Figure 2621, 2622, 2623 -- Interior of cinematograph camera as used on Duddell moving coil oscillograph for obtaining long records. The loose ends of the case are shown removed and one of the reels which carry the film lying in front.

The spool of film is placed on the loose reel A, passes over the guide pulley B, then vertically downward between the brass plate C.

The exposure aperture is in the plate C, and the springs which press the plate D flat on the plate C, prevent the film from having any but a vertical motion as it passes the exposure slit. E is the sprocket driving pulley which engages with the perforations on the film and unwinds it from reel A to reel H.

Outside the case on the far side of it is secured to the axle G a three-speed cone pulley. This is driven by a motor of about 1/7 horsepower, which also drives, the the gears shown, the sprocket pulley E. Close to the grooved cone pulley is a lever which is attached to the falling plate camera case, the brake can be suddenly released and at the same time the jockey pulley caused to tighten the belt onto the grooved cone pulley, so that the starting and stopping of the film is controlled independently of the driving motor, and being quickly accomplished avoids waste of film.

Both reels are alike and each is made in two pieces. The upper reel is loose on its axle and its motion is retarded slightly by a friction brake. The lower reel is also loose on its axle, but it is driven by means of a friction clutch, the clutch always rotating faster than the reel so that the used film delivered by the sprocket pulley E is wound up as fast as delivered.

K is the front face of one reel, the boss on it pushes into the tube on the other half H, which serves not only to unite the two halves, but also to secure the end of the film which is doubled through J.

• Hawkins Electrical Guide, Volume 6
• Chapter 63: Wave Form Measurement
• Page 1866, Figures 2621, 2622, 2623
• Copyright 1917 by Theo. Audel & Co.
• Printed in the United States

• Scanned by User:DMahalko, Dale Mahalko, Gilman, WI, USA -- Email: dmahalko@gmail.com
• Scanned at 600dpi, 8-bit grayscale
• Level-adjusted and touched up to remove dust and smudging from the printing process

For a list of all these illustrations used in Wikipedia please see the article Hawkins Electric Guide on the English Wikipedia.

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