Patent GB-797278-A (GB)
Title: Improvements in or relating to the synchronisation of cinematograph films
IPC: G03B21/40
Filed: 1955-04-13
Abstract: 797,278. Kinematograph apparatus. LEEVERS, F. N. G. July 6, 1956 [April 13, 1955], No. 1124/55. Class 97(1) Two or more films are synchronized by applying, either to a continuously running recording medium or to at least one film which is running, periodically-recurring identification marks corresponding to indentinable points on each film that is running and distinctive of each film that is running. The identification marks may be distinguished by colour, when colour film is used, or by being spaced across the width of the film. Thus when only two films have to be synchronized recurring marks may be applied in opposite margins according to which is running. Alternatively the marks may be applied in a single track, the distinction between films being indicated by the nature of the repetition of the markings. The markings may be applied mechanically or, preferably, optically. A master record may be made on one film which runs continuously or on a separate strip of, for example, paper. Thus the arrangement shown in Fig. 1 includes a main camera 10, which runs continuously and other cameras 11, 12, 13. Each contains a contact 14 which is closed when the camera is running to complete a circuit from a rectifier 34 through an inductance 16 and through a similar inductance in any other camera which is running if contacts 29, 30, 31, 32 in'series with the respective inductances are closed. When a circuit through an inductance is broken a voltage surge occurs to cause a flash in neon lamp 15 and produce a mask in the film margin. The comtacts 29-32 are operated by cams 25, 26, 27, 28 driven by a motor 21, the speed of which may be varied by a resistance 24, the sequence of operatiion being represented by lines M, 1, 2, 3, respectively, in Fig. 2, the thickened portions showing when the contacts are closed. The resulting film markings are shown in Fig. 4 wherein 50, 51, 52 respectively represent films in cameras 10, 11, 12 supposed to be moving from right to left. The contact 29 opens at. A but no film marks are produced until another camera, say 11, is started and its contact 14 is closed. Each break at A then produces a film mask 54 in camera 10 and simultaneously a mask 55 in camera 11 the contact 30 meanwhile being closed. Contact 30 then opens at B after contact 29 has reclosed, causing simultaneous masks 56, 57 in both cameras. The subsequent opening of contact 29 at X causes no mark as all the other contacts are then open. The pairs of marks are repeated in both cameras so long as both are running. When camera 12 is started marks 61 are produced also on film 52, corresponding to point X, with marks 59, 60 corresponding to point C, in cameras 10, 12. These also are repeated in both cameras so long as both are running, so that a composite set of marks is made in camera 10 when all three are running. An external neon lamp connected to an inductance 40 acts as an indicator and flashes when any of the lamps flash. In a modified embodiment no one camera runs continuously but repeating pairs of marks are made on the film in each camera that is running, the spacing of the two marks being characteristic of that camera, there being also added the marks of any other camera that is running.