Patent Publication Number: US-6219511-B1

Title: Image reading apparatus having a guide member and transport member

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image reading apparatus to read document images and used in copy machine and the like. 
     2. Description of the Related Art 
     Conventional image reading apparatuses (hereinafter referred to as “stationary platen panning devices”) are known which read the image of an entire document by placing a document on a glass platen at the image reading position of a static reader, and transporting said document over said glass platen at a constant speed. In stationary platen panning devices, a document must be transported onto the glass platen with precision in order to accurately read the document image. To this end, stationary platen panning devices are known to provide a transport roller to transport a document between said transport roller and the glass platen. 
     In such stationary platen panning devices, although a document can be transported with precision in the range of the nip formed between the glass platen and the transport roller when said document is gripped between the transport roller and the glass platen, a disadvantage arises insofar as the document curls along the transport roller on the upstream side and downstream side of said nip. 
     On the other hand, stationary platen panning devices typically have a reader with a reading range capable of reading the width of the document in the document transport direction in a single pass. When the stationary platen panning device is an analog copy machine, the single pass reading range of the reader is particularly broad. Accordingly, the nip width between the transport roller and glass platen must be broader than the single pass reading range of the reader. Since the diameter of the transport roller in contact with the glass platen must be increased, therefore, the size of the image reading apparatus is increased. 
     OBJECTS AND SUMMARY 
     An object of the present invention is to provide an image reading apparatus capable of accurately transporting documents without increasing the overall size of the apparatus. 
     Objects of the present invention are attained by providing an image reading apparatus comprising: a 
     a reader to read document images, said reader having a stationary image reading position; and 
     a transporter to transport a document at constant speed onto the image reading position, said transporter including guide members and a transport member, 
     said guide members to guide document transport and which are provided adjacent to the upstream side of a document reading position in the direction of document transport by said transporter, and 
     said transport member to transport a document without gripping between said guide members and itself and provided above said guide members. 
     These and other objects, advantages and features of the present invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate specific embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following description, like parts are designated by like reference numbers throughout the several drawings. 
     FIG. 1 is a section view of a copy machine related to an embodiment of the present invention; 
     FIG. 2 is a perspective view of a copy machine related to an embodiment of the present invention; 
     FIG. 3 is a section view showing the essential part of the image reading apparatus related to an embodiment of the present invention; and 
     FIG. 4 is an exploded perspective view showing the essential part of the image reading apparatus of an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The image reading apparatus of the present invention is described hereinafter in terms of an embodiment as an analog copy machine with reference to the accompanying drawings. 
     The analog copy machine shown in FIGS. 1 and 2 comprises a copier unit  2  and a document feeding device  1  situated on top of copier unit  2 . 
     Copier unit  2  copies a document image to a copy sheet via a well known electrophotographic process. The copier unit  2  comprises a photosensitive drum  3  supported so as to be rotatable, and sequentially arranged around the periphery of said drum  3  are charger  4 , developing device  5 , transfer charger  6 , and cleaner  7 . When an optical image of a document is exposed on the surface of photosensitive drum  3  which has been previously charged to a uniform charge by charger  4 , an electrostatic latent image of said document is formed on the surface of photosensitive drum  3 . This electrostatic latent image is developed by developing device  5  so as to produce a toner image. This toner image formed on the surface of the photosensitive drum  3  is transferred via transfer charger  6  onto a copy sheet transported from paper supply tray  8 . Residual toner remaining on the surface of the photosensitive drum  3  is removed by cleaner  7 . 
     A sheet lifting plate  9  which exerts an upward force via a spring  10  and is vertically moveable in one direction and an opposite direction is provided at the leading edge of paper supply tray  8 , such that a copy sheet placed on said sheet lifting plate  9  is directed toward a feed roller  11  located thereabove. Copy sheets fed one sheet at a time by feed roller  11  are transported to the position of charger  6  via a pair of timing rollers  13 . A copy sheet bearing the toner image transferred by transfer charger  6  is directed to a pair of fixing rollers  14  which fuse said toner image on said copy sheet, and thereafter the copy sheet is ejected to discharge unit  16   a  by a pair of discharge rollers  15 . 
     The present embodiment is provided with a mirror scanning mode to copy a document placed on the glass platen by an operator, and a panning mode to copy a document transported at constant speed by automatic document feeder  1 . The mirror scanning mode and panning mode are automatically selectable depending on whether or not a document is present in document tray  26  when the print key  50  is pressed by an operator. 
     On the top of copier unit  2  are sequentially arranged mirror scanning glass platen  17 , document scale  18 , and panning glass platen  19 . Located below glass platens  17 ,  19  and document scale  18  are a first slider  41  upon which are mounted exposure lamp  20  and mirror  21 , and a second slider  42  upon which are mounted mirrors  22  and  23 , said first and second sliders  41  and  42  being moveable in lateral directions in the drawings. A notch  43  is formed on the bottom surface of first slider  41 , and a sensor  44  is mounted on the copier unit  2  to detect said notch  43 . When notch  43  is detected by the aforesaid sensor  44 , the position of the first slider  41  is the first slider home position, which is the stationary position for the panning mode. 
     In the mirror scanning mode, the first slider  41  moves reciprocatingly below the mirror scanning platen  17 , and the second slider  42  moves reciprocatingly at one half the speed of said first slider  41 . At this time, the light reflected from a document illuminated by exposure lamp  20  is sequentially reflected by mirrors  21 - 25  and  16 , and subsequently irradiates the surface of photosensitive drum  3 . In the panning mode, however, the exposure lamp  20  and mirrors  21 - 23  all remain in a stationary state. At this time, exposure lamp  20  illuminates the panning platen  19 , and the optical image light of part of the document transported at constant speed over the panning platen irradiates the surface of photosensitive drum  3  via mirrors  21 - 25  and  16 . That is, the panning glass platen  19  corresponds to the image reading position of the present invention, and the exposure lamp  20  and mirrors  21 - 25  and  16  are correspond to the image reader. 
     Document feeding device  1  is described below. Document feeding device  1  corresponds to first transporter to transport a document at constant speed over the panning glass platen  19 . Document feeding device  1  is joined to the copier unit  2  on the interior side by hinges  40 , and opens upward relative to the body of the copier unit  2 . Document feeding device  1  briefly is a device to feed documents over panning platen  19 ; a document tray  26  is formed on the top surface of document feeding device  1  at a position above mirror scanning platen  17 , and accommodates stacked documents to be read by the reader. A document lifting plate  27  is provided at the edge of the document tray  26  in the document transport direction, and exerts an upward force via a spring  28  and is vertically moveable in one direction and an opposite direction. Document lifting plate  27  is lifted upward by spring  28  only when a document is transported, and at other times is pulled downward by a retracting means not shown in the illustration. Above document lifting plate  27  is provided a document sensor  45  to detect the presence/absence of a document. When an operator presses the print key  50  and document sensor  45  detects a document, the panning mode is set and the retracting means is released such that the document lifting plate  27  is raised. On the other hand, when print key  50  is pressed and document sensor  45  does not detect a document, the mirror scanning mode is set. 
     A sheet placed on document lifting plate  27  is directed upward to top pick-up roller  29 . A document fed one sheet at a time by pick-up roller  29  passes between top guide  37  and bottom guide  36  via the transporting force supplied by the pair of transport rollers  30  and pair of timing rollers  31 , and arrives at transport roller  32  which is the transport member directly upstream from the panning platen. A document that passes transport roller  32  then passes between panning glass platen  19  and top guide  38  located thereabove, passes between a pair of transport rollers  33 , and is ejected via a pair of discharge rollers  34  onto discharge tray  35  formed on the top surface of document feeding device  1  at a position above said transport mechanism. That is, transport roller  32  corresponds to the second transporter of the present invention, and document scale  18  corresponds to a guide member. 
     FIGS. 3 and 4 show details of the essential part of document feeding device  1  of the embodiment. 
     The previously mentioned top guides  37  and  38  are formed by a single guide panel  46 . The rotational axis of transport roller  32  is provided above guide panel  46 , but openings  46   a  are provided in guide panel  46  at a position corresponding to transport roller  32 , such that said transport roller  32  protrudes downward from said openings  46   a.    
     Transport roller  32  is positioned adjacent to the top surface of document scale  18  which is mounted on the side of copier unit  2 . Specifically, the bottom surface of transport roller  32  is disposed at a position of equal height to the top surface of document scale  18 . On the other hand, document scale  18  is provided with channels  18   a  at a position confronting the transport roller  32  and having a width sufficient to allow transport roller  32  to be accommodated therein so as to avoid direct contact with the transport roller  32 . Since transport roller  32  does not grip the document passing between said roller and the glass platen, the diameter of the roller need not be increased, thereby avoiding an increase in the size of the document feeding device  1 . 
     Flexible films  36   a  and  39   a  are respectively adhered to the top surface of bottom guide  36  directly upstream from document scale  18  and bottom guide  39  directly downstream from panning platen  19 . The flexible film  36   a  on the upstream side of document scale  18  functions to make contact with the document on the transport roller  32  side. The flexible film  39   a  directly downstream from the panning platen functions to make contact with the document on the top guide  38  side. 
     In this construction, a document transported by the pair of timing rollers  31  is moved downward at an angle toward transport roller  32 , and is fed by transport roller  32  between said transport roller  32  and document scale  18  parallel to panning platen  19 . A document that passes panning platen  19  is guided by top guide  38  and flexible film  39   a  at an upward angle. Since the document transport path has a convex curved shape under the position of transport roller  32 , the document makes contact with said transport roller  32  via the stiffness of the document sheet itself. Accordingly, transport roller  32  exerts a transporting force on the document without a mechanism to grip said document. Of course, transport roller  32  also may be constructed so as to make contact with the document scale  18 . A construction wherein the transport roller  32  does not make contact with the document scale  18  is advantageous, however, insofar as the document scale  18  is not subject to damage by contact with the transport roller. 
     Furthermore, since transport roller  32  is adjacent to the panning platen  19  at the image reading position, the portion of a document that has passed transport roller  32  arrives at the reading position without disruption. In particular, because the bottom surface of the transport roller  32  is positioned at the same height as the top surface of the panning platen  19 , the document transport path from the transport roller  32  to the image reading position is a straight horizontal line, thereby increasing the accuracy of transporting the document at constant speed at the image reading position. 
     Consider a construction wherein only the transport roller is eliminated, i.e., eliminating the transport roller  32  from the present embodiment, to eliminate the disadvantage of conventional apparatuses wherein the diameter of the transport roller must be increased when the transport roller is disposed so as to abut the platen. Even in a construction which eliminates the transport roller  32 , the lower limit of document transport precision can be maintained when a document is gripped by both the pair of rollers  31  on the upstream side of platen  19  and the pair of rollers  33  on the downstream side thereof. Sufficient document transport precision cannot be maintained when a document is gripped only by either the pair of rollers  31  on the upstream side or the pair of rollers  33  on the downstream side. Particularly in the form of the present embodiment, because the transport path to transport a document upward to the panning platen  19  must be provided above the mirror scanning platen  17 , the document transport path assumes a curved shape leading downward to the image reading position, whereby a document is transported downward in a curved state in opposition to the stiffness of the document sheet. Therefore, the trailing edge of the document passes the pair of timing rollers  31  as the transport of said document advances such that said document trailing edge assumes a free state when released from said rollers thereby releasing the curved condition of the document via the stiffness of the sheet and causing disruption of the document during transport. In contrast, in the present embodiment, the transport state of the document is not disrupted at the moment the document trailing edge is released from the timing rollers  31  because a transport roller is provided adjacent to the image reading position. 
     As described above, the present invention transports a document between a transport member and guide member on the upstream side of the image reading position in an image reading apparatus provided with a document transporter to read a document image by transporting a document at uniform speed onto an image reading position of a stationary reader. Therefore, enlargement of the overall reading apparatus is avoided because a large transport member is not required at the image reading position. Furthermore, a document can be transported with excellent precision at the image reading position because the transport member is disposed adjacent to the image reading position. 
     Although the present invention has been described by way of example relating to a document transporting device of an analog copier in the previously described embodiment, it is to be understood that the invention is also applicable to the document transporting device of digital copiers, and digital scanners having an auto document feeder function and like devices. 
     Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.