Abstract: A filter cartridge for use in a fluid filtering system, constructed to induce rotational flow in the unfiltered fluid, includes a pleated filter sleeve in which the individual sleeves are slanted relative to the sleeve circumference in a direction opposite to the direction of the rotational flow fluid. The slanted pleats can be constructed by creasing a sheet of filter media at alternatingly shorter and longer widths to form pleats having relatively shorter front legs and relatively longer back legs. The shorter front legs bias the pleats in the counter-rotational direction.

Abstract: A filter cartridge for use in a fluid filtering system, constructed to induce rotational flow in the unfiltered fluid, includes a pleated filter sleeve in which the individual sleeves are slanted relative to the sleeve circumference in a direction opposite to the direction of the rotational flow fluid. The slanted pleats can be constructed by creasing a sheet of filter media at alternatingly shorter and longer widths to form pleats having relatively shorter front legs and relatively longer back legs. The shorter front legs bias the pleats in the counter-rotational direction. Apparatus for manufacturing the pleated sleeve includes a pleater roll having pleater wires spaced to form the alternatingly shorter and longer pleat widths.

Abstract: The disclosure concerns a swimming pool-type filter comprising: (a) a stainless steel vertical cylindrical vessel with a removable domed cover and a horizontal partition sealed between the periphery of the cover and the open vessel, from which partition suspends a plurality of filter cartridges; and (b) a helically coiled heat exchanger coaxial of the vertical axis of the vessel and having its horizontal inlet and outlet ducts extending through the side of the vessel and supporting the coil. The filter cartridges fit inside and around the outside of the helical coil for easy removal, replacement and cleaning by lifting the partition after the cover has been removed. The inlet and outlet ducts for the liquid or water to be filtered and warmed are in the bottom of the vessel, with the outlet duct extending up through the vessel to the chamber above the partition in the domed cover.