TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
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ELECTRO-HYDRAULIC SYSTEM - CONTINUED
a.
General.
(1)
Auxiliary control valve (90) has all components in tilt control valve minus drift reduction solenoid valve
(93). Auxiliary valve controls auxiliary implements such as a logging fork, a side dump bucket, or a multi-
purpose bucket.
(2)
Oil from implement piston pump flows to auxiliary control valve at port (B). Auxiliary valve stem (113) is
controlled by pilot proportioning solenoids (95). Auxiliary valve stem is spring centered with a closed cen-
ter. Auxiliary valve stem has three positions: CLOSE, HOLD, and OPEN.
b.
HOLD Position.
(1)
Springs keep auxiliary valve stem (113) in HOLD position when pilot proportioning solenoids (95) have
not been actuated. Implement pump oil flows to auxiliary control valve (90) at pump port (B). Stem move-
ment is controlled by actuation of pilot proportioning solenoids that allow oil to flow to either end of aux-
iliary valve stem.
(2)
Position of auxiliary valve stem blocks oil in both ends of auxiliary cylinder, keeping cylinder from mov-
ing.
c.
CLOSE Position.
(1)
When joystick thumb lever is moved to CLOSE position, pilot oil is sent to left end of auxiliary valve stem
(113), moving it right. Implement oil is sent from pump port (B) around auxiliary valve stem to bottom of
compensation and load check valve (102). Compensation and load check valve is pushed up and flow goes
through openings in load check valve to bridge passage. Oil flows around auxiliary valve stem to auxiliary
cylinder head end work port.
(2)
Oil is allowed to flow to head end of auxiliary cylinder, causing it to extend. Solenoid valves (95) and aux-
iliary valve stem (113) respond in proportion to signal received from operator controls.
(3)
Oil from rod end of auxiliary cylinder enters through rod end work port and exits through tank port (C) to
hydraulic tank.
d.
OPEN Position Operation.
(1)
When joystick thumb lever is moved to OPEN position, pilot oil is sent to right end of auxiliary valve stem
(113), moving it left. Implement oil is sent from pump port (B) around auxiliary valve stem to bottom of
compensation and load check valve (102). Compensation and load check valve is pushed up and flow goes
through openings in load check valve to bridge passage. Oil flows around auxiliary valve stem to rod end
work port.
(2)
Oil flows to rod end of auxiliary cylinder, causing cylinder to retract. Solenoid valves (95) and auxiliary
valve stem (113) respond in proportion to movement of operator controls.
(3)
Oil from head end of auxiliary cylinder enters through head end work port and exits through tank port (D)
to hydraulic tank.
14.
Inlet Valve Manifold.
a.
Inlet valve manifold (91) contains signal duplicating reducing valve (105) and relief valve for load sensing (106).
Signal duplicating reducing valve reduces supply oil to signal pressure.
b.
When a circuit is active, signal duplicating reducing valve (105) duplicates pressure received from load signal
resolvers of active circuit with highest pressure. This signal pressure is then sent to implement piston pump at point
(E). Implement piston pump is upstroked in proportion to signal pressure received.
c.
Relief valve for load sensing (106) limits maximum signal pressure by draining oil above maximum signal pres-
sure back to hydraulic tank at point (F).
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