Patent GB-1219403-A (GB)
Title: Vehicle fluid pressure operated anti-skid braking systems
Inventor: KNIGHTS RICHARD NORTHAM
IPC: B60T8/32
Filed: 1967-02-02
Abstract: 1,219,403. Brake transmission linkages; fluidpressure operated brakes. DUNLOP CO. Ltd. 2 Feb., 1968 [2 Feb., 1967], No. 5016/67. Headings F2E and F2F. In a vehicle fluid-pressure operated antiskid braking system a control valve 1 for a fluid-pressure operated vehicle braking system is provided with an over-centre force transmission device 2 interposed between a driver's brake pedal (not shown) and an operating plunger 3 of the control valve such that at least one transmission member 6 transmits the brake applying forces and is normally arranged to lie in a first force-transmitting configuration and, when brake applying forces greater than a predetermined magnitude are applied to the brake pedal, the transmission member 6 yields to adopt a second force-transmitting configuration such that when the transmission member 6 yields a substantial further increase in force is transmitted thereby to the control valve. As shown in Fig. 1 the transmission member 6 is in the form of a disc-shape sheet metal spring arranged normally to lie in a first, dished, force-transmitting configuration as shown in Fig. 1 with its outer peripheral edge 7 standing clear of a first thrust member, in the form of a disc 4, integral with the end of the operating plunger 3. The inner peripheral edge 8 of the transmission member 6 is located on the central boss 5 of the operating plunger 3 of the control valve 1. A second thrust member 9, in the form of a circular pressed metal housing, is fitted over the transmission member 6 and comprises a disc portion 10 and a short axially extending portion 11 at the periphery of the disc portion with a radially inwardly turned lip 12 which is folded around the outer peripheral edge of the first thrust member 4. Operation.-The initial movement of the brake pedal effects movement of the push rod 13 to the right and a thrust is transmitted through the over-centre device 2 to the plunger 3 of the control valve 1 causing the plunger to move through a small distance and allow the low pressure to be built up in the brake operating mechanisms (not shown). The transmission member 6 of the over-centre device 2 is thus compressed and the disc portion 10 of the second thrust member 9 moves towards the first thrust member 4. When the force applied by the driver to the transmission member 6 exceeds a predetermined magnitude the transmission member 6 is arranged to reach its over-centre position at which it suddenly yields and adopts a second, substantially flat, force-transmitting configuration allowing the second thrust member 9 to press the outer edge of the transmission member 6 against the first thrust member 4 to cause a sudden reduction in the resistance offered by the brake pedal to the pressure exerted by the driver. The effect of the over-centre action of the spring described above is such that once a predetermined level of pressure is applied by the driver to the brake pedal the thrust then applied to the plunger of the control valve prevents the driver from operating the brakes with the degree of sensitivity which will be needed to cause the wheels gradually to approach the locked condition without causing the skidsensing device to operate, so that the device ensures that the skid sensing device will be able to operate to cause the brakes to be released, irrespective the way in which the driver attempts to apply the brakes. An alternative embodiment is disclosed in the Specification (Figs. 2-5, not shown) in which the single transmission member 6 is replaced by two or more transmission members, one of the transmission members being constructed and arranged so as to yield to a brake-applying force smaller than that required to cause another or the other transmission member to yield.