Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an image reading apparatus for reading an image while conveying a sheet material. 
     2. Description of Related Art 
     Usually an image reading apparatus of a type which reads the image surface of a sheet material while conveying the sheet material uses a close contact type image sensor as reading means, from the viewpoints of space and cost. 
     However, a lens used in the close contact type image sensor has a depth of field as small as 0.2-0.3 mm. Therefore, in a case where a sheet material cannot be held in the depth of field, that is, in a case where the sheet material cannot be brought into close contact with a focusing position (image reading surface) provided on a reading glass surface, blur occurs to a read image. 
     So, generally, as in an image reading apparatus  140  shown in  FIG. 7  of the accompanying drawings, a transparent image reading surface  145  is attached to a reading portion housing  141 , and a light source  144 , a lens  143  and a light receiving element  142  are provided in the interior of the housing. When an image surface on the upper surface side of a sheet material S is to be read, a platen roller  246  mounted on the fore end of an arm member  148  is biased in the direction indicated by the arrow by a tension spring  147  and the image surface of the sheet material S is urged against the image reading surface  145 . Thereby, the sheet material S is kept so as not to separate from the image reading surface  145  by a prescribed amount or greater. 
     Also, in Japanese Patent Application Laid-open No. H10-190938, as shown in  FIG. 8  of the accompanying drawings, driven rollers  131  and  132  are provided on the upstream side and the downstream side, respectively, of a reading portion housing  141 , and these are pressed against conveying rollers  121  and  122 , respectively, by compression springs  170 . Thereby, a sheet material S is brought into close contact with a sheet conveying guide  11  so as to bring the image surface of the sheet material S into close contact with an image reading surface. 
     Also, in Japanese Patent Application Laid-open No. 2000-115452, as shown in  FIG. 9  of the accompanying drawings, a crooked conveying path P for a sheet material S is constituted by two reading portion housings  141 . Thereby, the sheet material S conveyed through the conveying path P may be normally brought into close contact with image reading surfaces  145 . 
     Now, there is a desire to well read, by an image reading apparatus, a laminate-processed, rigid card having a thickness of 0.3 mm or greater such as a driver&#39;s license heretofore read by a flat bed scanner. 
     However, in the above-described image reading apparatus constructed on the premise that the sheet material is thin paper, a sheet material having a great thickness is conveyed with a rush while widening the gap between an image reading surface and a platen roller or an original plate and may therefore injure the image reading surface. If an injury occurs to the image reading surface, a streak will occur to a read image. 
     Likewise, in the image reading apparatus  140  shown in  FIG. 8 , the sheet material S widens the gap between a sheet conveying surface  103  and an image reading surface  145  and therefore, an injury occurs to the image reading surface  145  and a streak occurs to a read image. Further, provision is made of an upstream roller pair (a conveying roller  121  and a driven roller  131 ) and a downstream roller pair (a conveying roller  122  and a driven roller  132 ) and therefore, when the sheet material S is engaged with one roller pair alone and when the sheet material S is engaged with both roller pairs, the posture of the reading portion housing  141  changes. Therefore, blur occurs to the read image. 
     Also, in the image reading apparatus shown in  FIG. 9 , the conveying path P is crooked and therefore, if the sheet material S is thick or high in rigidity, this sheet material is not flexed and may therefore be caught by the conveying path to thereby cause jam (sheet jamming). 
     As a construction which does not injure the reading surface, as shown in  FIG. 10  of the accompanying drawings, there is also a method whereby conveying guide surfaces  141   d  and  141   e  provided before and behind an image reading surface  145  are a little protruded downwardly from the image reading surface  145 . 
     In this method, however, if the sheet material S is a hard card or the like, the abrasion of the conveying guide surfaces  141   d  and  141   e  will be promoted. Also, if the sheet material S is a thin sheet material, jam will occur. 
     SUMMARY OF THE INVENTION 
     So, the present invention has as an object thereof to provide an image reading apparatus which can well read thin and thick sheet materials without involving the occurrence of jam and the promotion of the abrasion of parts and moreover, is free of the occurrence of a streak or blur to a read image. 
     In order to achieve the above object, the present invention provides an image reading apparatus for reading the image surface of a sheet material brought into close contact with the image reading surface of an image reading unit while passing the sheet material through an image reading gap formed between the sheet conveying surface of a sheet conveying guide and the image reading surface, the image reading apparatus comprising: 
     a holding member for holding the image reading unit for movement in a direction to change the width of the image reading gap; 
     an upstream roller pair having a first roller member displaceable in accordance with the thickness of the sheet material, and for nipping and conveying the sheet material into the image reading gap; and 
     a downstream roller pair having a second roller member displaceable in accordance with the thickness of the sheet material, and for nipping and conveying the sheet material out of the image reading gap, 
     wherein the image reading unit changes the width of the image reading gap on the basis of the displacement of at least one of the first roller member and the second roller member. 
     Also, the present invention provides an image reading apparatus for reading the image surface of a sheet material brought into close contact with the image reading surface of an image reading unit while passing the sheet material through an image reading gap formed between the sheet conveying surface of a sheet conveying guide and the image reading surface, the image reading apparatus comprising: 
     a holding member for holding the sheet conveying guide for movement in a direction to change the width of the image reading gap; 
     an urging member for urging the sheet conveying guide in a direction to narrow the image reading gap; 
     an upstream roller pair having a first roller member displaceable in accordance with the thickness of the sheet material, and for nipping and conveying the sheet material into the image reading gap; and 
     a downstream roller pair having a second roller member displaceable in accordance with the thickness of the sheet material, and for nipping and conveying the sheet material out of the image reading gap, 
     wherein the sheet conveying guide changes the width of the image reading gap on the basis of the displacement of at least one of the first roller member and the second roller member. 
     Other objects and features of the present invention will become apparent from the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal cross-sectional view schematically showing the construction of an image reading apparatus according to Embodiment 1. 
         FIG. 2  is a perspective view schematically showing the construction of the image reading apparatus according to Embodiment 1. 
         FIG. 3  is a longitudinal cross-sectional view schematically showing the construction of an image reading apparatus according to Embodiment 2. 
         FIG. 4  is a longitudinal cross-sectional view schematically showing the construction of an image reading apparatus according to Embodiment 3. 
         FIG. 5  is a longitudinal cross-sectional view schematically showing the construction of an image reading apparatus according to Embodiment 4. 
         FIG. 6  is a longitudinal cross-sectional view schematically showing the construction of an automatic image reading apparatus according to Embodiment 5. 
         FIG. 7  is a longitudinal cross-sectional view schematically showing the construction of a conventional image reading apparatus. 
         FIG. 8  is a longitudinal cross-sectional view schematically showing the construction of another conventional image reading apparatus. 
         FIG. 9  is a longitudinal cross-sectional view schematically showing the construction of still another conventional image reading apparatus. 
         FIG. 10  is a longitudinal cross-sectional view schematically showing the construction of yet still another conventional image reading apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Some embodiments of the present invention will hereinafter be described with reference to the drawings. In the drawings, the same reference characters designate members similar in construction or action, and the duplicate description of these is suitably omitted. 
     Embodiment 1 
       FIGS. 1 and 2  show an image reading apparatus to which the present invention can be applied.  FIG. 1  is a longitudinal cross-sectional view of the image reading apparatus taken in a direction along the conveying direction of a sheet material S, and  FIG. 2  is a perspective view of the image reading apparatus as it is seen obliquely from above it. 
     The image reading apparatus  140  shown in  FIGS. 1 and 2  is provided with a sheet conveying guide  11 , an image reading unit  12 , a holding member  13 , an urging member  14 , an upstream roller pair  15  and a downstream roller pair  16 . 
     The sheet conveying guide  11  has its surface adjacent to the image reading unit  12  formed into a flat surface which provides a sheet conveying surface  103  for the sheet material conveyed in the direction indicated by the arrow. In the present embodiment, the sheet conveying surface  103  is horizontally disposed. 
     The image reading unit  12  has a reading portion housing  141 , an image reading sensor  146  and an image reading surface  145 . Of these, the entire image reading sensor  146  is fixedly disposed inside the reading portion housing  141 . The image reading sensor  146  has a light source  144  for applying light to the image surface of the sheet material S brought into close contact with the image reading surface  145 , a lens  143  for imaging reflected light from the image surface of the sheet material S, and a light receiving element  142  for converting the light imaged by the lens  143  into an electrical signal. The image reading surface  145  is attached to the lower portion of the reading portion housing  141  so as to be parallel to the sheet conveying surface  103  of the above-described sheet conveying guide  11 . A thin-plate-shaped image reading gap G is formed between the sheet conveying surface  103  and the image reading surface  145 . Design is made such that as will be described later, the sheet material S which is the object of image reading is conveyed into this image reading gap G by the upstream roller pair  15  and the image thereof is read with the image surface thereof brought into close contact with the image reading surface  145 , and after the image reading, the sheet material S is conveyed out of the image reading gap G by the downstream roller pair  16 . 
     In the present embodiment, a parallel moving mechanism is adopted as the holding member  13 . The parallel moving mechanism is constituted by vertical guide holes (guide portions)  141   c  formed in the longitudinal opposite end portions of the above-described image reading unit, and salients  101  and  102  protruded from an image reading apparatus main body M (see  FIG. 6 ) and engaged with these guide holes  141   c . By this parallel moving mechanism, the image reading unit  12  is held for movement in a vertical direction, i.e., a direction to change the width (the vertical dimension in  FIG. 1 ) of the above-described image reading gap G. 
     In the present embodiment, a compression spring  170  is used as the urging member  14 . This compression spring  170  urges the image reading unit  12  in a direction to narrow the width of the image reading gap G. 
     The upstream roller pair  15  is constituted by a drive roller  121  and a driven roller  131  brought into contact therewith from above it, and a conveying nip N 1  is formed between the two. The drive roller  121  is disposed so that the upper end thereof may slightly protrude from the sheet conveying surface  103  of the above-described sheet conveying guide  11 , and is rotatably driven by a drive source (not shown) such as a motor. On the other hand, the driven roller  131  is rotatably supported by an unrotatably disposed roller shaft  161 . The roller shaft  161  is vertically movably supported by a vertical guide hole  203  formed in the image reading apparatus main body M, and also is urged toward the drive roller  121  below it by a compression spring  180 . Also, the roller shaft  161 , near its longitudinal opposite end portions, is abutted against from below it by receiving portions  141   a  protruded from the above-described reading portion housing  141  toward an upstream side. Thereby, when the sheet material S is supplied to the conveying nip N 1  in an abutting state, the driven roller  131  is displaced relative to the drive roller  121  in accordance with the thickness of the sheet S, and the roller shaft  161  is adapted to be displaced by the same amount as this amount of displacement to thereby raise the entire image reading unit  12  through the receiving portions  141   a . Here, the vertical position of the lower end of the driven roller  131  is set so as to be substantially the same as the position of the underside of the image reading surface  145  of the image reading unit  12 . 
     The downstream roller pair  16  is constituted by a drive roller  122  and a driven roller  132  brought into contact therewith from above it, and a conveying nip N 2  is formed between the two. The drive roller  122  is disposed so that the upper end thereof may slightly protrude from the sheet conveying surface  103  of the above-described sheet conveying guide  11 , and is rotatably driven by a drive source (not shown) such as a motor. On the other hand, the driven roller  132  is rotatably supported by an unrotatably disposed roller shaft  162 . The roller shaft  162  is vertically movably supported by a vertical guide hole  204  formed in the image reading apparatus main body M, and also is urged toward the drive roller  122  below it by the compression spring  180 . Also, the roller shaft  162 , near its longitudinal opposite end portions, is abutted against from below it by receiving portions  141   b  protruded from the above-described reading portion housing  141  toward a downstream side. Thereby, when the sheet material S is supplied to the conveying nip N 2  in an abutting state, the driven roller  132  is displaced relative to the drive roller  122  in accordance with the thickness of the sheet material S, and the roller shaft  162  is adapted to be displaced by the same amount as this amount of displacement to thereby raise the entire image reading unit  12  through the receiving portions  141   b . Here, the vertical position of the lower end of the driven roller  132  is set so as to be substantially the same as the position of the under side of the image reading surface  145  of the image reading unit  12 . 
     Description will now be made of the operation of the image reading apparatus  140  of the above-described construction. 
     When the leading edge of the sheet material S conveyed from the upstream side comes into the conveying nip N 1  between the conveying roller  121  and driven roller  131  of the upstream roller pair  15 , the driven roller  131  is upwardly moved (displaced) in accordance with the thickness of the sheet material S, and the roller shaft  161  is upwardly moved against the urging force of the compression spring  180  to thereby push up the receiving portions  141   a  of the reading portion housing  141 . The image reading unit  12 , as described above, is vertically movably held by the parallel moving mechanism and therefore, by the receiving portions  141   a  being pushed up, the entire image reading unit  12  is pushed up. Thereby, the image reading gap G between the sheet conveying surface  103  of the sheet conveying guide  11  and the image reading surface  145  is widened. At this time, the image reading gap G is widened by an amount corresponding to the amount of movement of the above-described driven roller  131 , i.e., to the same width as the thickness of the sheet material S. Therefore, the sheet material conveyed into the image reading gap G by the upstream roller pair  15  is smoothly conveyed into the image reading gap G, and the image surface as the upper surface thereof is brought into close contact with the image reading surface  145  of the image reading unit  12 . Accordingly, the image surface of the sheet material S is read well by the image reading sensor  146 . 
     Next, the leading edge of the sheet material S of which the image surface has been read comes into the conveying nip N 2  between the conveying roller  122  and driven roller  132  of the downstream roller pair  16 . Thereby, the driven roller  132  is upwardly moved by an amount corresponding to the thickness of the sheet material S to thereby upwardly raise the roller shaft  162 , and contacts with the reading portion housing  141   b  which is already located above, from below it. When the trailing edge of the sheet material S passes through the upstream conveying nip N 1 , the driven roller  131  is returned to its original position, i.e., the position in which it contacts with the drive roller  121 , by the urging force of the compression spring  180 . Again in this state, the image reading gap G keeps a state in which a suitable width substantially equal to the thickness of the sheet material S is kept because the image reading unit  12  is raised by the roller shaft  162  through the receiving portions  141   b . This state continues until the trailing edge of the sheet material S completely passes through the conveying nip N 2 . 
     When the trailing edge of the sheet material S has completely passed through the downstream conveying nip N 2 , the driven roller  132  is returned to its original position, i.e., the position in which it contacts with the drive roller  121 , by the urging force of the compression spring  180 . 
     When the image surfaces of a plurality of sheet materials S are to be continuously read, the conveying timing of the sheet materials S can be set so that before the trailing edge of a preceding sheet material S completely passes through the downstream conveying nip N 2 , the leading edge of the succeeding sheet material S may come into the upstream conveying nip N 1 . 
     As described above, the width of the image reading gap G is always kept at a suitable width substantially equal to the thickness of the sheet material S during the time from after the leading edge of the sheet material S has come into the upstream conveying nip N 1  until the trailing edge thereof completely passes through the downstream conveying nip N 2 . That is, the thickness of the sheet material S and the width of the image reading gap G correspond to 1:1 and therefore, the image surfaces of thin and thick sheet materials S can be read well without the occurrence of jam and the promotion of the abrasion of parts being involved and moreover, the image surfaces of the sheet materials S are brought into close contact with the image reading surface  145  and therefore, it never happens that a streak or blur occurs to the read image. 
     In addition, the same effect can be obtained if the urging member  14  is composed of a weight provided on the image reading unit  12  instead of the compression spring  170 . In this case, urging member  14  urges the image reading unit  12  using the gravity of the weight. 
     Moreover, the urging member  14  may be composed of a weight formed integrally with the image reading unit  12  as a single entity. 
     Embodiment 2 
     In this embodiment shown in  FIG. 3 , a parallel link mechanism is adopted as a mechanism for moving the image reading unit  12  in a direction to change the width of the image reading gap G. Except the parallel link mechanism, the construction of this embodiment is similar to that of the above-described Embodiment 1 and therefore, the other members are given the same reference characters as in Embodiment 1 and the description thereof will be suitably omitted. 
     The parallel link mechanism supports the image reading unit  12  by two links  181  and  182  of the same shape. The upstream link  181  is obliquely disposed so that one end portion  181   a  thereof may be disposed above and the other end portion thereof may be located below downstream of the one end portion  181   a  with respect to the conveying direction of the sheet material S. The link  181  is such that the upstream end portion  181   a  thereof is pivotably supported by the image reading apparatus main body M and the other end portion  181   b  thereof is rotatably supported by the receiving portion  141   a  of the reading portion housing  141  of the image reading unit  12 . The downstream link  182  is also similar to the upstream link  181 . That is, the downstream link  182  is obliquely disposed so that one end portion  182   a  thereof may be disposed above and the other end portion thereof may be located below downstream of the one end portion  182   a  with respect to the conveying direction of the sheet material S. The link  182  is such that the upstream end portion  182   a  thereof is pivotally supported by the image reading apparatus main body M and the other end portion  182   b  thereof is rotatably supported by the receiving portion  141   b  of the reading portion housing  141  of the image reading unit  12 . This parallel link mechanism forms a parallelogram by the end portions  181   a ,  181   b ,  182   a  and  182   b  of the above-described links  181  and  182 . Accordingly, the image reading surface  145  of the image reading unit  12  disposed in parallelism to the sheet conveying surface  103  of the sheet conveying guide  11  is adapted to always keep parallelism when the image reading unit  12  is moved in a substantially vertical direction. 
     According to the present embodiment, in addition to the effect of the above-described Embodiment 1, the vertical movement of the image reading unit  12  is effected by the pivotal movements of the links  181  and  182  at their respective end portions  181   a ,  181   b ,  182   a  and  182   b  and therefore, the motion thereof can be made smooth, and the high durability of the holding mechanism can be obtained. 
     In addition, the same effect can be obtained if the urging member  14  is composed of a weight provided on the image reading unit  12  instead of the compression spring  170 . In this case, urging member  14  urges the image reading unit  12  using the gravity of the weight. 
     Moreover, the urging member  14  may be composed of a weight formed integrally with the image reading unit  12  as a single entity. 
     Embodiment 3 
       FIG. 4  shows an image reading apparatus according to Embodiment 3. The image reading apparatus  140  shown in  FIG. 4  is such that the image reading unit  12  is fixedly disposed below the image reading gap G and the sheet conveying guide  11  is substantially vertically movably disposed above the image reading gap G. The driven roller  131  (third roller member) of the upstream roller pair  15  has its roller shaft  161  upwardly brought into contact with the lower portion of a receiving portion  190   a  protruded to the upstream side from the sheet conveying guide  11 . Also, the driven roller  132  (fourth roller member) of the downstream roller pair  16  has its roller shaft  162  upwardly brought into contact with the lower portion of a receiving portion  190   b  protruded to the downstream side from the sheet conveying guide  11 . Further, in the present embodiment, the sheet conveying guide  11  is held by a parallel link mechanism similar to that in the above-described Embodiment 2. 
     In the present embodiment, design is made such that the sheet material S is conveyed through the image reading gap G with its image surface facing downwardly. 
     In the present embodiment of the above-described construction, design is made such that if the sheet material S is nipped by at least one of the conveying nip N 1  of the upstream roller pair  15  and the conveying nip N 2  of the downstream roller pair  16 , the sheet conveying guide  11  is upwardly moved and the image reading gap G is kept at a width substantially equal to the thickness of the sheet material S. 
     According to the present embodiment, there can be achieved an effect similar to that of the above-described Embodiment 2. 
     In addition, the same effect can be obtained if the urging member  14  is composed of a weight provided on the sheet conveying guide  11  instead of the compression spring  170 . In this case, urging member  14  urges the sheet conveying guide  11  using the gravity of the weight. 
     Moreover, the urging member  14  may be composed of a weight formed integrally with the sheet conveying guide  11  as a single entity. 
     Embodiment 4 
       FIG. 5  shows an image reading apparatus according to Embodiment 4. The image reading apparatus  140  shown in  FIG. 5  comprises a combination of the image reading apparatus of Embodiment 2 shown in  FIG. 3  and the image reading apparatus of Embodiment 3 shown in  FIG. 4  so as to read images on the two sides of the sheet material S at a time. 
     That is, the image reading unit  12  shown in  FIG. 4  is disposed below the image reading gap G, and the image reading unit  12  shown in  FIG. 3  is disposed above the image reading gap G. In the present embodiment, the image reading surface  145  of one image reading unit serves also as the sheet conveying surface of the other reading unit. 
     According to the present embodiment, in addition to the effect of Embodiment 3, there is the effect that the images on the two sides of the sheet material S can be read at a time. 
     In addition, the same effect can be obtained if the urging member  14  is composed of a weight provided on the image reading unit  12  instead of the compression spring  170 . In this case, urging member  14  urges the image reading unit  12  using the gravity of the weight. 
     Moreover, the urging member  14  may be composed of a weight formed integrally with the image reading unit  12  as a single entity. 
     Embodiment 5 
       FIG. 6  shows the construction of an automatic image reading apparatus for automatically reading the image surface of the sheet material S by the utilization of the image reading apparatus  140  shown in  FIG. 5 . 
     The automatic image reading apparatus  100  is provided with a sheet stacking portion  100   a  in which a plurality of sheet materials S which are the object of image reading are contained in their stacked state, a feeding and conveying apparatus  110  for feeding and conveying the sheet materials S, an image reading apparatus  140  for reading the images of the sheet materials S supplied form this feeding and conveying apparatus  110 , a discharging portion  111  for discharging the sheet materials S after image reading, and a discharged sheet stacking portion  100   b  in which the sheet materials S after image reading are contained in a stacked state. Of these, the feeding and conveying apparatus  110  has a sheet feeding roller  110   a  for supplying the sheet materials S one by one, a pair of separating and feeding rollers  110   b  and  110   c  for separating and supplying the sheet materials S fed by the sheet feeding roller  110   a  one by one, and an arm  110   d . for rotatably and substantially vertically rockably supporting the above-described sheet feeding roller  110   a . The image reading apparatus  140  is that shown in  FIG. 5  which can read the images on the two sides of the sheet material S at a time, as described above. As the image reading apparatus, use may be made of that described in the foregoing Embodiment 1, 2 or 3. 
     The discharging portion  111  has a pair of conveying rollers  123  and  133  for conveying the sheet material S after image reading, and a pair of sheet discharging rollers  124  and  134  for discharging the sheet material S to the discharged sheet stacking portion  110   b . Of these rollers, the rollers  123  and  124  are drive rollers, and the rollers  133  and  134  are driven rollers. 
     Description will now be made of the operation of the automatic image reading apparatus  100  of the above-described construction. 
     When the image reading operation is started, the plurality of sheet materials S stacked on the sheet stacking portion  100   a  are fed one by one by the feeding and conveying apparatus  110 , and are conveyed into the image reading gap G between upper and lower image reading units  12  by the upstream roller pair  15 . The sheet material S conveyed into the image reading gap G is conveyed with image surfaces formed on the two sides thereof being brought into close contact with the image reading surfaces  145  of the upper and lower image reading units  12  and at the same time, the image surfaces are read by image reading sensors  146 . The sheet material S after image reading is conveyed out of the image reading gap G by the downstream roller pair  16   b , and is further discharged onto the discharged sheet stacking portion  110   b  by the pair of conveying rollers  123  and  133  and the pair of sheet discharging rollers  124  and  134 . Thereby the image reading operation for a sheet material S is completed. When the image surfaces of a plurality of sheet materials S are to be continuously read, the supply timing of the sheet materials S by the feeding and conveying apparatus  110  can be set so that as described above, before the trailing edge of the preceding sheet material S completely passes through the downstream conveying nip N 2 , the leading edge of the succeeding sheet material S may come into the upstream conveying nip N 1 . 
     Again in the automatic image reading apparatus  100  described above, an effect similar to that previously described can be achieved by using the above-described image reading apparatus  140 . 
     According to the foregoing Embodiments 1 to 5, if the sheet material is nipped by at least one of the upstream roller pair and the downstream roller pair, the image reading apparatus or the sheet conveying guide is parallel-moved and the width of the image reading gap can be kept at a width corresponding to the thickness of the sheet material. Accordingly, the images of thin and thick sheet materials can be read well without the occurrence of jam and the promotion of the abrasion of parts being involved and moreover, it never happens that a streak or blur occurs to the read images. 
     This application claims priority from Japanese Patent Application No. 2004-143161 filed on May 13, 2004, which is hereby incorporated by reference herein.

Technology Category: 3