Patent Publication Number: US-7588246-B2

Title: Paper transportation device with adjustable separating pad holder

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a paper transportation device for transporting paper on a paper feed tray to a paper discharge tray. In particular, the present invention relates to a paper transportation device which nips a plurality of sheets of paper picked up from the paper feed tray by a separating roller and a separating pad and separates the papers one sheet at a time. 
   2. Description of the Related Art 
   A copier, a facsimile machine, and a scanner or the like includes an image scanning device for scanning an image of an original document, and an image forming device for printing image data scanned from the original document and image data received by facsimile onto printing paper. Many image scanning devices and image forming devices include a paper transportation device, which sequentially transports a plurality of sheets of original documents or printing papers on a paper feed tray, and discharges the original documents or the printing papers onto a paper discharge tray via a prescribed image scanning position and/or an image transfer position. For example, the image scanning device includes a paper transportation device known as an Auto Document Feeder (ADF) which transports an original document from a document tray, where original documents to be scanned are set, onto a paper discharge tray, where scanned original documents are stacked. 
   In the ADF, as a mechanism for sequentially picking up an uppermost sheet of the original documents stacked on the document tray and feeding the original documents to a transportation path, a paper feeding unit is provided near the document tray.  FIG. 4  is a schematic lateral cross-sectional view illustrating a conventional paper feeding unit  70 . As illustrated in  FIG. 4 , the paper feeding unit  70  includes a drive shaft  71 , a separating roller  72 , a pickup arm  73 , a pickup roller  74 , a separating pad  75 , a separating pad holder  76 , a cork pad  77 , a catching cover  78 , a supporting shaft  79 , a swinging bracket  80 , a coil spring  81 , and a separation pressure adjusting screw  82 . The separating roller  72  is rotatably driven by the drive shaft  71 . A base end of the pickup arm  73  is supported by the drive shaft  71 . The pickup roller  74  is rotatably supported on a leading end portion of the pickup arm  73 . The separating pad  75  separates a plurality of sheets of original documents picked up from a document tray (not illustrated) one sheet at a time. The separating pad holder  76  holds the separating pad  75  such that the separating pad  75  can be contacted against and separated from the separating roller  72 . The cork pad  77  arranged next to the separating pad holder  76  is mounted removably on the catching cover  78 . The swinging bracket  80  is provided below the separating pad holder  76  and the catching cover  78  such that the swinging bracket  80  swings with the supporting shaft  79  as a supporting point. The coil spring  81  is provided between the separating pad holder  76  and one end portion of the swinging bracket  80  on the other side of the supporting shaft  79 . The separation pressure adjusting screw  82  is screwed to another end portion of the swinging bracket  80 . 
   In the above-described paper feeding unit  70 , the coil spring  81  urges the separating pad holder  76 , and the separating pad  75  is contacted against the separating roller  72  under a prescribed separation pressure. Accompanying a start of rotation of the driving shaft  71 , the pickup arm  73  swings downward. When the pickup roller  74  at the leading end of the pickup arm  73  rotates while making contact with the original documents, several upper sheets of the original documents among the original documents stacked on the document tray are picked up. The picked-up original documents are fed into a nip portion between the separating roller  72  and the separating pad  75 . One sheet of the original documents is separated by a frictional force, and fed into the transportation path  83 . 
   In the above-described paper feeding unit  70 , when a separation failure is generated such that original documents are not separated at the nip portion and a plurality of sheets of the original documents are fed into the transportation path  83 , or when a pickup failure is generated such that an original document is not fed into the transportation path  83 , the separation pressure can be adjusted. That is, the cork pad  77  is removed from the catching cover  78 , and a screwdriver or the like is inserted into an exposed through-hole  84  to turn the separation pressure adjusting screw  82 . For example, when the separation pressure is insufficient, the separation pressure adjusting screw  82  is screwed inward. An end portion of the swinging bracket  80 , which is pressed by the separation pressure adjusting screw  82 , at the side of the separation pressure adjusting screw  82  is lowered, and an end portion of the swinging bracket  80  at the coil spring  81  side is elevated. Accordingly, a compressed amount of the coil spring  81  increases so as to increase its urging force. As a result, the separation pressure increases. 
     FIG. 5  is a schematic lateral cross-sectional view showing another conventional paper feeding unit  90 . As illustrated in  FIG. 5 , the paper feeding unit  90  includes a separating roller  91 , a separating pad  92 , a separating pad holder  93 , a coil spring  94 , and a separation pressure adjusting screw  95 . The separating pad  92  separates the original documents with the separating roller  91 . The separating pad holder  93  holds the separating pad  92 . The coil spring  94  urges the separating pad holder  93  to contact the separating pad  92  against the separating roller  91  under a prescribed separation pressure. The separation pressure adjusting screw  95  adjusts the separation pressure by changing a compressed amount of the coil spring  94 . An inner guide unit  96  mounted with the separating pad holder  93  is arranged to be capable of swinging around a supporting shaft  97  as a swing center. Accordingly, when the separation failure is generated and it is necessary to adjust the separation pressure, as illustrated in  FIG. 5 , the inner guide unit  96  is swung upward to expose a bottom surface  96   a  of the inner guide unit  96 . Then, a screwdriver or the like is inserted into a through-hole (not illustrated) formed on the bottom surface  96   a  to turn the separation pressure adjusting screw  95 . Accordingly, a compressed amount of the coil spring  94  changes, and the separation pressure is adjusted. 
   However, in the paper transportation device including the conventional paper feeding unit  70 , a troublesome work is required, i.e., the cork pad  77  is required to be removed from the catching cover  78  for adjusting the separation pressure adjusting screw  82 . Since a center axis of the separation pressure adjusting screw  82  does not coincide with a center axis of the coil spring  81 , the separation pressure cannot be adjusted under a stable state. In the paper transportation device including the conventional paper feeding unit  90 , a structure for swinging the inner guide unit  96  is required. Therefore, the complexity of the mechanism of the paper transportation device is increased, causing an increase in costs. 
   SUMMARY OF THE INVENTION 
   In order to overcome the problems described above, preferred embodiments of the present invention provide a mechanism for easily and reliably adjusting a separation pressure adjusting screw for adjusting a separation pressure in a paper transportation device in which a plurality of papers picked up from a paper feed tray are separated one sheet at a time by a separating roller and a separating pad that makes contact with the separating roller under a prescribed separation pressure. 
   According to a preferred embodiment of the present invention, a paper transportation device includes a transportation path, a separating roller, a separating pad, a separating pad holder, a coil spring, and a separation pressure adjusting screw. The transportation path connects a paper feed tray, where papers to be transported are stacked, and a paper discharge tray, where transported papers are discharged. The separating roller and the separating pad separate a plurality of sheets of papers picked up from the paper feed tray one sheet at a time, and feeds the papers into the transportation path one sheet at a time. The separating pad holder holds the separating pad such that the separating pad can be contacted against and separated from the separating roller. The coil spring urges the separating pad holder to contact the separating pad against the separating roller under a prescribed separation pressure. A screwed-in amount of the separation pressure adjusting screw is changed to change a compressed amount of the coil spring to adjust the separation pressure. In the paper transportation device, the separation pressure adjusting screw is provided in a transportation device main body provided under the separating pad holder. One end of the coil spring makes contact with the separation pressure adjusting screw, and another end of the coil spring makes contact with a position located away from the separating pad which is held in the separating pad holder. A screw adjusting hole is formed through the separating pad holder for adjusting the screwed-in amount of the separation pressure adjusting screw from above. 
   According to a preferred embodiment of the present invention, the separating pad holder is arranged to swing about a swing center located upstream of the separating pad in a paper transportation direction. One end of the coil spring makes contact with a downstream position of the separating pad holder. Further, the downstream position is located downstream of the separating pad held in the separating pad holder in the paper transportation direction. 
   According to a preferred embodiment of the present invention, a center axis of the separation pressure adjusting screw substantially coincides with a center axis of the coil spring. 
   According to a preferred embodiment of the present invention, a screwdriver or the like is inserted into the screw adjusting hole formed through the separating pad holder, and inserted into a hollow portion of the coil spring. Accordingly, the screwed-in amount of the separation pressure adjusting screw can be adjusted. The screwed-in amount of the separation pressure adjusting screw can be adjusted without removing a member such as the separating pad that covers the separation pressure adjusting screw. Therefore, an adjustment process of the separation pressure can be simplified. In addition, complexity of the mechanism of the paper transportation device is not increased. 
   According to a preferred embodiment of the present invention, in the paper transportation device, a distance from a position where the separating pad holder is urged by the coil spring to the swing center of the separating pad holder is longer than a distance from the separating pad to the swing center. Therefore, since an amount of change in the separation pressure of the separating pad becomes smaller than an amount of change in the urging force of the coil spring, a fine adjustment of the separation pressure can be carried out. 
   According to a preferred embodiment of the present invention, since the center axis of the separation pressure adjusting screw substantially coincides with the center axis of the coil spring, the separation pressure can be adjusted under a stable state in the paper transportation device. 
   Other features, elements, processes, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic lateral cross-sectional view of an image scanning device including a paper transportation device according to a preferred embodiment of the present invention. 
       FIG. 2  is an enlarged partial lateral cross-sectional view near a paper feeding unit in  FIG. 1 . 
       FIG. 3  is a view for describing a process for adjusting a separation pressure. 
       FIG. 4  is a schematic lateral cross-sectional view of a conventional paper feeding unit. 
       FIG. 5  is a schematic lateral cross-sectional view of another conventional paper feeding unit. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   A paper transportation device according to preferred embodiments of the present invention will be described with reference to the drawings.  FIG. 1  is a schematic lateral cross-sectional view showing a structure of an image scanning device G including an Auto Document Feeder (ADF)  1  as a paper transportation device. The image scanning device G is provided in an upper portion of a copy-and-facsimile Multi Function Peripheral (MFP) or the like. The image scanning device G is used for scanning image information of an original document to be copied and an original document to be transmitted by facsimile. The image scanning device G includes a device main body  4  and a document pressing portion  5 . The device main body  4  accommodates a scanning unit  2  inside, and a platen glass  3  is arranged on an upper surface of the device main body  4 . The document pressing portion  5  is arranged on the device main body  4  such that the document pressing portion  5  can be opened and closed. When scanning a thick booklet original document P or the like, the document pressing portion  5  is opened, and the original document P is placed on the platen glass  3 . Then, the document pressing portion  5  is closed, and under a state in which the original document P is contacted against the platen glass  3 , an image of the original document P is scanned by the scanning unit  2  moving below the platen glass  3 . 
   As illustrated in  FIG. 1 , a document tray  6 , a paper discharge tray  7 , and the ADF  1  are provided in the document pressing portion  5 . The original document P to be scanned is set on the document tray  6 . After a scanning process is completed, the scanned original document P is accumulated on the paper discharge tray  7 . The ADF  1  transports the original document P from the document tray  6  to the paper discharge tray  7 . When scanning a plurality of sheets of original documents P, the original documents P stacked on the document tray  6  are sequentially transported by the ADF  1 , and an image of the original documents P is scanned by the scanning unit  2  at a scanning position X in a transportation path  8 . 
   As illustrated in  FIG. 1 , the ADF  1  includes the transportation path  8 , a paper feeding unit  9 , a transportation roller  10 , and a discharge roller pair  11 . The transportation path  8  connects the document tray  6  and the paper discharge tray  7 . The paper feeding unit  9  separates the original documents P stacked on the document tray  6  one sheet at a time from an uppermost sheet, and feeds each of the original documents P into the transportation path  8 . The transportation roller  10  is provided in the transportation path  8 , and transports the original document P in a downstream direction. The discharge roller pair  11  is arranged at the most downstream end of the transportation path  8 . 
     FIG. 2  is an enlarged partial cross-sectional view of a portion near the paper feeding unit  9  in  FIG. 1 . The paper feeding unit  9  includes a pickup roller  12 , a cork pad  13 , a separating roller  15 , a separating pad holder  16 , a coil spring  17 , and a separation pressure adjusting screw  18 . The pickup roller  12  picks up several upper sheets of the original documents P stacked on the document tray  6 . The cork pad  13  is arranged so as to face the pickup roller  12 . The separating roller  15  operates with the separating pad  14  to separate only the uppermost sheet of the original documents P fed from the document tray  6 . The separating pad holder  16  holds the separating pad  14  such that the separating pad  14  can be contacted against and separated from the separating roller  15 . The coil spring  17  presses the separating pad  14  against the separating roller  15  under a prescribed separation pressure. The separation pressure adjusting screw  18  adjusts the separation pressure. 
   As illustrated in  FIG. 2 , the pickup roller  12  is rotatably supported on a leading end portion of a pickup arm  20 . A base end portion of the pickup arm  20  is supported by a rotatable driving shaft  19 . A rotational driving force of the driving shaft  19  is transmitted to the pickup roller  12  via a transmission mechanism (not illustrated) Accordingly, accompanying a start of rotation of the driving shaft  19 , the pickup arm  20  swings to lower its leading end. After the pickup roller  12  makes contact with an uppermost sheet of the original documents P, the pickup roller  12  starts rotating and several upper sheets of the original documents P stacked on the document tray  6  are fed towards the separating roller  15 . When only one sheet of the original documents P is remaining on the document tray  6 , the original document P is nipped between the pickup roller  12  and the cork pad  13  to reliably feed the original document P into the transportation path  8 . 
   As illustrated in  FIG. 2 , the separating roller  15  includes a silicone roller or the like provided around the rotatable driving shaft  19 . Either a forward rotation or a backward rotation of the driving shaft  19  is transmitted to the separating roller  15  via a clutch mechanism (not illustrated). Accordingly, accompanying a start of rotation of the driving shaft  19 , the separating roller  15  also starts rotating, and the original documents P picked up by the pickup roller  12  are fed into the transportation path  8 . A friction coefficient of the separating pad  14  with respect to the original document P is smaller than a friction coefficient of the separating roller  15  with respect to the original document P, and higher than a friction coefficient between the original documents P. For example, the separating pad  14  is preferably made of urethane resin or other suitable material. 
   Next, a description will be made of how the original documents P are separated by the separating roller  15  and the separating pad  14 . First, a plurality of sheets of original documents P picked up by the pickup roller  12  are nipped between the separating roller  15  and the separating pad  14 . Then, since a frictional force between the lowermost original document P and the separating pad  14  is greater than a frictional force between the lowermost original document P and an upper original document P, the lowermost original document P is stopped at the separating pad  14  without being transported into the transportation path  8 . The original documents P between the uppermost original document P and the lowermost original document P are stopped without being transported into the transportation path  8  since a frictional force of the original documents P with respect to the uppermost original document P and the lowermost original document P are balanced. Since a frictional force between the uppermost original document P and the separating roller  15  is greater than a frictional force between the uppermost original document P and a lower original document P, the uppermost original document P is transported towards the transportation path  8  by rotation of the separating roller  15 . Accordingly, only the uppermost sheet of the original documents P is separated and sequentially transported into the transportation path  8 . Then, when there is only one sheet of the original documents P left between the separating roller  15  and the separating pad  14 , since a frictional force between the original document P and the separating roller  15  is greater than a frictional force between the original document P and the separating pad  14 , the original document P is transported towards the transportation path  8  by the rotation of the separating roller  15 . As described above, all of the original documents P picked up by the pickup roller  12  are fed into the transportation path  8 . 
   The separating pad holder  16  includes a hollow holder main portion  21  having an opening at its bottom surface, and a pair of leg portions  22  protruding from the holder main portion  21 . A pair of regulation claws  23  protrude from the holder main portion  21  in a direction opposite from the leg portions  22 . A concave pad receiving portion  24  is provided in an upper surface of the holder main portion  21 . The separating pad  14  is preferably adhered on the pad receiving portion  24 . A spring receiving protrusion  25  is provided on an inner side surface of the holder main portion  21 . A spring adjusting hole  26  is provided in an upper surface of the holder main portion  21  and penetrates through the spring receiving protrusion  25 . Specifically, the spring adjusting hole  26  is formed at a position closer to the regulation claws  23  than the pad receiving portion  24 . A slanting surface  27  is formed at the leg portions  22  in the holder main portion  21  and is slanted towards the separating pad  14 . The original documents P stacked on the document tray  6  are displaced along the slanting surface  27 , and the closely contacting original documents P are separated from each other such that the uppermost sheet can easily be separated from other sheets. Additionally, an arc-shaped swing shaft  28  is provided at an end portion of the leg portions  22  opposite from the holder main portion  21 . 
   As illustrated in  FIG. 2 , the holder main portion  21  of the separating pad holder  16  is arranged in a concave portion  30  of an inner guide unit (transportation device main body)  29 . Further, the concave portion  30  is located at a position facing the separating roller  15 . The swing shaft  28  of each of the leg portions  22  is rotatably supported by the inner guide unit  29 . Accordingly, the separating pad holder  16  can be swung around a position of the swing shaft  28  as a swing center. Although details are not illustrated in the drawings, the regulation claws  23  of the holder main portion  21  are received in a groove having a prescribed width formed on a wall surface of the concave portion  30 . Accordingly, a swing range of the separating pad holder  16  is regulated within a prescribed range. 
   As illustrated in  FIG. 2 , the separation pressure adjusting screw  18  includes a head portion  31 , a flange portion  32 , a shaft portion  33 , and a mounting portion  34 . A screwdriver groove is formed in the head portion  31  for receiving a screwdriver or the like. A root portion of the head portion  31  protrudes in a peripheral direction to form the flange portion  32 . A screw is formed on the shaft portion  33 . The mounting portion  34  is screwed onto a prescribed position of the shaft portion  33 . The separation pressure adjusting screw  18  is mounted to the inner guide unit  29  by inserting the shaft portion  33  through a through-hole  35  formed on a bottom portion of the concave portion  30  and fixing the mounting portion  34  to the bottom portion of the concave portion  30 . Accordingly, by turning the separation pressure adjusting screw  18  and changing a screwed-in amount of the shaft portion  33  with respect to the mounting portion  34 , a protrusion height of the separation pressure adjusting screw  18  from the bottom portion of the concave portion  30  can be adjusted. That is, by inserting the separation pressure adjusting screw  18  into the inner guide unit  29  to lower a height position of the flange portion  32 , an interval between the flange portion  32  and the separating pad holder  16  is increased. Accordingly, compression of the coil spring  17  is relaxed, and the separation pressure is decreased. Additionally, by protruding the separation pressure adjusting screw  18  from the inner guide unit  29 , the height position of the flange portion  32  is elevated, and an interval between the flange portion  21  and the separating pad holder  16  is shortened. Accordingly, the coil spring  17  is compressed, and the separation pressure is increased. 
   As illustrated in  FIG. 2 , one end of the coil spring  17  surrounds the head portion  31  of the separation pressure adjusting screw  18 , and the coil spring  17  makes contact with the flange portion  32 . Another end of the coil spring  17  makes contact with the spring receiving protrusion  25  protruding from the inner side of the separating pad holder  16 . Accordingly, the separating pad holder  16  is urged upward by the coil spring  17 . When the original document P does not pass through, the separating pad  14  is contacted against the separating roller  15  under a prescribed separation pressure. When an original document P picked up from the document tray  6  passes through, the separating pad holder  16  receives a downward pressing force from the original document P. Accordingly, the separating pad holder  16  swings downward around the swing shaft  28  as the swing center against the urging force of the coil spring  17  by the thickness of the original document P. Then, as described above, only the uppermost sheet is separated from the plurality of the original documents P nipped between the separating pad  14  and the separating roller  15 , and fed into the transportation path  8 . 
   According to the structure of the paper feeding unit  9  described above, when a separation failure or a pickup failure is generated due to an inappropriate separation pressure, the separation pressure can be adjusted without removing a member such as the separating pad holder  16  of the paper feeding unit  9  from the inner guide unit  29 . For example, when the urging force of the coil spring  17  is strong and the separation pressure is excessive, the original document P picked up from the document tray  6  is nipped too strongly between the separating roller  15  and the separating pad  14 , and a pickup failure may occur such that the original document P is not fed into the transportation path  8 . When the urging force of the coil spring  17  is small and the separation pressure is too small, a separation failure may occur such that a plurality of the original documents P picked up from the document tray  6  are fed into the transportation path  8  without being separated one sheet at a time. 
   To adjust the separation pressure to an appropriate magnitude so as to solve the above-described problems, as illustrated in  FIG. 3 , first, an ADF cover  36  illustrated in  FIG. 1  is opened, and an upper surface of the inner guide unit  29  is exposed. Then, a screwdriver D or the like is inserted into the screw adjusting hole  26  of the separating pad holder  16  and passed through the hollow portion of the coil spring  17  to be engaged in the screwdriver groove formed on the head portion  31  of the separation pressure adjusting screw  18 . When reducing the separation pressure, the screwdriver D is turned to move the separation pressure adjusting screw  18  into the inner guide unit  29  to lower the height position of the flange portion  32 . Accordingly, the coil spring  17 , one end of which is making contact with the flange portion  32 , stretches and a compressed amount of the coil spring  17  is reduced. As a result, the urging force of the coil spring  17  with respect to the separating pad holder  16  decreases causing the separation pressure to decrease. When increasing the separation pressure, the screwdriver D is turned to protrude the separation pressure adjusting screw  18  from the inner guide unit  29  to elevate the height position of the flange portion  32 . Accordingly, the coil spring  17  is compressed and the compressed amount of the coil spring  17  increases. As a result, the urging force of the coil spring  17  with respect to the separating pad holder  16  increases causing the separation pressure to increase. 
   As described above, the separation pressure adjusting screw  18  can be adjusted without removing members such as the separating pad  14  of the paper feeding unit  9  from the inner guide unit  29 . Therefore, an adjustment process of the separation pressure is simplified. Since the center axis of the separation pressure adjusting screw  18  substantially coincides with the center axis of the coil spring  17 , the separation pressure can be adjusted under a stable state. 
   Further, in the above-described preferred embodiments, a position of the separating pad holder  16  located in a downstream side in the paper transportation direction with respect to the separating pad  14  is urged by the coil spring  17 . The urged position is not limited to the above-described example, and may be located at any position if the urged position is located away from the separating pad  14 . According to the urged position of the separating pad holder  16  urged by the coil spring  17 , a position of the separation pressure adjusting screw  18  and the screw adjusting hole  26  can be changed. However, as in the above-described preferred embodiments, if a portion of the separating pad holder  16  located downstream of the separating pad  14  is urged, the distance from the urged position urged by the coil spring  17  to the swing shaft  28 , which is the swing center of the separating pad holder  16 , becomes longer than the distance from the separating pad  14  to the swing shaft  28 . Therefore, an amount of change in the separation pressure of the separating pad  14  with respect to an amount of change in the urging force of the coil spring  17  becomes small. As a result, the separation pressure can be adjusted finely. 
   While the present invention has been described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that the disclosed invention may be modified in numerous ways and may assume many embodiments other than those specifically set out and described above. Accordingly, the appended claims are intended to cover all modifications of the present invention that fall within the true spirit and scope of the present invention.