Gradall 534B (9020-7317) Service Manual - Manual (Page 41)

General
The brake system furnished on the handler includes
a service brake, parking brake and Mico lock.
Because service braking and “inching” (slow travel)
functions overlap, some features of inching will be
discussed here. Refer to Drive Train Section for
additional information on inching travel.
Inching Travel
cylinder, brake fluid flows to wheel cylinders to
Overlap between service braking and inching occurs
because the same foot pedal controls both
functions. and also because both functions control
travel speed. However, the methods of controlling
travel speed are quite different. service braking
involves a controlled stopping force applied to the
front wheels while inching involves a controlled
driving force applied to the rear wheels.
The service brake/ inching pedal has three separate
functions:
As illustrated, the three functions occur in sequence
as service brake i inching pedal is depressed from top
to bottom of stroke.
BRAKE SYSTEM
Service Brakes
The power-assisted hydraulic service brake is
applied only to front wheels of handler.
The service brake system includes an accumulator
which is pressurized by the pilot hydraulic system.
Accumulator pressure is available at the pressure-
intensifier type service brake master cylinder.
When the service brake/inching pedal is depressed
far enough to actuate the service brake master
cylinder, brake fluid flows to wheel cylinders to
apply service brake. At the same time, accumulator
pressure is applied to a piston within master cylinder
to intensify (boost} pressure to wheel cylinders.
A Low Brake Pressure Light is provided to warn
the operator when accumulator pressure falls below
normal operating range. With engine running above
idle speed, the accumulator is charged to operating
pressure. When this pressure falls to 300 psi, the low
brake pressure light will glow.
As stated above, accumulator pressure provides the
power assist feature for service brakes. As pressure
falls, the power assist feature decreases.
Mico Lock
The Mico Lock can be used to reduce operator
fatigue by temporarily locking a service brake
application on using a hand lever rather than holding
brake pedal.
To Apply Mico Lock
1.
2.
It disconnects front drive axle from
transmission.
It controls hydraulic flow to rear axle drive
motors (hydraulic flow regulates speed).
It applies service brake.
1.
2.
3.
Practice inching/braking in a safe, open
area until you are thoroughly familiar with
response of machine to pedal travel.
Though it is possible to stop the handler
without the power assist feature, very
heavy foot pressure is required and
stopping distance will be significantly
greater.
Never use Mico Lock as a parking brake.
The brake application will bleed off after a
short time and allow the machine to roll.
9
Check to be sure Mico Lock lever is pushed
forward to release position (lever horizontal).
Depress service brake pedal fully and hold.
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