Abstract:
A flat-bed scanner in combination with a sheet feeder. The flat-bed scanner includes a first glass window having a top surface and a second glass window having a top surface. A height step is formed without increasing the difficult between the top surfaces of the first and second glass windows. When the sheet feeder is placed on the flat-bed scanner, the scanned documents may pass the first glass window smoothly, consequently, good scanning quality may be obtained.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a flat-bed scanner in combination with a sheet feeder. The sheet feeder is placed on the flat-bed scanner so as to automatically feed the sheets and the scanner scan the sheets. The feeder has an optical module set which has a function of scanning so as to cooperate with the flat-bed scanner to scan the double sides of the documents. 
   BACKGROUND OF THE INVENTION 
     FIG. 1  discloses a feeder  10  being placed on a scanner  20  and the feeder  10  includes an upper guide plate  12  and two low guide plates  14 ,  16  located therein so as to define a passage  18  for feeding the sheets. When the feeder  10  is installed on the scanner  20 , the low guide plates  14 ,  16  contact the glass window  22  of the scanner  20 . When a document  24  is fed and pass the passage  18 , the document is scanned by a scanning module set  23 . 
   Because the low guide plate  16  has a certain thickness so that an end  17  of the low plate  16  protrudes from the glass window  22  and the document is blocked by the end  17  when it is fed. 
   The low guide plate  14  is located close to a surface of the glass window  22  and an end  15  of the low guide plate  14  protrudes from the glass window  22 . However, the height difference between the end  15  and the glass window  22  is helpful for the feed of the document  24 . 
   In order to resolve the problem of the jamming of the document  24 , arranging the end  17  of the low guide plate  16  to be lower than the glass window  22  is a reasonable way. 
     FIG. 2  discloses that a first glass window  26  and a second glass window  28  are installed on the scanner  20 . The first glass window  26  and the second glass window  28  are located in separate and a gap  25  is defined between the first glass window  26  and the second glass window  28 . By this arrangement, the end  17  of the low guide plate  16  can be extended into the gap  25  and is located below the surface of the first glass window  26 . 
   The two separate first glass window  26  and second glass window  28  make the volume of the scanner to be bulky and require two times of assembly for the assemblers. 
     FIG. 3  discloses a recess  27  is defined in the glass window  22  and a block  29  is engaged with the recess  27 . The end  17  of the low guide plate  16  contacts the block  29 . When the document  24  is fed, the block  29  guides the document  24  to move toward the low guide plate  16  smoothly. 
   The recess  27  requires two times of machining on the surface of the glass window  22  and this increases the manufacturing cost of the glass window  22 . The block  29  protrudes from the glass window  22  and jams the feeding of the document  24 . 
   Furthermore, U.S. Pat. No. 5,379,095 discloses a small piece of glass window is adhered on a large glass window so as to form a height difference in  FIG. 8 . The thickness of the small glass window is required to be thin so as to keep the scope of the area to be scanned in the effective focal depth, thereby causing breakage during adhering. Alternatively, the area where the small glass window is to be adhered has to be maintained in a high standard of cleanness, or the dust located between the two glass windows affects the quality of scanning. 
   SUMMARY OF THE INVENTION 
   The first object of the present invention is to provide a flat-bed scanner in combination with a sheet feeder, and which makes the documents to be fed smoothly. 
   The second object of the present invention is to provide a flat-bed scanner in combination with a sheet feeder, and the assembly processes are simplified. 
   The third object of the present invention is to provide a flat-bed scanner in combination with a sheet feeder, and a good quality of scanning is obtained. 
   The fourth object of the present invention is to provide a flat-bed scanner in combination with a sheet feeder, wherein the volume of the scanner is reduced. 
   The fifth object of the present invention is to provide a flat-bed scanner in combination with a sheet feeder, wherein the manufacturing cost is reduced. 
   According to the objects and features, the present invention uses the height difference to move the documents from the first glass window to the low guide plate and thereby getting rid of the jamming during feeding of the document. 
   The present invention provides a flat-bed scanner which is used with a sheet feeder which feeds sheets of documents to be scanned. The flat-bed scanner includes a first glass window and a second glass window. The first glass window is installed on the flat-bed scanner so as to support the sheets of documents and has a top surface and a bottom surface. The top surface faces the sheet feeder and the bottom surface faces the interior of the scanner. The second glass window is located adjacent the first glass window, and includes a top surface and a bottom surface. The top surface faces the sheet feeder and the bottom surface faces the interior of the scanner. A height difference is formed between the two respective top surfaces of the two glass windows. 
   The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, preferred embodiments in accordance with the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a conventional feeder and scanner. 
       FIG. 2  shows another conventional feeder and scanner. 
       FIG. 3  shows yet another conventional feeder and scanner. 
       FIG. 4  shows the combination of the flat-bed scanner and a sheet feeder of the present invention. 
       FIG. 5  is a top view to show the scanner of the present invention. 
       FIG. 6  shows another arrangement of the combination of the flat-bed scanner and a sheet feeder of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 4  discloses a sheet feeder  30  which is installed above a scanner  40  and the sheet feeder  30  includes a top guide plate  32  and two low guide plates  34 ,  36 . The top guide plate  32  faces the two low guide plates  34 ,  36  so as to form a passage  38  therebetween. It is to be noted that the two low guide plates  34 ,  36  are separated from each other and a scanning gap  35  is defined between the two low guide plates  34 ,  36 . 
   Besides, a plurality of adjacent rollers  37  are located in the inside of the feeder  30  so as to transport the sheets  50  in the feeder  30 . 
   The scanner  40  is a flat-bed scanner and has a movable scanning module set  42  in the inside of the scanner  40 . The scanning module set  42  includes optical parts such as a light source, reflection mirror set and image sensor which can also be a contact-image-sensor (CIS) module set. 
   The scanner  40  has a first glass window  43  and a second glass window  46  which is adhered to the first glass window  43 . The adhering process can be done during the manufacturing of the glasses. 
   The surface of the first glass window  43  that faces the feeder  30  is defined as the top surface  44 , and the surface of the first glass window  43  that faces the interior of the scanner  40  is defined as the bottom surface  45 . Similarly, the surface of the second glass window  46  that faces the feeder  30  is defined as the top surface  47 , and the surface of the second glass window  46  that faces the interior of the scanner  40  is defined as the bottom surface  48 . 
   It is to be noted that the first glass window  43  is thicker than the second glass window  46 , and when the two glass windows  43 ,  46  are adhered with each other, the two respective bottom surfaces  45 ,  48  are located at the same horizontal plane. By this arrangement, the top surface  44  is higher than the top surface  47 . The height difference D is defined as the height difference  49 . 
   The feeder  30  is located above the scanner  40  and the scanning gap  35  faces the first glass window  43 . The end  39  of the bottom plate  36  is located in the height difference  49  such that the end  39  is located below the top surface  44  of the glass window  43 . 
   When proceeding scanning, the document  50  moves in the passage  38  and the scanning module set  42  is located below the first glass window  43 . When the document  50  moves over the scanning gap  35 , the scanning module set  42  scans the document  50 . 
   When the document  50  moves to the low guide plate  36 , because the end  39  of the low guide plate  36  is lower than the top surface  44  of the first glass window  43 , the document  50  can be smoothly moved to the surface of the low guide plate  36  by the height difference  49 . The document  50  is then moved out from the passage  38  by the rollers  37 . 
   The height difference  49  between the top surface  44  of the first glass window  43  and the top surface  47  of the second glass window  46  is described by the embodiment hereinabove makes the installation of the low guide plate  36  to be easy. The height difference  49  makes the end  39  of the low guide plate  36  to be below the top surface  44  such that the document  50  can be moved smoothly. 
   Furthermore, because the first glass window  43  and the second glass window  46  are adhered with each other when assembling the scanner  40 , so that the two glass windows  43 ,  46  can be installed to the scanner  40  in one assembling action. 
   The first glass window  43  and the second glass window  46  are two individual parts so that there needs no second time machining and can be made conveniently. For the cost of the raw material of a scanner  40 , no extra cost is suffered. 
   Because the first glass window  43  has even physical characteristics and the document  50  can be move smoothly so that the scanning module set  42  can have a good quality of scanning images. 
     FIG. 5  shows a top view of the scanner  40 , a small adhering width  52  is existed between the first glass window  43  and the second glass window  46 . The adhering width  52  can be reduced to minimum under the precise adhering process, such that the whole volume of the scanner  40  is not increased too much. In other words, by adhering the first glass window  43  and the second glass window  46 , the scanner can be made smaller. Alternatively, the combination of the two glass windows can be made by using the casing of the scanner or any way that is alike the previous way. Whether or not the two glass windows are to be adhered depends on the need of design. 
     FIG. 6  discloses another structure that includes the height difference  49 . The first glass window  62  and the second glass window  64  have the same thickness so that when the two glass windows are adhered with each other, the first glass window  62  is arranged to be higher than the second glass window  64 . The top surface  66  of the first glass window  62  is higher than the top surface  68  of the second glass window  64 . The difference D of the two top surfaces  66 ,  68  is defined as a height difference  49  which is helpful for assembling the low guide plate  36  and the movement of the document  50 . 
   In the embodiment above, the feeder  30  may have another scanning module set  42  which works in cooperation with the scanning module set  42  in the scanner  40  to proceed double-sided scanning. 
   While we have shown and described the embodiments in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.