Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1997-10-07
2001-09-11
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S068000, C347S054000
Reexamination Certificate
active
06286925
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention pertains to the art of printheads and, more particularly, to a method of controlling piezo elements in a printhead of a droplet generator.
An example of a method for operation of a printhead of an ink jet printer is disclosed in WO 95/25011. That printhead has a multitude of adjacently arranged channels, each of which is allocated to a nozzle. By activation of a channel, a droplet of ink is expelled from the respective nozzle. Through impulse control, the result is obtained that pressure waves within an activated channel will fade more rapidly. With this solution, the amplitude values of the impulses are adjusted, for which purpose linear amplifiers are needed. Such devices, though, have a poor efficiency and require expensive electronic components. The pulse widths are limited to whole number multiples of an acoustic period L/c, wherein L represents the length of the channel and c the sound velocity in the liquid. It is only possible, due to the complexity of the impulses, to operate all channels with the same impulse voltage and with the same pulse width.
Another example of an operating process for a piezo-electrical printhead is shown in U.S. Pat. No. 5,461,403. The width of the control impulses is varied in order to modulate the droplet velocity and the droplet volume. This is intended to create various stages of gray. A variation of the impulse width results in a change of the droplet size. The large number of impulse parameters requires expensive tabulation. Because of the complexity of the table, it is only possible to operate all channels with the same impulse voltage and the same impulse width.
In both of the previously known solutions, the print image may be affected if the printhead is moved at constant relative velocity vis-a-vis the paper to be imprinted.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the operation of a printhead which avoids the above drawback. The objective is solved by a combination of characteristics.
According to one aspect of the present invention, a method of controlling piezo-elements in a printhead of a droplet generator with a multitude of adjacently arranged ink channels is provided. The piezo-elements are controlled so that the exit velocity of the droplets is independent of the number of simultaneously activated neighboring channels
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.
REFERENCES:
patent: 5142296 (1992-08-01), Lopez et al.
patent: 5221931 (1993-06-01), Moriyama
patent: 5438350 (1995-08-01), Kerry et al.
patent: 5461403 (1995-10-01), Wallace et al.
patent: 5764247 (1998-06-01), Asai
patent: 0376532 (1990-07-01), None
patent: 0 713 773 A2 (1995-10-01), None
patent: WO 95/25011 (1995-09-01), None
Patent Abstracts of Japan, vol. 16, No. 480 (M-1321), Oct. 6, 1992; and JP 04175167A, Jun. 23, 1992.
Patent Abstracts of Japan, vol. 18, No. 173 (M-1581), Mar. 24, 1994; and JP 05338165, Dec. 21, 1993.
Beurer Gerhard
Heinzl Joachim
Kretschmer Joachim
Möstl Peter
Zollner Alfred
Barlow John
Brooke Michael S
Fay Sharpe Fagan Minnich & McKee LLP
Pelikan Produktions AG
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