Method and mold for making a pleated filter cartridge

1. A method for making a pleated filter cartridge using a mold that has an elastomeric surface for forming a seal with a bottom end of a pleated filter, the method comprising the steps of:

placing the bottom end of the pleated filter on an elastomeric surface of the mold, the pleated filter having pleats that define an inner cavity and a perimeter, the elastomeric surface comprising a circular bump protruding from the elastomeric surface, the circular bump being disposed within the inner cavity and having a height that is at a maximum at the center of the circumference of the circular bump and diminishes in height from the center of the circumference to the perimeter of the circumference, the center of the circumference intersecting a central longitudinal axis of the pleated filter;

applying a downward force to the top end of the pleated filter to cause the pleated filter to establish a seal with the elastomeric surface of the mold;

adding a polymerizable potting compound to the inner cavity and permitting the potting compound to cover the portion of the elastomeric surface of the mold that is encompassed by the pleats including the spaces between the pleats that are part of the inner cavity, the circular bump being shaped to guide the potting compound toward the pleats, the potting compound being selected to form a polyurethane after polymerization, wherein the polymerizable potting compound does not extend outside the perimeter of the pleated filter;

permitting the potting compound to polymerize to form a polyurethane bottom end cap; and

removing the polyurethane bottom end cap from the mold.

2. The method as recited in claim 1 , further comprising the step of forming an external support strap encompassing the circumference of the pleated filter.

3. The method as recited in claim 2 , wherein the external support strap is formed by extrusion.

4. The method as recited in claim 1 , wherein the step of adding a polymerizable potting compound adds an amount of potting compound to fill the inner cavity to a depth of about 0.5 cm to about 10 cm.

5. The method as recited in claim 1 , wherein the potting compound comprises an isocyanate monomer and a hydroxyl monomer.

6. The method as recited in claim 1 , wherein the elastomeric surface comprises a silicone elastomer.

7. The method as recited in claim 1 , wherein the elastomeric surface has a Shore A hardness of between 0 and 20.

8. The method as recited in claim 1 , wherein the step of applying a downward force to the top end of the pleated filter causes the elastomeric surface to be deformed by the pleats of the bottom end of the pleated filter to establish the seal.

9. The method as recited in claim 1 , further comprising the steps of:

adding a polymerizable resin to a second mold;

placing a top end of the pleated filter in the polymerizable resin;

permitting the polymerizable resin to cure to form a top end cap; and

removing the top end cap from the second mold.

10. The method as recited in claim 9 , wherein the polymerizable resin is selected to form a polyurethane after polymerization.

11. The method as recited in claim 1 , further comprising the step of inserting a support core into the pleated filter.

12. The method as recited in claim 1 , wherein the potting compound is selected to form a thermoplastic polyurethane after polymerization.

13. The method as recited in claim 1 , wherein the bump has a diameter that is at least 50% of a diameter of the inner cavity.

14. The method as recited in claim 1 , wherein the maximum of the height of the circular bump is at the center of the circumference and all other points on the circular bump are below the maximum.