Ultrasonic tool and method for machining workpiece by means of mechanical ultrasonic oscillation

Abstract

The invention relates to an ultrasonic tool and a method for machining a workpiece using ultrasonic mechanical oscillation.

Description

Summary of the invention

[0001] The invention relates to an ultrasonic tool and a method for machining a workpiece by means of mechanical ultrasonic oscillation.

[0002] For example, ultrasonic tools are used to weld or separate parts, in particular material webs. For this purpose, the ultrasonic tool has an ultrasonic vibration unit, which includes a converter component and a sonotrode. The sonotrode can be connected to the converter component directly or via an amplitude intensifier.

[0003] The workpiece, such as a plastic film, is usually arranged on a counter tool (anvil), wherein the workpiece can also be continuously conveyed via the counter tool. In any case, when processing the workpiece, the workpiece is located between the sonotrode and the counter tool.

[0004] The converter member comprises a converter, which usually comprises several piezoelectric elements and converts an applied AC voltage, usually provided by a generator, into a mechanical movement of the same frequency. Each piezoelectric element is connected on the one hand to a phase conductor of the generator and on the other hand to a neutral conductor of the generator. If an AC voltage is applied to these conductors, the piezoelectric elements alternately lengthen and shorten, thus generating ultrasonic oscillations.

[0005] The piezoelectric element is usually arranged in a converter housing, which serves to protect the piezoelectric element as much as possible from environmental influences. The converter housing is usually connected to the neutral conductor and is therefore at its electrical potential.

[0006] If the line between the generator and the neutral point fails, for example, is disconnected, a fault may occur. The phase conductors supply further charge, so that the piezoelectric elements are further excited. As a result, a potential is generated at the other end of each piezoelectric element, but due to the fault, this potential cannot be dissipated via the neutral conductor. This potential is then applied to the converter housing. For reasons of occupational safety, this is undesirable, since bystanders could come into contact with live components in this way. This problem is usually solved by additional grounding of the converter housing with the aid of a protective conductor.

[0007] At the same time, in some cases, the contact between the sonotrode and the countertool is to be detected. For example, it is known from EP 0 790 888 B1 that the change in resistance, current or voltage between the sonotrode and the countertool is detected with the aid of a measuring device. There, it is not yet possible to ground the converter housing via a protective conductor. Therefore, in the past, it was necessary to take extensive safety precautions in these applications, such as extensive insulation of the piezoelectric elements in the converter housing.

[0008] The invention is therefore based on the problem of increasing the occupational safety of ultrasonic tools, in which the contact between the sonotrode and the countertool is to be detected.

[0009] This problem is solved by an ultrasonic tool according to claim 1 .

[0010] The problem is solved by an ultrasonic tool for machining a workpiece by means of mechanical ultrasonic oscillations, the ultrasonic tool having a converter component and a sonotrode, wherein the converter component comprises a converter, the converter comprising at least one piezoelectric element, wherein the converter component comprises a phase conductor and a neutral conductor for supplying an AC voltage. The phase conductor and the neutral conductor form two poles of the converter or two poles of at least one piezoelectric element. The at least one piezoelectric element is arranged to convert the AC voltage into mechanical ultrasonic oscillations. The converter component can be arranged to oscillate resonantly with the mechanical ultrasonic oscillations of wavelength λ and is mechanically coupled to the sonotrode. The sonotrode and the converter component are tuned to each other so that the sonotrode can be arranged to oscillate resonantly with the mechanical ultrasonic oscillations of wavelength λ. The sonotrode has a sealing surface, which is arranged to contact the workpiece to be machined. The sealing surface of the sonotrode is galvanically isolated from the neutral conductor. In the event of a fault, an undissipated potential may be present on the neutral conductor. The galvanic isolation prevents this potential from being transferred to the sealing surface.

[0011] Preferably, the phase conductor is also galvanically isolated from the sealing surface of the sonotrode.

[0012] The piezoelectric elements are usually arranged one behind the other along the transducer axis.

[0013] The piezoelectric washers are polarized so that they deform in response to an applied voltage. The piezoelectric washers have a positive side and a negative side. The positive sides of all piezoelectric washers are connected to the same pole, for example a phase conductor, and the negative sides are connected to another pole, in this example a neutral conductor. This ensures that the piezoelectric washers all deform in a uniform manner, i.e. at a certain voltage, all piezoelectric washers expand (lengthen) or contract. Preferably, the piezoelectric washers are arranged one after another with opposite polarizations along the converter axis, so that two adjacent piezoelectric washers from the same electrode (contact washer) located between them can touch.

[0014] Preferably, an AC voltage source, also referred to as an ultrasonic generator, is provided for generating an AC voltage. The AC voltage source is connected to the phase conductors and the neutral conductor.

[0015] For example, the converter member and the sonotrode can be arranged continuously in the propagation direction of the ultrasonic oscillations. The length of both the converter member and the sonotrode in this propagation direction can be λ / 2 or a multiple of λ / 2. This ensures that in the case of excitation with oscillations of wavelength λ, a standing wave with maximum oscillations is formed at the interface of the sonotrode and the converter member due to the reflection of the ultrasonic oscillations at the end of the oscillation stack. The propagation direction can extend along the converter axis, but it is also possible, for example, that the converter axis and the propagation direction are perpendicular to each other. The propagation direction extends in particular from the converter towards the sonotrode and / or towards the sealing surface of the sonotrode area.

[0016] Machining of workpieces refers in particular to cutting, joining and welding of (multi-part) workpieces.

[0017] The entire sonotrode and converter component and optionally an amplitude booster arranged between the sonotrode and the converter component are also referred to as an oscillation stack. When an amplitude booster is used, it is also designed such that it is set to oscillate resonantly with an oscillation of wavelength λ. The length of the amplitude booster in the propagation direction is also advantageously λ / 2 or a multiple of λ / 2.

[0018] Advantageously, the oscillation stack is held (clamped) in a carrier, wherein the carrier is preferably engaged with the sonotrode, in particular in the region of the oscillation node. Alternatively, the carrier can also be engaged with the amplitude enhancer, the converter member or several components. The carrier of the ultrasonic oscillation unit can be present in a known manner, for example as disclosed in WO 96 / 14202 A2. A plurality of carriers are known to the person skilled in the art, so that for the sake of clarity, no specific carrier is shown here.

[0019] In an advantageous further development, the carrier is also provided with galvanic isolation in order to prevent the sonotrode from being grounded via the carrier. It is particularly advantageous that the carrier engages behind the galvanic isolation starting from the sealing surface of the sonotrode. Thus, additional insulation of the carrier can be omitted. In this case, the carrier does not have any additional insulation.

[0020] Galvanic isolation is understood to be a device that prevents the flow of current between the neutral conductor and the sealing surface. Usually, this can and will be an electrical insulation. However, it is also conceivable that the line connected to the neutral conductor via a non-conductive connecting element is connected to the sealing surface of the sonotrode, for example by means of induction to limit the exchange of signals. On the other hand, in the case of electrical isolation, there is no mutual influence between the circuits. In other words, when there is galvanic isolation and signal exchange is also excluded, it is referred to as electrical insulation below.

[0021] In an advantageous further development, it is provided that the sonotrode comprises an electrically connected signal terminal which is connected to the sealing surface and is used for an electrical signal voltage, wherein the neutral conductor is galvanically isolated from the signal terminal and preferably electrically insulated from one another. The signal voltage is applied in particular when detecting (contact detection) a contact between the sealing surface of the sonotrode and another part, such as a counter tool (anvil). The galvanic isolation of the neutral conductor and the signal terminal ensures that the signal voltage is not dissipated by the neutral conductor and that in the event of a fault, the signal voltage and the other voltages are always applied to the sealing surface. This protects the contact detection from destructive influences and also prevents people from coming into contact with high potentials via the sonotrode which do not correspond to the signal voltage.

[0022] If the carrier is engaged with the sonotrode, the carrier preferably comprises a galvanic isolation, wherein a portion of the carrier is conductively connected to the sonotrode, in particular in the region of the oscillation node, and another portion is galvanically isolated from the portion. In the context of the present invention, the signal terminal can then be arranged on the portion of the carrier that is conductively connected to the sonotrode, instead of being arranged on the sonotrode. In this way, the sealing surface of the sonotrode can also be influenced by the signal voltage. When the signal terminal is placed on the sonotrode, it influences the oscillation behavior of the oscillation stack. This is not the case with the carrier, so it is particularly advantageous to arrange the signal terminal on the carrier.

[0023] The converter component preferably comprises a converter housing, in which at least one piezoelectric element is arranged.

[0024] Advantageously, the ultrasonic tool comprises a protective conductor, which is preferably arranged on the converter housing. The protective conductor is connected or connectable to ground. The ultrasonic tool then preferably comprises a first part, a second part and a third part. The first part comprises at least a neutral conductor. The second part comprises at least a protective conductor and the converter housing. The third part comprises a sealing surface of the sonotrode and can output or receive a signal voltage via a signal terminal.

[0025] In a preferred embodiment, due to the invention, the galvanic isolation of the first and second parts can be omitted. The second and third parts are then galvanically isolated. This ensures that the signal voltage is not dissipated via the protective conductor. In some embodiments, due to the invention, an additional grounding of the converter housing is possible by means of the protective conductor. In the event of a fault in the neutral conductor, a potential on the converter housing is prevented, since all potentials are dissipated via the protective conductor. The additional grounding therefore means that there is no longer a risk of personal injury by contacting the converter housing. There is also no risk of applying a potential other than the desired potential of the signal voltage at the sealing surface of the sonotrode. In this way, contact detection can still be performed despite the additional grounding of the converter housing.

[0026] Furthermore, the first part and the second part can be galvanically isolated from each other and most preferably can be electrically insulated from each other. The second part is then galvanically isolated from the first part and the third part. The second part is advantageously located between the first part and the third part so that there are two electrical insulations between the neutral conductor (first part) and the sealing surface of the sonotrode (third part). In this way, an additional grounding part is created between the first part and the third part, to which a high voltage can be applied in the event of a fault and to which a signal voltage can be applied in the third part.

[0027] An insulating housing made of an electrically insulating material can be provided in the converter housing, which defines an insulating space, wherein at least one piezoelectric element and a neutral conductor are arranged in the insulating space. The insulating housing then forms a galvanic isolation between the first part and the second part. Particularly preferably, the insulating housing is annular or cylindrically hollow. In particular, the converter component comprises a shaft, in particular a converter screw having a shaft surrounded by an annular or cylindrically hollow insulating housing. The piezoelectric element is safely galvanically isolated from the rest of the converter component, in particular the converter screw, by means of which the piezoelectric element is strained. The insulating housing can be composed of several insulating components, in particular an axially arranged insulating washer and a radially insulated cylindrical insulating component. In this way, the piezoelectric element can be continuously compressed in the axial direction, thereby ensuring the transmission of ultrasonic oscillations. The insulating housing is particularly used for basic insulation of the converter.

[0028] Advantageously, the mating tool is provided with a sealing surface, which is positioned so that the workpiece to be machined can be arranged between the sealing surface of the sonotrode and the sealing surface of the mating tool during machining. The sealing surface of the mating tool is preferably grounded. By applying a signal voltage, as described above, a contact between the sealing surface of the sonotrode and the mating tool can then be detected. In the context of the present invention, it is also possible to apply a signal voltage to the mating tool and to ground the signal terminal. The mating tool is preferably a roller, in particular a rotating roller, which transports the workpiece during machining. In this way, continuous welding of the workpiece can be achieved. The mating tool is at least partially electrically conductive.

[0029] The sonotrode or the oscillating stack as a whole is preferably movable in an adjustment direction, in particular by means of an adjustment device of the ultrasonic tool. The adjustment device can be part of a carrier. In this way, the sonotrode can be moved toward and away from the counter tool. In this way, the distance between the sonotrode and the counter tool can be adjusted at any time. Furthermore, during processing, the sonotrode with the oscillating stack as a whole can be gradually moved toward the counter tool, in particular in the case of processing consisting of a separation operation.

[0030] In an advantageous further development, a voltage source is provided, with which the third part, in particular the signal terminal, can be subjected to a signal voltage, wherein a sensor is provided for detecting the voltage applied to the third part or dissipated from the third part. If a voltage is applied to the third part or dissipated from the third part, this is detected by the sensor. By means of this detection, contact between the sealing surfaces can be achieved.

[0031] The AC voltage applied to at least one piezoelectric element is preferably between 500Vrms (root mean square, effective voltage) and 3000Vrms, and preferably has a frequency between 20kHz and 70kHz. It has been shown that low voltages are advantageous for the signal voltage. Due to the high frequency and piezoelectric technology, the distance and contact time between the sealing surfaces during processing are very low. If the signal voltage is too high, voltage flickers (arcing) will occur even before actual contact between the sealing surfaces, whereby the sensor detects the current. On the other hand, if the voltage is too low, even in the case of slight contact, almost no current flows, which makes it difficult to detect contact earlier. The signal voltage is preferably a DC voltage, further preferably less than 30V, preferably less than 25V, and most preferably between 5V and 12V.

[0032] The inventors have found that the 5V range of 12V is best suited for contact detection, wherein voltages up to 25V also lead to acceptable results. On the other hand, above 30V, the voltage flash occurs too early in some applications. The voltage signal can also be an AC voltage, wherein a DC voltage is preferred because in the case of contact it results in a uniform discharge, which can be well detected.

[0033] If the sealing surface is touched, the current flows between the sealing surfaces. If the contact ends, the voltage source of the signal voltage accumulates the potential. Because the distance between the individual contacts can be very small, this accumulation must be carried out extremely quickly. For this reason, it has proven to be advantageous when the cable to which the signal voltage is applied is shielded and / or does not exceed a predetermined total capacity. Therefore, the third part is connected to the voltage source by means of an electrical cable, the shielded electrical cable and / or the total capacity of the electrical cable being <2500pF, in particular <1500pF. If the total capacity is <1500pF, very short-lived contacts that occur in succession can also be detected and distinguished. In the case of up to 2500pF, a large number of contacts can still be detected, while the detection is significantly affected in the case of more than 2500pF.

[0034] In an advantageous further development, an insulation resistance of at least 5 kΩ, in particular at least 7 kΩ, is provided between the second part and the third part. In principle, the greater the insulation resistance, the better the galvanic isolation. However, in certain cases, very large insulation resistances can only be achieved with considerable effort. Therefore, the limit of 100 MΩ can be regarded as an upper limit for the insulation resistance, wherein any greater values ​​are acceptable as long as no other boundary conditions are opposed.

[0035] Preferably, the amplitude enhancer is arranged between the converter member and the sonotrode. The converter member is mechanically coupled to the amplitude enhancer. And the amplitude enhancer is mechanically coupled to the sonotrode. The sonotrode, the amplitude enhancer and the converter member are tuned to each other so that the sonotrode can be set to resonate with a mechanical ultrasonic oscillation of wavelength λ. The sonotrode, the amplitude enhancer and the converter member form an oscillating stack.

[0036] The sonotrode, the amplitude intensifier and the converter element may also be referred to as interconnected components.

[0037] In an advantageous further development, at least one insulating device is provided, which results in a galvanic isolation, in particular an electrical insulation, of the sealing surface of the sonotrode from the neutral conductor. Various configuration options for the at least one insulating device are described below.

[0038] Particularly preferably, at least one insulating device is provided at exactly two locations, namely on the one hand at the location of the direct contact point between the two affected components, i.e. the components to be connected, i.e. the location at which the ultrasonic oscillations are transmitted in the propagation direction from one component to the corresponding continuous component, and on the other hand at the connection point at which the components are held together, which can be achieved in particular by a form-fitting and material-locking connection. Several connection points can also cooperate in order to hold the components together. Compressive forces are transmitted in particular at the contact points and tensile forces are transmitted in particular at the connection points.

[0039] The converter member and the ultrasonic welding electrode and / or the converter member and the amplitude enhancer and / or the amplitude enhancer and the ultrasonic welding electrode are preferably connected to each other via at least one connecting element. The connecting element particularly causes a force fit in the propagation direction. Thus, the respective components are connected to each other so that the ultrasonic oscillations can propagate along the length of the ultrasonic tool. Preferably, the connecting element is a screw and / or a threaded bolt and / or a threaded bushing. At least one connecting element particularly connects the respective components with a clamping force of at least 20 kN, preferably less than 150 kN, in particular at least 30 kN and / or less than 90 kN. With these clamping forces, it is ensured that the components are connected to each other so that the ultrasonic oscillations can propagate uniformly. The connecting element is preferably configured as an insulating device and is at least partially provided with an insulating coating and / or at least partially composed of an insulating material. In this way, current isolation is performed when the force fit between the respective components is closed. The threaded bushing can also be a cable threaded insert.

[0040] Preferably, at least one insulating element, in particular an insulating washer, is arranged between the converter component and the sonotrode, in particular between the converter component and the amplitude booster and / or between the amplitude booster and the sonotrode, the insulating element being at least partially configured as an insulating device and at least partially consisting of an insulating material and / or at least partially provided with an insulating coating. The insulating washer preferably comprises a hole, through which, for example, the connecting element can protrude, i.e. the insulating washer is preferably embodied as an annular washer. The insulating element brings about a galvanic isolation, in particular at the contact points between the affected components, to which the ultrasonic oscillations are transmitted in the propagation direction to the respective subsequent components. Therefore, it is particularly preferred that the connecting element and the insulating element are used in combination.

[0041] In an advantageous further development, the converter member and / or the amplitude enhancer and / or the ultrasonic welding electrode is constructed as an insulating device and is at least partially composed of an insulating material and / or is at least partially provided with an insulating coating. In this way, the galvanic isolation achieved by the connecting element and / or the insulating element can be omitted. Then, at the contact points where the ultrasonic oscillation is transmitted and / or friction is generated, the corresponding affected component is coated or is composed of an insulating material. In this way, the number of components used can be reduced, which is particularly advantageous for ultrasonic tools, because additional components change the oscillation behavior of the entire oscillation stack. The use of a coating has the particular advantage that it can be designed to be thin enough so that the oscillation behavior of the oscillation stack changes little or only slightly. If a component, such as an insulating washer made of an insulating material, is used, the thickness of the component must generally be significantly greater than the thickness of the coating. Then, the influence of the component on the oscillation behavior of the oscillation stack is stronger. This is especially true for the contact points between the two components.

[0042] It is possible to coat the threads with an insulating coating, but this is usually difficult due to the partially filamentous thread profile. In an advantageous further development, a cascade of several parts is provided as a connecting element, wherein a first cascade part is preferably held by a second cascade part in the propagation direction by means of a form fit, and the first cascade part and / or the second cascade part are provided with an insulating coating for a form fit on the corresponding contact surfaces. Alternatively, at least one cascade part can consist of an insulating material. An essential advantage of the cascade is that no threaded parts need to be coated, but only the contact surfaces. Depending on the design of the cascade, the insulating means at the contact points can also be realized by the cascade, or insulating elements, in particular insulating washers, can be used in addition to the cascade.

[0043] In an advantageous further development, the connecting element comprises a smooth, in particular cylindrical portion, which is provided with an insulating coating, wherein the portion is shrunk into the sonotrode or the converter member or the amplitude intensifier. For example, the sonotrode can be heated so as to widen the hole provided therein, whereupon the smooth portion can be inserted into the hole. After cooling, the hole shrinks again and then holds the connecting element in a friction-locked manner. In particular, smooth means that the portion has a uniform cross section along its axial extension, in particular without any thread. The cross section can be circular, as well as star-shaped or other shapes. The advantage of the circular shape is that the geometry is easier to manufacture, for example by grinding. During the shrinking process, very limited tolerances are maintained in order to achieve a sufficiently large force fit, but at the same time not to overload the substrate with too large a voltage. Also in these embodiments, a significant advantage is that the threaded portion does not need to be coated. Alternatively or additionally, the connecting element can comprise a smooth portion and a threaded attachment that is shrunk onto the smooth portion. The threaded attachment is then provided with an external thread that can be screwed into a hole of another component that has an internal thread.

[0044] In an advantageous further development, a through hole is provided in the amplitude enhancer, wherein the amplitude enhancer comprises a portion provided with an insulating coating. Alternatively, a portion of the converter component, in particular the converter lower part, can also comprise a through hole and a portion with an insulating coating. In these embodiments, a screw is also provided, which rests with its head against the coating portion and is spaced apart from the inner surface of the through hole. For the amplitude enhancer with a through hole, the screw can be screwed into the converter component or the ultrasonic welding electrode with its thread, and for the converter lower part with a through hole, the screw can be screwed into the amplitude enhancer or the ultrasonic welding electrode with its thread. In these embodiments as well, it is not necessary to provide a threaded portion with a coating. The screw can be a countersunk screw, so that the interconnected components are automatically centered.

[0045] Additional insulating means may be provided on the inner wall of the through-hole in order to ensure adequate insulation in the event of accidental contact. These insulating means have no main specifications, since they do not need to transmit large forces, but only need to ensure resistance. Thus, for example, these insulating means may be insulating sleeves, spray paints or insulating films.

[0046] In an advantageous further development, a transverse hole extending transversely to the propagation direction is provided in the converter member or the amplitude enhancer or the ultrasonic welding electrode, wherein the at least partially coated transverse portion is inserted with a threaded hole. The transverse portion can be a cuboid slot or a bolt. In addition to the transverse hole, the converter member, the amplitude enhancer or the ultrasonic welding electrode also includes a hole concentric with the threaded hole, in which a screw or a threaded bolt is arranged, wherein the screw or the bolt is connected to the transverse portion by means of the threaded hole. The screw or threaded bolt can then be connected to an adjacent part, i.e., in the case of a ultrasonic welding electrode with an amplitude enhancer or a converter member, in the case of an amplitude enhancer with a converter member or a ultrasonic welding electrode, and in the case of a converter member, the adjacent part is an amplitude enhancer or a ultrasonic welding electrode. Likewise, for a force-fit connection, the thread does not need to be coated. However, an insulating element, in particular an isolating washer or an insulating coating, is also required at the contact point between the components.

[0047] In an advantageous further development, a coupling piece, in particular a flange part, is provided as an insulating device, which is at least partially coated. The coupling piece is fastened to one of the components by means of screws, wherein the coupling piece is provided with the insulating coating at the location where the screws rest. Likewise, for a force-fit connection, the thread does not need to be coated.

[0048] In the case of ultrasonic tools, high forces and ultrasonic oscillations must be transmitted via insulating coatings or insulating materials. The inventors have found that, to date, not all electrically insulating materials are suitable for current isolation in ultrasonic tools. Preferably, the insulating coating and / or material comprises at least one of the following components: ceramic, in particular chromium oxide (Cr2O3) and / or aluminum oxide (Al2O3), glass, polymer composites, in particular glass reinforced plastic (GRP), and / or carbon reinforced plastic (CRP). These materials have proven to be particularly advantageous in terms of current isolation and force and ultrasonic oscillation transmission.

[0049] When choosing the coating thickness, it should be noted that, depending on the thickness, the coating has an effect on the entire oscillation stack. At the contact points between the affected components, the coating changes the propagation / transmission of the ultrasonic oscillations. If an insulating coating is applied to the threaded portion, the thread degree is changed, which must be taken into account in the original manufacture of the thread. Preferably, the thickness of the insulating coating is at least 0.02 mm. Further preferably, the thickness is at most 0.5 mm. It has been shown that coatings below 0.02 mm can have a sufficient insulating effect. However, particularly in the threaded area, screwing in a corresponding counterpart (e.g. a screw) may damage the insulating layer. If the coating is constructed too thin, in the event of such damage, there is a risk of voltage flashes, thereby reducing or completely losing the insulating effect. From the point of view of the insulating effect, a thickness > 0.5 mm is not necessary at all. In the range of conventional thread sizes, such a thick coating can also lead to the thread being almost flattened, thereby interfering with the connection process.

[0050] In an advantageous further development, the connecting element is a bolt having two axially adjacent external threaded portions, wherein each external threaded portion is provided with an external thread, wherein the external threads are isolated from each other, and wherein at least one external threaded portion, in particular exactly one external threaded portion, is coated with an insulating material. Thus, the connecting element constructed in this way comprises two threaded portions arranged axially one after the other, which have corresponding external threads, wherein the external threads do not merge with each other. If the connecting element is screwed into one of the components with one threaded portion, the screwing operation can at most reach the starting point of the second threaded portion. There, the internal thread present in the component does not match the thread of the second threaded portion, thus preventing further tightening. In these further developments, only one of the threaded portions needs to be coated, which significantly reduces the coating costs. However, with respect to the force-fit connection between the two components, a galvanic isolation between the components is achieved by the connecting element designed in this way. In a particularly advantageous further development, a protrusion, in particular a circumferential radially protruding flange, is provided between the threaded sections, which hinders further screwing out of the protrusion. The protrusion is preferably also coated because it can contact the uncoated counterpart.

[0051] In an advantageous further development, the connecting element is a screw or a threaded bolt with an additional annular washer, wherein the screw or the threaded bolt and the annular washer are constructed as a one-piece or multi-piece unit, wherein both the screw or the threaded bolt and the annular washer are constructed as insulating means and at least partially consist of an insulating material and / or are at least partially coated with an insulating material. The screw or the threaded bolt then produces a galvanic isolation with respect to the force fit between the two associated components and the annular washer produces a galvanic separation with respect to the contact surface between the two components. These embodiments are relatively easy to implement and in particular do not require any adjustments to the existing components (ultrasonic welding electrode, amplitude enhancer, converter member). The one-piece design complicates the insulating components but facilitates assembly of the components. Likewise, the annular washer must have a certain base thickness in a one-piece design, which can have an adverse effect on the oscillation behavior.

[0052] In an advantageous further development, the connecting element is an element engaging with the peripheral surface, in particular a union nut. A particular advantage of a union nut is that it is visible from the outside, for example, damage to the coating or the union nut itself can be detected more easily.

[0053] The various connecting elements described can generally be combined with one another.

[0054] In an advantageous further development, the converter component and the sonotrode and / or the converter component and the amplitude booster and / or the amplitude booster and the sonotrode are connected to one another via an insulating adhesive, in particular polyurethane and / or epoxy resin, wherein the connecting element is connected to the converter component and / or the sonotrode and / or the amplitude booster, in particular via the insulating adhesive. The use of an adhesive has the advantage that in one working step, a galvanic separation and a connection between the components can be achieved. Although it is generally conceivable that the adhesive can be used at the contact points between two components to be connected, a preferred field of application of the insulating adhesive is the connection of a connecting element, for example a screw or a threaded bolt, to one of the two components so that this component can be screwed into the second component.

[0055] Preferably, the ultrasonic tool comprises a control unit, in particular configured to perform contact detection. The control unit is preferably connected to a regulating device and a sensor for detecting the charge applied to the third part or the charge dissipated from the third part. The control unit can thereby drive the regulating device based on the sensor signal and move the ultrasonic weld closer to or away from the mating tool. The control unit can also be connected to a voltage source for the signal voltage, a voltage source for the AC voltage, other sensors and / or output devices, such as a display or a signal light. Thus, the voltage source can also be controlled depending on the sensor signal, for example, if too many or too long contacts are detected, the amplitude of the AC voltage is reduced, or the AC voltage is completely turned off. The output device allows the person to output the sensor signal visibly, for example as a warning in the case of too many contacts or as a list of all detected contacts.

[0056] According to the above description, the problem of the invention is also solved by means of a method for machining a workpiece by means of mechanical ultrasonic oscillations using an ultrasonic tool. The method is characterized in that the workpiece is arranged for machining between a sonotrode and a counter tool, and the workpiece is machined by means of an ultrasonic tool on a signal terminal of the sonotrode electrically connected to a sealing surface of the sonotrode, generating an electrical signal voltage, in particular a signal voltage of less than 100 V, preferably less than 30 V, most preferably between 5 V and 25 V, wherein a current flow between the neutral conductor and the signal terminal is prevented, and it is at least temporarily determined whether a current flows between the sonotrode area and the counter tool, and / or whether a voltage drops between the sonotrode and the counter tool. By applying the signal voltage and determining whether a current flows and / or whether a voltage drops, it can be determined whether contact occurs between the sonotrode and the counter tool. Due to the galvanic isolation in the ultrasonic tool, it is possible to prevent the signal voltage from being dissipated via the neutral conductor, so that contact detection is not impaired. In the event of a fault, there is no risk of a high potential being generated by the piezoelectric element abutting the sonotrode and / or the counter tool.

[0057] During machining, a force is preferably applied to the sonotrode, which force is transmitted from the sonotrode to the workpiece. This force ensures that the ultrasonic oscillations are transmitted uniformly to the workpiece.

[0058] The AC voltage (effective voltage) applied to the converter of the ultrasonic tool is preferably between 500 Vrms and 3000 Vrms, and preferably has a frequency between 20 kHz and 70 kHz. With these voltages and frequencies, ultrasonic oscillations for machining a workpiece can be effectively generated.

[0059] The ultrasonic oscillations on the sealing surface of the sonotrode preferably have a frequency of 20 kHz to 70 kHz and / or an amplitude of 5 μm to 50 μm. The frequency of the ultrasonic oscillations corresponds to the frequency of the AC voltage. The amplitude is significantly influenced by the amount of the AC voltage, the structural design of the converter component, the amplitude intensifier and the sonotrode, and the converter, i.e. the at least one piezoelectric element itself. Contact detection is particularly suitable for amplitudes of 5 μm to 50 μm.

[0060] Preferably, the workpiece at least partially comprises a polymer, in particular a thermoplastic polymer. Preferably, the workpiece consists entirely of a polymer in the contact surface area with the sonotrode. Preferably, the workpiece melts at least partially during processing by ultrasonic oscillation in the contact surface area with the sonotrode. For the contact detection, it is particularly advantageous when the workpiece consists of a polymer, in particular in the contact surface area with the sonotrode. In a particularly advantageous embodiment, the workpiece consists of several parts, in particular several material webs, which are connected together by processing. The material webs are preferably continuously conveyed through the area between the sonotrode and the counter tool, in particular by means of rollers. The contact detection according to the invention is particularly advantageous in the case of such thin components, because due to the small thickness, contacts between the sonotrode and the counter tool often occur. Each contact affects the service life of the sonotrode and the service life of the counter tool. Therefore, it is particularly advantageous to precisely adjust the gap between the sonotrode and the counter tool. This setting can be achieved by the method according to the invention.

[0061] In an advantageous further development, the duration of at least one current flow and / or voltage reduction between the sonotrode and the countertool is determined and, if the duration exceeds a predefined time limit, the current flow and / or voltage reduction is evaluated as a contact between the sealing surface of the sonotrode and the countertool, the contact time corresponding to the duration of the current flow or voltage reduction. The time limit is in particular >0.01 μs and particularly preferably ≥1 μs. The upper limit of the time limit can be set to 1000 μs to exclude accidents. It has been shown that the current flows not only when the sonotrode and the countertool are actually in contact, but also when the sonotrode and the countertool are in very close or partial contact. Since the sealing surface of the sonotrode oscillates at the frequency of the ultrasonic oscillations and moves back and forth, there is a voltage flashover between the sonotrode and the countertool, so that the current flows, in particular in an extreme position where the distance between the sealing surfaces is the smallest. It has therefore been shown that it is advantageous not to evaluate every current as a contact between the sonotrode and the countertool, but only to evaluate current flows / voltage reductions that last for a certain period of time, for example ≥1 μs. Preferably, current flows and / or voltage drops which last below a predefined time limit are therefore discarded and not considered as contacts. Said time limit range has proven to be particularly advantageous for the above-mentioned ultrasonic oscillation frequencies. If it is above 1000 μs, it can no longer be assumed to be a single contact.

[0062] In an advantageous further development, the current intensity of at least one current flow and / or voltage drop between the sonotrode and the countertool is determined and, if the current exceeds a predefined current limit, the current flow and / or voltage drop is evaluated as a contact between the sealing surfaces. The current limit is preferably >1 mA. For the current limit, an upper limit of 300 μs can be established in order to exclude accidents. The current intensity is also an indicator of the actual proximity of the sealing surfaces. Thus, the difference between contact and non-contact to be evaluated can also be distinguished based on the current. The sealing surfaces also have a flat extension, although the roughness is low. Therefore, even small areas of the sealing surface may have been in contact, resulting in current flows, but these currents are too low and should not be regarded as contacts. In these cases, the two limit values ​​are also suitable for the qualitative assessment of the contact. The determination of the current and the associated contact assessment can be used as an alternative or supplement to the duration of the current flow and / or voltage drop. Particularly preferably, the current flow and / or voltage drop is only evaluated as a contact if the time limit and the current limit are exceeded.

[0063] In an advantageous further development, at least one of the following parameters is determined within at least a predetermined (elapsed) time period, in particular within the last elapsed milliseconds, wherein the parameter is preferably stored and / or outputted:

[0064] Total number of contacts between sonotrode and counter tool

[0065] The longest contact time of all contacts

[0066] The sum of contact times for all contacts.

[0067] The determination of these parameters is used for the evaluation of contact detection. For example, if a small number of contacts occur within a specified time period, or if the total contact time is very short despite a large number of contacts, it can be concluded that the sealing surfaces have not been very close. A threshold value can be provided for each parameter, and when this threshold value is exceeded, a specific action occurs, such as an alarm signal.

[0068] These parameters can be further processed by the control unit of the ultrasonic tool. In particular, depending on one or more parameters, the position of the ultrasonic tool or the oscillation stack, in particular the sonotrode, is adjusted, the force applied to the sonotrode is reduced or increased, an alarm is output, and / or the processing operation is stopped. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] The present invention is illustrated and explained below with reference to the accompanying drawings. In the drawings:

[0070] Figure 1 A first embodiment of an ultrasonic tool is schematically shown in transverse section;

[0071] Figures 2 to 16Another embodiment of an ultrasonic tool is schematically shown. DETAILED DESCRIPTION

[0072] Figure 1 The ultrasonic tool 100 shown comprises a converter member 10 and a sonotrode 40. The converter member 10 comprises a converter 20, a converter lower part 12, an annular washer-shaped cover plate 16 and a converter screw 18. The converter 20 comprises four annular washer-shaped piezoelectric elements 22, which are arranged one after another between the converter lower part 12 and the cover plate 16. The converter 20 also comprises a total of five electrodes, also referred to as contact washers: three neutral electrodes 24 and two phase electrodes 26, which are also annular washer-shaped. The electrodes 24, 26 are arranged alternately with the piezoelectric elements 22 along the converter axis K between the converter lower part 12 and the cover plate 16. The electrodes 24, 26 alternate with each other. Therefore, one neutral electrode 24 is arranged at the lowest and highest.

[0073] The converter screw 18 rests with its screw head on the cover plate 16 and passes through all holes of the piezoelectric element 22, the electrodes 24, 26 and the cover plate 16. The converter screw 18 is screwed into the converter lower part 12 and ensures that the piezoelectric element 22 and the electrodes 24, 26 remain compact. Figure 1 Unlike the schematic representation of , the piezoelectric element and the electrodes 24, 26 are therefore in direct contact with one another and are held in close proximity by the converter screw 18. The converter screw 18 is tightened with a sufficient pretension, for example 70 kN.

[0074] The converter member 10 further comprises a phase conductor 31 for the AC voltage and a neutral conductor 33 for its dissipation. The phase conductor 31 and the neutral conductor 33 form two poles for the converter 20. The neutral electrode 24 is connected to the neutral conductor 33 and the phase electrode 26 is connected to the phase conductor 31. The piezoelectric element 22 is polarized and is arranged to be fully extended or fully clamped, respectively, except for the zero position at any given time.

[0075] If an AC voltage is applied to the phase conductor 31 and the neutral conductor 33, the piezoelectric element 22 converts the AC voltage into mechanical ultrasonic oscillations, wherein the converter member 10 is set to oscillate in resonance with the mechanical ultrasonic oscillations of wavelength λ. The ultrasonic oscillations extend in particular along the propagation direction R, which in the embodiment shown extends from the converter 20 to the sonotrode 40, i.e. downwards along the converter axis K. In the embodiment shown, the length of both the converter member 10 and the sonotrode 40 along the propagation direction R is λ / 2. Therefore, the sonotrode 40 and the converter member 10 are tuned to each other so that the sonotrode 40 is set to oscillate in resonance with the mechanical ultrasonic oscillations of wavelength λ.

[0076] The ultrasonic welding electrode 40 has a sealing surface 42, which is arranged to contact the workpiece 200 to be machined. The workpiece 200 is schematically shown here. Generally, the workpiece 200 comprises several parts welded together, in particular several material webs welded together, and then together to form the workpiece 200.

[0077] The ultrasonic tool 100 also includes a counter tool 110 having a sealing surface 111. The ultrasonic tool 100 is configured to process a workpiece 200 by mechanical ultrasonic oscillations. The workpiece 200 is placed between the sealing surfaces 42, 111 for processing, or is guided through the gap between the sealing surfaces 42, 111, wherein the workpiece 200 touches the sealing surfaces 42, 111 in any case. A force in the propagation direction R is also applied to the workpiece 200, which force can be generated by an adjustment device (not shown) of the bracket. If ultrasonic oscillations are now generated, the workpiece 200 is processed, wherein usually several parts, such as material webs, are connected to each other.

[0078] The insulating device 300 is arranged between the converter component 10 and the sonotrode 40. The insulating device 300 comprises a threaded bolt-shaped connecting element 310 and an insulating element 350 in the form of an insulating washer-shaped portion. The connecting element 310 and the insulating element 350 are arranged integrally. In the embodiment shown, the insulating device 300 consists entirely of a ceramic material. The insulating device 300 is screwed into the converter lower part 12 and the sonotrode 40 together with the connecting element 310. The converter lower part 12 and the sonotrode 40 do not contact each other because they are isolated from each other by the insulating device 300. In this way, the sealing surface 42 of the sonotrode 40 and the first neutral conductor 33 of the converter 20 are electrically isolated. The flow of current between the converter lower part 12 and the sonotrode 40 is prevented.

[0079] The converter component 10 comprises a schematically shown converter housing 11 which in particular shields the piezoelectric element 22 and the electrodes 24, 26 from the outside. A protective conductor 35 connected to ground is arranged on the converter housing 11. The converter housing 11 is connected to the converter lower part 12 in the region of the oscillation nodes.

[0080] The sonotrode 40 comprises a signal terminal 44 for an electrical signal voltage, which is electrically connected to the sealing surface 42. The neutral conductor 33 and the signal terminal 44 are galvanically isolated from each other by the insulating device 300.

[0081] The ultrasonic tool 100 comprises a voltage source 400 as a DC voltage source. The voltage source 400 is electrically connected to the signal terminal 44 of the sonotrode 40 via a sensor 410 in the form of a current measuring device on the one hand and to the counter tool 110 on the other hand. When used as intended, a DC voltage is applied to the signal terminal 44 by the voltage source 400 and thus to the sealing surface 42. If the sealing surface 42, 111 is touched during the processing of the workpiece 200, a current will flow. This current flow can be detected by means of the sensor 410. The sonotrode 40 and the counter tool 110 are constructed in an electrically conductive manner, in particular, consist of a metal material. Therefore, contact can be made between the sealing surfaces 42, 111 (contact detection) based on the signal of the sensor 410.

[0082] An AC voltage source 39 for generating an AC voltage for the converter 20 is provided, which is connected to the phase conductor 31 and the neutral conductor 33 .

[0083] If the line from the AC voltage source 39 to the neutral conductor 33 is disconnected, it may happen that the piezoelectric elements 22 are further excited, whereby they generate a potential on the neutral electrode 24 and thus on the neutral conductor 33. This potential is then also applied to the converter lower part 12. The protective conductor 35 ensures that the potential is dissipated in the event of a fault and that touching the converter housing 11 does not cause damage. The insulating device 300 also prevents this potential from abutting the sealing surface 42 of the sonotrode 40 in the event of a fault and affecting the contact detection. Instead, the protective conductor 35 is galvanically isolated from the sealing surface 42 and the signal terminal 44 by the insulating device 300, so as to prevent the signal voltage from being dissipated via the protective conductor 35.

[0084] In other embodiments, the insulating device 300 can also be made of non-ceramic materials, such as metal materials. In these embodiments, the insulating device 300 is then provided with an insulating coating on at least one side or the entire surface.

[0085] In other embodiments, an amplitude enhancer 60 may be provided between the converter lower part 12 and the ultrasonic welding electrode 40 . Then, the insulating device 300 may be arranged between the converter lower part 12 and the amplitude enhancer 60 or between the amplitude enhancer 60 and the ultrasonic welding electrode 40 .

[0086] exist Figure 2 In FIG. 1 , only an excerpt of the ultrasonic tool 100 is shown, namely the area around the contact point 112 between the sonotrode 40 and the amplitude booster 60 .

[0087] In this embodiment, two insulating devices 300 are provided between the sonotrode 40 and the amplitude enhancer 60. A connecting element in the form of a threaded bolt is provided, which is screwed into the sonotrode 40 and the amplitude enhancer 60. The threaded bolt is completely coated and connects the sonotrode 40 and the amplitude enhancer 60 to each other in a force-fitting manner, thereby forming a connection point between the components. In this way, the connecting element is configured as an insulating device 300. As a further insulating device 300, an insulating element 350 in the form of an insulating washer is also provided. The insulating washer is an annular washer and is arranged at the contact point 112 between the sonotrode 40 and the amplitude enhancer 60. The insulating washer is also provided with an insulating coating, wherein the insulating coating can be present completely or only on one of the axial sides, for example on the top surface 352 or the bottom surface 354. The connecting element 310 and the insulating element 350 together ensure the galvanic isolation of the sonotrode 40 and the amplitude enhancer 60.

[0088] Figure 2 The insulating device 300 shown in FIG. 1 can also be used in other embodiments for connecting the sonotrode 40 to the converter component 10 , or for connecting the amplitude enhancer 60 to the converter component 100 .

[0089] exist Figure 3 , an excerpt of the ultrasonic tool 100 around the contact point 112 between the sonotrode 40 and the amplitude enhancer 60 is shown. In this embodiment, the ultrasonic tool 100 comprises an insulating element 350 in the form of an insulating washer in the shape of a ring-shaped washer, and a wire thread insert 320 as the insulating device 300. The wire thread insert 320 can consist completely of insulating material or can be provided with an insulating coating. The wire thread insert 320 is screwed into the threaded hole of the sonotrode 40. The same is true for the insulating element 350. A connecting element 310 in the form of a threaded bolt is also provided. One end of the threaded bolt is screwed into the amplitude enhancer 60 and the other end is screwed into the wire thread insert 320. The insulating element 350 and the wire thread insert 320 together constitute a galvanic separation between the sonotrode 40 and the amplitude enhancer 60.

[0090] This type of connection can also be used in other exemplary embodiments between the sonotrode 40 and the converter component 10 or between the amplitude booster 60 and the converter component 10 .

[0091] exist Figure 4, the ultrasonic tool 100 is shown in detail around the contact point 112 between the sonotrode 40 and the amplitude enhancer 60. In this embodiment, neither the sonotrode 40 nor the amplitude enhancer 60 has a hole. Between the components 40, 60, an insulating element 350 in the form of an insulating washer without a hole is provided as an insulating device 300. In other embodiments, the insulating washer can also have a hole here, for example, if it is advantageous in terms of oscillation technology or uniform power transmission. The insulating element 350 constitutes a galvanic isolation at the contact point 112. The sonotrode 40 has an external thread 46 and the amplitude enhancer 60 has a circumferential shoulder 62. A connecting element 310 in the form of a union nut is also provided. The union nut has a radially inward projection 316 at its top end and an internal thread 314 at its bottom end. When used as intended, the union nut projections 316 rest together on the shoulder 62 and the internal thread 314 is screwed onto the external thread 46, thereby connecting the sonotrode 40 and the amplitude enhancer 60 to the connection point in a force-fitting manner. The union nut can be made completely of insulating material. However, it can also be provided with an insulating coating in separate areas, in particular in the area of ​​the projections 316, preferably wherever it rests on the shoulder 62. Thus, no current can flow from the amplitude enhancer 60 through the union nut to the sonotrode 40. Thus, the union nut and the insulating washer form two insulating means 300.

[0092] This type of galvanic isolation can also be used in other exemplary embodiments between the sonotrode 40 and the converter component 10 or between the amplitude booster 60 and the converter component 100 .

[0093] Figure 5 The ultrasonic tool 100 shown further comprises a sonotrode 40 and an amplitude enhancer 60. An insulating device 300 in the form of a flange portion is provided at the contact point 112 between the two components 40, 60, the insulating device 300 comprising an annular gasket as an insulating element 350 and a threaded bolt connected thereto as a connecting element 310. The connecting element 310 and the insulating element 350 are constructed integrally. In the embodiment shown, the bottom surface 354 of the insulating gasket is provided with an insulating coating. In other embodiments, the entire flange portion may consist of an insulating material, for example ceramic.

[0094] The insulating washer projects radially from the amplitude enhancer 60 and forms a flange shoulder 358 there. The flange shoulder 358 is circumferential. A union nut is also provided as an additional connecting element 310. The union nut has a radially inward projection 316 at the upper end and an internal thread 314 at the lower end. The projection 316 rests on the flange shoulder 358 and the thread 314 is screwed onto the external thread 46 of the sonotrode 40. The insulating washer is also provided with an insulating coating, on which the union nut rests, i.e. on the top side 352. This is not necessary when the flange part consists completely of insulating material.

[0095] The flange part is screwed into the threaded hole of the amplitude enhancer 60 by means of threaded bolts. The sonotrode 40 and the amplitude enhancer 60 are galvanically isolated by means of the insulating coating.

[0096] This type of connection can also be used in other exemplary embodiments between the sonotrode 40 and the converter component 10 or between the amplitude booster 60 and the converter component 10 .

[0097] exist Figure 6 , another embodiment of an ultrasonic tool 100 is shown, here also showing in detail the area around the contact point 112 between the two components 40, 60. The insulating device 300 is again arranged between the sonotrode 40 and the amplitude enhancer 60. In this form, a flange portion is provided which integrally comprises an insulating washer as an insulating element 350 and a threaded bolt as a connecting element 310. The flange portion consists of an insulating material, for example ceramic. The insulating device 300 comprises holes arranged along a circular track, through which flange screws 356 are respectively passed. The insulating device 300 is connected to the sonotrode 40 by means of flange bolts 356. For this purpose, the flange bolts 356 are rotated in the threaded holes of the sonotrode. The amplitude enhancer 60 is screwed onto the threaded bolts. The flange bolts 356 are provided with an insulating coating. Therefore, the flange bolts 356 also constitute the insulating device 300 and the connecting device 310. By means of the insulating coating and the insulating material, the sonotrode 40 and the amplitude enhancer 60 are galvanically isolated from each other. In alternative embodiments, the flange portion may also be provided with only an insulating coating and / or the flange bolts 356 may be made of an insulating material.

[0098] This type of connection and insulation can also be used in other exemplary embodiments between the sonotrode and the converter component 10 or between the amplitude booster 60 and the converter component 10 .

[0099] exist Figure 7 In the embodiment of the ultrasonic tool 100 shown, an annular insulating washer is provided as an insulating element 350 between the sonotrode 40 and the amplitude enhancer 60. The insulating washer forms a galvanic isolation at the contact point 112. A threaded hole is provided in the amplitude enhancer 60. In the sonotrode 40, a blind hole without a thread is provided. The two holes are concentric.

[0100] The ultrasonic tool 100 further comprises a bolt as a connecting element 310, which is provided with a thread at one end and has a smooth portion 311 at the other end. The bolt is bonded to the sonotrode 40 by means of an adhesive 360, i.e. connected in a material-locked manner. The bolt then protrudes beyond the upper end of the sonotrode 40. In this way, the amplitude enhancer 60 can be screwed onto the bolt. The adhesive 360 ​​is insulating and causes galvanic isolation at the connection point between the sonotrode 40 and the amplitude enhancer 60.

[0101] In other embodiments, the bolt can also be provided with a thread over its entire circumferential surface and / or the hole in the sonotrode 40 can be provided with a thread on the inside, wherein the holes do not fit into one another. If an adhesive 360 ​​is introduced into the resulting intermediate space, in addition to a material-locked connection, an undercut is achieved, thereby achieving a positive locking.

[0102] In other embodiments, the type of galvanic isolation between the sonotrode 40 and the amplitude enhancer 60 described herein may also be used for galvanic isolation between the sonotrode 40 and the converter component 10 or between the amplitude enhancer 60 and the converter component 10 .

[0103] Figure 8 An excerpt of an ultrasonic tool 100 according to another embodiment is shown. In this embodiment, the amplitude enhancer 60 includes a through hole 64, which ends at a shoulder 62 at its upper end. A screw is arranged in the through hole 64 as a connecting element 310. The bolt protrudes downward from the amplitude enhancer 60 or the through hole 64 and is screwed into the threaded hole of the ultrasonic welding electrode 40. Additional insulating means (not shown) are provided on the inner wall of the through hole. With these additional insulating means, the unplanned contact between the through hole 64 and the screw ensures sufficient insulation. These additional insulating means do not have to transmit large forces, but only need to ensure resistance. Even in other embodiments, when no insulating coating is provided between the two components but contact cannot be completely excluded, these additional insulating means can also be used.

[0104] An insulating washer is also arranged as an insulating element 350 at the contact point 112 between the sonotrode 40 and the amplitude enhancer 60. The insulating washer is provided with an insulating coating or is completely made of an insulating material, for example ceramic, thereby constituting the insulating device 300. The insulating coating is also provided on the shoulder surface 66 of the shoulder 62, i.e. on the surface on which the screw head of the screw rests. Otherwise, the screw would not contact the amplitude enhancer 60. In this way, the sonotrode 40 and the amplitude enhancer 60 are galvanically isolated. In this way, the amplitude enhancer 60 constitutes the insulating device 300.

[0105] Above the through-hole 64 , the amplitude enhancer has an internal thread into which the converter lower part 12 is screwed.

[0106] Fig. 9Another embodiment of the ultrasonic tool 100 is shown. In this embodiment, the amplitude enhancer 60 comprises a through hole 64 with a conical cone at the top end. A screw can be inserted into the through hole 64 from below as a connecting element 310, which rests on the shoulder surface 66 of the shoulder 62 of the conical cone. This is the location of the connection point. In this position, the screw protrudes upward from the through hole 64 and is screwed into the threaded hole of the converter lower part 12 there. Between the converter lower part 12 and the amplitude enhancer 60, an annular insulating gasket is arranged as an insulating element 350. An insulating coating is arranged on the shoulder surface 66 of the shoulder 62. In this way, the amplitude enhancer 60 constitutes an insulating device 300.

[0107] The insulating gasket is provided with an insulating coating or is made completely of insulating material, thereby forming the insulating device 300. In this way, the amplitude booster 60 and the converter lower part 12 are galvanically isolated.

[0108] In accordance with Fig.10 In the embodiment of the invention, the ultrasonic tool 100 comprises a sonotrode 40, an amplitude enhancer 60 and a converter lower part 12. The amplitude enhancer 60 comprises two concentric threaded holes, each of which has an internal thread. The sonotrode 40 is screwed into the lower hole. The converter lower part 12 comprises a through hole 13, which is concentric with the upper threaded hole in the amplitude enhancer. An insulating washer is arranged as an insulating element 350 between the converter lower part 12 and the amplitude enhancer 60. The insulating washer is made of an insulating material or is provided with an insulating coating, thereby constituting an insulating device 300. A bolt can be inserted into the through hole 13 from above as a connecting element 3120. Then, the screw abuts against one shoulder 15 of the converter lower part 12, wherein the through hole 13 in the region of the shoulder 15 is provided with an insulating coating. In this way, the converter lower part 12 constitutes the insulating device 300. The screw is screwed into the upper threaded hole of the amplitude enhancer and connects the amplitude enhancer 60 to the converter lower part 12 in a force-fitting manner. The amplitude enhancer 60 and the converter lower part 12 are galvanically isolated by the insulating coating and are additionally insulated by the insulating gasket.

[0109] The upper end of the through hole 13 is provided with an internal thread, into which the converter screw 18 can be screwed. In this embodiment, the piezoelectric element 22 can be added only after the converter lower part 12 and the amplitude enhancer 60 are connected, so that the converter 20 can be constructed as a whole.

[0110] The amplitude booster and the converter lower part 12 are galvanically isolated by insulating washers and coatings in the region of the shoulder 15 .

[0111] 11A, 11B and 11C show another embodiment of an ultrasonic tool 100. The region is around the contact point 112 between the ultrasonic horn 40 and the amplitude enhancer 60. The amplitude enhancer 60 comprises a through hole 64 having a shoulder 62 in the lower region. Between the ultrasonic horn 40 and the amplitude enhancer 60, an insulating washer is arranged as an annular insulating element 350. The insulating washer is made of an insulating material or provided with an insulating coating, thereby constituting an insulating device 300.

[0112] A transverse hole 48 and a central blind hole 49 are provided in the sonotrode 40, wherein the blind hole 49 opens into the transverse hole 48. The transverse hole 48 has a rectangular cross section and the blind hole 49 is circular. A cuboid transverse portion 330 in the form of a slot can be inserted into the transverse hole 48 from the side. The transverse portion 330 has a central threaded hole 332, which is arranged concentrically with the blind hole 49. Subsequently, a screw can be inserted from above through the through hole 64, which can be located on the shoulder 62 and can be screwed into the hole 332 of the slot. The slot is pulled upwards until it abuts the top of the transverse hole 48. If the screw is screwed in further, a clamping force is applied. The transverse portion 330 is provided with an insulating coating, wherein the hole is not coated. In this way, the transverse portion 330 constitutes the insulating device 300. Since the top side of the transverse portion 330 abuts against the top side of the transverse hole 48, a galvanic isolation is produced.

[0113] In other embodiments, the transverse portion 330 may also be cylindrical. If the transverse portion 330 is configured as a cylinder, the cross section of the transverse hole 48 is preferably circular or elliptical.

[0114] The galvanic separation between the sonotrode 40 and the amplitude enhancer 60 is created by the insulating washer and the transverse portion 330 .

[0115] The exemplary embodiment shown can also be used for the connection between a sonotrode and a converter component 10 or for the connection between an amplitude amplifier and a converter component 11 .

[0116] Alternatively, the transverse portion 330 may also be composed entirely of insulating material.

[0117] exist Fig.12 In the embodiment shown, the ultrasonic tool 100 comprises a converter lower part 12 and an amplitude enhancer 60, which are joined together at a contact point 112. The converter lower part 12 comprises a through hole 13. In this embodiment, a cascade of several components is provided as a connecting element 310. The cascade comprises a threaded bolt having two insulated threaded portions. With one threaded portion, the threaded bolt is screwed into the internal thread of the converter lower part 12. The other end of the threaded bolt can be screwed into a first cascade part 340. The first cascade part 340 holds the second cascade part 342 in the propagation direction R by means of a positive lock.

[0118] The second cascade part 342 has an outer thread, by means of which it is connected to the inner thread of the amplitude enhancer 60. The second cascade part 342 is provided with an insulating coating on the top surface 344 and the bottom surface 346. In this way, the second cascade part 342 constitutes the insulating device 300. With this top surface 334, the second cascade part 342 contacts the converter lower part 12. With this bottom surface 346, the second cascade part 342 contacts the first cascade part 340. The threaded bolt does not touch the second cascade part 342. Here, additional insulating devices, such as insulating sleeves, can also be provided between the threaded bolt and the second cascade part 342. In this way, the converter lower part 12 and the amplitude enhancer 60 are galvanically isolated from each other.

[0119] Such a cascade can also be used for the connection between the amplitude intensifier 60 and the sonotrode 40 or the connection between the sonotrode 400 and the converter component 10 .

[0120] Also according to Fig.13 In an embodiment, a cascade is provided as a connecting element 310. Fig.12 Compared with the embodiment of the present invention, the substantial difference is that the second cascade part 342 has a smaller diameter and ends upward at the amplitude enhancer 60. Therefore, an insulating washer as an insulating element 350 is provided between the amplitude enhancer 60 and the converter lower part 12. The insulating washer is made of an insulating material or provided with an insulating coating, thereby constituting the insulating device 300.

[0121] In addition, in this embodiment, the second cascade part 342 is not coated. On the contrary, the first cascade part 340 is provided with an insulating coating on the axial contact surface with the second cascade part 342. Alternatively, in this embodiment, the first cascade part 340 can also be completely composed of an insulating material, such as ceramic. In any case, the first cascade part 340 forms the insulating device 300. In the radial direction, the first cascade part 340 and the second cascade part 342 do not contact each other. Additional insulating devices, such as insulating sleeves, can also be provided here.

[0122] This type of connection can also be used between the sonotrode 40 and the amplitude intensifier 60 or between the sonotrode region 40 and the converter component 10 .

[0123] Fig.14Another embodiment of an ultrasonic tool 100 is shown. In this embodiment, a threaded bolt is provided as a connecting element 310 and comprises an external threaded portion and a smooth portion 311. The smooth portion 311 is provided with an insulating coating and the bolt is shrunk together with the smooth portion 311 into a blind hole of the sonotrode 40. In this way, the bolt forms the insulating device 300. The threaded portion of the bolt protrudes upward from the sonotrode 40. In this way, the amplitude enhancer 60 can be screwed onto the threaded portion by means of a threaded hole. An annular insulating washer is also provided as an insulating element 350 at the contact point 112, which is composed of an insulating material or provided with an insulating coating, thereby forming the insulating device 300. In this way, a galvanic isolation is established between the sonotrode 40 and the amplitude enhancer 60.

[0124] exist Fig.15 In the illustrated embodiment, the ultrasonic tool 100 includes a sonotrode 40 and an amplitude enhancer 60. An insulating washer is provided at the contact point 112 as an insulating element 350. The insulating washer is annular. The insulating washer is made of an insulating material or provided with an insulating coating, thereby forming an insulating device 300.

[0125] The sonotrode 40 has a bolt 47 which is manufactured integrally with the sonotrode 40. The bolt 47 protrudes upward through the recess of the annular gasket. The bolt 47 of the sonotrode 40 is provided with an insulating coating. In this way, the sonotrode 40 forms an insulating device 300. A threaded attachment 313 with an external thread is shrunk onto the bolt 47 as a connecting device 310. The amplitude enhancer 60 is screwed onto the external thread of the threaded attachment 313 by means of a threaded hole.

[0126] In an alternative embodiment, the insulating panel may be omitted if the entire top side of the sonotrode 40 is provided with an insulating coating.

[0127] This type of connection can also be used in other exemplary embodiments between the sonotrode 40 and the converter component 10 or between the amplitude booster 60 and the converter component 10 .

[0128] Fig.16 The embodiment shown is Figure 2 The embodiment of the invention differs substantially in that the threaded bolt forming the connection device 310 comprises two axially adjacent external threaded portions 317, 318, wherein each external threaded portion is provided with an external thread, wherein the external threads are isolated from one another, and wherein a circumferential flange is provided between the external threaded portions 317, 318, which isolates the external threads from one another. Only the first external threaded portion 317 and the flange are coated with insulating material. In this way, the threaded bolt forms the insulating device 300.

[0129] Instead of an insulating washer or a coating on an insulating washer, at least one of the two connected components, in the present case the sonotrode 40 and the amplitude booster 60, can also be provided with an insulating coating or at least partially consist of an insulating material, in particular on the corresponding contact surfaces. The entire insulating washer or its coating can then be omitted. This also applies to all embodiments with an insulating washer.

[0130] Reference numerals list

[0131] 10 Converter components

[0132] 11Converter housing

[0133] 12 Converter lower part

[0134] 13,64 through holes

[0135] 15,62 Shoulder

[0136] 16 Cover

[0137] 18 Converter screw

[0138] 20 Converters

[0139] 22 Piezoelectric element

[0140] 24 Neutral Electrode

[0141] 26-phase electrode

[0142] 31-phase conductor

[0143] 33 Neutral conductor

[0144] 35 Protective conductor

[0145] 39AC voltage source

[0146] 40 ultrasonic welding electrode

[0147] 42 Sealing surface

[0148] 44 signal terminals

[0149] 46 external thread

[0150] 47 bolts

[0151] 48 lateral holes

[0152] 49 blind holes

[0153] 60 Amplitude Enhancer

[0154] 66 Shoulder surface

[0155] 100 Ultrasonic Tools

[0156] 112 contact points

[0157] 110 Pairing Tool

[0158] 112 Sealing surface

[0159] 200 workpieces

[0160] 300 Insulation Device

[0161] 310 connection element / threaded bolt

[0162] 311 Smooth part

[0163] 313 threaded attachments

[0164] 314 internal thread

[0165] 316 protrusion

[0166] 317 first external thread part

[0167] 318 second external thread part

[0168] 320 Wire Thread Inserts

[0169] 330 Horizontal section

[0170] 332 threaded hole

[0171] 340 First cascade part

[0172] 342 Second cascade part

[0173] 350 Insulation Elements

[0174] 344,352 Top side

[0175] 346,354 bottom side

[0176] 356 flange screw

[0177] 358 flange shoulder

[0178] 360 Adhesive

[0179] 400 Voltage Source

[0180] 410 Sensor

[0181] K converter axis

[0182] R propagation direction

Claims

1. An ultrasonic tool for machining a workpiece by means of mechanical ultrasonic oscillations, the ultrasonic tool comprising a converter component and a sonotrode, wherein: The converter member comprises a converter with at least one piezoelectric element, wherein the converter member comprises a phase conductor and a neutral conductor for an AC voltage supply cable, wherein the at least one piezoelectric element is configured to convert the AC voltage into mechanical ultrasonic oscillations, wherein the converter member can be set to oscillate in resonance with the mechanical ultrasonic oscillations of a wavelength λ, wherein the converter member is mechanically coupled to the sonotrode and the sonotrode and the converter member are tuned to each other such that the sonotrode can be set to oscillate in resonance with the mechanical ultrasonic oscillations of the wavelength λ, wherein the sonotrode comprises a sealing surface, which is arranged to contact the workpiece to be machined, characterized in that the sealing surface of the sonotrode and the neutral conductor are galvanically isolated.

2. The ultrasonic tool according to claim 1, characterized in that The sonotrode comprises an electrically connected signal terminal connected to the sealing surface and for an electrical signal voltage, wherein the neutral conductor and the signal terminal are galvanically isolated.

3. The ultrasonic tool according to any one of the preceding claims, characterized in that The converter member comprises a converter housing, in which the at least one piezoelectric element is arranged and a protective conductor is provided, wherein the ultrasonic tool comprises: a first part, which comprises at least the neutral conductor; a second part, which comprises at least the protective conductor and the converter housing; and a third part, which comprises the sealing surface of the ultrasonic welding electrode and can output or receive a signal voltage via the signal terminal, wherein the second part and the third part are galvanically isolated, and wherein, optionally, the first part and the second part are additionally galvanically isolated.

4. The ultrasonic tool according to claim 3, characterized in that An insulating housing made of an electrically insulating material and defining an insulating space is disposed in the converter housing, wherein the at least one piezoelectric element and the neutral conductor are arranged in the insulating space, wherein the insulating housing is preferably hollow in an annular or cylindrical shape.

5. The ultrasonic tool according to any one of the preceding claims, characterized in that A counter tool, in particular a roller, is provided with a sealing surface which is positioned such that the workpiece to be machined can be arranged between the sealing surface of the sonotrode and the sealing surface of the counter tool during machining, wherein the sealing surface of the counter tool is preferably grounded.

6. The ultrasonic tool according to any one of claims 3 to 5, characterized in that: A voltage source is provided, with which the third portion can be subjected to a signal voltage, wherein a sensor is provided for detecting a charge applied to or dissipated from the third portion.

7. The ultrasonic tool according to claim 6, characterized in that The signal voltage is a DC voltage and is less than 30V, preferably less than 25V, and preferably between 5V and 12V.

8. The ultrasonic tool according to any one of claims 3 to 7, characterized in that: The third part is connected to the voltage source by means of an electrical cable, which is shielded and / or has a total capacitance of <2500 pF, in particular <1500 pF.

9. The ultrasonic tool according to any one of claims 3 to 8, characterized in that: The insulation resistance between the second portion and the third portion is at least 5 kΩ, in particular at least 7 kΩ, wherein the insulation resistance is preferably less than 100 MΩ.

10. The ultrasonic tool according to any one of the preceding claims, characterized in that An amplitude enhancer is arranged between the converter member and the sonotrode, wherein the converter member is mechanically coupled to the amplitude enhancer and the amplitude enhancer is mechanically coupled to the sonotrode, wherein the sonotrode, the amplitude enhancer and the converter member are tuned to one another such that the sonotrode can be set to oscillate in resonance with the mechanical ultrasonic oscillations of the wavelength λ.

11. The ultrasonic tool according to any one of the preceding claims, characterized in that A carrier is provided which engages the sonotrode, the converter component and / or the amplitude booster.

12. The ultrasonic tool according to any one of the preceding claims, characterized in that At least one insulating device is provided which effects a galvanic isolation of the sealing surface of the sonotrode and the neutral conductor.

13. The ultrasonic tool according to claim 12, characterized in that At least one insulating device is provided at exactly two locations, in particular at a contact point between the converter component, the sonotrode and / or the amplitude booster and at a connection point between the converter component, the sonotrode plate and / or the amplitude booster.

14. The ultrasonic tool according to any one of claims 12 or 13, characterized in that: The converter component and the sonotrode and / or the converter component and the amplitude intensifier and / or the amplitude intensifier and the sonotrode are connected to one another via at least one connecting element, in particular a screw and / or a threaded bolt and / or a threaded bushing, in particular with a clamping force of at least 20 kN, preferably less than 150 kN, in particular at least 30 kN and / or less than 90 kN, and the connecting element is designed as an insulating device and is at least partially provided with an insulating coating and / or consists at least partially of an insulating material.

15. The ultrasonic tool according to any one of claims 12 to 14, characterized in that At least one insulating element, in particular an insulating washer, is arranged between the converter component and the sonotrode, in particular between the converter component and the amplitude booster and / or between the amplitude booster and the sonotrode, the insulating element being designed as an insulating device and at least partially consisting of an insulating material and / or at least partially provided with an insulating coating.

16. The ultrasonic tool according to any one of claims 12 to 15, characterized in that The converter component and / or the amplitude booster and / or the sonotrode are designed as insulating devices and consist at least partially of insulating material and / or are at least partially provided with an insulating coating.

17. The ultrasonic tool according to any one of claims 14 to 16, characterized in that A cascade of several components is provided as the connecting element, wherein a first cascade part is preferably held by a second cascade part in the propagation direction by means of a form fit, and the first cascade part and / or the second cascade part are provided with an insulating coating for a form fit on respective contact surfaces.

18. The ultrasonic tool according to any one of claims 14 to 17, characterized in that The connecting element comprises a smooth portion which is provided with an insulating coating, wherein the smooth portion shrinks into the sonotrode or the converter member or the amplitude booster.

19. The ultrasonic tool according to any one of claims 14 to 18, characterized in that The connecting element comprises a smooth portion and a threaded attachment that is shrunk onto the smooth portion.

20. The ultrasonic tool according to any one of claims 10 to 19, characterized in that A through hole is provided in the amplitude enhancer, wherein the amplitude enhancer includes a portion provided with an insulating coating, wherein a screw is further provided, the head of the screw resting on the coated portion, being spaced apart from the inner surface of the through hole, and being screwed into the converter member or the ultrasonic welding electrode with its thread.

21. An ultrasonic tool according to any preceding claim, characterised in that A transverse hole is provided in the converter member or the amplitude enhancer or the sonotrode, into which the at least partially coated transverse section is inserted by means of a threaded hole, wherein, in addition to the transverse hole, the converter member, the amplitude enhancer or the sonotrode comprises a hole concentric with the threaded hole, in which a screw or a threaded bolt is arranged, wherein the screw or the threaded bolt is connected to the transverse section by means of the threaded hole.

22. The ultrasonic tool according to any one of claims 12 to 21, characterized in that A connecting piece, in particular a flange part, is provided as an insulating device, which is fastened to the converter component or the amplitude enhancer or the sonotrode by means of screws, wherein the connecting piece is provided with the insulating coating at a location supporting the screws.

23. The ultrasonic tool according to any one of claims 14 to 22, characterized in that The insulating coating and / or the insulating material comprises at least one of the following materials: ceramic, in particular chromium oxide (Cr2O3) or aluminum oxide (Al2O3), glass, polymer composite materials, in particular glass reinforced plastic (GRP) and carbon reinforced plastic (CRP).

24. The ultrasonic tool according to any one of claims 14 to 23, characterized in that The thickness of the insulating coating is at least 0.02 mm, preferably at most 0.5 mm.

25. The ultrasonic tool according to any one of claims 14 to 24, characterized in that The connecting element is a bolt having two axially adjacent external threaded portions, wherein each external threaded portion is provided with an external thread, wherein the external threads are isolated from each other, and wherein at least one of the external threaded portions, in particular exactly one of the external threaded portions, is coated with an insulating material.

26. The ultrasonic tool according to any one of claims 14 to 25, characterized in that The connecting element is a screw or a threaded bolt with an additional annular washer, wherein the screw or the threaded bolt and the annular washer are configured as a one-piece or multi-piece unit, wherein both the screw or the threaded bolt and the annular washer are configured as insulating devices and at least partially consist of an insulating material and / or are at least partially coated with an insulating material.

27. The ultrasonic tool according to any one of claims 14 to 26, characterized in that The connecting element is an element engaged with the outer peripheral surface, in particular a union nut.

28. The ultrasonic tool according to any one of claims 14 to 27, characterized in that The converter component and the sonotrode and / or the converter component and the amplitude booster and / or the amplitude booster and the sonotrode are connected to one another via an insulating adhesive, in particular polyurethane and / or epoxy resin, wherein the connecting element is connected to the converter component and / or the sonotrode and / or the amplitude booster, in particular via an insulating adhesive.

29. A method for machining a workpiece by mechanical ultrasonic oscillations using an ultrasonic tool as claimed in any one of the preceding claims, It is characterized in that The workpiece is arranged to be machined between the sonotrode and a counter tool and the workpiece is machined by means of the ultrasonic tool, generating an electrical signal voltage, in particular a signal voltage of less than 30 V, preferably less than 25 V, most preferably between 5 V and 12 V, at a signal terminal of the sonotrode electrically connected to the sealing surface of the sonotrode, wherein a current flow between the neutral conductor and the signal terminal is prevented, and It is at least temporarily determined whether a current is flowing between the sonotrode and the counter tool and / or a voltage is decreasing between the sonotrode and the counter tool.

30. The method according to claim 29, It is characterized in that The duration of at least one current flow and / or voltage reduction between the ultrasonic welding electrode and the counter tool is determined, and if the duration exceeds a predefined time limit, the current flow and / or voltage reduction is evaluated as a contact between the sealing surfaces, wherein the contact time corresponds to the duration of the current flow or the voltage reduction, wherein the time limit is in particular >0.01 μs and particularly preferably ≥1 μs.

31. The method according to claim 29 or 30, It is characterized in that The current intensity is used to determine at least one current flow and / or voltage drop between the ultrasonic welding electrode and the counter tool, and if the current exceeds a predefined current limit, the current flow and / or voltage drop is evaluated as contact between the sealing surfaces, wherein the current threshold is in particular >1 mA and particularly preferably <300 mA.

32. The method according to any one of claims 29 to 31, It is characterized in that At least one of the following parameters is determined within at least a predetermined period of time, in particular within the most recently elapsed milliseconds, wherein the parameters are preferably stored and / or output: - the total number of contacts between the sonotrode and the counter tool - The longest contact time of all contacts - The sum of contact time for all contacts.

33. The method according to claim 32, It is characterized in that Depending on one or more parameters, the position of the ultrasonic tool, in particular the position of the sonotrode, is adjusted, the force applied to the sonotrode is reduced or increased, an alarm is output, and / or the machining operation is stopped, in particular by switching off the AC voltage.

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