Patent GB-1031414-A (GB)
Title: Motor vehicle braking system
Inventor: TURNBULL JOHN BARTHOLOMEW
IPC: B60T8/1761
Filed: 1963-02-07
Abstract: 1,031,414. Hydraulic braking systems. FORD MOTOR CO. Ltd. Dec. 18, 1963 [Feb. 7, 1963], No. 4951/63. Heading F2F. [Also in Divisions B7 and H2]  In a motor vehicle braking system a device 7 is provided in the hydraulic braking system between a brake master cylinder 1 and a wheel brake cylinder 9 and is electrically oscillatable between a brake release position and a normal position to increase and reduce respectively the volume of the system in order to reduce skidding of the vehicle wheels. The device 7 includes a flexible diaphragm 33 secured to an armature rod 15, an inlet 19 from a cut-off valve 5 and the master cylinder 1, a solenoid 11 and an armature 13 movable downwardly when the solenoid is energized. When this condition occurs and the rod 15 is moved downwardly against spring washers 32 to permit the pressure in the brake master cylinder 1 to force a ball 23 on to a valve seat 21 to shut off the supply from the outlet 25 to the rear brakes 9 and to flex the diaphragm 33 downwardly to increase the volume of the upper part 35 of the chamber, the increase in volume releasing the pressure in the hydraulic system between the outlet 25 and the rear brakes 9 and consequently causes release of the rear brakes. When the solenoid is deenergized the spring washers 32 move the rod 15 upwardly to force the ball 23 off its valve seat and so reconnect the inlet 19 and the outlet 25 to provide re-application of the brakes provided there is still pressure in the master cylinder. The solenoid may be energized and de-energized at a fairly high frequency and this may be controlled by a damper unit 37 fitted below the solenoid. In the circuit shown in Fig. 4 the solenoid 11 is connected in series with two switches 57 and a conventional regulator 59 which supplies current to the switches and solenoid only when the generator driven by the engine of the vehicle is charging the battery so that when the engine is idling the solenoid is never energized. The switches 57 are of such a construction that they open the circuit through the solenoid whenever a wheel is locked by a brake and skids. A pressure switch 61 adapted to be operated by the driver of the vehicle in accordance with the road conditions may be provided as an alternative to the switches 57. As shown in Fig. 3 each switch 57 includes a contact sleeve 63 which is slidable axially on, but rotatable with a half shaft 65 on a rear axle of the vehicle, a spring 67 biasing the sleeve 63 axially into contact with a fixed contact 69 on the axle casing 71, and balls 72 rotatable by the half shaft 65 and movable outwardly by centrifugal force to engage a cam surface 73 on the sleeve 63 and force the contact sleeve 63 to the left away from the fixed contact 69 to open a switch. This is the condition which persists when the vehicle is travelling normally. Should one of the rear wheels lock, the half shaft ceases to rotate with the result that the spring 67 is able to force the sleeve 63 to the right into contact with a fixed contact 69 and the brakes are released. When the rear wheels start to rotate again the closed switch 57 is reopened, the solenoid 11 is de-energized and the rod 15 and diaphragm 33 return to their normal positions and the brakes are consequently reapplied. As long as the rear wheels skid when the brakes are applied the sequence of operations described above is repeated at a frequency of about five oscillations per second.