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Woodhouse & Rawson Incandescent lamps


The Electrical Review
March 10th, 1883


The following description of an incandescence electric lamp, patented by Messrs. Woodhouse and Rawson, may interest our readers. This firm for some time past has been, well known in the electrical engineering world, and the incandescence lamps made to order alone by them daring the last twelve months number between ten and twenty thousand. It is only lately that they have patented and introduced their own lamp to the public, still, however, continuing to make and experiment for other people. Fig. 1 shows a general view of the lamp and its holder, which is also a patent. The legs for making connection between the filament and the external wires are made of platinum, which at the filament end is flattened out (fig. 2), and rolled up by a special tool into a tube (fig. 3), and then bent over to hold the filament which passes through the tube thus formed (fig. 4), and is firmly secured on either side with a specially prepared cement, thus making a good mechanical joint. The other end of the platinum wire is turned into a loop and sealed into the glass as follows: The tube near the bulb is drawn off, heated at the point, and blown till it bursts; the neck is then widened out to receive the filament which is inserted, and the glass pressed tightly on to the platinum leg. This method of sealing in is known as "pinching in."

Every description of lamp is made in Messrs. Woodhouse and Rawson's factory, from 3-candle-power upwards, the different candle powers being made to work with a range of E. M. F. to suit the machines and batteries for which they are made. They also make a specialty of small lamps for batteries, including lamps for surgical and microscopical purposes, which work with two or three cells, of low internal resistance, giving an electromotive force of from 8 to 4 volts and upwards. The surgical lamps are sometimes made flattened on either side as in fig. 5. Lamps of different shapes, sizes, and colours, are constructed for theatrical purposes. The lamps are coloured by a special process after they are finished, and are found to stand the heat developed. "We understand that Messrs. Woodhouse and Rawson can apply this process to any other lamps, or to ordinary globes. The patent holder, as will be seen in fig. 1, is most ingenious, simple, and effective; holding the lamp firmly without putting any undue strain on the platinum loops, it also allows the lamp to be easily changed, if necessary. The small spirals at the bottom prevent any chance of an arc forming and burning the wires through loose contact. This is really the most efficient lamp-holder we have yet seen, and it is suitable for any type of incandescent lamp.

Great care is taken in the testing of these lamps, and they are all specially marked, enabling people requiring fresh lamps to order without difficulty exactly what they want.

The price of all systems of incandescence lamps has fallen very much during the last year-from 25s. to 8s. 6d., which is the price of a good lamp now. This is chiefly due to competition, but, at the same time, the work has been greatly cheapened by systematising it and introducing mechanical appliances. A great reduction has also taken place in the price of labour-for instance, glass-blowers who a year ago were earning as much as from £5 to £7 per week are now content with half this amount, and even less. No doubt through the introduction of glass-blowing machines, and the employment of girls, we shall see a still further reduction. The work in Messrs. Woodhouse and Rawson's factory is now chiefly done by girls, with the exception of the more important part of the glass work, and the exhausting and testing of the lamps."


Arc and Glow Lamps By Julius Maier

"The Woodhouse and Rawson Lamp.

Instead of a carbon thread, a thin ribbon is used as conductor in this lamp. As far as could be ascertained (the whole of the manufacturing process is kept secret by the makers), the raw material for the filament is cotton, and the deposition of carbon from a hydrocarbon decomposed by the current is a main feature of the lamp. In some instances, lamps of very high efficiency were turned out by the manufacturers. Mr. Preece, in his report to the City Commissioners, gives the following figures about two kinds of lamps:-

E. M. F. in volts 55

Current in amperes 1.15

Candles 20.2

Watts per candle 2.35

And another lamp gave the following results:-

E. M. F. in volts 60

Current in amperes 2.33

Candles 53

Watts per candle 2.4

We have no reliable information as to the life of these lamps, but it is doubtful whether it is advisable to burn them at less than 3 watts per candle. Messrs. Woodhouse and Rawson have objected to the tests made by the Franklin Institute, on the ground that their lamps were worked with an E. M. F. of 55 volts instead of 50 volts, and under these circumstances the tests cannot be considered conclusive as to the life of the lamps. The efficiency was found to be 3.4 watts per candle."


The Electrical Review
Jan.4th, 1889

"The Woodhouse and Rawson Incandescent Lamp.-

From an advanced proof of Messrs. Woodhouse and Rawson's new catalogue, we learn that continuous and lengthy experiments during the last few years have led to the production of an entirely new type of carbon, which is of such high quality that flashing is unnecessary. Filaments made from the usual materials and flashed are said to be, in comparison, soft and full of flaws, the nature of the flashing process inevitably causing the filament to consist of at least two, and, probably, of many different densities of carbon. It is further stated that the same care has also been taken to improve the many other processes by which the lamp is completed, every possible precaution being used to produce a lamp of uniform excellence."