Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
A HELMET FOR REDUCING ROTATIONAL FORCES
Document Type and Number:
WIPO Patent Application WO/2019/122498
Kind Code:
A1
Abstract:
In the invention a helmet (100) is formed that comprises a support part (101) and a protective part (102) and the protective part covers the head and is configured to move in a groove on the support part. The protective part is held in place by a locking mechanism that releases the protective part to move when an external force acts upon the protective part. The helmet therefore decreases rotational forces acting upon the head. The helmet is kept in place by a stretching arrangement (104). The helmet can also comprise a visor part (103) that is configured to move similarly as the protective part.

Inventors:
KETTUNEN, Pertti (Uusikatu 76 A 22, Oulu, 90120, FI)
TAURIAINEN, Markku (Koulukatu 31 B 14, Oulu, 90100, FI)
Application Number:
FI2018/000020
Publication Date:
June 27, 2019
Filing Date:
December 19, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
KETTUNEN, Pertti (Uusikatu 76 A 22, Oulu, 90120, FI)
TAURIAINEN, Markku (Koulukatu 31 B 14, Oulu, 90100, FI)
International Classes:
A42B3/06; A42B3/22; A42B3/32; F41H1/04
Foreign References:
US4012794A1977-03-22
GB191512765A1916-05-04
US2855604A1958-10-14
US20130283507A12013-10-31
US20130219599A12013-08-29
Download PDF:
Claims:
Patent claims

1. A helmet (100; 300; 400; 500) for reducing rotational forces comprising a sup- port part (101 ; 301 ; 401 ; 501 ), which support part comprise a front side (105; 305; 405; 505) and a back side (106; 306; 406; 506) and an upper part (107) and a bottom part (108), and the support part is configured to encircle the head when the helmet is worn, and there is a stretching arrangement (104; 404) fixed on the support part, and the helmet is configured to be fixed on the head with the stretching arrangement, characterised in that there is a circular slide groove (204; 508) in the support part, and the helmet further comprise a domelike protective part (102; 302; 402; 502), which protective part has a lower edge (510), which lower edge is configured to fit in the slide groove in such a way that the protective part is rotatable when fitted in the slide groove, and a protective part locking mechanism (203; 308, 309; 511 a, 511 b), which is for locking the protective part immobile in relation to the support part and the protective part locking mechanism is configured to release the protective part to be movable in the slide groove in relation to the support part when a sufficient external force acts upon the protective part, and the protective part locking mecha- nism comprises at least one magnet either in the protective part or the support part.

2. The helmet (100; 300; 400; 500) according to claim 1 , characterised in that the helmet has a visor part (103; 303; 403; 503), which is at least partly transparent, and in the support part (101 ; 301 ; 401 ; 501 ) is a circular visor part slide groove (201 ; 507), and the visor part is configured to fit in the visor part slide groove in such a way that the visor part is rotatable when fitted in the visor part slide groove.

3. The helmet (100; 300; 400; 500) according to claim 2, characterised in that in the visor part (103; 303; 403; 503) is a face-protection part (513) that is higher than other parts of the visor part.

4. The helmet (100; 300; 400; 500) according to any of claims 1 to 3, character- ised in that in the support part (101 ; 301 ; 401 ; 501 ) is an inner dome part (509) and the protective part (102; 302; 402; 502) is configured to fit over the dome part.

5. The helmet (100; 300; 400; 500) according to claim 4, characterised in that on the top of the dome part (509) is a bearing arrangement (515) which bearing arrangement is configured to interconnect the support part (101 ; 301 ; 401 ; 501 ) and the protective part (102; 302; 402; 502).

6. The helmet (100; 300; 400; 500) according to any of claims 1 to 5, character- ised in that the back side (106; 306; 406; 506) of the support part (101 ; 301 ; 401 ;

501 ) is higher than the front side (105; 305; 405; 505).

7. The helmet (100; 300; 400; 500) according to any of claims 1 to 6, characterised in that at least the lower edge (510) of the protective part (102; 302; 402; 502) or the slide groove (204; 508) or both are coated with a friction-reducing material.

8. The helmet (100; 300; 400; 500) according to any of claims 1 to 7, characterised in that there are two protective part locking mechanisms (203; 308, 309; 51 1 a, 51 1 b) and they are situated symmetrically opposed to each other on the sides of the helmet.

9. The helmet (100; 300; 400; 500) according to any of claims 2 to 8, characterised in that there is a visor part locking mechanism (202; 307, 310; 512a, 512b) for locking the visor part (103; 303; 403; 503) immobile in relation to the support part (101 ; 301 ; 401 ; 501 ) and the visor part locking mechanism is configured to release the visor part to move in the visor part slide groove (201 ; 507) in relation to the support part when a sufficient external force acts upon to the visor part.

10. The helmet (100; 300; 400; 500) according to claim 9, characterised in that the visor part locking mechanism (202; 307, 310; 512a, 512b) is configured in such a way that the user can release the visor part (103; 303; 403; 503).

1 1 . The helmet (100; 300; 400; 500) according to any of claims 9 to 10, characterised in that there are two visor part locking mechanisms (202; 307, 310; 512a, 512b) and they are situated symmetrically opposed to each other on the sides of the helmet.

12. The helmet (100; 300; 400; 500) according to claim 1 1 , characterised in that the visor part locking mechanisms (202; 307, 310; 512a, 512b) are configured in such a way that the visor part (103; 303; 403; 503) has a first position and a second position, and in both positions the visor part is locked, and in the first position the face-protection part (513) face the front side (105; 305; 405; 505) of the support part (101 ; 301 ; 401 ; 501 ) and in the second position the face-protection part face the back side (106; 306; 406; 506) of the support part.

13. The helmet (100; 300; 400; 500) according to any of claims 2 to 12, characterised in that the protective part (102; 302; 402; 502) and the visor part (103; 303; 403; 503) are configured to be detachable from the support part (101 ; 301 ; 401 ; 501 ) and to be reattachable to the support part.

14. The helmet (100; 300; 400; 500) according to any of claims 1 to 13, characterised in that the helmet has a dome-like outer shell that is configured to be on the protective part (102; 302; 402; 502) and to be attached either in an immobile or movable fashion to the support part (101 ; 301 ; 401 ; 501 ).

15. The helmet (100; 300; 400; 500) according to any of claims 2 to 14, characterised in that the plane of the visor part slide groove (201 ; 507) is dissimilar to the plane of the slide groove (204; 508).

Description:
A helmet for reducing rotational forces

The invention relates to a helmet comprising a support part, which support part comprises a front side and a back side and an upper part and a bottom part, and the support part is configured to encircle the head when the helmet is in use, and there is a stretching arrangement fixed on the support part, and the helmet is con- figured to fixed on the head with the stretching arrangement.

BACKGROUND

Protective gear such as sports, safety and military helmets are designed to reduce direct impact forces that can mechanically damage an area of contact. Protective gear will typically include padding and a protective shell to reduce the risk of phys- ical head injury. Liners are provided beneath a hardened exterior shell to reduce violent deceleration of the head in a smooth uniform manner and in an extremely short distance, as liner thickness is typically limited by helmet size. Concussions and other head injuries are a major concern for athletes and others participating in activities where the head may be subjected to impacts. Concus- sions are a form of traumatic brain injury (TBI) and can range in severity from mild to life-threatening. It is now known that concussions are more than temporary im- pairments of neurological functions which resolve spontaneously. Concussions may have long-lasting effects.

An angular impact exposes the head to rotational acceleration and is quite differ- ent from a linear impact. In this case, a force causes the head to rotate on its axis (corresponding to the neck) from side to side in a twisting motion. When the head is forced to rotate quickly over a large degree of rotation, nerve cells and blood vessels in the brain can be stretched, twisted and torn. The twisting and tearing of an axon may result in the death of the neuron. Consequently, the damage caused by rotational impacts may be particularly severe.

Current helmets protect against impacts through the use of a hard outer surface. Some applications may use an inner layer of heavy, snug-fitting and shock- absorbing padding that could be foam, air cells and such. The shock-absorbing padding fits snugly around the head. Such helmet designs may be effective at ab- sorbing the force of hard hits to the head and preventing both skull fractures and direct-impact concussions by distributing the force across the entire surface area of the helmet. Traditional helmets have the ability to withstand multiple impacts, by compressing and returning to their original dimensions. The outer shell also dis- perses kinetic energy.

However, if the helmet is subjected to a rotational impact that causes it to rotate, the head is subjected to the same rotational force and will also rotate on its verti- cal axis at the neck. Helmets in use today are not effective at providing protection against external forces that cause rotational impacts, which may lead to concus- sions. This is also quite evident with military helmets that should protect the user from bullets, ricochets and flying fragments and such. Fast-moving objects, even if they do not penetrate the helmet, subject it to such a rotational force that it leads to injury to the user. It is practically impossible for a conventional helmet to stop a modern high-velocity bullets that impacts the helmet at a 90° angle. Therefore, helmets are worn in combat more to protect the user from flying debris, shrapnel, and falling objects than from high-velocity bullets. Even if a high-velocity bullet in- variably penetrates the helmet when the bullet strikes the helmet at a 90° angle, a glancing hit may very well be deflected or channelled through the ballistic material, keeping of the bullet away from the soldier’s head, depending on the angle of the strike, and the composition of the helmet.

BRIEF DESCRIPTION

The object of the invention is a solution that can significantly reduce the disad- vantages and drawbacks of the prior art. In particular, the object of the invention is a solution that provides a helmet that protects its user from rotational forces and improves its bullet-deflecting properties. The objects of the invention are attained with an arrangement that is characterised by what is stated in the independent patent claims. Some advantageous embodi- ments of the invention are disclosed in the dependent claims.

In the invention a helmet is formed that comprises a support part and a protective part and the protective part covers the head and is configured to move in a groove on a support part. The protective part is held in place by a locking mechanism that releases the protective part to move when an external force acts upon the protec- tive part.

The invention particularly benefits safety helmets and military headgear. When reference is made in the text to the upper or the lower parts or other re- spective directions, a situation is described in which the helmet according to the invention is in its normal deployed configuration. By a user is meant a person that wears the helmet.

In one embodiment of the invention is a helmet comprising a support part, which support part comprise a front side and a back side and an upper part and a bot- tom part, and the support part is configured to encircle the head when the helmet is worn, and there is a stretching arrangement fixed on the support part, and the helmet is configured to be fixed on the head with the stretching arrangement. In one advantageous embodiment of the invention there is a circular slide groove in the support part, and the helmet further comprise a dome-like protective part, which protective part has a lower edge, which lower edge is configured to fit in the slide groove in such a way that the protective part is rotatable when fitted in the slide groove. The helmet also comprises a protective part locking mechanism, which is for locking the protective part immobile in relation to the support part and the protective part locking mechanism is configured to release the protective part to be movable in the slide groove in relation to the support part when a sufficient external force acts upon the protective part, and the protective part locking mech- anism comprises at least one magnet either in the protective part or in the support part.

In one embodiment of the helmet according to the invention, the helmet has a vi- sor part, which is at least partly transparent, and in the support part is a circular visor part slide groove, and the visor part is configured to fit in the visor part slide groove in such a way that the visor part is rotatable when fitted in the visor part slide groove. In a second embodiment of the helmet according to the invention in the visor part is a face-protection part that is higher than other parts of the visor part.

In a third embodiment of the helmet, the support part has an inner dome part and the protective part is configured fit over on the dome part.

In a fourth embodiment of the helmet the top of the dome part has a bearing ar- rangement which bearing arrangement is configured to interconnect the support part and the protective part.

In a fifth embodiment of the helmet the back side of the support part is higher than the front side. In a sixth embodiment of the helmet at least the lower edge of the protective part or the slide groove or both are coated with a friction-reducing material.

In a seventh embodiment of the helmet there are two protective part locking mechanisms and they are situated symmetrically opposed to each other on the sides of the helmet.

In an eighth embodiment of the helmet there is a visor part locking mechanism for locking the visor part immobile in relation to the support part and the visor part locking mechanism is configured to release the visor part to move in the visor part slide groove in relation to the support part when a sufficient external force acts upon the visor part. In a ninth embodiment of the helmet the visor part locking mechanism is configured in such a way that the user can release the visor part. In a tenth embodiment of the helmet there are two visor part locking mechanisms and they are situated symmetrically opposed to each other on the sides of the helmet. In an eleventh embodiment of the helmet the visor part locking mecha- nisms are configured in such a way that the visor part has a first position and a second position, and in both positions the visor part is locked, and in the first posi- tion the face-protection part faces the front side of the support part and in the sec- ond position the face-protection part faces the back side of the support part.

In a twelfth embodiment of the helmet the protective part and the visor part are configured to be detachable from the support part and to be reattachable to the support part.

In a thirteenth embodiment of the helmet the helmet has a dome-like outer shell that is configured to be on the protective part and to be attached either in an im- mobile or movable fashion to the support part.

In a fourteenth embodiment of the helmet the plane of the visor part slide groove is dissimilar to the plane of the slide groove i.e. the planes are divergent.

It is an advantage of the invention that it improves the safety of the user. Moreo- ver, it protects the user against rotational forces.

It is a further advantage of the invention that it increases the chance of bullets de- flecting and decreases the penetrating power of bullets and other projectiles.

It is a further advantage of the invention that it does not significantly increase the weight of the helmet. Another advantage of the invention that it is easy to implement and repair.

DESCRIPTIONS OF THE FIGURES

In the following, the invention is described in detail. The description refers to the accompanying drawings, in which

Figure 1 shows an example of a helmet according to the invention,

Figure 2 shows a cross-section of the helmet in accordance with Figure 1 ,

Figure 3 shows a second example of the helmet as a horizontal cut,

Figure 4 shows a third example of the helmet according to the invention, and Figure 5 shows a fourth example of the helmet according to the invention.

DETAILED DESCRIPTIONS OF THE FIGURES

The embodiments in the following description are given as examples only and someone skilled in the art can carry out the basic idea of the invention also in some other way than what is described in the description. Though the description may refer to a certain embodiment or embodiments in several places, this does not mean that the reference would be directed towards only one described em bodiment or that the described characteristic would be usable only in one de- scribed embodiment. The individual characteristics of two or more embodiments may be combined and new embodiments of the invention may thus be provided.

In Figure 1 is shown one embodiment of a helmet according to the invention. The helmet comprises a support part 101 , a protective part 102, a visor part 103 and a stretching arrangement 104. The helmet is in use i.e. it is fixed onto the user’s head by the stretching arrangement. The support part 101 is a frame of the helmet 100. The support part encircles the head. It has a front side 105 and a back side 106. The front side is on the face side of the user and the back side is on the neck side of the user when the helmet is worn. There is also an upper part 107 and a bottom part 108 of the support part. The stretching arrangement 104 is fixed to the support part. The back side of the support part is higher than the front side. On the upper part of the support part is a circular slide groove. On the lower part of the support part is a circular visor part slide groove.

The protective part 102 is dome-like and it is configured to protect the upper part of the head. The protective part has a lower edge. The protective part is config- ured to fit in the slide groove in such a way that the protective part is rotatable i.e. it can be turned in the slide groove. The protective part is essentially symmetrical. Therefore, the shape of the helmet does not change when the protective part is rotated. There is a protective part fixing arrangement in the support part 101 that keep the protective part in place. This can be implemented in a myriad of ways. In some embodiments at least the lower edge of the protective part or the slide groove or both are coated with a friction-reducing material. This material could be for example teflon or similar. When an impact, that would produce a rotational force onto the helmet, hits the protective part laterally, the protective part rotates and thus decreases the forces acting upon the head. In this example the lower parts of the protective part are covered by the support part 101 , but there are em bodiments where the protective part extends over the support part. Advantageous- ly in some embodiments there are some paddings or other arrangements that separate the head and the protective part so that the protective part does not touch the head when the protective part rotates.

The visor part 103 is for protecting the face and especially the eyes. It is at least partially transparent. The visor part is configured to fit in the visor part slide groove in such a way that the visor part is rotatable i.e. it can be turned in the visor part slide groove. Advantageously the visor part has a face-protection part that is high- er than other parts of the visor part. There is a visor part fixing arrangement in the support part 101 that keeps the visor part in place. This can be implemented in many ways. The visor part is configured to be rotatable in a similar way to the pro- tective part 102. This means that when the visor part is impacted laterally, the vi- sor part rotates and thus decrease the forces acting upon the head. In addition, the visor part is configured in such a way that it is movable by the user of the hel- met. It therefore allows the user to move the visor and especially the face- protection part of the visor part to uncover the eyes. There are embodiments where the face-protection part can be rotated inside the support part 101. Be- cause the back side 106 of the support part is higher than the other parts of the support part, the face-protection part is protected there and does not get dirty or wet. In some embodiments there are visor cleaning arrangements in the back side of the support part that wipe the visor clean when it is rotated in the visor part slide groove. These visor cleaning arrangements are for example tissue, cloth or simi- lar.

The stretching arrangement 104 is some conventional arrangement. It is fixed to the support part in such a way that it does not hinder the movements of the pro- tective part 102 or the visor part 103.

The materials of which the helmet and its parts are manufactured can vary. The choice of materials is optimised for the purpose of the helmet. They could be for example stainless steel, carbon steel, resins, polymers, ceramics, composites, polycarbonate, kevlar, alloys, plastics, a combination of materials, aluminium and so on.

In Figure 2 is shown a cross-section of the helmet 100. Parts and refence num- bers are the same as in the Figure 1. On the upper part 107 of the support part 101 is a circular slide groove 204. The lower edge 205 of the protective part 102 is configured to fit in a rotatable fashion in the slide groove. There is a protective part locking mechanism 203 that is configured to release the protective part to be movable in the slide groove in relation to the support part when a sufficient exter- nal force acts upon the protective part. The protective part locking mechanism fea- tures at least one magnet either in the protective part or in the support part. Using magnets in the locking mechanisms is advantageous in that the protective part can be easily set to a locked position after the protective part has been rotated. When the magnet is sufficiently strong there are no accidental movements of the protective part. The protective part locking mechanism is configured to release the protective part when there is a risk of undesired or harmful rotational movement of the helmet and the head inside the helmet.

On the lower part of the support part 101 is a circular visor part slide groove 201. The visor part 103 is configured to fit in the visor part slide groove in such a way that the visor part is rotatable when fitted in the visor part slide groove. There is a visor part locking mechanism 202 that is configured to release the visor part to be movable in the visor part slide groove in relation to the support part when a suffi- cient external force acts upon the visor part. The visor part locking mechanism is configured in such a way that the user can release the lock of the visor part. Flere the planes of both slide grooves are parallel. In some embodiments the plane of the visor part slide groove is different than the plane of the slide groove i.e. the directions of the planes diverge. In that case more positions for the visor part 103 are available and there are more shape options for the visor part to fit the purpose of the helmet.

In Figure 3 is shown a second embodiment of the helmet 300 as seen from above as a horizontal cut.

The helmet 300 comprises a support part 301 , a protective part 302, a visor part 303, a first protective part locking mechanism 308, a second protective part lock- ing mechanism 309, a first visor part locking mechanism 307 and a second visor part locking mechanism 310. There is a front side 305 and a back side 306 of the support part. These directions indicate how the user’s head is inside the helmet.

The horizontal cross-sections of the helmet parts on this cutting plane are essen- tially circular. This allows the movements of the protective part 302 and the visor part 303 to be smooth and to prevent possible jams.

The locking mechanisms, both protective part and visor part, are in this example situated on the sides of the helmet 300 and on the symmetry axis of the helmet. The first protective part locking mechanism 308 and the second protective part locking mechanism 309 are situated on the opposite sides of the helmet. The pro- tective part locking mechanism comprises parts that are on the support part 301 and on the protective part 302. At least one part of the locking mechanism fea- tures a magnet. Because the first protective part locking mechanism and the sec- ond protective part locking mechanism are situated symmetrically, there are two locking positions for the protective part. Of course, there are embodiments where the protective part locking mechanisms are not placed symmetrically. And natural- ly, there are embodiments where there are more than two protective part locking mechanisms.

The first visor part locking mechanism 307 and the second visor part locking mechanism 310 are situated on opposite sides of the helmet. The visor part lock- ing mechanism comprises parts that are on the support part 301 and on the visor part 303. At least one part of the visor part locking mechanism features a magnet. Because the first visor part locking mechanism and the second visor part locking mechanism are situated symmetrically, there are two locking positions for the visor part. If the visor part comprises a face-protection part, the visor part can be con- figured in such a way that in one position the face-protection part is covers the user’s eyes and in another position the face-protection part faces the back side 306 of the support part. Advantageously the face-protection part is in the latter position, shielded by the support part. Naturally, there can be more than two visor part locking mechanisms.

In Figure 4A and Figure 4B are shown a third embodiment of the helmet 400. The helmet comprises a support part 401 , a protective part 402, a visor part 403 and a stretching arrangement 404. The support part has a front side 405 and a back side 406. The visor part has a face-protection part that is higher than the other parts of the visor part. There are presented two positions of the part: in Figure 4A a first position and in Figure 4B a second position. In both figures the visor part is locked. This means that there should be at least two visor part locking mecha- nisms. In the first position the face-protection part covers the user’s face and es- pecially the user’s eyes. In the second position the face-protection part faces the back side of the support part. Because the face-protection part is higher than oth- er parts of the visor part, in the second position user’s face is uncovered. This could be beneficial if the user wants to perform an action that requires close in- spection that the visor part could otherwise inhibit. Also, there are embodiments where the inner walls of the support part include a cleaning arrangement that wipes the face-protection part clean when the visor part is moved to the second position or away from it.

In Figure 5 is shown a fourth embodiment of the helmet 500. The helmet compris- es a support part 501 , a protective part 502, and a visor part 503. These parts are presented separately from each other. When in use, the said parts are intercon- nected. They can be detachable from each other when some maintenance opera- tions are performed. Also, some parts could be exchanged. For example, if there are scratches on the visor part, it could be exchanged for a new one. The helmet also features a protective part locking mechanism which comprises two parts: a first part of the protective part locking mechanism 511 a and a second part of the protective part locking mechanism 511 b. The helmet further features a visor part locking mechanism which comprises two parts: a first part of the visor part locking mechanism 512a and a second part of the visor part locking mechanism 512b.

The support part 501 has a front side 505 and a back side 506. There is a slide groove 508 that opens upwards and a visor part slide groove 507 that opens downwards. The support part also comprises an inner dome part 509. The inner dome part conforms to the shape of the head. It covers the head wholly or partial- ly. Inside the inner dome part could be some padding or similar for cushioning purposes. The protective part 502 is a dome-like half-shell that has a circular lower edge 510. The lower edge is configured to fit in the slide groove 508. The shape of the protective part is configured in such a way that the protective part fits over the in- ner dome part 509 and is able to rotate in the slide groove. In the lower part of the protective part on the outer side near the lower edge is a receiving groove 514. The outer wall of the slide groove 508 has some arrangements that fit the said receiving groove and thus the protective part is kept in place. There may be similar arrangements on the inner wall of the slide groove and another receiving groove on the inner side of the protective part. The said fitting arrangements are config- ured not to obstruct the rotation of the protective part.

The visor part 503 is a circular object that has a face-protection part 513. The face-protection part is higher than other parts of the face-protection part. It is shaped in such a way that when it covers the user’s face, it is configured to protect at least the user’s eyes. The upper side of the visor part is modified to fit in a ro- tatable fashion in the visor part slide groove 507. In the outer side of the visor part near the top is a visor part receiving groove 515. The outer wall of the visor part slide groove 507 has some arrangements that fit on the said visor part receiving groove and thus the visor part is kept in place.

The first part of the protective part locking mechanism 511 a is on the outer side of the protective part 502. The second part of the protective part locking mechanism 511 b is on the outer wall of the slide groove 508. At least one part of the protec- tive part locking mechanism contains a magnet. When the protective part is rotat- ed slowly in the slide groove, the first part and the second part of the protective part locking mechanism will lock when they come to face each other. In some em bodiments the part or parts of the protective part locking mechanism are movable. There may be for example springs that keep the said locking mechanism part in its resting position. When the protective part locking mechanism parts come near each other the magnet or magnets will pull the parts together and lock them. When a sufficiently strong external force acts upon the protective part it will sepa- rate the protective part locking mechanism parts and release the protective part to rotate. When the protective part locking mechanism parts are separated, the spring or a similar arrangement pulls the protective part locking mechanism parts to their resting positions. If the helmet suffers an impact after the locking mecha- nism has released and the protective part remains undamaged, the protective part can be moved slowly to a position where the protective part locking mechanism parts lock and thus keep the protective part immobile in relation to the support part. Naturally there can be an embodiment where the protective part locking mechanism parts could be on the inner side of the protective part and on the inner wall of the slide groove. Naturally, there can be embodiments where there are the protective part locking mechanism parts on both sides of the protective part and on both walls of the slide groove.

The first part of the visor part locking mechanism 512a is on the outer side of the visor part 503. The second part of the visor part locking mechanism 512b is on the outer wall of the visor part slide groove 507. The visor part locking mechanism parts are similar to the protective part locking mechanism parts so they both be- have similarly and could have similar embodiments. Advantageously the visor part locking mechanism parts are easier to disengage than the protective part locking mechanism parts, i.e. less force is required to release the visor part locking mech- anism than the protective part locking mechanism. In that case the user himself or herself can move the visor part from one position to another. Since the back side 506 of the support part 501 is higher than the front side 505, the visor part slide groove is deeper at the back side. Therefore, the face-protection part 513 can be moved to a position where it is shielded inside the visor part slide groove.

In order to smoothen the rotation of the protective part 502 there could be embod- iments where a bearing arrangement 515 is placed at the top of the protective part. The bearing arrangement is configured to interconnect the support part 501 and the protective part. The bearing arrangement could be implemented with ball bearings or sliding elements or some pivoting arrangements or with some other arrangement. In addition to smoothening the rotation, the bearing arrangement can also be used to strengthen the overall structure of the helmet 500. Some advantageous embodiments of the helmet according to the invention have been described above. The invention is however not limited to the embodiments described above, but the inventive idea can be applied in numerous ways within the scope of the claims.