Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1999-01-19
2001-02-06
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06183073
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to filling a printbar with ink. More particularly, this invention is directed to methods and apparatus that initially fill the printbar, such as a full width array printbar, with ink using positive pressure.
2. Description of Related Art
Thermal ink-jet printers generally include a plurality of thermal printheads for ejecting ink onto a recording medium, such as, for example, paper. Each thermal printhead has a resistor to selectively vaporize ink near the nozzle of a capillary-filled ink channel. The vaporized ink forms a bubble that temporarily expels an ink droplet and propels it toward the paper. These types of thermal heads are incorporated in either a carriage-type printer or a page width or full width array (FWA) type printer.
U.S. Pat. No. 5,359,356 to Ecklund describes the use of a slidable primer rod featuring a plunger which uses gravity to assist in collapsing a flexible ink bag for an ink jet printer. The only force applied to the ink container is the weight of the rod and plunger. U.S. Pat. No. 5,621,445 to Fong et al. and U.S. Pat. No. 4,714,937 to Kaplinsky also describe printers featuring flexible ink containers. U.S. Pat. No. 4,240,052 to Yu describes a momentumless shutdown of a jet drop printer in which a positive pressure is created in an ink manifold by a pump located prior to the manifold.
SUMMARY OF THE INVENTION
The page width or full width array (FWA) printer includes a stationary printbar with a length equal to or greater than the width of the paper. The paper is continuously moved past the printbar at a constant speed or in a stepwise manner during the printing process. U.S. Pat. No. 4,463,359 to Ayata et al., the disclosure of which is incorporated herein by reference in its entirety, provides an example of a page width printhead. The paper is supported on the platen and located adjacent to the printbar to remain a precise distance away from the thermal printhead nozzles. The platen either supplies the motive force to the paper to convey the sheets past the printbar or acts as a support.
To improve their material compatibility life, full width array (FWA) printbars are usually shipped dry of ink. U.S. Pat. No. 5,691,753 to Hilton, the disclosure of which is incorporated herein by reference in its entirety, describes a valving connector and ink handling system for thermal ink jet printbars. An initial filling operation is required when the printbar is installed into the machine before the system becomes functional.
In one printbar filling method, a vacuum or suction system or the like provides negative pressure, which is applied to a manifold exhaust port to pull ink from the ink supply. The ink supply is typically located below the printbar. This conventional method can incidentally and undesireably draw air into the manifold through the ink jets. It is important that the manifold is filled only with ink to the greatest extent possible, as air bubbles can interfere with the delivery of ink into the channels, potentially leading to print quality degradation.
A positive pressure fill can be accomplished by raising the ink supply above the printbar and allowing the ink to flow down into the manifold under the force of gravity. However, the ink supply is typically stationary and space considerations often will not allow the ink supply to be raised higher than the printbar. Consequently, it is frequently not possible to supply the ink to the printbar using gravity alone.
This invention provides methods and apparatus that fill a printbar using positive pressure.
According to one exemplary embodiment of the methods and apparatus of this invention, a full width array (FWA) printbar is filled with ink by the application of a steady force of pressure against the ink supply. The pressure must be great enough to force the ink over the static head height of the system. The pressure forces the ink into the printbar manifold. The force is preferably additionally applied until ink appears in a ventline window, at which time the printbar manifold is completely filled with ink. Continued applied positive pressure forces ink to flow into the ink jet channels, assuring that the channels are primed and ready for regular operation. The channels could also be primed using a vacuum priming system.
In a second exemplary embodiment of the apparatus of this invention, a solenoid or a motor, including a gear and a cam, provide the motive force to create the pressure against the ink supply. Pressure limiting springs may provide the desired positive pressure against the ink supply to fill the ink manifold. A “Fill Printbars” switch or button may be provided to operate the positive pressure ink filling apparatus. A reflective light sensor may be used to detect ink in the ventline window and automatically deenergize the positive pressure ink filling apparatus. A delay may be provided to delay the amount of time prior to the deenergizing of the positive pressure ink filling apparatus to allow the printbar ink channels to become fully primed.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of the preferred embodiments.
REFERENCES:
patent: 3930258 (1975-12-01), Dick et al.
patent: 4240082 (1980-12-01), Yu
patent: 4301460 (1981-11-01), Miura et al.
patent: 4463359 (1984-07-01), Ayata et al.
patent: 4714937 (1987-12-01), Kaplinsky
patent: 5359356 (1994-10-01), Ecklund
patent: 5621445 (1997-04-01), Fong et al.
patent: 5691753 (1997-11-01), Hilton
Hilton Brian S.
Rottman Robert M.
Le N.
Oliff & Berridg,e PLC
Vo Anh T.N.
Xerox Corporation
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