Patent GB-354249-A (GB)
Title: Improvements in or relating to methods and apparatus for coding and decoding documents
IPC: G09C5/00
Filed: 1930-04-28
Abstract: 354,249. Coding-apparatus. ETABLISSEMENTS E. BELIN, 56, Faubourg St- Honore, Paris. April 28, 1930, No. 13079. Convention date, April 26, 1929. [Class 146 (ii).] The document to be coded is explored in narrow parallel bands in running order to produce a photographic copy with the bands transposed into some other order depending on the code setting and requiring retransposition into the original order for decoding. In addition to the transposition in order, the bands are also deformed longitudinally to variable extents. In the apparatus shown in Fig. 1, the document to be coded is wound on a cylinder 1 and is strongly illuminated along a band a parallel to the axis and about <1>/3 of a millimetre in width, the cylinder being progressively advanced this amount by means of an electromagnet 3 controlled from a cam 37 on a motor shaft M. The photographic paper is wound on a cylinder 6 enclosed within an inner fixed cylinder 7 having a longitudinal slot 71 and an outer cylinder 8 rotated by gearing 9; 10 from the shaft M and having a helicoidal slot 8<1> giving a progressive exposure along the slot 7<1>. The cylinder 8 is rotated half a turn during the photographing of each band, and during the subsequent half turn, to bring the helicoidal slot again into position, the cylinder 6 is advanced a variable amount by pawl-and-ratchet mechanism 20, 23, the pawl member 23 having a variable throw determined by a changeable series of stops 24, Fig. 3, on a carrier 25 intermittently advanced by gearing 28,33,25<1> from a cross shaft 29 geared to the shaft M. The pawl member 23 is actuated by crank mechanism 21, 22 from the shaft M. Longitudinal deformation of the bands is obtained by means of a mirror 35 mounted for variable oscillating movement of small amplitude through gearing 39, 34, 27, 33. The cylinder 6 is advanced in multiples of mullimetres so that the copy is first printed with a series of bands one millimetre apart. After this series is printed, a ratchet wheel 18 is actuated to advance the cylinder <4>/3 of a tooth of the ratchet-wheel 20, and a second series is printed adjacent to the first series, Subsequently another adjustment is made to print a third series in the remaining gaps. Since after a certain number of advances of the ratchet-wheel 20 the cylinder 6 will repeat a former position, provision is made to avoid superposed prints. For this purpose a shutter is controlled by the electromagnet 3, and the circuit of the latter is controlled so that shutter is not opened nor is the cylinder 1 advanced if the cylinder 6 repeats a former position, by means of a series of contact strips 41 on a crown-wheel 36 corresponding in number to the teeth on the ratchet-wheel 20 and projected by means of a pusher and linkage 37<1> from the cam 37, a contact strip once raised being inoperative if presented a second time to the pusher. The photographic paper is fixed on the cylinder 6 at the edges and by a longitudinal strip, and when this strip comes into exposure position the circuit of the electromagnet 3 is broken by means of a cam 15 at contacts 16. A revolution counter is provided for the wheel 27 to give a datum mark for setting the mirror gears for decoding. The cylinder 8 is replaced by another cylinder having a helicoidal slot of opposite pitch for decoding.