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THE INDIA RUBBER WORLD 



Tune 1. 1921 



xArtificial Lio^htin<^ in the Rubber Industry — V' 



By E. Leavenworth Elliott 



The Two Bases of Figuring the Efficiency of a Lighting System 



CONSIDERATIONS THAT DETERMINE THE SELECTION AND 

 ARRANGEMENT OF LIGHT UNITS 



IN the laying out of an industrial lighting installation there are 

 two considerations which will govern the selection of the units, 



and their arrangement in the several spaces to be lighted: (1) 

 The effect upon the efficiency of the operatives working under the 

 light, and (2) the mechanical efficiency of the apparatus itself. 



Obviously, the first of these considerations is by far the more 

 important. The theologian seeking arguments in support of the 

 dogma of "total depravity" would find a rich source in the field 

 of shop lighting. It is no uncommon thing to find a factory man- 

 ager who will select a lighting unit on a basis of a cent a day 

 difference in maintenance cost where the use of a twenty-thousand- 

 dollar machine and a twenty-dollar daily pay-roll are more or 

 less completely dependent upon the light supplied. Just stop a 



light, which determines the efifects of relief and contour. (4) 

 Incidental conditions which interfere with vision — the various 

 forms of glare, and unnaturally sharp or dark shadows. 



The selection of the light-source will be determined by a con- 

 sideration of the first and last of these conditions. The location 

 of the chosen units, or the "lay-out," will be determined by the 

 last three conditions. The facts to be considered in making the 

 selection of the light-source have been discussed in the preceding 

 articles, and also some of the problems pertaining to the lay-out. 

 There remains a little further consideration of the matter of loca- 

 tion of units, and a discussion of mechanical efficiency. 

 THE TWO METHODS OF LIGHTING 



In general, there are two ways to figure a lay-out : you can 

 either light the room, or light the job. Most "illuminating en- 

 gineering" formulas refer to room lighting. This is all right in 



General Electric Compdny 



A Good Ex.^mple of Room Lighting by Cooper-Hewitt L.\mps in the Vulcanizing Dep.\ktment 

 In This Case Directional Light Is Not Necessary, and a Good General Illumination .\ns\vers All Purposes 



moment and figure out the total cost of operating a heavy calender 

 — interest, depreciation, power, superintendence, general overhead, 

 wages of the operatives, and see what proportion of this total is 

 expended for the light used for its operation. Tlien figure the 

 value of the materials which it handles, and make a similar com- 

 putation. Can you think of a more exaggerated case of "saving 

 at the spigot and wasting at the bung-hole" than to trim on the 

 cost of light at the possible risk of trimming proportionately on 

 the efficiency of this operation? 



The effect of the illumination on the efficiency of production 

 will depend upon the following conditions: (1) The quality of 

 the light, which is determined by the different kinds of radiations 

 of which it is composed. (2) The intensity of illumination on 

 the objects concerned in the work. (3) The direction of the 



'Continued frcm The India Rlbher World, April I, 1921, pages 483-489. 



some cases and all wrong in others. In many cases lighting the 

 job will also light the room sufficiently. In other cases, lighting 

 the room is the most practical way to light the job. 



Lighting the job involves two general cases: machine lighting, 

 and bench lighting. The two important considerations in machine 

 lighting are sliadows, and direction of rays. To light the par- 

 ticular parts of the machine and materials that you want to see 

 — without shadows of yourself, or your tools, or other parts of 

 the material falling just where you must see the most clearly — 

 is not always an easy matter, and in practice is much less com- 

 mon than its importance demands. 



Take tire-building machines, for example ; the core and the 

 tire must be seen from both sides, and the liglit must come from 

 a position in front of the operator, and not too high up. This is 

 a good example of what we mean by "lighting the job." If the 



