Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-07-19
2002-10-01
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S040000
Reexamination Certificate
active
06457806
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to ink-jet printing and, more specifically, to microstepping the print media between printing passes in ink-jet hard copy apparatus having printheads firing the same colorant.
2. Description of Related Art
The art of ink-jet technology is relatively well developed. Commercial products such as computer printers, graphics plotters, 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 Hewlett-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. 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).
Generally, in the thermal ink-jet field, an ink-jet pen or print cartridge is provided with a printhead, having an orifice plate constructed in combination with heating elements. Thermal excitation of ink near nozzles at the orifice plate is used to eject ink droplets through the miniature nozzles and orifices onto a print medium, rendering alphanumeric characters or forming graphical images using dot matrix manipulation. Other types of ink droplet generators, such as the use of piezoelectric transducers, are also known in the art. This technology is also referred to a “pixel-array” printing; the term refers to a relatively large two-dimensional imposed array or matrix of uniformly spaced and sized cells called “picture elements,” or “pixels” for short. By “turning on” certain pixels with ink, light, or the like, an image of text and graphics can be formed on the array. The intrinsic binary nature of this image becomes less obvious and the perceived image quality improves as the number of pixels per unit area increases (from unaided visual perception of individual dots at low resolutions to continuous image perception at high resolutions such as in photo-quality printing).
FIGS. 1 and 2
depict ink-jet hard copy apparatus, in this exemplary embodiment a computer peripheral printer,
101
. A housing
103
encloses the electrical and mechanical operating mechanisms of the printer
101
. Operations are administrated by an electronic controller
102
(usually a microprocessor-controlled printed circuit board) connected by appropriate cabling to a computer (not shown).
Cut-sheet print media
105
, loaded by the end-user onto an input tray
107
, is fed by a suitable paper-path transport mechanism—illustrated schematically in FIG.
2
—to an internal printing station where graphical images or alphanumeric text is created. In an exemplary media transport as shown in
FIG. 2
, a sheet pick device
201
delivers a sheet
105
to a transport drum
203
and pinch roller
205
nip. The sheet
105
follows the drum
203
and paper guide
204
to the printing zone
207
. Looking back to
FIG. 1
also, a carriage
109
, mounted on a slider
111
, scans the print medium in the printing zone
207
. An encoder
113
is provided for keeping track of the position of the carriage
109
at any given time. A set
115
of ink-jet pens
117
IN
(where I=ink color, N=redundant colorant pen number), having multiple printheads firing identical ink and one black ink pen
117
K, is releasably mounted in the carriage
109
for easy access. In pen-type hard copy apparatus, separate, replaceable or refillable, ink reservoirs (not shown) are located within the housing
103
and appropriately coupled to the pen set
115
via ink conduits (not shown). Once a printed page is completed, the print medium is ejected by a selectively driven star wheel
209
(
FIG. 2
only) into an output tray
119
. The media advance axis is defined as the y-axis, the printhead scanning axis is the x-axis, and the printhead drop firing axis is the z-axis.
For convenience of description, the word “paper” will be used as synonymous for all types of print media; the word “ink” will be used for all compositions of colorants; the word “printer” will be used for all types of hard copy apparatus. No limitation on the scope of the invention is intended nor should any be implied.
The art and technology of ink drop placement are generally referred to as “print modes.” Improving print quality by placing multiple drops on each pixel or overlapped in adjoining pixels are known ink-jet printing techniques; see e.g., U.S. Pat. No. 4,963,882 filed in December 1988 by Hickman for PRINTING OF PIXEL LOCATIONS BY AN INK JET PRINTER USING MULTIPLE NOZZLES FOR EACH PIXEL OR PIXEL ROW (Hickman '882), and U.S. Pat. No. 5,583,550 first filed in September 1989 by Hickman for INK DROP PLACEMENT FOR IMPROVED IMAGING. Hickman '882 describes the use of using multiple nozzles per pixel location or per pixel row; this also was also known as the dot-on-dot, DOD, print mode. U.S. Pat. No. 4,999,646 filed in November 1989 by Trask for a METHOD FOR ENHANCING THE UNIFORMITY AND CONSISTENCY OF DOT FORMATION PRODUCED BY COLOR INK JET PRINTING describes a print mode of overlapping complementary dot patterns, called “shingling.” (Each is assigned to the common assignee herein and incorporated by reference.)
Multi-pass print modes are used to improve print quality by scanning each printed swath a number of times; see e.g., U.S. Pat. No. 4,967,203 filed in September 1989 by Doan et al. for an INTERLACE PRINTING PROCESS (assigned to the common assignee herein and incorporated by reference). In July 1989, Hickman filed for a now issued patent regarding PRINT QUALITY OF DOT PRINTERS, U.S. Pat. No. 4,965,593 (Hickman '593). No pixel locations adjacent to each other are printed on the same traverse by a printhead. In a single printhead having at least two colorant sources, the spacing between adjacent sources in the media advance direction is made an integer (greater than one) multiple of the fixed pixel spacing. The printhead traverses the paper in a direction perpendicular to the paper advance direction, simultaneously depositing droplets of the colorant such that colorant is not deposited onto transversely adjacent pixels by the colorant sources and achieving a higher print resolution than the nozzle spacing. Advancing a paper transport stepper motor in small increments is also discussed in Hickman '593.
In more recent ink-jet apparatus, separate printheads per color ink also have been used, mainly to improve throughput. In assignee's co-pending patent app. U.S. patent application Ser. No. 09/311,919, D. Pinkemell shows redundant pen sets mounted in the y-axis to allow simultaneous printing of multiple swaths. Multiple like-colorant printheads per swath have also been proposed, such as in the present applicant's U.S. patent application Ser. No. 09/233,575 for a DRUM-BASED PRINTER USING MULTIPLE PENS PER COLOR (also assigned to the common assignee here and incorporated by reference). In the basics, ink-jet pens are used in a printer so that the swaths printed by individual pens are combined into a resultant swath wider in the paper path advance axis than single pens of each ink could produce, increasing throughput. The print medium is carried on a drum and advanced through the printer. Sets of two pens, each set having the same color of ink, are carried near the drum with the two pens arranged such that the swath of one pen is adjacent to the swath of the other pen in a direction that is parallel to the drum axis. A carriage assembly provides an arrangement for combining the swath widths of the individual pens. The components of the carriage assembly are such that two pens of the same color ink are precisely positioned relative to each other, thereby to meet a very close tolerance requirement for arranging two pens of the same colorant.
Given the commercial desire for very high print resolutions, e.g., 1200+ dots-per-inch, and
Hewlett--Packard Company
Pham Hai
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