Patent GB-699634-A (GB)
Title: Improvements in or relating to fluorescent sign lamps
IPC: H01J61/04
Filed: 1949-10-07
Abstract: 699,634. Discharge lamps. SERENO, P. Oct. 7, 1949, No. 25818/49. [A Specification was laid open to inspection under Sect. 91 of the Acts, April 15, 1950]. Class 39(i) A fluorescent sign discharge lamp of the type formed by a sealed transparent tube carrying two electrodes adjacent opposite ends of the tube and containing an attenuated gas, the sign being eccentrically disposed with respect to the axis of the tube, is characterized in that the sign comprises a single plate of insulating material fixed inside the tube in such a manner as to divide the tube lengthwise into zones of different section and thus of different resistance to the discharge, the plate having fluorescent characters on that side thereof which faces the zone of greater section, and the plate being sufficiently shorter than the tube to leave at the ends of the tube spaces in which the electrodes are disposed. In the construction shown in Fig. 5 the glass sign plate 28 is held in eccentric position with respect to the axis of the tube 12 by means of a resilient member formed by a strip 30 of spring steel provided at its two ends with notches and bent into the shape of a ring, the strip having the ends overlapped and connected by the notches, and the connecting zone of the two ends of the strip being wrapped in a ribbon 34 of yielding, preferably insulating and poor heat conducting material, such as asbestos and glass fibre, making contact with the wall of the tube. The plate 28 is prevented from making contact with the wall of the tube by a ribbon 32 of similar material to the ribbon 34 wrapped round the end of the plate. The plate 28 is held against longitudinal movement by nubs 36 formed by locally heating the tube and then indenting the tube with a blunt rounded point. In the construction shown in Fig. 6 the plate 28<SP>1</SP> is held in position by means of twoended compression springs 44, each of which has a loop 46 intermediate its ends and ceramic beads 50 and 48 on its ends in contact with the sign plate 281, or a ribbon 321 around the plate, and with a depression 52 in the tube respectively. In the construction shown in Fig. 7 the sign plate 28<SP>11</SP> is rigidly held in position without touching the tube by means of a branched-off rod 56 the member 58 of which is provided with a notch engaging a corresponding notch on the end edge of the plate. The ends of the branched-off rod 56 have an indentation into which the wall of the tube 12<SP>11</SP> is pushed after heat softening. A thin ply of asbestos or glass wool ribbon may be inserted between the member 56 and the end of the plate 28<SP>11</SP> to prevent rocking. The ends of the tube 12, Fig. 5, are cemented to shells 24 of a phenol formaldehyde condensation resin, openings being provided in the shells for the passage and support of terminals 22. The filling may be argon or krypton at a pressure of between 0.5 and 2 mms. of mercury with or without a small amount of mercury. The electrodes may be of the cold type or of the oxide-coated heated type and may comprise elongated cylinders of nickel or iron coated with barium oxide. The characters 40 of the sign are provided by forming depressions of depth about 0.5 mms. in the plate 28 and filling the depressions with a fluorescent material. The depressions can be formed by sand-blasting through a stencil, chemical etching, photo-engraving or moulding when the plate is made. Over the area of the plate thus treated there is applied by brushing or spraying fluorescent powders in suspension in a varnish or lacquer carrier. If desired powders of different composition can be employed on diffent areas of the plate in order to obtain differently coloured characters when the lamp is activated. After the carrier is dry the front surface of the plate is scraped with a straight edge to remove excess fluorescent powder. The plate is then heated to volatilize the solidified carrier. Specification 518,578 is referred to.