Abstract: A charging electrode assembly for a continous multi-jet ink jet printer includes a substrate plate 1 of electrically insulated material provided with a series of parallel electrodes 5 extending across an edge of the plate and a series of parallel strip leads 6 extending across a face of the plate. The plate is formed with grooves, plated with metal, and then the faces of the plate are ground to leave the electrodes and strip leads in the grooves. Alternatively, the surfaces of the plate are metal plated and then grooves are cut in the edge and face of the plate to leave the electrodes and strip leads between the grooves. An independent feature of the invention recides in the provision of one or more eccentric dowels working in elongate slots in the plate so that rotation of the dowels provides fine adjustment of the plate, and hence of the electrodes relatively to trains of ink droplets.

Abstract: A modulating device for breaking ink jets in an ink jet printing machine into trains of uniform droplets comprises a nozzle plate 24 provided with a substantially linear array of nozzles and forming one wall of an ink cavity 23; and acoustic generator in the form of an elongate body 26 projecting towards the nozzle plate to transmit acoustic vibrations into ink into the cavity. The body is shaped and tuned to vibrate substantially only in the longitudinal mode and at a resonant frequency which is within ten percent of a frequency to excite natural resonant vibrations in the ink in the cavity between the end of the body and the nozzle plate, the width of the body being less than the length of the nozzle array or of that part of the array associated with that body.

Abstract: A continuous ink jet printer has main deflection electrodes 7 and 8 and a subsidiary deflection electrode 14 having a recess front face 16 which defines a cavity 17. Unwanted satellite droplets entrained by the main droplets 4 are deflected into, and form vortices in, the cavity 17, before coalescing on the surface of the electrode 14 for collection.