Journal of the Society of Motion Picture Engineers (1930-1949)

Nov., 1936] NEW MOTION PICTURE APPARATUS 585 in and out of its proper focal plane. Constant speed of the scanning drum is maintained by means of the specially designed double flywheel of the kinetic scanner. One flywheel is integral with the scanning drum, which effectively prevents high-frequency oscillations of the film ; the other is free-floating, and is coupled to the first by means of a mechanical filter which effectively suppresses slow oscillations. The kinetic scanner is so stabilized that a sudden change in the film speed or a disturbance in the film loop, such as the passage of a film splice, has no appreciable effect upon its uniformity of rotation. During the acceleration period of the scanning drum the two flywheels are coupled together by means of a centrifugal clutch. As shown in Fig. 2, the film is threaded into the projector mechanism in the usual manner, up to the intermittent sprocket, from which it passes directly through a film chute into the sound reproducer. Here it is guided by a pivoted guide roller onto the scanning drum of the kinetic scanner, around which the film is wrapped. From this point it passes up to the lower feed sprocket in the projector mechanism and thence down to the lower film magazine. A clear path is presented for easily threading the film and for accessibility of the parts of the mechanism inside the sound reproducer. The extremely low friction of the kinetic scanner allows the film wrapped around the scanning drum to rotate the scanner without being subjected to appreciable tension. This results in the formation of an elastic film loop between the scanning drum and the feed sprocket, introducing a compliance between the feed sprocket and the scanning drum and preventing the sprocket tooth impulses from being transmitted to the scanning point. The film chute can be readily dismantled for cleaning. Film scratching and abuse are eliminated by the use of highly polished film guides. The pivoted guide roller is supported between bronze bearings lubricated through covered oil-cups, and provides an adjustable means for guiding the film edgewise around the scanning drum and retaining the sound-track of the film in its proper path with respect to the center of the lightbeam. The flanges that guide the film edgewise are chromium-plated to resist wear. The guide roller adjustment is accomplished by a slotted knob accessible through an opening in the closed door. No film sprocket or sprocket drive mechanisms are employed in the sound reproducer, thus resulting in a simple construction. The location of the lower film magazine is such that the usual projection angles are readily attained. The exciter lamp constituting the light-source is mounted in a separate holder external to the sound reproducer. To eliminate adjustments and to facilitate replacements in case of lamp failure, a new type of lamp provided with a prefocus skirt on its base is employed. The lens tube assembly is hermetically sealed and is exceptionally efficient in terms of light output. It images the incandescent filament of .the high-intensity exciter lamp as a concentrated line of light directly upon the sound-track of the film by means of cylindrical lenses without the use of a mechanical slit. It operates in an over-all distance of 75 millimeters between lamp filament and film plane. The lens tube assembly may be adjusted when the compartment door is closed by removing a latch plate, thus exposing an opening through which the focusing adjustment at the back of the lens tube may be made and a screw and lock-nut for adjusting the light-beam azimuth. A totally reflecting prism having