Abstract:
The present invention relates to an automatic document feeder having a mechanism for releasing paper jam by disconnecting the transmission device. The automatic document feeder includes a driving motor, a transmission device, a plurality of paper transfer rollers, a swing arm and a releasing arm. The driving motor is used for providing driving power. The transmission device and is coupled to the driving motor for transmitting the driving power. The swing arm is coupled to some of the transmission elements and operated in either a connection state or a disconnection state. The releasing arm is selectively contacted with the swing arm to have the swing arm enter the disconnection state or separated from the swing arm to have the swing arm enter the connection state. The paper jam is released when the swing arm is operated in the disconnection state.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an automatic document feeder, and more particularly to an automatic document feeder having a mechanism for releasing paper jam. 
     BACKGROUND OF THE INVENTION 
     Image scanning apparatuses such as image scanners, copiers, printers and multi function peripherals (MFPs) are widely used in daily lives or offices for scanning images of objects such as paper sheets. As known, the image scanning apparatus usually has an automatic document feeder for automatically and continuously feeding many paper sheets one by one. During operation of the automatic document feeder, the paper sheet is readily jammed. For example, the paper sheets that are too thick or too thin may cause jams. In addition, if the paper sheet is too wet or too dry such that the paper sheet may be softened or hardened, or if the smoothness or length of the paper sheet is improper, the paper sheet is transported across the feeding path with difficulty. Moreover, if the paper feeding operation is abruptly interrupted, the possibility of getting jammed paper sheet is increased. Conventionally, the automatic document feeder has a paper release mechanism for removing the jammed paper sheet. 
     Referring to  FIG. 1 , a schematic cross-sectional view of an automatic document feeder having a mechanism for releasing paper jam is illustrated. The automatic document feeder includes a first transfer roller assembly  100 , a second transfer roller assembly  110  and a third transfer roller assembly  120 . During operation of the automatic document feeder, the paper sheet is moved along the feeding path  130  and successively transported across the first transfer roller assembly  110 , the second transfer roller assembly  110  and the third transfer roller assembly  120 . 
     The first transfer roller assembly  100  and the second transfer roller assembly  110  are coupled to the upper cover  140  of the automatic document feeder. A first transfer follower roller  111  of the first transfer roller assembly  100  and a second transfer follower roller  121  of the second transfer roller assembly  110  are both coupled to the upper cover  140 . In a case that the paper sheet is jammed in the vicinity of the first transfer roller assembly  100  or the second transfer roller assembly  110 , the user may uplift the upper cover  140  in the direction as indicated by the arrow  150  to release the first transfer roller assembly  100  and the second transfer roller assembly  110  while easily pulling out the jammed paper. 
     In contrast, if the paper sheet is jammed in the vicinity of the third transfer roller assembly  120 , the user needs to pull out the jammed paper in the direction as indicated by the arrow  160  or  170  by exerting a pulling force. Since the pulling force needs to be large enough to pull out the jammed paper, the paper sheet may be fractured or broken in the feeding path  130  of the automatic document feeder. 
     Please refer to  FIG. 1  again. A transmission mechanism is arranged between the third transfer roller assembly  120  and a motor  180 . The transmission mechanism includes a plurality of gears. These gears are engaged with each other. During the process of pulling out the paper sheet jammed in the third transfer roller assembly  120 , the motor  180  may generate a damping-reinforced effect and thus the resistive force is increased. That is why the paper sheet jammed in the third transfer roller assembly  120  is pulled out with difficulty. 
     In views of the above-described disadvantages resulted from the prior art, the applicant keeps on carving unflaggingly to develop an automatic document feeder having a mechanism for releasing paper jam in order to minimize the damping-reinforced effect and facilitate easily releasing the jammed paper. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an automatic document feeder having a mechanism for releasing paper jam in order to minimize the damping-reinforced effect and facilitate easily releasing the jammed paper. 
     Another object of the present invention provides an automatic document feeder having a mechanism for releasing paper jam by disconnecting the transmission device to interrupt indirect connection between the paper transfer roller and the driving motor, thereby facilitating easily releasing the jammed paper. 
     In accordance with an aspect of the present invention, there is provided an automatic document feeder having a mechanism for releasing paper jam. The automatic document feeder includes a driving motor, a transmission device, a plurality of paper transfer rollers, a swing arm and a releasing arm. The driving motor is used for providing driving power. The transmission device includes a plurality of transmission elements, and is coupled to the driving motor for transmitting the driving power. The paper transfer rollers are coupled to the transmission device for receiving the driving power to transport a paper sheet. The swing arm is coupled to some of the transmission elements and operated in either a connection state or a disconnection state. The releasing arm is selectively contacted with the swing arm to have the swing arm enter the disconnection state or separated from the swing arm to have the swing arm enter the connection state. The paper jam is released when the swing arm is operated in the disconnection state. The driving power provided by the driving motor is transmitted to the paper transfer rollers when the swing arm is operated in the connection state. The driving power provided by the driving motor fails to be transmitted to the paper transfer rollers when the swing arm is operated in the disconnection state. 
     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  is a schematic cross-sectional view of a conventional automatic document feeder having a mechanism for releasing paper jam; 
         FIG. 2  is a schematic cross-sectional view of an automatic document feeder according to a preferred embodiment of the present invention; 
         FIG. 3  is a schematic cross-sectional view illustrating partial inner components of the automatic document feeder shown in  FIG. 2 ; 
         FIG. 4  is a schematic cross-sectional view illustrating an operation of the transmission device of the automatic document feeder; 
         FIG. 5  is a schematic cross-sectional view illustrating another operation of the transmission device of the automatic document feeder; 
         FIG. 6  is a schematic cross-sectional view illustrating a mechanism for releasing the paper jam by disconnecting the transmission device; and 
         FIG. 7  is a schematic cross-sectional view illustrating reconnection of the transmission device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For overcoming the above described drawbacks resulting from the prior art, the present invention provides an improved automatic document feeder having a mechanism for releasing paper jam. By using a swing arm and a releasing arm to disconnect the transmission device, the driving power of the driving motor fails to be transmitted to the paper transfer roller, so that the user may remove the paper sheet jammed in the inner roller assembly without difficulty. 
     Referring to  FIG. 2 , a schematic cross-sectional view of an automatic document feeder according to a preferred embodiment of the present invention is illustrated. Recently, a duplex scanning apparatus is widely used in offices for scanning operation to scan both sides of the paper sheet. For illustration, the automatic document feeder of  FIG. 2  is a duplex automatic document feeder for use with a duplex scanning apparatus. The automatic document feeder of  FIG. 2  principally comprises a main body  201  and an upper cover  206 . The main body  201  includes a paper input tray  202 , a paper ejecting tray  204 , an inner roller assembly  230 , an ejecting roller assembly  240 , a first transfer path  250  and a second transfer path  260 . The inner roller assembly  230  includes a first paper transfer roller  231 , a second paper transfer roller  232  and a third paper transfer roller  233 . The ejecting roller assembly  240  includes a driving roller  241 . A pick-up roller assembly  210  and a transfer roller assembly  220  are coupled to the upper cover  206 . The transfer roller assembly  220  includes a transfer driving roller  221 . 
     Hereinafter, a procedure of performing a duplex scanning operation on a paper sheet is illustrated. First of all, the paper sheet to be scanned is placed in the sheet input tray  202 . By the pick-up roller assembly  210 , the paper sheet is transported into the first transfer path  250 . Then, the paper sheet is successively transported across the transfer roller assembly  220 , the inner roller assembly  230  and the ejecting roller assembly  240 . When the paper sheet  306  is transported across a scan region (not shown) in the first transfer path  250 , a first side of the paper sheet is scanned by a scanning module (not shown) under the scan region. Next, the driving roller  241  of the ejecting roller assembly  240  is rotated in an anti-clockwise direction to eject the paper sheet. After the first side of the paper sheet is scanned and a majority of the paper sheet is ejected to the paper ejecting tray  204 , the driving roller  241  of the ejecting roller assembly  240  is reversely rotated in the clockwise direction, so that the paper sheet is transported into the second transfer path  260 . Next, the paper sheet is successively transported across the transfer roller assembly  220 , the inner roller assembly  230  and the ejecting roller assembly  240 . When the paper sheet is transported across the scan region, a second side of the paper sheet is scanned by the scanning module. Next, the driving roller  241  of the ejecting roller assembly  240  is rotated in the anti-clockwise direction to have the paper sheet eject to the paper ejecting tray  204 . 
     It is noted that, however, those skilled in the art will readily observe that numerous modifications and alterations of the duplex scanning operation may be made while retaining the teachings of the invention. The details of the duplex scanning operation are not redundantly described herein. For example, the mechanism for releasing the paper sheet jammed in the pick-up roller assembly  210  or the transfer roller assembly  220  is identical to that shown in FIG.  1 , and is not redundantly described herein. In a case that the paper sheet is jammed in the vicinity of the pick-up roller assembly  210  or the transfer roller assembly  220 , the user may uplift the upper cover  206  to easily release the jammed paper. 
     Please refer to  FIG. 3 , which is a schematic cross-sectional view illustrating partial inner components of the automatic document feeder shown in  FIG. 2 . The mechanism for releasing paper jam includes a driving motor  300 , a transmission device  310 , a swing arm  320  and a releasing arm  330 . The transmission device  310  includes several transmission elements such as gears. In this embodiment, the transmission device  310  includes a first gear  311 , a second gear  312 , a third gear  313 , a fourth gear  314 , a fifth gear  315 , a sixth gear  316 , a seventh gear  317  and an eighth gear  318 . The sixth gear  316 , the seventh gear  317  and the eighth gear  318  are coupled to the swing arm  320 . The fifth gear  315  is coaxial with the first paper transfer roller  231  of the inner roller assembly  230  (as shown in  FIG. 2 ), so that the driving power provided by the driving motor  300  may be transmitted to the first paper transfer roller  231 . Similarly, the fourth gear  314  is coaxial with the driving roller  241  of the ejecting roller assembly  240  (as shown in  FIG. 2 ), so that the driving power provided by the driving motor  300  may be transmitted to the driving roller  241 . 
     Hereinafter, an operation of the transmission device is illustrated with reference to the schematic cross-sectional view of  FIG. 4 . After the paper sheet is fed into the first transfer path  250  (as shown in  FIG. 2 ) or the second transfer path  260  (as shown in  FIG. 2 ) and after the first or second side of the paper sheet is scanned, the driving motor  300  is rotated in the anti-clockwise direction. Correspondingly, the related gears  311 ˜ 318  of the transmission device  310  are rotated in a clockwise or anti-clockwise direction as indicated by the arrows shown in the figure. Since the eighth gear  318  is coupled to the swing arm  320  and the first gear  311  is rotated in the clockwise direction, the eighth gear  318  has a tendency to approach the fifth gear  315 . Once the eighth gear  318  is engaged with the fifth gear  315 , the driving power of the driving motor  300  is transmitted to the fifth gear  315 . Since the fifth gear  315  is coaxial with the first paper transfer roller  231  (as shown in  FIG. 2 ), the first paper transfer roller  231  and the fifth gear  315  are synchronously rotated in the clockwise direction. In addition, since the fourth gear  314  is coaxial with the driving roller  241  (as shown in  FIG. 2 ), the driving roller  241  and the fourth gear  314  are synchronously rotated in the anti-clockwise direction. 
     Another operation of the transmission device is illustrated with reference to the schematic cross-sectional view of  FIG. 5 . In order to scan the second side of the paper sheet, after a majority of the paper sheet is transported across the ejecting roller assembly  240  (as shown in  FIG. 2 ), the driving motor  300  is reversely rotated in the clockwise direction to feed the paper sheet into the second transfer path  260  (as shown in  FIG. 2 ). Correspondingly, the related gears  311 ˜ 318  of the transmission device  310  are rotated in a clockwise or anti-clockwise direction as indicated by the arrows shown in the figure. Since the sixth gear  316  is coupled to the swing arm  320  and the first gear  311  is rotated in the anti-clockwise direction, the sixth gear  316  and the seventh gear  317  have tendencies to approach the fifth gear  315 . Once the seventh gear  317  is engaged with the fifth gear  315 , the driving power of the driving motor  300  is transmitted to the fifth gear  315 . Since the fifth gear  315  is coaxial with the first paper transfer roller  231  (as shown in  FIG. 2 ), the first paper transfer roller  231  and the fifth gear  315  are synchronously rotated in the clockwise direction. In addition, since the fourth gear  314  is coaxial with the driving roller  241  (as shown in  FIG. 2 ), the driving roller  241  and the fourth gear  314  are synchronously rotated in the clockwise direction. 
       FIG. 6  is a schematic cross-sectional view illustrating a mechanism for releasing the paper jam by disconnecting the transmission device  310 . For clearly illustrating the application of the releasing arm  330  to disconnect the transmission device  310  and release the jammed paper sheet, only the main body  201 , the upper cover  206 , the driving motor  300 , the transmission device  310 , the swing arm  320  and the releasing arm  330  are shown in  FIG. 6 . In addition, the upper cover  206  further includes a protrusion structure  270 . The main body  201  includes a protruding shaft  275  and a first protruding button  280 . The releasing arm  330  includes a pivotal hole  331  and a concave portion  332 . The swing arm  320  includes a second protruding button  321 . The releasing arm  330  is connected to the main body  201  via a resilient element  285  such as a spring. A first end of the spring  285  is coupled to the releasing arm  330 ; and a second end of the spring  285  is coupled to the first protruding button  280  of the main body  201 . The pivotal hole  331  is sheathed around the protruding shaft  275  such that the releasing arm  330  is rotated with the protruding shaft  275 . 
     Please refer to  FIG. 6  and also  FIG. 2 . Generally, there are three possible situations that the paper sheet is jammed in the vicinity of the inner roller assembly  230  during the sheet feeding operation. For example, the paper sheet may be jammed between the first paper transfer roller  231  and the second paper transfer roller  232 , between the first paper transfer roller  231  and the third paper transfer roller  233 , or between the first paper transfer roller  231 , the second paper transfer roller  232  and the third paper transfer roller  233 . For releasing the jammed paper sheet, the upper cover  206  is uplifted. Due to the pulling force exerted by the spring  285 , the releasing arm  330  is rotated with respect to the pivotal hole  331 . Until the concave portion  332  of the releasing arm  330  is stopped and supported by the second protruding button  321 , the swing arm  320  is fixed at a specified position. As a consequence, both of the seventh gear  317  and the eighth gear  318  fail to come into contact with the fifth gear  315 . In this circumstance, the swing arm  320  is in a disconnect state because the fifth gear  315  is temporarily disconnected from the driving motor  300 . When the swing arm  320  is in the disconnect state, the fifth gear  315  and the first paper transfer roller  231  are synchronously and freely rotated. At this moment, the user may remove the paper sheet jammed in the inner roller assembly  230  without difficulty. 
       FIG. 7  is a schematic cross-sectional view illustrating reconnection of the transmission device  310 . Please refer to  FIG. 7  and also  FIG. 2 . After the paper sheet jammed in the inner roller assembly  230  is removed, the upper cover  206  is laid over the main body  201  such that the protrusion structure  270  presses down the releasing arm  330 . In response to the depressing force exerted by the protrusion structure  270 , the releasing arm  330  is rotated with respect to the pivotal hole  331 . As a result, the releasing arm  330  is separated from the second protruding button  321  and the swing arm  320  enters the connection state. Meanwhile, the fifth gear  315  is interacted with the driving motor  300  again. In a case that the driving motor  300  is rotated in the anti-clockwise direction, as described in  FIG. 4 , the eighth gear  318  is engaged with the fifth gear  315  so that the driving power of the driving motor  300  is transmitted to the fifth gear  315 . In another case that the driving motor  300  is rotated in the clockwise direction, as described in  FIG. 5 , the seventh gear  317  is engaged with the fifth gear  315  so that the driving power of the driving motor  300  is transmitted to the fifth gear  315  and the transmission device  310  is reconnected. 
     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.