Patent GB-740058-A (GB)
Title: A safety cut-off device for hydraulic braking systems
IPC: B60T11/32
Filed: 1954-04-09
Abstract: 740,058. Hydraulic brakes. KIRK, A. M. April 9, 1954, No. 10522/54. Class 103 (1). In a safety cut-off device for sealing a defective line in a hydraulic brake system, particularly vehicle braking systems, one or a number of fluid pressure units is or are interposed in the line or lines leading from the master cylinder for the above stated purpose. In the example illustrated in Fig. 1, applied to the hydraulic braking system of a road vehicle, four fluid pressure units 10 are incorporated in the lines; one for each wheel brake 31, between each line leading from the master cylinder 22 and the line leading to each wheel brake. The fluid pressure unit 10, as illustrated in Figs. 2 and 3; comprises a cylinder 12, within which floats a piston 11, a conduit 23 supplying hydraulic pressure from the master cylinder 22 into the inner end of cylinder 12 in the unit 10 via the chamber 20 and the restricted opening 25, a passage 33 leading at right angles from the chamber 20 to a by-pass 15 within which is mounted a spring 52 provided to force a manually operated valve 13 against the conical seat in the valve casing 34; the valve 13 controlling the entry of hydraulic fluid into the passage 36 leading to the cylinder 12 which has an outlet conduit 29 supplying hydraulic fluid to the wheel brakes 31. In operation, when the foot brake is depressed, hydraulic fluid is supplied from the master cylinder 22 through the lines 74 and 60 to the front and rear wheel brakes respectively, fluid is then supplied to each fluid pressure unit 10 via conduit 23 into the chamber 20 of each unit and thence into the cylinder 12 to move the piston 11 slightly to the left to create an increased pressure in the outlet conduit to apply the brakes. At the same time, hydraulic fluid is supplied via passage 33 and by-pass 15 and due to the fact that, in the operative position of the brake circuit, the manually operated valve 13 is closed (Figs. 2 and 3), hydraulic pressure is supplied via central bore 37 and port 38 to a pressure-responsive plug 16 so that a pilot light 19 is illuminated all the time the fluid pressure is supplied. Should a break develop in the line to any wheel brake 31, the piston 11 associated with the appropriate fluid pressure unit 10 will be forced to the outer end of the cylinder 12 to cut off the supply of hydraulic fluid to the affected brake and the sudden drop in pressure in the inlet side of the unit 10 will shut off the pilot light 19 to warn the driver that a break has developed in the line. By this method, no loss of pressure takes place in any of the other braking conduits. When the defective line has been repaired, the lever 14 of the valve 13 may be opened to permit flow through the central bore 37 and the passage 36 to replenish the system and by manipulation of the valve 13 all air may be dispelled from the line so that when the valve 13 is again turned to its closed position, as illustrated in Figs. 2 and 3, the brake system is again in operational condition. A modification is described wherein the cylinder 12 and by-pass 15 are mounted in separate interconnecting cylinders instead of being housed in the same casting.