Patent Publication Number: US-2006013627-A1

Title: Automatic document feeder and an image forming apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of Korean Patent Application No. 2004-55941, filed Jul. 19, 2004, in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an automatic document feeder (ADF) and an image forming apparatus having the same.  
      2. Description of the Related Art  
      Image forming apparatuses, such as digital photocopy machines, multi-function peripherals (MFP) and scanners, are able to scan and store documents, and are further able to print or transmit stored documents. A conventional multi-function peripheral (MFP) is schematically illustrated in  FIG. 1  as an example of the image forming apparatuses.  
      As shown in  FIG. 1 , an image forming apparatus  50  includes a cover  10  and a main body  30 . The cover  10  has an automatic document feeder (ADF)  20 , and the main body  30  has a reader part  40  for reading a document supplied by the ADF  20 .  
      The ADF  20  has a document path P generally formed in a substantial C-shape. The document stacked on a document tray  21  is guided to the reader part  40 , passing through a pickup roller  22 , a transfer roller  23  and a feeding roller  24 . After being read by the reader part  40 , the document is discharged by a discharging roller  25 .  
       FIG. 2  is an enlarged view of a portion G of  FIG. 1 . An ADF glass  27  is mounted on an upper part of the reader part  40  to support the document. A reference number ‘A’ denotes a position for scanning the document. A white bar  26  is urged toward the ADF glass  27  by resilient member  28  while maintaining a regular distance ‘g’ from the ADF glass  27 , thereby tightly contacting the document with the ADF glass  27 .  
      The document supplied by the feeding roller  24  ( FIG. 1 ) is transferred along a first path P 1  (illustrated as a solid line), scanned at the scanning position ‘A’ by the reader part  40  ( FIG. 1 ), and then discharged by passing through the white bar  26 . However, as the document passes through the white bar  26  to be discharged, a leading end E of the document touches a slope  34  of an ADF glass frame  32 , and this temporarily stops movement of the leading end E due to friction by the slope  34 . However, since the feeding roller  24  ( FIG. 1 ) keeps the operation of transferring the document in a moving direction of the first path P 1 , a rear part R of the document droops along a second path P 2  illustrated by a dotted line.  
      Due to the droop of the document, speed of the document is decreased when the rear part R thereof, which is located near a white bar entrance  37 , passes through the scanning position ‘A’ compared to when a front part F of the document passes through the scanning position ‘A’. More specifically, the front part F of the document enters the white bar  26  through the path P 1  and passes through the scanning position ‘A’. Here, when the leading end E of the document touches the slope  34 , the rear part R which has not yet passed through the scanning position ‘A’ advances along the second path P 2 . Therefore, as shown in  FIG. 3 , a distance d 2  for the rear part R of the document to pass through from the white bar entrance  37  to the scanning position ‘A’ becomes longer than a distance d 1  for the front part F of the document to perform the same.  
      As can be appreciated from the above, while the scanning position ‘A’ and scanning speed of the reader part  40  at the scanning position ‘A’ are regular, the distance of the path for transferring the document is increased at the rear part R, compared to at the front part F, as the document passes by. Accordingly, the speed of the rear part R passing through the scanning position ‘A’ is reduced, compared to that of the front part F.  
       FIG. 4  illustrates a document, as copied, passing through the scanning position ‘A’. Horizontal lines are scales uniformly dividing by 1 mm a printed letter ‘f’ of the document before being scanned. As shown in  FIG. 4 , the printed letter is uniformly read at the front part F, however, intervals between the horizontal lines are enlarged at the rear part R due to the reduced speed. According to the above, the quality of copied or scanned images in the conventional ADF is inferior.  
      Accordingly, a need exists for an image forming apparatus having an automatic document feeder that controls the speed of a document passing therethrough to improved the quality of copied and scanned images.  
     SUMMARY OF THE INVENTION  
      An object of the present invention is to provide an automatic document feeder (ADF) capable of controlling the speed of a document passing through a scanning position to be substantially constant, and an image forming apparatus having the same.  
      An ADF mounted above a reader part that reads a document automatically supplies the document to an ADF glass that supports the document. The ADF includes a pickup roller for supplying stacked documents. A transfer roller transfers the picked-up document. A feeding roller arranges and supplies the transferred document. A white bar is disposed above the ADF glass to bring the document into tight contact with the ADF glass. A controlling member is mounted on a document path to restrain vertical fluctuation of the document entering under the white bar.  
      The controlling member is implemented by at least one roller mounted at an upper stream of the white bar of the document path.  
      The roller is preferably integrally formed with the white bar.  
      At least one of the rollers is mounted in a length direction of the white bar, and idly rotates on a rotation shaft thereof.  
      The white bar is substantially U-shaped and has a bottom and two sides. The rotation shaft of the roller is connected to a fixing member fixed at one side of the white bar.  
      The roller is formed by enclosing a sponge on the rotation shaft.  
      A distance D 4  between the ADF glass and the roller is smaller than a distance D 3  between the ADF glass and a bottom of the white bar.  
      A distance D 2  refers to a width of a white bar entrance that is a pathway for the document to enter the white bar. A distance D 1  refers to a width of a white bar exit that is a pathway for the document to exit the white bar. The distances D 1 , D 2  and D 3  satisfy the relationship D 3 &lt;D 2 &lt;D 1 .  
      An image forming apparatus with a cover including an ADF having a document tray for stacking documents thereon, and a main body including at an upper part thereof a flat glass for leaf-scanning. An ADF glass continuously scans the documents supplied from the ADF. A reader part is mounted under the flat glass and the ADF glass. The ADF includes a pickup roller for supplying stacked documents. A transfer roller transfers picked-up documents. A feeding roller arranges and supplies the transferred documents. A white bar is disposed above the ADF glass to bring the documents into tight contact with the ADF glass. A controlling member is mounted on a document path to restrain vertical fluctuation of the documents entering under the white bar.  
      Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
      The above aspect and other features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawing figures, wherein;  
       FIG. 1  is a schematic sectional view of a conventional image forming apparatus;  
       FIG. 2  is an enlarged view of a portion G of  FIG. 1 ;  
       FIG. 3  shows a moving path of a printing paper through the apparatus of  FIG. 2 ;  
       FIG. 4  is a view of a document read by a conventional art;  
       FIG. 5  is a perspective view of an image forming apparatus according to an embodiment of the present invention;  
       FIG. 6  is a sectional view of an automatic document feeder according to an embodiment of the present invention;  
       FIG. 7  is an enlarged sectional view of the ADF of  FIG. 6 ;  
       FIG. 8  is a graphical representation of the speed of a document passing through a scanning position; and  
       FIG. 9  is a view showing a document read according to an embodiment of the present invention. 
    
    
      Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures.  
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      Hereinafter, certain embodiments of the present invention will be described in detail with reference to the accompanying drawing figures.  
      The matters defined in the description, such as a detailed construction and elements thereof, are provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that the present invention may be carried out without those defined matters. Also, well-known functions or constructions are not described in detail to provide a clear and concise description.  
      Referring to  FIG. 5 , an image forming apparatus according to an exemplary embodiment of the present invention includes a cover  210  and a main body  230 . The cover  210  has an automatic document feeder (ADF)  100  including a document tray  120 . The main body  230  has, at an upper part thereof, an ADF glass  150  for continuous scanning and a flat glass  240  for leaf-scanning. A reader part  160  ( FIG. 6 ) for reading a document is mounted under the ADF glass  150  and the flat glass  240 . When performing the leaf-scanning, the reader part  160  scans the document that is moved along and put on the flat glass  240 . For the continuous scanning, the reader part  160  scans the document that is transferred by the ADF  100  mounted to the cover  210  and put on the ADF glass  150 .  
      Referring to  FIG. 6 , a document inlet  121  and a document outlet  122  are disposed above and below in the ADF  100  to direct documents in the same direction. A document path P is formed as an open curve of a substantial C-shape and connects the document inlet  121  and the document outlet  122 .  
      The ADF  100  includes a pickup roller  112 , a transfer roller  114 , a feeding roller  116  and a discharge roller  118 , which are sequentially disposed along the document path P between the document inlet  121  and the document outlet  122 . First and second backup rollers  117  and  119  idly rotate, and are mounted at positions proximal the feeding roller  116  and the discharge roller  118 , respectively.  
      The pickup roller  112  picks up a document stacked on the document tray  120  and supplies the document to the document path P. A dotted line illustrates a position of the pickup roller  112  when the pickup roller  112  picks up the document.  
      The transfer roller  114  transfers the document supplied by the pickup roller  112 . By providing a friction pad  115  proximal the transfer roller  114  to correspond to the pickup roller  112 , the document sheet may be separated by the transfer roller  114 .  
      The feeding roller  116  and the first backup roller  117  restricts a leading end E of the document advancing to an upper part of the reader part  160  to control a time point of transfer, thereby transferring the document in a well arranged state onto the ADF glass  150 .  
      The discharge roller  118  and the second backup roller  119  discharge the document read by the reader part  160  to the document outlet  122 .  
      A white bar  130  and a roller  140  are mounted on the document path P between the feeding roller  116  and the discharge roller  118 . The white bar  130  is mounted above the ADF glass and supported by a resilient member  131 , such as a spring, to bring the document into tight contact with the ADF glass  150 . The roller  140  is mounted upstream of the white bar  130  in the document path P to substantially restrain vertical movement of the document. The roller  140  functions as a controlling member according to an exemplary embodiment of the present invention. The controlling member may also be implemented by a blade member. The white bar  130  is mounted to face the ADF glass  150 , and the reader part  160  is mounted under the ADF glass  150 .  
      The reader part  160  reads analog image information of the document and converts the read information to digital image information. For this, the reader part  160  includes a light source carriage (not shown) for receiving a light source that scans a light onto the document put on the ADF glass  150  and an image sensor, such as a charged coupled device (CCD) and a contact image sensor (CIS), for performing optical conversion in proportion to the light reflected from the document. A reference numeral A denotes a scanning position.  
      Referring to  FIG. 7 , the bottom  132  of the white bar  130  urges the document for tight contact with the ADF glass  150 , such that the reader part  160  ( FIG. 6 ) may read the image on the document. The white bar  130  has sidewalls  134  and  136  connected to the bottom  132 , thereby having a substantially U-shaped section. A white sheet  138  is formed below the bottom  132  of the white bar  130 . Above the bottom  132  of the white bar  130 , the spring  131  elastically biases the white bar  130  to the ADF glass  150 , being supported by a frame  170  to maintain tight contact between the ADF glass  150  and the document. A distance between the white bar  130  and the ADF glass  150  is maintained by projections (not shown) mounted on both ends of the white bar  130  at an interval greater than a width of the document, and the document passes between the projections (not shown).  
      A distance D 3  between the white sheet  138  mounted below the bottom  132  of the white bar  130  and the ADF glass  150  is controlled to be approximately 0.5 mm. This maintains a minimal distance D 3  because the reader part  160  reads fewer images from the document as the ADF glass  150  is distanced away from the document. However, if the distance D 3  is too small, a paper jam may result. Therefore, the distance D 3  is preferably about 0.5 mm.  
      On the document path P, a distance D 2  refers to a width of a white bar entrance  137  which is a pathway for the document to enter the white bar  130  after passing through the roller  140 . A distance D 1  refers to a width of a white bar exit  139  which is a pathway for the document to exit the white bar  130  after passing by the scanning position ‘A’. The distance D 2  is approximately 0.8˜1.0 mm, and the distance D 1  is approximately 1.0˜2.0 mm. The distance D 2  is preferably greater than the distance D 3  to prevent a paper jam or slip of the document when the document enters under the white bar  130 . The distance D 1  is preferably greater than each of the distances D 2  and D 3  to prevent paper jams and resistance by the slope  174  when the document is discharged. Accordingly, resistance of the document, which may occur during the transfer of the document, is minimized.  
      The roller  140  is disposed upstream of the white bar  130  on the document path P between the feeding roller  116  and the white bar  130  to restrain vertical movement of the document entering under the white bar  130 , thereby maintaining the constant distance between the document and the ADF glass  150 . The roller  140  includes a rotation shaft  142  and a sponge material enclosing the rotation shaft  142 .  
      The rotation shaft  142  of the roller  140  is connected to one sidewall  134  of the white bar  130  by a fixing member  144 . The roller  140  is integrally formed with the one sidewall  134  of the white bar  130  in a length direction, that is, in a direction of the width of the document. At least one roller  140  is provided, and more may be used as necessary. By integrally forming the roller  140  with the white bar  130 , the distance between the roller  140  and the ADF glass  150  may be constantly maintained. The roller  140  idly rotates by friction with the transferred document without being transmitted with a dedicated driving force. Since the roller  140  is made of a sponge material, the resistance applied to the document entering under the white bar  130  may be reduced, and further, lifespan of the roller  140  may be lengthened due to the high durability of the sponge material. The roller  140  is not limited to the sponge material but may be made of other materials capable of reducing the resistance applied to the document.  
      The distance D 4  refers to an interval between the roller  140  and the ADF glass  150 . Preferably, the distance D 4  is approximately 0.2 mm˜0.3 mm, and is smaller than the distance D 3 , which is the interval between the bottom  132  of the white bar  130  and the ADF glass  150 . By forming the distance D 4  to be smaller than the distance D 3 , the rear part R of the document entering under the white bar  130  may be restrained from vertically fluctuating although the resistance occurs at the leading end E of the document by the slope  174  when the leading end E is exiting the white bar  130  after reading of the document at the scanning position ‘A’. Accordingly, the moving speed of the document may be uniform both at the leading end E and the rear part R. Since the front part F and the rear part R may move along the same document path P by substantially preventing vertical fluctuation of the document entering under the white bar  130 , the speed of the document that passes through the scanning position ‘A’ may be uniformly maintained.  
      Hereinbelow, the operation of the ADF  100  having the above structure will be described with reference to FIGS.  6  to  9 .  
      The document stacked on the document tray  120  is supplied to the document path P, and is passed through the pickup roller  112  and the transfer roller  114  The supplied document enters under the white bar  130  after passing through the feeding roller  116 .  
      The document is passed between the roller  140  mounted at one sidewall  134  of the white bar  130  and the ADF glass  150 , read by the reader part  160  at the scanning position ‘A’, and is discharged out of the white bar  130 .  
      When the document is discharged, the leading end E is collided with the slope  174 , thereby generating resistance. During this resistance, however, a space for the fluctuation of the rear part R of the document is minimized due to the roller  140  tightly biasing the document toward the ADF glass  150 . Therefore, the rear part R of the document passes by the bottom  132  of the white bar  130  and the scanning position ‘A’ without causing a change in the moving speed compared to that of the leading end E. In the conventional image forming apparatus, the document path P is changed after the leading end E collides with the slope  174 , thereby causing the difference of the moving speed between the leading end E and the rear part R of the document passing by the scanning position ‘A’. However, according to an exemplary embodiment of the present invention, change of the document path P does not occur before and after the leading end E collides with the slope  174 , and therefore, the moving speed of the document passing by the scanning position ‘A’ may be constantly maintained. In  FIG. 8 , a horizontal axis refers to a length of the document divided by a certain interval, and a vertical axis refers to a speed of the document that is passing by the scanning position ‘A’. As shown in  FIG. 8 , the moving speed of the document passing by the scanning position ‘A’ is nearly uniform through the whole document. A minor change of the speed caused due to the resistance by the slope  174  is negligible.  
       FIG. 9  illustrates the document, as copied, passing through the scanning position ‘A’. Horizontal lines are scales dividing uniformly by 1 mm a printed letter ‘f’ of the document before scanning. As shown in  FIG. 9 , the printed letter is uniformly read through the scanning position ‘A’ because there is substantially no change of the document path P from the feeding roller  116  to the scanning position ‘A’.  
      As may be appreciated from the above description of the ADF and the image forming apparatus having the same, according to exemplary embodiments of the present invention, the document path P may be constantly maintained before and after the document passes through the white bar  130 . Accordingly, the moving speed at the leading end E and the rear part R of the document may be substantially uniform while the document passes by the scanning position ‘A’, thereby improving the quality of the image that is copied or scanned.  
      Also, by integrally forming the roller  140  with one sidewall of the white bar  130 , the distance between the roller  140  and the ADF glass  150  may be substantially constantly maintained. In addition, the sponge material for the roller  140  reduces the resistance during the transfer of the document and enables long lifespan.  
      While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.