Printer with vacuum device

Abstract

To provide a printer capable of efficiently suppressing cockles with a high level of design flexibility and low energy consumption.SOLUTION: A printer comprises: a print station (10); a media transport mechanism (12, 14) arranged for conveying print media (18) on a transport path past the print station (10), the media transport mechanism (12, 14) having a support surface (16) for supporting the media (18); and a vacuum device (22) arranged for attracting the media (18) against the support surface (16) on a section (14) of the transport path downstream of the print station (10), characterized in that the vacuum device (22) is divided, in the direction along the transport path, into at least two segments (24, 26), and the media are attractable with different non-zero suction pressures in the two segments (24, 26).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to: - a printing station, and - a media transport mechanism arranged to carry a printing medium on a transport path through the printing station, the media transport mechanism having a support surface for supporting the media, and - a vacuum device arranged to attract the media to a support surface on a portion of the transport path downstream of the printing station, and relates to a printer including the same. In particular, the present invention relates to an inkjet printer.

[0002]

Background Art

[0003] When ink or another marking material is applied to the surface of a printing medium sheet or web, such as a sheet of paper, the marking material may swell or shrink the sheet material in the area where the marking material is applied. In other areas where the marking material is not applied, the sheet does not swell or shrink, so the sheet will inevitably cockle. Such cockling endangers the quality of the printed image. Typically, cockling is maximized after the marking material is applied, for example, within less than 1 second, after a specific delay time. The delay time depends on the rate at which the marking material penetrates the sheet and swells or shrinks the sheet. Next, when the sheet is actively or passively dried, the cockling decreases to some extent, but internal stresses are generated in the sheet due to the swelling of the sheet, and these stresses remain even after drying, so a certain amount of cockling remains.

[0004] ​​​​​​​​​​​

[0005] An example of a printer of the above type is described in Patent Document 1.

[0006] Here, in order to reduce cockling, the media sheet is either flattened of the cockles or suctioned against the support surface with such a strong force that cockles are not even formed at all. Since the vacuum device extends over a specific length at the drying station of the printer, the sheet is dried and then suction pressure is applied until it remains flat and free of cockles.

[0007] However, this solution has the drawback that the generation of a high suction pressure leads to an increase in energy consumption and also an increase in the amount of friction when the sheet is conveyed over the suction device. For this reason, in known printers, the tendency of cockling of the media sheet is predicted based on the known material properties of the media and the marking material, and the suction pressure is adjusted accordingly.

[0008] It is also possible to extend the suction device upstream within the area under the printing station so that the sheet can be attracted to the support surface already when the marking material is applied. Since the sheet is in close contact with the support surface in this state, the suction pressure required to hold the sheet flat is smaller than the suction pressure that would be required to remove cockles after they are formed.

[0009] On the other hand, this solution has several drawbacks. In particular, this makes it more difficult to thermally decouple the printing station from the drying station. Typically, the printed sheet The sheet is actively dried by applying heat (e.g., radiant heat, etc.) to the sheet. . Therefore, an increase in temperature is desirable in the drying station, while in the printing station, since there is a risk of completely drying the ink in the nozzles of the print head, the likelihood of nozzle failure is high. Therefore, an increase in heat is not desirable.

[0010] Furthermore, an arrangement in which the suction device extends across both the printing station and the drying station regions makes the overall design of the printer larger and is incompatible with a modular design that can adapt independently to the changing requirements of the printing station and the drying station.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0012] Therefore, an object of the present invention is to provide a printer that can offer a high level of design flexibility and, nevertheless, has the ability to efficiently suppress cockling with a low energy consumption.

Means for Solving the Problems

[0013] To achieve this object, according to the present invention, the vacuum device is divided into at least two segments in the direction along the transport path, and in at least two segments, the medium can be attracted with different non-zero suction pressures. ​​​

[0014] By independently controlling the suction pressure in at least two segments, Therefore, the suction pressure should be adjusted to the actual requirements during the movement of the media on the suction device. This allows for finer adjustments to be made. This allows for minimal energy consumption and wear. The rubbing suppresses cockling without the need to extend suction into the area of ​​the printing station. can be done.

[0015] More specific optional features of the invention are set out in the dependent claims.

[0016] The media transport may include separate transport sections, one of which is connected to the print stage. one is used to move the media through the nozzle, and the other is used to move the media further on the vacuum device. It is used to transport the media downstream. The separation between the two transport parts is the printing station This allows for good thermal decoupling of the heating and drying stations.

[0017] The vacuum system begins at the approximate boundary between the two transport sections and a high vacuum pressure is created. This may include the upstream segment, ensuring that any cockles that may have already formed are flattened. Then, when the media sheet is fully attracted against the support surface, The associated portion of the media sheet is then moved to a downstream segment of the vacuum apparatus where a lesser vacuum pressure is applied. The pressure is just enough to prevent the sheet from cockling again. It's pressure. [Brief description of the drawings]

[0018] Examples of embodiments are now described in conjunction with the drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0019] As shown in FIG. 1, the inkjet printer includes a printing station 10 and a media conveyance mechanism 12, 14 including two separate conveyance parts 12 and 14 in this example. Each conveyance part includes an endless conveyor belt, the upper surface of which constitutes a support surface 16 for supporting the media sheet 18. The media sheet 18 is conveyed through the printing station 10 in the upstream conveyance part 12, and then passed through a drying station 20 and delivered to the downstream conveyance part 14 that moves the sheet 18.

[0020] The printing station 10 may include a print head assembly having a plurality of inkjet print heads arranged to eject ink droplets of different colors onto the surface of the media sheet 18. For example, the ink may be aqueous ink, and the media sheet 18 may be a sheet of paper that is wetted by the ink applied thereto.

[0021] The drying station 20 may include a radiator for irradiating the sheet 18 with infrared rays in order to dry the ink, for example, by raising the temperature of the sheet and evaporating the volatile ink components.

[0022] The downstream conveying portion 14 is provided with a vacuum device 22, and the vacuum device 22 includes two adjacent segments 24, 26 constituted by a separate plenum chamber, each of which is connected to blowers 28 and 30 respectively.

[0023] The plenum chambers in segments 24 and 26 have perforated upper walls, and since the conveyor belt in the conveying portion 14 is also perforated, air is sucked in through the perforations of the conveyor belt and the upper walls of the plenum chambers. In this way, as the sheet 18 passes over segments 24 and 26, it is attracted to the support surface 16. As a result, the conveyor belt is pressed against the perforated upper wall of the plenum chamber, and thus, as a part of the sheet 18 and the conveyor belt supporting it move together through the drying station 20, a certain amount of friction is generated.

[0024] The main purpose of the suction device 22 is to prevent the sheet 18 from cockling, which is an undesirable effect, and will be described in conjunction with FIGS. 2 and 3 below.

[0025] FIG. 2 is a plan view of the media sheet 18 on which the image 32 is printed. When the image 32 is printed at the printing station 10, liquid aqueous ink is applied to the sheet in the area of the image 32, and water penetrates into the paper of the sheet 18 and swells it.

[0026] This is symbolized in FIG. 3, where the image 32 is shown slightly enlarged due to swelling, and the original outline 32' of the image is shown by a dashed double-dotted line. The image 32 is It is surrounded by a non-swelling margin portion 34 of the sheet paper. This leads to internal strain in the paper and causes wrinkles or cockles 36 to form in the paper in the area of the image 32.

[0027] Figure 4 shows a part of the printer shown in Figure 1 on an enlarged scale. The media sheet 18 is just leaving the printing station 10, and the leading edge of the sheet has already reached the downstream segment 26 of the vacuum device within the drying station 20. A part of the sheet 18 on which ink has been applied to form the image 32 is starting to cause cockles at a specific delay time corresponding to the time for water to penetrate into the paper. As the sheet 18 moves from right to left in Figure 4, cockles 36 start to form slightly downstream of the printing station 10. For illustrative purposes, the height of the cockles 36 is exaggerated in Figure 4.

[0028] The cockles 36 pass over the transition region from the upstream conveying portion 12 to the downstream conveying portion 14. In this transition region, the sheet 18 cannot be attracted to the support surface (in practice, there is no support surface in the gap between the two conveyor belts), so the formation of cockles cannot be prevented. However, as soon as the cockles reach the region of segment 24, they are firmly attracted to the support surface 16. This is because the blower 28 associated with the plenum chamber in this segment is controlled to create a high vacuum pressure of about 3 kPa, for example. As a result, as shown in Figure 4, the height of the cockles 36 decreases from the upstream side to the downstream side of segment 24.

[0029] ​​​​​​​​​​​​​​The length of segment 24 in the conveying direction and the vacuum pressure in that segment are selected such that the cockles are completely removed at the transition between segments 24 and 26. Next, since sheet 18 mates with support surface 16 over its entire area, a relatively low vacuum pressure, e.g., 1 kPa, in the plenum chamber of segment 26 is sufficient to hold the sheet flat and prevent the reformation of cockles. Finally, when the corresponding area of sheet 18 leaves drying station 20, the paper is dried to such an extent that cockles are no longer formed. Thus, the zone above segment 24 can be considered a repair zone where a high suction pressure is applied to remove cockles 36. Since this repair zone is relatively short, the energy consumption of the associated blower 28 and the friction between the conveyor belt and the upper wall of the plenum chamber can be kept low. Next, when the sheet passes over the longer segment 26, the energy consumption and friction (of blower 30) are kept low due to the reduced vacuum pressure in this segment. Naturally, the above concept can be easily extended to designs having three or more consecutive suction zones where the suction pressures can be controlled independently of each other.

[0030]

[0031] ​​​​​​​​​​​​

Claims

1. a printing station; - arranged to convey the print medium on a transport path past said printing stations a media transport mechanism having a support surface for supporting the media; A feed mechanism. - placing the media against the support surface on a portion of the transport path downstream of the printing station; a vacuum device arranged to attract the media; A printer comprising: The vacuum device is divided into at least two segments in a direction along the transport path. In the two segments, the media is drawn with different non-zero suction pressures. the suction device having an upstream segment and a separate downstream segment; The suction pressure in the upstream segment is greater than the suction pressure in the downstream segment. Hey, printer.

2. 10. The printer of claim 1, which is an inkjet printer.

3. The media transport mechanism is adapted to transport the media through the printing stations. and a separate downstream conveying section in which the vacuum device is disposed.

3. The printer according to item 1 or 2.

4. 4. The process of claim 3, wherein the downstream conveying portion comprises a perforated endless conveyor belt. Rinta.

5. 5. The process according to claim 3 or 4, wherein a drying station is provided in the downstream conveying section. Rinta.

6. The ratio of the suction pressure in the upstream section to the suction pressure in the downstream section is 1.3:1 6. The printer according to claim 5, wherein the ratio of the ratio of the azimuth ...

7. 1. An inkjet printing method comprising: - moving a media sheet through a printing station and applying an image to said media sheet; and printing the - passing the media sheet through a drying station while it is supported on a support surface; conveying the media sheet having a printed image; - attracting the media sheet against the support surface by a suction device; Including, The attracting step may include applying high suction pressure to remove cockles from the sheet. a first sub-step of attracting the sheet against the support surface; applying a suction pressure lower than the suction pressure in step and a second substep of engaging and holding the ink on the support surface. Jet printing method.

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