JP7461709B2 - Printing System - Google Patents

Description

The present invention relates to a printing system.

In recent years, inkjet printing devices have become known that print by depositing ink onto a flat substrate such as paper or a steel strip in order to apply characters, figures, symbols, patterns, etc. to the surface of the substrate.

For example, on-demand inkjet printing devices are used primarily for printing on paper. In on-demand inkjet printing devices, for example, various actuators are used to simultaneously eject ink droplets from multiple ejection ports at the tip of the head, thereby printing onto the substrate.

Here, printing on a substrate such as a steel strip may be performed while the substrate is being transported at high speed (for example, 50 to 200 m/min). In this case, unlike when printing on paper, it becomes necessary to make the distance between the tip of the head and the substrate relatively long due to the variation in thickness between lots of the substrate and the occurrence of vibration in the thickness direction of the substrate. For example, when multiple steel strips of different thicknesses are transported at high speed on the same line and printed, the thickness of the steel strip varies between lots, such as 0.4 to 3.2 mm, and the vibration width in the thickness direction of the steel strip is expected to be several mm, so it becomes necessary to make the distance between the tip of the head and the substrate 10 mm or more. However, in an on-demand type inkjet printing device, the ejection force of the ink droplets is relatively small, so if the distance between the head and the substrate is relatively long, there is a risk that the ejection force of the ink droplets cannot be sufficiently secured.

In addition, when printing on a substrate such as a steel strip that is transported at high speed, the slower the speed at which the ink droplets ejected from the printing device come into contact with the substrate, the more likely the ink droplets will deform when they come into contact with the substrate, making the shape of the ink that adheres to the substrate more unstable. In on-demand inkjet printing devices, the particle size of the ejected ink droplets is relatively small, so the ejected ink droplets are more likely to decelerate due to air resistance. Therefore, the speed at which the ink droplets come into contact with the substrate tends to be slow, making the shape of the ink that adheres to the substrate more unstable.

Therefore, when printing on substrates such as steel strips that are transported at high speed, a printing device that ejects ink droplets with a relatively large ejection force and particle size is often used. For example, a continuous inkjet printing device can be used as such a printing device. In a continuous inkjet printing device, specifically, ink is ejected in droplets and the flight direction of the ink droplets is deflected in a direction that intersects with the transport direction of the substrate, thereby printing on the substrate. Technologies have been proposed to improve the printing accuracy when printing on such flat substrates that are transported at high speed.

For example, Patent Document 1 discloses a technology in which a continuous inkjet printing device uses multiple sensors to detect the transport speed of the print substrate, making it possible to print characters at a constant size in the transport direction even if the transport speed of the print substrate changes.

JP 2008-114471 A

However, the conventional technology exemplified in Patent Document 1 was not sufficient to improve the printing accuracy when printing on flat substrates transported at high speed.

Specifically, when the substrate is transported, the surrounding atmosphere moves with the substrate, forming an accompanying flow of the surrounding atmosphere on the surface of the substrate. Therefore, the ink droplets ejected from the tip of the head pass through the accompanying flow in the thickness direction of the substrate and reach the surface of the substrate.

Here, the greater the transport speed of the substrate, the greater the thickness and speed of the accompanying flow. Furthermore, the greater the transport speed of the substrate, the greater the need to increase the distance between the tip of the head and the substrate, and the more likely it is that the ejected ink droplets will decelerate before reaching the accompanying flow due to the effects of air resistance. Therefore, when printing on a flat substrate that is transported at high speed, the ink droplets ejected from the tip of the head are likely to be swept in the transport direction by the accompanying flow as they pass through the accompanying flow, due to the force exerted by the accompanying flow in the transport direction of the substrate. This means that the position at which the ink adheres on the surface of the substrate tends to become unstable.

The present invention has been made in consideration of the above problems, and the object of the present invention is to provide a new and improved printing system that can improve the printing accuracy when printing on flat substrates that are transported at high speed.

In order to solve the above problems, according to one aspect of the present invention, a printing system is provided that includes an inkjet printing device having a head that ejects ink droplets onto the surface of a flat substrate that is transported at high speed, and a suppression mechanism that suppresses an accompanying flow that is formed on the surface of the substrate.

The suppression mechanism may be disposed upstream of the head in the transport direction of the substrate and may include a contact member that contacts the accompanying flow.

The contact member may include a suction mechanism that sucks in the accompanying flow.

The suppression mechanism may include a partition member that partitions a space downstream of the head in the transport direction of the printing medium, and a pressurizing mechanism that pressurizes the space partitioned by the partition member.

As described above, the present invention makes it possible to improve the printing accuracy when printing on flat substrates that are transported at high speed.

1 is a schematic diagram showing a schematic configuration of a printing system according to a first embodiment of the present invention; FIG. 2 is a schematic diagram showing a schematic configuration of an inkjet printing apparatus according to the embodiment. A schematic diagram showing the state of ink droplets flying from the tip of the head to the surface of a steel strip in a printing system of a reference example, and the state of an accompanying flow formed on the surface of the steel strip. A schematic diagram showing the state of ink droplets flying from the tip of the head to the surface of the steel strip in the printing system according to the same embodiment, and the state of the accompanying flow formed on the surface of the steel strip. FIG. 11 is a schematic diagram showing a schematic configuration of a printing system according to a second embodiment of the present invention. A schematic diagram showing the state of ink droplets flying from the tip of the head to the surface of the steel strip in the printing system according to the same embodiment, and the state of the accompanying flow formed on the surface of the steel strip. FIG. 13 is a schematic diagram showing a schematic configuration of a printing system according to a third embodiment of the present invention. A schematic diagram showing the state of ink droplets flying from the tip of the head to the surface of the steel strip in the printing system according to the same embodiment, and the state of the accompanying flow formed on the surface of the steel strip. FIG. 13 is a schematic diagram showing a schematic configuration of a printing system according to a fourth embodiment of the present invention. FIG. 13 is a schematic diagram showing a schematic configuration of a printing system according to a fifth embodiment of the present invention.

The preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. Note that in this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals to avoid redundant description.

The printing systems 1, 2, 3, 4, and 5 according to the embodiments of the present invention described below are systems that print on a steel strip 70 by ejecting ink onto the steel strip 70, which is transported at high speed, thereby adhering the ink to the steel strip 70. The steel strip 70 is transported at high speed in the longitudinal direction, for example, by a drive roller. The steel strip 70 corresponds to an example of a flat-shaped printing substrate according to the present invention. In this specification, "high speed" specifically means a speed within the range of 50 to 200 m/min.

In the following, for ease of understanding, an example in which the number of inkjet printing devices 100 provided in the printing systems 1, 2, 3, 4, and 5 is one will be described, but the number of inkjet printing devices 100 provided in the printing systems 1, 2, 3, 4, and 5 is not limited to the above example and may be multiple. In that case, specifically, multiple inkjet printing devices 100 are arranged side by side along the width direction of the steel strip 70, and each inkjet printing device 100 prints the steel strip 70 at the installation position. For example, the number of inkjet printing devices 100 provided in the printing systems 1, 2, 3, 4, and 5 is determined based on the range that can be printed by each inkjet printing device 100 and the width of the steel strip 70. In addition, the arrangement of each inkjet printing device 100 is not particularly limited, and for example, the longitudinal positions of the steel strip 70 of each inkjet printing device 100 may be different from each other.

1. First embodiment
A printing system 1 according to a first embodiment of the present invention will be described with reference to FIGS.

[composition]
First, the overall configuration of a printing system 1 according to a first embodiment will be described with reference to FIGS.

Figure 1 is a schematic diagram showing the general configuration of the printing system 1. Note that in each drawing referred to in this specification, the width direction of the steel strip 70 is shown as the X direction, the longitudinal direction of the steel strip 70 (i.e., the conveying direction) is shown as the Y direction, and the thickness direction of the steel strip 70 perpendicular to the X and Y directions is shown as the Z direction.

As shown in FIG. 1, the printing system 1 includes an inkjet printing device 100 having a head 110 that ejects ink droplets 10 onto the surface of the steel strip 70, and a suppression mechanism 200 that suppresses the accompanying flow formed on the surface of the steel strip 70.

The inkjet printing device 100 is a printing device that prints on a substrate by ejecting ink in droplets from the tip of the head 110 onto the substrate and deflecting the flight direction of the ink droplets 10 in a direction intersecting the transport direction of the substrate. In the printing system 1, the inkjet printing device 100 ejects ink in droplets from the tip of the head 110 onto the steel strip 70 and prints on the steel strip 70 by deflecting the flight direction of the ink droplets 10 in the width direction X perpendicular to the transport direction Y of the steel strip 70. The distance D1 in the thickness direction Z between the tip of the head 110 and the steel strip 70 is set to a relatively long distance, for example, 10 to 30 mm, in order to suppress interference between the head 110 and the steel strip 70 due to thickness variations between lots of the steel strip 70 and vibrations of the steel strip 70 in the thickness direction Z. The configuration of the inkjet printing device 100 will be described in more detail below with reference to FIG. 2. FIG. 2 is a schematic diagram showing the general configuration of the inkjet printing device 100.

Specifically, as shown in FIG. 2, the inkjet printing device 100 includes a head 110, a tank 120, and a pump 130. Ink is stored in the tank 120, and the pump 130 supplies the ink from the tank 120 to the head 110. The ink supplied to the head 110 is ejected in droplet form from the tip of the head 110. The head 110 is disposed so that its tip faces the steel strip 70. FIG. 2 shows ink droplets 10 being ejected from the tip of the head 110. The particle size of the ink droplets 10 ejected from the tip of the head 110 is, for example, about 100 μm.

The head 110 includes, for example, an ink ejection device 111, a charging device 112, a pair of deflection plates 113, 113, and a gutter 114.

The ink ejection device 111 ejects the supplied ink as a liquid column by the pressure of the pump 130. The ejected liquid column splits into droplets 10 in the air immediately after ejection due to surface tension. An electric charge is added to the ink droplets 10 thus generated by the charging device 112. The charged droplets 10 are then deflected by an electric field generated by a pair of deflection plates 113, 113. The pair of deflection plates 113, 113 are arranged opposite each other, one of which is a negative electrode and the other is a positive electrode. The amount of deflection of the ink droplets 10 in the flight direction depends on the electric charge added by the charging device 112 and the magnitude of the electric field generated by the deflection plates 113, 113. The amount of deflection of the ink droplets 10 in the flight direction is controlled by controlling the electric charge and the magnitude of the electric field.

The ink droplets 10 ejected from the tip of the head 110 fly from the tip of the head 110 toward the surface of the steel strip 70, and then adhere to the surface of the steel strip 70 and dry. As a result, ink dots 11 are formed on the surface of the steel strip 70. At this time, for example, multiple dots 11 are formed on the steel strip 70 at intervals. Specifically, a row of dots 11 along the width direction X is formed by ejecting the ink droplets 10 while deflecting the flight direction to the width direction X. Such rows of dots 11 are formed sequentially along the transport direction Y (i.e., the longitudinal direction of the steel strip 70), thereby printing on the steel strip 70. In this way, the formation position of each dot 11 on the steel strip 70 can be controlled by controlling the amount of deflection of the flight direction of the ink droplets 10 and the timing of ejecting the ink droplets 10.

As shown in FIG. 1, the suppression mechanism 200 includes an abutment member 210.

The abutment member 210 is disposed upstream of the head 110 in the conveying direction Y of the steel strip 70, and as described below, comes into contact with the accompanying flow formed on the surface of the steel strip 70. Specifically, the abutment member 210 is a flat plate-shaped member extending on a plane perpendicular to the conveying direction Y of the steel strip 70 (i.e., a plane parallel to the X-Z plane). For example, the abutment member 210 has a rectangular parallelepiped cross-sectional shape in a cross section parallel to the Y-Z plane.

The dimensions and arrangement of the contact member 210 are appropriately set from the viewpoint of appropriately suppressing the accompanying flow formed on the surface of the steel strip 70. For example, the length W2 of the contact member 210 in the conveying direction Y is 1 to 10 mm. Also, for example, the length H2 of the contact member 210 in the thickness direction Z is 30 to 100 mm. Also, for example, the distance L2 between the contact member 210 and the head 110 in the conveying direction Y is 0 to 5 mm. Note that the length of the contact member 210 in the width direction X is approximately equal to the maximum width of the steel strip 70 (for example, 1500 mm if the width of the steel strip 70 is 800 to 1500 mm), taking into account the possibility that the width of the steel strip 70 may change depending on the lot.

Here, the distance D2 in the thickness direction Z between the contact member 210 and the steel strip 70 is set to a length that is at least shorter than the thickness of the accompanying flow formed on the surface of the steel strip 70. This allows the contact member 210 to be appropriately brought into contact with the accompanying flow. When the conveying speed of the steel strip 70 is 50 to 200 m/min as described above, the thickness of the accompanying flow is approximately 8 to 14 mm. Therefore, the distance D2 in the thickness direction Z between the contact member 210 and the steel strip 70 is set to a length that is shorter than 8 mm, for example. In addition, it is preferable that the distance D2 in the thickness direction Z between the contact member 210 and the steel strip 70 is set to a length that can suppress contact between the contact member 210 and the steel strip 70.

[Action]
Next, the operation of the printing system 1 according to the first embodiment will be described with reference to FIGS.

First, for ease of understanding, the behavior of ink droplets 10 ejected from the tip of the head 110 in the printing system 9 according to the reference example will be described with reference to FIG. 3.

Figure 3 is a schematic diagram showing the state of ink droplets 10 flying from the tip of the head 110 to the surface of the steel strip 70 in a printing system 9 according to a reference example, and the state of an accompanying flow 80 formed on the surface of the steel strip 70. In Figure 3, the thick arrows indicate the flow of the surrounding atmosphere in the accompanying flow 80. Note that in Figures 4, 6, and 8, which will be referred to later, the flow of the surrounding atmosphere in the accompanying flow 80 is also indicated by thick arrows, as in Figure 3.

The printing system 9 of the reference example differs from the printing system 1 described above in that the suppression mechanism 200 is not provided.

As shown in FIG. 3, an accompanying flow 80 that moves along with the steel strip 70 is formed on the surface of the steel strip 70. The thickness T1 (i.e., the length in the thickness direction Z) of the accompanying flow 80 increases as the conveying speed of the steel strip 70 increases. Therefore, when the steel strip 70 is conveyed at high speed, the thickness T1 of the accompanying flow 80 becomes relatively thick, specifically, about 8 to 14 mm as described above. The accompanying flow 80 corresponds to the boundary layer in the flow of the surrounding atmosphere near the surface of the steel strip 70, and for example, the 99% boundary layer thickness can be applied as the thickness T1 of the accompanying flow 80. The speed of the accompanying flow 80 in the conveying direction Y increases as it approaches the steel strip 70.

The ink droplets 10 ejected from the tip of the head 110 pass through the accompanying flow 80 in the thickness direction Z and reach the surface of the steel strip 70. Here, as the ink droplets 10 ejected from the tip of the head 110 pass through the accompanying flow 80, they are subjected to a force in the transport direction Y of the steel strip 70 by the accompanying flow 80 and are carried in the transport direction Y toward the steel strip 70, as shown in FIG. 3.

When the steel strip 70 is transported at high speed, the thickness T1 and speed of the accompanying flow 80 become relatively large. Furthermore, when the steel strip 70 is transported at high speed, the distance in the thickness direction Z between the tip of the head 110 and the steel strip 70 becomes relatively long, so the ejected ink droplets 10 tend to decelerate before reaching the accompanying flow 80 due to the influence of air resistance. Therefore, when printing on a steel strip 70 transported at high speed, the ink droplets 10 ejected from the tip of the head 110 tend to be carried by the accompanying flow 80 in the transport direction Y of the steel strip 70 as they pass through the accompanying flow 80. Therefore, the position at which the ink adheres on the surface of the steel strip 70 tends to become unstable.

When the steel strip 70 is transported at high speed, the thickness T1 of the accompanying flow 80 increases, and the time it takes for the droplet 10 to pass through the accompanying flow 80 becomes longer than when the transport speed of the steel strip 70 is low (for example, slower than 50 m/min), for example, about 3 to 10 msec. Also, as described above, when the thickness T1 of the accompanying flow 80 is about 8 to 14 mm and the diameter of the ink droplet 10 is about 100 μm, the ink droplet 10 ejected from the tip of the head 110 will travel a distance in the accompanying flow 80 that is several tens of times the diameter of the droplet 10. This also shows that the ink droplet 10 is easily carried by the accompanying flow 80 in the transport direction Y of the steel strip 70.

Next, referring to FIG. 4, we will explain the behavior of the ink droplets 10 ejected from the tip of the head 110 in the printing system 1 according to this embodiment.

Figure 4 is a schematic diagram showing the state of an ink droplet 10 flying from the tip of the head 110 to the surface of the steel strip 70 in the printing system 1 according to this embodiment, and the state of an accompanying flow 80 formed on the surface of the steel strip 70.

In the printing system 1, the contact member 210 of the suppression mechanism 200 is disposed upstream of the head 110 in the transport direction Y of the steel strip 70. As described above, the distance D2 in the thickness direction Z between the contact member 210 and the steel strip 70 is set to a length that is at least shorter than the thickness T1 of the accompanying flow 80 (for example, a length shorter than 8 mm). Therefore, as shown in FIG. 4, the end of the contact member 210 on the steel strip 70 side contacts the accompanying flow 80. As a result, the surface side portion of the accompanying flow 80 (the portion opposite the steel strip 70) can be blocked by the contact member 210, so that the growth of the accompanying flow 80 between the head 110 and the steel strip 70 can be inhibited, and the thickness and speed of the accompanying flow 80 can be reduced.

As described above, according to the printing system 1, the suppression mechanism 200 including the contact member 210 is provided, which inhibits the growth of the accompanying flow 80 between the head 110 and the steel strip 70, thereby reducing the flow rate and thickness of the accompanying flow 80. As a result, as shown in FIG. 4, it is possible to suppress the ink droplets 10 ejected from the tip of the head 110 from being carried in the transport direction Y of the steel strip 70 by the accompanying flow 80. Therefore, it is possible to stabilize the position where the ink adheres on the surface of the steel strip 70. This makes it possible to improve the printing accuracy when printing on a steel strip 70 transported at high speed.

2. Second embodiment
A printing system 2 according to a second embodiment of the present invention will be described with reference to Figures 5 and 6. The printing system 2 according to this embodiment is different from the printing system 1 described above in terms of the shape of the contact member.

[composition]
First, the configuration of a printing system 2 according to the second embodiment will be described with reference to FIG.

Figure 5 is a schematic diagram showing the general configuration of the printing system 2.

As shown in FIG. 5, unlike the printing system 1 described above, the printing system 2 is provided with a suppression mechanism 300 as a suppression mechanism for suppressing the accompanying flow formed on the surface of the steel strip 70.

As shown in FIG. 5, the suppression mechanism 300 includes an abutment member 310.

The contact member 310, like the contact member 210 in the printing system 1 described above, is positioned upstream of the head 110 in the transport direction Y of the steel strip 70, and contacts the accompanying flow 80 formed on the surface of the steel strip 70.

In the second embodiment, the surface 311 of the contact member 310 on the upstream side of the transport direction Y (i.e., the side opposite the head 110) is inclined in a direction toward the downstream side of the transport direction Y as it moves away from the steel strip 70, unlike the contact member 210 in the printing system 1 described above. Specifically, in a cross section parallel to the Y-Z plane, the contact member 310 has a right-angled triangular cross section that includes the side corresponding to the surface 311 as the hypotenuse, and is formed to extend in the width direction X of the steel strip 70.

The dimensions and arrangement of the contact member 310 are appropriately set from the viewpoint of appropriately suppressing the accompanying flow 80 formed on the surface of the steel strip 70, similar to the contact member 210 in the printing system 1 described above. For example, the length W3 of the contact member 310 in the transport direction Y is 5 to 10 mm. Also, for example, the length H3 of the contact member 310 in the thickness direction Z is 30 to 50 mm. Also, for example, the distance L3 between the contact member 310 and the head 110 in the transport direction Y is 0 to 5 mm. Note that the length of the contact member 310 in the width direction X is approximately equal to the maximum width of the steel strip 70 (for example, 1500 mm if the width of the steel strip 70 is 800 to 1500 mm), taking into account the possibility that the width of the steel strip 70 may change depending on the lot.

The distance D3 in the thickness direction Z between the contact member 310 and the steel strip 70 is set to a length (e.g., a length shorter than 8 mm) that is at least shorter than the thickness T1 of the accompanying flow 80 formed on the surface of the steel strip 70, similar to the contact member 210 in the printing system 1 described above. This allows the contact member 310 to be appropriately brought into contact with the accompanying flow 80. In addition, it is preferable that the distance D3 in the thickness direction Z between the contact member 310 and the steel strip 70 be set to a length that can suppress contact between the contact member 310 and the steel strip 70.

[Action]
Next, the operation of the printing system 2 according to the second embodiment will be described with reference to FIG.

Figure 6 is a schematic diagram showing the state of an ink droplet 10 flying from the tip of the head 110 to the surface of the steel strip 70 in the printing system 2 according to this embodiment, and the state of an accompanying flow 80 formed on the surface of the steel strip 70.

In the printing system 2, as shown in FIG. 6, the end of the contact member 310 on the steel strip 70 side contacts the accompanying flow 80. Here, as described above, the surface 311 on the upstream side of the contact member 310 in the conveying direction Y is inclined toward the downstream side of the conveying direction Y as it moves away from the steel strip 70. Therefore, as shown in FIG. 6, the surface side portion of the accompanying flow 80 (the portion opposite the steel strip 70) can be smoothly guided in the direction away from the steel strip 70 along the surface 311. FIG. 6 shows the flow F30 of the surface side portion of the accompanying flow 80 guided along the surface 311. Therefore, since the surface side portion of the accompanying flow 80 (the portion opposite the steel strip 70) can be more effectively blocked by the contact member 310, the growth of the accompanying flow 80 between the head 110 and the steel strip 70 can be more effectively inhibited, and the thickness and speed of the accompanying flow 80 can be more effectively reduced.

As described above, according to the printing system 2, the upstream surface 311 of the contact member 310 in the transport direction Y is inclined toward the downstream side of the transport direction Y as it moves away from the steel strip 70, which more effectively inhibits the growth of the accompanying flow 80 between the head 110 and the steel strip 70, and more effectively reduces the flow rate and thickness of the accompanying flow 80. This more effectively prevents the ink droplets 10 ejected from the tip of the head 110 from being carried in the transport direction Y of the steel strip 70 by the accompanying flow 80. Therefore, the position where the ink adheres on the surface of the steel strip 70 can be more effectively stabilized. This more effectively improves the printing accuracy when printing on a steel strip 70 transported at high speed.

<3. Third embodiment>
A printing system 3 according to a third embodiment of the present invention will be described with reference to Fig. 7 and Fig. 8. The printing system 3 according to this embodiment is different from the printing systems 1 and 2 described above in terms of the shape of the contact members.

[composition]
First, the configuration of a printing system 3 according to a third embodiment will be described with reference to FIG.

Figure 7 is a schematic diagram showing the general configuration of the printing system 3.

As shown in FIG. 7, unlike the printing system 1 described above, the printing system 3 is equipped with a suppression mechanism 400 as a suppression mechanism for suppressing the accompanying flow formed on the surface of the steel strip 70.

As shown in FIG. 7, the suppression mechanism 400 includes an abutment member 410.

The contact member 410, like the contact member 210 in the printing system 1 described above, is positioned upstream of the head 110 in the transport direction Y of the steel strip 70 and contacts the accompanying flow 80 formed on the surface of the steel strip 70.

In the third embodiment, the surface 411 of the contact member 410 on the upstream side of the transport direction Y (i.e., the side opposite the head 110) is inclined toward the downstream side of the transport direction Y as it moves away from the steel strip 70, similar to the contact member 310 in the printing system 2 described above.

Furthermore, in the third embodiment, the surface 412 of the contact member 410 facing the steel strip 70 is inclined in a direction away from the steel strip 70 as it moves downstream in the transport direction Y, unlike the contact member 210 in the printing system 1 and the contact member 310 in the printing system 2 described above. Specifically, in a cross section parallel to the Y-Z plane, the contact member 410 has a triangular cross-sectional shape that includes a side corresponding to the above surface 411, a side corresponding to the above surface 412, and a side along the thickness direction Z that corresponds to the surface on the head 110 side, and is formed to extend in the width direction X of the steel strip 70.

The dimensions and arrangement of the contact member 410 are appropriately set from the viewpoint of appropriately suppressing the accompanying flow 80 formed on the surface of the steel strip 70, similar to the contact member 210 in the printing system 1 described above. For example, the length W4 of the contact member 410 in the transport direction Y is 5 to 10 mm. Also, for example, the length H4 of the contact member 410 in the thickness direction Z is 30 to 50 mm. Also, for example, the distance L4 between the contact member 410 and the head 110 in the transport direction Y is 0 to 5 mm. Note that the length of the contact member 410 in the width direction X is approximately equal to the maximum width of the steel strip 70 (for example, 1500 mm if the width of the steel strip 70 is 800 to 1500 mm), taking into account the possibility that the width of the steel strip 70 may change depending on the lot.

The distance D4 in the thickness direction Z between the contact member 410 and the steel strip 70 (specifically, the distance between the edge 413 formed by the surfaces 411 and 412 of the contact member 410 and the steel strip 70) is set to a length shorter than at least the thickness T1 of the accompanying flow 80 formed on the surface of the steel strip 70 (e.g., a length shorter than 8 mm), similar to the contact member 210 in the printing system 1 described above. This allows the contact member 410 to be appropriately brought into contact with the accompanying flow. In addition, it is preferable that the distance D4 in the thickness direction Z between the contact member 410 and the steel strip 70 be set to a length sufficient to suppress contact between the contact member 410 and the steel strip 70.

[Action]
Next, the operation of the printing system 3 according to the third embodiment will be described with reference to FIG.

Figure 6 is a schematic diagram showing the state of an ink droplet 10 flying from the tip of the head 110 to the surface of the steel strip 70 in the printing system 3 according to this embodiment, and the state of an accompanying flow 80 formed on the surface of the steel strip 70.

In the printing system 3, as shown in FIG. 8, the end of the contact member 310 on the steel strip 70 side (specifically, the ridge 413 formed by the surface 411 and the surface 412) contacts the accompanying flow 80. Here, as described above, the surface 411 on the upstream side of the contact member 410 in the conveying direction Y is inclined in a direction toward the downstream side of the conveying direction Y as it moves away from the steel strip 70. Therefore, as shown in FIG. 8, the surface side portion of the accompanying flow 80 (the portion opposite the steel strip 70) can be smoothly guided along the surface 411 in a direction away from the steel strip 70.

However, when a contact member is provided to contact the accompanying flow 80, a vortex may occur in the portion of the accompanying flow 80 where it finishes passing between the contact member and the steel strip 70. Because the distance between the contact member and the head 110 is relatively short, such a vortex may disrupt the flight direction of the ink droplets 10 flying between the head 110 and the steel strip 70.

Here, in the printing system 3, as described above, the surface 412 of the contact member 410 on the steel strip 70 side is inclined in a direction away from the steel strip 70 as it moves downstream in the conveying direction Y. Therefore, the distance in the thickness direction Z between the surface 412 on the steel strip 70 side of the contact member 410 and the steel strip 70 becomes longer as it moves downstream in the conveying direction Y. Therefore, as shown in FIG. 8, a part of the accompanying flow 80 that has passed between the ridge portion 413 of the contact member 410 and the steel strip 70 can be guided gently away from the steel strip 70 along the surface 412. This makes it possible to suppress the generation of vortexes in the part of the accompanying flow 80 that has finished passing between the contact member 410 and the steel strip 70.

As described above, according to the printing system 3, the surface 412 of the contact member 410 facing the steel strip 70 is inclined away from the steel strip 70 as it moves downstream in the transport direction Y, thereby preventing vortexes from occurring in the accompanying flow 80 at the portion where it finishes passing between the contact member 410 and the steel strip 70. This prevents the flight direction of the ink droplets 10 flying between the head 110 and the steel strip 70 from being disturbed by vortexes. Therefore, the position where the ink adheres on the surface of the steel strip 70 can be more effectively stabilized. This makes it possible to more effectively improve the printing accuracy when printing on a steel strip 70 transported at high speed.

<4. Fourth embodiment>
A printing system 4 according to a fourth embodiment of the present invention will be described with reference to Fig. 9. The printing system 4 according to this embodiment is different from the printing system 1 described above in the configuration of the contact member.

[composition]
First, the configuration of a printing system 4 according to a fourth embodiment will be described with reference to FIG.

Figure 9 is a schematic diagram showing the general configuration of the printing system 4.

As shown in FIG. 9, unlike the printing system 1 described above, the printing system 4 is equipped with a suppression mechanism 500 as a suppression mechanism for suppressing the accompanying flow formed on the surface of the steel strip 70.

As shown in FIG. 9, the suppression mechanism 500 includes an abutment member 510.

The abutment member 510, like the abutment member 210 in the printing system 1 described above, is positioned upstream of the head 110 in the transport direction Y of the steel strip 70, and abuts against the accompanying flow 80 formed on the surface of the steel strip 70. Specifically, the abutment member 510 is a flat plate-shaped member extending on a plane perpendicular to the transport direction Y of the steel strip 70 (i.e., a plane parallel to the X-Z plane). For example, the abutment member 510 has a rectangular parallelepiped cross-sectional shape in a cross section parallel to the Y-Z plane.

The dimensions and arrangement of the contact member 510 are appropriately set from the viewpoint of appropriately suppressing the accompanying flow 80 formed on the surface of the steel strip 70, similar to the contact member 210 in the printing system 1 described above. For example, the length W5 of the contact member 510 in the transport direction Y is 1 to 10 mm. Also, for example, the length H5 of the contact member 510 in the thickness direction Z is 30 to 100 mm. Also, for example, the distance L5 between the contact member 510 and the head 110 in the transport direction Y is 0 to 5 mm. Note that the length of the contact member 510 in the width direction X is approximately equal to the maximum width of the steel strip 70 (for example, 1500 mm if the width of the steel strip 70 is 800 to 1500 mm), taking into account the possibility that the width of the steel strip 70 may change depending on the lot.

The distance D5 in the thickness direction Z between the contact member 510 and the steel strip 70 is set to a length (e.g., a length shorter than 8 mm) that is at least shorter than the thickness T1 of the accompanying flow 80 formed on the surface of the steel strip 70, similar to the contact member 210 in the printing system 1 described above. This allows the contact member 510 to be appropriately brought into contact with the accompanying flow 80. In addition, it is preferable that the distance D5 in the thickness direction Z between the contact member 510 and the steel strip 70 be set to a length that can suppress contact between the contact member 510 and the steel strip 70.

In the fourth embodiment, the abutment member 510 includes a suction mechanism 511 that sucks in the accompanying flow 80.

Specifically, the suction mechanism 511 has a suction port 511a formed at the end of the contact member 510 on the steel strip 70 side, and sucks the accompanying flow 80 from the suction port 511a into the inside of the contact member 510 by a pump, fan, or the like (not shown). The suction port 511a is formed, for example, in a slit shape extending in the width direction X of the steel strip 70 at the end of the contact member 510 on the steel strip 70 side. Figure 9 shows the flow F50 of the surface side portion of the accompanying flow 80 that is sucked into the inside of the contact member 510 via the suction port 511a.

[Action]
Next, the operation of the printing system 4 according to the fourth embodiment will be described.

In the printing system 4, as described above, the end of the contact member 510 on the steel strip 70 side contacts the accompanying flow 80. This allows the surface side portion of the accompanying flow 80 (the portion opposite the steel strip 70) to be blocked by the contact member 510. Furthermore, in the printing system 4, the contact member 510 includes a suction mechanism 511 that sucks the accompanying flow 80 as described above. This allows the thickness and speed of the accompanying flow 80 to be further reduced upstream of the head 110 in the conveying direction of the steel strip 70. Therefore, the growth of the accompanying flow 80 between the head 110 and the steel strip 70 can be more effectively inhibited, and the thickness and speed of the accompanying flow 80 can be more effectively reduced.

In the printing system 4, it is preferable to adjust the suction force of the suction mechanism 511 so that the absolute value of the pressure difference, which is the value obtained by subtracting the downstream pressure from the upstream pressure between the head 110 and the steel strip 70, is equal to or less than a target value (e.g., 5 kPa). For example, if the suction force of the suction mechanism 511 is excessively small, the pressure difference takes a positive value having an absolute value exceeding the target value. On the other hand, if the suction force of the suction mechanism 511 is excessively large, the pressure difference takes a negative value having an absolute value exceeding the target value. Therefore, by adjusting the suction force of the suction mechanism 511 as described above, the suction force of the suction mechanism 511 can be optimized so that the thickness and speed of the accompanying flow 80 can be appropriately reduced while preventing the suction mechanism 511 from disturbing the flight direction of the flying ink droplets 10.

As described above, according to the printing system 4, the contact member 510 includes a suction mechanism 511 that sucks in the accompanying flow 80, so that the growth of the accompanying flow 80 between the head 110 and the steel strip 70 can be more effectively inhibited, and the flow rate and thickness of the accompanying flow 80 can be more effectively reduced. This makes it possible to more effectively prevent the ink droplets 10 ejected from the tip of the head 110 from being carried in the transport direction Y of the steel strip 70 by the accompanying flow 80. Therefore, the position where the ink adheres on the surface of the steel strip 70 can be more effectively stabilized. This makes it possible to more effectively improve the printing accuracy when printing on a steel strip 70 that is transported at high speed.

<5. Fifth embodiment>
A printing system 5 according to a fifth embodiment of the present invention will be described with reference to Fig. 10. The printing system 5 according to this embodiment is different from the printing system 1 described above in the configuration of the suppression mechanism.

[composition]
First, the configuration of a printing system 5 according to the fifth embodiment will be described with reference to FIG.

Figure 10 is a schematic diagram showing the general configuration of the printing system 5.

As shown in FIG. 10, unlike the printing system 1 described above, the printing system 5 is equipped with a suppression mechanism 600 as a suppression mechanism for suppressing the accompanying flow formed on the surface of the steel strip 70.

As shown in FIG. 10, the suppression mechanism 600 includes a partition member 610 and a pressure mechanism 620.

The partitioning member 610 partitions the space 60 downstream of the head 110 in the conveying direction Y of the steel strip 70. Specifically, the partitioning member 610 partitions the space 60 having an approximately rectangular parallelepiped shape extending downstream along the conveying direction Y from the downstream end of the head 110. The length in the width direction X of the space 60 partitioned by the partitioning member 610 is approximately equal to the maximum width of the steel strip 70 (for example, 1500 mm if the width of the steel strip 70 is 800 to 1500 mm), taking into account the possibility that the width of the steel strip 70 may change depending on the lot. The partitioning member 610 is a member having an approximately hollow rectangular tube shape with an opening at the end on the steel strip 70 side, and is fixed to the downstream end of the head 110. The shape of the partitioning member 610 is such that it does not interfere with the space between the tip of the head 110 and the steel strip 70 through which the ink droplets 10 fly. Additionally, the partition member 610 may be formed by joining multiple flat plate-shaped members, or by bending a single flat plate-shaped member.

The shape, dimensions and arrangement of the partitioning member 610 are appropriately set from the viewpoint of properly partitioning the space 60 downstream of the head 110 in the conveying direction Y of the steel strip 70. For example, it is preferable that the distance D6 in the thickness direction Z between the partitioning member 610 and the steel strip 70 be set to a length sufficient to prevent contact between the partitioning member 610 and the steel strip 70.

The pressurizing mechanism 620 pressurizes the space 60 partitioned by the partition member 610. Specifically, the pressurizing mechanism 620 is connected to the partition member 610 and has a supply port 621 that supplies gas (specifically, air or an inert gas such as nitrogen) to the space 60 inside the partition member 610, and supplies the gas from the supply port 621 to the space 60 by a pump or fan (not shown). This increases the pressure in the space 60 partitioned by the partition member 610. Note that FIG. 10 shows an example in which the pressurizing mechanism 620 is connected to a part of the partition member 610 opposite the steel band 70, but the pressurizing mechanism 620 may be connected to another part of the partition member 610.

[Action]
Next, the operation of the printing system 5 according to the fifth embodiment will be described.

In the printing system 5, as described above, the space 60 downstream of the head 110 in the conveying direction Y of the steel strip 70 is partitioned by the partition member 610, and the space 60 partitioned by the partition member 610 is pressurized by the pressurizing mechanism 620. This allows a gas flow from the space 60 downstream of the head 110 toward the upstream side. Specifically, a gas flow can be generated from the opening at the end of the space 60 on the steel strip 70 side toward the space between the head 110 and the steel strip 70. FIG. 10 shows such a gas flow F60. This allows a gas flow in the opposite direction to the accompanying flow 80 to be generated near the surface of the steel strip 70, thereby inhibiting the growth of the accompanying flow 80 between the head 110 and the steel strip 70, and reducing the thickness and speed of the accompanying flow 80.

As described above, according to the printing system 5, the space 60 downstream of the head 110 in the transport direction Y of the steel strip 70 is partitioned by the partition member 610, and the space 60 partitioned by the partition member 610 is pressurized by the pressure mechanism 620, thereby inhibiting the growth of the accompanying flow 80 between the head 110 and the steel strip 70 and reducing the flow rate and thickness of the accompanying flow 80. This makes it possible to suppress the ink droplets 10 ejected from the tip of the head 110 from being carried in the transport direction Y of the steel strip 70 by the accompanying flow 80. Therefore, the position where the ink adheres on the surface of the steel strip 70 can be stabilized. This makes it possible to improve the printing accuracy when printing on a steel strip 70 transported at high speed.

The results of tests conducted to investigate the effect of improving printing accuracy when a suppression mechanism is provided to suppress the accompanying flow formed on the surface of the steel strip 70 in a printing system equipped with an inkjet printing device, such as the above-mentioned printing systems 1, 2, 3, 4, and 5, are described below.

In this test, tests were conducted under various different test conditions for a comparative example in which a suppression mechanism was not provided in the printing system, and for each of Examples 1 to 5 in which a suppression mechanism was provided in the printing system, to evaluate the printing accuracy. In each of Examples 1 to 5, the suppression mechanisms 200, 300, 400, 500, and 600 described above were used as the suppression mechanisms provided in the printing system.

Specifically, in this test, printing was performed on the steel strip 70 so that 32 rows of dots, each row having 32 ink dots aligned along the width direction X of the steel strip 70, were formed along the transport direction Y (i.e., the longitudinal direction of the steel strip 70). The ink dots formed on the steel strip 70 were approximately circular with a diameter of approximately 300 μm. The printing accuracy was evaluated based on the deviation dot number ratio, which is the ratio of the number of dots whose center positions were deviated from the target position by 120 μm or more out of the 1,024 ink dots formed on the steel strip 70.

Specifically, if the misaligned dot count ratio was between 0% and 10%, the print accuracy was evaluated as "◎". If the misaligned dot count ratio was between more than 10% and 20% or less, the print accuracy was evaluated as "○". If the misaligned dot count ratio was between more than 20% and 30% or less, the print accuracy was evaluated as "△". If the misaligned dot count ratio was over 30%, the print accuracy was evaluated as "×". The marks indicating each evaluation indicate increasing print accuracy in the order of "×", "△", "○", and "◎".

Specific test conditions for the comparative example and each embodiment were variously changed for the conveying speed of the steel strip 70 and the distance D1 in the thickness direction Z between the tip of the head 110 and the steel strip 70.

In addition, in Example 1 in which the suppression mechanism 200 is provided, the test conditions further include variously changing the distance D2 between the contact member 210 and the steel strip 70 in the thickness direction Z, the length H2 of the contact member 210 in the thickness direction Z, and the distance L2 between the contact member 210 and the head 110 in the conveying direction Y.

In Example 2, in which the suppression mechanism 300 is provided, the test conditions further include various changes to the distance D3 between the contact member 310 and the steel strip 70 in the thickness direction Z and the distance L3 between the contact member 310 and the head 110 in the conveying direction Y. In Example 2, the length H3 of the contact member 310 in the thickness direction Z was set to 30 mm.

In Example 3, in which the suppression mechanism 400 is provided, the test conditions further include various changes to the distance D4 between the contact member 410 and the steel strip 70 in the thickness direction Z and the distance L4 between the contact member 410 and the head 110 in the conveying direction Y. In Example 3, the length H4 of the contact member 410 in the thickness direction Z was set to 30 mm. In Example 3, the inclination angle of the surface 412 of the contact member 410 facing the steel strip 70 relative to the steel strip 70 (i.e., the angle between the surface 412 and the steel strip 70) was set to 60°.

In Example 4, in which the suppression mechanism 500 is provided, the test conditions further include various changes to the distance D5 in the thickness direction Z between the contact member 510 and the steel strip 70 and the differential pressure, which is the value obtained by subtracting the downstream pressure from the upstream pressure between the head 110 and the steel strip 70. In Example 4, the test conditions further include various changes to the length H5 in the thickness direction Z of the contact member 510 and the distance L5 in the conveying direction Y between the contact member 510 and the head 110, which were set to 30 mm and 0 mm, respectively.

In Example 5, in which the suppression mechanism 600 is provided, the test conditions further include various changes to the distance D6 between the partition member 610 and the steel strip 70 in the thickness direction Z and the internal pressure of the space 60 pressurized by the pressure mechanism 620.

The results of this test are shown in Tables 1 to 6. Table 1 shows the evaluation results of the print accuracy for a comparative example in which the printing system is not provided with a suppression mechanism. Table 2 shows the evaluation results of the print accuracy for Example 1 in which suppression mechanism 200 is provided as the suppression mechanism. Table 3 shows the evaluation results of the print accuracy for Example 2 in which suppression mechanism 300 is provided as the suppression mechanism. Table 4 shows the evaluation results of the print accuracy for Example 3 in which suppression mechanism 400 is provided as the suppression mechanism. Table 5 shows the evaluation results of the print accuracy for Example 4 in which suppression mechanism 500 is provided as the suppression mechanism. Table 6 shows the evaluation results of the print accuracy for Example 5 in which suppression mechanism 600 is provided as the suppression mechanism.

Referring to Table 1, it can be seen that in the comparative example in which the suppression mechanism is not provided, the evaluation is "○" when the conveying speed is 25 m/min, which is lower than 50 m/min, but the evaluation is "△" or "×" when the conveying speed is 50 m/min or more. On the other hand, referring to Tables 2 to 6, it can be seen that in all of the examples in which the suppression mechanism is provided, the evaluation is "○" or "◎" when the conveying speed is 50 m/min or more.

The above results confirm that by providing a suppression mechanism that suppresses the accompanying flow that forms on the surface of the steel strip 70 in a printing system equipped with an inkjet printing device, it is possible to improve the printing accuracy when printing on the steel strip 70 that is transported at high speed.

Also, referring to Tables 2 and 3, it can be seen that Example 2, in which the suppression mechanism 300 including the abutment member 310, which has an inclined surface 311 on the upstream side in the conveying direction Y, unlike the flat abutment member 210, is provided, tends to be rated higher than Example 1, in which the suppression mechanism 200 including the abutment member 210 is provided. For example, under common conditions of a conveying speed of 50 m/min, a distance D1 between the head 110 and the steel strip 70 of 10 mm, and a distance D2 (D3) between the abutment member 210 (310) and the steel strip 70 of 3 mm, Example 1 is rated as "○", while Example 2 is rated as "◎".

The above results confirm that when using a suppression mechanism including a contact member, the printing accuracy can be further improved when printing on a steel strip 70 transported at high speed by inclining the upstream surface of the contact member in the transport direction Y toward the downstream side of the transport direction Y as it moves away from the steel strip 70.

Also, referring to Tables 3 and 4, it can be seen that Example 3, in which a suppression mechanism 400 including an abutment member 410 with an inclined surface 412 on the steel strip 70 side, unlike the abutment member 310, is provided, tends to be rated higher than Example 2, in which a suppression mechanism 300 including an abutment member 310 is provided. For example, under common conditions of a conveying speed of 50 m/min, a distance D1 between the head 110 and the steel strip 70 of 30 mm, and a distance D3 (D4) between the abutment member 310 (410) and the steel strip 70 of 1 mm, Example 2 is rated as "○", while Example 3 is rated as "◎".

The above results confirm that when using a suppression mechanism including a contact member, the printing accuracy of printing on a steel strip 70 transported at high speed can be further improved by inclining the surface of the contact member facing the steel strip 70 in a direction away from the steel strip 70 as it moves downstream in the transport direction Y.

Also, referring to Tables 2 and 5, it can be seen that Example 4, in which a suppression mechanism 500 including a contact member 510 having a suction mechanism 511 that, unlike the contact member 210, sucks in the accompanying flow, is provided, tends to be rated higher than Example 1, in which a suppression mechanism 200 including a contact member 210 is provided. For example, under the common conditions of a conveying speed of 100 m/min and a distance D1 between the head 110 and the steel strip 70 of 10 mm, Example 1 is rated as "○", while Example 4 is rated as "◎".

The above results confirm that when using a suppression mechanism that includes a contact member, the printing accuracy can be further improved when printing on a steel strip 70 transported at high speed by providing a suction mechanism that sucks in the accompanying flow to the contact member.

Also, referring to Table 6, it can be seen that in Example 5, in which a suppression mechanism 600 including a partition member 610 and a pressure mechanism 620 is provided, the evaluation is "○" or "◎" under the condition that the conveying speed is 50 m/min or more, similar to Examples 1 to 4, which are examples in which a suppression mechanism including an abutment member is provided.

From the above results, it was confirmed that even when the suppression mechanism 600 including the partition member 610 and the pressure mechanism 620 is used as a suppression mechanism for suppressing the accompanying flow, it is possible to improve the printing accuracy when printing on the steel strip 70 transported at high speed, just as in the case of using a suppression mechanism including a contact member.

<6. Conclusion>
As described above, the printing system according to each embodiment of the present invention includes an inkjet printing device having a head that ejects ink droplets onto the surface of a flat substrate transported at high speed, and a suppression mechanism that suppresses an accompanying flow formed on the surface of the substrate. This inhibits the growth of an accompanying flow between the head of the inkjet printing device and the substrate, and reduces the flow speed and thickness of the accompanying flow. This prevents ink droplets ejected from the tip of the head from being carried in the transport direction of the substrate by the accompanying flow. This makes it possible to stabilize the position where the ink adheres on the surface of the substrate. This makes it possible to improve the printing accuracy when printing on a substrate transported at high speed.

The above describes in detail preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to these examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified examples or application examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

For example, the shape of each component in the suppression mechanism is not limited to the above example. Specifically, the shape of the abutting member provided in the suppression mechanism is not limited to the shape of the abutting members 210, 310, 410, 510 described above, and may have, for example, a polygonal, circular, or elliptical shape or a combination thereof in a cross section parallel to the Y-Z plane, and may be asymmetric in the width direction X of the steel strip 70. In addition, the shape of the partition member provided in the suppression mechanism is not limited to the shape of the partition member 610 described above, and may have, for example, an opening over the entire end on the steel strip 70 side, an opening in part of the end on the steel strip 70 side, may be an approximately hollow cylindrical shape, and may be asymmetric in the width direction X of the steel strip 70.

1, 2, 3, 4, 5 Printing system 70 Steel strip 80 Entrained flow 100 Inkjet printing device 110 Head 111 Ink ejection device 112 Charging device 113 Deflection plate 114 Gutter 120 Tank 130 Pump 200, 300, 400, 500, 600 Suppression mechanism 210, 310, 410, 510 Abutment member 511 Suction mechanism 610 Partition member 620 Pressurization mechanism

Claims (4)

a continuous inkjet printing device having a head for ejecting ink droplets for the purpose of applying characters, figures, symbols or patterns to a surface of a steel plate, which is a flat printing substrate transported at 50 to 200 m/min;
A suppression mechanism for suppressing an entrained flow formed on the surface of the printing substrate;
Equipped with
the suppression mechanism is disposed upstream of the head in a transport direction of the printing medium, and includes a contact member that contacts the accompanying flow,
A distance between the inkjet printing device and the contact member in a conveying direction of the printing medium is 0 to 5 mm;
A distance between the tip of the head and the printing material in a thickness direction of the printing material is 10 to 30 mm,
A distance between the contact member and the printing material in a thickness direction of the printing material is shorter than 8 mm.
Printing system. The contact member includes a suction mechanism that suctions the accompanying flow.
The printing system of claim 1 . The upstream surface of the contact member in the transport direction is inclined toward the downstream side in the transport direction as it moves away from the printing material.
The printing system according to claim 1 or 2. The surface of the contact member facing the printing material is inclined in a direction away from the printing material toward the downstream side in the conveying direction.
The printing system according to claim 3 .

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