helmet

Abstract

A helmet (1) comprising an outer part (3) having an inner surface arranged to face radially inward, towards the head of a wearer in use; and an interface layer (4) provided radially inward of the outer part, configured to provide an interface between the helmet and the wearer, wherein the interface layer is arranged at a position adjacent to the inner surface of the outer part and configured to slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet; wherein the interface layer comprises at least a sliding layer (4) arranged at a position adjacent to and facing the inner surface of the outer part, the sliding layer comprising at least one resilient portion (41) integrally formed therein and arranged at an interface between the interface layer and the outer part, connected to the outer part; and wherein the resilient portion is configured to deform such that the interface layer can slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet.

Description

[0001] HELMET

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a helmet.

[0004] BACKGROUND

[0005] Impact protection apparatuses generally aim to reduce the energy transferred to an object, such as a person to be protected, by an impact. This may be achieved by energy absorbing means, energy redirecting means, or a combination thereof. Energy absorbing means may include energy absorbing materials, such as foam materials, or structures configured to deform elastically and / or plastically in response to an impact. Energy redirecting means may include structures configured to slide, shear or otherwise move in response to an impact.

[0006] Impact protection apparatuses include protective apparel for protecting a wearer of the apparel. Protective apparel comprising energy absorbing means and / or energy redirecting means is known. For example, such means are implemented extensively in protective headgear, such as helmets.

[0007] Examples of helmets comprising energy absorbing means and energy redirecting means include WO 2001 / 045526 and WO 2011 / 139224 (the entirety of which are herein incorporated by reference). Specifically, these helmets include at least one layer formed from an energy absorbing material and at least one layer that can move relative to the head of the wearer of the helmet under an impact.

[0008] Implementing moving parts in a helmet has challenges. For example, ensuring that friction between moving parts under an impact can be overcome to allow enough relative movement between parts can be challenging. Ensuring that the helmet can be manufactured and assembled relatively easily can be challenging.

[0009] It is the aim of the present invention to provide a helmet that at least partially addresses some of the problems discussed above. SUMMARY OF THE INVENTION

[0010] According to a first aspect of the disclosure there is provided, a helmet comprising: an outer part having an inner surface arranged to face radially inward, towards the head of a wearer in use; and an interface layer provided radially inward of the outer part and configured to provide an interface between the helmet and the wearer, wherein the interface layer is arranged at a position adjacent to the inner surface of the outer part and configured to slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet; wherein the interface layer comprises at least a sliding layer arranged at a position adjacent to and facing the inner surface of the outer part, the sliding layer comprising at least one resilient portion integrally formed therein and arranged at an interface between the interface layer and the outer part, connected to the outer part; and wherein the resilient portion is configured to deform such that the interface layer can slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet.

[0011] Optionally, the outer part of the helmet comprises a recess for accommodating the resilient portion connected thereto. Optionally, the resilient portion substantially protrudes out of the plane defined by the rest of the sliding layer when the resilient portion is connected to the outer part of the helmet, into the recess, and the recess is arranged to surround the resilient portion. Optionally, the recess is arranged to allow the resilient portion to deform such that the interface layer can slide relative to the outer part. Optionally, the recess is configured to allow the resilient portion to deform such that the interface layer can slide relative to the outer part, while the resilient portion remains substantially protruding out of the plane defined by the rest of the sliding layer.

[0012] Optionally, the resilient portion comprises, in the plane of the sliding layer, an inner portion surrounded by a resilient structure. Optionally, the deformable portion is at least partially formed by at least one first cut-out in the sliding layer, the first cut-out defining the resilient structure. Optionally, the resilient structure is a spring structure. Optionally, resilient structure is configured to deform substantially by flexion of a material forming the resilient structure. Optionally, the resilient structure comprises one or more elements extending radially, in the plane of the sliding layer, between the inner portion and the rest of the sliding layer. Optionally, one or more of the elements is formed in a curve, in the plane or the sliding layer. Optionally, the curve is a spiral. Optionally, the curve is an arc. Optionally, the curve is a sinusoid.

[0013] Optionally, one or more of the elements is substantially linear. Optionally, one or more of the elements extends substantially in a direction oblique to a radial direction and a circumferential direction from the inner portion. Optionally, one or more of the elements extends in a circumferential direction and is connected by one or more further elements extending in a direction oblique to the circumferential direction or in a radial direction.

[0014] Optionally, the resilient portion is substantially rotationally symmetric.

[0015] Optionally, the resilient portion is formed substantially in a plane defined by the rest of the sliding layer, at least when the resilient portion is not connected to the outer part of the helmet. Optionally, the resilient portion substantially protrudes out of the plane defined by the rest of the sliding layer when the resilient portion is connected to the outer part of the helmet. Optionally, the resilient portion is in tension in a protrusion direction when the resilient portion is connected to the outer part of the helmet.

[0016] Optionally, resilient portion substantially protrudes out of a plane defined by the rest of the sliding layer, both when the resilient portion is not connected to the outer part of the helmet and when the resilient portion is connected to the outer part of the helmet.

[0017] Optionally, the inner portion comprises an attachment point for attachment to the outer part of the helmet, surrounded by the rest of the sliding layer and connected thereto by a resilient structure of the resilient portion. Optionally, n the attachment point comprises at least one hole through which a corresponding fixing member is passed, the fixing member connecting the resilient portion to the outer part of the helmet. Alternatively, the attachment point comprises at least one fixing member integrally formed therein, the fixing member connecting the resilient portion to the outer part of the helmet. Optionally, the fixing member is a snap-pin. Optionally, the outer part of the helmet comprises a corresponding snap-basket. Alternatively, the fixing member is sharp pin, optionally a barbed pin configured to penetrate the outer part of the helmet.

[0018] Optionally, the resilient portion is provided in a substantially central portion of the interface layer, substantially corresponding to the top of the wearer’s head in use.

[0019] Optionally, the resilient portion is formed from the same material as the rest of the sliding layer and is continuous with the rest of the sliding layer.

[0020] Optionally, the resilient portion is formed from a different material from the rest of the sliding layer and is co-moulded with the rest of the sliding layer. Optionally, the different material is an elastically deformable material.

[0021] Optionally, the resilient portion is formed into the sliding layer by moulding.

[0022] Optionally, the resilient portion is formed into the sliding layer by removing material from a component forming the sliding layer.

[0023] Optionally, the resilient portion is configured to deform such that the interface layer can slide relative to the outer part in substantially any direction in a plane of the sliding layer.

[0024] Optionally, the resilient portion is configured to deform such that the interface layer can slide relative to the outer part such that the interface layer can be displaced at least 10mm, or at least 15mm, in a plane of the sliding layer.

[0025] Optionally, the sliding layer is a stiff layer.

[0026] Optionally, the sliding layer is formed from a polymer, optionally one or more of polypropylene, polycarbonate, polytetrafluoroethylene, acrylonitrile butadiene styrene, polyvinyl chloride, Nylon, perfluoroalkoxy alkane, Fluorinated ethylene propylene, polyethylene, polyketone, ultra-high molecular weight polyethylene, and Teflon™.

[0027] Optionally, the sliding layer is moulded to have a predefined shape substantially corresponding to the shape of the inner surface of the outer part. Optionally, the interface layer comprises comfort padding facing the wearer, in use.

[0028] Optionally, the outer part comprises an energy absorbing layer. Optionally, the energy absorbing layer is formed from a polymer foam material.

[0029] Optionally, the outer part comprises a hard, outer shell.

[0030] According to a second aspect of the disclosure, there is provided a kit of parts for forming the helmet of any preceding claim, comprising: an outer part for the helmet, having an inner surface arranged to face radially inward, towards the head of a wearer, when the helmet is formed and in use; and an interface layer for the helmet, configured to be provided radially inward of the outer part and configured to provide an interface between the helmet and the wearer, when the helmet is formed and, wherein the interface layer is arranged at a position adjacent to the inner surface of the outer part and configured to slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet, when the helmet is formed and in use; the interface layer comprising at least an sliding layer arranged at a position adjacent to and facing the inner surface of the outer part, the sliding layer comprising at least one resilient portion integrally formed therein and arranged at an interface between the interface layer and the outer part, connected to the outer part to retain the interface layer at the position adjacent to the inner surface of the outer part; and wherein the resilient portion is configured to deform such the interface layer can slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet.

[0031] According to a third aspect of the disclosure, there is provided an interface layer for the helmet of any one of the preceding aspects, comprising: at least an sliding layer arranged at a position adjacent to and facing the inner surface of the outer part, the sliding layer comprising at least one resilient portion integrally formed therein and arranged at an interface between the interface layer and the outer part, connected to the outer part to retain the interface layer at the position adjacent to the inner surface of the outer part; wherein the resilient portion is configured to deform such the interface layer can slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet.

[0032] According to a fourth aspect of the disclosure, there is provided a method of manufacturing the interface layer of any preceding aspect, comprising: forming the sliding layer of the interface layer, including material forming the resilient portion and material forming the rest of the sliding layer, as a single component. Optionally, the method further comprises removing material from the single component to form the resilient portion.

[0033] BRIEF DESCRIPTION OF THE FIGURES

[0034] The invention is described in detail below, with reference to the accompanying figures, in which:

[0035] Fig. 1 schematically shows a cross-section through a first example helmet;

[0036] Fig. 2 schematically shows a cross-section through a second example helmet;

[0037] Fig. 3 schematically shows a cross-section through a third example helmet;

[0038] Fig. 4 schematically shows a cross-section through a fourth example helmet;

[0039] Fig. 5 shows a fifth example helmet;

[0040] Fig. 6 shows a sixth example helmet;

[0041] Fig. 7 shows a part of the sixth example helmet;

[0042] Fig. 8 shows a first view of a first example resilient portion;

[0043] Fig. 9 shows a second view of the first example resilient portion;

[0044] Fig. 10 shows a first view of a second example resilient portion;

[0045] Fig. 11 shows a second view of the second example resilient portion;

[0046] Fig. 12 shows a first view of a third example resilient portion;

[0047] Fig. 13 shows a second view of the third example resilient portion;

[0048] Fig. 14 shows a first view of a fourth example resilient portion;

[0049] Fig. 15 shows a second view of the fourth example resilient portion;

[0050] Fig. 16 shows further example resilient portions a-t; and Fig. 17 shows a fifth example resilient portion.

[0051] DETAILED DESCRIPTION

[0052] It should be noted that the Figures are schematic, the proportions of the thicknesses of the various layers, and / or of any gaps between layers, depicted in the Figures have been exaggerated for the sake of clarity and can of course be adapted according to need and requirements. Although the examples described below relate to helmets, it should be understood that the invention applies generally to protective apparatuses, including other types of headgear and other protective apparel.

[0053] Protective apparatuses can be understood to have parts corresponding to the parts of the helmets described below. For example, protective apparatuses may have a layered structure corresponding to the layered structure of the described helmets.

[0054] Terms that are specific to a helmet, such as “radial direction” can be understood to have equivalents in the context of other protective equipment, such as “thickness direction”. A “wearer” is to generally understood as corresponding to an object that is to be protected by the protective apparatus, and “head” as a specific part of the object, e.g. a different body part, with which the apparatus is in contact.

[0055] General features of the example helmets are described below with reference to Figs. 1 to 5.

[0056] Figs. 1 to 5 show example helmets 1 comprising an energy absorbing layer 3. The purpose of the energy absorbing layer 3 is to absorb and dissipate energy from an impact in order to reduce the energy transmitted to the wearer of the helmet. Within the helmet 1, the energy absorbing layer may be the primary energy absorbing element. Although other elements of the helmet 1 may absorb that energy to a more limited extent, this is not their primary purpose.

[0057] The energy absorbing layer 3 may absorb energy from a radial component of an impact more efficiently than a tangential component of an impact. The term “radial” generally refers to a direction substantially toward the centre of the wearers head, e.g. substantially perpendicular to an outer surface of the helmet 1. The term “tangential” may refer to a direction substantially perpendicular to the radial direction, in a plane comprising the radial direction and the impact direction.

[0058] The energy absorbing layer may be formed from an energy absorbing material, such as a foam material. Preferable such materials include expanded polystyrene (EPS), expanded polypropylene (EPP), expanded polyurethane (EPU), vinyl nitrile foam; or strain rate sensitive foams such as those marketed under the brand-names Poron™ and D3O™. Alternatively, or additionally, the energy absorbing layer may have a structure that provides energy absorbing characteristics. For example, the energy absorbing layer may comprise deformable elements, such as cells or finger-like projections, that deform upon impact to absorb and dissipate the energy of an impact.

[0059] In some examples, the energy absorbing layer 3 of the helmet 1 is divided into outer and inner parts.

[0060] In some examples, the energy absorbing layer 3 may be divided into multiple parts arranged adjacent each other in the circumferential direction of the helmet. For example, the inner parts may be formed in front and back parts and.

[0061] The energy absorbing layer is not limited to one specific arrangement or material. The energy absorbing layer 3 may be provided by multiple layers having different arrangements, i.e. formed from different materials or having different structures. The energy absorbing layer 3 may be a relatively thick layer. For example, it may be thickest layer of the helmet 1.

[0062] Figs. 1 to 5 show example helmets 1 comprising an outer layer 2. The purpose of the outer layer 2 may be to provide rigidity to the helmet. This may help spread the impact energy over a larger area of the helmet 1. The outer layer 2 may also provide protection against objects that might pierce the helmet 1. Accordingly, the outer layer may be a relatively strong and / or rigid layer, e.g. compared to an energy absorbing layer 3. The outer layer 2 may be a relatively thin layer, e.g. compared to an energy absorbing layer 3. The outer layer 2 may be an outer shell.

[0063] The outer layer 2 may be formed from a relatively strong and / or rigid material. Preferable such materials include a polymer material such as polycarbonate (PC), polyvinylchloride (PVC) or acrylonitrile butadiene styrene (ABS) for example. Advantageously, the polymer material may be fibre-reinforced, using materials such as glass-fibre, Aramid, Twaron, carbon-fibre and / or Kevlar.

[0064] In an example not shown, one or more outer plates may be mounted to the outer layer 2 of the helmet 1. The outer plates may be formed from a relatively strong and / or rigid material, for example from the same types of materials as from which the outer layer 2 may be formed. The selection of material used to form the outer plates may be the same as, or different from, the material used to form the outer layer 2.

[0065] In some example helmets, the outer layer 2 and / or the energy absorbing layer 3 may be adjustable in size in order to provide a customised fit. For example, the outer layer 2 may be provided in separate front and back parts. The relative position of the front and back parts may be adjusted to change the size of the outer layer 2. In order to avoid gaps in the outer layer 2, the front and back parts may overlap. The energy absorbing layer 3 may also be provided in separate front and back parts. These may be arranged such that the relative position of the front and back parts may be adjusted to change the size of the energy absorbing layer 3. In order to avoid gaps in the energy absorbing layer 3, the front and back parts may overlap.

[0066] Figs. 1 to 4 shows example helmets 1 comprising an interface layer 4. The purpose of interface layer 4 may be to provide an interface between the helmet and the wearer. In some arrangements, this may improve the comfort of the wearer. The interface layer 4 may be provided to mount the helmet on the head of a wearer. The interface layer 4 may be provided as a single part or in multiple sections.

[0067] The interface layer 4 may be configured to at least partially conform to the head of the wearer. For example, the interface layer 4 may be elasticated and / or may comprise an adjustment mechanism for adjusting the size of the interface layer 4. In an arrangement, the interface layer may engage with the top of a wearer’s head. Alternatively, or additionally, the interface layer 4 may comprise an adjustable band configured to encircle the wearer’s head.

[0068] The interface layer 4 may comprise comfort padding 4A. Multiple sections of comfort padding 4A may be provided. The comfort padding 4A may be provided on a substrate 4B for mounting the comfort padding to the rest of the helmet 1.

[0069] The purpose of the comfort padding 4 A is to improve comfort of wearing the helmet and / or to provide a better fit. The comfort padding may be formed from a relatively soft material, e.g. compared to the energy absorbing layer 3 and / or the outer layer 2. The comfort padding 4 A may be formed from a foam material. However, the foam material may be of lower density and / or thinner than foam materials used for the energy absorbing layer 3. Accordingly, the comfort padding 4A will not absorb a meaningful amount of energy during an impact, i.e. for the purposes of reducing the harm to the wearer of the helmet. Comfort padding is well recognised in the art as being distinct from energy absorbing layers, even if they may be constructed from somewhat similar materials.

[0070] The interface layer 4, and / or comfort padding 4A that may be part of it, may be removable. This may enable the interface layer 4 and / or comfort padding 4A to be cleaned and / or may enable the provision of an interface layer 4 and / or comfort padding 4 A that is configured to fit a specific wearer.

[0071] In some examples, the interface layer 4 may comprise comfort padding attached to a substrate. The substrate may be bonded to the outer side of the comfort padding. Such bonding could be through any means, such as by adhesive or by high frequency welding or stitching. The substrate of the interface layer faces radially outward towards the outer part of the helmet. The substrate may be formed from a relatively hard or stiff material, e.g. relative to the energy absorbing layer 3 and / or the comfort padding. For example, the substrate may be formed from a polymer material.

[0072] In other examples, the interface layer 4 may comprise only the substrate, without comfort padding, i.e. the interface layer may be formed from a relatively hard or stiff material, e.g. relative to the energy absorbing layer 3. For example, the interface layer 4 may be formed from a polymer material.

[0073] Straps, e.g. chin straps, may be provided to secure the helmet 1 to the head of the wearer.

[0074] The helmets of Figs. 1 to 4 are configured such that the interface layer 4 is able to move, for example slide, in a tangential direction relative to the energy absorbing layer 3 in response to an impact. As shown in Figs. 1 to 4, the helmet 1 may also comprise connectors 5 between the energy absorbing layer 3 and the interface layer 4 that allow relative movement between the energy absorbing layer 3 and the interface layer 4 while connecting the elements of the helmet together. The purpose of helmet layers that move or slide relative to each other may be to redirect energy of an impact that would otherwise be transferred to the head the wearer. This may improve the protection afforded to the wearer against a tangential component of the impact energy. A tangential component of the impact energy would normally result in rotational acceleration of the head of the wearer. It is well known that such rotation can cause brain injury. It has been shown that helmets with layers that move relative to each other can reduce the rotational acceleration of the head of the wearer. A typical reduction may be roughly 25% but reductions as high as 90% may be possible in some instances.

[0075] Preferably, relative movement between helmet layers results in a total shift amount of at least 0.5cm between an outermost helmet layer and an inner most helmet layer, more preferably at least 1cm, more preferably still at least 1.5cm. Preferably the relative movement can occur in any direction, e.g. in a circumferential direction around the helmet, left to right, front to back and any direction in between.

[0076] Relative movement can be considered to occur substantially in a plane over the relevant ranges, even though movement between layers may be rotational rather than linear. Accordingly, reference may be made below to movement in a plane.

[0077] Regardless of how helmet layers are configured to move relative to each other, it is preferable that the relative movement, such as sliding, is able to occur under forces typical of an impact for which the helmet is designed (for example an impact that is expected to be survivable for the wearer). Such forces are significantly higher than forces that a helmet may be subject to during normal use. Impact forces tend to compress layers of the helmet together, increasing the reaction force between components and thus increasing frictional forces. Where helmets are configured to have layers sliding relative to each other the interface between them may need to be configured to enable sliding even under the effect of the high reaction forces experienced between them under an impact.

[0078] As shown in Figs. 1 to 5, a sliding interface may be provided between the layers of the helmet 1 that are configured to slide relative to each other. At the sliding interface, surfaces slide against each other to enable relative sliding between the layers of the helmet 1. The sliding interface may be a low friction interface. Accordingly, friction reducing means may be provided at the sliding interface. Example sliding interfaces are described further below, in relation to each of the example helmets 1 shown in Figs. 1 to 5.

[0079] The friction reducing means may be a low friction material or lubricating material. These may be provided as a continuous layer, or multiple discrete patches, or portions of material, for example. In some examples, friction reducing means may be provided by a combination of a layer of specific material (e.g. one of the polymers below) and a lubrication material, as a coating.

[0080] Possible low friction materials for the friction reducing means include polymers such as PP (polypropylene), PC (polycarbonate), PTFE (polytetrafluoroethylene), ABS (acrylonitrile butadiene styrene), PVC (polyvinyl chloride), Nylon, PFA (perfluoroalkoxy alkane), FEP (Fluorinated ethylene propylene), PE (polyethylene) and UHMWPE (ultra-high molecular weight polyethylene), Teflon™, a woven fabric such as Tamarack™, a non-woven fabric, such as felt. Such low friction materials may have a thickness of roughly 0.1-5 mm, but other thicknesses can also be used, depending on the material selected and the performance desired. Possible lubricating materials include oils, polymers, microspheres, or powders. Combinations of the above may be used.

[0081] In one example the low friction material or lubricating material may be a polysiloxane- containing material. In particular the material may comprise (i) an organic polymer, a polysiloxane and a surfactant; (ii) an organic polymer and a copolymer based on a polysiloxane and an organic polymer; or (iii) a non-elastomeric cross-linked polymer obtained or obtainable by subjecting a poly siloxane and an organic polymer to a crosslinking reaction. Preferred options for such materials are described in WO 2017 / 148958 (the entirety of which is herein incorporated by reference).

[0082] In one example the low friction material or lubricating material may comprise a mixture of (i) an olefin polymer, (ii) a lubricant, and optionally one or more further agents. Preferred options for such materials are described in WO 2020 / 115063 (the entirety of which is herein incorporated by reference).

[0083] In one example the low friction material or lubricating material may comprise an ultra-high molecular weight (UHMW) polymer having a density of < 960 kg / m3, which UHMW polymer is preferably an olefin polymer. Preferred options for such materials are described in WO 2020 / 115063.

[0084] In one example the low friction material or lubricating material may comprise a polyketone. Preferred options for such materials are described in WO 2020 / 260185 (the entirety of which is herein incorporated by reference).

[0085] In some arrangements, it may be desirable to configure the low friction interface such that the static and / or dynamic coefficient of friction between materials forming sliding surfaces at the sliding interface is between 0.001 and 0.3 and / or below 0.15. The coefficient of friction can be tested by standard means, such as standard test method ASTM DI 894.

[0086] The friction reducing means may be provided on or be an integral part of one or both of the layers of the helmet 1 that are configured to slide relative to each other. In some examples, helmet layers may be configured to have a dual function, including functioning as a friction reducing means. Alternatively, or additionally, the friction reducing means may be separate from the layers of the helmet 1 that are configured to slide relative to each other, but provided between the layers.

[0087] For example, friction reducing means may be integrated into the interface layer 4 (e.g. substrate 4A). In such an arrangement, a part of the interface layer 4 at the sliding interface may be formed from one of the low friction materials above. Friction reducing means may alternatively or additionally be provided on the inner surface of the energy absorbing layer 3. In such an arrangement, the energy absorbing layer 3 may comprise an additional layer, at the sliding interface, formed from one of the low friction materials above.

[0088] Figs. 1 to 4 schematically show connectors 5. The connectors 5 are configured to connect two layers of the helmet while enabling relative movement, e.g. sliding or shearing, between the layers. Different numbers of connectors 5 may be provided than as shown in Figs. 1 to 4. The connectors 5 may be located at different positions than as shown in Figs. 1 to 4, for example at a peripheral edge of the helmet 1 instead of a central portion.

[0089] Typically, a connector 5 comprises first and second attachment parts respectively configured to attach to first and second parts of the helmet and a deformable part between the first and second attachment parts that enables the first and second attachment parts to move relative to each other to enable movement between the first and second parts of the helmet. Connectors 5 may absorb some impact energy by deforming.

[0090] The specific arrangements of each of the example helmets shown in Figs. 1 to 5 are described below.

[0091] Fig. 1 shows a helmet 1 comprising an outer layer 2, an energy absorbing layer 3 and an interface layer 4. The interface layer 4 is provided as a single layer and comprises comfort padding.

[0092] The helmet 1 of Fig. 1 is configured such that the interface layer 4 is able to slide relative to the energy absorbing layer 3 in response to an impact. A sliding interface is provided between the interface layer 4 and the energy absorbing layer 3.

[0093] A sliding layer 6 is provided on a surface of the energy absorbing layer 3 facing the sliding interface. The sliding layer 6 may be moulded to the energy absorbing layer 3 or otherwise attached thereto. The sliding layer 6 may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3. The sliding layer 6 is configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the sliding layer 6 from a low friction material, such as PP, PC, PTFE, ABS, PVC, Nylon, PF A, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the sliding layer 6, and / or applying a lubricant to the sliding layer 6.

[0094] Alternatively, or additionally, friction reducing means, to reduce the friction at the sliding interface, may be provided by forming the energy absorbing layer 3 from a low friction material, by applying a low friction coating to the energy absorbing layer 3, and / or applying a lubricant to the energy absorbing layer 3.

[0095] The helmet 1 shown in Fig. 1 also comprises connectors 5 attached to the interface layer 4. The connectors are also connected to the sliding layer 6 to allow relative sliding between the energy absorbing layer 3 and the interface layer 4. Alternatively, or additionally, one or more of the connectors 5 may be connected to another part of the remainder of the helmet 1, such as the energy absorbing layer 3 or the outer layer 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1.

[0096] It should be understood that such an arrangement of the energy absorbing layer 3 and the interface layer 4 may be added to any helmet described herein.

[0097] Fig. 2 shows a helmet 1 comprising an outer layer 2, an energy absorbing layer 3 and an interface layer 4. The interface layer 4 is provided as a plurality of independent sections each comprising comfort padding.

[0098] The helmet 1 of Fig. 2 is configured such that the sections of the interface layer 4 are able to slide relative to the energy absorbing layer 3 in response to an impact. A sliding interface is provided between the sections of the interface layer 4 and the energy absorbing layer 3.

[0099] A sliding layer 6 is provided on a surface of the energy absorbing layer 3 facing the sliding interface. The sliding layer 6 may be moulded to the energy absorbing layer 3 or otherwise attached thereto. The sliding layer 6 may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3. The sliding layer 6 is configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the sliding layer 6 from a low friction material, such as PP, PC, PTFE, ABS, PVC, Nylon, PF A, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the sliding layer 6, and / or applying a lubricant to the sliding layer 6.

[0100] Alternatively, or additionally, friction reducing means, to reduce the friction at the sliding interface, may be provided by forming the energy absorbing layer 3 from a low friction material, by applying a low friction coating to the energy absorbing layer 3, and / or applying a lubricant to the energy absorbing layer 3.

[0101] The helmet 1 shown in Fig. 2 also comprises connectors 5 attached to each independent section of the interface layer 4. The connectors 5 are also attached to the sliding layer 6 to allow relative sliding between the energy absorbing layer 3 and the sections of the interface layer 4. Alternatively, or additionally, one or more of the connectors 5 may be connected to another part of the remainder of the helmet 1, such as the energy absorbing layer 3 or the outer layer 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1.

[0102] It should be understood that such an arrangement of the energy absorbing layer 3 and the interface layer 4 may be added to any helmet described herein.

[0103] Fig. 3 shows a helmet 1 comprising an outer layer 2, an energy absorbing layer 3 and an interface layer 4. The interface layer 4 is provided as a single layer and comprises comfort padding 4A attached to a substrate 4B. The substrate 4B may be bonded to the outer side of the comfort padding 4A. Such bonding could be through any means, such as by adhesive or by high frequency welding or stitching.

[0104] The helmet 1 of Fig.3 is configured such that the interface layer 4 is able to slide relative to the energy absorbing layer 3 in response to an impact. A sliding interface is provided between the interface layer 4 and the energy absorbing layer 3.

[0105] The substrate 4B of the interface layer 4 faces the sliding interface. The substrate 4B may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3 and / or the comfort padding 4A. The substrate 4B is configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the substrate 4B from a low friction material, such as PP, PC, PTFE, ABS, PVC, Nylon, PF A, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the substrate 4B, and / or applying a lubricant to the substrate 4B. In an alternative example, the substrate 4B may be formed from a fabric material, optionally coated with a low friction material.

[0106] Alternatively, or additionally, friction reducing means, to reduce the friction at the sliding interface, may be provided by forming the energy absorbing layer 3 from a low friction material, by applying a low friction coating to the energy absorbing layer 3, and / or applying a lubricant to the energy absorbing layer 3.

[0107] The helmet 1 shown in Fig. 3 also comprises connectors 5 attached to the interface layer 4. The connectors are also connected to the energy absorbing layer to allow relative sliding between the energy absorbing layer 3 and the interface layer 4. Alternatively, or additionally, one or more of the connectors 5 may be connected to another part of the remainder of the helmet 1, such as the outer layer 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1

[0108] It should be understood that such an arrangement of the energy absorbing layer 3 and the interface layer 4 may be added to any helmet described herein.

[0109] Fig. 4 shows a helmet 1 comprising an outer layer 2, an energy absorbing layer 3 and an interface layer 4. The interface layer 4 is provided as a plurality of independent sections each comprising comfort padding 4A attached to a substrate 4B. The substrate 4B may be bonded to the outer side of the comfort padding 4A. Such bonding could be through any means, such as by adhesive or by high frequency welding or stitching.

[0110] The helmet 1 of Fig. 4 is configured such that the interface layer 4 is able to slide relative to the energy absorbing layer 3 in response to an impact. A sliding interface is provided between the interface layer 4 and the energy absorbing layer 3.

[0111] The substrate 4B of the sections of the interface layer 4 faces the sliding interface. The substrate 4B may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3 and / or the comfort padding 4A. The substrate 4B is configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the substrate 4B from a low friction material, such as PP, PC, PTFE, ABS, PVC, Nylon, PF A, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the substrate 4B, and / or applying a lubricant to the substrate 4B. In an alternative example, the substrate 4B may be formed from a fabric material, optionally coated with a low friction material.

[0112] Alternatively, or additionally, friction reducing means, to reduce the friction at the sliding interface, may be provided by forming the energy absorbing layer 3 from a low friction material, by applying a low friction coating to the energy absorbing layer 3, and / or applying a lubricant to the energy absorbing layer 3. The helmet 1 shown in Fig. 4 also comprises connectors 5 attached to the sections of the interface layer 4. The connectors 5 are also connected to the energy absorbing layer 3 to allow relative sliding between the energy absorbing layer 3 and the interface layer 4. Alternatively, or additionally, one or more of the connectors 5 may be connected to another part of the remainder of the helmet 1, such as the outer layer 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1

[0113] It should be understood that such an arrangement of the energy absorbing layer 3 and the interface layer 4 may be added to any helmet described herein.

[0114] Some helmets, such as those shown in Figs. 1 to 4, are configured to cover a top portion of the head and the above described helmet structures are appropriately located in the helmet to cover a top portion of the head. For example, a helmet may be provided to substantially cover the forehead, top of the head, back of the head, and / or temples of the wearer. The helmet may substantially cover the cranium of the wearer.

[0115] Some helmets may be configured to cover other parts of the head, alternatively or additionally to a top portion. For example, helmets such as the helmet shown in Fig. 5 may cover the cheeks and / or chin of the wearer. Such helmets may be configured to substantially cover the jaw of the wearer. Helmets of the type shown in Fig. 8, are often referred to as full-face helmets. As shown in Fig. 5, cheek pads 7 may be provided on either side of the helmet 1 (i.e. left and right sides). The cheek pads 7 may be arranged within an outer layer 2 of the helmet 1 to protect the side of the face of the wearer from an impact.

[0116] The cheek pads 7 may have the same layered structure as the example helmets described above. For example, the cheek pads 7 may comprise one or more energy absorbing layers as described above, and / or an interface layer as described above, and / or layers that move relative to each other as described above, optionally, layers may be connected by connectors as described above. Alternatively, or additionally, the cheek pads 7 themselves may be configured to move relative to the outer layer 2 and, optionally be connected to the outer layer by connectors as described above.

[0117] The present disclosure generally relates to how an interface layer 4 is retained within an outer part of a helmet 1. The outer part of the helmet 1 may refer to a main part of the helmet 1 that is radially outward of the interface layer 4. As described above with reference to Figs. 1 to 5, the outer part may comprise an energy absorbing layer 3 and / or an outer layer 2 (e.g. an outer shell).

[0118] Fig. 6 shows an example helmet 1 according to the disclosure. As shown, the helmet 1 comprises outer part, which in this example is an energy absorbing layer 3, and an interface layer 4. The energy absorbing layer 3 and the interface layer 4 may be as described above with reference to Figs. 1 to 4. As noted above, in other examples, the outer part may alternatively or additionally comprise an outer shell 2.

[0119] As shown in Fig. 6, the outer part comprises an inner surface arranged to face radially inward, towards the head of a wearer in use. As shown, the interface layer 4 is provided radially inward of the outer part 3 and arranged at a position adjacent to the inner surface of the outer part 3. Further, the interface layer is configured to slide relative to the outer part 3, against the inner surface thereof, in response to an oblique impact to the helmet. Accordingly, a sliding interface is provided between the outer part 3 and the interface layer 4, as described above with reference to Figs. 1 to 5.

[0120] Fig. 6 schematically shows an example helmet 1 according to the disclosure. As shown, the helmet 1 comprises an outer part 3 and interface layer 4. As shown, the outer part 3 comprises an inner surface arranged to face radially inwards, towards the head of the wearer. The interface layer 4 is provided radially inward of the outer part and is arranged at a position adjacent to the inner surface of the outer part 3. The interface layer 4 is configured to provide an interface between the helmet and the wearer. Further, the interface layer 4 is configured to slide relative to the outer part 3, against the inner surface of the outer part, in response to an oblique impact to the helmet.

[0121] In the example of Fig. 6, the interface layer is a sliding layer 4. In other examples, the interface layer may comprise additional layers arranged radially inward of the sliding layer, such as comfort padding. In general, the interface layer comprises at least a sliding layer 4 arranged at a position adjacent to and facing the inner surface of the outer part 3.

[0122] As shown schematically in Fig. 6, according to the disclosure, the sliding layer 4 comprises at least one resilient portion 41, arranged at an interface between the sliding layer 4 and the outer part 3 of the helmet. As shown, the resilient portion 41 is connected to the outer part 3. Thus, the resilient portion retains the interface layer at a position adjacent the inner surface of the outer part 3.

[0123] As shown in Fig. 8, the resilient portion 41 may be provided in a substantially central portion of the sliding layer 4, substantially corresponding to the top of the wearer’s head in use. In other examples, multiple resilient portions 41 may be provided, in the central portion and / or other portions, such as the locations shown in any of the preceding Figures.

[0124] As shown in Fig. 6, the resilient portion 41 is integrally formed in the sliding layer 4. The resilient portion 41 may be formed from the same material as the rest of the sliding layer 4 and may be continuous with the rest of the sliding layer 4.

[0125] Fig. 7 is a close-up view of the interface between the sliding layer 4 and the outer part 3 shown in Fig. 6. As shown in Fig. 7, the resilient portion 41 is configured to deform such that the sliding layer can slide relative to the outer part 3, against the inner surface of the outer part in response to an oblique impact to the helmet. Fig. 7 shows the sliding layer 4 displacing horizontally right to left in the figure, as illustrated by the arrow, while the resilient portion 41 is seen to deform compared to Fig. 6.

[0126] The resilient portion 41 may be configured to deform such that the sliding layer 4 can slide relative to the outer part 3 in substantially any direction in a plane of the sliding layer 4. The resilient portion 41 may be configured to deform such that the sliding layer 4 can slide relative to the outer part 3 such that the sliding layer 4 can be displaced at least 10mm, or at least 15mm, in a plane of the sliding layer 4.

[0127] As shown in Figs. 6 and 7, the outer part 3 may comprise a recess 31 for accommodating the resilient portion 41 when connected to the outer part 3. As shown, the resilient portion 41 may substantially protrude out of the plane defined by the rest of the sliding layer 4, towards the outer part 3, when the resilient portion 41 is connected to the outer part 3 of the helmet 1. As shown, the resilient portion 41 protrudes into the recess 31 and the recess 31 is arranged to surround the resilient portion 41. In some examples, the recess may also provide an additional function, such as providing a ventilation channel within the helmet 1.

[0128] As shown in Fig. 7, the recess 31 is arranged to allow the resilient portion 41 to deform such that the sliding layer 4 can slide relative to the outer part 3. For example, as shown, the recess 31 may be sufficiently wide to allow lateral deformation of the resilient portion 41, in the plane of the sliding layer, while the resilient portion remains within the recess 31. As shown, the resilient portion 41 remains substantially protruding out of the plane defined by the rest of the sliding layer 4 when the resilient portion 41 deforms allowing the sliding layer 4 to slide relative to the outer part 3.

[0129] It should be noted that Figs. 6 and 7 are highly schematic, particularly with respect to the details of resilient portion 41. Various examples of the resilient portion 41 are shown in the subsequent figures and described further below.

[0130] Fig. 8 shown an example resilient portion 41 integrated in the sliding layer 4. As shown, the resilient portion 41, denoted by the outer dashed line, comprises, with respect to the plane of the sliding layer 4, an inner portion 42, denoted by the inner dashed line, surrounded by a resilient structure 44.

[0131] As shown in Fig. 8, the inner portion 42 may comprise an attachment point for connecting the resilient portion 41 to the outer part 3. In the present example, the attachment point is in the form of a hole 43. The hole 43 is configured to have a corresponding fixing member passed through it for connecting the resilient portion 41 to the outer part 3. In other examples, the fixing member may be a snap-pin. In other examples, the fixing member may be a sharp pin such as a barbed pin, which may be configured to penetrate the outer part 3 of the apparatus.

[0132] As shown in Fig. 8, the deformable portion 41 may at least partially be formed by at least one cut-out 45 in the sliding layer 4. As shown, the cut-out 45 (only one in this example) defines the resilient structure 44. In general, the resilient structure 44 may comprise one or more elements extending radially in the plane of the sliding layer 4 between the inner portion 42 and the rest of the sliding layer 4, the elements being defined by one or more cut-outs. In the present example, the resilient structure 44 is a single element formed in a curve, specifically a spiral.

[0133] Fig. 9 shows the resilient portion 41 of Fig. 8 from the side, i.e. along the plane of the sliding layer 4, when protruding from the rest of the sliding layer 4, e.g. for connection to the outer part 3. As is illustrated by Fig. 9, the resilient structure 44 may be a spring structure. The spring structure may be configured to deform substantially by flection of the material forming the resilient structure 44, i.e. the material forming the elements of the resilient structure 44.

[0134] As is shown by Figs. 8 and 9, the resilient portion 41 may be formed substantially in a plane defined by the rest of the sliding layer 4, at least when the resilient portion is not connected to the outer part 3 of the helmet 1. As shown by Fig. 9, the resilient portion 41 may substantially protrude out of the plane defined by the rest of the sliding layer 4 when the resilient portion is connected to the outer part 3 of the helmet. In such an example, the resilient portion 41 may be in tension in the protrusion direction, when connected to the outer part 3 of the helmet 1.

[0135] It should be noted that cut-outs 45 need not be formed by actually cutting out a portion of material (although they may). In general, cut-outs 45 may also be moulded into the sliding layer 4. For the example shown in Figs. 8 and 9, the resilient portion 41 may be formed into the sliding layer 4 by moulding and / or by removing material from a component forming the sliding layer 4, e.g. by a clam-shell moulding process, or a stamp cutting process of a sheet material.

[0136] Figs. 10 and 11 show a variation of the example resilient portion 41 of Fig. 8. As shown, the example of Fig. 10 has a similar spiral-shaped resilient structure 44. As shown, the resilient structure may have rounded edges, which are not present in Fig. 8 which has square edges. The example of Fig. 10 further differs from the example of Fig. 8 in that the inner portion 42 of Fig. 10 does not comprise a hole as an attachment point. Instead, as shown in Fig. 11, the inner portion 42 comprises a fixing member 48 integrally formed therein as an attachment point. As shown, the fixing member 48 is a snap-pin in this example. Accordingly, the outer part 3 of the helmet 1 may comprise a corresponding opening configured to engage the snap-pin, e.g. forming part of a corresponding snapbasket. Figs. 12 and 13 show another variation of the resilient portion 41 of Fig. 8. As shown, instead of a single spiral element forming the resilient structure 42, the resilient structure comprises two spiral elements 46 defined by two cut-outs 45. The two spiral elements 48 may form a substantially double helical shape when protruding as shown in Fig. 13.

[0137] Figs. 14 and 15 show another variation of the resilient portion 41 of Fig. 8. As shown, instead of being formed in the plane of the sliding layer 4, then expanded to protrude from the plane, the resilient portion 41 may be performed in an arrangement in which the resilient portion substantially protrudes from the plane of the rest of the sliding layer 4. Further, as shown, the resilient structure may be formed with a thickness, perpendicular to the plane of the sliding layer, that is thicker than the rest of the sliding layer 4. The attachment point is not shown in this Figs. 14 and 15, though may be substantially the same as any of the examples described above.

[0138] The resilient portion 41, in particular the resilient structure 44 can be formed in any number of ways. For example, the possibilities for forming one or more cut-outs defining one elements of the deformable structure are practically infinite. Some such examples are shown in Fig. 16, labelled a- 1. In Fig. 16, the page represents the sliding layer and is shown as continuous with the resilient structure elements and the cut-outs are shown as closed shapes circumscribed by the solid lines. As shown, different examples comprise different combinations of different types of elements.

[0139] A number of the examples comprise at least one curved element. In some examples, the curved elements may be spirals (b, d, k, q, r), arcs (f, m, o) or sinusoids (e, i), for example. Such curves may substantially extend in a radial direction from the inner portion, or in a direction oblique to a radial direction and a circumferential direction from the inner portion. In some examples, curved elements may extend in a substantially circumferential direction around the inner portion (f, h, j) and other elements may extend radially outward to connect the circumferential elements to the inner portion and rest of the sliding layer. In such examples, said other elements may extend in a direction oblique to the circumferential direction or in a radial direction (f, h).

[0140] A number of the examples comprise at least one linear element. In some examples the straight elements may extend in a substantially radial direction form the inner portion (a, c, f, g, h, 1, n, p, t). In some examples, straight elements may extend perpendicular (s) or obliquely (1) to the radial direction.

[0141] In some of the examples, the inner portion is substantially circular (a, b, d, f, h, i, j, k, o, r, r). In other examples, the inner portion is substantially polygonal, e.g. substantially triangular (e, g, m, 1, p, s, t), square (c), or pentagonal (n).

[0142] In some of the examples, the elements are substantially the same width (b, e, f, h, I, j, k).

[0143] In other examples elements may vary in width, e.g. get thinner (a) or thicker (o) further from the inner portion. In some examples, elements may be thicker where the join the inner portion and / or the rest of the sliding layer (d, e, I, m, r, s).

[0144] Some examples, may comprise additional cut-out in the form of substantially circular holes (d, s) that are not an attachment point.

[0145] Some examples have rotational symmetry, e.g. of order 2 (f), 3 (a, b, e, g, I, k, 1, m, p, s, t), 4 (c, j, q), 5 (n) or higher (d, h, o, r).

[0146] In general, the width, thickness and / or cross-sectional shape of the resilient structure may at least partly determine the stiffness properties of the resilient portion and / or how portions of the resilient structure interact with each other when deforming. This may affect how the resilient portion deforms.

[0147] In variations of any of the example resilient structures described herein, the thickness of the resilient structure may deviate from the thickness of the rest of the sliding layer 4. Further, the thickness of the resilient structure may itself vary. For example, the resilient structure may be thicker than the rest of the sliding layer 4 in some portions, the same in some portions and / or thinner in some portions.

[0148] In variations of any of the example resilient structures described herein, the cross-sectional shape of the resilient structure may vary. For example, edges may be square (i.e. perpendicular to inner and outer surface of sliding layer 4), rounded, or chamfered. IN a single resilient structure one or more of these types of edges may be present. A variation with four chamfered corners, forming a hexagonal cross-section is shown in Fig. 17. In a specific example, which may include the features of any of examples of Figs. 6 to 17, the outer part 3 may be an energy absorbing layer. The energy absorbing layer 3 may be moulded, e.g. from a polymer foam material such as EPS, to have a specific predefined shape. Surface features may be formed in the energy absorbing layer 3 in the moulding process or separately.

[0149] Further, the sliding layer may be an outer layer of the interface layer and formed from a stiff material. Optionally, the interface layer may comprise an inner layer, comprising inner comfort padding on a radially inward surface of the outer layer. The outer layer may be moulded to have a specific predefined shape. The outer layer may be formed from a low friction material such as those described above. The outer layer of the interface layer may be moulded to have a predefined shape substantially corresponding to the shape of the inner surface of the energy absorbing layer 3. The moulding process for the interface layer may comprise vacuum moulding of a sheet material forming the outer layer of the interface layer.

[0150] In any of the above examples, the sliding layer 4 may be formed separately and the helmet assembled from these parts by arranging the interface layer 4 within the outer part 3 and connecting the resilient portion 41 to the outer part of the helmet 1.

[0151] Helmets as described above may be used in various activities. These activities include combat and industrial purposes, such as protective helmets for soldiers and hard-hats or helmets used by builders, mine-workers, or operators of industrial machinery for example. Helmets are also common in sporting activities. For example, protective helmets may be used in ice hockey, cycling, motorcycling, motor-car racing, skiing, snow-boarding, skating, skateboarding, equestrian activities, American football, baseball, rugby, soccer, cricket, lacrosse, climbing, golf, airsoft, roller derby, and paintballing.

[0152] Examples of injuries that may be prevented or mitigated by the helmets described above include Mild Traumatic Brain Injuries (MTBI) such as concussion, and Severe Traumatic Brain Injuries (STB I) such as subdural haematomas (SDH), bleeding as a consequence of blood vessels rapturing, and diffuse axonal injuries (DAI), which can be summarized as nerve fibres being over stretched as a consequence of high shear deformations in the brain tissue.

[0153] Depending on the characteristics of the rotational component of an impact, such as the duration, amplitude and rate of increase, either concussion, SDH, DAI or a combination of these injuries can be suffered. Generally speaking, SDH occur in the case of accelerations of short duration and great amplitude, while DAI occur in the case of longer and more widespread acceleration loads.

[0154] Variations of the above described examples are possible in light of the above teachings. It is to be understood that the invention may be practiced otherwise and specifically described herein without departing from the spirit and scope of the invention.

Claims

CLAIMS1. A helmet comprising: an outer part having an inner surface arranged to face radially inward, towards the head of a wearer in use; and an interface layer provided radially inward of the outer part and configured to provide an interface between the helmet and the wearer, wherein the interface layer is arranged at a position adjacent to the inner surface of the outer part and configured to slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet; wherein the interface layer comprises at least a sliding layer arranged at a position adjacent to and facing the inner surface of the outer part, the sliding layer comprising at least one resilient portion integrally formed therein and arranged at an interface between the interface layer and the outer part, connected to the outer part; wherein the resilient portion is configured to deform such that the interface layer can slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet.

2. The helmet of any preceding claim, wherein, the outer part of the helmet comprises a recess for accommodating the resilient portion connected thereto.

3. The helmet of claim 2, wherein the resilient portion substantially protrudes out of the plane defined by the rest of the sliding layer when the resilient portion is connected to the outer part of the helmet, into the recess, and the recess is arranged to surround the resilient portion.

4. The helmet of claim 2 or 3, wherein the recess is arranged to allow the resilient portion to deform such that the interface layer can slide relative to the outer part.

5. The helmet of claim 4, when dependent on claim 3, wherein the recess is configured to allow the resilient portion to deform such that the interface layer can slide relative to the outer part, while the resilient portion remains substantially protruding out of the plane defined by the rest of the sliding layer.

276. The helmet of any preceding claim, wherein the resilient portion comprises, in the plane of the sliding layer, an inner portion surrounded by a resilient structure.

7. The helmet of claim 6, wherein the deformable portion is at least partially formed by at least one first cut-out in the sliding layer, the first cut-out defining the resilient structure.

8. The helmet of claim 6 or 7, wherein the resilient structure is a spring structure.

9. The helmet of any one of claims 6 to 8, wherein resilient structure is configured to deform substantially by flexion of a material forming the resilient structure.

10. The helmet of any one of claims 6 to 9, wherein the resilient structure comprises one or more elements extending radially, in the plane of the sliding layer, between the inner portion and the rest of the sliding layer.

11. The helmet of claim 10 wherein one or more of the elements is formed in a curve, in the plane or the sliding layer.

12. The helmet of claim 11, wherein the curve is a spiral.

13. The helmet of claim 11, wherein the curve is an arc.

14. The helmet of claim 11, wherein the curve is a sinusoid.

15. The helmet of any one of claims 10 to 14, wherein one or more of the elements is substantially linear.

16. The helmet of claim 10 to 15, wherein one or more of the elements extends substantially in a direction oblique to a radial direction and a circumferential direction from the inner portion.

17. The helmet of claim 10 to 16, wherein one or more of the elements extends in a circumferential direction and is connected by one or more further elements extending in a direction oblique to the circumferential direction or in a radial direction.

18. The helmet of any one of the preceding claims, wherein the resilient portion is substantially rotationally symmetric.

19. The helmet of any preceding claim, wherein the resilient portion is formed substantially in a plane defined by the rest of the sliding layer, at least when the resilient portion is not connected to the outer part of the helmet.

20. The helmet of claim 19, wherein the resilient portion substantially protrudes out of the plane defined by the rest of the sliding layer when the resilient portion is connected to the outer part of the helmet.

21. The helmet of claim 20, wherein the resilient portion is in tension in a protrusion direction when the resilient portion is connected to the outer part of the helmet.

22. The helmet of any one of claims 1 to 21, wherein resilient portion substantially protrudes out of a plane defined by the rest of the sliding layer, both when the resilient portion is not connected to the outer part of the helmet and when the resilient portion is connected to the outer part of the helmet.

23. The helmet of any one of claims 6 to 22, wherein the inner portion comprises an attachment point for attachment to the outer part of the helmet, surrounded by the rest of the sliding layer and connected thereto by a resilient structure of the resilient portion.

24. The helmet of claim 23, wherein the attachment point comprises at least one hole through which a corresponding fixing member is passed, the fixing member connecting the resilient portion to the outer part of the helmet.

25. The helmet of clam 23, wherein the attachment point comprises at least one fixing member integrally formed therein, the fixing member connecting the resilient portion to the outer part of the helmet.

26. The helmet of claim 24 or 25, wherein the fixing member is a snap-pin.

27. The helmet of claim 26, wherein the outer part of the helmet comprises a corresponding snap-basket.

28. The helmet of claim 24 or 25, wherein the fixing member is sharp pin, optionally a barbed pin configured to penetrate the outer part of the helmet.

29. The helmet of any preceding claim, wherein the resilient portion is provided in a substantially central portion of the interface layer, substantially corresponding to the top of the wearer’s head in use.

30. The helmet of any preceding claim, wherein the resilient portion is formed from the same material as the rest of the sliding layer and is continuous with the rest of the sliding layer.

31. The helmet of any one of claims 1 to 29, wherein the resilient portion is formed from a different material from the rest of the sliding layer and is co-moulded with the rest of the sliding layer.

32. The helmet of claim 31, wherein the different material is an elastically deformable material.

33. The helmet of any preceding claim, wherein the resilient portion is formed into the sliding layer by moulding.

34. The helmet of any preceding claim, wherein the resilient portion is formed into the sliding layer by removing material from a component forming the sliding layer.

35. The helmet of any preceding claim, wherein the resilient portion is configured to deform such that the interface layer can slide relative to the outer part in substantially any direction in a plane of the sliding layer.

36. The helmet of any preceding claim, wherein the resilient portion is configured to deform such that the interface layer can slide relative to the outer part such that the interface layer can be displaced at least 10mm, or at least 15mm, in a plane of the sliding layer.

37. The helmet of any preceding claim, wherein the sliding layer is a stiff layer.

38. The helmet of claim any preceding claim, wherein the sliding layer is formed from a polymer, optionally one or more of polypropylene, polycarbonate, polytetrafluoroethylene, acrylonitrile butadiene styrene, polyvinyl chloride, Nylon, perfluoroalkoxy alkane, Fluorinated ethylene propylene, polyethylene, polyketone, ultra high molecular weight polyethylene, and Teflon™.

39. The helmet of claim any preceding claim, wherein the sliding layer is moulded to have a predefined shape substantially corresponding to the shape of the inner surface of the outer part.

40. The helmet of any preceding claim, wherein the interface layer comprises comfort padding facing the wearer, in use.

41. The helmet of any preceding claim, wherein the outer part comprises an energy absorbing layer.

42. The helmet of claim 41, wherein the energy absorbing layer is formed from a polymer foam material.

43. The helmet of any preceding claims wherein the outer part comprises a hard, outer shell.

44. A kit of parts for forming the helmet of any preceding claim, comprising: an outer part for the helmet, having an inner surface arranged to face radially inward, towards the head of a wearer, when the helmet is formed and in use; and an interface layer for the helmet, configured to be provided radially inward of the outer part and configured to provide an interface between the helmet and the wearer, when the helmet is formed and, wherein the interface layer is arranged at a position adjacent to the inner surface of the outer part and configured to slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet, when the helmet is formed and in use; the interface layer comprising at least an sliding layer arranged at a position adjacent to and facing the inner surface of the outer part, the sliding layer comprising at least one resilient portion integrally formed therein and arranged at an interface betweenthe interface layer and the outer part, connected to the outer part to retain the interface layer at the position adjacent to the inner surface of the outer part; and wherein the resilient portion is configured to deform such the interface layer can slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet.

45. An interface layer for the helmet of any one of claims 1 to 43, comprising: at least an sliding layer arranged at a position adjacent to and facing the inner surface of the outer part, the sliding layer comprising at least one resilient portion integrally formed therein and arranged at an interface between the interface layer and the outer part, connected to the outer part to retain the interface layer at the position adjacent to the inner surface of the outer part; wherein the resilient portion is configured to deform such the interface layer can slide relative to the outer part, against the inner surface thereof, in response to an oblique impact to the helmet.

46. A method of manufacturing the interface layer of claim 45, comprising: forming the sliding layer of the interface layer, including material forming the resilient portion and material forming the rest of the sliding layer, as a single component.

47. The method of claim 46, further comprising removing material from the single component to form the resilient portion.

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