Ultrasonic vibrating element with material-bonded mounting

Abstract

The present invention relates to an ultrasonic welding system with an ultrasonic vibrating element and a holding element to which the ultrasonic vibrating element is attached via a decoupling element, characterized in that the decoupling element is materially bonded to both the ultrasonic vibrating element and the holding element.

Description

[0001] The present invention relates to an ultrasonic welding system with an ultrasonic vibrating element and a holding element to which the ultrasonic vibrating element is attached via a decoupling element.

[0002] The ultrasonic vibrating element can be, for example, a sonotrode, which has a surface designed to come into contact with the material being processed. This surface is generally called the sealing surface or welding surface. The sonotrode is typically excited by a converter connected to it. The converter transforms an alternating electrical voltage into a mechanical vibration. Piezoelectric elements are usually used for this purpose.

[0003] An amplitude transformer can be positioned between the converter and the sonotrode, which modifies the amplitude of the mechanical vibration generated by the converter. Thus, by applying an alternating electrical voltage to the sealing surface of the sonotrode, an ultrasonic vibration can be generated that can be transmitted to the material being processed.

[0004] In this context, the converter, amplitude transformer, and sonotrode can all be considered individual ultrasonic oscillating elements, which are usually tuned to each other so that each can be individually brought into resonant vibration with the ultrasonic oscillation of frequency f and wavelength λ. Often, a standing wave with vibration maxima and at least one node forms along a longitudinal axis. These ultrasonic oscillating elements are bounded along this longitudinal axis by end faces that exhibit a vibration maximum at resonance. The respective end faces are connected to each other. If necessary, several ultrasonic oscillating elements can be manufactured as a single unit, eliminating the need for screws or welds.

[0005] The described ultrasonic vibrating unit must be held in some way to move it towards the material being processed and, if necessary, to exert a force on the material. A holding element is used for this purpose, but it should influence the vibration behavior of the ultrasonic vibrating unit and its individual ultrasonic vibrating elements as little as possible. Therefore, the holding element is generally designed to engage the outer surface of an ultrasonic vibrating element at a point that essentially corresponds to the described vibration node, i.e., at a location where the acoustic ultrasonic vibration exhibits a minimal amplitude in the longitudinal direction.

[0006] However, the ultrasonic vibrating element has a finite extent perpendicular to the longitudinal direction, with the consequence that the acoustic vibration in the longitudinal direction is accompanied by a thickness vibration. This means that the lateral surface of the ultrasonic vibrating element moves perpendicular to the longitudinal direction, so that the cross-sectional area perpendicular to the longitudinal direction alternately increases and decreases at the same frequency f.

[0007] The thickness vibration described also exhibits regions with larger and smaller amplitudes along the longitudinal axis. However, where the mounting engages the surface, i.e., where the described acoustic longitudinal vibration has a minimum amplitude, the thickness vibration amplitude is relatively large.

[0008] This results in the ultrasonic vibrating element inevitably exerting an oscillating force perpendicular to its longitudinal direction on the mounting element. Therefore, it is already common practice to provide a suitable decoupling element capable of absorbing these forces. For example, elastomers are used that can absorb the force through deformation. Alternatively, thin geometric structures have also been developed that are likewise deformed during operation of the ultrasonic vibrating unit.

[0009] However, all known mounting structures have disadvantages. Depending on the magnitude of the ultrasonic vibration in the mounting area and the design of the decoupling element, potentially high forces are exerted on the mounting element. If these forces exceed the clamping force provided by the elastomer or the attached geometric structure, friction occurs at the clamping point, leading to rapid wear and high local temperature generation. Furthermore, the mounting itself has a significant influence on the vibration behavior, as it depends crucially on how firmly the elastomer is pressed onto the ultrasonic vibration element and how tightly the geometric structure is screwed to other components of the mounting element.Neither the design using elastomers nor the design with a screwed, thin geometric structure can be practically modeled using FEM (Finite Element Method). Any attempt at modeling fails because the actual variations at contact points, manufacturing tolerances, and assembly tolerances are so large that sufficiently accurate simulation results cannot be generated. Therefore, the vibration behavior theoretically predicted by FEM modeling deviates to a greater or lesser extent from the actual vibration behavior.

[0010] Based on the described prior art, it is therefore an object of the present invention to provide an ultrasonic welding system of the type mentioned at the outset, which at least reduces the described disadvantages.

[0011] This problem is solved according to the invention by the fact that the decoupling element is materially bonded to both the ultrasonic vibration unit and the holding element.

[0012] A material-bonded connection encompasses both a one-piece construction, i.e., manufactured from a single piece or material, and a connection achieved through welding or soldering. Therefore, there are no clamping points that can move relative to each other during operation. The design of the connection is also independent of tightening pressures or similar factors. Multiple retaining elements can also be incorporated, each material-bonded to the ultrasonic vibrating element via a decoupling element.

[0013] The retaining element is designed to absorb virtually no vibration. Therefore, in a preferred embodiment, the decoupling element has a mass m1 and the retaining element has a mass m2, where m2 > m1. Preferably, m2 > 10 × m1, and particularly preferably, m2 > 50 × m1. This measure ensures that the retaining element absorbs practically no vibrational energy.

[0014] In a further preferred embodiment, the decoupling element is connected to the ultrasonic vibrating element at a vibration node along its longitudinal direction. Particularly preferred are several decoupling elements bonded to both the ultrasonic vibrating element and the retaining element. Advantageously, all decoupling elements are then connected to the ultrasonic vibrating element at a vibration node along its longitudinal direction.

[0015] Positioning the decoupling element at a node of the acoustic vibration in the longitudinal direction ensures that the acoustic ultrasonic vibration is influenced as little as possible by holding the ultrasonic vibration unit.

[0016] In a further preferred embodiment, the decoupling element and the retaining element are manufactured in one piece, and the decoupling element is connected to the ultrasonic vibrating element via a weld. Alternatively, several decoupling elements can be manufactured in one piece with the retaining element, or, if several retaining elements are provided, in one piece with at least one of the retaining elements.

[0017] This arrangement has proven to be particularly advantageous for vibration simulation using FEM.

[0018] In a further preferred embodiment, the ultrasonic vibrating element has two end faces oriented perpendicular or substantially perpendicular to the longitudinal axis and a circumferential side surface connecting the two end faces. The decoupling element is either connected to the side surface or the ultrasonic vibrating element has a rib on the side surface to which the decoupling element is connected. Furthermore, in a preferred embodiment, the decoupling element has a bearing surface and the ultrasonic vibrating element has a support surface, the support surface resting on the bearing surface. It is advantageous if the bearing surface and the support surface are arranged perpendicular or substantially perpendicular to the longitudinal axis. By providing corresponding surfaces, i.e.,With a contact surface and a support surface, the ultrasonic vibrator can be easily positioned relative to the mounting element, as the corresponding surfaces simply need to be placed on top of each other. In this position, the ultrasonic vibrator can then be bonded to the decoupling element, i.e., the two elements can be welded together, for example.

[0019] It is also possible to provide several decoupling elements, which are either all connected to the same retaining element or each connected to its own retaining element. If several retaining elements are provided, they can, in a preferred embodiment, be arranged on a common support, such as a support plate.

[0020] In a further preferred embodiment, the bearing surface has a chamfer or bevel on its side facing the support surface, and / or the support surface has a chamfer or bevel on its side facing the bearing surface. The chamfer creates a space that can be used to receive a welding or soldering compound in order to strengthen the metallurgical bond between the two elements.

[0021] For example, it is possible to connect the decoupling element and the retaining element by means of a weld on the support surface or the bearing surface, whereby the weld can be designed, for example, as a fillet weld or HV weld.

[0022] In a further preferred embodiment, the retaining element has a top surface on which the decoupling element is arranged. Either the decoupling element projects beyond the top surface, or a recess is provided in the top surface of the retaining element next to the decoupling element.

[0023] This allows the decoupling element to move in a direction perpendicular to the longitudinal direction in order to absorb the occurring thickness vibrations through elastic deformation.

[0024] The retaining element may have a through-opening in which the ultrasonic vibrating element is arranged.

[0025] In a preferred embodiment, the ultrasonic vibrating element is a sonotrode. Alternatively, the ultrasonic vibrating element can also be an amplitude transformer (booster) or a converter.

[0026] Further advantages, features, and applications of the present invention will become clear with reference to the following description of a preferred embodiment and the accompanying figures. These show: Fig. 1 a perspective view of a first embodiment of a sonotrode according to the invention in a holding element, Fig. 2 a partially cut-away side view of the embodiment of Fig. 1, Fig. 3 a sectional view along line AA of Fig. 2, Fig. 4 a detailed enlargement of the in Fig. 2 areas labelled Y, Fig. 5 a detailed enlargement of the in Fig. 3 areas marked with X Fig. 6 a perspective view of a second inventive embodiment, Fig. 7 a sectional view through the embodiment of Fig. 6, Fig. 8 a perspective view of a third inventive embodiment, Fig. 9 a perspective detail view of the embodiment of Fig. 8, Fig. 10 a perspective view of a fourth inventive embodiment, Fig. 11 a perspective detail view of the embodiment of Fig. 10 and Fig. 12 a sectional view of an amplitude transformation piece of a fifth inventive embodiment.

[0027] In Fig. Figure 1 shows a perspective view of a first embodiment according to the invention. A sonotrode 2 has two end faces 3, 11, one of which is designed as a sealing surface 3 and is therefore intended to come into contact with a material to be processed. The two end faces 3, 11 are connected to each other via a circumferential side surface 4. Furthermore, the sonotrode has three through-openings 5, which improve the vibration characteristics of the sonotrode.

[0028] To hold the sonotrode, a retaining element 6 is provided. The retaining element 6 has several decoupling elements 8, four in the example shown, which are integrally formed with the retaining element 6, i.e., manufactured from the same material in one piece. The side surface 4 of the sonotrode 2 has a total of four ribs 7, which are arranged approximately at a node of the resonant ultrasonic vibration of wavelength λ in the direction of the longitudinal axis 10. These ribs 7 have a downward-facing support surface, as shown in the illustration, which rests on a bearing surface on the decoupling elements 8.

[0029] The structure is shown in the partially cut-away side view in Fig. 2 is even more clearly visible.

[0030] The retaining element 6 has a through-opening in which the sonotrode 2 is held, namely on the bearing surfaces of the four decoupling elements 8. The sonotrode 2 is not in contact with the retaining element 6, but only via the overlapping support surfaces of the ribs 7 or the bearing surfaces of the decoupling elements 8.

[0031] As in the view of Fig. 3, which shows a sectional view along line AA of Fig. As can be seen in Figure 2, the decoupling elements 8 are formed by creating a corresponding recess 9 in the retaining element 6. As can be seen in particular... Fig. 4, which shows a close-up of detail Y from Fig. As can be seen from Figure 2, the rib 7 has a length in the transverse direction, i.e., perpendicular to the longitudinal direction 10 and parallel to the side surface 4 to which the rib 7 is attached, that is shorter than the length of the bearing surface of the decoupling element 8 in this direction. This ensures that the support surface of the rib 7 always rests completely on the bearing surface of the decoupling element 8, even if the adjustment of the sonotrode would require a slightly different position relative to the retaining element 6.

[0032] In Fig. Figure 5 is a detailed magnification of area X from Fig. Figure 3 shows the sectional view of the rib 7, which has a support surface on its underside, i.e., on the side facing the decoupling element 8. This support surface has a chamfered or beveled section 13. Similarly, the bearing surface of the decoupling element 8 also has a chamfered section 12. In the embodiment shown, the bearing surface of the decoupling element 8 is wider than the support surface of the rib 7, so that the bearing surface of the decoupling element 8, including the cavity created by the chamfered section 13, provides space for a corresponding weld, which can be a high-strength weld.

[0033] In Fig. Figure 6 shows a perspective view of a second embodiment according to the invention. Fig. Figure 7 shows a corresponding sectional view of the embodiment of Fig. 6 shown. Comparing Fig. 6 with Fig. 1, it becomes clear that the second embodiment differs from the first embodiment only by an additional support plate 14 on which the retaining element 6 is mounted.

[0034] In a preferred embodiment, the retaining element 6 is made of a different material than the support plate 14. The retaining element 6, the manufacture of which is complex, can be manufactured with significantly smaller external dimensions in the second embodiment, since it is held by the support plate 14.

[0035] In Fig. Figure 8 shows a perspective view of a third embodiment of the invention. Comparing... Fig. 8 with Fig. 6, it becomes clear that in the embodiment of Fig. 8 Instead of the retaining element 6 enclosing the sonotrode 2, two retaining elements 15 and 16 are now provided, which hold the sonotrode 2 and are attached to the support plate 14. This is particularly evident in the perspective detail view of Fig. Figure 9 shows that each holding element 15,16 is connected to the sonotrode 2 via two coupling elements.

[0036] In principle, in this embodiment the carrier plate 14 could be dispensed with if it is ensured that the retaining elements 15 and 16 are each attached accordingly.

[0037] In Fig. Figure 10 shows a perspective view of a fourth embodiment of the invention. Fig. Figure 11 shows a perspective detail view of the embodiment of Fig. 10.

[0038] If you compare Fig. 10 with Fig. 8 or Fig. 11 with Fig. 9, it becomes clear that in the fourth embodiment, instead of the two retaining elements 15 and 16, four retaining elements 17, 18, 19 and 20 are now provided, each of which is connected to the sonotrode 2 by means of a coupling element.

[0039] In Fig.Figure 12 shows a sectional view through a fifth embodiment of the invention. This figure illustrates that the connection between a retaining element 22 and an ultrasonic vibrating element, such as an amplitude transformer 21, can also be achieved by the amplitude transformer 21 having a rib 24 on its outer surface and a coupling element 23 having a contact surface extending parallel to the longitudinal axis, which is in contact with a corresponding contact surface of the rib 24. The connection between the coupling element 23 and the rib 24 is welded and thus metallurgically bonded. In this embodiment, a constriction 25 is provided above the rib 24, which reduces the vibrational energy transmitted via the coupling element 23. This design of the connection between the coupling element 23 and the amplitude transformer 21 can also be used in all other embodiments shown.

[0040] The depicted embodiments can be easily calculated using FEM, allowing the device's load limits to be predicted, leading to reproducible results in series production. Assembly has virtually no influence on the load limits. Due to the material-bonded connection, there are no fluctuations in the power input required to maintain the desired vibration amplitude, and heat generation at the clamping surfaces is significantly reduced. The number of components is considerably reduced, thereby lowering costs. Reference symbol list 1 sonotrode with holding element 2 sonotrodes 3 Sealing surface / End face 4 side surface 5 through openings 6 retaining element 7th rib 8 decoupling elements 9 Exclusion 10 Longitudinal direction 11 Front surface 12 beveled section of the bearing surface 13 beveled section of the support surface 14 Carrier plate 15-20 retaining elements 21 Amplitude Transformation Piece 22 retaining element 23 coupling element 24th rib 25 Constriction

Claims

[1] Ultrasonic welding system comprising an ultrasonic vibrating element and a holding element to which the ultrasonic vibrating element is attached via a decoupling element, characterized by that the decoupling element is materially bonded to both the ultrasonic vibrating element and the holding element. [2] Ultrasonic welding system according to claim 1, characterized by , that the ultrasonic vibrating element is designed to be excited by a longitudinal vibration with a wavelength λ such that a standing wave with vibration maxima and at least one vibration node is formed in a longitudinal direction, [3] Ultrasonic welding system according to claim 1 or 2, characterized by that the decoupling element has a mass m1 and the holding element has a mass m2, wherein m2> m1, preferably m2> 10 × m1 and particularly preferably m2> 50 × m1. [4] Ultrasonic welding system according to one of the preceding claims, characterized bythat the decoupling element is connected to the ultrasonic vibrating element at a vibration node in the longitudinal direction of the ultrasonic vibrating element, wherein preferably several decoupling elements are materially bonded to both the ultrasonic vibrating element and the retaining element, or several retaining elements are provided and several decoupling elements are each materially bonded to one of the several retaining elements. [5] Ultrasonic welding system according to any one of the preceding claims, characterized by that the decoupling element and the retaining element are manufactured in one piece, i.e., from a single piece, and that the decoupling element is connected to the ultrasonic vibrating element via a welded connection. [6] Ultrasonic welding system according to one of the preceding claims, characterized bythat the ultrasonic vibrating element has two end faces which are oriented perpendicular or substantially perpendicular to the longitudinal axis, and a circumferential side surface connecting the two end faces, wherein the decoupling element is connected to the side surface or the ultrasonic vibrating element has a rib on the side surface to which the decoupling element is connected. [7] Ultrasonic welding system according to one of the preceding claims, characterized by that the decoupling element has a bearing surface and the ultrasonic vibrating element has a support surface, wherein the support surface rests on the bearing surface, and preferably the bearing surface and the support surface are arranged perpendicular to the longitudinal direction. [8] Ultrasonic welding system according to claim 7, characterized bythat the bearing surface has a chamfer on its side facing the support surface and / or the support surface has a chamfer on its side facing the bearing surface, wherein preferably the decoupling element and the retaining element are materially joined via a weld on the support surface or the bearing surface, wherein the weld is particularly preferably designed as a fillet weld or HV weld. [9] Ultrasonic welding system according to claim 7 or 8, characterized by that the retaining element has a top surface on which the decoupling element is arranged, wherein either the decoupling element protrudes above the top surface or a recess is provided in the top surface next to the decoupling element. [10] Ultrasonic welding system according to claim 6, characterized bythat both the ultrasonic vibrating element and the coupling element have contact surfaces which are aligned parallel to the longitudinal direction and lie on top of each other, wherein preferably the decoupling element and the retaining element are materially joined via a weld seam, wherein the weld seam is particularly preferably designed as a fillet weld or HV weld. [11] Ultrasonic welding system according to one of the preceding claims, characterized by that the retaining element has a through-opening in which the ultrasonic vibrating element is arranged and / or a carrier plate is provided on which the retaining element is attached and which has a through-opening in which the ultrasonic vibrating element is arranged. [12] Ultrasonic welding system according to any one of the preceding claims, characterized by that the ultrasonic vibrating element is a sonotrode.

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