Abstract:
A paper feeding roller rotates to feed the continuous paper along a paper path. A print head performs printing on the continuous paper. The print head has a first side opposing to the paper path and a second side opposite to the first side. A cutter mechanism is overlappingly disposed with the print head, at a downstream of the paper path relative to the print head, to cut the continuous paper. A motor is disposed in the second side of the print head to provide a driving force to the paper feeding roller and the cutter mechanism. A cutter driving mechanism is disposed in the second side of the print head to transmit the driving force of the motor to operate the cutter mechanism.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a printer unit having a cutter mechanism for cutting continuous paper such as rolled paper, and a printing apparatus incorporating such a printer unit. 
   In the related art, one type of printing apparatus is known that includes a cutter mechanism for automatically cutting the paper to separate a printed portion from the rolled paper after printing. In order to reduce margins of the paper, the printing apparatus of this type preferably has a print head and a cutter mechanism, which are positioned as closely to each other as possible. To this end, in many printing apparatuses, the cutter mechanism is placed in an overlapping manner downstream of the print head. 
   Portable devices and multi-processing systems, which have features of printing apparatus(es), have recently achieved widespread use. In a device of this type, restrictions are imposed on an integration space of a printer unit including a print head and a cutter mechanism. Particularly in the case of a portable device, the overall thickness of the device is determined by the thickness of the printer unit. Hence, strong demand exists for reducing the size, or slimming of the printer unit. 
   However, in the case of the related-art printer unit, a cutter driving motor and a cutter driving mechanism are built into the cutter mechanism (cutter unit), and the cutter mechanism and the print head (head unit) are arranged in an overlapping manner, thus posing limitations on slimming of the printer unit. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to provide a slimmed printer unit while a print head and a cutter mechanism are arranged in the overlapping manner, and which enables a reduction in the number of parts and simplification of a control circuit by obviating a motor dedicated for a cutter. 
   It is also an object of the invention to provide a printing apparatus incorporating such a printer unit. 
   In order to achieve the above objects, according to the invention, there is provided a printer unit, comprising:
         a paper feeding roller, rotating to feed the continuous paper along a paper path;   a print head, which performs printing on the continuous paper, the print head having a first side opposing to the paper path and a second side opposite to the first side;   a cutter mechanism, overlappingly disposed with the print head, and downstream of the paper path relative to the print head, to cut the continuous paper;   a motor, disposed in the second side of the print head to provide a driving force to the paper feeding roller and the cutter mechanism; and   a cutter driving mechanism, disposed in the second side of the print head to transmit the driving force of the motor to operate the cutter mechanism.       

   In such a configuration, since the cutter driving mechanism is placed to utilize a back space behind the print head, the printer unit can be slimmed although the print head and the cutter mechanism are arranged in the overlapping manner. Further, a motor specifically designed for use with a cutter is obviated, thereby enabling a reduction in the number of parts and simplification of a control circuit. 
   Preferably, the cutter driving mechanism includes: a worm, extending parallel with a support axis of the paper feeding roller and a rotation axis of the motor, and rotated by the driving force of the motor; and a worm wheel, which meshes with the worm to transmit the driving force to the cutter mechanism. 
   In such a configuration, the driving force of the motor can be supplied to the paper feeding roller and the cutter driving mechanism by use of a simple gear mechanism while making the cutter mechanism compact. 
   Here, the cutter mechanism may include a movable blade formed with an elongated hole. The worm wheel may be provided with a joint extending parallel with a rotation axis of the worm wheel, and interlocked with the elongated hole. The movable blade may be reciprocated within a predetermined range in accordance with an interlocking movement of the joint in the elongated hole. 
   Here, the cutter mechanism may include a stationary blade arranged so as to oppose to the movable blade through the paper path in between. The movable blade is brought into slidable contact with the stationary blade to scissor off the continuous paper. 
   Further, it is preferable that the cutter driving mechanism includes a detector which detects a reference position of the worm wheel. 
   Here, the detector may include a cam formed with the worm wheel, and a sensor, which senses an outer circumferential face of the cam. 
   Preferably, the printer unit further comprises a switching mechanism, which selectively transmits the driving force of the motor to either the paper feeding roller or the cutter mechanism in accordance with a rotating direction of the motor. 
   In such a configuration, since a transmission channel is switched in accordance with the rotating direction of the motor, a clutch mechanism using a solenoid or the like is obviated, thereby enabling a reduction in the number of parts and simplification of structure of the motor. 
   Here, the switching mechanism may include: a sun gear, rotated by the motor; and a pair of planetary gears, meshed with the sun gear movably around an outer periphery of the sun gear. Either one of the planetary gear may mesh with one of the paper feeding roller and the cutter mechanism in accordance with the rotating direction of the motor. 
   In such a configuration, the transmission channel is switched by use of the planetary gear mechanism, thereby promoting a reduction in the number of parts and simplification of structure of the printer unit. 
   Preferably, the print head is a thermal head, and the paper feeding roller is a platen roller opposing to the print head. 
   Preferably, the print head, the cutter mechanism, the motor, and the cutter driving mechanism are disposed at a casing body of a printing apparatus having a housing section which houses the continuous paper therein, and the paper feeding roller is disposed at a cover body of the printing apparatus which opens or closes the housing section. 
   According to the invention, there is also provided a printing apparatus comprising the above described printer unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of a printing apparatus when a cover is closed; 
       FIG. 2  is a perspective view of the printing apparatus when the cover is opened; 
       FIG. 3  is a schematic cross-sectional view of the printing apparatus; 
       FIG. 4  is an entire perspective view of a printer unit; 
       FIG. 5  is a fragmentary side view of the printer unit when the cover is closed, showing a state that cutter-related members are omitted; 
       FIG. 6  is a perspective view of the printer unit when the cover is closed, showing a state that cutter-related members are omitted; 
       FIG. 7  is a perspective view of the printer unit when the cover is opened, showing a state that cutter-related members are omitted; 
       FIG. 8  is a perspective view of the printer unit shown in  FIG. 7  when viewed from another angle, showing a state that cutter-related members are omitted; 
       FIG. 9  is a perspective view of a platen frame; 
       FIG. 10  is a perspective view of a lock member; 
       FIG. 11  is a perspective view of a head support member; 
       FIG. 12  is a perspective view of the head support member on which the print head is provided; 
       FIG. 13  is an exploded perspective view of the printer unit; 
       FIG. 14  is a plan view showing a drive system; 
       FIG. 15  is a bottom view showing the drive system; 
       FIG. 16  is a side view of a gear train showing a paper feeding state; 
       FIG. 17  is a side view of the gear train showing a cutter actuating state; and 
       FIG. 18  is a plan view of a worm wheel. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the invention will be described hereinbelow by reference to the accompanying drawings. As will be known from  FIGS. 1  to  3 , the printing apparatus  10  comprises a housing section  12  for housing rolled paper P as type of continuous paper is provided in a casing  11 . An opening section  13  is formed above the housing section  12 , and rolled paper P is replaced through the opening section  13 . The opening section  13  is opened and closed by a cover  14  which is pivotable up and down while a rear end of the cover  14  is taken as a pivot. A slit-shaped discharging port  15  is formed between an front end of the cover  14  and a front edge of the opening section  13 . One end of the rolled paper P rotatably retained in the housing section  12  is withdrawn from the discharging port  15  by way of a paper path  16 . 
   Disposed along the paper path  16  are a thermal print head  17 , a platen roller (paper feeding roller)  18  for transporting the rolled paper P at a position opposite the print head  17 , and a cutter unit  19  (cutter mechanism  19   a ) for cutting the rolled paper P at a position downstream of the platen roller  18 . When the printing apparatus  10  has received a print instruction, the print head  17  effects printing on the rolled paper P while the platen roller  18  feeds the rolled paper P. Subsequently, the printed portion of the paper is further advanced toward the discharging port  15 . When the trailing end of the printed portion reaches a particular position relative to the cutter mechanism  19   a , the cutter mechanism  19   a  cuts the paper to separate the printed portion from the paper unwound from the rolled paper P. The separated portion is then supplied from the discharging port  15  as a single cut sheet to a user. 
   As shown in  FIGS. 4  to  8 , a printing mechanism and a cutter mechanism of the printing apparatus  10  are assembled into a unit such as a printer unit  20 , although cutter-related members are omitted from depiction. 
   The printer unit  20  comprises a head unit  21  to be provided on a main body of the printing apparatus (i.e., the casing  11 ), a platen unit (paper feeding unit)  22  to be provided on the cover  14 , a cutter unit  19  disposed above (downstream) of the head unit  21  in an overlapping manner, and a stationary blade  19   b  provided above the platen unit  22 . As a result, in a state in which the cover  14  is opened, the platen roller  18  and the stationary blade  19   b  retract from the print head  17 , thereby opening a paper path  16 . In other words, when the rolled paper P is replaced, the cover  14  is opened, and the rolled paper P is housed in the housing section  12 . Subsequently, one end of the rolled paper P is drawn to the outside of the casing  11 . In this state, the cover  14  is closed, whereby the rolled paper P is set along the paper path  16 . 
   The platen unit  22  comprises a platen frame  23  to be fixed on a lower face of the front end of the cover  14 ; a platen shaft  24  rotatably supported by the platen frame  23 ; a lock member  25  which pivots back and forth around the platen shaft  24 ; and springs  26  for urging the lock member  25  backward. As shown in  FIG. 9 , the platen frame  23  is formed so as to assume the shape of a gate when viewed from the front. Elongated platen support holes  23   b  are formed in respective side plates  23   a . The platen roller  18  is provided integrally in an intermediate portion of the platen shaft  24 . A platen gear  27  is provided integrally on the left end of the platen shaft  24 . Both ends of the platen shaft  24  penetrate through corresponding platen support holes  23   b  and are supported by the platen frame  23  via bearing members  28 . An inner side edge of each bearing member  28  extends toward the platen roller  18  so as to have a width wider than an additional thickness of a head frame  29  and a head support member  30  in an axial direction of the platen shaft  24 . 
   As shown in  FIG. 10 , the lock member  25  is formed so as to assume the shape of a gate when viewed from the front. A lock lever  25   a  is provided on either side of the lock member  25 . Integrally formed in the lock lever  25   a  are an engagement hook  25   b , a stopper piece  25   c , a spring engagement piece  25   d , an lock release piece  25   e , and a support hole  25   f . The support hole  25   f  is pivotably fitted around a corresponding bearing member  28 . The lock member  25  is supported so as to be pivotable back and forth around the platen shaft  24 . 
   Each of the springs  26  is interposed in a pulled state between a spring engagement piece  23   c  formed at the rear end of the platen frame  23  and the spring engagement piece  25   d  of the lock lever  25   a . Further backward pivotal movement of the lock levers  25   a , which are urged backward by the springs  26 , is restricted as a result of the stopper pieces  25   c  coming into contact with stopper pieces  23   d  of the platen frame  23 . At this time, the lock levers  25   a  are oriented in a direction substantially perpendicular to the cover  14 , thereby avoiding projection of the lock levers  25   a  from the extremity of the cover  14 . In place of the stopper pieces  23   d  of the platen frame  23 , projections projecting outside from side plates  23   a  may be formed. 
   The head unit  21  comprises a head frame  29  to be mounted on the main body of the printing apparatus; a head support member  30  to be provided on the head frame  29  so as to be pivotable back and forth; springs  31  for urging the head support member  30  to the platen roller  18 ; and a drive system  32  for transmitting driving force to the platen roller  18  and the cutter mechanism  19   a . The head frame  29  is formed so as to assume the shape of the letter U when viewed from the front. A step-shaped paper guide  29   a  (see  FIG. 3 ) is formed at the rear end of the head frame  29  for guiding the rolled paper P drawn from the housing section  12  into a space defined between the print head  17  and the platen roller  18 . A fitting groove  29   c  is formed in each of side plate sections  29   b  of the head frame  29 . When the cover  14  is closed, the bearing members  28  are fitted into the fitting grooves  29   c  from above. 
   As shown in  FIGS. 11 and 12 , the head support member  30  is formed so as to assume the shape of the letter U when viewed from the top. The print head  17  is bonded integrally to a supporting face  30   a  opposing the platen roller  18 . The thermal print head  17  has the shape of a flat plate of specified thickness. A print line (heating element)  17   a  is formed at an upper front end so as to extend from side to side. In order to ensure print quality, the print head  17  of this type is required to press the rolled paper P against the print line  17   a . In order to satisfy this requirement, the head support member  30  is disposed to rotate freely back and forth on the head frame  29  by way of the rotary shaft  33 , and is urged to the platen roller  18  side by the springs  31 . 
   An arm section  30   b  is provided on either side of the head support member  30  so as to extend backward. A fitting groove  30   c  is formed in each of the arm sections  30   b  such that the respective bearing members  28  fit into the grooves  30   c  from above when the cover  14  is closed. Further, a contact projection  30   d  is formed integrally on each arm section  30   b  so as to come into contact with a corresponding bearing member  28  and to cause the head support member  30  (print head  17 ) to temporarily retract from the platen roller  18 . A support hole  30   e  is formed proximally below the fitting groove  30   c  on each of the arm sections  30   b . The rotary shaft  33  penetrating through the support holes  30   e  is offset backward with reference to a printing face of the print head  17  (i.e., close to a pivot  14   a  of the cover  14 ). Both ends of the rotary shaft  33  also serve as locking shafts which engage the engagement hooks  25   b  of the lock levers  25   a.    
   The springs  31  are interposed in a compressed state between the pair of spring support pieces  29   d  standing on the head frame  29  and the head support member  30  to be urged backward. As a result of stopper pieces  30   f  projecting from both ends of the head support member  30  coming into contact with the stopper pieces  29   e  of the head frame  29 , further backward pivotal movement of the head support member  30  is restricted. 
   As shown in  FIGS. 13  to  17 , the drive system  32  comprises a motor  34  and a cutter driving mechanism  35  which are provided in a back space S behind the head frame  29  and the print head  17 ; and a gear train (switching mechanism)  36  for selectively transmitting drive power of the motor  34  to the platen gear  27  or the cutter driving mechanism  35 . The gear train  36  comprises a paper feeding transmission gear  37  which meshes with the platen gear  27  when the cover  14  is closed; a cutter driving transmission gear  39  provided on an input shaft  38  of the cutter driving mechanism  35 ; a sun gear  40  provided on a motor shaft  34   a  of the motor  34 ; and a pair of planetary gears  41 ,  42  which mesh with the sun gear  40  at all times. The pair of planetary gears  41 ,  42  are rotatably provided at respective ends of a planetary lever  43  which rotates around the motor shaft  34   a  so as to revolve along the outer periphery of the sun gear  40  is allowed. 
   As shown in  FIG. 16 , when the sun gear  40  is rotated in direction A, a paper feeding planetary gear  41  revolves in the direction A, thereby meshing with the paper feeding transmission gear  37 . In this state, drive power of the motor  34  is transmitted to the platen gear  27  by way of the sun gear  40 , the paper feeding planetary gear  41  and the paper feeding transmission gear  37 , whereby the platen roller  18  feeds paper. 
   As shown in  FIG. 17 , when the sun gear  40  is rotated in direction B, a cutter driving planetary gear  42  revolves in the direction B, thereby meshing with the cutter driving transmission gear  39 . In this state, the drive power of the motor  34  is transmitted to the cutter driving mechanism  35  via the sun gear  40 , the cutter driving planetary gear  42  and the cutter driving transmission gear  39 . The cutter driving mechanism  35  actuates the cutter mechanism  19   a . The input shaft  38  of the cutter driving mechanism  35  is provided with a handle  44  for manually actuating the cutter mechanism  19   a  in the event of occurrence of a problem. 
   The cutter driving mechanism  35  comprises the input shaft  38  arranged parallel to the platen roller  18  and the motor shaft  34   a ; a worm  45  provided integrally with the input shaft  38 , and a worm wheel  46  meshing with the worm  45 . As mentioned above, the cutter driving mechanism  35  is disposed in the back space S behind the print head  17 . The input shaft  38  is rotatably supported between the front end of the left side plate  29   b  of the head frame  29  and a raised piece  29   f  provided upright at an intermediate position along the front end of the head frame  29 . The worm wheel  46  is rotatably supported by the head frame  29  by way of a vertically-oriented wheel shaft  47 . A joint pin  48  is projectingly provided at an eccentric position on an upper face of the worm wheel  46 . The cutter driving mechanism  35  is linked to the cutter mechanism  19   a  by way of the joint pin  48 . 
   As shown in  FIG. 18 , a position detection cam  49  is provided integrally on a lower face of the worm wheel  46 . A detection lever  51  of a position detecting switch  50  is brought into pressing contact with an outer peripheral face of the cam  49 . A recess  49   a  is formed in the cam  49  for detecting an initial position (e.g., a standby position or a reference position). When the recess  49   a  has reached the detection lever  51  at the time of actuation of a cutter, the position detecting switch  50  detects displacement of the lever resulting from arrival of the recess  49   a , thereby deactivating the motor  34 . A projection may be formed in place of the recess  49   a , and the initial position may be detected when the position detecting switch  50  has detected the projection. Alternatively, the initial position may be detected in a non-contact manner through use of a photo-detector. 
   The cutter unit  19  comprises a thin cutter frame  52  and a movable blade  53  which is provided on the cutter frame  52  so as to be pivotable back and forth by way of a movable blade pivot  54 . A circular opening  52   a  matching the locus of movement of the joint pin  48  is formed in the cutter frame  52 . The joint pin  48  projects into the cutter unit  19  through the opening  52   a . The movable blade  53  has an elongated joint hole  53   a , and the joint pin  48  is engaged with the joint hole  53   a . Specifically, the movable blade  53  is constituted so as to make a round trip within a predetermined range of movement while following movement of the joint pin  48  when the worm wheel  46  has made one rotation. During the course of movement, the movable blade  53  comes into a slidable contact with the stationary blade  19  in the manner of scissors, thereby cutting the rolled paper P. 
   As mentioned above, according to the embodiment, since the cutter driving mechanism  35  is placed by utilization of the back space S behind the print head  17 , the printer unit  20  can be slimmed although the print head  17  and the cutter mechanism  19   a  are placed in an overlapping manner. Further, a motor specifically designed for use with a cutter is obviated, thereby enabling an attempt to reduce the number of parts and simplification of a control circuit. 
   In addition, the worm  45  of the cutter driving mechanism  35  is positioned in parallel to the platen shaft  24  and the motor shaft  34   a  and rotates in association with activation of the motor  34 . Correspondingly, the worm wheel  46  meshes with the worm  45  and activates the cutter mechanism  19   a  in accordance with rotation of the worm  45 . In short, the cutter driving mechanism  35  is constituted by use of a worm mechanism having a large reduction ratio. Hence, there can be achieved compact construction of the cutter driving mechanism  35 , as well as a reduction in the number of parts of the cutter driving mechanism  35 . Further, because the worm  45  is disposed in parallel to the platen shaft  24  and the motor shaft  34   a , the drive power of the motor can be supplied to the platen roller  18  and the cutter driving mechanism  35  through use of a simple gear mechanism. 
   Further, by providing the gear train  36  for selectively transmitting the drive power of the motor  34  to the platen roller  18  or the cutter mechanism  19   a  in accordance with the direction of rotation, a clutch mechanism using a solenoid is unnecessary, and the number of parts can be reduced and the structure can be simplified. 
   As mentioned above, the gear train  36  comprises the sun gear  40  which rotates in accordance with activation of the motor  34 ; and the planetary gears  41 ,  42  which mesh with the sun gear  40 , are movable along an outer periphery of the sun gear  40 , and selectively mesh with the paper feeding transmission gear  37  or the cutter driving transmission gear  39  in accordance with the direction of rotation of the sun gear  40 . Specifically, a transmission channel is switched by use of a planetary gear mechanism, thereby promoting a reduction in the number of parts and simplification of structure. 
   Although the embodiment of the invention has been described by reference to the drawings, the invention is not limited to the items described in connection with the embodiment and encompasses a range in which a person skilled in the art can modify the invention or realize an application of the invention on the basis of the scope of the invention, the detailed description of the invention, and the related art.