Filter cartridge

1. A filter cartridge comprising:

filtering media having an outer radial surface, an inner radial surface defining a fluid chamber, a first axial edge, and a second axial edge;

a first end cap having an axially inward side and an axially outward side and comprising a rigid adaptor ring and a seal structure;

wherein the rigid adaptor includes an annular shelf on which the first axial edge of the filtering media sits and an axially and outwardly protruding annular clip situated radially and axially outward from the filtering media;

wherein the seal structure encapsulates the shelf and a first end portion of the filter media including its first axial end and adjacent regions of the inner and outer radial surfaces; and

wherein the clip is not encapsulated by the seal structure whereby it is available for insertion into a housing channel.

2. A filter cartridge as set forth in claim 1 , further comprising a second cap sealing the second axial edge of the filtering media and closing a second axial end of the fluid chamber.

3. A filter cartridge as set forth in claim 1 , wherein the shelf and the clip are formed in one-piece.

4. A filter cartridge as set forth in claim 1 , wherein the shelf comprises a ledge situated flush against the first axial edge of the filtering media and another ledge perpendicular thereto situated flush against the outer radial surface of the filtering media.

5. A filter cartridge as set forth in claim 4 , wherein the shelf comprises circumferential ledge segments separated by radial slots.

6. A filter cartridge as set forth in claim 1 , wherein the clip comprises an annular skirt situated radially outward from the shelf and extends away therefrom in the axially outward direction.

7. A filter cartridge as set forth in claim 6 , wherein the clip comprises an annular flange extending radially outward from the distal edge of the skirt.

8. A filter cartridge as set forth in claim 7 , wherein the flange comprises circumferential flange segments separated by radial slots.

9. A filter cartridge as set forth in claim 6 , wherein the shelf and the skirt define an annular channel therebetween on the axially outward side and wherein the seal structure occupies a radially inward region, but not a radially outward, region of this channel.

10. A filter cartridge as set forth in claim 1 , wherein the adaptor ring further comprises an annular collar surrounding the first end portion.

11. A filter cartridge as set forth in claim 10 , wherein the collar is situated radially outward from the outer radial surface of the filtering media and extends axially away from the shelf in a direction towards the second axial edge of the filtering media.

12. A filter cartridge as set forth in claim 10 , wherein the outer radial surface of the filtering media and the collar define an annular trench therebetween on the axially inward side, and wherein the seal structure occupies this trench.

13. A filter cartridge as set forth in claim 10 , wherein the shelf, the clip, and the collar are formed in one piece.

14. A filter cartridge as set forth in claim 10 , wherein the adaptor ring further comprises an annular transition ridge connecting the shelf, the collar and the clip, and wherein the shelf, the collar, the clip, and the ridge are formed in one-piece.

15. A filter cartridge as set forth in claim 10 , wherein the shelf comprises a ledge situated flush against the first axial edge of the filtering media and another ledge perpendicular thereto situated flush against the outer radial surface of the filtering media;

wherein the clip comprises an annular skirt extending in the radially outward direction and an annular flange extending radially outward from the distal edge of the skirt;

wherein the shelf and the skirt define a moat therebetween on the axially outward side and wherein the seal structure occupies a radially inward region, but not a radially outward, region of this moat;

wherein the outer radial surface of the filtering media and the collar define an annular trench therebetween on the axially inward side, and wherein the seal structure occupies this trench.

16. A filter cartridge as set forth in claim 15 , wherein the shelf comprises circumferential ledge segments separated by radial slots and wherein the clip comprises circumferential flange segments separated by radial slots.

17. A filter cartridge as set forth in claim 15 , wherein the adaptor ring further comprises an annular transition ridge connecting the shelf, the collar and the clip, and wherein the shelf, the collar, the clip, and the ridge are formed in one-piece.

18. A filter cartridge as set forth in claim 1 and a housing having a clip-receiving channel, wherein the clip is inserted into the housing channel.

19. A filter cartridge as set forth in claim 18 functioning as a secondary filter cartridge, a housing having a channel in which the clip is inserted, and a primary filter cartridge, assembled together to form a filter assembly, wherein the secondary filter cartridge is mounted and sealed relative to the housing independently of the primary filter cartridge, whereby the filter assembly can be operated without the primary filter cartridge in emergency situations.

20. A filter cartridge comprising:

filtering media having an outer radial surface, an inner radial surface defining a fluid chamber, a first axial edge, and a second axial edge;

a first end cap having an axially inward side and an axially outward side and comprising a rigid adaptor ring and a seal structure;

wherein the rigid adaptor includes an annular shelf on which the first axial edge of the filtering media sits and an axially and outwardly protruding annular clip situated radially and axially outwardly from the filtering media and spaced radially outwardly from the seal structure,

wherein the seal structure and the clip define a furrow to receive an annular housing fence.