Helmet, comprising a reactive layer and reusable connectors

Abstract

The present invention relates to a helmet (1) comprising an impact mitigating structure, the impact mitigating structure comprising: an inner layer (30); at least one outer layer (10); and e.g. a plurality of elements (2) held between the inner layer (30) and the at least one outer layer (10), at least one connector (100) that provides a releasable connection between the inner layer (30) and the at least one outer layer (10), wherein, when the at least one outer layer (10) is subject to an oblique impact, the connection is released and the plurality of elements (2) are configured to roll to facilitate movement of the inner layer (30) and the at least one outer layer (10) with respect to each other.

Description

[0001] Helmet, comprising a reactive layer and reusable connectors

[0002] The present invention relates to an impact mitigation structure, particularly a helmet, particularly a helmet for cycling.

[0003] Injury to a person or damage to an object can occur when the person or object is subjected to an impact of sufficient magnitude. Considerable developmental effort has been expended to produce helmets which provide protection from potentially damaging or injurious impacts.

[0004] Head injuries, which can be incurred as a result of participation in sports such as cycling are a common cause of serious brain injuries.

[0005] A brain trauma may occur as a consequence of either a focal impact upon the head, a sudden acceleration or deceleration within the cranium, or a combination of both impact and movement. Impact protection is therefore important in preventing brain injuries as a result of impacts to the head.

[0006] Head protection, in the form of helmets, is designed to reduce the forces experienced by a user’s head during an impact. Generally, a helmet comprises at least one impact absorbing layer which is designed to absorb a portion of the forces to which the helmet is subjected during an impact.

[0007] However, helmets often do not provide adequate protection during an impact against both linear and tangential forces. As oblique impacts are common, impacts will often include both linear and tangential components. Particularly, an oblique impact means that the force acting on the outer surface of the helmet that is e.g. hitting the tarmac upon a crash comprises a component that extends tangentially with respect to said outer surface at the location of the impact.

[0008] Unfortunately, such tangential forces in particular result in the rotational acceleration of the brain, which has been linked to bridging vein rupture. In turn, this may be responsible for subdural hematomas, and diffuse axonal injuries. Tangential forces during an impact may also result in neck injuries. In this regard helmets are known in the prior art that comprise a so-called reactive layer, i.e., rollable elements that facilitate relative movement between an outer layer and an inner layer of the helmet when the outer layer is hit by an oblique impact causing the outer layer to get released and allowing rolling of the rollable elements between the inner layer and the outer layer such that the two layers move relative to one another.

[0009] Furthermore, once the outer layer has been released, it is difficult to re-assemble the rollable elements and the outer layer so that the helmet may be used again.

[0010] Furthermore, it may be desirable to also provide means for avoiding premature failure of the helmet leading to a release of the outer layer and / or said rollable elements.

[0011] Based on the above, the problem to be solved by the present invention is to provide a helmet that is capable of reducing the above-mentioned injuries related to oblique impacts comprising a tangential force acting on the helmet / head of the person wearing the helmet, wherein re-assembly of the helmet and / or avoidance of premature failure of the helmet shall be improved.

[0012] This problem is solved by a helmet having the features of claim 1. Preferred embodiments of this aspect of the present invention are stated in the dependent claims and are described below.

[0013] According to claim 1 , a helmet comprising an impact mitigating structure is disclosed, the impact mitigating structure comprising: an inner layer, at least one outer layer, an intermediary layer held between the inner layer and the at least one outer layer, and at least one connector that provides at least one releasable connection between the inner layer and the at least one outer layer, wherein, when the at least one outer layer is subject to an oblique impact, the at least one releasable connection is released and the intermediary layer is configured to facilitate movement of the inner layer and the at least one outer layer with respect to each other.

[0014] According to a preferred embodiment of the present invention, the intermediary layer comprises or is formed by a plurality of elements held between the inner layer and the at least one outer layer, wherein, when the at least one outer layer is subject to an oblique impact, the connection is released and the plurality of elements are configured to roll to facilitate movement of the inner layer and the at least one outer layer with respect to each other.

[0015] Particularly, in some cases it may be beneficial to re-connect the at least one (or several) outer layer(s) in case of premature failure; this could be complete release in multi-impact applications or minor movement between the layers. Other cases could be multi-impact sports where one has "spares" on the side such as outer layers and pre-assembled (rollable) elements on a substrate designed to mounted to the remainder of the helmet easily.

[0016] In the following, the invention is described predominantly with respect to a helmet. However, in principle, the disclosed impact mitigation structure can also be used in other devices, so that the notion of a helmet can be replaced in all embodiments and aspects of the present invention by the more general notion of a protection device. For example, apart from a helmet, such a protection device can be car bumper, a crash barrier, a paintwork (e.g. in key locations on a vehicle), a body part of a vehicle (e.g. car body), a protective armour. Particularly, in a preferred embodiment, a protective armour can be a body armour. In a preferred embodiment the body armour can be configured to provide one of: knee protection, elbow protection, back protection, shin protection.

[0017] In the following, features of the at least one outer layer are described as well as its interaction with the rollable elements and the inner layer. It should be noted however, that the helmet preferably comprises several such outer layers that can be arranged side-by-side on the inner layer of the helmet, with a plurality of elements arranged between the respective outer layer and the underlying inner layer. Thus, all features and embodiments described below with reference to one outer layer also apply to embodiments where the helmet comprises a plurality of outer layers and corresponding pluralities of (rollable) elements. Furthermore, in all embodiments, the inner layer can be formed in one piece, but can also be formed by multiple sheets arranged side by side (particularly on the energy absorbing layer, see below).

[0018] According to a preferred embodiment, the outer layer(s) and the inner layer are stiff layers, wherein said stiffness is particularly due to material (modulus of elasticity) and shape of said layers. A material that is stiff can withstand high loads without elastic deformation. Typically, thin sheets of polycarbonate can be used as basis of said layers which result in sufficiently stiff structures when being arranged in a curved configuration adapted to the shape of a head of a person.

[0019] Particularly, in preferred embodiments, the oblique impact is an oblique impact on the surface of the at least one outer layer (or of one of several outer layers) at an impact site having a non-vanishing force component running tangentially to the outer surface at the impact site, wherein particularly the at least one connector releases the connection and the plurality of elements are configured to roll when said force component comprises a magnitude in the range from 10 N to 150 N.

[0020] In a preferred embodiment, the inner layer and / or the at least one outer layer are configured to move substantially freely relative to each other, when the at least one outer layer is subject to the oblique impact.

[0021] Furthermore, according to a preferred embodiment, the at least one connector is configured to release the releasable connection in a destruction-free manner at a pre-defined load generated by the oblique impact. This means that the connector is re-usable.

[0022] Furthermore, according to a preferred embodiment, the at least one connector is located between the inner layer and the at least one outer layer.

[0023] Furthermore, according to a preferred embodiment, the at least one outer layer forms an outer surface of the helmet, wherein the at least one connector is arranged adjacent to the at least one outer layer. According to yet another preferred embodiment, the at least one connector comprises an array of first protrusions connected to the inner layer and an array of second protrusions connected to the at least one outer layer, wherein the first and the second protrusions are configured to engage with one another particularly through approaching each other (e.g. when pressed together, the protrusions engage with one another) and to disengage through a pulling motion pulling the first protrusions and the second protrusions away from one another. Particularly, the respective (first or second) protrusion comprises a broadened end section so that particularly the respective protrusion comprises a mushroom shape. Particularly, a dual locking system of 3M can be used as the at least one connector

[0024] Furthermore, according to a preferred embodiment, the at least one connector is a hook and loop connector, wherein the first protrusions form loops and the second protrusions form hooks, wherein the loops and the hooks are configured to engage through approaching one another (e.g. when pressed together, the hooks catch the loops), and to disengage through a pulling motion pulling the loops and the hooks away from one another, wherein the array of first protrusions (loops) is connected to the inner layer and the array of second protrusions (hooks) is connected to the at least one outer layer or vice versa. Particularly, the hook and loop connector can be a Velcro connector.

[0025] Further, in a preferred embodiment, the array of first protrusions is arranged on a first substrate and the array of second protrusions is arranged on a second substrate, wherein the first and the second substrate are connected by a connecting portion that can be integral with the first and the second substate, wherein the connecting portion is configured to rupture when the at least one outer layer is subject to the oblique impact, wherein particularly the connecting portion comprises a constriction configured to rupture when the at least one outer layer is subject to the oblique impact.

[0026] Furthermore, according to a preferred alternative embodiment, the at least one connector is a snap fastener, wherein the at least one connector comprises a protruding element and a receptacle (such as a cavity) configured to retain the protruding element, wherein the protruding element is configured to engage into the receptacle to provide the releasable connection, wherein the protruding element is connected to the inner layer and the receptacle is connected to the at least one outer layer or vice versa.

[0027] Furthermore, according to a preferred alternative embodiment, the at least one connector is a snap fastener comprising a protruding element that comprises a latching nose at an end of the protruding element, and an undercut structure, wherein the latching nose is configured to engage behind the undercut structure to provide the releasable connection, wherein the protruding element is connected to the inner layer and the undercut structure is connected to the at least one outer layer or vice versa. Particularly, the protruding element is a relatively stiff element that is configured to elastically deform upon engaging and disengaging with the undercut structure. Particularly, the undercut structure can be provided by a recess or an opening (formed e.g. in the inner layer or the at least one outer layer).

[0028] Furthermore, according to a preferred embodiment of the present invention, the at least one connector comprises at least one permanent magnet to provide the releasable connection.

[0029] Furthermore, according to a preferred alternative embodiment, the helmet comprises a plurality of connectors providing releasable connections between the inner layer and the at least one outer layer, wherein said plurality of connectors are configured to release the releasable connections at an oblique impact on the surface of the outer layer at an impact site having a non-vanishing force component running tangentially to the outer surface at the impact site, wherein said force component comprises a magnitude in the range from 10 N to 150 N.

[0030] Further, in a preferred embodiment, the helmet comprises an energy absorbing layer connected to the inner layer so that the inner layer is arranged between the energy absorbing layer and the at least one outer layer. Alternatively, the inner layer can be formed by the energy absorbing layer. Here, the intermediary layer, particularly its elements, can directly connect to the inner layer, e.g. by being bonded to the inner layer via an adhesive. Particularly, the energy absorbing layer can be an innermost layer of the helmet having an inner side facing the head of the wearer of the helmet. Cushioning can be provided on said inner side to increase comfortability of the helmet.

[0031] Further, in a preferred embodiment, the first inner layer, the second outer layer and / or the reactive layer are configured such that, when the impact mitigating structure is subject to the oblique impact, the majority of the rotational energy of the impact is transferred to the reactive layer.

[0032] Furthermore, according to a preferred embodiment, the at least one outer layer is attached to the remainder of the helmet such that, when the at least one outer layer is subject to the oblique impact, the at least one outer layer is configured to detach from the remainder of the helmet and to move freely with respect to the remainder of the helmet.

[0033] Furthermore, according to a preferred embodiment, when the at least one outer layer is subject to an oblique impact, the plurality of elements are free to move in three dimensions when said releasable connection is released and the plurality of elements are freed by the oblique impact.

[0034] Furthermore, according to a preferred embodiment, the number of elements of the plurality of elements is between 5 and 100,000, e.g. between 50 and 10,000, e.g. between 100 and 1,000, and / or wherein the ratio of the surface area of the inner layer covered by the plurality of elements to a surface area of the at least one outer layer arranged on tops of said plurality of elements (e.g. balls) is between 0.05 and 0.5, e.g. between 0.1 and 0.4, e.g. approximately 0.25.

[0035] Furthermore, according to a preferred embodiment, the plurality of elements (e.g. balls) are formed from a material having a Shore A hardness of greater than 50, e.g. greater than 100.

[0036] Furthermore, according to a preferred embodiment, one or more (or all) of the plurality of elements, the inner layer and the at least one outer layer comprise a high friction material and / or coating such that, when the at least one outer layer is subject to the oblique impact, the plurality of elements are configured to contact one or both the inner layer and the at least one outer layer, such that the high friction material causes the plurality of elements to roll to facilitate movement of the inner layer and the at least one outer layer with respect to each other.

[0037] Furthermore, according to a preferred embodiment, the hardness (as measured in Shore A hardness) of the plurality of elements is equal to or greater than the hardness of the first layer and / or the second layer.

[0038] According to a preferred embodiment of the helmet, the elements of the respective plurality of elements are rigid balls (e.g. spherical bodies), that particularly remain rigid during normal use of the helmet and are configured to roll at an impact threshold over an outer surface of the inner layer. This means that in case a predefined tangential force acts on the at least one outer layer (or on one of the outer layers) due to an oblique impact (e.g. helmet and head therein hitting the ground) exceeds a predefined threshold force, said at least one releasable connection between the respective outer and inner layer provided by the at least one connector is released and rolling of the elements (e.g. balls) is initiated.

[0039] In this context “rolling over” an outer surface of the inner layer does not necessarily mean that there is a contact between the balls and the outer surface of the inner layer, since intermediary layers can be arranged between the elements / balls and said outer surface of the inner layer. Therefore “rolling over” also includes rolling on such an intermediary layer. Particularly, as will be described further below, the elements / balls can be bonded to a substrate e.g. by means of an adhesive, wherein the substrate can be bonded by an adhesive layer to the outer surface of the inner layer. Thus, here, the elements (e.g. balls) may roll on the substrate and said adhesive. Particularly, the substrate can be a thin film, i.e. , a film having a thickness being smaller than its extensions orthogonal to said thickness.

[0040] Furthermore, the balls do not need to be spheres and may deviate from a perfect spherical shape. Therefore, the notion of a ball according to the present invention therefore includes rollable elements and the balls may also be referred to as rollable elements. Furthermore, the first and / or the second layer do not need to be homogenous layers, but can each consist of different materials and / or layers stacked on top of one another. In a preferred embodiment, the elements (e.g. balls) can be formed out of polycarbonate. According to alternative embodiments, the elements / balls can be formed out of one of the following materials: polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), poly(methyl methacrylate) (PMMA). Each of these materials can be used in conjunction with all other embodiments of the helmet described herein. Preferably, according to an embodiment, the elements / balls are formed from a material comprising a Young’s modulus (modulus of elasticity) in the range from 0.5 to 10 GPa.

[0041] Furthermore, according a preferred embodiment, the energy absorbing layer comprises a varying material density, and / or comprises different materials, and / or comprises different structures. Particularly, the energy absorbing layer can comprise different structures like foam and honeycomb or different materials like EPS, EPP, EPU.

[0042] According to yet another preferred embodiment, the inner layer and the at least one outer layer are not congruent to each other. Particularly, in case the helmet comprises multiple outer layers, the latter are not congruent (when taken together) with the inner layer in a preferred embodiment.

[0043] Furthermore, in a preferred embodiment, the at least one outer layer is configured to completely separate from the inner layer when the at least one outer layer is subject to an oblique impact.

[0044] Furthermore, according to a preferred embodiment, each element of said plurality of elements can be ball, particularly a sphere, having an outer diameter in the range from 0.5 mm to 5.0 mm, wherein particularly the diameter is 2 mm.

[0045] Furthermore, according to a preferred embodiment of the helmet the elements (e.g. balls) are bonded to a substrate via an adhesive that can be configured to undergo brittle failure in an embodiment. The substrate can be formed out of a polymer, particularly PVC. According to preferred embodiments the adhesive is one of the following adhesives: Cyanoacrylate, polyvinyl acetate (P A), epoxy. Furthermore, in a preferred embodiment, the elements are bonded to the at least one outer layer (or to the respective outer layer) by a hot melt adhesive, and / or the elements are bonded to the inner layer by a UV curable adhesive. Particularly, both the hot melt adhesive and the UV curable adhesive can be a pressure sensitive adhesive, so that the elements (e.g. balls) can re-stick to the respective surface if they become dislodged.

[0046] According to an embodiment, the elements (e.g. balls) are bonded to the substrate via a primarily brittle-failure-based adhesive. Furthermore, according to a preferred embodiment of the helmet, the substrate comprises a thickness smaller than 200 pm.

[0047] Further, according to a preferred embodiment of the helmet, the substrate film comprises an adhesive layer preferably consisting of a pressure sensitive adhesive arranged on a side of the substrate film facing away from said plurality of balls.

[0048] Furthermore, according to a preferred embodiment of the helmet, the plurality of elements (e.g. balls) and the substrate form an assembly for mounting the elements on the inner layer. Particularly, the assembly can comprise a vinyl both for wet and dry applications. Further, preferably, the substrate is bonded to the outer surface of the inner layer via said adhesive layer consisting of said pressure sensitive adhesive of the substrate.

[0049] Furthermore, in an embodiment, the plurality of elements (e.g. balls) is bonded to an inner surface of the at least one outer layer via an adhesive layer, preferably an adhesive layer comprising (or consisting of) a thermo-softening adhesive. Particularly, the adhesive becomes active during high temperature moulding and therefore allows to bond the elements / balls to the inner surface of the at least one outer layer in a mold in which a portion of the helmet is formed.

[0050] Furthermore, in an embodiment, the at least one outer layer comprises: a sheet (the sheet being preferably formed from a plastic material such as polycarbonate (PC)), a color layer (e.g. a colored ink layer) arranged on an inner surface of the sheet, a protective layer arranged on the color layer, wherein said adhesive layer that bonds the elements / balls to the inner surface of the at least one outer layer is bonded to the protective layer. A further coat such as a light bleed preventing coat (see also below) can be applied to the colour layer before the protective layer is arranged on the colour layer / further coat.

[0051] However, according to a further preferred embodiment of the present invention, instead of using a substrate, the elements (e.g. balls) can be bonded (e.g. directly) to the outer surface of the inner layer with an adhesive, particularly an adhesive comprising PVA (poly(vinyl alcohol)). Alternatively, this adhesive can also be a PSA (e.g. a holt melt or an UV curable adhesive), both of which can either be configured to undergo brittle failure or to be tacky.

[0052] Particularly, in all embodiments, the outer surface of the inner layer faces outwards, i.e. , away from a head of a person wearing the helmet, wherein the inner surface of the outer layer(s) faces towards the head of said person wearing the helmet.

[0053] In preferred embodiment of the helmet, the protective layer is a heat resistant ink layer. Particularly, the heat resistant ink layer can be screen printed or UV printed onto the colour layer (e.g. coloured ink layer) or the coated colour layer (see above).

[0054] According to a further embodiment of the helmet, the protective layer is a polymer layer, particularly a polyvinylchloride layer. Other materials such as PC can also be used instead of PVC.

[0055] Furthermore, preferably, the respective protective layer comprises a thickness below 0.1 mm and / or a yield strength larger than 20 MPa according to an embodiment of the helmet.

[0056] Further, according to a preferred embodiment of the helmet, the protective layer has a thermal expansion differing less than 5 % from a thermal expansion of a material of the first layer.

[0057] According to yet another embodiment of the helmet, the first layer is a twin sheet assembly comprising an outer sheet and an inner sheet being thermoformed simultaneously in particular, wherein both sheets preferably consist of polycarbonate (PC).

[0058] Preferably, in an embodiment, the inner sheet of the twin sheet assembly is perforated, particularly so as to allow the negative pressure of the forming to pass through to the outer sheet so that not only the inner sheet is pulled down onto the forming.

[0059] Furthermore, in an embodiment, a colour layer (particularly a coloured ink layer) and an adhesive layer (particularly an adhesive ink layer) are arranged between the outer and the inner sheet, wherein particularly the colour layer is arranged on the outer sheet and the inner sheet is bonded to the outer layer via the adhesive ink layer and the colour layer.

[0060] According to a preferred embodiment, the energy absorbing layer comprises polystyrene, preferably expanded polystyrene (EPS) or polyurethane, particularly expanded polyurethane (EPU), or polypropylene, particularly expanded polypropylene (EPP). For a molding process, where the energy absorbing layer is formed adjacent the first and the second layer and the intermediary reactive layer (e.g. membrane) using preferably an in-moulding (see also below), the material for the energy absorbing layer can be provide in the cavity of the mould as bulk material (e.g. in the form of pellets).

[0061] Further, according to a preferred embodiment of the helmet, the plurality of elements (e.g. balls) is configured to facilitate relative movement between the at least one outer layer and the inner layer by the rolling of said elements / balls between the at least one outer and the inner layer, wherein said rolling of elements / balls provides a low rolling resistance in the range from 0.0001 to 0.2, preferably in the range from 0.001 to 0.05, preferably in the range between 0.005 to 0.015 between the elements / balls and an inner surface of the at least one outer layer or an inner surface connected to the at least one outer layer or between the elements / balls and an outer surface of the inner layer or an outer surface connected to the inner layer, wherein particularly said range applies to the interface with the lower rolling resistance. A particularly preferred rolling resistance amounts to about 0.01. Another particularly preferred rolling resistance amounts to about 0.04.

[0062] It is to be noted that the rolling resistance relates to the surface that the elements / balls actually contact. Therefore, in case intermediary layers are present between the at least one outer layer and the elements / balls, the latter roll on a surface connected to the at least one outer layer (i.e. a surface formed by the respective intermediate layer). Likewise, in case intermediary layers are present between the inner layer and the elements / balls, the latter roll on a surface connected to the inner layer (i.e. a surface formed by the respective intermediate layer).

[0063] Preferably, the rolling of the balls between the surfaces of the at least one outer layer and the inner layer provides an extremely low resistance-to-motion (RTM). However, employing rolling does not intrinsically make the movement occur more readily, it merely lowers the lower limit, allowing other movement inhibiting mechanisms to become the dominant factors (i.e. adhesives and / or connectors initially connecting the at least one outer and the inner layers).

[0064] Particularly, relative movement is facilitated between the impacted surface, e.g. the outer layer hitting tarmac) and the inner layer being fixed with respect to a head of a person wearing the helmet thus reducing risk of traumatic brain injury (TBI). Preferably, a separation between the inner surface of the at least one outer layer and the outer surface of the inner layer remains as constant as possible. Should an impact occur where the balls are required to roll into an area where the separation between the said inner surface and said outer surface is smaller - then they would wedge and the RTM would shoot up. Particularly, according to an embodiment, upon a typical impact said separation varies less than 20%, particularly less than 15%, particularly less than 10%, preferably less than 5%.

[0065] According to a preferred embodiment of the present invention, the balls of the reactive layer are bodies (particularly round or ellipsoidal bodies) comprising a roundness above 0.7, more preferably a roundness above 0.8, more preferably a roundness above 0.9, more preferably a roundness above 0.95, more preferably a roundness above 0.97, more preferably a roundness above 0.99. Preferably, in an embodiment, the balls are spherical bodies.

[0066] With respect to a cross-section of a ball that extends orthogonally to an axis of rotation of the ball about which the ball can rotate, roundness is defined as the ratio between the area of a circle inscribed in the cross-section and the area of a circle circumscribing the cross-section, i.e. , the maximum and minimum sizes for circles just sufficient to fit within and enclose the cross-section.

[0067] According to an embodiment, the balls preferably comprise a constant diameter and / or volume. According to an alternative embodiment, the balls comprise different diameters and / or volumes.

[0068] According to yet another embodiment, the balls can be solid bodies or hollow bodies.

[0069] Further, as the inner layer moves relative to the at least one outer layer, particularly under the at least one outer layer, the outer surface of the inner layer and the inner surface of the at least one outer layer preferably maintain their congruent relationship. Therefore, according to a preferred embodiment, the inner surface of the at least one outer layer (A surface) and the outer surface of the inner layer (B surface) are concentric with respect to one another. During an impact there may be enough energy to flatten the A and / or B surfaces enough to affect the predetermined congruency and concentricity factors. Stiffening the B surface (in particular) reduces the deformation magnitude. Furthermore, as the B surface moves under the A surface, the B surface can become exposed as elements / balls roll away. If this exposed portion can make contact with the impacting surface, then a shear force can be transferred, increasing the RTM drastically. This issue can be mitigated by ensuring that all impactable locations are protected by the plurality of elements (e.g. balls). According to a preferred embodiment, the outer layer(s) with the respective plurality of elements (e.g. balls) thereunder cover at least 50% of the outer surface of the inner layer, preferably at least 70%, more preferably at least 80%, more preferably at least 90%. According to yet another preferred embodiment of the helmet according to the present invention, the substrate is congruent to the inner surface of the at least one outer layer.

[0070] Particularly, if the force of an impact is not spread over a large enough area then local loading of the impact mitigating structure can be too large which may lead to a flattening of elements / balls and / or indentations of an adjacent surface such as the inner surface of the at least one outer layer and / or the outer surface of the inner layer. This could lead to an increased RTM. To prevent either from happening, the camber and undulation of the inner surface of the at least one outer layer and an underlying portion of the outer surface of the inner layer is preferably as low as possible so that less point loading can occur. Preferably, at any point, a radius of curvature of said inner surface and / or of said portion of the outer surface is larger than 40mm, preferably larger than 60mm, preferably larger than 80mm, preferably larger than 100 mm.

[0071] Particularly, as the outer surface of the inner layer moves under the inner surface of the at least one outer layer, the inner surface of the at least one outer layer may start butting up against non-congruent portions of the outer surface of the inner layer. In case the outer surface of the inner layer is not ramped at these locations to encourage the inner surface of the at least one outer layer to bend away, then the inner surface of the at least one outer layer may lock up and the RTM will rise.

[0072] Furthermore, according to a preferred embodiment of the helmet, the inner layer forms at least one ramp to cause the at least one outer layer to bend away from the inner layer to avoid butting up of the at least one outer layer on a portion of the inner layer. This is also denoted as edge ramping.

[0073] Similar to edge ramping, but in the trailing direction, the inner surface of the at least one outer layer may hook onto details of the outer surface of the inner layer causing the RTM to rise. This is also denoted as edge hooking. Accordingly, in an embodiment, this is prevented by ensuring that the helmet geometry has no hard or sharp trailing edges. Particularly, according to an embodiment, the energy absorbing layer and / or the inner layer comprises an edge portion having a chamfered or rounded edge to prevent a trailing edge of the at least one outer layer from becoming caught on said edge portion when moving relative to the inner layer and / or energy absorbing layer over said edge portion.

[0074] Particularly, according to an embodiment, the at least one connector and the plurality of elements (e.g. balls) are configured to hold the at least one outer layer such that a tangential force required to release the connection provided by the at least one connector and to activate rolling of elements / balls is about 0.1 kN, or such that an energy introduced by the impact force has to exceed a threshold of 2.5 Joule to release said connection and activate rolling of the elements / balls.

[0075] In the following, embodiments of the present invention as well as further features and advantages shall be described with reference to the Figures, wherein

[0076] Fig. 1 shows an embodiment of the helmet according to the present invention, the helmet comprising at least one releasable connector connecting at least one outer layer of the helmet to an inner layer of the helmet in a destruction-free releasable fashion,

[0077] Fig. 2 shows a further detail of the helmet shown in Fig. 1 upon an oblique impact causing release of the connector,

[0078] Fig. 3 shows a schematic illustration of an embodiment of a helmet according to the present invention comprising at least one connector in form of a hook and loop connector,

[0079] Fig. 4 shows a schematic illustration of an embodiment of the helmet according to the present invention comprising at least one connector in form of a snap fastener,

[0080] Fig. 5 shows a modification of the connector shown in Fig. 4, Fig. 6 shows a schematic illustration of a further embodiment of the helmet according to the present invention comprising at least one connector in form of a snap fastener,

[0081] Fig. 7 shows a modification of the embodiment shown in Fig. 6, and

[0082] Fig. 8 shows a schematic illustration of a further embodiment of a helmet according to the present invention comprising at least one connector in form of a hook and loop connector, wherein the opposing substrates of the connector are connected by a connecting portion that ruptures upon an oblique impact on the at least one outer layer,

[0083] Fig. 8A shows a detail of the connecting portion shown in Fig. 8, wherein the connecting portion comprises a constriction forming a predetermined breaking point.

[0084] Fig. 1 shows an embodiment of a helmet 1 according to the present invention. According thereto, the helmet 1 comprises at least one outer layer 10, preferably a plurality of outer layers 10 forming an outer surface of the helmet 1 on which an oblique impact may occur, i.e. , an impact having a force component FT running tangentially with respect to said outer surface.

[0085] The helmet 1 further comprises an inner layer 30 and an intermediary layer, particularly a plurality of elements 2, particularly rigid balls 2, sandwiched between an associated outer layer 10 and the inner layer 30. In the following, the invention will be described in the context of multiple outer layers 10.

[0086] Apart from the elements 2, that can connect the outer layers 10 to the inner layer 30, the respective outer layer 10 is further connected by at least one releasable connector 100 to the inner layer 30. Particularly, a releasable connector provides a releasable connection, i.e., a connection that can be released without destroying the connector 100 in a manner that renders the connector 100 unusable (i.e. it cannot establish said connection anymore). The connector 100 can however be subject to wear which is not considered to be a destruction of the connector. Since the respective connector 100 is not destroyed upon release, it can be re-used multiple times.

[0087] Preferably, as indicated in Fig. 1, the at least one connector 100 is located between the inner layer 30 and the at least one outer layer 10. Particularly, each outer layer 10 is connected via at least one connector 100, particularly multiple connectors 100, to the inner layer 30. Particularly, the outer layers 10 form an outer surface of the helmet 1, wherein the respective connector 100 is adjacent to its associated outer layer 10.

[0088] Particularly, as shown in Figs. 1 and 2, the respective connector 100 comprises an array of first protrusions 101 connected to the inner layer 30 and an array of second protrusions 102 connected to the respective outer layer 10, wherein the first and the second protrusions 101, 102 are configured to engage through a pressing motion pressing the first protrusions 101 and the second protrusions 102 towards one another and to disengage through a pulling motion pulling the first protrusions 101 and the second protrusions 102 away from one another. Particularly, the first and the second protrusions 101 , 102 each comprise a broadened head 101a, 102a at the end of the respective protrusion 101, 102, wherein said heads 101a, 102a can engage with one another as indicated in Fig. 1. Fig. 2 shows the disengaged protrusions 101, 102 due to an oblique impact on the outer layer 10 of the helmet 1.

[0089] Figs. 3 to 7 show alternative designs of connectors 100 that can be used in the helmet shown in Figs. 1 and 2.

[0090] Particularly, according to Fig. 3, the respective connector 100 can be a hook and loop connector comprising an array of loops 103 and an opposing array of hooks 104, wherein the loops 103 and the hooks 104 are configured to engage through a pressing motion pressing the loops 103 and the hooks 104 towards one another so that the hooks104 engage with the loops 103, and to disengage through a pulling motion pulling the loops 103 and the hooks 104 away from one another.

[0091] Particularly, the array of loops 103 can be connected to the inner layer 30 and the array of hooks 104 can be connected to the respective outer layer 10 or vice versa. According to yet another preferred embodiment shown in Figs. 4 and 5, the at least one connector 100 can be a snap fastener, comprises a protruding element 105 and a receptacle 106 configured to retain the protruding element 105, wherein the protruding element 105 is configured to engage with the receptacle 106 to provide the releasable connection. Particularly, the protruding element 105 can be connected to the inner layer 30 and the receptacle 106 can be connected to the associated outer layer 10 or vice versa. As shown in Fig. 4, additional fasteners 105b, 106b can be used to connect protruding element 105 and receptacle 106 to the outer layer 10 and inner layer 30. Alternatively, as indicated in Fig. 5, the protruding element 105 and the receptacle can be bonded by adhesive layers 105b and 106b to the outer layer 19 and inner layer 30.

[0092] Furthermore, as indicated in Figs. 6 and 7, the respective connector 100 is a snap fastener comprising a protruding element 107 comprising a latching nose 107a at a free end of the protruding element 107, and an undercut structure 108, wherein the latching nose 107a is configured to engage behind the undercut structure 108 to provide the releasable connection. Particularly, the protruding element 107 can be connected to the inner layer 30 and the undercut structure 108 can be connected to the respective outer layer 10 or vice versa. Particularly, the protruding element 107 is a relatively stiff element that is configured to elastically deform to engage and disengage with the undercut structure 108 as shown on the right-hand side of Fig. 6. Particularly, the undercut structure 108 can be provided by a recess as e.g. shown in Fig. 6 or even an opening or a similar recess structure as shown in Fig. 7.

[0093] Furthermore, as shown in Fig. 1, the outer layers 10 can comprise a longitudinal shape and can extend along the longitudinal axis X of the helmet 1. Furthermore, preferably, the outer layers 10 can be arranged side by side in the direction of the cross-axis Y of the helmet 1. Further, the outer layers 10 are preferably configured as stiff outer layers 10 which can be achieved by selecting an appropriate material for the outer layers 10 and geometry during the curved shape of the outer layers 10 contributes to said stiffness. Particularly the outer layers 10 can be formed out of polycarbonate and can comprise a thickness in the range from 0.25 mm to 20 mm, preferably 0.4 to 1 mm. Furthermore, the outer layers 10 can each comprise a curvature in the direction of the longitudinal axis X as well as in the direction of the cross-axis Y. Other materials for the outer layers are also conceivable. Likewise, as the outer layers 10, the inner layer 30 being arranged beneath the outer layers 10 is also preferably adapted to be stiff in the sense described above. Furthermore, the inner layer 30 can be arranged on an energy absorbing layer 40 configured to absorb energy of an impact on the helmet 1 particularly in a normal direction of the outer surface of the helmet 1 (e.g. along the vertical axis of the helmet). The energy absorbing layer 40 can be formed out of an expanded polystyrene foam (EPS) and can be bonded to an inner surface 30b of the inner layer 30 by an adhesive layer 33 (e.g. acrilux or other suitable thermo-softening adhesives).

[0094] The inner layer 20 can comprise a thickness in the range from 0.25 mm to 20 mm and may also be formed out of polycarbonate. As shown in Fig. 1, the helmet may comprise through-openings 8 extending through the layers 10, 20, 40 for allowing venting of the head of a person wearing the helmet 1. Such through-openings 8 may by flanked by first layers 10 on either side of the respective through-opening. Preferably, the rollable elements / balls 2 can be rigid spherical bodies that can remain rigid during normal use of the helmet 1 (when no impact occurs) and are configured to roll at an impact threshold over an outer surface 30a of the inner layer 30 (also denoted as B surface).

[0095] The impact threshold corresponds to a pre-defined tangential force on an outer layer 10 that, if exceeded upon an oblique impact, causes the elements 2 to roll. In a preferred embodiment, the elements 2 comprise a diameter of about 2 mm. Further, the elements 2 can comprise the packing density as described herein. Preferably, the elements 2 and the at least one connector 100 can be configured to hold the respective outer layer 10 such that a tangential force required to activate release of a connection provided by the at least one connector and rolling of the elements 2 is about 0.1 kN (or higher).

[0096] Preferably, as indicated in Fig. 1, the respective plurality of elements 2 can be connected to a substrate 21 and can thus be handled in a convenient fashion during production of the helmet 1. Particularly, as indicated in the detail of Fig. 1 (in the lower part of Fig. 1), the elements 2 can be bonded to the respective substrate 21 via an adhesive 22 that is preferably configured to undergo brittle failure to allow the elements 2 to roll on the substrate 21 / over the inner layer 30 when said impact threshold is exceeded. Preferably, the substrate 21 can comprises a thickness smaller than 200 pm and can be formed out of a polymer such as PVC. Other materials are also conceivable. Furthermore, the substrate 21 can comprises an adhesive layer 23 such as a pressure sensitive adhesive (PSA) arranged on a side of the substrate 21 facing away from the balls 2. This allows one to easily place the substrate 21 with the elements 2 thereon onto the inner layer 30 as shown in Fig. 1 and bond the respective substrate 21 with the elements 2 thereon to the inner layer 30.

[0097] Furthermore, the elements 2 can be bonded to an inner surface 10a of the respective outer layer 10 by an adhesive layer 14 that bonds to the elements 2 to the respective outer layer 10.

[0098] However, in yet another preferred embodiment, each element can be directly bonded by an adhesive to the inner layer and can be directly bonded by an adhesive to the associated outer layer. Particularly the substrate 21 can be omitted.

[0099] Further, Fig. 8 shows in conjunction with Fig. 8A an embodiment of a hook and loop connector 100 that can be used with the helmet 1 of the present invention as e.g. shown in Figs. 1 and 2, wherein the array of loops 103 is arranged on a first substrate 113 and the array of hooks 104 is arranged on a second substrate 114, wherein the first and the second substrate 113, 114 are (particularly integrally) connected by a connecting portion 115, wherein the connecting portion 115 is configured to rupture when the at least one outer layer 10 is subject to the oblique impact, wherein particularly the connecting portion 115 comprises a constriction 115a as shown in Fig. 8A that is configured to rupture when the at least one outer layer 10 is subject to the oblique impact. Particularly, the first substrate 113 can be connected to the inner layer 30 and the second substrate 114 can be connected to the associated outer layer 10 or vice versa.

[0100] Furthermore, the same concept can also be applied to the connectors 100 shown in Fig. 1 and 2. Also here, the substrates 113, 114 to on which the first and the second protrusions 101, 102 are arranged can be connected by the connecting portion 115 shown in Figs. 8 and 8A. Also here, upon an oblique impact, the protrusions 101 , 102 will disengage and the connecting portion 115 will rupture. Afterwards, the connectors 100 can be used again (apart from the additional destructible connecting portion 115). Particularly, in all embodiments using substrates 113, 114 as described above, the connecting portion 115 can be integrally connected to the first and the second substrate 113, 114.

Claims

Claims1. A helmet (1) comprising an impact mitigating structure, the impact mitigating structure comprising: an inner layer (30), at least one outer layer (10), and an intermediary layer held between the inner layer (30) and the at least one outer layer (10), and at least one connector (100) that provides a releasable connection between the inner layer (30) and the at least one outer layer (10), wherein, when the at least one outer layer (10) is subject to an oblique impact, the releasable connection is released and the intermediary layer is configured to facilitate movement of the inner layer (30) and the at least one outer layer (10) with respect to each other.

2. The helmet according to claim 1 , wherein the intermediary layer comprises a plurality of elements (2) held between the inner layer (30) and the at least one outer layer (10), wherein, when the at least one outer layer (10) is subject to an oblique impact, the releasable connection is released and the plurality of elements (2) are configured to roll to facilitate movement of the inner layer (30) and the at least one outer layer (10) with respect to each other.

3. The helmet according to claim 1 or 2, wherein the at least one connector (100) is configured to release the releasable connection at a pre-determined load generated by the oblique impact without permanent damage of the at least one connector (100).

4. The helmet according to one of the preceding claims, wherein the at least one connector (100) is located between the inner layer (30) and the at least one outer layer (10).

5. The helmet according to one of the preceding claims, wherein the at least one outer layer (10) forms an outer surface of the helmet (1) and wherein the at least one connector (100) is adjacent to the at least one outer layer (10).

6. The helmet according to one of the preceding claims, wherein the at least one connector (100) comprises an array of first protrusions (101) connected to the inner layer (30) and an array of second protrusions (102) connected to the at least one outer layer (10), wherein the first and the second protrusions (101, 102) are configured to engage with one another to provide the releasable connection.

7. The helmet according to claim 6, wherein the at least one connector (100) is a hook and loop connector, wherein each first protrusion is a loop (103), and wherein each second protrusion is a hook (104).

8. The helmet according to claim 6 or 7, wherein the array of first protrusions (101 , 103) is arranged on a first substrate (113) and the array of second protrusions (102, 104) is arranged on a second substrate (114), wherein the first and the second substrate (113, 114) are connected by a connecting portion (115), wherein the connecting portion (115) is configured to rupture when the at least one outer layer (10) is subject to the oblique impact, wherein particularly the connecting portion (115) comprises a constriction (115a) configured to rupture when the at least one outer layer (10) is subject to the oblique impact.

9. The helmet according to one of the claims 1 to 5, wherein the at least one connector (100) is a snap fastener, wherein the at least one connector (100) comprises a protruding element (105) and a receptacle (106) configured to retain the protruding element (105), wherein the protruding element (105) is configured to engage into the receptacle (106) to provide the releasable connection, wherein the protruding element (105) is connected to the inner layer (30) and the receptacle (106) is connected to the at least one outer layer (10) or vice versa.

10. The helmet according to one of the claims 1 to 5, wherein the at least one connector (100) is a snap fastener comprising a protruding element (107) that comprises a latching nose (107a) at an end of the protruding element (107), and an undercut structure (108), wherein the latching nose (107a) is configured to engage behind the undercut structure (108) to provide the releasable connection, wherein the protruding element (107) is connected to the inner layer (30) and the undercut structure (108) is connected to the at least one outer layer (10) or vice versa.

10. The helmet according to one of the claims 1 to 5, wherein the at least one connector (100) comprises at least one permanent magnet to provide the releasable connection.

11. The helmet according to one of the preceding claims, wherein the helmet (1) comprises a plurality of connectors (100) providing releasable connections between the inner layer (30) and the at least one outer layer (10), wherein said plurality of connectors (100) are configured to release the releasable connections at an oblique impact on the surface of the at least one outer layer (10) at an impact site having a non-vanishing force component running tangentially to the outer surface at the impact site, said force component comprising a magnitude in the range from 10 N to 150 N.

12. The helmet according to one of the preceding claims, wherein the impact mitigating structure of the helmet (1) comprises an energy absorbing layer (40) connected to the inner layer (30) so that the inner layer (30) is arranged between the energy absorbing layer (40) and the at least one outer layer (10), or wherein the inner layer is an energy absorbing layer and the intermediary layer directly connects to the energy absorbing layer.

12. The helmet according to one of the preceding claims, wherein the energy absorbing layer comprises a varying material density, and / or comprises different materials, and / or comprises different structures.

13. The helmet according to one of the preceding claims, wherein the inner layer (30) and the at least one outer layer (10) are not congruent to each other.

14. The helmet according to one of the preceding claims, wherein the at least one outer layer (10) is configured to completely separate from the inner layer (30) when the at least one outer layer (10) is subject to an oblique impact.

15. The helmet according to one of the preceding claims, wherein the respective element (2) of said plurality of elements (2) of the intermediary layer comprises a rolling resistance with respect to a surface provided by or arranged on the innerlayer (30) and / or with respect to an inner surface provide by or arranged on the at least one outer layer of less than 0.2.

16. The helmet according to one of the preceding claims, wherein each element (2) of said plurality of elements (2) is a ball, particularly a sphere, having an outer diameter in the range from 0.5 mm to 5.0 mm, particularly in the range from 0.5 mm to 2.0 mm.

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