GB1304066A - - Google Patents

Abstract

1304066 Recording-apparatus VARIAN ASSOCIATES 1 July 1970 [2 July 1969] 31986/70 Heading G1J In electrographic charge image printing recording-apparatus with a charge-retentive surface of a web 4 disposed between an electrode structure 14 and an array of styli 3, means for sequentially and selectively energizing styli with writing potential to deposit a charge image on the web include (1) means 13 for producing pulses of potential insufficient to deposit a charge on the web, (2) means 2, 11, 12 for sequentially varying the energy of these pulses in accordance with the density of the charge images to be printed by selected ones of the styli and (3) means 16, 21, 22, 2, 7 for combining these pulses with other pulses of potential to produce summation pulses sufficient to deposit charges on the web 4 sequentially from the selected styli 3, the charges having an average density in accordance with the density of the charges to be printed. The apparatus may record spectral lines as the result of an analysis of a composite radio signal repetitively scanned to produce in each scan a set of sequential styli address binary codes each corresponding to a different frequency component and also, at 8, a sequence of binary coded signals representing respectively the intensities at the different frequencies (i.e. the intensities of spectral lines) and controlling the intensities of the charge images to be deposited on the web 4 and thus of the darkness on a grey-scale of lines 32 developed under a toner channel 30. Conveniently, the grey-scale is divided into eight levels with corresponding output lines 12 from a decoder 11 feeding a pulsed energy driver 13 to generate an output pulse in the range of 300 to 600 volts for application, together with a fixed bias potential of 100 volts, to the electrode 14 from which the voltage drop to the styli 3, fed with 300 volts pulses from a source 16, lies in the range 100 to 400 volts and is insufficient to deposit a charge if the gap-breakdown voltage is of the order of 400 volts. The decoders 7, 11 are synchronized so that when a stylus 3 is selected a gating transistor 22 is turned "on", the stylus is pulsed from 300 to zero volts and the voltage drop between electrode 14 and stylus increases into the range 400 to 700 volts so that a charge is deposited in accordance with the intensity coded for that stylus. In the embodiment of Fig. 8 (not shown) the charge density information is derived directly from an analog type signal by means of a sample and hold circuit.