ULTRASONIC WELDING SYSTEM AND METHOD FOR WELDING MATERIALS

Description

[0001] The present invention relates to an ultrasonic welding system comprising an ultrasonic oscillation unit and a counter-tool. The ultrasonic oscillation unit comprises a sonotrode and a converter, wherein the sonotrode and the converter are arranged one behind the other along a longitudinal axis, optionally with an amplitude transformer interposed. The ultrasonic oscillation unit is designed such that it can be resonated with an ultrasonic oscillation in the direction of the longitudinal axis with a wavelength λ.

[0002] The sonotrode has a sealing surface that is arranged parallel to the longitudinal axis or forms an angle of less than 90° with it. The counter tool has a counter tool sealing surface that is arranged such that the material to be processed can be positioned between the sealing surface of the sonotrode and the counter tool sealing surface for welding. The sonotrode and / or counter tool are movable in a processing direction perpendicular to the longitudinal axis, allowing the distance between the sealing surface of the sonotrode and the counter tool sealing surface to be adjusted.

[0003] Such an ultrasonic welding system is known from WO 2020 / 126845.

[0004] The sealing surface of the sonotrode and the counter-tool sealing surface must be movable relative to each other. Firstly, it is necessary to move the two sealing surfaces away from each other in order to position the material to be processed between the two sealing surfaces. Secondly, during the welding process—that is, when the sonotrode is subjected to ultrasonic vibration and its sealing surface comes into contact with the material to be processed—it is necessary to exert a welding force on the material, so the two sealing surfaces are moved toward each other.

[0005] For this purpose, the state of the art provides a linear guide that enables linear movement of the two sealing surfaces toward and away from each other. The ultrasonic vibration unit is mounted on a bracket, which in turn can be moved along the linear guide using a pneumatic cylinder.

[0006] To achieve optimal welding results, it is becoming increasingly important to very precisely adjust the welding force, i.e., the force with which the sealing surface of the sonotrodes presses against the material to be processed. Furthermore, very low welding forces are sometimes sufficient and necessary. However, this is very difficult to achieve using the aforementioned linear guide operated by a pneumatic cylinder. Firstly, friction in the guide and the pneumatic cylinder has a negative effect. Furthermore, hysteresis exists within the pneumatic cylinder, making good reproducibility of the welding force difficult. Furthermore, pneumatic cylinders are relatively slow with small changes in welding force, which has a negative impact on cycle time. CH 362 296 A discloses an ultrasonic welding device according to the preamble of claim 1.DE 10 2013 208749 A1 discloses another ultrasonic welding device with the possibility of a rotary and translatory positioning of a sonotrode.

[0007] Based on the described prior art, it is therefore the object of the present invention to provide an ultrasonic welding system which at least reduces the described disadvantages.

[0008] According to the invention, this object is achieved by an ultrasonic welding device according to claim 1 and by a method according to claim 8.

[0009] The term "perpendicular to the longitudinal axis" refers to any orientation of the rotation axis that lies within a plane oriented perpendicular to the longitudinal axis. Therefore, it is not necessary for the longitudinal axis and the rotation axis to intersect.

[0010] By moving away from the linear guide for adjusting the welding force, a much finer adjustment of the welding force is possible.

[0011] In a preferred embodiment, the sealing surface of the sonotrode has a size of at least 0.25 cm 2< , preferably at least 0.5 cm 2< and most preferably at least 1 cm 2< .

[0012] In a further preferred embodiment, the counter tool has a counter tool sealing surface which is designed to correspond to the sealing surface of the sonotrode, so that the distance between the sealing surfaces is constant during processing.

[0013] According to the invention, the ultrasonic vibration unit or the counter tool is held by a linear mount connected to a linear guide, with which the linear mount can be moved back and forth between two positions in the machining direction. Preferably, a first pneumatic drive is provided for moving the linear mount between the two positions. Thus, the ultrasonic welding system comprises both a rotary mount and a linear mount.

[0014] The linear guide allows the sonotrode and counter-tool to be moved away from each other, allowing the material to be processed to be positioned between the sealing surface of the sonotrode and the counter-tool surface. The linear guide then allows the sonotrode and counter-tool to be moved toward each other again. However, the welding force is adjusted by rotating the ultrasonic oscillating unit around its rotational axis. This allows the linear mount to provide most of the necessary movement, while the rotary mount is used solely for providing and varying the welding force.

[0015] A pneumatic drive may be provided for moving the linear mount between the two positions, as is also known from the prior art.

[0016] According to the invention, either the sonotrode or the counter-tool is held by both the rotary mount and the linear mount, with the sonotrode preferably being held by both the rotary mount and the linear mount. Thus, the function of the linear mount and the rotary mount can be realized by a single linear-rotary mount, which can preferably linearly displace the sonotrode relative to the counter-tool and rotate it about the rotation axis.

[0017] A second pneumatic drive can be provided to move the rotary mount around the rotation axis. This second pneumatic drive can act on a point on the rotary mount that is spaced from the rotation axis. The term "second pneumatic drive" is used here to distinguish it from the optional first pneumatic drive of the linear mount. Thus, embodiments with only a first pneumatic drive, with only a second pneumatic drive, and with both a first and a second pneumatic drive are possible.

[0018] In a particularly preferred embodiment, the drive of the rotary axis, e.g., a pneumatic cylinder, engages at a point on the rotary mount that is farther from the axis of rotation than the sonotrode sealing surface is from the axis of rotation. This allows for very fine adjustment of the welding force.

[0019] A spring, whose spring force is preferably adjustable, can also be provided for the movement of the rotary holder. A coil spring or a gas spring, for example, can be used as the spring. In a preferred embodiment, the spring is preloaded such that, in the intended working position in which a material is to be processed between the sonotrode and the counter-tool, the rotary holder presses the sonotrode and the counter-tool against each other. The spring thus applies a preferably adjustable welding force to the material.

[0020] In a further preferred embodiment, a control system is provided which causes the ultrasonic vibration unit or the counter-tool to rotate about the axis of rotation during welding. The rotation about the axis of rotation during welding, i.e. when both the sealing surface and the counter-tool sealing surface are in contact with the material to be processed, reduces the distance between the sealing surface and the counter-tool sealing surface. The control system is preferably designed such that, during welding, the distance between the sealing surface of the sonotrode and the counter-tool sealing surface is adjusted solely by rotation about the axis of rotation. Therefore, there is no movement of the linear mount.In other words, the movement of the linear holder is only intended to position the sealing surface relative to the counter-tool sealing surface, while the machining is then carried out exclusively by rotation around the rotation axis.

[0021] In a further preferred embodiment, the counter-tool has a receiving element which comprises the counter-tool sealing surface, wherein the receiving element can be fastened to the counter-tool in at least two receiving element positions.

[0022] Depending on the additional force exerted on the rotation axis or the angle by which the ultrasonic vibration unit is rotated around the rotation axis, the point at which the sealing surface of the sonotrode contacts the counter-tool sealing surface shifts. Therefore, in the preferred embodiment, the counter-tool sealing surface can be attached to the counter-tool in at least two positions.

[0023] In a preferred embodiment, the rotary mount comprises a rotary bearing or a flexure joint that enables the ultrasonic vibration unit to rotate about the rotation axis. In a preferred embodiment, the rotation axis does not intersect the longitudinal axis.

[0024] Furthermore, the present invention relates to a method for welding materials, such as metallic strands or metal foils. According to the invention, a method which overcomes the above-mentioned disadvantages is realized by using an ultrasonic welding system as just described. The material to be processed is arranged between the sealing surface of the sonotrode, on the one hand, and the counter-tool sealing surface, on the other. By moving the sealing surface of the sonotrode in the direction of the counter-tool sealing surface by means of the rotary holder, a welding force can then be exerted on the material to be processed. If the ultrasonic vibration unit is set into vibration at the same time, an ultrasonic vibration can be introduced into the material, thereby causing a weld.

[0025] In a preferred embodiment, the ultrasonic vibration unit is first moved along the linear guide in such a way that the distance between the sealing surface of the sonotrode and the counter-tool sealing surface is reduced. The ultrasonic vibration unit is then rotated about the rotation axis, thereby applying the force required for welding to the metallic material to be processed. The method is therefore used in particular for welding metal foils or metallic strands.

[0026] Further advantages, features, and possible applications of the present invention will become clear from the following description of a preferred embodiment and the accompanying figures. They show: Figure 1 shows a side view of an ultrasonic welding system according to the invention in a working position, Figure 2 shows a side view of the ultrasonic welding system of Figure 1in a basic position, Figure 3 a partially sectioned view through the drive for applying the welding force and Figure 4 an exploded view of the counter tool adjustment.

[0027] In Figure 1A working position of an embodiment of the ultrasonic welding system according to the invention is shown. The ultrasonic welding system 1 has an ultrasonic oscillation unit, which in the example shown consists of the sonotrode 2, a converter 3, and an amplitude transformer 4 arranged between the converter 3 and the sonotrode 2. The converter 3 receives a high-frequency electrical signal via the cable 14, which the converter converts into a mechanical longitudinal oscillation, the amplitude of which is modified by the amplitude transformer 4 and transmitted to the sonotrode 2. The converter 3, amplitude transformer 4, and sonotrode 2 are coordinated with one another in such a way that at a specific wavelength, the ultrasonic oscillation unit can be set into a resonant oscillation.

[0028] The ultrasonic oscillation unit is held by a holding element 5 designed as a casing element, which in the example shown encloses the amplitude transformer in a casing-like manner. The holding element 5 is connected to the amplitude transformer 4 in such a way that the oscillation of the ultrasonic oscillation unit is influenced as little as possible. If no amplitude transformer is provided, the holding element can, for example, hold the converter 3. The holding element 5 acts on a vibration node of the standing wave forming along the longitudinal axis. The longitudinal axis A runs in Figure 1 horizontally, so that the sonotrode 2, the amplitude transformer 4 and the converter 3 are arranged one behind the other along the longitudinal axis.

[0029] The sonotrode 2 has several sealing surfaces 12, 13 at its end facing away from the amplitude transformer 4, with one sealing surface 12 facing the counter-tool 11, while another sealing surface 13 faces away from the counter-tool 11. If the ultrasonic vibration unit is used in the position shown, only the sealing surface 12 of the sonotrode 2 is used. If the sealing surface 12 becomes worn during processing, the sonotrode 2 can be rotated about its longitudinal axis, e.g., by 180°, if the holding element 5 is temporarily released, so that the other sealing surface 13 of the sonotrode then lies opposite the counter-tool 11. Only two sealing surfaces 12, 13 can be seen in the figures. However, the sonotrode 2 can also have more than two sealing surfaces. For example, if the sonotrode has four sealing surfaces, these can be used one after the other if the sonotrode 2 is rotated 90° around its longitudinal axis.

[0030] The illustrated embodiment is intended for processing metals. The sealing surfaces 12, 13 are oriented parallel to the longitudinal axis. Particularly when no metallic materials are being processed, the sealing surface can also be arranged orthogonally to the longitudinal axis, so that the end face of the sonotrode facing away from the converter functions as the sealing surface. In this case, the counter-tool sealing surface should also be arranged orthogonally to the longitudinal axis of the ultrasonic vibration unit.

[0031] The holding element 5 is attached to a lever element 6, which is connected to a slide element 17 via a pivot bearing 7. The slide element 17 is movable back and forth between two positions in the vertical direction, i.e. perpendicular to the longitudinal axis, via a linear guide 15. To accomplish this, the pneumatic cylinder 9 is provided. When the pneumatic cylinder 9 is actuated, the slide element 17 is moved upwards. Such a position is in Figure 2 shown. The lever element 6 has a pivot bearing 8 remote from the rotation axis 7, which can be pulled downwards in a vertical direction via the second pneumatic cylinder 10, so that the lever element 6, including the ultrasonic vibration unit attached thereto, rotates clockwise about the rotation axis 7.

[0032] In Figure 2a basic position is shown in which both the pneumatic cylinder 9 has moved the carriage element 17 into its upper position and the second pneumatic cylinder 10 has moved the pivot bearing 8 into its lower position, causing the ultrasound system to tilt about the rotation axis 7.

[0033] In the Figure 2 In the position shown, the material to be processed, which is preferably a metallic material, can be positioned between the sealing surface 12 of the sonotrode and the counter-tool sealing surface 16.

[0034] When processing is now started, the carriage element 17 is first moved downward via the linear guide 15 with the aid of the first pneumatic cylinder 9, thereby reducing the distance between the sealing surface 12 of the sonotrode 2 and the counter-tool sealing surface 16. During this time, the ultrasonic vibration unit can already be excited with an ultrasonic vibration. However, this can also occur at a later time, immediately before the welding process.

[0035] For the welding process, only the second pneumatic cylinder 10 is required, which rotates the pivot bearing 8 and thus the lever element 6 counterclockwise around the axis of rotation 7 and thus exerts a welding force via the sealing surface 12 of the sonotrode 2 onto the material to be processed.

[0036] For clarification, Figure 3a partially sectioned detailed view of the pivot bearing 8 in the lever element 6 is shown. The second pneumatic cylinder 10 is connected to the carriage 17. By moving the piston, which is connected to the pivot bearing 8, the pivot bearing 8 can be moved toward the carriage 17 or away from it. Since the pivot bearing is rotatably connected to the lever element 6, the lever element 6 can be rotated a few degrees clockwise or counterclockwise about the axis 7, whereby the sealing surface 12 of the sonotrode 2 is also rotated about the axis of rotation 7.

[0037] In Figure 41 shows an exploded view of the counter tool 11. The counter tool 11 consists of a lower counter tool carrier 26, an upper counter tool carrier 18, and a receiving element 19 which can be fastened thereto and which comprises the sealing surface member 25 with the counter tool sealing surface 16. The upper counter tool carrier 18 can be adjusted in height relative to the lower counter tool carrier 26 in order to roughly adjust the distance between the counter tool 11 and the sonotrode 2. The upper counter tool carrier 18 has molded-in grooves 21 and protruding sliding blocks 22. The receiving element 19 can thus be placed on the counter tool carrier 18 such that the sliding blocks 22 of the upper counter tool carrier 18 come to rest in the corresponding grooves of the receiving element 19. In this position, the receiving element 19 can be moved relative to the upper counter tool carrier 18 along the alignment of the grooves.This displacement is achieved by means of the threaded rod 20, which rests in the groove 23 and rests against the groove base. By rotating the threaded rod 20, the receiving element 19 can be displaced in the direction of the grooves 21 relative to the upper counter-tool carrier 18. The receiving element 19 can be attached to the upper counter-tool carrier using fastening screws 24.

[0038] The receiving element 19 comprises a sealing surface member 25, which has the counter-tool sealing surface 16. Therefore, by rotating the threaded rod 20, the counter-tool sealing surface 16 can be moved. Reference symbol

[0039] 1 Ultrasonic welding system 2 Sonotrode 3 Converter 4 Amplitude transformer 5 Holding element 6 Lever element 7, 8 Pivot bearing 9 First pneumatic cylinder 10 Second pneumatic cylinder 11 Counter tool 12, 13 Sealing surface 14 Cable 15 Linear guide 16 Counter tool sealing surface 17 Slide element 18 Upper counter tool carrier 19 Mounting element 20 Threaded rod 21 Molded grooves 22 Protruding T-nuts 23 Groove 24 Fastening screws 25 Sealing surface element 26 Lower counter tool carrier

Claims

1. An ultrasonic welding installation (1) with an ultrasonic oscillating unit which comprises a sonotrode (2) and a converter (3), wherein the sonotrode (2) and the converter (3) are arranged one after the other along a longitudinal axis, optionally with the interposition of an amplitude transformer, and the ultrasonic oscillating unit can be caused to resonate with an ultrasonic oscillation with a wavelength λ in the direction of the longitudinal axis, and with a counterpart tool (11), wherein the sonotrode (2) comprises a sealing surface (12; 13) and the longitudinal axis extends parallel to the sealing surface (12, 13) or forms an angle of less than 90° with the latter, wherein the counterpart tool (11) comprises a counterpart tool sealing surface (16) which faces the sealing surface (12, 13) of the sonotrode (2), and the sonotrode (2) and the counterpart tool (11) are movable relative to one another in a processing direction perpendicular to the longitudinal axis, whereby the distance between the sealing surface (12, 13) of the sonotrode (2) and the counterpart tool sealing surface (16) can be adjusted, wherein the ultrasonic oscillating unit or the counterpart tool is held by a rotary holder which can be rotated about a rotation axis extending perpendicularly to the longitudinal axis, wherein the rotation axis is arranged in such a way that the distance between the sealing surface (12, 13) of the sonotrode (2) and the counterpart tool sealing surface (16) can be adjusted by rotating the rotary holder, wherein the ultrasonic oscillating unit or the counterpart tool is held by a linear mount which is connected to a linear guide by means of which the linear mount can be moved back and forth in the processing direction between two positions, characterized in that either the sonotrode or the counterpart tool is held by both the rotary holder and the linear mount.

2. The ultrasonic welding installation (1) according to claim 1, characterized in that a first pneumatic drive is provided for moving the linear mount between the two positions.

3. The ultrasonic welding installation (1) according to claim 1 or 2, characterized in that the sonotrode is held by both the rotary holder and the linear mount.

4. The ultrasonic welding installation (1) according to any one of claims 1 to 3, characterized in that a second pneumatic drive is provided for rotating the ultrasonic oscillating unit about the rotation axis, wherein the second pneumatic drive preferably engages a point of the first holder that is spaced from the rotation axis.

5. The ultrasonic welding installation according to any one of the preceding claims, characterized in that a control is provided which, during the welding processing, causes the ultrasonic oscillating unit or the counterpart tool to rotate about the rotation axis, wherein preferably the control is configured in such a way that, during the welding processing, the distance between the sealing surface (12, 13) of the sonotrode (2) and the counterpart tool sealing surface (16) is adjusted solely by the rotation about the rotation axis.

6. The ultrasonic welding installation (1) according to any one of claims 1 to 5, characterized in that the counterpart tool (11) provides a receiving element (19) which comprises the counterpart tool sealing surface (16), wherein the receiving element (19) can be fixed to the counterpart tool (11) in at least two receiving element positions.

7. The ultrasonic welding installation (1) according to any one of claims 1 to 6, characterized in that the rotary holder comprises a rotary bearing or a solid-state joint which enables the ultrasonic oscillating unit to be rotated about the rotation axis.

8. A method for welding processing of materials, such as metallic braids or metal foils, characterized in that an ultrasonic welding installation (1) according to any one of claims 1 to 7 is used, that a material to be processed is positioned between the sealing surface of the sonotrode and the counterpart tool sealing surface while the ultrasonic oscillating unit is excited with an ultrasonic vibration.

9. The method according to claim 8, characterized in that for applying a welding force to a metallic material arranged between the sealing surface (12, 13) of the sonotrode (2) and the counterpart tool sealing surface (16), the ultrasonic oscillating unit is rotated about its rotation axis.

10. The method according to claim 9, characterized in that first the ultrasonic oscillating unit is moved along the linear guide in such a way that the distance between the sealing surface (12, 13) of the sonotrode and the counterpart tool sealing surface (16) is reduced, and then, by rotating the ultrasonic oscillating unit about the rotation axis, the force necessary for the welding processing is applied to the metallic material to be processed.