COMMUTATOR FOR DYNAMO ELECTRIC MACHINES

(No Viodel.) N. TESLA, COMMUTATOR FOR DYNAMO ELECTRIC MACHINES, No. 334,823, Patented Jan. 26, 1886. cWaverzée. C4a2/4%d, /e66 (a 46. e/e/24 7 <ruz -26 22.4 6-66. lithographer. Washington, D.C.

UNITED STATES PATENT OFFICE. NIKOLATESLA, OF SMILJAN LIKA, AUSTRIA-HUNGARY, ASSIGNOR TO THE TESLAELECTRIC LIGHT AND MANUFACTURING COMPANY, OF RAHWAY, NEW JERSEY. COMMUTATO R F OR DYNAMO - ELECTRIC MACH NES. SFECIFICATION forming part of Letters Patent No. 334,823, dated January 26, 1886. Application filed May 6, 1885. To all athlon, it navy concern: Be it known that I, NIKOLA TESLA, of Smiljan Lika, border country of Austria-Hun gary, have invented an Improvement in Dy 5 namo-Electric Machines, of which the follow ing is a specification. My invention relates to the commutators on dynamo - electric machines, especially in machines of great electromotive force, adapted IO to arc lights; and it consists in a device by means of which the sparking on the commu tator is prevented It is known that in machines of great elec tromotive force-Such, for instance, as those I5 used for arc lights-whenever one commutator bar or plate comes out of contact with the col lecting-brush a Spark appears on the commu tator. This spark may be due to the break of the complete circuit, or of a shunt of low re 2O sistance formed by the brush between two or more commutator-bal’s. In the first case the Spark is more apparent, as there is at the mo ment when the circuit is broken a discharge of the magnets through the field-helices, pro 25 ducing a great spark or flash which causes an unsteady current, rapid wear of the commu tator bars and brushes, and waste of power. The sparking may be reduced by various de vices, such as providing a path for the car 3o rent at the moment when the commutator segment or bar leaves the brush, by short-cir cuiting the field-helices, by increasing the number of the commutator-bars, or by other similar means; but all these devices are ex 35 pensive or not fully available, and seldom at tain the object desired. My invention enables me to prevent the sparking in a simple manner. For this pur pose I employ with the commutator - bars 4o and intervening insulating material mica, as bestus paper or other insulating and pre?er ably incombustible material, which I arrange to bear on the surface of the commutator, near to and behind the brush. My invention will be easily understood by reference to the accompanying drawings. In the drawings, Figure 1 is a section of a commutator with an asbestus insulating de vice; and Fig. 2 is a similar view, represent 5o ing two plates of mica upon the back of the brush. In Fig. 1, C represents the commutator and 45 Serial No. 164,534. No model.) intervening insulating material; B B, the brushes. d d are sheets of asbestus paper or other suitable non-conducting material. ff 55 are springs, the pressure of which may be ad justed by means of the screws gg. In Fig. 2 a simple arrangement is shown with two plates of mica or other material. It will be seen that whenever one connnnutator segment passes out of contact with the brush the formation of the arc will be prevented by the intervening insulating material coming in contact with the insulating material on the brush. My invention may be carried out in many ways; and I do not limit myself to any particu lar device, as my invention consists, broadly, in providing a solid non-conducting body to bear upon the surface of the commutator, by the intervention of which body the sparking is partly or completely prevented. I prefer to use asbestus paper or cloth im pregnated with zinc-oxide, magnesia, zirconia, or other suitable material, as the paper and cloth are soft, and serve at the same time to wipe and polish the commutator; but mica, or any other suitable material may be employed, said material being an insulator or a bad con ductor of electricity. My invention may be applied to any elec tric apparatus in which sliding contacts are employed. I claim as my invention

1. The combination, with the commutator bars and intervening insulating material and brushes in a dynamo electric machine, of a solid insulator or bad conductor of electricity ar ranged to bear upon the surface of the com mutator adjacent to the end of the brush, for the purpose set forth.
2. In an electric apparatus in which sliding contacts with intervening insulating material are employed, the combination, with the con tact springs or brushes, of a solid insulator or bad conductor of electricity, as and for the purposes set forth. Signed by me this 2d day of May, A. D. 1SS5. 75 95 NIKOLA, TESLA. Witnesses: GEO. T. PINCKNEY, WILLIAM G. MOTT,