Tonejet Limited

Ammar Lecheheb

John Lawton Sharp

Ewan Hendrik Conradie

Andrew John Clippingdale

Ian Philip Butler Ingham

Robin Timothy Bacon

Jerzy Marcin Zaba

Peter James Brown

Jesse David Woolaston

Andrew Clippingdale

An apparatus for controlling ink pressure in a printhead, the apparatus comprising: an integrally formed structure having: at least one control reservoir separated into first and second chambers by a weir; at least one inlet passageway, extending from the first chamber to an inlet port on an edge of the structure, for supplying ink from a remote source into the first chamber of the reservoir; at least one fluid outlet passageway, extending from the second chamber to an outlet port on an edge of the structure, for recirculating fluid from the reservoir to the remote source of ink; and at least one ink supply port, in communication with the first chamber, for supplying ink to, or receiving ink from, a printhead.

Apparatus for controlling ink pressure

A method of cleaning an electrostatic printhead which has one or more ejection tips from which, in use, ink is ejected, the method comprising: stopping a prior flow of ink to a region around the ejection tip(s) for, in use, printing; causing a pressure differential to occur at the tip region thereby causing the ink meniscus to retreat from the tip; and passing a rinse into the tip region to clean the tip.

Method of cleaning electrostatic printhead

The invention relates to a method of printing a two-dimensional bit-mapped image having a number of pixels per row, the printhead having a row of ejection channels and each ejection channel having associated ejection electrodes to which voltages are applied in use. During printing, in order to cause volumes of fluid to be ejected from selected ejection channels of the printhead for printing, voltage pulses having values of predetermined amplitude and duration as determined by respective image pixel bit values generated by a raster image processor are applied, at a given pulse period, to the electrodes of the selected ejection channels. The part of the raster image corresponding to an ejection channel is scanned to determine the number of adjacent non-printing pixel periods prior to a pixel to be printed and, immediately prior to the printing of said pixel, a voltage pulse, having a value predetermined in accordance with the time, measured in units of the given pixel period, between the last pixel to be printed and said pixel to be printed, is applied to the ejection electrode.

Printhead calibration and printing

A method of reducing and/or preventing the accumulation of concentrated ink at an ejection point of a printhead of an electrostatic inkjet printer when ink is not being ejected at the ejection point, the method comprising reversing the electric field at the ejection point of the printhead during a non-printing phase of operation to reduce the concentration of ink at the ejection point.

Method of operating an electrostatic printhead

A method of calibrating a printhead, for printing two-dimensional bit-mapped images having a number of pixels per row, is disclosed for printheads () having a row of printing channels (). During printing, in order to cause volumes of charged particulate concentrations of one of a number of predetermined volume sizes to be ejected from selected ejection channels of the printhead to form printed pixels, control pulse values of respective predetermined amplitude and duration, as determined by respective image pixel bit values, are applied to the selected printing channels. The calibration method comprises providing an image () that causes each channel of the printhead to be driven with the same pulse value, and printing one or more test prints of the image. The pulse value for all channels is then varied () in a set of defined steps within the test print or between the test prints and the optical density of the test print or test prints measured () at positions arranged on a grid () to obtain data of print density and pulse value at positions across the printhead. A desired tone reproduction curve () is pre-selected for the print process represented by optical density versus image grey level. Then pulse values are calculated () from the measured test print or test prints that are estimated to produce the desired values of print density corresponding to selected values of image grey level and which may include non-printing pulse values, and the pulse value for each of said positions across the printhead for each of said image grey levels is recorded in memory ().

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Royston, United Kingdom

Ammar Lecheheb