Induction welding head

Abstract

Induction welding head (1) comprising an electrically insulating support body (2) and a conductive element (3) partially embedded in the support body (2). The conductive element (3) comprises a first welding branch (5) and a second welding branch (6) connected by a connecting section (7), each welding branch (5, 6) comprising a respective rib (8). The first welding branch (5) comprises a central portion (20) and branches, at one first end (30) of the central portion (20), into a first truncated segment (21) and into a second segment (22) connecting said first and second welding branches (5, 6). The rib (8) of the first welding branch (5) extends continuously along the central portion (20) and the first segment (21), and the first segment (21) is interposed between the second segment (22) and the second welding branch (6).

Description

[0001] DESCRIPTION

[0002] Title: INDUCTION WELDING HEAD

[0003] Technical field of the invention

[0004] The present invention relates to an induction welding head for an automatic machine, for example an automatic filling machine of containers for pourable products (e.g., wine, milk, fruit juices, syrups, beverages, sauces, creams, yoghurt, purees, preserves, vegetables, legumes, peeled tomatoes, etc.).

[0005] Prior art

[0006] A machine is known for forming and filling a container for pourable products by means of folding and thermally bonding a sheet of multilayer wrapper (e.g., formed by an outer layer of transparent polyethylene, a subsequent cardboard carrier layer, a subsequent aluminium barrier layer, and an inner layer of transparent polyethylene). The welding device which performs the transverse welding comprises an induction welding head provided with a tubular (or internally hollow) conductive element which is bent into a "U" to form two distinct and separate welding branches between which a blade operates which performs the transverse cutting of the folded and welded wrapper sheet. The tubular conductive element is placed in a support body of plastic material. Part of the support body and part of the tubular conductive element are removed by milling to make the operational surface which is substantially flat with the exception of a pair of straight ribs which protrude perpendicularly to the flat surface.

[0007] EP3318391A1 describes an induction welding head comprising a tubular conductive element having, on the operational face, a pair of non-straight welding branches, provided with straight ribs, and a support body made of insulating material which supports the tubular conductive element. The tubular conductive element is connected to two electrical terminals, which, in use, are connected to an electrical circuit comprising an electrical generator and adapted to circulate inside the tubular conductive element an alternating electrical current of relatively high frequency which induces heat in the metal layer of the wrapper sheet, which in turn melts the polyethylene to perform the thermal bonding.

[0008] Summary of the invention

[0009] In the aforesaid context, the Applicant has addressed the problem related to edge effects in an induction welding head, due to which the electromagnetic field generated by the welding branches tends to close on itself at the edges of the wrapper sheet placed between the aforesaid branches and subject to welding, creating a deformation and / or thinning of the width of the weld at the ends of the weld on the edges of the wrapper sheet.

[0010] To try to mitigate this problem, the aforementioned EP3318391A1 teaches to suitably shape the conductive element: the two welding branches, which in the central welding zone extend straight and parallel to each other, move away from each other at the longitudinal ends of the central welding zone. Each welding branch therefore has a straight central welding portion at a certain distance from the central welding portion of the other branch, and two straight lateral portions each at a distance from the corresponding lateral portion of the other branch which is greater than the aforesaid distance in the central portion. Each central welding portion is connected with the lateral portions by a respective "S" connecting section. This shape, possibly in combination with the presence of suitable electromagnetic field concentrators (for example ferrite), is adapted to modify the conformation of the electromagnetic field at the edges of the wrapper sheet subject to welding, opposing the aforesaid closure of the electromagnetic field on itself.

[0011] The Applicant has observed that this known solution has some design constraints on the shape of the welding branches of the conductive element. Such constraints can, in certain situations, prevent the achievement of optimal solutions. For example, the presence of the aforesaid ribs, which extend straight along each welding branch of the conductive element to ensure a pressure line on the wrapper sheet and at which the thermal bonding is carried out, imposes limitations on the shape of the conductive element, in particular at the aforesaid "S" connecting sections. For example, the misalignment between the lateral portions and the respective central portion must be less than the transverse dimension of the welding branch, to ensure that the straight ribs remain on the welding branch.

[0012] The Applicant has therefore felt the need to modify the electromagnetic field in the edge zones at will to overcome the problem of deformation of the weld in such edge zones. The Applicant has sensed that it is advantageous to decouple the problem related to the shape of the electromagnetic field from the problem related to the pressure on the wrapper sheet by the welding head.

[0013] The Applicant has therefore found that by suitably bifurcating the welding branch, it is possible to modify the electromagnetic field in the edge zones at will, while maintaining a desired pressure zone on the wrapper sheet.

[0014] According to the Applicant, the aforesaid problem related to the edge effects of the electromagnetic field in a welding head is solved by an induction welding head in accordance with the appended claims and / or according to the following aspects and embodiments.

[0015] Preferably, the welding head comprises a support body made of electrically insulating material.

[0016] Preferably, the welding head comprises a conductive element partially embedded in said support body at an operational face of the welding head. Preferably, the operational face of the welding head is substantially flat.

[0017] Preferably, said conductive element comprises, on said operational face, a first welding branch and a second welding branch. Preferably, the first and second welding branches are electrically connected to each other by a connecting section of said conductive element.

[0018] Preferably, each of said first and second welding branches comprises a respective rib protruding from said operational face.

[0019] Preferably, said first welding branch comprises a central portion.

[0020] Preferably, at at least one first end of said central portion, said first welding branch branches into a first segment and a second segment.

[0021] Preferably, said first segment is truncated ("dead-end").

[0022] Preferably, said second segment, in use, electrically connects said first and second welding branches in a closed electrical circuit.

[0023] Preferably, said rib of said first welding branch extends continuously along said central portion and first segment.

[0024] Preferably, said first segment is interposed between said second segment and said second welding branch.

[0025] According to the Applicant, the bifurcation of the welding branch in a first truncated segment on which the rib is obtained and in a second segment, distinct from the first segment and arranged in a more distal position of the first segment with respect to the opposite welding branch (since the first segment is interposed between the second segment and the opposite welding branch), allows to appropriately modify the electromagnetic field in the corresponding edge zone of the wrapper sheet, acting on the geometry of the second segment, without modifying the pressure zone on the wrapper sheet, which is determined by the rib on the first segment. That is, the simultaneous presence of the first and second segments allows to decouple the problem related to the pressure zone on the wrapper sheet, which is solved by the rib on the first segment, from the problem related to the edge effects, which is solved by the second segment whose geometry can be designed at will in an optimal manner regardless of the geometry of the first segment.

[0026] In fact, on the one hand, the rib on the first segment allows to achieve the pressure on the wrapper sheet on a hot and thermally conductive surface. On the other hand, the second segment, in use, electrically connects the first and second welding branches in a closed electrical circuit, including an electrical generator (depending on the case, the second segment can be electrically connected to the facing second segment of the other branch or to a pole of the electrical generator). That is, the second segment is part of the electrical induction circuit and is crossed by the induction current, and therefore the geometry of the second segment affects the shape of the electromagnetic field at the transverse edge of the weld.

[0027] The invention in one or more of its aspects can have one or more of the following preferred characteristics.

[0028] Preferably, at at least one second end of said central portion of said first welding branch opposite to the aforesaid first end, said first welding branch branches into a respective first segment and a respective second segment. Preferably, said first segment at the second end of said first welding branch is truncated. Preferably, said second segment at the second end of said first welding branch, in use, electrically connects said first and second welding branches in said closed electrical circuit. Preferably, said rib of said first welding branch extends continuously also along said first segment at the second end of said first welding branch. Preferably, said first segment at the second end of said first welding branch is interposed between said second segment at the second end of said first welding branch and said second welding branch. Thereby, the effects described above are obtained at both transverse edges of the weld made by the first welding branch. Preferably, said second welding branch comprises a respective central portion. Preferably, at at least one first end of said central portion of said second welding branch, said second welding branch branches into a respective first segment and a respective second segment. Preferably, said first segment at the end of said second welding branch is truncated. Preferably, said second segment of said second welding branch, in use, electrically connects said first and second welding branches in said closed electrical circuit. Preferably, said rib of said second branch extends continuously along said central portion and first segment of said second welding branch. Preferably, said first segment of said second welding branch is interposed between said second segment of said second welding branch and said first welding branch. Thereby, the effects described above are obtained also at a transverse edge of the weld made by the second welding branch.

[0029] Preferably, at at least one second end of said central portion of said second welding branch opposite to the said first end of said central portion of said second welding branch, said second welding branch branches into a respective first segment and a respective second segment. Preferably, said first segment at the second end of said second welding branch is truncated. Preferably, said second segment at the second end of said second welding branch, in use, electrically connects said first and second welding branches in said closed electrical circuit. Preferably, said rib of said second welding branch extends continuously also along said first segment at the second end of said second welding branch. Preferably, said first segment at the second end of said second welding branch is interposed between said second segment at the second end of said second welding branch and said first welding branch. Thereby, the effects described above are obtained at both transverse edges of the weld made by the second welding branch.

[0030] Preferably, said central portions of said first and second welding branches are parallel to each other.

[0031] Preferably, said connecting section of the conductive element electrically connects two respective second segments of said first and second welding branches, more preferably two respective second segments at the respective second ends of said first and second welding branches.

[0032] Preferably, said connecting section of the conductive element is at least partially located on said operational face. Likewise preferred, said connecting section of the conductive element extends at least in part inside said support body, preferably away from said operational face.

[0033] Preferably, the welding head comprises two electrical terminals, for example made of copper, directly electrically connected respectively to two second segments of the aforesaid first and second welding branches. Thereby, the two electrical terminals, which are part of the aforesaid closed electrical circuit, allow the connection of the conductive element to the electrical generator.

[0034] Preferably, each first segment is straight, more preferably it is aligned with said respective central portion of the respective welding branch. Preferably, said respective rib is straight. Thereby, a straight weld is obtained.

[0035] Preferably, each second segment comprises a respective first section that diverges from the respective first segment, moving away from the respective central portion. Preferably, each second segment comprises a respective second straight section, more preferably parallel to the respective first segment. Thereby, the electromagnetic field is suitably modified.

[0036] Preferably, said operational face is symmetrical with respect to a first line of symmetry interposed between, and parallel to, said first and second welding branches. Preferably, said operational face is symmetrical with respect to a second line of symmetry orthogonal to said first line of symmetry. Thereby, the welding head has a rational geometry.

[0037] Preferably, a main extension line of the conductive element has a substantially "U" conformation, more preferably lying on a plane.

[0038] Preferably, the conductive element is tubular, i.e. , internally hollow.

[0039] Preferably, said conductive element is provided with a conduit extending along a main extension line of said conductive element. Preferably, said conduit extends continuously along said central portions, along said second segments and along said connecting section (not necessarily along the first segments). Thereby, in use, it is possible to effectively cool the conductive element.

[0040] Preferably, the support body comprises a pair of channels in fluid communication with said conduit, more preferably with two ends of said duct, respectively.

[0041] Preferably, each welding branch (e.g., said connecting section and / or each first and second segment and / or each central portion) has a substantially quadrangular section (taken on a plane orthogonal to the main extension line). Preferably, said conduit has a quadrangular or circular or oval section.

[0042] Preferably, said welding head comprises an electromagnetic flux concentrator, for example ferrite, e.g., soft / hard.

[0043] In an embodiment, said flux concentrator is dispersed and / or embedded in said support body.

[0044] In an alternative embodiment or in combination with the aforesaid embodiment, said flux concentrator is one or more sheets which at least partly cover said conductive element, more preferably interposed between said conductive element and said support body. Preferably, said conductive element is made of copper.

[0045] Preferably, said support body is made of thermally insulating material. In an embodiment, said support body is made of a homogeneous polymeric material, for example resin.

[0046] Brief description of the figures

[0047] Figure 1 is a perspective, schematic and partial view of an induction welding head according to the present invention;

[0048] Figure 2 is a sectional, schematic and partial view of the induction head along the plane of section ll-ll of Figure 1 ;

[0049] Figure 3 is a perspective and schematic view of the conductive element of the welding head of Figure 1 and 2;

[0050] Figure 4 schematically and partially shows a front view of the operational face of the welding head of Figure 1 .

[0051] Detailed description of several embodiments of the invention

[0052] The features and advantages of the present invention will be further clarified from the following detailed description of some embodiments, presented by way of non-limiting example of the present invention, with reference to the attached figures.

[0053] An induction welding head 1 according to the present invention is exemplarily shown in the figures. The welding head 1 is applied, for example, in an automatic filling machine of containers for pourable products, not shown or described as, for example, of known type. Preferably, the welding head 1 comprises a support body 2 made of electrically and thermally insulating material.

[0054] Preferably, the welding head 1 comprises a conductive element 3, exemplarily made of copper, partially embedded in the support body 2 at a substantially flat operational face 4 of the welding head 1 .

[0055] Preferably, the conductive element 3 comprises, on the operational face 4, a first welding branch 5 and a second welding branch 6, electrically connected to each other by a connecting section 7 of the conductive element 3.

[0056] Preferably, the main extension line of the conductive element 3 has a substantially "U" conformation, more preferably lying on a plane. It is noted that in some embodiments, not shown, the connecting section 7 can at least partly extend completely embedded in the support body 2 (i.e. , not be visible on the operational face 4).

[0057] Preferably, the welding head 1 comprises two electrical terminals 15, for example made of copper, electrically connected respectively to two ends of the conductive element 3 to connect the latter to an electrical generator (not shown). Preferably, each welding branch 5, 6 comprises a respective rib 8 protruding from said operational face 4.

[0058] Preferably, the support body 2 comprises, at the operational face 4, a cavity 11 (not shown in Figure 4 for greater clarity) interposed between, and parallel to, the first welding branch 5 and the second welding branch 6, to allow, in use, the insertion of a blade (not shown) which performs the transverse cutting of the welded wrapper sheet, for example in a known manner.

[0059] Preferably, the first welding branch 5 and the second welding branch 6 each comprise a respective central portion 20. In Figure 4, the dashed-dotted lines 14 exemplarily indicate where the central portions 20 end. Preferably, the central portions 20 are parallel to each other.

[0060] In Figure 4, the dashed lines 16 exemplarily show the edge of the wrapper sheet during induction thermal bonding.

[0061] In the example shown, the operational face 4 (Fig. 4) is symmetrical with respect to a first line of symmetry 12 interposed between, and parallel to, the first welding branch 5 and the second welding branch 6 and with respect to a second line of symmetry 13 orthogonal to the first line of symmetry 12. Therefore, the conductive element 3 has four branches as described below, symmetrical to each other. However, the present invention contemplates any number of such branches, including only one.

[0062] In light of the aforesaid symmetries, a single branch will be described in detail below, arbitrarily referring to the first welding branch 5 at the first end 30, the latter arbitrarily referring to the side of the electrical generator. However, the expressions "first welding branch" and "second welding branch" can refer indifferently to one or the other welding branch. Similarly, the expressions "first end of the central portion" and "second end of the central portion" can refer indifferently to one or the other end of the central portion.

[0063] Preferably, at the first end 30 of the respective central portion 20, the first welding branch 5 branches into a first truncated segment 21 and a second segment 22, which, in use, electrically connects the first welding branch 5 and the second welding branch 6 in a closed electrical circuit comprising the electrical generator.

[0064] Preferably, the rib 8 of the first welding branch 5 extends continuously along the respective central portion 20 and along the first segment 21 at the respective first end 30. Preferably, such a first segment 21 is straight and aligned with the respective central portion 20 of the first welding branch 5, the respective rib 8 being straight. Preferably, at the first end 30 of the first welding branch 5, the respective first segment

[0065] 21 is interposed between the respective second segment 22 and the second welding branch 6, such a second segment 22 being on the opposite side of the respective first segment 21 with respect to the second welding branch 6. Preferably, the second segment

[0066] 22 comprises a first section 22’, which diverges from the respective first segment 21 , moving away from the respective central portion 20, and a straight second section 22" parallel to the respective first segment 21. In embodiments not shown, the first section 22’ of the second segment 22 can extend orthogonally to the respective first segment 21 . Overall, the rib 8 extends continuously straight over the entire respective central portion 20 and over the two respective first segments 21 of each welding branch 5, 6. It should be noted that the rib 8 also continues on the support body 2, for reasons of constructive simplicity, although such sections of the rib 8 do not have a function during the use of the welding head 1 .

[0067] In the example shown, the second segment 22, for example the second section 22", arranged at the first end 30 of each welding branch 5, 6 is directly electrically connected to the respective electrical terminal 15.

[0068] In the example shown, the connecting section 7 of the conductive element 3 electrically and directly connects the two respective second segments 22 (e.g., the respective second section 22") of said first and second welding branches 5, 6 arranged at the second end 31.

[0069] Preferably, the conductive element 3 is internally provided with a conduit 40 extending along the main extension line of the conductive element 3, in particular along the two central portions 20, along all the second segments 22 and along the connecting section 7 (but not necessarily along the first segments 21 ). Preferably, the support body 2 comprises a pair of channels 41 in fluid communication with two ends 42 of the conduit 40 (Fig. 3), respectively.

[0070] Preferably, each single section of the welding branch (e.g., the connecting section and / or each first and second segment and / or each central portion), and / or the conduit 40 has a section orthogonal to the main extension line of rectangular shape.

[0071] Preferably, the welding head 1 comprises an electromagnetic flux concentrator (not shown because for example of known type), for example ferrite, e.g., soft / hard.

[0072] The support body 2 can be made of vitron ite , also known as epoxy glass, or resin, possibly with ferrite dispersed in the resin. The induction welding head 1 according to the present invention can be produced by any manufacturing method.

[0073] In an embodiment, the conductive element 3, including the conduit 40, can be made by additive manufacturing or 3D printing. The conductive element 3 can be co-moulded to the support body 2 or can be inserted and glued by means of structural adhesive in a suitable housing seat previously obtained in the support body 2 (e.g., by milling).

[0074] Finally, it is preferably envisaged to make, for example by milling, the operational face 4, removing material from the support body 2 and the conductive element 3, simultaneously obtaining the two ribs 8.

Claims

CLAIMS1. Induction welding head (1 ) comprising:- a support body (2) made of electrically insulating material;- a conductive element (3) partially embedded in said support body (2) at an operational face (4) of the welding head (1 ), the operational face (4) being substantially flat; wherein said conductive element (3) comprises, on said operational face (4), a first welding branch (5) and a second welding branch (6), electrically connected to each other by a connecting section (7) of said conductive element (3), each of said first and second welding branches (5, 6) including a respective rib (8) protruding from said operational face (4), wherein said first welding branch (5) comprises a central portion (20), wherein, at at least one first end (30) of said central portion (20), said first welding branch (5) branches into a first segment (21 ) and a second segment (22), wherein said first segment (21 ) is truncated, wherein said second segment (22), in use, electrically connects said first and second welding branches (5, 6) in a closed electrical circuit, wherein said rib (8) of said first welding branch (5) extends continuously along said central portion (20) and said first segment (21 ), and wherein said first segment (21 ) is interposed between said second segment (22) and said second welding branch (6).

2. Welding head (1 ) according to claim 1 , wherein at a second end (31 ) of said central portion (20) of said first welding branch (5), opposite to said first end (30) of said central portion (20) of said first welding branch (5), said first welding branch (5) branches into a respective first segment (21 ) and a respective second segment (22), wherein said first segment (21 ) at the second end (31 ) of said first welding branch (5) is truncated, wherein said second segment (22) at the second end (31 ) of said first welding branch (5), in use, electrically connects said first welding branch (5) and second welding branch (6) in said closed electrical circuit, wherein said rib (8) of said first welding branch (5) also extends continuously along said first segment (21 ) at the second end (31 ) of said first welding branch (5) and wherein said first segment (21 ) at the second end (31 ) of said first welding branch (5) is interposed between said second segment (22) at the second end (31 ) of said first welding branch (5) and said second welding branch (6).

3. Welding head (1 ) according to claim 1 or 2, wherein said second welding branch (6)comprises a respective central portion (20) and wherein, at at least one first end (30) of said central portion (20) of said second welding branch (6), said second welding branch (6) branches into a respective first segment (21 ) and a respective second segment (22), wherein said first segment (21 ) of said second welding branch (6) is truncated, wherein said second segment (22) of said second welding branch (6), in use, electrically connects said first welding branch (5) and second welding branch (6) in said closed electrical circuit, wherein said rib (8) of said second welding branch (6) extends continuously along said central portion (20) and said first segment (21 ) of said second welding branch (6) and wherein said first segment (21 ) of said second welding branch (6) is interposed between said second segment (22) of said second welding branch (6) and said first welding branch(5).

4. Welding head (1 ) according to claim 3, wherein at a second end (31 ) of said central portion (20) of said second welding branch (6) opposite to said first end (30) of said central portion (20) of said second welding branch (6), said second welding branch (6) branches into a respective first segment (21 ) and a respective second segment (22), wherein said first segment (21 ) at the second end (31 ) of said second welding branch (6) is truncated, wherein said second segment (22) at the second end (31 ) of said second welding branch(6), in use, electrically connects said first welding branch (5) and second welding branch(6) in said closed electrical circuit, wherein said rib (8) of said second welding branch (6) also extends continuously along said first segment (21 ) at the second end (31 ) of said second welding branch (6) and wherein said first segment (21 ) at the second end (31 ) of said second welding branch (6) is interposed between said second segment (22) at the second end (31 ) of said second welding branch (6) and said first welding branch (5).

5. Welding head (1 ) according to claim 3 or 4, wherein said central portions (20) of said first and second welding branches (5, 6) are parallel to each other.

6. Welding head (1 ) according to any of the claims 3 to 5, wherein said connecting section(7) of the conductive element (3) electrically connects two respective second segments (22) of said first welding branch (5) and second welding branch (6).

7. Welding head (1 ) according to any of the preceding claims, wherein each first segment (21 ) is aligned with said respective central portion (20) of the respective welding branch (5, 6), said respective rib (8) being straight.

8. Welding head (1 ) according to any of the preceding claims, wherein each second segment (22) comprises a respective first section (22’) that diverges from the respectivefirst segment (21 ), moving away from the respective central portion (20), and a respective second straight section (22”).

9. Welding head (1 ) according to any of the preceding claims, wherein said operational face (4) is symmetric with respect to at least one among a first line of symmetry (12) positioned between, and parallel to, said first welding branch (5) and second welding branch (6) and a second line of symmetry (13) orthogonal to said first line of symmetry (12).

10. Welding head (1 ) according to any of the preceding claims, wherein said conductive element (3) is equipped with a conduit (40) that extends continuously along each central portion (20), along each second segment (22), and along said connecting section (7).

11. Welding head (1 ) according to any of the preceding claims, wherein said conductive element (3) is made of copper.

12. Welding head (1 ) according to any of the preceding claims, wherein said conductive element (3) is manufactured using additive manufacturing.

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