International projectionist (Jan-Dec 1946)

The New MOTIOGRAPH AA Projector THE housing of the AA projector is a one-piece casting enclosing all the working parts of the mechanism, including the twin-rotor, double rear shutter. The large cast door, hinged at the front, has double windows permitting the upper and lower film loops to be readily observed during operation. A tubular extension of the main frame casting supports the lens carriage with exceptional rigidity. The drive gear compartment on the drive side of the mechanism is equipped with a dustproof cast cover firmly held in place by Allen cap screws. This construction is made possible by the fact that little access to the drive side is required, and thus harmful dirt and grit are excluded. Most of the working parts are supported by the reinforced center frame, which is an integral part of the housing casting. It stiffens the housing and provides the rigid and stable supporting means for the film drive components and for the optical elements. The entire housing is quite large by former standards, being 15 inches high. 11 deep, and 18 long. The weight is not cumbersome, however, for all of the major castings are made of light but strong aluminum alloy. Housing corners are rounded and contours are smooth. The AA projector is of unit construction, with all major components easily removable for inspection, cleaning or FIGURE 1. Monograph AA projector mechanism and rod are By EMIL J. WIENKE Chief Design Engineer, Motiograph, Inc. The new Model AA 35-mm theatre projector is the eighth to be produced by Motiograph and comes, fittingly enough, on the golden anniversary of the founding of the company in 1896. To those who have already viewed demonstrations of the AA projector in various sections of the country the appended technical data will serve as reference material, while for those who have not yet seen this mechanism it will serve as a guide to a better understanding of the AA when finally viewed. servicing without the necessity for disassembling the machine. In the drive gearing, this has been accomplished by the virtual elimination of long shafts carrying numerous gears. Power is transmitted to the various film drive points by hardened steel gears meshing smoothly into laminated bakelite gears. The AA Gear Train The gears run on grease-packed, doublerow ball bearings which are rigidly supported by studs locked into the mechanism center frame. The gear meshes require no lubrication other than an original film of lubricant as long as they are kept clean, for experience indicates that gear wear results primarily from the lapping action caused by dirt and grit brought in by frequent hand oiling or by poorly-filtered lubrication systems. Figure 1 shows the simple and rugged gear train of the AA projector. Power , drive side, cover removed. Shutter setting knob clearly shown. from the drive shaft at the bottom of the mechanism is transmitted by gear combinations to the ball-bearing-supported vertical shaft just back of the intermittent movement flywheel. This shaft passes through and is keyed to a wide, movable pinion which meshes with the drive pinion on the intermittent movement cam shaft, thus permitting the movement to be shifted vertically for picture framing. Furthermore, the position of the wide pinion with respect to its mating pinion on the movement is adjustable to provide a continuously variable shutter timing control which may be operated with the projector running. Since this control moves with the intermittent carriage, it is extended to the front of the mechanism housing by means of a flexible shaft. Both the upper and lower feed sprockets of the projector are driven by stub shafts carrying on their drive ends suitable gears to mesh into the main gear train at the required points. The lower such shaft is just above the main drive shaft, and it also carries the drive gear for the vertical shaft. The gear on the upper is above the upper large bakelite idler gear. This idler and those to the right of it transmit power to the shafts carrying the shutter rotors and to the shaft of the blower and fire-shutter actuator. The main drive of the AA projector is made in the form of a socket shaft into which the soundhead drive unit may be clamped in order to eliminate the need for oiling of the sound reproducer's projector drive assembly, and to provide a more rugged construction at this critical point. Referring to Fig. 2. the tubular shaft and socket unit [item 1] runs in the sealed ball bearing [item 3] and in a similar bearing set into the center frame of the mechanism. The item 3 bearing is seated in an auxiliary rib of the main housing by easily operated clamps, so that the entire drive unit may be quickly 12 INTERNATIONAL PROJECTIONIST December 1946