JPH05246100A - Thermal transfer printer - Google Patents

Abstract

PURPOSE:To prevent a wrinkle in an ink sheet to prevent an occurrence of an unsatisfactory printing by shaping a guide roller into a recessed form. CONSTITUTION:A guide roller l is so shaped as to have the center of a small diameter and both end parts of a large diameter. A guide pipe 2 having an inner diameter larger than the diameter of the end part of the guide roller 1 can be rotated by a small force. A tension is applied to an ink sheet 3 by a take-up force of an ink sheet take-up roll 3a. A force F acts to the ink sheet in the direction of a resultant force of the tension. The guide pipe 2 having an elasticity is deflected to be concaved in the center part thereof by the force F. In this state, the distribution of the force F is not constant in the ink sheet 3. A force Fs at both end parts is larger than a force Fc at the center part. Since the forces act to pull the ink sheet 3 to both sides thereof, a wrinkle in the ink sheet can be prevented from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer printer,
In particular, the present invention relates to a thermal transfer printer that can obtain good printing without wrinkling of the ink sheet.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a guide roller for an ink sheet has a cylindrical guide roller made of metal or the like, which is passed through a guide pipe, and the guide pipe is rotated around the guide roller by a frictional force with the ink sheet. A method of forming a running path of an ink sheet with such a structure is generally performed in the industry.

[0003]

In a thermal transfer type printer, a wrinkle on an ink sheet causes printing defects such as print omission, and a mechanism that does not cause wrinkling of the ink sheet,
A wrinkle prevention mechanism is required. The guide roller part is an important part for the ink sheet to stably run, and there is a problem in the conventional thermal transfer type printer that wrinkles or amplification of the ink sheet occurs in the guide roller part to cause printing failure. It was

Therefore, an object of the present invention is to provide a thermal transfer printer having a guide roller shape in which wrinkles of an ink sheet do not occur in order to solve the conventional problems described above.

[0005]

In order to solve the above-mentioned problems, the present invention provides an ink sheet in which a cylindrical guide pipe having elasticity is loosely inserted into the guide roller with both ends of the guide roller being thick and the center being concave. The tension distribution is inclined so that the tension is weak at the center of the ink sheet and strong at both ends.

[0006]

As described above, in the ink sheet having the gradient of the tension distribution, a force is generated which approaches the one having the higher tension, so that the ink sheet tends to extend to both sides.
Wrinkles do not occur in the ink sheet, or the generated wrinkles act so as to escape to both ends, so that printing defects due to wrinkles in the ink sheet can be prevented.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 4, the print sheet 4 is supplied from the right side to the left side of the figure by a print sheet supply mechanism (not shown). At this time, the thermal head 5 is in an up state by a thermal head elevating mechanism (not shown), and there is a gap between the thermal head 5 and the platen roller 6. Printing paper 4
When the thermal head 5 is fed between the thermal head 5 and the platen roller 6, the thermal head 5 is brought into a down state, the ink sheet 3 and the printing paper 4 are nipped between the thermal head 5 and the platen roller 6, and printing is started. An applied voltage corresponding to an image signal is supplied to the thermal head 5, but electric circuits such as a signal processing circuit and a power supply are omitted in FIG.

When printing is started, the ink sheet take-up roll 3a is given a rotational torque in a clockwise direction by an ink sheet drive mechanism (not shown), and a tension for taking up the ink sheet is given. Ink sheet supply roll 3
Although b does not have a driving force and is a so-called swinging motion, a frictional force is applied to the shaft 3c of the ink sheet supply roll 3b so that the ink sheet 3 has a tension. This tension is necessary to prevent the ink sheet 3 from wrinkling and to obtain good printing.

The platen roller 6 is rotated counterclockwise by a drive mechanism (not shown) to convey the printing paper 4 leftward. The ink sheet 3 includes the thermal head 5 and the printing paper 4.
The conveyance speed of the ink sheet 3 is the same as the conveyance speed of the printing paper 4 because it is sandwiched between the sheets. In this embodiment, the printing paper 4 is carried by the platen roller 6, but a device for carrying the printing paper 4 by separately providing a capstan roller is also general, and the present invention can be applied. Guide roller 1
Is a shaft made of metal such as SUS, and both ends thereof are fixed to a frame (not shown). The guide pipe 2 is a pipe made of an elastic material such as resin such as polyacetal, acrylic, vinyl chloride, or hard rubber, and rotates with respect to the guide roller 1 by a frictional force with the ink sheet 3.

FIG. 1 shows a sectional view of the guide roller 1 and the guide pipe 2 of the present invention. In this way, the guide roller 1 has a thin center and thick ends. The inner diameter of the guide pipe 2 is larger than the diameters of both ends of the guide roller 1, and the guide pipe 2 can be rotated by a light force. FIG. 2 shows the force applied to the ink sheet of the embodiment of the present invention. Tension is applied to the ink sheet 3 by the take-up force of the ink sheet take-up roll 3a of FIG. 4, and a force F acts in the direction of the resultant force of the tension. The guide pipe 2 has elasticity, and due to the force F, The center is bent to form a concave shape. In this situation,
The distribution of the force F is not constant in the ink sheet 3, and the force Fs at both ends is larger than the force Fc at the center.

Therefore, the tension of the ink sheet 3 also increases as it approaches both ends, and becomes weaker in the center. Ink sheet 3
When there is such a gradient of the tension distribution during the traveling of the ink sheet 3, a force is exerted on the ink sheet 3 to move toward the side with a larger tension. In FIG. 2, the ink sheet 3 tries to move toward both ends in the width direction. The force to do is represented by force P. For this reason, the force acts so that the ink sheet 3 is pulled to both sides.
Ink sheet wrinkles can be prevented. Further, even when wrinkles are generated, the wrinkles are pushed out to both ends as the ink sheet 3 runs, and the influence on printing can be minimized.

In this embodiment, the guide pipe 2 is
The wall thickness of the guide pipe is about 1 using polyacetal.
With a diameter of 0.5 mm, the amount of deflection of the central portion of the guide pipe 2 was set to 0.5 mm, and good results were obtained. The length of the central small diameter portion of the guide roller 1 is set to be substantially the same as the width of the printing area. The elasticity of the guide pipe 2 is set so as to have the maximum amount of deflection when the tension of the ink sheet 3 is maximum. The tension of the ink sheet 3 changes depending on the size of the diameter of the ink sheet take-up roll 3a.

FIG. 5 is a sectional view showing a state in which the ink sheet take-up roll according to the embodiment of the present invention is thick. In the thick state of the ink sheet take-up roll, the angle at which the ink sheet 3 is wound around the guide pipe 2 is large, and a force of F _{1 is} exerted by the resultant force of the tension T _1. FIG. FIG. In this state, the ink sheet tension T ₂ is equal to the ink sheet roll 3a.
Is larger than the above-mentioned T ₁ when driven with a constant torque. However, since the winding angle of the ink sheet 3 becomes smaller and the angle formed by the tension T ₂ becomes larger, the resultant force F _{2 of} T ₂ becomes as shown in the figure, and the difference between F ₁ and F ₂ can be reduced. If the position of the guide roller 1 is set at such a position that the force F can be kept as constant as possible, a better effect can be obtained.

In this embodiment, the center of the guide roller is made thin and the guide pipe is bent, but in another embodiment not shown, both ends of the guide pipe are held in the frame without using the guide roller. Bend or S
A structure in which the guide roller itself of the US machine is made to have a smooth concave shape and the ink sheet runs can be easily applied, and the tension of the ink sheet is weakened at the central portion of the roller and strengthened at both ends to cause the wrinkle of the ink sheet. Any structure that prevents the above is included in the present invention. Needless to say, when the present invention is applied to the roller 7 on the ink sheet supply roll side, the same effect as in this embodiment can be obtained.

The same effect can be obtained when the present invention is applied to a guide roller in the path of the ink sheet other than the one described above.

[0016]

As described above, the present invention has a simple structure in which the guide roller is formed in a concave shape, and it is possible to obtain a high-quality printer which prevents the ink sheet from wrinkling and causes no printing defects.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a guide roller portion of the present invention.

FIG. 2 is a cross-sectional view showing a force applied to the ink sheet according to the embodiment of the invention.

FIG. 3 is a sectional view showing a guide roller portion of a conventional example.

FIG. 4 is a sectional view of an apparatus according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a thick state of the ink sheet take-up roll according to the embodiment of the invention.

FIG. 6 is a cross-sectional view showing a thin state of the ink sheet take-up roll according to the embodiment of the invention.

[Explanation of symbols]

 1 Guide Roller 2 Guide Pipe 3 Ink Sheet 3a Ink Sheet Winding Roll 3b Ink Sheet Supply Roll

Claims (3)

[Claims] 1. A thermal transfer printer having a roller for guiding an ink sheet, wherein the guide roller has a cylindrical shape with a thin center and thick ends, and a cylindrical guide pipe having elasticity is loosely inserted into the guide roller, and A thermal transfer printer characterized by guiding an ink sheet. 2. A thermal transfer printer having a roller for guiding an ink sheet, wherein the guide roller is concave with respect to the contact surface of the ink sheet. 3. A thermal transfer printer, wherein an ink sheet is guided by a cylindrical guide pipe having elasticity.