Theatre Catalog (1947-48)

projection and insuring a steady projection without undue strain on the film perforations. Edge guiding flanged rollers are mounted at the top of the film rails and are hardened and of adequate diameter to insure a solid film guide to the correct lateral position. Side sway is also held to less than 0.25 percent at a 100-foot projection distance. Projection Film Shoes Film is held securely to the film rails by means of film shoes (Figure 4) from a position well above the aperture to the intermittent sprocket. This is accomplished by three pressure shoes, the aperture film shoe being adjustable in pressure to allow compensation for various conditions of film and can be adjusted during projection. The intermittent sprocket pressure shoe holds the film on the intermittent sprocket and guarantees a four-tooth engagement with the sprocket at all times. Clearances between the individual shoes, as illustrated in (Figure 4) are of the order of 1/16 inch and this nearly 100 percent film contact with the rails guarantees freedom from film slap, thus aiding in the reduction of film jump or weave. Film Shoe Gate Assembly The assembly plate mounting all of the four tension shoes is removable by a single knurled thumb nut for cleaning purposes and is positioned by guide pins to insure correct replacement alignment in the operating condition. All springs used for the gate assembly are tested thoroughly as to tension. Power Drive All power is transmitted in the 12000 Series of projectors by means of silent chain drives, which drives accomplish a positive mechanical drive system additionally allowing rapid replacement of worn assemblies without the necessity of skilled mechanical craftsmanship. The chain-drive system, as such, has been field tested throughout a 15-year period and has certainly proven its dependability and long life in actual operation, over 10,000 projector mechanisms having been made with this drive system, to the users’ complete satisfaction. Power Source The main driving motor normally supplied is a % hp., split-phase, self-starting, single-phase induction motor, statically and dynamically balanced, and so adjusted as to starting characteristics that no undue strain is placed on the film or mechanism during acceleration to operating speed. It will function satisfactorily between voltage variations of 110 to 120 volts and at these variations operates with less than 0.5 percent variation in the mean speed of the film. Other special purpose motors are available for the operation of the projector in all field conditions from 25 cycles to 100 cycles. This line of a.c. motors is implemented by governor controlled types of universal characteristics which guarantee correct performance of the projector over wide voltage variations such as are encountered in poorly regulated power areas, both domestic and foreign. In all cases motors are adjusted as to acceleration characteris 1947-48 THEATRE CATALOG FIGRUE 2—The intermittent movement is of the 90-cegree Geneva cross type, the cam and star operating in an oil chamber. The entire movement is readily replaceable and is doweled to the framing mechanism so that proper timing may be maintained when removed for inspection, repair, or replacement. Lubrication of bearings is by oil canals ground on the shaft, oil-feeding from the reservoir. FIGURE 3—One hundred percent synchronous framing is accomplished in an ingenious manner, utilizing the chain drive feature so as to maintain perfect synchronization between the star and cam crossover and the shutter position. This is accomplished by rotation of the intermittent housing and sprocket around sprocket axis through sufficient angle to allow framing over two picture frames. 325