EP3169528B1 - Suction box, system for transporting flat supports, and printing machine provided therewith - Google Patents

Description

The present invention relates to a suction box for a planar media transport system in a planar media printing machine. The invention relates to a plane support transport system comprising at least one suction box. The invention also relates to a planar media printing machine, equipped with a planar 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. The machine can easily accept different media formats. 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 of the media introduced, but also the quality and accuracy of the system (s). 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 group (s).

State of the art

The document 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 endless 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. 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 drawbacks. The created vacuum is reflected in the leaves and more precisely in the position of the guided sheets. This can have an effect on the printing process, as spurious air streams are generated at the front, back, and side edges of the sheets.

The air void also generates disturbances in the dryers. Indeed, these dryers include a suction part which is necessary to suck the moisture generated during drying. In order to achieve optimum drying, the suction is made from the printed side of the sheets and upwards. However, the presence of two air gaps in opposite directions, both underneath for holding the sheets on the web and above for drying the sheets, will affect the flatness of the sheets and the accuracy of the transport.

JP2005096135 discloses a transport system with an endless belt comprising suction means and a suction compartment.

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 transporting media to be printed which ensures a good hold of these media on the conveyor belt of the transport system. A third objective is to develop a suction box to minimize losses when a carrier is transported. A fourth objective is to make a box with band disturbances reduced to a minimum. A fifth objective is to adapt an endless conveyor system for printing flat supports comprising at least one suction box. A sixth 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.

In accordance with the present invention, a transport system is defined in claim 1.

The suction box is characterized in that the suction compartment has an open upper face provided with a holding arrangement, allowing movement of the band.

In other words, the open upper surface of the compartment makes it possible to directly transfer the air vacuum to the strip and thus to the plane supports. The band is held and circulates at the upper face.

The dimensionally adjustable suction chamber makes it easy to adjust the intensity of the applied air vacuum. The face at which the strip passes thus has a variable suction zone, depending on the adjustable chambers. This makes it possible to maintain a strong and optimal suction at the suction zone or zones, in order to maintain the flatness of the flat supports, the absence of displacement of the flat supports with respect to the transport belt and thus the precision of the transport. .

The surface of this area varies for example according to the format of the flat supports to be transported and printed. The operation of the media printing machine will be optimal, the air vacuum being applied directly under the conveyor belt whose extent is limited to the area in which the transported plane support is located. The size of the chambers providing the air space under the transported supports will be adapted, so as not to disturb the operation of the dryers.

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.

Brief description of the drawings

• la Figure 1 représente une vue en perspective d'une machine d'impression, comprenant un système de transport et des caissons d'aspiration selon l'invention;
• les Figures 2 à 5 représentent chacune respectivement une vue latérale, du dessus, de dessus en perspective aval et de dessus en perspective amont d'un caisson d'aspiration selon un premier mode de réalisation de l'invention; et
• la Figure 6 représente une vue de dessus en perspective amont d'un caisson d'aspiration selon un deuxième mode de réalisation de l'invention.

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:

• the Figure 1 is a perspective view of a printing machine, comprising a transport system and suction boxes according to the invention;
• the Figures 2 to 5 each respectively represent a side view, from above, from above in perspective downstream and from above in perspective upstream of a suction box according to a first embodiment of the invention; and
• the Figure 6 represents a top view in perspective upstream of a suction box according to a second embodiment of the invention.

Detailed description of preferred embodiments

As illustrated by Figure 1 a printing machine 1 is used to print plate-type supports, for example corrugated sheets. As a main example of embodiment, the machine 1 is a digital printing machine, which for example incorporates certain constituent elements described in the document US 6,471,430 . The machine 1 comprises in particular a set of four printer groups 2, arranged in line one after the other.

Each of the printing units 2 is provided with at least one digital printing head, without contact for example ink jet. For example, a set of heads is oriented downwards, the upper face of the sheets transported by the strip 6 is then printed. The inks black, cyan, magenta and yellow are successively printed by the printer groups 2 on the sheets.

The leaves are introduced (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, circulate longitudinally F, and leave F printed at a receiving station (not shown), mounted downstream of the printing machine 1. Two dryers 3, with evacuation pipes of water vapor, 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 band 6. The cylinders 7 and 8 and the band 6 are mounted on a frame 10.

The sheets remain plated on the strip 6, thanks to suction boxes also called vacuum boxes 11, and pass under the printer groups 2 and dryers 3. Only the vacuum boxes 11 upstream of the printer groups 2, between the printer groups 2 , and downstream of the printing units 2 have been represented in dotted 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.

Seven suction boxes 11 are mounted on the frame 10 under the strip 6. The boxes 11 are located between the upper part of the strip 6 which carries the sheets and the lower part of the strip 6 which makes the return. Each box suction 11 comprises an upper face, 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 level of the upper face. Each of the dryers 3 is associated with a suction box 11. Each interval between the printing units 2 is associated with a suction box 11.

The casing 11 according to a first embodiment comprises at the upper face a holding arrangement of the band 6 comprising a series of transverse rollers, equidistant and parallel to each other 14 (FIG. Figs. 2 , 3 , 4 and 5 ). For the sake of clarity, the central roll 14 has been removed for the box 11 shown in FIG. Fig. 3 . The rollers 14 are kept free to rotate by bearings. The rollers 14 are flush with the upper face of the compartment 16. The band 6 moves on the rollers 14, which limits the friction and vibrations.

The suction box 11 comprises ( Figs. 2 and 3 ) a suction compartment 16, delimited by two upstream and downstream side walls 17 and 18, two longitudinal front and rear walls 19 and 21, and a bottom 22. For the sake of clarity, the front wall 19 has been removed for the box 11 represented in Fig. 4 . The box 11 with the suction compartment 16 has an open upper face.

The box 11 with its compartment 16 is in communication with suction means 23 comprising for example a motor 24 able to generate an air gap in the compartment 16.

According to the invention, the compartment 16 is divided into at least two chambers, in this case three chambers 26, 27 and 28. A second front chamber 26 and a second rear chamber 27 surround a first central aspiration chamber 28. The chamber Central 28 is adjustable and has a variable capacity selected by the operator. The two front and rear chambers 26 and 27 remain at ambient pressure.

The central chamber 28 is in communication with the suction means 23, for applying through the holes of the strip 6 the vacuum of air to the supports carried by the strip 6. In the center of the box 11, the compartment 16, and so of the central chamber 28, there is an opening 29 which is connected to the suction means 23 used to create the vacuum.

The central chamber 28 is delimited by two movable partitions 31 and 33. A movable partition before 31 separates the second front chamber 26 of the first central chamber 28. A rear movable partition 33 separates the second rear chamber 27 from the first central chamber 28. The suction box 11 adjusts to the size of the sheet transported. Soft plastic seals or flaps (not visible) ensure sealing the central chamber 28 by rubbing against the upstream and downstream side walls 17 and 18 and against the bottom 22.

Preferably, the central chamber 28 and the ambient pressure chambers 26 and 27 are oriented longitudinally, the movable partitions 31 and 33 being generally oriented longitudinally from upstream to downstream.

The movable partitions 31 and 33 are divergent from each other, advantageously being inclined with respect to each other. As is visible in Fig. 3 , the partitions 31 and 33 are favorably inclined to each other (angles a1) with respect to a median longitudinal vertical plane passing through the median longitudinal axis L of the box 11 and the machine 1. In such a configuration, it becomes impossible to completely close the central chamber 28 between the two movable partitions 31 and 33. The partitions have a V-shaped configuration seen from above, when they are close to one another, which makes it possible to avoid closing the opening 29 of the suction means 23.

The casing 11 advantageously comprises actuating means 34 for the two movable partitions 31 and 33 (see FIG. Figs. 2 and 4 ). The actuating means 34 preferably comprise at least one motor, in this case a single motor 36 actuating and moving the two partitions 31 and 33 by translation. The motor 36 is installed in a housing located behind the front wall 19. This housing is particularly advantageous because it allows the addition of the motor 36 inside the volume of the suction box 11, rather than outside. of it.

The actuating means 34 may comprise a worm 37. The screw 37 extends transversely through the compartment 16 substantially in its center. The screw 37 is kept rotated by bearings. The screw 37 passes through each of the two movable partitions 31 and 33 with the aid of a slider piece.

A pinion 38 is fixed to the worm 37 at its front end. The motor 36 is mechanically connected to a driving means such as a chain or belt 39, which rotates (arrows A and B in Fig. 2 ) the worm 37 through pinion 38.

The rotation of the worm 37 makes it possible to bring the partitions 31 and 33 closer or away from them as a function of the direction of rotation of the screw 37. The two partitions 31 and 33 are favorably positioned symmetrically with respect to each other . The two partitions 31 and 33 move transversely from front to back and vice versa (arrows C and S in Fig. 3 ), symmetrically with respect to each other.

Preferably, the casing 11 comprises guiding means for each of the movable partitions 31 and 33. These guide means can be of the bar type. 41. The bars 41 extend transversely through the compartment 16 substantially at the upstream and downstream side walls 17 and 18. Four bars 41 are provided, with an upstream upper bar, an upstream lower bar, a downstream upper bar, a downstream lower bar.

In a second embodiment of the invention (see Fig. 6 ), a suction box 42 comprises the suction compartment 16, delimited by the two upstream and downstream side walls 17 and 18, the two longitudinal front and rear walls 19 and 21, and the bottom 22. The box 42 and the suction compartment 16 has an open upper face.

The box 42 with its compartment 16 is in communication with suction means 23. In the center of the box 42, the compartment 16, and thus the central chamber 28, there is an opening 29 which is connected to the suction means 23 used to create the vacuum. The two partitions used 31 and 33 are substantially similar to those of the first embodiment.

The box 42 according to the second embodiment comprises at the upper face a holding arrangement of the strip 6, comprising a first set of front rollers 43. These front rollers 43, for example five in number, are transverse, equidistant and parallel to each other. The holding arrangement of the band 6 also comprises a first set of rear rollers 44. These rear rollers 44, for example five in number, are transverse, equidistant and parallel to each other. The front rollers 43 and rear 44 are kept free to rotate through bearings. The front rollers 43 are located in the continuity of the rear rollers 44.

The holding arrangement comprises three longitudinally disposed pads, a front pad 46, a center pad 47, and a rear pad 48. The front rollers 43 are separated from the rear rollers 44 by the pads 46, 47, and 48. The top edge these pads 46, 47 and 48 comes flush with the upper face of the compartment 16.

The band 6 moves while being held on the front and rear rollers 44 and 44. The central part of the band 6 slides on the upper edge of these pads 46, 47 and 48. The holding of the band 6 by the series of rollers 43 and 44 and the pads 46, 47 and 48 prevents the band 6 to vibrate, and consequently to disrupt the printing of the sheets by the printing units 2.

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.

Such a box 11 can also be used in other parts of the printing machine 1, for example under printing units 2 or other modules. Alternatively, a motor may be provided by partition 31 and 33 with actuating means (worm or other) specific to each engine torque-movable partition.

Claims (12)

1. System for conveying planar supports with at least one endless belt (6) arranged with a set of through holes, in a machine for printing supports (1) equipped with at least one printing unit (2), comprising at least one suction box (11), comprising:

   suction means (23), able to generate an air vacuum, and

   a suction compartment (16), divided into at least two separate chambers (26, 27, 28), with

   a first suction chamber (28) having an adjustable volume with variable capacity, in communication with the suction means (23), for applying through the holes of the belt (6) the air vacuum to the supports conveyed by the belt (6), and

   a second chamber at ambient pressure (26, 27),

   the first and second chambers (28, 26, 27) being oriented longitudinally, and being separated one from the other by a movable partition (31, 33), so as to adjust the suction box (11) to the format of the planar supports conveyed,

   characterised in that the suction compartment (16) has an open upper face provided with a holding arrangement (14, 43, 44, 46, 47, 48), the belt (6) moving on the holding arrangement (14, 43, 44, 46, 47, 48).
2. System according to claim 1, wherein the holding arrangement comprises at least one roller (14, 43, 44).
3. System according to claim 1 or 2, wherein the holding arrangement comprises at least one pad (46, 47, 48).
4. System according to any one of the previous claims, comprising a central suction chamber (28) and two chambers at ambient pressure (26, 27), the central suction chamber (28) being delimited and separated from the two chambers at ambient pressure (26, 27) by two movable partitions (31, 33).
5. System according to any one of the previous claims, comprising actuating means (34) of the partition (31, 33), with at least one motor (36) and an endless screw (37).
6. System according to any one of the previous claims, comprising guiding means (41) of the partition (31, 33).
7. System according to any one of claims 4 to 6, wherein the two partitions (31, 33) are positioned and move symmetrically one in relation to the other.
8. System according to any one of claims 4 to 7, wherein the partitions (31, 33) are inclined (a1) one to the other in relation to a median longitudinal vertical plane.
9. System according to any one of the previous claims, wherein the belt (6) is mounted between a first and a second cylinder (7, 8), driven in rotation by at least one drive motor (9), and driving the belt (6) in the direction of conveyance (F).
10. Printing machine of planar supports, equipped with at least one printing unit (2), comprising a system for conveying the supports (4), according to any one of the previous claims.
11. Machine according to claim 10, comprising a drier (3) associated with a suction box (11).
12. Machine according to claim 10 or 14, wherein the printing unit (2) is provided with at least one digital printing head.

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