Typewriting machines – Sheet or web – For feeding sheet from stack or pack holder
Reexamination Certificate
2000-03-27
2001-04-03
Eickholt, Eugene (Department: 2854)
Typewriting machines
Sheet or web
For feeding sheet from stack or pack holder
C347S104000
Reexamination Certificate
active
06210055
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to hard copy methods and apparatus, more particularly to print media handling and, more specifically to a print media transport belt used in a wet colorant printing apparatus such as an ink-jet printer.
2. Description of Related Art
For convenience of explanation, while the present invention is useful for all wet colorant hard copy apparatus, it is described with respect to an ink-jet printer. The use of this exemplary embodiment is not intended as a limitation on the scope of the invention nor should any such intention be implied as the invention can be adapted to implementations using other wet colorant printing techniques, e.g., pigment-based and dye-based inks used in ink-jet printing, Wet toner laser printing systems, and the like, also synonymously referred to hereinafter as a “wet dye” printing; the terms “colorant” or “dye” shall be construed to encompass both color and black and grey scale wet printing techniques.
The art of the exemplary embodiment in ink-jet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, copiers, and facsimile machines employ ink-jet technology for producing hard copy. The basics of this technology are disclosed, for example, in various articles in the assignee's
Packard Journal
, Vol. 36, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No, 4 (August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No.1 (February 1994) editions, incorporated herein by reference for general background. Ink-jet devices are also described by W. J. Lloyd and H. T. Taub in
Output Hardcopy [sic] Devices
, chapter 13 (Ed. R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988). Further details to facilitate an understanding of the present invention are provided below with respect to FIG.
1
. For convenience of description, print media of all shapes, sizes, and varieties are referred to hereinafter simply as “paper.”
A well-known phenomenon of wet-colorant printing is “paper cockle,” the irregular surface produced in paper by the saturation and drying of ink deposits on the fibrous medium. As a sheet of paper gets saturated with ink, the paper grows and buckles in a seemingly random manner. Paper printed with images are more saturated with colorant than simple text pages and thus exhibit great paper cockle. Colors formed by mixing combinations of other color ink drops form greater localized saturation areas and also exhibit greater cockle tendencies.
In general, the prior art has approached the problem by using ribs that support the sheet of paper at various points along the width. In the state of the art, ink-jet printhead to paper separation is only about 0.5 to 1.5 millimeters. These ribbed paper support constructs allow any cockle growth to grow down away from the printing mechanism instead of toward it where contact could occur and cause further problems. Moreover, the use of ribbed paper support constructs alone is not adequate for larger dimensioned print zones. In order to hold print media flat under larger printheads a different holddown is required, such as a vacuum platen.
It has been discovered that media fiber directionality has a significant influence on the directionality of cockle growth. Papers generally have a grain in one direction longer than the other. Rib support constructs may thus be inadequate, depending on the nature of the media being printed. Feeding a sheet into a printing station of the hard copy apparatus with an orientation that minimizes cockle is impractical since it would limit the end-user's ability to select different media types.
There is a need for a paper transport and printing station paper holding device to substantially reduce and for practical purposes substantially eliminate problematical paper cockle.
SUMMARY OF THE INVENTION
In its basic aspects, the present invention provides a wet colorant hard copy device for reducing print media cockle. The device includes a belt mechanism for transporting print media through a wet colorant printing zone. The print media has a first surface and a second surface. The print media first surface adheres to at least one belt of the belt mechanism during transport. The print media is maintained in a substantially planar orientation on the belt mechanism at least through the printing zone such that the wet colorant is deposited on the print media second surface. The belt mechanism is splayed from a first cross dimension perpendicular to direction of travel of the print media as the print media enters the printing zone to a second cross dimension perpendicular to direction of travel of the print media as the print media exits the printing zone. The second dimension is greater than the first dimension. The belt mechanism includes at least one belt having a belt surface of a material for contacting the first surface wherein the belt surface has a coefficient of friction sufficient for gripping the first surface for applying lateral forces thereon or mechanisms for exerting a vacuum force on the first surface, or both.
In another basic aspect, the present invention provides a method for compensating for paper cockle in a wet colorant hard copy apparatus having a printing zone. The method includes the steps of: transporting a sheet of paper in a substantially planar orientation along a paper path through the printing zone, and gradually stretching the sheet of paper perpendicularly to the paper path from at least a point of entry of the printing zone in the paper path to at least a point of exit of the sheet from the printing zone in the paper path. The stretching includes stretching the sheet of paper at least over a distance greater than a paper path length of the printing zone when the ink dry time so requires.
In another basic aspect, the present invention provides an ink-jet hard copy apparatus for print media, including: an ink-jet printing mechanism for depositing wet colorant on the print media; and, mounted in the printer in relationship to the printing mechanism, a belt mechanism for sequentially transporting sheets of print media through a printing zone of the apparatus such that the print media has a first surface that adheres to at least one belt of the belt mechanism during the transporting and the print media is maintained in a substantially planar orientation on the belt at least through the printing zone such that the wet colorant is deposited on a print media second surface by the printing mechanism and wherein the belt is splayed from a first cross dimension perpendicular to direction of travel of the print media as the print media enters the printing zone to a second cross dimension perpendicular to direction of travel of the print media as the print media to at least a position wherein the print media exits the printing zone wherein the second dimension is greater than the first dimension.
It is an advantage of the present invention that it allows paper to grow due to wet colorant saturation, yet keeps the paper substantially flat.
It is an advantage of the present invention that it combines the functions of a paper transport and a paper platen.
It is another advantage of the present invention that it compensates for paper cockle regardless of print media fiber orientation.
Other objects, features and advantages of the present invention will become apparent upon consideration of the following explanation and the accompanying drawings, in which like reference designations represent like features throughout the drawings.
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patent: 0603505A1 (1
Chen Angela S.
Downing Steven P.
Eickholt Eugene
Hewlett--Packard Company
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