Patent GB-1496511-A (GB)
Title: Fluid pressure braking systems for vehicles
IPC: B60T8/30
Filed: 1974-01-28
Abstract: 1496511 Anti-skid braking systems AUTOMOTIVE PRODUCTS Ltd 27 Jan 1975 [28 Jan 1974] 03935/74 Heading F2F A fluid-pressure braking system is responsive to differential loading between a wheel on one and the other side of a vehicle to reduce the braking pressure supplied to the more lightly loaded wheel only on differential loading. In Fig. 1 respective proportioning valves 14 to 17 are provided between a liquid pressure master cylinder 13 and brake actuators at the four wheels, a biasing force tending to move a valve plunger 51 (Fig. 3) to increase the braking pressure being provided by respective torsion bars 69, 70 with increasing wheel load at the rear valves 16, 17 and a biasing force being provided at the valves 14, 15 by a pivotal link 18 coupled by torsion bars 22, 28 to the front wheels on differential wheel movements. The link is pivoted about its centre on pivots 65, 66 (Fig. 3) by equal -wheel movements but on differential wheel movements it is translated together with a hollow member 58 which is slidably. coupled to the plungers 51 which are urged apart by a bias spring 68 to provide differential braking. As shown in Fig. 3 on rightward movement of the link 18 the spring 68 urges the plunger 51 of the valve 49, having inlet and outlet ports 44 and 45, to the right delaying the closing of the valve head 50 on its seat 55 due to the fluid pressure acting on the differential areas on its opposite faces to increase the braking pressure. On leftward movement of the link the plunger head 50 is moved towards its seat to close the valve and on further plunger movement the seat 55 is moved to increase the volume of the output chamber of the valve and hence to reduce the braking pressure. On increase of the input pressure the output pressure increases at a lower rate once the valve has seated. In an alternative valve assembly (Figs. 7 and 9) there are lost-motion pin and slot connections 127/125 and 128/126 between the link 18 and the valve plungers 88 so that on movement of the link 18 only the braking pressure on the more lightly laden wheel is reduced. The plunger 88 encloses an axial valve 99 which is opened by abutment of a pin 102 with an end wall 86 and closes when the plunger is moved to the left by the hydraulic bias and the bias from the link 18 opposed by the bias of the springs 109, 110. For use at the rear of a vehicle for an individual wheel the internal bias springs 109, 110 are not used (Fig. 10, not shown). In the further alternative in Fig. 11 a valve 137 similar to the valve in Fig. 9 is used, the plunger 88 having a tongue and slot lost-motion connection with a double armed torsion bar 145 which is connected by a cable 156 or rod to a similar assembly on the other side of a vehicle. In Figs. 13, 14 a pair of interlinked transverse torsion bars 183, 184 control a pair of valves 158, 159 for two opposed wheels, the inner ends 183B, 184B of the bars acting as a beam and pivoting about roller-like abutments 187 to provide a differential bias on the valve plungers 171 on roll of the vehicle and remaining stationary, the central bar portions twisting on equal wheel movements. The valves are arranged so that once communication between the inlet 179 and outlet 186 is closed by seating of a disc 175 the valve is not opened by increasing inlet pressure but opens on removal of the load bias or release of the brakes. For use with independent valves for rear wheels the torsion bars end adjacent the abutments 188 and do not overlap (Figs. 16, 17, not shown). A differential biasing device as described may be provided at the rear wheels of a vehicle to control the braking pressure thereto or a device at either the front or rear may control the braking pressure for all the wheels on one side relative to all the wheels on the other side.