Protection helmet with improved adjustable neckband

A protective helmet, comprising:

• a crown made from plastic material;
• a semi-rigid neckband having two opposite adjustable ends;
• and
• adjustment means having a pair of sliding mechanical links joined to said ends of the neckband, each of the sliding mechanical links comprising position indexing means controlled from a slide which is able to be moved from outside in a slit of the crown, the sliding mechanical links being positioned symmetrically on opposite lateral sides of the crown,
• wherein a length of the neckband remains constant during adjustment, the indexing means being molded directly along with the crown,
• said position indexing means are securely attached to an inside wall on each lateral side of the crown, and are formed by a rack having two series of notches separated by said slit, and
• an unlocking button of said slide has a coupling part bearing pins cooperating by clipping with the rack by action of a return spring that is a compression type spring that is arranged between a centering pin securely attached to a securing prong associated with each end of said neckband, and a hole arranged in the coupling part.