Abstract:
A thermal printer capable of easily attaching and detaching a thermal head frame having a thermal head mounted thereon. A thermal printer ( 10 ) in which a thermal head frame ( 34 ) having a thermal head ( 26 ) mounted thereon is attachable to and detachable from a printer body ( 16 ), includes: the thermal head frame has a protrusion ( 34   a ) at one end and a claw portion ( 36   b ) at the other end; a pair of thermal head frame mounting portions ( 40   a ) and ( 40   b ) in the printer body ( 16 ) oppose each other at a distance that is smaller than a width of the thermal head frame ( 34 ); a hole ( 42   a ) in portion ( 40   a ) receives the protrusion and a hole ( 42   b ) in portion ( 40   b ) receives the claw portion; and spring members ( 44   a ) and ( 44   b ) between the pair of thermal head frame mounting portions ( 40   a ) and ( 40   b ) urge the thermal head frame to a position setting the holes ( 42   a,    42   b ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §371 National Phase conversion of PCT/JP2013/054764, filed Feb. 25, 2013, which claims priority of Japanese Patent Application No. 2012-043619, filed Feb. 29, 2012, the contents of which are incorporated by reference herein. The PCT International Application was published in the Japanese language. 
     TECHNICAL FIELD 
     The present invention relates to a thermal printer which performs printing on a sheet using a thermal head, and more particularly to a thermal printer in which a thermal head frame having a thermal head mounted thereon can be attached to and detached from a printer body. 
     BACKGROUND ART 
     There exist thermal printers which perform printing using a thermal head. The thermal head may be a so-called line thermal head in which a number of heating elements are formed on a substrate so as to be arranged in a row, and the arrangement direction of the row of heating elements is perpendicular to a sheet transport direction. 
     A platen roller is disposed to oppose the thermal head, and the thermal head is biased against and comes into pressure contact with the platen roller. A sheet transport path on which sheets are transported is formed between the thermal head and the platen roller. 
     The sheet is printed by the thermal head while being transported as the platen roller rotates. 
     In Patent Literature 1, the thermal head is fixed to a head frame. The head frame is provided in a thermal printer body via a head frame shaft, a coil spring, and the like which are provided in the head frame. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 6-143736 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the thermal head frame having the thermal head mounted thereon, as in Citation Literature 1, has a problem in that it is difficult to attach and detach the thermal head frame to and from the thermal printer body during assembly, maintenance, or the replacement of the thermal head. Typically, the thermal head is damaged by wear, disconnection, or the like due to a long-term use, and the thermal head needs to be replaced. 
     The invention takes the foregoing circumstances into consideration. An object thereof is to provide a thermal printer capable of easily performing operations of attaching and detaching a thermal head frame having a thermal head mounted thereon, preferably without an increase in cost. 
     Solution to Problem 
     According to the invention, a thermal printer in which a thermal head frame having a thermal head mounted thereon is attachable to and detachable from a printer body, includes: a thermal head frame which has a flat protruding portion  34   a  provided at one end thereof and has a claw portion  36   b  provided at the other end thereof; a pair of thermal head frame mounting portions which are provided in the printer body to oppose each other at an interval or distance that is smaller than a width of the thermal head frame and in which a hole into which the protruding portion is inserted and a hole into which the claw portion is inserted are formed; and a spring member which is provided between the pair of thermal head frame mounting portions. According to the invention, a dedicated tool and the like are not necessary for attaching and detaching the thermal head frame having the thermal head mounted thereon, and in a reasonable configuration which should not result in an increase in the cost of the thermal printer, and thus an operation of attaching and detaching the thermal head frame can be easily performed. It is preferable that a protrusion be provided in a part of the thermal head frame where the spring member abuts on the thermal head frame during attachment and detachment. Furthermore, it is preferable that a vertical cross-section of the protrusion between the pair of thermal head frame mounting portions have an arc shape. According to the invention, friction between the parts of the thermal head frame where the spring members from the printer body abut on the thermal head frame and the spring members can be reduced during the attachment and detachment. Thus the thermal head frame having the thermal head mounted thereon is more easily attached to and detached from the printer body. 
     Advantageous Effects of Invention 
     According to the thermal printer according to the invention, it is possible to provide a thermal printer that is capable of easily performing the operation of attaching and detaching the thermal head frame having the thermal head mounted thereon preferably without an increase in cost. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic side view of the configuration of a thermal printer according to an embodiment of the invention. 
         FIG. 2  is a perspective view illustrating a thermal head frame on which a thermal head of the thermal printer according to the embodiment of the invention is mounted. 
         FIG. 3  is a schematic front view of the thermal printer according to the embodiment of the invention. 
         FIGS. 4(A) to 4(C)  are schematic front views illustrating a process of attaching and detaching the thermal printer according to the embodiment of the invention. 
         FIG. 5  is a perspective view illustrating a rear surface of the thermal head frame on which the thermal head of the thermal printer according to the embodiment of the invention is mounted. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a preferred embodiment of a thermal printer according to the invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic side view of the configuration of a thermal printer  10  according to the invention. The thermal printer  10  is a printer which prints and issues predetermined information on an upward label surface of a label  12 . 
     The label  12  is guided to a label guide which is comprised of an upper guide plate  20  and lower guide plates  22  and  23 , and the label is fed to a printing unit  30  comprising a thermal head  26  and a platen roller  28 . The rotatable shaft of the platen roller  28  is connected to the drive shaft of a motor which is rotatable normally and reversely via a timing belt or a gear (not illustrated). When the drive shaft is rotated, its rotational force is transmitted to the platen roller  28  via the timing belt or the gear, which transports the label  12  in the arrow A direction (from the upstream side to the downstream side in the transport direction) in  FIG. 1 . 
     A printer body  16  of the thermal printer  10  is generally comprised by a printer lower portion  16   a  and a printer upper portion  16   b . The printer upper portion  16   b  can be opened and closed. 
     The printing unit  30  is comprised of the thermal head  26  and the platen roller  28  which are arranged to oppose each other with a label transport path  32  interposed therebetween. 
     The thermal head  26  is a so-called line thermal head in which a number of heating elements (not illustrated) are formed on a substrate (not illustrated) to be arranged in a row, and the thermal head is provided in such a manner that the arrangement direction of the heating elements is perpendicular to the label transport direction. At the surface of the substrate which is opposed to the surface where the heating elements are formed, a heat sink which is formed of metal to have conductivity is attached. 
     The thermal head  26  includes a connector (not illustrated) for a power source and a printing signal, and a wiring connector (not illustrated) from the printer body  16  is connected to the connector. 
     As illustrated in  FIG. 2 , the thermal head  26  is mounted on a thermal head frame  34  to which the thermal head  26  is fixed. 
     The thermal head frame  34  a flat portion  34   a  is provided at one end of the thermal head frame  34 , and an L-shaped claw portion  34   b  is provided at the other end thereof. 
     As illustrated in  FIG. 3 , a pair of thermal head frame mounting portions  40   a  and  40   b  are mounted in the printer upper portion  16   b  of the printer body  16 . In the thermal head frame mounting portions  40   a , there is a respective hole  42   a  into which the flat protruding portion  34   a  of the thermal head frame  34  is inserted. In the portion  40   b , there is a respective hole  42   b  into which the L-shaped claw portion  34   b  is inserted. 
     The pair of thermal head frame mounting portions  40   a  and  40   b  oppose each other at a distance which is smaller than the width of the thermal head frame  34 . Specifically, the pair of thermal head frame mounting portions  40   a  and  40   b  are separated at an interval which is equal to or greater than the width obtained by subtracting the width of the convex portion  34   a  from the width of the thermal head frame  34 . 
     Spring members  44  and  44  are provided between the pair of thermal head frame mounting portions  40   a  and  40   b.    
     The action of the thermal printer of this embodiment configured as described above is described. 
     First, the thermal head  26  is mounted by mounting the thermal head frame  34  having the thermal head  26  mounted thereon (see  FIGS. 4(A) to 4(C) ). The thermal head frame  34  having the thermal head  26  mounted thereon is mounted in a state where the printer upper portion  16   b  is opened and the thermal head  26  is separated from the platen roller  28 . 
     First, the flat protruding portion  34   a  of the thermal head frame  34  is inserted into the hole  42   a  of the thermal head frame mounting portion  40  provided in the printer upper portion  16   b  ( FIG. 4(A) ). Subsequently, while the spring members  44  and  44  are pressed upward by protrusions  36  and  36 , which will be described later, formed on a rear surface  35  of the thermal head frame  34  against the biasing forces of the spring members  44  and  44 , the thermal head frame  34  is shifted toward the hole  42   b  of the thermal head frame mounting portion  40   b , and the L-shaped claw portion  34   b  of the thermal head frame  34  is inserted into the hole  42   b  of the thermal head frame mounting portion  40   b  ( FIG. 4(B) ). Accordingly, the thermal head frame  34  having the thermal head  26  mounted thereon can be mounted in the printer body  16  ( FIG. 4(C) ). By engaging the L-shaped claw portion  34   b  with the hole  42   b , movement of the heating elements of the thermal head frame  34  in the arrangement direction with respect to the thermal head frame mounting portions  40   a  and  40   b  is restricted. In addition, since the biasing forces of the spring members  44  and  44  are applied to the rear surface  35  of the thermal head frame  34 , the claw portion  34   b  is fixed by being engaged with the hole  42   b  while abutting on the inner wall of the hole  42   b.    
     In  FIGS. 3 to 4(C) , a gap (see  FIG. 4(C) ) is provided between the thermal head frame mounting portion  40   b  and the end surface of the thermal head  26 . In practice, it is preferable that a gap B between the L-shaped claw portion  34   b  and the end surface of the thermal head  26  be approximately equal to the thickness of the thermal head frame mounting portion  40  so that there is substantially no gap between the thickness of the thermal head frame mounting portion  40  and L-shaped claw portion  34   b . In this structure, the movement of the heating elements of the thermal head frame  34  in their arrangement direction can be reliably restricted. 
     Since the biasing forces are always applied to the thermal head frame  34  by the biasing actions of the spring members  44  and  44 , backlash of the thermal head  26  in the longitudinal direction and in the direction perpendicular to the longitudinal direction can be prevented. Thereafter, when the printer upper portion  16   b  is closed, the operation of mounting the thermal head frame  34  having the thermal head  26  mounted thereon is finished, and the biasing forces of the spring members  44  and  44  are applied to the platen roller  28  side such that an appropriate printing pressure is applied. 
     Next, the thermal head frame  34  having the thermal head  26  mounted thereon is also removed in the state where the printer upper portion  16   b  is opened and the thermal head  26  is separated from the platen roller  28 . In this state, the thermal head frame mounting portion  40   b  is slid toward the thermal head frame mounting portion  40   a  side in the state where the L-shaped claw portion  34   b  is pushed into the hole  42   b  as in  FIG. 4(C)  so that the claw portion  34   b  is removed from the hole  42   b . Accordingly, the engagement between the L-shaped claw portion  34   b  and the thermal head frame mounting portion  40   b  is released, and the thermal head frame  34  having the thermal head  26  mounted thereon can be removed by performing the operations of  FIGS. 4(C) ,  4 (B), and  4 (A) in this order. 
     As described above, according to the thermal printer of the invention, the operation of attaching and detaching the thermal head  26  to and from the printer body  16  can be very easily performed, and the positioning of the thermal head  26  can be easily performed. Particularly, a dedicated tool and the like are not necessary for attaching and detaching the thermal head frame  34  having the thermal head  26  mounted thereon. In addition, the thermal head frame  34  having the thermal head  26  mounted thereon according to the invention has a reasonable configuration which does not result in an increase in cost of the thermal printer. 
     In the invention, as illustrated in  FIG. 3  or  FIGS. 4(A) to 4(C) , it is preferable that the protrusions  36  and  36  be provided in parts of the rear surface  35  of the thermal head frame  34  where the spring members  44  and  44  abut on the thermal head frame  34  during the attachment and detachment of the thermal head frame  34 . Furthermore, as illustrated in  FIG. 5 , it is preferable that the protrusions  36  in vertical cross-sections A-A have an arc shape, extending along the head frame in the direction between the ends thereof. In addition, it is preferable that the protrusions  36  and  36  be formed to have lengths along the head frame over the parts on which the spring members  44  and  44  abut when the thermal head frame  34  is slid during the attachment and detachment of the thermal head frame  34 . 
     Since the protrusions  36  and  36  are provided in the parts where the spring members  44  and  44  abut on the thermal head frame  34  during the attachment and detachment as described above, friction between the parts of the thermal head frame  34  where the spring members  44  and  44  abut on the thermal head frame  34  and the spring members can be reduced during the attachment and detachment, and thus the thermal head frame  34  having the thermal head mounted thereon is more easily attached to and detached from the printer body  16 . As illustrated in  FIG. 4(B) , the thermal head frame  34  is shifted toward the hole  42   b  side by the protrusions  36  and  36  in a state of being pressed against the biasing forces of the spring members  44  and  44 . At this time, the tip ends of the spring members  44  and  44  come into contact with the apexes of the protrusions  36  and  36  of which the vertical cross-sections have the arc shape, and thus friction generated when the thermal head frame  34  is shifted toward the hole  42   b  side is reduced. Accordingly, the thermal head frame  34  can be easily mounted. In addition, the friction can also be reduced during the removal, and thus the attachment and detachment can be easily performed. 
     The configuration of the thermal printer described above in the embodiment is not limited to the above-described embodiment. For example, in the figures of this embodiment, two spring members  44  are illustrated. However, one spring member or two or more spring members may be provided. In addition, in the figures of this embodiment, the spring member  44  is illustrated as a member formed by a spring. However, the spring member may be, for example, a leaf spring. 
     In addition, in this embodiment, the thermal printer is exemplified so that the label is fed from the outside of the thermal printer. However, the application of the invention is not limited thereto. For example, as a matter of course, a label roll may be supported by a thermal printer body. 
     REFERENCE SIGNS LIST 
       10  thermal printer 
       12  label 
       16  printer body 
       16   a  printer lower portion 
       16   b  printer upper portion 
       20  upper guide plate 
       22  lower guide plate 
       23  lower guide plate 
       26  thermal head 
       28  platen roller 
       30  printing unit 
       32  label transport path 
       34  thermal head frame 
       34   a  convex portion 
       34   b  claw portion 
       35  rear surface of thermal head frame 
       40   a ,  40   b  thermal head frame mounting portion 
       42   a ,  42   b  hole 
       44  spring member