Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-09-28
2003-01-28
Hsieh, Shih-wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06511150
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet printer, to an initialization control method therefor, and to a computer-readable data storage for storing a computer program achieving this initialization control method. More specifically, the invention relates to a novel method for improving the initialization of a printer when power supply to the printer is interrupted while a print head cleaning process is in progress.
2. Description of the Related Art
Ink jet printers use a non-contact printing method whereby ink inside an ink chamber is pressurized at very short time intervals, causing ink droplets to be ejected by the generated pressure from the ink nozzles and adhere to the recording medium. Movement of the print head with a carriage and advancement of a recording medium enables the ink drops to be arrayed in a two-dimensional dot matix on the recording medium surface to form text, graphics, and other print images. When compared with impact printers, ink jet printers are, generally speaking, quieter, faster, cost less to operate, and can be easily adapted for color printing.
The use of liquid ink, however, makes the maintenance and care of ink jet printers more troublesome. In particular, ink and foreign matter such as paper dust adhering to the nozzle area can clog the nozzles and thus affect the trajectory of ink drops. When there is a build-up of ink and dust on the nozzle surface, they can also smear the recording medium and thus contribute directly to soiling the recording medium and waste.
Dirty nozzles also contribute directly to reduced print quality, and keeping the nozzles as clean as possible is therefore important. For this reason, conventional ink jet printers typically have a cleaning mechanism for regularly cleaning the nozzles and maintaining consistent print quality.
Some types of ink jet printers are capable of cleaning with an ink suction process or two different levels of so-called sweeping operations.
The ink suction process puts the nozzles of the print head in surface contact with a cap, which is connected to a suction pump, to suck a specific amount of ink from the ink chambers of the head or ink supply path. Ink that has increased in viscosity inside the nozzles, and bubbles that have entered the ink path from the nozzles, are removed from the head by this process.
Sweeping processes use a flexible blade made, for example, by laminating together two different materials such as felt and rubber. During cleaning, this flexible blade is projected into the path of print head movement so that an edge of the blade wipes ink, paper dust, and other foreign matter from the nozzle surface as the print head moves. Because the surface of the flexible blade contacting the nozzle surface differs according to the direction of print head movement, the cleaning effect on the head differs according to the differences in the blade material. For example, the blade surface made of felt has higher contact resistance as it moves against the nozzle surface and greater ink absorbency compared with the rubber blade surface. It therefore acts to wipe away foreign material on the nozzle surface, and therefore has a good cleaning effect. Due to the differences in their cleaning effects, sweeping the nozzle surface with a felt material is referred to below as a “rubbing” process, and sweeping the nozzle surface with a rubber material is referred to as a “wiping” process.
When the power supply to an ink jet or other type of printer is turned off and then on again, an initialization process is required to assure normal operation. One step of this initialization process is to transport the print head on a carriage to a home position. A cleaning process as described above is also performed in conjunction with returning the print head to the home position.
However, if there is a power failure or the power cord is accidentally unplugged, power supply to printer mechanisms will be cut off and operations that are in progress will be interrupted. If an initialization or cleaning process is in progress at the time the power supply to the printer is cut off, operation of all mechanisms involved with the cleaning process stops.
When power is next turned on to a conventional ink jet printer, a specific initialization operation is performed regardless of the printer status when power was previously turned off. If the printer is in the middle of a cleaning process at the time the power supply is cut off as noted above, a number of problems can occur as described below.
More specifically, if the power is cut off during an ink suction process, that is, while ink is being suctioned from the nozzles, ink that was pulled from inside the nozzles remains in the cap when the power is turned on again. If the print head is moved as part of the initialization process when power supply resumes, the nozzle surface is separated from the cap and any ink remaining inside the cap can spill into the printer. If the ink is electrically conductive, electrical circuits and components can also misoperate. If this happens immediately after ink suction ends and the pressure inside the cap is lower than the air pressure outside the cap, the sudden change in pressure when the cap is remove can drive air bubbles from the nozzles into the head. When this happens, the ink meniscus at the nozzle opening (ink ejection opening) may not be properly formed. This can prevent ink from being normally ejected from the nozzles, and thus degrades print quality.
In addition, if the power is cut off during a sweeping operation, that is, while the flexible blade is in contact with the nozzle surface, the print head stops with the flexible blade bent in the direction opposite the direction of relative movement between the blade and nozzle surface. When the power is then turned on again, the print head may move in the direction opposite that in which it was moving before it stopped because the initialization process is typically performed in a conventional ink jet printer regardless of the printer status when the power supply is turned off. In this case the print head moves against the curvature of the flexible blade, thus subjecting the blade and its means of support to an undesirable external force and accelerating wear and deterioration of the blade.
The blade also exerts excessive force on the nozzle surface in this case, and can damage the water resistant film formed on the nozzle surface. Friction between the flexible blade and nozzle surface also increases, and impedes print head movement.
OBJECTS OF THE INVENTION
With consideration for the aforementioned problems, an object of the present invention is therefore to enable an initialization process, possibly including a cleaning operation, to be performed normally when power is turned on again after the power supply is cut off due to a power failure or unplugging of the power supply cord when a cleaning process is in progress.
More specifically, an object of the present invention is to provide an ink jet printer and an initialization control method therefor whereby an appropriate initialization process can be performed according to the status of a print head cleaning process at the time the power supply was cut off when the power is next turned on again.
SUMMARY OF THE INVENTION
To achieve the above object, an ink jet printer according to the present invention comprises an ink jet head having a nozzle for ejecting ink; a cleaner or cleaning means for cleaning said ink jet head; an initialization controller or control means for initializing the ink jet printer when power supply starts; a power interruption detector or detecting means for detecting interruption of power supply to the printer; an operating status memory or storage means for storing a current operating status of the cleaning means when the power interruption detecting means detects interruption of the power supply; and an operation selector or selecting means for selecting an operation to be performed by the initialization control means based on the operating status
Nishioka Atsushi
Teradaira Mitsuaki
Yoda Satoshi
Hsieh Shih-wen
Seiko Epson Corporation
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