Patent GB-675291-A (GB)
Title: Improvements in or relating to brake control apparatus for a motor vehicle
IPC: B60T11/10
Filed: 1949-04-19
Abstract: 675,291. Controlling motor vehicles. KIRBY, J. C. April 19, 1950 [April 19, 1949], No. 10392/49. Class 79(v) [Also in Group XXXIV] A brake control apparatus, for a motor vehicle, which comprises a brake holding device for automatically holding the brake on, a release member therefor, the release member being connected to and operated by a clutch or an element responsive to vehicle-engine speed, and means for putting the device out of action by the driver at will or automatically when the gear box is put into neutral, the holding device being constituted by a hydraulic lock comprising piston and cylinder means connected to an element of the brake into which cylinder liquid flows from a reservoir when the brakes are applied and from which the liquid must be exhausted before the brakes can be released and a valve between the reservoir and the cylinder allowing flow from the reservoir to the cylinder but preventing reverse flow, is characterized by the release member being an electromagnetically operated release valve controlling a duct which byepasses the non- return valve. As shown in Figs. 1 and 2 the apparatus is adapted for use with cable operated brakes and comprises a casing 11 forming the reservoir 12 which communicates through the non-return valve 16 and a duct 14 to the cylinder containing the piston 18 connected by a rod 19 to a lever 22 to the brake pedal, so that on depression 20 pivoted at 21 and connected by an arm of the pedal liquid passes from the reservoir into the cylinder through the valve 16 by movement of the piston 18. Pressure in the cylinder 13 is reduced by the opening of the needle valve 17 controlling the byepass 23, allowing return of the piston lever and arm to their original position The needle valve is controlled by the electromagnet 25 supplied with current from the vehicle battery by a lead 51. The armature 26 of the electromagnet is carried on a lever 27 pivoted to the casing 11 at 28 and adapted to bear on the stem of the needle valve, the lever being urged outwardly by a spring 30 and the needle valve being urged to its open position by a spring 15. The lead 51 carries series switches 31, 32, the switch 31 being connected to the gear shift mechanism in such manner that when the gears are disconnected and also when the higher gear is engaged the switch is open, but the switch is closed when the reverse or lowest forward gear is engaged, and the switch 32 being associated with the movable part of the clutch so that when the clutch is disengaged the switch is closed and the switch open as the clutch is engaged. In a modification, Fig. 3, the apparatus is adapted for use with hydraulically operated brakes and comprises the non-return valve 37 arranged between a pipe 39 leading to the master cylinder of the brake operating mechanism and a pipe 41 connected to the brakes and a casing 33 forming the liquid reservoir houses the byepass 42 for the non-return valve, the byepass being controlled by the needle valve 43. The valve 43 is urged into its open position by a spring 52 and closed by an arm 46 controlled by the electromagnet 44 controlled in a similar manner as in the embodiment shown in Figs. 1 and 2. If the vehicle is fitted with a preselector gear-box and conventional clutch, one switch may be operated by movement of an element of the gear mechanism upon actual engagement of low forward or reverse gear or alternatively if the gear selection is electrically operated such switch may be dispensed with and the lead to the electromagnet connected to the gear actuating solenoids. If the vehicle is fitted with a torque converter in a fully automatic transmission the normally clutch operated switch may be arranged to be operated in response to engine speed by a centrifugal operated member, the switch being closed when the engine is idling, or to be connected to the accelerator pedal, or to be operated by an electromagnet energized by an electromagnet energized by the battery-charging dynamo to open the switch when the charging rate reaches a predetermined value as the engine speed increases. The switch normally controlled by the gear mechanism may be operated by a push button under the control of the driver. The battery may be connected to the electromagnet only when the engine ignition is in operation.