International Business Machines Corporation

Gary L Fillmore

Gregory Lawrence Ream

Thomas R Young

James D Hill

Van Clifton Martin

Arthur R Hoffman

Thomas H Williams

William F Robinson

In a multinozzle ink jet printing system, a closed loop servo system drives the drop generator so that the distance between the streams at which ink droplets are detached is maintained at an optimum range. One or more sensors are positioned downstream from the multinozzle plate of the ink jet printing system. The sensors sense the flight time of ink droplets and output signals which are developed into a variable voltage for controlling the drop generator.

Break-off uniformity maintenance

An inner cylindrical tube has its outer cylindrical surface spaced from an inner cylindrical surface of outer means to have an ink cavity therebetween from which ink is supplied through one or more ink jet nozzles. At least the inner tube is a piezoelectric material so that the inner tube vibrates radially when electrically excited to produce vibrations at a desired operating frequency whereby a stream of ink droplets is supplied from each of the ink jet nozzles. The spacing between the inner surface, which has its longitudinal axis coaxial with the longitudinal axis of the inner cylindrical tube, of the outer means and the outer surface of the inner cylindrical tube is selected so that the ink cavity is resonant at the operating frequency of the inner cylindrical tube. To maintain the lowest frequencies of perturbations in the axial direction of the inner cylindrical tube substantially greater than the operating frequency, the inner cylindrical tube can be formed of a plurality of longitudinal segments acoustically isolated from each other in the axial direction. In another form, the outer means is a body formed with a membrane providing acoustical communication from a liquid cavity between the inner tube and the body and each ink cavity, which has ink jet nozzles at its end. The liquid cavity preferably has a liquid of substantially the same density as the ink. This enables each of the ink cavities to have a different colored ink if desired.

Ink jet head

The invention relates to an ink jet printer and in particular to correcting the flight path of drops from the printer to reduce print position error on the print media. It has been found that drops as far as 30 drop positions ahead of a drop in the ink stream can have an effect on the flight path of that drop to the print media. Using a memory to store 2.sup.30 compensation values to correct the flight of the drop for all possible combinations of drop patterns in the ink stream is not practical. Disclosed herein is a method and apparatus for using a smaller number of compensation values to correct the flight path for all possible combinations. This is accomplished by grouping the drops remote in position from the drop being compensated into blocks of drops and treating the entire block of drops as contributing one effect on the flight of the drop. Accordingly, drops close to the compensated drop are treated as having an individual effect on the flight path while drops remote from the compensated drop are grouped into one of more blocks and each block is treated as having a single effect on the compensated drop.

Ink drop compensation based on print-data blocks

Insertion of guard drops on a variable basis within a drop segment of an ink jet raster has been found to be highly successful in producing quality printing. A typical sequence is

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Boulder, CO, United States of America

Gary L Fillmore