Patent Publication Number: US-2020298604-A1

Title: Ribbon transport mechanism and tape printing apparatus

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-051758, filed Mar. 19, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     This application relates to a ribbon transport mechanism that transports an ink ribbon and a tape printing apparatus with the ribbon transport mechanism. 
     2. Related Art 
     JP-A-2013-159409 discloses a tape printing apparatuses equipped with a ribbon transport mechanism that transports an ink ribbon. This ribbon transport mechanism includes a paying-out-side clutch mechanism and a winding-side clutch mechanism. The paying-out-side clutch mechanism selectively transmits the rotational power generated by a drive motor to a paying-out-side drive shaft, whereas the winding-side clutch mechanism selectively transmits the rotational power to a winding-side drive shaft. Further, the paying-out-side clutch mechanism includes a paying-out-side sun gear and a paying-out-side planet gear; the paying-out-side planet gear engages with or is disengaged from a paying-out-side input gear while rotating and moving around the paying-out-side sun gear. 
     In a known tape printing apparatus as described above, after the paying-out-side drive shaft stops rotating and before the winding-side drive shaft starts rotating, the paying-out-side planet gear engages with the paying-out-side input gear, so that the drive motor is coupled to the paying-out-side drive shaft via the paying-out-side clutch mechanism. In this state, if a ribbon paying out core abuts against a paying-out-side drive shaft to disturb its rotation, the tape cartridge may be unable to be attached to the cartridge mount section. 
     SUMMARY 
     The disclosed embodiment is a ribbon transport mechanism provided in a tape printing apparatus. The ribbon transport mechanism includes a paying out rotor and a winding rotor. When a cartridge that includes a paying out core around which an ink ribbon is wound and a winding core that winds the ink ribbon paid out from the paying out core is attached to a cartridge mount section of the tape printing apparatus, the paying out rotor engages with the paying out core and the winding rotor engages with the winding core. The ribbon transport mechanism further includes a transport motor that generates rotational power and a transport gear train that transmits the rotational power from the transport motor to the paying out rotor. The transport gear train includes an input gear, an intermediate gear, a clutch mechanism, and an elastic member. The input gear receives the rotational power from the transport motor. The intermediate gear, which engages with the input gear, receives the rotational power from the transport motor via the input gear and transmits the received rotational power to the paying out rotor. When the cartridge is attached, the clutch mechanism suppresses the input gear from rotating in a first input direction and the intermediate gear from rotating in a first intermediate direction and permits the input gear to rotate in a second input direction and the intermediate gear to rotate in a second intermediate direction; the second input direction is opposite to the first input direction, and the second intermediate direction is opposite to the first intermediate direction. The elastic member applies force to the intermediate gear in the second intermediate direction to reserve a clearance between the input gear and the intermediate gear and next to a front end of the intermediate gear in the first intermediate direction. 
     The present disclosure is a tape printing apparatus to which a cartridge is to be attached. The cartridge includes a paying out core around which an ink ribbon is wound and a winding core that winds the ink ribbon paid out from the paying out core. The tape printing apparatus includes a cartridge mount section to which the cartridge is to be attached. A paying out rotor, when the cartridge is attached to the cartridge mount section, engages with the paying out core. A winding rotor, when the cartridge is attached to the cartridge mount section, engages with the winding core. A transport motor generates rotational power. A transport gear train transmits the rotational power from the transport motor to the paying out rotor. A printing head performs a printing operation on a print tape. A transport gear train includes an input gear, an intermediate gear, a clutch mechanism, and an elastic member. The input gear receives the rotational power from the transport motor. The intermediate gear, which engages with the input gear, receives the rotational power from the transport motor via the input gear and transmits the received rotational power to the paying out rotor. When the cartridge is attached, the clutch mechanism suppresses the input gear from rotating in a first input direction and the intermediate gear from rotating in a first intermediate direction and permits the input gear to rotate in a second input direction and the intermediate gear to rotate in a second intermediate direction; the second input direction is opposite to the first input direction, and the second intermediate direction is opposite to the first intermediate direction. The elastic member applies force to the intermediate gear in the second intermediate direction to reserve a clearance between the input gear and the intermediate gear and next to a front end of the intermediate gear in the first intermediate direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a tape printing apparatus in which a tape cartridge is attached to a cartridge mount section, as viewed from an attachment direction. 
         FIG. 2  illustrates the tape printing apparatus in which a ribbon cartridge is attached to the cartridge mount section, as viewed from the attachment direction. 
         FIG. 3  illustrates the tape printing apparatus in which neither the tape cartridge nor the ribbon cartridge is attached to the cartridge mount section, as viewed from the attachment direction. 
         FIG. 4  illustrates, in perspective, the tape printing apparatus in which neither the tape cartridge nor the ribbon cartridge is attached to the cartridge mount section. 
         FIG. 5  illustrates the first paying out rotor in perspective. 
         FIG. 6  illustrates the first winding rotor in perspective. 
         FIG. 7  illustrates the transport gear train in perspective. 
         FIG. 8  illustrates the transport gear train as viewed from the attachment direction; the directions in which the individual gears and rotors in the transport gear train rotate in conjunction with the rotation of the transport motor in a first motor direction are denoted by the arrows. 
         FIG. 9  illustrates the transport gear train as viewed from the attachment direction; the directions in which the individual gears and rotors in the transport gear train rotate in conjunction with the rotation of the transport motor in a second motor direction are denoted by the arrows. 
         FIG. 10  is an exploded, perspective view of the one-way clutch unit. 
         FIG. 11  is an exploded, perspective view of the twin gear. 
         FIG. 12  is another exploded perspective view of the twin gear, as viewed from a direction different from that of  FIG. 11 . 
         FIG. 13  illustrates a clearance between the input-gear-side engaging section and the intermediate-gear-side engaging section. 
         FIG. 14  is an enlarged view of the first paying out core and the second winding core in the tape cartridge. 
         FIG. 15  illustrates a rotational state of the paying-out-side gear train before the tape cartridge is attached to the cartridge mount section of the tape printing apparatus. 
         FIG. 16  illustrates the rotation of the first paying out rotor in a second paying out direction which has been in the state of  FIG. 15 . 
         FIG. 17  illustrates the rotation of the first paying out rotor in a first paying out direction which has been in the state of  FIG. 15 . 
         FIG. 18  illustrates a clutch mechanism in a tape printing apparatus according to a modification. 
         FIG. 19  illustrates a state of the clutch mechanism when the transport motor rotates in a first motor direction. 
         FIG. 20  illustrates a state of the clutch mechanism when the transport motor rotates in a second motor direction. 
         FIG. 21  illustrates the first paying out rotor that transits from the state of  FIG. 18  to the state of rotating in the second paying out direction. 
         FIG. 22  illustrates the first paying out rotor that transits from the state of  FIG. 18  to the state of rotating in the first paying out direction. 
         FIG. 23  illustrates an input gear and an intermediate gear in a tape printing apparatus according to another modification. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     With reference to the accompanying drawings, a description will be given below of a tape printing apparatus  1  according to some embodiments of the present disclosure. These drawings employ an X-Y-Z orthogonal coordinate system, but it should be noted that this coordinate system is used for the sake of the explanation and thus not intended to limit embodiments that will be described below. Furthermore, the number and numeric values of individual components are examples and thus not intended to limit the embodiments. 
     Outline of Tape Printing Apparatus, Tape Cartridge, and Ribbon Cartridge 
     Referring to  FIGS. 1 to 3 , the tape printing apparatus  1  includes a cartridge mount section  2  to which a tape cartridge  101  and a ribbon cartridge  201  are to be selectively attached. In addition, the tape printing apparatus  1  further includes an unillustrated mount section cover that covers or exposes the cartridge mount section  2 . 
     As illustrated in  FIG. 1 , the tape cartridge  101  includes a tape core  102 , a first platen roller  103 , a first paying out core  104 , a first winding core  105 , and a first cartridge case  106 . Wound around the tape core  102  is a first print tape  107 , which is to be paid out from the tape core  102  to the outside of the first cartridge case  106  via a tape outlet  108 . The tape outlet  108  is disposed on the −X-side surface of the outer wall of the first cartridge case  106 . Wound around the first paying out core  104  is a first ink ribbon  109 , which is to be paid out from the first paying out core  104  to the first winding core  105  and wound around the first winding core  105 . The first cartridge case  106 , which forms the exterior of the tape cartridge  101 , contains the tape core  102 , the first platen roller  103 , the first paying out core  104 , the first winding core  105 , the first print tape  107 , and the first ink ribbon  109 . The first cartridge case  106  has a first head insertion hole  111  that penetrates the first cartridge case  106  along the Z axis. 
     As illustrated in  FIG. 2 , the ribbon cartridge  201  includes a second platen roller  203 , a second paying out core  204 , a second winding core  205 , and a second cartridge case  206 . Wound around the second paying out core  204  is a second ink ribbon  209 , which is to be paid out from the second paying out core  204  to the second winding core  205  and wound around the second winding core  205 . The second cartridge case  206 , which forms the exterior of the ribbon cartridge  201 , contains the second platen roller  203 , the second paying out core  204 , the second winding core  205 , and the second ink ribbon  209 . The second cartridge case  206  has a second head insertion hole  211  that penetrates the second cartridge case  206 . The second cartridge case  206  is provided with a second tape route  212 . Furthermore, an unillustrated tape roller around which a second print tape is wound is disposed outside the tape printing apparatus  1  and introduces the second print tape to the second tape route  212 . 
     The second print tape around the tape roller and the second ink ribbon  209  contained in the ribbon cartridge  201  may have any given initial lengths. In this embodiment, the second print tape may be greater in initial length than the first print tape  107  contained in the tape cartridge  101 . Likewise, the second ink ribbon  209  may be greater in initial length than the first ink ribbon  109  contained in the tape cartridge  101 . For example, if the tape printing apparatus  1  prints many labels at one time, the ribbon cartridge  201  is typically attached to the cartridge mount section  2 . 
     As illustrated in  FIGS. 3 and 4 , the cartridge mount section  2  has a recess that is open toward the +Z-side, and a head section  4  and a core projection  5  are disposed on a mount bottom surface  3  of this recess while protruding in the direction opposite to the attachment direction of the cartridge mount section  2 . The head section  4  includes a printing head  6  and a head cover  7  that covers at least +X-, −Y-, and +Z-side surfaces of the printing head  6 . In one embodiment, the printing head  6  may be a thermal head with a heater element. When the tape cartridge  101  is attached to the cartridge mount section  2 , the head cover  7  is inserted into the first head insertion hole  111  and guides the attaching of the tape cartridge  101 . Likewise, when the ribbon cartridge  201  is attached to the cartridge mount section  2 , the head cover  7  is inserted into the second head insertion hole  211  and guides the attaching of the ribbon cartridge  201 . In addition, when the tape cartridge  101  is attached to the cartridge mount section  2 , the core projection  5  is accommodated in an unillustrated core recess provided in the tape cartridge  101 . 
     Disposed on the mount bottom surface  3  are a platen shaft  8 , a first winding shaft  11 , a first paying out shaft  9 , a second paying out shaft  12 , and a second winding shaft  13  so as to be arranged in this order from the −X-side to the +X-side while protruding toward the +Z-side. 
     The platen shaft  8  is disposed close to the +Y-side surface of the printing head  6  while protruding in the direction opposite to the attachment direction. The protrusion of the platen shaft  8  is greater in amount than any of the first paying out shaft  9 , the first winding shaft  11 , the second paying out shaft  12 , and the second winding shaft  13 . When the tape cartridge  101  is attached to the cartridge mount section  2 , the platen shaft  8  is inserted into the first platen roller  103  and guides the attaching of the tape cartridge  101  together with the head cover  7 . Likewise, when the ribbon cartridge  201  is attached to the cartridge mount section  2 , the platen shaft  8  is inserted into the second platen roller  203  and guides the attaching of the ribbon cartridge  201  together with the head cover  7 . Hereinafter, the direction in which the tape cartridge  101  or the ribbon cartridge  201  is attached is referred to as the attachment direction. The attachment direction is parallel to the direction in which the platen shaft  8  protrudes or the Z axis. In this case, the attachment direction corresponds to the direction toward the −Z-side, whereas the direction opposite to the attachment direction corresponds to the direction toward the +Z-side. 
     The platen shaft  8  rotatably supports a platen rotor  14  (see  FIG. 8 ); the first paying out shaft  9  rotatably supports a first paying out rotor  15 ; the first winding shaft  11  rotatably supports a first winding rotor  16 ; the second paying out shaft  12  rotatably supports a second paying out rotor  17 ; and the second winding shaft  13  rotatably supports a second winding rotor  18 . When the tape cartridge  101  is attached to the cartridge mount section  2 , the platen rotor  14  is inserted into and engages with the first platen roller  103 , the first paying out rotor  15  is inserted into and engages with the first paying out core  104 , and the first winding rotor  16  is inserted into and engages with the first winding core  105 . Likewise, when the ribbon cartridge  201  is attached to the cartridge mount section  2 , the platen rotor  14  is inserted into and engages with the second platen roller  203 , the second paying out rotor  17  is inserted into and engages with the second paying out core  204 , and the second winding rotor  18  is inserted into and engages with the second winding core  205 . Each of the platen rotor  14 , the first paying out rotor  15 , the first winding rotor  16 , the second paying out rotor  17 , and the second winding rotor  18  receives the rotational power from a transport motor  20  via a transport gear train  19  that will be described later. Herein, the mechanism constituted by at least the first paying out rotor  15 , the first winding rotor  16 , the second paying out rotor  17 , the second winding rotor  18 , the transport gear train  19 , and the transport motor  20  corresponds to an example of a “ribbon transport mechanism”. 
     Provided on the outer circumference of the first paying out rotor  15  are three first-paying-out-rotor-side engaging projections  31 , which are arranged at substantially equal intervals on the outer circumference. Likewise, provided on the outer circumference of the first winding rotor  16  are three first-winding-rotor-side engaging projections  32 , which are arranged at substantially equal intervals on the outer circumference. Provided on the outer circumference of the second paying out rotor  17  are three second-paying-out-rotor-side engaging projections  33 , which are arranged at substantially equal intervals on the outer circumference. Likewise, provided on the outer circumference of the second winding rotor  18  are three second-winding-rotor-side engaging projections  34 , which are arranged at substantially equal intervals on the outer circumference. Furthermore, provided on the outer circumference of the platen rotor  14  are three unillustrated platen-shaft-rotor-side engaging projections. 
     As illustrated in  FIG. 5 , each of the first-paying-out-rotor-side engaging projections  31  is formed into a substantially quadrangular prism shape that is elongated in parallel to the axis of the first paying out rotor  15 . In addition, each first-paying-out-rotor-side engaging projection  31  has a front surface, as viewed from the attachment direction, that is chamfered at two corners. More specifically, the front surface is provided with a first front engagement slope  31   a  and a first rear engagement slope  31   b . When the first paying out rotor  15  rotates in a second paying out direction  15   b , the first front engagement slope  31   a  is positioned ahead of the first rear engagement slope  31   b  in the second paying out direction  15   b . The second paying out direction  15   b  corresponds to the direction (see  FIG. 9 ) in which the first paying out rotor  15  rotates in conjunction with the rotation of the transport motor  20  in a second motor direction  20   b . When the first paying out rotor  15  rotates in the second paying out direction  15   b , the first ink ribbon  109  is wound around the first paying out core  104 . Details of this will be described later. The configuration, described above, of the first-paying-out-rotor-side engaging projections  31  is similar to an unillustrated configuration of the second-paying-out-rotor-side engaging projections  33 . Further, the front surface of each of the second-paying-out-rotor-side engaging projections  33  as viewed from the attachment direction is also provided with a second front engagement slope and a second rear engagement slope. 
     As illustrated in  FIG. 6 , each of the first-winding-rotor-side engaging projections  32  in the first winding rotor  16  is formed into a narrow, substantially quadrangular prism shape, which is elongated in parallel to the axis of the first winding rotor  16 . The rear surface of each first-winding-rotor-side engaging projection  32  as viewed from the attachment direction is referred to as a first-winding-rotor-side engaging end  32   a , which is formed into a sharp shape. The configuration, described above, of the first-winding-rotor-side engaging projections  32  is similar to an unillustrated configuration of the second-winding-rotor-side engaging projections  34 . Further, the front surface of each second-winding-rotor-side engaging projection  34  as viewed from the attachment direction is also provided with a second-winding-rotor-side engaging end. 
     Transport Gear Train 
     Referring to  FIGS. 7 to 9 , the tape printing apparatus  1  further includes a transport gear train  19 . The transport gear train  19  includes a motor-side gear train  21 , a platen-side gear train  22 , a ribbon-side gear train  23 , a one-way clutch unit  24 , a paying-out-side gear train  25 , a first winding-side gear train  26 , and a second winding-side gear train  27 . 
     The motor-side gear train  21  transmits the rotational power generated by the transport motor  20  to both the platen-side gear train  22  and the ribbon-side gear train  23 . When receiving the rotational power from the transport motor  20  via the motor-side gear train  21 , the platen-side gear train  22  transmits the received rotational power to the platen rotor  14 . When receiving the rotational power from the transport motor  20  via the motor-side gear train  21 , the ribbon-side gear train  23  transmits the received rotational power to the one-way clutch unit  24 . 
     When receiving the rotational power from the transport motor  20  via the ribbon-side gear train  23 , the one-way clutch unit  24  selectively transmits the received rotational power to one or more of the paying-out-side gear train  25 , the first winding-side gear train  26 , and the second winding-side gear train  27 , depending on in which direction the transport motor  20  rotates. More specifically, when the transport motor  20  rotates in a first motor direction  20   a , namely, in a clockwise direction as illustrated in  FIG. 8 , the one-way clutch unit  24  receives the rotational power from the transport motor  20  and transmits the received rotational power to both the first winding-side gear train  26  and the second winding-side gear train  27 . When the transport motor  20  rotates in the second motor direction  20   b , which is opposite to the first motor direction  20   a , namely, in a counterclockwise direction as illustrated in  FIG. 9 , the one-way clutch unit  24  receives the rotational power from the transport motor  20  and transmits the received rotational power to the paying-out-side gear train  25 . Herein, the clockwise and counterclockwise directions correspond to those as viewed from the attachment direction. Details of the configuration of the one-way clutch unit  24  will be described later. 
     When receiving the rotational power from the transport motor  20  via the one-way clutch unit  24 , the paying-out-side gear train  25  transmits the received rotational power to both the first paying out rotor  15  and the second paying out rotor  17 . The paying-out-side gear train  25  includes an input gear  41  and an intermediate gear  42 , both of which constitute a twin gear  40 ; the input gear  41  engages with the paying-out-side one-way clutch  55 , details of which will be described later, and the intermediate gear  42  is positioned in front of the input gear  41  in the attachment direction and engages with the input gear  41 . The paying-out-side gear train  25  further includes a first output gear  43  and a second output gear  44 ; the first output gear  43  is positioned on the −X-side of the intermediate gear  42  and engages with the intermediate gear  42 , and the second output gear  44  is positioned on the +X-side of the intermediate gear  42  and engages with the intermediate gear  42 . The first output gear  43  is coupled to the first paying out rotor  15  so as to be rotatable around the first paying out shaft  9 . The second output gear  44  is coupled to the second paying out rotor  17  so as to be rotatable around the second paying out shaft  12 . Details of the configuration of the twin gear  40  will be described later. 
     When receiving the rotational power from the transport motor  20  via the one-way clutch unit  24 , the first winding-side gear train  26  transmits the received rotational power to the first winding rotor  16 . When receiving the rotational power from the transport motor  20  via the one-way clutch unit  24 , the second winding-side gear train  27  transmits the received rotational power to the second winding rotor  18 . 
     When the transport motor  20  rotates in the first motor direction  20   a  as illustrated in  FIG. 8 , the individual gears constituting the transport gear train  19  rotate in respective directions, which are referred to as first directions of the individual gears. When the transport motor  20  rotates in the second motor direction  20   b  as illustrated in  FIG. 9 , the individual gears constituting the transport gear train  19  rotate in respective opposite directions, which are referred to as second directions of the individual gears. In this case, the second direction of the input gear  41  is referred to as a second input direction  41   b , whereas the second direction of the intermediate gear  42  is referred to as a second intermediate direction  42   b . Both of the second input direction  41   b  and the second intermediate direction  42   b  correspond to the clockwise direction, as illustrated in  FIG. 9 . The second intermediate direction  42   b  is opposite to a first intermediate direction  42   a  (see  FIG. 17 ). 
     When the transport motor  20  rotates in the first motor direction  20   a  as illustrated in  FIG. 8 , the platen rotor  14 , the first winding rotor  16 , and the second winding rotor  18  rotate in respective directions, which are first directions of the individual rotors. In this case, the first direction of the first winding rotor  16  is referred to as a first winding direction  16   a , which corresponds to the counterclockwise direction as illustrated in  FIG. 8 . Likewise, when the transport motor  20  rotates in the second motor direction  20   b  as illustrated in  FIG. 9 , the platen rotor  14 , the first paying out rotor  15 , and the second paying out rotor  17  rotate in respective other directions, which are second directions of the individual rotors. In this case, the second direction of the first paying out rotor  15  is referred to a second paying out direction  15   b , which corresponds to the clockwise direction as illustrated in  FIG. 9 . The second paying out direction  15   b  is opposite to a first paying out direction  15   a  (see  FIG. 17 ). 
     Printing Process Performed with Tape Cartridge Attached 
     When the tape cartridge  101  is attached to the cartridge mount section  2  of the tape printing apparatus  1  as illustrated in  FIG. 1 , the first platen roller  103  in the tape cartridge  101  engages with the platen rotor  14  in the cartridge mount section  2  as illustrated in  FIG. 3 , the first paying out core  104  in the tape cartridge  101  engages with the first paying out rotor  15  in the cartridge mount section  2 , and the first winding core  105  in the tape cartridge  101  engages with the first winding rotor  16  in the cartridge mount section  2 . As a result, the transport motor  20  can transmit its rotational power to the first platen roller  103 , the first paying out core  104 , and the first winding core  105 . 
     In addition to the above, the head section  4  in the cartridge mount section  2  is inserted into the first head insertion hole  111  in the tape cartridge  101 . Then, the mount section cover is attached to the cartridge mount section  2 , after which a head moving mechanism  52  (see  FIG. 7 ) moves the printing head  6  to the platen shaft  8 , thereby nipping both the first print tape  107  and the first ink ribbon  109  between the printing head  6  and the first platen roller  103 . 
     Following the above, when the transport motor  20  rotates in the first motor direction  20   a , the rotational power generated by the transport motor  20  is transmitted to both the platen rotor  14  and the first winding rotor  16  via the transport gear train  19 . As a result, the first platen roller  103  rotates in a feeding direction, and the first winding core  105  rotates in a winding direction. Herein, the expression “the first platen roller  103  rotates in a feeding direction” means that the first platen roller  103  rotates in such a way that the first print tape  107  is fed to the tape outlet  108  and that the first ink ribbon  109  is paid out from the first paying out core  104  to the first winding core  105 . The expression “the first winding core  105  rotates in a winding direction” means that the first winding core  105  rotates in such a way that the first ink ribbon  109  paid out from the first paying out core  104  is wound around the first winding core  105 . In this case, the first platen roller  103  rotates in the clockwise direction, and the first winding core  105  rotates in the counterclockwise direction as in the example of  FIG. 1 . 
     When the transport motor  20  rotates in the second motor direction  20   b , the rotational power generated by the transport motor  20  is transmitted to both the platen rotor  14  and the first paying out rotor  15  via the transport gear train  19 . As a result, the first platen roller  103  rotates in a reverse direction, and the first paying out core  104  rotates in a rewinding direction. Herein, the expression “the first platen roller  103  rotates in a reverse direction” means that the first print tape  107  is fed back from the tape outlet  108  to the first print tape  107  and that the first ink ribbon  109  is fed back from the first winding core  105  to the first paying out core  104 . The expression “the first paying out core  104  rotates in a rewinding direction” means that the first ink ribbon  109  paid out from the first paying out core  104  is rewound around the first paying out core  104 . In this case, both the first platen roller  103  and the first paying out core  104  rotate in the counterclockwise direction as in the example of  FIG. 1 . 
     The tape printing apparatus  1  rotates the transport motor  20  in the first motor direction  20   a  and heats the printing head  6 . Then, the tape printing apparatus  1  prints information that has been received via an input device, such as a keyboard, on a predetermined portion of the first print tape  107  while feeding both the first print tape  107  and the first ink ribbon  109 . After having printed the information, the tape printing apparatus  1  uses an unillustrated cutter disposed between the cartridge mount section  2  and a tape ejection hole to cut the portion off the first print tape  107 . Then, the tape printing apparatus  1  rotates the transport motor  20  in the second motor direction  20   b , thereby feeding back the first print tape  107  until its end is positioned close to a predetermined site between the printing head  6  and the first platen roller  103 . In this way, the tape printing apparatus  1  successfully minimizes a margin of the first print tape  107  at its forward end which is to be used for the next printing. 
     The tape printing apparatus  1  also performs the printing operation in the same manner when the ribbon cartridge  201  is attached to the cartridge mount section  2 . 
     In short, the tape printing apparatus  1  prints information on the second print tape while feeding both the second print tape and the second ink ribbon  209  between the printing head  6  and the second platen roller  203 . 
     One-Way Clutch Unit 
     Referring to  FIG. 10 , the one-way clutch unit  24  includes a drive gear  53 , a clutch shaft  54 , a paying-out-side one-way clutch  55 , and a winding-side one-way clutch  56 . Herein, the paying-out-side one-way clutch  55  corresponds to an example of a “clutch mechanism”. 
     Since the drive gear  53  engages with the gear in the ribbon-side gear train  23  (see  FIG. 8 ), the drive gear  53  receives the rotational power from the transport motor  20  via the ribbon-side gear train  23 . 
     The clutch shaft  54  rotates together with the drive gear  53  and transmits the rotational power from the drive gear  53  to both the paying-out-side one-way clutch  55  and the winding-side one-way clutch  56 . 
     The paying-out-side one-way clutch  55  includes a feeding-side inner ring member  64  and a paying-out-side outer ring member  65 . The clutch shaft  54  is fitted into the paying-out-side inner ring member  64  so that both the clutch shaft  54  and the paying-out-side inner ring member  64  rotate together. The paying-out-side outer ring member  65  is disposed on the outer circumference of the paying-out-side inner ring member  64  and engages with an input gear  41  that will be described later. 
     When the drive gear  53  rotates in the first direction, the paying-out-side inner ring member  64  rotates in the first direction, but the paying-out-side outer ring member  65  does not rotate. In other words, the paying-out-side inner ring member  64  rotates at idle. This is because the paying-out-side inner ring member  64  does not engage with the paying-out-side outer ring member  65  so that the torque of the paying-out-side inner ring member  64  is suppressed from being transmitted to the paying-out-side outer ring member  65 . When the drive gear  53  rotates in the second direction, both the paying-out-side inner ring member  64  and the paying-out-side outer ring member  65  rotate together in the second direction. This is because the paying-out-side inner ring member  64  engages with the paying-out-side outer ring member  65  so that the torque of the paying-out-side inner ring member  64  is permitted to be transmitted to the paying-out-side outer ring member  65 . In short, when the transport motor  20  rotates in the first motor direction  20   a  as illustrated in  FIG. 8 , the paying-out-side one-way clutch  55  receives the rotational power from the transport motor  20  via the drive gear  53  but suppresses the received rotational power from being transmitted to the paying-out-side gear train  25 . When the transport motor  20  rotates in the second motor direction  20   b  as illustrated in  FIG. 9 , the paying-out-side one-way clutch  55  receives the rotational power from the transport motor  20  via the drive gear  53  and permits the received rotational power to be transmitted to the paying-out-side gear train  25 . It should be noted that the paying-out-side inner ring member  64  does not necessarily have to be configured to receive the rotational power from the transport motor  20 . Alternatively, the paying-out-side outer ring member  65  may be configured to receive the rotational power. 
     The configuration, described above, of the paying-out-side one-way clutch  55  is similar to that of the winding-side one-way clutch  56 . The winding-side one-way clutch  56  includes a winding-side inner ring member  71  and a winding-side outer ring member  72 . When the transport motor  20  rotates in the first motor direction  20   a  as illustrated in  FIG. 8 , the winding-side one-way clutch  56  receives the rotational power from the transport motor  20  via the drive gear  53  and permits the received rotational power to be transmitted to both the first winding-side gear train  26  and the second winding-side gear train  27 . When the transport motor  20  rotates in the second motor direction  20   b  as illustrated in  FIG. 9 , the winding-side one-way clutch  56  receives the rotational power from the transport motor  20  via the drive gear  53  and suppresses the received rotational power from being transmitted to both the first winding-side gear train  26  and the second winding-side gear train  27 . 
     Twin Gear 
     Referring to  FIG. 11 , the twin gear  40  includes: the input gear  41 ; an intermediate gear  42  disposed in back of the input gear  41  in the attachment direction; and a clearance reserving gear  88  disposed between the input gear  41  and the intermediate gear  42 . Further, the input gear  41  is coaxial with the intermediate gear  42 . 
     The input gear  41  is provided with an input-gear-side engaging recess  81  and an input-gear-side engaging section  82  on one of its surfaces which is closer to the intermediate gear  42 , namely, on the front surface as viewed from the attachment direction. The input-gear-side engaging recess  81  is concentric with the input gear  41  and has a substantially circular shape. The input-gear-side engaging section  82  is disposed around the input-gear-side engaging recess  81  while protruding in the direction opposite to the attachment direction. Further, the input-gear-side engaging section  82  is concentric with the input gear  41  and has a substantially arc shape. Disposed in substantially the longitudinal center of the input-gear-side engaging section  82  is an input-gear-side spring retainer  83 . 
     Referring to  FIG. 12 , the intermediate gear  42  is provided with a spring mount recess  84 , an intermediate-gear-side mating projection  85 , and an intermediate-gear-side engaging section  86  on one of the surfaces which is closer to the input gear  41 , namely, on the rear surface as viewed from the attachment direction. Further, the spring mount recess  84  is concentric with the intermediate gear  42  and has a substantially circular shape. The intermediate-gear-side mating projection  85  protrudes in the attachment direction from the bottom surface of the spring mount recess  84 . Further, the intermediate-gear-side mating projection  85  is concentric with the intermediate gear  42  and has a substantially circular shape. The intermediate-gear-side mating projection  85  is fitted into the input-gear-side engaging recess  81 . The intermediate-gear-side engaging section  86  is disposed around the intermediate-gear-side mating projection  85  while protruding in the attachment direction. The intermediate-gear-side engaging section  86  is concentric with the intermediate gear  42  and has a substantially arc shape. Disposed in substantially the longitudinal center of the intermediate-gear-side engaging section  86  is an intermediate-gear-side spring retainer  87 . 
     The clearance reserving gear  88  is disposed in the spring mount recess  84  and around the intermediate-gear-side mating projection  85 . In one embodiment, the clearance reserving gear  88  may be a torsion coil spring. A first end of the clearance reserving gear  88  is placed in the input-gear-side spring retainer  83  of the input gear  41 , whereas a second end of the clearance reserving gear  88  is placed in the intermediate-gear-side spring retainer  87  of the intermediate gear  42 . When being placed in the input gear  41 , the clearance reserving gear  88  applies force to the intermediate gear  42  in the second intermediate direction  42   b . Referring to  FIG. 13 , a clearance  89  is reserved between the input-gear-side engaging section  82  and the intermediate-gear-side engaging section  86  and next to the front end of the input-gear-side engaging section  82  in the first intermediate direction  42   a . Herein, the clearance reserving gear  88  corresponds to an example of an “elastic member”. 
     First Winding Core and First Paying Out Core 
     Referring to  FIG. 14 , the rear surface of the first paying out core  104  in the tape cartridge  101  as viewed from the attachment direction is provided with six first-paying-out-core-side engaging recesses  112  and six first-paying-out-core-side ends  113 , which are alternately arranged along the inner circumference of the first paying out core  104 . When the tape cartridge  101  is attached to the cartridge mount section  2  of the tape printing apparatus  1 , the three first-paying-out-rotor-side engaging projections  31  (see  FIG. 3 ) of the first paying out rotor  15  engage with corresponding ones of the six first-paying-out-core-side engaging recesses  112 . The first paying out core  104  thereby can rotate together with the first paying out rotor  15 . Each of the first-paying-out-core-side ends  113  is chamfered on both side surfaces. The configuration, described above, of the first paying out core  104  is similar to that of the second paying out core  204 . 
     The first winding core  105  is provided with six first-winding-core-side engaging projections  114  that protrude from the inner circumferential surface. The first-winding-core-side engaging projections  114  are arranged at substantially equal intervals on the inner circumferential surface of the first winding core  105  while extending in the axial direction of the first winding core  105 , namely, in the attachment direction. When the tape cartridge  101  is attached to the cartridge mount section  2  of the tape printing apparatus  1 , the three first-winding-rotor-side engaging projections  32  (see  FIG. 3 ) of the first winding rotor  16  enter into the first winding core  105  and engage the corresponding ones of the first-winding-core-side engaging projections  114 . The first winding core  105  thereby can rotate together with the first winding rotor  16 . Each of the ends of the first-winding-core-side engaging projections  114  in the attachment direction is provided with a first-winding-core-side engagement slope  115 . The configuration, described above, of the first winding core  105  is similar to that of the second winding core  205 . 
     Attaching of Tape Cartridge 
     When the tape cartridge  101  is attached to the cartridge mount section  2  of the tape printing apparatus  1  configured above, the ends, in the attachment direction, of the first-winding-core-side engaging projections  114  in the tape cartridge  101  abut against the first-winding-rotor-side engaging ends  32   a  (see  FIG. 6 ) of the first-winding-rotor-side engaging projections  32  in the tape printing apparatus  1 . Then, owing to the first-winding-core-side engagement slopes  115  provided at the ends of the first-winding-core-side engaging projections  114 , the first winding core  105  rotates in the winding direction denoted by the arrow A in  FIG. 14 . As a result, the first-winding-rotor-side engaging projections  32  are permitted to enter into the first winding core  105 . This configuration helps smooth attaching of the tape cartridge  101  to the cartridge mount section  2 . In addition, the first winding core  105  suppresses the first ink ribbon  109  from becoming loose by rotating in the winding direction. 
     Following the above, the first paying out rotor  15  of the tape printing apparatus  1  is inserted into the first paying out core  104  of the tape cartridge  101 . In which case, the first paying out rotor  15  rotates, but the first paying out core  104  does not rotate. This configuration helps smooth attaching of the tape cartridge  101  to the cartridge mount section  2 . The reason is as follows: if the first paying out core  104  rotates in the rewinding direction, the portion of the first ink ribbon  109  on which the information has been printed may be fed back, or if the first paying out core  104  rotates in the paying out direction, the first ink ribbon  109  may become loose. 
     When the tape cartridge  101  is attached to the cartridge mount section  2 , the first-paying-out-core-side ends  113  of the first paying out core  104  abut against the first rear engagement slopes  31   b  (see  FIG. 5 ) of the first-paying-out-rotor-side engaging projections  31  of the first paying out shaft  9 . Then, the first paying out rotor  15  that has been in the state of  FIG. 15  rotates in the second paying out direction  15   b , as illustrated in  FIG. 16 . In which case, the paying-out-side outer ring member  65  rotates, but the paying-out-side inner ring member  64  does not rotate. In other words, the paying-out-side outer ring member  65  rotates at idle because the paying-out-side outer ring member  65  does not engage with the paying-out-side inner ring member  64 . Hence, the input gear  41  is permitted to rotate in the second input direction  41   b , and the intermediate gear  42  is permitted to rotate in the second intermediate direction  42   b . In response, the first paying out rotor  15  rotates in the second paying out direction  15   b . As a result, the first-paying-out-rotor-side engaging projections  31  of the first paying out shaft  9  enter into the first-paying-out-core-side engaging recess  112 . This configuration helps smooth attaching of the tape cartridge  101  to the cartridge mount section  2 . It should be noted that the intermediate gear  42  is shorter in diameter than the input gear  41  in  FIGS. 15 to 22 , but their actual diameters are identical to each other. 
     When the tape cartridge  101  is attached to the cartridge mount section  2 , the first-paying-out-core-side ends  113  of the first paying out core  104  abut against the first front engagement slopes  31   a  (see  FIG. 5 ) of the first-paying-out-rotor-side engaging projections  31  of the first paying out shaft  9 . Then, the first paying out rotor  15  that has been in the state of  FIG. 15  rotates in the first paying out direction  15   a , as illustrated in  FIG. 17 . In this case, both the paying-out-side inner ring member  64  and the paying-out-side outer ring member  65  rotate together, because the paying-out-side outer ring member  65  engages with the paying-out-side inner ring member  64 . Hence, the input gear  41  is suppressed from rotating in the first input direction  41   a , and the intermediate gear  42  is suppressed from rotating in the first intermediate direction  42   a . As illustrated in  FIG. 15 , the clearance  89  is reserved, by the clearance reserving gear  88 , between the input-gear-side engaging section  82  and the intermediate-gear-side engaging section  86  and next to the front end of intermediate-gear-side engaging section  86  in the first intermediate direction  42   a . Thus, the intermediate gear  42  rotates in the first intermediate direction  42   a , as illustrated in  FIG. 17 , until the clearance  89  is eliminated, in other words, until the end of the intermediate-gear-side engaging section  86  in the first intermediate direction  42   a  makes contact with the end of the input-gear-side engaging section  82  in the direction opposite to the first intermediate direction  42   a . In accordance with this rotation, the first paying out rotor  15  also rotates in the first paying out direction  15   a . As a result, the first-paying-out-rotor-side engaging projection  31  enters into the first-paying-out-core-side engaging recess  112 . This configuration helps smooth attaching of the tape cartridge  101  to the cartridge mount section  2 . 
     The above mechanism is also applicable to the attaching of the ribbon cartridge  201  to the tape printing apparatus  1 . More specifically, when the ribbon cartridge  201  is attached to the cartridge mount section  2 , the second winding core  205  rotates in the winding direction. This configuration helps smooth attaching of the ribbon cartridge  201  to the cartridge mount section  2 . Moreover, when the ribbon cartridge  201  is attached to the cartridge mount section  2 , the second paying out rotor  17  is rotatable in both the first and second directions. This configuration also helps smooth attaching of the ribbon cartridge  201  to the cartridge mount section  2 . 
     Modifications 
     The foregoing embodiment may be modified in various ways without departing from the scope of the present disclosure. Some conceivable modifications will be described below. 
     As illustrated in  FIG. 18 , the tape printing apparatus  1  may include a clutch mechanism  90  instead of the paying-out-side one-way clutch  55 . The clutch mechanism  90  includes a first clutch gear  91 , a second clutch gear  92 , a third clutch gear  93 , and a gear support member  94 . The first clutch gear  91  receives the rotational power from the transport motor  20 . The second clutch gear  92  continuously engages with the first clutch gear  91  while moving around the first clutch gear  91  and temporarily engages with or is disengaged from the third clutch gear  93 . The third clutch gear  93  engages with the input gear  41 . The gear support member  94  is rotatably disposed on the support shaft of the first clutch gear  91  and rotatably supports the second clutch gear  92 . 
     When the transport motor  20  rotates in the first motor direction  20   a , the rotational power is transmitted from the transport motor  20  to the first clutch gear  91  in the clutch mechanism  90 , as illustrated in  FIG. 19 . Then, the first clutch gear  91  rotates in the first direction. In response, the gear support member  94  rotates together with the first clutch gear  91 , and the second clutch gear  92  is thereby disengaged from the third clutch gear  93 . As a result, the rotational power is not transmitted from the transport motor  20  to the first paying out rotor  15 . When the transport motor  20  rotates in the second motor direction  20   b , the rotational power is transmitted from the transport motor  20  to the first clutch gear  91  in the clutch mechanism  90 , as illustrated in  FIG. 20 . Then, the first clutch gear  91  rotates in the second direction. In response, the gear support member  94  rotates together with the first clutch gear  91 , and the second clutch gear  92  thereby engages with the third clutch gear  93 . As a result, the rotational power is transmitted from the transport motor  20  to the first paying out rotor  15 . 
     As described above, when the tape cartridge  101  is attached to the cartridge mount section  2  of the tape printing apparatus  1 , if the first-paying-out-core-side ends  113  of the first paying out core  104  abut against the corresponding first rear engagement slopes  31   b  of the first-paying-out-rotor-side engaging projections  31 , the first paying out rotor  15  that has been in the state of  FIG. 18  attempts to rotate in the second paying out direction  15   b , as illustrated in  FIG. 21 . In this case, since the second clutch gear  92  is disengaged from the third clutch gear  93 , the input gear  41  is permitted to rotate in the second input direction  41   b , and the intermediate gear  42  is permitted to rotate in the second intermediate direction  42   b . As a result, the first paying out rotor  15  rotates in the second paying out direction  15   b , thereby allowing the first-paying-out-rotor-side engaging projections  31  of the first paying out shaft  9  to enter into the first-paying-out-core-side engaging recess  112 . This configuration helps smooth attaching of the tape cartridge  101  to the cartridge mount section  2 . 
     When the tape cartridge  101  is attached to the cartridge mount section  2  of the tape printing apparatus  1 , if the first-paying-out-core-side ends  113  of the first paying out core  104  abut against the corresponding first front engagement slopes  31   a  of the first-paying-out-rotor-side engaging projections  31  in the cartridge mount section  2 , the first paying out rotor  15  that has been in the state of  FIG. 18  attempts to rotate in the first paying out direction  15   a , as illustrated in  FIG. 22 . In this case, since the second clutch gear  92  keeps engaging with the third clutch gear  93 , the input gear  41  is suppressed from rotating in the first input direction  41   a , and the intermediate gear  42  is suppressed from rotating in the first intermediate direction  42   a . As illustrated in  FIG. 18 , the clearance  89  is reserved, by the clearance reserving gear  88 , between the input-gear-side engaging section  82  and the intermediate-gear-side engaging section  86  and next to the front end of intermediate-gear-side engaging section  86  in the first intermediate direction  42   a . Thus, the intermediate gear  42  rotates in the first intermediate direction  42   a , as illustrated in  FIG. 22 , until the clearance  89  between the input-gear-side engaging section  82  and the intermediate-gear-side engaging section  86  is eliminated. In accordance with the rotation of the intermediate gear  42 , the first paying out rotor  15  rotates in the first paying out direction  15   a , thereby allowing the first-paying-out-rotor-side engaging projections  31  of the first paying out shaft  9  to enter into the first-paying-out-core-side engaging recess  112 . This configuration helps smooth attaching of the tape cartridge  101  to the cartridge mount section  2 . 
     In the twin gear  40 , the input gear  41  does not necessarily have to be coaxial with the intermediate gear  42 . Alternatively, the input gear  41  may engage with the intermediate gear  42 , for example. In this case, as illustrated in  FIG. 23 , an elastic member may be provided in addition to an input gear  41  and an intermediate gear  42  that engage with each other. This elastic member may apply force to the intermediate gear  42  in a second intermediate direction  42   b  so as to reserve a backlash, or a clearance  89 , between the input gear  41  and the intermediate gear  42  and next to the front end of the intermediate gear  42  in the first intermediate direction  42   a.    
     The cartridge mount section  2  of the tape printing apparatus  1  is not necessarily configured to selectively accommodate the tape cartridge  101  and the ribbon cartridge  201 . As an alternative example, the cartridge mount section  2  may be configured to accommodate only the tape cartridge  101 , in which case the second paying out rotor  17  and the second winding rotor  18  are unnecessary. As another alternative example, the cartridge mount section  2  may be configured to accommodate only the ribbon cartridge  201 , in which case the first paying out rotor  15  and the first winding rotor  16  are unnecessary. Moreover, the present disclosure may be applied to ribbon transport mechanisms without the printing head  6 . 
     The configurations in the foregoing embodiment and modifications may be combined together. 
     Supplementary Notes 
     A description will be given below of supplementary notes of a ribbon transport mechanism and a tape printing apparatus according to some aspects of the present disclosure. 
     A ribbon transport mechanism provided in a tape printing apparatus includes a paying out rotor and a winding rotor. When a cartridge that includes a paying out core around which an ink ribbon is wound and a winding core that winds the ink ribbon paid out from the paying out core is attached to a cartridge mount section of the tape printing apparatus, the paying out rotor engages with the paying out core and the winding rotor engages with the winding core. The ribbon transport mechanism further includes a transport motor that generates rotational power and a transport gear train that transmits the rotational power from the transport motor to the paying out rotor. The transport gear train includes an input gear, an intermediate gear, a clutch mechanism, and an elastic member. The input gear receives the rotational power from the transport motor. The intermediate gear, which engages with the input gear, receives the rotational power from the transport motor via the input gear and transmits the received rotational power to the paying out rotor. When the cartridge is attached, the clutch mechanism suppresses the input gear from rotating in a first input direction and the intermediate gear from rotating in a first intermediate direction and permits the input gear to rotate in a second input direction and the intermediate gear to rotate in a second intermediate direction; the second input direction is opposite to the first input direction, and the second intermediate direction is opposite to the first intermediate direction. The elastic member applies force to the intermediate gear in the second intermediate direction to reserve a clearance between the input gear and the intermediate gear and next to a front end of the intermediate gear in the first intermediate direction. 
     The above configuration, when the cartridge is attached, permits the input gear to rotate in the second input direction and the intermediate gear to rotate in the second intermediate direction. As a result, the paying out rotor is rotatable in a second paying out direction, which is related to both the second input direction and the second intermediate direction. In addition, since the clearance is reserved between the input gear and the intermediate gear and next to the front end of the intermediate gear in the first intermediate direction, the intermediate gear is rotatable in the first intermediate direction until the clearance is removed. As a result, the paying out rotor is rotatable in a first paying out direction, which is related to the first intermediate direction. Therefore, the cartridge can be attached smoothly to the cartridge mount section even if the paying out core abuts against the paying out rotor in the course of the attaching. 
     In the above ribbon transport mechanism, the input gear may be coaxial with the intermediate gear. One of the surfaces of the input gear which is closer to the intermediate gear may be provided with an input-gear-side engaging section. One of the surfaces of the intermediate gear which is closer to the input gear may be provided with an intermediate-gear-side engaging section; the intermediate-gear-side engaging section may engage with the input-gear-side engaging section. Both the input-gear-side engaging section and the intermediate-gear-side engaging section may reserve a clearance in-between. 
     The above configuration can reserve a large clearance in a simple manner, compared to the configuration in which an input gear engages with an intermediate gear. Therefore, the paying out core is rotatable largely when the cartridge is attached to the cartridge mount section. 
     In the above ribbon transport mechanism, the clutch mechanism may include an inner gear member and an outer gear member; the outer gear member may be disposed on an outer circumference of the inner gear member. When the cartridge is attached, in a case in which the input gear attempts to rotate in the first input direction and the intermediate gear attempts to rotate in the first intermediate direction, the clutch mechanism may cause the inner gear member to engage with the outer gear member to suppress the input gear from rotating in the first input direction and the intermediate gear from rotating in the first intermediate direction. When the cartridge is attached, in a case in which the input gear attempts to rotate in the second input direction and the intermediate gear attempts to rotate in the second intermediate direction, the clutch mechanism may disengage the inner gear member from the outer gear member to permit the input gear to rotate in the second input direction and the intermediate gear to rotate in the second intermediate direction. 
     The above configuration can achieve a clutch mechanism in a simple manner. 
     In the above ribbon transport mechanism, the clutch mechanism may include a first clutch gear that receives the rotational power from the transport motor, a second clutch gear that engages with the first clutch gear, and a third clutch gear that engages with or is disengaged from the second clutch gear. When the cartridge is attached, in a case in which the input gear attempts to rotate in the first input direction and the intermediate gear attempts to rotate in the first intermediate direction, the clutch mechanism may cause the second clutch gear to engage with the third clutch gear to suppress the input gear from rotating in the first input direction and the intermediate gear from rotating in the first intermediate direction. When the cartridge is attached, in a case in which the input gear attempts to rotate in the second input direction and the intermediate gear attempts to rotate in the second intermediate direction, the clutch mechanism may disengage the second clutch gear from the third clutch gear to permit the input gear to rotate in the second input direction and the intermediate gear to rotate in the second intermediate direction. 
     The above configuration can achieve a clutch mechanism in a simple manner. 
     A tape printing apparatus to which a cartridge that includes a paying out core around which an ink ribbon is wound and a winding core that winds the ink ribbon paid out from the paying out core is to be attached includes a cartridge mount section to which the cartridge is to be attached. A paying out rotor, when the cartridge is attached to the cartridge mount section, engages with the paying out core. A winding rotor, when the cartridge is attached to the cartridge mount section, engages with the winding core. A transport motor generates rotational power. A transport gear train transmits the rotational power from the transport motor to the paying out rotor. A printing head performs a printing operation on a print tape. A transport gear train includes an input gear, an intermediate gear, a clutch mechanism, and an elastic member. The input gear receives the rotational power from the transport motor. The intermediate gear, which engages with the input gear, receives the rotational power from the transport motor via the input gear and transmits the received rotational power to the paying out rotor. When the cartridge is attached, the clutch mechanism suppresses the input gear from rotating in a first input direction and the intermediate gear from rotating in a first intermediate direction and permits the input gear to rotate in a second input direction and the intermediate gear to rotate in a second intermediate direction; the second input direction is opposite to the first input direction, and the second intermediate direction is opposite to the first intermediate direction. The elastic member applies force to the intermediate gear in the second intermediate direction to reserve a clearance between the input gear and the intermediate gear and next to a front end of the intermediate gear in the first intermediate direction. 
     The above configuration reserves the clearance between the input gear and the intermediate gear and next to the front end of the intermediate gear in the first intermediate direction when the cartridge is attached to the cartridge mount section. The intermediate gear is thus rotatable in the first intermediate direction until the clearance is removed. As a result, the paying out rotor is rotatable in a first paying out direction. Therefore, the cartridge can be attached smoothly to the cartridge mount section even if the paying out core abuts against the paying out rotor in the course of the attaching.