Gradall 534B (9020-7317) Service Manual - Manual (Page 91)

The inching feature allows the operator, when
carrying a load, to move the handler very slowly for
maneuvering in tight places.
To operate the inching feature, the operator
depresses the brake-inching foot pedal (A)
approximately 1/2" to 1". This creates movement of
the linkage (B) up to rocker arm (C) which has a tab
on it making contact with the low torque inching
switch (D). As this first movement occurs and
physical contact is broken, the switch is energized
and it activates the low torque inching solenoid
valve (E). This sends pilot circuit oil down to the de-
clutch valve (F) on the transmission and the
transmission de-clutches and there is no power to
the front axle.
As the rocker arm (C) continues to move the
linkage in the inching panel moves. Spring (G)
serves as an adjustable buffer. The linkage
movement then forces the control arm on the
potentiometer (H) to rotate. The potentiometer is
basically a rheostat in the electrical circuit going to
the Forward/Reverse Pilot Pressure Control Valve
(J)
GRADALL LOED MATERIALS HANDLER 534B SYSTEM OPERATION
I N C H I N G
As the operator continues to depress the brake-
inching pedal (A) and the potentiometer (H) rotates,
the electrical current controlling the Fwd/Rev Pilot
Control Valve varies.
The Fwd/Rev Pilot Pressure Control Valve sends
pilot oil pressure to either end cap of the Fwd/Rev
valve (K). Depending on the strokes of plunger,
in the Fwd/Rev control valve varying, volume of oil
is routed on the series/parallel valve and to the rear
drive motors.
The further down the operator depresses the brake-
inching pedal, the lower oil volume goes to the
motors.
As the operator continues to depress the brake-
inching pedal, the front axle brakes are applied and
normal braking occurs.
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