Ultrasonic Machine Tool Comprising Two Sonotrodes and Method for Operating Same

Abstract

The present invention relates to an ultrasonic machine tool comprising a first sonotrode (2) with a first resonant frequency f.sub.1, a first converter (4) which is connected to the first sonotrode (2), and a generator (1) with a generator output for generating a first electrical alternating voltage with the first frequency f.sub.1 and for outputting the first electrical alternating voltage at the generator output, the generator output being connected to the first converter (4). According to the invention, a second sonotrode (3) with a second resonant frequency h and a second converter (5) which is connected to the second sonotrode (3) are provided, wherein the generator output is connected to the second converter (5) and the generator (1) is designed to produce a mix signal which has the first electrical alternating voltage and a second electrical alternating voltage with the second frequency h, and to output the mix signal at the generator output, and wherein the first frequency f.sub.1 and the second frequency f.sub.2 differ from one another.

Claims

1. Ultrasonic machine tool comprising a first sonotrode (2) with a first resonant frequency f.sub.1, a first converter (4), which is connected to the first sonotrode (2), and a generator (1) with a generator output for generating a first electrical alternating voltage with the first frequency f.sub.1 and for outputting the first electrical alternating voltage at the generator output, wherein the generator output is connected to the first converter (4), characterized in that a second sonotrode (3) with a second resonant frequency f.sub.2 and a second converter (5), which is connected to the second sonotrode (3), are provided, wherein the generator output is connected to the second converter (5), and the generator (1) is formed so as to generate a mixed signal which has the first electrical alternating voltage and a second electrical alternating voltage with the second frequency f.sub.2, and to output the mixed signal at the generator output, and wherein the first frequency f.sub.1 and the second frequency f.sub.2 differ from one another.

2. Ultrasonic machine tool according to claim 1, characterized in that the difference between the first frequency f.sub.1 and the second frequency f.sub.2 is greater than 300 Hz.

3. Ultrasonic machine tool according to claim 1, characterized in that a first ammeter is provided for measuring the current flowing through the first converter (4) and a second ammeter is provided for measuring the current flowing through the second converter (5).

4. Ultrasonic machine tool according to claim 3, characterized in that a first controller is provided which, on the basis of the current flowing through the first converter (4), determines the ACTUAL vibration amplitude of the first sonotrode (2) and, in the case of a difference between the ACTUAL vibration amplitude determined and a predetermined TARGET vibration amplitude, changes the amplitude of the first electrical alternating voltage.

5. Method for simultaneously operating a first ultrasonic vibration unit consisting of a first converter (4) and a first sonotrode (2) with a resonant frequency f.sub.1 and a second ultrasonic vibration unit consisting of a second converter (5) and a second sonotrode (3) with a resonant frequency f.sub.2, characterized by the steps: a) providing the first and second ultrasonic vibration units, b) providing a generator (1) with a generator output, c) connecting the generator output to a signal input of the first converter (4) and to a signal input of the second converter (5), d) generating a mixed signal consisting of a first electrical alternating voltage with the first frequency f.sub.1 and a second electrical alternating voltage with the second frequency f.sub.2, e) outputting the mixed signal at the generator output.

6. Method according to claim 5, characterized in that the second resonant frequency f.sub.2 is selected at least 1% greater than the first resonant frequency f.sub.1.

7. Method according to claim 5, characterized in that the mixed signal is the sum of the first electrical alternating voltage and the second electrical alternating voltage.

8. Method according to claim 7, characterized in that the current I.sub.1 through the first converter (4) and/or the current I.sub.2 through the second converter (5) is measured.

9. Method according to claim 8, characterized in that the ACTUAL vibration amplitude of the first sonotrode (2) is calculated from the current I.sub.1 through the first converter (4) and the amplitude U.sub.1 of the first electrical alternating voltage.

10. Method according to claim 9, characterized in that the vibration amplitude of the first sonotrode (2) is controlled, wherein the first amplitude U.sub.1 of the first alternating voltage is used as control variable.

11. Ultrasonic machine tool according to claim 2, characterized in that the difference between the first frequency f.sub.1 and the second frequency f.sub.2 is greater than 500 Hz.

12. Ultrasonic machine tool according to claim 11, characterized in that the difference between the first frequency f.sub.1 and the second frequency f.sub.2 is greater than 1000 Hz.

13. Ultrasonic machine tool according to claim 4 wherein a second controller is preferably provided which, on the basis of the current flowing through the second converter (5), determines the ACTUAL vibration amplitude of the second sonotrode (3) and, in the case of a difference between the ACTUAL vibration amplitude determined and a predetermined TARGET vibration amplitude, changes the amplitude of the second electrical alternating voltage.

14. Method according to claim 6, characterized in that the second resonant frequency f.sub.2 is selected at least 2% greater than the first resonant frequency f.sub.1.

15. Method according to claim 9, wherein the ACTUAL vibration amplitude of the second sonotrode (3) is preferably also calculated from the current I.sub.2 through the first converter (4) and the amplitude U.sub.2 of the first electrical alternating voltage.

16. Method according to claim 10 wherein the vibration amplitude of the second sonotrode (3) is preferably also controlled, wherein the second amplitude U.sub.2 of the second alternating voltage is used as control variable.

Description

[0036] Further advantages, features and possible applications of the present invention become clear with reference to the following description of a preferred embodiment as well as the associated figure. There is shown in:

[0037] FIG. 1 a schematic representation of a preferred embodiment of the invention.

[0038] FIG. 1 shows a schematic representation of an ultrasonic machine tool. The ultrasonic machine tool has a first sonotrode 2 and a second sonotrode 3.

[0039] The first sonotrode 2 is connected to a first converter 4. An amplitude transformer could be arranged between first sonotrode 2 and first converter 4. The converter 4 converts the electrical alternating voltage applied at its input into a mechanical vibration. The ultrasonic vibration system consisting of the first sonotrode 2 and the first converter 4 has a first resonant frequency. If an electrical alternating voltage with the resonant frequency or a frequency which differs slightly from the resonant frequency is applied at the input of the converter 4, the first ultrasonic vibration unit is set vibrating and the sonotrode 2 can be used for machining a material.

[0040] The second sonotrode 3 is connected to a second converter 5. The first ultrasonic vibration unit with the first sonotrode 2 and the first converter 4 is constructed just like the second ultrasonic vibration unit consisting of the second sonotrode 3 and the second converter 5, wherein the resonant frequencies of the two ultrasonic vibration systems differ from one another.

[0041] Furthermore, a generator 1 is provided, which provides a signal at an output, which signal is connected both to the first converter 4 and to the second converter 5.

[0042] The generator 1 generates a mixed frequency which is composed of the sum of the individual electrical alternating voltages for the individual ultrasonic vibration systems. In the example shown, the mixed frequency is therefore the sum of the first electrical alternating voltage for driving the first sonotrode 2 and the second electrical alternating voltage for exciting the second sonotrode 3.

[0043] The mixed frequency generated by the generator 1 is supplied to a power stage integrated in the generator. The power stage can be a digital power stage, which outputs the corresponding mixed frequency and supplies it to the two converters 4 and 5.

[0044] The high-frequency currents are measured by means of so-called ammeters. The amplitude of the connected system can be ascertained from the measured currents via a calculation method. The ACTUAL amplitudes ascertained in this way are each supplied to one controller and the frequency and/or the voltage are correspondingly controlled. The corresponding calculation method is for example described in WO 2013/017452.

LIST OF REFERENCE NUMBERS

[0045] 1 generator

[0046] 2, 3 sonotrode

[0047] 4, 5 converter