434

INVENTIONS OF NIKOLA TESLA.

coils are taken off bv the collector segments and thence conveyedoff by suitable conductors leading from the collector segments.This is the general plan of the construction adopted. Aside fromcertain adjuncts, the nature and functions of which are set forthlater, this means of commutation will be seen to possess many im-portant advantages. In the first place the short-circuiting and thebreaking of the armature coil connected to the commutator-seg-ments occur at the same instant, and from the nature of the con-struction this will be done with the greatest precision ; secondly, theduration of both the break and of the short circuit will be reducedto a minimum. The first results in a reduction which amountspractically to a suppression of the spark, since the break andthe short circuit produce opposite effects in the armature-coil.The second has the effect of diminishing the destructive effectof a spark, since this would be in a measure proportional to theduration of the spark ; while lessening the duration of the shortcircuit obviously increases the efficiency of the machine.

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Fig. 246 . Fig. 247 .

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The mechanical advantages will be better understood by re-ferring to the accompanying diagrams, in which Fig. 246 is acentral longitudinal section of the end of a shaft with the im-proved commutator carried thereon. Fig. 247 is a view of theinner or bearing face of the collector. Fig. 248 is an end viewfrom the armature side of a modified form of commutator. Figs.