Patent Description:
Air filters for capturing dust, particulate matter, and other airborne materials such as animal hair and dander are available in varieties of prescribed rectangular sizes that are typically incremented by inches along each of two sides. Each typical home or business HVAC air-handling system requires periodic or occasional replacement of a particularly dimensioned filter, and consumers are thus burdened with finding an appropriately sized replacement. In reality, the receptacle structures of the air-handling systems are ultimately not precisely dimensioned according to even their nominal dimensions, and so even when an appropriately labeled filter is found, a perfect fit, with well-sealed edges, without any deformation of the replacement filter is ultimately not assured.

Compromises are thus made, including for example the use of filters that are bit small or large in one or both rectangular dimensions, and frustrated consumers even delay or neglect suggested periodic filter replacement. When air driven through an air-handling system bypasses an improperly fitted filter, airborne matter is not optimally trapped at the filter, which can permit the accumulation of matter on HVAC system components and cause or aggravate respiratory problems. When filter replacement schedules are missed, filter blockage by matter accumulated in an old filter can increase system power consumption and wear, and can harbor microbial growth, which also can also adversely affect respiratory health.

<CIT> refers to collapsible filter assemblies for use with pleated or other filter media. A collapsible filter assembly can include at least one filter element including a filter media supported within a collapsible filter frame. <CIT> discloses an apparatus and method for filtering air in residential and commercial applications is described herein. The air filter may have a support frame which secures to the intake grille of an HVAC system.

The dependent claims describe optional embodiments of the invention. This summary is provided to briefly introduce concepts that are further described in the following detailed descriptions.

An air filter assembly according to at least one embodiment includes a filter element having at least one variable dimension, and a frame for engaging and supporting the filter element.

The frame includes a plurality of linear segments forming a rectangular configuration.

The air filter assembly may further include a plurality of clips for connecting the linear segments together at corners of the rectangular configuration.

The air filter assembly may further include at least one elasticized cord joining the linear segments.

The elasticized cord may have two terminal ends engaged together by at least one connector.

The elasticized cord may include a first end having a first connector; and a second end comprising a second connector.

The first connector may include a first magnet, and wherein the second connector may include a second magnet.

The linear segments form a rectangular configuration of variable dimensions.

The linear segments may be formed by bending or segmenting a primary strip into four segments.

Each of the linear segments may include a slotted edge, and two of the linear segments may engage when a slot of the slotted edge of one linear segment aligns with a slot of the slotted edge of another linear segment.

The frame includes a flexible arm biased toward a linear state.

The flexible arm includes a spring steel element having a cylindrically concave side and an opposing cylindrically convex side.

The profiled spring steel element may be self-biased toward a linear state, in which it extends along a longitudinal channel axis defined along the cylindrically concave side.

The air filter assembly may further include at least one grate element spanning an area defined by the frame for supporting the filter element.

The at least one grate element may include an elasticized cord passed through holes defined in the frame.

The frame may include frame elements having portions that are overlapped, and wherein the elasticized cord is passed through aligned holes in the overlapping portions thereby maintaining engagement of the frame elements.

The frame elements may include linear segments and corner pieces having overlapping portions maintained in engagement by the elasticized cord.

The grate element may include multiple parallel arms.

Each arm may include, at each of two ends thereof, a respective tooth for engaging the frame.

The arms may be interconnected by and regularly spaced along a cord.

The arms and cord may be rollable into a bundle.

The frame may include a first frame section having first teeth, and a second frame section having second teeth. The two frame sections may be configured to capture at least a portion of the filter element between the first teeth and second teeth when interlocked.

The at least one edge portion filter element may extend outward from the frame and captured portion of the filter element to define a gasket.

The air filter assembly may include a grate assembly having posts for aligning with and engaging notches defined by the frame.

The notches may each be wedge shaped, having an open mouth and narrowing toward a hole for receiving and retaining a post of the grate assembly.

The frame may include a frame segment having at least a first slot for retaining an edge of the filter element.

The air filter assembly may further include a screen, and the frame segment may have a second slot for retaining an edge of the screen.

The filter element may include a filter medium and an edge cuff mounted on an edge of the filter medium, and the edge cuff may be configured to be removably captured in the first slot.

The frame may include a folding hub and arms connected to the folding hub.

The arms may be connected to the filter element.

The folding hub may have a folded configuration and an expanded configuration.

The air filter assembly may further include an edge treatment for forming a peripheral seal.

The filter element may have a pattern of creases or fold lines to facilitate folding thereof from an expanded configuration to a reduced configuration.

The filter element may include a filter media element for filtering air passed therethrough, the filter media element may have at least one peripheral edge, and an edge treatment for attachment to the peripheral edge of the filter media element.

The edge treatment may include a deformable gasket, flange, or layer for forming a seal at the peripheral edge of the filter media element.

The edge treatment may form a seal between the filter media element and the frame.

The filter element may be twice foldable from an expanded rectangular configuration to a reduced configuration for shipping or storage.

The filter element may have a preformed fold pattern that facilitates reduction in two-dimensions.

The previous summary and the following detailed descriptions are to be read in view of the drawings, which illustrate particular exemplary embodiments and features as briefly described below. The summary and detailed descriptions, however, are not limited to only those embodiments and features explicitly illustrated.

These descriptions are present particular embodiments with sufficient details to provide an understanding of broader subject matters of this invention.

Any dimensions expressed or implied in the drawings and these descriptions are provided for exemplary purposes. Thus, not all embodiments within the scope of the drawings and these descriptions are made according to such exemplary dimensions. The drawings are not made necessarily to scale. Thus, not all embodiments within the scope of the drawings and these descriptions are made according to the apparent scale of the drawings with regard to relative dimensions in the drawings. However, for each drawing, at least one embodiment is made according to the apparent relative scale of the drawing.

Unless described or implied as exclusive alternatives, features throughout the drawings and descriptions should be taken as cumulative, such that features expressly associated with some particular embodiments can be combined with other embodiments.

The drawings illustrate various embodiments of filter assemblies and their components including, for example, frames, filter elements supported along their outer edges by frames, and grates that span the areas defined between frame elements to further support the filter elements. The filter elements include filter media elements for filtering air passed therethrough. The filter media elements are generally porous and may be layered and may include woven and non-woven materials such as fabrics, piles, felts, and foams. The media elements may include materials that are spun bonded or molded. The media elements may include materials having antimicrobial properties. Other filter media materials and properties are within the scope of these descriptions. In some cases, the filter elements include sub-frames and various particular layers and edge treatments.

Throughout, some degree of size variability of the frames, filter elements, and other components is enabled by the drawings and descriptions. The descriptions describe features with reference to a filter plane, referring to a generally planar configuration or geometry of a filter assembly deployed and ready for use.

<FIG> shows a variable filter assembly according to at least one embodiment having a frame termed herein as a "foldable simple frame. " The assembly includes an expandable filter media element <NUM> supported by a peripheral frame <NUM> of linear segments arranged in a rectangular form in the filter plane. As shown in <FIG>, the linear segments <NUM> are formed by folding a C-channel strip <NUM>, which is foldable anywhere along its length, at spaced fold locations according the dimensions desired. The terminal ends of the folded strip are then cut to length, to remove any excess strip material, and joined as shown in <FIG>. Holes formed along the strip facilitate measuring and folding to form segments, and facilitate joining the two end segments at their terminal ends as shown in <FIG>. As shown in <FIG>, edges of the filter media element <NUM> can be wrapped partially around a respective peripheral frame segment <NUM> and secured thereto by a respective spike bar <NUM>. Each spike bar <NUM> has spikes spaced equivalently as the holes in the C-channel strip <NUM> from which the linear frame segments <NUM> are formed.

<FIG> shows a variable filter assembly according to at least one embodiment having a frame <NUM> termed herein as a "pole frame. " The assembly includes an expandable filter media element <NUM> supported by the peripheral frame <NUM>, which has tubular pole segments <NUM> arranged in a rectangular form in the filter plane. The pole segments are joined by an internally captured shock cord <NUM> (<FIG>) having two opposing ends terminating at respective connectors <NUM>, which may be magnetic. The shock cord can be an elasticized cord, such as a bungee cord, having elastic strands forming a core covered in a woven fibrous sheath, for example made of polypropylene or other natural or synthetic fibers. The frame is maintained in a rigid configuration by tension of the shock cord <NUM> when the pole segments are arranged in the rectangular form and the two connectors at the ends of the shock cord are joined as shown in <FIG>. Secondary shock cord segments <NUM> stretched across the filtration area of the expanded filter media element form an expandable grate <NUM>. Grate hooks <NUM> through which the secondary shock cord segments are passed can slide along the pole segments as shown in <FIG> to vary the grate pattern. Each grate hook <NUM>, as shown in <FIG>, has a bolt movably captured within a pole segment, a shank extending from the bolt through a longitudinal slit formed in the wall of the pole segment, and a loop or eye carried by the shank for engaging a shock cord segment.

<FIG> shows a variable filter assembly according to at least one embodiment having a frame termed herein as a "box divider. " The assembly includes an expandable filter media element <NUM> supported by a segmented frame <NUM> of linear frame segments <NUM> arranged as crossed in an hourglass form in the filter plane. The linear segments are formed by folding and segmenting a notched strip <NUM> (<FIG>) having spaced notches <NUM> along a longitudinal edge. The frame segments mutually engage when the slotted edge of one segment is brought into engagement with another where two notches align at the intersection of two frame segments as shown in <FIG>. The hourglass form is defined by two parallel outer frame segments and two inner frame segments crossing and intersecting at the center of the frame as shown in <FIG>. The filter media element can be expanded onto the frame with marginal portions of the filter media element adhered to the outer frame segments. Once assembled, the variable filter assembly has an overall outer rectangular form.

<FIG> shows a variable frame assembly <NUM> according to at least one embodiment termed herein as a "foldable frame. " The assembly includes four linear L-channel segments <NUM> defining an outer rectangular form of variable dimensions. The linear segments are formed by bending or segmenting a primary strip <NUM> into four segments (<FIG>). The strip has a longitudinal crease or embossed line <NUM> that extends the length of the strip between its longitudinal edges to facilitate formation of the L-channel segments by <NUM> degree fold of each segment about the crease or embossed line <NUM> (<FIG>). The four corner junctions (<FIG>) of the segments are maintained by a corner clip <NUM> (<FIG>) at each corner. The variable frame assembly is useful to support or strengthen various filter assembly embodiments described herein.

<FIG> shows a frame assembly <NUM> according to at least one embodiment termed herein as a "modular frame with corner clips. " The assembly includes four linear L-channel segments <NUM> (<FIG>) defining an outer rectangular form of variable dimensions in the filter plane. The linear segments are formed by bending or segmenting a primary strip <NUM> (<FIG>) into four segments. The strip <NUM> has a longitudinal crease or embossed line that extends the length of the strip between its longitudinal edges to facilitate formation of the L-channel segments by <NUM> degree fold of each segment at the crease or embossed line. The four corner junctions of the segments are maintained by a corner clip <NUM> (<FIG>) at each corner. The variable frame assembly is useful to support or strengthen various filter assembly embodiments described herein.

<FIG> shows a frame and grate assembly according to at least one embodiment, having a frame termed herein as a "collapsible frame. " The assembly includes a frame <NUM> (<FIG>) having four linear L-channel segments <NUM>, and four L-channel <NUM>-degree bend corner pieces <NUM>. The linear segments can variably overlap linear portions extending from the corner pieces to define an outer rectangular form of variable dimensions. Preformed holes in the L-channel faces corresponding to the filter plane are regularly spaced to as to align at incremental variable dimensions. A flexible tensile cord <NUM>, such as a shock cord, is laced through the holes forming a grate across the area within the frame in the filter plane. The cord, passing through aligned respective holes of overlapping portions of the linear-segment and corner-piece frame elements, maintains engagement of the linear segments and corner pieces at desired dimensions of the frame. The frame <NUM> in <FIG> is reduced in a first direction relative to the expanded state of <FIG>. The frame <NUM> in <FIG> is further reduced in a second direction perpendicular to the first direction.

<FIG> shows a frame and grate assembly <NUM> according to at least one embodiment, termed herein as a "collapsible frame + grid. " The assembly <NUM> includes four corner area pieces <NUM> and multiple edge area pieces <NUM> arranged according to desired outer rectangular dimensions. Each of the corner area pieces and edge area pieces has peripheral L-channel frame segments and additional frame arms extending therefrom in the filter plane to together define a grate. Three configurations are shown by varying the overlapping arrangement of corner area and edge area pieces. In the largest of the configurations shown, a central grid section <NUM> is installed in the filter plane between edge area pieces. The frame <NUM> in <FIG> is reduced in a first direction relative to the expanded state of <FIG>. The frame <NUM> in <FIG> is further reduced in a second direction perpendicular to the first direction.

<FIG> shows a frame <NUM>, for example as shown in <FIG>, and a grate assembly <NUM> according to at least one embodiment, termed herein as a "grid roll. " The grate assembly includes multiple parallel grate arms <NUM> (<FIG>) each having, at each end thereof, a tooth <NUM> for piercing the filter plane portions of the frame segments. The grate arms are interconnected and regularly spaced along a cord <NUM>, which may be inextensible or may be of variable length such as a shock cord. The grate arms can be conveniently rolled (<FIG>) into a bundle for shipping and storage. The grate assembly <NUM> (<FIG>) can also be used with frames (<FIG> and <FIG> for example) where holes to accommodate the teeth are to be formed by piercing frame segments, and used with frames (for example <FIG>) where holes are already formed in the frame in the filter plane.

<FIG> shows a frame <NUM>, for example as shown in <FIG>, and a grate assembly <NUM> according to at least one embodiment, termed herein as a "fold & snap grate. " The grate assembly <NUM> includes multiple grate arms <NUM> each having, at each end thereof, a tooth <NUM> for piercing or engaging the filter plane portions of the frame segments. As shown in <FIG>, each grate arm is formed from a strip <NUM> have regularly spaced notches <NUM> where the strip can be terminated or folded. The teeth extending from the grate arm are the two inter-notch sections of the strip at its ends folded to <NUM> degrees. Each tooth can be passed through the frame segment and folded flat to secure the ends of each grate arm. The grate assembly <NUM> can also be used with frames (<FIG> and <FIG> for example) where holes to accommodate the teeth are to be formed by piercing frame segments and used with frames (for example <FIG> where holes are already formed in the frame in the filter plane.

<FIG> shows a variable filter assembly according to at least one embodiment having a filter media element <NUM> termed herein as a "magnetic fold up filter. " The expandable filter media element is supported by a peripheral frame <NUM> of linear segments arranged in a rectangular form in the filter plane. The frame segments and filter media element are engaged by magnetic attraction (<FIG>), in at least one embodiment. The filter media element <NUM> can be collapsed along parallel accordion fold lines <NUM> (<FIG>), and, then halved in length by bending as shown in <FIG> at the center of the accordion folded configuration for a twice-kind folded configuration for shipping and storage in a reduced shipping size or state as shown in <FIG>.

<FIG> shows a filter assembly according to at least one embodiment having a filter media element termed herein as a "magnetic foldable filter. " The frame (<FIG>) includes four linear L-channel segments joined by four corner clips. The filter media element (<FIG>) includes multiple panels joined together by creases or fold lines parallel to the edges of the rectangular filter media element. Thus the filter media element can be folded along crease lines extending in two dimensions so as to be map folded or otherwise reduced to a minimized configuration (see "ship size" of <FIG>) convenient for shipping and storage. Magnetic strips along the outer edges of the filter media element engage the frame, which also has magnets or other appropriate material for magnetic attachment. The frame may have one (<FIG>) or more grate arms spanning between opposing outer frame segments so as to form a grate to support the filter media element.

<FIG> shows a filter assembly according to at least one embodiment termed herein as a "flat filter sandwich design. " A flexible and foldable filter media element is captured between interlocking teeth of two rectangular frame sections. As shown in <FIG>, extra edge portions of the filter media element, serving as a flexible outer gasket, extend outward from the sides of the frame formed when the two frame sections are engaged by their interlocking teeth (<FIG>).

<FIG> show a variable frame and grate assembly according to at least one embodiment termed herein as a "foldable frame snap in grid. " The assembly includes a peripheral frame of linear segments arranged in a rectangular form in the filter plane. The linear segments are formed by folding an L-channel strip, which is foldable at spaced notches formed in the filter plane face of the strip. The notches are wedge shaped, having a wide mouth and narrowing inward toward a hole that retains knobbed posts of a snap-in mesh or grid that forms a grate when installed. The notches and posts are equivalently spaced so as to align and permit variable sizing. Any excess of the frame strip can be cut free of the rectangular form, and the mesh or grid is cut or preformed to the desired dimensions. The engagement of the posts along the outer edges of the mesh with the holes in the frame segments maintains the assembly in any final desired dimensions and configuration. Various filter media elements can be installed or used with the assembly of <FIG>, with support across the filter plane by the grate.

<FIG> shows a cover for a filter assembly, the cover having a logo or other graphic for aesthetic purpose according to at least one embodiment. The cover may, for example, have cutout areas so as to serve as a grate to support a filter media element. In the illustrated embodiment, an elephant logo or graphic is represented. Other graphic illustrations, logos, and artworks are within the scope of these descriptions.

<FIG> show an expandable filter media element, according to at least one embodiment, in three configurations. The filter media element has a pair of panels that can each be folded along parallel accordion fold lines to collapse the filter media element in one of two filter plane dimensions. The two panels are joined by an edge strip having a central crease or fold line facilitating the bending of the edge strip so as to halve the filter media element in length thus further reducing the filter media element in the second of the two filter plane dimensions. Thus, the expandable filter media element can be reduced to a collapsed and folded configuration for shipping and storage.

<FIG> show a frame assembly according to at least one embodiment termed herein as a "linear frame - straight + corners. " The assembly includes four linear L-channel segments defining an outer rectangular form of variable dimensions in the filter plane according to the lengths of the segments. The four corner junctions of the segments are maintained by a corner clip at each corner. Two diagonal inner frame segments, serving as a grate to support a filter media element, cross and intersect at the center of the frame. Each inner frame segment spans the interior area of the frame between diagonally opposing corners. The inner frame segments snap into place, with a joint at their centers at which they are engaged. The frame segments are partially rotatable relative to each other at the joint permitting the joined inner frame segments to be placed in an almost parallel reduced configuration for shipping and storage. The variable frame assembly is useful to support or strengthen various filter assembly embodiments described herein.

<FIG> shows a variable frame and grate or filter assembly according to at least one embodiment termed herein as a "planar frame. " The assembly includes a filter plane element supported by a peripheral frame of linear segments arranged in a rectangular form. The illustrated filter plane element can represent a grate, a filter assembly, and both among other examples. The frame segments are angle cut, for example at <NUM> degrees, at their ends to define abutting corner joints.

<FIG> show a filter assembly according to at least one embodiment. A filter media element (<FIG>) having a rectangular periphery is supported by a removable grate having four arms extending outwards from a central hub, on which a logo or other graphic is shown in <FIG>.

<FIG> show a filter assembly, according to at least one embodiment, which can be twice folded from an expanded rectangular configuration to a reduced configuration convenient for shipping and storage. The filter assembly includes a filter media element supported by a rectangular peripheral frame of foldable linear segments and a grate defined by a grid of arms crossing the rectangular interior defined within the peripheral frame.

The filter media element of FIGS. <NUM>-20D, and various other filter assemblies and media elements illustrated in the drawings and described herein, may have a layered filter medium using an undulating non-woven pile layer and a supporting grid fiber layer.

<FIG> show a foldable filter media element <NUM>, according to at least one embodiment, in an expanded state. A pattern of crease or fold lines facilitate folding of the media element from the expanded configuration (<FIG>) to a reduced configuration (<FIG>) convenient for shipping and storage. The reduced configuration has an area that is one fourth in size relative to the expanded configuration in the filter plane. The particularly illustrated fold pattern is termed herein an "origami crane fold. " Avantageously, the four outer corners <NUM> of the expanded configuration are brought together in the reduced configuration at a location diagonally across the reduced configuration from the center <NUM> of the media element, which occupies an opposite corner of the reduced configuration.

<FIG> is a shipping or storage package into which a filter media element, according to at least one embodiment, can be placed in a reduced configuration as shown in <FIG>. The filter media element for example may be that of <FIG> or others according to various embodiments. The package shown in <FIG> is a soft-walled envelope or bag having a sealing flap shown as open.

In the filter assembly according to <FIG>, a peripheral frame segment <NUM> serves as a clip retaining a screen <NUM> and an expandable replaceable filter element <NUM>. The frame segment may, for example, be an extruded strip segment. In cross-sectional view, the frame segment has an outer edge wall <NUM> and three inward extending strips between which two slots are formed for respectively retaining the screen and filter. The screen is retained in a first slot defined between a lower strip <NUM> and a central strip <NUM>. The filter element is retained in a second slot defined between the central strip and an upper strip <NUM>. A downward extending bead <NUM> along the lower face of the inward edge of the upper strip helps to retain the filter element. The filter element <NUM> has an accordion folding filter medium <NUM> and an edge cuff <NUM> in which a peripheral edge of the filter medium is captured. The filter element is retained along the frame segment by engagement of the edge cuff <NUM> within the second slot and with the bead <NUM>.

In the filter assembly according to <FIG>, a peripheral frame segment serves as a clip retaining a screen and an expandable replaceable filter element. The frame segment may, for example, be formed of extruded strip segments. In cross-sectional view the frame segment has an outer edge wall and three inward extending strips between which two slots are formed for respectively retaining a screen and a filter element. The screen is retained in a first slot defined between a fixed lower strip and a fixed central strip. The filter element is retained in a second slot defined between the central strip and a folding upper strip. The upper strip is connected to the edge wall by a hinge allowing the second slot to open to receive the filter element and close upon the filter element for retention. The filter element has an accordion folding filter medium and an edge cuff in which a peripheral edge of the filter medium is captured. The filter element is retained along the frame segment by engagement of the edge cuff within the second slot and with the folding upper strip.

In the filter assembly according to <FIG>, a peripheral frame segment serves as a clip retaining an expandable replaceable filter element between front and back screens. The frame segment may, for example, be an extruded strip segment. In cross-sectional view the frame segment has an outer edge wall and three inward extending strips between which two slots are formed for retaining the screens and filter element. The back screen is retained in a first slot defined between a lower strip and a central strip. The filter element and front screen are retained in a second slot defined between the central strip and an upper strip. An inward barb-like fold along the edge of the front screen helps to retain the filter element. The filter element has an accordion folding filter medium and an edge cuff in which a peripheral edge of the filter medium is captured. The filter element is retained along the frame segment by engagement of the edge cuff within the second slot and with the barb-like fold of the upper screen.

In the filter assembly according to <FIG>, a peripheral frame segment serves as a clip retaining an expandable replaceable filter element between front and back screens. The frame segment may, for example, be an extruded strip segment. In cross-sectional view the frame segment has an outer edge wall and four inward extending strips between which three slots are defined. A back slot, a central slot, and a front slot are defined for respectively retaining the back screen, filter element, and front screen. The filter element has an accordion folding filter medium and an edge cuff in which a peripheral edge of the filter medium is captured. The filter element is retained along the frame segment by engagement of the edge cuff within the central slot.

In the filter assembly according to <FIG>, a peripheral frame segment serves as a clip retaining a screen and an expandable replaceable filter element. The frame segment may, for example, be an extruded strip segment. In cross-sectional view the frame segment has an outer edge wall and three inward extending strips between which two slots are formed for respectively retaining the screen and filter element. The screen is retained in a first slot defined between a lower strip and a central strip. The filter element is retained in a second slot defined between the central strip and an upper L-shaped strip. A bezel clip mounts onto an upper extending arm of the L-shaped strip and further engages to retain the filter element. The filter element has an accordion folding filter medium and an edge cuff in which a peripheral edge of the filter medium is captured. The filter element is retained along the frame segment and bezel clip by engagement of the edge cuff within the second slot and with the bezel clip.

In the filter assembly according to <FIG>, a peripheral frame segment serves as a clip retaining a screen and an expandable replaceable filter element. The frame segment may, for example, be an extruded strip segment. In cross-sectional view the frame segment has an outer edge wall and three inward extending strips between which two slots are formed for respectively retaining the screen and filter element. The screen is retained in a first slot defined between a lower strip and a central strip. The filter element is retained in a second slot defined between the central strip and an upper strip. A bezel clip mounts onto the upper strip and further engages to retain the filter element. An inward extending bead along a lower face of the bezel clip helps to retain the filter element. The filter element has an accordion folding filter medium and an edge cuff in which a peripheral edge of the filter medium is captured. The filter element is retained along the frame segment and bezel clip by engagement of the edge cuff within the second slot and with the bead of the bezel clip.

<FIG> shows a filter assembly, according to at least one embodiment, in which a peripheral frame retains an expandable replaceable filter element. The frame, as shown in <FIG>, has four linear segments, each having a hinging bezel that snaps onto a respective edge of the filter element. The filter element is foldable for reduction to convenient size for shipping and storage as shown for multiple embodiments of the drawings. The frame is shown without the filter element in the other of the two views.

<FIG> show a filter assembly according to at least one embodiment. A peripheral frame retains an expandable replaceable filter element. The frame has four linear segments. The filter element is foldable for reduction to convenient size for shipping and storage as shown for multiple embodiments of the drawings. The frame is shown with the filter element in place in <FIG>, and with the filter element raised in <FIG>. The filter element has a C-channel outer sub-frame and a filter media element having edges retained by the outer sub-frame. A particular embodiment of a support insert is shown as a grid of arms parallel to the sub-frame edges and joined at the center of the filter element to serve as a grate.

<FIG> show a filter assembly according to at least one embodiment. A peripheral frame retains an expandable replaceable filter element. The frame has four linear segments. The filter element is foldable for reduction to a convenient size for shipping and storage as shown for multiple embodiments of the drawings. The frame is shown with the filter element in place in <FIG>, and with the filter element raised in <FIG>. The filter element has a C-channel outer sub-frame and a filter media element having edges retained by the outer sub-frame. A particular embodiment of a support insert is shown as a grid of arms, each of two arms extending corner to corner angled relative to the sub-frame edges and joined at the center of the filter element to serve as a grate.

<FIG> show a filter assembly according to at least one embodiment. A peripheral frame retains an expandable replaceable filter element. The frame has four linear segments. The filter element is foldable for reduction to convenient size for shipping and storage as shown for multiple embodiments of the drawings. The filter element has a C-channel outer sub-frame and a filter media element having edges retained by the outer sub-frame. A particular embodiment of a support insert is shown as a single arm having a tapered end that engages removably under an edge of the sub-frame so as to support and retain the filter media element. The support insert is shown in place in <FIG>, and raised in <FIG>.

<FIG> shows a filter assembly, according to at least one embodiment. A peripheral frame retains an expandable replaceable filter element. The frame has four linear segments joined at four corners. The frame includes fasteners at the four corners to retain the filter element. The filter element is foldable for reduction to convenient size for shipping and storage as shown for multiple embodiments of the drawings. The filter element (<FIG>) has a C-channel outer sub-frame and a filter media element having edges retained by the outer sub-frame. A particular embodiment of a support insert is shown in <FIG> as a grid of four arms attached to a central hub. The arms can fold together out of the filter plane for reduction to a convenient size. For use, the arms spread apart into the filter plane, extending at <NUM> degree intervals, to engage the sub-frame or frame segments so as to serve as a grate as shown in <FIG>.

<FIG> show a similar embodiment as shown in <FIG>. In <FIG> the four arms of the support insert in this embodiment meet and are joined by a hub element at the center of the rectangular form of the filter element.

<FIG> shows a filter element in a folded state in a package, according to at least one embodiment, for shipping or storage. <FIG> shows the filter element of <FIG>, removed from the package and at least partially unfolded. <FIG> shows the foldable filter element having magnetic strips at outer edges to engage corresponding magnets or magnetically responsive materials at the inner edges of a frame.

<FIG> show a frame and grate for a filter assembly according to at least one embodiment termed herein as a "snap frame. " The assembly includes four linear segments defining an outer rectangular form of variable dimensions in the filter plane according to the lengths of the segments. A grid of spaced arms defining rectangular spaces therebetween extends across the interior of the filer assembly to serve as a grate to support a filter media element. At least one clip along each frame segment secures the grid to the frame. The clips may secure the edges of a filter media element to the frame and grid as well. A variety of alternative grid patterns are also shown in <FIG>.

<FIG> shows an edge portion of a filter assembly according to at least one embodiment. A peripheral frame segment serves as a clip retaining an expandable replaceable filter element and optionally a screen (see for example <FIG> for a screen). The frame segment may, for example, be an extruded strip segment. As shown in <FIG>, the frame segment has an outer edge wall and three inward extending strips between which two slots are formed for respectively retaining the screen and filter element. The screen or grate may be retained in a first slot defined between a lower strip and a central strip. The filter element is retained in a second slot defined between the central strip and an upper strip. A bezel clip, shown separately in <FIG>, mounts onto the upper strip as shown in <FIG>, and further engages and retains the filter element as shown in <FIG>.

<FIG> shows a filter assembly according to at least one embodiment. A filter element (<FIG>), which is foldable for reduction to convenient size for shipping and storage, has an outer sub-frame and a filter media element having edges retained by the outer sub-frame. A grid of linear arms (<FIG>) attached together at the center of the assembly in the filter plane serves as a grate to support the filter media element.

<FIG> shows a filter assembly, according to at least one embodiment, in which a filter element, which is foldable for reduction to convenient size for shipping and storage, has an outer sub-frame and a filter media element having edges retained by the outer sub-frame. A grid of linear arms attached together at the center of the assembly in the filter plane serves as a grate to support the filter media element. In the expanded configuration, the filter assembly has a square form. The four arms are joined by a folding bracket hub (<FIG>), termed herein a "boomerang bracket," having a hinge aligned along a <NUM> degree central axis of the filter media element relative to the sides of the square form. Folding the bracket hub about the hinge advantageously facilitates reducing the filter element to the illustrated fold pattern of <FIG>.

<FIG> show a filter assembly according to at least one embodiment. The illustrated filter assembly is similar to that shown in <FIG>, and is foldable by use of the folding bracket hub to the illustrated fold pattern of <FIG>, also shown in <FIG>.

<FIG> further show the construction of the folding bracket hub of <FIG>, according to at least one embodiment. The folding bracket hub has two base elements, joined by the hinge, which are brought together when the bracket hub is reduced to the folded configuration, and which spread into the filter plane when the bracket hub is opened to the expanded configuration. Each base element carries two sockets, each for receiving an inner end of an arm in male-female engagement. The sockets are directed at <NUM> degree intervals from each other so that, in the expanded configuration with an arm carried by each socket, the arms are arranged at <NUM> increments in the filter plane, each extending outward to a respective outer edge of the filter assembly (see <FIG> and <FIG> for example).

<FIG> shows a variety of arms for use with the folding bracket hub of <FIG>. The sockets of the bracket hub in <FIG> are shown as circularly cylindrical with longitudinal slits to accommodate some size range or shape variety in the arms they retain. The sockets in other embodiments may take other forms corresponding to or otherwise accommodating any of the arms shown in <FIG>. Other cross-sectional shapes of both arms and sockets are within the scope of these descriptions beyond those explicitly illustrated.

<FIG> show an edge treatment for a filter media element, according to at least one embodiment. An edge treatment, in one embodiment, includes a C-channel strip that clips onto and retains an edge of the filter media element. The C-channel strip for example may be rigid along its length, and may be formed for example by extrusion. An edge treatment, in another embodiment, includes a deformable C-channel gasket, formed of foam or other resilient compressible material, serving as a seal between edges of the filter media element and any outer frame or other host structure.

<FIG> shows an expandable filter media element having an advantageous fold pattern to facilitate reduction of the media element two dimensions so as to take up a smaller area for convenient shipping, storage, or variable sizing.

<FIG> shows an expandable filter media element having a preferential fold pattern to facilitate two-dimensional reduction of the media element for convenient shipping, storage, or variable sizing. In <FIG>, a collapsible cross grate having four arms connected to a central strip can be formed of profiled spring steel having a cylindrical concave side and opposing cylindrically convex side. Such material with such form is advantageously flexible and biases toward an expanded configuration when deployed.

<FIG> shows an expandable filter media element <NUM> having a filter medium <NUM> that features an advantageous fold pattern to facilitate two-dimensional reduction of the filter media element <NUM> for convenient shipping, storage, or variable sizing. A collapsible cross grate <NUM> having four arms <NUM> connected to a central strip <NUM> can be formed of profiled spring steel elements having opposing curvatures on opposing sides. Additional edge segments <NUM> of same, similar, or other semi-rigid resilient material are shown along edges and corners of the media element <NUM>. As shown in <FIG>, the profiled spring steel element <NUM> has a cylindrical concave (channeled) side <NUM> and an opposing cylindrically convex side <NUM>. Advantageously, the profiled spring steel <NUM> is self-biased from any flexed or folded state toward its linear state, in which it extends along its longitudinal channel axis <NUM> defined along its cylindrically concave side <NUM>, and thus provides opening and unfolding forces and self-expanding action in the filter media element <NUM> to the planar state of <FIG> when a folded filter media element is released for example from a package or other binding used for shipping and storage in a reduced state.

<FIG> shows a first side of an expandable filter element having a creased filter media element having a preferential fold pattern to facilitate two-dimensional reduction of the media element for convenient shipping, storage, or variable sizing. The filter element is engaged along its outer edges by a foldable frame having mechanical hinges for size reduction for storage and shipping, and expansion for deployment. The filter element may have a pleated paper top layer (<FIG>) over a foam substrate (<FIG>), according to at least one embodiment.

<FIG> shows a second side of the expandable filter element of <FIG>. The filter media element has four quadrants, with each being symmetric with a diagonally opposing element, such that two quadrant types each having a characteristic fold pattern are shown. Two first-type fold quadrants <NUM> are diagonally opposed across the center of the media element, and two second-type fold quadrants <NUM> are diagonally opposed across the center of the media element adjacent to and between the first-type fold quadrant <NUM>. As shown, a folding bracket hub and arms may be included with the expandable filter element of <FIG>. Semi-rigid struts, for example constructed of a plastic such as PET, may also be included along edges of the filter element. An edge treatment, formed of foam or other resilient compressible material (<FIG>), may also be included serving as a seal between edges of the filter element and any outer frame or other host structure.

<FIG> shows a first side ("TOP VIEW") of an expandable filter having a creased filter media element having an advantageous fold pattern to facilitate two-dimensional reduction of the media element for convenient shipping, storage, or variable sizing. The filter element is engaged along its outer edges by a foldable foam frame, which may serve as a seal between edges of the filter element and any outer frame or other host structure.

<FIG> shows a second side ("BACK VIEW") of the expandable filter element of <FIG>. A grid of linear arms attached together at the center of the assembly in the filter plane serves as a grate to support the filter media element. In the expanded configuration, the filter assembly has a square form. The four arms are joined by a folding hub having a locking hinge with springs. The hub is foldable along two axes, perpendicular to each other and each parallel to a side of the square form of the expanded filter assembly. Four arms extend from the hub defining four square quadrants in the square form. The folding hub and arms define a folding grate for supporting the filter media element. <FIG> and <FIG> show the folding grate of <FIG> without a filter media element.

Claim 1:
An air filter assembly for a heating and ventilation air conditioner, "HVAC", system, the filter assembly comprising:
an expandable filter element (<NUM>) having a filter medium (<NUM>) that features a fold pattern to facilitate two-dimensional reduction of the filter element (<NUM>); and
a frame for engaging and supporting the filter element (<NUM>), the frame configured for being adjusted to accommodate the two-dimensional reduction and secure the filter element (<NUM>) therein,,
wherein the frame is positioned within an HVAC return to secure the filter within an airflow of the HVAC system;
wherein the frame comprises a plurality of linear segments forming a rectangular configuration;
characterized in that the frame comprises four flexible arms (<NUM>), wherein the four flexible arms (<NUM>) form a collapsible cross grate (<NUM>),
wherein the four flexible arms (<NUM>) of the collapsible cross grate (<NUM>) are connected to a central strip (<NUM>), and
wherein each of the four flexible arms (<NUM>) is a profiled spring steel element (<NUM>) having a cylindrically concave side (<NUM>) and an opposing cylindrically convex side (<NUM>) such that the flexible arm (<NUM>) is biased towards a linear state.