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DE-102024132909-A1 - Ultrasonic vibration system with surge protection and ultrasonic welding system with such a

DE102024132909A1DE 102024132909 A1DE102024132909 A1DE 102024132909A1DE-102024132909-A1

Abstract

The present invention relates to an ultrasonic vibration system with overvoltage protection and an ultrasonic welding system with such an ultrasonic vibration system, characterized in that a voltage-limiting protective component with a first and a second connection is provided.

Inventors

  • Thomas Weber
  • Stefan Raststetter
  • Kui Chen
  • Mathias Bach

Assignees

  • HERRMANN ULTRASCHALLTECHNIK GMBH & CO. KG

Dates

Publication Date
20260513
Application Date
20241111

Claims (10)

  1. Ultrasonic vibration system with a converter for converting an alternating electrical voltage into a mechanical vibration and a sonotrode connected to the converter, wherein the converter is preferably connected to the sonotrode via an amplitude transformer, wherein the converter has at least one piezoelectric element, characterized in that a voltage-limiting protective component with a first and a second connection is provided, wherein the first connection is electrically connected to the sonotrode and the second connection is electrically connected to a neutral conductor or ground, wherein the voltage-limiting protective component is designed such that, when a voltage U greater than U <sub>max</sub> is applied between the first and second connections, it provides an electrical connection between the first and second connections, and when a voltage U less than U<sub> min </sub> is applied between the first and second connections, it does not provide an electrical connection between the first and second connections, wherein U <sub>max</sub> is greater than or equal to U<sub> min</sub> .
  2. Ultrasonic vibration system according to Claim 1 , characterized in that the voltage-limiting protective component is a protective diode, a varistor, a thyristor or a gas discharge tube, wherein preferably the voltage-limiting protective component is a Zener diode or a TVS diode.
  3. Ultrasonic vibration system according to one of the preceding claims characterized in that the converter has a housing in which the at least one piezoelectric element is arranged, wherein the housing is electrically connected to the sonotrode.
  4. Ultrasonic vibration system according to one of the preceding claims characterized in that the ultrasonic vibration system has a holder which is provided for connecting the ultrasonic vibration system to a machine stand, wherein the holder is electrically connected to the sonotrode and the first connection of the voltage-limiting protective component is connected to the holder.
  5. Ultrasonic welding system with an ultrasonic vibration system according to one of the preceding claims, characterized in that a voltage and/or current source is provided which is capable of applying a voltage U k relative to ground to the sonotrode which is smaller than U max and preferably smaller than U min .
  6. Ultrasonic welding system according to Claim 5 , characterized in that a current measuring device is provided which is arranged and configured in such a way as to measure a current flow from the voltage and/or current source to the sonotrode.
  7. Ultrasonic welding system according to Claim 5 or 6 , characterized in that a control device is provided which is arranged and set up to check the function of the voltage-limiting protective component.
  8. Ultrasonic welding system according to Claim 7 , characterized in that the control device ensures that a control voltage U c is applied between sonotrode and ground, wherein U c is greater than U MAX , and, if the current measuring device does not measure a current I greater than zero, evaluates the function of the voltage-limiting protective component as faulty.
  9. Ultrasonic welding system according to Claim 8 , characterized in that if the function of the voltage-limiting protective component is deemed faulty, the control device is configured in such a way as to prevent a voltage from being applied to the piezoelectric element.
  10. Ultrasonic welding system according to Claim 8 or 9 , characterized in that the ultrasonic welding system is arranged and set up in such a way that whenever an alternating electrical voltage is to be applied to the at least one piezoelectric element, the ultrasonic welding system first checks the function of the voltage-limiting protective component by means of the control device, and only applies the alternating electrical voltage to the at least one piezoelectric element if the test has been passed.

Description

The present invention relates to an ultrasonic vibration system with overvoltage protection and an ultrasonic welding system with such an ultrasonic vibration system. A typical ultrasonic vibration system consists of a converter, which transforms an alternating electrical voltage into a mechanical vibration, and a sonotrode connected to the converter. The converter contains at least one piezoelectric element, and in practice often several. An alternating electrical voltage is applied to these piezoelectric elements, causing them to deform due to the piezoelectric effect and generate a mechanical vibration. The voltage is supplied via a phase conductor and discharged via a neutral conductor. The sonotrode is rigidly coupled to the converter and is also excited by its mechanical vibration. Both the converter and the sonotrode are tuned to a common resonant frequency, resulting in a high vibration intensity. Often, an amplitude transformer is located between the converter and the sonotrode, changing the amplitude of the oscillation while keeping the frequency constant. The sonotrode is designed to come into contact with a material in order to shape, weld, or cut it. For this purpose, the material to be processed is usually positioned between the sonotrode and a counter-tool, also called an anvil. The piezoelectric elements are usually housed in a converter casing that protects them from environmental influences. This casing is typically connected to the neutral conductor and assumes its potential. However, if the line between the generator and the neutral conductor is interrupted, for example by a break, a fault occurs: The phase conductor continues to supply the piezoelectric elements, and the excitation continues. A potential builds up at the other end of the piezoelectric elements, which, due to the missing connection to the neutral conductor, is not dissipated. This potential can then be present on the metallic converter housing or arc to the converter housing and is transmitted to the sonotrode via the metallic mounting of the ultrasonic transducer. Since this poses a potential safety hazard, a person could unintentionally touch live parts. To prevent this, the converter housing is usually additionally grounded via a protective conductor. However, in certain applications, contact between the sonotrode and the counter-tool should also be detected. In the EP 0 790 888 B1 It is described that a measuring device is used to detect changes in resistance, current flow, or voltage between the sonotrode and the counter-tool. In this configuration, grounding the converter housing via a protective conductor has not been feasible until now, which is why complex safety precautions such as insulating the piezoelectric elements within the converter housing were necessary. The WO 2024/051918 A1 It is therefore proposed to galvanically isolate the sealing surface of the sonotrode from the neutral conductor. In the event of a fault, a potential can now be present on the neutral conductor without being transferred to the sealing surface. This galvanic isolation is achieved, for example, by an insulating element between the sonotrode and the converter. However, this solution is complex to manufacture, as it is necessary to ensure the most loss-free transmission of the mechanical vibration generated by the piezoelectric elements to the sonotrode, despite the insulation between the sonotrode and the converter. The object of the present invention is therefore to provide an ultrasonic vibration system or an ultrasonic welding system that allows safe operation and at the same time dampens the mechanical vibration generated by the converter as little as possible. With regard to the ultrasonic vibration system, this problem is solved by providing a voltage-limiting protective component with a first and a second terminal, wherein the first terminal is electrically connected to the sonotrode and the second terminal is electrically connected to a neutral conductor or ground. The voltage-limiting protective component is designed such that, if a voltage U greater than U<sub>max</sub> is applied between the first and second terminals, it provides an electrical connection between the first and second terminals, and if a voltage U less than U<sub> min </sub> is applied between the first and second terminals, it does not provide an electrical connection between the first and second terminals, where U <sub>max </sub> is greater than or equal to U <sub>min</sub> . As a rule, the voltage-limiting protective component will have its second terminal electrically connected to ground, as this is the preferred embodiment. Therefore, it will always be assumed in the following that the second terminal is connected to ground. Reason In addition, the present invention also works when the second connection is connected to the neutral conductor, since this conductor carries away the charge provided via the phase conductor, but is usually also connected to