GB586733A - Improvements in and relating to bases for electric lamps and the like - Google Patents

Abstract

586,733. Electric lamp caps. BRITISH THOMSON-HOUSTON CO., Ltd. July 3, 1944, No. 12642. Convention date, July 1, 1943. [Class 39 (ii)] [Also in Group XXXVI] A bulb for electric incandescent lamps and discharge tubes is provided with a screw threaded neck to receive a similarly threaded metal cap which is screwed thereon and held against disengagement by a film of adhesive provided between the engaging surfaces, and one of the leading-in wires is mechanically clamped into electrical contact with the cap while the other is mechanically clamped to a centre or end contact which is located in insulating material closing the end of the cap. In one method of clamping the leading-in wire 15 to a cap B, Fig. 3, the screw threads in the bulb neck 10 are traversed by a groove 30 which runs vertically across them the wire being brought across the closed end 13 of the neck and down the groove, so that when the cap is screwed in position its corrugations bear upon the wire, the depth of the groove in the neck being such that the wire is flexed resiliently by the pressure on it. The centre contact comprises a rivet-like metal eyelet with a hollow shank 26 secured within a vitreous conical mass 21 which closes the end of the cap, the upper end of the shank having a disc or flange 25 formed with a radial slit 27 so that one adjacent edge of the metal can be turned upwardly to form a tongue beneath which the upper end of the leading-in wire 16 is bent after bringing it up through the central hole, and' is then bent around the shank and clamped by pressure upon the disc 25. The adhesive 34 applied between the cap and the neck of the bulb L may be of the varnish type, comprising rubber, gum, resin &c. in a suitable volatile solvent, or may consist of a water soluble silicate or a slow setting gum or plastic. In a modification, Fig. 4, the end insulator 21a supporting the centre contact 25a consists of a bevelled button, preferably of glass, secured in the upper end of the cap by turning the latter inwardly to form an annular lip 36 which overhangs the bevelled edge, the leading-in wire 15 being clamped between the edge and an annular seat 35 produced in the formation of the lip 36. In a further modification, Fig. 5 (not shown) the overhanging annular lip is replaced by a series of metal tongues, e.g., three, which project inwardly and engage within notches in the adjacent edge of the insulating button supporting the centre contact, this engagement also serving to clamp one leading-in wire against the rim of the cap. The centre contact comprises a resilient cylindrical member with a head which clamps its leading-in wire in position by a snap-action. Specification 424,621 is referred to.