Welding device and method for product packaging machines

Abstract

A welding device (1) for product packaging machines comprises a welding unit (110, 210) comprising a welding tool (110) and a countertool (210) mutually movable in rotation about an axis (X), the welding tool (110) defining at least one active welding surface (111), and the countertool (210) defining at least one opposing surface (212); a movement unit comprising at least one first movement device (220, 240) configured for performing a mutual rotation between the welding tool (110) and the countertool (210) about the axis (X) between a disengaged configuration, in which the active welding surface (111) is spaced from the opposing surface (212), and a welding configuration, in which the active welding surface (111) and the opposing surface (212) are pressed together at a welding surface (PS); wherein the axis (X) is substantially parallel to the welding surface (PS).

Description

[0001] DESCRIPTION

[0002] WELDING DEVICE AND METHOD FOR PRODUCT PACKAGING MACHINES.

[0003] Technical field

[0004] This invention addresses the technical field of automatic product packaging machines and relates, specifically, to a welding device and a welding method for product packaging machines, in particular, for automated welding of product wrappers, both discrete wrappers and flow pack wrappers.

[0005] Background art

[0006] In the packaging field, longitudinal and transverse welds are typically made using conventional systems such as, for example, hot air, cold and ultrasonic welding tools.

[0007] Generally speaking, welding is carried out by moving a tool and countertool towards each other, where the tool constitutes an active welding element while the countertool acts as an anvil against which the tool applies compression.

[0008] In traditional welding, the mutual movement between tool and countertool is a rectilinear translation, in particular along a direction perpendicular to the area to be welded.

[0009] The Applicant has found that this solution has the disadvantage that at times the weld is not of optimum quality because the mutual, perpendicular engagement between the tool and the countertool may give rise to local deformation and / or wrinkling of the material to be welded in the welding area, also on account of the thermal stresses generated. This may lead to localized dilation of the material which, because the material is unable to expand, results in the formation of permanent wrinkling.

[0010] In particular, any defects present in the coupled set to be welded (existing wrinkles, air bubbles, overlap imperfections) inevitably remain trapped and are made permanent by prior art welding, and, in practice, become impossible to eliminate.

[0011] The larger or more complex the welding area is, the more marked this problem is, since a larger welding area corresponds to a greater thermal dilation effect on the material and a greater tendency towards wrinkling.

[0012] Moreover, wrinkling in the welding area may reduce the hermetic seal of the weld, making the wrapper potentially subject to being scrapped.

[0013] The Applicant has therefore found that moving and pressing the welding surfaces of the tool and the countertool against each other with rotational motion has the effect of redistributing the compressing action on the material to be welded, allowing the material to stretch and / or dilate in at least one direction, thus compensating for local stresses and preventing the formation of wrinkles or air bubbles. The welds made this way are therefore high quality and much less subject to being scrapped.

[0014] According to a first aspect of it, therefore, this invention relates to a welding device for product packaging machines.

[0015] The device comprises a welding unit for making at least one weld on at least one web or sheet of material.

[0016] The welding unit comprises at least a welding tool and a countertool, where the tool defines at least one active welding surface, while the countertool defines at least one opposing surface.

[0017] Preferably, the active welding surface and the opposing surface face, or are or adapted to face, each other to compress the web or sheet during welding. The term "active welding surface" is used to mean the surface of a part which actively performs the welding operation, hence, for example, a heating element, a sonotrode or the like.

[0018] Preferably, the active welding surface and the opposing surface are mutually movable in rotation about an axis.

[0019] Preferably, this is achieved by mutually rotating the welding tool and the countertool about the axis. Preferably, the active welding surface and the opposing surface are mutually movable in rotation about the axis between a disengaged configuration in which the active welding surface is spaced from the opposing surface, and a welding configuration, in which the active welding surface and the opposing surface are pressed together at a welding surface.

[0020] The expression "welding surface" is used to mean a surface, whether planar or otherwise configured, extending over the entire contact area between the active welding surface and the opposing surface.

[0021] In other words, the device is configured to reach the welding configuration, in which the active welding surface and the opposing surface are pressed against each other at the welding surface by rotation about the axis.

[0022] Thanks to this operating mode, the mutual engagement between the active welding surface and the opposing surface occurs in such a way as to allow localized stretching of the material, so as to prevent wrinkling, thus making a geometrically correct weld all along the welding surface.

[0023] Preferably, the axis is substantially parallel to the welding surface.

[0024] By "substantially parallel" is meant an inclination of between + / -100, preferably between + / -5° and still more preferably 0°, between an axis and a surface, between axes or between surfaces.

[0025] In the case of a welding surface with a non-planar shape, the concept of parallelism is understood as referring to a mean plane of the welding surface. For example, in the case of a welding surface with a curved shape, be it convex or concave, symmetrical about a plane of symmetry through the concavity or convexity, the mean plane is understood as being perpendicular to that plane of symmetry. In the case of a complex surface made up of two or more concave / convex surfaces, the concept of parallelism is understood as referring to the mean planes of the surfaces.

[0026] More generally speaking, the term "mean plane" is used to denote the positioning plane of the coupled set to be welded (or a plane parallel to it) before reaching the welding configuration, hence before the active welding surface 111 and the opposing surface 212 are pressed against each other, where such mean plane intersects the active welding surface 111 and / or the opposing surface 212 in the welding configuration.

[0027] According to a second aspect of it, this invention relates to a welding method for product packaging machines.

[0028] The method is implemented by a device comprising a welding tool and a countertool positioned to face each other.

[0029] Preferably, the tool defines at least one active welding surface, while the countertool defines at least one opposing surface.

[0030] Preferably, the welding tool is an ultrasonic welding tool.

[0031] Alternatively, the welding tool is a hot air welding, cold welding or induction welding tool.

[0032] The invention is, in any case, applicable to any type of welding tool, suitable for acting in conjunction with a countertool.

[0033] Preferably, the active welding surface and the opposing surface face, or are or adapted to face, each other to compress the web or sheet during welding.

[0034] Preferably, the active welding surface and the opposing surface are mutually movable in rotation about an axis.

[0035] Preferably, this is achieved by mutually rotating the welding tool and the countertool about the axis.

[0036] Preferably, the active welding surface and the opposing surface are mutually movable in rotation about the axis between a disengaged configuration in which the active welding surface is spaced from the opposing surface, and a welding configuration, in which the active welding surface and the opposing surface are pressed together at a welding surface.

[0037] Preferably, the method comprises positioning the welding surface and the opposing surface in the disengaged configuration, where at least one sheet or web to be welded is interposed between the welding surface and the opposing surface. Preferably, the method also comprises mutually rotating the welding tool and the countertool about the axis until reaching the welding configuration, thus welding the at least one sheet or web.

[0038] According to least one of the above mentioned aspects, this invention may also comprise at least one of the preferred features described below.

[0039] In an embodiment, the axis lies substantially on the welding surface. In other words, the welding surface is substantially planar and the axis is substantially coplanar with the welding surface.

[0040] In a different embodiment, the axis is spaced from the welding surface. Preferably, the welding surface has a main direction of extension.

[0041] Preferably, the orientation of the axis is parallel to the main direction of extension of the welding surface. This allows obtaining optimum engagement between the active welding surface and the opposing surface when the weld material is pressed between them. In effect, the pressing action can be carried out in a way which substantially copies a translational movement, with a slight or even zero deviation between the front edge and the rear edge (corresponding to the long sides of the welding surface). In other words, positioning the axis of rotation so it is parallel to the main direction of extension allows minimizing or eliminating the deviation in the distances between the active welding surface and the opposing surface, measured at the frontmost point of engagement and the rearmost point (corresponding, as stated above, to the long sides of the welding surface).

[0042] In a different embodiment, the orientation of the axis is such as to make an acute angle with the main direction of extension of the welding surface.

[0043] Preferably, the axis is kept stationary relative to the welding surface during at least part of the mutual rotation between the welding tool and the countertool about the axis.

[0044] More preferably, the axis is kept stationary relative to the welding surface at least during the mutual rotation between the welding tool and the countertool about the axis between the disengaged configuration and the welding configuration.

[0045] Preferably, the device comprises a movement unit comprising at least one first movement device configured for performing a mutual rotation between the welding tool and the countertool about the axis between the disengaged configuration and the welding configuration.

[0046] Preferably, the at least one first movement device comprises a support, to which the welding tool and / or the countertool is rotatably connected, in particular by means of a pin or a hinge or an arcuate guide, and at least one actuator for moving the welding tool and / or the countertool in rotation relative to the support.

[0047] In an embodiment, the at least one first movement device comprises a support, to which the welding tool is rotatably connected, in particular by means of a pin or a hinge or an arcuate guide, and at least one actuator for moving the welding tool in rotation relative to the support.

[0048] In a different embodiment, there is only one first movement device comprising a support, to which the countertool is rotatably connected, in particular by means of a pin or a hinge or an arcuate guide, and one actuator for moving the countertool in rotation relative to the support.

[0049] In a different embodiment, there is only one first movement device comprising a support, to which the tool and countertool are rotatably connected, in particular by means of a pin or a hinge or an arcuate guide, and one actuator for moving the tool and the countertool in rotation relative to the support.

[0050] Preferably, in the case of rotation of the countertool, the countertool comprises a base element defining the opposing surface and having, on opposite sides of it, protrusions which are hinged to the support about the axis and which protrude in height beyond the opposing surface. In other words, the countertool has the shape of a C. That way, the axis can be positioned at, or in proximity to, the opposing surface and / or the welding surface. Preferably, the movement unit also comprises at least a second movement device configured for performing a relative movement to draw the welding tool and the countertool towards / away from each other along a trajectory between a close-together configuration, in which the welding tool and the countertool are close together along the trajectory, and a spaced-apart configuration, in which the welding tool and the countertool are spaced apart along the trajectory.

[0051] Preferably, the trajectory is incident on the welding surface.

[0052] Preferably, the trajectory is substantially rectilinear.

[0053] Preferably, the trajectory is substantially perpendicular to the welding surface at least in the close-together configuration.

[0054] By "substantially perpendicular" with reference to a trajectory and a surface is meant an inclination angle, between trajectory and surface, of 90°, with a tolerance of between + / -10°, preferably between + / -5° and, still more preferably, 0°.

[0055] In an embodiment, the second movement device operates on the support of the welding tool. In this situation, the welding tool is subjected to a rotation about the axis and a translation along the trajectory. The countertool may be stationary or also movable along the trajectory via an additional second movement device.

[0056] In an embodiment, the second movement device operates on the support of the welding tool. In this situation, the welding tool is subject only to a translation along the trajectory. The countertool may be stationary or also movable along the trajectory via an additional second movement device and is rotatable via the first movement device.

[0057] In a different embodiment, the second movement device operates on the support of the countertool. In this situation, the welding tool is subjected to a rotation about the axis and a translation along the trajectory. The countertool may be stationary or also movable along the trajectory via an additional second movement device.

[0058] In a different embodiment, the welding tool is rotatably mounted on the respective support, which is stationary (fixed, preferably adjustable), while the countertool is mounted (preferably fixedly, i.e. not rotatably) on a respective support which is translatable along the trajectory, in particular via a respective actuator.

[0059] In a different embodiment, the countertool is rotatably mounted on the respective support, which is stationary (fixed, preferably adjustable), while the welding tool is mounted (preferably fixedly, i.e. not rotatably) on a respective support which is translatable along the trajectory, in particular via a respective actuator.

[0060] According to an aspect of the invention, the device is also configured for performing at least one cutting action or an additional welding operation, through interaction between the welding tool and the countertool.

[0061] Preferably, one between the welding tool and the countertool has a distal portion which faces towards the other between the welding tool and the countertool, where the distal portion is adapted to define, in conjunction with the other between the welding tool and the countertool, a welding or cutting line or area. Preferably, the welding or cutting line or area is substantially parallel to the axis.

[0062] The Applicant has found that in such a configuration, in the case of an additional weld, it is possible to make two types of welds with optimum geometry, in particular avoiding misalignments between the two welds.

[0063] Preferably, the mutual rotation between welding tool and countertool about the axis is performed while keeping the distal portion pressed. That way, a hold-down action is applied on the at least one web or sheet, thereby ensuring correct alignment during the subsequent welding operation performed between the active welding surface and the opposing surface.

[0064] Preferably, the axis is positioned at or in proximity to the distal portion so that during the mutual rotation between welding tool and countertool about the axis, the distal portion is not separated from the at least one web or sheet. Separation is, however, possible when necessary by positioning the distal portion at a distance from the distal portion and / or by performing a controlled spacing movement between tool and countertool between the two welds.

[0065] In an embodiment, the distal portion is defined on the welding tool. Preferably, the distal portion is parallel to the active welding surface.

[0066] In a different embodiment, the distal portion is defined on the countertool. Preferably, the distal portion is parallel to the opposing surface.

[0067] Preferably, the distal portion and / or the other between the welding tool and the countertool is configured in such a way as to define a weld which is different from the weld between the active welding surface and the opposing surface. For example, the weld made by the distal portion may be a hermetic weld (for example, by a distal portion defined by an edge or a continuous protrusion) and the weld made between the active welding surface and the opposing surface may be a cosmetic weld (for example, defined by a textured, relief pattern, that is to say, defined by reliefs distributed according to a two-dimensional trend.

[0068] In this solution, welding by the distal portion may be accomplished during the relative movement between tool and countertool to draw them closer together, while they are in the disengaged configuration.

[0069] Cutting, on the other hand, may be accomplished by first positioning tool and countertool in the welding configuration, then drawing tool and countertool closer together to make a weld at the active welding surface and the opposing surface and then performing a mutual rotation between welding tool and countertool in the disengaged configuration to make the cut.

[0070] In a different embodiment, the aforesaid distal portion is defined by a front protuberance acting in conjunction with a recess opposite thereto.

[0071] In particular, one between the welding tool and the countertool has a front protuberance facing the other between the welding tool and the countertool, while the other between the welding tool and the countertool has a front recess.

[0072] Preferably, the front protuberance and the front recess face each other to make, in the close-together configuration, the cut in at least one sheet or web to be welded interposed between tool and countertool or a local bend in a sheet or web to be welded interposed between tool and countertool, suitable for stably holding the at least one sheet or web during the mutual rotation between welding tool and countertool.

[0073] Preferably, the front protuberance and the front recess have respective main directions of extension which are parallel to the axis.

[0074] That way, the at least one web or sheet is held firmly in place during the subsequent welding action.

[0075] Preferably, the device also comprise a conveyor which is movable, preferably with a circular or closed-loop movement or a reciprocating movement along a movement path which is at least partially parallel and / or coplanar with the welding surface. In this case, the welding unit and the movement unit are mounted on the conveyor and are movable along the movement path in such a way as to make a seam tracking weld.

[0076] Preferably, the welding tool is an ultrasonic welding tool.

[0077] Alternatively, the welding tool is a hot air welding, cold welding or induction welding tool.

[0078] The invention is, in any case, applicable to any type of welding tool, suitable for acting in conjunction with a countertool.

[0079] Preferably, the mutual rotation between the welding tool and the countertool is performed by rotating only the countertool.

[0080] Alternatively, the mutual rotation between the welding tool and the countertool is performed by rotating only the welding tool.

[0081] Alternatively, the mutual rotation between the welding tool and the countertool is performed by rotating both the welding tool and the countertool, either simultaneously or not simultaneously.

[0082] Preferably, the method also comprises performing a relative movement between the welding tool and the countertool along a trajectory defining a relative movement between the welding tool and the countertool to draw them towards / away from each other between a close-together configuration, in which the welding tool and the countertool are close together along the trajectory, and a spaced-apart configuration, in which the welding tool and the countertool are spaced apart along the trajectory. Preferably, the trajectory is incident on the welding surface.

[0083] In an embodiment, the relative movement between the welding tool and the countertool along the trajectory is performed by moving only the countertool along the trajectory, while the welding tool remains fixed along the trajectory. In this configuration, it is possible to impart the rotational movement about the axis only to the welding tool, only to the countertool or to both.

[0084] Alternatively, the relative movement between the welding tool and the countertool along the trajectory is performed by moving only the welding tool along the trajectory, while the countertool remains fixed along the trajectory. In this configuration, it is possible to impart the rotational movement about the axis only to the welding tool, only to the countertool or to both.

[0085] Alternatively, the relative movement between the welding tool and the countertool along the trajectory is performed by moving both the welding tool and the countertool, either simultaneously or not simultaneously, along the trajectory.

[0086] Preferably, the welding tool is moved along the trajectory while the countertool is moved in rotation about the axis.

[0087] Alternatively, the welding tool is moved in rotation about the axis while the countertool is moved along the trajectory.

[0088] Alternatively, the welding tool is moved both along the trajectory and in rotation about the axis. In this case, the countertool remains fixed or, alternatively, the countertool may also move along the trajectory and / or move in rotation about the axis.

[0089] Alternatively, the countertool is moved both along the trajectory and in rotation about the axis. In this case, the welding tool remains fixed or, alternatively, the welding tool may also move along the trajectory and / or move in rotation about the axis.

[0090] Preferably, performing the relative movement between the welding tool and the countertool along the trajectory comprises performing a relative movement between the welding tool and the countertool to draw them closer together along the trajectory and the mutual rotation between the welding tool and the countertool about the axis towards the welding configuration is performed at least partly after performing the relative movement between the welding tool and the countertool to draw them closer together along the trajectory.

[0091] In other words, at least part of the mutual rotational movement between the welding tool and the countertool is performed when the relative movement between the welding tool and the countertool along the trajectory has been completed.

[0092] Preferably, also, at least part of the relative movement between the welding tool and the countertool to draw them closer together along the trajectory is performed before the mutual rotational movement between the welding tool and the countertool about the axis.

[0093] Preferably, after reaching the welding configuration, a relative movement between the welding tool and the countertool to draw them away from each other along the trajectory is performed.

[0094] Preferably, the relative movement between the welding tool and the countertool to draw them closer together along the trajectory comprises a step of pressing a distal portion of one between the welding tool and the countertool against the other between the welding tool and the countertool to make a weld along a welding line or area.

[0095] Preferably, the welding line or area is substantially parallel to the axis.

[0096] Preferably, the step of pressing the distal portion to make a weld along a welding line or area is carried out at least partly before mutually rotating the welding tool and the countertool about the axis towards the welding configuration.

[0097] Preferably, the weld made by pressing the distal portion is different from the weld made between the active welding surface and the opposing surface.

[0098] Preferably, the weld made by pressing the distal portion is a hermetic weld while the weld made between the active welding surface and the opposing surface is a cosmetic weld.

[0099] Alternatively, the relative movement between the welding tool and the countertool to draw them closer together along the trajectory comprises a step of pressing a distal portion of one between the welding tool and the countertool against the other between the welding tool and the countertool to make the cut along a cutting line of the at least one web or sheet interposed between welding tool and countertool.

[0100] Preferably, the cutting line is substantially parallel to the axis.

[0101] Preferably, the step of pressing the distal portion to make the cut may be carried out at least partly before mutually rotating the welding tool and the countertool about the axis towards the welding configuration or at least partly after mutually rotating the welding tool and the countertool about the axis towards the welding configuration.

[0102] Alternatively, one between the welding tool and the countertool has a front protuberance facing the other between the welding tool and the countertool, and the other between the welding tool and the countertool has a front recess such that the front protuberance and the front recess face each other.

[0103] Preferably, the relative movement between the welding tool and the countertool to draw them closer together along the trajectory makes, in the close-together configuration, a cut in the sheet or web to be welded or a local bend in the sheet or web to be welded, in a manner suitable for stably holding the sheet or web to be welded during the mutual rotation between the welding tool and the countertool.

[0104] Disclosure of the invention

[0105] In the case of cutting, the front protuberance and / or the front recess are configured to make a cut and, for that purpose, they interact with a cutting action and / or at least one of them has a cutting element such as a blade, for example.

[0106] In the case of bending, the front protuberance and / or the front recess are configured to make at least one bend in the path followed by the at least one web or sheet to be welded.

[0107] Preferably, the front protuberance and the front recess have respective main directions of extension. Preferably, these main directions of extension of the front protuberance and the front recess are parallel to the axis.

[0108] Preferably, the method also comprises performing a relative movement between the welding tool and the countertool along a movement path, preferably transverse, more preferably perpendicular to the trajectory defining the relative movement between the welding tool and the countertool to draw them towards / away from each other.

[0109] Preferably, mutually rotating the welding tool and the countertool about the axis is performed during the movement of the welding tool and the countertool along movement path in such a way as to make a seam tracking weld.

[0110] Preferably, the movement of the welding tool and the countertool along the movement path is accomplished by moving the welding tool and the countertool in a mutually synchronous manner along the movement path.

[0111] In a variant embodiment of the invention, the countertool is not an anvil but a second sonotrode. In this configuration, the first sonotrode defines a first active welding surface, while the second sonotrode defines a second active welding surface, the two active welding surfaces being pressed together on a welding surface in the welding configuration.

[0112] Brief description of drawings Further features and advantages of this invention are more apparent in the following detailed description of preferred embodiments of it, with reference to the accompanying drawings.

[0113] In these drawings:

[0114] - Figure 1 is a perspective view of a welding device according to this invention in a non-operating configuration;

[0115] - Figure 2 is a perspective view of the device of Figure 1 in an operating configuration;

[0116] - Figure 3 is a perspective view of a component of the device of Figure 1 ;

[0117] - Figure 4 is a cross section of the device of Figure 1 in the non-operating configuration;

[0118] - Figures 5 and 6 are cross sections of the device of Figure 1 in two different operating configurations;

[0119] - Figure 7 is an enlarged view of the non-operating configuration of Figure 4;

[0120] - Figures 8 and 9 are enlarged views of the operating configurations of Figures 5 and 6 respectively;

[0121] - Figures 10 and 11 are enlarged views of a detail of the welding device of the invention, according to a first variant embodiment of it and in two different operating configurations;

[0122] - Figures 12 and 13 are enlarged views of a detail of the welding device of the invention, according to a second variant embodiment of it and in two different operating configurations;

[0123] - Figures 14 and 15 are enlarged views of a detail of the welding device of the invention, according to a third variant embodiment of it and in two different operating configurations.

[0124] Detailed description of preferred embodiments of the invention

[0125] With reference to the accompanying drawings, the numeral 1 denotes in its entirety a welding device according to the invention.

[0126] The welding device 1 comprises a tool block 100 and a countertool block 200 facing each other at a position such as to define between them a passage for at least one web or sheet to be welded.

[0127] In the context of this invention, by "at least one web or sheet to be welded" is meant a coupled set of two or more layers, either the same or different from each other, overlapped to be joined to each other by welding. The two or more layers may be defined by different portions of a single web or sheet (for example, when forming a tube or when a tube is transversely welded) or by two or more different, overlapped webs or sheets. Additionally, the invention is applicable both to precut sheets or segments and to continuous webs. In the accompanying drawings, the web or sheet to be welded is shown in the form of an end edge of a product P in the form of a pouch or packet.

[0128] The tool block 100 and the countertool block 200 may be mounted on the same machine frame or on different frames.

[0129] The tool block 100 comprises a welding tool 110 which, in the drawings, is illustrated in the form of an ultrasonic tool but which may be in other forms (for example, a hot air welder, a cold welder or an induction welder). The tool block 100 also comprises a support 120, on which the welding tool 110 is mounted and a base 130 on which the support 120 is mounted. In the embodiment illustrated, the support 120 is coupled to the base 130 by a sliding guide defining a translational, preferably rectilinear, trajectory D. For this purpose, the support 120 and the base 130 may be connected to each other by a guide 140, in particular a linear sliding guide, for example, a dovetail guide or a bar-sleeve guide. The support 120 is made to slide on the base 130 by an actuator, not illustrated, for example a linear actuator of a rotary type (lead nut and screw, rack and pinion or rod and crank), or an actuator based on other linear systems (for example, a hydraulic or pneumatic cylinder or a linear motor).

[0130] The aforesaid support 120 is optional, in particular when the linear movement of the welding tool 110 along the trajectory D or a generic movement of the welding tool 110 is required, or when indirect mounting of the welding tool 110 on the base 130 is required. Alternatively, the welding tool 110 might be fixed directly to the base 130.

[0131] The welding tool 110, at the front of it, has an active welding surface 111 which is intended to come into contact with the at least one web or sheet to be welded.

[0132] Preferably, the active welding surface 111 is planar in shape. However, it might have a different shape, for example, concave or convex.

[0133] Preferably, also, the active welding surface 111 has a main direction of extension, and thus has an elongated shape. For example, the welding surface 111 may have a length / width ratio of between 4 and 20.

[0134] Preferably, the active welding surface 111 is smooth or substantially smooth. By "substantially smooth" is meant that it is such as to present a smooth aspect on a preponderant part of its surface, provided, if necessary, with local recesses or cavities having a specific, non-welding function.

[0135] Alternatively, the active welding surface 111 has a relief configuration, in particular defining one or more parallel reliefs or a textured pattern, that is to say, an alternating two-dimensional distribution of reliefs and recesses. The configuration of the active welding surface 111 is linked to the type of weld to be made.

[0136] The countertool block 200 comprises a countertool 210 intended to operate in conjunction with the welding tool 110 (defining a welding unit therewith) so as to make a weld on at least one web or sheet interposed between them.

[0137] The countertool block 200 may also comprise a support 220 (optional), on which the countertool 210 is mounted and a base 230 on which the support 220 or the countertool 210 is mounted. In the embodiment illustrated, the support 220 is coupled to the base 230 by a fixed connection. The support 220 may be provided if the movement of the countertool 210 is such that the countertool 210 moves relative to the support 220, the latter being fixed to the base 230 or coupled to it movably according to a different movement.

[0138] In a variant embodiment, the support 220 of the countertool 210 may be coupled to the base 230 by a sliding guide defining a translational, preferably rectilinear, trajectory D. The trajectory D of the countertool 210 may coincide with the trajectory of the welding tool 110 or it may be different. For this purpose, the support 220 and the base 230 of the countertool 210 may be connected to each other by a guide, in particular a linear sliding guide, for example, a dovetail guide or a bar-sleeve guide. The support 220 is made to slide on the base 230 by an actuator, for example a linear actuator of a rotary type (lead nut and screw, rack and pinion or rod and crank), or an actuator based on other linear systems (for example, a hydraulic or pneumatic cylinder or a linear motor).

[0139] According to the invention, the linear movement along the trajectory D may be applied to welding tool 110, to the countertool 210 or to both.

[0140] In particular, Figure 1 shows a non-operating configuration in which welding tool 110 and countertool 210 are spaced from each other, achieved (not necessarily) by retracting the welding tool 110.

[0141] Figure 3 shows a detail view of the countertool 210.

[0142] The countertool 210 is defined by a base element 21 1 , preferably having an elongated shape and frontally defining an opposing surface 212, intended to work in conjunction with the active welding surface 111 of the welding tool 110 to make the weld on the at least one web or sheet.

[0143] In particular, the opposing surface 212 and the active welding surface 111 are suitable for creating a welding configuration (Figures 2, 6 and 9) in which they are pressed against each other on a welding surface PS.

[0144] The expression "welding surface" is used to mean a surface, whether plane or otherwise configured, extending over the entire contact / overlap area between the active welding surface 111 and the opposing surface 212, hence equal in extent to the contact / overlap area.

[0145] Preferably, the opposing surface 212 has a planar shape. However, it might have a different shape, for example, concave or convex. More preferably, the opposing surface 212 lies in a plane corresponding to the plane the active welding surface 111 lies in so as to apply a substantially uniform compression on the at least one web or sheet disposed between the active welding surface 111 and the opposing surface 212.

[0146] Preferably, also, the opposing surface 212 has a main direction of extension, and thus has an elongated shape. For example, the opposing surface may have a length / width ratio of between 4 and 20.

[0147] Preferably, the opposing surface 212 has a relief configuration, in particular defining one or more parallel reliefs or a textured pattern, that is to say, an alternating two-dimensional distribution of reliefs and recesses. The configuration of the opposing surface 212 is linked to the type of weld to be made.

[0148] The invention comprises performing a mutual rotation between the welding tool 110 and the countertool 210 about the axis X.

[0149] In the embodiment illustrated, the countertool 210 is rotatable about an axis X, in particular thanks to the base element 211 being rotatably mounted on the support 220.

[0150] Preferably, the axis X is substantially coplanar with the welding surface PS. By "substantially coplanar" is meant exact coplanarity or a minimum deviation, preferably less than 5%, preferably less than 2% of the length of the welding surface PS.

[0151] In the case of a welding surface which is not planar, reference is made to a mean plane intersecting the welding surface PS at a position such as to be a midplane thereof and to separate the welding surface PS into portions disposed on opposite sides of the midplane and "balanced" with each other.

[0152] Alternatively, the axis X is spaced from the welding surface PS.

[0153] Alternatively, the axis X is substantially coplanar with the opposing surface 212. By "substantially coplanar" is meant exact coplanarity or a minimum deviation, preferably less than 5%, preferably less than 2% of the length of the opposing surface 212.

[0154] Alternatively, the axis X is spaced from the opposing surface 212.

[0155] In the embodiment illustrated, the base element 211 is hinged, at opposite ends of it, to the support 220. For that purpose, the support 220 has the shape of a C defining side walls 221 to which the base element 211 is hinged. Preferably, the side walls 221 are parallel to each other and perpendicular to the axis X.

[0156] Additionally, in order to ensure that the axis X is coplanar or substantially coplanar with the welding surface PS and / or the opposing surface 212, the base element 211 has, on opposite sides of it, respective protrusions 213 hinged to the support 200 (and in particular to the side walls 221 ) about the axis X. The protrusions 213 protrude in height beyond the opposing surface 212 so as to "retract" the base element 211 , positioning the opposing surface 212 in proximity to the axis X or in such a way that the axis X is coplanar with the opposing surface 212. In this case, the countertool 210 also has the shape of a C, with concavity, in use, facing the same direction as the concavity of the C shape of the support 220.

[0157] In order to perform a controlled rotation of the countertool 210 about the axis X, relative to the support 220, an actuator 240 is provided which is mounted on the support 220 and interposed between the support 220 and the countertool 210. More in detail, the actuator 240 has one end connected to the support 220, in particular hinged, and another end which is hinged to the countertool 210 at an eccentric position relative to the axis X. Preferably, the actuator 240 is hinged to a flange 214 protruding from the base element 211 , in particular protruding along a direction perpendicular or substantially perpendicular to the direction of extension of the aforesaid protrusions 213 protruding from the base element 211 .

[0158] The actuator 240 is preferably of the lead nut / screw type but, alternatively, it may be a hydraulic or pneumatic cylinder, a linear motor or other technically equivalent solutions.

[0159] In variant embodiments, the mutual rotation between the welding tool 110 and the countertool 210 may be accomplished by mounting the welding tool 110 rotatably, for example on the related support 120, or by mounting both of them rotatably about a common axis X.

[0160] Thanks to the rotation about the axis X, the device 1 may form a disengaged configuration (Figures 5 and 8), in which the active welding surface 111 is spaced from the opposing surface 212, and the aforementioned welding configuration (Figures 2, 6 and 9). These configurations are separated from each other by a rotation about the axis X between the welding tool 110 and the countertool 210.

[0161] In particular, starting from a spaced-apart configuration between welding tool 110 and countertool 210 (Figures 1 , 4 and 7), a relative movement is performed between welding tool 110 and countertool 210 to draw them closer together, to reach the aforementioned disengaged configuration (Figures 5 and 8). Next, a rotation performed about the axis X by welding tool 110 and / or countertool 210 causes active welding surface 111 and opposing surface 210 to be pressed against each other, thus making a weld on the at least one web or sheet interposed between them.

[0162] In a variant not illustrated, the rotation about the axis X might be defined by an arcuate sliding guide, concentric with the axis X, instead of a pin or hinge connection.

[0163] Figures 7 to 9 illustrate a preferred embodiment of the invention in detail.

[0164] According to this solution, the countertool 210 has a distal portion 215 facing towards the welding tool 110 and adapted to define, in cooperation with the welding tool 110, a welding or cutting line or area substantially parallel to the axis X. This welding or cutting action performed by the distal portion 215 is accomplished by applying a predetermined pressure of the distal portion 215 on the welding tool 110 (Figure 8).

[0165] Preferably, the distal portion 215 is defined by a protuberance or front corner of the base element 211 and / or of the opposing surface 212.

[0166] Preferably, the distal portion 215 protrudes from the opposing surface 212. Preferably, the distal portion 215 is substantially parallel to the opposing surface 212. By "substantially parallel" is meant a parallelism with an angular tolerance of ±10°.

[0167] Preferably, the distal portion 215 is located on the outside of the opposing surface 212.

[0168] Preferably, the distal portion 215 is configured in such a way as to define a weld which is different from the weld made between the active welding surface 111 and the opposing surface 212. For example, the distal portion 215 defines a "localized" hermetic weld, while the weld made between the active welding surface 111 and the opposing surface 212 is a "cosmetic" weld. Alternatively, they may both be hermetic but with different structures (one a seam weld and the other a weld with textured pattern).

[0169] In a variant embodiment, the distal portion is defined on the welding tool 110. In such a case, the distal portion preferably protrudes from the active welding surface 111.

[0170] Additionally, in such a case, the distal portion is preferably parallel or substantially parallel to the active welding surface 111.

[0171] Additionally, in such a case, the distal portion is preferably located on the outside of the active welding surface 111.

[0172] In a variant embodiment, the distal portion may be made on both sides (welding tool 110 and countertool 210) and the two distal portions may operatively cooperate to make a respective weld.

[0173] According to a different aspect of the invention, and in a first embodiment illustrated in Figures 10 and 11 , the countertool 210 has a front protuberance 216 facing towards the welding tool 110, while the welding tool 110 has a corresponding front recess 112 configured to receive at least part of the front protuberance 216.

[0174] Front protuberance 216 and front recess 112 face each other so as to make, in a sheet or web to be welded interposed between welding tool 110 and countertool 210 in a close-together configuration, a local bend suitable for stably holding the sheet or web to be welded during the mutual rotation between the welding tool 110 and the countertool 210. Preferably, front protuberance 216 and front recess 112 have respective main directions of extension parallel to the axis X.

[0175] Preferably, the front protuberance 216 is located on the outside of the opposing surface 212.

[0176] Preferably, the front recess 112 is located on the outside of the active welding surface 111.

[0177] In a variant embodiment, the front protuberance is made on the welding tool 110 while the front recess is made on the countertool 210.

[0178] Preferably, the local bend is held for the entire step of welding.

[0179] Preferably, therefore, in a first step where the relative movement between welding tool 110 and countertool 210 draws them closer together, the front protuberance 216 engages the material which is bent at least partly into the front recess 112 (Figure 10).

[0180] Next, the mutual rotation between welding tool 110 and countertool 210 is performed to make the weld in the material (Figure 11 ).

[0181] Preferably, the axis X is positioned in proximity to, or at, the front recess 112 and / or the front protuberance 216. By "in proximity to" is meant a distance less than or equal to 2 mm, preferably less than or equal to 1 mm.

[0182] In a second embodiment illustrated in Figures 12 and 13, front protuberance 216 and front recess 112 face each other to make, in a close-together configuration, the cut in at least one sheet or web to be welded interposed between welding tool 110 and countertool 210.

[0183] Preferably, in this case too, the axis X is positioned in proximity to, or at, the front recess 112 and / or the front protuberance 216. By "in proximity to" is meant a distance less than or equal to 2 mm, preferably less than or equal to 1 mm. Preferably, also, in the case of welding the end edges of pouches, front protuberance 216 and front recess 112 are located at a position distal to the content of the pouches. In other words, the active welding surface 111 and the opposing surface 212 are interposed between the pouch content and said front protuberance 216 and said front recess 112.

[0184] Preferably, therefore, in this case too, in a first step where the relative movement between welding tool 110 and countertool 210 draws them closer together, the front protuberance 216 engages and makes a cut in the material (Figure 12).

[0185] Next, the mutual rotation between welding tool 110 and countertool 210 is performed to make the weld in the material (Figure 13).

[0186] It is evident that also in the embodiment of Figures 12 and 13, the front protuberance may be made on the welding tool 110, while the front recess may be made on the countertool 210.

[0187] In a third embodiment illustrated in Figures 14 and 15, front protuberance 216 and front recess 112 face each other to make, in a close-together configuration, the cut in least one sheet or web to be welded interposed between welding tool 110 and countertool 210.

[0188] Unlike Figures 12 and 13, however, front recess 112 and front protuberance 216 are positioned at a position distal to the axis X. In other words, the active welding surface 111 is interposed between the front recess 112 and the axis X, while the opposing surface 212 is interposed between the front protuberance 216 and the axis X.

[0189] That way, the mutual engagement between front protuberance 216 and front recess 112 with simultaneous cutting of the material occurs as a result of the mutual rotation between welding tool 110 and countertool 210 towards the welding configuration. Initially, therefore, in the step of drawing welding tool 110 and countertool 210 closer together (Figure 14), front recess 112 and front protuberance 216 remain disengaged from each other.

[0190] Next, the mutual rotation between welding tool 110 and countertool 210 into the welding configuration results in the mutual engagement between front protuberance 216 and front recess 112 and cutting of the material (Figure 15).

[0191] In an embodiment, the tool block 100 and the countertool block 200 are mounted on a conveyor movable along a movement path which is at least partially parallel and / or coplanar with the welding surface PS. In this solution, therefore, the welding unit defined by the welding tool 110 and the countertool 210 is movable along said movement path in such a way as to make a seam tracking weld.

[0192] In use, the welding surface 111 and the opposing surface 212 are positioned in the disengaged configuration (Figures 5, 8), with at least one sheet or web to be welded interposed between the welding surface 111 and the opposing surface 212, and then a mutual rotation between the welding tool 110 and the countertool 210 about the axis X is performed until reaching the welding configuration (Figures 2, 6, 9) to make the weld on the at least one sheet or web.

[0193] Preferably, the axis X is kept stationary relative to the welding surface PS at least during part of the mutual rotation between the welding tool 110 and the countertool 210 about the axis X, preferably during the entire rotation about the axis X from the disengaged configuration to the welding configuration.

[0194] The mutual rotation may be accomplished by rotating only the welding tool 110, only the countertool 210, or both.

[0195] Additionally, in order to allow advancing the web or sheet to be welded and / or inserting it into the welding zone and removing it on completion of welding, there is also a relative movement between the welding tool 110 and the countertool 220 along the aforesaid trajectory D, drawing them towards / away from each other between a close-together configuration, in which the welding tool 110 and the countertool 210 are close together along the trajectory D (Figures 2, 5 and 8), and a spaced-apart configuration, in which said welding tool 110 and countertool 220 are spaced apart along the trajectory D (Figures 1 , 4 and 7).

[0196] Performing the relative movement between the welding tool 110 and the countertool 210 along the trajectory D is carried out by moving only the welding tool 110, only the countertool 210, or both, along the trajectory D. Preferably, the relative movement towards / away is controlled independently of the rotation about the axis X. Preferably, the relative movement towards / away is in any case performed synchronously with the rotation about the axis X so as to optimize the welding process, according to predefined movements in optimal sequences.

[0197] Preferably, the mutual rotation between the welding tool 110 and the countertool 210 about the axis X from the disengaged configuration towards the welding configuration is carried out at least partly after the relative movement which draws the welding tool 110 and the countertool 210 closer together along the trajectory D. Additionally, a movement which spaces the welding tool 110 and the countertool 210 apart along the trajectory D is carried out after reaching the welding configuration and after completing the weld.

[0198] Additionally, in use, the distal portion 215 of the welding tool 110 and / or of the countertool 210 is pressed against the other between the welding tool 110 and the countertool 210, thereby making a weld along a welding line or area substantially parallel to the axis X. The step of pressing the distal portion 215 is carried out at least partly before mutually rotating the welding tool 110 and the countertool 210 about the axis X towards the welding configuration.

[0199] In a variant embodiment, the welding tool 110 and the countertool 210 are drawn closer together along the trajectory D until reaching the close- together configuration in which the front protuberance 216 is at least partly inserted into the front recess 112 thereby making a cut in the sheet or web to be welded or a local bend in the sheet or web to be welded, in a manner suitable for stably holding the sheet or web to be welded during the mutual rotation between the welding tool 110 and the countertool 210.

[0200] According to the general nature of the invention, therefore, the device 1 comprises a movement unit configured for performing a controlled relative movement between welding tool 110 and countertool 210. This movement unit comprises, in particular, at least a first movement device configured for performing the mutual rotation between welding tool 110 and countertool 210 about the axis X. The first movement device comprises, in particular, the support 220, to which the countertool 210 is hinged, and the respective actuator 240. The movement unit preferably comprises a second movement device configured for performing a relative movement to draw welding tool 110 and countertool 210 towards / away from each along the direction D. The movements are preferably controlled by a control unit, not illustrated, programmed to perform the movements in a presettable, controllable manner as a function of different requirements and / or operating parameters (thickness of material, to be welded, type of material, type of weld, and so on).

[0201] This invention thus achieves the proposed aims. The use of a rotational movement to engage and disengage the welding and opposing surfaces relative to the material to be welded allows reducing or eliminating the effects of the local dilation of the material, and in particular of the resulting wrinkling, thus obtaining high-quality, reliable welds.

Claims

CLAIMS1 . A welding device (1 ) for product packaging machines, comprising:- a welding unit (110, 210) comprising a welding tool (110) and a countertool (210) mutually movable in rotation about an axis (X), the welding tool (110) defining at least one active welding surface (111 ), and the countertool (210) defining at least one opposing surface (212),- a movement unit comprising at least one first movement device (220, 240) configured for performing a mutual rotation between the welding tool (110) and the countertool (210) about the axis (X) between a disengaged configuration, in which the active welding surface (111 ) is spaced from the opposing surface (212), and a welding configuration, in which the active welding surface (111) and the opposing surface (212) are pressed together at a welding surface (PS), wherein the axis (X) is substantially parallel to the welding surface (PS).

2. The device according to claim 1 , wherein the welding surface (PS) is substantially planar in shape and the axis (X) is substantially coplanar with the welding surface (PS).

3. The device according to claim 1 , wherein the axis (X) is spaced from the welding surface (PS).

4. The device according to any one of the preceding claims, wherein the axis (X) is kept stationary relative to the welding surface (PS) at least during the mutual rotation between the welding tool (110) and the countertool (210) about the axis (X).

5. The device according to any one of the preceding claims, wherein the at least one first movement device (220, 240) comprises a support (220), to which the welding tool (110) and / or the countertool (210) is rotatably connected, in particular by means of a pin or a hinge or an arcuate guide, and at least one actuator for moving the welding tool and / or the countertool in rotation relative to the support.

6. The device according to claim 5, wherein the countertool (210) comprises a base element (211 ) frontally defining the opposing surface(212), and wherein the base element (211 ) has, on opposite sides of it, respective protrusions (213) hinged to the support (200) about the axis (X).

7. The device according to claim 6, wherein the protrusions (213) protrude in height beyond the opposing surface (212) so as to position the base element (211 ) at a retracted position, positioning the opposing surface (212) in proximity to the axis (X) or in such a way that the axis (X) is coplanar with the opposing surface (212).

8. The device according to claim 6 or 7, wherein the support (220) has the shape of a C defining side walls (221 ) to which the base element (211 ) is hinged, in particular by hinging the protrusions (213) to the side walls (221 ).

9. The device according to claim 8, wherein the countertool (210) also has the shape of a C, with concavity facing the same direction as the concavity of the C shape of the support (220).

10. The device according to claim 8 or 9, wherein the side walls (221 ) are parallel to each other and perpendicular to the axis (X).

11. The device according to any one of claims 6 to 10, wherein the base element (211 ) is elongated in shape along the axis (X).

12. The device according to any one of the preceding claims, comprising only one first movement device, operating on the welding tool (110).

13. The device according to any one of claims 1 to 11 , comprising only one first movement device (220, 240), operating on the countertool (210).

14. The device according to any one of the preceding claims, wherein the movement unit comprises at least one second movement device configured for performing a relative movement between said welding tool (110) and said countertool (210) to draw them towards / away from each other along a trajectory (D) incident on the welding surface (PS) between a close-together configuration, in which the welding tool (110) and the countertool (210) are close together along the trajectory (D), and a spaced-apart configuration, in which the welding tool (110) and the countertool (210) are spaced apart along the trajectory (D).

15. The device according to claim 14 when dependent on claim 5, wherein the at least one second movement device operates on the welding tool (110) to move the welding tool (110) along the trajectory (D).

16. The device according to claim 15, wherein said support (220) is mounted on a guide and wherein said at least one second movement device comprises a respective actuator connected to said support (220) to move said support (220) along said guide.

17. The device according to any one of claims 14 to 16, wherein the trajectory (D) is substantially rectilinear and perpendicular to the welding surface (PS) at least in the close-together configuration.

18. The device according to any one of claims 14 to 17, wherein one between the welding tool (110) and the countertool (210) has a distal portion (215) which faces towards the other between the welding tool (110) and the countertool (210) and which is adapted to define, in conjunction with the other between the welding tool (110) and the countertool (210), a welding or cutting line or area substantially parallel to the axis (X).

19. The device according to claim 18, wherein the distal portion is defined on the welding tool (110) and is parallel to the active welding surface (111 ) or the distal portion (215) is defined on the countertool (210) and is substantially parallel to the opposing surface (212).

20. The device according to claim 18 or 19, wherein the distal portion (215) and / or the other between the welding tool (110) and the countertool (210) is configured in such a way as to define a weld which is different from the weld between the active welding surface (111 ) and the opposing surface (212).

21. The device according to any one of claims 14 to 17, wherein one between the welding tool (110) and the countertool (210) has a front protuberance (216), facing towards the other between the welding tool (110) and the countertool (210), and wherein the other between the welding tool (110) and the countertool (210) has a front recess (112), the front protuberance (216) and the front recess (112) having respective maindirections of extension which are parallel to the axis (X) and facing each other so that, in the close-together configuration, they cut a sheet or web to be welded, interposed between welding tool (110) and countertool (210) or locally bend a sheet or web to be welded, interposed between welding tool (110) and countertool (210), in a manner suitable for stably holding the sheet or web to be welded during the mutual rotation between the welding tool (110) and the countertool (210).

22. The device according to any one of the preceding claims, further comprising a conveyor movable along a movement path which is at least partially parallel and / or coplanar with the welding surface (PS), wherein the welding unit (110, 210) and the movement unit are mounted on the conveyor and are movable along the movement path in such a way as to make a seam tracking weld.

23. The device according to any one of the preceding claims, wherein the welding tool (100) is an ultrasonic welding tool.

24. A welding method for product packaging machines, implemented by a device (1 ) comprising a welding tool (110) and a countertool (210) positioned to face each other, wherein the welding tool (110) defines at least one active welding surface (111 ), and the countertool (210) defines at least one opposing surface (212), and wherein the welding tool (110) and the countertool (210) are configured to form a disengaged configuration, in which the active welding surface (111 ) is spaced from the opposing surface (212), and a welding configuration, in which the active welding surface (111) and the opposing surface (212) are pressed together at a welding surface (PS), the method being preferably implemented by a device (1 ) according to any one of the preceding claims, and wherein the method comprises:- positioning the welding surface (111 ) and the opposing surface (212) in the disengaged configuration, with at least one sheet or web to be welded interposed between the welding surface (111 ) and the opposing surface (212);- performing a mutual rotation between the welding tool (110) and the countertool (210) about an axis (X) substantially parallel to the welding surface (PS) until reaching the welding configuration where the at least one sheet or web is welded.

25. The method according to claim 24, wherein the axis (X) is kept stationary relative to the sheet or web to be welded at least during the mutual rotation between the welding tool (110) and the countertool (210) about the axis (X).

26. The method according to claim 24 or 25, wherein performing the mutual rotation between the welding tool (110) and the countertool (210) is carried out by rotating only the welding tool (110) or only the countertool (210).

27. The method according to any one of claims 24 to 26, further comprising performing a relative movement between said welding tool (110) and said countertool (210) to draw them, towards / away from each other along a trajectory (D) incident on the welding surface (PS) between a close-together configuration, in which the welding tool (110) and the countertool (210) are close together along the trajectory (D), and a spaced-apart configuration, in which the welding tool (110) and the countertool (210) are spaced apart along the trajectory (D).

28. The method according to claim 27, wherein performing the relative movement between the welding tool (110) and the countertool (210) along the trajectory (D) is carried out by moving only the welding tool (110) or the countertool (210) along the trajectory (D).

29. The method according to claim 27 or 28, wherein performing the relative movement between the welding tool (110) and the countertool (210) along the trajectory (D) comprises drawing the welding tool (110) and the countertool (210) close together along the trajectory (D), the mutual rotation between the welding tool (110) and the countertool (210) about the axis (X) towards the welding configuration being carried out at least partially after the welding tool (110) and the countertool (210) havebeen drawn closer together along the trajectory (D), and further comprises drawing the welding tool (110) and the countertool (210) away from each other along the trajectory (D) after reaching the welding configuration.

30. The method according to claim 29, wherein performing the relative movement between the welding tool (110) and the countertool (210) to draw them towards each other along the trajectory (D) comprises a step of pressing a distal portion (215) on one between the welding tool (110) and the countertool (210) against the other between the welding tool (110) and the countertool (210), thus making a weld along a welding line or area substantially parallel to the axis (X), the step of pressing the distal portion (215) being carried out at least partially before mutually rotating the welding tool (110) and the countertool (210) about the axis (X) towards the welding configuration.31 . The method according to claim 30, wherein the weld made by pressing the distal portion (215) is different from the weld made between the active welding surface (111 ) and the opposing surface (212).

32. The method according to claim 29, wherein one between the welding tool (110) and the countertool (210) has a front protuberance (216), facing towards the other between the welding tool (110) and the countertool (210), and wherein the other between the welding tool (110) and the countertool (210) has a front recess (112), the front protuberance (216) and the front recess (112) having respective main directions of extension which are parallel to the axis (X) and facing each other, and wherein the relative movement between the welding tool (110) and countertool (210) to draw them closer together along the trajectory (D) makes, in the close- together configuration, a cut in the sheet or web to be welded or a local bend in the sheet or web to be welded, in a manner suitable for stably holding the sheet or web to be welded during the mutual rotation between the welding tool (110) and the countertool (210).

33. The method according to any one of claims 24 to 32, further comprising moving the welding tool (110) and the countertool (210) alonga movement path, rotating the welding tool (110) and the countertool (210) relative to each other about the axis (X) being carried out during the step of moving the welding tool (110) and the countertool (210) along the movement path in such a way as to make a seam tracking weld.

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