Abstract:
An auto document feeder cooperated with an image processing machine defines a feeding path and has a base, a frame and a sensor device. The base has a background under the feeding path. The frame is mounted on the base. The sensor couples with the frame and has a sensor arm. The sensor arm has an optical sensor located in the feeding path and faced to the background of the base. The sensor device recognizes a sheet is present in the feeding path or not by that the optical sensor recognizes the energy of the light reflected from the background and the sheet. The sensor device also recognizes characteristic of the sheet by that the optical sensor recognizes the energy of the light reflected from the sheet. Therefore, the image processing machine executes different processes for the sheet according to the characteristic of the sheet.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to an auto document feeder. More specifically, an auto document feeder with a sensor device capable of recognizing the characteristic of a sheet and that the sheet is present in a feeding path or not. 
         [0003]    2. The Related Art 
         [0004]    According to the progress of the image processing technology, many image processing products are popularly used, such as printers, scanners, fax machines, copy machines, etc. According to processing a large amount of documents, an auto document feeder is developed for cooperating with image processing products described above. 
         [0005]    The auto document feeder can catch one sheet from a stack of the document and transfers the sheet to the image processing products continuously. Therefore, the image processing products can uninterrupted process a large amount of document without feeding the sheet to the image processing products manually. 
         [0006]    A conventional auto document feeder  900  is shown in  FIG. 6  and  FIG. 7 . The auto document feeder  900  cooperates with an image processing product (not shown in figures) and has a base  901  and a frame  902  mounted on the base  901 , which defines a feeding path  903 . One end of the feed path  903  is arranged a first sensor device  904  mounted on the base  901 , and the other end of the feeding path  903  is arranged a second sensor device  905  mounted on the frame  902 . 
         [0007]    The first sensor device  904  detects material of a sheet (not shown in figures) fed into the feeding path  903  and sends a signal to a processing circuit (not shown in figures) for adjusting operation of sheet processing according to the signal. While different sheets are fed into the feeding path  903 , the first sensor device  904  can send different signals to the processing circuit corresponding to the different sheets. The processing circuit therefore adjusts operation of sheet processing, according to the different signals. 
         [0008]    The second sensor device  905  has a detecting module  906  and a swing module  907 . The swing module  907  has a shaft  908 , a first swing arm  909  extending from the shaft  908  in one of radial direction of the shaft  908  and a second swing arm  910  extending from the shaft  908  in another one radiating direction of the shaft  908 . 
         [0009]    While the swing module  907  mounted on the frame  902 , a spring  911  interconnects between the frame  902  and the swing module  907 . The swing module  907  is hitched on the frame  902  by the spring  911 . The first swing arm  909  of the swing module  907  is located in the feeding path  903  and the second swing arm  910  of the swing module  907  is located to corresponding to the detecting module  906  mounted on the frame  902 . 
         [0010]    While the sheet is fed into the feeding path  903  and passed through the swing module  907 , the sheet pushes the first swing arm  909  of the swing module  907 . Therefore, the first swing arm  909  of the swing module  907  is shifted an angle and the second swing arm  910  is shafted same angle together with the first swing arm  909 . The detecting module  906  detects shift of the second swing arm  910  of the swing module  907  and sends a signal to the processing circuit to recognize that the sheet is fed into the feeding path. 
         [0011]    However, the conventional auto document feeder  900  has a first sensor device  904  and a second sensor device  905  for recognizing material of the sheet and recognizing that the sheet is present in the feeding path  903  or not. Therefore, the cost of the conventional auto document feeder  900  is increased and the structure of the conventional auto document feeder  900  is complex. 
         [0012]    While the conventional auto document feeder  900  is shook, the swing module  907  of the second sensor device  905  is moved. While the detecting module  906  detects shift of the second swing arm  910  of the swing module  907  caused by shaking the conventional auto document feeder  900 , the detecting module  906  may erroneously recognize that the sheet is fed into the feeding path  903 . 
       SUMMARY OF THE INVENTION 
       [0013]    An object of the present invention is to provide an auto document feeder defining a feeding path. The auto document feeder has a base, a frame mounted on the base and a sensor device. The base has a background arranged under the feeding path. The frame has a front wall located above the feeding path, a first engaging base and a second engaging base projected from the front wall, a slot and a through hole opened on the front wall. 
         [0014]    The sensor device has a base element defining opposite ends. One end of the base element is projected a spring engaging portion and the other end of the base element is projected a fixing portion for engaging with the second engaging base of the frame. The base element is extended a first engaging portion for coupling with the first engaging base of the frame, a second engaging portion for coupling with the second engaging base of the frame and a sensor arm. 
         [0015]    The sensor arm has a supporting portion connected to the base element and arranged above the feeding path, a sensor portion connected to the supporting portion and arranged in the feeding path and an optical sensor arranged at the sensor portion and faced to the background of the base. A spring interconnects between the spring engaging portion of the sensor device and the slot and the through hole of the frame. 
         [0016]    The sensor device recognizes that a sheet is present in the feeding path or not according to that the optical sensor recognizes the light reflection factor of the background and the light reflection factor of the sheet. Also, the sensor device recognizes characteristic of the sheet according to that the optical sensor recognizes the light reflection factor of the sheet. While the auto document feeder cooperates with an image processing machine, the image processing machine adjusts the operation of sheet processing according to the characteristic of the sheet. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which: 
           [0018]      FIG. 1  shows a cross section of an auto document feeder according to the present invention; 
           [0019]      FIG. 2  is a perspective view showing a frame of the auto document feeder according to the present invention; 
           [0020]      FIG. 3  is a top view showing a sensor device of the auto document feeder according to the present invention; 
           [0021]      FIG. 4  is a bottom view showing the sensor device of the auto document feeder according to the present invention; 
           [0022]      FIG. 5  shows the sensor device configured to the frame of the auto document feeder according to the present invention; 
           [0023]      FIG. 6  shows a cross section of a conventional auto document feeder; and 
           [0024]      FIG. 7  is a perspective view showing a swing module of a second sensor device of the conventional auto document feeder. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    Please refer to  FIG. 1 . A preferred embodiment of the auto document feeder  100  according to the present invention is shown. The auto document feeder  100  has a base  1  and a frame  2  mounted on the base  1 . The auto document feeder  100  defines a feeding path  10  and sheet reversing path  11  communicated with the feeding path  10 . A sensor device  3  is configured to the frame  2 . The base  1  has a background  12  with a predetermined light reflection factor. In this case, the background is black. 
         [0026]    Please refer to  FIG. 2 . The frame  2  has a front wall  20  located above the feeding path  10 . A first engaging base  21  and a second engaging base  22  spaced from the first engaging base  21  are projected from the front wall  20  of the frame  2  respectively. The first engaging base  21  and the second engaging base  22  have a supporting plate  23  horizontally extending from the front wall  20  of the frame  2 , a first fixing plate  24  perpendicular to the supporting plate  23  and a hole  25  opened through the first fixing plate  24 . 
         [0027]    In this case, the first fixing plate  24  projects upwards and extends from the supporting plate  23 . The vicinity of the first engaging base  21  is opened a slot  26 . In this case, the slot  26  is horizontally opened on the front wall  20  of the frame  2  and close to the first engaging base  21 . The vicinity of the slot  26  is opened a through hole  27 . In this case, the through hole  27  is opened above the slot  26 . 
         [0028]    Please refer to  FIG. 3  and  FIG. 4 . The sensor device  3  has a processing circuit (not shown in figures) and a base element  30 . In this case, the base element  30  is formed as a post shape and defined opposite ends. One end of the base element  30  is projected a spring engaging portion  31  along axial direction of the base element  30 . In this case, the spring engaging portion  31  has a first post  310  projected from one end of the base portion  30  along axial direction of the base element  30 , a first protrusion  311  extending from free end of the first post  310  and perpendicular to the first post  310 , and an engaging hole  312  opened on the first protrusion  311 . 
         [0029]    The other end of the base element  30  is projected a fixing portion  32 . The fixing portion  32  has an elastic arm  320  projected from the other end of the base portion  30  along axial direction of the base element  30 , a block  321  extending from free end of the elastic arm  320  and perpendicular to the elastic arm  320 , and a second protrusion  322  projected from the block  321 . 
         [0030]    The base element  30  has a first engaging portion  33 , a second engaging portion  34  and a sensor arm  35 . The first engaging portion  33  has a first engaging plate  330  projected from the base element  30  along radial direction of the base element  30  and a first shaft  331  projected from the first engaging plate  330 . In this case, the first shaft  331  is perpendicular to the first engaging plate  330 . The first shaft  331  of the first engaging portion  33  and the first post  310  of the spring engaging portion  31  project to same direction. 
         [0031]    The second engaging portion  34  has a second engaging plate  340  projected from the base element  30  along radial direction of the base element  30 , a second post  341  projected from the second engaging plate  340 , and a second shaft  342  projected from freed end of the second post  341  along axial direction of the second post  341 . In this case, the second post  341  is perpendicular to the second engaging plate  340 . The second post  341  and the second shaft  342  of the second engaging portion  34  and the elastic arm  320  of the fixing portion  32  project to same direction. The block  321  of the fixing portion  32  is projected towards the second shaft  342  of the second engaging portion  34 . 
         [0032]    The sensor arm  35  extends from the base element  30  along radial direction of the base element  30 . The sensor arm has a supporting portion  350  extending from the base element  30 , a sensor portion  351  connecting to the supporting portion  350  and a sensor  352  having a light-emitting diode (LED)  3520  and a receiver  3521  and mounted on the sensor portion  351  and connected to a processing circuit (not shown in figures). In this case, the sensor portion  351  is formed as a curved-shape. The sensor  352  is mounted on tip of the sensor portion  351 . 
         [0033]    Please refer to  FIG. 1  to  FIG. 5 . The sensor device  3  is configured to the frame  2  by engagement of the first engaging base  21  of the frame  2  and the first engaging portion  33  of the sensor device  3 , and engagement of the second engaging base  22  of the frame  2  and the second engaging portion  34  of the sensor device  3 . In this case, the first shaft  331  of the first engaging portion  33  of the sensor device  3  is received in the hole  25  of the first engaging base  21  of the frame  2 . The second shaft  342  of the second engaging portion  34  of the sensor device  3  is received in the hole  25  of the second engaging base  22  of the frame  2 . 
         [0034]    The fixing plate  24  of the second engaging base  22  is pressed to between the second post  341  of the second engaging portion  34  and the block  321  of the fixing portion  32 . The second protrusion  322  of the fixing portion  32  presses the fixing plate  24  of the second engaging base  22  by the elastic force of the elastic arm  320  of the fixing portion  32 . Therefore, the sensor arm  35  of the sensor device  3  is pivoted on the frame  2  by the first shaft  331  of the first engaging portion  33  and the second shaft  342  of the second engaging portion  34 . 
         [0035]    The first post  310  of the spring engaging portion  31  is surrounded a spring coil  4 . One end of the spring coil  4  is clasped to the engaging hole  312  of the spring engaging potion  31 . The other end of the spring coil  4  is passed through the slot  26  of the frame  2  and clasped to the through hole  27  of the frame  2 . 
         [0036]    According to the engagement of the first engaging portion  33  of the sensor device  3  and the first engaging base  21  of the frame  2 , the engagement of the second engaging portion  34  of the sensor device  3  and the second engaging portion  35  of the second engaging base  22  and the engagement of the spring engaging portion  31  of the sensor device  3 , the spring coil  4  and the slot  26  and the through hole  27  of the frame  2 , the sensor device  3  is hitched on the frame  2 . 
         [0037]    In this case, the supporting portion  350  of sensor arm  35  of the sensor device  3  is located upon the feeding path  10  and the tip of the sensor portion  351  is located on the feeding path  10 . Therefore, the sensor  352  of the sensor arm  35  of the sensor device  3  is arranged on the feeding path  10 . While a sheet (not shown in figures) is fed to the feeding path  10  and passed through the sensor portion  351  of the sensor arm  35  of the sensor device  3 , the sensor portion  351  is pressed on the front surface of the sheet else the sensor portion  351  of the sensor arm  35  of the sensor device  3  is pressed on the background  12  of the base  1 . 
         [0038]    While the sheet is fed in the feeding path  10  and passed through the sensor portion  351  of the sensor arm  35  of the sensor device  3 , the LED  3520  of the sensor  352  illuminates the front surface of the sheet. According to the material of the sheet with individual reflection ratio, the receiver  3521  of the sensor  35  receives different light energy while different sheets are passed through the sensor portion  351  of the sensor device  3 . 
         [0039]    Because the different light energy are reflected form the different sheets and received by the receiver  3521  of the sensor  35 , the sensor  35  sends different signals corresponding to the different light energy to the processing circuit. The processing circuit executes different processes for different sheets according to different signals received from the sensor  35  of the sensor device  3 . 
         [0040]    For example, the processing circuit adjusts the amount of the ink printed on the sheet according to different signals received from the sensor  35  of the sensor device  3  while the auto document feeder  100  cooperates with a printer (not shown in figures). While the sheet  6  is not fed through the sensor portion  351  of the sensor device  3 , the LED  3520  of the sensor  352  illuminates the black area of the base  1 . Because reflection ratio of the black area is the lowest, the receiver  3521  receives few light energy Therefore, the processing circuit recognizes “no sheet” while the light energy received by the receiver  3521  of the sensor device  35  is below the predetermined threshold. 
         [0041]    After the printer prints ink on the front surface of the sheet  6 , the sheet  6  is fed into the sheet reversing path  11 . The black surface of the sheet  6  is passed through the sensor portion  351  of the sensor device  35  after the sheet  6  is extracted from the sheet reversing path  11  and fed into the feeding path  10 . The sensor device  3  detects material of the sheet again as described above. 
         [0042]    Therefore, the sensor device  3  provides different signals to the processing circuit according to the status of the sheet such as material of the sheet and present of the sheet in the feeding path  10 . The processing circuit can execute different processes according to different signals. 
         [0043]    Furthermore, the present invention is not limited to the embodiments described above; various additions, alterations and the like may be made within the scope of the present invention by a person skilled in the art. For example, respective embodiments may be appropriately combined.