GB740096A - Method of applying a coating in powder form to the inside surface of a lamp bulb and a device for carrying out the method - Google Patents

Abstract

740,096. Luminescent. screens. LUMALAMPAN AKTIEBOLAG. Feb. 4, 1954 [Feb. 6, 1953], No. 3360/54. Class 39 (1). [Also in Group XI] In order to apply a coating in powder form to the inside surface of a lamp bulb a combustible medium is burnt within the bulb in oxygen or air which is supplied in a stream to the bulb, and the powder is blown into the bulb in the said stream. The combustible medium may comprise ethyl alcohol or other organic liquid having a high combustion value. Apparatus for applying the coating comprises a vertical cylindrical casing or sleeve 10 supported in bearings in brackets 9, 16 and provided with a pulley 14 for a driving belt 13, the upper end of the sleeve providing a frusto-conical seating 6 for the neck of an inverted bulb 4. Extending upwardly within the sleeve 10 and into the lamp bulb is a tube 5 the lower end of which is connected to aT-junction 17 with one limb connected by a pipe 19 to the outlet 29, Fig. 3, of a powder receptacle 24. A spherical or ellipsoidal container 2 for ethyl alcohol is provided at the upper end of a tube 18 which extends upwardly through the tube 5 and is connected at its lower end to a tube 20 leading to a supply vessel for the liquid. A stream of oxygen is fed into the vessel 24 through a tube 27 which has its outlet below the surface of a supply 30 of the powder that is to be applied, the supply being maintained from a hopper 25 by a screw-conveyer 26. The container 24 is vibrated continuously during the operation. When a light is applied at the outlet 3 at the upper end of the tube 5 and an inverted bulb is placed upon the conical seating 6 the intensity of the flame is increased by the evaporation of the ethyl alcohol from within the container 2, and the application of the powder coating upon the inside wall of the bulb takes place.. A rod 1 inserted into the open top of the container 2 and standing on the bottom thereof is formed with a head 23 substantially of mushroom shape to spread the flame and reduce the risk of overheating the top of the lamp bulb. As described, a mixture of powdered tinting materials are applied to an incandescent lamp bulb by the stream of oxygen, but the method may be used to apply an inner coating of fluorescent powders such as zinc silicate, magnesium tungstate, zinc germanate or aluminium oxide, without the use of a binding medium. Specification 704,189, [Group XI], is referred to.