Forced air system air filter

An air filter including a filter media having a plurality of flat pleats defining a plurality of truncated pleat tips and sloping side surfaces along a front face and a rear face. The truncated pleat tips are oriented perpendicular to the direction of pleating and are configured with a planar tip portion. The reinforcement structure includes at least one generally planar first reinforcing strip oriented in the direction of the pleating and connected to the truncated pleat tips along the rear face. The reinforcing structure further includes at least one generally planar second reinforcing strip oriented in the direction of pleating and connected to the truncate pleat tips along the front face.

BACKGROUND

The present disclosure relates to an air filter for forced air heating, ventilating and/or air conditioning (“HVAC”) systems. More specifically, the present disclosure relates to an air filter having a plurality of flat pleats which facilitates better bonding with a reinforcing structure and strengthens the filter media such that the surface area of the filter media is greater and the pressure drop of the air moving through the air filter is lower than conventional air filters.

Pleated paper filter elements of the type used in forced air systems require replacement when filter surfaces become so covered by dust and dirt particles that they clog the paper filter, that they restrict air flow. For a required air flow rate and filtration, the useful life of the filter or the time between cleaning depends on its surface area. Thus, to increase the useful life of a filter element, the surface areas typically increase.

One method to increase filter surface area is to increase the size the of the pleated filter, the depth of the pleats or the pleat density. In many HVAC systems, the height and width dimensions of a pleated filter usually cannot be increased due to physical constraints of the forced air system. Accordingly, reasonable methods to increase the surface area are limited to increasing the depth of the pleats and the pleat density. However, the surface area of the filter media is also a major factor in determining flow resistance (i.e., pressure drop) and loading capacity of the pleated filter.

The ability of an air filter media to withstand operating pressures is typically dependent upon the pleat count, the pleat depth and the stiffness of the filter media. The filter media can become unsteady when air pressure is applied to one side. In the event the pleats deform or collapse, a portion of the surface area can be reduced and the pressure drop or across filter element will increase, further increasing the force applied to the filter media.

For example, in one prior art design an accordion folded filter element includes planar reinforcing strips bonded to pleat tips by an adhesive. Another prior art design utilizes a glue bead applied prior to folding of the filter media which connects the folds with one another at the point of application. Yet another prior art design spaces the folds of the pleated filter media using a tapered assembly comb having uniformly spaced teeth. Still another prior art design utilizes a truss-type of reinforcing structure.

Therefore, there is a need for an air filter that provides more filter filter media area, reduces pressure drop, provides better bonding between the filter media and a reinforcing structure, has more uniform pleats, aids in the processing of the filter media and decreases material and manufacturing costs.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles disclosed herein, reference will now be made to the preferred embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope is thereby intended, such alterations and further modifications in the illustrated apparatus or assembly thereof, and such further applications of the principles disclosed as illustrated therein being contemplated as would normally occur to one skilled in the art to which this disclosure relates.

In one aspect of the present invention, an air filter includes a filter media having a plurality of flat pleats defining a plurality of truncated pleat tips and sloping sides surfaces along a front face and a rear face of the filter. The truncated pleat tips are oriented perpendicular to the direction of pleading and are configured with a planar tip portion. A reinforcing structure includes at least one generally planar first reinforcing strip oriented in the direction of pleating and connected to the truncated pleat tips along the rear face. The reinforcing structure further includes at one generally planar second reinforcing strip oriented in the direction of pleating and connected to the truncated pleat tips along the front face.

In another aspect of the present invention, an air filter includes a filter media having a plurality of flat pleats defining a plurality of truncated pleat tips and sloping sides surfaces along a front face and a rear face of the filter media. The truncated pleat tips are oriented perpendicular to the direction of pleating and are configured for the planar tip portion. A reinforcing structure includes at least one reinforcing number oriented perpendicular to the direction of pleading. Each such reinforcing member has a first planar element extending along one sloping side surface of the rear face from a first edge to a second edge adjacent to a rear face. The reinforcing structure further includes at least one generally planar first reinforcing strip oriented in the direction of pleating and connected to the truncated pleat tips along the rear face and the reinforcing member.

In another aspect of the present invention, an air filter includes a filter media having a plurality of flat pleats defining a plurality of truncated pleat tips and sloping side surfaces along a front face and a rear face. The truncated pleat tips are oriented perpendicular to the direction of the pleating and are configured with a planar tip portion defined by a pair of offset score lines formed in the filter media as opposing longitude of the edges of the planar tip portion. In one embodiment, the offset score lines were spaced apart from each other by a distance of approximately 0.03125 inches. The distance between the pairs of score lines will be determined by the desired pleat depth.

A reinforcing structure includes at least one reinforcing member oriented perpendicular to the direction of the pleating. Each such reinforcing member has a first planar element extending along one sloping side surface other face from a first edge to second edge adjacent the rear face. The reinforcing structure further includes at least one generally first planar reinforcing strip oriented in the direction of the pleating and connected to the planar tip portions along the rear face and each reinforcing member. The reinforcing structure still further includes at least one generally second planar reinforcing strip oriented in the direction of pleating and connected to the planar tip portions along the front face.

FIG. 1is an exploded view of an air filter20that includes a filter media element22having a plurality of “fan-folded” or “accordian folded” a flat pleats44. Each fold or pleat is defined by a section of two-sided or planar filter media that is folded. Each fold defines a truncated pleat tip46between adjacent sloping side surfaces48along a front face24(shown in cross-section inFIGS. 2B,3B and4B) and a rear face26(shown in cross section inFIGS. 2A,3A and4A). The truncated pleat tips46are oriented perpendicular to the direction of pleating (as indicated by the double-headed arrow42). Each pleat tip has a planar tip portion50, described in detail below.

The air filter20preferably includes a plurality of frame members that support the media element22. The frame members include opposing side frame members34,36and opposing end frame members38,40. As shown inFIG. 1, the side frame members and the end frame members are orthogonal to each other. The filter media22is connected to the frame members34,36,38,40in any conventional manner to provide a leak-proof seal there between. The air filter20can also include one or more planar reinforcing strips28on both the top and bottom surfaces of the filter20. The “top” reinforcing strip is identified by reference numeral30whereas the bottom reinforcing strip is identified by reference numeral31. Those of ordinary skill in the art will recognize that the planar reinforcing strips30do not need to be planar and that other cross-sectional shapes could also be used. Square, circular, L-shaped or rectangular cross sections should all be considered equivalent embodiments. For claim construction purposes, the term “planar reinforcing strip” and “reinforcing strip” should be construed to include at least all of the above-identified geometries.

The filter20also includes one or more reinforcing members32, first reinforcing strip30or second reinforcing strip31. Each reinforcing member32is oriented perpendicular to the direction of pleating42. Each planar first reinforcing strip30is oriented in the direction of pleating42and abuts the planar tip portions50along the rear face26and each reinforcing member32. Each planar second reinforcing strip31is oriented in the direction of pleating42and is connected to the planar tip portions50along the front face24. Preferably, the first and second reinforcing strips30,31extend over and are connected to opposing end frame sections38,40to provide additional support, as shown inFIG. 2.

Those of ordinary skill in the art will recognize that the frame members, the planar reinforcing strips and the pleat-conforming member can each be made out of metal or plastic as needed by the application in which the filter20is to be used.

FIG. 2Ais a perspective view of the rear face26of the air filter20assembled in accordance withFIG. 1. The filter media22is disposed within a volume defined by the aforementioned frame members34,36,38,40and provided with an airtight seal so that when the filter20is installed into an air stream, the applied air stream passes through the air filter20instead of around it. The reinforcing member32is located to align with and fit snugly within one of the flat pleats along the rear face26, thereby providing support for the filter media22. As the terms are used herein, an air stream that impinged on the front face24, passes through the media22from the front face24and exits the filter22from the rear face26.

FIG. 2Bis a perspective view of the front face24of an alternative embodiment of the air filter20wherein the reinforcing member32is located to align with and fit snugly within one of the flat pleats along the front face24, thereby providing support for the filter media22.

The first reinforcing strips30, which are connected to the planar tip portions50, are preferably attached to the planar tip portion50of each of the truncated pleat tips46along the rear face26and/or front face24by an appropriate adhesive or a mechanical connector.

The opposing distal ends of the first reinforcing strips30are also connected to surfaces of the end frame sections38,40. It will be recognized by those of skill in the art that the first reinforcing strips30extend in the direction of pleating42.

FIG. 3Ais a partial section view of the air filter20ofFIG. 2Ataken along line3A—3A and more clearly illustrates the configuration of the filter media22, first and second reinforcing strips30,31and the reinforcing member32. Likewise,FIG. 3Bis a partial section view of the air filter20ofFIG. 2Btaken along line3B—3B and more clearly illustrates the configuration of the filter media22, first and second reinforcing strips30,31and the reinforcing member32in this embodiment. It will be recognized by those of skill in the art that the two embodiments ofFIGS. 3A and 3Bare similar and accordingly, will be discussed simultaneously. The filter media22may be constructed of any material to provide the desired filtration characteristics of an intended application. One such construction may include a composition of one hundred percent (100%) low melt fibers. It will be recognized by those of skill in the art that various different filter media structural compositions may be successfully used in connection with the present invention because of the aforementioned advantages, namely, lower pressure drop, increased amount of media, more uniformed pleats, etc.

As set forth above, the filter media22has a plurality of pleats44, each pleat having a pleat tip46between the sloping side surfaces48the shape of which is reminiscent of an accordion bellows. A planar tip portion46is defined by folding the media22at each of two score lines54that are scored, cut or otherwise formed in the filter media22. The score lines54may be depressions or compressions of the media22, or cuts or slices in the media22that do not extend completely through the media22. By folding the media twice, i.e., at both score lines, a substantially flat or planar tip portion46is formed in the filter media to aid in forming a crisp fold and a planar pleat tip46. The score lines54are off-set by a dimension represented by the arrow56. It will be recognized by those of skill in the art that the dimension56may be adjusted and/or varied according to the needs of a particular application to provide planar tip portions50of different widths. It will be further recognized that the dimension56may be different for the pleats on the front face in comparison to the pleats on the rear face.

The planar tip portion50provides a flat area on which an adhesive52can be applied. Applying an adhesive to a flat or planar tip portion50is much easier than applying an adhesive to a narrow, pointed peak that would result if the filter media were folded once instead of at both score lines56. Accordingly, manufacturability is greatly eased because less precision is required to place the adhesive52atop the planar tip portion50of the flat pleats44of the present invention.

By bonding, gluing or otherwise affixing the planar tip portions46to the reinforcing strips, the filter media22is provided with an increased bending strength. Each second reinforcing strip31is connected with and preferably bonded to, the planar tip portion50of the truncated pleat tips46, along the front face24. The adhesive52which is used to connect the second reinforcing strip31to the planar tip portion50along the front face24and the first reinforcing strip30to the planar tip portion along the rear face and the pleat-conforming reinforcing member32may be an adhesive which connects the aforementioned parts together. Adhesives that are suitable for use in an HVAC system and which can bond the media to the reinforcing strips are known in the art.

FIG. 4Ais a partial section view of the air filter ofFIG. 2Ataken along line4A—4A that more clearly illustrates the filter media22and reinforcing member32without the reinforcing strips30,31. Likewise,FIG. 4Bis a partial section view of the air filter ofFIG. 2Btaken along line4B—4B that more clearly illustrates the filter media22and reinforcing member32without the reinforcing strips30,31. It will be recognized by those of skill in the art that the two embodiments ofFIGS. 4A and 4Bare similar and accordingly, will be discussed simultaneously. The planar tip portions46and the inclined surface48of a filter media pleat are inclined with respect to each other. The exterior angle formed between these two surfaces is at an angle that is more than ninety degrees. Conversely, the interior angle between these two surfaces is less than ninety degrees. Increasing the exterior angle74(decreasing the interior angle) will decrease the number of pleats that can be folded into a given space and decreasing the filter media22surface area in a filter20of a given height and width. Decreasing the exterior angle74toward ninety degrees will increase the number of pleats and as a result, the filter media surface area in a filter20of a given height and width. It should be apparent to those of ordinary skill in the art that in one embodiment the distance between adjacent truncated pleat tips across the front or rear face is substantially the same. In an alternative embodiment, the distances between adjacent truncated pleat tips can be varied. For example, pleat tips next to one end of the frame might be very close to each other but with the distance between successively adjacent pleat tips gradually increasing as the distance from the one end of the frame increases.

FIGS. 3A,3B,4A and4B show an end-view of one embodiment of the reinforcing member32that includes a first inclined planar element60which extends along one sloping side surface48of the rear face26from a first edge62to a second edge64adjacent the rear face26. The reinforcing member32may also further include a second planar element66extending from the second edge64to a third edge68between adjacent truncated pleat tips46. The reinforcing member may further still include a third planar element70which extends from the third edge68to a fourth edge72which is contiguous with the first planar element60between the first and second edges62,64. The reinforcing member32may be connected to the filter media when disposed within one of the flat pleats44along the rear face26and/or front face24either along a face of the first planar element60which is contiguous with one of the sloping slide surfaces48, at the first edge62, second edge64or third edge68. It will be recognized by those of skill in the art that the reinforcing member32is not required to be connected to the filter media22in order to perform the intended function. The reinforcing member32may be formed from a single sheet of material which is folded into the preferred configuration or may be formed from a plurality of pieces. In one embodiment, the fourth edge bisects the first planar element.

FIGS. 3C and 4Care partial section views of the air filter ofFIGS. 3A and 3BandFIGS. 4A and 4B, respectively, showing an alternative reinforcing member32similar to the reinforcing member described above with respect toFIGS. 3A,3B,4A and4B. However, this embodiment of the reinforcing member32includes a fourth planar element80that extends from the fourth edge72to a fifth edge82. The fourth planar element80is preferably parallel to and contiguous with a portion of the first planar element60. It will be recognized by those of skill in the art that the fourth planar element80is not required to be connected to the first planar element60in order to perform the intended function.

FIGS. 5A,5B, and5C are each a perspective view of other embodiments of the frame members34,36,38,40. As shown inFIG. 5A, frame members36,38and40can be formed from a single U-shaped channel, bent to form two corners. In particular, frame members36is bounded by two corners37and39from which the other two frame members38and40extend. The extension of the members38and40from the first section36is itself a U-shaped structure, which is formed from U-shaped channel. A fourth frame members34is removably attached to the other three members36,38and40, such as by way of adhesive or mechanical fastener such as screws or pins or the like.

InFIG. 5B, a first frame member40is bounded at one end by a corner37as shown. Frame member34extends from the corner37, substantially orthogonal to the first frame member40. The two frame members34and40form an “L”-shaped frame by the frame members34and40being fixedly attached to each other at the corner37. The other two frame members36and38are hinged however, to open and close the frame into which a filter media is installed.

Members36and38are each hingedly attached to the frame members40and34respectively so that they can independently “open” and “close.” A first hinge47A between frame members36and40allow them to close. A second hinge47B between frame members34and38also allow them to close. Closing members36and38using the two hinges47A and47B allows the four members34,36,38and40to form the frame for the filter media.

InFIG. 5C, two half-frame members (34/38and36/40) can be removably attached to each other to form a closed frame. Each of the two half-frames are joined together using adhesive or mechanical fastener such as screws or pins or the like. Both of the two half-sections can be joined together to form the frame shown inFIG. 1.

FIGS. 6A and 6Bshow yet two other embodiments of the filter frame.FIG. 6Ashows an alternate embodiment of the frame wherein the aforementioned planar reinforcing strips30and31are integrally formed with the frame members. Note that inFIG. 6A, there are no seams between the planar reinforcing strips and the frame members38and40. The planar reinforcing strips are instead formed as part of the frame member38. Integrally-formed planar reinforcing strips31simplify the filter20assembly by eliminating placement and attachment of the planar reinforcing strips.

FIG. 6Bshows yet another alternate embodiment. InFIG. 6B, the first and second reinforcing strips30and31are located just outside the filter media (not shown inFIG. 6Bbut just inside cross-braced frames33and35. The upper cross-braced frame33is formed with (or “include”) the opposing frame members34,36,38and40. The upper cross bracing frame33keeps the opposing frame members square, i.e., at right angles to each other.

The lower cross-bracing frame35includes mounting flanges37. Adhesive or mechanical fasteners (not shown) attach the lower cross bracing frame35to the opposing frame member34,36,38and40and add additional structural rigidity to the filter20.

FIG. 6Cshows yet another alternate embodiment of the filter20. InFIG. 6C, the frame members34,36,38and40are attached to each other by adhesive or mechanical fastener or the like and form a lower or bottom half41of a frame43for the filter20. Cross bracing35keeps the frame members34,36,38and40of the bottom half41square. Optional planar reinforcing strips in the bottom half41help keep the filter media (not shown) flat.

The filter20shown inFIG. 6Chas an upper half45that includes its own cross bracing33. Like the bottom half41, the upper half45accepts optional planar reinforcing strips30to keep filter media flat. Like the bottom half cross bracing35, the upper half cross bracing33keeps the upper half45square as it's opened and closed by way of a hinge47that runs along (or is attached to) one frame member40of the bottom half41and a corresponding edge of the upper half45. The hinge47allows the upper half45and lower half47to be opened and closed to ease replacement of filter media (not shown).

Finally,FIGS. 7A and 7Bshow how the filter media22of the filter20may be configured to have a fixed as well as a variable “frequency.” As shown inFIG. 7A, successive truncated pleat tips46have a regular and periodic spacing Y1between them across the width of the media, including the location X of the reinforcing member32. As is well-known, such a generally saw-tooth like wave has a “wavelength” equal to the spacing between pleat tips46and “frequency” that is inversely proportional to the wavelength. For purposes of claim construction, filter pleats have a “frequency” that corresponds to the spacing between them. The pleat “frequency” is considered fixed when the spacing between pleats Y1and X is uniform. Pleat “frequency” is considered to be variable when the pleat spacing is not uniform but instead varies.

FIG. 7Billustrates the filter media22with a variable pleat frequency. The successive truncated pleat tips46on either side of the reinforcing member32have a regular and periodic spacing Y2(i.e., the wavelength and hence the inverse of the pleat frequency) which is larger or greater than the spacing X of the pleat where the reinforcing member is located, hence the pleat spacing inFIG. 7Bis “varying” or “variable. The spacing X is the same inFIGS. 7A and 7B. However, the spacing Y1is less than the spacing Y2.

AlthoughFIG. 7Bdepicts only a single pleat having a different spacing effectuated by the reinforcing member32having a width the same as shown inFIG. 7A, alternate and equivalent embodiments of a variable pleat spacing include having pleats across a filter, the spacing of which varies continuously from pleat to pleat or any other configuration as may be required by design or economy. By varying pleat frequency, a single media element can be expanded or contracted to fit different-sized filter media frames simply by increasing or decreasing pleat frequency.