INCANDESCENT LAMPS

New Zealand Mail, Issue 1746, 23 August 1905, Page 59

INCANDESCENT LAMPS

The question of a substitute for the expensive platinum connection between the filament and the leading-in wires of incandescent lamps has engaged the attention of inventors from time to time, but hitherto without any definite result. It is claimed by Mr J. H. Guest, of Blooklyn, N.Y.', that a device, which is described in the “Electrical World,” recently patented by him in the States provides a solution of the problem. That part of the leadingin wire which is sealed in the glass is stamped in such a manner as to introduce a ring into its length, the walls of which are highly attenuated and integral with the straight parts of the conductor. Since copper has about six times the conductivity of platinum, the part of the conductor which constitutes the ring can be made of much smaller cross-section than a platinum wire, and the cross-section of each side of the ring is reduced much more than half that of the wire itself, thus minimising the strain at heating and cooling. It is claimed that owing to the circular form given to the seal-ed-in portion, any strain due to expansion or contraction is not transferred to the integral straight portions of the conductor on either side. It is stated that some lamps constructed on this principle are still in good condition after burning over 700 hours. Another advantage is claimed for this form of connection with respect to high candle-power lamps, in which two or more pairs of the connections may he easily sealed into the glass. As there are two paths for th© current ip. the ring part of the conductor, and the conductivity is so much greater than that of the platinum, the conductor used for a 16-c.p. lamp may be used for a 32-c.p. lamp. The outlay for material being negligible, and the manufacture involving a minimum of manipulation, the inventor’s claim that the cost is only a fraction of that attaching to the usual method appears feasible.