JPH03215059A - Thermal printer - Google Patents

Abstract

PURPOSE:To minimize print irregularities by making a part for supporting a printing sheet on a platen flat and providing an elastic material as the part for supporting the printing sheet. CONSTITUTION:A surface contact type platen 5 consists of a heat-resistant porous soft rubber 6 which works as an elastic material provided on the support part 50b of a main platen system and a low friction-type film 11 which covers the surface of the thermal head side of the soft rubber 6. An opposite surface to the soft rubber thermal head base 4 of a part for supporting a printing sheet P of the surface contact-type platen 5, is formed into a plane S extending in the element oriented direction of a thermal element part 41, almost along the thermal head base 4. The main platen system 50 equipped with the soft rubber 6 and film 11 is uniformly pressed against the thermal head base 4 side by two torsion springs 10 wound around a shaft 12. Thus print irregularities are minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing mechanism for a line printing type thermal printer.

[Conventional technology]

Conventionally, a thermal printer using a line-type thermal head is equipped with a cylindrical rubber platen, which has a length corresponding to the thermal head and has a central axis rotatably supported at both ends, facing the heat generating part of the thermal head. It was getting worse.

During printing, the platen is rotated about the central axis to friction feed the printing paper, and the printing paper is moved while being pressed against the heat generating part of the thermal head.

[Problem to be solved by the invention]

However, in the conventional thermal printer mentioned above,
The following problems occurred.

That is, in order to friction-feed the print paper using the above-mentioned cylindrical platen, it is necessary to press the print paper against the thermal head using the platen, and use this pressing force to generate a frictional force between the platen and the print paper. However, in this case, there was a problem in that the platen supported at both ends was bent and the printing paper could not be evenly pressed against the thermal head, resulting in uneven printing.

In order to solve this problem, it is possible to strengthen the structure of the platen by increasing the diameter of the platen itself, making the central axis of the platen thicker, and so on to make it less likely to bend. Another problem was that the rotational torque of the platen increased, making it necessary to increase the capacity of the motor and its drive circuit.

In addition, when using a cylindrical platen, the direction in which the central axis of the platen extends and the direction in which the heat generating parts of the thermal head are arranged are aligned, and the curved surface of the platen allows the printing paper to be transferred to the thermal head. It is necessary to press the printing paper evenly, but due to manufacturing errors, there may be a slight misalignment between the direction in which the central axis of the platen extends and the direction in which the heat generating parts of the thermal head are arranged. There was a problem in that the force applied to the head was uneven, resulting in uneven printing.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a thermal printer that can press printing paper against a thermal head with uniform force and has less uneven printing.

[Means to solve the problem]

A thermal printer according to the present invention includes a thermal head including a plurality of heat generating parts arranged in a line, a platen that supports printing paper and presses it against the heat generating part side of the thermal head, and a printing paper supported by the platen. In a thermal printer having a feed mechanism that conveys paper in a direction substantially perpendicular to the arrangement direction of the heat generating parts of the thermal head, a portion of the platen that supports the printing paper is made flat and supports the printing paper. It is characterized by having parts made of an elastic body.

[For production]

According to the present invention, the part of the platen that presses and supports the printing paper against the plurality of heat generating parts arranged in a line on the thermal head is made flat, so that due to manufacturing errors, the platen or the Even if the platen is installed with a deviation in the direction in which the flat part spreads, as long as the error is within the range of the spread of the flat part, it will not affect the force with which the platen presses the printing paper against the thermal head.

In addition, since the platen is prevented from rotating and the friction feed function of printing paper from the platen is eliminated, it is no longer necessary to support the platen only at both ends, and by supporting parts other than both ends, the platen is prevented from warping. This makes it easier for the platen to press the printing paper against the thermal head with uniform force. In addition, since the part of the platen that presses and supports the printing paper is made of an elastic material, even if the platen is installed with a deviation in the direction perpendicular to its flat surface during manufacturing, such deviation will be avoided due to the elastic deformation of the elastic material. can be absorbed and the pressing force can be made uniform.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a schematic configuration of an embodiment of a thermal printer according to the present invention.

As shown in FIG. 1, the thermal printer in this embodiment is roughly composed of a printing section 2 and a conveyance section 3, which are provided in a side frame 1 that constitutes the frame of the printer. A thermal head substrate 4, a heating element section 41 arranged in a line on the thermal head substrate 4, and a surface contact type platen 5 that supports the printing paper P by pressing the printing paper P against the heating element section 41. Become.

Further, the conveying section 3 includes a sheet guide frame 8 forming a curved running surface 20, and this sheet guide frame 8.
Together with the sheet guide adupah 9 that constitutes a path for conveying the printing paper P, and the printing paper P inserted from the direction A is pressed from both sides to be conveyed along the running surface 20 B.
Drive roller 7 and counter roller 7 for discharging in the direction
Consists of o.

The surface contact type platen 5 of the printing section 2 will be explained in more detail below. Here, FIG. 2 is an enlarged sectional view of the main part of FIG.
3 is a perspective view of the main part of FIG. 1, and FIG. 4 is an exploded perspective view of the surface contact type platen 5 of this embodiment.

As shown in FIGS. 2, 3, and 4, the surface contact platen 5 of this embodiment includes a shaft 12 supported by a side frame (not shown) and a shaft hole 51 through which the shaft 12 is inserted. A platen main body 50 consisting of three arm parts 50a and a soft rubber support part 50b supported by the three arm parts 50a.
and has.

Further, the contact type platen 5 has the platen main body 50
The support portion 50b is equipped with a heat-resistant bolus-shaped soft rubber 6 that acts as an elastic material, and the surface of the soft rubber 6 on the thermal head side is covered with a low-friction film 11. Here, the surface of the soft rubber 6 that supports the printing paper P of the surface contact type platen 5, which faces the thermal head substrate 4, is a flat surface formed almost parallel to the thermal head substrate 4, and is formed in a line shape. The heating element portion 41 in which heating elements are arranged has a thousand planes S extending in the element arrangement direction.

The platen main body 50 is formed to be rotatable in the C direction or the D direction about the shaft 12, and is provided with the soft rubber 6 and the film 11 by two torsion springs 10 wound around the shaft 12. The platen main body 50 is pressed against the thermal head substrate 4 side.

When printing with the thermal printer of this embodiment having the above configuration, as shown in FIG. 2, first the printing paper P is inserted in direction A, and the drive roller 7 and 1. The printing paper P is pinched from both sides by the counter rollers 70 and friction fed along the curved running surface 20 to the position of the heating element section 41 on the thermal head substrate 4. When the printing paper P comes to the position of the heating element section 41,
The platen 5 pressed toward the thermal head side by the torsion spring 10 rotates in the C direction about the shaft 12, and the 1,000-sided surface S of the soft rubber 6 covered with the heat-resistant film 11 moves the printing paper P into the heating element section 41. Printing is performed by applying heat from the heating element portion 41 to the printing paper P.

Thereafter, the printing paper P is friction fed in the direction B on the running surface 20, and when the necessary printing is completed, it is ejected from the printer.

As explained above, since the portion of the platenra that presses and supports the printing platen P is formed into a plane that extends almost parallel to the thermal head substrate 4 and in the direction of the heating element portions 41 arranged in a line, Even if the platen 5 is installed with a deviation in the direction in which the 1,000 planes S in contact with the printing paper P spread due to manufacturing errors, if the error is within the range of the spread of the 1,000 planes S, the platen 5 will be placed in the printing direction P. It does not affect the force with which it is pressed against the thermal head. That is, there is an effect that printing unevenness can be suppressed.

In addition, apart from the platen 5, it is equipped with a feed mechanism (drive roller 7, counter roller 70) that pinches the printing paper P along the running surface 20 and conveys it from the A direction to the B direction. There is no need to support the central axis of the platen only at both ends in order to rotate the platen. Therefore, the platen 5 can be supported at three or more locations, making it difficult for the platen to bend. Therefore, the problems that conventionally occurred when eliminating platen deflection (increase in power consumption, increase in the number of parts used, etc.) can be eliminated, and the light force of the three torsion spring springs 10 can be used to tighten the platen 5. The supported printing plate P can be pressed against the heating element portion 41 with uniform force.

Furthermore, since the surface of the part of the platen 5 that presses and supports the printing paper P is covered with a low-friction film 11, and the soft rubber 6 is made of a heat-resistant porous elastic material, unevenness in the pressing force can be suppressed. There is also the effect that the force when feeding the printing paper P can be reduced and power consumption can be suppressed.

Furthermore, in contrast to the conventional cylindrical platen, which has a diameter of about 30 mm due to pressure and friction feed accuracy for printing, this embodiment has a surface contact platen. Since the mold platen 5 has the actual size shown in FIG. 4, the use of this surface contact type platen 5 has the effect of providing a line printing type thermal printer that is smaller than the conventional one.

By the way, in the transport section 3 of the thermal printer of this embodiment,
The printing paper P is sandwiched between a drive roller 7 and a counter roller 70 from both sides, and the printing paper P is friction-fed along the curved running surface 20 by rotation of each roller.

FIG. 5 is a diagram showing a comparative example of the conveying section 3 of the present embodiment shown in FIG. 2. In FIG. In this figure, the same components as in FIG. 2 are given the same reference numerals.

The feed mechanism shown in FIG. 5 is different from the conveying section 3 of this embodiment in that the feeding mechanism shown in FIG.
is a point that has a planar shape.

In this case, a feed force F1 is applied to the printing paper P by the drive roller 7 and the counter roller 70, and a drag force F1 is applied to the printing paper P by the thermal board 4 and the platen 5.
2, the print paper P, which is easy to bend, was skewed or curved, causing a feed failure and making it impossible to feed reliably. However, in this embodiment, the running surface 20 is curved from the position of the drive roller 7 to the position of the heating element section 41 by approximately 90 degrees in the paper conveyance direction, and the printing sleeve P, which is easily bent, is bent between the drive roller 7 and the heating element part 41. counter roller 7
Since the printing paper P is caused to run closely along the running surface 20 with a rotational driving force of 0, highly accurate friction feeding is performed with fewer conveyance defects due to skew or curvature of the printing paper P.

In this embodiment, the surface of the soft rubber 6 is covered with a low-friction film 11, but the present invention is not limited to this, and the soft rubber 6 may be made of a low-friction and heat-resistant material. It is not necessary to use the film 11 in this case.

〔Effect of the invention〕

As described above, in the thermal printer of the present invention, the portion of the platen that presses and supports the printing paper is made flat, so the platen uniformly distributes the printing paper to the line-type thermal head compared to the conventional cylindrical platen. It has the effect of making it easier to press with more force and suppressing uneven printing.

Furthermore, since the platen does not have the function of friction feeding the printing paper, there is no need to support the platen at both ends as in the past; in other words, it can be supported at three or more places, eliminating uneven printing due to platen deflection. It has the effect of being able to.

Furthermore, since the part of the platen that presses and supports the printing paper is made of a heat-resistant elastic material, uneven printing can be suppressed. Because it is covered with a low-friction material,
Another effect is that increase in power consumption when feeding printing paper can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
3 is a perspective view of the main part of FIG. 1, FIG. 4 is an exploded perspective view of the surface contact type platen of this embodiment, and FIG. 5 is a Hiei diagram of the conveyance section of this embodiment. It is a diagram. DESCRIPTION OF SYMBOLS 1...Side frame, 2...Printing part, 3...Transporting part, 4...Thermal head board, 41...Heating element part,
5... Surface contact type platen, 50... Platen body, 51... Shaft hole, 6...
- Porous soft rubber, 7... Drive roller, 70... Counter roller, 8... Sheet guide frame, 9... Sheet guide upper 10... Torsion spring, 11... Film, 12 ...Shaft, 20...Running surface.

Claims (1)

[Scope of Claims] A thermal head including a plurality of heat generating parts arranged in a line, a platen that supports printing paper and presses it against the heat generating part of the thermal head, and a printing paper supported by the platen. A thermal printer having a feed mechanism that conveys the print paper in a direction substantially perpendicular to the arrangement direction of the heat generating parts of the thermal head, wherein a portion of the platen that supports the print paper is made flat, and a portion that supports the print paper is made flat. A thermal printer characterized in that it is made of an elastic body.