Thermal printer

Abstract

To provide a thermal printer which can reduce a load of paper conveyance caused by friction resistance.SOLUTION: A thermal printer in an embodiment includes: a platen which has a rotatable columnar shape, and conveys a print medium of a variety of widths while making it contact with an outer circumferential part with respect to a center part in a rotation shaft direction; and a print head which is oppositely arranged along the platen, is pressed to the outer peripheral part, and prints on the print medium by applying heat. The platen includes a shaft for structuring a rotation shaft, and a rubber which has the outer peripheral part arranged on an outer circumference of the shaft, and has a first area with the center part as a center, and a second area on both outer sides in the rotation shaft direction from the first area. A diameter of the platen in the first area and a diameter of the platen in the second area are the same. A thickness of the rubber in the first area is smaller than that of the rubber in the second area.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a thermal printer. [Background technology]

[0002] 2. Description of the Related Art In a thermal printer that conveys and prints on paper such as label sheets and receipts, printing is performed on the paper by a printing unit that has a print head in which heating elements are arranged in a substantially single row, and a platen.

[0003] Such thermal printers use paper of various sizes depending on the application, hold the paper between the print head and the platen, and print on the paper while rotating the platen to transport the paper.

[0004] These thermal printers use wide print heads and platens so that they can print on large paper sizes. Therefore, when printing on narrow paper, printing is performed near the center of the printing area, so there is no paper on either end of the print head and the rotating platen comes into direct contact with the print head.

[0005] At this time, frictional resistance occurring between the print head and the platen creates a load when the paper is transported, which is an obstacle to paper transport. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a thermal printer capable of reducing the load caused by frictional resistance during paper transport. [Means for solving the problem]

[0007] The thermal printer of the embodiment includes a rotatable cylindrical platen that conveys print media of various widths by contacting the outer periphery thereof with respect to the center in the direction of the rotation axis, and a print head that is disposed opposite the platen and pressed against the outer periphery to apply heat to the print medium to perform printing, the platen including a shaft that constitutes the rotation axis, and a rubber having the outer periphery provided on the outer periphery of the shaft, the platen including a first region centered on the center and a second region on both sides outside the first region in the direction of the rotation axis, a diameter of the platen in the first region and a diameter of the platen in the second region are the same; and The diameter of the shaft in the first region is larger than the diameter of the shaft in the second region, and the first region has a length that substantially matches the width of the print medium having the shortest width that is transported. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of the appearance of a printer according to the present embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional side view showing the internal configuration of the printer. [Diagram 3] FIG. 3 is an explanatory diagram showing an example of the structure of the platen. [Figure 4] FIG. 4 is an explanatory diagram showing a first modified example of the platen structure. [Diagram 5] FIG. 5 is an explanatory diagram showing a second modified example of the platen structure. [Figure 6] FIG. 6 is an explanatory diagram showing a third modified example of the platen structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A thermal printer according to an embodiment will be described in detail below. Note that in the embodiment, a label made of thermal paper will be described as an example of a print medium. Note that the present invention is not limited to the embodiment described below.

[0010] Fig. 1 is an external perspective view of a thermal printer 1 of this embodiment. As shown in Fig. 1, the thermal printer 1 comprises a left-side case 2 and a case 8 connected to the right side of the case 2 by a hinge 7. The front panel 3 of the case 2 comprises a display unit 4 and an operation unit 5. The display unit 4 is formed of a backlit liquid crystal display, although other types of display devices may be used.

[0011] The case 8 on the right side is structured so that the inside of the housing (i.e., cases 2, 8) can be opened widely from the side by rotating upward around the hinge 7. As will be described later with reference to FIG. 2, the thermal printer 1 has label paper 20 wound in a roll and a printing unit 23 that prints on labels 201 (printing medium) inside the housing. The case 8 is structured so that the label paper 20 can be easily replaced or the interior can be easily maintained by rotating the case 8 upward around the hinge 7. A label issuing port 10 is provided on the front panel 9 of the case 8. The thermal printer 1 issues printed labels from the label issuing port 10.

[0012] Fig. 2 is a schematic side cross-sectional view showing the internal configuration of the thermal printer 1. As shown in Fig. 2, the thermal printer 1 mainly comprises a paper holding unit 21, a printing unit 23, and a frame 26 inside the housing.

[0013] The paper holding unit 21 is a shaft that holds the label paper 20 that is wound into a roll together with a backing paper. The label paper 20 has multiple labels 201 arranged along the conveying direction. The label paper 20 is pulled out of the paper holding unit 21, and after the labels 201 are printed by the printing unit 23, the label paper 20 is discharged from the label issuing port 10.

[0014] The conveying path 24 is a path along which the label paper 20 pulled out from the paper holding unit 21 is conveyed to the positions of the print head 32 and platen 31, which will be described later. The conveying path 24 also has a paper detection unit 57 that detects the pulled-out label 201. The paper detection unit 57 is located in the conveying path 24, between the position where the label 201 is pulled out and the print head 32 and platen 31, which will be described later.

[0015] Further, on the conveying path 24, downstream in the conveying direction from the printing unit 23, a label peeling plate 25 is provided. The label peeling plate 25 bends the backing of the label paper 20 being conveyed at an acute angle to peel off the label 201 from the backing. The backing is taken up on a winding shaft (not shown), while the label 201 peeled off from the backing is issued from the label issuing port 10.

[0016] The printing unit 23 mainly includes a print head 32 composed of a thermal head in which heat elements are arranged in a row in a direction (i.e., the width direction of the label 201) substantially perpendicular to the conveying direction of the label 201. The platen 31, which is formed in a cylindrical shape, is rotatably attached to the frame 26 and rotates when driven by a platen motor (not shown).

[0017] The print head 32 is fixed to a head holding section 35 that is rotatably attached to a frame (not shown). The print head 32 is urged in a direction pressing against the platen 31 in accordance with the rotational movement of the head holding section 35, and abuts against and moves away from the platen 31. The thermal printer 1 has a head-up mechanism for lifting the print head 32, and a head abutment mechanism for abutting the print head 32 against the platen 31 (both not shown). When the head-up mechanism operates, the print head 32 moves away from the platen 31, and when the head abutment mechanism operates, the print head 32 is urged (pressed) toward the platen 31 and abuts against it.

[0018] From here, the platen 31 will be described. Fig. 3 is an explanatory diagram showing an example of the internal structure of the platen 31. As shown in Fig. 3, the platen 31 and the print head 32 are arranged facing each other. The print head 32 has heating elements (not shown) arranged in a row along the print head 32 (i.e., in the direction of the rotation axis K of the platen 31), and the heating elements selectively generate heat to print characters, figures, and the like on the label 201. The label 201 (more precisely, the label 201 and a backing paper (not shown) to which the label 201 is affixed) is sandwiched between the platen 31 and the print head 32.

[0019] As described below, the platen 31 has a first region 311 and a second region 312. The first region 311 is located in the center of the platen 31 with the center at the central portion T, and is a portion with a length A (mm) between dotted lines 102 and 103. The second region 312 is connected to both ends of the first region 311, and is a portion with a length B (mm) between dotted lines 101 and 102, and a portion with a length B between dotted lines 103 and 104.

[0020] The platen 31 includes a shaft 33 that can rotate around a rotation axis K, a rubber 34 formed on the outer circumference of the shaft 33, a gear H, and the like. The shaft 33 is made of a metal such as aluminum. The shaft 33 has a first region 331 including a central portion T, and a second region 332 on both sides of the first region 331 in the direction of the rotation axis K. The first region 331 of the shaft 33 has a length A (mm) between dotted lines 102 and 103 on both sides of the central portion T in the direction of the rotation axis K of the shaft 33. The length A is approximately equal to the width of the smallest label 201 that can be printed by the thermal printer 1. The second region 332 of the shaft 33 is connected to both ends of the first region 331, and is a portion of length B (mm) between dotted lines 101 and 102, and a portion of length B between dotted lines 103 and 104. The length of the platen 31 in the direction of the rotation axis K is A+2×B.

[0021] The diameter of the first region 331 of the shaft 33 is M (millimeters (mm)), and the diameter of the second region 332 of the shaft 33 is J (mm) which is smaller than M. In the shaft 33, four stepped portions G are provided at the boundary (the positions of the dotted lines 102 and 103) between the first region 331 and the second region 332, with an inclination of approximately 45°. This makes it possible to omit one manufacturing process when molding the shaft 33.

[0022] The rubber 34 is formed by, for example, pouring molten silicone rubber into a mold and solidifying it with the shaft 33 positioned at the cylindrical center. After formation, the rubber 34 is polished to have an exact diameter and formed into a cylindrical shape with an outer peripheral portion 310. The rubber 34 has a first region 341 and a second region 342. The first region 341 is a region having the same length as the first region 331 and is the length A (mm) between the dotted line 102 and the dotted line 103. The second region 342 is the same region as the second region 332 and is the portion with a length B (mm) between the dotted line 101 and the dotted line 102 and the portion with a length B between the dotted line 103 and the dotted line 104. The thickness of the rubber 34 in the first region 341 is N (mm), and the thickness of the rubber 34 in the second region 342 is a thickness F (mm) that is thicker than the thickness N. That is, the thickness of the rubber 34 in the first region 341 is thinner than the thickness of the rubber 34 in the second region 342.

[0023] The first region 331 of the shaft 33 and the first region 341 of the rubber 34 are the first region 311 of the platen 31. The second region 332 of the shaft 33 and the second region 342 of the rubber 34 are the second region 312 of the platen 31. Note that the diameters of both the first region 311 and the second region 312 of the platen 31 are R (mm). Therefore, in the first region 311, M + N = R. Also, in the second region 312, J + F = R.

[0024] Since one type of rubber 34 is used for the platen 31 of the embodiment, the hardness of the rubber 34 is the same at any location. However, for the rubber 34, when the thickness is thin, the apparent hardness when pressing the outer peripheral portion 310 becomes high, and when the thickness is thick, the apparent hardness when pressing the outer peripheral portion 310 becomes low. That is, for the rubber 34 of the platen 31, the thickness of the second region 342 is F with respect to the thickness N of the first region 341. And since N < F, the apparent hardness in the first region 341 is higher than the apparent hardness in the second region 342. Therefore, the deformation amount of the rubber 34 in the first region 341 when pressing the outer peripheral portion 310 is less than the deformation amount of the rubber 34 in the second region 342.

[0025] In addition, gear H is fixed to shaft 33. The platen 31 is rotatably attached with shaft 33 fitted into frame 26. By transmitting rotational force from the platen motor to gear H, shaft 33 of platen 31 rotates about rotation axis K. Rotation of shaft 33 rotates platen 31. When platen 31 rotates, friction between rubber 34 and label 201 transports label 201 held between platen 31 and print head 32.

[0026] The platen 31 has an outer periphery 310 on its circumferential surface. The clamped label 201 (more precisely, a backing paper) abuts against the outer periphery 310. The platen 31 transports the label 201 with a center T (position indicated by dotted line T) as a reference position. That is, the platen 31 transports the label 201 so that the center of the width of the label 201 is located at the center T, regardless of whether the length of the label 201 in the direction perpendicular to the transport direction (the width of the label 201, more precisely, the width of the backing paper, hereinafter referred to as "label width") is long or short. That is, the platen 31 transports the label 201 with the center as a reference.

[0027] In this embodiment, when the platen 31 is rotated and the label 201 with the shortest label width is sandwiched between the platen 31 and the print head 32 and conveyed, the label 201 is conveyed between the dotted line 102 and the dotted line 103 (first region 311). However, the label 201 is not present between the dotted line 101 and the dotted line 102 (second region 312) and between the dotted line 103 and the dotted line 104 (second region 312). Since the print head 32 is biased toward the platen 31, the print head 32 and the platen 31 are in direct contact with each other at the positions between the dotted line 101 and the dotted line 102 and between the dotted line 103 and the dotted line 104, except for positions near both ends of the label 201. However, since the thickness N of the rubber 34 in the first region 311 is thin, the apparent hardness of the outer periphery 310 in the first region 341 of the rubber 34 is high. Therefore, even when a pressing force is applied by the print head 32, the rubber 34 in the first region 341 is not significantly crushed (that is, the rubber 34 in the first region 341 is not significantly deformed) and holds the label 201.

[0028] If the rubber 34 in the first region 341 is not significantly crushed, the distance between the platen 31 and the print head 32 can be maintained with the label 201 sandwiched between them. Therefore, although the print head 32 comes into contact with the second region 342 of the rubber 34 in the second region 312 of the platen 31, the pressing force from the print head 32 is not high. Therefore, the amount of deformation of the second region 342 of the rubber 34 caused by the pressing force of the print head 32 is small, and the contact area between the print head 32 and the second region 342 is small. Therefore, the frictional resistance between the print head 32 and the second region 342 can be kept small.

[0029] In order to prevent the platen 31 from bending due to the pressure of the print head 32, the diameter of the shaft 33 needs to be thick to a certain extent. Therefore, it is desirable to form the shaft 33 so that the diameter of the second region 332 of the shaft 33 is set as a reference diameter and the diameter of the first region 331 is set to be thicker than the reference diameter. However, for example, in the case of a large-sized platen 31, the diameter of the first region 331 may be set as the reference diameter and the diameter of the second region 332 may be set to be thinner than the reference diameter.

[0030] From here, a first modified example of the embodiment will be described. FIG. 4 is an explanatory diagram showing a first modified example of the structure of the platen 31. In the regions at both ends of the label 201, the print head 32 and the platen 31 are unlikely to come into direct contact with each other due to the influence of the paper thickness of the label 201. Therefore, in the first modified example, the first region 311 (i.e., the first region 331 and the first region 341) is slightly wider on both ends of the platen 31 than in the embodiment. Specifically, in the first modified example, the first region 311 is widened by E (mm) on both ends to a length C (C=A+2×E (A is the width of the label 201)). That is, the first region 341 of the rubber 34 is longer by 2×E than in the embodiment. Therefore, the region of the rubber 34 with a thickness of N in the first region 341 is wider than in the embodiment. Therefore, the apparent hardness of the rubber 34 in the first region 341 is higher than in the embodiment, and the deformation amount of the rubber 34 in the first region 341 is smaller than in the embodiment. Then, in the second region 312 of the platen 31, although the print head 32 comes into contact with the second region 342 of the rubber 34, the pressing force received from the print head 32 is not higher than in the embodiment. Therefore, the amount of deformation of the second region 342 of the rubber 34 caused by the pressing force of the print head 32 is small, and the contact area between the print head 32 and the second region 342 is small. Therefore, the frictional resistance between the print head 32 and the second region 342 can be kept small.

[0031] From here, a second modified example of the embodiment will be described. FIG. 5 is an explanatory diagram showing a second modified example of the structure of the platen 31. In the embodiment and the first modified example, the diameters of the second regions 332 of the shaft 33 in the second region 312 of the platen 31 are all diameter J, and the thicknesses of the second regions 342 of the rubber 34 are all thickness F. That is, in the embodiment and the first modified example, the thickness of the second region 332 of the shaft 33 in the second region 312 and the thickness of the second region 342 of the rubber 34 are the same. As shown in FIG. 5, in the second modified example, the thickness of the second region 332 of the shaft 33 and the thickness of the second region 342 of the rubber 34 are gradually changed in the second region 312 of the platen 31.

[0032] That is, in the second modified example, between the dotted line 102 and the dotted line 107 in the second region 312, the diameter of the second region 332 of the shaft 33 is diameter J, and the thickness of the second region 342 of the rubber 34 is thickness F. Similarly, between the dotted line 103 and the dotted line 108 in the second region 312, the diameter of the second region 332 of the shaft 33 is diameter J, and the thickness of the second region 342 of the rubber 34 is thickness F. However, between the dotted line 107 and the dotted line 101 in the second region 312, the diameter of the second region 332 of the shaft 33 is diameter P (<diameter J), and the thickness of the second region 342 of the rubber 34 is thickness Q (>thickness F). Similarly, between the dotted line 108 and the dotted line 104 in the second region 312, the diameter of the second region 332 of the shaft 33 is diameter P (<diameter J), and the thickness of the second region 342 of the rubber 34 is thickness Q (>thickness F).

[0033] Even in such a second modified example, if the rubber 34 in the first region 341 is not crushed much, the platen 31 can maintain a distance from the print head 32, which is positioned across the label 201. Therefore, although the print head 32 contacts the second region 342 of the rubber 34 in the second region 312 of the platen 31, the pressing force from the print head 32 is not high. Therefore, the amount of deformation of the second region 342 of the rubber 34 due to the pressing force of the print head 32 is small, and the contact area between the print head 32 and the second region 342 is small. Therefore, the frictional resistance between the print head 32 and the second region 342 can be kept small. Furthermore, in the second modified example, the thickness of the rubber 34 is made to differ more gradually than in the embodiment, so that the label 201 can be transported more stably.

[0034] From here, a third modified example of the embodiment will be described. FIG. 6 is an explanatory diagram showing a third modified example of the structure of the platen 31. As shown in FIG. 6, in the third modified example, the thickness of the second region 332 of the shaft 33 and the thickness of the second region 342 of the rubber 34 are continuously changed in the second region 312 of the platen 31. That is, in the third modified example, the diameter of the first region 331 of the shaft 33 is diameter M in the first region 311, but the diameter of the second region 332 in the second region 312 gradually becomes smaller from diameter M toward both ends. Also, the thickness of the first region 341 of the rubber is N in the first region 311, but the thickness of the second region 342 in the second region 312 gradually becomes thicker from N toward both ends.

[0035] Even in such a third modified example, if the rubber 34 in the first region 341 is not crushed much, the platen 31 can maintain a distance from the print head 32, which is positioned across the label 201. Therefore, in the second region 312 of the platen 31, although the print head 32 contacts the second region 342 of the rubber 34, the pressing force from the print head 32 is not high. Therefore, the amount of deformation of the second region 342 of the rubber 34 caused by the pressing force of the print head 32 is small, and the contact area between the print head 32 and the second region 342 is small. Therefore, the frictional resistance between the print head 32 and the second region 342 can be kept small. Furthermore, in the third modified example, the thickness of the rubber 34 is made to vary more continuously than in the embodiment, so that the label 201 can be conveyed more stably.

[0036] As described above, the thermal printer 1 of the embodiment is rotatable and cylindrical, and includes a platen 31 that conveys labels 201 of various widths by contacting the outer periphery 310 with respect to the center T in the direction of the rotation axis K, and a print head 32 that is arranged opposite the platen 31 and is pressed against the outer periphery 310 to apply heat to the label 201 to print. The platen 31 includes a shaft 33 that constitutes the rotation axis K, and a rubber 34 having an outer periphery 310 provided on the outer periphery of the shaft 33, and has a first region 311 centered on the center T and a second region 312 on both sides outside the first region 311 in the direction of the rotation axis K, the diameter of the platen 31 in the first region 311 and the diameter of the platen 31 in the second region 312 are the same, and the thickness of the rubber 34 in the first region 311 is thinner than the thickness of the rubber 34 in the second region 312.

[0037] The thermal printer 1 of this embodiment having such a configuration can reduce the contact area between the print head 32 and the platen 31 in the second region 312. This makes it possible to reduce the load on paper transport caused by frictional resistance between the print head 32 and the platen 31.

[0038] Although the embodiment and the modified examples of the present invention have been described above, these embodiments and the modified examples are presented as examples and are not intended to limit the scope of the invention. This new embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. This embodiment and the modified examples are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0039] For example, in the embodiment, the label 201 is used as the print medium. However, the print medium is not limited to this, and may be, for example, a linerless label, receipt paper, cut paper, or the like.

[0040] In the embodiment, the step portion G between the first region 331 and the second region 332 in the shaft 33 is inclined, but this inclination is not an essential configuration. [Explanation of symbols]

[0041] 1. Thermal printer 10 Label issuing port 20 Label paper 23 Printing section 25 Label peeling plate 26 Frames 31 Platen 32 Print Head 33 Shaft 34 Rubber 201 Label 310 Outer periphery 311 First area 312 Second area 331 First area 332 Second area 341 First area 342 Second area [Prior art documents] [Patent documents]

[0042] [Patent Document 1] Japanese Patent Application Publication No. 09-267413

Claims

1. a platen having a rotatable cylindrical shape, which conveys print media of various widths by contacting the outer periphery of the platen with respect to the center of the platen in the direction of the rotation axis; a print head disposed along the platen to face the platen and pressed against the outer circumferential portion, the print head applying heat to the print medium to perform printing; Equipped with the platen includes a shaft constituting the rotation axis, and a rubber having the outer circumferential portion provided on the outer circumferential portion of the shaft, and has a first region centered on the central portion and a second region on both outer sides of the first region in the direction of the rotation axis, a diameter of the platen in the first region and a diameter of the platen in the second region are the same, and a diameter of the shaft in the first region is larger than a diameter of the shaft in the second region; The first region has a length that is approximately equal to the width of the print medium having the shortest width that is transported. A thermal printer characterized by:

2. The shaft is made of metal.

2. The thermal printer according to claim 1.

3. The first region is slightly longer on both sides than the width of the print medium having the shortest width to be transported.

3. The thermal printer according to claim 1, wherein the first and second electrodes are arranged in a first direction.

4. The diameter of the shaft is formed in a stepped manner at the boundary between the first region and the second region.

3. The thermal printer according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. The diameter of the shaft in the second region is formed in a plurality of steps so as to become smaller toward the outer side of the platen.

3. The thermal printer according to claim 1, wherein the first and second electrodes are arranged in a first direction.

6. The diameter of the shaft in the second region is formed to be continuously smaller toward the outer side of the platen.

3. The thermal printer according to claim 1, wherein the first and second electrodes are arranged in a first direction.

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