Patent ID: 8856974

Claim:
A safety helmet comprising: an outer shell in the form of a crown made from shock-resistant plastic material, a headband arranged inside the crown and composed of a neckband at the rear and a securing strap at the front, an adjustment mechanism provided with at least one rotary adjustment knob to adjust the headband to the size of the user's head, and a latch designed to occupy a latched position or an unlatched position to respectively prevent and allow driving of the knob in rotation, wherein the adjustment mechanism comprises a first double cog-wheel and a second double cog-wheel, wherein the first double cog-wheel has a first sprocket associated with a first drive rack of the neckband, and a second sprocket associated with a first drive rack of the strap, the first and second sprockets of the first double-cog wheel having different diameters to achieve differential driving of the strap and of the neckband, wherein the second double cog-wheel has a first sprocket associated with a second drive rack of the neckband, and a second sprocket associated with a second drive rack of the strap, the first and second sprockets of the second double-cog wheel having different diameters to achieve differential driving of the strap and of the neckband, wherein either one of the first and second double cog-wheels and corresponding control knob are fitted on each of the two sides around a common axis of rotation extending perpendicularly to the internal surface of the shell, and wherein the first and second sprockets of the first and second double-cog wheels are fitted coaxially on the same axis.