GB1069269A - Electrostatic printing system - Google Patents

Abstract

1,069,269. Printing apparatus. ELECTROSTATIC PRINTING CORPORATION OF AMERICA. Dec. 3, 1963 [Feb. 1, 1963]. No. 47630/63. Headings,B6C and B6F. In a screen-stencilling apparatus utilizing an electrostatic field for screen printing on an article with a powdered pigment the latter is moved from a storage container through the screen by the application of a magnetic field. This field attracts to the screen carrier particles of magnetic material which are mixed with the powdered pigment in the container and are each of a size too large for passage through the openings in the screen. In the apparatus of Fig. 2, an article 34 is screen-printed with an image 28A by passage through an electrostatic field between an aluminium conductive backplate 30 and a container 22 which accommodates a mixture of powdered pigment 24 and magnetic particles 26 and incorporates in its upper wall a screen 28. Magnetic attraction to the screen of the particles 26 and hence upward propulsion of the pigment 24 is effected by the reciprocation of a magnet 36. In a modification of this apparatus six magnets similar to 36 are mounted on a movable endless band the runs of which are parallel to the back-plate 30. Fig. 4 shows an electromagnetic arrangement in which windings 50A to 50E are successively energized through a sliding contact 56 whereby the magnetic particles are drawn to the screen in a " wavesweeping " motion. In further embodiments the containers 22 are above the article 34 and magnets are also used to withdraw the magnetic particles from the screen. In one such arrangement permanent magnets, weaker in field strength than that used for printing, are mounted above the container, whilst in another arrangement these " weak " magnets are replaced by an electromagnet which may be switched off during the printing operation. Fig. 7 (not shown) discloses an arrangement having " switched " electromagnets for moving the magnetic particles to and from the screen, a suitable control being provided for energizing and de-energizing the magnets as required. In yet another embodiment the screen 92, Fig. 9. which is imaged with the letter " A ", is formed in an end face of a container 90 and magnetic particles are advanced rapidly up to the screen to introduce pigment powder into the electrostatic field through the successive energization of electromagnets 98, 100 and 102 positioned adjacent one another so that the container 90 is enclosed between their pole faces. By using a plurality of the structures shown in Fig. 9, a printer can be constructed having a different letter aperture in the front faces of each one of the containers 90. The letter desired to be printed is selected and then printed by selective actuation of the particular selector switch 112 associated with the desired letter.