Compensation for thermal deformation on sonotrodes

Abstract

A sonotrode for an ultrasonic welding apparatus, having a lower portion of length u and an upper portion of length o, the upper portion and the lower portion adjacent on a longitudinal axis of the sonotrode, and the total length of the sonotrode in the direction of the longitudinal axis being u+o, the lower portion having a sealing surface oriented perpendicular to the longitudinal axis, the sealing surface contacting a material to be processed. The lower portion has a slot, wherein the slot extends from the sealing surface to a side of the lower portion opposing the sealing surface, such that the lower portion of the sonotrode is divided into a plurality of segments which lie adjacent each other in a direction perpendicular to the longitudinal axis.

Claims

1. A sonotrode for an ultrasonic welding apparatus, the sonostrode comprising: a lower portion of length u and an upper portion of length o, the upper portion and the lower portion being arranged adjacent to each other on a longitudinal axis of the sonotrode, and a total length of the sonotrode in a direction of the longitudinal axis being u+o, the lower portion having a sealing surface oriented perpendicular to the longitudinal axis, the sealing surface configured to contact with a material to be processed, wherein the lower portion has a slot, wherein the slot extends from the sealing surface to a side of the lower portion opposing the sealing surface, such that the lower portion of the sonotrode is divided into a plurality of segments which lie adjacent to each other in a direction perpendicular to the longitudinal axis, the slot having two slot walls, and a spacing between the two slot walls tapering in the direction of the sealing surface.

2. The sonotrode according to claim 1, wherein u >0.25o.

3. The sonotrode according to claim 1, wherein 0.8o<u<1.5o.

4. The sonotrode according to claim 1, wherein the sealing surface is bordered by two opposing side surfaces of the sonotrode which extend essentially parallel to each other, and the slot in a region of the sealing surface forms an angle of <90 with each of the two side surfaces of the sonotrode.

5. The sonotrode according to claim 1, wherein the tapering is stepped.

6. The sonotrode according to claim 5, wherein said spacing is less than or equal to 1 mm.

7. The sonotrode according to claim 1, wherein the slot has a widening on an end facing away from the sealing surface, and wherein the widening is circular when viewed on a plane of two opposing side surfaces of the sonotrode.

8. The sonotrode according to claim 1, wherein the sealing surface is bordered by two opposing side surfaces which are essentially parallel to each other, and bordered by a front surface and a rear surface of the sonotrode, wherein a width of the lower portion between the front surface and the rear surface essentially corresponds to a width of the upper portion between the front surface and the rear surface.

9. The sonotrode according to claim 1, wherein the lower portion has a plurality of slots, each slot having two slot walls, a width of the segments between two adjacent slot walls of two adjacent slots being at most (u+o)/3.

10. The sonotrode according to claim 1, wherein the sealing surface is bordered by two opposing side surfaces which extend essentially parallel to one another, and bordered by a front surface and a rear surface of the sonotrode, wherein the front surface is arranged, at least on the sealing surface, at an angle of less than 90 to the two opposing side surfaces.

11. The sonotrode according to claim 10, wherein the rear surface is also arranged, at least on the sealing surface, at an angle smaller than 90 to the two opposing side surfaces.

12. The sonotrode according to claim 1, wherein the upper portion of the sonotrode has at least one gap, wherein the gap is not arranged along an extension of the slot of the lower portion, or wherein the gap has a gap width that is larger than a spacing of the slot walls of the slot, or both.

13. The sonotrode according to claim 1, further comprising: a support provided for holding the sonotrode in the ultrasonic welding apparatus, the support arranged on the segments of the lower portion of the sonotrode.

14. A method for ultrasonic processing of a material, the method comprising the following steps: a) providing the sonotrode according to claim 1, b) providing a counter-tool having a sealing surface, c) arranging the material between the sealing surface of the sonotrode and the sealing surface of the counter-tool, d) exciting the sonotrode with an ultrasonic oscillation of wavelength , e) transferring an ultrasonic vibration from the sonostrode to the material.

15. The method according to claim 14, wherein 0.8(u+o)<<1.2(u+o).

16. The method according to claim 15, wherein 0.9(u+o)<<1.1(u+o).

17. The method according to claim 15, wherein 0.4<u<0.6.

18. The method according to claim 17, wherein /2=u.

19. The method according to claim 14, wherein during step e) the material is passed at a feed rate of v>0 m/s in a feed direction between the sealing surface of the sonotrode and the sealing surface of the counter-tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, features, and possible applications of the present invention will become apparent from the following description of embodiments and the associated drawings. In the drawings, the same elements are identified using the same reference numbers.

(2) FIG. 1 is a schematic view of a first embodiment according to the invention.

(3) FIG. 2a shows a top plan view of the sealing surface of the embodiment shown in FIG. 1.

(4) FIG. 2b shows an enlargement of the marked region in FIG. 2a.

(5) FIG. 3a shows a side view onto a side surface of the embodiment shown in FIG. 1.

(6) FIG. 3b shows an enlargement of the region marked in FIG. 3a.

(7) FIG. 4 shows another side view onto the front surface of the embodiment shown in FIG. 1.

(8) FIG. 5 shows a three-dimensional, schematic representation of a further embodiment of the sonotrode according to the invention.

(9) FIG. 6 shows a schematic representation of an embodiment of the sonotrode according to the invention in an ultrasonic welding apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) The embodiment of the sonotrode 1 according to the invention for an ultrasonic welding apparatus shown in FIG. 1 can be divided into a lower portion 10 of the length u and an upper portion 20 of the length o. The upper portion 20 and the lower portion 10 are arranged adjacent each other on a longitudinal axis 100 of the sonotrode 1. The total length of the sonotrode 1 in the direction of the longitudinal axis 100 is u+o. In addition, the length u of the lower portion 10 corresponds to the length o of the upper portion 20. Moreover, a width 19 of the lower portion 10 corresponds to a width 29 of the upper portion 20.

(11) It can be seen from FIG. 4 that the front surface 13 tapers towards the sealing surface 11. A widening of the sonotrode 1 in the upper portion 20 and in an upper region of the lower portion 10 on a plane of the front surface 13 is therefore larger than a widening of a lower region of the lower portion 10, which adjoins the sealing surface 11. The rear surface 14 is designed in the same way as the front surface 13.

(12) Furthermore, the lower portion 10 has a sealing surface 11 oriented perpendicular to the longitudinal axis 100, the sealing surface is shown in FIG. 2a. The sealing surface 11 is provided to come into contact with a material 40 to be processed (see FIG. 6). The width 19 corresponds to the width at which an ultrasonic processing of the material 40 takes place by means of the sonotrode 1 according to the invention.

(13) The lower portion 10 of the sonotrode 1 comprises three slots 15, the slot 15 extending from the sealing surface 11 to one of the sides of the lower portion 10 opposite the sealing surface 11. The slot 15 has two slot walls, which are spaced from one another at a spacing 17 (see FIG. 2b).

(14) Based on FIG. 3b, it can also be seen that the slot 15 faces the sealing surface 11, with the tapering taking place in a stepwise manner. Arranged in the region of stepped tapering is a widening 18, which has a circular cross-section on a plane of the side surface 12. The spacing of the slot walls in the region 15 of the slot 15 arranged between the widening 18 and the sealing surface 11 is also significantly less than a spacing 17 of the slot walls of the slot 15 above the widening 18.

(15) In addition to the widening 18 in the region of the stepped tapering, the slot has a further widening 18 which is arranged at an end of the slot 15 facing away from the sealing surface 11. The widening 18 also has a circular cross-section when viewed on a plane of the side surface 12 (see FIG. 3a).

(16) By means of the widenings 18, 18, stresses that might form between the segments 10 during operation of the sonotrode 1 in an ultrasonic welding apparatus due to the vibrations and thermal expansion of the sonotrode material are avoided or at least reduced.

(17) FIGS. 2a and 2b also show that the slots 15 in the region of the sealing surface 11 with the side surface 12 of the sonotrode 1 include an angle 16 of 81. The side surfaces 12, 12 extend parallel to each other, they are arranged opposite each other, and they border the sealing surface 11 of the sonotrode 1. As shown in FIG. 3a, the slots 15 are only arranged in a small region 15 of a few millimeters from the sealing surface 11 in the direction of the longitudinal axis 100 at this angle 16 to the side surface 12. In the adjoining region in the direction of the longitudinal axis 100, the slots 15 are arranged perpendicular to the two side surfaces 12, 12.

(18) In addition, it can be seen from FIG. 2a that a front surface 13 and a rear surface 14 of the sonotrode 1, which surfaces border the sealing surface 11 in addition to the side surfaces 12, 12, are also arranged at an angle of <90 to the side surfaces 12. The sonotrode 1 according to the invention can thus be connected to further sonotrodes in order to increase the processing width of an ultrasonic welding apparatus.

(19) By means of the slots 15, the lower portion 10 of the sonotrode 1 is divided into a plurality of segments 10 which lie adjacent to each other in a direction perpendicular to the longitudinal axis 100. The arrangement of the slots 15 in the lower portion 10 of the sonotrode 1 reduces thermal deformation of the sealing surface 11 so that a more homogeneous weld result is achieved over the width 19 of the lower portion 10.

(20) In addition, two gaps 21 with a gap width 27 are arranged in the upper portion 20 (see FIG. 3a). The gaps 21 serve to minimize a widening of the sonotrode 1 in the width 29 of the upper portion 20 during operation of the sonotrode 1 in an ultrasonic welding apparatus.

(21) As shown in FIGS. 1 and 3, the gaps 21 are arranged independently of the slots 15, i.e., not along an extension of the slots or along a common line, and they also have a greater gap width 27, since a different deformation effect of the sonotrode 1 is compensated for by the gaps 21 than by the slots 15.

(22) Finally, the embodiment 30 shown in FIGS. 1-4 includes supports, which are arranged in a region of the segments 10 of the lower portion 10.

(23) The embodiment of the sonotrode 1 according to the invention shown in FIG. 5 differs from the embodiment shown in FIGS. 1-4 in that the supports 30 are not arranged in the lower portion 10, but in the upper portion 20.

(24) In FIG. 6, the embodiment of the sonotrode 1 shown in FIG. 5 is shown schematically in an ultrasonic welding apparatus. Arranged between the sonotrode 1 and an opposing tool 50 is a material 40 to be processed. The material 40 moves at a feed rate v>0 m/s in a feed direction 101 between the sonotrode 1 and the counter tool 50.

(25) During operation of the ultrasonic welding apparatus, the sonotrode 1 is excited with an ultrasonic vibration of wavelength and this ultrasonic vibration is transferred to the material 40 via the sealing surface 11. The material 40 is pressed by means of the ultrasonic vibration against a sealing surface 51 of the counter-tool 50, so that the transmitted ultrasonic vibrations process the material 40 ultrasonically. For example, the material 40 can be multiple layers of nonwoven fabric to be joined together in a bonded connection. Upon impact of the sonotrode 1 on the nonwoven fabric 40, the latter begins to melt due to the generated heat of friction and joins with a layer of material arranged beneath.

(26) The overall length o+u of the sonotrode 1 is selected such that it essentially corresponds to the wavelength of the exciting ultrasonic vibration. In addition, the length of the slots 15, i.e., the length u of the lower portion 10, corresponds to half of the wavelength .

(27) By selecting these dimensions, it is ensured that the slots 15 optimally compensate for the thermal deformation of the sealing surface 11, but, at the same time, the oscillating behavior of the sonotrode 1 is not significantly influenced. Even very thin layers of material 40 can thus be homogeneously welded together or generally processed using ultrasonic vibration by means of the sonotrode 1 according to the invention.

(28) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. By essentially it is meant that the value is within +/10% or +/5% or +/1%.

(29) This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

LIST OF REFERENCE NUMBERS

(30) 1 Sonotrode 10 Lower portion 10 Segments 11 Sealing surface of the sonotrode 12, 12 Opposing side surfaces which extend parallel to each other 13 Front surface 14 Rear surface 15 Slot 15 Portion of the slot arranged towards the sealing surface 16 Angle 17 Spacing of the slot walls 18, 18 Widening 19 Width of the lower portion 20 Upper portion 21 Gap 27 Gap width 29 Width of the upper portion 30 Support 40 Material 50 Counter-tool 51 Sealing surface of the counter-tool 100 Longitudinal axis 101 Feed direction