Patent Publication Number: US-8534663-B2

Title: Automatic document feeder

Description:
FIELD OF THE INVENTION 
     The present invention relates to an automatic document feeder, and more particularly to an automatic document feeder with a function of correcting a skewed paper. 
     BACKGROUND OF THE INVENTION 
     For facilitating the user to print or scan a large number of papers, an office machine (e.g. a printer, a scanner or a multifunction peripheral) is usually equipped with an automatic document feeder. By means of the automatic document feeder, a stack of papers can be successively fed into the office machine without the need of using the man power. Consequently, the papers can be printed, scanned or processed at a fast speed and in a labor-saving manner. 
     However, if the paper is not exactly placed on the inlet tray of the automatic document feeder in the beginning, the paper is aslant fed into the internal portion of the office machine. Under this circumstance, the printing or scanning quality of the office machine is deteriorated, and the paper is readily jammed in the automatic document feeder. The jammed paper becomes hindrance from performing the subsequent tasks. For preventing the skewed paper from being fed into the office machine through the automatic document feeder and obviating erroneous operations of the office machine, an automatic document feeder with a function of correcting a skewed paper was disclosed. Please refer to  FIG. 1 , which schematically illustrates a conventional automatic document feeder. 
     As shown in  FIG. 1 , the conventional automatic document feeder  10  comprises a paper pick-up device  11  and a transfer roller assembly  12 . The paper pick-up device  11  comprises a pick-up roller  111  and a separation roller  112 . The pick-up roller  111  is used for transporting a paper S into the automatic document feeder  10 . The separation roller  112  is located downstream of the pick-up roller  111  for providing a friction force to separate the paper S, thereby preventing a plurality of papers S from being simultaneously transmitted into the automatic document feeder  10 . 
     Please refer to  FIG. 1  again. The transfer roller assembly  12  is located downstream of the paper pick-up device  11 . In addition, the transfer roller assembly  12  comprises a shaft  121  and a roller  122 . The shaft  121  is connected to a power source (not shown). The roller  122  is sheathed around and connected with the shaft  121 . Consequently, the roller  122  is synchronously rotated with the shaft  121 . Whereas, in a case that the shaft  121  is in a static status, the roller  122  is also in the static status. 
     When the pick-up roller  111  of the paper pick-up device  11  is rotated and contacted with the paper S, the paper S is transmitted to the separation roller  112  to be separated. The subsequent actions of the conventional automatic document feeder  10  will be illustrated with reference to  FIG. 2 .  FIG. 2  schematically illustrates the actions of the conventional automatic document feeder. 
     As shown in  FIG. 2 , when the paper S transmitted through the separation roller  112  is moved to the transfer roller assembly  12 , the shaft  121  and the roller  122  of the transfer roller assembly  12  are in the static status in order to hinder the paper S from being continuously advanced. Meanwhile, the paper S is continuously transmitted into the automatic document feeder  10  by the paper pick-up device  11 , which is located upstream of the transfer roller assembly  12 . Consequently, the front edge of the paper S is moved to the static roller  122  and slightly upturned. After the front edge of the paper S is completely moved to the roller  122 , the function of correcting the skewed paper S is achieved. 
     After a preset time period, the front edge of the paper S is completely moved to the roller  122 , and the function of correcting the skewed paper S is achieved. Then, the shaft  121  of the transfer roller assembly  12  acquires the electric power again to drive rotation of the roller  122 . Consequently, the paper S is allowed to be transmitted through the transfer roller assembly  12 . 
     Although the conventional automatic document feeder  10  is effective to correct the skewed paper S, there are still some drawbacks. For example, for correcting the skewed paper S by the conventional automatic document feeder  10 , the rotation of the shaft  121  is an important factor for determining whether the paper S is continuously advanced or not. As previously described, the paper S is hindered by the static shaft  121  until the front edge of the paper S is completely moved to the roller  122 . Once the front edge of the paper S is completely moved to the roller  122 , the shaft  121  starts to rotate again. However, it takes an additional time period to accelerate the shaft  121  from the static status to a normal speed. Since each of the papers S to be transmitted needs the accelerating process, if a large number of papers are frequently processed by the conventional automatic document feeder  10 , the paper-feeding efficiency is impaired and the processing time is largely prolonged 
     SUMMARY OF THE INVENTION 
     The present invention provides an automatic document feeder with a high paper-feeding efficiency. 
     In accordance with an aspect of the present invention, there is provided an automatic document feeder. The automatic document feeder includes a paper pick-up device, a shaft, a first roller, a second roller, a first idler, and a power-coupling device. The paper pick-up device is used for transmitting a paper into the automatic document feeder. The shaft is located downstream of the paper pick-up device and rotated at a first speed. The first roller is sheathed around the shaft. The second roller is disposed on the shaft for transmitting the paper. A diameter of the second roller is greater than a diameter of the first roller. The second roller is driven to be rotated at a second speed by the shaft. The first idler is located upstream of the shaft for performing a skew correction on the paper. The first idler is driven to be rotated by the first roller. The power-coupling device is disposed on the shaft, and located at a side of the first roller. When the power-coupling device is connected with the shaft and the first roller, the first roller is driven to be rotated at a third speed by the shaft, and the first idler is driven to be rotated by the first roller to start to transmit the paper. When the paper is transmitted through the first roller and the second roller simultaneously, the first roller is driven to be rotated at the second speed by the paper, so that a power connection between the shaft and the first roller is released by the power-coupling device. The second speed is higher than the third speed. After the paper is completely departed from the first roller and during the power connection between the shaft and first roller is established by the power-coupling device again, the first roller and the first idler reach a static status. 
     In an embodiment, the power-coupling device is a clutch spring. 
     In an embodiment, the paper pick-up device includes a pick-up roller and a separation roller. 
     In an embodiment, the automatic document feeder further includes a second idler. The second idler is just disposed over the second roller, wherein the second idler is driven to be rotated by the second roller. 
     In an embodiment, the automatic document feeder further includes a duplex feeding channel for duplex feeding the paper, wherein the shaft is disposed in the duplex feeding channel. 
     In an embodiment, the power-coupling device has a protrusion structure, and the first roller has a concave structure, wherein the protrusion structure is disposed in the concave structure. 
     The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a conventional automatic document feeder; 
         FIG. 2  schematically illustrates the actions of the conventional automatic document feeder; 
         FIG. 3  schematically illustrates an automatic document feeder according to an embodiment of the present invention; 
         FIG. 4  is a schematic exploded view illustrating the transfer roller assembly of the automatic document feeder according to the first embodiment of the present invention; and 
         FIGS. 5˜10  schematically illustrate the paper-feeding operation of the automatic document feeder according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 3  schematically illustrates an automatic document feeder according to an embodiment of the present invention. As shown in  FIG. 3 , the automatic document feeder  20  comprises a paper pick-up device  21 , a transfer roller assembly  22 , a duplex feeding channel  23 , and a power source (not shown). The paper pick-up device  21  is located at a paper entrance. The duplex feeding channel  23  is located downstream of the paper pick-up device  21 . The transfer roller assembly  22  is disposed in the duplex feeding channel  23  for correcting a skewed paper during a duplex feeding operation is performed. 
     In this embodiment, the automatic document feeder  20  at least has a duplex feeding function. For complying with the small-sized requirement of the automatic document feeder  20 , a front-side feeding path and a back-side feeding path of the automatic document feeder  20  are integrated, so that a portion of a common feeding channel is defined by the front-side feeding path and the back-side feeding path collaboratively. In such way, the volume required for installing the feeding channel is reduced. In this context, the duplex feeding channel  23  is a common feeding channel for transmitting the double sides of the paper during the duplex feeding operation is performed by the automatic document feeder  20 . Moreover, the use of the duplex feeding channel  23  is not limited to the implementation of the duplex feeding operation. 
     Hereinafter, the configurations of the paper pick-up device  21  and the transfer roller assembly  22  will be illustrated in more details. Please refer to  FIG. 3  again. The paper pick-up device  21  comprises a pick-up roller  211  and a separation roller  212 . The pick-up roller  211  is used for transmitting a paper into the automatic document feeder  20 . The separation roller  212  is located downstream of the pick-up roller  211  for providing a friction force to separate the paper, thereby preventing a plurality of papers from being simultaneously transmitted into the automatic document feeder  20 . 
     The transfer roller assembly  22  is located downstream of the paper pick-up device  21 . After the paper is transmitted into the automatic document feeder  20 , the paper may be transmitted by the transfer roller assembly  22  to be continuously advanced. In this embodiment, the transfer roller assembly  22  comprises a shaft  24 , a first roller  25 , a second roller  26 , a first idler  27 , a second idler  28 , and a power-coupling device  29 . In accordance with the present invention, there is a speed difference between the second roller  26  and the first roller  25  in order to achieve the function of correcting the skewed paper. For resulting in the speed difference, the radius d 2  of the second roller  26  is greater than the radius d 1  of the first roller  25 . That is, the diameter of the second roller  26  is greater than the diameter of the first roller  25   
     Please refer to  FIG. 3  again. The shaft  24  of the transfer roller assembly  22  is located downstream of the paper pick-up device  21 , and disposed in the duplex feeding channel  23 . The first roller  25  is sheathed around the shaft  24 . The second roller  26  and the power-coupling device  29  are disposed on the shaft  24 . In addition, the second roller  26  and the power-coupling device  29  are driven to be rotated by the shaft  24 . 
     The first idler  27  is disposed over the first roller  25 . The first idler  27  is driven to be rotated by the first roller  25 , so that the function of correcting the skewed paper is achieved. The second idler  28  is just disposed over the second roller  26 . The second idler  28  is driven to be rotated by the second roller  26 . Since the second roller  26  is continuously driven by the shaft  24 , the second roller  26  is continuously rotated. Since the second idler  28  is driven by the second roller  26 , the second idler  28  is continuously rotated. If the first idler  27  and the second idler  28  are arranged at the same horizontal line, when the paper is transmitted to the transfer roller assembly  22 , the paper is contacted with the first roller  25  and the second roller  26  simultaneous. Since the paper is contacted with the second roller  26 , the paper can be continuously advanced without the need of performing any skew correction on the paper. Since the first idler  27  is not only disposed over the first roller  25  but also located upstream of the shaft  24 , the skewed paper can be well corrected before the paper is transmitted through the transfer roller assembly  22 . 
     The power source of the automatic document feeder  20  is connected with the shaft  24  for driving the shaft  24  to be rotated at a first speed V 1 . The second roller  26  is driven by the shaft  24  to be rotated at a second speed V 2 . In this context, the first speed V 1  denotes a path length of a particle moving on a shaft surface of the shaft  24  in a unit time; and the second speed V 2  denotes a path length of a particle moving on a roller surface of the second roller  26  in a unit time. 
     Moreover, for enhancing the stability of transmitting the papers, the automatic document feeder  20  of the present invention may have two first rollers  25  and two second rollers  26 . In such way, during the paper is transmitted through the first rollers  25  and two second rollers  26 , the force is uniformly exerted on the paper to reduce the possibility of causing the skewed paper. 
     Hereinafter, the configurations of the transfer roller assembly  22  will be illustrated with reference to  FIG. 4 .  FIG. 4  is a schematic exploded view illustrating the transfer roller assembly of the automatic document feeder according to the embodiment of the present invention. As shown in  FIG. 4 , the transfer roller assembly  22  comprises a shaft  24 , a first roller  25 , a second roller  26 , a first idler  27 , a second idler  28 , and a power-coupling device  29 . A protrusion structure  291  is located at an end of the power-coupling device  29 . In addition, a concave structure  251  is formed in an inner surface of the first roller  25 . The protrusion structure  291  of the power-coupling device  29  is disposed in the concave structure  251  of the first roller  25 . 
     In this embodiment, the power-coupling device  29  is a clutch spring. The power-coupling device  29  is sheathed around the shaft  24 , and located at a side of the first roller  25 . Especially, the power-coupling device  29  is disposed on the inner surface of the first roller  25 . When a first end A of the concave structure  251  is pushed by the protrusion structure  291 , the power-coupling device  29  is connected with the shaft  24  and the first roller  25 , thereby driving rotation of the first roller  25 . 
     Moreover, for preventing from the horizontal movement of the rotating first roller  25  and reducing the adverse influence on the paper-feeding operation, a C-shaped ring  30  is located beside the first roller  25 . The C-shaped ring  30  is sheathed around the shaft  24  for limiting the position of the first roller  25 . 
     Hereinafter, the actions of the components of the transfer roller assembly  22  and the duplex feeding operation of the automatic document feeder  20  will be illustrated with reference to  FIGS. 5 ,  6 ,  7 ,  8 ,  9  and  10 .  FIGS. 5-10  schematically illustrate the paper-feeding operation of the automatic document feeder according to the embodiment of the present invention. 
     Firstly, as shown in  FIG. 5 , the pick-up roller  211  is contacted with a paper S 1 , so that the paper S 1  is transmitted into the automatic document feeder  20 . The separation roller  212  is located downstream of the pick-up roller  211  for providing a friction force to separate the paper S 1 , thereby preventing a plurality of papers from being simultaneously fed into the automatic document feeder  20 . The paper S 1  is introduced into the duplex feeding channel  23  and then moved to the transfer roller assembly  22 . 
     Meanwhile, the shaft  24  is rotated at the first speed V 1 . In addition, the second roller  26  and the power-coupling device  29  are synchronously rotated with the shaft  24 . Since the protrusion structure  291  has not been sustained against the first end A of the concave structure  251 , the shaft  24  fails to drive synchronous rotation of the first roller  25  through the power-coupling device  29 . Under this circumstance, the first roller  25  is in the static status. In addition, the first idler  27  in contact with the first roller  25  is also in the static status for hindering the paper S 1  from being continuously advanced. 
     Next, the paper S 1  is continuously transmitted by the paper pick-up device  21 , which is located upstream of the transfer roller assembly  22 . Consequently, the front edge F of the paper S 1  is moved to the static first roller  25  and the first idler  27 , and the front edge F of the paper S 1  is slightly upturned. Then, a preset waiting time is required for allowing the front edge F of the paper S 1  to be completely moved to the first roller  25 . 
     After the preset waiting time, the front edge F of the paper S 1  is completely moved to the first roller  25  (see  FIG. 6 ), and the function of correcting the skewed paper S 1  is achieved. Meanwhile, the protrusion structure  291  of the power-coupling device  29  is moved from a second end B of the concave structure  251  toward the first end A of the concave structure  251 . Meanwhile, the power-coupling device  29  becomes a connecting medium between the shaft  24  and the first roller  25 . Consequently, the power-coupling device  29  is ready to drive rotation of the first roller  25 . 
     As shown in  FIG. 7 , the first end A of the concave structure  251  is pushed by the protrusion structure  291 , so that the first roller  25  is driven to be rotated by the shaft  24  and the first roller  25  is rotated at a third speed V 3 . Meanwhile, the paper S 1  originally hindered by the first roller  25  and the first idler  27  is transmitted by the first roller  25  (at the third speed V 3 ) to the second roller  26 . 
     Since the diameter of the second roller  26  is greater than the diameter of the first roller  25  and the motive power is supplied to the shaft  24  by the same power source, the second speed V 2  is certainly higher than the third speed V 3 . Similarly, the third speed V 3  denotes a path length of a particle moving on a roller surface of the first roller  25  in a unit time. 
     As shown in  FIG. 8 , the front edge F of the paper S 1  is moved to the second roller  26 , and the paper S 1  has not been completely departed from the first roller  25 . Meanwhile, the paper S 1  is transmitted by the second roller  26 . Meanwhile, the speed of moving the paper S 1  is switched from the third speed V 3  to the second speed V 2 . In addition, the first roller  25  is driven to be rotated at the second speed V 2  by the paper S 1 . 
     When the first roller  25  is rotated at the second speed V 2  higher than third speed V 3 , the shaft  24  is still rotated at the first speed V 1 . Since the power-coupling device  29  is disposed on the shaft  24 , the power-coupling device  29  is also rotated at the original speed. Meanwhile, the angular variation α of the shaft  24  which is rotated at the first speed V 1  is obviously smaller than the angular variation β of the first roller  25  which is rotated at the second speed V 2 . Meanwhile, the protrusion structure  291  is gradually moved from the first end A of the concave structure  251  toward the second end B of the concave structure  251 . 
     After the protrusion structure  291  is moved to the second end B of the concave structure  251 , the power-coupling device  29  is synchronously rotated with the first roller  25 . Consequently, the power-coupling device  29  is no longer driven by the shaft  24 . After the paper S 1  is completely departed from the first roller  25 , the external force acting on the first roller  25  is eliminated and the first roller  25  loses the motive power, so that the first roller  25  reaches the static status. Under this circumstance, the first idler  27  is also in the static status. 
     In a case that the a single-sided feeding operation is being performed by the automatic document feeder  20 , a next paper S 2  is hindered by the first roller  25  and the first idler  27  from being continuously advanced, so that the skew phenomenon of the next paper S 2  can be corrected (see  FIG. 9 ). Until the protrusion structure  291  is sustained against the first end A of the concave structure  251  again, the front edge G of the next paper S 2  is allowed to pass through the first roller  25 . 
     In a case that the a duplex feeding operation is being performed by the automatic document feeder  20 , after the paper S 1  is completely departed from the transfer roller assembly  22 , the paper S 1  will be transmitted through the duplex feeding channel  23  again. That is, the paper S 1  is hindered by the first roller  25  and the first idler  27  from being continuously advanced, so that the skew phenomenon of the paper S 1  can be corrected again. Until the protrusion structure  291  is sustained against the first end A of the concave structure  251  again (see  FIG. 10 ), the front edge H of the paper S 1  is allowed to pass through the first roller  25 . 
     In a preferred embodiment, for facilitating the first roller  25  to quickly reach the static status, the first idler  27  further comprises an anti-slip cover  271  (see  FIG. 3 ). As shown in  FIG. 3 , the anti-slip cover  271  is disposed on the surface of the first idler  27 . After the paper is completely departed from the first roller  25 , the first roller  25  is directly contacted with the anti-slip cover  271  of the first idler  27 , so that a friction force is generated. Due to the friction force, the rotating speed of the first roller  25  is quickly lowered down, and the first roller  25  can quickly reach the static status. 
     From the above embodiments, the automatic document feeder of the present invention comprises a paper pick-up device, a transfer roller assembly, and a duplex feeding channel. The transfer roller assembly comprises a shaft, a first roller, a second roller, a first idler, a second idler, and a power-coupling device. The first roller is sheathed around the shaft. The second roller and the power-coupling device are disposed on the shaft. In addition, the power-coupling device is located at a side of the first roller. 
     When the power-coupling device is connected with the shaft and the first roller, the first roller is driven to be rotated at a third speed by the shaft, and the first idler is driven to be rotated by the first roller. Consequently, the first roller has the function of transmitting the paper. When the first roller is driven to be rotated at the second speed by the paper, the power connection between the first roller and the shaft is released by the power-coupling device. After the paper is completely departed from the first roller and during the power connection between the shaft and first roller is established again through the power-coupling device, the first roller and the first idler reach the static status. Consequently, the first roller and the first idler have the function of correcting the skewed paper. 
     From the above description, the present invention provides an automatic document feeder. Since the diameter of the first roller is different from the diameter of the second roller, the first roller and the second roller have a speed difference. Due to the speed difference between the first roller and the second roller and the arrangement of the power-coupling device, the power connection between the shaft and the first roller is selectively established or released. Consequently, without the need of changing the speed of the shaft, the first roller is still in the static status in the initial stage of feeding the paper in order to correct the skewed paper. In such design, the paper skew problem can be effectively solved. Moreover, the time period for accelerating the shaft from the static state to the normal speed can be saved. Consequently, the automatic document feeder of the present invention has enhanced paper-feeding efficiency and reduced operating time. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.