Method and device for welding individual multi-layer product

Abstract

To provide a method for quickly and reliably sealing an individual product in a continuous process.SOLUTION: A method for welding an individual multi-layer product 100 using an ultrasonic tool 30 comprising a generator 36, an anvil 32, a converter 46, a sonotrode 42 and, optionally, a vibration structure including a transducer component (amplitude amplifier), includes: moving the product through a gap formed between the sonotrode and the anvil, having a gap width S; pressing the sonotrode and / or the anvil against the product with a force to excite the sonotrode by the generator so as to vibrate at a predetermined amplitude and to transmit the vibrations to the product; and welding the (individual) product while moving the product along a welding path by the ultrasonic tool. At least one welding parameter, preferably the amplitude and / or the force and / or the gap width, is adjusted and changed during the movement of the product.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for welding a unified multi-layer product.

Background Art

[0002] Ultrasonic welding has proven to be a very advantageous method in many fields of product manufacturing. Two main fields of ultrasonic welding are, for example, a continuous method of continuously welding a web of multi-layer material and a discontinuous method in which an operator individually and repeatedly joins two parts of an assembly. The continuous method is known from DE 10 2014 110 634 A1.

[0003] In the field of manufacturing technology, there are joining methods that have not yet been realized using ultrasonic welding, for example, continuous welding of unified containers, especially bags. In the case of welding, a unified but open container is closed by a weld seam. The container is usually pre-filled with, for example, food, animal feed, or body care products. The weld seam welds a plurality of layers of the container, usually two walls that divide the container. In the case of a sealed weld, it is very important to seal the container airtight by the weld seam in order to protect the contents from the outside air.

[0004] DE 10 2013 100 474 A1 relates to an ultrasonic welding apparatus for sealing the gable seam of a unified product, especially a milk carton. DE 10 2015 110 387 A1 discloses an ultrasonic welding apparatus that can also be used for welding individual composite packages. US 3,294,616 shows an ultrasonic welding apparatus in which a minimum gap is set using a stop. Two methods for intermittent ultrasonic processing of a material web are known from DE 10 2017 107 617 A1 and DE 10 2022 105 944 A1.

[0005] The ultrasonic welding methods known in the prior art are not fully suitable for the continuous sealing / packaging of single-piece containers. In past attempts at continuous ultrasonic welding, the containers were unacceptable because they were damaged, especially at their edges, or the weld seams were not sealed by the welding method.

[0006] For the sealed welding of single-piece bags, discontinuous methods can be considered. However, they are often more time-consuming and require a great deal of labor to incorporate into manufacturing methods involving flow production.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, the problem to be solved by the present invention is to provide a method for quickly and reliably sealing a single-piece product in a continuous method.

Means for Solving the Problems

[0008] This problem is solved by the method and apparatus according to the present invention.

[0009] A method of welding a single-piece multi-layer product using an ultrasonic tool having a generator, an anvil, a converter, a sonotrode, and an optional vibration structure having a conversion part (amplitude amplifier), the method comprising moving the product within a gap having a gap width S formed between the sonotrode and the anvil. The ultrasonic tool welds the (single-piece) product while moving it along a welding path, where the sonotrode and / or the anvil are pressed against the product with a force, and the generator excites the sonotrode to vibrate at a predetermined amplitude and transmit the vibration to the product. At least one welding parameter, preferably the amplitude and / or the force and / or the gap width, is adjusted and changed during the movement of the product.

[0010] It can be controlled without changing other welding parameters. And they can be set to a certain target value, for example.

[0011] When welding a unified product, for example, in the case of continuous welding of a material web, the situation in the gap is not always the same. There are situations where there is a product in the gap and situations where there is not. The transition between the edge regions of the unified product, that is, between the situation where there is a product in the gap and the situation where there is not, is particularly a problem. By changing one of the welding parameters, the welding can be adapted to the situation currently existing in the gap and the transition therebetween. For example, if the amplitude of the edge region of the product is reduced, the welding energy is reduced, so that damage to the edge can be prevented. Therefore, it is advantageous that the welding path starts at the first edge region of the product and / or ends at the second edge region of the product. This can avoid damage to the edge.

[0012] Amplitude is a common process variable. A predetermined amplitude is understood as a target value that can be input to the ultrasonic tool, for example.

[0013] The method according to the present invention is particularly a method for welding a plurality of unified multi-layer products. In this case, a plurality of products are sequentially moved within the gap, and each product is welded by the ultrasonic tool along the welding path during its movement. Here, in particular, the products are arranged at intervals from each other.

[0014] One use of this method is the sealing of bags and similar packaging. Such bags usually consist of at least two layers of material, which are usually of the same size and are overlapped with each other. And these layers are joined to each other at three edges (left, right and bottom) by material adhesion, usually heat sealing. Other joining methods such as ultrasonic welding are also possible. The open bag thus manufactured can be filled with contents. Then, in order to protect the contents from environmental influences, the opening of the bag must be sealed. The heat-sealed edge region forms a rigid edge. Since the ultrasonic tool is subject to strong impacts at this edge, damage occurs in the edge region in tests using certain welding parameters. The method according to the present invention is particularly suitable for sealing welding because it is also possible to apply it to layers pre-joined by material adhesion by changing the welding parameters. Therefore, in a further advantageous development, the product is sealed by material adhesion at at least one of the edge regions before moving within the gap. The width of the edge region is preferably 5 - 8 mm. Therefore, the product of this method is preferably a bag, especially an open bag and / or a bag filled with contents.

[0015] The welding energy introduced into the product is greatly affected by the amplitude. Therefore, it has been found that it is particularly advantageous to change the amplitude. Therefore, advantageously, the sonotrode is excited to vibrate at an amplitude A high for welding the product, where A high is preferably 20 μm to 40 μm, and at other times, the sonotrode is excited to vibrate at an amplitude A high smaller than A low , preferably: 0 < A low and / or A low < 0.5 * A high is applied. The low amplitude A low is used especially when the product is not placed within the gap. By reducing the amplitude, the impact received by the ultrasonic tool when moving the edge of the product into the gap is reduced. As a result, the damage received by the edge region is reduced. 0.5 * A highIf it is less, almost no welding effect can be obtained, but since the layers are already connected to each other by material adhesion, this is not necessary in the edge region. The amplitude is preferably A high is not decreased to 0 so that the time taken for the increase to A is shortened. This can increase the speed at which the product is moved within the gap and / or can reduce the distance between the products. This speeds up the overall manufacturing method. If it is less than 20 μm, welding will be insufficient, and if it exceeds 40 μm, welding may be damaged and leakage may occur. The preferred distance between products is from 10 mm to 250 mm, particularly from 30 mm to 180 mm.

[0016] The welding parameters of the ultrasonic tool are preferably controlled according to the movement or position of the product. In particular, when the product reaches the gap or in front of it, the amplitude is set to A high and / or when the product leaves the gap, the amplitude is set to A low This ensures that the actual welding method is executed along the desired welding path. In the case of a heat-sealed bag, a tight and strong seal can be achieved without damaging the edge.

[0017] The change of the welding parameters can be executed according to various mechanisms. The change can be executed according to time. That is, this is time-controlled. In this case, a program for changing the welding parameters over time can be stored in the control of the generator. If the speed of the product is known, such control is sufficient. The speed of the product may be used as an input variable for changing the welding parameters. In order to achieve a more accurate adjustment of the welding parameters, if further development is advantageous, it is conceivable to detect the position of the product to be welded at least once. In this way, a sensor unit can be used to detect whether the product has reached the gap or has left the gap. And the welding parameters can be adjusted accordingly. The sensor unit directly transmits a signal to the generator, and the generator optionally changes the amplitude to A high or Alow Set it to. By directly connecting between the sensor unit and the generator, the time loss due to signal processing in the control unit can be avoided. The signal is preferably a binary signal that can save time when the generator processes it. When the location where the sensor unit or the product is detected is away from the gap, the time delay can be used to correct the time required for the product to reach the gap.

[0018] To avoid damage to the product and the ultrasonic tool, preferably by continuously adjusting (ramping) the amplitude, the current amplitude A now to the target amplitude, especially A high or A low There is a transition to, and the slope of the ramp is preferably continuously controlled, and / or the ramp is within one range of the edge region or overlaps one of the edge regions. It is preferably applicable to other welding parameters as well.

[0019] At various points in the process of the method according to the present invention, the product may be located in the gap or the gap may be empty. In the latter case, the gap width S of the gap is preferably continuously set by moving the sonotrode and / or the anvil relative to each other so that the next coming product can enter the gap and at the same time immediate processing of the product becomes possible. Preferably, detection of metal contact and / or measurement of distance are used as input variables for controlling the size of the gap, and / or the target size of the gap is set and used as an input variable for controlling the gap width S. For example, in a continuous welding method of a material web, in any case, since there is always material between the sonotrode and the anvil, control of the gap width is not useful. The gap width S is preferably the shortest distance between the anvil and the sonotrode.

[0020] As described above, the product is preferably filled with the content before being moved and welded in the gap. This avoids subsequent working steps, and the method according to the present invention can be the final working step in the production of the filled product.

[0021] The economic efficiency of the method highly depends on the speed of the product. The speed also affects the quality of welding. At the same time, it is necessary to ensure that the product is welded uniformly and reliably. The product is preferably moved in the gap at a speed of 5 m / min to 100 m / min. If the speed is less than 5 m / min, sufficient products cannot be manufactured per unit time. If the speed exceeds 100 m / min, there may be problems in welding.

[0022] In addition to the speed, the number and thickness of the layers of the product also affect the quality of welding. The product preferably comprises at least two layers with each layer thickness being 50 μm to 300 μm. If the layer thickness is less than 50 μm, the welding energy applied is too high and the layer may be damaged, resulting in insufficiently sealed welding. If the layer thickness exceeds 300 μm, the welding energy applied is too low, and in this case, it may also result in insufficiently sealed welding.

[0023] The apparatus for welding a unified multilayer product according to the present invention has an ultrasonic tool and a conveying device. The ultrasonic tool includes a generator, a converter, a sonotrode, and an anvil. A gap with a gap width S is formed between the sonotrode and the anvil. The generator is set to excite the sonotrode to vibrate at a certain amplitude. The ultrasonic tool is set to press the sonotrode and / or the anvil against the product with a force. At least one welding parameter of the ultrasonic tool, preferably the amplitude and / or the force and / or the gap width, can be controlled and changed. The conveying device is set to move the unified product within the gap, preferably to move the product along a welding path so that the product is welded by the ultrasonic tool during its movement. Here, the generator excites the sonotrode to vibrate at a predetermined amplitude and transmit the vibration to the product.

[0024] The converter and the sonotrode form the vibration unit of the ultrasonic tool. The vibration unit may include an amplitude amplifier.

[0025] The ultrasonic tool, particularly the generator and the conveying device, are preferably connected to a common control device.

[0026] As described above, the detection of the product is advantageous in welding. Therefore, preferably, the apparatus also includes a sensor unit set to detect whether the product reaches the gap or in front of it, or whether the product leaves the gap. And the desired welding parameters can be changed according to the sensor signal. The sensor unit is preferably directly connected to the generator. This can avoid the time delay caused by the most recent control. In this case, the generator is set to change the welding parameters, particularly the amplitude, according to the signal from the sensor unit. The amplitude can be changed, for example, by changing the frequency at which the generator excites the converter.

[0027] In a further advantageous development, the sensor unit comprises at least one sensor, preferably an optical sensor and / or a capacitive sensor, arranged such that when the product reaches the gap or in front of it and / or when leaving the gap, the product moves into and / or out of the detection range of the sensor. In this way, it is possible to reliably detect the arrival at or departure from the gap. The sensor may be, for example, a light reflection switch.

[0028] The conveying device preferably includes a movable gripper configured to grip one or more products respectively. More preferably, the conveying device includes a continuous conveyor, particularly a conveyor belt, capable of moving the gripper. Most preferably, the conveying device is a linear axis system provided with the gripper.

[0029] In a further advantageous development, the sonotrode and / or the anvil has at least a partially circular outer shape and is rotatably mounted. The circular outer shape represents a physical ramp for the product reaching the gap. This serves to mitigate the upward momentum when the product reaches the gap. The ability of the sonotrode or anvil to move with the product and being rotatable also serves to reduce the momentum. Preferably, the rotating part rotates more actively, especially when it moves with the product.

[0030] As described above, the gap width S is preferably controlled. Therefore, in the apparatus, the sonotrode and / or the anvil are preferably displaceable relative to each other. Preferably, a gap control device between the sonotrode and the anvil is electrically connected to a metal contact detection device. Alternatively or additionally, a sensor for detecting the distance between the sonotrode and the anvil is also possible. The gap width S can be adjusted by being displaceable. The distance sensor provides an input signal for controlling the gap width S. Alternatively, the gap width S can also be set to a fixed value. Thereby, the apparatus becomes less complex overall.

[0031] The present invention will be described with reference to the drawings by way of examples.

Brief Description of the Drawings

[0032]

Figure 1

Figure 1x

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0033] The apparatus 10 shown in FIG. 1 includes a conveying device 20 and an ultrasonic tool 30. In this embodiment, the conveying device 20 includes a conveyor belt 22 having gripping elements 24. The gripping elements 24 can be moved in the conveying direction R by the conveyor belt 22. The conveyor belt 22 moves at a constant speed. The gripping elements 24 are designed to grip individual products 100, in this case bags. In this way, the products 100 are continuously moved in the conveying direction R at the same speed. Since the gripping elements 24 are arranged at intervals from each other, the products 100 are also conveyed at intervals from each other.

[0034] In the case of product 100, the embodiment shown here relates to a multilayer bag that is open at the top and filled with contents. The bag is shown only schematically.

[0035] In FIGS. 1x and 2, ultrasonic tool 30 is shown in more detail. Ultrasonic tool 30 includes a vibration unit 40 having a generator 36, an anvil 32, a sonotrode 42, an amplitude amplifier 44, and a converter 46. Anvil 32 is rotatably mounted and rotates actively. Converter 46 is supplied with voltage by generator 36. Vibration unit 40 is designed to resonate when converter 46 is excited with a voltage of a specified frequency by generator 36. Sonotrode 42 vibrates with an amplitude corresponding particularly to the excitation frequency. The amplitude is measured particularly along the main axis of vibration unit 40. Generator 36 can set sonotrode 42 or vibration unit 40 to be excited with different amplitudes, particularly high amplitude A high and low amplitude A low .

[0036] Sonotrode 42 and anvil 32 form a gap 34 therebetween having a gap width S. Gap width S is preferably the shortest distance between anvil 32 and sonotrode 42. In the illustrated embodiment, low amplitude A low is 30% of high amplitude A high (A low = 0.3·A high ). At low amplitude A low , when the bag is within gap 34, welding is not performed or hardly performed. On the other hand, high amplitude A high welds the layers of the bag at the point where the bag abuts between anvil 32 and sonotrode 42.

[0037] The gap control device between sonotrode 42 and anvil 32 is connected to a metal contact detector. Controls that can be used for this are known, for example, from EP 0 790 888 B1. The metal contact detector is used to continuously control gap width S. At the same time, when product 100 is within gap 34, a force is applied to sonotrode 42 and anvil 32 to apply a force to that product 100.

[0038] As described above, the product 100 is moved in the conveying direction R by a conveying device 20 (not shown in FIG. 2). As a result, the products 100 successively enter the gap 34, pass through it, and leave the gap 34 again. When the vibration unit 40 is activated during the movement, the layers of the products 100 are welded to each other when each product 100 is within the gap 34. In this way, the bag is closed at the top.

[0039] The apparatus 10 also includes a sensor unit 60 having a sensor 62. The sensor 62 has a detection range in which the products 100 are moved when the product 100 reaches in front of the gap 34, i.e., before each product 100 enters the gap 34. This state is shown in FIG. 2. When there is no product 100 in the gap 34, the generator excites the vibration unit 40 so that the sonotrode 42 vibrates at a low amplitude A low therein.

[0040] The sensor 62 is arranged at a position away from the gap 34, and the distance is known. Since the speed of the bag is also known, the elapsed time from the detection until the bag enters the gap can now be calculated (time = distance / speed). The sensor 62 directly transmits a detection signal to the generator 36 of the ultrasonic tool 30. After a preset time delay, the generator 36 excites the vibration unit 40 of the sonotrode 42 to vibrate at a high amplitude A high therein. The time delay is selected according to the distance of the sensor 62 from the gap 34 and the speed of the bag (see above).

[0041] The distance between the sensor 62 and the end of the gap 34 is also known. Therefore, in combination with the speed of the product 100, it is also possible to determine when the detected product 100 leaves the gap 34. Therefore, after a further time delay, the generator 36 re-excites the vibration unit 40 to vibrate at a low amplitude A low therein. Alternatively, the transition to A low may also be actuated by the fact that the sensor 62 no longer detects the product 100. Here too, a predetermined time delay can be provided.

[0042] A high from A low The transition from A to A and vice versa does not occur suddenly, but rather occurs steadily and evenly. This transition is schematically shown in FIG. 3. The product 100 to be welded is, as described above, a bag that opens at the upper end 108. This bag is already closed by material adhesion at its edge regions 102, 104 and bottom 106. Therefore, the contents can be filled before closing the bag. Here, the conveying direction R is also shown.

[0043] The change in the amplitude of the sonotrode 42 during the movement of the bag is schematically shown in FIG. 3. In the initial state, the sonotrode 42 vibrates at a low amplitude A low The edge region 102 of the bag first faces the ultrasonic tool 30. As described above, the sensor 62 detects in advance that the product 100 is approaching the gap 34. In response to this, the amplitude of the sonotrode 42 is set to a high amplitude A high The transition from A to A occurs along a slope (ramp), that is, it is performed continuously and uniformly. The increase in amplitude starts a little before the edge region 102 enters the gap 34. Before the edge region 102 is completely disposed within the gap 34, it reaches the high amplitude A low from A high to A. The ramp overlaps with the edge region 102. high When the second edge region 104 leaves the gap 34, the amplitude of the sonotrode 42 is decreased along the slope to the low amplitude A

[0044] low The start of the decrease occurs a little after the edge region 104 leaves the gap 34. The decrease ends a little after the edge region 104 completely leaves the gap 34.

[0045] Due to the intended increase and decrease in amplitude, the high amplitude A highEnsure that the desired welding is carried out completely. The path where the bag is welded is referred to as the welding path. Thus, in the illustrated embodiment, the welding path starts at the edge region 102 and ends at the edge region 104. This method has been found to be effective particularly with regard to the quality of the processing at the edges of the bag. So to speak, by starting and ending the welding at the edge regions 102, 104, the edges of the bag remain almost in their previous state. The region that was open at the tip of the bag is thus closed, and the edges are hardly affected.

Explanation of Reference Numerals

[0046] 10 Device 20 Conveying Device 22 Conveyor Belt 24 Gripping Element 30 Ultrasonic Tool 32 Anvil 34 Gap 36 Generator 40 Vibration Unit 42 Sonotrode 44 Amplitude Amplifier 46 Converter 60 Sensor Unit 62 Sensor 100 Product 102 Edge Region 104 Edge Region 106 Bottom 108 Upper End R Conveying Direction S Gap Width

Claims

1. A method for welding a unified multi-layer product using an ultrasonic tool comprising a generator, a sonotrode, and an anvil, wherein the product is moved within a gap having a gap width S formed between the sonotrode and the anvil, the sonotrode and / or the anvil is pressed against the product with a force, and the generator excites the sonotrode to vibrate at a predetermined amplitude and transmit the vibration to the product, so that the ultrasonic tool welds the product while moving it along a welding path, characterized in that at least one welding parameter, preferably the amplitude and / or the force and / or the gap width, is adjusted and changed during the movement of the product.

2. The method according to claim 1, wherein the welding path starts at a first edge region of the product and / or ends at a second edge region of the product, and the product is preferably closed by material adhesion at at least one of the edge regions before moving within the gap.

3. Excite the sonotrode to vibrate with an amplitude A to weld the product high where A high is preferably from 20 μm to 40 μm, and at other times, the sonotrode is excited to vibrate with an amplitude A high smaller than A low such that preferably: 0 < A low < 0.5 * A high The method according to claim 1 or 2, to which this is applied

4. Set the amplitude to A when the product reaches the gap or before it, and / or set the amplitude to A when the product leaves the gap. The method according to claim 3. high Set the amplitude to A when the product reaches the gap or before it, and / or set the amplitude to A when the product leaves the gap. The method according to claim 3. low Set the amplitude to A when the product reaches the gap or before it, and / or set the amplitude to A when the product leaves the gap. The method according to claim 3.

5. Using a sensor unit, it is detected whether the product has reached the gap or left the gap, and the sensor unit directly transmits a signal to the generator, and the generator optionally sets the amplitude to A high or A low The method according to claim 3 or 4, wherein the method is set to

6. Current amplitude A now to the target amplitude, in particular A high or A low The transition to is effected by a continuous adaptation (gradient) of the amplitude, the slope of the gradient being preferably continuously controlled and / or the gradient being within or overlapping one of the edge regions, according to any one of claims 3 to 5

7. The width S of the gap is continuously set by moving the sonotrode and / or the anvil relative to each other, preferably using detection of metal contact, and / or distance measurement is used as an input variable for controlling the size of the gap, and / or the target size of the gap is set and used as an input variable for controlling the gap width S, according to any one of claims 1 to 6.

8. The method according to any one of claims 1 to 7, wherein a plurality of products are sequentially moved within the gap and each is welded along a welding path.

9. The product is filled with contents before being moved within the gap for welding, and / or the product is moved within the gap at a speed of 5 m / min to 100 m / min, and / or the product preferably comprises at least two layers each having a layer thickness of 50 μm to 300 μm, according to any one of claims 1 to 8.

10. An apparatus for welding a unified multi-layer product, An ultrasonic tool having a generator, a converter, a sonotrode, and an anvil, and a transport device, wherein a gap with a gap width S is formed between the sonotrode and the anvil, the generator is set to excite the sonotrode to vibrate at a certain amplitude, the sonotrode and / or the anvil is set to press against the product with a force, and at least one welding parameter of the ultrasonic tool, preferably the amplitude and / or the force and / or the gap width, can be controlled and changed. The transport device moves the unified product into the gap, preferably, by the generator exciting the sonotrode to vibrate at a predetermined amplitude and transmit the vibration to the product, the product is set to be moved so that it is welded by the ultrasonic tool along the welding path during its movement. A device characterized by that.

11. A sensor unit is further provided which is set to detect whether the product reaches the gap or in front of it, or whether the product leaves the gap, and the sensor unit is preferably directly connected to the generator. The device according to claim 10.

12. The sensor unit is provided with at least one sensor, preferably an optical sensor and / or a capacitive sensor, arranged such that when the product reaches the gap or in front of it and / or when it leaves the gap, the product moves into and / or out of the detection area of the sensor. The device according to claim 11.

13. The device according to any one of claims 10 to 12, wherein the transport device comprises a movable gripper set to grip one or more products respectively.

14. The device according to any one of claims 10 to 13, wherein the sonotrode and / or the anvil is rotatably mounted with at least a partially circular outer shape.

15. The sonotrode and / or the anvil are displaceable relative to each other, preferably a gap control device is electrically connected to a metal contact detection device, and / or a sensor is provided to detect the distance between the sonotrode and the anvil. The device according to any one of claims 10 to 14.

Images