Bus Brake and Door Lock Patented
Page 52
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PATENTS have been taken out jointly by Mr. W. M. Little, general manager, Edinburgh Transport Department, and Leyland Motors, Ltd., for a device which interlocks the hand brake of a bus and its pneumatically operated doors. The arrangement also includes an interlock affecting gearbox operation.
The layout is such that the doors are not opened until the rear-wheel brakes have been applied, and the gear lever of the Pneumo-Cyclic transmission cannot be operated until the doors have been closed. Door operation is controlled by movement of the gear lever into an additional gate which is normally used for the fifth ratio of a five-speed transmission.
An air line is taken from the dooroperating valve to a diaphragm located below the normal hand-brake cross-shaft, so that the rear-wheel brakes are applied as soon as the door-operating control is moved.
There is a positive delay in the system so that the hand brake is not released immediately when the doors are closed. This has been found necessary when a bus stop is on a gradient. The rearbrake interlock is completely independent of the normal braking system, and unauthorized interference with the doors cannot affect the normal braking.
The system has the benefit that the driver can apply and release the rearwheel brakes, and open and close the doors merely by movement of the gear change lever. The door-gearbox interlock has been used on 50 Leyland Tiger Cub single-deckers which have been operating in Edinburgh for nearly 12 months, and the braking interlock has been incorporated in nine of these vehicles since October and November last year.
A further 50 Tiger Cubs are on order and these will have the complete interlocking system.