JP4153964B2 - Double-sided thermal printer - Google Patents

Description

  The present invention relates to a double-sided printing thermal printer that performs printing on both sides of a thermal paper, and more particularly to a technique that can smoothly carry a sheet.

  A double-sided printing thermal printer for performing double-sided printing on thermal paper is known (see, for example, Patent Document 1). In such a double-sided printing thermal printer, in order to print on both sides of the thermal paper, two thermal heads are provided corresponding to each side.

Each thermal head is provided with a platen. The thermal paper passes between the thermal head and the platen, and printing is performed on the thermal paper by heat applied to the thermal head.
Japanese Patent Laid-Open No. 11-286147

  The double-sided printing thermal printer described above has the following problems. That is, the two platens are generally driven by the same drive motor. In such a case, unless the outer diameters of both platens are strictly controlled, the thermal paper is pulled or loosened. There was a risk of problems in printing.

  Accordingly, the present invention provides a double-sided printing thermal printer capable of smoothly transporting thermal paper without strictly managing the outer diameter of the platen when two platens are driven by the same drive motor. The purpose is that.

  In order to solve the above problems and achieve the object, the duplex printing thermal printer of the present invention is configured as follows.

A thermal paper transport mechanism for transporting the thermal paper along the paper transport path, a first thermal head provided along the paper transport path and disposed opposite to the first surface of the paper transport path, and the first thermal head. A first platen roller disposed with respect to the thermal head across the paper conveyance path; provided along the paper conveyance path and on the thermal paper supply side with respect to the first thermal head; A second thermal head disposed opposite to the second surface side of the sheet conveying path; a second platen roller disposed across the sheet conveying path with respect to the second thermal head; the first platen roller; a drive mechanism for driving the second platen roller, the second platen roller only when rotating in the discharge side of the heat-sensitive paper, e Bei a selective torque transmission mechanism which disconnects the driving force from the driving mechanism ,Up The selective rotational force transmission mechanism includes a one-way gear, and the peripheral speed of the second platen when the thermal paper is transported in the reverse transport direction is set to be greater than the peripheral speed of the first platen, and The difference between the product of the rotation angle and the outer diameter of the first platen and the rotation angle and the outer diameter of the second platen is the backlash angle until the one-way gear is locked from the free state and the second platen. It is characterized by being set smaller than the product with the outer diameter .

  According to the present invention, when two platens are driven by the same drive motor, the thermal paper can be smoothly conveyed without strictly managing the outer diameter of the platen.

  FIG. 1 is a longitudinal sectional view schematically showing a duplex printing thermal printer 10 according to an embodiment of the present invention, and FIG. 2 is a side view showing a main part of a printing mechanism 30 incorporated in the duplex printing thermal printer 10. . In addition, P in FIG. 1 has shown the thermal paper which has a printing surface on both surfaces.

  The double-sided printing thermal printer 10 includes a casing 11, and includes a casing main body 12 that houses each mechanism, and an open / close lid 13 that can be opened and closed with respect to the casing main body 12.

  In the housing 11, a thermal paper roll R around which the thermal paper P is wound is rotatably supported, a thermal paper supply unit 20 that supplies the thermal paper P, and a printing mechanism that performs printing on the supplied thermal paper P. 30 are accommodated.

  The thermal paper supply unit 20 includes a holding unit 21 that holds the thermal paper roll R, and a feed mechanism 23 that transports the thermal paper P from the holding unit 21 to the printing mechanism 30 along the paper transport path 22. In the figure, F indicates the transport direction and F ′ indicates the reverse transport direction.

  The printing mechanism 30 includes a driving mechanism 40, a first printing unit 50, a second printing unit 60, and a cutting mechanism 70 provided along the paper transport path 22.

  The drive mechanism 40 includes a drive motor 41 and a gear mechanism 42 that transmits the rotational force generated by the drive motor 41 to each part.

  The first printing unit 50 includes a first thermal head 51 disposed to face one side (first surface side) orthogonal to the extending direction of the sheet conveyance path 22, and the sheet conveyance path 22 to the first thermal head 51. The first platen 52 and the spring 53 for urging the first thermal head 51 toward the first platen 52 are provided. The first platen 52 is driven by the gear mechanism 42.

  The second printing unit 60 includes a second thermal head 61 disposed opposite to the other side (second surface side) orthogonal to the extending direction of the sheet conveyance path 22, and the sheet conveyance path 22 to the second thermal head 61. The second platen 62 disposed opposite to each other, the spring 63 that urges the second thermal head 61 toward the second platen 62, and the rotational force from the gear mechanism 42 are selectively transmitted to the second platen 62. And a one-way gear (selective rotational force transmission mechanism) 64. When the second platen 62 rotates in the conveyance direction of the thermal paper P (arrow Q in FIG. 2), the one-way gear 64 becomes free rotation (free state) and cuts the rotational force to align the printing position. When rotating in the reverse conveyance direction of the thermal paper P, it engages with the gear mechanism 42 (locked state), and the rotational force is transmitted. That is, both the first platen 52 and the second platen 62 are driven by the gear mechanism 42.

  The one-way gear 64 has a backlash angle θ when the rotation direction changes from the conveyance direction to the reverse conveyance direction, that is, when the rotation force is transferred from the free state where the rotation force is cut. is doing. Accordingly, the locked state is not immediately changed from the free state, but the locked state is not reached several times, and the second platen 62 does not start rotating even though the first platen 52 rotates in the reverse conveyance direction. For this reason, the thermal paper P is loosened between the first platen 52 and the second platen 62. In order to eliminate this slack, the peripheral speed of the second platen 62 is set to be faster than the peripheral speed of the first platen 52.

  If the peripheral speed of the second platen 62 is higher than the peripheral speed of the first platen 52, an excessive tensile force is applied to the thermal paper P, but the reverse conveyance distance is usually as short as about 10 mm, and the backlash There is no problem because reverse conveyance over longer distances is usually not performed to the extent that slack due to angles is eliminated.

  Specifically, when the backlash angle θ is 2.5 degrees, the reverse conveyance amount is 10.0 mm, and the reduction ratio of the first platen 52 and the second platen 62 is the same, the outer diameter of the first platen 51 is 10 If it is .50 mm, its rotation angle is 109.13 degrees. On the other hand, the rotation angle of the second platen 61 may be set to be 2 degrees smaller than the backlash angle θ of 2.5 degrees, that is, 107.13 degrees. May be 10.69 mm or less.

  In the above-described example, the case where the rotation angles of the first platen 52 and the second platen 62 are the same has been described, but the present invention can also be applied to cases where the rotation angles are different. That is, the difference between the product of the rotation angle and the outer diameter of the first platen 52 and the rotation angle and the outer diameter of the second platen 62 is the backlash angle θ until the one-way gear 64 changes from the free state to the locked state. It may be set smaller than the product of the outer diameter of the two platens 62.

  The double-sided thermal printer 10 configured as described above performs printing as follows. That is, when an external print command is input, the drive motor 41 rotates in a certain direction. The rotation of the drive motor 41 drives the feed mechanism 23 via the gear mechanism 42 and drives the thermal paper P in the discharge direction.

  The gear mechanism 42 further rotates the first platen 52 in the conveyance direction of the thermal paper P. On the other hand, the rotational force of the second platen 62 is cut by the one-way gear 64 and is merely driven. As a result, a tensile force by the first platen 52 acts on the thermal paper P, and regardless of the outer diameter dimensions of the first platen 52 and the second platen 62, a constant tension is always maintained in the discharge direction. Be transported.

  In such a state, the thermal paper P is conveyed to the second printing unit 60. The second printing unit 60 starts printing on the second surface P2 of the thermal paper P. When the thermal paper P reaches the first printing unit 50, printing on the first surface P1 of the thermal paper P is started.

  Note that when the thermal paper P is rotated in the reverse conveyance direction for alignment of the printing position, the first platen 52 and the second platen 62 are both engaged by the gear mechanism 42 when engaged with the gear mechanism 42 (locked state). Driven. At this time, considering the backlash angle θ of the one-way gear 64, the peripheral speed of the second platen 62 is set to be faster than the peripheral speed of the first platen 52. The slack is eliminated and the generation of wrinkles can be prevented.

  When printing on both sides of the thermal paper P is finished, the thermal paper P is sent to the cutting mechanism 70 by the feed mechanism 23 and cut.

  As described above, according to the double-sided printer 10 according to the present embodiment, printing can be performed on both sides of the thermal paper P, and the first platen 52 and the second platen 62 are driven by the same drive motor 41. In this case, the thermal paper P can be transported smoothly without strictly managing the outer diameters of the first platen 52 and the second platen 62. Further, it is possible to eliminate the slack of the thermal paper P that occurs during reverse conveyance.

  It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

1 is a longitudinal sectional view schematically showing a double-sided printing thermal printer according to an embodiment of the present invention. The side view which shows the principal part of the printing mechanism integrated in the double-sided printing thermal printer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Duplex printing thermal printer, 20 ... Thermal paper supply part, 22 ... Paper conveyance path, 23 ... Feed mechanism (thermal paper supply mechanism), 30 ... Printing mechanism, 40 ... Drive mechanism, 50 ... 1st printing part, 51 ... 1st thermal head, 52 ... 1st platen, 53 ... 1st actuator, 60 ... 2nd printing part, 61 ... 2nd thermal head, 62 ... 2nd platen, 64 ... one-way gear, 70 ... cutting mechanism.

Claims (1)

A thermal paper transport mechanism for transporting thermal paper along the paper transport path;
A first thermal head provided along the paper transport path and disposed opposite to the first surface of the paper transport path;
A first platen roller disposed with respect to the first thermal head across the paper conveyance path;
A second thermal head provided along the paper conveyance path and on the thermal paper supply side with respect to the first thermal head, and disposed opposite to the second surface side of the paper conveyance path;
A second platen roller disposed with respect to the second thermal head across the paper conveyance path;
A drive mechanism for driving the first platen roller and the second platen roller;
The second platen roller only when rotating in the discharge side of the heat-sensitive paper, e Bei a selective torque transmission mechanism which disconnects the driving force from the drive mechanism,
The selective rotational force transmission mechanism includes a one-way gear,
The peripheral speed of the second platen when transporting the thermal paper in the reverse transport direction is set larger than the peripheral speed of the first platen, and the product of the rotation angle and the outer diameter of the first platen The difference between the rotation angle and the outer diameter of the second platen is set to be smaller than the product of the backlash angle until the one-way gear changes from the free state to the locked state and the outer diameter of the second platen. Features a double-sided printing thermal printer.

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