Multiple-head ink jet printer

Incremental printing of symbolic information – Ink jet – Ejector mechanism

Reexamination Certificate

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C347S105000

Reexamination Certificate

active

06309046

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to ink jet printers and particularly to those having a plurality or multiplicity of ink jet heads in alignment for printing as many characters or symbols on a continuous strip of paper or like printable material traveling along a predefined path.
One of the essentials for production of high quality printings by ink jet printers of the kind under consideration is that there be an unvarying spacing between the series of ink jet heads and the surface of the strip of paper to be printed. Typical of contrivances heretofore made to attain this objective are those described and claimed by Japanese Unexamined Patents Publication Nos. 5-124284 and 6-199457. They are alike in teaching a single ink jet head or pen printer wherein a continuous web or individual sheets of paper or the like are printed upon while traveling on a fixed, flat platen, by which is held constant the spacing between head and paper.
The fixed flat platen has proved unsatisfactory, however, when incorporated in multiple head ink jet printers in which a multiplicity of ink jet heads are aligned along a predefined path of a continuous strip of paper or like printable material for printing as many characters or symbols thereon. Consider an elongate flat platen mounted opposite to the series of ink jet heads, and with the paper strip fed over the platen by guide rollers or pairs of feed rollers disposed adjacent to both ends of the platen. The paper strip has been very easy to flutter over the platen by reason of the inconveniently long distance between the guide rollers or the like, thereby giving rise to variations in the spacing between the paper strips surface and the heads.
Such inconveniences have become even more pronounced in printers using an aqueous ink. Almost unavoidably stretched out, slackened, or creased by the ink moisture, the paper strip has often failed to travel at a desired constant distance from the ink jet heads, no matter how much it is tensioned as by increased feeding force or braking.
The Japanese unexamined patent publications cited above employ means in addition to the flat platen for holding the paper against it. However, such means are effective only in single-head printers, not applicable to multiple head devices where the paper must travel stably a much longer distance past a row or rows of multiple heads.
SUMMARY OF THE INVENTION
It is an object of this invention to keep the strip, ribbon or web of paper or like printable material from fluttering while traveling any elongate distance past a row or rows of multiple heads in ink jet printers of the kind defined.
Another object of the present invention is to minimize the noted adverse side effects of use of an aqueous ink in attaining the first recited object.
Still another object of the present invention is to accomplish the foregoing objects by use of practically the simplest possible means that can be readily incorporated in multiple head ink jet printers of various known general constructions.
Summarized in brief, the present invention provides a multiple-head ink jet printer for printing on a continuous strip of paper or like printable material, comprising a pair of guide means spaced from each other for guiding a continuous strip of printable material through a printing station within the printer, at least one intermediate guide member disposed intermediately between the pair of guide means for providing therebetween a guide path having a bend in it along which the strip of printable material is to travel through the printing station, and a plurality of ink jet heads positioned for printing on the strip of printable material traveling between one of the guide means and the intermediate guide member and between the intermediate guide member and the other of the guide means.
In the practice of this invention the pair of guide means may take the form of guide rollers, although such means may perform the additional function of feeding the strip. The intermediate guide member may then be in the form of a roller, disposed intermediately between the pair of guide rollers and offset from a plane tangent to both guide rollers, preferably toward that side of the plane which is opposite to the side where the guide rollers lie.
There is thus provided a V-shaped guide path, having a bend, preferably obtuse-angled, in it. The strip may travel along such a bent path under greater tension than along the conventional straight path. The guide path according to the instant invention may be restated as a succession of two or more short, straight divisions instead of a single rectilinear path according to the prior art.
In the representative embodiments of the invention to be disclosed subsequently, two or four ink jet heads are provided by the side of each straight part of the guide path for printing on the strip traveling along that part. However, only one head may be provided for each division of the path if it is desired to make each path division sufficiently short to preclude any likelihood of the strip slacking, wrinkling, or otherwise going out of shape, particularly as in the case of a printer for use with an aqueous ink.
How many intermediate guide rollers should be employed, that is, how many straight parts the guide path should be divided into, depends at least in part upon how many ink jet heads the printer has. It is among the advantages of this invention that in printers having very large numbers of ink jet heads, correspondingly large numbers of intermediate guide rollers may be employed according to the principles of the invention without substantially adding to the manufacturing costs of the printers.


REFERENCES:
patent: 5828814 (1998-10-01), Cyman et al.
patent: 5906156 (1999-03-01), Shibuya et al.
patent: 5-124284 (1993-05-01), None
patent: 6-199457 (1994-07-01), None

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