Nasal mask

1. A mask including: a shell; a cushion connected with said shell; said shell having a side wall; a retaining ring permanently secured to the shell inside said side wall, said side wall and said retaining ring defining a gap between said side wall and said retaining ring, said gap extending around said shell, wherein said retaining ring has a notch in cross-section; wherein said shell includes a plurality of projecting posts, and said retaining ring includes a plurality of sleeves receiving said posts to permanently secure said retaining ring inside said side wall of said shell; said cushion having a side wall with an outer peripheral edge portion including a tongue extending around said cushion, said tongue having a retaining flange that extends transverse to the tongue in cross-section; said retaining flange of said cushion tongue and said notch of said retaining ring being configured such that said tongue is repeatably insertable into said gap while the retaining ring is secured to the shell so that the retaining flange of the tongue engages the notch of the retaining ring to secure said cushion to said shell and the retaining flange of the tongue is repeatably removeable from the notch of the retaining ring while the retaining ring is secured to the shell to remove the cushion from the shell.

2. The mask of claim 1 wherein said sleeves are heat staked on said posts to permanently secure the retaining ring to the shell.

3. A nasal mask including:

a shell; and

a cushion connected with said shell for engagement with the face of a user;

said cushion having a side wall, an inner wall extending from the side wall transverse to said side wall, and an outer wall extending from the side wall transverse to said side wall;

wherein said outer wall is defined by first and second sides that are spaced apart by a thickness of the outer wall, wherein said first side of the outer wall is adapted to engage and seal against a face of a user of the mask;

wherein both of said first and second sides of said outer wall of said cushion extend from said side wall extending completely around said cushion;

wherein said inner wall is defined by first and second sides that are spaced apart by a thickness of the inner wall, wherein said first side of said inner wall is spaced apart from said second side of said outer wall;

wherein both of said first and second sides of said inner wall of said cushion are discontinuous in a nasal bridge region of said cushion, such that a gap is formed between ends of the inner wall in said nasal bridge region.

4. A nasal mask as set forth in claim 3 wherein said inner wall of said cushion is thicker and stronger than said outer wall of said cushion for supporting said outer wall.

5. A nasal mask as set forth in claim 3 wherein the outer wall extends laterally inward from the side wall, and the inner wall extends around the side wall.

6. A nasal mask as set forth in claim 3 wherein the inner wall of the cushion is stiffer than the outer wall for supporting the outer wall.

7. A nasal mask as set forth in claim 6 wherein the inner wall of the cushion is thicker than the outer wall and is spaced from the user's face when the outer wall seals against a face of a user of the mask.

8. A nasal mask as set forth in claim 3 wherein the inner wall of the cushion is thicker than the outer wall and is spaced from the user's face when the outer wall seals against a face of a user of the mask.

9. The mask of claim 3 wherein said inner wall of said cushion does not extends from the side wall in said nasal bridge region of said cushion.

10. The mask of claim 3 wherein a gap is formed between two ends of the inner wall of said cushion in said nasal bridge region of said cushion.

11. A mask including:

a shell having a side wall;

a cushion;

a retaining ring permanently secured to the shell inside said side wall by sleeves that are heat staked on posts;

said side wall and said retaining ring defining a gap between said side wall and said retaining ring, said gap extending around said shell wherein said retaining ring has a notch in cross-section;

said cushion having a side wall with an outer peripheral edge portion including a tongue extending around said cushion, said tongue having a retaining flange that extends transverse to the tongue in cross-section;

said retaining flange of said cushion tongue and said notch of said retaining ring being configured such that the tongue is repeatably insertable into said gap while the retaining ring is secured to the shell so that the retaining flange of the tongue engages the notch of the retaining ring to secure said cushion to said shell and the retaining flange of the tongue is repeatably removeable from the notch of the retaining ring while the retaining ring is secured to the shell to remove the cushion from the shell.

12. A method of assembling, cleaning, and reassembling a mask comprising: securing a retaining ring to a shell inside a side wall of the shell to define a gap and a notch between said side wall and said retaining ring that extends around the shell; inserting a tongue of the cushion into said gap while the retaining ring is secured to the shell so that a retaining flange that extends transverse to the tongue engages the notch to secure said cushion to said shell; a retaining ring permanently secured to the shell inside said side wall by sleeves that are heat staked on posts: removing the tongue and retaining flange from the gap and notch while the retaining ring is secured to the shell to remove the cushion from the shell; cleaning said cushion; inserting the tongue of the cushion into said gap while the retaining ring is secured to the shell so that the retaining flange of the tongue engages the notch to resecure said cushion to said shell.

13. A mask as set forth in claim 12 wherein said securing said retaining ring to said shell comprises heat staking a plurality of sleeves of said retaining ring onto a plurality of projecting posts of said shell.