Conveyor device with at least one vacuum lifter assembly

Abstract

The proposed solution relates to a conveyor device for a corrugator, comprising: - a conveyor mechanism (F) for conveying corrugated cardboard sheets (WP) towards a stacking unit (E7) of the corrugator; and - at least one adjustable lifting element (20) for separating sets (S1-S4) of corrugated cardboard sheets (WP) from one another within a stream of corrugated cardboard sheets (WP) when conveying the corrugated cardboard sheets (WP) towards the stacking unit (E7) via the conveyor mechanism (F), wherein the at least one lifting element (20) is adjustable to lift a back portion (WP31) of a first corrugated cardboard sheet (WP3) of a first set (S3) for separating the first corrugated cardboard sheet (WP3) of the first set (S3) from a last corrugated cardboard sheet (WP2) of another second set (S2) downstream of the first set (S3). The conveyor device (1) further comprises at least one vacuum lifter assembly (3) for separating the first corrugated cardboard sheet (WP3) of the first set (S3) from the last corrugated cardboard sheet (WP2) of the second set (S2), wherein the at least one vacuum lifter assembly (3) is configured to lift a front portion (WP30) of the first corrugated cardboard sheet (WP3).

Description

[0001] The proposed solution relates to our conveyor device for a corrugator.

[0002] A conveyor device in a corrugator is typically used for conveying and thus transporting corrugated cardboard sheets towards a stacking unit of the corrugator where the corrugated cardboard sheets are to be stacked in one pile per set each set including a predetermined number of produced corrugated cardboard sheets. A conveyor device is thus typically arranged downstream a slitting unit or creasing unit and downstream a cross-cutting unit of the corrugator splitting unit and / or increasing unit where - after having finished a corrugated cardboard web in a double facer - the corrugated cardboard web is cut into sheets of a size depending on the type of cardboard sheets to be produced in the corrugator. At the conveyor device sets of corrugated cardboard sheets are thus to be separated from each other so as to provide the stacker unit arranged downstream of the conveyor device with a steady flow of separable sets of corrugated cardboard sheets having a defined quantity. At the stacker unit the corrugated cardboard sheets of each set are then staggered so as to provide one pile of corrugated cardboard sheets per set in a storage area of the stacker unit from which each pile may be transported away.

[0003] The corrugated cardboard sheets reach the conveyor device in a continuous stream in which the corrugated cardboard sheets are arranged in a scaled configuration at least partially overlapping each other. In order to continually define sets of corrugated cardboard sheets from the stream, the conveyor device is typically configured to slow down a first corrugated cardboard sheet of a new set from a last corrugated cardboard sheet of a preceding set. In this context, it is known to use at least one adjustable, longitudinal ledge in the conveyor device via which a back portion of the first corrugated cardboard sheet of a new set may be lifted in order to separate this first corrugated cardboard sheet of the new set from the last corrugated cardboard sheet of another preceding set (which preceding set is located downstream of the new set with respect to a conveying direction of the corrugated cardboard sheets within the corrugator and thus within the conveyor device).

[0004] Slowing down a first corrugated cardboard sheet of a new set however bears the risk that a portion of the first corrugated cardboard sheet still contacts the last corrugated cardboard sheet of the preceding set and therefore at least partially sticks to this last corrugated cardboard sheet. Incorrect separations of two sets from each other in the conveyor device and / or undesired displacements of corrugated cardboard sheets may result therefrom.

[0005] Accordingly, it is an object of the proposed solution to provide improvements in this respect.

[0006] This object is addressed by the proposed conveyor device. A proposed conveyor device for a corrugator comprises a conveyor mechanism for conveying corrugated cardboard sheets towards a stacking unit of the corrugator (where corrugated cardboard sheets are to be stacked in sets of a defined number of corrugated cardboard sheets). At least one adjustable lifting element, for example at least one ledge or block, for separating sets of corrugated cardboard sheets from one another within a stream of corrugated cardboard sheets is provided as part of the proposed conveyor device. By means of the at least one adjustable lifting element the sets may be separated when conveying the corrugated cardboard sheets towards the stacking unit via the conveyor mechanism. For separating a first corrugated cardboard sheet of a first set from a last corrugated cardboard sheet of another, second set downstream of the first set (and thus preceding the first set in the conveying direction), the at least one lifting element is adjustable to lift a back portion of the first corrugated cardboard sheet of the first set. In addition, the conveyor device comprises at least one vacuum lifter assembly for separating the first corrugated cardboard sheet, wherein the at least one vacuum lifter assembly is configured to lift a front portion of the first corrugated cardboard sheet of the first set.

[0007] Lifting in the context of the disclosed solution in particular includes displacing a portion of the first corrugated cardboard sheet with a component of movement upwards and perpendicular to a conveying direction of the stream of corrugated cardboard sheets in the conveyor device. Accordingly, both the at least one adjustable lifting element and the at least one vacuum lifter assembly contribute to a separation of two sets of corrugated cardboard sheets from one another. With the aid of both the at least one lifting element and the at least one vacuum lifter portions of a corrugated cardboard sheet may be lifted upwards. A front portion to be lifted by the at least one vacuum lifter assembly is located in a distance to the back portion downstream with respect to the conveying direction of the stream of corrugated cardboard sheets. Accordingly, the at least one lifting element allows for a (mechanically) lifting of the first corrugated cardboard sheet at a portion including a trailing edge of the first corrugated cardboard sheet, e.g., by pushing the portion including the trailing edge upwards by the at least one lifting element, whereas the at least vacuum lifter assembly allows for lifting the same first corrugated cardboard sheet at another portion including a front edge of the first corrugated cardboard sheet, thereby ensuring that the front edge is spaced apart from a top surface of the last corrugated cardboard sheet bellowing to a preceding, second set of cardboard sheets. The at least one vacuum lifter assembly is thus configured to apply a lifting force (resulting from a vacuum generated at the vacuum lifter assembly) at first half or a first third of length (measured along the conveying direction) of the first corrugated cardboard sheet. The separation of different sets within the stream of corrugated cardboard sheets at a proposed conveyor device may thus become more reliable, even at high production speeds.

[0008] In an exemplary embodiment, the at least one vacuum lifter assembly is configured to suck the front portion of the first corrugated cardboard sheet of the first / new set upwards. The at least one lifting element may be configured to push the back portion of this first corrugated cardboard sheet upwards. Due to the typically scaled and overlapping arrangement of the corrugated cardboard sheets when arriving at the conveyor device, the lifting element and the vacuum lifter assembly applying lifting forces (a) at different portions of a first corrugated cardboard sheet of a new set and (b) on opposing sides and in opposing directions is advantageous to guarantee a precise and easily controllable lifting of the first corrugated cardboard sheet and to reliably define sets of sheets for piles to be generated in the downstream stacker unit.

[0009] In an exemplary embodiment, the at least one lifting element is a longitudinal component extending transversely with respect to a conveying direction along which the stream of corrugated cardboard sheets is to be carried towards the stacking unit by the conveyor device. By the at least one lifting element extending transversely to the conveying direction, the lifting element may extend over the complete width of the corrugated cardboard sheets in order to uniformly lift the back portion of a corrugated cardboard sheet. For example, a continuous ledge may be provided as a lifting element in this respect, wherein the ledge extends along a cross direction extending transversely to the conveying direction. In addition or in the alternative, a row of at least two (e.g., a plurality of) short ledges or blocks may be provided as lifting elements arranged side by side along the cross direction, wherein the row of at least two short ledges or blocks simultaneously act on a portion of a corrugated cardboard sheet for locally pushing it upwards. A ledge or a block of at least two ledges or blocks may, for example, be arranged between at least two conveyor belts of the conveyor device. Each ledge or block may thus be respectively arranged in a gap between two parallel conveyor belts provided for conveying the corrugated cardboard sheets.

[0010] The at least one lifting element may be attached to a mover element (of an adjustment assembly also comprising the at least one adjustable lifting element). The at least one lifting element may then be configured to be moved, via the mover element, below the stream of corrugated cardboard sheet in a conveying direction along which a stream of corrugated cardboard sheet is to be carried towards the stacking unit by the conveyor device. The at least one lifting element may thus apply a lifting force from the bottom at the back portion of the corrugated cardboard sheet and may then be moved together with the corrugated cardboard sheet in the conveying direction to maintain the back portion at least temporarily in an uplifted position.

[0011] The mover element may, for example, be a motor-driven belt or chain to which the at least one lifting element is attached. In particular, for supporting maintaining an uplifted position of the first corrugated cardboard sheet but also for allowing uplifting of further, subsequent cardboard sheets of the set, at least two lifting elements may be arranged, with respect to the conveying direction, one behind the other and respectively attached to the mover element so as to be moved together by the one mover element. In one embodiment, several lifting elements, e.g., in the form of ledges, are provided in a jalousie arrangement. The lifting elements may then be moved below the stream of corrugated cardboard sheets to lift up one or more sheets of a new set to separate the one or more sheets from our preceding set. A movement velocity of the one or more lifting elements in the conveying direction is harmonized with a conveying velocity with which the stream of corrugated cardboard sheets is conveyed towards the stacking unit by the conveyor mechanism. Thereby, the timing for contacting a back portion of the first corrugated cardboard sheet of a new set is tuned with respect to the conveying velocity.

[0012] In an alternative embodiment, the at least one lifting element is merely adjustable linearly in opposite directions with a component of movement perpendicular to a conveying direction along which a stream of corrugated cardboard sheets is to be carried towards the stacking unit by the conveyor device. In such an embodiment, the at least one lifting element remains in a stationary position along the conveying direction but is adjustable below the stream of corrugated cardboard sheets to move upwards and downwards for selectively pushing a back portion of a first corrugated cardboard sheets of a new set upwards to separate the new set from a preceding set.

[0013] Generally, the at least one vacuum lifter assembly may comprise at least one suction member for lifting the front portion of a first corrugated cardboard sheet of a new set. The at least one suction member is located above a conveyor element of the conveyor mechanism, which conveyor element is configured to convey the stream of corrugated cardboard sheets along the conveying direction towards the stacking unit. Accordingly, the at least one suction member of the at least one vacuum lifter assembly may, for example, be located above a conveyor belt of the conveyor mechanism by means of which conveyor belt the stream of corrugated cardboard sheet is to be conveyed towards the stacking unit.

[0014] In an exemplary embodiment, the at least one suction member is adjustable from an inactive position downwards in a direction of the conveyor element to an active position. In the active position, the at least one suction member is positioned closer to the conveyor element and thus, during operation of the conveyor device in the corrugator, closer to the stream of corrugated cardboard sheets. A portion of a cardboard sheet can therefore more reliably lifted up by a vacuum generated at the suction member. For displacing the at least one suction member from its inactive position towards its active position, the at least one suction member is adjustable with a component of movement towards the conveyor element. In particular, the at least one suction member may be adjustable linearly, e.g., perpendicular to the conveying direction.

[0015] In particular in case the at least one lifting element is not movable along the conveying direction but just linearly upwards and downwards, also the at least one suction member of the at least one vacuum lifter assembly may also be merely linearly adjustable from its inactive position to its active position and vice versa.

[0016] In the alternative, the at least one suction member may be adjustable along the conveying direction. This includes an embodiment in which the at least one suction member is adjustable along an adjustment axis parallel to the conveying direction or along an adjustment axis inclined (upwards) with respect to the conveying direction. In the latter case, the inclined adjustment axis defines an upwardly inclined downstream adjustment path for the suction member, wherein the front portion sucked towards the suction member and thereby held / clamped at a defined distance to the suction member or held / clamped at the suction member (based on a generated vacuum) will be lifted further upwards when the suction member moves along this adjustment path. Accordingly, due to the course of the inclined adjustment path, a distance of the suction member to the conveyor element increases, in particular continuously increases. A corresponding configuration is however obviously not mandatory. A linear adjustment path parallel to the conveying direction is obviously also a feasible option.

[0017] For adjusting the at least one suction member from its inactive position to its active position, the at least one vacuum lifter assembly may comprise an adjusting mechanism. At least one part of such an adjusting mechanism may then be adjustable along the conveying direction in order to provide for an adjustability of the at least one suction member along the conveying direction. The at least one suction member may be attached to this at least one part of the adjusting mechanism so that the at least one suction member may be adjusted along the adjustments path following the conveying direction by displacing the at least one part of the adjusting mechanism. Thereby, the at least one suction member may be moved along the conveying direction maintaining its active position and holding a front portion of the corrugated cardboard sheet in an uplifted position when a vacuum is generated at the suction member. For the adjustment along the conveying direction, the at least one vacuum lifter assembly may comprise at least one drive motor for driving the adjustment.

[0018] The at least one suction member may be adjustable from a start position along the conveying direction to and end position, wherein the at least one suction member is configured to keep the front portion of the first corrugated cardboard sheet in an uplifted position when being adjusted towards the end position. After having reached the end position, the at least one suction member may be adjustable back to the start position for separating another first corrugated cardboard sheet of a third and thus subsequent set of sheets following the first set. Accordingly, the at least one suction member may be automatically moved back to its start position for initiating a new separation process for another set of sheets. The back movement may be controlled by at least one drive motor so that the at least one suction member arrives at its start position in time. In this context, it might be expedient - depending on the configuration of the conveying device and / or the corrugator - that the vacuum lifter assembly is configured with at least one drive motor to adjust the at least one suction member from its end position back into its start position with an adjustment velocity in the range of 1 m / s and 6 m / s.

[0019] In an exemplary embodiment, the start position and / or the end position of the at least one suction member along the conveying direction is variable depending on the type of the corrugated cardboard sheets to be stacked. For example, the start position and / or end position of the at least one suction member may be varied depending on size, in particular width and / or depending on weight of the corrugated cardboard sheets. This allows for additional flexibility in a separating process of the conveying device within a corrugator.

[0020] For using a vacuum generated at the at least one suction member for lifting up at least a portion of a corrugated cardboard sheet, the at least one suction member may comprise a plurality of suction openings and / or suction slots. These suction openings and / or suction slots may, for example, be arranged in one or more rows at a bottom side of the suction member facing the conveyor element. Alternatively, the at least one suction member may just comprise a single elongated suction opening or slot. Such a suction opening or slot is also present at a bottom side of the at least one suction member facing the conveyor element.

[0021] In an exemplary embodiment, the at least one suction member comprises a vacuum crossbar extending transversely with respect to the conveyor direction (along a cross direction)f. Accordingly, the at least one suction member may in particular be formed by a vacuum crossbar arranged above a conveyor element of the conveyor mechanism for conveying the stream of corrugated cardboard sheets towards the stacking unit of a corrugator. The at least one suction member may, for example, be arranged above a conveyor belt. A corresponding vacuum crossbar may extend over the complete width of the corrugated cardboard sheets to be manufactured.

[0022] In an exemplary embodiment, the vacuum lifter assembly may include two suction members which are configured to engage at different sections of the front portion of the first corrugated cardboard sheet for lifting a front portion (and thereby separating a new set from a preceding one). The two suction members are separated from each other in the conveyor direction and are arranged one behind the other. Depending on the type of corrugated cardboard sheets it may be selectable whether one or both of the two suction members are activated for lifting a front portion. In case of corrugated cardboard sheets being heavier and / or bigger in size the suction members may be used together to lift up one front portion, whereas for smaller and / or a lighter corrugated cardboard sheets merely one of the two suction members may be in use.

[0023] In another exemplary embodiment, the vacuum lifter assembly includes a first suction member and at least one further second suction member, wherein the first and second suction members are spaced apart from one another along the conveyor direction. The at least one second suction members is configured to, at a start position of the first and second suction members, lift a front portion of a first corrugated cardboard sheet of a subsequent, third set following the first set, while the first suction member had lifted the front portion of the first corrugated cardboard sheet of this first set and had already been moved from the start position to an end position along the conveying direction. In such an embodiment, a new set of corrugated cardboard sheets can thus be separated by the at least one second suction member without the first suction member already having moved back to the start position. Such a configuration may thus allow for separating sets of corrugated cardboard sheets in faster operated corrugators. While one of the two suction members is driven to an end position holding a front portion of the first corrugated cardboard sheet in an uplifted position, the other suction member is on its way back to the start position for lifting up another first corrugated cardboard sheet of a subsequent set.

[0024] In an exemplary embodiment, one or more suction members of the at least one vacuum lifter assembly comprise multiple suction openings or suction slots arranged in at least two sections at a bottom face of the respective suction member. A first section of the at least two sections may then be (electronically) activated separately from a second section of the at least two sections. In such an embodiment, the numbers of sections active for lifting a front portion of a corrugated cardboard sheet up may thus be varied, for example depending on the type of the corrugated cardboard sheets to be stacked. This may allow for activating more or less sections of suction openings or suction slots at a suction member, for example depending on a size, including a width and / or depending on a weight over the corrugated cardboard sheets to be stacked.

[0025] The proposed solution also relates to a corrugator including an embodiment of a proposed conveyor device.

[0026] The attached figures illustrate exemplary embodiments of the proposed solution. Figure 1A shows a side view of a conveyor device according to the proposed solution comprising an adjustable suction member of a vacuum lifter assembly in an inactive position above a conveyor belt for conveying a stream of corrugated cardboard sheets towards a stacking unit. Figure 1B shows the conveyor device of Figure 1A with the suction member in an active position having lifted up a front portion of a first corrugated cardboard sheet of a new set to be separated from a preceding set of corrugated cardboard sheets. Figure 1C shows the conveyor device of Figures 1A and 1B with the suction member in its active position and moved to an end position along a conveying direction of the conveying device where the generation of a vacuum is stopped and the first corrugated cardboard sheet is released from the suction member. Figure 2A shows the conveying device of Figures 1A to 1C with further details in the suction member in an active state at a starting position. Figure 2B shows the conveying device of figure 2A with the active suction member at an end position. Figures 3A to 3D show the conveyor device of Figures 2A and 2B with the vacuum lifter assembly and its suction member in the different positions during a separation process for separating two sets of corrugated cardboard sheets from one another. Figure 4A shows a further embodiment of a conveying device according to the proposed solution in side views corresponding to Figures 3A-3D, wherein the suction member of this embodiment is merely linearly adjustable perpendicular to the conveying direction and the suction member is shown in its inactive position. Figure 4B shows the conveying device of Figure 4A with the suction member in its active position and with a lifting element in the form of a ledge for pushing a back portion of a first corrugated cardboard sheet upwards in an upper position. Figure 5 shows, in a view corresponding to Figures 3A-3D and 4A-4B, another embodiment of a conveying device according to the proposed solution in which the conveying device comprises two separate suction members. Figure 6 shows, in a view corresponding to Figure 5, another embodiment of a conveying device according to the proposed solution, wherein a single suction member of the vacuum lifter assembly comprises sections of suction openings or suction slots which may be activated separately from each other. Figure 7 shows a section of a single flute corrugated cardboard sheet in a perspective view. Figure 8 shows a section of a double flute corrugated cardboard sheet in a perspective view. Figure 9 schematically shows a corrugator for manufacturing a single flute corrugated cardboard sheet in which the conveyor device according to the proposed solution may operate.

[0027] Figures 7 and 8 each show a sectional and perspective view of the structure of a corrugated board WP. Figure 7 shows a single flute corrugated board WP. This corrugated board WP has a single corrugated layer 121, which is arranged between two cover layers 11 and 12. The corrugated layer 121 has a sinusoidal cross-section, while the cover layers 11 and 12 are flat. One cover layer 11 is referred to as the inner layer or inner liner, while the other cover layer 12 is referred to as the outer layer or outer liner.

[0028] In a double-wall corrugated board WP as shown in Figure 8, two corrugated layers 121 and 122 are provided between the two top layers 11 and 12. A flat intermediate layer 13 is arranged between these corrugated layers 121 and 122. The flute types of the flute layers 121 and 122 can in principle be different or identical to one another. In other words, in the first case mentioned, the sinusoidal courses of the corrugated layers 121 and 122 can differ from one another in terms of wave pitch, i.e. the distance between two directly successive wave crests or between two directly successive wave troughs, and / or in terms of wave height.

[0029] The corrugated board WP is typically produced in a corrugator. Figure 9 illustrates an example of a possible design variant of such a corrugator.

[0030] In the corrugator shown in Figure 9, two unwinding devices 101 and 102, for example in the form or reel stands, are provided for two material webs M1 and M2 in order to feed the material webs M1, M2, typically made of paper, to a first single-sided machine E1, for example in the form of a so-called "single facer". A second material web M2 is fed between two corrugating rolls W1 and W2 of the first single-sided machine E1. The pair of corrugating rollers W1 and W2 creates a corrugation in the second material web M2 and thus produces a corrugated layer from the second material web M2, which - after passing a gluing device L of the first single-sided machine E1 - is joined to the first material web M1 under the action of a pressing device AP. This provides a single-sided corrugated board web WPB at the output of the first single-sided machine E1. This corrugated board web WPB is transported for further processing via a (high-) transport device to a bridge B of the corrugator.

[0031] The corrugated board web WPB is fed to a preheating unit E2 along a conveying direction R as the production process continues. A third material web M3 also passes through this preheating unit E2. This third material web M3 is provided by a further separate unwinding device 103 and, if necessary, printed via a printing unit DR before entering the preheating unit E2.

[0032] After passing through the preheating unit E2, glue is applied to one of the webs WPB, M3 in a gluing unit E3. In the further production process, for example, the glued corrugated board web WPB is then joined to the third material web M3 in a pressure unit E4. For this purpose, the pressure unit E4 can comprise one or more heating plates - in particular when using conventional starch glue for the connection between the corrugated board web WPB and the material web M3. The corrugated board web WPB and the third material web M3 are pressed together, for example, by means of a motor-driven endless pressure belt guided by guide rollers. The pressure unit E4 can be designed as a pulling and heating section and / or as a part of a so-called double facer. The second material web M2 is therefore used, for example, to produce a corrugated layer 21 for a corrugated board WP of Figure 7. The first material web M1 is used here to form one of the cover layers 11 or 12. The third material web M3 is in turn used to produce the other cover layer 12 or 11 for the single wall corrugated board WP.

[0033] In the embodiment of a corrugator shown in Figure 9, a single-wall corrugated board is obtained from the pressure unit E4, which is fed to a slitting unit or creasing unit E5 of the corrugator in the subsequent production process. The continuous single-wall corrugated board web is cut lengthwise by the slitting unit or creasing unit E5.

[0034] A further cut is then made in a cross-cutting unit E6 to provide further processable corrugated board WP in the form of corrugated cardboard sheets from the endless corrugated board web. These corrugated cardboard sheets are transported via a conveyor belt F of the corrugator in Figure 9 to a stacking unit E7. The corrugated sheets can then be transported away in stacks from the stacking unit E7.

[0035] The conveyor belt F serves as a conveyor element of a conveyor device 1 for which different embodiments are shown in Figures 1A-1C, 2A-2B, 3A-3D, 4A-4B, 5, and 6. The conveyor belt F is part of a conveyor mechanism of such a conveyor device 1 for conveying corrugated cardboard sheets WP towards the stacking unit E7 of the corrugator.

[0036] The corrugated cardboard sheets WP reach the conveyor device 1 as a continuous stream of corrugated cardboard sheets WP in which the corrugated cardboard sheets WP are arranged in a scaled configuration at least partially overlapping each other. In the conveyor device 1 sets S1, S2, S3, S4 each with a predefined number of corrugated cardboard sheets WP have to be separated from one another so that the sets S1, S2, S3, S4 subsequently reach the stacking unit E7 where the corrugated cardboard sheets WP of a set S1, S2, S3, S4 are stacked to form a separate pile.

[0037] As shown in Figures 1A, 1B and 1C, a first embodiment of a proposed conveyor device 1 comprises an adjustment assembly 2 having a mover element in the form of a ledge belt or ledge chain 21 and several lifting elements in the form of rod-shaped ledges 24 for separating the sets S1-S4 of corrugated cardboard sheets WP from one another. Each rod-shaped ledge 20 extends transversely to the conveying direction R along a cross direction and over the full width of the corrugated cardboard sheets WP. The ledges 20 are arranged one behind the other at the ledge belt or ledge chain 21 so that the ledges 20 are provided in a jalouse-like arrangement and may positioned below the stream of corrugated cardboard sheets WP.

[0038] A velocity at which the ledges 20 are moved along the conveying direction R is tuned to a conveying velocity of the stream of corrugated cardboard sheets WP in the conveying direction R. Thereby, a first ledges 20 of the plurality of ledges 20 may be brought into contact with a back portion WP31 of a first corrugated cardboard sheet WP3 of a new set - in Figures 1A-1C set S3 - when this new set S3 has to be separated from a preceding set S2. Upon contact of one or more ledges 20 with a back portion WP31 of this first corrugated cardboard sheet WP3 the back portion WP31 is pushed upwards from below, thereby slowing down the first corrugated cardboard sheet WP3 so as to separate the first corrugated cardboard sheet WP3 from a last corrugated cardboard sheets WP2 of the preceding set S2. By means of the following ledges 20 of the adjustment assembly 2, the back portion WP31 of the first corrugated cardboard sheet WP3 as well as the portions of at least some of the following corrugated cardboard sheets of the set S3 are held in an uplifted position.

[0039] In the conveyor device 1 of Figures 1A, 1B and 1C an additional vacuum lifter assembly 3 is included. An operation of this vacuum lifter assembly 3 is harmonized with the operation of the adjustment assembly 2. The vacuum lifter assembly 3 is configured to lift a front portion WP30 of the first corrugated cardboard sheet WP3 of the new set S3 upwards, when the back portion WP31 of this first corrugated cardboard sheet WP3 is lifted upwards by the adjustment assembly 2. A suction member of the vacuum lifter assembly 3 is located above the conveyor belt F and thus above the stream of corrugated cardboard sheets WP. A vacuum generated at the vacuum lifter assembly 3 results in lifting force for pulling the front portion WP31 of the first corrugated cardboard sheet WP3 upwards, thereby spacing a front edge of the first corrugated cardboard sheet WP3 from the last corrugated cardboard sheet WP2 2 of the preceding set S2 with which the first corrugated cardboard sheet WP3 overlaps.

[0040] Before sucking the front portion WP31 upwards, the suction member of the vacuum lifter assembly 3 is in an inactive position as shown in Figure 1A. If the new set S3 is to be separated from the preceding set S2, the suction member of the vacuum lifter assembly 3 is automatically adjusted to move downwards along an adjustment direction V1 perpendicular to the conveying direction R. Due to the movement along the adjustment direction V1, the suction member of the vacuum lifter assembly 3 is moved closer to the stream of corrugated cardboard sheets WP.

[0041] As shown in Figure 1B, the suction member of the vacuum lifter assembly 3 then reaches an active position in which, due to the generated vacuum at the vacuum lifter assembly 3, the front portion WP30 of the first corrugated cardboard sheet WP3 of set S3 to be separated is lifted upwards. While the vacuum lifter assembly 3 lifts the front portion WP30 upwards by a pulling force, the adjustment assembly 2 lift the back portion WP31 upwards by a pushing force. While maintaining the suction member of the vacuum lifter assembly 3 in the active position, the vacuum lifter assembly 3 is moved longitudinally along a displacement direction V2 from a starting position shown in Figure 1B towards an end position shown in Figure 1C. The displacement direction V2 runs in parallel to the conveying direction R so that the vacuum lifter assembly 3 follows the first corrugated cardboard sheet WP3 of set S3. The displacement velocity of the vacuum lifter assembly 3 is thus harmonized with a conveying velocity resulting from the movement of conveyor belt F.

[0042] Having reached the end position of Figure 1C, the vacuum lifter assembly 3 releases the front portion WP30 of the first corrugated cardboard sheet WP 3, thereby terminating the separation process for the sets S3, S2. Afterwards, the suction member of the vacuum lifter assembly 3 is moved upwards to its inactive position and also moved backwards to its starting position for separating a subsequent set S4 from set S3. Typically, the vacuum lifter assembly 3 is to be moved backwards with a displacement velocity in the range of 1 m / s to 6 m / s to arrive in time at its starting position for separating a new set of corrugated cardboard sheets WP to be stacked.

[0043] Figures 2A and 2B show further details of the conveyor device 1 of the embodiment illustrated in Figures 1A-1C.

[0044] Figure 2A shows the conveyor device 1 with the adjustment assembly 2 and the vacuum lifter assembly 3 at the starting position. In Figure 2A a suction member of the vacuum lifter assembly 3 in the form of a vacuum crossbar 30 already is in its active position for lifting up the front portion of the first corrugated cardboard sheet WP3 of set S3. For adjusting the vacuum crossbar 30 from its inactive position to its active position and vice versa an adjustment mechanism 31 is provided at the vacuum lifter assembly 3. This adjustment mechanism 31 for example includes a guiding pole at which the vacuum crossbar 30 is slidably engaged. The vacuum crossbar 30 may thus be lowered and lifter along the guiding pole.

[0045] Furthermore, the vacuum lifter assembly 3 includes a guiding mechanism 32 for guiding the longitudinal displacement of the vacuum crossbar 30 from the starting position to the end position. Such a guiding mechanism 32 may for example comprise one or more guiding rails for sliding the adjustment mechanism 31 along the displacement direction V2 (which is identical to the conveying direction R) and backwards. The displacement of the vacuum crossbar 30 is controlled by at least one drive motor 33 of the vacuum lifter assembly 3.

[0046] When the vacuum crossbar 30 has reached the end position at the guiding mechanism 32, as shown in Figure 2B, the first corrugated cardboard sheet WP3 of set S3 is released. The vacuum crossbar 30 is then again moved upwards along direction -V1 towards the inactive position. At the same time or subsequently, the vacuum crossbar 30 is moved backwards in a direction -V2 towards the starting position.

[0047] By not only uplifting the back portion WP31 of the first corrugated cardboard sheet WP3 from below but also lifting up the front portion WP30 of the same first corrugated cardboard sheet WP3, a process for separating two subsequent cardboard sheet sets S3, S2 within the stream of corrugated cardboard sheets WP at a conveyor device 1 may be improved and is more reliable, since in particular sticking of a front edge of the first corrugated cardboard sheet WP3 on a top surface of the last corrugated cardboard sheet WP2 of the preceding set S2 (e.g., by adhesion) is excluded.

[0048] Figures 3A-3D further illustrate the different phases of movement of the vacuum lifter assembly 3 during a separation process.

[0049] Figure 3A shows the vacuum crossbar 30 in its inactive position and at a starting position P 0 . After being adjusted to the active position the vacuum crossbar 30 is moved along the displacement direction V2 from the starting position P 0 towards an end position P 1 , as illustrated in Figure 3B. Having reached the end position P 1 , the vacuum crossbar 30 is again moved upwards along direction -V1 towards the inactive position, see Figure 3C. Then the vacuum crossbar 30 is again moved back to the starting position P 0 along direction -V2, as shown in Figure 3D.

[0050] As illustrated in Figure 3A, the starting position P 0 and / or the end position P 2 may be varied for example for taking into account different types of corrugated cardboard sheets WP to be manufactured in the corrugator. As an example, Figure 3A shows a different starting position P 2 at distance along the conveying direction R from the original starting position P 0 . In addition or in the alternative, different numbers and types of vacuum crossbars 30 may be provided in the conveyor device 1 for different paper or board grades and / or paper or board weights.

[0051] Whereas the embodiments shown in Figures 1A-1C, 2A-2B and 3A-3D illustrate the vacuum lifter assembly 3 with the vacuum crossbar 30 not only being adjustable perpendicular to the conveying direction R (so as to be able to be lowered from an inactive position and lifted from an inactive position) but also being displaceable parallel to the conveying direction R and backwards, such an adjustability is not mandatory. As shown for another embodiment in Figures 4A and 4B, the vacuum crossbar 30 may also remain in a stationary position along the conveying direction R and may merely be adjustable between the active position and the inactive position for locally lifting a front portion of a first corrugated cardboard sheet of a set to be separated from a preceding one.

[0052] A corresponding stationary vacuum lifter assembly 3 may, for example, also be combined with a stationary adjustment assembly 2, as also illustrated in Figures 4A and 4B. Such a stationary adjustment assembly 2 may comprise merely one rod-shaped ledge 20 extending transversely to the conveying direction R and being merely adjustable perpendicular to the conveying direction R or along an adjustment direct extending under an angle different form 90°, e.g., in the range of 45° to 85°, with respect to the conveying direction. Accordingly, a single ledge 20 may be moved in an upward direction -V1 (as shown in Figure 4A) to push a back portion of the first corrugated cardboard sheet WP3 upwards. After the first corrugated cardboard sheet WP3 has completely passed the ledge 20 in the conveying direction R, the ledge 20 is retracted downwards (in direction V1 in Figure 4B). The ledge 20 then remains in this retracted position until a new set is to be separated.

[0053] In an embodiment illustrated in Figure 5, the vacuum lifter assembly 3 includes two vacuum crossbars 30 and 30' which are separately adjustable between active and inactive positions by adjusting mechanisms 31, 31'. Controlled via the at least one drive motor 33 and control electronics 34 of the vacuum lifter assembly 3 or the conveyor device 1, the vacuum crossbars 30, 30' may be separately controlled. For example, it is possible that those vacuum crossbars 30, 30' are operated together to lift in a front portion WP30 of a first corrugated cardboard sheet WP3, wherein by the two vacuum crossbar 30, 30' a higher suction force may be applied. For another setup of the conveyor device 1, merely one of the vacuum crossbars 30, 30' may be operated.

[0054] In the embodiment of Figure 6, a vacuum crossbar 30 comprises two section sections 301, 302. Whereas a vacuum crossbar 30 or 30' of the previously discussed embodiments comprise a single section with one or more suction openings and / or suction slots for using a generated vacuum to suck a front portion WP30 of a first corrugated cardboard sheet WP3 upwards, the vacuum crossbar 30 of the embodiment of Figure 6 includes at least two separate suctions sections each with one or more suction openings and / or suction slots. Depending on the suction force needed (which may for example vary depending on the type of corrugated cardboard sheets WP to be manufactured and for example their sizes and weights), both sections 301, 302 or just one of these sections 301, 302 may be active for the upward lifting. Activation of the different sections 301, 302 may for example be controlled by one or more valves of the vacuum lifter assembly 3 and / or one or more shutters for selectively opening or closing the suction openings or suction slots. For electronically controlling a valve and / or a shutter the control electronics 34 are used.

[0055] In the above description of the figures it was merely referred to lifting elements in the form of ledges 20 each ledge 20 extending longitudinally along the cross direction. The proposed solution is however not limited to such a configuration. For example, at least one ledge 20 or all ledges 20 may be (respectively) replaced by a row of at least two (e.g., a plurality of) shorter ledges or blocks as lifting elements arranged side by side along the cross direction.

[0056] A row of at least two short ledges or blocks then simultaneously acts on a portion of a corrugated cardboard sheet WP3 for locally pushing it upwards. A shorter ledge or block may, for example, be arranged between at least two conveyor belts F of the conveyor device 1, i.e., respectively in a gap between two conveyor belts F provided for conveying the corrugated cardboard sheets WP.List of reference numerals

[0057] 1conveyor device 101, 102, 103unwinding device 11inner layer 12outer layer 121, 122corrugated layer 13intermediate layer 2adjustment assembly 20ledge (lifting element) 21ledge belt (mover element) 3vacuum lifting assembly 30, 30'vacuum crossbar (suction member) 301, 302suction section 31, 31'adjustment mechanism 32guiding mechanism 33drive motor 34control electronics APpressing device Bbridge DRprinting unit E1single-sided machine E2preheating unit E3gluing unit E4pressure unit / double facer E5slitting unit or creasing unit E6cross-cutting unit E7stacking unit Fconveyor belt (conveyor element) Lgluing device M1, M2, M3material web P 0 , P 2 start position P 1 end position Rconveying direction S1, S2, S3, S4sheet set SEcontrol electronics V1adjustment direction V2displacement direction W1, W2corrugating rolls WPcorrugated board / corrugated cardboard sheet WP2, WP3corrugated cardboard sheet WP30front portion WP31back portion WPBcorrugated board web

Claims

1. A conveyor device for a corrugator, comprising: - a conveyor mechanism (F) for conveying corrugated cardboard sheets (WP) towards a stacking unit (E7) of the corrugator; and - at least one adjustable lifting element (20) for separating sets (S1-S4) of corrugated cardboard sheets (WP) from one another within a stream of corrugated cardboard sheets (WP) when conveying the corrugated cardboard sheets (WP) towards the stacking unit (E7) via the conveyor mechanism (F), wherein the at least one lifting element (20) is adjustable to lift a back portion (WP31) of a first corrugated cardboard sheet (WP3) of a first set (S3) for separating the first corrugated cardboard sheet (WP3) of the first set (S3) from a last corrugated cardboard sheet (WP2) of another second set (S2) downstream of the first set (S3), characterized in that the conveyor device (1) further comprises at least one vacuum lifter assembly (3) for separating the first corrugated cardboard sheet (WP3) of the first set (S3) from the last corrugated cardboard sheet (WP2) of the second set (S2), wherein the at least one vacuum lifter assembly (3) is configured to lift a front portion (WP30) of the first corrugated cardboard sheet (WP3).

2. The conveyor device of claim 1, characterized in that the at least one lifting element (20) is configured to push the back portion (WP31) of the first corrugated cardboard sheet (WP3) upwards.

3. The conveyor device of claim 1 or 2, characterized in that the at least one lifting element (20) extends transversely to a conveying direction (R) along which the stream of corrugated cardboard sheets (WP) is to be carried towards the stacking unit (E7) by the conveyor device (1).

4. The conveyor device of any one of claims 1 to 3, characterized in that the at least one lifting element (20) is attached to a mover element (21) and is configured to be moved, via the mover element (20), below the stream of corrugated cardboard sheets (WP) in a conveying direction (R) along which the stream of corrugated cardboard sheets (WP) is to be carried towards the stacking unit (E7) by the conveyor device (1).

5. The conveyor device of claim 4, characterized in that at least two lifting elements (20) are arranged, with respect to the conveying direction (R), one behind the other and are attached to the mover element (21) so as to be moved together by the mover element (21).

6. The conveyor device of any one of claims 1 to 3, characterized in that the at least one lifting element (20) is merely adjustable linearly in opposite directions (-V1, V1) with a component of movement perpendicular to a conveying direction (R) along which the stream of corrugated cardboard sheets (WP) is to be carried towards the stacking unit (E7) by the conveyor device (1).

7. The conveyor device of any one of the preceding claims, characterized in that the at least one vacuum lifter assembly (3) comprises at least one suction member (30, 30') for lifting the front portion (WP30) of the first corrugated cardboard sheet (WP3), wherein the at least one suction member (30, 30') is located above a conveyor element (F) of the conveyor mechanism configured to convey the stream of corrugated cardboard sheets (WP) along a conveying direction (R) towards the stacking unit (E7).

8. The conveyor device of claim 7, characterized in that the at least one suction member (30, 30') is adjustable from an inactive position downwards in direction of the conveyor element (F) to an active position.

9. The conveyor device of claims 6 and 8, characterized in that the at least one suction member (30') is merely linearly adjustable from the inactive position to the active position and vice versa.

10. The conveyor device of claim 7 or 8, characterized in that the at least one suction member (30, 30') is adjustable along the conveying direction (R).

11. The conveyor device of claims 8 and 10, characterized in that the at least one suction member (30, 30') is adjustable from the inactive position to the active position via an adjusting mechanism (31, 31') of the at least one vacuum lifter assembly (3), wherein at least one part of the adjusting mechanism (31, 31') to which the at least one suction member (30, 30') is attached is adjustable along the conveying direction (R).

12. The conveyor device of claim 10 or 11, characterized in that the at least one suction member (30, 30') is adjustable from a start position (P0, P2) along the conveying direction (R) to an end position (P1) and is configured to keep the front portion (WP30) of the first corrugated cardboard sheet (WP3) in an uplifted position when being adjusted towards the end position (P1), wherein the at least one suction member (30, 30') is adjustable from the end position (P1) back to the start position (P0, P2) for separating a first corrugated cardboard sheet of a third set (S4) following the first set (S3).

13. The conveyor device of claim 12, characterized in that the start position (P0, P2) and / or the end position (P1) is variable depending on a type of the corrugated cardboard sheets (WP) to be stacked.

14. The conveyor device of any one of claims 7 to 13, characterized in that the at least one suction member comprises a vacuum crossbar (30, 30') extending transversely with respect to the conveyor direction (R).

15. A corrugator comprising the conveyor device (3) of any one of the preceding claims.

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