Pleated filter

A cylindrical filter arrangement comprising:

• a first filter element;
• a second filter element, wherein the second filter element comprises a plurality of radially outwardly extending primary pleats positioned between inwardly radially extending secondary pleats, wherein at least some of the inwardly extending secondary pleats are shorter than some of the outwardly extending primary pleats, wherein at least some of the inwardly extending secondary pleats are of different lengths;
• wherein the first and second filter elements are generally cylindrical and concentrically arranged;
• wherein the first filter element comprises a material having an average pore size that is greater the average pore size of the material used in the second filter element.

A method of manufacturing a filter comprising:

• providing a first filter element;
• providing a second filter element, wherein the second filter element comprises a plurality of radially outwardly extending primary pleats positioned between inwardly radially extending secondary pleats, wherein at least some of the inwardly extending secondary pleats are shorter than some of the outwardly extending primary pleats, wherein at least some of the inwardly extending secondary pleats are of different lengths;
• arranging the second filter element concentrically around the first filter element;
• and
• configuring the first and second filter elements such that their estimated effective lives are about the same for the type of fluid to be filtered.

A cylindrical filter arrangement comprising:

• a first filter element;
• a second filter element,
• wherein the first and second filter elements are generally cylindrical and are concentrically arranged such that at least a portion of the second filter element surrounds at least a portion of the first filter element;
• a housing configured to direct the flow of fluid between the outer side surface of the second filter element and a center opening in the first filter element;
• wherein an outer diameter of the second filter element is at least twice as large as the inner diameter of the second filter element and the outer diameter of the first filter element;
• wherein the first and second filter elements comprise a plurality of radially outwardly extending primary pleats positioned between radially inwardly extending secondary pleats;
• wherein at least some of the inwardly extending secondary pleats are shorter than some of the outwardly extending primary pleats;
• wherein some of the secondary pleats vary in length;
• and
• wherein the first filter element comprises a material having an average pore size that is different than the average pore size of the material used in the second filter element.