Abstract:
A thermal printer including a thermal head, a platen roller, a frame having platen roller receiving parts that receive the platen roller in a detachable manner, is disclosed. The thermal head is fixed to a thermal head supporting member that is operatively coupled to the frame. The thermal head supporting member includes platen roller lock parts that lock the platen roller received by the platen roller receiving part so as to resist or prevent the platen roller from exiting the platen roller receiving part.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to thermal printers and apparatuses having a thermal printer, and more particularly, to a thermal printer in which a platen roller is detachable from a frame. 
     2. Description of the Related Art 
     Regarding thermal printers mounted in hand-held devices and POS terminals, a clamshell type that allows easy setting of a paper roll is becoming the mainstream. In the clamshell type, when a cover is rotated and closed, a platen roller is pressed against a thermal head via paper and is fit and fixed to a frame. Thus, it is necessary to provide a lock mechanism so that the fixed platen roller not be easily separated from the frame. 
     FIG. 1 shows a thermal printer  10  of a conventional clamshell type. In FIG. 1, the thermal printer  10  includes a frame  11 , a platen roller  12 , a thermal head  13 , a paper roll  14 , paper  15  (a part of the paper roll  14 ), a lock arm  16 , a cam  17 , an operation lever  18 , and a spring  19 . 
     The platen roller  12  is moved downward from above, and pressed against the thermal head  13  via the paper  15 . On this occasion, a shaft  12   a  of the platen roller  12  provided at an end of the platen roller  12  is fit into a U-shaped slot  11   a  of the frame  11  and locked by the lock arm  16 . 
     For setting a new paper roll  14 , an operator operates the operation lever  18  so as to rotate the cam  17  and rotate the lock arm  16  for a little in the clockwise direction. Consequently, the lock of the shaft  12   a  is released (for example, refer to Japanese Laid-Open Patent Application No. 2000-318260, paragraph No. 0015, FIG.  2 ). 
     The thermal printer  10  shown in FIG. 1 is additionally provided with three dedicated components, that is, the lock arm  16 , the cam  17 , and the operation lever  18 , in order to lock and release the platen roller  12 . Thus, there is a problem in that the increase in the number of components increases the manufacturing cost, the assembly processes, and the size and weight of the thermal printer. 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide an improved and useful thermal printer, and an apparatus having the thermal printer, in which the above-mentioned problems are eliminated. 
     In order to achieve the above-mentioned object, according to one aspect of the present invention, there is provided a thermal printer that includes: 
     a thermal head; 
     a platen roller; 
     a frame having platen roller receiving parts that receive the platen roller in a detachable manner; and 
     a thermal head supporting member to which the thermal head is fixed, the thermal head supporting member being operatively coupled to the frame, 
     the thermal head supporting member including platen roller lock parts that lock the platen roller received by the platen roller receiving parts so as to resist or prevent the platen roller from exiting the platen roller receiving part. 
     Accordingly, components dedicated to locking the platen roller are not required, which is advantageous for reducing the size of a thermal printer. Moreover, since the number of assembly processes is decreased, it is possible to reduce manufacturing costs. 
     Also, in a thermal printer, the thermal head supporting member may include platen roller lifting parts that move the platen roller in the direction in which the platen roller exits the platen roller receiving parts when the thermal head is moved in the direction in which the thermal head is separated from the platen roller. 
     Accordingly, components dedicated to lifting (pushing up) the platen roller in the direction in which the platen roller exits the platen roller receiving parts are not required, which is advantageous for reducing the size of a thermal printer. Moreover, the number of assembly processes is decreased. Thus, it is possible to reduce manufacturing costs. 
     In addition, in a thermal printer, the thermal head supporting member may include an operation part that displaces the thermal head in a direction in which the thermal head is separated from the platen roller. 
     Accordingly, it is possible to simplify the construction of a part operated so as to displace the thermal head supporting member. 
     Further, the thermal head supporting member may include a head pressure biasing spring portion that biases head pressure whereby the thermal head presses the platen roller. 
     Accordingly, head pressure biasing spring members are not required, which is advantageous for reducing the size of a thermal printer. Moreover, the number of assembly processes is decreased. Thus, it is possible to reduce manufacturing costs 
     Additionally, a thermal printer may further include: 
     a head pressure biasing spring member for pressing the thermal head supporting member so as to bias head pressure whereby the thermal head presses the platen roller, and 
     the head pressure biasing spring member may include a spring portion that is pressed and deflected by the platen roller received in the platen roller receiving parts, and when the lock of the platen roller is released, restored so as to move the platen roller in the direction in which the platen roller exits the platen roller receiving part. 
     Accordingly, it is possible to realize, with a small number of components, a thermal printer in which the platen roller pops up when the lock of the platen roller is released. 
     Furthermore, according to another aspect of the present invention, there is provided an apparatus that includes: 
     a thermal printer including: 
     a thermal head; 
     a platen roller; 
     a cover supporting the platen roller, the cover being rotatably opened and closed; 
     a frame having platen roller receiving parts that receive the platen roller in a detachable manner, the platen roller being received by the platen roller receiving parts when the cover is closed; and 
     a thermal head supporting member to which the thermal head is fixed, the thermal head supporting member being operatively coupled to the frame, 
     the thermal head supporting member including platen roller lock parts that lock the platen roller received by the platen roller receiving part so as to resist or prevent the platen roller from exiting the platen roller receiving part. 
     Accordingly, since the size of the thermal printer is reduced, the size of the apparatus is also reduced. 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view showing a conventional thermal printer; 
     FIG. 2 is a perspective view showing a hand-held device according to one embodiment of the present invention; 
     FIGS. 3A and 3B are side views showing the operation of closing a cover of a clamshell type thermal printer; 
     FIGS. 4A and 4B are side views showing the operation of opening the cover of the clamshell type thermal printer; 
     FIG. 5 is a perspective view showing a thermal printer unit; 
     FIGS. 6A and 6B are perspective views showing a thermal head supporting member; 
     FIG. 7 is a side view showing the shapes of a lock part and a lifting part in an enlarged manner; 
     FIGS. 8A,  8 B,  8 C, and  8 D are side views showing an operation in which a platen roller is locked when closing the cover; 
     FIGS. 9A,  9 B,  9 C, and  9 D are side views showing the operation in which a lock of the platen roller is released and the platen roller is lifted; 
     FIGS. 10A and 10B are a perspective view and a side view, respectively, showing a first variation of the thermal head supporting member; 
     FIGS. 11A and 11B are a perspective view and a side view, respectively, showing a second variation of the thermal head supporting member; 
     FIG. 12 is a perspective view showing a third variation of the thermal head supporting member; 
     FIGS. 13A,  13 B, and  13 C are side views showing a thermal printer unit in which the thermal head supporting member shown in FIG. 12 is incorporated; and 
     FIG. 14 is a perspective view showing a fourth variation of the thermal head supporting member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 shows a hand-held device  30  according to one embodiment of the present invention. In FIG. 2, X 1 -X 2  indicates the width direction, Y 1 -Y 2  indicates the longitudinal direction, and Z 1 -Z 2  indicates the height direction. The hand-held device  30  is provided with a line thermal printer  40  of a clamshell type on Y 1  side and includes a liquid crystal display part  31 , key switches  32 , and an operation knob  33  at the top surface. 
     FIGS. 3A and 3B show a closing operation of the clamshell type thermal printer  40 , and FIGS. 4A and 4B show an opening operation of the clamshell type thermal printer  40 . As shown in FIG. 3A, the clamshell type thermal printer  40  is formed by a case  42 , a cover  44  that can be opened/closed and is supported by the case  42  via a shaft  43  at one end, and a thermal printer unit  50  (shown in greater detail in FIG. 5) fixed to the case  42 . A paper roll holding part  41  holding a paper roll is formed in the case  42 . The cover  44  covers the paper roll holding part  41 . A platen roller  60  is supported at the head of the cover  44 . 
     As is shown in FIG. 5, in the thermal printer unit  50 , a motor  52  and a gear box  53  are fixed to a frame  51 . Moreover, a thermal head supporting member  55  to which a thermal head  54  shown in FIGS. 6A and 6B is fixed, and a head pressure biasing spring member (hereinafter referred to as a “spring member”)  56  that is a leaf spring are operatively coupled to the frame  51  of the thermal printer unit  50 , for example, in the manner illustrated in FIG.  5 . Further, a flexible print cable  57  extends from the thermal head  54 , and a platen roller  60  is fixed to the frame  51  in a detachable manner. The thermal head supporting member  55  serves to support the thermal head  54  and serves as a heat sink that diffuses heat generated in the thermal head  54 . It should be noted that the present invention includes the thermal printer unit  50 . 
     As is shown in FIG. 3A, the lower side of the thermal head supporting member  55  is interposed between and supported by pivots  51   a  and  51   b . Pin parts  55   a  and  55   b  shown in FIG. 6A, provided on both upper sides of the thermal head supporting member  55 , are fit to slots  51   c  and  51   d  (only one of which is shown). The spring member  56  forms a V-shape, is mounted between the thermal head supporting member  55  and the frame  51 , and presses the thermal head  54  against the platen roller  60 . 
     The platen roller  60  includes shaft parts  60   a  and  60   b  at its opposite ends and includes a gear  60   c  on one end. The platen roller  60  is supported by the frame  51  such that the shaft parts  60   a  and  60   b  are fit to respective platen roller receiving parts  51   e  and  51   f  of the frame  51 , the receiving parts  51   e  and  51   f  each being formed into a U-shape slot. The gear  60   c  is engaged with an output gear (not shown) of the gear box  53 . 
     In accordance with the present invention, the thermal head supporting member  55  can be pivoted, as illustrated, over a predetermined range of angles with respect to the frame  51  via the pin parts  55   a  and  55   b  sliding within the corresponding slots  51   c  and  51   d , and a bottom portion of the thermal head supporting member  55  being guided by the pivots  51   a  and  51   b . The thermal head supporting member  55  is formed by performing press work on a metal plate. The thermal head supporting member  55  includes arm parts  70  and  75  extending in the direction indicated by Y 1  (hereinafter referred to as the “Y 1  direction”) at both ends and also includes an arm part  80  in the middle as an operation part extending in the Y 2  direction. As shown in FIG. 3A, the operation knob  33  is fit to a rising part  81  at an end of the arm part  80 . Bifurcate portions  71  and  76  are provided at the tips of the arm parts  70  and  75 , respectively. The bifurcate portion  71  includes an upper platen roller lock part (hereinafter referred to as a “lock part”)  72  and a lower platen roller lifting part (hereinafter referred to as a “lifting part”)  73 . The bifurcate portion  76  includes an upper platen roller lock part (hereinafter referred to as a “lock part”)  77  and a lower platen roller lifting part  78 . The lock part  72  and the lifting part  73  are located at the position corresponding to the platen roller receiving part  51   e . The platen roller lock part  77  and the platen roller lifting part  78  are located at the position corresponding to the platen roller receiving part  51   f.    
     In the description that follows, the operation of the thermal printer is described with reference to the X 1  portion of the thermal printer (for example, the shaft part  60   a , the bifurcate portion  71 , and the platen roller receiving part  51   e ). For sake of brevity, the description relating to the X 2  portion (for example, the shaft part  60   b , the bifurcate portion  76 , and the platen roller receiving part  51   f ) is omitted. 
     FIG. 7 shows the shapes of the lock part  72  and the lifting part  73  in an enlarged manner, in conjunction with the shaft part  60   a  and the platen roller receiving part  51   e.    
     The platen roller receiving part  51   e  includes an arcuate bottom portion  51   e   1  having a point O 1  as the center. The reference numeral  90  designates the center line of the platen roller receiving part  51   e , which center line is drawn through the point O 1  and extends in the directions indicated by Z 1 -Z 2 . The reference numeral  91  designates a line drawn through the point O 1  and orthogonal to the center line  90 . The line  91  extends in the directions indicated by Y 1 -Y 2 . In FIG. 7, the two-dot chain line indicates the shaft part  60   a  assuming that the platen roller  60  is mounted. 
     The lock part  72  extends into the platen roller receiving part  51   e  in the Y 1  direction at a position above the shaft part  60   a . That is, the lock part  72  extends alongside the platen roller receiving part  51   e  and into a X 1 -X 2  projecting path of the platen roller receiving part  51   e . A tip  72   a  of the lock part  72  is displaced in the Y 1  direction relative to the center line  90  by a distance ΔY. A tangent line  72   b  is declined downward to the right, that is, declined in the direction indicated by Z 2  (hereinafter referred to as the “Z 2  direction”) as the tangent line  72   b  extends in the Y 1  direction. The tangent line  72   b  intersects the line  91  at an angle θ. The upper surface of the lock part  72  is referred to herein as an inclined surface  72   c.    
     The lifting part  73  extends in the Y 1  direction to form an upward sloping arc-like shape that is lower in the Z 2  direction than the platen roller receiving part  51   e . A tip  73   a  of the lifting part  73  is located farther in the Y 1  direction than the platen roller receiving part  51   e . Moreover, the tip  73   a  of the lifting part  73  is displaced in the direction indicated by Z 1  (hereinafter referred to as the “Z 1  direction”) relative to the lowermost portion of the bottom portion  51   e   1  of the platen roller receiving part  51   e  by a distance Δz. A spacing  100  in the directions indicated by Y 1 -Y 2  exists between the lifting part  73  and the platen roller receiving part  51   e . The spacing  100  enables lock release and lifting (pushing up)(that are described below) to be performed with desired timing. 
     Next, a description will be given of the opening and closing operations of the cover  44  of the clamshell type thermal printer  40 , and the operations of the bifurcate portions  71  and  76  then. 
     The paper roll  110  is set inside the paper roll holding part  41 , and the cover  44  is pivoted to be closed with the paper  111  pulled out. The cover  44  is rotated from the state shown in FIG. 3A to a substantially closed position as shown in FIG. 3B as an initial stage in which the shaft part  60   a  of the platen roller  60  enters the platen roller receiving part  51   e  from the Z 1  side, and contacts and is supported by the upper surface of the lock part  71 . In this state, the operator manually presses the cover  44 . With this operation, the cover  44  is pivoted to a final position shown in FIG. 4A, at which the cover  44  is completely closed, and locked by the lock part  71  at the position then as a final stage. On this occasion, the spring member  56  causes the thermal head  54  and the platen roller  60  to press towards each other with the paper  111  interposed therebetween. In addition, in a last stage of the pivot of the cover  44 , the spring member  56  is temporarily elastically deformed as shown in FIG. 4B, and the thermal head supporting member  55  is rotated in the counterclockwise direction. 
     FIGS. 8A through 8D show the operation of the bifurcate portion  71  then in an enlarged manner. As is shown in FIG. 8A, the shaft part  60   a  of the platen roller  60  enters, from the Z 1  side, the platen roller receiving part  51   e . Then, as shown in FIG. 8B, the shaft part  60   a  contacts the inclined surface  72   c  of the lock part  72  and urges the lock part  72  in the direction indicated by Y 2  (hereinafter referred to as the “Y 2  direction”). Thereafter, as shown in FIG. 8C, the shaft part  60   a  makes the lock part  72  retract from the platen roller receiving part  51   e . The shaft part  60   a  slides by the lock part  72  and reaches the bottom portion  51   e   1  as shown in FIG.  8 D. 
     After the shaft part  60   a  slides by the lock part  72 , the bifurcate portion  71  is displaced in the Y 1  direction by the spring force of the spring member  56 , and as shown in FIG. 8D, the lock part  72  comes above the shaft part  60   a  and locks the shaft part  60   a . That is, the lock part  72  restricts the shaft part  60   a  from being displaced in the Z 1  direction and locks the shaft part  60   a  with respect to the bottom portion  51   e   1  of the platen roller receiving part  51   e . Similarly, the bifurcate portion  76 , which is on the other side, locks the shaft part  60   b.    
     Here, the tip  72   a  of the lock part  72  locks the shaft part  60   a  at a position Q 1  that is displaced from the peak P in the Y 1  direction. Thus, even if a force in the Z 1  direction, urging the shaft part  60   a  to exit from the platen roller receiving part  51   e , is exerted due to dropping impact, for example, a component force in the Y 2  direction is not generated in the lock part  72 . That is, the lock part  72  fully locks the shaft part  60   a.    
     Hence, the platen roller  60  is locked such that the shaft parts  60   a  and  60   b  on both ends are locked by the lock parts  72  and  77 , respectively. Thus, even if the hand-held device  30  is erroneously dropped, for example, the cover  44  is not opened. 
     In addition, since the lock part  72  is temporarily retracted by the shaft part  60   a , the thermal head  54  is temporarily separated from the platen roller  60 , and then contacts the platen roller  60 . However, since the platen roller  60  is made of rubber, the impact then is small and insignificant. 
     When the paper roll  110  is used up and a new paper roll  110  needs to be set, the operator pulls the operation knob  33  in the Y 2  direction in the state shown in FIG.  4 A. With this operation, as shown in FIG. 4B, the thermal head supporting member  55  is translated in the counterclockwise direction, that is, in the direction in which the thermal head supporting member  55  becomes substantially perpendicular. Thus, the lock of the shaft part  60   a  is released and the cover  44  can be opened. Moreover, the shaft part  60   a  is lifted (pushed up) by the lifting part  73 , and the cover  44  is lifted a relatively small amount. In this state, the operator manually opens the cover  44 . 
     FIGS. 9A through 9D show the operation then of the bifurcate portion  71  in an enlarged manner. The bifurcate portion  71  is moved substantially in the Y 1  direction from the state shown in FIG.  9 A. As shown in FIGS. 9B and 9C, on one hand, the lock part  72  is displaced such that the lock part  72  exits from the platen roller receiving part  51   e  in the Y 2  direction, and thus the lock of the shaft part  60   a  is gradually released. On the other hand, the lifting part  73  is displaced in the Y 2  direction, enters the platen roller receiving part  51   e , and contacts and lifts the lower portion of the shaft part  60   a . Finally, as shown in FIG. 9D, the lock part  72  exits from the platen roller receiving part  51   e  and the lock of the shaft part  60   a  is released. Moreover, the tip  73   a  of the lifting part  73  lifts the shaft part  60   a  for ΔZ. 
     As described above, the lock parts  72  and  77 , and the lifting parts  73  and  78  are parts of the thermal head supporting member  55 . Thus, components dedicated to locking of the platen roller  60  are not used. Accordingly, compared with conventional printers, it is possible to manufacture the thermal printer  40  with a smaller size and less weight without increasing the number of components, thus, with less assembly processes and at lower manufacturing cost. 
     It should be noted that the thermal printer  40  may be applied to not only the hand-held device  30 , but also stationary apparatuses. 
     Next, a description will be given of variations of the thermal head supporting member  55 . 
     FIGS. 10A and 10B show a thermal head supporting member  55 A according to a first variation of the thermal head supporting member  55 . 
     The thermal head supporting member  55 A differs from the thermal head supporting member  55  shown in FIGS. 6A,  6 B, and  7  in lock parts  72 A and  77 A. The lock parts  72 A and  77 A are shorter than the lock parts  72  and  77 . As shown in FIG. 10B, the tip  72 Aa of the lock part  72 A locks the shaft part  60   a  at a position Q 2  that is displaced from the peak P in the Y 2  direction by a distance ΔY. In other words, the lock part  72 A locks the shaft part  60   a  in a state where a component force in the Y 2  direction is generated in the lock part  72 A if a force in the Z 1  direction is exerted on the platen roller  60 . The lock part  77 A thereby locks the shaft part  60   a  in a similar manner. 
     When a strong force is exerted on the platen roller  60  in the Z 1  direction, the shaft part  60   a  pushes away the lock part  72 A in the Y 2  direction and is separated from the platen roller receiving part  51   e . That is, the platen roller  60  is locked by simple locking. 
     FIGS. 11A and 11B show a thermal head supporting member  55 B according to a second variation of the thermal head supporting member  55 . 
     The thermal head supporting member  55 B differs from the thermal head supporting member  55  shown in FIGS. 6A,  6 B, and  7  in that the thermal head supporting member  55 B does not include the lifting parts  73  and  78 . The thermal head supporting member  55 B includes the lock parts  72  and  77 . The lock part  72  locks the shaft part  60   a  as shown in FIG.  11 B. The lock part  77  locks the shaft part  60   a  in a similar manner. 
     FIG. 12 shows a thermal head supporting member  55 C according to a third embodiment of the thermal head supporting member  55 . 
     The thermal head supporting member  55 C is formed such that head pressure biasing coil springs (head pressure biasing spring members)  120  and  121  are fixed to the back surface of the thermal head supporting member  55 B shown in FIGS. 11A and 11B. The head pressure biasing coil springs  120  and  121  include wire-like spring portions  120   a  and  121   a  extending in the Y 1  direction, respectively. The wire-like spring portions  120   a  and  121   a  possess functions of popping up the shaft parts  60   a  and  60   b , respectively. 
     As is shown in FIG. 13A, the thermal head supporting member  55 C is incorporated in a thermal printer unit  50 A. The wire-like spring portions  120   a  and  121   a  cross the platen roller receiving part  51   e.    
     As is shown in FIG. 13B, in the state where the platen roller  60  is locked and fixed, the wire-like spring portion  120   a  is elastically deformed (deflected) in the Z 2  direction. When the lock is released as shown in FIG. 13C, the platen roller  60  is popped up by the spring force of the wire-like spring portion  120   a.    
     FIG. 14 shows a thermal head supporting member  55 D according to a fourth variation of the thermal head supporting member  55 . 
     In the thermal head supporting member  55 D, in addition to the lock parts  72  and  77 , the lifting parts  73  and  78 , and the arm part  80 , a pair of leaf spring portions  130  and  131  are formed out of the back surface, as by cutting, and project from the back surface at a non-zero angle relative thereto. The leaf spring portions  130  and  131  bias head pressure. Thus, the spring member  56  in FIG. 3A is not required. Accordingly, the number of components of the thermal printer  40  is further reduced. 
     Additionally, in order to form the leaf spring portions  130  and  131 , the material of the thermal head supporting member  55 D preferably is relatively thinner than normal (for example, the material of the aforementioned thermal head supporting members  55 ,  55 A,  55 B or  55 C). Moreover, since the leaf spring portions  130  and  131  are formed, the area where the thermal head  54  contacts the thermal head supporting member  55 D is decreased, resulting in slight degradation of the function of the thermal head supporting member  55 D as a heat sink. The degradation of the function as a heat sink, however, does not present a problem in thermal printers that are not used continuously. 
     The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 2002-367091 filed on Dec. 18, 2002, the entire contents of which are hereby incorporated by reference.