Abstract: A headgear adjustment mechanism is provided that includes a worm having a central axis of rotation, a first headband element, a second headband element, a spur gear, and a housing. The first headband element includes (i) a worm rack disposed in operative engagement with the worm, and (ii) a first pinion rack. The second headband element includes a second pinion rack. The spur gear is disposed in simultaneous operative engagement with the first pinion rack and the second pinion rack, and the housing at least partially encloses the first and second headband elements. During operation of the adjustment mechanism, rotation of the worm about the axis of rotation causes the first headband element and the second headband element to translate in opposite directions with respect to the worm, thereby adjusting a fit of the headgear.

Abstract: A headgear adjustment mechanism is provided that includes a worm having a central axis of rotation, a first headband element, a second headband element, a spur gear, and a housing. The first headband element includes (i) a worm rack disposed in operative engagement with the worm, and (ii) a first pinion rack. The second headband element includes a second pinion rack. The spur gear is disposed in simultaneous operative engagement with the first pinion rack and the second pinion rack, and the housing at least partially encloses the first and second headband elements. During operation of the adjustment mechanism, rotation of the worm about the axis of rotation causes the first headband element and the second headband element to translate in opposite directions with respect to the worm, thereby adjusting a fit of the headgear.

Abstract: A releasable two-part buckle having a first part and a second part is provided. The first and second parts have forward and rearward ends. A hook extends towards the forward end of the first part, while an arm extends towards the forward end of the second part. The hook has a first engagement surface. The arm has a center axis and a loop with a second engagement surface. The arm moves between an engaged state having the engagement surfaces engaged at a contact surface and a disengaged state having the engagement surfaces disengaged. In some embodiments, the buckle is configured so that the contact surface bisects the center axis in the engaged state. In other embodiments, the buckle is configured so that, when in the engaged state, a tension applied to the buckle induces substantially no bending moment in the arm towards the disengaged state.