This resolver valve directs the highest load signal to load sensing spool (26).The load signal from resolver valve (32) in steering manifold (39) acts with the spring in load sensing spool (26). This action increases the system pressure to the level required to meet operational needs. In this case, the pump operates at standby pressure and generates only enough flow to maintain pressure in the system.Output from feeder pump (28) is sent directly to steering priority valve (35). The steering priority valve ensures that the steering system receives oil before the systems supported by main implement manifold (1). Under heavy hydraulic loading, the priority valve reduces the flow of supply oil to the main implement manifold. This reduction of flow helps to maintain sufficient flow to the steering circuit.The main implement manifold contains relief valve (31) and one pressure reducing valve (25). The relief valve limits the pressure available to the material feed systems. Pressure is limited to 21 000 1000 kPa (3050 150 psi).When the material feed system is in HOLD, the solenoids on control spools (49) are not energized. Under these conditions, the control spools are spring-centered. In this situation, the control spool opens both sides of each motor to tank pressure and the motors can free-wheel.Note: For additional information on the steering system, tow point system, or screed lift system, refer to the auxiliary system section in this publication.
Illustration 2 g06063269
Material Feed Hydraulic Schematic Forward
(1) Main implement manifold
(2) Left tow point cylinder
(3) Right tow point cylinder
(4) Screed lower valve
(5) Screed upper lock valve
(6) Screed lift cylinders
(7) Screed lower lock valve
(8) Screed-assist pressure sensor
(9) Left conveyor motor
(10) Left conveyor control valve
(11) Right conveyor motor
(12) Right conveyor control valve
(13) Left auger motor
(14) Left auger control valve
(15) Right auger motor
(16) Right auger control valve
(17) Pilot operated check valves
(18) Resolver valve
(19) Tow-point-lower valve
(20) Tow-point-raise valve
(21) Flow compensator
(22) Resolver check valve
(23) Screed-raise