US20130298317A1

US20130298317A1 - Protective padding utilizing superelastic three-dimensional spacer fabric comprising shape memory materials (smm)

Info

Publication number: US20130298317A1
Application number: US13/942,287
Authority: US
Inventors: Matthew Fonte; Matthew Palmer
Original assignee: MX Orthopedics Corp
Current assignee: Arthrex Inc
Priority date: 2012-02-09
Filing date: 2013-07-15
Publication date: 2013-11-14

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.

Description

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

This patent application:

- (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);
- (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
- (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).

The nine (9) above-identified patent applications are hereby incorporated herein by reference.

FIELD OF THE INVENTION

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

Protective padding is well known for protecting the body against impact, e.g., during sporting events, hazardous activities, military situations, etc.
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.
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.
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.
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.
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.
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.
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
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.
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

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.
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.
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.
In one preferred form of the present invention, there is provided protective padding comprising:

In another preferred form of the present invention, there is provided 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.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 is a schematic view showing a neoprene foam sheet;

FIG. 2 is a schematic view showing a conventional polymer spacer fabric, with the spacer fabric being compressed;

FIG. 3 is a schematic view showing various conventional polymer spacer fabrics with different mechanical properties;

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;

FIG. 5 is a schematic view showing creep behavior for polymer materials;

FIG. 6 is a schematic view showing a spacer fabric made from shape memory material;

FIG. 7 is a schematic view showing a spacer fabric made from Nitinol;

FIG. 8 is a schematic view showing the stress-strain curves for steel and Nitinol;

FIG. 9 is a schematic view showing the damping capacity of Nitinol, aluminum, stainless steel and brass as a function of temperature;

FIG. 10 is a schematic view showing the storage modulus capacity of Nitinol, aluminum, stainless steel and brass as a function of temperature;

FIG. 11 is a schematic view showing the stress-strain diagram for bone, Nitinol and stainless steel;

FIG. 12 is a schematic view showing a double needle bar warp knitting machine for the production of Nitinol spacer fabrics;

FIG. 13 is a schematic view showing how superelastic spacer fabrics can be layered on top of each other;

FIG. 14 is a schematic view showing the formation of stress-induced martensite;

FIG. 15 is a schematic view showing the use of Nitinol spacer fabric to form protective padding for a helmet;

FIG. 16 is a schematic view showing the use of Nitinol spacer fabric to form protective padding for a lacrosse application;

FIG. 17 is a schematic cross-sectional view showing protective padding formed out of shape memory material (SMM) spacer fabric;

FIG. 18 is a schematic view showing the use of Nitinol spacer fabric to form protective padding for a football application;

FIG. 19 is a schematic view showing the use of Nitinol spacer fabric to form protective padding for a hockey application; and

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

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.
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.
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.
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).
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.
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.
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).
It is the polymer's hysteretic elastic effects that make the spacer fabric structure so resilient to compressive set.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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° C./min with a frequency of 1 Hz and 5 μm of oscillation amplitude. See FIG. 9.
The NiTi SMA showed, in the martensitic state (between room temperature and about 70° 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° C. and 90° 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° 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.
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.
The nickel-titanium ratio of Nitinol can be modified to lower the phase transformation temperature to keep the material martensitic between freezing and 90° C.
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.
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.
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.
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.
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.
Further details of the present invention are described below.
Shape Memory Material (SMM) Spacer Fabric
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.
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.
As seen in FIG. 12, a double needle bar warp knitting machine can be used to produce Nitinol spacer fabrics.
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.
Additionally, it is possible to knit a multi-level spacer fabric using specialized equipment.
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.
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.
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° C.), and after being heated above body temperature, return to its original shape.
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.
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° 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.
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.
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.
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.
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.
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.
Use Of SMM Spacer Fabric For Protective Padding
A SMM spacer fabric can be used for protective padding in various applications.
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.
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.
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.
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.
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.
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).
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.
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.
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).
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.
Superelastic spacer fabrics can also be formed into clothing so as to provide protective padded clothing.
Modifications Of The Preferred Embodiments
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.

Claims

What is claimed is:

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.