Method of multi-tone printing

A drop-on-demand ink jet printing apparatus comprising an array of parallel channels, disposed side by side and having side walls which extend in a lengthwise direction of the channels and separating one channel from another, the channels having an identical longitudinal acoustic resonant frequency at least some of the channels being arranged into first and second interleaved groups of channels, a series of nozzles which communicate respectively with said channels for ejection of ink therefrom;

• connection means for connecting the channels with a source of ink;
• electrically actuable means for effecting transverse displacement in opposite senses of a portion at least of a channel separating side wall of a selected channel to effect ink ejection therefrom;
• and control means for receiving print information and, responsive thereto, selecting a band of adjacent channels for ink ejection and actuating the electrically actuable means to apply sequences of pulses of energy at or near the longitudinal acoustic resonant frequency in anti-phase to first and second interleaved groups of channels within said selected band and varying a number of adjacent channels in the band in successive cycles of the resonant frequency to control print density.

A drop-on-demand ink jet printing apparatus comprising an array of parallel channels at least some being arranged into first and second interleaved groups of channels, a series of nozzles which communicate respectively with said channels for ejection of ink therefrom;

• a common ink manifold for connecting the channels with a source of ink;
• electrically actuable means associated with the channels for effecting ink ejection therefrom;
• and control means for receiving print information and, responsive thereto, selecting a band of adjacent channels for ink ejection and actuating the electrically actuable means to apply sequences of pulses of energy at an operating frequency in anti-phase to first and second interleaved groups of channels within said selected band and varying a number of adjacent channels in the band in successive cycles of the operating frequency to control print density.

A method of multi-tone printing employing a drop-on-demand ink jet apparatus comprising an array of parallel channels having an acoustic resonant frequency, at least some of the channels being arranged in first and second interleaved groups, a series of nozzles which communicate respectively with said channels for ejection of ink therefrom;

• a common ink manifold connecting the channels with a source of ink and electrically actuable means associated with the channels for effecting ink ejection therefrom;
• the method comprising the steps of receiving print data;
• selecting channels of first and second interleaved groups of channels for ink ejection in accordance with the print data and actuating the electrically actuable means to apply sequences of pulses at said acoustic resonant frequency to effect ink ejection from the nozzles of the first and second groups of channels at said acoustic resonant frequency, ink ejection from said first and second groups of channels being in antiphase.

A method of multi-tone printing employing a drop-on-demand inkjet apparatus comprising an array of parallel channels, at least some of the channels being arranged in first and second interleaved groups, a series of nozzles which communicate respectively with said channels for ejection of ink therefrom;

• a common ink manifold connecting the channels with a source of ink and electrically actuable means associated with the channels for effecting ink ejection therefrom;
• the method comprising the steps of receiving print data;
• selecting channels of first and second interleaved groups of channels for ink ejection in accordance with the print data and actuating the electrically actuable means to apply sequences of pulses at an operating frequency to effect ink ejection from the nozzles of the first and second groups of channels, ink ejection from said first and second groups of channels being in anti-phase at said operating frequency, wherein the channels of the array are assigned in a regular manner one to each of a least two phases, the phases being successively enabled for ink ejection at a phase enabling frequency which is substantially lower than said operating frequency.