The motion picture projectionist (Oct 1927-Sept 1928)

July, 1928 The Motion Picture Projectionist 13 The New Model 1002 Motiograph By O. F. SPAHR Enterprise Optical Manufacturing Company H THE new Model H Motiograph DeLuxe projector is radically different in principles involved and construction than the present types of projectors employing the outside rotating disc-type of shutter. It depends upon a new type of shutter of peculiar design for its important function of eliminating the heat from the film. The new shutter is of a horizontal or cylindrical type. It is mounted on the film gate of the mechanism and operates between the film and the light source. It differs in construction from the rotating disc-type of shutter in that it has two circular vanes and is rotated on a horizontal axis. By these two vanes the light beam is cut off in a horizontal plane from top and bottom simultaneously. This being across the narrow dimension of the aperture, results in what may be termed a "quick cut-off." Thus, a gain in illumination over the old type front shutter is accomplished. The action of the two vanes cutting the light beam simultaneously also is an advantage in that a cleaner cut-off is obtained, a more uniform distribution of the intervals of light and darkness, and a smoother shutter action with entire absence of back-lash travel ghost is the result. Radical Heat Reduction In the second purpose, the vanes of the shutter cutting off the light, and incidentally the heat, between the film and the light source, it is easy to reason that since the light is cut off during the whole interval of film motion before the aperture, there can be no heating, or rather pre-heating, of the film before it comes to a stop before the aperture, as is the case in the old type front shutter where the full action of the light beam is operating to heat the film both during the full film movement as well as during the whole time the film is at rest before the aperture. A further cutting of the light beam during that portion of time when the film is stationary before the aperture is accomplished at that period known as the flicker interception. Thus, it will be seen with this new shutter that the entire action of the light beam and its incident heat is cut off from reaching the film while the film is in travel before the aperture, and once while it is stationary before the aperture. The heat of the light beam is only allowed to reach the film at two short intervals : once when the film comes to a stop before the aperture and again after the flicker Spahr interception has passed and until the film starts in motion again. An idea of the construction of the new type shutter may be gained from the close up view in Fig. 1, in which the shutter vanes and construction is clearly indicatedComparative Tests So efficiently has this worked out to reduce the heat at the film that actual tests conducted in the Motiograph laboratory show a reduction in temperature of the film heat at the aperture. (See table). Thus, in the Model H the temperature at the aperture is 922° less than the old type projector, or 62j4%. Tests were taken in each case over a period of 30 minutes or more of operation of each projector with a reflecting arc type of lamp as illuminant operated at 25 amperes. The heat at the point just between the cooling plate and gate door taken after 30 minutes operation to determine the comparative heating of the metal surroundings the aperture opening in gate door showed that with the Model H the temperature at this point remained constant at 100° as against a temperature of 270° on the old type projector — all temperature readings in degrees Fahrenheit. This actual comparison of heat of film temperatures at the aperture is really astonishing, and film runs cooler in the Model H even when the new high-powered Comparative Temperature Tests on Model H Motiograph De Luxe Projector — in Comparison with Regular Projector with Old Type Outside Revolving Disc Shutter: Heat at Aperture .,Jodel H Old Type Film Speed— 80 ft. per min 565° 1486° Film Speed — 90 ft. per min 570° Temperature Film Speed — 100 ft. per min 564° the same at Film Speed — 110 ft. per min 555° all speeds. Average Temperature 564° Fig. 1 — A close-up rear view of the new shutter illuminants are used than it did in the old projectors when the regular arc lamp and only 35-40 amperes at the arc was employed. Raises Projection Standards So evident is the result that it is not necessary to have the testing engineer's report of aperture temperatures to prove it. In the old type front shutter projector the film will feel decidedly hot and it will be extremely uncomfortable to leave the fingers on the film for any length of time. In the Model H the film will leave the lower feed sprocket practically as cool as when it