Device for unlocking the rotation of a crash-helmet chin guard

A releasing device for enabling rotation of a chin guard hinged to the sides of the cap of a crash helmet, in particular a helmet for motor-cyclists, which comprises at least one mechanism for engagement/release of the chin guard with respect to the cap, first means for actuation of the engagement/release mechanism and second means for inhibition of release, in which said first and second means can be actuated by the user. The aforesaid second means for inhibition of release prevent, when not actuated by the user, operation of the first actuation means and/or of the engagement/release mechanism.

This application claims priority to EP Application No. 03425497.9, filed Jul. 25, 2003. The entire contents of this application is incorporated herein by reference.

The present invention relates to a releasing device for enabling rotation of a chin guard (i.e. to a device for unhooking the rotation of a crash-helmet chin guard) hinged to the sides of the cap of a crash helmet, in particular for motor-cyclists, of the type which comprises at least one mechanism for engagement/release of the chin guard with respect to the cap and means for actuation of the engagement/release mechanism having at least one control element which can be actuated by the user.

A known technique is to equip crash helmets for motor-cyclists with a portion for protecting the chin of the user, also referred to as chin guard, which is made separately from the cap designed to protect the motor-cyclist's head and is pivoted to said cap on the lateral surfaces of the latter. This solution likewise envisages that the chin guard may be rotated from a raised position, in which the chin guard is set above the window of the helmet (in which the visor is present) to a lowered position, in which the chin guard is set in a position corresponding to the chin and the mouth of the user.

In the latter position, the chin guard is withheld against the cap by one or more engagement/release mechanisms, so that the helmet may be likened, to all effects, to the type of helmet commonly defined as integral. As compared to the latter type, in which the chin guard cannot be tilted back with respect to the cap, helmets with chin guards that can be tilted back offer considerable advantages for the motor-cyclist as regards putting on and taking off the helmet and as regards putting on and taking off his goggles, and furthermore, in the case of stops, this type of helmet enables the motor-cyclist to have a greater degree of freedom, without him having to remove the helmet from his head.

The engagement/release mechanism is consequently in this case designed to prevent, in a non-permanent way, relative rotation of the chin guard with respect to the cap and thus to prevent any accidental impact, or the flow of air that impinges on the helmet during motion, or any improper use of the helmet from causing undesirable lifting of the chin guard itself.

The engagement/release mechanism usually comprises at least one pawl (or hook), which is fixed to the chin guard and is removably engageable with a corresponding seat (or pin) made on the cap (or vice versa) and is operatively connected to manual actuation means, which enable the user to release the pawl from its seat and thus to rotate and raise the chin guard.

Known to the art are crash helmets provided with raisable chin guards, in which two engagement and release devices of the type referred to above are set laterally on the chin guard, and each of them is equipped with a lever (or alternatively with a slider or a push-button) for manual actuation, designed to disengage the pawl from the corresponding seat. In order to be able to release the chin guard from the cap, the user must therefore act simultaneously on both of the levers (or sliders or push-buttons) for manual actuation and then rotate the chin guard.

The above solution forces the motor-cyclist to use both hands simultaneously and consequently, whilst rendering rather difficult any accidental release of the chin guard itself, involves a certain difficulty of actuation.

Recent embodiments of crash helmets equipped with raisable chin guards envisage two engagement/release mechanisms set symmetrically on the side walls of the chin guard, as well as means for actuation of the engagement/release mechanism consisting of just one mobile control element, which, when actuated by the user, is able to release both of the pawls from the corresponding seats simultaneously.

In particular, the mobile control element may be a slider, a push-button, or a lever, which, being mounted in a translatable way on the chin guard, has an outer region, on which the user may exert an appropriate force of translation, or rotation, and an inner region shaped for constraining one or more tie rods, which are operatively connected to the engagement/release mechanisms. The slider is in this case translatable between an inoperative position with respect to the engagement/release mechanisms and a position for actuation of the tie rods, which causes release of the chin guard from the cap.

A releasing (unlocking) device of the type referred to above is, for example, described in the German patent application DE-A-4040172, filed in the name of BMW, and in the European patent application EP-A-0518178, which is also filed in the name of BMW.

The above releasing devices equipped with a single actuating slider or push-button, albeit undoubtedly effective and simple to use, are, however, subject to considerable limits as regards their reliability of use and sometimes may induce the motor-cyclist to resort to improper manoeuvring of the system for actuation of the engagement/release mechanisms.

In fact, the presence of just one element for actuation of the engagement/release mechanisms makes it particularly simple for the user to actuate the releasing device with just one hand even when the vehicle is moving, and may likewise not prevent involuntary release of the chin guard by the user, when the latter is performing the normal operations of opening the visor or the ventilation devices present on the helmet chin guard itself.

With a view to increasing safety of use of said devices, the patent application EP-A-0972461 (in the name of SHOEI) proposes mounting the slider for actuation of the engagement/release mechanisms on the chin guard so that the direction and the sense of translation of the slider will be different from and opposite to those for raising the chin guard.

The above solution, albeit rendering difficult any undesirable or involuntary raising of the chin guard, is unable to prevent accidental rotation of the chin guard effectively when the slider undergoes impact in its direction of translation. It is in fact sufficient that, in the instant in which the slider is accidentally displaced in its actuation position, the helmet is subjected to oscillations or impact acting in a direction different from that of translation of the slider, to cause raising of the chin guard.

Furthermore, it is always possible that the user may involuntarily displace the slider connected to the engagement/release mechanisms during while the motor vehicle is in motion and then impose an albeit limited rotation on the chin guard which can set the hooks or pawls out of line with respect to the pins or seats and prevent, upon release of the slider, the engagement/release mechanisms from returning to the position where they withhold the chin guard itself, with the consequent risk of a subsequent accidental opening of the chin guard.

It is consequently a purpose of the present invention to provide a releasing device for enabling rotation of a chin guard hinged to the sides of the cap of a crash helmet, in particular for motor-cyclists, which will not present the drawbacks of the known art, and one which will reduce as far as possible the risk of the user performing involuntary manoeuvres that might cause any accidental rotation of the chin guard itself with respect to the cap of the helmet. Such a solution will thus ensure considerable safety of use.

Yet another purpose of the present invention is to provide a releasing device for enabling rotation of a chin guard hinged to the sides of the cap of a crash helmet, in particular for motor-cyclists, distinguished by presenting a high ergonomic level and a high degree of reliability and by being easy to make and inexpensive to manufacture.

A further purpose of the present invention is to provide a crash helmet for motor-cyclists which, having a device for releasing a chin guard hinged to the sides of the cap, will be practical and simple to use in those situations in which, with the vehicle stationary, the chin guard has to be opened with just one hand, i.e., without having to (or without being able to) act simultaneously on the engagement/release mechanisms with both hands, as for example in the case of a stop for refuelling at a service station, a motorway toll-gate, traffic lights, etc.

Another purpose of the present invention is to propose a method for the use of a crash helmet provided with raisable chin guard which will prevent the user from performing involuntary manoeuvres such as might cause accidental or dangerous rotations of the chin guard itself with respect to the cap of the helmet.

These and other purposes are achieved by the releasing device for enabling rotation of a chin guard hinged to the sides of the cap of a crash helmet according to the first independent claim and the subsequent dependent claims, by the helmet according to Claim18, and by the method for releasing and enabling rotation of a chin guard hinged to the sides of the cap of a crash helmet according to the independent Claim19.

According to the present invention, the releasing device for enabling rotation of a chin guard hinged to the sides of the cap of a crash helmet, in particular for motor-cyclists, comprises at least one mechanism for engagement/release of the chin guard with respect to the cap, first means for actuation of the engagement/release mechanism, and second means for inhibition of release, in which said first and second means can be actuated by the user. The aforesaid second means for inhibition of release prevent, when not actuated by the user, operation of the first actuation means and/or of the engagement/release mechanism.

Consequently, the solution claimed not only forces the user to act simultaneously on two separate control means to obtain release and enabling of rotation of the chin guard, but also imposes on the user the need to actuate said separate control means according to a pre-defined sequence; i.e., said solution envisages that the user will first set in operation auxiliary means of inhibition designed to enable subsequent operation of the means for actuating the device for releasing the chin guard from the cap, and will then act on the aforesaid actuation means, keeping the inhibition means simultaneously actuated so as to be able to raise the chin guard.

The above procedure substantially prevents involuntary actuation of the releasing device, for example on account of erroneous operation of just the first actuation means during execution of the normal manoeuvres for opening the visor and/or the front ventilation devices, or else on account of an accidental impact; in this way, any risk of accidental raising of the chin guard by the user is reduced, which is particularly important when the vehicle is moving.

According to a particularly advantageous aspect of the present invention, the aforesaid first actuation means comprise at least one control element, which can move between a position for actuation of the engagement/release mechanism and an inoperative position as regards the engagement/release mechanism, and the second inhibition means prevent, for example by contrast of parts, when not actuated by the user, any displacement of the control element from the inoperative position to the position for actuation of the engagement/release mechanism.

In this way, both the actuation means and the inhibition means can be mounted, for example, on the chin guard, and the engagement/release mechanisms can be set in operation to obtain release of the chin guard, by means of the steps of actuation of the inhibition means, with the purpose of releasing the actuation means, and of subsequently triggering the actuation means, for enabling rotation of the chin guard.

According to a particular feature of the present invention, the releasing device for enabling rotation of the chin guard is provided with two devices for engagement/release of the chin guard with respect to the cap, which are set on opposite sides in positions corresponding to the sides of the cap, and with a single control element, preferably a slider, designed for actuating both of the engagement/release mechanisms. In this case, the means for inhibition of release comprise at least one removable arrest, which engages, by interposition of parts, with the control element and which can move between a position of engagement with the control element and a position of disengagement from the latter.

According to a further aspect of the present invention, there is provided a crash helmet for motor-cyclists, equipped with the releasing device for enabling rotation of the chin guard referred to above, in which for release of the chin guard it is necessary first to actuate the second inhibition means for enabling operation of the first actuation means and/or of the engagement/release mechanism, and then to actuate the first means for operation of the engagement/release mechanism.

With reference toFIGS. 1,2,3a,3band4, in a particular embodiment of the present invention, the releasing device for enabling rotation of a chin guard10, which is hinged, in positions corresponding to the projections16,16′, to the sides of the cap (not illustrated) of a crash helmet for motor-cyclists, comprises two engagement/release mechanisms3,3′ of the chin guard to/from the cap, first actuation means1,5,11,2,2′ of the engagement/release mechanisms3,3′, which can be actuated by the user, and second inhibition means6,7,8and9for preventing release of the chin guard, which can also be actuated by the user.

In the embodiment illustrated, when not actuated by the user, the means6,7,8,9for inhibition of release of the chin guard10prevent, by contrast of parts, operation of the actuation means1,5,11,2,2′ and, at the same time (in embodiments not illustrated) said inhibition means6,7,8,9may also prevent, for example by interposition of mechanical parts, operation of the engagement/release mechanisms3,3′ by for instance not enabling their displacement.

In particular, in the embodiment ofFIGS. 1 to 3b, each of the engagement/release mechanisms of the chin guard10to/from the cap comprises, according to a known technique, a rotatable pawl3,3′, which is hinged to the chin guard10itself along one of its internal side walls and is designed to engage with a corresponding seat, or pin, provided in a position corresponding to a side of the cap. The pawls3,3′ are operatively connected to the means for actuation of the engagement/release mechanisms by means of the tie rods2,2′, which extend between a control element1, which can be actuated by the user, and the pawls3,3′ themselves.

The tie rods2,2′ perform the function of transmitting the motion exerted by the user on the control element1onto the rotatable pawls3,3′ so as to impose on the latter a rotation which will be able to disengage the pawls3,3′ themselves from the corresponding seats of the cap in order to enable raising of the chin guard10.

In alternative embodiments (not illustrated), said tie rods2,2′ may be replaced by a single tie rod (as, for example, described in the patent DE-A-4040172) or by any other kinematic chain capable of transmitting the motion imposed by the user on the control element1for controlling the actuation means to the engagement/release mechanisms, when this transmission of motion is not prevented by the aforesaid inhibition means6,7,8and9, with the purpose of enabling disengagement of the chin guard10from the cap.

The means for actuation of the device, represented inFIGS. 1 to 4, comprise, in greater detail, a slider1mounted slidably, so that it can move according to the direction indicated by the arrow B, within a guide window11made on a central portion of the chin guard10, and a fixed structure5, which is also constrained to the chin guard10by means of rivets or screws that are housed within seats15, and is equipped with two guide portions13,13′, on which there are slidably constrained two tie rods2,2′, connected to the pawls3,3′.

The slider1comprises two fastener (claw) elements12,12′ (which can be seen inFIG. 3a), designed to withhold one end of the two tie rods2,2′, and a projection4, which protrudes outside the chin guard10and on which the user may exert a force of translation for the slider1itself, directed according to the arrow B. The slider1, when not withheld by the aforesaid inhibition means6,7,8,9, is thus able to move between an inoperative position (FIG. 1) with respect to the engagement/release mechanisms, in which the tie rods2,2′ do not act on the pawls3,3′, and an actuation position (FIG. 2) of said devices, in which the tie rods2,2′ withhold said pawls3,3′ in a position shifted away from the corresponding seats, or pins, of the cap.

The actuation means described above may also comprise elastic means (not illustrated in the figures), designed to withhold the rotatable pawls3,3′ in a position of engagement with the seats of the cap. The aforesaid elastic means, via the tie rods2,2′, may induce the slider1to remain in its aforesaid inoperative position and may oblige the user to overcome the force exerted by them in order to displace the slider1itself.

The external surface of the chin guard10, at the sides of the guide window11in which the slider1slides, moreover has surrounding structures for protecting the projection4so that it can be actuated only if the user voluntarily exerts the force B at a point corresponding to the projection4itself, and not as a result, for example, of involuntary impact or other manoeuvres of actuation of the visor or of the systems of ventilation normally located on the chin guard.

The means for inhibiting release that are present in the device ofFIGS. 1 to 4comprise an arrest6assembled on the chin guard10so that it can move between a position of engagement, by contrast of parts, with the slider1(visible inFIG. 1) and a position of disengagement from said slider1(visible inFIG. 2). The arrest6coincides, in the particular embodiment of the device according to the present invention described herein, with one of the arms of a two-armed safety lever6,7, which is constrained elastically in rotation to the support5by means of a pin8and a retention spring9. The support5is accordingly provided with a seat14,14′ for the pin8and is rendered fixed to the chin guard itself10by threaded means, which engage in the holes15.

The retention spring9, in the absence of external forces, pushes the arrest6into engagement with the slider1, so preventing any translation of the latter in the sense indicated by the arrow B.

The other arm7of the two-armed lever projects from a central bottom portion of the chin guard10and enables the user to control rotation, in the direction and sense indicated by the arrow A, of the lever6,7about the pin8, by overcoming the resistance exerted by the spring9, in order to displace the arrest6from its position of engagement with the slider1.

When the user wishes to raise the chin guard10with respect to the cap of the crash helmet, starting from the situation illustrated inFIG. 1, in which the chin guard10is lowered and is withheld by the devices3,3′, he must act first on the lever6,7, pushing the arm7in the sense indicated by the arrow A, to counteract the force exerted by the spring9so as to disengage the arrest6from the slider1.

Then, keeping the lever6,7rotated and acting on the projection4, the user must impose on the slider1, which is now free to displace within the guide defined by the window11and by the support5, a translation in the sense indicated by the arrow B, which is able to actuate the tie rods2,2′ and, in this way, to cause rotation of the pawls3,3′ and their consequent disengagement from the corresponding seats or pins of the cap (seeFIG. 2). At this point, the user can rotate the chin guard10, by acting directly on the latter, into a raised position with respect to the cap. The displacements A and B, in the aforesaid correct succession, may for example be performed, respectively, with the thumb and forefinger of just one hand; the consequent release of the chin guard and the rotation of opening thereof are consequently simple, practical and ergonomic.

The lever6,7, which is pivoted elastically to the support5thanks to the pin8and to the spring9, consequently forces the user who wishes to open the chin guard10, firstly to actuate the lever6,7, and next to actuate the slider1, and only then, with these two prior actions maintained simultaneously operative, is it possible for him to start rotating the chin guard with respect to the cap.

Likewise, said lever6,7, which, together with the pin8and the spring9, constitutes the aforesaid means for inhibition of release, substantially behaves as a safety lever since it is unlikely that the aforesaid sequence may arise by accident.

In one embodiment (not illustrated), with the purpose of increasing the reliability of the device according to the present invention, in accordance with a known technique, the engagement/release mechanisms, and in particular the pawls3,3′ ofFIGS. 1,2,3aand3b, may be equipped with individual actuation means (such as, for example, levers, push-buttons or sliders), which enable the user to disengage said pawls3,3′ from the corresponding seats present on the cap of the helmet in a mutually separate way and in a way independent of the actuation of the device according to the present invention. In this way, in the case of possible malfunctioning or jamming of the device for releasing the chin guard, the user is always able to release the chin guard10with respect to the cap by acting simultaneously on the individual means for actuation of the engagement/release mechanisms3,3′. With reference now toFIGS. 5 to 7, described in what follows is a further embodiment of the present invention, in which the slider for actuation of the tie rods is set in, in its inoperative position, with respect to the engagement/release mechanisms, flush with the outer surface of the chin guard, and therefore requires, for its displacement by the user, a prior rotation, which will enable its extraction.

More in particular, the releasing device for enabling rotation of a chin guard110hinged to the sides of the cap of a crash helmet for motor-cyclists, illustrated inFIGS. 5 to 7, comprises at least one device (not shown) for engaging/releasing the chin guard110with respect to the cap of the helmet, means for actuation of said device equipped with a slider101, which is constrained in a slidable and rotatable way to the chin guard110itself, and inhibition means, which have a two-armed safety lever106, which acts by contrast of parts on the slider101.

The slider101comprises: an actuation portion104, which is built-in, in a resting position of the slider101itself, within an opening111made frontally on the chin guard110; a front projection114, which rests on the safety lever106, a rear projection115, which rests on of a support120; and an end region, which has the conformation of a cam or a pin117for engagement with the aforesaid lever106.

The slider101is moreover mounted in a rotatable way by means of a pin113, which is inserted in a hole made in the aforesaid front projection114, on a slide119, which is in turn slidably mounted within a fixed structure, or support,120constrained to the chin guard110by means of screws or rivets, which are housed in appropriate seats made on the support120itself.

Said slide119, and consequently the slider101, is also operatively connected to the engagement/release mechanism, for example by means of one or more tie rods (not illustrated) so that its translation in the direction and sense indicated by the arrow B will bring about disengagement of the chin guard110from the cap of the crash helmet.

A spring112, set between the slider101and the slide119, withholds the slider101itself in the resting position, in which the actuation portion104is built-in within the opening111, and the slider101, fixed to the slide119, does not exert any action on the engagement/release mechanisms of the chin guard110.

In said resting (or inoperative) position, the bottom end of the portion104rests on a bottom edge of the opening111, and the rear projection115rests on a top wall of the support120, fixed to the chin guard110, so that translation of the slider101will be prevented by said supports.

For displacement in translation of the slider101, in order to actuate the devices for engagement/release of the chin guard110it is consequently first necessary to rotate the slider101, overcoming the resistance exerted by the spring112, about the pin113(as indicated by the arrow C) and thus to obtain the consequent expulsion of the actuation portion104from the opening111and disengagement of the projection115from the top wall of the support120, so as to enable possible subsequent translation in the direction and sense indicated by the arrow B of the slider101, or else of the slide119, with respect to the chin guard110.

The safety lever106comprises an arrest116, located at one end of an arm118of the lever106itself, and an actuation arm107located in opposition, with respect to the fulcrum of the lever106itself, to the arrest116. The fulcrum of the safety lever106consists of a pin108, which is constrained to the support120fixed to the chin guard110. A contrast spring109, extending between the chin guard110and the arm107, moreover withholds, in the absence of external forces acting on the arm107itself, the lever106in a position of support for the arrest116on the projection114of the slider101. In this supporting position of the lever106on the slider101, the arrest116constitutes a further constraint to sliding of the latter.

The actuation arm107of the safety lever106moreover extends advantageously inside the chin guard110and is protected against any accidental impact by a shaped projection121, which likewise constitutes a gripping area for raising the chin guard itself110.

The rotation of the lever106about its pin108, obtained by overcoming the resistance exerted by the spring109, causes departure of the arrest116from the front projection114, which is thus no longer resting on the arrest116, and the cam-like coupling of the arm118with the pin117, which causes rotation of the slider101about its pin113and the consequent expulsion of the actuation portion104from the opening111of the chin guard110.

In said position of the safety lever106, translation in the sense indicated by the arrow B of the slider101causes, at a given point of the translation path of the slider, resting of the projection115of the slider101on the arrest116of the lever106so that said resting position may constitute an end-of-travel arrest for the slider101.

In the absence of external forces acting on the lever106and/or on the slider101, the contrast springs109and112withhold, respectively, the safety lever106in the position of engagement of the arrest116with the supporting projection114, and the slider101in the inoperative position with respect to the engagement/release mechanisms, where the portion104is set inside the opening111, as may be seen inFIG. 5.

For actuation of the engagement/release mechanisms to enable rotation of the chin guard110from the cap of the crash helmet, the user, starting from the position of engagement ofFIG. 5, must thus actuate the safety lever106by acting on the arm107in the direction and sense indicated by the arrow A in order to counteract the spring109so as to rotate said lever about its pin108and thus simultaneously cause the projection114of the slider101no longer to rest on the arrest116and induce a rotation of the slider101about its pin113, thanks to the cam-like coupling between the curved lateral surface of the arm118of the lever106and the pin117of the slider101.

Rotation of the slider101with respect to the pin113in the direction and sense indicated by the arrow C (FIG. 6) causes expulsion of the actuation portion104from the opening111of the chin guard110and disengagement of the rear projection115from the top edge of the support120, so enabling the user to exert a force, having direction and sense indicated by the arrow B, sufficient to translate the slider101and the slide119downwards so as to obtain release of the chin guard110from the cap of the helmet as a result of the tensile force exerted by the tie rods which connect the cap to the engagement/release mechanisms.

The end of the travel of translation of the slider101(as may be seen inFIG. 7) is provided both by the contrast of parts between the bottom edge of the opening111and the actuation portion104and by the resting of the rear projection115on the arrest116when the safety lever106is withheld by the user in a position of release and expulsion of the portion104itself.

The displacements A of the safety lever106and B of the slider101, in the aforesaid correct succession, may for example be made, respectively, with the thumb and forefinger of just one hand.

After obtaining, as described above, release of the chin guard110with respect to the cap, the user can then raise the chin guard110by imposing a rotation on the latter, preferably via the gripping area121and again his thumb, which is already engaged for maintaining the displacement A. It follows that release of the chin guard and rotation thereof for tilting it back are simple, practical and ergonomic.

Release of the arm107and of the slider101by the user, thanks to the return springs112and109, enables the device described herein to be brought back into the initial position represented inFIG. 5.

The structure of the device shown inFIGS. 5 to 7, in addition to rendering rotation of the safety lever106or of the slider101very difficult on account of the different interposition of shaped parts provided and of the contrast springs109,112, is such that neither mere rotation of the lever106nor rotation of the slider101with respect to its pin108can cause release of the chin guard110with respect to the cap of the helmet, which is enabled only following upon the additional translation of the slider101.

Consequently, according to the present invention, for releasing the chin guard10,110with respect to the cap, the user of a crash helmet for motor-cyclists of the type which comprises a rotatable chin guard10,110, hinged to the sides of the cap of the helmet, and a releasing device for enabling rotation of the chin guard10,110, provided with at least one device3,3′ for engagement/release of the chin guard to/from the cap, and with first means1,2,2′,5,101,112,113,119for actuation of said engagement/release mechanism, as well as with second inhibition means6,7,8,9,106,108,109for inhibiting release, in which said first and second means can be actuated by the user and in which the aforesaid second means6,7,8,9,106,108,109prevent, when not actuated, operation of the first actuation means1,2,2′,5,101,112,113,119and/or of the engagement/release mechanism3,3′, must follow the steps of:firstly actuating the aforesaid second inhibition means6,7,8,9,106,108,109with the purpose of enabling operation of the first actuation means1,2,2′,5,101,112,113,119and/or of the engagement/release mechanism3,3′;subsequently actuating the first actuation means1,2,2′,5,101,112,113,119of the engagement/release mechanism3,3′.

Preferably, actuation of the second inhibition means must be maintained for a time interval sufficient for enabling subsequent actuation of the first means so that the user can perform, only voluntarily and with just one hand, the unique and correct sequence of said operations for releasing and enabling rotation of the chin guard10,110, and only subsequently is it possible, once again using the same hand already engaged in keeping actuated the second inhibition means and the first actuation means, for him to rotate the chin guard.

The above method confers on the helmet of the present invention a high degree of practicality and safety of use and at the same time guarantees a lower risk of involuntary or accidental opening of the chin guard occurring both in the case of improper use of the chin guard by the user (for example when the vehicle is moving) and during execution of other manoeuvres frequently performed during use of the helmet, such as opening or closing of the visor, actuation of the ventilation systems present on the chin guard itself, or the mere operations of readjustment/repositioning of the helmet on the user's head.