Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-07-17
2001-06-19
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06247797
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of and apparatus for ejecting material from a liquid. More particularly, the method and apparatus employed may be generally of the type described in WO-A-93-11866, PCT/GB95/01215 and WO-A-94-18011, the disclosure of which is incorporated by reference. In the methods described in these patent applications an agglomeration or concentration of particles is achieved at an ejection location and from the ejection location particles are then ejected onto a substrate, eg. for printing purposes. In the case of an array printer, plural cells may be arranged in one or more rows. In other types of printing apparatus, in which charged liquid droplets are jetted onto a substrate, such as shown in JP-A-05 116 322, U.S. Pat. Nos. 3,060,429 & 3,887,928, additional electrodes may be provided for guiding the charged droplets to a charged substrate.
It is thus known in the art to generate and eject particles by use of electrostatic fields, but problems exist with this type of ejection, such as (a) controlling the direction of movement of ejected droplets or particles, which depends upon close control of the electrostatic field in the vicinity of the ejection electrode, (b) the difficulty of switching and the remote location of electrical earthing, (c) the dependence of ejection on the gap between the ejection electrode and substrate, and (d) the attraction of airborne particles into the ejector during the application of the electrostatic field.
SUMMARY OF THE INVENTION
According to the present invention there is provided an apparatus for ejecting particulate material from a liquid, the apparatus comprising a plurality of ejection locations disposed in a linear array, each ejection location having a corresponding ejection electrode, whereby the ejection electrodes are disposed in a row defining a plane; means to apply an electrical potential to the ejection electrodes to form an electric field at the ejection locations; means for supplying liquid containing the particulate material to the ejection locations; and a secondary electrode disposed transverse to the plane of the ejection electrodes.
A plurality of secondary electrodes may be provided or else a secondary electrode common to the ejection locations.
Thus, the sensitivity of the apparatus to influence by external electric fields may be reduced as may its sensitivity to variations in the distance between the ejection location and the substrate onto which the particles are ejected.
The invention also includes a method of operating such apparatus to eject agglomerations of particles onto the substrate.
In use the voltage on the secondary electrode or electrodes relative to the voltage of the ejection electrodes is controlled by a suitable electronic control circuit.
The use of a secondary electrode is particularly advantageous in such an array system in which there are a plurality of cells in a row to reduce the number of connections necessary to the electrodes at the ejection location. For example, by connecting adjacent electrodes at the electrode location together in pairs and similarly for the secondary electrode the number of connections required for each set of electrodes is reduced by half. Then, by disposing the connected pairs of the secondary electrodes offset with respect to the connected pairs of electrodes at the ejection location, control of ejection and thus of printing can be achieved by selective application of voltages to the electrodes at the ejection location and the secondary electrodes in a “matrix addressing” mode since each ejection location electrode of a connected pair will be disposed opposite a secondary electrode of a different connected pair, ie. the opposing secondary electrodes will not be electrically connected. Thus, ejection voltages can be applied to the ejection location electrodes of a pair and ejection can be individually controlled from each of the respective cells by the application of different voltages on the opposing secondary electrodes. Further multiplexing can be achieved if desired.
Preferably, the secondary electrode is insulated and the ejection electrode is not, but in certain designs both may be non-insulated or both may be insulated or the ejection electrode insulated and the secondary electrode non-insulated.
REFERENCES:
patent: 3887928 (1975-06-01), Ohno et al.
patent: 4477869 (1984-10-01), Rudd, III
patent: 4568955 (1986-02-01), Hosoya et al.
patent: WO 93/11866 (1993-06-01), None
patent: 0703080 A2 (1996-03-01), None
patent: 57-027760 (1982-02-01), None
patent: 57 -027759 (1982-02-01), None
patent: 01206062 (1993-06-01), None
Emerton Neil
Janse Van Rensburg Richard Wilhelm
Newcombe Guy Charles Fernley
Taylor Peter John
Teape John
Barlow John
Dykema Gossett PLLC
Gordon Raquel Yvette
Tonejet Corporation PTY, Ltd.
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