U.S. patent application number 13/162219 was filed with the patent office on 2011-10-06 for alternating core composite wire.
This patent application is currently assigned to FORT WAYNE METALS RESEARCH PRODUCTS CORPORATION. Invention is credited to Jeremy E. Schaffer.
Application Number | 20110245824 13/162219 |
Document ID | / |
Family ID | 40557905 |
Filed Date | 2011-10-06 |
United States Patent
Application |
20110245824 |
Kind Code |
A1 |
Schaffer; Jeremy E. |
October 6, 2011 |
ALTERNATING CORE COMPOSITE WIRE
Abstract
A wire having an outer shell and a core, the core including at
least a first plurality of core segments that may be made of a
first core material and a second plurality of core segments that
may be made of a second core material different from the first core
material. The first and second core segments are arranged in a
periodic alternating arrangement along the length of the wire. The
outer shell may be made of a metal, such as a biocompatible metal,
and the core segments may be made of different materials to provide
periodic material properties along the length of the wire. The wire
is manufactured by inserting the core segments into the outer shell
to form a wire construct, followed by subjecting the wire construct
to one or more initial draws while applying a compressive force to
the core segments on an upstream side of the die to maintain the
core segments in contact with one another upon dense contact
between the outer shell and core segments, following by closing of
the outer shell onto the core segments, as the wire is pulled
through a drawing die. The resulting wire may then be subjected to
a plurality of finishing draws. Exemplary applications of the wire
include medical devices, such as in vivo heating devices,
thermally-actuated snares, in vivo positioning devices, stents, and
tissue scaffolds.
Inventors: |
Schaffer; Jeremy E.; (Leo,
IN) |
Assignee: |
FORT WAYNE METALS RESEARCH PRODUCTS
CORPORATION
Fort Wayne
IN
|
Family ID: |
40557905 |
Appl. No.: |
13/162219 |
Filed: |
June 16, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12395090 |
Feb 27, 2009 |
7989703 |
|
|
13162219 |
|
|
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|
61032508 |
Feb 29, 2008 |
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Current U.S.
Class: |
606/27 |
Current CPC
Class: |
A61N 1/05 20130101; Y10T
29/49826 20150115 |
Class at
Publication: |
606/27 |
International
Class: |
A61B 18/08 20060101
A61B018/08 |
Claims
1-15. (canceled)
16. A medical device for use in in vivo heating, comprising: a
wire, comprising: an outer shell made of a biocompatible metal; and
a core disposed within said outer shell, said core including a
plurality of first core segments made of a first material having a
first electrical resistance and at least one second core segment
made of a second material, said second material different from said
first material and having a second electrical resistance greater
than said first electrical resistance, said first core segments and
said at least one second core segment arranged in a periodic
alternating arrangement along a length of said wire; and an
insulating layer at least partially covering said wire.
17. The medical device of claim 16, wherein at least a portion of
said at least one second core segment is not covered by said
insulating layer.
18. The medical device of claim 16, wherein said first core
segments are formed of a material selected from the group
consisting of silver, platinum, and tantalum.
19. The medical device of claim 16, wherein said at least one
second core segment is formed of a material selected from the group
consisting of stainless steel, a
cobalt-nickel-chromium-tungsten-iron-manganese alloy, a
nickel-titanium shape memory alloy, and a cobalt-nickel-chromium
alloy.
20. The medical device of claim 16, wherein said outer shell
includes an inner diameter and said core segments each include an
outer diameter equal to said inner diameter of said outer shell
whereby, when viewed in section, each of said core segments
completely fills said outer shell.
21. The medical device of claim 16, wherein said at least one
second core segment is disposed at a distal end of said medical
device and is exposed from said layer of insulating material and
twisted in an outwardly splayed fashion.
22. The medical device of claim 16, wherein at least a portion of
said wire is twisted into a double helix profile.
23. The medical device of claim 16, further comprising a
temperature measurement feedback device.
24. The medical device of claim 16, wherein said temperature
measurement feedback device is selected from a thermocouple and a
thermistor, and is disposed proximate said at least one second core
segment.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under Title 35, U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application Ser. No.
61/032,508, entitled ALTERNATING CORE COMPOSITE WIRE, filed on Feb.
29, 2008, the disclosure of which is expressly incorporated by
reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a wire having an outer
shell and a core disposed within the outer shell, the wire being
manufactured via a drawing process and useful in medical
applications, for example.
[0004] 2. Description of the Related Art
[0005] Medical grade wires, and medical leads and/or devices that
include medical grade wires, are disclosed in U.S. patent
application Ser. Nos. 10/524,387 and 11/203,986, published as U.S.
Patent Application Publication Nos. 2006/0106443 and 2006/0106444,
respectively, each assigned to the assignee of the present
application, the disclosures of which are expressly incorporated
herein by reference.
[0006] These wires generally include a metal outer shell and a core
disposed within the outer shell. The outer shell and the core are
each made of biocompatible metals and, in some embodiments, the
core may include a plurality of twisted wire strand elements each
including a metallic tube filled with a metal. To manufacture the
wire, the wire strand elements are inserted within the outer shell
to form a wire construct, followed by drawing the wire construct
down to reduce the diameter of the wire construct, wherein the wire
strand elements are compacted together within the outer shell such
that substantially no voids exist within the outer shell.
Optionally, the drawn wire may be coated with an insulation layer
and incorporated into a medical device, such as a medical lead, for
example.
[0007] In this manner, the wire includes an outer shell containing
a plurality of wire elements that may be differently constructed
for providing different properties to the wire. These types of
wires will have the same construction, in cross section, along
their entire length.
SUMMARY OF THE INVENTION
[0008] The present invention provides a wire having an outer shell
and a core, the core including at least a first plurality of core
segments that may be made of a first core material and a second
plurality of core segments that may be made of a second core
material different from the first core material. The first and
second core segments are arranged in a periodic alternating
arrangement along the length of the wire. The outer shell may be
made of a metal, such as a biocompatible metal, and the core
segments may be made of different materials to provide periodic
material properties along the length of the wire. The wire is
manufactured by inserting the core segments into the outer shell to
form a wire construct, followed by subjecting the wire construct to
one or more initial draws while applying a compressive force to the
core segments on an upstream side of the die to maintain the core
segments in contact with one another upon dense contact between the
outer shell and core segments, following by closing of the outer
shell onto the core segments, as the wire is pulled through a
drawing die. The resulting wire may then be subjected to a
plurality of finishing draws.
[0009] In one embodiment, the core segments may be formed of first
and second metals having different properties such as atomic
weight, shape memory, or electrical resistance, for example. In
another embodiment, the core segments may be formed of one or more
metals together with one or more polymeric materials to provide
differing properties such as electrical resistance or
radiofrequency-opacity, for example. Also disclosed is a method for
selectively marking the outer shell to indicate the presence of
certain core sections along the length of the wire.
[0010] In one form thereof, the present invention provides a wire,
including an outer shell made of a biocompatible metal; and a core
disposed within the outer shell, the core including a plurality of
first core segments made of a first material and at least one
second core segment made of a second material different from the
first material, the first and second core segments arranged in a
periodic alternating arrangement along a length of the wire.
[0011] In another form thereof, the present invention provides a
method of manufacturing a wire, including the steps of: providing
an outer shell made of a biocompatible metal; inserting a plurality
of first core segments and at least one second core segment into
the outer shell to form a wire construct, the first and second core
segments disposed in a periodic alternating arrangement along a
length of the outer shell; and drawing the wire construct from a
first outer diameter to a second outer diameter less than the first
outer diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention itself will be better understood by
reference to the following description of embodiments of the
invention taken in conjunction with the accompanying drawings,
wherein:
[0013] FIG. 1A is longitudinal sectional view of a portion of a
wire in accordance with a first embodiment of the present
invention;
[0014] FIG. 1B is a cross sectional view taken along line 1B-1B of
FIG. 1;
[0015] FIG. 1C is a cross sectional view taken along line 1C-1C of
FIG. 1;
[0016] FIG. 2A is a longitudinal sectional view through an outer
shell, showing insertion of core segments within the outer shell to
form a wire construct;
[0017] FIG. 2B is a longitudinal sectional view through a die,
showing the drawing of the wire construct of FIG. 2A;
[0018] FIG. 3A is a longitudinal sectional view through a wire
construct showing the initial clearance between the outer shell and
the core segments;
[0019] FIG. 3B is a sectional view taken along line 3B-3B of FIG.
3A;
[0020] FIG. 3C is a longitudinal sectional view through a die,
showing the drawing of the wire construct of FIG. 3A using a back
support rod;
[0021] FIG. 4A is longitudinal sectional view of a portion of a
wire in accordance with a second embodiment of the present
invention;
[0022] FIG. 4B is a cross sectional view taken along line 4B-4B of
FIG. 4A;
[0023] FIG. 4C is a cross sectional view taken along line 4C-4C of
FIG. 4A;
[0024] FIG. 5A is a longitudinal sectional view of a portion of a
wire in accordance with a third embodiment of the present
invention;
[0025] FIG. 5B is a cross sectional view taken along line 5B-5B of
FIG. 5A;
[0026] FIG. 5C is a cross sectional view taken along line 5C-5C of
FIG. 5A;
[0027] FIG. 5D is a cross sectional view taken along line 5D-5D of
FIG. 5A;
[0028] FIG. 6A is a view of a portion of a wire in accordance with
a fourth embodiment of the present invention, shown in a first
orientation;
[0029] FIG. 6B is longitudinal sectional view of a portion of the
wire of FIG. 6A;
[0030] FIG. 6C is a cross sectional view taken along line 6C-6C of
FIG. 6B;
[0031] FIG. 6D is a cross sectional view taken along line 6D-6D of
FIG. 6B;
[0032] FIG. 6E is a view of a portion of a wire in accordance with
a fourth embodiment of the present invention, shown in a second
orientation;
[0033] FIG. 7 is a view of a portion of a wire including a core
made of different core segments;
[0034] FIG. 8 is a view illustrating a first exemplary method of
marking the outer shell of the wire of FIG. 7 to indicate the
location of one or more of the core segments thereof;
[0035] FIG. 9 is a view illustrating a second exemplary method of
marking the outer shell of the wire of FIG. 7 to indicate the
location of one or more of the core segments thereof;
[0036] FIG. 10A is a longitudinal sectional view of an in vivo
heating apparatus including a wire made in accordance with the
present invention;
[0037] FIG. 10B is a fragmentary sectional view of a portion of the
distal end of the apparatus of FIG. 10A;
[0038] FIG. 10C is a sectional view taken along line 10C-10C of
FIG. 10B;
[0039] FIG. 10D is a sectional view taken along line 10D-10D of
FIG. 10B; and
[0040] FIG. 11A is a longitudinal sectional view of a thermally
activated snare device including a wire made in accordance with the
present invention, shown in a relatively low temperature state;
[0041] FIG. 11B is a sectional view taken along line 11B-11B of
FIG. 11A;
[0042] FIG. 11C is a sectional view taken along line 11C-11C of
FIG. 11A;
[0043] FIG. 11D is a perspective view of the device of FIG. 11A,
shown in a relatively high temperature state;
[0044] FIG. 12A is a longitudinal sectional view of a thermally
activated linear motion device for in vivo positioning or
mechanical actuation, including a wire made in accordance with the
present invention, shown in a relatively low temperature state;
[0045] FIG. 12B is a longitudinal sectional view of the device of
FIG. 12A, shown in a relatively high temperature state;
[0046] FIG. 13A is a perspective view of a tissue scaffold or stent
including a wire made in accordance with the present invention;
[0047] FIG. 13B is a sectional view taken along line 13B-13B of
FIG. 13A;
[0048] FIG. 13C is a sectional view taken along line 13C-13C of
FIG. 13A;
[0049] FIG. 13D is a sectional view taken along line 13D-13D of
FIG. 13A;
[0050] FIG. 14A is a perspective view showing the manufacture of
individual wire segments from a long wire, each made in accordance
with the present invention;
[0051] FIG. 14B is a fragmentary view of a wire segment obtained
from the wire of FIG. 14A; and
[0052] FIG. 15 is a plot of electrical resistance and ultimate
tensile strength of segments of a wire made in Example 1.
[0053] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate embodiments of the invention, and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION
[0054] Referring to FIGS. 1A-C, wire 20 is shown in accordance with
a first embodiment of the present invention, referred to herein as
an alternating core composite wire, which generally defines a
longitudinal axis and a desired length, and includes outer shell 22
and core 24. Outer tube or shell 22 is formed as a tube and may be
made of a metal such as stainless steel and, in particular, other
biocompatible metals such as titanium, titanium alloys,
cobalt-nickel-chromium alloys, nitinol, platinum, platinum alloys,
tantalum, and tantalum alloys, for example. Outer shell 22 may be
formed as a uniform and continuous surface or jacket, such that
wire 20 may be coiled, braided, or stranded as desired.
[0055] Specific materials for outer shell 22 include ASTM F562
cobalt-nickel-chromium alloys, such as MP35N.RTM. and 35N LT.RTM.,
available from Fort Wayne Metals Research Products Corp. of Fort
Wayne, Ind., including the materials disclosed in U.S. patent
application Ser. No. 10/656,918 (published as U.S. Patent
Application Publication No. 2005/0051243), entitled
"cobalt-chromium-nickel-molybdenum alloys with reduced level of
titanium nitride inclusions", assigned to the assignee of the
present application, the disclosure of which is expressly
incorporated herein by reference. Other suitable materials for
outer shell 22 include ASTM F1058
cobalt-chromium-nickel-molybdenum-iron alloys, such as FWM
1058.TM., nickel-titanium shape memory alloys, such as NiTiNOL,
cobalt-nickel-chromium-tungsten-iron-manganese alloy, such as L605
alloy, 300 series stainless steels or other similar metals also
available from Fort Wayne Metals Research Products Corp. of Fort
Wayne, Ind.
[0056] Core 24 includes a first plurality of core segments 26 made
of a first material and a second plurality of core segments 28 made
of a second material. As may be seen in FIGS. 1A-1C, first and
second core segments 26 and 28 are disposed in a periodic
alternating arrangement along the length of wire 20. The term
"periodic alternating arrangement", as used herein, is meant to
refer to any arrangements in which a core segment of a first type
is followed by a core segment of a second type, and thence by
another core segment of the first type, and so on, to form a
pattern of [A-B-A-B- . . . ], as well as any other arrangement
which demonstrates periodicity along at least a portion of the
length of the wire. For example, one alternative arrangement may
include one core segment 26 of a first type followed by two or more
core segments of a second type to form a pattern of [A-B-B-A-B-B- .
. . ]. Other exemplary patterns include [A-B-C-A-B-C- . . . ],
[A-A-B-B- . . . ], [A-B-C-D-A-B-C-D- . . . ],
and[A-B-A-B-C-A-B-A-B-C- . . . ], etc.
[0057] In this regard, the specific arrangement of the alternating
first and second core segments 26 and 28 and/or additional core
segments may vary, so long as at least some periodicity, or
repeating pattern, is present along at least a portion of the wire.
Also, the lengths of first and second core segments 26 and 28 along
the longitudinal axis of wire 20 may vary, either with respect to
individual core segments 26 or 28 themselves, or between core
segments 26 and core segments 28, for example. As described below,
this feature allows specific and desirable mechanical, electrical,
chemical, and/or other properties to be imparted in a periodic
arrangement along the length of wire 20.
[0058] In one embodiment, the material of first core segments 26
differs from the material of second core segments 28, and first and
second core segments 26 and 28 may be made of the metals set forth
above with respect to outer shell 22, and/or may be made of other
metals such as iron, silver, copper, gold, etc.
[0059] Wire 20 may be made in one embodiment via a process
generally illustrated in FIGS. 2A and 2B, and which is described in
further detail below in connection with FIGS. 3A-3C. In a first
step, an outer shell 22 having a first diameter is provided, which
is subsequently filled with a desired number and arrangement of
core segments, such as first and second core segments 26 and 28 in
an alternating pattern as shown, to form a wire construct 25, as
shown in FIG. 2A. Thereafter, as shown in FIG. 2B, the wire
construct 25 is drawn through a lubricated die 27 from an upstream
side 27a of the die to a downstream side 27b of the die along a
draw direction indicated by arrow A.sub.1 to reduce the diameter of
wire construct 25 from the first diameter to a second, lesser
diameter while compacting core segments 26 and 28 such that the
outer diameters of core segments 26 and 28 is equal to the inner
diameter of outer shell 22. In this manner, when viewed in section
as in FIGS. 1B and 1C, for example, each of the core segments 26
and 28 completely fills the outer shell 22 with no voids present
therebetween. As also shown in FIG. 2B, the drawing of wire
construct 25 results in a length increase of outer shell 22, and a
corresponding length increase in core segments 26 and 28 along the
direction of outer shell 22 from an initial length L.sub.1 to a
final length L.sub.2, which is proportionate to the diameter
reduction, as discussed in detail below. Optionally, either before
or after drawing, or in place thereof, wire 20 may be processed by
hot working, annealing, cleaning, coiling, braiding, and/or
cabling, for example.
[0060] With reference to FIGS. 3A-3C, the drawing of a wire
construct 25 to form wire 20 is described in further detail. In
particular, as described below, wire construct 25 may be drawn in a
manner which ensures that each of the core segments, such as core
segments 26 and 28, are maintained in abutting contact with one
another to provide a uniform periodicity of the core segments
within the drawn wire.
[0061] Referring to FIGS. 3A and 3B, outer shell 22 of wire
construct 25 includes outer diameter d.sub.1 and inner diameter
d.sub.2, and core segments 26 and 28 include outer diameter
d.sub.3. Once core segments 26 and 28 are loaded into outer shell
22 as shown in FIG. 2A and described above to form wire construct
25, there will be a small clearance between inner diameter d.sub.2
of outer shell 22 and outer diameter d.sub.3 of core segments 26
and 28, designated c.sub.1 in FIG. 3A. This clearance c.sub.1 may
vary between the core segments, for example, if core segments 26
and 28 have different outer diameters d.sub.3.
[0062] As described below, when wire 20 is subjected to one or more
initial draws, due to the presence of the clearance c.sub.1 there
will be an initial reduction in the outer diameter d.sub.1, and a
corresponding length increase, of outer shell 22 prior to contact
of the inner diameter d.sub.2 of outer shell 22 with core segments
26 and 28. Thereafter, upon subsequent initial draws, when outer
shell 22 is drawn to a sufficient extent, the inner diameter
d.sub.2 of outer shell 22 will contact core segments 26 and/or 28,
which contact will be referred to hereinafter as dense contact, or
the dense contact point. More than one dense contact point may
exist, for example, when the outer diameter of core segments 26 and
28 is different, with a first dense contact point occurring when
outer shell 22 closes on the core segment having the greater outer
diameter d.sub.3, and a second dense contact point occurring when
outer shell 22 closes on the core segment having the lesser outer
diameter d.sub.3. Just after dense contact, further reduction of
the inner diameter d.sub.2 of outer shell 22 will physically secure
the outer shell 22 to the core segment 26 or 28, or stated
differently, will fix the position of, or capture, the core segment
26 or 28 within the outer shell, and will also begin to reduce the
outer diameter d.sub.3 of the core segments 26 or 28. This will be
referred to hereinafter as closing, or the closing point. The
closing point is chosen such that slight reduction of core segments
26 and/or 28 occurs after dense contact.
[0063] The length increase of outer shell 22 prior to the dense
contact point, the length increase in wire 20 just after the dense
contact point and through the closing point, and the length
increase in wire 20 following the closing point are each described
in detail below.
[0064] During round die reduction of the wire, the cross-sectional
area of outer shell 22 is reduced, and the length of outer shell
increases, at a constant material density. In the initial draws
prior to the dense contact point, the length increase (A) of the
wire is given by formula (I) below:
Start area Final area = .DELTA. = ( d 1 2 - d 2 2 ) ( d 11 2 - d 21
2 ) ( I ) ##EQU00001##
where d.sub.11 is outer diameter corresponding to d.sub.1 of outer
shell 22 after drawing, and d.sub.21 is inner diameter
corresponding to d.sub.2 of outer shell 22 after drawing.
[0065] For a small amount of reduction (<40% by area), and for
an outer shell 22 having a relatively thin wall (wall thickness
<0.35.times.d.sub.1), die reduction of outer shell 22 in the
absence of support from core segments 26 and/or 28 prior to the
dense contact point and closing point (known in the art as "sync
drawing") results in a final wall thickness that is similar to the
initial value, i.e., (d.sub.1-d.sub.2) is approximately equal to
(d.sub.11-d.sub.21). Thus, formula (I) may be modified per formula
(II) below to give the length increase (.DELTA.) in the initial
draws at the point of dense contact:
.DELTA. = ( d 1 2 - d 2 2 ) ( d 11 2 - d 3 2 ) ( II )
##EQU00002##
where the extent of drawing is selected such that
d.sub.21<d.sub.3.
[0066] After the closing point, subsequent finishing draws of the
resulting wire 20 will result in a reduction in cross-sectional
area, and corresponding increase in length, for both outer shell 22
and core segments 26 and 28 in the same manner as if wire 20 were
formed of a continuous, single material of uniform cross-section
according to the following formula (III):
.DELTA.=(D/d).sup.2 (III)
where D is the outside diameter after the closing point and d is
the outside diameter to which the overall section is drawn.
[0067] At the dense contact point and through the closing point,
due to the discrete core segments 26 and 28 not being physically
joined to one another when initially inserted into outer shell 22,
the continuous elongation of outer shell 22 will tend to
inconsistently separate core segments 26 and 28, creating gaps
between core segments 26 and 28 which could compromise the periodic
consistency of the final composite wire. Stated another way, core
segments 26 and 28 tend to separate from one another upon entry of
each respective core segment into die 27, which separation will be
repeated as outer shell 22 makes dense contact with, and then
closes, on each core segment upon entering die 27, resulting in
gaps between each of the individual core segments. Thus, there is a
need to adequately constrain core segments 26 and 28 to overcome
wall interface friction between the inner diameter d.sub.2 of outer
shell 22 and core segments 26 and 28 at the dense contact and
through closing.
[0068] Referring to FIG. 3C, a solution to this concern is provided
by applying continuous compressive force, or back force F.sub.b, to
the core segments 26 and 28 using a back support rod 29, which
ensures that core segments 26 and 28 are maintained in contact with
one another throughout the drawing process, both prior to dense
contact and through closing. Back support rod 29 applies a back
force F.sub.b to core segments 26 and 28 that is sufficient to
overcome wall friction between inner shell 22 and core segments 26
and 28, and maintain contact therebetween, until outer shell 22 is
deformed by drawing die 27 into contact with core segments 26 and
28 and closes on core segments 26 and 28. A lack of a back force
would result in the relative motion between core segments 26 and 28
and outer shell 22, designated V, in FIG. 3C, to create
inconsistent and unpredictable gaps between segments thereby
disrupting the designed periodicity. The draw force, F.sub.d, is
applied to the end of the wire protruding from drawing die 27,
which is sized to deform core segments 26 and 28 slightly after
dense contact is made, and the reduction in cross sectional area of
outer shell 22 and core segments 26 and 28 may range from 0 to 20%
after dense contact through closing.
[0069] Processing of the wire beyond the closing point then may
proceed without the use of back support rod 29 according to
standard wire processing techniques, including further draws and
anneals, as if wire 20 were formed of a continuous, single material
of uniform cross-section.
[0070] The above construction, wherein core segments 26 and 28 are
disposed in a periodic alternating arrangement, allows wire 20 to
exhibit varying property periodicity along its length. In one
embodiment, first core segments 26 may be formed of a relatively
higher electrical resistance material such as stainless steel, pure
iron, tantalum, platinum, etc., and second core segments 28 may be
formed of a relatively lower electrical resistance material such as
silver, copper, gold, platinum, etc., to provide localized and/or
periodic heating along wire 20, which may be useful in medical
devices such as cauterization snares for the removal of body
tissue, a blood heating device, a heat ablation device, or a device
including a heated cutting section.
[0071] In another embodiment, core segments 26 may be formed of a
relatively higher atomic weight material, such as platinum, other
platinum group elements, platinum-iridium, tantalum, gold,
tungsten, etc., and second core segments 28 may be formed of a
relatively lower atomic weight material, such as stainless steel,
silver, or nitinol, etc., to facilitate the location of a medical
device via x-ray fluoroscopy, for example.
[0072] Referring to FIGS. 4A-C, a wire in accordance with a second
embodiment of the present invention is shown. Except as described
below, wire 30 is identical or substantially identical to wire 20,
and the same reference numerals will be used to indicate identical
or substantially identical features therebetween.
[0073] In wire 30, core segments 26 are made of a metallic material
as described above while core segments 32 are formed of a polymeric
material. Suitable polymeric materials include polyethylene,
polypropylene, polyether ether ketone (PEEK), aramids including
Nylon materials, and polyethylene tetrafluoroethylene (PTFE), for
example. Other materials useful for core segments 30 include
composite materials, such as fiber-reinforced composite materials
including carbon fiber reinforced PTFE, Kevlar fiber reinforced
polymers, and metallic fiber reinforced polymers, for example.
Otherwise, wire 30 may be manufactured in the same manner as wire
20 described above.
[0074] In one embodiment, core segments 32 of polymeric material
may be used to provide periodic differences in electrical
conductivity or radio-opacity with respect to the metal material of
core segments 26 along the length of wire 30.
[0075] Referring to FIGS. 5A-D, a wire in accordance with a third
embodiment of the present invention is shown. Except as described
below, wire 40 is identical or substantially identical to wires 20
and 30, and the same reference numerals will be used to indicate
identical or substantially identical features therebetween.
[0076] Wire 40 includes core segments 26, 28, and/or 32, as well as
core segments 42 made of a third material, such as a suitable metal
or polymeric material of the type described above. Three possible
configurations for the core segments of wire 40, and their
resulting periodic property variations imparted to wire 40, are set
forth in Table 1 below:
TABLE-US-00001 TABLE 1 Material of first Material of second
Material of third Wire core segments 26 core segments 28/32 core
segments 42 1 High atomic Low electrical High electrical weight
resistance resistance 2 High mechanical High atomic Low electrical
strength weight resistance 3 High electrical Low electrical
Superelastic or resistance resistance shape memory property
[0077] Referring to FIGS. 6A-E, a wire in accordance with a fourth
embodiment of the present invention is shown. Except as described
below, wire 50 is identical or substantially identical to wires 20,
30, and 40, and the same reference numerals will be used to
indicate identical or substantially identical features
therebetween.
[0078] Referring to FIGS. 6A and 6B, wire 50 generally includes a
first section 52, a second section 54 of a different construction
than first section 52 as described below, and a third section 56
which may be of the same construction as first section 52. As may
be seen from FIG. 6B, first section 52 may include a core 24 made
of a uniform material, while second section 54 is formed of an
alternating core construction similar to the embodiments described
above. In particular, second section 54 is formed of first segments
58 of a first metal, and second segments 60 of a second metal which
exhibits a superelastic or shape memory property, such as nitinol,
for example.
[0079] The superelastic or shape memory properties of nitinol are
well known, by which such material may change shape upon heating,
such as via application of electrical energy. For example, in one
exemplary construction shown in FIG. 6E, the application of
electrical energy to wire 50 may cause localized heating in the
high electrical resistance periods of the wire thereby causing a
pre-defined 90.degree. bend to form in second section 54 of wire
50, for example. In this case, the sections of low relative
electrical resistance would dissipate heat less than the high
resistance sections in proportion to the electrical resistance
ratio and according to simple ohmic heating. Such a feature could
be used to stiffen, steer, or otherwise manipulate specific regions
of wire 50, and thence may be used to stiffen, steer, or otherwise
manipulate any medical devices with which wire 50 is used, such as
guide wires, stents, catheters, or other devices.
[0080] As discussed above, the wires disclosed herein may include
an outer shell made of a first material, and a core comprising a
plurality of differing core segments, such as a plurality of core
segments of first material and a plurality of core segments of a
second material, and optionally, additional core segments of third
or more materials. Given the fact that the outer shell 22 may be
uniform in construction, in some instances it may be useful to mark
the outer shell to indicate the locations of the core segments
therewithin based upon a property of the core segments, such as
resistance, radiopacity, or any other property.
[0081] Referring to FIG. 7, wire 20 of FIG. 1 is again shown, which
includes outer shell 22 and core segments 26 and 28 (not visible in
FIG. 7) therewithin which are covered by outer shell 22. Core
segments 26 may be formed of a relatively conductive material,
while core segments 28 may be formed of a relatively resistive
material. The locations of core segments 26 and 28 are indicated in
FIG. 7 as regions R.sub.1 and R.sub.2, respectively, though same
would not be discernable by viewing of wire 20.
[0082] Referring to FIG. 8, one exemplary method of marking outer
shell 22 to indicate the locations of core segments 26 and 28
therewithin is illustrated. In this method, electrical current,
such as AC or DC voltage, may be applied from current source 70
from first lead 72 to second lead 74 along a given length of wire
20. The application of electrical current to wire will allow the
current to pass relatively easily through relatively conductive
core segments 26 but will cause resistance within relatively
resistive core segments 28. As shown schematically in FIG. 8, core
segments 28 will heat, which will in turn heat the portions of
outer shell 22 which cover core segments 26. Heating these portions
of outer shell 22 will cause oxidation of the material of outer
shell 22, causing the material of outer shell 22 to change color on
those portions which overly core segments 26. The extent of
oxidation, and corresponding color change, observed on the sections
of outer shell 22 overlying core segments 26 will vary depending
upon the applied current. In this manner, a desired length of wire
20, or the total length of wire 20, may be marked to indicate which
sections of wire 20 are conductive and which are resistive, for
example.
[0083] Referring to FIG. 9, a second method of marking wire 20
which includes varying core segments is illustrated. In this
embodiment, one or more properties of one or more of the core
segments of the wire may be detected by a continuous process, and
outer shell 22 of wire 30 may be marked to indicate the location of
one or more core segments. For example, referring to FIG. 9, a
power source 70 includes first and second leads 72 and 74 for
applying electrical current to a designated section of wire 20 as
wire passes power source 70. A feedback loop 76 is provided within
the circuit to interface with a controller (not shown) which
controls the applied power and determines the electrical resistance
as wire passes power source 70. When wire 20 is moved across the
location of the circuit and the controller detects a relatively
conductive section of wire, the controller may cease application of
electrical current. Thereafter, when the controller detects a
section of wire having a greater resistance, the circuit may apply
a greater amount of power to cause localized heating of the
resistive core segments and resulting oxidation and color change of
outer core 22 as is described above with respect to the embodiment
of FIG. 8. In this manner, wire 20 may be marked on a continuous
basis during manufacture to indicate the locations of relatively
conductive and relatively resistive core segments therein.
[0084] In a further embodiment, a circuit may be configured to
detect electrical resistance or any other property of the core
segment(s) of wire, such as radiopacity, for example, and may
trigger a marking element 78, such as a paint gun, to mark wire 20
and thereby indicate the locations along wire 20 of such segments.
For example, if radiopacity is a desired property to be detected,
the circuit may be configured to provide an X-ray through wire 20
with feedback loop 76 detecting the presence of relatively
radiopaque versus relatively radio translucent sections, with
marking element(s) 78 configured to mark either or both of such
sections with one or more markings.
[0085] Exemplary applications of wires 20 with differing core
segments 26 and 28 in accordance with the present invention are set
forth below in FIGS. 10A-13D in connection with medical
devices.
[0086] In FIGS. 10A-10D, an in vivo heating apparatus 100 is shown,
which includes wire 20 made in accordance with the present
invention, and which extends from proximal end 102 to distal end
104 of device 100. Wire 20 includes outer shell 22 of any suitable
biocompatible metal, and core segments 26 and 28 made of different
materials. Core segments 26 are made of a material having a
relatively low electrical resistance, such as silver, platinum, or
tantalum, for example. Core segments 28 are made of a material
having a relatively high electrical resistance, such as 300 series
stainless steels, cobalt-nickel-chromium-tungsten-iron-manganese
alloys, such as L605 alloy, nickel-titanium shape memory alloys,
such as NiTiNOL, or cobalt-nickel-chromium alloys, such as
MP35N.RTM. and 35N LT.RTM., available from Fort Wayne Metals
Research Products Corp. of Fort Wayne, Ind.
[0087] Wire 20 is twisted or stranded in a double helix, and is
formed at distal end 104 of device 100 in an outwardly-splayed
fashion to provide a working end 106 of device 100. The ends of
wire 20 include anode 108 and cathode 110, respectively, at
proximal end 102 of device 100, and device 100 includes an
overmolded insulation layer or jacket 112 made of an insulating
material such as silicone, Nylon II, or urethane, for example. A
temperature measurement feedback device includes a wire 114
extending from proximal end 102 of device 100, where wire 114 is
connected to a power source (not shown), to distal end 104 of
device 100 through the center of wire 20. Wire 114 terminates in a
temperature-sensing probe 116, such as a thermocouple or
thermistor, disposed within working end 106 of device 100.
[0088] When an electric current is applied across anode 108 and
cathode 110 of wire 20, the relatively high electrical resistance
of core segments 28 causes same to be heated, in turn causing
heating around and within the working end 106 of device 100, with
the temperature being sensed by probe 116 to provide feedback to a
control unit (not shown) used with device 100. Device 100 may be
used in applications such as thermal tissue ablation or
cauterization, thermal scar generation and vessel occlusion, for
example, to include the Fallopian tubes and sterilization, or for
local tissue or fluid heating with feedback control, for example,
to heat blood or to warm and dissolve a kidney stone.
[0089] Referring to FIGS. 11A-11D, a thermally activated snare
device 120 is shown, which includes wire 20 made in accordance with
the present invention. The distal end 122 of device 120 is shown in
FIG. 11A in section and in a relatively low temperature state, and
is shown in FIG. 11D in perspective and a relatively high
temperature state. The difference in temperature between states is
necessarily sufficient to affect properties in the shape memory or
superelastic material. The difference between low and high
temperature may vary between 1 and 50.degree. C. depending on the
specific application. The proximal end (not shown) of device 120 is
connected to a power source (not shown).
[0090] Wire includes outer shell 22 and core segments 26 and 28.
Outer shell 22 is made of a shape memory alloy, such as a
nickel-titanium shape memory alloys, such as NiTiNOL. Core segments
26 are made of a material having a relatively low electrical
resistance, such as silver, platinum, or tantalum, for example.
Core segment 28 is a single core segment extending through a loop
124 in outer shell 22, and is made of a material having a
relatively high electrical resistance, such as 300 series stainless
steels, cobalt-nickel-chromium-tungsten-iron-manganese alloys, such
as L605 alloy, nickel-titanium shape memory alloys, such as
NiTiNOL, or cobalt-nickel-chromium alloys, such as MP35N.RTM. and
35N LT.RTM., available from Fort Wayne Metals Research Products
Corp. of Fort Wayne, Ind.
[0091] In the configuration shown in FIG. 11A, the power source is
deactivated and electrical current is not carried through wire 20.
In this non-energized or relatively low temperature configuration,
the shape memory material of outer shell 22 is shaped such that
same forms an open loop 124 at the distal end 122 of device 120.
Upon activation of the power source and flow of electrical current
through wire 20, core segments 28 are heated to a relatively higher
temperature state, causing the shape memory material of outer shell
22 to in turn heat and change to the shape shown in FIG. 11D, in
which loop 124 at the distal end 122 of device 120 is closed.
Device 120 may be used as a thermally/electrically activated snare
to entrap a target device for removal, such as a lesion, for
example.
[0092] Referring to FIGS. 12A and 12B, a thermally activated linear
motion device 130 is shown, for in vivo positioning or mechanical
actuation. Device 130 includes a distal end 132 including wire 20
made in accordance with the present invention, having outer shell
22 and core segments 26 and 28. Outer shell 22 is made of a shape
memory alloy, such as a nickel-titanium shape memory alloys, such
as NiTiNOL. Core segments 26 are made of a material having a
relatively low electrical resistance, such as silver, platinum, or
tantalum, for example. Core segments 28 are made of a material
having a relatively high electrical resistance, such as a 300
series stainless steel,
cobalt-nickel-chromium-tungsten-iron-manganese alloys, such as L605
alloy, nickel-titanium shape memory alloys, such as NiTiNOL, or
cobalt-nickel-chromium alloys, such as MP35N.RTM. and 35N LT.RTM.,
available from Fort Wayne Metals Research Products Corp. of Fort
Wayne, Ind. The proximal end (not shown) of device 130 is connected
to a power source (not shown).
[0093] Device 130 has an initial nominal length D.sub.1, measured
from a given point on device 130 to the tip of device 130. In the
configuration shown in FIG. 12A, the power source is deactivated
and electrical current is not carried through wire 20. In this
non-energized or relatively low temperature configuration, the
shape memory material of outer shell 22 is as shown in FIG. 12A, in
which the material is relatively straight or alternatively, is
linearly elongated. Upon activation of the power source and flow of
electrical current through wire 20, core segments 28 are heated to
a relatively higher temperature state, causing the shape memory
material of outer shell 22 to in turn heat and change to the shape
shown in FIG. 12D, in which the material is bent as shown in FIG.
12D or alternatively, is linearly reduced in length. The reduction
in length reduces the nominal length by dimension A to a reduced
nominal length D.sub.2. Alternatively, the configuration of device
130 may change from that shown in FIG. 12D to that shown in FIG.
12A upon application of electrical current, i.e., device 130 may be
designed to extend in length upon application of electrical
current.
[0094] Exemplary applications of device 130 include applications in
which a positional adjustment of an implant device, such as a
stent, for example, is desired within a precise, defined
dimensional range. In one embodiment, several devices 130 may be
provided in a kit, with the devices designed or calibrated to
provide respective dimensional changes A in known increments, such
as 1 mm, 5 mm, or 10 mm, for example. A medical practitioner may
select a particular device 130 from the kit which has the desired
nominal adjustment increment for use in a particular application
based on medical imaging data, for example.
[0095] Referring to FIGS. 13A-13D, a tissue scaffold or vessel
stent device 140 is shown which is made from one or more wires 20
in accordance with the present invention, which are looped together
to form the cylindrical cross-sectional shape of device 140 as
shown in FIGS. 13A and 13B. Wire 20 includes an outer shell 22 made
of 300 series stainless steels,
cobalt-nickel-chromium-tungsten-iron-manganese alloys, such as L605
alloy, nickel-titanium shape memory alloys, such as NiTiNOL, or
cobalt-nickel-chromium alloys, such as MP35N.RTM. and 35N LT.RTM.,
available from Fort Wayne Metals Research Products Corp. of Fort
Wayne, Ind. Core segments 26 comprise the majority portion of the
core of wire 20, and are made of a radio-translucent material, such
as NiTiNOL, for example. Core segments 28 comprise the minority
portion of the core of wire 20, and are made of a radio-opaque
material, such as platinum, tantalum, niobium, palladium, tungsten,
or a platinum/iridium alloy, for example. In this manner, the
relatively more expensive radio-opaque material is conserved in the
device, while still providing a number of relatively short,
periodic segments of radio-opacity for visualization of device 140
in medical imaging such as fluoroscopy, for example, as
schematically indicated by the darker areas in wire 20 of device
140 in FIG. 13A. In addition, an increase in the performance and/or
the radial force of the scaffold or stent device 140 may be
improved due to a greater net proportion of core segments 26 over a
majority of the length of wire 20.
[0096] Advantageously, referring to FIGS. 14A and 14B, with the
present method, an elongated length wire 20 may be formed by
drawing processes as described above and in the Examples below,
having a periodic alternating arrangement of core segments 26 and
28. This wire 20 may be manufactured by drawing, as described
above, and wound onto a spool 150, as shown in FIG. 14A, for
example, for shipping or storage, with the wire 20 having a very
long length, such as tens or hundreds of meters, for example. Then,
individual wire portions or segments 152 may be cut from the wire
20 by a cutting or separating device 154, with each wire segment
152 having a desired number and arrangement of periodically
alternating core segments 26 and 28 as shown in FIG. 14B for use in
a desired application, such as those described above. In this
manner, manufacture of a large number of individual wire portions
or segments 152 of alternating core construction is facilitated by
initial manufacture of a very long continuous wire 20 as described
above, which may also be marked as described above and in the
Examples below, followed by cutting the individual wire portions or
segments 152.
EXAMPLES
Example 1
Production of an Alternating Core Composite Wire
[0097] In this Example, an alternating core composite wire was made
in accordance with the present invention, including an outer shell
made of MP35N alloy, specifically, 35N LT.RTM. alloy, available
from Fort Wayne Metals Research Products Corporation of Fort Wayne,
Ind. This material is described in further detail in the
above-incorporated U.S. patent application Ser. No. 10/656,918. The
outer shell had an initial outer diameter of 0.144 inches (0.366
cm) and an initial inner diameter of 0.098 inches (0.249 cm).
[0098] Two different types of core segments were used, made of 304V
stainless steel and of 99.95% silver, respectively, with the wire
including thirty (30) individual core segments of each of these
materials. The 304V stainless steel core segments had an initial
outer diameter of 0.064 inches (0.163 cm), with each segment
ranging in length from 0.060 inches (0.152 cm) to 0.080 inches
(0.203 cm). The 99.95% silver core segments had an initial outer
diameter of 0.088 inches (0.224 cm), with each segment ranging in
length from 0.20 inches (0.508 cm) to 0.25 inches (0.635 cm). The
core segments were loaded into the outer shell in an alternating
periodic arrangement of [A-B-A-B- . . . ].
[0099] The wire was successively drawn using 10-12 degree reduction
angle diamond dies, with a nominal 20% area of reduction between
each draw. Following each draw, the wire was annealed at
927.degree. C. in a furnace under a hydrogen atmosphere with a 30
second dwell time for each anneal. The draw schedule for the wire
is set forth in Table 2 below.
TABLE-US-00002 TABLE 2 Draw Outer diameter (inches) -- 0.144 (0.366
cm) 1 0.128 (0.325 cm) 2 0.102 (0.259 cm) 3 0.064 (0.163 cm) 4
0.0453 (0.115 cm) 5 0.032 (0.081 cm) 6 0.0266 (0.0676 cm) 7 0.0159
(0.0404 cm) 8 0.0113 (0.0287 cm) 9 0.0089 (0.023 cm) 10 0.0063
(0.016 cm) 11 (final) 0.005 (0.013 cm)
[0100] In the first draw, the wire was drawn from an outer diameter
of 0.144 inches (0.366 cm) to an outer diameter of 0.128 inches
(0.325 cm), using a back support rod as described above, and the
outer shell closed on the silver core segments. The back support
rod was not used in subsequent draws. In the second draw, the wire
was drawn from an outer diameter of 0.128 inches (0.325 cm) to an
outer diameter of 0.102 inches (0.259 cm), and the outer shell
closed on the stainless steel core segments.
[0101] An alternate draw schedule, which includes less cold work in
the early stage draws, is set forth in Table 3 below:
TABLE-US-00003 TABLE 3 Draw Outer diameter (inches) -- 0.144 (0.366
cm) 1 0.128 (0.325 cm) 2 0.102 (0.259 cm) 3 0.081 (0.206 cm) 4
0.064 (0.163 cm) 5 0.0508 (0.129 cm) 6 0.0359 (0.0912 cm) 7 0.0253
(0.0643 cm) 8 0.0179 (0.0454 cm) 9 0.0126 (0.032 cm) 10 0.0089
(0.023 cm) 11 0.0063 (0.016 cm) 12 (final) 0.005 (0.013 cm)
[0102] In Table 4 below, outer diameters of the wire are given,
most of which correspond to the outer diameters of the wire
provided in the draw schedule of Table 2 above. In Table 4, the
minimum and maximum lengths of the silver and stainless steel core
segments have been calculated based on the wire outer diameters and
the calculations outlined in the above description.
TABLE-US-00004 TABLE 4 Length Stainless Stainless increase Ag core
Ag core steel core steel core Wire after dense segment segment
segment segment Outer contact length, length, length, length,
Diameter [(D/d){circumflex over ( )}2] (MIN) (MAX) (MIN) (MAX)
(inches) (inches) (feet) (feet) (feet) (feet) 0.134 0.017 0.021
0.0050 0.0067 (0.340 cm) (0.005 m) (0.006 m) (0.002 m) (0.002 m)
0.11 1.484 0.025 0.031 0.0050 0.0067 (0.279 cm) (3.769 cm) (0.008
m) (0.009 m) (0.002 m) (0.002 m) 0.072 2.334 0.058 0.072 0.012
0.016 (0.183 cm) (5.928 cm) (0.018 m) (0.022 m) (0.004 m) (0.001 m)
0.064 1.266 0.073 0.091 0.015 0.020 (0.163 cm) (3.216 cm) (0.022 m)
(0.028 m) (0.005 m) (0.006 m) 0.0453 1.996 0.15 0.18 0.029 0.039
(0.115 cm) (5.070 cm) (0.046 m) (0.055 m) (0.009 m) (0.012 m) 0.032
2.004 0.29 0.37 0.059 0.079 (0.081 cm) (5.090 cm) (0.088 m) (0.113
m) (0.018 m) (0.024 m) 0.0226 2.005 0.59 0.73 0.12 0.16 (0.0574 cm)
(5.093 cm) (0.180 m) (0.223 m) (0.037 m) (0.049 m) 0.0159 2.020 1.2
1.5 0.24 0.32 (0.040 cm) (5.131 cm) (0.366 m) (0.457 m) (0.073 m)
(0.098 m) 0.0113 1.980 2.3 2.9 0.47 0.63 (0.029 cm) (5.029 cm)
(0.701 m) (0.884 m) (0.143 m) (0.192 m) 0.0089 1.612 3.8 4.7 0.76
1.02 (0.023 cm) (4.094 cm) (1.158 m) (1.433 m) (0.232 m) (0.311 m)
0.0063 1.996 7.5 9.4 1.5 2.0 (0.016 cm) (5.070 cm) (2.286 m) (2.865
m) (0.457 m) (0.610 m) 0.005 1.588 12.0 15.0 2.4 3.2 (0.013 cm)
(4.034 cm) (3.658 m) (4.572 m) (0.732 m) (0.975 m)
[0103] As set forth in Table 4 above, for the final wire having an
outer diameter of 0.005 inches (0.013 cm), the silver core segments
are expected to range between 12.0 feet (3.658 m) and 15.0 feet
(4.572 m) in length, and the stainless steel core segments are
expected to range between 2.4 feet (0.732 m) and 3.2 feet (0.975 m)
in length. Thus, the period length, i.e., the sum of the lengths of
one silver core segment plus one stainless steel core segment, is
expected to range between 14.4 feet (4.389 m) and 18.2 feet (5.547
m).
Example 2
Evaluation of an Alternating Core Composite Wire
[0104] In this Example, the wire formed in Example 1 was tested to
validate the predicted segment length of the core segments of the
wire and to mark the wire to indicate the presence of the various
different core segments within the wire.
[0105] A 30 ft. (9.144 m) segment of the wire of Example 1 was
stretched out and suspended in air. Then, the wire segment was
contacted with electrical conductive clips and connected across a
115/120V, 60 Hz electrical power source. The high resistance
sections of the wire, namely, the stainless steel core segments,
heated sufficiently to create a brown oxide layer on the portions
of the outer shell surrounding these segments, thereby indicating
the presence of the stainless steel core segments beneath the outer
shell. The portions of the outer shell surrounding the low
resistance sections of the wire, namely, the silver core segments,
maintained their as-drawn silvery luster, thereby indicating the
presence of silver core segments beneath the outer shell. This
method provided an easy visual discernment of the presence of the
silver and the stainless steel core segments beneath their
respective portions of the outer shell.
[0106] Then, the wire segment was cut into segments, each 12 inches
(30.4 cm) in length, and the direct current electrical resistance
and ultimate tensile strength of each section was tested. The
electrical resistance was measured using a temperature-compensated,
four wire resistance measurement bridge, available from Valhalla
Scientific, Inc. The ultimate tensile strength was tested using a
tensile strength test device, available from Instron, Inc., by
clamping the ends of each segment in the hydraulic grips of the
device and applying a monotonically increasing pull force to the
sections until rupture.
[0107] The results of the foregoing tests are shown below in Table
5 and are plotted in FIG. 15.
TABLE-US-00005 TABLE 5 Distance/ Ultimate location along Tensile
Segment the wire Resistance Strength # (feet) (ohm/ft)
(.times.10.sup.3 psi) 1 0 1.072 191 2 1 1.039 189 3 2 1.081 193 4 3
1.099 193 5 4 1.113 193 6 5 1.151 196 7 6 1.306 209 8 7 9.48 239 9
7.5 18 245 10 8 18.14 251 11 8.5 17.3 248 12 9 5.88 230 13 10 1.15
195 14 11 1.072 193 15 12 1.039 191 16 13 1.081 193 17 14 1.072 193
18 15 1.072 193 19 16 1.081 195 20 17 1.065 193 21 18 1.075 193 22
19 1.081 193 23 20 1.151 196 24 21 1.306 209 25 22 9.48 239 26 22.5
17.5 246 27 23 18.14 251 28 23.5 17.5 249 29 24 5.88 230 30 25 1.15
195 31 26 1.072 193 32 27 1.039 191 33 28 1.081 193
[0108] As may be seen from the data in Table 5 and from FIG. 15,
the portions of the wire having higher electrical resistance and
higher ultimate tensile strength indicate the presence of the
stainless steel core segments in the wire, while the portions of
the wire having lesser electrical resistance and lesser ultimate
tensile strength indicate the presence of the silver core segments.
In FIG. 15, the period length was measured between the centers of
the curves of higher electrical resistance, and thereby indicates
the distance between the central portions of a pair of successive
stainless steel core segments. This period length was calculated to
be 15 feet (4.572 m), within the predicted range of 14.4 feet
(4.389 m) to 18.2 feet (5.547 m) as calculated in Example 1
above.
[0109] While this invention has been described as having a
preferred design, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *