Cross-Reference to Related Applications

[0001] This is a non-provisional of pending U.S. provisional patent application serial number 61/434,750, filed January 20, 2011, the entirety of which provisional application is incorporated by reference in its entirety.

Field of the Disclosure

[0002] The present disclosure relates generally to air purifying filters, and more particularly to a stackable air purifying filters for use in air purifying respirators.

Background of the Disclosure

[0003] Current personal air purification filters generally have a traditional cylindrical flow pattern in which a particulate filter portion is placed adjacent to a sorbent filter portion and air is pulled through the two portions in series to obtain a desired degree of purification. FIGS. 1A and IB show such a traditional cylindrical filter design in which filter 1 has a particulate filter portion 2 stacked on top of a sorbent bed portion 3. Arrows "A" indicate the movement of air flow into and out of the filter 1.

[0004] Each individual filter can be used only once, and if the filter service life is passed, the wearer must evacuate to a safe place and replace with a new filter.

Current filters cannot be stacked together to extend their life. [0005] It would be desirable to provide a stackable filter design that would enable multiple filter particulate and sorbent filter portions to be stacked in a way that extends the service life of the filter.

Summary of the Disclosure

[0006] A new air purifying filter is disclosed that can be stacked with other similar filters to make a bigger filter having proportionally longer service life and inverse-proportionally lower breathing resistance.

[0007] An air purifying filter system is disclosed, comprising a set of air purifying filter units. Each air purifying filter unit of the set of air purifying filter units may include an exterior opening in communication with inlet air. In some embodiments, each air purifying filter unit of the set of air purifying filter units may include a plurality of exterior openings in communication with inlet air. Each air purifying filter unit may further include an outlet passage. Each air purifying filter unit may be connected to one or more adjacent air purifying filter units via a sealed

interconnection port that unites the outlet passages of each air purifying filter unit into a single passage. Each air purifying filter unit may comprise a ring-shaped sorbent bed having a consistent bed depth in a direction of air flow. Each air purifying filter unit may comprise a ring-shaped particulate filtration element having a consistent element depth in a direction of air flow. Each air purifying filter unit may comprise a concentric sorbent bed and particulate filter element that allow air to pass through the sorbent bed and particulate filter element. At least one end surface of the concentric sorbent bed and particulate filter element may have a shape that is conformal to a user's ergonomic surface, while maintaining respective depths of the sorbent bed the particulate filter element constant.

[0008] The sorbent bed may comprise one or more types of sorbent material that captures target chemical via adsorption or reaction. The sorbent bed of each air purifying filter unit may be made by filling a first amount of sorbent material into a filter chamber, and inserting a cylindrical member comprising the outlet passage through the filled sorbent material.

[0009] A first end of the single passage of the set air purifying units may be blocked, and a second end of the single passage may be connected to an outlet port of the air purifying filter system. The air purifying filter system of claim 1 , wherein the set of air purifying filter units is scalable based on at least one of a service time and an anticipated pressure drop of the system. The flow direction of the units may be reversible such that the single passage comprises an air inlet port and the exterior openings comprise as an air outlet.

[0010] A method of making an air purifying filter is disclosed. The method may comprise: providing an outer casing having an opening to allow movement of air therethrough; inserting a particulate filter portion within the outer casing, the particulate filter portion contacting an outer wall of the outer casing; inserting a filter screen adjacent to the particulate filter portion to sandwich the particulate filter portion between the inner screen and the outer wall of the outer casing; disposing a first quantity of sorbent material in an inner portion of the filter adjacent to the filter screen; positioning a sorbent bed screen beneath the outer casing and in alignment with an opening in the casing, the sorbent bed screen having a screen cap disposed at one end; forming a passage through the sorbent material by moving the sorbent bed screen upward through the opening in the casing so that the sorbent bed screen is forced through sorbent material, wherein the sorbent bed screen is rotated about its longitudinal axis as it is moved upward; leveling the sorbent bed; applying a compression pad to a top surface of the sorbent bed; and applying a top cover over the compression pad. In some embodiments, the outer casign may have a plurality of openings to allow movement of air therethrough.

[0011] The particulate filter portion may be a high efficiency particulate air (HEP A) filter. The particulate filter portion may be affixed at one end to the outer casing. The sorbent material may comprise one or more types of sorbent material capable of capturing a target chemical via adsorption or reaction. The filter screen may include a plurality of openings to allow air to flow therethrough. The outer casing may have a plurality of grooves configured to mate with corresponding pleats in the particulate filter portion. In addition, inserting a particulate filter portion may comprise spinning the particulate filter portion until the pleats of the particulate filter portion engage the plurality of grooves in the outer casing.

Brief Description of the Drawin2S

[0012] By way of example, a specific embodiment of the disclosed device will now be described, with reference to the accompanying drawings:

[0013] FIGS. 1A and IB are cross section and isometric cutaway views, respectively, of a conventional cylindrical air purification filter; [0014] FIG. 2A and 2B are cross section and isometric cutaway views, respectively, of an exemplary stackable air purification filter in accordance with the disclosure;

[0015] FIG. 3A and 3B are cross section and isometric cutaway views, respectively, of a pair of stackable radial-flow air purification filters in accordance with the disclosure;

[0016] FIG. 4A and 4B are cross section and isometric cutaway views, respectively, of an exemplary stackable air purification filter with conformal outer and inner surface profiles in accordance with the disclosure;

[0017] FIGS. 5A-12 are a series of cross section and isometric cutaway views, illustrating a series of exemplary method steps for making the disclosed stackable air purification filter; and

[0018] FIG. 13 is an isometric cutaway view of the disclosed stackable air purification filter.

Detailed Description

[0019] A stackable radial flow filter design is disclosed. The disclosed filter can be stacked together with similar filters to make a larger filter unit. The disclosed design will result in better performance as compared to traditional cylindrical filters of the same exterior dimension. Service lift will be increased, and breathing resistance will be reduced. The disclosed filter may be especially useful for users seeking a longer service life and/or lower breathing resistance than is currently specified by the manufacturer and by approval agencies. [0020] The disclosed design uses a radial flow scheme rather than the traditional cylindrical design used with current filters. Referring to FIGS. 2A and 2B, the disclosed filter 4 is shown having a particulate filtering portion 5 and a sorbent bed portion 6. The portions 5, 6 are provided in a radial configuration in which the particulate filter portion 5 surrounds the sorbent bed portion 6 such that air is introduced into the filter from the sides 7 rather than from the end of the filter 8. Arrows "B" indicate the direction of airflow into the filter 4.

[0021] An open central portion 9 is enclosed by the sorbent bed portion, and purified air from the particulate filter portion 5 and the sorbent bed portion 6 is directed out of the end of the filter 4 in the direction of arrow "C."

[0022] The filter 4 may include first and second openings 10, 11. The first opening 10 may include a male mounting interface that enables the filter to be mounted onto a mask or powered air purification respirators (PAPR) having a female mounting interface (or vise versa). The second opening 11 may include a female mounting interface and is capped using cap 12 when the filter 4 is shipped from the factory. When used as an individual filter, the cap 12 on the second opening 11 may be left in place so that air is pulled from the sides 7 of the filter and drawn into the open central portion 9 and out of the first opening 10.

[0023] Referring to FIGS. 3A and 3B, a pair of filters 4A, 4B is shown stacked together. To achieve this arrangement, the cap 12 covering the second opening 11 of a first filter 4 may be removed, and a second filter 4 may be mounted onto the first filter 4 by engaging the second opening 11 of the first filter with the first opening 10 of the second filter. The cap 12 covering the second opening 11 of the second filter 4 is kept in place such that air is now driven from the sides of both filter 4A and filter 4B into the combined inner conduit 9 and then into the respirator (not shown). The two air flow streams ("B") are parallel, thus the incoming air flow velocity is reduced by 50%. This in turn increases the service life of the filter, and decreases breathing rate by the same amount.

[0024] It will be appreciated that the disclosed stackable filter arrangement will find applicability in industrial individual air purification respirators, military individual respiratory protection, and powered air purification respirators (PAPR)

[0025] The male/female mounting interfaces employed for the first and second openings 10, 11 of the disclosed filter 4 may include any of a variety of connection types, including threaded connections, bayonet connections, stab connections, and the like. Similar connection types, or a plain cap connector, may be used for the caps that will be fit to the openings 10, 11 during manufacture. Thus, in use, a wearer can simply remove the appropriate caps and mount any number of filters together as desired. .

[0026] Advantages of the disclosed design include the ability to stack multiple filters together to make a single unitary larger filter. For individual filters, the disclosed radial flow design provides enhanced performance as compared to traditional axial flow cylindrical filter designs because the disclosed radial flow design provides a more evenly-distributed air flow through the filter. In addition, the disclosed design better utilizes the space inside the filter, which enables more sorbent to be packed into the filter. The disclosed filter also has comparatively smaller sorbent bed depth, which results in decreased breathing resistance. In addition, manufacturing of the disclosed filter design is simplified as compared to current end- flow designs, particularly where a particulate filter is required. . [0027] The simple male/female stacking arrangement makes it possible for an end-user to easily assemble an air purification filter having a desired number of individual filter units. In addition, since the sorbent beds are oriented perpendicular to the mask interface (i.e., the first opening 10), the filter 4 can be manufactured to have a shape that more closely conforms to the face of the wearer. Referring to

FIGS. 4A and 4B, a filter 4 is shown in which the wearer-facing inner surface 13 and the outer surface 14 are curved to conform to the shape of a wearer's face, thus providing a more "low profile" appearance which may be more comfortable to wear, and which is less likely to snag external objects during use. The filter 4 of this embodiment has a particulate filter portion 5 and the sorbent bed portion 6 arranged similar to that described in relation to FIGS. 2A and 3A.

[0028] In one embodiment, the sorbent bed portion 6 comprises activated carbon. In other embodiments, the sorbent bed 6 comprises activated alumina, zeolite, silica gel or combinations thereof. In some embodiments, the particulate filter portion 5 comprises a high efficiency particulate air (HEPA) filter.

[0029] Referring now to FIGS. 5A-11, a method of making the disclosed filter 4 will be described. In FIGS. 5A and 5B, the outer casing 15 of the filter 4 may be formed with a plurality of grooves 16 configured to mate with pleats in the particulate filter portion 5. In one embodiment, the particulate filter portion 5 is a high HEPA filter. The number of grooves may be equal to the number of pleats in the HEPA filter 5. To seat the HEPA filter pleats in the grooves of the outer casing 15, the filter may be inserted into the casing and spun until the pleats engage the grooves. The particulate filter portion 5 may be glued or otherwise affixed at one end 17 to the casing 15. [0030] The outer casing 15 of the filter may be formed with a plurality of openings 28 (see FIG. 13A) to allow ingress of air therethrough.

[0031] FIGS. 6A and 6B show installation of an inner screen 18 that, together with the outer casing 15, sandwiches particulate filter portion 5 therebetween. The inner screen 18 may have a plurality of grooves 19 formed thereon to engage corresponding pleats in the particulate filter portion 5. The inner screen 18 may have a plurality of openings 19 therein to allow air to flow therethrough.

[0032] FIGS. 7A-9A illustrate formation of the sorbent bed portion 6 of the filter 4. In FIG. 7A and 7B, the inner volume of the filter is filled with a quantity of carbon filtration material 20. A sorbent bed screen 21, having a screen cap 22 positioned at one end, is positioned below the casing 15 in alignment with an opening in the casing 15. As shown in FIGS. 8A and 8B, the sorbent bed screen 21 is forced up into the carbon filtration material 20. The sorbent bed screen 21 is spun in the direction indicated by arrow "S" as it is inserted, making the sorbent bed 6 evenly packed. Once the sorbent bed screen 21 is fully inserted, the sorbent bed 6 is leveled to further facilitate even packing.

[0033] In FIGS. 9A and 9B, a compression pad 23 is applied to the top of the sorbent bed 6. The screen cap 22 may then be removed. In FIGS. 10A and 10B, a top cover 26 is applied, and may be capped with the removable filter cap 12. The top cover 26 may be glued or otherwise affixed as indicated at 27 (see FIG. 10A).

[0034] To stack a pair of filters 4A, 4B, the cap 12 is removed from one of the filters 4A as shown in FIGS. 11A and 11B. The second filter 4B may be screwed directly to the first filter 4A in the manner previously described. Alternatively, the second filter 4B may be connected to the first filter 4B using an adapter 24 (FIG. 12A). Regardless, the open central portions 9 of the filters 4A, 4B will be aligned, and the bodies of the filters 4A, 4B may be in direct contact along line 25 to enhance mechanical strength of the resulting stack.

[0035] FIGS. 12A and 12B show a fully assembled stacked filter arrangement including the pair of filters 4A, 4B, in accordance with the described embodiments. FIG. 13 shows an exemplary assembled filter 4 in accordance with the described embodiments. As will be appreciated, the filter 4 of FIG. 13 can be used in a stacked arrangement with another filter of its type, or it could be used by itself.

[0036] As previously noted, the disclosed filter 4 provides a variety of advantages in comparison to conventional cylindrical filters. For example, the disclosed filter may reduce flow resistance as compared to conventional cylindrical filters.

[0037] In one example, a cylindrical filter having a 9.5 centimeter (cm) diameter, 3.5 cm carbon (sorbent) bed depth, 248 cm ³ carbon volume, and 181 cm ³ HEPA volume is compared to the disclose filter having an inner diameter of 3.2 cm, an intermediate diameter of 7.6 cm, and outer diameter of 9.5 cm, a sorbent bed depth of 2.2 cm, and a carbon volume of 263 cm ³ , and a HEPA volume of 179 cm ³ .

[0038] Thus, for two filters having substantially the same outer dimensions, carbon volume is increased for the disclosed filter, HEPA volume is substantially similar, while carbon (sorbent) bed depth is substantially reduced. It will be appreciated that the design can be optimized to maintain the same bed depth and increase the volume of carbon, hence increasing the protection time. [0039] Other advantages of the disclosed design as compared to conventional cylindrical filters will be appreciated. For example, cylindrical filters must be cut into a circular shape, whereas the disclosed filter uses a pleated filter element so there is no need to cut the media into a circular shape. Cylindrical filters can use up to 30% more media, and require more glue to seal as compared to the disclosed design.

[0040] Further, for filters of similar dimensions and overall cartridge weights, pressure drop for the disclosed filter may be reduced by 40% through carbon (sorbent) bed depth reduction and enhanced HEPA pleating. Service life may be increase through increased sorbent volume and through the radial flow effect present in the disclosed design.

[0041] In addition, manufacturing costs may be reduced by savings on HEPA material, easier manufacturing, and better quality control. Moreover, the disclosed design is expected to be more robust than conventional cylindrical designs.

[0042] While certain embodiments of the disclosure have been described herein, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.