GB936495A - Improvements in or relating to liquid pressure braking systems for vehicles - Google Patents

Abstract

936,495. Braking systems. AUTOMOTIVE PRODUCTS CO. Ltd. June 22, 1961 [Sept. 1, 1960], No. 30194/60. Class 103 (1). A liquid pressure braking system for a vehicle includes a master cylinder 10 or other liquid pressure source, motor cylinders 16, 17 in which liquid pressure from the source acts to apply, respectively, front and rear wheel brakes 12, 14, and means operated when the rate of deceleration of the vehicle exceeds a predetermined value for reducing the pressure in the motor cylinders 17 relative to that in the motor cylinders 16, the said means comprising a plunger 28 having a face of smaller area exposed to the pressure in the pressure source and an oppositely directed face of larger area exposed to the pressure at the rear brakes 14, a non-return valve 35 being provided in a passage 33 through the plunger to prevent flow of liquid through the passage from the pressure source to the brakes 14 and there being means 38 for holding the valve 35 unseated and which is rendered inoperative by deceleration responsive means when the predetermined rate of deceleration is exceeded. As shown, when the pedal 11 is operated, liquid is displaced through conduits 18, 21, 22 and 24 to operate the motor cylinders 16, 17 and to apply the brakes; liquid is also displaced through a conduit 44 to act in the space 43 on a plunger 41 and to compress a spring 42 to hold the plunger 28 against a stop 39, a ball valve 35 being thus held off the seat thereof by a pin 38 and the pressure acting on the rear wheel motor cylinders 17 being the same as that acting on the front wheel motor cylinders 16. As the thrust on the pedal 11 is increased, the pressure in the motor cylinders 16, 17 and the space 43 is also increased, the pressure in the space 43 holding, through the medium of the spring 42, the plunger 29 against the stop 39. When the braking applied is sufficient to cause the rate of deceleration to exceed a predetermined value the eccentrically pivoted disc 47 of the means 45 is caused to swing about a horizontal axis, which is transverse to direction of movement of the vehicle, to close the conduit 44 and thus prevent further rise of pressure in the space 43. The further increase in thrust on the pedal 11 results in an increase in thrust on the face of the plunger 28 in the space 34 so that the plunger moves away from the stop 39 to allow the ball valve 35 to close. The pressure acting on the motor cylinders 17 therefore increases at a rate less than does the pressure acting on the motor cylinders 16. In a modification, the valve 23 comprises a ball valve 35 and a plunger 28 which abuts the piston 51 of a vacuum servomotor 52 which when energized holds the plunger against the stop 39 and is connected through a control valve 54 to a vacuum reservoir 55 or to atmosphere, the valve being operated by deceleration responsive means consisting of a suspended arm carrying a weight 58 and connected by a link 57 to the plunger of the valve 54.