WO2024013017A1

WO2024013017A1 - Protective apparel and helmet

Info

Publication number: WO2024013017A1
Application number: PCT/EP2023/068861
Authority: WO
Inventors: Amy Louise POMERING; Patrik BINKOWSKI
Original assignee: Mips Ab
Priority date: 2022-07-11
Filing date: 2023-07-07
Publication date: 2024-01-18
Also published as: GB202210126D0

Abstract

An item of protective apparel comprising: first and second components (41, 42) that are configured to move relative to one another; and a sliding interface provided between the first and second components; wherein the sliding interface comprises first and second surfaces (41, 42) that oppose one another and are configured to slide relative to each other; the first surface has at least a first region (45) which is divided into at least first and second areas (47, 48) that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against the second surface is different from the second area against the second surface; the first surface has a second region configured such that the static and/or dynamic coefficient of friction of the first surface against the second surface is different in the first region from the second region (46); the second region is divided into at least first and second areas (49, 50) that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against the second surface is different from the second area against the second surface; and the arrangement of the first and second areas in the first region is different from the arrangement of the first and second areas in the second region.

Description

PROTECTIVE APPAREL AND HELMET

TECHNICAL FIELD

The present disclosure relates to a protective apparel, such as a helmet.

BACKGROUND ART

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 a 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.

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.

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.

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.

Furthermore, connecting two layers of an apparatus in such a way that permits enough relative movement between parts of the apparatus under an impact but maintains the structural integrity of the apparatus can be challenging. Ensuring that the connector can be manufactured and assembled relatively easily can be challenging.

It is the aim of the present invention to provide a helmet that at least partially addresses some of the problems discussed above.

STATEMENTS OF THE INVENTION

According to an aspect of the disclosure, there is provided an item of protective apparel comprising: first and second components that are configured to move relative to one another; and a sliding interface provided between the first and second components; wherein the sliding interface comprises first and second surfaces that oppose one another and are configured to slide relative to each other; and the first surface has at least a first region which is divided into at least first and second areas that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against the second surface is different from the second area against the second surface.

According to another aspect of the disclosure, there is provided a helmet comprising: first and second shells that are configured such that, in response to an oblique impact on the helmet the first shell can move relative to the second shell; and a sliding interface provided between the first and second shells; wherein the sliding interface comprises first and second surfaces, that are each part of one of the respective shells, that oppose one another and are configured to slide relative to each other; and the first surface has at least a first region and a second region that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first region against the second surface is different from the second region against the second surface.

According to another aspect of the disclosure, there is provided a method of manufacturing a component of a helmet, comprising: forming a sheet of material into a shaped form that approximately conforms to the shape of a head, having a concave surface on one side of the shaped form and a convex surface on the other side of the shaped form; securing the shaped form in a mould such that one of the concave and convex surfaces forms part of the mould; co-moulding a second material to the shaped form within the mould; wherein the other of the concave and convex surfaces than the one forming part of the mould has at least a first region which is divided into at least first and second areas that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against a surface of another component of the helmet slid against it is different from the second area against said surface of another component of the helmet.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

Fig. 5 schematically shows a cross-section through a fifth example helmet;

Fig. 6 schematically shows a cross-section through a sixth example helmet;

Fig. 7 schematically shows a cross-section through a seventh example helmet;

Fig. 8 shows an eighth example helmet;

Fig. 9 shows a first example of body armour;

Fig. 10 shows a second example of body armour;

Fig. 11 shows an arrangement of a sliding interface; and

Figs. 12 to 16 show patterns of areas that may be used in the sliding interface of Fig. H.

DETAILED DESCRIPTION

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 headgear and other protective apparel.

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.

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.

General features of the example helmets are described below with reference to Figs. 1 to 7.

Figs. 1 to 7 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.

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.

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.

As illustrated in Fig. 6, the energy absorbing layer 3 of the helmet 1 is divided into outer and inner parts 3A, 3B.

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.

Figs. 1 to 7 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 shell 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 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.

As shown in Fig. 7, one or more outer plates 7 may be mounted to the outer layer 2 of the helmet 1. The outer plates 7 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 7 may be the same as, or different from, the material used to form the outer layer 2.

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.

Figs. 1 to 4 shows example helmets 1 comprising an interface layer 4. Although not shown in Figs. 5 to 7, these example helmets may also comprise 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.

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.

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.

The purpose of the comfort padding 4A 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 4A 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.

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 passing 4A to be cleaned and/or may enable the provision of an interface layer and/or comfort padding 4A that is configured to fit a specific wearer.

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

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 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 helmet of Fig. 5 is configured such that the outer layer 2 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 Fig 5, the helmet 1 may also comprise connectors 5 between the energy absorbing layer 3 and the outer layer 2 that allow relative movement between the energy absorbing layer 3 and the outer layer 2 while connecting the elements of the helmet together.

The helmet of Fig. 6 is configured such that the outer part 3 A of the energy absorbing layer 3 is able to move, for example slide, in a tangential direction relative to the inner part 3B of the energy absorbing layer 3 in response to an impact. As shown in Fig 6, the helmet 1 may also comprise connectors 5 between the outer part 3A of the energy absorbing layer 3 and the inner part 3B of the energy absorbing layer 3, that allow relative movement between the outer part 3A of the energy absorbing layer 3 and the inner part 3B of the energy absorbing layer 3, while connecting the elements of the helmet together.

The helmet of Fig. 7 is configured such that the outer plates 8 are able to move, for example slide, in a tangential direction relative to the outer layer 2 in response to an impact. As shown in Fig 7, the helmet may also comprise connectors 5 between the outer plates 8 and the outer layer 2 that allow relative movement between the outer plates 7 and the outer layer 2, 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 know 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.

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.

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.

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.

As shown in Figs. 1 to 7, 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 7.

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. Possible low friction materials for the friction reducing means include waxy polymers such as PC, PTFE, ABS, PVC, Nylon, PFA, FEP, PE and UHMWPE, Teflon™, a woven fabric such as Tamarack™, a non-woven fabric, such a 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.

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; (i) 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 polysiloxane and an organic polymer to a crosslinking reaction. Preferred options for such materials are described in WO2017148958.

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 W02020115063.

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 W02020/115063.

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. 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.

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 have a dual function, including functioning as a friction reducing means. Alternatively, or additionally, the friction reducing means may be a separate from the layers of the helmet 1 that are configured to slide relative to each other, but provided between the layers.

Instead of the sliding interface, in some examples, a shearing interface may be provided between the layers of the helmet 1 that are configured to move relative to each other. At the shearing interface, a shearing layer shears to enable relative movement between the layers of the helmet 1. The shearing layer may comprise a gel or liquid, which may be retained within a flexible envelope. Alternatively, the shearing layer may comprise two opposing layers connected by deformable elements that deform to enable shearing between the two opposing layers.

A single shearing layer may be provided that substantially fills the volume between two layers of a helmet. Alternatively, one or more shearing layers may be provided that fill only a portion of the volume between two layers of a helmet, e.g. leaving substantial space around the shearing layers. The space may comprise a sliding interface, as described above. As such, helmets may have a combination of shearing and sliding interfaces. Such shearing layers may act as connectors 5, which are described further below.

Figs. 1 to 7 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 7. The connectors 5 may be located at different positions than as shown in Figs. 1 to 7, for example at a peripheral edge of the helmet 1 instead of a central portion.

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 of the helmet. Connectors 5 may absorb some impact energy by deforming.

The specific arrangements of each of the example helmets shown in Figs. 1 to 7 are described below.

Fig. 1 shows a helmet 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.

The helmet 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.

A sliding layer 7 is provided on a surface of the energy absorbing layer 3 facing the sliding interface. The sliding layer 7 may be moulded to the energy absorbing layer 3 or otherwise attached thereto. The sliding layer 7 may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3. The sliding layer 7 is configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the sliding layer 7 from a low friction material, such as PC, PTFE, ABS, PVC, Nylon, PFA, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the sliding layer 7, and/or applying a lubricant to the sliding layer 7.

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. 1 also comprises connectors 5 attached to the interface layer 4. The connectors are also connected to the sliding layer 7 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 shell 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1.

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.

Fig. 2 shows a helmet 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.

The helmet of Fig. 2 is configured such that the section 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.

An sliding layer 7 is provided on a surface of the energy absorbing layer 3 facing the sliding interface. The sliding layer 7 may be moulded to the energy absorbing layer 3 or otherwise attached thereto. The sliding layer7 may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3. The sliding layer 7 is configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the sliding layer 7 from a low friction material, such as PC, PTFE, ABS, PVC, Nylon, PFA, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the sliding layer 7, and/or applying a lubricant to the sliding layer 7.

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 7 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 shell 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1.

Fig. 3 shows a helmet 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.

The helmet 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.

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 PC, PTFE, ABS, PVC, Nylon, PFA, 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 alternative example, the substrate 4B may be formed from a fabric material, optionally coated with a low friction material.

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 shell 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1

Fig. 4 shows a helmet 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 4 A 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.

The helmet 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.

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 PC, PTFE, ABS, PVC, Nylon, PFA, 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 alternative example, the substrate 4B may be formed from a fabric material, optionally coated with a low friction material.

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 shell 2. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1

Fig. 5 shows a helmet comprising an outer layer 2 and an energy absorbing layer 3. Although not shown, an interface layer may additionally be provided.

The helmet of Fig. 5 is configured such that the outer layer 2 is able to slide relative to the energy absorbing layer 3 in response to an impact. A sliding interface may be provided between the outer layer 2 and the energy absorbing layer 3

Although not shown, an additional layer may be provided on a surface of the energy absorbing layer 3 facing the sliding interface. The additional layer may be moulded to the energy absorbing layer 3 or otherwise attached thereto. The additional layer may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3. The additional layer may be configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the additional layer from a low friction material, such as PC, PTFE, ABS, PVC, Nylon, PFA, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the additional layer and/or applying a lubricant to the additional layer.

Alternatively or additionally, friction reducing means, to reduce the friction at the sliding interface, may be provided by forming the outer layer 2 from a low friction material, providing an additional low friction layer on a surface of the outer layer 2 facing the sliding interface, by applying a low friction coating to the outer layer 2 and/or applying a lubricant to the outer layer 2.

The helmet 1 shown in Fig. 5 also comprises connectors 5 attached to the outer layer 2.

The connectors 5 are also attached to the energy absorbing layer 3 (or additional layer) 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 an interface layer. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1.

It should be understood that such an arrangement of the outer shell 2 and the energy absorbing layer 3 may be added to any helmet described herein.

Fig. 6 shows a helmet comprising an outer layer 2 and an energy absorbing layer 3. As illustrated, the energy absorbing layer 3 of the helmet shown in Fig. 6 is divided into outer and inner parts 3A, 3B. Although not shown, an interface layer may additionally be provided.

The helmet of Fig. 6 is configured such that the outer part 3 A of the energy absorbing layer 3 is able to slide relative to the inner part 3B of the energy absorbing layer 3 in response to an impact. A sliding interface may be provided between the outer part 3A of the energy absorbing layer 3 and the inner part 3B of the energy absorbing layer 3.

Although not shown, an additional layer may be provided on a surface of one or both of the inner and outer parts 3A, 3B of the energy absorbing layer 3 facing the sliding interface. The additional layer may be moulded to the inner or outer parts 3A, 3B of the energy absorbing layer 3 or otherwise attached thereto. The additional layer may be formed from a relatively hard material, e.g. relative to the energy absorbing layer 3. The additional layer may be configured to provide friction reducing means to reduce the friction at the sliding interface. This may be achieved by forming the additional layer from a low friction material, such as PC, PTFE, ABS, PVC, Nylon, PFA, FEP, PE and UHMWPE. Alternatively, or additionally, this may be achieved by applying a low friction coating to the additional layer and/or applying a lubricant to the additional layer.

Alternatively or additionally, friction reducing means, to reduce the friction at the sliding interface, may be provided by forming one or both of the inner and outer parts 3A, 3B of the energy absorbing layer 3 from a low friction material, providing an additional low friction layer on a surface of the inner and outer parts 3A, 3B of the energy absorbing layer 3 facing the sliding interface, by applying a low friction coating to the inner and outer parts 3 A, 3B of the energy absorbing layer 3 and/or applying a lubricant to the inner and outer parts 3 A, 3B of the energy absorbing layer 3.

The helmet 1 shown in Fig. 6 also comprises connectors 5 attached to the outer layer 2.

It should be understood that such an arrangement of inner and outer parts 3A 3B of the energy absorbing layer 3 may be added to any helmet described herein.

Fig. 7 shows a helmet comprising an outer layer 2 and an energy absorbing layer 3. As shown in Fig. 7, one or more outer plates 7 are mounted to the outer layer 2 of the helmet 1. The outer plates 7 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. Although not shown, an interface layer may additionally be provided.

The helmet of Fig. 7 is configured such that the outer plates 8 are able to slide relative to the outer layer 2 in response to an impact. A sliding interface may be provided between the outer plates 8 and the outer layer 2.

Friction reducing means, to reduce the friction at the sliding interface, may be provided by forming the outer layer 2 and/or the outer plates 8 from a low friction material, providing an additional low friction layer on a surface of the outer layer 2 and/or the outer plates 8 facing the sliding interface, by applying a low friction coating to the outer layer 2 and/or the outer plates 8, and/or applying a lubricant to the outer layer 2 and/or the outer plates 8.

The helmet 1 shown in Fig. 7 also comprises connectors 5 attached to the outer plates 7 The connectors 5 are also attached to the outer layer 2 to allow relative sliding between the plates 7 and the outer layer 2. 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. The connectors 5 may also be connected to two or more parts of the remainder of the helmet 1.

In such an arrangement, in the event of an impact on the helmet 1, it can be expected that the impact would be incident on one or a limited number of the outer plates 17. Therefore, by configuring the helmet such that the one or more outer plates 7 can move relative to the outer layer 2 and any outer plates 7 that have not been subject to an impact, the surface receiving the impact, namely one or a limited number of outer plates 7, can move relative to the remainder of the helmet 1. In the case of an impact, this may reduce the rotational acceleration of the head of a wearer.

It should be understood that such an arrangement of outer plates 7 may be added to any helmet described herein, namely an arrangement having a sliding interface between at least two of the layers of the helmet 1.

Some helmets, such as those shown in Figs. 1 to 6, 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.

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. 8 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. 8, cheek pads 30 may be provided on either side of the helmet 1 (i.e. left and right sides). The cheek pads 30 may be arranged within an outer shell 2 of the helmet 1 to protect the side of the face of the wearer from an impact.

The cheek pads 30 may have the same layered structure as the example helmets described above. For example, the cheek pads 30 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 30 themselves may be configured to move relative to the outer shell 2 and, optionally be connected to the outer shell by connectors as described above.

Although, the above examples relate to helmets, as stated above, the disclosure may also relate to alternative protective apparel, such as body armour, as shown in Figs. 9 and 10. Body armour 100 may provide protection for other parts of the body, such as the shins, knees, thighs, forearms, elbows, upper arms, shoulders, chest and back. Individual items of body armour may be provided to protect individual body parts (as shown in Fig. 9), or alternatively may be combined in apparel comprising multiple armoured regions 101 to protect more than one body part (as shown in Fig. 10). Such body armour 100 may be worn for the same activities as helmets, discussed above, including for combat, sports, and motorcycling.

The body armour 100 may have the same layered structure as the example helmets described above. For example, the body armour 100 may comprise an outer shell 2 as described above, one or more energy absorbing layers 3 as described above, and/or an interface layer as described above, and/or layers that move relative to each other with a sliding interface between them as described above, and/or layers may be connected by connectors 5 as described above.

The present disclosure relates to the provision of sliding interfaces within protective apparel such as any of those discussed above. Predominantly, arrangements of the present disclosure will be described in the context of helmets and, in particular, the sliding interface between two shells, or layers, of a helmet. However, it should be appreciated that the described arrangements of sliding interfaces may also be applied to other protective apparel, such as body armour, and/or may be applied to sliding interfaces provided within connectors, such as those discussed above, that may be used to connect two parts of an item of protective apparel in a manner that permits relative movement between the two parts of the item of protective apparel.

As schematically depicted in Figure 11, a sliding interface according to the present disclosure may be provided between first and second components 41, 42 that are configured to move relative to one another, for example first and second shells of a helmet. At the sliding interface, the first and second components 41, 42 have respective first and second surface 43, 44 that oppose one another and are configured to slide relative to each other.

In a sliding interface according to the present disclosure, the first surface 43 has at least a first region 45 that is divided into at least first and second areas 47, 48. The first and second areas 47, 48 are configured to differ from each other in how they interact with the second surface 44. In particular, the first and second areas are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against the second surface is different from the static coefficient of friction or the dynamic coefficient of friction for the second area against the second surface.

A plurality of the first and second areas 47, 48 may be provided across the first region 45. In a preferred arrangement, the first and second areas 47, 48 may be evenly distributed across the first region 45, namely such that in a representative sample of the first surface 43 taken anywhere in the first region 45, the proportion of the sample that is the first and/or second area will be largely consistent.

One way in which an even distribution of the first and second areas 47, 48 may be provided is to use a repeating pattern across the first region 45. For example, as shown in Figure 12, the first area 47 may be provided by a plurality of stripes 51, with the second area 48 comprising the regions 52 between the stripes 51. It will be appreciated that any striped pattern need not have straight lines as shown in Figure 12. Accordingly, for example, the stripes 51 may be curved, for example in a pattern of a plurality of contours such as is depicted in Figure 13. Alternatively as depicted in Figure 14, the first area 47 may comprise a plurality of non-tessellating shapes 53 provided at a regular spacing, with the second area 48 comprising the spaces 54 between the non-tessellating shapes 53. Alternatively, as depicted in Figures 15 and 16, the first area 47 may comprise a plurality of spots 55 provided at a regular spacing, with the second area 48 comprising the spaces 56 between the spots 55. As shown, depending on requirements and the mechanism used to provide the pattern, as discussed below, the size of the spots 55 relative to the size of the first area 47 may differ.

It will be appreciated that many other ways may be used to distribute the first and second areas 47, 48 across the first region. By selecting the ratio of the first area 47 to the second area 48 within the first region 45, the overall static and/or dynamic coefficient of friction of the first surface 43 against the second surface 44 in the first region 45 may be controlled. In particular, the overall static and/or dynamic coefficient of friction of the first region 45 of the first surface 43 against the second surface 44 is the area-weighted average of the static and/or dynamic coefficient of friction of the first and second areas 47, 48 of the first surface 43 against the second surface 44.

Such an arrangement may be beneficial because the present applicants have identified that for each design of an item of protective apparel, there may be an optimum level of the static and/or dynamic coefficient of friction between the first and second surfaces 43, 44 at a sliding interface. For example, as explained above, it may be desirable to have a sufficiently low static and/or dynamic coefficient of friction at a sliding interface between two shells of a helmet such that, in response to an oblique impact on the outside of a helmet, an outer shell may move, for example rotate, relative to the inner shell and/or the wearer’s head in order to reduce the rotational energy imparted to the wearers head, which may cause brain injury. However, it has also been found that if the static and/or dynamic coefficient of friction at the sliding interface is too low, in some impact scenarios, the wearer’s head may counter-rotate, namely rotate in an opposite direction to that which is directly imposed by the oblique impact. This counter-rotation in an impact may also cause brain injury. In between, there may be an optimum level of the static and/or dynamic coefficient of friction that minimises rotation of the head. Accordingly, it is desirable to be able to set a desired level of static and/or dynamic coefficient of friction between the first and second surface 43, 44 for each specific arrangement, for example for each specific design of helmet.

It will be appreciated that the static and/or dynamic coefficient of friction between two surfaces may be altered by changing the material of one or both of the surfaces. However, in the context of adjusting the performance of a particular helmet or designing a new sliding interface for a new helmet, for example, it may not be convenient to have to select different materials because this may have significant cost implications and/or may make the manufacturing process more difficult. In contrast, the present arrangement may be more convenient because, from one design to another, there is no difference in the materials or manufacturing techniques being used. Instead, it is merely necessary to change the proportion of the first area to the second area.

In an arrangement, the first region 45 may extend across substantially the entirety of the first surface 43 of the sliding interface. Alternatively, however, the first surface 43 may include at least a second region 46 that is configured differently from the first region 45. For example, the second region 46 may be configured to have a static and/or dynamic coefficient of friction against the second surface 44 that is different from the static and/or dynamic coefficient of friction of the first region 45 against the second surface 44.

In an arrangement, the second region 46 may be un-pattemed, namely may simply correspond to one of the first and second areas 47, 48 of the first region 45. This may be appropriate if the second region 46 of the first surface 43 of the sliding interface is in a location in which the particular level of the static and/or dynamic coefficient of friction is not particularly significant. In that case, the level of static and/or dynamic coefficient of friction against the second surface 44 afforded by an arrangement of one of the first and second areas 47, 48 of the first region 45 may provide adequate performance in the context of the overall apparatus. For example, in the context of a helmet having a sliding interface between two shells, it may be more significant to tune the specific level of friction in some regions around the head than others.

In an alternative arrangement, the second region 46 may be divided into at least first and second areas 49, 50 and are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area 49 against the second surface 44 is different from the second area 50 against the second surface 44. The arrangement of the first and second areas 47, 48 in the first region 45 may be different from the arrangement of the first and second areas 49, 50 in the second region.

In an arrangement, the nature of at least one of the first and second areas 47, 48 of the first region may be different from the nature of the corresponding first and second areas 49, 50 of the second region, for example such that the static and/or dynamic coefficient of friction against the second surface 44 is different.

Alternatively, in an advantageous arrangement, the nature of the first area 47 of the first region 45 may match that of the first area 49 of the second region 46 and the nature of the second area 48 of the first region 45 may match that of the second area 50 of the second region 46. For example, the static and/or dynamic coefficient of friction against the second surface 44 in both first areas 47, 49 may be the same and the static and/or dynamic coefficient of friction against the second surface 44 in both second areas 48, 50 may be the same.

In such an arrangement, the difference between the first region 45 and the second region 46 may be a difference in the distribution, for example the pattern, of the first and second areas 47, 48 in the first region 45 compared to the first and second areas 49, 50 in the second region 46. Alternatively or additionally, the first region 45 may have a different proportion of the first and/or second areas 47, 48 compared to the proportion of the first and/or second areas 49, 50 in the second region 46.

The present disclosure therefore provides a convenient way in which to provide a sliding interface that has regions with static and/or dynamic coefficient of friction that differ from each other. In particular, rather than the configuration of the first and second surfaces 43, 44 forming the sliding interface being entirely different in separate regions 45, 46, they may be largely the same, and at least formed from the same constituents, and only differ in the distribution of areas within them.

Such an arrangement may, for example, may be beneficial for a sliding interface provided between two shells of a helmet because the applicant has identified that it would be beneficial to provide different levels of static and/or dynamic coefficient of friction between the first and second surfaces 43, 44 in different regions of a helmet. Accordingly, a helmet may be provided having a sliding interface between first and second shells with a sliding interface between the shells formed from first and second surfaces that are each part of the respective shells and that oppose one another and are configured to slide relative to each other. The first surface may have at least first and second regions that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first region against the second surface is different from the second region against the second surface.

In such an arrangement, the first region may be selected to be, for example, one or more of a frontal region, a posterior region, a left lateral region, a right lateral region and a crown region of the head. Alternatively or additionally, the first region may be selected to correspond to the position of one or more of the lobes of the brain of a wearer of the helmet, namely at least one of the frontal lobe, parietal lobe, temporal lobe and occipital lobe of one or both of the two cerebral hemispheres. The second region may be selected to be a different one or more of a frontal region, a posterior region, a left lateral region, a right lateral region, a crown region and a region corresponding to one of the lobes of the brain of a wearer of the helmet.

It should be appreciated, however, that a helmet may be provided having plural regions within a sliding interface between two shells that have differing static and/or dynamic coefficients of friction provided by a means other than having different arrangements of first and second areas within the regions. For example, the materials forming the first and second surfaces 43, 44 may differ from a first region 45 to a second region 46.

It should also be appreciated that, although the above description has described the first and/or second region 45, 46 as having first and second areas in which the static and/or dynamic coefficient of friction against the second surface 44 differ, if desired the first and/or second region 45, 46 may be divided into any number of areas that are configured to be different from each other. Similarly, a sliding interface may be divided into any number of regions that are configured to have a different overall level of static and/or dynamic coefficient of friction from each other. Furthermore, it should be appreciated that there may not be a distinct boundary between regions 45, 46 or areas 47, 48, 49, 50. Instead, there may be a gradual transition of, for example, the static and/or dynamic coefficient of friction against the second surface 44 at a boundary between regions 45, 46 or areas 47, 48, 49, 50.

In order to provide a difference between the static and/or dynamic coefficient of friction against the second surface 44 between two areas 47, 48 of, for example, the first surface 43 of the sliding interface, any of a number of different approaches may be taken.

In an arrangement, at least one of the areas 47, 48 of the first surface 43 may have a coating provided to it that changes the static and/or dynamic coefficient of friction against the second surface 44 in comparison to the first surface 43 without a coating. Such a coating may be configured to either increase or decrease the static and/or dynamic coefficient of friction against the second surface in comparison to the first surface without a coating. For example, the coating may be any one of the low friction or lubricating materials discussed above. Such an arrangement may reduce the static and/or dynamic coefficient of friction against the second surface in comparison to the first surface without a coating.

Alternately or additionally, at least one area may have a coating applied that increases the static and/or dynamic coefficient of friction against the second surface 44 in comparison to the first surface 43 without a coating. An example of such a coating may be any of the commonly used lacquers that are used, for example, as a surface finish for layers of expanded polystyrene (EPS) within helmets.

Alternatively or additionally, at least one area of the first surface 43 is abraded, for example scratched or roughened, in order to increase the static and/or dynamic coefficient of friction against the second surface 44 in comparison to the un-abraded first surface.

Alternatively or additionally, at least one area of the first surface 43 may be provided with plural protrusions, for example integrally formed within the first surface 43, that engage with the second surface in order to increase the effective static and/or dynamic coefficient of friction in comparison to the first surface 43 without protrusions.

Alternatively or additionally, the component 41 on which the first surface 43 is provided may have at least an outer layer that is formed from different materials in different areas, with the materials selected to exhibit a different static and/or dynamic coefficient of friction against the second surface 44 in comparison to each other.

In an alternative or additional arrangement, the component 41 on which the first surface 43 is provided may be formed from a base layer formed of a first material, covered by a relatively thin layer of a second material. In such an arrangement, the first area 47 of the first region 45, for example, may correspond to openings provided in the layer of second material that expose the first material beneath the layer of second material to provide part of the first surface 44. For example, the base layer may be an energy absorbing material, such as expanded polystyrene (EPS), and the layer of second material may be formed from a relatively hard material, such as polycarbonate (PC), that is co-moulded to the EPS layer. By forming the PC layer with openings in it, when the EPS layer is co-moulded to the PC layer, the EPS may slightly protrude through the openings in the PC layer such that some areas of the first surface will be provided by the PC layer and some areas will be provided by the EPS slightly protruding though the openings in the PC layer.

As noted above, the present disclosure may conveniently apply to the formation of a helmet in which a component of the helmet includes an energy absorbing base layer comoulded a relatively thin layer of a relatively hard material. Such an arrangement may conveniently form a shell of a helmet that provides a level of protection to radial impacts on a helmet by means of the energy absorbing layer but also provides a relatively hard surface that may form one side of a sliding interface that, as discussed above, may be used to provide protection against oblique impacts to the helmet.

For such an arrangement, the configuration of the sliding interface according to the present disclosure may also provide benefits for the manufacturing process. For example, the component of the helmet may be manufactured by a process that starts by forming a sheet of material into a shaped form that approximately conforms to the shape of a head, having a concave surface on one side of the shaped form and a convex surface on the other side of the shaped form. For example, the shaped form may be produced by a vacuum forming process. The shaped for may then be secured in a mould such that one of the concave and convex surfaces of the shaped form functions as part of the mould. A second material may then be introduced into the mould and co-moulded to the shaped form.

In accordance with the preceding disclosure, the components of the helmet formed by this process may have an external surface that has at least a first region divided into first and second areas that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against another component of the helmet, once the helmet is assembled, is different from the second area. In order to achieve this, a modification to the surface in order to provide the first and second areas could be performed after the co-moulding step or after the sheet of material has been formed into the shaped form. Alternatively, it may be more convenient to form the first and second areas on the sheet of material before it is formed into the shaped form. For example, if the provision of the first and second areas is to be provided by application of a coating to the surface, this may be most easily performed to a flat sheet such that, for example, a screen printing process may be used.

Forming the first and second areas on the surface before the co-moulding step may also facilitate the co-moulding process. In particular, before the second material is introduced into the mould, the shaped form may be secured in the mould. In a convenient process, the shaped form may be secured in the mould using an adhesive-backed strip of material. In such an arrangement, the adhesive-backed stripped of material must adhere to the surface of the shaped form other than the surface forming part of the mould, namely the external surface of the component on which the first and second areas are provided. The adhesive- backed strip of material may adhere more easily to one of the first and second areas than the other. In particular, this may be the case if a coating is applied to the surface. In that case, the adhesive-backed strip of material may adhere better to a surface that has some areas without a coating than it would to a surface of a different design that has been entirely covered with a coating, even if both surfaces achieve the same overall level of coefficient of friction when used as part of a sliding interface within a helmet.

In order to ensure this benefit, the size and distribution of the first and second areas may be selected relative to the size of the strip of adhesive-backed material to be used such that, when the adhesive-back strip is adhered to any part of the first region, at least a part of it adheres to each of the first and second areas. It should be appreciated that this would not be achieved, for example, if the first and second areas were very much larger than the size of the strip of adhesive-backed material, such that in use it could be placed solely in one of the first and second areas.

As noted above, in an arrangement the first and second areas may be provided on a surface of a flat sheet of material before the step of shaping it into the shaped form. This may include a step of applying a coating to at least one of the first and second areas of a region of the flat sheet of material. Alternatively or additionally, this may include performing an abrasion process to one of the first and second areas. Alternatively or additionally, at least one of the first and second areas may be formed during the shaping operating that forms the shaped form from the flat sheet of material. For example, during the shaping operation, plural protrusions may be formed in one of the first and second areas. It will be appreciated that the above described methods of forming a component that could be used within a sliding interface according to the present disclosure are merely examples that may be appropriate for some sliding interfaces. Alternative manufacturing approaches may be used for such sliding interfaces or may be used for forming components to be used in other sliding interfaces.

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.

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.

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.

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

1. An item of protective apparel comprising: first and second components that are configured to move relative to one another; and a sliding interface provided between the first and second components; wherein the sliding interface comprises first and second surfaces that oppose one another and are configured to slide relative to each other; the first surface has at least a first region which is divided into at least first and second areas that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against the second surface is different from the second area against the second surface; the first surface has a second region configured such that the static and/or dynamic coefficient of friction of the first surface against the second surface is different in the first region from the second region; the second region is divided into at least first and second areas that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against the second surface is different from the second area against the second surface; and the arrangement of the first and second areas in the first region is different from the arrangement of the first and second areas in the second region.

2. An item of protective apparel according to claim 1, wherein the first and second areas are evenly distributed across the first region.

3. An item of protective apparel according to claim 1 or 2, wherein the first and second areas are provided in a repeating pattern across the first region.

4. An item of protective apparel according to any one of the preceding claims, in which the ratio of the first area to the second area is selected such that the area- weighted average of the static and/or dynamic coefficient of friction of the first surface against the second surface in the first region is a desired level.

5. An item of protective apparel according to any one of the preceding claims, wherein, in at least one of the first and second areas of a region of the first surface, a coating is provided that changes the static and/or dynamic coefficient of friction against the second surface in comparison to the first surface without a coating.

6. An item of protective apparel according to claim 5, wherein the coating is configured to increase the static and/or dynamic coefficient of friction against the second surface in comparison to the first surface without a coating.

7. An item of protective apparel according to claim 5, wherein the coating is configured to reduce the static and/or dynamic coefficient of friction against the second surface in comparison to the first surface without a coating.

8. An item of protective apparel according to any one of the preceding claims, wherein in at least one of the first and second areas of a region of the first surface, the surface is abraded in order to increase the static and/or dynamic coefficient of friction against the second surface in comparison to the unabraded first surface.

9. An item of protective apparel according to any one of the preceding claims, wherein at least one of the first and second areas of a region of the first surface is provided with plural protrusions that engage with the second surface to increase the effective static and/or dynamic coefficient of friction in comparison to the first surface without protrusions.

10. An item of protective apparel according to any one of the preceding claims, wherein the component on which the first surface is provided is formed as a layer formed from different materials in the first and second areas respectively.

11. An item of protective apparel according to any one of claims 1 to 9, wherein the component on which the first surface is provided is formed from a base layer made from a first material, covered by a layer of a second material; and the first areas correspond to openings in the layer of second material exposing the first material to provide part of the first surface.

12. An item of protective apparel according to any one of the preceding claims, wherein the item is a helmet; and the first and second components are first and second shells, respectively, configured such that in response to an oblique impact on the helmet the first shell can move relative to the second shell by sliding at the sliding interface.

13. An item of protective apparel according to any one of claims 1 to 11, wherein the item of protective apparel is a helmet that comprises first and second shells and is configured such that in response to an oblique impact on the helmet the first shell can move relative to the second shell; and first and second components are provided in a connector that connects the first and second shells together but permits movement of the first shell relative to the second shell by sliding at the sliding interface within the connector.

14. An item of protective apparel comprising: first and second components that are configured to move relative to one another; and a sliding interface provided between the first and second components; wherein the sliding interface comprises first and second surfaces that oppose one another and are configured to slide relative to each other; and the first surface has at least first and second regions that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first region against the second surface is different from the second region against the second surface.

15. A helmet comprising: first and second shells that are configured such that, in response to an oblique impact on the helmet the first shell can move relative to the second shell; and a sliding interface provided between the first and second shells; wherein the sliding interface comprises first and second surfaces, that are each part of one of the respective shells, that oppose one another and are configured to slide relative to each other; and the first surface has at least a first region and a second region that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first region against the second surface is different from the second region against the second surface. A helmet according to claim 15, wherein the wherein the first region is at least one of a frontal region, a posterior region, a left lateral region, a right lateral region, a crown region and a region corresponding to one of the lobes of the brain of a wearer of the helmet; and the second region is a different at least one of a frontal region, a posterior region, a left lateral region, a right lateral region, a crown region and a region corresponding to one of the lobes of the brain of a wearer of the helmet from the first region. A method of manufacturing a component of a helmet, comprising: forming a sheet of material into a shaped form that approximately conforms to the shape of a head, having a concave surface on one side of the shaped form and a convex surface on the other side of the shaped form; securing the shaped form in a mould such that one of the concave and convex surfaces forms part of the mould; co-moulding a second material to the shaped form within the mould; wherein the other of the concave and convex surfaces than the one forming part of the mould has at least a first region which is divided into at least first and second areas that are configured such that at least one of the static coefficient of friction and the dynamic coefficient of friction for the first area against a surface of another component of the helmet slid against it is different from the second area against said surface of another component of the helmet. A method of manufacturing a component of a helmet according to claim 17, wherein the step of securing the shaped form to the mould comprises using an adhesive-backed strip of material to hold the shaped form in place in the mould; and the size and distribution of the first and second areas is selected relative to the size of the strip of adhesive-backed material such that, when the adhesive- backed strip is adhered to any part of the first region, part of it adheres to each of the first and second areas.

19. A method of manufacturing a component of a helmet according to claim 17 or 18, wherein the step of forming the shaped form comprises performing a shaping operation to a flat sheet of material; and before performing the shaping operation, a coating is provided in at least one of the first and second areas of a region of the other of the concave and convex surfaces than the one used to form part of the mould, the coating configured to change the static and/or dynamic coefficient of friction against the surface of another component of the helmet in comparison to the surface without a coating.

20. A method of manufacturing a component of a helmet according to any one of claims 17 to 19, wherein the step of forming the shaped form comprises performing a shaping operation to a flat sheet of material; and before performing the shaping operation, one of the first and second areas of a region of the other of the concave and convex surfaces than the one used to form part of the mould is abraded in order to increase the static and/or dynamic coefficient of friction against the surface of another component of the helmet in comparison to the surface that has not been abraded.

21. A method of manufacturing a component of a helmet according to any one of claims 17 to 20, wherein the step of forming the shaped form comprises performing a shaping operation to a flat sheet of material; and in addition to shaping the flat sheet into the shaped form, the shaping operation forms plural protrusions in one of the first and second areas of a region of the other of the concave and convex surfaces than the one used to form part of the mould, the plural protrusions configured to engage with the surface of another component of the helmet to increase the effective static and/or dynamic coefficient of friction in comparison to the surface without protrusions.

22. A method of manufacturing a helmet comprising the method of any one of claims 17 to 21.