Patent Publication Number: US-8985314-B2

Title: Driven roller unit and paper feeding device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 100146901, filed on Dec. 16, 2011. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a driven roller unit and a paper feeding device, and more particularly relates to a driven roller unit capable to balance the force exerting thereon and a paper feeding device using the driven roller unit and capable to prevent paper from skewing. 
     2. Description of Related Art 
       FIG. 1  is a schematic view of a conventional paper feeding device. Referring to  FIG. 1 , the conventional paper feeding device  100  is adapted to be assembled on the base (not shown) of the multi-function printer and includes an driving roller  110 , a driven roller  120  and a frame  130 , wherein the frame  130  may be fixed on the base of the multi-function printer, and the frame  130  has a recess  132  with a shape corresponds with the driven roller  120 , and the rod-shaped driven roller  120  is disposed in the recess  132  of the frame  130 . 
     In general, the printed document may often skew due to the tilt of the paper during paper feeding process. The reason of paper skew is probably because a bad parallelism is formed between the driving roller  110  and the driven roller  120  of the paper feeding device  100 , or because the pressure exerting from the driving roller  110  to the driven roller  120  is not uniformly distributed. It needs a mechanism to control the parallelism between the driving roller  110  and the driven roller  120 . In other words, the assembly precision and tolerance of the components are required to be so good and thus the cost of components and human labor for assembling is further increased. In addition, so far in current technology, the parallelism between the driving roller  110  and the driven roller  120  cannot be automatically calibrated. Moreover, the crimp depth of the driving roller  110  exerting on the driven roller  120  cannot be precisely controlled by mechanism, and thus the problem of uneven distributed force exerting on the driven roller  120  has not been unable to be effectively improved. 
     SUMMARY OF THE INVENTION 
     The present invention provides a driven roller unit capable to balance the force exerting thereon. 
     The present invention also provides a paper feeding device capable to prevent paper from skewing. 
     The present invention provides a driven roller unit having an omnidirectional ball, and thus when the driven roller unit is pressed the omnidirectional ball rotates so as to balance the force acting on the driven roller unit. 
     According to an embodiment of the present invention, the driven roller unit includes a fixing support and a driven roller, wherein the omnidirectional ball is disposed below the fixing support, and the driven roller is disposed on the fixing support. 
     According to an embodiment of the present invention, the fixing support further has a pair of sidewalls and a base connected between the pair of sidewalls, and the omnidirectional ball is connected to the bottom of the base. 
     According to an embodiment of the present invention, the driven roller has an assembling shaft passing through the pair of sidewalls of the fixing support. 
     According to an embodiment of the present invention, each of the sidewalls has an assembling structure and the assembling shaft passes through the assembling structure. 
     According to an embodiment of the present invention, the assembling structures are openings disposed on the sidewalls along the altitudinal direction thereof. 
     According to an embodiment of the present invention, the driven roller unit further includes a pair of elastomers disposed within the openings. 
     According to an embodiment of the present invention, each of the sidewalls has at least one hollow portion so as to form an elastic structure. 
     According to an embodiment of the present invention, the driven roller has an assembling shaft passing through the fixing support. 
     The present invention further provides a paper feeding device including a frame, the driven roller unit mentioned above from any of the embodiments and a driving roller, wherein the driving roller is disposed above the driven roller and the frame and adapted to exert a force on the driven roller unit. The frame has a dome concave, and the omnidirectional ball of the driven roller is located in the dome concave. 
     According to an embodiment of the present invention, the frame further has a recess and the dome concave is disposed in the recess. 
     In light of the above, in the driven roller unit and the paper feeding device using the driven roller unit of the present invention, when the driving roller presses on the driven roller, the included angle formed between the driving roller and the driven roller is adjusted since the omnidirectional ball rotates relative to the dome concave, and therefore the force applied on the driven roller unit is uniform and the paper skew is prevented. 
     In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanying figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings constituting a part of this specification are incorporated herein to provide a further understanding of the invention. Here, the drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic view of a conventional paper feeding device. 
         FIG. 2  is a schematic view of a driven roller unit according to the first embodiment of the present invention. 
         FIG. 3  is an exploded view of the driven roller unit of  FIG. 2 . 
         FIG. 4  is a schematic view of a paper feeding device according to an embodiment of the present invention. 
         FIG. 4-1  is a schematic view of the paper feeding device according to  FIG. 4  with the ball located in the dome concave being pressed by the driving roller. 
         FIG. 5  is a schematic view of a frame of the paper feeding device of  FIG. 4 . 
         FIG. 6  and  FIG. 7  are schematic views illustrating when the driven roller is pressed by the driving roller, the omnidirectional ball rotates so that the force applied on the driven roller unit is uniform relative to the driving roller. 
         FIG. 8  is a schematic view of a driven roller unit according to the second embodiment of the present invention. 
         FIG. 9  is a schematic view of a driven roller unit according to the third embodiment of the present invention. 
         FIG. 10  is a schematic view of a driven roller unit according to the fourth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Terminologies such as “up”, “down”, “left” and “right” are applicable to the embodiments shown and described in conjunction with the drawings. These terminologies are merely for the purposes of description and do not necessarily applied to the position or manner in which the invention may be constructed for actual use. 
       FIG. 2  is a schematic view of a driven roller unit according to the first embodiment of the present invention. Referring to  FIG. 2 , the driven roller unit  200  has an omnidirectional ball  210 , wherein when the driven roller  200  is applied by a force, the omnidirectional ball  210  of the driven roller unit  200  may rotate so that the moment of the driven roller unit  200  is balanced and the force applied on the driven roller unit  200  is uniform. The driven roller unit  200  is applied to the paper feeding device  300  (shown in  FIG. 4 ) of a multi-function printer is described as an exemplary embodiment as follows. However, people having ordinary skill in the art can apply the driven roller unit  200  to any other technical field in which the driven roller unit  200  capable to uniform the distributed force thereon is required, the present invention is not limited thereto. 
     Accordingly, the paper feeding device  300  (as shown in  FIG. 4 ) is disposed on the multi-function printer and used to feed documents into the body of the multi-function printer for printing, scanning or other process, and descriptions of other parts of the multi-function printer are omitted herein. 
       FIG. 3  is an exploded view of the driven roller unit of  FIG. 2 .  FIG. 4  is a schematic view of a paper feeding device according to an embodiment of the present invention.  FIG. 4-1  is a schematic view of the paper feeding device according to  FIG. 4  with the ball located in the dome concave being pressed by the driving roller. Referring to  FIG. 2 ,  FIG. 3 ,  FIG. 4 , and  FIG. 4-1  together, the paper feeding device  300  includes a frame  310 , the driven roller unit  200  and a driving roller  320 , wherein the driving roller  320  is disposed above the driven roller unit  200  and the frame  310  and adapted to exert force on the driven roller unit  200  so as to proceed to the paper feeding process.  FIG. 5  is a schematic view of a frame of the paper feeding device of  FIG. 4 . Referring to  FIG. 2 ,  FIG. 4 ,  FIG. 4-1  and  FIG. 5  together, the frame  310  of the embodiment is fixed on the body of the multi-function printer and has a dome concave  312 . And the omnidirectional ball  210  of the driven roller unit  200  is located in the dome concave  312 . 
     In detailed, the driven roller unit  200  includes a fixing support  220  and a driven roller  230 , wherein the omnidirectional ball  210  is disposed below the fixing support  220 , and the driven roller  230  is disposed on the fixing support  220 . More specifically, the fixing support  220  further has a pair of sidewalls  222  and a base  224  connected between the pair of sidewalls  222 . The omnidirectional ball  210  is connected to the bottom of the base  224  and located at the center of the bottom of the base  224 . In addition, the driven roller  230  has an assembling shaft  232  passing through the sidewalls  222  of the fixing support  220 . And each of the sidewalls  222  has an assembling structure  222   a , and the assembling shaft  232  is disposed to pass through the assembling structures  222   a  so that the driven roller  230  is assembled on the fixing support  220 . In addition, a portion of the driven roller  230  used to contact with the driving roller  320  can be integrally formed with the assembling shaft  232 , and the portion of the driven roller  230  used to contact with the driving roller  232  can be a sleeve sleeving the assembling shaft  232 . And the material of the driven roller  230  can be selected according to the requirements, and the present invention is not limited thereto. The assembling structures  222   a  are openings disposed on the sidewalls  222  along the altitudinal direction thereof, wherein the depth of the opening can be shallow, or deep enough to be able to reach the base  224  of the sidewall  222 . 
     In order to prevent the omnidirectional ball  210  being separated from the dome concave  312  and resulting in the driven roller unit  200  horizontally moving in a large range relative to the frame  310 , the frame  310  can have a recess  314  and the dome concave  312  is disposed in the recess  314 . The recess  314  is substantially in a rectangular shape, and the fixing support  220  of the driven roller unit  200  is accommodated in the recess  314 . 
       FIG. 6  and  FIG. 7  are schematic views illustrating when the driven roller is pressed by the driving roller, the omnidirectional ball rotates so that the force applied on the driven roller unit is uniform relative to the driving roller. Referring to  FIG. 5 ,  FIG. 6  and  FIG. 7  together, during the paper feeding process, the driving roller  320  approaches to the driven roller unit  200 , and then the driving roller  320  presses the driven roller unit  200 . More specifically, the driving roller  320  may contact with the driven roller  230  of the driven roller unit  200  first. And when the axis A 1  of the driven roller  230  of the driven roller unit  200  (shown in  FIG. 2 ) is not parallel to the axis A 2  of the driving roller  320 , the driving roller  320  may contact an end of the driven roller  230  and exerts a force F 1  to that end. 
     In the meantime, the omnidirectional ball  210  located in the dome concave  312  may rotate relative to the dome concave  312 , and the included angle between the driven roller  230  located on the fixing support  220  (shown in  FIG. 3 ) and the driving roller  320  may further be adjusted to let the axis A 1  of the driven roller  230  and the axis A 2  of the driving roller  320  be parallel. Accordingly, the force applied by the driving roller  320  to the driven roller  230  is balanced to be uniform, i.e., the forces F 1  and F 2  respectively applied to the two opposite ends of the driven roller  230  are equal and the feeding paper is further prevented to be skewed. 
     The shape of the dome concave  312  is corresponding to that of the omnidirectional ball  210 , and the size of the dome concave  312  is slightly greater than the size of the omnidirectional ball  210 , in order to prevent a tight fit being formed between the omnidirectional ball  210  and the dome concave  312 . If the omnidirectional ball  210  is tightly fitted to the dome concave  312 , the driving force of the driving roller  320  exerting on the driven roller  230  has to be greater than the friction force between the omnidirectional ball  210  and the dome concave  312  so that the omnidirectional ball  210  can just rotate relative to the dome concave  312  and let the axis A 1  of the driven roller  230  and the axis A 2  of the driving roller  320  be parallel. In other words, in the embodiment, since the size of the dome concave  312  is slightly greater than the omnidirectional ball  210 , under the condition of the force of the driving roller  320  exerting on the driven roller  230  capable to be comparatively smaller, the omnidirectional portion  210  can rotate relative to the dome concave  312 . 
     In addition, since the size of the recess  314  of the frame  310  is slightly larger than the size of the fixing support  220  of the driven roller unit  200 , and thus the recess  314  has a sufficient space to let the fixing support  220  rotate within the recess  314  due to the rotation of the omnidirectional ball  210  relative to the dome concave  312 , and the fixing support  220  may not be interfered with the recess  314 . 
     According to the descriptions mentioned above, since the driven roller unit  200  has the omnidirectional ball  210 , when the force is applied to a specific point of the driven roller unit  200 , the omnidirectional ball  210  can rotate relative to a datum plane propped against by the omnidirectional ball  210  and the driven roller unit  200  can further be adjusted, so that the axis A 1  of the driven roller  230  of the driven roller unit  200  is parallel to the axis A 2  of the driving roller  320 , and thus the applied force exerting on the driven roller unit  200  is uniformly distributed. 
       FIG. 8  is a schematic view of a driven roller unit according to the second embodiment of the present invention. Referring to  FIG. 8 , the assembling structures  222   a ′ of the embodiment pass through the sidewalls  222  and the assembling structures  222   a ′ are disposed to reach the openings of the base  224  along the altitudinal direction of the sidewalls  222 . And a pair of elastomers  240 , for example springs, are disposed in the openings, and the driven roller  230  props against on the two elastomers  240 . Through the configuration of the elastomers  240 , the crimp between the driving roller  320  and the driven roller  230  can be properly fit. 
       FIG. 9  is a schematic view of a driven roller unit according to the third embodiment of the present invention. Referring to  FIG. 9 , in the embodiment, a portion of each of the sidewalls  222 ″ of the fixing support  220 ″ is disposed hollow to form an elastic structure, and the driven roller  230  (shown in  FIG. 3 ) is disposed on the elastic structure. Through the configuration of the elastic structure, the crimp between the driving roller  320  (shown in  FIG. 4 ) and the driven roller  230  (shown in  FIG. 2 ) can be properly fit. 
       FIG. 10  is a schematic view of a driven roller unit according to the fourth embodiment of the present invention. Referring to  FIG. 10  in the embodiment, the fixing support  220 ′″ has two pairs of sidewalls  222 ″, and two driven rollers  230  are included, and each of the driven rollers  230  is respectively disposed corresponding to a pair of sidewalls  222 ′″. The omnidirectional ball  210  is disposed at the center of the bottom of the base  224  of the fixing support  220 . According to the embodiment, the number of the sidewalls  222 ′″ and the driven rollers  230  is not limited and can be adjusted as required. 
     In light of the foregoing, since the driven roller unit of the present invention has the omnidirectional ball, when the applied force exerting on the driven roller is uneven, the omnidirectional ball rotates so that the axis of the driven roller can be parallel to the axis of the driving roller to balance the applied force exerting on the driven roller. The driven roller unit can be applied in a paper feeding device. And through the simple mechanism, the driven roller unit can self-calibrate relative to the driving roller, and the accuracy of paper feeding can be improved to prevent the paper skew problem. And the quality of the paper feeding device of the multi-function printer using the driven roller unit can be further improved. 
     Though the disclosure has been disclosed above by the embodiments, they are not intended to limit the disclosure. Persons skilled in the art may make some modifications and variations without departing from the spirit and scope of the disclosure. Therefore, the protecting range of the disclosure falls in the appended claims.