Incremental printing of symbolic information – Ink jet – Ejector mechanism
Patent
1991-07-26
1996-02-13
Fuller, Benjamin R.
Incremental printing of symbolic information
Ink jet
Ejector mechanism
347 75, B41J 214
Patent
active
054914990
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an inkjet nozzle for an inkjet printer.
Inkjet printers generally have at least one inkjet nozzle and an ink supply system which supplies ink at a suitable pressure to the inkjet nozzle. The ink is forced out of an outflow aperture and injected in the form of a series of small drops of equal size onto a substrate, such as a sheet of paper. The ink drops pass a charging electrode where the drops are selectively provided with an electric charge, and then pass a pair of deflections plates. The charged drops are deflected as a reaction to a voltage which is applied to the deflection plates, so that the drops either go onto the substrate or are deflected and collected. The collected ink can be recirculated to the supply system.
Inkjet printers can work according to two different principles, the continuous inkjet principle and the drop on demand principle. In the continuous inkjet principle, an inkjet is generated by forcing ink at high pressure through an inkjet nozzle. The pressure lies between 20 and 60 bar. This products an inkjet which by means of excitation is converted into a series of small ink drops which hit the substrate at high velocity. The number of drops which is generated lies between 100,000 and 2,000,000 drops per second. In this case of the drop on demand principle, an inkjet is not generated under high pressure, but individual drops are generated and discharged onto the substrate. This technique is characterized by a low pressure (2-10 bar) which is offered in the form of pulses. The number of drops generated lies between 1,000 and 30,000 drops per second.
In inkjet nozzles for the continuous inkjet principle, drop information is generally stimulated by an ultrasonic vibration element which produces a high-frequency vibration. The pressure pulse needed for drop formation is 0.1% of the working pressure. For a working pressure of 30 bar, this is approximately 0.03 bar, which is very small compared with inkjet printers operating by the drop on demand principle, where the pressure pulses are a hundred times that.
IBM-Technical Disclosure Bulletin, Vol. 20, No. 11A, April 1978, p 4485 "Inkjet nozzle fabrication" by J. M. Huellemeier et al. discloses an inkjet nozzle for an inkjet printer comprising a housing made of an essentially undeformable material and containing an ink supply channel, which at its outflow end is closed by an end wall which is fixed to the housing and which is provided with an ink outflow channel lying in line with the ink supply channel. This known inkjet nozzle has no vibration element and the document is silent about the dimensions of the ink outflow channel.
The object of the invention is to provide an improved inkjet nozzle for an inkjet printer working on the continuous inkjet principle.
According to the invention this object is attained by an inkjet nozzle comprising a housing made of an essentially undeformable material and containing an ink supply channel, which at its outflow end is closed by an end wall which is fixed to the housing and which is provided with an ink outflow channel lying in line with the ink supply channel, wherein the housing of the inkjet nozzle is essentially block-shaped, the outflow channel has a diameter between 3 and 30 microns (.mu.m) and a length which is 3 to 30 times greater than its diameter, and near the outflow end of the ink supply channel the housing is provided with an ultrasonic vibration element.
The inkjet nozzle according to the invention is sturdy, of compact construction, and stable during use. During use it produces a stable inkjet consisting of a series of small ink drops with reproducible characteristics. The inkjet nozzle is also reliable and easy to clean.
U.S. Pat. No. 4,228,440 describes an inkjet nozzle for an inkjet printer comprising a housing containing an ink supply channel which at its outflow end is closed by an end wall which is fixed to the housing and which is provided with an ink outflow channel lying in line with the ink supply channel. The inkjet nozzle is further provided
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"Ink Jet Nozzle Fabrication", IBM Corp., Technical Disclosure Bulletin, vol. 20, No. 11A, Apr. 1978, p. 4485.
Bibbe Christiaan P. M.
Hester Martinus J.
Prinsen Wilhelmus J. C.
van de Weyer Fransiscus J. M.
Bobb Alrick
Fuller Benjamin R.
Stork X-cel B.V.
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