Theory of Operation
FLOW COMBINER VALVE OPERATION
well as the right propel valve to ensure that the
Pilot oil from the pilot pump (C) flows through the
machine does not mistrack during combined propel
orifice (L), into the dig pilot pressure signal passage
and dig function operations. The flow combiner check
(G), past each dig function valve spool, and then to the
valve (N) prevents back flow past the flow combiner
return circuit. The flow combiner valve (D), propel flow
valve. The left propel valve does not receive supply oil
control valve (M), and the swing motor park brake
from the rear pump (Q) except through the propel flow
release valve (K) are connected to the signal passage
control valve if the upstream pressure is higher than
between the orifice and spools.
the pressure in the flow combiner circuit.
When one or more dig functions are actuated, pilot oil
The dig and propel pressure switches are actuated to
flow through the signal passage to return is blocked by
send an electrical signal to engine and pump controller
a valve spool (arm II valve shown) (O). The pressure
when the propel and dig functions are actuated.
in the blocked portion of the signal passage increases
shifting the flow combiner, propel flow control, and
When just the propel function is actuated, the left
swing park brake release valve spools.
propel valve is supplied with oil from the rear pump
and the right propel valve is supplied with oil from the
Supply oil from the front pump (P) now flows through
the flow combiner valve to the left propel valve (E) as
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