Rate responsive, stretchable devices further improvements
Inventors
Wetzel, Eric D. • Nenno, Paul T.
Assignees
United States Department of the Army
Publication Number
US-9958023-B2
Publication Date
2018-05-01
Expiration Date
2033-06-26
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Abstract
Rate-dependent, elastically-deformable devices according to various embodiments can be stretched and recovered at low elongation rates. Yet they become stiff and resistive to stretching at high elongation rates. In one embodiment, a rate-dependent, elastically-deformable device includes an elastically-deformable confinement member; one or more filaments placed inside the elastically-deformable confinement member; and a fluid that substantially fills the remaining volume inside the elastically-deformable confinement member. The resistance force to extension of the device is designed to increase as the extension rate of the device increases. At low elongation rates the filaments can readily slide past each other. At high elongation rates, the fluid transforms to a less flowable material that greatly increases the force and energy required for elongation; or transforms to a non-flowable material that resists elongation. The devices thus can be stretched and recovered at low elongation rates, but become extremely stiff and resistive to stretching at high elongation rates.
Core Innovation
The invention provides rate-dependent, elastically-deformable devices that can be stretched and recovered easily at low elongation rates but become stiff and resist stretching at high elongation rates. Such devices comprise an elastically-deformable confinement member housing one or more internal filaments and a fluid filling the remaining volume. The force resisting extension increases with the rate of elongation, enabling the filaments to slide past each other at low rates while the fluid becomes less flowable or non-flowable at high rates, significantly increasing resistance.
Problems addressed include the limited ability of conventional elastic devices, such as knee braces and elastic bands, to restrict rapid motions that cause injuries. Rapid twisting and translations of limbs are common injury causes, especially for soldiers carrying heavy equipment. Traditional devices do not effectively resist these rapid, injurious motions, leading to musculoskeletal injuries and lost work time.
The devices use fluids with rate-dependent rheological properties, including shear thickening fluids, electrorheological fluids, or magnetorheological fluids, to enable transition from a flowable state at low elongation rates to a stiffened or locked state at high elongation rates. The confinement member can be made from various elastomers or polymers with possible anisotropic properties to optimize performance. Filaments may have shapes or surface features to enhance fluid shearing and device responsiveness.
Claims Coverage
The patent contains four independent claims describing different embodiments of rate-dependent, elastically-deformable devices featuring inventive characteristics related to their structural components and rate-dependent resistance properties.
Filament-integrated barbed plug sealing and coupling
The device comprises an elastically-deformable confinement member with one or more filaments having integrally formed barbed plugs inserted into the confinement member ends to contain the fluid. The filaments are configured to provide shear to the internal fluid, seal the confinement member ends to prevent leakage, and mechanically couple with the confinement member. The plugs form a friction or interference fit with the confinement member and can be cut from a single sheet of various materials. Attachment sections such as loops or buckles may be integrated.
Filaments with discrete positions or steps for mechanical engagement
The device includes filaments inside the elastically-deformable confinement member having a series of discrete positions or steps that sequentially engage another structure within the confinement member, such as another filament or a fixed detent. These positions can be regularly or irregularly spaced and may employ ratcheting structures, ball and socket means, or bristle/line comb elements. Filament shapes include helical, wavy, sinusoidal, triangular wave, square wave, or sawtooth.
Opposing filament pair with selective attachment and fluid containment
The device features a pair of opposing filaments inside the confinement member, each attached at one end to opposite ends of the confinement member but unattached at the other ends, with a fluid substantially filling the remaining volume. The filaments at least partially overlap in the undeformed state and can be cables or ribbons. The confinement member can have anisotropic properties, with higher resistance to radial extension. The fluid can be non-Newtonian but not shear thickening, including shear thinning, thixotropic, rheopectic, Bingham, viscoplastic, or viscoelastic fluids.
Shear-thickening fluid with non-spherical solid particle suspension
The device contains a shear-thickening fluid comprising a suspension of non-spherical solid particles in a liquid inside the elastically-deformable confinement member with internal filaments. The resistance force to extension increases with extension rate. The non-spherical particles have an aspect ratio of about 2:1 or more and may comprise precipitated calcium carbonate (PCC) particles.
The claims cover structural innovations in elastically-deformable devices involving integrally formed barbed plugs for sealing and coupling, filament configurations with discrete engaging steps for mechanical locking, opposing filament pairs with selective attachments, and use of shear-thickening fluids with specific non-spherical particle suspensions to achieve rate-dependent extension resistance.
Stated Advantages
Devices become stiff and resistive to rapid stretching events while remaining flexible and stretchable under low-rate elongations.
Provides higher resistance to motion during high-speed events, preventing injuries such as twisted knees and ankles.
Rapid response time reaching high resistance within less than 100 milliseconds after force application.
Tailorable elongation rate response suitable for diverse applications by adjusting device materials and configurations.
Improved energy absorption during elongation due to plateau force behavior at high rates.
Enables new designs for orthotic devices, wearable closures, and safety equipment with dynamic stiffness.
Manufacturing advantages from integrated barbed ribbon filaments cut from single sheets eliminating adhesive joints.
Documented Applications
Orthotic devices including knee braces, ankle braces, head and neck restraint devices, back braces, wrist braces, slings, and similar wearable support apparatus.
Wearable protective and athletic equipment such as gloves with wrist closures and shoes or boots with ankle closures enabling self-adjusting, slip-on fits.
Head and neck restraint systems coupling helmets to protective vests or clothing for reduced injury during impacts or blasts.
Safety equipment, sporting/athletic equipment, and robotic assembly applications requiring rate-dependent elastic deformation.
Strapping materials and mechanical assemblies such as replacements for elastic straps or Velcro-type fasteners.
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