Stripping electrical wires using ultrasound

Description

[0001] The present invention relates to methods and devices for at least partially stripping electrical conductors, as well as to at least partially stripped electrical conductors. The conductor, which may be designed, for example, as a round conductor, has a longitudinal direction and contains at least one electrical conductor and insulation that, in particular, completely encloses the conductor in the circumferential direction.

[0002] Various methods are used to at least partially strip the insulation from cables. One possibility is to score the insulation with a sharp cutting blade. In other methods, the insulation is melted by applying thermal energy. Alternatively, the insulation can also be removed by laser welding. However, this process sometimes vaporizes substances that are hazardous to health and must be extracted. Furthermore, not all technically relevant materials can be processed using laser welding, for example, if they are of an unsuitable color.

[0003] It is also known from the prior art to strip electrical conductors using tools that can be excited to ultrasonic vibrations, which facilitate the stripping process. For example, document JP 2000-92644 A discloses an ultrasonically assisted stripping of round conductors using two opposing cutting devices, which may, for example, have V-shaped sharp cutting edges.

[0004] US Patent 3,909,911 deals with the removal of insulating or shielding material from flat conductors. This involves moving a tool toward the electrical conductor and exciting it to ultrasonic vibrations, and then removing the insulation through a peeling motion.

[0005] A problem with known methods and devices is that, in practice, electrical wires and their conductors never have a perfectly uniform thickness and roundness, and the conductors are not always centered. Without knowledge of these parameters for each individual wire, it can happen that, in the case of a wire with an above-average conductor thickness, part of the conductor, especially individual strands, is notched, scraped, or even completely severed, and / or that, in the case of a wire with a below-average conductor thickness, the insulation is not completely removed. This can lead to significant variations in the properties and thus the quality of the stripped wires, including reduced conductivity and subsequent ultrasonic welding.

[0006] Document US 6,442,833 B1 discloses a method for stripping an insulated electrical wire, in which circumferential cuts are made in an insulating coating of the wire using circumferential cutters, and then the circumferential cutters are moved in a longitudinal direction along the wire to separate the cut pieces of the coating from one another. After longitudinal cuts have been made in the coating using longitudinal cutters, the coating is removed by an airflow, and any upper waste coating is suctioned away by a vacuum. An ultrasonic sonotrode can be used to press the coating against the longitudinal cutters while generating ultrasonic vibrations.

[0007] CN 105790169 A discloses an ultrasonic wave wire stripping machine. This machine features a cable clamping function, which allows the stripping of mineral-insulated cables of various specifications to be adapted. This enables high stripping efficiency, high stripping speed, and low power loss.

[0008] Document JP 2000-092644 A addresses the task of precisely stripping the insulating film from a cable without cutting the core wire and preventing wear on the cutters. This is achieved through a cable stripping device and a procedure. These include cable chucks for holding the cable and ultrasonic cutters for cutting the cable's insulating film. Stripping pliers for pulling the insulating film away are positioned adjacent to the cutters. The cable is held by the cable chucks, and then the insulating film is cut alternately by the cutters using ultrasonic vibrations. After the insulating film has been cut by the cutters, it is pulled off the cable and removed using the stripping pliers.

[0009] JPH 6-6922 A teaches how to control the cutting depth of a wire stripper blade when stripping an sheathed cable for any type of electrical equipment. A sheathed cable, consisting of a core wire and a sheathed layer, is fed through an opening between the stripper edges into a cable holder tube. The stripper edges cut into the sheathed layers by driving a ball nut via a motor. A conductivity sensing device detects the electrical conductivity through contact between the stripper edges and the core wire and stops the motor. The sheathed layer is stripped by rotating feed rollers.

[0010] Document US 3,909,911 A describes how insulating and / or shielding materials can be removed from a flat cable, etc., and discloses a method according to the preamble of claim 1 and a device according to the preamble of claim 8.

[0011] For this purpose, an ultrasonically excited tool is provided. Pressure is applied to the tool so that its tip penetrates the surface of the flat conductor. The tool tip and the conductor are then moved relative to each other in a peeling motion that removes the insulating and / or shielding material. The ultrasonic movement of the tool tip occurs in a plane that is generally parallel to the conductor surface. Furthermore, the end face of the tool tip is essentially flat and engages the conductor surface at a shallow angle (or very close to it). This allows the insulating and / or shielding substances to be removed without damaging the conductor. In addition, any desired cable length can be stripped effectively and quickly without applying large amounts of pressure or force.

[0012] It is an object of the present invention to further develop the known methods and devices in such a way as to prevent the aforementioned disadvantages as far as possible. In particular, it should be ensured that the conductor is damaged as little as possible, but that the insulation is nevertheless removed to a sufficient extent.

[0013] In a first aspect, these and other problems are solved by a method according to claim 1 for at least partially stripping an electrical conductor. The conductor has a longitudinal direction and can, for example, be a round conductor with a substantially circular cross-section perpendicular to the longitudinal direction. The electrical conductor contains at least one electrical conductor and insulation that, in particular, completely encloses the at least one conductor in the circumferential direction. The conductor can be designed as a coaxial conductor containing an inner electrical conductor and one or more outer electrical conductors. The electrical conductor can contain or consist of a single wire, in particular an enamelled wire, or it can contain or consist of several wires. An electrical shield, such as a braided shield, is also considered an electrical conductor within the scope of the invention.

[0014] The process includes the following steps: a) Bringing a working surface of at least one ultrasonic tool capable of being excited to ultrasonic vibrations into contact with an area of ​​influence of the insulation spaced apart from one end of the line, b) Introducing ultrasound into the area of ​​influence by means of the ultrasonic tool in order to displace the insulation exclusively in the area of ​​influence and there at least along a part, in particular along the entire circumferential direction.

[0015] The insulation can consist, for example, of a plastic such as PVC, silicone, or PTFE, or of a textile insulating material. In many embodiments—particularly when the insulation is made of a thermoplastic material—the insulation can be displaced from the conductor by melting due to the action of the ultrasonic vibrations. Even high-temperature-resistant insulation such as PTFE can be displaced by the ultrasonic action, even if it does not melt. The invention also includes embodiments in which the insulation is merely displaced from the area of ​​effect, without necessarily being spatially separated from the conductor.

[0016] Outside the area of ​​influence – and thus, among other places, at the end of the cable located away from the area of ​​influence – the insulation is not displaced. The area of ​​influence can be located at a distance from the end of the cable that is, for example, at least 2 mm and preferably at least 4 mm. The distance can be at most 8 mm or even at most 6 mm. However, it can also be greater than 8 mm, for example, if the insulation is to be displaced to create a center tap. Displacement of the insulation only occurs within the area of ​​influence, and at least along a portion of it, in particular along the entire circumferential direction of the cable.

[0017] According to the invention, the working surface is blunt and oriented relative to the electrical conductor in such a way that the conductor is not damaged by the working surface during stripping – i.e., during step b). If the conductor contains multiple conductors, particularly if it is designed as a coaxial conductor, the working surface is blunt and oriented relative to the electrical conductor in such a way that none of the conductors are damaged during stripping. This contrasts with the device known from JP 2000-92644 A, which contains two cutting devices with sharp cutting edges that can damage the conductor, for example, by completely severing individual wires. Instead, according to the invention, the ultrasonic tool only displaces the insulation (for example, by briefly melting it) so that the ultrasonic tool can penetrate it.

[0018] Damage prevented according to the invention is understood here and in the following to mean notching, scraping, or cutting one or more wires of the electrical conductor. Mere deformation of the electrical conductor that does not alter its electrical properties or its mechanical strength, particularly during subsequent ultrasonic welding of the conductor, is not considered damage. If, particularly during subsequent ultrasonic welding, mere deformation does not result in breakage, it is not considered damage.

[0019] In contrast to the sharp cutting edges known from the prior art, in whose area the amplitude of the ultrasonic vibrations is particularly large, the ultrasonic power is distributed over a larger area on a blunt working surface according to the invention, which allows a more controlled displacement of the insulation, in particular by melting the insulation.

[0020] According to the invention, the bluntness of the working surface is characterized by its first profile in a first cross-sectional plane that includes the longitudinal direction of the conductor. As has been shown, damage to the conductor during stripping can be prevented particularly effectively if, according to the invention, the first profile of the working surface has a radius of curvature of at least 0.2 mm at every point. By definition, a straight section of the first profile has a curvature of infinity greater than 0.2 mm. To limit the extent of the working surface in the longitudinal direction of the conductor, the radius of curvature in at least one section of the first profile can be at most 6 mm.

[0021] Additionally, to prevent damage to the conductor during stripping, the first profile of the working surface can have a wedge angle of at least 60°, preferably at least 90°, and particularly preferably at least 120° at each point. The wedge angle at a point of the first profile is (similar to the definition in DIN 6581 for angles on cutting parts) the internal angle measured with respect to that point between the sections of the first profile running on either side of the point, as shown below. Figures 4b to 4d This will be demonstrated. The radii of curvature and wedge angles can be determined, for example, in a manner known per se, using an optical or mechanical profile meter.

[0022] Within the scope of the invention, the working surface is understood to be the part of the ultrasonic tool that comes into contact with the conductor during the execution of the method. The radius of curvature and the wedge angle can depend on the material and the thickness of the insulation. Surface sections of the ultrasonic tool that do not belong to the working surface may well have a radius of curvature and / or a wedge angle outside the aforementioned range in the first section plane.

[0023] The electrical conductor can be made of copper or aluminum, for example. Since aluminum is softer than copper, this material is particularly susceptible to damage without special precautions, making the effect of the invention even more pronounced.

[0024] In one variation of the method, the insulation can be displaced substantially along the entire circumference of the conductor by rotating the ultrasonic tool around the conductor at least temporarily during step a) and / or step b). This allows the insulation to be displaced particularly uniformly along the entire circumference.

[0025] In a second variant, several ultrasonic tools, each equipped with a working surface and capable of being excited to ultrasonic vibration, can be used. In particular, the multiple ultrasonic tools can act on the cable from opposite sides. This eliminates the need for the more complex mechanics required for a rotating ultrasonic tool.

[0026] According to the invention, step b) is terminated when contact between the ultrasonic tool and the conductor is detected. This further minimizes the remaining risk of the ultrasonic tool's blunt working surface damaging a conductor, such as one with above-average or unexpectedly large thickness, one with an elliptical cross-section instead of an expected circular cross-section, or one that is unexpectedly off-center. Such detection is particularly advantageous when the ultrasonic tool oscillates radially with respect to the conductor's longitudinal direction and / or with a large amplitude, for example, with an amplitude greater than 6 µm, preferably greater than 8 µm.

[0027] Preferably, the movement of the ultrasonic tool, particularly its movement in a direction radial to the longitudinal direction of the conductor, can be stopped when contact between the ultrasonic tool and the conductor is detected. This allows for even more effective prevention of potential damage to the conductor.

[0028] To strip a batch of electrical wires of the same type, a control unit connected to the detection unit can be set to the minimum conductor and insulation thicknesses expected within the batch. This ensures sufficient stripping in every case. If one or more wires in the batch have greater thicknesses, the control unit can terminate step b) after receiving a corresponding signal from the detection unit. Due to the bluntness of the working surface, the conductors are not yet damaged at this point.

[0029] For the aforementioned purpose, contact between the ultrasonic tool and the conductor can be detected extremely quickly and reliably via the voltage present between the working surface of the ultrasonic tool and the conductor, i.e., a potential difference between the working surface of the ultrasonic tool and the conductor. The conductor's potential can be tapped, for example, at an end face of the conductor or at a circumferential surface that has been previously made accessible, for example, by selectively removing the insulation.

[0030] In many cases, the conductor is not welded by the application of ultrasound in step b). However, it is often not harmful, or can even be advantageous, if the conductor is welded by the application of ultrasound in step b).

[0031] Preferably, the method includes a further step c), carried out after step b), in which the insulation in the affected area is separated into a first part and a second part opposite the affected area. For example, a first part of the insulation can be completely removed from the remaining part of the conductor, so that the stripped conductor can be processed immediately afterwards, for example in an ultrasonic welding process. Alternatively, the first part can also be removed only to a certain, in particular predetermined, distance from the second part, without completely removing it from the remaining part of the conductor. This can, in particular, prevent fraying of the conductor end. This is advantageous, for example, if the conductor is to be subjected to an ultrasonic welding process only later, in particular after storage or transport.

[0032] It is particularly advantageous if the insulation separation in step c) is carried out using the ultrasonic tool itself. No further tool is then required for separation, for example, for complete removal or partial removal over a certain distance.

[0033] In a structurally simple embodiment, it is provided that during step a) and / or during step b), the ultrasonic tool is moved at least temporarily at an axial position of the conductor in a radial direction relative to its longitudinal direction, and in particular, the working surface penetrates the insulation. Advantageously, during and / or after step b), the ultrasonic tool is moved away from the conductor in the radial direction at the same axial position. A further advantage is that the ultrasonic tool remains essentially at the same axial position from the movement toward the conductor until the movement away from the conductor. Thus, the ultrasonic tool is not moved along the conductor in the longitudinal direction (apart from the ultrasonic vibration, which may occur in this direction). In contrast to the method disclosed in US 3,909,911, the insulation is therefore not peeled away.This results in narrower impact zones in the longitudinal direction and a more precise cutting of the insulation.

[0034] For example, depending on the geometry of the conductor, it can be advantageous if a second profile of the working surface has a curvature, particularly a concave curvature, at least partially in a second section plane perpendicular to the longitudinal direction. For this purpose, the radius of curvature in the second section plane can be adapted to, and in particular substantially match, the radius of the electrical conductor. To prevent damage to the conductor, the second profile of the working surface preferably has a radius of curvature in the range of 0.1 mm to 100 mm at each point. With a concavely curved second profile, displacement of the insulation along a larger portion of the conductor's circumference can be achieved than with a straight second profile.

[0035] Alternatively or additionally, the second profile of the work surface can have an interior angle of at least 60°, preferably at least 120°, more preferably at least 180°, even more preferably at least 240°, and particularly preferably at least 300° at any point. The invention also includes work surfaces that have no curvature in the aforementioned second sectioning plane.

[0036] It has also proven advantageous for the working surface of the ultrasonic tool to vibrate along the length of the conductor. This prevents the ultrasonic tool from "hammering" against the insulation and, subsequently, against the conductor itself. Instead, the working surface of the ultrasonic tool penetrates the insulation and then displaces it along the length of the conductor with the vibration amplitude. This significantly reduces the risk of conductor damage. Alternatively, and within the scope of the invention, it is also conceivable that the working surface vibrates in a direction radial to the length of the conductor or in a direction perpendicular to both the length and the radial directions.

[0037] The ultrasonic tool can be formed, for example, by a linear transducer, a torsional transducer, or a bending transducer. A linear transducer oscillates along an axis of vibration. The working surface of a linear transducer can, for example, be parallel or perpendicular to the axis of vibration. A torsional transducer oscillates around a torsional axis. The working surface of a torsional transducer can, for example, be located on an end face perpendicular to the torsional axis or on a circumferential surface parallel to the torsional axis.

[0038] The torsion oscillator can have a disc-shaped working area, which can be essentially cylindrically symmetrical with respect to the axis of torsion. In this embodiment, the working surface is formed by the circumferential surface of the working area. A particular advantage is that this torsion oscillator can be rotated about its axis of torsion during the stripping of a cable and / or between the stripping of a first cable and the stripping of a second cable. This ensures uniform wear of the entire working surface and thus a particularly long service life for the torsion oscillator.

[0039] A torsional oscillator with a disc-shaped working area can also be used particularly advantageously in the embodiment already described above, in which it rotates around the conduit in the circumferential direction. Optionally, the torsional oscillator can also be rotated about its torsional axis. It is further conceivable, and covered by the invention, that during step a) and / or during step b) the conduit rotates at least temporarily around the torsional oscillator with the disc-shaped working area.

[0040] Furthermore, it is conceivable and covered by the invention that the ultrasonic tool is designed as a combined oscillator whose vibrations contain both linear and torsional components.

[0041] A further advantage of the ultrasonic tool is that it comprises a base body and at least one detachably or connectably attached tool insert containing the working surface. This allows only the tool insert to be adapted to the specific type of pipe being processed. Furthermore, in the event of wear to the working surface, only the tool insert needs to be replaced, not the entire base body.

[0042] In the inventive method, the insulation can also be displaced at two or more areas of action spaced apart along the longitudinal direction of the conductor. Additionally, the insulation can be displaced in a linear section extending along the longitudinal direction of the conductor, connecting the areas of action. The linear section can be displaced with or without ultrasonic application. In this way, the insulation can be removed from the conductor in a cylindrical section, thus enabling a center tap.

[0043] The ultrasound used in the inventive method can have a frequency in the range of 15 kHz to 70 kHz.

[0044] In a further aspect, the invention also relates to a device according to claim 8 for at least partially stripping an electrical conductor. The method described above can be carried out with this device.

[0045] The device comprises at least one ultrasonic tool capable of being excited to ultrasonic vibrations, with a working surface that can be brought into contact with an area of ​​influence on the insulation spaced apart from one end of the cable. Ultrasound can be introduced into the area of ​​influence in such a way that the insulation is displaced exclusively within the area of ​​influence and at least along a portion of it, in particular along the entire circumferential direction of the cable, especially by being meltable there.

[0046] According to the invention, the working surface is blunt and can be aligned relative to the electrical conductor in such a way that the conductor is not damaged by the working surface during stripping. The first profile of the working surface has a radius of curvature of at least 0.2 mm at every point. In at least one section of the first profile, the radius of curvature can be at most 6 mm. Additionally, the first profile of the working surface can have a wedge angle of at least 60°, preferably at least 90°, and particularly preferably at least 120° at every point.

[0047] The ultrasonic tool can be rotated around the circumference of the pipe. Alternatively or additionally, the ultrasonic tool can be moved radially to the longitudinal direction of the pipe. The process steps described above can then be carried out in this way.

[0048] The device can contain several ultrasonic tools, each equipped with a working surface, that can be excited to ultrasonic vibrations. These ultrasonic tools can be arranged or arranged in a circumferential distribution around the line, in particular in a uniform distribution.

[0049] For the purpose already explained, the device includes a detection unit with which contact of the ultrasonic tool with the conductor can be detected, as well as a control unit which is designed to stop the introduction of ultrasound into the area of ​​influence when contact of the ultrasonic tool with the conductor has been detected.

[0050] The detection unit can have a first sampling element for detecting an electrical potential on the working surface of the ultrasonic tool, and a second sampling element for detecting a second electrical potential on the conductor. Furthermore, the detection unit can include a voltmeter for determining the voltage difference between the first and second potentials. The second sampling element for detecting the electrical potential on the conductor can be located, for example, on an end face at the end of the conductor or on a circumferential surface that has been previously made accessible, for example, by selectively removing the insulation.

[0051] The working surface can have a curvature, in particular a concave curvature, at least partially, in a second section plane perpendicular to the longitudinal direction of the conductor. For this purpose, the radius of curvature in the second section plane can be adapted to the radius of the electrical conductor and, in particular, substantially coincide with it. To prevent damage to the conductor, the second profile of the working surface can preferably have a radius of curvature in the range of 0.1 mm to 100 mm at every point and / or an internal angle of at least 60°, preferably at least 120°, more preferably at least 180°, even more preferably at least 240°, and most preferably at least 300°.Alternatively or additionally, the second profile of the work surface can have an interior angle of at least 60°, preferably at least 120°, more preferably at least 180°, even more preferably at least 240°, and particularly preferably at least 300° at any point. The invention also includes work surfaces that have no curvature in the aforementioned second sectioning plane.

[0052] As already explained above, the inventive method is particularly advantageous when the working surface of the ultrasonic tool vibrates in the longitudinal direction of the conductor. This significantly reduces the risk of damage to the conductor. The conductor of a cable at least partially stripped using this advantageous method exhibits abrasion marks in the longitudinal direction of the cable, which are attributable to the vibrations. The invention is explained in detail below with reference to several exemplary embodiments and drawings. Figure 1: A schematic view of a first device according to the invention with a rotatable longitudinal oscillator and a cable in a schematic sectional view parallel to the longitudinal direction of the cable; Figure 2a: A schematic view of a second device according to the invention with two longitudinal oscillators and a cable in a schematic sectional view parallel to the longitudinal direction of the cable; Figure 2b: The second device according to the invention in a schematic sectional view perpendicular to the longitudinal direction of the cable; Figure 3: A schematic view of a third device according to the invention with a torsional oscillator; Figures 4a to 4d: Possible first contours of working surfaces; Figure 5: A schematic representation of a fourth device according to the invention with a longitudinal oscillator, a detection unit, and a control unit;Figure 6: a schematic representation of a linear oscillator of a fifth device according to the invention, comprising a base body and a tool insert; Figures 7a and 7b: further pairs of working surfaces according to the invention in a second sectional plane; Figure 8a: a partially stripped conductor according to the invention in a side view; Figure 8b: the conductor according to the invention; Figure 8a in a top view.

[0053] Figure 1 Figure 10 schematically shows a device 10 according to the invention for at least partially stripping an electrical conductor 50, which here is designed as a round conductor 50. The conductor 50 extends along a longitudinal direction L and contains an electrical conductor 51 and insulation 52 that completely encloses it in the circumferential direction U. The conductor 51 can, for example, be made of copper or aluminum, and the insulation 52 of a plastic known per se for this use or a textile insulating material.

[0054] The device 10 comprises an ultrasonic tool capable of being excited to ultrasonic vibrations and is designed as a linear transducer 26 with a working surface 21. In a first section plane E containing the longitudinal direction L, which is aligned with the drawing plane of the Figure 1 Since the working surface 21 agrees, it has a first profile which has a radius of curvature at every point that, depending on the material and the thickness of the insulation 52, can be at least 0.2 mm and at least partially at most 6 mm. Given the absence of edges, the wedge angle at every point is 180°, i.e., greater than 120° (see also the details in the Figures 4a to 4d ).

[0055] To at least partially strip the electrical conductor 50, in a first step a) of the inventive method, the linear oscillator 26 is moved at an axial position A of the conductor 50 in a direction R radial to the longitudinal direction L towards the conductor 50. The axial position A defines an area of ​​contact 53 of the insulation 52, which is spaced apart from one end 56 of the conductor 50. In this way, the working surface 21 is brought into contact with the area of ​​contact 53 of the insulation 52.

[0056] In a subsequent step b), ultrasound is introduced into the area of ​​influence 53 by means of the linear transducer 26. The working surface 21 of the linear transducer 26 oscillates in the direction of an axis of oscillation S, which runs parallel to the longitudinal direction L of the conductor 50. Alternatively, the linear transducer could also oscillate in the radial direction R. The ultrasound causes the insulation 52 in the area of ​​influence 53 to melt and be displaced. This displacement occurs exclusively in the area of ​​influence 53, and thus not, for example, at the end 56 of the conductor 50. Meanwhile, a mechanism (not shown here) ensures that the linear transducer 26 rotates around the conductor 50 in the circumferential direction U. In the area of ​​influence 53, the insulation 52 is melted and thereby displaced essentially along its entire circumferential direction U.

[0057] Due to the aforementioned radii of curvature of the first profile of the working surface 21, the working surface 21 is so blunt that the conductor 51 is not damaged by it during stripping. In particular, no individual wires of the conductor 51 are severed. This allows electrical conductors 50 to be produced with significantly improved and more uniform quality and less waste than was possible with previously known methods and devices.

[0058] Without welding the conductor 51, the linear oscillator 26 is moved away from the conductor 50 again in the radial direction R after step b) at the same axial position A. Between the movement towards the conductor 50 and the movement away from the conductor 50, the linear oscillator 26 remains essentially at the same axial position A, i.e., it is not moved along the longitudinal direction L.

[0059] In an optional further step c), the insulation 52 can be separated in the area of ​​influence 53 into a first part 54 and a second part 55 opposite the area of ​​influence 53. Particularly preferably, the separation of the insulation 52 in step c) is carried out using the linear vibrator 26 itself. In this way, a further tool can be dispensed with. If the conductor 50 is not to be processed further immediately, it is advantageous if the first part 54 is only drawn to a distance of, for example, 1 mm from the second part 55.

[0060] The in the Figures 2a and 2bThe second device 10 according to the invention, as illustrated, contains not one, but two ultrasonic tools that can be excited to ultrasonic vibrations, both of which are designed in the form of linear transducers 26 with a respective working surface 21. The two linear transducers 26 are thus arranged evenly distributed around the line 50 in the circumferential direction U.

[0061] As the Figure 2b As shown, the working surface 21 has a second profile with a concave curvature in a second section plane F perpendicular to the longitudinal direction L, the radius of curvature of which corresponds to the radius of the conduit 50 and which facilitates melting and thus displacement essentially along the entire circumferential direction U.

[0062] In the inventive method, both linear oscillators 26 are moved in step a) at an axial position A of the conductor 50 in a radial direction R with respect to the longitudinal direction L towards the conductor 50, thus penetrating the insulation 52 in an area of ​​influence 53, where they act on the conductor 50 from opposite sides. In a subsequent step b), both linear oscillators 26 are moved away from the conductor 50 again at the same axial position A in the radial direction R. During the entire process, no welding of the conductor 51 takes place, and the two linear oscillators 26 are not moved along the longitudinal direction L of the conductor 50, i.e., they remain at the same axial position A.

[0063] The third device according to the invention 10 in Figure 3The device contains an ultrasonic tool in the form of a torsion oscillator 22. This oscillator has a disk-shaped working area 23, which is cylindrically symmetrical with respect to a torsion axis T of the torsion oscillator 22. The working surface 21 is formed by the circumferential surface of the working area 23. The torsion oscillator 22 is rotatable around the conductor 50 in the circumferential direction U of the conductor 50. By rotating the torsion oscillator 22 around the conductor 50, the insulation 52 can be melted and displaced uniformly along the entire circumferential direction U of the conductor 50 in a particularly simple manner. The torsion oscillator 22 can be rotated about its torsion axis T during the stripping of a conductor 50 and / or between the stripping of a first conductor 50 and the stripping of a second conductor 50, thereby extending the service life of the torsion oscillator 22.

[0064] The Figures 4a to 4dshow sectional views of possible first profiles of the work surface 21 in the first section plane E. Figure 4a The first profile has a central straight section 27 which, by definition, has a curvature of ∞ and is bounded on both sides by a convex rounding 28 with a radius of curvature in the range of 0.2 mm to 6 mm.

[0065] The in Figure 4b The first profile shown, which is not in accordance with the invention, does contain an edge 29 formed between two straight sections 27 with a radius of curvature less than 0.2 mm; however, the wedge angle β = 90°, so that damage to a conductor 51 can also be prevented with this working surface 21. Figure 4c For a profile not according to the invention, two edges 29 with a wedge angle β=60° are provided, which enclose a convex curve 28. The ultrasonic tool 26 in Figure 4dIt does have two comparatively sharp edges with a wedge angle β=90°; however, these edges do not belong to the working surface 21, since they do not come into contact with the line during the execution of the inventive method.

[0066] The in Figure 5 The fourth device 10 shown in the invention is similar to the one shown in Figure 1The device shown, however, further comprises a detection unit with which contact between the linear transducer 26 and the conductor 51 can be detected, as well as a control unit 12 with which the introduction of ultrasound into the area of ​​influence 53 of the insulation 52 and also the movement of the linear transducer 26 can be terminated when contact between the linear transducer 26 and the conductor 51 has been detected. The detection unit includes a first sampling element 12 for sampling a first electrical potential of the working surface 21 of the linear transducer 26 and a second sampling element 13 for sampling a second electrical potential on the conductor 51. The detection unit also includes a voltmeter 14 for determining the voltage present between the first and the second potential.The control unit 12 can be configured to detect contact between the linear transducer 26 and the conductor 51 when the voltage measured by the voltmeter 14 falls below a predefined threshold. If this threshold is undershot, the control unit 12 can terminate the introduction of ultrasound into the area of ​​influence 53 and the movement of the linear transducer 26 by appropriately activating a generator 15 connected to the linear transducer 26. Such a detection unit can prevent potential damage to the conductor 51 even more effectively.

[0067] The in Figure 6The linear oscillator 26 of a fifth device according to the invention comprises a base body 24 and a tool insert 25 detachably connected thereto, which contains the working surface 21. This makes it possible to adapt only the tool insert 25 to the respective pipe type. Furthermore, in the event of wear of the working surface 21, only the tool insert 25 needs to be replaced, and not the base body 24.

[0068] The Figures 7a and 7b The second profiles of further pairs of inventive working surfaces 21 are shown in a second section plane F, which, when used as intended, runs perpendicular to the longitudinal direction L of the line 50. Figure 7a Both work surfaces 21 are straight, meaning they have an interior angle α=180° everywhere. Figure 7b The work surfaces 21 have a V-shape and an interior angle α>180° at the center point.

[0069] In the Figures 8a and 8bFigure 50 shows a partially stripped electrical conductor 50, from which a first part of the insulation 52 (not shown here) has been removed. In the area of ​​the separation point 57, the electrical conductor 51 has two [unclear] for better illustration. Figure 8a The exaggeratedly large indentations 58 are shown, which are due to the contact of the conductor 51 with the working surfaces of ultrasonic tools. These indentations 58 merely represent deformations of the electrical conductor 51, which do not alter its electrical properties or its mechanical strength, particularly during subsequent ultrasonic welding of the conductor 50.

[0070] The top view in Figure 8b The diagram shows abrasion marks 59 on conductor 51, which run in the longitudinal direction L of the conductor 50. These abrasion marks 59 indicate that vibrations were introduced during the stripping process, which occurred in this direction.

Claims

1. Method for at least partially stripping an electrical cable (50), in particular a round cable (50), with a longitudinal direction (L), which contains at least one electrical conductor (51) and insulation (52) completely enveloping the latter, in particular in the circumferential direction (U), comprising the steps a) Bringing a working surface (21) of at least one ultrasonic tool (22; 26), which can be excited to ultrasonic vibrations, into contact with an effective region (53) of the insulation (52) that is spaced from one end (56) of the cable (50). b) Introducing ultrasound into the effective region (53) using the ultrasonic tool (22; 26) in order to displace the insulation (52) exclusively in the action region (53) and there at least along a portion, in particular along the entire circumferential direction (U), the working surface (21) is oriented relative to the electrical cable (50) and has a first profile in a first plane (E) containing the longitudinal direction (L) that is so blunt that the conductor (51) is not damaged by the working surface (21) during stripping, wherein the first profile of the working surface (21) has a radius of curvature of at least 0.2 mm at each point, characterized in that step b) is terminated when contact between the ultrasonic tool (22; 26) and the conductor (51) is detected.

2. Method according to claim 1, wherein the first profile of the working surface (21) has a radius of curvature of at most 6mm at each point.

3. Method according to one of the preceding claims, wherein the first profile of the working surface (21) has a wedge angle (β) of more than 60°, preferably more than 90°, and particularly preferably more than 120° at each point.

4. Method according to one of the preceding claims, wherein contact between the ultrasonic tool (22; 26) and the conductor (51) is detected via the voltage present between the working surface (21) of the ultrasonic tool (22; 26) and the conductor (51).

5. Method according to one of the preceding claims, comprising the further step of: c) Separating the insulation (52) in the effective region (53) into a first part (54) and a second part (55) opposite the effective region (53).

6. Method according to claim 5, wherein the separation of the insulation (52) in step c) is performed using the ultrasonic tool (22; 26).

7. Method according to one of the preceding claims, wherein the working surface (21) of the ultrasonic tool (22; 26) oscillates in the longitudinal direction (L) of the cable (50).

8. Device (10) for at least partially stripping a cable (50), in particular a round cable (50) with a longitudinal direction (L), which contains at least one electrical conductor (51) and insulation (52) completely enveloping the latter, in particular in the circumferential direction (U), in particular a device (10) for at least partially stripping insulation in a method according to one of the preceding claims, wherein the device (10) comprises at least one ultrasonic tool (22; 26) that can be excited to produce ultrasonic vibrations, with a working surface (21) that, by moving the ultrasonic tool (22, 26) in a direction (R) radial to the longitudinal direction (L) towards the cable (50) with an effective region (53) of the insulation (52) spaced from one end (56) of the cable (50), whereby ultrasound can be introduced into the effective region (53) in such a way that the insulation (52) can be displaced exclusively in the effective region (53) and there at least along a part, in particular along the entire circumferential direction (U), wherein the working surface (21) can be oriented relative to the electrical cable (50) and has a first profile in a first plane (E) containing the longitudinal direction (L) that is so blunt that the conductor (51) is not damaged by the working surface (21) during stripping, wherein the first profile of the working surface (21) has a radius of curvature of at least 0.2 mm at each point, characterized in that the device (10) includes a detection unit with which contact between the ultrasonic tool (22; 26) with the conductor (51) can be detected, as well as a control unit (12) which is designed to terminate the introduction of ultrasound into the effective region (53) when contact between the ultrasonic tool (22; 26) and the conductor (51) has been detected.

9. Device (10) according to claim 8, wherein the first profile of the working surface (21) has a radius of curvature of no more than 6 mm at each point.

10. Device (10) according to one of claims 8 and 9, wherein the first profile of the working surface (21) has a wedge angle (β) of more than 60°, preferably more than 90°, and particularly preferably more than 120°, at each point.