Patent Publication Number: US-7594655-B2

Title: Paper feed apparatus for duplex printing apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a duplex printing apparatus, and more particularly to a paper feed apparatus for reversing a paper feed path for duplex printing. 
   2. The Related Art 
   A duplex printing apparatus includes a duplex printing master on which two sides of a sheet are printed in series. The sheet is printed by pressing a front side of the sheet against the duplex printing master through a paper feed apparatus. The other side of the sheet is printed by pressing a reverse side of the sheet against the duplex printing master through the paper feed apparatus. So the paper feed apparatus can achieve the reverse of the sheet. 
   Referring to  FIG. 1 , a conventional paper feed apparatus  700  includes a gate  710 , an actuator  720 , a transmission  730 , a pickup device  740 , a reversing device  750 , a paper feed device  760 . 
   Referring to  FIG. 2  and  FIG. 3 , the actuator  720  comprises a pickup gear  721 , an arm  722  and a pickup idler gear  723  which has a same angular speed with the pickup gear  721 . The arm  722  mounted between the pickup gear  721  and the pickup idler gear  723  has a friction spring  724  that can cause a torque. 
   Refer to  FIG. 4  and  FIG. 5 . When a sheet is fed to the paper feed device  760 , the gate  710  is in a closed position while the arm  722  is pressed by the actuator  720 . The pickup gear  721  is reversed following a motor while the sheet will leave the paper feed device  760 , and then the torque caused between the pickup gear  721  and the arm  722  rises the arm  722  to make the gate  710  be in an open position. The sheet is fed to the paper feed device  760  through the reversing device  750  again to achieve duplex printing. 
   Based on the conventional art, the components of the paper feed apparatus  700  are too many to ensure the paper feed apparatus  700  working effectively. So, it would be desirable to provide a paper feed apparatus  700  that is of simple design and low cost. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a paper feed apparatus being of simple design and low cost. The paper feed apparatus includes a gate, an actuator, a transmission, a pickup device, a reversing device, a paper feed device. The gate has a rack defined at one end thereof and a resilient arm connecting to an outer portion of the rack. The resilient arm has a pillar-base and a plurality of external teeth apart from each other extending outward from an outer portion of the pillar-base. The outer surfaces of the external teeth are in a same ball surface. The external teeth have a top portion with a biggest outer diameter between an inner portion and an outer portion. The actuator has a pickup gear with a disc-shaped body, an external wheel connecting to the outside of the body and an external gear connecting to the outside of the external wheel. A stepper gear is overlaid about the external wheel and connected with the body. A receiving passage is defined through the pickup gear along the axis thereof, the receiving passage has a holding hole at the inner side and an external hole communicating with the holding hole with a smaller size at the outer side, then a shoulder is formed between the holding hole and the external hole. The external teeth of the resilient arm are inserted into the receiving passage with an inward shrink, the top portion of the external teeth abuts against the inner surface of the holding hole, the outer portion of the external teeth presses against the shoulder. 
   As described above, the friction created between the resilient arm and the pickup gear can control the gate to allow the sheet to enter into the reversing device for duplex printing. As the component of the paper feed apparatus are small, the paper feed apparatus works smoothly to avoid the gate not working effectively. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent to those skilled in the art by reading the following description of a preferred embodiment thereof, with reference to the attached drawings, in which: 
       FIG. 1  is a perspective view of a conventional paper feed apparatus; 
       FIGS. 2-3  are exploded views of an actuator of the conventional paper feed apparatus; 
       FIGS. 4-5  are perspective views for describing operations of the conventional paper feed apparatus; 
       FIG. 6  is a perspective view of a paper feed apparatus; 
       FIGS. 7-8  are perspective views of a gate and an actuator of the paper feed apparatus; 
       FIG. 9  is a partial enlarged view of the encircled portion labeled IX shown in  FIG. 8 ; 
       FIG. 10  is a cross-sectional view of a pickup gear of the paper feed apparatus; 
       FIGS. 11-12  are perspective views of a transmission of the paper feed apparatus; 
       FIG. 13  is a cross-sectional view of the resilient arm, by inserting into the pickup gear; 
       FIG. 14  is a partial enlarged view of the encircled portion labeled X IV shown in  FIG. 13 ; and 
       FIGS. 15-16  are perspective views for describing operations of the paper feed apparatus. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to  FIG. 6 , a paper feed apparatus  100  includes a gate  10 , an actuator  20 , a transmission  30 , a pickup device  40 , a reversing device  50 , a paper feed device  60 . 
   Referring to  FIG. 7  and  FIG. 8 , the gate  10  has a thin and level board-shaped base  11 , and a set of pivotal portions  12  extending outward from one side of the base  11 . Each of the pivotal portions  12  has three pivotal boards  13 . Two of the pivotal boards  13  which are located at two sides of the pivotal portions  12  have a plurality of teeth  14  extending outward from the outside of the pivotal boards  13 . One of the pivotal boards  13  which is located at the middle of the pivotal portions  12  has a pressboard  15  extending outward from the outside thereof. 
   Referring to  FIG. 7 ,  FIG. 8  and  FIG. 9 , a rack  16  is defined at one end of the gate  10  which is near to the actuator  20 . The rack  16  defines a resilient arm  17  that connects to an outer portion of the rack  16 . The resilient arm  17  has a pillar-base  171  and a plurality of external teeth  172  apart from each other extending outward from an outer portion of the pillar-base  171 . The outer surfaces of the external teeth  172  are in a same ball surface. The external teeth  172  have a top portion  173  with a biggest outer diameter between an inner portion  174  and an outer portion  175 . 
   Referring to  FIG. 7  and  FIG. 8  again, the actuator  20  comprises a pickup gear  21  with a disc-shaped body  22 , an external wheel  23  connecting to the outside of the body  22  and an external gear  24  adjacent to the outside of the external wheel  23 . A stepper gear  25  connected with the body  22  is overlaid about the external wheel  23 . A belt is sleeved on both the stepper gear  25  and a motor (not shown), and impels the pickup gear  21  to rotate. A receiving passage  26  that receives the resilient arm  17  is defined through the pickup gear  21  along the axis thereof. 
   Referring to  FIG. 7 ,  FIG. 8  and  FIG. 10 , the receiving passage  26  comprises a holding hole  260  at one side of the receiving passage  26  which is near to the rack  16  and an external hole  261  connecting with the holding hole  260  at the other side of the receiving passage  26  which is distant from the rack  16 . The size of the holding hole  260  is bigger than the size of the external hole  261 , therefore, a shoulder  262  is formed between the holding hole  260  and the external hole  261 . 
   Referring to  FIG. 6 ,  FIG. 11  and  FIG. 12 , the transmission  30  has a first gear  31  engaging with the external gear  24 , a second gear  32 , a third gear  33 . 
   Referring to  FIG. 6  again, the pickup device  40  has a picking roller  41 , a short shaft  42 , a picking gear  43 . The picking roller  41  is twined on one end of the short shaft  42  to extract pluralities of sheets and the picking gear  43  that engages with the second gear  32  is twined on the other end of the short shaft  42  to provide a power of the picking roller  41  for rotating. 
   The reversing device  50  has a reversing roller  51 , a long shaft  52 , a reversing idle roller  53  and a reversing gear  54 . The reversing roller  51  is twined on the middle of the long shaft  52 . The reversing idle roller  53  is mounted in a corresponding location of the paper feed apparatus  100  to couple with the reversing roller  51  to reverse the sheets. The reversing gear  54  is twined on end of the long shaft  52  that is near to the transmission  30  to engage with the third gear  33 . 
   The paper feed device  60  has a pickup roller  61  and a pickup idle roller  62  coupled with the pickup roller  61 . The paper feed device  60  is configured in a corresponding location to guide the sheets to enter into the paper feed apparatus  100 . The pickup roller  61  presses against the pickup idle roller  62  to extract the sheets. 
   When the paper feed apparatus  100  is in assembly, the belt is sleeved on both the external gear  24  and the motor. The external teeth  172  of the resilient arm  17  are inserted into the receiving passage  26  with an inward shrink. The top portion  173  of the external teeth  172  abuts against the inner surface of the holding hole  260 , the outer portion  175  of the external teeth  172  presses against the shoulder  262  (shown in  FIG. 13 ,  FIG. 14 ). The short shaft  42  and the long shaft  52  are sleeved in the corresponding places of the paper feed apparatus  100 . 
   Referring to  FIG. 7 ,  FIG. 14  and  FIG. 15 , when the paper feed apparatus  100  picks up the sheet, the motor drives the stepper gear  25  to rotate anti-clockwise, and the external gear  24  rotates anti-clockwise following the stepper gear  25 , then the picking gear  43  rotates clockwise, and the picking roller  41  also rotates clockwise. The picking roller  41  extracts the sheet by a friction created between the picking roller  41  and the sheet. Meanwhile, as the resilient arm  17  moves downward, the gate  10  is in a closed position to guide the sheet into the paper feed device  60  to be printed one side of the sheet through a duplex printing master (not shown). 
   Referring to  FIG. 16 , on the contrary, when the sheet will leave the paper feed device  60 , the motor drives the pickup gear  21  to rotate clockwise, then the picking gear  43  rotates anti-clockwise, and the picking roller  41  also rotates anti-clockwise. The picking roller  41  doesn&#39;t extract the sheet. Meanwhile, as the resilient arm  17  moves upward by the friction created between the holding hole  260  and the resilient arm  17 , the gate  10  is in an open position to guide the sheet one side of which have been printed to enter into the reversing device  50 . The reversing gear  54  rotates clockwise, and the reversing roller  51  also rotates clockwise. The friction created between the reversing roller  51  and the sheet guides the sheet into the paper feed device  60  to be printed the other side of the sheet through the duplex printing master. 
   As described above, the resilient arm  17  of the paper feed apparatus  100  replaces the arm  22 ′ of the conventional paper feed apparatus  100 ′. The friction created between the resilient arm  17  and the pickup gear  21  can control the gate  10  to allow the sheet to enter into the reversing device  50  for duplex printing. As the components of the paper feed apparatus  100  are small, the paper feed apparatus  100  works smoothly to avoid the gate  10  not working effectively.