Patent GB-1107451-A (GB)
Title: Vehicle braking systems
Inventor: THOMAS GORDON FREDERICK FRANK
IPC: B60T13/40
Filed: 1964-08-31
Abstract: 1,107,451. Fluid-pressure brakes. WESTING- HOUSE BRAKE & SIGNAL CO. Ltd. 17 Aug., 1965 [31 Aug., 1964; 17 Sept., 1964], No. 35552/64 and 38019/64. Heading F2F. A compressed-air braking system for a vehicle includes dual brake lines 20 and 21 feeding separate sections of actuators 23, 24, 31, 32 which are of multiple diaphragm type, the pressure in the lines being controlled by a dual driver's valve 17 having sections 15, 16 which are simultaneously controlled in such a way that pressure in one line, e.g. the line 20 is always higher than pressure in the other line, during normal braking, i.e. before maximum pressure is reached, this being accomplished by arranging that, as the driver's pedal is depressed, one section, e.g. the section 15, comes into operation before the other section which becomes operable during further depression of the pedal. The system may be adapted for tractor-trailer vehicles, as shown by the chain-line connections to three coupling heads 50, 51 and 52 which correspond respectively to the lines 21, 20 and line 13 which feeds one section of the driver's valve 17 from a reservoir 12 and therefore provides the usual emergency line for the trailer reservoir (74, Fig. 2, not shown) via a conventional relay valve 72 on the trailer which is also controlled via line 70 and coupling 51 from line 20, to provide for normal service operation of first chambers 77 of the trailer actuators 68, 69 via the relay valve, additional actuation via line 21 (on further depression of the driver's pedal) being by way of a double check valve 57, relay valve 54, coupling 50, line 65 on the trailer and second chambers 67 of the trailer actuators. Actuators 23, 24 for the front wheels of the tractor also comprise two chambers 25, 28 communicating with lines 21, 20, respectively, while the actuators 31, 32 for the rear wheels of the tractor each have three chambers 33, 35, 37 communicating respectively with line 21, line 20 and a line 40 fed by a valve 43 controlled by a handbrake lever 44. Valve 43 is effective also on the trailer brakes via line 59 and double check valve 57. The valve 43 is supplied from a reservoir 6 charged via a one-way valve 7, while the driver's valve 17 has its sections 15, 16 separately supplied by sections 10, 11 of the reservoir 12, which is charged via an unloader valve 4 and one-way valves 8 and 9. The pressures supplied to the lines 20, 21 by the valve sections 15 and 16 are continuously monitored by a double gauge 48 in the driver's cab, and a warning device 49 is connected across the lines 20 and 21 to warn the driver if the pressures should become equal, e.g. owing to a ruptured diaphragm in one of the actuators, in which event full braking will still be possible, although in some oases further depression of the driver's pedal may be necessary. A number of other situations, e.g. failure of one of the lines leading to the trailer or of either of the lines 20 or 21, are discussed in the Specification, in all of which full braking is still possible. In the modified arrangement of Figs. 3 and 4 (not shown), there are only two trailer couplings (51) and (52), there being no connection between line (20) and the trailer. Instead, by virtue of a second relay valve (91) on the trailer and a line (83) between the valve (43) controlled by the handbrake lever and a double check valve (82) which is also fed by a relay valve (85) controlled by the line (21), braking of the trailer is still possible in the case of failure of line (21) by operation of the handbrake lever, while automatic braking of the trailer is ensured by supplying chambers (67), (77) of the trailer brake actuators separately via separate sections of a double reservoir (94) on the trailer and the respective relay valves (91) and (72), the latter acting also as a charging valve for one reservoir section (92) and providing for automatic operation of the actuators (68), (69) from this reservoir section in the event of trailer break-away. An additional warning device (100) is provided to warn the driver should pressures in the chambers (66) and (77) become equal due, e.g. to failure of a diaphragm. Emergency line (90) is supplied in this case from the reservoir (6). In a further embodiment (Figs. 1 and 2 of the drawings accompanying the second Provisional, not shown) the arrangement is similar to that of the preceding embodiment, except that the valve (43) controlled by the handbrake lever is connected to a relay valve (54) so as to control the supply, via line (60) from reservoir (6) to the emergency line (90) on the trailer, the double check valve (82) and line (83) of the previous embodiment being omitted.