GB728963A - Improvements in or relating to electrical devices having envelopes fitted with caps - Google Patents

Abstract

728,963. Capping electric lamps and like devices. GENERAL ELECTRIC CO., Ltd., BREADNER, R. L., LEEDS, R. E., and SIMMS, C. H. June 5, 1953 [June 5, 1952], No. 14253/52. Class 39 (2). In securing a cap or base to the neck of a bulb or envelope of an electric incandescent lamp or similar device by providing one or more keys on the neck to interengage with corresponding parts on the cap to prevent relative motion of envelope and cap without the aid of cement, the neck portion is formed by blowing the heat softened glass thereof into a surrounding mould formed with inverse key portions or recesses and at the same time assisting the shaping of the glass into engagement with the surfaces of the said inverse key portions by applying suction at those surfaces. Fig. 3 shows a transverse section in a plane at right-angles to the axis of the glass neck 1 of a bulb and through four protuberances or pips 2 which are engaged within apertures 8 in the wall of a cap 3. The mould which is used in forming the protuberances 2 comprises two complementary parts 9, 10, each provided with two inverse key portions 11, 12 and 13, 14 respectively into which the softened glass of the neck is blown after fitting the mould around it. Chambers 15, 16 provided behind the respective pairs of inverse key portions communicate therewith through a number of channels 17, and each chamber is connected to an exhaust pump through connection 18 or 19, whereby suction is applied simultaneously with the application of air pressure to the interior of the bulb neck. In order to fit the cylindrical skirt 3 of a cap on to the neck 1 the skirt may be provided with holes 8, Fig. 6, located in positions to receive the protuberances 2, and with slits 24 which extend from the holes to the rim of the skirt and allow the rim to be pushed over the protuberances. The edges of the slits 24 may be subsequently welded or soldered together, or a locking ring may be provided to clamp them together. The securement of the cap may be strengthened by providing one or more short circumferential grooves 25 in the bulb neck during moulding, and slitting the skirt of the cap to form tongues 26 which are pressed into the adjacent grooves 25 after fitting the cap upon the neck. Rattling of the cap upon the neck may also be prevented by slitting the cap to form tongues 27 which are pressed inward to provide a resilient seating for the bottom of the envelope. In an alternative arrangement, Fig. 7, the skirt 3 is pressed out to form a pocket 28 which receives a protuberance 2 on the bulb neck, a transverse slit 29 being provided at or slightly below the level of the top of the protuberance 2 so that by pushing the face of the pocket inwardly at the part above the slit, the axial withdrawal of the cap from the envelope is prevented. The cap may be made of plastic material and attached by moulding in situ on the glass neck of the bulb.