Head massager and helmet size adjusting structure thereof

A helmet size adjusting structure, wherein the structure is disposed between a front housing and a rear housing of a helmet of a head massager and comprises two racks that connect the front housing and the rear housing;

• rear ends of the two racks overlap each other, and an overlapping part is relatively contracted or expanded by using an adjusting apparatus;
• the adjusting apparatus comprises a revolving shaft that extends from outside to inside and a gear disposed on an inner end of the revolving shaft, an upper part and a lower part of the gear are separately engaged with the racks, and a knob component and a locking component that locks the knob component are further disposed on an outer end of the revolving shaft;
• and the helmet size adjusting structure further comprises two tension springs, wherein front ends of the tension springs are fixed on the rear housing and rear ends of the tension springs are separately fixed on the two racks;
• the knob component comprises a knob outer ring, a knob shell that matches the knob outer ring, and a gear stand that is disposed inside the knob shell and can turn with the knob outer ring and the knob shell;
• the locking component comprises a knob lock disposed inside the knob outer ring and the knob shell, an upper cover of the knob lock that is clamped with the knob lock, and an elastic element;
• the gear stand is located inside the knob lock, a unidirectional gear ring is disposed on the gear stand, a lock that can be clamped on the unidirectional gear ring is disposed on the knob lock, and the elastic element is disposed on the upper cover of the knob lock and configured to press against the upper cover of the knob lock so as to press on the knob lock, thereby matching the lock with the unidirectional gear ring for locking;
• teeth are further disposed on the gear stand, wherein the teeth pass through the knob lock and the knob shell in turn to engage with the gear.