Air filter assembly

#The present invention generally relates to air filters. More particularly, this invention relates to non-mechanical filtering of small size particulate matter in air.

#Air filtering systems to remove deleterious particulate matter are important for general health and particularly important for persons having allergies, asthmatic conditions and the like. Building air ventilation systems generally include air filtering means that requires the use of mechanical blowers and other large equipment. Air filter systems specifically designed to remove small size particulate matter also generally employ some type of mechanical air-moving equipment. Conventional window screens are generally limited to preventing the entry of insects and the like and therefore are not useful for filtering small particulate matter.

#Various non-mechanical air filtering means have been proposed in the prior art. Such air filtering means generally function by capturing or collecting the particulate matter on or in a screening media. This results in a requirement that the filter be periodically cleaned or replaced. Where the air is heavily contaminated with particulate matter, such air filters must be cleaned or replaced quite often. U.S. Pat. No. 570,219 to Fletcher illustrates an air filtering systems of this type. In the Fletcher patent a filtering material is disclosed wherein warp-threads are interwoven to form closely-woven selvages. Dust or fine particles collect on the selvages and air passes between them. U.S. Pat. No. 1,056,722 to Adler discloses a dust-collecting screen consisting of a fabric formed from strands of coarse and linty textile adapted to be saturated with a non-evaporating liquid such as oil. The moistened linty textile collects small size particulate matter and air passes through the openings between the coarse and linty strands. In U.S. Pat. No. 2,478,097 to Glanzer a woven-screen air filter is shown having cloth-covered wire threads. The cloth covering for the wire threads collect particulate matter and may be saturated with a liquid to facilitate collection of dust and the like. U.S. Pat. No. 2,551,175 to Smith discloses a filter cloth formed from strands so tightly woven that filterable material will not pass through the inter-filament spaces of the woven strands and thereby limits air passage to the spaces between adjacent strands. U.S. Pat. No. 2,615,477 to Crawley discloses an air filtering media comprising woven fabrics formed entirely of yarns formed from continuous filaments of a vinyl resin and discontinuous filaments of a vinyl resin, the respective filaments alternating in a regular pattern throughout the fabric. U.S. Pat. No. 4,728,349 to Oshitari discloses a composite air filter medium comprising a glass fiber layer of desired dust-collecting efficiency and a supporting fiber layer of low dust-collecting efficiency. In U.S. Pat. No. 4,904,288 to d'Augereau a reusable air filter assembly is disclosed comprising a composite structure including an outlet stage filter medium consisting of two fabric layers woven in an egg-crate pattern.

#FIG. 1 is a front perspective view of window air filter assembly constructed in accordance with the teachings of the present invention.

#FIG. 2 is a cross-sectional view of the window air filter assembly taken along line 2--2 of FIG. 1.

#FIG. 3 is an enlarged fragmentary section of the woven filtering medium of the present invention.

#FIG. 1 illustrates in a front perspective view a preferred embodiment of the window air filter assembly 1 of the present invention. Air filter assembly 1 generally comprises a laterally-adjustable frame assembly 10 and a woven filtering medium 20 fixedly disposed in frame assembly 10. In the preferred embodiment of air filter assembly 1, frame assembly 10 includes a first frame member 11 and a second frame member 12 cooperably and slidably engageable. The first and second frame members 11, 12 are formed having a substantially C-shaped configuration. The respective second horizontal legs 12a, 12b of second frame member 12 slidably engage the respective first horizontal legs 11a, 11b of first frame member 11. As can be seen in the cross-sectional view of the air filter assembly 1 illustrated in FIG. 2 a vertically-extending first filtering medium support channel 13 is fixedly attached perpendicularly to the first frame member 11 and a vertically-extending second filtering medium support channel 14 is fixedly attached perpendicularly to the second frame member 12. The respective first and second filtering medium support channels 13, 14 have a substantially C-shaped cross-section with the respective horizontal legs 13 a, 13b and 14a, 14b extending angularly inward toward each other. Respective first and second support channel slots 13c and 14c are formed by the marginally-displaced ends of the respective horizontal legs 13a, 13b and 14a, 14b of the respective first and second support channels 13, 14. A first filtering medium anchor 15 is centrally disposed and fixedly attached in an interior portion of first filtering medium support channel 13 and a second filtering medium anchor 16 is eccentrically disposed in an interior portion of second filtering medium support channel 14. Second filtering medium anchor 16 is rotatably attached to second frame member 12 and is spring-biased for lateral rotation. Respective ends of filtering medium 20 are fixedly attached to the respective first and second filtering medium anchors 15, 16.

#Frame assembly 10 is preferably formed from a waterproof material. The slidable attachment of first frame member 11 and second frame member 12 permits lateral adjustment of frame assembly 10 to fit the air filter assembly 1 in variously-sized windows or other openings. The spring-biased second filtering medium anchor 16 rolls up filtering medium 20 as the frame assembly 10 is narrowed.

#Filtering medium 20 is preferably formed from woven smooth-surfaced microfilament strands 21, 22, for example, polyester, nylon, polypropylene, carbon, fiberglass, ceramic or metal strands. The microfilaments may or may not be electrostatically treated. The filtering medium 20 of the present invention is provided to prevent the passage of microscopic particles through the spaces between strands 21, 22. Tightly woven filter cloths as shown in the prior art are limited to use with mechanical blowers and the like. To provide a fine mesh filtering medium that permits natural ventilation, that is, air flow under small differential pressures without the aid of forced-air blowers, the Applicant has discovered that at least 16% of the surface area of the filtering medium must be open.