FR2786671A1 - Protective head ware for sports use, riding and industrial applications, comprises variable density areas and fracture zones - Google Patents

Abstract

The protective head ware is comprised of a hard outer shell that encases a central core and cushioning areas that have differing densities such that during an impact, the deformation of each area varies with the area of the head that is covered. Other areas disintegrate upon impact thus dissipating the impact force.

Description

-1-

  The invention relates to the production of a shell for cranial protection helmets.

  cerebral. The skull has two segments: the neuro-skull which contains the brain and the viscero-skull which represents the skeleton of the face. The present invention relates to

  mainly the shell covering the neurocranium.

  The principles of the design of protective helmets date back to before the appearance of the scanner. For more than 15 years it has become the benchmark examination in craniocerebral trauma. Our medical knowledge evolves and presents

invention is a consequence.

  Current protective helmets contain two components which must meet biomechanical safety requirements: - an external shell which ensures, during an impact, the distribution of the energy delivered to a larger area than that affected by the external shock. It also provides

  increased resistance to the penetration of the cap.

  - an intermediate cap intended for the partial absorption of the transmitted energy and

distributed by the outer shell.

  In the case of helmets for motorcyclists (or similar), by the use of increasingly resistant and rigid materials, the shell today only provides a surface distribution function of the forces developed during an impact, even if is a

  high neurological risk impact (NRI). It restores almost to the intermediate cap

  all of the energy received. In the case of helmets for cyclists (or similar), by the use of very flexible materials, the shell does not, or practically not, ensure

  biomechanical function. In all cases, after partial absorption of this energy by the.

  intermediate cap, the residual kinetic energy is transmitted to the skull and ultimately to the brain. The immediate neurological disturbances that can result are all the more serious the higher the energy transmitted to the brain. By IRN we understand the impacts that expose the subject to the onset of neurological disorders (transient or persistent)

  despite wearing a helmet designed in the state of the art.

  The aim of this invention is the reduction of post traumatic neurological disorders in the wearers of a protective helmet by the reduction of immediate neurological disorders

  thanks to better absorption of energy by the helmet in the event of a violent impact.

  -2- The protective helmet industry is faced with two questions: 1. How to make more efficient helmets without increasing the thickness and volume of the helmet beyond acceptable limits? Apart from the lack of comfort and the fatigue inflicted on the neck muscles, this increase can in itself favor accidents by reducing the perception (visual and sound) of the surrounding environment. Moreover, for these reasons, the exaggerated increase in the volume of the headphones can

  easily become a brake for its use.

  2. When to better protect the head: in the event of violent impacts (rare) or in the event of moderate impacts (frequent)? The work published by Corner (1987), Mills (1991), Smith (1993) show that if current helmets are designed to better absorb violent impacts,

  they will be hard and less effective in the event of a medium energy impact.

  The shell according to the invention answers these two questions. Its main characteristic consists in its capacity to undergo deformations (D) or fractures (F) preferably with regard to the regions of maximum resistance of the human skull, in case of IRN. The energy thus absorbed

  or consumed ensures the reduction of the energy transferred to the head and also to the cervical spine.

  The risks of post-traumatic quadriplegia secondary to a fracture of the cervical spine will be

thus also decreased.

  D or F occur in regions of the hull containing layers of low resistance (CBR) or zones of mechanical low resistance (ZBR). In the event of a low energy impact, the shell according to the invention operates on the same principle as the shell of current motorcycle helmets and distributes the energy of the impact on the surface. From this point of view the ZBR and the CBR operate on the same principle as the "safety valves" of the containers

under pressure.

  All the solutions envisaged are applicable in compliance with current standards. At the same time these new hulls will allow in the future the development of new standards and

  better when it comes to hard hats.

  The deformation or fracture of the shell has important mechanical consequences:

  1. the duration (t) of the impact increases.

  2. the kinetic energy (E0 = mV2 / 2) received by the head (E.3) decreases because the energy absorbed by

the headset (AE I + AE2) increases.

  E, 0 = kinetic energy of the assembly before impact AE 1 = energy absorbed by the shell AE2 = energy absorbed by the cover E.3 = Ej - (AEI + AE2) -3- The average acceleration ( a) developed during normative tests decreases because Ec3 decreases and t increases. (a = V / t = (2Ecy3m) '2 / t) The "Head Injury Criterion" (HIC), used to evaluate the damping of normative shocks, is expressed in its simplified form: HIC = dV2 5 / dt1'5 = (dV2 / dt) (dV / dt) "2 It is proportional to the kinetic energy (dV2) and inversely proportional to the duration of the energy transfer during impact (dt). For the reasons already explained, it will drop,

  thus demonstrating better shock absorption.

  The practical implementation methods presented below are simply given by way of non-limiting examples. Different combinations between solutions presented and their

  variants are also being considered.

  Two groups of practical solutions and some examples will be presented: A. The deformation D occurs by the crushing of the CBR, preferably opposite the point of impact. B. Fracture F occurs by tearing the ZBRs, preferably at a distance from the point of impact. The CBRs are placed outside the thickness of the hull. The CBRs can be placed on one or both surfaces (internal and external) of the hull. The ZBRs are arranged in

the thickness of the shell.

  Preferably these CBR or ZBR are concentrated opposite at least two of the six zones of maximum mechanical resistance of the human skull which are represented by the two fronto-lateral pillars, the two retro-auricular pillars and the two parietal bones. The regions of the anterior midline and temporal lines will preferably be exempt from their presence to reduce the risk of injury to the upper longitudinal sinus and respectively to the middle meningeal artery. These anatomical structures are particularly exposed by their

  position at high risk of bleeding if nearby skull fracture.

  Low resistance areas or layers can cover less than 20% of the surface

total of the hull.

  -4- Several ZBR or CBR can be in contact or located less than 10 mm between them or any continuity solution such as ventilation holes, fixing (chin strap, visor,

  etc.) and thus form a low resistance spatial grouping (GSBR).

  ZBR or CBR can be in contact or located less than 5 mm from the edge of the hull - frontal (BFC), lateral (BLC) or posterior (BPC). The highest point of the shell, for a helmet positioned on the head, will be called the center of the shell (CC). The large circumference of the shell covering the cranial vault will be called hereinafter "the large circumference of the shell" (GCC). Its direction is approximately horizontal. It coincides in front with the front edge of the shell (BFC) for both full-face helmets and other types of helmet and is defined by the

  crossing between the plane containing the BFC and the external surface of the hull.

  Low resistance zones (ZBR) Each ZBR can have a point with minimal resistance to tearing or shearing. Thereafter this point will be called "the point of minimum resistance" (PRM) of the ZBR. The PRM of any ZBR will preferably be located at the level of the most distant third of the ZBR

of the CC.

  Each ZBR has, thanks to its conformation, a direction of minimum resistance which corresponds with the direction of the shell fracture which will occur in the event of IRN. This direction will

  hereinafter called "the direction of minimum resistance" (DRM) of the ZBR.

  The angle defined between the DRM and the CCG is preferably between 60 and 120.

  The surface dimensions of the ZBRs are variable. The maximum surface diameter - the length - can be at least 20 times greater than their minimum diameter - width. The DRM of a ZBR often corresponds with its length. So the angle defines between the length of the

  ZBR and GCC is preferably between 60 and 120.

  The ZBRs can be produced in a variant by reducing the thickness of the hull and producing depressions or grooves on at least one of the two surfaces, external or internal, of the hull. Their depth and their surface can be variable or gradually variable. The dimensions of the depressions or furrows measured on the surface on sections parallel to the edge of the shell may vary gradually. The depth may exceed, at least in places, 50% of the thickness of the shell measured near the

  ZBR on a parallel cut with the edge of the helmet.

  -5- It can represent, at least in places, 100% of the thickness of the hull and thus produce continuity solutions (SC). The length of the SCs can be at least 20 times greater than their width in the same plane. Their length can be greater than 70 mm. The length of the SC measured on any direction which passes through the center of the hull can be less than 7 mm, in particular for the SC located in contact or less than 5 mm from the edge of the hull (BFC, BLC or BPC) or within 10 mm of other hull continuity solutions (such as ventilation or fixing holes) or other areas or layers of low resistance. At

  minus a diameter of the SC can be less than 3 mm.

  In another variant, the ZBRs can be obtained by including in the thickness of the shell gas bubbles or other structures made of a material different or similar to the rest of the shell. In the case of a solid material, the inclusion can also be made on at least one of the surfaces of the shell. This situation corresponds to a furrow or a depression, see a CS filled with the material in question. Thus the lack of substance in the thickness of the shell can be at least partially occupied by metallic inclusions whose areas having a thickness less than 80% of the thickness of the shell, are covered at least partially towards the two surfaces of the shell by the component

main hull.

  One of these variants is represented by the inclusion in the thickness of the shell of the flattened structures and of variable shapes, having rigidity, hardness and high mechanical strength. They can be carried out with the use of metal structures or other materials such as resins, other polymers or composite materials. Unlike composite materials, when resistant fibers are used to reinforce the tear resistance of the shell, and the case of which will be described later, the use of the solid structures described here achieves a decrease in tear resistance, favoring thus, in the event of a violent impact, the occurrence of fractures at a distance from the point of impact and with an optimal direction. At the same time, by their rigidity and their increased resistance to penetration, they increase the resistance of these zones in the event of direct impact, even by a

sharp object.

  The thickness of such a structure is variable and preferably measures between 0.5 mm and 3 mm.

  It can also be equal, at least in places, to the thickness of the shell but, preferably, does not exceed it. The surface of the shell corresponding to such a structure is variable and will preferably be between 0.3 and 5 cm2. The surface of the hull segments which contains such

  structures can represent less than 10% of the total surface of the hull.

  -6- These structures can measure between 1 and 3 mm2 on at least two sections perpendicular to their maximum dimension and placed at least 10 mm between them. They can have an oval or polygonal shape in section. Preferably, they are made of metal and have an isosceles triangle shape on the surface, with the base thicker in section and parallel to the maximum perimeter of the hull, see situated in contact with or less than 5 mm from the edge of the hull. In another variant, for the hulls made of composite materials, the ZBRs can also be obtained by modifying the density or the orientation of the fibers used (glass fibers, carbon, aramid, metallic) before the injection of the resin or polymer in the mold. The areas of low resistance can be obtained by reducing the density of the fibers by at least 50% compared to the regions close to the areas of low resistance. In another variant, the zones of low resistance are obtained by reducing the density of the non-radial and long fibers by at least 30% compared to the density of the fibers parallel with their directions and located in regions close to the zones.

low resistance.

  Non-radial fibers are defined as fibers whose direction crosses the CCG according to

  an angle less than 70 or greater than 110.

  Long fibers are defined as fibers that exceed the opposite limits of the

ZBR of at least 10 mmn.

  Another variant consists in interrupting more than 50% of the long fibers which cross the direction of minimum resistance at any angle, or preferably at an angle between 30 and 150. The decrease in the density of long fibers can be at least 50% compared to parallel fibers, or making with their directions angles less than 10, and located

in areas close to ZBRs.

  In these ZBRs, the long fibers which cross the direction of minimum resistance at any angle may be absent or interrupted by cutting. In another variant, additional layers of fibers, the direction of which crosses the direction of minimum strength of the ZBR, are added in the areas close to the ZBR before the injection of the polymer or of the resin. Another variant is that which consists of including in the zones close to the ZBRs additional bundles of fibers making angles of 30 - 150 with the length of the ZBRs. Another variant of obtaining the ZBRs is the arrangement of more than% of the fibers contained in the surface corresponding to the ZBRs, in directions

  parallel to the direction of minimum resistance or the length of the ZBR.

  -7- The zones of low resistance can also consist of several orifices located at

less than 10 mmn between them.

  In another variant, the hull can be produced by sectors. The sectors can form a common part with each other towards the center of the hull and thus create, from the start, a single polygonal part. The number of sectors to be assembled at least partially is variable and will preferably be between 2 and 5. The sectors are then assembled making ZBRs facing these junctions. The tear resistance of the joints can vary and preferably represents between 30% and 70% of the tear resistance of the neighboring shell segments. Stamping, hot gluing, the use of adhesive substances or the interlocking of structures with hooks at least partially removable and adjustable can be envisaged. The hook structures can be partially removable, secured with one of the segments to be assembled, adjustable, and thus form "bracelet" structures. They can be manufactured at the same time as the rest of the hull or be added to it later by any technical process (stamping, gluing, crossing the hull over part or all of its thickness). The hook structures can be detachable from the two segments to be assembled and thus form "bridge" structures. The hook structures can be arranged on a single surface of the shell, preferably the internal surface. This variant is particularly suitable for the situation when the sectors form a common unit with one another towards the center of the hull. In another variant, the hook structures can be arranged on the two surfaces of the shell. By their alternative nesting (external - internal in section, right - left on the surface) they ensure the

solidity of the whole.

  The resistance base layers (CBR) The CBRs can be located in contact with the external or internal face of the shell, or at a distance from the internal face of the shell, in the thickness of the intermediate cap. In the last variant exposed, the CBRs come into contact with the hull upon impact

  violent, after the crushing of the intermediate cap between the shell and the head.

  The CBRs can be obtained by making pleated structures in "U", "M", each having several contacts with the shell seen in section, or in "T", in "L", each having a single contact with the shell seen in section. The thickness of the materials used is variable and can be less than 75% of the thickness of the opposite shell. The thickness of the CBRs can exceed 5 mm or even 10 mm. The surface of the hull covered by each CBR can vary between 0.5 cm2 and 30 cm2. At least two-thirds of the CBRs can measure

surface between 3 cm2 and 15 cm2.

  -8- Materials identical, similar or different from the rest of the shell can be used for their manufacture. They will preferably be identical with the polymer or the resin used for the rest of the shell. The CBRs can thus be manufactured at the same time as the rest of the hull by modifying the injection mold. In another variant they can be manufactured separately.

  The CBRs can also have hooks fitted into the hull.

  The shell described may also present continuity solutions the length of which is at

  minus 20 times its width.

  The shell according to the invention is intended for making the caps of protective helmets of any type (integral or non-integral) and particularly used in the civil fields

  (motorcycle - testing, competition and users; cars - testing, competition; bicycle -

  competition, users; other sports - roller skating, skateboarding, winter sports; industrial environment).

-9-

Claims (18)

  1) A shell for a cranio-cerebral protective helmet characterized in that it comprises layers or zones of low resistance which ensure absorption of energy in the event of impact at neurological risk by their deformation or fracture and prolongs the duration   the impact thus reducing the acceleration developed.   2) A shell for a cranio-cerebral protective helmet according to claim 1 characterized in that the zones or the layers of low resistance are concentrated opposite at least two of the six zones of maximum mechanical resistance of the human skull which are represented by the two fronto-lateral pillars, the two retroauricular pillars and the two parietal bones.   3) A shell for a craniocerebral protective helmet according to claims I - 2   characterized in that the zones or layers of low resistance cover less than 20% of the total surface of the hull.   4) A shell for a craniocerebral protective helmet according to claims I - 3   characterized in that at least part of the layers or zones of low resistance are located within 10 mm of any solution of continuity such as the ventilation orifices,   fixing, other zone or layer of low resistance.   ) A shell for a cranio-cerebral protective helmet according to claims 1 - 4   characterized in that it comprises layers or zones of low resistance located at least 5 mm from the edge of the hull.   6) A shell for a craniocerebral protective helmet according to claims 1 - 5   characterized in that the areas of low resistance are obtained by reducing the thickness of the shell and producing depressions or grooves on at least one of the surfaces of the hull.   7) A shell for a cranio-cerebral protective helmet according to claim 6   characterized in that the depth of the depressions or furrows is variable. -10-   8) A shell for a craniocerebral protective helmet according to claims 6 - 7   characterized in that the depressions or furrows have a depth which represents, at least in places, from 50% up to 100% of the thickness of the hull measured near the area   of low resistance on a parallel cut with the edge of the helmet.   9) A shell for a craniocerebral protective helmet according to claim 8 characterized in that the segment crossing the entire thickness of the shell measures less than 7   mm on any direction that passes through the center of the hull.   10) A shell for a cranio-cerebral protective helmet according to claim 6 characterized in that the dimensions of the depressions or grooves measured on the surface on   cuts parallel to the edge of the shell are variable.   11) A shell for a cranio-cerebral protective helmet according to claims I - 10   characterized in that the lack of substance in the thickness of the shell is at least partially occupied by metallic inclusions whose areas having a thickness less than 80% of the thickness of the shell, are covered at least partially towards the   two hull surfaces by the main hull component.   12) A shell for a craniocerebral protective helmet according to claims 1 - 5   characterized in that it is made of composite materials and the areas of low resistance are obtained by reducing the density of the fibers by at least 50% compared to   regions close to areas of low resistance.   13) A shell for a crino-cerebral protective helmet according to claims I - 5   characterized in that it is made of composite materials and the areas of low resistance are obtained by reducing the density of the non-radial fibers by at least 30% (the direction of which crosses the large circumference of the shell, described at its turn by the intersection between the plane containing the front edge of the helmet and the external surface of the shell, at an angle less than 70 or greater than 110) and long (which exceed the opposite limits of the low resistance zone by at least 10 mm) relative to the density of the parallel fibers with   their directions and located in regions close to areas of low resistance.   14) A shell for a cranio-cerebral protective helmet according to claims 1 - 13   characterized in that the point of minimum resistance to fracture of the zones of low resistance -l- as represented by the point where the depth or the width of the depressions or furrows measured on a section parallel to the edge of the helmet is maximum, by the point where the   density in oblique and horizontal fibers of hulls in composite materials is minimal -   is located at their third furthest from the center of the hull.   ) A shell for a cranio-cerebral protective helmet according to claims 1 - 5   characterized in that it comprises at least one low resistance zone consisting of   several orifices located less than 10 mm between them.   16) A shell for a cranio-cerebral protective helmet according to claims 1 - 5   characterized in that it comprises zones of low resistance represented by junctions between hull segments, produced at least in part with the use of   at least partially removable, adjustable hook structures.   17) A shell for a cranio-cerebral protective helmet according to claims 1 - 5   characterized in that the low resistance layers are produced in the form of pleated structures in U, M, T, L of a material having a thickness of maximum 75% of the thickness of the shell opposite.   18) A shell for a cranio-cerebral protective helmet according to claims I - 5 and   17 characterized in that the low resistance layers have a thickness greater than 5 min.   19) A shell for a cranio-cerebral protective helmet according to claims 1 - 5 and   17 - 18 characterized in that at least two thirds of the layers of low resistance   cover each area of 3 - 15 cm2.   ) A shell for a cranio-cerebral protective helmet according to claims I - 5 and   17 - 19 characterized in that the layers of low resistance are located in the thickness of the intermediate cap and come into contact with the internal surface of the shell only in   case of impact by crushing the cap between the shell and the head.   21) A shell for a crino-cerebral protective helmet according to claims 1 - 20   characterized by the presence of continuity solutions whose maximum diameter is at least   20 times greater than the minimum diameter.