Patent Document

BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a medium conveying mechanism in an image equipment such as a printer or a scanner, and more particularly, to a de-skew mechanism. 
   2. Description of the Prior Art 
   Sometimes images are printed or scanned to be oblique due to skew of the medium or tolerances of the roller assembly. To avoid the above condition, various methods are utilized to de-skew before the medium enters the printing or scanning area. 
   U.S. Pat. No. 6,011,948 discloses a correcting device in an image formation equipment. Please refer to  FIG. 10 ,  11 . The correcting device includes shutter members  15  and a connecting member  16 . The shutter members  15  are integrally connected to one another via the connecting member  16 . The correcting device is engaged in a rotating manner with the rotary shaft  18 , to which the free conveyer rollers  13  are fixed. The twisted coil spring  24  is engaged in a sliding manner with a rotary shaft  18  with the end  24   b  thereof on the side of the connecting member  16 . The shutter members  15  are provided with the collision surfaces  20   a , which act as sheet leading edge collision surfaces. The sheet S forms a curved loop when pushing the shutter members  15 , and after the shutter members  15  turn a certain angle, skew of the sheet S is corrected. After sheet S passes through the roller group, the shutter members  15  return to their initial positions by the twisted coil spring  24 . The correcting device has a simple structure and lower cost, but it has some disadvantages. For example, when the sheet S passes through the roller group, the shutter members  15  will exert greater force onto the sheet S by the twisted coil spring  24 , and this tends to damage sheet S. In addition, the skew generated by the tolerance of roller assembly cannot be corrected by the correcting device since the correcting device is disposed on the rotary shaft  18 . Furthermore, when the leading edge of the sheet S contacts the shutter members  15 , the correcting process for the skew is performed while conveying the sheet S, which has counterproductive effects on the correction effort. 
   SUMMARY OF THE INVENTION 
   It is therefore one of the objectives of the present invention to provide a de-skew mechanism, wherein when skew of the medium is corrected and leading edge of the medium reaches a nip portion of the roller group, the force that the correcting member brings to the medium will reduce to zero, and thus the medium will not be damaged by the correcting member while being conveyed. 
   According to an embodiment of the present invention, a de-skew mechanism is disclosed to solve the above problem. The de-skew mechanism includes: a rotary shaft, rotated by a motor; a driving roller, disposed on the rotary shaft and rotated with the rotary shaft; a pinch roller, rotating in an opposite direction to the driving roller to form a nip portion to convey a medium; a correcting member, disposed on the rotary shaft along a conveying direction of the medium, for rotating at a disposed position of the correcting member between a correcting position and a releasing position of the correcting member; a suppressing member, selectively contacting with the correcting member, for exerting a suppressing force on turning of the correcting member with the driving roller to allow the correcting member to be in the correcting position; and a driving member, disposed on the rotary shaft and connected to the correcting member and the driving roller, for turning the correcting member with the driving roller, and for letting the correcting member come off the suppressing member with the medium conveying force to unload the suppressing force to let the correcting member move to the releasing position from the correcting position. 
   The correcting member has a bearing portion, and the bearing portion and the suppressing member selectively connect to each other to load the suppressing force. The correcting member further has a correcting portion for correcting a skew of the medium, and the bearing portion and the correcting portion are positioned on two sides of the correcting member, respectively. The correcting portion is a protruding object. The bearing portion is a protruding object or a recess fillister. 
   The suppressing member has a suppressing end, and the suppressing end and the suppressing member selectively connect to each other to load the suppressing force. The suppressing member further has a fixed end connected to an adjusting structure. The adjusting structure includes at least two adjacent protruding pillars. The suppressing portion is an elastic object, and the elastic object can be a torque spring or an elastic sheet. The driving member is a spring. A contacting surface between the correcting portion and the medium for correcting skew of the medium better and align the medium. 
   Since an elastic device is disposed between the driving roller and the correcting member in the de-skew mechanism, when the leading edge of the medium reaches the nip portion of the roller group, the elastic device comes off the bearing portion, and the correcting member turns with the driving roller by the elastic device between them. The force that the correcting member brings to the medium reduces to zero, and thus the medium is not damaged by the correcting member while being conveyed. The elastic device disposed on the frame matches with the bearing portion on the correcting member, and the correcting member is static during the process of correcting the skew of the medium to realize a better de-skew effect. At least two protruding objects are disposed on the frame, and skews of mediums having different thicknesses can be corrected via pushing the torque spring on the different protruding objects. 
   These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of a scanner paper-feeding mechanism adopting a de-skew mechanism according to a first embodiment of the present invention. 
       FIG. 2  is a schematic diagram of the de-skew mechanism according to the first embodiment of the present invention. 
       FIG. 3  is a schematic diagram of the correcting member shown in  FIG. 2 . 
       FIG. 4-7  are cross-sectional diagrams of the de-skew mechanism shown in  FIG. 2 . 
       FIG. 8  is a cross-sectional diagram of a de-skew mechanism according to a second embodiment of the present invention. 
       FIG. 9  is a schematic diagram of the correcting member shown in  FIG. 8 . 
       FIG. 10  is a cross-sectional diagram of a de-skew device according to prior art. 
       FIG. 11  is an enlarged 3-D diagram of A 1  portion shown in  FIG. 10 . 
   

   DETAILED DESCRIPTION 
   The present invention is further illustrated with figures in the following. 
     FIG. 1  is a schematic diagram of a scanner paper-feeding mechanism adopting a de-skew mechanism according to a first embodiment of the present invention, which includes medium M stacked in a paper-feeding plate  210 . A paper-taking roller  230  is disposed on a start end of a medium-feeding path. The paper-taking roller  230  takes the medium M out from the paper-feeding plate  210  one by one, and feeds the medium M into a medium-conveying path  243 . A feeding roller  220  feeds the medium M in a direction F along the medium-conveying path  243 . After passing through a driving roller  246  and a pinch roller  247 , the medium M is scanned by a scanning module. The scanned medium is conveyed to a paper-exiting plate  260  by a paper-exiting roller  250 . The driving roller  246 , the pinch roller  247 , and a correcting member  251  connected to the driving roller  246  are disposed on the medium-conveying path  243 . 
   Please refer to  FIG. 2 . A rotary shaft  245  is disposed on a scanner frame, and the driving roller  246  is fixedly disposed on the rotary shaft  245  and rotated by a motor (not shown). The pinch roller  247  is disposed below the driving roller  246  and rotates oppositely to the driving roller  246  to form a nip portion to nip and convey the medium. The correcting member  251  is installed on the rotary shaft  245  and turns according to the rotary shaft  245 . The correcting member  251  is disposed on a side of the driving roller  246  and close to a frame  241 . A spring  252  is installed on the rotary shaft  245  and between the correcting member  251  and the driving roller  246 . Two sides of the spring  252  are tightly connected to a connecting surface  257  of the correcting member  251  and a surface of the driving roller  246 , respectively. In this way, when the driving roller  246  rotates along the paper-conveying direction, the correcting member  251  rotates with the driving roller  246  by the spring  252 , due to the connection between them. 
   The correcting member  251  disposed on the rotary shaft  245  has a correcting position and a releasing position. The correcting position can be perpendicular to a leading edge of the medium M from the paper-conveying direction, since the correcting portion  255  protruding on the surface of the correcting member  251  adjacent to the connecting surface is vertical. The bearing portion  256  protruding on the correcting member  251  can contact with a suppressing end  267  of suppressing torque spring  253  to suppress the correcting member  251  to prevent the correcting member  251  from turning with the driving roller  246 . Please refer to  FIG. 3 . The correcting portion  255  is disposed near the connecting surface of the correcting member  251 , and the bearing portion  256  is disposed near the free surface of the correcting member  251 . 
   Meanwhile, the torque spring  253  is disposed above the correcting member  251 , and fixedly engaged with a protruding pillar  264  of the frame  241 . There are three protruding pillars  261 ,  262 ,  263  disposed on the frame  241  as an adjusting structure. The torque spring  253  has two functional ends including a fixing end  266  leaning against one of the protruding pillars  261 ,  262 ,  263  according to the medium thickness. In this embodiment, the fixing end  266  leans against the protruding pillar  262 . The suppressing end  267  of the torque spring  253  contacts the bearing portion  256  on the correcting member  251  and leans against the bearing portion  256  properly to prevent the correcting member  251  from continuously turning with the driving roller  246 . In this way, the correcting portion  255  can stop the medium M from skewing. 
   Please refer to  FIG. 4 . The driving roller  246  makes the correcting member  25  start to turn via the spring  252  in the paper-feeding process. When the suppressing end  267  of the torque spring  253  on the frame  241  leans against the bearing portion  256  on the correcting member  251 , the correcting member  251  stops turning. A free end  2551  of the correcting portion  255  is in the medium-conveying path  243 . When the conveyed medium M is skewed, a corner of the leading edge of the conveyed medium M contacts a flat surface  2552  of the correcting portion  255  first. When a common force of the conveyed medium M and the turning driving roller  246  to the correcting member  251  are not enough for the correcting member  251  to overcome the elastic force of the torque spring  253  to stop turning, the medium M will gradually form a curved portion since the medium M still moves by the force of the feeding roller  220 . Please refer to  FIG. 5 . After the leading edge of the medium M stays completely in contact to the flat surface  2552  of the correcting portion  255 , the skew of the medium M is corrected. Next, the pushing force of the medium M to the correcting portion  255  will gradually increase, and force of the driving roller  246  to the correcting member  251  will increase when the torque spring  253  is gradually deformed. When the common force of the medium M and the turning driving roller  246  to the correcting member  251  increases to be larger than the elastic force of the torque spring  253  to the correcting member  251 , the correcting member  251  will start to turn, and the leading edge of the medium M still stays close to the correcting portion  255  under the force of the feeding roller  220 . Please refer to  FIG. 6 . When the correcting member  251  turns to a certain angle and the leading edge of the medium M reaches to the nip portion of the driving roller  246  and the pinch roller  247 , the suppressing end  267  of the torque spring  253  on the frame  241  will come off from the bearing portion  256  on the correcting member  251 , and the correcting member  251  keeps turning with the driving roller  246  under the force of the torque spring  253 . Please refer to  FIG. 7 . The force that the bearing portion  256  on the correcting member  251  brings to the leading edge of the medium M will reduce to zero. The correcting member  251  moves to the releasing position from the correcting position. The driving roller  246  and the pinch roller  247  convey the de-skewed medium M to the scanning unit  200  and prevent the correcting member  251  from damaging the medium M. When the correcting member  251  turns and the bearing portion  256  thereon is leaned on by the suppressing end  267  of the torque spring  253  again, a correcting process for skew of the next medium M will be started. 
   Please refer to  FIG. 8 ,  9 . A difference between a second embodiment of the present invention and the first embodiment is only in the structure of the correcting member  283 . The correcting member  283  has three bearing portions  100 ,  101 ,  102 , and three correcting portions  110 ,  111 ,  112  corresponding to the three bearing portions. When performing a correcting process for skew of a medium M, the suppressing end  267  of the torque spring  253  leans against the bearing portion  100 , and a side of the correcting portion  110  corresponding to the bearing portion  100  is in the medium-conveying path  243 . After correcting the skew of the medium M, the suppressing end  267  of the torque spring  253  leans against the bearing portion  101 , and a free end of the correcting portion  111  corresponding to the bearing portion  101  is in the medium-conveying path  243  to correct skew of the next medium M. 
   Please note that the de-skew mechanism of the present invention can not only be applied to a scanner paper-feeding mechanism, but also to printers, auto paper-feeding machines, and copiers. The de-skew mechanism of the present invention can be applied to single-side paper-feeding mechanisms and double-side paper-feeding mechanisms. The medium above can be paper or similar objects. The bearing portion  256  in this embodiment is a protruding object contacting the suppressing end  267  of the torque spring  253 . Of course, the bearing portion  256  also can be a recessed fillister, and the suppressing end  267  of the torque spring  253  can insert into the recessed fillister to suppress the turning of the correcting member  251 . A common force of the feeding force of the medium and the torque force of the driving roller  246  to the correcting member  251  via the spring  252  can overcome the suppressing force on the correcting member  251 . Thus, the recess fillister has the same effect as the protruding object does. 
   Of course, the torque spring also can be an elastic sheet having an end fixed on the frame and another end matching with the bearing portion on the correcting member. The torque spring also can be other elastic objects. In addition, the above number of the protruding objects can be adjusted according to different requirements. For example, the present invention can implement two pairs or four pairs of the correcting portions and the corresponding bearing portions. In any case, similar modifications and alterations of the mechanism above should fall into the disclosed scope of the present invention. 
   Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention.

Technology Category: b