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The Optical Magic Lantern Journal and Photographic Enlarger.
185
How Cinematographic Machines Work.
By MAGNET.
R. R. W. PAUL’S improvements in apparatus for projecting kinetoscope pictures, which form the subject matter of his patent No. 4686 of 1896, may interest the readers of this journal, as it contains many instruc
tive points. In some of the forms of
apparatus, as film is intermittently fed
over rollers through the optical system of a
projecting lantern, the light being cut off by an
intermittently moving shutter whilst the film is in motion, Mr. Paul considers that they are imperfect in the following way, viz., they have not held the film perfectly flat and taut in advance of and in rear of the opening through which the light shines to project the picture; consequently the pictures successively projected do not accurately register with one another, and they do not lie exactly in the same plane while being projected, and further, the film is liable to curl, with the result that the effect obtained on the screen is blurred and unsteady. |.-The film c is provided with perforations along its edges as at , and before use is preferably
Fig. I.
in the perforation b of the film.in front of the opening a the film is conducted
over a second sprocket-wheel:F, the pins ¢ of which engage in like manner with the film. The wheels © F are mounted on arbors E! F!, which turn in bearings in the frame B, and which are provided at their outer ends with specially formed gear wheels d e; the ’ teeth of these wheels d are curved at the ends f/f to correspond with the curvature of a disc G mounted on the main driving shaft 4, continuous rotatory motion being given by a pulleys’. The disc G is provided with teeth g, which are adapted to simultaneously engage in notches f/! in the gear wheels d and e respectively, as in Fig. II., and this turns the wheels © F through an angle corresponding to the pitch of the consecutive pictures on the film c. When the motion is completed the wheels E F are immediately locked in position by the engagement of the periphery of the disc G with the curved surfaces f at the ends of the teeth of the gear wheels g and e.
In order to ensure sufficient contact of the film with the wheel £ and Ff, guide rollers h z are provided. The speed of the spool pD is controlled by a brake-pad mounted on a spring. By this means the tension of the film is regulated and over-running of the spool prevented. Other pads press against either side of the picture arranged round the window a, and hold it in a constant position relative to the optical system of the lantern. The continuously rotating shutter Pp consists of two segments of a cylinder P' (No. 4686 of 1896).
Mr. H. W. Short obtains an intermittent motion of the film by means of a helix so
Fig. II.
Fig. III.
arranged upon a spindle that there is an interval
| between the time of contact of the two ends of ; the helix with the teeth upon a toothed wheel.
wound on a spool p supported in the frame B. | From the spool 11. the film passes over a | sprocket-wheel , the teeth c of which engage | After passing |
In Fig. IIL, d is the helix, e the toothed wheel which lies underneath the helix shaft and is almost hidden, a the rotary disc,z the strip of film, j a shutter spool controlled by a brake / (No. 3777 of 1896).