Patent GB-739538-A (GB)
Title: Improvements relating to electric lamp making machines
IPC: H01J9/38
Filed: 1954-04-01
Abstract: 739,538. Making electric lamps and discharge devices. BRITISH THOMSON-HOUSTON CO., Ltd. April 1, 1954 [April 1, 1953], No. 9613/54. Class 39 (2). [Also in Group XII] Electric lamps and discharge devices in course of manufacture in a machine which advances them along a horizontal path of movement are conveyed through an oven provided with vertical walls 9, 10 defining a horizontal passaga 8 with an opening at each end to permit entrance of a succession of lamps 4 carried in heads 1 on the conveyer, the oven consisting of a heating chamber C adjacent to and in communication with one end of the passage and having means to heat air substantially uniformly within the chamber, which contains a blower 28 with its intake side communicating with the heating chamber and its outlet leading into a duct 29 connecting with the other end of the passageway, thereby establishing a closed circuit within the oven. In the example, the lamp-making machine comprises a rotary turret 2 with a series of work-holding heads 1 around its periphery, each head comprising a stationary vertical rod 18 and a parallel rotary rod 19 extending downwardly and provided respectively with a pair of jaws 14, 15 and a cooperating jaw 16 which grip a lamp tube inserted between them when separated at a loading-station. Heat is derived from a burner 25, using either gas or oil, directed downwardly from the upper wall of the heating chamber towards a heat distributing tube or muffle 24 which spreads heat from the burner evenly from top to bottom of the chamber, and the blower 28, mounted approximately midway relative to the height of the oven, takes in the heated air and projects it at high velocity into the duct 29. Adjustable vanes 43 within the entrance of the duct 29 spread the heated air vertically, and the other end of the duct, the height of which is increased to that of the oven is turned through an angle of approximately 120 degrees by a baffle 44. This turn is adjacent to the exit opening 11 through which the lamps 4 leave the oven, and is so arranged that the heated air passes across the exit opening and forms an air curtain preventing the escape of heat. The heated stream of air flows through the channel 8 in the direction opposite to that of the travel of the lamps and is again turned through an angle of 120 degrees across the entrance opening 5 and back into the heating chamber C where it is reheated and recirculated through the oven. To avoid the escape of air from the entrance 5, a second air curtain is preferably provided from a vertical manifold 35 provided with a series of small holes through which air is supplied at a low pressure, e.g. 3.5 pounds per square inch. To avoid discomfort to the operators of the machine due to heated air that may escape from the opening 5, the manifold 35 is provided with an additional series of small holes 37 so that hot air in escaping is blown behind a shield 38. The escape of hot air from the top of the passage 8 is prevented by providing each tube-carrying head 1 with a metal shoe-plate 21 which slides upon inwardly directed track rails 22 extending along the top of the oven, a space 7 being left between the edges of the rails to permit the passage of the exhausting tube 12 at the upper end of the lamp tube. The sides of the oven are insulated by relatively large sheets of expanded mica rock 46 adhered together by a binding substance and attached to sheet metal outer sections so arranged and secured that all expansion of the heating apparatus is in a vertical direction downward. The bottom 39 of the oven is independently mounted on blocks 59 so that it does not follow the expansion of the sides, to which it is connected by slip joints 61, 62 to prevent leakage of air at the junction. Specification 543,079, [Group XXVIII], is referred to.