JPH06238965A - Impact dot printer - Google Patents

Abstract

PURPOSE:To eliminate breakage of a ribbon of a thin sheet and to perform printing at a high speed by providing means for altering an interval between a platen and a print head in response to a thickness of a print sheet, and selecting a surface of the platen opposed to the head. CONSTITUTION:Control means 14 detects a position of a lever 9 of interval altering means by a sensor 15 and controls a motor 13. When a thin sheet is printed, a film 10 is interposed between the sheet and a platen plate 8, and an impact of printing is conducted with a platen having a soft surface. An impact force to be received by an ink ribbon is diminished by a buffering action of the film 10 and the ribbon is scarcely broken. When a thick sheet such as a multi-part sheet is printed, the film 10 runs short from below the sheet, and an impact is applied on a hard surface of the plate 8, a clear print is obtained up to a sheet of a lowermost layer of the multi-part sheet. In this case, since the multi-part sheet has a buffering action, the ribbon is not broken.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact dot printer.

[0002]

2. Description of the Related Art In recent years, in impact dot printers, the impact force has increased as the printing speed has increased. In other words, by increasing the speed, the time between the previous impact and the next impact is shortened, and the dot wire returned from the previous impact bounces and tries to move toward the platen side again. Since the impact of is started, the impact force is increased. Further, it has been desired to use an iron platen that is harder than a rubber platen in order to improve the copy performance for a multi-part paper such as slip paper in which a large number of sheets are stacked, or to improve the plane accuracy of the platen.

[0003]

However, the thin 1
When only one sheet of printing paper is used, if the iron platen has too much impact force, the ink ribbon may break.
For that reason, it was necessary to reduce the printing speed to reduce the impact force.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an impact dot printer capable of high-speed printing, good copy performance for multi-part paper, and ink ribbon tearing even on thin paper.

[0005]

In order to achieve this object, an impact dot printer of the present invention comprises a print head, and a platen capable of switching a surface facing the print head between a hard surface and a soft surface. Distance changing means for changing the distance between the platen and the print head according to the thickness of the printing paper, and the surface of the platen facing the print head is switched between a hard surface and a soft surface based on the operation of the distance changing means. The platen surface facing the print head is selected according to the paper thickness.

[0006]

In the impact dot printer of the present invention having the above-mentioned structure, when the distance between the print head and the platen is changed according to the thickness of the paper to be printed, the hard surface and the soft surface of the platen are selectively changed to the print head. opposite. If it is thick like multi-part paper, the hard side of the platen is selected to improve copy performance. Even if the impact force is strong, the multi-part paper itself has a buffering effect, so that the ink ribbon does not break. For thin paper, the soft side of the platen is selected,
Even if the impact force is strong, the buffering action of the soft surface does not cause the ink ribbon to break, and high-speed printing can be performed.

[0007]

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

FIG. 1 shows a first embodiment of the present invention, in which a print head 1 and an ink ribbon cassette 2 are mounted on a carriage 3 and supported slidably along guide bars 4 and 5 by a motor 6. It is reciprocally moved via the belt 7. The platen plate 8 is located opposite to the print head 1,
Long in the direction parallel to the guide bars 4 and 5. The platen plate 8 is a so-called iron platen made of hard steel.

One guide bar 5 has eccentric shaft portions 5a at both ends.
Is supported by a frame (not shown) of the printer by both shaft portions 5a. When the lever 9 connected to one of the eccentric shaft portions 5a is oscillated in the arrow A direction, the carriage 3 moves in the arrow B direction, that is, in the direction in which the print head 1 approaches and separates from the platen plate 8. That is, the eccentric shaft portion 5a and the lever 9 can change the distance between the print head 1 and the platen plate 8 in accordance with the thickness of the paper as a distance changing means.

A flexible soft film 10 is provided between the platen plate 8 and the printing paper placed on the platen plate 8 as a cushioning material so that the flexible soft film 10 can be put in and taken out. The film 10 is supported by a frame-shaped carrier 11 and is supported by a shaft of the printer 11 by a shaft of the printer 11 so as to be slidable in a direction C parallel to the upper surface of the platen plate 8 and orthogonal to the guide bars 4 and 5. There is. The film 10 can be loaded and unloaded with one axis 1
The gear 12 is meshed with the rack 11b formed on one side of the la 1a, and the gear 13 is rotated by the motor 13 to perform the operation.

The control means 14 controls the motor 13 by detecting the position of the lever 9 of the space changing means by the sensor 15. In other words, move the lever 9 to the print head 1 as shown in the figure.
Is operated to a position closer to the platen plate 8, the sensor 1
5, the control means 14 drives the motor 13 so that the film 10 is superposed on the platen plate 8. Further, when the lever 9 is operated upward in the drawing to separate the print head 1 from the platen plate 8, the sensor 15 causes the lever 9 to move.
The movement of the film 10 is detected by the control means 14
Drives the motor 13 so that the withdraws from the platen 8.

Therefore, when printing on thin paper, the film 10 is interposed between the paper and the platen plate 8 to make an impact as a platen having a soft surface. The impact force applied to the ink ribbon due to the buffering action of the film 10 is reduced, and the ink ribbon is less likely to tear. When printing on thick paper such as multi-part paper, the film 10 disappears from under the paper, and the hard surface of the platen plate 8 makes an impact. This makes it possible to obtain clear printing even on the lowermost sheet of multi-part paper. That is, high copy performance can be obtained. In this case, since the multi-part paper itself has a buffering action, the ink ribbon will not be broken. In either case, high impact printing with strong impact can be performed.

FIG. 2 shows another embodiment of the present invention. In the case of this embodiment, the motor 17 is connected to the end of the eccentric shaft portion 5a of the guide bar 5 via the gear train 16. As is known, the rotation angle of the motor from the surface of the platen to the farthest position of the print head 1 is stored in advance, and the rotation angle from the farthest position until the print head hits the sheet on the platen is obtained, The thickness of the paper can be measured by calculating the difference between the former rotation angle and the latter rotation angle. To perform the printing operation, after the print head hits the paper as described above, the motor 17 is rotated in the reverse direction, and the distance between the two is determined when the print head is separated from the paper by a predetermined distance.

The platen 18 is in the shape of a cylindrical part having a hard surface 18a parallel to the guide bars 4 and 5 and a soft surface 18b made of rubber or the like on the outer circumference. The platen 18 is configured to be rotatable around an axis 18c parallel to the guide bars 4 and 5, and a motor 20 is connected to a gear 19 connected to one end of the platen 18.

After the thickness of the sheet is measured as described above, the control means 14 drives the motor 20 to rotate the platen 18 based on the value, and the hard surface 18a and the soft surface 1 are rotated.
8b is selectively opposed to the print head 1. If the paper is thin, the soft surface 18b, if thick, the hard surface 18a
Is selected as in the above embodiment.

[0016]

As described above, according to the impact dot printer of the present invention, it is possible to perform high-speed printing without ribbon breakage on thin paper and to improve copy performance for multi-part paper. become.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing another embodiment.

[Explanation of symbols]

 1 Print Head 5 Guide Bar 5a Eccentric Shaft Section 8 Platen Plate 9 Lever 10 Film 11 Carrier 14 Control Means 18 Platen

Claims (3)

[Claims] 1. A print head, a platen capable of switching a surface facing the print head between a hard surface and a soft surface, and an interval for changing a distance between the platen and the print head according to a thickness of a print sheet. The changing means and the control means for switching the surface of the platen facing the print head to the hard surface and the soft surface on the basis of the operation of the space changing means and facing the print head according to the thickness of the paper. An impact dot printer characterized in that the platen surface is selected. 2. The platen according to claim 1, wherein the platen comprises a platen plate having a hard surface, and a carrier means for supporting a flexible soft film which is inserted and withdrawn between the platen plate and the printing paper. An impact dot printer characterized in that the control means moves the carrier means such that the flexible soft film is interposed or not interposed between the printing paper and the platen plate. 3. The platen according to claim 1, wherein the platen has a hard surface and a soft surface in parallel and is movable in a direction in which both surfaces are lined up, and the control means separates the hard surface and the soft surface from each other. An impact dot printer, wherein the platen is moved so as to selectively face the print head.