International projectionist (Jan-Dec 1946)

speaker case is equipped with removable front and back covers, both of which are removed for operation, at which time the speakei is protected by a separate grill. The motor is a universal, series type, with automatic speed control for either silent (1.000 rpm) or sound speed (1,440 rpm). The ventilating system includes not only a blower which is effective in either direction but also an automatic deflector, operated by the air stream, which assumes different positions according to the direction of rotation of the blower and thus deflects the air stream into the identical path regardless of whether the motor is being operated in reverse or not. The general path of the air is: intake past amplifier and motor; exhaust past projection lamp. Projection lenses are readily interchangeable: an /. 6, 2-inch focal length compound lens is normal equipment. The sound drum is stabilized by means of a flywheel. Exciter lamp current is a. c. above audible frequency. The threestage amplifier is transformer-coupled to the push-pull output stage, and includes a tone-control-inverse-feedback circuit. The speaker is a 12-inch permanent magnet cone with a rated frequency response of 100-5,000 cps. Shuttle and Claw The intermittent shuttle-and-claw provisions are unusual. Two vertical cams are used, although only one actuates the shuttle. The purpose of this arrangement is to assure dynamic balance in the shuttle action. The external surfaces of the shuttle, which might otherwise wear grooves in interacting parts, are turned over to produce wide, flat bearing surfaces that cannot groove anything. Eight holes, which have nothing to do with operation, have been drilled through the shuttle for the sole purpose of removing excess weight of material. Two other features are the use of three instead of two claw teeth and a very faint trace of rotary motion on the part of the claw. The teeth, of course, move forward to engage the sprocket holes, move downward to pull the film down, retract, and then come up again, eventually to repeat the process. But there is an extremely slight rocking component in their downward motion, and the top tooth is slightly shorter than the other two. By reason of this shortness of the top tooth, combined with the slightly circular motion incorporated in the downward action, only the two lower teeth engage the film at first; but near the end of the pull-down the faintly circular motion causes the top tooth to engage also. This top claw-tooth serves as a hold-back to check the momentum of the film. Because of this hold-back feature, gate tension can be adjusted more loosely than would otherwise be practicable, and the screen image still remains steady. This light tension at the gate is responsible for the fact, mentioned previously, that the loop can be lost without tearing the film. If it should be lost, the pressure roller, seen directly under the thumb in Fig. 2. can be moved to rear position and then brought back, thus restoring the lower loop. Normal operation and sound synch, are thus restored while the picture is running. Additionally, this loose tension assures that the claw teeth cannot scratch the film even when a misplaced patch or other difficulty allows them to strike the film instead of engaging the sprocket holes. The upper and lower sprockets are of polished stainless steel, as are the gate and gate shoes. Sprocket idler tension is loose, thus the film will not be marred even should it ever ride up. If this should happen, the design of the sprocket which (as can be seen in Fig. 2) has a railway type flange outside the teeth, will ease the film back into position, and the light idler tension will enable the sprocket holes to re-engage. None of these provisions compromises in the slightest degree the quality of the screen image, which is entirely steady. The manufacturers attribute this to the steadying action of the top, or hold-back tooth of the three-tooth claw. Utmost Illumination Attained The claw teeth do not engage the film every time they move down but only at each second downward motion. This double-cycle action permits faster shutter operation and the use of narrower shutter blades, with a consequent increase in screen illumination. The projection shutter is of the rotary cylinder type which produces the dissolving effect of a double shutter, although consisting of only a single unit. This type of shutter is by no means uncommon, being well-known to many professional projectionists, but its application to the 16 mm. field is not without significance. This is usually referred to as a "barrel-type" shutter and is positioned horizontally between the lamp and the aperture. There is also a safety shutter (concentrically mounted with the projection shutter), which drops automatically if the motor runs too slowly because of low line voltage or when the film is stopped by means of the clutch in order to show single stills. Stills are projected through an aperture in the safety shutter. The motor is connected to the projector through a fabric belt, and spring belts drive the reels during projection and rewind; but the mechanism itself is completely gear-driven, both fibre and metal gears being employed in the unit. The amplifier is mounted under the casing, behind the mechanism, with the tubes lined up along the driving side. They are protected by a tube guard grill. The bottom of the mechanism and casing are fully enclosed by a metal housing or plate which is held in position by six screws. Maintenance Requirements The Ampro Premier 10 has a single oil cup, located at the top left of the casing, through which the entire mechanism receives routine lubrication. When the projector is in constant use, three to five drops of oil should be added at this point every day. The same point should be lubricated once every thirty days when the projector is not in useAdditionally, the spindle assemblies at the ends of the upper and lower reel arms should be lubricated with one or two drops of oil every three days; and the clutches at the ends of the reel arms with two drops of oil every week,, as long as the mechanism is used steadily. No other lubrication is ever needed except at times of general overhauling. The film path and projection lens should of course be cleaned daily or whenever the projector is returned to use. Reel belt tension also should be checked daily. The projection lamp should be checked weekly for darkening or sagging of the filament. Two thumbscrews are removed, after which the top of the housing comes off and the lamp is lifted out with the help of the lamp glove, which is normally carried in the upper part of the projector carrying case. Removing three cover screws gives access to the reflector-and-condenser assembly. This can be cleaned in place, or it can be taken out of the mechanism by removing two additional screws, after which the entire assembly comes apart and goes back together without any use of tools. The exciter lamp cover comes off by removing two thumb screws. THREE NEW MEXICAN THEATRES TO HAVE RCA EQUIPMENT Lorenzo Cue, Rene Becena and Manuel Espinoza, all of Mexico City, recently completed plans in New York for the building and equipping of three new de luxe motion picture theatres in Mexico City. Following conversations with the visitors while in New York, Karl Streuber, manager of the theatre and sound equipment department of the RCA International Division, stated that all three theatres will be furnished with RCA projection and sound equipment. Sites for the three theatres, all first run houses to seat four to five thousand patrons each, already have been selected. Mr. Espinoza is managing director of the Operadora de Cines and owner of a large circuit of theatres in Mexico. Messrs. Cue and Becena are associated with him financially in the new project. 10 INTERNATIONAL PROJECTIONIST