Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1999-10-29
2001-11-06
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06312113
ABSTRACT:
FIELD OF THE INVENTION
The present invention in general relates to a circulation system for mixing ink jet ink and in particular to a circulation system for mixing pigmented ink jet ink.
BACKGROUND OF THE INVENTION
Ink jet printing is a well-known technique by which printing is accomplished without contact between the printing device and the substrate on which the printed characters are deposited. Briefly described, ink jet printing involves the technique of projecting a stream of ink droplets to a surface and controlling the direction of the stream so that the droplets are caused to form the desired printed image on that surface. This technique of noncontact printing is well suited for application of characters onto a variety of surfaces including porous and non-porous surfaces.
Reviews of various aspects of ink jet printing can be found in these publications: Kuhn et al., Scientific American, April, 1979, 162-178; and Keeling, Phys. Technol., 12(5), 196-303 (1981). Various ink jet apparatuses are described in the following U.S. Pat. Nos. 3,060,429, 3,298,030, 3,373,437, 3,416,153, and 3,673,601.
Pigmented ink, which includes insoluble pigment particles, is frequently used in ink jet printing. Although it has a number of desirable characteristics, pigmented ink also has a significant drawback. The pigment particles tend to agglomerate and settle at the bottom surface of the ink supply container, causing nozzle clogging and disruption in printing, as well as a decrease in print contrast. The nozzles typically have a diameter around about 2.5 to 3.0 thousandths of an inch.
Attempts have been made to maintain pigment particles uniformly suspended in the ink jet ink. However, many of these attempts have not been successful or provide techniques having drawbacks. For example, one technique involves the use of a magnetic stirrer disposed in the ink container. The rod-shaped magnetic stirrer, usually disposed at the bottom of the container, is driven by a varying magnetic field generated by rotating magnets outside of the container.
Use of this technique in ink jet printing, however, is costly and complex. The system occupies a large volume of printer space. In addition, the system has a relatively short service life, because it involves moving mechanical parts causing significant mechanical wear. Further, it is time-consuming to extract the magnetic rod from a depleted ink container and deposit the magnetic rod in a full container every time a depleted ink container is replaced by a new ink container.
The foregoing indicates that there exists a need for a system that reduces or eliminates pigment settling. There further exists a need for an ink jet printing system that prints without nozzle clogging for extended periods of time.
These and other advantages of the present invention as well as additional inventive features will be apparent from the detailed description of the invention set forth herein below.
BRIEF SUMMARY OF THE INVENTION
Many of the foregoing needs have been fulfilled by the present invention which provides a circulation system for mixing ink and overcomes the drawbacks of the conventional techniques. The present invention utilizes the technique of circulation to maintain the pigment particles suspended in the ink and prevent agglomeration of pigment particles.
In accordance with one aspect of the invention, a circulation system for mixing ink jet ink includes a container, a pump, and first and second tubes. The container has a bottom surface and a top portion opposing the bottom surface. The pump has an inlet port and an outlet port. The first tube has first and second ends. The first end of the first tube is connected to the inlet port of the pump, and the second end of the first tube includes a plurality of openings in close proximity to the bottom surface of the container. The second tube has first and second ends. The first end of the second tube is connected to the outlet port of the pump, and the second end of the second tube has an opening disposed in the top portion.
In accordance with another aspect of the invention, a method for mixing ink jet ink includes drawing ink from a bottom surface of a container through a first tube having a plurality of openings in close proximity to the bottom surface of the container; and returning the ink drawn from the container to the container through a second tube having an opening disposed in a top portion of the container.
In accordance with a further aspect of the invention, a method for ink jet printing onto a substrate includes drawing ink from a bottom surface of a container through a first tube having a plurality of openings in close proximity to the bottom surface of the container, returning the ink, which is drawn from the container through the first tube, to the container through a second tube, drawing ink from the container through a third tube, directing a stream of ink droplets, formed from the ink from the third tube, to the substrate, and controlling the direction of the droplets to form a desired image.
The circulation system in accordance with embodiments of the present invention has a number of advantages over known devices. For example, a printer device incorporating the circulation system of the present invention is relatively simple to operate and inexpensive. Embodiments of printer devices can be of small size. In addition, the device involves a minimum number of moving mechanical parts, reducing mechanical wear and increasing its service life. Further, because the tube connected to the inlet port of the pump includes a number of openings disposed in close proximity to the bottom surface of the container, the device is effective in collecting pigment particles from substantially all portions of the bottom surface and return the particles to other portions of the container, thus resulting in pigment particles uniformly suspended in the container.
While the invention has been described and disclosed below in connection with certain embodiments and procedures, it is not intended to limit the invention to those specific embodiments. Rather it is intended to cover all such alternative embodiments and modifications as fall within the spirit and scope of the invention.
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Le N.
Leydig , Voit & Mayer, Ltd.
Marconi Data Systems Inc.
Nghiem Michael
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