Abstract:
To provide a thermal printer in which cutting performance with respect to a recording sheet is enhanced, a thermal printer ( 1 ) includes a thermal head ( 34 ) for performing printing on successively supplied recording sheets, a platen roller ( 65 ) for feeding the recording sheets, and a cutter for cutting the recording sheets. The thermal printer includes: a fixed blade ( 30 ) and a movable blade ( 10 ) that constitutes the cutter; a main body unit ( 4 ) which supports the fixed blade ( 30 ); a cover unit ( 3 ) which is removable with respect to the main body unit ( 4 ) and which supports the movable blade ( 10 ); and a pinion gear ( 42 ) which meshes with a rack ( 44 ) constructed integrally with the movable blade ( 10 ) to move the movable blade ( 10 ), wherein the main body unit ( 4 ) supports the pinion gear ( 42 ), and the cover unit ( 3 ) supports only the movable blade ( 10 ) and the platen roller ( 65 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a printer. 
         [0003]    2. Description of the Related Art 
         [0004]    Various types of thermal printers that perform printing by pressing a thermal head against a thermal recording sheet and emit color by heating are currently provided. In particular, the thermal printers are suitably used for printing various types of labels, receipts, tickets, and the like because printing of smooth characters and colorful graphic printing can be realized without using toner, ink, and the like. 
         [0005]    As represented by a thermal printer, various printers with cutter, which is provided with a cutter for cutting the printed recording sheet, are known. The cutter (auto cutter) including a drive source is normally set to automatically cut the recording sheet when the printing is completed, and hence the cut recording sheet can be rapidly used as receipt, ticket, and the like. 
         [0006]    The thermal printer is used while being incorporated in a cash register, portable terminal device, and the like. 
         [0007]    The thermal printer includes a casing provided with a housing unit for a roll-type recording sheet (roll sheet), and an open/close door of the roll sheet housing unit. A casing is mounted with a main body unit, and the open/close door is mounted with a cover unit. The main body unit supports a thermal head and the cover unit supports a platen roller for feeding the roll sheet. The thermal printer also includes a platen drive system for rotatably driving the platen roller. 
         [0008]    The cutter includes a fixed blade, and a movable blade that linearly moves so as to approach to or separate from the fixed blade. For instance, the fixed blade is supported by the main body unit, and the movable blade is supported by the cover unit. When cutting the recording sheet, the recording sheet is sandwiched and cut with both blades like with scissors by moving the movable blade toward the fixed blade. 
         [0009]    The thermal printer also includes a movable blade drive system for moving the movable blade. The movable blade drive systems adopting a rack-pinion type, a cam type, or the like are known. The movable blade drive system adopting the rack-pinion type includes a rack constructed integrally with the movable blade, a pinion gear that meshes with the rack, and a pinion drive system for driving the pinion gear. 
         [0010]    Patent Document JP 2001-121764 A describes a printer in which the movable blade drive system is mounted on the cover unit. In the invention of Patent Document JP 2001-121764 A, the weight load applies on the hinge portion of the open/close door because the cover unit becomes heavy, and may be detrimental to the opening/closing operation of the open/close door due to change over time. Further, the electrical wiring of the movable blade drive system is formed on the main body side, and hence the wiring may break in accordance with the opening/closing of the cover. The drive system may break down due to vibration and impact in opening and closing. 
         [0011]    Patent Document 2 describes a printer in which part of the movable blade drive system is mounted on the cover unit.  FIG. 8B  is a schematic configuration diagram of the printer described in Patent Document JP 2004-237555 A. In this printer, at least a rack  44  and a pinion gear  42  of the movable blade drive system are mounted to a cover unit  3 . This printer has a driving wheel train mechanism mounted to the cover unit that is subjected to vibration and impact in opening and closing, and thus may break down. 
         [0012]    In both inventions of Patent Documents 1 and 2, an acting point for moving the movable blade is at a backward position of the movable blade (movable blade push-out method). In this case, a large rotational moment acts on the cover unit due to a sheet cutting reaction force that acts from the fixed blade to the movable blade and a frictional force between the fixed blade and the movable blade. Due to such rotational moment, bite occurs in a direction the fixed blade and the movable blade open, the pressure between the fixed blade and the movable blade lowers, and the cutting operation becomes unstable. As a result, the cutting performance lowers. 
       SUMMARY OF THE INVENTION 
       [0013]    In view of the above-mentioned problem, it is an object of the present invention to provide a printer in which the cutting performance with respect to the recording sheet is enhanced. 
         [0014]    In order to solve the above-mentioned problem, a printer according to the present invention is provided with: a main body unit which supports one of a thermal head and a platen roller and one of a movable blade constructed integrally with a rack and a fixed blade; a cover unit which supports another of the thermal head and the platen roller and another of the movable blade and the fixed blade, which are not supported by the main body unit; and a movable blade drive mechanism for driving the movable blade and a platen drive mechanism for driving the platen roller, wherein: a pinion gear rotated by the movable blade drive mechanism is provided on a unit different from the unit supporting the movable blade; the cover unit is provided to be freely openable/closable with respect to the main body unit; and, when the cover unit is closed with respect to the main body unit, the pinion gear meshes with the rack and reciprocates the movable blade so that the movable blade and the fixed blade cooperate to cut a recording sheet at a predetermined position. 
         [0015]    According to such configuration, the fixed blade and the pinion gear are proximally arranged in the arrangement unit of the fixed blade, and hence the movable blade is pulled in toward the fixed blade by the pinion gear when cutting the recording sheet (pull-in method). In this case, the driving force from the pinion gear to the movable blade and the reaction force from the fixed blade to the movable blade act in close proximity in horizontally opposite directions, and thus the rotational moment that acts on the arrangement unit of the movable blade becomes small. The lowering in pressure between the fixed blade and the movable blade thus can be reduced, and the cutting operation can be stabilized so that the cutting performance can be enhanced. Lighter weight is achieved because the arrangement unit of the movable blade only supports the platen roller or the thermal head other in addition to the movable blade. Thus, the weight load in opening and closing the cover unit with respect to the main body unit can be alleviated. 
         [0016]    Further, a printer comprises: a main body unit which supports a thermal head and a fixed blade; a cover unit which supports a platen roller and a movable blade constructed integrally with a rack; and a movable blade drive mechanism for driving the movable blade and a platen drive mechanism for driving the platen roller which are provided in the main body unit; wherein: a pinion gear rotated by the movable blade drive mechanism is provided in the main body unit; the cover unit is provided to be freely openable/closable with respect to the main body unit; and, when the cover unit is closed with respect to the main body unit, the pinion gear meshes with the rack and reciprocates the movable blade so that the movable blade and the fixed blade cooperate to cut a recording sheet at a predetermined position. 
         [0017]    In a structure in which the platen roller and the movable blade constructed integrally with the rack are supported by the cover unit, the drive mechanism of the gear train and the like, as well as electrical components such as the thermal head and the drive source are not arranged on the cover unit that opens and closes with respect to the main body unit. Thus mechanical and electrical break down due to impact and vibration in opening and closing the cover unit can be significantly reduced. 
         [0018]    Further, it is desirable that the printer further comprise a pinion gear release mechanism for enabling the pinion gear to freely rotate. 
         [0019]    Further, it is desirable that the pinion gear comprises a pair of pinion gears respectively provided on left and right with respect to one axis, the rack constructed integrally with the movable blade arranged on the cover unit mesh with the pinion gear on the movable blade drive mechanism side and then mesh with the another pinion gear, and thereafter, the pinion gear on the movable blade drive mechanism side and the movable blade drive mechanism mesh with each other when the cover unit is closed with respect to the main body unit. 
         [0020]    Further, it is desirable that the rack and the pinion gear have tooth shapes in which tooth tops mesh with each other without locking when shifting the cover unit from an opened state to a closed state with respect to the main body unit. 
         [0021]    Further, it is desirable that the rack comprise with a claw for rotating the pinion gear before the pinion gear meshes with the rack when shifting the cover unit from the opened state to the closed state with respect to the main body unit. 
         [0022]    According to such configuration, the rack and the pinion gear can be smoothly meshed when shifting the cover unit from the opened state to the closed state with respect to the main body unit. 
         [0023]    The movable blade may be provided with a plurality of holes that engage the pinion gear in place of the rack. 
         [0024]    Further, it is desirable that the rack comprise a regulation member for regulating the rack not to be detached from the pinion gear, and the regulation member is supported by an arrangement unit of the fixed blade. 
         [0025]    According to such configuration, the fixed blade and the regulation member are proximally arranged in the arrangement unit of the fixed blade. In this case, the regulation force from the regulation member to the movable blade and the pressure contacting force from the fixed blade to the movable blade act in close proximity in vertically opposite directions, and thus the rotational moment that acts on the arrangement unit of the movable blade becomes small. The lowering in pressure between the fixed blade and the movable blade thus can be reduced, and the cutting operation can be stabilized so that the cutting performance can be enhanced. 
         [0026]    Further, the rack may comprise a regulation member for regulating the rack not to be detached from the pinion gear, and the regulation member may be supported by an arrangement unit of the movable blade. 
         [0027]    According to such configuration, the movement of the movable blade in the vertical direction can be regulated by the regulation member by simply closing the cover unit with respect to the main body unit. Therefore, a switching mechanism for regulating or deregulating the movement of the movable blade in the vertical direction is unnecessary, and the manufacturing cost can be reduced. 
         [0028]    Further, it is desirable that the rack comprise a regulation member for regulating the rack not to be detached from the pinion gear, and the regulation member be arranged on the fixed blade side with respect to a rotation shaft of the platen roller. 
         [0029]    According to such configuration, the regulation member is proximally arranged to the fixed blade, and hence the rack is effectively prevented from being detached from the pinion gear by the pressure contacting force from the fixed blade to the movable blade. 
         [0030]    Further, it is desirable that the movable blade be removable with respect to the supporting unit so as to be replaceable. 
         [0031]    According to such configuration, only the platen roller and the movable blade are arranged on the cover unit, and hence only the movable blade can be easily replaced without dissembling the movable blade drive mechanism. 
         [0032]    According to the thermal printer of the present invention, the rotational moment that acts on the arrangement unit of the movable blade becomes small because the movable blade is pulled in toward the fixed blade by the pinion gear when cutting the recording sheet. The lowering in pressure between the fixed blade and the movable blade thus can be reduced, and the cutting operation can be stabilized so that the cutting performance can be enhanced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    In the accompanying drawings: 
           [0034]      FIG. 1  is a perspective view of an outer appearance of a thermal printer; 
           [0035]      FIG. 2  is a side cross-sectional view of a state in which an open/close door of the thermal printer is opened; 
           [0036]      FIG. 3  is a side cross-sectional view of a state in which the open/close door of the thermal printer is closed; 
           [0037]      FIG. 4  is a schematic configuration view of a main body unit and a cover unit; 
           [0038]      FIG. 5  is a perspective view of a fixed blade and a movable blade in printing; 
           [0039]      FIG. 6  is a perspective view of the fixed blade and the movable blade in cutting; 
           [0040]      FIGS. 7A-7B  are explanatory views of a recovery operation of when the recording sheet is bitten; 
           [0041]      FIGS. 8A-8B  are explanatory views of a force in a horizontal direction, which acts on the movable blade and the cover unit, where  FIG. 8A  illustrates a case of the pull-in method of the embodiment and  FIG. 8B  illustrates a case of the push-out method of the related art; 
           [0042]      FIGS. 9A-9B  are explanatory views of the force in the vertical direction, which acts on the movable blade and the cover unit, where  FIG. 9A  illustrates a case of the pull-in method of the embodiment and  FIG. 9B  illustrates a case of the push-out method of the related art; 
           [0043]      FIGS. 10A-10C  are explanatory views of the meshing of the rack and the pinion gear; 
           [0044]      FIGS. 11A-11C  are explanatory views of a pinion gear separation mechanism in the movable blade drive system; 
           [0045]      FIG. 12  is perspective views of a regulation mechanism; 
           [0046]      FIGS. 13A-13B  are a plan view and a side view of the regulation mechanism; 
           [0047]      FIGS. 14A-14C  are cross-sectional views at the portion corresponding to the line A-A of  FIG. 13A ; 
           [0048]      FIGS. 15A-15C  are cross-sectional views at the portion corresponding to the line B-B of  FIG. 13A ; 
           [0049]      FIGS. 16A-16B  are explanatory views of a movable blade socket; 
           [0050]      FIGS. 17A-17B  are explanatory views of the movable blade socket; 
           [0051]      FIGS. 18A-18B  are plan views of the movable blade for cutting the recording sheet while leaving the connecting points; 
           [0052]      FIG. 19  is a schematic configuration view of when the pinion gear is arranged closer to the platen roller; and 
           [0053]      FIG. 20  is a perspective view of the fixed blade and the movable blade during printing. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0054]    An embodiment of the present invention is described below with reference to the accompanying drawings. 
       (Thermal Printer) 
       [0055]      FIG. 1  is a perspective view of an outer appearance of a thermal printer,  FIG. 2  is a side cross-sectional view of a state in which an open/close door is opened, and  FIG. 3  is a side cross-sectional view of a state in which the open/close door is closed. In this embodiment, the upper and lower direction in the plane of drawing of  FIG. 2  and  FIG. 3  is referred to as “vertical direction” (upper side in the plane of drawing is referred to as “upper” and the lower side in the plane of drawing is referred to as “lower”), and the left and right direction in the plane of drawing is referred to as “horizontal direction”. 
         [0056]    A thermal printer  1  of this embodiment is a printer that can appropriately cut, after performing printing on a recording sheet P, recording sheet P pulled out from a roll sheet R to use as a ticket, a receipt, and the like, and mainly includes a casing  2 , a main body unit  4 , an open/close door  6 , and a cover unit  3 , as illustrated in  FIG. 1  and  FIG. 2 . 
         [0057]    The casing  2  is a casing molded from molding of plastic or a metal material, and is formed to a box-shape with an insertion port  2   a  opened at the upper surface. A roll sheet housing unit  2   b  for housing the roll sheet R inserted from the insertion port  2   a  is arranged in the interior of the casing  2 . The housing unit  2   b  is formed to be curved in an arcuate shape, and enables the cylindrical roll sheet R to be stably mounted. 
         [0058]    An open/close door  6  fixed in an openable/closable manner through an intermediation of a hinge portion  5  is attached to the upper surface of the casing  2 . The open/close door  6  opens and closes within a range of a constant angle from an opened state illustrated in  FIG. 2  to a closed state illustrated in  FIG. 3 . The insertion port  2   a  appears when the open/close door  6  is opened, and hence the roll sheet R can be inserted into or be taken out from the casing  2 . A discharge port  2   c  is designed to be formed between the distal end of the open/close door  6  and the casing  2  when the open/close door  6  is closed. The recording sheet P is pulled out from the interior of the casing  2  through such a discharge port  2   c.    
         [0059]    Note that the open/close door  6  automatically locks with respect to the casing  2  when closed. The lock mechanism unlocks with one-touch from the outer side of the casing  2 , and hence the open/close door  6  can be promptly opened. 
         [0060]    The main body unit  4  is a unit mainly incorporating a fixed blade  30 , a thermal head  34 , to be hereinafter described, and a respective drive mechanism for driving a movable blade and a platen roller, and is provided in the casing  2 , as illustrated in  FIG. 1  to  FIG. 3 . In other words, an internal plate  2   d  is integrally formed with a roll sheet housing unit  2   b  of a casing  2 , and the main body unit  4  is fixed on the internal plate  2   d . Note that, in  FIG. 1  to  FIG. 3 , the fixed blade  30  and the thermal head  34  are representatively illustrated. 
         [0061]    The cover unit  3  is a unit mainly incorporating a movable blade  10  and a platen roller  65 , to be hereinafter described, and is provided on an inner surface on a distal end side of the open/close door  6 . Thus, the cover unit  3  moves with the opening/closing operation of the open/close door  6  to be coupled to the main body unit  4  or to be separated from the main body unit  4 . 
       (Main Body Unit, Cover Unit) 
       [0062]      FIG. 4  is a schematic configuration diagram of the main body unit and the cover unit. The cover unit  3  includes the platen roller  65  made of an elastic body such as rubber for feeding the recording sheet P, and the movable blade  10  that linearly moves so as to approach or separate from the fixed blade  30 . 
         [0063]    The platen roller  65  is arranged to sandwich the recording sheet P with the thermal head  34  when the open/close door  6  is closed and the cover unit  3  and the main body unit  4  are coupled as illustrated in  FIG. 3 . The platen roller  65  rotates by the rotational force transmitted from the main body unit  4  side after closing the open/close door  6 , and hence the recording sheet P pulled out from the roll sheet R can be fed out to the exterior of the casing  2  from a discharge port  2   c.    
         [0064]    The movable blade  10  functions as a cutter in cooperation with the fixed blade  30 , and is arranged to ride on the fixed blade  30  when the open/close door  6  is closed and the main body unit  4  and the cover unit  3  are coupled. As illustrated in  FIG. 5 , the movable blade  10  is a plate-shaped blade formed to a substantially V-shape in top view such that the length from a proximal end portion to a cutting edge  10   a  of a distal end portion gradually becomes shorter from both ends in a width direction toward the central part. When the movable blade  10  is sled toward the fixed blade  30 , the recording sheet P is sandwiched and cut between the movable blade  10  and the fixed blade  30 , as illustrated in  FIG. 6 . As illustrated in  FIG. 4 , the movable blade  10  is biased so as to separate from the fixed blade  30  in the horizontal direction by an elastic body (coil spring)  37 . 
         [0065]    Returning back to  FIG. 4 , the main body unit  4  includes the fixed blade  30 , one part of a movable blade drive system  40  for linearly moving the movable blade  10 , a platen drive system  60  for rotatably driving the platen roller  65 , and the thermal head  34  for performing printing on the pulled-out recording sheet P. The fixed blade  30  is a plate-shaped blade extending in the width direction of the recording sheet P. Note that the fixed blade  30  is biased toward the movable blade  10  on the upper side by a coil spring and the like (not shown) to stabilize the cutting operation. 
         [0066]    The movable blade drive system  40  is arranged on the front side in the plane of drawing of  FIG. 4 , and includes a rack  44  integrally attached to the movable blade  10 , a pinion gear  42  that meshes with the rack  44 , and a pinion drive system  41  for rotatably driving the pinion gear  42 . The pinion drive system  41  includes a gear train that meshes with the pinion gear  42 , and a forward and reverse rotatable movable blade motor  41   a  that meshes with the gear train. Of the movable blade drive system  40 , the rack  44  is constructed integrally with the movable blade  10  and is supported by the cover unit  3 , but the pinion gear  42  and the pinion drive system  41  are supported by the main body unit  4 . 
         [0067]    The platen drive system  60  is arranged on the deep side in the plane of drawing of  FIG. 4 , and includes a driven wheel  64  arranged on a center axis of the platen roller  65 , a gear train that meshes with the driven wheel, and a platen motor (feed motor)  61   a  that meshes with the gear train. Of the platen drive system  60 , the gear train and the platen motor  61   a  other than the driven wheel  64  are supported by the main body unit  4 . 
         [0068]    In this embodiment, the movable blade drive system  40  is arranged on the front side in the plane of drawing of  FIG. 4 , and the platen drive system  60  is arranged on the deep side in the plane of drawing of  FIG. 4 , but may be respectively arranged on opposite sides or may be arranged on the same side. 
         [0069]    As illustrated in  FIG. 1 , the thermal head  34  is formed to extend in the width direction of the recording sheet P and is arranged at a position facing the platen roller  65  when the open/close door  6  is closed. The thermal head  34  includes great number of heater elements (not shown), and is biased to the platen roller  65  side by a coil spring and the like (not shown). With this, the thermal head  34  is thus reliably pressed against the recording sheet P fed out by the platen roller  65 , and satisfactory printing can be carried out. 
         [0070]    As illustrated in  FIG. 4 , in the main body unit  4 , there is formed a fit-in hole  66  to be fitted with a bearing  65   a  covered on a rotation shaft  65   b  of the platen roller  65  without space. An inclined portion for drawing the bearing  65   a  into the fit-in hole  66  is provided on the upper side of the fit-in hole  66 . That is, when the open/close door  6  is closed, the bearing  65   a  of the platen roller  65  naturally fits into the fit-in hole  66 . As a result, the main body unit  4  and the cover unit  3  are thereby coupled. 
       (Printing and Cutting Operations) 
       [0071]    The printing and cutting operations of the above-mentioned thermal printer  1  are described below. 
         [0072]    First, the roll sheet R is set. Specifically, as illustrated in  FIG. 1  and  FIG. 2 , the roll sheet R is inserted into the casing  2  from an insertion port  2   a  with the open/close door  6  opened. In this case, the recording sheet P is pulled out to the outer side of the casing  2  in advance. When the open/close door  6  is closed, the bearing  65   a  of the platen roller  65  is fitted into the fit-in hole  66  of the main body unit  4 , and a lock shaft (not shown) is fitted into a lock groove (not shown) on the main body unit  4  side and automatically locked. The main body unit  4  and the cover unit  3  are thereby coupled. 
         [0073]    As illustrated in  FIG. 3 , the recording sheet P is sandwiched between the platen roller  65  and the thermal head  34 , and is pulled out to the outer side of the casing  2  from the discharge port  2   c.    
         [0074]    The rack  44  and the pinion gear  42  illustrated in  FIG. 4  are meshed when the open/close door  6  is closed. In this embodiment, the position of the pinion gear  42  is under the fixed blade  30 , and hence the movable blade  30  overlays the fixed blade  30  from the beginning when the open/close door is closed. In this case, the manufacturing of the movable blade  10  is simplified because the distal end of the movable blade  10  does not need to be subjected to a bending process. In contrast, as illustrated in  FIG. 19 , in the configuration in which the position of the pinion gear  42  is arranged on the platen roller  65  side with respect to the fixed blade  30 , the distal end of the movable blade  10  does not overlay the fixed blade  30  when the open/close door is closed. In this case, the distal end of the movable blade  10  needs to smoothly ride on the fixed blade  30  when the movable blade  10  is pulled in by the pinion gear  42 . In this case, a bent shape  10   b  is desirably formed at the distal end of the movable blade  10  (see  FIG. 20 ). The projections of both end portions of the movable blade  10  from the cover unit  3  thus can be reduced, which is suitable in designing the printer. 
         [0075]    Then, various types of information are printed on the recording sheet P. First, as illustrated in  FIG. 4 , the platen motor  61   a  is driven, and the platen roller  65  is rotatably driven by way of the gear train and the driven wheel  64 . As a result, as illustrated in  FIG. 3 , the recording sheet P sandwiched between the outer circumferential surface of the platen roller  65  and the thermal head  34  is pulled out from the roll sheet R housed in the housing unit  2   b , and fed to the upper side of the casing  2 . 
         [0076]    The thermal head  34  is activated at the same time to have the great number of heater elements of the thermal head appropriately generate heat, whereby various types of characters, figures, and the like can be clearly printed on the fed recording sheet P. The printed recording sheet P is fed by the platen roller  65 , and passed between the fixed blade  30  and the movable blade  10 . 
         [0077]    Then, the recording sheet P is cut. Specifically, the movable blade motor  41   a  illustrated in  FIG. 4  is driven, and the pinion gear  42  is rotated through the gear train. The rack  44  meshed with the pinion gear  42  then linearly moves, the movable blade  10  constructed integrally with the rack slidably moves toward the fixed blade  30 , and the respective cutting edges  10   a ,  30   a  overlap as illustrated in  FIG. 6 . As a result, the recording sheet P can be sandwiched and cut between the fixed blade  30  and the movable blade  10 . After the cutting, the movable blade motor  41   a  illustrated in  FIG. 4  is reverse rotated to return the movable blade  10  to the original position. 
         [0078]    Here, description is made of the recovery operation of when the recording sheet P is bitten between the fixed blade  30  and the movable blade  10  and the movable blade  10  cannot be driven in the cutting direction nor the reverse direction with the movable blade motor  41   a.    
         [0079]      FIG. 7A  illustrates a state in which the recording sheet is bitten between the fixed blade and the movable blade, and  FIG. 7B  is an explanatory view of the recovery operation. As illustrated in  FIG. 7A , the recording sheet is sometimes bitten between the fixed blade  30  and the movable blade  10  while moving the movable blade  10  toward the fixed blade  30  side and cutting the recording sheet (not shown). If the biting force is large, the movable blade  10  cannot be pulled away from the fixed blade  30  even by reverse rotating the movable blade motor. 
         [0080]    In this case, as illustrated in  FIG. 7B , the open/close door is opened and the cover unit  3  is separated from the main body unit  4 . As a result, the movable blade  10  separates from the fixed blade  30  in the vertical direction, and hence the recording sheet bitten between the blades can be removed. In this embodiment, the pinion gear  42  is supported by the main body unit  4 , and hence the rack  44  separates from the pinion gear  42  along with the movable blade  10  when the open/close door is opened. The movable blade  10  thus becomes freely movable, and the movable blade  10  separates from the fixed blade  30  in the horizontal direction by the restoring force of the elastic body  37 . As a result, the movable blade  10  returns to the home position. 
       (Pull-In Method and Push-Out Method) 
       [0081]    Next, examination is made on the force that acts on the movable blade and the cover unit when cutting the recording sheet. Hereinafter, cases of the related art (push-out method) and this embodiment (pull-in method) are reviewed in order for the force in the horizontal direction and the force in the vertical direction. 
       (Horizontal Direction) 
       [0082]      FIG. 8  are explanatory views of the force in the horizontal direction that acts on the movable blade and the cover unit, where  FIG. 8A  is a case of this embodiment (pull-in method) and  FIG. 8B  is a case of the related art (push-out method). 
         [0083]    In the conventional technique illustrated in  FIG. 8B , the pinion gear  42  is supported by the cover unit  3 . In this case, a gear meshing portion G of the rack  44  and the pinion gear  42  is arranged spaced apart from the fixed blade  30 . Thus, when cutting the recording sheet, the movable blade  10  is pushed out toward the fixed blade  30  by the pinion gear  42  (push-out method). 
         [0084]    In the push-out method illustrated in  FIG. 8B , the force in the horizontal direction that acts on the movable blade  10  is examined. At the gear meshing portion G of the rack  44  and the pinion gear  42 , the movable blade  10  receives the driving force Fxg from the pinion gear  42 . Meanwhile, at a blade contacting portion S of the movable blade  10  and the fixed blade  30 , the movable blade  10  receives a sheet cutting reaction force and a frictional force Fxs from the fixed blade  30 . 
         [0085]    In this case, the pinion gear  42  and the movable blade  10  integrated with the rack  44  are supported by the cover unit  3 , and the cover unit  3  is connected to the main body unit  4  at a unit connecting portion U. 
         [0086]    Thus, the force Fxs received by the cover unit  3  from the main body unit  4  at the blade contacting portion S acts as a rotational moment in the clockwise direction in the figure on the cover unit with the unit connecting portion U as the fulcrum. Since a slight play exists between the bottom surface of the cover unit  3  and the main body unit  4 , the cover unit  3  slightly rotates in the clockwise direction with the unit connecting portion U as the center. As a result, the movable blade  10  separates from the fixed blade  30  in the vertical direction, whereby the pressure between the fixed blade  30  and the movable blade  10  lowers. Therefore, there is a problem that the cutting operation becomes unstable to deteriorate the cutting performance. 
         [0087]    In contract, in this embodiment illustrated in  FIG. 8A , the pinion gear  42  is supported by the main body unit  4 . Further, the gear meshing portion G of the rack  44  and the pinion gear  42  is proximally arranged to the fixed blade  30 . Thus, when cutting the recording sheet, the movable blade  10  is pulled in toward the fixed blade  30  by the pinion gear  42  (pull-in method). 
         [0088]    In the pull-in method, the force in the horizontal direction that acts on the movable blade  10  is similar to the push-out method. The movable blade  10  receives the driving force Fxg from the pinion gear  42  at the gear meshing portion G, and the movable blade  10  receives the sheet cutting reaction force and the frictional force Fxs from the fixed blade  30  at the blade contacting portion S. 
         [0089]    In this case, the pinion gear  42  is supported by the main body unit, and hence the force Fxg of pulling in the movable blade  10  and the sheet cutting reaction force and the frictional force Fxs from the fixed blade  30  to the movable blade  10  substantially cancel each other out, whereby the force and the rotational moment on the cover unit  3  do not act. 
         [0090]    More specifically, since the movable blade  10  is connected to the cover unit with the elastic body  37 , a force in the counterclockwise direction with the unit connecting portion U as the center acts on the cover unit, oppositely to the push-out method described above, but such force is a negligible force. Even if such force is acted, the force acts in a direction in which the movable blade  10  pressure contacts the fixed blade  30  in the vertical direction. As a result, the cutting operation of the cutter can be stabilized, and the cutting performance can be enhanced. 
         [0091]    As described above, in this embodiment, the fixed blade  30  and the pinion gear  42  are proximally arranged in the main body unit  4 , and the movable blade  10  is pulled in toward the fixed blade  30  by the pinion gear  42  when cutting the recording sheet (pull-in method). In this case, the lowering in pressure between the fixed blade  30  and the movable blade  10  of when cutting the recording sheet can be prevented, the cutting operation can be stabilized, and the cutting performance can be enhanced. Accompanied therewith, an inexpensive thin blade can be used for the movable blade  10  and the fixed blade  30 . 
       (Vertical Direction) 
       [0092]      FIG. 9  are explanatory views of the force in the vertical direction that acts on the movable blade and the cover unit, where  FIG. 9A  is a case of the pull-in method in this embodiment and  FIG. 9B  is a case of the push-out method in the related art. 
         [0093]    In the related art technique illustrated in  FIG. 9B , the pinion gear  42  is supported by the cover unit  3 . Note that the fixed blade  30  is biased toward the movable blade  10  on the upper side, and the pressure contacting force is exerted on the movable blade  10 . Further, the rack  44  receives a meshing reaction force in the vertical direction from the pinion gear  42 . In order to prevent unmeshing of the rack  44  and the pinion gear  42  by the pressure contacting force and the meshing reaction force, a regulation member  35  for regulating the movement of the rack to the upper side is provided. The regulation member  35  is arranged on the opposite side of the pinion gear  42  with the rack  44  in between, and is supported by the cover unit  3  same as the pinion gear  42 . 
         [0094]    First, in the push-out method illustrated in  FIG. 9B , the force in the vertical direction that acts on the movable blade  10  includes the meshing reaction force Fzt the rack  44  receives from the pinion gear  42  and the pressure contacting force Fzs the movable blade  10  receives from the fixed blade  30  biased to the upper side. 
         [0095]    The meshing reaction force Fzt is received by the regulation member  35 , and is canceled out in the cover unit  3  since the pinion gear  42  and the regulation member  35  are both supported by the cover unit  3 . On the other hand, the movable blade  10  supported by the cover unit  3  receives the pressure contacting force Fzs from the fixed blade  30  supported by the main body unit  4  at the blade contacting portion S. 
         [0096]    In this case, the cover unit  3  is connected to the main body unit  4  at the unit connecting portion U, and the pressure contacting force Fzs at the blade contacting portion S acts as the rotational moment in the clockwise direction with respect to the cover unit  3 . Note that, because a slight play exists between the bottom surface of the cover unit  3  and the main body unit  4 , the cover unit  3  slightly rotates in the direction of separating from the main body unit  4  in receiving the rotational moment. As a result, the movable blade  10  then separates from the fixed blade  30  in the vertical direction, whereby the pressure between the fixed blade  30  and the movable blade  10  lowers to cause a problem that the cutting operation becomes unstable, and the cutting performance lowers. 
         [0097]    In contrast, In this embodiment illustrated in  FIG. 9A , the pinion gear  42  is supported by the main body unit  4 . In this embodiment as well, a regulation mechanism  80  for regulating the movement of the rack to the upper side is provided to prevent unmeshing of the rack  44  and the pinion gear  42 . The regulation mechanism  80  is provided on the opposite side of the pinion gear  42  with the rack  44  in between, and is supported by the main body unit  4 . Note that the regulation mechanism  80  may be provided on the cover unit  3 . However, in this case, the regulation mechanism  80  is provided on the main body unit  4  same as the pinion gear  42 . The structure of the regulation mechanism  80  is hereinafter described. 
         [0098]    The force in the vertical direction that acts on the movable blade  10  in the pull-in method is the meshing reaction force Fzt the rack  44  receives from the pinion  42  and the pressure contacting force Fzs the movable blade  10  receives from the fixed blade  30  biased to the upper side. 
         [0099]    The meshing reaction force Fzt is received by the regulation mechanism  80 , and the pinion gear  42  and the regulation mechanism  80  are both supported by the main body unit  4 . Therefore, the meshing reaction force is canceled out in the main body unit  4  The pressure contacting force Fzs is received by the regulation mechanism  80  from the fixed blade  30  via the movable blade  10 , and the fixed blade  30  and the regulation mechanism  80  are both supported by the main body unit  4 . Therefore, the pressure contacting force is canceled out in the main body unit  4 . 
         [0100]    Therefore, in the pull-in method illustrated in  FIG. 9A , the force in the vertical direction is canceled out in the main body unit, the force and the rotational moment on the cover unit  3  do not act, the cutting operation of the cutter can be stabilized, and the cutting performance can be ensured. 
       (Meshing of Rack and Pinion Gear) 
       [0101]    As illustrated in  FIG. 7B , in this embodiment, the pinion gear  42  is supported by the main body unit  4 . Thus, the rack  44  supported by the cover unit  3  and the pinion gear  42  supported by the main body unit  4  need to be smoothly meshed when re-coupling the cover unit  3  separated from the main body unit  4  to the main body unit  4 . 
         [0102]      FIG. 10  are explanatory views of the meshing of the rack and the pinion gear. As illustrated in  FIG. 10A , the tooth shapes of the general rack  44  and the pinion gear  42  are involute shape. In this case as well, the rack  44  and the pinion gear  42  can be smoothly meshed by forming the tooth tops to tapered shapes. 
         [0103]    Further, as illustrated in  FIG. 10B , the tooth shapes of the rack  44  and the pinion gear  42  may be triangular shape. In this case, the tooth tops are formed to sharp tapered shapes, and hence the rack  44  and the pinion gear  42  can be smoothly meshed with each other. 
         [0104]    As described above, the tooth shapes of the rack  44  and the pinion gear  42  are shapes that enable the tooth tops of the rack  44  and the pinion gear  42  to mesh with each other without colliding when shifting the cover unit from the opened state to the closed state with respect to the main body unit. 
         [0105]    Further, as illustrated in  FIG. 10C , the distal end of the rack  44  may be folded back toward the pinion gear  42  and a claw  45  may be provided at the distal end. When the rack  44  approaches the pinion gear  42  in shifting the cover unit from the opened state to the closed state with respect to the main body unit, the claw  45  contacts the teeth of the pinion gear  42  before the rack  44  meshes with the pinion gear  42  and rotates the pinion gear  42 . In this case, by rotating the pinion gear  42  to a position where the rack  44  and the pinion gear  42  smoothly mesh with each other, the rack  44  and the pinion gear  42  can be smoothly meshed. 
         [0106]    Further, by having the pinion gear rotatable in the state in which the cover unit  3  is separated, the rack  44  and the pinion gear  42  can be smoothly meshed when coupling the cover unit. 
         [0107]      FIG. 11  are explanatory views of a pinion release mechanism.  FIG. 11A  is a view seen from the arrow E of  FIG. 4 , and  FIG. 11B  and  FIG. 11C  are views seen from the arrow F of  FIG. 11A . As illustrated in  FIG. 16B , since a pair of racks  44 ,  44  is provided on both sides in the width direction of the movable blade  10 , a pair of pinion gears  42 ,  42  is provided on both sides in the width direction, as illustrated in  FIG. 11A . The pair of pinion gears  42 ,  42  are connected by a shaft  72 . Further, sleeves  42   a ,  42   a  are formed in a projecting manner from the pair of pinion gears  42 ,  42  toward the inner side. Note that a drive gear  43  that meshes with the gear train of the pinion drive system is provided on the outer side of one pinion gear  42 . 
         [0108]    As illustrated in  FIG. 11B , a vertically long through-hole  75  is formed in a frame  74  of the printer in the pinion release mechanism  70  of this embodiment. The sleeve  42   a  is inserted to the through-hole  75 , and the pinion gear  42  is supported by the frame  74 . A plate spring  76  for biasing the sleeve  42   a  to the upper side is provided below the through-hole  75 . 
         [0109]    When the cover unit  3  is coupled as illustrated in  FIG. 7A , the pinion gear  42  is pushed down by the rack  44 . In this case, the sleeve  42   a  is arranged on the lower side of the through-hole  75  against the biasing force of the plate spring  76 , as illustrated in  FIG. 11B . In contrast, when the cover unit is separated as illustrated in  FIG. 7B , the pushing down of the pinion gear  42  by the rack  44  is resolved. In this case, the sleeve  42   a  is arranged on the upper side of the through-hole  75  by the biasing force of the plate spring  76 , as illustrated in  FIG. 11C . 
         [0110]    In the state of  FIG. 11C , the pinion gear  42  is rotatable since the gear train (see  FIG. 4 ) arranged on the lower side of the drive gear  43  and the drive gear  43  are unmeshed. Thus, the rack  44  can rotate the pinion gear  42  when coupling the cover unit  3  to the main body unit  4 . Therefore, the rack  44  and the pinion gear  42  can be smoothly meshed. 
         [0111]    Note that the curvature radius at the lower side of the through-hole  75  illustrated in  FIG. 11B  is formed to be equal to the radius of the sleeve  42   a , and the curvature radius at the upper side of the through-hole  75  is formed to be larger than the radius of the sleeve  42   a . Thus, the pinion gear  42  is not only rotatable but is also movable upward, downward, to the left, and to the right when the sleeve  42   a  is arranged on the upper side of the through-hole  75 . As a result, the rack  44  can rotate the pinion gear  42  while moving the same when coupling the cover unit  3  to the main body unit  4 . Therefore, the rack  44  and the pinion gear  42  can be more smoothly meshed. 
         [0112]    Note that as illustrated in  FIG. 4 , an idle gear  41   b  at the most downstream (closest to the pinion gear  42 ) of the pinion drive system  41  is arranged obliquely downward of the pinion gear  42 . Thus, the pinion gear  42  pushed down by the rack  44  and the idle gear  41   b  can be smoothly meshed when coupling the cover unit  3  to the main body unit  4 . 
         [0113]    Further, in the pinion release mechanism  70  described above, the pinion gear  42  is lifted and made rotatable, but the pinion gear  42  may be made rotatable by detaching the idle gear  41   b  from the pinion drive system  41 . 
         [0114]    Further, in the embodiment described above, a case in which the pinion release mechanism  70  is provided to one pinion gear  42  has been described, but similar pinion release mechanism  70  may be provided with respect to both pinion gears  42 ,  42  and hence both pinion gears  42 ,  42  can be simultaneously lifted and made rotatable. 
         [0115]    Note that, as in this embodiment illustrated in  FIG. 4  and  FIGS. 11A-11C , according to the configuration in which the pinion release mechanism  70  is provided only on one pinion gear  42  side provided with the drive gear  43  that meshes with the gear train of the pinion drive system, and the one pinion gear  42  provided with the pinion release mechanism  70  is positioned on the upper side with respect to the other pinion gear  42 , the one pinion gear  42  provided with the drive gear  43  and one rack  44  corresponding thereto first mesh with each other, and the other pinion gear  42  and the other track  44  corresponding thereto mesh with each other following the first meshing when shifting the cover unit  3  from the opened state to the closed state with respect to the main body unit  4 . Therefore, the rack  44  and the pinion gear  42  can be more smoothly and easily meshed. 
       (Regulation Mechanism) 
       [0116]      FIGS. 12 to 14  are explanatory views of the regulation mechanism. Note that  FIG. 12  is a perspective view of the regulation mechanism, each figure of  FIGS. 13A-13B  is a plan view and a side view of the regulation mechanism, and  FIG. 14A-14C  are cross-sectional views at the portion corresponding to the line A-A of  FIG. 13A . Further,  FIGS. 15(   a ) to  15 ( c ) are cross-sectional views at the portion corresponding to the line B-B of  FIG. 13A . 
         [0117]    As illustrated in  FIG. 12 , the regulation mechanism  80  is arranged on the main body unit  4 , and includes a plate  82 , a lever  84 , and a regulation member  90  (see  FIGS. 13A-13B ). As illustrated in  FIG. 12 , the plate  82  is arranged on the upper surface of the main body unit  4 , and is formed to a crank-shape in plan view. A rotation shaft  83  extending in the vertical direction is arranged at the center part of the plate  82 , the plate  82  being formed to be rotatable about the rotation shaft  83 . Meanwhile, the lever  84  is arranged at the side surface of the main body unit  4 . The plate  82  can be rotated by pushing down the lever  84 . 
         [0118]    As illustrated in  FIG. 13A , a regulation member  90  is arranged on the lower side at both ends of the plate  82 . The regulation member  90  is formed to be rotatable about a rotation shaft  91  extending in the horizontal direction. The rotation shaft  91  is arranged parallel to the side surface of the plate  82  in plan view. 
         [0119]    As illustrated in  FIG. 14A  and  FIG. 15A , a regulating portion  94  projecting to the lower side and an engagement portion  95  projecting to the upper side are formed at the end on the plate  82  side of the regulation member  90 . The regulating portion  94  regulates the movement of the movable blade  10  to the upper side by contacting the movable blade  10  arranged below the regulation member  90 , and the engagement portion  95  engages the lower surface of the plate  82 . Meanwhile, An elastic body (coil spring)  86  for biasing the regulation member  90  in a direction in which the regulating portion  94  separates from the movable blade  10  is provided at the end of the regulation member  90  on the opposite side of the plate  82  with the rotation shaft  91  in between. 
         [0120]    As illustrated in  FIG. 13A  when cutting the recording sheet, the engagement portion  95  of the regulation member  90  engages the lower surface of the plate  82 . In this case, as illustrated in  FIG. 14A  and  FIG. 15A  the regulating portion  94  is contacting the movable blade  10  because the plate  82  pushes down the engagement portion  95  against the biasing force of the elastic body  86 . The movable blade  10  thus can be regulated from moving to the upper side by the pressure contacting force from the fixed blade  30  to the movable blade  10 , and detachment of the rack  44  from the pinion gear  42  can be prevented. As a result, the movable blade  10  can be smoothly moved by the driving force of the pinion gear  42 . Further, the lowering in pressure between the movable blade  10  and the fixed blade  30  thus can be prevented, and the recording sheet can be reliably cut. 
         [0121]    When the recording sheet is bitten between the fixed blade  30  and the movable blade  10 , as illustrated in  FIG. 13B , the lever  84  is pushed down to rotate the plate  82  thereby disengaging the lower surface of the plate  82  and the engagement portion  95  of the regulation member  90 . In this case, as illustrated in  FIG. 14B  and  FIG. 15B , the regulating portion  94  rises by the biasing force of the elastic body  86 , and separates from the movable blade  10 . The rack  44  thereby moves to the upper side, and the pinion gear  42  becomes rotatable by the biasing force of the plate spring  76  illustrated in  FIG. 11C . As a result, as illustrated in  FIG. 14B  and  FIG. 15B , the movable blade  10  returns to the home position by the restoring force of the elastic body  37 . After that, as illustrated in  FIG. 14C  and  FIG. 15C , the cover unit  3  fixed to the open/close door is opened to remove the recording sheet bitten between the fixed blade  30  and the movable blade  10 . The cover unit  3  can be separated without the movable blade  10 , the regulation member  90 , and the plate  82  interfering because the movable blade  10  returns to the home position. 
         [0122]    A torsion coil spring (not shown) is provided on a rotation shaft  84   a  of the lever  84  illustrated in  FIG. 13B , and hence the lever  84  automatically returns to the state of  FIG. 13A  by stopping the push-down of the lever  84  and releasing the hand. In conjunction therewith, the plate  82  also returns to the state of  FIG. 13A , the lower surface of the plate  82  and the engagement portion  95  of the regulation member  90  engage with each other, and the regulating portion of the regulation member  90  lowers. 
         [0123]    Subsequently, when resuming the printing and the cutting of the recording sheet, the cover unit  3  is first closed as illustrated in  FIG. 14B  and  FIG. 15B . The regulating portion  94  is then lowered as illustrated in  FIG. 14A  and  FIG. 15A  to regulate the movement of the movable blade  10  to the upper side. The driving force is thereby transmitted from the pinion gear  42  to the rack  44 , and the movable blade  10  can be moved to cut the recording sheet. 
         [0124]    Although the regulation mechanism  80  is arranged on the main body unit  4  side of  FIG. 12  to  FIG. 14 , the regulation member  35  may be arranged on the cover unit  3  side as illustrated in  FIG. 7A . 
         [0125]    The main body unit  4  and the cover unit  3  are locked by the rotation shaft  65   b  of the platen roller  65 , or locked when the lock shaft (not shown) installed on the cover unit  3  on the fixed blade  30  side with respect to the rotation shaft  65   b  is fitted to the lock groove (not shown) on the main body unit  4  side, and the regulation member  35  is arranged on the fixed blade  30  side with respect to the rotation shaft  65   b  of the cover unit  4 . 
         [0126]    In other words, with the coupling region (lock region) of the main body unit  4  and the cover unit  3  being formed in the vicinity of the pinion gear  42  and the fixed blade  30 , the regulation member  35  is arranged on the fixed blade  30  side immediately above with respect to the coupling region of the main body unit  4  and the cover unit  3 . 
         [0127]    The upward pressure contacting force Fzs which the movable blade  10  receives from the fixed blade  30  and the upward meshing reaction force Fzt which the rack  44  receives from the pinion gear  42  illustrated in  FIG. 9A  are exerted on the regulation member  35  supported by the cover unit  3  in  FIG. 7A . Most of such forces can be received at the coupling region (lock region) by adopting the above-mentioned arrangement, and thus the rotational moment having the coupling region (lock region) as the center that acts on the cover unit  4  can be minimized. 
         [0128]    The regulation member  35  may be configured simply by a rigid body. Thus, as illustrated in  FIG. 7A , the movement of the movable blade  10  to the upper side can be regulated by the regulation member  35  by merely coupling the cover unit  3  to the main body unit  4 . Further, as illustrated in  FIG. 7B , the movement of the movable blade  10 , which is regulated by the regulation member  35 , can be deregulated by merely separating the cover unit from the main body unit  4 . Therefore, a complex mechanism for regulating the movement of the movable blade  10  is unnecessary, and the manufacturing cost can be reduced. 
       (Movable Blade Socket) 
       [0129]    The thermal printer  1  includes a movable blade socket (supporting unit) with which the movable blade  10  can be replaced. 
         [0130]      FIG. 16  and  FIG. 17  are explanatory views of the movable blade socket.  FIG. 16A  is a side cross-sectional view taken along the line B-B of  FIG. 16B , and  FIG. 16B  is a bottom view.  FIG. 17A  is a plan view, and  FIG. 17B  is a partial cross-sectional view taken along the line C-C of  FIG. 17A . 
         [0131]    As illustrated in  FIG. 16A , the cover unit  3  is provided below the open/close door  6 , and the movable blade socket  110  is provided in the interior of the cover unit  3 . The movable blade socket  110  is made of resin material and the like, is formed to a box-shape with one surface opened, and is able to interiorly accommodate the movable blade  10 . As illustrated in  FIG. 16A  and  FIG. 15B , a cutout  112  for exposing the cutting edge  10   a  of the movable blade  10  is provided on the upper surface and the lower surface of the movable blade socket  110 . 
         [0132]    As illustrated in  FIG. 16B , a stopper  103  is arranged on the opposite side of the fixed blade (not shown) with the movable blade socket  110  in between. The elastic body  37  for biasing the movable blade socket  110  toward the stopper  103  is also provided. The movable blade  10  is arranged at the home position when the movable blade socket  110  contacts the stopper  103 . The rack  44  is formed on both sides in the width direction of the bottom surface of the movable blade socket  110 . 
         [0133]    As illustrated in  FIG. 17A , a pair of fixation holes  14  is provided on the proximal end side of the movable blade  10 . As illustrated in  FIG. 17B , a pair of projections  114  is formed on the inner surface of the movable blade socket  110 . The movable bade  10  is fixed to the movable blade socket  110  when each projection  114  engages each fixation hole  14 , with the movable blade  10  being accommodated inside the movable blade socket  110 . 
         [0134]    As illustrated in  FIG. 17A , a replacement hole  12  is provided on the distal end (cutting edge  10   a ) side of the movable blade  10 . The replacement hole  12  is exposed from the cutout  112  formed on the upper surface and the lower surface of the movable blade socket  110 . A movable blade replacement jig having a hook at the distal end is prepared, and the hook is inserted to the replacement hole  12  so that the movable blade  10  is pulled to the opening side of the movable blade socket  110 . The projection  114  and the fixation hole  14  illustrated in  FIG. 17B  are thereby disengaged, and the movable blade  10  can be pulled out from the movable blade socket  110 . 
         [0135]    After that, a different movable blade  10  is inserted and fixed to the movable blade socket  110 , and the replacement of the movable blade  10  is completed. 
         [0136]    The movable blade  10  is replaced when changing the type of the movable blade  10  other than when discarding the movable blade  10  which cutting edge  10   a  has degraded. 
         [0137]      FIG. 18  are plan views of the movable blade for cutting the recording sheet while leaving the connecting points, where  FIG. 18A  is a movable blade for leaving one point and  FIG. 18B  is a movable blade for leaving two points. The movable blade  10  illustrated in  FIG. 18A  includes a cutout  16  at a central valley portion of the V-shaped cutting edge  10   a . When the movable blade  10  is moved so that the fixed blade  30  overlaps up to the middle of the cutout  16 , the recording sheet is not cut at the portion of the cutout  16 , and the recording sheet is cut at other portions. The recording sheet thus can be cut leaving one connecting point at the central part in the width direction. The movable blade  10  illustrated in  FIG. 18B  includes the cutouts  16 ,  16  at a central part of the inclined side of the V-shaped cutting edge  10   a . When the movable blade  10  is moved so that the fixed blade  30  overlaps up to the middle of the cutouts  16 ,  16  beyond the central valley portion of the cutting edge  10   a , the recording sheet can be cut while leaving two connecting points. The scattering of the recording sheet discharged from the printer can be prevented by leaving the connecting point. The connecting point can be easily broken to separate the recording sheet by simply pulling the discharged recording sheet. 
         [0138]    In the techniques disclosed in Patent Documents 1 and 2, it is impossible to replace only the movable blade, and the whole movable blade unit including the platen roller and the pinion gear needs to be replaced, and thus the waste in replacing the movable blade is large. 
         [0139]    In this embodiment, on the other hand, the pinion gear  42  is mounted to the main body unit  4  as illustrated in  FIG. 4 , and thus a simple structure in which only the movable blade  10  and the platen roller  65  are mounted to the cover unit  3  is obtained. Thus, only the movable blade  10  can be replaced without replacing the pinion gear  42  and the pinion drive system  41 , and the waste in replacement can be eliminated. 
         [0140]    The technical scope of the present invention is not limited to the above-mentioned embodiments, and various modifications may be made to the above-mentioned embodiments without departing from the gist of the present invention. In other words, the specific material and layer configuration described in the embodiment are merely examples, and may be appropriately changed. 
         [0141]    For instance, while the thermal printer has been described as an example of the printer with cutter in each embodiment, this should not be construed restrictively. For instance, an inkjet printer for printing the pulled out recording sheet using ink droplets, with the thermal head as the inkjet head, may be adopted. 
         [0142]    The thermal printer having the open/close door provided on the upper surface of the casing has been described. However, the open/close door may be provided on the front surface of the casing and the printed recording sheet may be discharged from the front surface side. The thermal printer of drop-in type in which the roll sheet is inserted and simply placed on the mounting board has been described. However, instead of such type, a pivot supporting type thermal printer in which a pivot supporting mechanism for pivotally supporting (rotatably supporting) the roll sheet inside the casing is provided may be adopted.