JPH0524272A - Thermal printer - Google Patents

Abstract

PURPOSE:To make a printer small in size and prevent a blur in printing even on thick printing paper, such as a postal card, in a thermal printer provided with a flat platen. CONSTITUTION:The thermal printer is provided with a flat platen 4, the lower end of which is disposed 1mm or more lower than the lower end of a printing area 1. In this construction, a restoring force can be made small even using thick printing paper 7, and the printing paper 7 can be opposed to the flat platen 4 in parallel to each other within the printing area. Therefore, a good printing quality is secured under a predetermined printing 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 used in a word processor or the like.

[0002]

2. Description of the Related Art A conventional thermal printer will be described below.

As shown in FIGS. 4 to 6, a carriage 1 is slidably mounted on a carriage shaft 2. Similar to the carriage 1, the thermal head 3 is arranged so as to be slidable on the carriage shaft 2 and to be brought into contact with and removed from the flat platen 4 about the carriage shaft 2 as a supporting shaft. The printer frame 6 is a print sheet 7
The feed roller 8 for feeding the paper is rotatably attached.
The thermal transfer ribbon 9 is stored in a ribbon cassette 10 mounted on the carriage 1. Reference numeral 5 in the drawing denotes a platen attachment to which the flat platen 4 is attached.

The operation of the thermal printer configured as described above will be described below.

The user sets the printing paper 7 at a predetermined position for printing, but the thermal head 3 moves toward the flat platen 4 and presses the thermal transfer ribbon 9 against the printing paper 7. The pressed printing paper 7 is received by the flat platen 4. In this state, the carriage 1 and the thermal head 3 move along the carriage shaft 2, and at this time, the thermal head 3 is heated according to the print data to melt the thermal transfer ribbon 9 and transfer it to the printing paper 7. At this time, the thermal transfer ribbon 9 is further wound in synchronization with the movement of the thermal head 3.

In order to obtain good printing by such printing operation, a head pressing force of about 200 to 500 g is usually applied. If the head pressing force is weak, the transfer is insufficient due to insufficient pressure, and if the pressure is too strong, the thermal transfer ribbon 9 is transferred to the printing paper 7 side only by the pressure and the printing paper 7 is soiled. Therefore, with proper head pressing,
Even when the printing paper 7 is a thick printing paper 7 such as a postcard, it must be configured to be parallel to the flat platen 4.

That is, when printing on a thick print sheet 7 such as a postcard, the portion of the flat platen 4 facing the print sheet 7 is faced so that the surface of the thick print sheet 7 such as a postcard is substantially parallel. If not, the thick print paper 7 is wound around the paper feed roller 8 and then the restoring force of returning to the original causes the pressure of the thermal head 3 to be applied only to the upper portion of the thermal head 3 as shown in FIG. The lower part of the printing range 1 on the thermal head 3 floats and pressure is not applied.

In order to normally feed the paper, a paper feed roller having a diameter of 20 to 35 mm is usually used. However, in order to construct the thick printing paper 7 in parallel with the flat platen 4. It is necessary to arrange so that the extension line of the portion of the flat platen 4 facing the print sheet and the direct side of the discharge side from the paper feed roller are substantially aligned with each other. Therefore, the flat platen 4 and the paper feed roller 8 are vertically separated from each other. However, it becomes necessary to increase the height, and the thermal printer becomes large.

[0009]

In the above-mentioned conventional structure, the flat platen 4 is designed so as to miniaturize the thermal printer.
However, if the paper feed roller 8 is placed close to the thermal head 3, pressure is applied only to the upper part of the thermal head 3, and the thick print paper 7 has a problem that print blur occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal printer which solves the above-mentioned problems of the prior art and which can be miniaturized and which does not cause print blur even on thick print paper.

[0011]

In order to achieve this object, the thermal printer of the present invention comprises a flat platen formed such that the lower end portion of the flat platen is located 1 mm or more below the lower end of the printing range of the thermal printer. It has a configuration provided.

[0012]

With this construction, the bent portion 12 of the print sheet generated by the lower end of the flat platen serves as a fulcrum to reduce the substantial restoring force of the print sheet in the print range of the thermal head.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

1 to 3 showing an embodiment of the present invention, the same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. Further, the description of the operation of one embodiment which is the same as that of the conventional example is omitted.

As shown in FIGS. 1 and 2, the flat platen 4
On the other hand, the feed roller 8 is arranged diagonally to reduce the size. The flat platen 4 is formed so that the dimension m from the lower end of the upper and lower printing areas 1 of the thermal head 3 to the lower end 11 of the flat platen 4 is 1 mm or more.

In the printing operation, the printing paper 7 is bent by the lower end 11 of the flat platen 4.

As shown in FIG. 3, in the conventional example, the dimension n from the lower end of the printing range 1 to the lower end 11 of the flat platen 4 is about 0.5 mm, so that the head against the restoring force of the printing paper 7 is used. The pressing force is weak, and the lower part of the print range 1 may have a defective print.

In this embodiment, as shown in FIG. 2, the dimension m from the lower end of the printing range 1 to the lower end 11 of the flat platen 4 is m.
Is 1 mm or more, the substantial restoring force of the printing paper 7 can be reduced, and the flat platen 4 can be used within the printing range 1 of the thermal head 3.
The portion facing the printing paper 7 can be made parallel, and the head pressing force can be made appropriate and uniform, and good printing can be performed.

[0019]

As is apparent from the above description of the embodiments, the present invention is designed so that the thermal printer is 1 from the lower end of the printing range.
With a flat platen that is formed so that the lower end of the flat platen is positioned below mm, it is possible to realize an excellent thermal printer that is compact and does not cause print blur even on thick print paper. Is.

[Brief description of drawings]

FIG. 1 is a side view showing a section of a thermal printer according to an embodiment of the present invention, in which a part of essential parts is not shown.

FIG. 2 is a schematic sectional view showing a state of a flat platen and printing paper of the thermal printer.

FIG. 3 is a schematic cross-sectional view showing a state of a flat platen and printing paper of a conventional thermal printer.

FIG. 4 is a side view showing a cross section of the thermal printer without a part of a main part thereof shown.

FIG. 5 is a schematic plan view showing the concept of the main part of the thermal printer.

FIG. 6 is a schematic cross-sectional view showing the concept of the main part of the thermal printer.

[Explanation of symbols]

 3 Thermal head 4 Flat platen 7 Printing paper 8 Feed roller 9 Thermal transfer ribbon

Claims (1)

Claim: What is claimed is: 1. A thermal printer using a flat platen for printing on a printing sheet by a thermal head via a thermal transfer ribbon, wherein the thermal head is located at a position 1 mm or more below the lower end of the printing range of the thermal head. A thermal printer including a flat platen formed so that the lower end of the flat platen is located.