Patent GB-413696-A (GB)
Title: Improvements in safety devices for electrically driven vehicles
IPC: B60L3/02
Filed: 1933-01-18
Abstract: 413,696. Controlling electric vehicles. HIGGS, G. R., Lintrathen, Kirriemuir, Angus, Forfarshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Jan. 18, 1933, No. 1672. [Class 79 (v).] Safety control means for an electric vehicle comprises a fluid-operated relay adapted in its unoperated condition to put out of action means for cutting off the power supply and/or applying the brakes, and a fluid reservoir connected to the relay so that after a pre-determined time interval the relay is operated to cut off the power supply and apply the brakes, unless, at intervals of time not exceeding the predetermined time interval, a push-button or any one of a series of push-buttons is operated to close the circuit controlling a normally-open valve which controls the supply of fluid to the reservoir. In the construction shown in Fig. 1, the relay comprises three parts A, B, C connected to a reservoir 1 supplied with compressed air from a pipe 2 through a valve 9 adapted to be held open by a spring 8, but closed when a coil 3 is energized. When this happens the valve 9 closes to shut off the supply of air and an exhaust valve 5 is opened by its spring 12 so that the reservoir 1 and the three relays are connected to the atmosphere. The relays are arranged so as to operate at different intervals, the time intervals being for example, for C 5 seconds, B 25 seconds, and A 30 seconds. In the normally inoperative condition shown, the relay A bridges contacts A1, A2 to close a circuit 20 controlling an exhaust device for the vacuum brake, contacts A3, A4 to close circuit 21 controlling the supply of power to the electric driving motors, and contacts A5, A6 to energize the coil 22 of a valve 26 which admits compressed air to a cylinder 29 which closes a valve 30 and thereby shuts off the connection 34 between the vacuum train pipe 24 and an atmospheric inlet 32. Contact A6, which is connected to the supply conductor L2, is also connected to a contact A7 in the inoperative condition of relay A and thereby supplies energy to contacts of relays B and C when the latter become operative. When relay B is operative it closes contacts B1, B2 and completes the circuit of a warning signal 37. Relay C controls the circuit of coil 3 and also the coils of contactors or switches 41, 42 which must be closed before coil 3 can be energized. A number of press-button switches 40 are also arranged in connection with relay C. When all the relays are inoperative the vehicle is in normal driving condition, the coil 3 is deenergized and compressed air is supplied to the reservoir 1. After the pre-determined interval, relay C is operated and closes contacts C1, C2 and C3, C4. After a further interval, relay B is operated and gives a warning signal. With the switches 40 in the unoperated position shown an energizing circuit is completed from L1 through the switches 40 across the coil of the contactor 41 to conductor L2, and the contactor is closed. A holding circuit for the coil of this contactor independent of switches 40 is now established across the contactor itself and the contacts C1, C2 of relay C. If now the driver depresses any one of the switches 40 an energizing circuit for the coil of contactor 42 is completed through contactor 41 and switch 40, and therefore contactor 42 is closed. A holding circuit for this contactor is now established through contacts C3, C4 of relay C. With both contactors closed the circuit of coil 3 is completed, the valve 9 closes and exhaust valve 5 opens so that the relays and reservoir 1 are connected to the atmosphere and relays B and C return to their inoperative conditions. The coil 3 is thus again de-energized and air admitted once more to the relays to start them operating again. If the driver does not depress one of the switches 40 in time, then relay A is operated and breaks the contacts A1-A7 so that the power supply is cut off, the brakes are applied, and power is cut off from the relays B and C. Means may be provided for permitting the driver to leave his compartment without the safety equipment being brought into operation. Thus, an interlocking switch BR may be provided which is opened by a spring and closed by a piston operated by fluid pressure when the brakes are applied. When this switch is closed the coil 3 is always energized so that compressed air is shut off from the reservoir 1 and the relays cannot be operated. When the relay A has been operative the energizing circuits for relays B and C can be completed by means of a re-setting switch R which bridges contacts A6, A7. The relays may be constructed as shown in Fig. 3 in which compressed air is supplied past a valve 56 loaded by a spring 57 to the space behind a piston. 51 loaded by a spring 55, the rate at which the piston is raised being determined by the strength of the valve spring 57. The piston, when fully raised, closes contacts 52, 53. In a modification, the relay C is dispensed with, relays A and B acting as in Fig. 1, the circuit of coil 3 being completed when one of the switches 40 is pressed, and broken again unless the switch 40 is released.