Adjusting Braking to Load
Page 45
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AA MEANS of automatically adjusting an air-pressure brake so as to increase the line pressure with an increase of load is shown in patent No. 917,494. (Girling Ltd., Kings Road, Tyseley, Birmingham H.)
The essence of the scheme is the device shown in the drawing. In operation, compressed air is applied to a piston (1) which is then forced upwards. As it rises, it causes a bellerank to roll up an inclined plane (2) and in doing so thrusts on a rod (3).
The other end of the rod forces open a valve (4) and allows air to pass from
the inlet (5) to the brake line (6). At the same time, the air is also applied to a piston (7) which acts in opposition to the bellcrank and so sets up equilibrium at a predetermined pressure.
To vary the action in accordance with the load, the main suspension system is arranged to tilt the inclined plane and so give an adjustable leverage between the primary piston and the horizontal member. The range of variation of angle is from 30° to 60° from the vertical, making the pressure variation 4 to 1.