Patent GB-290713-A (GB)
Title: Improvements relating to braking systems for motor road vehicles
IPC: B60T8/32
Filed: 1927-02-15
Abstract: 290,713. Cruickshank, W. R. Feb. 15, 1927. Fluid-pressure. - A braking system for road vehicles, comprising a master controller adapted to control the admission of hydraulic pressure from a pump or pumps to the brake cylinders of all the wheels of a vehicle, is provided with an automatic control device actuated by each wheel of the vehicle and controlling the flow of pressure fluid to the brake cylinder of that wheel independently of the other wheels, so as to reduce gradually the braking force applied to that wheel as the wheel is decelerated and to withdraw the braking force when the wheel is locked. The control may be hydraulic, mechanical or electric. Each wheel may drive its own pump and the master controller operate a valve between each pump and brake or a single pump may supply all the brake cylinders or the master controller may operate clutches to connect the pumps to the wheels when the brake is to be applied. In one modification the wheel drives a gear wheel pump circulating fluid which is bye-passed into the brake cylinder by a valve operated by the master-controller on application of the brakes. The fluid enters the cylinder 16 through a port 10 and a port 15 raising a piston 13, which cuts off an exhaust port 17. When the wheel locks the piston is no longer sustained by pressure from the pump and it is returned by a spring 13<2> to open the exhaust port 17. A non-return valve 15<1> is provided on the port 15 or the piston 13 may be formed with a recess. The pipe leading to the port 10 may be provided with a safety-valve. In another modification of the invention the fluid supply to the brake cylinder is controlled by a valve maintained open against spring pressure, by a piston acted on by pressure from a pump driven from the road wheel. This pump normally circulates fluid which is bye-passed to the valve controlling piston by a valve operated, when the brake is applied. The mechanism shown in the first modification may be used to operate the control valve. In a further modification the control valve is maintained open by a spring-loaded piston acted on by pressure from a pump clutched to the road wheel by operation of the master controller. To allow for reversal of the road wheel the pumps may be connected to the fluid supply reservoir by a second system of pipes provided with non-return valves. In a further modification of the invention a disc fixed or adapted to be clutched to the road wheel or its axle is housed in a casing between which and the disc is an oil film. The control valve is connected to the casing and is maintained open by the restoration of the disc due to the viscosity of the oil. In a further modification the control valve is maintained open by a spring-returned shoe pressed against a ring, revolving with the road wheel, by a cam operated on operation of the master-controller. The cam does not jam tightly on to the shoe so that the shoe may be able to move back while the cam is in operative position. In a further mechanical arrangement a disc 34 clutched, on operation of the master controller, or fixed to the road wheel carries a lever 35 swung out by centrifugal force to engage a spring controlled pin 37 in a ring 38 connected bv rod 18<4> to the control valve and carries the ring against a stop 39 and opens the control valve, the lever 35 then swings clear by raising the pin 37 and a second lever, of which the disc is provided with a plurality, engages the pin 5 and the ring maintains the valve open, until the wheel locks when the spring 26<2> returns the ring and opens the valve. In an electrical arrangement the control valve is maintained open by a solenoid supplied with current from a dynamo driven by the road wheel. Centrifugal governors may be used. The automatic control means to each wheel may be connected to the master control valve so as to withdraw the other brakes when one brake is withdrawn. The first Provisional Specification also describes an electrical arrangement in which the solenoids operate switches in the circuits of electrically operated brakes, or the solenoids may operate the brakes directly. In another arrangement the brake shoes may be floatingly mounted on a fixed member on the axle and may move in the direction of rotation of the axle in opposition to a spring. Between the brake pedal and the brake actuating arm is interposed a link which is shortened or lengthened according to the position of the shoes. According to the second Provisional Specification the mechanical arrangements described in the complete Specification may be modified by connecting the rod 18<4> direct to the, brake cam or the rod 18<4> may be connected to a link or toggle joint interposed between the brake pedal and the brake cam, this link being lengthened or shortened according to the position of the rod.