INVENTION TITLE

AIR FILTER ASSEMBLY

DESCRIPTION

Background

[Para 1 ] Protection of personnel from toxic or hazardous agents in the air they breathe is an important goal in many fields. Personnel entering a combat zone where chemical and/or biological weapons are a possibility, or responding to attacks in which such weapons have been used currently depends on particulate filtration plus carbon adsorbent technology to avoid inhalation of toxic materials. Other fields in which such protective equipment is used include, for example, those in which personnel handle hazardous chemical materials, including fuel, pesticides, cleaning chemicals, etc.

[Para 2] Carbon cartridges and other similar adsorbent technologies can be an inadequate solution to the problem of personnel protection. They accumulate the toxins within the cartridge during use, and may become saturated if not frequently changed, or they are ineffective against low molecular weight compounds, and they can be ineffective during periods of high humidity. Once close to saturation, they may become a source of these toxins instead of a sink for toxins, and represents a hazardous material which must be disposed of safely. Use of such cartridges also requires the presence of a supply chain to replenish them and dispose of spent cartridges. High Efficiency Particulate Air (HEPA) filters are usually added to carbon cartridges to prevent fouling of the carbon by particulate matter (including biological agents).

Summary

[Para 3] The present invention relates generally to an improved air filter assembly. In one illustrative embodiment, a respirator is disclosed that includes a respirator housing, a filtration media element disposed

adjacent the respirator housing, and a respiration assist pump adjacent to the filtration media element. The respiration assist pump assists the flow of gas through the filtration media element.

[Para 4] In another illustrative embodiment, a filtration module is disclosed. The filtration module includes a filtration media element having a photocatalytic agent and a photon source and a gas pump coupled to the filtration media element to assist the flow of gas through the filtration media element.

[Para 5] Another illustrative filtration module includes a filtration media element having a photocatalytic agent and a plurality of photon sources disposed on or in the filtration media element and illuminating the photocatalytic agent, and a plurality of electrostatic gas pumps coupled to and spaced from the filtration media element to assist the flow of gas through the filtration media element.

[Para 6] Methods of providing a respirator air stream are also disclosed. The illustrative methods includes the steps of providing a respirator housing comprising a filtration media element disposed adjacent the respirator housing, and a respiration assist pump coupled to the filtration media element and adjacent the respirator housing, and pumping respiration air through the filtration media element and into the respirator.

Brief Description of the Drawings

[Para 7] Fig. I is a schematic front elevation view of an illustrative respirator;

[Para 8] Fig. 2 is a perspective view of an illustrative filtration module shown on the respirator of Fig. 1 ;

[Para 9] Fig. 3 is a partial cut away perspective view of an illustrative filtration module shown in Fig. 2; and

[Para 1 0] Fig. 4 is a schematic cross-sectional view of the filtration module shown in Fig. 3.

Detailed Description

[Para 1 1 ] The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected illustrative embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, and materials are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized.

[Para 1 2] Fig. I is a schematic front elevation view of an illustrative respirator 100. The respirator 100 can be useful for removing contaminates from a user's breathing or air supply. One illustrative respirator 100 is shown in Fig. 1 , but it is contemplated that the respirator 100 can have any useful form, as desired. In some embodiments, the respirator 100 is a face mask that is capable of being secured to and covers at least a portion of a user's face. In some cases, the respirator 100 may be a helmet covering a majority of a user's head.

[Para 1 3] The illustrative respirator 100 includes a respirator housing 105. The housing 105 has an outer surface exposed to environmental conditions and an opposing inner surface that is disposed adjacent to a user's face. In some embodiments, the respirator 100 may include a clear face shield 1 10 disposed within the respirator housing 105. The respirator housing 100 can be formed of any useful material such as, for example, polymeric material.

[Para 14] The illustrative respirator housing 105 may include an air inlet 120 and an air outlet 1 30. The air inlet 1 20 can extend through the respirator housing 1 05 and an air outlet 1 30 can extend through the respirator housing 105. In some embodiments, the respirator housing 105 includes a two, three, four, or more air inlets 1 20 and one, two, or more air outlets 130, as desired.

[Para 1 5] A filtration module, such as filtration module 1 50, can be coupled to the air inlet 1 20 or a surface of the filtration module 1 50 can define the air inlet 120, and can be disposed on or adjacent to the respirator housing 105. In many embodiments, the filtration module 1 50 forms a unitary article with the respirator housing 105. Fig. 1 illustrates a respirator 100 having two air inlets 1 20 and a four filtration modules 1 50 disposed adjacent to each air inlet 1 20. Fig. 2 is a perspective view of an illustrative filtration module 150 shown on the respirator 100 of Fig. 1 .

[Para 1 6] Fig. 3 is a partial cut away perspective view of an illustrative filtration module 1 50 shown in Fig. 2. Fig. 4 is a schematic cross- sectional view of the filtration element 1 50 shown in Fig. 3. The illustrative filtration module 1 50 includes a filtration media element 1 51 and an adjacent respiration assist pump 1 55, where the respiration assist pump 1 55 is in fluid communication with and coupled to the filtration media element 1 51 . In some cases, an air flow cavity 1 54 is defined between the filtration media element 1 51 , the respiration assist pump 1 55, and cavity walls 1 57. In the embodiment shown, the filtration media element 1 51 is adjacent and coupled or connected to the respiration assist pump 1 55 via the cavity walls 1 57. In many embodiments, the filtration media element 1 51 and respiration assist pump 1 55 forms a unitary article.

[Para 1 7] The respiration assist pump 1 55 can be any useful pump of suitable size. In some embodiments, the respiration assist pump 1 55 is a diaphragm pump or an electrostatic diaphragm pump. One or more respiration assist pumps 1 55 can be disposed adjacent the filtration media element 1 51 . In some embodiments, 5 to 500, or 10 to 250, or 25 to 200 or 50 to 1 50 respiration assist pumps 1 55 are disposed adjacent the filtration media element 1 51 . The illustrative respiration assist pumps 1 55 may be disposed adjacent the filtration media element 1 51 in a two or three dimensional array of respiration assist pumps 1 55. The illustrative respiration assist pumps 1 55 are adapted to pump air through the filtration media element 1 51 and into the interior surface of the respirator housing 105. The respiration assist pumps 1 55 can pump any useful amount of respiration air through the filtration media element 1 51

(indicated by the direction of the arrows labeled F). In some embodiments, the respiration assist pumps 1 55 provide 1 5 to 30 liters/min of air at a pressure of 1 -10 psig. The respiration assist pumps 1 55 may provide enough air flow and pressure to maintain a positive air pressure within the interior of the respirator 100 while a user of the respirator is breathing. This may help prevent contaminated outside air from leaking into the interior of the respirator housing 105, for example, through seal leaks.

[Para 1 8] While it is contemplated that the respirator assist pumps 1 55 can take any suitable form, in some embodiments, the respirator assist pumps 1 55 can be mesopumps having a single diaphragm as described in U.S. Patent No., 5,836,750, incorporated by reference herein. Alternatively or in addition, the respiration assist pumps 1 55 can be a mesopump having a dual diaphragm as described in U.S. Patent No., 6,1 79,586, incorporated by reference herein. Also it is contemplated that the respiration assist pumps 1 55 can include a plurality of such mesopumps in a two dimensional and/or three dimensional array as described in U.S. Patent Publication No., 2004/0020265, incorporated by reference herein. These mesopumps can be manufactured using microelectromechanical systems (MEMS) technology and may operate under electrostatic forces. The mesopumps may include electrical connectors 1 56 for electrical connection with control electronics (not shown) and/or an electrical energy source such as, for example, a battery (not shown). In some cases, the battery may be disposed on or adjacent to the respirator housing 105, if desired.

[Para 1 9] Referring to Fig. 3, the illustrative filtration module 1 50 may include a filtration media element 1 51 . The filtration media element 1 51 can be formed of any useful filtration media for filtering one or more airborne contaminates. As used herein, the phrase "airborne contaminant" refers to any airborne pollutant or other agent or compound, such as, for example, particulate matter, volatile organic compounds (VOCs), bacteria, pesticides, carbon monoxide, ammonia, hydrogen sulfide, odors, etc. In addition, the phrase "airborne contaminant" can refer to any biological agent such as, for example, viruses, bacteria, spores, and the like. Such biological agents can include human pathogens.

[Para 20] In some cases, the filtration media element 1 51 may include media that filters particulate matter such as, a HEPA filter. HEPA is an acronym for "High Efficiency Particulate Air." HEPA filters can capture 99.9% of all particles, including sub-micron sized particles. Alternately or in addition, the filtration media element 1 51 may include media that filters organic compounds or materials, such as a photocatalytic oxidation filter. The photocatalytic oxidation filter can include a photocatalytic agent disposed on a support structure, and one or more photon sources.

[Para 21 ] In some cases, the filter module 1 50 can include a plurality of filtration media elements 1 51 arranged in series. For example, the filtration module 1 50 may include a first media element 1 51 that includes a media that filters particulate matter such as a HEPA filter and a second media element (also labeled 1 51 ) arranged to accept air filtered by the HEPA filter. The second media element 1 51 may include a media that filters organic compound or material, such as a photocatalytic oxidation filter.

[Para 22] Photocatalytic oxidation involves the cleansing of air using a photocatalytic filter. The photocatalytic filter can includes one or more filter media elements coated with a photocatalytic agent. In many embodiments, an ultraviolet lamp can then be used to illuminate the photocatalytic agent, and a catalytic reaction is created when airborne contaminants in the air contact the illuminated photocatalytic agent, causing the airborne contaminant to degrade.

[Para 23] Fig. 3 and Fig. 4 both illustrate the illustrative filtration media elements 1 51 with integrated or adjacent photon sources 1 52. Each photon source 1 52 may be capable of generating a photon or light beam that is directed toward the photocatalytic agent coated on the filter media element 1 51 . The photon sources 1 52 can be aimed or focused so that the collective light beams substantially or completely cover the photocatalytic agent disposed within or on the filter media element 1 51 .

[Para 24] The photon sources 1 52 can be a UV light source such as, for example, a light emitting diode and/or a laser emitting diode. The quantity of airborne contaminants that are oxidized per unit of time is

proportional to the intensity of the light sources, so increased oxidation can be obtained by using a greater intensity light sources. In some embodiments, the photon sources 1 52 may be ultraviolet (UV) lamps such as mercury vapor lamps or xenon lamps, UV light emitting diodes (LEDs), or UV laser diodes. In one specific example, the photon sources 1 52 may be LEDs capable of producing UV light having a wavelength of between about 200 nanometers (nm) and about 400 nm. In various embodiments, the photon sources 1 52 can be UV LEDs such as model numbers NSHU55OA (375 nm), NSHU55OB (365 nm), NSHU590A (375 nm), and NSHU590B (365 nm), all manufactured by Nichia Corporation of Japan.

[Para 25] The actual wavelength selected can be dependent upon the adsorption range of the photocatalytic agent. The wavelength of the UV LED can be set so that the UV light is absorbed by the photocatalytic agent. That is, the wavelength of the UV light may be matched to the absorption band of the photocatalytic agent. For example, if the photocatalytic agent is a titanium dioxide having an absorption band of between about 200 nm and 400 nm, then the wavelength of the UV LED can be between about 250 nm and 390 nm. In another embodiment, if the photocatalytic agent is a titanium dioxide having an absorption band of less than about 410 nm, then the wavelength of the UV LED can be less than about 410 nm. Sometimes, a broadband light source may be used, so long as at least part of the spectrum overlaps at least part of the absorption band.

[Para 26] In some embodiments, the photon source 1 52 includes electrical connectors 1 53 for electrical connection with control electronics (not shown) and/or an electrical energy source such as, for example, a battery (not shown). In some cases, the battery may be disposed on or adjacent to the respirator housing 105, but this is not required.

[Para 27] In the illustrative embodiment, the photon sources 1 52 are positioned adjacent to the filtration media element 1 51 to illuminate the filtration media element 1 51 with, for example, ultraviolet light and thereby activate the photocatalytic agent on the filtration media element 1 51 , to oxidize airborne contaminates in the air flowing through the

filtration media element 1 51. In some illustrative embodiments, 10 to 100 photon sources 1 52 may extend along each side of the filtration media element 1 51 and may extend along a majority of the width of the filtration media element 1 51 , sometimes along the top, bottom, and/or side walls in any configuration to maximize illumination of the filtration media element 1 51 .

[Para 28] As respiration air passes through each filtration module 1 50, airborne contaminants may become trapped in a particulate filter, when provided, and/or degraded by oxidation with the photocatalytic oxidation filter. Oxidation of an airborne contaminate can occur when an airborne contaminant contacts a portion of the photocatalytic agent that has been activated by the photon source. Increasing a filtration media 1 51 thickness or surface area containing photocatalytic agent can improve the photocatalytic oxidation filter efficiency. However, this also typically increases the pressure drop across the filtration media element 1 51 forcing the breathing of the user of the respirator 100 to become less efficient or adds to the stress of the user. Addition of the respiration assist pump 1 55 counteracts such a pressure drop perceived by a respirator 100 user, allowing the user to breath with less strain. In some cases, the pump 1 55 can create a positive pressure in the respirator 100 to help prevent contaminates from leaching in through any seals.

[Para 29] In some embodiments, the respirator 100 can include a mechanical particulate filter (HEPA) positioned upstream or downstream of a photocatalytic oxidation filter 1 50. The mechanical particulate filter functions to remove particulates from an air stream prior to or after the air stream reaches the photocatalytic oxidation filter 1 50. In other embodiments, a mechanical particulate filter is not included in the respirator 100, or additional mechanical filtering stages can be added, as desired.

[Para 30] Illustrative photocatalytic agents are generally semiconductor materials having a band gap similar in energy to the energies of photons in the visible or UV range. Absorption of light results in the promotion of

an electron from the ground state, generating a hole-electron pair. The hole then reacts with adsorbed water to generate hydroxyl radicals.

[Para 31 ] The size of the band gap required can be determined by the desired wavelength of light. Energy of a photon is inversely proportional to wavelength, and can be specified in units of either Joules/mole, or electron-volts. In many embodiments, the wavelengths corresponding to the following energies:

[Para 32] In some embodiments, the semiconductor material band gaps are between 2.7 and 4. Examples of useful material include, but are not limited to, titanium dioxide (3.2 eV), tungsten oxide (2.8 eV), strontium titanate (3.2 eV), alpha-Fe2O3 (3.1 eV), zinc oxide (3.2 eV), and zinc sulfide (3.6 eV). In some embodiments, the light sources can emit wavelengths shorter than are required for these band-gaps. Further useful materials include, tantalum oxide, barium titanate (BaTi4θg), sodium titanate (Na2Ti6θi3), zirconium dioxide, cadmium sulfide, HUNbeOi?, Rb4Nb6θi7, K2Rb2Nb6θi7, and Pbι- _x K2χNb2θ6, to list a few. Those materials can be used as a single material or a combination of two or more materials.

[Para 33] Among the above, titanium dioxide is suitable from the viewpoints of the photocatalysis and economical efficiency. There are rutile and anatase types for titanium dioxide. The photocatalytic agent can be a semiconductor metal oxide, more particularly titanium dioxide (in a mixture of the rutile and anatase forms) available under the tradename Aeroxide Tiθ2 P25, manufactured by Degussa Chemical Company, Dusseldorf, Germany. In one illustrative embodiment, the photocatalytic

agent has a surface area of between about 100-1000 square meters/gram and a thickness of between about 3.0 micrometers and about 5.0 micrometers. The photocatalytic agent can have a relatively large surface area and can be highly active. The photocatalytic agent can be disposed onto a support substrate using conventional methods. Other semiconductive agents that absorb light can also be used, such as, for example, zinc oxide, cadmium sulfide, and zinc sulfide.

[Para 34] Any suitable photocatalytic agent may be disposed on the filtration media element 1 51 . Any suitable material may be used as a substrate material for filter media element 1 51 such as, for example, a ceramic substrate, an aluminum substrate, an FeCrAIY alloy substrate, and/or a paper/fiber material. Any suitable substrate geometry for the filtration media element 1 51 may also be used such as, for example, honey-combs, fins, mesh, a filter-type structure, a fibrous type, or a filamentous structure.

[Para 35] Having thus described the several embodiments of the present invention, those of skill in the art will readily appreciate that other embodiments may be made and used which fall within the scope of the claims attached hereto. Numerous advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size and arrangement of parts without exceeding the scope of the invention.