Imperial Chemical Industries Limited

Thorn Electrical Industries Limited

Thorn Lighting Ltd.

John Michael Rees

Anthony Peter Downing

James Richard Coaton

Christopher Arthur Horler

Roger N Rothon

David Robert Mason

Susan Margaret Cole

The invention relates to electric incandescent lamps having a gas fill containing halogen. The internal surface of the lamp envelope and optionally also the exposed surface of internal components of the lamp are protected from attack by halogens including fluorine by a continuous imperforate coating composed of a metal oxide resistant to halogen attack. In order to achieve the necessary degree of continuity of the coating the oxide is formed in situ from a compound of the metal deposited as a solution on the surface. The preferred oxide is alumina, the other oxides of polyvalent and transition metals, including metals of the lanthanide series may be used. The coatings are preferably formed from solutions of halides of the metals in polar organic solvents such as methanol. The invention prolongs the life of lamps provided with the protective coating and enable such resistant and possibly cheaper materials to be employed for certain lamp components.

Incandescent halogen lamp with protective envelope coating

The invention relates to the manufacture of electric lamps containing fluorine in their gas fill. Fluorine can be accurately and conveniently introduced into an electric lamp envelope in the form of a fluorocarbon polymer. If a soluble fluorocarbon polymer, such as a degraded PTFE, is dissolved in a suitable solvent, for example a fluorine-substituted hydrocarbon or halocarbon solvent, the resulting solution can be metered with great accuracy into the lamp envelope and the solvent subsequently evaporated. The invention avoids the difficulties otherwise inherent in dispensing accurate quantities of an extremely reactive gaseous material.

Method of introducing fluorine into a lamp

Manufacture of electric lamps

Tungsten-halogen lamps of extended life are obtained by coating internal surfaces of the discharge tube and exposed surfaces of internal components with metal phosphate or arsenate glasses. The preferred glass is aluminium titanium phosphate. The coatings may be formed by applying a liquid composition capable of generating the desired phosphate or arsenate to the surfaces to be coated, and subsequently heating them to remove the liquid medium and form a vitreous coating. The medium may be water or an organic solvent such as an alcohol, and may contain a dissolved compound of the metal and an oxyacid of phosphorus or arsenic.

Incandescent lamps

Growing community of inventors

London, United Kingdom

John Michael Rees