GB715288A - Improvements in or relating to a fluid pressure braking system for a vehicle - Google Patents

Abstract

715,288. Fluid-pressure brakes. FAWICK, T. L. March 11, 1952, No. 6275/52. Class 103(1) In a vehicle braking system a wheel-brake is associated with the axle structure 11, 17 and the system comprises two fluid-impelled members 20, 30 operable each independently of the other's operation, for actuating the brake, fluid-confining means 22, 25, 28 being mounted directly upon the said axle structure for containing and effecting actuation of both said members, and respective means each operable independently of the other's operation for supplying pressure fluid to said members alternatively. The control system comprises two independent systems; one air-pressure, the other hydraulic. The air-braking system is of the normal type comprising a motor driven air compressor 39 which supplies air to service tanks 41, 42 which, in turn, supply air, via relay valves 50 and 53 respectively through brake chambers 51, 51 and 54, 54 to the rear wheels of the tractor 51a and the trailer 54a and also air is supplied from the tanks to operate the front brakes of the tractor. In addition to the foregoing normal air braking system is incorporated an hydraulic system consisting of a line 64 from the compressor's output line 40 to a reserve and emergency air pressure tank 67 via a non-return valve 65. From this tank air is supplied via line 68 through a second footoperated valve 69 to a servo-cylinder 70 whose piston-rod 71 is hinged to the outer-end of a piston rod 76 of an hydraulic master cylinder 77 which supplies oil or brake-fluid to brake chambers 51, 51 and 54, 54 to operate the rear brakes of the tractor and trailer respectively and also through a supply line 79 to operate the front brakes of the tractor. The brakes may also be operated in this system by the actuation of the hand-brake lever 96. The brake chambers are situated adjacent the axle structure 11 and consist essentially of two chambers; one operated by air pressure, the other by hydraulic means. Air pressure is admitted to one chamber through a pipe 26 and exerts a pressure on a diaphragm 20 which pushes head 24 of a stem 19 against the resistance of a spring 23. This movement operates rocker arm 18 secured to stem 19 and operates rock-shaft 14 which turns cam head 13 to operate the brake shoes 10 against the brakedrum 12. Hydraulic fluid enters the cylinder 28 by socket 29 and operates piston 30, the stem 31 of which extends through slide bearing 32 and has a flat head 33 which impinges against the diaphragm 20, thus operating the stem 19 as previously described. Special means are provided for disconnecting the coupling at 61 and 63 when the trailer is not required so that no air is admitted to the hydraulic lines when they are uncoupled. Pipe 26 may alternatively be coupled to a source of vacuum to assist in freeing locked brakes should such an emergency arise.