Method for producing a cable core for a cable, in particular for an induction cable

Abstract

A cable core for a cable, in particular, for an induction cable that includes multiple such cable cores which have a conductor that is interrupted in the longitudinal direction at specified longitudinal positions at multiple separation points, thereby forming two conductor ends. An insulating intermediate piece is provided for connecting the conductor ends, and the conductor ends are arranged on both sides of the intermediate piece. The conductor and the intermediate piece are surrounded together by a continuous insulating jacket in order to form the cable core. In a preferred concept, a respective intermediate piece is arranged between the two conductor ends by two adapter elements. In another preferred concept, a respective intermediate piece, in particular, a ceramic intermediate piece, is connected directly to two conductor ends. A cable is formed from a plurality of such cable cores.

Claims

1. A method for producing a cable core, which comprises: providing a sheathless conductor separated in a recurring manner at predetermined longitudinal positions such that the conductor has an intermediate space and two conductor ends spaced apart by the intermediate space; providing an insulating intermediate piece as a core end cap having an end with a recess formed therein; introducing the insulating intermediate piece into the intermediate space; fitting one of the two conductor ends of the conductor in the recess of the insulating intermediate piece; and jointly providing the conductor and the insulating intermediate piece with a continuous insulating sheath to form the cable core.

2. The method according to claim 1, wherein: the conductor is provided with a plurality of conductor sections separated from one another by the predetermined longitudinal positions such that each one of the conductor sections has a section length; and the insulating intermediate piece is provided with an intermediate piece length being at least 0.5% and at most 4% of the section length.

3. The method according to claim 1: wherein the insulating intermediate piece has an intermediate piece length that is at least 0.5% and at most 4% of 100 m.

4. The method according to claim 1, further comprising: providing a sleeve-shaped adapter element, and providing the insulating intermediate piece with an intermediate piece length; the two conductor ends being spaced apart by the intermediate piece length; and connecting each of the two conductor ends to the insulating intermediate piece via the sleeve-shaped adapter element.

5. The method according to claim 1, wherein the insulating intermediate piece is configured as a flexible, tension-resistant element.

6. The method according to claim 1, wherein the insulating intermediate piece includes a tension-resistant core and an insulating sheathing which surrounds the tension-resistant core.

7. The method according to claim 1, further comprising: providing an injection-molded joint; and surrounding each of the conductor ends by the injection-molded joint which is in turn surrounded by the continuous insulating sheath.

8. The method according to claim 1, wherein the continuous insulating sheath is configured with at least two layers having different materials that have different dielectric constants.

9. The method according to claim 8, wherein one of the at least two layers is produced from polytetrafluoroethylene (PTFE) and is sintered.

10. The method according to claim 1, wherein the cable core has a length extending in a longitudinal direction; and the insulating intermediate piece and the conductor are aligned in the longitudinal direction such that the cable core has a substantially identical diameter over the length of the cable core.

11. The method according to claim 1, wherein the recess is formed by a cylindrical and profiled internal wall.

12. The method according to claim 1, further comprising: attaching an adapter element to each end of the insulating intermediate piece to form a prepared intermediate piece, the adapter element being a conductor piece similar or identical to the conductor used for the sheathless conductor; and attaching a respective one of the one of the two conductor ends to a respective adapter element.

13. The method according to claim 1, further comprising separating the conductor at the predetermined longitudinal positions such that a section having a particular length is separated out of the conductor.

14. The method according to claim 1, further comprising separating the intermediate piece into at least two subsections following a connection at a separation point.

15. The method according to claim 1, further comprising providing the conductor with a plurality of sheathless conductor sections and providing a plurality of intermediate pieces, each of the plurality of intermediate pieces separating two of the plurality of sheathless conductor sections from one another such that the plurality of sheathless conductor sections and the plurality of intermediate pieces form a continuous strand; wherein the continuous insulating sheath is extruded directly onto the continuous strand consisting of the plurality of sheathless conductor sections and the plurality of intermediate pieces.

16. A method producing a cable, further comprising: providing a plurality of cable cores, each of the plurality of cable cores manufactured by the method according to claim 1; and stranding the plurality of cable cores together to form the cable.

17. The method according to claim 16, wherein the step of stranding the plurality of cable cores together includes: providing a plurality of core bundles, wherein each one of the plurality of core bundles is formed by stranding some of the plurality of cable cores together; providing a plurality of part-cables, wherein each one of the plurality of part-cables is formed by stranding some of the plurality of core bundles together; and stranding the plurality of part-cables together to form the cable.

18. The method according to claim 16, further comprising disposing an insulating intermediate piece at each particular longitudinal position, the insulating intermediate piece having an intermediate piece length corresponding to at least 0.5% and at most 4% of a section length of 100 m.

19. The method according to claim 16, further comprising manufacturing the cable with a non-round cross-sectional area in a manner of a rounded triangle.

20. The method according to claim 16, further comprising combining the plurality of cable cores as a ribbon cable such that a plurality of conductors are disposed in a plane alongside one another and the continuous insulating sheath functions as a common, extruded insulating sheath.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIGS. 1A to 1C are illustrations showing a production of a cable core according to the invention;

(2) FIG. 2 is a longitudinal sectional view showing the cable core with an intermediate piece;

(3) FIG. 3 is a longitudinal sectional view showing a further cable core with a prepared intermediate piece for connecting two conductor ends;

(4) FIG. 4 is a longitudinal sectional view showing the further cable core with an alternative intermediate piece;

(5) FIG. 5 is a longitudinal sectional view showing the further cable core with the alternative intermediate piece;

(6) FIG. 6 is a longitudinal sectional view showing a further cable core containing a conductor in the form of a hollow wire;

(7) FIG. 7 is a longitudinal sectional view showing a further cable core with a long intermediate piece;

(8) FIG. 8 is a longitudinal sectional view showing a further cable core with a long intermediate piece;

(9) FIG. 9 is a cross sectional view showing a cable; and

(10) FIG. 10 is a cross sectional view showing an alternative embodiment of the cable according to FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

(11) Referring now to the figures of the drawings in detail and first, particularly to FIGS. 1A-1C thereof, there is shown a method for producing a cable core in a view in longitudinal section. In this regard, FIG. 1A shows a conductor 4 in the form of a raw wire which is separated at predetermined longitudinal positions 6, forming an intermediate space 8. To this end, a punching tool 10 having a punching direction S is provided in the exemplary embodiment shown here, the punching tool 10 punching a section 14 with a predetermined length L out of the conductor 4, forming two separation points, wherein two conductor ends 16 are formed.

(12) FIG. 1B shows the conductor ends 16 with an intermediate piece 18 arranged in between. The intermediate piece 18 has two end faces 20 at a predetermined spacing A from one another, wherein this spacing is expediently identical to the separated-out length L1. The conductor ends 16 are connected, for example welded, to the intermediate piece 18.

(13) In the exemplary embodiment illustrated, the intermediate piece 18 and the conductor 4 each have the same diameter and are thus aligned with one another.

(14) After the introduction of the intermediate piece 18, a conductor strand similar to a raw wire is formed, which is provided so to speak as an endless strand, that is to say as what is known as material obtainable by the meter, and can be used for example for the subsequent process steps and if necessary also be temporarily stored in a manner rolled up on a reel. The conductor strand is composed of a multiplicity of conductor sections in particular of identical length, which are each connected to an intermediate piece 18.

(15) Each particular conductor 4 typically has a diameter in the region of a few millimeters, in particular 1 to 3 mm. It is in particular a solid wire, in particular copper wire. The latter is preferably provided with a coating, for example a nickel coating or silver coating. The layer thickness is in this case a few micrometers, for example 1 to 1.5 μm.

(16) The intermediate piece 18 has a length in the region of a few millimeters, for example in the range of 3 to 10 mm and in particular in the region of 5 mm. Accordingly, the spacing between the opposite conductor ends 16 amounts to the length of the intermediate piece 18. The intermediate piece 18 is in the form of a cylindrical intermediate piece in the exemplary embodiment.

(17) The spacing between two successive intermediate pieces 18 in the longitudinal direction and thus the length of each particular conductor section is typically in the region of several tens of meters, for example in the region of 50 m or a multiple thereof, for example in the region of about 100 m. The intermediate pieces 18 are in this case arranged in a manner spaced apart from one another at such a defined contact spacing having this spacing length. The overall length of such a cable core 2 is in the range of several hundred meters to several kilometers.

(18) Following the provision of such a conductor strand consisting of individual conductor segments, connected to the intermediate pieces 18, an insulating sheath 22 is applied, as illustrated in FIG. 1C, the insulating sheath 22 being extruded on from a plastics material here. In this case, the insulating sheath 22 has a constant diameter D1 along the entire cable core 2, in particular also in the region of the intermediate piece 18.

(19) FIGS. 2 to 6 schematically show further exemplary embodiments of the cable core 2 in a view in longitudinal section. Shown in each case is a detail of the cable core 2 in the region of the intermediate piece 18 fitted in the intermediate space 8.

(20) The intermediate piece 18 illustrated in FIG. 2 is embodied in one piece and in a substantially cylindrical manner, with a lateral surface 24 which is provided with an undulating profile. As a result, leakage currents are avoided and the safety of the cable core 2 with regard to partial discharges is increased. Furthermore, the intermediate piece 18 is aligned with the conductor 4. The end faces 20 are formed in a concave manner in the exemplary embodiment shown here. Each of the two end faces 20 is assigned an end face 21 of one of the conductor ends 16, which is formed in a correspondingly complementary manner, that is to say in this case in a convex manner. The end faces 20 are metalized and welded to each particular conductor end 16.

(21) The intermediate piece 18 is produced from a ceramic in the exemplary embodiment shown here. Alternatively, the intermediate piece 18 is produced from plastics material. In a further alternative, not shown here, the intermediate piece 18 is configured as an injection-molding and is formed directly between the two conductor ends 16 by a suitable injection mold. As a result, it is expediently possible to produce the intermediate piece 18 with a precise fit.

(22) FIG. 3 shows an alternative exemplary embodiment of the cable core 2, with a prepared intermediate piece 18, to each of the end faces 20 of which an adapter element 19 is fastened which is in the form of a conductor section here and is produced in particular from the same material as the conductor 4. As a result of the combination of the intermediate piece 18 with an adapter elements 19, a prepared intermediate piece 18 is formed. The latter is connected to the conductor ends 16 by the adapter elements 19, in the exemplary embodiment shown here by a cold welding method, preferably by a soldering method, in particular brazing. The adapter element 19 is in particular a few millimeters long, for example 1 to 5 mm. It preferably consists of the same material as or at least a similar material to the conductor 4.

(23) FIG. 4 shows an alternative intermediate piece 18 which in this case contains two core end caps 26. In particular, the intermediate piece 18 illustrated here is separated at a separation point 28. The separation can be realized here either directly by the use of two core end caps 26 or alternatively by an intermediate piece 18 in the form of a joint that is severed after being connected to the conductor ends 16.

(24) The core end caps 26 each have a head 30 which contains in particular the end face 20. From the head 30, an annular collar 32 extends in the longitudinal direction R. The collar 32 has profiling on its internal wall 34, the profiling being a thread in this case. Furthermore, the collar 32 extends around a cylindrical recess with a predetermined depth T. The conductor ends 16 have a reduced diameter D2 at a length L2, which expediently corresponds to the depth T, and have been screwed into the core end cap 26. In an alternative configuration, the cutout is conical and the conductor ends 16 are likewise formed in a conical manner in a correspondingly complementary manner thereto.

(25) The heads 30 of the core end caps 26 bear against one another in the exemplary embodiment shown here, and the insulating sheathing 22 is embodied in a continuous manner in this case. In an alternative configuration, the two core end caps 26 are connected together, for example adhesively bonded or welded. The conductor ends 16 fitted in the core end caps 26 can also be adhesively bonded or welded in addition.

(26) FIG. 5 shows a further exemplary embodiment. In the figure, the intermediate piece 18 is embodied as two core end caps 26 which have been fitted on the conductor ends 16 and fastened by a press-fit. To this end, each particular conductor end 16 is cooled and inserted into the core end cap 26. In an embodiment that is not shown here, the core end cap 26 has a profiled internal wall 34 and/or a profiled end face 20 which is developed as per one of the abovementioned configurations.

(27) As FIG. 5 shows, the core end cap 26 has a diameter D3 which is greater than the diameter D4 of the conductor 16. In order that the intermediate piece 18 does not become too thick, the insulating sheath 22 is embodied in a thinner manner in the region of the intermediate piece 18.

(28) A further exemplary embodiment of the cable core is illustrated in FIG. 6. Therein, the conductor 4 is in the form of a hollow wire having a cavity 4a extending in the longitudinal direction R. The cavity 4a has an inside diameter D5 transversely to the longitudinal direction. At the conductor ends 16, the intermediate piece 18 has been inserted in the cavity 4a by means of suitably configured protrusions 18a. In an embodiment that is not shown here, the protrusions 18a have a thread or some other profiling on an internal lateral surface bearing against the cavity 4a, in order to improve the stability of the connection. In a further alternative configuration, the cavity 4a is filled with a strain relief means which is advantageously connected cohesively to the protrusions 18a.

(29) FIGS. 7 and 8 each show a preferred variant of the cable core 2, in which the intermediate piece 18 is in the form of a long intermediate piece 18. This is connected to the connector end 16 by an adapter element 19 in a similar manner to in FIG. 3 and is thus configured in particular as a prepared intermediate piece 18. In this case, FIG. 7 illustrates in each case a complete conductor section 4′ and an intermediate piece 18 adjoining it. The intermediate piece 18 has a sleeve-like adapter 19 at each of its ends, for connecting to a particular conductor section 4′ at each particular longitudinal position 6. FIG. 8 shows only one longitudinal position 6, i.e. only one of two ends of the intermediate piece 18, which is connected to the conductor end 16 via the adapter element 19; an analogous connection takes place at the other end, not shown here. The conductor 4 is in this case divided into conductor sections 4′ which each have a section length L3 which corresponds to the spacing between two conductor ends 16 of a conductor section 4′.

(30) In the exemplary embodiment shown in FIGS. 7 and 8, the intermediate piece 18 has a certain intermediate piece length Z which corresponds to about 1 to 4% of the section length L3. For a section length L3 of about 100 m, the intermediate piece 18 is then for example about 2 m long. In this way, a production-related offset of several intermediate pieces 18 at a separation point 12 is compensated. As a result of the intermediate piece length Z, an overlap of the long intermediate pieces 18 transversely to the longitudinal direction R of the cable 2 is ensured in this case.

(31) Here, the intermediate piece is additionally in the form of a flexible, tension-resistant element and contains a tension-resistant core 18b of aramid and an insulating sheathing 18c, surrounding the core 18b, of PFA.

(32) In FIGS. 7 and 8, the adapter element 19 is in the form of a brass sleeve into the ends of which the intermediate piece 18 and the conductor end 16 of the conductor section 4′ are inserted. The entire arrangement is surrounded by a joint 35 which is configured as an injection-molding and is preferably made of PFA. In this case, the joint 35 completely surrounds the adapter element 19 and the conductor end 16 attached thereto. Advantageously, the joint 35 additionally fills the interstice formed by the adapter element 19 in each case with the conductor section 4′ and the intermediate piece 18.

(33) In order to form the cable core, the insulating sheath 22 is finally applied around this overall arrangement, the insulating sheath 22 being embodied in three layers in the exemplary embodiments in FIGS. 7 and 8, in a manner not shown in more detail, specifically with an internal taping of modified PTFE, a further taping of PTFE applied thereto, and an external layer of extruded PFA, wherein the two tapings are additionally sintered.

(34) In FIG. 7, a further insulating layer 22′ of PFA is additionally arranged inside the insulation 22. By contrast, in FIG. 8, the conductor section 4′ is surrounded by an additional conductor insulation 33 which is omitted at the conductor ends 16, however.

(35) The cable cores 2 in FIGS. 7 and 8 are then preferably produced such that the conductor 4 is initially split up into a plurality of conductor sections 4′ and an adapter element 19 is placed on each of the conductor ends 16 formed thereby. Subsequently, a long intermediate piece 18 is inserted into the respectively remaining end of an adapter element 19, the intermediate piece 18 then being arranged between the two conductor ends 16. The adapter element 19 is then in particular squeezed in order to fix the conductor end 16 respectively fitted therein and the intermediate piece 18. Subsequently, each particular adapter element 19 is encapsulated with PFA to form the joint 35. The entire arrangement is optionally surrounded by an insulating layer 22′ of PFA along its length. Finally, the continuous insulating sheath 22 is applied. To this end, first of all simple or double taping with PTFE, which is subsequently sintered, is carried out; finally, an outermost layer of PFA is extruded on.

(36) In order to produce a cable 36, a number of cable cores 2 are stranded together. An exemplary embodiment of such a cable 36 is illustrated schematically in cross section in FIG. 9. The cable 36 shown here contains three stranded-together part-cables 38. Each of the part-cables 38 contains six core bundles 42 stranded around a strain relief device 40. Each of these core bundles 42 in turn has eighteen cable cores 2 which are arranged around a strain relief device 44. In this case, the core bundle 42 has an internal layer 46 containing six cable cores 2 and an external layer 48 containing twelve cable cores 2. The internal layer 46, the external layer 48, the part-cable 38 and the entire cable 36 are preferably each surrounded by an additional sheath 50, which for example is extruded on or embodied as a taping.

(37) In a variant embodiment, the internal layer 46 and/or the external layer 48 are configured in each case as a ribbon cable with six and twelve conductors 4, respectively, and are wrapped around the strain relief device 44 in the manner of a taping method. As a result, the manufacturing outlay for the core bundle 42 and thus in particular also for the entire cable 36 is reduced.

(38) The cable 36 shown in FIG. 9 additionally has a sensor module 52 having a sensor 54. In order to generate an induction field, a current and a voltage are applied to each of the cable cores 2 at a predetermined frequency. The sensor 54 is then for example a Hall sensor, by which the sensor module 52 monitors the induction field. In an embodiment that is not shown here, a number of functional lines are provided in the cable 36, for example temperature sensors configured as optical fibers. These are then connected to one or more sensor modules 52.

(39) An alternative configuration of the cable according to FIG. 9 is shown in FIG. 10. In this case, the outermost sheath 50 surrounding the three part-cables 38 is embodied as a taping. The resulting cross-sectional profile of the cable is as a result a triangle with rounded corners.

(40) In the case of the cables 36 illustrated in FIGS. 9 and 10, the individual core bundles 42 are each formed as stranded elements with a 1-6-12 stranding of individual elements. The central strand is in this case configured as a strain relief device 44. The core bundle 42 produced in such a way has for example a diameter in the range of about 8 to 15 mm, in particular in the region of about 12 mm.

(41) The individual part-cables 38 are in turn configured as a stranded assembly consisting of the central strain relief means 40 and six core bundles 42 stranded around the latter. In the exemplary embodiment, this stranded assembly is still surrounded, although it does not have to be, by a sheath which is configured for example as an injection-molded, extruded sheath 50 or as a taping for example by means of a polyester tape. This part-cable 38 preferably has a diameter in the region of a few centimeters, for example in the range of 2.5 to 6 cm, and in particular in the region of about 4 cm.

(42) Expediently, a central strain relief core is additionally introduced, in a manner not illustrated in more detail, between the total of three part-cables 38.

(43) The maximum width of the cable 36, i.e. in the case of FIG. 9 the diameter and in the case of the triangular configuration according to FIG. 10 a side length of the isosceles triangle, is in turn several centimeters, in particular about 6 to 12 cm and preferably about 8 cm. The three part-cables 38 are in turn stranded together. Both cable types according to FIGS. 9 and 10 are expediently also surrounded by a sheath 50 which is formed by an extrusion method. Expediently, it has a sheath thickness in the region of a few millimeters, in particular in the range of 2.5 to 5 mm.

(44) The cable 36 formed has a length of preferably several 100 meters to a few kilometers.

(45) The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: 2 Cable core 4 Conductor 4a Cavity 4′ Conductor section 6 Longitudinal position 8 Intermediate space 10 Punching tool 12 Separation point 14 Section 16 Conductor end 18 Intermediate piece 18a Protrusion 18b Core 18c Sheathing 19 Adapter element 20 End face (intermediate piece) 21 End face (conductor) 22 Insulating sheath 22′ Insulating layer 24 Lateral surface 26 Core end cap 28 Separation point 30 Head 32 Collar 33 Conductor insulation 34 Internal wall 35 Joint 36 Cable 38 Part-cable 40 Strain relief means (part-cable) 42 Core bundle 44 Strain relief means (core bundle) 46 Internal layer 48 External layer 50 Sheath 52 Sensor module 54 Sensor A Spacing D1 Diameter (insulating sheath) D2 Diameter (conductor end) D3 Diameter (core end cap) D4 Diameter (conductor) D5 Inside diameter L1 Length L2 Length (conductor end) L3 Section length R Longitudinal direction S Punching direction T Depth Z Intermediate piece length