Patent GB-489223-A (GB)
Title: Improvements in or relating to apparatus for sound recording
Filed: 1936-12-21
Abstract: 489,223. Optical sound-recording apparatus. KLANGFILM GES. Dec. 21, 1936, No. 35108. Convention date, Dec. 21, 1935. [Class 40 (ii)] [Also in Group XX] An optical sound-recording apparatus has film spools 2, 3 mounted side by side in a casing 1, but spaced apart so that the sound drum and guide rolls may be disposed between the film spools. The casing has doors 4, 5 hinged at 7, 8 on further doors hinged at 10, 9 so that the whole of the apparatus may be exposed if required, the doors hinged at 10, 9 normally being secured by spring - pressed latches which may be released by wings on a spindle, access to the spindle being obtained by opening the doors 4, 5. The apparatus is mounted by means of two pins 24 seating in apertures 29, 30, Fig. 3, in a bar 28 carried by resilient cross-bars 26 in a base 25 which is formed as a shallow box to accommodate various electrical connections, and which has a cover formed as two slides so that access may be had to the interior of the base without removing the sound recording apparatus. The sound drum 37, Fig. 5, and some or all of the guide rolls are mounted as a unit on a plate 47 as described in Specification 487,748. Separate motors are provided for driving the spools and the sprocket 13. A metric counter 21, Fig. 1, for the film is driven by a crank 87, Fig. 9a, on a toothed wheel 86 which is rotated tooth by tooth by a pin on a disc on the shaft of the sprocket 13. The optical system is mounted at 46 on the plate 47, Fig. 5, and the sound recording lamp 103, Fig. 11, is mounted in a casing 104 so that light may be directed on to the film by way of a mirror and the optical system, or may, if desired, be used to illuminate the interior of the casing 1 by swinging downwards the hinged lower face 105 of the casing 104, by pressing a leaf spring 107. Photo-electric cells may be inserted selectively into the path of the light beam for actuating indicating instruments, ear-phones or loud-speakers through amplifiers. For this purpose, a slide 111, Fig. 12, is adapted to move over the cover 109 of the casing 46 of the optical system. When a photo-electric cell is to be inserted, the slide 111 is advanced to cover the aperture 110, a spring pin 114 snapping into a hole 113 in the slide. The photo-electric cell 116, Fig. 12c, in its casing 117, is then applied so that a pin 118 on the casing 117 enters the hole 113 in the slide 111 and presses the pin 114 to release the slide, whereupon the slide can be drawn along to align the photo-electric cell with the lightaperture 110. The apparatus is fitted with guide rolls as described in Specification 487,748 ; with means for applying an initial pressure to the film on the sound drum at starting, as described in Specification 487,749 and with means for regulating and indicating the tension of the film as described in Specification 487,303. Light from the optical system may be diverted on to a photo-electric cell 90, Fig. 10, in a monitoring circuit when desired, by a prism 89 on an arm 91, Fig. 10a, which is normally held against a fixed stop 101 by a spring 9 but which may be displaced into contact with a stop 102 (in which position of the arm the prism is in the light path), by a press-button 96 actuating a wedge face 93 on the arm.