Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2001-08-13
2003-12-23
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06666536
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an ink-jet image forming apparatus for forming images on recording paper by ejection of ink droplets. In particular, the present invention relates to a method of performing stable image formation by keeping the distance between the recording head and recording paper constant at all times without regard to the type of recording paper.
(2) Description of the Prior Art
In general, in an image forming apparatus of an ink-jet type(to be referred to hereinbelow as ink-jet printers) which can form micro dots at high densities while making relatively low noise during printing, image forming is performed by ejecting ink droplets onto the surface of recording sheets which are fed successively. More specifically, a generally known scenario is that the recording head, which is set with an ink cartridge on a carriage, ejects ink droplets onto the recording paper that moves intermittently in the auxiliary direction while the carriage reciprocates in the main scan direction that is perpendicular to the direction of conveyance of the recording paper.
As the ink cartridge, one which supplies black ink and color inks, i.e., yellow, cyan and magenta is provided. Accordingly, an ink-jet printer not only produces text printing with black ink but also is able to perform full color printing by adjusting the ratio of the amounts of color inks ejected toward the recording paper.
In ink-jet printers of this type, the distance between the position of the ink nozzle of the ink head and the recording paper surface (head to medium gap) can be considered one of the critical factors that determine the print quality.
Since the sheets to be used for ink-jet printers are generally diverse, from typical recording paper (e.g., about 0.05 to 0.2 mm thick) to postcards, envelopes, etc., the distance from the ink nozzle position of the recording head to the recording paper surface varies due to variations in sheet thickness. Further, an ink droplet ejected from the ink nozzle to the recording paper varies in its shape and speed depending on the head to medium gap. For these reasons, setting of the head to medium gap is critically important to obtain the shape and speed of ink droplets suitable for printing.
Illustratively, when the head to medium gap is narrow, the speed at which an ink droplet reaches the recording paper remains high, so that ink droplet splashes on the recording paper surface. That is, ink may scatter over the non-printing area beyond the area on the sheet that the ink droplet should be ejected onto for printing, or may contaminate the recording head.
On the other hand, when the head to medium gap is wide, the actual travel route of the ink droplet ejected from the carriage whilst it is being moved deviates from the expected path. Since the point at which the ink droplet arrives thus deviates from the proper position, this will cause distortion in the resulting image.
In order to prevent degradation of print quality due to inappropriate head to medium gap, there have been many proposals up to now for adjusting the head to medium gap in the technical field of ink-jet printers.
For example, there is a method of adjustment as to the head to medium gap by manually switching the height of the recording head in accordance with the thickness of the recording paper to be used for printing. This method involves selection modes such as ‘thick paper mode’, ‘normal paper mode’, ‘thin paper mode’, etc., so as to allow the user to select the desired mode with a lever handle.
Japanese Patent Application Laid-Open Hei 9 No.109460 discloses an ink-jet printer configuration in which the carriage or recording head is moved in accordance with the head to medium gap detected by a sensor so as to adjust the distance to the user-desired text size to be printed.
However, as to the configuration in which the height of the recording head is manually selected, the user needs to decide the thickness of the recording paper in order to obtain beneficial print quality. Accordingly, this configuration needs complicated print handling and potentially can cause breakdown of the recording head due to user's misjudgment. When switching of the height of the recording head is performed by shifting the carriage up and down, the whole carriage configuration inevitably becomes complicated, which leads to a marked rise in manufacturing cost. Further, the change of the height of the carriage could hinder the stability of the scanning movement of the carriage in the main scan direction and may cause degradation of image quality. Further, in the waiting mode the carriage is positioned at a maintenance station located at one side with respect to the main scan direction, however there is a possibility that the carriage cannot be set at an appropriate position relative the maintenance station when the height is changed. In order to avoid this, it is necessary to make the height of the maintenance station adjustable or provide other measures, hence the result is complexity of the entire printer.
In the configuration disclosed in the above publication, part of the sensor for detecting the head to medium gap and the mechanical arrangement for adjusting the head to medium gap are mounted on the carriage for moving the recording head. Therefore, the carriage needs to carry the sensor and the mechanical arrangement together with the recording head, thus consuming extra electric energy.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the above problems, it is therefore an object of the present invention to provide an ink-jet image forming apparatus with which the distance between the recording head and recording paper can be kept constant at any time regardless of the type of recording paper without increasing in any way the complexity of the carriage configuration and without inducing any increase in power consumption.
In order to achieve the above object, in the present invention, the platen for guiding the recording paper is moved in the direction away from the recording head so as to set the gap between the recording head and recording paper at a proper distance.
Specifically, the invention is assumed to involve an ink-jet type image forming apparatus having a platen for guiding recording media and a recording head disposed opposing the platen for ejecting ink droplets onto recording media. This ink-jet type image forming apparatus is provided with a platen actuating means which moves the platen so as to adjust the gap between the recording head and the recording medium.
By this limitation, it becomes possible to adjust the distance between the ink nozzle position of the recording head and the recording medium surface on the platen (the head to medium gap) and set it constant by moving the platen which will serve as a guide table for recording media during printing(during image forming) and keep the recording medium flat and adjust the height of the recording medium relative to the ink nozzle. With this arrangement, it is possible to perform printing of different types of recording media having different thicknesses under the same conditions. In the present invention, since the head to medium gap can be set correctly without shifting the recording head or the carriage having the recording head mounted thereon, there is no need to provide a motor or other parts in order to drive the recording head or the carriage up and down. Therefore, it is possible to avoid increase of the carriage in weight, hence increase in power consumption can be inhibited while the carriage can be moved smoothly. Here, examples of applicable recording media include, recording paper, OHP film and any other material as long as it is printable by sprayed ink.
Specific examples of the platen actuating means include the following configurations. First, the ink-jet type image forming apparatus may further include paired conveyer rollers for holding the recording medium being image formed by ejected ink droplets from the recording head and conveying it. In this
Deguchi Masanobu
Fukada Yasuaki
Hashimoto Susumu
Kubo Takashi
Matsutomo Yasushi
Birch & Stewart Kolasch & Birch, LLP
Huffman Julian D.
Meier Stephen D.
Sharp Kabushiki Kaisha
LandOfFree
Ink jet device with movable platen does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet device with movable platen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet device with movable platen will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3144561