A facial mask assembly for covering at least the nose and nares of a patient's face and compensating for any unequal forces that may be generated in the straps holding the mask on the patient's face. The assembly includes a rigid, cup-shaped shell with a soft seal engaging and sealing against the patient's...http://www.google.fr/patents/US5662101?utm_source=gb-gplus-shareBrevet US5662101 - Respiratory facial mask
