GB387875A - Means for ensuring safety in use of trackless electric road vehicles such as trolley buses, supplied by overhead conductors - Google Patents

Abstract

387,875. Protective arrangements. SOC. DES V•HICULES ET TRACTEURS ELECTRIQUES (VETRA), 38, Avenue KlÛber, Paris. April 14, 1932, No. 10724. Convention date, April 11, 1931. [Class 38 (iv).] To prevent electrification of trolley buses and other more or less insulated trackless road vehicles supplied by overhead conductors, the two supply lines are maintained at equal potentials of opposite sign with respect to earth, the vehicle body being thus normally at the mean thereof. The body may be connected to the mid-point of a resistance or series of resistances branched across the two supply wires on the vehicle, accidental flow of current therein acting through relays to bring into operation audible, visible, or other signals, or to cut out the main switch on the vehicle or effect other safety measures. The current is collected by contacts 1, 2, a two-pole switch 3 being closed as soon as there is current in the lines by a coil 4 in the line circuit, the direct-current driving-motor 6 being regulated through a controller 5. The vehicle chassis is connected as at 13 to the mid-points of two pairs of equal resistances 7, 8 and 9, 10 branched across the supply circuit, a coil 12 between the connections controlling a relay 11 whereby, in the event of accidental or stray passage of current, such as by an earthing at 14, a luminous or other signal 15 is actuated or a switch in the control circuit 4 may be opened causing the main switch 3 also to open. Alternatively, a low resistance galvanometer may be provided to indicate a drop in the potential of either line. Mechanical or magnetic looking means may be provided whereby, when the relay has been operated, manual resetting is necessary.