Abstract:
A paper reversing assembly includes a paper roller, a driving member, and a plurality of balls. The paper roller includes a recess defined in an end portion thereof and a plurality of concave portions formed on the internal circumferential sidewall of the recess. The driving member is received in the recess and includes a plurality of lobes, which interact with the balls to allow the free rotation of the paper roller when the paper is being pulled out.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a printer and a paper reversing assembly thereof. 
         [0003]    2. Description of Related Art 
         [0004]    Referring to  FIG. 1 , many printers  100  with a duplex or two-sides printing function have an input roller  10 , a printing roller  20 , a paper reversing assembly  30 , a paper tray  40  and an inkjet nozzle  50 . The input roller  10 , the printing roller  20  and the paper reversing assembly  30  can be driven by the same motor. When the printing roller  20  is rotated clockwise by the motor, the rollers of the paper reversing assembly  30  are unmoving; when the motor reverses and the printing roller  20  rotates counterclockwise, the rollers of the paper reversing assembly  30  are also driven to rotate, in the directions indicated in  FIG. 1 . 
         [0005]    In implementing two-sides printing, the input roller  10  rotates to carry a piece of paper from the paper tray  40  to the printing roller  20 , with a first side upward and its opposed side (which is named the second side hereinafter) unavailable to the printer  100 . Then, driven by the rotation of the printing roller  20 , the paper is moved to a location underneath the inkjet nozzle  50  to be printed on its first side, as the first side is upward. After the printing is over, the motor reverses and drives the printing roller  20  to rotate counterclockwise, sending the paper backward into the reversing assembly  30  to be turned upside down. 
         [0006]    Once the paper has been turned upside down by the reversing assembly  30 , it is pushed out of the reversing assembly  30 , while its front portion reaches the printing roller  20  and the second side is facing up then. At that moment, the motor reverses again, switching the printing roller  20  back to rotate clockwise, and carrying the paper to the inkjet nozzle  50  to be printed on its second side. Meanwhile, the rollers of the paper reversing assembly  30  are still. 
         [0007]    However, the aforesaid printer  100  has the following problem: when the reversing of the paper is finished, its front portion reaches the printing roller  20  while its rear portion is still inside the reversing assembly  30 . Since the reversing assembly  30  has stopped rotating, the rear portion of the paper is trapped between the lowest roller of the reversing assembly  30  and its corresponding auxiliary roller  300 . Under these circumstances, the paper is pulled out by the force provided by the rotation of the printing roller  20  while the lowest roller is still, and the still roller will block the moving of the paper. Thus, not only will ugly indentations be made on the paper, but also the printed image may be blurred since the transmission of the paper is unsteady. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The components of the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments of a printer and a paper reversing assembly thereof. Moreover, in the drawings, like reference numerals designate corresponding parts throughout several views. 
           [0009]      FIG. 1  is a schematic view of the structure of a conventional printer. 
           [0010]      FIG. 2  is a schematic view of the structure of a printer of the present disclosure. 
           [0011]      FIG. 3  is an exploded view of a roller of a paper reversing assembly of the printer of the present disclosure. 
           [0012]      FIG. 4  is an exploded view of the roller from another aspect. 
           [0013]      FIG. 5  is a cross-sectional view of the roller mechanism of the paper reversing assembly. 
           [0014]      FIG. 6  is a cross-sectional view of the paper reversing assembly indicating its motion. 
           [0015]      FIG. 7  is a cross-sectional view of the paper reversing assembly of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The present disclosure is related to a printer and a paper reversing assembly thereof, more particular to an improved paper reversing assembly which can replace the paper reversing assembly  30  of the conventional printer  100  shown in  FIG. 1 . 
         [0017]      FIG. 2  is a schematic view of a printer  100   a,  according to an exemplary embodiment of the present disclosure. The printer  100   a  includes an input roller  10 , a printing roller  20 , a paper reversing assembly  30   a,  an paper tray  40  and an inkjet nozzle  50 . The paper reversing assembly  30   a  includes a first roller  301 , a second roller  302  and a third roller  303 . One or more motors (not shown) are configured for driving the input roller  10 , the printing roller  20 , and the aforesaid rollers  301 - 303 . 
         [0018]    In this embodiment, the paper entry point into the paper reversing assembly  30   a  adjacent to the first roller  301  is defined as the paper-in access; and the paper exit point from the paper reversing assembly  30   a  adjacent to the third roller  303  is defined as the paper-out portion. 
         [0019]    In implementing the printing of both sides of a piece of paper, the input roller  10  and the printing roller  20  rotate clockwise as indicated, and the rollers  301 - 303  of the paper reversing assembly  30   a  do not move then. Then, once the paper is required to be turned upside down, the printing roller  20  rotates counterclockwise to send the paper backward into the reversing assembly  30   a.  At this time, the first roller  301  and the third roller  303  rotate counterclockwise and the second roller  302  rotates clockwise as indicated. The first roller  301 , the second roller  302  and the third roller  303  cooperate with their corresponding auxiliary rollers  300  in handling the paper. The paper is turned upside down thereby. 
         [0020]    The rollers  301 - 303  have the same structure in the embodiment.  FIGS. 3 ,  4  and  5  will show one of the rollers  301 - 303  alone for clearly illustrating such structure. Meanwhile, any other components of the printer  100   a  will not be shown in  FIGS. 3 ,  4  and  5 , since the structure of the rollers  301 - 303  are the main improvement of the printer  100   a.    
         [0021]    Referring to  FIGS. 3 and 4 , the roller includes a driving member  31 , several balls  32  and a paper roller  33 . The balls  32  are made of a material of metal, which is preferably steel. One end of the driving member  31  communicates with a driving machine  60 , and the driving machine  60  is driven by the motor (not shown). The driving member  31  includes a shaft  311  and a tri-lobular wheel  312 , wherein the wheel  312  is fixed on the middle of the shaft  311  and has several lobes  3121  radially extending from one side of it. The lobes  3121  are spaced from each other, while each of the lobes  3121  further includes a curved surface at a first side and a substantially flat surface  3122  at an opposing second side. 
         [0022]    The paper roller  33  includes a shaft body  331  and at least one rolling wheel  334 , wherein the rolling wheel  334  may be made of, but is not limited to, rubber. A recess  332  is defined in an end face on each end of the shaft body  331 . Several concave portions  333  are recessed in an internal circumferential surface of the shaft body  331  in the recess  332 . The lobes  3121  of the driving member  31  are for engagingly received in the recess  332 . 
         [0023]    Referring to  FIG. 5 , a cross-sectional view of the roller is shown. Each of the concave portions  333  includes a first surface  3331  and a second surface  3332 . The first surface  3331  is tangentially adjoining to the internal circumferential surface of the recess  332 , and the second surface  3332  is steeply inclined to the internal circumferential surface. Several spaces  34  are defined, while each space  34  is defined by a flat surface  3122  of one lobe  3121  and a curved surface of another lobe  3121 , with limitation of the internal circumferential sidewall of the recess  332 . The balls  32  are movably contained in each space  34 . Each of the balls  32  has their camber matching the second surface  3332  of the corresponding concave portion  333 , thus for being engagingly received in. 
         [0024]    Referring to  FIGS. 5-7 , when the driving member  31  rotates counterclockwise as a predefined rotating direction, each ball  32  is pushed by the substantially flat surface  3122  of the corresponding lobe  3121  and is retained by the second surface  3332  of one corresponding concave portion  333 , as shown in  FIG. 5  and  FIG. 6 . The balls  32  are trapped between the driving member  31  and the paper roller  33 , therefore enabling the paper roller  33  to rotate with the driving member  31 . The wheel  312  drives the paper roller  33  by means of the balls  32 , making the rolling wheel  334  and its corresponding auxiliary roller (shown in  FIG. 2 ) cooperate to reverse the paper. 
         [0025]    Referring to  FIG. 2 , when the paper has reversed, the motor reverses and the printing roller  20  rotates clockwise. The assembly of the motor and the driving machine  60  allows the motor to drive the driving machine  60  when the motor is in a forward direction, and not to drive the driving machine  60  when the motor is reversed. Thus, the driving member  31  will stop rotating when the printing roller  20  rotates clockwise. 
         [0026]    Referring to  FIGS. 6-7  when referring to  FIG. 2 , the front portion of the reversed paper is moved to the inkjet nozzle  50  by the printing roller  20 , as the rear portion of the paper is still between the third roller  303  and its corresponding auxiliary roller. Since the paper reversing assembly  30   a  does not challenge or fight the friction which exists between the rear portion of the paper and the third roller  303 , a pulling force F produced by the printing roller  20  carries the paper forward and therefore rotates the third roller  303 , smoothly drawing out the paper leaving the paper reversing assembly  30   a,  and preventing ugly indentations on the paper and avoiding bad printing quality. The pulling force is bigger than a maximum static friction force between the paper and the third roller  303  and acts as the force F as shown in  FIG. 6 . 
         [0027]    In another embodiment, the paper reversing assembly  30   a  has only one roller of the aforesaid structure, with the other rollers being conventional. 
         [0028]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.