JP2008006670A - Thermal printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal printer which can carry out printing on both sides in a state that a suitable tension is applied on a thermal paper. <P>SOLUTION: The thermal printer 10 comprises a first thermal head 40 which touches one heat-sensitive layer 13 of the thermal paper 11, a first platen roller 30, a first urging means 42, a second thermal head 60 which touches the other heat-sensitive layer 14 of the thermal paper 11, a second platen roller 50, a second urging means 63, etc. The second thermal head 60 is arranged at the upstream side in the feeding direction of the paper to the first thermal head 40. A paper feeding rate to the thermal paper 11 of the first platen roller 30 is larger than a paper feeding rate of the second platen roller 50. The second platen roller 50 is held in touch while being easier to slip than the first platen roller 30 to the thermal paper 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a thermal printer capable of printing on a front surface and a back surface.

  As a thermal printer for simultaneously printing on both the front and back sides of a thermal paper, a double-sided thermal printer including two platen rollers and two thermal heads has been proposed as described in, for example, Patent Document 1 below.

In this type of double-sided thermal printer, the first platen roller and the second platen roller are rotated at the same feed speed in synchronization with each other. As the thermal paper passes between the first platen roller and the first thermal head, printing is performed on one surface of the thermal paper by the first thermal head. Further, when the thermal paper passes between the second platen roller and the second thermal head, printing is performed on the other surface of the thermal paper by the second thermal head.
Japanese Patent Laid-Open No. 11-2147

  In the conventional double-sided thermal printer, if the feeding speed of the first platen roller and the feeding speed of the second platen roller are slightly different, the thermal paper is loosened between the pair of platen rollers, or conversely, Too much tension can cause print quality problems. For this reason, it is necessary to manage the outer diameter and feed speed of each platen roller with high precision, but there is a limit to managing the outer diameter and feed speed of a platen roller made of a material having rubber elasticity with high precision. .

  Accordingly, it is an object of the present invention to provide a thermal printer capable of duplex printing with an appropriate tension applied to thermal paper.

  A thermal printer according to an example of the present invention is a thermal printer for printing on a double-sided thermal paper in which a heat-sensitive layer is provided on both front and back sides of a base paper, and is in contact with the heat-sensitive layer on one side of the thermal paper. A first thermal head disposed; a first platen roller facing the first thermal head with the thermal paper sandwiched therebetween; and a first biasing member that presses the first thermal head toward the first platen roller. Means, a first platen gear that rotates integrally with the first platen roller, and a second thermal plate disposed upstream of the first thermal head and in contact with the heat-sensitive layer on the other surface of the thermal paper. A head, a second platen roller that faces the second thermal head across the thermal paper, and the second thermal head A second urging means that presses against the two platen rollers; a second platen gear that rotates integrally with the second platen roller; a motor; and an output of the motor to transmit the output to the first platen gear and the second platen gear. And a power feeding mechanism of the first platen roller with respect to the thermal paper is larger than a paper feeding speed of the second platen roller, and the second platen roller with respect to the thermal paper It is in contact with the first platen roller in a state where it slips more easily.

  According to the present invention, the paper feed speed of the first platen roller with respect to the thermal paper is larger than the paper feed speed of the second platen roller, and the second platen roller slips with respect to the thermal paper than the first platen roller. By making the state easy to do, an appropriate tension can be applied to the thermal paper.

A thermal printer 10 according to an embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 schematically shows the inside of the thermal printer 10. The thermal printer 10 can print on both the front and back sides of the thermal paper 11, and can be used for a cash register in a store, for example.

  As shown in FIG. 2, the thermal paper 11 (hereinafter simply referred to as thermal paper) has a base paper 12 and heat-sensitive layers 13 and 14 formed on both front and back surfaces of the base paper 12. That is, the first heat-sensitive layer 13 is formed on one surface (for example, the front surface) of the base paper 12, and the second heat-sensitive layer 14 is formed on the other surface (for example, the back surface) of the base paper 12. These heat sensitive layers 13 and 14 are made of a material that develops a desired color such as black or red when heated to a predetermined temperature or higher. As shown in FIG. 1, the thermal paper 11 is wound in a roll shape so that the first heat-sensitive layer 13 faces inward.

  The thermal printer 10 has a printer body 20 and a cover 21 that can be opened and closed. The cover 21 can be opened and closed in the vertical direction about the shaft 23 of the hinge portion 22 provided in the printer main body 20. When the cover 21 is opened, the upper surface side of the printer main body 20 is opened. 1 shows a state where the cover 21 is closed, and FIG. 4 shows a state where the cover 21 is opened.

  A first platen roller 30 is provided at the front end of the cover 21 so as to extend in the horizontal direction. The first platen roller 30 is formed in a cylindrical shape, and has a roller body 31 made of an elastic material having rubber elasticity such as NBR (nitrile rubber) and having a friction coefficient larger than that of metal. The surface of the roller body 31 is subjected to a rough surface treatment, for example, an elephant-like polishing eye is formed on the surface. Thereby, the frictional force in the conveyance direction is increased.

The first platen roller 30 is attached to a first platen shaft 34 that is rotatably supported by the cover 21 via a pair of left and right bearing portions 33 (only one is shown in FIG. 3). The first platen shaft 34 is rotated integrally with the first platen shaft 34.
A paper container 24 in which the roll-shaped thermal paper 11 is disposed is formed outside the printer main body 20.

  A first thermal head 40 is provided inside the front of the printer main body 20. The first thermal head 40 is disposed in a sideways (substantially horizontal) and upward orientation so as to face the first platen roller 30 with the thermal paper 11 being sandwiched between them. The first thermal head 40 is disposed so as to be in contact with one surface of the thermal paper 11, that is, the first heat-sensitive layer 13 downstream in the paper feeding direction.

  The first thermal head 40 is attached to a heat sink 41 as a heat radiating member that is rotatably attached to the printer body 20 about a shaft 41a. A first urging means 42 is provided on the back side of the heat sink 41, that is, below the heat sink 41. An example of the first urging means 42 is a spring member such as a compression coil spring or a torsion spring, and is arranged in a compressed state between a spring seat 43 provided on the printer main body 20 and the heat sink 41. The center of the first thermal head 40 is pressed by the first urging means 42 and is urged toward the first platen roller 30 in the direction of arrow A in FIG.

  A second platen roller 50 is disposed in the rear portion of the printer main body 20 upstream of the first platen roller 30 in the paper feeding direction so as to extend in the horizontal direction. The second platen roller 50 is formed in a columnar shape, and includes a roller body 51 made of an elastic material having rubber elasticity such as NBR (nitrile rubber) and having a friction coefficient larger than that of metal. Further, the second platen roller 50 has a coating layer 52 made of a material such as PTFE (tetrafluoroethylene resin) having a smaller coefficient of friction than the roller body 51 and excellent in heat resistance and covering the outer periphery of the roller body 51. Have.

  The second platen roller 50 is attached to a second platen shaft 53 that is rotatably supported by the cover 21 via a pair of left and right bearings 52 (only one is shown in FIG. 3). The second platen roller 50 rotates integrally with the second platen shaft 53 around the second platen shaft 53.

  Here, the outer diameter of the first platen roller 30 is configured to be slightly larger than the outer diameter of the second platen roller 50. Therefore, even if the rotation speeds of the first platen shaft 34 and the second platen shaft 53 are the same, the paper feed speed of the first platen roller 30 is slightly faster than the paper feed speed of the second platen roller 50.

  Further, since the outer surface of the second platen roller 50 is formed of PTFE, the friction coefficient is smaller than that of the outer surface of the first platen roller 30, and the second platen roller 50 is configured to be slippery.

  A second thermal head 60 is disposed on the upstream side of the first thermal head 40 in the feeding direction of the thermal paper 11. The second thermal head 60 is attached to a heat sink 62 as a heat radiating member that is rotatably attached to the cover 21 portion around a shaft 61. The second thermal head 60 is disposed above the second platen roller 50 so as to be inclined downwardly to the left. The second thermal head 60 is arranged so as to face the second platen roller 50 with the thermal paper 11 being sandwiched with the cover 21 closed. The second thermal head 60 is disposed in contact with the other surface of the thermal paper 11, that is, the second heat sensitive layer 14.

  A second urging means 63 is provided on the back side of the heat sink 62, that is, on the front side and the upper side. An example of the second urging means 63 is a spring member such as a compression coil spring or a torsion spring, and is arranged in a compressed state between a spring seat 64 provided on the cover 21 and the heat sink 62. The second urging means 63 presses the center of the second thermal head 60 and urges it toward the second platen roller 50 in the direction of arrow B in FIG.

  A motor 70 as drive means for rotating the first platen roller 30 and the second platen roller 50 is disposed below the printer main body 20. An output gear 72 is attached to the rotating shaft 71 of the motor 70. The motor 70 is, for example, a stepping motor that can rotate forward and backward, and can perform reverse feed. A power transmission mechanism 73 for transmitting the output of the motor 70 to the first platen roller 30 and the second platen roller 50 includes a reduction gear 74, a drive gear 77, a second platen gear 80, idler gears 82 and 85, a first platen gear 88, and the like. Including.

  A reduction gear 74 is provided in mesh with the output gear 72 of the motor 70. The reduction gear 74 is attached to a shaft 76 supported by the printer main body 20 via a bearing 75 and rotates integrally with the shaft 76. Next to the reduction gear 74, a drive gear 77 attached to the shaft 76 is provided. The drive gear 77 rotates integrally with the reduction gear 75 and the shaft 76.

  Next to the second platen roller 50, a second platen gear 80 is provided in mesh with the drive gear 77. The second platen gear 80 is fixed to the second platen shaft 53, and rotates together with the second platen shaft 53 and the second platen roller 50.

  An idler gear 82 is provided in front of and below the second platen gear 80 so as to mesh with the second platen gear 80. The idler gear 82 is attached to a shaft 84 supported on the printer body 20 via a bearing 83 and rotates integrally with the shaft 84.

  An idler gear 85 that meshes with the idler gear 82 in the closed state is provided in front and above the idler gear 82. The idler gear 85 is attached to a shaft 87 rotatably supported by the cover 21 via a bearing 86 and rotates integrally with the shaft 87.

  As shown in FIG. 3, a first platen gear 88 that meshes with an idler gear 85 is provided adjacent to the first platen roller 30. The first platen gear 88 is fixed to the first platen shaft 34 and is rotated integrally with the first platen shaft 34 and the first platen roller 30.

  The roll-shaped thermal paper 11 stored in the paper storage unit 24 passes through the second thermal head 60 obliquely forward and downward, and then the feed direction is changed so that the first thermal head 40 is substantially horizontal. Is discharged in the direction of arrow C forward through the horizontal direction.

  As described above, in the thermal printer 10 of the present embodiment, the first thermal head 40, the second platen roller 50, the motor 70, the second platen gear 80, the idler gear 82, and the like are arranged in the printer body 20. On the other hand, the first platen roller 30, the first platen gear 88, the idler gear 85, the second thermal head 60, and the like are disposed on the cover 21 side.

  For this reason, when the cover 21 is opened as shown in FIG. 4, the first thermal head 40 is separated from the first platen roller 30 and the second thermal head 60 is separated from the second platen roller 50. Further, when the idler gear 85 is separated from the idler gear 82, the upper surface side of the printer main body 20 is opened, and the first thermal head 40, the second thermal head 60, the first platen roller 30, the second platen roller 50, etc. are completely exposed to the outside. It will be exposed.

Below, the effect | action of the thermal printer 10 of this embodiment is demonstrated.
When the cover 21 is closed as shown in FIG. 1, the first thermal head 40 is pressed against the first platen roller 30 by the first biasing means 42, and the second thermal head 60 is pressed by the second biasing means 63. The idler gear 82 and the idler gear 82 are engaged with each other by being pressed by the second platen roller 50. Here, the thermal paper 11 is set so as to pass between the first thermal head 40 and the first platen roller 30 and between the second thermal head 60 and the second platen roller 50.

  When the motor 70 rotates in this state, the output gear 72 rotates in the direction indicated by the arrow R1 in FIG. 1, whereby the reduction gear 74 and the drive gear rotate in the R2 direction. Accordingly, the second platen gear 80 and the second platen roller 50 rotate in the R3 direction. Here, as the second platen roller 50 rotates, the thermal paper 11 moves obliquely leftward toward the first thermal head 40 while contacting the second thermal head 60. At this time, printing can be performed on the second heat-sensitive layer 14 of the thermal paper 11 by the second thermal head 60.

  Further, the rotation of the second platen gear 80 causes the idler gear 82 to rotate in the R4 direction and the idler gear 85 to rotate in the R5 direction. Accordingly, the first platen gear 88 rotates in the R6 direction integrally with the first platen shaft 34 and the first platen roller 30. As the first platen roller 30 rotates in the R6 direction, the thermal paper 11 advances in the direction indicated by the arrow C in FIG. 1 while being in contact with the first thermal head 40. Therefore, the first thermal head 40 can print on the first heat sensitive layer 13 of the thermal paper 11.

  Here, since the outer diameter of the first platen roller 30 is larger than the outer diameter of the second platen roller 50, the paper feeding speed at the first platen roller 30 is larger than the paper feeding speed at the second platen roller 50. Therefore, tension is generated in the thermal paper 11. Further, since the surface of the second platen roller 50 is formed of PTFE and has a small friction coefficient, the frictional force applied to the thermal paper 11 is smaller than the frictional force of the first platen roller 30. The thermal paper 11 slides on the second platen roller 50. That is, the paper is transported while the thermal paper 11 is maintained at an appropriate tension.

  The printed thermal paper 11 is fed from the first thermal head 40 by a predetermined amount by the rotation of the motor 70 and then cut by the cutter mechanism 44.

  When the cover 21 is opened as shown in FIG. 4, the first thermal head 40 is separated from the first platen roller 30 and the second thermal head 60 is separated from the second platen roller 50. Further, the idler gear 82 is separated from the idler gear 85. In this open state, the upper surface side of the printer main body 20 is opened, and the first thermal head 40, the second thermal head 60, the first platen roller 30, and the second platen roller 50 are completely exposed to the outside. Therefore, it is possible to easily replace or refill the thermal paper 11, or troubleshoot when a paper jam occurs.

  According to the thermal printer 10 according to the present embodiment, the paper feed speed of the first platen roller 30 is larger than the paper feed speed of the second platen roller 50, and the second platen roller 50 is in relation to the thermal paper 11. Thus, the thermal paper 11 can be given an appropriate tension by being more slippery than the first platen roller 30. Furthermore, since the paper feed speed is faster downstream in the paper feed direction, this tension is maintained. For this reason, the thermal paper 11 can be prevented from being loosened or pulled too much during printing, and simultaneous printing on both sides can be performed with high quality by the pair of thermal heads.

  Further, by making the outer diameter of the first platen roller 30 larger than the outer diameter of the second platen roller 50, it is possible to make a difference in the sheet feeding speed. Therefore, the sheet feeding speed can be adjusted without changing the rotation speeds of the first platen roller 30 and the second platen roller 50. For this reason, the plurality of gears constituting the power transmission mechanism can have the same number of teeth, and the configuration can be simplified.

  By causing the second platen gear 80 to function as a power transmission mechanism, the first platen roller 30 and the second platen roller 50 can be driven by a single motor 70 with a simple configuration. Further, reverse feed printing is possible by rotating the first platen roller 30 and the second platen roller 50 in reverse. Here, in the present embodiment, the first platen roller 30 on the downstream side of the paper feed is used as the reference speed and the friction coefficient is large, so that the thermal paper 11 is shifted between the first platen roller 30 and the first thermal head 40. There is no. Therefore, it is possible to accurately perform reverse feed printing on the thermal paper 11 at the end on the downstream side of the paper feed.

[Second Embodiment]
Next, a thermal printer 100 according to a second embodiment of the present invention will be described. Here, since the components other than the first platen roller 30 and the second platen roller 50, the first urging means 91 and the second urging means 92 have the same configuration as in the first embodiment, The same reference numerals are given and description thereof is omitted.

  In the present embodiment, the first platen roller 30a and the second platen roller 50a are each composed of roller bodies 31a and 51a formed of NBR. Here, the diameter of the first platen roller 30a is configured to be slightly larger than the diameter of the second platen roller 50a.

  The spring constant of the first biasing means 91 is configured to be larger than the spring constant of the second biasing means 92. For example, the wire diameter of the spring of the first biasing means 91 is configured to be larger than the wire diameter of the spring of the second biasing means 92. For this reason, the force that presses the first thermal head 40 against the first platen roller 30a by the first urging means 91 causes the second thermal head 60 to move to the second platen roller by the second urging means 92. It becomes larger than the force which presses to 50a.

  Further, the printing current supplied to the first thermal head 40 is set smaller than the printing current supplied to the second thermal head 60.

  Also in this embodiment, the same effect as the thermal printer 10 according to the first embodiment described above can be obtained. That is, by making the pressing force of the first urging unit 91 larger than the pressing force of the second urging unit 92, the sheet can be configured to be slippery between the second platen roller 30a and the second thermal head 40. Further, by reducing the printing current in the first thermal head 40 having a large pressing force, it is possible to print on both sides with high accuracy. Further, instead of adjusting the printing current, as the thermal paper 11, the thermal paper 11 in which the second thermosensitive layer 13 in contact with the second thermal head 60 having a small pressing force is more likely to develop color than the first thermosensitive layer 13 is used. However, both sides can be printed accurately. Also in the present embodiment, since the speed of the first platen roller 30 downstream in the paper feed direction is used as a reference and the pressing force of the first platen roller 30 is configured to be large, reverse feed printing for printing on the downstream end of the thermal paper 11 in the paper feed direction is performed. Can be done accurately.

  In addition, although 2nd Embodiment demonstrated the case where the spring constant was adjusted by adjusting the wire diameter of a spring, pressing force can also be adjusted by adjusting arrangement | positioning in an initial state. For example, in the closed state, the first urging means 91 is arranged in a compressed state larger than the second urging means 92 so that the pressing force by the first urging means 91 is greater than the pressing force by the second urging means 92. Can be bigger. In this case, since the same member can be used for the first urging unit 91 and the second urging unit 92, it is economical and has good productivity.

  In addition, in 1st Embodiment, it made it slippery with a frictional force, and in 2nd Embodiment, it comprised so that it might slip easily with pressing force, However, You may combine these. That is, the coating layer 32 is formed on the second platen roller 50, the first platen roller 30 is roughened, and the pressing force of the first biasing means 42 is smaller than the pressing force of the second biasing means 63. May be. In each of the above embodiments, the case where the sheet feeding speed is adjusted by the outer diameters of the first and second platen rollers 30 and 50 is exemplified. However, by changing the shape of each gear constituting the power transmission mechanism, It is also possible to adjust the rotation speed and adjust the paper feed speed.

  The thermal printer 10 of the present invention can also be used when printing on a single-sided thermal paper 11 having a heat-sensitive layer only on one side.

  In carrying out the present invention, it goes without saying that the constituent elements of the present invention, such as the specific shapes of the respective constituent members, can be variously modified without departing from the spirit of the invention.

1 is a side view schematically showing the inside of a thermal printer according to a first embodiment of the present invention. Sectional drawing which shows a double-sided thermal paper typically. FIG. 2 is a cross-sectional view of a part of the thermal printer along F3-F3 in FIG. The side view which shows typically the state which opened the cover of the thermal printer shown by FIG. The side view which shows typically the inside of the thermal printer which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,100 ... Thermal printer 11 ... Thermal paper 13.14 ... Thermal layer 20 ... Printer main body 21 ... Cover 30 ... 1st platen roller 40 ... 1st thermal head 42 ... 1st biasing means 50 ... 2nd platen roller 52 ... Coating layer 60 ... second thermal head 63 ... second biasing means 70 ... motor 77 ... drive gear 80 ... second platen gear 82 ... idler gear 85 ... idler gear 88 ... first platen gear 91 ... first biasing means 92 ... second attachment Means

Claims (7)

A thermal printer for printing on a double-sided thermal paper provided with heat-sensitive layers on both sides of the base paper,
A first thermal head arranged to contact the heat-sensitive layer on one side of the thermal paper;
A first platen roller facing the first thermal head across the thermal paper;
First biasing means for pressing the first thermal head toward the first platen roller;
A first platen gear that rotates integrally with the first platen roller;
A second thermal head disposed upstream of the first thermal head and in contact with the heat-sensitive layer on the other surface of the thermal paper;
A second platen roller facing the second thermal head across the thermal paper;
Second urging means for pressing the second thermal head toward the second platen roller;
A second platen gear that rotates integrally with the second platen roller;
A motor,
A power transmission mechanism for transmitting the output of the motor to the first platen gear and the second platen gear;
Have
A paper feed speed of the first platen roller to the thermal paper is greater than a paper feed speed of the second platen roller, and
The thermal printer, wherein the second platen roller is in contact with the thermal paper in a state in which the second platen roller slips more easily than the first platen roller.   2. The thermal printer according to claim 1, wherein a friction coefficient of a portion of the second platen roller in contact with the thermal paper is smaller than a friction coefficient of the first platen roller.   The second platen roller has a roller body made of an elastic material common to the first platen roller, and a coating layer made of a material having a smaller friction coefficient than the roller body and covering the outer periphery of the roller body. The thermal printer according to claim 2, wherein:   4. The power transmission mechanism rotates the first platen gear and the second platen gear so that a rotational angular velocity of the first platen roller is larger than a rotational angular velocity of the second platen roller. Thermal printer as described in   The thermal printer according to claim 3, wherein a portion of the first platen roller that comes into contact with the thermal paper is roughened.   The force that presses the second thermal head against the second platen roller by the second urging means is smaller than the force that presses the first thermal head against the first platen roller by the first urging means. The thermal printer according to claim 1.   The thermal printer according to claim 6, wherein a printing current supplied to the second thermal head is larger than a printing current supplied to the first thermal head.

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