Welding device and method for product packaging machines

Abstract

A welding device for product packaging machines comprising a welding tool (2) and a counter-tool (3), wherein one of them has a first projection (4) configured to make a respective first welding (S1) of a material and wherein the other one of them has a second projection (5) configured to make a respective second welding (S2) of the material. The first projection (4) is configured make a different type of welding with respect to the second projection (5).

Description

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

[0002] Technical field

[0003] The present invention relates to the technical field of automatic product packaging machines and it relates, in detail, to welding a device and method for product packaging machines, 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. 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.

[0009] The Applicant has found that the known solutions are improvable, particularly in terms of flexibility of use.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] Furthermore, arranging one of the two projections on the welding tool and the other projection on the counter-tool allows 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.

[0015] It is also economically and technologically 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.

[0016] Disclosure of the invention

[0017] The present invention, therefore, relates, in a first aspect thereof, to a welding device for product packaging machines. "Product" means a general weldable item, for example, but not limited to, a bag, a pouch, a general rigid or floppy packaging or related semi-finished products (e.g., for processing of the flow-pack type). Preferably, the product is defined by at least two layers of film or other heat-weldable material, such layers being in sheet form (and therefore having a significant surface area in a bidirectional direction).

[0018] 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.

[0019] Preferably, one of the two components is a welding tool, and the respective front surface is an active welding surface.

[0020] Preferably, the other component is a counter-tool, and the respective front surface is a contrast surface.

[0021] 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.

[0022] 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.

[0023] According to one aspect of the invention, the at least a first projection is configured to produce a different type of welding with respect to said 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.

[0024] According to an alternative solution, the at least a first projection is configured to produce a welding of the same type as the at least a second projection and is preferably identical to the at least a second projection.

[0025] The present invention relates, in a second aspect thereof, to a welding method in product packaging machines.

[0026] 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, and in which the at least a first projection is configured to make a welding of a different type with respect to said at least a second projection.

[0027] In at least one of the aforesaid aspects, the present invention can also have at least one of the preferred features set forth below. Preferably, the at least a first projection and the at least a second projection are arranged so as to make respective weldings on dent areas of the material or aggregate.

[0028] 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 non-overlapping.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] Preferably, the projections extend substantially along the entire length of the respective front surface, "substantially" meaning at least 80%.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Preferably, the at least one backing portion of the second front surface is planar and / or smooth.

[0038] 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.

[0039] Preferably, the material or aggregate comprises one or more layers of a heat-weldable material, such as a film.

[0040] 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.

[0041] 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).

[0042] 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.

[0043] 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.

[0044] 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).

[0045] 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.

[0046] 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 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Alternatively, the longitudinal recess and the cutting tool can be provided on the first component.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] In one embodiment, the at least a first projection has an elongated rib shape and preferably a smooth surface.

[0055] Preferably, the at least a first projection has a constant width along the main direction of extension thereof.

[0056] 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.

[0057] Preferably, the at least a second projection has a structured surface, in particular knurled or provided with a two-dimensional distribution of projections and / or recesses.

[0058] In accordance with possible variations, the at least a first projection can have a structured surface, in particular knurled or provided with a two- dimensional distribution of projections and / or recesses, and / or the at least a second projection can have an elongated rib shape, preferably with a smooth surface.

[0059] Preferably, the at least a second projection has a variable width along the main direction of extension thereof, preferably having at least one section with a constant width adjacent to a section having a decreasing width.

[0060] Alternatively, the at least a first projection has a variable width along the main direction of extension thereof, preferably having at least one section with a constant width adjacent to a section having a decreasing width, and / or the at least a second projection has a constant width along the main direction of extension thereof.

[0061] 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.

[0062] 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.

[0063] In one embodiment, such a solution includes a single second projection, preferably centered on said longitudinal plane of symmetry of the second surface.

[0064] Alternatively, such a solution includes a pair of second projections arranged specular with respect to said longitudinal plane of symmetry of the second surface.

[0065] 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.

[0066] Preferably, the welding tool is an ultrasonic tool.

[0067] Preferably, furthermore, the counter-tool is an anvil.

[0068] In accordance with a possible alternative embodiment, both the first component and the second component are sonotrodes.

[0069] The invention is, however, applicable to any type of welding tool, of the type suitable for cooperating with a counter-tool.

[0070] Brief description of drawings

[0071] Further features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof, made with reference to the accompanying drawings. In such drawings: - Figure 1 shows a diagrammatic perspective view of a welding device in accordance with the present invention, according to a first embodiment;

[0072] - Figure 2 shows a perspective view of a first component of the device in Figure 1 ;

[0073] - Figure 2A shows an enlarged detail of the view in Figure 2;

[0074] - Figure 3 shows a perspective view of a second component of the device in Figure 1 ;

[0075] - Figure 3A shows an enlarged detail of the view in Figure 3;

[0076] - Figure 3B shows a further enlarged detail of the view in Figure 3;

[0077] - Figure 4 shows a perspective view of a first component of the device according to the invention, in a different embodiment;

[0078] - Figure 5 shows a perspective view of a first component of the device according to the invention, in a different embodiment;

[0079] - Figure 5A shows an enlarged detail of the view in Figure 5;

[0080] - Figures 6-8 show cross-section views of three different embodiments of the welding device according to the invention;

[0081] - Figures 9-14 show different weld imprints which can be made with corresponding different embodiments of the welding device according to the invention.

[0082] With reference to the accompanying Figures, a welding device according to the invention is overall indicated by reference numeral 1 .

[0083] Detailed description of preferred embodiments of the invention

[0084] 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 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.

[0085] 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.

[0086] In accordance with a possible alternative embodiment, both components are sonotrodes.

[0087] 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.

[0088] 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).

[0089] 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 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 interposed between the components.

[0090] 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.

[0091] In the embodiment shown in Figures 1 -3, the first front surface 2a has two first projections 4, placed side by side to each other and preferably arranged and configured so as to have a shape and distribution which is specular with respect to a longitudinal plane of symmetry of the first component 2, while the second front surface 3a has a single second projection 5, arranged and configured so as to have a shape and distribution which is specular 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.

[0092] Preferably, the aforesaid projections 4, 5 are arranged so as to make respective weldings “S1”, “S2” on different areas of the material or aggregate.

[0093] More preferably, the aforesaid projections 4, 5 are arranged so that the first and second weldings “S1”, “S2” 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.

[0094] In particular, in the embodiment shown in Figures 1 -3, the projections 4, 5 are arranged so that in the approached welding position, the second projection 5 is interposed between the first two projections 4, thus defining a minimum gap in the transverse direction.

[0095] Furthermore, in accordance with the invention, the at least a first projection 4 is configured to make a type of welding which is different with respect to the at least a second projection 5. In an embodiment, the first welding “S1” is a hermetic welding and the second welding “S2” is a cosmetic welding. In particular, “hermetic” welding means a welding defined by at least one continuous and uniform welding area, while “cosmetic” welding means a welding characterized by a lower level of sealing with respect to a hermetic welding, in particular defined by a welding area with a non-uniform or discontinuous sealing.

[0096] 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.

[0097] It follows that, in the approached welding position, the projections 4, 5 are oriented parallel to each other.

[0098] Furthermore, it follows that, in the approached welding position, the respective weldings “S1”, “S2” on the material or aggregate are arranged in sequence along a direction perpendicular to the main directions of extension of the front areas 2a, 3a. In particular, the different weldings “S1”, “S2” form a weld imprint, some examples of which are shown in Figures 6-11 , which will be described below.

[0099] 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, a backing abutment for the material or aggregate, 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.

[0100] In the specific embodiment in Figures 1 -3, only a second projection 5 faces the aforesaid backing portion 6 of the first component 2.

[0101] 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, a backing for the material or aggregate 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.

[0102] In the specific embodiment in Figures 1 -3, 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. 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.

[0103] 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.

[0104] 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.

[0105] Preferably, each first projection 4 (intended, in particular, to make a hermetic welding) has an elongated rib shape and preferably a smooth surface.

[0106] Preferably, each second projection 5 (intended, in particular, to make a cosmetic welding) has a structured surface, particularly knurled or provided with a two-dimensional distribution of projections and / or recesses. In the embodiments shown, which do not form a limitation of the possible embodiments, such a structured surface is defined by a two- dimensional distribution of pyramidal or truncated-pyramidal shaped projections.

[0107] Preferably, each first projection 4 has a constant width along the main direction of extension thereof.

[0108] 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.

[0109] Furthermore, the first projections 4 can extend along the entire longitudinal dimension of the first surface 2a.

[0110] Preferably, each at least a second projection 5 has a variable width along the main direction of extension thereof. In particular, each second projection 5 can have at least one section of constant width adjacent to a section of decreasing width.

[0111] Alternatively, each at least a second projection 5 has a constant width along the main direction of extension thereof.

[0112] With reference to the specific embodiment in Figures 1 -3, the first two projections have only a partially rectilinear extension, in particular having a first rectilinear portion 10 and a second rectilinear portion 11 , staggered and connected by a preferably rectilinear connecting portion 12 therebetween, so that the area between the first two projections 4 has an end widening.

[0113] Furthermore, in such an embodiment, the second projection 5 has a constant width and preferably extends along the entire longitudinal length of the second front surface 3a.

[0114] Such a solution defines a weld imprint visible in Figure 10, where the first weldings "S1" and the second welding "S2" have a shape corresponding to the aforesaid first projections 4 and second projection 5.

[0115] In the case of entirely rectilinear first projections 4, the weld imprint is visible in Figure 9.

[0116] Figure 4 shows a constructional variant in which the second component 3 has a single second projection 5 having a cross-section with a variable width, in particular having a first portion 21 of a smaller width and a second portion 22 of a larger width, connected to each other by a connecting portion 23 of increasing width. Preferably, the first two portions 21 , 22 have a rectilinear style and aligned with each other. The solution in Figure 4 is still compatible with the front surface 2a of the first component 2 in Figures 1 -3, in particular by providing a shape coupling between the two front surfaces 2a, 3a so that the second, wider portion 22 of the second projection 5 is positioned within the end widening defined by the first two projections 4.

[0117] Such a solution defines a weld imprint visible in Figure 12, where the first weldings "S1" and the second welding "S2" have a shape corresponding to the aforesaid first projections 4 and second projection 5.

[0118] Figure 5 shows a constructional variant which differs from the solution in Figure 4 in that the second projection 5 extends only for a portion of the longitudinal dimension of the second front surface 4a, preferably for a length shorter than 50% of the length of the second front surface 4a. Specifically, such a second projection 5 can have only the portion intended to be positioned in the end widening defined by the first two projections 4. Such a solution defines a weld imprint visible in Figure 11 , where the first weldings "S1" and the second welding "S2" have a shape corresponding to the aforesaid first projections 4 and second projection 5.

[0119] With reference to Figures 13 and 14, further possible embodiments of the weld imprints are shown, which correspond to respective shapes of the projections 4, 5, and, in particular: Figure 13 shows a solution where the second welding “S2” has two end areas of increased width and the first weldings “S1” are spaced further apart from each other at the ends thereof, to conform to the second welding “S2”, defining in particular a symmetrical shape of the weld imprint both with respect to a longitudinal plane and with respect to a plane perpendicular thereto; Figure 14 shows a variant of Figure 13, where the weld imprint does not have the central portion (with smaller width) of the second welding “S2” but the latter is replaced by two distinct portions longitudinally spaced apart from each other, also in this case defining in particular a symmetrical shape of the weld imprint both with respect to a longitudinal plane and with respect to a plane perpendicular thereto. Figure 6 shows a section view, in the approached welding position, of the first and second components 2, 3. Such a Figure highlights the heights “H1”, “H2” of the two projections 4, 5 with reference to the embodiment in Figures 1 -3. Figure 7 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 being welded. Finally, Figure 8 shows a non-symmetrical solution in which only a first projection 4 and a second projection 5 are provided, and in which each component 2, 3 has only one respective backing portion 6, 7.

Claims

CLAIMS1. A welding device 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 (2, 3) 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 to be welded therebetween; wherein one of said components (2, 3) is a welding tool and the respective front surface (2a) is an active welding surface and wherein the other of said components (2, 3) is a counter-tool and the respective front surface (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 (S1) of the material or aggregate 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 (S2) of the material or aggregate interposed between said components (2, 3); and 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).

2. A device according to claim 1 , 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, preferably so that said areas are separated from each other, in particular spaced apart.

3. 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).

4. A device according to claim 3, wherein said first and second projections (4, 5) are configured and / or arranged so that the respective weldings (S1 , S2) on the material or aggregate 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).

5. 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.

6. A device according to claim 5, wherein said at least a first projection (4) has a height (H1 ), 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 front surface (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.

7. A device according to claim 5 or 6, wherein the first front surface (2a) has a pair of first projections (4), preferably the backing portion (6) of the first front surface (2a) being interposed between said first projections (4).

8. A device according to claim 7, wherein the second front surface (3a) has at least a second projection (5) and at least one backing portion (7) for said first projections (4), preferably a pair of backing portions (7) arranged externally to said at least a second projection (5) and each facing a respective first projection (4).

9. A device according to claim 8, 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).

10. 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 preferably parallel to each other.11 . A device according to any one of the preceding claims, wherein said at least a first projection (4) has an elongated rib shape and preferably has a smooth surface.

12. A device according to any one of the preceding claims, wherein said at least a first projection (4) has a constant width along the prevalent direction of extension thereof.

13. A device according to any one of the preceding claims, wherein said at least a first projection (4) has an at least partially rectilinear extension, in particular formed by at least two rectilinear sections (10, 11 ) inclined with respect to each other.

14. A device according to any one of the preceding claims, wherein said at least a second projection (5) has a structured surface, in particular knurled or provided with a two-dimensional distribution of projections and / or recesses.

15. A device according to any one of the preceding claims, wherein said at least a second projection (5) has a variable width along the prevalent direction of extension thereof, preferably having at least one section with a constant width (22) adjacent to a section having a decreasing width (23).

16. 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), said projections (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).

17. A device according to claim 16, wherein said first projections (4) have a specular distribution with respect to a longitudinal plane of symmetry of the at least a second projection (5).

18. 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.

19. A method for welding 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 an aggregate to be welded;- approaching said components (2, 3) to each other, tightening a portion of said material or aggregate;- performing a welding of said portion of the material or aggregate tightened between the components (2, 3); wherein said welding performing of said portion of the material or aggregate realizes on said portion of the material a weld imprint formed by at least a first welding (S1), realized by means of said at least a first projection (4), and at least a second welding (S2), realized by means ofsaid at least a second projection (5), said first and second weldings (S1 , S2) being simultaneously realized on welding areas that are different from each other and being of a different type or structure.

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

21. A method according to claim 19 or 20, wherein said first welding is a hermetic welding and / or wherein said second welding is a cosmetic welding.

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