Journal of the Society of Motion Picture Engineers (1930-1949)

206 NEW MOTION PICTURE APPARATUS [J. S. M. P. E. roller of this series nearest the sound sprocket is equipped with spring-retained flanges to guide the film past the recording light-beam so that the sound-track is located within 0.001 inch of its correct position upon the film. After leaving the sound sprocket, the film passes as a loose loop over guide rollers and through a punch (to be described later), and thence over a guide roller to the pull-down sprocket, which maintains the loop against the pull of the film take-up mechanism. In going from this sprocket into the magazine, the film passes a switch mechanism which is tripped when a loop forms in this section due to any failure of the film to take up in the magazine. The tripping of this switch, due to the piling up of film, closes a contact that lights a signal lamp on the instrument panel and also operates a relay to stop the motor. By this means the is film is stopped before it can pile up in the machine and cause damage. All film-guiding and controlling rollers are ruggedly mounted and rotate on precision ball bearings having exceptionally low and uniform friction. They are lubricated for ordinary life and sealed against leakage of lubricant and entrance of dirt. The worm-gear and sprocket shafts of the film-driving mechanism are also mounted upon the same type of ball bearings. A brake is provided which may be operated from a lever on the instrument panel to stop the recorder quickly after current to the motor has been cut off, and thereby reduce film wastage. The brake may also be arranged to be operated by an electromagnet for remote control. The film take-up mechanism contained in the housing on top of the machine in back of the magazine consists of a frictional slip clutch driven by a silent chain and sprocket gearing from the main drive gears, and is arranged to be coupled to the spool in the magazine upon which the film is wound. This slip clutch may be adjusted while the machine is in operation. An adjustable slip friction drag mechanism also is included in this housing which couples with the pay-off spool in the magazine to prevent the film from unwinding too rapidly and to keep it slightly taut as it enters the recorder. Either the Mitchell or the Bell & Howell film magazine may be used with this recorder. A film footage counter mounted on the right-hand door is so arranged that when the door is closed it is coupled through gearing to the pull-down sprocket shaft. Fig. 5 is a front view with the doors opened exposing the film sprockets and guide rollers, film punch mechanism, and shutter, in the film compartment at the right; and in the compartment at the left, the recording optical system, lightvalve, monitoring system, slater, and drive motor. All manual controls for operating the recorder are accessibly arranged on an inclined instrument panel located at the bottom of the housing. Modulator and Monitoring System. — Light-valves and their associated optical systems to modulate the recording light in either the standard or push-pull method of recording may be interchangeably mounted upon an optical bench located in the left-hand compartment of the recorder. This optical bench is equipped with adjusting screws to locate the recording lamp and to focus the recording light-beam upon the film. Associated with the modulator is an optical system, photoelectric cell, and amplifier which provide for high-quality photoelectric cell monitoring of either standard or push-pull recording. In the optical system a thin glass plate, located