Ring band adjustment structure of crash helmet

A ring band adjustment structure of a crash helmet, comprising:

• a ring band;
• a connection sheet of panel-shaped sheet;
• a locating bar joined on said connection sheet and divided into two symmetrically arranged halves, outer faces of said two half locating bars respectively having strip-shaped unidirectional locating elements, which are arranged opposed to each other, a guide slit being respectively disposed above and below between said locating bar and said connection sheet;
• and
• two locating adjusters each connected to one end of said ring band, a top side and a bottom side of said locating adjuster extending rearwards to form a pair of L-shaped locks, said pair of L-shaped locks being embedded in said guide slits of said locating bar to let said locating adjuster straddle said locating bar and move along the edge of said locating bar, said locating bar having a press element, a back face of said locating adjuster toward said locating bar having a point-shaped unidirectional locating element, said point-shaped unidirectional locating element being locked at said strip-shaped unidirectional locating element on said locating bar;
• whereby when pressing said press element, said point-shaped unidirectional locating elements will leave from said corresponding strip-shaped unidirectional locating elements on said locating bar, and the diameter of said ring band can be adjusted through the sliding of said locating adjuster.