Patent GB-1214094-A (GB)
Title: Improved vehicular brake system
IPC: B60T17/18
Filed: 1968-11-27
Abstract: 1,214,094. Fluid or electrical control of brakes; emergency application; leakage indicators. KELSEY HAYES CO. 27 Nov., 1968 [27 Nov., 1967], No. 56385/68. Headings F2E and F2F. A vehicular brake system comprises first and second brakes, means for selectively actuating the first brake, and means for operating the second brake, the latter means being responsive to failure of the first brake to operate upon actuation of its actuating means. Preferably the "first brake" comprises the front and rear brakes of a tractor vehicle and the "second brake" comprises the brakes of a trailer vehicle; a second actuating means for selective actuation of the trailer brakes may then be provided in the tractor vehicle, together with connecting means to permit simultaneous actuation of all the brakes. Preferably a warning light is provided for indicating failure of the front or rear tractor brakes and the "means responsive to failure" are operative in response to energization of the warning light. Tractor brake operation.-The tractor brakes 13 to 16, Fig. 1, are conventionally operated by a dual master cylinder assembly 24 actuated by a pedal 22. If either the front or the rear fluid circuit should fail, an indicator light 72 is energized by operation of a failure indicating device 28. Trailer brake operation.-The driver may apply the trailer brakes independently of the tractor brakes by depressing a control lever 94, Figs. 1 and 2. This lever is pivoted at 92 and serves to depress an operating arm 104 to which is secured a spring contact arm 102. The arm 102 first makes contact with, and then progressively short-circuits, a rheostat 97 located between a battery 74, Fig. 1, and solenoids 79, 80, which actuate the trailer brakes 77, 78. The other end of the battery and the other ends of the solenoids are earthed. The degree of application of the brakes is governed by the degree of depression of lever 94 and by the position along lever 94 of a threaded operationg member 107. Combined brake operation.-A pressure conduit 115, Fig. 1, extends from a T-connection in the rear brake conduit 34 to a cylinder 117 housing a piston 118, so that when pedal 22 is depressed the pressure generated in conduit 34 depresses lever 94 by means of piston 118 to apply the trailer brakes. Safety device embodying the invention.-A brake or stop light, not illustrated, is provided, and is energized upon actuation of a switch 121, Fig. 1, upon movement away from the switch of the brake pedal 22. This switch is in series with a further switch constituted by contact points 128, 129 in a line from the battery to the trailer brake solenoids. In parallel with the indicator light 72 and in series with the failure indicating device 28 is a relay coil 133, Fig. 1, which, when energized, serves to close the contacts 128, 129. The sequence of steps resulting in safety operation of the trailer brakes (the "second brake") is as follows. When pedal 22 is depressed, switch 121 closes. If one of the two tractor hydraulic circuits fails the failure indicating device 28 operates, energizing relay coil 133. Contacts 128, 129 are thereby closed, completing the circuit through the solenoids 79 and 80 and thereby applying the brakes. A variable resistor 132 for setting the maximum force exerted by the trailer brakes in this situation may be provided.