Welding device and method for product packaging machines

Abstract

A welding method for product packaging machines, implemented by a device (1) comprising a welding tool (100) and a countertool (200) respectively defining an active welding surface (110) and an opposing surface (210), where the welding tool (100) and the countertool (200) are mutually rotatable about an axis (X) and are configured to form a welding configuration, in which the active welding surface (110) and the opposing surface (210) are held tightly together at a weld imprint (IS). The method comprises spacing the active welding surface (110) and the opposing surface (210) from each other, interposing at least one sheet or web (300) to be welded between the active welding surface (110) and the opposing surface (210) and performing a mutual rotation between welding tool (100) and countertool (200) until reaching the welding configuration. The active welding surface (110) and the opposing surface (210) are positioned and / or configured in such a way that on reaching the welding configuration, the active welding surface (110) and the opposing surface (210) are tightened substantially simultaneously on the whole of the weld imprint (IS).

Description

[0001] DESCRIPTION WELDING DEVICE AND METHOD FOR PRODUCT PACKAGING MACHINES.

[0002] Technical field

[0003] 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.

[0004] Background art

[0005] 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.

[0006] 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.

[0007] 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.

[0008] The Applicant has found that such a solution is not flexible because the configuration of traditional tools requires predetermined dimensions which are often incompatible with the available space in the machine. It should be considered that besides the parts to be welded, the welding zone normally contains movable components which support the tool and the countertool and which comprise respective slides and, if necessary, adjustment systems.

[0009] Moreover, welds need to comply with increasingly stringent requirements and such a situation calls for adjustment systems capable of controlling the welding parameters very precisely. Disadvantageously, the use of traditional welding devices is subject to structural complications which have a negative impact on performance in terms of precision. In particular, the systems used for moving and adjusting the welding tool and / or the countertool in prior art systems include complex and bulky mechanical transmission systems which, besides occupying a lot of space, inevitably introduce dimensional backlash which is not conducive to adjustment precision.

[0010] The Applicant has thus found that in order to obtain a satisfactory weld, it is sufficient to mime the relative translational movement between tool and countertool only at the instant of contact and detachment between tool and countertool, while in the remaining part of the relative movement, the trajectories followed by tool and / or countertool need not be rectilinear.

[0011] In other words, the Applicant has found that it is sufficient to perform a substantially rectilinear movement only locally, at the weld imprint zone where tool and countertool are held tightly together, without any restrictions on the rest of the movement, provided always that engagement in the contact zone occurs almost simultaneously on the whole imprint (that is to say, on all of the contact surface between tool and countertool). Based on that, the Applicant has developed a technical solution constituting an improvement over the prior art, where the translation in the contact zone is mimed by a purely rotational mutual movement between tool and countertool about an axis, where the action of movement between tool and countertool in the contact zone is substantially linear (rectilinear) and, in particular, tangent to the rotary trajectory.

[0012] For that reason, in the solution developed, the tool and / or the countertool is configured in such a way as to mime the relative translational movement, in the contact zone, via a purely rotational mutual movement between tool and countertool, where engagement in the contact zone occurs substantially simultaneously on the whole weld imprint (that is to say, on all of the contact surface between tool and countertool). Such an engagement in the contact zone occurs by causing the tool and the countertool to be pressed together by a substantially linear relative movement.

[0013] In this situation, the expression "configured in such a way that" takes into account the fact that, irrespective of the position and orientation of the axis of mutual rotation between tool and countertool, the tool and the countertool are set up in such a manner as to ensure that engagement between tool and countertool is substantially simultaneous on the whole of the weld imprint.

[0014] Thanks to the purely rotational movement, the Applicant has noticed a considerable benefit in terms of structural compactness and operating precision. In effect, the rotational movement is easier to be actuated directly via rotary actuators (for example, a brushless motor and a reduction unit) which are compact and easily controlled without necessitating complex mechanisms, linkages or mechanical transmissions which would introduce mechanical backlash, hence positional imprecision in the welding zone.

[0015] This invention regards a welding method for product packaging machines. The method is implemented by a welding device comprising a welding tool and a countertool, positioned to face each other, where the tool defines at least one active welding surface, and the countertool defines at least one opposing surface.

[0016] The welding tool and the countertool are configured to form a disengaged configuration in which the active welding surface is spaced from the opposing surface, in particular suitable for the insertion of at least one web or sheet to be welded and for the extraction of the at least one web or sheet after welding, and a welding configuration, in which the active welding surface and the opposing surface are pressed tightly together at a weld imprint lying on a welding surface. Additionally, the welding tool and the countertool are movable between the welding and disengaged configurations via a mutual rotational movement about an axis.

[0017] Preferably, the method comprises initially positioning the welding and opposing surfaces in the disengaged configuration.

[0018] Preferably, also, the method comprises interposing at least one sheet or web to be welded between the welding and opposing surfaces.

[0019] In accordance with the method, the welding tool and the countertool are moved in rotation about the axis until reaching the welding configuration, thus welding the at least one sheet or web.

[0020] In accordance with the method, the active welding surface and the opposing surface are positioned and / or configured in such a way that on reaching the welding configuration, the active welding surface and the opposing surface are pressed tightly together substantially simultaneously on the whole of the weld imprint.

[0021] In particular, interposing the at least one sheet or web to be welded between the welding and opposing surfaces may be carried out while the welding and opposing surfaces are in the disengaged configuration or during the rotational movement between welding tool and countertool towards the welding configuration.

[0022] The expression "substantially simultaneously" referred to the action of pressing tightly together is used in the sense of positioning the active welding surface and the opposing surface so they are substantially parallel to each other. The term "substantially" implies that, also as a function of the thickness of the material to be welded, in the pressed together configuration, it is possible to allow for a minimum angle of deviation from such parallelism. Preferably, such an angle of deviation included within the meaning of "substantially" is less than 1 ° and, more preferably, less than 0.5°. Therefore, as a function of the allowable angle of deviation, it is possible to configure the welding tool and / or the countertool and / or accordingly select the position of the axis of rotation between welding tool and countertool.

[0023] This method allows optimum pressing together at the weld imprint, making a quality weld and at the same time employing a simplified machine architecture thanks to the use of one or more rotary actuators such as, for example, brushless motors. Such actuators are easy to control and reduced in size and do not necessitate mechanical transmissions thanks to the rotary actuation of the welding tool and / or of the countertool. This invention may also comprise at least one of the preferred features described below.

[0024] Preferably, the weld imprint has an elongated shape with a main direction of extension. This makes welds suitable for closing discrete packages or for welding continuous tubes, longitudinally and transversely, for example in flow-pack machines.

[0025] Preferably, the weld imprint has a polygonal shape, for example, rectangular.

[0026] Preferably, the weld imprint (hence the welding surface it lies in) has a planar shape. This may translate as the fact that the active welding surface and the opposing surface have respective planar shapes. Such shapes are intended to be positioned in a substantially parallel configuration when at least one sheet or web to be welded is pressed tightly in the welding configuration.

[0027] In an embodiment, the weld imprint is defined by a single area which is, for example, polygonal (rectangular) in shape.

[0028] In a different embodiment, the weld imprint is defined by two or more distinct regions.

[0029] Preferably, such two or more regions are planar in shape.

[0030] Preferably, such two or more regions are substantially coplanar with each other.

[0031] Preferably, such two or more regions have respective main directions of extension which are parallel to each other. Alternatively, such two or more regions have respective main directions of extension which are inclined to each other (for example, coplanar and inclined, or skew to each other).

[0032] In an embodiment, such two regions are configured to make welds of the same kind.

[0033] In a different embodiment, such two regions are configured to make welds of different kinds, for example, a hermetic weld and a cosmetic weld.

[0034] More preferably, such two or more regions have respective main directions of extension which are parallel to each other and parallel to the aforementioned main direction of extension of the weld imprint.

[0035] Such two or more regions may be defined by protrusions which are juxtaposed or parallel to a single welding member and / or by protrusions of a single opposing member. In other words, such two or more regions may be separated from each other by at least one respective separating zone, for example, a recess.

[0036] In a first embodiment, the axis of mutual rotation between the welding tool and the countertool is parallel to the welding surface (or, in other terms, to the weld imprint). By "parallel" is meant having any orientation provided it lies in a plane which is parallel to the welding surface.

[0037] In particular, in a variant, the axis is parallel to the main direction of extension of the weld imprint.

[0038] In a different variant, the axis is inclined to the main direction of extension of the weld imprint.

[0039] In another different variant, the axis is perpendicular to the main direction of extension of the weld imprint.

[0040] In each of these variants, the axis may lie substantially on the welding surface.

[0041] Alternatively, the axis is spaced from the welding surface. This may translate as a configuration in which the axis is spaced from the welding surface towards the countertool or as a configuration in which the axis is spaced from the welding surface towards the welding tool. In a second embodiment, the axis of mutual rotation between the welding tool and the countertool is inclined to the welding surface. In other words, given a generic plane passing through the axis, such a plane is not parallel to the welding surface.

[0042] In an embodiment, the countertool is defined by a rotary element which is hinged around the axis. In this embodiment, performing a movement of mutual rotation between the welding tool and the countertool about the axis is obtained by moving the countertool in rotation about the axis, preferably by moving only the countertool in rotation about the axis. Preferably, in this situation, the welding tool is defined by an element which does not move with rotational motion about the axis.

[0043] In a different embodiment, the welding tool is defined by a rotary element which is hinged around the axis. In this embodiment, performing a movement of mutual rotation between the welding tool and the countertool about the axis is obtained by moving the welding tool in rotation about the axis, preferably by moving only the welding tool in rotation about the axis. Preferably, in this situation, the countertool is defined by an element which does not move with rotational motion about the axis.

[0044] In a different embodiment, the welding tool and the countertool are each defined by a respective rotary element which is hinged around the axis. In this embodiment, performing a movement of mutual rotation between the welding tool and the countertool about the axis is obtained by moving both the welding tool and the countertool in rotation, preferably simultaneously, about the axis.

[0045] Preferably, in the case of a countertool which is rotatable about the axis, the countertool has a concave portion located between the axis and the opposing surface. This concave portion is preferably defined by an arcuate or "elbow-shaped" structure of a central zone of the countertool. This concave portion operatively faces towards the welding tool during the rotation of the countertool between the disengaged configuration and the welding configuration. That way, the concave portion forms a "retracted" portion of the countertool which remains at a suitable distance from the welding zone, hence from the welding tool and from the at least one web or sheet to be welded, during the welding process. This provides high structural robustness combined with good operating safety.

[0046] Preferably, the countertool is defined by a monolithic element which, in particular at a first end, is hinged around the axis and which, in particular at the other end, defines the opposing surface. This monolithic element, which is suitably connected to an actuator, is operable in rotation about the axis in a simple, compact and robust manner.

[0047] Preferably, the axis is kept stationary relative to the at least one sheet or web to be welded at least for a welding configuration hold time.

[0048] More preferably, the axis is kept stationary relative to the at least one sheet or web to be welded also during the mutual rotation between the welding tool and the countertool about the axis.

[0049] In particular, this occurs in a fixed axis configuration, where the axis may be permanently stationary both relative to the at least one sheet or web to be welded and also at other stages.

[0050] Additionally, this may occur in configurations in which the countertool (or in any case, whichever component, between welding tool and countertool, is the one that moves with rotational motion about the axis) is mounted on a movement element movable along a trajectory having a synchronous, and preferably rectilinear stretch, with an advancing movement of the at least one web or sheet to be welded (having a preferably planar shape in the welding zone) so as to make a seam tracking weld.

[0051] Disclosure of the invention

[0052] For this purpose, the method comprises moving the welding tool and / or the countertool along a movement path, for example on a carousel or on a conveyor, preferably having at least one rectilinear stretch at the welding zone. Preferably, the movement path runs along a closed line, for example a loop having, where necessary, a rectilinear stretch. Alternatively, the movement path is a to-and-fro movement along a rectilinear direction.

[0053] Preferably, also, mutually rotating the welding tool and the countertool about the axis is performed during the movement of the welding tool and / or the countertool along the movement path, in particular while the axis is stationary relative to the at least one sheet or web to be welded, so as to make a seam tracking weld.

[0054] Preferably, 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. The front protuberance and the front recess have respective main directions of extension and face each other to define, in the welding configuration, the cut in the at least one sheet or web interposed between the welding tool and the countertool.

[0055] Preferably, the welding tool is an ultrasonic welding tool.

[0056] Alternatively, the welding tool is a hot air welding, cold welding or induction welding tool.

[0057] 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.

[0058] The invention is, in any case, applicable to any type of welding tool, suitable for acting in conjunction with a countertool.

[0059] Brief description of drawings

[0060] 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.

[0061] In these drawings:

[0062] - Figures 1 a-1d represent a first embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0063] - Figures 2a-2d represent a second embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0064] - Figures 3a-3d represent a third embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0065] - Figures 4a-4d represent a fourth embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0066] - Figures 5a-5d represent a fifth embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0067] - Figures 6a-6d represent a sixth embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0068] - Figures 7a-7d represent a seventh embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0069] - Figures 8a-8d represent an eighth embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0070] - Figures 9a-9d represent a ninth embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0071] - Figures 10a-10d represent a tenth embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles;

[0072] - Figures 11 a-11d represent an eleventh embodiment of a welding device usable for implementing the method according to the invention and shown from different viewing angles; - Figures 12a-12b represent two components of a welding device usable for implementing the method according to the invention, in a first embodiment;

[0073] - Figure 12c represents the two components of Figures 12a and 12b in an operating welding configuration;

[0074] - Figures 13a-13b represent two components of a welding device usable for implementing the method according to the invention, in a second embodiment;

[0075] - Figure 13c represents the two components of Figures 13a and 13b in an operating welding configuration;

[0076] - Figure 14 represents a step of the welding method according to the invention, in a variant embodiment of it.

[0077] Detailed description of preferred embodiments of the invention

[0078] With reference to the accompanying drawings, the numeral 1 denotes in its entirety a welding device suitable for carrying out the method according to the invention.

[0079] The welding device 1 comprises a welding tool 100 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), and a countertool 200 intended to operate in conjunction with the welding tool 100 to perform a welding action on at least one web or sheet 300 interposed between them.

[0080] 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, for example in the form of a pouch or packet.

[0081] The welding tool 100 and the countertool 200 may be mounted on the same machine frame or on different frames.

[0082] The welding tool 100, at the front of it, has an active welding surface 110 which is intended to come into contact with the at least one web or sheet 300 to be welded. Similarly, the countertool 200 has an opposing surface 210, intended to work in conjunction with the active welding surface 110 of the welding tool 100 to make the weld on the at least one web or sheet 300. Preferably, but not necessarily, the countertool 200 comprises, or is defined by, a base element with a rigid, preferably monolithic structure.

[0083] In a detail not illustrated in the drawings, the opposing surface 210 may be defined by a raised or relief portion formed on an end surface of the countertool.

[0084] The welding tool 100 and the countertool 200 are positioned to face each other so as to press the at least one sheet or web 300 between them in clamp-like manner.

[0085] Additionally, the welding tool 100 and the countertool 200 are mutually movable in rotation about an axis X.

[0086] In the embodiments illustrated in the accompanying drawings, the countertool 200 is rotatable about the axis X, while the welding tool, although it may have possible degrees of freedom (for example, a linear movement towards and away from the countertool 200) is preferably stationary relative to a rotation about the axis X.

[0087] More in detail, the welding tool 100 and the countertool 200 are mutually movable in rotation about the axis X between a disengaged configuration in which the active welding surface 110 is spaced from the opposing surface, 210 and a welding configuration, in which the active welding surface 110 and the opposing surface 210 are pressed together at a weld imprint IS lying on a welding surface S.

[0088] Thus, the welding configuration, in which the welding tool 100 and the countertool 200 are rotated relative to each other so as to position the active welding surface 110 and the opposing surface 210 at a mutually spaced-apart position, not illustrated in the accompanying drawings, while, the welding configuration is shown, for example, in Figures 1 b, 1 c; 2b, 2c; ... 11 b, 11 c.

[0089] According to the invention, the active welding surface 110 and the opposing surface 210 are positioned and / or configured in such a way that on reaching the welding configuration, the active welding surface 110 and the opposing surface 210 are pressed together substantially simultaneously on the whole of the weld imprint IS.

[0090] In other words, the configuration of the welding tool 100 and of the countertool 200 is such that, at the welding instant, the active welding surface 110 and the opposing surface 210 perform a substantially rectilinear, simultaneous tightening action on the whole of the weld imprint IS. That is because the mutual rotational movement between welding tool 100 and countertool 200 substantially copies, in the welding zone, a perpendicular translational movement between the active welding surface 110 and the opposing surface 210. Furthermore, the rotational movement also offers some advantages such as, for example, considerable structural simplification and greater ease of control. In effect, preferably, the mutual rotation between welding tool 100 and countertool 200 may be accomplished using a rotary actuator (not illustrated), for example, a brushless motor, which is easy to control and without having to interpose complex mechanical transmissions.

[0091] From a structural viewpoint, the rotation (which, in the accompanying drawings, is performed by the countertool 200) is defined by a rotational movement about a supporting body (not illustrated) which may be fixed or mounted on a movement element (for example, a rotary turret), the latter case being suitable for a seam tracking weld.

[0092] Therefore, following the rotational movement about the axis X, the active welding surface 110 and the opposing surface 210 come into contact with the at least one sheet or web 300 to be welded with an instantaneous action of movement which identifies a substantially simultaneous tightening action on the entire weld imprint IS.

[0093] The expression "substantially simultaneous" referred to the tightening action is used in the sense of positioning the welding surface 110 and the opposing surface 210 substantially parallel to each other. The term "substantially" implies that, also as a function of the thickness of the material to be welded, in the pressed together configuration, it is possible to allow for a minimum angle of deviation from such parallelism. Preferably, such an angle of deviation included within the meaning of "substantially" is less than 1 ° and, more preferably, less than 0.5°.

[0094] More in detail, the action of movement during tightening is substantially rectilinear and produces the aforementioned substantially simultaneous engagement on the whole of the weld imprint IS. In the case shown in the drawings, the weld imprint IS is defined by the entire front surface of the countertool 200, although more generally speaking it corresponds to the overlap surface identified between the active welding surface 110 and the opposing surface 210 in the welding configuration.

[0095] In the embodiments illustrated, the weld imprint IS has an elongated shape with a main direction of extension and has a preferably rectangular shape. In embodiments not illustrated, however, the shape could be different.

[0096] Additionally, in the embodiments illustrated, the weld imprint IS has a planar shape. By "planar shape" is meant a shape having a main positioning plane, without excluding the presence of local reliefs or recesses which have specific functions but which do not in any case alter the overall appearance of planarity. The term "planar" should not be understood as lying exclusively and entirely in one plane. That means that the definition of planar may encompass the fact that the weld imprint IS not smooth but may have a textured surface (for example, with reliefs, knurling, parallel grooves and so on), provided the overall shape of the imprint lies generally in one plane.

[0097] In embodiments not illustrated, however, the weld imprint IS may have a non-planar shape: for example, it may have an arcuate (convex or partly convex, concave or partly concave) corrugated or other shape.

[0098] The accompanying drawings illustrate different embodiments of the device 1 used for the method according to the invention.

[0099] Figures 1 a-1d show a first embodiment of the welding device 1 , suitable for implementing the welding method according to the invention.

[0100] In particular, Figure 1a shows a front view, while Figure 1 b shows a side view. In this embodiment, the rotation axis X of the countertool 200 is parallel to the welding surface S, hence to the weld imprint IS. In particular, in the image of Figure 1 b, the rotation axis X is perpendicular to the sheet.

[0101] Additionally, in this embodiment, the rotation axis X is parallel to the main direction of extension of the weld imprint IS, which is also perpendicular to the sheet in the image of Figure 1 b.

[0102] Lastly, in this embodiment, the rotation axis X lies substantially on the welding surface S. By "lies substantially" is meant, in the context of this invention, a precise overlap between the rotation axis X and the welding surface S or a deviation of minimum extent, for example, an extent substantially equal to the thickness of the material to be welded, in particular between ±2 mm, preferably ±1 mm and, still more preferably, ±0.5mm.

[0103] Figure 1 c shows the device in a perspective view, while Figure 1d shows the device from above (in any case, the specific spatial orientation of the device does not constitute a limitation to the protection of this invention).

[0104] The embodiment of Figures 2a-2d differs from that of Figures 1 a-1d in that the rotation axis X, although it also lies in a plane parallel to the welding surface S (and in particular, but not necessarily, lies substantially on the surface S), is inclined to the main direction of extension of the weld imprint IS, in particular at an angle a which may be defined as "inclination angle" in the sense that it is the angle at which the main direction of extension is inclined to the weld imprint IS. Preferably, the inclination angle a is between 1 ° and 89°.

[0105] The embodiment of Figures 3a-3d differs from that of Figures 1 a-1d in that the rotation axis X is not parallel to the welding surface S but is inclined to it, in particular at an angle [3 which may be defined as "deviation angle" in the sense that it is a deviation from the parallelism with the welding surface S. Preferably, the deviation angle [3 is between 1 ° and 60°.

[0106] Additionally, in this embodiment, the rotation axis X is preferably positioned so as to intersect the welding surface S at a point subtending the extension of the weld imprint IS perpendicularly to the main direction of extension of the weld imprint IS itself. This is visible in Figure 3d, where it may be noticed that the intersection between the rotation axis X and the welding surface S is inside the segment defined by the weld imprint IS viewed from above.

[0107] The embodiment of Figures 4a-4d is similar to the embodiments of Figures 2a-2d and 3a-3d and is characterized in that the rotation axis X has both the aforementioned inclination angle a and the deviation angle [3.

[0108] The embodiment of Figures 5a-5d is substantially similar to that of Figures 1 a-1d except that the rotation axis X, which is again parallel to the welding surface S but, in this case, is spaced from the welding surface S, in particular in the direction of the countertool 200.

[0109] The embodiment of Figures 6a-6d is substantially similar to that of Figures 2a-2d except that the rotation axis X, which is again parallel to the welding surface S but, in this case, is spaced from the welding surface S, in particular in the direction of the countertool 200.

[0110] The embodiment of Figures 7a-7d is substantially similar to that of Figures 3a-3d except that the rotation axis X, which is again inclined at the inclination angle a relative to the welding surface S but is spaced from the welding surface S, in particular in the direction of the countertool 200, in particular at the point such that the intersection between the rotation axis X and the welding surface S is outside the projection of the weld imprint IS perpendicularly to the main direction of extension of the weld imprint IS itself (see Figure 7d in particular).

[0111] The embodiment of Figures 8a-8d is similar to the embodiments of Figures 6a-6d and 7a-7d and is characterized in that the rotation axis X has both the aforementioned inclination angle a and the deviation angle [3.

[0112] The embodiment of Figures 9a-9d is a "limit" version of the embodiment of Figures 2a-2d in that the inclination angle is 90°. In other words, the rotation axis X is perpendicular to the main direction of extension of the weld imprint IS. In this variant, the rotation axis X may be spaced from the welding surface S, in particular towards the countertool 200 (specific embodiment of Figures 9a-9d) or towards the welding tool 100 (variant not illustrated), or the rotation axis X may substantially lie on the welding surface S (variant not illustrated).

[0113] The embodiment of Figures 10a-10d differs from the embodiment of Figures 9a-9d in that the rotation axis X has the deviation angle [3 relative to the welding surface S.

[0114] The embodiment of Figures 11 a-11d is substantially similar to that of Figures 2a-2d except that the rotation axis X, which is again parallel to the welding surface S but, in this case, is spaced from the welding surface S, in particular in the direction of the welding tool 100.

[0115] Figures 12a and 12b respectively illustrate the welding tool 100 and the countertool 200 in an embodiment where the respective surfaces (active welding surface 110 and opposing surface 210) are defined by a single region whose shape is preferably polygonal, in particular rectangular and which has a main direction of extension, thus defining a contact imprint IS defined by a single region whose shape is preferably polygonal, in particular rectangular and which has a main direction of extension.

[0116] Figure 12c shows the contact imprint in the welding configuration where the welding tool 100 and the countertool 200 have the at least one sheet or web to be welded 300 pressed between them. Figures 13a-13c respectively illustrate the welding tool 100 and the countertool 200 in a different embodiment where the weld imprint IS is defined by two or more distinct regions IS1 and IS2 having respective main directions of extension which are parallel to each other and parallel to the main direction of extension of the weld imprint IS.

[0117] Preferably, these two or more regions IS1 , IS2 are planar in shape and more preferably are coplanar with each other.

[0118] More in detail, these two or more regions IS1 , IS2 are defined by a specific contour of the countertool 200 which, at the opposing surface 210, has two juxtaposed, parallel protrusions 220, each defining a respective portion of opposing surface 210 and separated from each other by at least one respective separating zone, in particular a recess 230.

[0119] In all the embodiments, the concept of parallelism or of angle to the welding surface S and / or to the weld imprint IS refers not only to the situation where the welding surface S and / or the weld imprint IS is planar, but also to the situation where the welding surface S and / or the weld imprint IS is not planar, for example, curved, corrugated and so on.

[0120] In the case of a welding surface with a non-planar shape, the concept of parallelism or of included angle is understood as referring to a mean plane of the welding surface S. For example, in the case of a welding surface S with a curved shape, (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.

[0121] More generally speaking, the term "mean plane" is used to denote the positioning plane of the coupled set to be welded before reaching the welding configuration, hence before the active welding surface 110 and the opposing surface 210 are pressed against each other, where such mean plane intersects the active welding surface 110 and / or the opposing surface 210 positioned in the welding configuration.

[0122] According to the invention, the welding method is carried out by positioning the active welding surface 110 and the opposing surface 210 in the disengaged configuration, with at least one sheet or web to be welded 300 interposed between them, and then performing a mutual rotation between the welding tool 100 and the countertool 200 about the axis X until reaching the welding configuration to make the weld on the at least one sheet or web 300.

[0123] In this process, the engagement of the active welding surface 110 and the opposing surface 210 with the at least one sheet or web 300 to be welded occurs substantially simultaneously on the whole of the weld imprint IS.

[0124] The expression "substantially simultaneous" referred to the tightening action is used in the sense of positioning the active welding surface and the opposing surface substantially parallel to each other. The term "substantially" implies that, also as a function of the thickness of the material to be welded, in the pressed together configuration, it is possible to allow for a minimum angle of deviation from such parallelism at the instant when the countertool 200 and the at least one web or sheet 300 to be welded start contacting each other. Such an angle is, in particular, the angle made between the outside surface of the at least one sheet or web 300 and the opposing surface 210 (or the active welding surface 110 in the case of a welding tool 100 which is rotatable about the axis X), measured around the rotation axis X. Preferably, such an angle of deviation included within the meaning of "substantially simultaneous" is less than 1 ° and, more preferably, less than 0.5°. Therefore, as a function of the allowable angle of deviation, it is possible to configure the welding tool 100 and / or the countertool 200 and / or accordingly select the position of the axis of rotation X between welding tool 100 and countertool 200.

[0125] Preferably, the axis X is kept stationary relative to the at least one sheet or web 300 to be welded at least for the time the welding configuration is in place and preferably also during the mutual rotation between the welding tool 100 and the countertool 200 about the axis X. That means the axis X remains fixed at least during these steps, in the case where the at least one sheet or web 300 stops or where the axis X moves synchronously with the at least one sheet or web 300 during these steps.

[0126] The latter is the situation, for example, in the case of seam tracking welding.

[0127] In this situation, the method comprises moving the welding tool 100 and / or the countertool 200 along a movement path, for example defined by a conveyor (in particular a rotating carousel), where the mutual rotation between the welding tool 100 and the countertool 200 about the axis X is carried out during this movement of the welding tool 100 and / or the countertool 200 along a movement path to make a seam tracking weld.

[0128] Figure 14 shows a variant embodiment where the countertool 200 has a front protuberance 240 facing towards the welding tool 100, while the welding tool 100 has a front recess 120, where the front protuberance 240 and the front recess 120 are configured to engage each other. They preferably have respective main directions of extension and face each other so that, in the welding configuration, the front protuberance 240 at least partly penetrates into the front recess 120 and makes a cut in the at least one sheet or web 300 interposed between the welding tool 100 and the countertool 200.

[0129] Preferably, the front protuberance 240 and the front recess 120 are made on the outside of the respective surfaces (opposing surface 210 and active welding surface 110), preferably at a position distal to the rotation axis X.

[0130] In a variant embodiment not illustrated, the front protuberance is made on the welding tool 100 and the front recess is made on the countertool 200. Additionally, in all the embodiments, the countertool 200 preferably has a concave portion 250 positioned between the axis X and the opposing surface 210, where the concave portion 250 is directed towards the welding tool 100 during the rotation of the countertool 200 between the disengaged configuration and the welding configuration. In other words, the countertool has a central or intermediate portion which "encircles" the welding zone, surrounding it and in any case keeping it at a safe distance even in the welding configuration.

[0131] 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, while continuing to ensure a simultaneous engagement on the whole weld imprint, irrespective of the position of the rotation axis, allows making quality weld with a machine whose structure is simple and which is easy to control.

Claims

CLAIMS1. A welding method for product packaging machines, implemented by a device (1 ) comprising a welding tool (100) and a countertool (200) positioned to face each other, wherein said welding tool (100) defines at least one active welding surface (110), and said countertool (200) defines at least one opposing surface (210), and wherein said welding tool (100) and said countertool (200) are configured to form a disengaged configuration, in which said active welding surface (110) is spaced from said opposing surface (210), and a welding configuration, in which said active welding surface (110) and said opposing surface (210) are held tightly together at a weld imprint (IS) on a welding surface (S), wherein said method comprises:- positioning said active welding surface (110) and said opposing surface (210) in the disengaged configuration,- placing at least one sheet or web (300) to be welded between said active welding surface (110) and said opposing surface (210);- performing a relative movement between said welding tool (100) and said countertool (200) in rotation about an axis (X) until reaching said welding configuration where said at least one sheet or web (300) is welded, wherein said active welding surface (110) and said opposing surface (210) are positioned and / or configured in such a way that on reaching the welding configuration, said active welding surface (110) and said opposing surface (210) are tightened substantially simultaneously on the whole of the weld imprint (IS).

2. The method according to claim 1 , wherein said weld imprint (IS) has an elongated shape with a main direction of extension and has a preferably rectangular shape.

3. The method according to claim 1 or 2, wherein said axis (X) is parallel to the welding surface (S).

4. The method according to claims 2 and 3, wherein said axis (X) is parallel to the main direction of extension of the weld imprint (IS).

5. The method according to claims 2 and 3, wherein said axis (X) is inclined to the main direction of extension of the weld imprint (IS).

6. The method according to claims 2 and 3, wherein said axis (X) is perpendicular to the main direction of extension of the weld imprint (IS).

7. The method according to any one of the preceding claims, wherein the axis (X) lies substantially on the welding surface (S).

8. The method according to any one of the preceding claims, wherein the axis (X) is spaced from said welding surface (S).

9. The method according to claim 8, wherein the axis (X) is spaced from said welding surface (S) towards the countertool (200).

10. The method according to claim 8, wherein the axis (X) is spaced from said welding surface (S) towards the welding tool (100).11 . The method according to claim 1 or 2, wherein said axis (X) is inclined to the welding surface (S).

12. The method according to any one of the preceding claims, wherein the weld imprint (IS) has a planar shape.

13. The method according to any one of the preceding claims, wherein the weld imprint (IS) is defined by two or more regions (IS1 , IS2) which are distinct, in particular separated by a separating zone, preferably a recess on the welding tool and / or on the countertool.

14. The method according to claim 13, wherein, on reaching the welding configuration, said two or more regions (IS1 , IS2) make welds of different kinds, in particular at least one hermetic weld and one cosmetic weld, in particular at least one between said active welding surface (110) and said opposing surface (210) comprising a first and a second portion (220) having a different shape and / or structure and defining said two or more regions (IS1 , IS2) of the weld imprint (IS).

15. The method according to any one of the preceding claims, wherein the countertool (200) is defined by a rotary element which is hinged around said axis (X) and wherein performing said relative movement between the welding tool (100) and the countertool (200) in rotation about the axis (X)is accomplished by moving the countertool (200) in rotation about the axis (X), preferably by moving only the countertool (200) in rotation about the axis (X).

16. The method according to claim 15, wherein the countertool (200) has a concave portion (250) positioned between the axis (X) and the opposing surface (210) and wherein said concave portion (250) is directed towards the welding tool (100) during the rotation of the countertool (200) between the disengaged configuration and the welding configuration.

17. The method according to any one of the preceding claims, wherein said axis (X) is kept stationary relative to the at least one sheet or web (300) to be welded at least for the time the welding configuration is in place and preferably also during the mutual rotation between the welding tool (100) and the countertool (200) about said axis (X).

18. The method according to any one of the preceding claims, wherein one between said welding tool (100) and said countertool (200) has a front protuberance (240), facing towards the other between said welding tool (100) and said countertool (200), and wherein said other between said welding tool (100) and said countertool (200) has a front recess (120), said front protuberance (240) and said front recess (120) having respective main directions of extension and facing each other so that, in said welding configuration, the cut in said at least one sheet or web (300) to be welded is made between the welding tool (100) and the countertool (200).

19. The method according to any one of the preceding claims, further comprising moving the welding tool (100) and / or the countertool (200) along a movement path, where mutually rotating the welding tool (100) and the countertool (200) about the axis (X) is carried out during said movement of the welding tool (100) and / or of the countertool (200) along said movement path in such a way as to make a seam tracking weld.

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

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