6
Description of components
DESCRIPTION OF BRAKE COMPONENTS
1-37
1.17 PARKING-BRAKE VALVE
PARKING-BRAKE VALVE WITH
(SEMI-)TRAILER CONNECTION
Purpose
The parking-brake valve enables simultaneous,
controlled operation of both the parking-brake
system of the tractor and the (semi-)trailer
brakes.
Operation
The parking-brake valve has 3 positions:
A:
driving position
B:
parking position
C:
test position
Driving
With the handle in the driving position, there is a
through connection for the reservoir pressure
(port 1) to the connections for the spring-brake
cylinders (21) and the (semi-)trailer (22). The
exhaust is closed now.
The output pressure at ports (21) and (22) is
now approx. 8 bar (see graph).
Emergency brake
When the handle is moved backwards against
the spring pressure, stem (3) will be forced
downwards by eccentric (2). Chamber (a) can
now be vented and as a result the pressure at
port (22) will drop. Via the bore in valve (10) the
pressure at port (22) will also drop. Spring (4)
forces piston (5) down until valve (6) comes into
contact with the seal collar of stem (3). A state
of balance is now achieved.
When the handle is moved against stop (7), the
exhaust will remain open, so that the spring
brakes and the (semi-)trailer brakes will be
applied to their maximum (max.
emergency-brake position).
R600089
A
B
C
3
21
1
22
a
2
3
5
4
6
8
7
9
10
R600092
3
ǹ 0006