However, on the other hand, the one-piece full-face helmet also has defects: first, from the perspective of use, when the wearer needs to perform activities such as drinking water, talking, resting, etc., he must first take it off The helmet can complete the corresponding actions. Undoubtedly, the performance of the traditional one-piece structure full-face helmet is relatively sluggish and inconvenient; secondly, from the production point of view, the one-piece structure full-face helmet also has a large internal cavity with a small The structural characteristics of the gap make the mold very complicated, so the production efficiency is not high, which is the reason for the high manufacturing cost of the integrated structure full helmet
[0005] However, although the variable jaw structure helmet proposed by the Chinese patent application CN105901820A has self-evident advantages, it needs to adopt a long arc-shaped restraint groove with a penetrating characteristic to keep its rotating external gear and fixed internal gear. and its rotating external gear follows the chin guard to make a large-scale swinging motion, which also brings some disadvantages. The specific performance is: 1) The long and arc-shaped restraint groove makes the helmet There are hidden dangers in the reliability of the chin guard, which is because when the chin guard is in the process of changing its posture, especially when the chin guard is in a certain intermediate position between the full helmet structure and the half helmet structure to form a so-called face-opening helmet ( The helmet at this time belongs to the form of a "quasi-half-helmet structure helmet". This state is conducive to the wearer's activities such as drinking water, conversation and temporary ventilation, and is especially suitable for tunnel operations), because the jaw guard cannot completely cover In other words, it is difficult for the body of the jaw guard to effectively cover the penetrating long arc-shaped restraint groove. As a result, foreign matter enters the meshing motion pair formed by the rotating external gear and the fixed internal gear to create a chance. Once this happens This situation will make the gear restraint pair extremely prone to jamming. In other words, there is a certain hidden danger in the reliability of the helmet during use; 2) The existence of the long and arc-shaped restraint groove also makes The noise of the helmet is relatively large, and it is also because the jaw guard needs to be in a middle position between the full helmet structure and the half helmet structure during the process of changing its position. In other words, because the jaw guard cannot completely cover the restraint groove, the whistling sound generated by the external airflow passing through the outer surface of the helmet can easily be transmitted into the interior of the helmet from the through-shaped restraint groove. Notice these The restraint groove is just arranged near the two ears of the wearer, so the sound insulation effect of the helmet is poor or its comfort is poor; 3) The planetary rotation of the external gear layout and the mode of operation weaken the safety of the helmet to a certain extent , this is because when the jaw guard changes its structural position, the outer gear moves with the jaw guard and presents a planetary rotation behavior. It is obvious that fastening screws or other fastening structures cannot be arranged in the area. At this time, the bottom support with long arc-shaped restraint grooves will be forced to be arranged as a thin shell-shaped component with a large span. It is well known that this structural form of components is The intrinsic rigidity of the helmet is relatively small, which means that the rigidity of the helmet shell is weak, in other words, the safety of the helmet is weakened
[0006] To sum up, although the gear-constrained variable jaw guard structure type helmet can realize the conversion of the jaw guard between the full helmet position and the half helmet position, it also has the disadvantages of poor reliability, comfort and safety.
In a word, there is still room for further improvement and promotion of existing variable jaw structure helmets