Filter assembly

A filter assembly includes a reusable filter frame and a collapsible and expandable filter element. The filter frame includes a base and a cover connected with the base. The base includes a plurality of longitudinal rails and a plurality of transverse ribs for supporting and spacing the filter element. The filter frame also includes a securing mechanism for securing the filter element to the frame and maintaining the filter element in its expanded condition. The filter element includes filter media having a plurality of pleats adapted to mesh with the ribs of the filter frame and a flexible spacing structure attached to the pleated media that provides the pleated media with uniform pleat spacing but allows the media to be collapsed to a compact form.

FIELD OF THE INVENTION

The present invention relates generally to filters and, more particularly, to a filter assembly including a reusable frame and a collapsible, replaceable, pleated filter element.

BACKGROUND OF THE INVENTION

Many conventional residential heating and cooling systems include a disposable filter. These filters typically include a frame, a filter material formed of glass fibers or similar material, and a mesh screen or the like that supports the filter material. After a period of use, these filters become dirty or clogged and must be replaced. This is accomplished by replacing the entire filter assembly with a new filter and discarding the old one. Depending on the use of the filter, replacement may be required several times a year. Because the frame and screen are discarded with the assembly even though it is only the filter material that is no longer functional, there is unnecessary waste and cost associated with such filters. In addition, because these filters are rather bulky, they are often purchased as they are needed rather than keeping a large supply on hand. Because purchasing a new filter is not always convenient, replacement can be delayed resulting in reduced efficiency of the system.

Filter assemblies with frames and removable filter elements are known in the prior art. U.S. Pat. No. 3,280,984 (Sexton et al.), for example, discloses a filter assembly comprising a support frame including upstream and downstream grid retaining panels and a flat pad of filter medium disposed in the frame.

U.S. Pat. No. 3,774,377 (Bishop) discloses a filter assembly with a replaceable filter element including a frame, a disposable and replaceable filter medium, and means for retaining the filter medium in a fixed position in the frame.

U.S. Pat. No. 3,789,589 (Delany et al.) discloses a filter assembly including a casing and a drawer arranged in the casing that contains pleated filter media. The drawer includes a plurality of comb-like assemblies having pointed fingers that are disposed in the pockets of the pleated filter media to prevent the filter from collapsing. The filter includes strips extending across each end portion of the downstream side of the filter so the side edges of the downstream folds will be equally spaced.

U.S. Pat. No. 4,042,358 (Frohmader) discloses an air filter formed into an accordion-shaped body having reverse folds forming pockets. The filter includes a string-like pleat spacing member that passes through a series of openings in the pleat walls. The spacing member is intended to equally space the pleats when the filter is in its expanded condition.

U.S. Pat. No. 5,840,094 (Osendorf et al.) discloses a filter assembly including first and second frame members, a filter element, and separate comb-like spacers for retaining the filter pleats in an open spaced manner.

U.S. Pat. No. 6,033,453 (Weddell, III) discloses a reusable frame support rack for supporting and retaining an outstretched, replaceable pleated media filter core. The frame includes a pair of longitudinal angles extending between a pair of transverse angles which carry a flat expanded metal support or reinforcement system.

There remains a need, however, for a filter assembly including a reusable frame and a collapsible, replaceable, pleated filter element that is easy to assemble and use.

It would therefore be desirable to provide a filter assembly including a reusable frame and a collapsible replaceable pleated filter element that can be collapsed for compact shipping, storage, and disposal but can be quickly and easily expanded with uniform spacing and installed in the frame.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides a filter assembly including a filter frame and a reversibly expandable filter element that can be collapsed for compact shipping, storage, and disposal but can be quickly and easily expanded and inserted in the frame. The base includes at least one longitudinal rail for supporting the filter element. The filter element comprises filter media having a plurality of pleats and a flexible spacing structure attached to the filter media, each pleat including a fold line defining a pleat tip and a pair of adjacent panels. The length of the spacing structure between successive pleats is less than the length of a panel measured from one pleat tip to the next alternating pleat tip.

In another embodiment, the present invention provides a filter assembly comprising a filter frame including a base having at least one longitudinal rail and a plurality of transverse ribs, a cover movably connected with said base, and a replaceable filter element removably arranged in the filter frame. The filter element comprises filter media having a plurality of pleats adapted to mesh with the ribs and a flexible spacing structure attached to said filter media, each pleat including a fold line defining a pleat tip and a pair of adjacent panels. The length of the spacing structure between successive pleat tips is less than the length of a panel measured from one pleat tip to the next alternating pleat tip.

In another embodiment, the number of ribs generally corresponds to the number of upstream or downstream pleat openings in the filter element, whereby a rib is provided in each downstream pleat opening, and the ribs mesh with the pleats in the filter element. In this manner, the filter element can be expanded and placed into the filter frame such that the pleats mesh with the ribs.

DETAILED DESCRIPTION

Referring now to the drawings, wherein like reference numerals refer to like or corresponding parts throughout the several views,FIGS. 1-5show a reusable filter frame2including a base4and an optional cover6for use with a removable pleated filter element8having an appropriate size and configuration to fit into the base4. Alternatively, the function of the base4and cover6may be reversed so that the filter element8is arranged in the cover6and the base4is closed with the cover6. The filter frame2has a generally planar rectangular configuration and intended for use in an air duct of a residential air handling system, such as a furnace.

The filter element8generally includes filter media10having a plurality of pleats12and a spacing structure14attached to successive pleat tips. The filter element8is described more fully below with reference toFIGS. 6-8.

The base4and cover6include perimeter structures4a,6a, respectively, having corresponding first ends16,18and second ends20,22, respectively, and first sides24,26and second sides28,30, respectively. A plurality of equally spaced transverse ribs32extend from the first side24of the base4to the second side28of the base4that mesh with the pleats12and thereby support the filter media10and provide uniform spacing of the pleats12. To provide complete and uniform spacing of each pleat12, the ribs32are preferably continuous, other than discontinuities that may be required as part of the molding process, and have a uniform height. In addition, the number of ribs32is preferably corresponds to the number of pleats12on the downstream side of the filter element8so that one rib32is arranged in each downstream pleat opening. The ribs32may be molded with the perimeter structure4aof the base4or they may be wires, dowels, or other members that are attached to the perimeter structure4aof the base4.

The base4also optionally includes a plurality of longitudinal rails34extending from the first end16to the second end20that combine with the transverse ribs32to form a grid structure. The ribs32and rails34can be formed as separate members or as a unitary structure. The rails34are shown with optional triangularly-shaped spacer portions34athat generally follow the contour of the filter pleats12, thereby providing spacing for the pleats12. Each spacer portion34aincludes a base36along the rail34and an apex38adjacent a corresponding rib32. The ribs32and rails34are preferably formed of a synthetic plastic material such as ABS (acrylonitrile butadiene styrene) or HIPS (high impact polystyrene) but may also be formed of other conventional materials such as wire or flat metal fins.

The cover6contains a central opening38that allows air to flow through the frame2to the filter element8so that contaminants can be removed from the air stream. The cover6inter-engages the periphery of the base4to securely retain the filter element8in the frame2and to prevent air from flowing around the filter element8. The base4and cover6are pivotally connected along their second sides28,30, respectively, via hinge members40(FIG. 4) in the form of flexible straps. Other conventional hinges may also be used. In this manner, the frame2is movable between an open condition (FIG. 1) wherein the base4and cover6first side edges24,26, respectively, are displaced to allow the filter element8to be installed in or removed from the frame2, and a closed condition (FIG. 4) wherein the base4and cover6first side edges24,26respectively, are engaged to enclose the filter element8in the frame2. It will be recognized that any conventional hinge may also be used to connect the base4with the cover6. Alternatively, the frame2may have a single-piece unitary construction wherein the base4and cover6are joined by a living hinge, formed, for example, by injection molding. It will be recognized that the base4and cover6may also be formed as two separate pieces that snap together or otherwise interlock.

A pair of optional latches42(FIG. 4) each including a flexible cantilevered bar member44(FIG. 1) that snap fits over an aligned protrusion46(FIG. 1) are provided to maintain the frame2in its closed condition. Other conventional closures or mechanical fasteners such as hook and loop, elastic bands, locks, or the like may also be used.

The cover6may also optionally include transverse and/or longitudinal support bars (not shown) similar to those provided in the base4that serve to further retain the filter media10in the frame. Such support bars serve a safety function and prevent the filter media10from ballooning out of the frame in case the frame is inadvertently inserted backward in an air duct. When inserted backward, the filter will not perform properly because the pleats are not supported by the ribs32and will therefore tend to collapse in use, but the filter media will be retained in the frame2so that any damage to the system is avoided.

To ensure that the frame2is installed correctly in the air duct with the cover6upstream and the base4downstream so that air travels successively through the cover6, the filter element8, and the base4, a visual indicator47is provided on the frame2showing the proper orientation of the frame relative to the direction of the air flow. Additional instructions may be provided to ensure the frame is properly arranged in the air duct.

Protrusions48provided in the first16and second20ends of the base4serve as securing mechanisms to attach the filter element8to the base4when the filter element8is installed in the frame2. Each protrusion48engages an aligned hole50contained in the first18and second22ends of the cover6. Other suitable securing mechanisms include adhesive, hook and loop fasteners, clips, clamps, clasps, hooks, or the like. Alternatively, the filter element8may be secured in the frame2by simply capturing or pinching the ends of the filter element between the base4and the cover6.

The frame2is generally intended as a frame for a residential air filter for use in, for example, a furnace, a window air conditioning unit, or a kitchen range hood. Accordingly, the frame2generally has a depth or thickness of ½ inch to 5 inches, preferably between ¾ inch to 1¼ inches, and more preferably approximately an inch thick. The height of the frame2is generally between 5 inches and 24 inches, and preferably between 10 inches and 20 inches. The width of the frame is generally between 18 inches and 10 inches, and preferably between 20 inches and 30 inches.

To facilitate the installation and removal of the frame2from an air duct, indentations52are provided in the ends16,20of the base4and side26of the cover6. The indentations provide a narrow gripping region along the periphery of the frame that can be readily grasped by a user during the installation and removal process.

Referring now toFIGS. 6-8, there is shown the accordion pleated replaceable filter element8in greater detail. The filter element8includes reversibly expandable and collapsible filter media10having an inlet face54and an outlet face56, and a flexible inelastic spacing structure14arranged over the inlet face54. The spacing structure14allows the filter element8to be quickly and easily expanded to a fixed spacing and inserted into the base4. While the outlet face56is preferably left open to allow the ribs32to enter the pleat structure, the filter element8may additionally include a second spacing structure (not shown) along the filter media outlet side56. Such a filter element would preferably be constructed from a self-supporting media and would be used with a filter frame that does not include ribs32.

This construction allows the filter element8to be collapsed to a compact form for shipping and storage and to later be re-expanded to a fixed spacing and attached to the frame2. The spacing structure14is thin and flexible so it can fold in between the pleats12or outwardly away from the pleats12when the filter element8is collapsed into its compressed state as shown in FIG.8. Suitable spacing structures14include scrims, screens, nets, mesh structures, or the like formed of, for example, metals, synthetic plastic materials, or natural fibers such as cotton thread. The spacing structure14may also have filtration properties in addition to acting as a spacer.

To ensure reliable uniform down web spacing and cross web stability, and to ensure easy handling of the filter element8, the spacing structure14is preferably provided over the entire inlet face54. If not provided over the entire inlet face54, the spacing structure14is preferably provided over an interior face region58of the media10. This may be accomplished, for example, by providing the spacing structure14in the form of one or more strips extending across the interior face region58of the media10arranged perpendicular to the direction of pleating and attached to successive pleats12. The expression “interior face region” refers to the area extending inwardly from the peripheral region of the media10adjacent the outer edge of the filter element8and includes the central area of the filter element8. By providing the spacing structure at least in the interior face region58of the media10, the filter element8is easy to expand to its full length while preventing over expansion.

The media10includes a plurality of pleats12each including a fold line60defining a pleat tip62and a pair of adjacent panels64. Successive pleat tips on the inlet side54define a planar attachment surface to which the spacing structure14is attached. The spacing structure14is preferably adhesively bonded to the media10but other conventional attachment means such as heat lamination or ultrasonic welding may also be used.

The length66of the spacing structure14between successive pleat tips62forming the attachment surface is less than two times the length68of a panel64as measured from one pleat tip62to the next alternating pleat tip62. In this manner, when the filter element8is fully expanded, the spacing structure14forms a generally planar structure and adjacent panels64form an angle α of less than 180 degrees. The length of the spacing structure14between successive pleat tips62is preferably less than the length68of a panel64measured from one pleat tip62to the next alternating pleat tip, whereby adjacent panels64form an angle α of less than 60 degrees when the filter element8is in its fully expanded condition. To achieve equal and uniform spacing of the pleats12, the length of the spacing structure14between each successive pleat tip62is the same.

The spacing distance between successive pleat tips62depends of the size of the filter but generally ranges from about 2 millimeters to about 40 millimeters. For most applications, however, the spacing distance between successive pleat tips62is preferably at least 5 millimeters and, more preferably, at least 8 millimeters.

Elongate attachment members70are provided along opposite ends72,74of the filter element8parallel to the fold lines60. The attachment members70preferably have a stiffness greater than the stiffness of the filter media10. The attachment members70provide the ends72,74of the filter element8with increased stiffness, thereby improving the handlability of the filter element8and allowing the filter element8to be expanded easily and uniformly. In addition, the attachment members70provide the ends72,74with increased strength and rigidity so that the filter element8can be quickly and easily attached to the base4.

Optional holes76that mate with protrusions48are provided in the attachment members70and serve to attach the filter element8to the base4and maintain the filter element8in its expanded condition when the filter element8is placed in the base4. Other conventional means for attaching the filter element8to the frame2such as pinching the attachment members70between the base4and cover6, hook and loop fasteners, adhesive, clips, clamps or the like may also be used. The attachment members70may be formed of any suitable material including metal foils, paperboard, cardboard, chipboard, synthetic plastic materials including plastic film, or multiple layers of filter media laminated together.

While any pleated fibrous filter media may be used, a preferred filter media is an electrostatically charged media. The media may be either relatively stiff and self-supporting or relatively soft and non self-supporting. By “self-supporting” it is meant that the media, with or without a spacing structure, generally maintains its shape when subjected to an air stream. Thus, whether the media is self-supporting or not depends on the physical properties of the media itself, the geometry or construction of the media, and the conditions to which the media is subjected in a particular end use application.

Generally, a stiff self-supporting media has a Gurley stiffness of greater than 50 milligrams for a sample size having a width of 2 inches and a length of 1.5 inches, preferably greater than 100 milligrams for such a sample size, and a soft non self-supporting media has a Gurley stiffness of less than 30 milligrams for a sample size having a width of 2 inches and a length of 1.5 inches. For media having stiffness values between these values, whether the media is self-supporting depends on the construction of the media and on the end use application.

If the media is self-supporting, the support ribs32may not be required because the media will maintain its shape when subjected to the air stream. On the other hand, if the media is non self-supporting, ribs32are needed to support and space the media when the filter element is placed in an air stream to prevent the pleats12from bowing or collapsing.

A generally self-supporting filter media is Accuair 2.0 ounce per square yard filter media available from Kimberly Clark Corporation, Neenah, Wis. having a Gurley stiffness of approximately 120 milligrams for a sample size having a width of 2 inches and a length of 1.5 inches. A non self-supporting filter media is Filtrete GCB 40 filter media available from 3M Company, St. Paul, Minn. having a Gurley stiffness of approximately 15 milligrams for a sample size having a width of 2 inches and a length of 1.5 inches. A suitable spacing structure is a reinforcing fabric available from Bayex Inc., Albion, N.Y. under the product number DPM 4410 P3A-2-24. This product is an open scrim having four strands per inch of 70 denier polyester thread. The scrim is provided with an adhesive that allows the scrim to be applied directly to the filter media.

To install the filter element8into the frame2, the frame2is placed on a surface so that the base4is beneath the cover6. The frame2is then opened as shown inFIG. 1by releasing the latches44and pivoting the cover6upwardly away from the base4. The filter element8is then fully expanded by first orienting the filter element8so the scrim14facing up, and then grasping the attachment members70and separating them until the scrim14is flat and the pleats are evenly spaced. The filter element8is then placed in the base4so that the pleats12mesh between the ribs32. The holes76in the attachment member70are then placed on the protrusions48to attach the filter element8to the base4. The cover6is then closed to retain the filter element8in place, and the latches44are re-connected to lock the cover with the base4. Constructed in this manner, the media10is supported from the back which allows the dirty side of the media to be facing up when changing the filter element8, thereby resulting in less mess. The filter element8is removed from the frame2by reversing the above steps.

It will be recognized that the filter element8may be attached to the cover6rather than the base4. In this manner, the ribs32move into the pleats12as the frame2is closed. This, however, is less desirable because the pleats may require slight manipulation to properly mesh with the ribs32, and the dirty filter element will be laying with the dirty side facing down during replacement. This, in turn, will produce a mess that must be cleaned up.

The patents, patent documents, and patent applications cited herein are incorporated by reference in their entirety as if each were individually incorporated by reference. It will be apparent to those of ordinary skill in the art that various changes and modifications may be made without deviating from the inventive concept set forth above. Thus, the scope of the present invention should not be limited to the structures described in this application, but only by the structures described by the language of the claims and the equivalents of those structures.