HOUSING 7N7012 - Caterpillar

Illustration 6 g03841842
(1) From implement pump
(2) Implement control valve
(3) To auxiliary valve supply
(4) Margin relief valve
(5) Tilt spool
(6) Lift spool
(7) Ride control manifold
(8) From brake/fan combination valve
(9) Check valve
(10) Hydraulic lockout valve
(11) Tilt back pilot solenoid valve
(12) Raise pilot solenoid valve
(13) Ride control activation solenoid
(14) Lower pilot solenoid valve
(15) Dump pilot solenoid valve
(16) Auxiliary pilot solenoid valves
(17) Check valve
(18) Implement pump compensator valve
(19) Load sense relief/bleed valve
(20) Auxiliary pressure compensator valve
(21) Tilt pressure compensator valve
(22) Lift pressure compensator valve
(23) Manual lower valve
(24) Lift cylinders
(25) Hydraulic tank
(26) Pilot accumulator
(27) Back-pressure valve
(28) Return oil filter
(29) Pump and motor case drain
(30) Case drain return screen
(31) Tilt cylinder
(32) Makeup and line relief valve
(33) Tilt anti-drift valve
(34) Ride control valve
(35) Lift anti-drift valve
(36) Balance valve solenoid
(37) Balance valve
(38) Ride control accumulators
(39) Check valveWhen the lift control lever is moved into the RAISE position, the current proportional to the movement of the control lever is directed to the coil on the raise pilot solenoid valve (12). The solenoid valve sends a proportional amount of pilot oil to the raise end of the lift spool (6). The lift spool begins to shift down.As the lift spool shifts down, supply oil from the implement pump (1) is directed to the lift pressure compensator valve (22) and through an orifice and check valve to the implement pump compensator valve (18). The orifice stabilizes the load sensing signal pressure to the implement pump, to the spring chamber on each compensator valve, and to the margin relief valve (4). The load sensing signal moves the pump load sensing spool in the pump control valve to upstroke the pump.The load sensing pressure acts on the top of the margin relief valve. During the upstroke of the implement pump, the margin relief valve maintains an implement pressure equal to the load sensing pressure and the value of the spring. When the control lever is released, the load sensing pressure goes to approximately zero pressure. The margin relief valve opens to relieve supply oil pressure, eliminating pressure spikes in the closed center system.When the lift spool directs the pump supply oil to the pressure compensator valve, the valve moves down and oil flows through the lift spool and around the lift anti-drift valve (35) to the head end of the lift cylinders (24). As the pressure changes in the head end of the lift cylinders, the pressure compensator valve opens and closes to maintain a constant flow for a given control spool displacement.If the machine is equipped with the optional ride control, the balance valve solenoid (36) will be energized, allowing oil on the right side of the balance valve (36) to flow to the hydraulic tank. As the pressure in the head end of the lift cylinders increases to raise the implements, the oil pressure on the left side of the balance valve will force the balance valve to shift to the right. Supply oil flows over the check valve, through the balance valve to the ride control accumulators (38), charging the