International projectionist (Jan-Dec 1946)

are instantly released l>y pulling out a small plunger near the top of the gate body. The shoe unit is therefore removable for routine cleaning almost as easily as the film itself, and there is no chance for disturbance of either the alignment or the tension adjustment. Operation of the film gate is by a rackand-pinion type control device just below the lens barrel. A quarter turn of its large control knob opens the gate, and another version of the gunlock mechanism within the control shaft automatically locks the gate open as the knob is releast a. ii.c gaie closes and locks closed by simply pressing inward on this same knob to release the first locking device. The gate assembly base casting has an extension at the left to support the track and aperture unit, while the gate body moves in long V-rails on steel balls. These same V-rails also support and guide the lens carriage. Obviously, all components concerned in the relationship between the film plane and the lens optical axis are part of a single major assembly which may be aligned with precision. The degree of tension is determined by a cam-type tension control. The pressure applied to the shoe unit in the "standard" position of this control is approximately 350 grams, this value being satisfactory for films in average condition. The "low" position of the control reduces the pressure to about 225 grams to accommodate new, green film, and the "high" position increases the tension to around 675 grams to aid in flattening badly buckled older films. The control setting may be changed with the projector in operation. The tracks and aperture of the AA are combined into one sturdily constructed unit of hardened and ground steel. This unit is drawn securely against the support casting, the engagement being between an anchoring stud on its rear surface and a long cone-point, socket-head set screw. The unit is thus very easily Projectionist was 'Mr. Big' in Motiograph AA Design NO news to I.P. but serving admirably to refute those who constantly seek to minimize the importance of projectionists in purchases <>f theatre equipment is the statement of Motiograph that the projectionist v»a* reallj MR. BIG in the overall design of the new AA projector, lir-i consideration in all elements of design of this new mechanism was aceorded projectionists' preferences in a nation-wide pre-design survey. Virtual unanimity among projectionists was found for the following features: a one-piece housing with a reinforced center frame to prevent vibration and resulting picture unsteadiness; a film gate that would eliminate picture jump and side sway; double shutters and a perfect optical alignment through the projector; rust-proofing and hardening of all steel gears., shafts, studs, shoes, sprockets, guide rollers and intermittent parts, and silent running. Also, a roomy white interior, illuminated threading and picture apertures, an easily-operated and wide-opening gate, self-adjusting guide rollers, elimination of manual lubrication, framing and focusing from either side, and the easy removability and replacement of tracks, shoes, apertures, lenses, sprockets, idler rollers gears and, of course, the intermittent. A prime favorite was for a massive lens barrel to accommodate any size lens of any make or model. removable for inspection and cleaning without disturbing other components. The lateral guiding of the film over the tracks is accomplished by the two guide roller assemblies. Each has a fixed flange, or roller half, for the sound track side of the film, and a movable flange under small spring tension for the opposite side, to accommodate films having various degrees of shrinkage without producing film buckling or failure of the guiding action. The roller assemblies are relatively close to the aperture opening and constitute the most efficient means for eliminating film sidesway. The rollers are large in diameter so as to derive sufficient turning torque from the moving film, and are fabricated from very tough and thoroughly hardened steel alloy to resist wear. They turn freely on hardened pivot-type bearings lubricated internally through small openings in the tips from grease reservoirs within the bodies of the bearings. EXHAUSTIVE tests were made with many different types of intermittent movements, including some which were FIGURE 4. Motiograph AA intermittent movement. provided with complex gearing and auxiliary cams to decrease the pull-down time. While it was finally determined that the movement of the AA should be basically of the conventional 90-degree Geneva type, it nevertheless incorporates numerous original design features. The tension shoe assembly for holding the film in place on the sprocket is mounted directly on the movement case. Outboard ball bearings for both the sprocket, or star shaft, and for the cam shaft are provided. The movement case design and the mounting arrangements in the projector are such as to permit the entire movement to be quickly and easily removed from the operating side of the machine without disturbing any other components except the movement balance wheel. The cam shaft is directly driven from the main projector gear train, and carries on its outboard end a balance wheel of sufficient diameter and weight to have adequate inertia to effectively equalize the pulsating torque requirements of the intermittent action. The star shaft bearing and grease seal construction is similar to that of the cam shaft, with a threaded, locking collar to take up end and radial play in the bearings. A movable indicator cap is provided with engraved lines spaced 90 degrees. In conjunction with a single line on the locking collar, it may be set to provide a ready indication of the points where the cam drive pin just starts to engage a star slot, thus facilitating shutter timing. A unique method is used for anchoring the sprocket to the star shaft. The shaft is hollow as far back as the sprocket, and is provided with a threaded, tapered screw engaging two steel balls which it pushes outward through hole? in the shaft wall to lock into matching. (Continued on page 33) INTERNATIONAL PROJECTIONIST December 1946 15