Patent Publication Number: US-9902174-B2

Title: Printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based upon and claims priority to Japanese Patent Application No. 2016-091893, filed on Apr. 28, 2016, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to printers. 
     2. Description of the Related Art 
     Printers are widely used for shop registers and automated teller machines (ATMs) or cash dispensers (CDs) in banks. 
     Some of these printers include, for example, a printer body and a lid pivotably supported on the printer body. The lid is opened to allow a roll of recording paper to be loaded into a paper holder of the printer body. 
     Reference may be made to, for example, Japanese Patent No. 2585769 and Japanese Laid-Open Patent Application Nos. 2003-246104 and 2009-28910 for related art. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, a printer includes a body configured to accommodate recording paper, a lid attached to the body to be openable and closable relative to the body, a pressing part on the lid, a platen roller attached to the lid, a movable shaft in the body, a spring that urges the movable shaft, and a lever configured to support bearings of the platen roller with the lid being closed. The movable shaft is provided at a position corresponding to the pressing part to be movable in a longitudinal direction of the movable shaft, and is pressed by the pressing part to generate a spring force in the spring during closure of the lid. 
     According to an aspect of the present invention, a printer includes a body configured to accommodate recording paper, a lid attached to the body to be openable and closable relative to the body, a platen roller attached to the lid, a lever configured to support bearings of the platen roller with the lid being closed, a spring in the body, and a pressing part on the lid. The pressing part is provided at a position corresponding to the spring. The spring is pressed by the pressing part to generate a spring force during closure of the lid. 
     According to an aspect of the present invention, a printer includes a body configured to accommodate recording paper, a lid attached to the body to be openable and closable relative to the body, a platen roller attached to the lid, a lever configured to support bearings of the platen roller with the lid being closed, and a spring on the lid. The spring includes a first part connected to the lid. The body includes a contact part provided at a position corresponding to a second part of the spring. The second part of the spring is pressed by the contact part to generate a spring force during closure of the lid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a printer with a lid closed; 
         FIG. 2  is a cross-sectional view of the printer with the lid open; 
         FIG. 3  is a front elevational view of the printer; 
         FIG. 4  is a cross-sectional view of the printer with the lid open; 
         FIG. 5  is a cross-sectional view of the printer with the lid closed; 
         FIG. 6  is a diagram illustrating the closure of the lid of the printer; 
         FIGS. 7A through 7C  are diagrams depicting the printer with the lid completely closed; 
         FIG. 8  is a diagram illustrating the opening of the lid of the printer; 
         FIGS. 9A through 9C  are diagrams depicting the lid of the printer in a half-lock state; 
         FIGS. 10A through 100  are diagrams depicting the lid of the printer in a half-lock state; 
         FIG. 11  is a diagram illustrating the occurrence of the half-lock state of the lid of the printer; 
         FIG. 12  is a cross-sectional view of a printer with a lid open according to a first embodiment; 
         FIG. 13  is a front elevational view of the printer according to the first embodiment; 
         FIG. 14  is a diagram illustrating the printer according to the first embodiment; 
         FIG. 15  is a diagram illustrating the printer according to the first embodiment; 
         FIG. 16  is a diagram illustrating the printer according to the first embodiment; 
         FIG. 17  is a diagram illustrating the printer according to the first embodiment; 
         FIG. 18A  is a perspective cross-sectional view of the printer according to the first embodiment; 
         FIG. 18B  is a perspective view of a pressing part of the printer according to the first embodiment; 
         FIG. 18C  is a perspective view of a movable shaft of the printer according to the first embodiment; 
         FIG. 18D  is a perspective view of a stopper of the printer according to the first embodiment; 
         FIGS. 18E and 18F  are diagrams for illustrating the movement of the movable shaft according to the first embodiment; 
         FIG. 19  is a cross-sectional view of a first variation of the printer according to the first embodiment; 
         FIG. 20  is a cross-sectional view of a second variation of the printer according to the first embodiment; 
         FIG. 21  is a cross-sectional view of a third variation of the printer according to the first embodiment; 
         FIG. 22  is a cross-sectional view of a fourth variation of the printer according to the first embodiment; 
         FIG. 23  is a cross-sectional view of a fifth variation of the printer according to the first embodiment; 
         FIGS. 24A and 24B  are diagrams depicting a structure of a printer according to a second embodiment; 
         FIGS. 25A and 25B  are diagrams illustrating the printer according to the second embodiment; 
         FIGS. 26A through 26C  are diagrams depicting a structure of a first variation of the printer according to the second embodiment; 
         FIGS. 27A and 27B  are diagrams illustrating the first variation of the printer according to the second embodiment; 
         FIGS. 28A through 28C  are diagrams depicting a structure of a second variation of the printer according to the second embodiment; 
         FIGS. 29A and 29B  are diagrams illustrating the second variation of the printer according to the second embodiment; 
         FIGS. 30A through 30C  are diagrams depicting a structure of a third variation of the printer according to the second embodiment; 
         FIGS. 31A and 31B  are diagrams illustrating the third variation of the printer according to the second embodiment; 
         FIG. 32  is a diagram illustrating a printer according to a third embodiment; and 
         FIG. 33  is a diagram illustrating the printer according to the third embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Printers including a printer body and a lid are also used for information apparatus terminals used by various users, such as ticket machines. When such ticket machines run out of recording paper, a user opens the lid to load a paper holder with recording paper and thereafter closes the lid. When closing the lid, for example, the bearings of a platen roller enter locks provided in the printer body to lock the lid. As a result, the printer becomes ready to perform printing on the recording paper. 
     In the case where the locks are provided one on each side of the printer, however, it may occur that one of the bearings enters one of the locks while the other of the bearings stops on the way to be out of the other of the locks when the lid is pressed to be closed. Such a state is referred to as a “half-lock” state, in which the platen roller is incorrectly positioned relative to a print head to prevent the printer from performing printing. In this half-lock state, the lid appears to be closed to a user, who may therefore think that printing is not performed although the lid is closed, thus determining that something is wrong with the printer. In order to eliminate the half-lock state, for example, the lid may be pressed on the side on which the other of the locks is provided, or may be opened and closed again. Users, however, are reluctant to perform such operations once determining that the printer is out of order. Therefore, the printer is prevented from performing printing, so that an information apparatus terminal in which the printer is installed becomes out of service. 
     Therefore, there is a demand for printers in which no half-lock state occurs when closing a lid. 
     According to a printer of an embodiment of the present invention, the closure of a lid is secured without the occurrence of a half-lock state when the lid is closed. 
     Embodiments of the present invention are described below with reference to the accompanying drawings. The same elements are referred to using the same reference numeral, and a repetitive description thereof is omitted. 
     First, the occurrence of a half-lock state at the time of closing a lid in printers is described with reference to  FIGS. 1 through 11 . A printer depicted in  FIGS. 1 through 11  is a clamshell type, in which a roll of recording paper is dropped to be loaded into a paper holder.  FIG. 1  is a perspective view of the printer with a lid closed.  FIG. 2  is a cross-sectional view of the printer with the lid open.  FIG. 3  is a front elevational view of the printer with the lid closed.  FIGS. 4 and 5  are cross-sectional views of the printer taken along the one-dot chain line  3 A- 3 B in  FIG. 3 , depicting a state where the lid is open and a state where the lid is closed, respectively. The printer is schematically depicted in and may differ in detail among the drawings. 
     Referring to, for example,  FIGS. 1 through 5 , the printer includes a body  10  and a lid  20  pivotally attached to the body  10 . The body  10  includes a paper holder (“holder”)  11  and a print head (“head”)  30 . The holder  11  accommodates a roll of recording paper  100 . A platen roller  40  and a cutter unit  50  for cutting the recording paper  100  are attached to the lid  20 . 
     The recording paper  100  is placed in the holder  11  and then the lid  20  is closed, so that the recording paper  100  is set in the printer. Specifically, the recording paper  100  is placed in the holder  11  with the lid  20  open as depicted in  FIG. 4 , and thereafter, the lid  20  is pivoted about a shaft in the direction indicated by the dashed arrow A to be closed as depicted in  FIG. 5 . 
     The operation of closing the lid  20  is described in more detail with reference to  FIGS. 6 and 7A through 7C .  FIG. 6  depicts the printer during the process of closing the lid  20  by pivoting the lid  20  in the direction indicated by the dashed arrow A.  FIGS. 7A, 7B and 7C  are diagrams depicting the printer in which the lid  20  is completely closed.  FIG. 7A  is a plan view of the printer.  FIGS. 7B and 7C  are cross-sectional views of the printer, depicting a cross section near the right end and a cross section near the left end, respectively, of the printer of  FIG. 7A . 
     First and second bearings  41   a  and  41   b  are provided one at each axial end of the platen roller  40 . A lock lever (“lever”)  60  configured to support and securely lock the first and second bearings  41   a  and  41   b  when the lid  20  is closed is provided in the body  10 . The lever  60  includes a first lock  61   a  and a second lock  61   b  at opposite ends. An opening  62   a  that accommodates the first bearing  41   a  is formed in the first lock  61   a . An opening  62   b  that accommodates the second bearing  41   b  is formed in the second lock  61   b . The lever  60  includes an operation part  63  at the same end as the first lock  61   a . The operation part  63  is operated to pivot the lever  60 . 
     As depicted in  FIGS. 7A through 7C , when the lid  20  is closed, the first bearing  41   a  and the second bearing  41   b  are accommodated in the opening  62   a  and the opening  62   b , respectively, to be locked to prevent the lid  20  from opening. Printing is performed on the recording paper  100  with the head  30  with the first and second bearings  41   a  and  41   b  being thus locked. 
     When opening the lid  20 , the operation part  63  is moved in the direction indicated by the dashed arrow B as depicted in  FIG. 8 . As a result, the first and second bearings  41   a  and  41   b  exit from the openings  62   a  and  62   b , respectively, to be unlocked. Accordingly, the lid  20  pivots in the direction indicated by the dashed arrow C to open. 
     According to this printer, the half-lock state occurs when the first bearing  41   a  or the second bearing  41   b  is out of the opening  62   a  or  62   b . Specifically, the half-lock state occurs when the second bearing  41   b  stops on the way to be incompletely accommodated in the opening  62   b  while the first bearing  41   a  is accommodated in the opening  62   a  as depicted in  FIGS. 9A through 9C  (a first half-lock state) or when the first bearing  41   a  stops on the way to be incompletely accommodated in the opening  62   a  while the second bearing  41   b  is accommodated in the opening  62   b  as depicted in FIGS.  10 A through  10 C (a second half-lock state). 
     In these states, while one of the first and second bearings  41   a  and  41   b  is accommodated in one of the openings  62   a  and  62   b , the other of the first and second bearings  41   a  and  41   b  is not accommodated in the other of the openings  62   a  and  62   b  to incorrectly position the platen roller  40  relative to the head  30  to prevent the printer from performing printing.  FIG. 9A  is a plan view of the printer in the first half-lock state.  FIGS. 9B and 9C  are cross-sectional views of the printer, depicting a cross section near the right end and a cross section near the left end, respectively, of the printer of  FIG. 9A .  FIG. 10A  is a plan view of the printer in the second half-lock state.  FIGS. 10B and 10C  are cross-sectional views of the printer, depicting a cross section near the right end and a cross section near the left end, respectively, of the printer of  FIG. 10A . 
     Referring also to  FIG. 11 , the first half-lock state depicted in  FIGS. 9A through 9C  may occur when the lid  20  is pressed only on the right side to be closed as indicated by the dashed arrow D. The second half-lock state depicted in  FIGS. 10A through 10C  may occur when the lid  20  is pressed only on the left side to be closed as indicated by the dashed arrow E. 
     [a] First Embodiment 
     Next, a printer according to a first embodiment is described with reference to  FIGS. 12 through 18F . The printer of this embodiment is a clamshell type.  FIG. 12  is a perspective view of the printer with a lid open.  FIG. 13  is a front elevational view of the printer with the lid closed.  FIGS. 14 and 15  are cross-sectional views of the printer taken along the one-dot chain line  13 A- 13 B in  FIG. 13 , depicting a state where the lid is open and a state where the lid is closed, respectively. 
     The printer according to this embodiment includes a body  110  and a lid  120  pivotably attached to the body  110  to be openable and closable relative to the body  110 . 
     The body  110  includes a holder  111 , a head  130  for printing on recording paper, a control circuit board, and motors. The head  130  is a thermal head. The holder  111  is configured to accommodate the roll of recording paper  100 , which is thermal paper according to this embodiment. The motors include a motor for driving a platen roller  140  to convey recording paper and a motor for driving a cutter unit  150  to cut the recording paper  100 . 
     Referring also to  FIGS. 18A through 18F , a pressing part  170  protruding toward the holder  111  is provided on the lid  120 . A movable shaft  180  and a coil spring  191  are provided at a position corresponding to the pressing part  170  in the body  110 . The movable shaft  180  and the coil spring  191  are placed on a support  114  formed in the body  110 . The movable shaft  180  is provided through an opening in a wall  115  provided in the body  110  to partly project from the wall  115 . The movable shaft  180  includes a thick portion  180   a  at a first longitudinal end, a flange  180   e  at a second longitudinal end, a thin portion  180   d  extending from the flange  180   e  toward the first longitudinal end, and a shaft portion  180   c  extending between the thick portion  180   a  and the thin portion  180   d . The thick portion  180   a  is thicker (wider) than the shaft portion  180   c . The thin portion  180   d  is thinner (narrower) than the shaft portion  180   c  and has a predetermined length in the longitudinal direction of the movable shaft  180 . The shaft portion  180   c  is inserted into the coil spring  191 . Part of the thin portion  180   d  is positioned in a slit  200   a  of a stopper  200  attached to the wall  115 . By way of example, the stopper  200  is screwed to the wall  115  according to this embodiment. The movable shaft  180  is movable in its longitudinal direction for the length of the thin portion  180   d  minus the thickness of the stopper  200  as depicted in  FIGS. 18E and 18F .  FIG. 18A  is a perspective cross-sectional view of the printer with the lid  120  closed.  FIG. 18B  is a perspective view of the pressing part  170 .  FIG. 18C  is a perspective view of the movable shaft  180 .  FIG. 18D  is a perspective view of the stopper  200 .  FIGS. 18E and 18F  are diagrams for illustrating the movement of the movable shaft  180 , depicting the state where the movable shaft  180  projects most from the wall  115  and the state where the movable shaft  180  is pressed and retracted most into the wall  115 , respectively. For example, when the lid  120  is open, the movable shaft  180  is not pressed by the pressing part  170  to be in the state depicted in  FIG. 18E . In this state, the flange  180   e  contacts the stopper  200  to prevent the movable shaft  180  to project further from the wall  115 . For example, when the lid  120  is closed, the movable shaft  180  is pressed by the pressing part  170  to be in the state depicted in  FIG. 18F . 
     A first end  191   a  of the coil spring  191  contacts a surface of the wall  115 . A second end  191   b  of the coil spring  191  contacts an inner surface of the thick portion  180   a . The pressing part  170  and the movable shaft  180  are formed of a metal material such as stainless steel. When closing the lid  120  or when the lid  120  is closed, an outer surface  180   b  of the thick portion  180   a  contacts an end surface  170   a  of the pressing part  170 . 
     A lever  160  configured to support bearings  141  of the platen roller  140  when the lid  120  is closed is provided in the body  110 . The lever  160  includes right and left locks at opposite ends. An opening that accommodates one of the bearings  141  is formed in the right lock. An opening that accommodates the other of the bearings  141  is formed in the left lock. The lever  160  is supported to be pivotable about a shaft, and is urged by a spring or the like in a direction to move the locks toward the bearings  141 . The lever  160  includes an operation part  163  at the same end as the right lock. The operation part  163  is operated to pivot the lever  160 . In the following, for convenience of description, the right-side portion of the lever  160  is described, referring to the right lock as “lock  161 ” and to the opening formed in the right lock as “opening  162 .” 
     Referring to  FIG. 14 , when closing the lid  120 , the lid  120  that is open is pivoted with a hand in the direction indicated by the dashed arrow F, namely, clockwise. As a result, as depicted in  FIG. 16 , the end surface  170   a  of the pressing part  170  and the outer surface  180   b  of the movable shaft  180  come into contact. In this state, the bearing  141  (one of the bearings  141  corresponding to the lock  161 ) of the platen roller  140  is out of contact with the lever  160 . 
     Referring to  FIG. 17 , when the lid  120  is further pivoted clockwise, the pressing part  170  presses the outer surface  180   b  to move the movable shaft  180  in its longitudinal direction, and the coil spring  191  is pressed by the thick portion  180   a  to be compressed. As a result, the lid  120  is urged in a direction to be opened, and a spring force is generated. In this state, the bearing  141  is about to enter but is not completely accommodated in the opening  162 . Thus, the spring force of the coil spring  191  is greater than a force for locking the bearing  141  to prevent the bearing  141  from disengaging from the lock  161 . Therefore, if the hand is taken off the lid  120  in this state, a force to pivot the lid  120  in a counterclockwise direction opposite to the direction indicated by the dashed arrow F ( FIG. 16 ) is exerted by the spring force of the coil spring  191 . Thus, in the half-lock state where at least one of the bearings  141  is not accommodated in one of the openings  162 , the lid  120  is opened by the spring force of the coil spring  191 . 
     When the lid  120  is further pivoted clockwise from the position depicted in  FIG. 17 , the movable shaft  180  moves in its longitudinal direction to further compress the coil spring  191 . As a result, the lid  120  is completely closed as depicted in  FIG. 15 . In this state, the bearing  141  is accommodated in the opening  162 , and the bearings  141  at the right and left ends of the platen roller  140  are locked by the locks  161  at the right and left ends of the lever  160 . In this state, a force to lock the bearings  141  to prevent the bearings  141  from disengaging from the locks  161  is greater than the spring force of the coil spring  191 . Therefore, even when the hand is taken off the lid  120 , the lid  120  is prevented from being opened by the spring force of the coil spring  191  because the bearings  141  are locked by the locks  161 . 
     According to the printer of this embodiment, the half-lock state occurs when one of the bearings  141  is not accommodated in one of the openings  162  as depicted in  FIG. 17  although the other of the bearings  141  is accommodated in the other of the openings  162 . In this state, the bearings  141  of the platen roller  140  are not locked by the locks  161 , and the spring force of the coil spring  191  is greater than a force of the locks  161  to lock the bearings  141 . Therefore, when a hand with which the lid  120  is pivoted is taken off the lid  120 , the spring force of the coil spring  191  opens the lid  120 . 
     That is, according to the printer of this embodiment, when one of the bearings  141  is not locked, the spring force of the coil spring  191  opens the lid  120 . In other words, according to the printer of this embodiment, the lid  120  is either closed as depicted in  FIG. 15  or open as depicted in  FIG. 14 , and no half-lock state occurs. 
     As depicted in  FIG. 19 , a helical torsion spring  192  may be used instead of the coil spring  191 . A first arm  192   a  of the helical torsion spring  192  is fixed to a spring fixation part  116  provided in the body  110 . A second arm  192   b  of the helical torsion spring  192  contacts the inside of the thick portion  180   a . When the movable shaft  180  is pressed by the pressing part  170 , the helical torsion spring  192  is pressed by the inside of the thick portion  180   a  to deform as indicated by the dashed line to generate a spring force in a direction to open the lid  120 . 
     Alternatively, as depicted in  FIG. 20 , a leaf spring  193  may be used instead of the coil spring  191 . A first end portion  193   a  of the leaf spring  193  is fixed to the support  114  provided in the body  110 . A second end portion  193   b  of the leaf spring  193  contacts the inside of the thick portion  180   a . When the movable shaft  180  is pressed by the pressing part  170 , the leaf spring  193  is pressed by the inside of the thick portion  180   a  to deform as indicated by the dashed line to generate a spring force in a direction to open the lid  120 . 
     As another alternative, the printer of this embodiment may omit the movable shaft  180 . Referring to  FIG. 21 , a projection  118  in the surface of the wall  115  is inserted into the coil spring  191 , and the first end  191   a  of the coil spring  191  contacts the surface of the wall  115 . When the lid  120  is closed, the second end  191   b  of the coil spring  191  directly contacts the end surface  170   a  of the pressing part  170  to be pressed by the end surface  170   a  to generate a spring force in the coil spring  191 . 
     As yet another alternative, as depicted in  FIG. 22 , the movable shaft  180  may be omitted in the case of using the helical torsion spring  192 . In this case, when the lid  120  is closed, the second arm  192   b  of the helical torsion spring  192  directly contacts the end surface  170   a  of the pressing part  170  to be pressed by the end surface  170   a . As a result, the second arm  192   b  deforms as indicated by the dashed line to generate a spring force in the helical torsion spring  192 . 
     As still another alternative, as depicted in  FIG. 23 , the movable shaft  180  may be omitted in the case of using the leaf spring  193 . In this case, when the lid  120  is closed, the second end portion  193   b  of the leaf spring  193  directly contacts the end surface  170   a  of the pressing part  170  to be pressed by the end surface  170   a . As a result, the second end portion  193   b  deforms as indicated by the dashed line to generate a spring force in the leaf spring  193 . 
     In the arrangements as depicted in  FIGS. 21 through 23 , the stopper  200  may be omitted. 
     [b] Second Embodiment 
     Next, a second embodiment is described with reference to  FIGS. 24A, 24B, 25A and 25B . According to a printer of this embodiment, as depicted in  FIGS. 25A and 25B , the outer surface  180   b  of the movable shaft  180  includes a projection  181 , and the end surface  170   a  of the pressing part  170  includes an opening  171  corresponding to the projection  181 .  FIG. 24A  is a cross-sectional view of the printer of this embodiment.  FIG. 24B  is a perspective view of the pressing part  170 .  FIG. 25A  depicts a state before the projection  181  enters the opening  171 .  FIG. 25B  depicts the state where the projection  181  is in the opening  171 . 
     According to this embodiment, when the lid  120  is pivoted in the direction indicated by the dashed arrow F in  FIG. 24A  to be closed, the pressing part  170  and the movable shaft  180  contact. At this point, first, the projection  181  of the movable shaft  180  and the end surface  170   a  of the pressing part  170  contact as depicted in  FIG. 25A . As the lid  120  is pivoted in the direction indicated by the dashed arrow F, the projection  181  is pressed while moving on the end surface  170   a . As a result, the movable shaft  180  is pressed by the pressing part  170  in the direction indicated by the dashed arrow G in  FIG. 25A  to compress the coil spring  191 . 
     When the lid  120  is further pivoted in the direction indicated by the dashed arrow F to relatively move the projection  181  to the position of the opening  171  provided in the end surface  170   a , the movable shaft  180  moves in the direction indicated by the dashed arrow H in  FIG. 25B  because of the spring force of the coil spring  191  to have the projection  181  enter the opening  171 . At this point, the end surface  170   a  and the outer surface  180   b  contact to generate an impact and an impact sound. 
     Thus, a user who has been closing the lid  120  can perceive the complete closure of the lid  120  tactilely and aurally through the impact and the impact sound generated by the contact of the end surface  170   a  and the outer surface  180   b.    
     Alternatively, according to the printer of this embodiment, as depicted in  FIGS. 26A, 26B, 26C, 27A and 27B , the end surface  170   a  may include a projection  172  and the outer surface  180   b  may include a circular opening  182 . In this case as well, the same as described above, when the lid  120  is closed, the end surface  170   a  and the outer surface  180   b  contact because of the spring force of the coil spring  191  to generate an impact and an impact sound. A user who has been closing the lid  120  can perceive the complete closure of the lid  120  through the impact and the impact sound thus generated.  FIG. 26A  is a cross-sectional view of the printer.  FIG. 26B  is a perspective view of the pressing part  170 .  FIG. 26C  is a perspective view of the movable shaft  180 .  FIG. 27A  depicts a state before the projection  172  enters the opening  182 .  FIG. 27B  depicts the state where the projection  172  is in the opening  182 . 
     As another alternative, according to the printer of this embodiment, as depicted in  FIGS. 28A, 28B, 28C, 29A and 29B , a groove  183  may be formed in the outer surface  180   b  instead of the opening  182 .  FIG. 28A  is a cross-sectional view of the printer.  FIG. 28B  is a perspective view of the pressing part  170 .  FIG. 28C  is a perspective view of the movable shaft  180 .  FIG. 29A  depicts a state before the projection  172  enters the groove  183 .  FIG. 29B  depicts the state where the projection  172  is in the groove  183 . 
     As yet another alternative, as depicted in  FIGS. 30A, 30B, 30C, 31A and 31B , an annular projection  184  may be formed in the outer surface  180   b  to define the opening  182 .  FIG. 30A  is a cross-sectional view of the printer.  FIG. 30B  is a perspective view of the pressing part  170 .  FIG. 30C  is a perspective view of the movable shaft  180 .  FIG. 31A  depicts a state before the projection  172  enters the opening  182 .  FIG. 31B  depicts the state where the projection  172  is in the opening  182 . Furthermore, according to the second embodiment, a depth d of the opening  182  (or the groove  183 ) and a height h of the projection  172  (or the depth of the opening  171  and the height of the projection  181 ) may be changed to change the magnitude of the impact and the impact sound generated by the contact of the end surface  170   a  and the outer surface  180   b  caused by the spring force of the coil spring  191 . Therefore, the depth d of the opening  182  and the height h of the projection  172  may be controlled to generate an impact of a desired magnitude and an impact sound of a desired magnitude. 
     According to the printer of this embodiment, a helical torsion spring or a leaf spring may be used instead of the coil spring  191 . In other respects than those described above, the second embodiment may be the same as the first embodiment. 
     [c] Third Embodiment 
     Next, a third embodiment is described. According to a printer of this embodiment, as depicted in  FIGS. 32 and 33 , a coil spring  291  is provided on the lid  120 , and a tubular part  285  configured to accommodate the coil spring  291  when the lid  120  is closed is provided in the body  110 . Furthermore, a contact part  286  configured to contact the coil spring  291  is provided at the bottom of the tubular part  285 . A projection  270  provided on the lid  120  is inserted into the coil spring  291 . 
     A first end  291   a  of the coil spring  291  contacts part of the lid  120 . A second end  291   b  of the coil spring  291  contacts the contact part  286  at the bottom of the tubular part  285  to be compressed to generate a spring force in a direction to open the lid  120 , when the lid  120  is closed. Therefore, according to the printer of this embodiment, even when at least one of the bearings  141  is not accommodated in one of the openings  162 , the occurrence of a half-lock state is prevented because the lid  120  is opened by the spring force of the coil spring  291 . 
     According to the printer of this embodiment, a helical torsion spring or a leaf spring may be used instead of the coil spring  191 . In other respects than those described above, the second embodiment may be the same as the first embodiment. 
     All examples and conditional language provided herein are intended for pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventors to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority or inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.