Abstract:
A thermal sublimation imaging apparatus and a thermal sublimation printer using the same are described. A print head of the thermal sublimation imaging apparatus is fixed, a platen capable of contacting or separating from the fixed print head is lifted up to contact the fixed print head, and an elastic component is used in conjunction to provide a pressure for printing. The platen lays flat in paper feed/reverse mode, and presses downwardly to drive a paper pickup plate to fetch paper. These actions are achieved by a stepper motor together with a sensor through a worm shaft, a worm gear, and at least a gear. Therefore, the number and the cost of the gears are reduced, and the time for switching the printing action is greatly reduced since the switching can be implemented within a very small rotation angle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 200710031419.3 filed in China, P.R.C. on Nov. 13, 2007 the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to an imaging apparatus, in particularly to a thermal-sublimation imaging apparatus and a thermal sublimation printer using the same. 
         [0004]    2. Related Art 
         [0005]    Thermal-sublimation imaging technique is widely used in photo printing, and works according to the following principle. Dry solid ink on a ribbon, i.e., a mixture of a toning agent and a polymer thinly coated on the ribbon may be divided into yellow, cyan, and magenta, and the size of the ribbon is slightly larger than that of the photo paper to be printed. When printing, the photo paper and ribbon pass through a platen simultaneously, and are heated together under a print head. The heat-generating dots array of monocrystalline silicon with a diameter less than 40 μm on the print head is supplied with power, so as to melt the dry solid ink coated on the ribbon. During heating, polymer molecules are separated at about 320 Fahrenheit degrees. When the print head has passed, the temperature drops, and the ink is changed from gas state into solid state, thus the ink is embedded in the polymer, and then the polymer molecules are polymerized together. After one color is printed, the printing is repeated automatically to print next color. Accordingly, the ribbon is sublimated to generate a mixture of millions of colors on a photo paper, thereby achieving an optimal photo effect. 
         [0006]    The printing process has three steps including paper pickup, paper feeding/reversing with ribbon spooling, and printing. In printing, only one color is printed on the paper at a time, and after transferring three colors onto the paper, a protection layer must be added. Therefore, the paper feeding/reversing with ribbon spooling step and the printing step must be repeated four times. In the printing step, a pressure is required between the platen and the print head to uniformly transfer the dyes onto the paper. 
         [0007]    In the conventional thermal sublimation printers, in order to realize the actions such as providing pressure for printing, paper pickup, and paper feeding/reversing, a cam or other mechanisms are generally required to switch among these actions, thus increasing the manufacturing cost and the time for printing. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is directed to a low-cost thermal sublimation imaging apparatus capable of saving the time for printing and a thermal sublimation printer using the same. 
         [0009]    The present invention provides a thermal sublimation imaging apparatus, which includes a fixed print head; a platen, capable of contacting or separating from the print head and having a roll shaft; and a rotating shaft of the platen, mounted in parallel with the roll shaft, capable of rotating within a certain range of angle, and fitted with a first shaft bush, an elastic component, and a second shaft bush sequentially from two ends towards a center thereof. The second shaft bush is solidly connected on the rotating shaft. Two ends of the elastic component are respectively connected to the first shaft bush and the second shaft bush. The first shaft bush has a first connection hole and a second connection hole. One end of the rotating shaft is fitted in the first connection hole, and one end of the roll shaft of the platen is fitted in the second connection hole. When the platen separates from the print head, the first shaft bush sways up and down with the rotation of the rotating shaft to drive the platen to move up and down. When the platen contacts the print head, the rotating shaft rotates relative to the first shaft bush, so as to deform the elastic component to generate a torsion. 
         [0010]    Preferably, the second shaft bush and the rotating shaft are solidly connected through a D-shaped slot combination. The elastic component includes a torsion spring. 
         [0011]    In order to initialize the phase of the rotating shaft of the platen, a sensor is disposed on a frame where the thermal sublimation imaging apparatus is disposed at an end adjacent to the rotating shaft of the platen. A positioning block is disposed and solidly connected to the rotating shaft to work in cooperation with the sensor. The sensor has a first end for emitting signals and a second end for receiving signals. The positioning block rotates with the rotating shaft to a position between the first end and the second of the sensor, so as to block the transmission of the signals of the sensor. 
         [0012]    Furthermore, the thermal sublimation imaging apparatus further includes a stepper motor drive system for driving and precisely controlling the rotating shaft of the platen to rotate within a certain range of angle. 
         [0013]    Furthermore, the thermal sublimation imaging apparatus further includes a transmission system having a worm shaft and a worm gear for driving the rotating shaft of the platen to rotate. The worm gear is engaged with a gear for driving the rotating shaft of the platen to rotate. The transmission system further includes a first gear coaxial with the worm gear and a second gear engaged with the first gear. The power of the stepper motor drive system is transmitted to the rotating shaft of the platen through the second gear. 
         [0014]    The present invention further provides a thermal sublimation printer using the thermal sublimation imaging apparatus. The printer includes a paper pickup unit, a printing unit, and a paper cassette for accommodating paper. The paper pickup unit includes at least one paper pickup roller and a paper lift plate. The paper lift plate has a first end adjacent to the at least one paper pickup roller and a second end adjacent to the printing unit. The second end has a fulcrum, and the paper lift plate rotates around the fulcrum within a certain range of angle. The printing unit is the thermal sublimation imaging apparatus. When the platen contacts the print head, the rotating shaft rotates relative to the first shaft bush, so as to deform the elastic component to generate a torsion. When the platen separates from the print head, the first shaft bush sways up and down with the rotation of the rotating shaft, so as to drive the platen to move up and down to a laid flat position (i.e., a first position) or a press-down position (i.e., a second position). When the platen moves to the press-down position, a portion of the second end of the paper lift plate adjacent to the platen is pressed, such that the paper lift plate rotates around the fulcrum to make the paper lift plate to tilt upwardly, thus the paper in the paper cassette is lifted up to contact the paper pickup roller, thereby starting to pickup paper. 
         [0015]    In detail, the paper cassette includes a base, a paper tray, and a cover. The base includes a bottom having a hollowed out portion. The first end of the paper lift plate is fitted deeply in the hollowed out portion. The paper tray is disposed on the bottom and includes a movable end and an opposite fixed end. The movable end is covered on the hollowed out portion. When the first end of the paper lift plate tilts upwardly, the movable end of the paper tray is lifted up. 
         [0016]    Preferably, the first end and the second end of the paper lift plate are connected through a shaft. The shaft is fitted with a torsion spring, and two ends of the torsion spring are solidly connected to the first end and the second end of the paper lift plate respectively. 
         [0017]    Furthermore, the printer further includes a transferring unit. When the platen moves to a laid flat position, the transferring unit performs a paper feeding/reversing action. 
         [0018]    Compared with the prior art, in the thermal sublimation printer of the present invention, the platen is only required to move up and down in a small extent when switching between the paper feeding/reversing step and the printing step. It needs to be done 8 times switching to finish printing one image product, and thus the time for printing of the printer can be effectively reduced. Further, in the course of paper pickup, paper feeding/reversing, and printing, a self-locking function of the worm shaft and worm gear helps to suspend the supply of power to the stepper motor that drives the rotating shaft of the platen, thereby reducing power consumption and the cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The present invention will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present invention, and wherein: 
           [0020]      FIG. 1  is an exploded view of a thermal sublimation imaging apparatus according to an embodiment of the present invention, in which a drive system and a transmission system for actuating a rotating shaft of the platen of the thermal sublimation imaging apparatus are not shown; 
           [0021]      FIG. 2  is a perspective view of a thermal sublimation imaging apparatus according to an embodiment of the present invention, in which a drive system and a transmission system for driving a rotating shaft of the platen of the thermal sublimation imaging apparatus are not shown; 
           [0022]      FIG. 3  is a perspective view of a thermal sublimation printer according to an embodiment of the present invention; 
           [0023]      FIG. 4  is a three-dimensional perspective view of a paper lift plate in  FIG. 3 ; 
           [0024]      FIG. 5  is a three-dimensional perspective view of the paper lift plate with a first end removed; 
           [0025]      FIG. 6  is a three-dimensional schematic view of the paper lift plate in conjunction with a paper cassette; 
           [0026]      FIG. 7  is a partial enlarged view of a connection portion of the paper lift plate in  FIG. 6  and a frame; 
           [0027]      FIG. 8  is a schematic side view of the thermal sublimation printer according to the embodiment of the present invention when picking up a paper; 
           [0028]      FIG. 9  is a schematic side view of the thermal sublimation printer according to the embodiment of the present invention when feeding/reversing a paper; and 
           [0029]      FIG. 10  is a schematic side view of the thermal sublimation printer according to the embodiment of the present invention when printing. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Referring to  FIG. 1 , a thermal sublimation imaging apparatus  1  includes a fixed print head  20 , a platen  30  contacting or separating from the print head  20 , and a rotating shaft  40  of the platen rotating within a certain range of angle. The rotating shaft  40  is sequentially sleeved with first shaft bushes  41 ,  42 , torsion springs  43 ,  44 , and second shaft bushes  45 ,  46  from two ends towards a center thereof. The second shaft bushes  45 ,  46  are connected with the rotating shaft  40  through a D-shaped slot combination, and thus the rotating shaft  40  cannot rotate relative to the second shaft bushes  45 ,  46 . The torsion springs  43 ,  44  are sleeved with the rotating shaft  40 . The torsion spring  43  is connected at one end to the second shaft bush  45 , and at the other end to the first shaft bush  41 . Likewise, the torsion spring  44  is connected at one end to the second shaft bush  46 , and at the other end to the first shaft bush  42 . The first shaft bush  41  includes a first connection hole  411  and a second connection hole  412 . One end of the rotating shaft  40  is sleeved in the first connection hole  411 , and one end of a roll shaft  31  of the platen  30  is sleeved in the second connection hole  412 . Likewise, the first shaft bush  42  includes a first connection hole  421  and a second connection hole  422 . The other end of the rotating shaft  40  is sleeved in the first connection hole  421 , and the other end of the roll shaft  31  of the platen  30  is sleeved in the second connection hole  422 . When the rotating shaft  40  rotates, the first shaft bushes  41 ,  42  sway up and down with the rotation of the rotating shaft  40  to drive the platen  30  to move up and down, thereby making the platen  30  to contact or separate from the print head  20 . Since the first shaft bushes  41 ,  42  is in a common circular shaft connection with the rotating shaft  40 , the rotating shaft  40  may rotate relative to the first shaft bushes  41 ,  42  under a certain force. That is, as shown in  FIG. 2 , the rotating shaft  40  of the platen rotates in anticlockwise direction. The first shaft bushes  41 ,  42  sway upwardly to drive the platen  30  to move upwardly, so as to contact the print head  20 . After the platen  30  contacts the print head  20 , the rotating shaft  40  of the platen continues rotating in the anticlockwise direction. As being blocked by the print head  20 , the platen  30  cannot further move upwardly, and the first shaft bushes  41 ,  42  suspend rotating. At this time, the continuous rotation of the rotating shaft  40  drives the second shaft bushes  45 ,  46  to rotate continuously, thus deforming the torsion springs  43 ,  44  to generate a torsion in the anticlockwise direction, such that the first shaft bushes  41 ,  42  is prone to sway upwardly, thereby providing an upward printing pressure for the platen  30 . 
         [0031]    The rotating shaft  40  of the platen is actuated by a drive system and a transmission system (not shown in  FIGS. 1 and 2 ). The details of the drive system and the transmission system may be described in an embodiment of a thermal sublimation printer  100  using the thermal sublimation imaging apparatus I with reference to  FIG. 3 . 
         [0032]    Referring to  FIG. 3 , a thermal sublimation printer  100  using the thermal sublimation imaging apparatus  1  includes a frame  10 . The print head  20  is solidly mounted on the frame  10 . The rotating shaft  40  of the platen is mounted on the frame  10  and is rotatable within a certain range of angle. The power for driving the rotating shaft  40  of the platen to rotate originates from a stepper motor  60  and is transmitted to the rotating shaft  40  through a worm shaft  70 , a worm gear  71  engaged with the worm shaft  70 , a first gear  72  coaxial with the worm gear  71 , and a second gear  73  engaged with the first gear  72  successively. The rotating shaft  40  and the second gear  73  are associated through a D-shaped slot. The stepper motor  60  precisely controls the parameters, such as rotation directions and the numbers of rotation step of the worm shaft  70 . Therefore, the rotating shaft  40  rotates precisely in anticlockwise or clockwise direction within a certain range of angle. The first shaft bushes  41 ,  42  connect the rotating shaft  40  and the platen  30 , such that the platen  30  moves up and down with the rotation of the rotating shaft  40 , thereby making the platen  30  to contact or separate from the print head  20 . 
         [0033]    Referring to  FIGS. 4 to 7 , a paper lift plate  80  is mounted at the bottom of the frame  10 . First, referring to  FIG. 4 , the paper lift plate  80  includes a first end  81  and a second end  82 . The first end  81  and the second end  82  are connected in a hinge manner by a shaft  83 . In detail, one end of the first end  81  connected to the shaft  83  extends to form a bending portion  811  extending upwardly. The bending portion  811  has two sidewalls  812  in which a shaft bore  813  is formed respectively. The first end  81  is sleeved on the shaft  83  through the shaft bore  813 . Likewise, a connection portion of the second end  82  and the shaft  83  also extends along a first portion adjacent to the first end  81  from the second end  82  to form at least one bending portion  831  extending upwardly. The bending portion  831  is also formed with a shaft bore  832 . The second end  82  is sleeved on the shaft  83  through the shaft bore  832 . The first end  81  is sleeved on the inner side of the second end  82 . Particularly, the shaft  83  further has a torsion spring  84  sleeved thereon. The torsion spring  84  has tow ends, in which one end  841  is engaged at the outer side of the sidewall  812  of the bending portion  811  of the first end  81  of the paper lift plate  80 , and the other end  842  is engaged at the lower side of the bottom of the second end  82  of the paper lift plate  80 , as shown in  FIG. 5 . Further, the second end  82  extends in a direction departing from the first end  81  to a second portion adjacent to the platen  30 . The width of the second portion of the second end  82  is enlarged to be greater than the length of the platen  30 . Two ends along the width direction of the second portion of the second end  82  extend vertically to form sidewalls  821 ,  822  respectively. The sidewalls  821 ,  822  may contact the roll shaft  31  of the platen  30 , and have respective pivot points  825 ,  826  through which the paper lift plate  80  and the frame  10  are connected. The pivot points  825 ,  826  are located on a same horizontal level and form an imaginary axis according to the principle that two points define a line. The paper lift plate  80  rotates around the imaginary axis formed by the pivot points  825 ,  826 . That is, when the platen  30  moves downwardly, the roll shaft  31  of the platen  30  presses the sidewalls  821 ,  822  downwardly, so as to press down the portion at the side of the pivot points  825 ,  826  on the paper lift plate  80  adjacent to platen. Thus, the other side of the pivot points  825 ,  826  on the paper lift plate  80  away from the platen, i.e., the portion adjacent to the paper cassette tilts upwardly according to the lever principle, thereby lifting up the paper in the paper cassette. Preferably, one end of the sidewalls  821 ,  822  adjacent to the platen  30  has a pair of fitting slots  823 ,  824 . When the platen  30  moves downwardly, the roll shaft  31  just falls into the fitting slots  823 ,  824  and presses the paper lift plate  80  to rotate around the imaginary axis formed by the pivot points  825 ,  826 . In detail, the pivot points  825 ,  826  may be an engagement slot structure as shown in  FIG. 4 . In more detail, as shown in  FIG. 7 , the paper lift plate  80  and the frame  10  are connected by a bushing  86  and a rivet  861  solidly connected with the frame  10 . The paper lift plate  80  is engaged with the rivet  861  extending from the frame to the bushing  86  through the engagement slot structure. The paper lift plate  80  can rotate around the rivet  861 . Definitely, the rivet  861  can also be replaced by a shaft extending on the frame  10 . One of the pivot points  825 ,  826  can have a round-hole structure, as long as the paper lift plate  80  can be connected to the frame  10  and rotate with the frame  10  as a fulcrum. 
         [0034]    Next, as shown in  FIG. 6 , the thermal sublimation printer includes a paper cassette  200 . The paper cassette  200  includes a base plate  210 , a paper tray  220 , and a cover  230 . The base plate  210  includes a bottom  211  with a hollowed portion  212 . The paper tray  220  is disposed on the bottom  211  and includes a movable end  221  and a fixed end  222  positioned relative to the movable end  221 . The movable end  221  is positioned on the hollowed portion  212 . The first end  81  of the paper lift plate  80  is fitted deeply in the hollowed portion  212 . When the first end  81  of the paper lift plate  80  tilts upwardly, the movable end  221  of the paper tray  220  is lifted up. The force provided by the rotating shaft of the platen for forcing the second end  82  of the paper lift plate to move downwardly is the same at each time the paper is picked up, and the arm of force is also the same. Therefore, when different pieces of papers is placed on the paper tray  220 , due to the different total weight of the papers, the first end  81  of the paper lift plate  80  tilting upwardly encounters different resistances. In order to provide a certain paper pickup pressure (i.e., the force for making the first end  81  to tilt upwardly to press the paper on paper pickup roller  51 ), the present invention adopts the paper lift plate  80  divided into the first end  81  and the second end  82 , and the torsion spring  84  disposed between the first end  81  and the second end  82 , so as to ensure the consistent paper pickup pressure for the first paper through the last paper in the paper cassette. 
         [0035]    Referring to  FIG. 3 , the frame  10  further has a paper pickup roll shaft  50  disposed above the first end  81  of the paper lift plate  80 . The paper pickup roll shaft  50  has paper pickup rollers  51 ,  52 . The paper pickup rollers  51 ,  52  have a pair of paper exit rollers  57 ,  58  thereabove correspondingly. 
         [0036]    Further, the thermal sublimation printer further includes a transferring unit. The transferring unit includes a pair of transfer rollers and a transmission system. The pair of transfer rollers includes a paper pickup roller and a paper press roller for delivering paper, feeding/reversing paper, and precisely locating paper when switching between the printing and ribbon spooling processes. In detail, the paper pickup rollers of the pair of transfer rollers have needle-like spurs, and after being pressed tightly with the paper press rollers, a portion of the spurs pierce into a rubber layer on the back of the paper, so as to ensure the paper is at the same position when being printed back and forth. As shown in  FIGS. 8 and 3 , when picking up the paper, the worm shaft  70  rotates in clockwise direction indicated by the arrow, and the rotating shaft  40  also rotates in clockwise direction. The first shaft bushes  41 ,  42  sway downwardly, and thus the platen  30  moves downwardly. The roll shaft  31  is embedded in the fitting slots  823 ,  824  and presses the portion at the side of pivot points  825 ,  826  on the paper lift plate  80  adjacent to the platen  30  to move downwardly, and thus the paper lift plate  80  rotates with the pivot points  825 ,  826  as fulcrums, that is, the portion at the other end of the pivot points  825 ,  826  away from the platen and the first end  81  tilt upwardly according to the lever principle. Thus, the paper in the paper cassette is lifted up to contact the paper pickup rollers  51 ,  52 . In the course of paper pickup, the supply of power to the stepper motor  60  can be suspended. Since the worm shaft and the worm gear have the self-locking function, when the stepper motor  60  suspend working, the parts, such as the worm shaft  70 , the worm gear  71 , the first gear  72 , the second gear  73 , and the rotating shaft  40  of the platen are in a quiescent state and will not keep on rotating or rotate in reverse direction under other forces. 
         [0037]    After the paper is picked up, the worm shaft  70  rotates in the anticlockwise direction, and the rotating shaft  40  also rotates in the anticlockwise direction. The first shaft bushes  41 ,  42  sway upwardly to lift up the platen  30  to the laid flat position, at this time, the paper lift plate  80  is returned to the laid flat position, as shown in  FIG. 9 , and the paper is transferred by a transferring unit to a printing region. When transferring paper, the supply of power to the stepper motor  60  can also be suspended. 
         [0038]    When the paper is transmitted to a printing waiting position, the worm shaft  70  continues to rotating in anticlockwise direction, the rotating shaft  40  also rotates in anticlockwise direction, and the first shaft bushes  41 ,  42  sway upwardly continuously, so as to make the platen  30  to contact the print head  20 , as shown in  FIG. 10 . At this time, the rotating shaft  40  of the platen continues rotating in the anticlockwise direction. Since being blocked by the print head  20 , the platen  30  cannot move upwardly, thus the first shaft bushes  41 ,  42  suspend rotating. The continuous rotation of the rotating shaft  40  drives the second shaft bushes  45 ,  46  to rotate continuously, thus deforming the torsion springs  43 ,  44  connected to the first shaft bush and the second shaft bush to generate an anticlockwise torsion. Thus, the first shaft bushes  41 ,  42  are prone to sway upwardly, thereby providing an upward printing pressure for the platen  30 . When the printing pressure is adequate, the supply of power to the stepper motor  60  is suspended. Due to the self-locking function of the worm shaft  70 , the parts, such as the worm shaft  70 , the worm gear  71 , the first gear  72 , the second gear  73 , and the rotating shaft  40  of the platen will not move, and the torsion springs  43 ,  44  maintains a stable torsion, thereby providing a stable printing pressure. 
         [0039]    When printing, a color of an image to be printed on the entire paper is first printed on the paper. That is, the entire paper starts from the printing waiting position and then passes through the primary printing region. Next, the stepper motor  60  is actuated and the worm shaft  70  is controlled to change the rotation direction, i.e., to rotate in clockwise direction, such that the rotating shaft  40  is also made to rotate in the clockwise direction. Then, the torsion of the torsion springs  43 ,  44  is released, and the first shaft bushes  41 ,  42  are made to sway downwardly, such that the platen  30  separates from the print head  20 , and moves downwardly to return to the laid flat position as shown in  FIG. 9 . Then, the paper is reversed, that is, the paper printed with a color is sent back to the printing waiting position. When the paper is reversed, the stepper motor  60  is not supplied with power. After the paper is sent back to the printing waiting position, the stepper motor  60  is actuated again, and the platen  30  is returned to the printing position, so as to start printing another color. This process is repeated three or four times. After the whole image is printed, the paper is completely ejected out of the machine, and the platen  30  is lowered to the lowest position as shown in  FIG. 8  so as to pick up the next paper to be printed. 
         [0040]    It should be particularly noted that in the course of switching between the paper feeding/reversing and the printing state, according the embodiment, the rotating shaft  40  of the platen is only required to rotate by  35  degrees. In printing, the switching action needs to be done  8  times, thus the apparatus of the present invention can effectively reduce the time for printing. Furthermore, in the course of feeding/reversing and printing paper, the self-locking function of the worm shaft and the worm gear can be fully used to suspend supplying power to the stepper motor  60 , so as to save energy. 
         [0041]    It should be illustrated that referring to  FIG. 3 , in order to initialize the phase of the rotating shaft  40  of the platen, a sensor  90  is disposed on the frame  10  at one end adjacent to the rotating shaft  40  and a positioning block  91  disposed for working with the sensor  90  is solidly connected to the rotating shaft  40 . The sensor  90  has a signal transmitter and a signal receiver. When the thermal sublimation printer is actuated, the sensor  90  starts to send a signal. If no signal is received when the printer actuated, the stepper motor  60  controls the rotating shaft  40  of the platen to rotate in clockwise direction, and the positioning block  91  solidly mounted on the rotating shaft  40  rotates with the rotation of the rotating shaft  40  of the platen until the sensor  90  receives the signal, and then rotates in anticlockwise direction by a certain angle to the initial position. On the contrary, if a signal is received when the printer is actuated, the rotating shaft  40  rotates in the anticlockwise direction to a position at which no signal will be received, and then rotates in the clockwise direction by the same angle to the initial position. 
         [0042]    Compared with the prior art, in the thermal sublimation printer of the present invention, the platen is only required to move up and down in a small extent in the course of switching between the paper feeding/reversing and the printing step. It needs to be done  8  times switching to finish printing one image product, and thus the time for printing of the printer can be effectively reduced. Further, in the course of paper pickup, paper feeding/reversing, and printing, a self-locking function of the worm shaft and worm gear helps to suspend the supply of power to the stepper motor driving the rotating shaft of the platen, thereby reducing power consumption and the cost.