Patent GB-779737-A (GB)
Title: Improvements relating to accumulator lamps
Inventor: ROSE JOHN
IPC: F21L4/00
Filed: 1954-03-08
Abstract: 779,737. Battery charging systems. ALKALINE BATTERIES, Ltd. March 8, 1955 [March 8, 1954], No. 6655/54. Class 38 (4). [Also in Groups XI and XXXVI] An electric lighting unit of the kind wherein a lamp is supplied with current from a storage battery or accumulator, and comprising external contacts on one part for connection to the terminals of a charging rack, is provided with a safety-switch whereby no exterior part is electrically live with respect to any other exterior part when the unit is removed from the charging rack, the safety-switch comprising a movable member which disconnects one of the exterior contacts from the accumulator as the unit is being removed from the charging rack and, in addition, one exterior contact is movable and biased to touch the other external contact when the unit has been removed from the rack, a fuse being provided in the connection between the external contacts and the battery so as to blow instantly if the safety-switch has failed to operate and allows the battery to become short-circuited. A metal lid 2 on the accumulator casing 1 is provided with a metal turret 3 having a pair of lateral contact lugs 6 secured at opposite ends of a diameter and forming the positive charging contact, the negative charging contact 7 being located within an opening in the top of the turret and supported by an insulating diaphragm 8 which tends to hold a bottom peripheral flange of the contact 7 against the underside of the turret. A positive lug 6 of the accumulator is connected through a heating element 10, Fig. 2, to a switch contact 11 associated with a snap-action bimetallic strip 12 which operates between the contact 11 and a contact 14 connected to the negative terminal of the accumulator through a fuse 15. Fig. 2 shows diagrammatically a lamp bulb 16 with a switch 17 and fuse 18 which may be mounted in a miner's cap lamp. The charging rack comprises a cylindrical member 21, Fig. 1, secured to a support at its upper end and provided with a telescopic outer member 22 which can be moved downwardly against the action of a helical spring 25 and connected to the lateral lugs 6 of the turret 3 by means of radial slots in a flange 23 at its lower end. The positive supply lead 20 is connected to the member 21, and the negative lead 27 to a headed contact 19 mounted in an insulator 26 in the member 22 and carrying a spring- biased metal washer 29. To place the battery on charge the rack member 22 is pulled downwardly on to it and then rotated, so that the contact 19 engages and depresses the negative battery contact 7, and the underside of the ring 23 is below the lugs 6, whereupon the pull'is released and the ring engages the lugs. Current from the charging-leads 20, 27 then flows through the heater 10 and bimetallic strip 12 until the latter snaps into the position shown in full lines and closes the charging circuit. Although carrying the charging current the bimetallic strip 12 cools down but remains in its new position until deflected mechanically into the position shown in broken lines by depression of the contact 7 on removal of the battery from the charging rack.