brushes may be employed as shown in Figs. 9 and 10. Instead of shunting the whole of the field helices a portion only of such helices may be shunted as shown in Fig. 8 and 10.
The arrangement shown in Fig. 10 is advantageous as it diminishes the sparking upon the commutator, the main circuit being closed through the auxiliary brushes at the moment of the break of the circuit at the main brushes.
The field helices may be wound in the same direction or a part may be wound in opposite directions.
The connection between the helices and the auxiliary brush or brushes may be made by a wire of small resistance, or a resistance may be interposed (R. Fig. 11) between the point x and the auxiliary brush or brushes to divide the sensitiveness when the brushes are adjusted.
I claim as my invention:—
1st. The combination with the commutator having two or more main brushes, and an auxiliary brush, of the field helices having their ends connected to the main brushes, and a branch or shunt connection from an intermediate point of the field helices to the auxiliary brush and means for varying the relative position upon the commutator of the respective brushes, substantially as set forth.
2nd. The combination with the commutator, and main brushes and one or more auxiliary brushes, of the field helices in the main circuits and one or more shunt connections
