Patent Publication Number: US-2023157399-A1

Title: Sports helmet

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit and priority of German Patent Application No. 102021130533.0 filed on Nov. 22, 2021 and German Utility Model Application No. 202022100276.2 filed on Jan. 19, 2022. The entire disclosures of the above applications are incorporated herein by reference. 
     FIELD 
     The invention relates to a sports helmet, in particular a bicycle helmet, a motorcycle helmet, a riding helmet or a ski helmet, having a shock-absorbing helmet shell and a strap fixing system for fixing the helmet shell to the head of a user. 
     BACKGROUND OF THE INVENTION 
     A sports helmet serves to protect the user against head injuries, particularly in the event of a fall. For this purpose, the sports helmet includes a helmet shell having a generally concave shaped inner side facing the user&#39;s head and a generally convex shaped outer side facing away from the user&#39;s head. In the event of an impact, the helmet shell should absorb to the greatest extent possible the kinetic energy acting on the sports helmet through inelastic and/or elastic deformation. Furthermore, a strap fixating system may be mounted at the helmet shell, by means of which the helmet shell may be fixed to the user&#39;s head and which may comprise, for example, a plurality of neck and chin straps. 
     In the present context, the term “sports helmet” is to be understood broadly and refers not only to helmets designed exclusively or specifically for the practice of a sport (such as a riding helmet or a ski helmet), but may also be used, for example, for a recreational activity (e.g. as a bicycle helmet or motorcycle helmet). 
     Such sports helmets in different variations are known. In general, a distinction may be made between sports helmets having rigid chin bars (e.g. for mountain-biking sport) and sports helmets without chin bars. In particular, sports helmets without chin bars are characterized by a high level of wearing comfort compared to sports helmets with rigid chin bars due to their open construction and relatively low weight. Sports helmets without chin bars are also far more widespread than sports helmets with rigid chin bars. However, sports helmets without chin bars do not offer comparable protection of a user&#39;s facial area. Thus, for certain impacts, in particular a user&#39;s chin region and/or regions of the cheekbone may be exposed to injury because a sports helmet without a chin bar does not specifically protect these regions. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a sports helmet not having a rigid chin bar which provides protection at least for a portion of the user&#39;s face. 
     This object is achieved by a sports helmet having at least the features of claim  1 . 
     The sports helmet according to the invention comprises a shock-absorbing helmet shell and a strap fixing system for fixing the helmet shell to a user&#39;s head. The sports helmet comprises an airbag device comprising at least one gas generator and at least one airbag which is inflatable by gas, wherein the at least one airbag is configured to protect at least a portion of the user&#39;s face in an inflated state. 
     The invention is based on the following consideration: known sports helmets already offer good protection of the user&#39;s head. However, in some falls, the facial region of the user is problematic. However, protection of the facial region by rigid devices such as for example a chin bar, a face visor or the like is not desired by many users, since a sports helmet should offer as free a field of vision as possible and should be as easy as possible to put on. Aesthetic considerations also play a role for many users in deciding whether or in which situations even to wear a sports helmet, which may ultimately be at the expense of safety. In equestrian sports, for example, it is absolutely unusual to wear a riding helmet with a chin bar. However, in order to nevertheless protect the face region or at least parts of the user&#39;s face region even with sports helmets not having a rigid chin bar, the sports helmet may comprise an airbag device. For example, airbags are proven devices in the automotive field to provide a user with added protection in addition to seatbelts and to protect the user from injuries caused by an impact against hard parts, such as a steering wheel or a dashboard. 
     The airbag device of the sports helmet according to the invention may comprise several components. An airbag, which may be configured in particular from a flexible plastic material such as, for example, polyamide, may be held in readiness in a folded state. When a dangerous situation is detected, such as the user falling from a bicycle or a horse, the airbag is filled in a short time (e.g. &lt; 1/10 second) with a gas from the gas generator. In this context, the term “gas” is to be understood broadly and may comprise only a single gas (e.g. nitrogen) or a mixture of gases (e.g. an argon-helium mixture) including air or a gas/air mixture. The gas out of or from the gas generator may in particular come directly from the gas generator (e.g. be stored in the gas generator or be generated in the gas generator from a liquid or solid), or the gas for the airbag may be taken from the ambient air by the gas generator (e.g. by pumping and/or compressing). For this purpose, the gas generator may be fluidly (i.e. flow-technically) connected to the airbag. 
     Thus, the gas generator provides the gas for filling the airbag, wherein the gas generator may be configured, for example, as a cold gas generator or as a pyrotechnic gas generator or as a combination thereof, or as a pump and/or as a compressor. In some embodiments, the gas generator may be realized as a cartridge and/or a pressure accumulator. 
     In the inflated i.e. filled state, the airbag can protect at least a portion of the user&#39;s face depending on its geometric design and arrangement at the helmet shell. In the inflated state, the airbag, due to its arrangement, shape and flexible structure, forms a protective cushion that, in the event of an impact, may come to rest between a region of the user&#39;s face and an object (e.g., the ground). The airbag may cushion an impact and/or ensure a planar distribution of forces so as to mitigate excessive force and/or peak loads in the user&#39;s facial region. For this purpose, it may be sufficient for the airbag to occupy a predetermined shape in the inflated state for only a short period of time (e.g. approximately one or more seconds), but thereafter to slacken. However, the airbag may also be configured to occupy the predetermined form of the inflated state for a longer period of time. 
     In some embodiments, the airbag may be configured to cover a chin region (lower jaw) and/or regions of the user&#39;s cheekbones in the inflated state. In this context, a covering may be understood as a radial envelope of a portion of the user&#39;s head, in particular the face, with the airbag, wherein a clearance between a surface of the face and the airbag in the radial viewing direction remains. In this model, the user&#39;s head is assumed to be substantially spherical. 
     In some embodiments, the airbag may be configured such that in the inflated state at a side facing the user&#39;s face it is modelled to correspond to a human face. For example, the airbag may be configured as a curved shape in the manner of a chin bar and/or as curved cheek portions on either side of the user&#39;s nose. In particular, the airbag may comprise a cutout of a nose region of the user&#39;s face; through such a cutout the shape of the user&#39;s face may be replicated, wherein the airbag in the inflated state may cover with a small clearance the surrounding regions of the face. 
     In some embodiments, the airbag may be formed from a transparent material. A transparent material may be understood to mean a see-through material, i.e. the user can see through the airbag when in the inflated state. This may bring particular advantages when the airbag in the inflated state is in the user&#39;s field of vision. In some embodiments, the airbag in the inflated state may thus cover the user&#39;s entire facial region, wherein the user may see through the transparent material of the airbag and thus perceive the surroundings. 
     In some embodiments, the airbag may be configured to leave out an eye region of the user in the inflated state. Thus, a largely unobstructed field of vision of the user may also be maintained through a cutout of the airbag around the user&#39;s eye region. For this purpose, the region around the eyes of the user may be left free in the inflated state of the airbag, i.e. the region around the user&#39;s eyes is not covered by the airbag in the inflated state. 
     In some embodiments, the gas generator may be arranged in a center-symmetrical position, in particular at an occipital region of the helmet shell. Such a center-symmetrical arrangement may be advantageous, particularly for embodiments of the airbag device having only a single gas generator, in order to achieve a substantially center-symmetrical weight distribution of the airbag device. In the context of the invention, the term center-symmetrical is to be understood as follows: the sports helmet may be divided into a left-half and a right-half by a center plane of symmetry, wherein the center plane of symmetry is perpendicular to a horizontal plane and is oriented in a longitudinal direction of the sports helmet, i.e. includes a longitudinal axis of the sports helmet. 
     In some embodiments, the airbag device may comprise two airbags. The two airbags may cover different regions of the user&#39;s face. Various embodiments of the airbag device having two airbags are explained below. 
     In one such embodiment, the two airbags may be configured to cover a portion of the user&#39;s face starting from a left side and another portion of the user&#39;s face starting from a right side. The two airbags may be arranged respectively at the left side of the sports helmet and at the right side of the sports helmet, for example at side temple regions of the user. 
     The covering of the respective part of the user&#39;s face by the two airbags may take place simultaneously, i.e. the airbag device may thus be configured to fill the two airbags simultaneously with gas. Through this, an undesired transfer of torque to the user&#39;s head due to the filling of the airbags may be prevented, in particular if the two airbags are arranged and aligned center-symmetrically. 
     However, in some embodiments, a slight time-offset may be provided between the inflation of one airbag and the inflation of the other airbag, i.e. one of the two airbags is filled with gas prior in time to the other of the two airbags. In embodiments where the two inflated airbags should cover one another (i.e. overlap), a time-offset filling of the two airbags may prevent the two airbags from meeting and repelling each other during deployment. 
     In some embodiments, the two airbags may be configured to be center-symmetrically arranged in the inflated state and, for example, on impact, to rest against one another so as to form a substantially closed surface that covers a portion of the user&#39;s face. 
     In some embodiments, however, the two airbags may be configured that in the inflated state each of the two airbags crosses a center plane of symmetry of the sports helmet. Through the respective crossing of the center plane of symmetry, which may be defined as described above, the two airbags overlap at least partially either next to one another or one on top of the other (in particular with respect to a front view of the sports helmet). This, for example, may avoid a straight-line dividing plane running between the two inflated airbags along which the two airbags could be spread apart in the event of an impact and could expose a previously covered area of the user&#39;s face. For example, the two airbags may be configured such that, in the inflated state the two airbags engage with each other when the two airbags have crossed the center plane of symmetry. 
     In some embodiments, the airbag device may comprise a single common gas generator for inflating the two airbags. The common gas generator may be fluidly connected to the two airbags via a respective connecting conduit. The common gas generator may be arranged in particular center-symmetrical at the helmet shell. On the one hand, this may have advantages with regard to a weight distribution of the gas generator at the sports helmet as explained above, and, on the other hand, with regard to a noise development arising from an igniting of the gas generator. By a central arrangement of the gas generator, the gas generator may be arranged at a large distance from the user&#39;s ears. 
     In some embodiments, the airbag device may comprise two gas generators, wherein one of the two gas generators is fluidly connected to one of the two airbags and the other of the two gas generators is fluidly connected to the other of the two airbags. When two gas generators are used, they may be configured to be correspondingly smaller, i.e. with a smaller geometric dimension than when a single gas generator is used. Also with regard to a uniform weight distribution, two gas generators may provide advantages over a single gas generator. In addition, the use of two gas generators may also be advantageous with regards to system redundancy. Furthermore, in some embodiments, the airbag device may also comprise a plurality of gas generators. 
     In some such embodiments, one of the two gas generators may be arranged at a left side of the helmet shell and the other of the two gas generators may be arranged at a right side of the helmet shell. This may benefit a center-symmetrical weight distribution of the gas generators. 
     In some embodiments, the two gas generators may be arranged at a respective ear region or at a respective temple region or at a respective lateral neck region (occipital region) of the helmet shell. When the gas generators are arranged in a rear region of the helmet shell and the airbags are however arranged in a front region of the helmet shell, connecting conduits from the respective gas generator to the associated airbag may be provided and may run, for example, along or within the helmet shell. 
     In some embodiments, the helmet shell may comprise an integrated frame structure. For example, the helmet shell may comprise a so-called skeleton made of plastic that is molded over or foamed around so as to form a shock-absorbing helmet body (e.g., using the so-called in-mold method). The frame structure may comprise one or more strips (flexible or rigid), strap(s) and/or anchors, which extend at least partially within the helmet shell. In such embodiments, the at least one gas generator and/or the at least one airbag of the airbag device may be mounted at the integrated frame structure of the helmet shell. For this purpose, suitable access points and/or mechanical interfaces may be provided at the frame structure. Through the mounting at a frame structure of the helmet shell, a particularly stable fit of the gas generator and/or the airbag is ensured in particular regarding reaction forces that may occur when inflating the airbag. The mounting of the airbag device to an integrated frame structure may also be advantageous in a retrofit option. 
     In some embodiments, the airbag device may comprise a sensor device for sensing an impact situation, a trigger for triggering the at least one gas generator, and an energy supply for supplying electrical energy to the sensor device and/or the trigger. 
     The sensor device of the airbag device may comprise, for example, at least one multi-axis acceleration sensor. Furthermore, the sensor device may comprise an evaluation and triggering circuit. The evaluation and triggering circuit may evaluate data from the at least one acceleration sensor. The evaluation and triggering circuit may be configured, for example, to monitor predetermined threshold values and/or to evaluate temporal acceleration profiles and/or acceleration directions which are indicative of an impending impact, for example due to a fall. For example, the evaluation and triggering circuit may compare data from the at least one sensor with at least one predetermined threshold value. If the sensor data exceeds at least one threshold value, the evaluation and triggering circuit may generate a trigger signal, for example, an electronic signal or an igniting current for the trigger. 
     The evaluation and triggering circuit is connected to a trigger of the airbag device, for example, an explosive device or an igniter. The trigger signal generated by the evaluation and triggering circuit triggers a filling of the at least one airbag. This may be done, for example, by igniting a pyrotechnic gas generator, wherein a pyrotechnic material burns and the generated gas fills the at least one airbag. Alternatively, a gas stored under pressure in the gas generator may be released, wherein the released gas fills the at least one airbag via at least one connecting conduit. Since during triggering, for example by igniting an explosive device, a bang or a loud noise is caused, the trigger may be provided with sound damping, for example, a cover made of sound-insulating material. 
     Electrical energy is required to determine and monitor the sensor signals and/or to activate the trigger. For this purpose, the airbag device comprises an electrical energy supply which may be configured as a battery and/or an accumulator. In some embodiments, the accumulator may be rechargeable in particular via a solar cell, which is arranged for example at an outer surface of the helmet shell. As an alternative to electrical activation, activation of the trigger may also take place mechanically, for example via a pressure switch. 
     In some embodiments, the at least one gas generator, the at least one airbag, the sensor device, the trigger and the energy supply may form a modular unit. By way of the modular unit, the airbag device may be retrofitted, in particular, also for existing sports helmets. For this purpose, an arrangement of the modular unit may in particular be provided at the ear region, which for many sports helmets provides a suitable free space of the helmet shell. In such embodiments, the gas generator and/or the associated trigger may be arranged below the user&#39;s ear. The modular unit may be mounted at the helmet shell, for example, by way of clip connectors or screw solutions. 
     In such an embodiment, the modular unit may be detachably, in particular replaceably, mounted at the helmet shell. The mounting of the modular unit may be provided for example at an outer edge of the helmet shell, i.e. at a transition between an inner side and an outer side of the helmet shell. A mechanical interface for mounting the modular unit may be configured at the helmet shell, for example, as a type of anchor. Thus, the modular unit may easily be selectively retrofitted. 
     In some embodiments, the sports helmet may be configured without a rigid chin bar. It is particularly advantageous if a sports helmet of the widely used type not having a rigid chin bar is given increased protection of the user&#39;s facial region as a result of the airbag device according to the invention. 
     In some embodiments, the helmet shell may comprise a helmet body having padding on the inner side and/or an outer shell on the outer side. The outer shell may also perform a protective function (e.g. absorbing shock or reducing the coefficient of friction for a sliding of the helmet along a rough surface), or it may fulfil substantially just a decorative function. The outer shell may comprise a shell, for example of acrylonitrile butadiene styrene (ABS), or comprise a film, for example of polyvinyl chloride (PVC), polyethylene terephthalate (PET) or a polycarbonate (PC). 
     In some embodiments, the helmet body may be made of a hard foam, in particular from an expanded polystyrene hard foam (EPS). In other embodiments, a part of the helmet shell, in particular the helmet body, may be manufactured by 3D-printing. In other embodiments, the helmet shell may be formed by a so-called injection-molding mesh. 
     In some embodiments, the strap fixing system may be mounted to an occipital region of the helmet shell and to lateral temple regions of the helmet shell. In some embodiments, the strap fixing system may comprise a length adjustment device at the neck region of the user. 
     In some embodiments, the helmet shell may comprise a plurality of ventilation openings distributed over the surface of the helmet shell. 
    
    
     
       DRAWINGS 
       The invention is described below by way of examples of embodiments with reference to the drawings in which: 
         FIG.  1    shows a perspective view of a bicycle helmet; 
         FIG.  2    shows a front view of an airbag in an inflated state; 
         FIG.  3    shows a front view of a further embodiment of an airbag in an inflated state; 
         FIG.  4    shows a front view of a further embodiment of an airbag in an inflated state; 
         FIG.  5    shows a front view of two airbags in an inflated state; 
         FIG.  6    shows a front view of a bicycle helmet with two overlapping airbags in an inflated state; 
         FIG.  7    shows a schematic overhead view of two overlapping airbags; 
         FIG.  8    shows a front view of a further embodiment of a bicycle helmet with two overlapping airbags in an inflated state; 
         FIG.  9    shows an overhead view of a bicycle helmet; and 
         FIG.  10    shows a perspective view of a bicycle helmet with a modular unit of an airbag device. 
     
    
    
     DESCRIPTION OF THE INVENTIONS 
       FIG.  1    shows a sports helmet in the form of a bicycle helmet  10  having a shock-absorbing helmet shell  12  and a strap fixing system  14  for fixing the helmet shell  12  to the head of a user (not shown). The helmet shell  12  may comprise a helmet body comprising a padding on the inner side and/or a thin outer shell on the outer side. The helmet body of the helmet shell  12  may be made of a hard foam, in particular an expanded polystyrene hard foam (EPS). The strap fixing system  14  may be mounted at a neck region  40  of the helmet shell  12  and at the lateral temple regions  42  of the helmet shell  12 . In some embodiments, the strap fixing system  14  at the neck region  40  of the user may comprise a ring section with a length adjustment device (not shown). The helmet shell  12  may comprise a plurality of ventilation openings  13  distributed over the surface of the helmet shell  12 . 
     The bicycle helmet  10  comprises an airbag device  16 , wherein the airbag device  16  comprises at least one gas generator  18  and at least one airbag  20  inflatable by gas from the gas generator  18 . The gas generator  18  and the airbag  20  may be arranged in close proximity to each other at the temple region  42  of the bicycle helmet  10  ( FIG.  1   ). In some embodiments, the gas generator  18  and the airbag  20  may also be spatially separated, arranged at any location on the bicycle helmet  10  and fluidly connected via a respective connecting conduit. For example, the gas generator  18 , or a plurality of gas generators  18 , may be arranged at a front end, i.e. at a forehead region  44 , at an upper head region  50  or at an occipital region  38  of the bicycle helmet  10 . To reduce a moment of inertia of the gas generator  18  resulting from a distance to a pivotal point, for example the neck of the user, an arrangement of the gas generator  18  in particular at the neck region  40  may be provided. 
     The airbag  20  is schematically shown in  FIG.  1    in a non-inflated state, i.e. the airbag  20  is not filled with gas and is arranged in a space-saving manner, for example folded, in a housing, a cover or a suitable storage device at the bicycle helmet  10 , in particular at the helmet shell  12 . The airbag  20  may be filled with gas from the gas generator  18  in a short time so as to occupy an inflated state and in the inflated state to occupy a predetermined shape. The airbag  20  is configured so that in the inflated state, at least a portion of the user&#39;s face  30  is covered (see e.g.  FIGS.  2  to  4   ) and thus offers protection against a frontal impact. In order to achieve this protection, the airbag  20  may be mounted in a predetermined orientation, for example, at one of the lateral temple regions  42  or at the forehead region  44  of the bicycle helmet  10 , in particular at the helmet shell  12 . The respective airbag  20  may comprise a mounting end with which the airbag  20  is mounted at the helmet shell  12  in a predetermined orientation. The respective airbag  20  may further comprise at least one free end which moves along the user&#39;s face  30  by the inflation of the airbag  20  so that the inflated airbag  20  covers the face  30 . Additionally, in particular during a first phase of deployment, the airbag  20  may move at least partially along a forward direction, i.e. along a longitudinal axis of the bicycle helmet  10 . Optionally, in the inflated state, the airbag  20  at a side facing the user&#39;s face  30  may be modeled (e.g. curved) according to a human face shape, so as to cover with a closely contoured shape the user&#39;s face  30 . 
       FIG.  2    shows in a schematic representation a front view of an airbag  20  in an inflated state. For better orientation, a user&#39;s face  30  is also shown schematically. For greater clarity, the bicycle helmet  10  is not shown in  FIG.  2    (and correspondingly also not shown in  FIGS.  3 ,  4  and  5   ). However, it is understood that the airbag  20  is arranged at a suitable position of the helmet shell  12  of the bicycle helmet  10 , as described above. In the exemplary embodiment according to  FIG.  2   , the airbag  20  covers at least a portion of the user&#39;s face  30 . In particular, the airbag  20  covers a chin region  32  and a left and right cheekbone region  34  of the user&#39;s face  30 . The airbag  20  may include a cutout  58  of a nose region  46  of the user&#39;s face  30 . By way of the cutout  58 , the shape of the user&#39;s face may be replicated, and the airbag  20  in the inflated state may cover with a small clearance the surrounding regions of the face  30 . The outline of the cutout  58  is closed at three sides and open only at the top (for the bridge of the nose). 
       FIG.  3    shows a further embodiment of an airbag  20  in an inflated state. Compared to the embodiment of  FIG.  2   , the airbag  20  covers in particular the chin region  32  of a user&#39;s face  30  and thus substantially fulfills the function of a chin bar. The chin region  32  (lower jaw) may be particularly vulnerable in the event of the user having a fall. The embodiment of the airbag  20  shown in  FIG.  3    may protect the chin region  32  of the user, but has a simpler geometric structure than, for example, the embodiment of  FIG.  2    described above. In the inflated state, the airbag  20  may be configured as a convexly curved, substantially rectangular surface. Alternatively, the airbag  20  may be constructed to be tubular in shape, replicating a chin bar. 
       FIG.  4    shows a further embodiment of an airbag  20  in an inflated state. In this embodiment, the airbag  20  covers almost the entire face  30  of the user, wherein only an eye region  36  is not covered. In addition to the above described chin region  32  and cheekbone regions  34 , the airbag  20  also covers a forehead region  44  and lateral temple regions  42  of the user&#39;s face  30 . Only the eye region  36  of the face  30  is not covered by the airbag  20  due to a cutout  60  of the airbag  20 , i.e. the eye region  36  is left free. This embodiment has the advantage that, on the one hand, almost all regions of the face  30  are covered by the airbag  20  and, for example in the event of a fall, are thus protected. On the other hand, due to the cutout  60  of the airbag  20  it is still possible for the user to orient himself even when the airbag  20  is inflated, since a user&#39;s minimal field of vision is substantially kept free by the airbag  20 . In this context, the term “substantially” means that edge regions of the field of vision may be covered by the airbag  20  in the inflated state. 
     In an alternative embodiment to the embodiment described in  FIG.  4   , the cutout  58  of the airbag  20  may also be omitted, i.e. the airbag  20  covers the entire user&#39;s face  30 . In this case in particular, it is advantageous if the airbag  20  is configured entirely or partially from a transparent material. This still makes it possible for the user to orient himself even when the airbag  20  is in the inflated state, since he can see through the transparent material of the airbag  20 . In the other described embodiments, a transparent design of the airbag  20  is also possible. Alternatively to such a transparent design, in the various embodiments it may also be provided for that the airbag  20  slackens again after inflation (for example, after about one second), for example as a result of specifically introduced pressure-reducing openings. 
     The airbags  20  shown in  FIGS.  2  to  4    may be configured as a single-piece and may be mounted, for example, at one of the temple regions  42  of the helmet shell  12 . Alternatively, the covering of the user&#39;s face  30  shown in  FIGS.  2  to  4    however, may be accomplished also by two complementary airbags  20 . In the following, embodiments of an airbag device  18  comprising two airbags  20  are described. 
       FIG.  5    shows a front view of two airbags  20  in an inflated state, wherein the two airbags  20  are configured to cover a portion of the user&#39;s face  30  starting from a left side  51  and another portion of the user&#39;s face  30  starting from a right side  52 . The left side  51  and the right side  52  are thus defined, as described above, by the center plane of symmetry E, which centrally divides in a vertical direction the bicycle helmet  10  (in the representation according to  FIG.  5   , perpendicular to the plane of the paper). The two airbags  20  may be configured such that in the inflated state they meet in the center plane of symmetry E and cover at least the chin region  32  and the cheekbone regions  34  of the user&#39;s face  30 , wherein the nose region  46  is left out by a respective cutout  58  of the respective airbag  20 . The airbags  20  may also only cover the chin region  32 . This corresponds to the above described embodiments in  FIG.  2    and in  FIG.  3   , wherein the airbag  20  is shown there as a single-piece. 
     Through the meeting of the two airbags  20 , a gap  54  may be formed at the center plane of symmetry E. However, the airbags  20  may be configured so as to strongly press against each other at the center plane of symmetry E that the gap  54  is closed by the forces acting substantially perpendicular to the center plane of symmetry E. Thus, a region of the face  30  where the two airbags  20  meet, in particular the chin region  32 , may also be completely covered by the two airbags  20 . 
       FIG.  6    shows a front view of a further embodiment of the bicycle helmet  10  according to the invention. The bicycle helmet  10  comprises an airbag device  16  (not shown) with two airbags  20  overlapping in the inflated state. In an inflated state, each of the two airbags  20  crosses the center plane of symmetry E of the bicycle helmet  10 , so that in the region of the center plane of symmetry E a region of the user&#39;s face  30  is covered by both airbags  20 . This can be advantageous since, due to the overlapping of the two airbags  20 , in the event of an impact in the region of the center plane of symmetry E the two overlapping airbags  20  do not expose the chin region  32 . 
     In this embodiment, the airbag device  16  may comprise two gas generators  18 . One of the two gas generators  18  may be arranged at a left side  51  of the helmet shell  12  and may be fluidly connected to one of the two airbags  20  so as to inflate this airbag  20  when needed. The other of the two gas generators  18  may be arranged at a right side  52  of the helmet shell  12  and fluidly connected to the other of the two airbags  20  so as to inflate this other airbag  20  when needed. The two gas generators  18  may be arranged, for example, at a respective ear region  48  or at a respective temple region  42  or at a respective lateral neck region  40  of the bicycle helmet  10 . Of advantage is a symmetrical arrangement of the two gas generators  18  with respect to the center plane of symmetry E of the bicycle helmet  10 . The terms of a left side  51  and a right side  52  only serve to distinguish two sides and do not limit the features described with respect to the left side  51  and the right side  52  to these sides, i.e. the features with respect to the left side  51  may also be features with respect to the right side  52 , and vice versa. 
       FIG.  7    shows a schematic overhead view of two overlapping airbags  20  formed by tubular-shaped elements. The two airbags  20  overlap in a region of the center plane of symmetry E. In order to ensure that when the two airbags meet, in particular the two free ends  56  of the respective airbags  20 , that the two airbags  20  slide past each other, the two ends  56  of the airbags  20  which meet may also have, for example, a trapezoidal structure or a chamfer. 
       FIG.  8    shows a further embodiment of two overlapping airbags  20 . In this case, the overlapping does not occur as one on top of the other, but rather side by side, i.e. in a front view, the two airbags  20  do not overlap or cover each other, although each of the two airbags  20  crosses the center plane of symmetry E of the bicycle helmet  10 . With this embodiment, it can be achieved for example, that the chin region  32  is completely covered by one of the two airbags  20  and for example, a mouth region  49  of the user is covered by the other of the two airbags  20 . 
     In an alternative embodiment, the bicycle helmet  10  or airbag device  16  may comprise a single common gas generator  18  for inflating the two airbags  20 , wherein the single gas generator  18  is fluidly connected to both airbags. Gas can thus flow from the single gas generator  18  into both airbags  20 . As described above, the single gas generator  18  may be arranged in a center-symmetrical position, i.e. symmetrical with respect to the center plane of symmetry E, for example at an occipital region  38  of the helmet shell  12 . However, it is also possible for the single gas generator  18  to be arranged at any position symmetrical to the center plane of symmetry E, for example at a forehead region  44  of the helmet shell  12 . 
       FIG.  9    shows an top view of a bicycle helmet  10 . A center plane of symmetry E may divide the bicycle helmet  10  symmetrically into a left side  51  and a right side  52 . The gas generator  18  may be arranged at various locations in a center-symmetrical position. By a center-symmetrical arrangement of the gas generator  18 , a symmetrical weight distribution with respect to the center plane of symmetry E may be achieved, which may result in increased wearing comfort for the user. As described above, the gas generator  18  may also be arranged center-symmetrical with respect to the center plane of symmetry E in the forehead region  44  or center-symmetrical with respect to the center plane of symmetry E in the neck region  40  or center-symmetrical with respect to the center plane of symmetry E in the upper head region  50 . Corresponding arrangements are shown with a dashed line in  FIG.  9   . 
       FIG.  10    shows a perspective view of a bicycle helmet  10  having a modular unit  28  of an airbag device  16 . The airbag device  16  may comprise a sensor device  22  for detecting an impact situation, a trigger  24  for triggering the at least one gas generator  18  and an energy supply  26  for supplying electrical energy to the sensor device  22  and/or the trigger  24 . Together with an airbag  20  (shown in  FIG.  10    in a folded state), the sensor device  22 , the trigger  24 , the gas generator  18  and the energy supply  26  may be arranged at the bicycle helmet  10  as a modular unit  28 . This may allow retrofitting of an airbag device  16  to existing bicycle helmets  10  (additive design). However, the sensor device  22 , the trigger  24 , the gas generator  18 , the energy supply  26  and the airbag  20  may also be arranged in a distributed manner at the bicycle helmet  10 , which may also be referred to as an integrative design. 
     The operation of the airbag device  16  may be described by way of example, by the following steps. The sensor device  22  continuously monitors, for example at regular time intervals, relevant parameters that may describe a fall or an impact threatened thereby. For example, detected acceleration values may be used as a criterion for a fall if these exceed predefined threshold values, wherein in particular a direction-dependent evaluation may be performed. For this purpose, the sensor device  22  compares the values measured by at least one sensor with predefined threshold values. If at least one measured parameter exceeds the associated threshold value, the sensor device  22  sends a trigger signal to a trigger  24 . The signal may be formed, for example, by an electrical pulse that causes a gas stored in at least one gas generator  18  to flow out. This may be caused, for example, by the ignition of an explosive device at the gas generator  18 . The gas flows into the associated airbag  20  via at least one connecting conduit which connects the respective gas generator  18  with an associated airbag  20 . Due to the inflow of the gas, the airbag  20  unfolds and the airbag  20  is suddenly almost fully inflated. The airbag  20  unfolds around the user&#39;s face  30  such that the inflated airbag  20  covers at least portions of the user&#39;s face  30 . 
     Energy is required both to monitor the measured values by the sensing device  22  and also to ignite the trigger  24 . This energy may be provided by an electrical energy supply  26 . The energy supply  26  may be configured as a battery or as an accumulator. If an accumulator is used as the energy supply, the accumulator may be supplied with energy optionally via solar units that may be arranged at a surface of an outer side of the helmet shell  12 . 
     With regard to the embodiments in accordance with the drawings, it should also be noted that the invention may also be applied to a different type of sports helmet, in particular a motorcycle helmet, a riding helmet or a ski helmet.