Patent Publication Number: US-2022227598-A1

Title: Printing apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-006186, filed Jan. 19, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a printing apparatus. 
     2. Related Art 
     As disclosed in JP-A-2010-274379, a printer that includes a home-position detection sensor of a switch type for detecting a home position of a cutter is known. 
     When the printer uses, instead of the home-position detection sensor of the switch type, an optical sensor including a light-emitting element and a light-receiving element, foreign substances, such as grease spattered from a cutter drive section and paper dust generated during paper cutting, may enter the optical sensor. 
     SUMMARY 
     A printing apparatus of the disclosure includes: a first blade configured to cut a printing medium; a cutter motor; a drive gear configured to engage the first blade and configured to be rotated by the cutter motor to drive the first blade; a rotator configured to rotate in accordance with rotation of the drive gear; a photosensor configured to output a detection signal in accordance with rotation of the rotator and configured to include a light-receiving/emitting section including a light-emitting element and a light-receiving element and a sensor substrate at which the light-receiving/emitting section is provided, a first cutter frame configured to support the photosensor; and a cover member configured to cover the sensor substrate, wherein the sensor substrate is provided between the cover member and the first cutter frame. 
     A printing apparatus of the disclosure includes: a first blade configured to cut a printing medium; a cutter motor; a drive gear configured to engage the first blade and configured to be rotated by the cutter motor to drive the first blade; a rotator configured to rotate in accordance with rotation of the drive gear; a photosensor configured to output a detection signal in accordance with rotation of the rotator and configured to include a light-receiving/emitting section including a light-emitting element and a light-receiving element and a sensor substrate at which the light-receiving/emitting section is provided, a first cutter frame configured to rotatably support the drive gear; and a cover member configured to include at least one of a first annular wall located along an inner side of a rotation path of the rotator and a second annular wall located along an outer side of the rotation path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a printing apparatus in which an opening/closing cover is closed. 
         FIG. 2  is a perspective view of the printing apparatus in which the opening/closing cover is opened. 
         FIG. 3  is a sectional view of the printing apparatus. 
         FIG. 4  is a perspective view of an internal structure of the printing apparatus. 
         FIG. 5  illustrates a cutter unit, excluding a first cutter frame, viewed from the +Z direction side. 
         FIG. 6  illustrates the cutter unit viewed from the +Z direction side. 
         FIG. 7  is a sectional view along line VII-VII in  FIG. 6 . 
         FIG. 8  is an enlarged view of a portion surrounded by line VIII in  FIG. 6 . 
         FIG. 9  illustrates components of the cutter unit, which are supported by a second cutter frame. 
         FIG. 10  illustrates components of the cutter unit, which are supported by a first cutter frame. 
         FIG. 11  is a sectional view along line XI-XI in  FIG. 10 . 
         FIG. 12  is a perspective view of a detection gear. 
         FIG. 13  is a perspective view of a detection gear shaft. 
         FIG. 14  is a perspective view of a cover member. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     An embodiment of a printing apparatus will be described below with reference to the accompanying drawings. A printing apparatus  1  of the present embodiment is used as, for example, a receipt printer in a POS system. The following description will be given with directions in the XYZ orthogonal coordinate system illustrated in the drawings. However, such directions are used merely for convenience of description and should not limit the embodiment described below. Note that the vertical direction corresponds to the Z direction in  FIGS. 1 to 4 , and a direction parallel to a rotational axis of a drive gear  59  illustrated in  FIG. 5  corresponds to the Z direction in  FIGS. 5 to 14 . 
     External Structure of Printing Apparatus 
     An external structure of the printing apparatus  1  will be described with reference to  FIGS. 1 and 2 . The printing apparatus  1  includes an apparatus main body  3  and an opening/closing cover  5 . The apparatus main body  3  has a substantially rectangular parallelepiped shape and includes an opening  6  on the +Z direction side, and a paper-roll container  7  is provided in the apparatus main body  3 . A paper roll R obtained by rolling recording paper P, which is a printing medium, into a roll shape is accommodated in the paper-roll container  7  (refer to  FIG. 3 ). The opening/closing cover  5  is attached to the +Y direction end of the apparatus main body  3  so as to be rotationally movable and opens/closes the opening  6 . 
     The exterior of the printing apparatus  1  is constituted by a main body outer case  9 , a cutter unit cover  11 , an opening outer case  12 , and a cover outer case  13 . 
     The exterior of the apparatus main body  3  is constituted by the main body outer case  9 , the cutter unit cover  11 , and the opening outer case  12 . The main body outer case  9  has a substantially rectangular parallelepiped box shape that is open on the +Z direction side. The cutter unit cover  11  is provided in the −Y direction with respect to the opening/closing cover  5 . Opening the cutter unit cover  11  exposes an automatic cutter  37  (refer to  FIG. 3 ) described later. A discharge port  15  is provided at a boundary between the cutter unit cover  11  and the opening/closing cover  5 . The recording paper P drawn from the paper roll R accommodated in the paper-roll container  7  is discharged from the discharge port  15 . The opening outer case  12  is provided in an edge portion of the opening  6 . The exterior of the opening/closing cover  5  is constituted by the cover outer case  13 . 
     The printing apparatus  1  includes a cover open button  17 , a feed button  19 , and a panel  21 . The cover open button  17 , the feed button  19 , and the panel  21  are provided in the +X direction end on the +Z direction surface of the printing apparatus  1 . When the cover open button  17  is pressed, the opening/closing cover  5  is opened. When the feed button  19  is pressed, a platen roller  35  described later rotates, and the recording paper P is fed to the discharge port  15 . The panel  21  displays various information about an error or the like for a user. 
     Internal Structure of Printing Apparatus 
     An internal structure of the printing apparatus  1  will be described with reference to  FIGS. 3 and 4 . The printing apparatus  1  includes a base frame  23 , a main body frame  25 , a cover frame  27 , a thermal head  29 , a feed motor  31 , a gear train  33 , the platen roller  35 , the automatic cutter  37 , and a lock mechanism  39 . 
     The base frame  23  and the main body frame  25  are provided in the main body outer case  9 . The base frame  23  supports the main body frame  25 . The main body frame  25  includes a first main body frame  41  and a second main body frame  43 . Both the first main body frame  41  and the second main body frame  43  have a substantially rectangular plate shape extending in the Y direction. The second main body frame  43  is provided in the +X direction with respect to the first main body frame  41 . A cover support shaft  45  extending in the X direction is provided in the +Y direction end of the first main body frame  41  and the +Y direction end of the second main body frame  43 . 
     The cover frame  27  is provided in the cover outer case  13 . The cover frame  27  has a substantially rectangular frame shape and is supported by the main body frame  25  via the cover support shaft  45  so as to be rotationally movable. A shaft hole for the cover support shaft (not illustrated) that engages the cover support shaft  45  is provided in the +Y direction end of the cover frame  27 . 
     The thermal head  29  is supported by the main body frame  25 . The thermal head  29  includes a plurality of heating elements (not illustrated) and performs printing on the recording paper P drawn from the paper roll R. 
     The feed motor  31  is fixed to the −Y direction end of the first main body frame  41 . The feed motor  31  is a drive source of the platen roller  35 . Note that, for example, a direct current (DC) motor may be used as the feed motor  31 . 
     The gear train  33  is provided in the first main body frame  41 . The gear train  33  includes a plurality of gears and transfers power of the feed motor  31  to the platen roller  35 . 
     The platen roller  35  is rotatably supported by the −Y direction end of the cover frame  27 . When the opening/closing cover  5  is closed, the platen roller  35  faces the thermal head  29 . A force is applied by a roller spring (not illustrated) such that the platen roller  35  is directed toward the thermal head  29 . Thus, the platen roller  35  holds the recording paper P against the thermal head  29 . The platen roller  35  feeds the recording paper P held against the thermal head  29  to the discharge port  15 . That is, when the platen roller  35  rotates, the recording paper P is drawn from the paper roll R and fed to the discharge port  15 . 
     A roller gear  47 , which is located in the −X direction with respect to the platen roller  35 , is provided on the same shaft as the platen roller  35 . The roller gear  47  engages a transfer gear  49  of the gear train  33  and rotates integrally with the platen roller  35 . 
     The automatic cutter  37  is provided between the platen roller  35  and the discharge port  15  and cuts the recording paper P, which has been fed to the discharge port  15 , on a rear side of a printed portion in the X direction, that is, a width direction of the recording paper P. Note that the automatic cutter  37  cuts the recording paper P while the −X direction end of the recording paper P remains uncut such that the cut recording paper P stays in the discharge port  15 . 
     Automatic Cutter 
     As illustrated in  FIGS. 3 and 4 , the automatic cutter  37  includes a cutter unit  51  and a second blade  52 . The cutter unit  51  is provided in the −Y direction end of the first main body frame  41  and the −Y direction end of the second main body frame  43  across a space between the first main body frame  41  and the second main body frame  43 . The second blade  52  is provided in the −Y direction end of the cover frame  27  so as to face a first blade  53  of the cutter unit  51  when the opening/closing cover  5  is closed. When the first blade  53 , which is a movable blade, is operated with respect to the second blade  52 , which is a fixed blade, to perform cutting, the recording paper P is cut. 
     As illustrated in  FIGS. 5 and 6 , the cutter unit  51  includes the first blade  53 , a cutter motor  55 , a power transfer member  57 , the drive gear  59 , a detection gear  61 , a photosensor  63 , a cover member  65 , and a cutter frame  67  in which the above-described components are accommodated. 
     The cutter frame  67  has a flat substantially rectangular parallelepiped case shape. The cutter frame  67  includes a first cutter frame  69  and a second cutter frame  71 . The first cutter frame  69  and the second cutter frame  71  are detachably combined with each other by, for example, a small screw. The second cutter frame  71  is provided in the −Z direction with respect to the first cutter frame  69 . The first blade  53 , the cutter motor  55 , the power transfer member  57 , the drive gear  59 , the detection gear  61 , the photosensor  63 , and the cover member  65  are accommodated between the second cutter frame  71  and the first cutter frame  69 . The cutter motor  55 , the power transfer member  57 , the drive gear  59 , the detection gear  61 , the photosensor  63 , and the cover member  65  are supported by the first cutter frame  69  (refer to  FIG. 10 ). On the other hand, the first blade  53  is supported by the second cutter frame  71  (refer to  FIG. 9 ). Note that the first cutter frame  69  may be referred to as a first cutter cover, and the second cutter frame  71  may be referred to as a second cutter cover. 
     Here, a region in which the first blade  53  rotationally moves is referred to as a blade rotational-movement region  73 . A region in which the cutter motor  55 , the power transfer member  57 , and the drive gear  59  are provided is referred to as a drive region  75 . A region in which the detection gear  61 , the photosensor  63 , and the cover member  65  are provided is referred to as a detection region  77 . As described above, of the components accommodated in the cutter frame  67 , the first blade  53  is supported by the second cutter frame  71 , and the other components are supported by the first cutter frame  69 . Thus, as illustrated in  FIG. 7 , the drive region  75  and the detection region  77  are provided side by side in the X direction between the blade rotational-movement region  73  and the first cutter frame  69 . As a result, space in the cutter frame  67  is able to be used efficiently, thus achieving a reduction in size of the cutter unit  51 . 
     The first cutter frame  69  includes a shaft engaging hole  79 , a first mark opening  83 , a second mark opening  85 , and an operation opening  87 . 
     The shaft engaging hole  79  engages a first shaft end  125  of a detection gear shaft  113  described later (refer to  FIG. 11 ). The shaft engaging hole  79  is a D-shaped hole the −X direction end of which extends linearly. The linear portion of the shaft engaging hole  79  is referred to as a hole linear section  89 . 
     The first mark opening  83  is provided at a position corresponding to a portion in which the drive gear  59  engages the detection gear  61 . The second mark opening  85  is provided between the first mark opening  83  and the rotational center of the drive gear  59 . The operation opening  87  is provided in the −Y direction with respect to the first mark opening  83 . 
     Note that a manual cutter  91  is provided outside the first cutter frame  69 , that is, on the +Z direction surface of the first cutter frame  69 . The manual cutter  91  enables the user to tear off the recording paper P by hand. 
     As illustrated in  FIG. 9 , a cutter support shaft  93  is provided in a corner of the second cutter frame  71 , which is located in the +X direction and the +Y direction. The cutter support shaft  93  supports the first blade  53  such that the first blade  53  is rotationally movable. 
     The first blade  53  is supported by the second cutter frame  71  via the cutter support shaft  93  so as to be rotationally movable. The first blade  53  includes a first cutting edge  95 , a shaft hole for the cutter support shaft (not illustrated), and a cutter engaging hole  99 . The first cutting edge  95  extends in the longitudinal direction of the first blade  53 . The shaft hole for the cutter support shaft is provided in one end of the first blade  53  in the longitudinal direction, that is, the +X direction end of the first blade  53 . The cutter support shaft  93  is inserted into the shaft hole for the cutter support shaft. The cutter engaging hole  99  is provided in the vicinity of the back of the first blade  53  and is a rectangle with rounded ends elongated in the longitudinal direction of the first blade  53 . The cutter engaging hole  99  engages a drive pin  109  (refer to  FIG. 10 ) provided in the drive gear  59 . 
     Here, a position at which the first blade  53  starts a cutting operation is referred to as a cutting start position. The cutting start position of the first blade  53  is a position at which the first blade  53  is farthest from the second blade  52 . On the other hand, a position at which the first blade  53  performs cutting-into processing by approaching the second blade  52  such that the first cutting edge  95  of the first blade  53  is substantially parallel to a second cutting edge (not illustrated) of the second blade  52  extending in the X direction is referred to as a cutting-into position. The first blade  53  illustrated in the drawings, such as in  FIG. 9 , is at the cutting start position. Note that the cutting start position may be referred to as a standby position, and the cutting-into position may be referred to as a cutting position. 
     As illustrated in  FIG. 10 , the cutter motor  55  is located in the +X direction end of the first cutter frame  69  and fixed to the first cutter frame  69 . The cutter motor  55  is a drive source of the first blade  53 . An output gear  101  is provided in an output shaft of the cutter motor  55 . For example, a DC motor may be used as the cutter motor  55 . 
     The power transfer member  57  is located in the −Y direction end of the first cutter frame  69  and rotatably supported by the first cutter frame  69 . The power transfer member  57  transfers power of the cutter motor  55  to the drive gear  59 . The power transfer member  57  has a substantially column-like shape as a whole and extends in the X direction. The power transfer member  57  includes a first gear section  103 , a second gear section  105 , and an operation section  107  in this order from the +X direction side, that is, in order from the cutter motor  55 . The first gear section  103 , the second gear section  105 , and the operation section  107  rotate integrally. 
     The first gear section  103  engages the output gear  101 . The second gear section  105  engages the drive gear  59 . Here, the output gear  101  and the power transfer member  57  rotate about an axis parallel to the X-axis direction. On the other hand, the drive gear  59  and the detection gear  61  rotate about an axis parallel to the Z-axis direction. That is, the second gear section  105  and the drive gear  59  correspond to a worm and a worm wheel, respectively. 
     The operation section  107  has a substantially short column shape, and a plurality of grooves extending in an axial direction of the operation section  107  are provided on a peripheral surface of the operation section  107 . The operation section  107  is able to be operated through the operation opening  87  provided in the first cutter frame  69  (refer to  FIG. 6 ). When the user inserts a finger through the operation opening  87  to rotate the operation section  107 , the user is able to rotate the drive gear  59  and rotationally move the first blade  53 . 
     The operation section  107  is used, for example, when the first blade  53  does not return to the cutting start position and becomes stuck due to jamming of the recording paper P or the like in the cutter unit  51 . That is, when the user opens the cutter unit cover  11  described above and inserts a finger through the operation opening  87  to rotate the operation section  107 , the first blade  53  is able to return to the cutting start position. 
     The drive gear  59  is rotatably supported by the first cutter frame  69 . The drive gear  59  is provided in the +Y direction with respect to the second gear section  105  and engages the second gear section  105 . The drive gear  59  is provided in the +Z direction with respect to the first blade  53  (refer to  FIG. 7 ). The drive pin  109  protrudes from a second drive end surface  59   b , which is the −Z direction end surface of the drive gear  59 , to the first blade  53  in the −Z direction. The drive pin  109  engages the cutter engaging hole  99  of the first blade  53 . When power of the cutter motor  55  is transferred to the drive gear  59  via the power transfer member  57  and when the drive pin  109  rotates about the rotational center of the drive gear  59 , the first blade  53  that engages the drive pin  109  rotationally moves. 
     Here, a rotational position of the drive gear  59  when the first blade  53  is at the cutting start position is referred to as a drive gear home position. When the drive gear  59  completes rotation from the drive gear home position, the first blade  53  rotationally moves clockwise from the cutting start position to the cutting-into position when viewed from the +Z direction side and further rotationally moves counterclockwise from the cutting-into position to the cutting start position. The drive gear  59  illustrated in the drawings, such as in  FIG. 10 , is at the drive gear home position. 
     As illustrated in  FIGS. 5, 6, and 8 , a first drive mark  111   a  and a third drive mark  111   c  are provided on a first drive end surface  59   a , which is the +Z direction end surface of the drive gear  59 . The first drive mark  111   a , the third drive mark  111   c , and the drive pin  109  are provided so as to have a given positional relationship in the rotational direction of the drive gear  59 . That is, the first drive mark  111   a  is on an inter-gear imaginary line La passing through the rotational center of the drive gear  59  and the rotational center of the detection gear  61  when the drive gear  59  is at the drive gear home position. When the drive gear  59  is at the drive gear home position, the first drive mark  111   a  is visible through the first mark opening  83 . The third drive mark  111   c  is provided between the first drive mark  111   a  and the rotational center of the drive gear  59 . When the drive gear  59  is at the drive gear home position, the third drive mark  111   c  is visible through the second mark opening  85 . 
     As illustrated in  FIG. 10 , a second drive mark  111   b  is provided on the second drive end surface  59   b  of the drive gear  59 . The second drive mark  111   b  and the drive pin  109  are provided so as to have a given positional relationship in the rotational direction of the drive gear  59 . That is, when the drive gear  59  is at the drive gear home position, the second drive mark  111   b  is on the inter-gear imaginary line La. 
     The detection gear  61  is rotatably supported by the first cutter frame  69  via the detection gear shaft  113 . A first-gear-side shaft insertion hole  115  and a second-gear-side shaft insertion hole  117  are provided in the center of the detection gear  61  (refer to  FIG. 11 ). The second-gear-side shaft insertion hole  117  is provided in the −Z direction with respect to the first-gear-side shaft insertion hole  115  and is larger in diameter than the first-gear-side shaft insertion hole  115 . The detection gear shaft  113  is inserted into the first-gear-side shaft insertion hole  115  and the second-gear-side shaft insertion hole  117 . 
     The detection gear  61  is provided in the −X direction with respect to the drive gear  59  and engages the drive gear  59 . The rotational rate of the detection gear  61  is the same as the rotational rate of the drive gear  59 . That is, the number of teeth of the detection gear  61  is the same as the number of teeth of the drive gear  59 . 
     As illustrated in  FIG. 12 , a rotator  119  protrudes from a first detection end surface  61   a , which is the +Z direction end surface of the detection gear  61 , in the +Z direction. The rotator  119  has a substantially arced shape about the rotational center of the detection gear  61 . The rotator  119  rotates in conjunction with the drive gear  59 . In other words, the rotator  119  rotates upon rotation of the drive gear  59 . That is, when the detection gear  61  that engages the drive gear  59  rotates, the rotator  119  rotates about the rotational center of the detection gear  61 . The rotational rate of the rotator  119  is the same as the rotational rate of the drive gear  59 . When the rotator  119  rotates upon rotation of the detection gear  61 , the rotator  119  passes between a light-emitting element  141  and a light-receiving element  143  of the photosensor  63 . That is, the rotator  119  functions as a light-blocking member for blocking detection light emitted from the light-emitting element  141  to the light-receiving element  143 . Note that  FIG. 11  illustrates a state in which the rotator  119  is not located between the light-emitting element  141  and the light-receiving element  143 . As described below, when the detection light is not blocked by the rotator  119 , the photosensor  63  outputs a first detection signal, and when the detection light is blocked by the rotator  119 , the photosensor  63  outputs a second detection signal. 
     Here, a rotational position of the detection gear  61  when the rotator  119  causes the photosensor  63  to output the first detection signal, that is, when the rotator  119  is not located between the light-emitting element  141  and the light-receiving element  143 , is referred to as a detection gear home position. The detection gear  61  illustrated in the drawings, such as in  FIG. 10 , is at the detection gear home position. 
     As illustrated in  FIGS. 6 and 8 , a first detection mark  121   a  is provided on the first detection end surface  61   a  of the detection gear  61 . The first detection mark  121   a  and the rotator  119  are provided so as to have a given positional relationship in the rotational direction of the drive gear  59 . That is, when the detection gear  61  is at the detection gear home position, the first detection mark  121   a  is on the inter-gear imaginary line La. When the detection gear  61  is at the detection gear home position, the first detection mark  121   a  is visible through the first mark opening  83 . 
     As illustrated in  FIG. 10 , a second detection mark  121   b  and a third detection mark  121   c  are provided on a second detection end surface  61   b , which is the −Z direction end surface of the detection gear  61 . The second detection mark  121   b , the third detection mark  121   c , and the rotator  119  are provided so as to have a given positional relationship in the rotational direction of the detection gear  61 . That is, when the detection gear  61  is at the detection gear home position, the second detection mark  121   b  is on the inter-gear imaginary line La. When the detection gear  61  is at the detection gear home position, the third detection mark  121   c  is on a cover imaginary line Lb passing through the rotational center of the detection gear  61  and a cover mark  153  described later. 
     As described above, the second drive mark  111   b  is provided on the second drive end surface  59   b  of the drive gear  59 , the second detection mark  121   b  and the third detection mark  121   c  are provided on the second detection end surface  61   b  of the detection gear  61 , and the cover mark  153  is provided on the −Z direction surface of the cover member  65 . Thus, when assembling the cutter unit  51 , a worker matches the third detection mark  121   c  of the detection gear  61  with the cover mark  153  of the cover member  65 , that is, positions the third detection mark  121   c  on the cover imaginary line Lb, as illustrated in  FIG. 10  and is thus able to position the detection gear  61  at the detection gear home position. At this time, the second detection mark  121   b  of the detection gear  61  is on the inter-gear imaginary line La. 
     Next, the worker matches the second drive mark  111   b  of the drive gear  59  with the second detection mark  121   b  of the detection gear  61 , that is, positions the second drive mark  111   b  on the inter-gear imaginary line La, and is thus able to position the drive gear  59  at the drive gear home position. In this manner, by using the second drive mark  111   b , the second detection mark  121   b , the third detection mark  121   c , and the cover mark  153 , the worker is able to easily position the drive gear  59  at the drive gear home position and the detection gear  61  at the detection gear home position. 
     Note that, although a procedure for positioning the drive gear  59  and the detection gear  61  has been described here by exemplifying a procedure in which the worker matches the third detection mark  121   c  of the detection gear  61  with the cover mark  153  of the cover member  65  and then matches the second drive mark  111   b  of the drive gear  59  with the second detection mark  121   b  of the detection gear  61 , the procedure is not limited thereto. For example, the worker may match the second drive mark  111   b  of the drive gear  59  with the second detection mark  121   b  of the detection gear  61 , that is, position the second drive mark  111   b  and the second detection mark  121   b  on the inter-gear imaginary line La, by using neither the third detection mark  121   c  nor the cover mark  153 . Also in this instance, the worker is able to position the drive gear  59  at the drive gear home position and the detection gear  61  at the detection gear home position. 
     As described above, the first drive mark  111   a  and the third drive mark  111   c  are provided on the first drive end surface  59   a  of the drive gear  59 , and the first detection mark  121   a  is provided on the first detection end surface  61   a  of the detection gear  61 . The first mark opening  83  and the second mark opening  85  are provided in the first cutter frame  69 . Thus, to return the first blade  53  to the cutting start position by rotating the operation section  107 , the user rotates the operation section  107  until the third drive mark  111   c  is visible through the second mark opening  85  as illustrated in  FIGS. 6 and 8 , and the user is thus able to return the first blade  53  to the cutting start position. By viewing the first drive mark  111   a  and the first detection mark  121   a  through the first mark opening  83 , the worker is able to check the drive gear  59  at the drive gear home position and the detection gear  61  at the detection gear home position. 
     As illustrated in  FIGS. 11 and 13 , the detection gear shaft  113  is fixed to the first cutter frame  69  by a shaft fixing screw  123 . The detection gear shaft  113  includes the first shaft end  125 , a second shaft end  127 , and a shaft middle section  129 . 
     The first shaft end  125  is provided in the +Z direction end of the detection gear shaft  113  and is smaller in diameter than the shaft middle section  129 . The first shaft end  125  includes a first cut section  131  subjected to D-cut processing. The first shaft end  125  is slightly smaller in diameter than the shaft engaging hole  79 , which is provided in the first cutter frame  69 , and engages the shaft engaging hole  79 . The first shaft end  125  subjected to D-cut processing engages the shaft engaging hole  79 , which corresponds to the D-shaped hole, thus suppressing the detection gear shaft  113  from rotating. 
     The second shaft end  127  is provided in the −Z direction end of the detection gear shaft  113  and is larger in diameter than the shaft middle section  129 . The second shaft end  127  is slightly smaller in diameter than the second-gear-side shaft insertion hole  117  and engages the second-gear-side shaft insertion hole  117 . The second shaft end  127  includes a second cut section  133  subjected to D-cut processing. The second cut section  133  is provided at the same position as the first cut section  131  in a circumferential direction of the detection gear shaft  113 . 
     The shaft middle section  129  is located between the first shaft end  125  and the second shaft end  127  and has a substantially column-like shape. The shaft middle section  129  is slightly smaller in diameter than the first-gear-side shaft insertion hole  115  and a cover-side shaft insertion hole  155  described later and engages the first-gear-side shaft insertion hole  115  and the cover-side shaft insertion hole  155 . 
     When assembling the cutter unit  51 , the detection gear shaft  113  is inserted into the second-gear-side shaft insertion hole  117 , the first-gear-side shaft insertion hole  115 , and the cover-side shaft insertion hole  155  in this order from the −Z direction side and is screwed by the shaft fixing screw  123  in a state in which the first shaft end  125  engages the shaft engaging hole  79 . The first cut section  131  of the first shaft end  125  needs to be aligned with the hole linear section  89  of the shaft engaging hole  79  to cause the first shaft end  125  to engage the shaft engaging hole  79 . Here, since the first cut section  131  is hidden by the detection gear  61  and the cover member  65  and is not visible to the worker, in the configuration in which the second shaft end  127  includes no second cut section  133 , which differs from the present embodiment, it is difficult for the worker to identify the orientation of the first cut section  131 , thus requiring time and effort to cause the first shaft end  125  to engage the shaft engaging hole  79 . 
     On the other hand, in the present embodiment, since the second shaft end  127  has the second cut section  133  provided at the same position as the first cut section  131  in the circumferential direction of the detection gear shaft  113 , the worker is able to identify the orientation of the first cut section  131  by viewing the second cut section  133 . That is, by orienting the second cut section  133  in the −X direction so as to be aligned with the hole linear section  89  as illustrated in  FIG. 10 , the worker is able to align the first cut section  131  with the hole linear section  89  and cause the first shaft end  125  to engage the shaft engaging hole  79  smoothly. Also when the orientation of the second cut section  133  deviates from the orientation of the hole linear section  89 , by inserting forceps or the like into a gap generated between an inner circumferential surface of the second-gear-side shaft insertion hole  117  and the second cut section  133  to rotate the detection gear shaft  113 , the worker is able to align the second cut section  133  with the hole linear section  89  and cause the first shaft end  125  to engage the shaft engaging hole  79 . 
     As illustrated in  FIG. 11 , the photosensor  63  is located in the −X direction end of the first cutter frame  69  and provided between the first cutter frame  69  and the cover member  65 . The photosensor  63  is fixed to the cover member  65  by a sensor screw  135  (refer to  FIG. 7 ). That is, the photosensor  63  is supported by the first cutter frame  69  via the cover member  65 . The photosensor  63  is provided in the +Z direction with respect to the detection gear  61 . 
     The photosensor  63  includes a light-receiving/emitting section  137  and a sensor substrate  139 . The light-receiving/emitting section  137  includes the light-emitting element  141  and the light-receiving element  143 , is provided at the sensor substrate  139 , and protrudes from the sensor substrate  139  in the −Z direction. The light-receiving/emitting section  137  is provided on a rotation path of the rotator  119 . Thus, as described above, when the rotator  119  rotates upon rotation of the detection gear  61 , the rotator  119  passes between the light-emitting element  141  and the light-receiving element  143 . As a result, the detection light emitted from the light-emitting element  141  to the light-receiving element  143  is switched between a state of being blocked by the rotator  119  and a state of not being blocked by the rotator  119 . Note that, although the light-receiving element  143  is provided inward of the light-emitting element  141  in the radial direction of the detection gear  61  in  FIG. 11 , the light-emitting element  141  may be provided inward of the light-receiving element  143  in the radial direction of the detection gear  61 . 
     The sensor substrate  139  outputs either the first detection signal or the second detection signal in accordance with whether or not the detection light emitted from the light-emitting element  141  to the light-receiving element  143  is blocked by the rotator  119 . That is, as described above, when the detection light is not blocked by the rotator  119 , the sensor substrate  139  outputs the first detection signal, and when the detection light is blocked by the rotator  119 , the sensor substrate  139  outputs the second detection signal. Note that the first detection signal and the second detection signal may be, for example, signals that differ from each other in voltage or current. 
     The first detection signal or the second detection signal that is output from the sensor substrate  139  is received by a control circuit (not illustrated) provided in the printing apparatus  1 . The control circuit includes a processor and memory. When the first detection signal is received, the control circuit determines that the first blade  53  is at the cutting start position. When the second detection signal is received, the control circuit determines that the first blade  53  is not at the cutting start position. 
     After a portion of the recording paper P, which is to be cut, is fed to the automatic cutter  37 , the control circuit determines whether or not the first detection signal is received from the photosensor  63 . When determining that the first detection signal is received from the photosensor  63 , the control circuit determines that the first blade  53  is at the cutting start position, and the control circuit operates the cutter motor  55  to start the cutting operation performed by the first blade  53 . Note that, when determining that the first detection signal is not received from the photosensor  63 , that is, determining that the second detection signal is received, the control circuit performs error processing. 
     After the cutting operation performed by the first blade  53  starts, the control circuit determines whether or not the first detection signal is received from the photosensor  63 . When determining that the first detection signal is not received from the photosensor  63 , that is, determining that the second detection signal is received, the control circuit determines that the first blade  53  has not returned to the cutting start position, and the control circuit continues the operation of the cutter motor  55 . When determining that the first detection signal is received from the photosensor  63 , the control circuit determines that the first blade  53  has returned to the cutting start position, and the control circuit stops the cutter motor  55  to end the cutting operation performed by the first blade  53 . 
     As illustrated in  FIGS. 11 and 14 , the cover member  65  is located in the −X direction end of the first cutter frame  69  and provided between the first cutter frame  69  and the detection gear  61 . The cover member  65  includes a sensor container  145  and a gear facing section  147 . 
     The sensor container  145  has a flat substantially polygonal prism shape that is open on the +Z direction side. The sensor container  145  accommodates the sensor substrate  139  and covers the sensor substrate  139  between the sensor container  145  and the first cutter frame  69 . That is, the −Z direction side and the periphery of the sensor substrate  139  are covered by the sensor container  145 , and the +Z direction side of the sensor substrate  139  is covered by the first cutter frame  69 . A sensor opening  149  is provided in the −Z direction wall of the sensor container  145 . The light-receiving/emitting section  137  of the photosensor  63  protrudes from the sensor opening  149  in the −Z direction. 
     When the sensor substrate  139  is covered by the sensor container  145  as described above, it is possible to suppress foreign substances from entering the sensor substrate  139 . This makes it possible to suppress an error in the detection result from the photosensor  63  due to entry of foreign substances and suppress a failure of the photosensor  63  due to entry of foreign substances. Here, examples of foreign substances include paper dust and paper pieces generated when the recording paper P is cut, grease spattered from a drive section of the cutter unit  51 , and water that is spilled by the user and enters through the discharge port  15 . 
     A cover base  151  protruding in the −Z direction is provided on the −Z direction surface of the sensor container  145 , that is, an outer surface of the cover member  65 . The cover base  151  has a substantially rectangular shape elongated in the radial direction of the detection gear  61  when viewed from the −Z direction side. The cover mark  153  is provided on the −Z direction surface of the cover base  151  in a portion closest to the rotational center of the detection gear  61 . 
     The gear facing section  147  has a substantially circular plate shape and faces the first detection end surface  61   a  of the detection gear  61 . The cover-side shaft insertion hole  155  into which the detection gear shaft  113  described above is inserted is provided in substantially the center of the gear facing section  147 . The cover-side shaft insertion hole  155  is substantially the same in diameter as the first-gear-side shaft insertion hole  115  described above. 
     A first annular wall  157  and a second annular wall  159  protrude from the −Z direction surface of the gear facing section  147  to the detection gear  61  in the −Z direction. The first annular wall  157  and the second annular wall  159  are formed concentrically around the center of the cover-side shaft insertion hole  155 . The first annular wall  157  is provided along the inner side of the rotation path of the rotator  119 , and the second annular wall  159  is provided along the outer side of the rotation path of the rotator  119 . That is, the rotator  119  is located between the first annular wall  157  and the second annular wall  159 . 
     A first cut-out section  161  is provided in the first annular wall  157  at a position corresponding to the sensor opening  149 . Similarly, a second cut-out section  163  is provided in the second annular wall  159  at a position corresponding to the sensor opening  149 . The light-receiving/emitting section  137  protruding from the sensor opening  149  is located in the first cut-out section  161  and the second cut-out section  163 . 
     Since the first annular wall  157  is provided along the inner side of the rotation path of the rotator  119  and the second annular wall  159  is provided along the outer side of the rotation path of the rotator  119  as described above, it is possible to suppress foreign substances or ambient light from entering the rotation path of the rotator  119 . This makes it possible to suppress an error in the detection result from the photosensor  63  due to entry of foreign substances or ambient light and suppress a failure of the photosensor  63  due to entry of foreign substances. 
     Note that a pinching suppressing section  165  protrudes from the −Z direction surface of the gear facing section  147  in the −Z direction. The pinching suppressing section  165  is provided between the operation section  107  described above and a portion in which the drive gear  59  engages the detection gear  61  (refer to  FIG. 11 ). The pinching suppressing section  165  suppresses a finger of the user inserted through the operation opening  87  to operate the operation section  107  from being pinched between the drive gear  59  and the detection gear  61 . 
     As described above, according to the printing apparatus  1  of the present embodiment, in the cutter unit  51 , the sensor substrate  139  is covered by the sensor container  145 , thus making it possible to suppress foreign substances from entering the sensor substrate  139 . In addition, according to the printing apparatus  1  of the present embodiment, in the cutter unit  51 , the first annular wall  157  is provided along the inner side of the rotation path of the rotator  119 , and the second annular wall  159  is provided along the outer side of the rotation path of the rotator  119 , thus making it possible to suppress foreign substances or ambient light from entering the rotator  119 . 
     Other Modified Examples 
     Needless to say, the disclosure is not limited to the embodiment described above and can employ various configurations without departing from the scope of the disclosure. For example, the embodiment described above can be changed to incorporate the following aspects in addition to those described above. A configuration in which the embodiment and a modified example are combined may be adopted. 
     The rotator  119  is not limited to being configured to be provided in the detection gear  61  as long as the rotator  119  rotates in conjunction with the drive gear  59 . For example, the rotator  119  may be configured to be provided in the drive gear  59 , in a gear that rotates integrally with the drive gear  59 , in a gear that does not engage the drive gear  59  but rotates by receiving power from the drive gear  59 , or in a gear located between the cutter motor  55  and the drive gear  59 . 
     The cover member  65  is not limited to being configured to include both the first annular wall  157  and the second annular wall  159  and may be configured to include either the first annular wall  157  or the second annular wall  159 . 
     The sensor substrate  139  is not limited to being configured to output the first detection signal, by which the control circuit determines that the first blade  53  is at the cutting start position, when the detection light is not blocked by the rotator  119 . That is, the sensor substrate  139  may be configured to output the first detection signal, by which the control circuit determines that the first blade  53  is at the cutting start position, when the detection light is blocked by the rotator  119 . In this instance, the position of the rotator  119  in the detection gear  61  may be changed such that the first blade  53  is at the cutting start position when the detection light is blocked by the rotator  119 . 
     Additional Notes 
     Hereinafter, additional notes on a printing apparatus will be described. 
     A printing apparatus includes: a first blade that cuts a printing medium; a cutter motor; a drive gear that engages the first blade and is rotated by the cutter motor to drive the first blade; a rotator that rotates in conjunction with the drive gear; a photosensor that includes a light-receiving/emitting section including a light-emitting element and a light-receiving element and that includes a sensor substrate that outputs either a first detection signal or a second detection signal in accordance with whether or not detection light emitted from the light-emitting element to the light-receiving element is blocked by the rotator; a first cutter frame that supports the photosensor; and a cover member that covers the sensor substrate between the cover member and the first cutter frame. 
     According to such a configuration, since the sensor substrate is covered by the cover member, it is possible to suppress foreign substances from entering the sensor substrate. 
     Note that the recording paper P is an example of a printing medium. 
     A printing apparatus includes: a first blade that cuts a printing medium; a cutter motor; a drive gear that engages the first blade and is rotated by the cutter motor to drive the first blade; a rotator that rotates in conjunction with the drive gear; a photosensor that includes a light-receiving/emitting section including a light-emitting element and a light-receiving element and that includes a sensor substrate that outputs either a first detection signal or a second detection signal in accordance with whether or not detection light emitted from the light-emitting element to the light-receiving element is blocked by the rotator; a first cutter frame that rotatably supports the drive gear; and a cover member that includes a first annular wall located along an inner side of a rotation path of the rotator or a second annular wall located along an outer side of the rotation path, or both. 
     According to such a configuration, since the first annular wall is provided along the inner side of the rotation path or the second annular wall is provided along the outer side of the rotation path, it is possible to suppress foreign substances or ambient light from entering the rotator. 
     In this instance, the printing apparatus may further include a detection gear that engages the drive gear, in which the detection gear has a first detection end surface, and the rotator is provided on the first detection end surface. 
     According to such a configuration, the rotator provided on the first detection end surface of the detection gear is able to function as a light-blocking member for blocking detection light. 
     In this instance, the printing apparatus may further include a second cutter frame that accommodates the first blade, the cutter motor, the drive gear, the detection gear, the photosensor, and the cover member between the second cutter frame and first cutter frame, in which the cutter motor, the drive gear, the detection gear, the photosensor, and the cover member are supported by the first cutter frame, and the first blade is supported by the second cutter frame. 
     According to such a configuration, a drive region in which the cutter motor and the drive gear are provided and a detection region in which the detection gear, the photosensor, and the cover member are provided are provided between a blade rotational-movement region in which the first blade rotationally moves and the first cutter frame. As a result, space between the first cutter frame and the second cutter frame is able to be used efficiently. 
     In this instance, the drive gear may have a second drive end surface facing a direction opposite to the first detection end surface, a second drive mark may be provided on the second drive end surface, the second drive mark being located on an inter-gear imaginary line passing through a rotational center of the drive gear and a rotational center of the detection gear when the drive gear is at a drive gear home position, which causes the first blade to be at a cutting start position, the detection gear may have a second detection end surface facing a direction opposite to the first detection end surface, and a second detection mark may be provided on the second detection end surface, the second detection mark being located on the inter-gear imaginary line when the detection gear is at a detection gear home position, which causes the sensor substrate to output the first detection signal. 
     According to such a configuration, by positioning the second drive mark and the second detection mark on the inter-gear imaginary line, a worker is able to easily position the drive gear at the drive gear home position and the detection gear at the detection gear home position. 
     In this instance, the drive gear may have a first drive end surface facing a direction identical to the first detection end surface, a first drive mark may be provided on the first drive end surface, the first drive mark being located on an inter-gear imaginary line passing through a rotational center of the drive gear and a rotational center of the detection gear when the drive gear is at a drive gear home position, which causes the first blade to be at a cutting start position, a first detection mark may be provided on the first detection end surface, the first detection mark being located on the inter-gear imaginary line when the detection gear is at a detection gear home position, which causes the sensor substrate to output the first detection signal, a first mark opening may be provided in the first cutter frame, the first drive mark and the first detection mark located on the inter-gear imaginary line being configured to be viewed through the first mark opening. 
     According to such a configuration, by viewing the first drive mark and the first detection mark through the first mark opening, the worker is able to check the drive gear at the drive gear home position and the detection gear at the detection gear home position. 
     In this instance, a cover mark may be provided on an outer surface of the cover member, the detection gear may have a second detection end surface facing a direction opposite to the first detection end surface, and a third detection mark may be provided on the second detection end surface, the third detection mark being located on a cover imaginary line passing through a rotational center of the detection gear and the cover mark when the detection gear is at a detection gear home position, which causes the sensor substrate to output the first detection signal. 
     According to such a configuration, by positioning the third detection mark on the cover imaginary line, the worker is able to position the detection gear at the detection gear home position. 
     In this instance, the drive gear may have a first drive end surface facing a direction identical to the first detection end surface, a third drive mark may be provided on the first drive end surface, and a second mark opening may be provided in the first cutter frame, the third drive mark being configured to be viewed through the second mark opening when the drive gear is at a drive gear home position, which causes the first blade to be at a cutting start position. 
     According to such a configuration, by viewing the third drive mark through the second mark opening, a user is able to check the drive gear at the drive gear home position. 
     In this instance, the printing apparatus may further include a detection gear shaft that is fixed to the first cutter frame and rotatably supports the detection gear, in which a shaft engaging hole may be provided in the first cutter frame, the shaft engaging hole engaging a first shaft end, which is one end of the detection gear shaft in an axial direction of the detection gear shaft, a first cut section subjected to D-cut processing is provided in the first shaft end, a second cut section subjected to D-cut processing is provided in a second shaft end, which is another end of the detection gear shaft in the axial direction of the detection gear shaft, and the first cut section and the second cut section are provided in an identical position in a circumferential direction of the detection gear shaft. 
     According to such a configuration, by viewing the second cut section, the worker is able to identify the orientation of the first cut section. 
     In this instance, the printing apparatus may further include an operation section that is operated by a finger to rotate the drive gear without using the cutter motor, in which an operation opening for operating the operation section by a finger is provided in the first cutter frame, and the cover member includes a pinching suppressing section provided between the operation section and a portion in which the drive gear engages the detection gear. 
     According to such a configuration, it is possible to suppress a finger of the user inserted through the operation opening to operate the operation section from being pinched between the drive gear and the detection gear.