Counter tool, ultrasonic welder and method for producing a seal weld and a decorative weld

Abstract

To provide an ultrasonic welding machine, a counter tool, and a method for reliably and easily manufacturing a seal welding part and a decorative welding part.SOLUTION: The invention relates to a counter tool for an ultrasonic welder, comprising two separate sealing surfaces intended to come into contact with the material to be processed, characterized in that the counter tool is formed in two parts, the two parts of the counter tool being movable relative to each other, each of the two parts comprising one of the two sealing surfaces.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a counter tool for an ultrasonic welding machine, an ultrasonic welding machine having the counter tool, and a method for manufacturing seal welds and cosmetic welds used by the ultrasonic welding machine. [Background technology]

[0002] Packaging technology is constantly changing. Recently, recyclable stand-up pouches made from, for example, monomaterial polypropylene are being used more frequently. These pouches are used, for example, for packaging wet animal feed. In this case, two layers of material cut into roughly rectangular shapes are welded together to form the package.

[0003] To join the two layers of material, a so-called seal weld is created, whose purpose is to ensure that the package is tightly sealed. On the side of the seal weld facing away from the product, there remain edge portions of the material layers that are not part of the seal weld. For aesthetic and other reasons, it is undesirable to weld these unwelded edge portions of the material layers together, even if these components are not required for sealing the package. A so-called cosmetic weld is applied immediately adjacent to the seal weld, which substantially improves the appearance of the package and prevents debris, such as product residue, from accumulating in the still-open portion of the package.

[0004] This material often comprises a support layer and a sealing layer. Modern recyclable monomaterials, especially for stand-up bags, have a low melting temperature difference between the support layer and the sealing layer, which therefore requires a very high level of process reliability when welding the two layers of material. Therefore, the welding temperature is selected as low as possible to avoid thermal damage to the support layer. This prevents unwanted shrinkage of the top edge of the bag due to excessive heat input. However, it significantly increases the risk of the weld reopening.

[0005] Welds are often introduced into the material using heat-sealing jaws. Alternatively, welds can be produced with an ultrasonic welding machine. For this purpose, a layer of material is placed between the sonotrode and a counter tool before the sonotrode is placed under ultrasonic vibration and pressed against the layer of material. The advantage of ultrasonic processing is that heat is generated only where it is actually needed for the welding process.

[0006] Typically, the seal weld and cosmetic weld are applied to the material in two separate welding stations. Early attempts to apply both to the package in a single welding station using an ultrasonic welder failed because reliable process control was not possible. If the sonotrode and counter tool are pressed together with too little force during welding, there is a risk that the cosmetic weld will reopen after welding. To prevent this, the force with which the sonotrode and counter tool are pressed together must be increased during the welding process of the two layers of material, which can lead to damage to the seal weld. There are instances where the force must be reduced for an optimal seal weld and increased for an optimal cosmetic weld, or vice versa. However, both requirements cannot be met simultaneously. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, starting from the above-mentioned prior art, the object of the present invention is to provide an ultrasonic welding machine, a counter tool and a method that allows for the reliable and simple production of sealing welds and cosmetic welds. [Means for solving the problem]

[0008] This object is achieved by a counter tool for an ultrasonic welding machine, which has two separate sealing surfaces provided for contacting the material to be processed. One sealing surface is provided for producing a seal weld, and the other sealing surface is provided for producing a cosmetic weld. According to the invention, the counter tool is formed in two parts, the two parts of the counter tool being movable relative to each other, and each of the two parts is provided with one of the two sealing surfaces.

[0009] Due to the relative movement of the two parts, the force applied by the counter tool to the material being processed can then be increased or decreased independently on the two separate sealing surfaces, which significantly increases the process reliability of the method. Furthermore, the welding processes for the seal weld and the cosmetic weld can be separated in time, which allows the process parameters to be evaluated to verify the weld quality between the two separate welding processes, ensuring reliable process control.

[0010] In a preferred embodiment, at least one of the two parts is provided with a drive by which one part can be moved relative to the other part, and in a particularly preferred embodiment, only one of the two parts is provided with a drive by which one part can be moved relative to the other part, which one part is best attached to.

[0011] In a preferred embodiment, it is provided that the two parts of the counter tool are movable relative to each other so that in a first position the first sealing surface protrudes beyond the second sealing surface and in a second position the second sealing surface protrudes beyond the first sealing surface.

[0012] This may ensure that welding can only take place via the first sealing surface or via the second sealing surface.

[0013] Furthermore, the counter tool can be equipped with a deflecting element that pushes the package into a slot provided for this purpose in the ultrasonic welding tool (sonotrode), thus preventing the package from slipping during the welding process. This package fixation may be necessary to ensure a reliable and reproducible ultrasonic welding process for the seal weld. The deflecting element can be located between the two sealing surfaces. Alternatively, the package fixation (clamping) can be performed directly above the sealing tool by an additional clamping device, thus eliminating the need for a deflecting element and slot in the ultrasonic welding tool (sonotrode). Since cosmetic welds do not have tightness requirements, welding of cosmetic welds can be performed without package fixation.

[0014] Further, the first part of the counter tool can have a front surface having a protruding portion with a first sealing surface, and the second part of the counter tool is positioned on the front surface of the first part of the counter tool but not on the protruding portion and is movable relative to the front surface.

[0015] In a further preferred embodiment, it is provided that the first sealing surface of the counter tool is an elongated sealing contour with a non-structured surface, and the second sealing surface of the counter tool provided for producing the cosmetic weld has a sealing contour with a structured surface. The term "non-structured surface" is understood to mean that the surface is smooth. The term "structured surface" is understood to mean that the surface comprises a plurality of separate or interconnected structural elements that protrude from or are recessed into the surface to form recesses. The first sealing surface may be flat. However, the first sealing surface may also be convexly curved. For example, the first sealing surface may be in the form of a bead with a radius of 1 mm to 5 mm.

[0016] With regard to the ultrasonic welding machine, the aforementioned object is achieved by an ultrasonic welding machine having a sonotrode operable to ultrasonic vibrations and equipped with a counter tool as described above.

[0017] In a preferred embodiment, the sonotrode has a flat, optionally discontinuous, sealing surface with two sealing surface portions, each of which is arranged opposite a sealing surface of the counter tool, one of which is provided for interaction with a first sealing surface of the counter tool to produce a sealing weld, and the other of which is provided for interaction with a second sealing surface of the counter tool to produce a cosmetic weld.

[0018] In a further preferred embodiment, the separation of the two sealing surface portions in the sonotrode may be omitted.

[0019] With respect to the method, the objective is to A) providing a superwelder according to any one of claims 6 to 7; B) placing the multilayer material to be welded between the sonotrode and the counter tool; C) positioning the two parts of the counter tool such that the first sealing surface of the counter tool is positioned closer to the sonotrode than the second sealing surface of the counter tool; D) moving the sonotrode and the counter-tool relative to each other so that the multi-layer material to be welded is in contact with both the sealing surface of the sonotrode and the first sealing surface of the counter-tool, wherein during and / or after step D) the sonotrode is subjected to ultrasonic vibrations; E) moving the second part of the counter tool relative to the first part of the counter tool so that the multilayer material to be welded is in contact with both the sealing surface of the sonotrode and the second sealing surface of the counter tool, During and / or after step E) the sonotrode is subjected to ultrasonic vibrations.

[0020] In step E), the movement can be performed so that the first sealing surface of the counter tool does not come into contact with the multi-layer material to be welded.

[0021] Activation of the sonotrode can occur already during movement step D) or E). However, it is also possible that ultrasonic activation of the sonotrode only takes place when movement step D) or E) is finished and the multilayer material is in contact with the sonotrode and the first or second part of the counter tool. Furthermore, after movement step D) or E), a pause phase of, for example, 20 milliseconds can be provided before the sonotrode is activated with ultrasonic vibrations.

[0022] Furthermore, it may be advantageous if during steps D) and / or E) the multi-layer material to be welded is held by a holding device so that relative movement of the individual layers of the multi-layer material is prevented.

[0023] By separating the two welding processes, it is also possible to select a different vibration amplitude for the sonotrode in the operating state after step D) than after step E). According to the present invention, both the seal weld and the cosmetic weld can then be produced at a single welding station, but the two welds are produced chronologically consecutively depending on the position of the second part of the counter tool. In embodiments according to the present invention, the force applied to the multilayer material through the first part of the counter tool to produce the seal weld has no effect on the cosmetic weld because the second part of the counter tool is not in contact with the multilayer material at that moment. Similarly, the force applied to the multilayer material through the second part of the counter tool to produce the cosmetic weld has no effect on the seal weld because the first part of the counter tool is not in contact with the multilayer material at that moment.

[0024] Further advantages, features and possible applications of the present invention will become apparent from the following description of preferred embodiments and the associated drawings. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of a first embodiment according to the present invention. [Figure 2] FIG. 2 shows the embodiment of FIG. 1 in a first position. [Figure 3] FIG. 3 shows the embodiment of FIG. 1 in a second position. [Figure 4] FIG. 4 is a side view of the second embodiment in a first position. [Figure 5] FIG. 5 is a side view of the second embodiment in a second position. DETAILED DESCRIPTION OF THE INVENTION

[0026] FIG. 1 shows a schematic diagram of a first embodiment of the invention. A sonotrode 1 has two sealing surface portions 8, 9 located on a common sealing surface. The two sealing surface portions 8, 9 are separated from each other by a recess 12. The sonotrode 1 is arranged on one side of a material 5, which consists of at least two layers of material to be welded together. A counter tool 2 according to the invention is arranged opposite the material 5. The counter tool also has two sealing surfaces, specifically sealing surface 6 and sealing surface 7. A deflecting element 10 is arranged between the two sealing surfaces; when the sonotrode and the counter tool are moved together, the deflecting element 10 enters the sonotrode recess 12 and fixes the material 5 in the sonotrode recess 12 so that the individual layers of the multi-layer material cannot slide relative to each other.

[0027] The counter tool 2 comprises two parts, specifically a first part 3 and a second part 4. The first part 3 has a first sealing surface 6. The second part 4 has a second sealing surface 7, which in the illustrated example is structured on its surface. To perform the method according to the invention, the counter tool is first moved to the position shown in FIG. 2 , i.e., the second part 4 of the counter tool 2 is moved relative to the first part 3 of the counter tool 2 by a mechanism 11 so that the first sealing surface 6 protrudes toward the sonotrode 1 compared to the second sealing surface 7. In this position, the sonotrode and the counter tool are then moved toward each other, so that the material 5 is clamped between the sealing surface 8 of the sonotrode and the sealing surface 6 of the first part 3 of the counter tool 2, welding the layers of material together. In this way, a sealing weld is produced.

[0028] In a next step, the mechanism 11 of the counter tool is activated in order to move the counter tool into the position shown in Figure 3. In this position, the second part 4 of the counter tool 2 protrudes towards the sonotrode 1 compared to the first part 3 of the counter tool 2. The distance between the highest elevations of the sealing surfaces 6 and 7 is b and a, respectively, as shown in Figures 2 and 3. In an embodiment according to the invention, a and b each measure approximately 1 mm. In the position shown in Figure 3, given the advanced position of the second part 4 of the counter tool 2, a welding process is then carried out between the sealing surface 7 of the counter tool 2 and the sealing surface 9 of the sonotrode 1.

[0029] It is also possible to first produce the cosmetic weld using the second part 4 of the counter tool 2 and then produce the seal weld using the first part 3 of the counter tool 2 .

[0030] The counter tool can also have a different structure, as shown in Figures 4 and 5. In this case, the counter tool is also made in two parts, with a first part 3' having a step surface aligned towards the sonotrode 1, and in the position shown in Figure 4, the sealing surface 6 that presses the material 5 onto the sonotrode 1 is on the protruding part of the step. In the position shown in Figure 4, the second part 4' of the counter tool 2 is not in contact with the material. The second part 4' is arranged on the step surface of the first part of the counter tool so that it does not protrude beyond the step.

[0031] However, as can be seen in Figure 5, the second part 4' of the counter tool can be moved towards the sonotrode 1, so that it protrudes from the stepped part of the first part 3' and only the second part 4' or its sealing surface, which is provided with the structural elements, comes into contact with the material 5, which is pressed against the sonotrode 1. Comparing the position shown in Figure 4 with the position shown in Figure 5, it becomes clear that in Figure 5 the first part 3' of the counter tool has moved away from the sonotrode 1, while the second part 4' has moved towards the sonotrode.

[0032] In the embodiment shown, the second part 4' is moved back and forth relative to the first part 3' of the counter tool 2 by a pneumatic cylinder. To determine the welding position shown in Figure 5 for the cosmetic weld, a stop can be provided which interacts with either the second part 4' or the pneumatic cylinder to prevent the second part 4' from moving towards the sonotrode 1 beyond the position shown in Figure 5.

[0033] The invention then allows the production of both the seal weld and the cosmetic weld at one welding station, where the two parts of the counter tool can be pressed into the material with the desired welding force. [Explanation of symbols]

[0034] 1 Sonotrode 2 Counter Tools 3. First Part 3' First part 4. Second Part 4' Second part 5 Material 6 First sealing surface 7 Second sealing surface 8 Sealing surface part 9 Sealing surface part 10 deflection elements 11 Mechanism 12 recess

Claims

1. 1. A counter tool for an ultrasonic welding machine, said counter tool comprising two separate sealing surfaces intended to come into contact with the material to be processed, A counter tool characterized in that the counter tool is formed in two parts, the two parts of the counter tool are movable relative to each other, and each of the two parts has one of the two sealing surfaces.

2. 2. The counter tool according to claim 1, wherein the two parts of the counter tool are movable relative to each other such that in a first position the first sealing surface protrudes beyond the second sealing surface and in a second position the second sealing surface protrudes beyond the first sealing surface.

3. Counter tool according to claim 1 or 2, characterized in that the counter tool comprises a biasing element, preferably arranged between the two sealing surfaces.

4. the first portion of the counter tool having a front surface with a protruding portion and the first sealing surface; A counter tool according to any one of claims 1 to 3, characterized in that the second part of the counter tool is not located on the protruding part of the first part of the counter tool but is movable relative to the front surface.

5. 5. The counter tool according to claim 1, wherein one of the two sealing surfaces of the counter tool, preferably the first sealing surface, has an elongated seal contour with an unstructured surface, and the other of the two sealing surfaces of the counter tool, preferably the second sealing surface, has a seal contour with a structured surface.

6. An ultrasonic welding machine having a sonotrode operable to ultrasonic vibrations and having a counter tool according to any one of claims 1 to 5.

7. 7. The ultrasonic welding machine according to claim 6, wherein the sonotrode has a flat, optionally discontinuous, sealing surface, the sealing surface having two sealing surface portions, each of the two sealing surface portions being arranged opposite the sealing surface of the counter tool.

8. 1. A method for producing seal welds and cosmetic welds, comprising: The method comprises: A) providing a superwelder according to any one of claims 6 to 7; B) placing the multi-layer material to be welded between the sonotrode and the counter tool; C) positioning the two parts of the counter tool such that the first sealing surface of the counter tool is positioned closer to the sonotrode than the second sealing surface of the counter tool; D) moving the sonotrode and the counter tool relative to each other so that the multi-layer material to be welded is in contact with both the sealing surface of the sonotrode and the first sealing surface of the counter tool, wherein during and / or after step D) the sonotrode is subjected to ultrasonic vibrations; E) moving the second part of the counter tool relative to the first part of the counter tool so that the multi-layer material to be welded is in contact with both the sealing surface of the sonotrode and the second sealing surface of the counter tool, wherein during and / or after step E) the sonotrode is subjected to ultrasonic vibrations.

9. 9. The method according to claim 8, wherein in step E), the movement is performed such that the first sealing surface of the counter tool does not come into contact with the multi-layer material to be welded.

10. 10. The method according to claim 8 or 9, wherein the multi-layer material to be welded is held by a holding device during step D) and / or step E) such that relative movement of the individual layers of the multi-layer material is prevented.

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