Shuttle Valve - Terex TR60 Maintenance Manual

Braking System - Braking System Schematic
Section 250-0000
The differing maximum operating pressures required for
the front and rear brakes are achieved within the treadle
valve. These can be adjusted, BUT, only together, i.e.
adjustments are made to both circuits simultaneously.
Stop Light Pressure Switch (13) - The normally open
(NO) pressure switch is located in the front plate of the
treadle valve in the 'B1' circuit. As brake pressure
increases to 2.7 bar (39 lbf/in²) and above, the circuit
should close and send a signal to illuminate the brake
lights. As pressure drops below 2.7 bar (39 lbf/in²) the
circuit should open and brake lights go out.
Lockup Drop Out Pressure Switch (17) - The
normally open (NO) pressure switch is located in the
front plate of the treadle valve in the 'B2' circuit. As
brake pressure increases to 20 bar (290 lbf/in²) and
above, the circuit should close and send a signal to the
lockup drop out solenoid, which in turn drops the
transmission out of lockup. As pressure drops below
20 bar (290 lbf/in²) the circuit should open and lockup
can be engaged.
Front Brake Callipers (5)
Refer to Section 165-0020, BRAKE PARTS.
The service brakes are of the calliper disc type. The
calliper brake head is designed for use with hydraulic
oils meeting the specifications outlined in
Section 300-0020, LUBRICATION SYSTEM. DO NOT
USE BRAKE FLUID (J1703).
The calliper head is bolted to a mounting plate on the
spindle and the disc is bolted to the wheel. There is
one brake head at each wheel. Each calliper brake
head assembly consists of a torque plate, two brake
pads; one on each side of the disc, and six brake
pistons; three on each side of the disc.
The brake is actuated by hydraulic oil entering the
brake head through one of the bleeder ports. The
piston bores on each side of the torque plate are
interconnected by internal passages. When the brake
is actuated, the hydraulic pressure forces the pistons
against the brake pads which are in turn forced
against each side of the brake disc, slowing or
stopping the disc and wheel rotation.

Shuttle Valve (6)

Refer to Section 250-0140, SHUTTLE VALVE.
The shuttle valve allows the distribution of pressure
from either the treadle valve, to activate the rear
2
service brakes, or, the retarder control valve, to utilise
the rear service brakes as a retarder.
The shuttle valve consists of a well fitting spool which
is pushed under pressure, depending on flow direction,
to one end position, where it seals against an 'O' ring
seal. The 'O' ring is protected by a metal housing.
Oil Cooled Disc Brakes (7)
Refer to Section 165-0030, BRAKE PARTS.
Service Brakes
The service brakes are of 'Upright Design', i.e.
requiring pressure to hold the brakes on.
The rear service brakes are hydraulically actuated to
slow or stop drive wheel rotation. When the treadle
valve in the operators' compartment is depressed, or
when the retarder control lever on the centre console
is actuated, with the retarder selection switch (if fitted)
at the disc brake position, hydraulic pressure is
transmitted to the disc brake assembly. Hydraulic
pressure entering the disc brake assembly forces the
service piston against the brake disc pack consisting
of damper assemblies, rotating friction discs and
splined plates.
The rotating friction discs, which are driven by the
wheel through wheel drivers and disc drivers, are
compressed between the splined plates. This slows
down and stops rotation of the driving wheels. The
force applied against the disc pack is directly
proportional to the degree of which the service brake
treadle valve is depressed, or, retarder control lever is
moved.
When the service brake treadle valve, or retarder
control lever, is released, hydraulic pressure against
the service piston is relieved allowing the service
piston to return to its original position, thus, relieving
the pressure against the brake disc pack.
Parking Brakes
The parking brake is of 'Inverted Design', i.e. requiring
pressure to hold the brakes off.
The parking brakes are controlled by the park/
emergency brake control mounted on the right hand
side of the dash panel. The parking brakes are applied
by spring tension and released by hydraulic pressure.
With the park/emergency control 'Out', the parking
brakes are held off. With the park/emergency control
'In' the parking brakes are held on.
SM 1222 Rev 1 9-99