Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2000-03-02
2003-12-09
Evanisko, Leslie J. (Department: 2854)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C400S636000, C400S646000, C271S188000
Reexamination Certificate
active
06659603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording apparatus that records images, such as characters, graphics, and patterns, by depositing ink to a recording medium by use of recording means.
2. Related Background Art
When recording is performed by the deposition of ink droplets to a recording medium, ink is absorbed into the recording medium, and the portion where ink is thus absorbed is subjected to swelling. Then, depending on the difference in the concentration of ink that adheres to the recording medium, a portion having a difference in stretching may occur. The largely stretched portion is caused to bend in the direction perpendicular to the recording surface of a recording medium of a sheet type. So-called cockling irregularities may take place. Here, the more time elapses, the more ink droplets are absorbed into the recording medium to bring about the swelling. Thus, the irregularities increase. When image data or the like is recorded, a technique is adopted to minimize the influence exerted by uneven pitches of feeding on the quality of recorded images by shortening the feeding pitches of the recording medium, while dividing the image data at random, so that the scanning frequency is increased for the carriage having recording means thereon for recording. When the feeding pitches are smaller as in this case, the recording time becomes longer to bring about a larger cockling. As a result, during the recording operation, the recording medium tends to bend in the direction toward recording means from the platen side where the recording medium is supported to face the recording means. In such condition, the sheet floating may take place with the result that the recording means is in contact with the recording medium to rub each other, and that the quality of recorded images is degraded eventually in some cases.
For the recording apparatus that adopts the ink jet recording method to record by discharging ink, the shorter the flying passage of ink, the higher becomes the accuracy of the landing positions of ink. For a recording apparatus of this kind, it is required to set the gap between the recording surface of a recording medium and the recording head (hereinafter referred to as a “head gap”) as narrow as possible. On the other hand, if the head gap is made narrower, a rubbing of the kind as described above tends to occur more often.
Therefore, it is desirable to provide a method that can minimize the sheet floating that may be caused by cockling so that no rubbing occurs between recording means and a recording medium.
To prevent the sheet floating of a recording medium from the platen, a structure (a first conventional example) is disclosed in the specification of Japanese Patent Application Laid-Open No. 61-95966 in which a plurality of small holes are provided in the platen or suction force is allowed to act upon a recording medium through small holes by use of negative pressure generating means, thus the recording medium being held closely in contact with the platen.
Also, in the specification of Japanese Patent Application Laid-Open No. 4-69264, a mechanism (a second conventional example) that presses a recording medium by use of a paper pressure member arranged on the upstream side in the carrying direction of the recording medium is disclosed.
Further, in the specification of Japanese Patent Application Laid-Open No. 9-48161, an ink jet recording apparatus (a third conventional example) is disclosed in which a plurality of ribs, which are extended on a flat platen in the carrying direction of a recording medium, are arranged in the direction intersecting the carrying direction of the recording medium, and, on the upstream side of the ribs, a pressure plate is arranged extending in the direction intersecting the carrying direction of the recording medium in order to nip the recording medium together with each tip of the ribs. Also, for this ink jet recording apparatus, extrusions are arranged on the respective positions of the pressure plate corresponding to each of the gaps between ribs, thus exerting the force that presses the recording medium downward.
For the first conventional example described above, there is a need for the provision of negative pressure generating means, which inevitably makes the apparatus larger, and the costs of manufacture higher as well. There is also a problem that the noise level increases when the air is taken in and exhausted. Further, when recording is effected on a smaller recording medium, the suction efficiency is extremely lowered to the extent that the dependability becomes inferior if many of the fine holes arranged for the platen are located outside of the edges of the recording medium to be used. If the arrangement is such that all the fine holes are covered even by a smaller sized recording medium, it becomes impossible to exert the suction force over the entire surface of a larger recording medium. As a result, the dependability also becomes inferior. In order to solve such problems, it is necessary to provide means for closing the fine holes that may be located outside of the edges of a smaller sized recording medium. However, the structure becomes considerably complicated to make the costs of manufacture higher.
For the second conventional example, there is a possibility that a recording medium is not pressed sufficiently close to the platen if the recording area is wide. In other words, the recording medium is pressed by the paper pressure member to the platen on the upstream side, while being nipped by the sheet exhaust roller or the like on the downstream side. However, the recording medium is not pressed at all at the recording area or the like which exists between these sides. As a result, if the recording area is wide so that each line portion of the recording head is correspondingly wider, there is a fear that the recording medium is caused to float from the platen or that cockling takes place on the recording medium at the recording area with downward pressure being exerted only by the paper pressure member on the upstream side and by the exhaust rollers on the downstream side. Further, in order to suppress the paper sheet floating, if the nipping portion of the exhaust roller pair is positioned lower than the guiding surface of the platen, there is a problem encountered that the trailing end of the recording medium is allowed to float after the recording sheet is conveyed away from the paper pressure member.
For the third conventional example, the paper pressure plate is arranged without any exception on a position that is substantially in contact with the leading end of each of the ribs on the upstream side thereof. However, it is impossible to exert any force to press the recording medium to the platen side by the nipping portion of the recording medium by each of the leading ends of ribs and the paper pressure plate. Also, there is a problem that the ribs, which are set on the lower face of the paper pressure plate and arranged upstream in the gaps between adjacent platen ribs, cannot prevent the floating of a recording medium from the platen completely in a case where a comparatively robust recording medium, such as cardboard, is carried or recording is performed on a wide recording area, although there is an effect that the recording medium is pressed in the direction of the platen when the recording medium is placed in a position between ribs.
SUMMARY OF THE INVENTION
The present invention is designed with a view to solving the problems discussed above. It is an object of the invention to provide an ink jet recording apparatus capable of preventing a recording medium from floating toward recording means with a simple structure at lower costs.
Also, it is another object of the invention to provide an ink jet recording apparatus, which records with deposition of ink droplets to a recording medium by use of ink jet recording means, and comprises a platen for supporting a recording medium in a position facing the ink jet recording means; a plurality of carrier
Kida Akira
Matsumoto Toshiya
Nishiberi Nozomu
Ohyama Kazuo
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