TECHNICAL FIELD This invention relates generally to protective helmets and particularly to those helmets which are adjustable to the shape and size of the users' head.

BACKGROUND The need for a small and thin protective helmet has existed for many years in several athletic or entertainment sports. Requirements for such helmets are maximum impact protection, minimal weight and maximum stability and comfort. Current helmets make use of substantially one-piece rigid outer shells, which are available in several shapes and sizes in order to accommodate individual user's needs and demands. These shells are usually lined with impact absorbing materials and constructed large enough to accommodate additional padding structures for the purpose of responding to the shape, and to the size of the users' head. The use of such padding therefore, increases the overall size, weight and thickness of the helmet, which increases the dimensional profiles and often reduces stability.

In the past solutions have been disclosed which aim at providing a thinner profile and/or adjustability to the size of a user's head. In the following such solutions are discussed.

USA patent 3,197,784 by Carlisle discloses a protective headgear, and more particularly a helmet the periphery of which is divided into a plurality of segments for adjusting to a head of any desired size and shape.

US patent 5,515,546 by Shifrin discloses a combined protective helmet and pouch for a bicyclist or the like is constructed from a plurality of sector shaped pads of shock absorbing material connected together in an inextensible manner to define a helmet. The connectors between the pads at the side of the helmet may be folded to bring the front and rear halves of the helmet together to define a pouch. Adjustable members are provided to adjust the spacing between the pads and a suitable chin strap and carrying strap are connected to the helmet. US patent 5,5,44,367 by March discloses an aerodynamically streamlined flexible protective helmet assembly comprising an outer layer of impact resistant segments confined within fabric chambers overlying an inner layer of closely abutting impact resistant energy absorbing structures confined within elastic fabric chambers and including an elliptically annular crown structure confined within a fabric chamber.

A disadvantage of the current art solutions is that complexity is increased as well as the number of parts. Often a negative consequence of using segments in the current adjustable helmets is that they show either bulgings or do not fully protect the user's head because of open slots between the segments.

DISCLOSURE OF INVENTION

There are many examples of sports where wearing a helmet is not common or considered normal. This is for example the case in sailing, baseball, basketball and soccer. This seems strange, because accidents do happen also in these sport. Head injuries are often a consequence of these accidents. One of the reasons is that the players do not find regular helmets fashionable and/or comfortable.

It is an object of the present invention to provide an adjustable protective helmet with a minimum thickness and weight and sufficient comfort for a user to wear it as long as necessary. It is a further object of the invention to provide a helmet which can be worn underneath a regular hat or cap of choice, without being noticeable to public and without being limited in the choice of the hat or cap by the user. This will stimulate to wear the invented helmet, especially in sports where wearing a helmet is not considered fashionable or considered to be only appropriate for rookies or fainthearted people.

The object is realized by the following clauses.

1 . An adjustable protective headgear comprising multiple radially extending, outwardly expanding, elongated and concave members, the inner ends of which are rotatably joined at an apex; each member comprising:

longitudinal sides;

inner ends and outer ends; inner layers and outer layers;

said inner ends joined at an apex;

said multiple members arranged for being radially displaced towards each other or away from each other within a limited range;

said inner layers comprised of resilient material, characterized in that, the outer layers are arranged for constituting a practically closed hard shell when the multiple members are positioned within the limited range.

2. A headgear according to clause 1 , characterized in that the material of the inner layer comprises a microcellular urethane foam, such as Poron or Poron XRD. 3. A headgear according to any one of the preceding clauses, characterized in that the inner layer comprises a laminated layer of two materials, whereby the material closest to the outer layer comprises high impact resisting characteristics, whereas the material closest to the user's head when worn by the user, comprises high cushioning characteristics.

4. A headgear according to any one of the preceding clauses, characterized in that the material of the outer layer comprises an impact resistant material such as polycarbonate. 5. A headgear according to any one of the preceding clauses, characterized in that the multiple members comprise slots close to the outer ends, arranged for a strap to be passed laterally through the multiple members, whereby said strap is further arranged for being adjustable in length, whereby shortening of the length of the strap forces the multiple members to be displaced towards each other and loosening the strap allows the multiple members to be displaced away from each other. 6. A headgear according to any one of the preceding clauses, characterized in that a longitudinal side of a first member of the multiple members overlaps a longitudinal side of a second adjacent member of the multiple members. 7. A headgear according to any one of the preceding clauses, characterized in that the headgear is arranged for being invisibly worn underneath a hat or a cap.

The present invention, also described in detail below, enables a construction of a helmet that is adjustable in size while providing complete protection from impact over the surface of the users' head where covered by the helmet. Due to the overlapping pieces of the outer segments there is no point on the helmet surface which does not present a structurally sound resistance to impact. The helmet therefore provides protection from impacts equivalent to rigid one-piece outer shells. This approach therefore provides a flexible helmet with superior responsiveness and conformity to the users' head shape and size while simultaneously providing sufficient protection from impacts. This concept of construction also permits a very compact, lightweight and thin assembly resulting in a construction which can be worn under a cap or hat of choice without being visible.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures show views of embodiments in accordance with the present invention. FIGURE 1 shows an isometric view of an embodiment of the present invention, showing the outside of the protective headgear.

FIGURE 2 shows an isometric view of a detail of the embodiment of figure 1 .

FIGURE 3 shows an isometric view of an embodiment of the present invention, showing the inside of the protective headgear. DETAILED DESCRIPTION

The invention is now described by the following aspects and embodiments, with reference to the figures. FIGURE 1 shows an isometric view of an embodiment of the present invention, showing the outside of the protective headgear 100. Outwardly expanding, elongated and concave members 101 a,b have an overlap 103b. Members 101 a,b have inner ends 104 and outer ends 105. Members 101 a,b are connected to apex 106 at the inner ends 104. Along the longitudinal side of member 101 b an overlap 103b is provided which is slid at the inside of member 101 a, thus forming a closed shell. Members 101 a,b are preferably arranged for being movable from each other to a certain limit, in order to maintain the overlap 103b. For this purpose for example a small ridge may be provided along the overlap which prevents member 101 a from moving beyond the overlap 103b. The members may be biased to have as default position the furthest position from each other. A wide position in this case implies also a lower profile of the headgear. Holes 102a,b are provided per member 101 a,b for allowing a strap (not shown) to be tied through the holes 102a,b and along the preferably outer ends 105 of the members 101 a,b. By tightening the strap the members 101 a,b are moved towards each other and therefore the headgear becomes narrower (i.e. the diameter of the headgear decreases) in order to fit a certain head size. Members 101 a,b are preferably comprised of at least two layers, of which the outer layer preferably comprises a relatively hard material which is impact resistant and of which the inner layer has characteristics which provide additional impact resistance and provides comfort for the user by being relatively resilient. The material of the inner layer therefore acts cushioning.

FIGURE 2 shows an isometric view of a detail of the described embodiment 100 of figure 1 , in order to further illustrate the overlap 103a,b.

FIGURE 3 shows an isometric view of an embodiment of the present invention, showing the inside of the protective headgear 100, in order to further illustrate the positions of the members 101 a,b and overlap 103b.