DESCRIPTION

TECHNICAL FIELD [0001] The invention relates to methods and equipment for cutting paper, non- woven fabric, or other continuous web materials into strips. Embodiments described below relate to methods and equipment for cutting continuous web materials formed of fiber materials. In the present context, the term 'fiber' generally refers to discon tinuous fibers (staple fibers) or continuous fibers, i.e. filaments. BACKGROUND ART

[0002] Currently, sheets of paper, for example tissue paper, non-woven fabric and other web materials, typically made of continuous or staple fibers, are produced from large rolls, known as parent reels or“jumbo reels”, which are produced by continu- ous machines, for example machines for the production of paper, or non-woven fab- ric. These reels have a large diameter and a large axial dimension. They are trans formed into finished products or semi-finished products by means of a process of unwinding and possible re-winding into rolls of a smaller size. For example, the reels can be unwound and cut into longitudinal strips with a width smaller than the axial dimension of the jumbo reel and the same width as the finished products desired. [0003] The strips can be re-wound onto rolls, or can be further cut transversally in to sheets that are then folded and collected in packs, for example.

[0004] Converting processes of this type are used, for example, for the production of rolls of non-woven fabric intended to be used on subsequent machines for the pro duction of sanitary pads, nappies, or others. In other applications, the process of un- winding, cutting and re-winding is used for the production of rolls of toilet paper, kitchen towels or other products made of tissue paper. The process of unwinding, longitudinally cutting, transversely cutting and folding is used, for example, to pro duce paper hankies, paper napkins and other products made of folded tissue paper.

[0005] The process of unwinding web material and cutting it into strips is a contin- uous process.

[0006] In some cases, the parent reel is formed of a single ply of web material. In other cases, the parent reel is obtained by winding two or more plies together. During the unwinding phase, it is possible to unwind and convert the web material from a single parent reel, or from several parent reels in parallel. In this way it is possible, for example, to bond two plies coming from two parent reels to form a multi-ply con tinuous web material, which is cut continuously into longitudinal strips, intended to be rewound to form single rolls, or intended to be cut and folded into single multi-ply sheets.

[0007] Cutting on rewinders is generally carried out by means of rotating blades, in continuous contact with the sheets to be cut. The blades may co-act with counter blades.

[0008] Cutting by means or rotating blades is subject to major drawbacks, includ ing the fact that the blades tend to become worn, as a result of continuous contact with the material, and therefore they need to be frequently sharpened or replaced.

[0009] Furthermore, cutting by means of rotating blades is often not very neat and precise due to the formation of debris. Cutting results in the formation of harmful, highly- inflammable dusts, which increase the risk of fires in factories for the convert ing of web material.

[0010] The web material to be cut, in continuous contact with the rotating blade, tends to adhere to the rotating blade and consequently to be subject to expansion and deformation. For this reason, the longitudinal cut is often not very precise and not very neat. In some cases, unwanted lacerations may also be made to the web material during cutting.

[0011] The lack of precision in the longitudinal cutting of the strips, in the case of rewinding into rolls, causes adhesion between adjacent rolls, because two adjacent strips of web material, wound into two contiguous rolls, can give rise to coils that can get tangled up with each other along the adjacent edges of the strips.

[0012] As mentioned above, in many cases the products obtained from these con verting processes comprise a multi-layer or multi-ply structure. For example, typical- ly in the field of production of articles made of tissue paper, such as toilet paper, kitchen towels, paper hankies and napkins, the finished or semi-finished products are formed by bonding two or more plies of cellulose fiber material. The plies are bond- ed together by means of calendering, embossing, mechanical ply-bonding or gluing processes, or combinations thereof Nevertheless, in many cases the plies that form the finished or semi-finished product thus obtained often tend to separate. The sepa ration of plies is an unwanted phenomenon, since it makes the products unusable, or at least reduces their quality and/or makes subsequent processing, including packag ing, difficult or problematic.

[0013] Ultrasonic systems have also been suggested for cutting continuous strips. For example, DE 199541129 discloses a device for cutting web materials using ultra sound. A sonotrode with a straight cutting-edge co-acts with an anvil formed of a ro tating sphere. FR2914577 discloses an ultrasonic cutting system for fabrics made of heat-fusible material. W02007011272 discloses an ultrasonic device for welding plies of continuous web material. A vertical sonotrode co-acts with an anvil in the form of a cylinder on which the plies to be welded are guided.

[0014] Ultrasonic cutting and/or welding devices currently known have proved to be inefficient in dealing with cellulose plies and/or non-woven fabrics.

[0015] Therefore, a need exists to improve the methods and equipment used for unwinding web materials from parent reels and cutting them into longitudinal strips, in order wholly or partially to overcome one or more of the drawbacks of known art.

SUMMARY OF THE INVENTION

[0016] The invention relates to a device for longitudinally cutting a continuous web material. The device comprises an advancement path for the continuous web materi al, at least one cutting tool provided with a cutting edge co-acting with an anvil member. The cutting tool is associated with a sonotrode adapted to cause a vibration of the cutting tool in a direction having at least one component orthogonal to an anvil surface of the anvil member. The cutting tool is movable with a reciprocating move ment with respect to the anvil member. The reciprocating movement has at least one component parallel to the cutting edge. [0017] The reciprocating movement can be very slow with respect to the advance- ment movement of the continuous web material. For example, a complete cycle of the reciprocating cutting movement may take several hours to complete. In particu- larly advantageous embodiments, the cutting tool has a circular cutting edge and the reciprocating movement in this case may be a reciprocating rotation movement around a substantially through-passing axis.

[0018] According to another aspect, the invention concerns a method for longitudi- nally cutting a continuous web material (N) using ultrasound, comprising the steps of:

feeding the continuous web material along an advancement path between a cutting tool and an anvil member;

using a sonotrode to cause the cutting tool to vibrate against the anvil mem ber, resulting in cutting of the continuous web material in a longitudinal direction, parallel to the direction of advancement of the continuous web material along the advancement path;

moving in a reciprocating manner the cutting tool, the reciprocating move ment having a component parallel to a cutting edge of the cutting tool.

[0019] Further advantageous features and embodiments of the method and of the device according to the invention are indicated in the appended claims, which form an integral part of the present invention, and in the detailed description below, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention will be better understood by following the description and the accompanying drawings, which illustrate an exemplary and non-limiting embodi ment of the invention. More particularly, in the drawings:

Figs. 1, 2 and 3 show three layouts of a cutting device with the respective ad vancement path of a continuous web material;

Fig.4 shows a view according to IV-IV of a portion of continuous web material divided into two strips by means of a longitudinal cut;

Fig.5 shows a side view of a cutting tool;

Fig. 6 shows a view according to VI- VI of Fig. 5; Fig.7 shows an axonometric view of the cutting tool shown in Figs. 5 and 6; Figs. 8, 9 and 10 show alternative profile shapes for the cutting edge, or bevel, of the cutting tool shown in Figs. 5 to 7;

Fig.11 shows a schematic enlargement of a cutting tool and relative sonotrode in a side view;

Fig.12 shows a side view of a cutting tool with the relative supporting frame and the anvil roller with which it co-acts;

Fig.13 shows a section according to XIII-XIII shown in Fig.12, illustrating the anvil roller support means;

Fig. 13A shows an enlargement of detail A shown in Fig. 13;

Fig. l3B shows a control diagram for the actuators that generate the cutting thrust;

Fig.14 shows a side view of a second embodiment of the ultrasonic cutting de- vice; and

Fig.15 shows a side view of a third embodiment of the ultrasonic cutting de- vice.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] Fig.l shows a schematic view of an embodiment of a device 1 for cutting a continuous web material N in longitudinal strips, along longitudinal cutting lines, i.e. lines oriented according to the direction of advancement of the web material N along an advancement path P. In the embodiment shown in Fig.l, the advancement path P of the web material N is defined by a feed roller 3, a tension roller 5 and an anvil roller 7, co-acting with one or more cutting tools 9. The reference number 7S indi- cates the cylindrical surface of the anvil roller 7, which co-acts with the cutting tools 9.

[0022] Fig. 1 shows a single cutting tool 9 dividing the continuous web material N into two continuous strips Sl, S2 (Fig.4) along a longitudinal cutting line T, parallel to the direction of advancement F of the web material N along the advancement path P. However, it should be understood that the cutting device 1 may comprise a plurali ty of cutting tools 9, for example aligned along a direction transversal to the direction of advancement F of the web material N along the advancement path P, to obtain a plurality of strips S. The transversal position of the cutting tools 9 can be adjusted to obtain strips S of different width, as required. There may also be several groups of cutting tools arranged in different angular positions around the anvil roller 7.

[0023] The cutting tool 9 is controlled by a sonotrode, illustrated schematically with the reference number 11 , which generates a vibration applied to the cutting tool 9 in a direction of vibration V, oriented along the axis of the sonotrode 11. As will be clarified below, the cutting tool 9 and the sonotrode 11 have a reciprocating move- ment in a direction such that the cutting edge of the cutting tool 9 moves parallel to it. In the embodiment shown Fig. 1 the tool 9 and the sonotrode 11 have a reciprocat ing rotation movement in the direction of the double arrow f9. As a result of the re- ciprocating rotation f9 the direction of vibration V of the sonotrode 11 and of the tool 9 varies during operation, around a median position which can be approximately ra dial with respect to the anvil roller 7. In Fig.1 the median direction of the vibration V is approximately horizontal.

[0024] During the rotation movement of the cutting tool 9, the vibration movement imparted by the sonotrode always has one component orthogonal to the anvil surface 7S of the anvil roller 7, and more precisely orthogonal to the anvil surface 7S at the point of contact with the cutting edge of the cutting tool 9 which, as will be described below, has an arc shape.

[0025] In practical embodiments, the reciprocating rotation of the cutting tool 9 in the direction of the double arrow f9 is very slow. For example, the cutting tool 9 can complete one complete rotation cycle in both directions in several hours, typically more than two hours, preferably more than five hours, for example more than eight hours, and typically less than twelve hours. The rotation may be continuous, or it may be in steps.

[0026] The slow reciprocating rotation movement of the cutting tool 9 around a median position makes it possible to distribute wear uniformly over the entire arc of the cutting edge of the cutting tool 9.

[0027] The vibration frequency of the sonotrode and therefore of the cutting tool 9 may be between around 20kHz and 200 kHz, and preferably between around 20 kHz and 100 kHz, and more preferably between 20 kHz and 80 kHz. [0028] The advancement path P of the web material N extends around the anvil roller 7 by an angle a, which may for example be between around 120° and 170°, and in some embodiments between around 140° and 170°, and preferably between around 150° and 160°. The afore-mentioned figures should be considered as exem plifying and non-limiting. The zone in which the cutting tool 9 acts is in an interme diate position along the length of the contact arc between the web material N and the anvil roller 7.

[0029] The peripheral rotation speed of one or more of the rollers 3, 5 and 7 along the advancement path P can be controlled so as to stretch the web material N in an appropriate manner before it is subjected to the action of the cutting tool or tools 9. In some embodiments the rollers 3 and 5 can be idle. In some embodiments, the roll er 7 can be idle. In other embodiments, the roller 7 is motorized and rotates at a con trolled speed.

[0030] The advancement speed of the web material N may vary, for example based on the type of material used. The web material may in fact consist of a cellulose fiber material, such as paper, for example, and especially tissue paper. In some cases the web material N may be a ply of non-woven fabric, for example obtained by mechan ical needle-punching, by water needle-punching, by casting on metallic tape, using spun-bonded or spun-laid techniques, melt-blown, or other known techniques in the field, and suitably consolidated, for example using thermal and/or chemical consoli dation systems, or using any other technique.

[0031] In some forms of implementation, the speed of advancement of the web ma terial N can be between 200 m/min and 2500 m/min. Preferably the speed of ad vancement may be between 1000 m/min and 2200 m/min. In some embodiments, continuous web material N in paper may advance at speeds between 1500 and 2000 m/min, for example. In some embodiments, continuous web material N made of non- woven fabric may advance at speeds between 1000 m/min and 1500 m/min.

[0032] To improve control of the web material N at such high advancement speeds, in some embodiments one or more of the guide rollers around which the web materi al N is guided, different from the anvil roller 7, may have a movable axis, so as to enable reciprocal adjustment of the position of the rollers defining the advancement path of the web material N. In the exemplary embodiment shown in Fig.l, the ten sion roller 5 can be adjusted in one or other of the directions f5x, f5y, or both. By modifying the position of the axis of the tension roller 5, with respect to the position of the anvil roller 7, it is possible to modify and adjust the contact arc between the web material N and the anvil rollers 7.

[0033] Fig.2 shows an embodiment similar to that shown in Fig.l, with a different position of the cutting member 9 and the relevant sonotrode. The same numbers indi- cate the same or equivalent parts to those shown in Fig.l, which will not be described again. In the embodiment shown in Fig.2, the direction V of vibration of the tool 9 imparted by the sonotrode 11 , in its median position, is oriented almost vertically and the zone of action of the cutting tool 9 on the web material N is adjacent to the point where the web material N detaches from the anvil roller 7. In substance, the tool 9 is shifted by 90° with respect to the position shown in Fig.1.

[0034] Fig. 3, where the same numbers indicate the same or corresponding parts to those shown in Figures 1 and 2, shows two cutting tools 9.1 and 9.2 with relevant sonotrodes 11.1 and 11.2, in positions corresponding to those shown in Figs. 1 and 2. As with the tools 9 and sonotrodes 11 shown in Figs.l and 2, also in Fig. 3, in each of the two positions (staggered by 90°) of the two cutting tools 9.1 and 9.2, there may be in reality a series of cutting tools and relevant sonotrodes aligned transversal- ly to the direction of advancement F of the web material N along the advancement path P. The arrangement shown in Fig.3 makes it possible to place a greater number of cutting tools 9 transversally to the advancement path P, staggered between each other, so as to be able to make cuts T close together and divide the web material N into a plurality of relatively narrow strips S, for example with a width of only a few centimeters.

[0035] Figs.5, 6 and 7 show in detail an embodiment of a cutting tool 9. In general, the cutting tool 9 comprises a body 9A which is in one piece with a shank 9B for rig id connection between the cutting tool 9 and the respective sonotrode 11, which pro vides the vibration movement to the cutting tool 9. On the side opposite the shank 9B, the tool 9 has a cutting edge 9C formed on a bevel 9D. In the embodiment shown, the cutting edge 9C of the tool 9 is advantageously circular, i.e. it has an arc shape. In Fig.5 the center of the circumference of the cutting edge 9C is indicated by the letter C, while the letter R indicates the radius of curvature of the cutting edge 9C. The symbol b indicates the angle subtended by the arc along which the cutting edge 9C extends. In some embodiments, the angle b may be between around 20° and 60°, preferably between around 20° and 30°. The figures given above should be con sidered exemplifying and non-limiting. As mentioned, and as described in greater de tail below, during operation of the cutting device 1, the cutting tool 9 and the sono- trode 11 rotate slowly with a reciprocating movement around an axis passing through the center C and substantially parallel to the axis of the anvil member 7. In practice, the axis of the reciprocating rotation movement of the cutting tool 9 is oriented at 90° with respect to the direction of advancement of the continuous web material N at the cutting point, i.e. at the point of contact between the cutting tool 9 and the anvil member 7. The angle of the reciprocating rotary movement is equal to or less than the angle b.

[0036] The bevel 9D and the cutting edge 9C may have different shapes, for exam ple as a function of the type of web material N to be cut. Figs. 8, 9 and 10 shows three different alternative shapes for the profile of the bevel 9D. In Fig. 8 the bevel 9B defines a cutting edge 9C with a sharp edge. In Fig. 9 the sides of the bevel 9D end before their intersection point, thereby defining a cutting edge 9C with a cylin drical shape and having a thickness for example of 0.05-0.3 mm, and preferably be tween around 0.1 and 0.2 mm. In Fig.10 the cutting edge 9C is rounded and can have a radius of curvature, for example, of between 0.05 and 0.3 mm, and preferably be tween around 0.1 and 0.2 mm. The opening angle of the bevel (indicated by g) may be between around 10° and 60°, and preferably between around 10° and 15°. The figures given above should be considered exemplifying and non-limiting.

[0037] Fig.11 shows an enlarged schematic side view of the unit formed by a cut ting tool 9 and the respective sonotrode 11. The sonotrode 11 may be mounted in a sonotrode-holder block 13 which is in turn mounted on a beam, described below, which rotates with a reciprocating movement around an axis C, coincident with the center of curvature of the cutting edge 9C of the cutting tool 9.

[0038] Fig. 12 shows a side view of an embodiment of the unit carrying the cutting tools 9 and the relative sonotrodes 11, in combination with an anvil roller 7. In the embodiment shown in Fig. 12 the sonotrode/cutting tool units are carried by a frame 15 which can be mounted on a load-bearing structure 17, for example by means of guides 18. In this way, the frame 15 can move in the direction of the double arrow fl 5 towards and away from the anvil roller 7.

[0039] The frame 15 supports a beam 19 extending parallel to the rotation axis C of the cutting tools 9 and therefore transversally to the direction of advancement F of the web material N along the advancement path P, as well as parallel to the rotation axis 7A of the anvil roller 7. Reference number 20 indicates heads (only one of which is visible in Fig. 12), by means of which the beam 19 is fixed to the frame 15. The beam 19 is adapted to rotate with a reciprocating movement at an angle equal to or less than b around its own longitudinal axis. The reciprocating rotation is con trolled by a suitable actuator. In the example shown in the drawings, the actuator 21 is shown schematically as a linear actuator, for example a cylinder-piston actuator, which can be connected between an appendage 15A of the frame 15 and an append age 19A of the beam 19. The lengthening and shortening movement of the actuator 21 is indicated by £21. It causes the rotation of the beam 19, and therefore also of the cutting tool l9-sonotrode 11 unit/units in the direction of the arrow f9. In other em bodiments the actuator 21 may comprise a rotating actuator, for example a motor, typically an electric motor.

[0040] One or more units may be mounted on the beam 19, each unit comprising a cutting tool 9 and a respective sonotrode 11. In the drawing, a single unit can be seen. The support block 13 for the sonotrode 11 and the respective cutting tool 9 is mounted on an advancement slide 31 adjustable along guides 32 by means of a man ual or automatic adjustment member 33. In the example shown, adjustment is carried out by means of a manual device, for example a micrometer 33 or other similar de vice. The position of the block 13, and thus of the sonotrode 11 and of the cutting tool 9, with respect to the beam 19 can be adjusted with the adjustment member 33.

[0041] The guides 32 are in turn fixed to plates 34, 36 attached to a transversal translation slide 35, which makes it possible to adjust, preferably automatically, the transversal position of the cutting tool 9 and of the sonotrode 11 in a transversal di rection, i.e. along the longitudinal extension of the beam 19, parallel to the rotation axis 7A of the anvil roller 7. To that end, the beam is provided with guides 38 with which the runners 37 of the slide 35 are slidingly engaged. A plurality of slides 35 can be arranged and adjusted along the beam 19 in order to position respective cut ting tools 9 as a function of the number and width of the strips S into which the web material N has to be cut. Each slide 35 can be equipped with a brake 40 for fixing the slide 35 in a determined position along the length of the beam 19. The transversal ad justment mechanism for the slides 35 and thus also for the cutting tools 9 can be made in various ways, known to those skilled in the art, for example in a manner similar or the same as that used for the positioning of support slides for rotating disc shaped cutting tools, used in the field of winding and rewinding machines.

[0042] Fig.l3A shows an enlargement of the adjustment member 33 comprising, in the example shown, a un centesimal micrometer. The micrometer is fixed to the plate in one piece with the slide 35, for example to the plate 34. Said plate 34 may consti tute the limit stop for the slide 31. A rod 33A from the micrometer 33 is fixed to the slide 31 and passes through the plate 34 and a reaction plate 42. Between the reaction plate 42 and the plate 34 there is at least one resilient member 44, for example a compression coil spring. The reaction plate 42 is movable in the direction of the ar row f42 with respect to the limit stop plate 34 for the purposes described. In normal operating conditions, the position of the slide 31 with respect to the trolley 35 and to the limit stop plate 34 is determined by the reaction plate 42 striking against a stop ping element defined by a nut 46 screwed onto a screw 48. This position can be ad justed initially by means of the micrometer 33 so as to compensate for any run-out differences that may exist on the cylindrical surface of the anvil roller 7. The position is maintained by the compression spring 44 which acts as a damping element. If an anomalous thrust is exerted on the cutting tool 9, tending to move it away from the anvil roller 7, said thrust is compensated for by a backward movement of the slide 31 allowed by compression of the spring 44. In this way, overloading of the cutting tool 9 is avoided. Anomalous thrust stresses on the structure may be due, for example, to defects in the web material N, which may have sudden variations in thickness, to vi brations in the cutting system as a whole, to variations in the dynamic camber of the anvil roller, or to other anomalous factors.

[0043] When an anomaly of this type occurs, the increased thrust temporarily ex erted on the cutting tool 9 causes the compression of the spring 44 and thus move ment in the direction f42 of the slide 31 and the cutting tool 9, as well as the sono- trode 11 mounted on the slide 31. Once the cause of the overloading on the cutting tool 9 has ceased, the spring 44 extends once again, returning the slide 41 to its orig inal position, defined by the adjustment member 33.

[0044] In practice, therefore, each cutting tool 9 is associated with a system for ab sorbing or compensating for overloads on the tool.

[0045] The anvil roller 7 faces the frame 15. The former can be equipped with pins 7C inserted in support bearings 41, which may be housed in respective uprights 43. The two uprights 43, the bearings 41 and the anvil roller 7 form an assembly that can be adjusted in the direction of the double arrow f7. To this end, there may be provid ed a guide system parallel to the rotation axis 7A of the anvil roller 7. The guide sys tem may comprise runners 45 in one piece with the uprights 43 and engaged with guides 47.

[0046] In the drawing, the anvil roller 7 is mounted idly on the respective support bearings 41. Nevertheless it should be understood that in some embodiments the roll er can be motorized. To that end, one of the pins 7C may extend beyond the support bearing and can be connected to a drive motor, for example by means of a belt or gear transmission, or with a direct coupling.

[0047] In some embodiments there may be an adjustment member 49 (Fig.13), with which the transversal position of the anvil roller 7 is adjusted in the direction of the double arrow f7. Using the adjustment member 49 it is possible to adjust the position of the anvil roller 7 parallel to the axis thereof. This can be useful, for example to avoid localized wear on the cylindrical surface 7S of the anvil roller 7, or to distrib ute wear caused by the cutting tools 9 over a larger portion of the side cylindrical surface 7S of the anvil roller S. Adjustment in the direction of the double arrow f7 can be manual. In other embodiments, adjustment can be automatic.

[0048] The adjustment member 49 may be carried by a slide 51, on which the guides 47 for one of the uprights 43 are mounted. A slide 53 carries the guides 47 for the other of the two uprights 43. The two slides 51, 53 are engaged, for example by means of respective runners, with guides 55, 57 oriented at 90° with respect to the guides 47. In this way the assembly formed by the slides 51, 53, by the uprights 43 and by the anvil roller 7 can translate along the guides 55, 57 in the direction of the double arrow f53 to move the anvil roller 7 towards or away from the frame 15. Ex- pandable plenums 60, 61 may be associated with the uprights 43, in order to control the movement in the direction f43 by alternatively inflating and deflating one or oth er of said expandable plenums. Movement in the direction of the double arrow f53 may bring the anvil roller either to a working position where it co-acts with the cut ting tools 9, or to a non-working position, where there is no reciprocal contact be tween the anvil roller 7 and cutting tools 9, and between said two components there may be sufficient space to introduce the web material N to be cut, or to remove resi dues of web material which may accumulate, for example in the case of a fault or blockage in the cutting device.

[0049] In some embodiments, there may be members for adjusting the reciprocal position between the anvil roller 7 and the frame 15 carrying the beam 19. These ad justment members may serve for example to adjust the parallelism between the beam 19 and the rotation axis 7 A of the roller 7.

[0050] The adjustment members may, for example, comprise stop elements 66 that can be adjusted using electronic actuators, for example electronic gear motors, or manual adjustment systems. In the embodiment shown, the uprights 43 are associated by way of example with micrometric jacks 65 that adjust the position of adjustable stop elements 66 between the uprights 43 (and thus the anvil roller 7) and the frame 15 (and thus the cutting tools 9 mounted on the rotating beam 19 supported by the frame 15). In his way it is possible to adjust micrometrically the reciprocal position of the cylindrical surface of the anvil roller 7 and the rotating beam 19. By having two adjustment systems on the two uprights 43, for example two electronic adjust ment actuators or two manual micrometric jacks, it is also possible to adjust the anvil roller 7 so that the rotation axis 7A thereof is parallel to the rotation axis T of the ro tating beam 19.

[0051] In some embodiments, the device 1 may comprise a system for pushing the frame 15 against the adjustable stop elements 66. In the embodiment shown, the pushing system comprises at least one actuator, for example a linear actuator 71 , and preferably two actuators 71, one on each side of the device. The linear actuator 71 may be a hydraulic-type cylinder-piston actuator.

[0052] The linear actuator 71 may be fastened on one side to a fixed structure 73 carrying the sliding guides 55, 57 for the slides 51, 53. The linear actuator 71 may also be fastened to an appendage 15B of the frame 15 carrying the rotating beam 19. A load cell 74, for example associated with a hinge with which the linear actuator 71 is fastened to the frame 15, may be provided to measure the force exerted between the frame 15 and the adjustable stop elements 66. This thrust is correlated to the pressure between each tool 9 and the anvil roller 7.

[0053] A control unit 75 may be interfaced with the actuator 71 and with the load cell 74, in order to adjust the thrust with which the frame 15 is pressed against the adjustable stop elements 65. Fig.l3B shows a functional block diagram of the control system. The same numbers indicate the same or equivalent parts as those described and shown in Figure 12. Reference number 76 indicates an amplifier for the signal coming from the load cell 71 and applied to the control unit 75. Reference number 78 indicates an electronic card to which the control unit 75 is connected or on which it is mounted, while reference number 80 indicates a user interface connected to the con trol unit 75. The electronic card 78 is connected, in addition to the control unit 75, to pressure transducers 82A,82B, to a position transducer 84 for the actuator 71, and to one or more control valves 86 for supplying pressure fluid to the actuator 71. Using the user interface, for example a touchscreen or other suitable interface, the operator can set the data for the operating force of the cutting device. Based on the collected data, the central control unit 75 can keep the position of the frame 15 with respect to the anvil roller 7 under control, so as to have the correct reaction force on the stop el ements 66 and thus the correct cutting force of the cutting tools 9 on the anvil roller 7.

[0054] Operation of the device described above is as follows. After performing the individual adjustments described above, so as to position each cutting tool 9 correctly with respect to the anvil roller 7, the continuous web material N is fed in the direc tion of the arrow F along the advancement path P. Each cutting tool 9 is caused to vibrate by the respective sonotrode 11 in a direction parallel to the axis of the sono- trode 11 with an ultrasonic frequency. The vibration movement has at least one com ponent orthogonal to the cylindrical anvil surface 7S of the anvil roller 7. The co action between the anvil roller 7 and the vibrating cutting tool 9 causes cutting of the web material N, which passes between the cutting tool 9 and the anvil roller 7. The high temperature that develops due to the vibration can cause local melting of the fi- bers forming the web material N, thereby avoiding the formation of dusts or micro- fibers which could be dispersed in the environment.

[0055] During cutting, the assembly formed by the sonotrode 11 and the respective cutting tool 9 is rotated gradually or in steps in the direction of the double arrow f9, so as to obtain more uniform wear of the cutting edge 9C. As mentioned above, the movement can be very slow, such that a movement cycle in both directions during one working session, for example, could take eight hours.

[0056] If the device 1 comprises a plurality of cutting tools 9 and respective sono- trodes 11 in operation, all the cutting tools 9 may be made to vibrated by the sono- trodes and at the same time they rotate in one piece with the rotating beam 19.

[0057] Fig.14 shows a schematic view of a second embodiment of the ultrasonic cutting device described herein. The reference number 1 still indicates the cutting device as a whole. The reference letter N indicates the continuous web material ad- vancing in the direction of the arrow F along the advancement path P. The path is de- fined by guide rollers 101 and 103, between which there is placed an anvil roller, in dicated by reference number 7 as in the described previously embodiment. One or more cutting tools 9 co-act with the anvil roller 7. Each cutting tool 9 may be driven by a sonotrode 11 and may be mounted on a beam or other support causing a recip- rocal rotation in the direction f9, in a manner similar to that described with reference to the previous embodiment.

[0058] In some embodiments the anvil roller 7 may be formed by a cylindrical bar. The anvil roller 7 may be supported in a rotation seat formed in a support 105. The anvil roller 7 may be free to rotate in the seat formed in the support 105, for example due to the force of friction exerted by the web material N. In other embodiments, the anvil roller 7 may be motorized.

[0059] The support 105 may be associated with a loading system, which may com prise a pair of plenums that are inflatable preferably with a gaseous fluid, for exam ple air. The plenums are indicated by the reference number 107 and may be posi tioned between a plate 109, on which the support 105 is rigidly mounted, and a beam 111. The position of the support 105 can be adjusted by means of an adjustable block 113 and a screw 115. [0060] A conduit 105 A for delivery of coolant air to the anvil roller 7 may be pro- vided in the support 105.

[0061] The operation of the device 1 shown in Fig.14 is substantially the same as the operation of the device described with reference to Figs. 1 to 13.

[0062] Fig.15 shows a further embodiment of an ultrasonic cutting device, again indicated by the reference number 1. Reference number 9 indicates the cutting tool. This is constrained to a sonotrode (not shown) in a manner similar to that described with reference to the previous embodiments. The device 1 may comprise a plurality of cutting tools and respective sonotrodes aligned transversally to the advancement path P, i.e. orthogonal to the plane shown in Fig.15.

[0063] The cutting unit formed by the cutting tool 9 and the sonotrode may be sup- ported on a slide or on a beam with a reciprocating movement in the direction of the double arrow f9. The trajectory of the reciprocating movement in this case is a straight line, rather than an arc. The direction of movement according to the double arrow f9 is parallel to the cutting edge of the cutting tool 9, which in this case is also straight.

[0064] The cutting tool 9 co-acts with an anvil member indicated by 125, in the form of a bar with a width that can be approximately the same as the length of the cutting edge of the tool 9, and a sufficient length as a function of the width of the continuous web material N to be cut. If the device 1 comprises several cutting tools 9, they are aligned along the longitudinal extension of the anvil bar 125.

[0065] In some embodiments the anvil bar 125 may be housed in a seat 127 and may be associated with one or more thrust actuators that push the anvil bar 125 against the cutting tools 9. For example, to this end there may be provided an inflata ble plenum 129 or a plurality of inflatable plenums, housed inside the seat 127, be- tween the bottom of the seat and the anvil bar 125. The expansion of the plenum or plenums 129 causes the anvil bar 125 to be pushed against the cutting edge of the tool or tools 9 so as to exert the contrasting force needed for cutting while the (or each) cutting tool 9 vibrates under the control of the respective sonotrode 11.

[0066] The form of the cutting tool 9 and the anvil bar 125 shown in Fig. 15 are such that the cutting action is distributed over a certain distance, equal to the length of the cutting edge of the tool or equal to the portion of the cutting edge that is in contact with the anvil bar 125. The reciprocating movement in the direction of the double arrow f9 can permit more uniform wear.

[0067] Advantageously, the anvil members, i.e. the anvil bar 125 shown in Fig.15, the rotating anvil bar 7 shown in Fig. 14 and the anvil roller 7 shown in Figs. 1 to 13, may have a smooth anvil surface, so that the cutting tool 9 or each cutting tool 9 may be arranged in any position along the longitudinal extension of the anvil member. Furthermore, the anvil member may have a movement transversal to the direction of feed of the continuous web material N to ensure uniform wear on the anvil surface.

[0068] In some embodiments, the anvil member 7, 125 has a surface hardness low- er than the cutting edge 9C of the cutting tool 9. This enables wear to be concentrated on the anvil member, which may have a lower cost, or may have an anvil surface which may be restored or machined more easily than the cutting bevel 9D of the cut ting tool 9.

[0069] In some embodiments the anvil surface of the anvil member 7, 125 may have a hardness between around 40 HRC and 65 HRC, preferably between around 45 HRC and 60 HRC. The bevel 9D of the cutting tool 9 may have a greater hardness, for example equal to or greater than around 65 HRC, and preferably between around 68 HRC and 75 HRC. The hardness may be obtained for a cutting bevel depth of be- tween around 1 mm and 2 mm, preferably around 1.3- 1.7 mm.

[0070] The anvil member may be made, for example, of steel, for example tem pered steel. In other embodiments the anvil member can be provided with an outer coating, possibly interchangeable or renewable depending on wear. In some embod iments the lining of the anvil member, which forms the anvil surface of said anvil member, may be made of a synthetic material, for example with a hardness of be tween 10 and 20 PJ (Pousei Jones), values that should be considered exemplifying and non- limiting.

[0071] In other embodiments, the anvil surface of the anvil member may be coated with metallic inserts, for example made of chrome oxide, tungsten oxide, stellite (co balt-chrome alloy) and similar. [0072] In the case of anvil surfaces made of bare steel, i.e. without any lining or metallic inserts, there may be a surface hardness of between around 50 and 65 HRC, for example between around 55 and 61 HRC.

[0073] Suitable inserts may have hardness, for example, of between around 40 and 65 HRC, preferably between around 45 and 60 HRC.

[0074] As mentioned above, the position of the anvil member 7, 125 may be ad- justed in a direction parallel to the longitudinal extension of the anvil member, and thus in a transversal direction with respect to the direction of advancement of the web material N to be cut. This movement is performed advantageously with the de- vice stationary and with the anvil member 7, 125 and cutting tools being moved apart beforehand. In the embodiment shown in Figs. 1-13 the moving apart may be achieved by acting on the inflatable plenums 60, 61; in the exemplary embodiment shown in Fig. 14 it is possible to act on the inflatable plenum 107 and in the embod- iment shown in Fig. 15 it is possible to act on inflatable plenum 129. [0075] In the case of anvil members with a lining, this may be restored following wear, for example by forming a new lining and possible grinding. In the case of anvil members made of bare steel, the worn anvil member can be ground to obtain a new anvil surface with suitable surface characteristics.