Patent Publication Number: US-8994767-B1

Title: Printing device with duplex printing function

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printing device, and more particularly, to a printing device with duplex printing function. 
     2. Description of the Prior Art 
     Generally speaking, a printing device (e.g. a printer) is used for printing texts or patterns onto a printing media (e.g. paper). When a duplex printing for the printing media is required, it needs to manually turn the printing media with one side been printed over, so as to print the opposite side of the media. However, when an amount of the printing media with the duplex requirement increases, it results in increase of labor time due to turning operation for the printing media, leading to inconvenience in operation. 
     SUMMARY OF THE INVENTION 
     Thus, the present invention provides a printing device with duplex printing function for solving above drawbacks. 
     According to an embodiment of the present invention, a printing device with duplex printing function includes a print head, a paper roll, a first paper path, a second paper path, a third paper path, a cutting mechanism and a fourth paper path. The paper roll is for rolling a printing media. The first paper path has a first end and a second end, and the first end is connected to the paper roll. The second paper path is connected to the second end of the first paper path and oriented reverse to the first paper path for being connected to the print head. The second paper path is for turning a bottom surface of the printing media to face the print head when the printing media is fed to the print head via the first paper path and the second paper path. The third paper path extends from the second end of the first paper path. The cutting mechanism is disposed on the third paper path. The cutting mechanism is for cutting the printing media into a printing sheet when the printing media is fed into the third paper path via the first paper path. The fourth paper path connects the third paper path and the second paper path, such that the printing sheet is fed from the third paper path into the second paper path via the fourth paper path, so as to be fed to the print head with a top surface opposite to the bottom surface of the printing sheet facing the print head. 
     According to another embodiment of the present invention, the printing device further includes a feeding mechanism coupled to the paper roll. The feeding mechanism is for driving the paper roll to rotate, so as to feed the printing media into the first paper path along a first direction or to feed the printing media out of the first paper path along a second direction opposite to the first direction. 
     According to another embodiment of the present invention, the feeding mechanism includes a first actuating member, an actuating gear, a first gear, a second gear, a third gear, a fourth gear, a fifth gear and a sixth gear. The actuating gear is combined with the first actuating member. The first gear has a first tooth portion and a second tooth portion, and the first tooth portion engages with the actuating gear. The second gear engages with the second tooth portion. The third gear is coupled to the second gear. The fourth gear is combined with the paper roll and engages with the third gear. The fifth gear engages with the fourth gear. The sixth gear engages with the fifth gear. 
     According to another embodiment of the present invention, the printing device further includes a feeding roller set coupled to the feeding mechanism and for moving the printing media along the first direction or along the second direction. 
     According to another embodiment of the present invention, the feeding roller set includes a feeding active roller and a feeding idle roller. The feeding idle roller rotably abuts against the feeding active roller. The feeding active roller and the feeding idle roller are cooperatively for moving the printing media. 
     According to another embodiment of the present invention, the printing device further includes a first guiding gate mechanism disposed on the second end of the first paper path and for selectively communicating the first paper path with the second paper path or with the third paper path. 
     According to another embodiment of the present invention, the printing device further includes a second guiding gate mechanism disposed on a conjunction where the third paper path is connected to the fourth paper path and for selectively communicating the third paper path with the fourth paper path. 
     According to another embodiment of the present invention, the printing device further includes a first paper head sensor disposed within the first paper path and for sensing a paper head of the printing media. 
     According to another embodiment of the present invention, the printing device further includes a second paper head sensor disposed within the third paper path and for sensing the paper head of the printing media, wherein a path length of the third paper path between the second paper head sensor and the cutting mechanism is substantially equal to a first paper length. 
     According to another embodiment of the present invention, the printing device further includes a third paper head sensor disposed within the third paper path and for sensing the paper head of the printing media, wherein a path length of the third paper path between the third paper head sensor and the cutting mechanism is substantially equal to a second paper length, and the second paper length is greater than the first paper length. 
     According to another embodiment of the present invention, the printing device further includes a paper end sensor disposed within the third paper path and for sensing a paper end opposite to the paper head of the printing sheet. 
     According to another embodiment of the present invention, the printing device further includes a first roller set disposed within the third paper path and for moving the printing media or the printing sheet along the third paper path. 
     According to another embodiment of the present invention, the first roller set includes a first active roller and a first idle roller. The first idle roller rotably abuts against the first active roller. The first active roller and the first idle roller are cooperatively for moving the printing media or the printing sheet. 
     According to another embodiment of the present invention, the printing device further includes a second roller set disposed within the fourth paper path and for moving the printing sheet along the fourth paper path. 
     According to another embodiment of the present invention, the second roller set includes a second active roller and a second idle roller. The second idle roller rotably abuts against the second active roller. The second active roller and the second idle roller are cooperatively for moving the printing media or the printing sheet. 
     According to another embodiment of the present invention, the printing device further includes a roller transmission mechanism coupled to the first roller set and the second roller set. The roller transmission mechanism is for driving the first roller set and the second roller set to rotate. 
     According to another embodiment of the present invention, the roller transmission mechanism includes a second actuating member, an actuating pulley, a first step wheel, a second step wheel, a third step wheel, a fourth step wheel, a seventh gear, an eighth gear, a ninth gear, a pulley, a first belt, a second belt and a third belt. The actuating pulley is combined with the second actuating member. The first step wheel has a first gear portion and a first pulley portion. The second step wheel has a second gear portion and a second pulley portion. The third step wheel is coupled to the second active roller, and the third step wheel has a third gear portion and a third pulley portion. The fourth step wheel has a fourth gear portion and a fourth pulley portion. The eighth gear is engaging with the seventh gear and the first gear portion. The ninth gear engages with the second gear portion of the second step wheel and the third gear portion of the third step wheel. The first belt connects the actuating pulley and the pulley. The second belt connects the first pulley portion of the first step wheel and the second pulley portion of the second step wheel. The third belt connects the third pulley portion of the third step wheel and the fourth pulley portion of the fourth step wheel. 
     According to another embodiment of the present invention, the printing device further includes a printing roller set coupled to the roller transmission mechanism and for moving the printing media or the printing sheet to the print head. 
     According to another embodiment of the present invention, the printing roller set includes a printing active roller and a printing idle roller. The printing idle roller rotably abuts against the printing active roller. The printing active roller and the printing idle roller are cooperatively for moving the printing media or the printing sheet. 
     According to another embodiment of the present invention, e printing device further includes a printing roller set disposed within the second paper path and located in a position near the print head. The printing roller set is for moving the printing media or the printing sheet to the print head. 
     In summary, the present invention utilizes the second paper path to turn the bottom surface of the printing media to face the print head when the printing media is fed, such that the print head is able to perform printing operation on the bottom surface of the printing media. The present invention further utilizes the cutting mechanism to cut the printing media within the third paper path into the printing sheet. Then, the printing sheet is fed into the second paper path via the fourth paper path, and further fed to the print head via the second paper path, such that the print head is able to perform printing operation on the top surface of the printing sheet. In such a manner, the present invention can perform duplex printing operation, so as to decrease labor time and enhance convenience in operation. 
     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 an internal diagram of a printing device according to an embodiment of the present invention. 
         FIG. 2  and  FIG. 3  are internal transmission diagrams of the printing device according to the embodiment of the present invention. 
         FIG. 4  is a partly diagram of a feeding mechanism shown in  FIG. 3 . 
         FIG. 5  is an inter transmission diagram of the printing device in another view according to the embodiment of the present invention. 
         FIG. 6  is a partly diagram of a roller transmission mechanism shown in  FIG. 5 . 
         FIG. 7  to  FIG. 13  are respectively diagrams of the printing device in different printing statuses according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of the embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” etc., is used with reference to the orientation of the Figure(s) being described. The components of the present invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” and “installed” and variations thereof herein are used broadly and encompass direct and indirect connections and installations. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
     Please refer to  FIG. 1 .  FIG. 1  is an internal diagram of a printing device  3  according to an embodiment of the present invention. The printing device  3  includes a casing  30 , a print head  32  and a paper roll  34 . The print head  32  and the paper roll  34  are both disposed inside the casing  30 . The paper roll  34  is for rolling a printing media  36 , so as to enable the print head  32  print texts, patterns and so on onto the printing media  36 . In this embodiment, the printing device  3  is a thermal printer, and the print head  32  is a thermal print head of the thermal printer. 
     Furthermore, the printing device  3  further includes a first paper path  38 , a second paper path  40 , a third paper path  42  and a fourth paper path  44 . The first paper path  38  has a first end  381  and a second end  383  opposite to the first end  381 , and the first end  381  is connected to the paper roll  34 . The second paper path  40  is connected to the second end  383  of the first paper path  38  and oriented reverse to the first paper path  38  for being connected to the print head  32 . The third paper path  42  extends from the second end  383  of the first paper path  38 . The fourth paper path  44  connects the third paper path  42  and the second paper path  40 . In practical application, the first paper path  38 , the second paper path  40 , the third paper path  42  and the fourth paper path  44  are formed by ribs on internal components which is disposed inside the casing  30 , such as housing, plate and so on. 
     Please refer to  FIG. 2  and  FIG. 3 .  FIG. 2  and  FIG. 3  are internal transmission diagrams of the printing device  3  according to the embodiment of the present invention. The printing device  3  further includes a feeding mechanism  46  and a feeding roller set  48 . The feeding mechanism  46  is coupled to the paper roll  34 , and the feeding roller set  48  is coupled to the feeding mechanism  46 . Furthermore, the feeding roller set  48  includes a feeding active roller  481  and a feeding idle roller  482 . The feeding idle roller  482  rotably abuts against the feeding active roller  481 . Please refer to  FIG. 2  to  FIG. 4 .  FIG. 4  is a partly diagram of the feeding mechanism  46  shown in  FIG. 3 . The feeding mechanism  46  includes an actuating gear  460 , a first actuating member  461 , a first gear  462 , a second gear  463 , a third gear  464 , a fourth gear  465 , a fifth gear  466  and a sixth gear  467 . The first gear  462  has a first tooth portion  4621  and a second tooth portion  4622 . The actuating gear  460  is combined with the first actuating member  461 . The first actuating member  461  is used for driving the actuating gear  460  to rotate. The actuating gear  460  engages with the first tooth portion  4621  of the first gear  462 , and the second gear  463  engages with the second tooth portion  4622  of the first gear  462 . The third gear  464  is coupled to the second gear  463 . In this embodiment, the third gear  464  is coupled to the second gear  463  by a shaft, but the present invention is not limited thereto. For example, the third gear  464  and the second gear  463  can be integrally formed as well. The fourth gear  465  is combined with the paper roll  34  and engages with the third gear  464  and the fifth gear  466 . The sixth gear  467  is coupled to the feeding active roller  481  and engages with the fifth gear  466 . 
     As shown in  FIG. 2 , when the first actuating member  461  drives the actuating gear  460  to rotate in a clockwise direction CW, the actuating gear  460  activates the first tooth portion  4621  of the first gear  462  for driving the first gear  462  to rotate in a counterclockwise direction CCW opposite to the clockwise direction CW. Then, the second tooth portion  4622  of the first gear  462  activates the second gear  463  to rotate in the clockwise direction CW. Since the third gear  464  is coupled to the second gear  463 , the third gear  464  activates with the second gear  463  simultaneously and rotates in the clockwise direction CW. Accordingly, the third gear  464  is capable of activating the fourth gear  465  to rotate in the counterclockwise direction CCW. Since the fourth gear  465  is combined with the paper roll  34 , the paper roll  34  activates with the fourth gear  465  simultaneously and rotates in the counterclockwise direction CCW, so as to feed the printing media  36  into the first paper path  38  along a first direction X1. In other words, when the first actuating member  461  drives the actuating gear  460  to rotate in the clockwise direction CW, the first actuating member  461  is capable of driving the paper roll  34  to rotate in the counterclockwise direction CCW by the feeding mechanism  46 , so as to feed the printing media  36  into the first paper path  38  along the first direction X1. 
     Furthermore, when the paper roll  34  rotates in the counterclockwise direction CCW, the fourth gear  465  activates the fifth gear  466  to rotate in the clockwise direction CW. Then, the fifth gear  466  activates the sixth gear  467  to rotate in the counterclockwise direction CCW. Since the sixth gear  467  is coupled to the feeding active roller  481 , the feeding active roller  481  activates with the fifth gear  466  simultaneously and rotates in the counterclockwise direction CCW, and the feeding active roller  481  further activates the feeding idle roller  482  to rotate reversely. Thus, when the first actuating member  461  drives the paper roll  34  to feed the printing media  36  to the feeding roller set  48  along the first direction X1, the feeding active roller  481  and the feeding idle roller  482  of the feeding roller set  48  can respectively clamp a top surface  361  and a bottom surface  363  of the printing media  36  for moving the printing media  36  along the first direction X1. 
     In summary, when the first actuating member  461  drives the actuating gear  460  to rotate in the clockwise direction CW, the feeding mechanism  46  is used for activating the paper roll  34  to rotate together with the feeding active roller  481 , so as to move the printing media  36  along the first direction X1. Similarly, when the first actuating member  461  drives the actuating gear  460  to rotate in the counterclockwise direction CCW opposite to the clockwise direction CW, the feeding mechanism  46  is used for activating the paper roll  34  to rotate together with the feeding active roller  481 , so as to move the printing media  36  out of the first paper path  38  along the second direction opposite to the first direction X1. 
     As shown in  FIG. 1  to  FIG. 4 , the printing device  3  further includes a first roller set  50 , a second roller set  52 , a roller transmission mechanism  54  and a printing roller set  56 . The first roller set  50  is disposed within the third paper path  42 . The second roller set  52  is disposed within the fourth paper path  44 . The printing roller set  56  is disposed within the second paper path  40  and located in a position near the print head  32 . The roller transmission mechanism  54  is coupled to the first roller set  50 , the second roller set  52  and the printing roller set  56 . Furthermore, the first roller set  50  includes a first active roller  501  and a first idle roller  502 . The second roller set  52  includes a second active roller  521  and a second idle roller  522 . The printing roller set  56  includes a printing active roller  561  and a printing idle roller  562 . The first idle roller  502  rotably abuts against the first active roller  501 . The second idle roller  522  rotably abuts against the second active roller  521 . The printing idle roller  562  rotably abuts against the printing active roller  561 . 
     Please refer to  FIG. 5  and  FIG. 6 .  FIG. 5  is an inter transmission diagram of the printing device  3  in another view according to the embodiment of the present invention.  FIG. 6  is a partly diagram of the roller transmission mechanism  54  shown in  FIG. 5 . The roller transmission mechanism  54  includes an actuating pulley  540 , a second actuating member  541 , a seventh gear  542 , an eighth gear  543 , a ninth gear  544 , a pulley  545 , a first step wheel  546 , a second step wheel  547 , a third step wheel  548 , a fourth step wheel  549 , a first belt  551 , a second belt  552  and a third belt  553 . The first step wheel  546  has a first gear portion  5461  and a first pulley portion  5462 . The second step wheel  547  has a second gear portion  5471  and a second pulley portion  5472 . The third step wheel  548  has a third gear portion  5481  and a third pulley portion  5482 . The fourth step wheel  549  has a fourth gear portion  5491  and a fourth pulley portion  5492 . The actuating pulley  540  is combined with the second actuating member  541 . The pulley  545  and the seventh gear  542  are respectively coupled to two sides of the printing active roller  561 , as shown in  FIG. 3 . The second active roller  521  is coupled to the third step wheel  548 . The first active roller  501  is combined with the fourth step wheel  549 . 
     Furthermore, the first belt  551  connects the actuating pulley  540  and the pulley  545 . The eighth gear  543  engages with the seventh gear  542  and the first gear portion  5461  of the first step wheel  546 . The second belt  552  connecting the first pulley portion  5462  of the first step wheel  546  and the second pulley portion  5472  of the second step wheel  547 . The ninth gear  544  engages with the second gear portion  5471  of the second step wheel  547  and the third gear portion  5481  of the third step wheel  548 . The third belt  553  connects the third pulley portion  5482  of the third step wheel  548  and the fourth pulley portion  5492  of the fourth step wheel  549 . 
     As shown in  FIG. 2 , when the second actuating member  541  drives the actuating pulley  540  to rotate in the counterclockwise direction CCW, the pulley  545  is activated by the actuating pulley  540  via the first belt  551 , so as to rotate in the counterclockwise direction. Since the printing active roller  561  respectively couples with the pulley  545  and the seventh gear  542  (as shown in  FIG. 3 ), the pulley  545  activates the printing active roller  561  and the seventh gear  542  to rotate in the counterclockwise direction simultaneously, and the printing active roller  561  is further capable of activating the printing idle roller  562  to rotate reversely, such that the printing media  36  is moved in the second paper path  40  along a third direction X3. 
     Furthermore, the third step wheel  548  is capable of activating the fourth pulley portion  5492  of the fourth step wheel  549  via the third belt  553 , so as to drive the fourth step wheel  549  to rotate in the counterclockwise direction. Since the first active roller  501  is coupled to the fourth step wheel  549 , as shown in  FIG. 3 , the first active roller  501  activates with the fourth step wheel  549  and rotates in the counterclockwise direction, and the first active roller  501  activates the first idle roller  502  to rotate reversely, such that the printing media  36  is moved in the third paper path  42  along a fifth direction X5. In summary, when the second actuating member  541  drives the actuating pulley  540  to rotate in the counterclockwise direction CCW, the roller transmission mechanism  54  is used for activating the printing active roller  561 , the second active roller  521  and the first active roller  501  to rotate simultaneously, so as to move the printing media  36  in a direction approaching the print head  32 . 
     As mentioned above, when the second actuating member  541  drives the actuating pulley  540  to rotate in the clockwise direction CW opposite to the counterclockwise direction CCW, the roller transmission mechanism  54  is used for activating the printing active roller  561 , the second active roller  521  and the first active roller  501  to rotate simultaneously, so as to move the printing media  36  in a direction departing from the print head  32 . In other words, when the second actuating member  541  drives the actuating pulley  540  to rotate in the clockwise direction CW, the printing active roller  561  activates the printing media  36  to move in the second paper path  40  along a sixth direction X6 opposite to the third direction X3; the second active roller  521  activates the printing media  36  to move in the fourth paper path  44  along a seventh direction X7 opposite to the fourth direction X4; the first active roller  501  activates the printing media  36  to move in the third paper path  42  along an eighth direction X8 opposite to the fifth direction X5. 
     As shown in  FIG. 1 , the printing device  3  further includes a cutting mechanism  58 , a first guiding gate mechanism  60 , a second guiding gate mechanism  62 , a first paper head sensor  64 , a second paper head sensor  66 , a third paper head sensor  68  and a paper end sensor  70 . The cutting mechanism  58  is disposed on the third paper path  42  and located between the second paper path  40  and the fourth paper path  44 . The cutting mechanism  58  is used for cutting the printing media  36 , so as to cut printing media  36  rolled on the paper roll  34  from a roll type into a sheet type, and principles are provided hereinafter. The first guiding gate mechanism  60  is disposed on the second end  383  of the first paper path  38  and for selectively communicating the first paper path  38  with the second paper path  40  or with the third paper path  42 . The second guiding gate mechanism  62  is disposed on a conjunction where the third paper path  42  is connected to the fourth paper path  44  and for selectively communicating the third paper path  42  with the fourth paper path  44 . The first paper head sensor  64  is disposed within the first paper path  38  and for sensing a paper head  365  of the printing media  36 . The second paper head sensor  66  and the third paper head sensor  68  are both disposed within the third paper path  42  and for sensing the paper head  365  of the printing media  36 , respectively. The paper end sensor  70  is disposed within the third paper path  42  and located near the second guiding gate mechanism  62 . 
     Detailed descriptions for principles of the printing device  3  for duplex printing are provided as follows. Please refer to  FIG. 7  to  FIG. 13 .  FIG. 7  to  FIG. 13  are respectively diagrams of the printing device  3  in different printing statuses according to the embodiment of the present invention. As shown in  FIG. 7 , the first guiding gate mechanism  60  is driven to communicate the first paper path  38  with the second paper path  40 . Meanwhile, the first actuating member  461  drives the paper roll  34  and the feeding active roller  481  to rotate in the counterclockwise direction CCW, such that the printing media  36  rolled on the paper roll  34  is fed into the first paper path  38  along the first direction X1 and further from the first paper path  38  into the second paper path  40  via the first guiding gate mechanism  60 . On the other hand, as shown in  FIG. 7  and  FIG. 8 , the second actuating member  541  drives the printing active roller  561  to rotate in the counterclockwise direction CCW, such that the printing media  36  within the second paper path  40  is fed to the print head  32  for printing along the third direction X3. 
     Since the second paper path  40  is extended reverse to the first paper path  38  for being connected to the print head  32 , the second paper path  40  is able to turn the bottom surface  363  of the printing media  36  to face the print head  32  when the printing media  36  is fed to the print head  32  via the second paper path  40 . In such a manner, when the printing media  36  is fed to the print head  32  via the first paper path  38  and the second paper path  40 , the print head  32  is able to perform printing operation on the bottom surface  363  of the printing media  36 . 
     As shown in  FIG. 8 , when the bottom surface  363  of the printing media  36  has been printed by the print head  32 , the second actuating member  541  drives the printing active roller  561  to rotate in the clockwise direction CW, so as to feed the printing media  36  out of the second paper path  40  along the sixth direction X6 opposite to the third direction X3; the first actuating member  461  drives the paper roll  34  and the feeding active roller  481  to rotate in the clockwise direction CW, so as to feed the printing media  36  out of the first paper path  38  along the second direction X2 opposite to the first direction X1. When the printing media  36  is moved to a position shown in  FIG. 9  within the first paper path  38  along the second direction X2, the first paper head sensor  64  senses the paper head  365  of the printing media  36 , such that the first guiding gate mechanism  60  is driven to communicate the first paper path  38  with the third paper path  42 . 
     Afterwards, the first actuating member  461  drives the paper roll  34  and the feeding active roller  481  to rotate in the counterclockwise direction CCW again, such that the printing media  36  rolled on the paper roll  34  is fed into the first paper path  38  along the first direction X1 and further guided by the first guiding gate mechanism  60  from the first paper path  38  into the third paper path  42 . On the other hand, as shown in  FIG. 9 , the second actuating member  541  drives the first active roller  501  to rotate in the clockwise direction CW, so as to move the printing media  36  within the third paper path  42  along the eighth direction X8. When the printing media  36  is moved within the third paper path  42  to a position shown in  FIG. 10  along the eighth direction X8, the second paper head sensor  66  senses the paper head  365  of the printing media  36 , such that the cutting mechanism  58  is driven to cut the printing media  36  into a printing sheet  36 ′, as shown in  FIG. 11 . 
     As shown in  FIG. 10 , a path length of the third paper path  42  between the second paper head sensor  66  and the cutting mechanism  58  is substantially equal to a first paper length L1. When the second paper head sensor  66  senses the paper head  365  of the printing media  36  to enable the cutting mechanism  58  to cut the printing media  36  into the printing sheet  36 ′, the paper length of the printing sheet  36 ′ is substantially equal to the first paper length L1. In other words, by utilizing the structure that the path length of the third paper path  42  between the second paper head sensor  66  and the cutting mechanism  58  is substantially equal to the first paper length L1, the cutting mechanism  58  is capable of forming the printing sheet  36 ′ with the paper length substantially equal to the first paper length L1. In this embodiment, the cutting mechanism  58  can be designed to cut the printing media  36  when the third paper head sensor  68  senses the paper head  365  of the printing media  36 , wherein a path length of the third paper path  42  between the third paper head sensor  68  and the cutting mechanism  58  is substantially equal to a second paper length L2. When the third paper head sensor  68  senses the paper head  365  of the printing media  36  to enable the cutting mechanism  58  to cut the printing media  36  into the printing sheet  36 ′, the paper length of the printing sheet  36 ′ is substantially equal to the second paper length L2. As shown in  FIG. 10 , the second paper length L2 is greater than the first paper length L1. 
     When the cutting mechanism  58  cuts the printing media  36  into the printing sheet  36 ′, the first actuating member  461  stops for staying the printing media  36 , and the second actuating member  541  drives the first active roller  501  to rotate in the clockwise direction CW continuously, so as to move the printing sheet  36 ′ to a position shown in  FIG. 12  along the eighth direction X8. Meanwhile, the paper end sensor  70  senses a paper end  367  opposite to the paper head  365  of the printing sheet  36 ′. When the paper end sensor  70  senses the paper end  367  of the printing sheet  36 ′, the second guiding gate mechanism  62  is driven to communicate the fourth paper path  44  in advance. Then, the second actuating member  541  drives the first active roller  501  to rotate in the counterclockwise direction CCW, such that the printing sheet  36 ′ is moved within the third paper path  42  along the eighth direction X8 continuously and further guided into the fourth paper path  44  by the second guiding gate mechanism  62 . 
     Furthermore, the second actuating member  541  simultaneously drives the second active roller  521  to rotate in the counterclockwise direction CCW, so as to feed the printing sheet  36 ′ from the fourth paper path  44  to the second paper path  40 . The second actuating member  541  further drives the printing active roller  561  to rotate in the counterclockwise direction CCW simultaneously, so as to feed the printing sheet  36 ′ to the print head  32  for printing. During the above-mentioned feeding process, the third paper path  42 , the fourth paper path  44  and the second paper path  40  do not turn the printing sheet  36 ′ over. Accordingly, the top surface  361  of the printing sheet  36 ′ faces the print head  32  during the above-mentioned process. In such a manner, when the printing sheet  36 ′ is fed to the print head  32  via the third paper path  42 , the fourth paper path  44  and the second paper path  40 , the print head  32  is able to perform printing operation on the top surface  361  of the printing media  36 . 
     Compared to the prior art, the present invention utilizes the second paper path to turn the bottom surface of the printing media to face the print head when the printing media is fed, such that the print head is able to perform printing operation on the bottom surface of the printing media. The present invention further utilizes the cutting mechanism to cut the printing media within the third paper path into the printing sheet. Then, the printing sheet is fed into the second paper path via the fourth paper path, and further fed to the print head via the second paper path, such that the print head is able to perform printing operation on the top surface of the printing sheet. In such a manner, the present invention can perform duplex printing operation, so as to decrease labor time and enhance convenience in operation. 
     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. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.