Patent Publication Number: US-8537188-B2

Title: Portable thermal printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2011-035964 filed on Feb. 22, 2011, the entire content of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a portable thermal printer, which can be held by a user. 
     BACKGROUND 
     A thermal printer, which includes a thermal printer head composed of a heater element array extending in a width direction, is already commercially available. In the thermal printer, a thermal paper as a print paper is fed through between the thermal printer head and a platen roller rotating in contact with the thermal printer head. The thermal printer head performs printing while applying a constant pressure on the print paper. 
     In recent years, a portable thermal printer that can be held by a user has been developed as a thermal printer of the type described above. The portable thermal printer is easy to carry. For example, it can be carried to, e.g., a place of sale where a discount sale often called a special sale or a time-limited sale is underway and can be operated there to print any necessary information. 
     The portable thermal printer includes a drive power source with a driving gear arranged within a housing and a platen roller with a driven gear arranged in a cover for being able to open or close an opening portion of the housing. When the cover is kept closed with respect to the housing, the platen roller makes contact with a thermal printer head and the driven gear meshes with the driving gear. 
     Under these circumstances, the driven gear is exposed to the outside if the cover is opened. Thus, dusts or other alien substances are likely to adhere to the driven gear and may possibly be brought into between the driven gear and the driving gear, thereby hindering a smooth rotation of the platen roller. Accordingly, there is a strong demand for a portable thermal printer capable of assuring a smooth rotation of the platen roller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external perspective view showing a portable thermal printer. 
         FIG. 2  is a schematic configuration view of the portable thermal printer with a cover opened. 
         FIG. 3  is a schematic configuration view of the portable thermal printer having the cover being opened and a rolled paper loaded within the printer. 
         FIG. 4  is a schematic configuration view showing a belt mechanism according to a first embodiment. 
         FIG. 5  is a schematic plan view of the belt mechanism shown in  FIG. 4 . 
         FIG. 6  is a schematic configuration view showing a belt mechanism according to a second embodiment. 
         FIG. 7  is a schematic plan view of the belt mechanism shown in  FIG. 6 . 
         FIG. 8  is a schematic plan view showing a belt mechanism according to a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a portable thermal printer includes a housing provided with a thermal printer head, and a cover openably attached to an opening portion of the housing by a pivotal shaft. The cover is provided with a platen roller arranged to make contact with the thermal printer head when the opening portion of the housing is closed by the cover. The portable thermal printer further includes a drive power source provided within the housing. The drive power source, the pivotal shaft and the platen roller are connected by a belt mechanism. 
     According to another embodiment, a portable thermal printer includes a housing provided with a thermal printer head, and a cover openably attached to an opening portion of the housing by a pivotal shaft. The cover is provided with a platen roller arranged to make contact with the thermal printer head when the opening portion of the housing is closed by the cover. The portable thermal printer further includes a drive power source provided within the housing. Further, the portable thermal printer includes a first pulley connected to the drive power source, a second pulley attached to the pivotal shaft, a third pulley arranged to rotate with being joined together with the second pulley, a fourth pulley attached to the platen roller, a driving belt stretched between the first pulley and the second pulley, and a driven belt stretched between the third pulley and the fourth pulley. 
     A portable thermal printer S according to the present embodiment will now be described with reference to the drawings. 
       FIG. 1  is an external perspective view showing a portable thermal printer S with a cover  4  closed.  FIG. 2  is a schematic configuration view of the portable thermal printer S with the cover  4  opened.  FIG. 3  is a schematic configuration view of the portable thermal printer S with the cover  4  opened and a rolled paper P loaded within the printer. 
     In  FIGS. 2 and 3 , the printer S is divided into a plurality of portions along a width direction. If the portions are combined together at the dividing lines, then the width dimension of the printer S becomes substantially equal to the actual width dimension. 
     The portable thermal printer S is capable of performing two-inch printing and has a rectangular parallelepiped shape of about 88 mm in width, about 119 mm in length and about 65 mm in height. The weight of the portable thermal printer S with a battery is about 450 g. Due to the reduced weight thereof, the portable thermal printer S can be carried to any spot and be operated at the spot to perform printing as set forth later. 
     The printer S includes a housing  1  configured to hold therein all types of components of the printer S. The housing  1  can store a roll-shaped paper P as a thermal paper (the roll-shaped paper will be referred to as the “rolled paper” hereinafter). On the upper surface of the housing  1 , there is defined an opening portion  2  through which the rolled paper P can be put into the housing  1 . The opening portion  2  can be opened or closed by a cover  4  attached to the housing  1  through a pivotal shaft  3 . 
     The pivotal shaft  3  is extended along the inside edge of the housing  1  forming one edge of the opening portion  2 . When the cover  4  is closed, an elongated gap  5  is formed between the outer tip edge of the cover  4  and the side edge of the housing  1 , i.e., one edge of the opening portion  2  that faces the outer tip edge of the cover  4 . The gap  5  is extended in the width direction of the housing  1  over an area other than the both end areas of the housing  1 . 
     The rolled paper P is drawn out from the gap  5  and the printed paper P is discharged through the gap  5  when the printing is finished. Thus, the gap  5  serves as a “paper outlet  5 .” The front edge of the housing  1  or the outer tip edge of the cover  4 , which defines the paper outlet  5 , is formed into a sharp shape to readily cut the rolled paper P discharged from the paper outlet  5 . A connector portion  6  and a battery storage portion  7  are arranged on the right side surface of the housing  1 . 
     A paper storage portion  8  storing the rolled paper P is defined within the housing  1 . The rolled paper P is stored in the paper storage portion  8  with a roll axis thereof extending in the width direction of the housing  1 . The rolled paper P is drawn by a below-mentioned platen roller  10  and conveyed toward the paper outlet  5 . 
     When the rolled paper P is drawn by the platen roller  10 , an oblique motion prevention mechanism D prevents the rolled paper P from making an oblique motion. The oblique motion prevention mechanism D includes a rail member that is extended in the width direction of the housing  1  and a pair of guide fences  11   a  and  11   b  slidably attached to the rail member in an opposing relationship (the oblique motion prevention mechanism D is partially shown). The guide fences  11   a  and  11   b  are connected to the both ends of a rack-and-pinion mechanism installed on the rail member. A lever  12  is pivotally attached to the outer surface of the right guide fence  11   a  when the printer S is seen from the front side. 
     Depending on the rotational position thereof, the lever  12  is either allowed to move in the longitudinal direction of the rail member or restrained from making such a movement. More specifically, as indicated by double-dot chain lines in  FIGS. 2 and 3 , the lever  12  is gripped and rotated toward the front side. Then, the lever  12  is moved to the right side of the printer S. The guide fences  11   a  and  11   b  are moved away from each other by the rack-and-pinion mechanism. The space between the guide fences  11   a  and  11   b  is used as the paper storage portion  8  stated above. Subsequently, the rolled paper P is stored in the paper storage portion  8 . 
     If the lever  12  is moved to the left while keeping the lever  12  in the rotated position, then the guide fences  11   a  and  11   b  are moved toward each other by the rack-and-pinion mechanism. This makes it possible to bring the guide fences  11   a  and  11   b  into close contact with the left and right end surfaces of the rolled paper P stored between the guide fences  11   a  and  11   b.    
     As indicated by solid lines in  FIGS. 2 and 3 , the lever  12  is rotated from this position to the inside. Thus, the movement of the lever  12  is restrained with the guide fences  11   a  and  11   b  kept in close contact with the both end surfaces of the rolled paper P. During a printing operation, the guide fences  11   a  and  11   b  kept in close contact with the both end surfaces of the rolled paper P serve to prevent the rolled paper P from making an oblique motion as it is fed out. 
     A thermal printer head  13  is arranged within the housing  1 . The thermal printer head  13  includes a heater element array provided at the same direction as the width of paper. The heater element array generates heat under the control of a control unit not shown in the drawings, whereby the thermal printer head  13  performs printing on the rolled paper P. 
     A head bracket (not shown) for upwardly biasing inside the thermal printer head  13  is arranged at the front side of the thermal printer head  13 . At the inside of the thermal printer head  13 , there is arranged a head cover  14 . If necessary, the head cover  14  is mounted to the housing  1 . The head cover  14  presses and biases the thermal printer head  13  to prevent the occurrence of vibration in the thermal printer head  13 . 
     A platen roller  10  as a paper feeding mechanism and a paper pressing roller  16  are arranged near the outer edge of one surface of the cover  4  facing the paper storage portion  8 . The platen roller  10  and the paper pressing roller  16  are rotatably supported by support shafts extending in the width direction of the housing  1 . 
     The platen roller  10  is arranged in the cover  4  so that when the cover  4  is closed, the platen roller  10  can be contacted with the heater element array of the thermal printer head  13 . The paper pressing roller  16  is arranged in the cover  4  so that when the cover  4  is closed, the paper pressing roller  16  can be contacted with the head cover  14 . 
     Within the housing  1 , a belt mechanism K to be described below is provided. When seen at the front side of the printer S, the belt mechanism K is extended from the left and right end portions of the thermal printer head  13  to the left and right end portions of the platen roller  10  through the left and right end portions of the pivotal shaft  3  supporting the cover  4 . Since the portions of the belt mechanism K that is extended from the left and right end portions of the thermal printer head  13  to the left and right end portions of the pivotal shaft  3  are installed within the housing  1 , there is a little possibility that even if the cover  4  is opened, the belt mechanism K is partially touched by the fingers of an operator. 
     In contrast, the remaining portions of the belt mechanism K that is extended from the left and right end portions of the pivotal shaft  3  to the left and right end portions of the platen roller  10  are exposed to the outside when the cover  4  is opened, and may be touched by the operator&#39;s fingers. Given this, belt covers  17  schematically indicated by double-dot lines are attached to the cover  4  to hide the exposed portions of the belt mechanism K. 
     Accordingly, even if the cover  4  is opened, there is little or no possibility that the outward appearance of the printer S is impaired by the belt covers  17  or the belt mechanism K is partially touched by the operator&#39;s fingers. This makes it possible to prevent damage of the belt mechanism K and to give a dust-proof effect to the belt mechanism K. 
     In the portable thermal printer S configured as above, the rolled paper P is stored in the paper storage portion  8  and the tip end of the rolled paper P is drawn out, after which the cover  4  is closed. The rolled paper P thus drawn out is pinched between the thermal printer head  13  and the platen roller  10  and also between the head cover  14  and the paper pressing roller  16 . 
     When the cover  4  is closed, the thermal printer head  13 , the platen roller  10 , the head cover  14  and the paper pressing roller  16  define a guide path that guides the rolled paper P to the paper outlet  5 . 
     If a drive signal is inputted from a control unit (not shown) to the belt mechanism K, the rolled paper P is guided along the guide path while preventing the oblique motion of the rolled paper P by the oblique motion prevention mechanism D. That is, the rolled paper P is guided toward the paper outlet  5  through the clearance between the thermal printer head  13  and the platen roller  10 . The thermal printer head  13  as a printing unit is arranged somewhere along the guide path. As the heater element array generates heat under the control of a control unit, the thermal printer head  13  prints a specified content on the rolled paper P conveyed. 
     Next, the belt mechanism K will be described in detail. 
       FIGS. 4 and 5  show a belt mechanism K according to a first embodiment.  FIG. 4  is a schematic configuration view of some major parts of the printer S and the belt mechanism K, which depicts the cover  4  in a closed state.  FIG. 5  is a schematic plan view of some major parts of the printer S and the belt mechanism K, which depicts the cover  4  in an open state. 
     When the printer S is seen at the front side, a drive motor (drive power source)  20  is arranged near the left end portion of the thermal printer head  13 . The drive motor  20  includes a rotating shaft  20   a  that is extended in the axial direction of the drive motor  20  just in front of the thermal printer head  13 . 
     The tip end of the rotating shaft  20   a  is supported by a bearing not shown in the drawings. Driving gears  21  are attached to the portions of the rotating shaft  20   a  opposing to one end portion and the other end portion of the thermal printer head  13 . Support shafts  22  supported by bearings not shown in the drawings are arranged along the left and right end portions of the rotating shaft  20   a . Driven gears  23  meshed with the driving gears  21  are fitted to the support shafts  22 . 
     First pulleys  24  are fitted to the support shafts  22  in a side-by-side relationship with the driven gears  23 . The drive motor  20 , the driving gears  21 , the driven gears  23  and the first pulleys  24  make up a driving unit  25  of the belt mechanism K. 
     As mentioned above, the cover  4  for opening and closing the opening portion  2  of the housing  1  is supported by the pivotal shaft  3 . Second pulleys  27  are rotatably attached to the left and right end portions of the pivotal shaft  3 . Third pulleys  28  are rotatably attached to the pivotal shaft  3  in a side-by-side relationship with the second pulleys  27 . 
     The second pulleys  27  and the third pulleys  28  may be integrally formed with each other or may be independently formed beforehand and then connected to each other by an end-to-end relationship before attaching the pulleys  27  and  28  to the pivotal shaft  3 . The second pulleys  27  and the third pulleys  28  make up an intermediate unit  29  of the belt mechanism K. 
     The platen roller  10  attached to the tip end portion of the cover  4  includes a pair of support shafts  10   a  are axially protruded from the both end portions of the platen roller  10 . The support shafts  10   a  are supported on the left and right end portions of the cover  4 . Fourth pulleys  30  are fitted to the both end portions of the support shafts  10   a  of the platen roller  10 . The fourth pulleys  30  make up a driven unit  31  of the belt mechanism K. 
     Driving belts  33  are stretched over the first pulleys  24  and the second pulleys  27 . Driven belts  34  are stretched over the third pulleys  28  and the fourth pulleys  30 . The belt mechanism K is configured as above. 
     When the opening portion  2  of the housing  1  is closed by the cover  4 , the platen roller  10  attached to the cover  4  makes contact with the thermal printer head  13  supported on the housing  1 . At the printing startup time, the rolled paper P waits in a state wherein the rolled paper P is pinched between the thermal printer head  13  and the platen roller  10 . 
     Upon receiving a printing signal, the control unit transmits a drive signal to the drive motor  20 . As shown in  FIG. 4 , the rotating shaft  20   a  of the drive motor  20  is rotationally driven counterclockwise and the driving gears  21  are rotated in the same direction together with the rotating shaft  20   a . The driven gears  23  meshed with the driving gears  21  are rotated clockwise and the first pulleys  24  are rotated in the same direction together with the driven gears  23 . 
     When the driving belts  33  is operated, the second pulleys  27  and the third pulleys  28  are rotated in the same direction as the operation direction of the driving belts  33 . When the driven belts  34  are operated, the fourth pulleys  30  are rotated in the same direction as the operation direction of the driven belts  34 . The platen roller  10  rotates clockwise with being joined together with the fourth pulleys  30 . 
     Simultaneously, the control unit transmits a printing control signal to the thermal printer head  13  which in turn performs printing on the rolled paper P pinched between the platen roller  10  and the thermal printer head  13 . Under the action of the belt mechanism K, the platen roller  10  is rotationally driven to feed the rolled paper P from the opening portion  2  in a direction in which the rolled paper P is discharged to the outside through the paper outlet  5 . 
     In the portable thermal printer S, upon receiving a printing startup signal, a drive signal is inputted to the belt mechanism K to cause the belt mechanism K to rotationally drive the platen roller  10  kept in contact with the thermal printer head  13 . Thus, the rolled paper P pinched between the platen roller  10  and the thermal printer head  13  is smoothly discharged to the outside through the paper outlet  5 . 
     On the other hand, the cover  4  needs to be opened with respect to the housing  1 , e.g., when the rolled paper P is put into the paper storage portion  8  or when the used rolled paper P is taken out from the paper storage portion  8 . In the open state, the driven belts  34  and the fourth pulleys  30  of the belt mechanism K arranged in the cover  4  are protected by the belt covers  17 . This eliminates the possibility that dusts or other alien substances adhere to the driven belts  34  and the fourth pulleys  30  of the belt mechanism K. 
     However, in a conventional structure wherein the driven gears are attached in a coaxial relationship with a platen roller and are exposed to the outside when a cover is opened, dusts or other alien substances are likely to adhere or stick to the driven gears. If the cover is closed again, then the platen roller makes contact with a thermal printer head and the driven gears mesh with driving gears. As the driving gears are rotationally driven, the dusts or other alien substances adhering or sticking to the driven gears are brought into between the driven gears and the driving gears, consequently hindering a smooth rotation of the platen roller and causing a reduction of the printing accuracy. 
     According to the present embodiment, even if the cover  4  is opened, only the driven belts  34  and the fourth pulleys  30  of the belt mechanism K are exposed to the outside. Accordingly, even if the cover  4  is opened in a place where a myriad of dusts or other alien substances flies, there is no possibility that dusts or other alien substances are infiltrated into the belt mechanism K. This makes it possible to maintain drive efficiency and to assure smooth rotation of the platen roller  10 . 
       FIG. 6  is a schematic configuration view of some major parts of the printer S and the belt mechanism Ka according to a second embodiment, which depicts the cover  4  in a closed state.  FIG. 7  is a plan view of some major parts of the printer S and the belt mechanism Ka of the second embodiment, which depicts the cover  4  in an open state. 
     In this embodiment, the belt mechanism Ka includes a driving unit  25   a  wherein the first pulleys  24  are directly fitted to the rotating shaft  20   a  of the drive motor  20 . More specifically, unlike the belt mechanism K of the first embodiment, the belt mechanism Ka of the present embodiment does not employ the driving gears  21  and the driven gears  23  making up the driving unit  25 . Instead, the driving unit  25   a  of the belt mechanism Ka includes only the drive motor  20  and the first pulleys  24 . This means that a motor capable of rotating at a low speed needs to be used the drive motor  20 . 
     The second pulleys  27  and the third pulleys  28  are integrally formed with each other to make up the intermediate unit  29 . The fourth pulleys  30  are installed on the support shafts  10   a  of the platen roller  10  to make up the driven unit  31 . The driving belts  33  are stretched over the first pulleys  24  and the second pulleys  27 . The driven belts  34  are stretched over the third pulleys  28  and the fourth pulleys  30 . 
     If a drive signal is inputted to the drive motor  20 , then the first pulleys  24  are directly rotated by the drive motor  20  and the driving belts  33  is operated. As a result, the driven belts  34  are operated so that the platen roller  10  is rotationally driven. Thus, the rolled paper P pinched between the platen roller  10  and the thermal printer head  13  is fed and discharged through the paper outlet  5 . 
     In the second embodiment, the driving unit  25   a  of the belt mechanism Ka arranged within the housing  1  does not employ the meshing structure of the driving gears  21  and the driven gears  23  employed in the first embodiment. As such, even if dusts or other alien substances are infiltrated into the housing  1 , it is possible to reliably prevent reduction of the drive efficiency and to assure smooth rotation of the platen roller  10 . 
       FIG. 8  is a schematic plan view of some major parts of the printer S and the belt mechanism Kb according to a third embodiment, which depicts the cover  4  in an open state. The third embodiment has essentially the same configuration as that of the first embodiment. The belt mechanism Kb of the third embodiment is characterized in that the first pulley  24 , the second pulley  27 , the third pulley  28 , the fourth pulley  30 , the driving belt  33  and the driven belt  34  are provided only in one end portions of the thermal printer head  13 , the pivotal shaft  3  and the platen roller  10 . 
     This assists in maintaining the drive efficiency of the belt mechanism Kb, assuring smooth rotation of the platen roller  10 , reducing the transverse dimension of the housing  1  and the cover  4 , enhancing the portability of the portable thermal printer S and reducing the cost. 
     The configuration of the third embodiment may be modified to a configuration in which the first pulleys  24  is directly fitted to the drive motor  20  as in the second embodiment to thereby omit the meshing structure of the driving gears  21  and the driven gears  23  employed in the first embodiment. This modified configuration can additionally enjoy the same effects as provided by the second embodiment. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel printers described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.