Welding sheet material

Abstract

A sheet material welding device for product packaging machines comprises a welding tool (2) and a counter-tool (3), wherein one has a first projection (4) configured to make a respective first weld (S1) of a material (M) and wherein the other has a second projection (5) configured to make a respective second weld (S2) of the material. The first projection (4) and the second projection are arranged to make respective welds on different areas of the material (M). The first projection (4) and second projection (5) may have different heights. Preferably the welding tool (2) is an ultrasonic tool while the counter-tool (3) is an anvil.

Description

[0001] WELDING SHEET MATERIAL

[0002] Technical field

[0003] The present invention relates to the technical field of automatic product packaging machines and it relates, in detail, to a device and a method for welding sheet material, in particular for the automated welding of product packages, both discrete packages and packages of the flow-pack type.

[0004] Background art

[0005] In the product packaging industry, longitudinal and transverse weldings are known to be used, using conventional systems, such as hot, cold, or ultrasonic tools.

[0006] In general, the welding is done by mutually approaching a tool and a counter-tool, where the tool forms an active welding member while the counter-tool defines a backing anvil during the compression application by the tool.

[0007] Simultaneous weldings are also known to be performed, where two close welding lines are simultaneously made. This occurs, for example, in machines of the flow-pack type, where two transverse weldings, identical to each other, are made simultaneously by means of a compression exerted between a welding tool and a counter-tool, where the two weldings are spaced far enough apart to then cut, therebetween, the welded material, so that one of the two weldings forms the bottom welding of one package and the other welding forms the top welding of the next package.

[0008] A hermetic welding and a cosmetic welding are also known to be created, close to each other and adapted to close a bag containing a product, where the cosmetic welding has a structured pattern while the hermetic welding offers a strong sealing.

[0009] In known solutions, the two weldings are performed by providing a special pair of protrusions on the counter-tool, generally the anvil of a sonotrode, while the welding tool has a front abutment surface against which the protrusions of the counter-tool press, thus generating the weldings at the two protrusions.

[0010] The Applicant has found that the known solutions are improvable, particularly in terms of flexibility of use.

[0011] In the known solutions, each change to the welding layout necessarily requires replacing the anvil, even when only a minimal modification is required, such as a change in the distance between the two weldings, for example.

[0012] Furthermore, in the known solutions, the provision of systems for tightening the material to be welded, which must not be subject to movement during the welding process, is advisable.

[0013] In such a context, the Applicant has found that, by arranging one of the two projections on the welding tool and the other projection on the counter-tool, the aforesaid drawbacks can be overcome, since a mutual adjustment of the position of the projections (and therefore between the weldings) is possible by simply adjusting the position of the welding tool and / or the counter-tool, thus obtaining a geometrically varied weld imprint without requiring structural replacements to the device.

[0014] Furthermore, this allows modifying the geometry and / or type of weldings by selectively replacing just the welding tool or the counter-tool, allowing several different welding combinations with only a limited number of replacements.

[0015] Furthermore, arranging one of the two projections on the welding tool and the other projection on the counter-tool allows for making a tortuous path for the material or aggregate, which is more securely held between the welding tool and the counter-tool, thus reducing the risk of misalignment and therefore the risk of producing non-compliant weldings.

[0016] It is also economically advantageous to make more complex welding projections on the counter-tool, in particular those with a more complex surface structure or style (e.g., the cosmetic welding profile) whereby, for example, it is preferable to make the most complex imprint or an imprint which is subject to more frequent format changes on the counter-tool.

[0017] Disclosure of the invention

[0018] The present invention, therefore, relates, in a first aspect thereof, to a sheet material welding device.

[0019] In particular, the material can consist of a single folded sheet (e.g., in a bag or pocket or, in the case of flow-pack machines, in a tubular form) or of two separate sheets ("aggregate") at least partially overlapping each other.

[0020] Possible applications of the invention are the welding of containers (e.g., bags) made of single-layer or multi-layer film, or the welding of containers made of multi-layer material, particularly multi-layered materials (e.g., cartons).

[0021] In accordance with the invention, the welding device comprises a first component defining a first front surface and a second component defining a second front surface, where the first and second components are mutually movable between an approached position and a distanced position so that in the approached position the two front surfaces face each other and are capable of tightening a material or aggregate to be welded therebetween.

[0022] Preferably, one of the two components is a welding tool, and the respective front surface is an active welding surface.

[0023] Preferably, the other component is a counter-tool, and the respective front surface is a contrast surface.

[0024] Preferably, the first front surface has at least a first projection configured to make at least one respective first welding of the material or aggregate interposed between the two components.

[0025] Preferably, the second front surface has at least a second projection configured to make at least one respective second welding of the material or aggregate interposed between the two components. By means of such a technical solution, it is therefore possible to obtain a weld imprint adaptable to several formats, since by replacing the first and / or second component, it is possible to achieve a high number of weld imprints.

[0026] Furthermore, the weld imprint is also modifiable by simply adjusting the mutual positioning between the first two components.

[0027] The provision of projections on both components further creates a tortuous or "wavy" style of the material between the two components, which has the effect of achieving a stable locking of the material itself without the need to provide special locking means.

[0028] Furthermore, it is both economically and technologically advantageous to optimize the realization of the two components, in particular by providing complex profiles (structured surfaces) on the counter-tool, leaving the simpler projections on the welding tool.

[0029] The present invention relates, in a second aspect, to a method for welding a sheet material.

[0030] The method is preferably performed by means of a device comprising a first component defining a first front surface and a second component defining a second front surface, mutually movable between an approached position (for tightening and welding) and a distanced position so that in the approached position the two front surfaces face each other and are capable of tightening a material or aggregate to be welded therebetween, in which one of the two components is a welding tool and the respective front surface is an active welding surface and in which the other component is a counter-tool and the respective front surface is a contrast surface, where the first front surface has at least a first projection configured to make at least one respective first welding of the material or aggregate interposed between the two components and in which the second front surface has at least a second projection configured to make at least one respective second welding of the material or aggregate interposed between the two components In at least one of the aforesaid aspects, the present invention can also have at least one of the preferred features set forth below.

[0031] Preferably, the at least a first projection and the at least a second projection are arranged so as to make respective weldings on different areas of the material or aggregate. In greater detail, the front surfaces of the two components define, in a tightening configuration adapted to make the welding of the material or aggregate, a weld imprint with a predetermined shape and size, preferably at least partially (and more preferably exclusively) defined by the at least a first projection and the at least a second projection. In such a context, the welding created by the at least a first projection is made on an area different from the welding created by the at least a second projection. "Different" means nonoverlapping.

[0032] Preferably, the at least a first projection and the at least a second projection are arranged so that the respective welding areas are separated from each other, in particular spaced apart. "Separated" means that they are individually distinguishable and do not define a single uniform area. "Spaced apart" means that at least one interruption area of non-zero distance is defined therebetween. Such a feature allows distributing the material or aggregate among the projections with a style such as to be held firmly by the projections during compression and welding.

[0033] Preferably, each of the front areas has an elongated shape in accordance with a respective main direction of extension, for example, rectangular or substantially rectangular. In such a situation, each projection has an elongated shape parallel to the main direction of extension of the respective front area. In other words, each projection has a main direction of extension thereof, consistent with and preferably parallel to the main direction of extension of the respective front area.

[0034] Preferably, the at least a first projection and the at least a second projection are configured and / or arranged so that the respective weldings on the material or aggregate are arranged in sequence along a direction perpendicular to the main directions of extension of the front areas. In other words, the respective weldings on the material or aggregate are side by side and parallel to each other (laterally staggered with respect to each other).

[0035] Preferably, the projections are made on the respective front surfaces in the form of longitudinal ribs. For the purposes of the present invention, "longitudinal" means a direction parallel to the main direction of extension of the front surfaces.

[0036] Preferably, the projections extend substantially along the entire length of the respective front surface, "substantially" meaning at least 80%.

[0037] In accordance with an aspect of the invention, the at least a first projection is configured to make a welding of the same type with respect to the at least a second projection (e.g., a welding of the hermetic type) and is preferably identical to the at least a second projection.

[0038] In accordance with an alternative solution, the at least a first projection is configured to make a welding of a different type with respect to the at least a second projection. For example, the at least a first projection is configured to produce a sealing of the hermetic type while the at least a second projection is configured to produce a welding of the cosmetic type, or vice versa.

[0039] Preferably, the first front surface has at least one backing portion facing the at least a second projection in the approached (tightening) position, so as to define a rear backing abutment for the material or aggregate during welding. During welding, therefore, the material or aggregate is compressed between the at least a second projection and the at least one backing portion opposite thereto.

[0040] Preferably, the at least one backing portion of the first front surface is planar and / or smooth. This allows precisely calibrating the width of the gap between the two components and performing an optimal welding.

[0041] Preferably, the second front surface has at least one backing portion facing the at least a first projection in the approached (tightening) position, so as to define a rear backing abutment for the material or aggregate during welding. During the welding, therefore, the material or aggregate is compressed between the at least a second projection and the at least one backing portion opposite thereto.

[0042] Preferably, the at least one backing portion of the second front surface is planar and / or smooth.

[0043] Preferably, the at least a first projection and the at least a second projection are arranged so that they are laterally placed side by side to each other in the tightening position, i.e., so that they are "meshed" with each other. Such a configuration makes, in the tightening position of the components, a tortuous path for the material or aggregate to be welded, which is more stably held with respect to known solutions where the projections are defined on the same component.

[0044] Preferably, the material or aggregate comprises one or more layers of a sheet material, where "sheet material" means a material with a main surface extension in length and width.

[0045] In an embodiment, the at least a first projection and the at least a second projection have different heights, in particular with respect to the respective adjacent backing portions. This is particularly useful for welding a material or aggregate having variable thickness, for example, an aggregate having folds such as to define areas with a first number of layers and areas with a second number of layers, or for making weldings of different types.

[0046] Preferably, the at least a first projection has a height, with respect to the backing portion of the first front surface, between 0.1 mm and 10 mm, preferably between 0.3 mm and 5 mm, and even more preferably between 0.5 mm and 3 mm. Such a height thus is the elevation of the first projection with respect to a base surface defined by the first front surface. Preferably, the at least a second projection has a height, with respect to the backing portion of the second front surface between 0.1 mm and 10 mm, preferably between 0.3 mm and 5 mm, and even more preferably between 0.5 mm and 3 mm. Such a height thus is the elevation of the second projection with respect to a base surface defined by the second front surface.

[0047] In one embodiment, at least one of the front surfaces, preferably both, is symmetrical with respect to a longitudinal centerline (parallel to the main direction of extension of the front surface itself).

[0048] Preferably, the first front surface has a pair of first projections, and the backing portion of the first front surface is interposed between the first projections.

[0049] Preferably, in such a configuration, the second front surface has at least a second projection, facing the backing portion of the first front surface, and a pair of backing portions arranged externally to the at least a second projection and each facing a respective first projection. Such at least a second projection can be a single second projection, preferably central, or a pair of second projections spaced apart from each other, in any case facing the aforesaid backing portion of the first front surface.

[0050] This solution is optimal for defining a cosmetic welding between two adjacent hermetic weldings, in which the cosmetic welding is double-wide and intended to cut in the centerline. This solution is suitable for bags where the end flap of each bag has a cosmetic welding.

[0051] Alternatively, the first front surface has a pair of first projections, and the backing portion of the first front surface is external with respect to the first projections. In such a configuration, the second front surface has at least a second projection, facing the backing portion of the first front surface, and a backing portion arranged externally to the at least a second projection and facing the first projections. Such at least a second projection can be a single second projection, preferably central, or a pair of second projections spaced apart from each other, in any case facing the aforesaid backing portion of the first front surface.

[0052] In one embodiment, the second front surface has a pair of second projections spaced apart from each other by a longitudinal recess. Preferably, the second component comprises a cutting tool accommodated in the longitudinal recess and provided with a relative sliding movement with respect to the second projections to take on at least one position extended from the recess, adapted to cut the material or aggregate, and one position retracted into the recess, adapted to weld the material or aggregate.

[0053] Alternatively, the longitudinal recess and the cutting tool can be provided on the first component.

[0054] Preferably, in the case of the presence of two or more first projections, they have respective main directions of extension which are preferably parallel to each other.

[0055] Preferably, in the case of the presence of two or more second projections, they have respective main directions of extension which are preferably parallel to each other.

[0056] Preferably, the at least a first projection and the at least a second projection have respective main directions of extension which are parallel to each other.

[0057] In one embodiment, the at least a first projection has an elongated rib shape and preferably a smooth surface.

[0058] Preferably, the at least a first projection has a constant width along the main direction of extension thereof.

[0059] Preferably, the at least a first projection has an at least partially rectilinear extension. In one embodiment, the at least a first projection has an entirely rectilinear extension. Alternatively, the at least a first projection is formed by at least two rectilinear sections which are inclined with respect and / or connected to each other.

[0060] Preferably, the at least a second projection has a smooth surface.

[0061] Preferably, the at least a second projection has a constant width along the main direction of extension thereof.

[0062] Preferably, the at least a second projection has an at least partially rectilinear extension. In one embodiment, the at least a second projection has an entirely rectilinear extension.

[0063] In accordance with possible variants, the at least a first projection and / or the at least a second projection features a structured surface, in particular knurled or provided with a two-dimensional distribution of projections and / or recesses.

[0064] In one embodiment, the first front surface has a pair of first projections which are transversally spaced apart from each other, and the second front surface comprises at least a second projection, in which the projections are arranged so that, when the components are in the approached position, the at least a second projection is arranged between the first projections.

[0065] Preferably, in such a solution, the at least a second projection has a shape and / or distribution which is specular with respect to a longitudinal plane of symmetry of the at least a second projection and / or the second surface.

[0066] In one embodiment, such a solution includes a single second projection, preferably centered on said longitudinal plane of symmetry of the second surface.

[0067] Alternatively, such a solution includes a pair of second projections arranged specular with respect to said longitudinal plane of symmetry of the second surface.

[0068] Furthermore, preferably, in such a solution, the first projections have a specular distribution with respect to the longitudinal plane of symmetry of the second surface and / or to a longitudinal plane of symmetry of the first surface.

[0069] Preferably, the welding tool is an ultrasonic tool.

[0070] Preferably, furthermore, the counter-tool is an anvil.

[0071] In accordance with a possible alternative embodiment, both the first component and the second component are sonotrodes.

[0072] The invention is, however, applicable to any type of welding tool, of the type suitable for cooperating with a counter-tool. Brief description of drawings

[0073] Further features and advantages of the present invention will be more apparent from the following detailed description of preferred embodiments thereof, made with reference to the accompanying drawings.

[0074] In such drawings:

[0075] - Figure 1 shows a section view of a welding device in accordance with the present invention, in accordance with a first embodiment;

[0076] - Figure 2 shows a perspective view of a first component of the device in Figure 1 ;

[0077] - Figure 3 shows a perspective view of a second component of the device in Figure 1 ;

[0078] - Figure 4 shows a front view of the first component in Figure 2;

[0079] - Figure 5 shows a front view of the second component in Figure 3;

[0080] - Figure 6 shows a section view of a welding device in accordance with the present invention, in accordance with a second embodiment;

[0081] - Figure 7 shows a perspective view of a first component of the device in Figure 6;

[0082] - Figure 8 shows a perspective view of a second component of the device in Figure 6;

[0083] - Figure 9 shows a front view of the first component in Figure 7;

[0084] - Figure 10 shows a front view of the second component in Figure 8;

[0085] - Figure 11 shows a section view of a welding device in accordance with the present invention, in accordance with a third embodiment;

[0086] - Figure 12 shows a section view of a welding device in accordance with the present invention, in accordance with a fourth embodiment;

[0087] - Figure 13 shows a section view of a welding device in accordance with the present invention, in accordance with a fifth embodiment.

[0088] With reference to the accompanying Figures, a welding device according to the invention is overall indicated by reference numeral 1 .

[0089] Detailed embodiments of the invention The device 1 , shown in diagrammatic form, comprises a first component 2 defining a first front surface 2a and a second component 3 defining a second front surface 3a. The two components 2, 3 are mutually movable between an approached position (shown in Figure 1 ), which is for welding, and a distanced position (not shown), which is inoperative, so that in the approached position the two front surfaces 2a, 3a face each other and are capable of tightening a material or aggregate “M” to be welded therebetween. Such a movement is transverse to the front surfaces 2a and 3a, preferably perpendicular. For example, such a movement can be rectilinear, circular (rotary motion), or can occur along a general movement line.

[0090] In one embodiment, the first component 2 is a welding tool and the second component 3 is a counter-tool. In this situation, the welding tool 2 can be of any type, for example, an ultrasonic or hot tool, while the counter-tool is an anvil, suitable for receiving and / or exerting a force or reaction while welding. Alternatively, the first component 2 is a counter-tool while the second component 3 is a welding tool.

[0091] In accordance with a possible alternative embodiment, both components are sonotrodes.

[0092] The front surface 2a of the welding tool (first component 2) is an active welding surface, i.e., suitable for providing welding energy (e.g., thermal or vibrational energy), while the front surface 3a of the counter-tool (second component 2) is a contrast surface, i.e., a surface defining a passive abutment, thus a constraining reaction to the thrust.

[0093] With reference to the approach thrust, it can be provided by the first component 2, the second component 3, or both. To this end, at least one of them is associated with a respective movement actuator (not shown).

[0094] In accordance with the invention, the first front surface 2a has at least a first projection 4 configured to make at least one respective first welding "S1" of the material or aggregate “M” interposed between the components 2, 3, while the second front surface 3 has at least a second projection 5 configured to make at least one respective second welding "S2" of the material or aggregate “M” interposed between the components.

[0095] Each of the front surfaces 2a, 3a has an elongated shape, i.e., it has a main direction of extension, preferably rectangular. Furthermore, preferably, the two front surfaces 2a, 3a have a substantially identical extension, so that they substantially overlap in the approached welding position.

[0096] In the embodiment in Figures 1 -5, the first front surface 2a has a single first projection 4, while the second front surface 3a has a single second projection 5, for example arranged so that, in the approached welding configuration, the first and second projections are arranged symmetrically with respect to a longitudinal plane of symmetry of the second component 3. For the purposes of the present description, "longitudinal" means a direction coinciding with or parallel to the main direction of extension of the front surfaces 2a, 3a.

[0097] Preferably, the aforesaid projections 4, 5 are arranged so as to make respective weldings on different areas of the material or aggregate “M”.

[0098] More preferably, the aforesaid projections 4, 5 are arranged so that the first and second weldings are separated from each other, in particular spaced apart. “Separated” means that they are individually identifiable, while “spaced apart” means that they are physically spaced apart by means of specifically identifiable separating elements or recesses.

[0099] Furthermore, in accordance with an embodiment of the invention, the at least a first projection 4 is configured to make a welding of the same type with respect to the at least a second projection 5. In an embodiment, the weldings are of the hermetic type and, to this end, they are defined by a continuous and uniform welding area.

[0100] In accordance with a different embodiment of the invention, the at least a first projection 4 is configured to make a welding of a different type with respect to the at least a second projection 5. In an embodiment, the first welding is a hermetic welding and the second welding is a cosmetic welding (the latter being characterized by a lower sealing level than the hermetic welding, in particular defined by a welding area with a non- uniform or discontinuous sealing).

[0101] Preferably, each of the front areas 2a, 3a has an elongated shape in accordance with a respective main direction of extension, and each projection 4, 5 has an elongated shape parallel to the main direction of extension of the respective front area 2a, 3a.

[0102] It follows that, in the approached welding position, the projections 4, 5 are oriented parallel to each other.

[0103] Furthermore, it follows that, in the approached welding position, the respective weldings on the material or aggregate “M” are arranged in sequence along a direction perpendicular to the main directions of extension of the front areas 2a, 3a.

[0104] Preferably, the first front surface 2a has at least one backing portion 6, preferably planar and / or smooth, facing the at least a second projection 5 in the approached position. Such a backing surface 6 is arranged and configured to define, during the welding of the material or aggregate “M”, a backing abutment for the material or aggregate “M”, which is then compressed between the at least a second projection 5 and the backing portion 6 of the first component 2. The second component 3 can be configured so that only a second projection 5 faces the aforesaid backing portion 6 of the first component 2, or so that two or more second projections 5 face the aforesaid backing portion 6 of the first component 2. In the specific embodiment in Figures 1 -3, only a second projection 5 faces the aforesaid backing portion 6 of the first component 2.

[0105] Preferably, the second front surface 2b has at least one backing portion 7, preferably planar and / or smooth, facing the at least a first projection 4 in the approached position. Such a backing surface 7 is arranged and configured to define, during the welding of the material or aggregate “M”, a backing for the material or aggregate “M” which is therefore compressed between the at least a first projection 4 and the backing portion 7 of the second component 3. The first component 2 can be configured so that only a first projection 4 faces the aforesaid backing portion 7 of the second component 3, or so that two or more first projections 4 face the aforesaid backing portion 7 of the second component 3.

[0106] In the specific embodiment in Figures 1 -5, a single backing portion 6, 7 is provided on each component 2, 3. The distribution of the projections and the backing portions, however, could be different, depending on the number and distribution of the projections provided, preferably providing that each projection has a corresponding backing portion on the opposite component.

[0107] Preferably, the at least a first projection 4 has a height "H1", measured from the adjacent backing portion 6, from 0.1 mm to 10 mm, preferably between 0.3 mm and 5 mm, and even more preferably between 0.5 mm and 3 mm.

[0108] Preferably, the at least a second projection 5 has a height "H2", measured from the adjacent backing portion 7, between 0.1 mm and 10 mm, preferably between 0.3 mm and 5 mm, and even more preferably between 0.5 mm and 3 mm.

[0109] In the embodiment in Figures 1 -5, the height "H1 " of the first projection 4 is different from the height "H2" of the second projection 5. This is particularly useful where the material or aggregate "M" has variable thickness and, therefore, a lower height corresponds to areas of the material or aggregate "M" having a greater thickness (e.g., a greater number of layers, due to folds or other conditions).

[0110] Preferably, the first projection 4 and the second projection 5, intended in particular to make a respective welding of the hermetic type, have an elongated rib configuration and preferably have a smooth surface.

[0111] Alternatively, at least one of the first and second projections 4, 5 (intended in particular to make a welding of the cosmetic type) has a structured surface, in particular knurled or provided with a two-dimensional distribution of projections and / or recesses (e.g., with a pyramidal or truncated-pyramidal shape).

[0112] Preferably, each first projection 4 has a constant width along the main direction of extension thereof.

[0113] Furthermore, each first projection 4 can have an entirely rectilinear extension or a non-rectilinear extension, for example, featuring two or more rectilinear sections which are staggered or inclined with respect to each other, preferably connected thereto.

[0114] Furthermore, the first projections 4 can extend along the entire longitudinal dimension of the first surface 2a.

[0115] Preferably, each second projection 5 has a constant width along the main direction of extension thereof.

[0116] Furthermore, each second projection 5 can have an entirely rectilinear extension or a non-rectilinear extension, for example, featuring two or more rectilinear sections which are staggered or inclined with respect to each other, preferably connected thereto.

[0117] Furthermore, the second projections 5 can extend along the entire longitudinal dimension of the second surface 3a.

[0118] Figures 6-10 show a second embodiment in which the first component 2 has, on the first front surface 2a, two first projections 4 parallel to each other, while the second component 3 has a single second projection 5 on the second front surface 3a. In particular, the projections 4, 5 are arranged so that in the approached welding position, the second projection 5 is interposed between the two first projections 4.

[0119] Furthermore, in this embodiment, two backing portions 7 are provided on the second component 3, arranged on opposite sides of the single second projection 5, and a single first projection 4 faces each backing portion 7 of the second component 3, while the backing portion of the first component 2 is arranged in a position between the two first projections 4.

[0120] Furthermore, preferably, the two first projections 4 have respective heights "Hi" "HIwhich are different from each other, due to the corresponding different thickness of the material or aggregate "M" welded by them. However, in the case of the material or aggregate "M" having a constant thickness, the height of the first projections 4 can be identical. Such a solution is shown in Figure 11 , which shows a preferably symmetrical arrangement and shape of the projections with respect to a longitudinal plane of symmetry of the two components 2, 3 in the approached position. In detail, the two first projections 4 have a shape and / or arrangement being specular with respect to a longitudinal plane of symmetry of the second projection 5.

[0121] Figure 12 shows a constructional variant in which the second front surface 3a of the second component 3 has a pair of second projections 5 spaced apart from each other by a longitudinal recess 8 and in which a cutting tool 9 is accommodated in the recess 8. Such a cutting tool 9 is provided with a relative sliding movement with respect to the second projections 5 to take on at least one position extracted from the recess 8 and one position retracted into the recess 8, for example under the action of an elastic or actuating element 9a. The cutting tool 9 preferably operates in association with the corresponding backing portion 6 of the first component 2 to cut the material or aggregate “M” being welded.

[0122] Figure 13 shows a further embodiment in which the first component 2 has two first projections 4 defining the backing portion 6 of the first component 2 therebetween, while the second component 3 has a single central second projection 5, facing the backing portion 6 of the first component 2. This differs from the solution in Figure 11 in that the two first projections 4 have different heights, due to different localized thicknesses of the material or aggregate "M".

Claims

1. CLAIMS1 . A device for welding sheet material for product packaging machines, comprising a first component (2) defining a first front surface (2a) and a second component (3) defining a second front surface (3a), said first and second components (2a, 3a) being mutually movable between an approached position and a distanced position so that in said approached position the two front surfaces (2a, 3a) face each other and are capable of tightening a material or aggregate (M) to be welded therebetween; wherein one of said components (2, 3) is a welding tool and the respective front surface (2a, 3a) is an active welding surface and wherein the other of said components (2, 3) is a counter-tool and the respective front surface (2a, 3a) is a contrast surface; wherein the first front surface (2a) has at least a first projection (4) configured to realize at least one respective first welding of the material or aggregate (M) interposed between said components (2, 3) and wherein the second front surface (3a) has at least a second projection (5) configured to realize at least one respective second welding of the material or aggregate (M) interposed between said components (2, 3).

2. A device according to claim 1 , wherein said at least a first projection (4) is configured to realize a welding of a different type with respect to said at least a second projection (5).

3. A device according to claim 1 , wherein said at least a first projection (4) is configured to realize a welding of the same type as said at least a second projection (5).

4. A device according to any one of the preceding claims, wherein said at least a first projection (4) and said at least a second projection (5) are arranged so as to realize respective weldings on different areas of said material or aggregate (M), preferably so that said areas are separatedfrom each other, in particular spaced apart.

5. A device according to any one of the preceding claims, wherein each of said front surfaces (2a, 3a) has an elongated shape in accordance with a respective prevalent direction of extension and wherein each of said projections (4, 5) has an elongated shape which is parallel to the prevalent direction of extension of the respective front surface (2a, 3a).

6. A device according to claim 5, wherein said at least a first and a second projections (4, 5) are configured and / or arranged so that the respective weldings on the material or aggregate (M) are arranged in sequence with respect to one another along a direction perpendicular to the prevalent directions of extension of the front surfaces (2a, 3a).

7. A device according to any one of the preceding claims, wherein said at least a first projection (4) and said at least a second projection (5) have different heights.

8. A device according to any one of the preceding claims, wherein the first front surface (2a) has at least one backing portion (6), preferably planar and / or smooth, facing said at least a second projection (5) in the approached position and wherein the second front surface (3a) has at least one backing portion (7), preferably planar, facing said at least a first projection (4) in the approached position.

9. A device according to claim 8, wherein said at least a first projection (4) has a height (H1 , HT), with respect to the backing portion (6) of the first front surface (2a), comprised between 0.1 mm and 10 mm, preferably between 0.3 mm and 5 mm and even more preferably between 0.5 mm and 3 mm and / or wherein said at least a second projection (5) has a height (H2), with respect to the backing portion (7) of the second frontsurface (3a), comprised between 0.1 mm and 10 mm, preferably between 0.3 mm and 5 mm and even more preferably between 0.5 mm and 3 mm.

10. A device according to claim 8 or 9, wherein the first front surface (2a) has a pair of first projections (4), and the backing portion (6) of the first front surface (2a) is interposed between said first projections (4).11 . A device according to any one of the preceding claims 8 to 10, wherein the second front surface (3a) has at least a second projection (5) and at least one backing portion (7), preferably a pair of backing portions (7) arranged externally to said at least a second projection (5).

12. A device according to claim 11 , wherein the second front surface (3a) has a pair of second projections (5) spaced apart from each other by a longitudinal recess (8) and wherein said second component (3) comprises a cutting tool (9) accommodated in said recess (8) and provided with a relative sliding movement with respect to said second projections (5) to take on at least one position extracted from said recess (8) and one position retracted into said recess (8).

13. A device according to any one of the preceding claims, wherein said at least a first projection (4) and said at least a second projection (5) have respective prevalent directions of extension parallel to each other.

14. A device according to any one of the preceding claims, wherein said at least a first projection () and / or said at least a second projection (5) has an elongated rib shape and preferably has a smooth surface.

15. A device according to any one of the preceding claims, wherein the first front surface (2a) has a pair of first projections (4) and the second front surface (3a) comprises at least a second projection (5), saidprojections (4, 5) being arranged so that in said approached position of the components (2, 3) the at least a second projection (5) is arranged between said first projections (4).

16. A device according to claim 15, wherein said first projections (4) have a shape and / or arrangement which is specular with respect to a longitudinal plane of symmetry of the at least a second projection (5).

17. A device according to any one of the preceding claims, wherein said welding tool is an ultrasonic tool and wherein said counter-tool is an anvil.

18. A method for welding sheet material in machines for packaging products, operated by means of a device (1 ) in accordance with any one of the preceding claims, comprising:- preparing a material or aggregate (M) to be welded, said material or aggregate (M) comprising at least two layers of sheet material;- approaching said components (2, 3) to each other, tightening a portion of said material or aggregate (M);- performing a welding of said portion of the material or aggregate (M) tightened between the components (2, 3); wherein said step of welding performing of said portion of the material or aggregate (M) realizes on said portion of the material or aggregate (M) a weld imprint formed by at least a first welding, realized by means of said at least a first projection (4), and at least a second welding, realized by means of said at least a second projection (5), said first and second weldings being simultaneously realized on areas of the material or aggregate (M) which are different from each other.

19. A method according to claim 18, wherein said first and second weldings are of a different type or structure.

20. A method according to claim 18 or 19, wherein said material or aggregate (M) comprises a plurality of layers of a film material.

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