Patent GB-1424019-A (GB)
Title: Vehicle braking system
IPC: B60T11/10
Filed: 1973-03-08
Abstract: 1424019 Controlling vehicles LABAVIA-SGE 8 March 1973 [10 March 1972] 11339/73 Heading B7H [Also in Division F2] The piston 2 of a master cylinder 3 is moved to actuate the brakes of a vehicle by operation of the piston 7 of a vacuum-suspended servobooster 6 when atmospheric pressure is applied to a compartment B of the servobooster 6, such application of atmospheric pressure being brought about by depression of a brake pedal 5 or alternatively by other means such as the release of the vehicle accelerator pedal 35 (as shown) a command transmitted by radio or optically or by manual actuation of a knob mounted on the vehicle dashboard; said other means control the opening of a valve 30 mounted in a duct 29 extending between compartment B and atmosphere to thereby control the pressure prevailing in compartment B. In the embodiment of Fig. 1, the brake pedal 5 acts on a link-rod 16 which engages a small piston 18 slidable in a bore 19 of a hollow hub 14 fast with the piston 8. The hub 14 defines a valve seat 20 and the piston 18 defines a valve seat 21, which seats 20, 21 are engageable by a valve member 22 in the form of a washer borne by an elastically flexible cup 23. The hub 14 incorporates passages 25, 26 and passage 26 includes a valve 49. In the unactuated position of the booster as illustrated valve 21, 22 is closed whereby compartment B is cut off from communication with the atmosphere via an air filter 28, and valve 20, 22 is open whereby compartment B is connected to a compartment A via passages 25, 26 and via compartment A and a pipe 12 to a suction or vacuum source 13 in the intake pipe of the vehicle engine. When the pedal 5 is depressed valve 20, 22 is closed to disconnect compartments A and B and valve 24, 22 is opened to connect compartment B to atmosphere via filter 28 whereby piston 7 and hub 14 are moved leftwards to move piston 2 leftwards to operate the brakes. The valve 30 interposed in the duct 29 is an electro valve in a circuit 32 comprising a switch 34 closed when the pedal 35 is released, a general (e.g. ignition) switch 36, and a switch 37 opened when the clutch pedal 37 is depressed. A throttle apparatus 31 is interposed between atmosphere and the valve 30 and acts to reduce the crosssection of the throttled passage through the apparatus 31 as the suction of source 13 increases. To this end the throttle apparatus 31 has an enclosure 38 connected to the suction source 13 via a passage 39 and bounded by a diaphragm 40; a ribbed finger 45 is inserted between the diaphragm 40 and a ball valve 42, 44, and as the suction of source 13 increases diaphragm 40 is sucked rightwards allowing ball 42 to move towards seat 44 to reduce the cross-section of the throttled passage. The apparatus 31 also comprises an adjusting screw 47 which acts via a cup 48 and a spring 41 to enable the separation between the ball 42 and seat 44 to be adjusted; such adjustment may be manual or dependent on variations of a suitable parameter such as time, speed or deceleration of the vehicle. When the pedal 35 is released, switch 34 closes to complete circuit 32 which opens valve 30 to connect compartment B to atmosphere via duct 29, apparatus 31 and air filter 51, and air is fed into compartment B to initiate braking to an extent determined by throttle apparatus 31. The valve 49 prevents all but negligible flow of air from compartment B into compartment A. The switch 37 which is opened when the clutch pedal is depressed acts to prevent braking during a gear change when the accelerator pedal 35 is released. In the embodiment of Fig. 2, the accelerator pedal 35 when depressed acts via a compression spring 60 on a lever 58 to close a valve 30 which is biased open. When the accelerator pedal 35 is released, valve 30 opens to connect compartment B to atmosphere via valve 30 and throttle apparatus 31, throttle apparatus 31 being adjustable. Air introduced into compartment B is finally aspirated to suction source 13 via passages 25, 26 and compartment A. The installation of Fig. 2, is primarily intended for vehicles with an automatic gearbox ; with a manual gear-box means to neutralize the release of pedal 35 during depression of the clutch pedal may be provided.