Abstract:
A transmission mechanism comprising three drive rollers, one idle roller, one belt, and an elastic member. The belt is tightened around the drive rollers, where they drive the belt to rotate. The elastic member activates the idle roller causing the idle roller to exert a force on the belt for moving a document between the idle roller and belt during transportation of the document.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the priority benefit of Taiwan application serial no. 91119633, filed Aug. 29, 2002.  
         BACKGROUND OF INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention is generally related to the transmission mechanism of a sheet feeder, and particularly, to the transmission mechanism of a shrunk-size sheet feeder.  
           [0004]    2. Description of Related Art  
           [0005]    Following the advancement and rapid development in the electronics industry, it has risen to become the most important industry of our current society. A variety of different processing systems are introduced therefore leading to the popularization of electronic products in our daily lives. In the recent years, the processing speed and storage capability of CPUs and personal computers have greatly increased. As a result, the efficiency of image processing is greatly enhanced allowing consumers to enjoy image-processing devices such as optical scanners and digital cameras.  
           [0006]    The different categories of image document inputs are optical pocket scanner, sheet feed scanner, drum scanner, and flatbed scanner, or the like. Sheet feed scanners are geared towards lighter, thinner, shorter, and smaller, and therefore the feed mechanism of the sheet feed scanner has to be correspondingly reduce in size.  
           [0007]    Please refer to FIG. 1, a schematic diagram of a conventional sheet feeder is shown. The sheet feeder  110  is used for feeding a document  150  and the sheet feeder  110  comprises of a sheet feeder body  162 , a feed-in tray  112 , a feed-out tray  128 , three drive rollers  114 , three idle rollers  118 , a separate roller  126 , a feed roller  122 , and a separate plate  124 . Feed roller  122  is located inside the sheet feeder  110  at one end of the feed-in tray  112 . The drive rollers  114  and idle rollers  118  are located inside the sheet feeder  110 , where the drive roller  114  and idle roller  118  are grouped together to transport a document  150  by having a pair of drive roller  114  and idle roller  118  to make contact with different faces of the document  150 . The separate roller  126  and the separate plate  124  are both located inside the sheet feeder  110 , wherein the separate roller  126  is placed above the separate plate  124  and they are both in contact. The material of the separate roller  126  is a flexible material, therefore when a stack of sheets passes through the separate roller  126  and the separate plate  124  the separate roller will only allow one piece of paper to pass through under ideal situation. This is due to the friction between the separate roller  126  and the to-be-fed sheet is greater than that between sheets and between the sheet and the separate plate  124 .  
           [0008]    Feed roller  122  feeds a document  150  in a first direction  120  towards the passage created between the separate roller  126  and the separate plate  124  and by combining the design of the separate roller  126 , the separate roller  126  and the separate plate  124  will only allow one document  150  to pass through at each time. After passing through the passageway between the separate roller  126  and separate  124  plate, the document  150  will be fed in a second direction  140  towards the passage between the drive roller  114  and the idle roller  118 . The drive roller  114  and the idle roller  118  together clamp both sides of the document  150  and then feed in a third direction  160 . When the document  150  is at the scan entrance  116 , the document  150  is fed through the scan entrance  116  in the third direction  160  until the scanner  132  has finished scanning the image of the document  150  and the drive rollers  114  exits the document to the feed-out tray  128 .  
           [0009]    In the above-described sheet feeder  110 , the drive rollers  114 , the idle rollers  118 , the separate roller  126 , the feed roller  122 , and the separate plate  124 , etc. . . of the sheet feeder  110  all occupy significant space inside the sheet feeder  110 . Therefore the sheet feeder  110  requires a relatively large volume to accommodate all these components. Furthermore, the conventional sheet feeder  110  relies on pairs of drive rollers  114  and idle rollers  118  to feed a document  150 . The drive rollers and idle rollers  118  use a point-contact method to feed documents, which easily causes slippage of document  150  that affects the quality of the scan.  
           [0010]    An object of the present invention is to provide a transmission mechanism which reduces the total number of rollers to reduce the space occupied by the rollers and furthermore to effectively shrink the size of the sheet feeder.  
           [0011]    Another object of the present invention is to provide a transmission mechanism which uses face-contact method to feed documents, which feeds in accurately for scanning to improve scan quality.  
         SUMMARY OF INVENTION  
         [0012]    In order to achieve the above objects, the present invention provides a transmission mechanism comprising three drive rollers, a idle roller, a belt, and an elastic member. The belt tightens around the drive rollers to drive all of drive rollers simultaneously. The elastic member activates the idle roller causing the idle roller to exert a force on the belt to move the document between the idle roller and belt during transportation. This setup can reduce the total number of rollers (including drive rollers and idle rollers) to reduce the size occupied by the rollers for effectively reducing the size of the sheet feeder. The elastic member exerts an elastic force, which is tangent to the document and the idle roller, on the idle roller to generate a friction between the belt and the document in order to move the document. The elasticity of the elastic member can adjust the distance between the belt and idle roller so the transmission mechanism can accommodate documents that are relatively thick. Furthermore, the contact between the belt and idle roller is a face-to-face method to transport the document so the surface friction between the belt and document is greater than that between the idle roller and document. As a result the transportation of the document is more accurate. The elasticity of the elastic member will push the idle roller towards the belt so slacking of the belt will be tightened to resume normal operation of the transmission mechanism.  
           [0013]    In accordance to the above, the present invention reduces the total number of rollers (including drive rollers and idle rollers) to reduce the space occupied by the rollers for effectively reducing the overall size of the sheet feeder. The transmission mechanism uses a face-contact method to transport documents so that the document and belt can have direct face contact for a more accurate delivery.  
           [0014]    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  
       [0015]    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.  
         [0016]    [0016]FIG. 1 is a schematic diagram of a conventional sheet feed scanner.  
         [0017]    [0017]FIG. 2 is a schematic diagram of the sheet feed scanner according to one preferred embodiment of the present invention.  
         [0018]    [0018]FIG. 3 is schematic diagram the transmission mechanism of the sheet feed scanner according to one preferred embodiment of the present invention.  
         [0019]    [0019]FIG. 3A is the top view of the transmission mechanism illustrated in FIG. 3.  
         [0020]    [0020]FIG. 3B is a schematic diagram illustrating the relationship between the belt, idle roller, elastic member, and document of FIG. 3.  
         [0021]    [0021]FIG. 3C is a schematic diagram illustrating a tightened belt in the relationship between the belt, idle roller, elastic member, and document of FIG. 3.  
         [0022]    [0022]FIG. 3D is a schematic diagram illustrating a slacked belt in the relationship between the belt, idle roller, elastic member, and document of FIG. 3. 
     
    
     DETAILED DESCRIPTION  
       [0023]    Please refer to FIG. 2. FIG. 2 shows the schematic diagram of the sheet feed scanner according to one preferred embodiment of the present invention. The sheet feeder  210  comprises of a body  262 , a feed-out tray  213 , a feed-in tray  212 , a feed-in roller  222 , a feed-out roller  228 , and a transmission mechanism  300 . The feed-in tray  212  and feed-out tray  213  are located outside the body  262  where the feed-in tray  212  is located above the feed-out tray  213 . The feed-in roller  222 , feed-out roller  228 , and transmission mechanism  300  are all located inside body  262 . The feed-in roller  222  is disposed at one end of the feed-in tray  212  and the feed-out roller  228  is disposed at one end of the feed-out tray  213 . The transmission mechanism  300  is located at a side of the feed-in roller  222  and feed-out roller  228 . Furthermore, the sheet feeder  210  has a scan entrance  216  located directly below the sheet feeder  210 . The scan module  232  receives the document  250  by the sheet feeder  210  through the scan entrance  216  of sheet feeder  210 . The document  250  will be automatically transported through scan entrance  216  allowing the scan module to perform a scan of the image of the document  250 . After scanning of the document  250  by the scan module  232 , the document will be transported to the feed-out tray  213 . In this preferred embodiment, the document  250  is a piece of paper.  
         [0024]    Please simultaneously refer to FIG. 3 and FIG. 3A. FIG. 3 is a schematic diagram of the transmission mechanism and FIG. 3A is the top view of the transmission mechanism according to the preferred embodiment of the present invention. The transmission mechanism  300  comprises of three drive rollers  214 , a idle roller  226 , a belt  229 , and an elastic member  227 . Each drive roller  214  further comprises an axle  218 , which penetrates the center of the drive roller  214  and has its two ends fixed on the body  262 . The drive rollers  214  revolves about the axle  218 , whereby at least one of the drive rollers  214  must provide a driving motion to drive belt  229  and other passive drive rollers  214 . The arrangement of the three drive rollers  214  forms a substantially triangular shape with the drive rollers  214  at the three edges. The triangular shape can be an acute triangle, right-angle triangle, or obtuse triangle. The number of rollers  214  of the present invention is not limited to only 3 as shown in the preferred embodiment but can be any other integer number of rollers. The belt  229  tightens around the drive rollers  214 . The belt  229  can be multiple pieces of belt tightened around drive rollers  214 . The idle roller  226  further comprises a shaft  219  which penetrates the center of the idle roller  226  and has its two ends fixed on the body  262 . The idle roller  226  revolves about the shaft  219 . One end of the elastic member  227  is fixed on the shaft  219  and the other end of the elastic member  227  is fixed on the body  262 . The elastic member  227  is a spring in this preferred embodiment and furthermore can be manufactured as a whole with the body  262  by injection molding. The body of elastic member  227  possesses elasticity which allows the idle roller  226  to be pressed against the belt  229  to maintain a certain tightness of the belt  229 . In effect of the above, the transmission mechanism  300  reduces the total number of rollers (including drive rollers and idle rollers) to reduce the size occupied by them for reducing the overall size of the sheet feeder  210 .  
         [0025]    Please simultaneously refer to FIG. 2, FIG. 3, and FIG. 3B. FIG. 2 is a schematic diagram of the sheet feed scanner, FIG. 3 is a schematic diagram of the transmission mechanism, and FIG. 3A and FIG. 3B is a schematic diagram showing the relationship between the belt, idle roller, elastic member, and document according to the preferred embodiment of the present invention. The transmission mechanism uses a motor (not illustrated) for providing a driving source to one of the drive rollers  214  to turn feed-in roller  222  and feed-out roller  228  for feeding a document  250  in the feed-in tray  212  towards a first translation direction  220 , whereas the document is a piece of paper. After passing the feed-in roller  222 , the document  250  is moved towards the passageway between the idle roller  226  and belt  229 . The drive rollers  214  rotate in a first rotation direction  301  to drive the belt  229 , and the belt  229  drives the idle roller  226  in a second rotation direction  302 . As a result the document  250  passing through the passageway between the belt  229  and idle roller  226  is fed in a second translation direction  240 . As illustrated in FIG. 3B, the document  250  causes the idle roller to move to the right resulting in a tangent force on the document  250  by the idle roller  226 . Therefore a friction is generated between the document  250  and belt  229  for transporting the document  250  forward to pass through the passageway between the belt  229  and idle roller  226  towards a third translation direction  260 . The contact between the belt  229  and document  250  is a face-contact method, whereas the contact surface friction between the belt  229  and document  250  is greater than that between the idle roller  226  and document  250 . Furthermore, the elasticity of the elastic member  227  can adjust the distance between the idle roller  226  and document  250  to accommodate documents of different thickness.  
         [0026]    Please simultaneously refer to FIG. 3C and FIG. 3D. FIG. 3C shows a schematic diagram of the relationship of the tightened belt, idle roller, and elastic member of FIG. 3. FIG. 3D shows a schematic diagram of the relationship of the slacked belt, idle roller, and elastic member of FIG. 3. When transmission mechanism  300  is in normal operation and before the belt  229  becomes slack, the contact between the belt and the idle roller  226  is balanced. At this instant, the distance of the elastic member  227  from the center of the shaft  229  to the body  262  is a first distance of 30, as shown in FIG. 3C. After long operation of the belt  229 , slacking will occur in belt  229  but it is compensated by the elasticity of the elastic member  227  by pushing the idle roller  226  towards the belt  229  until the belt  226  and belt  229  maintain a balance. At this moment, the distance of the elastic member  227  from the center of the shaft  229  to the body  262  becomes a second distance of 40, wherein the second distance 40 is greater than the first distance 30. In other words, even after slacking occurs, the elasticity of the elastic member  227  can retain the belt in a condition without slacking to resume normal operation of transmission mechanism  300 .  
         [0027]    According to the above, the advantage of the present invention is a reduced total number of rollers (including drive rollers and idle rollers) to reduce the space occupied by the rollers for reducing the overall size of the sheet feeder.  
         [0028]    The second advantage of the present invention is the face-contact method used in the transportation for better accuracy of document feeding.  
         [0029]    The third advantage of the present invention is that the elasticity of the elastic member can adjust the distance between the idle roller and belt for accommodating documents of different thickness.  
         [0030]    The fourth advantage of the present invention is the slacking of the belt can be compensated for resuming normal operation of the transmission mechanism.  
         [0031]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structure and method of the present invention without departing from the scope or spirit of the present invention. In view of the foregoing description, it is intended that the present invention covers modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.