Patent GB-257013-A (GB)
Title: Improvements in or relating to the reproduction of pictures, drawings and other representations by the aid of telegraphy
IPC: H04N7/24
Filed: 1925-02-24
Abstract: 257,013. Creed & Co., Ltd., and Creed, F. G. Feb. 24, 1925. Copying-telegraphs. - In a system in which current variations derived from the exploration of the picture or the like at the transmitting station are utilized for perforating a tape according to a code, and the tape is used for reproducing the picture as an arrangement of printed dots, the exploration is effected by a pencil of light or heat rays and the resultant variations of resistance in an electric circuit are translated by electromagnetic means into variations of the position of an arm which controls the perforator mechanically. Tape punching mechanism of the kind described in Specification 191,033. [Class 31 (ii), Punching and perforating machines &c.], may be employed. Picture exploring and translating devices. The picture 2, Fig. 1, in the form of a photographic negative or positive on a transparent base, is mounted on a glass cylinder 1 on a shaft 3 to which rotary and axial movements are imparted from a motor 4 through gearing 6, shaft 7, bevel gears 8, shaft 9, worm 10, and a worm wheel 11 provided with a key slidable in a keyway in the shaft 3. The end 3<a> of this shaft is threaded to engage a fixed nut 12. The exploring pencil 16, concentrated on an aperture 15 in an opaque screen 14, passes through the picture at successive points along a helical line on the cylinder, and is incident on a selenium or like light-sensitive cell or a bolometer or like heat-sensitive device 19. This cell or device is in an electric circuit including an adjustable resistance 22 and an electromagnetic device such as movable coil 24 mounted in a magnetic field and carrying an arm 25. The movement of this arm is connected preferably by the use of a fluid-pressure amplifying device as described in Specification 256,285, into an amplified movement of an arm 25<a> about a pivot 25<b>. Punch-selecting mechanism. The free end of the arm 25a moves beneath the free. ends of four fingers 34, 34a, 34<b>, and 34<c> each pivoted on a spindle 35 and carrying an upward extension 34<A>, Fig. 2, against which an arm 54 pivoted on the spindle is held by a spring 55. The fingers 34 - - 34<c> are each normally held by a spring 36 against a plate 37 forming one arm of a lever pivoted at 37<*>, the other arm 37a being connected by a link 38 to the lower end of a lever 39 pivoted at 40, a spring 43 holding a roller 41 on the upper end of the lever 39 against a cam surface 42 on the shaft 7. Three combination bars 46. mounted to slide in line with the three punches 62 co-operate. with four T-shaped members 45 each provided with a deep notch 45<a> above the corresponding arm 45 and each mounted to slide vertically in a guide 50 and normally held in lowered position by a spring 51. During one rotation of the shaft 7 the rays explore a small area, e.g. 1/60 in. square, of the picture 2. and, in accordance with the density of that area, the arm 25a takes up one of the following six positions in relation to the fingers 34 - - 34<c> (a) beneath 34. (b) beneath 34 and 34<a>, (c) beneath 34<a>, (d) beneath 34<a> and 34<b>, (e) beneath 34b, (f) beneath 34b and 34<c>. A cam projection 56a on the shaft 7 operates a lever 47<a>, 47 to raise the members 45, and immediately thereafter the roller 41 enters a recess 42a, Fig. 2, in the cam 42, thus lowering the lever 37 and allowing the springs 36 to lower the fingers 34 - - 34c except the one or the adjacent two of which the movement is prevented by the arm 25<a>. The arms 54 corresponding to the lowered fingers each engage a shallow notch 45b in the end of the corresponding member 45 thus preventing the subsequent lowering of that member by the spring 51, and the members 45 which are subsequently lowered lock a selection of the bars 46 against backward movement. Punch-actuating mechanism. The tape A provided with feed perforations B is punched along one edge, the six degrees of density in the picture being represented by perforations corresponding to the six selections from the three punches 62 as indicated at a - - f , Fig. 6. The tape-feeding wheel 73 is rotated intermittently by a ratchet and a pawl 76 on a lever 77 operated through a rod 78 from an eccentric 79 on the shaft 9. The tape is guided in a passage 72 in a die plate 71 formed with perforations in line with the punches. The block 63, in which slide the punches 62, is carried by a frame 64 pivoted at 65 and connected by a link 67 to a lever 68 actuated by engagement with a cam groove 70 on the shaft 7 to restore the bars 46 to normal position. A fixed member 84 prevents forward movement of the punches 62 with the block 63. Reproducing the picture from the perforated tape. Dots of six different sizes. corresponding to the six degrees of density in the picture are printed by levers 87, Fig. 7, substituted for the type-carrying levers in a type-printing machine adapted to be actuated either directly by the tape or by telegraphic impulses transmitted by passing the tape through an automatic transmitter. e.g. a Wheatstone transmitter with one pecker mechanism omitted. The telegraphic receiving and printing mechanism may be of the kind described in Specification 228,842. Alternatively the received impulses may produce a second perforated tape by the use of apparatus such as those described in Specifications 5490/05 and 165,820, the tape so produced being used to operate the printing mechanism e.g. as described in Specifications 164,370 and 184,558, [both in Class 100 (iv), Typewriting &c.]. The paper or like surface receiving the printed dots may be carried by a cylinder moved longitudinally, stepby-step, past the printing-wheel 85, Fig. 7, until a line of dots corresponding to a circumferential length of the cylinder 1, Fig. 1, has been printed, whereupon a. special signal is received which effects a rapid return of the paper-carrying cylinder to its initial position and its rotation through e.g. 1/60 in. for printing the next line of dots. The paper-carrying cylinder may be constructed and operated as described in Specification 240,200. The special signal may be obtained by punching in the tape A a series of three holes i, Fig. 6, at the end of each rotation of the cylinder 1. The three punches 62 are, for this purpose, locked by the members 45 by preventing the lowering of any of the fingers 34 - - 34<c>, this being effected by the energizing of a, magnet 87<1>, Fig. 2, upon closure of a circuit 88, Fig. 1, once per revolution of the shaft 3 by a contact carried by the worm wheel 11, a bar 85<1> being thus positioned by the magnet armature beneath projections 34<*> carried by the fingers.