Abstract:
A recording apparatus for performing a recording operation to a recording medium, conveyed by a conveyor, by using ink jet heads, and comprising an optical detector, arranged within the recording apparatus, for optically detecting desirable information and light-shielding for preventing light entering the interior of the recording apparatus from reaching the optical detector.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a recording apparatus for recording an image to a recording medium and having an optical type detecting means within this recording apparatus. 
     2. Related Background Art 
     FIG. 6 is a perspective view showing the schematic construction of a conventional recording apparatus. 
     In FIG. 6, reference numeral  101  designates an ink tank of each color. Each ink tank is exchangeably mounted to a carriage  102 . A recording head (not shown) for recording or printing an image to a recording medium (not shown)is arranged in the carriage  102 . The image is recorded to the recording medium in accordance with a recording signal transmitted from an unillustrated substrate through an unillustrated flexible cable. Plural patterns showing information corresponding to a shifting amount of a printing position are printed to the recording medium by the recording head so as to relatively align the printing position at a first printing time to the recording medium with a printing position at a second printing time. 
     The recording apparatus shown in FIG. 6 is a so-called serial type printer. The carriage  102  is guided and supported so as to freely reciprocate in the direction of an arrow A along a guide shaft (not shown) arranged in a chassis  108 . The carriage  102  is operated and controlled in position and movement by a driving mechanism such as a carriage motor (not shown), a motor pulley (not shown), a driven pulley  106 , a timing belt  107 , etc. 
     The recording medium such as a sheet of recording paper, etc. is fed by a paper feeder  110  until a nipping position of a conveying roller  111  and a pinch roller  113  within a body of the recording apparatus. The pinch roller  113  is held by a pinch roller holder  112 . The pinch roller holder  112  is held by a pinch roller holder attaching plate  109  fastened and fixed to the chassis  108  by vises, etc. The pinch roller  113  comes in press contact with the conveying roller  111  by a pressing member such as a spring, etc. The recording medium conveyed to the above nipping position is further conveyed by the conveying roller  111  rotated by a driving mechanism (not shown). 
     Reference numeral  130  designates an optical type sensor of a reflection type as an optical detecting means mounted to the carriage  102 . The optical type sensor  130  detects a printing pattern of the recording medium conveyed onto a platen  114  by scanning the carriage  102  in the direction of the arrow A. The optical type sensor  130  has a light emitting portion and a light receiving portion. Light emitted from the light emitting portion is reflected on a surface of the recording medium and the reflected light is detected by the light receiving portion. 
     A density of the pattern is detected by utilizing that intensity of the reflected light is changed in accordance with the density of the pattern printed on the recording medium. 
     However, in the prior art explained above, a problem exists in that external light enters the interior of the recording apparatus and no optical type sensor is normally operated in a certain case. 
     FIG. 7 is a cross-sectional view showing a conveying path of the recording medium in the conventional recording apparatus shown in FIG.  6 . 
     In FIG. 7, reference numeral  116  designates the recording medium and shows a state in which the recording medium  116  is conveyed by the paper feeder  110 . Reference numeral  115  designates a paper feed plate for guiding the recording medium  116  conveyed by the paper feeder  110  until the conveying roller  111 . 
     Since the recording medium  116  stacked in the paper feeder  110  is arranged outside the recording apparatus body, the recording medium  116  is exposed to external light  117 . Further, since the recording medium  116  is normally formed by a white color system, the external light  117  is well reflected on the recording medium  116 . Accordingly, as shown in FIG. 7, the external light  117  is guided into the recording apparatus by the recording medium  116 . 
     Further, since no member for pressing the recording medium  116  is arranged between the pinch roller holder  112  and the paper feed plate  115 , there is a case in which the recording medium  116  is floated upward as shown by a dotted line in FIG.  7 . In recent years, a high accuracy of about ±10 μm is also required in conveyance of the recording medium. However, when the recording medium is floated upward as mentioned above, a conveying position is correspondingly shifted so that conveying accuracy is reduced. 
     FIG. 8 is a perspective view showing a conveying path of the recording medium shown in FIG.  7 . 
     As shown in FIG. 8, plural pinch roller holders  112  are arranged in parallel with each other in a transversal one line in the conventional recording apparatus. However, since there is a clearance B between the respective pinch roller holders  112 , the external light  117  is leaked from this clearance B and further enters the platen  114  (see FIGS.  6  and  7 ). 
     As mentioned above, the optical type sensor  130  detects the density of the pattern by intensity of the reflected light from the pattern printed on the reflected light from the pattern printed on the recording medium  116  conveyed onto the platen  114 . However, when the external light  117  further enters the recording medium  116  on the platen  114 , no reflected light of the optical type sensor  130  can be exactly detected by an influence of this external light  117  so that no density of the pattern can be exactly detected. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a recording apparatus for performing a recording operation to a recording medium conveyed by conveying means by using recording means, and comprising optical detecting means for optically detecting desirable information and arranged within the recording apparatus; and light-shielding means for preventing light entering the interior of said recording apparatus from reaching said optical detecting means. 
     Another object of the present invention is to provide a recording apparatus able to stably operate the optical detecting means since a fear of an error in operation of the optical detecting means caused by light entering the interior of the recording apparatus is restrained. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing a conveying path of a recording medium in a first embodiment of a recording apparatus of the present invention. 
     FIG. 2 is a cross-sectional view of the conveying path shown in FIG.  1 . 
     FIG. 3 is a perspective view showing a conveying path of a recording medium in a second embodiment of the recording apparatus of the present invention. 
     FIG. 4 is a perspective view showing a schematic construction of the second embodiment of the recording apparatus of the present invention. 
     FIG. 5 is a cross-sectional view showing a conveying path of a recording medium in a third embodiment of the recording apparatus of the present invention. 
     FIG. 6 is a perspective view showing the schematic construction of a conventional recording apparatus. 
     FIG. 7 is a cross-sectional view showing a conveying path of a recording medium in the conventional recording apparatus shown in FIG.  6 . 
     FIG. 8 is a perspective view showing the conveying path of the recording medium shown in FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention will next be explained with reference to the drawings. 
     (First Embodiment) 
     FIG. 1 is a perspective view showing a conveying path of a recording medium in a first embodiment of a recording apparatus of the present invention. FIG. 2 is a cross-sectional view of the conveying path shown in FIG.  1 . 
     Each of constructions of an ink tank, a recording head as a recording means, a carriage, a driven pulley, a timing belt, a chassis  8 , a pinch roller holder attaching plate  9 , a paper feeder  10 , a conveying roller  11 , a pinch roller  13 , a platen  14 , a paper feed plate  15  and an optical type sensor as an optical detecting means in this embodiment is similar to that in the conventional recording apparatus shown in FIG. 6, etc. Accordingly, a detailed explanation of these constructions is omitted here. Further, similar to the prior art, a pattern showing information corresponding to a shifting amount between a printing position at a first printing time to the recording medium  16  and a printing position at a second printing time is printed to the recording medium  16 . 
     As shown in FIG. 1, each of plural pinch roller holders  12  is pivotally mounted to the pinch roller attaching plate  9  by a rotating shaft  12   c  and holds the pinch roller  13  (see FIG. 2) and makes the pinch roller  13  come in press-contact with the conveying roller  11  by a pressing member such as a spring, etc.(see FIG.  2 ). A conveying means for conveying the recording medium  16  (see FIG. 2) is constructed by the conveying roller  11 , the pinch roller  13  and the pinch roller holders  12 . 
     Each of the pinch roller holders  12  is arranged in a state in which the pinch roller holders  12  are arranged in a line in a direction perpendicular to a conveying direction of the recording medium  16 . Light-shielding walls  12   a ,  12   b  as a light-shielding means for shielding external light  17  (see FIG. 2) entering the interior of the recording apparatus are respectively arranged as light-shielding portions of the pinch roller holders in both side portions of each of the pinch roller holders  12 . The clearance C between the light-shielding walls  12   a  and  12   b  adjacent to each other is formed such that the clearance C is narrower than the clearance B between the pinch roller holders  12  adjacent to each other. 
     With reference to FIG. 2, similar to the prior art explained by using FIG. 7, etc., the external light  17  is reflected on the recording medium  16  stacked to the paper feeder  10  and enters the interior of the recording apparatus. The external light  17  enters the interior of the recording apparatus through lower sides of the chassis  8  and the pinch roller holder attaching plate  9 . Further, while the external light  17  is alternately reflected between the recording medium  16  and the pinch roller holders  12 , the external light  17  is advanced toward a platen (not shown). However, since the external light  17  is shielded by the light-shielding walls  12   a ,  12   b  arranged in each of the pinch roller holders  12 , an amount of the external light  17  reaching the platen can be reduced. 
     Accordingly, the external light  17  reaching an optical type sensor (not shown) for detecting a printing pattern printed on the recording medium  16  conveyed onto the platen as an image recording area by a recording head is reduced. Therefore, a fear of the generation of an error in operation of the optical type sensor caused by the external light  17  is restrained so that the optical type sensor can be stably operated. 
     When the light-shielding walls  12   a ,  12   b  are formed integrally with the pinch roller holders  12 , the light-shielding walls  12   a ,  12   b  can be arranged by only changing shapes of the conventional pinch roller holders without increasing the number of parts of the recording apparatus. Further, the respective pinch roller holders  12  are preferably formed in the same shape. 
     A so-called ink jet recording head for forming an image to the recording medium  16  by injecting ink from a nozzle may be used in the above recording head. 
     In the above example, a pattern displaying information corresponding to a shifting amount of the printing position printed to the recording medium  16  is detected by the optical type sensor. However, a detecting object of the optical type sensor is not limited to such a pattern, but may be also another arbitrary information able to be optically detected. 
     (Second Embodiment) 
     As explained with reference to FIG. 1, etc., the amount of the external light  17  entering the platen is considerably reduced by the light-shielding walls  12   a ,  12   b  arranged in the pinch roller holders  12  in the recording apparatus in the first embodiment. However, since the clearance C is formed between the respective pinch roller holders  12 , the external light  17  slightly passes through the clearance C and it is impossible to perfectly prevent the external light  17  from entering the platen. In this embodiment, the advancement of this slight external light onto the platen is also shielded. 
     FIG. 3 is a perspective view showing a conveying path of a recording medium in a second embodiment of the recording apparatus of the present invention. FIG. 4 is a perspective view showing a schematic construction of the second embodiment of the recording apparatus of the present invention. 
     Each of constructions of an ink tank  21 , a carriage  22 , a driven pulley  26 , a timing belt  27 , a chassis  28 , a pinch roller holder attaching plate  29 , a paper feeder  30 , a conveying roller  31 , a pinch roller  33 , a platen  34 , a paper feed plate, an optical type sensor  38  and a recording medium  36  in this embodiment is similar to that in the conventional recording apparatus shown in FIG. 6, etc. Accordingly, a detailed explanation of these constructions is omitted here. 
     As shown in FIG. 3, a light-shielding wall  32   a  is integrally formed on a left-hand side face of each pinch roller holder  32 . A clearance D is formed between the light-shielding wall  32   a  and a right-hand side face  32   b  of a pinch roller holder  32  adjacent to the pinch roller holder  32  forming the light-shielding wall  32   a  therein. A clearance E is formed between the pinch roller holders  32  adjacent to each other. The clearance E is formed to avoid a mutual interference of operations of the respective pinch rollers  33 , or to easily attach the pinch rollers  33  to the pinch roller holders  32 . Each light-shielding wall  32   a  is arranged in a position relation overlapped with the clearance E in an advancing direction of the external light  37  entering the interior of the recording apparatus. 
     Thus, the external light  37  entering the interior of the recording apparatus is shielded by the light-shielding wall  32   a  and is further shielded by a front side wall  32   c  of each of the pinch roller holders  32  even when the external light  37  passes through the clearance D. Therefore, no external light  37  passes through the clearance E between the pinch roller holders  32 . 
     Accordingly, the external light  37  is prevented from reaching the optical type sensor  38  for detecting a pattern printed to the recording medium  36  conveyed onto the platen so that the optical type sensor  38  can be more stably operated. 
     (Third Embodiment) 
     FIG. 5 is a cross-sectional view showing a conveying path of a recording medium in a third embodiment of the recording apparatus of the present invention. 
     Each of constructions of an ink tank, a carriage, a driven pulley, a timing belt, a chassis  48 , a pinch roller holder attaching plate  49 , a paper feeder  50 , a conveying roller  51 , a pinch roller  53 , a platen  54 , a paper feed plate  55 , an optical type sensor and a recording medium  56  in this embodiment is similar to that in the conventional recording apparatus shown in FIG. 6, etc. Accordingly, a detailed explanation of these constructions is omitted here. 
     Similar to the second embodiment shown in FIG. 3, a light-shielding wall  52   a  is integrally formed on a left-hand side face of each pinch roller holder  52  in this embodiment. However, the light-shielding wall  52   a  in this embodiment is constructed such that an end tip portion of the light-shielding wall  52   a  is located near a surface of the recording medium  56  conveyed between the pinch roller holder  52  and the paper feed plate  55 . 
     Thus, it is prevented that the recording medium  56  is floated upward as shown by a dotted line in FIG. 5 between the pinch roller holder  52  and the paper feed plate  55 . Accordingly, it is prevented that conveying accuracy of the recording medium is reduced. 
     As explained above, the recording apparatus in each of the present embodiments has a light-shielding means for preventing light entering the interior of the recording apparatus from reaching the optical detecting means so that the optical detecting means can be stably operated.