Specification

The invention relates to a helmet, particularly a cycling helmet.

Such a helmet can comprise an inner layer comprising an outer surface, and an outer protective layer arranged on the inner layer, the outer protective layer comprising an inner surface facing the outer surface of the inner layer, wherein under an impact force having at least a tangential force component along an outer surface of the outer protective layer, the outer protective layer is configured to move relative to the opposing outer surface of the inner layer.

Such a relative movement can decisively mitigate a rotation of the head of the person (e.g. cyclist) that would otherwise be feared due to the tangential impact on the head, and a risk of injury can be reduced accordingly.

Regarding such assemblies of layers moving relative to one another upon impact it is therefore of utmost important to avoid a mechanical looking between the layers that could restrict the movement between the layers and in turn cause rotation of the head with a high risk of severe injury to the person wearing the helmet.

Therefore, the problem to be solved by the present invention is to provide a helmet that reduces the likelihood of mechanical locking of said layers.

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

According to claim 1 a helmet, particularly cycling helmet, is disclosed, comprising:

- an inner layer comprising an outer surface, and

- an outer protective layer arranged on the inner layer, the outer protective layer comprising an inner surface facing the outer surface of the inner layer, wherein under an impact force having at least a tangential force component along an outer surface of the outer protective layer, the outer protective layer is configured to move relative to the opposing outer surface portion of the inner layer,

- wherein the inner surface of the outer protective layer is separated from the outer surface of the inner layer by a plurality of spacers configured to reduce a mechanical locking between the inner layer and the outer protective layer upon said relative movement of the outer protective layer with respect to the inner layer.

Particularly, in the context of the present invention according to the first aspect, mechanical locking is understood to mean any mechanical interaction between the two layers, particularly any type of interaction between the two layers in which the protective layer collides with the inner layer or other layers involved such that the desired movement of the outer protective layer with respect to the inner layer is impeded (and thus rendered less effective in terms of preventing injury to the person wearing the helmet).

In other words, geometric structures (spacers) are provided that provide a standoff between said outer protective layer and said inner layer to prevent mechanical locking. The geometric structures / spacers can be separate bodies arranged between the layers but may also be protrusions of one of the layers that can be integrally formed with the layer or otherwise connected with the latter. In this respect, a corrugated surface can also provide a plurality of spacers (that are integrally formed with the surface / respective layer).

According to an embodiment of the first aspect of the present invention, due to the spacers, a hollow gap is formed between the outer surface of the inner layer and the inner surface of the outer protective layer. Preferably, this gap or standoff between the two outer protective layer and the inner layer is preferably larger than 0.5, mm, particularly larger than 1 mm, particularly larger than 5 mm. In an embodiment, the gap is smaller than 10 mm.

Further, in an embodiment of the first aspect of the present invention, the spacers are integrally formed with the inner surface of the outer protective layer and protrude towards the outer surface of the inner layer.

In an alternative embodiment of the first aspect of the present invention, the spacers are integrally formed with the outer surface of the inner layer and protrude towards the inner surface of the outer protective layer. According to yet another alternative embodiment of the first aspect of the present invention, the spacers are separate elements (regarding the outer protective layer and inner layer) arranged between the outer surface of the inner layer and the inner surface of the outer protective layer.

Furthermore, in an embodiment of the first aspect of the present invention, the outer protective layer comprises a plurality of shells arranged side by side on the inner layer. Furthermore, it is also possible that neighbouring shells overlap.

Further, according to an embodiment of the first aspect of the present invention, the outer protective layer (or the respective shell of the outer protective layer) comprises a plurality of sub layers arranged on top of one another. Furthermore, it is possible that sub layers overlap with neighbouring sub layers.

The other layers described herein can in principle also comprise a sub structure and do not necessarily have to form homogeneous layers.

According to a further embodiment of the first aspect of the present invention, the size of the spacers and/or the distribution of the spacers along the outer protective layer varies. However, it is also possible that the spacers are equidistantly spaced along the outer protective layer.

Furthermore, in an embodiment of the first aspect of the present invention, the outer protective layer comprises a thickness in the range from 0.05 mm to 10 mm.

Furthermore, the movement of the outer protective layer with respect to the inner layer upon tangential impact can have different characteristics. Particularly, said relative movement of the outer protective layer with respect to the inner layer can comprises at least one of: a folding of the outer protective layer, a hinging of the outer protective layer, a crumpling of the outer protective layer.

Furthermore, regarding said relative movement, the outer protective layer is constrained to the inner layer according to an embodiment, particularly by at least one tether (e.g. a string or an elastic band) that is configured to limit a movement of the outer protective layer or components thereof. In an embodiment of the first aspect of the present invention, the inner layer comprises an energy absorbing layer or can be formed as an energy absorbing layer. The energy absorbing layer may comprise expanded polystyrene (particularly EPS, i.e., expanded polystyrene) or similar compounds or foams that provide similar properties as e.g., EPS.

It is noted that on a side facing the head of a person wearing the helmet, a lining layer or lining elements may be arranged for adjusting the fit of the helmet and or for reasons of comfort.

Furthermore, according to an embodiment of the first aspect of the present invention, the helmet comprises an intermediary layer forming a part of the inner layer, the intermediary layer being arranged between the energy absorbing layer and the outer protective layer. Particularly, the intermediary layer is fixed to the energy absorbing layer or is suspended above the inner layer. Suspension can be achieved by rigid structures, but may also be achieved by means of a liquid being arranged between the intermediary layer and the energy absorbing layer.

Further, in an embodiment of the first aspect of the present invention, the intermediary layer comprises a plurality of elements (e.g. rolling elements) that are configured to rotate on impact or that embed into the energy absorbing layer on impact. Particularly, said elements are formed by the spacers. Alternatively said elements are separate elements with respect to the spacers.

Furthermore, in an embodiment of the first aspect of the present invention, the outer protective layer is formed out of a stiff material. Particularly the material is stiffer than a material forming the energy absorbing layer. Particularly, said material of the outer protective layer comprises or is one of the following materials: a thermoplastic material, a metal.

Further, according to an embodiment of the first aspect of the present invention, the respective spacer is formed by a dot-like, or post-like protrusion of the outer surface of the inner layer or of the inner surface of the outer protective layer. This means that the respective spacer is rather localized along the surfaces of the outer protective layer / inner layer. However, in an alternative embodiment of the first aspect of the present invention, the respective spacer can also be designed as elongated curved rib, wherein the length of the rib/spacer in a longitudinal direction of the respective rib/spacer is significantly larger than a diameter of the rib in a plane extending orthogonal to the longitudinal direction.

Furthermore, the respective spacer (e.g. dot-like / post-like spacers or rib-shaped spacers) can taper.

Particularly in case the respective spacer is formed by a separate body, the respective spacer is formed as one of: a cylinder, a cone, a pyramid, a cuboid, a truncated cone. Other shapes are also conceivable. Particularly, the respective spacer comprises a face side having a circumferential rounded edge to provide a rounded contact surface for the opposing layer.

Furthermore, in an embodiment of the first aspect of the present invention, the respective spacer is configured to be embedded into an opposing layer of the helmet on impact (opposing layer can be inner layer, particularly intermediary layer or energy absorbing layer).

According to yet another embodiment of the first aspect of the present invention, the inner surface of the outer protective layer is corrugated so that the inner surface forms a plurality of surface areas comprising a spherical curvature and being concentric with respect to an opposing surface area of the inner layer. In other words, varying the standoff allows moving (particularly sliding) of an undulated surface onto a corresponding spherical shape.

Furthermore, a second aspect of the present invention relates to a helmet, particularly a cycling helmet, particularly a helmet with reduced geometrical locking. This second aspect will be described in the following.

An objective of the second aspect of the present invention is to provide a helmet with enhanced safety features that can be manufactured particularly cost efficient.

Particularly, the second aspect of the present invention aims to improve a helmet that comprises an outer protective layer that is movable with respect to an inner layer under an impact force acting on the protective layer that comprises a tangential force component along an outer surface of the protective layer. A particular objective of the helmet according to the second aspect of the present invention is to prevent geometric locking/catching of individual sections of the outer protective layer of the helmet when these sections move under a tangential impact force. In single shell helmets (i.e., helmets comprising a single monolithic outer protective layer), the inner surface of the whole protective layer needs to be hemispherical to be able to move on an opposing hemispherical outer surface of the inner layer without interference.

These objectives are achieved by the device having the features of claim 26.

Embodiments of this second aspect of the present invention are stated in the corresponding dependent claims and are described in the following.

According to claim 26, a helmet is disclosed comprising:

- an inner layer comprising an outer surface, and

- an outer protective layer arranged on the inner layer, the outer layer comprising at least two sections, wherein each section comprises an inner surface facing an outer surface portion of the inner layer, wherein upon exposure to an impact force having at least a tangential force component along an outer surface of the respective section, the respective section is configured to move relative to the opposing outer surface portion of the inner layer and separate from the at least one other section (and particularly from the inner layer), wherein the inner surface of each section comprises at least one region that comprises a spherical curvature and is concentric to the opposing outer surface portion of the inner layer.

Preferably, a major part of the inner surface of each section (in particular, apart from an edge region of the respective section or recesses formed in the inner surface of the respective section) is spherically curved throughout and substantially concentric with the opposing outer surface portion of the inner layer.

Likewise, preferably, the corresponding outer surface portion of the inner layer is spherically curved as well to allow moving (particularly sliding / rolling) of the respective section on the underlying outer surface portion of the inner layer in response to a tangential impact. According to an embodiment of the second aspect of the present invention, said at least one region of the inner surface of the respective section corresponds to the whole inner surface of the respective section. Alternatively, said at least one region of the inner surface of the respective section corresponds to at least 5%, particularly at least 10%, particularly at least 20%, particularly at least 30%, particularly at least 40%, particularly at least 50%, particularly at least 60%, particularly at least 70%, particularly at least 80%, particularly at least 90% of the total area of the inner surface of the respective section.

Further, according to an embodiment of the second aspect of the present invention, the inner surface comprises a plurality of disconnected regions, each region comprising a spherical curvature and being concentric to the opposing outer surface portion of the inner layer, wherein particularly a transition region between each two neighbouring regions comprises a non-spherical curvature. Particularly, said disconnected regions of the inner surface of the respective section correspond to at least 5%, particularly at least 10%, particularly at least 20%, particularly at least 30%, particularly at least 40%, particularly at least 50%, particularly at least 60%, particularly at least 70%, particularly at least 80%, particularly at least 90% of the total area of the inner surface of the respective section.

Further, according to an embodiment of the second aspect of the present invention, each section of the outer protective layer comprises an edge region.

Particularly, in an embodiment of the second aspect of the present invention, the edge regions of the at least two sections are connected to one another to form a smooth transition region between the at least two sections of the outer protective layer to prevent geometric locking / catching of the respective section when the respective section moves relative to the opposing outer surface portion of the inner layer under said impact force and separates from the at least one other section. However, according to an embodiment, the sections of the outer protective layer can also be formed by separate panels that can be arranged adjacent to one another or can be spaced apart from one another.

According to an embodiment of the second aspect of the present invention, the edge regions of the at least two sections are integrally connected to one another. Particularly other suitable connection means can also be used such as a positive connection, a force-locked connection, a substance-to-substance bond, a welding connection / weld seam. Furthermore, the respective edge region can be bonded, particularly welded, to the inner layer or an energy absorbing layer. The inner layer can be or comprise an energy absorbing layer (this also applies to the other embodiments).

Furthermore, according to yet another embodiment of the second aspect of the present invention, the respective edge region is configured to yield under the impact force to prevent catching of the respective section when the respective section moves relative to the opposing outer surface portion of the inner layer under said impact force and separates from the at least one other section. Particularly, the respective section moves relative to the opposing outer surface portion and separates from the at least one other section if an energy is introduced by the impact force that exceeds an energy threshold of at least 2.5 Joule.

Particularly, the edge region of each section needs to yield slightly in reverse proportion to the level of a curvature of the transition region between the at least two sections - i.e., more smoothing, less yielding needed.

Furthermore, in an embodiment of the second aspect of the present invention, to provide yielding of the respective edge region, the respective edge region comprises a thickness that is smaller than a thickness of an adjacent central portion of the respective section.

Further, according to an embodiment of the second aspect of the present invention, to provide yielding of the respective edge region, the respective edge region is formed out of material that is softer than a material of an adjacent central portion of the respective section.

Further, in an embodiment of the second aspect of the present invention, to provide yielding of the respective edge region, the respective edge region comprises recesses and/or perforations.

Particularly, the inner layer can be or can comprise an energy-absorbing layer that is configured to dissipate and absorb mechanical forces acting on the helmet, in order to protect the head of a person wearing the helmet. As such, the energy-absorbing layer may form the innermost layer of the helmet that is arranged closest to the head. The energy-absorbing layer particularly comprises a comparably soft material, i.e. softer than the material of the intermediate layer and/or the outer protective layer. The energy-absorbing layer may comprise expanded polystyrene (particularly EPS, i.e., expanded polystyrene) or similar compounds or foams that provide similar properties as e.g., EPS.

It is noted that on a side facing the head of a person wearing the helmet, a lining layer or lining elements may be arranged for adjusting the fit of the helmet and or for reasons of comfort.

The energy-absorbing layer may comprise a plurality of sub layers. Such sub layers can be stacked on top of one another and/or may be arranged side by side laterally.

Similarly, the outer protective layer and/or its individual sections (and also other layers of the helmet) may comprise multiple sub layers that can be stacked on top of another and/or can be arranged side by side laterally.

Particularly, the outer protective layer (particularly its sections) can comprise a different material than the inner layer / energy-absorbing layer.

Particularly, the inner layer can comprise an intermediate layer of the helmet, the intermediate layer can be arranged between the energy-absorbing layer and the outer protective layer.

Particularly, in an embodiment of the second aspect of the present invention, the intermediate layer is the stiffest and the hardest layer of the helmet.

Furthermore, the inner layer can be a reactive layer comprising spheres so that the outer protective layer can move on the rolling spheres with respect to the inner layer upon impact.

According to another embodiment of the second aspect of the invention, the intermediate layer is formed and designed to provide a low-friction surface on which the outer protective layer may move in case the outer protective layer is exposed to the impact force.

Particularly, the low-friction is achieved by forming the intermediate layer harder than the outer protective layer / sections of the outer protective layer.

The intermediate layer may comprise or consist of a polycarbonate.

The intermediate layer may be connected to the energy-absorbing layer by means of a substance-to-substance bond, e.g., it may be glued to the energy-absorbing layer, such as to be permanently attached to the energy-absorbing layer. Particularly, the intermediate layer is configured to stay attached to the energy-absorbing layer even upon an impact force that causes the deformation of the outer protective layer.

Particularly, the outer protective layer is arranged on a side of the intermediate layer that faces away from the energy-absorbing layer (here the intermediate layer forms the outer surface portions on which the sections of the protective layer are arranged). The outer protective layer may form the outmost layer of the helmet.

The exposure impact force may happen during an accident where the head of the person protected by the helmet hits an object such that a tangential force component causes a shear stress on the helmet. In order to reduce the shear stress, the section(s) of the outer protective layer affected by the impact is/are configured to be released with respect to the inner layer (particularly with respect to the intermediate layer), and to move relative to the inner layer according to the tangential force acting on the respective section of the outer protective layer.

Particularly, the outer protective layer (or its sections) may be connected to the inner layer (e.g., energy-absorbing layer) or to the intermediate layer by means of connectors or a substance-to-substance bond or other suitable means.

Particularly, the connectors fail or deform upon exposure to the impact force so as to allow the outer protective layer to plastically deform relative to the energy-absorbing layer.

Further, according to an embodiment of the second aspect of the present invention, upon exposure to an impact force having at least a tangential force component along an outer surface of the respective section, the respective section is configured to move a moving distance relative to the opposing outer surface portion of the inner layer, and wherein the respective section comprises a width in the direction of the moving distance as well as an overhang length extending at an angle to the direction of the moving distance, wherein the sum of said width and said overhang length is preferably larger than the moving distance.

Furthermore, also the following embodiments apply to both aspects of the present invention. Particularly, in a preferred embodiment, the outer protective layer is configured to fracture under said impact force to allow relative movement of the outer protective layer (or fragments thereof) and the outer surface of the inner layer.

Further, in a preferred embodiment, the outer protective layer is configured to mechanically unlock from the inner layer, particularly in a non-destructive fashion, e.g. by releasing a friction locking and/or a positive connection between the protective layer and the inner layer.

Further, in a preferred embodiment, the outer protective layer is connected via an adhesive to the inner layer and is configured to separate, particularly completely separate (i.e. move away) from the inner layer under said impact force.

Furthermore, exemplary embodiments are described below in conjunction with the Figures. Further, the features disclosed herein in conjunction with a specific aspect of the present invention can be combined with embodiments of other aspects of the present invention in every sensible way.

In the following, embodiments of the present invention according to the first and second aspect of the present invention as well as further features and advantages of the present invention according to the first and second aspect shall be described with reference to the Figures. The Figures are appended to the claims and are accompanied by text explaining individual features of the shown embodiments and aspects of the present invention. Each individual feature shown in the Figures and/or mentioned in said text of the Figures may be incorporated (also in an isolated fashion) into a claim relating to the device according to the present invention, wherein

Fig. 1 shows an embodiment of a helmet according to the first aspect of the present invention comprising spacers integrally connected to an outer protective layer of the helmet and facing an inner layer of the helmet, the inner layer comprising an intermediary layer suspended above an energy absorbing layer;

Fig. 2 shows an embodiment of a helmet according to the first aspect of the present invention comprising spacers integrally connected to an outer protective layer of the helmet and facing an inner layer of the helmet, the inner layer comprising an intermediary layer arranged and fixed on an energy absorbing layer;

Fig. 3 shows a modification of the embodiment of Fig. 2, wherein the respective spacer comprises a protrusion protruding from the energy absorbing layer and being covered by a portion of the intermediary layer protruding from the intermediary layer towards the outer protective layer;

Fig. 4 (A) to (F) show various possible shapes of separate spacers according to embodiments of the first aspect of the present invention,

Fig. 5 shows an embodiment of a helmet according to the first aspect of the present invention comprising separate spacers arranged in a gap between an outer protective layer of the helmet and an inner layer of the helmet;

Fig. 6 shows an embodiment of a helmet according to the first aspect of the present invention comprising spacers of two different length being integrally connected to a corrugated outer protective layer;

Fig. 7 shows an embodiment of a helmet according to the first aspect of the present invention wherein the spacers are protrusions of an inner layer and comprise a dot-like footprint;

Fig. 8 shows an alternative embodiment according to the first aspect, wherein the spacers are elongate structures;

Fig. 9 shows an embodiment of a helmet according to the first aspect of the present invention, wherein the spacers are configured to become embedded into a surface of the inner layer upon impact;

Fig. 10 demonstrates forces acting on a helmet worn by a person. Particularly the tangential friction force (also denoted as impact force herein) results in a dangerous rotation introduced into the helmet and head of the person that can cause severe injury; Fig. 11 shows an outer protective layer of a single shell helmet (A) moving with respect to an inner layer (B). Also shown (C) is an outer protective layer that comprises an inner surface that is not spherical and concentric with respect to the underlying outer surface of an inner layer of the helmet causing a severe deterioration of the ability of the protective layer to move with respect to the inner layer under a tangential force (cf. Fig. 10);

Fig. 12 shows a schematic cross-sectional view of an embodiment of a helmet according to the present invention before an impact (A) and after an impact causing one of the sections of the outer protective layer to move with respect to the inner layer (B) to prevent the introduction of excessive rotation into the head of the person wearing the helmet under the tangential impact;

Fig. 13 shows a tangential impact on the outer protective layer (or a section thereof) and a movement of this layer / section along a moving distance during the impact;

Fig. 14 shows a schematic illustration of a width and an overhang length of a section of the outer protective layer; and

Fig. 15 indicates the relation between overhang length and angle Q of the overhang length.

Fig. 1 shows a schematic cross-section of an embodiment of a helmet 1 according to the first aspect of the present invention. The helmet 1 comprises an inner layer 3 comprising an outer surface 31a, and an outer protective layer 2 arranged on the inner layer 3, the outer protective layer 2 comprising an inner surface 2a facing the outer surface 31a of the inner layer 3, wherein under an impact force F having at least a tangential force component along an outer surface of the outer protective layer 2, the outer protective layer 2 is configured to move relative to the opposing outer surface 31a of the inner layer 3. Particularly, the inner layer 3 comprises an energy absorbing layer 30 and an intermediary layer 31 arranged between the outer protective layer 2 and the energy absorbing layer 30. Particularly, the intermediary layer 31 can be suspended above the energy absorbing layer (e.g. using rigid mounting structures and / or a liquid layer arranged between the intermediary layer 31 and the energy absorbing layer 30. Further, according to the invention, the inner surface 2a of the outer protective layer 2 is separated from the outer surface 31a of the inner layer 3 (here of the intermediary layer 31) by a plurality of spacers 4 for reducing a mechanical locking between the inner layer 3 and the outer protective layer 2 upon said relative movement M of the outer protective layer 2 with respect to the inner layer 3 / intermediary layer 31. Due to the standoff provided by the spacers 4, the risk of a mechanical locking between the two layers 2 and 31 is significantly reduced. Particularly, the spacers 4 are integrally formed with the outer protective layer 2 and can taper towards the opposing inner layer 3 / intermediary layer.

Fig. 2 shows a schematic cross-section of a modification of the embodiment shown in Fig. 1, wherein in contrast to Fig. 2, the intermediary layer 31 is bonded to the energy absorbing layer 30.

Fig. 3 shows a schematic cross-section of a further embodiment of a helmet according to the first aspect of the present invention, wherein here, in contrast to Figs. 1 and 2, the respective spacer is integrally formed with the inner layer 3, wherein the respective spacer 4 is comprises a protrusion of the energy absorbing layer being covered by a portion of the intermediary layer. Particularly, the respective spacer 4 tapers towards the outer protective layer 2.

Fig. 4 shows cross-sectional views of possible spacer shapes. According to Fig. 4, the respective spacer 4 can comprise a triangular cross-section or can be a pyramid or a cone (A). Further, the respective spacer 4 can be formed as a truncated cone as shown in (B). Furthermore the respective spacer 4 can be formed as cuboid as shown in (C) to (F) or can comprise a rectangular cross section. Further, as indicated in (C) to (F), the respective spacer 4 can comprise a face side 4a for making contact with an opposing layer, wherein the face side 4a can have a rounded edge portion 4b, particularly a circumferential rounded edge 4b.

The shapes shown in Fig. 4 can also apply to spacers 4 being integrally formed to one of the layers 2, 3, 31 described herein. Furthermore, the respective elongated shaper 4 (cf. Fig.8) can comprise a cross-section that corresponds to one of the shapes shown in Fig. 4.

Fig. 5 shows an embodiment of a helmet 1 according to the first aspect of the present invention comprising separate spacers 4 (having e.g. a rectangular cross section, respectively) arranged in a gap between an outer protective layer 2 of the helmet 1 and an inner layer 3 of the helmet 1. Particularly, the outer protective layer 2 can comprise protrusions 200 protruding from the inner surface 2a of the outer protective layer 2, wherein the respective protrusion 200 extends into a gap between two neighbouring spacers 4.

Fig. 6 shows an embodiment of a helmet 1 according to the first aspect of the present invention comprising spacers 4, 40 of two different lengths being integrally connected to a corrugated outer protective layer 2. Particularly, the inner surface 2a of the outer protective layer 2 is corrugated so that the inner surface 2a forms a plurality of surface areas 20 being spaced apart from one another and comprising a spherical curvature and being concentric with respect to an opposing surface area 31a of the inner layer 3.

Fig. 7 shows an embodiment of a helmet 1 according to the first aspect of the present invention wherein the spacers 4 are protrusions of an inner layer 3 and comprise a dot like footprint.

In contrast thereto, Fig. 8 shows an illustration of an alternative embodiment, wherein the spacers 4 are formed as elongated structures. Particularly, the spacers can be formed as elongated curved ribs 4 that can be integrally formed with the inner layer 3. Preferably, the ribs 4 extend along a longitudinal direction L of the helmet 1.

Finally, Fig. 9 shows an embodiment of a helmet 1 according to the first aspect of the present invention, wherein the respective spacer 4 is formed as a separate body 4 and arranged between the outer protective layer 2 and the inner layer 3 (e.g. energy absorbing layer). Particularly, the respective spacer 4 is configured to be embedded into the inner layer 3 on impact. Particularly, the respective spacer 4 is configured to be embedded into the inner layer 3 with its larger face side ahead.

Particularly, the first aspect of the present invention relates to the use of spacers between two layers of a helmet. The spacers described herein can also be combined in a suitable manner, i.e. , a combination of different spacer shapes can be used between the outer protective layer and the inner layer.

It is a particular object of the second aspect of the present invention to prevent geometric locking of an outer protective layer B2 of a helmet B1 under a tangential impact FT as shown in Fig. 10. In case such a locking or catching of the protective layer B2 occurs, the latter is prevented from moving without interference with respect to an inner layer B3 of the helmet B1 causing a rotation of the helmet B1 and head of the person wearing the helmet B1 which bears the risk of severe injury.

As shown in Fig. 11, in case of a single shell helmet B1 comprising an essentially hemispherical outer protective layer B2 arranged on an inner layer B3 of the helmet B1, the necessary movement upon tangential impact (as shown in Fig. 11(A)) can be significantly hampered in case the single outer shell B2 does not comprise a sufficient spherical curvature and concentricity with respect to the outer surface of the inner layer B3, as schematically depicted in Fig. 11(C).

Fig. 12 shows an embodiment of a helmet 1 according to the second aspect of the present invention, wherein each section / panel B21 , B22 of the outer protective layer B2 can separate from adjacent ones during an impact. Particularly, each section B21, B22 is spherically curved and concentric regarding an associated outer surface portion B31, B32 of the inner layer B3 on which the respective section/panel B21,

B22 is arranged. Preferably a transition region B4 formed between edge regions B210, B220 of the sections B21, B22 is sufficiently smooth to prevent catching (cf. detail (C) of Fig. 12). Thus, due to the fact that each section B21, B22 now satisfies the conditions of a spherical curvature and concentricity with respect to the surface portion B31, B32 beneath, an unhindered compensation movement is possible for each section / panel B21, B22. For simplicity, Fig. 12 only shows two sections B21, B22. However, generally, in the framework of the present invention a plurality of such sections can be provided, particularly more than two such sections.

Further, the edge region B210, B220 of each section / panel B21, B22 is preferably able to yield slightly in reverse proportion to the level of smoothing (or in proportion to the level of curvature of the transition region B4) between the two spherically curved sections B21, B22 - more smoothing (less curvature), less yielding needed (yielding could come from thinner material choice of edge regions B210, B220, weaker material of edge regions B210, B220, and/or recesses or perforations formed into the sections B21, B22, of course, the measures to achieve said yielding can be combined).

Preferably, in addition to the above considerations, the sections / panels B21, B22 cover a sufficiently extended area beyond where impact may happen. As the sections B21, B22 move, the inner layer B3 (outer surface portions B31, B32) may become exposed, if this exposed surface B31, B32 directly contacts the impacted sections B21, B22 of the outer protective layer B2, the relative-movement systems can be rendered less effective.

Furthermore, Fig. 13 illustrates a tangential impact on the outer protective layer B2 during which the outer protective layer B2 or a section B22 thereof travels a moving distance d in a moving direction. Also shown is an intermediate layer B20 comprising spheres to improve moving of the layer B2 / section B22 on the inner layer B3.

Further, Fig. 14 shows a schematic illustration of a section B22 of the outer protective layer B2 comprising a width w in the direction of the moving distance d and an overhang length I extending at an angle Q to the direction of the moving distance d

Fig. 15 indicates the relation between overhang length I and angle Q of the overhang length I. Particularly geometric locking is caused by negative draft angles that can be addressed in particular by having essentially perfectly spherical layers, but also by utilizing the parabolic relationship between the angle Q and the overhang length I shown in Fig. 15. As an example, in order to have good moving properties of the opposing layers B2, B3 (or B21, B22, B3) one has an overhang length being equal or smaller to 10mm in case the angle Q equals 45° and about 1 mm in case the angle Q equals 90°.

Furthermore, with respect to Fig. 14, to ensure effective movement between the outer protective layer B2 (or sections B21 , B22 thereof) and the inner layer B3 (intermediate layer B20), the sum of the width w and the overhang length I is preferably larger than the moving distance d.