JPH0924650A - Linear ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable paper to be printed in a highly qualified manner and not being stained with ink by keeping a state of the head cap constant. SOLUTION: A part of the peripheral surface of a platen roller 11 is utilized as a printing reference surface 8, and a pinch roller 21 and a star wheel 31 for pressing paper against the peripheral surface of the platen roller 11 are provided upstream and downstream from the nozzle part 2 of an ink jet head 1 in the paper conveying direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an ink jet head having a nozzle portion having a print width corresponding to the effective print area width of a sheet, and a print reference surface formed so as to face the nozzle portion of the ink jet head. The present invention relates to a line-type inkjet printer that prints by ejecting ink from a nozzle portion of an inkjet head onto a sheet conveyed on a print reference surface.

[0002]

2. Description of the Related Art A conventional structure of a line type ink jet printer is shown in FIG. In these figures, 1 is an inkjet head. The inkjet head 1 has a nozzle portion 2 corresponding to the paper width and is fixed to a predetermined portion of a printer body (not shown). The inkjet head 1 is configured to eject ink from the nozzle portion 2 to a region of one line or several lines in a direction orthogonal to the paper transport direction (direction orthogonal to the paper surface in FIG. 3).

Reference numeral 5 is a feed roller, and 6 is a leaf plate. Reference numeral 7 is a paper guide, and a print reference surface 8 is formed on a predetermined upper surface portion of the paper guide so as to face the nozzle portion 2 of the inkjet head 1.

Specifically, the feed roller 5 comprises a rotary shaft 5a.
Is provided so as to be rotatable in a predetermined direction (for example, a clockwise direction in FIG. 3) about the axis of the paper, and the paper (P) delivered from a paper supply unit (not shown) is directed toward the print reference plane 8. It is configured to be transportable.

The leaf plate 6 is provided so as to press the paper (P) against the peripheral surface of the feed roller 5. Due to the pressing action of the leaf plate 6, the paper (P) is pressed against the print reference surface 8 of the paper guide 7, and the ink is ejected in a state where the gap (head gap G) from the nozzle portion 2 of the inkjet head 1 is constant. Will be sprayed.

In the above ink jet printer, the paper (P) is fed onto the print reference surface 8 by the cooperation of the feed roller 5 and the leaf plate 6. Then, the print reference surface 8
In the above, the ink is ejected from the nozzle portion 2 of the inkjet head 1 to the region of one line or several lines on the paper (P) to perform printing. In this way, the printed paper (P) is discharged to the paper receiver 9.

[0007]

By the way, in the above ink jet printer, the paper (P) is the leaf plate 6
The ink is sprayed from the nozzle portion 2 while being pressed against the print reference surface 8 by the head gap (G), and the ink is sprayed on the paper (P).
Elongation occurs at the part.

The expansion of the paper affects the paper (P) portion on the print reference surface 8 and lifts the paper (P) portion from the print reference surface 8 to keep the head gap (G) constant. In some cases, printing may not be possible in this state. In extreme cases, the paper (P) may come into contact with the nozzle portion 2 and stain the ink.

Therefore, in order to prevent the above-mentioned situation from occurring, the leaf plate 6 may be forced to press the paper strongly. However, if the paper is pressed too much, the paper cannot be smoothly sent to the print reference surface 8. Occurs.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a line type ink jet printer which can perform high quality printing without contaminating a paper sheet with a constant head gap.

[0011]

According to the present invention, there is provided an ink jet head having a nozzle portion having a print width corresponding to an effective print area width of a sheet, and a print reference surface formed so as to face the nozzle portion of the ink jet head. And a platen roller corresponding to the nozzle portion of the inkjet head, in which the ink is ejected from the nozzle portion of the inkjet head to print on a sheet conveyed on the print reference surface. And the print reference surface is formed from a part of the peripheral surface of the platen roller facing the nozzle portion, and presses the paper against the peripheral surface of the platen roller upstream of the nozzle portion of the inkjet head in the paper conveyance direction. A possible pressing means is provided, and the paper is pressed on the peripheral surface of the platen roller on the downstream side in the paper conveying direction. Characterized in that a sharp rotating body.

In the case of the present invention having the above-mentioned structure, the paper is pressed against the peripheral surface of the platen roller by the pressing means on the upstream side of the nozzle portion of the ink jet head and the sharp rotating body on the downstream side.

Here, the peripheral surface portion of the platen roller on which the paper is pressed by the pressing means and the sharp rotating member is
Since it is an arcuate surface having a constant radius of curvature (radius), the paper can be uniformly and strongly pressed against the peripheral surface portion.

Therefore, it is possible to print by ejecting the ink from the nozzle portion of the ink jet head onto the paper portion supplied on the print reference surface while keeping the head gap constant.

At this time, since the nozzle portion is configured to eject the ink to the area of one line or several lines in the direction orthogonal to the sheet conveying direction, a part of the peripheral surface of the platen roller is used as the print reference surface. Even if used, the difference in the head gap of each line can be ignored for printing.

Further, even if the sharp rotating body comes into contact with the printed portion of the paper, the contact area is extremely small, so that the ink adhesion amount is practically negligible, and the paper is not contaminated with ink. Can be pressed against the platen roller.

[0017]

Embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the present inkjet printer has a basic configuration similar to that of the conventional example (FIG. 3), but uses a part of the peripheral surface of the platen roller 11 as the print reference surface 8 and the inkjet printer. Head 1
The peripheral surface (12a, 12b) of the platen roller 11 holds the sheet (P) on the upstream side and the downstream side of the nozzle portion 2 in the sheet conveying direction.
A pressing means (21) for pressing against and a sharp rotating body (31)
Is provided, and high quality printing can be performed on the paper (P) with the head gap (G) kept constant without causing ink contamination.

The same components as those in the conventional example (FIG. 3) are designated by the same reference numerals, and the description thereof will be simplified or omitted. In FIG. 1, reference numeral 51 denotes a paper feeding unit, which is a paper cassette 52 rotatable about a fulcrum 52a and a paper cassette 5.
A pressure spring 53 for pressing the uppermost sheet in 2 against the platen roller 11, and a cam device 54 for separating the uppermost sheet from the platen roller 11 against the urging force of the pressure spring 53.
It is composed of

The platen roller 11 is arranged at a position corresponding to the nozzle portion 2 of the ink jet head 1.
Specifically, the platen roller 11 also serves as a paper feed roller, is rotatably mounted on the printer body 3 via a shaft 5a, and is driven in a predetermined direction (for example, a clock in FIG. 1) by a driving unit (not shown). It is configured to be rotationally driven in the circumferential direction).

The print reference surface 8 is formed by a part of the peripheral surface of the platen roller 11 facing the nozzle portion 2 of the ink jet head 1. Therefore, the print reference surface 8 is an arc surface, but the nozzle portion 2 of the inkjet head 1
Has a configuration in which the ink is ejected to a region of one line or several lines in the direction orthogonal to the transport direction of the paper (P) (that is, the axial direction of the platen roller 11), and therefore the print reference surface 8 is an arc surface. Even if there is, the difference in the head gap (G) of each line can be ignored for printing.

The pressing means is arranged on the upstream side of the nozzle portion 2 of the ink jet head 1 in the paper conveying direction and presses the paper (P) against the peripheral surface of the platen roller 11. Specifically, the pressing unit presses the paper (P) against the platen roller peripheral surface portion 12a in the vicinity of the nozzle portion 2 and upstream of the print reference surface 8 in the paper conveying direction.
Is formed. The pinch roller 21 is rotatably attached to the printer body 3.

The sharp rotating member is arranged downstream of the nozzle portion 2 of the ink jet head 1 in the sheet conveying direction and is a means for pressing the sheet (P) against the peripheral surface 12 of the platen roller 11. Specifically, the sharpened rotary member is formed of a star wheel 31 that presses the paper (P) against the platen roller peripheral surface portion 12b on the downstream side of the print reference surface 8 in the paper transport direction in the vicinity of the nozzle portion 2. .

The star wheel 31 is, as shown in FIG.
The rotary shaft 33 is formed of a disk portion 32 and a rotary shaft 33. The rotary shaft 33 is supported by the printer body 3 so that the rotary disk 33 can rotate while the disk portion 32 is in contact with the platen roller peripheral surface 12b by its own weight. A plurality of acute-angled projections 35 are formed at a predetermined pitch on the outer peripheral portion of the disk portion 31 of the star wheel 32.

Here, each projection 35 of the star wheel 31 has a very small contact area even when it comes into contact with the printed portion of the paper (P), so that the amount of ink adhered is also extremely small. Therefore, even if the printed portion of the paper (P) is brought into contact with the white background portion of the paper (P), there is no problem in practical use as far as it is a dot of the ink that is difficult to recognize with the naked eye, but further improvement of the printing quality is possible. For this reason, in this embodiment, the cleaning wheel 4 is used.
1 is provided to remove an extremely small amount of ink attached to each projection 35 of the star wheel 31.

The cleaning wheel 41 is made of a material that is impregnated with ink, and is rotatably supported by the printer body 3 so that its peripheral surface contacts the protrusions 35 of the star wheel 31. Therefore, the cleaning wheel 41 can rotate following the rotation of the star wheel 31 to remove the ink attached to each protrusion 35 of the star wheel 31.

Next, the operation of this embodiment will be described. The sheet (P) urged by the platen roller 11 is urged by the pinch roller 21 on the upstream side of the nozzle portion 2 of the inkjet head 1 and the star wheel 31 on the downstream side of the nozzle section 2 of the inkjet head 1 to surround the peripheral surface (1) of the platen roller 11.
2a, 12b).

Here, since the peripheral surface portion 12 of the platen roller 11 on which the paper (P) is pressed by the pinch roller 21 and the star wheel 31 is an arc surface having a constant radius of curvature (radius), the paper ( P) can be uniformly and strongly pressed against the peripheral surface portion 12.

Therefore, the nozzle portion 2 of the ink jet head 11 is attached to the paper (P) portion supplied on the print reference surface 8.
It is possible to print by ejecting ink with the head gap (G) kept constant.

At this time, since the nozzle portion 2 is configured to eject the ink to the area of one line or several lines in the direction orthogonal to the conveying direction of the paper (P), a part of the peripheral surface of the platen roller 11 is formed. Even if a portion is used as the print reference surface 8, the difference in the head gap (G) of each line can be ignored for printing.

The star wheel 31 is used for the paper (P).
Even if it comes into contact with the printed portion of the paper, since the contact area is extremely small, the amount of ink adhered is practically negligible, and the adhered ink is always removed by the cleaning wheel 41. ) Can be pressed against the platen roller 11 without soiling the ink.

According to this embodiment, however, a part of the peripheral surface of the platen roller 11 is used as the print reference surface 8 and the nozzle portion 2 of the ink jet head 1 is used.
Since the pinch roller 21 and the star wheel 31 that press the sheet (P) against the peripheral surface of the platen roller 11 are provided on the upstream side and the downstream side of the sheet conveying direction of the sheet, the sheet (P) has a constant head gap (G). In this state, high quality printing can be performed without causing ink stains.

Further, since the pressing means is formed by the pinch roller 21, it is possible to further reduce the load on the paper (P) when the paper (P) is supplied to the print reference surface 8. As a result, the paper (P) can be more smoothly supplied to the print reference surface 8 for printing.

Further, since the sharp rotating body is formed of the star wheel 31, the amount of ink adhered is further reduced,
Printing can be performed by pressing the peripheral surface 12 of the platen roller without further contaminating the printed paper portion with ink.

Further, since the cleaning wheel 41 removes an extremely small amount of ink adhering to the star wheel 31, it is possible to completely prevent the paper (P) from being contaminated with ink.

[0035]

According to the present invention, a part of the peripheral surface of the platen roller is used as a printing reference surface, and the paper is surrounded by the peripheral surface of the platen roller by the upstream side and the downstream side of the nozzle portion of the ink jet head in the paper conveying direction. Since the pressing means for pressing the surface and the sharp rotating member are provided, it is possible to perform high-quality printing on the paper without contaminating the ink with the head gap kept constant.

[Brief description of drawings]

FIG. 1 is a diagram for describing an embodiment of the present invention.

FIG. 2 is also a diagram for explaining a star wheel and a cleaning wheel.

FIG. 3 is a diagram for explaining a conventional configuration of an ink jet printer.

[Explanation of symbols]

 1 Inkjet Head 2 Nozzle Part 11 Platen Roller 12 Peripheral Surface Part 21 Pinch Roller (Pressing Means) 31 Star Wheel (Sharp Rotating Body) 41 Cleaning Wheel

Claims (1)

[Claims] 1. A print reference comprising: an ink jet head having a nozzle portion having a print width corresponding to an effective print area width of a sheet; and a print reference surface formed so as to face the nozzle portion of the ink jet head. In a line type inkjet printer that performs printing by ejecting ink from a nozzle portion of an inkjet head onto a sheet conveyed on a surface, a platen roller is provided corresponding to the nozzle portion of the inkjet head, and the print reference surface is A part of the peripheral surface of the platen roller facing the nozzle portion is provided, and a pressing means capable of pressing the paper on the peripheral surface of the platen roller is provided upstream of the nozzle portion of the inkjet head in the paper transport direction, A sharp rotating body that presses the sheet against the peripheral surface of the platen roller is provided on the downstream side in the sheet conveying direction. Line type ink jet printer according to claim.