Abstract: A method is provided for adjusting the operating amplitude of a modulation signal which influences the separation of drops from an ink jet of an ink jet printer. The method includes (1) determining the phase relationship between the modulation signal and the instants when successive drops separate from the ink jet for a plurality of amplitudes of said modulation signal (2) identifying the amplitude of the modulation signal at a predetermined characteristic point in the function of the phase relationship with the amplitude from the magnitude of the change of the phase relationship with the change of the amplitude; and (3) selecting the operating amplitude for the modulation signal in accordance with the amplitude identified in step (2).

Abstract: An ink jet printer automatically adjusts the amplitude of the modulation signal applied to a transducer (159) to break the ink jet into droplets. Correct modulation amplitude is determined from changes in jet break-up length, as determined by changes in jet break-up length, as determined by changes in jet break-up phase relative to the modulation signal.The printer has interchangeable print heads (3), which may have different nozzle sizes. A calibration code, specifying the particular values of ink pressure, jet velocity and charge correction required for optimum performance of a particular print head (3), may be entered into control logic (93), which operates the printer accordingly.Most print head components are mounted on a mounting subtract (111), with all connections being made to the underside of the mounting subtract (111) and sealed with a potting compound, to avoid damage.Ink viscosity is controlled in response to ink pressure, which is in turn controlled in response to ink jet velocity.

Abstract: Fluid is applied in droplet form to a substrate by feeding the fluid to a nozzle so that the fluid issues from the nozzle as a single substantially coherent jet following a single jet flight path, causing the jet to break up into a series of substantially uniformly sized droplets, and applying a sufficiently large electrical charge to the fluid by means of a charge electrode so as to form mutually repellant droplets having flight paths which diverge from one another. The single jet path is directed into a catching device by which the fluid is caught and prevented from being applied to the substrate. The jet of fluid is broken up into a stream of substantially uniformly spaced droplets and the divergent stream of droplets is directed away from the catching device and allowed to reach the substrate so as to deposit fluid on the substrate.

Abstract: An ink jet array printer has at least one row of printing guns. The guns deposit drops which are charged and deflected for printing on a printing surface moving relatively to the printer in line sections which together form a transverse printing line. The charging of the drops is effected by applying to the charge electrode of each gun, under the control of printing information, a periodic voltage waveform of sufficient period to span a raster of successively formed drops which are employed for printing the corresponding line section, the printing lines being successively formed at the frequency of the voltage waveform.

Abstract: An ink jet array printer in which the printing voltage waveform applied to each raster of drops formed in each printing gun comprises at least two successive sets of voltage levels which each arrange the raster drops in a group in time order of drop formation for each set of voltage levels so that corresponding drops in each of the groups formed in the raster, if charged for printing, have similar differences of voltage level and have similarly spaced print locations in the line section of drops printed by the printing gun. First and second correction voltages are applied to the charging voltage levels, the first to correct for the influence of the preceding drop and the second for the electrostatic and aerodynamic drag forces of a small number of drops influencing the drop being corrected. The set of second correction voltages derived for any particular drop being used also for corresponding drops in the other group(s).