METHOD FOR WELDING CONDUCT LINES TO FORM A Y- OR X-CONNECTION USING ULTRASOUND

Description

Field of invention

[0001] The present invention relates to a method for welding at least three conductors to form a Y or X connection using ultrasound. Background of the invention

[0002] Electrical cables with two or more strands, for example high-voltage cables as used in automotive engineering, can be joined to form so-called X or Y connections by ultrasonic welding (English). X-splice or Y-splice ) are welded together (X-joints are also called H-joints, English H-splice, (designated). In multi-core cables, for example, the strands that are each assigned to the same pole can be welded together.

[0003] A Y-connector can, for example, connect three electrical cables, each with two strands, via two solder joints. In the case of two-core cables, each solder joint can connect the three strands that are assigned to the same pole, for example, positive or negative.

[0004] An X-connection can, for example, connect four electrical conductors, each with two strands, via two weld nodes. In the case of two-core cables, each weld node can connect the four strands that are assigned to the same pole, for example, positive or negative.

[0005] The number of welding nodes can correspond to the number of strands in the electrical cables (e.g., two welding nodes for two strands per cable).

[0006] To achieve short cycle times, it is common practice to weld the strands to be joined together in a single step using ultrasound. Depending on their number and size, inserting and fixing the strands can be quite complex and require a certain amount of practice. If the strands are positioned inaccurately, welding defects can occur, which can significantly reduce the quality of the resulting weld (hereinafter also referred to as a knot).

[0007] JP 2007 134307 A, US 2020 / 171597 A1, JP 2013 118196 A and JP H11 114673 A each describe methods for joining cables using welding processes, in particular partially by ultrasonic welding. Summary of the invention and advantageous embodiments

[0008] Therefore, there may be a need for a process that enables improved production of Y and / or X connections, for example, an improvement in weld quality and / or reliability in ultrasonic welding of Y and / or X connections, compared to conventional methods.

[0009] This need can be met by the subject matter of the independent claim. Advantageous embodiments are set forth in the dependent claims, the following description, and the accompanying figures.

[0010] The invention relates to a method for welding at least three conductors to form a Y or X connection as defined in claim 1, wherein each conductor comprises at least two strands, each with an exposed strand section.The method comprises at least the following ultrasonic welding steps: a first ultrasonic welding step in which at least two output nodes are formed, each output node being formed by welding at least two of the strand sections using ultrasound; a second ultrasonic welding step following the first ultrasonic welding step in which at least two total nodes are formed, at least one of the total nodes being formed by welding at least one of the previously formed output nodes with at least one of the remaining strand sections that have not yet been welded in an output node, and / or with at least one other of the previously formed output nodes using ultrasound.

[0011] As mentioned at the beginning, handling the strands when welding Y or X connections made of more than two strands can be very time-consuming if the connections are each welded in a single step.

[0012] For example, in the conventional manufacturing of a Y-connection from three cables, each with two strands, two nodes, each consisting of three strands, can be welded. To weld the first node, one strand can be inserted into the welding chamber from one side, and two more strands from the other side. The three strands are then welded together in one step. The remaining strands must be positioned so that they do not obstruct the welding of the first node. A second node can then be welded analogously to the first node using the remaining three strands, again positioning the strands connected via the first node so that they do not interfere with the welding of the second node.

[0013] In a conventional manufacturing process for an X-connection made from four conductors, each with two strands, four strands can be welded together to form a node in each welding step, for example, four negative pole strands to form a first node in a first welding step and four positive pole strands to form a second node in a second welding step.

[0014] In contrast, the strands in the process presented here are welded together in multiple stages to form knots. This simplifies the handling of the strands, particularly their arrangement and / or fixation inside and / or outside the welding area. This helps avoid welding errors, which in turn reduces scrap and improves process reliability and product quality.

[0015] In particular, at least one of the following errors can be avoided using the method presented here: a) If at least one of the strands protrudes too far into the welding area: brushing, protruding individual conductors, damage to the sheathing of one or more strands and / or cables. b) If at least one of the strands does not protrude far enough into the welding area: over-welding, damaged individual conductors near the weld point, damage to the sheathing of one or more strands and / or cables. c) Reduced knot strength due to a symmetrical knot design (this can be remedied, for example, by using a suitable insertion aid, also antiside splice kit(mentioned, should be avoided). d) When welding three or more strands together in one step, it can happen that some of the strands are not compressed correctly (or at all) between the sonotrode and the anvil. The wires may then no longer be weldable or may need to be reprepared, for example, stripped again and / or cut to the correct length. Usually, this is no longer possible due to specifications, so the wires must be disposed of. It is also possible that individual, uncompressed strands may not be detected by the process monitoring system due to their small size.

[0016] In general, the above-mentioned errors can result in the cables either having to be disposed of or, if possible, having to be painstakingly prepared for another welding attempt.

[0017] Some terms are defined in more detail below.

[0018] The term "stranded wire" can be understood, both before and after, as an electrical conductor formed from several individual wires (e.g., made of copper, copper alloy, aluminum, or aluminum alloy). The stranded wire may be sheathed, at least partially, on its outer surface with one or more layers of an electrically insulating material.

[0019] The term "conductor" can be understood, both before and after, as an electrical conductor consisting of several strands. The conductor may be sheathed, at least partially, on its outer surface with one or more layers of electrically insulating material. Additionally or alternatively, the conductor may include a sheath made of an electrically conductive material for shielding against electromagnetic fields. The strands of the conductor may run, at least partially, within this sheath.

[0020] The term "strand section" can refer in particular to the end section of a stranded wire. For example, a strand section can be a stripped (end) section of the wire.

[0021] The term "node," as in "starting node" or "total node," can refer to a weld joint produced by ultrasonic welding of at least two joining partners. Such a node can be either a so-called through node or a so-called end node. To form a through node, the respective joining partners are inserted into the welding chamber from different, especially opposite, directions. To form an end node, however, the respective joining partners are inserted into the welding chamber from the same direction.

[0022] The output nodes can differ from the total nodes in that they connect fewer strands electrically than the total nodes.

[0023] In particular, a composite node can have at least one more strand than the initial node that was formed as an intermediate to create that composite node. For example, a composite node configured as an X-connection can connect twice as many strands as the preceding initial node or each of the preceding initial nodes. Preferably, each composite node can connect twice as many strands as each initial node. For example, each composite node can connect at least four of the strands, while each initial node connects at least two of the strands.

[0024] A welded part produced directly by the process described above and below may comprise: at least three conductors, each conductor comprising at least two strands; at least two total nodes, each total node being formed by at least two-stage ultrasonic welding of at least three of the strands, the total node having, in cross-section, at least one characteristic line extending along flattened areas of cross-sections of individual strands of the conductors.

[0025] Such a characteristic line can be seen, for example, in a microscopic image of a polished section.

[0026] It is possible that the characteristic line extends over a large part of the total width or height of the cross-section of the entire node, for example over more than 50%, more than 70% or more than 90% of the total width or height.

[0027] The characteristic line can, in particular, be a straight line. The term "straight" can be understood here to mean that the characteristic line runs between two imaginary parallel lines with a distance of 2 mm or less, 1 mm or less, or 0.5 mm or less.

[0028] Embodiments of the invention can, without limiting the invention, be considered to be based on the ideas and findings described below.

[0029] According to one embodiment, in order to weld at least three conductors to form a Y-connection, in the second ultrasonic welding step each total node can be formed by welding at least one of the output nodes with at least one of the remaining strand sections using ultrasound.

[0030] According to one embodiment, in order to weld at least four conductors to form an X-connection, in the second ultrasonic welding step each total node can be formed by welding at least two of the output nodes using ultrasound.

[0031] According to one embodiment, to weld at least four conductors into an X-connection, a first and a second node can be formed in the second ultrasonic welding step. The first node can be formed by welding the at least two initial nodes using ultrasound. The second node can be formed by welding the remaining stranded wire sections using ultrasound. In other words, it is possible for at least one of the nodes to be welded in two or more stages, and for at least one other node to be welded in a single stage.

[0032] According to one embodiment, welding by means of ultrasound can include: positioning the respective joining partners in a space between a sonotrode and an anvil; pressing together the joining partners positioned in the space; setting the sonotrode into ultrasonic vibrations.

[0033] The joining partners can be, for example, at least two or at least four of the strand sections, at least two of the output nodes, or a combination of at least one of the output nodes and at least one of the strand sections.

[0034] The joining partners positioned in the gap can be pressed together, for example, by moving the sonotrode and the anvil towards each other along a first axis.

[0035] Additionally, the joining partners positioned in the gap between two wall elements opposite each other along a second axis orthogonal to the first axis, for example a side slider and a marking plate or two side sliders, can be pressed together. For this purpose, the wall elements can be moved relative to each other along the second axis.

[0036] By changing the distance between the wall elements, for example, a desired width of the respective starting or total node, hereinafter also referred to as weld width, can be set.

[0037] The space between the layers can also be referred to as the welding or compression space.

[0038] The term "ultrasonic vibrations" can be understood to mean vibrations with frequencies in the ultrasonic range from 16 kHz to 1 GHz, preferably from 16 kHz to 100 kHz.

[0039] Depending on the design, the respective joining partners can be inserted into the gap either from different, especially opposite, directions or from the same direction.

[0040] According to one embodiment, the at least two strand sections can be positioned when forming at least one or each output node such that they protrude into the space from the same side. This has the effect that at least one or each output node is formed as an end node (see above).

[0041] According to one embodiment, the at least two stranded wire sections can be positioned when forming at least one or each output node such that they project into the space from different, in particular opposite, sides. This has the effect that at least one or each output node is formed as a through node (see above).

[0042] It is also conceivable that at least one of the output nodes is formed as a terminal node, while at least one other of the output nodes is formed as a through node.

[0043] According to one embodiment, at least two of the respective joining partners can be positioned when forming at least one of the or each of the overall nodes such that they project into the gap from the same side. This has the effect that at least one of the or each of the overall nodes is formed as an end node (see above).

[0044] According to one embodiment, at least two of the respective joining partners can be positioned when forming at least one of the or each of the overall nodes such that they project into the gap from different, in particular opposite, sides. This has the effect that at least one of the or each of the overall nodes is formed as a through node (see above).

[0045] For example, when forming the second overall node, at least two of the remaining stranded wire sections (which may originate from at least two of the conductors) can protrude into the space from a first side, and at least two more of the remaining stranded wire sections (which may originate from at least two more of the conductors) can protrude into the space from a second side, which may be opposite the first side.

[0046] According to one embodiment, sections of the pipes not to be welded can be held outside the gap by means of a retaining device. For this purpose, the retaining device can be arranged adjacent to or at least near the gap, for example, by being designed as part of a side slide or anvil. It is possible that the retaining device is located inside a soundproof housing during welding. Depending on the embodiment, the retaining device can comprise at least one of the following elements for fixing the sections not to be welded: a recess, a projection, a bracket, a hook, a clamping device, a gripping element, a spring, or a hold-down device. This prevents sections not to be welded from unintentionally entering the gap.

[0047] According to one embodiment, the sections not to be welded can comprise at least one of the following sections of the conductors: one of the output nodes, one of the overall nodes, or one of the stranded wire sections. In other words, the retaining device can be specially shaped to keep one or more of these sections away from the gap.

[0048] According to one embodiment, different ultrasonic welding parameters can be used when forming the initial nodes than when forming the final nodes. The ultrasonic welding parameters can, for example, include at least one of the following: an ultrasonic amplitude; a welding power; a welding energy; a welding time; a pressure with which the respective joining partners are pressed together; a contact area; a welding width (see above); a height difference between a height of the respective joining partners measured before welding in the pressed state and a height of the respective joining partners measured after welding in the welded state.

[0049] For example, the ultrasonic welding parameters used in the first ultrasonic welding step may differ from the ultrasonic welding parameters used in the second ultrasonic welding step by more than 5%, more than 10%, more than 20%, more than 40%, more than 60%, or more than 80%.

[0050] The contact surface can be defined by a weld width and a weld length.

[0051] Welding can be carried out by so-called energy welding using a predetermined welding energy, by so-called altitude welding, also called welding at absolute height or absolute-h welding, and / or by so-called delta-h welding.

[0052] In vertical welding, the welding process continues until a predetermined height of the weld metal, in this case the starting or overall joint, is reached. Unlike energy welding, the welding process does not end after a predetermined energy input, but rather upon reaching the predetermined height.

[0053] In delta-h welding, the welding process continues until a predetermined difference is reached between the so-called compaction dimension and the so-called welding dimension. The compaction dimension is the thickness of the weld metal before welding and is measured by moving the tools onto the weld metal to compact it and measuring the height of the compacted weld metal. The welding dimension is the thickness of the weld metal after welding and is measured after welding. The welding dimension is generally smaller than the compaction dimension because the thickness of the weld metal decreases during welding.

[0054] In height and delta-h welding, the welding energy is therefore not a predetermined value (as in energy welding), but a resultant.

[0055] This allows for targeted adaptation of the individual welding steps to the properties of the respective joining partners and thus better control of the entire welding process compared to designs where the same ultrasonic welding parameters are used for all welding steps.

[0056] According to an advantageous embodiment, the welding width can be set differently, in particular larger or smaller, when forming the initial knot than when subsequently forming the overall knot. This allows similar advantageous effects to be achieved as described in the applicant's earlier patent application WO 2022 / 022833 A1. The content of the earlier application is hereby incorporated in its entirety by reference.

[0057] According to one embodiment, at least one of the following ultrasonic welding parameters can be selected to be smaller during the formation of the initial nodes, for example, by more than 5%, more than 10%, more than 20%, more than 40%, more than 60%, or more than 80%, than during the formation of the total nodes: an ultrasonic amplitude; a welding power; a welding energy; a welding time; a contact area; a welding width; a pressure with which the respective joining partners are pressed together. This can, for example, ensure that the strand sections are only pre-compacted during the formation of the initial nodes, i.e., the initial nodes have, for example, a lower strength and / or density than the total nodes. This can have a beneficial effect on the weld quality.

[0058] According to one embodiment, the initial nodes can be formed on a different ultrasonic welding machine than the final nodes. For example, the initial nodes can be formed on a standard production machine, while the final nodes can be formed on a specially adapted machine. This special machine can be equipped with at least one of the following components: a holding device, a special insertion aid to prevent symmetrical node configurations, a clamping device for securing the wires, or an insulation stop. Alternatively, all welding steps can be performed on the same ultrasonic welding machine, provided it is appropriately equipped.

[0059] According to one embodiment, at least one or each output node can be formed from stranded wire sections from at least two of the conductors. In other words, at least one or each output node can electrically connect strands from different conductors, for example, strands that are assigned to the same pole as positive or negative.

[0060] According to one embodiment, at least one or each output node can be formed from stranded wire sections of the same conductor. In other words, at least one or each output node can electrically connect strands of the same conductor to each other.

[0061] According to one embodiment, each output node can be formed from different strand sections than each other output node. In other words, different output nodes can combine different strands.

[0062] According to one embodiment, each node can be formed from different joining partners than any other node. In other words, different nodes can combine different strands.

[0063] According to one embodiment, at least one of the strand sections can have been compacted by ultrasound in an ultrasonic compaction step preceding the first and / or second ultrasonic welding step. For this purpose, the strand section can be positioned in the gap and compressed, whereby the sonotrode is set into ultrasonic vibrations. Brief description of the characters

[0064] Embodiments of the invention are described below with reference to the accompanying drawings. Neither the description nor the drawings are to be interpreted as limiting the invention. Fig. 1shows an ultrasonic welding machine for use in a process according to an embodiment of the invention. Fig. 2a and Fig. 2b Illustrate steps in the production of an X-connection from four conductors in a method according to an embodiment of the invention. Fig. 3a and Fig. 3b Illustrate steps in the production of an X-connection from four conductors in an alternative method according to an embodiment of the invention. Fig. 4 illustrates steps in the production of a Y-connection from three wires in a method according to an embodiment of the invention. Fig. 5 shows a cross-section through a complete node that was welded in a process according to an embodiment of the invention.

[0065] The drawings are schematic only and not to scale. Identical reference symbols in different drawings denote identical or equivalent features. Description of advantageous embodiments

[0066] Fig. 1Figure 1 shows a basic structure of an ultrasonic welding machine 1, which is suitable for performing one or more of the welding processes described below. The ultrasonic welding machine 1 comprises a sonotrode 3 for generating ultrasonic vibrations and an anvil 5. The sonotrode 3 and the anvil 5 can be displaced relative to each other. During welding, the sonotrode 3 and the anvil 5 can be positioned opposite each other, with the parts 9 to be welded being positioned in a space 11 between the sonotrode 3 and the anvil 5 and being pressed together with a specific pressure by means of the sonotrode 3 and the anvil 5. This causes the sonotrode 3 to vibrate ultrasonically. This results in the parts 9 being welded together. Additionally, the space 11 can be bounded on two further sides by two wall elements, in this case a (horizontally displaceable) side slide 13 and a spotting plate 15.

[0067] Furthermore, the ultrasonic welding machine 1 can be equipped with a retaining device 17 designed to keep one or more non-weldable sections 19 of the joining partners 9, for example, sections of cables, away from the gap 11. In this example, the retaining device 17 is formed by a groove in the side slide 13 into which the non-weldable section(s) 19 can be inserted, for example, hooked.

[0068] As in Fig. 2a and Fig. 2b As shown, the ultrasonic welding machine 1 can be used, for example, to weld four electrical conductors 21, each comprising two strands 23, such as high-voltage cables used in electric vehicles, together to form a so-called X or H connection. Fig. 2a and Fig. 2b They show, as examples, individual steps of a corresponding welding process.

[0069] Each strand 23 has an exposed strand section 25 where the strand 23 is to be welded. The strand section 25 is represented here by an example of a stripped end of the strand 23.

[0070] First, two of the strand sections 25 are welded together as joining partners 9 in a pre-compaction step to form an output node 27 (see Fig. 2a ). With eight strands 23, a total of four output nodes 27 are welded in four pre-compaction steps.

[0071] In the pre-compaction step, the two strand sections 25 are each positioned so that they protrude into the space 11 from the same side and the resulting output node 27 is a so-called end node.

[0072] As in Fig. 2a As can be seen, each output node 27 can electrically connect the strands 23 of two different lines 21.

[0073] Subsequently, two of the initial nodes 27 are welded together as joining partners 9 in a finishing welding step to form a total node 29 (see Fig. 2b ). With four starting nodes 27, a total of two nodes 29 are welded in two finishing welding steps.

[0074] As in Fig. 2b As can be seen, each total node 29 can electrically connect the strands 23 of four different lines 21 together.

[0075] For example, in a two-pole connection, one of the total nodes 29 can connect all the negative pole strands together, while the other total node 29 connects all the positive pole strands together.

[0076] An alternative welding process for creating an X-joint is described in Fig. 3a and Fig. 3b shown.

[0077] In a first pre-compaction step, two stranded wire sections 25 of a first of the lines 21 are joined together, and in a second pre-compaction step, two stranded wire sections 25 of a second of the lines 21 are joined together. In each pre-compaction step, the respective stranded wire sections 25 are positioned as joining partners 9 such that they protrude into the space 11 from different, in particular opposite, sides, and the resulting output node 27 is a so-called through node (see Fig. 3a ).

[0078] Subsequently, the two starting nodes 27 are welded together as joining partners 9 in a first finishing welding step to form a first overall node 29a.

[0079] The remaining four strand sections 25 can then be welded together as joining partners 9 in a second finishing welding step, i.e. without pre-compaction, to form a second overall node 29b (see Fig. 3b ).

[0080] Additionally or alternatively, the ultrasonic welding machine 1 can be used to weld at least three lines 21, each comprising two strands 23, together to form a so-called Y-connection.

[0081] For example, a total of two pre-compaction steps can be carried out, whereby in each pre-compaction step two of the strand sections 25 are welded together as joining partners 9 to form an output node 27. The output nodes 27 can be designed as end nodes, for example as shown in Fig. 2a This is illustrated. Alternatively, each output node 27 can be configured as a through node.

[0082] Subsequently, one of the starting nodes 27 and one of the two remaining strand sections 25 are welded together as joining partners 9 in a finishing welding step to form a total node 29 (see Fig. 4). With two starting nodes 27, a total of two nodes 29 are welded in two finishing welding steps.

[0083] The Y-connection can also be formed from four or more than four conductors 21. In this case, it is possible that in a pre-compaction step, three or more than three stranded wire sections 25 are simultaneously inserted from one side into the space 11 to form one of the output nodes 27.

[0084] The pre-compaction steps may differ from the final welding steps in that at least one of the following ultrasonic welding parameters is selected to be smaller in the pre-compaction steps than in the final welding steps: an ultrasonic amplitude; a welding power; a welding energy; a welding time; a contact area; a welding width; a pressure with which the respective joining partners 9 are pressed together.

[0085] In each of the pre-compaction and final welding steps, the sections 19 of the lines 25 that are not to be welded, i.e., other strand sections, other exit nodes and / or other total nodes, can be kept away from the space 11 by means of the retaining device 17.

[0086] The conductors 21 can each comprise more than two strands 23, which can be welded together using one or more of the methods described above. Furthermore, different conductors 21 can comprise a different number of strands 23.

[0087] For example, shielded or unshielded copper stranded wires with a cross-section of 6 mm² each can be used as conductors 21. The strands 23 can be at least partially insulated. The respective cross-sections of the strands 23 can also differ from one another. Other types of conductors 21 are also possible.

[0088] As in Figs. 2a to 4As shown, the output nodes 27 can each be formed from stranded wire sections 25 originating from different conductors 21. However, it is also possible that at least one or each output node 27 is additionally or alternatively formed from at least two stranded wire sections 25 of the same conductor 21.

[0089] Fig. 5 Figure 1 schematically shows a cross-section through one of the total nodes 29, 29a, as it can be seen, for example, in a microscopic image. A transition region between the two welded starting nodes 27 ( Fig. 2b , Fig. 3b ) or between the starting node 27 and the stranded section 25 welded to it ( Fig. 4The characteristic line 31 is recognizable as a horizontal line extending across the entire width of the node 29, 29a. This line 31 results from a series of flattened sections of individual strands 33 from which the connection was welded and is characteristic of connections welded using one of the methods described above. Experiments have shown that cross-sections of X- or Y-connections welded using conventional single-stage ultrasonic methods do not exhibit such a dividing line.

[0090] The following section describes different variations of the procedures in other words.

[0091] The aforementioned pre-compression and finishing welding steps can be performed on one and the same ultrasonic welding machine (hereinafter referred to as the machine). The welding of an X-connection consisting of four lines 21, each with two strands 23, can then proceed, for example, as follows. a) Pre-compression of the first two strands 23 of the first two cables 21. Each cable 21 is inserted into the machine so that the respective strand 23, with its sheathing, abuts an insulation stop. The cable 21 is then clamped to the machine, and the strand 23 is positioned in the welding chamber. The two cables 21 can each be inserted into the machine either from the same side or from different, in particular opposite, sides. The two strands 23 not to be welded are kept away from the welding chamber in a suitable manner, for example, by bending them (e.g., by 90°) and placing them outside a soundproof housing or in the retaining device 17. Subsequently, the two inserted strands 23 are welded, or more precisely, pre-compressed, to form an exit node 27.b) Pre-compact the two remaining strands 23 of the first two conductors 21 to form an output node 27 analogously to step a). The output node 27 from step a) is positioned outside the welding area using the retaining device 17. c) Pre-compact the first two strands 23 of the two remaining conductors 21 to form an output node 27 analogously to step a). d) Pre-compact the two remaining strands 23 of the two remaining conductors 21 to form an output node 27 analogously to step a). e) Weld the first two output nodes 27, which, for example, connect only negative-pole strands. One of the output nodes 27 is positioned in the welding area from one side and the other output node 27 from the other, for example, opposite side. The two remaining output nodes 27 are kept away from the welding area in a suitable manner (see step a)).The two output nodes 27 are then welded together to form a total node 29. f) Welding the two remaining output nodes 27, which, for example, only connect positive pole strands, to form a total node 29 analogously to step e). Since, due to space constraints, it is generally not possible to position the total node 29 from step e) outside the soundproof housing, the total node 29 can, in this case, be fixed inside the soundproof housing, e.g., by means of the retaining device 17, so that it does not obstruct the welding of the other total node.

[0092] Alternatively, the pre-compaction and final welding steps can be performed on different machines.

[0093] For example, pre-compaction steps a) to d) can be performed on a standard production machine. Theoretically, finishing welding steps e) and f) can also be performed on a production machine. However, such machines typically lack auxiliary equipment such as insulation stops or wire clamps.

[0094] The finishing welding step f) should be carried out on a special machine with a suitable holding device 17, since the total node 29 from step e) usually has to be positioned inside the welding chamber for space reasons (series machines usually do not have such a holding device).

[0095] Theoretically, the finishing welding step f) can also be carried out on a correspondingly retrofitted series machine.

[0096] Alternatively, the two nodes can be welded in different ways, as illustrated below.a) Pre-compacting the first two strands 23 of the first two conductors 21. One of the strands 23 is inserted into the welding chamber from one side and the other strand 23 from the opposite side, i.e., the two strands 23 are aligned in a line ("inline") with each other. The remaining two strands 23 are kept away from the welding chamber in a suitable manner (see above). Subsequently, the two inserted strands 23 are welded together, more precisely pre-compacted, to obtain an output node 27. b) Pre-compacting the first two strands 23 of the two remaining conductors 21 to form an output node 27 analogously to step a). c) Welding the two output nodes 27 to form a first composite node 29a. d) Pre-compacting the two remaining strands 23 of the first two conductors 21 to form an output node 27 analogously to step a).The first total node 29a can be housed within the soundproof enclosure in the retaining device 17. d) Pre-compact the two remaining strands 23 of the two remaining lines 21 to form an output node 27 analogous to step a). e) Weld the two remaining output nodes 27 together to form a second total node 29b analogous to step c).

[0097] As described above, the second node 29b can also be welded without pre-compaction (see Fig. 3b ).

[0098] It is possible that on at least one side more than two lines 21 are welded together.

[0099] At least in the pre-compaction steps, a special insertion aid can also be used, which is designed to create symmetrical node structures, also side splices to prevent.

[0100] Finally, it should be noted that terms such as "having," "comprising," "with," etc., do not exclude other elements or steps, and indefinite articles such as "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the foregoing embodiments may also be used in combination with features or steps described with reference to other of the foregoing embodiments. Reference numerals in the claims are not to be considered as a limitation. List of reference symbols

[0101] 1 Ultrasonic welding machine 3 Sonotrode 5 Anvil 9 Joining partner 11 Gap 13 Side slide 15 Spotting plate 17 Retaining device 19 Section not to be welded 21 Conduit 23 Strand 25 Strand section 27 Exit node 29 Total node 29 First total node 29 Second total node 31 Characteristic line 33 Conductor

Claims

1. Method for welding at least three lines (21) to form a Y or X splice, each line (21) comprising at least two stranded wires (23), each having an exposed stranded wire portion (25) and each stranded wire being sheathed at its outside at least partially with an electrically isolating material composed of one or more layers, wherein the method comprises: a first ultrasonic welding step in which at least two initial nodes (27) are formed, each initial node (27) being formed by welding at least two of the stranded wire portions (25) using ultrasound; a second ultrasonic welding step following the first ultrasonic welding step, in which at least two overall nodes (29, 29a, 29b) are formed, at least one of the overall nodes (29, 29a, 29b) being formed by welding at least one of the initial nodes (27) to at least one of the remaining stranded wire portions (25) which have not yet been welded in an initial node (27) and / or to at least one other of the initial nodes (27) using ultrasound.

2. Method according to claim 1, wherein, in order to weld at least three lines (21) to form a Y splice in the second ultrasonic welding step, each overall node (29, 29a, 29b) is formed by welding at least one of the initial nodes (27) to at least one of the remaining stranded wire portions (25) using ultrasound.

3. Method according to claim 1, wherein, in order to weld at least four lines (21) to form an X splice in the second ultrasonic welding step, each overall node (29, 29a, 29b) is formed by welding at least two of the initial nodes (27) using ultrasound.

4. Method according to claim 1, wherein, in order to weld at least four lines (21) to form an X splice in the second ultrasonic welding step, a first overall node (29a) and a second overall node (29b) are formed, the first overall node (29a) being formed by welding the at least two initial nodes (27) using ultrasound, the second overall node (29b) being formed by welding the remaining stranded wire portions (25) using ultrasound.

5. Method according to any of the preceding claims, wherein welding using ultrasound comprises: positioning the respective joining partners (9) in an intermediate space (11) between a sonotrode (3) and an anvil (5); pressing together the joining partners (9) positioned in the intermediate space (11); setting the sonotrode (3) into ultrasonic vibration.

6. Method according to claim 5, wherein, when forming at least one of the initial nodes (27), the at least two stranded wire portions (25) are positioned such that they project into the intermediate space (11) from the same side; and / or wherein, when forming at least one of the initial nodes (27), the at least two stranded wire portions (25) are positioned such that they project into the intermediate space (11) from different, in particular opposite, sides.

7. Method according to claim 5 or 6, wherein, when forming at least one of the overall nodes (29, 29a, 29b), at least two of the respective joining partners (9) are positioned such that they project into the intermediate space (11) from the same side; and / or wherein, when forming at least one of the overall nodes (29, 29a, 29b), at least two of the respective joining partners (9) are positioned such that they project into the intermediate space (11) from different, in particular opposite, sides.

8. Method according to any of claims 5 to 7, wherein portions (19), that are not to be welded, of the lines (21) are held outside the intermediate space (11) by means of a retaining device (17).

9. Method according to claim 8, wherein the portions (19) not to be welded comprise at least one of the following portions of the lines (21): one of the initial nodes (27), one of the overall nodes (29, 29a, 29b), one of the stranded wire portions (25).

10. Method according to any of the preceding claims, wherein, when forming the initial nodes (27), different ultrasonic welding parameters are used than when forming the overall nodes (29, 29a, 29b).

11. Method according to claim 10, wherein, when forming the initial nodes (27), at least one of the following ultrasonic welding parameters is chosen to be smaller than when forming the overall nodes (29, 29a, 29b): an ultrasonic amplitude; a welding power; a welding energy; a welding time; a contact surface; a welding width; a pressure with which the respective joining partners (9) are pressed together.

12. Method according to any of the preceding claims, wherein the initial nodes (27) are formed on a different ultrasonic welding machine (1) than the overall nodes (29, 29a, 29b).

13. Method according to any of the preceding claims, wherein at least one of the initial nodes (27) is formed from stranded wire portions (25) of at least two of the lines (21); and / or wherein at least one of the initial nodes (27) is formed from stranded wire portions (25) of the same line (21).

14. Method according to any of the preceding claims, wherein each initial node (27) is formed from different stranded wire portions (25) than any other initial node (27); and / or wherein each overall node (29, 29a, 29b) is formed from different joining partners than any other overall node (29, 29a, 29b).

15. Method according to any of the preceding claims, wherein at least one of the stranded wire portions (25) has been compacted using ultrasound in an ultrasonic compaction step preceding the first and / or second