Better Brakes for Passenger Vehicles
Page 50
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A BRAKING system suitable for rIbuses and coaches is dealt with in patent No. 700,574 (British Transport Commission, 55 Broadway, London, S.VV.1). The novelty lies in the means for co-ordinating the hydraulic and mechanical systems.
The view shown in the drawing is one looking outwards from between the wheels. The hub assembly is mounted on a casting (1) stiffened by webs which extend to form bosses (2). These carry tubular members which pro:0:ct leftwards and are rigidly attached to a unit (3) abutting on a helical spring (4).
The spring forms the main suspension member, whilst the whole assembly eau swing on parallelogram links pivoted on two pins (5 and 6). The drive to the wheel is transmitted by a universally jointed shaft which passes through the central opening 7.
The brake shoes are operated by a cam mounted on spindle 8, which is worked by the arm 9. The arm can be moved by a push-rod extending into the lower tube which houses a hydraulic cylinder (10). This gives one mode of operation, the other being by pull-rods coupled to lever 11.
This works rod 12, which is fitted with a sealing piston inside the hydraulic cylinder. The admission of liquid under pressure to space 13 operates the brakes hydraulically, whilst mechanical operation is given by the inward movement of the left-hand rod. It abuts the piston rod and moves it, taking with it the sealing piston so that the hydraulic volume is not altered.