Abstract:
A printer having a roll paper compartment  8  for housing a recording paper roll and a movable divider  83  for adjustably setting one side of the roll paper compartment  8  to adjustably accommodate different widths of roll paper and to facilitate placement of a remaining paper detector  90  in the roll paper compartment  8  for detecting how much paper remains on the paper roll. The divider facilitates installation of an after market remaining paper detector in the printer. The remaining paper detector can be positioned at a plurality of different angular positions around an axis of rotation substantially parallel to the widthwise direction of the printer. The roll paper compartment  8  of the printer  1  has a bottom  81  and a fixed side panel  82  for defining the other side of the roll paper compartment. The divider  83  is removably connected to the bottom  81 , and can be selectively fixed to any one of a multiple number of positions along the width of the printer parallel to the longitudinal axis thereof.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Technology  
           [0002]    The present invention relates generally to a receipt printer or other type of printer used in a POS system, and relates more particularly to a printer in which a remaining paper detector is removably installed for detecting how much paper remains on a paper roll in the roll paper compartment.  
           [0003]    2. Description of Related Art  
           [0004]    Paper rolls made by winding a recording paper tape as a recording medium onto a core are commonly used in receipt printers. A paper roll is then housed in a roll paper compartment, the paper is pulled from the roll and printed using a thermal print head, for example, and the printed paper is then cut to a suitable length by a paper cutter for issuance as a receipt. To make replacing the roll paper easier, some printers of this type have the paper roll set directly on the bottom of the roll paper compartment and pull the paper tape from the compartment with the paper roll rotating directly against the compartment bottom rather than passing a spindle through the core of the roll and rotatably supporting the roll on this spindle.  
           [0005]    So that different widths of roll paper can be used in printers using this type of roll paper compartment, Japanese Unexamined Patent Appl. Pub. 2002-3022 teaches a printer in which one side of the roll paper compartment is a movable divider. This divider can be moved widthwise to the printer and set to the width of roll paper loaded in the roll paper compartment.  
           [0006]    Printers that have a remaining paper detector in the roll paper compartment for detecting when the amount of paper left on the roll declines to a specific threshold level are also known. One such remaining paper detector has a detector element that enters the hollow core of the paper roll when the amount of paper left on the roll drops to a predefined level. When this detector element enters the hollow core, a switch operates to output a signal indicating that there is only a little paper left. See, for example, Japanese Unexamined Patent Appl. Pubs. 2002-3022 and H09-295436.  
           [0007]    Obviously not all receipt printers, for example, have a remaining paper detector pre-installed in the roll paper compartment, and there are therefore cases in which a remaining paper detector (also called a near-end detector) is later added.  
           [0008]    If the remaining paper detector operates by means of a detector element that enters the hollow core of the paper roll, it may also be necessary to adjust the height and orientation of the detector element according to the attitude of the printer, for example, so that the detector operates correctly.  
         SUMMARY OF THE INVENTION  
         [0009]    An object of the present invention is therefore to provide a printer that simplifies after-market installation of a remaining paper detector and adjusting the installation position of the remaining paper detector.  
           [0010]    To achieve this object, a printer according to the present invention has a roll paper compartment for housing a recording paper roll. This roll paper compartment has a bottom panel; a fixed side panel defining one side of the roll paper compartment widthwise to the printer; and a divider defining an other side of the roll paper compartment widthwise to the printer. The divider is removably assembled to the bottom panel and has a detector mounting part for removably installing a remaining paper detector. The remaining paper detector is used to detect if an amount of paper remaining on a paper roll stored in the roll paper compartment is less than or equal to a predetermined amount.  
           [0011]    This aspect of the invention provides a mounting part for a remaining paper detector on a removable divider. To install the remaining paper detector, the divider is removed from the roll paper compartment, the remaining paper detector is then installed to the mounting part of the divider, and the divider is then reinstalled to the roll paper compartment. Installing an after-market remaining paper detector is therefore easier compared with other configurations in which the remaining paper detector is installed to a fixed location inside the roll paper compartment of the printer.  
           [0012]    In order to accommodate paper rolls of different widths, the divider can be assembled to the bottom panel positioned to one of multiple positions widthwise to the printer.  
           [0013]    In this case the divider preferably has a plurality of protruding pins or recessed holes, and the bottom panel has a set of holes for inserting the pins, or a set of pins for insertion into the recessed holes, at the multiple positions widthwise to the printer. This enables the divider to be easily fixed at one of multiple positions widthwise to the printer.  
           [0014]    Yet further preferably, the printer has a remaining paper detector removably installed to the detector mounting part of the divider.  
           [0015]    This remaining paper detector preferably has a detector element positioned at a specified height from the bottom panel. This detector element contacts a side of the roll paper stored in the roll paper compartment, and enters the hollow core of the paper roll when the remaining roll paper drops below a predetermined level.  
           [0016]    The outside diameter of the hollow core of commercially available recording paper rolls is typically 18 mm or 22 mm. To accurately detect the near-end of roll paper wound to either size of core, the remaining paper detector is preferably installed to the divider so that the detector element height can be adjusted.  
           [0017]    While this printer is typically placed horizontally, it could be used in a vertical orientation, which case the back end of the printer becomes the bottom. This makes it necessary to change the position of the detector element of the remaining paper detector. The remaining paper detector is therefore further preferably installed to the divider so that the detector element can be positioned to a plurality of angular positions around an axis of rotation substantially parallel to the widthwise direction of the printer.  
           [0018]    A further aspect of the invention is a printer having a compartment for holding roll paper. This compartment has a fixed first side against which the roll paper is set, and an adjustable second side that is movable to the printer according to the roll paper width. The printer has a roll paper near-end detector disposed to said second side.  
           [0019]    Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is an oblique external view of a printer according to the present invention;  
         [0021]    [0021]FIG. 2 is a schematic longitudinal section view of the printer shown in FIG. 1;  
         [0022]    [0022]FIG. 3 is a schematic longitudinal section view of the printer shown in FIG. 1 with the cover open;  
         [0023]    [0023]FIG. 4 is an enlarged partial section view showing the paper feed mechanism of the printer shown in FIG. 1;  
         [0024]    [0024]FIG. 5 is an oblique view of the printer unit assembled into the printer shown in FIG. 1;  
         [0025]    [0025]FIG. 6 is an oblique view showing the opening unit of the printer unit shown in FIG. 5 open;  
         [0026]    [0026]FIG. 7 is an oblique view from the left front side of the roll paper compartment in the printer shown in FIG. 1;  
         [0027]    [0027]FIG. 8 is an oblique view from the right front side of the roll paper compartment shown in FIG. 7;  
         [0028]    [0028]FIG. 9 is a right side view of the roll paper compartment shown in FIG. 7;  
         [0029]    [0029]FIG. 10 is a partially exploded oblique view of the roll paper compartment shown in FIG. 7;  
         [0030]    [0030]FIG. 11 is a partially exploded oblique view showing the divider and remaining paper detector in the roll paper compartment shown in FIG. 7;  
         [0031]    [0031]FIG. 12 is a right side view of the divider shown in FIG. 11; and  
         [0032]    [0032]FIG. 13 describes the detection operation of the remaining paper detector in the printer shown in FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    A preferred embodiment of a printer according to the present invention is described below with reference to the accompanying figures.  
         [0034]    (General Configuration)  
         [0035]    As shown in these figures, a printer  1  according to the present invention has a rectangular case frame  2  enclosing the four sides of the printer  1 , a front cover  3  that covers the top front and a back cover  4  that covers the top back part of the printer  1 . Together these parts form the printer case. A printer unit  11  is assembled into this printer case, and a paper exit  5  is formed between the front and back covers  3 ,  4 . Operating a sliding button  6  releases a locking mechanism (not shown in the figure) so that the back cover  4  can be opened to the back as shown in FIG. 3. Roll paper  7  is held in a compartment  8  in the printer unit  11 , and opening the back cover  4  opens the roll paper compartment  8  so that the roll paper  7  can be replaced. A ribbon cassette  9  holding the ink ribbon for the printer unit  11  is loaded to a loading unit  10 . Opening the front cover  3  similarly exposes this loading unit  10  so that ink ribbon cassette  9  can be replaced.  
         [0036]    The internal structure of the printer  1  is described next.  
         [0037]    The roll paper  7  compartment  8  formed in the back of the printer unit  11  has a substantially curved bottom that is open to the top when seen from the side as shown in FIG. 2. Recording paper  7   a  pulled from a paper roll  7  held in the compartment  8  passes guide roller  14  at the front of the compartment  8  and is guided to the paper transportation path  15 . The paper transportation path  15  has a first inclined path part  16  that slopes gradually upward from the back to the front of the printer, a second inclined path part  17  that rises at a sharp angle from the front end of the first inclined path part  16 , and a third inclined path part  18  that slopes from the top end of the second inclined path part  17  toward the back of the printer  1  and leads to the paper exit  5 . Note that the recording paper  7   a  is indicated by a dotted line in FIG. 2 and FIG. 4.  
         [0038]    The first inclined path part  16  is composed of a transportation guide  16   a  and an opposing transportation surface  16   b . The second inclined path part  17  downstream from the first inclined path part  16  is composed of the print head surface  20   a  of a dot impact print head  20 , and a platen  21  that is opposite the print head surface  20   a  with a specific gap therebetween. The second inclined path part  17  is thus where the roll paper is printed by the print head  20 , and is also referred to as the printing position herein. The print head  20  is disposed so that the head surface  20   a  is inclined and faces up and toward the back of the printer  1 . The platen  21  is rendered such that the platen surface is inclined facing downward and to the front of the printer corresponding to the angle of the print head  20 . The print head  20  is mounted on a head carriage  22 . The head carriage  22  travels bidirectionally widthwise to the printer along a carriage guide shaft  23 .  
         [0039]    The loading unit  10  for the ink ribbon cassette  9  is formed on the top of the head carriage  22 . The ribbon cassette loading unit  10  is also inclined rising upward toward the back of the printer  1 .  
         [0040]    As a result, the ink ribbon  9   a  delivered from an ink ribbon cassette  9  installed to the ribbon cassette loading unit  10  travels parallel to and between the print head  20  and platen  21 .  
         [0041]    The third inclined path part  18  continuing from the second inclined path part  17  is described by a transportation guide  28  curving to the back of the printer  1  from the top end of platen  21 . Disposed along this third inclined path part  18  is a paper transportation mechanism composed of paper feed roller  25 , pressure roller  26 , and torsion bar  27  as an urging means pushing the pressure roller  26  to the paper feed roller  25 . The paper feed roller  25  is located at the back side of the third inclined path part  18 . The pressure roller  26  is supported in front of the paper feed roller  25  on a roller mounting plate  29  so that the pressure roller  26  can move toward the paper feed roller  25 , and is constantly urged by the spring force of the torsion bar  27  toward the paper feed roller  25 .  
         [0042]    Recording paper  7   a  pulled from the roll paper  7  is held between the paper feed roller  25  and pressure roller  26 , and is conveyed through the paper transportation path  15  by rotation of the paper feed roller  25  by a drive means not shown. It should be noted that the platen  21  and transportation guide  16   a  communicating with the bottom of the platen  21  are formed by a platen frame  55 , which is a discrete part, and the transportation guide  28  is assembled to the top end of this platen frame  55 .  
         [0043]    A scissors-type automatic cutter unit  30  for cutting the recording paper is disposed near the paper exit  5 . This automatic cutter unit  30  is composed of a fixed knife  31  located on one side (the front) and a movable knife  32  on the other side (the back) of the paper transportation path, and a drive mechanism  33  for operating the movable knife  32 . The movable knife  32  and drive mechanism  33  are housed in a case  34 . Recording paper  7   a  held between the fixed knife  31  and movable knife  32  is cut by the movable knife  32  sliding across the fixed knife  31 .  
         [0044]    Another knife  35  for manually cutting the recording paper  7   a  is rendered at the front edge of the paper exit  5 .  
         [0045]    [0045]FIG. 5 is an oblique view of the printer unit  11  assembled into the printer case. The printer unit  11  is composed of a stationary unit  12  and an opening unit  13 . The opening unit  13  is pivotably supported on the stationary unit  12  so that the opening unit  13  can rotate open and closed on an axis of rotation at the back of the unit. FIG. 6 is an oblique view showing the opening unit  13  open.  
         [0046]    To facilitate replacing the roll paper  7  in this printer unit  11 , opening the back cover  4  of the roll paper compartment  8  also opens the paper transportation path  15  configured as described above. As a result, the components of one side of the paper transportation path  15  are assembled to the stationary unit  12 , and the back cover  4  and components of the other side of the paper transportation path  15  are assembled to the movable opening unit  13 . As a result, opening the opening unit  13  opens the roll paper  7  compartment  8  as well as the paper transportation path  15 .  
         [0047]    More specifically, the roll paper compartment  8 , transportation surface  16   b  of first inclined path part  16 , print head  20 , pressure roller  26 , and fixed knife  31  of automatic cutter unit  30  are assembled to the stationary unit  12 . The platen frame  55  of first inclined path part  16 , second inclined path part  17 , and third inclined path part  18  (that is, transportation guide  16   a  and platen  21 ), transportation guide  28 , paper feed roller  25 , movable knife  32  of automatic cutter unit  30 , drive mechanism  33 , and back cover  4  are assembled to the opening unit  13  as shown in FIG. 3.  
         [0048]    This configuration assures that the opening unit  13  can still be opened even if there is a problem with the movable knife  32 , such as the movable knife  32  stopping while crossing the fixed knife  31 , because the movable knife  32  is located above the fixed knife  31 .  
         [0049]    As will be known from FIG. 3 and FIG. 6, when the opening unit  13  is fully open, the roll paper  7  can be loaded by the extremely simple operation of simply dropping the roll paper  7  into the compartment  8  from above. Furthermore, because the paper transportation path  15  is open at this time, the recording paper  7   a  can be threaded through the paper transportation path  15  by the extremely simple operation of simply pulling the recording paper  7   a  from the roll paper  7  along the paper transportation path  15 .  
         [0050]    When the opening unit  13  is then closed, restoring the arrangement shown in FIG. 2, FIG. 4, and FIG. 5, the recording paper  7   a  is automatically loaded between the print head  20  and platen  21  and between the paper feed roller  25  and pressure roller  26  with the end of the recording paper  7   a  protruding externally from the paper exit  5 .  
         [0051]    The stationary unit  12  and opening unit  13  are described in detail next.  
         [0052]    The stationary unit  12  has a main frame  40 , and the carriage guide shaft  23  is disposed widthwise to the front of the main frame  40 . As noted above, this carriage guide shaft  23  supports the head carriage  22  carrying the print head  20  so that the head carriage  22  can travel bidirectionally along the guide shaft  23 . A ribbon frame  41  is disposed covering the head carriage  22  and print head  20 . The outside perimeter of this ribbon frame  41  is the loading unit  10  for the ink ribbon cassette  9 .  
         [0053]    The compartment  8  for loading the roll paper  7  is formed at the back part of the main frame  40 , and a shaft  43  on which the opening unit  13  pivots is disposed at the back of the compartment  8  widthwise to the main frame  40 .  
         [0054]    The opening unit  13  has an opening frame  51  composed of right and left arms  52 ,  53  extending front-back, and a front connecting bracket  54  linking the front ends of these arms  52 ,  53 . The back ends of these right and left arms  52 ,  53  are freely rotatably supported by the ends of the pivot shaft  43 . The platen frame  55  is affixed to the front of the front connecting bracket  54  of the opening frame  51 , and paper feed roller shaft  25   a  is assembled therebehind. The outside surfaces of two paper feed rollers  25   b  affixed coaxially to the paper feed roller shaft  25   a  protrude to the front from openings  28   a  formed in the transportation guide  28  of platen frame  55 . The movable knife  32  and drive mechanism  33  of the automatic cutter unit  30  are mounted on the front connecting bracket  54  of the opening frame  51 .  
         [0055]    As will be known from FIG. 2 and FIG. 3, the print head  20  is disposed facing upward at an angle on the stationary unit  12 , and the ink ribbon cassette  9  loaded to the loading unit  10  is also disposed at a corresponding angle in the same direction. The platen  21  is disposed on the opening unit  13  side at a downward facing angle so that it is parallel to and equidistant from the head surface  20   a  of the print head  20 . The center of rotation for the opening unit  13 , that is, the height of the axial center of the shaft  43 , is below the head surface  20   a  of the print head  20 .  
         [0056]    As a result, when the opening unit  13  pivots open from the position where the platen  21  is equidistantly opposite the print head  20  (that is, the closed position of the opening unit  13 ), the path of the distal end of the opening unit  13 , that is, the path of the top and bottom edges of the platen  21  opposite the print head  20 , is not a forward or upward direction relative to the head surface  20   a  of the print head  20 , but rather an arc moving away from the head surface  20   a  to the back of the printer  1 . As a result, when the opening unit  13  opens and closes, this path does not intersect with the print head  20 .  
         [0057]    Furthermore, because the axis of rotation  43   a  of the opening unit  13  is located below the head surface  20   a  of the print head  20 , the movement of the top and bottom edges of the platen  21  toward the back in conjunction with movement of the opening unit  13  is great. This forms a space (an inverted triangle when seen from the side) directly above the printing position  17  through which the opening unit  13  does not travel. This space is used in this embodiment of the invention to locate the pressure roller  26 , torsion bar  27 , fixed knife  31  of automatic cutter unit  30 , and knife  35 . This affords a small, compact printer mechanism.  
         [0058]    As described above, the loading unit  10  for the ink ribbon cassette  9  is disposed at an incline corresponding to the incline of the print head  20  in this embodiment of the invention. The ink ribbon cassette  9  can therefore be loaded to and removed from the loading unit  10  at an angle from the front of the printer. While the pressure roller  26 , fixed knife  31  of automatic cutter unit  30 , and knife  35  are located directly above the second inclined path part  17 , these do not interfere with loading and unloading the ink ribbon cassette  9 . The ink ribbon cassette  9  can therefore be installed or removed by means of a simple one-step operation.  
         [0059]    Furthermore, the path of opening unit  13  movement can be changed by adjusting one or both of the inclination angle of the print head  20  and platen  21 , and the height of the axis of rotation  43   a  of the opening unit  13 . This makes it possible to increase the space directly above the printing position  17  that is not intersected by the top and bottom ends of the platen when the opening unit  13  opens/closes, and thus provides greater freedom for the parts layout.  
         [0060]    (Roll Paper Compartment and Remaining Paper Detector)  
         [0061]    [0061]FIG. 7 is an oblique view from the left front side of the roll paper compartment  8  provided in the back part of the stationary unit  12 , FIG. 8 is an oblique view from the right front side of the roll paper compartment  8 , and FIG. 9 is a right side view of the compartment  8 . FIG. 10 is a partially exploded view of the compartment  8 , FIG. 11 is a partially exploded oblique view showing the divider and remaining paper detector in the roll paper compartment, and FIG. 12 is a right side view of the divider.  
         [0062]    Referring to these figures, the roll paper compartment  8  is composed of a bottom  81 , a fixed side panel  82  defining the left side wall of the roll paper compartment  8 , and an adjustable divider  83  defining the right side of the roll paper compartment  8 . The bottom  81  and fixed side panel  82  are a single plastic molding. The divider  83  is a separate plastic molding that can be removably assembled to the bottom  81 . A remaining paper detector  90  for detecting when the amount of paper left on the roll paper  7  has dropped to a specified level or less is affixed to the divider  83 .  
         [0063]    Referring now to FIG. 11 and FIG. 12, the divider  83  has a side member  831  and a bottom member  832  formed to the bottom edge of the side member  831 , and insertion pins  833 ,  834  projecting straight down are formed at the front and back on the bottom of the bottom member  832 . Corresponding thereto, as will be known from FIG. 10, a pair of holes  811   a ,  811   b  is formed at the front and back parts near the right edge in the bottom  81 . Another similar pair of holes  812   a ,  812   b  is formed to the inside of the compartment from the first set of holes  811   a ,  811   b , and a third pair of holes  813   a ,  813   b ′ is formed yet further to the inside from holes  812   a ,  812   b . The position of the divider  83  on the bottom  81  can thus be adjusted relative to the width of the printer by selectively inserting the insertion pins  833 ,  834  of this divider  83  in the appropriate pair of holes.  
         [0064]    A screw hole  835  is also formed in the bottom member  832  of divider  83  (see FIG. 11), and three corresponding holes  814 ,  815 ,  816  (Reference numbers  815 ,  816  not shown in FIG. 10 or  11 ) are formed in bottom  81  at appropriate positions widthwise to the printer (see FIG. 10). The divider  83  can thus be removably fixed to the bottom  81  by first inserting the insertion pins  833 ,  834  of the divider  83  into the selected pair of holes in the bottom  81 , and then screwing a screw through screw hole  835  into the corresponding hole  814 ,  815 ,  816 .  
         [0065]    The divider  83  can thus be selectively assembled to one of three positions in a line widthwise to the printer. In other words, the distance between the divider  83  and the opposing fixed side panel  82  of the roll paper compartment  8  can be changed to one of three positions so that three different widths of roll paper  7  can be loaded to the compartment  8  without excessive side-to-side play.  
         [0066]    Pairs of support surfaces  86 ,  87  each having a protruding curved surface for supporting the outside surface of the roll paper  7  are formed on the right and left sides on the front and back sides of the roll paper  7  on the bottom of the compartment  8  defined by bottom  81  and bottom member  832  of divider  83 . Between these support surfaces  86 ,  87  is formed a front/back pair of support surfaces  88 ,  89  which are inclined relative to the horizontal and function to catch the roll paper  7  when the size of the roll decreases to smaller than the distance between support surfaces  86 ,  87 . These inclined support surfaces  88 ,  89  are formed widthwise to the printer on the bottom of the compartment  8  across the full width of the compartment. A level surface  90  of a specific width is formed between these inclined support surfaces  88 ,  89 . This level surface  90  determines the maximum depth at the bottom of the compartment  8 .  
         [0067]    An elliptical opening  836  with the long axis oriented vertically, a rectangular opening  837  with the long sides vertically oriented, and a flat detector mounting surface  838  recessed from the outside in the widthwise direction of the printer are formed in order from bottom to top in the side member  831  of the divider  83  starting from the level surface  90 . A screw hole  839  for fastening a remaining paper detector  90  is formed in the center of the detector mounting surface  838 .  
         [0068]    The remaining paper detector  90  is mounted to the outside surface of the side member  831  of divider  83 , and comprises a detector element  91  and stud  92  shaped like a truncated pyramid. The detector element  91  projects to the inside of the compartment  8  from the outside of the bottom opening  836  in side member  831 , and stud  92  projects to the inside of the compartment  8  from the outside of the top opening  837 . In this embodiment of the invention the detector element  91  and stud  92  are unitarily formed to a single pivoting lever  93 . A pair of support studs  94 ,  95  projecting in the front/back direction of the printer are unitarily formed at the top end of pivoting lever  93 . A pair of bearing channels  97 ,  98  is formed in the front and back edges of the top part of rectangular mounting frame  96 . The support studs  94 ,  95  are supported rotatably to the width of the printer in these bearing channels  97 ,  98 . A mounting hole  100  is formed in the middle at the top of the mounting frame  96 . This mounting hole  100  is vertically long and is shaped like an hourglass or a cocoon with a constricted waist. The mounting frame  96  is fixed to the divider  83  by passing a detector mounting screw  101  from the inside of the divider  83  through the screw hole  839  and the top or bottom end of the mounting hole  100 , and then tightening a nut  102  onto the outside end of this screw  101 .  
         [0069]    Passing the screw  101  through at the top end of the mounting hole  100  lowers the remaining paper detector  90  relative to the divider  83  so that the detector element  91  is at the bottom. This position corresponds to paper rolls wound to a core with a small outside diameter. Conversely, passing the screw  101  through the bottom end of the mounting hole  100  raises the remaining paper detector  90  relative to the divider  83  and sets the detector element  91  at the top position. This position corresponds to paper rolls with a large diameter core. The height of the detector element  91  and stud  92  can thus be adjusted to two vertical positions.  
         [0070]    A support  103  protruding perpendicularly to the outside is formed at the top part of the mounting frame  96 , and a limit switch  104  for remaining paper detection is mounted on this support  103 . The limit switch  104  is positioned so that the switch pin  105  is level and projects toward the inside in the widthwise direction of the printer. This switch pin  105  constantly contacts a contact face  106  formed on the lever  93  (see FIG. 13). The limit switch  104  is on when the switch pin  105  projects into the compartment  8 , and thus outputs a signal indicating that the amount of paper left on the roll has dropped below a specific level. When the switch pin  105  is pressed by the contact face  106  and retracts, the limit switch  104  turns off.  
         [0071]    [0071]FIG. 13 describes the detection operation of the remaining paper detector  90 . The remaining paper detection operation of the remaining paper detector  90  is described next with reference to FIG. 13. When the amount of paper left on the roll paper  7  equals or exceeds a predetermined level, the roll paper  7  is supported by the curved support surfaces  86 ,  87  in the compartment  8 . As shown in FIG. 13( a ), the core  7 A is positioned above the detector element  91  and stud  92 , and the detector element  91  and stud  92  touch the side  7   b  of the roll paper  7 . The lever  93  on which these are formed is therefore pushed to the outside, the switch pin  105  of limit switch  104  is pushed by the contact face  106  of lever  93 , the switch pin  105  thus retracts and the limit switch  104  turns off.  
         [0072]    As the recording paper  7   a  is then consumed by printing, the outside diameter of the roll paper  7  gradually decreases and the core  7 A descends. When the roll paper  7  moves vertically, the upper stud  92  remains in contact with the side of the roll paper  7 . Therefore, as indicated by the dotted line in FIG. 13( a ), the stud  92  touches the side  7   b  of the roll paper  7  even if the roll paper  7  moves up from the detector element  91  and loses contact therewith. As a result, the detector element  91  will not enter the hollow core  7 A of the roll paper  7  and the remaining paper detector  90  will not erroneously detect a near-end state.  
         [0073]    When the remaining paper level then drops below a predetermined level, the roll paper  7  drops down between the front/back curved support surfaces  86 ,  87 , and is supported by the pair of front/back inclined support surfaces  88 ,  89 . When the roll paper  7  drops onto these inclined support surfaces  88 ,  89 , the hollow center of the core  7 A is positioned opposite the detector element  91 . The detector element  91  thus enters the hollow core  7 A as shown in FIG. 13( b ). This causes the limit switch  104  to turn on and output a detection signal indicating that the amount of paper remaining on the roll paper  7  has dropped below the predetermined level, that is, the near-end of the roll has been detected.  
         [0074]    If the printer  1  is used in a vertical position with the back end of the printer  1  down, a support plate  110  shaped as indicated by the double-dot dash line in FIG. 9 is attached at the back end of bottom  81  of compartment  8 . Parts corresponding to the front/back pair of curved support surfaces  86 ,  87  and inclined support surfaces  88 ,  89  disposed to the bottom  81  are also formed on this support plate  110 , and when the outside diameter of the roll paper  7  becomes small enough, the roll paper  7  drops between these support surfaces as described above. In this case the remaining paper detector  90  is also rotated  90  degrees to the divider  83  to match the vertical orientation of the printer as indicated by the double-dot dash line  93 A in FIG. 9.  
         [0075]    The remaining paper detector  90  can be repositioned according to the printer attitude with the divider  83  removed from the bottom  81 . Compared with a conventional configuration in which the remaining paper detector  90  is assembled to a fixed side panel  82  formed unitarily with the bottom  81 , the configuration of the present invention thus makes it significantly easier to change the orientation of the remaining paper detector  90 .  
         [0076]    It should be noted that the remaining paper detector  90  shall not be limited to using a limit switch  104 , and could be configured to detect how much paper remains on the roll paper  7  by means of an optical detection means, for example. An advantage of using a limit switch as described above, however, is that the paper end can be detected easily and reliably.  
         [0077]    The support plate  110  assembled to the back end of the bottom  81  could also be formed unitarily with the bottom  81 .  
         [0078]    As will be obvious from the preceding description, a printer according to the present invention uses a movable divider to set one side of the roll paper compartment, and enables a remaining paper detector to be assembled to this divider. The divider can also be removed to install an after-market remaining paper detector to the divider, and installing an after-market remaining paper detector is therefore simple. Installing and adjusting the remaining paper detector is also easier because the position of the remaining paper detector on the divider can be adjusted with the divider removed from the printer.  
         [0079]    Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.