Patent GB-1392997-A (GB)
Title: Fluidpressure control device
IPC: B60T13/12
Filed: 1972-10-25
Abstract: 1392997 Drivers valves; brake pedals; valves; springs COMPAGNIE DES FREINS ET SIGNAUX WESTINGHOUSE 25 Oct 1972 [29 Oct 1971] 49092/72 Headings F2F F2S F2V and F2E A twin circuit brake valve apparatus has a link member 19, 21 supported on two valve operators 6 of respective valves 2 and 3 the link member being displaceable by a control member 17 and including a resilient portion in the form of one or more flexible blades 21 through which the force is transmitted, adjustable stops 27 limiting the displacement of the link member. As shown in Fig. 1, the valves 2, 3 are selflapping valves with a feed compartment 8 to the respective brake circuit, a compartment 9 fed with pressurized fluid and a reaction compartment 10. A brake pedal 11 engages, by means of a roller 13, a peg 14 passing through a compression spring 15 consisting of a rubber ring which provides flexible reaction linear in relation to the stroke of the pedal 11 up to the point where end 16 of peg 14 engages the control member 17: the control member 17 is in the form of a plunger which bears upon a rod 18 located between the plunger 17 and a plate 19. Spring steel blades 21 are secured to the plate 19 by U-bolts (22) and the valve operators 6 pass through bores 24 in plate 19 to abut blades 21. Threaded rods 25 also pass through apertures 26 in plate 19 to provide the stops 27. In the embodiment of Fig. 2 (not shown), the plate (19) has a central hollow (29) whereby the flexible blade (21) can be curved by tightening U-bolts (22). Figs. 3, 4 (not shown), illustrate blades (21) with a breadth increasing towards the centre (29) of the blades and in Fig. 4, the blades (21) have recesses (30) on either side operating in conjunction with the U-bolts to hold the blades (21). When the pedal 11 is depressed the peg 14 moves to force plunger 17 towards plate 19 through the action of spring 15 and the rod 18 is moved to force blades 21 against operators 6 to operate self-lapping valves 2, 3. The pressure within compartments 8, 10 increases up to the moment when the reaction of the pressure within compartment 10 against a piston assembly 4 balances the force transmitted to the operators 6 by the blades 21. Spring 15 is eventually crushed sufficiently for peg 14 to contact plunger 17 and there is now a rigid link between pedal 11 and operators 6 through the link member 19, 21 and the pressure in compartments 8, 10 is now determined by the force on pedal 11 until this force increases to a point where the blades 21 are flexed away from plate 19. This flexing permits plate 19 to move downwardly until it contacts stops 27 and maximum pressure is now reached in compartments 8, 10. Should one circuit fail, e.g. that of valve 3, the brake effort is increased in the other circuit as determined by the ratio of the length of lever arm between stop 27 of valve 3 and operator 6 of valve 2 to the length of lever arm between stop 27 of valve 3 and the bearing point of rod 18 against blades 21-as illustrated this ratio is less than 2.  The blades are pre-stressed during assembly on the valve and a previously curved and highly flexible blade can be associated with an originally flat and low flexibility blade. In a preferred embodiment, the blade has on each side a lateral stop operating in conjunction with the branches of the U-bolt to limit longitudinal and transverse movement of the flexible blade. In further modifications the self-lapping valves can be replaced by hydraulic or pneumatic single-piston control valves. The spring (15) can be eliminated or replaced by a helical spring. The stops 27 can be located between the operators 6. The blades 21 can be secured to the plate 19 by other methods and separate flexible blades can be provided for each control valve. The recesses (30) of Fig. 4, can be replaced by strips projecting between two limbs of the U- bolts.