GB1227740A - - Google Patents

Abstract

1,227,740. Measuring speed electrically. ASTON MARTIN LAGONDA Ltd. Sept.25, 1968 [Sept. 27, 1967], No.43883/67. Heading G1H. [Also in Division F2] An anti-skidding pneumatic braking system comprises means to interrupt a fluid-flow from a pedal-operated master cylinder 10 to slave cylinders 23 when the deceleration of a wheel (or wheels) rises above a predetermined value. Electronic counters 24, one adjacent the periphery (25) of each brake disc 26, supply pulse trains, of which the repetition frequencies depend on the wheel velocities, to a comparator 29 via respective rectifiers 27 and amplifiers 28. The output voltage of the comparator is fed to a solenoidoperated valve 13 in which energization of a solenoid 21 draws a plunger 19, against a spring 20, so that spring 17 urges a ball 16 to seal an orifice 15 in the fluid-flow path between a first chamber 12, of the valve, connected via conduit 11 to the master cylinder and a second chamber 14 connecting via conduits 22 to the slave cylinders. The effective volume of this latter chamber is increased by the introduction of a reduced-diameter section 18 of the plunger into the chamber, thus the fluid-pressure at the slave cylinders is decreased and the brakes are released. When the deceleration falls below the predetermined level the solenoid is de-energized and braking pressure is re-applied. In a second embodiment Fig.2 (not shown) pulses from the two front wheel counters 24 are combined and led via rectifier (30) and amplifier (31) to a first input of a comparator 29, to which a second input is applied being similarly derived from the two rear wheel counters, so that when the difference exceeds a predetermined level the output voltage is applied to one of two solenoid operated valves (34, 35) which control the fluid-flow to the slave cylinders on the front and rear wheels respectively. Fig. 4 (not shown) illustrates the notches on the periphery (25) of the disc, which produce pulses by interaction with the magnetic field of a counter. An alternative embodiment Fig. 5 (not shown) illustrates a plurality of equi-spaced axial holes (36) drilled in a concentric row near the disc periphery, the counter 24 being mounted parallel to the axis of the disc and at the same radius as the row of holes so that the rotating holes interact with the magnetic field of the counter to generate pulses. In a third embodiment Fig. 6 (not shown) the holes are radially disposed at the periphery and the counter 13 mounted radially. The discs may be replaced by similarly notched drums.