Patent Application
20190110545
The present invention relates generally to the field of protecting a human brain upon exposure to shock waves of a blast injury. More specifically, the present invention provides a protective headgear to reduce amplitude of the shock waves of the blast injury to the human brain.
Boundary effect of mechanical waves including shock waves can be exploited for reducing amplitude of the mechanical waves delivered to a brain tissue, using a multi-layered shell to protect the brain tissue. In a model of a two-layer medium panel with a first layer adjoining a second layer without a gap, it is known that there is no phase change at a boundary between the first layer and the second layer having a lower hardness than that of the first layer in reflected mechanical waves from incident mechanical waves traveling from the first layer to the second layer. Combination of both the incident and reflected mechanical waves in phase with each other temporarily induces constructive interference resulting in an increase in amplitude of the incident mechanical waves which in turn increases an amplitude of transmitted mechanical waves in the second layer from the incident mechanical waves. If a series of the incident mechanical waves impacts the first layer, an amplitude of the reflected mechanical waves off the boundary merges with an amplitude of successive mechanical waves following a first wave of the mechanical waves coming toward the first layer. The amplitude of the successive mechanical waves following the first wave of the mechanical waves temporarily increases upon the addition of the amplitude of the reflected mechanical waves in phase with the successive mechanical waves, which increases a magnitude of an impact of the successive mechanical waves following the first wave of the mechanical waves to the second layer. If the first layer is made of a material that has a lower hardness than that of the second layer, the reflected mechanical waves off the boundary between the first and the second layers from the first wave reverse the phase and merge with the successive mechanical waves coming toward the first layer resulting in destructive interference decreasing the amplitude of the successive mechanical waves to the second layer.
Incident shock waves reflect off a boundary in either convergent or divergent way. If a first shock waves are reflected at the boundary of a headgear in a hemispherical configuration, there is a single point of maximum divergent reflection off the boundary depending on a direction of the incident shock waves toward the headgear. The single point of the maximum divergent reflection on the boundary of the headgear also becomes a single point of entry of maximum transmitted shock waves toward the brain tissue. Transmission of the maximum transmitted shock waves from the single point of entry focuses the maximum transmitted shock waves on a small area of the brain tissue, in a way the small area of the brain tissue would receive a highest amplitude of the maximum transmitted shock waves. A concave inner wall of a hemispherical bowel of a protective headgear serves as an acoustic lens which focuses transmitted shock waves into a geographically confined area of the brain. Based on the hemispherical configuration of all existing protective headgears having the concave inner wall, the incident shock waves from any direction hitting a spherical outer wall of the protective headgear would generate the transmitted shock waves through the concave inner wall focusing mostly on a mid brain of the brain tissue.
A method to reduce focused tissue damage to the mid brain is to produce multiple points of divergent reflection of the incident shock waves which are identical to multiple points of entry of the transmitted shock waves to the brain tissue in a way the transmitted shock waves are rendered to be unfocused and diffused. It requires elimination of a spherical surface of the protective headgear, which can be accomplished by a configuration of hemispherical polyhedron of a layer of a shell. The hemispherical polyhedron comprises a plurality of polygons adjoining each other along a border between two adjacent polygons. The border between the two adjacent polygons of the hemispherical polyhedron layer is configured to be raised to form an outwardly protruding ridge which serves as a point of the divergent reflection of the incident shock waves and a point of entry of the transmitted shock waves. If the hemispherical polyhedron layer is fixedly encased by an outer hemispherical layer, and the hardness of the hemispherical polyhedron layer is harder than the outer hemispherical layer, this particular configuration would induce the destructive interference of the incident shock waves reflected off a plurality of protruding ridges at a boundary between the outer hemispherical layer and the hemispherical polyhedron layer, and would transmit the transmitted shock waves mostly through the protruding ridges so as to diffuse the transmitted shock waves across the hemispherical polyhedron layer.
There is a potential for constructive interference between two symmetrically opposite transmitted shock waves through the inner layer of the protective headgear facing each other at a substantially right angle since each transmitted shock waves has come off the inner layer in phase with each other. When these two symmetrically opposite transmitted shock waves heading toward a mid point of the brain tissue merge in phase inside the brain tissue, there would be an increase in amplitude of the shock waves due to the constructive interference. Another source of the tissue damage to the brain tissue comes from repetitive forced vibrations of the brain tissue by the transmitted shock waves inside the protective headgear in a configuration of a hemispherical bowel ricocheting as reflected shock waves off an inner wall of the inner layer of the protective headgear. Once ricocheting off inside the hemispherical headgear, the ricocheting shock waves would run across inside a skull containing the brain tissue back and forth amplifying the tissue damage. Process of these two opposite transmitted shock waves ricocheting multiple times off the inner layer as the reflected shock waves would protract the tissue damage to the brain tissue.
One method to reduce the constructive interference between the two symmetrically opposite transmitted shock waves is to produce a phase of one transmitted shock waves coming off the inner layer of the protective headgear out of sync with a phase of the other transmitted shock waves coming off the inner layer of the protective headgear. Since the phase of the shock waves is known to be affected by differences in hardness of two adjoining layers, the inner layer of the protective shell would be configured with a first part of the inner layer harder than a second part located symmetrically opposite to the first part of the inner layer. A second method is to produce the hemispherical polyhedron layer of the shell in an axi-asymmetrical configuration in which the first part of the inner layer is asymmetrically misaligned with the second part of the inner layer across an axial center of the hemispherical polyhedron layer of the shell. Although there will be a constructive interference between the transmitted shock waves coming off the first part and the transmitted shock waves coming off the first part, at least these two shock waves may not merge maximally at one particular area of the brain tissue. This way the constructive interference can be modified from focused to unfocused constructive interference. Similarly, two oppositely ricocheting shock waves from the transmitted shock waves across the axial center may not merge maximally at the particular area of the brain tissue. In a three-dimensional model of the hemispherical polyhedron layer of the shell, the axi-asymmetric configuration of the hemispherical polyhedron layer of the shell would diffuse points of the maximum constructive interference inside the brain tissue.
It would be advantageous to reduce amplitude of the transmitted shock waves coming off the protective headgear as much as possible before the transmitted shock waves reaches the brain tissue. One method to reduce the amplitude of the transmitted shock waves is to generate a second destructive interference of the transmitted shock waves with a two-layered inner shell. An innermost layer is configured with a higher hardness than a layer in between the innermost layer and the hemispherical polyhedron layer of the shell and tightly adherent to the other layer. The layer in between the innermost layer and the hemispherical polyhedron layer of the shell is configured with a plurality of cut-pile projections facing an inner surface of the hemispherical polyhedron layer and is not adherent to the inner surface of the hemispherical polyhedron layer. The transmitted shock waves coming off the hemispherical polyhedron layer head toward the layer with the cut-pile projections. At a boundary between the innermost layer and the layer with the cut-pile projections, part of the transmitted shock waves off the hemispherical polyhedron layer are reflected out of phase with successive transmitted shock waves off the hemispherical polyhedron layer. Along individual cut-pile projections, there will be a merging process of incident transmitted shock waves off the hemispherical polyhedron layer with out-of-sync reflected shock waves and diffracted shock waves at the individual cut-pile projections. The diffracted shock waves off the cut-pile projections are out of phase with the incident transmitted shock waves. Consequently, there is a destructive interference on the cut-pile projections between the incident transmitted shock waves and the diffracted shock waves, and between the incident transmitted shock waves and reflected transmitted shock waves. Both the reflected shock waves and the diffracted shock waves are in phase with each other, which amplifies amplitude of merged outward shock waves between the reflected shock waves and the diffracted shock waves. The merged outward shock waves would increase efficiency of the destructive interference with the incident transmitted shock waves.
One of critical shortcomings of protective headgears is that the shock waves behave much the same way as fluid in that the shock waves seep into any opening around a human head wearing a protective headgear and induce the tissue damage to the brain tissue. The other practical issue is that a person wearing the protective headgear needs to maintain enough space inside the protective headgear to ventilate and to avoid heat build-up. These two issues may be addressed by an inner liner that has a plurality of cut-pile projections on an inner circumferential rim of the inner liner. The cut-pile projections are configured to sealably encircle a circumference of the human head around the circumferential rim of the protective headgear and stacked up in such as way that seepage of the shock waves would be limited by filtrative trapping across the cut-pile projections while letting the space ventilated.
In one embodiment to attenuated shock waves to a human head wearing a protective headgear, a basic motif of the present invention comprises the protective headgear having an at-least three-layered outer shell, and an inner liner. The at-least three-layered outer shell comprises a first and outermost layer being softer than a second layer which is provided in a hemispherical polyhedron configuration. Both the first and second layers are configured to be hard and undeformable enough to withstand direct hit from ballistic projectiles without material failure. A third and innermost layer of the at-least three-layered outer shell is softer than a human skull and is provided in a cut-pile configuration having a plurality of cut-piles projected from a surface facing an inner surface of the second layer. Each layer is configured to have a measurable thickness and to be placed next to adjacent layers tightly without a gap. There is provided an inner liner which is hemispherically encased by the at-least three-layered outer shell. The inner liner is provided in a cut-pile configuration around a circumferential rim of the inner liner having a plurality of cut-piles projected from the inner liner contact with the human head.
In one embodiment, the outermost layer and the second layer are made of identical materials having high strength reinforcement fibers mixed with a resin. The high strength reinforcement fibers are provided in a configuration of multiple plies stacked up together, which is then immersed and glued with the resin under pressure. The second layer in the hemispherical polyhedron configuration is molded under high pressure to reach a Rockwell hardness score above 100 so as to withstand a blunt impact without deformation of a planar surface of the second layer over a gravitational force up to 300 g±30 g (10% S.D.) and over a range of temperature from −10° F. to 750° F. without material failure. The outermost layer in a hemispherical configuration is molded under low pressure to reach a Rockwell hardness score of between 50 and 100. Sequence of manufacturing starts with a first molding process of the second layer comprising multiple individual plies stacked up with the resin under the high pressure. Once the first molding process of the second layer is completed, an individual ply of the outermost layer is sequentially layered together with the resin on an outer surface of the second layer until stacking up process of a full multi-ply outermost layer is completed. A low pressure is then applied for a second molding process to a two-layered shell comprising the outermost layer and the second layer fixedly attached to each other layer. Examples of the high strength reinforcement fibers include but not limited to Kevlar such as Kevlar 129 fibers, KM2 fibers, thermoplastic polymers, hybrid thermoplastic, or Spectra Shield material. Examples of the resin include but not limited to thermoset resin or phenolic resin.
In one embodiment, the hemispherical polyhedron configuration of the second layer is configured to form a hemispherical bowel shape which is configured to enclose a third layer. On an outer surface of the hemispherical polyhedron of the second layer, an outwardly protruding linear ridge is provided between two adjacent polygons of the hemispherical polyhedron of the second layer, wherein the outwardly protruding linear ridge serves as a point of divergent reflection of incident shock waves and a point of entry of transmitted shock waves through the second layer. Each polygon of the hemispherical polyhedron is configured in a pentagonal polygon or a hexagonal polygon, and has a flat surface surrounded by the outwardly protruding linear ridges. No protruding linear ridges are provided on an inner surface of the hemispherical polyhedron of the second layer. A triangular apical point on the inner surface of the second layer established by three adjacent polygons is configured to be reinforced by a triangular planar buttress block made of the same materials as for the second layer.
In one embodiment, the hemispherical polyhedron of the second layer is provided in an axi-asymmetrical configuration in which a first polygon of the hemispherical polyhedron is asymmetrically misaligned with a second polygon disposed oppositely to the first polygon across an axial center of the hemispherical polyhedron of the second layer. The axi-asymmetric configuration is provided in a way that an axis coming out from a center of the first polygon at a right angle to a flat surface of the first polygon does not converge with an axis coming out from a center of the second polygon at a right angle to a flat surface of the second polygon.
In one embodiment, the third layer is provided in a hemispherical bowel shape comprising a hemispherical polymeric panel and a plurality of stiff cut piles projecting from an outer surface of the hemispherical polymeric panel at a right angle for a distance. The plurality of cut piles face the inner surface of the second layer, and cover an entire area of the outer surface of the third layer. A base of the cut pile is fixedly attached to the outer surface of the hemispherical polymeric panel, and a free end of the cut pile opposite to the base projects to the inner surface of the second layer. The plurality of cut piles are provided in a configuration having a cut pile arranged in parallel with other cut piles surrounding the cut pile. The third layer is configured to be compressible and depressibly deformable by an impact of a blunt trauma at an angle to a planar surface of the third layer in a similar way to compressible polymer foams, and to have a 25% indentation force deflection value of higher than 45 and a foam support factor of between 1.5 and 3.0. Compressibility resides in the stiff cut piles having a vertical length of the cut piles resist to a compressive force at the angle to the planar surface of the third layer. The polymeric base layer is configured to be deformable. The third layer is configured to have a hardness of a Shore D scale value of between 65 and 90, as a Shore D scale value of bone such as skull is known to be just below 100. Examples of polymers for the third layers include but not limited to polyimide, polybenzimidazole, polybenzoxazole, or polybenzthiazole. The third layer is configured to enclosably cover an area of the human head comprising a part of frontal, an entire parietal, a majority of temporal and occipital regions.
In one embodiment, the inner liner is provided in a configuration comprising a plurality of suspending bands made of mesh fabric and a rim portion. The inner liner is reversibly encased in the at-least three-layered outer shell, wherein the suspending bands are configured to enclosably sit atop on the human head and the rim portion is configured to encirclably surround a peripheral circumference of a lower portion of the human head. A plurality of soft cut piles project from an inner surface of the inner liner at a right angle for a distance in a way the plurality of soft cut piles cover a circumferential space between a lower portion of the human head and the inner surface of the inner liner. The plurality of cut piles are provided in a configuration having a cut pile arranged in parallel with other cut piles surrounding the cut pile, and having a gap between adjacent cut piles. The gap between the adjacent cut piles is configured to ventilate the circumferential space between the lower portion of the human head and the inner surface of the inner liner. Individual gaps between the adjacent cut piles of a first circumferential row of the cult piles are configured to be blocked by cut piles of a second circumferential row of the cut piles, which is configured to form filtrative barrier against the shock waves coming into the circumferential space between the lower portion of the human head and the inner surface of the inner liner. Examples of polymers for the soft cut piles include but not limited to polyimide, polybenzimidazole, polybenzoxazole, or polybenzthiazole.
As described below, the present invention provides a shock-waves attenuating protective headgear. It is to be understood that the descriptions are solely for the purposes of illustrating the present invention, and should not be understood in any way as restrictive or limited. Embodiments of the present invention are preferably depicted with reference to
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It is to be understood that the aforementioned description of the apparatus is simple illustrative embodiments of the principles of the present invention. Various modifications and variations of the description of the present invention are expected to occur to those skilled in the art without departing from the spirit and scope of the present invention. Therefore the present invention is to be defined not by the aforementioned description but instead by the spirit and scope of the following claims.
