Patent Publication Number: US-8992001-B2

Title: Printer

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a printer that conveys roll paper pulled from a paper roll stored in a roll paper compartment passed the printing position of a printhead by means of a paper feed roller and prints. More particularly, the invention relates to a printer that guides recording paper to the paper feed roller while maintaining specified tension on the recording paper by means of an elastically displaceable tension guide in order to reduce variation in the feed load on the paper feed roller. 
     2. Related Art 
     In printers that print on roll paper delivered from a paper roll, the paper feed load on the paper feed roller changes greatly according to variation in the inertial weight of the paper roll, for example, and can easily cause the roll paper feed precision to vary. For example, if the paper feed precision varies when printing a barcode with precise spacing, the thickness of the bars and the spaces between bars varies if the paper feed precision changes, and it may not be possible to print a barcode that can be accurately read. To solve this problem, Japanese Unexamined Patent Appl. Pub. JP-A-2009-269399 teaches a method of guiding the recording paper delivered from a paper roll to the paper feed roller while maintaining specific tension on the recording paper by means of an elastically displaceable tension guide, and using this elastic displacement of the tension guide to suppress variation in the roll paper feed load acting on the paper feed roller. 
     Different types of recording paper are also known. There is, for example, recording paper for creating wrist bands that are attached and worn around the patient&#39;s wrist or ankle in hospitals as described in Japanese Unexamined Patent Appl. Pub. JP-A-2005-133265. This recording paper is a narrow band of a constant width that can be cut to a certain length, and is used as a wrist band after printing the required information using an inkjet printer, for example, and then cutting the paper to length. This type of recording paper can also be supplied in rolls. 
     In addition to having different widths, the recording paper can thus be made of different materials, have a coated surface, and vary in other ways. Recording paper for making wrist bands, for example, may be made from a non-woven cloth, and the back side that is worn against the patient&#39;s skin may be surface treated to increase the friction coefficient for greater comfort and prevent the wrist band from slipping, for example. The recording paper may be coated with a high friction coefficient material, for example, or be treated to increase surface roughness and improve sliding resistance. 
     Problems such as described below can result in a printer that guides the recording paper to the paper feed roller while maintaining tension on the recording paper by means of a tension guide when printing on recording paper with different surface characteristics, particularly different friction coefficients. 
     For example, because the friction coefficient is higher when conveying recording paper for making wrist bands than when conveying plain recording paper, sliding resistance between the recording paper and the paper feed guide is high. More specifically, because the tension guide urges the recording paper with a specific elastic force, the sliding resistance is much greater than other recording paper guide parts inside the printer. When the friction coefficient of the recording paper is high, the sliding resistance with the tension guide may exceed the paper feed force of the paper feed roller, and it may not be possible to feed the recording paper. 
     SUMMARY 
     A printer according to the invention prevents paper conveyance being disabled by the tension guide even when printing on recording paper with a high friction coefficient. 
     A printer according to a first aspect of the invention has a printhead; a paper feed roller that conveys a web of recording paper to the printhead printing position; a tension guide that has a first guide surface that guides the recording paper in the direction of the paper feed roller, and can be elastically displaced to apply specific tension to the recording paper; and a removable guide that has a second guide surface with a different friction coefficient than the first guide surface, and is removably installable to the tension guide; wherein when the removable guide is installed to the tension guide, the removable guide is elastically displaceable in unison with the tension guide, and the recording paper is guided by the second guide surface. 
     A tension guide having the first guide surface could be provided as standard equipment, and a removable guide having a second guide surface with a lower friction coefficient than the first guide surface could also be provided. When printing on recording paper that is used to make wrist bands and has a higher friction coefficient than regular recording paper (plain paper), the removable guide is installed to the tension guide for printing. Recording paper with a high friction coefficient is therefore guided by the second guide surface having a low friction coefficient, the sliding resistance acting on the recording paper can be suppressed to the same level as plain paper, and becoming unable to convey the recording paper can be prevented. Furthermore, because the removable guide can be elastically displaced in unison with the tension guide, the recording paper can always be held in an appropriately tensioned state and tension guide functionality is not lost. In addition, because compatibility with recording paper having a high friction coefficient can be achieved by simply installing the removable guide, the invention is significantly more cost effectiveness than using a dedicated printer. 
     In another aspect of the invention, the friction coefficient of the first guide surface is greater than or equal to 0.3; and the friction coefficient of the second guide surface is less than or equal to 0.2. 
     This aspect of the invention enables using a tension guide with the first guide surface when printing on commonly used recording paper, using the removable guide with the second guide surface when using recording paper with a higher friction coefficient, thereby enabling a paper feed operation suitable to the recording paper being used. 
     In another aspect of the invention, the removable guide includes a main guide that is removably installable to the tension guide, and at least one roller that is freely rotatably supported by the main guide, and determines the second guide surface. 
     If a roller or other type of rolling body is used, the roller rotates in contact with the recording paper, the sliding resistance acting on the recording paper is therefore effectively zero, and recording paper having a surface with a high friction coefficient can be guided smoothly. Furthermore, because roller surface wear is significantly less than when the recording paper slides over the guide surface, the service life of the guide surface can be extended. 
     Further alternatively, the removable guide includes a main guide that is removably installable to the tension guide, and a film, sheet, or plate with a lower friction coefficient than the first guide surface applied to the surface of the main guide, or a surface layer made of a material with a lower friction coefficient than the first guide surface formed on the surface of the main guide; and the second guide surface is determined by the film, sheet, or plate, or by the surface of the surface layer. 
     In another aspect of the invention, the removable guide has a pair of paper width guide surfaces formed on opposite sides of the second guide surface. Because the paper width is narrower than common recording paper when using recording paper for making wrist bands, for example, recording paper of different widths can be appropriately guided without skewing or meandering by disposing a paper width guide surface to the removable guide. 
     In another aspect of the invention, a plurality of removable guides each having a different surface characteristics on the second guide surface are used as the removable guide, and the removable guides can be selectively installed to the tension guide. 
     This aspect of the invention enables guiding different types of recording paper with appropriate sliding resistance by using removable guides suitable to plural different recording papers having different friction coefficients. 
     A printer according to another aspect of the invention also has a roll paper compartment that stores the recording paper wound in a paper roll, and the recording paper supplied from the paper roll stored in the roll paper compartment can be guided to the paper feed roller passed the intervening tension guide. 
     Effect of the Invention 
     When a removable guide with a second guide surface having a different friction coefficient is provided, the removable guide can be removably installed to the tension guide having a first guide surface in a printer according to the invention. When the removable guide is installed, the recording paper is guided by the second guide surface, and the removable guide can be elastically displaced in unison with the tension guide. 
     Therefore, when printing on recording paper that has a high friction coefficient, for example, the removable guide is installed to guide the recording paper by means of the second guide surface having a low friction coefficient. As a result, the recording paper can be guided to the paper feed roller with a suitable sliding load, and being unable to convey the recording paper due to the sliding resistance between the tension guide and recording paper having a high friction coefficient can be reliably prevented. Furthermore, because recording paper with different friction coefficients can be handled by installing or removing the removable guide as needed, a configuration that can desirably feed recording paper with different friction coefficients passed the tension guide can be provided at an extremely low price. 
     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 
         FIG. 1  is an external oblique view of a printer according to a preferred embodiment of the invention. 
         FIG. 2  is an external oblique view of the printer with the access cover open. 
         FIG. 3  describes the internal structure of the printer. 
         FIG. 4A  and  FIG. 4B  are oblique views of the removable guide from the top and back sides thereof. 
         FIG. 5A  and  FIG. 5B  are oblique views of the removable guide before and after installation. 
         FIG. 6  describes guiding the recording paper by means of the tension guide. 
         FIG. 7  describes guiding the recording paper by means of the removable guide. 
         FIG. 8  is an oblique view of a removable guide according to another embodiment of the invention. 
         FIG. 9  describes guiding the recording paper by means of the removable guide shown in  FIG. 8 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A preferred embodiment of a printer according to the invention is described below with reference to the accompanying figures. 
     General Configuration 
       FIG. 1  is an external oblique view of a printer according to a preferred embodiment of the invention, and  FIG. 2  is an external oblique view of the printer with the access cover fully open. The printer  1  has a housing  2  that is a basically rectangular box, and a cover unit  3  attached to the front of the housing  2 . The cover unit  3  includes an access cover  3   a  and an opening mechanism  3   b  such as a four-joint linkage mechanism for opening and closing the access cover  3   a . A paper exit  4  of a specific width is formed in the front of the outside case  2   a  of the printer housing  2 . A discharge guide  5  projects forward below the paper exit  4 , and a cover release lever  6  is disposed beside the discharge guide  5 . A rectangular opening  7   a  for loading and removing roll paper in the roll paper compartment  7  formed inside the printer housing  2  is formed in the outside case  2   a  below the discharge guide  5  and cover release lever  6 , and this opening  7   a  is closed by the access cover  3   a.    
     Internal Structure 
       FIG. 3  describes the internal structure of the printer housing  2 . A main printer frame  11  made of sheet metal is disposed inside the printer housing  2 , and the roll paper compartment  7  is formed in the widthwise center of the main printer frame  11 . A sheet metal platen frame  12  that extends horizontally widthwise to the printer is disposed above the roll paper compartment  7 . A platen  13  that extends horizontally widthwise to the printer is disposed on top of the platen frame  12 . 
     A head unit frame  14  is disposed above the platen  13 , and the head unit frame  14  is attached horizontally to the top end of the main printer frame  11 . A carriage guide shaft  15  is disposed to the head unit frame  14  widthwise to the printer, and a carriage  16  is supported on the carriage guide shaft  15  so that the carriage  16  can move along the carriage guide shaft  15 . The carriage  16  is moved bidirectionally along the carriage guide shaft  15  by a carriage drive mechanism that includes a carriage motor  17  and timing belt  18 . An inkjet head  19  (printhead) is mounted on the carriage  16 . The nozzle surface  19   a  of the inkjet head  19  opposes the top of the platen  13  with a specific gap therebetween, and the printing position A is defined by the top surface of the platen  13 . 
     The internal structure of the printer along the paper transportation path from the roll paper compartment  7  passed the printing position to the paper exit  4  is described next. 
     A supply roller  21  that extends horizontally widthwise to the printer is disposed at a position toward the back of the printer inside the roll paper compartment  7 , and a pressure roller  22  is pressed against the supply roller  21  from the side to the front of the printer. The pressure roller  22  is attached to the distal end of a pressure lever  23 , which is attached to the bottom of the platen frame  12 , and the pressure roller  22  is pressed to the supply roller  21  by the pressure lever  23 , which is urged downward by a spring force not shown. The supply roller  21  is rotationally driven by a motor not shown mounted on the main printer frame  11 . The web of recording paper  25  supplied from the paper roll  24  stored in the roll paper compartment  7  is pulled upward between the supply roller  21  and pressure roller  22  toward the back end of the platen frame  12 . 
     A tension guide  26  is attached to the back end part of the platen frame  12  horizontally widthwise to the printer so that the tension guide  26  can pivot vertically. The tension guide  26  is constantly urged upward by a spring member not shown, and can be elastically displaced downward against the force of the spring. The tension guide  26  has a convex guide surface  27  that projects toward the back of the printer. Recording paper  25  pulled upward between the lower supply roller  21  and pressure roller  22  travels around the guide surface  27  of the tension guide  26 , curves from the bottom to the front around the guide surface  27 , and is pulled horizontally to the front toward the printing position A. 
     A paper feed roller  30  extends horizontally widthwise to the printer at a position in front of the tension guide  26  on the platen frame  12 . A pressure roller  31  of a specific width is pressed from above with specific pressure to the paper feed roller  30 . The paper feed roller  30  is driven by a paper feed motor  32  mounted on the main printer frame  11 . The recording paper  25  pulled horizontally to the front passed the tension guide  26  passes between the paper feed roller  30  and pressure roller  31  and is pulled to the front printing position A. 
     An automatic cutter  34  is disposed to the front end of the platen frame  12 . The automatic cutter  34  includes a fixed knife  34   a  that extends widthwise to the printer on the main printer frame  11  side, a movable knife  34   b  that extends widthwise to the printer on the head unit frame  14  side, and a movable knife drive mechanism  34   c  that is also disposed on the head unit frame  14  side. After passing the printing position, the recording paper  25  is discharged to the outside from the paper exit  4  after passing the cutting position of the automatic cutter  34 . 
     When loading a paper roll  24  into the roll paper compartment  7  in this printer  1 , the cover unit  3  is opened until it is horizontal. When the cover unit  3  opens, the platen frame  12 , tension guide  26 , paper feed roller  30 , pressure lever  23 , and pressure roller  22  move to the front of the printer together with the access cover  3   a , and the paper transportation path is opened. The paper roll  24  from which a leader of recording paper  25  is pulled off is then dropped into the roll paper compartment  7 . 
     When the access cover  3   a  then closes, the platen frame  12 , tension guide  26 , paper feed roller  30 , pressure lever  23 , and pressure roller  22  return to their original positions. As a result, the recording paper  25  is threaded between the supply roller  21  and pressure roller  22 , around the guide surface  27  of the tension guide  26 , between the paper feed roller  30  and pressure roller  31  passed the printing position A, and out the paper exit  4 . When the recording paper  25  is thus loaded, the paper feed roller  30  is driven and the supply roller  21  is driven synchronously to the paper feed roller  30 , the recording paper  25  is conveyed toward the printing position A, printed on by the inkjet head  19  at the printing position, and then discharged from the paper exit  4  passed the cutting position of the automatic cutter  34 . 
     When printing on recording paper  25  of a specific width wound into a paper roll  24  in the printer  1  according to this embodiment of the invention, the recording paper  25  is conveyed over the guide surface  27  (first guide surface) of the tension guide  26  as shown in  FIG. 3 . 
     However, when printing to a paper roll  24 A of recording paper  25 A (see  FIG. 7 ) that is used for making wrist bands and is narrower than recording paper  25 , the removable guide  40  (see  FIG. 4 ,  FIG. 7 ) or removable guide  80  (see  FIG. 8 ,  FIG. 9 ) described below is installed to the tension guide  26 , and the recording paper  25 A is conveyed around the removable guide. 
     To install the removable guide to the tension guide  26 , the cover release lever  6  is operated to unlock the cover unit  3 , and the discharge guide  5  mounted on the cover unit  3  is pulled forward. As a result, as shown in  FIG. 2 , the cover unit  3  pivots forward and open on the bottom end thereof to a substantially horizontal position. Because the platen frame  12  moves forward with the cover unit  3 , the removable guide can be attached to the tension guide  26  disposed to the back end part of the platen frame  12 . 
     Removable Guide 
       FIG. 4A  is an oblique view of the removable guide from the side, and  FIG. 4B  is an oblique view of the removable guide from the back side. As shown in these figures, the removable guide  40  has a guide panel  41  and a left and right pair of paper width guides  43 ,  44  disposed to middle of the width  40   a  of the convexly curved outside surface  42  of the guide panel  41 . The guide panel  41  is long and narrow, curved when seen in section, and has a substantially constant thickness, and the paper width guides  43 ,  44  rise perpendicularly to the outside surface  42 . The inside surfaces of the paper width guides  43 ,  44  are paper width guide surfaces  43   a ,  44   a . Two rollers  45 ,  46  extending parallel to the width  40   a  are disposed between the paper width guides  43 ,  44  with the ends of the roller shafts  45   a ,  46   a  freely rotatable. A recording paper guide surface (second guide surface) is rendered by these two rollers  45 ,  46 . 
     A rectangular notch  47  is formed between the left and right paper width guide surfaces  43   a ,  44   a  at the front end of the guide panel  41 . Notches  48 ,  49  are also formed at the front end of the guide panel  41  on opposite sides of the notch  47 , and engagement arms  50 ,  51  that extend straight diagonally to the back side of the guide panel  41  are formed in these notches  48 ,  49 . Hooks  52 ,  53  that protrude upward are formed at the distal ends of the engagement arms  50 ,  51 . 
       FIG. 5A  is an oblique view of the removable guide  40  before it is installed to the tension guide  26 , and  FIG. 5B  is an oblique view of the removable guide  40  when installed to the tension guide  26 . As shown in  FIG. 5A , the tension guide  26  has a main guide panel  61  and a protrusion  62 . The main guide panel  61  has a convex guide surface  27  that curves down toward the back of the printer. The protrusion  62  projects upward diagonally toward the back of the printer from one widthwise side of the main guide panel  61 . 
     Mounting units  63 ,  64  for removably installing the removable guide  40  are formed on opposite sides of the width of the main guide panel  61 . The mounting units  63 ,  64  respectively have rectangular notches  65 ,  66 ; flat upper installation guides  67 ,  68  that extend widthwise to the printer at the tops of the notches  65 ,  66 ; and lower installation guides  69 ,  70  that extend widthwise to the printer at the bottom ends of the notches  65 ,  66 . 
     The removable guide  40  is installed to the tension guide  26  by inserting the left and right engagement arms  50 ,  51  to the left and right mounting units  63 ,  64  of the tension guide  26 . When the removable guide  40  is installed to the tension guide  26 , the concave back surface of the guide panel  41  of the removable guide  40  contacts the convex guide surface  27  of the tension guide  26 , and the hooks  52 ,  53  engage the upper installation guides  67 ,  68 . 
     Operating Effect of the Removable Guide 
       FIG. 6  describes the paper transportation path of the printer  1 , and  FIG. 7  shows the paper transportation path when the removable guide is installed. 
     When printing on recording paper  25  delivered from normal paper roll  24 , the recording paper  25  is threaded over the guide surface  27  of the tension guide  26 . The recording paper  25  is thus urged by the guide surface  27  and held in a specific tensioned state. When the recording paper is conveyed, the recording paper  25  slides over the guide surface  27  and is conveyed by the paper feed roller  30  to the printing position A and printed on. The guide surface  27  is a guide surface with a friction coefficient of approximately 0.35 to 0.4. 
     In order to print on recording paper  25 A supplied from a paper roll  24 A of narrow media for making wrist bands, the removable guide  40  is installed to the tension guide  26 . When the recording paper  25 A is threaded through the paper transportation path with the removable guide  40  installed, the recording paper  25 A travels over the two rollers  45 ,  46  of the removable guide  40  as shown in  FIG. 7 . In other words, the recording paper  25 A is guided by the guide surface (second guide surface) defined by the round outside surfaces of the freely rolling rollers  45 ,  46 . 
     The back side of the recording paper  25 A (the side that contacts the rollers  45 ,  46 ) has a higher friction coefficient than normal recording paper  25 , and when passed over the guide surface  27  of the tension guide  26 , the friction coefficient between the paper and the guide surface may exceed the conveyance force of the paper feed roller  30 , possibly resulting in being unable to convey the recording paper. However, because this embodiment of the invention guides the recording paper  25 A with a high friction coefficient by means of rolling contact with a pair of rollers  45 ,  46 , the paper feed load between the rollers and the recording paper is extremely low. As a result, installing the removable guide  40  prevents being unable to convey recording paper  25 A with a high friction coefficient. 
     The removable guide  40  is mounted on the elastically displaceable tension guide  26 , and is elastically displaceable in unison with the tension guide  26 . The removable guide  40  therefore also functions as a tension guide, and can hold the recording paper  25 A properly tensioned. 
     The removable guide  40  also has a pair of paper width guide surfaces  43   a ,  44   a . The removable guide  40  can therefore also be adjusted to the width of narrow recording paper  25 A. The recording paper  25 A can therefore be prevented from skewing and meandering, and can be conveyed appropriately. 
     A large rectangular notch  47  is formed in the middle of the front end of the guide panel  41  of the removable guide  40  in this embodiment of the invention. As will be known from  FIG. 6 , this disposes the downstream-side guide surface portion  27   a  (the portion on the downstream side in the paper feed direction) at the top end of the convex guide surface  27  of the tension guide  26  with a narrow gap to the upper guide panel  71  disposed thereabove. 
     Therefore, when this downstream-side guide surface portion  27   a  is covered and hidden by the guide panel  41  of the removable guide  40 , enough space to guide the recording paper  25 A between the downstream-side guide surface portion  27   a  and the upper guide panel  71  cannot be assured. A notch  47  is therefore formed in this embodiment of the invention at the front end of the guide panel  41  of the removable guide  40  so that the recording paper  25 A can pass through. If there is sufficient space between the guide surface  27  of the tension guide  26  and the upper guide panel  71 , forming the notch  47  in the removable guide  40  is not necessary. 
     Variations of the Removable Guide 
       FIG. 8  is an oblique view showing a variation of the removable guide, and  FIG. 9  shows this removable guide when installed. 
     Similarly to the removable guide  40  described above, the removable guide  80  shown in these figures has a guide panel  81  that is long, narrow, and convexly curved when seen in section; a pair of paper width guides  82 ,  83  disposed to middle of the width of the outside surface of the guide panel  81 ; and engagement arms  84 ,  85  formed on opposite sides of the guide panel  81 . The inside surfaces of the paper width guides  82 ,  83  are paper width guide surfaces  82   a ,  83   a , and hooks  86 ,  87  are formed at the distal ends of the engagement arms  84 ,  85 . 
     This removable guide  80  differs from the foregoing removable guide  40  in that a film or sheet  88  made of a material with a low friction coefficient is applied to the outside surface of the guide panel  81  between the paper width guide surfaces  82   a ,  83   a , and the surface of this sheet  88  renders a guide surface  89  (second guide surface) with a low friction coefficient. The friction coefficient of the guide surface  89  of this sheet  88  is •0.2, and is preferably approximately 0.2 to 0.15. A sheet  88  made of a fluoro plastic such as Nitoflon® (manufactured by Nitto Denko Corp.) can be used as the sheet  88 . 
     This removable guide  80  is used in the same way as the removable guide  40  as shown in  FIG. 9 . When the removable guide  80  is installed and recording paper  25 A is loaded, the recording paper  25 A is guided by the guide surface  89  of the sheet  88 . Because the friction coefficient of the guide surface  89  is •0.2, the paper feed load caused by sliding resistance with the high friction coefficient recording paper  25 A can be kept low. Problems conveying the recording paper  25 A as a result of the removable guide  80  being pressed against the recording paper  25 A by the force of a spring can therefore be avoided. 
     This embodiment of the invention forms a guide surface with a low friction coefficient by applying a film or sheet made from a material with a low friction coefficient to the removable guide, but the guide surface could alternatively be created by coating or laminating the surface of the guide panel with a low friction coefficient material to form a surface layer with a low friction coefficient. Further alternatively, the guide surface could be made by affixing a plate made from a low friction coefficient material, such as a molded plastic plate, to the removable guide. 
     OTHER EMBODIMENTS 
     An embodiment that prints on recording paper  25 A used to make wrist bands is described above, but a removable guide suitable for printing on other types of recording paper can obviously also be made. Further alternatively, a plurality of removable guides each having a guide surface (second guide surface) with a different friction coefficient can be prepared, and the removable guide with a friction coefficient suitable to the recording paper used for printing could be used selectively. In addition, a removable guide with a guide surface having a lower friction coefficient than the tension guide is prepared in the embodiment described above, but a removable guide having a higher friction coefficient than the tension guide is also conceivable. 
     A roll paper compartment  7  is rendered in the printer  1  in the embodiment described above, but the invention can also be applied to printers that do not have a roll paper compartment. For example, the invention can also be used with printers that print on a recording paper web supplied from an external roll paper holder, or on continuous paper. The printhead is also not limited to an inkjet head, and could be a thermal head, for example. 
     The invention being thus described, it will be obvious that it may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.