The invention relates to a device for welding rod-shaped electrical conductors provided with an outer insulating sheath and having blank regions free of the sheath at their ends, whose length is defined by an axial sheath end surface, the device comprising a compression space for receiving connecting regions of the conductors to be connected to each other, the compression space being limited in a first axial direction at two opposing sides by a working surface of a sonotrode transmitting ultrasonic vibrations in the first axial direction and by an opposing surface of an opposing electrode and in a second axial direction at two opposing sides by a limiting surface of a slider element displaceable in the second axial direction and by a limiting surface of a limiting element.
A device of the kind mentioned above is known from EP 1 765 545 A1, said device being provided with an auxiliary device supporting the formation of an overlapping arrangement of the connecting regions in the compression space in that a leading or guiding element ensures that the connecting regions overlap each other in an axial direction transverse to the longitudinal extension of the conductors with longitudinal axes of the connecting regions being aligned parallel to each other. This kind of overlapping arrangement is necessary in order to enable a reliable connection between the connecting regions after closure of the compression space by corresponding displacing motions of the surfaces limiting the compression space and subsequent application of vibrations to the connecting regions arranged in the stacked arrangement by the sonotrode.
Aside from a flawless connection of the connecting regions for the formation of weld nodes, it is also necessary for the quality of ultrasonically welded connections of this kind that the weld nodes meet specific geometrical requirements, which vary greatly depending on the type and size of the weld nodes.
For instance, in case of continuous weld nodes, which connect the connecting regions of conductors arranged in opposite directions, it is important that predefined distances between an end cross-section of a connecting region of a conductor extending in one direction and the sheath end surface of an insulating sheath of another conductor connected to the first conductor and extending in the opposite direction are observed. In case of a terminal weld node, which serves to connect a connecting region of a conductor with a connecting piece, also called a terminal in technical terminology, a predefined distance between the end cross-section of the conductor and a surface of the terminal arranged on the longitudinal axis of the conductor should be observed as well.
Defined distances are observed to ensure, among other things, that the connecting regions including the end cross-sections are compressed and welded together by the application of vibrations without allowing filaments or leads of the conductors to radially stick out because of an incomplete compression or welding of the connecting regions. Otherwise, filaments or leads radially sticking out might destroy the sheaths of adjacent conductors in a cable installation, which may cause short circuits.
Therefore, the object of the present invention is to provide a device of the kind described above that allows producing defined weld nodes between electrical conductors, thus increasing the reliability of cable installations.
To attain this object, the device according to the invention has the features of claim 1.
According to the invention, the device is provided with a compression space having a marking device for axial positioning of the connecting regions, said marking device comprising a radiation-emitting device interacting in a contactless manner with end cross-sections of the connecting regions in such a manner that the axial position of the end cross-sections within the compression space is defined in a third axial direction (x-axis) parallel to the working surface of the sonotrode by a position mark realized as a point of reflection or point of absorption of the radiation on the working surface of the sonotrode or the limiting surface of the limiting element.
Thus, according to the invention, the adjustment of a defined axial position of the end cross-section becomes possible without having to move the end cross-sections against an axial stop or the like. Instead, the end cross-section can be positioned by axially aligning the end cross-section relative to a reference mark or position mark. This position mark is produced by means of a radiation-emitting device in such a manner that the position mark is realized as an optically perceivable marking without having to form a mechanical stop or the like. The desired axial positioning of the end cross-section is thus achieved without having to move the end cross-section against a mechanical stop, i.e. in a contactless manner.
The terms point of reflection and point of absorption used here to describe the position mark should not be construed in a limiting manner to indicate a punctual design of a point of reflection or a point of absorption, but as a denotation of a geometrical place or region. Hence, the region of reflection or absorption can also have a linear shape or be an irregularly designed area.
The conductors welded together in the device according to the invention are usually rod-shaped conductors, i.e. conductors substantially determined in their dimension by their longitudinal extension, which additionally have an at least slight flexural stiffness so as to maintain their longitudinal extension despite their flexible nature as long as there is no radial load acting on the conductors. Conductors of this kind can be realized as an insulated stranded wire, for example, which, in particular if designed as a stranded wire and combined in stranded-wire packets made of a plurality of stranded wires, can be inserted into the compression space.
According to a preferred embodiment, a radiation-guiding device comprising at least one beam guide is arranged between the radiation-emitting device and the working surface of the sonotrode or the limiting surface of the limiting element in such a manner that a beam path defined by the beam guide and impinging upon the working surface of the sonotrode or the limiting surface of the limiting element serves to form the position mark arranged at a defined distance a from a side edge of the working surface of the sonotrode. Since a reference edge formed anyway by the side edge of the working surface is taken as a reference for adjusting the defined distance in addition to the position mark, no further adjustment or change of the compression space is necessary other than the installation of the radiation-emitting device and of the radiation-guiding device in order to realize the device.
It is particularly advantageous if the beam guide is realized in such a manner that the position mark extends linearly at a right angle to the third axial direction (x-axis) so that the end cross-sections of all connecting regions arranged on the working surface can be aligned at the linear position mark in particular in case of a stacked arrangement of connecting regions having several connecting regions arranged in one stacking plane, i.e. parallel to the working surface of the sonotrode.
If the beam guide is provided with a beam deflection device, the arrangement of the radiation-emitting device is independent of the point of reflection or point of absorption of the radiation forming the position mark, allowing the radiation-emitting device to be arranged in particular in a plane parallel to the working surface of the sonotrode and in a manner laterally offset from the compression space so that the emitting device does not adversely affect the accessibility of the compression space for inserting the conductors or the connecting regions of the conductors into the compression space.
It is particularly advantageous if the beam guide is realized as an optical waveguide, allowing the radiation-emitting device to be realized also as a separate device fully independent from the welding device and being connectable to the welding device via a coupling device. For this purpose, the use of an optic fiber cable as an optical waveguide is advantageous.
If the beam deflection device is preferably realized integrally in the beam guide, as is the case when a flexible optical waveguide, i.e. an optic fiber cable, is used, for example, the beam deflection device does not have to be designed as a device that is independent from the wave- guide. Alternatively, it is also possible of course to realize the beam deflection device as a prism so as to deflect a beam path impinging horizontally upon a refracting surface of the prism into a beam path. exiting the prism vertically and serving to form the position mark.
To achieve a particularly compact design of a combination of a compression space of the welding device and a radiation-emitting device serving to form the position mark, the radiation-emitting device can be arranged above the limiting element and opposite the slider element at a distance from the working surface of the sonotrode in such a manner that a beam path exiting the radiation-emitting device extends toward the beam deflection device arranged above the working surface of the sonotrode and the beam path exiting the beam deflection device impinges upon the working surface of the sonotrode so as to form the position mark.
If the radiation-emitting device has two beam guides forming two beam paths serving to form two position marks arranged at a defined distance a from the side edges of the working surface of the sonotrode and at a defined distance b from each other, end cross-sections of connecting regions of two conductors can be advantageously axially positioned, said conductors being welded together so as to form a continuous weld node of two conductors arranged opposite each other.
Independently of whether the device according to the invention is realized in such a manner that a welded connection formed as a continuous weld node is formed between axially positioned end cross-sections of connecting regions of conductors oriented opposite each other or whether the device according to the invention serves to form a welded connection realized as an end weld node between connecting regions of conductors extending parallel to each other, it is advantageous in any case if the radiation-emitting device serving to form the position marks is realized as a radiation source emitting optical radiation. The use of a laser radiation source as a radiation source proves particularly advantageous owing to the high beam density and the thus possible particularly high-contrast formation of the position mark.
In the following description, preferred embodiments of the device will be explained in more detail with the aid of the drawing.
In the drawing:
In the embodiment of the compression space 18 illustrated in
The stacked arrangement of the connecting regions 26, 27 of the conductors 28, 29 illustrated in
To allow for a corresponding axial positioning of the end cross-sections 31, 32 of the conductors 28, 29 in the open compression space 18, the compression space 18 is provided with a marking device 37, which is schematically illustrated in
In order to form a defined beam path 39, the beam path 39 can be adjusted by means of the beam deflection device 41 or by means of a radiation-guiding device comprising the beam deflection device 41, such as a fiber optic cable (not illustrated), in such a manner that the position mark 42 is formed at the point on the working surface 19 of the sonotrode 16 that defines the desired distance a between the side edge 43 and the end cross-sections 31, 32 of the conductors 28, 29. In practice, this means that an operator who inserts the blank regions 33, 34 of the conductors 28, 29 into the open compression space 18 merely has to axially position the end cross-sections 31, 32 of the blank regions 33, 34 on the working surface 19 of the sonotrode 16 in such a manner that the end cross-sections 31, 32 are located at the position mark 42 so as to ensure that the weld node formed between the conductors 28, 29 by welding exhibits the required node geometry having the length l1 of the connecting regions 26, 27 and the distance l2 between the connecting regions 26, 27 and the sheath end surface 35, 36.
As can be taken from
When producing the terminal weld node 45 illustrated in
In the axial positioning of the end cross-sections 31, 32 of the conductors 28, 29 illustrated in
The use of a marking device 50 for forming the continuous weld node 46 is shown in
As illustrated in
As becomes clear from a combined view of
Number | Date | Country | Kind |
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10 2013 222 939.9 | Nov 2013 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/073939 | 11/6/2014 | WO | 00 |