In-tank fluid filter with plastic retainer

1. An in-tank fluid filter for a pump having an inlet fitting and a retention post with a post cross-section, the filter comprising:

a filter body made of porous material;

a plastic outlet port attached to the filter body for connecting the filter to the inlet fitting, the outlet port having a flow axis defined by an intended direction of fluid flow from the filter to the pump; and

a plastic retainer unitarily molded on the outlet port, the retainer comprising a tab extending in a plane perpendicular to the flow axis, the tab having a first surface facing the pump and a second surface facing away from the pump, the tab having an aperture for receiving the retention post, the aperture extending from the first surface to the second surface, the aperture having an effective cross-section at the first surface that is larger than the post cross-section, and the aperture having an effective cross-section smaller than the post cross-section in at least one radial plane intersecting with the flow axis between the first and second surfaces including the second surface.

2. The filter of claim 1 , wherein the effective cross-section is continuously reduced from the first surface toward the second surface and reaches a minimum proximate the second surface.

3. The filter of claim 1 , wherein the aperture has a tapered centering guide proximate the first surface.

4. The filter of claim 1 , wherein the aperture has two or more lugs extending radially inward for reducing the effective cross-section.

5. The filter of claim 4 , wherein the lugs are tapered so as to effect different effective cross-sections in different planes intersecting with the flow axis.

6. The filter of claim 4 , wherein the lugs each have a contour that makes a point-shaped contact with the effective cross-section in at least one radial plane intersecting with the flow axis.

7. The filter of claim 4 , wherein the lugs are distributed along the periphery of the aperture.

8. The filter of claim 4 , wherein the lugs are truncated, partial cones.

9. The filter of claim 4 , wherein the lugs have an inner contour adapted to the retention post.

10. The filter of claim 1 , wherein the retainer is made of a plastic material with embedded reinforcement material.

11. The filter of claim 10 , wherein the reinforcement material comprises at least one member of the group consisting of glass fibers and glass spheres.

12. The filter of claim 1 , wherein the retainer is made of a thermoplastic, fluid-resistant material.

13. The filter of claim 12 , wherein the thermoplastic, fluid-resistant material contains polyoxymethylene.

14. The filter of claim 1 , wherein the retainer obtains a non-positive lock with the retention post by deformation of the retainer.

15. The filter of claim 14 , wherein the deformation is at least in part elastic.

16. The filter of claim 1 , wherein the aperture has a frustoconical centering guide proximate the first surface and a plurality of lugs proximate the second surface, the effective cross-section at the centering guide being larger than the post cross-section and decreasing in a direction from the first surface toward the second surface, the effective cross-section at the lugs being larger than the post cross-section proximate the centering guide and decreasing in the direction from the first surface toward the second surface to become smaller than the post cross-section remote from the centering guide.

17. The filter of claim 1 , wherein the post cross-section is wider in one radial direction than in a radial direction perpendicular thereto and wherein the effective cross-section is defined as having mathematically similar proportions as the post cross-section.

18. The filter of claim 17 , wherein the post cross-section is rectangular.

19. The filter of claim 17 , wherein the post cross-section is oval.