EP4410556A1

EP4410556A1 - Printbar and printing system

Info

Publication number: EP4410556A1
Application number: EP23155135.9A
Authority: EP
Inventors: José-Manuel ROMERO; Roberto Valterio
Original assignee: Bobst Mex SA
Current assignee: Bobst Mex SA
Priority date: 2023-02-06
Filing date: 2023-02-06
Publication date: 2024-08-07

Abstract

A printbar (20) and a printing system comprising a printbar (20) are described. The printbar (20) for printing on cardboard sheets (30) comprises a base body (32) and a print head (34). The printbar (20) further has a protection device (36) comprising a guard rail (41, 42) for preventing unintended contact between the print head (34) and the cardboard sheets (30) during printing, the guard rail (41, 42) being fixed to the base body (32).

Description

The invention relates to a printbar for printing on cardboard sheets, comprising a base body and a print head. The invention further relates to a printing system comprising such a printbar.
Printing systems comprising a printbar for printing on cardboard sheets are known.
The printing heads of these printing systems are very delicate. Thus, great care has to be taken to prevent parts of the cardboard sheets to contact the printing head so the printing head is not damaged.
Usually the cardboard sheets are scanned for damaged sections during printing and the printbar is lifted away from the cardboard sheet when a damaged section of cardboard is detected. In this way, the print head can reliably be protected. However, in doing so, the printing is interrupted and the particular cardboard sheet has to be scrapped.
The object of the invention is to provide a printbar for printing on cardboard sheets with a print head which is reliably protected from damaged cardboard during printing. The object of the invention is to provide a printing system comprising such a printbar.
In order to achieve this object, the invention provides a printbar for printing on cardboard sheets, comprising a base body and a print head. The printbar further has a protection device comprising a guard rail for preventing unintended contact between the print head and the cardboard sheets during printing, the guard rail
being fixed to the base body.
According to the invention, it has been recognized that by providing a guard rail, damaged sections of cardboard can be reliably deflected from the print head during printing. In this way, there is no risk of contact between the cardboard sheet and the print head so that the printing can continue without any interruption. Thus, the efficiency of the printing system comprising said printbar is improved, in particular if the damage to the cardboard sheet is so minor that it does not have to be scrapped.
According to one aspect of the invention, the guard rail extends in a working direction from a first side of the base body to an opposite second side of the base body. The working direction being the direction the cardboard sheet moves relative to the printbar during printing. Thus, the guard rail spans the complete width of the base body and thus likewise protects the print head over its full width.
According to a further aspect of the invention, the guard rail is made of a ferromagnetic material, in particular a ferromagnetic metal, and thus can be attracted via magnetic forces.
According to one embodiment of the invention, the printbar further comprises a magnet, in particular a permanent magnet, the guard rail being fixed to the base body via the magnet. Thus, the guard rail is reliably fixed to the base body in an effective way and further can be detached from the base body and/or displaced to another position relative to the base body without damaging the printbar.
The object is also achieved by a printing system comprising a printbar according to the invention which has the above mentioned advantages.
According to one aspect of the invention, the printbar is movable between a work zone and a maintenance zone, in particular in a direction perpendicular to the working direction and/or in a plane parallel to the printing plane a cardboard sheet is positioned in during printing. Thus, the printbar can be moved from the work zone to the maintenance zone for maintenance, to move a capping on the print heads to protect the same from dust (from the cardboard and/or to protect the print head, e.g. from a section of cardboard that is damaged in such a way that there is a risk of the cardboard contacting the print head despite the guard rail.
According to another aspect of the invention, the printing system further comprises an adjustment device for positioning the guard rail relative to the base body between a first position and a second position, wherein the first position and the second position are spaced apart from each other in a direction perpendicular to the working direction and/or in a plane parallel to the printing plane a cardboard sheet is positioned in during printing. In this way, the guard rail can be positioned such that its protective function is most effective, e.g. opposite one of the edges of the cardboard sheet which are the sections most commonly damaged or warped.
In one embodiment, the adjustment device comprises a stop for aligning the guard rail when the guard rail is positioned via the adjustment device. Thus, a defined position relative to the base body can be achieved with low effort.
In another embodiment, the stop is adjustable between a first position in which the stop works as a stop for the guard rail and a second position in which the stop does not work as a stop for the guard rail. In this way, the stop can be used when it is needed and does not interfere when it is not needed.
The stop can have a U-shaped profile, in particular to contact the guard rail at two spaced apart sections with the legs of the U.
According to one aspect of the invention, the adjustment device comprises an actuator and a holding device attached to the actuator. The holding device is movable by the actuator between a receive position in which the holding device is in a position to receive the guard rail, and a release position in which the holding device releases the guard rail. Thus, the adjustment device can pick up and let go of the guard rail to effectively position the guard rail relative to the base body.
The adjustment device can comprise an extractor for separating the guard rail from the holding device, when the actuator is moved to the release position, to reliably release the guard rail.
According to another aspect of the invention, the holding device is movable by the actuator to a holding position spatially arranged between the receive position and the release position to hold the guard rail in a stable position when the guard rail is transferred from the first position to the second position.
In one embodiment, the holding device comprises a magnet, in particular a permanent magnet, wherein the magnet of the holding device has a larger magnetic field than a magnet of the printbar for fixing the guard rail to the base body. Thus, the guard rail can be removed from the base body via the holding device by getting the holding device in such close proximity to the guard rail that the attraction of the magnet of the holding device is larger than the attraction of the magnet of the printbar.
According to a further aspect of the invention, the protection device comprises two guard rails, one for each cardboard edge extending in working direction. Thus, the print head is protected from both cardboard edges at the same time during printing.
Any individual feature of any of the embodiments disclosed above may be part of any of the embodiments disclosed above thus forming a further embodiment of the invention. In other words, any or all of the individual features disclosed above can be combined in a further embodiment of the invention.
The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

Figure 1 schematically shows a printing system according to the invention with a printbar according to the invention in a perspective view;
Figure 2 schematically shows the printing system of figure 1 in a top view;
Figure 3 schematically shows the printbar of figure 1 in a perspective view;
Figure 4 shows a sectional view of the printbar of figure 1;
Figure 5 shows a guard rail of the printbar of figure 1 in a perspective view;
Figures 6 to 10 show different steps of a method for positioning the guard rail via an adjustment device of the printing system of figure 1 in a side view;
Figure 11 shows a stop of the adjustment device of figure 6 in a front view; and
Figures 12 to 14 each show a sectional view of the adjustment device during positioning of the guard rail.

Figure 1 schematically shows a printing system 10 comprising a rack 12, a control unit 14, a printbar 20 and an adjustment device 22.
Printbar 20 is mounted to rack 12 via two tracks 24 (see Figure 2) and is movable by control unit 14 along tracks 24 in Y-direction between a work zone 26, an adjustment zone 27 and a maintenance zone 28. In Figure 2, the printbar 20 is positioned in the work zone 26, while the maintenance zone 28 is illustrated by the dashed rectangle.
In the present embodiment, adjustment zone 27 is located in Y-direction between work zone 26 and maintenance zone 28.
Adjustment device 22 is located in the adjustment zone 27.
The printing system 10 is designed for printing via the printbar 20 on a cardboard sheet 30 which is positioned in an X-Y-plane and moved in X-direction relative to the printbar 20 during printing by an appropriate conveyor mechanisms (not shown). In other words, the X-direction is the working direction of the printing system 10.
In addition or in the alternative, the printbar 20 can be moved in X- and Y-direction relative to the cardboard sheet 30 when the printbar is in a maintenance situation.
The X-Y-plane forms a printing plane 31 of the printing system 10. This means that the cardboard sheet 30, more specifically the print side of the cardboard sheet 30, extends in the printing plane 31 during printing.
As shown in Figure 3 and 4, printbar 20 comprises a base body 32, a print head 34 housed inside the base body 32 and a protection device 36 for protecting the front 38 of the print head 34 from contact with the cardboard sheet 30 during printing.
The protection device 36 has two guard rails 41, 42 which are identical in design.
In an alternative embodiment the protection device 36 can comprise any number of guard rails 41, 42, but at least one.
Further, in an embodiment with multiple guard rails 41, 42, each guard rail 41, 42 can be designed individually.
Each guard rail 41, 42 has a flat middle section 44, two opposite ends 46 and two end sections 48 which each connect one of the ends 46 with the middle section 44 (see also Figure 5).
The end sections 48 are designed to flatten or displace damaged sections of cardboard sheet 30 protruding in Z-direction from the printing plane 31 when the cardboard sheet 30 is moved in X-direction relative to the printbar 20 during printing. Thus, preventing contact between the cardboard sheet 30 and the print head 34.
In the embodiment shown, each end section 48 has a C-shape.
Guard rails 41, 42 are spaced from each other in Y-direction and extend in X-direction form a first side 50 of the base body 32 to an opposite second side 52 of the base body 32.
Further, guard rails 41, 42 are made of a ferromagnetic metal, for example stainless steel, in particular martensitic steel.
In an alternative embodiment, guard rails 41, 42 can be made of any kind of material, in particular any kind of ferromagnetic material.
Guard rails 41, 42 are fixed to the base body 32 via two first magnets 54 mounted to the base body 32 at opposite sides from the print head 34 in X-direction.
First magnets 54 can be permanent magnets.
In the present embodiment, each first magnet 54 is formed by a magnetic strip running in Y-direction along the base body 32, in particular along the whole distance, i.e. from one end to the other.
In an alternative embodiment each first magnet 54 can comprise multiple magnetic elements and/or be designed in any form.
However, in all embodiments, first magnets 54 are located in a position in Y-direction relative to the base body 32, which is designed for a guard rail 41, 42 to be fixed to the base body 32 to prevent contact of the front 38 of the print head 34 with cardboard sheets 30 during printing, as described later. In other words, first magnets 54 cover at least the relevant sections of the base body 32 depending on the width in Y-direction of the cardboard sheets 30 the printing system 10 is designed for printing on.
In this context, each side 50, 52 of the base body 32 comprises a guide slot 56 in which the ends 46 of the guard rails 41, 42 project into for guiding the respective guard rail 41, 42 relative to the base body 32.
However, the guide slots 56 are dimensioned in such a way that the ends 46 of the guard rails 41, 42 are spaced apart in Z-direction from a retaining section 58 (see Figure 4) of the base body 32 when the guard rails 41, 42 are fixed to the base body 32 via the first magnets 54, so that guard rails 41, 42 can be lifted from the base body 32 against Z-direction for positioning the guard rails 41, 42 relative to the base body 32, as described later.
The retaining sections 58 retain the guard rails 41, 42 in Z-direction relative to the base body 32 and thus prevent the guard rails 41, 42 from being detachable from the base body 32 against Z-direction.
As shown in Figure 3, each guard rail 41, 42 is positioned opposite one of the two side edges 61, 62 of the cardboard sheet 30 extending in X-direction.
In this way, print head 34 is reliably protected from damaged sections of side edges 61, 62 by guard rails 41, 42 while the section of the print head 34 between the guard rails 41, 42 in Y-direction remains free for printing on the middle section of the cardboard sheet 30, i.e. the section between side edges 61, 62 not covered by guard rails 41, 42 during printing.
To adapt the printbar 20 to multiple formats of cardboard sheets 30, the position of guard rails 41, 42 relative to the base body 32 is adjustable by adjustment device 22.
Design and function of adjustment device 22 are described in the following with reference to Figures 6 to 14. Please note that Figures 5 to 10 and 12 to 14 only show a section of the printbar 20, while the print head 34 is not shown at all.
Adjustment device 22 has two actuators 64 (see Figure 12) connected to control unit 14, each actuator 64 comprising an extractor 66 as well as a holding device 68 with a second magnet 70.
The second magnets 70 are more powerful than the first magnets 54.
In one embodiment, second magnets 70 are permanent magnets.
Actuators 64 are spaced apart in X-direction, so that the first magnets 54 of the printbar 20 and the second magnets 70 of the actuators 64 are positioned opposite each other in Z-direction when the printbar 20 is located in the adjustment zone 27 (see Figure 12).
In one embodiment, actuators 64 are linear actuators or pneumatic actuators.
Each actuator 64 is designed to position in Z-direction its respective holding device 68 in a standby or release position (see Figure 12), a receive position (see Figure 13) as well as a holding position (see Figure 14).
The holding position is located in Z-direction between the receive position and the standby or release position.
In the present embodiment, extractors 66 are formed by the rim of a cylindrical section 72 of the respective actuator 64.
In an alternative embodiment, extractors 66 can be of any design.
In all embodiments, extractors 66 are positioned in Z-direction between the receive position and the release position.
Adjustment device 22 further comprises a stop 74 (see Figure 6) and a stop actuator 76 connected to control unit 14. Please note that Figures 1 and 2 do not show stop 74 and stop actuator 76.
Stop 74 has a profile in the X-Z-plane in the form of a U (see Figure 11) with legs 78.
Stop actuator 76 is designed to position the stop 74 in a first position (see Figure 6) and a second position (see Figure 8) spaced apart in Z-direction.
In the first position, legs 78 extend in Z-direction over the guard rail 41, in particular over end sections 48, when the guard rail 41 is fixed to base body 32 so that stop 74 works as a stop in Y-direction for the guard rail 41.
In the second position, legs 78 do not extend in Z-direction over guard rail 41 when the guard rail 41 is fixed to base body 32 so that stop 74 does not work as a stop for the guard rail 41.
To change the position of guard rail 41 from a first position (see Figure 6) to a second position (see Figure 10) relative to the base body 32, the following method is used.
In Figure 6, holding devices 68 are positioned in the release position which forms a standby position, here. Stop 74 is in the first position. Guard rails 41, 42 are fixed to the base body 32 via first magnets 54, spaced apart by a distance d in Y-direction.
In a first step, printbar 20 is moved in Y-direction until guard rail 41 is aligned at stop 74 (see Figures 7 and 12), i.e. guard rail 41 extends parallel to stop 74 in X-direction.
Afterwards, holding devices 68 are moved in Z-direction to the receive position (see Figure 13) and thus in contact with guard rail 41.
Next, the holding devices 68 are moved against Z-direction to the holding position (see Figure 14). In this way, guard rail 41 is detached or lifted from base body 32 due to the attraction of the second magnets 70 which is higher than the attraction of the first magnets 54.
Stop 74 is moved to a second position (see Figure 8) after guard rail 41 has been aligned. This step is optional if stop 74 does not interfere with the positioning of the guard rail 41, as is the case here.
In a further step, base body 32 is moved against Y-direction and thus relative to guard rail 41 which remains fixed to holding devices 68 (see Figure 9), until guard rails 41, 42 are spaced apart by a distance D which is larger than distance d, here.
Next, holding devices 68 are moved against Z-direction to the release position (see Figure 12). Thereby, guard rail 41 is detached by extractor 66 from the holding devices 68. In other words, holding devices 68 release guard rail 41 by moving against Z-direction past the extractor 66 which acts as a stop for the guard rail 41.
The distance between the detached guard rail 41 and the first magnets 54 is so low and the first magnets 54 are so powerful that guard rail 41, attracted by the first magnets 54, snaps to the base body 32 and becomes fixed in the second position relative to the base body 32 (see Figure 10).
In this way, the position of guard rail 41 relative to the base body 32 can be adjusted by the adjustment device 22 from the first position with distance d between guard rails 41, 42 to the second position with distance D between guard rails 41, 42.
Of course, each guard rail 41, 42 can be positioned by the adjustment device 22 in the same way and in both directions, i.e. in or against Y-direction. Also, by positioning the guard rails 41, 42 relative to base body 32, the distance d, D between guard rails 41, 42 can increase, decrease or remain the same.
In an alternative embodiment, adjustment device 22 comprises a second set of two actuators 64 so that both guard rails 41, 42 can be adjusted at the same time.
In addition or in the alternative, adjustment device 22 can further comprise a second stop actuator 76 with a second stop 74 so that both guard rails 41, 42 can be aligned at the same time.
In a further embodiment, adjustment device 22 comprises sensors for sensing the orientation and/or proximity of guard rails 41, 42 to the actuators 64 and/or stop 74 to further ensure a defined alignment and precise position of guard rails 41, 42 relative to base body 32.
In this way, a printbar 20 is provided where the front 38 of print head 34 is reliably protected by the protection device 36 from contact with damaged or warped sections of cardboard sheets 30 during printing.
Further, a printing system 10 with printbar 20 is provided where the protection device 36 can be adapted to various formats and sizes of cardboard sheets 30 via the adjustment device 22.

Claims

Printbar (20) for printing on cardboard sheets (30), comprising a base body (32) and a print head (34), characterized in that the printbar (20) further has a protection device (36) comprising a guard rail (41, 42) for preventing unintended contact between the print head (34) and the cardboard sheets (30) during printing, the guard rail (41, 42) being fixed to the base body (32).
Printbar (20) according to claim 1, characterized in that the guard rail (41, 42) extends in a working direction (X) from a first side (50) of the base body (32) to an opposite second side (52) of the base body (32).
Printbar (20) according to claim 1 or 2, characterized in that the guard rail (41, 42) is made of a ferromagnetic material, in particular a ferromagnetic metal.
Printbar (20) according to claim 3, characterized in that the printbar (20) further comprises a magnet (54), in particular a permanent magnet, the guard rail (41, 42) being fixed to the base body (32) via the magnet (54).
Printing system (10) comprising a printbar (20) according to any of the preceding claims.
Printing system (10) according to claim 5, characterized in that the printbar (20) is movable between a work zone (26) and a maintenance zone (28), in particular in a direction perpendicular to the working direction (X) and/or in a plane parallel to the printing plane (31) a cardboard sheet (30) is positioned in during printing.
Printing system (10) according to claim 5 or 6, characterized in that the printing system (10) further comprises an adjustment device (22) for positioning the guard rail (41, 42) relative to the base body (32) between a first position and a second position, wherein the first position and the second position are spaced apart from each other in a direction perpendicular to the working direction (X) and/or in a plane parallel to the printing plane (31) a cardboard sheet (30) is positioned in during printing.
Printing system (10) according to claim 7, characterized in that the adjustment device (22) comprises a stop (74) for aligning the guard rail (41, 42) when the guard rail (41, 42) is positioned via the adjustment device (22).
Printing system (10) according to claim 8, characterized in that the stop (74) is adjustable between a first position in which the stop (74) works as a stop for the guard rail (41, 42) and a second position in which the stop (74) does not work as a stop for the guard rail (41, 42).
Printing system (10) according to claim 8 or 9, characterized in that the stop (74) has a U-shaped profile.
Printing system (10) according to any one of claims 7 to 10, characterized in that the adjustment device (22) comprises an actuator (64) and a holding device (68) attached to the actuator (64), wherein the holding device (68) is movable by the actuator (64) between a receive position in which the holding device (68) is in a position to receive the guard rail (41, 42), and a release position in which the holding device (68) releases the guard rail (41, 42).
Printing system (10) according to claim 11, characterized in that the adjustment device (22) comprises an extractor (66) for separating the guard rail (41, 42) from the holding device (68), when the actuator (64) is moved to the release position.
Printing system (10) according to claim 11 or 12, characterized in that the holding device (68) is movable by the actuator (64) to a holding position spatially arranged between the receive position and the release position.
Printing system (10) according to any one of claims 11 to 13, characterized in that the holding device (68) comprises a magnet (70), in particular a permanent magnet, wherein the magnet (70) of the holding device (68) has a larger magnetic field than a magnet (54) of the printbar (20) for fixing the guard rail (41, 42) to the base body (32).
Printing system (10) according to any one of claims 5 to 14, characterized in that the protection device (36) comprises two guard rails (41, 42), one for each cardboard edge (61, 62) extending in working direction (X).