CA1236540A - Method and apparatus for providing extremely low- resistance connection between the end sections of two superconductors - Google Patents
Method and apparatus for providing extremely low- resistance connection between the end sections of two superconductorsInfo
- Publication number
- CA1236540A CA1236540A CA000457700A CA457700A CA1236540A CA 1236540 A CA1236540 A CA 1236540A CA 000457700 A CA000457700 A CA 000457700A CA 457700 A CA457700 A CA 457700A CA 1236540 A CA1236540 A CA 1236540A
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- Prior art keywords
- superconductors
- superconductive
- connecting device
- welding
- welding mould
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R4/00—Electrically-conductive connections between two or more conductive members in direct contact, i.e. touching one another; Means for effecting or maintaining such contact; Electrically-conductive connections having two or more spaced connecting locations for conductors and using contact members penetrating insulation
- H01R4/58—Electrically-conductive connections between two or more conductive members in direct contact, i.e. touching one another; Means for effecting or maintaining such contact; Electrically-conductive connections having two or more spaced connecting locations for conductors and using contact members penetrating insulation characterised by the form or material of the contacting members
- H01R4/68—Connections to or between superconductive connectors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/10—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating making use of vibrations, e.g. ultrasonic welding
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F6/00—Superconducting magnets; Superconducting coils
- H01F6/06—Coils, e.g. winding, insulating, terminating or casing arrangements therefor
- H01F6/065—Feed-through bushings, terminals and joints
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N60/00—Superconducting devices
- H10N60/80—Constructional details
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/32—Wires
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Manufacturing Of Electrical Connectors (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
- Pressure Welding/Diffusion-Bonding (AREA)
- Connections Effected By Soldering, Adhesion, Or Permanent Deformation (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus and method for connecting the end sections of two superconductors which are to be cooled down to cryogenic operating temperatures wherein each of the superconductors contains at least one superconducting conductor filament embedded in a matrix of normal-conducting stabilizing material is disclosed. The ends of the superconducting conductor filaments are stripped at least partially of the stabilizing material, are directly placed together and welded to each other, and an electrically highly-conducting bridge of normal-conducting material is formed between the stabilizing material of the superconductors. In order to assure an extremely low-resistance connection between the ends of the superconducting conductor filaments, it is provided that these ends be joined together by ultrasonic metal welding. In particular, the ends can be arranged in a special welding form and at least partially welded to the welding form.
An apparatus and method for connecting the end sections of two superconductors which are to be cooled down to cryogenic operating temperatures wherein each of the superconductors contains at least one superconducting conductor filament embedded in a matrix of normal-conducting stabilizing material is disclosed. The ends of the superconducting conductor filaments are stripped at least partially of the stabilizing material, are directly placed together and welded to each other, and an electrically highly-conducting bridge of normal-conducting material is formed between the stabilizing material of the superconductors. In order to assure an extremely low-resistance connection between the ends of the superconducting conductor filaments, it is provided that these ends be joined together by ultrasonic metal welding. In particular, the ends can be arranged in a special welding form and at least partially welded to the welding form.
Description
i5'~0 BACKGROUND OF THE INVENTION
_ _ _ _ The present invention relates to a method and an apparatus for providing extremely low-resistance connections between the end sections of two superconductors which are to be cooled to cryogenic operating tempera-tures wherein each superconductor contains at least one superconducting conductor filament embedded in a matrix of normal-conducting stabilizing material, and wherein the ends of these superconducting conductor filaments are stripped at least partially of the stabilizing material, are placed in contact and are welded to each other, and wherein an electrically highly conducting bridge of normal-conducting material is developed between the stabilizing material of the superconductors.
For superconducting magnet coil windings, so-called short circuit operation may be required. Once the magnetic field of the magnet winding is built up, the ends of the winding can be short-circuited by means of an extremely low-resistance persistent-current switch for storing the electric energy fed into the winding. The current then flows in -the so-des:igned short circuit and the power supply required Eor exciting -the magnet w:inding can thereEore be interrupted. The attenuation of the current, i.c., its decreasc behavior, then depends essentially on the contact resistances between the individual superconducting parts of the circuit.
Such contact resistances occur not only at the continuous-current switch but are found also in connections of the end sections of individual super-conductor parts, of which the magnet winding is generally comprised.
In nuclear magnetic resonance apparatus, great constancy of the field generated by the field magnets of the apparatus over time is 5~0 generally required. High-resolution systems with superconducting field coils are therefore available which operate as a short circuit. Corres-ponding systems of nuclear spin tomography mustJ for instance, have a constancy of the field in time of ~ B/B clo 7, where B is the magnetic field induction. The total resistance in the circuit of the magnet wind-ing, which is composed of the resistance contribution of the conductor connections within the winding and the contact resistance of the persist-ent current switch must therefore be smaller than 2 X 10-9 ohm for an inductance of 74 H. Since the individual magnet windings of such a system are composed, for instance, of 17 individual conductor sections, a contact resistance of approximately 10 11 ohm is desired for a single connection between the end sections of two superconductors.
Connecting devices with contact resistances of this small magnitude can generally be produced by superconducting contacts. The con-ductor wires of multifilament conductors are, for instance, joined directly together without the interposition of normal-conducting materials.
SUCh 1 joining technique is indicated, for :instance in German OS 1 939 224. According to this technique, the ends of these conductor wires are stripped of the stabilizing material at the end sections of two super-conductors which are to be joined together. As explained, the superconduc-tors generally contain several superconducting conductors embedded in normal-conducting stabilizing material. Subsequently, the conductors are directly placed together and finally joined together with low resistance, for instance7 by welding or soldering. So as not to interrupt the stabilization in the I1 ~23~;Sq~
.
1 ~ vicinity of the connecting device provided in thi3 matter~ a
_ _ _ _ The present invention relates to a method and an apparatus for providing extremely low-resistance connections between the end sections of two superconductors which are to be cooled to cryogenic operating tempera-tures wherein each superconductor contains at least one superconducting conductor filament embedded in a matrix of normal-conducting stabilizing material, and wherein the ends of these superconducting conductor filaments are stripped at least partially of the stabilizing material, are placed in contact and are welded to each other, and wherein an electrically highly conducting bridge of normal-conducting material is developed between the stabilizing material of the superconductors.
For superconducting magnet coil windings, so-called short circuit operation may be required. Once the magnetic field of the magnet winding is built up, the ends of the winding can be short-circuited by means of an extremely low-resistance persistent-current switch for storing the electric energy fed into the winding. The current then flows in -the so-des:igned short circuit and the power supply required Eor exciting -the magnet w:inding can thereEore be interrupted. The attenuation of the current, i.c., its decreasc behavior, then depends essentially on the contact resistances between the individual superconducting parts of the circuit.
Such contact resistances occur not only at the continuous-current switch but are found also in connections of the end sections of individual super-conductor parts, of which the magnet winding is generally comprised.
In nuclear magnetic resonance apparatus, great constancy of the field generated by the field magnets of the apparatus over time is 5~0 generally required. High-resolution systems with superconducting field coils are therefore available which operate as a short circuit. Corres-ponding systems of nuclear spin tomography mustJ for instance, have a constancy of the field in time of ~ B/B clo 7, where B is the magnetic field induction. The total resistance in the circuit of the magnet wind-ing, which is composed of the resistance contribution of the conductor connections within the winding and the contact resistance of the persist-ent current switch must therefore be smaller than 2 X 10-9 ohm for an inductance of 74 H. Since the individual magnet windings of such a system are composed, for instance, of 17 individual conductor sections, a contact resistance of approximately 10 11 ohm is desired for a single connection between the end sections of two superconductors.
Connecting devices with contact resistances of this small magnitude can generally be produced by superconducting contacts. The con-ductor wires of multifilament conductors are, for instance, joined directly together without the interposition of normal-conducting materials.
SUCh 1 joining technique is indicated, for :instance in German OS 1 939 224. According to this technique, the ends of these conductor wires are stripped of the stabilizing material at the end sections of two super-conductors which are to be joined together. As explained, the superconduc-tors generally contain several superconducting conductors embedded in normal-conducting stabilizing material. Subsequently, the conductors are directly placed together and finally joined together with low resistance, for instance7 by welding or soldering. So as not to interrupt the stabilization in the I1 ~23~;Sq~
.
1 ~ vicinity of the connecting device provided in thi3 matter~ a
2 ¦ special bridge of the stabilizing material is further provided
3 between the stabilizing material.
4 In order to obtain extremely low contact resistances 1l of the order of magnitude mentioned above~ the superconducting 6 1I conductor filaments can be brought into contact directly by 7 mechanical pressure. Such a method i5 described, for 8 1l in3tance, in U.S. Patent 3,422,529. According to thi3 known g Imethod, two superconducting conductor filaments are twisted o lltogether~ then taken to an appropriate pressing mold and 11 finally joined together by cold deformation.
12 ,~ Since, as is well known, superconducting alloy~ such 13 as NbTi or Nb~r have a strong affinity to oxygen, their ¦ surfaces are always coated with an oxide layer which, in )l addition, is normal-conducting. So that a low-resistance 16 ~Isuperconducting contact can be made with these superconducting 17 ~I materials, the interfering oxide layer mu~t therefore be 18 1l removed at the contact point. In the above-mentioned method, 19 1l a special cleaning treatment of the superconducting oonductor 20 ¦I filament~ and the mold by means of a chemical cleaning 21 1 solution is provided before the individual parts of the 22 ¦I connecting devlce are connected together. Due to the pressure 23 ' action, direct contact or welding at individual contact points 24 ~1 is thus made possible. Nevertheless, it has been found that I such connecting devices have only a relatively small current-2~ I carrying capacity and, in addition, exhibit a distinct 27 li decrease of the critical current with the magnetic field 28 1l applied, vis-a-vis the superconducting original conducting 29 1I material.
30 ¦I SUMMARY OF THE INYENTION
. ll -3-s~o It is an object of the present invention to provide a method and apparatus for connecting the end sections of two superconductors in such a manner that their contact resistance is extremely lowO
It is a further object to provide such a connecting apparatus and method which meets the mentioned requirements for magnet windings of nuclear spin (nuclear magnetic resonance) tomography systems.
The above and other objects of the present invention are achieved in a superconducting connecting device and method wherein the superconducting conductor filaments are joined together by means of ultrasonic metal welding.
Thus, in accordance with a broad aspect of the invention, there is provided a connecting device for joining end pieces of two superconductors which are to be cooled down to cryogenic operating temperature and which each contain superconductive conductor filaments embedded in a matrix of normaLly conducting tabilising material, where the enas of the ~a superconducting conductor filaments which are to be connected are stripped of the stabilising material, brought into direct contact with one another, and welded to one another, and where an electrically highly conductive bridge of normally conductive material is provided bewteen the stabilising material of the superconductors, characterised in that the ends of the superconducting conductor filaments of the two superconductors to be connected and which have been etched out of the matrix ~23b~S~
material are inserted into one another, placed intermingled in a welding mould, and by means of ultrasonic metal welding are connected to one another and at least in part also to the welding mould.
In accordance with another broad aspect of the invention there is provided a connecting device between the end pieces of two superconductors which are to be cooled down to cryogenic operating temperature and which each contain superconductive conductor filaments embedded in a matrix of normally conductive stabilising material, where the superconductive conductor filaments which are to be connected are partially stripped of the stabilising material, brought into direct contact with one another, and welded to one another, and where an electrically highly conductive bridge of normally conducting material is provided between the stabilising material of the superconductors, characterised in that the superconductors have a layer made of a plurality of superconductive conductor filaments twisted together; that at the ends of the superconductors on one side in each case, a window-like zone of the superconductive conductor filaments is exposed by etching away the stabilising material, the extension of these window-like zones in the longitudinal direction of the conductors being a multiple of the twist length of the individual superconductive conductor filaments and that the superconductive conductor filaments are connected to one another within the window-like zones by ultrasonic metal welding.
h~ 4 ~
1~;3~;S4(:~
Ultrasonic metal welding is generally known per se.
See, for instance, "Der Elektriker", 1978, nos. 7/8, pages 190 and 191, or "Werkstatt and Betrieb", vol. 114, 1981, no. 7, pages 441 to 443 or "DVS-Berichte", vol. 70, 1981, pages 128 to 135. This welding technique is also used for joining superconducting and normal-conducting material in the production of stabilized superconductors. See e.g., German Patent 16 65 790. It has now been discovered that with this weldlng technique, joints can also be made advantageously between two superconducting conductor wires in a relatively simple manner and with extremely low resistance. By using ultrasonic metal welding, the oxide coatings on the individual superconductin~ conductor wires can be broken up and removed as planned, so that an intimate weld with a large area can be achieved at the mutual contact place. Special pretreatments of the parts to be welded together can therefore be dispensed with.
Other objects, features and advantages oE the present invention will be apparent from a reading of the - 4b -~' Z3~;5~0 !~
1 ¦ detailed description which follows.
3 1I The invention will be explained in detail in the 4 1~ following detailed description, with reference to the drawings ~l in which:
6 ¦~ FIG. 1 shows one embodiment of a joining device 7 1 according to the present invention in perspective view;
8 1l FIG 2 is a cross sectional view of the joining 9 ~Idevice shown in FIGS. 1;
i FIGS. 3 and 4 show, respectively, a top and side 11 I view of a superconducting end section of a further connecting 12 l~device according to the present invention which can be made with the machine indicated in FIG. 5; and FIG. 5 is a side view of the machine for making the I connecting device shown in FIGS. 3 and 4.
~ _ 17 With reference now to the drawing~, FIG. 1 shows 18 I schematically the essential parts of a connecting device 19 according to the invention. Thi3 connecting device is to be I developed between the end section~ 2 and 3 of two 21 I multifilament superconductor3 of a superconducting magnet 22 I winding, such as must be provided particularly for a System 23 ¦I for nuclear spin tomography. Each superconductor contains a 24 1I multiplicity of superconducting conductor filaments 4 which 1', are embedded in a matrix material 5 of normal-conducting 26 1I stabilizing material ~uch as copper or aluminum. In the 27 ¦' vicinity of the ~oint to be made, the matrix material 5 is 28 1; etched off the superconducting conductor filament~ 4 and the 29 11 ends 4' of the conductor filament~ exposed in this manner are I pushed or twi~ted together to form a bundle. In this bundle, 65~3 i 1 !I conductor filament ends 4' are arranged mixed advantageously 2 ~ as well as possible, 50 that conductor filaments of the one 3 I superconductor end section 2 and of the other end section 3 4 1 meet in an alternating fashion, as well as possible. The 1I conductor filament ends 4' are placed in a metal profile piece 6 'l~ 6 of U-shaped cross section which serves as the welding form 7 1l and is covered with a mating metal plate. The U-shaped piece 1~ , 8 1 and the cover 7 may comprise an electrically and thermally g ll highly conducting material such as copper. Also harder I materials such as CuSn, ~u~e, and NbTi are particularly well 11 , suited because these materials can couple the ultrasonic 12 1 energy efficiently into the filament zone of the arrangement.
13 1 In addition, also material pairings such as Cu U-profiles with 14 1l inserted NbTi bottom and cover can also be used.
l According to the invention, the superconducting 16 1I conductor filament ends 4~ which are in~erted into the welding 17 ll form and are covered by the cover 7 are joined together by 18 I means of ultrasonic metal weldine. The ultrasonic energy is 19 I coupled-in, for ln3tance, via an appropriately profiled 20 ¦¦ ~onotrode which generates longitudinal vibrations. The 21 ¦1 sonotrode is placed on the cover 7 with a predetermined 22 pressure. Parameters in ultrasonic metal welding are the 23 ll welding time and the amplitude of the energy, besides the 24 !! contact pressure~ Typical welding times are between 0.7 to 3 25 ¦l ~ec ~or amplitudes of about 20 um, while the contact 2S 1¦ pres~ure is variable between 70 and 120 No 20 kHz, for 27 ~ instance, can be chosen as the ultrasonic frequency. However, 2~ I it is also possible to work with frequencies in the sound 29 ~I range in addition to frequencies in the ultrasonic range.
3~ ¦ If welding forms 6 and covers 7 are made of copper, , ; -6-1~3~;5~
1 l¦ thls material can be coupled by ~oldering to additional 2 I stabilizing ~aterial which, after the ultrasonic metal 3 l welding, subsequently takes up the entire joint. For this 4 purpose, a copper tube or sleeve 8, for instance, can be provided. As is indicated in the figure by dashed lines, this 6 l sleeve is closed in the circumferential direction. It is 7 Islipped over the welded joint and is soldered to it with a 8 l, normal-conducting s~lder, for instance, PbSn or AgSn solder, 9 ' or in particular with a superconducting solder such as PbBi.
j' This measure can lead to an increase of the current-carrying 11 capacity by a factor of about 1.5.
12 I FIG. 2 shows a cross section of the joint made accordingly in the region of the welding die 6. Parts coinciding with FIG. 1 are provided here with the same I referenoe symbols. In particular, the superconducting soft 16 I solder 9 dispersed within the stabilizing sleeve 8, is 17 Il illustrated, which surrounds the conductor wire end~ 4' in the 18 ll welding form 6 welded to each other and optionally also to the 19 1 weldin~ form.
1 A~ ls further indlcated in FIG. 1, the two end 21 1l sections 2 and 3 of the superconductors to be joined are ~2 I placed against each other with their flat sides adjacent and 23 il are soldered together over a large area. This purpose is 24 ll served by a normal-conducting soft solder 11, which provides 25 ll an electrically highly conducting bridge between the 26 !I stabilizing material 5 of the two superconductors in the 27 1 region of the connecting device.
28 , For the further stabilization of the welded joint, 29 1 additional material can also be inaorporated into the U-shaped 30 ll welding form 6 prior to the welding operation. For instance, ~2~S~o i 1 I copper wires or chips can be placed into the inside region of 2 , the filament zone. An internally stabilized conductor 3 ~ arrangement thereby is obtained after the welding. In a 4 ~ similar manner, inserting additional superconducting filaments ll or chips of suitable dimensions leads to an increased packing 6 l density and an increased number of contact points between the 7 superconductlng conductor filament ends. In particular, voids 8 within the junction can thereby be eliminated.
9 According to the embodiment shown in FIGS. 1 and 2, it was assumed that the end sections of superconducting 11 multifilament conductors are to be joined together. The 12 ll connecting device according to the invention is suited equally 13 I well, however, for joining ~tabilized superconductors with 14 only a ~ingle conductor wire. Also conductors with very thin 15 1I superconductor filaments and single-layer filament zones can 16 l~ be joined together in accordance with the invention. An 17 1 embodiment of the end section of a conductor of the last-18 ¦¦ mentioned type i~ schematically illustrated in FIG. 3 in a top 19 I view and in FIG. 4 in a side view. In each conductor end ~ection 13, a window 14 is etched on one side out of the 21 enclosing stabilizing matrix 15 so that a corresponding zone 22 ~ 16 of the conductor wire is exposed on one side. The axial 23 ll extent of the window 14 is advantageously provided o~ a length 24 1I which is a multiple of the twist lay of the individual 25 ll conductor wire, whereby all exposed conductor wires 26 ¦I participate uniformly in the current transfer. The welding 27 ll can be accomplished advantageously in a rolled-seam welding 2~ 1¦ machine such as is indicated schematically, for instance, in 29 ~, FIG. 5 in a side view onto the end face of the welded end 30 ll sections. Parts identical with FIGS. 3 and 4 are indicated by 1'
12 ,~ Since, as is well known, superconducting alloy~ such 13 as NbTi or Nb~r have a strong affinity to oxygen, their ¦ surfaces are always coated with an oxide layer which, in )l addition, is normal-conducting. So that a low-resistance 16 ~Isuperconducting contact can be made with these superconducting 17 ~I materials, the interfering oxide layer mu~t therefore be 18 1l removed at the contact point. In the above-mentioned method, 19 1l a special cleaning treatment of the superconducting oonductor 20 ¦I filament~ and the mold by means of a chemical cleaning 21 1 solution is provided before the individual parts of the 22 ¦I connecting devlce are connected together. Due to the pressure 23 ' action, direct contact or welding at individual contact points 24 ~1 is thus made possible. Nevertheless, it has been found that I such connecting devices have only a relatively small current-2~ I carrying capacity and, in addition, exhibit a distinct 27 li decrease of the critical current with the magnetic field 28 1l applied, vis-a-vis the superconducting original conducting 29 1I material.
30 ¦I SUMMARY OF THE INYENTION
. ll -3-s~o It is an object of the present invention to provide a method and apparatus for connecting the end sections of two superconductors in such a manner that their contact resistance is extremely lowO
It is a further object to provide such a connecting apparatus and method which meets the mentioned requirements for magnet windings of nuclear spin (nuclear magnetic resonance) tomography systems.
The above and other objects of the present invention are achieved in a superconducting connecting device and method wherein the superconducting conductor filaments are joined together by means of ultrasonic metal welding.
Thus, in accordance with a broad aspect of the invention, there is provided a connecting device for joining end pieces of two superconductors which are to be cooled down to cryogenic operating temperature and which each contain superconductive conductor filaments embedded in a matrix of normaLly conducting tabilising material, where the enas of the ~a superconducting conductor filaments which are to be connected are stripped of the stabilising material, brought into direct contact with one another, and welded to one another, and where an electrically highly conductive bridge of normally conductive material is provided bewteen the stabilising material of the superconductors, characterised in that the ends of the superconducting conductor filaments of the two superconductors to be connected and which have been etched out of the matrix ~23b~S~
material are inserted into one another, placed intermingled in a welding mould, and by means of ultrasonic metal welding are connected to one another and at least in part also to the welding mould.
In accordance with another broad aspect of the invention there is provided a connecting device between the end pieces of two superconductors which are to be cooled down to cryogenic operating temperature and which each contain superconductive conductor filaments embedded in a matrix of normally conductive stabilising material, where the superconductive conductor filaments which are to be connected are partially stripped of the stabilising material, brought into direct contact with one another, and welded to one another, and where an electrically highly conductive bridge of normally conducting material is provided between the stabilising material of the superconductors, characterised in that the superconductors have a layer made of a plurality of superconductive conductor filaments twisted together; that at the ends of the superconductors on one side in each case, a window-like zone of the superconductive conductor filaments is exposed by etching away the stabilising material, the extension of these window-like zones in the longitudinal direction of the conductors being a multiple of the twist length of the individual superconductive conductor filaments and that the superconductive conductor filaments are connected to one another within the window-like zones by ultrasonic metal welding.
h~ 4 ~
1~;3~;S4(:~
Ultrasonic metal welding is generally known per se.
See, for instance, "Der Elektriker", 1978, nos. 7/8, pages 190 and 191, or "Werkstatt and Betrieb", vol. 114, 1981, no. 7, pages 441 to 443 or "DVS-Berichte", vol. 70, 1981, pages 128 to 135. This welding technique is also used for joining superconducting and normal-conducting material in the production of stabilized superconductors. See e.g., German Patent 16 65 790. It has now been discovered that with this weldlng technique, joints can also be made advantageously between two superconducting conductor wires in a relatively simple manner and with extremely low resistance. By using ultrasonic metal welding, the oxide coatings on the individual superconductin~ conductor wires can be broken up and removed as planned, so that an intimate weld with a large area can be achieved at the mutual contact place. Special pretreatments of the parts to be welded together can therefore be dispensed with.
Other objects, features and advantages oE the present invention will be apparent from a reading of the - 4b -~' Z3~;5~0 !~
1 ¦ detailed description which follows.
3 1I The invention will be explained in detail in the 4 1~ following detailed description, with reference to the drawings ~l in which:
6 ¦~ FIG. 1 shows one embodiment of a joining device 7 1 according to the present invention in perspective view;
8 1l FIG 2 is a cross sectional view of the joining 9 ~Idevice shown in FIGS. 1;
i FIGS. 3 and 4 show, respectively, a top and side 11 I view of a superconducting end section of a further connecting 12 l~device according to the present invention which can be made with the machine indicated in FIG. 5; and FIG. 5 is a side view of the machine for making the I connecting device shown in FIGS. 3 and 4.
~ _ 17 With reference now to the drawing~, FIG. 1 shows 18 I schematically the essential parts of a connecting device 19 according to the invention. Thi3 connecting device is to be I developed between the end section~ 2 and 3 of two 21 I multifilament superconductor3 of a superconducting magnet 22 I winding, such as must be provided particularly for a System 23 ¦I for nuclear spin tomography. Each superconductor contains a 24 1I multiplicity of superconducting conductor filaments 4 which 1', are embedded in a matrix material 5 of normal-conducting 26 1I stabilizing material ~uch as copper or aluminum. In the 27 ¦' vicinity of the ~oint to be made, the matrix material 5 is 28 1; etched off the superconducting conductor filament~ 4 and the 29 11 ends 4' of the conductor filament~ exposed in this manner are I pushed or twi~ted together to form a bundle. In this bundle, 65~3 i 1 !I conductor filament ends 4' are arranged mixed advantageously 2 ~ as well as possible, 50 that conductor filaments of the one 3 I superconductor end section 2 and of the other end section 3 4 1 meet in an alternating fashion, as well as possible. The 1I conductor filament ends 4' are placed in a metal profile piece 6 'l~ 6 of U-shaped cross section which serves as the welding form 7 1l and is covered with a mating metal plate. The U-shaped piece 1~ , 8 1 and the cover 7 may comprise an electrically and thermally g ll highly conducting material such as copper. Also harder I materials such as CuSn, ~u~e, and NbTi are particularly well 11 , suited because these materials can couple the ultrasonic 12 1 energy efficiently into the filament zone of the arrangement.
13 1 In addition, also material pairings such as Cu U-profiles with 14 1l inserted NbTi bottom and cover can also be used.
l According to the invention, the superconducting 16 1I conductor filament ends 4~ which are in~erted into the welding 17 ll form and are covered by the cover 7 are joined together by 18 I means of ultrasonic metal weldine. The ultrasonic energy is 19 I coupled-in, for ln3tance, via an appropriately profiled 20 ¦¦ ~onotrode which generates longitudinal vibrations. The 21 ¦1 sonotrode is placed on the cover 7 with a predetermined 22 pressure. Parameters in ultrasonic metal welding are the 23 ll welding time and the amplitude of the energy, besides the 24 !! contact pressure~ Typical welding times are between 0.7 to 3 25 ¦l ~ec ~or amplitudes of about 20 um, while the contact 2S 1¦ pres~ure is variable between 70 and 120 No 20 kHz, for 27 ~ instance, can be chosen as the ultrasonic frequency. However, 2~ I it is also possible to work with frequencies in the sound 29 ~I range in addition to frequencies in the ultrasonic range.
3~ ¦ If welding forms 6 and covers 7 are made of copper, , ; -6-1~3~;5~
1 l¦ thls material can be coupled by ~oldering to additional 2 I stabilizing ~aterial which, after the ultrasonic metal 3 l welding, subsequently takes up the entire joint. For this 4 purpose, a copper tube or sleeve 8, for instance, can be provided. As is indicated in the figure by dashed lines, this 6 l sleeve is closed in the circumferential direction. It is 7 Islipped over the welded joint and is soldered to it with a 8 l, normal-conducting s~lder, for instance, PbSn or AgSn solder, 9 ' or in particular with a superconducting solder such as PbBi.
j' This measure can lead to an increase of the current-carrying 11 capacity by a factor of about 1.5.
12 I FIG. 2 shows a cross section of the joint made accordingly in the region of the welding die 6. Parts coinciding with FIG. 1 are provided here with the same I referenoe symbols. In particular, the superconducting soft 16 I solder 9 dispersed within the stabilizing sleeve 8, is 17 Il illustrated, which surrounds the conductor wire end~ 4' in the 18 ll welding form 6 welded to each other and optionally also to the 19 1 weldin~ form.
1 A~ ls further indlcated in FIG. 1, the two end 21 1l sections 2 and 3 of the superconductors to be joined are ~2 I placed against each other with their flat sides adjacent and 23 il are soldered together over a large area. This purpose is 24 ll served by a normal-conducting soft solder 11, which provides 25 ll an electrically highly conducting bridge between the 26 !I stabilizing material 5 of the two superconductors in the 27 1 region of the connecting device.
28 , For the further stabilization of the welded joint, 29 1 additional material can also be inaorporated into the U-shaped 30 ll welding form 6 prior to the welding operation. For instance, ~2~S~o i 1 I copper wires or chips can be placed into the inside region of 2 , the filament zone. An internally stabilized conductor 3 ~ arrangement thereby is obtained after the welding. In a 4 ~ similar manner, inserting additional superconducting filaments ll or chips of suitable dimensions leads to an increased packing 6 l density and an increased number of contact points between the 7 superconductlng conductor filament ends. In particular, voids 8 within the junction can thereby be eliminated.
9 According to the embodiment shown in FIGS. 1 and 2, it was assumed that the end sections of superconducting 11 multifilament conductors are to be joined together. The 12 ll connecting device according to the invention is suited equally 13 I well, however, for joining ~tabilized superconductors with 14 only a ~ingle conductor wire. Also conductors with very thin 15 1I superconductor filaments and single-layer filament zones can 16 l~ be joined together in accordance with the invention. An 17 1 embodiment of the end section of a conductor of the last-18 ¦¦ mentioned type i~ schematically illustrated in FIG. 3 in a top 19 I view and in FIG. 4 in a side view. In each conductor end ~ection 13, a window 14 is etched on one side out of the 21 enclosing stabilizing matrix 15 so that a corresponding zone 22 ~ 16 of the conductor wire is exposed on one side. The axial 23 ll extent of the window 14 is advantageously provided o~ a length 24 1I which is a multiple of the twist lay of the individual 25 ll conductor wire, whereby all exposed conductor wires 26 ¦I participate uniformly in the current transfer. The welding 27 ll can be accomplished advantageously in a rolled-seam welding 2~ 1¦ machine such as is indicated schematically, for instance, in 29 ~, FIG. 5 in a side view onto the end face of the welded end 30 ll sections. Parts identical with FIGS. 3 and 4 are indicated by 1'
5~
~ I
1 ,the ~ame reference qymbols.
2 ll The machine indicated in FIG. 5 contains an upper 3 1Iguide roller 17 which is coupled to an ultrasonic welding 4 ldevice, as well as a corresponding lower counter roller 18.
The regions to be welded of the sections 13 and 13' of the
~ I
1 ,the ~ame reference qymbols.
2 ll The machine indicated in FIG. 5 contains an upper 3 1Iguide roller 17 which is coupled to an ultrasonic welding 4 ldevice, as well as a corresponding lower counter roller 18.
The regions to be welded of the sections 13 and 13' of the
6 ll Superconductors are conducted between the two rollers, whereby
7 !la predetermined contact pressure on the exposed zones of the
8 ' superconducting conductor filaments devoid of the stabilizing
9 llmatrix material 15 and 15'1 respectively, is provided. These I zones, welded together, are designated by reference numeral 11 19 in FIG. 5. In order to guide the end sections, guiding 12 ' slots 20 and 21 matching the dimensions of the respective end 13 sections are provided in the rollers for guiding the end 14 ll sections in the circumferential direction. The welded joint I~made in this manner can then be provided further from the 16 1, outside with additional stabilizing material, for instance, in 17 ¦¦ accordance with the embodiment described in connection with 18 1~ FIGS. 1 and 2.
19 11 In the foregoing specification, the invention has 20 ¦I been de~cribed with reference to specific exemplary 21 ll embodiments thereoE. It will, however, be evident that 22 ll various modifications and changes may be made thereunto 23 without departing from the broader spirit and scope of the 24 ~ invention as set forth in the appended claims. The I specification and drawings are, accordingly, to be regarded in 26 1 an illustrative rather than a re~trietive ~ense.
27 !!
I _g_ , !l I
19 11 In the foregoing specification, the invention has 20 ¦I been de~cribed with reference to specific exemplary 21 ll embodiments thereoE. It will, however, be evident that 22 ll various modifications and changes may be made thereunto 23 without departing from the broader spirit and scope of the 24 ~ invention as set forth in the appended claims. The I specification and drawings are, accordingly, to be regarded in 26 1 an illustrative rather than a re~trietive ~ense.
27 !!
I _g_ , !l I
Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A connecting device for joining end pieces of two superconductors which are to be cooled down to cryogenic operating temperature and which each contain superconductive conductor filaments embedded in a matrix of normally conducting stabilising material, where the ends of the superconducting conductor filaments which are to be connected are stripped of the stabilising material, brought into direct contact with one another, and welded to one another, and where an electrically highly conductive bridge of normally conductive material is provided bewteen the stabilising material of the superconductors, characterised in that the ends of the superconducting conductor filaments of the two superconductors to be connected and which have been etched out of the matrix material are inserted into one another, placed intermingled in a welding mould, and by means of ultrasonic metal welding are connected to one another and at least in part also to the welding mould.
2. A connecting device as claimed in Claim 1, characterised in that the welding mould consists of a U-shaped metal profiled part and a corresponding cover.
3. A connecting device as claimed in Claim 1, characterised in that the welding mould consists at least in part of normally conductive material.
4. A connecting device as claimed in Claim 3, characterised in that the welding mould consists at least in part of electrically highly conductive material, in particular, the stabilising material of the superconductors.
5. A connecting device as claimed in one of Claims 1 to 3, characterised in that the welding mould consists at least in part of superconductive material.
6. A connecting device as claimed in Claim 4, characterized in that the welding mould consists at least in part of superconductive material.
7. A connecting device as claimed in one of Claims 1 to 3, characterised in that the superconductive conductor filament ends and their welding mould are surrounded by superconductive soldering material.
8. A connecting device as claimed in Claim 4 or 6, characterised in that the superconductive conductor filament ends and their welding mould are surrounded by superconductive soldering material.
9. A connecting device as claimed in one of Claims 1 to 3, characterized in that the welding mould consists at least in part of superconductive material and in that the superconductive conductor filament ends and their welding mould are surrounded by superconductive soldering material.
10. A connecting device between the end pieces of two superconductors which are to be cooled down to cryogenic operating temperature and which each contain superconductive conductor filaments embedded in a matrix of normally conductive stabilising material, where the superconductive conductor filaments which are to be connected are partially stripped of the stabilising material, brought into direct contact with one another, and welded to one another, and where an electrically high conductive bridge of normally conducting material is provided between the stabilising material of the superconductors, characterised in that the superconductors have a layer made of a plurality of superconductive conductor filaments twisted together; that at the ends of the superconductors on one side in each case, a window-like zone of the superconductive conductor filaments is exposed by etching away the stabilising material, the extension of these window-like zones in the longitudinal direction of the conductors being a multiple of the twist length of the individual superconductive conductor filaments and that the superconductive conductor filaments are connected to one another within the window-like zones by ultrasonic metal welding.
11. A process for the production of a connecting device as claimed in Claim 10, characterised in that the end pieces of the superconductors which are to be welded are brought between two rollers of a roller seam welder where, through the rollers, each of which is provided with a guide groove adapted to the dimensions of the respective end piece of the superconductor, a predetermined pressure is exerted on the window-like zones of the superconductors which have been freed from the stabilising material and which are to be welded, and where the ultrasonic metal welding is carried out by way of one of the rollers.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3323576.7 | 1983-06-30 | ||
| DE19833323576 DE3323576A1 (en) | 1983-06-30 | 1983-06-30 | EXTREMELY RESISTANT CONNECTING DEVICE BETWEEN THE END PIECES OF TWO SUPER LADDERS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1236540A true CA1236540A (en) | 1988-05-10 |
Family
ID=6202784
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000457700A Expired CA1236540A (en) | 1983-06-30 | 1984-06-28 | Method and apparatus for providing extremely low- resistance connection between the end sections of two superconductors |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0130442B1 (en) |
| JP (2) | JPS6035484A (en) |
| CA (1) | CA1236540A (en) |
| DE (2) | DE3323576A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2498961A (en) * | 2012-02-01 | 2013-08-07 | Siemens Plc | Methods of joining superconducting wires |
| GB2562477A (en) * | 2017-05-12 | 2018-11-21 | Oxford Instruments Nanotechnology Tools Ltd | Joining method |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4584547A (en) * | 1983-12-30 | 1986-04-22 | General Electric Company | Superconducting joint for superconducting wires and coils |
| US4630881A (en) * | 1985-11-04 | 1986-12-23 | General Electric Company | Immediately testable superconductor joint |
| JPH06101255B2 (en) * | 1985-12-13 | 1994-12-12 | 矢崎総業株式会社 | Method of forming branch connection part of wire harness |
| JP2523524B2 (en) * | 1986-08-26 | 1996-08-14 | 株式会社東芝 | Superconducting wire manufacturing method |
| US4901429A (en) * | 1988-02-17 | 1990-02-20 | General Electric Company | Method and apparatus for making a superconducting joint |
| DE4017553C1 (en) * | 1990-05-31 | 1991-09-19 | Kernforschungszentrum Karlsruhe Gmbh, 7500 Karlsruhe, De | |
| JPH055424U (en) * | 1991-07-04 | 1993-01-26 | 積水化学工業株式会社 | Injection molding machine for injection molding |
| GB2260446A (en) * | 1991-10-07 | 1993-04-14 | Hitachi Ltd | Joining superconducting magnet coils |
| DE102006021422B8 (en) * | 2006-05-05 | 2008-06-26 | Schunk Ultraschalltechnik Gmbh | Method of making a passage or end node, and passage or end nodes |
| CN105309042B (en) * | 2013-01-09 | 2017-06-16 | 松下知识产权经营株式会社 | Sensing heating body and induction heating cooking instrument |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3422529A (en) * | 1963-12-09 | 1969-01-21 | North American Rockwell | Method of making a superconductive joint |
| GB1073207A (en) * | 1966-04-28 | 1967-06-21 | Mullard Ltd | Forming electrical connections |
| DE1665790C3 (en) * | 1966-10-25 | 1975-12-18 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Process for the production of a conductor composed of superconducting and normally electrically conductive metals |
| CH468095A (en) * | 1967-10-13 | 1969-01-31 | Bbc Brown Boveri & Cie | Process for the electrical connection of the ends of two conductors, at least one of which consists of a hard superconducting material, as well as an electrical connection produced according to this process |
| CH482317A (en) * | 1969-01-31 | 1969-11-30 | Oerlikon Maschf | Connection between stabilized superconductors |
| JPS558202Y2 (en) * | 1975-11-13 | 1980-02-23 |
-
1983
- 1983-06-30 DE DE19833323576 patent/DE3323576A1/en not_active Withdrawn
-
1984
- 1984-06-15 DE DE8484106870T patent/DE3467474D1/en not_active Expired
- 1984-06-15 EP EP84106870A patent/EP0130442B1/en not_active Expired
- 1984-06-28 CA CA000457700A patent/CA1236540A/en not_active Expired
- 1984-06-29 JP JP59134985A patent/JPS6035484A/en active Granted
- 1984-06-29 JP JP59134981A patent/JPS6035478A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2498961A (en) * | 2012-02-01 | 2013-08-07 | Siemens Plc | Methods of joining superconducting wires |
| GB2562477A (en) * | 2017-05-12 | 2018-11-21 | Oxford Instruments Nanotechnology Tools Ltd | Joining method |
| GB2562477B (en) * | 2017-05-12 | 2022-05-18 | Oxford Instruments Nanotechnology Tools Ltd | Joining method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0223993B2 (en) | 1990-05-28 |
| EP0130442B1 (en) | 1987-11-11 |
| DE3467474D1 (en) | 1987-12-17 |
| JPS6035484A (en) | 1985-02-23 |
| JPS6035478A (en) | 1985-02-23 |
| EP0130442A1 (en) | 1985-01-09 |
| DE3323576A1 (en) | 1985-01-10 |
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