Patent Publication Number: US-2004041338-A1

Title: Automatic document feeder

Description:
[0001] This application incorporates by reference Taiwan application Serial No. 091120221, filed Sep. 4, 2000.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The invention relates in general to an automatic document feeder (ADF), and more particularly to an automatic document feeder, which is used in a scanner.  
       [0004] 2. Description of the Related Art  
       [0005] A scanner with an automatic document feeder is an essential device in various PC peripheries. An automatic document feeder can effectively feed papers to be scanned into and out of a flatbed in the scanner and also make the scanner process document scans more quickly.  
       [0006] Referring to FIG. 1, a schematic view of a conventional automatic document feeder is shown. The conventional automatic document feeder  100  includes an opening for feeding papers (not shown in FIG. 1). The automatic document feeder  100  is used to feed papers placed on a paper holder (not shown in FIG. 1) out the opening and in the feed direction D.  
       [0007] The automatic document feeder  100  includes an inert-wheel holder  110 , an inert wheel  120 , a transmission shaft  130 , and a rolling wheel  140 . The inert-wheel holder  110  further includes a holding shaft  150  and an inert-wheel trough  160 , where the holding shaft  150  is vertical to the feed direction D of the feed paper.  
       [0008] The inert-wheel holder  110  is installed at the opening to feed papers into the automatic document feeder  100 . The inert wheel  120 , installed in the inert-wheel trough  160 , can roll in the direction of the holding shaft  150 , and the inert-wheel surface  170  of the inert wheel  120  projects off the inert-wheel trough  160 . The transmission shaft  130  rolls in the direction of the holding shaft  150 . In addition, the rolling wheel  140  is fixed on the transmission shaft  130  coaxially, and the inert-wheel surface  170  is in contact with the rolling-wheel surface  180  of the rolling wheel  140 .  
       [0009] The transmission shaft  130  transmits power to drive the rolling wheel  140  in the direction shown in FIG. 1. The rolling-wheel surface  180  thus applies a first force F1 on the inert-wheel surface  170 , which drives the inert wheel  120  in the opposite direction of the rolling wheel  140  thereby feeding papers into the opening between the rolling wheel  140  and the inert wheel  120  in the feed direction D.  
       [0010] The paper holder can be a flatbed of a scanner, and the rolling wheel  140  and inert wheel  120  can be made of a flexible material with a rough surface, such as rubber.  
       [0011] As mentioned above, the conventional automatic document feeder has the following disadvantages: if the friction force between the feed paper and the inert-wheel holder  110  is greater than the total force applied to the feed paper by the wheel surface  180  and the inert-wheel surface  170  in the feed direction D, the feed paper will become jammed in the opening and cannot be released from the automatic document feeder  100 , thereby negatively influencing the scanning process.  
       SUMMARY OF THE INVENTION  
       [0012] It is therefore an objective of the invention to provide an automatic document feeder in which the friction between the feed paper and the inert-wheel surface can be reduced so that feed papers can be fed out of the feeder easily and the scanning process can be smooth and uninterrupted.  
       [0013] The invention achieves the above-identified objective by providing an automatic document feeder. The automatic document feeder includes an opening for feeding papers into the scanner. The automatic document feeder is used to feed papers from the paper holder through the opening in the feed direction. The automatic document feeder includes at least an inert-wheel holder, an inert wheel, a transmission shaft, a rolling wheel, and a paper-wiping element. The inert-wheel holder is installed at the opening and includes a holding shaft, an inert-wheel shaft, and a paper-wiping trough, where the holding shaft is vertical to the feed direction. Additionally, the inert wheel is installed in the inert-wheel trough and can roll in the direction of the holding shaft, and the inert-wheel surface projects off the inert-wheel trough. The transmission shaft can roll in the direction of the holding shaft. The rolling wheel is installed on the transmission shaft coaxially and the rolling-wheel surface is in contact with the inert-wheel surface. The paper-wiping element is installed on the transmission shaft with a position corresponding to the paper-wiping trough. The transmission shaft drives the rolling wheel and the paper-wiping element. The rolling wheel, as driven by the transmission shaft, will apply a first force on the inert wheel causing it to roll in the opposite direction of the rolling wheel, thus feeding paper into the opening between the rolling wheel and the inert wheel in the feed direction. The paper-wiping element, as driven by the transmission shaft, can apply a second force to the feed paper, where the direction of the second force is parallel to the feed direction. The paper holder can be a flatbed of a scanner, and the paper-wiping element can be made of a flexible film, for example, mylar.  
       [0014] Other objectives, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0015]FIG. 1 (Prior Art) is a schematic view of a conventional automatic document feeder; and  
     [0016]FIG. 2 illustrates a schematic view of an automatic document feeder according to a preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0017] The automatic document feeder in the invention is designed to include a paper-wiping element on the transmission shaft and a corresponding paper-wiping trough on the inert-wheel holder of a conventional automatic document feeder (so that the paper-wiping element can slightly touch or not touch the inert-wheel holder as it rolls with the transmission shaft). The function of the paper-wiping element is to apply a second force to the feed paper in the feed direction in order to make up for the insufficient force applied to the feed paper by the rolling wheel and the inert wheel alone. With the help of the paper-wiping element, the feed paper can overcome friction with the inert-wheel holder and pass through the paper feed path more smoothly. Therefore, the paper feed opening will not become jammed, and the overall scanning quality can be improved.  
     [0018] Referring to FIG. 2, a schematic view of an automatic document feeder according to a preferred embodiment of the invention is shown. The automatic document feeder  200  includes a paper-wiping element  210  and a paper-wiping trough  220  on the inert-wheel holder  110 , in addition to the original components of the conventional automatic document feeder  100  shown in FIG. 1.  
     [0019] The paper-wiping element  210  is installed on the transmission shaft  130  with a position corresponding to the paper-wiping trough  220 .  
     [0020] The transmission shaft  130  rolls in the direction shown in FIG. 2 and drives the rolling wheel  140  and the paper-wiping element  210 . FIG. 1 shows that when the rolling wheel  140  rolls, it applies a first force F1 on the inert wheel  120 , which rolls in the opposite direction of the rolling wheel  140 . As a result, the feed paper can be fed into the opening between the rolling wheel  140  and inert wheel  120  in the feed direction D. The total force in the feed direction D, applied to the feed paper by the rolling wheel  140  and the inert wheel  120 , is provided to feed papers out of the paper holder (not shown in FIG. 2).  
     [0021] However, in the typical automatic document feeder  100 , in spite of the total force applied to the feed paper by the rolling wheel and the inert wheel, the total force in the feed direction D can be smaller than the friction between the feed paper and the inert-wheel holder  110 . In this case, the feed paper will not be fed out of the feeder, and this can result in a paper jam.  
     [0022] The paper-wiping element  210  in the invention, which is absent in the conventional automatic document feeder  100 , applies a second force F2 to the feed paper in the feed direction D. The second force F2 added up to the force originally applied by the rolling-wheel surface  180  and the inert-wheel surface  170  will overcome the friction force between the feed paper and the inert-wheel holder  100 . As a result, the feed paper can be fed out of the automatic document feeder  200  smoothly, preventing a paper jam.  
     [0023] The paper-wiping trough  220  is designed for the flexible paper-wiping element  210  to roll through the inert-wheel holder  110  with little or no contact with the inert-wheel holder  110 . The greatest second force F2 applied to the feed paper by the paper-wiping element  210  is generated when the second force F2 is applied to the fringe of the feed paper parallel to the holding shaft  150 .  
     [0024] The paper holder as mentioned above can be a flatbed of a scanner. The paper-wiping element  210  can be made of a flexible film, such as mylar.  
     [0025] The paper-wiping element  210 , when added to the transmission shaft  130 , can roll with the transmission shaft  130  and apply a second force F2 to the feed paper. Therefore, the feed paper will not become jammed in the automatic document feeder due to insufficient total force in the feed direction D applied to the feed paper by the rolling-wheel surface  180  and the inert-wheel surface  170 .  
     [0026] The automatic document feeder according to the preferred embodiment of the invention has at least the following advantages: even if the friction force between the feed paper and the inert-wheel holder is great enough to block the paper feed, the paper-wiping element added on the automatic document feeder in the invention will apply a second force to the feed paper, which results in a greater total force to the feed paper in the feed direction than the conventional type so that the feed paper can be fed out of the paper holder smoothly. Therefore, paper jams, which occur frequently in conventional automatic document feeders, can be eliminated, and the scanning process can continue smoothly.  
     [0027] While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.