Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-10-29
2003-07-01
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S033000
Reexamination Certificate
active
06585348
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to printer cartridges and methods and more particularly relates to an inkjet printer cartridge adapted for enhanced cleaning thereof, and method of assembling the printer cartridge.
An ink jet printer produces images on a recording medium by ejecting ink droplets onto the recording medium in an image-wise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the ability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
In this regard, an ink jet printer comprises a print head cartridge that includes a plurality of ink ejection chambers and a plurality of ink ejection orifices in communication with respective ones of the ink ejection chambers. At every orifice a pressurization actuator is used to produce an ink droplet. In this regard, either one of two types of actuators may be used. These two types of actuators are heat actuators and piezoelectric actuators. With respect to piezoelectric actuators, a piezoelectric material is used. The piezoelectric material possesses piezoelectric properties such that an electric field is produced when a mechanical stress is applied. The converse also holds true; that is, an applied electric field will produce a mechanical stress in the material. Some naturally occurring materials possessing this characteristic are quartz and tourmaline. The most commonly produced piezoelectric ceramics are lead zirconate titanate, lead metaniobate, lead titanate, and barium titanate. When a piezoelectric actuator is used for inkjet printing, an electric pulse is applied to the piezoelectric material causing the piezoelectric material to bend, thereby squeezing an ink droplet from an ink body in contact with the piezoelectric material. The ink droplet thereafter travels toward and lands on the recording medium. One such piezoelectric inkjet printer is disclosed by U.S. Pat. No. 3,946,398 titled “Method And Apparatus For Recording With Writing Fluids And Drop Projection Means Therefor” issued Mar. 23, 1976 in the name of Edmond L. Kyser, et al.
With respect to heat actuators, such as found in thermal ink jet printers, a heater locally heats the ink body and a quantity of the ink phase changes into a gaseous steam bubble. The steam bubble raises the internal ink pressure sufficiently for an ink droplet to be expelled towards the recording medium. Thermal inkjet printers are well-known and are discussed, for example, in U.S. Pat. No. 4,500,895 to Buck, et al.; U.S. Pat. No. 4,794,409 to Cowger, et al.; U.S. Pat. No. 4,771,295 to Baker, et al.; U.S. Pat. No. 5,278,584 to Keefe, et al.; and the Hewlett-Packard Journal, Vol. 39, No. 4 (August 1988), the disclosures of which are all hereby incorporated by reference.
The print head cartridge itself may be a carriage mounted print head cartridge that reciprocates transversely with respect to the recording medium (i.e., across the width of the recording medium) as a controller connected to the print head cartridge selectively fires individual ones of the ink ejection chambers. Each time the print head traverses the recording medium, a swath of information is printed on the recording medium. After printing the swath of information, the printer advances the recording medium the width of the swath and the print head cartridge prints another swath of information in the manner mentioned immediately hereinabove. This process is repeated until the desired image is printed on the recording medium. Alternatively, the print head cartridge may be a page-width print head cartridge that is stationary and that has a length sufficient to print across the width of the recording medium. In this case, the recording medium is moved continually and normal to the stationary print head cartridge during the printing process.
Inks useable with piezoelectric and thermal ink jet printers, whether those printers have carriage-mounted or page-width print head cartridges, are specially formulated to provide suitable images on the recording medium. Such inks typically include a colorant, such as a pigment or dye, and an aqueous liquid, such as water, and/or a low vapor pressure solvent. More specifically, the ink is a liquid composition comprising a solvent or carrier liquid, dyes or pigments, humectants, organic solvents, detergents, thickeners, preservatives and other components. Moreover, the solvent or carrier liquid may be water alone or water mixed with water miscible solvents such as polyhydric alcohols, or organic materials such as polyhydric alcohols. Various liquid ink compositions are disclosed, for example, by U.S. Pat. No. 4,381,946 titled “Ink Composition For Ink-Jet Recording” issued May 3, 1983 in the name of Masafumi Uehara, et al.
Such inks for inkjet printers, whether of the piezoelectric or thermal type, have a number of special characteristics. For example, the ink should incorporate a nondrying characteristic, so that drying of the ink in the ink ejection chambers is hindered or slowed to such a state that by occasional spitting of ink droplets, the ejection chambers and corresponding orifices are kept open and free of dried ink. Of course, the inkjet print head cartridge is exposed to the environment where the inkjet printing occurs. Thus, the previously mentioned orifices are exposed to many kinds of air born particulates, such as dust, dirt and paper fibers. Particulate debris may accumulate on surfaces formed around the orifices and may accumulate in the orifices and chambers themselves. That is, the ink may combine with such particulate debris to form an interference burr those blocks the orifice or that alters surface wetting to inhibit proper formation of the ink droplet. Blocking the orifice interferes with proper ejection of ink droplets, thereby altering the flight path of the ink droplets and causing the ink droplets to strike the recording medium in unintended locations. The particulate debris should be cleaned from the surface and orifice to restore proper droplet formation and proper ink droplet trajectory. In the prior art, this cleaning is commonly accomplished by brushing, wiping, spraying, vacuum suction, and/or spitting of the ink through the orifice.
A representative inkjet print head cartridge cleaner is disclosed by U.S. Pat. No. 5,907,335 titled “Wet Wiping Printhead Cleaning System Using A Non-Contact Technique For Applying A Printhead Treatment Fluid” issued May 25, 335 in the name of Eric Joseph Johnson, et al. The Johnson, et al. patent discloses cleaning in printers employing a “wiper” which slidingly engages and wipes a nozzle orifice plate surface of a print head cartridge to remove excess ink and accumulated debris. Removal of excess ink and accumulated debris is intended to improve print head performance and print quality. According to the Johnson, et al. disclosure, the cleaning system comprises a print head service station including a source of treatment fluid located near a cap belonging to the service station. The cap is brought into sealing contact with the print head and vacuum is applied. A wiper, which is included in one embodiment of the service station, comes into contact with the print head for removing dried ink and debris. When the wiper is used, the treatment fluid lubricates the wiper to reduce wear of the wiper. Also, the treatment fluid dissolves some of the dried ink residue accumulated on the print head. In addition, the treatment fluid leaves a thin film, which does not dry, so that ink residue and other debris subsequently deposited on the print head over the layer of the fluid are more easily wiped-off.
Although prior art print head cartridge cleaning techniques, such as disclosed by the Johnson, et al. patent, may function satisfactorily, it has been observed that a tight seal between the cap and print head cartridge is sometimes prevented due to surface roughness, or other non-flatness, of the print head cartridge. In this regard, the surface of the print head cartridge may beco
Courian Kenneth J
Gast Paul David
Reed Douglas J.
Hewlett--Packard Development Company, L.P.
Nguyen Thinh
Stevens Walter S.
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