| 主权项 |
1. A breathable gas mask arrangement, comprising:
a mask shell having a portion adapted to receive a supply of pressurized breathable gas and a user side; a gusset portion having a first side attached to the user side of the shell and having a second side; a cushion having a first portion constructed and arranged to attach to the second side of the gusset portion and a second portion constructed and arranged to contact a user's face in use and provide a seal between the mask arrangement and the user's face; and a headgear constructed and arranged to attach the mask shell to the user; wherein, the gusset portion is constructed and arranged such that it can expand and contract to alter a distance between the mask shell and the cushion, an interior of the gusset portion being exposed to the supply of pressurized breathable gas and having a projected area on the user's face Ag which is greater than an area Ac of contact of the cushion with the user's face such that the supply of pressurized breathable gas acting on the area Ag provides a component of a contact force Fc of the cushion on the user's face, and a ratio of Ag/Ac is at least 1.30. |
