JP2002029107A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal printer capable of printing a high quality image by uniformizing the contact pressure of a thermal head to be applied on a recording paper evenly in the case a thermal head is in contact with pressure on a platen at the time of printing. SOLUTION: A platen 1 of a thermal head has a holder 3 projecting to the thermal head 9 side. A thin elastic member 2 with a less than 0.5 mm thickness is provided in the holder 3 at least in a part contacted with the thermal head 9 with pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly to a thermal printer capable of printing by pressing a thermal head against a platen.

[0002]

2. Description of the Related Art As shown in FIG. 5, a conventional thermal printer can move toward and away from a platen 21 and can reciprocate in the longitudinal direction of the platen 21 (a direction perpendicular to the plane of the drawing). A thermal head 23 is provided. The platen 21 has an elastic member 21a made of rubber or the like, and the elastic member 21a is attached to a holder 22 made of a metal plate with an adhesive (not shown) or the like. In addition, the printing surface 21b of the surface of the elastic member 21a is formed to be flat. The thermal head 23 has a plurality of heating elements 23a arranged in parallel, and can be pressed down and pressed against the platen 21.

The printing operation of such a conventional thermal printer will be described with reference to a thermal transfer printer.
The recording paper (not shown) is conveyed between the thermal head 23 in the head-up state shown in FIG. 1 and the printing surface 21b of the platen 21, and an ink ribbon (not shown) is provided between the recording paper and the thermal head 23. ). Next, the thermal head 23 is moved down as shown in FIG. 6, and the recording paper and the ink ribbon are pressed against the printing surface 21 b of the platen 21. Then, the heating elements 23a are selectively heated according to the print information, and the thermal head 23 is moved in the longitudinal direction of the platen 21 which is the main scanning direction. Can be printed.

After printing one or more lines of images on the recording paper, the thermal head 23 is moved up to carry out a line feed operation for transporting the recording paper to the downstream side of the thermal head 23. By repeating, a desired image can be printed on one recording sheet. Such a thermal printer is capable of printing an image of high print quality even on a recording sheet having a low surface smoothness such as recycled paper, and has recently been attracting attention as an environmentally friendly printer. I have.

[0005]

However, in the conventional thermal printer as described above, as shown in FIG. 6, a pressure contact weight W is applied to the thermal head 21 which has been lowered during printing. Due to the pressing load W, the left and right ends of the elastic member 21a in the figure expand outward in the direction of the arrow A. For this purpose, the elastic member 21a is
The repulsion B at the portion where the left and right ends of FIG. 3 are located is smaller than the repulsion C at the portion near the center of the thermal head 23 in the illustration.

That is, the pressing pressure of the thermal head 21 applied to the recording paper and the ink ribbon during printing is smaller in the portion where both ends of the thermal head 23 are located than in the portion near the center of the thermal head 23. Becomes smaller. For this reason, there is a possibility that unevenness in shading occurs in an image printed by transferring the ink of the ink ribbon to the recording paper, and print quality is degraded. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and when printing a thermal head against a platen at the time of printing, the pressure of the thermal head applied to the recording paper is made uniform to print a high-quality image. It is an object of the present invention to provide a thermal printer capable of performing the above.

[0007]

As a first means for solving the above problems, a thermal printer according to the present invention comprises:
A thermal head, and a platen that allows the thermal head to be pressed down while the thermal head is down.The platen has a holder protruding toward the thermal head, and a thin wall is formed at least at a portion of the holder where the thermal head is pressed. The elastic member was provided.

As a second means for solving the above-mentioned problems, the elastic member is made of rubber, and the holder is made of a material which is not deformed by the pressure of the thermal head.

According to a third aspect of the present invention, the holder comprises a flat base and a head receiving portion projecting from the base toward the thermal head. Was formed of a metal plate, and the head receiving portion was formed of a resin material.

As a fourth means for solving the above-mentioned problem, the elastic member is formed to have a small thickness of less than 0.5 mm.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal printer according to the present invention will be described below with reference to FIGS. First, FIG. 1 is a perspective view illustrating a printing unit according to the thermal printer of the present invention, FIG. 2 is a cross-sectional view illustrating a platen structure according to the present invention, and FIG. 3 is another embodiment according to the present invention. FIG. 4 is a cross-sectional view illustrating a platen structure according to an embodiment, and FIG. 4 is a diagram in which a thermal head is pressed against a platen according to the present invention.

First, the thermal printer according to the present invention is provided with a printing means S as shown in FIG. 1, and the printing means S is provided from a paper feeding unit (not shown) at the lower part in the figure to an upper part in the figure. The conveyed recording paper P is positioned. Further, the printing means S is provided with a horizontally long platen 1 formed to be longer than the width of the recording paper P.
The platen 1 includes an elastic member 2 having a small thickness, and a holder 3 having the elastic member 2 attached to a surface thereof.

The elastic member 2 is made of vulcanized rubber such as neoprene (registered trademark) rubber, and has a thickness of at least 0.5 mm at a portion where a thermal head 9 described below is pressed.
And is attached to the surface of the holder 3. As shown in FIG. 1, the holder 3 has a cross-shaped base 3a extending in the vertical direction in the figure and a head receiving portion 3b integrally formed with the base 3a and protruding toward a thermal head 9 described later. It is formed horizontally long by processing or the like. The thin elastic member 2 is attached to the outer peripheral surface of the head receiving portion 3b by, for example, an adhesive.

The elastic member 2 has a flat printing surface 2a formed on the upper surface of the elastic member 2 shown in FIG. 2, and a thermal head 9 to be described later can be pressed down and pressed against the printing surface 2a. I have. Such an elastic member 2 is attached to at least a portion of the holder 3 where the thermal head 9 is pressed, and serves as a cushion for the thermal head 9 pressed against the platen 1. Also, the elastic member 2
Is a flat printed surface 2a on the upper surface of the elastic member 2 shown in FIG.
Is formed, and a thermal head 9 described later can be pressed against the printing surface 2a.

Further, below the platen 1 shown in FIG.
A paper feed roller 4 made of rotatable rubber or the like is
a are attached at predetermined intervals. A rotatable pressure roller 5 is independently pressed against the plurality of paper feed rollers 4, and when the paper feed roller 4 rotates, the pressure roller 5 rotates following the rotation. Then, the recording sheet P conveyed from a sheet feeding unit (not shown) below the figure is pressed and held by the feed roller 4 and the pressure contact roller 5, and the recording sheet P is conveyed in the direction of arrow E, It can be transported between the platen 1 and the thermal head 9.

A carriage 6 reciprocally movable along the longitudinal direction of the platen 1 is provided on a side facing the platen 1.
Are arranged. The carriage 6 is supported by a rod-shaped guide shaft 7 and has an appropriate drive belt 8 wound around a pair of drive pulleys (not shown). The driving belt 8 is driven by rotating the driving pulley, and the carriage 6 reciprocates along the longitudinal direction of the platen 1. A flat cassette mounting surface 6a is formed on the upper surface of the carriage 6, and a pair of rotatable bobbins 6b, 6b are located above the center of the cassette mounting surface 6a at predetermined intervals. The protrusion is formed.

A thermal head 9 is mounted on the carriage 6 on the side opposite to the printing surface 2a of the platen 1 so that the thermal head 9 can be pressed down and pressed against the elastic member 2 of the platen 1. Further, a plurality of heating elements 9a are formed near the right end of the thermal head 9 shown in FIG. And a plurality of heating elements 9
a is based on print information from a control unit (not shown),
It is possible to selectively generate heat.

The thermal head 9 can be moved toward and away from the platen 1, ie, can be moved up and down, in conjunction with the rotation of a rotatable cam member (not shown). When the thermal head 9 moves down, the thermal head 9 can be pressed against the printing surface 2 a of the platen 1. A ribbon cassette 10 can be mounted on a cassette mounting surface 6a of the carriage 6, and the ribbon cassette 10 has a pair of hole-shaped reels 10 with which a pair of bobbins 6b, 6b of the carriage 6 can be engaged.
a, 10a, around which a pair of reels 10a, 10a are wound with an ink ribbon 11 coated with a heat-meltable ink of a predetermined color.

In the printing means S, the left and right ends of the platen 1, the paper feed roller 4, the pressing roller 5, the guide shaft 7, and the like are attached to a pair of frames (not shown). Is constructed. In the printing operation of the thermal printer according to the present invention, first, the uppermost recording sheet P stored in a sheet feeding unit (not shown) is conveyed in the direction of arrow E by a sheet feeding roller (not shown). And transported to the printing means S. Then, the recording paper P
Is transported between the thermal head 9 and the platen 1 in the head-up state by rotating the paper feed roller 4 with its front end pressed and held by the paper feed roller 4 and the pressure roller 5.

Next, the thermal head 9 is lowered, and the ink ribbon 11 and the recording paper P are pressed against the platen 1. When the thermal head 9 is lowered, a pressure contact weight W is applied to the thermal head 9.
The heating element 9 becomes a cushion by the thin elastic member 2.
a is not damaged. Further, since the holder 3 is formed of a rigid synthetic resin or the like, which is not deformed by the pressing pressure of the pressing load W of the thermal head 9, FIG.
As shown in (1), the repulsive force D of the platen 1 applied to the thermal head 9 can be made uniform at both the center and both ends of the thermal head 9.

Next, while the thermal head 9 is head-down and pressed against the platen 1, a plurality of heating elements 9a are selectively heated based on print information, and the carriage 6 is moved along the longitudinal direction of the platen 1. As a result, the ink of the ink ribbon 11 is thermally transferred to the recording paper P, and, for example, an image of one line or a plurality of lines is printed. After printing one or more lines, the thermal head 9 is moved up to return the carriage 6 to the initial position, and the paper feed roller 4 is rotated to perform a line feed operation. Images can be printed.

The thermal printer according to the present invention has the following features.
When the thermal head 9 is head-down and pressed against the platen 1, the repulsive force D of the platen 1 applied to the thermal head 9 as shown in FIG.
And both ends are equal. Therefore, the pressing pressure of the thermal head 9 applied to the recording paper P and the ink ribbon 11 during printing can be made uniform at the central portion and the left and right ends.

As another embodiment of the present invention, as shown in FIG. 3, the holder 13 has a base 13a formed of a flat metal plate, and a thermal base on one side of the base 13a. A head receiving portion 13b made of a resin material may be attached to the head 9 by bonding. In such a platen 31, since the base 13a is formed of a metal plate having high rigidity, it is possible to prevent warping or the like generated in the head receiving portion 13b in the longitudinal direction. Further, even if the head receiving portion 13b formed separately from the base 13a has a warp, the head receiving portion 13b is pressed against and adhered to the base 13a made of a metal plate to form the head receiving portion 13b. Sled can be corrected. In the description of the embodiment of the present invention, a thermal transfer printer has been described. However, the present invention may be applied to a thermal printer that uses thermal paper without using an ink ribbon.

[0024]

As described above, the platen of the thermal printer according to the present invention has a holder protruding toward the thermal head, and a thin elastic member is disposed at least in a portion of the holder where the thermal head is pressed. Therefore, even if the thermal head is pressed against the elastic member, the deformation amount is small because the elastic member is thin. Therefore, it is possible to provide a thermal printer that can make the pressure contact pressure of the thermal head applied to the recording paper uniform and can print a high-quality image with no shading on the recording paper.

Further, since the elastic member is formed of rubber and the holder is formed of a material which is not deformed by the pressing pressure of the thermal head, the pressing pressure when the thermal head during printing is head-down is applied to the recording paper. Can be added uniformly. Therefore, a high-quality image without shading can be printed on the recording paper.

The elastic member has a thickness of 0.5 mm
Since it is formed to be thinner than that, even if the thermal head is strongly pressed against the elastic member, the amount of deformation of the elastic member can be reduced.
Therefore, the pressure contact pressure of the thermal head applied to the recording paper can be made more uniform.

The holder comprises a flat base and a head receiving portion projecting from the base toward the thermal head. The base is formed of a metal plate, and the head receiving portion is formed of a resin material. Therefore, even if the base is formed of a rigid metal plate and a warp or the like is generated in the head receiving portion, the warp can be pressed against the rigid base and corrected and adhered. . Therefore, the printing surface of the platen can be formed with high precision without warping, and a high-quality image can be formed.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a printing unit according to the present invention.

FIG. 2 is a sectional view of a platen according to the present invention.

FIG. 3 is a sectional view of another embodiment of a platen according to the present invention.

FIG. 4 is a view for explaining pressure contact of a thermal head to a platen according to the present invention.

FIG. 5 is a diagram illustrating a conventional platen and a thermal head.

FIG. 6 is a view for explaining a conventional thermal head pressed against a platen.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Platen 2 Elastic member 2a Printing surface 3 Holder 3a Base 3b Head receiving part 4 Paper feed roller 4a Rotating shaft 5 Pressure contact roller 6 Carriage 6a Cassette mounting surface 6b Bobbin 7 Guide shaft 8 Drive belt 9 Thermal head 9a Heating element 10 Ribbon cassette 10a Reel 11 Ink ribbon

Claims (4)

[Claims] 1. A thermal head, comprising: a thermal head; and a platen which can be pressed down to contact the thermal head. The platen has a holder protruding toward the thermal head, and at least the thermal head of the holder is pressed against the thermal head. A thermal printer, wherein a thin elastic member is disposed in a portion to be formed. 2. The thermal printer according to claim 1, wherein the elastic member is formed of rubber, and the holder is formed of a material that is not deformed by the pressure of the thermal head. 3. The holder comprises a flat base and a head receiving portion projecting from the base toward the thermal head, wherein the base is formed of a metal plate, and the head receiving portion is formed of a resin material. The thermal printer according to claim 1, wherein the thermal printer is formed by: 4. The thermal printer according to claim 1, wherein the elastic member is formed to be thin with a thickness of less than 0.5 mm.