Patent GB-1351398-A (GB)
Title: Hydraulic power braking circuit
IPC: B60T13/14
Filed: 1972-12-04
Abstract: 1351398 Hydraulic braking systems; valves; level indicators AISIN SEIKI KK 4 Dec 1972 [4 Dec 1971] 55855/72 Headings F2F F2V and F2E An hydraulic power braking circuit for a motor vehicle includes a reservoir 10 divided by a partition wall 13 into two reservoir chambers 11, 12 which respectively supply pumps 14, 14a, the two chambers 11, 12 being interconnected unless the fluid in both chambers 11, 12 falls below the level of wall 13, and the two pumps 14, 14a being connected to (a) brake operating valve(s) 27, 27a via a valve arrangement for interrupting hydraulic communication between the pump 14a and control valve(s) 27, 27a except when pump 14 or its associated circuitry is damaged. In the embodiment of Figs. 1-5, each pump 14, 14a is provided with a respective charging valve 16, 16a; the valve 16 has two outlets, one to chamber 11 and one to a port 18 of a first safety valve 19, and the valve 16a has two outlets, one to chamber 12 and the other to a port 18a of valve 19. The valve 19 has ports (23), 23a connected to accumulators 21, 21a and the higher pressure in accumulators 21, 21a is led into the valves 16, 16a via a port 55 in valve 19 and a pilot pipe 22. The accumulators 21, 21a are further connected with inlet ports 25, 25a of a second safety valve 26 and outlet ports thereof 271, 27<SP>1</SP>a are connected respectively with control valves 27, 27a. The valves 27, 27a are connected with wheel cylinders 29, 29a and also to chamber 12. The valves 27, 27a may be arranged in parallel or in tandem. Safety-valve 19.-The valve 19 shown in Figs. 2, 3 includes check valves 48, 48a defining the ports 18, 18a which are interconnected by a passageway 49. The passageway 49 communicates with an annular chamber 50 formed around the central portion of a cylinder 34 which cylinder 34 accommodates a slidable piston 36 having passageways 37, 38 therethrough and valve seats 39 at each end for co-operation with ball valves 40, 40a. The cylinder 34 is disposed transversely of and spaced from a stepped bore 33 which incorporates a tubular insert 51 containing a valve ball 52. The ports (23), 23a respectively communicate with chambers 46, 46a which communicate with chambers 60, 60a via passageways 58, 59, the chambers 60, 60a having associated valve seats 56, 56a and pressure responsive electrical switches 61, 61a. Safety valve 26.-Inlet ports 25, 25a, Fig. 4, include check valves 78, 78a, and these ports communicate with outlet ports 27<SP>1</SP>, 27<SP>1</SP>a via passageways 64, 64a, a centre chamber 69 formed between two pistons 66, 66a, orifices 71, 7 la in pistons 66, 66a and apertured dished guide plates 76, 76a. The plates 76, 76a are urged into contact with pistons 66, 66a by springs 68, 68a and a pair of valve members 72, 72a held on plates 76, 76a are adapted to be seated on or unseated from seats 73, 73a to close and open ports 27<SP>1</SP>, 27<SP>1</SP>a. Operation.-In normal operation the higher of the fluid pressures produced by pumps 14, 14a is accumulated in accumulators 21, 21a via valves 16, 16a, 19. The charging valve 16 can be a relief valve or an unloading valve and the valve 16a an unloading valve, with the pump 14 normally supplying accumulators 21, 21a and the pump 14a delivering its fluid to drain via pipe 17a. Braking pressure is transmitted to cylinders 29, 29a by pedal actuation of valves 27, 27a. Damage to the circuitry upstream of valve 26 causes closure of valve 72, 73 or valve 72a, 73a to isolate the damaged section. Damage between valves 19, 26 is accommodated by actuation of piston 36 to operate ball 40 or 40a. When the pressures in accumulators 21, 21a are unequal valve ball 52 prevents loss of fluid from the high pressure accumulator. Failure of pump 14, valve 16 or the associated pipe 20 causes pump 14a to supply fluid to the braking circuit. A warning light W indicates when tank 11 is empty. Other embodiments.-In the embodiment of Fig. 6 the valve 19 is replaced by separate oneway valves 79, 79a and the valve 26 is replaced by separate one-way valves 80, 80a. A single control valve 27b controls the braking pressure. Only one accumulator 21 or 21a is effective at any one time. The pilot pressure for charging valves 16, 16a is obtained from valve 27b. In the embodiment of Fig. 7 (not shown), valve 19 is replaced by one-way valves 81, 81a and the pilot pressure for charging valves 16, 16a is supplied from safety valve 26. In the embodiment of Fig. 8 (not shown) there is no second safety valve 26.