Method and apparatus for electromagnetic spot welding of molded parts

Abstract

An apparatus (1) for electromagnetic spot welding of molded parts (2, 3) is described. The apparatus (1) comprises a press body (10) and a first displacement device (50) for moving a press surface (100) of the press body (10) against or vice versa a molded part (2, 3) to join contact surfaces (20, 30) of the molded parts (2, 3) to be fused by welding under pressure. The press body (10) further comprises an inductor (11) generating an electromagnetic field at least in the contact surfaces (20, 30) of the molded parts (2, 3). A shield (12) disposed in the press body (10) around at least a portion of the inductor (11) prevents overheating. A heat sink (13) is disposed in the press body (10) between the inductor (11) and the press surface (100). The inductor (11) is equipped with a cooling device (111) configured for cooling the inductor (11), the shield (12) and the heat sink (13). A method for electromagnetic welding of molded parts (2, 3) using the apparatus (1) is also disclosed.

Description

Technical Field

[0001] This invention relates to a method for electromagnetic spot welding molded parts and to apparatus for electromagnetic spot welding. In the context of this application, spot welding produces a discontinuous weld at a single weld point by providing a fixed inductor that generates an electromagnetic field under alternating voltage. This contrasts with continuous welding, in which the inductor moves along a welding path on the molded parts to be welded together. Spot welding and continuous welding are not comparable. For example, the heat generation in the molded parts to be welded may be entirely different. Background Technology

[0002] There are many techniques available for joining molded parts, such as fiber-reinforced thermoplastic or thermosetting composite parts. Traditionally, mechanical fastening and adhesive bonding are used to join the two contact surfaces of molded parts. However, both mechanical fastening and adhesive bonding are expensive and time-consuming. For example, mechanical fastening requires costly hole positioning, drilling, caulking, and fastener installation, while adhesive bonding requires complex surface pretreatment that may involve chemicals.

[0003] Electromagnetic welding eliminates the need for separate fasteners and potentially provides the ability to join the contact surfaces of molded composite parts at relatively high speeds and with minimal pretreatment (if any). Electromagnetic welding generates an electromagnetic field in the inductively sensitive component of one or more molded parts to heat the thermofusible joining device of the molded parts to above the melting temperature of the joining device. The contact surfaces of the molded parts are joined together by the molten joining device. The joining device can be, for example, a thermoplastic resin in one or more parts to be joined, or it can be a separately applied thermoplastic resin. For welding thermoplastic and thermosetting molded parts together, the molten thermoplastic resin in the inductively sensitive component can act as, for example, a hot-melt adhesive.

[0004] WO2014 / 196268A1 discloses a joining device for joining multiple resin components using self-piercing rivets.

[0005] US2014 / 0356053A1 discloses a method for joining components together. It includes pressing the components against each other while heating the components using either induction heating or dielectric heating, thereby melting a thermoplastic resin that is part of at least one component.

[0006] Many welding methods can be used to form spot welds between molded parts, such as fiber-reinforced composite molded parts. In resistance welding, an external material is required to serve as the welding element. For conduction welding, the composite part or laminate is heated and passed through, creating a tool mark on the surface, and ultrasonic welding requires specific energy to guide the material and is highly sensitive to geometric tolerances and local recrystallization, for example. Known electromagnetic spot welding methods can produce poor-quality joints, particularly in advanced applications where relatively high mechanical strength and load-bearing capacity are desired, such as in the aerospace industry.

[0007] Another problem is that spot welded joints cannot provide sufficient strength in the direction perpendicular to the plane of the welded molded part. So-called out-of-plane loads tend to cause delamination of (partial) spots welded molded parts. Summary of the Invention

[0008] The object of this invention is to provide an improved method and apparatus for spot welding molded parts. Another object of this invention is to provide a method and apparatus for spot welding molded parts that can produce welded molded parts with improved resistance to out-of-plane loads and delamination.

[0009] Therefore, the present invention provides an apparatus for electromagnetic spot welding of molded parts, comprising: a pressure body; and a first displacement device configured to move the pressure surface of the pressure body against the molded part or vice versa, to join the contact surfaces of the molded parts to be fused by welding under pressure; wherein the pressure body further comprises: an inductor disposed in the pressure body and configured to generate an electromagnetic field at least in the contact surfaces of the molded part; a shield disposed in the pressure body surrounding at least a portion of the inductor and configured to prevent overheating; and a heat sink disposed between the inductor and the pressure surface, in direct contact with the inductor and the pressure surface; wherein the inductor includes a cooling device configured to cool the inductor, the shield, and the heat sink.

[0010] This equipment enables the rapid and efficient achievement of high-quality spot welding connections between molded parts, resulting in spot-welded products with exceptionally good mechanical load-bearing capacity. The molded parts include a thermomeltable joining device and an induction-sensitive component. The claimed device generates an electromagnetic field at least in the contact surfaces of the molded parts by means of an inductor in a pressure body, thereby thermomelting the joining device by heating the induction-sensitive component. The claimed device, including the features of the claimed pressure body, is configured to provide a geometrically concentrated heating volume within the molded part.

[0011] The heat sink is positioned between the inductor and the pressurized surface, and is in direct contact with both. The heat sink material is electrically insulating but thermally conductive, and is configured to extract heat from the surrounding environment. The heat sink acts as a passive heat exchanger, transferring heat generated in the top of the molded part to the surrounding air or the inductor's cooling system. Suitable materials for the heat sink have high thermal conductivity but very low electrical conductivity.

[0012] A preferred embodiment of the device includes a heat sink whose planar dimension in contact with the pressurized surface is larger than the cross-sectional dimension of the inductor. This embodiment not only improves heat transfer but also provides more dispersed and uniform pressure on the molded component.

[0013] A shield is disposed around at least a portion of the inductor and configured to prevent overheating. In an exemplary embodiment of the device, the pressure body has two side surfaces in addition to the pressure surface and a top surface opposite the pressure surface, and the shield is positioned between the inductor and the side surfaces.

[0014] The material of the shielding component is preferably thermally insulating. Suitable materials for manufacturing the shielding component include, but are not limited to, magnetic dielectric materials and materials with metal particles embedded in an adhesive (e.g., electrically insulating iron particles embedded in an organic adhesive). These materials are commercially available, for example, under trade names.

[0015] The geometry of an inductor (e.g., its cross-sectional shape) can, in principle, be chosen as needed. The cross-section can be, for example, triangular or circular. A useful embodiment relates to a device in which the inductor has a quadrilateral cross-section.

[0016] The 3D shape of the inductor can also be selected as needed. This may be relevant because in some embodiments disclosed further below, the inductor requires not only the molded parts at the heating and soldering locations but may also require other parts of the heating equipment. Therefore, in some embodiments, it is necessary to extend the electromagnetic field.

[0017] This can also be provided in embodiments where the inductor of the pressurized body includes a first inductor, a second inductor, or even multiple inductors.

[0018] In one embodiment, an apparatus is provided in which the inductor has a linear segment, such that the inductor is configured to generate a generally cylindrical electromagnetic field, at least in the contact surface of the molded part. This allows the contact surface to be heated in a highly selective manner, thereby achieving a precise spot weld connection.

[0019] The position of the inductor within the pressure body can also be selected as needed. In an actual embodiment of the device, the inductor is positioned within the pressure body such that the linear segment extends approximately parallel to the pressure surface of the pressure body.

[0020] To enhance the spot welds formed by the device of the present invention, particularly in the out-of-plane direction extending at a non-zero angle with the contact surface, the device according to an embodiment further includes: a mechanical fastener configured to be heated by an electromagnetic field generated by an inductor or by other means; and a second displacement device configured to move the mechanical fastener toward the molding member and embed the heated mechanical fastener into the mating molding member at a position further than the contact surface of the molding member.

[0021] In this embodiment, the second displacement device is preferably configured to insert the heated mechanical fastener into the mating molded part in a direction at a non-zero angle to the contact surface, and more preferably in a direction approximately perpendicular to the contact surface.

[0022] Practical embodiments relate to devices in which a pressure body has a cavity optionally located at the center, extending to the pressure surface, and a second displacement device is configured to move a mechanical fastener through the cavity.

[0023] The device according to the invention applies pressure to the molded part to be spot-welded by means of a pressure body. Another embodiment of the device includes a counter-pressure device, which is located on the side of the joined molded part opposite to the first displacement device, and is either passive or active.

[0024] In practical embodiments, the protected device may be positioned at the end of a robotic arm or other tool as an end effector. This allows for precise positioning of the pressurized body on the mating molded parts to enable multiple spot welds.

[0025] One or more molded parts are preferably made of a thermoplastic material that can be welded by fusion, although it is also conceivable that thermoplastic material or a heat-fusible adhesive is arranged only on the contact surfaces between the molded parts as a thermal bonding device.

[0026] Another aspect of the present invention relates to a method for electromagnetic spot welding molded parts. The method includes the following steps:

[0027] A) Provide the device according to the invention;

[0028] B) The pressure surface of the pressurizing body is moved against the molding component by a first displacement device or vice versa, so as to join the contact surfaces of the molding components to be fused by welding under pressure, wherein the molding component includes a heat-fusible joining device and a sensing component.

[0029] C) By means of an inductor of a pressure body, an electromagnetic field is generated at least in the contact surface of the molded part, thereby thermally melting the connection device by heating the sensitive component;

[0030] D) Molded parts are joined under pressure using a molten, heat-fusible joining device; simultaneously

[0031] E) Use the inductor's cooling device to cool the inductor, shielding, and heat sink of the pressurized body.

[0032] In this method, the molded parts are typically provided with a conductive component, such as a metal mesh, or this component is arranged between the molded parts. Foucault currents or eddy currents are induced in the conductive component by a undulating electromagnetic field, generated by an inductor, preferably supplied with alternating current by a generator. Due to the Joule effect, these Foucault currents generate the heat required to melt the thermofused joint. By positioning the inductor above the location to be spot-welded, the molded parts are connected to each other at the welding point.

[0033] In one embodiment of the method, a generally cylindrical electromagnetic field is used to achieve controlled, uniform, and targeted heating, thereby minimizing overheating in molded parts that do not require welding. Overheating can lead to material degradation, resulting in undesirable structural weakening. Furthermore, the cylindrical electromagnetic field can be made very narrow, up to 10 mm to 20 mm in width.

[0034] In order to heat the inductively sensitive components in the molded part, they must come into thermal contact with the heat-fusible bonding device. This is possible, for example, by mixing the inductively sensitive components and the heat-fusible bonding device (e.g., in an injection-molded compound).

[0035] Based on the materials used, particularly the sensing element and the distance between the inductor and the element, the appropriate power and frequency can be determined. This frequency, in particular, determines the penetrating power of the electromagnetic field; the inductor's power determines the intensity of the fluctuating electromagnetic field, thereby determining the degree of heat generated in the sensing element.

[0036] It is advantageous if the thermoplastic joining device comprises a thermoplastic polymer. Thermoplastic polymers can be joined in a simple manner by fusion. Furthermore, it is easy to mix thermoplastic polymers with induction-sensitive components (such as metal mesh or carbon fibers). Examples of particularly suitable thermoplastic polymers are polypropylene, polyamide, polyetherimide, polyetheretherketone, and polyphenylene sulfide, but the method is applicable in principle to any thermoplastic plastic.

[0037] Components that can be heated by induction preferably include carbon fibers and / or metals. These materials can be readily heated by induction and, in addition to being electrically conductive, have good thermal conductivity, allowing the generated heat to be well dispersed. The inclusion of carbon fibers in thermoplastic polymers is recommended because carbon fibers also improve the material's strength.

[0038] In another preferred embodiment of the method, the heatable component by induction comprises ferromagnetic particles. Suitable particles are described, for example, in WO0185827, and have the additional advantage that when the particles reach the so-called Curie temperature, they lose their magnetic dipoles and thus cease to heat further. This provides protection against overheating.

[0039] The Foucault current, or eddy current, induced in the contact surface is defined by the geometry of the molded part. Edges, corners, and holes in the molded part affect the distribution of the Foucault current, and therefore also the generated heat. Disruption of this magnetic field can lead to heating of components that do not need to be heated during welding. Conversely, some parts may be difficult to heat. These problems can be addressed by repositioning the boundaries of areas where the Foucault current can begin to appear at specific locations in the thermoplastic molded part. Using this preferred embodiment, previously difficult-to-heat parts can still be heated, and high temperatures at undesirable locations can be prevented.

[0040] Another embodiment of the method further includes: moving a mechanical fastener configured to be heated by an electromagnetic field generated by an inductor or by other means toward the molded part via a second displacement device, and embedding the heated mechanical fastener into the engaged molded part at a position further than the contact surface of the molded part.

[0041] Preferably, the heated mechanical fastener is inserted into the mating molded part by a second displacement device at a non-zero angle to the contact surface, preferably approximately perpendicular to the contact surface.

[0042] In a practical embodiment, the pressure body has a cavity extending to the pressure surface, and the second displacement device moves the mechanical fastener through the cavity. The cavity can be located at any position, but is preferably located near the center of the pressure body.

[0043] Pressure can be applied to the side of the molded component opposite to the first displacement device by means of a counter-pressure device.

[0044] For applications as claimed in the method of this invention, the inductor is connected to an alternator, wherein the alternator is electrically connected to an electrical connection device of the inductor. Available frequencies are typically between 0.1 MHz and 10 MHz. A frequency between 0.1 and 0.5 MHz is preferred, and more preferably between 0.15 and 0.4 MHz. At this preferred frequency, an optimal balance is achieved between the penetrating power of the electromagnetic field and the heating rate.

[0045] The inductor preferably has multiple windings. Such an inductor can be implemented compactly and preferably has flat sides. The inductor can be adapted for precisely defined induction.

[0046] It is advantageous if the inductor is generally flat. This is possible, for example, by specifically implementing the inductor as an electrical conductor located in a plane. Such a flat inductor is particularly compact and suitable for applying electromagnetic fields at defined locations in a very precise and uniform manner.

[0047] In another preferred embodiment, the inductor is provided with at least one feed channel suitable for the passage of a cooling medium (e.g., in a sheathed cooler). Accordingly, the temperature of the inductor can be kept constant during use, which is also advantageous for the inductor's resistance. The cooling medium is preferably a liquid with a high heat capacity, such as water. The sensing element can be, for example, a metal tube bent into a desired shape, through which the cooling medium is pumped when an electromagnetic field is generated by an alternating voltage passing through the metal of the tube itself. Attached Figure Description

[0048] The invention will now be explained with reference to the following figures, but the invention is not limited thereto. In the figures:

[0049] Figure 1 A welding system is schematically illustrated with a device provided as an end effector according to an embodiment of the present invention;

[0050] Figure 2 A cross-sectional view of a device according to an embodiment of the present invention is shown schematically;

[0051] Figure 3 This schematically illustrates another step in the method according to an embodiment of the invention. Figure 1 A cross-sectional view of the equipment;

[0052] Figure 4 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 1 A sectional view of the equipment;

[0053] Figure 5 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 1 A cross-sectional view of the equipment;

[0054] Figure 6 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 1 A cross-sectional view of the equipment;

[0055] Figure 7 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 1 A sectional view of the equipment;

[0056] Figure 8 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 1 A sectional view of the equipment;

[0057] Figure 9 A cross-sectional view schematically illustrates the steps of another method according to an embodiment of the present invention;

[0058] Figure 10 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 9 A sectional view of the equipment;

[0059] Figure 11 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 9 A sectional view of the equipment;

[0060] Figure 12 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 9 A sectional view of the equipment; and

[0061] Figure 13 The illustration schematically shows another step in the method according to an embodiment of the invention. Figure 9 A cross-sectional view of the equipment. Detailed Implementation

[0062] Figure 1 A spot welding system 5 equipped with a device 1 according to an embodiment of the present invention is shown. Device 1 acts as the end effector of a robot arm 50, which is part of an industrial six-axis robot 51. It should be noted that the robot arm 50 is not essential to the present invention, and other displacement devices, such as static actuators, can be contemplated for device 1. The robot 51 is programmed to move the first displacement device in the form of the robot arm 50 and the end effector device 1 toward a plurality of discrete positions toward which the molded parts (2, 3) to be spot welded must be formed. An inductor 11 (see [reference]) is incorporated into the pressure body 10 of device 1. Figure 2 During operation, an alternator 52 arranged on the robot 51 is connected to generate an electromagnetic field. However, the alternator 52 can be located elsewhere, or even incorporated into the pressurizing body 10 of the device 1. In the illustrated embodiment, a counter-pressure device 4 is disposed on one side of the joined molded parts (2, 3), opposite to the side of the first displacement device or robot arm 50 approach assembly (2, 3). The counter-pressure device 4 can be implemented as a solid, or it can be active in the sense that it can be pressed against said side of the joined molded parts (2, 3).

[0063] like Figure 2 As shown in more detail, the device 1 for electromagnetic spot welding molded parts (2, 3) includes a pressure body 10 and a first displacement device, for example, in the form of a robotic arm 50 (in... Figure 2(Schematally indicated by arrow 50). The pressure body 10 may be a solid block of metal (e.g., iron), or may be implemented in other ways as long as it can apply pressure to the substrate. Figure 2 The pressurizing body 10 has two side surfaces (101a, 101b) in addition to the pressurizing surface 100, and a top surface 102 opposite to the pressurizing surface 100. As shown in some embodiments described further below, the pressurizing body 10 also has a central cavity 103, but the central cavity is not an essential feature of the invention. Please note that... Figure 2 This shows a cross-sectional view of the vertical mid-plane of device 1. Although cavity 103 may be presented as open at the front, in embodiments it is enclosed by the material of pressurized body 10, for example in a central cylindrical cavity disposed in, for example, a solid block.

[0064] The robotic arm 50 is programmed to move the pressure surface 100 of the pressure body 10 against the molded parts (2, 3) or vice versa. For example... Figure 3 As shown, the contact surfaces (20, 30) of the molded parts (2, 3) that will be fused together by welding are then joined under pressure (but not yet welded).

[0065] according to Figure 2 The pressure body 10 also includes an inductor 11 disposed within it. The inductor 11 is configured to generate an electromagnetic field 12 at least in the contact surfaces (20, 30) of the molded parts (2, 3). In the illustrated embodiment, the inductor 11 has a quadrilateral cross-section and is further provided with a linear segment, such that the inductor is configured to generate a generally cylindrical electromagnetic field at least in the contact surfaces (20, 30) of the molded parts (2, 3). In this way, the electromagnetic field can be concentrated to extend no further than the location to be welded. Figure 2 One or more linear segments extend generally parallel to the pressurizing surface 100 of the pressurizing body 10, at a distance 104 from the pressurizing body 10. Another segment may be located at a greater distance 105 from the pressurizing surface 100. This other segment may be part of the same inductor 11, or it may be part of a second inductor 11 disposed at a higher height in the pressurizing body 10.

[0066] In the pressurizing body 10, a shield 12 is also provided around at least a portion of the inductor 11. This shield is configured to prevent overheating and is for this purpose made of a suitable heat-insulating material, such as... The shield 12 includes a plate-like structure and is positioned between the inductor 11 and the sides (101a, 101b) of the pressure body 10.

[0067] The device 10 of the present invention further includes a heat sink 13 incorporated in the pressure body 10 and disposed between the inductor 11 and the pressure surface 100. Furthermore, the heat sink 13 is positioned such that it is in direct contact with the inductor 11 (its lower surface) and the pressure surface 100. If suitable, additional heat-dissipating material 13a may also be provided between the inductor components 11. The heat sink 13 may be specifically implemented as a plate-like structure, and this plate-like structure may have a planar dimension 106 in contact with the pressure surface 100, which is larger than the cross-sectional dimension 110 of the inductor 11. The heat sink 13 is preferably made of a ceramic material.

[0068] As also shown in the figure, the inductor 11 is provided with a sheath cooler 111, implemented for example by a conduit through which a cooling liquid such as water flows. The sheath cooler not only cools the inductor 11, but is also adapted to at least partially cool the shield 12 and the heat sink 13.

[0069] The embodiment shown in the figure also includes a mechanical fastener in the form of a ribbed rivet 6, which is configured to be heated by an electromagnetic field generated by an inductor 11, or by other means (e.g., a separate thermal, IR, ... heater (not shown)). In this embodiment, the device 1 is also equipped with a second displacement device in the form of a plunger 7, such as... Figures 5 to 8 As shown, the second displacement device is configured to move the rivet 6 toward the molded parts (2, 3) and insert the heated rivet 6 approximately perpendicular to the contact surfaces (20, 30) into the mating molded parts (23) to a position further than the contact surfaces (20, 30) of the molded parts (2, 3), such as... Figure 6 As shown. Therefore, rivet 6 is welded to the joined and welded molded parts (2, 3). This provides a spot-welded connection between the molded parts (2, 3), which is mechanically reinforced by rivet 6, particularly in the out-of-plane direction 8. In this embodiment, the pressure body 10 is provided with an optional central cavity 103 extending to the pressure surface 100 of the pressure body 10. A second displacement device or plunger 7 is then configured to move rivet 6 through cavity 103.

[0070] refer to Figures 2 to 4 The diagram illustrates several method steps for electromagnetic spot welding of molded parts (2, 3) using the apparatus 1 of the present invention.

[0071] In the initial steps ( Figure 2 Device 1 is provided near the first molded part 2 and the second molded part 3 that need to be spot welded. The molded parts (2, 3) are currently separated from each other.

[0072] In a subsequent step, the robotic arm 50 moves the pressure surface 100 of the pressure body 10 against the molded parts (2, 3) or vice versa, thereby causing the contact surfaces (20, 30) of the molded parts (2, 3) to be spot-welded together to come together or join (but not weld) under pressure. The molded parts (2, 3) include a heat-fusible joining device and a sensing element to be heated under the influence of an electromagnetic field generated by the inductor 11. For this purpose, the molded parts (2, 3) can be made of a carbon fiber reinforced thermoplastic polymer, wherein the carbon fiber can be used as the sensing element and the thermoplastic polymer can be used as the heat-fusible joining device. The molded parts (2, 3) can, for example, include carbon fiber reinforced polyphenylene sulfide, for example having a material thickness of 1 mm to 3 mm. The first molded part 2 has folded edges and can, for example, represent a reinforcement, while the second molded part 3 is a flat plate. Obviously, the two molded parts (2, 3) can have another shape, such as curved.

[0073] refer to Figure 4 Another step involves generating an electromagnetic field at least in the contact surfaces (20, 30) of the molded parts (2, 3) using the inductor 11 of the pressurized body 10, while simultaneously cooling the inductor 11 with the sheath cooler 111. This heats (and may melt) the thermoplastic polymer of the molded parts (2, 3) in volume 21 of the two molded parts (2, 3) by heating the carbon fibers in the molded parts (2, 3). The temperature in volume 21 may not be completely uniform, and the central portion of volume 21 may only have a temperature exceeding the melting temperature of the thermoplastic polymer. To confine volume 21 to where it is needed (around the point to be welded), a cylindrical electromagnetic field is preferred. This field can be induced by the inductor 11 having one or more linear segments. The specific construction of the pressurized body 10, including the shield 12, the heat sink 13, and the sheath cooler 111, provides a controlled and well-concentrated volume 21. The molded parts (2, 3) in the joining configuration are heated to a temperature high enough to heat molten thermoplastic polymer (or optionally a heat-melt adhesive applied to the contact surfaces (20, 30)) to fuse the two molded parts (2, 3) together at least in the volume surrounding the point to be welded. During heating and / or optionally for a short time after heating, the contact surfaces (20, 30) are preferably pressed together by the pressure body 10 itself and the counter-pressure device 4, so as to thus create a connection between the molded parts (2, 3). This connection has a particularly high mechanical load-bearing capacity. The pressure body 10 is then removed from the spot-welded molded parts (2, 3) by a robotic arm 50.

[0074] For another location where a spot weld needs to be formed, the above process can be repeated. Move the pressure device 10 to that other location and repeat... Figures 2 to 4 The series of events shown.

[0075] Another embodiment of the present invention is in Figures 5 to 8 As shown in the figure. This embodiment also includes setting a mechanical fastener (e.g., rivet 6) to the... Figure 3 In the molded parts (2, 3) joined in the steps shown. According to... Figure 4 After the electromagnetic field is induced by the inductor 11, the rivet 6 is heated by the electromagnetic field generated by the inductor 11 or by other means (e.g., heating separately).

[0076] In the next step, the heated rivet 6 is moved toward the mating molded parts (2, 3) by the plunger 7, which are heated in volume 22 by an electromagnetic field generated by the inductor 11. This volume 22 may be slightly larger than volume 21, for example, because the rivet 6 is also heated. The plunger 7 moves along a cavity 103 extending to the pressure surface 100 of the pressure body 10, thereby moving the heated rivet 6 through the cavity 103.

[0077] refer to Figure 6 Then, the robotic arm 50 inserts the heated rivet 6 into the joined and heated molded parts (2, 3) along a direction 8 approximately perpendicular to the contact surfaces (20, 30), reaching a position 60 lower than the contact surfaces (20, 30) of the molded parts (2, 3). During this process, the rivet 6 can move any carbon fiber to the side that effectively strengthens the formed connection. The heated rivet 6 is easily inserted because the thermoplastic polymer of the molded parts (2, 3) is heated, and specifically heated above its melting temperature in the core portion.

[0078] refer to Figure 7 Disconnecting inductor 11 from alternator 52 disables the electromagnetic field. This cools the heated volume 22 while still applying pressure. The cooling solidifies the thermoplastic polymer and geometrically locks rivet 6 into the spot-welded molded parts (2, 3). The head 6a of rivet 6 extends laterally to prevent rivet 6 from being embedded too far into the molded parts (2, 3).

[0079] In the final step, the pressure body 10 is removed from the spot-welded and mechanically riveted molded parts (2, 3) using a robotic arm 50.

[0080] For another location where a riveted weld joint needs to be formed, the above process can be repeated. Move the pressure device 10 to that other location and repeat... Figures 2 to 8 The series of events shown.

[0081] refer to Figures 9 to 13 This illustrates another embodiment of the method and apparatus 1 for electromagnetic spot welding of molded parts (2, 3) using the apparatus 1 of the present invention. Reference numerals correspond to items indicated by the same reference numerals used in other figures, although in some cases in a different embodiment. Figure 9 The pressurizing body 10 includes an inductor 11 disposed within it. The inductor 11 has a single winding and is configured to generate an electromagnetic field at least in the contact surfaces (20, 30) of the molded parts (2, 3). In the illustrated embodiment, the inductor 11 has a quadrilateral cross-section. See Figure 9 The linear segment of the inductor 11 extends approximately parallel to the pressurizing surface 100 of the pressurizing body 10 and is a certain distance 104 from the pressurizing body 10.

[0082] In the pressurizing body 10, a shield 12 is also provided around at least a portion of the inductor 11. This shield is configured to prevent overheating and is for this purpose made of a suitable heat-insulating material, such as... The shield 12 includes a plate-like structure and is positioned above the inductor 11 and between the inductor 11 and the sides (101a, 101b) of the pressure body 10.

[0083] The device 10 of the present invention in the illustrated embodiment further includes a heat sink 13, which is incorporated into the pressure body 10 and disposed between the windings of the inductor 11 and between the inductor 11 and the pressure surface 100. Furthermore, the heat sink 13 is positioned such that it is in direct contact with the lower surface of the inductor 11 and the pressure surface 100. The heat sink 13 may be specifically implemented as a plate-like structure, and this plate-like structure may have a planar dimension 106 in contact with the pressure surface 100, which is larger than the cross-sectional dimension 110 of the inductor 11. The heat sink 13 is preferably made of a ceramic material.

[0084] As also shown, the inductor 11 is provided with a sheath cooler 111, as described above with respect to other embodiments.

[0085] In the initial step of the method according to this embodiment ( Figure 9 The device 1 is provided near the first molded part 2 and the second molded part 3 that need to be spot welded. The molded parts (2, 3) are currently separated from each other.

[0086] exist Figure 10 In the subsequent steps shown, the robotic arm 50 moves the pressure surface 100 of the pressure body 10 against the molded parts (2, 3) or vice versa, thereby causing the contact surfaces (20, 30) of the molded parts (2, 3) to be spot-welded together to come together or join (but not weld) under pressure. The molded parts (2, 3) include heat-fusible joining devices and sensing components to be heated under the influence of the electromagnetic field generated by the inductor 11, as described above in the context of other embodiments.

[0087] refer to Figure 11Another step involves generating an electromagnetic field at least in the contact surfaces (20, 30) of the molded parts (2, 3) using the inductor 11 of the pressurized body 10, while simultaneously cooling the inductor 11 with the sheath cooler 111. This heats (and may melt) the thermoplastic polymer of the molded parts (2, 3) in the volume 21 of the two molded parts (2, 3) by heating the carbon fibers in the molded parts (2, 3). The specific construction of the pressurized body 10, including the shield 12, the heat sink 13, and the sheath cooler 111, provides a controlled and well-concentrated volume 21. Heating the molded parts (2, 3) in the joining configuration to a temperature high enough to heat the molten thermoplastic polymer (or optionally a heat-fusible adhesive applied to the contact surfaces (20, 30)) at least in the volume surrounding the point to be welded fuses the two molded parts (2, 3) together. During heating and / or optionally for a short period after heating, the contact surfaces (20, 30) are preferably pressed together by the pressure body 10 itself and the counter-pressure device 4, so as to create a connection between the molded parts (2, 3). This connection is provided by the cooling volume 21 (by shutting off the electromagnetic field), as... Figure 12 As shown. Then, the pressure body 10 is removed from the spot-welded molded parts (2, 3) by the robotic arm 50, as shown. Figure 13 As shown.

[0088] For another location where a spot weld needs to be formed, the above process can be repeated. Move the pressure device 10 to that other location and repeat... Figures 9 to 13 The series of events shown.

Claims

1. An apparatus for electromagnetic spot welding molded parts, comprising: - Pressurized body; - A first displacement device configured to move the pressurized surface of the pressurized body against the molded part or vice versa, so as to join the contact surfaces of the molded parts to be fused by welding under pressure. The pressurizing body further includes: - An inductor disposed in the pressurizing body and configured to generate an electromagnetic field at least in the contact surface of the molded part; - A shielding element, disposed within the pressurizing body surrounding at least a portion of the inductor, and configured to prevent overheating; and - A heat sink disposed between the inductor and the pressure surface and in direct contact with the inductor and the pressure surface; The inductor includes a cooling device configured to cool the inductor, the shield, and the heat sink.

2. The device according to claim 1, wherein, The planar dimension of the heat sink in contact with the pressurized surface is larger than the cross-sectional dimension of the inductor.

3. The device according to claim 1 or 2, wherein, The inductor has a quadrilateral cross-section.

4. The device according to any one of the preceding claims, wherein, The inductor has a linear segment, such that the inductor is configured to generate a generally cylindrical electromagnetic field at least in the contact surface of the molded part.

5. The device according to claim 4, wherein, The inductor is positioned in the pressurizing body such that the linear segment extends substantially parallel to the pressurizing surface of the pressurizing body.

6. The device according to any one of the preceding claims, wherein, The inductor of the pressurizing body includes a first inductor and a second inductor.

7. The device according to any one of the preceding claims, wherein, Also includes: Mechanical fasteners configured to be heated by the electromagnetic field generated by the inductor or by other means; A second displacement device is configured to move the mechanical fastener toward the molded part and embed the heated mechanical fastener into the engaged molded part at a position further than the contact surface of the molded part.

8. The device according to claim 7, wherein, The second displacement device is configured to insert the heated mechanical fastener into the mating molded part in a direction at a non-zero angle to the contact surface.

9. The device according to claim 7 or 8, wherein, The pressure body has a cavity that extends to the pressure surface, and the second displacement device is configured to move the mechanical fastener through the cavity.

10. The device according to any one of the preceding claims, wherein, It also includes a counter-pressure device on the side of the molded component opposite to the first displacement device.

11. The device according to any one of the preceding claims, wherein, It also includes an alternator connected to the inductor.

12. The device according to any one of the preceding claims, wherein, The radiator is made of ceramic material.

13. The device according to any one of the preceding claims, wherein, The shielding element is made of a magnetic dielectric material.

14. The device according to any one of the preceding claims, wherein, The pressurizing body has two side surfaces in addition to the pressurizing surface and a top surface opposite the pressurizing surface, and the shield is positioned between the inductor and the side surfaces.

15. The device according to any one of the preceding claims, wherein, The device is positioned at the end of a robot arm or other tool as an end effector.

16. A method for electromagnetic spot welding molded parts, comprising the steps of: A) To provide the device according to any one of the preceding claims; B) Using the first displacement device, the pressure surface of the pressurizing body is moved against the molded component, or vice versa, to join the contact surfaces of the molded components to be fused by welding under pressure, wherein... The molded component includes a heat-fusible connection device and a sensing component; C) An electromagnetic field is generated at least in the contact surface of the molded part by means of the inductor of the pressurizing body, thereby thermally melting the coupling device by heating the sensing component; D) The molded parts are joined under pressure using a molten, heat-fusible joining device; simultaneously E) Cool the inductor, the shield, and the heat sink of the pressurized body using the cooling device of the inductor.

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