JPH1024633A - Medium transport device for printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the stable traveling of a medium, maintain print quality at high level and prevent color shift from occurring by releasing the holding of the medium by roller pairs in relation to the pressing operation of a printing head against a platen roller. SOLUTION: A medium 9 is guided to a paper guide 10 and a paper guide 11 by a roller 7 and a roller 8, and is transported to a printing position between T/H2 and a platen roller 1. The T/H2 is brought into contact with the plate roller 1 under pressure by the operation of a cam 3 to print the medium 9. A cam lever 6 is activated by rotating a T/H cam shaft 4 which fixes the cam 3 and an F roller cam 5 fixed concentrically. The cam lever 6 is activated by the F roller cam 5 when the T/H 2 presses the cam lever 6 to the platen roller 1 side, and the roller 8 is separated from the roller 7 to release the holding of the medium 9. Consequently, it is possible to prevent color shift and print irregularities from occurring during multicolor printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a media transport device for a printer, and more particularly to a media transport device for a printer which is improved so as to avoid uneven printing during printing in a line thermal printer.

[0002]

2. Description of the Related Art A line thermal printer capable of printing on a medium (recording paper) such as cut plain paper or thermal paper can be used as an output device of a word processor, a personal computer, a facsimile machine, or the like. Widely used. Particularly, in the case of multi-color printing by a thermal transfer method using an ink ribbon or the like, the medium (paper) is reciprocated to print a plurality of colors on the same paper surface. It is necessary to have a mechanism to make it work.

As a medium transporting device for such a printer, for example, a device having a configuration as shown in FIG. 5 is known. This example is a printer that performs multicolor printing on cut plain paper. In the drawing, a cut plain paper (hereinafter, referred to as a medium) 9 is conveyed from the illustrated a direction to the b direction. . Here, a pair of rollers (the roller 7 and the roller 8) is employed as the conveying means, and the medium 9 is guided by the paper guide 10 and the paper guide 11 and reaches the pair of rollers. Part
The recording head is guided to a recording position between the thermal head (hereinafter, referred to as T / H) 2 and the platen roller 1, and the recording is performed here.

Further, the medium 9 is moved in the direction b by rollers 14 and 15 as its main feeding means.
Or, conversely, it is conveyed in the a direction. This is because it is necessary to perform three-color printing of yellow, magenta, and cyan, or four colors including black in multicolor printing, so that when the printing of the first color is completed, the rollers 14 and The roller 9 changes the transport direction of the medium 9 in the direction a, returns the medium 9 to the first print portion, changes the transport direction in the direction b again, and starts printing of the second color. Hereinafter, the third color and the fourth color are similarly printed.

The T / H 2 is vertically attached to the platen roller 1 and is attached to the mounting plate 12 so as to move toward and away from the platen roller 1. The platen roller 1 is moved by the cam 3 with the positioning pin 13 as a fulcrum. Urged to push in the direction. Further, the T / H 2 is switched between the direction a and the direction b in order to complete the printing of the medium 9 and perform the next printing. 1 so that the positioning pin 1 is separated from the pressing direction by the cam 3 so as to be separated from the pressing direction.
It operates with 3 as a fulcrum and is returned.

As another case, Japanese Patent Laid-Open No.
A transfer device described in Japanese Patent Publication No. 294180 is also known (see FIG. 6). Here, as means for transporting the thermal cut paper 29, the paper feed roller 26 and the paper feed roller 2 are used.
The detection switch 2 detects the leading edge and the trailing edge of the sheet. Then, the paper feed roller 26
The recording is performed when the thermal cut sheet 29 is discharged along the paper guide 20 by the steps 27 and 27 and guided to the recording position between the T / H 21 and the platen roller 22.

The T / H 21 is a platen roller 22
The platen roller is attached to the mounting plate 24 so as to be vertically opposed to the platen roller, and is urged so as to rotate around the positioning pin 23 and press the platen roller in the direction of the arrow shown in the figure.

Further, a positioning guide 25 fitted to the platen roller 22 is mounted on the mounting plate 24 so that the T / H 21 is vertically opposed to the platen roller 22. These T / H21, positioning pin 23,
A head unit is constituted by the mounting plate 24 and the positioning guide 25, and a cam 30 that contacts the positioning pin 23 from below acts to separate the T / H 21 from the platen roller 22. That is, as the cam 30 rotates, the T / H 21 comes into pressure contact with the platen roller 22 or separates.

[0009]

In these prior arts, in the first prior art shown in FIG.
At the moment when the medium 9 separates from the rollers 7 and 8, and in FIG.
6 and 27, a load change occurs at each moment, and particularly when the load change occurs during printing at a printing portion, the load change adversely affects printing, resulting in uneven printing (uneven feeding) and multi-color printing. There is a possibility that problems such as color misregistration during printing may occur. Further, in the related art, if printing is always performed within a range that does not deviate from the pair of rollers for conveyance, printing of the rear end of the medium may be shortened.

An object of the present invention is to solve the problems described above, and an object thereof is to achieve stable running of a medium (paper), maintenance of print quality, prevention of color misregistration, and the like.

[0011]

Therefore, in the present invention,
In a medium transport device of a printer which transports a medium to a printing portion with a pair of rollers and performs printing on the medium between a platen roller and a print head, the medium is related to a pressing operation of the print head against the platen roller. Then, it is characterized in that the holding of the roller pair with the medium is released.

In this case, when the print head is pressed against the platen roller, the nipping and releasing operations of the roller pair are performed so that the nipping of the roller pair with the medium is released. Providing an interlocking mechanism is effective as a simple mechanical structure. Further, it is preferable that the interlocking mechanism includes a cam for moving the print head toward and away from the cam and a cam lever interlocking with the cam.

Therefore, the release of the roller pair is synchronized with the press-contact / separation of the print head, so that the pinching of the roller pair is released during printing, and the load on the medium does not fluctuate during printing. Therefore, it is possible to stably convey the medium, and it is possible to prevent print unevenness (feed unevenness), color misregistration in multicolor printing, and the like.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to FIGS. FIG. 1 shows a transport roller release mechanism according to the present invention,
A state before printing is shown in which H2 is separated from the platen roller 1 and a pair of conveying rollers is pressed against each other so as to pinch a sheet 9 as a medium.

FIG. 2 shows the details of the roller pair shown in FIG. 1. FIG. 3 shows a transport roller releasing mechanism according to the present invention. The state at the time of printing in which the pair is separated from each other is shown. FIG. 4 shows details of the roller pair of FIG.

The medium transport device of the present invention is shown in FIGS.
, A pair of rollers (roller 7 and roller 8), a paper guide 10 and a paper guide 11 are provided in a medium transport path to a printing portion, and a main feed roller of the medium 9 is provided downstream of the printing portion. , As before,
Equipped with a roller pair (not shown).

As an example of means for printing on a medium, the medium 9 is sandwiched between the platen roller 1 and
T / H2 are opposed via the ink ribbon 15,
During printing, the medium 9 is printed by being pressed by the platen roller 1 by a cam mechanism described later.

That is, the T / H 2 is mounted on the mounting plate 12 so as to be vertically opposed to the platen roller 1.
The platen roller 1 is supported by a structure that comes into contact with and separates from the platen roller 1 in the direction of the arrow.

Further, the T / H 2 is reciprocated when the medium 9 has completed printing and the next printing is performed. At this time, the T / H 2 and the ink ribbon 15 are separated from the medium 9. Further, the cam 3 is operated in the release direction with the positioning pin 13 as a fulcrum.

In the present invention, a T / H camshaft 4 on which the above-described cam 3 is mounted is coaxial with the T / H camshaft 4 as an interlocking device between the roller pair (the roller 7 and the roller 8) and the T / H2. And a release cam lever 6 for separating the rollers 7 and 8 from each other is provided on a support frame of the roller 8.

In such a configuration, in a state before printing as shown in FIGS. 1 and 2, the medium 9 is guided by the rollers 7 and 8 to the paper guide 10 and the paper guide 11, and the T / H2 and The sheet is conveyed to a print portion (recording position) between the platen roller 1 and the platen roller 1.

When transported to the printing site, the rollers 7
And the roller 8 function as a main feed roller of the medium 9, and are in close contact with each other so as to sandwich the medium 9. At this time, T / H 2 is in a state of being separated from the platen roller 1 by the operation of the cam 3.

FIGS. 3 and 4 show the state during printing, as described above. The T / H 2 is pressed against the platen roller 1 by the operation of the cam 3 and printed on the medium 9. Are doing. At this time, the T / H cam shaft 4 where the cam 3 is fixed and the F roller cam 5 fixed coaxially are rotating, and the cam lever 6 is operated. The cam lever 6 is moved by the F roller cam 5 when the T / H 2 is pressed toward the platen roller 1 as shown in FIG.
, The roller 8 is separated from the roller 7, and a state in which the nipping of the medium 9 is released is achieved.
Therefore, at this time, that is, for the medium 9 at the end of printing,
There is no adverse effect from the rollers 7 and 8 such as applying a load.

Further, when the first printing is completed and the second printing is performed, the medium 9 is returned to the first printing position. In this case, the T / H 2 is separated from the platen roller 1. As described above, the cam 3 operates, and the state shown in FIGS.
On the other hand, the roller 7 and the roller 8 are again brought into close contact with each other by the interlocking device described above.

In the above-described embodiment, a thermal head is used as the print head, and a line printer for multi-color printing is used as the printer. Of course, it is applicable.

[0026]

According to the present invention, as described in detail above, a medium is conveyed to a printing portion with a pair of rollers sandwiching the medium, and printing is performed on the medium between a platen roller and a print head. In the medium transport device, in relation to the pressing operation of the print head against the platen roller,
Since the pinching of the roller pair to the medium is released, by releasing the roller pair during printing on the print head side, adverse effects such as load fluctuations generated when the medium comes off the roller pair (especially , The effect on printing) can be eliminated, and it is possible to prevent color misregistration, printing unevenness (feed unevenness), etc., in multicolor printing, which has conventionally occurred frequently.

Further, when press contact / separation of the print head is performed, by using a mechanical component such as a cam as an interlocking device, the operation means of the roller pair can be constituted, so that a special mechanism is provided. , For example, a dedicated solenoid,
Since a motor or the like is not required, the structure of the apparatus can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state before printing (roller contact) according to an embodiment of the present invention.

FIG. 2 is a detailed view of a portion A in FIG. 1 in a state in which a conveying roller is in close contact with the roller.

FIG. 3 is also a cross-sectional view showing a state during printing (roller release).

FIG. 4 is a detailed view of a portion B in FIG. 3 and shows a state in which a conveyance roller is released.

FIG. 5 is a cross-sectional view illustrating a structure of a line thermal printer of Conventional Example 1.

FIG. 6 is a cross-sectional view illustrating the structure of a line thermal printer according to Conventional Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Platen roller 2 Thermal head (T / H) 3 Cam 4 T / H cam shaft 5 F roller cam 6 Release cam lever 7, 8 Roller 9 Medium 10, 11 Paper guide 12 Mounting plate 13 Positioning pin 14, 15 Roller 16 Ink ribbon 21 Thermal head 22 Platen roller 23 Positioning pin 24 Mounting plate 25 Positioning guide 26, 27 Feed roller 28 Detection switch 29 Thermal cut paper

Claims (3)

[Claims] 1. A print medium conveying device for a printer, wherein a medium is conveyed to a printing portion with a pair of rollers interposed therebetween and printing is performed on the medium between a platen roller and a print head. A medium conveying device for a printer, wherein the pressing of the roller pair is released with respect to the pressing operation. 2. The pressing and releasing operation of the roller pair is interlocked with the contact and separation operation of the print head so as to release the holding of the roller pair with the medium during the pressing operation of the print head against the platen roller. The medium transport device for a printer according to claim 1, further comprising an interlocking mechanism that operates. 3. The printer according to claim 2, wherein the interlocking mechanism comprises a cam for moving the print head toward and away from the print head, and a cam lever interlocking with the cam. .