Abstract:
A paper guide used in an ink-jet printer. The paper guide for the ink-jet printer includes a plurality of first guide ribs which protrude on the paper guide to face a front-half swath of a printhead and forms a predetermined interval therebetween, and a plurality of second guide ribs which protrude on the paper guide to face a rear half-swath of the printhead and forms an interval therebetween to be wider than the interval between the first guide ribs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of Korean Patent Application No. 2002-67060, filed on Oct. 30, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a paper guide used with an ink-jet printer and an ink-jet printer having the same, by which when multi-pass printing is performed to improve printing quality of an ink-jet printer, a first printing portion of a paper is flattened and a waveform size of a second printing portion of the paper is reduced.  
           [0004]    2. Description of the Related Art  
           [0005]    An ink-jet printer includes a paper guide on which a material used in printing e.g., paper supplied from a feed roller is to be placed and flattened. A paper guide rib is provided on the paper guide so as to be parallel with a paper feeding direction.  
           [0006]    [0006]FIG. 1 is a cross-sectional view schematically illustrating the structure of an ink-jet printer having a conventional paper guide. Referring to FIG. 1, a friction roller  14  contacts a feed roller  10  which receives paper P supplied from a pickup roller (not shown) on a paper path and feeds the paper P by an amount (swath S) which corresponds to a printing area. The friction roller  14  is rotatably connected to one end of a friction roller holder  15 , and the other end of the friction roller holder  15  is connected to a printer body. The feed roller  10  comprises a rubber roller  12  coupled to a metal shaft  11 , and a gear (not shown) is coupled at an end of the shaft  11  to connect with the power of a driving motor (not shown). The friction roller  14  contacts the circumference of the feed roller  10 . The friction roller  14  applies a predetermined pressure to the feed roller  10  by a weight of the friction roller holder  15 . If the feed roller  10  is rotated by a driving motor (not shown), the friction roller  14  is rotated by a rotation of the feed roller  10 .  
           [0007]    An ink-jet cartridge  20  and a paper guide  30  are disposed downstream of the feed roller  10  in a paper path. The paper guide  30  is spaced apart downwardly from a printhead  21  under the ink-jet cartridge  20  by a predetermined gap G, and supports the paper P thereon.  
           [0008]    [0008]FIG. 2 is a plane view illustrating paper guide ribs  32 , illustrated in FIG. 1 in cross-section only, disposed on the paper guide. Referring to FIG. 2, ribs  32  are placed at a predetermined interval I with the interval I spacing from 5-20 mm, and parallel with a paper path. The paper guide rib  32  is formed to a height of about 1-2 mm above the paper guide surface ( 30   a ) such that the paper P does not contact directly the surface  30   a  of the paper guide  30  and supports the paper P to be flattened during a printing.  
           [0009]    A plurality of holes  35  are formed in a rear portion of the paper guide  30  downstream of the printhead  21 , a paper output roller  40  is placed in each of the plurality of holes  35 , and a star wheel  42  is provided on the paper output roller  40 .  
           [0010]    Printing steps of an ink-jet printer having the above structure will be described in detail with reference to FIGS. 1 and 2.  
           [0011]    First, the paper P supplied from the pickup roller (not shown) is fed between the rotating friction roller  14  and the feed roller  10  in a feed direction as illustrated. If the paper P is fed by a friction force between the feed roller  10  and the paper P, the paper P is entered into the paper path by a distance of one swath S at the same velocity as a linear velocity of the circumference of the rubber roller  12 . In this case, the paper P is fed toward the printhead  21  and is printed on by the printhead  21 , which receives a printing file from a controller (not shown), and ejects ink, and subsequently, printing is performed while the feed roller  10  feeds the paper P by one swath S. If it is determined from the controller that the printing is terminated, the paper output roller  40  outputs the paper P.  
           [0012]    However, when multi-pass printing is performed by an inkjet printer having the paper guide having the above structure so as to attempt to print a high-quality image, the feed roller  10  feeds the paper P by a distance of a half-swath S to the paper path. Thus, the swath S may include a front-half part S 1  and a rear-half part S 2  which each correspond to a half-swath S. After a first printing is performed at the front-half part S 1 , the paper P is fed by a half-swath S and a second printing is performed on the first-printed portion at the rear-half part S 2  in a state when ink on the first-printed portion is not yet dried. Thus, the second printing is performed at a position different from a target position due to an excessive waveform (see the paper P marked by a dotted line W 1  of FIG. 5) of the first-printed portion of the paper P at the rear-half part. As a result, printing quality is lowered, and a protruded portion of the first-printed portion of the paper P contacts the printhead  21  and is smeared by the printhead  21 .  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention provides a paper guide used with an ink-jet printer and an ink-jet printer having the same, by which when multi-pass printing is performed by an ink-jet printer, the paper is flattened by a paper guide rib at a front-half part which is a first printing area of the paper and the paper is prevented from being contaminated by contacting a printhead when a second printing is performed, because a printed portion is not protruded at a rear-half part of the paper guide which is a second printing area of the paper.  
           [0014]    According to one aspect of the present invention, there is provided a paper guide used with an ink-jet printer. The paper guide used with an ink-jet printer includes a plurality of first guide ribs which protrude on the paper guide to face a front-half swath of a printhead, the first guide ribs with a predetermined interval therebetween, and a plurality of second guide ribs which protrude on the paper guide to face a rear-half swath of the printhead, the second guide ribs with an interval therebetween to be wider than the interval between the first guide ribs.  
           [0015]    According to one aspect of the present invention, each of the second guide ribs is linearly connected to the corresponding first guide rib, and at least one first guide rib is further formed between the first guide ribs connected to the corresponding second guide rib.  
           [0016]    Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments accompanying drawings in which:  
         [0018]    [0018]FIG. 1 is a cross-sectional view schematically illustrating the structure of an ink-jet printer having a conventional paper guide;  
         [0019]    [0019]FIG. 2 is a plane view illustrating conventional paper guide ribs disposed on the paper guide of FIG. 1;  
         [0020]    [0020]FIG. 3 is a perspective view illustrating an embodiment of a paper guide for an ink-jet printer according to the present invention;  
         [0021]    [0021]FIG. 4 is a plane view illustrating paper guide ribs disposed on the paper guide of FIG. 3; and  
         [0022]    [0022]FIG. 5 illustrates the function of a second guide rib. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. Thicknesses of layers or regions shown in drawings are exaggerated for clarity of a specification.  
         [0024]    [0024]FIG. 3 is a perspective view illustrating an embodiment of a paper guide for an ink-jet printer according to the present invention, and FIG. 4 is a plane view illustrating paper guide ribs disposed on the paper guide of FIG. 3. The same reference numerals refer to like elements, and descriptions thereof will be omitted.  
         [0025]    Referring to FIG. 3, a friction roller  14  contacts a feed roller  10  which receives paper P, supplied from a pickup roller (not shown) on a paper path and feeds the paper P by an amount (swath) which corresponds to a printing area. The friction roller  14  is rotatably connected to one end of a friction roller holder  15 , and the other end of the friction roller holder  15  is connected to a printer body. The friction roller  14  contacts the circumference of the feed roller  10 . The friction roller  14  applies a predetermined pressure to the feed roller  10  by a weight of the friction roller holder  15 . If the feed roller  10  is rotated by a driving motor (not shown), the friction roller  14  is rotated by a rotation of the feed roller  10 .  
         [0026]    An ink-jet cartridge  20  and a paper guide  130  are disposed downstream of the feed roller  10  on a paper path. The paper guide  130  is spaced apart downwardly from a printhead  21  under the ink-jet cartridge  20  by a predetermined gap to support the paper P thereon.  
         [0027]    Referring to FIG. 4, a plurality of paper guide ribs  132  are formed on the paper guide  130  so as to be parallel with a paper path. The paper guide ribs  132  include first guide ribs  132   a  formed at a front-half part S 1  of a swath S in which a first printing is performed during a multi-pass printing, and second guide ribs  132   b  formed in a rear-half part S 2  of the swath S in which a second printing is performed. A feature of the present invention is that the interval  11  between the first guide ribs  132   a  where the first printing is performed is narrower than the interval I 2  between the second guide ribs  132   b  where the second printing is performed.  
         [0028]    The paper guide rib  132  is formed to a height of about 1-2 mm such that the paper P does not contact directly a top surface  130   a  of the paper guide  130  and supports the paper P to be flattened during a printing.  
         [0029]    Each of the second guide ribs  132   b  can be linearly connected to a corresponding first guide rib  132   a , and one first guide rib  132   a  can be further formed between the first guide ribs  132   a  connected to the second guide rib  132   b  as illustrated in FIG. 4.  
         [0030]    Although each of the second guide ribs  132   b  is shown as connected to a first guide rib  132   a  in the present embodiment, the present invention is not limited to this. Also, the present invention is not limited so that only one first guide rib  132   a  disposed between the first guide ribs  132   a  that are connected to the second guide ribs  132   b.    
         [0031]    A plurality of holes  35  are formed in a rear end of the paper guide  130 , and paper exhausting rollers  40  are placed in each of the plurality of holes  35 , and a star wheel  42  is provided on the paper exhausting roller  40 .  
         [0032]    Multi-pass printing operations of an ink-jet printer having the above structure will be described in detail with reference to FIGS. 3 and 4.  
         [0033]    First, the paper P supplied from the pickup roller (not shown) is fed between the rotating friction roller  14  and the feed roller  10 . If paper P is fed by a friction force between the feed roller  10  and the paper P, the paper P is entered into the paper path by a half-swath S at the same velocity as a linear velocity of the circumference of the rubber roller  12 . In this case, the paper P fed toward the printhead  21  is first printed on by the printhead  21  which receives a printing file from a controller (not shown) and ejects ink. In this case, a first printing is performed in a state when the paper P placed on the first guide ribs  132   a  is flattened by the first guide ribs  132   a  formed at a comparatively narrow interval  11 , and thus printing quality is improved.  
         [0034]    Subsequently, the paper P in which the first printing is completed is fed by another half-swath S, a first-printed portion is moved to the rear-half part S 2 , and multi-pass printing is performed on the first-printed portion of the paper. In this case, the first-printed portion placed on the second guide ribs  132   b  is depressed between the second guide ribs  132   b , formed at a comparatively wide interval I 2 , by its weight, and is flattened as by the solid line W 2  in FIG. 5, such that the height of the waveform is reduced. That is, the dotted line W 1  of FIG. 5 indicates a case where the interval between the second guide ribs  132   b  is narrow e.g., the same as I 1 , and the solid line of FIG. 5 indicates a case where the interval between the second guide ribs  132   b  is wide e.g., I 2 . Thus, a multi-pass printing is performed on the first-printed portion which is flattened such that printing quality is improved. Subsequently, the printing is continuously performed while the feed roller  10  feeds the paper P by the half-swath S. If it is determined from the controller that the printing is terminated, the paper output roller  40  outputs the paper P.  
         [0035]    As described above, the paper guide of the ink-jet printer according to the present invention, by preventing a first-printed portion from forming an excessive waveform during a second printing when multi-pass printing is performed, can prevent a printhead from smearing the printing and improve printing quality.  
         [0036]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.