Abstract
A DESCRIPTION is given in the Electrical Review of July 11 of a method of almost completely blacking–out in a few seconds a factory by simply pressing a button. A camouflage installation recently completed at a large factory provides for blacking out 550,000 sq. ft. of roof lights in 15 sec. Originally hard wall–boards were fitted to the outside of all thenorth lights and other windows. Alternate panels have been removed from the north light windows and fixed into a frame in their respective positions over the windows, the frame being made to move laterally across thewhole span of lights through grooves cut in the sections fixed to the glazing bars. Steel cables were fixed to each end of the frame, passed over spring–tensioned pulleys and secured to a winch mounted on the wall inside the factory. The winch is operated by a ¼ h.p. D.C. compound–wound G.E.C. Witton motor. The forward and reverse movements of the shutters are obtained by reversing the direction of the motor, which is controlledby forward and reverse contactors operated by two limit switches. The latter are tripped by ‘fingers’ mounted on steel rods secured by the cables, which travel up and down through a distance equivalent to the movement of the steel frame. Each span of lights of approximately 1,000 sq. ft.is operated by one ¼ h.p. motor, and more than 500 motors have been installed. In the event of damage to the electrical equipment, the motors can be disconnected and the winches operated by hand in each individual bay.
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Rapid Black–out of a Factory. Nature 148, 193 (1941). https://doi.org/10.1038/148193a0
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DOI: https://doi.org/10.1038/148193a0