Page:Popular Science Monthly Volume 92.djvu/290

 Drawing Twenty Shades at Once

The stereopticon operator pushes a button and presto! the shades are raised or lowered

���A simple push of a button by the stereopticon operator and all the shades in the auditorium are lowered simultaneously. Another push and they are raised

��THE inconvenience of having to draw each window shade separately in an assembly room when motion pic- tures or stereopticon views are to be shown, has been overcome by an electrical de- vice, which makes it possible to draw all the shades simultaneously by simply pushing a button. This new device is installed in the auditorium of the Bureau of Standards building, Washington, D. C, and is manipulated by the motion picture or stereopticon operator.

Two horizontal shafts extend on each side the full length of the room within the wall, directly over the window frames. Each shaft is revolved by means of a small electric motor, placed in a pocket in the wall just outside of the auditorium, as shown in the accompanying il- lustration. A special

��Motor outside of room

, 'Limit 5witch

���Wires in conduits to limit -switches

Details of the limit switch which opens and closes the circuits

��switch is installed near the motion-picture projector, by means of which the operator can easily turn the shaft in either direction, so as to raise or lower the shades. Power is transferred from the motor shafts to the shades by means of gears on the shafts, which mesh with smaller gears mounted on one end of each roller. A limit switch controlled by the operator's main switch, breaks the cir- cuit when the curtain has been pushed down to its lowest or up to its topmost position. The direction of revolution of the motor shaft is con- trolled by the operator's switch, and the gear on the motor shaft drives that on the end of the roller, as shown. The revolution of the motor shaft causes the threaded nut around the motor

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