TORSIONAL ULTRASONIC MACHINING SYSTEM AND METHOD FOR TUNING A TORSIONAL OSCILLATOR

Description

[0001] The invention relates to torsional ultrasonic processing systems, in particular ultrasonic welding systems, comprising a torsional oscillator that can be excited to torsional vibrations about a torsional axis and a processing surface, in particular a welding surface, that is vibration-coupled thereto. Such ultrasonic welding systems are known, for example, from EP 1 930 148, DE 10 2009 027 021, WO 2011 / 138404, and WO 2012 / 069413.

[0002] US 3,257,712 A discloses the support of a torsional oscillator in a vibration node, i.e. in an amplitude minimum of the torsional vibrations.

[0003] JP S57 178826 shows an oscillator connected to a holder via a horn. Ultrasonic waves are generated by the oscillator, causing the holder to rotate alternately in different directions to generate frictional heat around the abutting surfaces and facilitate their fusion.

[0004] Although state-of-the-art torsional ultrasonic welding systems have proven their worth, there is still a need for further improvements in some areas. For example, in every ultrasonic welding process, the vibrating parts should be acoustically decoupled from the static parts as much as possible to minimize energy losses and heat generation. One of the problems is that a disruptive, broadband second torsional resonance often occurs during idle operation or when the welding surface is fully blocked, within a desired operating range. For example, at a mean frequency of 20 kHz, this can have a width of ± 1 kHz. Furthermore, tuning the torsional oscillator to the correct resonance frequency is often challenging.

[0005] It is therefore an object of the present invention to further develop known ultrasonic processing systems, in particular ultrasonic welding systems, in this regard. In particular, the aim is to achieve the best possible acoustic decoupling, facilitate tuning of the torsional oscillator, occupy the smallest possible space, reduce mass, and / or suppress bending vibrations.

[0006] These and other objects are achieved by an ultrasonic processing system according to the invention as defined in claim 1. The ultrasonic processing system can be, for example, an ultrasonic joining system with which two or more components can be connected, in particular welded and / or soldered. In these embodiments, the processing surface can be configured as a welding surface or soldering surface. Alternatively, the ultrasonic processing system can also be, for example, an ultrasonic punching system.

[0007] The ultrasonic processing system, in particular the ultrasonic welding system, can further comprise at least one fastening ring that at least partially surrounds and holds the torsional oscillator.

[0008] The mounting ring holds the torsional oscillator in the range of a maximum amplitude of the torsional oscillations. By definition, in the "range of a maximum amplitude of the torsional oscillations," the amplitude of the torsional oscillations is at least 30% of the maximum amplitude of the torsional oscillations.

[0009] This is a departure from the prior art, for example, from that disclosed in US Pat. No. 3,257,712 A, which proposes mounting in the region of an amplitude minimum. This arrangement of the mounting ring has the advantage that the otherwise disruptive, broadband second torsional resonance during idle operation or when the machining surface is fully blocked is no longer within a desired operating range, which, for example, can have a width of ± 1 kHz at a mean frequency of 20 kHz.

[0010] To generate torsional vibrations of the torsional oscillator, at least two vibration generators are provided in a conventional manner. The vibration generator contains at least one ultrasonic converter and at least one transmission piece, which can be formed integrally with one another. In the ultrasonic converter, which can contain, for example, a stack of piezoelectric discs, electrical vibrations are converted into mechanical ultrasonic vibrations. The ultrasonic converter is vibrationally coupled to the torsional oscillator via the transmission piece, with the transmission piece being designed to execute longitudinal vibrations and coupled tangentially to the torsional oscillator.

[0011] Advantageously, the fastening ring has a flange-shaped portion and a sleeve-shaped portion extending from the flange-shaped portion in the direction of the torsion axis. The flange-shaped portion can be attached in an outer region to a static part of the ultrasonic processing system, preferably via first damping means explained in more detail below. The sleeve-shaped portion preferably extends from the inner region of the flange-shaped portion.

[0012] Furthermore, the fastening ring can have a retaining ring that extends radially inward from the axial end of the sleeve-shaped section facing away from the flange-shaped section. A radially inner end of the retaining ring can hold the torsional oscillator and, for example, be shrunk onto it. This design results in overall sound decoupling over a very short distance, which, among other things, can reduce the installation space. The torsional oscillator can expediently be tapered in the area where it is held by the retaining ring. This enables clean mechanical processing and eliminates bending vibrations.

[0013] Particularly advantageously, at least one decoupling opening is formed in the sleeve-shaped section of the fastening ring. The decoupling opening penetrates the sleeve-shaped section in the radial direction. For example, the decoupling opening can be designed as an elongated hole whose longitudinal axis extends in the direction of the torsion axis. Preferably, the sleeve-shaped section contains several decoupling openings, in particular elongated holes, which are advantageously evenly distributed around the circumference. The webs formed between such decoupling openings, in particular elongated holes, can effectively absorb torsional forces and torsional deflections, which ensures improved sound decoupling. Alternatively, it is also conceivable and within the scope of the invention for the elongated holes to extend in the circumferential direction with respect to the torsion axis.

[0014] A fastening ring is particularly advantageous when the machining surface is arranged on a front side of the torsional oscillator, i.e., essentially perpendicular to the torsional axis. This is because, in this arrangement, the direction of force and movement is parallel to the torsional axis. This arrangement is implemented, for example, in the SoniqTwist system marketed by the applicant. However, it is also conceivable that a fastening ring according to the first aspect is used when the machining surface is arranged on a circumferential side of the torsional oscillator.

[0015] The mounting ring can be positioned between a coupling point, where the torsional oscillator is excited to oscillate, and the welding surface with respect to the torsion axis. Alternatively, the mounting ring can be positioned opposite the welding surface with respect to a coupling point. The second variant allows for a more symmetrical arrangement and a shorter distance between the welding surface and the coupling point.

[0016] A second aspect also relates to a method according to claim 15 for tuning a torsional oscillator of a torsional ultrasonic processing system, in particular an ultrasonic welding system, that can be excited to torsional oscillations about a torsional axis. In this method, at least one tuning ring is selected and connected to the torsional oscillator in such a way that it at least partially surrounds it, and the torsional oscillator, with the tuning ring connected thereto, has an operating frequency in a predetermined frequency range.

[0017] The tuning ring expands the possibilities for changing the geometry of the torsional oscillator without having to change its operating frequency. For example, it is possible to change the length of the torsional oscillator, particularly by reducing it. This can be useful for suppressing interfering resonances, such as broadband second torsional resonances. Without further measures, however, this change in geometry would also change the operating frequency. By selecting the appropriate tuning ring, this shift in the operating frequency can be at least partially or even completely compensated.

[0018] The tuning ring is preferably tuned to the torsional oscillator based on its mass such that the torsional oscillator and the connected tuning ring have an operating frequency within the specified frequency range. This allows for particularly simple tuning. For example, the mass of the tuning ring can be adjusted by selecting its outer diameter and / or its axial height.

[0019] The tuning ring can, for example, be shrunk onto the torsional oscillator.

[0020] It is particularly advantageous to connect the tuning ring to the torsional oscillator in the area of ​​a maximum amplitude of the torsional vibrations. As already mentioned above, in the "area of ​​a maximum amplitude of the torsional vibrations," the amplitude of the torsional vibrations is at least 30% of the maximum amplitude of the torsional vibrations. This arrangement enables particularly effective tuning, because the influence of the tuning ring is greater the closer it is to a maximum amplitude of the torsional vibrations. This allows the mass of the tuning ring to be kept as small as possible.

[0021] For practical purposes, the torsional oscillator can be tapered in the area of ​​the tuning ring. This allows for clean machining and eliminates bending vibrations.

[0022] A tuning ring according to the second aspect is particularly advantageous when the machining surface is arranged on a circumferential side of the torsional oscillator, i.e., runs essentially parallel to the torsion axis. This arrangement is realized, for example, in the PowerWheel system marketed by the applicant.

[0023] The ultrasonic processing system can include first damping means, in particular for passively damping the torsional oscillator. In particular, the first damping means are designed, in particular, for passively damping vibrations of the torsional oscillator in the range from 10 Hz to 10 kHz. In this way, in some embodiments, crack formation in the region of the connection between the torsional oscillator and a vibration generator, in particular an ultrasonic converter of a vibration generator, can be prevented. Alternatively, however, the first damping means can also be used for actively damping the torsional oscillator, such as piezo actuators in a frequency range from 10 Hz to 10 kHz.

[0024] If the ultrasonic processing system includes a mounting ring, it is advantageously mounted on a static part of the ultrasonic connection system via the first damping means. This allows for particularly effective reduction of disruptive resonant vibrations, particularly in a frequency range of 10 Hz to 10 kHz. Passive first damping means can, for example, include at least one layer of an elastic, damping material, such as rubber.

[0025] In the case of an ultrasonic joining system, for example an ultrasonic welding system, second damping means are advantageously provided alternatively or additionally, particularly for passively damping an anvil of the ultrasonic joining system. The anvil is preferably mounted on an anvil holder via the second damping means. This also allows disruptive resonant vibrations to be reduced particularly effectively. Passive second damping means can, for example, contain at least one layer of an elastic, damping material, for example rubber. Alternatively, second damping means can be provided for actively damping the anvil, such as piezo actuators in a frequency range of 10 Hz to 10 kHz.

[0026] The ultrasonic processing system according to the invention contains at least one torsional oscillator, at least one processing surface vibrationally coupled to the torsional oscillator, at least two vibration generators, each with at least one ultrasonic converter and at least one transmission piece connected thereto, in particular integrally, at a connection point, which can be excited to longitudinal vibrations along an vibration axis by means of at least one of the ultrasonic converters and is coupled tangentially to the torsional oscillator at a coupling point in order to excite it to torsional vibrations about a torsional axis.

[0027] In the ultrasonic converter, which can, for example, contain a stack of piezoelectric discs in a conventional manner, electrical vibrations are converted into mechanical ultrasonic vibrations.

[0028] According to the invention, at least two of the vibration generators are connected to each other via an intermediate web. This allows for static and / or dynamic amplification, resulting in increased stability.

[0029] The transmission sections of at least two vibration generators connected by an intermediate web have parallel vibration axes. With such an arrangement of the vibration axes, the aforementioned effect of the intermediate web is particularly pronounced.

[0030] Preferably, the intermediate web is connected to the vibration generator at both ends via a connection point as described above. This allows for particularly effective amplification.

[0031] At least one of the transmission pieces has a length along its oscillation axis from the connection point to the coupling point that is at least approximately equal to a quarter wavelength of the longitudinal oscillations during normal operation of the ultrasonic processing system. A length l is considered "at least approximately equal to a quarter wavelength" λ / 4 if 0.9 λ / 4 ≤ 1 ≤ 1.1 λ / 4.

[0032] In contrast to previously known ultrasonic processing systems, the dimension of the transmission piece is not an integer multiple of half the wavelength, but at least approximately equal to a quarter wavelength. This shorter design allows disruptive bending vibrations to be largely suppressed. In this way, in some embodiments, crack formation in the area of ​​the connection between the torsional oscillator and the vibration generator, in particular its ultrasonic converter, can be prevented. Furthermore, the mass and size of the ultrasonic processing system can be reduced. Surprisingly, it has also been discovered that such a short design is sufficient to efficiently excite the torsional oscillator to torsional vibrations.

[0033] The ultrasonic converter can also have a length along the oscillation axis equal to a quarter wavelength (λ / 4) of the longitudinal oscillations during normal operation of the ultrasonic processing system. In the case of a single ultrasonic converter and a single transmission piece, the overall length of the oscillation generator along the oscillation axes is equal to half a wavelength (λ / 2) of the longitudinal oscillations during normal operation of the ultrasonic processing system.

[0034] The invention will be explained in more detail below with reference to exemplary embodiments and drawings. Figure 1: a perspective view of a first torsional ultrasonic processing system with four ultrasonic converters and a mounting ring; Figure 2a: a perspective view of a second torsional ultrasonic processing system with four ultrasonic converters and a tuning ring; Figure 2b: a partially sectioned side view of the second torsional ultrasonic processing system; Figure 2c: a detailed view of section A from Figure 2b; Figure 3a: a perspective view of a part with two ultrasonic converters and a fastening ring; Figure 3b: a further perspective view of a third ultrasonic processing system; Figure 3c: a side sectional view of the third ultrasonic processing system; Figure 4: a perspective view of a fourth ultrasonic processing system with two ultrasonic converters and a tuning ring; Figure 5a: a perspective view of a fifth embodiment according to the invention with two short vibration generators; Figure 5b: a side view of the fifth embodiment according to the invention; Figure 5c: a top view of the fifth embodiment according to the invention; Figure 5d: a front view of the fifth embodiment according to the invention; Figure 6: a side sectional view of a sixth embodiment according to the invention, showing damping of an anvil.

[0035] The Figure 1The partially illustrated torsional ultrasonic welding system 10 contains a torsional oscillator 11, which can be excited to torsional oscillations with the aid of four ultrasonic converters 21, in a manner known per se, for example, from DE 10 2009 027 021. In the ultrasonic converters 21, which can contain stacks of piezoelectric disks, for example, electrical oscillations are converted into mechanical ultrasonic oscillations. Four transmission pieces 26 are each connected at one of their ends 28 to one of the ultrasonic converters 21 and can thereby be excited to longitudinal oscillations along an oscillation axis S. Two ultrasonic converters 21 and a transmission piece 26 arranged between them form a vibration generator 36. The other ends of the transmission pieces 26 are coupled tangentially to the torsional oscillator 11 at coupling points 27.The transmission pieces 26 and the torsional oscillator 11 are formed integrally with one another. This allows the latter to be excited to torsional vibrations about a torsional axis T. The ultrasonic welding system 10 further includes a welding surface 12 that is vibrationally coupled to the torsional oscillator 11 and is arranged on an end face of the torsional oscillator 11. Furthermore, the ultrasonic welding system 10 includes, among other things, a . Figure 1 anvil not shown.

[0036] A fastening ring 13 surrounds and holds the torsional oscillator 11 in the region of an amplitude maximum M. The fastening ring 13 is arranged between the coupling points 27 and the welding surface 12 with respect to the torsion axis T. It has a flange-shaped section 23 and a sleeve-shaped section 14 extending from the flange-shaped section 23 in the direction of the torsion axis T. In said section, elongated holes 15 are formed, evenly distributed around the circumference, which penetrate the sleeve-shaped section 14 in the radial direction and whose longitudinal axes extend in the direction of the torsion axis T. The webs 22 formed between the elongated holes 15 can effectively absorb torsional forces and torsional deflections, which ensures improved sound decoupling. In addition, the risk of cracks or even fractures in the area of ​​the connection between the torsional oscillator 11 and the ultrasonic converters 21 can be reduced.Furthermore, the fastening ring 13 has a retaining ring 30, which extends radially inward from the axial end of the sleeve-shaped section 14 facing away from the flange-shaped section 23. A radially inner end of the retaining ring is shrunk onto the torsional oscillator 11 and thus holds it (see also . Figure 3c , which shows a sectional view of a similar ultrasonic processing system according to the invention).

[0037] The Figures 2a to 2cThe second ultrasonic welding system 10 according to the invention shown contains a tuning ring 16 instead of a fastening ring. The tuning ring 16 surrounds the torsional oscillator 11 and is connected to it and tuned to it in such a way that the torsional oscillator 11, with the tuning ring 16 connected to it, has an operating frequency in a predetermined frequency range. This makes it possible to design the torsional oscillator 11 to be comparatively short, whereby disruptive resonances can be suppressed. The shift in the operating frequency that occurs without further measures can be at least partially or even completely compensated for by suitable selection of the tuning ring 16. For this purpose, for example, the outer diameter and / or the axial height of the tuning ring 16 can be selected accordingly.

[0038] The Figures 3a to 3cshow a further ultrasonic welding system 10 according to the invention, which also contains a fastening ring 13, but only two instead of four ultrasonic converters 21. Here, only a single ultrasonic converter 21 and a transmission piece 26 connected thereto form a vibration generator 36. These excite the torsional oscillator 11 in the manner shown in principle in WO 2011 / 138404 to torsional vibrations about a torsional axis T. The fastening ring 13 surrounds and holds the torsional oscillator 11 in the area of ​​an amplitude maximum M (see also Figure 3c ).

[0039] The Figures 3b and 3c show how the Figure 3aillustrated components of the third embodiment according to the invention are mounted. The flange-shaped section 23 of the fastening ring 13, of which only the retaining ring 30 is visible here, is fastened to a static part 33 of the ultrasonic welding device 10 with the aid of two fastening plates 31 and several fastening screws 32. Between an underside of the flange-shaped section 23 and the static part 33, as well as between an upper side of the flange-shaped section 23 and the fastening plate 31, there is a layer 17 made of an elastic, damping material, for example rubber. The layers 17 form first damping means for passively damping the torsional oscillator 11 and can prevent cracks from forming in the region of the connection between the torsional oscillator 11 and the ultrasonic converters 21.

[0040] In Figure 4another ultrasonic welding system 10 according to the invention with two ultrasonic converters 21 and a tuning ring 16 is shown.

[0041] The Figures 5a to 5d The partially illustrated ultrasonic welding system 10 contains a torsional oscillator 11 with a welding surface 12, a fastening ring 13, and two oscillators 36. Each of the oscillators 36 contains two ultrasonic converters 21 and a transmission piece 26 arranged between the ultrasonic converters 21, which are connected, in particular integrally, at connection points 39. At two opposite coupling points 27, the transmission pieces 26 are coupled to the torsional oscillator 11 at their centers 38.

[0042] In contrast to the examples according to Figures 1 and 3a to 3cHere, the fastening ring 13 is arranged opposite the welding surface 12 with respect to the coupling points 27. This allows a more symmetrical arrangement and a shorter distance between the welding surface 12 and the coupling points 27. Also in contrast to the embodiments according to Figures 1 and 3a to 3c the fastening ring 13 here contains elongated holes 15 whose longitudinal axes extend in the circumferential direction with respect to the torsion axis T.

[0043] The transmission pieces 26 have a length l along their oscillation axes S from the connection points 39 to the coupling point 27, which is equal to a quarter wavelength λ / 4 of the longitudinal oscillations during normal operation of the ultrasonic processing system 10. The ultrasonic converters 21 also have a length L along the oscillation axes S, which is equal to a quarter wavelength λ / 4 of the longitudinal oscillations during normal operation of the ultrasonic processing system 10. Overall, the oscillation generators 36 have a length along the oscillation axes S that is equal to a whole wavelength λ of the longitudinal oscillations during normal operation of the ultrasonic processing system 10.

[0044] At the connection points 39, three retaining clamps 24 are arranged, evenly distributed in the circumferential direction, to which the vibration generators 36 are held on a static part of the ultrasonic welding system 10. The connection points 39 are arranged at vibration nodes.

[0045] The shorter design of the vibration generators 36 along the vibration axes S allows for the large suppression of disruptive bending vibrations. This prevents crack formation in the area of ​​the connection between the torsional oscillator 11 and the vibration generators 36. Furthermore, the size and mass of the ultrasonic welding system 10 are reduced. Nevertheless, such short vibration generators 36 are sufficient to efficiently excite the torsional oscillator 11 to torsional vibrations.

[0046] As especially in Figure 5cAs can be seen, the two transmission pieces 36 are connected to each other via two intermediate webs 25. Each intermediate web 25 is connected at its two ends to a connection point 39 of the vibration generators 36. This ensures static and dynamic amplification of the vibrating components.

[0047] In Figure 6 1 schematically shows part of another ultrasonic welding system 10 according to the invention. It shows an anvil 19 and an anvil mount 20. A layer 18 made of an elastic, damping material, such as rubber, is formed between the anvil 19 and the anvil mount 20. The layer 18 thus represents a second damping means 18, via which the anvil 19 is mounted on the anvil mount 20.

Claims

1. Torsional ultrasonic processing system (10), in particular ultrasonic welding system (10), comprising - at least one torsional oscillator (11), - at least one working surface (12) coupled to the torsional oscillator (11) in an oscillating manner, - at least two vibration generators (36), each having at least one ultrasonic converter (21) and at least one transmission piece (26) which is connected thereto, in particular integrally, at a connection point (39), which transmission piece can be excited to longitudinal vibrations along a vibration axis (S) by means of at least one of the ultrasonic converters (21) and is coupled tangentially to the torsional oscillator (11) at a coupling point (27) in order to excite the latter to torsional vibrations about a torsional axis (T), characterized in that the at least two vibration generators (36) are connected to one another via an intermediate bar (25) connected in each case to the connection point (3) of the vibration generators (36), and in that the connection point (3) is arranged at a vibration node, with the transmission pieces (26) of at least two vibration generators (36) connected to one another via an intermediate bar (25) having vibration axes (S) which are parallel to one another.

2. Ultrasonic processing system (10) according to claim 1, wherein the intermediate bar (25) is connected at its two ends to a respective connection point (39) of the vibration generator (36).

3. Ultrasonic processing system (10) according to one of the preceding claims, wherein at least one of the transmission pieces (26) has a length (l) along its oscillation axis (S) from the connection point (39) to the coupling point (27) which is at least approximately equal to a quarter wavelength (λ / 4) of the longitudinal oscillations during intended operation of the ultrasonic processing system (10).

4. Ultrasonic processing system (10) according to claim 3, wherein the at least one of the transmission pieces (26) is connected at each end (28) to a respective ultrasonic converter (21), in particular in one piece, and the coupling point (27) is arranged in a center (29) of the transmission piece (26).

5. Ultrasonic machining system (10) according to one of the preceding claims, further comprising at least one fastening ring (13) at least partially surrounding and holding the torsional transducer (11), wherein the fastening ring (13) holds the torsional transducer (11) in the region of a maximum amplitude (M) of the torsional vibrations.

6. Ultrasonic machining system (10) according to claim 5, wherein the torsional oscillator (11) can be excited to torsional oscillations about a torsional axis (T) and the fastening ring (13) has a flange-shaped section (23) and a sleeve-shaped section (14) extending from the flange-shaped section (23) in the direction of the torsional axis (T), in which at least one decoupling opening (15) is formed, which penetrates the sleeve-shaped section (14) in the radial direction.

7. Ultrasonic machining system (10) according to one of the preceding claims, wherein the ultrasonic processing system (10) comprises at least one tuning ring (16) which at least partially surrounds the torsional transducer (11) and which is connected to the torsional transducer (11) and tuned thereto in such a way that the torsional transducer (11) with the tuning ring (16) connected thereto has an operating frequency in a predetermined frequency range.

8. Ultrasonic machining system (10) according to claim 7, wherein the tuning ring (16) is connected to the torsional transducer (11) in the region of a maximum amplitude (M) of the torsional vibrations.

9. Ultrasonic machining system (10) according to one of the preceding claims, further comprising first damping means (17) for in particular passively damping the torsional vibrator (11), preferably for in particular passively damping vibrations of the torsional vibrator (11) in the frequency range from 10 Hz to 10 kHz.

10. Ultrasonic machining system (10) according to claim 9, wherein the ultrasonic machining system (10) comprises at least one fixing ring (13) at least partially surrounding and holding the torsional oscillator (11), wherein the fastening ring (13) holds the torsional oscillator (11) in the region of a maximum amplitude (M) of the torsional oscillations, and the fastening ring (13) being mounted on a static part of the ultrasonic connection system (10) via the first damping means (17).

11. Ultrasonic processing system (10) according to claim 10, wherein the first damping means (17) comprise at least one layer of an elastic, damping material, for example rubber.

12. Ultrasonic processing system (10) according to one of the preceding claims, which is designed as an ultrasonic welding system (10) and further comprises an anvil (19) and second damping means (18) for in particular passively damping the anvil (19), preferably for in particular passively damping vibrations in the frequency range from 10 Hz to 10 kHz.

13. Ultrasonic processing system (10) according to claim 12, wherein the second damping means (18) comprise at least one layer of an elastic, damping material, for example rubber.

14. Method for tuning a torsional oscillator (11) of an ultrasonic processing system (10), which can be excited to torsional oscillations about a torsional axis (T), according to one of the preceding claims, wherein at least one tuning ring (16) is selected and connected to the torsional transducer (11) in such a way that it at least partially embraces the latter and the torsional transducer (11) with the tuning ring (16) connected thereto has an operating frequency in a predetermined frequency range.