TW202300047A - Helmet - Google Patents

Abstract

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.

Description

helmet

The present invention relates to a helmet.

Impact protection devices generally aim to reduce the energy transferred from an impact to an object, such as a person to be protected. This can be achieved by energy absorbing means, energy redirecting means, or combinations thereof. The energy absorbing member may comprise an energy absorbing material, such as a foam material, or a structure configured to elastically and/or plastically deform in response to impact. Energy redirecting members may include structures configured to slide, shear, or otherwise move in response to impact.

Impact protection equipment includes protective clothing used to protect the wearer of the garment. Protective garments comprising energy absorbing members and/or energy redirecting members are known. For example, such components are widely implemented in protective headgear such as helmets.

Examples of helmets comprising energy absorbing members and energy redirecting members include WO 2001/045526 and WO 2011/139224 (the entire contents of which are incorporated herein by reference). In particular, such helmets comprise at least one layer formed of energy absorbing material and at least one layer that is movable under impact relative to the head of the wearer of the helmet.

Implementing the moving part in a headset is challenging. For example, it can be challenging to ensure that friction between moving parts under impact can be overcome to allow sufficient relative movement between the parts. Ensuring that helmets can be manufactured and assembled relatively easily can be challenging.

It is an object of the present invention to provide a helmet which at least partly solves some of the problems discussed above.

According to one aspect of the present invention, there is provided a helmet comprising: at least one protective layer; a head mount configured to fit on top of the head of a wearer of the helmet, wherein the head mount is suspended from within the cavity formed by the at least one protective layer such that, in normal use and under impact to the helmet below a threshold force, an air gap is provided separating the head mount from the at least one protective layer, and Under impact above the threshold force, the one or more protective layers contact the head mount; and a sliding interface, disposed between the head mount and the at least one protective layer, is configured such that The at least one protective layer is capable of sliding relative to the head mount when the at least one protective layer contacts the head mount under impact to the helmet above the threshold force.

The sliding interface is optionally provided at least partly by a layer of low friction material attached to or integrated with the surface of the at least one protective layer facing the head mount. The layer of low friction material is optionally molded to the surface facing the at least one protective layer of the head mount.

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

The low friction material is optionally formed from a waxy polymer and/or fabric.

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

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

The head mount optionally includes one or more straps.

The head mount optionally includes a headband configured to engage at least the forehead of the wearer of the helmet.

The at least one protective layer optionally includes an energy absorbing layer.

The at least one protective layer optionally comprises a hard shell. if there is no impact on the helmet, the separation provided by the air gap between the outer shell and the head mount at a position corresponding to the top of the wearer's head is optionally at least 10 mm, optionally at least 15 mm, Optionally at least 20 mm, optional at least 30 mm, optional at least 40 mm.

It should be noted that the figures are schematic and that the thicknesses of the various layers and/or the proportions of any gaps between layers depicted in the figures may have been exaggerated or reduced for clarity and can of course be adapted as needed and required.

General features of an example helmet are described below with reference to FIGS. 1-4 .

Figures 1 to 4 show an example helmet 1 comprising an outer layer 2 or shell. The purpose of the outer layer 2 may be to provide stiffness to the helmet. This can help to spread the impact energy over a larger area of the helmet 1 . The outer layer 2 can also provide protection against objects that can penetrate the helmet 1 . Thus, the outer layer 2 may be a relatively strong and/or rigid layer compared to, for example, the energy absorbing layer 3 . The outer layer 2 may be a relatively thin layer compared to, for example, the energy absorbing layer 3 .

The outer layer 2 may be formed from a relatively strong and/or rigid material. Preferably, such materials include, for example, polymeric materials such as polycarbonate (PC), polyvinyl chloride (PVC), high-density polyethylene (HDPE) or acrylonitrile-butadiene-styrene (ABS) . Advantageously, the polymeric material may be fiber reinforced with materials such as glass fibres, Aramid, Twaron, carbon fibers and/or Kevlar.

As shown in FIG. 4 , one or more outer panels 7 may be mounted to the outer layer 2 of the helmet 1 . The outer panel 7 may be formed of a relatively strong and/or rigid material, for example of the same type of material as that from which the outer layer 2 may be formed. The choice of material used to form the outer panel 7 may be the same as or different from the material used to form the outer layer 2 .

The helmet of Figure 4 is configured such that the outer panel 7 is able to slide relative to the outer layer 2 in response to impact. The sliding interface can be arranged between the outer plate 7 and the outer layer 2 .

The friction reducing means for reducing friction at the sliding interface can be achieved by forming the outer layer 2 and/or the outer plate 7 from a low friction material, providing additional low friction on the surface of the outer layer 2 and/or outer plate 8 facing the sliding interface layer, provided by applying a low-friction coating to the outer layer 2 and/or the outer panel 7 and/or applying a lubricant to the outer layer 2 and/or the outer panel 7 .

The helmet 1 shown in FIG. 4 also includes a connector 5 attached to the outer panel 7 . Connectors 5 are also attached to the outer layer 2 to allow relative sliding between the plate 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 connector 5 can also be connected to two or more parts of the remainder of the helmet 1 .

In this configuration, if the helmet 1 is impacted, it can be expected that the impact will occur on one or a limited number of outer panels 7 . Thus, by configuring the helmet so that one or more of the outer panels 7 can move relative to the outer layer 2 and any outer panels 7 not subjected to an impact, the impact-receiving surface (i.e., one or a limited number of outer panels 7) can be moved relative to The rest of the helmet 1 moves. This reduces the rotational acceleration of the wearer's head in the event of an impact.

It should be understood that this configuration of the outer panel 7 can be added to any helmet described herein.

2 to 4 show an example helmet 1 including an optional energy absorbing layer 3 . The purpose of the energy absorbing layer 3 is to absorb and dissipate energy from impacts to reduce the energy transmitted to the wearer of the helmet. Within the helmet 1 the energy absorbing layer may be the main energy absorbing element. Although other elements of the helmet 1 can absorb this energy to a more limited extent, this is not its main purpose.

The energy absorbing layer 3 can more efficiently absorb energy from the radial component of the impact rather than the tangential component of the impact. The term "radial" generally refers to a direction substantially towards the center of the wearer's head (eg substantially perpendicular to the outer surface of the helmet 1). The term "tangential" may refer to a direction substantially perpendicular to the radial direction in a plane including the radial direction and the impact direction.

The energy absorbing layer may be formed from an energy absorbing material such as a foam material. Preferably, such materials comprise expanded polystyrene (EPS), expanded polypropylene (EPP), expanded polyurethane (EPU), vinyl nitrile foam or strain rate sensitive foam ( Strain rate sensitive foams such as those commercially available under the trade names Poron ^™ and D3O ^™ ).

Alternatively or additionally, the energy absorbing layer may have a structure that provides energy absorbing properties. For example, an energy absorbing layer may include deformable elements such as cells or fingers that deform after impact to absorb and dissipate the energy of the impact.

As shown in Fig. 3, the energy absorbing layer 3 of the helmet 1 can be divided into an outer 3A and an inner 3B. These portions 3A, 3B may be configured to rotate relative to each other.

The energy absorbing layer is not limited to one particular configuration or material. The energy absorbing layer 3 may be provided by multiple layers having different configurations, ie formed of different materials or having different structures. The energy absorbing layer 3 may be a relatively thick layer. For example, it may be the thickest layer of the helmet 1 .

When used, the layer of energy absorbing material may be provided as the shell on substantially all surfaces of the hard shell facing the wearer's head, but ventilation holes may be provided. Alternatively or additionally, a localized area of energy absorbing material may be disposed between the hard shell and the head mount (described below). For example, a strip 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 sit above the wearer's head.

In some example helmets, the outer layer 2 and/or the energy absorbing layer 3 can be resized to provide a customized fit. For example, the outer layer 2 may be provided in separate front and rear parts. The relative positions of the front and rear can be adjusted to change the size of the outer layer 2 . To avoid gaps in the outer layer 2, the front and rear can overlap. The energy absorbing layer 3 can also be provided in separate front and rear parts. These can be configured such that the relative position of the front and rear can be adjusted to vary the size of the energy absorbing layer 3 . To avoid gaps in the energy absorbing layer 3, the front and rear parts can overlap.

FIG. 1 shows an example helmet 1 including a head mount 20 . Although not shown in FIGS. 2-4 , these example helmets also include a head mount 20 . The head mount 20 may be arranged so that the helmet 1 is worn on the wearer's head. In some configurations, this can improve wearer comfort.

The head mount 20 may be provided in any form that can be used to facilitate mounting of the helmet to the wearer's head. In some configurations it may help to secure 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 wearer's head. The head mount 20 may be elastic and/or may include an adjustment mechanism for adjusting the size of the interface layer 20 . In one configuration, the head mount 20 is engageable with the top of the wearer's head.

The head mount 20 is removable. This may enable the head mount 20 to be cleaned and/or provided with an interface layer configured to suit a particular wearer.

As shown in FIG. 1 , the head mount 20 is suspended within the remainder of the helmet (e.g., the cavity formed therein for receiving the head (e.g., the outer shell 2 and/or the optional energy absorbing layer 3)) such that the air A gap 21 is provided between the remainder of the helmet and the head mount 20 . The head mount 20 can be connected to the rest of the helmet (eg the outer shell 2 and/or the optional energy absorbing layer 3 ) via connectors 25 . This type of helmet is often used for industrial purposes, such as construction workers, miners or operators of industrial machinery. However, a helmet based on this configuration can 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 loads caused by impacts on the outer shell 2 travel across the wearer's Head spread. In particular, the load is not limited to a point on the wearer's head adjacent to the point of impact on the helmet 1 . Instead, the load is spread across the outer shell 2 and then across the head mount 20 and thus across the wearer's skull.

During impact, some of the impact energy may be absorbed by deforming portions of the helmet, such as the head mount, to reduce the size of the air gap. Therefore, the size of the air gap 21 between the outer shell 2 and the head mount 20 can be selected to ensure that the head mount 20 does not come into contact with the outer shell under impacts on the helmet below the threshold force for which the helmet is designed to withstand. The bodies 2 are in contact (ie, the air gap 21 is not completely eliminated), so that shocks can be transferred directly from the rigid shell to the head mount 20 . However, in some example helmets, when the impact is above a threshold force, the air gap 21 may be eliminated (eg, at a canonical location such as the location of the impact), allowing the remainder of the helmet to contact the head mount 20 . These example helmets may include an energy absorbing layer 3 disposed in an otherwise empty space forming an air gap 21 . In other words, part of the air gap 21 can be replaced by an energy absorbing layer. This allows the rest of the helmet to be brought closer to the head mount 20 .

In one configuration, the helmet 1 may be configured such that, when there is no impact on the helmet, the separation between the outer shell 2 and the head mount 20 at a position corresponding to the top of the wearer's head 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 the helmet 1 is designed to withstand and thus the size of the air gap 21 may depend on the intended use of the helmet 1 . It should be understood that the size of the air gap 21 may be different at different locations depending on the intended use of the helmet. For example, the air gap 21 may be smaller at the front, rear or sides of the helmet than it is at a location corresponding to the top of the wearer's head.

In helmet configurations that include an energy absorbing layer, the energy absorbing layer contributes to the ability of the helmet to withstand radial impacts. In particular, in configurations in which the energy absorbing material is located within the air gap between the outer shell 2 and the head mount 20 at a location corresponding to the top of the wearer's head, it will be appreciated that the head mount and the energy absorbing layer The gap between the surfaces will be smaller than the gap between the outer shell and the head mount and can be completely eliminated. Additionally, due to the contribution of the energy absorbing material in the event of a radial impact, the clearance required between the outer shell and the head mount may be less than would be the case without the energy absorbing material.

In some configurations, the head mount 20 may include a headband or headband that at least partially surrounds the wearer's head. Alternatively or additionally, the head mount 20 may include one or more straps extending across the top of the wearer's head. Alternatively or additionally, the head mount 20 may comprise a cover or shell that encapsulates the upper portion of the wearer's head. The straps or straps forming part of the head mount may be formed from nylon fabric. Alternatively or additionally, other materials may be used.

5-7 show example helmets of the type schematically depicted in FIG. 1 . As shown in the figures, the head mount comprises a plurality of straps 20 extending across the top of the wearer's head of the helmet 1 . The strip 20 can be connected to the outer casing 2 at the connection point by any of a number of known methods. For example, the outer housing 2 may be molded to include a receptacle into which the connector 25 may be inserted.

In the configuration depicted in FIG. 5, the head mount is formed by two straps 20 each extending between a pair of connectors 25 positioned so that the straps 20 span the head of the wearer of the helmet. extend. For example, the first strap 20 may extend from a left rear position to a right front position and the second strap 20 may extend from a right rear position to a left front position. However, it should be appreciated that many other configurations may be used. For example, as shown in Figures 6 and 7, additional straps may be provided such that three, four or more straps extend across the top of the wearer's head. As shown in Figure 6, additional strips are provided to run from left to right. As shown in Figure 6, another additional strip is provided to extend from front to back. Similarly, the location of the attachment point of the strap 20 to the remainder of the helmet is different than that depicted in FIGS. 5-7 .

In configurations in which different straps 20 are close to each other (eg, at the top of the wearer's head), the straps 20 may not be connected to each other to allow slight movement of one strap relative to the other. In other configurations, the strips 20 may be connected to each other where they cross. In another configuration, the head mount may comprise one of the straps extending from a connection point to the remainder of the helmet 1 to a point where it connects to other straps (for example, at a location corresponding to the crown of the wearer's head of the helmet). or multiple strips. Finally, as mentioned above, in other configurations the head mount may be formed by components other than the straps, for example by a cover or shell mountable to the top of the wearer's head of the helmet 1 .

As shown in FIGS. 5-7 , the head mount may include a headband 20A that engages at least the wearer's forehead of the helmet and may enclose a portion of the wearer's head. It will be appreciated that this headband 20A may be attached to the helmet 1 , separate from the remainder of the head mount, such as the strap 20 . Alternatively, the headband 20A can be connected to the helmet 1 by means of straps 20 . As another alternative, the strap 20 may be connected to the remainder of the helmet 1 by means of a headband 20A.

Further straps, such as chin straps, may be provided to secure the helmet 1 to the wearer's head.

8 and 9 show another example helmet with the above-mentioned suspended head mount 20 . In addition, a sliding interface is provided between the head mount 20 and the rest of the helmet. In the configuration shown, the helmet comprises an energy absorbing layer 3 , whereby a sliding interface is provided between the head mount 20 and the energy absorbing layer 3 . The sliding interface is configured such that the remainder of the helmet can slide relative to the head mount 20 when it contacts the head mount 20 under impact to the helmet 1 above a threshold force. The sliding interface may improve the protection given to the wearer of the helmet when the head mount 20 contacts the remainder of the helmet under impact.

The purpose of helmet layers that move or slide relative to each other may be to redirect the energy of an impact that would otherwise be diverted to the wearer's head. This can provide improved protection to the wearer from the tangential component of impact energy. The tangential component of the impact energy will generally result in rotational acceleration of the wearer's head. This rotation is known to cause brain damage. The results show that a helmet with layers that move relative to each other can reduce the rotational acceleration of the wearer's head. A typical reduction may be about 25%, but in some instances, reductions of up to 90% may be possible.

Preferably, the relative movement between the helmet layers results in a total displacement between the outermost helmet layer and the innermost helmet layer of at least 0.5 cm, more preferably at least 1 cm, more preferably at least 1.5 cm. Preferably, relative movement may occur in any direction, eg in a circumferential direction around the helmet, from left to right, from front to back and anywhere in between.

Regardless of how the helmet layers are configured to move relative to each other, relative movement, such as sliding, is preferably able to occur at forces typical of impacts for which the helmet is designed, such as impacts for which the wearer is expected to survive. These forces are significantly higher than what a helmet can withstand during normal use. Impact forces tend to compress the layers of the helmet together to increase reaction forces between components and thus increase friction. When a helmet is configured to have layers that slide relative to each other, the interface between the layers needs to be configured to be able to slide even under the influence of the high reaction forces experienced between the underlying layers upon impact.

As shown in Figure 8, the sliding interface may be provided at least in part by a layer of low friction material 4 attached to or integrated with the surface facing the remainder of the helmet of the head mount. In the example shown, this means the surface of the energy absorbing layer 3 . However, in an example, this may mean the outer shell 2 (or other protective layer) if there is no energy absorbing layer 3 .

The layer of low friction material includes holes for allowing a connector 25 to connect the head mount 20 directly to the rest of the helmet, such as the energy absorbing layer 3 or the outer shell 2 . Alternatively, the connector 25 may be connected to the remainder of the helmet via the layer 4 of low friction material. For example, the connector 25 may only be directly connected to the layer of low friction material 4 which in turn is directly connected to the rest of the helmet, such as the energy absorbing layer 3 or the outer shell 2 . Alternatively, the layer of low-friction material 4 may be connected to the rest of the helmet by means of connectors 25 . For example, the connector 25 may be connected directly to the layer of low-friction material 4 and also to the rest of the helmet, such as the energy absorbing layer 3 or the outer shell 2 .

The low-friction material layer 4 may be a sheet-like layer. The layer of low friction material may be molded to the surface to which it is attached or integrated. This provides a tight fit between the low friction material and the surface.

As shown in Figure 10, the sliding interface may be provided at least in part by a layer of low friction material 4 attached to the head mount 20 facing the rest of the helmet (eg energy absorbing layer 3 or outer shell 2) surface or integrated with the surface. As shown in the figure, layers may be disposed in discrete segments or patches. Alternatively, the low friction material may be provided over substantially the entire surface of the strip 20 .

Possible low friction materials include waxy polymers such as PC, TPU, nylon (eg brushed nylon), PTFE, ABS, PVC, PFA, EEP, PE and UHMWPE, Teflon™. Alternatively, the low-friction layer 4 may be formed from a woven or non-woven fabric. These low friction materials can have a thickness of about 0.1 mm to about 5 mm, although other thicknesses can also be used, depending on the material chosen and the performance desired.

If the layer 4 of low-friction material is provided on two opposing surfaces (i.e. the surface of the head mount 20 and the surface of the remainder of the helmet (e.g. the energy absorbing layer 3 or the outer shell 2), these can be made of the same material. or formed of 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 have a fabric material.

In some examples, the sliding interface may be disposed between two sheets of ribbed fabric configured such that the directions of the ribs are perpendicular to each other, thus forming a sliding interface between them. Preferably, the ribbed fabric is a warp knitted fabric. Preferably, the warp knitted fabric has a dark side and a light side and the respective light sides face each other at the sliding interface. Two pieces of fabric may be provided to the head mount 20 and the remainder of the helmet (eg energy absorbing layer 3 or outer shell 2 ) respectively.

Alternatively or additionally, lubricating materials comprising oils, polymers, microspheres or powders, or combinations thereof may be used at the sliding interface. For example, these can be applied to the surface of the helmet facing the head mount 20 .

In one example, the low-friction or lubricating material can be a polysiloxane-containing material. In particular, materials may include: (i) organic polymers, polysiloxanes, and surfactants; (ii) organic polymers and copolymers based on polysiloxanes and organic polymers; or (iii) by Or non-elastomeric crosslinked polymers obtainable by subjecting polysiloxanes and organic polymers to a crosslinking reaction. Preferred options for these materials are described in WO2017148958.

In one example, the low friction or lubricating material may include a mixture of (i) olefin polymer, (ii) lubricant, and optionally one or more additional agents. Preferred options for these materials are described in WO2020115063.

In one example, the low friction material or lubricating material may comprise an ultra high molecular weight (UHMW) polymer, preferably an olefin polymer, having a density < 960 kg/m ³ . Preferred options for these materials are described in WO2020115063.

In one example, the low friction or lubricating material can include polyketones.

In some configurations, it may be desirable to configure the sliding interface such that the static and/or dynamic coefficient of friction between the materials forming the sliding surface 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 methods such as standard test method ASTM D1894.

In some examples, the sliding interface may be provided by a shear layer rather than a layer of low friction material. In such examples, the aforementioned layer of low friction material may be replaced by a shear material or structure. These materials generally include two layers that are capable of shearing relative to each other to allow relative sliding between the layers of the helmet.

The helmets described above can be used in a variety of activities. These activities include combat and industrial purposes such as, for example, protective helmets for soldiers and hard hats or helmets used by construction workers, miners or operators of industrial machinery. Helmets are also commonly used in sports activities. For example, protective helmets can be used for ice hockey, bicycles, motorcycles, auto racing, skiing, snowboarding, skating, skateboarding, equestrian sports, American football, baseball, rugby, soccer, cricket, lacrosse, rock climbing, golf, airsoft , Roller Derby and Paintball Survival.

Examples of injuries that can be prevented or mitigated by the above helmets include mild traumatic brain injury (MTBI) such as concussion and severe traumatic brain injury (STBI) such as subdural hematoma (SDH), bleeding from a ruptured blood vessel and diffuse axonal injury (DAI), which can be summarized as overstretching of nerve fibers caused by high shear deformation in brain tissue).

Depending on the characteristics of the rotational component of the shock, such as duration, amplitude, and rate of increase, concussion, SDH, DAI, or a combination of these injuries may be encountered. In general, SDH occurs in short-duration and large-amplitude accelerations, while DAI occurs in longer and broader acceleration loads.

Variations of the above examples can be made 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.

1: helmet 2: Outer layer/housing 3: Energy absorbing layer 3A: External 3B: Internal 4: Low friction material layer 5: Connector 7: Outer plate 20: Head Mount/Strap 20A: head ring 21: air gap 25: Connector

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

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

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

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

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

Figure 5 schematically shows a first example head mount;

Figure 6 schematically shows a second example head mount;

Figure 7 schematically shows a third example head mount;

Figure 8 shows another example helmet;

Figure 9 shows a portion of the helmet shown in Figure 8;

Figure 10 shows another example head mount.

2: Outer layer/housing

3: Energy absorbing layer

4: Low friction material layer

20: Head Mount/Strap

20A: head ring

21: air gap

25: Connector

Claims (16)

A helmet comprising: at least one protective layer; A head mount configured to fit on top of the head of the wearer of the helmet, wherein the head mount is suspended within the cavity formed by the at least one protective layer so that in normal use and at a temperature below Under impact to the helmet at a threshold force, an air gap is provided separating the head mount from the at least one protective layer, and at impacts above the threshold force, the one or more protective layers contact the head mounts; and a sliding interface disposed between the head mount and the at least one protective layer configured such that when the at least one protective layer contacts the head mount under impact to the helmet above the threshold force , the at least one protective layer can slide relative to the head mount. The helmet according to claim 1, wherein the sliding interface is at least partially provided by a layer of low-friction material attached to or integrated with the surface of the at least one protective layer facing the head mount. The helmet of claim 2, wherein the layer of low friction material is molded to the surface facing the at least one protective layer of the head mount. The helmet according to any one of claims 1 to 3, wherein the sliding interface is at least partially provided by a layer of low-friction material attached to the surface of the head mount facing the at least one protective layer or in contact with The surface is integrated. The helmet according to claim 2 or 3, wherein the low-friction material is formed of waxy polymer and/or fabric. The helmet according to any one of claims 1 to 3, wherein the sliding interface is at least partially provided by a lubricating material located on or integrated with the surface of the at least one protective layer facing the head mount. The helmet according to claim 6, wherein the lubricating material is one of a mixture of polysiloxane material, olefin polymer and lubricant, and ultra-high molecular weight (UHMW) polymer. The helmet according to any one of claims 1 to 3, wherein the head mount is connected to the at least one protective layer by a connector. If the helmet of claim 8 is also attached to claim 2, wherein the low-friction layer is also connected to the rest of the helmet through the connectors. The helmet according to claim 8, when claim 2 is also attached, wherein the connectors are connected to the at least one protective layer through the low-friction layer. The helmet of claim 8, wherein the connectors are deformable to allow the head mount to rotate relative to the at least one protective layer. The helmet according to any one of claims 1 to 3, wherein the head mount comprises one or more straps. 3. The helmet of any one of claims 1 to 3, wherein the head mount includes a headband configured to engage at least the forehead of a wearer of the helmet. The helmet according to any one of claims 1 to 3, wherein the at least one protective layer comprises an energy absorbing layer. The helmet according to any one of claims 1 to 3, wherein the at least one protective layer comprises a hard shell. The helmet of claim 15, wherein if there is no impact on the helmet, the spacing provided by the air gap between the outer shell and the head mount at a position corresponding to the top of the wearer's head is at least 10 mm, Optionally at least 15 mm, optional at least 20 mm, optional at least 30 mm, optional at least 40 mm.

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