Patent GB-734909-A (GB)
Title: Electrostatic recording of images of characters
IPC: G03G15/32
Filed: 1953-08-19
Abstract: 734,909. Photographic processes. CARLSON, C. F. Aug. 19, 1953 [Aug. 29, 1952], No. 22844/53. Class 98 (2). [Also in Group XVI] Electrostatic images of characters to be recorded, such as numbers, letters, words'or other symbols, produced, e.g., by an electronic digital computer or high-speed accounting and tabulating machine, are made on a web or sheet of insulating material by producing an electric discharge between an electrode and the web. As described, the web 13 on which the image is to be made, Figs. 1, 2, 4, may be fed, under steady tension from a reel 12, Fig. 1, through a charging device 20, where it passes through a field of adjustable intensity and either polarity to an image recording drum or wheel 21, around the periphery of which are arranged in helical fashion symbols 35 to be selectively recorded. The pitch of the helix is related to the rate of feed of the web 13, both being moved at accurate pre-determined speeds by a motor M so that horizontal rows of images may be recorded on the web, as shown in Fig. 4. The charging device 20, Fig. 1, comprises a chamber containing an electrode 28 coated on the face which confronts the web with a radioactive source of ionizing particles, such as a polonium layer. As ions of one polarity deposit their charge on the web 13 the field is altered by the charge on the web until equilibrium is reached. A small positive potential may be applied to the web by setting the potentiometer contact 29. The recorded electrostatic images may be developed in a machanism 22, Fig. 1, by depositing thereon, as by spraying, a finelydivided material such as ink mist, or a plastic in solution, which is afterwards fixed by drying, or heating the web in a fuser 15. Electrical circuits are associated with the recording drum 21 to supply recording pulses in accordance with information received electrically from a computer or other signal source 52 to record with the aid of a set of commutators and photo-electric timers in a housing 24 on shaft 34 of motor M, characters selected thereby. The web is curved into an arcuate shape to lie close to and equidistant at all points across the width from the edge of the wheel 21, the faces of the characters 35 on which are ground to lie on a cylinder coaxial with shaft 34. The character faces may be coated with colloidal graphite followed by a layer of magnesium oxide to improve their emission characteristics and reduce the necessary voltage. The set of commutators or electrodes 39 ... 42, one for each column of images it is desired to record on the web (four columns are shown in Fig. 4), are insulated from one another and are mounted against the back of the web 13 facing the wheel 21 and an insulating segment plate 33 which is mounted parallel to and just above the wheel, Fig. 2. Images of the characters are recorded on the web by producing an intense electric field of short duration between a character and an electrode, such as 40, at the instant the character comes opposite the electrode of the desired column. A similar and separate control circuit is applied to each electrode 39 ... 42 from information or signals received from storage circuits of a computer, manual key-board or other source, and an impulse circuit 52 leading from such a source is shown for recording numeral 1, there being a separate circuit for each numeral or other character to be recorded. A capacitor 53 is charged at the beginning of each cycle of rotation of wheel 21, when the number " 1 " is to be recorded in the column of electrode 40, and remains uncharged if it is not to be recorded. A commutator arm 54 on shaft 34 earths contacts 55, in which one side of the circuits 52 terminate, in turn, and, if the circuit capacitor 53 carries a charge, a positive charge is applied to grid of triode 47 connected to arm 54 through a photo-electric cell 56 energized by lamp 57 under control of a rotating disc 58 on shaft 34 and, through slits 59 on which light may be allowed to reach the cell when each character is centred opposite the electrode, e.g. 40, associated with the circuit. A reset control circuit 63 is controlled by a rotating disc 60 and single slot 61 which controls the operation of a photo-electric cell 62 which receives a light pulse immediately after commutator completes traverse of the contacts 55 to reset the charges on the condensers 53 when a blank portion of wheel 21 is passing in front of the web 13. Two or more webs may be provided at spaced points around a single wheel with independent circuits to record the same or different information simultaneously or, by providing two or more series of identical faces around a wheel, duplicate copies using additional electrodes 39 ... 42 connected to the same impulse circuits and angularly spaced around the wheel to correspond with the angular spacing of identical character faces may be made. Two or more wheels synchronously operated may have their respective electrodes 39 ... 42 connected in parallel to the impulse circuits. The characters may be of small size and recorded on a narrow web of transparent film for compact storage, and full-scale copies may be produced by xerographic or photographic enlargement or optically projected for reading. Instead of fixing the powder images on the original web, they may be transferred to another sheet or surface by an electrostatic transfer method or by rolling against an adhesive coated surface for use in offset printing of multiple copies. Copying documents.-The electrostatic images may be in the form of mirror images and by using a developing powder carrying a spiritsoluble dye of high colour value, additional copies can be produced by bringing alcoholmoistened paper into contact with the fused images. Specifications 675,398, 679,533, and 693,905 and U.S.A. Specifications 2,551,582 and 2,624,652 are referred to.