Patent GB-1247049-A (GB)
Title: Brake control device for preventing a rotating wheel from locking during braking
Inventor: EKENBERG ULF CHRISTER
IPC: B60T8/74
Filed: 1968-10-25
Abstract: 1,247,049. Anti-skid braking systems. U. C. EKENBERG, M. J.-O. HOLST, and R. E. NORDSTROM. 25 Oct., 1968 [27 Oct., 1967; 19 Dec., 1967; 26 April, 1968], No. 50794/68. Heading F2F. A device for preventing a wheel from locking when it is braked comprises sensing means 1 arranged to be driven in oscillatory movement by pulses of a frequency corresponding to the angular speed of the wheel, a mechanical oscillatory system including a mass, 2, 3, the system having a resonant frequency and being drivable in oscillation by the sensing means 1, and means 4, 8, movable by the oscillatory system when the latter is driven at its resonant frequency by the sensing means 1 to release the braking of the wheel during the movement of the oscillatory system in one of its directions of oscillation. The parts and manner of operation of the apparatus are illustrated in Fig. 1. A sensing device 1 contacts a member such as a cam, (not shown), provided on the wheel or the wheel shaft of the vehicle and thus delivering to the sensing device pulses corresponding to the angular speed of the wheel. The sensing device is connected to a resilient element 2 such as a helical spring, in turn connected to a mass 3 which at its remote end merges into a reduced elongate part 4. During braking, brake fluid under pressure admitted at 13 to a chamber 10 assisted by a spring 12 forces a ball 8 into contact with end 5 of elongate part 4, this pressure being transmitted via the spring 2, which has low intrinsic attenuation, to the sensing device 1 which is accordingly forced into contact with the cam. Ball 8 is not forced into contact with a seat 7 in a partition 17, so an aperture 7a in the partition remains open, permitting the brake fluid to reach another chamber 9 and pass from there through an outlet 14 to the brakes. As the wheel speed falls, a certain critical speed, (referred to later), is reached at which the frequency of oscillation imparted to the sensing device 1 corresponds to the resonant frequency of the whole oscillating system 1, 2, 3, 4. The amplitude of oscillation is now so great that during leftward movement of the system the elongate part 4 permits seating of ball 8 on seat 7, whereby aperture 7a is closed and the feeding of brake fluid to the brakes is checked. Moreover, the continued withdrawal of part 4 increases the volume of chamber 9, so that fluid can flow back from the brakes, thereby relieving the braking pressure. Owing to the release of the brakes the wheel speed will again increase, so the frequency of oscillation of sensing device 1, and hence of the oscillating system, will now be above the resonant frequency, and ball 8 will be unseated again, permitting re-application of the brakes. With a critical peripheral wheel speed of 17 km/hr., (within the range 10-20 km/hr.), this cycle is repeated two or three times a second. The critical wheel speed is arbitrarily related to the characteristics of the oscillating system as follows: the square root of the ratio of the spring constant and the mass 3 is chosen to be equal to the angular speed corresponding to the critical peripheral speed. Fig. 3 (not shown) depicts a practical embodiment of the invention. In Fig. 4, the spring- loaded ball valve is omitted: instead, the elongate member 4 is extended to form a valve spool 5 having a bore 18 with a port 7a. During braking, fluid admitted at 13 to a chamber 15 reaches the brakes by way of port 7a, bore 18, another chamber 10 (beyond a partition gasket 7), and an outlet 14. A further chamber 9 is provided, to which fluid is admitted at 17 to equalize pressures on the valve spool 5. On leftward movement of the valve spool during the critical, resonant, phase, port 7a is obturated by a gasket 16 to check the flow, and the volume of chamber 10 is increased by withdrawal of the valve spool 5. In Figs. 1 and 4 the spring itself may constitute the mass of the system, thus obviating the need for a separate mass 3. It is stated that brake fluid under pressure is supplied by a main brake cylinder, the fluid being hydraulic or pneumatic, and that the device is applicable to apparatus for feeding tape, web, wire or the like, besides vehicles.