Patent GB-1341432-A (GB)
Title: Fluid control systems
IPC: B60T8/00
Filed: 1971-01-07
Abstract: 1341432 Fluid pressure braking systems; valves S LEKARSKI P HARDY L HARDY and J GACHOT 7 Jan 1971 [8 Jan 1970] 763/71 Headings F2F and F2V A fluid pressure braking system has a pressure reducing valve 1 controlling fluid pressure from a source to brake cylinders the ratio of inlet and outlet pressures of the valve being varied by a profiled plate 35 actuated by a brake pedal. Valve 1 comprises rigid plates 11, 12 sandwiching elastic layers 13, 14 therebetween and diaphragms 15, 16 are held by an intermediate member 17 and end member 18. Diaphragms 15, 16 have bosses 21 ,22 respectively the latter obturating a central aperture 24 in layer 14. Compressed fluid is directed from a pressure source to a recess 23 and, initially, acts on boss 22 biasing diaphragm towards boss 21. The pressure is not sufficient to overcome the force of a spring 37 acting on diaphragm 16 and elastic layer remains in contact with boss 22 thereby obturating aperture 24. When plate 30 is moved in direction A by the brake pedal its engagement is slot 33 in a slide 32 causes the latter by virtue of the profiled plate surface 34 to move rightwardly. Leaf springs 27 (27a) Fig. 3 (not shown) fixed between diaphragm 16 and a stop 28 by pins, are caused to move thereby reducing the effective length thereof and increasing their bias applied to diaphragm 15 in a sense to lift the latter. Boss 2t is lifted and fluid in recess 23 acts on boss 22 lifting diaphragm 16 and central portion of layer 14 until the latter abuts against layer 13 and closes an atmosphere connection 25. A passage is thereby provided between rigid plate 12 and diaphragm 16 and fluid passes from recess 23 through this passage into a conduit 26 connected to the brake cylinders via an amplifying valve 6. The fluid also passes through an orifice 40 to act on diaphragm 15 which is moved to establish an equilibrium position. Further movement of plate A displaces the equilibrium and passes fluid to the brake cylinders until a further equilbrium is reached. Valve 6 is identical in construction to valve 1 exept that the pulses from the valve 1 outlet relpace the springs 27, 27a. The system may be made responsive to vehicle loading and in the embodiment shown in Fig. 7, having a vehicle mechanical spring suspension the distance between the chassis 52 and the axle 56 varies according to load and is determined by a punched card 51 fixed to the chassis and having three columns 53a, 53b, 53c. A pneumatic pickup 54 corresponding to each column is fixed to axle 56 and is fed from a pressure source. The signals from the pickups controls three cells 57a, 57b, 57c having a NO function which are connected to three cylinders 58a, 58b, 58c in series. According to the load, for example a fully loaded condition at which the card 51 is at a level C cylinders 58a, 58b, 58c are pressurized causing a stop member 60 to displace plate 35 through a surface 63 thereon opposed to surface 34 thereby increasing the rightward movement of control member 30. The pistons 59a, 59b, 59c, may have identical or different strokes and be arranged in parallel and the punched card be replaced by a plate having a surface with contours of varying shape controlling pnuematic relays feeding directly to cylinders 58a, 58b, 58c. Two punched cards may be provided, one for the front and one for the rear wheels. If the suspension is pneumatic having pnuematic cushions 65, Fig. 10 (not shown), an elastic housing (66) confining the cushion acts as a valve member for valve (67) connected to a pressure source (68) and to a calibrated orifice and cell 57a controlling a cylinder 58a. If no suspension is provided the axle load may be converting into an electric signal by a piezoelectrical pickup the signal being converted into a pneumatic signal for controlling pistons 59a, 59b, 59c. In a further embodiment an emer-  gency brake is provided in which a manually operated electric or pneumatic switch 80, Fig. 13 (not shown), of a switch (81) operated by the brake pedal operates a control member (82) acting on a stop (84) which abuts a plate (35c) to operate the latter thereby controlling valves (1c) and (6c) feeding a cylinder (79) of the emergency brake. A wheel slip detector 85, Fig. 14 (not shown) may be connected to a control member 88 acting on plate 35 to provide a further control.