GB491554A - Method of and apparatus for sealing off vessels containing gases - Google Patents

Abstract

491,554. Sealing gas - filled electric lamps and discharge devices. EGYESULT IZZOLAMPA ES VILLAMOSSAGI R. T. June 21, 1937, No. 17210. Convention date, June 20, 1936. [Class 39 (ii)] In a method of sealing-off the heat-softened glass or vitreous exhausting and filling tube of a gas-filled electric incandescent lamp or discharge device, more particularly when the gas filling is at a pressure above atmospheric, the tube 1 is pinched together by a tool comprising elements 2, 3 which are heated at least to a bright red heat and possess a non- adhering surface and a coefficient of thermal expansion corresponding substantially to that of the tube material, the tool being preferably pressed resiliently against the tube and being cooled down together with the tube, while still in contact with the latter, after pinching has taken place. The pinching- elements 2, 3 consist of thin U-shaped plates of chromium-nickel alloy held between clamping-jaws 2a, 2b and 3a, 3b, which press them against the glass tube 1. A heating current may be fed through the jaws, or gas flames may be directed upon the portions in contact with the tube. The jaws are movable to and from each other and are actuated by springs or a pneumatic pressure device. The parts of the tube adjacent to the zone of action of the tool are preferably cooled by blasts of air, indicated by the arrows 4, 5, and the tube and tool are similarly cooled after sealing has taken place. To prevent the tool from sticking to the softened glass its surface may be polished, or coated before each pinching operation with a layer of material such as graphite, or tools of graphite or carbon may be used. The tool may also be shaped so that it severs the lower end of the tube 1 after pinching it. In a modification the tool comprises two resilient portions so shaped that they substantially embrace the tube. The operations are preferably carried out in a rotary automatic machine and, in order to reduce delay due to the pinching-tool remaining in contact with the filling tube until cooled down, the tool may be mounted on an auxiliary apparatus adjacent to the main machine carrying the tube, so that, after pinching, the sealed tube is carried away on the auxiliary apparatus and cools down in transit.