33 - 7
Boom Raise (BM) Operation (cont’d)
When pilot pressure is applied to port br1, by operating the
right hand joystick controller, spool B moves to the left
closing off the neutral gallery, allowing oil from pump P2 to
enter the gallery J. Pilot pressure is also applied to port C in
the load holding valve X. Check valve D opens, causing
piston E to open poppet valve F, connecting passageways
G and H. Because check valve K is closed, ports G and L
are shut off. Oil bleeds from check valve M through pilot hole
P to gallery J, causing check valve M to open allowing oil to
enter the outlet port BR1.
Combined flow from both pumps is achieved when pilot
pressure is applied to port N in the logic check valve Y. Oil
from pump P2 flows through gallery T. When this pressure
falls below the pressure delivered by pump P1 to port R, the
check valve S moves to the left against the spring pressure
and allows oil to flow from port R into gallery T and to the
outlet port BR1.
Section E Hydraulics
9803/6410
Section E
33 - 7
Issue 1
Control Valve
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