EP3169527A1

EP3169527A1 - Suction plenum for a system for transporting flat supports and printing machine thus equipped

Info

Publication number: EP3169527A1
Application number: EP15739523.7A
Authority: EP
Inventors: Jean-Philippe BESSON; Pascal MARCIANO
Original assignee: Bobst Mex SA
Current assignee: Bobst Mex SA
Priority date: 2014-07-18
Filing date: 2015-07-17
Publication date: 2017-05-24
Also published as: KR101900625B1; IL249487A0; CN106536207A; CN106536207B; KR20170023127A; US20170210146A1; JP6335391B2; WO2016008597A1; US9764566B2; TWI610815B; TW201623015A; JP2017522209A

Abstract

A suction plenum, intended for a system for transporting flat supports (4) with at least one endless belt (6), formed with a collection of through-holes, in a support-printing machine (1), equipped with at least one printing unit (2), comprises a face (16) past which the belt (6) passes, and suction means (17), which are able to generate a vacuum. The face (16) is formed with at least one zone at a first suction pressure (22, 23, 24), in communication with the suction means (17), so as to apply the vacuum through the holes in the belt (6) to the supports being transported by the belt (6), and at least one zone at a second pressure (26, 27), which zone is situated in the region of the printing unit (2), the magnitude of the second pressure being greater than the magnitude of the first pressure.

Description

The present invention relates to a suction box for a planar support transport system. The invention relates to a plane support transport system comprising at least one suction box. The invention also relates to a printing machine of these flat supports equipped with a flat media transport system comprising at least one suction box.

A printing machine is used in the packaging industry for printing flat media, such as sheets, or a web of paper or cardboard. The machine comprises several successive stations. A first station located furthest upstream is an introductory station successively introducing the support. The introductory station supplies several printing stations, in the form of one or more printing units placed one after the other. Each of the printing units prints a specific color with an ink having the equivalent coloring. A receiving station which collects the printed medium with an image is provided at the end of the machine.

In the case of printing cardboard sheets, more particularly corrugated cardboard, the most frequently used technology is flexographic printing, using flexo group. Digital printing is also developing more and more, with the use of printing units provided with digital printing heads, for example of inkjet type. This printing technology allows the packaging manufacturer to change jobs very quickly to print new sheets from a computer file representative of the package.

The printing machines comprise one or more printing units, depending on the number of colors desired. The support is moved longitudinally from upstream to downstream from the introduction station, to the printing units, to the receiving station. To obtain a final image of quality on the printed medium, it is especially necessary that all the printed dots of different colors arise exactly next to each other. It is also necessary that the printed dots are not deformed.

The quality of the printing obtained on the flat support depends not only on the quality of the printing machines, the quality of the inks used, the quality introduced media, but also the quality and accuracy of the transport system or systems used.

The transport of the support is provided by a vacuum transport system using either a belt, flat belts, or driven steel rollers to move the support longitudinally from one printing unit to another from upstream to downstream from the introductory station to the receiving station. To get the best print quality, one of the basic principles is that transport ensures the most consistent media speed possible. Another principle is that the support must be maintained as firmly as possible and must be perfectly guided by the transport system, so as not to deviate during printing by the printing group (s) or between the printing unit (s).

State of the art

US 6,471,430 discloses a paper or cardboard type media printing machine comprising a transport system. For printing, the sheets are taken from a sheet feed and transported on a first endless conveyor belt. The sheets are maintained during their transport by means of a suction system and pass under first printing units and under a first ink dryer downstream of the first printing units. The sheets are then returned and transported by a second conveyor belt under second printing units and under a second ink dryer for subsequent recovery at an output station.

The conveyor belts are made with a series of through-holes to allow the air to be drawn in and to obtain the holding effect for transporting the sheets into the machine. In addition, suction boxes are placed under the strips so as to generate the vacuum of air.

However, the use of a suction system to apply an air gap under the conveyor belt and thereby to press the sheets to be printed has certain disadvantages. The created vacuum is reflected in the support and has an influence on the deposition of the ink itself and thus on the quality of the printing.

Presentation of the invention

A main object of the present invention is to provide a suction box for a planar media transport system in a planar media printing machine. A second objective is to provide a suction box for carrying media to be printed which ensures a good holding these supports on the conveyor belt of the transport system. A third objective is to develop a suction box that has a negligible influence on the printing process, so that it retains the required accuracy. A fourth objective is to adapt an endless conveyor system to print flat supports comprising at least one suction box. A fifth objective is to solve the technical problems mentioned for caissons and transport systems of the state of the art. Yet another object is to further improve the print quality for a flatbed printing machine equipped with at least one printing unit.

According to one aspect of the present invention, a suction box is intended for a planar media transport system, with at least one endless conveyor belt, formed with a set of through holes, in a printing machine of flat supports, equipped with at least one printing unit. The suction box includes:

a face, at the level of which the endless belt passes, and

suction means capable of generating an air vacuum.

In the suction box, the face is formed with:

at least one zone under a first suction pressure, the zone under a first suction pressure being in communication with the suction means, for applying through the through holes of the endless band the air gap generated. the flat supports transported by the endless belt, and

at least one zone under a second pressure, the zone under a second pressure being located at the printing unit, the value of the second pressure being greater than the value of the first pressure.

In other words, the suction generated by the suction means is interrupted at the printing unit, so as not to disturb the printing. This suction is active at the level of the conveyor belt before and after the printing unit. The zone or zones under a second pressure do not communicate with the suction means. The flat support to be printed by the printing unit thus remains perfectly driven by the belt, to its position of arrival at the printer unit and to its output position of the printing unit. This makes it possible to maintain a strong and optimum suction at the suction zone or zones, in order to preserve the flatness of the flat supports, the absence of displacement of the planar supports with respect to the conveyor belt and thus the precision of the transport.

A planar support is defined, by way of non-exhaustive example, as a sheet, plate, continuous web material such as paper, cardboard, corrugated cardboard, laminated corrugated cardboard, flexible plastic, for example polyethylene (PE), polyethylene terephthalate (PET), bioriented polypropylene (BOPP), or other polymers, or other materials. The planar support is defined, by way of non-exhaustive example, as a sheet intended to form a blank, and then a packaging box.

The longitudinal direction is defined by reference to the trajectory of the plane support in the printing machine, according to its median longitudinal axis. The upstream and downstream directions are defined with reference to the direction of travel along the path of the support, in the longitudinal direction throughout the printing machine.

In another aspect of the invention, a planar media transport system with at least one endless belt formed with a set of through holes, in a media printing machine equipped with at least one printing unit, comprises at least a suction box having one or more technical features described below and claimed.

In another aspect of the invention, a flat media printing machine, equipped with at least one printing unit, comprises a media transport system, comprising at least one suction box having one or more technical features described herein. below and claimed.

According to yet another aspect of the invention, a flat media printing machine, equipped with at least one printing unit, comprises a media transport system having one or more technical features described below and claimed.

Brief description of the drawings

The invention will be better understood and its various advantages and different characteristics will become more apparent in the following description, of the nonlimiting exemplary embodiment, with reference to the appended diagrammatic drawings, in which:

- Figure 1 shows a perspective view of a printing machine, comprising a transport system and suction boxes according to the invention; - Figures 2 and 3 show a perspective view from above of a suction box, respectively according to a first and a second embodiment of the invention;

- Figures 4 and 5 show a top view of the box of Figure 2, respectively of the box of Figure 3;

- Figure 6 shows a perspective view of the top of the box of Figure 2, without plate;

- Figure 7 shows a top view of the box of Figure 2, without plate; and

- Figure 8 shows a perspective view of the bottom of the box of the

Figure 2

Detailed description of preferred embodiments

As illustrated in Figure 1, a printing machine 1 is used to print plate-like media, for example corrugated sheets. As a main example of embodiment, the machine 1 is a digital printing machine, which includes for example some constituent elements described in US 6,471, 430. The machine 1 comprises in particular a set of four printer groups 2, arranged in line one after the other. The water-based black, cyan, magenta and yellow inks are successively printed by the printing units 2 on the sheets.

The sheets are fed (arrows F in Fig. 1) by a feed station (not shown) mounted upstream of the printing machine 1 (not shown). The sheets are then seized, transported, move longitudinally F, and leave F printed at a receiving station (not shown), mounted downstream of the printing machine 1. Two dryers 3, with steam evacuation pipes, are placed downstream of the printing units 2.

The sheets to be printed are conveyed from upstream to downstream by a transport system 4. The transport system 4 comprises at least one carpet or belt, in this case a single endless metal band 6, which is mounted between an upstream first cylinder 7 and a second downstream cylinder 8. The endless belt 6 is formed with a set of through holes (not visible in Fig. 1). At least one of the two cylinders 7 and 8 is rotated (arrow R in Fig. 1) by means of a motor 9, which causes the strip 6. The cylinders 7 and 8 and the strip 6 are mounted on a chassis 10. The sheets remain plated on the strip 6, thanks to suction boxes also called vacuum boxes 1 1, and pass under the printer groups 2 and the dryers 3. Only the vacuum boxes 1 1 under the printer groups 2 were represented in FIG. lined lines in FIG. 1.

In order to promote the grip and holding of the inks which will be deposited by printing on the sheets of cardboard to be printed, the printing machine 1 advantageously comprises an upstream coating group 12. This upstream coating group 12 is arranged upstream of the first printer group 2, just after the feed station. The upstream coating unit 12 is placed in line with the upstream cylinder 7. In order to dry the coating, a dryer 3 may be inserted between the upstream coating unit 12 and the first printing unit 2.

In order to favor the holding and the protection of the inks which are deposited by printing on the cardboard sheets which have just been printed, the printing machine 1 advantageously includes a downstream coating group 13. This downstream coating group 9 is arranged downstream of the last printer group 2, and downstream of the dryers 3, just before the receiving station. The downstream coating group 13 is placed in line with the downstream cylinder 8.

In the printing machine 1, each of the printing units 2 is provided with at least one digital printing head 14, without contact for example ink jet. For example, a set of twelve heads 14 (shown in dotted lines in Fig. 2) is provided, each of the heads 14 being oriented downwards, the upper face of the sheets conveyed by the strip 6 being then printed. The printing unit 2 and thus the machine 1 preferably comprises a first series or upstream row 14a of digital printing heads 14 arranged transversely with respect to the strip 6. The printing unit 2 and thus the machine 1 preferably comprises a second series or row downstream 14b of digital printing heads 14 arranged transversely to the strip 6. In order to cover the entire width without interruption, the heads 14 of the first series 14a are transversely offset from the heads 14 of the second series 14b.

Four suction boxes 1 1 are mounted on the frame 10 under the strip 6.

A box 1 1 is located between the upper portion of the strip 6 which carries the sheets and the lower portion of the strip 6 which returns. Each suction box January 1 comprises a substantially flat upper face 16, oriented towards the lower face of the strip 6, the sheets being pressed on the lower face of the strip 6. The strip 6 passes at the upper face 16. Each suction box January 1 comprises suction means 17 adapted to generate an air vacuum. The suction means 17 comprise at least one suction pipe or pipe 18 and a suction system 19, in the form of a motor 21.

When printing with the printheads 14, it is important that the ink jet microdroplets coming out of the heads 14 keep an optimal path and shape to maintain the print quality desired by the operator. So that these microdroplets do not deviate from their trajectory or accelerate before arriving on the sheet, and according to a first embodiment of the invention (see Figs 2 and 4), the face 16 is all of first formed with at least one zone under a first suction pressure, in this case three suction zones 22, 23 and 24. The three suction zones 22, 23 and 24 communicate with the suction means 17 to apply through the holes of the strip 6 the vacuum of air to the sheets conveyed by the strip 6. For each box 1 1, the face 16 is formed with an upstream suction zone 22, a central suction zone 23, and a downstream suction zone 24.

And according to the first embodiment of the invention, the face 16 is then formed with at least one zone under a second pressure, this second pressure having a different value and greater than that of the first suction pressure. As an example shown in Figs. 2 and 4, the face 16 has in this case two ambient pressure zones 26 and 27. For each caisson 1 1, the face 16 is formed with a first upstream ambient pressure zone 26 and a second downstream ambient pressure zone 27.

In the well 1 1, the ambient pressure zone 26 and 27 is preferably surrounded by a suction zone 22, 23 and 24. In more detail, the two ambient pressure zones 26 and 27 alternate favorably with the three zones Aspiration 22, 23 and 24, each ambient pressure zone 26 and 27 being surrounded by a suction zone 22, 23 and 24. The two ambient pressure zones 26 and 27 are located at the printer unit 2, and more particularly preferably under the printing unit 2. Preferably, and more specifically, the ambient pressure zones 26 and 27 are situated at the right of the printing heads 14. The ambient pressure zones 26 and 27 open out into the open air.

And, the suction zones 22, 23 and 24 are located longitudinally offset from the printing heads 14. The zones 22, 23, 24, 26 and 27 are oriented transversely with respect to the strip 6. The first zone at ambient pressure 26 is located at the right of the first series of heads 14a. The second zone at ambient pressure 27 being situated in line with the second series of heads 14b. As soon as the beginning of the sheet has been printed by the first series of heads 14a, it is maintained by being taken up by the central aspiration zone 23, then it returns under the second series of heads 14b to be printed, to be then maintained by being taken up by the downstream suction zone 24.

Each suction zone 22, 23 and 24 is associated with a suction compartment respectively 28, 29 and 31, underlying, forming part of the box 1 1, and forming part of the suction means 17 (see FIGS. to 7). The upstream compartment 28 makes it possible to generate the vacuum of air at the level of the upstream suction zone 22. The central compartment 29 makes it possible to generate the air vacuum at the level of the central aspiration zone 23. The downstream compartment 31 allows to generate the vacuum of air at the downstream suction zone 24. The compartments 28, 29 and 31 each form a substantially parallelepipedal transverse volume. The compartments 28, 29 and 31 are separated from each other, which makes it possible to delimit the zones at ambient pressure 26 and 27.

Each compartment 28, 29 and 31 is in communication with a suction duct 18a, 18b and 18c (see FIG 7), opening in the center of each of the compartments 28, 29 and 31. The suction ducts 18a, 18b and 18c converge in the suction system 19 and are part of the suction means 17.

In a favorable manner, each suction zone 22, 23 and 24 is equipped with a plate pierced with orifices 32. The plate and its orifices make it possible to homogenize the suction at the suction zones 22, 23 and 24. A single upper plate pierced with orifices 32 may cover the whole of the face 16. The strip 6 passes directly on the plate 32. The plate 32 comprises longitudinal rods 33 for separating and connecting the upstream suction zone 22 with the central aspiration zone 23, and the central aspiration zone 23 with the downstream suction zone 24. The length of the rods 33 defines the length of the ambient pressure zones 26 and 27.

In a second embodiment of the invention (see Figs 3 and 5), the face 16 is first formed with at least one zone under a first suction pressure, in this case three upstream suction zones. 22, central 23 and downstream 24, substantially similar and have a substantially similar operation to that of the first embodiment.

The face 16 is then formed with at least one zone under a second pressure, this second pressure having a different value and greater than that of the first suction pressure. As an example shown in Figs. 3 and 5, the face 16 has in this case two zones at a pressure different from the ambient pressure, and lower than the ambient pressure 26 and 27. In a favorable manner, each suction zone 22, 23 and 24 is equipped with a plate pierced with orifices 32. The plate and its orifices 32 make it possible to homogenize the suction at the suction zones 22, 23 and 24 A single upper plate pierced with orifices 32 may cover the whole of the face 16. The strip 6 passes directly on the plate 32. The plate 32 comprises in the second embodiment (FIGS. pads 34, arranged longitudinally, and for maintaining the band 6. The band 6 slides by sliding on the upper edge of these pads 34.

The sheets being printed must avoid going up and down, and waving at the print heads 14, depending on the suction pressure exerted on them. It is thus advantageous to reduce the difference between the first suction pressure and the second pressure, while keeping the value of the first pressure to keep the suction lower than the value of the second pressure.

To do this, aligned orifices 36 are formed at the ribs 34 and allow to connect the zones under a first suction pressure 22, 23 and 24 with the zones under a second pressure 26 and 27. The orifices 36 located upstream form an interconnection between the upstream suction zone 22, the first zone under a second upstream pressure 26, and the central aspiration zone 23. The downstream orifices 36 form an interconnection between the central aspiration zone 23, the second zone under a second downstream pressure 27, and the downstream suction zone 24.

The present invention is not limited to the embodiments described and illustrated. Many modifications can be made, without departing from the scope defined by the scope of the set of claims.

The number of print heads 14 and head series 14a and 14b can be variable. It is the same with the number of suction zones 22, 23 and 24 and ambient pressure zone 26 and 27. A common suction system can be provided as suction means 17 for several boxes 1 1 .

Claims

Suction box, for a plane support transport system (4) with at least one endless band (6), formed with a set of through-holes, in a media printing machine (1), equipped with at least one printing unit (2), comprising:

a face (16) at which the strip (6) passes, and

suction means (17) capable of generating an air vacuum,

wherein the face (16) is formed with:

at least one zone under a first suction pressure (22, 23, 24), in communication with the suction means (17), for applying through the holes of the strip (6) the vacuum of air at carriers conveyed by the belt (6), and

- At least one zone under a second pressure (26, 27), located at the printing unit (2), the value of the second pressure being greater than the value of the first pressure.

Box according to claim 1, wherein the area under a second pressure (26, 27) is located at the right of at least one digital printing head (14), which is provided with the printing unit (2), and wherein the area under a first suction pressure (22, 23, 24) is located longitudinally offset from the print head (14).

Casing according to claim 1 or 2, comprising an area under a second pressure (26, 27) and two zones under a first suction pressure (22, 23, 24), the area under a second pressure (26, 27) being surrounded by an area under a first suction pressure (22, 23, 24).

Casing according to one of the preceding claims, wherein the zones (22, 23, 24, 26, 27) are oriented transversely.

Casing according to one of the preceding claims, wherein the area under a first suction pressure (22, 23, 24) is equipped with a plate pierced with orifices (32).

6. Housing according to one of the preceding claims, wherein each zone under a first suction pressure (22, 23, 24) is associated with a suction compartment (28, 29, 31). 7. Housing according to one of the preceding claims, wherein the suction means (17) comprise at least one suction duct (18) and a suction system (19).

The cabinet of claim 7, wherein each compartment (28, 29, 31) is in communication with a suction duct (18a, 18b, 18c).

9. System for transporting flat supports with at least one endless belt (6) formed with a set of through holes, in a media printing machine (1) equipped with at least one printing unit (2), comprising at least one at least one suction box (1 1) according to one of the preceding claims.

The system according to claim 9, wherein the strip (6) is mounted between a first and a second cylinder (7, 8), rotated by at least one drive motor (9), and driving the belt ( 6) in the direction of transport (F).

1 1. Flatbed printing machine, equipped with at least one printing unit (2), comprising a carrier transport system (4) according to claim 9 or 10.

12. Flatbed printing machine, equipped with at least one printing unit (2), comprising a carrier transport system, comprising at least one suction box according to one of claims 1 to 8. 13. Machine according to claim 1 1 or 12, wherein each printing unit (2) is associated with a suction box (1 1).

14. Machine according to one of claims 1 1 to 13, wherein the printing unit (2) is provided with at least one digital printing head (14). Machine according to one of claims 1 1 to 14, comprising a first series (14a) of digital printing heads (14) arranged transversely, a first zone under a second pressure (26) being located at the right of the first series ( 14a), and a second series (14b) of digital printing heads (14) arranged transversely, a second zone under a second pressure (27) being located in line with the second series (14b).