Patent Publication Number: US-9840094-B2

Title: Bobbin for thermal transfer sheet or image-receiving sheet, assembly of bobbin and sheet, and thermal transfer printer

Description:
TECHNICAL FIELD 
     The present invention relates to a bobbin for a thermal transfer sheet or an image-receiving sheet, an assembly of a bobbin and a sheet, and a thermal transfer printer. 
     BACKGROUND ART 
     Thermal transfer printers are widely prevalent which print characters or images on an object, such as an image-receiving sheet, by using an ink ribbon (thermal transfer sheet). The ink ribbon includes a ribbon (support layer) extending in a strip shape, and an ink layer containing a dye, etc. and formed on the ribbon. The ink ribbon is mounted and wound on a bobbin. 
     The bobbin, on which the ink ribbon is wound, generally includes a bobbin body and a driving flange mounted to the bobbin body as a separate member from the bobbin body. 
     However, the provision of such a driving flange, as a separate member, in a bobbin body increases the number of structural parts and increases the production cost and, in addition, involves a cumbersome operation when disposing of the bobbin. 
     It is conceivable to form driving irregularities in the outer surface of a bobbin body. However, when winding a ribbon on the bobbin, a rubber touch roll pressing on the ribbon can make contact with the driving irregularities, resulting in the formation of scratches on the touch roll. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent document 1: Japanese Patent Laid-Open Publication No. 2001-122523 
     Patent document 2: Japanese Patent Laid-Open Publication No. 2001-150775 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The present invention has been made in view of the above situation. It is therefore an object of the present invention to provide a bobbin for a thermal transfer sheet or an image-receiving sheet, an assembly of a bobbin and a sheet, and a thermal transfer printer which can reduce the number of structural parts and can avoid scratching on a touch roller. 
     Means for Solving the Problems 
     The present invention provides a bobbin for a thermal transfer sheet or an image-receiving sheet, comprising a cylindrical bobbin body, wherein a gear including a number of teeth is formed in one end surface of the bobbin body, and wherein when the bobbin body is viewed from the side, the teeth each have the shape of a trapezoid composed of an upper base, a lower base, and a pair of lateral sides, one of the lateral sides extending parallel to the axis of the bobbin body. 
     In a preferred embodiment of the present invention, the sum of the circumferential lengths of the tooth tops of the teeth is 20% to 70% of the circumferential length of the bobbin body. 
     In a preferred embodiment of the present invention, the bobbin body is provided with a circumferential groove or a circumferential projection which performs positioning of the bobbin body when setting it in a case. 
     In a preferred embodiment of the present invention, the bobbin body is provided, in the other end surface, with an engagement groove which performs positioning of a flange when mounting it to the bobbin body. 
     The present invention also provides an assembly of a bobbin and a sheet, comprising: the above-described bobbin for a thermal transfer sheet or an image-receiving sheet; and a thermal transfer sheet or an image-receiving sheet wound on the bobbin. 
     In a preferred embodiment of the present invention, the assembly of a bobbin and a sheet further comprises a case for housing the bobbin and the thermal transfer sheet or the image-receiving sheet. 
     The present invention also provides a thermal transfer printer incorporating the above-described assembly of a bobbin and a sheet, comprising: a mounting section in which the assembly of a bobbin and a sheet is to be set; and a drive section including a drive shaft extending coaxially with the bobbin body, wherein a drive gear that engages the gear of the bobbin body is provided in an end surface of the drive shaft. 
     Advantageous Effects of the Invention 
     The present invention makes it possible to reduce the number of structural parts and, in addition, to provide a bobbin body having a smooth surface without any driving irregularities. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a bobbin for a thermal transfer sheet or an image-receiving sheet according to the present invention; 
         FIG. 2  is a plan view of an assembly of a sheet and bobbins; 
         FIG. 3  is a plan view of the assembly of a sheet and bobbins set in a thermal transfer printer; 
         FIG. 4A  is a side view of a supply bobbin, and  FIG. 4B  is an enlarged view of the supply bobbin; 
         FIG. 5  is a cross-sectional side view of the supply bobbin; 
         FIG. 6  is a perspective view of the supply bobbin; 
         FIG. 7  is a side view of the supply bobbin having a flange portion; 
         FIG. 8  is a side view of the flange portion; 
         FIG. 9  is a side view of a bobbin body according to a variation of the present invention; and 
         FIG. 10  is a side view of a bobbin body according to another variation of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 
     An embodiment of the present invention will now be described with reference to the drawings. 
       FIGS. 1 through 8  are diagrams illustrating the embodiment of the present invention. 
     At the outset, a ribbon cartridge (assembly of bobbins and a sheet)  1  incorporating a bobbin  10  for a thermal transfer sheet or an image-receiving sheet according to the present invention will be described with reference to  FIG. 2 . 
     The ribbon cartridge  1  includes the supply bobbin  10 , a take-up bobbin  20 , a case  2  for housing the supply bobbin  10  and the take-up bobbin  20 , and an ink ribbon (thermal transfer sheet)  3  comprising a support layer and an ink layer, provided between the supply bobbin  10  and the take-up bobbin  20 . The ink ribbon  3  is mounted on the supply bobbin  10  and on the take-up bobbin  20 . 
     The take-up bobbin  20  of the thus-constructed ribbon cartridge  1  includes a cylindrical bobbin body  21 , a gear flange  22  formed integrally with the bobbin body  21  at one end of the bobbin body  21 , and a support shaft  25  formed integrally with the bobbin body  21  at the other end of the bobbin body  21 . 
     The gear flange  22  has a number of teeth  22   a  formed in the inner peripheral surface. The teeth  22   a  engage a drive section  40  of a thermal transfer printer  50  so that the drive section  40  rotationally drives the take-up bobbin  20  (see  FIG. 3 ). As shown in  FIG. 3 , the bobbin body  21  of the take-up bobbin  20  has a circumferential projection  23  formed in the vicinity of the gear flange  22 . A portion of the bobbin body  21 , lying between the gear flange  22  and the circumferential projection  23 , engages the case  2 , whereby the take-up bobbin  20  is positioned along the axial direction within the case  2 . 
     The drive section  40  of the thermal transfer printer  50  includes a drive shaft  41  which, in its end surface, has a drive gear  42  that engages the teeth  22   a  of the gear flange  22 . 
     The supply bobbin  10  (bobbin for a thermal transfer sheet or an image-receiving sheet according to the present invention) of the ribbon cartridge  1  will now be described in detail with reference to  FIGS. 1 through 8 . The supply bobbin  10  includes a cylindrical bobbin body  11  having a gear  12  formed in its one end surface and consisting of a number of teeth  13  and tooth grooves  14  formed between the teeth  13 . As described below, the gear  12  engages a drive gear  32  of a drive shaft  31  provided in a drive section  30  of the thermal transfer printer  50 . 
     A plurality of engagement grooves  17  are formed in the other end surface of the bobbin body  11  so that when mounting a flange portion  18  to the other end of the bobbin body  11 , engagement projections  18   e  of the flange portion  18  engage the engagement grooves  17 . 
     The supply bobbin  10  will now be described in greater detail with reference to  FIGS. 4A, 4B through 8 . As described above, the supply bobbin  10  includes the cylindrical bobbin body  11  having the gear  12  formed in its one end surface. The gear  12  consists of the teeth  13  and the tooth grooves  14  formed between the teeth  13 . Each tooth  13  has a trapezoidal shape when viewed from the side of the bobbin body  11  (see  FIGS. 4A and 4B . 
     Each tooth  13  has the shape of a trapezoid composed of an upper base  13   a  corresponding to a tooth top  13   a , a lower base  13   d  extending from the tooth groove  14 , and a pair of lateral sides  13   b ,  13   c  extending between the upper base  13   a  and the lower base  13   d . The upper base  13   a  and the lateral sides  13   b ,  13   c  are each not limited to a linearly-extending one, and may be curved slightly. 
     The one lateral side  13   b  of each tooth  13  extends parallel to the axis of the bobbin body  11 , whereas the other lateral side  13   c  is inclined with respect to the axis of the bobbin body  11 . 
     Since the teeth  13  of the gear  12  each have a trapezoidal shape when viewed from the side of the bobbin body  11 , the drive gear  32  of the drive shaft  31  can be easily engaged with the gear  12  of the supply bobbin  10  simply by pressing the drive shaft  31  of the thermal transfer printer  50  against the teeth  13  of the gear  12 . 
     Since the one lateral side  13   b  of each tooth  13  extends parallel to the axis of the bobbin body  11 , the gear  12  of the bobbin body  11  can securely engage the drive gear  32  of the drive shaft  31  without displacement as compared to the case where both of the lateral sides of each tooth  13  are inclined with respect to the axis of the bobbin body  11 . If both of the lateral sides of each tooth  13  are inclined with respect to the axis of the bobbin body  11 , the teeth  13  may not securely engage the teeth of the drive gear  32  when the driving force is large. 
     According to this embodiment, on the other hand, the one lateral side  13   b  of each tooth  13  extends parallel to the axis of the bobbin body  11 . Therefore, even when a large driving force is applied from the drive shaft  31  of the thermal transfer printer  50  to the bobbin body  11 , there will occur no disengagement or displacement between the teeth  13  of the gear  12  of the bobbin body  11  and the teeth of the drive gear  32 . 
     The sum of the circumferential lengths of the tooth tops  13   a  of the teeth  13  is 20% to 70%, preferably 20% to 60% of the circumferential length of the bobbin body  11 . If the sum is more than 70%, the circumferential length of each tooth groove  14  is too short for easy engagement between the gear  12  and the drive gear  32 . 
     On the other hand, if the sum is less than 20%, it is difficult to transmit a large driving force from the drive gear  32  to the bobbin body  11 . The sum is set in the above range also in view of the possibility of a user touching the gear. The term “circumferential length” herein refers to the circumferential length in terms of the outer periphery. 
     The thus-constructed bobbin body  11  is disposed coaxially with the drive shaft  31  of the thermal transfer printer  50  and transmits the driving force of the drive shaft  31  in the rotational direction to the bobbin body  11  via the drive gear  32  and the gear  12 . 
     The flange portion  18  to be mounted to the bobbin body  11  will now be described. As shown in  FIGS. 7 and 8 , the flange portion  18  is to be mounted to the other end of the bobbin body  11 , and includes a first flange  18   a , a second flange  18   b , and an engagement portion  18   c  which is formed between the first flange  18   a  and the second flange  18   b  and engages the case  2 . A cylindrical portion  18   d , which is to be inserted into the bobbin body  11 , is coupled to the first flange  18   a.    
     The engagement projections  18   e , which are to engage the engagement grooves  17  of the bobbin body  11 , are provided in the cylindrical portion  18   d  of the flange portion  18  at positions adjacent to the first flange  18   a.    
     The cylindrical portion  18   d  of the flange portion  18  is also provided with axial ribs  18   f  whose height is lower than the height of the engagement projections  18   e  and which extend in the axial direction. The axial ribs  18   f  of the flange portion  18  are to engage axial grooves (not shown) formed in the inner surface of the bobbin body  11 . 
     The thus-constructed flange portion  18  is constructed as a separate member from the bobbin body  11  and mounted to the bobbin body  11 . The supply bobbin  10  is thus constructed. 
     The flange portion  18  has a built-in RFID for identifying the type of the ink ribbon  3  to be supplied. 
     The operation of the thus-constructed ribbon cartridge  1  of this embodiment will now be described. 
     First, the supply bobbin  10  with the ink ribbon  3  wound thereon and the take-up bobbin  20  are prepared. When the ink ribbon  3  is wound on the supply bobbin  10 , it is kept pressed against the supply bobbin  10  by a touch roller. 
     Next, the supply bobbin  10  and the take-up bobbin  20  are set in the case  2 , thereby obtaining the ribbon cartridge (assembly of bobbins and a sheet)  1  including the case  2 , the supply bobbin  10  with the ink ribbon  3  wound thereon, and the take-up bobbin  20 . 
     Next, the ribbon cartridge  1  is set in a mounting section  50 A of the thermal transfer printer  50 . The take-up bobbin  20  of the ribbon cartridge  1  aligns coaxially with the drive shaft  41  of the drive section  40  of the thermal transfer printer  50 , and the supply bobbin  10  aligns coaxially with the drive shaft  31  of the drive section  30  of the thermal transfer printer  50 . 
     Next, the drive section  40  is pressed against the take-up bobbin  20 , whereby the drive gear  42  of the drive section  40  engages the gear flange  22  (the teeth  22   a  formed in the inner peripheral surface) of the take-up bobbin  20 . 
     Similarly, the drive section  30  is pressed against the supply bobbin  10 , whereby the drive gear  32  formed in the drive shaft  31  of the drive section  30  engages the gear  12  of the supply bobbin  10 . 
     Since the teeth  13  of the gear  12  each have a trapezoidal shape when viewed from the side, the drive gear  32  of the drive section  30  can be easily engaged with the gear  12  of the supply bobbin  10  simply by pressing the drive section  30  against the supply bobbin  10 . 
     Next, the supply bobbin  10  is driven by the drive section  30  and the take-up bobbin  20  is driven by the drive section  40 , whereby the ink ribbon  3  wound on the supply bobbin  10  is supplied. The ink ribbon  3 , extending between the supply bobbin  10  and the take-up bobbin  20 , is heated by a thermal head (not shown), whereby the ink of the ink ribbon  3  is transferred onto an image-receiving sheet (not shown). A thermal transfer operation is performed in this manner. 
     As described above, according to this embodiment, the gear  12  having the teeth  13  is formed in one end surface of the bobbin body  11  of the supply bobbin  10 . By engaging the drive gear  32  of the drive section  30  of the thermal transfer printer  50  directly with the gear  12 , the driving force of the drive shaft  31  of the drive section  30  in the rotational direction can be transmitted directly to the bobbin body  11 . 
     Accordingly, there is no need to provide the bobbin body  11  with a flange that engages the drive shaft  31 ; thus, the number of parts can be reduced. Furthermore, there is no need to provide driving irregularities, which engage the drive shaft  31  of the drive section  30 , in the outer surface of the bobbin body  11 . The outer surface of the bobbin body  11  can therefore be a smooth surface. This can avoid scratching on a rubber touch roller which is used to wind the ink ribbon  3  on the supply bobbin  10 . 
     Further, since the teeth  13  of the gear  12  each have a trapezoidal shape when viewed from the side, the drive gear  32  of the drive section  30  can be easily engaged with the gear  12  simply by pressing the drive section  30  against the gear  12 . 
     Variations 
     Variations of the present invention will now be described with reference to  FIGS. 9 and 10 . 
     Though in the embodiment illustrated in  FIGS. 1 through 8  the flange portion  18  is mounted to the other end of the bobbin body  11 , the present invention is not limited to this feature. For example, as shown in  FIG. 9 , it is possible to provide a circumferential groove  28 , which engages the case  2  to perform positioning of the supply bobbin  10 , at the other end of the bobbin body  11 . 
     As shown in  FIG. 9 , as with the embodiment illustrated in  FIGS. 1 through 8 , the gear  12 , consisting of the teeth  13  and the tooth grooves  14  formed between the teeth  13 , is formed at the one end of the bobbin body  11 . 
     As shown in  FIG. 9 , the supply bobbin  10  consists solely of the bobbin body  11  and has no flange portion; thus, the number of parts can be further reduced. 
     Though in the embodiment illustrated in  FIGS. 1 through 8  the flange portion  18  is mounted to the other end of the bobbin body  11 , the present invention is not limited to this feature. For example, as shown in  FIG. 10 , it is possible to provide a pair of circumferential projections  29 , which engages the case  2  to perform positioning of the supply bobbin  10 , at the other end of the bobbin body  11 . 
     As shown in  FIG. 10 , as with the embodiment illustrated in  FIGS. 1 through 8 , the gear  12 , consisting of the teeth  13  and the tooth grooves  14  formed between the teeth  13 , is formed at the one end of the bobbin body  11 . 
     As shown in  FIG. 10 , the supply bobbin  10  consists solely of the bobbin body  11  and has no flange portion; thus, the number of parts can be further reduced. 
     Though in the above-described embodiment the ink ribbon (thermal transfer sheet)  3  is wound on the supply bobbin  10  and on the take-up bobbin  20 , it is also possible to wind an image-receiving sheet on the supply bobbin  10  and on the take-up bobbin  20 . Thus, the supply bobbin  10  and the take-up bobbin  20  may be used as bobbins for an image-receiving sheet. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
           1  ribbon cartridge 
           2  case 
           3  ink ribbon 
           10  supply bobbin 
           11  bobbin body 
           12  gear 
           13  tooth 
           13   a  tooth top 
           13   b ,  13   c  lateral sides 
           13   d  lower base 
           17  engagement groove 
           20  take-up bobbin 
           21  bobbin body 
           22  gear flange 
           30  drive section 
           31  drive shaft 
           32  drive gear 
           40  drive section 
           41  drive shaft 
           42  drive gear 
           50  thermal transfer printer 
           50 A mounting section