Fluid sprinkling – spraying – and diffusing – Processes – Vibratory or magneto-strictive projecting
Patent
1998-07-17
1999-11-30
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Processes
Vibratory or magneto-strictive projecting
2391022, 347 54, 347 55, B05B 1704
Patent
active
059927569
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for generation and ejection into air of discrete agglomerations of particulate material with a proportion of liquid from a liquid having the particular material therein. Such a method is disclosed in WO-A-93/11866 (PCT/AU92/00665) and includes providing the particulate material to an ejection location, applying an electrical potential to the ejection location to form an electric field and causing agglomerations to form at the ejection location. The agglomerations are ejected away from the ejection location by electrostatic means.
In order to control the ejection of agglomeration and particles the electrical potential needs to be varied from below a threshold to above a threshold. However, it has been found that, in certain constructions, it is difficult to achieve full control and true drop-on-demand performance. The present invention sets out to overcome this problem.
SUMMARY OF THE INVENTION
According to the present invention there is provided an apparatus for generation and ejection into air of discrete agglomerations of a particulate material with a proportion of liquid from a liquid having the particulate material therein, comprising an ejection location, means to apply an electrical potential to the ejection location to form an electric field at the location and means to supply liquid with the particulate material to the ejection location characterised by magnitude of said voltage being below that required to cause ejection of particles from the ejection location; and, additively with the oscillating voltage in order to cause the sum of the voltages at the ejection location to exceed the threshold required for ejection, when required.
By this means, the ejection voltage superimposed upon the oscillating voltage, when applied for less than one period of the oscillation voltage will enable a single drop to be ejected from the head thus enabling drop-on-demand operation.
The invention also includes the method of using that apparatus wherein an oscillating voltage is applied to the ejection location, the magnitude of the oscillating voltage being below that required to cause ejection of particles from the ejection location and an ejection voltage being superimposed on the oscillating voltage additively with the oscillating voltage in order to cause some of the voltages at the ejection location to exceed the threshold required for ejection, when required.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
One example of a method and apparatus according to the present invention will now be described with reference to the accompanying drawings in which:
FIG. 1 illustrates, diagrammatically, a cell of a printhead in section, together with flow vectors;
FIGS. 2,2A, 3 & 3A illustrate the same cell in greater detail, in section;
FIGS. 4A & 4B illustrate waveforms for the voltages applied to the electrode in the cell; and
FIG. 5 is a block diagram of an incipient drive control;
FIG. 6 is a partial perspective view of a portion of a second printhead incorporating ejection apparatus according to the present invention;
FIG. 7 is a view similar to FIG. 6 showing further and alternative features of the ejection apparatus; and
FIGS. 8 and 9 are partial sectional views through a cell of FIG. 6 and a modification thereof.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 to 3A show one cell of a printhead which incorporates a plurality of such cells for use in accordance with the present invention, the printhead using an electrophoretic method (as described generally in PCT/GB95/01215) in connection with FIG. 1) of concentrating insoluble ink particles. The printhead shown and described provides single pixel printing on a surface.
The printhead utilises concentration cells 120 of generally triangular internal shape, providing a cavity 121 to which an ink 122 is supplied under pressure (for example from a pump--not shown) through an inlet 123 and defining an ejection location for the particles in the fluid. To enable continuous
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patent: 3979756 (1976-09-01), Helinski et al.
patent: 4245225 (1981-01-01), Fillmore et al.
patent: 4523202 (1985-06-01), Gamblin
patent: 4719480 (1988-01-01), Elrod et al.
Goodchild Martin
Newcombe Guy Charles Fernley
Douglas Lisa Ann
Kashnikow Andres
Tonejet Corporation Pty. Ltd.
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