Theory of Operation
The brake system of this lift truck is to be used as
a parking brake and for emergency stopping only.
Slowing or stopping the lift truck is normally done
through "plugging" of the traction motors.
Plugging is a method of slowing the rotation of the
drive wheels by changing the direction of current
flow through the traction motor. In an emergency,
the truck can be stopped by lifting the foot off of
the brake pedal.
The brake system is designed to mechanically
apply the brakes when the operator removes his
foot from the pedal. The brakes are electrically
released when the operator depresses the pedal.
The brake system consists of a brake pedal, an
electric brake relay, and two self-contained disc
brake units. The disc brake units are attached to
the commutator end of the drive motors to take
advantage of the increase in torque supplied by
the gearbox.
Internal coil springs in the disc brake units supply
the force which clamps the rotating friction plate.
An electric solenoid coil acts against these springs
to release the brakes. The friction plate floats on
the arbor so that equal pressure is applied to both
sides.
When the operator releases the brake pedal, two
micro-switches are actuated. One signals the
system controller to cut power to the traction
motors. The second signals the brake relay to cut
power to the disc brake units, thus applying the
brakes. The system controller does not monitor
the operation of the disc brake units or the relay.
NOTE
Many of the brake adjustments interact with
one another. When performing any
adjustments on the brake system, please
follow the order of the list below. When
servicing the brakes, check all of the
adjustments listed below (See Brake
Adjustments).
1. Brake Pedal Height
2. Brake Switch Adjustment
3. Disc Brake Air Gap
4. Braking Force (Clamping Pressure)
The brakes should stop a fully loaded truck on a
dry, level floor within 1.1 feet per MPH the truck is
traveling. For example a fully loaded truck
traveling 6 MPH should stop within about 6.6 feet.
The brakes should hold a fully loaded truck on a
10% grade.
E
lectric
C
ounterbalance
H
igh
O
utput
Brakes
REV W1 12/02/99
3.1
