Ratchet mechanism for the headband of protective headgear used in high temperature environments

A ratchet mechanism for the headband of a protective helmet or other headgear is designed to function in high-temperature environments, while still allowing for ready adjustment of the size and fit of the headband. In this regard, the ratchet mechanism includes a rotational element that has a pinion adapted to mate with and engage the respective rack gears of the overlapping rear end portions of the headband, such that rotation of the rotational element causes lateral movement of the overlapping rear end portions with respect to one another. A spring assembly associated with the rotational element engages a ring gear defined by an insert received and retained in the housing so as to resist rotation of the rotational element relative to said housing sections. Since the spring assembly and insert are preferably manufactured from metal, they do not suffer from warping problems, and therefore, the ratchet mechanism continues to function properly even in high-temperature environments.