MEASURING ELEMENT WITH STRUCTURE ELEMENT

Description

[0001] The present invention relates to a processing element for ultrasonic processing of a material, such as a sonotrode or an anvil. A corresponding processing element is described, for example, in EP 3 209 433 B1 and WO 2018 / 064340 A1.

[0002] Ultrasound is increasingly being used, especially for joining nonwoven materials. Two nonwoven sections to be joined are placed one on top of the other in a gap between a sonotrode and an anvil, and the sonotrode is subjected to ultrasonic vibration. The friction induced by the ultrasonic vibration causes localized heating at the contact surfaces, melting the thermoplastic components of the nonwoven. The molten components of the material sections to be joined flow into one another and, once cooled, form a strong bond. This makes it possible to join corresponding nonwoven sections together to form a side seam in the manufacture of diapers.

[0003] When processing nonwovens, gathering of the material is often desired. For this purpose, additional elastic threads are inserted between the nonwoven sections to be joined. The nonwoven sections to be joined are then connected to each other at at least two connecting surfaces. During ultrasonic processing, a thread is fixed between the two connecting surfaces in such a way that a positive connection is created between the thread and the nonwoven sections in two spatial directions that are oriented perpendicular to each other. In this way, gathering of the material can be achieved.

[0004] The machining element can have a substantially cylindrical or cylindrical-segment-shaped support surface designed to come into contact with the material during machining. The machining element is then rotated about its longitudinal axis during machining, so that the support surface rolls over the material to be machined.

[0005] The support surface often has at least one structural element that protrudes radially above the support surface, so that the structural element has an upper surface intended to come into contact with the material to be processed. The actual welding then takes place in the area between the upper surface of the structural element and a sealing surface of a counter-element arranged at a distance from it.

[0006] In the case of thread fixation, the elongated structural element typically extends along the longitudinal axis of the processing element, so that the structural element is usually aligned at an angle, usually a right angle, to the orientation of the thread. The structural element therefore connects the thread section by section to the nonwoven sections. Areas in which the thread is freely movable alternate with areas in which the thread is connected to the nonwoven sections. This connection can be achieved either by a force-fit connection or by a material-fit connection between the nonwoven fabric and the thread in the spatial direction in which there is no form-fit connection. If the thread is stretched during ultrasonic processing, the section-by-section fixation of the thread creates gathers in the nonwoven fabric when the thread is relaxed after processing.

[0007] For example, the counter element can be a sonotrode and the machining element an anvil. The invention will be explained below using this example, as this is the preferred embodiment. In principle, however, it is possible to design the machining element as a sonotrode and the counter element as an anvil.

[0008] During processing, the carrier surface with the structural elements rolls on the material to be processed, so that the structural elements in particular cause welding.

[0009] The processing speed is limited with state-of-the-art devices.

[0010] In principle, the feed rate, i.e. the speed at which the material is moved through the gap between the machining element and the counter element, can be increased.

[0011] However, the sonotrode, which acts on the material at a fixed frequency, no longer delivers enough energy to enable reliable welding. This is because at a higher feed rate, the material is in contact with the sealing surface of the sonotrode for a shorter time, and therefore fewer "strokes" are applied by the sonotrode to the material.

[0012] This can be partially compensated by increasing the force with which the sonotrode is pressed onto the material being processed. This transfers more energy into the material "per impact" of the sonotrode. However, this creates higher friction and leads to the molten components that form at the interfaces between the material layers to be welded as a result of ultrasonic processing, i.e., in the so-called joining zone, being pushed out of the joining zone by the structural elements. This also leads to a poorer weld, as there are no longer enough thermoplastic components available in the joining zone. Alternatively, or in combination, the oscillation amplitude of the ultrasonic oscillation could also be increased. This also transfers more energy into the material "per impact" of the sonotrode. However, this is only possible to a limited extent.If the sonotrode is operated with too high a vibration amplitude, the sonotrode material may be damaged.

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

[0014] If threads are to be bonded to the nonwovens, there is the additional problem that structural elements that are too narrow result in insufficient thread clamping, as the clamping force is reduced due to the small interaction surface, which corresponds to the top surface of the structural elements, with the nonwoven sections. If the structural element is too wide, however, the interaction surface and thus the clamping force are larger; however, the larger interaction surface also leads to increased friction with the material being processed. Furthermore, if structural elements are too wide, the space within which the thread can move freely is reduced, which negatively impacts the gathering properties of the material.

[0015] Based on the described prior art, it is therefore the object of the present invention to provide a processing element with which reliable welding is possible.

[0016] According to the invention, this object is achieved in that the upper side has a base section and at least one recess section which is at a smaller distance from the longitudinal axis than the base section, wherein in a sectional view perpendicular to the longitudinal axis, the base section and the recess section are arranged next to one another, wherein the recess formed by the recess section does not extend to the support surface, wherein preferably the recess has a depth of less than 1 mm and particularly preferably between 0.05 mm and 0.2 mm, in accordance with claim 1.

[0017] When the structural element rolls on the material, plasticized components can be accommodated in the recess section, so that the described pushing out of the plasticized components from the joining zone is reduced.

[0018] In the case of thread fixation, the thread clamping is further improved by the concentration of the melt in the recess section.

[0019] The recessed section also reduces the effective interaction surface and thus the friction with the material. At the same time, the structural element can be made wider, ensuring sufficient fixation of the thread. Furthermore, the recessed section means that less force needs to be applied between the processing element and the counter element to achieve the same processing result. Furthermore, an improved feel of the resulting product was observed.

[0020] In a further preferred embodiment, the recessed section is formed as a groove, which, if possible, is not oriented solely in the circumferential direction. If the groove is oriented in the circumferential direction, the groove preferably does not completely encircle the support surface, but rather extends only over a circumferential angle of < 360°, preferably over a circumferential angle of less than 45° and most preferably less than 25°. It is also possible for several grooves to be arranged at a distance from one another in the circumferential direction.

[0021] The groove is not intended to interrupt the welding process, but rather to simply absorb molten material so that it essentially remains in place and can serve to connect the material layers.

[0022] It has been shown that this groove can prevent the detrimental delocalization of the melt due to the increased pressure of the sonotrode on the material being processed at the location of the groove. The melt is then only moved as far as the groove. The groove thus serves as a receptacle for the melt material.

[0023] In a preferred embodiment, the groove has a width of less than 1 mm, and preferably less than 0.6 mm. The groove width is most preferably between 0.2 and 0.4 mm.

[0024] Depending on the material to be welded, it may be sufficient for the groove to have a cross-sectional area of ​​less than 0.15 mm 2 . Preferably, the cross-sectional area is even less than 0.05 mm 2 , and ideally, the cross-sectional area is between 0.015 mm 2 and 0.04 mm 2 .

[0025] In a preferred embodiment, the structural element has a plurality of grooves, preferably at least three grooves, in the upper side, which are not aligned in the circumferential direction, wherein the grooves are preferably arranged parallel to one another. The grooves make it possible to hold molten material in the respective position, therefore multiple grooves are advantageous.

[0026] In a further preferred embodiment, the upper side of the structural element has a main section that is substantially flat or with a convex curvature with a radius of curvature that corresponds to the distance of the main section from the cylinder axis, and at least one chamfer section adjoining the main section in the circumferential direction. The chamfer section is either angled relative to the main section, so that the main and chamfer sections form an angle of less than 180°, or the chamfer section is convexly curved, wherein, if the main section is convexly curved, the radius of curvature of the chamfer section is smaller than the radius of curvature of the main section. Preferably, the at least one recess section is arranged in the main section.The chamfer section serves to gradually prepare the material for the welding contact between the main section and the counter element. At the transition between the main and chamfer sections, the slope or curvature of the top surface changes. This ensures that when the machining element is used, the distance between the structural element and the counter element continuously decreases until the smallest distance between the structural element and the counter element is achieved.

[0027] In a further preferred embodiment, the upper side has two chamfer sections adjoining the main section on opposite sides in the circumferential direction, which are angled relative to the main section so that the main section and the chamfer section each enclose an angle of less than 180°. During machining, the upper side of the structural element thus has not only an incoming chamfer section, but also a tapered chamfer section, whereby the force applied by the counter element to the machining element is only gradually reduced even at the end of machining the structural element.

[0028] In a further preferred embodiment, the upper side of the structural element has an elongated shape with a length l and a width b, where l > b. The length preferably extends not parallel to the longitudinal axis, but rather essentially perpendicular thereto.

[0029] In a further embodiment, the structural element and the recessed section arranged in the upper side extend continuously over an entire length l of the processing element, wherein the length l is oriented substantially parallel to the longitudinal axis. In this case, the length l of the structural element is preferably significantly greater than the width b of the structural element, which is arranged substantially perpendicular to the length l. In a further embodiment, the structural element also extends substantially along the longitudinal axis of the processing element, wherein the structural element and the recessed section arranged in the upper side run in a serpentine manner. It is understood that in this case the base section also runs in a serpentine manner.

[0030] The present invention also relates to an ultrasonic welding device according to claim 11, comprising a processing element as just described. In addition to the processing element, this ultrasonic welding device comprises a counter-element having a sealing surface that can be arranged opposite the processing element, so that a gap forms between the upper side of the structural element of the processing element and the sealing surface of the counter-element, in which gap a material to be processed can be arranged. In a sectional view perpendicular to the longitudinal axis of the processing element, the sealing surface has a welding section that is concavely curved at least in sections.

[0031] As already mentioned above, the counter element can be a sonotrode and the processing element an anvil. The curvature of the welding section extends the contact time between the sonotrode and anvil, allowing more energy to be introduced into the material. This also allows the feed rate to be increased without having to increase the force with which the sonotrode is pressed against the material to be processed.

[0032] In a further preferred embodiment, the radius of curvature of the concavely curved portion of the counter-element approximately corresponds to the radius of curvature of the main portion of the processing element. In fact, it is particularly preferred if the radius of curvature of the concavely curved portion of the counter-element is slightly larger than the radius of curvature of the main portion of the processing element. The difference between the two radii of curvature corresponds to the width of the gap remaining between the sealing surface and the top side of the structural element during welding.

[0033] In a further embodiment, the counter element has grooves for at least partially receiving at least one thread, which are oriented in a feed direction in which the material to be processed is moved through the gap between the processing element and the counter element. The material to be processed consists of at least two material web sections and the at least one thread, with the at least one thread being positioned between the two material web sections. In this way, gatherable materials can also be produced using the processing element according to the invention in an ultrasonic processing device.

[0034] In a further preferred embodiment, the sealing surface has an inlet section arranged next to the welding section and is either non-curved or concavely curved with a radius of curvature that is greater than the radius of curvature of the welding section. Here, too, the gradient or curvature of the sealing surface changes at the transition between the inlet section and the welding section, so that in the region of the inlet section, the distance between the processing element and the counter-element becomes successively smaller until the smallest distance is reached, which corresponds to the distance between the welding section and the top side of the structural element. This inlet section is arranged such that a material moved through the gap in the feed direction first comes into contact with the inlet section and then with the welding section.

[0035] It is advantageous if the inlet section and the welding section are approximately the same size.

[0036] Further advantages, features and possible applications of the present invention will become clear from the following description of a preferred embodiment and the associated figures.

[0037] They show: Figure 1 shows an ultrasonic welding device in a perspective view, Figure 2 shows a detailed enlargement of the area marked with X of Figure 1 , Figure 3 a detailed enlargement of Figure 2 , Figure 4 a side view of the ultrasonic welding device of Figure 1 and Figure 5 an enlarged partial view of Figure 4 . Figure 6 is a schematic representation of a further embodiment of the processing element according to the invention. Figure 7 is an enlargement of the schematic representation in Figure 6 .

[0038] In Figure 1A perspective view of an ultrasonic welding system is shown. The ultrasonic welding system has a processing element 1 designed as an anvil, which here is configured as a roller that can rotate about a longitudinal axis 10. At least one transverse seam bar 11 with a support surface 2 is arranged on the roller. A counter element 3 designed as a sonotrode is arranged opposite.

[0039] The counter element 3 can be excited here with an ultrasonic vibration. The material to be processed is then moved between the support surface 2 and the sealing surface of the sonotrode 3 facing the support surface 2, with the material's movement speed matching the peripheral speed of the processing element 1. The gap between the support surface 2 and the sonotrode 3 must be selected such that the ultrasonic vibration is transmitted to the material during processing, resulting in melting of the thermoplastic components at the interfaces.

[0040] In Figure 2 is a detailed enlargement of Figure 1 shown.

[0041] It can be seen that a plurality of structural elements 4 are arranged on the support surface 2. The structural elements 4 have an elongated shape and are oriented in the circumferential direction. The structural elements 4 come into contact with the material during processing and determine the welding pattern that is introduced into the material during processing. The ultrasonic welding system can be used, for example, to create side seams on nonwoven diapers.

[0042] In Figure 3 is a detailed enlargement of Figure 2 , in which the structural elements 4 are clearly visible. Two structural elements 4 are arranged next to one another in the circumferential direction (relative to the longitudinal axis 10). In the axial direction, a plurality of such pairs of structural elements are arranged next to one another.

[0043] Each structural element has a main section 6 and two chamfered sections 7, 8, which are more strongly curved than the main section 6. Grooves 5 have been introduced into the main section 6, which, in the embodiment shown, run perpendicular to the circumferential direction. It is not necessary for the grooves to run perpendicular to the circumferential direction. However, to achieve the inventive effect, they should not be arranged parallel to the circumferential direction. If the grooves are arranged parallel to the circumferential direction, they should not extend over the entire structural element 4.

[0044] During welding, the structural elements 4 roll on the material to be processed, so that the chamfered section 8 initially comes into contact with the material to be processed. Due to the angled arrangement of the chamfered section 8, the distance between the structural element 4 and the opposite sealing surface of the counter element 3 gradually decreases in this area until the smallest distance is reached in the area of ​​the main section 6. The main section 6 can be convexly curved, with the radius of curvature essentially corresponding to the distance between the top side of the structural element 4 and the longitudinal axis 10 of the processing element 1.

[0045] Grooves 5 with a depth of 0.1 mm and a width of 0.3 mm have been introduced into the main section 6. Molten material can penetrate into the resulting recesses, so that it essentially remains in place and is not squeezed out of the joining zone by the structural elements.

[0046] In Figure 4 is a side view of the ultrasonic welding device from Figure 1 shown. The sealing surface, ie the surface facing the support surface or the structural elements 4, is surface 9.

[0047] In Figure 5 is an enlarged partial view of the Figure 4shown. The surface 9 here consists of an inlet section 9a and a welding section 9b. The welding section 9b is concavely curved, essentially with the same radius of curvature as the radius of curvature of the main section of the processing element. This measure ensures that the material remains in contact with the sonotrode for longer during processing, so that more energy can be introduced into the material to be processed. The inlet section 9a is not curved in this embodiment and thus ensures that the material to be processed is initially guided into a narrowing gap in the area of ​​the inlet section 9a. In the area of ​​the welding section 9b, the gap is then minimal and is kept essentially constant in the area of ​​the welding section.The welding takes place mainly through the welding section 9b, but the inlet section 9a can already contribute to the welding at its end facing the welding section 9b.

[0048] In the Figures 6 and 7 Finally, an alternative embodiment of the processing element 1 according to the invention is shown, which is particularly suitable for the production of gatherable materials. For this purpose, at least one thread is guided between two material web sections of the material to be processed, which thread is connected to the material web sections in sections by means of the structural elements 4 in a force-fitting or material-locking manner. The structural elements 4 extend continuously over the entire extent of the anvil 1 in the direction of the longitudinal axis 10. Furthermore, the structural element 4 and thus also the grooves 5 run in a serpentine manner (see Figure 7 ). Through the Figures 6 and 7In the embodiment shown, the thread is stably connected to the material web cuts, while at the same time the friction between processing element 1 and material is reduced. List of reference symbols

[0049] 1Processing element (anvil) 2Support surface 3Counter element (sonotrode) 4Structural elements 5Grooves 6Main section 7, 8Chamfer sections 9Sealing surface 9aInlet section 9bWelding section 10Longitudinal axis 11Transverse seam strip

Claims

1. A processing element (1) for processing a material, such as a sonotrode or an anvil, comprising a substantially cylindrical or cylinder-segment-shaped carrier surface (2) which is intended to come into contact with the material during processing, the processing element (1) being intended to be rotated about its longitudinal axis during processing so that the carrier surface (2) moves in a circumferential direction and rolls on the material to be processed, at least one structural element (4) being arranged on the carrier surface (2), projecting in a radial direction above the carrier surface (2), the structural element (4) having an upper side intended to come into contact with the material to be processed, characterized in that the upper side has a base section and at least one recess section (5) which is at a smaller distance from the longitudinal axis (10) than the base section, wherein in a sectional view perpendicular to the longitudinal axis (10) the base section and recess section (5) are arranged next to one another, wherein the recess formed by the recess section (5) does not extend as far as the carrier surface (2), wherein preferably the recess has a depth of less than 1 mm and particularly preferably between 0.05 mm and 0.2 mm.

2. The processing element (1) according to claim 1, characterized in that the recess section is formed as a groove (5) which is preferably not aligned in the circumferential direction.

3. The processing element (1) according to claim 2, characterized in that the groove (5) has a width which is less than 1 mm and is preferably less than 0.6 mm and is particularly preferably between 0.2 mm and 0.4 mm.

4. The processing element (1) according to claim 2 or 3, characterized in that the groove (5) has a cross-sectional area of less than 0.15 mm2, preferably less than 0.05 mm2, and particularly preferably the cross-sectional area is between 0.015 mm2 and 0.04 mm2.

5. The processing element (1) according to any one of claims 2 to 4, characterized in that the structural element (4) has a plurality of grooves (5), preferably at least three grooves (5), in the top surface, which are not aligned in the circumferential direction, preferably the grooves (5) being arranged parallel to each other.

6. The processing element (1) according to any one of the preceding claims, characterized in that the top surface comprises a main section (6) which is substantially flat or with a convex curvature with a radius of curvature corresponding to the distance of the main section (6) from the cylinder axis, and at least one chamfer section (7, 8) adjoining the main section (6) in the circumferential direction, which chamfer section is either angled with respect to the main section (6), so that the main section and the chamfer section (6, 7, 8) form an angle < 180°, and / or is convexly curved, wherein, if the main section (6) is convexly curved, the radius of curvature of the chamfer section (7, 8) is smaller than the radius of curvature of the main section (6), wherein preferably the at least one recess section (5) is arranged in the main section (6).

7. The processing element (1) according to any one of the preceding claims, characterized in that at least two structural elements (4) spaced apart from one another in the circumferential direction are provided.

8. The processing element (1) according to any one of the preceding claims, characterized in that it is designed as an anvil (1).

9. The processing element (1) according to any one of the preceding claims, characterized in that the top surface has an elongate shape with a length I and a width b, where l>b.

10. The processing element (1) according to one of the preceding claims, wherein the structural element (4) as well as the recess section (5) arranged on the top surface extend continuously over an overall length I of the processing element (1), wherein the length I is substantially oriented parallel to the longitudinal axis (10).

11. An ultrasonic welding apparatus comprising a processing element (1) according to any one of the preceding claims and a counter-element (3), wherein the counter-element (3) having a sealing surface (9) which can be arranged opposite the processing element (1) so that a gap is formed between the top surface and the sealing surface (9) in which a material to be processed can be arranged, wherein, in a sectional view perpendicular to the longitudinal axis (10) of the processing element (1), the sealing surface (9) has a welding section (9b) which is concavely curved at least in sections, wherein preferably the radius of curvature of the concavely curved section of the counter-element (3) corresponds approximately to the radius of curvature of the main section (6) of the processing element (1).

12. The ultrasonic welding apparatus according to claim 11, characterized in that the counter-element (3) comprises grooves for at least partially receiving at least one thread, which grooves are oriented in a feed direction in which the material to be processed is moved through the gap between the processing element (1) and the counter-element (3), wherein the material to be processed consists of at least two material web sections and the at least one thread, wherein the at least one thread is positioned between the two material web sections, wherein preferably the processing element (1) is intended to be rotated in a feed direction in which a material to be processed is passed between the processing element (1) and the counter-element (3), wherein the inlet section (9a) and the welding section (9b) are arranged such that a material moved in the feed direction through the gap comes into contact first with the inlet section (9a) and then with the welding section (9b).

13. The ultrasonic welding apparatus according to claim 11, characterized in that the sealing surface (9) has an inlet section (9a) arranged adjacent to the welding section (9b) and is either non-curved or concavely curved with a radius of curvature which is larger than the radius of curvature of the welding section (9b).

14. The ultrasonic welding apparatus according to claim 12 or 13, characterized in that the inlet section (9a) and the welding section (9b) are approximately equal in size.

15. The ultrasonic welding apparatus according to any one of claims 11 to 14, characterized in that the counter-element (3) is designed as a sonotrode.