Patent GB-718686-A (GB)
Title: Improvements in and relating to electric lamps
IPC: H01J5/62
Filed: 1952-12-29
Abstract: 718,686. Capping electric lamps. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 29, 1952, [Dec. 26, 1951.] No. 32856/52. Class 39 (2). [Also in Group XXII] A welded electrical connection between a leading-in wire and the metal cap of an electric lamp is effected by the fusing and intermingling of the metals of the wire and base without any addition of extraneous metal thereto. The method of welding is particularly applicable to lamps of the type provided with a screw-threaded cap connected to a leading-in wire having an end portion located between the neck of the bulb and the adjacent portion of the cap, a projecting end portion of the wire being tensioned upwardly around the rim of the cap to make a lowresistance between the wire and rim, and an electric current passed directly through the wire and shell. The pre-arrangement of the wire, and the welding, may be performed automatically by apparatus located at successive work stations adjacent to the turret of a lamp-making machine of known type. A lamp bulb 1, Fig. 3, supported by a workholder comprising a pair of spring- closed jaws 20 and a spring-pressed supporting-cup 17 mounted on the periphery of a turret, has a screw-threaded cap 2 secured thereto by basing- cement in known manner, and the side leading-in wire is drawn out between the neck of the bulb and the cap so that the protruding portion 11a lies adjacent to the bulb and points downwardly with respect to the vertical axis. Mechanism located at a work station A comprises a finger 24 which has a downwardly bevelled front edge 33 and is pressed forwardly by a spring 31 located within a passage in a lever 25 pivoted on a standard 27, so that when the rear end of the lever 25 is tilted upwardly by a connecting-rod 35, the finger 24 engages the wall of the bulb; a subsequent downward movement of the connecting rod 35 causes the front edge of the finger 24 to lift the end of the leading-in wire away from the bulb wall and raise it against a wire stop 34 fixed to the standard 27. The connecting rod 35 is actuated by a cam-controlled rocker-arm 38 and, when the edge of the finger 24 abuts against the rim of the lamp cap, a limited overtravel of the rocker arm is permitted by having the connecting rod 35 in two parts connected by a spring 42 and a sleeve 41. At the next station B, to which the lamp is indexed, the leading-in wire is embedded into the edge of the shell and its cross-section reduced at that point by means of a wiper 47, Fig. 4, carried on the end of a spring-pressed plunger rod 28<SP>1</SP> supported in a lever 25<SP>1</SP> operating in the same manner as the lever 25 of Fig. 3. The wiper 47 has a rounded lip or edge 48 which engages the leading-in wire 11c and presses it into the ridge or edge of the shell of the cap, and a curved blade 49 mounted on the top of the wiper engages the wire on the downward stroke of the wiper and brings its free end portion into the horizontal position 11d, shown in Fig. 5a, wherein the lamp has been indexed to station C at which a pair of jaws 51, 52 constituting a welding electrode grip the wire portion 11d and a stationary brush 59 engages the side of the metal cap. Due to the tension exerted upon the wire by the jaws 51, 52, its cross-section is reduced in the region where it is embedded in the rim of the cap, so that the resistance of the wire at a point immediately beyond its contact with the cap is relatively high, and the wire fuses and separates there. The welding jaws are pivoted upon an insulated bracket 54, the lower jaw 52 being movable by an insulated connecting rod 58, whilst the upper jaw 51 is normally held down upon a stop plate 57 by a spring 56.