HK1107032A - Antimicrobial refrigerator air filter - Google Patents

Description

Antibacterial air filter for refrigerator

Cross reference to related applications

This application claims priority from U.S. provisional patent application No. 60/580,646 filed on 17.6.2004.

Technical Field

The present invention relates generally to air filters and, more particularly, to an antimicrobial air filter suitable for use in refrigerated volumes.

Background

Refrigerated compartments (particularly the interior of domestic food storage refrigerators) are often subject to significant changes in humidity and may contain high levels of moisture. While refrigeration can slow the growth and proliferation of undesirable microorganisms, microorganisms can rapidly spoil food stored within the refrigerator and multiply on the interior surfaces of the refrigerated compartment and objects therein.

Modern refrigeration systems are designed to utilize airflow throughout the refrigerated compartment to help achieve a uniform temperature distribution within the refrigerated compartment. Unfortunately, this airflow also serves as a medium through which bacteria can be transported throughout the interior of the refrigerated compartment.

Various devices have been used to filter and purify air in a space such as a room, office space or home. One focus of such efforts at filtration has been on the removal of allergens from the indoor air of living spaces.

A variety of particles and organisms, such as mold spores, bacteria, viruses, and other small particles that cannot be captured by conventional filters, can be suspended in the air within the refrigerated compartment. If left untreated, microorganisms can multiply within the refrigerated compartment, causing food spoilage and adverse effects on the taste and odor of certain foods stored within the refrigerated compartment.

In the prior art, efforts in air filtration have used size filters (including microfilters) for removing contaminants, ultraviolet radiation to inhibit microorganisms, and carbon or charcoal filters to absorb odors.

Filters, including high efficiency particulate air filters (HEPA filters), may be used to "reject" contaminants by particle size to purify the air within a refrigerated compartment (e.g., a residential refrigerator, commercial freezer, vehicle air conditioning unit, refrigerated transport vehicle).

U.S. patent nos. 6,454,841 and 6,736,885 discuss air filtration systems designed specifically for refrigerated compartments. The air filtration system includes a refrigerator and a plenum having an air inlet and an air outlet. The plenum may be inside or outside the refrigerator and connected to a fan that draws air through the plenum. The plenum chamber houses an air filtration assembly, which may include a UV radiation source or a polymeric HEPA filter. The' 079 document discusses a polymeric filter media having a biocide molded into the polymer.

Drawings

FIG. 1 is a front view of a first embodiment of a refrigerated compartment having an air filtration system as disclosed herein.

Fig. 2 is a cross-sectional side view of the air filtration system of fig. 1.

Detailed Description

In one broad aspect, an air filtration system for a refrigerated compartment reduces or substantially eliminates microorganisms, including but not limited to bacteria, mold, and fungi, from the air within the refrigerated compartment. More specifically, the air filtration system reduces or substantially eliminates bacteria, mold, fungi, and other microbial species from the air within a refrigerated compartment, such as a household refrigerator for storing food items.

For ease of discussion, the air filtration system disclosed herein will be described in the context of a domestic refrigerator embodiment.

The present air filtration system 10 is capable of bioremediating (biornediate) air within a refrigerator to reduce the growth and transport of microorganisms within the refrigerator. This purification is accomplished through the use of an antimicrobial air filtration system 10.

The air filtration system 10 according to the present disclosure preferably includes a filter assembly 20. The filter assembly 20 has an air inlet 22 and an air outlet 24. The filter assembly 20 holds a fibrous filter media 30, the fibrous filter media 30 being interposed between the air inlet 22 and the air outlet 24. The fibrous filter media 30 is treated with an antimicrobial agent.

The air drawn through the air inlet 22 contacts the filter media 30 where it comes into intimate contact with the media 30 and the associated antimicrobial agent. Antimicrobial agents work by their different biocidal pathways to eliminate airborne microorganisms. The air then returns to the interior of the refrigerated compartment C through the air outlet 24.

In a preferred embodiment, the filter is a microfilter. The microfilter has micropores permeable to air and oxygen and provides the ability to filter out fine particles such as bacteria and other microorganisms and airborne pollutants. The microfilter may be constructed from a variety of materials, which may be woven or non-woven materials. One example of a filter material is polyester.

Microfilter foils (foil) may also be used for cross-flow filtration requirements. High efficiency particulate air filters (HEPA filters) with a filter size on the order of about 0.3 microns are also very effective for removing particulates such as mold spores and pollen.

Referring now to FIG. 1, the fibrous filter media 30 is preferably formed from polymeric fibers. The filter media 30 may be woven or non-woven (the latter being shown in fig. 1). Although the selection of polymer fibers is not critical to the function of the filter media 30, polyester is a preferred polymer.

The polymer fibers may have any denier suitable for use as the filter media 30. In general, however, smaller denier fibers are preferred because they provide enhanced filtration capabilities. In an exemplary filter embodiment, the fibers used are polyester fibers, which are less than 10 denier, and, more preferably, 6 denier or less.

The embodiment of fig. 1 includes two forms of polyester fibers. The first fibers are 6 denier and comprise about 60% of the filter media 30. The second fibers are 3 denier and comprise about 40% of the filter media 30.

In one embodiment, the fibrous filter media 30 is imparted with antimicrobial properties by topically treating it with an antimicrobial agent. Unlike methods in which the antimicrobial agent is added to the polymer melt and distributed throughout the body of the polymeric article, topical application concentrates the antimicrobial agent on the surface of the individual fibers within the fibrous filter media 30. This increased surface concentration increases the efficacy against microorganisms and reduces the total amount of antimicrobial agent required to achieve a particular result.

Many antimicrobial agents are suitable for use in the air filtration system 10, and antimicrobial agents commonly used with polymeric resins are preferred. Particularly preferred antimicrobial agents include chlorinated phenols (e.g., 2, 4, 4 '-trichloro-2' -hydroxybiphenyl), silver and silver-containing compounds, pyrrole, and zinc-containing compounds (e.g., 2-hydroxypyridine zinc oxide).

In a first preferred embodiment, the antimicrobial agent is added to a binder that is used to form the polymer fibers into the nonwoven fibrous filter media 30. Suitable binders include those used to make nonwoven materials. Preferred binders include polymeric resins, with polyester and latex acrylic resins being preferred polymeric resins. The antimicrobial agent and the binder should be compatible with each other.

When the antimicrobial agent is used to form the nonwoven fibrous filter media 30, the antimicrobial agent is added to the binder in an amount sufficient to achieve acceptable efficacy. Of course, achieving acceptable efficacy will also depend on how much binder is used and the nature of the antimicrobial agent selected. Those skilled in the art will be able to determine the appropriate amount of binder and antimicrobial agent without undue experimentation

By way of example, the fibrous filter media 30 shown in FIG. 1 is formed using 6 denier and 3 denier polyester fibers (as described above). An acrylic binder containing about 4000ppm of 2-hydroxypyridine zinc oxide was used to form the nonwoven fibrous filter media 30. The binder is used so that the resulting filter media 30 is approximately 75% (by weight) fiber and 25% resin binder.

Analytical testing indicated that the resulting filter media 30 contained about 1000ppm of 2-hydroxypyridine zinc oxide. Preliminary testing has shown that the resulting filter media 30 is capable of reducing bacteria-sized airborne particulates in refrigerators by approximately 45%.

Referring now to FIG. 2, the fibrous filter media 30 of this embodiment remains disposed within the filter assembly 20 with the aid of various support devices that may be provided as part of the air filter assembly 20. By way of example, a matable or insertable frame (frame)30 is employed, wherein the filter media 30 may be inserted to slide in and out as desired. The frame 30 may form an enclosure having the air inlet 22 and the air outlet 24.

In an alternative arrangement, the frame 30 may form only one side of the enclosure by covering the side opening of the refrigerated compartment C. In this case, the air outlet 24 becomes an opening on the side of the refrigerating compartment C. In a second alternative arrangement, the filter media 30 may be inserted through a slit or hole in the housing without interfering with the air inlet and outlet 22. In either case, the fibrous filter media 30 is positioned between the gas inlet 22 and the gas outlet 24 for the gas.

The air inlet 22 and the air outlet 24 (FIG. 2) are fluidly connected to the interior of the refrigerated compartment C such that air within the refrigerated compartment C is able to flow through the fibrous filter media 30, and/or into intimate contact with the fibrous filter media 30.

The filter assembly 20 may be held in place by one or more brackets or other suitable mechanical attachment means. In addition, adhesives on the exterior of the assembly 20 may also be utilized.

Multiple filters may be arranged in series with decreasing pore size to extend microfilter life. Thus, larger particles are captured in an upstream filter having an appropriate pore size, while smaller particles pass through the upstream filter and are then captured by a microfilter having a restricted pore size.

In such a series filter arrangement, it is not necessary to combine the antimicrobial agent with a large pore filter media through which microorganisms can typically pass. However, a large pore upstream filter having antimicrobial properties may also be employed without departing from the air filtration system 10 disclosed herein.

Means 40 for directing air through the filter assembly 20 are also provided. In one instance, the air-directing device 40 is a fan that may be incorporated into the filter assembly 20. Alternatively, the filter assembly 20 may be placed adjacent to and in fluid communication with an air directing device already present within the refrigerated compartment C. Still another arrangement is where the filter media 30 may be combined with the air-directing device 40, for example, by forming the non-woven filter media 30 into or combining the filter media 30 with a material shaped as a fan, turbine, or other suitable structure for use in an air-moving device.

Alternatively, the air filtration system 10 may be disposed outside the refrigerated compartment C. It is desirable to provide air contact with the filter media 30 and, preferably, circulation through the filter media 30. In most cases, the circulation will be achieved by means of a pipeline (reduction) or piping (piping), the construction of which can be achieved by a person skilled in the art.

It can be readily appreciated that the air residing within the refrigerated compartment can be recirculated therein (which is preferred for maintaining reduced temperatures with reduced energy input), however, fresh outside air can also be sent to the interior of the refrigerated compartment. In the latter case, the filters disclosed herein may also be effectively employed to reduce or substantially eliminate the introduction of microorganisms into the interior of the refrigerated compartment.

The filter system 10 is suitable for use in any type of commercial or residential refrigeration unit. For example, the refrigerated compartment may be a retail display case, a commercial transport vehicle, a large cold/freezer compartment, or other industrial equipment.

It is to be understood that while specific embodiments of the air filtration system have been illustrated and discussed herein, the invention is not to be limited to the specific forms or arrangements of parts set forth in the specification and drawings. It will be appreciated by those skilled in the art that variations may be made without departing from the essential characteristics disclosed herein and in the appended claims.

Claims (20)

1. A refrigerated compartment having an air filtration system comprising:

a plurality of walls defining the refrigerated compartment;

a filter assembly having an air inlet and an air outlet in fluid communication with the refrigerated compartment; and

a fibrous filter media positioned between the air inlet and the air outlet, at least a portion of the fibrous filter media being coated with a binder, the binder comprising an antimicrobial agent.

2. The refrigerated compartment of claim 1, wherein the fibrous filter media comprises a polymer.

3. The refrigerated compartment of claim 2, wherein the polymer comprises polyester.

4. The refrigerated compartment of claim 1, wherein the adhesive comprises an acrylic adhesive.

5. The refrigerated compartment of claim 1 wherein the antimicrobial agent comprises an agent selected from the group consisting of chlorinated phenols, pyrroles, metals and zinc 2-hydroxypyridine oxide.

6. The refrigerated compartment of claim 5, wherein the antimicrobial agent is zinc 2-hydroxypyridine oxide.

7. The refrigerated compartment of claim 1, further comprising:

means for directing air through the filter assembly.

8. A cooling device air filtration system comprising:

a filter housing having an inlet and an outlet, at least one of the inlet and outlet in gaseous communication with the volume cooled by the cooling device;

a fibrous filter media disposed between the inlet and the outlet;

an adhesive coating disposed on at least a portion of the fibrous filter media; and

an antimicrobial agent in combination with the adhesive.

9. The system of claim 8, wherein at least one of the inlet or the outlet is in communication with a volume cooled by the cooling device.

10. The system of claim 8, wherein the fibrous filter media comprises polymeric fibers.

11. The system of claim 10, wherein the polymer fibers have a denier of 10 or less.

12. The system of claim 10, wherein the polymer fibers have a denier of 6 or less.

13. The system of claim 10, wherein the fibrous filter media comprises first polymeric fibers having a first denier rating and second polymeric fibers having a second denier rating.

14. The system of claim 10, wherein the polymer comprises a polyester.

15. The system of claim 8, wherein the adhesive comprises a latex acrylic adhesive.

16. The system of claim 8, wherein the antimicrobial agent comprises an agent selected from the group consisting of chlorinated phenols, silver and silver-containing compounds, pyrroles, and zinc-containing compounds.

17. The system of claim 16, wherein the antimicrobial agent comprises zinc 2-hydroxypyridine oxide.

18. The system of claim 16, wherein the antimicrobial agent comprises 2, 4, 4 '-trichloro-2' -hydroxybiphenyl.

19. The system of claim 16, wherein the antimicrobial agent comprises silver.

20. The system of claim 8, further comprising:

an air flow element adapted to flow air into gaseous contact with the fibrous filtration media.