Exhibitors Herald and Moving Picture World (Oct-Dec 1928)

October 27, 1928 EXHIBITORS HERALD and MOVING PICTURE WORLD 121 Close-up of cone, shutter and mechanism. A close-up rear view of the nezv shutter Above are sectional views of the nev: Motiograph Less Heat on Film, Claimed for Improved Projector Heat on film reduced 6^/2 Per cent, declares Enterprise ADDITIONAL heat impressed upon the k film with the advent of the high intensity lamp, the reflecting arc lamps and more recently the high intensity reflecting arc lamp brought about the development of the Model "H" Motiograph DeLuxe Projector and the new type shutter, reducing by 6'/> per cent the heat on the film, says the Enterprise Optical Manufacturing Company. "The necessity for some form of practical solution became evident through the complaints of projectionists to the effect that these forms of illuminants caused a buckling or warping of the film which seriously interfered with their efforts to project a picture in true sharp focus," says the statement. "It became more evident when film distributing companies reported that in many cases film had been returned to them from theatres using these high powered illuminants in a condition not suitable for rcshowing and in some cases actually ruined. "In view of these circumstances, which most of us are familiar with, our company began about two years ago to seek some practical solution of the problem, the result of which was the announcement to the trade some few months ago of the new Model 'H' Motiograph DeLuxe Projector, in which is incorporated what has been later proven a practical solution of the problem of eliminating the heat from the film. "Our engineers in seeking a solution for this problem, considered all of the known methods of heat dissipation, including cooling cells, heat absorbing filters, forced air and other devices, all of which offered no practical or satisfactory solution. The transposition of the ordinary disc type of revolving shutter positioned between the lens and the screen to a position between the film and light source was also considered and discarded. While it was found that this would have the effect of eliminating the heat from the film, there was a tendency to increased flicker, which was objectionable due to positioning the shutter near the focal plane. "Horizontal, cylindrical type of shutter rotating on a horizontal axis and positioned between the film and light source was finally found to be the correct type and one that while affording the all important function of eliminating the heat from the film, would as well not only permit the maintenance of the present standard of projection but improve projection. The axis of the shutter is positioned four and onequarter inches from the film and the diameter is three and one-quarter inches. The cutting blades of the shutter, of which there are two, are positioned around the circumference of the cylindrical casting forming the shutter and are equally spaced, the shutter having the appearance of a hollow cylinder with sections cut out, and these cut out sections affording the passage of the light through the system. "By designing the shutter in cylindrical formation, we are able to secure two distinct advantages for better projection. The position of the two blades being such that during the cut-off action the edge of the shutter blade nearest the film intercepts the light beginning at the bottom of the light beam and cutting off toward the center of the beam and near the focal plane. Simultaneously the other blade intercepts the light beginning at the top of the beam and also cutting off toward the center of the beam. The blades being an integral part of the shutter casting, it will be readily seen that first blade cutting off from the bottom of the beam and toward the center would take an upward course during the rotation of the shutter and its cutting off action would occur near the focal plane while the opposite blade would take* a downward course and its cutting off action would be further away from the focal plane. * * * "In the action of these two shutter blades, one cutting off near the focal plane and the other cutting off at a point further away, we obtain the first advantage in that with the edges of the cutting off blades functioning at different points in relation to the focal plane, we secure what might be termed a blending of the cut-off which tends to eliminate the objectionable flicker. "The second advantage is also a result of this cylindrical design of the shutter in that with the action of the two cut-off blades operating to intercept the light beam horizontally from the top and bottom simultaneously and across the narrow dimension of the aperture, a gain in efficiency is secured. This results in an increase in illumination of the projected image of about 15 per cent. "We are able to proportion the blades of the new type shutter so that we have a period of darkness representing that time during which no light reaches the screen of only 45 per cent with the new shutter and a period of light of 55 per cent in contrast with the old type of disc shutter, in which we have a period of darkness of 60 per cent and a period of light of 40 per cent. * * * "The action of the new shutter in eliminating the heat from the film is due naturally to the interception of the light beam and incidentally the heat between the light source and the film. As the shutter makes one complete revolution during the cut-off action and another complete revolution during what might be termed the flicker interception, the entire action of the light beam and its incident heat is prevented from acting on the film while the film is in motion before the aperture and once while the film is at rest before the aperture, the heat of the light beam being allowed to reach the film only at two short intervals, once when the film comes to a stop before the aperture and again after the flicker interception and until the film starts in motion again. "Some interesting data were secured as a result of tests conducted in our factory in which a regular Model 'H' Motiograph DeLuxe Projector equipped with a Motiograph Reflecting Arc Lamp as an illuminant was used, operated at 25 amperes. Temperatures were recorded with a pyrometer, the thermo-couple being positioned at the aperture center or film position. Tests were conducted in each case over a period of thirty minutes operation, the Model 'H' projector being operated at different speeds