The load sensing signal system consists of the following components: implement pump (2), combination valve (3) and implement control valve (5).
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| Illustration 1 | g00859212 |
(1) Hydraulic tank (2) Implement pump (3) Combination valve (4) Steering cylinders (5) Implement control valve (6) Shear cylinders (if equipped) (7) Tilt cylinders (8) Lift cylinders (9) Collector arm cylinders (10) Grapple arm cylinders (AA) Pressure tap (load signal pressure) (BB) Pump pressure oil (CC) Return oil (DD) Case drain oil | |
The load signal network is a network of passages and shuttle valves between the implement control spools. The shuttle valves are more commonly known as resolver valves. The load signal network directs true load signal pressure from each control spool through the resolver valves. The true load signal pressure is the actual pressure which is present in the cylinder. The highest true load signal pressure will pass through the network to the connection at port (PL) of implement control valve (5) to the port (LS) of combination valve (3) .
When the engine starts, there is no pressure in the load sensing signal system. Implement pump (2) is stroked to maximum output. As the implement pump begins to turn, the pressure in the signal system increases. The pump strokes to low pressure standby until a function is activated.
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| Illustration 2 | g00859275 |
(2) Implement pump (3) Combination valve (11) Solenoid valve (12) Low brake pressure switch (13) Brake accumulator (14) Service brake charging switch (15) Brake pressure reducing valve (16) Shuttle valve (17) Check valve (18) Priority relief valve (19) Spool (steering) (20) Shuttle valve (A) Steering (LEFT) (B) Steering (RIGHT) (P2) Pump pressure to implement control valve (PL) Signal pressure from implement control valve (SB) Pump pressure to service brake (T3) Return to tank (TP4) Return to tank (XA) Pilot pressure from LH pilot control valve (STEERING LEFT) (XB) Pilot pressure from LH pilot control valve (STEERING RIGHT) (AA) Pressure tap (load signal pressure) (BB) Pressure tap (brake accumulator) | |
Electrical current will energize solenoid valve (11) when the operator turns the engine start switch. The current causes solenoid valve (11) to shift downward. This blocks signal pressure oil. The implement pump is prevented from upstroking which decreases the load on the engine. Thus, the engine is easier to start.
When the operator releases the key, current is cutoff to solenoid valve (11). Solenoid valve (11) shifts upward. This allows the signal pressure oil to flow to the implement pump.
Solenoid valve (11) is energized when the brake accumulator pressure drops below 10350 kPa (1500 psi). Solenoid valve (11) is de-energized when the brake accumulator pressure reaches 13800 kPa (2000 psi). When the brake accumulator pressure drops below 10350 kPa (1500 psi), service brake charging switch (14) and low brake pressure switch (12) are activated.
Service brake charging switch (14) will activate solenoid valve (11). Low brake pressure switch (12) will activate a low brake pressure indicator in the cab. Low brake pressure switch (12) will deactivate when the brake accumulator pressure reaches 10350 kPa (1500 psi). Once brake accumulator (13) is charged to 13800 kPa (2000 psi), service brake charging switch (14) will deactivate. This will cause solenoid valve (11) to deactivate.
Use pressure tap (AA) in order to measure the signal pressure.