GB1101078A - Improvements in or relating to vehicle brake systems - Google Patents

Abstract

1,101,078. Fluid-pressure brakes. MULLARD Ltd. 12 Feb., 1965 [21 April, 1964; 30 July, 1964], Nos. 16474/64 and 30214/64. Heading F2F. An arrangement for facilitating control of brake pressure in a vehicle hydraulic braking system by anti-skid devices, comprises a control piston B1 arranged to operate in a cylinder having large and small diameter bores separated by a shoulder R and which is located between a master cylinder connection MC and a wheel brake cylinder W, a rod C through which movement can be imparted to piston B1 to move it from the position shown, where fluid is free to by-pass it, to a position beyond the shoulder R where the fluid supply is cut off, whereby continued movement forces fluid back to the master cylinder and allows fluid to flow away from wheel cylinder W, and a positive feedback arrangement between the master cylinder connection MC and the piston B1 which consists of a second piston Bf subjected to master cylinder pressure and acting via a suitably shaped cam or equivalent force-balancing member FB on the rod C. The arrangement is such that the forces acting on piston B 1 are balanced or nearly balanced at all times so that only a small additional force, e.g. one produced by an electromagnet energized in response to a signal from a skid-sensing device, is needed to move the piston B1, while resulting in a much greater transfer of energy away from the wheel cylinder than that which is expended in moving the piston B1. The energy transferred away from the wheel cylinder W on operation of the antiskid device is shown, by mathematical formulµ, to be only partially expended in moving the piston Bf which has a smaller bore X stroke than that of piston B1. The remaining energy is transferred either to the master cylinder (Fig. 4, not shown) which would result in undesirable kick-back of the driver's pedal, or preferably, as shown in Fig. 5, to a spring S1 It is shown mathematically that spring S1 cannot absorb all the surplus energy at every position, so that the alternative arrangement of Fig. 6 may be preferred, in which the fluid displaced by piston B1 is exactly compensated by a second, gauged, piston B2, a spring S2 acting between piston Bf and the cam FB then operating as a non-linear energy absorbing device. Spring S2 may be replaced by an accumulator bulb S2(a). A single piston having a valve arrangement (Fig. 7, not shown) operating in a plain bore without shoulders R, R<SP>1</SP> may be substituted for the arrangement shown in Fig. 6. Fig. 8 (not shown) is a modification of the arrangement of Fig. 7. Figs. 9 and 10 (not shown) disclose modifications of the simpler arrangement of Figs. 4 and 5 to reduce pedal kick back in this case. A suitable electromagnetic actuator for moving the rod C in response to electrical impulses is indicated diagrammatically in Fig. 11 (not shown), the impulses being supplied, after amplification, by a magnetic sensing unit indicated diagrammatically in Figs. 13 and 14 (not shown).