Systems and methods for ultrasonic welding

Abstract

This invention relates to a system and method for ultrasonic welding. To create improved welded joints, the system (10, 10', 10'') proposed in this invention includes an ultrasonic generator (11) for emitting ultrasonic energy into a joint region (12) between a first part (13) and a second part (14) to be joined together. A binder (15; 15') applies pressure to the surfaces (16; 17) of one of the first part (13) and the second part (14) to bind the joint region (12). The binder (15, 15') is conformable to the surfaces (16; 17) of one of the first part (13) and the second part (14) to bind the joint region (12).

Description

Technical Field

[0001] This invention relates to systems and methods for ultrasonic welding. These systems and methods can be used to create welded joints between two or more parts. The method can be applied to components of vehicles, such as aircraft, for example, to join components such as the skin of an aircraft to one or more structural parts such as stringers, shells, or clamps of an aircraft fuselage. Background Technology

[0002] Welding describes a process in which two or more parts are joined together by melting the base materials of the parts and fusing the base materials between the parts. Energy is supplied to the joint area between the parts to melt the base materials near the joint area. In ultrasonic welding, energy in the form of ultrasonic waves and supplied by an ultrasonic generator is used.

[0003] Ultrasonic welding can be used to weld thermoplastic parts, including composite materials. US 4,618,516 A discloses a method for joining two thermoplastic parts along their respective opposing surfaces using ultrasonic energy, wherein one part surface has an energy guide portion, and the other part surface has a rough textured surface. A compressive force is applied between the workpieces, and then ultrasonic energy is applied to the workpieces using an ultrasonic amplitude transformer, also known as an ultrasonic generator. The dissipation of ultrasonic energy in the thermoplastic parts creates molten thermoplastic material at the joint between the workpieces. After a predetermined time interval, the ultrasonic energy is removed, allowing the molten thermoplastic material to solidify, thus providing a fused joint between the workpieces.

[0004] Energy directing portions can be used to concentrate energy within the welding area, reducing the amount of energy required to soften and melt thermoplastic materials and increasing the strength of the joint or weld. In US 4,618,516 A, the energy directing portion is formed by a protrusion, such as a tapered or ridged portion, which is formed in the base material of one of the workpieces and protrudes from the surface of one workpiece to contact the rough surface of the other component. Summary of the Invention

[0005] The purpose of this invention is to provide better consolidation in materials, thereby expanding the range of applications that can utilize ultrasonic welding.

[0006] This objective is achieved through the subject matter of the independent claim. The preferred embodiment is the subject matter of the dependent claim.

[0007] According to the present invention, a system for ultrasonic welding is provided, the system comprising: an ultrasonic generator for emitting ultrasonic energy into a bonding region between first and second parts to be joined together; and a bonding agent for applying pressure to the surface of one of the first and second parts to bond the bonding region. The bonding agent is adaptable to the surface of one of the first and second parts to bond the bonding region.

[0008] Conformability means that the lower surface of the binder can conform to and fit the surface, such that all angles between the intersecting curves of the paths of the lower surface of the binder remain substantially constant relative to the paths of the surfaces of the first and second parts. Therefore, the binder can move along the surfaces of the first and second parts, keeping the overlap area between the lower surface of the binder and the surface as uniform as possible. More uniform pressure applied by the binder to the surfaces and the mating area enables the production of reliable welded or fused joints.

[0009] In some embodiments, gas is used as a pressure medium. In these embodiments, the solid parts of the consolidator have limited contact with the workpiece (i.e., the surface of one of the first and second parts), or may not contact the surfaces of the first and second parts at all.

[0010] In this embodiment, the binder does not physically contact the surface of either the first or second part to bind the joint area, but is spaced apart from the surface. The binder is arranged close to the surface, for example, at a distance of less than 1 mm. Pressure on the surface is applied by a non-contact method formed between the binder and the surface, such as a high-pressure gas zone, for example, an air cushion.

[0011] In another embodiment, the binder does not physically contact the surface of either the first or second part to bind the joint area, and is spaced apart from the surface. Pressure is applied non-contactly in the form of a gas or air stream, which is directed and impacts the surface to apply pressure.

[0012] In one embodiment, the binder is brought into contact with the surface of one of the first and second parts to bind the joint region, and pressure is applied to the surface of one of the first and second parts to bind the joint region.

[0013] By using these methods, better consolidation of the material is provided before, during, and after ultrasonic welding, while limiting physical contact with the workpiece. Improved consolidation of the joint area can also have the effect of expanding the range of applications where ultrasonic welding can be used.

[0014] A first part and a second part are arranged in a stack, and a joining region is formed between the first part and the second part, and an assembly is provided. In some embodiments, the first part and the second part are in contact such that the joining region includes the interface between the first part and the second part. In some embodiments, an energy guide is positioned between the first part and the second part such that the joining region includes the interface between the first part and the energy guide and the interface between the energy guide and the second part. The energy guide may be in the form of a mesh or a sheet. After the stack of the first part, the energy guide, and the second part has been ultrasonically welded, a resin-rich area will exist at the interface between the first part and the second part.

[0015] In some embodiments, the binder is brought into contact with the outer surface of the first or second part. In other embodiments, the binder is brought close to the outer surface of the first or second part, such that the binder is positioned slightly above and spaced apart from the outer surface of the first or second part.

[0016] An ultrasonic generator and a binder are typically arranged adjacent to the same side of the assembly of the first and second parts, such that ultrasonic energy is directed into the surface contacted by the binder. The system and assembly are typically moved relative to each other, such that ultrasonic energy is first emitted into a predetermined area of ​​the bonding region where a welded joint is to be formed, which then melts to form a molten region. The binder is then brought into contact with the surface of the assembly above or below the molten region to bind the molten region as it cools and before it solidifies, thus forming a fused (welded) joint between the first and second parts. The ultrasonic generator and the binder are arranged adjacent to each other such that the ultrasonic generator first heats the bonding region by transmitting vibrational energy, and then the binder applies pressure to the joint until it cools to a certain temperature.

[0017] This system is particularly advantageous for subassemblies in which one of the first and second parts has a non-planar surface profile, because the binder can conform to the non-planar surface. Therefore, variations in the surface profile, such as inclined surfaces (e.g., ramps, bends, double bends, peaks and valleys), can be compensated for, allowing the binder to apply pressure more uniformly to the non-planar surface. Preferably, the conformable binder can apply uniform pressure to the assembly in every region of the surface profile.

[0018] This system is advantageous for continuous welding in which an ultrasonic generator and a consolidator move continuously on a surface to form an elongated weld joint (also known as a weld seam), and is also advantageous for continuous welding of non-planar parts.

[0019] This system is useful for forming welded joints between parts of vehicles such as aircraft. For example, it can be used to join tenoned stringers to the skin.

[0020] The binder can have different structures to allow the binder, or at least its lower surface, to conform to the surface of one of the first and second parts. In one embodiment, the system includes a source of gas, such as air. The gas can be pressurized.

[0021] In one embodiment, the consolidator directs a gas flow onto the surface of one of the first and second parts. This gas flow applies pressure to the surface, which is used to consolidate the molten joint region. The gas flow is directed onto the surface of one of the first and second parts such that the consolidation pressure provided by the gas flow from the consolidator upon impact with the surface conforms to the surface shape.

[0022] In one embodiment, the system includes a gas source, such as air. The gas may be pressurized. The consolidator directs the gas flow into the cavity to form a high-pressure zone between the consolidator and the surfaces of one of the first and second parts. This high-pressure zone has a pressure higher than the ambient pressure outside the cavity, and an air cushion is formed above and on the surface having a pressure higher than the ambient pressure outside the cavity. This air cushion applies pressure to the surface. The pressure on the surface is used to consolidate the molten joint region. The air cushion of the consolidator, such as an air pad, conforms to the surface and allows the consolidator to move conformally across the surface.

[0023] In one embodiment, the binder includes a mounting element and a flexible, e.g., elastic membrane connected to the mounting element. The flexible membrane laterally surrounds the cavity and has an open underside that, during system operation, faces the surface of one of the first and second parts. The mounting element includes an inlet for guiding a gas flow, such as pressurized gas, into the cavity to provide an air cushion for applying pressure to the mating region. The flexible membrane guides the gas flow to the surface of one of the first and second parts to bind the mating region by applying pressure to the surface in an area at least partially defined by the flexible membrane. For example, the flexible membrane may be annular and have a lower surface including a peripheral edge portion that laterally surrounds a circular opening through which air is guided to the surface. The peripheral edge portion of the flexible membrane provides a section of the outer surface of the binder conforming to the surface of one of the first and second parts. The flexible membrane may be referred to as a skirt.

[0024] In an alternative embodiment, the binder includes a lower surface conformable to the surface of one of the first and second parts to apply pressure to the joint and bind the joint. For example, the binder may be formed of a flexible material. In another example, the binder may include a flexible outer skin and a flexible body. In an alternative embodiment, the binder may include a bundle of needles movable relative to each other, such that when the tips of the needles move on a non-planar surface, the individual needles can move to conform to the contour and shape of that surface.

[0025] In one embodiment, the ultrasonic generator is supported by a mounting component, and a flexible membrane laterally surrounds the ultrasonic generator such that the ultrasonic generator is located within the cavity of the consolidator.

[0026] In one embodiment, the consolidator, including the flexible membrane, is positioned laterally adjacent to the ultrasonic generator, such that the ultrasonic generator and the consolidator can be applied sequentially to the surface of one of the first and second parts.

[0027] In one embodiment, the system further includes a drive system for driving the ultrasonic generator and the binder on the surface along the welding direction, with the binder positioned downstream of the ultrasonic generator relative to the welding direction. Thus, the ultrasonic generator is first brought into contact with the surface of one of the first and second parts, and then the binder is brought into contact with the surface of the first and second parts. This system can be used to provide a welding system for continuous ultrasonic welding.

[0028] In an alternative embodiment, the system further includes a drive system for driving the ultrasonic generator and the consolidator on the surface along the welding direction, with the consolidator located upstream and downstream of the ultrasonic generator. This arrangement is provided for an embodiment in which the ultrasonic generator is located within a cavity of a flexible membrane. In this embodiment, the upstream portion of the consolidator provides a pre-compressor for pre-compressing the joint prior to ultrasonic welding. The downstream portion of the consolidator provides consolidation of the molten region. The system can be used for continuous ultrasonic welding.

[0029] In one embodiment, the system further includes a pre-compression device, such as a roller located upstream of the ultrasonic generator. The roller is configured to apply pressure to the surface of one of the first and second parts to pre-compress the joint prior to ultrasonic welding. In embodiments where the ultrasonic generator and the binder are separate, the roller is located on the side of the ultrasonic generator opposite to the binder. For example, the roller is located upstream of the ultrasonic generator relative to the welding direction, while the binder is located downstream of the ultrasonic generator.

[0030] In this embodiment, one or both of the first and second parts comprise a thermoplastic polymer, such as a fiber-reinforced thermoplastic composite. Thermoplastic composites can be used in applications requiring high strength and low weight, such as aircraft.

[0031] Ultrasonic welding of thermoplastic polymers, whether unfilled or filled with fiber reinforcement, is based on the principle that when sound waves with ultrasonic frequencies pass through the interface into adjacent parts, some of the kinetic energy of the sound waves propagating internally is dissipated as heat. This heat melts the thermoplastic polymer in the region near the interface, causing the macromolecules of the matrix of the two parts—the thermoplastic material—to diffuse and form a weld joint between the two parts upon cooling.

[0032] The fibers in fiber-reinforced thermoplastic composites may include at least one of the groups consisting of glass fibers and carbon fibers. The thermoplastic plastics may include at least one of the groups consisting of PAEK (polyaryletherketone), PEKK (polyetherketoneketone), PEEK (polyetheretherketone), PEI (polyetherimide), PA (polyamide), PPS (polyphenylene sulfide), PB (polybutene), PBC (polyester block copolymer), PV (polyethylene compound), and PC (polycarbonate).

[0033] In some embodiments, an energy guide portion is disposed between the first part and the second part. In this embodiment, the bonding area into which ultrasonic energy or ultrasonic waves are emitted and melted includes a portion of the first part, a portion of the energy guide portion, and a portion of the second part. A fusion portion or welded joint is formed between the base material of the first and second parts and the energy guide portion.

[0034] An energy guide is used to concentrate energy in the welding area, reducing the amount of energy required to soften and melt the thermoplastic material and increasing the strength of the joint or weld. In some embodiments, the energy guide is in the form of a filler sheet or mesh. The energy guide may include a polymer that is the same as or compatible with the polymers of the first and second parts, such that ultrasonic welding causes intermolecular diffusion between the energy guide and the first and second parts.

[0035] The filler sheet may include thermoplastic materials; for example, the thermoplastic material of the filler sheet may have a melting temperature of at least 120°C. The filler sheet may be free of fibers or other fillers and may consist only of thermoplastic materials. Alternatively, in addition to thermoplastic materials, the filler sheet may include fillers such as fibers. The fibers may be carbon fibers, glass fibers, ceramic fibers, or metal fibers. Continuous fibers, long fibers, or short fibers may be used. The filler sheet may include various types of thermoplastic materials, including PAEK (polyaryletherketone), PEKK (polyetherketoneketone), PEEK (polyetheretherketone), PEI (polyetherimide), PA (polyamide), PPS (polyphenylene sulfide), PB (polybutene), PBC (polyester block copolymer), PV (polyethylene compound), and PC (polycarbonate).

[0036] In some embodiments, the filler sheet providing the energy guide is a planar continuous sheet. In some embodiments, the filler sheet includes holes or perforations. In some embodiments, the filler sheet is structurally integral and self-supporting, and is not formed in situ. This type of sheet is easy to handle. In some embodiments, the filler material is applied, for example, in liquid form, to the area to be joined, and the sheet is formed in situ on a first surface of the component.

[0037] In one embodiment, the first component is the aircraft skin, and the second component includes one of the group consisting of the aircraft's stringers, Ω-shaped stringers, tenon stringers, and cryogenic tanks. In an alternative embodiment, the second component is the aircraft skin, and the first component includes one of the group consisting of the aircraft's stringers, Ω-shaped stringers, tenon stringers, and cryogenic tanks.

[0038] According to another aspect of the invention, a method for ultrasonic welding is provided. The method includes forming an assembly to be ultrasonically welded by arranging a first part on a second part and forming a joint region between the first and second parts; emitting ultrasonic energy into the joint region between the first and second parts and forming a molten region thereat; and contacting a consolidator with the surface of the assembly to apply pressure to the joint region and solidify the joint region. The consolidator is conformable to the surface profile of one of the first and second parts to solidify the joint region.

[0039] Ultrasonic energy is supplied to the interface or joint area between parts to melt the base materials of the first and second parts near the interface or joint area. After a predetermined time interval, the ultrasonic energy is removed, causing the molten material to solidify and thereby providing a fused joint at the joint area between the parts. A consolidator is used to apply pressure to the molten material to eliminate voids and solidify the joint area. The ultrasonic energy can be provided by an ultrasonic generator.

[0040] In some implementations, the surface profile or shape of the component is non-planar. For example, the surface profile may include ramps, bends, or double bends. The conformal relationship between the binder and the component's surface allows the binder to apply more uniform pressure to the non-planar surface profile and mating area of ​​the component.

[0041] In one embodiment, ultrasonic energy is supplied by an ultrasonic generator, and the method includes driving the ultrasonic generator and a binder on the assembly along the welding direction to continuously form an elongated weld joint by sequentially applying the ultrasonic generator and the binder along a desired location of the weld joint. The binder is located downstream of the ultrasonic generator relative to the welding direction.

[0042] Alternatively, the consolidator can be located upstream and downstream of the ultrasonic generator relative to the welding direction. The portion of the consolidator upstream of the ultrasonic generator relative to the welding direction can be used to pre-compress the joint before it is fused by the ultrasonic generator. The portion of the consolidator downstream of the ultrasonic generator in the welding direction is used to consolidate the molten zone, i.e., to apply pressure to the molten zone to eliminate voids. After the molten zone solidifies, a reliable weld joint is formed.

[0043] In the welding direction, the distance between the component surface and the binder varies due to the non-planar surface profile. The conformal relationship between the binder and the component surface allows the binder to compensate for the changes in surface profile and apply more uniform pressure to the component surface profile and the fusion bonding area.

[0044] The binder can have different structures to provide conformability to the surface of the component. In one embodiment, the binder is coupled to a source of pressurized gas (e.g., air) and directs the gas flow to the surface of the component, thereby applying pressure to the joint and binding the joint.

[0045] In one embodiment, the consolidator includes a mounting element and a flexible membrane connected to the mounting element and laterally surrounding the cavity, wherein the flexible membrane has an opening on a lower side facing one of the first and second parts, wherein the mounting element includes an inlet for guiding a gas flow into the cavity, and the flexible membrane guides the gas flow to the surface of the assembly to consolidate the bonding region.

[0046] In one embodiment, the binder is coupled to a gas source and includes a mounting and a flexible membrane connected to the mounting and laterally surrounding the cavity. The flexible membrane has an opening on its underside facing one of a first part and a second part. The mounting includes an inlet for directing the gas source into the cavity. The binder is positioned close to and spaced apart from the surface of the assembly. Gas is directed into the cavity to form a high-pressure gas zone between the binder and the surface of the assembly. The high-pressure zone applies pressure to the surface of the assembly to bind the mating region. In one embodiment, at least a portion of the binder is in contact with a surface. For example, the flexible membrane may come into contact with the surface as the binder moves across it. The flexible membrane is conformable to the surface because it is flexible.

[0047] In one embodiment, the binder includes an outer surface that is conformable to the surface of the component, namely the surface of one of the first part and the second part, to bind the joint region.

[0048] In one embodiment, the binder includes a bundle of needles movable relative to each other, and the needles contact the surface of one of the first and second parts and apply pressure to the surface to bind the joint area.

[0049] If a flexible membrane is provided, its lower surface can conform to the surface of the component, i.e., the surface of one of the first and second parts. In other embodiments, the binder is formed of a flexible material.

[0050] In one embodiment, the method further includes bringing a roller located upstream of the ultrasonic generator into contact with the surface of the assembly to apply pressure and pre-compress the joint area. The ultrasonic generator is then applied to the joint area to form a molten joint, and a consolidator is then used to apply pressure to the molten joint to remove voids and solidify the joint. This method can be used for continuous ultrasonic welding to form elongated, continuous welded joints.

[0051] In one embodiment, the method further includes arranging an energy guide between the first part and the second part. For example, the energy guide may be placed on the second part in a predetermined area overlapping with the first part, and then the first part may be arranged on the energy guide to form a stack in which the energy guide is located at the joint between the first part and the second part.

[0052] Ultrasonic welding methods can be used to join parts or components of an aircraft or an aircraft subassembly. In one embodiment, the first part is the aircraft skin, and the second part includes one of the following groups: aircraft stringers, Ω-shaped stringers, tenon stringers, and cryogenic tanks. Alternatively, the second part is the aircraft skin, and the first part includes one of the following groups: aircraft stringers, Ω-shaped stringers, tenon stringers, and cryogenic tanks.

[0053] In the example, ultrasonic waves with a frequency in the range of 20 kHz to 60 kHz and an amplitude in the range of 10 μm to 200 μm are supplied by an ultrasonic generator to the loose assembly of the first and second parts for a predetermined time interval, such as several seconds. During this time, the energy guide portion—if present—and the area adjacent to the joint between the first and second parts melt, resulting in the fusion of the base materials. The ultrasonic generator is then turned off or removed, allowing the components and the joint formed by the fusion of the base materials of the first and second parts to cool and solidify, thus creating a welded joint between the first and second parts. A consolidator is applied to the assembly during this cooling process to apply pressure to the molten area and reduce any voids present, thereby improving the welded joint.

[0054] The methods described herein can also be used to join more than two components to form an assembly. Welding is a partial joining method, so in embodiments where the assembly comprises more than two components, each welded joint is formed sequentially, for example, by repeating the method or repeating the welding process.

[0055] In some embodiments, the first and / or second parts comprise plastic materials, such as thermoplastic materials, or thermosetting materials having a thermoplastic layer at the surfaces to be joined. In some embodiments, the first and / or second parts comprise composite materials. Composite materials may include reinforcing materials (such as fibers or granules) and a matrix formed from a thermoplastic material. For example, the composite material may be a fiber-reinforced composite material in which a thermoplastic plastic provides the matrix. The fibers may be graphite, graphene, carbon fibers, glass fibers, or ceramic fibers or granules. Furthermore, bio-derived fibers may be used. Continuous fibers, long fibers, or short fibers may be used. In some embodiments, the first and / or second parts may be laminated materials. Furthermore, recycled, degraded, or reused fibers or granules may be used.

[0056] The thermoplastic material of the first and / or second parts may have a melting temperature of at least 120°C. The thermoplastic material of the first and / or second parts may be PAEK, PEKK, PEEK, PEI, PA, PPS, PB, PBC, PV, and PC. In addition, other matrix materials are also suitable, such as bio-based matrices.

[0057] In some embodiments, the energy guiding portion is in the form of a filler sheet comprising the same thermoplastic material as the first and / or second components. This is advantageous because the filler sheet and the thermoplastic material of the first and / or second components melt at the same temperature, enabling good macromolecular diffusion between the filler sheet and the first and / or second components. This facilitates fusion, which is beneficial for providing high weld quality.

[0058] Welding of thermoplastic composite structures is an attractive alternative to conventional mechanical fastening, eliminating the need for drilling into the composite material and reducing the weight added by fasteners. Ultrasonic welding is fast, energy-efficient, and can create high-strength joints. The ultrasonic welding system described in this paper reduces system complexity and increases system versatility. For example, the system can be used to weld 3D geometries, such as double-bend and tenoned stringers, to the skin of aircraft, and can also be used to weld sealing joints in hydrogen tank systems made of thermoplastic carbon fiber reinforced polymer composites (CFRP).

[0059] The system described herein can be used to weld long seams in a continuous ultrasonic welding process, wherein a vibrating ultrasonic generator and a consolidator move continuously along the overlap / joint region. During any phase of the process, the overlap behind the ultrasonic generator remains molten, and the material needs to be consolidated by the consolidator until the temperature reaches below the material's glass transition temperature and solidifies to form the weld joint.

[0060] The advantages of this invention include: conformal consolidation of non-planar surfaces without load peaks, low friction allowing for better surface quality, cheaper positioning systems, reduced system complexity, and increased system versatility. In some designs, cooling of the weld area is provided via airflow. Attached Figure Description

[0061] The embodiments will now be described with reference to the accompanying drawings, in which:

[0062] Figure 1 A schematic diagram of a system for ultrasonic welding according to an embodiment is depicted;

[0063] Figure 2 The illustration shows a schematic diagram of a system for ultrasonic welding according to an embodiment;

[0064] Figure 3 The illustration shows a schematic diagram of a system for ultrasonic welding according to an embodiment;

[0065] Figure 4A The illustration shows a comparison system and method for ultrasonic welding, which is not part of the currently claimed invention.

[0066] Figure 4B The illustration shows a schematic diagram of a system and method for welding according to an embodiment;

[0067] Figure 5A The diagram illustrates a cryogenic vessel that can be manufactured using ultrasonic welding.

[0068] Figure 5B The illustration shows a schematic cross-sectional view of a cryogenic vessel manufactured using ultrasonic welding.

[0069] Figure 5C The illustration shows a perspective view of a sub-assembly including skin panels and stringers, which can be joined by ultrasonic welding.

[0070] Figure 5D The diagram shows Figure 5C Cross-sectional view.

[0071] Figure 6 The illustration depicts an aircraft comprising one or more sub-components, said one or more sub-components including one or more welded joints manufactured using a system or method of ultrasonic welding according to any of the embodiments described herein. Detailed Implementation

[0072] Figure 1 A schematic diagram of a system 10 for ultrasonic welding according to an embodiment is illustrated. System 10 includes a device 11 for emitting ultrasonic energy into a joint region 12 located between a first part or component 13 and a second part or component 14 to be welded together. Device 11 may be referred to as an ultrasonic generator. System 10 also includes a binder 15 that applies pressure to the surface of one of the first part 13 and the second part 14 to bind the joint 12. The first part 13 is disposed on the second part 14 to form the joint 12 between the first part 13 and the second part 14. The ultrasonic generator 11 and the binder 15 are positioned adjacent to one side of the first part 13 or the second part 14. Figure 1 In this configuration, the ultrasonic generator 11 and the binder 15 are arranged adjacent to and very close to the outer surface 16 of the first part 13. The binder 15 applies pressure to the outer surface 16 of the first part 13 but does not contact it. For example, the gap between the binder 15 and the surface 16 may be 1 mm or less. The binder 15 is conformable to the surface 16 of the first part 13 to bind the joint. "Conformable" describes the ability of the binder 15 to conform to and adapt to the shape / profile of the surface 16. Alternatively, the binder 15 may also apply pressure to the outer surface 17 of the second part 14.

[0073] The tip 34 of the ultrasonic generator 11 contacts the surface 16 of the first part 13 and emits ultrasonic energy into the first part 13 and the joint 12 to melt the materials of the first part 13 and the second part 14 and create a molten zone 18.

[0074] During the cooling process of the molten material 20, the consolidator 15 is applied and, as in... Figure 1 Pressure is applied to the molten material 20, as illustrated by arrow 37, to solidify the bonding region 12. The solidification of the bonding region 12 eliminates any voids that may occur during the arrangement of the first part 13 and the second part 14 and / or during melting by the ultrasonic generator 11.

[0075] System 10 can be used for continuous ultrasonic welding. An ultrasonic generator 11 and a consolidator 15 are connected to and driven by a drive unit 30, and moved by the drive unit along the desired position of the weld joint in the welding direction indicated by arrow 19. The weld joint may be elongated. As the ultrasonic generator 11 moves along the welding direction 19, the area below it is melted to form a molten region 18. The consolidator 15 is positioned downstream of the ultrasonic generator 11 and above the molten material 20 relative to the welding direction 19. Because the molten material 20 is no longer subjected to ultrasonic energy as the ultrasonic generator 11 moves to the right, the molten material 20 cools and then solidifies to form the ultrasonic weld joint 21.

[0076] One or both of the first part 13 and the second part 14 may be formed of a fiber-reinforced thermoplastic composite material, such as a carbon fiber reinforced composite material having a thermoplastic matrix.

[0077] In some embodiments, an energy guide 32 is positioned between the first part 13 and the second part 14. The energy guide 32 can be used to concentrate energy in the welding area and reduce the amount of energy required to soften and melt the thermoplastic materials of the first part 13 and the second part 14. The energy guide 32 can be in the form of a thermoplastic filler sheet. The thermoplastic material of the filler sheet can have a melting temperature of at least 120°C. The filler sheet may be free of fibers or other fillers and may consist only of thermoplastic material. Alternatively, in addition to thermoplastic material, the filler sheet may also include fillers, such as fibers. The fibers can be carbon fibers, glass fibers, ceramic fibers, or metal fibers. Continuous fibers, long fibers, or short fibers can be used.

[0078] The binder 15 is conformable to the surface 16 of the first part 13. Figure 1In the embodiment illustrated, the consolidator 15 includes a mounting member 22 and a flexible membrane 23 extending from the lower surface of the mounting member 22 and laterally surrounding a cavity 24. The membrane 23 has an opening 25 on its lower surface, which can be laterally surrounded by a peripheral portion 26 of the membrane 23. The opening 25 faces a surface 16 on which pressure is applied. The flexible membrane 23 can be considered as a skirt. The mounting member 22 includes a through opening 27 for guiding a source 28 of pressurized gas (e.g., pressurized air) from the source 28 into the cavity 24. The cavity 24 provides a volume of pressurized gas.

[0079] The flexible membrane 23 guides the airflow from the source 28 through the opening 25 and into the cavity 24, where a high-pressure gas zone is formed on the surface 16 of the first part 13. The pressure within the cavity 24 is higher than the ambient pressure. The high-pressure gas zone can be considered as an air cushion, or an air cushion in which the gas is air. This air cushion generates force and applies pressure, as schematically shown by arrow 37, to the surface 16 of the first part 13 and to the molten material 20 formed at the joint region 12 between the first part 13 and the second part 14, in order to solidify the joint region 12. In this embodiment, the pressure on the surface 16 is provided by gas static pressure. Because an air cushion is formed on the surface 16, the binder 15 can move on the surface 16 of the first part 13 and conform to the contour of the surface 16 without contacting the surface 16. When the binder moves on the surface 16, the flexible membrane 23 can contact the surface 16. Because the flexible membrane 23 is flexible, it can conform to the surface 16.

[0080] As indicated by arrow 29, air from the high-pressure zone formed in the cavity can escape around the edge of the opening 25 in the flexible membrane 23.

[0081] Figure 1 The binder 15 shown has the advantage that the lower portion of the binder 15, provided by the flexible membrane 23 and the cavity 24 that guides pressurized gas to the surface 16 of the first part 13, is not rigid. The binder 15 is capable of conformal movement and conforming to any change in the surface profile of the surface 16 of the parts to be joined.

[0082] In another embodiment, the pressure on surface 16 is provided by a flow of gas impacting surface 16 of the first part 13.

[0083] In another embodiment not shown, the binder 15 is contacted with surfaces 16, 17 of one of the first part 13 and the second part 14, and pressure is applied to these surfaces to secure the joint 12. For example, the binder 15 may comprise a bundle of needle-like members movable relative to each other. This allows the lower surface of the binder, provided by the needle-like members, to contact surfaces 16, 17 and conform to surface 16 of the first part 13 or surface 17 of the second part 14.

[0084] exist Figure 1 In this design, the surface 16 of the first part 13 is depicted as planar. However, many parts to be joined may have non-planar surfaces, such as inclined or curved surfaces, or double-curved surfaces, like peaks or valleys. The flexible binder 15 can conform to these surface profiles to apply pressure more uniformly to the non-planar surfaces. Therefore, a more uniform binding force is applied along the entire length of the molten region 20, allowing the molten region 20 to cool and form a more uniform weld joint 21.

[0085] An example ultrasonic generator 11 that can be used in system 10 includes a pneumatic press, a frequency converter, a piezoelectric converter, a booster, and an ultrasonic generator tip 11. The ultrasonic generator tip 11 is brought into contact with one of the parts to be welded. Figure 1 In the embodiment illustrated, the ultrasonic generator 11 applies static pressure and high-frequency (20 kHz), low-amplitude (10 μm to 50 μm) lateral mechanical vibration to components 13 and 14. Heat is generated by a combination of friction and viscoelastic heating. Ultrasonic energy is transferred to components 13, filler sheet 32, and components 14, thereby melting the thermoplastic material of filler sheet 32 ​​and the thermoplastic material of components 13 and 14 in the interface region between components 13 and 14 to form a molten region 18. Compared to fiber-reinforced components 13 and 14, the melting of the energy guide 32 may be caused by higher cyclic strain due to the lower stiffness of the energy guide.

[0086] Figure 2 The illustration shows a system 10' for ultrasonic welding according to another embodiment. System 10' includes, as shown in the figure... Figure 1The ultrasonic generator 11 and the bonding agent 15 are illustrated in the figure. In this embodiment, the system 10' also includes a pre-compression device in the form of a roller 31, which is positioned upstream of the ultrasonic generator 11 relative to the welding direction 19, and thus on the side of the ultrasonic generator 11 opposite to the bonding agent 15. The roller 31 contacts the upper surface 16 of the first part 13 and applies pressure to the upper surface 16 of the first part 13, and is used to pre-compress the bonding region 12 before the ultrasonic generator 11 emits ultrasonic energy into the bonding region 12. This pre-compression can help to form an increased contact area between the first part 13 and the second part 14, or, in the case of the energy guide 32, an increased contact area between the first part 13 and the energy guide, and between the energy guide 32 and the second part 14.

[0087] The upstream roller 31 can also help to block or prevent vibrations from the ultrasonic generator 11 from being transmitted to parts upstream of the ultrasonic generator 11, which further improves the quality and reliability of the welded joint 21. The upstream roller 31 can also help to limit the lateral extent of the molten area generated by the ultrasonic generator 11, to further improve the quality and reliability of the welded joint 21.

[0088] Figure 3 The illustration shows a system 10'' for ultrasonic welding according to another embodiment. System 10'' includes an ultrasonic generator 11 and a binder 15, the binder 15 having a flexible diaphragm 23 surrounding a cavity 24, but... Figure 1 and Figure 2 The difference between systems 10 and 10' lies in the arrangement of the ultrasonic generator 11 relative to the consolidator 15. In this embodiment, the mounting member 22 includes another opening 33 in which the ultrasonic generator 11 is mounted.

[0089] In another embodiment, the ultrasonic generator 11 extends through the mounting member 22 via the through-hole 23, without being rigidly connected to the mounting member 22 of the binder 15. The ultrasonic generator 11 is mechanically disconnected from the binder 15 to avoid transmitting binding force to the ultrasonic generator 11. The ultrasonic generator 11 may be sealed against the mounting member 22, for example, by an O-ring or another type of seal.

[0090] The opening 27 for pressurized gas 28 in the mounting member 22 is located downstream of the center of the mounting member 22. The ultrasonic generator 11 is mounted approximately in the center of the mounting member 22. Therefore, the ultrasonic generator 11 is located within the cavity 24 and is laterally surrounded by the flexible membrane 23. The tip 34 of the ultrasonic generator 11 protrudes through the opening 25 in the lower surface of the consolidator 15. Pressurized air or gas is distributed throughout the entire annular portion of the cavity laterally surrounding the ultrasonic generator 11.

[0091] The consolidator 15 applies pressure to the mating region 12 on both the upstream and downstream sides of the ultrasonic generator 11. The consolidator 15 has a first portion 35 located upstream of the ultrasonic generator 11 and thus above the non-molten portion of the mating region 12 between the first part 13 and the second part 14. The consolidator 15 also includes a portion 36 located downstream of the ultrasonic generator 11 and thus above the cooling molten material 20.

[0092] The first portion 35, located upstream of the ultrasonic generator 11 relative to the welding direction 19, provides pre-compression of the joint 12, similar to... Figure 2 The effect of roller 31 shown in the figure. The portion 36 of the binder 15 located downstream of the binder 11 relative to the welding direction 19 provides consolidation of the molten material 20 and the weld joint 21 formed after the solidification of the molten material 20.

[0093] Figure 4A A comparison system 1 and method for ultrasonic welding are illustrated, which are not part of the currently claimed invention. The comparison system 1 for ultrasonic welding includes an ultrasonic generator 11 and a binder 15' for applying pressure to a first surface 16 of a first part 13. The binder 15' is located downstream of the ultrasonic generator 11 relative to the welding direction 19. In this embodiment, the binder 15' is rigid. For example, the binder 15' may be formed of a metal, such as copper, and has a solid lower surface that contacts the surface 16 of the first part 13 to apply pressure to the joint area 12 and bind the joint area 12.

[0094] Figure 4A The illustration depicts three stages of an ultrasonic welding method, in which a comparison system 1 is used to weld a surface 16 having a non-planar surface profile, which may include ramps, tenons, or bends. The illustrated surface profile has a ramp 40 between a lower horizontal platform 41 and an upper horizontal platform 42. The ultrasonic generator 11 moves to the right along the lower platform 41 along the welding direction 19, upwards along the inclined ramp 40, and then along the upper platform 42. Figure 4A As can be seen, when the binder 15' moves upward along the ramp 40 and along the upper platform 42, the solid lower surface of the binder 15' cannot maintain contact with the surface 16 over its entire area. Therefore, the pressure applied to the surface 16 by the binder 15' varies, potentially causing variations in the quality of the resulting weld. When welding long lap welds, the binder 15' may heat up to very high temperatures. This heated binder 15' then reduces the cooling rate of the weld area, thereby affecting the weld quality.

[0095] Figure 4B The diagram illustrates the use of Figure 3 The diagram illustrates a three-stage method for ultrasonically welding a surface 16 with a non-planar profile using a consolidator 15'. The surface profile has a ramp 40 between a lower horizontal platform 41 and an upper horizontal platform 42. As the system 10'', containing an ultrasonic generator 11 located within the consolidator 15, moves along the welding direction 19 and upwards on the ramp 40, the lower surface of the consolidator 15—provided by an opening 25 laterally surrounded by a flexible membrane 23—can be positioned parallel to the inclined surface of the ramp 40, allowing an air cushion formed by pressurized gas in the cavity 24 to be guided to the ramp, and providing a pressure on the ramp 40 similar to or the same as the pressure applied to the lower platform 41. Therefore, the consolidator 15' moves at the same angle as the surface 16 and along a path following the surface profile, resulting in a more uniform overlap area and pressure applied to the surface 16. As the consolidator 15' moves upward along the ramp 40 and onto the upper platform 42, the flexible membrane 23 and cavity 24 adapt to the angle between the ramp 40 and the upper platform 42, allowing air to be guided to the surface 16 throughout the entire movement of the system 10''. Although the profile of the surface 16 is non-planar, this also allows the consolidator 15' to provide a more similar pressure along the welding direction 19 on the first main surface 16 over the entire weld length.

[0096] The systems 10, 10', 10'' and the ultrasonic welding method described herein can be used to manufacture a variety of objects and subassemblies. Because ultrasonic welding can be used to weld parts comprising thermoplastics, and particularly fiber-reinforced thermoplastic composites, this method can be used to form components with desired low weight and high strength. For example, the system or method can be used to manufacture components or subassemblies for aircraft. Figures 5A to 5D Figure 5 illustrates an example of a component that can be manufactured using the systems and methods described herein.

[0097] Figure 5A The illustration shows a cryogenic tank 50, which can be used to store liquid hydrogen as fuel for propelling vehicles such as aircraft. The cryogenic storage tank 50 typically has an end member 52 and a generally cylindrical body 53, and includes an opening 54 for allowing the tank 50 to be filled with hydrogen and for supplying the stored liquid hydrogen to an engine. The hollow body 53 is formed of a fiber-reinforced polymer-based composite material.

[0098] Figure 5B The diagram illustrates the use of Figure 3 The system 10'' depicted in the diagram is a cross-sectional view of the fiber-reinforced thermoplastic layer 51 bonded to the prefabricated metal end component 52 of the cryogenic tank 50. Alternatively, it can be used... Figure 1and Figure 2 The systems 10 and 10' shown are illustrated. The outer surface of the fiber-reinforced layer 51 has a non-planar shape because it adapts to the non-planar flange of the end member 52. A hybrid joint is provided between each end of the hollow body 53 and its corresponding metal end member 52 to attach the metal end member 52 to the fiber-reinforced polymer matrix composite 51 of the wall of the hollow body 53. In some embodiments, the fiber-reinforced polymer matrix composite is a carbon fiber reinforced polymer composite (CFRP) or a fiber-reinforced thermoplastic composite. The thermoplastic material may have a melt temperature of at least 200°C or at least 220°C. The fiber may be carbon fiber, glass fiber, or ceramic fiber. Continuous fibers, long fibers, or short fibers may be used. Thermoplastic materials can be PAEK (polyaryletherketone), PEKK (polyetherketoneketone), PEEK (polyetheretherketone), PEI (polyetherimide), PA (polyamide), PPS (polyphenylene sulfide), PB (polybutene), PBC (polyester block copolymer), PV (polyethylene compound), and PC (polycarbonate).

[0099] Figure 5C The illustration shows an embodiment in which the stringer 60 is attached to the skin panel 61 of the aircraft. In this embodiment, a tenon joint 62 is used. Figure 5D The illustration shows a cross-sectional view of the skin panel 60, energy deflector 63, and tenon joint 62. The stringers extend along the length of the aircraft fuselage (longitudinally) or along the wingspan of the wing. The purpose of the stringers is to act as structural components, transferring loads and stresses from the aircraft skin to the bulkhead. The stringers 60 can be connected to the skin 61 via ultrasonic welding using systems 10, 10', and 10''.

[0100] Figure 6 The illustration shows a schematic diagram of an aircraft 100, which may include one or more components or sub-assemblies, including one or more joints manufactured by ultrasonic welding using the methods or systems described herein. The aircraft 100 has a fuselage 101, wings 102, at least one fuel consumption device 103, such as an engine, and at least one fuel storage tank 104. The fuel may be hydrogen, and the tank 104 is a cryogenic storage tank. In some embodiments, one or both of components 13 and 14 may be a reinforcing or strengthening component, such as a stringer 105, a shell, or a clamp, while the other component is a skin 106.

[0101] This invention provides a consolidation device for consolidating weld lines during ultrasonic welding of CFRP (carbon fiber reinforced polymer) parts—but excluding other parts. The consolidation device utilizes air pressure and an air cushion to apply force / pressure to a surface. In an embodiment, the consolidator has a rigid base or mounting member serving as a point of attachment, and a flexible, e.g., elastic skirt with an opening facing downwards towards the weld line. A volume enclosed between the rigid top structure, the skirt, and the part surface is pressurized by a gas flow, such as pressurized air. The pressure within the cavity consolidates the weld line. This allows for conformal consolidation of complex / non-planar surfaces, such as curved surfaces and ramps / mortise joints. Furthermore, the airflow generated due to leakage between the skirt and the part surface increases the cooling effect on the weld line, carrying away heat generated during the previous welding process. Due to the air cushion and the airflow between the skirt and the part surface, friction between the consolidator and the part can be significantly reduced, potentially allowing for cheaper, less rigid positioning systems, such as industrial robots.

[0102] This invention provides, but is not limited to, two consolidator-ultrasonic generator configurations. In a first configuration, the consolidator follows the ultrasonic generator. In a second configuration, the consolidator surrounds the ultrasonic generator and provides a through-structure with a small air gap to disconnect the ultrasonic generator from the consolidator, thereby preventing consolidation forces from acting on the ultrasonic generator, or directly mounting the consolidator assembly at the standing wave non-excitation point of the ultrasonic generator to prevent energy transfer from the ultrasonic generator to the consolidator body. If the assembly has rotational symmetry, the positioning system can be less complex because the positioning system does not need to provide rotation along the axis of the ultrasonic generator. Furthermore, this second configuration can eliminate the need for rollers located in front of the ultrasonic generator for pre-compressing the welding area and energy guide. List of reference numerals 1. Comparison System 10 Systems for Ultrasonic Welding 10' System for Ultrasonic Welding 10'' System for Ultrasonic Welding 11. Ultrasonic generator 12 Joint Area 13 First Part 14 Second part 15. Consolidator 16 Surface 17 Surface 18 Melting Zone 19 Welding direction 20 Molten Material 21 Welded joint 22 Installation components 23 Flexible membrane 24 chambers 25 Opening 26. Peripheral portion of the membrane 27 Opening 28. Sources of pressurized gas 29 arrows 30 Drive unit 31 rolls 32 Energy Guiding Unit 34. Tip of the ultrasonic generator 35 The first part of the consolidator 36. Second part of the consolidator 37 arrows 40. Inclined slope 41 Lower Platform 42. Go to the platform 50 Cryogenic Tank 51 Fiber-reinforced thermoplastic layer 52-end component 53 body 54 Opening 60 stringers 61 Skin Panel 62 Mortise and tenon joint 100 aircraft 101 fuselage 102 Wings 103 Fuel Consumption Device 104 Fuel Storage Tank 105 stringers

Claims

1. A system (10, 10', 10'') for ultrasonic welding, said system comprising: An ultrasonic generator (11) is used to emit ultrasonic energy into the bonding area (12) between the first part (13) and the second part (14) to be joined together; A binder (15) applies pressure to the surfaces (16; 17) of one of the first part (13) and the second part (14) to bind the joint region (12), wherein the binder (15) is adaptable to the surfaces (16; 17) of one of the first part (13) and the second part (14) to bind the joint region (12).

2. The system (10, 10', 10'') according to claim 1, wherein, The system (10, 10', 10'') includes a gas source (28), and the consolidator (15) directs the gas flow to the surface (16; 17) of one of the first part (13) and the second part (14) to consolidate the joint area (12).

3. The system (10, 10', 10'') according to claim 1, wherein, The system (10, 10', 10''), wherein the consolidator (15) comprises a bundle of needles movable relative to each other, and the needles contact the surface (16; 17) of one of the first part (13) and the second part (14) and apply pressure to the surface (16; 17) to consolidate the joint area (12).

4. The system (10, 10', 10'') according to claim 1, wherein, The system (10, 10', 10'') includes a gas source (28), and the consolidator (15) includes a mounting (22) and a flexible membrane (23) connected to the mounting (22) and laterally surrounding a cavity (24), wherein the flexible membrane (23) has an opening lower side (25) facing one of the surfaces (16; 17) of the first part (13) and the second part (14), wherein the mounting (22) includes an inlet (27) for guiding gas into the cavity (24), and the flexible membrane (23) guides the gas to form an air cushion between the consolidator (15) and the surfaces (16; 17) of the first part (13) and the second part (14) for consolidating the mating region (12).

5. The system (10'') according to claim 4, wherein, The ultrasonic generator (11) is surrounded by the mounting member (22) and mechanically disconnected from the mounting member (22), and the flexible membrane (23) laterally surrounds the ultrasonic generator (11) such that the ultrasonic generator (11) is located in the cavity (24).

6. The system (10, 10', 10'') according to any one of claims 1 to 5, further comprising a drive system (30) for driving the ultrasonic generator (11) and the consolidator (15) on the surfaces (16; 17) along the welding direction (19), wherein, The consolidator (15) is located downstream of the ultrasonic generator (11), or the consolidator (15) is located upstream and downstream of the ultrasonic generator (11).

7. The system (10, 10', 10'') according to any one of claims 1 to 6, further comprising a roller (31) located upstream of the ultrasonic generator (11), wherein, The roller (31) is configured to apply pressure to the surfaces (16; 17) of one of the first part (13) and the second part (14) to pre-compress the joint area (12).

8. A method for ultrasonic welding, the method comprising: An assembly to be ultrasonically welded is formed by arranging a first part (13) on a second part (14) and forming a joint area (12) between the first part (13) and the second part (14); Ultrasonic energy is emitted into the joint area (12) between the first part (13) and the second part (14), and a molten area (18) is formed at the joint area (12). The binder (15) is brought close to the surface (16; 17) of the component and pressure is applied to the joint area (12) to bind the joint area (12), wherein the binder (15) is conformable to the surface profile of one of the first part (13) and the second part (14) to bind the joint area (12).

9. The ultrasonic welding method according to claim 8, wherein, The surface profile of one of the first part (13) and the second part (14) is non-planar.

10. The ultrasonic welding method according to claim 8 or claim 9, wherein, The ultrasonic energy is supplied by an ultrasonic generator (11), and the method includes driving the ultrasonic generator (11) and the consolidator (15) on the assembly along the welding direction (19) to continuously form a welded joint, wherein the consolidator (15) is located downstream of the ultrasonic generator (11), or upstream and downstream of the ultrasonic generator (11).

11. The ultrasonic welding method according to any one of claims 8 to 10, in, The consolidator (15) is connected to a gas source (28) and directs the gas flow to the surface (16; 17) of the assembly, thereby applying pressure to the joint area (12) and consolidating the joint area (12), or The consolidator (15) includes a bundle of needles that are movable relative to each other, and the needles contact the surfaces (16; 17) of one of the first part (13) and the second part (14) and apply pressure to the surfaces (16; 17) to consolidate the joint area (12).

12. The method according to any one of claims 8 to 10, wherein, The consolidator (15) is coupled to a gas source (28), and the consolidator (15) includes a mounting (22) and a flexible membrane (23) connected to the mounting (22) and laterally surrounding the cavity (24), wherein the flexible membrane (23) has an opening lower side (25) facing one of the surfaces (16; 17) of the first part (13) and the second part (14), wherein the mounting (22) includes an inlet (27) for guiding the gas source into the cavity (24), wherein the consolidator (15) is brought close to the surface (16; 17) of the assembly and the gas is guided into the cavity (24) to form a high-pressure gas zone between the consolidator and the surface (16; 17) of the assembly, the high-pressure gas zone applying pressure on the surface (16; 17) of the assembly to solidify the joint region (12).

13. The method according to any one of claims 8 to 12, further comprising contacting a roller (31) located on the upstream side of the ultrasonic generator (11) with the surface (16; 17) of the assembly to apply pressure and pre-compress the engagement region (12).

14. The method according to any one of claims 8 to 13, wherein, The first part (13) and / or the second part (14) comprise fiber-reinforced thermoplastic composite material.

15. The method according to any one of claims 8 to 14, wherein, The first part (13) is the skin (60) of the aircraft (100), and the second part (14) comprises one of the following groups: the stringers (105) of the aircraft, the Ω-shaped stringers, the tenon stringers, and the cryogenic tank (50). The second part (14) is the skin (6) of the aircraft (100), and the first part (13) includes one of the group consisting of the aircraft stringers (105), Ω-shaped stringers, tenon stringers and cryogenic chamber (105).

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