Tool for ultrasonic welding device and method therefor

Abstract

The invention relates to a tool for an ultrasonic welding device having a base surface. The base surface has a first ridge, which extends from the base surface in a direction perpendicular to the base surface. The first ridge has a first partial sealing surface, which has a second ridge, which extends from the first partial sealing surface in a direction perpendicular to the first partial sealing surface, which has a second partial sealing surface. It is an object of the invention to provide a tool with which aluminum-free plastic materials, in particular polypropylene sealing layers, can also be reliably welded. According to the invention, the object is achieved in that the first partial sealing surface and the second partial sealing surface are provided for processing the material.

Description

[Technical field]

[0001] The present invention relates to a tool for an ultrasonic sealing apparatus having a base surface with a first ridge extending perpendicularly thereto from the base surface at a height H1, the first ridge having a first partial sealing surface, the first partial sealing surface having a second ridge extending perpendicularly thereto from the first partial sealing surface at a height H2, the second ridge having a second partial sealing surface.

[0002] The present invention further relates to an ultrasonic machining apparatus and a method for ultrasonic machining. [Background technology]

[0003] Ultrasonic welding is a method that has been established for a long time for connecting thermoplastics to one another with a positive or material bond. Areas of application range from the automotive and electronics industries to the packaging, medical and hygiene industries.

[0004] Typically, an ultrasonic welding device comprises an ultrasonic generator, a converter, a sonotrode and a counter tool. The ultrasonic generator generates a high voltage of the desired ultrasonic frequency from an applied supply voltage, which is converted into mechanical longitudinal vibrations in the converter using the inverse piezoelectric effect and transmitted to the sonotrode. As the actual active welding tool, the sonotrode transmits the mechanical vibrations into the material to be processed. The sonotrode has a sealing surface through which it comes into contact with the material to be processed. To generate pressure in the material, a counter tool is usually arranged opposite the sonotrode and has a sealing surface that comes into contact with the material to be processed. The material is thus guided between the sealing surface of the sonotrode and the sealing surface of the counter tool.

[0005] When referring to a tool in the present invention, it is possible to mean both a tool in the form of a sonotrode and a tool in the form of a counter-tool of an ultrasonic welding device. The tool according to the present invention is suitable for both components of an ultrasonic welding device, as will be shown further below.

[0006] Mechanical vibrations with frequencies in the ultrasonic range generate frictional heat within the material being processed, stimulating the molecules within the material to move, so that the material softens and begins to melt, so that the components to be joined bond together when a predetermined pressure is applied to the components for a predetermined time, and the components are then firmly bonded to each other at the molecular level.

[0007] Depending on the respective application, certain requirements are imposed on the weld seam to be produced, for example, both the sealing surface of the sonotrode and the sealing surface of the counter tool can have a certain contour, which produces a weld seam with a certain pattern.

[0008] However, the welding result also depends heavily on the type of material being processed. Especially in the packaging industry, plastic materials are used whose viscosity drops sharply during melting, which can lead to uncontrollable melt splashing during ultrasonic processing. This is the case, for example, of aluminum-free materials with a polypropylene sealing layer. Such uncontrollable melt splashing can lead on the one hand to damage of the printed image and on the other hand to micro-leakage.

[0009] To avoid these drawbacks, parameters such as pressure and ultrasonic frequency can be adjusted during the ultrasonic processing process in such a way that melt splashes of this kind are prevented. In this case, the pressure in the material to be processed or the temperature generated is kept low. However, there is a high risk of leakage, since a sufficiently stable weld seam is not formed between the components to be joined. This problem is exacerbated when the seam area is contaminated by the product to be packaged, as is often the case in the packaging industry. In this case, the energy in the material brought about by the ultrasonic processing is not enough to melt the material to such an extent that a stable weld seam is formed.

[0010] However, if process parameters and mold geometries are used that ensure sufficient strength, it will result in excessive, turbulent melt flow that cannot be controlled, as discussed above. Summary of the Invention [Problem to be solved by the invention]

[0011] It is therefore an object of the present invention to provide a tool or an ultrasonic processing device or method, with which aluminum-free plastic materials, in particular polypropylene sealing layers, can also be reliably welded. [Means for solving the problem]

[0012] According to the invention, this problem is solved by a tool of the type mentioned at the beginning, in which both the first and the second partial sealing surfaces are provided for processing preferably two- or multi-layer materials in one operation of the ultrasonic welding device.

[0013] Thus, according to the invention, only the first partial sealing surface of the first ridge and the second partial sealing surface of the second ridge come into contact with the sealing surface of a corresponding second tool, for example a sonotrode, so that the material to be processed is welded only in these areas. Conversely, the tool can also be a sonotrode, which comes into contact with an optionally formed sealing surface of a counter tool in order to process the material in the aforementioned areas.

[0014] The tool according to the invention is designed in such a way that almost no melt is generated by the second partial sealing surface of the second raised part, so that only a few melt splashes occur. At the same time, the first partial sealing surface is also pressed into the material to be processed, so that the tightness of the weld seam is increased by the cooperation of the first partial sealing surface of the first raised part. Due to the second partial sealing surface of the second raised part, any melt splashes that may occur are additionally pressed by the first partial sealing surface of the first raised part. In this way, the melt flow can be better controlled and a homogeneously closed melt area is produced.

[0015] The height H1 is defined by a line perpendicular to the base surface, which line connects a point on the base surface and a point on the first partial sealing surface with the greatest possible distance from each other. The same definition applies to the height H2 of the second ridge. The height H2 is defined by the longest connecting line perpendicular to the base surface between two points of the first and second partial sealing surfaces.

[0016] According to the invention, furthermore, a second ridge is arranged on the first partial sealing surface of the first ridge, so that the second ridge cannot penetrate too deeply into the material to be processed, since the first partial sealing surface, which is preferably much larger than the second partial sealing surface, forms a kind of stop. This likewise prevents excessive melt generation or cutting of the material to be processed due to the pointed shape of the second partial sealing surface. The height H2 of the second ridge is selected in some embodiments to be smaller than the total thickness of the two- or multi-layer material to be processed.

[0017] In one embodiment, the second protuberance has a semicircular cross section with a radius r2 in a first plane perpendicular to the base surface, with the radius r2 of the semicircular cross section being preferably at most 2 mm, particularly preferably at most 1.5 mm. Both the semicircular cross section and the small radius compared to the remaining tool structure provide the advantage that on the one hand the melt is generated more easily due to improved energy concentration and on the other hand the risk of material damage is reduced, since the generated melt volume is smaller and can be better controlled, and therefore undesirable melt splashes can be more reliably avoided.

[0018] In another embodiment, the first partial sealing surface is flat, preferably parallel to the base surface, or convexly curved with a radius of curvature r1 relative to the base surface. In a preferred embodiment, r2 is smaller than r1.

[0019] In another embodiment, the first ridge has a trapezoidal cross-section in a first plane perpendicular to the base surface. In the sense of the present application, a trapezoid is a quadrilateral with only two of its four sides parallel to one another. The legs of the trapezoidal cross-section, and thus the sides that are not parallel to one another, preferably run towards one another when viewed from the bottom, so that the base side of the trapezoidal cross-section forming the first partial sealing surface is shorter than the base side of the trapezoidal cross-section that is arranged on the base surface.

[0020] The trapezoidal cross section of the first ridge has the advantage that the first ridge does not produce too sharp edges that could damage the material being processed. At the same time, the first partial sealing surface of the first ridge is flat, i.e. it does not have a curvature, unlike the second partial sealing surface of the second ridge. In this way, any molten splashes that may occur can be pressed off particularly efficiently.

[0021] In another embodiment, the first and / or second ridges have a greater extent in the transverse direction perpendicular to the first plane than in the longitudinal direction parallel to the first plane. The first and second ridges are therefore not point-like ridges on the base surface of the tool, but planar, e.g. rib-shaped ridges, which extend in the transverse direction over at least a part of the base surface. Preferably, the first and second ridges extend over a width of the base surface that corresponds to the width of the material to be processed, so that a consistent weld seam is formed by the tool according to the invention. However, other configurations of the first and second ridges in the longitudinal and transverse directions are of course possible if other welding patterns are to be obtained.

[0022] In another embodiment, exactly one second ridge is disposed on the first partial sealing surface of the first ridge, preferably the second ridge is disposed centrally on the first partial sealing surface.

[0023] Arranging the second ridge centrally on the first partial sealing surface has the advantage that possible molten splashes can likewise be pressed particularly efficiently, since, viewed in the first plane, equal proportions of the first partial sealing surface are arranged on either side of the second ridge.

[0024] In another embodiment, the length of the short base side of the trapezoidal cross-section of the first ridge corresponds to the extent of the first partial sealing surface in the first plane, so that the first partial sealing surface extends over the entire extent of the first ridge in the first plane, but in other words only over that part of the trapezoidal cross-section which is arranged parallel to the base surface of the tool.

[0025] In another embodiment, the height H2 of the second ridge is smaller than or equal to the height H1 of the first ridge. This provides the advantage that the second ridge cannot penetrate into the material to be processed to such a depth that it would cause damage to the material to be processed. The parts of the first partial sealing surface on the sides of the second ridge thus prevent the second ridge from penetrating too deeply into the material layer to be processed. This avoids, on the one hand, excessive melt formation and, on the other hand, damage to the material layer. At the same time, the larger height H1 of the first ridge ensures that the base surface of the tool, which does not belong to the first and second partial sealing surfaces, does not contribute to the ultrasonic processing of the material.

[0026] In particular, for the same purposes as described above, the height H2 in one embodiment is selected to be smaller than the total thickness of the bilayer or multilayer material to be processed, and the height H1 is selected such that the sum of the heights H1 and H2 is greater than the total thickness of the bilayer or multilayer material.

[0027] In another embodiment, the extent of the second partial sealing surface in a first plane perpendicular to the base surface is smaller than the extent of the first partial sealing surface in the first plane. In other words, this means that the first ridge in the first plane is longer than the second ridge, so that there are parts of the first partial sealing surface on the sides of the second ridge, respectively. These parts of the first partial sealing surface provide efficient pressing of the resulting molten splash.

[0028] In another embodiment, a third ridge is provided on the base surface, the third ridge extending from the base surface in a direction perpendicular to the base surface with a height H3. The third ridge is located neither on the first partial sealing surface nor on the second partial sealing surface, and is provided such that it contacts the material to be processed but does not process the material. The height H3 of the third ridge is at least equal to the sum of the height H1 of the first ridge and the height H2 of the second ridge, and is preferably greater than the sum of the height H1 of the first ridge and the height H2 of the second ridge.

[0029] The third ridge is only used to fix the layer of material to be processed during the ultrasonic welding process by fitting the third ridge into a corresponding recess in the opposing sealing surface of a corresponding second tool, e.g. a sonotrode. A clamping of the material to be processed between the tool and the corresponding second tool is provided so that the material does not shift during the ultrasonic welding process. However, the pressure applied by the third ridge to the material to be processed is not sufficient to provide ultrasonic processing.

[0030] However, by clamping the material being processed, a more accurate weld seam can be formed using the first and second partial sealing surfaces.

[0031] As already mentioned at the beginning, the tool according to the invention can be used as a sonotrode in one embodiment or as a counter tool in another embodiment.

[0032] The problem underlying the present invention is further solved by an ultrasonic welding device having an ultrasonic generator, a converter, a sonotrode and a counter tool, the converter being arranged to be connected to the sonotrode in such a way that during operation of the ultrasonic welding device, the converter converts the ultrasonic frequency generated by the ultrasonic generator into mechanical vibrations which are transferred to the sonotrode. The sonotrode and the counter tool each have a sealing surface which is in contact with the material to be processed during operation of the ultrasonic welding device. The sealing surface of the sonotrode faces the sealing surface of the counter tool. The material to be processed can be arranged between the sealing surface of the sonotrode and the sealing surface of the counter tool, the sonotrode or the counter tool being a tool according to any of the above-mentioned embodiments.

[0033] According to the invention, the sonotrode clamps the material to be processed between the sealing surface of the sonotrode and the sealing surface of the counter tool in such a way that only in the area of ​​the first and second partial sealing surfaces there is sufficient pressure to ultrasonically process the material to be processed. In all other areas of the sealing surface of the sonotrode and the sealing surface of the counter tool no ultrasonic processing takes place. It should be noted that if the tool according to the invention is a counter tool, the sealing surface of the counter tool corresponds to the base surface of the tool with the corresponding partial sealing surface, and if the tool according to the invention is a sonotrode, the sealing surface of the sonotrode corresponds to the base surface of the tool with the corresponding partial sealing surface. A tool without the sealing surface structure of the tool according to the invention can alternatively be described as a second tool corresponding to the tool.

[0034] The problem underlying the present invention is further solved by a method for processing a material, preferably a bilayer or multilayer material, by means of ultrasound, which method comprises the following steps: a. providing a sonotrode having a sealing surface; b. providing a counter tool having a sealing surface, the sonotrode or counter tool being a tool according to any of the embodiments described above; c. guiding the material in the feed direction between a sealing surface of the sonotrode and a sealing surface of a counter tool; d. Applying ultrasonic vibrations to the sonotrode, whereby the sonotrode brings about pressure via the sealing surface of the sonotrode against the material and the sealing surface of the counter tool, whereby the material is ultrasonically machined in the area of ​​the first and second partial sealing surfaces of the tool.

[0035] In one embodiment of the method according to the invention, the first tool is arranged such that the first plane is perpendicular to the feed direction of the material, i.e. perpendicular to the direction in which the material moves through between the second tool and the tool, for ultrasonic processing the movement of the material is preferably stopped for a short time, after which the material is further fed to form another weld seam at another location on the material.

[0036] The tool according to the invention therefore makes it possible to produce sealing seams parallel to the feed direction of the material being processed, which finds application in the packaging industry, where individual products are to be packaged in portions in bags or strips of material.

[0037] Other advantages, features and applicability of the present invention will become apparent from the following description of embodiments of the invention and the accompanying drawings, in which like elements are designated with like reference numerals. [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 shows diagrammatically a cross-section of an embodiment of a tool according to the invention. [Diagram 2] FIG. 2 shows a schematic partial cross-section of an embodiment of an ultrasonic processing device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Figure 1 shows a cross-section of a tool 1 according to the invention in a first plane. The tool 1 has a base surface 2 on which a first ridge 3 with a height H1 is arranged. The first ridge 3 has a first partial sealing surface 4 perpendicular to the sealing surface 2, which extends parallel to the base surface 2. The first ridge 3 further has a trapezoidal cross-section perpendicular to the base surface in the plane shown in Figure 1.

[0040] A second ridge 5 is arranged exactly in the center on the first partial sealing surface 4, which extends perpendicularly to the first partial sealing surface 4 from the first partial sealing surface 4 at a height H2. The second ridge 5 has a second partial sealing surface 6. The first partial sealing surface 4 extends parallel to the base surface 2 of the tool 1, i.e. is flat, whereas the second partial sealing surface 6 is curved, since the second ridge 5 has a partially semicircular cross section. The radius of the semicircular cross section is 1.5 mm in the illustrated embodiment. The height H2 of the second ridge 5 is selected to be, for example, 0.14 mm for a material to be processed having a thickness of 0.2 mm, in which case the height H1 is greater and such that the base surface does not come into contact with the material to be processed during the welding process. This is ensured if the sum of the heights H1 and H2 is greater than the total thickness of the two layers of material to be processed.

[0041] The second ridge 5 is arranged centrally on the first partial sealing surface 4 of the first ridge 3 so that a part of the first partial sealing surface 4 still remains on each side of the second ridge 5, and its extent is 1 mm in the plane shown in FIG.

[0042] Furthermore, the base surface 2 of the tool 1 has a third ridge 7, which extends perpendicularly from the base surface 2 to a height H3. The third ridge 7 is then neither located on the first partial sealing surface 4 nor on the second partial sealing surface 6, but is located next to the first ridge 3 in the longitudinal direction 11.

[0043] The third ridge 7 has a height H3, which is greater than the sum of the height H2 of the second ridge 5 and the height H1 of the first ridge 3.

[0044] When ultrasonic machining is performed, the third ridge 7 clamps the material 8 to be machined between the tool 1, in this case a counter tool, and a second tool 9 corresponding to the tool 1, in this case a sonotrode 9 (see FIG. 2).

[0045] Figure 2 shows how the material 8 to be processed is arranged between the sonotrode 9 and the counter tool 1 according to the invention. The material is then guided in a feed direction 12, which corresponds to the transverse direction 10 and runs into the sheet plane. Both the sonotrode 9 and the counter tool 1 extend in the transverse direction 10, which in the embodiment shown in Figures 1 and 2 runs into the sheet plane. The cross section of the counter tool 1 shown in Figure 1 is then constant over its width, which corresponds to the width of the material 8.

[0046] The sonotrode 9 is pressed onto the material 8 to be processed with such pressure that both the first partial sealing surface 4 and the second partial sealing surface 6 are in contact with the material to be processed, whereby ultrasonic processing is carried out in the area of ​​the first partial sealing surface and the second partial sealing surface.

[0047] In all other areas of the sealing surface 13 of the sonotrode 9 and the base surface 2 of the counter-tool 1 no ultrasonic machining takes place.

[0048] In this way, aluminum-free plastic materials can also be welded to one another without melt splashes occurring which would impair the sealing quality of the weld seam. [Explanation of symbols]

[0049] 1 Tool / counter tool 2 Tool base surface 3 First ridge 4 First partial seal surface 5 Second ridge 6 Second partial sealing surface 7. The third ridge 8 Materials 9 Second Tool / Sonotrode 10 Horizontal 11 Vertical 12 Feed direction 13 Sonotrode sealing surface

Claims

1. A tool (1, 9) for an ultrasonic welding device having a base surface (2), The base surface (2) has a first protrusion (3), the first protrusion (3) extending perpendicularly to the base surface (2) at a height H1 from the base surface (2); the first ridge (3) has a first partial sealing surface (4), the first partial sealing surface (4) has a second ridge (5), the second ridge (5) extends perpendicular to the base surface (2) from the first partial sealing surface (4) at a height H2; The tool (1, 9), wherein the second ridge (5) has a second partial sealing surface (6), Both the first partial sealing surface (4) and the second partial sealing surface (6) are provided for processing preferably two-layer or multi-layer materials (8) during operation of the ultrasonic welding device, The tool (1, 9), characterized in that the second raised portion (5) has a part-circular cross section with a radius r2 in a first plane perpendicular to the base surface (2).

2. 2. The tool (1, 9) according to claim 1, wherein the radius r2 of the part-circular cross section is preferably at most 2 mm, particularly preferably at most 1.5 mm.

3. 3. The tool (1, 9) according to claim 1 or 2, wherein the first partial sealing surface (4) of the first raised portion (3) is flat, preferably parallel to the base surface (2), or curved convexly with respect to the base surface (2) with a radius of curvature r1, preferably greater than the radius r2 of the second partial sealing surface (6).

4. 2. The tool (1, 9) according to claim 1, wherein the first ridge (3) has a trapezoidal cross section in the first plane perpendicular to the base surface (2).

5. 5. The tool (1, 9) according to claim 2 or 4, wherein the first ridge (3) and / or the second ridge (5) have a greater extent in a transverse direction (10) perpendicular to the first plane than in a longitudinal direction (11) parallel to the first plane.

6. 2. The tool (1, 9) according to claim 1, wherein exactly one second ridge (5) is arranged on the first partial sealing surface (4) of the first ridge (3), and preferably the second ridge (5) is arranged centrally on the first partial sealing surface (4).

7. 5. The tool (1, 9) according to claim 4, wherein the length of the shorter base side (13) of the trapezoidal cross section of the first ridge (3) corresponds to the extent of the first partial sealing surface (4) in the first plane.

8. 2. The tool (1, 9) according to claim 1, wherein the height H2 of the second ridge (5) is less than or equal to the height H1 of the first ridge (3).

9. 2. The tool (1, 9) according to claim 1, wherein the extent of the second partial sealing surface (6) in the first plane perpendicular to the base surface (2) is smaller than the extent of the first partial sealing surface (4) in the first plane.

10. a third protrusion (7) is provided on the base surface (2), the third protrusion (7) extending perpendicularly to the base surface (2) at a height H3 from the base surface (2); the third protuberance (7) is arranged neither on the first partial sealing surface (4) nor on the second partial sealing surface (6) and is in contact with the material (8) to be processed but does not process the material (8); 2. The tool (1, 9) according to claim 1, wherein the height H3 of the third ridge (7) corresponds at least to the sum of the height H1 of the first ridge (3) and the height H2 of the second ridge (5), and is preferably greater than the sum of the height H1 of the first ridge (3) and the height H2 of the second ridge (5).

11. 2. The tool (1, 9) according to claim 1, wherein the tool (1, 9) is a sonotrode (9) or an anvil (1) of an ultrasonic welding device.

12. An ultrasonic welding device comprising an ultrasonic generator, a converter, a sonotrode (9) and a counter tool (1), the converter is installed and connected to the sonotrode (9) such that during operation of the ultrasonic welding device, the converter converts the ultrasonic frequency generated by the ultrasonic generator into mechanical vibrations and transmits them to the sonotrode (9); the sonotrode (9) and the counter tool (1) each have a sealing surface (4, 6), which contacts the material (8) to be processed during operation of the ultrasonic welding device; the sealing surface (13) of the sonotrode (9) faces the sealing surfaces (4, 6) of the counter tool (1); a material (8) to be processed can be placed between the sealing surface (13) of the sonotrode (9) and the sealing surfaces (4, 6) of the counter tool (1); 2. An ultrasonic welding device, wherein the sonotrode (9) or the counter tool (1) is a tool (1, 9) according to claim 1.

13. A method for ultrasonically processing a material (8), preferably a bi- or multi-layer material (8), comprising the steps of: The following steps: a. providing a sonotrode (9) having a sealing surface (13); b) providing a counter tool (1) having a sealing surface (4, 6), said sonotrode (9) or said counter tool (1) being a tool (1, 9) according to claim 1; c) guiding the material (8) in a feed direction (12) between the sealing surface (13) of the sonotrode (9) and the sealing surfaces (4, 6) of the counter tool (1); and d) applying ultrasonic vibrations to the sonotrode (9), whereby the sonotrode (9) applies pressure via the sealing surface (13) of the sonotrode (9) to the material (8) and the sealing surfaces (4, 6) of the counter tool (1), thereby ultrasonically processing the material (8) in the area of the first partial sealing surface (4) and the second partial sealing surface (6) of the tool (1, 9).

14. 14. The method according to claim 13, wherein a tool (1, 9) according to claim 1 is provided, and wherein the first plane is perpendicular to the feed direction (12).

15. 14. The method according to claim 13, wherein the height H2 of the second ridge (5) is selected to be smaller than the total thickness of the bi- or multi-layer material (8) to be processed, and the height H1 of the first ridge (3) is selected such that the sum of the height H1 and the height H2 is greater than the total thickness of the bi- or multi-layer material (8).

Images