Dual media filter cartridge construction

A filter assembly for filtering particles from a liquid which comprises:

• a housing having an inlet for liquid to be filtered and an outlet for filtered liquid,
• a filter cartridge including a first cylindrical seamless depth filter and a pleated filter positioned within said housing, said pleated filter having a first percent retention efficiency of particles of a given size,
• said first cylindrical seamless depth filter formed of a plurality of filtration media formed from thermoplastic fibers including a first of said filtration media having a lowest percent retention efficiency of said particles positioned adjacent said fluid inlet means and a second of said filtration media having a highest percent retention efficiency of said particles being positioned adjacent said pleated filter,
• said pleated filter being positioned adjacent said outlet,
• a screen supporting said pleated filter, said pleated filter having a higher percent retention efficiency of said particles than said second of said filtration media,
• said first cylindrical seamless depth filter and said pleated filter surrounding a central opening which extends the length of said first cylindrical seamless depth filter and said pleated filter,
• said first cylindrical seamless depth filter and said pleated filter defining a first surface at one end which is sealed and said first cylindrical seamless depth filter and said pleated filter defining a second surface at an end opposite to said first end which is sealed with a second seal having a second opening that communicates with said central opening,
• said filter assembly having a pressure drop between said inlet and said outlet less than a predetermined pressure drop when challenged with water containing fine hard particle test dust for a time period at least about 100% longer than a second filter element formed from said first cylindrical seamless depth filter and a second cylindrical seamless depth filter having a percent retention efficiency of said particles substantially the same as said first percent retention efficiency of said particles of said pleated filter.

A filter element for filtering particles from a liquid which comprises:

• a pleated filter having a first percent retention efficiency of particles of a given size,
• a first wound depth filter being formed of a plurality of filtration media, a first of said filtration media being formed of fibers in sheet form and having a lowest percent retention efficiency of said particles being positioned adjacent an inlet means for introducing a liquid to be filtered into said element, a second of said filtration media being formed of fibers in sheet form and having a highest percent retention efficiency of said particles being positioned adjacent said pleated filter,
• said pleated filter being positioned adjacent an outlet means for removing filtered liquid from said filter element,
• a screen supporting said pleated filter, said pleated filter having a higher percent retention efficiency of said particles than said first wound depth filter,
• said first wound depth filter and said pleated filter surrounding a central opening which extends the length of said first wound depth filter and said pleated filter,
• said first wound depth filter and said pleated filter defining a first surface at one end which is sealed and said first wound depth filter and said pleated filter defining a second surface at an end opposite to said first end which is sealed with a second seal having a second opening that communicates with said central opening,
• said filter element having a pressure drop across said depth filter and said pleated filter less than a predetermined pressure drop when challenged with water containing fine hard particle test dust for a time period at least about 100% longer than a second filter element formed from said first wound depth filter and a second wound depth filter having a percent retention efficiency of said particles substantially the same as said percent retention efficiency of said particles of said pleated filter.

A filter assembly which comprises:

• a housing having an inlet for introducing liquid to be filtered into said assembly and an outlet for removing filtered liquid from said filter element,
• a filter cartridge including a first wound depth filter and a pleated filter positioned within said housing,
• said first wound depth filter being formed of a plurality of filtration media including a first of said filtration media being formed of fibers in sheet form and having a lowest percent retention efficiency of particles of a given size positioned adjacent said inlet and a second of said filtration media being formed of fibers in sheet form and having a highest percent retention efficiency of said particles being positioned adjacent said pleated filter,
• said pleated filter being positioned adjacent said outlet,
• a screen supporting said pleated filter, said pleated filter having a higher percent retention efficiency of said particles than said second of said filtration media,
• said first wound depth filter and said pleated filter surrounding a central opening which extends the length of said first wound depth filter and said pleated filter,
• said first wound depth filter and said pleated filter defining a first surface at one end which is sealed and said first wound depth filter and said pleated filter defining a second surface at an end opposite to said first end which is sealed with a second seal having a second opening that communicates with said central opening,
• said filter assembly having a pressure drop between said inlet and said outlet less than a predetermined pressure drop when challenged with water containing fine hard particle test dust for a time period at least about 100% longer than a second filter element formed from said first wound depth filter and a second wound depth filter having a percent retention efficiency of said particles substantially the same as said first percent retention efficiency of said particles of said pleated filter.

A process for filtering particles from a liquid which comprises:

• introducing a liquid to be filtered into a filter assembly which includes a housing having an inlet for introducing liquid to be filtered and an outlet for filtered liquid,
• a filter cartridge including a first cylindrical seamless depth filter and a pleated filter positioned within said housing, said pleated filter having a first percent retention efficiency of particles of a given size
• said first cylindrical seamless depth filter formed of a plurality of filtration media formed from the thermoplastic fibers including a first of said filtration media having a lowest percent retention efficiency of said particles positioned adjacent said inlet and a second of said filtration media having a highest percent retention efficiency of said particles being positioned adjacent said pleated filter,
• said pleated filter being positioned adjacent said outlet,
• a screen supporting said pleated filter, said pleated fiber having a higher percent retention efficiency of said second of said filtration media,
• said first cylindrical seamless depth filter and said pleated filter surrounding a central opening which extends the length of said first cylindrical seamless depth filter and said pleated filter,
• said first cylindrical seamless depth filter and said pleated filter defining a first surface at one end which is sealed and said first cylindrical seamless depth filter and said pleated filter defining a second surface at an end opposite to said first end which is sealed with a second seal having a second opening that communicates with said central opening,
• said filter assembly having a pressure drop between said inlet and said outlet less than a predetermined pressure drop when challenged with water containing fine hard particles test dust at a given flow rate for a time period at least about 100% longer than a second filter element challenged with said water containing said fine hard particle test dust at said flow rate and formed from said first cylindrical seamless depth filter and a second cylindrical seamless depth filter having a percent retention efficiency of said particles substantially the same as said first percent retention efficiency of said particles of said pleated filter,
• passing said liquid to be filtered through said cylindrical seamless filter and said pleated filter,
• and removing filtered liquid from said outlet.

A process for filtering particles from a liquid which comprises:

• introducing a liquid to be filtered into a filter assembly which includes a housing having an inlet for introducing liquid to be filtered and an outlet for removing filtered liquid from said filter element,
• a filter cartridge including a first wound depth filter and a pleated filter positioned within said housing,
• said first wound depth filter being formed of a plurality of filtration media including a first of said filtration media being formed of fibers in sheet form and having a lowest percent retention efficiency of particles of a given size positioned adjacent said inlet and a second of said filtration media being formed of fibers in sheet form and having a highest percent retention efficiency of said particles being positioned adjacent said pleated filter,
• said pleated filter being positioned adjacent said outlet,
• a screen supporting said pleated filter, said pleated filter having a higher percent retention efficiency of said particles than said second of said filtration media,
• said first wound depth filter and said pleated filter surrounding a central opening which extends the length of said first wound depth filter and said pleated filter,
• said first wound depth filter and said pleated filter defining a first surface at one end which is sealed and said first wound depth filter and said pleated filter defining a second surface at an end opposite to said first end which is sealed with a second seal having a second opening that communicates with said central opening,
• said filter assembly having a pressure drop between said inlet and said outlet less than a predetermined pressure drop when challenged with water containing fine hard particle test dust at a given flow rate for a time period at least about 100% longer than a second filter element challenged with said water containing said fine hard particle test dust at said flow rate and formed from said first would depth filter and a second wound depth filter having a percent retention efficiency of said particles substantially the same as said first percent retention efficiency of said particles of said pleated filter
• passing said liquid to be filtered through said first wound depth filter and said pleated filter,
• and removing filtered liquid from said outlet.