Abstract:
Provided is a document reading apparatus in which an original document fed by feeding means to contact glass having a predetermined reading position is read by reading means. Then, the document reading apparatus is provided with a guide unit having a guide member for guiding the original document to be fed to the contact glass, and a backup unit to back up the original document to be read, and the guide unit is configured to be able to travel between a close position to near the contact glass and an open position to distance from the contact glass. In the guide unit is formed a concave portion for removably accommodating the backup unit, and the backup unit is configured so that an original document guide face of the guide member and an original document guide face in the backup unit form a continuous guide face when the guide unit travels to the close position. 
     Then, the guide unit is moved to the open position to perform cleaning of the backup unit and contact glass. Further, the backup unit is removed to perform maintenance.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image reading apparatus for reading a transported original document, and more specifically, to an image reading apparatus having a shading unit provided opposite to a reading surface to read an original document. 
     2. Description of the Related Art 
     There has conventionally been known the so-called sheet-through type image reading apparatus which is an apparatus for reading an image of an original document passed through a reading section of a transport path by a reading unit at rest. In such an image reading apparatus, concentration differences occur in a read image by fluctuations in sensitivity for each pixel of a photoelectric converter constituting an image reading means, fluctuations in quantity of light and characteristics of a light source, reflecting mirrors and the like, variations in image formation by a lens and the like, etc. To correct the concentration differences, a shading plate formed of a plate-shaped white member is disposed in a position opposite to a reading platen, the shading plate is read at arbitrary timing to obtain shading correction data, and an excellent read image is formed by capturing the shading correction data into the image data (for example, Japanese Laid-Open Patent Publication Nos. H05-130330 and H07-231378). 
     In general, the shading plate often has a structure where the plate is fixed in the position opposite to the reading surface on the reading unit side, or the plate is attached by inserting into an insertion hole in the opposite position provided integrally with the reading surface. 
     However, in the structure where the white shading plate to acquire the shading correction data is fixed in the position opposite to the reading surface, when dust, stain or the like adheres to the surface of the shading plate, to remove the dust or stain, the problem arises that the apparatus body with the shading plate attached needs to be disassembled. Further, when the shading plate is attached after once the apparatus body is disassembled, another problem occurs that alignment with the reading surface is not easy. 
     Moreover, even when part of the shading plate is stained, the shading plate needs to be replaced. Alternately, when the shading plate is in film form, a new film needs to be bonded after removing the old film. Therefore, it takes time to perform cleaning and maintenance, interfering with the operation of the image reading apparatus. 
     Hence, it is an object of the invention to provide a document reading apparatus having a detachable structure to facilitate cleaning and maintenance of a shading plate to form a transport path of an original document and perform shading processing, while enabling reading processing for an excellent image to be executed even when the shading plate is stained or the like. 
     SUMMARY OF THE INVENTION 
     To solve the above-mentioned problems, a document reading apparatus of the invention is configured so that a backup unit, disposed opposite to contact glass to read an original document, having a white member to back up the read original document, is removably attached to a guide member, and that the guide member is rotated to a position enabling the backup unit to be attached and detached. 
     In this way, by rotating the guide member with the backup unit inserted, it is made possible to attach and detach the backup unit, while the contact glass is exposed, it is thereby possible to concurrently perform maintenance such as cleaning of the backup unit, position adjustment of the white member and the like, and maintenance such as cleaning of the contact glass and the like, and the maintenance work is thus made ease. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view showing the entire image reading apparatus provided with a document feeding apparatus according to the invention; 
         FIG. 2  is a perspective view of the document feeding apparatus; 
         FIG. 3  is a cross-sectional view of a principal part of the document feeding apparatus; 
         FIG. 4  is a perspective view showing a state before inserting a backup unit into a guide member; 
         FIG. 5  is a perspective view showing a state where the backup unit is inserted into the guide member; 
         FIG. 6  is a perspective view showing a support structure for supporting a white member; 
         FIG. 7  is a cross-sectional view showing a state where a guide unit is distanced from the document feeding apparatus; 
         FIG. 8  is a cross-sectional view showing a state immediately before the guide unit is set in the document feeding apparatus; 
         FIG. 9  is a cross-sectional view showing a state where the guide unit is set in the document feeding apparatus; 
         FIG. 10  contains a plan view and cross-sectional view showing a state where the white member is set in a normal position; and 
         FIG. 11  contains a plan view and cross-sectional view showing a state where the white member is displaced and set. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a cross-sectional view showing an image reading apparatus installed with a document feeding apparatus,  FIG. 2  is a perspective view of the document feeding apparatus, and  FIG. 3  is an enlarged cross-sectional view of the document feeding apparatus. 
     In  FIGS. 1 and 2 , “A” denotes the document feeding apparatus mounted on the top of the image reading apparatus body H. This document feeding apparatus A is disposed so that an original document is passed and transported on first platen glass  1  provided on the top surface of the image reading apparatus H. 
     The image reading apparatus H is provided with a first reading unit  3  for applying light emitted from a light source such as a lamp or the like to an original document through the first platen glass  1 , reflecting the reflected light with a plurality of mirrors, performing photoelectric conversion on the light via a lens with a photoelectric conversion means such as a CCD or the like, and thereby reading the original document image, and a first reading section  5  of the image reading apparatus H is formed on the top surface of the first contact glass  1 . Further, the image reading apparatus H is provided with second platen glass  2  at the back of the first platen glass  1 . The second platen glass  2  is configured to read an original document image by opening the document feeding apparatus A upward, mounting a thick original document such as a book, magazine and the like on the second platen glass  2 , and shifting the first reading unit  3  in the sub-scanning direction. 
     The document feeding apparatus A is provided with a paper feed tray unit  10  to mount an original document, a paper discharge tray  11  disposed below the paper feed tray unit  10  to store the original document such that the original document image is read by the image reading apparatus H, a pressing cover  12  to press the second platen glass  2 , and a U-shaped transport path  13  to transport the original document to the paper discharge tray  11  from the paper feed tray unit  10 . In addition, the pressing cover  12  is formed of a porous member such as, for example, sponge or the like, and a film member such as a white Mylar sheet or the like. Further, the paper feed tray unit  10  is formed of a paper feed tray  10   a  for supporting the rear end side of an original document, and an up-and-down tray  10   b  for moving up and down between a set position for mounting the original document and a feeding position for feeding the document. 
     Further, in the document feeding apparatus A, a second reading unit  4  for reading an image on the back side of the original document is provided in a bend of the U-shaped transport path  13 . As shown in  FIG. 3 , the second reading unit  4  has a light source  41  such as a lamp or the like for applying light to an original document transported on contact glass  7 , a plurality of mirrors  42 ,  43 ,  44 ,  45  for leading the reflected light from the original document in a predetermined direction, a lens  46  for causing the reflected light lead by the plurality of mirrors  42 ,  43 ,  44 ,  45  to converge, and a photoelectric conversion element  47  for performing photoelectric conversion on the light gathered by the lens  46 . 
     Then, an original document is irradiated with the light emitted from the light source  41  such as the lamp or the like through the contact glass  7  forming part of the transport path  13 , the reflected light is reflected by the plurality of mirrors  42 ,  43 ,  44 ,  45 , and subjected to photoelectric conversion by the photoelectric conversion means  47  such as a CCD or the like via the lens  46 , and the original document image is thus read. In addition, herein, the top surface of the contact glass  7  is formed as a second reading section  6  of the image reading apparatus H. 
     In the document feeding apparatus A, the second reading unit  4  reads an original document image on one side of the original document passed through the second reading section  6  at some midpoint in the transport path  13 , while the first reading unit  3  reads an original document image on the other side of the original document passed through the first reading section  5 , and it is thereby possible to greatly reduce the image reading time of a two-sided original document. 
     The U-shaped transport path  13  has a feeding roller  21  to feed original documents from the paper feed tray unit  10 , separating means formed of a paper feed roller  22  and separating pad  23  to separate the documents fed from the feeding roller  21  on a sheet basis to feed, and a resist roller pair  24  for aligning the front end of the original document by the front end of the document fed from the paper feed roller  22  hitting a nip point of the resist roller pair  24 , thereby removing skew, and then being driven to send the document to the downstream side. Further, the transport path  13  has a sending roller pair  25  for sending the document from the resist roller pair  24  toward the second reading section  6  and first reading section  5 , a first read roller pair  26  that is a guide member to supply the document from the sending roller pair  25  to the second reading section  6 , and a second read roller pair  27  for supplying the document of which one side is read by the second reading section  6  to the first reading section  5 . Furthermore, the transport path  13  has a third read roller pair  28  for carrying out the document of which two sides are read by the second reading section  6  and first reading section  5  from the first reading section  5 , and a paper discharge roller pair  29  for receiving the document, which is passed through the first reading section  5  and of which two sides are read, from the third read roller pair  28  to transport toward the paper discharge tray  11 . In this embodiment, the transport path  13  is configured as a transport unit F with a plurality of members incorporated thereinto. 
     Herein, as shown in  FIG. 3 , a guide unit  9  is disposed in a position opposite to the contact glass  7  of the second reading unit  4 . As shown in  FIGS. 4 and 5 , the guide unit  9  is formed of a guide member  51  and a backup unit  20  inserted removably in the guide member  51 . The guide member  51  is provided with a concave portion  56  to insert the backup unit  20  therein. On the side opposite to the contact glass  7  above the concave portion, a guide portion  51   d  is formed which is part of the outside transport guide for guiding an original document to the second reading section  6 , and a driven roller of the first read roller pair  26  is provided. The original document is guided to the contact glass  7  by the guide portion  51   d  and first read roller pair  26 . Further, the guide member  51  is attached to side plates  80  of the document feeding apparatus A as shown in  FIG. 2  through a rotation shaft  51   e  provided on the lower side of the member  51 , and attached to be opened and closed by the upper side rotating around the rotation shaft  51   e  to enable the backup unit  20  to be attached and detached to/from the concave portion  56 . The backup unit  20  is provided with a box-shaped holder member  54  inserted in the concave portion  56 , a white member  53  attached to the front of the holder member  54 , and a transparent member (backup glass)  52  for protecting the top surface of the white member  53 . In addition, the white member  53  is used to acquire reference data to make a shading correction. 
     Meanwhile, the entire inner wall of the holder member  54  is black, and it is configured to make a backup color of an original document white by shifting the white member  53  to the position opposite to the contact glass  7 , and switch the backup color of the original document to black by withdrawing the white member  53  from the position opposite to the contact glass  7 . Then, by this configuration, the document is prevented from reflecting by its back side. 
     The concave portion  56  of the guide member  51  has an upper inner wall  51   a  and lower inner wall  51   b  extending in the longitudinal direction. A pair of protrusions (ribs)  57  are provided closer to the opposite ends in the longitudinal direction of the upper inner wall  51   a , and an engagement hole  58  is provided in the substantially center portion in the longitudinal direction of the lower inner wall  51   b . Further, in the bottom  51   c  of the concave portion  56  is disposed a compression spring  55  toward the backup glass  52 . 
     As shown in  FIGS. 4 to 6 , the holder member  54  is configured in the shape of a box with an upper side  54   a  and lower side  54   b  mating with the upper inner wall  51   a  and lower inner wall  51   b  of the concave portion  56 , the back  54   c  coming into contact with the compression spring  55 , and a left side  54   d  and right side  54   e  holding the opposite end portions in the longitudinal direction of the white member  53 , and to a front portion  53  are attached the white member  53  and the backup glass  52  to cover the white member  53 . Further, an engagement click  59  engaging in the engagement hole  58  of the guide member  51  is provided in the substantially center portion in the longitudinal direction of the lower side  54   b , and as shown in  FIG. 6 , a pair of holding members  70 ,  71  are provided in both side portions of the left side  54   d  and right side  54   e  to hold the opposite end portions in the longitudinal direction of the white member  53  by cooperating with the left side  54   d  and right side  54   e , while holding the backup glass  52  attached to the front portion  54   f.    
     The holder member  54  is inserted in a temporary joint state into the concave portion  56  with the lower side  54   b  fixed, as shown in  FIG. 5 , by the upper side  54   a  coming into contact with the pair of ribs  57  and engaging in the ribs by friction force, and concurrently the engagement click  59  being inserted in the engagement hole  58 . At this point, as shown in  FIG. 7 , since the back  54   c  of the holder member  54  receives the elastic force and is held by the compression spring  55 , the holder member  54  is in a rest state while the upper side  54   a  is pushed slightly forward with respect to the lower side  54   b  where the engagement click  59  is engaged in the engagement hole  58 . Accordingly, the white member  53  is inclined with respect to the opening of the concave portion  56 . 
       FIG. 8  shows a state where the backup unit  20  is inserted in the guide member  51 , and then the guide unit  9  is rotated toward the contact glass  7  of the reading unit of the document feeding apparatus A. As described above, since the backup unit  20  is inserted in the guide member  51  so that the upper face side is inclined forward, when the guide unit  9  is rotated to the position opposite to the contact glass  7 , the white member  53  protected by the backup glass  52  can be opposed in a position substantially parallel with the contact glass  7 , and in this state, by pressing the backup glass  52  to the contact glass  7  as shown in  FIG. 9 , the guide unit  9  is set in the document feeding apparatus A with the backup unit  20  held elastically in the guide member  51  via the compression spring  55 . 
     Further, a plurality of protrusions  60  is provided in opposite end portions out of the document transport range in the document main scanning direction of the guide member  51  of the guide unit  9 . Then, by biasing the guide unit  9  to the second reading unit  4  side by the compression spring  55 , the plurality of protrusions  60  comes into contact with the document reading surface of the contact glass  7  of the second reading unit  4 , and is configured to keep a distance between the contact glass  7  and backup glass  52  at a minimum distance. 
     Next, the configuration of the backup unit  20  will be described. The white member  53  provided in the backup unit  20  has a flexible white film bonded to its surface, and is attached with the white film surface faced to the front  54   f  side of the holder member  54 , and the white film surface is protected by the backup glass  52 . Further, as shown in  FIGS. 6 ,  10  and  11 , the white member  53  is provided in its opposite end portions in the longitudinal direction respectively with engagement protrusions  61   a ,  61   b  faced outward, and the engagement protrusions  61   a ,  61   b  engage in engagement grooves  70   a ,  71   a  of the holding members  70 ,  71  attached to the left side  54   d  and right side  54   e  of the holder member  54 , respectively. 
     The holding members  70 ,  71  will specifically be described below. In addition, this pair of the holding members  70 ,  71  have the same configuration, and for the sake of convenience, the holding member  70  that is one of the pair will be described herein. As shown in  FIG. 6 , in this holding member  70  are provided the engagement groove  70   a , supporting portions  70   b ,  70   c  for sandwiching the backup glass  52  with the edge of the front portion  54   f  of the holder member  54  to support, the protrusions  60  for coming into contact with the document reading surface of the contact glass  7  to maintain the distance between the contact glass  7  and backup glass  52  at the minimum distance, positioning holes  73  to fit with a plurality of bosses  72  protruding from the left side  54   d  of the holder member  54 , a first insertion hole  75  to insert a mounting screw  65  so as to attach the holding member  70  to the left side  54   d  of the holder member  54  at normal times, and a second insertion hole  63  to insert a mounting screw  65  in adjusting the position of the white member  53 . 
     In addition, in the left side  54   d  of the holder member  54 , screw holes are formed in portions respectively associated with the first and second insertion holes  75 ,  63 . The mounting screw  65  is inserted into one of the first and second insertion holes  75 ,  63  and fastened to the corresponding screw hole, and the holding member  70  is thereby attached to the left side  54   d  of the holder member  54 . Further, the first insertion hole  75  is a circular hole to enable the holding member to be positioned reliably, and the second insertion hole  63  is a long hole to enable the holding member  70  to slide. Therefore, the white member  53  enables its end portion to slightly slide on the holder member  54  depending on the fastened position of the mounting screw. 
     In other words, at normal times, as shown in  FIG. 10(   b ), the mounting screw  65  is inserted into the first insertion hole  75  to attach the holding member  70 . At this point, the engagement position of the engagement protrusion  61   a  held by the holding member  70  is in a state where the white member  53  is straight and parallel to the holder member  54  in the longitudinal direction as shown in  FIG. 10(   a ). 
       FIG. 11(   a ) shows a state where one holding member  70  is slid and shifted i.e. a state where the white member  53  is slid. Thus, when the white member  53  is slid, as shown in  FIG. 11(   b ), the mounting screw  65  is removed, one holding member  70  is slid rightward as viewed in the figure, the mounting screw  65  is inserted into the long hole of the second insertion hole  63  and fastened to the screw hole, and as shown in  FIG. 11(   a ), the white member  53  is set while being tilted with respect to the holder member  54 . 
     As shown in  FIGS. 10 and 11 , by slightly adjusting the position of the white member  53  by sliding, it is possible to displace the background position of a read line X through the contact glass  7 . By this means, when dust and/or stain is present on the normal read line X, it is possible to perform shading processing in the position for avoiding the dust and/or stain by sliding the white member  53 . 
     Further, on the back of the backup glass  52  is provided a regulating member  70  with which the white member  53  comes into contact. The regulating means  70  is to secure a gap between the backup glass  52  and white member  53  in the reading position, and securing the gap prevents the occurrence of Newton ring which is caused by the white member  53  coming into contact with the backup glass  52 . 
     According to this embodiment, since such a configuration is provided that the backup unit  20  is removably attached to the guide member  51 , maintenance is made ease such as cleaning, position adjustments and the like of the white member  53  and backup glass  52 . 
     Further, the guide member  51  is configured to be able to rotate to the position for removing the backup unit  20  to perform maintenance, it is further configured that by this rotation operation of the guide member  51 , the contact glass  7  is exposed and also undergoes maintenance, and therefore, maintenance of the contact glass  7  is also made ease, as well as maintenance such as cleaning, position adjustments and the like of the white member  53  and backup glass  52 . 
     Furthermore, it is possible to temporarily install the backup unit  20  with the white member  53  inclined, by the engagement hole and engagement click respectively provided in the concave portion  56  and backup unit  20 , and the ribs and compression spring provided in the concave portion  56 . By this means, in rotating the guide unit  9  toward the document feeding apparatus A, without requiring any particular adjustment, the white member  53  is opposed to the contact glass  7  surface of the reading unit to be substantially parallel therewith, and in this state, the guide member  51  elastically accommodates the backup unit  20 . 
     Moreover, since the white member  53  is attached to the holder member  54  to enable its slide adjustment, even when dust and/or stain adheres to the background of the reading surface via the contact glass  7  of the white member  53 , it is possible to perform shading processing while avoiding the dust and/or stain without exchanging the white member  53 .