TECHNICAL FIELD The present invention relates to 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.

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

According to an aspect of the disclosure there is provided a helmet, comprising: at least one protective layer; a head mount, configured to be mounted on the top of the head of a wearer of the helmet, wherein the head mount is suspended within a cavity formed by the at least one protective layer such that, in normal use and under an impact to the helmet below a threshold force, an air gap is provided that separates the head mount and the at least one protective layer, and, under an impact above the threshold force, the one or more protective layers contacts the head mount; and a sliding interface provided between the head mount and the at least one protective layer, configured such that the at least one protective layer is able to slide relative to the head mount as the at least one protective layer contacts the head mount under an impact to the helmet above the threshold force.

Optionally, the sliding interface is provided, at least partially, by a layer of low friction material attached to, or integrated with, a surface of the at least one protective layer facing the head mount. Optionally, the layer of low friction material is moulded to the surface of the at least one protective layer facing the head mount.

Optionally, the sliding interface is provided, at least partially, by a layer of low friction material attached to, or integrated with, a surface of the head mount facing the at least one protective layer.

Optionally, the low friction material is formed from a waxy polymer and/ or a fabric.

Optionally, the sliding interface is provided, at least partially, by a lubricating material on, or integrated with, the a surface of the at least one protective layer facing the head mount. Optionally, the lubricating material is one of a polysiloxane-containing material, a mixture of an olefin polymer and a lubricant, and an ultra high molecular weight (UHMW) polymer.

Optionally, the head mount is connected to the at least one protective layer by connectors. Optionally, the low friction layer mentioned above is also connected to the rest of the helmet by the connectors. Optionally, the connectors are connected to the at least one protective layer via the low friction layer mentioned above. Optionally, the connectors are deformable to allow the head mount to rotate relative to the at least one protective layer.

Optionally, the head mount comprises one or more straps.

Optionally, the head mount comprises a head ring that is configured to engage at least the forehead of a wearer of the helmet.

Optionally, the at least one protective layer includes an energy absorbing layer.

Optionally, the at least one protective layer includes a hard outer shell. Optionally, in the absence of an impact on the helmet, the separation between the outer shell and the head mount at a location corresponding to the top of the head of a wearer provided by the air gap is at least 10mm, optionally at least 15mm, optionally at least 20mm, optionally at least 30mm, optionally at least 40mm.

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 first example head mount;

Fig. 6 schematically shows a second example head mount;

Fig. 7 schematically shows a third example head mount;

Fig. 8 shows a further example helmet;

Fig. 9 shows a portion of the helmet shown in Fig. 8;

Fig. 10 shows an further example head mount.

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 may have been exaggerated or diminished for the sake of clarity and can of course be adapted according to need and requirements.

General features of the example helmets are described below with reference to Figs. 1 to 4.

Figs. 1 to 4 show example helmets 1 comprising an outer layer 2, or shell. 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 2 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), high density polyethylene (HDPE) 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. 4, 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.

The helmet of Fig. 4 is configured such that the outer plates 7 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 7 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 7 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 7, and/or applying a lubricant to the outer layer 2 and/or the outer plates 7. The helmet 1 shown in Fig. 4 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 an 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 7. 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.

Figs. 2 to 4 show example helmets 1 comprising an optional 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 D30™.

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. 3, the energy absorbing layer 3 of the helmet 1 may be divided into outer and inner parts 3A, 3B. These parts 3A, 3B may be configured to rotate relative to each other.

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.

Where used, the energy absorbing material layer may be provided as a shell over substantially all of the surface of the hard shell facing the wearer’s head, although ventilation holes may be provided. Alternatively or additionally, localised regions of energy absorbing material may be provided between the hard shell and a head mount (described below). For example, a band of energy absorbing material may be provided around the lower edge of the outer shell and/or a section of energy absorbing material may be provided to be located above the top of the wearer’s head.

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.

Fig. 1 shows an example helmet 1 comprising a head mount 20. Although not shown in Figs. 2 to 4, these example helmets also comprise a head mount 20. The head mount 20 may be provided to mount the helmet 1 on the head of a wearer. In some arrangements, this may improve the comfort of the wearer.

The head mount 20 may be provided in any form that can function to contribute to mounting the helmet to the wearer’s head. In some configurations, it may assist in securing the helmet 1 to the wearer’s head but this is not essential. The head mount 20 may be configured to at least partially conform to the head of the wearer. For example, the head mount 20 may be elasticated and/or may comprise an adjustment mechanism for adjusting the size of the interface layer 20. In an arrangement, the head mount 20 may engage with the top of a wearer’s head.

The head mount 20 may be removable. This may enable the head mount 20 to be cleaned and/or may enable the provision of an interface layer that is configured to fit a specific wearer.

As shown in Fig. 1 the head mount 20 is suspended within the rest of the helmet, e.g. a cavity formed therein for accommodating the head, (e.g. the outer shell 2 and/or optional energy absorbing layer 3) such that an air gap 21 is provided between the rest of the helmet and the head mount 20. The head mount 20 may be connected to the rest of the helmet (e.g. to the outer shell 2 and/or optional energy absorbing layer 3) by connectors 25. Helmets of this type are commonly used for industrial purposes, such as by builders, mine- workers or operators of industrial machinery. However, helmets based on such an arrangement may be used for other purposes.

In a helmet 1 such as that depicted in Fig. 1, the provision of an air gap 21 between the inner surface of the outer shell 2 and the head mount 20 is intended to ensure that loading caused by an impact on the outer shell 2 is spread across a wearer’s head. In particular, the load is not localised on a point on the wearer’s head adjacent the point of impact on the helmet 1. Instead, the load is spread across the outer shell 2 and, subsequently, spread across the head mount 20 and therefore spread across the wearer’s skull.

During an impact, some of the energy of the impact may be absorbed by deformation of parts of the helmet, such as the head mount, reducing the size of the air gap. Accordingly, the size of the air gap 21 between the outer shell 2 and the head mount 20 may be chosen to ensure that, under an impact on the helmet below a threshold force that the helmet is designed to withstand, the head mount 20 does not come into contact with the outer shell 2, namely the air gap 21 is not entirely eliminated, such that the impact may be directly transferred from the hard shell to the head mount 20. However, in some example helmets, for impacts above the threshold force, the gap 21 may be eliminated, e.g. at a specification location such as the location of impact, such that the rest of the helmet contacts the head mount 20. Such example helmets may comprise an energy absorbing layer 3, which is provided in the space that would otherwise be empty and forming the air gap 21. In other words, part of the air gap 21 may be replaced by an energy absorbing layer. This may bring the rest of the helmet closer to the head mount 20.

In an arrangement, the helmet 1 may be configured such that, in the absence of an impact on the helmet, the separation between the outer shell 2 and the head mount 20 at a location corresponding to the top of the head of a wearer is at least 10 mm, optionally at least 15 mm, optionally at least 20 mm, optionally at least 30 mm, optionally at least 40 mm. The magnitude of the impact that the helmet 1 is designed to withstand, and therefore the size of the air gap 21, may depend upon the intended use of the helmet 1. It should be understood that, depending on the intended use of the helmet the size of the air gap 21 may be different at different locations. For example, the air gap 21 may be smaller at the front, back or side of the helmet than it is at the location corresponding to the top of the head of the wearer.

In arrangements that include energy absorbing layer, the energy absorbing layer may contribute to the helmet’s ability to withstand radial impacts. In particular in arrangements in which the energy absorbing material is located within the air gap between the outer shell 2 and the head mount 20 at the location corresponding to the top of the wearer’s head, it will be appreciated that the gap between the head mount and the surface of the energy absorbing layer will be smaller than the gap between the outer shell and the head mount, and may be eliminated altogether. Additionally, as a result of the energy absorbing material’s contribution in the event of a radial impact, a smaller gap between the outer shell and the head mount may be required than would be the case in the absence of the energy absorbing material.

In some arrangements, the head mount 20 may include a head band, or head ring, that at least partially surrounds the wearer’s head. Alternatively or additionally, the head mount 20 may include one or more straps that extend across the top of the wearer’s head. Alternatively or additionally, the head mount 20 may include a cap or shell that encapsulates an upper portion of the wearer’s head. Straps or bands that form part of the head mount may be formed from Nylon fabric. Other materials may alternatively or additionally be used.

Figs. 5 to 7 show example helmets the type schematically depicted in Fig. 1. As shown, the head mount includes a plurality of straps 20 that extend across the top of the head of a wearer of the helmet 1. The straps 20 may be connected at connection points to the outer shell 2 by any of a plurality of known methods. For example, the outer shell 2 may be moulded to include sockets into which connectors 25 may be inserted.

In the arrangement depicted in Fig. 5, the head mount is formed from two straps 20 that each extend between a pair of connectors 25 positioned such that the straps 20 extend across the head of the wearer of the helmet. For example, a first strap 20 may extend from a rear left position to a forward right position and a second strap 20 may extend from a rear right position to a forward left position. However, it should be appreciated that many other arrangements may be used. For example, additional straps may be provided, as shown in Figs. 6 and 7, such that there are three, four or more straps extending across the top of the head of the wearer. As shown in Fig. 6, an additional strap is provided extending from left to right. As shown in Fig., 6 a further additional strap is provided extending from front to back. Similarly, the position of the connection points of the straps 20 to the remainder of the helmet 1 may be different from that depicted in Figs. 5 to 7.

In an arrangement where different straps 20 are in proximity to each other, for example, at the top of the wearer’s head, the straps 20 may not be connected to each other, permitting some movement of one strap relative to another. In other arrangements, the straps 20 may be connected to each other where they cross. In a further arrangement, the head mount may include one or more straps that extend from a connection point to the remainder of the helmet 1 to a point at which it is connected to other straps, for example, at a location corresponding to the top of the head of a wearer of the helmet. Finally, as noted above, in other arrangements, the head mount may be formed from components other than straps, for example from a cap or shell that can be mounted to the top of the head of the wearer of the helmet 1.

As shown in Fig. 5 to 7, the head mount may include a head ring 20A that engages at least the forehead of a wearer of the helmet and may surround a portion of the head of the wearer. It should be appreciated that such a head ring 20A may be connected to the helmet 1 separately from the remainder of the head mount, such as straps 20. Alternatively the head ring 20A may be connected to the helmet 1 by means of the straps 20. As a further alternative, the straps 20 may be connected to the rest of the helmet 1 by means of the head ring 30.

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

Figs. 8 and 9 show a further example helmet, with a suspended head mount 20 as described above. Additionally, a sliding interface is provided between the head mount 20 and the rest of the helmet. In the arrangement shown, the helmet comprises an energy absorbing layer 3, so the sliding interface is provided between the head mount 20 and the energy absorbing layer 3. The sliding interface is configured such that rest of the helmet is able to slide relative to the head mount 20 as the rest of the helmet contacts the head mount 20 under an impact to the helmet 20 above the threshold force. The sliding interface may improve the protection afforded to the wearer of the helmet when the head mount 20 comes into contact with the rest of the helmet under an impact.

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.

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 Fig. 8 the sliding interface may be provided, at least partially, by a layer of low friction material 4 attached to, or integrated with, a surface of the rest of the helmet facing the head mount. In the example shown, this means a surface of the energy absorbing layer 3. However, in examples, without an energy absorbing layer 3, this may mean the outer shell 2 (or other protective layer).

As shown in Fig. 9, the layer of low friction material may comprise holes 41 for allowing the connectors 41 to directly connect the head mount 20 to the rest of the helmet, e.g. an energy absorbing layer 3 or outer shell 2. Alternatively, the connectors 25 may be connected to the rest of the helmet via the layer of low friction material 4. For example, the connectors 25 may directly connect to only the layer of low friction material 4, which is in turn directly connected to the rest of the helmet, e.g. an energy absorbing layer 3 or outer shell 2. Alternatively, the layer of low friction material 4 may be connected to the rest of the helmet by the connectors 25. For example, the connectors 25 may directly connect to the layer of low friction material 4 and also to the rest of the helmet, e.g. an energy absorbing layer 3 or outer shell 2.

The layer of low friction material 4 may be a sheet-like layer. The layer of low friction material may be moulded to the surface it is attached to, or integrated with. This may provide a close fit between the low friction material and the surface.

As shown in Fig. 10, the sliding interface may be provided, at least partially, by a layer of low friction material 4 attached to, or integrated with, a surface of the head mount 20 facing the rest of the helmet (e.g. an energy absorbing layer 3 or outer shell 2). As shown, the layer may be provided in discrete sections, or patches. Alternatively, the low friction material may be provided substantially over the entirety of the surfaces of the straps 20.

Possible low friction materials include waxy polymers such as PC, TPU, Nylon (e.g. brushed Nylon), PTFE, ABS, PVC, PFA, EEP, PE and UHMWPE, Teflon™. Alternatively, the low friction layer 4 may be formed from a woven or nonwoven fabric. 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.

If layers of low friction material 4 are provided on both opposing surfaces, namely the surface of the head mount 20 and the surface of the rest of the helmet (e.g. an energy absorbing layer 3 or outer shell 2), these may be formed from the same materials or different materials. In one example, a polymer material, such as PC, may be provided to the surface facing the head mount 20 and the surface of the head mount 20 may be provided with a fabric material.

In some examples, a sliding interface may be provided between two sheets of ribbed fabric arranged such that the rib directions are perpendicular to each other, thus forming the sliding interface between. Preferably, the ribbed fabric is a tricot fabric. Preferably, the tricot fabric has a dull side and a shiny side and the respective shiny sides face each other at the sliding interface. The two sheets of fabric may be provided respectively to the head mount 20 and the rest of the helmet (e.g. an energy absorbing layer 3 or outer shell 2). Alternatively, or additionally, lubricating materials include oils, polymers, microspheres, or powders, or combinations thereof may be used at the sliding interface. For example, these may be applied to a surface of the helmet facing the head mount 20.

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 cross- linking 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/m ³ , which UHMW polymer is preferably an olefin polymer. Preferred options for such materials are described in W02020115063.

In one example the low friction material or lubricating material may comprise a polyketone.

In some arrangements, it may be desirable to configure the sliding 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 D1894.

In some examples, the sliding interface may be provided by a shearing layer, rather than a layer of low friction material. In such examples, the layer of low friction materials described above may be replaced by shearing materials or structures. These materials generally comprise two layers that are able to shear with respect to each other to allow relative sliding between layers of the helmet. 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.