U.S. patent application number 13/942287 was filed with the patent office on 2013-11-14 for protective padding utilizing superelastic three-dimensional spacer fabric comprising shape memory materials (smm).
The applicant listed for this patent is MX Orthopedics, Corp.. Invention is credited to Matthew Fonte, Matthew Palmer.
Application Number | 20130298317 13/942287 |
Document ID | / |
Family ID | 49551862 |
Filed Date | 2013-11-14 |
United States Patent
Application |
20130298317 |
Kind Code |
A1 |
Fonte; Matthew ; et
al. |
November 14, 2013 |
PROTECTIVE PADDING UTILIZING SUPERELASTIC THREE-DIMENSIONAL SPACER
FABRIC COMPRISING SHAPE MEMORY MATERIALS (SMM)
Abstract
Protective padding comprising: a spacer fabric comprising a
first fabric layer, a second fabric layer, and a plurality of
interconnecting filaments extending between said first fabric layer
and said second fabric layer; wherein at least one of said first
fabric layer, said second fabric layer and said plurality of
interconnecting filaments comprise a shape memory material.
Inventors: |
Fonte; Matthew; (Concord,
MA) ; Palmer; Matthew; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MX Orthopedics, Corp. |
Billerica |
MA |
US |
|
|
Family ID: |
49551862 |
Appl. No.: |
13/942287 |
Filed: |
July 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13843656 |
Mar 15, 2013 |
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13942287 |
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13764188 |
Feb 11, 2013 |
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13843656 |
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13936866 |
Jul 8, 2013 |
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13764188 |
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13843656 |
Mar 15, 2013 |
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13936866 |
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61596900 |
Feb 9, 2012 |
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61612496 |
Mar 19, 2012 |
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61661086 |
Jun 18, 2012 |
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61738574 |
Dec 18, 2012 |
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61738574 |
Dec 18, 2012 |
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61668732 |
Jul 6, 2012 |
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61671129 |
Jul 13, 2012 |
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61671129 |
Jul 13, 2012 |
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Current U.S.
Class: |
2/414 ; 2/455;
36/44 |
Current CPC
Class: |
B32B 2307/51 20130101;
A63B 71/08 20130101; A63B 2102/24 20151001; A63B 2243/007 20130101;
A41D 31/285 20190201; B32B 2307/558 20130101; B32B 2262/0276
20130101; A63B 2102/14 20151001; B32B 2260/046 20130101; B32B
2307/7145 20130101; B32B 2437/00 20130101; B32B 2571/00 20130101;
A63B 2209/14 20130101; B32B 5/026 20130101; B32B 2255/26 20130101;
B32B 2262/0261 20130101; B32B 2307/56 20130101; A43B 13/386
20130101; A41D 13/05 20130101; A63B 2071/1208 20130101; B32B 5/26
20130101; B32B 2250/40 20130101; A41D 13/015 20130101; A42B 3/125
20130101; B32B 2255/02 20130101; B32B 2260/021 20130101; A63B 71/12
20130101; B32B 5/06 20130101 |
Class at
Publication: |
2/414 ; 2/455;
36/44 |
International
Class: |
A41D 13/015 20060101
A41D013/015; A42B 3/12 20060101 A42B003/12; A43B 13/38 20060101
A43B013/38 |
Claims
1. Protective padding comprising: a spacer fabric comprising a
first fabric layer, a second fabric layer, and a plurality of
interconnecting filaments extending between said first fabric layer
and said second fabric layer; wherein at least one of said first
fabric layer, said second fabric layer and said plurality of
interconnecting filaments comprise a shape memory material.
2. Protective padding according to claim 1 wherein said shape
memory material is superelastic.
3. Protective padding according to claim 2 wherein said shape
memory material is Nitinol.
4. Protective padding according to claim 2 wherein said shape
memory material is a titanium near-beta alloy.
5. Protective padding according to claim 1 wherein said plurality
of interconnecting filaments comprise a shape memory material.
6. Protective padding according to claim 5 wherein said plurality
of interconnecting filaments comprise a shape memory material and
wherein at least one of said first fabric layer and said second
fabric layer do not comprise a shape memory material.
7. Protective padding according to claim 5 wherein wherein said
first fabric layer, said second fabric layer and said plurality of
interconnecting filaments all comprise a shape memory material.
8. Protective padding according to claim 1 wherein said shape
memory material is engineered to have a martensitic state between 0
degrees C. and 90 degrees C.
9. Protective padding according to claim 1 wherein the shape memory
material is engineered to oscillate between phase transformations
so as to maximize its peak dampening characteristics and storage
modulus.
10. Protective padding according to claim 1 wherein said protective
padding is contoured so as to provide increased support to specific
regions of a wearer's anatomy.
11. Protective padding according to claim 10 wherein said
contouring is achieved by shape-setting said protective padding
using a heating source.
12. Protective padding according to claim 1 wherein voids in said
spacer fabric are filled with a material.
13. Protective padding according to claim 12 wherein said material
is a gel.
14. Protective padding according to claim 12 wherein said material
comprises a polymer capable of transitioning between a solid state
and a viscous state due to loading and unloading of said shoe
insole.
15. Protective padding according to claim 1 wherein said shape
memory material is coated with silver to impart antibacterial and
antifungal properties to said shape memory material.
16. Protective padding according to claim 1 wherein said spacer
fabric is disposed between an outer surface and an inner
surface.
17. Protective padding according to claim 16 wherein said outer
surface comprises the shell of a helmet, and said inner surface
comprises a harness for attaching the shell of the helmet to the
head of a wearer.
18. Protective padding according to claim 16 wherein said outer
surface comprises a hard plastic.
19. Protective padding according to claim 16 wherein said inner
surface comprises a soft material.
20. Protective padding according to claim 1 wherein at least a
portion of said spacer fabric is coated with a polymer.
21. Protective padding according to claim 20 wherein said polymer
is Teflon.
22. Protective padding according to claim 20 wherein said entire
spacer fabric is coated with said polymer.
23. Protective padding according to claim 20 wherein only selected
portions of said spacer fabric are coated with said polymer.
24. Protective padding according to claim 20 wherein said polymer
coating is applied to the SMM wire before the SMM wire is knit into
the spacer fabric construct.
25. Protective padding comprising: an outer surface; an inner
surface; and a spacer fabric disposed between said outer surface
and said inner surface, said spacer fabric comprising a first
layer, a second layer, and a plurality of interconnecting filaments
extending between said first layer and said second layer; wherein
at least one of said first layer, said second layer and said
plurality of interconnecting filaments comprise a shape memory
material.
Description
REFERENCE TO PENDING PRIOR PATENT APPLICATIONS
[0001] This patent application: [0002] (i) is a
continuation-in-part of pending prior U.S. patent application Ser.
No. 13/843,656, filed Mar. 15, 2013 by Matthew Fonte et al. for
DYNAMIC POROUS COATING FOR OTHOPEDIC IMPLANT (Attorney's Docket No.
FONTE-15171824), which patent application (a) is a
continuation-in-part of prior U.S. patent application Ser. No.
13/764,188, filed Feb. 11, 2013 by Matthew Fonte et al. for POROUS
COATING FOR ORTHOPEDIC IMPLANT UTILIZING POROUS, SHAPE MEMORY
MATERIALS (Attorney's Docket No. FONTE-15), which patent
application claims benefit of prior U.S. Provisional Patent
Application Ser. No. 61/596,900, filed Feb. 9, 2012 by Matthew
Fonte et al. for POROUS, SHAPE MEMORY MATERIAL, ORTHOPEDIC IMPLANT
COATING (Attorney's Docket No. FONTE-15 PROV); (b) claims benefit
of prior U.S. Provisional Patent Application Ser. No. 61/612,496,
filed Mar. 19, 2012 by Matthew Fonte et al. for POROUS, SHAPE
MEMORY MATERIAL, ORTHOPEDIC IMPLANT COATING (Attorney's Docket No.
FONTE-17 PROV); (c) claims benefit of prior U.S. Provisional Patent
Application Ser. No. 61/661,086, filed Jun. 18, 2012 by Matthew
Fonte et al. for "DYNAMIC" ORTHOPEDIC COATINGS MADE OF SPACER
FABRIC (Attorney's Docket No. FONTE-18 PROV); and (d) claims
benefit of prior U.S. Provisional Patent Application Ser. No.
61/738,574, filed Dec. 18, 2012 by Matthew Fonte et al. for POROUS,
SHAPE MEMORY MATERIAL, ORTHOPEDIC IMPLANT COATING (Attorney's
Docket No. FONTE-24 PROV); [0003] (ii) is a continuation-in-part of
pending prior U.S. patent application Ser. No. 13/936,866, filed
Jul. 8, 2013 by Matthew Fonte et al. for INSOLE AND FOOT ORTHOTICS
MADE OF SHAPE MEMORY MATERIAL (SMM) THREE-DIMENSIONAL SPACER
FABRICS (Attorney's Docket No. FONTE-2021), which patent
application (a) is a continuation-in-part of the aforementioned
U.S. patent application Ser. No. 13/843,656 and claims benefit of
the aforementioned prior U.S. patent applications Ser. Nos.
13/764,188, 61/596,900, 61/612,496, 61/661,086, and 61/738,574, and
(b) claims benefit of prior U.S. Provisional Patent Application
Ser. No. 61/668,732, filed Jul. 6, 2012 by Matthew Fonte et al. for
SHOE INSOLE AND FOOT ORTHOTICS MADE OF SHAPE MEMORY MATERIAL
THREE-DIMENSIONAL SPACER FABRICS (Attorney's Docket No. FONTE-20
PROV), and (c) claims benefit of pending prior U.S. Provisional
Patent Application Ser. No. 61/671,129, filed Jul. 13, 2012 by
Matthew Fonte et al. for SUPERELASTIC THREE-DIMENSIONAL SPACER
FABRIC USING SHAPE MEMORY MATERIALS (Attorney's Docket No. FONTE-21
PROV); and [0004] (iii) claims benefit of pending prior U.S.
Provisional Patent Application Ser. No. 61/671,129, filed Jul. 13,
2012 by Matthew Fonte et al. for SUPERELASTIC THREE-DIMENSIONAL
SPACER FABRIC USING SHAPE MEMORY MATERIALS (Attorney's Docket No.
FONTE-21 PROV).
[0005] The nine (9) above-identified patent applications are hereby
incorporated herein by reference.
FIELD OF THE INVENTION
[0006] This invention relates to protective padding in general, and
more particularly to improved approaches for absorbing shock and
distributing forces in protective padding.
BACKGROUND OF THE INVENTION
[0007] Protective padding is well known for protecting the body
against impact, e.g., during sporting events, hazardous activities,
military situations, etc.
[0008] Foam materials such as neoprene and polyurethane are often
used in protective padding applications, due to their ability to
provide cushioning, compression, stability, resilience, elasticity
and/or flexibility. Foam may be open-cell or closed-cell in nature.
Open-cell foam has air pockets that are connected to each other.
Closed-cell foam has air pockets that form unconnected discrete
voids within the foam. One major drawback of such open-cell and
closed-cell foam materials is that they are largely impermeable to
gases and liquids. This can be undesirable where foams are used in
applications that come in contact with the body. For example,
Neoprene foams (see FIG. 1) used to stabilize a limb or a joint do
not breathe well and can trap moisture, which can lead to
infections. In an effort to counter this problem, attempts have
been made to perforate foam sheets so as to increase their
breathability; however, such perforation decreases the mechanical
properties of the foam, which can undermine the effectiveness of
the foam. Furthermore, the repeated application of a load causes
foam to "wear out" over time and loose the resilient properties
which made them useful in the original application.
[0009] Spacer fabrics were developed to address the inadequacies of
foams. Spacer fabrics are manufactured using knitting or weaving
techniques, are elastic in structure, and have been employed in
many applications including clothing, mattresses, seats, and
patient-support materials in the medical industry.
[0010] As seen in FIG. 2, a three-dimensional knit spacer fabric 5
includes a first fabric layer 10, a second fabric layer 15 and
yarns 20 interconnecting the two layers 10, 15. Some of the yarns
20 interconnecting the two layers 10, 15 are substantially
perpendicular to the first and second fabric layers 10, 15, while
the remaining interconnecting yarns 20 are disposed at an acute
angle between the two layers 10, 15.
[0011] Knit manufacturing is the most common method for producing
spacer fabrics. The double-face spacer fabric 5 is prepared by
knitting a three-dimensional knit fabric on a double-needle bar
warp knitting machine commonly used in the manufacture of velvet. A
synthetic material such as polyester, acrylic or nylon is used to
form the yarn which is knit into the spacer fabric construct. The
yarn may be a filament or spun, textured or fully oriented. The
yarn 20 interconnecting the two layers 10, 15 of the spacer fabric
5 has sufficient resilience and stiffness to keep the two fabric
layers 10, 15 separated from one another when pressure is applied
to either (or both) of the construct's fabric layers 10, 15.
[0012] The interconnecting pile yarns 20 can be made of the same or
different materials from that of the two surface fabric layers 10,
15. The two surface fabric layers 10, 15 can be made of the same
material or they can be made of different materials. More
particularly, in order to render the interconnecting pile yarns 20
resilient, the yarns 20 may be made of a resilient material such as
a monofilament or multifilament polyester or nylon.
[0013] By changing one or more of (i) the material(s) used to form
the spacer fabric, (ii) the thickness(es) (i.e., diameter(s)) of
the filaments used, and (iii) the space between fabric layers 10,
15, the material properties of the spacer fabric 5 can be altered.
A thicker spacer fabric manufactured using finer gauge filaments is
generally more compliant than a thinner spacer fabric manufactured
from thicker filaments. Additionally, the pore size of the top and
bottom layers 10, 15 can be altered by changing the needle spacing
and the thickness(es) of the filament(s) used. See FIG. 3.
[0014] Thus, spacer fabrics address many of the inadequacies of
traditional foams. The highly porous nature of spacer fabrics
allows them to have excellent fluid flow and thermal properties.
Spacer fabrics are highly tailorable to specific applications, and
are cost-effective since they use a low-cost starting plastic
material. See FIG. 4
[0015] The primary disadvantage of polymeric spacer fabrics is that
plastics are relatively weak, are prone to creep, suffer from
fatigue degradation and exhibit permanent compression set. More
particularly, and looking now at FIG. 5, when a plastic material is
subjected to a constant load, it deforms continuously. The initial
strain is roughly predicted by its stress-strain modulus. The
plastic material will continue to deform slowly with time,
indefinitely, until rupture or yielding causes failure, e.g.,
permanent set. As seen in the graph shown in FIG. 5, the initial
region is the early stage of loading when the creep rate decreases
rapidly with time. Then it reaches a steady state, which is called
the secondary creep stage, followed by a rapid increase (tertiary
stage) and fracture. This phenomenon of deformation under load with
time is called creep. Some materials do not have the aforementioned
secondary stage, while tertiary creep only occurs at high stresses
and for ductile materials. All plastics creep to a certain extent.
The degree of creep depends on several factors, such as the type of
plastic, whether the material is wet or dry, the magnitude of the
load, the cyclical load rate, the temperature of the material and
the time duration of the applied load. The standard test method for
creep characterization is ASTM D2990.
[0016] Thus, while protective padding formed out of foam has proven
generally beneficial, it tends to suffer from poor gas and liquid
permeability, and loss of resiliency over time. Furthermore, while
protective padding formed out of polymer spacer fabrics have proven
generally beneficial, they tend to suffer from overall weakness,
creep, fatigue degradation and permanent compression set.
SUMMARY OF THE INVENTION
[0017] As noted above, spacer fabrics are a generic term for three
dimensional fabrics that have a first fabric layer, a second fabric
layer, and an intervening fabric layer that interconnects the first
fabric layer to the second fabric layer. Spacer fabrics are used
commonly in many industries, and are often used in applications
where fluid flow, cushioning, and vibration absorption are
necessary. Spacer fabrics may be manufactured using knitting or
weaving techniques. Currently, spacer fabrics are manufactured
using monofilament polymeric yarns, or polyamide or polyester
fibers. These materials are highly flexible, kink resistant, and
common in the textile field. However, polymer spacer fabrics suffer
from weakness, creep, fatigue degradation and permanent compression
set.
[0018] The present invention relates to the provision and use of
spacer fabrics which utilize a shape memory material (SMM), e.g.,
Nitinol or a titanium near-beta alloy, as a filament for
constructing the spacer fabric (e.g., as a filament for
constructing the top fabric layer, the bottom fabric layer and the
intervening fabric layer that interconnects the top fabric layer to
the bottom fabric layer). See FIG. 6. SMMs, unlike other metallic
filaments, are highly flexible and kink resistant, allowing them to
be woven or knit. SMM filaments are substantially stronger than
polymer monofilaments, and are not susceptible to deleterious creep
and fatigue which often shortens the life of polymeric materials.
Spacer fabrics created from shape memory materials (SMM) can be
designed to be strong, superelastic, exhibiting a hysteresis for
large shape recovery strains and can be designed to change shape
based on temperature changes.
[0019] More particularly, the present invention relates to the
provision and use of shape memory material (SMM) spacer fabrics for
protective padding. Since shape memory material (SMM) spacer
fabrics are elastic and compressible, and do not suffer from the
disadvantages associated with plastic deformation discussed above,
their resilient structure makes them ideal for protective padding
applications where a force must be dampened. The resilient nature
of shape memory material (SMM) spacer fabrics permits them to
absorb and dampen impact without suffering permanent deformation or
loss of resiliency. Thus, shape memory material (SMM) spacer
fabrics are ideally suited for protective padding applications.
[0020] In one preferred form of the present invention, there is
provided protective padding comprising: [0021] a spacer fabric
comprising a first fabric layer, a second fabric layer, and a
plurality of interconnecting filaments extending between said first
fabric layer and said second fabric layer; [0022] wherein at least
one of said first fabric layer, said second fabric layer and said
plurality of interconnecting filaments comprise a shape memory
material.
[0023] In another preferred form of the present invention, there is
provided protective padding comprising: [0024] an outer surface;
[0025] an inner surface; and [0026] a spacer fabric disposed
between said outer surface and said inner surface, said spacer
fabric comprising a first layer, a second layer, and a plurality of
interconnecting filaments extending between said first layer and
said second layer; [0027] wherein at least one of said first layer,
said second layer and said plurality of interconnecting filaments
comprise a shape memory material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] These and other objects and features of the present
invention will be more fully disclosed or rendered obvious by the
following detailed description of the preferred embodiments of the
invention, which is to be considered together with the accompanying
drawings wherein like numbers refer to like parts, and further
wherein:
[0029] FIG. 1 is a schematic view showing a neoprene foam
sheet;
[0030] FIG. 2 is a schematic view showing a conventional polymer
spacer fabric, with the spacer fabric being compressed;
[0031] FIG. 3 is a schematic view showing various conventional
polymer spacer fabrics with different mechanical properties;
[0032] FIG. 4 is a schematic view showing how three-dimensional
spacer fabrics comprise multiple discrete layers, are lightweight,
breathable, will wick away moisture and will cool or insulate;
[0033] FIG. 5 is a schematic view showing creep behavior for
polymer materials;
[0034] FIG. 6 is a schematic view showing a spacer fabric made from
shape memory material;
[0035] FIG. 7 is a schematic view showing a spacer fabric made from
Nitinol;
[0036] FIG. 8 is a schematic view showing the stress-strain curves
for steel and Nitinol;
[0037] FIG. 9 is a schematic view showing the damping capacity of
Nitinol, aluminum, stainless steel and brass as a function of
temperature;
[0038] FIG. 10 is a schematic view showing the storage modulus
capacity of Nitinol, aluminum, stainless steel and brass as a
function of temperature;
[0039] FIG. 11 is a schematic view showing the stress-strain
diagram for bone, Nitinol and stainless steel;
[0040] FIG. 12 is a schematic view showing a double needle bar warp
knitting machine for the production of Nitinol spacer fabrics;
[0041] FIG. 13 is a schematic view showing how superelastic spacer
fabrics can be layered on top of each other;
[0042] FIG. 14 is a schematic view showing the formation of
stress-induced martensite;
[0043] FIG. 15 is a schematic view showing the use of Nitinol
spacer fabric to form protective padding for a helmet;
[0044] FIG. 16 is a schematic view showing the use of Nitinol
spacer fabric to form protective padding for a lacrosse
application;
[0045] FIG. 17 is a schematic cross-sectional view showing
protective padding formed out of shape memory material (SMM) spacer
fabric;
[0046] FIG. 18 is a schematic view showing the use of Nitinol
spacer fabric to form protective padding for a football
application;
[0047] FIG. 19 is a schematic view showing the use of Nitinol
spacer fabric to form protective padding for a hockey application;
and
[0048] FIG. 20 is a schematic view showing the use of Nitinol
spacer fabric to form protective padding for a mountain biking
application.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0049] In accordance with the present invention, there is provided
novel protective padding utilizing superelastic three-dimensional
spacer fabric comprising shape memory materials (SMMs) such as
Nitinol. The superelastic vertical fibers of the spacer fabric
(i.e., the interconnecting yarns which extend between the top
fabric layer and the bottom fabric layer) create the desired
elastic response in the spacer fabric when compressed by an outside
force and allowed to shape recover, which addresses the
deficiencies of the prior art.
[0050] See FIG. 7, which shows a three-dimensional knit spacer
fabric 105 includes a first fabric layer 110, a second fabric layer
115 and yarns 120 interconnecting the two layers 110, 115, wherein
some of the yarns 120 interconnecting the two layers 110, 115 are
substantially perpendicular to the first and second fabric layers
110, 115, while the remaining interconnecting yarns 120 are
disposed at an acute angle between the two layers 110, 115, and
further wherein at least the yarns 120 are formed out of a shape
memory material (SMM) such as Nitinol.
[0051] In one preferred form of the invention, first fabric layer
110, second fabric layer 115 and interconnecting filaments 120 are
all formed out of filaments made from a shape memory material (SMM)
such as Nitinol.
[0052] In another preferred form of the invention, interconnecting
yarns 120 are formed out of shape-memory material such as Nitinol,
and first fabric layer 110 and second fabric layer 115 are formed
out filaments made from a non-shape memory material (SMM).
[0053] With shape-memory metals such as Nitinol, pseudoelasticity,
sometimes called superelasticity, is an elastic (reversible)
response to an applied stress, caused by a phase transformation
between the austenitic and martensitic phases of a crystal.
Pseudoelasticity is from the reversible motion of domain boundaries
during the phase transformation, rather than just bond stretching
or the introduction of defects in the crystal lattice (thus it is
not true superelasticity but rather pseudoelasticity). Even if the
domain boundaries do become pinned, they may be reversed through
heating. Thus, a pseudoelastic material may return to its previous
shape (hence, shape memory) after the removal of relatively high
applied strains. One special case of pseudoelasticity is called the
Bain Correspondence which involves the austenite-to-martensite
phase transformation between a face-centered crystal lattice and a
body-centered tetragonal crystal structure.
[0054] Superelastic alloys belong to the larger family of
shape-memory alloys. When mechanically loaded, a superelastic alloy
deforms reversibly to very high strains--up to 10%--by the creation
of a stress-induced phase (i.e., stress-induced martensite). When
the load is removed, the new (i.e., stress-induced) phase becomes
unstable and the material regains its original shape. Unlike
shape-memory alloys that utilize shape memory effect, in
superelasticity no change in temperature is needed for the alloy to
recover its initial shape. Superelastic devices take advantage of
their large, reversible deformation. Superelastic products include
antennas, eyeglass frames and biomedical stents.
[0055] Among other things, the present invention provides a dynamic
spacer fabric made of metallic shape memory material (SMM) that has
vastly improved fatigue life compared to polymeric alternatives.
Metal and polymeric fatigue is the progressive and localized
structural damage that occurs when a material is subjected to
cyclic loadings. Among other things, metals and polymers are
different in the fact that polymers are viscoelastic and commonly
show hysteretic elastic effects. Most metals, however, tend to only
have linear elastic behavior. Yet the relationship between stress
or strain amplitude and fatigue life are asserted for polymers in
the same way as for metals. Most polymeric materials exhibit vastly
less endurance fatigue levels compared to structural metals, i.e.,
steel, stainless steel, titanium and Nitinol (nickel-titanium
alloy).
[0056] It is the polymer's hysteretic elastic effects that make the
spacer fabric structure so resilient to compressive set.
[0057] While in most engineering materials load increases with
deflection upon loading in a linear way, and decreases along the
same path upon unloading, shape memory metals (e.g., Nitinol)
exhibit a distinctly different behavior, i.e., they have a
hysteretic elastic behavior like weak polymers but large strength
like metals.
[0058] Looking now at FIG. 8, with Nitinol, upon loading, stress
first increases linearly with strain up to approximately 1% strain.
After a first "yield point", several percent strain can be
accumulated with only a small stress increase. The end of this
plateau ("loading plateau") is reached at about 8% strain. After
that, there is another linear increase of stress with strain.
Unloading from the end of the plateau region causes the stress to
decrease rapidly until a lower plateau ("unloading plateau") is
reached. Strain is recovered in this region with only a small
decrease of stress. See FIG. 8.
[0059] Nitinol exhibits a hysteresis stress-stain curve allowing
for 8% shape recovery before permanent set, a degree of shape
recovery which is unique for metals. The last portion of the
deforming strain is finally recovered in a linear fashion again.
The unloading stress can be as low as 25% of the loading stress.
For comparison, the straight line representing the linear elastic
behavior according to Hook's law for steel is also shown in FIG.
8.
[0060] Nitinol has a hysteresis stress-strain curve similar to
polymers but unique to metals. When the spacer fabric is made of
strong Nitinol, it can support heavy loads, eventually deflect
under these weight-bearing loads and cushion the loads, and then
recover its shape when the loads are removed.
[0061] In one preferred form of the invention, the Nitinol spacer
fabric 105 has enhanced cushion energy (CE), enhanced cushion
factor (CF) and enhanced resistance to dynamic compression as
compared to polymer spacer fabrics. Cushion energy (CE) is the
energy required to gradually compress a specimen of the material up
to a standard pressure with a tensile-compression testing machine.
Cushion factor (CF) is a bulk material property and is assessed
using a test specimen greater than sixteen millimeters thick. The
pressure on the surface of the test specimen at a pre-defined
loading is multiplied by the volume of the test specimen under no
load. This pressure is then divided by the cushion energy (CE) of
the specimen at the pre-defined load. Lastly, the resistance to
dynamic compression measures changes in dimensions and in cushion
energy (CE) after a prolonged period of dynamic compression.
[0062] And in one particularly preferred form of the present
invention, the spacer fabric comprises a shape memory material
(e.g., Nitinol) that is kink resistant. Unlike most metals, Nitinol
wires have a unique quality of being kink resistant. These wires
can be bent 10 times more than stainless steel wires can be bent
without experiencing permanent deformation. For example, a 0.035
inch Nitinol wire can be wrapped around a 0.50 inch diameter
mandrel without taking a set, while a stainless steel wire of the
same diameter can only be bent around a 5 inch diameter mandrel
without taking a set or being plastically deformed.
[0063] Kink resistance is an important feature of Nitinol spacer
fabrics when being produced on the double bar knitting machines.
Other metals will not allow for tight radii bending during knitting
without kinking, however, Nitinol does allow for tight radii
bending during knitting without kinking. In application, Nitinol
spacer fabric can be completely compressed (crushed) flat and will
return to its original height when the deforming force is removed
without kinking. Other structural metals such as steel, stainless
steel and titanium will kink after being crushed.
[0064] In another preferred form of the present invention, the
Nitinol spacer fabric has enhanced dampening and cushioning
characteristics compared to other metals, and even polymers, by
exploiting the shape memory material's unique ability to recover
large strains due to a solid-solid phase transformation and to
dissipate energy because of the resulting internal friction.
[0065] It is known that the high damping capacity of the
thermoelastic martensitic phase of Nitinol is related to the
hysteretic movement of crystallographic interfaces in the alloy
(martensite variant interfaces and twin boundaries). Also, the
damping capacity of a shape memory material (SMM) depends directly
on external variables such as heating rate, frequency and
oscillation amplitude; and internal variables such as the type of
material, grain size, martensite interface density and structural
defects. In Nitinol, a high damping capacity and a low storage
modulus in the martensitic state is observed. It has been verified
that during phase transformation, there is the presence of a peak
in damping capacity and an equivalent increase of storage modulus.
The storage modulus, represented by the elastic component and
related to a material's stiffness.
[0066] A comparative study on the dynamic properties of structural
materials was carried out and clearly demonstrates the superior
damping behavior of shape memory alloy (SMA) Nitinol over classical
structural materials under the same external conditions. Among
other things, Nitinol (NiTi) shape memory alloy (SMA) specimens
were compared to commercial aluminum, stainless steel and brass as
samples of classical materials. All beam specimens were submitted
to Dynamic Mechanical Analysis (DMA) tests using a commercial
apparatus in a single cantilever mode under temperature variation.
Damping capacity and storage-modulus variation were analyzed.
[0067] Dynamic modulus is the ratio of stress-to-strain under
vibratory conditions calculated from data obtained from either free
or forced vibration tests, in shear, compression or elongation. It
is a property of viscoelastic materials. The storage modulus and
loss modulus in viscoelastic solids measure the stored energy,
representing the elastic portion, and the energy dissipated as
heat, representing the viscous portion, respectively. Damping
behavior of all specimens were observed, with the NiTi SMA,
aluminum, stainless steel and brass specimens being submitted to a
temperature ramp of 5.degree. C./min with a frequency of 1 Hz and 5
.mu.m of oscillation amplitude. See FIG. 9.
[0068] The NiTi SMA showed, in the martensitic state (between room
temperature and about 70.degree. C.), a higher damping capacity in
comparison with the other studied materials. This difference in
damping capacity increases even more in the phase transformation
temperature range (between 70.degree. C. and 90.degree. C.), when
the NiTi specimen presents a significant peak in its damping
capacity; while aluminum, stainless steel and brass samples present
relatively modest, incremental increases. For temperatures higher
than 90.degree. C., the NiTi SMA is fully in the austenitic state,
which intrinsically presents smaller energy absorption than the
martensitic state. The fact that the NiTi SMA alloy is in its fully
austenitic state explains the decrease in its damping capacity in
this temperature range, as compared to the NiTi SMA alloy when it
is in its martensitic state. Better damping capacity values can
also be obtained from the NiTi SMA as the oscillation amplitude
and/or frequency decreases and as the heating rate increases.
[0069] The storage modulus variation is better visualized in
relation to room temperature. While a reduction of 5% is perceived
in classical materials, a clearly superior increase of about 17%
occurs in NiTi SMA. See FIG. 10.
[0070] The nickel-titanium ratio of Nitinol can be modified to
lower the phase transformation temperature to keep the material
martensitic between freezing and 90.degree. C.
[0071] This comparative study has shown the high damping capacity
of NiTi SMA in the martensitic state and during phase
transformation. Even better damping values can be obtained from
NiTi SMA as the oscillation amplitude, frequency and heating rate
varies. The study also showed a significant increase in storage
modulus during phase transformation.
[0072] Nitinol can be very useful when designing a spacer fabric
that requires stiffness control, since the phase transformation is
reversible. By contrast, classic structural materials (e.g.,
stainless steel, aluminum, brass, etc.) present an almost-linear
increase in damping capacity and similar decrease in storage
modulus. Other metals and polymers do not have this unique phase
transformation and therefore will not provide a spacer fabric
construct with an improved storage modulus due to a shock-absorbing
attenuation from hysteresis.
[0073] Nitinol is characterized by a specific stress-strain diagram
that is different from the deformation behavior of conventional
materials. Typical stress-strain diagrams for stainless steel, NiTi
alloy, and living tissues are illustrated. See FIG. 11. In the case
of stainless steel, the elastically recovered strain (linear
portion) is lower than 0.5%. Once the elastic limit is exceeded,
stainless steel yields (dislocation slip) and considerable increase
in strain is achieved. This increase in strain, where the metal
appears to flow like a viscous liquid, is called plastic
deformation and allows the materials to acquire a permanent set
that cannot be recovered after the stress is released.
[0074] In one preferred form of the invention, the protective
padding is constructed out of a shape memory material which is
engineered to oscillate between phase transformations so as to
maximize its peak dampening characteristics and storage
modulus.
[0075] In shape memory materials (SMMs) like Nitinol, early
deformation is also linearly proportional to the applied stress.
Thereafter, deformation continues without a significant increase in
the force (upper loading plateau). During unloading, the
constraining force is again constant over a wide range of shapes
(unloading plateau). Up to 8% of deformation is recoverable in
Nitinol. When NiTi is used as a spacer fabric, the fibers are
superelastic and the three dimensional structure can recover up to
100% of its shape after being compressed.
[0076] Further details of the present invention are described
below.
[0077] Shape Memory Material (SMM) Spacer Fabric
[0078] As noted above, spacer fabrics are two separate fabrics
faces, usually knitted independently and then connected by a
separate filler spacer fiber. See, for example, FIG. 7, which shows
a three-dimensional knit spacer fabric 105 which includes a first
fabric layer 110, a second fabric layer 115 and yarns 120
interconnecting the two layers 110, 115, wherein some of the yarns
120 interconnecting the two layers 110, 115 are substantially
perpendicular to the first and second fabric layers 110, 115, while
the remaining interconnecting yarns 120 are disposed at an acute
angle between the two layers 110, 115, and further wherein at least
the yarns 120 are formed out of a shape memory material (SMM) such
as Nitinol. In one preferred form of the invention, first fabric
layer 110, second fabric layer 115 and interconnecting filaments
120 are all formed out of a shape memory material (SMM) such as
Nitinol.
[0079] The SMM spacer fabric 105 can be produced on both circular
and flat knitting machines, using either warp or weft techniques.
They may be produced as a flat sheet, or as a cylindrical tube.
[0080] As seen in FIG. 12, a double needle bar warp knitting
machine can be used to produce Nitinol spacer fabrics.
[0081] SMM spacer fabrics have three distinct layers. The three-ply
SMM structures have good breathability, wettability, crush
resistance, and a 3D porous appearance. Each layer of the SMM
spacer fabric can be made of different materials and have different
porosity levels and geometry. These SMM spacer fabrics can be
stacked on one another to form a multi-level spacer fabric
construct. See FIG. 13, which shows a multi-level spacer fabric
construct 125 comprising a first layer 130, a second layer 135, a
plurality of interconnecting filaments 140 extending between the
first and second layers 130, 135, a third layer 145, a fourth layer
150, and a plurality of interconnecting filaments 155 extending
between the third and fourth layers 145, 150, etc.
[0082] Additionally, it is possible to knit a multi-level spacer
fabric using specialized equipment.
[0083] The SMM spacer fabric can be designed to have an overall
porosity ranging from 10% to 98%, with pore sizes ranging from
100-5000 microns depending on the application. The modulus of
elasticity of this stand-alone SMM spacer fabric material can be
engineered to have a modulus between 25 and 100 kN/m. The SMM
spacer fabric material can be designed to deform almost 100% under
an applied load.
[0084] The diameter of the starting fiber greatly determines the
mechanical properties of the final SMM spacer fabric structure.
Thicker fibers result in a stiffer final construct. The upper limit
for the fiber diameter is determined by the knitting machine being
used. Preferably, the diameter of the fiber is between 0.05 inch
and 0.0002 inch. Most preferably, the fiber is between 0.01 inch
and 0.003 inch.
[0085] A SMM spacer fabric is superelastic (SE), meaning that if it
is deformed, it is capable of returning to its original shape once
the deforming force is removed. Additionally, a SMM spacer fabric
can exhibit a shape memory effect (SME), meaning that it can be
dynamic under the influence of temperature change, i.e., body
temperature. As an example of an SME application, the dynamic
spacer fabric can be in a compressed state at a temperature below
body temperature (37.degree. C.), and after being heated above body
temperature, return to its original shape.
[0086] Polyester, a typical polymeric material used in spacer
fabrics, has a stiffness of 2 GPa, and a tensile strength of 80
MPa. Nitinol has superior mechanical properties to polyester.
Nitinol has an austenitic modulus of 83 GPa, and an austenitic
tensile strength of 690 MPa. Nitinol can form a weaker
stress-induced martensite phase at approximately 400 MPa (58,000
PSI). It is possible to engineer the shape memory material spacer
fabric construct so that its superelastic regime toggles between
martensite and austenite phases for enhanced dampening
characteristics. See FIG. 14.
[0087] SMM spacer fabric is also advantageous when used for custom
protective padding. Instead of having to scan a patient's anatomy
and custom machine the custom protective padding, custom SMM spacer
fabric can be made by shape setting the SMM spacer fabric. In one
example of this, where the custom protective padding is to be used
in a helmet, the patient presses their head against a "bed" of
stainless steel pins, deforming the stainless steel pins to the
geometry of their head. The far side of the stainless steel pins
presses against the SMM spacer fabric, deforming the SMM spacer
fabric to the shape of the head. The stainless steel pins can then
be locked into place against the SMM spacer fabric, and the
patient's head removed from the "bed" of stainless steel pins. The
deformed SMM spacer fabric can then be heated to 450.degree. C. for
2 minutes and quenched so that, when the stainless steel pins are
removed, the spacer fabric will permanently hold this shape. The
heating to shape-set the SMM spacer fabric can also be accomplished
by applying a current to the SMM spacer fabric and heating it
through resistive heating effects. This represents a much more
rapid and cost effective method for producing custom protective
padding.
[0088] The SMM spacer fabric can also be impregnated with a gel,
such as a silicone gel, and/or other various polymeric materials.
The metallic spacer fabric acts as a spring, absorbing the energy
imparted through the SMM spacer fabric during impact (e.g., when
hit by a ball, a stick, etc.). The SMM spacer fabric also provides
cushioning, by supporting the surface area of the adjacent anatomy.
The gel material (or other impregnating material) acts as a damper,
dissipating this energy efficiently. The SMM spacer fabric can give
support to the gel (or other impregnating material) so as to
increase its stiffness and fatigue endurance limit and can be
viewed as somewhat analogous to the use of rebar and mesh in
concrete. The gel (or other impregnating material) can be made with
Shore 00 hardness of 30 (Extra Soft) to a Shore D hardness of 30
(Hard). Additionally, impregnating the SMM spacer fabric with the
gel or other material keeps the individual wires of the SMM spacer
fabric in place. Thus, if SMM spacer fabric should be cut during
use, fraying of the Nitinol spacer fabric can be mitigated.
[0089] Alternatively, a polymeric material that exhibits a
solid-to-viscous fluid transition under applied load can be used to
impregnate the spacer fabric. One example of such a polymer is
Ultra High Molecular Weight Polyethelyne (UHMPE). Energy from the
impact of an object is absorbed by the solid UHMPE. The peak force
of impact causes the solid UHMPE to undergo a phase change and
become liquid. The energy from the loading of the protective
padding is absorbed by the UHMPE, and the wearer experiences
increased cushioning from this effect. As the protective padding is
unloaded, the liquid UHMPE reverts back to the solid state, and is
ready for the next impact.
[0090] The SMM spacer fabric can be coated with a thin layer of
silver to impart antifungal and antibacterial properties. In one
preferred embodiment of the invention, the silver is
electrochemically coated onto the SMM spacer fabric. Alternatively,
the layer of silver can be deposited using a chemical or physical
vapor deposition method.
[0091] The silver coating can also be applied to the Nitinol wire
before Nitinol wire is knit into the spacer fabric construct. The
Nitinol wire can be plated with silver using one of the
aforementioned techniques. Alternatively, the silver-coated Nitinol
wire can be created by drawing a metal on metal composite (e.g., a
Nitinol core and a silver outer tube) so as to create the final
silver-coated Nitinol wire.
[0092] If desired, the SMM spacer fabric can be coated with a
polymer coating such as Teflon (PTFE) so as to change the texture
of the spacer fabric (i.e., to make it smooth and give it a plastic
feel instead of a metallic feel). In this form of the invention,
the polymer coating can be applied to the entire spacer fabric, or
the polymer coating can be applied to only selected portions of the
spacer fabric (e.g., to the outer fabric layer, the inner fabric
layer, and/or to the interconnecting filaments which extend between
the outer fabric layer and the inner fabric layer). Alternatively,
the polymer coating can be applied to the Nitinol wire before the
Nitinol wire is knit into the spacer fabric construct.
[0093] Use Of SMM Spacer Fabric For Protective Padding
[0094] A SMM spacer fabric can be used for protective padding in
various applications.
[0095] By way of example but not limitation, SMM spacer fabric can
be used to form a helmet lining. More particularly, FIG. 15
illustrates a helmet 200 comprising a hard outer shell 205 (which
may be made out of metal, a hard plastic, etc.), a fabric harness
210 for seating helmet 200 on the head of a wearer, and a gap 215
located between fabric harness 210 and the inside surface of hard
outer shell 205. SMM spacer fabric 105 is disposed within gap 215,
interposed between the inside surface of hard outer shell 205 and
fabric harness 210, e.g., with first fabric layer 110 being
disposed adjacent to (or attached to) the inside surface of hard
outer shell 205 and second fabric layer 115 being disposed adjacent
to (or attached to) fabric harness 210, and with yarns 120 spanning
the distance between first fabric layer 110 and second fabric layer
115. By interposing SMM spacer fabric 105 between fabric harness
210 and hard outer shell 205, a protective padding layer is
provided, whereby to protect the head of a wearer from impact.
Thus, when hard outer shell 205 of helmet 200 is impacted by a
force, the resilient SMM spacer fabric compresses, whereby to
absorb the force and protect the head of the wearer from
injury.
[0096] If desired, helmet 200 can be in the form of a military
helmet, whereby to protect a soldier from blast injury, etc., or
helmet 200 can be in the form of a sports helmet (e.g., a football
helmet, a hockey helmet, a bicycle helmet, etc.), whereby to
protect an athlete from impact injury.
[0097] In this example, the stiffness of the SMM spacer fabric can
be modified so as to provide sufficient protection to a wearer's
head, with the force of impact being attenuated by the SMM spacer
fabric's dampening construct. Additionally, the SMM spacer fabric
can be heat set, i.e., by resistive heating, so as to contour to
the wearer's head for a better fit. By increasing the surface area
of the skull that is in contact with the SMM spacer fabric, the
impact forces can be dissipated and desirably lessened over a
larger area.
[0098] Superelastic spacer fabrics can also be incorporated into
various protective padding for other sporting applications. See,
for example, FIGS. 16 and 17, which illustrate body padding 220
(e.g., for lacrosse). Such body padding 220 may comprise a
protective torso guard 225, elbow protectors 230, gloves 235, etc.,
all of which incorporate SMM spacer fabric 105 in their
construction. In one preferred form of the invention, and looking
now at FIG. 17, the protective padding 220 may comprise an outer
surface 240 for receiving impact (and which may comprise a hard
plastic, a flexible material, etc.) and an inner surface 245 for
contacting the body of the wearer (and which may comprise a
suitable fabric such as felt). In such a configuration, second
fabric layer 115 of SMM spacer fabric 105 may reside adjacent to
(or be attached to) outer surface 240 and first fabric layer 110 of
SMM spacer fabric 105 may reside adjacent to (or be attached to)
inner surface 245, with yarns 120 spanning the gap between first
fabric layer 110 and second fabric layer 115. When a force (e.g.,
the impact of a lacross ball, of a lacross stick, of another
player, etc.) contacts outer surface 240, yarns 120 are temporarily
compressed, whereby to absorb the impact and protect the wearer
from injury. Because yarns 120 are resilent, when the force is
removed, the SMM spacer fabric returns to its original
configuration, thereby maintaining its ability to shield the wearer
from another impact. Thus, SMM spacer fabric 105 is used to form a
layer of protective padding for absorbing an impact and protecting
the body of a wearer from injury.
[0099] Looking next at FIG. 18, SMM spacer fabric 105 can be
incorporated into hip padding 250, thigh padding 255, and torso
padding 260 for football applications. With the hip padding 250 and
thigh padding 255, the outer layer 240 may comprise the fabric of a
uniform, whereas with torso padding 260, outer layer 240 may
comprise a hard plastic.
[0100] Looking next at FIG. 19, for a hockey application, SMM
spacer fabric 105 can be incorporated into collar padding 265,
shoulder padding 270, elbow padding 275, torso padding 280 and/or
hip padding 285. As with the lacrosse and football padding
discussed above, collar padding 265, shoulder padding 270, elbow
padding 275, torso padding 280 and/or hip padding 285 each
incorporate SMM spacer fabric 105 between an inner surface 245 and
an outer surface 240. Again, outer surface 245 may be a hard
plastic (e.g., for collar padding 265, shoulder padding 270, elbow
padding 275 and torso padding 280), or fabric (e.g., for hip
padding 285).
[0101] In still another application, and looking now at FIG. 20,
SMM spacer fabric 105 can be incorporated into torso padding 290
and shoulder padding 295 for mountain biking applications. In the
mountain biking application, it is preferred that the outer layer
240 of the protective padding be a hard plastic.
[0102] It should be appreciated that for any protective padding
application, including but not limited to the sporting equipment
discussed above, SMM spacer fabric 105 may be used alone or in
combination with traditional padding. For example, different areas
of the protective padding may incorporate SMM spacer fabric 105
while other areas of the protective padding may incorporate
traditional padding materials (e.g., foam), or SMM spacer fabric
105 may be used in combination with (i.e., on top of or beneath) a
layer of traditional padding materials (e.g., foam), or multiple
layers of SMM spacer fabric 105 may be used, or any combination
thereof.
[0103] Moreoever, different varieties of SMM spacer fabric 105 may
be utilized, depending on the desired application. For example,
critical areas may incorporate SMM spacer fabric having longer
yarns 120 (and therefore a wider gap between first fabric layer 110
and second fabric 115) so as to be able to better absorb an impact
and protect the wearer, while less critical areas may incorporate
SMM space fabric having shorter yarns 120 (and therefore a smaller
gap).
[0104] Additionally, first fabric layer 110 and second fabric layer
115 can vary depending on the application or area of the equipment
on which they are employed.
[0105] Superelastic spacer fabrics can also be formed into clothing
so as to provide protective padded clothing.
[0106] Modifications Of The Preferred Embodiments
[0107] It should be understood that many additional changes in the
details, materials, steps and arrangements of parts, which have
been herein described and illustrated in order to explain the
nature of the present invention, may be made by those skilled in
the art while still remaining within the principles and scope of
the invention.
* * * * *