Thorn Emi Plc

Ian Connor

Roger Alan Hume

Paul V Crawshaw

A tungsten halogen incandescent filament lamp is provided having a fill of inert gas and halogen. In such lamps and especially in lamps provided for studio and theatre applications having operating temperatures between 2200K and 3450K there is a tendency to arc over between the filament limbs. According to the invention this problem can be solved by adding hydrogen gas in an amount between 0.05% and 1% by pressure at 20.degree. C. This hydrogen gas is in addition to any hydrogen which is present as part of the halogen or halogens. A preferred halogen is the solid hydrogen, bromophosphonitrile (PN Br.sub.2).sub.n which introduces phosphorus as a getter into the lamp.

Tungsten halogen incandescent lamp with arc preventing fill

The invention provides a tungsten halogen linear incandescent lamp having a gas fill comprising a mixture of CHI.sub.3 and (PNBr.sub.2).sub.3. Gas fills according to the invention comprise from 6 to 32 micrograms of (PNBr.sub.2).sub.3 per c.c. of the lamp internal volume with a ratio of CHI.sub.3 to (PNBr.sub.2).sub.3 of from 1:1 to 5:1 and result in lamps having a increased efficacy and a life of more than 2,000 hours.

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Leicester, United Kingdom

Ian Connor