Patent Application
20150047508
Framed, pleated filters are commonly used in air filtration applications. In such filters, support is often provided with support on the downstream side of the pleated filter media.
Herein is disclosed a framed pleated air filter, including a non-self-supporting, compressible, pleated air filter media with a plurality of oppositely-facing pleats and with a plurality of upstream pleat tips and downstream pleat tips, the pleated air filter media further including a plurality of bridging filaments that are bonded to at least some of the upstream pleat tips. The framed pleated air filter does not comprise any support member on the downstream face of the pleated air filter media. These and other aspects of the invention will be apparent from the detailed description below. In no event, however, should this broad summary be construed to limit the claimable subject matter, whether such subject matter is presented in claims in the application as initially filed or in claims that are amended or otherwise presented in prosecution.
Like reference symbols in the various figures indicate like elements. Unless otherwise indicated, all figures and drawings in this document are not to scale and are chosen for the purpose of illustrating different embodiments of the invention. In particular the dimensions of the various components are depicted in illustrative terms only, and no relationship between the dimensions of the various components should be inferred from the drawings, unless so indicated.
Although terms such as “top”, bottom”, “upper”, lower”, “under”, “over”, “front”, “back”, “up” and “down”, and “first” and “second” may be used in this disclosure, it should be understood that those terms are used in their relative sense only unless otherwise noted. As used herein as a modifier to a property, attribute or relationship, the term “generally”, unless otherwise specifically defined, means that the property, attribute or relationship would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within +/−20% for quantifiable properties); the term “substantially” means to a high degree of approximation (e.g., within +/−10% for quantifiable properties) but again without requiring absolute precision or a perfect match. Terms such as “outer”, “outward”, “outwardmost”, “outwardly”, and the like, mean in a direction generally away from the geometric center of the framed air filter. Terms such as “inner”, “inward”, “inwardmost”, “inwardly”, and the like, mean in a direction generally toward the geometric center of the framed air filter media. The term “upstream” is used to denote the side of an air filter from which moving air (in an HVAC system) impinges on the filter media. The upstream side corresponds to the lower side of framed filter 1 as shown in
The term “non-self-supporting” denotes a pleated air filter media that is not capable, in the absence of a support frame that is mounted to the major edges of the pleated filter media to form a framed air filter, of withstanding the forces encountered due to forced-air flow in a typical residential HVAC system, as discussed in detail later herein. Such non-self-supporting pleated air filter media by definition does not encompass pleated air filter media (such as those described e.g. in U.S. Pat. Nos. 8,231,700, 7,896,940 and 6,521,011, all to Sundet, and U.S. Patent Application Publication 2013/0101477 to Both) for which the use of a frame is described as optional.
The term “nestable” denotes framed filters that are configured so that two or more such filters (of like shape, size, and thickness) can be stacked together, without significantly deforming the frames of the filters, at a nesting spacing that is less than 85% of the thickness of each filter, as discussed in detail herein.
The term “compressible” with reference to a pleated filter medium denotes that the pleats of the filter medium can reversibly compress when moderate force is applied to the pleats (e.g., when the framed air filter is nested with other framed air filters of like size and shape), and that the pleats can spring back to their original pleated configuration when the force is removed (e.g., when the filter is removed from a nested condition).
Shown in
In
Pleated filter media 10 comprises an upstream face 25 and a downstream face 35. As shown in further detail in
Bridging Filaments
Framed air filter 1 comprises a plurality of bridging filaments 40 on upstream face 25 of pleated filter media 10. At least portions of at least some of the bridging filaments 40 are bonded to at least portions of at least some of the upstream pleat tips 21 of pleated filter media 10 and can help locally stabilize pleated filter media 10 as disclosed herein.
By definition, a bridging filament is not pleated along with pleated filter media 10. Also by definition, a bridging filament is one that extends between, and is bonded to, at least two upstream pleat tips 21 of pleated filter media 10; or, that is bonded to and/or entangled with other filaments so that the filaments collectively bridge the distance between at least two upstream pleat tips 21 of pleated filter media 10 (with at least some of the filament portions that are in contact with the upstream pleat tips being bonded to the pleat tips). That is, in some exemplary embodiments bridging filaments might be collectively supplied by e.g. filaments of a spun-bonded web (scrim), which filaments, even if they are too short and/or are oriented so that they do not extend between upstream pleat tips, are bonded to other filaments so as to collectively bridge the distance between the upstream pleat tips (with the filament portions that are in contact with the upstream pleat tips being bonded thereto). In other exemplary embodiments bridging filaments might be collectively supplied by e.g. filaments of an expanded metal (such as e.g. the products available from Wallner Tooling/Expac, Rancho Cucamonga, Calif.), even though individual segments of the metal filaments (between junction points with other individual segments) may (or may not) be long enough to extend between two upstream pleat tips.
In at least some embodiments, however, bridging filaments 40 will comprise an average length that is at least 100%, 200%, 400%, or 800% of the spacing between consecutive upstream pleat tips 21, and/or will be arranged so that at least some individual filaments extend between, and are bonded to, at least two upstream pleat tips 21 of pleated filter media 10.
Not being pleated, bridging filaments 40 will often comprise a generally planar configuration (as shown in exemplary embodiment in
Bridging filaments may be provided on the upstream face of pleated filter media 10 in any suitable manner and in any suitable arrangement. An exemplary arrangement of a plurality of bridging filaments 40 is shown in
Bridging filaments 40 can advantageously locally stabilize pleated filter media 10 to minimize any local deformation of a pleat due to the pressure of an airstream impinging on upstream face 25 of pleated filter media 10. Specifically, filaments 40 as provided on the upstream face 25 of pleated filter media 10 can the minimize local deformation of at least upstream pleats 20, in a way that may not be possible were filaments 40 to be provided only on the downstream face 35 of pleated filter media 10. If filaments 40 (or, in general, any other type of support) were to be provided on the downstream face of pleated filter media 10, the pressure of the impinging air could cause upstream pleats 20 to locally deform, e.g. collapse, toward the downstream side of the pleated filter media, a process that filaments 40 could do little or nothing to prevent. In contrast, with filaments 40 placed on the upstream face of the pleated filter media and bonded to the upstream pleat tips, the filaments may largely prevent the upstream pleats from locally collapsing or deforming toward the downstream side of the pleated filter media under the air pressure. Moreover, since the pressure of the moving air will tend to “inflate” the downstream pleats, the filaments, being bonded to the upstream pleat tips, may also locally stabilize the downstream pleats, e.g. by limiting the inflation of the downstream pleats so as to e.g. prevent any unacceptable billowing or ballooning of the downstream pleats. It will thus be appreciated that bridging filaments 40 can act to locally stabilize pleated filter media 10, without causing pleated media 10 to be self-supporting (and without compromising the ability of framed air filters 1 to be optionally nested if this is desired).
Any suitable filaments 40 may be used, made of any suitable materials. In some embodiments, filaments 40 may be non-elastic. Non-elastic as defined herein encompasses any material that does not have the relatively high reversible extensibility (characterized e.g. by the ability to be reversibly elongated to e.g. 100% or more without undergoing plastic deformation) characteristic of elastic materials such as natural rubber, SBR rubber, lycra, etc. Thus, common polymeric materials, e.g. extrudable materials (including but not limited to e.g. polypropylene, poly(lactic acid), polyethylene terephthalate and the like), may be used to form filaments 40. In other embodiments, filaments 40 may be made of an elastic material. Regardless of the specific composition of filaments 40, it may be desired that in at least some embodiments, filaments 40 may not extend or elongate to any significant extent (e.g., more than about 10%) under the forces present upon the exposure of framed air filter 1 to a typical residential HVAC airstream. In some embodiments, filaments 40 as disclosed herein are flexible, meaning that filaments 40 can (individually and collectively) be easily and reversibly bent, curved, rolled up etc. In specific embodiments, bridging filaments 40 are not comprised of a shape-memory polymer.
In various embodiments, filaments 40 may comprise an average diameter (or equivalent diameter in the case of filaments with a non-circular or irregular cross-section) of at most about 2, 1, 0.5, 0.2, or 0.1 mm. In further embodiments, filaments 40 may comprise an average diameter or equivalent diameter of at least about 0.05, 0.10, or 0.20 mm. Filaments 40 may comprise any suitable shape when viewed in cross section, (e.g., generally round, square, oblong, etc.). Filaments 40 can comprise suitable spacings between individual filaments as desired (e.g., when filaments 40 are arranged e.g. in parallel to each other so that such an average spacing can be measured). In various embodiments, the filament spacing can be at least about 2 mm, at least about 4 mm, or at least about 6 mm. In additional embodiments, the filament spacing can be at most about 20 mm, at most about 15 mm, at most about 10 mm, or at most about 8 mm. The filament spacings can be relatively constant or can be varied. Some inherent variation in filament spacing may occur in production and handling of filaments, of course. Regardless of the specific arrangements, a suitable set of filaments 40 will collectively comprise a highly open structure (in various embodiments, comprising greater than at least 80, 90, or 95% open area) so as to allow sufficient airflow into pleated filter media 10.
Filaments 40 may be made of any material, provided in any form and in any manner, as long as the material, in combination with the dimensions (e.g., width, thickness) of the filaments, provides the desired combination of physical properties (e.g., flexibility and inextensibility). Such materials may include organic polymeric materials (whether naturally occurring or synthetic, including those already mentioned above), inorganic materials (e.g., fiberglass), metals (such as metal meshes, e.g. expanded metals) and so on. In some embodiments, filaments 40 are not made of metal or of inorganic materials such as fiberglass.
As discussed above, in some embodiments, filaments 40 may be individual filaments that are individually provided (e.g., polymeric filaments that are extruded onto the upstream pleat tips 21 of pleated filter media 10 as described later herein). In other embodiments, filaments 40 may be provided as filaments of a scrim. In this context, the term scrim is used to broadly encompass any collection of filaments that are in contact with each other, achieved by any method of manufacture. Specifically, the term scrim is not limited to organic polymeric materials but rather includes metal meshes or netting (e.g. expanded metals as mentioned earlier herein), inorganic scrims made of e.g. fiberglass, and so on. In some embodiments, such a scrim may be a pre-existing scrim, meaning a scrim that has been pre-made and that has sufficient mechanical integrity to be handled, and brought into contact with the upstream pleat tips, as a unit.
In some embodiments, such a scrim (whether pre-existing or not) may comprise at least some bridging filaments 40 that are oriented generally perpendicular to the pleat direction and that are parallel to each other (e.g., that are oriented in similar manner to the filaments 40 of
In some embodiments, rather than filaments being present that are oriented at least generally perpendicular to the pleat direction, filaments may be present at a wide variety of orientations (and spacings). Such filaments may follow curves, loops, tortuous paths, and so on, as long as a sufficient number of filaments bridge the gaps between upstream pleat tips 21 to serve as bridging filaments. That is, filaments 40 may be provided as part of a scrim that comprises a collection of randomly-oriented filaments, as long as such filaments are sufficiently long and are bonded and/or entangled with each other to serve as bridging filaments as defined herein. Such a scrim might be e.g. a spun-bonded web, spun-laced web, a carded web, a Rando web, a laminate of multiple webs, and so on.
It is thus emphasized that bridging filaments 40 may be provided in a wide variety of ways. However, in some particular embodiments as discussed above, bridging filaments 40 are provided only in the form of filaments that are oriented at least generally parallel to each other and that are not connected with each other by any other filaments. Such embodiments preclude the use of filaments that are part of e.g. a pre-existing scrim that includes filaments oriented in a wide variety of directions; e.g. scrims with multi-directional fibers such as tri-directional scrims and the like. Regardless of the specific nature of the bridging filaments on the upstream face of the pleated filter media, no bridging filaments of any kind will be present on the downstream face of the pleated filter media. In fact, no support member of any kind will be present on the downstream face of the pleated filter media, as discussed in detail later herein.
Filter Media
Pleated filter media 10 may be any suitable media that is pleatable and that is capable of air filtration. Potentially suitable materials may include e.g. paper; porous films of thermoplastic or thermoset materials; nonwoven, such as melt blown or spunbond, webs of synthetic or natural fibers; scrims; woven or knitted materials; foams; electret or electrostatically charged materials; fiberglass media; or laminates or composites of two or more materials. A nonwoven polymeric web comprised of polyethylene, polypropylene or poly(lactic acid) may be suitable, for example. Any suitable method of making a nonwoven web (e.g., melt-blowing, melt-spinning, carding, and so on) may be used. Filter media 10 may also include sorbents, catalysts, and/or activated carbon (granules, fibers, fabric, and molded shapes).
Laminated media can also be used as filter media 10. Such media may consist of laminated layers of the media discussed above or of other substrates laminated to one or more layers of filter media, for example. In some embodiments, a prefilter layer may be used on the upstream side of filter media 10. Such a prefilter layer may comprise e.g. polypropylene, polyethylene, polyethylene terephthalate, poly(lactic acid), or blends of these materials. In other words, in some embodiments pleated filter media 10 may comprise a base (e.g., filtration) layer, along with any other layer or layers as desired for any purpose, as long as it allows pleated media 10 to remain non-self-supporting as defined and described herein. For example, a highly open plastic netting or mesh might be laminated to the pleated media, in order to e.g. enhance the abrasion resistance of the media. Any such layer may be bonded to e.g. a base (e.g. filtration) layer by any suitable method, e.g. by melt-bonding, by way of an adhesive (hot melt adhesive, pressure-sensitive adhesive, and so on).
In specific embodiments, electret filter webs can be formed of split fibrillated charged fibers e.g. as described in U.S. Pat. No. RE 30,782. Such charged fibers can be formed into a nonwoven web by conventional means and optionally joined to a scrim such as disclosed in U.S. Pat. No. 5,230,800 forming an outer support layer. In other specific embodiments, filter media 10 can be a melt blown microfiber nonwoven web, e.g. such as disclosed in U.S. Pat. No. 4,813,948, which can optionally be joined to a secondary layer during web formation as disclosed in that patent, or subsequently joined to a secondary web in any conventional manner.
Filtration media that may be particularly suitable for certain applications might include e.g. media of the general type described in U.S. Pat. No. 8,162,153 to Fox; media of the general type described in U.S. Patent Application Publication 2008/0038976 to Berrigan; and, media of the general type described in U.S. Patent Application Publication 2004/0011204 to Both.
Pleated filter media 10 may comprise any suitable pleat frequency. In various embodiments the pleat frequency may be at most about 1.6, 1.2, 1.0, or 0.8 pleats per cm; in further embodiments the pleat frequency may be at least about 0.3, 0.4, or 0.5 pleats per cm. (In this context the pleat frequency means the number of times that a reference point, e.g. an upstream pleat tip, repeats per cm of distance). In various embodiments, the pleat height (pleat amplitude) of media 10 (defined as the distance in an upstream-downstream direction (i.e., a direction orthogonal to the overall major plane of filter 1/filter media 10), from the upstream surface of an upstream pleat tip to the downstream surface of a downstream pleat tip), can be at least about 2, 4, 6 or 8 mm. In further embodiments, the pleat height may be at most about 12, 6, 4, 2, or 1 cm. In some embodiments the pleats of pleated media 10 may be sinusoidal, meaning that the tips of such pleats have an average radius of curvature of at least about 2 mm. In various embodiments, such sinusoidal pleats may comprise tips with an average radius of curvature of at least about 3, 4, 5, or 6 mm. Sinusoidal pleats as disclosed herein (and as shown in exemplary embodiment in
Non-Self-Supporting Pleated Filter Media
As discussed earlier herein, pleated filter media 10 is non-self-supporting, even in the presence of bridging filaments 40 on the upstream face thereof. That is, even though bridging filaments 40 may help to stabilize the pleats of pleated filter media 10 against local deformation as disclosed earlier herein, the presence of bridging filaments 40 is not sufficient to render pleated filter media 10 self-supporting. By non-self-supporting is meant a pleated air filter media that is not capable, in the absence of a support frame that is mounted to the major edges of the pleated filter media to form a framed air filter, of withstanding the forces encountered due to forced-air flow in a typical residential HVAC system. Specifically, non-self-supporting denotes a pleated air filter media that, when placed in a conventional holding fixture of a residential HVAC system without a supporting edge frame, is unable to withstand the forces developed when air impinges the upstream face of the air filter media so as to develop a pressure of at least 0.10 kPA (0.4 inch of water). (By unable to withstand such forces means that the pleated air filter media collapses, deforms, becomes dislodged, ruptures, or the like, so as to render the performance of the air filter media unsatisfactory.)
Methods of Making
Filter media 10 can be pleated by any suitable method by which pleats may be formed in a media prior to bridging filaments 40 being bonded to upstream pleat tips thereof (noting that the term pleated filter media as used herein does not encompass filter media that is formed into a folded or puckered shape by way of the e.g. shrinking of a shape-memory polymer that is attached to portions thereof). Particularly advantageous methods might include the processing of the media through a set of corrugating gears, e.g. in any suitable variation of the methods disclosed in e.g. U.S. Pat. No. 5,256,231. Bridging filaments 40 may be bonded to upstream pleat tips of a pleated filter media 10 by any suitable method. If the filaments are provided as a pre-existing scrim, such a scrim can be applied to the upstream face of pleated filter media 10, and bonded to at least some of the upstream pleat tips thereof, by any suitable method. For example, a scrim may be obtained e.g. as a continuous roll, a bonding adhesive can be applied thereto (e.g., by coating the adhesive onto at least some surfaces of filaments of the scrim), and the scrim then contacted with the pleated media so as to cause bonding between adhesive-coated portions of the filament and portions of the upstream pleat tips that they are contacted with.
Other bonding methods (e.g., ultrasonic bonding, melt-bonding (including e.g. heat-sealing), and so on), are also possible. In embodiments in which filaments 40 are not provided as part of a pre-existing scrim, they may be conveniently melt-extruded onto the upstream pleat tips of a pleated filter media, e.g. while the media is still resident on a corrugating (pleating) gear or any other kind of corrugating apparatus. Such methods could be any suitable variation of the methods disclosed in e.g. U.S. Pat. Nos. 5,256,231; 5,620,545; and 7,052,565, all of which are incorporated by reference herein in their entirety. In embodiments in which filaments 40 are melt-bonded to the upstream pleat tips of media 10, the composition of filaments 40 and the fibers of media 10 (specifically, the outermost fibers of media 10, if media 10 comprises multiple layers) may be advantageously chosen to facilitate such melt-bonding. For example, the filaments and fibers may be made of materials that are sufficiently compatible to allow melt-bonding to occur. In specific embodiments, filaments 40 and the fibers of media 10 may be comprised of the same type of polymer (e.g., they may both be polypropylene; they may both be poly (lactic acid), etc.). It will be noted that in some circumstances (e.g., when the filaments 40 are melt-extruded onto the pleat tips) some penetration of the molten filament material into the spaces between the fibers of media 10 may occur, which may augment the bonding process by achieving at least some physical entanglement or entrapment.
However provided, in at least some embodiments filaments 40 may be provided (in a spaced-apart manner) generally across the entire width (that is, the dimension that is generally orthogonal to the pleat direction and to the upstream-downstream axis of the filter media) of the pleated filter media. Pleated filter media 10 may be trimmed or cut to the desired final width before or after the bonding of the filaments thereto, as desired.
The pleat direction of filter media 10 relative to frame 12 (and thus to the finished filter 1) and the orientation (i.e., of the long axes) of filaments 40 relative to frame 12, may each be chosen as desired. In some embodiments in which filter 1 is non-square, the pleat direction may oriented generally perpendicular to the long axis of filter 1 (as in the design of
Frame
A frame (i.e., a support frame) 12 is applied to the perimeter of pleated filter media 10 (comprising filaments 40 bonded to upstream pleat tips thereof) to form framed pleated air filter 1. Pleated filter media 10 being non-self-supporting (even in the presence of filaments 40) as defined earlier herein, frame 12 is required in order for pleated filter media 10 to be properly supported in place in a residential HVAC system. Frame 12 may conveniently take the form of a rectangular frame with four major elongate frame portions that are each mounted on one of the four major edges of the filter media. For convenience in describing such generally rectangular geometry, the four major portions of frame 12 may occasionally be referred to herein by a lettered subscript (e.g., a, b, c, or d). It will be recognized that in a rectangular filter, opposing frame portions (e.g., portions 12a and 12c; and, portions 12b and 12d, as shown in
In many embodiments, support frame 12 may be a “pinch” frame as shown in exemplary embodiment in
It will be appreciated that some asymmetry will be present in framed filter 1 owing to the pleating of filter media 10. Specifically, with reference to
In many cases, most or all of the area of frame flanges 130 and 160 (not just inward terminal ends thereof) may be pinched together; often, most or all portions of flanges 130 and 160 will be at least generally parallel to each other (as shown e.g. in
In some embodiments each major portion of frame 12 may comprise an outer sidewall 140, which extends outward and downstream from flange 130 and is foldably connected thereto by fold line 135; and, inner sidewall 150, which extends outward and downstream from flange 160 and is foldably connected thereto by fold line 155, with outer sidewall 140 and inner sidewall 150 being foldably connected by fold line 145. (In many embodiments, fold line 145 may provide a terminal downstream end/edge of frame 12.) Thus, in some embodiments a major portion of frame 12 may be conveniently formed by the folding of a suitable precursor material (e.g., paperboard) along fold lines so as to provide flanges 130 and 160 and sidewalls 140 and 150. However, any suitable frame construction may be used; i.e. any major portion of frame 12 may be made of any suitable material (whether paperboard, plastic etc.) and may be formed e.g. by folding of a single frame piece, by the assembling of multiple pieces to each other, and so on. In many embodiments, all four major frame portions may each comprise upstream and downstream flanges and inner and outer sidewalls and foldable connections therebetween.
As used herein, the term foldable signifies that the frame portion is formed (i.e., into the general configuration shown in
Details of particular support frames that may be suitable for the uses disclosed herein are provided in U.S. patent application Ser. No. 13/490,545, filed 7 Jun. 2012 and entitled Framed Air Filter with Offset Slot, and Method of Making, which is incorporated herein by reference in its entirety. The finished (framed) filter may be of any suitable size for any desired application.
Each major portion of a frame 12 (e.g., portions 12a-12d as shown in
The sidewalls of major portions of frame 12 can have any suitable angle. As a convenient reference, the angle established by outer sidewall 140 (as seen most easily in
In some embodiments, each major portion of frame 12 may comprise a sidewall angle ranging from e.g. about 60 degrees to 100 degrees. In particular embodiments, such a sidewall angle may be about 90 degrees. In some embodiments, each major portion of frame 12 may optionally comprise an outwardly angled outer sidewall to facilitate optional nesting of the framed filters. That is, a sidewall angle of e.g. at least about 100, 110, 120, or 130 degrees, and of at most about 160, 150, or 140 degrees, will facilitate the nesting of framed filters as disclosed herein. (By way of specific example, the sidewall angle of frame portion 12b as shown in
Optional Nestability
The disclosures herein allow the optional production of framed filters that are nestable. The term “nestable” denotes framed filters that are configured such that two or more such filters (of like shape, size, and thickness) can be stacked together, without significantly deforming the frames of the filters, at a nesting spacing that is less than 85% of the thickness of each filter. This ratio of nesting spacing to filter thickness (as a percentage) can be referred to as a nesting factor. For purposes of such calculations, the thickness of a framed filter “t” is the distance (as shown in
By way of a representative example, portions of three exemplary nested framed air filters 1, 1′ and 1″ are shown in
It is noted that for a particular filter design, a nesting factor as defined herein will be a constant that is set by the design. However, it will be appreciated that the amount of space that can be saved in packing the framed filters will increase with the number of filters that are nested together. By way of a specific representative example, nestable framed air filters might each have a thickness of 20 mm and might have a nesting factor of e.g. 70%, so that any two such filters, when nested together, comprise a thickness “overlap” of 6 mm. Thus, instead of two such filters adding to a total thickness of 40 mm, they would add to a total nested thickness of 34 mm and would provide a space (thickness) savings of (40-34)/40 or 15%. Three such filters would add to a total nested thickness of 48 mm and would provide a space savings of (60-48)/60 or 20%; five such filters would add to a total nested thickness of 76 mm and would provide a space savings of (100−76)/100 or 24%, and so on. It will thus be appreciated that nesting filters as disclosed herein can provide significant savings in packaging, shipping, and storage costs, and it will be further appreciated that the greater the number of filters that are nested together the greater the savings can be.
Further details of nestable filters are disclosed in U.S. patent application Ser. No. ______, filed evendate herewith, under attorney docket number 74411US002 and entitled NESTABLE FRAMED PLEATED AIR FILTER AND METHOD OF MAKING, which is incorporated by reference herein in its entirety.
Compressibility of Pleated Filter Media
It is noted that even if pleated media 10 is compressible, it may not be necessary that any compression of any or all pleats thereof actually occurs during a nesting process (if nesting is performed), depending on the specific design of the filter (e.g., the filter thickness, pleat height, and so on). It is further noted that although not shown e.g. in
Absence of Downstream Support
Beyond the requirement that a compressible pleated filter medium cannot have a reinforcing layer of permanently deformable material (e.g., metal) pleated along therewith and continuously bonded to it, a framed pleated filter media as disclosed herein will not comprise any support member on the downstream face of the pleated air filter media. The term support member is used broadly in this context, and signifies any single member, or group of members, that provide downstream support. Such a support member or members include, but are not limited to: one or more strips of paperboard, plastic or metal; any perforated sheetlike layer (such as e.g. a perforated layer of paperboard, plastic, or metal); and any collection of filaments (such as e.g. a wire mesh, a scrim of polymeric materials, a scrim or mesh of inorganic materials such as fiberglass, a netting of polymeric material, a collection of bridging filaments as described herein, an expanded-metal mesh, a woven-wire material, and so on). Any such support member or members are prohibited on the downstream face of pleated media 10, whether or not the member or members are attached to any portion of the downstream face (e.g., the downstream pleat tips), and whether or not the member or members are attached to any portion of the support frame.
In short, the only item(s) of support that are allowed on the downstream face of the framed pleated air filter are the downstream flanges 160 of the frame itself. In fact, any portion that extends (e.g. integrally extends) from a downstream flange 160 of a major portion of frame 12, inwardly to a location that is more than 50% of the distance from the outwardmost edge of that portion of the framed filter toward the geometric center of the framed filter, is considered to be a support member and is not permitted.
The ordinary artisan will appreciate the surprising nature of the herein-presented disclosures that a framed pleated filter can be made, e.g. in sizes as large as e.g. 41×64 cm, that can survive the pressures typically encountered in a residential HVAC system, without downstream support of any kind (excepting the edge support provided by the support frame), without the pleated media having any reinforcing layer of permanently deformable material (e.g., metal) pleated along therewith, and even (in some embodiments) with the pleated media having a sinusoidal pleat pattern rather than being arranged in “zig-zag” style pleats that effectively form triangular trusses that substantially increase the stiffness of the pleated media.
Framed air filters as disclosed herein do not necessarily require pleat registration between the different filters, although this may be optionally done if desired. Thus in at least some embodiments, framed air filters as disclosed herein comprise pleat patterns that are unregistered, meaning that when the various individual framed, pleated filters are manufactured, the placement of the pleats of any one filter media (relative to its frame) is different from the placement of the pleats of at least one other filter media relative to that other filter media's frame. In other words, the pleats of any two framed pleated filters do not necessarily need to line up exactly when the two framed pleated filters are stacked (e.g., nested) together (even though the pleat spacings may often be similar or identical). Such an arrangement is shown in exemplary embodiment in
A framed pleated air filter, comprising: a non-self-supporting, compressible, pleated air filter media with an upstream face and a downstream face and a generally rectangular perimeter with four major edges, wherein the non-self-supporting, compressible, pleated air filter media comprises a plurality of oppositely-facing pleats with a pleat direction and with a plurality of upstream pleat tips and upstream pleat valleys and downstream pleat tips and downstream pleat valleys, the media further comprising a plurality of bridging filaments that are in discontinuous contact with the upstream face of the media and that are bonded to at least some of the upstream pleat tips; and, a pinch frame comprising four major frame portions, with each major frame portion being mounted on one of the four major edges of the media, wherein the framed pleated air filter does not comprise any support member on the downstream face of the pleated air filter media.
The filter of embodiment 1 wherein portions of the bridging filaments are melt-bonded to at least some of the upstream pleat tips.
The filter of any of embodiments 1-2 wherein at least some of the bridging filaments are at least generally parallel to each other and are oriented at least generally perpendicular to the pleat direction.
The pleated filter of embodiment 3 wherein the bridging filaments comprise a spacing between filaments of from around 3 mm to around 12 mm.
The pleated filter of any of embodiments 1-4 wherein the bridging filaments are provided as part of a pre-existing scrim that is adhesively bonded to at least some of the upstream pleat tips.
The filter of any of embodiments 1-5 wherein the plurality of oppositely-facing pleats of the media collectively define a pleating plane, wherein upstream and downstream flanges of the four frame portions collectively define a pinch plane, and wherein the pleating plane of the media is offset downstream from the pinch plane.
The filter of any of embodiments 1-6 wherein each major frame portion comprises a sidewall angle of from about 100 degrees to about 160 degrees and wherein the framed pleated air filter is nestable.
The filter of embodiment 7 wherein the non-self-supporting, compressible, pleated air filter media exhibits a pleat height and wherein the nestable framed pleated air filter exhibits a nesting spacing that is less than about 70% of the pleat height.
A kit comprising a plurality of framed pleated air filters of embodiment 7 of like size and shape, wherein the framed pleated air filters are packaged together so as to occupy a total thickness that is less than about 70% of the collective total of the thicknesses of the individual framed pleated air filters.
The kit of embodiment 9 wherein the pleated air filter media of at least one of the framed pleated air filters of the kit comprises pleats that are not registered with the pleated air filter media of at least one other of the framed pleated filters of the kit.
The filter of any of embodiments 1-8 wherein the non-self-supporting, compressible, pleated air filter media comprises a nonwoven web comprising organic polymeric fibers.
The filter of any of embodiments 1-8 and 11 wherein the pleats are sinusoidal pleats in which the upstream pleat tips and the downstream pleat tips exhibit an average radius of curvature of at least about 2 mm and in which none of the upstream pleat tips nor downstream pleat tips are score-pleated.
The filter of any of embodiments 1-8 and 11-12 wherein the pleat frequency is from about 0.3 to about 1.2 pleats per cm and wherein the pleat height is from about 4 to about 20 mm.
The filter any of embodiments 1-8 and 11-13 wherein the sidewall of each frame portion comprises an outwardly angled inner sidewall and an outwardly angled outer sidewall that meet at a downstream edge of the frame portion, and wherein the inner sidewall and the outer sidewall are positioned at an angle relative to each other, of from about 10 to about 40 degrees.
The filter of any of embodiments 1-8 and 11-14 wherein the air filter media comprises an electrostatically charged material.
A method of making a framed pleated air filter with an upstream face and a downstream face and a generally rectangular perimeter, the method comprising: providing a non-self-supporting, compressible, pleated air filter media that comprises a plurality of oppositely-facing pleats with a pleat direction and with a plurality of upstream pleat tips and upstream pleat valleys and downstream pleat tips and downstream pleat valleys; bonding a plurality of bridging filaments to at least some of the upstream pleat tips, so that the bonded bridging filaments are in discontinuous contact with the upstream face of the pleated air filter media; and, mounting a pinch frame onto the generally rectangular perimeter of the filter media, wherein the framed pleated air filter does not comprise any support member on the downstream face of the pleated air filter media.
The method of embodiment 16 wherein the bridging filaments are extruded as a molten extrudate and are contacted with the upstream pleat tips while still at least semi-molten.
The method of embodiment 16 wherein the bridging filaments are provided as part of a pre-existing scrim that is adhesively bonded to at least some of the upstream pleat tips.
Numerous Working Examples were made of a variety of designs and configurations. Air filter media were produced or obtained of a variety of compositions, including unpleated media of the general type described in U.S. Pat. No. 8,162,153 to Fox; unpleated media of the general type described in U.S. Patent Application Publication 2008/0038976 to Berrigan; unpleated media obtained from Kimberly Clark (Irving, Tex.) under the trade designation 353H; and, unpleated media (of the general type described in U.S. Patent Application Publication 2004/0011204 to Both) comprising a layer of electrostatically charged fibrillated fibers (30 g/m2) ultrasonically bonded to a 15 g/m2 polymeric netting.
Samples of these media were corrugated (pleated) by being passed through a first nip comprising intermeshing gears of first and second corrugating rolls, in generally similar manner to the methods described e.g. in U.S. Pat. No. 5,256,231. The corrugation (pleating) pattern ranged from a pleat frequency of approximately 1.2 pleats per cm to approximately 0.3 pleats per cm; the pleat height ranged from approximately 3 mm to approximately 19 mm. (The media were not scored before, during or after the process of corrugating.) The resulting pleat patterns were generally sinusoidal.
The pleated media was maintained in contact with the second corrugating roll through a wrap angle to reach a second nip which was between the second corrugating roll and a smooth-faced backing roll. A strand die was provided (of generally similar type to that described in U.S. Pat. No. 7,052,565 to Seth) through which multiple streams of molten extrudate was extruded into the nip between the second corrugating roll and the backing roll, so as to provide bridging filaments that (after the molten extrudate had cooled and solidified) were melt-bonded to the upstream tips of the pleated media. Often, the bridging filaments and the filter media comprised similar compositions (e.g. both comprised polypropylene), to enhance the melt-bonding. The bridging filaments were oriented substantially perpendicular to the pleat direction (e.g., in similar manner to that shown in
In this manner numerous samples of non-self-supporting pleated air filter media were produced, bearing bridging filaments (in this case, continuous bridging filaments) on one face thereof. The samples were then framed with pinch frames in generally similar manner to that described in U.S. patent application Ser. No. 13/490,545, with the bridging filaments being present on what would become the upstream face of the finished framed filter. The thus-formed framed filters (many of which were of a nominal size of approximately 36 cm×64 cm×2.5 cm (14 inches×25 inches×1 inch)) typically had a sidewall angle in the range of approximately 130 degrees. Many of these framed filters could be nested (as defined herein) with each other, with compression of the pleats occurring during nesting if necessitated by the pleat height in relation to the nesting spacing (in such cases, the media satisfactorily regained its pleated configuration upon removing the filters from a nested condition). Framed filters were also made of nominal size of approximately 51 cm×64 cm×2.5 cm (20 inches×25 inches×1 inch), which framed filters of this size were also found to be self-supporting.
Air filtration efficiency of various of these framed pleated filters was tested and was found to be generally satisfactory (e.g., similar to various control samples such as the same filtration media which had been e.g. pleated along with a support layer, e.g. wire mesh).
The property of a pleated filter media (in the absence of a support frame) being self-supporting or not could be tested e.g. by placing a piece of the pleated filter media (that is, a pleat pack, without a support frame having been mounted to the edges thereof), of a nominal size of e.g. approximately 36 cm by 64 cm or 41 cm by 64 cm, into an opening of a frame tester e.g. of the general type described in U.S. Patent Application Publication 2012/0317944. Such a frame tester may comprise an opening with flanges that support the perimeter edges of the pleated filter media to an overlap of approximately 1.3 cm (inwardly from the edge of the media) on each perimeter edge. A pressure differential could then be applied to the pleated filter media (with the higher pressure being applied to the upstream face of the filter), which differential may be gradually stepped up to higher values. In such testing, prototypes of non-self-supporting pleated filter media of the general type described herein (i.e., including upstream-side bridging filaments) would typically fail (e.g., would deform/bow in a downstream direction so as to become dislodged from the frame tester opening) at an applied air pressure of no more than 0.05-0.07 kPA (i.e., 0.2-0.3 inches of water). In fact, many of the pleated filter media samples described above could be easily discerned as being non-self-supporting even without performing such a test (e.g., merely by inspection of how limp and floppy the pleated media was, even in the presence of bridging filaments, as would be readily apparent to the ordinary artisan). The framed filters as made were found to be able to satisfactorily withstand the air pressure of a typical residential HVAC system (as discussed herein).
It will be apparent to those skilled in the art that the specific exemplary structures, features, details, configurations, etc., that are disclosed herein can be modified and/or combined in numerous embodiments. All such variations and combinations are contemplated by the inventor as being within the bounds of the conceived invention. Thus, the scope of the present invention should not be limited to the specific illustrative structures described herein, but rather by the structures described by the language of the claims, and the equivalents of those structures. To the extent that there is a conflict or discrepancy between this specification and the disclosure in any document incorporated by reference herein, this specification will control.
