Patent GB-1430931-A (GB)
Title: Braking systems
IPC: B60T17/18
Filed: 1972-05-02
Abstract: 1430931 Braking systems; valves BENDIX WESTINGHOUSE Ltd 3 April 1973 [2 May 1972] 20352/72 Headings F2F and F2V A braking system comprises a compressor 1 supplying fluid under pressure to a tank 4 which is connected to first and second braking circuits 2, 3 via respective pressure-delivery valves 7, 8, each valve 7, 8 being arranged to open to allow delivery of fluid pressure to the circuit 2, 3 to which it is connected at a respective first lower pressure in the absence of fluid pressure in the other circuit and at a respective second higher pressure in the presence of fluid pressure in the other circuit, the first lower pressure of each valve 7 or 8 being less than the second higher pressure of the valve 7 or 8. As particularly described, the lower pressures are substantially equal as are the higher pressures. The systems illustrated in Figs. 1-3 show valve 7 connected to circuit 3 by a line 18 and valve 8 connected to circuit 2 by a line 17 but Fig. 4 shows a construction of a combination of the valves 7, 8. As seen in Fig. 4 each valve 7, 8 comprises a valve closure element 50 co-operable with a valve seat 51 which is positioned between a common inlet conduit 52 and a respective chamber 53, conduit 52 being connected to tank 4 and chambers 53 to the respective circuits 2, 3. Each element 50 is biased by a respective spring 55 which also abuts a respective piston 56 above which is formed a respective chamber 57. The chamber 53 of valve 7 is connected to chamber 57 of valve 8 and chamber 53 of valve 8 is connected to chamber 57 of valve 7. The spring 55 will determine the first lower pressure at which each valve 7, 8 will open, and the presence of pressure in chamber 57 will move piston 56 downwardly to supplement the force exerted by spring 55 so that the valve will now open at the second higher pressure. In the system of Fig. 1 first circuit 2 divides into two circuits 9, 10 used for operation of a "service" braking system and each including a respective reservoir 11, 12 fed via a respective check valve 13, 14. The second circuit 3 operates a "secondary/park" braking system and includes a reservoir 15 arranged to be fed with pressure via a check valve 16. The embodiment of Fig. 2 has the first circuit 2 incorporating a first service/secondary reservoir 20 and the second circuit 3 incorporating a second service/secondary reservoir 21. A third circuit 22 for parking brake operation connects with points 23, 24 in circuits 2, 3 via a dual check valve means 25 (or two single check valves) and a third pressure delivery valve 28. In the embodiment of Fig. 3 (not shown), the third circuit (22) is connected to a point (40) between the tank (4) and the valves (7, 8) via a cock (41) operable to selectively connect third circuit (22) to tank (4) or to atmosphere. Such an arrangement is particularly applicable if the parking braking means are spring-applied brake actuators. In each of embodiments of Figs. 1-3 an emergency line is provided-as part of the second circuit 3 in Fig. 1 and as part of the third circuit 22 in Figs. 2, 3. Also a governor 6 responsive to the pressure in tank 4 controls the output of compressor 1.