Welding device and method for product packaging machines

Abstract

A welding device for machines for packaging products comprises a first sonotrode (2) and a second sonotrode (3), wherein one of them has a first projection (4) configured to form a respective first welding (SI) of a material and wherein the other has a second projection (5) configured to form a respective second welding (S2) of the material.

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] Simultaneous welding is also known where two welding lines close together are formed simultaneously. This occurs, for example, in machines of the flow-pack type where two transversal weldings identical to each other are performed simultaneously by compression applied between a welding tool and a counter-tool, where the two weldings are positioned at a sufficient distance to subsequently cut, between them, the welded material in such a way that one of the two weldings constitutes the bottom welding of one package and the other welding constitutes the top welding of the next package.

[0008] It is also known to form a hermetic seal and a cosmetic seal, which are close together and suitable for closing a bag containing a product, where the cosmetic welding has a structured pattern whilst the hermetic welding has a high level of seal. In prior art solutions, the two weldings are formed using a suitable pair of projections on the counter-tool, generally the anvil of a sonotrode, whilst the welding tool has a front contact surface on which the projections of the counter-tool are pressed, generating the weldings at the two projections. Weldingis also known by means of a pair of opposite sonotrodes, wherein one of the two sonotrodes is provided with a profile suitable for defining the desired welding impression.

[0009] The Applicant has found that the prior art solutions can be improved, in particular with reference to the flexibility of use.

[0010] In the prior art solutions, every variation in the layout of the welding necessarily requires the replacement of one of the two components (sonotrode or anvil), even in the cases where it is necessary to perform a minimum modification, for example a variation of the distance between the two weldings.

[0011] Moreover, in the prior art solutions, systems should be provided for blocking the material to be welded, which must not be subjected to movements during the welding step.

[0012] In this context, the Applicant has found that by positioning one of the two projections on the first sonotrode and the other projection on the second sonotrode it is possible to overcome the above-mentioned drawbacks, since it is possible to mutually adapt the position between the projections (therefore between the weldings) by simply adjusting the position between the two sonotrodes, obtaining a welding impression geometrically varied without carrying out structural replacements of the device.

[0013] Moreover, this makes it possible to modify the geometry and / or type of weldings by selective replacement of a single sonotrode, allowing numerous combinations of different weldings operating only a limited number of replacements.

[0014] Moreover, positioning one of the two projections on a sonotrode and the other projection on the other sonotrode allows a twisting path to be formed for the material or aggregate which is more retained with stability between the two sonotrodes, reducing the risk of misalignment and therefore the risk of performing non-compliant welding.

[0015] Aim of the invention

[0016] According to a first aspect of it, therefore, this invention relates to a welding device for product packaging machines. The term “product” means a generic article which can be welded, for example but without limiting the scope of the invention, a bag, a generic rigid or soft package or relative semi-finished items (for example for processing of the “flow-pack” type). Preferably, the product is defined by at least two layers made of film or other heat-sealable material; the layers are in the form of a sheet (therefore having a significant surface extension in a two-way direction).

[0017] According to the invention, the welding device comprises a first sonotrode defining a first front surface and a second sonotrode defining a second front surface, wherein the first and the second sonotrodes are movable relative to each other between a close-together position and a spacedapart position in such a way that in the close-together position the two front surfaces face each other and are able to clamp between them a material or aggregate to be welded.

[0018] Preferably, the first front surface has at least a first projection configured to form at least a respective first welding of the material or aggregate interposed between the two sonotrodes.

[0019] Preferably, the second front surface has at least a second projection configured to form at least a respective second welding of the material or aggregate interposed between the two sonotrodes.

[0020] According to a second aspect of it, this invention relates to a welding method for product packaging machines.

[0021] The method is preferably performed by means of a device comprising a first sonotrode defining a first front surface and a second sonotrode defining a second front surface, mutually movable between a close- together position (for clamping and welding) and a spaced-apart position in such a way that in the close-together position the two front surfaces face each other and are able to clamp between them a material or aggregate to be welded, wherein the first front surface has at least a first projection configured to form at least a respective first welding of the material or aggregate interposed between the two sonotrodes and wherein the second front surface has at least a second projection configured to form at least a respective second welding of the material or aggregate interposed between the two sonotrodes.

[0022] According to least one of the above mentioned aspects, this invention may also comprise at least one of the preferred features described below.

[0023] In accordance with an aspect of the invention, the at least one first projection is configured to form a welding of a different type with respect to at least a second projection. For example, the at least a first projection is configured to form a welding of the hermetic type whilst the at least a second projection is configured to form a cosmetic welding, or vice versa.

[0024] According to an alternative embodiment, the at least a first projection is configured to form a seal of the same type relative to the at least a second projection and is preferably identical to the at least a second projection.

[0025] Preferably, the at least a first projection and the at least a second projection are positioned in such a way as to form respective weldings on different areas of the material or aggregate.

[0026] In more detail, the front surfaces of the two sonotrodes define, in a clamped configuration suitable for forming the welding of the material or aggregate, a welding impression with predetermined shape and dimensions, preferably defined at least partly (and more preferably exclusively) by the at least a first projection and by the at least a second projection. In this context, the welding formed by the at least a first projection is made on an area different from the welding formed by the at least a second projection. The term “different” means not superposed.

[0027] Preferably, the at least a first projection and the at least a second projection are positioned in such a way that the respective welding areas are separate from each other, in particular spaced apart. The term “separate” means that they are individually distinguishable and do not define a single uniform area. The expression “spaced apart” means that at least one zone for interruption is defined between them with a distance which is not zero. This feature allows the material or aggregate to be distributed between the projections with a trend such as to be stably retained by the projections during the compression and welding.

[0028] Preferably, each of the front areas has an elongate shape according to a respective main direction of extension, for example rectangular or substantially rectangular. In this situation, each projection has an elongate shape parallel to the main direction of extension of the respective front area. In other words, each projection has a respective main direction of extension which is concordant and preferably parallel to the main direction of extension of the respective front area.

[0029] Preferably, the at least a first projection and the at least a second projection are configured and / or positioned in such a way that the respective weldings on the material or aggregate are positioned one after another 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 alongside and parallel to each other (laterally offset from each other).

[0030] Preferably, the projections are formed on the respective front surfaces in the form of longitudinal ribs. In the context of this invention, the term “longitudinal” means a direction parallel to the main direction of extension of the front surfaces.

[0031] Preferably, the projections extend substantially for the entire length of the respective front surface, where the term “substantially” refers to at least 80%.

[0032] Preferably, the first front surface has at least one supporting portion facing the at least a second projection in the close-together position (for clamping), in such a way as to form a rear supporting contact element for the material or aggregate during the welding. Therefore, during the welding, the material or aggregate is compressed between the at least a second projection and the at least one supporting portion opposite it.

[0033] Preferably, the at least one supporting portion of the first front surface is planar and / or smooth. This makes it possible to precisely calibrate the amplitude of the gap between the two sonotrodes and to perform an optimum welding.

[0034] Preferably, the second front surface has at least one supporting portion facing the at least a first projection in the close-together position (for clamping), in such a way as to form a rear supporting contact element for the material or aggregate during the welding. Therefore, during the welding, the material or aggregate is compressed between the at least a first projection and the at least one supporting portion opposite it.

[0035] Preferably, the at least one supporting portion of the second front surface is planar and / or smooth.

[0036] Preferably, the at least a first projection and the at least a second projection are positioned in such a way as to be laterally side by side in the clamped position, that is to say, in such a way as to be “meshed” with each other. This configuration forms, in the clamped position of the sonotrodes, a winding path for the material or aggregate to be welded which is retained with greater stability compared with the prior art solutions where the projections are defined on the sonotrode.

[0037] Preferably, the material or aggregate comprises one or more layers of a heat-sealable sheet material.

[0038] In particular, the material may be defined by a single folded sheet (for example, in the form of a bag or pocket or, in the case of flow-pack machines, in a tubular shape) or by two separate sheets (“aggregate”) which are at least partly superposed on each other.

[0039] Possible applications of the invention are the welding of containers (for example, bags) made of film, with a single layer or multi-layer, or the welding of containers made of multi-layer material, in particular poly- coupled (for example Brik).

[0040] Preferably, the at least a first projection has a height, relative to the supporting portion of the first front surface, of 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. This height therefore constitutes the elevation of the first projection relative to a base surface defined by the first front surface.

[0041] Preferably, the at least a second projection has a height, relative to the supporting portion of the second front surface (), of 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. This height therefore constitutes the elevation of the second projection relative to a base surface defined by the second front surface.

[0042] According to an embodiment, at least one of the front surfaces, preferably both, is symmetrical relative to a longitudinal centre plane (parallel to the main direction of extension of the front surface).

[0043] Preferably, the first front surface has a pair of first projections and the supporting portion of the first front surface is interposed between the first projections.

[0044] Preferably, in this configuration the second front surface has at least a second projection, facing the supporting portion of the first front surface, and a pair of supporting portions positioned outside the at least a second projection and each facing a respective first projection. The at least a second projection may be a single second projection, preferably central, or a pair of second projections spaced from each other, in any case facing the above-mentioned supporting portion of the first front surface.

[0045] This solution is optimum for defining a cosmetic welding between two adjacent hermetic weldings, wherein the cosmetic welding has twice the width and is intended for cutting in a centre line, a solution which can be adopted for bags where the end flap of each bag has a cosmetic seal.

[0046] Alternatively, the first front surface has a pair of first projections and the supporting portion of the first front surface is outside the first projections. In this configuration, the second front surface has at least a second projection, facing the supporting portion of the first front surface, and a supporting portion positioned outside the at least a second projection and facing the first projections. The at least a second projection may be a single second projection, preferably central, or a pair of second projections spaced from each other, in any case facing the above-mentioned supporting portion of the first front surface.

[0047] According to an embodiment, the second front surface has a pair of second projections spaced apart from each other by a longitudinal recess. Preferably, one of the two sonotrodes comprises a cutting tool housed in the longitudinal recess and provided with a relative sliding movement with respect to the second projections to adopt at least an extracted position of the recess, suitable for cutting the material or aggregate, and a retracted position in the recess, suitable for performing a welding operation of the material or aggregate.

[0048] Preferably, if there are two or more first projections, they have respective main directions of extension preferably parallel to each other.

[0049] Preferably, if there are two or more second projections, they have respective main directions of extension preferably parallel to each other.

[0050] Preferably, the at least a first projection and the at least a second projection have respective main directions of extension preferably parallel to each other.

[0051] According to an embodiment, the at least a first projection has the shape of an elongate rib and preferably has a smooth surface.

[0052] Preferably, the at least a first projection has a constant width along the relative main direction of extension.

[0053] Preferably, the at least a first projection has an extension at least partly rectilinear. According to an embodiment, the at least a first projection has a completely rectilinear extension. Alternatively, the at least a first projection is formed by at least two rectilinear stretches which are inclined and / or joined to each other.

[0054] 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.

[0055] According to possible variants, the at least a first projection may 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 may have an elongate rib shape preferably with a smooth surface.

[0056] In particular, according to an embodiment, the at least a first projection and the at least a second projection may all have a smooth surface.

[0057] According to a further embodiment, the at least a first projection and the at least a second projection may all have a structured surface.

[0058] Preferably, the at least a second projection has a variable width along the respective main direction of extension, preferably having at least a stretch of constant width adjacent to a stretch having a decreasing width.

[0059] Alternatively, the at least a first projection has a variable width along the relative main direction of extension, preferably having at least one stretch with a constant width adjacent to a stretch having a decreasing width, and / or the at least a second projection has a constant width along the relative main direction of extension.

[0060] According to an embodiment, the first front surface has a pair of first projections transversely spaced from each other and the second front surface comprises at least a second projection, wherein the projections are positioned in such a way that in the close-together position of the sonotrodes the at least a second projection is positioned between the first projections.

[0061] Preferably, in this solution the at least a second projection has a specular shape and / or distribution relative to a longitudinal plane of symmetry of the at least a second projection and / or of the second surface.

[0062] According to an embodiment, this solution comprises a single second projection preferably centred on said longitudinal plane of symmetry of the second surface.

[0063] Alternatively, this solution comprises a pair of second projections positioned specularly relative to said longitudinal plane of symmetry of the second surface.

[0064] Moreover, preferably, in this solution the first projections have a specular distribution relative to the longitudinal plane of symmetry of the second surface and / or to a longitudinal plane of symmetry of the first surface. Preferably, the sonotrodes are operated simultaneously.

[0065] Preferably, the sonotrodes are operated in such a way as to have at least one different operating parameter.

[0066] Preferably, the operating parameter is selected between: oscillation amplitude; oscillation frequency; oscillation phase.

[0067] According to an embodiment, the welding of the material or aggregate is performed by operating the two sonotrodes with oscillation frequencies different to each other. Preferably, the solution is performed if the at least one first projection is configured for forming a welding of a type different from the at least one second projection.

[0068] Alternatively, the welding of the material or aggregate is performed by operating the two sonotrodes with oscillation frequencies equal to each other.

[0069] Preferably, the two oscillation frequencies have a ratio equal to a whole number. In other words, the oscillation frequency of one sonotrode is a multiple of the oscillation frequency of the other sonotrode.

[0070] Alternatively, the two oscillation frequencies have a ratio equal to a rational or irrational number.

[0071] Preferably, the two oscillation frequencies have a ratio of between 1 and 1000, more preferably between 1 and 100, even more preferably between 1 and 10.

[0072] According to an embodiment, the welding of the material or aggregate is performed by operating the two sonotrodes with oscillation amplitudes different to each other. Preferably, the solution is performed if the at least one first projection is configured for forming a welding of a type different from the at least one second projection.

[0073] Preferably, the two oscillation amplitudes have a ratio of between 1 and 50, more preferably between 1 and 20, even more preferably between 1 and 10.

[0074] Alternatively, the welding of the material or aggregate is performed by operating the two sonotrodes with oscillation amplitudes equal to each other.

[0075] According to an embodiment, the welding of the material or aggregate is performed by operating the two sonotrodes with oscillation amplitudes and frequencies different to each other.

[0076] According to an embodiment, the welding of the material or aggregate is performed by operating the two sonotrodes in a synchronised or countersynchronised fashion.

[0077] Alternatively, the welding of the material or aggregate is performed by operating the two sonotrodes with an offset of between 0% and 100% of the oscillation period.

[0078] According to an embodiment, one of the two sonotrodes is kept switched off and the welding of the material or aggregate is performed by oscillating only the other sonotrode.

[0079] Advantageously, performing a welding with different operating parameters for the two sonotrodes allows the quality of welding to be optimised, preserving the integrity of the material or aggregate, in particular, but not exclusively, in the case of fragile materials and / or materials having non- uniform characteristics.

[0080] Brief description of the drawings

[0081] 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. In these drawings:

[0082] - Figure 1 shows a schematic perspective view of a first embodiment of welding device according to this invention;

[0083] - Figure 2 shows a perspective view of a first component of the device of Figure 1 ;

[0084] - Figure 2A shows an enlarged detail of the view of Figure 2;

[0085] - Figure 3 shows a perspective view of a second component of the device of Figure 1 ;

[0086] - Figure 3A shows an enlarged detail of the view of Figure 3;

[0087] - Figure 3B shows a further enlarged detail of the view of Figure 3;

[0088] - Figure 4 shows a perspective view of a different embodiment of a first component of the device according to the invention;

[0089] - Figure 5 shows a perspective view of a different embodiment of a first component of the device according to the invention;

[0090] - Figure 5A shows an enlarged detail of the view of Figure 5;

[0091] - Figures 6-8 show transversal cross sections of three different embodiments of the welding device according to the invention;

[0092] - Figures 9-14 show different welding impressions which can be formed with corresponding different embodiments of the welding device according to the invention.

[0093] With reference to the accompanying drawings, the numeral 1 denotes in its entirety a welding device according to the invention.

[0094] Detailed description of preferred embodiments of the invention

[0095] The device 1 , illustrated schematically, 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 movable relative to each other between a close-together welding position (shown in Figure 1 ) and a spaced-apart, non-operating position (not illustrated), in such a way that in the close-together position the two front surfaces 2a, 3a face each other and are able to clamp together a material or aggregate to be welded. This movement has a direction transversal to the front surfaces 2a, 3a, preferably perpendicular. By way of example, this movement may be rectilinear, circular (rotary movement) or it may occur along a generic line of movement.

[0096] According to the invention, the first component 2 is a first sonotrode and the second component 3 is a second sonotrode.

[0097] With reference to the pushing towards each other, it may be carried out by the first sonotrode 2, by the second sonotrode 3 or by both. For this purpose, at least one of them is associated with a respective movement actuator (not illustrated).

[0098] According to the invention, the first front surface 2a has at least a first projection 4 configured to form at least a respective first welding “S1” of the material or aggregate interposed between the sonotrodes 2, 3 whilst the second front surface 3 has at least a second projection 5 configured to form at least a respective second welding “S2” of the material or aggregate interposed between the sonotrodes.

[0099] Each of the front surfaces 2a, 3a has an elongate shape, that is to say, having a main direction of extension, preferably rectangular. Moreover, preferably, the two front surfaces 2a, 3a have substantially identical extension, in such a way that they are substantially superposed on each other in the close-together welding position.

[0100] According to the embodiment of Figures 1 to 3, the first front surface 2a has two first projections 4, arranged side by side and preferably positioned and configured in such a way as to have a specular shape and distribution relative to a longitudinal plane of symmetry of the first sonotrode 2, whilst the second front surface 3a has a single second projection 5, positioned and configured in such a way as to have a specular shape and distribution relative to a longitudinal plane of symmetry of the second sonotrode 3. The term “longitudinal” means, in the context of this description, a direction coinciding with or parallel to the main direction of extension of the front surfaces 2a, 3a. Preferably, the above-mentioned projections 4, 5 are positioned in such a way as to form respective weldings “S1”, “S2” on different areas of the material or aggregate.

[0101] More preferably, the above-mentioned projections 4, 5 are positioned in such a way that the first and second weldings “S1”, “S2” are separate from each other, in particular spaced apart. The term “separate” means that they are individually identifiable, whilst the term “spaced apart” means that they are physically spaced, by means of separating elements or recesses which can be specifically identified.

[0102] In particular, in the embodiment shown in Figures 1 to 3 the projections 4, 5 are positioned in such a way that in the close-together, welding position the second projection 5 is interposed between the two first projections 4 forming a minimum clearance in a transversal direction.

[0103] Moreover, in accordance with an embodiment of the invention, the at least a first projection 4 is configured for forming a welding of a different type with respect to the at least a second projection 5. According to an example embodiment, the first welding “S1” is a hermetic welding and the second welding “S2” is a cosmetic welding. In particular, the term “hermetic” welding means a welding defined by at least one continuous and uniform welding area whilst the term “cosmetic” welding means a welding characterised by a level of seal less than the hermetic welding, in particular defined by a welding area with a non-uniform or discontinuous sealing.

[0104] In accordance with a different embodiment, the at least one first projection 4 is configured for forming a welding of the same type as the welding formed by the at least one second projection 5, for example both hermetic or both cosmetic.

[0105] Preferably, each of the front areas 2a, 3a has an elongate shape in accordance with a respective main direction of extension and each projection 4, 5 has an elongate shape parallel to the main direction of extension of the respective front area 2a, 3a. Consequently, in the close-together welding position, the projections 4, 5 are oriented parallel to each other.

[0106] Moreover, it follows that, in the close-together welding position, the respective weldings “S1”, “S2” on the material or aggregate are positioned one after another along a direction perpendicular to the main directions of extension of the front areas 2a, 3a. In particular, the different weldings ‘ST, ‘S2’ form a welding impression some examples of which are shown in Figures 6 to 11 , which will be described below.

[0107] Preferably, the first front surface 2a has at least a supporting portion 6, preferably planar and / or smooth, facing the at least a second projection 5 in the close-together position. The supporting surface 6 is positioned and configured to define, during the welding of the material or aggregate, a supporting contact for the material or aggregate which is therefore compressed between the at least a second projection 5 and the supporting portion 6 of the first sonotrode 2. The second sonotrode 3 may be configured in such a way that the above-mentioned supporting portion 6 of the first sonotrode 2 only faces a second projection 5 or in such a way that two or more second projections 5 face the above-mentioned supporting portion 6 of the first sonotrode 2.

[0108] According to the specific embodiment shown in Figures 1 to 3, there is only one second projection 5 facing the above-mentioned supporting portion 6 of the first sonotrode 2.

[0109] Preferably, the second front surface 2b has at least a supporting portion 7, preferably planar and / or smooth, facing the at least a first projection 4 in the close-together position. The supporting surface 7 is positioned and configured to define, during the welding of the material or aggregate, a support for the material or aggregate which is therefore compressed between the at least a first projection 4 and the supporting portion 7 of the second sonotrode 3. The first sonotrode 2 may be configured in such a way that the above-mentioned supporting portion 7 of the second sonotrode 3 only faces a first projection 4 or in such a way that two or more first projections 4 face the above-mentioned supporting portion 7 of the second sonotrode 3.

[0110] In the specific embodiment shown in Figures 1 to 3, there are two supporting portions 7 on the second sonotrode 3, positioned on opposite sides of the single second projection 5, and facing each supporting portion 7 of the second sonotrode 3 there is a single first projection 4. The distribution of the projections and supporting portions might, however, differ due to the number and distribution of the projections provided, preferably by providing each projection with a corresponding supporting portion on the opposite sonotrode.

[0111] Preferably, the at least one first projection 4 has a height “H1”, measured starting from the supporting portion 6 adjacent to it, of 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.

[0112] Preferably, the at least one second projection 5 has a height “H2”, measured starting from the supporting portion 7 adjacent to it, of 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.

[0113] Preferably, each first projection 4 (intended in particular for forming a welding of the hermetic type) has an elongate rib shape and preferably has a smooth surface.

[0114] Preferably, each second projection 5 (intended in particular to make a cosmetic type welding) has a structured surface, in particular knurled or provided with a two-dimensional distribution of projections and / or recesses. According to the embodiments illustrated, which do not limit possible embodiments, the structured surface is defined by a two- dimensional distribution of projections having a pyramidal or truncated pyramid shape.

[0115] Preferably, each first projection 4 has a constant width along its main direction of extension.

[0116] Moreover, each first projection 4 may have a completely rectilinear extension or a non-rectilinear extension, for example having two or more rectilinear stretches which are offset or inclined to each other, preferably joined.

[0117] Moreover, the first projections 4 may extend for the entire longitudinal dimension of the first surface 2a.

[0118] Preferably, each at least a second projection 5 has a variable width along its main direction of extension. In particular, each second projection 5 may have at least one stretch of constant width adjacent to a stretch having a decreasing width.

[0119] Alternatively, each at least a second relief projection 5 has a constant width along its main direction of extension.

[0120] With reference to the specific embodiment shown in Figures 1 to 3, the two first projections have an extension which is only partly rectilinear, in particular having a first rectilinear portion 10 and a second rectilinear portion 11 , offset from each other and joined by a connecting portion 12 preferably rectilinear, in such a way that the zone between the first two projections 4 has an end widening.

[0121] Moreover, according to this embodiment, the second projection 5 has a constant width and extends preferably for the entire longitudinal length of the second front surface 3a.

[0122] This solution defines a welding impression shown in Figure 10, where the first weldings “S1” and the second welding “S2” have a shape corresponding to the above-mentioned first projections 4 and second projection 5.

[0123] In the case of first projections 4 which are entirely rectilinear, the welding impression is shown in Figure 9.

[0124] Figure 4 shows a variant embodiment wherein the second sonotrode 3 has a single second projection 5 having a transversal cross-section with a variable width, in particular having a first portion 21 with a smaller width and a second portion 22 with an upper width, joined together by a connecting portion 23 with increasing width. The first two portions 21 , 22 preferably have a rectilinear trend and are aligned with each other.

[0125] The solution of Figure 4 is still compatible with the front surface 2a of the first sonotrode 2 of Figures 1 to 3, in particular comprising a shape coupling between the two front surfaces 2a, 3a in such a way that the second portion with a greater width 22 of the second projection 5 is positioned in the end widening defined by the two first projections 4.

[0126] This solution defines a welding impression shown in Figure 12, where the first weldings “S1” and the second welding “S2” have a shape corresponding to the above-mentioned first projections 4 and second projection 5.

[0127] Figure 5 shows a variant embodiment that differs from the embodiment of Figure 4 in that the second projection 5 extends only for a part of the longitudinal dimension of the second front surface 4a, preferably for a length less than 50% of the length of the second front surface 4a. More specifically, the second projection 5 may have only the portion intended to be positioned in the end widening defined by the two first projections 4.

[0128] This solution defines a welding impression shown in Figure 11 , where the first weldings “S1” and the second welding “S2” have a shape corresponding to the above-mentioned first projections 4 and second projection 5.

[0129] Figures 13 and 14 show further possible embodiments of the welding impressions, corresponding to respective shapes of the projections 4, 5, and in particular: Figure 13 shows a solution where the second welding “S2” has two end zones with a larger width and the first weldings “S1” are further spaced from each other at the ends to conform to the second welding “S2”, defining in particular a symmetrical shape of the welding impression both relative to a longitudinal plane and relative to a plane perpendicular to it; Figure 14 shows a variant of Figure 13, wherein the welding impression 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 from each other, also in this case defining in particular a symmetrical shape of the welding impression both relative to a longitudinal plane and relative to a plane perpendicular to it.

[0130] Figure 6 shows a cross-section, in the close-together welding position, of the first and second sonotrodes 2, 3. This drawing highlights the heights “H1”, “H2” of the two projections 4, 5 with reference to the embodiment of Figures 1 to 3.

[0131] Figure 7 shows a variant embodiment wherein the second front surface 3a of the second sonotrode 3 has a pair of second projections 5 spaced from each other by a longitudinal recess 8 and wherein the recess 8 houses a cutting tool 9. The cutting tool 9 is provided with a relative sliding movement with respect to the second projections 5 to adopt at least a position extracted from the recess 8 and a position retracted in the recess 8, for example under the action of an elastic or actuation element 9a. The cutting tool 9 preferably operates in association with the corresponding supporting portion 6 of the first sonotrode 2 for cutting the material or aggregate subjected to welding.

[0132] Figure 8 shows lastly a non-symmetrical solution wherein there is a single first projection 4 and a single second projection 5 and wherein each sonotrode 2, 3 has only a respective supporting portion 6, 7.

Claims

CLAIMS1. A welding device for product packaging machines, comprising a first sonotrode (2) defining a first front surface (2a) and a second sonotrode (3) defining a second front surface (3a), said first and second sonotrodes (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 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 sonotrodes (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 sonotrodes (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) and said at least a second projection (5) are configured to realize weldings of the same type.

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, preferably so that said areas are separated from 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 arespective 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 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).

7. 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.

8. A device according to claim 7, 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.

9. A device according to claim 7 or 8, 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).

10. A device according to claim 9, 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).11 . 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.

12. 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.

13. 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.

14. 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.

15. 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.

16. 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 aconstant width (22) adjacent to a section having a decreasing width (23).

17. 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 sonotrodes (2, 3) the at least a second projection (5) is arranged between said first projections (4).

18. A device according to claim 17, 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).

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 aggregate to be welded;- approaching said sonotrodes (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 sonotrodes (2, 3); wherein said welding performing of said portion of the material or aggregate realizes on said portion of the material or aggregate 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 of said at least a second projection (5), said first and second weldings (S1 , S2) being simultaneously realized on areas of the material or aggregate which are different from each other.

20. A method according to claim 19, wherein said first and second weldings (S1 , S2) are of a different type or structure.

21. A method according to claim 19, wherein said first and second weldings (S1 , S2) are of the same type or structure.

22. A method according to any one of the preceding claims 19 to 21 , wherein said material or aggregate comprises a plurality of layers of a film material.

23. A method according to any one of the preceding claims 19 to 22, wherein said first welding is a hermetic welding and / or wherein said second welding is a cosmetic welding.

24. A method according to any one of the preceding claims 19 to 23, wherein said sonotrodes are simultaneously operated so as to have at least one different working parameter, said working parameter being preferably selected from: oscillation amplitude; oscillation frequency; oscillation phase.

Images