Ring band adjustment structure of crash helmet

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

• a ring band having long grooves respectively at two end portions thereof, a dentation being formed above one said long groove of one said end portion, and a dentation being formed below the other said long groove of the other said end portion;
• a connection seat having openings respectively on two side faces thereof to be inserted by said two end portions of said ring band, said connection seat having a ring sheet on a back face thereof, a stepped inner edge being formed at an inner edge of said ring sheet, said connection seat having a circular groove on a front face thereof, said connection seat having a pair of locating grooves at an upper side and a lower side thereof;
• a guide element inserted into said ring sheet of said connection seat to penetrate through said two long grooves, said guide element having a tooth portion therein to join said dentations in said two long grooves, said guide element having, a stepped outer edge to be located at said stepped inner edge;
• an adjuster fixedly joined with said guide element, said guide element being driven to turn by said adjuster to let said inserted end portions of said ring band move toward or away from each other, said adjuster having radially arranged con e teeth on an inner face thereof;
• and
• a locating sheet having a ring, said ring having tabs respectively at an upper end portion and a lower end portion thereof said tabs being embedded in said locating grooves, said ring having V-shaped tabs respectively at a left end portion and a right end portion thereof, said V-shaped tabs being radially arranged to correspond to said cone teeth, said ring projecting upwards from two sides with said tabs at the upper and lower end portions as axis, said V-shaped tabs being used to locate said cone teeth of said adjuster to let said adjuster be stationary when not used.