Patent Application
20060059606
The invention relates generally to protective headgear. More specifically, the invention relates to a layered construction of protective headgear using compressible materials.
Concussions, also called mild traumatic brain injury, are a common, serious problem in sports known to have detrimental effects on people in the short and long term. With respect to athletes, a concussion is a temporary and reversible neurological impairment, with or without loss of consciousness. Another definition for a concussion is a traumatically induced alteration of brain function manifested by 1) an alteration of awareness or consciousness, and 2) signs and symptoms commonly associated with post-concussion syndrome, such as persistent headaches, loss of balance, and memory disturbances, to list but a few. Some athletes have had their careers abbreviated because of concussions, in particular because those who have sustained multiple concussions show a greater proclivity to further concussions and increasingly severe symptoms. Although concussions are prevalent among athletes, the study of concussions is difficult, treatment options are virtually non-existent, and “return-to-play” guidelines are speculative. Accordingly, the best current solution to concussions is prevention and minimization.
Concussion results from a force being applied to the brain, usually the result of a direct blow to the head, which results in shearing force to the brain tissue, and a subsequent deleterious neurometabolic and neurophysiologic cascade. There are two primary types of forces experienced by the brain in an impact to the head, linear acceleration and rotational acceleration. Both types of acceleration are believed to be important in causing concussions. Decreasing the magnitude of acceleration thus decreases the force applied to the brain, and consequently reduces the risk or severity of a concussion.
Protective headgear is well known to help protect wearers from head injury by decreasing the magnitude of acceleration (or deceleration) experienced by their wearers. Currently marketed helmets, primarily address linear forces, but generally do not diminish the rotational forces experienced by the brain. Helmets fall generally into two categories: single-impact helmets and multiple-impact helmets. Single-impact helmets undergo permanent deformation under impact, whereas multiple-impact helmets are capable of sustaining multiple blows. Applications of single-impact helmets include, for example, bicycling and motorcycling. Participants of contact sports, such as hockey and football, use multiple-impact helmets. Both categories of helmets have similar construction. A semi-rigid outer shell distributes the force of impact over a wide area and a crushable inner layer reduces the force upon the wearer's head.
The inner layer of single-impact helmets are typically constructed of fused expanded polystyrene (EPS), a polymer impregnated with a foaming agent. EPS reduces the amount of energy that reaches the head by permanently deforming under the force of impact. To be effective against the impact, the inner layer must be sufficiently thick not to crush entirely throughout its thickness. A thick inner layer, however, requires a corresponding increase in the size of the outer shell, which increases the size and bulkiness of the helmet.
Inner layers designed for multiple-impact helmets absorb energy through elastic and viscoelastic deformation. To absorb multiple successive hits, these helmets need to rebound quickly to return to their original shape. Materials that rebound too quickly, however, permit some of the kinetic energy of the impact to transfer to the wearer's head. Examples of materials with positive rebound properties, also called elastic memory, include foamed polyurethane, expanded polypropylene, expanded polyethylene, and foamed vinylnitrile. Although some of these materials have desirable rebound qualities, an inner layer constructed therefrom must be sufficiently thick to prevent forceful impacts from penetrating its entire thickness. The drawback of a thick layer, as noted above, is the resulting bulkiness of the helmet. Moreover, the energy-absorbing properties of such materials tend to diminish with increasing temperatures, whereas the positive rebound properties diminish with decreasing temperatures. There remains a need, therefore, for an improved helmet construction that can reduce the risk and severity of concussions without the aforementioned disadvantages of current helmet designs.
In one aspect, the invention features protective headgear comprising an outer layer having an internally facing surface, an inner layer having a surface that faces the outer layer, and a middle layer having a plurality of compressible members disposed in a fluid-containing interstitial region bounded by the inner and outer layers. Each compressible member is attached to the surface of the inner layer and to the internally facing surface of the outer layer. The protective headgear also has at least one passageway by which fluid can leave the middle layer when the protective headgear experiences an impact.
In another aspect, the invention features a method for making protective headgear comprising forming a multi-layered shell by forming a plurality of individually compressible members, providing an outer layer and a inner layer, and producing a composite structure with the individually compressible members being disposed in an interstitial region bounded by the outer and inner layers, each compressible member being attached to an internally facing surface of the outer layer and to a surface of the inner layer facing the outer layer.
The above and further advantages of this invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like numerals indicate like structural elements and features in various figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
The present invention relates to protective headgear designed to lessen the amount of force that reaches the brain of the wearer from an impact to the head. The headgear has a shell with a multilayer construction for cushioning the impact, thus slowing the change in velocity of the wearer's head, producing a corresponding decrease in the magnitude of acceleration or deceleration experienced by the wearer, and reducing the risk or severity of concussion. As described further below, the shell has an outer layer, an energy-absorbing layer, and an inner layer, with one or more of these layers being constructed of an energy-absorbing compressible material. In a preferred embodiment, this compressible material is a thermoplastic elastomer (TPE).
Various embodiments of the energy-absorbing layer of the shell function to provide an air cushion during an impact to the headgear. In a preferred embodiment, an impact causes air to be expelled from the energy-absorbing layer. Protective headgear of the invention can respond to an impact by moving in any one or combination of ways, including (1) globally compressing over a broad area of the shell, (2) locally compressing at the point of impact, (3) flexing by the outer layer of the shell, and (4) rotating by the outer layer and the energy-absorbing layer with respect to the inner layer.
The layered construction of the invention can be used to construct a variety of types of protective headgear including, but not limited to, safety helmets, motorcycle helmets, bicycle helmets, ski helmets, lacrosse helmets, hockey helmets, and football helmets, batting helmets for baseball and softball, headgear for rock and mountain climbers, and headgear for boxers. Other applications can include helmets used on construction sites, in defense and military applications, and for underground activities. Although the following description focuses primarily on protective headgear, it is to be understood that the layered construction of the invention applies to other types of equipment used for sports activities or for other applications, e.g., face masks, elbow pads, shoulder pads, and shin pads.
The helmet 2 has ventilation openings 6 near the top to permit air to flow for cooling the wearer's head. Here, the ventilation openings 6 are teardrop shaped, each pointing toward the rear 10 of the helmet 2 to give a visual sensation of speed. For clarity sake, the various layers of the materials used in the construction of the helmet 2 appear in the openings 6 as a single layer 14. Ventilation openings can also be on the other side of the helmet 2 (not shown) if the helmet has a symmetric design. Such openings 6 are exemplary, and can have various other shapes or be omitted altogether, depending upon the type of helmet. Also, helmets constructed in accordance with the invention can have other types of openings, such as ear holes.
As described in detail below, each of the layers can be constructed of a lightweight material, thus contributing towards the construction of a lightweight helmet. Although not drawn to scale,
The outer shell layer 20 covers the middle layer 24 and serves various functions. For example, the outer shell layer 20 can provide durability by protecting the helmet 2 from punctures and scratches. Other functions include presenting a smooth surface for deflecting tangential impacts, waterproofing, and displaying cosmetic features such as coloring and identifying the product brand name. In a preferred embodiment, this outer shell layer 20 is made of a thermoplastic material.
Beneath the outer shell layer 20, the compressible middle layer 24 covers an outer surface of the inner shell layer 28. The middle layer 24 attaches to the inner shell layer 28. A primary function of the middle layer 24 is impact energy absorption. Preferably, the middle layer 24 is constructed of a thermoplastic elastomer material.
Thermoplastic elastomers or TPEs are polymer blends or compounds, which exhibit thermoplastic characteristics that enable shaping into a fabricated article when heated above their melting temperature, and which possess elastomeric properties when cooled to their designed temperature range. Accordingly, TPEs combine the beneficial properties of plastic and rubber, that is, TPEs are moldable and shapeable into a desired shape when heated and are compressible and stretchable when cooled. In contrast, neither thermoplastics nor conventional rubber alone exhibits this combination of properties. Further, introduction of a chemical foaming agent during processing can change certain TPEs into foam. This foaming serves to reduce the density and weight of the material, and to increase its compressibility. The resulting foam material remains a TPE.
To achieve satisfactory purposes, conventional rubbers must be chemically crosslinked, a process often referred to as vulcanization. This process is slow, irreversible, and results in the individual polymer chain being linked together by covalent bonds that remain effective at normal processing temperatures. As a result, vulcanized rubbers do not become fluid when heated to these normal processing temperatures (i.e., the rubber cannot be melted). When heated well above normal processing temperatures, vulcanized rubbers eventually decompose, resulting in the loss of substantially all useful properties. Thus, conventional vulcanized rubbers cannot be formed into useful objects by processes that involve the shaping of a molten material. Such processes include injection molding, blow molding and extrusion, and are extensively used to produce useful articles from thermoplastics.
Thermoplastics are generally not elastic when cooled and conventional rubbers are not moldable using manufacturing processes and equipment currently used for working with thermoplastics, such as injection molding and extrusion. These processes, however, are applicable for working with TPEs.
Most TPEs have a common feature: they are phase-separated systems. At least one phase is hard and solid at room temperature and another phase is elastomeric and fluid. Often the phases are chemically bonded by block or graft polymerization. In other cases, a fine dispersion of the phases is apparently sufficient. The hard phase gives the TPEs their strength. Without the hard phase, the elastomer phase would be free to flow under stress, and the polymers would be unusable. When the hard phase is melted, or dissolved in a solvent, flow can occur and therefore the TPE can be processed. On cooling, or upon evaporation of the solvent, the hard phase solidifies and the TPEs regain their strength. Thus, in one sense, the hard phase of a TPE behaves similarly to the chemical crosslinks in conventional vulcanized rubbers, and the process by which the hard phase does so is often called physical crosslinking. At the same time, the elastomer phase gives elasticity and flexibility to the TPE.
Examples of TPEs include block copolymers containing elastomeric blocks chemically linked to hard thermoplastic blocks, and blends of these block copolymers with other materials. Suitable hard thermoplastic blocks include polystyrene blocks, polyurethane blocks, and polyester blocks. Other examples of TPEs include blends of a hard thermoplastic with a vulcanized elastomer, in which the vulcanized elastomer is present as a dispersion of small particles. These latter blends are known as thermoplastic vulcanizates or dynamic vulcanizates.
TPEs can also be manufactured with a variety of hardness values, e.g., a soft gel or a hard 90 Shore A or greater. One characteristic of the TPE material is its ability to return to its original shape after the force against the helmet 2 is removed (i.e., TPE material is said to have memory). Other characteristics of TPE include its resistance to tear, its receptiveness to coloring, and its rebound resilience elasticity. Rebound resilience elasticity is the ratio of regained energy in relation to the applied energy, and is expressed as a percentage ranging from 0% to 100%. A perfect energy absorber has a percentage of 0%; a perfectly elastic material has a percentage of 100%. In general, a material with low rebound resilience elasticity absorbs most of the applied energy from an impacting object and retransmits little or none of that energy. To illustrate, a steel ball that falls upon material with low rebound resilience elasticity experiences little or no bounce; the material absorbs the energy of the falling ball. In contrast, the ball bounces substantially if it falls upon material with high rebound resilience elasticity.
Preferred embodiments of the middle layer 24 are constructed of a TPE material with low rebound resilience elasticity (here, a low rebound resilience elasticity corresponds to a rebound percentage of approximately 50% or less, and preferably 25% or less). Examples of TPEs with low rebound resilience elasticity include Trefsin™, manufactured by Advanced Elastomer Systems of Akron, Ohio, and the product TP6DAA manufactured by Kraiburg TPE Corp of Duluth, Ga. An advantage of these TPEs is that their low rebound characteristic exists over a wide range of temperatures. Preferably, the TPE material of the middle layer 24 has a glass-transition temperature of less than −20 degrees Fahrenheit. The glass-transition temperature is the temperature below which the material loses its soft and rubbery qualities. A TPE material with an appropriate glass-transition temperature can be selected for the middle layer 24 depending on the particular application of the helmet 2 (e.g., a glass-transition temperature of 0 degrees Fahrenheit may be sufficient for baseball helmets, whereas a glass-transition temperature of −40 degrees Fahrenheit may be needed for football and hockey helmets).
TPEs can also be formed into a variety of structures. In one embodiment, the middle layer 24 is processed into individual members, such as cylindrical columns, or other shapes such as pyramids, spheres, or cubes, allowing for independent movement of each member structure, and for the free flow of air around the members during an impact. Preferably, the individual members each have an air-filled chamber, as described in more detail below. In another embodiment, the layer has a honeycomb structure (i.e., waffle-type). The interconnected hexagonal cells of a honeycombed structure provide impact absorption and a high strength-to-weight ratio, which permits construction of a lightweight helmet. The interconnected cells absorb and distribute the energy of an impact evenly throughout the structure. The honeycomb structure also reduces material costs because much of the material volume is made of open cells. This structure can be any one in which the material is formed into interconnected walls and open cells. The cells can have a shape other than hexagonal, for example, square, rectangular, triangular, and circular, without departing from the principles of the invention.
The formation of the middle layer 24 on the inner shell layer 28 can be accomplished using an extrusion, blow molding, casting, or injection molding process. The compressible middle layer 24 and inner shell layer 28 can be manufactured separately and adhered together after production, or they may be manufactured as one component, with the two layers being adhered to each other during manufacturing. TPEs bond readily to various types of substrates, such as plastic, and, thus, TPEs and substrates are commonly manufactured together. With respect to solid and foam forms of TPE structures, the softness (or conversely, the hardness) of the middle layer 24 can also be determined over a range of durometers. Preferably, the hardness range for these forms is between 5 and 90 on the Shore A scale, inclusive. The thickness of the middle layer 24 can be varied without departing from the principles of the invention. In one embodiment, the middle layer 24 is approximately ¼ to one inch thick.
The inner shell layer 28 is constructed of a hardened material, such as a rigid thermoplastic, a thermoplastic alloy, expanded polystyrene, or a fiber-reinforced material such as fiberglass, TWINTEX®, KEVLAR®, or BP Curv™. The inner shell layer 28 operates to provide structure to the helmet 2, penetration resistance, and impact energy distribution to the internal liner 32. In one embodiment, the thickness of the inner shell layer 28 is 1/16th of an inch. The thickness of the inner shell layer 28 can be varied without departing from the principles of the invention.
Providing another impact energy-absorbing layer, the internal liner 32 contacts the wearer's head. Other functions of the internal liner 32 may include sizing, resilience, airflow, and comfort. In general, the internal liner 32 is constructed of a thermoplastic elastomer, a foam material of, for example, approximately ½ to 1 inch thickness, or it may be constructed of expanded polystyrene. The compressible internal liner 32 is attached to an inner surface of the inner shell layer 28. The method of attachment depends upon the type of materials used (of the inner shell layer 28 and of the internal liner 32).
Embodiments of the internal liner 32 include one or more of the following, either alone or in combination: thermoplastic elastomer (TPE), expanded polystyrene, expanded polypropylene, vinyl nitrile, silicone gel, silicone foam, viscoelastic or memory foam, and polyurethane foam. The thickness and type of foam material can be varied without departing from the principles of the invention.
Important to the use of the helmet of the invention is for the helmet to fit properly and to remain in place during the impact. In an embodiment not shown, the helmet extends downwards from the regions near the ears and covers the angle of the wearer's jaw. This extension may be flexible, and when used in conjunction with a chinstrap, may be drawn in tightly to provide a snug fit around the jaw.
Members 50 can range from approximately one-eighth inch to one inch in height and one-eighth inch to one-half inch in diameter, and need not be of uniform height or diameter. Although shown to have the shape of columns, the members 50 can have a variety of shapes, for example, pyramidal, cubic, rectangular, spherical, disc-shaped, and blob-shaped. Preferably, the members 50 are constructed of TPE material (e.g., solid form, foam), although other types of compressible materials can be used for producing the members 50, without departing from the principles of the invention, provided such materials can make the members sufficiently resilient to respond to various types of impact by leaning, stretching, shearing, and compressing.
In one embodiment, there is a spatial separation between each member 50. Referred to herein as an interstitial region 52, the spacing between the members 50 bounded between the inner and outer layers 28′, 20′ defines a volume of fluid. As used herein, this fluid is any substance that flows, such as gas and liquid. The distance between adjacent members 50 can be designed so that a desired proportion of the volume of the shell 30′ (e.g., >50%) is comprised of fluid. In a preferred embodiment, the fluid within the interstitial region 52 is air. An air-containing interstitial region 52 provides for lightweight headgear.
In
The TPE foam structure 61 is placed (step 68) between and attached to a first sheet 62 of material, to serve as the inner layer 28′, and a second sheet 63 of material to serve as the outer layer 20′. The compressible members may be attached to the inner layer 28′ one member 50 at a time, for example, by adhesive. Alternately, each member 50 can have a point, nozzle, stem, which can be inserted into an appropriately shaped opening in the inner layer 28′ to hold that member in place. In one embodiment, the TPE foam structure 61 has a common chemical component as the sheets 62, 63 for the inner and outer layers, thus enabling chemical adhesion between the TPE foam structure and each layer during the manufacturing process. Thus, secondary adhesives are unnecessary, although not precluded from being used, to attach the TPE foam structure to these layers. The resulting sheet of composite structure 65 can then be cut (step 72) and formed (step 76) into the desired shape of the shell 30′ (only a portion of the shell being shown).
Instead of cutting and shaping the inner, middle, and outer layers together, as described above, the manufacture and shaping of each of the three layers of the shell can occur independently, and then the independently formed layers can be adhered to one another. As another embodiment, the middle and inner layers can be shaped together and the outer layer independently; then, the outer layer can be adhered to the middle layer. This embodiment can lead to the modularization of the manufacture of helmets. For instance, the interior components of a helmet, i.e., the liner, inner layer, and middle layer, can have standardized construction (i.e., the same appearance irrespective of the type of sports helmet for which the interior components are to be used), with the outer sport-specific layer, which is adhered to the middle layer, or injection molded around the interior components, providing the customization of the helmet for a particular sport.
As shown in
The shell 30′ of the invention may reduce both linear acceleration and rotational acceleration experienced by the head of the headgear wearer. Linear acceleration occurs when the center of gravity of the wearer's head becomes rapidly displaced in a linear direction, such as might occur when the headgear is struck from the side. Rotational acceleration, widely believed to be a primary cause of concussion, can occur when the head rotates rapidly around the center of gravity, such as might occur when the headgear is struck tangentially. Most impacts impart both types of accelerations.
The size of the opening 136 is designed to produce a rate-sensitive response to any impact causing compression of the member 50′. For instance, if the application of force upon the member 50′ is gradual or of relatively low energy, the opening 136 permits sufficient air to pass through so that the member 50′ compresses gradually and presents little resistance against the force. For example, an individual may be able to compress the shell of the protective headgear manually with a moderate touch of a hand or finger, because the energy-absorbing middle layer and, in some embodiments, the outer and inner layers are made of compressible materials. Because the application of the force is gradual, the wearer's head is not likely to accelerate significantly and thus is less likely to experience concussion. In addition, the wearer may feel the air being expelled from the members 50′ onto his or her head, as described further below.
If, as illustrated by
As an illustration of an exemplary use of the invention,
While the invention has been shown and described with reference to specific preferred embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the following claims. For example, more than one type of compressible member can be combined to construct a shell for a protective headgear.
This application is a continuation-in-part application claiming priority to co-pending U.S. patent application Ser. No. 10/946,672, filed Sep. 22, 2004, titled “Layered Construction of Protective Headgear with one or More Compressible Layers of Thermoplastic Material,” the entirety of which patent application is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10946672 | Sep 2004 | US |
| Child | 11059427 | Feb 2005 | US |
