Abstract:
A sheet-size detecting mechanism includes a sheet holder composed of a paper tray and a paper guide. The mechanism also includes a logic board and a sensor module. Adjusting the width of the paper guide corresponding to the sheet width may cause a lot of digital information to be generated due to relative motion between the logic board and the sensor module. Then the sheet-size may be determined accordingly.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a detecting mechanism used on an image scanning device so as to automatically detect the size of the sheet of a document to be scanned.  
         BACKGROUND OF THE INVENTION  
         [0002]    A conventional scanner has to be connected to a computer and a preview procedure is taken before scanning the sheet of document and a proper or preferable size or range is chosen to be scanned. Alternatively, the image of the document that is scanned by the scanner is sent to the software for dealing with the images, and then the user chooses the desired range. Therefore, the conventional scanner needs not to detect the size of the sheet frequently.  
           [0003]    An automatic document feeder is usually cooperated with the scanner and generally is an A4-size automatic document feeder because this size of sheet is often used so that the conventional scanners do not equip with the sheet-size detecting mechanism.  
           [0004]    If an A3-size automatic document feeder is used, the A4 sheets can also be fed in transverse direction so as to reduce the period of time of scanning. This benefit is especially significant when a lot amount of sheets are to be scanned. Nevertheless, the sheet-size detecting mechanism has to be able to distinguish the sheet size such as the A3 sheets and A4 sheets. Therefore, the sheet-size detecting mechanism is necessary.  
           [0005]    Besides, the peripheral devices of computers are gradually combined as a multi-function machines, or the digital copy machines and scanners are connected with each other. Before using the multi-function machines or the copy machines, the sheet size has to be decided and then scanning the sheets while printing. This may obtain a better efficiency so that a sheet-size detecting mechanism for detecting the sizes of sheets is necessary.  
           [0006]    A mechanical-electrical sheet-size detecting device is a detecting switch which could malfunction if the sheet is too thin. Besides, one part can only detect one size of the sheets and the same amount of parts is needed when detecting the amount sheets of paper. The parts occupy too much space and the number of the sheets is limited, therefore, the number of sizes of the sheets is limited.  
           [0007]    Another resistor type sheet-size detecting mechanism includes a sheet guiding plate which has a conductive member thereon which is moved relative to the resistor on the circuit board. The resistance difference generated from the position difference between the conductive member and the resistor results in a difference of electric current or voltage which corresponds to the different sizes of sheets. However, the frequent movement and friction between the conductive member and the resistor reduces the term of use of the sheet-size detecting mechanism. Besides, the fluctuation of the current or the electric voltage and the complicity of the sheet sizes result malfunctions in detection of the sheet sizes. It does not meet the requirements if the detecting mechanism can only detect few sizes of the sheets.  
           [0008]    Electric capacitor type and inductor type sheet-size detecting mechanisms employ the same feature to detect the sizes of the sheets and the functions are similar to those obtained by the resistor type sheet-size detecting mechanism.  
         SUMMARY OF THE INVENTION  
         [0009]    The first object of the present invention is to provide a sheet-size detecting mechanism which is used to detect the size of the sheet in the automatic document feeder.  
           [0010]    The second object of the present invention is to provide a sheet-size detecting mechanism which employs the relative movement between a logic board and a sensor module so as to detect the width of the sheet.  
           [0011]    The third object of the present invention is to provide a sheet-size detecting mechanism which may detect the width of the sheet by way of the logic arrangements.  
           [0012]    The fourth object of the present invention is to provide a sheet-size detecting mechanism which has a sensor module put in the lengthwise direction of the sheets so as to recognize the different lengths of the sheets with the same width.  
           [0013]    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, a preferred embodiment in accordance with the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a perspective view to show the combination of the scanner and the mechanism of the present invention.  
         [0015]    [0015]FIG. 2 is a perspective view to show the mechanism of the present invention.  
         [0016]    [0016]FIG. 3 is an enlarged view to show a part of the mechanism of the present invention.  
         [0017]    [0017]FIG. 4 shows the logic board and the sensor modules.  
         [0018]    [0018]FIG. 5A shows the first position of the sheet-size detecting mechanism.  
         [0019]    [0019]FIG. 5B shows the second position of the sheet-size detecting mechanism.  
         [0020]    [0020]FIG. 5C shows the third position of the sheet-size detecting mechanism.  
         [0021]    [0021]FIG. 5D shows the fourth position of the sheet-size detecting mechanism.  
         [0022]    [0022]FIG. 5E shows the fifth position of the sheet-size detecting mechanism.  
         [0023]    [0023]FIG. 5F shows the sixth position of the sheet-size detecting mechanism.  
         [0024]    [0024]FIG. 5G shows the seventh position of the sheet-size detecting mechanism.  
         [0025]    [0025]FIG. 5H shows the eighth position of the sheet-size detecting mechanism.  
         [0026]    [0026]FIG. 6 is a chart to show the signals that the sensor module outputs. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]    Referring to FIG. 1, an automatic document feeder module comprises an input tray  10  and an output tray  20 . The input tray  10  receives the document to be scanned. The sheets of the document can be automatically fed in by an automatic document feeder.  
         [0028]    Referring to FIG. 2, the input tray  10  includes a plate  12  and two paper guides  14 ,  16 . The surface of the plate  12  is defined as a facing surface  13  on which sheets are put and the opposite surface of the plate  12  is defined as a bottom  15 .  
         [0029]    The two paper guides  14 ,  16  are located on the plate  12  and protrude from the facing surface  13 . The two paper guides  14 ,  16  can be moved toward or away from each other.  
         [0030]    Referring to FIGS. 3 and 4, a sensor module  30  is fixed to the bottom  15  of the plate  12  and has a plurality of sensors  32 A,  32 B,  34 A,  34 B,  36 A and  36 B.  
         [0031]    The sensors  32 A and  32 B are together to be a sensing unit  32 , the sensors  34 A and  34 B are together to be a sensing unit  34 , and the sensors  36 A and  36 B are together to be a sensing unit  36 .  
         [0032]    A passage  33  is defined between the sensors  32 A,  32 B, a passage  35  is defined between the sensors  34 A,  34 B, and a passage  37  is defined between the sensors  36 A,  36 B.  
         [0033]    A logic board  40  is mounted to the bottom  15  of the plate  12  and is fixed to the paper guide  14  such that the logic board  40  is able to move with the paper guide  14 . The logic board  40  has ribs  42  extending from the surface and the ribs  42  are located corresponding to the passages  33 ,  35 ,  37 . Gaps  44  are defined between the ribs  42  in the same row. The logic board  40  moves with the movement of the paper guide  14  such that the ribs  42  may enter or leave the passages  33 ,  35 ,  37 .  
         [0034]    [0034]FIG. 4 shows that none of the ribs  42  enters the passages  33 ,  35 ,  37  of the sensor module  30 . Therefore, the sensing units  32 ,  34  and  36  are not separated and they are in an open status which is defined as a digit “1”. On the contrary, the sensing units  32 ,  34  and  36  may be separated and in a close status which is defined as a digit “0”.  
         [0035]    Referring to FIGS. 5A and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5A, because the sensing units  32 ,  34  and  36  are not located in correspondence with the ribs  42 , the sensing units  32 ,  34  and  36  are in the open status. A result is obtained as shown in FIG. 6A and the status is defined as a digit information “111”.  
         [0036]    Referring to FIGS. 5B and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5B, because the sensing unit  32  is separated, sensing units  34  and  36  are not located in correspondence with the ribs  42  to form an open status. A result is obtained as shown in FIG. 6B and the status is defined as a digit information “011”.  
         [0037]    Referring to FIGS. 5C and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5C, because the sensing units  32  and  34  are separated, the sensing unit  36  is not located in correspondence with the ribs  42  to form an open status. A result is obtained as shown in FIG. 6C and the status is defined as a digit information “001”.  
         [0038]    Referring to FIGS. 5D and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5D, because all the sensing units  32 ,  34  and  36  are located in correspondence with the ribs  42  so that the sensing units  32 ,  34 ,  36  are in close statuses. A result is obtained as shown in FIG. 6D and the status is defined as a digit information “000”.  
         [0039]    Referring to FIGS. 5E and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5E, because the sensing unit  32  is not located in correspondence with the ribs  42  and the sensing units  34  and  36  are separated by the ribs  42  to form a close status. A result is obtained as shown in FIG. 6E and the status is defined as a digit information “100”.  
         [0040]    Referring to FIGS. 5F and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5F, because the sensing units  32  and  34  are not located in correspondence with the ribs  42  and the sensing unit  36  is separated by the rib  42  to form a close status. A result is obtained as shown in FIG. 6F and the status is defined as a digit information “110”.  
         [0041]    Referring to FIGS. 5G and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5G, because the sensing units  32  and  36  are separated by the ribs  42  and the sensing unit  34  is not located in correspondence with the rib  42  to form an open status. A result is obtained as shown in FIG. 6G and the status is defined as a digit information “010”.  
         [0042]    Referring to FIGS. 5H and 6, when the ribs  42  and the sensing units  32 ,  34  and  36  are located in the status as shown in FIG. 5H, because the sensing units  32  and  36  are not located in correspondence with the rib  42  and the sensing unit  34  is separated by the rib  42  to form a close status. A result is obtained as shown in FIG. 6H and the status is defined as a digit information “101”.  
         [0043]    By the movement of the logic board  40  relative to the sensing units  32 ,  34 ,  36 , there are eight arrangements obtained. By adjusting the position of the paper guide  14 , the width of the sheets on the plate  12  can be detected and eight different widths can be detected. It is understandable that the number of the widths of the sheets that can be detected by the sheet-size detecting mechanism increases in a way of powers of a base which is 2, by increasing the number of the sensor modules  30  and the number of the ribs  42  on the logic board  40 .  
         [0044]    By using the relative movement of the logic board  40  and the sensor modules  30 , the ribs  40  on the logic board  40  can be moved corresponding to the sensing units  32 ,  34 ,  36  of the sensor module  30  so as to form several results and decide the width of the sheets accordingly. In the above mentioned embodiment, the logic board  40  is movable and the sensor module  30  is fixed. It is also available that the logic board  40  is fixed and the sensor module  30  is movable.  
         [0045]    Referring to FIG. 2, the plate  12  has a sensor  18  which is located in parallel with the direction that the sheets move, preferably located away from the input end  19 . The purpose of the installation of the sensor  18  is to detect the longitudinal direction of the sheet. Because the sheet is rectangular so that there is a difference for the sheet to be fed in a specific direction, such as the A3 sheets and the transverse A4 sheets have the same width, so that the length of the sheet can be recognized by using the sensor  18 .  
         [0046]    The comparison between the sensor module  30  and the logic board  40  is cooperated with the result from the sensor  18  so as to obtain 8×2=16 different results.  
         [0047]    In the above mentioned embodiment, the sensors output a signal according to the separation by the ribs so that the sensors are penetration sensors. However, reflection sensors can be used to replace the penetration sensors. The reflection sensors submit signals and detect the responses whether or not the signals bounce back by the ribs so as to have different information. Holes or recesses are defined in the logic board when using the reflection sensors. It is to be noted that the recesses, holes and the ribs are called feature sections on the logic board.  
         [0048]    Therefore, the present invention uses logic arrangements so as to reduce the number of the sensors and can detect more types of sheet sizes. This reduces the manufacturing cost and can precisely detect the sizes of the sheets. The sensors for detecting the sizes of the sheets do not need to contact the sheets so that they are not worn out and may keep the precision.  
         [0049]    While we have shown and described the embodiment 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.