Motography (Apr-Dec 1911)

October, 1911. MOTOGRAPHY 167 Problems of the Operating Room By William T. Braun FUNCTIONS OF MACHINE PARTS. THERE are about a dozen different makes of projecting machines in use in this country at the present time. Each one has one or more special features, but the working mechanism of all of them is very similar ; that is, they all have certain parts in common which may be somewhat different in design and construction, yet serve the same purpose. If every operator understood the functions or duties of each part of the machine he was operating, he could handle his machine much more intelligently and adjust it when out of order. He could anticipate every breakdown in advance, thus saving much trouble and annoyance. Commencing at the top of the machine head we have the upper film magazine. This box is made without the use of solder so that in case of fire it will not open up and expose the contents to the flames. It is equipped with two sets of fire rollers and a trap connecting them. If the film should catch afire, it would be smothered before getting inside the magazine. In threading the Motiograph the film can be slipped through the side of the magazine between the rollers. On the Powers one of the lower rollers slides loose in a groove so that it may be pushed back when threading. Be sure to keep the fire rollers clean, scraping off the dry emulsion, because in case of fire this would help things along. A few machines are made with a rewind attachment connected to the upper reel hanger so that the rewinding may be done on the machine. This is not always satisfactory, as it generally must be done while projecting slides and the rewinding shakes the machine causing the slides to jiggle. Generally another reel must be threaded up immediately, not giving time to rewind on the machine. Therefore, the separate rewind is perfectly satisfactory. The upper feed sprocket which is geared to the rest of the mechanism pulls the film from the upper reel and feeds it into the machine. On some machines the sprocket is a solid drum, but lately the sprockets are made with a hollow center — that is, with the teeth on bosses. This makes the sprocket lighter in weight. In the drum type any dirt or dry emulsion on the drum will scratch the surface of the film. Each sprocket is equipped with one or more rollers for keeping the film engaged on the teeth. When only one roller is used it is mounted on a spring bracket so that it can be lowered out of the way when threading up. Each roller has a set screw with a locknut on it. This screw rests against the hub of the sprocket keeping the roller at the desired distance from the sprocket. The roller should be about two thicknesses of film away from the sprocket. If it rests directly on the sprocket the film will have a tendency to climb or jump the teeth, especially when a patch .^oes over it. The Powers No. 6 has two rollers on the upper sprocket, one on each side, keeping the film in close engagement with about half the teeth of the sprocket. In this way riding of the film is prevented. On several machines the sprockets have flanges on the sides. With the use of the flanges and rollers film jumping is almost eliminated. The film next travels through the gate. The machine gate serves as a covering for the film, protecting it from the heat of the light, and also as a carrier for the tension spring, cooling plate, automatic fire shutter, and film guards. At the top of the gate is a guide roller for feeding the film as it comes from the upper loop so that it does not slip to one side of the springs in passing through the gate. The roller is generally held in position on the spindle with a light coil spring allowing a very small sidewise movement of the film. On some machines this roller is made in two parts. The film now passes between the tension spring of the gate and the aperture plate. The tension springs are one of the most important parts of the machine. Their duties are two in number; to flatten the film against the aperture-plate, and to keep the film stationary while being projected. To secure an absolutely sharp picture all over the entire screen the film must be absolutely in one plane, or in other words flat against the plate. Film always has a tendency to curl up and the springs must exert enough pressure on the film to overcome this. The film when being pulled down by the intermittent sprocket always has a tendency to keep moving after the intermitten movement has come to rest. The pressure of the springs overcomes this motion, keeping the film still while being projected, thus insuring a steadier picture on the screen. These springs usually consist of thin strips of hardened steel just a trifle longer than the aperture. Several manufacturers are beginning to realize that an even tension throughout the entire length of the plate will flatten the film before it gets to the aperture and secure better results. Therefore they are making the springs, or shoes as they are sometimes called, the entire length of the plate. Also the wear on them will not be as great. The springs can be made to bear more tightly against the film by driving the screw on which the gate latch is fastened further in. This in reality brings the whole gate closer to the plate when the gate is closed. This adjustment is not as even as it might be, as the' hinged side remains stationary. The spring must be watched for wear, as the film wears long grooves in them, and they should be renewed when in this condition, or the film will not be in one plane as before mentioned. Do not tighten the springs so hard that the machine runs hard, as this will only cause undue wear on them. If the intermittent movement is in correct adjustment the springs will not have to be too tight to obtain a steady picture. Tension springs should be kept clean from any gelatine which may come from the film. This is especially true of new film. Wipe the springs off with a rag that has been dampened in oil. The cooling plate on the front of the gate absorbs all of the heat from the light which does not go through the aperture. This plate being about .^2 of an inch from the gate shields it from the heat, thereby reducing danger from fire. On nickel-finished machines