Sonotrode for an ultrasonic welding device

Abstract

Sonotrode (10) for an ultrasonic welding device with at least one sealing surface (20) for contacting a workpiece, wherein a planar welding structure (30) is provided on the sealing surface (20) which is designed to introduce welding energy into the workpiece, wherein a suppression structure (40) is further provided on the sealing surface (20), wherein the suppression structure (40) extends around the welding structure (30) and has a closed contour.

Description

[0001] The present invention relates to a sonotrode for an ultrasonic welding device.

[0002] In ultrasonic welding, sonotrodes are used to transfer the energy supplied by a converter into the workpiece being welded. The design of the sonotrode has a significant influence on the weld quality.

[0003] Ultrasonic welding can be used to join a wide variety of materials. This includes both plastics and metals. One problem that arises with ultrasonic metal welding is the formation of flakes. These are small chips that are created when the tool penetrates the weld pool and during the ultrasonic process. These flakes are undesirable because they can break off or fall off during further handling and, for example, cause short circuits. They can also gradually contaminate the work area during production. Flakes can be removed by manual post-treatment (brushing), but this is very time-consuming. To prevent flake formation, the welding parameters can be adjusted. However, in this case, compromises must be made between flake prevention and weld quality.

[0004] It is therefore an object of the present invention to avoid the formation of flakes without impairing the quality of the weld.

[0005] This problem is solved by a sonotrode according to claim 1. Advantageous further developments are the subject of the dependent claims.

[0006] The advantages of the invention are particularly evident in metal welding. In metal welding, flakes can, for example, cause short circuits, which is why suppressing flake formation is of particular importance. The sonotrode is therefore preferably a metal welding sonotrode and, in particular, has a coupling surface that is essentially perpendicular to the sealing surface.

[0007] The sonotrode preferably has several sealing surfaces. The sealing surfaces can be identical or differently designed. Preferably, all sealing surfaces have a welding structure and a suppression structure.

[0008] The inventors have determined that the suppression structure largely welds any flakes that form into the workpiece material. Post-processing is unnecessary, and there is no longer a risk of flakes detaching later. The welding parameters can be adjusted independently of flake formation.

[0009] In advantageous embodiments, the suppression structure has at least one burr. A burr is an elongated projection. The burr preferably extends perpendicularly from the sealing surface. The burr allows any flakes formed to be efficiently incorporated into the workpiece. The burr is preferably wedge-shaped in cross-section. This ensures that the burr makes essentially linear contact with the workpiece. In advantageous embodiments, the burr has a rounded tip. This prevents unnecessary wear of the burr and allows it to retain its shape and thus its properties during flake suppression over a long period.

[0010] The suppression structure has a maximum height H1, which is preferably defined by the burr. Particularly preferably, the maximum height H1 is the distance by which the burr projects perpendicularly from the sealing surface. The weld structure preferably has a maximum height H2, which is also measured perpendicular to the sealing surface. The maximum height H1 of the suppression structure is preferably less than the maximum height H2 of the weld structure. This ensures that the weld structure performs the actual welding process, i.e., introduces the welding energy into the workpiece, and that the suppression structure primarily fulfills its primary function of suppressing the flakes.

[0011] If the maximum height H1 is too small, flake formation is not sufficiently suppressed. If H1 is too large, the contact between the suppression structure and the workpiece is too extensive, requiring additional welding energy. Preferably, the maximum height H1 of the suppression structure corresponds to approximately half the maximum height H2 of the weld structure. Deviations of 10% are acceptable. This achieves a good compromise between suppression effectiveness and the additional welding energy required.

[0012] The maximum height H1 is preferably between 0.1 mm and 1 mm. The maximum height H2 is preferably between 0.3 mm and 3 mm.

[0013] The welded structure preferably has a rectangular base area.

[0014] The suppression structure has a maximum width B1, which is preferably a dimension of the ridge. Particularly preferably, the maximum width B1 is the maximum width of the ridge perpendicular to the contour and parallel to the sealing surface. In the case of a wedge-shaped ridge, this is the width of the ridge's base. The weld structure has a maximum width B2, which preferably corresponds to its overall width and can differ in several dimensions. For example, a weld structure with a rectangular base has two mutually perpendicular maximum widths B2.

[0015] The suppression structure can be significantly narrower than the weld structure, as it only performs an auxiliary function. Therefore, the maximum width B1 of the suppression structure is preferably less than the maximum width B2 of the weld structure in at least one dimension. Particularly preferably, the maximum width B1 of the suppression structure is less than 10%, and more preferably less than 5%, of the maximum width B2 of the weld structure in at least one dimension.

[0016] The maximum width B1 is preferably between 0.2 mm and 1 mm. The maximum width B2 is preferably between 5 mm and 50 mm.

[0017] The sealing surface can have a border region between the suppression structure and an edge of the sealing surface. In other words, the border region lies radially outside the suppression structure. Starting from the suppression structure, the border region preferably slopes down continuously. In other words, there are no further elevations on the sealing surface radially outside the suppression structure. This prevents flakes from forming outside the suppression structure or any other contact between the sealing surface and the workpiece. The border region preferably has a circumferential radius.

[0018] The weld structure is preferably uniformly formed to enable controlled transfer of the welding energy into the workpiece. In advantageous embodiments, the weld structure comprises a plurality of pyramid-shaped elements, preferably arranged in a grid. Pyramid-shaped elements are particularly advantageous in strand welding, as they can insert themselves between the individual strands and thus transfer the welding energy with exceptional efficiency. Elements of other shapes are also possible. The elements can also be spaced apart from one another.

[0019] If the welded structure comprises several elements, for example pyramid-shaped elements, the maximum width B1 of the suppression structure is preferably less than a maximum width B3 of the elements, in particular the pyramid-shaped elements, in at least one dimension.

[0020] The maximum width B3 of the elements is preferably between 0.8 mm and 3 mm.

[0021] The sealing surface is preferably essentially flat. Deviations from flatness result from the weld structure and the suppression structure. Further deviations can occur, for example, due to the continuously sloping edge area.

[0022] The contour of the suppression structure can have various shapes. For example, the contour can also be round or oval. Preferably, the contour has at least one kink or curve. It is particularly advantageous if the contour is adapted to the base surface of the weld structure. For this purpose, the contour can, for example, maintain a substantially uniform distance from the weld structure.

[0023] The object of the invention is also achieved by a sonotrode in which the suppression structure does not have a closed contour, but rather runs along a path on the sealing surface, at least partially around the weld structure, wherein the path deviates from a straight line or, in other words, is non-linear. The sonotrode can be further developed by the features described above. Due to the non-closed path, a portion of the suppression structure can be omitted, and, for example, only those sections where flakes frequently occur can be provided with a suppression structure.

[0024] The path of the suppression structure preferably has at least one kink or curve. This allows several sections adjacent to the weld structure to be covered by a single suppression structure.

[0025] The object of the invention is also achieved by an ultrasonic welding device with a sonotrode according to the above description.

[0026] The invention is illustrated and explained by way of example with reference to the drawings. The following figures are shown in the drawings: Fig. 1 An embodiment of a sonotrode in a perspective view Fig. 2 the sealing surface of the sonotrode of the Fig. 1 in a top view Fig. 3 the sonotrode of the Fig. 1 in a partial section

[0027] The sonotrode 10 shown in the figures is a sonotrode for metal welding. The sonotrode 10 comprises a coupling surface 12 at one end and a sonotrode head 14 at the opposite end (see Fig. 1) A mechanical vibration is introduced into the sonotrode 10 at the coupling surface 12 by a converter or an amplitude amplifier (neither shown). During normal use, the vibration causes the sonotrode 10 to be periodically stretched and compressed in a direction perpendicular to the coupling surface 12; the sonotrode 10 oscillates in this direction.

[0028] The sonotrode head 14 has a total of four sealing surfaces 20, arranged on its four radial sides. Each of the four sealing surfaces 20 is essentially flat and perpendicular to the coupling surface 12. The vibration of the sonotrode 10 causes the sealing surfaces 20 to move back and forth. If one of the sealing surfaces 20 is in contact with a workpiece (not shown), energy is transferred into the workpiece through friction, which can, for example, fuse one metallic component to another. The four sealing surfaces 20 can be identical or different.

[0029] In the Fig. 2 and Fig.Figure 3 shows one of the sealing surfaces 20. The sealing surface 20 is essentially flat. A planar welding structure 30 is located at the center of the sealing surface 20. The welding structure 30 comprises a multitude of pyramid-shaped elements 32, which are arranged in a uniform grid on a rectangular base and project perpendicularly from the sealing surface 20. During normal use, the pyramid-shaped elements 32 contact the workpiece and transfer the welding energy into the workpiece as described above.

[0030] Furthermore, a suppression structure 40 is arranged on the sealing surface 20. The suppression structure 40 has a burr 42 that extends around the weld structure 30 and has a closed contour. In other words, the suppression structure 40 lies radially outside the weld structure 30. The burr 42 has a wedge-shaped cross-section and a rounded tip. The contour has four curves 44 with a very small radius.

[0031] In the lower region, where the ridge 42 originates from the sealing surface 20, the ridge 42 has a maximum width B1, which is measured perpendicular to the contour and parallel to the sealing surface. The weld structure 30 has a maximum width B2 in a dimension parallel to the sealing surface 20. The width B1 is significantly smaller than the width B2. In the embodiment shown here, the width B1 is only about 2.5% of the width B2. The width B1 is also smaller than the width B3 of the pyramidal elements.

[0032] The ridge 42 has a maximum height H1 extending from the sealing surface 20. The pyramidal elements 32 have a maximum height H2 extending from the sealing surface 20. The height H1 is approximately half the height H2. This ensures that the welding is primarily effected by the welding structure 30 and that the suppression structure 40 primarily suppresses the formation of flakes.

[0033] Radially outside the suppression structure 40 is a boundary region 22 of the sealing surface 20. This boundary region 22 extends from the suppression structure 40 to an edge 24 of the sealing surface 20. The boundary region 22 slopes continuously downwards from the suppression structure 40. In other words, there are no further elevations on the sealing surface 20 radially outside the suppression structure 40. This prevents flakes from forming outside the suppression structure 40 or any other contact between the sealing surface 20 and the workpiece. Reference symbol list 10 sonotrodes 12 coupling area 14 Sonotrode head 20 seal area 22 Edge area 24 Rand 30 weld structure 32 Pyramid-shaped element 40 oppression structure 42 degrees 44 Curve B1 Maximum width of the suppression structure B2 Maximum width of the weld structure B3 Maximum width of the pyramid-shaped element H1 Maximum height of the suppression structure H2 Maximum height of the welded structure

Claims

Sonotrode (10) for an ultrasonic welding device with at least one sealing surface (20) for contacting a workpiece, wherein a planar welding structure (30) is provided on the sealing surface (20) which is configured to introduce welding energy into the workpiece, wherein a suppression structure (40) is further provided on the sealing surface (20), wherein the suppression structure (40) extends around the welding structure (30) and has a closed contour. Sonotrode (10) according to claim 1, wherein the suppression structure (40) has at least one ridge (42) which preferably projects perpendicularly from the sealing surface (20). Sonotrode (10) according to one of the preceding claims, wherein the ridge (42) is wedge-shaped in cross-section. Sonotrode (10) according to one of the preceding claims, wherein the ridge (42) has a rounded tip. Sonotrode (10) according to one of the preceding claims, wherein a maximum height H1 of the suppression structure (40) is less than a maximum height H2 of the welded structure (30). Sonotrode (10) according to one of the preceding claims, wherein the maximum height H1 of the suppression structure (40) corresponds to approximately half the maximum height H2 of the welded structure (30). Sonotrode (10) according to one of the preceding claims, wherein a maximum width B1 of the suppression structure (40) is less than a maximum width B2 of the welded structure (30) in at least one dimension. Sonotrode (10) according to one of the preceding claims, wherein the maximum width B1 of the suppression structure (40) in at least one dimension is less than 10% of the maximum width B2 of the welded structure (30). Sonotrode (10) according to one of the preceding claims, wherein a boundary region (22) between the suppression structure (40) and a boundary (24) of the sealing surface (20) slopes continuously from the suppression structure (40). Sonotrode (10) according to one of the preceding claims, wherein the weld structure (30) is uniform. Sonotrode (10) according to one of the preceding claims, wherein the welded structure (30) comprises a plurality of pyramid-shaped elements (32) which are preferably arranged in a grid. Sonotrode (10) according to one of the preceding claims, wherein the maximum width B1 of the suppression structure (40) is less in at least one dimension than a maximum width B3 of the pyramidal elements (32). Sonotrode (10) according to one of the preceding claims, wherein the welded structure (30) has a rectangular base area. Sonotrode (10) according to one of the preceding claims, wherein the sealing surface (20) is essentially flat. Sonotrode (10) according to one of the preceding claims, wherein the contour has at least one kink or curve (44). Sonotrode (10) for an ultrasonic welding device with at least one sealing surface (20) for contacting a workpiece, wherein a welding structure (30) is provided on the sealing surface (20) which is configured to introduce welding energy into the workpiece, wherein a suppression structure (40) is further provided on the sealing surface (20), wherein the suppression structure (40) extends along a path at least partially around the welding structure (30), the path deviating from a straight line. Sonotrode (10) according to claim 16, wherein the track has at least one kink or curve (44).

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