Patent GB-306992-A (GB)
Title: Improvements in and relating to fluid pressure braking apparatus
IPC: B60T13/24
Filed: 1927-11-30
Abstract: 306,992. Barty, T., and Westinghouse Brake & Saxby Signal Co., Ltd. Nov. 30,1927. Fluid-pressure; hand, foot, and personal actuation. - In combined fluid pressure and mechanical brakes for automobile and the like vehicles the control valve for the fluid pressure brake is connected by flexible transmission to an actuating member connected to a mechanical brake actuating member and adapted to control the mechanical brake through substantially the whole range of braking, the valve being arranged to assume its lap condition without relative displacement of the two actuating members so that while a predetermined relative displacement of the two members is maintained a corresponding fluid pressure braking effort is maintained. The actuating member or pedal 16 controls the valve 11 by means of a Bowden wire 13 operated by relative movement of the pedal 16 and the mechanical brake actuating member or brake lever 1. Operation of the pedal 16 moves the brake lever 1 to apply the brake shoes to the drum by means of the rod 20, relative movement of the pedal 16 and lever 1 being prevented by the spring which maintains the Bowden wire in release position. This spring 39, Fig. 5, may be arranged in the control valve or between the pedal 16 and the lever 1 and is compressed when the brake shoes are applied to the drum so that the valve 11 is operated to bring the fluidpressure brake cylinder 7 into action which acts through a lost motion connection 9, a lever 5, and the rod 20. The control valve comprises a piston 34, Fig. 5, adapted to be moved by means of a spring 36 to seat against the exhaust valve 31 and raise the inlet valve 30, to connect the vacuum pipe 12 to the brake cylinder pipe 10. Vacuum acting below the piston causes it to descend, compressing the spring 36 and re-closing the inlet valve to obtain the lap position without causing relative movement of the Bowden wire Members or the brake actuating members. When the valve 11 is fully open the pedal 16, Fig. 1, comes in contact with the lever 1 and further movement of the pedal and the lever does not effect the valve. The outer member of the Bowden casing is located between a lug 14 on the spindle 15 of the pedal 16 and the casing of the control valve. The inner member is connected to a lug 19 on the lever 1 and to the movable element of the valve 11. A spring may be arranged between the lugs 14, 19. An ordinary brake lever may be adapted for the invention by means of a hinged pedal against an extended lug on which the outer casing of the Bowden wire bears, the inner cable being attached to the ordinary brake pedal. Another arrangement is shown comprising a pedal, connected to the inner cable, and hinged on the pedal lever, the bracket having a lug for the outer casing. In Fig. 6 the slotted stem 15 slides in a hollow extension of the lever 1. The end of the outer cable is received in a split bush 45 in the end of the stem 15 and the nipple 47 of the inner cable is held by means of a split pin 46 held in apertures in the extension 1<a> and passing through the slot in the stem 15. To assemble the parts an aperture 49 in the stem 15 is brought opposite the aperture for the split pin 46 in the extension 1<a> and the split pin is inserted over the cable 18, the parts are then drawn into normal position, the stem 15 sliding on flat surfaces on the split pin and being maintained in position by a nut.