All Implements In HOLD
The schematic shows all of the implement control valves in the HOLD position.
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| Illustration 1 | g01078758 |
All implements in HOLD position (1) Return pilot oil from stabilizer circuit (2) Return oil from stabilizer circuit (3) Load signal from stabilizer circuit (4) Pressure reducing valve (pilot) (5) Pilot shutoff valve (6) Supply oil to stabilizer circuit (7) Pilot oil to stabilizer circuit (8) Return oil from brake circuit (9) Supply oil to braking circuit (10) Boom cylinder (11) Load control valve (boom cylinder) (12) Compensating cylinders (13) Control valve (boom raise) (14) Load Control valves (15) Control valve (coupler tilt) (16) Quick disconnects (auxiliary services) (17) Line relief valve (18) Control valve (auxiliary) (19) Main control valve (Implement) (20) Control valve (boom extend) (21) 100 micron filter (22) Proportional pilot reducing valve (23) Telescoping cylinder (24) Flow Control Valve (Drain) (25) Load control valve (telescoping cylinder) (26) Manually lowering the pump (27) Inlet Section (28) Priority valve (29) Supply to steering (30) Pump supply (Steering priority signal) (31) Pump supply (32) Load signal to pump (33) Relief valve (load signal) (34) Return to tank (35) Boom dampening system | |
The illustration shows the standard implement valve that is used in all the B - SeriesTelehandlers.
The centering spring that centers the spool is located on the right side of the valve. In HOLD, the centering spring will center the spool in the valve body. The valve may feature a combination of the line relief valve and of the makeup valve.
Part of the control valves are equipped with a manual lowering screw. As an example, this screw is used to assist in lowering the boom when the engine is not running. Load check valves prevent implement drift whenever the supply pressure is less than the load pressure or the work port pressure.
The pressure compensator maintains a controlled pressure differential across the spool in order to control flow to the circuit. If more than one circuit is used at a time, the circuit with the highest port pressure is used to regulate the flow through each control valve.
The hydraulics of the main control valves are similar to the former machines. The valves are similar to PPPC hydraulic system that is used in other Caterpillar machines. The system that is shown incorporates the flow control and the resolver into one component called a pressure compensator valve. This is different from other hydraulic systems that had resolvers. The pressure compensator acts as a resolver to compare the different port pressures. The pressure compensator sends signal pressure that is equal to the highest circuit pressure back to the pump. As shown, another circuit has been activated. The load sensing oil flows to the compensator valve. The oil then causes the compensator valve to move down. The compensator valve sends part of the supply oil through the signal passage. The oil then becomes signal oil. The signal network consists of all of the pressure compensator, internal passages and signal lines. This signal is sent to the pump control and to all of the other pressure compensator valves. Also, passages in the valve drain will allow oil to flow back to the tank. The passages prevent pressure from building up. High pressure leakage around the spool may cause an increase in the pressures in the ports.
Note: The passages are shown for the control valve in HOLD.