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Patent 2342604 Summary

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(12) Patent: (11) CA 2342604
(54) English Title: SUPERCONDUCTING LEADS
(54) French Title: FILS DE CONNEXION SUPRACONDUCTEURS
Status: Expired and beyond the Period of Reversal
Bibliographic Data
(51) International Patent Classification (IPC):
  • H01R 4/68 (2006.01)
(72) Inventors :
  • SPILLER, DARREN MICHAEL (United Kingdom)
  • WEBB, MICHAEL PATRICK (United Kingdom)
  • BEDUZ, CARLOS (United Kingdom)
  • YANG, YIFENG (United Kingdom)
(73) Owners :
  • PRYSMIAN CABLES & SYSTEMS LIMITED
(71) Applicants :
  • PRYSMIAN CABLES & SYSTEMS LIMITED (United Kingdom)
(74) Agent: KIRBY EADES GALE BAKER
(74) Associate agent:
(45) Issued: 2007-05-15
(86) PCT Filing Date: 1999-09-09
(87) Open to Public Inspection: 2000-03-16
Examination requested: 2004-09-08
Availability of licence: N/A
Dedicated to the Public: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): Yes
(86) PCT Filing Number: PCT/US1999/020526
(87) International Publication Number: WO 2000014827
(85) National Entry: 2001-03-09

(30) Application Priority Data:
Application No. Country/Territory Date
9819545.6 (United Kingdom) 1998-09-09

Abstracts

English Abstract


A superconducting lead comprises a supporting board (1) with at least one
superconducting tape (3) adhered to it and extending from one terminal area of
the lead
to another. Respective metal end-fittings soldered to the superconducting tape
(3) at each
of its ends, and in each of the terminal areas at least one metal insert is
bonded to the
board (1) and also soldered to the corresponding one of the said end-fittings,
so relieving
the tapes (3) of mechanical stress. The board (1), or each of them, is
preferably flat and
may support two or more superconducting tapes (3) coplanar with one another on
one or
on each of its major faces. The metal inserts are preferably of copper and may
be made
by removing most of the copper cladding from a commercially available circuit
board (1).


French Abstract

L'invention porte sur un fil de connexion supraconducteur qui comprend une carte support (1) à laquelle est fixé au moins un ruban supraconducteur (3) s'étendant d'une zone d'extrémité du fil à une autre. Des raccords d'extrémité métalliques respectifs sont soudés à chaque extrémité du ruban supraconducteur (3) et, à chaque zone d'extrémité, au moins une pièce métallique est fixée à la carte (1) et soudée également au raccord d'extrémité qui lui correspond pour libérer les rubans (3) de la contrainte mécanique. La carte (1), ou chaque carte, est de préférence plate et peut recevoir deux ou plusieurs rubans supraconducteurs (3) coplanaires l'un avec l'autre, sur une ou chacune de ses principales faces. de préférence, De préférence, les pièces métalliques sont en cuivre et peuvent être fabriquées par élimination de la majeure partie du surfaçage en cuivre d'une carte à circuits imprimés (1) disponible dans le commerce.

Claims

Note: Claims are shown in the official language in which they were submitted.


Claims:
1. A superconducting lead comprising a supporting
board, at least one superconducting tape adhered to the
supporting board, a terminal member forming a metal end-
fitting soldered to the superconducting tape at each end
of the supporting board and at least one metal insert
bonded to the supporting board and soldered to the
corresponding one of the said metal end-fittings.
2. A superconducting lead comprising two terminal
members, a supporting board extending between the
terminal members, at least one superconducting tape
adhered to the supporting board, wherein each terminal
member forms a metal end-fitting soldered to the
superconducting tape at respective ends of the
supporting board and at each end of the supporting board
a metal insert bonded to the supporting board and
soldered to the corresponding one of the said metal end-
fittings.
3. A superconducting lead as claimed in claim 1 or
claim 2, wherein the board is flat and supports two or
more superconducting tapes coplanar with one another on
one or on each major face of the board.
4. A superconducting lead as claimed in claim 1 or
claim 2, wherein the metal inserts and the terminal
members are copper.
5. A superconducting lead as claimed in claim 1 or
claim 2, wherein the metal inserts and the terminal
members, are of high conductivity oxygen-free copper.
7

6. A superconducting lead as claimed in claim 1 or
claim 2, wherein the metal inserts are rectangular
strips along an edge of the board.
7. A superconducting lead as claimed in claim 1 or
claim 2, further comprising two or more said boards
which differ in width, with or without the number of
tapes differing.
8. A superconducting lead as claimed in claim 1 or
claim 2, wherein each superconducting tape is coated to
protect said tape from contact with coolant.
9. A superconducting lead as claimed in claim 8
further comprising a tubular shroud with apertures for
vapour flow.
10. A superconducting lead as claimed in claim 1 or
claim 2, further comprising a closely fitting enclosure
and potting resin in remaining clearances.
11. A superconducting lead as claimed in claim 1 or
claim 2, wherein the terminal members project laterally.
8

Description

Note: Descriptions are shown in the official language in which they were submitted.


CA 02342604 2001-03-09
WO 00/14827 1 PCT/US99/20526
Superconducting Leads
This invention relates to superconducting leads,
primarily for use as "current leads", meaning (as customary
among superconductivity experts) leads for conveying current
to a apparatus operating at a cryogenic temperature from a
source at a substantially higher temperature. In most
applications the cryogenic temperature will be a "liquid
helium" temperature in the vicinity of 4K and the higher
temperature will be liquid nitrogen temperature (around 77K)
or lower.
Superconducting current leads are preferred, when the
level of the higher temperature makes it possible, both
because their own losses electrical are smaller than for
comparable metal current leads and also because they can have
substantially higher thermal resistance and often appreciably
reduce overall refrigeration losses of the apparatus.
Superconducting current leads have been made with "bulk"
ceramic superconductor powder, either compressed and sintered
into self-supporting blocks or packed into a silver (or
silver alloy) tube and suitably compressed. They have also
been made with ceramic superconductors in tape form, as they
would now normally be used for winding coils or making power
cables. However, "bulk" superconductor leads are brittle,
mechanically weak, and are liable to be destroyed if fault
conditions lead to loss of superconductivity; superconducting
tapes are self-protecting from such faults as the
silver/silver alloy content is sufficient to carry the
current as a normal conductor for short periods and they are
flexible and somewhat more resistant to thermal cycling
shock, but they still have little inherent strength, and as
the thermal stresses are necessarily rather large in a
current lead operating with its ends at very different
temperatures and subject at least occasionally to cycles to
room temperature, they need mechanical support.
One satisfactory way of giving mechanical support is to
bond the tapes with a suitable adhesive to support (this may

CA 02342604 2004-09-08
be of various cross-sections but our own preference is
that it should be flat and for convenience we refer to
it as a "board") of a resin-bonded fibre glass or other
material having thermal expansion characteristics
reasonably similar to those of the tape. Even then,
substantial stresses arise at the terminations, where
the tapes will normally be connected to a solid copper
conductor by soldering, and it is the applicants'
experience that this may result in partial or complete
failure of the soldered connection and that, even under
favourable conditions, the contact resistance at the two
terminations may account for as much as a fifth of the
total losses in the current lead.
It is an object of the invention to provide a
superconducting lead suitable for use as a current lead
in which the terminations are secure and the terminal
contact resistance stabilised at a low value.
In accordance with one aspect of the present
invention there is provided a superconducting lead
comprising a supporting board, at least one
superconducting tape adhered to the supporting board, a
terminal member forming a metal end-fitting soldered to
the superconducting tape at each end of the supporting
board and at least one metal insert bonded to the
supporting board and soldered to the corresponding one
of the said metal end-fittings
In accordance with another aspect of the present
invention there is provided a superconducting lead
comprising two terminal members, a supporting board
extending between the terminal members, at least one
superconducting tape adhered to the supporting board,
wherein each terminal member forms a metal end-fitting
soldered to the superconducting tape at respective ends
of the supporting board and at each end of the
2

CA 02342604 2004-09-08
supporting board a metal insert bonded to the supporting
board and soldered to the corresponding one of the said
metal end-fittings.
The superconducting lead in accordance with an
exemplary embodiment of the present invention comprises
a supporting board, at least one superconducting tape
adhered to the supporting board, a terminal member
forming a metal end-fitting soldered to the
superconducting tape at an end of the supporting board
and at least one metal insert bonded to the supporting
board and soldered to the metal end-fitting.
In this way, longitudinal mechanical stresses can
be carried from the end-fittings directly to the board,
bypassing and so relieving of stress the soldered joints
to the tape.
There may be more than one board, and the board, or
each board as the case may be, may support any
convenient number of superconducting tapes. Preferably
the board, or each of them, is flat and supports two or
more tapes coplanar with one another on one or on each
of its major faces, so that the whole flat side and both
edges of each tape are accessible for soldering without
requiring a complex shape for the terminal member.
However, two or three tapes (or more, at an
2a

CA 02342604 2001-03-09
WO 00/14827 3 PCT/US99/20526
increasing penalty) can be superposed on one another if
compactness is of over-riding importance.
The metal inserts, as well as the terminal members, are
preferably of copper, especially high-condutivity
5"oxygen-free" copper(and the terminal members preferably
plated with gold or silver). They are conveniently simple
rectangular strips along (or parallel and close to) the
appropriate edges of the board. Strips only a few millimetres
wide are effective and considerered adequate, but if desired
they could be wide enough to facilitate reinforcement by
drilling to accomodate a transverse pin of metal or other
hard material.
Suitable boards with copper very strongly bonded over
substantially its whole area is readily available as it is
widely used to make circuit boards for electronics
applications. One suitable board is a resin-bonded fibreglass
board clad with about 35um of copper and coated with a
positive working photoresist to comply with BS 4581, sold
under the trademark "Fotoboard" and grade code "FR4" by Mega
Electronics. Copper can be removed, except for the required
inserts, by imagewise exposure to UV light, development and
etching (for which the board is designed) or by machining. It
is the applicants' understanding that this board is made by
in-situ curing of the fibre-bonding resin on a pre-formed and
specially prepared (etched) copper sheet.
Preferably the (or each) superconducting tape is bonded
to the board over the whole area of the tape. A suitable
adhesive is manufactured by Grace Specialty Polymers and sold
in the United Kingdom by Emerson Cumming (UK) Ltd under the
trademark "Eccobond 286" and is understood to be an epoxy
resin product filled with an oxide of aluminium or of
zirconium to improve matching of thermal expansion
characteristics.
The lead may incorporate two or more boards with
superconducting tapes as described, preferably but not
necessarily arranged parallel to one another; they may be

CA 02342604 2001-03-09
WO 00/14827 4 PCT/US99/20526
alike (typically resulting in a rectangular cross-section) or
may differ in width (with or without the number of tapes
differing), for example to give an overall round cross-
section.
Silver/silver alloy clad ceramic superconductor tapes
can be successfully soldered to the terminal members by a
suitable solder; we prefer solders comprising (by weight)
equal parts of lead and bismuth or 2 parts of lead, 5 parts
of bismuth and 3 parts of tin, but ordinary tin/lead eutectic
solder can be used.
If it is desired that the lead should be "vapour-
cooled", the superconducting tape(s) is/are preferably coated
to protect from contact with coolant; Nova Tran Ltd offer a
custom coating service under the trademark "Parylene" and for
this coating a thickness of about 30-40 um is recommended;
but other coatings can be used. The applicants do not know
whether the process operated by Nova Tran Ltd (described as a
gas phase deposition) resembles the technique using pyrolysed
poly-para-xylylene described in US patent 4508760. In most
such cases a tubular shroud with appropriate apertures for
vapour flow will be added after coating.
If "vapour-cooling" is not desired, then we prefer to
protect the lead by adding a closely-fitting enclosure and
"potting" by introduction of a suitable hardening resin (such
as Eccobond 286 referred to above) into the remaining
clearances. Such enclosure is suitable made from a resin-
bonded fibre glass material similar to the material of the
board or boards; a suitable material is sold by Tufnol Ltd
under their trademark TUFNOL and the product code 10G/40.
The terminal members may project axially for external
connection, but where the installation geometry permits we
prefer that they project laterally, so as to accomodate the
maximum length of superconductor, and thus minimise thermal
conductance of the lead.
The invention will be further described, by way of
example, with reference to the accompanying drawing in which:

CA 02342604 2001-03-09
Ficrure 1 is a partly dxagrammatic elevation of an end part of one
form of lead in accordance with the invention;
Figure 2 is a cross-section on the line II-TI in Figure 1;
5 and
Fiaure 3 is an elevation, corresponding to Figure 1, showi an
alternative foz-Ltt of lead in accordance with the invention a d
incorporating a number of independent options; this figure hows
the lead in an unfurnislzed condition, as wz.ll be expZained elow.
The lead of Figures 1 and 2 is based azi a narrow strip of
double-aided FOTflBOP.RD circuit board 1 with the copper laye s
entirely etched away except for narrow stri.ps 2,'~at each end;(only
one end is shown, the other may be identical). On each of tLhe so
exposed faces of the board superconductxng tapes 3 each consisting
of one or ntore "filament" of a"hzgh temperature', ceramic
euperconducting material (preferably of the BISCCO faniily) ayre
adhered using Eccobond 286 iow-exnansion opoxy adhesive. 1'rie end of tbo
board is Insert.e.d in a slot in s gold-plated coppez
terminal member 4 and banded to it by a solder 5 consisting pf '!
equal parts by weight of lead and bismuth. The solder bonds
securely hoth to the tapes 3 (providing a low-resistance
electrical con,necci.on) nnci Le the eopper sLr~.ps 2 (providing a
strong ntechanical coruzection rrom the board 7. to the terminal
meccwer 4 which is wholly independent of the tapes 3).
2S T_n the case of a vapour-cooled lead, the exposed sur.EaeL of
the ta,pes (aricl opr.i,onally those of the bonr.de as well) are ttiinly
coated with tfie PARYLENF, polymer coat--ng idcntified above and the
board enclosed by 3 plastics shroud 6 provided with openings 7 for
tlze flow of c:oolant.
Note thaL in t.hie design, LtLe: terminaZ metuber 4 cXt_ends to
. ti
the side of tlze leac3 propcr - it 3s a"fla3" rather than a sPadell
type termirial. Tl:i:, pesmit:: t',je superconciuctizig, and L=elaLiveJ.y
thermally insulatiny, pdrt oL r_lae Icad to be as long as che n4tur!.
of the ir_:;tall at ion pe.Lmics.
The a7t=rnativy de:,ign t;hown in r=igu.Le 3~11u: trat.rs a
AMEWED S~~

CA 02342604 2001-03-09
6 i
number of variazts, any of which may be used separately as well as
together.
First, it is a"spade" type terminal wich the axes of the
lead and the terminal member coincident, and so it is sua.t IC for
direct substitution for a conventional current lead of simi ar
shape.
Second, it comprises tw4 similar boards 1 for increas d
supercurrent capacity. Higher numbers can be used, and difrereat
widths of board with the same or different nucnbers of tapes can be
used to tneeZ design requirements: for example, three paraZzel
boards with the central one wider than the others allows an
approximation to circular cross-sectiori, when desired.
Third, it is not intendccl for use with vapour cooling. C,
Consequent].y, instead of coating the tapes and adding an opd.n
tubular housing, the assembly is cocnpleted by a jacket made up of
two cornponents of resin-bonded fibreglass (TUFNOL IQG/40) ma!chined
to fit around the boards and tcrminal members with only a sm~a11
clearance. Figure 3 shoWs one of the9e jacket eontponents 91in
place and om~te the other for clarity_ Once both componezats, are
in place, the rernainir_9 clearancen B are filled with an epoxjr
resin by a vacuum ;mpregnaL-ion technique to form a Lu11y potred
l ead.
C~ .
AMENDED SHEET

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

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Event History

Description Date
Time Limit for Reversal Expired 2010-09-09
Letter Sent 2009-09-09
Letter Sent 2007-10-30
Letter Sent 2007-10-30
Letter Sent 2007-08-15
Grant by Issuance 2007-05-15
Inactive: Cover page published 2007-05-14
Pre-grant 2007-03-05
Inactive: Final fee received 2007-03-05
Notice of Allowance is Issued 2006-09-18
Letter Sent 2006-09-18
Notice of Allowance is Issued 2006-09-18
Inactive: Approved for allowance (AFA) 2006-07-27
Letter Sent 2004-09-28
Amendment Received - Voluntary Amendment 2004-09-08
Request for Examination Requirements Determined Compliant 2004-09-08
All Requirements for Examination Determined Compliant 2004-09-08
Request for Examination Received 2004-09-08
Letter Sent 2001-09-19
Letter Sent 2001-09-19
Inactive: Single transfer 2001-08-09
Inactive: Cover page published 2001-05-29
Inactive: First IPC assigned 2001-05-23
Inactive: Notice - National entry - No RFE 2001-05-11
Application Received - PCT 2001-05-02
Inactive: Courtesy letter - Evidence 2000-05-15
Application Published (Open to Public Inspection) 2000-03-16

Abandonment History

There is no abandonment history.

Maintenance Fee

The last payment was received on 2006-08-23

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  • the late payment fee; or
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Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
PRYSMIAN CABLES & SYSTEMS LIMITED
Past Owners on Record
CARLOS BEDUZ
DARREN MICHAEL SPILLER
MICHAEL PATRICK WEBB
YIFENG YANG
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Representative drawing 2001-05-29 1 4
Abstract 2001-03-09 1 63
Description 2001-03-09 6 301
Claims 2001-03-09 2 66
Drawings 2001-03-09 1 30
Cover Page 2001-05-29 1 33
Description 2004-09-08 7 323
Claims 2004-09-08 2 63
Representative drawing 2007-04-27 1 5
Cover Page 2007-04-27 1 39
Reminder of maintenance fee due 2001-05-10 1 111
Notice of National Entry 2001-05-11 1 193
Courtesy - Certificate of registration (related document(s)) 2001-09-19 1 137
Courtesy - Certificate of registration (related document(s)) 2001-09-19 1 136
Reminder - Request for Examination 2004-05-11 1 116
Acknowledgement of Request for Examination 2004-09-28 1 185
Commissioner's Notice - Application Found Allowable 2006-09-18 1 161
Maintenance Fee Notice 2009-10-21 1 170
Correspondence 2001-05-11 1 24
PCT 2001-03-09 20 770
PCT 2001-04-06 1 50
Correspondence 2007-03-05 1 37