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1 Introduction
The air actuated disc brake has been designed to incorporate a
direct mounted air actuator which is mounted axially as shown in
Fig. 4.
The Brake, detailed in the exploded view (Fig. 1), can be fitted to
any axle and can be used for vehicle parking when a service /
spring brake actuator is fitted.
The basic operation of the Brake is simple, but it is important that
the features of the load insensitive automatic adjuster are clearly
understood.
It is essential that the correct service procedures be observed to
ensure that the Brake gives satisfactory service throughout its
working life.
How it works
(Refer to Cross Sections – Figures 2 & 3)
The air actuator is attached to the brake housing and operates
directly onto the internal operating shaft assembly, thus removing
the necessity for the conventional external lever and linkage
arrangement.
Sealing between the air actuator and housing is achieved by seals
located in the housing and actuator assembly.
The carrier, secured to the vehicle, straddles the rotor and
supports the brake pads.
The housing assembly slides on two fully sealed guide sleeves
bolted to the brake carrier.
As the pads wear, adjustment takes place automatically and
independently of load.
NOTE
: "Load Independent" means adjustment takes place under
very small clamping forces only, therefore preventing over
adjustment and minimizing air consumption.
Two guide sleeves (24,26) are bolted on to the brake carrier (2)
by means of guide sleeve screws (25,27). The brake carrier is
connected to the axle. The housing (18) is mounted so that it
floats on the guide sleeves and a bridge (1) is fixed to the housing
(18) to provide the reaction force on the outboard pad (3).
Fig. 4
The housing and bridge slide on 3 bushes (14,14,16) that are
pressed into the housing (18). On the short guide sleeve side (26),
the bush (16) is oval to accommodate brake deflection during
braking, whereas the longer sleeve (24) the bush is round and
provides a more positive location for the housing. The guide sleeves
are sealed externally by dust excluders (12) and end caps (28).
The force introduced from the air actuator is amplified by the
geometry of the operating shaft (21). This clamping force is
transferred to the inboard pad (3) via the half-bearings (20), the
rollers (19), the tappets (34), the pistons (35) and the Piston
Heads (7). Once the inboard pad (3) has been applied, the force
of reaction acting through the floating housing (18) and bridge (1)
pulls the outboard pad (3) on to the brake rotor. The forces
created by the friction of the brake pads on the brake rotor are
transferred at the ends of the pads on to the carrier (2), which is
rigidly mounted to the axle.
The brakes are released by reducing the input force on the
operating shaft (21), thus reducing the clamp force of the brake.
The return spring (46) then returns the clamping mechanism and
the operating shaft back to their starting position, leaving the
pads with a defined running clearance to the rotor. The small run
out of the brake rotor and hub-bearing clearances will then
generate a small clearance for the outboard pad (3) through only
a few revolutions of the rotor.
ArvinMeritor Air Disc Brake ELSA 195
11
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