Gradall 534B (9103-1390) Service Manual - Manual (Page 58)

LIFT CIRCUIT
The lift circuit allows the operator to raise the boom
assembly up 70ø and lower it to a -4ø angle.
Movement of the boom control lever back, raises
the boom and a forward motion, lowers the boom.
An angle indicator is located on the left side of the
main boom section.
At the base of both lift cylinders is a counterbalance
valve. The valves serve as a lock-out valve to hold oil
in the cylinder should a hose break or to prevent
the engine is shut off. It also serves as a flow valve to
control the downward movement of the boom at a
controlled speed.
The 534B-6 models have 4 1/2 cylinder. The 534B-8
models have 5" cylinder.
MANUAL “QUICK-SWITCH” ASSEMBLY
A manual, lever operated “Quick-Switch” Assembly
is used at the front of the boom head to attach the
fork and carriage, truss boom or material bucket.
To engage the attachment a button is depressed and
a locking pin (A) removed. Raising the lever moves
the engaging plunger (B) up. Lowering the lever
moves the plunger down.
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