Patent GB-987234-A (GB)
Title: Process and apparatus for forming an electrostatic charge pattern
IPC: G03G15/32
Filed: 1961-06-28
Abstract: 987,234. Selective printing. RANK-XEROX Ltd. June 28, 1961 [July 1, 1960], No. 23444/61. Headings B6C and B6F. [Also in Divisions G2, G4 and H4] Electrographic printing. - An electrostatic printer or recording apparatus selectively operating from pulses from a computer or from a magnetic tape comprises two spaced electrical conductive structures through which a dielectric record is passed, means to apply a voltage to the structures to form a charge pattern on the record, e.g. a character, and means for irradiating the space between the character structure and the record with ultraviolet radiation. The ultra-violet radiation in the gap greatly increases the reliability of electrostatic discharge in conditions of low relative humidity and is provided by a 100 watt ultra-violet lamp in a quartz envelope. The lamp 40 is placed opposite the gap, Fig. 5A, or may be used through a screen electrode used as a backing electrode 55, Fig. 3A. As shown in Fig. 2 the character structures are formed on a continuously rotating drum 52 and a steady potential is applied between the drum and a series of fixed structures or electrodes 55. A latent electrostatic image is formed in the record 25 when an additional potential is applied by digital selecting circuits. In the circuits shown data from the computer or tape is received at 67 and compared in a comparison circuit 66 with signals in a counter 65 which is actuated by marks 62 and magnetic head 64. A second magnetic head 58 picks up a pulse for each revolution and transmits it to a revolution counter 59. For each position of the counter 59, one only of the lines 1 to N on a line selection matrix 60 is energized. The appropriate gate 61 only causes a pulse to be transmitted to a voltage amplifier 68 if at the same time it is activated by a pulse from the comparison circuit. In an embodiment described, instead of printing one column at a time an electrode assembly may be employed with a suitable line storage memory device to produce line-byline printing. In an embodiment described with regard to Fig. 3 (not shown) the electrostatic character structures are fixed in line with the direction of travel of the web and are selected by the timed operation as the paper moves relatively to the character structures. If the various columns are actuated after the elements they may be slightly skewed to compensate for the travel of the web. The structures may be pin electrodes, Fig. 5, selectively operated as the web 25 travels past. Web tensioning arrangements.-The web 25 is held taut by a plate 26 hinged to framework 23 and bearing on the web supply roll 24. Pressure is adjustable by means of weight 27. Inking arrangements.-After the electrostatic image is formed in the web 25, Fig. 1, at the recording mechanism 20 the image is made permanent at station 21. This station comprises a development mechanism 28 wherein finely-divided material, such as an ink mist or an electroscopic pigmented powder is deposited and which adheres to the charge areas. The powdered images are then heated to fuse the resin in the powder. In the case where liquid ink is used, the fuser serves as a drier. As an alternative, instead of fusing the original web, the powdered image may be transferred to another sheet. In a further embodiment, Fig. 6, the developing mechanism 28 may comprise two rollers 80, 85. Roller 80 being simply a pair of spaced discs 82 over which only the edges of the web 25 pass. Flanges 81 confine the web and the web and discs 82 form a hopper in which the ink powder is contained.