Ratchet diving mask strap

A ratchet diving mask strap comprising:

• two elastic straps with a first end of each strap secured to a frame of a diving mask, a second end of the straps being connected with upper and lower racks, respectively the upper rack including a depression area with a row of teeth on an upper inner surface thereof, the lower rack including a depression area with a row of teeth on an lower inner surface thereof, with the upper and lower racks being disposed in a guard cover so as to overlap, thereby forming a region with teeth on a top side and teeth on a lower side;
• the guard cover including an arced hollow body with an adjusting knob seat and a check catch seat on a front side thereof;
• a gear disposed in the guard cover and engaged with the teeth so that the gear can actuate the upper and lower racks, thus tightening and loosening the elastic strap when the gear is turned;
• an adjusting knob including a plurality of tooth recesses at a lower end thereof, the adjusting knob being disposed in an adjusting knob seat in the guard cover and connected with the gear;
• and
• a check device comprising a latch button and a spring disposed in the check catch seat of the guard cover, a protruding pin provided at a front end of the latch button, the rear end of the protruding pin being nested with the spring, the spring thereby urging the protruding pin into the tooth recesses of the adjusting knob, the front end of the protruding pin including a unidirectional inclined plane which permits the adjusting knob to run in only one direction when the protruding pin is engaged.