GB300996A - Improvements in and relating to sound record film printing apparatus - Google Patents

Abstract

300,996. British Thomson-Houston Co., Ltd., (Assignees of Kellogg, E. W.). Nov. 22, 1927, [Convention date]. Feeding webs.-A method of printing a photographic film record on to another film, particularly applicable to the production of a combined sound record and motion picture film, consists in limiting the area being printed at any instant to a narrow band and moving the record film and print film by means of smooth rollers whose speeds are free from appreciable fluctuations. In the apparatus shown, a negative sound record film 1 is drawn from a reel 2 and wound upon a reel 3, the film being moved by means of a friction drum 30 driven by an electromotor 28 and associated with a fly-wheel, and by a sprocket 26 driven by a motor 25. The speed of the motor 28 is automatically controlled by a rheostat 36, of any suitable type, having an adjustable arm 37, the position of which is governed by the size of the film loop between the drum 30 and the sprocket 26. A similar arrangement is used for the sensitized film 4 on which the print is to be made, and which may or may not have a picture record thereon, the motor 25 driving both sprockets 26, 27 for the films 1, 4 respectively. Both films are drawn over oppositely-disposed narrow slits 17, 18 in a printing device consisting of a casing 14 into which light passes from a source 19, a collecting lens 21 being preferably used. A lens 22 may be arranged within the casing, but may be dispensed with if the interior of the casing is covered with light-reflecting material. When the lens 22 is used, it is preferably placed slightly out of focus, to assist in preventing a grainy quality in the print. The means described in Specification 295,378 may be adopted for enabling the lengths of the film loops to control the speeds of the drums 30, 31. An alternative method is to utilize the tension in the film between the sprocket and drum to control the speed of the latter. This may be done by passing the film over an idler roller, spring-mounted between the sprocket and the drum, and causing the film to drive the drum, which is associated with a fly-wheel, and has an auxiliary drive if necessary. The idler mounting may be provided with a dashpot to prevent " hunting," or damping means may be provided on the drum shaft for this purpose. Such damping may be effected by mounting a copper disc on the shaft, and causing it to move between magnet poles. The magnets may be rotated slightly faster than the drum, so as to constitute, in addition, an auxiliary drive.