[001] The present invention relates to the field of helmet. The present invention in particular relates to a brain strain mitigating low cost, anti-rotational helmet pads.
DESCRIPTION OF THE RELATED ART:
[002] The basic idea behind this type of invention is to protect the wearer's head during blunt impact, blast load, IED induced blast wave, automotive accident, and contact sports. To make the helmet more protective many techniques are used, like using foam, lining, and making helmet in two parts outer and inner shell and allowing both shell to slide relatively each other to mitigate the effect of impact force coming on the helmet to wearer’s head. Each technique has its specialty in this field, and the overall effort was to make the helmet more protective. The available techniques focus and demonstrate the reduction in head acceleration. None of the studies have demonstrated reduction in brain strain and local brain deformation that is responsible for diffuse axonal injuries.
[003] Reference may be made to the following:
[004] Publication No. CN210539116 relates to a multifunctional protective helmet for public security. The device comprises a knob, a quick adjusting mechanism, a rear neck support, a screw and a threaded sleeve, according to the utility model, the quick adjusting mechanism is arranged in the helmet body; screw rod is rotated, the screw drives the first swing rod to swing; therefore, the first oscillating rod drives the second oscillating rod to oscillate; the second swing rod drives the connecting rod to move towards the upper end; the connecting rod drives the clamping rod to swing; the clamping rod drives the silica gel pad to move towards the inner side of the helmet body; therefore, the size of the internal space of the helmet body is adjusted; the size of the internal space of the protective helmet can be quickly adjusted; the helmet has the advantages that the structure is simple, the use comfort is improved, the head of a user can be protected through the protection mechanism and the protection pad, when the upper end of the helmet body is impacted, the protection pad needs to fix the spring, the spring deforms and contracts, impact force is buffered, and the use safety is improved.
[005] Patent No. US7849525 relates to a helmet worn by a person, with additional elements to dampen, restrain or totally block rotational movement upon the sensing of severe rotational movement of the head. This device prevents serious brain and cervical spine injury by restraining or totally blocking rotational movement of the head in response to severe acceleration/deceleration.
[006] Publication No. CN206284467 relates to a cushion safety helmet of simply being under construction, includes the cap shell, the cap shell is inside to be equipped with the inlayer, and a plurality of springs of interval arrangement and sponge between cap shell and the inlayer, spring upper portion is fixed on the cap shell, and spring lower part hook stretches out the inlayer to connect the upper end of the inside connecting band that is equipped with of inlayer, the lower extreme and the strap of connecting band are connected, and strap and lower jaw area are connected, and one deck silica gel pad is spread to the inlayer upper surface, provides the buffering anti effect of hindering through spring, sponge and silica gel pad for the safety helmet, the spring provides the pulling force through connecting band, strap for the lower jaw area, has increased the laminating degree of safety helmet with human chin, the utility model discloses wear comfortably, the protective capability is good.
[007] Publication No. CN203416851 relates to a silica gel helmet pad which comprises a silica gel body. The silica gel body is provided with a plurality of supporting portions. The supporting portions are arranged at intervals and extend outwards to form contact angles. Air holes are formed in the silica gel body. A fiber layer is stuck to the lower surface of the silica gel body. The silica gel helmet pad is ventilated and breathable, absorbs sweat and is easy to fix.
[008] Publication No. WO2020078913 relates to a pad for mounting to a helmet, the pad comprising a support member, a first layer of material arranged to cover a first side of the support member and a second layer of material arranged to cover the first layer of material, wherein a low friction interface is arranged between the first layer of material and the second layer of material to enable sliding of the first layer of material relative to the second layer of material, wherein each layer of material is formed from at least one of a textile, a cloth, a fabric and a felt.
[009] Publication No. US2019350297 relates to a sports helmet for protecting a head of a wearer, comprising: an outer shell comprising an external surface of the sports helmet; inner padding disposed between the outer shell and the wearer's head; an adjustment mechanism operable by the wearer to vary an internal volume of the cavity to adjust a fit of the sports helmet on the wearer's head; and a rotational impact protection device disposed between the external surface of the sports helmet and the wearer's head when the sports helmet is worn, the rotational impact protection device comprising a surface movable relative to the external surface of the sports helmet in response to a rotational impact on the outer shell to absorb rotational energy from the rotational impact, the surface of the rotational impact protection device undergoing displacement when the adjustment mechanism is operated by the wearer to vary the internal volume of the cavity.
[010] Patent No. US7299505 relates to a site-selectable, helmet-installable load-cushioning pad structure employable inside a helmet shell as a part of a plural-spaced-pad distribution featuring a compressible viscoelastic foam core which resists rapid, but not slow-movement, compression. Associated methodology includes the steps of providing such a structure for installation inside the shell of a helmet, and pre-arming the core of that structure with a load-response characteristics which resists sudden-movement, rapid compression, yet offers less resistance to slow-movement compression. An encapsulating moisture barrier layer may be provided around the foam core.
[011] Publication No. AU2018201419 relates to a safety helmet with a rotary impact buffering function comprises a shell and an elastic liner arranged in the shell, wherein a gap is formed between the shell and the elastic liner, and a rotary impact buffering device enabling the shell to rotate relative to the elastic liner is arranged between the shell and the elastic liner. When the safety helmet is impacted by external force, the shell has the tendency to rotate relative to the elastic liner under the effect of component force applied to the shell in the tangential direction; however, through tangential deformation of the rotary impact buffering device, the shell can rotate relative to the elastic liner by a certain angle on the premise of keeping the elastic liner unmoved, and thus the impact to users from external force is greatly reduced.
[012] Patent No. US10143258 relates to a protective helmet includes a shell provided with an outer surface and an inner surface, at least one pad adapted, in use, to abut against the head of a user who wears the protective helmet, including at least one first surface and a second surface that are opposite each other, elements for the connection of at least one pad to the shell associated with the at least one first surface, wherein the at least one pad is shaped as a substantially laminar body and includes at least one layer deformable and configured in a manner such to allow the sliding and/or the relative rotation between the at least one first surface and the second surface following a shear stress.
[013] Patent No. US9314061 relates to an apparatus for use in reducing the impact to the head during sporting activities. The present disclosure provides a helmet cap that covers an underlying hard shell helmet. The helmet cap has a durable, energy absorbing outer shell, which lessens the initial impact to the helmet. The outer shell is formed into segments of padded material that may deform on impact. The outer shell has an inner surface that allows the outer shell to slide over the surface of a helmet thereby reducing forces applied to a wearer. The helmet cap may be securely attached to helmets without modification of the helmets. The helmet cap may include an adjustable fastener that allows the helmet cap to be securely attached to helmets of varying dimensions.
[014] Patent No. US9474316 relates to a protective helmet which employs an inner shell, an outer shell, and dampeners positioned between the inner and outer shells which facilitate rotational movement between the inner and outer shells. The dampeners also provide shock absorption to counter the rotational acceleration caused by an impact to the helmet.
[015] Publication No. US2020029644 relates to a helmet having an outer liner and an inner liner. The inner liner is positioned at least partially inside the outer liner. The helmet includes at least one chin strap anchored to the outer liner and passing through an opening in the inner liner. The helmet further includes a plurality of return springs, each having a first end coupled to the outer liner, and a second end distal to the first end and coupled to the inner liner. The return springs bias the inner liner to a first position with respect to the outer liner. The inner liner is slidably coupled to the outer liner through the plurality of return springs and slidably movable relative to the outer liner between the first position and a second position where the inner liner and outer liner are rotated away from the first position.
[016] Publication No. CN110545686 relates to a cushion for use in a helmet comprising an outer shell for impact with an incoming force, the cushion disposed between the outer shell and a head when the helmet is worn, the cushion comprising: a sealed bladder comprising a flexible membrane; a pad housed within the bladder, said pad comprising a compressible member having interstices open to the exterior of the pad; and a liquid within the interior of the bladder. The pad absorbs at least some of said liquid when uncompressed and expels said liquid when compressed; the volume of liquid within the bladder is sufficient to allow opposing surfaces of the bladder to be displaced in a shearing motion relative to each other when the cushion is compressed and subjected to shear forces, to decouple shear forces between said helmet and the head.
[017] Publication No. US2021106091 relates to the protective helmet, the fit pod assemblies and the respective components relates to methods, devices, and systems for improved helmet systems to enhance athletic performance by dispersing impact forces and/or improving helmet comfort and/or fit through size customization and/or conforming to contours of a wearer's head. If desired, the various fit pod assemblies can include modular features to provide a semi-custom and/or customized feel for plug and play assembly and/or retrofitting a commercially available helmet and/or other item of protective clothing.
[018] Publication No. CA3018280 relates to a sports helmet for protecting a head of a wearer, comprising: an outer shell comprising an external surface of the sports helmet; inner padding disposed between the outer shell and the wearer's head; an adjustment mechanism operable by the wearer to vary an internal volume of the cavity to adjust a fit of the sports helmet on the wearer's head; and a rotational impact protection device disposed between the external surface of the sports helmet and the wearer's head when the sports helmet is worn, the rotational impact protection device comprising a surface movable relative to the external surface of the sports helmet in response to a rotational impact on the outer shell to absorb rotational energy from the rotational impact, the surface of the rotational impact protection device undergoing displacement when the adjustment mechanism is operated by the wearer to vary the internal volume of the cavity.
[019] Patent No. US10645982 relates to a protective helmet having an upper section and a lower section, each having an inside and an outside surface. A gap is formed between the upper section and the lower section. Resilient members in the form of a plurality of spaced apart compression struts are provided for connecting the upper section to the lower section. The upper section is movable with respect to the lower section whereby a portion of the force of an impact to the upper section will be absorbed and will not be transmitted to the lower section. A suspension harness is attached to the inside surface of the lower section. The suspension harness is adapted to receive a portion of the helmet user's head and to keep the helmet user's head from contacting the inside surface of the upper section.
[020] The article entitled “Patent patrol: Specialized’s slip-layer helmet padding patent a likely MIPS alternative” by Greg Kopecky; bikerumor; October 15, 2019 talks about the anti-rotation protection in helmets. Using inner helmet pads with multiple low-friction layers, the innovation could add additional safety to new helmets – and perhaps retrofit into older-style helmets that don’t currently include MIPS or similar technologies. The helmet pads would use multiple low-friction layers inside to allow for a controlled amount of slip. The pads could be attached via a standard hook-and-loop adhesion system, allowing for pad replacement if they become damaged or dirty. The added bonus is that this system could be applied to older helmets that don’t currently contain MIPS technology, giving an added measure of safety. And, our guess is this would be lighter than competing anti-rotation measures, and less expensive.
[021] All of the above studies only demonstrate the effect of pads for mitigation of head accelerations during blunt impact loading.
[022] Above prior art demonstrates the effectiveness of the pads in mitigating head kinematics only. Head kinematics is measured on the scalp of a human whereas brain strains represent local tissue response to the mechanical loading. Mitigation of head kinematics does not always imply the mitigation of brain strains. The relationship between head kinematics and brain strains are not completely understood and several investigations have demonstrated that brain can experience significant local strains despite mitigation of head kinematics. Thus, mitigation of head kinematics is a necessary condition but not sufficient condition for mitigation of brain biomechanics and traumatic brain injuries. On the contrary, numerous investigations have indicated that the brain strains correlate well and good predictor of traumatic brain injuries.
[023] When a blunt mass or improvised explosive device (IED) induced blast waves strike the head with some velocity, the skull accelerates and rotates, causing brain injury. Many investigations studying head kinematics suggest that conventional helmets reduce the risk of injury due to linear accelerations; however, they are not effective in mitigating the rotational motion of the head. The conventional helmets available mainly reduce the effect of linear acceleration during the impact on the head with little to no mitigation from the angular acceleration. Recent literature has shown that angular acceleration plays a vital role in causing diffuse axonal injury to the brain. Thus, a helmet with the capability of reducing the angular motion of the head is critically needed.
[024] In order to overcome above listed prior art, the present invention aims to provide a low cost anti-rotational silica sand pads, which are attached inside the helmet. The present invention is able to mitigate brain strain as well as head acceleration (kinematics) during blunt impact, blast load, IED induced blast wave, automotive accident, and contact sports.
OBJECTS OF THE INVENTION:
[025] The principal object of the present invention is to provide low cost anti-rotational silica sand pads, which are attached inside the helmet.
[026] Another object of the present invention is to provide helmet with anti-rotational pads which mitigates brain strain as well as head acceleration (kinematics) during blunt impact, blast load, IED induced blast wave, automotive accident, and contact sports.
SUMMARY OF THE INVENTION:
[027] The present invention relates to a helmet with low cost anti-rotational silica sand pads, which are attached inside the helmet. The anti-rotational pads that are capable of mitigating head acceleration and brain strain and to minimizes the effect of angular motion on the head acceleration and brain strain. The present invention is able to mitigate brain strain as well as head acceleration (kinematics) during blunt impact, blast load, IED induced blast wave, automotive accident, and contact sports.
[028] The proposed invention is able to mitigate the head accelerations and brain strains during blunt, blast, and ballistic impact loading (i.e., wide range of loading modalities). The aforementioned loading regimes are characterized by different strain rates. Strain rates implied in blunt impact is on the order of 100-103 s-1, strain rate implied in ballistic impact is on the order of 102-104 s-1, and stain rate implied during blast is on the order of 103-106 s-1. Higher strain rates are characterized by rate dependent response of helmet and head that induce larger strains in the brain and less time available for mitigation. Thus, mitigation of the head kinematics and brain strains over a wide range of loading modalities (i.e., strain rates) is not trivially achieved. The pads are capable to mitigate the head kinematics and brain strains over a wide range of loading modalities involving strain rate range of 100-106 s-1.
[029] Present invention demonstrates the effectiveness of the proposed pads in mitigating global and local brain strains (in addition to the mitigation of head kinematics). The pads were optimized in terms of composition, geometry and thickness of pads, and their arrangement on the helmet.
[030] The proposed pads are made from material available in the nature and do not contain specialized man made materials. Further, manufacturing of pads does not require specialized manufacturing process. Hence, the proposed pads are less expensive and more environment friendly with respect to the prior art. This aspect is crucial for mass production of pads for wide range of applications including automotive, military, contact sports, mining safety, and industrial applications.
BREIF DESCRIPTION OF THE INVENTION
[031] It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.
[032] Figure 1 shows position of the silica sand pads inside the helmet;
[033] Figure 2 shows schematic diagram according to the present invention;
[034] Figure 3 shows maximum Principal Strain (MPS) and Maximum Shear Strain (MSS) in the brain simulant for sagittal plane rotation for impactor velocity of 3 m/s.(A) with conventional helmet (B)Conventional helmet with silica sand pads.
DETAILED DESCRIPTION OF THE INVENTION:
[035] The present invention provides a used low cost anti-rotational silica sand pads, which are attached inside the helmet. The present invention is able to mitigate brain strain as well as head acceleration (kinematics) during blunt impact, blast load, IED induced blast wave, automotive accident, and contact sports.
[036] When the head experiences a blunt impact or blast wave, impact forces are transmitted to the brain through linear and angular motion of the head. The motive of the newly designed helmet pads is to reduce the effects of both linear and angular motion. The proposed low cost, anti-rotational pads inserted/mounted on the conventional helmet is capable of reducing linear and angular motion, and brain strain. Thus, proposed anti-rotational pads are more effective in the mitigation of brain strain. Further, these pads are cost-effective with respect to the existing technologies available.
[037] Silica sand pads have been used to mitigate the effect of angular motion due to impact on the helmeted head. An open face helmet consisting of outer shell (1), intermediate liner (2), and inner comfort layer (4) was used (Fig. 1). The color red, blue, yellow, and black is used to represent the hard outer shell (1), intermediate liner (2), comfort layer (4), and pads (3), respectively. The outer shell is made up of polycarbonate material. The intermediate impact-absorbing liner comprises expanded polystyrene (EPS) foam, and the inner layer is made up of open-cell foam that provides comfort.
[038] To investigate the efficacy of shearing (relative) motion based anti-rotational technologies, small bags filled with granular material silica sand (i.e., silica pads (3)) were fixed (using double-sided tape and glue) on the inner side of the intermediate layer of the conventional helmet. The pads' position is one in the top, one is in front and back, and two on the sides Fig. 1. A comfort layer is added on top of the pads. This comfort layer keeps the pads in their position. For this innovation, seven pads are used with a total mass of 0.120 kg. The arrangement of silica sand pads inside, on the intermediate layer of the helmet is illustrated in front, side, and top view in Fig. 1. To see the effectiveness of the silica sand pads, experiments were performed with conventional helmets, and helmets with silica pads, measured the head kinematics and brain strain in quantifying maximum principal strain (MPS) and maximum shear strain (MSS).
[039] The schematic diagram has a linear impactor system and fixture mechanism for the human head surrogate. The system consists of a compressed air tank (5), pressure gauge (5a), propulsion cylinder (6), impactor (7), support table (8), 3D printed GHBMC human head surrogate (10) with helmet (9) and pads (15), Hybrid III neck (11), Sliding table (12), high speed camera (13) ( Fig. 2).
[040] A linear impactor system was employed to impact the surrogate head, with an impactor velocity of 3 m/s and 1 m/s. The tests were carried out in two different orientations, resulting in rotations in sagittal and coronal planes, respectively. These impactor velocities of 3 m/s induce injurious head acceleration to the head. The head surrogate consists of skin, skull, and brain simulant, with the geometry based on a 50th percentile male. The brain simulant motion is captured using high speed camera and brain strains were obtained after performing the image analysis using NCOOR. Strain invariants MPS and MSS are depicted, as they are more suitable and compact for comparison of the helmet effects.
[041] Silica has a peculiar property of dilation under bulk shearing motion. Shearing based technologies have been proposed for the mitigation of rotational motion. Under the impact, silica particles slide relatively to each other and also undergoes inter granular friction, thus effectively mitigating the rotational motion to the head. The results clearly demonstrate the role of silica pads in mitigating the rotational motion and brain strain.
[042] Dynamic, 2D deformations in a head surrogate for aforementioned loading scenarios, with and without the silica sand pads inside the helmet are measured. Representative results for the sagittal plane rotation and impactor velocity of 3 m/s is shown in Figure 3.
[043] With the anti-rotational pads, the head kinematics is reduced by ~20 -30 %, while the reduction in the brain strain (i.e., MPS and MSS) is~50 % (Table 1). The rotational modes dominate response of the head as a result of impact. Brain simulant undergoes large deformation with wave propagation dynamics playing out in ~100 ms.
[044] Table 1 (a) Peak head kinematics with and without silica sand pads in the helmet for sagittal plane rotation for impactor velocity of 3 m/s.
case peak resultant linear acceleration (m/s2) peak resultant angular velocity (rad/s) peak resultant angular acceleration (rad/s2)
Conventional helmet 97.89 ± 7.19 7.83 ± 0.25 1343.19 ± 35.63
Helmet with silica pads 75.29 ±3.18 5.48 ± 0.48 926.57 ± 23.67
% reduction with the helmet with silica pads wrt the conventional helmet* 23.08 30.01 31.02
[045] (b) 90th and 95th percentile MPS and MSS with and without silica sand pads in the helmet for sagittal plane rotation for impactor velocity of 3 m/s.
case MPS MSS
90th percentile 95th percentile 90th percentile 95th percentile
Conventional helmet 0.37 ± 0.05 0.44 ± 0.09 0.25 ± 0.04 0.29 ± 0.05
Helmet with silica pads 0.19 ± 0.0005 0.21 ± 0.001 0.12 ± 0.0007 0.13 ± 0.0005
% reduction with the helmet with silica pads wrt the conventional helmet* 48.64 52.27 52 55.17

[046] Mitigating the rotational motion of the head and incoming blast wave is critical for the mitigation of resulting traumatic brain injuries. In this regard, it was critical to investigate and fully establish the mechanics of interaction of external mechanical stimulus with the helmet-head parenchyma.
[047] (a) Blast wave head interactions are inherently complex, especially due to the fluid (compressed medium travelling at speed greater than the speed of sound)-structure (head) interaction and time scales involved. Blast wave traverses the head in a few milliseconds; however, soft biological tissues do not respond immediately due to relatively small shear wave speeds in these materials. Thus, there is inherent time-scale separation that needs to be adequately accounted for and captured.
[048] As a first step of invention, a high-fidelity computational framework is provided to simulate blast wave interactions with targets. Using well-validated, full-body human computer models, the critical loading pathways and mechanisms of energy transfer to the head due to the blast waves generated from IEDs are identified. In response to blast head undergoes both translation and rotational motion that can potentially produce contusion and diffuse axonal brain injuries, respectively. Through experiments and concurrent computer simulations, the response of military helmets under the blast is analyzed. The phenomenon occurs very fast to be realized intuitively, without a computer simulation or carefully conducted experiments with ultrahigh speed camera and sensors. In addition to focusing, the response at longer times (>10 ms) is dominated by significant head rotation.
[049] (b) The next part is strategies to mitigate the rotational motion of the head under wide range of loading modalities. If relative motion (sliding) is allowed between the head and the helmet then the rotational motion of the head and resulting brain strains can be minimized.
[050] (c) In the next step, is candidate materials that can potentially mitigate the rotational motion of the head. Benchtop experiments were carried out to assess the effectiveness of each material and to visualize relative motion (sliding) between the head and the helmet with each material. The silica-based pads give optimum performance under various loading modalities studied (i.e., blunt, blast, ballistic).
[051] (d) In the next step, using computational simulations and concurrent experiments, the geometry and thickness of silica-based pads, total number of pads, their arrangement, and placement within the helmet is optimized.
[052] (e) Lastly, the proposed pads are able to mitigate the global and local brain strains for wide range of loading modalities, which has never been demonstrated before.
[053] Pads were prepared by enclosing anti-rotational material within a cotton fabric. Anti-rotational material was prepared by mixing 84% of free silica (SiO2), 5.6% magnesia (Mgo), 4.33% alumina (Al2O3), 1.56% iron oxide (Fe2O3), 4.42% wollastonite. To obtain homogenized material, the mixture was mixed using sand mixture. The mixture was cured at 35° C for 4 hours using hot-air oven. It was ensured that moisture content was zero. Average grain size of the resulting pads is 400 ± 55 microns. Grain size distribution is shown in Table 1. The anti-rotational material was wrapped in a cotton fabric and finely sealed using a sewing machine. Each pad has a dimension of 70 mm x 50 mm x 10 mm and weight of 20 ± 4 gram. Using computational simulations and concurrent experiments, the geometry and thickness of pads, total number of pads, arrangement and placement of pads within the helmet is optimized. The final configuration is shown in Fig. 1. This configuration gives minimum head acceleration and local strains within the brain under wide range of loading modalities involving strain rate range of 100-106 s-1.
[054] Table 1: Percentage passing of sand from sieve of different diameters
Sr. No. Sieve Number Opening (microns) Percent passing
1 1000 1000 100
2 850 850 82
3 425 425 72.83
4 300 300 63.77
5 250 250 23.16
6 106 106 5.59
[055] Numerous modifications and adaptations of the system of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the true spirit and scope of this invention.

WE CLAIM:

1. An anti-rotational pads for helmet to mitigate the effect of rotational motion during the blunt impact and blast wave and corresponding brain strain is arranged on the inner side of the intermediate liner of the helmet to mitigate the effect of angular motion due to impact on the helmeted head comprises outer shell (1), intermediate liner (2) characterizing expanded polystyrene (EPS) foam, and inner comfort layer (4) made up of open-cell foam and pads characterizing the outer shell made up of polycarbonate material, intermediate impact-absorbing liner wherein comfort layer is added on top of the pads which keeps the pads in their position.
2. The anti-rotational pads, as claimed in claim 1, wherein the pads are fixed on the intermediate layer of the helmet using glue and double-sided tape.
3. The anti-rotational pads, as claimed in claim 1, wherein the wherein pads are capable of reducing the linear acceleration, angular velocity, and angular acceleration of the head under wide range of loading modalities involving strain rate range of 100-106 s-1.
4. The anti-rotational pads, as claimed in claim 1, wherein the pads are capable of reducing the maximum principal strain (MPS) and the maximum shear strain (MSS) under wide range of loading modalities involving strain rate range of 100-106 s-1.
5. The anti-rotational pads, as claimed in claim 1, wherein the pads mitigates the relative motion between brain and skull, the cortical brain strains, strains in the midbrain region and reducing the local strains in the brain simulant under wide range of loading modalities involving strain rate range of 100-106 s-1.