Patent Description:
Fluid filters are commonly used for removing contaminants from liquid or gas to prevent damage to downstream components, such as an engine. Filtration systems are generally configured so that incoming contaminated fluid moves along a flow path until it encounters filter material. As the fluid passes through the filter material, a sufficient amount of the contaminants will be captured by the filter material so that the fluid exiting the filter is considered to be clean enough for the particular use of the resultant fluid.

A wide variety of filter configurations are available for use in different applications. In relatively simple configurations, a single flat sheet of filter material is positioned in the fluid path so that contaminated fluid flows from a "dirty" side of the filter material to the "clean" side, wherein the flat filter sheet is particularly designed of filter material that will capture contaminants of a certain size and/or composition. In order to provide additional filtration capabilities, it is common to pleat the filtration material to increase the amount of filter material used in a given space. In particular, the filter material can be folded in an accordion-like manner to produce multiple pleats across the width of material. The pleats for these arrangements typically include pleats of the same or similar height across the width of the media pack.

In order to fit into a particular opening and/or to further increase the amount of filter material provided in a given volume, pleated filter material can also be arranged into cylindrical configurations in which pleats extend in a radial direction, such as from a central core area. The core may be circular or may have a rectangular cross-sectional shape, for example. In either case, the pleats will be relatively densely packed in the area closest to the central core, thereby "masking" portions of the filter material and making it unusable. Document <CIT> discloses a filter element of an air filter. The filter element comprises a plurality of sections of filter materials, which are folded into continuous V shape which are connected end to end to form a cylinder body. The outer wall of the cylinder body is cylinder-shaped and the shape of the inner wall of the cylinder body is divided into a plurality of sections of arc surfaces with different radiuses
Document <CIT> discloses a filter element comprising a filter medium and end discs, wherein the filter medium has a plurality of adjoining pleats having a pleat height formed between a pleat base and a pleat tip. The pleat height between adjacent pleats increases and decreases over a plurality of pleats.

While configurations described above can be adequate for many filtration applications, there is a need to provide pleat configurations that use the existing outside filter geometry while increasing the amount of usable or "unmasked" filter material within the given filtration space.

A filter element according to the invention is disclosed in any one of claims <NUM>-<NUM>.

The present invention will be further explained with reference to the appended Figures, wherein like structure is referred to by like numerals throughout the several views, and wherein;.

Referring now to the Figures, wherein the components are labeled with like numerals throughout the several Figures, and initially to <FIG>, a top view of an example of a cylindrical filter <NUM> not according to the present invention is illustrated. Filter <NUM> includes a central core <NUM> that extends along at least a portion of the height of the filter <NUM>. Filter <NUM> further includes pleated filter material <NUM> arranged around the central core <NUM> and extending generally radially outward from the core <NUM>. As shown, the filter <NUM> has an outer peripheral boundary represented by the circle <NUM>, which may be provided by a shell that extends along at least a portion of the filter height, filter caps at one or both ends of the filter material, and/or another structure. In any case, the outer peripheral boundary <NUM> is generally circular and can optionally be designed to fit into existing applications that utilize filters of a certain size and shape, or can be designed for new applications.

<FIG> illustrate an example of the central core <NUM> that can be used in the filter embodiment of <FIG>. As shown, the end or top of central core <NUM> has an elongated shape that includes a convex curved central portion <NUM> and first and second end portions <NUM>, <NUM>. The core <NUM> may be centered about a central longitudinal axis <NUM> or may be at least slightly offset from the central axis <NUM>. The core <NUM> also may be symmetric about the central axis <NUM>, as shown, or the two portions on opposite sides of the central axis <NUM> can have at least a slightly different shape from each other. However, in the illustrated filter <NUM>, the core <NUM> is symmetric about the central axis <NUM>. In this embodiment, the first and second end portions <NUM>, <NUM> have the same width <NUM>, which is less than a maximum width <NUM> of the curved central portion <NUM>. However, the end portions <NUM>, <NUM> can instead have widths that are at least slightly different from each other.

The curve of the central portion <NUM> of the core <NUM> is generally constant such that the width of the core <NUM> tapers generally constantly from the width <NUM> at the central area of the core to the width <NUM> at the first and second ends <NUM>, <NUM>. However, it is understood that the curve of the central portion <NUM> can instead vary such that the radius of the curve varies across the length of the core <NUM>. In any case, the ends <NUM>, <NUM> are shown as being generally flat, with end surfaces that are generally perpendicular to the length of the core, although the end surfaces can be differently configured, such as curved, angled, or the like.

<FIG> illustrate one exemplary structural configuration for the central core <NUM> along its height, which includes a number of support structures. Although the configuration of support structures can vary considerably, they are to be selected to provide sufficient structural integrity to the core while allowing for a desired flow volume through the core during filtration (i.e., designed such that the material flow is not significantly obstructed). The support structures illustrated extend both longitudinally and laterally, with spacing that provides for a desired filtration performance. The relative number of support structures can be higher or lower than illustrated. In any configuration, however, the outer perimeter of the core should have surfaces that provide structure against which pleat tips of the filter material can be supported.

In embodiments of the invention, a single central core <NUM> extends along the entire height of the cylindrical filter <NUM>. In other embodiments, the core <NUM> extends along only a portion of the height of the cylindrical filter <NUM>. In configurations where the core <NUM> extends along only a portion of the height of the filter <NUM>, it is possible that multiple cores <NUM> are "stacked" on each other along the height of the filter <NUM>, either with or without spaces between them.

With particular reference again to <FIG>, the filter material <NUM> is pleated and positioned within the space between the central core <NUM> and the outer peripheral boundary <NUM> of the filter <NUM>. The folds or tips that are positioned nearest the central core <NUM> are referred herein as the inner tips while the folds or tips that are positioned nearest the outer peripheral boundary <NUM> are referred to as the outer tips. Because the outer shape of the core <NUM> and the shape of the outer peripheral boundary <NUM> are different, the space between them varies around the perimeter of the filter, and therefore the pleated filter material <NUM> has pleats of varying length around the filter <NUM>. That is, the areas nearest the first and second end portions <NUM>, <NUM> of the core <NUM> are shorter than those that are adjacent to the curved central portion <NUM>. This oval-like cross-sectional shape of the central core <NUM> helps to naturally space the pleats from each other around the periphery of the filter <NUM> while allowing more media to be fit into the space than with a central core that is circular. This is due to the geometry of a circular central core where spacing the inner tips adjacent the core with a desired spacing between them provides for relatively large spacing of the outer tips from each other, thereby not maximizing the amount of filter material that can be fit into the available space.

The pleated filter material can be selected from a number of different materials, such as a non-woven material sheet (e.g., melt blown material) or micro porous membranes (e.g., nylon, poly(tetrafluoroethylene) (PTFE), polypropylene, polyethylene, and the like). The pleated filter material can be provided as a sheet that is foldable multiple times to create the desired pattern and therefore is provided with a thickness that will allow it to fold back on itself and maintain the folded pattern.

The term "pleat" used herein refers generally to the V-shaped configurations of filter material that include two adjacent arms with distal ends that meet at an outer periphery of the cylindrical filter at a "peak". Each of those arms also includes a proximal end that is spaced radially inward from the outer periphery to define a portion of a V-shaped configuration internal to the outer filter periphery at a "valley. " Further, while a V-shape is described, the tip or point of the V-shape can be at least slightly rounded, where the radius of the tip is a function of the pleating method and tools used, along with the thickness of the filter material.

In order to provide a certain amount of filter material <NUM> in a particular filter, the parameters of the central core <NUM> can be designed and adjusted accordingly. That is, the core dimensions can be selected to provide a cross-section that is more oval, circular, or rectangular than shown. For another example of such a central core shape, <FIG> provides for a filter <NUM> with a central core <NUM> that has first and second ends <NUM>, <NUM> that are more rounded than the central core <NUM> of <FIG>, and which has an overall more "flattened" shape. As such, the filter material <NUM> is arranged so that its inner tips are adjacent the central core <NUM> along its longitudinal curved surfaces, but no inner tips are positioned directly adjacent to the tips of the first and second ends <NUM>, <NUM>. That is, the pleats in this embodiment do not extend radially outward from the tips of the first and second ends <NUM>, <NUM> toward an outer peripheral boundary <NUM> of the filter <NUM>. Thus, there are no corresponding outer tips of the filter material spaced radially from the tips of the first and second ends <NUM>, <NUM>.

Referring now to <FIG>, a top view of an embodiment of a cylindrical filter <NUM> is illustrated. Filter <NUM> includes a central core <NUM> that extends along at least a portion of the height of the filter <NUM>. Filter <NUM> further includes pleated filter material <NUM> arranged around the central core <NUM> and extending generally vertically outward from the core <NUM>, wherein the term "vertically" is used with regard to the orientation of the filter <NUM> in <FIG>. As shown, the filter <NUM> has an outer peripheral boundary represented by the circle <NUM>, which may be provided by a shell that extends along at least a portion of the filter height, filter caps at one or both ends of the filter material, and/or other structure. In any case, the outer peripheral boundary <NUM> is generally circular and designed or selected to fit into new and existing applications that utilize filters of this size and shape.

<FIG> illustrate an exemplary embodiment of the central core <NUM> that can be used in the filter embodiment of <FIG>. As shown, the end or top of central core <NUM> has an elongated shape that includes a convex curved central portion <NUM> with first and second end portions <NUM>, <NUM>, along with wing portions <NUM>, <NUM> extending from first and second end portions <NUM>, <NUM>, respectively. The core <NUM> may be centered about a central longitudinal axis <NUM> or may be at least slightly offset from the axis <NUM>. The core <NUM> also may be symmetric about the central axis <NUM>, as shown, or the two core portions on opposite sides of the axis <NUM> can have at least a slightly different shape from each other. However, in the illustrated filter <NUM>, the core <NUM> is symmetric about the central axis <NUM>. In this embodiment, the first and second end portions <NUM>, <NUM> have the same width <NUM>, which is less than a maximum width <NUM> of the curved central portion <NUM>. The wing portions <NUM>, <NUM> have a width <NUM> that is illustrated as being greater than the width <NUM> of the central portion <NUM> and the width <NUM> of the first and second end portions <NUM>, <NUM>, although it is understood that the width <NUM> can be less than the width <NUM> of the central portion <NUM> and/or the width <NUM> of the first and second end portions <NUM>, <NUM>.

The curve of the central portion <NUM> of the core <NUM> is generally constant such that the width of the core <NUM> tapers generally constantly from the width <NUM> at the center of the core to the width <NUM> at the first and second ends <NUM>, <NUM>. However, it is understood that the curve of the central portion <NUM> can instead vary such that the radius of the curve varies across the length of the core <NUM>. In any case, the ends <NUM>, <NUM> are shown as being generally flat, with end surfaces that are generally perpendicular to the length of the core, although the end surfaces can be differently configured, such as curved, angled, or the like. The wing portions <NUM>, <NUM> are shown as relatively thin and elongated members that are identically sized and shaped. However, these wing portions <NUM>, <NUM> can instead have a different shape and relative size than shown and can have different configurations (e.g., shape, size, and the like) from each other.

<FIG> illustrate one exemplary embodiment of support structures for the central core <NUM>. Although the configuration of vertical and horizontally arranged support structures can vary considerably, they are to be selected to provide sufficient structural integrity to the core while allowing for a desired flow volume through the core during filtration. The support structures illustrated extend both longitudinally and laterally, with spacing that provides for the desired performance. The relative number of support structures can be higher or lower than illustrated. In any configuration, however, the outer perimeter of the core <NUM> should have surfaces that provide structure against which pleat tips of the filter material <NUM> can be supported.

In this embodiment, the filter material <NUM> is arranged so that its inner tips are adjacent the central core <NUM> along its longitudinal curved surfaces, but no inner tips are positioned adjacent to the first and second ends <NUM>, <NUM> or the wing portions <NUM>, <NUM>. That is, the pleats in this embodiment do not extend radially outward from the first and second ends <NUM>, <NUM> or wing portions <NUM>, <NUM> toward an outer peripheral boundary <NUM> of the filter <NUM>. Instead, filter material <NUM> generally follows an outer contour of each of the wing portions <NUM>, <NUM>, as shown.

Referring now to <FIG>, a top view of another embodiment of a cylindrical filter <NUM> is illustrated. Filter <NUM> includes a central core <NUM> that extends along at least a portion of the height of the filter <NUM>. Filter <NUM> further includes pleated filter material <NUM> arranged around the central core <NUM>. As shown, the filter <NUM> has an outer peripheral boundary represented by the circle <NUM>, which may be provided by a shell that extends along at least a portion of the filter height, filter caps at one or both ends of the filter material, and/or other structure. In any case, the outer peripheral boundary <NUM> is generally circular and designed or selected to fit into new and existing applications that utilize filters of this size and shape.

In this embodiment, the end or top of central core <NUM> has an elongated shape that includes a convex curved central portion <NUM> with first and second end portions <NUM>, <NUM>, along with two extending portions <NUM>, <NUM> extending from each of the first and second end portions <NUM>, <NUM>, respectively. The core <NUM> may be centered about a central longitudinal axis <NUM> or may be at least slightly offset from the axis <NUM>. The core <NUM> also may be symmetric about the central axis <NUM>, as shown, or the two core portions on opposite sides of the axis <NUM> can have at least a slightly different shape from each other. However, in the illustrated filter <NUM>, the core <NUM> is symmetric about the central axis <NUM>. In this embodiment, the first and second end portions <NUM>, <NUM> have the same width, which is less than a maximum width of the curved central portion <NUM>. The extending portions <NUM>, <NUM> can have a length such that their tips extend beyond the outer width of the central portion <NUM> and the width of the first and second end portions <NUM>, <NUM>, although it is understood that the tips can extend by a distance that is less than the width of the central portion <NUM> and/or the width of the first and second end portions <NUM>, <NUM>.

The curve of the central portion <NUM> of the core <NUM> is generally constant such that the width of the core <NUM> tapers generally constantly from the width at the center of the core to the width at the first and second ends <NUM>, <NUM>. However, it is understood that the curve of the central portion <NUM> can instead vary such that the radius of the curve varies across the length of the core <NUM>. The extending portions <NUM>, <NUM> are shown as relatively pointed members that are identically sized and shaped. However, these extending portions <NUM>, <NUM> can instead have a different shape and relative size than shown and can have different configurations (e.g., shape, size, and the like) from each other.

In this embodiment, the filter material <NUM> is arranged so that its inner tips are adjacent the central core <NUM> along its longitudinal curved surfaces, but no inner tips are positioned adjacent to the first and second ends <NUM>, <NUM> or the extending portions <NUM>, <NUM>. That is, the pleats in this embodiment do not extend directly radially outward from an edge of the first and second ends <NUM>, <NUM> in a direction that is generally perpendicular to the width of the curved central portion <NUM>. Instead, the pleats at the area of the extending portions <NUM>, <NUM> generally surround the shape of the extending portions <NUM>, <NUM> and extend toward an outer peripheral boundary <NUM> of the filter <NUM>. That is, filter material <NUM> generally follows an outer contour of each of the extending portions <NUM>, <NUM>, as shown.

In embodiments of the central cores shown and described herein, each of the cores is at least partially defined by an outer curved surface of its central portion. This outer curved surface generally has a radial curve that is flatter than a radial curve of the outer peripheral boundary of the cylindrical filter. In this way, the core is more "flattened" in shape as compared to the larger curve of outer peripheral boundary of the filter. For example, the central core can be elliptical while the outer peripheral bounder can be circular or cylindrical, as is described herein relative to exemplary embodiments of the filter elements of the invention.

In an aspect of the invention, a cylindrical filter element comprises a central longitudinal axis extending along a height of the filter element, a core element extending along at least a portion of the height of the filter element, the core element comprising a convex curved central portion extending from a first end to a second end to define a width of the core element, wherein the convex curved central portion comprises a maximum height through the central longitudinal axis that is larger than a height of at least one of the first and second ends, and filter material comprising a plurality of pleats extending radially from an outer periphery of the core element, wherein an outer cylindrical periphery of the filter material is defined by an outer pleat tip of each of the plurality of radially extending pleats, and wherein an inner pleat tip of each of the radially extending pleats is adjacent to the core element.

With this cylindrical filter element, any or all of the following aspects may be provided: the first and second ends of the core element have the same height; at least one inner pleat tip is adjacent to one of the first and second ends of the central portion of the core element; an area adjacent at least one of the first and second ends does not comprise any radially extending pleats; the core element further comprises a wing portion extending from at least one of the first and second ends, and wherein at least one of the wing portions comprises a height that is greater than the height of at least one of the first and second ends; the pleat depth of the plurality of pleats varies across the width of the core element such that each pleat increases in depth from the first end in the direction of the central longitudinal axis and then decreases in depth from a pleat adjacent to the central longitudinal axis in the direction of the second end; the core element is symmetrical or not symmetrical about the central longitudinal axis; the core element is offset from the central longitudinal axis; and/or the convex curved central portion of the core element tapers generally constantly from an area adjacent the central longitudinal axis to at least one of the first and second ends.

The present invention has now been described with reference to several embodiments thereof. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the invention. Thus, the scope of the present invention should not be limited to the structures described herein, but only by the structures described by the language of the claims.

Claim 1:
A cylindrical filter element (<NUM>; <NUM>) comprising:
a central longitudinal axis (<NUM>; <NUM>) extending along a height of the filter element (<NUM>; <NUM>);
a core element (<NUM>; <NUM>) extending along at least a portion of the height of the filter element (<NUM>; <NUM>), the core element comprising a convex curved central portion (<NUM>; <NUM>) extending from a first end to a second end (<NUM>, <NUM>; <NUM>, <NUM>) to define a width of the core element (<NUM>; <NUM>), wherein the convex curved central portion (<NUM>; <NUM>) comprises a maximum height through the central longitudinal axis (<NUM>; <NUM>) that is larger than a height of at least one of the first and second ends; and
filter material (<NUM>; <NUM>) comprising a plurality of pleats extending radially from an outer periphery of the core element (<NUM>; <NUM>), wherein an outer cylindrical periphery of the filter material (<NUM>; <NUM>)is defined by an outer pleat tip of each of the plurality of radially extending pleats, and wherein an inner pleat tip of each of the radially extending pleats is adjacent to the core element (<NUM>; <NUM>),
wherein:
- in a first alternative, the core element (<NUM>) has wing portions (<NUM>, <NUM>) extending from the first and second end (<NUM>, <NUM>); or
- in a second alternative, the core element (<NUM>) has two extending portions (<NUM>, <NUM>) extending from each of the first and second end (<NUM>, <NUM>),
characterized in that:
- in the first alternative, the wing portions (<NUM>, <NUM>) have a width (<NUM>) greater than the width (<NUM>) of the central portion (<NUM>);
- in the second alternative, the extending portions (<NUM>, <NUM>) have a length such that their tips extend beyond the outer width of the central portion (<NUM>) and the width of the first and second end portions (<NUM>, <NUM>).