Machine and method for providing plate-like elements which comprise corrugated material

Abstract

A machine (90) for providing plate-like elements which comprise corrugated material (W), the machine comprising an applicator device (10, 10') for applying adhesive, in particular hot-melt glue, on the corrugated material, the applicator device comprising a spreading head (18) which is configured to: discharge the adhesive directly onto the corrugated material (W) and spread the adhesive on the corrugated material.

Description

[0001] MACHINE AND METHOD FOR PROVIDING PLATE-LIKE ELEMENTS WHICH COMPRISE CORRUGATED MATERIAL

[0002] The present invention relates to a machine and a method for providing plate-like elements which comprise corrugated material.

[0003] In the context of the invention, “corrugated material” means, as is known, a material that has a “wavy” longitudinal extension (i.e., with ridges and troughs), and is made by means of an adapted corrugation process.

[0004] In particular, the corrugated material to which reference is made is intended to form a corrugated layer of plate-like elements such as, for example, corrugated cardboard, corrugated polyethylene slabs or the like.

[0005] As is likewise known, “barrel pitch” means one width of the corrugated material, measured transversely with respect to the longitudinal extension of the “wave”.

[0006] The machine and the method according to the invention are particularly, but not exclusively, useful and practical for the industrial application of the kind of adhesive commonly known as hot-melt glue.

[0007] It is known from IT 102019000023418 that an adhesive can be spread on a corrugated material by way of a roller on the outer surface of which a layer of the adhesive is present.

[0008] Basically, when an applicator device like that shown in the accompanying Figure 1 has a roller 40 like the one mentioned above, a rotation R of the roller 40 enables a transfer of adhesive from that roller 40 to the corrugated material W.

[0009] Although useful and practical, roller applicator devices (i.e., applicator devices that use a roller to spread the adhesive) are not devoid of drawbacks.

[0010] A first drawback lies in the fact that it entails evident waste of adhesive. In fact, in roller applicator devices, the roller spreads the adhesive on the entire barrel pitch and it is not possible to reduce the width of spreading or to perform the spreading in “stripes”. Another drawback lies in the fact that, in roller applicator devices, the corrugated material tends to remain stuck to the roller, owing to the adhesive. Owing to this adhesive bonding, the corrugated material tends to leave its conveyance seat 36 (see Figure 1).

[0011] To reduce the risk of such egress, the use is known of containment elements (commonly called “corrugation containment elements”) which are adapted to keep the corrugated material in position. In Figure 1, these containment elements are indicated by the reference numerals 30, 32. However, for the roller to be able to rotate (and, therefore, execute the spreading of the adhesive), the containment elements must not touch the roller. As a consequence, when the containment elements are paired with a roller applicator device, the efficacy of such containment elements is not assured.

[0012] A further drawback lies in the fact that the corrugation spread with adhesive tends to excessively smear the containment elements that are placed where the roller exits. For example, in Figure 1, the adhesive can build up on the containment element 32. As a consequence, in roller applicator devices, the containment elements must be constantly heated by way of adapted electric heating elements, in order to prevent solidification of the adhesive on those containment elements, and they need to be cleaned periodically.

[0013] Another drawback is due to the fact that, by virtue of the corrugation process, the corrugated material can have ridges of irregular height, which complicate the even distribution of the adhesive.

[0014] The aim of the present invention is to overcome the limitations of the known art described above, by devising a machine and a method that make it possible to optimize the application of adhesive on a corrugated material.

[0015] Within this aim, an object of the present invention is to prevent waste during the application of adhesive on the corrugated material.

[0016] Another object of the invention is to optimize the distribution of adhesive on the corrugated material.

[0017] Another object of the invention is to make the provision of plate-like elements that comprise corrugated material more economical.

[0018] A further object of the invention is to minimize the quantity of adhesive to be applied on the corrugated material, while at the same time ensuring that such quantity is sufficient to glue the corrugated material to at least one planar layer (or element).

[0019] Another object of the invention is to obtain a precise distribution of the adhesive on the ridges of the corrugation, so ensuring in particular that a precise quantity of adhesive (expressed in weight per surface unit) is present on those ridges and that the portion of material spread can be regulated and / or controlled by applying adhesive to sectors / stripes.

[0020] Another object of the invention is to provide a machine with an applicator device that is extremely versatile, and capable of evenly distributing the adhesive on the ridges during any stage of production of a plate-like element that comprises the corrugated material.

[0021] Another object of the invention is to provide a machine in which the applicator device is capable of distributing the adhesive on corrugations of irregular height.

[0022] An additional object of the invention is to improve the applicator device of the machine according to IT 102019000023418.

[0023] Another object of the invention is to regulate a discharge port of the applicator device in a simple and rapid manner, so as to be able to subject corrugated materials with mutually different barrel pitches to the spreading process.

[0024] Another object of the invention is to apply the adhesive on the corrugated material in a manner that is highly reliable, easily and practically implemented, and economically competitive when compared to the known art.

[0025] This aim and these and other objects which will become more apparent hereinafter are achieved by the machine according to claim 1. Preferred embodiments are defined by the dependent claims.

[0026] Further characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of the machine according to the invention, which is illustrated by way of non-limiting example with the aid of the accompanying drawings wherein:

[0027] Figure 1 is a detail side view of a machine that comprises a conventional roller applicator device;

[0028] Figure 2 is a perspective view of a machine according to the invention;

[0029] Figure 3 is a side view of a variation of the machine of Figure 2;

[0030] Figure 3Ais a detail view of Figure 3;

[0031] Figure 4 is a partially cross-sectional side view of another machine according to the invention;

[0032] Figure 5 is a side view of a spreading device belonging to the machine of Figure 3;

[0033] Figure 6 is a front elevation view of the spreading device of Figure 5, from which a front cover has been removed and a handwheel has been added;

[0034] Figure 6 A is a detail view of Figure 6;

[0035] Figure 7 is a front elevation view of a modified version of the spreading device of Figure 6;

[0036] Figure 8 is a side view showing a particularly advantageous variation of the spreading head of the applicator device of Figure 5, arranged above a corrugated material; and

[0037] Figure 9 is a detail view of Figure 8.

[0038] In the figures, the reference numeral 10 designates the first applicator device, while the reference numeral 10’ designates the modified version of the applicator device 10. Except where explicitly stated, the applicator device 10’ can be entirely identical to the applicator device 10.

[0039] In each embodiment, the applicator device 10 or 10’ is part of a machine 90 for providing plate-like elements that comprise corrugated material W.

[0040] The applicator device 10 or 10’ is (configured) to apply the adhesive on the corrugated material W.

[0041] In each embodiment, the applicator device 10 comprises a spreading head 18.

[0042] The spreading head 18 is configured both to discharge the adhesive directly onto the corrugated material W, and to spread that adhesive on the corrugated material W. In other words, the spreading head 18 is an entity adapted to spread the adhesive on the corrugated material, and comprises a discharge channel 16 through which the adhesive can be discharged directly onto the corrugated material W.

[0043] Basically, when the spreading head 18 is supplied with the adhesive, the adhesive is discharged downstream of the spreading head 18 by way of the discharge channel 16. As a consequence, when the corrugated material W is positioned at the outlet of the discharge channel 16 (for example, as shown in Figures 2-4 and / or 8-9), the spreading head 18 discharges the adhesive directly on the corrugated material W. Subsequently, the spreading head 18 spreads the adhesive on the corrugated material W.

[0044] Therefore, differently from conventional roller applicator devices (where the adhesive is applied to the corrugated material W indirectly, i.e., after having been deposited on the outer surface of the roller 40), the spreading head 18 of the applicator device 10 makes it possible to apply the adhesive directly on the corrugated material W. Furthermore, the spreading head 18 makes it possible to distribute the adhesive on the ridges of the corrugated material W in a simple but effective manner both during a step of coupling the corrugation W2 and the substrate Wl, and during an optional step of application and adhesive bonding of an additional layer of material (such as, for example, the second planar layer T2).

[0045] Preferably, the spreading head 18 is made of metallic material.

[0046] In Figures 2 and 3, the spreading head 18 (and, therefore, the applicator device 10 or 10’) belongs to a first fixing station 50. By contrast, in Figure 4, the spreading head 18 (and, therefore, the applicator device 10 or 10’) belongs to a second fixing station 50’.

[0047] The first fixing station 50 is configured to fix a first planar layer T1 to the corrugated material W using the adhesive.

[0048] In particular, the first planar layer T1 forms (or is intended to form) a substrate W1 of the corrugated material W.

[0049] The second fixing station 50’ is configured to fix a second planar layer T2 to the corrugated material W and / or to the substrate Wl, using the adhesive.

[0050] In particular, the second planar layer T2 is a layer (intended to be) applied to a corrugation W2 that has already been formed and glued to the substrate Tl.

[0051] Basically, in the cited figures, the corrugation W2 is produced starting from a flat ribbon P which is undulated (i.e., shaped in a “wave”) in an undulation station 52.

[0052] The fixing stations 50, 50’ and / or the undulation station 52 can belong either to the same machine 90 or to separate machines.

[0053] Because the applicator device 10 is incorporated in the machine 90, the presence of the discharge channel 16 makes it possible to position the containment elements 30, 32 directly in contact with the spreading head 18 (as shown for example in Figure 3 A). As a consequence, providing the spreading head 18 with the discharge channel 16 makes it possible to prevent the problems of egress of the corrugation W2 which affect conventional roller applicator devices.

[0054] In the preferred and illustrated embodiments, the discharge channel 16 takes the form of a slit. In particular, the slit (and, therefore, the discharge channel 16) has a width that is calibrated to provide a (substantially) uniform output of a (thin) film of adhesive.

[0055] Basically, the discharge channel 16 makes it possible to discharge a (substantially) uniform layer of adhesive on the corrugated material W.

[0056] In the preferred and illustrated embodiments, the discharge channel 16 extends through a spout 18B of the spreading head 18.

[0057] In particular, the spout 18B defines an outlet port 18C which places the discharge channel 16 in fluid communication with the outside of the spreading head 18. In other words, the spout 18B defines at least a terminal portion 16A of the slit that forms the discharge channel 16.

[0058] Preferably, the outlet port 18C is formed by two lips 18B1, 18B2 of the spout 18B.

[0059] In the preferred and illustrated embodiments, the spout 18B is shaped like a “blade”.

[0060] In particular, the spout 18B forms a distribution blade, adapted to distribute the adhesive on the corrugated material W.

[0061] Basically, in the cited figures, the spout 18B serves both to apply the adhesive on the corrugated material W (by way of the discharge channel 16), and to spread (i.e., distribute) the adhesive on the corrugated material W.

[0062] In the preferred and illustrated embodiments, the spreading head 18 includes a chamber 24, adapted to contain the adhesive.

[0063] The chamber 24 is in fluid communication with the outside of the spreading head 18, by way of the discharge channel 16.

[0064] In Figures 2-5 and 8, the chamber 24 is hidden by a front cover 18A of the spreading head 18.

[0065] The spreading head 18 can be fed with adhesive at one or more points of the spreading head 18.

[0066] In the preferred and illustrated embodiments, the spreading head 18 can be supplied with adhesive by way of a tube 12, preferably of the type that can be heated.

[0067] In particular, the tube 12 is configured to introduce into the spreading head 18 an adhesive of the “hot melt” type, which has previously been brought to the liquid state and / or to its melting temperature using classic melting systems.

[0068] In the preferred and illustrated embodiments, the spreading head 18 includes at least one inlet port 18D which is adapted to introduce the adhesive into the chamber 24.

[0069] In particular, the tube 12 is in fluid communication with the chamber 24 by way of the inlet port 18D.

[0070] One or more heating cartridges 13 A, 13B can furthermore be inserted in the spreading head 18, and are adapted to keep the adhesive in the liquid state during the application process of that adhesive.

[0071] Basically, during the application of the adhesive, the presence of the heating cartridges 13A-B makes it possible to keep the liquid present in the spreading head 18 (and, in particular, in the chamber 24) in the liquid state.

[0072] In some preferred embodiments, the applicator device 10 includes one or more pads 15, which are adapted to dose a quantity of adhesive in the chamber 24.

[0073] In particular, each pad 15 is arranged (at least partially) inside the discharge channel 16, so as to delimit an outlet opening for the adhesive.

[0074] Basically, the pads 15 and the discharge channel 16 contribute to define a spreading port of the spreading head 18.

[0075] In the cited figures, the pads 15 delimit the chamber 24 laterally.

[0076] Preferably, each pad 15 is made of a metallic material, in particular bronze.

[0077] In some preferred embodiments, the applicator device 10 further comprises an adjustment system configured to adjust a positioning of one or more of the pads 15.

[0078] In particular, the adjustment system comprises an adjustment screw 14.

[0079] The adjustment screw 14 is configured to move one or more (preferably, all) of the pads 15 along a longitudinal direction.

[0080] In the cited figures, the longitudinal direction is represented by a Y axis.

[0081] Basically, the adjustment screw 14 makes it possible to adjust (or vary) the dimensions of the spreading port.

[0082] In the preferred and illustrated embodiments, the adjustment screw 14 is arranged inside the spreading head 18.

[0083] In particular, the adjustment screw 14 extends longitudinally (along the Y axis) through the chamber 24. In this manner, the dimensions of the spreading head 18 can be contained in a length (measured along the Y axis) that is slightly greater than the length of the chamber 24 and / or of the discharge channel 16 (again measured along the Y axis).

[0084] In the preferred and illustrated embodiments, the adjustment screw 14 comprises a left-handed threading 14A and a right-handed threading 14B.

[0085] Preferably, each threading 14A-B and / or each pad 15 are arranged symmetrically with respect to the inlet port 18D (see, for example, Figures 6-7). In this manner, it is possible to ensure an even distribution of pressure between a central zone, a right-hand zone and a left-hand zone of the chamber 24.

[0086] In some preferred embodiments, the adjustment system further comprises an actuation member.

[0087] The actuation member is configured to actuate the adjustment screw 14 from outside the spreading head 18.

[0088] Basically, the actuation member is configured to make the adjustment screw 14 rotate and, as a consequence, adjust the distance between the pads 15.

[0089] In some variants, the adjustment screw 14 is actuated manually. For example, in the cited figures, the actuation member is a handwheel 17. However, technologically more advanced variants are also conceivable, in which the adjustment screw 14 is activated automatically (for example, by way of a brushless motor).

[0090] Basically, the discharge channel 16, the adjustment screw 14, and the pads 15 constitute the critical parts of the applicator device 10. In fact, these specific parts make it possible both to retain the adhesive inside the chamber 24 in a precise manner, and to even out the pressure of the adhesive between the various zones of the chamber 24. As a consequence, these critical parts need to be made with extremely precise tolerances.

[0091] In some preferred embodiments, the discharge channel 16 ends with a plurality of discharge openings which are physically separate from each other. For example, either or both of the discharge channel 16 and the outlet port 18C can include one or more elements which form the plurality of discharge openings.

[0092] In some variants, the plurality of discharge openings is defined by at least one separator element which partially occludes the discharge channel 16. In other words, each separator element is arranged so as to partially engage the discharge channel 16.

[0093] In particular, the applicator device 10’ comprises separator elements 22 which subdivide the discharge channel 16 (and the chamber 24) into multiple portions 60-64 which are spaced out along a longitudinal direction. In Figure 7, this longitudinal direction corresponds to the Y axis.

[0094] Basically, the separator elements 22 are arranged so as to exclusively occlude some zones 26 of the discharge channel 16 (and of the chamber 24), leaving the portions 60-64 free. As a consequence, during the application of the adhesive, each separator element 22 acts as an adhesive containment element. At the same time, each portion 60-64 defines a respective dispensing zone through which the discharge channel 16 can discharge the adhesive out from the spreading head 18.

[0095] In alternative variants (not shown), the discharge openings are respective calibrated passages of one or more grilles arranged in the discharge channel 16 (for example, at the outlet port 18C).

[0096] Basically, during the application of the adhesive, the presence of multiple discharge openings enables the applicator device 10’ to spread the adhesive “in a comb-like manner” on the corrugated material W. In this manner, a plurality of adhesive strips is obtained, which extend substantially parallel to an advancement direction of the corrugated material W and, therefore, substantially transversely to the barrel pitch of that corrugated material. In the cited figures, the advancement direction of the corrugated material W is indicated by an X axis.

[0097] Basically, the spreading head 18 can be configured to execute a spreading “in a comb-like manner”.

[0098] Spreading “in a comb-like manner” is particularly useful and practical in order to reduce the quantity of adhesive necessary for gluing the corrugated material W. Furthermore, spreading “in a comb-like manner” makes it possible to position the containment elements 30, 32 in alignment with the separator elements 22 (in particular, along the advancement direction of the corrugated material W). In this manner, a risk of contact between the adhesive and the containment elements 30, 32 is appreciably reduced, so removing the need to heat those containment elements 30, 32.

[0099] Advantageously, the applicator device 10 can further comprise a leveling member 28 which is adapted to level in height a plurality of ridges of the corrugated material W.

[0100] In the preferred and illustrated embodiments, the leveling member 28 is a conveyor plate, positioned in the immediate vicinity of the outlet port 18C.

[0101] In particular, the conveyor plate 28 is arranged so as to be located upstream of the outlet port 18C with respect to the advancement direction of the corrugated material W.

[0102] The leveling member 28 is particularly useful and practical, during the production of a plate-like element that comprises the corrugated material W, when the function of that leveling member 28 is to even out the height of the corrugation before the ridges come into contact with a spreading zone (in particular, with the spout 18B) of the spreading head 18.

[0103] In the preferred and illustrated embodiments, the leveling member 28 protrudes downward from the spreading head 18.

[0104] In particular, a lower end 28A of the leveling member 28 is arranged at a lower elevation than a lower end (of the lip 18B2) of the spout 18B.

[0105] Basically, when a ridge W2A that is (slightly) higher than the other ridges of the corrugation W2 meets the leveling member 28, the ridge W2A is slightly deformed. As a result of this deformation, a height Hw of the corrugation W2 decreases. Therefore, the leveling member 28 makes it possible to even out the height of the corrugation W2 before the latter comes into contact with the spout 18B.

[0106] In some preferred embodiments, the spreading head 18 can be brought closer along a direction (substantially) perpendicular to the advancement direction of the corrugated material W.

[0107] In particular, the machine 90 can also be configured to move the spreading head 18 (or the entire applicator device 10, 10’) cyclically along a movement direction (substantially) perpendicular to the advancement direction of the corrugated material W.

[0108] In Figures 2-4, the movement direction of the spreading head 18 is (substantially) parallel to the Z axis.

[0109] Preferably, the machine 90 is configured so that the alternating movement of the spreading head 18 along the movement direction is synchronized with the advancement of the corrugated material W along the advancement direction.

[0110] Basically, in the figures, the spreading head 18 can be moved parallel to the Z axis, and the advancement of the corrugated material W along the X axis can be synchronized with the movement of the spreading head 18. The presence of synchrony between the movement of the spreading head 18 and the advancement of the material W enables both a more precise distribution of the adhesive on the ridges of the corrugation W2, and a minimization of the quantity of adhesive used.

[0111] The alternating movement of the spreading head 18 can be obtained by way of a link rod / crank mechanism, a cam mechanism, or other movement systems.

[0112] Preferably, the machine 90 comprises an oscillation system which is configured to provide an oscillating, synchronous relative motion between two or more of:

[0113] - the spreading head 18;

[0114] - the corrugated material W;

[0115] - a conveyance system for the corrugated material W (for example: the conveyance seat 36);

[0116] - a supporting surface for the corrugated material W.

[0117] As a consequence, in the figures, the spreading head 18 and the corrugated material W can be brought together and moved apart cyclically according to a cyclic motion such that an axial distance (measured along the Z axis) between the corrugated material W and the spreading head 18 is minimal when the outlet port 18C (or, more generally, the discharge channel 16) faces one or more ridges of the corrugation W2. In this manner, the adhesive can be applied exclusively to the ridges of the corrugation W2, so optimizing the consumption of adhesive.

[0118] Basically, a method for providing plate-like elements that comprise corrugated material W (i.e., the operation of the machine 90) comprises:

[0119] - discharging the adhesive directly onto the corrugated material W, using the spreading head 18; and

[0120] - spreading the adhesive on the corrugated material W, using the same spreading head 18.

[0121] In particular, the adhesive is discharged exclusively on the ridges of the corrugated material W.

[0122] Preferably, the adhesive is spread in a comb-like manner.

[0123] Once spread, the adhesive can be used to glue a lower planar element and / or an upper planar element to the corrugated material W.

[0124] In some preferred embodiments, the lower planar element and the upper planar element correspond, respectively, to the planar layers T1 and T2.

[0125] In practice it has been found that the machine and the method according to the present invention fully achieve the set aim and objects, in that they make it possible to overcome the limitations of the known art explained above.

[0126] In particular, the invention enables both an even distribution of the adhesive and a reduction of the quantity of adhesive used, with consequent reduction of waste (and therefore of costs). Further advantages of the invention that can be obtained include the capacity to vary the spreading port, as well as a reduction in the encumbrance of the spreading head.

[0127] The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

[0128] Except where indicated otherwise, the various embodiments described above can be combined in order to provide further and / or alternative embodiments.

[0129] Moreover, all the details may be substituted by other, technically equivalent elements.

[0130] In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.

[0131] The disclosures in Italian Patent Application No. 102024000018925 from which this application claims priority are incorporated herein by reference. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

CLAIMS1. A machine (90) for providing plate-like elements comprising corrugated material (W), said machine comprising an applicator device (10; 10') for applying adhesive, in particular hot-melt glue, to said corrugated material (W); characterized in that said applicator device (10; 10') comprises a spreading head (18) configured to:- discharge said adhesive directly onto said corrugated material (W); and- spread said adhesive on said corrugated material (W).

2. The machine (90) according to claim 1, wherein said spreading head (18) comprises a discharge channel (16) which extends through a spout (18B) of said spreading head (18), said discharge channel (16) ending in particular with a plurality of discharge openings (60-64) which are physically separated from each other.

3. The machine (90) according to claim 1, wherein said applicator device (10; 10') further comprises a leveling member (28) which is adapted to level in height a plurality of ridges of said corrugated material (W).

4. The machine (90) according to any one of the preceding claims, wherein said spreading head (18) belongs to a first fixing station (50) which is configured to fix a first planar layer (Tl, T2) to said corrugated material (W) by means of said adhesive.

5. The machine (90) according to claim 4, wherein said spreading head (18) belongs to a second fixing station (50') which is configured to fix a second planar layer (T2, Tl) to one or both of said corrugated material (W) and said first planar layer (Tl, T2) by means of said adhesive.

6. The machine (90) according to any one of the preceding claims, wherein said applicator device (10; 10') further comprises an adjustment system (14, 17) which is configured to adjust a positioning of one or more pads (15) of said spreading head (18), said adjustment system (14, 17)comprising in particular an adjustment screw (14) which is configured to move one or more of said pads (15) along a longitudinal direction (Y).

7. The machine (90) according to any one of the preceding claims, wherein: said applicator device (10; 10') is configured to provide a spreading in strips and / or in a comb-like manner, by means of using suitable pads; and said machine (90) comprises containment elements (32) which are positioned at sectors where said glue is not spread.

8. The machine (90) according to claim 6, wherein said adjustment system (14, 17) further comprises an actuation member (17) which is configured to actuate said adjustment screw (14) from outside said spreading head (18).

9. The machine (90) according to any one of the preceding claims, wherein said spreading head (18) can be brought closer to an advancement direction (X) of said corrugated material (W).

10. The machine (90) according to any one of the preceding claims, further comprising an oscillation system which is configured to provide an oscillating, synchronous relative motion between two or more of:- said spreading head (18),- said corrugated material (W),- a conveyance system (36) for said corrugated material (W);- a supporting surface for said corrugated material (W).

11. A method for providing plate-like elements that comprise corrugated material (W), which comprises:- discharging adhesive, in particular hot-melt glue, directly onto said corrugated material (W), using the spreading head (18) of the applicator device (10; 10') of the machine (90) according to any one of the preceding claims; and- spreading said adhesive onto said corrugated material (W), using said spreading head (18).1812. The method according to claim 10, further comprising the gluing of a lower planar element (Tl, T2) to said corrugated material (W) using said adhesive.

13. The method according to claim 10, further comprising the gluing of an upper planar element (T2, Tl) to said corrugated material (W) using said adhesive.

14. The method according to any one of the preceding claims, wherein said adhesive is discharged exclusively on ridges of said corrugated material (W), said adhesive being spread preferably in a comb-like manner.

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