Sonotrode with optimized pore geometry

Abstract

The invention relates to an ultrasonic vibration element (1) capable of resonantly vibrating with longitudinal ultrasonic vibrations in a longitudinal direction (9). The ultrasonic vibration unit is delimited in the longitudinal direction (9) as a rear face on the one hand and a front face on the other hand, the front face being designed as or adjacent to a sealing face (2) intended to be in contact with another ultrasonic vibration element (1) for transmitting ultrasonic vibrations to the other ultrasonic vibration element (1) or intended to be in contact with a workpiece and transmit ultrasonic vibrations to the workpiece. A circumferential side face (3) is provided, connecting the rear face and the front face to each other. The ultrasonic vibration element (1) has a pore 4 in the side face (3), the pore 4 having a pore length l in the pore longitudinal direction (15), a pore width b in the pore transverse direction and a pore depth t in the pore depth direction. The pore longitudinal direction (15), the pore transverse direction and the pore depth direction are arranged perpendicular to one another, the pore depth t is selected such that the pores (4) completely penetrate the ultrasonic element, and the pore length l is greater than the pore width b. According to the invention, it is proposed that the pores (4) are not axially symmetrical in cross-section with respect to the pore longitudinal axis (9) along the pore longitudinal direction (15) in order to provide an alternative pore geometry and arrangement that meets the requirements of maximum permissible mechanical stress values, has high vibration amplitudes and does not require pores inclined with respect to the longitudinal axis of the sonotrode.

Description

[Technical field]

[0001] The present invention relates to an ultrasonic vibration element that can be resonantly vibrated with longitudinal ultrasonic vibrations, the ultrasonic vibration unit of which is bounded in the longitudinal direction as a rear face on one side and a front face on the other side, the front face being designed as or adjacent to a sealing face intended to come into contact with another ultrasonic vibration element for transmitting ultrasonic vibrations to another ultrasonic vibration element, or intended to come into contact with another ultrasonic vibration element for transmitting ultrasonic vibrations to another ultrasonic vibration element. [Background technology]

[0002] The ultrasonic element usually has a circumferential side surface connecting the rear surface and the front surface. Such an ultrasonic element is designed as a sonotrode and is known from EP 2 774 746 A1. In this ultrasonic element, the front surface is designed as a sealing surface. The ultrasonic element can also be designed as an amplitude converter or converter.

[0003] In principle, the sonotrode is a half-wave resonator, i.e. the total length of the sonotrode along the longitudinal direction corresponds to half the wavelength of the sonotrode's resonant vibration.

[0004] The ultrasonic transducer element has a series of pores on its side. The pores have a pore length l in a pore length direction, a pore width b in a pore width direction, and a pore depth t in a pore depth direction. The pore length, pore width, and pore depth directions are arranged perpendicular to one another. The pore depth t is selected so that the pores pass completely through the ultrasonic element, and the pore length l is greater than the pore width b.

[0005] The pores are used, among other things, to reduce the stresses induced in the material by excitation with longitudinal ultrasonic vibrations and to allow the sonotrode to be excited at higher vibration amplitudes. Depending on the dimensioning and positioning of the pores, the vibration amplitude and position of unwanted vibration modes can also be influenced.

[0006] The maximum allowable mechanical stress values ​​in the material are often also taken into account when sizing the pores, however the introduction of pores usually gives rise to additional unwanted vibration modes, the excitation frequencies of which must be kept as far as possible from those of the main frequency for operation.

[0007] The prior art details the drawbacks of arranging the pores parallel to the longitudinal direction, so in EP 2 774 746 the pores are arranged at an angle to the longitudinal axis of the sonotrode. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] European Patent Publication No. 2774746 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, based on the above-mentioned prior art, the object of the present invention is to provide an alternative pore geometry and arrangement which meets the requirements of maximum permissible mechanical stress values, has a high vibration amplitude and does not require pores inclined with respect to the longitudinal axis of the sonotrode. [Means for solving the problem]

[0010] This problem is solved by providing pores which, in cross-sectional view, are not axially symmetrical with respect to a longitudinal axis of the pores along the longitudinal direction of the pores. Effect of the Invention

[0011] In contrast to known pores, the pores according to the invention are designed asymmetrically relative to the pore longitudinal direction. Then, it is not necessary to arrange the pores at an angle as in the prior art, instead the pore longitudinal direction and the longitudinal direction may form an angle of less than 25°, preferably less than 5°, preferably 0°. In this manner, the desired vibration results are achieved through a non-axisymmetric design of the pores.

[0012] In a preferred embodiment, two pores are provided that are axially symmetrically arranged with respect to a longitudinal axis. In a particularly preferred embodiment, four slots are provided, two of the four slots being axially symmetrically arranged with respect to the longitudinal axis. The provision of multiple pores improves the mechanical stress of the ultrasonic transducer element, and also improves the location of unwanted secondary resonance.

[0013] In a preferred embodiment, the ultrasonic transducer element has a first, second and third portion, the first portion having a thickness less than the third portion, the second portion having a varying thickness and connecting the first portion to the third portion, the three portions being arranged one behind the other in the longitudinal direction. The different thicknesses allow for tuning and / or amplifying the amplitude of the ultrasonic vibrations.Thus, the first portion is preferably arranged to comprise a front surface, while the third portion comprises a rear surface.

[0014] In a preferred embodiment, the first part has a sealing surface intended to come into contact with the work piece. This ensures that when the ultrasonic vibration element is excited, ultrasonic vibrations of a relatively large oscillation amplitude are generated at the sealing surface.

[0015] In another preferred embodiment, the third part has a recess in which at least one piezoelectric element is placed. The ultrasonic element is therefore very compact and vibrations are generated in the ultrasonic element by the piezoelectric element and transmitted to the workpiece via the ultrasonic element. This ultrasonic element thus integrates the sonotrode, the amplitude converter and the converter in a single element.

[0016] In a further preferred embodiment, the pore is bounded by two longitudinal walls and two transverse walls, a first of the two longitudinal walls being at least partially further away from the longitudinal axis of the pore than a second of the two longitudinal walls. Essentially, such a pore can be formed by first forming a pore with two parallel longitudinal walls and then providing a recess in the first longitudinal wall. Preferably, the first vertical wall is positioned farther away from a central longitudinal axis of the ultrasonic transducer element than the second vertical wall. As a result, mechanical stresses within the ultrasonic vibration element can be further reduced.In a further preferred embodiment, the two lateral walls are concavely curved, and the two lateral walls are preferably curved with the same radius of curvature. Furthermore, it is advantageous if the first longitudinal wall is designed to be at least partially concave.

[0017] Further advantages, features and possible applications will become apparent from the following description of preferred embodiments and the accompanying drawings. [Brief description of the drawings]

[0018] The drawings are as follows: FIG. 1 is a perspective view of an ultrasonic vibration element according to the present invention. 2 is a partial cross-sectional plan view of the acoustic wave vibration element of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 1 shows a perspective view of an embodiment of an ultrasonic transducer 1 according to the invention. A front face 2 designed as a sealing face 2 intended to come into contact with the workpiece is shown. A rear face (not shown) is arranged opposite the front face 2. The front face 2 and the rear face are connected to each other via circumferential side faces 3.

[0020] The ultrasonic vibration element has three axial portions along its longitudinal axis 9, namely a first portion 6 having a thickness that corresponds approximately to the width of the sealing surface 2, a third portion 8 designed to be significantly thicker than the first portion 6, and a second portion of varying thickness located between the first portion 6 and the third portion 8.

[0021] In this embodiment, the ultrasonic vibration element has a recess in the third portion 8, in which a plurality of piezoelectric elements 5 capable of ultrasonically vibrating the ultrasonic vibration element 1 are disposed. In this embodiment, the piezoelectric elements 5 have through openings through which the screws 18 engage. The upper part 17 is pressed against the piezoelectric elements 5 by the nuts 16, so that the piezoelectric elements 5 are sandwiched between the upper part 17 and the ultrasonic vibration element 1.

[0022] In order to prevent excessive mechanical stresses in the material and to optimise the location of unwanted secondary resonances, four fine holes 4 are provided which penetrate the material completely in depth. According to the invention, the pore has a special shape: it has two transverse walls 10 as well as a first longitudinal wall 11 and a second longitudinal wall 12.

[0023] The pores extend along a pore longitudinal direction 15. In the example shown, the pore longitudinal direction 15 forms an angle of 0° with the longitudinal direction 9 of the ultrasonic transducer elements, in other words it extends parallel to the longitudinal direction 9 of the ultrasonic transducer elements.

[0024] The two transverse walls 10 of the pore are curved. The second longitudinal wall of the pore 12 is also parallel to the longitudinal axis 9. The longitudinal wall 11 of the pore 4 has a concave curvature.

[0025] The pores according to the invention can basically be formed by first forming two parallel longitudinal walls and then forming a corresponding recess in the first wall 11. As shown for the two pores 4 located closer to the rear face, multiple recesses 13, 14 may be formed for one pore. [Explanation of symbols]

[0026] 1 Ultrasonic vibration element 2 Sealing surface, front 3. Aspects 4. Pore 5 Piezoelectric element 6 Part 1 7 Part 2 8 Part 3

Claims

1. an ultrasonic vibration element (1) capable of resonantly vibrating with longitudinal ultrasonic vibrations in a longitudinal direction (9), the ultrasonic vibration unit of which is delimited in said longitudinal direction (9) as a rear surface on one side and a front surface on the other side, the front surface being intended to be in contact with another ultrasonic vibration element (1) in order to transmit ultrasonic vibrations to the other ultrasonic vibration element (1), or being designed as or adjacent to a sealing surface (2) intended to be in contact with a workpiece and transmit ultrasonic vibrations to the workpiece, a circumferential side surface (3) connecting the rear surface and the front surface to each other; The ultrasonic vibration element (1) has a pore (4) on the side surface (3), The pore (4) has a pore length 1 in the pore longitudinal direction (15), a pore width b in the pore transverse direction, and a pore depth t in the pore depth direction, The pore longitudinal direction (15), the pore lateral direction, and the pore depth direction are arranged perpendicular to each other, The pore depth t is selected so that the pore (4) passes completely through the ultrasonic element, In the ultrasonic vibration element (1), the pore length l is greater than the pore width b. The ultrasonic vibration element (1) is characterized in that the pore (4) is not axially symmetrical with respect to a pore longitudinal axis (9) along the pore longitudinal direction (15) in a longitudinal cross-sectional view.

2. 2. An ultrasonic vibration element (1) according to claim 1, characterized in that the longitudinal direction (15) of the pores and the longitudinal direction (9) form an angle of less than 25°, preferably less than 5°, preferably 0°.

3. 2. An ultrasonic vibration element (1) according to claim 1, characterized in that it is provided with two pores (4) arranged symmetrically with respect to an axis along the longitudinal direction (9).

4. An ultrasonic vibration element (1) as described in claim 2, characterized in that it has two pores (4) arranged axially symmetrically with respect to an axis along the longitudinal direction (9).

5. 4. The ultrasonic vibration element (1) according to claim 3, characterized in that four pores (4) are provided, two of the four pores (4) being arranged axially symmetrically with respect to an axis along the longitudinal direction (9).

6. 6. An ultrasonic vibration element (1) according to claim 3 or 5, characterized in that the ultrasonic vibration element has first, second and third parts (6, 7, 8), the thickness of the first part (6) being smaller than the thickness of the third part (8), and the second part (7) having a varying thickness and connecting the first part (6) to the third part (8).

7. 7. Ultrasonic vibration element (1) according to claim 6, characterized in that the first part (6) has a sealing surface (2) intended to come into contact with the workpiece.

8. 7. An ultrasonic vibration element (1) according to claim 6, characterized in that the third part (8) has a recess in which at least one piezoelectric element 5 is arranged.

9. the pore (4) is bounded by two longitudinal walls (11, 12) and two transverse walls (10), the first of the two longitudinal walls (11, 12) being at least partially farther from the pore longitudinal axis (9) than the second of the two longitudinal axes (9); Preferably, the first vertical wall (11) is arranged farther from the central axis of the ultrasonic vibration element (1) extending in the vertical direction (9) than the second vertical wall (12).

10. 10. An ultrasonic vibration element (1) according to claim 9, characterized in that the two lateral walls (10) are concavely curved, the two lateral walls (10) preferably being curved with the same radius of curvature.

11. 10. Ultrasonic vibration element (1) according to claim 9, characterized in that the first longitudinal wall (11) is at least partially concavely curved.

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