Abstract:
A document guiding device for a document feeder. The document guiding device mainly comprises an inner wall, an outer wall and a lubricating element. The spatial area between the outer wall and the inner wall form a reversing passageway that accommodates a transiting document. The reversing passageway has a document inlet end and an outlet end both positioned on the same side of the document guiding device. The lubricating element is attached to the interior surface of the outer wall close to the area of contact between the front end of the document and the bend of the outer wall. The lubricating element facilitates the forward movement of the document so that the document is able to travel smoothly from the inlet to the outlet.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of Invention  
           [0002]    The present invention relates to a document guiding device. More particularly, the present invention relates to the document guiding device of a document feeder capable of preventing the clogging of paper along the forward feeding path.  
           [0003]    2. Description of Related Art  
           [0004]    Due to rapid progress in the electronic industry, many types of high performance computer systems are produced to be used almost anywhere. The development of high-speed processors and large capacity memory devices in recent years has also lead to the production of highly efficient image processors. Image processors including optical scanners and digital cameras are more frequently used.  
           [0005]    In general, optical scanners can be divided into pocket scanners, sheet feed scanners, drum scanners and flatbed scanners, according to the document input method. For a sheet feed scanner, an optical resolution exceeding 600 dpi is currently achievable. Almost all sheet-feed scanners use a contact image sensor (CIS) scanning structure to reduce volume. Since each scanner occupies only a very small volume, the scanner is often carried along with a notebook computer.  
           [0006]    To facilitate the scanning of a large number of documents, an automatic document feeder (ADF) is frequently used. When an automatic document feeder is used, documents are fed to a flatbed scanner or a sheet feed scanner one after the other and then sequentially scanned.  
           [0007]    In general, a document guiding device is employed inside a document feeder to reduce overall volume of the feeder and facilitate user operation. The document guiding device turns an incoming document by 180 degrees so that both document inlet and document outlet are on the same side of the document feeder.  
           [0008]    [0008]FIG. 1 is a schematic cross-sectional view of the document guiding device of a conventional document feeder. As shown in FIG. 1, the document guiding device  100  has a reversing passageway  102 . The reversing passageway  102  is actually a spatial channel between an outer wall  104  and an inner wall  106 . Furthermore, the outer wall  104  is constructed by joining an upper wall section  104   a  and a lower wall section  104   b  together. Similarly, the inner wall  106  is constructed by joining an upper wall section  106   a  and a lower wall section  106   b  together.  
           [0009]    A document  116  is fed in the forward direction  122  into a document inlet port  108 . Through the continuous rotation of a pair of rollers  112  and  114 , the document  116  is pushed forward into the reversing passageway  102 . As soon as the front end of the document  116  hits a document outlet port  110 , the document  116  is expelled from the document guiding device  100  through a pair of rotating rollers  118  and  120 . Since the inlet port  108  and the outlet port  110  are both on the same side, overall length of the document feeder is reduced.  
           [0010]    However, aside from reducing the overall length of the document feeder, the height of the document feeder must be reduced as well. As shown in FIG. 1, the document guiding device  100  has a sharp bend along the reversing passageway  102 .  
           [0011]    When the document  116  moves forward along the reversing passageway  102  following the curve surface of the outer wall  104 , the front end of the document  116  will encounter this sharp bend. Due to roughness and friction, the document  116  is easily clogged up somewhere close to the bend so that the document  116  can no longer come out through the outlet port  110 . Hence, the document  116  is forced to wrinkle up inside the document guiding device, ultimately leading to some non-reversible damages. Moreover, the jammed document  116  must be removed before resuming the scanning operation.  
         SUMMARY OF INVENTION  
         [0012]    Accordingly, one object of the present invention is to provide a document guiding device for a document feeder. The document guiding device prevents the jamming of documents inside the device and guides the transiting document out smoothly.  
           [0013]    To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a document guiding device for a document feeder. The document guiding device mainly comprises of an inner wall, an outer wall and a lubricating element. The spatial area between the outer wall and the inner wall form a reversing passageway that accommodates a transiting document. The reversing passageway has a document inlet end and an outlet end both positioned on the same side of the document guiding device. The lubricating element is attached to the interior surface of the outer wall close to the area of contact between the front end of the document and the bend of the outer wall. Hence, the document can move forward smoothly from the inlet to the outlet without jamming inside the reversing passageway.  
           [0014]    This invention also provides an alternative type document guiding device for a document feeder. The document guiding device mainly comprises an inner wall, an outer wall and a roller. The spatial area between the outer wall and the inner wall form a reversing passageway that accommodates a transiting document. The reversing passageway has a document inlet end and an outlet end both positioned on the same side of the document guiding device. The roller is attached to the interior surface of the outer wall close to the area of contact between the front end of the document and the bend of the outer wall. Hence, the document can move forward smoothly from the inlet to the outlet without jamming inside the reversing passageway.  
           [0015]    In this invention, a lubricating element or a roller is attached to the contact area between the front end of the document and the bend inside the document guiding device. When the front end of a document touches the bend of the reversing passageway, the document is smoothly guided by the lubricating element or the roller. Ultimately, the document is able to turn around smoothly without clogging up the reversing passageway or causing any damage to the document.  
           [0016]    It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.  
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0017]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,  
         [0018]    [0018]FIG. 1 is a schematic cross-sectional view of the document guiding device of a conventional document feeder;  
         [0019]    [0019]FIG. 2 is a schematic cross-sectional view of a document guiding device according to a first preferred embodiment of this invention; and  
         [0020]    [0020]FIG. 3 is a schematic cross-sectional view of a document guiding device according to a second preferred embodiment of this invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]    Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0022]    [0022]FIG. 2 is a schematic cross-sectional view of a document guiding device according a first preferred embodiment of this invention. As shown in FIG. 2, the document guiding device  200  has an outer wall  204 , an inner wall  206  and a lubricating element  230 .  
         [0023]    The outer wall  204  is formed by joining an upper wall  204   a  and a lower wall  204 b together. Close to the junction between the upper wall  204   a  and the lower wall  204   b , the upper wall  204   a  gradually thickens in the direction of the inner wall  206 . In other words, there is a step at the junction between the upper wall  204   a  and the lower wall  204   b . The design of the outer wall  204  as an upper wall/lower wall assembly separable at the junction facilitates the removal of any document  21   6  jammed inside the reversing passageway  202  of the document guiding device  200 . Furthermore, the protruding upper wall  204   a  relative to the lower wall  204   b  near the junction also facilitates a smooth transition of the document  216  from the upper wall  204   a  to the lower wall  204   b . Hence, the frequency of clogging inside the reversing passageway  202  is minimized.  
         [0024]    Similarly, the inner wall  206  is also formed by joining an upper wall  206   a  and a lower wall  206   b . However, the inner wall  206  may also be manufactured as an integrative unit. Since the inner wall  206  has a U-shaped profile, forming the inner wall  206  from two separate pieces facilitates material transport and stacking before assembly.  
         [0025]    The space between the outer wall  204  and the lower wall  206  forms a turnaround passageway  202  suitable for the passage of a document. The reversing passageway  202  has an inlet port  208  and an outlet port  210  on the same side of the document guiding device  200 . The upper wall  204   a  extends from the junction between the upper wall  204   a  and the lower wall  204   b  towards the inlet end  208 . Similarly, the lower wall  204   b  extends from the junction between the upper wall  204   a  and the lower wall  204   b  towards the outlet end  210 .  
         [0026]    The lubricating element  230  is attached to the interior surface of the lower wall  204  next to the junction. The lubricating element  230  is a thin layer of extra-smooth material such as Teflon or Mylar (a polyresin film). To reduce friction and facilitate the smooth transition of the document inside the passageway  202 , the lubricating element  230  is attached close to the contact region between the lower wall  204   b  and the front end of the document  216 . Preferably, the lubricating element  230  is positioned at the point of first contact between the document  216  and the sharp bend along the reversing passageway  202 . In other words, the document  216  is able to turn smoothly around the bend without clogging up the passageway  202 . Furthermore, the lubricating element  230  has a thickness smaller than the difference in step height between the upper wall  204   a  and the lower wall  204   b . In addition, one end of the lubricating element  230  is preferably attached to the junction between the upper wall  204   a  and the lower wall  204   b  so that the possibility of a document caught by the element  230  is minimized.  
         [0027]    A pair of transmission rollers  212 ,  214  may also be installed near the inlet port  208  to facilitate the entrance of document into the reversing passageway  202 .  
         [0028]    Similarly, a pair of transmission rollers  218 ,  220  may also be installed near the outlet port  210  to facilitate the emission of document from the document guiding device  200 .  
         [0029]    To turn a document  216  around using the document guiding device  200 , the document  216  is slipped in through the document inlet  208 . The rollers  212 ,  214  drag the document  216  into the reversing passageway  202  in a forward direction  222 . Continuous rotation of the rollers  212 ,  214  brings the document  216  forward. When the front end of the document  216  bypasses the upper wall  204   a  to contact the lower wall  204   b , the presence of lubricating element  230  facilitates a smooth transition of the document around the bend in the passageway  202 . Thereafter, the document  216  is pushed forward to the rollers  218 ,  220 . The rollers  218 ,  220  rotate and hence push the document  216  out through the outlet port  210 .  
         [0030]    In the first embodiment, the lubricating element  230  is attached to the interior surface of the lower wall  204   b  close to the bend of the passageway  202 . However, the scope of this invention is not limited to the attachment of a lubricating element as such. Alternative arrangements capable of achieving the same goal include polishing the interior wall of the lower wall  204   b  or material having a smooth surface may be used to manufacture the lower wall  204   b.    
         [0031]    [0031]FIG. 3 is a schematic cross-sectional view of a document guiding device according a second preferred embodiment of this invention. As shown in FIG. 3, the document guiding device  300  has an outer wall  304 , an inner wall  306  and a roller  330 .  
         [0032]    The outer wall  304  is formed by joining an upper wall  304   a  and a lower wall  304   b  together. Close to the junction between the upper wall  304   a  and the lower wall  304   b , the upper wall  304   a  gradually thickens in the direction of the inner wall  306 . In other words, there is a step at the junction between the upper wall  304   a  and the lower wall  304   b.    
         [0033]    Similarly, the inner wall  306  is also formed by joining an upper wall  306   a  and a lower wall  306   b . However, the inner wall  306  may also be manufactured as an integrative unit.  
         [0034]    The space between the outer wall  304  and the lower wall  306  forms a turnaround passageway  302  suitable for the passage of a document. The reversing passageway  302  has an inlet port  308  and an outlet port  310  on the same side of the document guiding device  300 . The upper wall  304   a  extends from the junction between the upper wall  304   a  and the lower wall  304   b  towards the inlet end  308 . Similarly, the lower wall  304   b  extends from the junction between the upper wall  304   a  and the lower wall  304   b  towards the outlet end  310 .  
         [0035]    The roller  330  is attached to the interior surface of the lower wall  304  close to the junction. The roller  330  rotates in a direction that drags a document  316  towards the outlet port  310 . According to the forward direction  322  in the second embodiment (shown in FIG. 3), the roller  330  rotates in a clockwise direction. On the contrary, if the document  316  moves forward in a direction opposite to  322 , the roller  330  will rotate in an anti-clockwise direction. To facilitate the smooth transition of the document  316  inside the passageway  302 , the roller  330  is attached close to the contact region between the lower wall  304   b  and the front end of the document  316 . Preferably, the roller  330  is positioned at the point of first contact between front end of the document  316  and the sharp bend along the reversing passageway  302 . In other words, the document  316  is able to turn smoothly around the bend without clogging up the passageway  302 . Furthermore, the top of the roller  330  is preferably at a level smaller than the difference in step height between the upper wall  304   a  and the lower wall  304   b.    
         [0036]    In addition, a pair of transmission rollers  312 ,  314  may also be installed near the inlet port  308  to facilitate the entrance of document into the reversing passageway  302 . Similarly, a pair of transmission rollers  318 , 320  may also be installed near the outlet port  310  to facilitate the emission of document from the document guiding device  300 .  
         [0037]    To turn a document  316  around using the document guiding device  300 , the document  316  is slipped in through the document inlet  308 . The rollers  312 ,  314  drag the document  316  into the reversing passageway  302  in a forward direction  322 .  
         [0038]    Continuous rotation of the rollers  312 ,  314  brings the document  316  forward. When the front end of the document  316  bypasses the upper wall  304   a  to contact the lower wall  304   b , the presence of the roller  330  lowers friction and facilitates the passage of document around the bend of the passageway  302 . Thereafter, the document  316  is pushed forward to the rollers  318 ,  320 . The rollers  318 ,  320  rotate and hence push the document  316  out through the outlet port  310 .  
         [0039]    In summary, a lubricating element or a roller is attached to the contact area between the front end of a document and a curve bend inside the document guiding device. When the front end of a document contacts the bend of the reversing passageway, the document is smoothly guided by the lubricating element or the roller. Consequently, the document turns around smoothly without clogging up the reversing passageway or causing any damage to the document.  
         [0040]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.