Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2003-11-17
2004-10-05
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06799836
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to printers, and in particular to digital inkjet printers.
Co-Pending Applications
Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee of the present invention on 24 May 2000:
PCT/AU00/00578 PCT/AU00/00579 PCT/AU00/00581 PCT/AU00/00580
PCT/AU00/00582 PCT/AU00/00587 PCT/AU00/00588 PCT/AU00/00589
PCT/AU00/00583 PCT/AU00/00593 PCT/AU00/00590 PCT/AU00/00591
PCT/AU00/00592 PCT/AU00/00584 PCT/AU00/00585 PCT/AU00/00586
PCT/AU00/00594 PCT/AU00/00595 PCT/AU00/00596 PCT/AU00/00597
PCT/AU00/00598 PCT/AU00/00516 PCT/AU00/00517 PCT/AU00/00511
Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending application, PCT/AU00/01445 filed by the applicant or assignee of the present invention on 27 Nov. 2000. The disclosures of these co-pending applications are incorporated herein by cross-reference. Also incorporated by cross-reference, is the disclosure of a co-filed PCT application, PCT/AU01/00238 (deriving priority from Australian Provisional Patent Application No. PQ6059).
BACKGROUND OF THE INVENTION
Recently, inkjet printers have been developed which use printheads manufactured by micro-electro mechanical system(s) (MEMS) techniques. Such printheads have arrays of microscopic ink ejector nozzles formed in a silicon chip using MEMS manufacturing techniques.
Printheads of this type are well suited for use in pagewidth printers. Pagewidth printers have stationary printheads that extend the width of the page to increase printing speeds. Pagewidth printheads do not traverse back and forth across the page like conventional inkjet printheads, which allows the paper to be fed past the printhead more quickly.
To reduce production and operating costs, the printheads are made up of separate printhead modules mounted adjacent each other on a support beam in the printer. To ensure that there are no gaps or overlaps in the printing produced by adjacent printhead modules it is necessary to accurately align the modules after they have been mounted to the support beam. Once aligned, the printing from each module precisely abuts the printing from adjacent modules.
Unfortunately, the alignment of the printhead modules at ambient temperature will change when the support beam expands as it heats up during printhead operation. Furthermore, if the printhead modules are accurately aligned when the support beam is at the equilibrium operating temperature, there may be unacceptable misalignments in any printing before the beam has reached the operating temperature. Even if the printhead is not modularized, thereby making the alignment problem irrelevant, the support beam and printhead may bow because of different thermal expansion characteristics. Bowing across the lateral dimension of the support beam does little to affect the operation of the printhead. However, as the length of the beam is its major dimension, longitudinal bowing is more significant and can affect print quality.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a printhead assembly for a digital ink-jet printer, the printhead assembly including:
a support member for attachment to the printer;
a printhead adapted for mounting to the support member;
the support member having an outer shell and a core element defining at least one ink reservoir such that the effective coefficient of thermal expansion of the support member is substantially equal to the coefficient of thermal expansion of the printhead.
Preferably, the outer shell is formed from at least two different metals laminated together and the printhead includes a silicon MEMS chip. In a further preferred form, the support member is a beam and the core element is a plastic extrusion defining four separate ink reservoirs. In a particularly preferred form, the metallic outer shell has an odd number of longitudinally extending layers of at least two different metals, wherein layers of the same metal are symmetrically disposed about the central layer.
It will be appreciated that by laminating layers of uniform thickness of the same material on opposite sides of the central layer, and at equal distances therefrom, there is no tendency for the shell to bow because of a dominating effect from any of the layers. However, if desired, bowing can also be eliminated by careful design of the shells cross section and variation of the individual layer thicknesses.
In some embodiments, the printhead is a plurality of printhead modules positioned end to end along the beam.
REFERENCES:
patent: 6270196 (2001-08-01), Uno et al.
patent: 10157105 (1998-06-01), None
patent: 11010861 (1999-01-01), None
patent: 2000263768 (2000-09-01), None
Gordon Raquel Yvette
Silverbrook Research Pty Ltd
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