Thermal printer

Abstract

To provide a thermal printer that can reduce loads in paper conveyance caused by friction resistance.SOLUTION: A thermal printer according to an embodiment comprises: a rotatable platen, formed in a cylindrical shape, which conveys printing media with various widths while contacting the printing media with an outer periphery part thereof with a central part in a rotary shaft direction as a reference; and printing heads, arranged to oppose to each other along the platen, which are pressed against the outer periphery part, and perform printing on the printing media held between the outer periphery part and the heads while applying heat. In the outer periphery part of the platen, first grooves are formed, in a direction crossing the rotary shaft direction, on second outer periphery parts closer to both outsides in the rotary shaft direction than the first outer periphery part with which the printing medium with the shortest width that can be conveyed contacts.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, which conveys and prints on paper such as label sheets and receipts, printing is performed on the paper by a printing unit having a platen and a print head in which heating elements are arranged in a line.

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

[0004] These thermal printers use wide print heads and platens so that they can print on large sizes. Therefore, when printing on small size (width) paper, printing is done 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 platen having a rotatable cylindrical shape, which conveys print media of various widths by contacting the outer periphery with respect to the center in the direction of the rotation axis, and a print head disposed along the platen to face the platen and pressed against the outer periphery, and which applies heat to the print medium sandwiched between the platen and the outer periphery to perform printing. The above A first groove is formed in a direction intersecting the direction of the rotation axis in a second outer peripheral portion on both sides of a first outer peripheral portion that contacts the print medium and has the shortest width that can be transported. The first grooves are a plurality of grooves provided at a first predetermined interval on the second outer periphery, and second grooves are formed at a second predetermined interval on the first outer periphery that is wider than the first predetermined interval. [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 an example of the structure of the platen. [Diagram 5] FIG. 5 is an explanatory diagram showing a first modified example of the platen structure. [Figure 6] FIG. 6 is an explanatory diagram showing a second modified example of the platen structure. [Figure 7] FIG. 7 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, label paper 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 it can rotate about the hinge 7 to open up the inside of the housing (i.e., cases 2, 8) widely from the side. As will be described later with reference to FIG. 2, the thermal printer 1 has label paper (printing medium) 20 wound in a roll inside the housing, and a printing unit 23 that prints on the labels. The case 8 can be rotated about the hinge 7 and raised to the top, making it easy to replace the label paper 20 or perform internal maintenance. 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 wound in a roll together with a backing paper. The label paper 20 is pulled out from the paper holding unit 21, printed by the printing unit 23, and then discharged from the label issuing port 10. An example of the label paper 20 that can be used is a backing paper with a label 201 affixed thereto.

[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, which is a line-type thermal head in which heating elements are arranged in a line 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 configured 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 33 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 33, and comes into contact with 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 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 along the print head 32 (i.e., in the direction of the rotation axis G 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] The platen 31 includes a rod-shaped rotating shaft G, a conveying section S formed around the rotating shaft G, and a gear H. The rotating shaft G is made of, for example, metal. The conveying section S is formed into a cylindrical shape by pouring molten hard rubber into a mold and solidifying it around the rotating shaft G, and polishing it to have an accurate diameter. The formed conveying section S has an elastic function. In addition, the gear H is fixed to the rotating shaft G. The platen 31 is rotatably attached by fitting the rotating shaft G into the frame 26. By transmitting power from the platen motor to the gear H, the rotating shaft G of the platen 31 rotates around the axis K. The rotation of the rotating shaft G rotates the platen 31. When the platen 31 rotates, the conveying section S conveys the label 201 sandwiched between the platen 31 and the print head 32.

[0020] The conveying section S of 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 conveys the label 201 with reference to a center T (position indicated by dotted line T) in the direction of the rotation axis G of the conveying section S. That is, the platen 31 conveys the label 201 with reference to the center of the width of the label 201 as the position of the center T, regardless of whether the length of the conveyed label 201 in the direction perpendicular to the conveying direction (the width of the label 201, more precisely the width of the backing paper, hereinafter referred to as "the label width") is long or short. That is, the platen 31 conveys the label 201 with reference to the center.

[0021] 3 is a diagram showing a state in which the platen 31 is conveying the label 201 with the shortest label width that can be conveyed. The outer periphery 310 of the platen 31 has a first outer periphery 311 and a second outer periphery 312. The first outer periphery 311 is a portion of the outer periphery 310 from the center T to positions a distance of A / 2 on both sides (a portion between the dotted lines 102 and 103 including the dotted line T). The distance A between the dotted lines 102 and 103 is approximately equal to the width of the label 201 with the shortest label width. Furthermore, the label 201 with the shortest label width is conveyed between the dotted lines 102 and 103 with the center T as the center, as shown in FIG. 3.

[0022] The second outer periphery 312 is located on both sides of the first outer periphery 311 in the direction of the rotation axis G. The second outer periphery 312 is a portion of the outer periphery 310, which is a distance B between the dotted line 101 and the dotted line 102. The second outer periphery 312 is a portion of the outer periphery 310, which is a distance B between the dotted line 103 and the dotted line 104. The second outer periphery 312 is located outside the area where the label 201 with the shortest label width is conveyed. In other words, the second outer periphery 312 is not used to convey the label 201 with the shortest label width. The length of the conveying section S in the direction of the rotation axis G is distance A + distance B + distance B.

[0023] As shown in Fig. 3, in this embodiment, a plurality of annular grooves M (second grooves) are formed in the first outer periphery 311 of the platen 31. The grooves M are, for example, 0.05 mm to 0.15 mm deep and have an angle of approximately 90°. The grooves M are spaced apart by an interval F (a second predetermined interval). Note that, for the sake of explanation, the grooves M are enlarged and depicted within a circle in Fig. 3, but in reality, the grooves M are formed in the first outer periphery 311. The same is true for Figs. 4 to 5 (grooves M are not formed in the first outer periphery 311 in Figs. 6 and 7).

[0024] In the embodiment, a plurality of annular grooves M (first grooves) are formed in the second outer periphery 312 on both sides of the platen 31. The grooves M have the same shape as the grooves M formed in the first outer periphery 311. The interval between the grooves M is an interval E (first predetermined interval). The interval E is narrower than the interval F, and is, for example, approximately 1 mm. Note that in FIG. 3, the grooves M are enlarged and depicted within a circle for the purpose of explanation, but in reality the grooves M are formed in the second outer periphery 312. The same applies to FIGS. 4 to 7.

[0025] That is, in the platen 31, a plurality of grooves M are formed at intervals E between the dotted lines 101 and 102, a plurality of grooves M are formed at intervals F between the dotted lines 102 and 103, and a plurality of grooves M are formed at intervals E between the dotted lines 103 and 104. In other words, in the platen 31, the grooves M are formed at wider intervals between the dotted lines 102 and 103 (first outer circumferential portion 311) which is the center portion, and the grooves M are formed at narrower intervals than in the center portion between the dotted lines 102 and 103 (second outer circumferential portion 312) and between the dotted lines 103 and 104 (second outer circumferential portion 312) which are both outer sides.

[0026] 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 outer periphery 311). However, the label 201 is not present between the dotted line 101 and the dotted line 102 (second outer periphery 312) and between the dotted line 103 and the dotted line 104 (second outer periphery 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, a plurality of grooves M are formed at intervals E between the dotted line 101 and the dotted line 102 and between the dotted line 103 and the dotted line 104. This interval E is shorter than the interval F. As a result, the contact area between print head 32 and platen 31 is smaller at the position between dotted lines 101 and 102 and at the position between dotted lines 103 and 104 than between dotted lines 102 and 103, and therefore the frictional resistance caused by sliding between print head 32 and platen 31 as platen 31 rotates can be kept small.

[0027] Furthermore, between dotted line 102 and dotted line 103, a plurality of grooves M are formed at intervals F. This increases the contact area between platen 31 and label 201. Thus, even if label 201 is sandwiched between print head 32 and platen 31, label 201 can be transported stably.

[0028] From here, a case where a label 201 with a wider label width than the label 201 with the shortest label width is used in the embodiment will be described. FIG. 4 is an explanatory diagram showing an example of the structure of the platen 31. In FIG. 4, the structure of the platen 31 is the same as that in FIG. 3. As shown in FIG. 4, when the platen 31 conveys the wide label 201, the label 201 is in contact with the first outer periphery 311 of the platen 31 and the front or part of the second outer periphery 312 on both sides of the first outer periphery 311. When the platen 31 rotates in this state, the label 201 is conveyed. At this time, in the region of the second outer periphery 312, the print head 32 and the platen 31 do not directly contact each other, or even if they do contact, the area is small. Moreover, the groove M provided in the second outer periphery 312 can suppress the frictional resistance caused by sliding between the print head 32 and the platen 31 to be small. Therefore, the platen 31 can stably convey the label 201.

[0029] From here, a first modified example of the embodiment will be described. FIG. 5 is an explanatory diagram showing a first modified example of the structure of the platen 31. As described above, in the area close to 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 second outer periphery 312 is provided slightly away from the boundary with the label 201. That is, the area of ​​the dotted line 105 and the dotted line 101 at a distance D (=distance B-distance L) that is distance L from the dotted line 102 is set as the second outer periphery 312. Then, a plurality of grooves M are formed in the second outer periphery 312 between the dotted line 105 and the dotted line 101. Also, the area of ​​the dotted line 106 and the dotted line 104 at a distance D (=distance B-distance L) that is distance L from the dotted line 103 is set as the second outer periphery 312. Then, a plurality of grooves M are formed at intervals E in the second outer periphery 312 between the dotted line 106 and the dotted line 104. In this case, the area between dotted line 105 and dotted line 106 is first outer periphery 311, and the length of first outer periphery 311 is distance A + distance L + distance L = distance C. Furthermore, multiple grooves M are formed at intervals F in first outer periphery 311.

[0030] In this first modified example, the grooves M formed in the second outer periphery 312 are formed at a position slightly away from the end of the label 201. Even in this first modified example, the grooves M formed in the first outer periphery 311 have an interval F, and the grooves M formed in the second outer periphery 312 have an interval E narrower than the interval F. Therefore, the contact area with the print head 32 in the second outer periphery 312 can be reduced, and the frictional resistance caused by sliding with the platen 31 due to the rotation of the print head 32 in the second outer periphery 312 can be kept low, as in the embodiment. Therefore, the platen 31 can stably transport the label 201.

[0031] From here, a second modified example of the embodiment will be described. Fig. 6 is an explanatory diagram showing a second modified example of the structure of the platen 31. As shown in Fig. 6, in the second modified example, no groove M is provided in the first outer periphery 311. A plurality of grooves M are formed at intervals E in the second outer periphery 312, as in the embodiment. That is, in the second modified example, the first outer periphery 311 contacts the label 201 with the shortest width on all sides. On the other hand, a plurality of grooves M are formed in the second outer periphery 312.

[0032] In the second modified example, as in the embodiment, the contact area between the second outer periphery 312 and the print head 32 can be reduced, so that the frictional resistance caused by sliding between the second outer periphery 312 and the platen 31 as the print head 32 rotates can be kept low, as in the embodiment. In addition, the first outer periphery 311 contacts the label 201 on all surfaces. Therefore, the platen 31 can transport the label 201 stably.

[0033] From here, a third modified example of the embodiment will be described. Fig. 7 is an explanatory diagram showing a third modified example of the structure of the platen 31. As shown in Fig. 7, in the third modified example, no groove M is provided in the first outer periphery 311. In the second outer periphery 312, multiple grooves M are formed at intervals E, similar to the first modified example. That is, in the third modified example, the first outer periphery 311 comes into contact with the label 201 having the shortest width on all sides. On the other hand, multiple grooves M are formed at intervals E in the second outer periphery 312.

[0034] In the third modified example, as in the embodiment, the contact area between the second outer periphery 312 and the print head 32 can be reduced, so that the frictional resistance caused by sliding between the second outer periphery 312 and the platen 31 as the print head 32 rotates can be kept low, as in the embodiment. In addition, the first outer periphery 311 contacts the label 201 on all surfaces. Therefore, the platen 31 can transport the label 201 stably.

[0035] As described above, the thermal printer 1 of the embodiment has a rotatable cylindrical shape and is equipped with a platen 31 that transports labels 201 of various widths by contacting them with the outer periphery 310 based on the center T in the direction of the rotation axis G, and a print head 32 that is arranged opposite the platen 31 and pressed against the outer periphery 310, printing by applying heat to the label 201 held between the outer periphery 310 and the platen 31.The thermal printer 1 is characterized in that a plurality of grooves M are formed in the direction intersecting the direction of the rotation axis G in the second outer periphery 312 on both sides of the first outer periphery 311 that contacts the label 201 with the shortest width that can be transported.

[0036] 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 at the second outer periphery 312. This makes it possible to reduce the load of paper transport caused by frictional resistance between the print head 32 and the platen 31.

[0037] 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.

[0038] For example, in the embodiment and the first to third modified examples, it has been described that a plurality of grooves M are formed in the second outer periphery 312. However, this is not limited to the above, and for example, one spiral groove M may be provided in the second outer periphery 312. In this case, the interval between adjacent grooves M is the interval E. Also, in this case, the spiral groove M provided in the second outer periphery 312 on one side of the first outer periphery 311 and the spiral groove M provided in the second outer periphery 312 on the other side of the first outer periphery 311 are arranged so that the spiral directions are opposite (symmetrical). In this way, when a wide label 201 as shown in FIG. 4 is conveyed, for example, it is possible to prevent the conveyed label 201 from being biased in one direction due to the influence of the spiral shape.

[0039] In the embodiment, the grooves M formed in the first outer circumferential portion 311 and the grooves formed in the second outer circumferential portion 312 have the same shape. However, the present invention is not limited to this, and the shapes (groove width, groove depth, groove angle, etc.) of the grooves formed in the first outer circumferential portion 311 and the grooves formed in the second outer circumferential portion 312 may be different.

[0040] 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, or cut paper.

[0041] In the embodiment, the multiple grooves formed in the second outer periphery 312 are uniformly spaced apart at intervals E. However, this is not limiting, and for example, the intervals between the multiple grooves formed in the second outer periphery 312 may be gradually narrowed toward both ends of the platen 31. In this case, the intervals between all of the grooves formed in the second outer periphery 312 are narrower than the interval F. [Explanation of symbols]

[0042] 1. Thermal printer 20 Label paper 23 Printing section 31 Platen 32 Print Head 201 Label 310 Outer periphery 311 First outer periphery 312 Second outer periphery H Gear K axis center M groove S Conveyor section T center part [Prior art documents] [Patent documents]

[0043] [Patent Document 1] Japanese Utility Model Application Publication No. 01-72763

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 sandwiched between the platen and the outer circumferential portion to perform printing; Equipped with a first groove is formed in a second outer periphery on both sides in the direction of the rotation axis of the platen, the second groove being formed in a direction intersecting with the direction of the rotation axis of the platen, the second outer periphery being located outside a first outer periphery that contacts the print medium and has a smallest width that can be conveyed; the first grooves are a plurality of grooves provided at a first predetermined interval in the second outer circumferential portion, A second groove is formed in the first outer periphery at a second predetermined interval that is wider than the first predetermined interval. A thermal printer characterized by:

2. The first groove is formed in the second outer periphery at a certain distance outward from the first outer periphery.

2. The thermal printer according to claim 1.

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