GB935830A - - Google Patents

Abstract

935,830. Fluid pressure braking systems. AUTOMOTIVE PRODUCTS CO. Ltd. Feb. 29, 1960 [March 16, 1959], No. 9039/59. Class 103 (1). [Also in Group XXXVII] A liquid pressure braking system has. between the master cylinder 17 and brake cylinder 16a, apparatus 19, Fig. 1, operable by a deceleration-responsive device 31 as a result of the deceleration of a wheel 13 exceeding a predetermined rate, the apparatus 19 acting to isolate cylinder 16a from master cylinder 17 and to enlarge the volume of the liquid space in the isolated part of the system including brake cylinder 16a, whereby the braking pressure is reduced without releasing liquid from the system and without reducing the master cylinder pressure. The apparatus 19, Fig. 4, comprises a servomotor 22 having an atmospheric chamber 66 and a chamber 67 normally connected by a pipe 23 and valve 29, Fig. 1, to a vacuum reservoir 26, and a valve 68 having a plunger 77 abutting servo piston 65 and housing a valve 87 normally raised from seat 85 by an adjustable stop 90 abutting a valve rod. The master cylinder 17 is connected directly to the brakes 16, 16a of the front wheels and is normally also connected to the rear wheel brakes via line 18, port 91 in valve 68, chamber 78, port 92 in plunger 77, past the valve 87, slots 75 in the end bushing 74, and port 93. When deceleration of the rear wheels exceeds a predetermined value, the deceleration device 31 operates valve 24 to close pipe 25 and vent servo chamber 67 to atmosphere; fluid pressure acting on plunger 77 moves the plunger and the servo piston to first close valve 87 on to seat 85 to cut-off the rear brake cylinders from the master cylinder 17 and then further movement of the plunger 77 with valve 92 allows fluid from the brake cylinder to flow into valve 68 to relieve the braking pressure. When deceleration decreases sufficiently, chamber 67 is again evacuated and plunger 77 moved to re-open the connection between the master cylinder and the rear brakes. The valve 24 is combined with the device 31, Fig. 6, and comprises a casing 39 rotated on valve 24 by a V-belt from the rear wheel transmission 15; a flywheel 53, rotatably mounted on a stud 55, engages a screw-threaded stud 57 prevented from rotation relative to the casing 39 by a key 59 on stud 55. Rotation of the flywheel is limited by a peg 60 co-operating with opposite radial arms 61 of the flywheel; a spiral spring 62, anchored to the peg 66 and to the flywheel, tends to rotate the flywheel 53 in a direction opposite to that in which it is normally rotated by the transmission 15 and is such that at a predetermined deceleration of the wheels 13, the flywheel rotates relative to the casing to move stud 57 axially to transmit thrust through rod 63, 64 to move a valve 43 from port 45 to connect servo chamber 67 to atmosphere via ports 49, chamber 44 and ports 47, and to close chamber 67 from the vacuum reservoir via ports 49, chamber 44 and ports 48. In Figs. 2 and 7 (not shown), the rod 63 closes two electric contacts which actuate a solenoid controlled valve to vent chamber 67 to atmosphere on deceleration exceeding a predetermined value. In apparatus 19, Fig. 5 (not shown), a spring- biased ball valve is used to close the communication between the master cylinder and brake cylinder when deceleration exceeds a predetermined value. The deceleration responsive device in Figs. 8 and 9 comprises flywheel 156 freely mounted on a stud 155 fixed to a casing 154 rotating with wheel hub 152. A plate 157 carried by the stud 155 supports a pin 158 and a U-shaped bracket 160 in two diametrically-opposed notches in the flywheel, the pin 158 carrying two contacts 159 and a plate 161 carrying a pair of contacts 162 being mounted on but insulated from flywheel 156. A carbon brush 163 in an insulated mounting in axle 153, engages plate 161 and is connected by a conductor 164 to a solenoid-operated valve; a pair of carbon brushes 165, 166 in flywheel 156 ensure that pin 158 is earthed to the vehicle structure. Two discs 167 are pressed apart by a spring 168 in bracket 160 to engage abutments 169 on the flywheel 156 to set the flywheel so that contacts 159, 162 are equally spaced. Excessive deceleration of the wheel causes flywheel 156 to rotate against spring 168 to close a set of contacts 159, 162 to energize a solenoid-operated valve as before. In the system of Fig. 3 (not shown), the deceleration device of Figs. 8 and 9 is employed on the front wheels of the vehicle and the device described with respect to Fig. 7 is used on the rear wheel transmission.