JP2766566B2 - Printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer for conveying a sheet while holding a leading end thereof and winding the sheet around a platen roller for printing.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing a main part of a conventional thermal printer in a state where paper is conveyed, and FIG. 10 is a diagram showing a main part in a printing state of FIG. In the drawing, reference numeral 1 denotes a platen roller provided on the printer main body; 2, a thermal head provided so as to be able to contact and separate from the platen roller 1;
Is a pinch roller that is provided so as to be able to contact and separate from the platen roller 1, is driven by rotation of the platen roller 1, 4 is a guide roller that is provided rotatably in parallel with the platen roller 1, 5 is wound around the platen roller 1, A sheet 6 on which printing is performed is a clamper that conveys the sheet 5 while holding the leading end of the sheet 5.

In the conventional thermal printer as described above, the paper 5 is transported by the clamper 6 holding the leading end of the paper 5 and moving along the paper transport path.
At the time of paper transport, the thermal head 2 and the pinch roller 3 are separated from the platen roller 1 as shown in FIG.
When the sheet 5 is fed to a predetermined position and wound around the platen roller 1, the thermal head 2 and the pinch roller 3 come into contact with the platen roller 1 as shown in FIG.
Printing is started.

[0004]

In the conventional thermal printer configured as described above, the paper 5 conveyed by the clamper 6 is not tightly wound around the platen roller 1 as shown in FIG. There is. As described above, when the thermal head 2 and the pinch roller 3 are moved toward the platen roller 3 with the gap between the platen roller 1 and the sheet 5, the sheet 5 becomes slack as shown in FIG. As a result, the paper 5 cannot be fed in a fixed size. Such looseness of the paper 5 is generated non-uniformly in the width direction of the paper 5 as shown in FIG. 11, for example. Therefore, in a conventional thermal printer, a printing shift occurs and printing quality deteriorates. There was a point. In particular, in a color printer in which multiple colors are applied repeatedly, there has been a problem that color misregistration occurs and printing quality is significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to prevent a sheet from being loosened and to wind the sheet in close contact with a platen roller. An object of the present invention is to obtain a printer capable of improving printing quality.

[0006]

According to the present invention, there is provided a printer in which the width of a sheet is set upstream of a platen roller in a sheet conveying path.
Are arranged side by side, and each touches the lower surface of the paper and is independent
Lower rollers driven by
Are arranged in the width direction of the paper so that the paper is sandwiched between
That are independently driven in contact with the top surface of the paper
Through the upper roller and the leaf spring that extends in the paper transport direction.
To the printer body so that it can be displaced in the paper width direction.
Elastically supported, at least the lower roller and the upper roller
And a support member for supporting either one of them.
Equipped with a back tension roller device to add tension
Those were example.

[0007]

In the present invention, the back tension is applied to the sheet by the back tension roller device, thereby preventing the sheet from being loosened and bringing the sheet into close contact with the platen roller.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a configuration diagram of a main part of a thermal printer according to one embodiment of the present invention. The same or corresponding parts as those in FIGS. 9 and 10 are denoted by the same reference numerals, and description thereof is omitted.

In the figure, reference numeral 11 denotes an annular 2 provided along the paper transporting path and having both ends of the clamper 6 fixed thereto.
These belts 11 move the clamper 6. A lower roller 12 is provided upstream of the platen roller 1 and the guide roller 4 in the paper transport path so as to contact the lower surface of the paper 5.
Numerals 12 are arranged side by side in the paper width direction, and each of them rotates following the movement of the paper 5. 13 is the lower roller 12
Are two upper rollers arranged side by side so as to sandwich the paper 5 therebetween. Further, the rotation shaft of the lower roller 12 is connected to a back tension generating unit 20 such as a powder clutch, and rubber is wound around the lower roller 12 to increase friction with the paper 5. The lower roller 12 applies back tension to the paper 5.

FIG. 2 is an enlarged perspective view showing a supporting portion of the upper roller 13 of FIG. 1, and FIG. 3 is a plan view showing a part of FIG. In the figure, reference numeral 14 denotes an upper roller mounting member which is mounted on the printer main body. The upper roller mounting member 14 is provided with two hooks 14a. Reference numeral 15 denotes a support member whose base end is attached to a hook 14a so as to be rotatable about a pivot shaft 15a extending in the paper width direction. An upper roller 13 is independently provided at a distal end of the support member 15. And is rotatably supported. As shown in FIG. 3, on both sides of the base end portion of the support member 15, plate spring portions 15b extending in the paper transport direction are formed, so that the support member 15 moves along the upper surface of the paper 5 It is elastically supported so as to be displaceable also in the paper width direction. Further, a projection 15c is provided substantially at the center of the upper surface of the support member 15.

Reference numeral 16 denotes a contact pressure spring provided between the convex portion 15c and the upper roller mounting member 14 for pressing the upper roller 13 toward the lower roller 12, and 17 denotes a lower roller 12, a back tension generator 20, The back tension roller device includes an upper roller 13, an upper roller mounting member 14, a support member 15, and a contact pressure spring 16.

In the thermal printer constructed as described above, when the thermal head 2 and the pinch roller 3 are separated from the platen roller as shown by the solid line in FIG. 5, a tension in the direction opposite to the transport direction, that is, a back tension is applied in advance by the back tension roller device 17. Therefore, the sheet 5 is not loosened, and the sheet 5 is tightly wound around the platen roller 1. Therefore, even if the thermal head 2 and the pinch roller 3 move toward the platen roller 1 as indicated by the broken line in FIG. In the case of (1), no color shift occurs, and the printing quality is improved.

In addition, for example, as shown in FIG. 5, when the slack occurs unevenly in the width direction of the sheet 5 due to the inclination of the platen roller 1 or the guide roller 4 or the difference between the left and right lengths of the sheet 5. , Lower and upper rollers 1 at both ends
The lengths L _L and L _R from the contact portion with the second and the thirteen to the leading end of the sheet are different from each other. In such a case, paper 5
A tension acts as shown by an arrow in FIG. As described above, when an oblique tension is generated with respect to the paper transport direction, the upper roller
A force shown by an arrow A in FIG. 7 acts on 13, and the leaf spring portion 15b is elastically deformed. Thereby, the upper roller 13 is
Displaced to the left in FIG. 7 by δ ₀ .

Due to such displacement, the direction of the back tension becomes oblique with respect to the sheet conveying direction so as to correct uneven tension, and as shown by the solid arrow in FIG. 8 (the arrow in FIGS. 7 and 8). Indicates the magnitude of the tension.),
The tension on the left side of the figure decreases, and the tension on the right side occurs in the same manner as the left side. Thereby, the tension becomes uniform in the sheet width direction, and the slack of the sheet 5 is corrected. Accordingly, the amount of displacement of the upper roller 13 from the center in the paper width direction also decreases (δ ₁ <δ ₀ ).

In the above embodiment, two upper rollers 13 are provided, each of which is independently rotated, so that slack is more effectively removed. Further, in the above embodiment, the contact pressure spring 16 is provided at the center of the support member 15 by one.
Since only one piece is provided and a one-point load is applied, the number of parts can be reduced, and the contact pressure becomes equal to the left and right. The contact pressure spring 16 also serves to prevent the support member 15 from coming off the hook 14a.

In the above embodiment, a thermal printer is shown, but the present invention can be applied to other types of printers.

[0017]

As described above, the printer according to the present invention is driven by the movement of the sheet and the back tension roller device for applying the back tension to the sheet is provided with the sheet upstream of the platen roller in the sheet transport path. Since the sheet is provided so as to be sandwiched from both sides, it is possible to prevent the sheet from being loosened, to wind the sheet in close contact with the platen roller, and to improve the printing quality. Also, a plurality of upper rollers and lower rollers
Are arranged side by side in the width direction of the paper, and
The paper feed speed
Absorb the difference in degree and prevent wrinkles from occurring on the paper
The roller touches the paper in the width direction of the paper.
Can be placed at multiple locations spaced in the direction
To provide a stable back tension. Sa
In addition, the support member is elastically attached to the printer body via the leaf spring.
Because it is supported, tension that is oblique to the paper transport direction
When the plate acts, the leaf spring part is elastically deformed and the tension is uneven.
The back tension direction is oblique so that
Paper slack can be corrected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a thermal printer according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a support portion of an upper roller of FIG. 1;

FIG. 3 is a plan view showing a part of FIG. 2;

FIG. 4 is a side view of FIG. 1;

FIG. 5 is a perspective view of a main part of the thermal printer of FIG. 1, showing a state in which unevenness in the width direction has occurred on a sheet;

FIG. 6 is a perspective view showing tension acting on a sheet in the state of FIG. 5;

FIG. 7 is a developed view showing a force applied to an upper roller and a displacement when a tension as shown in FIG. 6 acts on a sheet.

8 is a developed view showing a state in which the slack of the sheet as shown in FIG. 5 has been removed by the upper roller of FIG. 1;

FIG. 9 is a main part configuration diagram showing a sheet conveyance state of an example of a conventional thermal printer.

10 is a main part configuration diagram showing a printing state of FIG. 9;

11 is a perspective view showing a state in which the sheet of FIG. 10 is slackened.

[Explanation of symbols]

 1 Platen roller 5 Paper 17 Back tension roller device

Claims (1)

(57) [Claims] 1. A conveying the sheet while holding the leading edge, in a printer which performs printing by winding the sheet to the platen roller, prior to upstream of the platen roller of the sheet conveying path
Are provided side by side in the width direction of the recording paper,
A plurality of lower rollers that are independently driven in contact with the lower surface;
So that the paper is sandwiched between these lower rollers.
Provided side by side in the width direction of the paper,
A plurality of upper rollers independently driven in contact with
Via a leaf spring portion extending in the paper transport direction, the width of the paper
Elastically supported by the printer body in a state where it can be displaced in the
At least one of the lower roller and the upper roller
A support member for supporting one of the sheets, and a back tension roller device for applying a back tension to the sheet.