GB1238210A - - Google Patents

Abstract

1,238,210. Selective printing; printing surfaces. INTERNATIONAL STANDARD ELECTRIC CORP. 16 Oct., 1968 [24 Oct., 1967], No. 49008/68. Headings B6C and B6F. In a selective printer, characters are serially formed on a continuously moving endless carrier band 11 at a stationary station 13, and are transferred electrostatically or magnetically across an air gap from the band 11 to a copy sheet 18 moving continuously and at right angles to the direction of movement of the band. The characters are formed on the band in one of a number of ways. In (Fig. 2) a row of fluid expulsion nozzles (14) deposit discrete ink droplets (15) on to the moving transfer band 11, in response to electrical pulse commands. The ink droplets are held to the surface of the band 11 by capillary adhesive force which is overcome when printing is desired by the electrostatic field force of transfer station 19 (Fig. 2A). In an alternative embodiment, Fig. 4, a roller band conditioner 21 applies a non-wettable material 25 to fill empty impressions 26 in the coating on the band 11<SP>1</SP>. An impression maker 22 creates new impressions 27 in the non- wettable material 25 in response to pulse commands, so that an ink-coated roller 23 fills the empty impressions 27 with ink droplets 24. The impression maker 22 comprises a row of air jet nozzles as shown, or a row of needle point electrodes which form electrical arcs to rupture the non-wettable coating 25 and form the desired depressions 27. Alternatively, a row of fluid expulsion nozzles may deposit a negative of the image to be formed of non-wettable fluid upon a previously cleaned band surface. The negative so formed need not remain in liquid form, but could be solidified upon deposit on the band so that the ultimate cleaning is accomplished by reheating to effect removal. In Fig. 4, the ink is magnetic, comprising a suspended solution of iron particles in a coloured solvent. The band 11<SP>1</SP> is a permanent magnet with north and south poles 29 located on opposite sides of the band. The deposited droplets are held to the band magnetically until such time as the electrostatic or magnetic field transfer station 19 exerts an attractive force on the ink droplets to transfer them rapidly to the copy paper surface. As an alternative, if after depositing the droplets on the band, they are passed through an electrical corona discharge station or the band is maintained at a constant electrical voltage, a static charge, opposite in sign to the field used for printing is produced, which enhances the transfer of the droplets to the copy paper 18. The transfer band may be of non-magnetic material if a permanent magnet is located adjacent the band surface opposite to the surface on which the droplets are deposited. In an alternative embodiment (Fig. 5) similar to Fig. 4, the ink droplets are retained in the depressions (32), 27, solely by capillary action. In an alternative embodiment (Fig. 6), a row of electromagnets (34) create selectively magnetized areas (33) on a magnetizable band, which areas retain droplets of magnetic ink (40) applied by a roller (38).