Patent GB-1009434-A (GB)
Title: Improvements relating to electrical warning devices for braking systems
IPC: B60T11/20
Filed: 1962-04-27
Abstract: 1,009,434. Retractive switches; switches held set and freed mechanically; momentary-contact switches. R. T. HAMILTON. July 29, 1963 [April 27, 1962], No. 29046/63. Divided out of 1,009,433. Heading H2B. [Also in Division F2] In an electrical switch for use in a vehicle braking system (Division F2) and for connection to an indicator device to give an indication of the varying degrees of efficiency of the hydraulic system, a switch rod 127 (Fig. 16), operated by a brake pedal lever, moves a switch block 126 relatively to a spring-urged switch plunger 129 to illuminate a lamp 130 when an electrically conductive portion 132 of the switch block 126 contacts the plunger 129 (Diagram B), the lamp 130 being extinguished should the electrically insulated portions 131, 133 contact the plunger 129 (Diagrams A or C), further advancement of the switch rod 27 causing the switch to take up the position shown in Diagram D wherein the lamp is extinguished, removal of the actuating force causing the switch to take up the position shown in Diagram E in which the lamp is illuminated and the switch remains locked. Referring to Fig. 16, diagram A, the normal oroff position of the brake is shown and the switch plunger 129 contacts the electrically insulating portion 131 and the lamp is not illuminated. Diagram B illustrates the position when the brakes are fully applied and the brake system is in an efficient condition and in this position the electrically conductive portion 132 of the switch block 126 makes contact with the switch plunger 129 so that the lamp 130 is illuminated. Diagram C illustrates the position when the brake system is faulty but still operative to some extent but which results in excess movement of the switch block 126 so that the switch plunger 129 bears against the electrically insulating portion 133 so that the lamp is not illuminated whilst the brakes are applied. Diagram D illustrates the position when a brake system failure of a serious nature takes place and in this position the switch plunger 129 moves inwardly into contact with the switch rod 127 which is of an electrically insulating nature so that the lamp 130 remains not illuminated whilst the attempt is maintained to operate the brakes. Diagram E indicates the final position attained by the switch block after, release of the brake pedal lever in which the switch block 126 is spring- urged against a side of the switch plunger 129 which makes contact with an electrically conductive portion 134 at an end of the switch block so that the lamp 130 remain permanently illuminated to give a constant reminder to the driver that the brake system is in need of repair. Other embodiments are disclosed in the Specification wherein the switch may be associated with a hand brake lever (Fig. 14, not shown) or with a combined master cylinder and mechanical brake actuating device. Instead of the switch plunger 129, spring-blade contacts may be provided (Figs. 4 and 5 of the drawings accompanying the Provisional Specification not shown). The switch may be integral with the master cylinder (Figs. 6 to 10 inc. of the drawings accompanying the Provisional Specification not shown). Specification 1,009,433 is referred to.