GB336640A - Improvements in or relating to the braking of vehicles - Google Patents

Abstract

336,640. Dewandre, A., and Soc. Anon. du Servo Frein Dewandre. June 17, 1929. Fluid-pressure.-In a motor-vehicle braking system some only of the brakes, e.g. the front brakes a, a<1> are operated for all degrees of braking by the effort of a manually deflected lever or pedal b in combination with effort due to a vacuum or other servo mechanism f<1> controlled by said lever or pedal, as described in Specification 232,738, while the other brakes, e.g. the near brakes a<2>, a<3>, are simultaneously operated solely by power mechanism k fluid-coupled only to the servo mechanism f<1>. When the pedal b is depressed a valve h is opened and the power effort of the vacuum &c. cylinder f<1> is applied to the front wheel brakes only, through rods g, e, lever d, shaft c, levers d<1>, d<2> and rods e<1>, e<2>, manual effort being applied to the pedal to overcome reaction. A pipe l transmits the vacuum &c. through a. reducing valve o to the cylinder k having a piston m connected by a wire n, levers d<5>, d<6>, d<7>, shaft c<1> and rods n', n<2> to the rear wheel brakes. The regulatable reducing valve o enables the ratio of the braking efforts on the front and rear wheels to be altered according to the loading of the vehicle and comprises a casing o<1>, Fig. 2, having a valve o<3> held on its seat o<2> by a spring o<4> the tension of which is adjustable by a screw o<5>. The space below the valve is in communication with the induction pipe &c. or the vacuum cylinder f<1> by a pipe l<1> so that the tension of the spring o<4> determines the vacuum in the pipe l leading to the brake cylinder k for the rear wheels. For effecting release of the vacuum in the cylinder k a second valve o<10> is pressed by a light spring o<15> against a seat o<11> in an opening through the valve o<3>. The back of the valve o<10> is in communication with the pipe l so that when the vacuum below the valve o<3> is released the valve o<10> is opened maintaining equilibrium between the pressures in the cylinders k and f<1>. A hand lever p is provided for the rear wheel brakes, being connected by a rod p<2>, lost-motion device p<1> and arm d<9> with the shaft c<1>. Instead of using separate cylinders for the front and rear brakes a single cylinder with two opposed pistons may be used, the reducing valve o being arranged in a partition between the pistons. In a further modification, the vacuum cylinder k has a separate distributor valve connected by a Bowden wire with the valve h so that the valves are operated simultaneously or, if the cylinder k is in alignment with the cylinder f<1>, the valves may be connected by a rod. The reducing valve o may be replaced by mechanical means in the transmission for altering the ratio of braking forces. Pressure systems may be used instead of vacuum and the invention may be applied to hydraulic transmission systems.