EP3976355A1

EP3976355A1 - System and method for welding two thermoplastic workpieces

Info

Publication number: EP3976355A1
Application number: EP20722544.2A
Authority: EP
Inventors: Alexei Vichniakov; Filipp Köhler
Original assignee: Airbus Operations GmbH
Current assignee: Airbus Operations GmbH
Priority date: 2019-05-29
Filing date: 2020-04-27
Publication date: 2022-04-06
Also published as: WO2020239341A1; CN113905875A; US20220134675A1; DE102019114446A1

Abstract

The invention relates to a system (2) and a method for welding two thermoplastic workpieces. The system (2) has an ultrasonic tool (8), a support (10) and a cooling unit (12). The ultrasonic tool (8) is designed to generate mechanical vibrations. The system (2) is designed to clamp together the workpieces in the receiving region (16) by means of the ultrasonic tool (8) and the support (10) if at least one fastening portion (18) of the workpieces (4, 6) opposite one another is arranged in the receiving region (16). The ultrasonic tool (8) is designed to introduce the mechanical vibrations into the fastening portion (18) of the workpieces (4, 6) in order to weld the workpieces (4, 6) in a joining zone (20). The cooling unit (12) is designed to cool, with cooling fluid (22), at least a part of the fastening portion (18) of the workpieces (4, 6) and/or a cooling portion (24) of the workpieces (4, 6) directly adjacent to the fastening portion (18).

Description

System and method for welding two thermoplastic

Work pieces

The invention relates to a system and a method for welding two thermoplastic workpieces. It is known from the prior art that two thermoplastic workpieces can be welded to one another by ultrasound. For this purpose, an ultrasonic tool is pressed onto the workpieces arranged opposite one another, so that ultrasound acts on the thermoplastic workpieces in the form of high-frequency mechanical vibrations. With sufficient duration and / or a suitable amplitude of the mechanical vibrations, the workpieces are heated by molecular and interfacial friction. This creates a joining zone between the two thermoplastic workpieces. It is often desirable that the thermoplastic workpieces are not welded to one another at a single point. Rather, it is not uncommon for the ultrasonic tool to be moved slowly along one of the two workpieces, so that the joining zone, in which the two workpieces are so strongly heated that they connect to one another, moves with the movement of the ultrasonic tool. The mechanical vibrations can, however, also extend into an area that is to the side of the joining zone. In order to prevent an already welded but still very warm area of the workpieces from being separated again due to the effects of the mechanical vibrations, holding tools are known from the prior art which hold the workpieces together immediately after welding and continuously with the movement of the ultrasonic tool, so that the moving ultrasonic tool does not lead to the previously welded sections of the workpieces being severed again.

In practice, however, it was found that the holding tools have to be carried along continuously with a small distance from the ultrasonic tool in order to attack the workpieces in a section immediately adjacent to the joining zone. This tracking of the holding tools is technically very complex and often requires individual adaptation to the workpieces to be welded. The invention is therefore based on the object of providing a simple way of welding two thermoplastic workpieces by means of ultrasound, so that a weld seam can be produced between the two workpieces without a section of the weld seam that has already been welded previously being destroyed or mechanically strong during ultrasonic welding is affected. In particular, it should be prevented that the introduction of ultrasound at a joining zone between the two workpieces leads to an adjacent weld joint created shortly beforehand being canceled and / or destroyed, which could result in the two workpieces being separated.

The object is achieved according to a first aspect of the invention by a system having the features of claim l. A system is therefore provided for welding two thermoplastic workpieces. The system includes an ultrasonic tool, a support and a cooling unit. The ultrasonic tool is designed to generate mechanical vibrations with a frequency between 20 kHz and 100 kHz. A head of the ultrasonic tool is arranged opposite the support so that a receiving area for the workpieces is formed between the head of the ultrasonic tool and the support. The system is designed to clamp the workpieces together by means of the ultrasonic tool and the support in the receiving area when at least one fastening section of the workpieces is arranged opposite one another in the receiving area. The ultrasonic tool is designed to introduce the mechanical vibrations into the fastening section of the workpieces in order to weld the workpieces in a joining zone. The cooling unit is designed to cool at least part of the fastening section of the workpieces and / or a cooling section of the workpieces immediately adjacent to the fastening section with cooling liquid.

In order to arrange the workpieces in the receiving area, one workpiece must first be arranged opposite the other workpiece, with an additional body, in particular designed as a thermoplastic additional plate, being able to be arranged between the two workpieces. This creates a sandwich arrangement of the two workpieces and the additional body. In principle, however, it is also possible for the two workpieces to be arranged directly opposite one another and in direct physical contact. If reference is made in the following to the additional plate, the additional body should be able to be common to it in an analogous manner. The workpieces arranged opposite one another are brought into the receiving area, in particular with the thermoplastic additional plate arranged in between, in order to then be clamped by the ultrasonic tool and the support. For this purpose, the ultrasonic tool can be moved in the direction of the support or else the support can be moved in the direction of the ultrasonic tool. It is also possible that the ultrasonic tool and the support are moved towards one another. This creates the mechanical clamping connection between the ultrasonic tool, the workpieces and the support. The fastening section of the workpieces each comprises a part of both workpieces and can also comprise a part of the additional plate. The fastening section is arranged in the receiving area. The fastening section can therefore have the same size as the receiving area. However, it is also possible that the fastening section is larger than the receiving area and thus extends laterally beyond the receiving area. The joining zone is preferably at least that part of the fastening section into which the mechanical vibrations are introduced. This is preferably the area of the fastening section that is directly between the ultrasonic tool and the support. In relation to the workpieces, the joining zone can therefore shift if the workpieces are moved laterally relative to the ultrasonic tool and a new section of the workpieces is thus continuously pushed into the receiving area. This results in a weld seam between the workpieces that can be continuously pushed out of the joining zone. The weld seam can still be in the fastening section, at least in sections, or, if it is pushed out laterally out of the fastening section of the workpieces, it can enter the cooling section of the workpieces.

The cooling unit of the system is designed to cool at least part of the cooling section and / or at least a part of the fastening section with cooling liquid. As mentioned above, the joining zone can form part of the fastening section. However, the joining zone is not necessarily the entire fastening section. The cooling with cooling liquid can therefore also take place in part of the fastening section of the workpieces. By cooling at least part of the fastening section and / or the cooling section of the workpieces with cooling liquid, it can be ensured in a particularly simple and efficient manner that the weld seam pushed out of the joining zone is cooled quickly and reliably. This increases the strength of the weld seam and the resulting material connection between the workpieces. The mechanical ones that occur beyond the joining zone Vibrations therefore do not lead to the weld seam pushed out of the joining zone being severed and / or mechanically weakened in such a way that only a poor connection between the workpieces is achieved. In addition, the cooling unit offers the advantage that it can be adapted particularly easily to different workpieces in order to cool the respective part of the fastening section of the workpieces and / or the cooling section of the workpieces with cooling liquid. This is because the cooling liquid used can be adapted particularly easily to a wide variety of geometrical configurations of the workpieces. As a result, a cooling effect can be efficiently guaranteed even with geometrically very complex workpieces.

Each or one of the two thermoplastic workpieces can consist exclusively of thermoplastic material. However, this is not absolutely necessary. Rather, it can be provided that a thermoplastic workpiece has a thermoplastic base material in which fibers are embedded. A thermoplastic workpiece should therefore also be understood to mean a fiber-reinforced, thermoplastic workpiece. The fibers for reinforcement can for example be formed from glass fibers, carbon fibers, aramid fibers and / or textile fibers. The fibers are preferably so-called continuous fibers. These fibers preferably have an average length of at least 5 cm, at least 10 cm or at least 20 cm. It can also be possible for the fibers to have an average length which corresponds to between 70% and 100% of an edge length of the respective workpiece. However, the fibers can also be formed from long fibers or short fibers. The fibers can be formed from glass fibers, carbon fibers, aramid fibers and / or textile fibers. Matrix material can be formed from PEKK, PEEK, LMPAEK, PEI, PPS and / or PA. A volume content of the fibers can be between 1% and 70%, preferably between 40% and 60%, on the respective workpiece.

It can also be provided that at least one of the thermoplastic workpieces can be provided with so-called Lighting Strike Protection (LSP). This is preferably a copper ECF (Expanded Copper Foil) or copper PCF (Perforated Copper Foil). The LSP can be applied or have been applied to the surface of the respective workpiece during the manufacture of the respective workpiece.

In particular, if at least one of the thermoplastic workpieces consists of a fiber-reinforced, thermoplastic material, it was found that the fibers can be under a bias, in particular a tensile bias. This prestress is also at least partially maintained when a weld seam pushed out of the joining zone is formed. This part of the weld seam can therefore be subject to mechanical prestress, in particular tensile prestress, which can lead to the weld seam being severed if the weld seam, which is already under tensile stress, is influenced by mechanical vibrations that are introduced into the joining zone in the immediate vicinity by means of the ultrasonic tool . The separation of the weld seam can be effectively prevented if the strength of the weld seam is increased as quickly as possible after exiting the joining zone and / or in the immediate vicinity of the joining zone. This can be ensured by means of the cooling liquid made available by the cooling unit for cooling the fastening area and thus for cooling the weld seam. This is because the cooling unit guides the cooling liquid to at least part of the fastening section of the workpieces and / or a cooling section of the workpieces.

The preceding explanations apply analogously if both thermoplastic workpieces are each formed from fiber-reinforced, thermoplastic material. However, it is also possible that the respective workpiece is only partially formed from thermoplastic material and / or only partially from fiber-reinforced, thermoplastic material. In this case it is relevant that the thermoplastic component or fiber-reinforced thermoplastic component of the respective workpiece is used to form a fastening section with the other workpiece, which can be arranged in the receiving area in order to subsequently weld the workpieces to be carried out by ultrasound.

An advantageous embodiment of the system is characterized in that an additional body is arranged in the fastening area between the first workpiece and the second workpiece when the workpieces are to be clamped together in the receiving area, the two workpieces being weldable by means of the additional body in the joining zone. The additional body can have any shape. The additional body is preferably designed as a thermoplastic additional body. The additional body can therefore be formed completely or at least partially from thermoplastic material. The additional body is preferably designed as a thermoplastic additional plate. If reference is made in the following to the additional plate, the additional body, in particular in any form, can be meant in an analogous manner. At least in the Fastening section, the thermoplastic additional plate can be arranged between the first and second workpiece. This results in a sandwich arrangement. This can be arranged in the receiving area so that the two workpieces and the additional plate arranged between them can be clamped together in the receiving area by means of the ultrasonic tool and the support in order to introduce mechanical vibrations into the fastening section of the workpieces by means of the ultrasonic tool and the workpieces at least partially in the joining zone to be welded. Because the additional plate can thus also be in the joining zone. The additional plate is made entirely from a thermoplastic material or, for example, from a fiber-reinforced thermoplastic material. As a result of the introduction of the mechanical vibrations, the thermoplastic material component causes heating between each of the workpieces and the additional plate, namely through molecular and / or interface friction. As a result, the additional plate is welded to each of the two workpieces so that the additional plate acts as a connecting means between the two workpieces. It can therefore also be said that the two workpieces are welded or can be welded by means of the additional plate. It has been found to be advantageous if the additional plate has a lower rigidity than each of the two workpieces. As a result, a particularly resistant and at the same time firm connection between the workpieces can be achieved due to the welding. In addition, it has proven to be advantageous if the additional plate is arranged at least essentially only along the planned weld seam between the workpieces, so that due to the shape of the additional plate it can at least be determined where the welding between the additional plate and the two workpieces takes place.

A further advantageous embodiment of the method is characterized in that the cooling liquid is water or at least comprises water. For example, at least 70% of the cooling liquid can be water. The cooling liquid can therefore also be largely based on water. The use of water as a cooling liquid has proven to be particularly advantageous in practice. The heating that occurs in the joining zone due to molecular and / or interfacial friction leads to a temperature in the joining zone that is greater than 100 ° C., preferably greater than 140 ° C. Due to the mentioned temperature in the joining zone, it can be ensured that cooling liquid penetrating in the direction of the joining zone evaporates before reaching the joining zone This prevents the cooling liquid from actually penetrating into the joining zone. The joining zone is therefore free of coolant.

Another advantageous embodiment of the system is characterized in that the cooling unit is designed to convey the cooling liquid to the fastening section and / or cooling section so that the cooling liquid conveyed there flows over the fastening section and / or cooling section of the workpieces in order to cool the workpieces . As the cooling liquid flows onto the fastening section and / or cooling section of the workpieces, the workpieces are cooled in the immediate vicinity of the joining zone. It can thus be ensured that a weld seam pushed out of the joining zone is cooled quickly and / or in the immediate vicinity of the joining zone. This ensures that the weld seam pushed out of the joining zone has the appropriate strength to remain non-destructive and / or without significant adverse effects in the event of mechanical vibrations, even if such mechanical vibrations can be passed on from the joining zone via the material of the workpieces. Since the cooling liquid is conveyed by the cooling unit, it can be ensured in a particularly simple manner that the cooling liquid has a temperature which is in a desired and / or predetermined temperature range. This is because, in particular, the cooling liquid can have been brought to a desired temperature before being conveyed so that the cooling liquid flows to the fastening section and / or cooling section of the workpieces at a previously known temperature. This makes it possible to predict how the workpiece is cooled in a particularly reliable and simple manner.

Another advantageous embodiment of the system is characterized in that the cooling unit has a liquid tank, a pump and a pipeline, the cooling unit being designed to convey cooling liquid from the liquid tank by means of the pump through the pipeline to a line end of the pipeline so that the cooling liquid escaping at the end of the line reaches the fastening section and / or cooling section of the workpieces. In particular, the use of the pipe line offers the possibility of the line end being placed at a desired location so that the cooling liquid reaches the fastening section and / or cooling section of the workpieces. The arrangement of the line end can thus be adapted particularly easily and individually to the workpieces to be welded. This makes the system particularly adaptable to those to be welded Work pieces. In particular, particularly small workpieces or particularly large workpieces can also be welded together. This is because the size of the workpieces to be welded only has a minimal influence in this configuration of the system. It is also possible for the liquid tank to be arranged at a distance from the ultrasonic tool. Because it is possible that only the pipe line extends up to the vicinity of the ultrasonic tool. Thus, the line end of the pipeline string can be arranged laterally next to the ultrasonic tool, preferably at a distance of less than 10 cm.

An advantageous embodiment of the system is characterized in that the support is formed by an anvil, a table or a frame. The support can preferably be formed by a solid and / or stable body. This offers the advantage that the workpieces, preferably with the additional plate arranged in between, can be arranged between the support and the ultrasonic tool in the receiving area so that the workpieces can be clamped, preferably with the additional plate arranged in between. For this purpose, forces can be exerted by the ultrasonic tool in the direction of the support, or vice versa, so that a clamping force acts on the workpieces. The clamping force acting during the welding ensures that a material connection is created between the thermoplastic material of the workpieces and / or the thermoplastic material of the additional plate. On the basis of the preceding explanation, however, it is also evident that it is indeed advantageous if at least one of the workpieces is arranged directly on the support in order to achieve the clamping of the workpieces. However, it is not absolutely necessary that one of the two workpieces is arranged directly and directly on the support.

Another advantageous embodiment of the system is characterized in that the cooling unit has a liquid container, the interior of which is at least partially filled with cooling liquid, the liquid container being arranged on the support and / or the bottom of the liquid container being at least partially formed by the support, wherein the head of the ultrasonic tool is immersed in the cooling liquid in the interior of the liquid container, so that the receiving space is within the interior of the liquid container filled with cooling liquid. The workpieces must therefore be brought into the liquid in the interior of the liquid container in order to be arranged in the receiving space. The workpieces arranged there can thus be submerged in liquid or welded under water in the joining zone. Strictly speaking, however, the welding as such does not take place in the cooling liquid, since the cooling liquid does not penetrate into the joining zone but evaporates shortly before the joining zone due to the heating of the workpieces. However, the area around the joining zone is cooled well and quickly with cooling liquid, in particular with water. In this way, particularly simple and efficient cooling of at least part of the fastening area and / or the cooling area of the workpieces can be ensured. The liquid container can be designed in the manner of a shell. The shell can be arranged on the support and / or the bottom of the shell can be at least partially formed by the support. But even if the shell is arranged on the support, clamping of the workpieces, in particular with the intermediate plate arranged in between, can be ensured by creating a clamping force between the ultrasonic tool and the support, which due to the arrangement also acts on the aforementioned workpieces . In this case, the clamping force also acts on the shell, but this has no negative influence. The liquid container, in particular in the form of a shell, is preferably made of metal. The support can also be made of metal. This effectively prevents a welding between one of the workpieces and the liquid container and / or a welding between the workpiece and the support from occurring.

An advantageous embodiment of the system is characterized in that the ultrasonic tool is designed in such a way that the mechanical vibrations generated by the ultrasonic tool have an amplitude and / or frequency that causes the mechanical vibrations at least essentially to affect the workpieces, and here particularly preferably acts essentially on the interfaces of the workpieces. In addition, the ultrasonic tool is preferably designed such that the mechanical vibrations act at least essentially only in the receiving area. The joining zone is in the receiving area.

Another advantageous embodiment of the system is characterized in that the system has a first handling unit to which the ultrasonic tool is attached, the system being designed to control the first handling unit in such a way as to move the ultrasonic tool along a predetermined movement path relative to the support and / or to move the workpieces. For example, it can be provided that the support supports the workpieces over a larger area. In this case, the first Handling unit can be controlled in such a way that the ultrasonic tool is guided along the predetermined movement path over the workpieces, so that the joining zone migrates or is moved with the movement of the ultrasonic tool. The cooling liquid has the effect that the weld seam caused by the movement of the joining zone is cooled in the immediate vicinity of the joining zone. This can effectively prevent the mechanical vibrations caused by the moving ultrasonic tool from influencing a weld seam moved out of the joining zone in such a way that the weld seam is destroyed and / or mechanically negatively influenced by it. The first handling unit can comprise and / or be formed by a robot with a controllable robot arm. For example, the ultrasonic tool can be arranged on one arm end of the robot arm. The robot can also be controlled in such a way that the robot arm moves the head of the ultrasonic tool along the predetermined path of movement over one of the workpieces, and thereby clamps the workpieces together continuously and / or continuously.

An advantageous embodiment of the system is characterized in that the system has a drive which is coupled to the support in such a way as to move the support along a predetermined drive path, in particular relative to the ultrasonic tool. The drive can be designed as a linear drive with which the support can be moved in one plane. The linear drive can be designed as a multi-axis linear drive so that the support can be moved in the plane along any desired, in particular curved, drive path. The support is preferably designed to hold the workpieces, so that the workpieces are held by the support and are moved with the support along the predetermined drive path. The ultrasonic tool can be arranged in a stationary manner. The movement of the support, in particular together with the workpieces, results in a relative movement between the support or the workpieces and the ultrasonic tool. This allows a weld seam to be achieved between the workpieces.

A further advantageous embodiment of the system is characterized in that the system has a holding unit which is designed to hold the workpieces and to arrange the workpieces, so that the workpieces are arranged opposite one another in the fastening section and the fastening section of the workpieces is arranged in the receiving area. The additional plate can be arranged between the workpieces. This can also be held by the holding unit with the workpieces and be arranged. In addition, the system preferably has one or the first handling unit to which the ultrasonic tool is attached. The system is also preferably designed to control the first handling unit in such a way as to move the ultrasonic tool along a predetermined movement path along the workpieces. In addition, it is preferably provided that the system has a second handling unit to which the support is attached, the system being designed to control the second handling unit in such a way as to move the support parallel to the ultrasonic tool. During the movement of the ultrasonic tool and the support by means of the first and second handling unit, the workpieces are continuously clamped between the ultrasonic tool and the support. The ultrasonic tool is moved parallel to the support, so that a weld seam is created along the predetermined movement path between the workpieces or between the additional plate and the workpieces. This should also be understood as welding the workpieces. The workpieces are thus welded along the movement path. The holding unit can hold the workpieces stationary. There is therefore no movement of the workpieces for welding the workpieces. This is particularly advantageous when the workpieces are very large.

According to a second aspect of the invention, the aforementioned object is achieved by a method having the features of claim io. A method is therefore provided for welding two thermoplastic workpieces, the method comprising the following steps: a) Arranging a fastening section of the opposing workpieces in a receiving area between a head of an ultrasonic tool and a support, the ultrasonic tool for generating mechanical vibrations is formed with a frequency between 20 kHz and tookHz; b) clamping together the workpieces lying opposite one another in the fastening section by means of the ultrasonic tool and the support; c) Introducing mechanical vibrations into the fastening section of the workpieces by means of the ultrasonic tool, so that the workpieces are welded in a joining zone; and d) cooling with cooling liquid of at least a part of the fastening section of the workpieces and / or a cooling section of the workpieces directly adjoining the fastening section by means of a cooling unit.

With regard to the method, reference is made to the preceding explanations, preferred features, effects and / or advantages, as they have been explained in an analogous manner for the system according to the first aspect of the invention and / or one of the associated configurations. The same applies to each of the advantageous refinements of the method specified below. Repetitions are therefore avoided.

An advantageous embodiment of the method is characterized in that in step a) a thermoplastic additional plate is arranged in the fastening section between the workpieces, and in step c) the two workpieces are welded in the joining zone by means of the additional plate.

A further advantageous embodiment of the method is characterized in that the cooling liquid is water or at least comprises water.

Another advantageous embodiment of the method is characterized in that steps b), c) and d) are carried out simultaneously.

A further advantageous embodiment of the method is characterized in that the workpieces are heated in a joining zone in step c) to a temperature of at least 150 ° C., which is at least 20 ° C. higher than a boiling point of the cooling liquid. The cooling liquid can thus be evaporated in the immediate vicinity of the joining zone. This is especially true when the cooling liquid is water.

Another advantageous embodiment of the method is characterized in that the cooling liquid in step d) is conveyed to the fastening section and / or cooling section by means of the cooling unit, so that the cooling liquid conveyed there flows over the fastening section and / or cooling section of the workpieces, around which To cool workpieces.

Another advantageous embodiment of the method is characterized in that the cooling unit has a liquid tank, a pump and a pipe line, the cooling liquid in step d) from the liquid tank passing through by means of the pump the pipe line is conveyed to a line end of the pipe line so that the cooling liquid exiting at the line end reaches the fastening section and / or cooling section of the workpieces.

Another advantageous embodiment of the method is characterized in that the cooling unit has a liquid container, the interior of which is at least partially filled with cooling liquid, the liquid container being arranged on the support and / or the bottom of the liquid container being at least partially formed by the support, wherein the head of the ultrasonic tool dips into the cooling liquid in the interior of the liquid container during step c), so that the receiving space is within the interior of the liquid container which is filled with cooling liquid.

Another advantageous embodiment of the method is characterized in that the ultrasonic tool and the support are moved relative to one another by means of a first handling unit and / or a drive during step c).

Further features, advantages and possible applications of the present invention emerge from the following description of the exemplary embodiments and the figures. All of the features described and / or shown in the figures, individually and in any combination, form the subject matter of the invention, regardless of their composition in the individual claims or their references. In the figures, the same reference symbols are also used for the same or similar objects.

Figures 1 to 5 each show an advantageous embodiment of the system in a schematic representation.

Figure 6 shows a flow chart of an advantageous embodiment of the

Method in a schematic representation.

An advantageous embodiment of the system 2 is shown schematically in FIG. The system 2 is used to weld two thermoplastic workpieces 4, 6. With the system 2, the first workpiece 4 can therefore be welded to the second workpiece 6. Each of the two workpieces 4, 6 is a thermoplastic workpiece. Each of the two workpieces 4, 6 can consist of thermoplastic material or at least have thermoplastic material. Each of the two workpieces 4, 6 can have reinforcing fibers which are embedded in the thermoplastic material of the respective workpiece 4, 6. If in the following from a welding of the two Workpieces 4, 6 are spoken of, this can be understood to mean a direct welding of the thermoplastic material of the first workpiece 4 to the thermoplastic material of the second workpiece 6. The welding of the two workpieces 4, 6 can, however, also be understood to mean that the two workpieces 4, 6 are welded by means of further thermoplastic material that is arranged between the two workpieces 4, 6 before welding. For example, a thermoplastic additional plate 26 can be arranged between the first workpiece 4 and the second workpiece 6 before the two workpieces 4, 6 are actually welded by means of the thermoplastic material of the additional plate 26. The additional, thermoplastic material arranged between the two workpieces 4, 6 can also be understood as a so-called energy steering element or a so-called “energy director”. The two workpieces 4, 6 are welded together by ultrasonic welding. The welding can thus also be understood as an ultrasonic welding. The welding is achieved by mechanical vibrations with a frequency between 20 kHz and 100 kHz, which between the workpieces 4, 6 or between the additional plate 26 and the workpieces 4, 6 leads to heating of the thermoplastic material by molecular and / or interface friction, which reaches a temperature at which the thermoplastic material softens and / or melts. However, it is preferably provided that the heating is limited to a temperature at which the thermoplastic material, the two workpieces 4, 6 and preferably also the thermoplastic material of the additional plate 26 changes into plastic flow, but without the thermoplastic material melting down . The flow is sufficient so that a material connection between the thermoplastic material of the additional plate 26 and the thermoplastic material of each of the two workpieces 4, 6 is created. If the welding is to take place directly between the two workpieces 4, 6, the plastic flow of the thermoplastic material of the two workpieces 4, 6 leads to a material bond between the two workpieces 4, 6.

In order to produce the mechanical vibrations for welding the two thermoplastic workpieces 4, 6, the system 2 has an ultrasonic tool 8. A head of the ultrasonic tool 8 presses directly on one of the two workpieces 4, 6 in order to transmit the mechanical vibrations and to produce the clamping force. The ultrasonic tool 8 can have a so-called converter 48, a booster 50 and a sonotrode 52. The converter 48, the booster 50 and the sonotrode 52 are preferably arranged one behind the other in a mechanical series connection mechanically coupled to each other. The converter 48 can be designed to convert an electrical signal into mechanical vibrations. Mechanical vibrations can therefore be caused by the converter 48. For this purpose, the converter 48 can have piezo elements, for example, which can be controlled by an electrical signal, which leads to mechanical vibrations, insofar as the electrical signal is an alternating signal. The booster 50 is preferably designed in such a way as to change the amplitude of the mechanical vibrations generated by the converter 48 in terms of amplitude level and / or frequency. For example, the booster 50 can be designed in such a way that the booster 50 can only vibrate mechanically in the frequency range between 20 kHz and 100 kHz. The sonotrode 52 is mechanically coupled to the booster 50. The sonotrode 52 has a head 14 which is designed to be brought into direct contact with one of the two workpieces 4, 6 in order to achieve the welding. The head 14 of the sonotrode 52 can also form the head 14 of the ultrasonic tool 8. In order to set the ultrasonic tool 8 in mechanical vibrations, the ultrasonic tool 8 can be coupled via an electrical connecting line to a control unit 46, which is designed to generate and transmit an electrical signal via the connecting line to the ultrasonic tool 8, so that the ultrasonic tool 8 due to the electrical Signal is set into mechanical vibrations. The control unit 46 does not form part of the system 2. The ultrasonic tool 8 is designed to generate mechanical vibrations with a frequency between 20 kHz and 100 kHz, preferably between 20 kHz and 40 kHz.

The system 2 also has a support 10. The support 10 is shown schematically and by way of example in FIG. The support 10 can be designed in the manner of an anvil or as a table. The support 10 can also be formed by a frame or some other solid body. The support 10 is often significantly larger than the sonotrode 52. This is because the support 10 can also be designed to hold and / or fasten the workpieces 4, 6 in a supporting manner. In particular, the support 10 can be designed to detachably hold the workpieces 4, 6, although this is not shown schematically in FIG.

The head 14 of the ultrasonic tool 8 is arranged opposite the support 10 in such a way that a receiving area 16 for the workpieces 4, 6 is formed between the head 14 of the ultrasonic tool 8 and the support 10. The workpieces 4, 6 can thus be arranged between the head 14 of the ultrasonic tool 8 and the support 10, so that a fastening section 18 of the two workpieces 4, 6 is arranged between the head 14 of the ultrasonic tool 8 and the support 10. In this case, at least part of the fastening section 18 of the two workpieces 4, 6 is arranged in the receiving area 16 between the head 14 of the ultrasonic tool 8 and the support 10. The system 2 is also designed to clamp the workpieces 4, 6 together in the receiving area 16 by means of the ultrasonic tool 8 and the support 10. For this purpose, the ultrasonic tool 8 can be fastened to a handling unit 42, as can be seen schematically in FIG. By means of the handling unit 42, the head 14 of the ultrasonic tool 8 can press on one of the two workpieces 4, 6 so that the two workpieces 4, 6 are clamped between the head 14 of the ultrasonic tool 8 and the support 10. The receiving area 16 is preferably determined by the contact area between the head 14 of the ultrasonic tool 8 and the longitudinal axial direction of the ultrasonic tool 8. This is because the ultrasonic tool 8 is preferably designed to introduce the mechanical vibrations in the longitudinal axial direction of the ultrasonic tool 8 into the workpieces 4, 6 that are clamped together. This is preferably done over the entire contact area between the head 14 and one of the two workpieces 4, 6. Outside the receiving area 16, the mechanical vibrations will only occur to a lesser extent, so that the workpieces 4, 6 can be welded in a targeted manner in the receiving area 16 . The ultrasonic tool 8 is therefore designed to introduce the mechanical vibrations into the part of the fastening section 18 of the workpieces 4, 6 that overlaps with the receiving area 16 in order to weld the workpieces 4, 6 in a joining zone 20. The joining zone 20 is preferably within the receiving area 16. If the two workpieces 4, 6 are welded by means of the additional plate 26, which is arranged between the two workpieces 4, 6, the joining zone 20 is in each case at the boundary layers between the additional plate 26 and the workpieces 4, 6 be within the receiving area 16. Because precisely at the transition areas from the additional plate 26 to the respective workpiece 4, 6, the molecular and interface friction occurs due to the mechanical vibrations, which leads to the desired heating of the thermoplastic material of the additional plate 26 or the respective workpiece 4, 6. Ultrasonic welding takes place in the joining zone 20.

The ultrasonic tool can be moved along a predetermined movement path relative to the support 10 and / or the workpiece 4, 6. With the movement of the ultrasonic tool 8, the receiving area 16 and the Joining zone 20. The part of the welded workpieces 4, 6 pushed out of the receiving area 16 can, however, still have a high level of heat at the weld seam. In order to prevent this still very warm weld seam from being destroyed and / or mechanically negatively influenced due to the mechanical vibrations carried outwards, the system 2 has a cooling unit 12. The cooling unit 12 is designed to cool at least part of the fastening section 18 of the workpieces 4, 6 and / or a cooling section 24 of the workpieces 4, 6 immediately adjacent to the fastening section 18 with cooling liquid 22. The part of the fastening section 18 which can be cooled with cooling liquid 22 is preferably arranged on the outside around the receiving area 16, in particular in a ring shape. The cooling section 24 can again be arranged on the outside of the fastening section 18, preferably also in an annular manner.

An advantageous embodiment of the cooling unit 12 is shown in FIG. For this purpose, the cooling unit 12 can have, for example, a liquid tank 28, a pump 30 and a pipe line 32. The pipe line 32 preferably extends from the liquid tank 28 to a line end 34, the pump 30 being integrated in the pipe line 32. Cooling liquid 22 can thus be conveyed from the liquid container 36 to the line end 34 by means of the pump 30. The line end 34 is preferably arranged in such a way that the cooling liquid 22 exiting at the line end 34 reaches the fastening section 18 and / or cooling section 24 of the workpieces 4, 6. The system 2 can also have a plurality of cooling units 12. This is shown by way of example in FIG. The part of the fastening section 18 which is on the outside of the receiving area 16 is cooled particularly quickly and efficiently by the cooling liquid 22. In addition, the cooling section 24 of the workpieces 4, 6 is also efficiently cooled by means of the cooling liquid 22.

If the sonotrode 52 is used to produce a weld seam, so that the sonotrode 52 is moved along the predetermined movement path relative to the support 10 and / or the workpieces 4, 6, the weld seam that is continuously pushed out of the joining zone 20 is quickly and efficiently due to the Cooling with the cooling liquid 22 is cooled. Mechanical vibrations that are transmitted from the receiving area 16 to the outside into the aforementioned part of the fastening section 18 or even into the cooling section 24 cannot therefore destroy the previously lead mentioned weld seam. As the weld seam cools down, it solidifies and thus gains greater strength. This higher strength prevents the aforementioned mechanical vibrations from leading to destruction and / or mechanical, negative influence on the weld seam.

Another advantageous embodiment of the system 2 is shown schematically in FIG. Except for the support 10, the system 2 corresponds to the system 2 explained above in connection with FIG. 1. Reference is therefore made to the corresponding explanations in an analogous manner.

The support 10 for the system 2 shown in Figure 2 is designed to be smaller than the support 10 as it was used before. In particular, the support 10 can have a base area with which the support 10 presses against the second workpiece 6. The sonotrode 52 can press against the first workpiece 4 with the same base area. The support 10 and the sonotrode 52 can be arranged opposite one another, so that the aligned section between the base areas defines the receiving area 16.

Another advantageous embodiment of the system 2 is shown schematically in FIG. Except for the cooling unit 12, the system 2 corresponds to the system 2 explained above in connection with FIG. 1. Reference is therefore made to the corresponding explanations in an analogous manner.

The cooling unit 12 of the system 2, as shown schematically in FIG. 3, has a liquid container 36, the interior 38 of which is at least partially filled with the cooling liquid 22. The liquid container 36 is arranged on the support 10. In addition, the head 14 of the ultrasonic tool 8 is immersed in the cooling liquid 22 in the interior 38 of the liquid container 36, so that the receiving area 16 is within the interior 38 of the liquid container 36, which is filled with cooling liquid 22. The workpieces 4, 6 and the additional plate 26, which is preferably arranged in between, are also immersed in the cooling liquid 22, so that the fastening section 18 and the cooling sections 24 are within the interior space 38 of the liquid container 36, which is filled with cooling liquid 22. In other words, it is preferably provided that the receiving area 16 as well as the fastening section 18 and the cooling section 24 are below the surface of the cooling liquid 22. The bottom 40 of the liquid container 36 is arranged between the support io and the workpieces 4, 6. This is not disadvantageous, however, since the workpieces 4, 6 and preferably also the thermoplastic additional plate 26 arranged between them can be clamped between the ultrasonic tool 8 and the support 10 in the receiving area 16. In an embodiment variant not shown in FIG. 3, the bottom 40 of the liquid container 36 can be formed by the support 10.

If mechanical vibrations are introduced into the receiving area 16 by means of the ultrasonic tool 8, the joining zone 20 is created between the clamped workpieces 4, 6. The cooling liquid 22 evaporates due to the strong heating in the joining zone 20 or evaporates before it reaches the joining zone 20, so that the welding in the joining zone 20 is not negatively influenced by the cooling liquid 22. The cooling liquid 22 is preferably water or at least comprises water. For example, the cooling liquid 22 can be formed based on water with additional substances. In the joining zone 20, a temperature arises due to the heating that is often greater than 150 ° C. This causes the cooling liquid 22 to evaporate, in particular if the cooling liquid 22 is water or is based on water.

Since the part of the fastening section 18 arranged around the joining zone 20 and the cooling section 24 are arranged in the cooling liquid 22, particularly rapid and efficient cooling will also take place here. This in turn has the consequence that a weld seam pushed out of the joining zone 20 cools particularly efficiently and quickly, so that the weld seam is protected from mechanical influences or mechanical destruction by mechanical vibrations.

Another advantageous embodiment of the system 2 is shown in FIG. The system 2 corresponds at least essentially to the system 2 explained in connection with FIG. 3. However, the system 2 from FIG. 4 has a first handling unit 42 to which the ultrasonic tool 8 is attached. The first handling unit 42 can be designed as a robot with a robot arm 54. The ultrasonic tool 8 is attached to an arm end 56 of the robot arm 54. The first handling unit 42 is designed to move the ultrasonic tool 8 in space. In addition, the ultrasonic tool 8 can press on the workpieces 4, 6 by means of the first handling unit 42 in such a way that the workpieces 4, 6, and in particular also the additional plate 26 arranged between them, between the head 14 of the ultrasonic tool 8 and the Support io are jammed. In addition, the system 2 is designed to control the first handling unit 42 in such a way as to move the ultrasonic tool 8 along a predetermined movement path relative to the support 10 and the workpieces 4, 6. For this purpose, the first handling unit 42 can be coupled to the control unit 46 via a control line. The system 2 can thus control the first handling unit 42 by means of the control unit 46 in such a way as to move the ultrasonic tool 8 along said predetermined path of movement. The contact between the head 14 and the workpieces 4, 6 is maintained. During the movement of the ultrasonic tool 8, the workpieces 4, 6 continue to be pressed together. The movement of the ultrasonic tool 8 creates a weld seam to connect the workpieces 4, 6, in particular with the aid of the additional plate 26. The workpieces 4, 6 can be detachably held directly or indirectly on the support 10 to prevent the workpieces 4, 6 from slipping to prevent the movement of the ultrasonic tool 8.

Another advantageous embodiment of the system 2 is shown in FIG. The system 2 shown in FIG. 5 essentially corresponds to the system 2, as has been explained in connection with FIG. Analogous reference is made to the corresponding explanations. The system 2 shown in FIG. 5, however, has a drive 44 which is coupled to the support 10 in such a way as to move the support 10 along a predetermined drive path, preferably relative to the ultrasonic tool 8. The drive 44 is preferably designed as a linear drive 44. The support 10 can thus be moved in one plane by means of the linear drive 44, for example. The drive 44 can be controlled by the control unit 46. For this purpose, the control unit 46 can be coupled to the drive 44 via a signal control line (not shown). While the support 10 is being moved by means of the drive 44, the ultrasonic tool 8 can be arranged and / or held in a stationary manner. For this purpose, a holding device (not shown) can be provided by means of which the ultrasonic tool 8 is held in a stationary manner. It can also be provided that the workpieces 4, 6 are held directly or indirectly by the support 10 and / or in the liquid container 36 in order to prevent the workpieces 4, 6 from slipping during the movement of the support 10 by means of the drive 44. The movement of the support 10 by means of the drive 44 therefore also leads to an analogous movement of the workpieces 4, 6, preferably relative to the ultrasonic tool 8. This enables a weld seam to be achieved between the workpieces 4, 6, in particular by means of the additional plate 26 . In the figure 6 a flow chart of an advantageous embodiment of the method is shown schematically. The method is used to weld the thermoplastic workpieces 4, 6. The method has the following steps a) to d): a) Arranging a fastening section 18 of the opposing workpieces 4, 6 and a receiving area 16 between a head 14 of an ultrasonic tool 8 and a support 10, wherein the ultrasonic tool 8 is designed to generate mechanical vibrations with a frequency between 20 kHz and 100 kHz. b) Clamping together the workpieces 4, 6 opposite one another in the fastening section 18 by means of the ultrasonic tool 8 and the support 10. c) Introducing mechanical vibrations into the fastening section 18 of the workpieces 4, 6 by means of the ultrasonic tool 8, so that the workpieces 4, 6 are Joining zone 20 are welded. d) Cooling with a cooling liquid 22 of at least part of the fastening section 18 of the workpieces 4, 6 and / or a cooling section 24 of the workpieces 4, 6 directly adjacent to the fastening section 18 with a cooling unit 12.

With the method explained, the analogous advantages and / or effects are achieved as they have already been explained in connection with the system 2. The advantageous explanations, preferred features, effects and / or advantages, as they have been explained in connection with the system 2, are referred to in an analogous manner for the method.

Steps b), c) and d) are preferably carried out simultaneously. As a result, the workpieces 4, 6 are welded in the joining zone 20, while the workpieces 4, 6 are clamped together in the fastening section 18 by means of the ultrasonic tool 8 and the support 10. In addition, the cooling takes place at the same time by means of the cooling liquid 22.

In addition, it should be pointed out that “having” does not exclude any other elements or steps and “a”, “an”, “first” and “second” do not exclude a plurality. It should also be noted that features that are created with reference to one of the above Embodiments have been described, can also be used in combination with other features of other embodiments described above. Reference signs in the claims are not to be regarded as a restriction.

Claims

Expectations

1. System (2) for welding two thermoplastic workpieces (4, 6), the system (2) comprising:

an ultrasonic tool (8),

a support (10), and

a cooling unit (12),

wherein the ultrasonic tool (8) is designed to generate mechanical vibrations with a frequency between 20 kHz and 100 kHz, a head (14) of the ultrasonic tool (8) being arranged opposite the support (10) so that a receiving area (16 ) is formed for the workpieces (4, 6) between the head (14) of the ultrasonic tool (8) and the support (10), wherein the system (2) is formed, the workpieces (4, 6) by means of the ultrasonic tool (8 ) and to clamp the support (10) together in the receiving area (16) when at least one fastening section (18) of the workpieces (4, 6) is arranged opposite one another in the receiving area (16),

wherein the ultrasonic tool (8) is designed to introduce mechanical vibrations into the fastening section (18) of the workpieces (4, 6) in order to weld the workpieces (4, 6) in a joining zone (20), and

wherein the cooling unit (12) is designed, at least a part of the fastening section (18) of the workpieces (4, 6) and / or a cooling section (24) of the workpieces (4, 6) directly adjoining the fastening section (18) with cooling liquid ( 22) to cool.

2. System (2) according to the preceding claim, characterized in that an additional body (26) is arranged in the fastening section (18) between the workpieces (4, 6) when the workpieces (4, 6) are to be clamped together in the receiving area (16) are, the two workpieces (4, 6) being weldable in the joining zone (20) by means of the additional body (26).

3. System (2) according to any one of the preceding claims, characterized in that the cooling liquid (22) is water or at least comprises water.

4. System (2) according to any one of the preceding claims, characterized in that the cooling unit (12) has a liquid container (36), the interior (38) of which is at least partially filled with cooling liquid (22), the liquid container (36) on the support (10) is arranged and / or the bottom (40) of the liquid container (36) is at least partially formed by the support (10), the head (14) of the ultrasonic tool (8) in the cooling liquid (22) in the interior (38) of the liquid container (36) is immersed, so that the receiving space (16) is within the interior (38) of the liquid container (36) which is filled with cooling liquid (22).

5. System (2) according to one of the preceding claims, characterized in that the cooling unit (12) is designed to convey the cooling liquid (22) to the fastening section (18) and / or cooling section (24) so that the there conveyed cooling liquid (22) flows over the fastening section (18) and / or cooling section (24) of the workpieces (4, 6) in order to cool the workpieces (4, 6).

6. System (2) according to any one of the preceding claims, characterized in that the cooling unit (12) has a liquid tank (28), a pump (30) and a pipe line (32), wherein the cooling unit (12) is designed as cooling liquid (22) from the liquid tank (28) by means of the pump (30) through the pipeline (32) to a line end (34) of the pipeline (32) so that the cooling liquid (22) exiting at the line end (34) on the Fastening section (18) and / or cooling section (24) of the workpieces (4, 6) arrives.

7. System (2) according to one of the preceding claims, characterized in that the system (2) has a first handling unit (42) to which the ultrasonic tool (8) is attached, wherein the system (2) is formed, the first To control the handling unit (42) in such a way as to move the ultrasonic tool (8) along a predetermined movement path relative to the support (10) and / or the workpieces (4, 6).

8. System (2) according to one of the preceding claims, characterized in that the system (2) has a drive (44) which is coupled to the support (10) in this way is to move the support (io) along a predetermined drive path, in particular relative to the ultrasonic tool (8).

9. System (2) according to one of the preceding claims 1 to 6, characterized in that the system (2) has a holding unit which is designed to hold the workpieces (4, 6) and to arrange the workpieces (4, 6), so that the workpieces (4, 6) are arranged opposite one another in the fastening section (18) and the fastening section (18) of the workpieces (4, 6) is arranged in the receiving area (16), the system (2) having a first handling unit (42 ) to which the ultrasonic tool (8) is attached, the system (2) being designed to control the first handling unit (42) in such a way as to move the ultrasonic tool (8) along a predetermined movement path along the workpieces (4, 6) to move, and wherein the system (2) has a second handling unit to which the support (10) is attached, the system (2) being designed to control the second handling unit in such a way as to move the support (10) parallel to the Ultrasonic tool (8) for b because of it.

10. A method for welding two thermoplastic workpieces (4, 6), the method comprising the following steps:

a) Arranging a fastening section (18) of the opposing workpieces (4, 6) in a receiving area (16) between a head (14) of an ultrasonic tool (8) and a support (10), the ultrasonic tool (8) for generating is formed by mechanical vibrations with a frequency between 20 kHz and 100 kHz;

b) clamping together of the workpieces (4, 6) lying opposite one another in the fastening section (18) by means of the

Ultrasonic tool (8) and the support (10);

c) Introducing mechanical vibrations into the fastening section (18) of the workpieces (4, 6) by means of the ultrasonic tool (8), so that the workpieces (4, 6) are welded in a joining zone (20); and

d) cooling with cooling liquid (22) of at least part of the fastening section (18) of the workpieces (4, 6) and / or of one the cooling section (24) of the workpieces (4, 6) directly adjoining the fastening section (18) by means of a cooling unit (12).

11. The method according to the preceding claim, characterized in that in step a) a thermoplastic additional plate (26) is arranged in the fastening section (18) between the workpieces (4, 6), and wherein in step c) the two workpieces (4, 6) are welded in the joining zone (20) by means of the additional plate (26).

12. The method according to the preceding claim, characterized in that the cooling liquid (22) is water or at least comprises water.

13. The method according to any one of the preceding claims 8 to 9, characterized in that steps b), c) and d) are carried out simultaneously.

14. The method according to any one of the preceding claims, characterized in that the workpieces (4, 6) in a joining zone (20) in step c) are heated to a temperature of at least 150 ° C, which is at least 20 ° C higher than a The boiling temperature of the cooling liquid (22) is.

15. The method according to any one of the preceding claims 8 to 13, characterized in that the cooling unit (12) has a liquid container (36), the interior (38) of which is at least partially filled with cooling liquid (22), the liquid container (36) the support (10) is arranged and / or the bottom (40) of the liquid container (36) is at least partially formed by the support (10), wherein the head (14) of the ultrasonic tool (8) during step c) into the cooling liquid ( 22) is immersed in the interior (38) of the liquid container (36), so that the receiving space (16) is within the interior (38) of the liquid container (36) which is filled with cooling liquid (22).