ENGLISH-MADE EDISON LAMPS

New Zealand Mail, Issue 1747, 30 August 1905, Page 10

ENGLISH-MADE EDISON LAMPS

(From "Engineering” for June.)

At the time of our visit last .week to the Britiah-Thomson Houston Rugby works to see the -Curtis turbine, we had also an opportunity of inspecting the modern lamp works in full ©wing. The making of incandescent lamps has always been associated hitherto with expert© in glass-blowing. 'We were, therefore, surprised to find that in a factory turning out lamps to the extent of 30,1KK) a week there was only one glass-blower employed. All the rest of the many operations involving glass work were performed by automatic machines fed by girls. ' These machines were designed for a great variety of purposes, but in general principle they were, not unLke. They consisted, as a rule, of a revolving frame with a number of cl.ps in which the lamps in various stages of manufacture could be held. The girl who placed lamps into these clips moved the frame round by one step each time. This brought the lamp successively opposite one or more bLow-pipe flames, wh.ch automatically performed the operation required. The girl had then only to remove the bulb which had been advanced one stage in manufacture and replace it by another to be operated upon. In this way the bulb© received into the factory passed through a variety of processes. For instance, they first have a small hole made at the upper end. The next step is to fix to the edge® of this hole a small glass tube through which, the lamp is exhausted. The larger tube at the other end is then prepared to receive the mounted filament, which has already gone through*', a number of _ stage© of manufacture. The filament is introduced into the lamp, sealed iu, and the lamp passes on to the exhausting benches in a very short space of time. These glassblowing machines are the outcome of year 3 of experimental work, and it would be unfair to the company to -describe them in detail. It suffices to say that they allow of comparatively -unskilled labour carrying out excellent work in a minimum of time.

THE REMOVAL OF THE AIR from the lamps is done entirely by mechanical pumps. The first part of the exhaustion process is effected by one pump while the lamps are cold. After a certain stage the operation is continued by a second pump, which create® a better vacuum. At the same time current is switched on to the filament, which renders it incandescent. Before the process is commenced, a small quantity of a certain chemical is introduced into, the tube through which the lamp is exhausted. This tube is imw heated by a blow-pipe, and the substance gives off a gas which combines readily with the remaining traces of air within the lamp. The operator is able to judge by the colour of the light given off by the filament when th: vacuum is satisfactory, and she then seals off the tip of lamp. The process of mechanical exhaustion with this final aid in removing the last traces of air is much more rapid than with mercury pumps. We need hardly say that it is also much more healthy for the operators. - • .•’

As regard© the grading of the lamps, the carbon filaments are all flashed to a uniform thickness before they are mounted. Slight variation in the voltage , required is then met by varying the length of the filament. The practice adopted by the company is to cut the filament© to praeticallv the right length for a medium voltage, and then to accurately grade the lamps after completion. This is done on the photometer. The voltage applied to the lamp under test is varied until 't. gives the required candle-power. The girl who feeds the testing lampholder socket of the photometer bench reads off this voltage on a scale, the indication of which is automatically given by the operator when adjusting the same to get the correct candle-power. This voltage is marked on the lamp, which is then put with others from the same batch needing equal voltage to give THE' RATED GANDUB-POWER. Thus, out of one series of lamps, the variation may be from, ©ay, 210 volts up to 230 volts by steps of five volts. The grading ensures that the nominal can-dle-power will be obtained when the lamp is connected to a circuit of the voltage marked on the glass. Both the standard lamp and the lamp under test are made to revolve while being tried, so as to avoid any error due to the angular positions of the filaments with respect to each other. •

The details for testing the lamps for mechanical strength in those parts most likely to be injured were most interesting, and we saw quite a number of lamps being discarded which otherwise would have vexed consumers by their short life. It is in the repairs to these defective lamp© that the single glassblower is employed. The net result of the introduction of so many automatic processes is that a large number of highclass lamps which are well graded as to voltage and candle-power can be turned out in a comparatively small factory four storeys in height. At present the ground floor is used for other work, but the increase in the demand for lamp© will shortly necessitate the moving of this to another building.