Patent GB-848421-A (GB)
Title: Improvements relating to apparatus for high speed photographic type-composing
Inventor: SCARROTT GORDON GEORGE
IPC: B41B21/28
Filed: 1957-03-01
Abstract: 848,421. Photographic type-composing. FERRANTI Ltd. Feb. 25, 1958 [March 1, 1957], No. 6822/57. Class 98(1) Apparatus for photographic type-composing n different characters in lines of p characters includes a transparent drum 10, Fig. 1, having opaque characters in n rows parallel to the drum axis and in p bands normal thereto, each band containing all the n different characters; a row of p light sources 11; means for continuously rotating the drum to bring the p characters in any row into optical register with the p light sources; selecting means for energising one or more of the light sources simultaneously in accordance with the positions of the characters to be recorded in any line; means 13, 14 for projecting on to a continuously-moving photographic surface (such as photographic paper 16) an image of each selected character in a row as it is illuminated during the optical registration of the characters in that row with the light sources; means 15 for moving the images at the same velocity as 'the surface 15; and optical means for counteracting movement of the characters as the drum rotates. Associated with the optical apparatus is a storage device, Fig. 2, which consists of magnetic cores 19 of a material having a substantially square hysteresis loop, arranged in n rows and p columns and interconnected by two sets of wires 20, 21. Wires 21 are connected to a character decoder 25 and to a drum position decoder 26, while wires 20 are connected through amplifiers 23 to p light sources 11, which can be triggered to give out brief but intense light flashes. The arrangement is such that when any core receives an electric pulse along one wire, the flux generated is half the saburation flux and leaves the magnetisation of the core substantially unaltered. When pulses arrive on both wires at once, however, the core is changed from a "reset" state, in which it is fully magnetised in one direction, to a "set" state in which it is fully magnetised in the opposite direction. Information to be recorded as lines of type, originally recorded on a magnetic or perforated tape, punched cards or the like, or supplied direct from a computer, is fed into a reader 28 and passed to character decoder 25, which passes a pulse to the wire 21, corresponding to the character represented by the input signal. At the same time a pulse for each character is passed from the reader 28 to the column decoder 22, which is a counter, and passes the pulse to the wire 20 corresponding to the position of the character in the line. Each signal thus results in the setting of a core in the row corresponding to the character represented and in the column corresponding to the position of the character in the line. During the storage process the drum 10, which rotates continuously in synchronism with the movement of the paper 16, makes two revolutions. Printing is effected during the third revolution of the drum, during which the tape reader 28, the character decoder and the column decoder 22 are rendered inoperative. The drum position decoder 26 receives signals from a synchronising means 17 (Fig. 1) which cause it to count down one wire 21 as each row of characters passes the light sources 11, so that a pulse is sent along the wire 21 corresponding to the row of characters in position. This pulse "resets" all the "set" cores in the row and in so doing sends a pulse along each wire 20 corresponding to a column which, amplified by an amplifier 23, causes a lamp to flash. Thus, in the example shown, first all the A's in a line are printed, then all the B's, then the C's and so on, each character being printed in its proper position. At the end of the cycle all the "set" cores have been "reset" and the storage device is ready to receive the information pertaining to the next line. As shown in Figs. 1 and 4, the rows of characters, opaque on a transparent ground, are formed on concave strips 31, 33 of the drum; the radius of curvature of each strip being such that the light beam emerging from the drum appears to originate from an image on the axis 34 of the drum. The astigmatism of this image is corrected by a cylindrical lens 13, and spherical lenses 14 (one for each band of characters) are provided to form images of the characters, when illuminated, on the continuously moving paper 16. A parallel-sided transparent block 15, rotating at one-sixth of the drum speed, displaces the characters so that, although they are not all printed at the same time, their images consist of a single line. Since printing occurs in one revolution in three of the drum, it can be arranged that the angle between the normal to the surface of block 15 and the optical axis never exceeds 30 degrees during printing.