Richardson's handbook of projection (1927)

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MANAGERS AND PROJECTIONISTS 614 worm gear attached to the shaft connecting the controllei to the motor; in other words, to the main driving shaft. This worm drives worm gear 18, which is mounted upon, but is not attached to shaft 19; in other words, shaft 19 merely serves as a spindle upon which gear 18 revolves. When the motor is running, but with insufficient speed to cause the governor to operate, or in other words when the motor is running and the arc not being fed, gear 18 and wheel 16 are driven continuously. Wheel 16, which is also loose on shaft 19, being free to turn, gear 29 simply runs around on gear 14, but without revolving gear 14 which is pinned to shaft 19, as is also gear 10 which operates gear 44, the latter in the right-hand illustration. When the governor operates, however, it forces out tooth 31, which engages with one of the teeth on wheel 16, thus preventing the wheel from revolving, whereupon, (remember that gear 18 and wheel 16 are loose on shaft 19) since gears 18 and 17 revolve continuously, and since gear 29 locks gears 14 and 17 together when wheel 16 is not revolving, shaft 19 is rotated, together with gear 10 and gears 44 and 50, and thus the carbon feeding mechanism is operated, and the carbons fed together until the arc voltage is sufficiently reduced to slow the motor down until spring 41 pulls governor weights back again, thus releasing wheel 16 and unlocking the differential, whereupon the carbon feeding mechanism stops. All that sounds very complicated, but it really is not. On the contrary it is very simple once you get the idea of the action of the differential. All gearing is fully inclosed, therefore protected from the grinding action of dust mixed with lubricant. ADJUSTMENT.— The longer the arc the higher its voltage, therefore the faster will the motor of the controller run, and the speed necessary to cause tooth 31, Plate III, to engage with the teeth on wheel 16, Plate I, will depend upon the tension given spring 41, Plate I, by adjusting dial on wheel 20, Plate I, to maintain any desired arc length. Plate IV, Figure 214.