JPH0811385A - Head retraction mechanism of line thermal printer - Google Patents

Abstract

PURPOSE:To prevent the dislocation of a printing position for each color in a sheet by pressing a thermal head on a paper feeding platen constantly at the same position in a simple structure. CONSTITUTION:A support plate 5 is fixed on a support stud 11, and a head frame 10 is attached to an energized support spring 13 freely movably. The support plate 5 is pressed on a retraction cam 4 which is fixed to a cam shaft 3 by a pressure spring 8. Between a thermal head 2 fixed on the head frame 10 and a paper feeding platen 1, a color ribbon 7 is pressed on a sheet 6 for printing. During the discrimination of the color ribbon 7, the support plate 5, the head frame 10, etc., are slanted rightward by the rotation of the retraction cam 4 in the arrow direction so that the thermal head 2 is separated from the paper feeding platen 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head retraction mechanism for a line thermal printer, and more particularly to a mechanism for constantly pressing a thermal head and a sheet feed platen at the same position by a support spring.

[0002]

2. Description of the Related Art In a line thermal printer, particularly high accuracy is required for facing (positioning) a print head and a paper feed platen, and a difficult mechanism is required. In the conventional line thermal printer, as shown in FIG. 4, the paper feed platen 1, the thermal head 2, and the thermal head 2 have the paper feed platen 1.
Camshaft 3 for applying the load required for printing on
It has a mechanism including a retraction cam 4, a support plate 5, a pressure spring 8 and a base frame 9.

FIG. 4 is a diagram showing a printing state, in which the paper 6
The retraction cam 4 rotates while the color ribbon 7 is being fed, and the support plate 5 is stopped at a position where it reaches the maximum height as shown in FIG. 4. At that time, the thermal head 2 is moved to the paper feed platen 1. By applying a load,
Is printed.

FIG. 5 is a diagram when the color ribbon 7 is performing color identification without printing. In the case of color printing, the following mechanical operation is required when identifying the color of the color ribbon 7. This is because the retraction cam 4 rotates and pushes the support plate 5 down to the lowest point to stop it, releasing the load of the thermal head 2 on the paper feed platen 1 and allowing the color ribbon 7 to perform color identification. The head 2, the paper 6, the paper feed platen 1
It is a mechanism that does not let you touch.

After the color identification is completed, the retraction cam 4 rotates again and stops at the same rotational position as in FIG. 4, and the printing state is set and the next color is printed.

Although the concept or means is different from the above-mentioned conventional technique, the following can be mentioned as another conventional technique.

(1) A thermal head press for performing color transfer with high image quality by eliminating color misregistration by forming a fastening portion connecting the thermal head and the two sets of head pressing levers with a fastening material having an elastic body. Device (JP-A-1-294
No. 081).

(2) By moving the recording roller and the thermal head in the front-rear direction with respect to the mounting metal member through the eccentric cam, the eccentric collar, and the like, the relative positional deviation between the recording roller and the thermal head is corrected. A positioning mechanism for a thermal head for printing that always prints in an appropriate state (Japanese Utility Model Laid-Open No. 1-175826).

(3) A printer in which the positions of the thermal head and the platen roller are accurately set by the elastic force of the coil springs to prevent misalignment of printing (Actual development 6
3-149746).

[0010]

In the conventional printing mechanism requiring color identification shown in FIGS. 4 and 5, since there is no positioning mechanism for the thermal head 2 and the paper feed platen 1, the retraction cam 4 is repeatedly used. When the support plate 5 is moved up and down by the rotation of, the facing positions of the thermal head 2 and the paper feed platen 1 do not always coincide with each other, and when each color is overlaid and printed on the paper 6, a printing position shift occurs for each color. There was a drawback.

Further, the other conventional techniques have drawbacks in that the structure of the printer is complicated and it is insufficient to prevent the deviation of the printing position for each color that occurs on the paper.

In view of the above, the present invention has improved the drawbacks of the above-mentioned conventional techniques, and the thermal head is constantly pressed against the paper feed platen at the same position by a simple structure so that the printing position of each color does not shift on the paper. It is intended to be.

[0013]

In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems by using a paper feed platen having platen bushes at both ends, a head frame having a thermal head, and a support operated by a retraction cam. Consists of a plate, a support stud mounted so that the head frame and the support plate can move relative to each other, and a support spring wound around the support stud by pressing the head frame against the platen bushes at both ends of the paper feed platen. The head retraction mechanism of the line thermal printer is adopted as a means.

[0014]

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

FIG. 1 is a side view of the mechanism operation of the present invention during printing. In the printing state, the thermal head 2 sandwiches the paper 6 and the color ribbon 7 on the paper feed platen 1 to apply a constant load. The thermal head 2 is attached to the head frame 10, and is operated by the support plate 5 and the support stud 11 in conjunction with the movement of the support plate 5. Support plate 5
With the rotation of the retraction cam 4 attached to the cam shaft 3, the support plate 5 moves up and down, and the positions of the head frame 10 and the thermal head 2 also move up and down at the same time.

In the printing state, the thermal head 2 applies a constant load to the paper feed platen 1, so that when the support plate 5 is at the uppermost position, the retraction cam 4 stops rotating and the paper 6 and the color ribbon 7 are separated. Is a state in which the thermal head 2 is pressed against the paper feed platen 1, and the pressure spring 8 fixed to the base frame 9 applies a load to the support plate 5. This load is transmitted to the head frame 10 and then to the thermal head 2. In this printed state, the support stud 11 has a support spring 13 and
The mechanism includes an E-ring 12 and a support spring 13 applies a load to the head frame 10. This causes the head frame 10 to constantly apply a load to the platen bush 14 attached to the shaft of the paper feed platen 1, so that the state in which the head frame 10 abuts against the platen bush 14 is maintained, and the thermal head 2 is The paper 6 and the color ribbon 7 can always be pressed against the same position of the paper feed platen 1.

As shown in FIG. 3, the platen bush 14 is attached to the shafts at the left and right ends of the paper feed platen 1.
If the head frame 10 is attached and the load is applied from both left and right ends, the left and right thermal heads 2
The position of is always determined by the left and right sides even during printing in which the thermal head 2 is repeatedly moved up and down, so that the thermal head 2 and the paper feed platen 1 can be positioned opposite to each other.

As shown in FIG. 2, even during color identification of the color ribbon 7, the head spring 10 receives a load by the support spring 13, and the head frame 10 abuts against the platen bush 14. It is possible to prevent the misregistration of the superposed colors of the color printing to be performed, and the thermal head 2 can always perform the left-right opposed positioning by the load of the support spring 13 even in every moment of 360 ° rotation of the retraction cam 4. That is, when the retraction cam 4 rotates and the thermal head 2 moves up and down, the head frame 10
Is constantly abutted against the platen bush 14 during the vertical movement due to the load of the support spring 13. This mechanism can be achieved by the action of the support spring 13 because the head frame 10 and the support plate 5 can move relatively freely on the support stud 11.

[0019]

As described above, according to the present invention, the support spring applies a load to the head frame, and the head frame hits the platen bushes attached to both ends of the paper feed platen, whereby the thermal frame fixed to the head frame is fixed. Since the head always presses the paper feed platen at the same position, it is possible to prevent the printing position of each color from deviating on the paper with a simple structure.

[Brief description of drawings]

FIG. 1 is a side view when an embodiment of the present invention is in a printing state.

FIG. 2 is a side view showing color ribbon color identification according to an embodiment of the present invention.

FIG. 3 is a top view when one embodiment of the present invention is in a printing state.

FIG. 4 is a side view when an example of a conventional technique is in a printing state.

FIG. 5 is a side view showing an example of a conventional technique during color ribbon color identification.

[Explanation of symbols]

 1 Paper Feed Platen 2 Thermal Head 3 Cam Shaft 4 Retraction Cam 5 Support Plate 6 Paper 7 Color Ribbon 8 Pressure Spring 9 Base Frame 10 Head Frame 11 Support Stud 12 E Ring 13 Support Spring 14 Platen Bushing

Claims (2)

[Claims] 1. A paper feed platen, a head frame to which a thermal head is attached, a support plate operated by a retraction cam, and a support stud attached so that the head frame and the support plate can be moved relative to each other. , A head retraction mechanism for a line thermal printer, comprising: a support spring for pressing the head frame to both ends of a paper feed platen. 2. The head retraction mechanism of the line thermal printer according to claim 1, wherein platen bushes are attached to both ends of the paper feed platen, and the support spring is wound around the support stud.