6-28
Boom raise position
(2)
B2
A2
b2
a2
P
T
B1
A1
B2
A2
LS
a2
b2
b1
a1
Pst
T
Dump
Roll back
Up
Down
Floating
P
Bucket
Boom
Hydraulic circuit
Load holding
valve
75796WE52
When the pilot pressure is led to the port b2, the boom spool moved to raise position.
Oil from the pump flows to the cylinder port B2 through the load holding valve and oil from the
cylinder flows into the tank passage through the cylinder port A2.
Load holding valve
When the load pressure is higher than the pump pressure, the load holding valve shuts off the
passage between the high pressure feed passage and the center bypass passage and prevents
the reverse flow from the cylinder.
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Содержание HL955
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