JPH01202468A - Thermal printer - Google Patents

Abstract

PURPOSE:To obtain a thermal printer which prevents a paper from staggering or skewing in a paper feeding and brings the paper into good contact with a thermal head, by providing a pinch roller in which the wall thickness of the center part of a rubber roller part is larger than that of the end parts thereof. CONSTITUTION:A platen is composed of a core bar 11 having a uniform diameter and a rubber roller part 12 which is provided around the core bar 11 so that the wall thickness of the center part is larger than that of the end parts; it is a rubber roller having approximately a barrel-shape. Therefore, the core bar 11 is deflected by being abutted by a thermal head 2, and the center part of the axis of the platen is more spaced from the surface of the thermal head than the end parts thereof. However, the large wall thickness of the rubber ensures a predetermined pressing force applied over the full length of the head and enables a uniform printing. Then, since the platen has a larger rotation radius in the center part than in the both ends parts, with the rotation of the platen a paper 3 is fed convergently. thereby being automatically corrected to a proper feed direction.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a line-tod type thermal printer, and in particular to an improved thermal printer that does not cause meandering or skew when paper is fed. The purpose of this thermal printer is to provide a thermal printer equipped with a platen that brings paper into good contact with the head, and in which paper is fed by pressing the paper against a rotating platen with a thermal head, the platen has a uniform diameter. A rubber roller having a substantially drum-shaped outer shape, which is composed of a rod-shaped core metal having a diameter of 100 mm, and a rubber roller portion provided around the core metal such that the thickness of the center portion is thicker than that of both ends. do.

[Industrial application field]

The present invention relates to a line-tod type thermal printer,
In particular, the present invention relates to a thermal printer having a platen that does not cause meandering or skewed paper feeding.

In line-tod thermal printers, a rubber roller (platen) is placed in contact with the thermal head to press the recording paper (thermal paper, plain paper, and thermal transfer film) to be printed on and move it relative to the thermal head using friction. Rotate.

In order to maintain good printing quality and prevent clogging problems, it's:
It is important that the paper is fed in a direction perpendicular to the direction in which the printed dots of the thermal head are arranged.

[Conventional technology]

FIG. 2 is a diagram showing the main structure of a line-tod type thermal printer to which the present invention is applied, and FIG. 3 is a sectional view showing the platen shape of a conventional thermal printer.

Normally, a line-tod type thermal printer has a rotating shaft 1a.
A platen 1 made of a rubber roller and a thermal head 2 having a plurality of heating elements 2a formed in the paper width direction are provided so as to abut each other with a predetermined pressing force P, and the recording paper 3 is sandwiched between the abutting portions. As the platen 1 is rotated as shown by the arrow, the static friction coefficient and contact area between the platen 1 and the paper 3 are significantly larger than the kinetic friction coefficient and contact area between the thermal head 2 and the paper 3. , recording is performed on the paper 3 while being conveyed under the thermal head 2.

As shown in FIG. 3, the platen 1 in a conventional thermal printer is made by making the core metal 11 as thick as possible in order to bring the rubber surface closer to the cylindrical surface so that it does not bend when cutting the surface of the rubber roller part 11. Efforts have been made to make the wall thickness uniform in the length direction of the platen.

Making the core metal 11 as thick as possible reduces the deflection δ of the platen 1 supported at both ends, which is pressed in the longitudinal direction by the thermal head 2 as shown in P during recording, and the thermal head and the recording paper are It was also necessary to ensure good contact with the

[Problem to be solved by the invention]

By the way, in the thermal printer with the above configuration, paper 3
If the paper does not move in the direction perpendicular to the axis of the platen 1 and the paper 3 is skewed or meandered, the position of the Searl head 2 in relation to the width of the paper 3 may change, resulting in the paper not being recorded at the specified position or a paper jam occurring. do.

The closer the platen is to a true cylindrical shape, the more likely it is that meandering or oblique movement will occur.In order to prevent this, thermal printers equipped with the conventional platen have a mechanism that applies bank tension to the paper, and a mechanism that applies bank tension to the paper on both sides of the paper feed path. There was a problem in that a complicated mechanism such as adding a guide rail was required, which increased the cost.

The present invention was created in view of the above problems, and an object of the present invention is to provide a thermal printer equipped with a platen that does not meander or skew when feeding paper and brings the paper into good contact with the thermal head. That is, an object of the present invention is to provide a thermal printer having improved paper feeding performance that allows paper to be fed straight even without a back tension application mechanism or a paper feeding guide.

[Means to solve the problem]

The above problem is solved by a thermal printer that feeds paper by pressing the paper against a rotating platen using a thermal head. This problem is solved by the thermal printer of the present invention, characterized in that the external shape is a substantially drum-shaped rubber roller formed by a rubber roller section surrounding the core bar so as to be thicker than the wall thickness.

[For production]

When the thermal head makes contact, the core metal flexes, and the central part of the platen's axis moves away from the surface of the thermal head compared to the edges, but because the rubber is thick, the specified pressing force is maintained over the entire length of the head, making it uneven. It is possible to print uniformly without any blemishes. The distance (rotation radius) from the center of rotation of the platen to the rubber surface (paper contact surface) is larger at the center than at both ends, so as the platen rotates, the paper is conveyed so that it gathers in the center, even if it is set diagonally. Since continuous paper is automatically corrected in the correct feeding direction, there is no need for back tension application or extra mechanisms such as guide rails.

〔Example〕

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

FIG. 1 is a sectional view showing a platen for a thermal printer according to the present invention, in which (a) shows a free state, and (b) shows a printing state when pressed by a thermal head.

In the figure, a platen 1 is for conveying A4 size paper, and is composed of a core bar 11 and a rubber roller portion 12 that covers the core bar 11.

The core metal 11 is made of stainless steel and has a diameter of 8m1I+, 260m.
m Rotatably supported by the printer body at both ends. The rubber roller part 12 has a rubber hardness of 30 to 40.
Made of rubber material with a length of 220 mm and an outer diameter of approximately 18 m.
It is m. Therefore, the thickness of the rubber roller part is approximately 5n+m, but the thickness tc at the center is 0 compared to the thickness th at both ends.
, is processed to be approximately 2 mm larger. (The difference in thickness is exaggerated in the figure.) Normally, the rubber roller part 12 is formed by supporting both ends of the core metal 11 and grinding the cylindrical surface, but the pressure of the grinding tool causes the core metal 11 to bend along its axis. Deformation occurs, and the outer diameter of the central portion of the rubber roller portion 12 increases. At this time, the core metal has the above dimensions,
If grinding conditions are appropriately set, it is extremely easy to provide the above-mentioned thickness difference in the rubber roller portion.

When the thermal head 2, which has sufficiently large bending rigidity and excellent flatness, is brought into contact with the platen 1 having the above configuration with a pressing force P of about 4 kg through the paper 3, the platen 1 will be moved along the axis. When subjected to a substantially uniformly distributed load, the receiver bends so that the center of its axis moves away from the head surface, as shown in FIG. 1(b).

This deflection is reduced by creating a difference of about 0.1 mm in the amount of compression of the rubber wall thickness between both ends and the center, and the amount of deflection at the core's axis (i.e., rotation center) is reduced. 0.1m
It will be about m.

It should be noted that since the central part of the rubber roller part is thicker than both end parts as described above, it contacts the surface of the thermal head almost in a straight line, and the required contact force is ensured over the entire length, so that uniform printing can be achieved.

Due to the above deflection, the effective radius r at both ends of the rubber
h is 0.11IllIl than the actual radius rc of the central part
The platen operates as a platen with a diameter of lj1, and a force is applied to the paper conveyed by this platen in a direction that pulls it toward the center where the radius is large, and meandering and oblique feeding are automatically avoided.

〔Effect of the invention〕

As described above, the thermal printer of the present invention has a function of automatically correcting meandering and skew when feeding paper by providing a pinch roller in which the thickness of the central part of the rubber roller part is larger than that of both ends. Therefore, small size and low cost can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a platen for a thermal printer according to the present invention, FIG. 2 is a view showing the main structure of the thermal printer, and FIG. 3 is a cross-sectional view showing the platen shape of a conventional thermal printer. In the figure, ■ - platen, 11 - core metal, 12 -
Rubber roller part, 2.-Thermal.Grot 3.
-Recording paper 1, is.

Claims (1)

[Claims] In a thermal printer that feeds paper by pressing paper (3) against a rotating platen (1) with a thermal head (2), the platen (1) has a rod-like shape having a uniform diameter. Core metal (
11), and a rubber roller part (12) provided around the core metal (11) so that the thickness of the center part is thicker than that of both ends.
A thermal printer characterized in that it is a rubber roller with an approximately drum-shaped outer shape.