Opposed elements for ultrasonic machining

Abstract

The invention relates to a counter element (3) for machining a material by means of ultrasound, which has a sealing surface (9) with a fusion portion (9b) which is at least partially concavely curved. In order to provide a counter element (3) which enables reliable fusion at a higher feed speed, according to the invention the sealing surface (9) has a feed portion (9a) which is arranged adjacent to the fusion portion (9b) and is not curved or is concavely curved with a radius of curvature which is greater than the radius of curvature of the fusion portion (9b).

Description

Technical Field

[0001] The present invention relates to a counter element for ultrasonic processing of materials, such as an ultrasonic welding head or anvil. Background Technology

[0002] Ultrasonic waves are being used increasingly, particularly for joining nonwoven materials. To do this, two portions of the nonwoven fabric to be joined are introduced, one on top of the other, into the gap between an ultrasonic welding head and an anvil, and ultrasonic vibrations are applied to the welding head. Point heating occurs on the contacting surfaces due to friction caused by the ultrasonic vibrations, melting the thermoplastic components, especially those of the nonwoven material. The molten components of the material portions to be joined flow into each other, providing a strong bond as they cool.

[0003] Therefore, in the production of diapers, the corresponding nonwoven material parts can be joined together to form side seams.

[0004] Typically, the processing element is located on the side of the counter-element, so that the material to be processed, such as a system of multiple material webs, can be placed in the gap between the counter-element and the processing element or move through the gap between the counter-element and the processing element, while ultrasonic oscillations are applied to the material to be processed by at least the counter-element or the processing element.

[0005] The machining element may have a support surface that is substantially cylindrical or cylindrical segment-shaped, which is used to contact the material during machining. Then, during machining, the machining element rotates about its longitudinal axis, causing the support surface to roll on the material to be machined.

[0006] The support surface typically includes at least one structural element that projects radially above the support surface, such that the structural element includes an upper side for contacting the material to be processed. The actual welding then takes place in the region between the upper side of the structural element and the sealing surfaces of opposing elements spaced apart therefrom for this purpose.

[0007] For example, the opposing element can be an ultrasonic welding head, and the processing element can be an anvil. Hereinafter, this example is used to illustrate the invention since it is a preferred embodiment. However, in principle, the processing element can be constructed as an ultrasonic welding head, and the opposing element as an anvil.

[0008] During the processing, the support surface and the structural element roll together on the material to be processed, causing the structural element to undergo welding.

[0009] Processing speed is limited by existing equipment technology.

[0010] In principle, the feed rate can be increased, that is, the speed at which the material moves through the gap between the processing element and the opposing element.

[0011] However, because the ultrasonic welding head acts on the material at a fixed frequency, sufficient energy is no longer introduced into the material to achieve reliable welding. This is because, at higher feed rates, the material is in contact with the sealing surface of the ultrasonic welding head for a shorter time, thus the ultrasonic welding head exerts less "impact" on the material.

[0012] This can be partially compensated for by increasing the force applied to the material being welded by the ultrasonic welding head. Therefore, each "impact" of the ultrasonic welding head transfers more energy into the material. However, this results in greater friction and causes the molten components formed by ultrasonic processing to be extruded from the bond zone by the structural elements in the boundary region between the layers of material to be welded, i.e., the so-called bonding zone. This also leads to a poorer seam because there is no longer a sufficient amount of thermoplastic component available in the bonding zone. Alternatively, or in combination, the amplitude of the ultrasonic vibrations can be increased. Again, this transfers more energy into the material with each "impact" of the ultrasonic welding head. However, this can only be achieved to a limited extent. If the ultrasonic welding head is operated at excessively high amplitudes, damage to the ultrasonic welding head material can occur.

[0013] To achieve higher processing speeds, so-called "welding wheels" have previously been used, in which multiple ultrasonic welding heads are arranged on a wheel to increase the contact time during the wheel's rotation. However, this solution is very complex.

[0014] US2010 / 243172A1 describes, by way of example, an ultrasonic processing apparatus having an ultrasonic welding head and an opposing tool, wherein the opposing tool has a raised portion through which the processing gap between the ultrasonic welding head and the opposing tool is changed when the opposing tool rotates relative to the ultrasonic welding head, and the sealing surface of the ultrasonic welding head additionally has a basic helical surface through which the sealing gap moves helically along the surface when the raised portion of the opposing tool rotates beyond the sealing surface of the ultrasonic welding head.

[0015] EP 1 477 293 B1 also describes an ultrasonic processing apparatus having an ultrasonic welding head and an opposing tool, wherein the opposing tool has a raised portion and its surface can be curved. DE 2 154 057 discloses a method for perforating plate-like articles. A horn with a gentle curved surface and slope is used in this method. Summary of the Invention

[0016] Therefore, based on the prior art, the object of the present invention is to provide a counter element that enables reliable welding at a higher feed rate.

[0017] According to the invention, this object is achieved by having opposing elements having a sealing surface having at least a partially recessed, bent weld portion.

[0018] The increased contact time between the opposing element and the processing element due to the curvature of the weld section allows more energy to be introduced into the material, thereby increasing the feed rate without having to increase the force of the ultrasonic welding head or anvil on the material to be processed.

[0019] According to the invention, the sealing surface of the opposing element further includes a feed portion arranged adjacent to the welding portion, and the feed portion is not curved, but rather convexly curved or concavely curved, wherein the radius of curvature is greater than the radius of curvature of the welding portion. Thus, the slope or curvature of the sealing surface changes at the transition between the feed portion and the welding portion, such that when an opposing element with a cylindrical or cylindrical truncated support surface is used in the region of the feed portion, the distance between the processing element and the support surface of the opposing element gradually decreases until a minimum distance is reached, corresponding to the distance between the welding portion and the support surface and / or the distance between the welding portion and the upper side of the structural element arranged on the support surface. The feed portion is arranged such that material moving through the gap in the feed direction first contacts the feed portion and then contacts the welding portion. In a preferred embodiment, the feed portion is not curved, or is concavely curved, wherein the radius of curvature is greater than the radius of curvature of the welding portion.

[0020] In a preferred embodiment, the feed section is 0.2 to 5 times the size of the welding section. Particularly preferred is that the feed section and the welding section are approximately the same size.

[0021] The above objective is also achieved by an ultrasonic welding apparatus having an opposing element and a processing element as described above, wherein the processing element has a support surface that is substantially cylindrical or cylindrically truncated, the support surface being configured to contact the material during processing, wherein the processing element is configured to rotate about its longitudinal axis during processing, such that the support surface moves circumferentially and rolls on the material to be processed, wherein the sealing surface of the opposing element is arrangable opposite to the processing element such that a gap is formed between the support surface and the sealing surface, the material to be processed being arranged in the gap, wherein in a cross-sectional view perpendicular to the longitudinal axis of the processing element, the welded portion is at least partially concave and bent.

[0022] In particular, since the aforementioned opposing element cooperates with the processing element having a support surface that is substantially cylindrical or cylindrically shaped, the time length during ultrasonic processing is increased. In a preferred embodiment, the support surface is cylindrical or cylindrically shaped, wherein minor deviations do not affect the effects according to the invention.

[0023] In a particularly preferred embodiment, the ultrasonic welding apparatus is constructed and designed such that one or more material webs can move between a processing element and a counter element. One or more pull-out rollers may be provided on which the material web to be processed is wound and pulled out and moved through the gap between the processing element and the counter element. Web guide rollers or multiple web guide rollers may also be provided between the processing element and the counter element to guide the material web to be processed.

[0024] In a further preferred embodiment, at least one structural element is arranged on the support surface, the structural element protruding radially above the substantially cylindrical or cylindrical cross-section support surface, wherein the structural element has an upper side configured to contact the material to be processed, wherein the upper side includes a base and at least one recess, the recess having a smaller distance between it and the longitudinal axis than the base, wherein in a cross-sectional view perpendicular to the longitudinal axis, the base and the recess are arranged adjacent to each other.

[0025] As the structural element rolls on the material, the plasticizing component can be incorporated into the recess, thereby reducing the likelihood of the plasticizing component being extruded from the bonding area.

[0026] In a preferred embodiment, the recess formed by the recess does not extend to the support surface, but preferably has a depth of less than 1 mm, and most preferably 0.05 mm to 0.2 mm.

[0027] In a further preferred embodiment, the recess is constructed as a groove, which is preferably not oriented solely in the circumferential direction. If the groove is oriented circumferentially, it preferably does not completely surround the support surface, but extends only at circumferential angles of <360°, and more preferably at circumferential angles of less than 45° and most preferably less than 25°. Multiple grooves may also be arranged circumferentially spaced apart from each other.

[0028] The groove is not used to interrupt the weld, but only to receive the molten material, thus keeping it essentially in place, and can be used to join material layers.

[0029] It has been found that the groove can prevent undesirable delocalization of the melt due to increased pressure on the material to be processed caused by the ultrasonic welding head at the groove location. The melt then moves only to the groove. Therefore, the groove acts as a container for the melt material.

[0030] In a preferred embodiment, the width of the groove is less than 1 mm, preferably less than 0.6 mm. Most preferably, the width of the groove is between 0.2 mm and 0.4 mm.

[0031] Depending on the material to be welded, if the cross-sectional area of ​​the groove is less than 0.15 mm... 2 That's sufficient. Preferably, the cross-sectional area is even less than 0.05 mm. 2 And most preferably, the cross-sectional area is 0.015 mm. 2 up to 0.04mm 2 .

[0032] In a preferred embodiment, the structural element includes a plurality of grooves, preferably at least three, not oriented in the circumferential direction, on its upper side, wherein the grooves are preferably arranged parallel to each other. The grooves enable the molten material to be held in its respective position, thus multiple grooves are advantageous.

[0033] In a further preferred embodiment, the upper side of the structural element has a main portion, which is configured to be substantially planar or have a convex curvature with a radius of curvature corresponding to the distance between the main portion and the axis of the cylinder, and has at least one chamfered portion adjacent to the main portion in the circumferential direction. The chamfered portion is angled relative to the main portion such that the main portion and the chamfered portion form an angle of less than 180°, or the chamfered portion is convexly curved, wherein if the main portion is convexly curved, the radius of curvature of the chamfered portion is smaller than the radius of curvature of the main portion. The at least one recess is preferably set within the main portion. The chamfered portion is used to gradually prepare material for the weld contact between the main portion and the opposing element. The slope or curvature of the upper side changes at the transition between the main portion and the chamfered portion. This ensures that when a processing element is used, the distance between the structural element and the opposing element continuously decreases until the minimum distance between the structural element and the opposing element is reached.

[0034] In a further preferred embodiment, the upper side includes two chamfered portions adjacent to opposite sides of the main portion in the circumferential direction. These two chamfered portions are angled relative to the main portion, such that the main portion and the chamfered portions each include an angle of less than 180°. Therefore, during processing, the upper side of the structural element has not only a feed chamfered portion but also a delivery chamfered portion, thereby ensuring that at the end of processing of the structural element, the force applied to the processed element by the opposing element only gradually decreases.

[0035] In a further preferred embodiment, the upper side of the structural element has an elongated shape with a length of l and a width of b, where l > b. The length preferably does not extend parallel to the longitudinal axis, but preferably extends substantially perpendicular to the longitudinal axis.

[0036] In a further preferred embodiment, the processing element is used to rotate the material to be processed in a feed direction between the processing element and the opposing element, wherein the feed portion and the welding portion are arranged such that the material moving through the gap in the feed direction first contacts the feed portion and then contacts the welding portion.

[0037] As mentioned above, the opposing element can be an ultrasonic welding head, and the processing element can be an anvil.

[0038] Further advantages, features and possible applications of the present invention will become apparent from the following description of preferred embodiments and the accompanying drawings. Attached Figure Description

[0039] In the diagram:

[0040] Figure 1 A three-dimensional view of the ultrasonic welding device is shown.

[0041] Figure 2 It shows Figure 1 Magnified details of the area represented by X.

[0042] Figure 3 It shows Figure 2 Magnified details

[0043] Figure 4 It shows Figure 1 A side view of the ultrasonic welding device, and

[0044] Figure 5 It shows Figure 4 A magnified view of a portion of the image. Detailed Implementation

[0045] Figure 1 A perspective view of an ultrasonic welding apparatus is shown. The ultrasonic welding apparatus includes a processing element 1 configured as an anvil, which is configured as a roller rotatable about a longitudinal axis 10. At least one transverse seam strip 11 with a support surface 2 is disposed on the roller. Opposing elements 3 configured as ultrasonic welding heads are arranged in their opposite positions.

[0046] Here, the opposing element 3 can be excited by ultrasonic oscillation. The material to be processed then moves between the support surface 2 and the sealing surface of the ultrasonic welding head 3 facing the support surface 2, wherein the material's movement speed matches the circumferential speed of the processing element 1. The gap between the support surface 2 and the ultrasonic welding head 3 must be selected such that ultrasonic vibrations are transmitted to the material during processing, and the thermoplastic component melts at the boundary surface.

[0047] Figure 2 It shows Figure 1 Zoomed-in details.

[0048] As can be seen, multiple structural elements 4 are arranged on the support surface 2. The structural elements 4 have an elongated shape oriented in the circumferential direction. During processing, the structural elements 4 come into contact with the material and define the weld pattern introduced into the material during processing. For example, an ultrasonic welding device can be used to manufacture the side seams of diapers made of nonwoven materials.

[0049] exist Figure 3 In, it is shown Figure 2 The magnified details show that structural element 4 is clearly visible. Two structural elements 4 are arranged adjacent to each other in the circumferential direction (relative to the longitudinal axis 10). Multiple pairs of such structural elements are arranged adjacent to each other in the axial direction.

[0050] Each structural element has a main portion 6 and two chamfered portions 7 and 8, which are more strongly curved than the main portion 6. A groove 5 is introduced into the main portion 6, and in the illustrated embodiment, the main portion extends perpendicular to the circumferential direction. The grooves do not need to extend perpendicular to the circumferential direction. However, to achieve the effects according to the invention, they should not be arranged parallel to the circumferential direction. If the grooves are indeed arranged parallel to the circumferential direction, they should not extend through the entire structural element 4.

[0051] During the welding process, the structural element 4 rolls on the material to be processed, causing the chamfered portion 8 to contact the material first. Due to the angled arrangement of the chamfered portion 8, the distance between the sealing surfaces of the structural element 4 and the opposing element 3 decreases continuously in this region until it reaches a minimum distance in the region of the main portion 6. The main portion 6 can be formed to be convexly curved, wherein the radius of curvature substantially corresponds to the distance between the upper side of the structural element 4 and the longitudinal axis 10 of the processing element 1.

[0052] A groove 5 with a depth of 0.1 mm and a width of 0.3 mm is introduced into the main part 6. Molten material can penetrate into the resulting groove, so that it remains essentially in place and is not squeezed out of the joint area by the structural elements.

[0053] Figure 4 It shows Figure 1 A side view of the ultrasonic welding device. The sealing surface, that is, the surface facing the support surface and / or structural element 4, is surface 9.

[0054] Figure 5 It shows Figure 4A partially enlarged view. Here, 9 consists of a feed section 9a and a welding section 9b. The welding section 9b is concave and curved, specifically with a radius of curvature substantially the same as that of the main part of the processed element. This ensures that the material remains in contact with the ultrasonic welding head for a longer period during processing, allowing more energy to be introduced into the material to be processed. In this embodiment, the feed section 9a is not curved, thus ensuring that the material to be processed is first guided into the narrow gap in the region of the feed section 9a. The dimensions of the welding section and the feed section are approximately the same. The gap is smallest in the region of the welding section 9b and remains substantially constant in the region of the welding section. Welding is mainly performed by the welding section 9b, but the feed section 9a can also contribute to the welding at its end facing the welding section 9b.

[0055] The dashed line shows the boundary between the feed section 9a and the welding section 9b. In the illustrated embodiment, this boundary is arranged at the center of the sealing surface 9 such that the feed section 9a and the welding section 9b have the same dimensions. The boundary should preferably be arranged such that the welding section occupies 20% to 80% of the surface 9, preferably 30% to 70%.

[0056] List of reference numerals

[0057] 1. Machining component (anvil)

[0058] 2 Support surface

[0059] 3. Opposing element (ultrasonic welding head)

[0060] 4 Structural Components

[0061] 5 grooves

[0062] 6 main part

[0063] 7 and 8 chamfered edges

[0064] 9 Sealing surface

[0065] 9a Feed Section

[0066] 9b Welded section

[0067] 10. Vertical axis

[0068] 11. Horizontal joint strip

Claims

1. An ultrasonic welding device having a counter element (3) and a processing element (1), characterized in that, The opposing element (3) is used to process materials by ultrasonic waves and has a sealing surface (9), the sealing surface (9) having at least a partially recessed curved weld portion (9b), the sealing surface (9) including a feed portion (9a) arranged adjacent to the weld portion (9b), and the feed portion being either convex or concave curved, wherein the radius of curvature is greater than the radius of curvature of the weld portion; The processing element (1) has a support surface (2) that is substantially cylindrical or cylindrically truncated, the support surface being for contacting the material during processing, wherein the processing element (1) is for rotating about its longitudinal axis (10) during processing, such that the support surface (2) moves circumferentially and rolls on the material to be processed, wherein the sealing surface (9) of the opposing element (3) is arrangable opposite to the processing element (1), such that a gap is formed between the support surface (2) and the sealing surface (9), the material to be processed being arranged in the gap, wherein in a cross-sectional view perpendicular to the longitudinal axis (10) of the processing element (1), the weld (9b) is at least partially concave and bent, and The processing element (1) is used to rotate in the feed direction, wherein the material to be processed moves between the processing element (1) and the opposing element (3), wherein the feed part (9a) and the welding part (9b) are arranged such that the material moving through the gap in the feed direction first contacts the feed part (9a) and then contacts the welding part (9b).

2. The ultrasonic welding device according to claim 1, characterized in that, At least one structural element (4) is arranged on the support surface (2), the structural element protruding radially above the support surface (2) which is substantially cylindrical or cylindrical cross-section, wherein the structural element (4) has an upper side for contacting the material to be processed, wherein the upper side includes a base and at least one recess, the recess being smaller in distance from the longitudinal axis (10) than the base, wherein the base and the recess are arranged adjacent to each other in a cross-sectional view perpendicular to the longitudinal axis (10).

3. The ultrasonic welding device according to claim 2, characterized in that, The recess formed by the recess does not extend to the support surface (2).

4. The ultrasonic welding device according to claim 3, characterized in that, The depth of the depression is less than 1 mm.

5. The ultrasonic welding device according to claim 4, characterized in that, The depth of the depression is 0.05 mm to 0.2 mm.

6. The ultrasonic welding device according to claim 2, characterized in that, The recess is constructed as a groove (5), wherein the groove (5) is not oriented in the circumferential direction, and / or the width of the groove (5) is less than 1 mm.

7. The ultrasonic welding device according to claim 6, characterized in that, The width of the groove (5) is less than 0.6 mm.

8. The ultrasonic welding device according to claim 7, characterized in that, The width of the groove (5) is 0.2 mm to 0.4 mm.

9. The ultrasonic welding device according to claim 6, characterized in that, The cross-sectional area of ​​the groove (5) is less than 0.15 mm. 2 .

10. The ultrasonic welding device according to claim 9, characterized in that, The cross-sectional area of ​​the groove (5) is less than 0.05 mm. 2 .

11. The ultrasonic welding device according to claim 10, characterized in that, The cross-sectional area of ​​the groove (5) is 0.015 mm. 2 up to 0.04mm 2 .

12. The ultrasonic welding device according to claim 6, characterized in that, The structural element (4) has a plurality of grooves (5) on the upper side that are not oriented in the circumferential direction.

13. The ultrasonic welding device according to claim 12, characterized in that, The structural element (4) has at least three grooves (5) on the upper side that are not oriented in the circumferential direction.

14. The ultrasonic welding device according to claim 13, characterized in that, The grooves (5) are arranged parallel to each other.

15. The ultrasonic welding device according to claim 2, characterized in that, The upper side has a main portion (6) which is configured to be substantially planar or have a convex curvature with a radius of curvature corresponding to the distance between the main portion (6) and the axis of the cylinder, and the upper side has at least one chamfered portion (7,8) which is adjacent to the main portion (6) in the circumferential direction and is angled relative to the main portion (6) such that the main portion (6) and the chamfered portion (7,8) form an angle of <180°, and / or the chamfered portion is convexly curved, wherein if the main portion (6) is formed to be convexly curved, the radius of curvature of the chamfered portion (7,8) is smaller than the radius of curvature of the main portion (6).

16. The ultrasonic welding device according to claim 15, characterized in that, The at least one recess is arranged in the main part (6).

17. The ultrasonic welding device according to claim 15, characterized in that, The main part (6) of the processing element (1) is convexly curved, and its radius of curvature is substantially corresponding to the radius of curvature of the concave curved part of the opposing element (3).

18. The ultrasonic welding apparatus according to any one of claims 2 to 17, characterized in that, The assembly includes at least two structural elements (4) spaced apart from each other in the circumferential direction, and / or the processing element (1) is configured as an anvil and / or the upper side has an elongated form with a length of l and a width of b, where l>b.

19. The ultrasonic welding apparatus according to any one of claims 1 to 17, characterized in that, At least one pull-out roller and / or at least one web guide roller are provided on which a web of material to be processed is wound and / or the web guide roller is guided, wherein the pull-out roller and / or the web guide roller are arranged such that one or more webs of material can move between the processing element (1) and the opposing element (3).

20. The ultrasonic welding apparatus according to any one of claims 1 to 17, characterized in that, The feed section (9a) and the welding section (9b) are approximately the same size.

21. The ultrasonic welding apparatus according to any one of claims 1 to 17, characterized in that, The opposing element (3) is an ultrasonic welding head.

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