Air Purifier

Abstract

An air purifier is provided for purifying air in rooms of a home, office, or other commercial establishment. Air is filtered by a mechanical filter, then odors are removed from the air, and the air is exposed to germicidal lamps for killing bacteria, then the air passes through a high efficiency electrostatically enhanced filter, and then it is returned to the room by blowers.

Description

Air contamination is generally broken down into two separate and distinct areas. The first area concerns itself with particulate contamination of the air and consists of particles of airborne lint, fly ash, dust, pollen, fungus spores, bacteria, and minute liquid aerosols. The second area concerns itself with gaseous contaminates such as carbon monoxide, sulfur dioxide, etc. which are in solution with the air molecules. Each of these contaminations is present to a certain extent within the home and commercial establishments.

In the home, contaminants include aerosols of cooking fat and food particles, asbestos from floor tiles and wallboard material, aerosol spray disinfectants, cleaners, insecticides, and many other contaminants. Airborne and condensed tars and nicotine from tobacco smoke present such a pollution hazard in a building as do automobile exhausts to the outside environment. In addition, unpleasant contaminants such as body odor, dandruff, cooking odors, etc. are present within a home.

In accordance with the present invention, the effective removal of pollutants is best accomplished by attacking separately the two areas of pollution referred to above, that is, particulate and gaseous. Simple filtration will remove many airborne particulates but their efficiency and the minimum size particle removed have been limited. Ordinary dust and lint are of various sizes down to 10 microns. These size particles can be removed with good filtration practices.

Many particles in the atmosphere which are undesirable and harmful are smaller than 10 microns. Fly ash and some dusts have a particle size of 0.5 microns. Pollen has a size on the order of 5 microns. Fungus spores and bacteria range from 0.3 to 10 microns. These particles are not removed by ordinary filter materials.

Heretofore, the filtration of ultrafine particles of a size less than 10 microns were filtered by either high voltage electrostatic precipitation or by high efficiency mechanical entrainment filter systems having a tortuous path.

Filtration of odors heretofore has been generally accomplished by absorbing small quantities of gaseous contaminants on a materail such as activated charcoal. As concentrations increase over short periods of time, or if the activated charcoal absorbs gases and then experiences a significant temperature or humidity change, the charcoal will desorb. This desorption results in the readmission of such gases as carbon monoxide and sulfur dioxide as well as the odor molecules. In addition to requiring extreme care in application and maintenance in order to be effective, activated charcoal is limited in its effectiveness by several serious air pollution ingredients such as hydrogen sulfide, methane, and some unburned hydrocarbons.

In accordance with the present invention, gaseous contamination is removed by the use of an odor oxident. The odor oxident oxidizes the gaseous contaminants so as to completely destroy their nature and convert them into a secondary inert chemical substance. There is no tendency whatsoever to desorb and re-emit the odor particles.

Viruses are considerably smaller than bacteria and fungus spores. Neither electrostatic precipitators nor particulate entrainment cells have proven to be capable of destroying viruses. In accordance with the present invention, the purifier is provided with a germicidal ultraviolet lamp which irradiates the air passing through the purifier to kill bacteria, fungus spores, viruses, etc.

After the air has passed through a roughing filter, the odors may be removed by an oxident, and the air may then be subjected to the action of the germicidal lamp. The air is subjected to a high efficiency filter. The high efficiency filter is alternately charged with opposite voltage levels to enhance the passive filtration by increasing the path length of charged particulates. The otherwise straight line flow path of particulates is changed to a zig-zag pattern so that they collide with the filter media many times. The path length of micron and submicron sized particles can be increased by a factor of 10 to 100 using relatively low voltages. The low voltages involved in the present invention, such as 100 to 170 volts, are to be compared with the 20,000 volts utilized in electrostatic precipitators. The inherent advantages of using a low voltage system will be readily apparent from the viewpoint of cost, safety to personnel, and the manner in which the voltages perform their respective functions.

It is an object of the present invention to provide a novel air purifier.

It is another object of the present invention to provide an efficient, compact, relatively inexpensive air purifier.

It is an object of the present invention to provide an air purifier which will remove particulates as well as gaseous contaminants in a manner which is more efficient and effective than systems proposed heretofore.

It is another object of the present invention to provide a home air purifier which will remove particulates and gaseous contaminants in a highly efficient manner, with efficiency being approximately 99.9 percent for contaminants having a size of at least 0.3 microns.

For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIG. 1 is a vertical sectional view of an air purifier in accordance with the present invention.

FIG. 2 is a sectional view taken along the line 2--2 in FIG. 1.

FIG. 3 is a schematic wiring diagram for the low voltage power supply.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIG. 1 an air purifier in accordance with the present invention designated generally as 10. The air purifier 10 includes a housing having a front wall 12, a back wall 14, side walls 16 and 18, a top wall 20, and a bottom wall 22. While the housing is preferably rectangular, other configurations may be utilized.

The inlet to the air purifier 10 is through the top wall. The top wall 20 is provided with a depending flange 24 defining an opening within which is mounted an intake grille 26. Below the grille 26, there is supported in any convenient manner a roughing filter 28 which constitutes a first filter means for the air. The roughing filter 28 removes large particles having a size of approximately 20 microns or more. When deoxidation is desired, there is provided a second filter means in the form of a wetted screen 30. The screen 30 may include a close knit fabric layer such as cotton cheesecloth or polyester wool connected by a wick 32 to a source of an oxidixing agent within container 34.

The container 34 is supported on a shelf in chamber 36. Chamber 36 is defined by wall panel 38 and side wall 18. An entrance door or panel for providing access to chamber 36 is provided but not shown. The oxidizing agent in container 34 may be any one of a variety of inorganic compounds in solution with water. Notable among these oxidizing agents are the salts of permanganate, dichromate, nitrate, and peroxide. These compounds form negative ions in solution which will oxidize almost all organic and inorganic compounds. Oxidation will, in may cases, break compounds down to simpler forms changing odorful constituents to carbon dioxide, water, and various other odorless compounds.

The second filter means removes the gaseous or odorous contaminants from the air stream. This is accomplished by capillary action wherein the wick 32 feeds the oxidizing agent to the wetted screen 30. The wick 32 is preferably wrapped about a negatively charged electrode. This promotes the evaporation of droplets from the wetted screen 30 with a net negative charge by driving negative ions to the surface where the thermodynamic evaporation takes place. This introduces negatively charged droplets into the stream. If particles of positive charge are present in the air stream, they will be attracted to the negative droplets for reaction. Particles are known to carry odor-producing gases. One of the common problems with highly efficient particle entrapment is that trapped particles outgas odorful gases. In the present invention, the absorbed gases will oxidize.

The oxidation may be enhanced by heat from an ultraviolet source such as the germicidal lamps 40 and 42. The germicidal lamps 40 and 42 are conveniently supported by wall 16 and panel 38 below the wetted screen 30. The germicial lamps are provided with shields so as to direct the ultraviolet rays towards each other. The negative charge associated with the wetted screen 30 will cause electrons to be emitted when struck by the ultraviolet rays from the lamps 40 and 42. The electrons will strike particles in the air stream knocking off outer shell electrons and giving the struck particles a net positive charge. Thus, the ultraviolet ray sources serve as an ionizer. In addition, the lamps 40 and 42 may be provided when it is desired to destory bacteria, viruses, fungus spores, etc., which are present as contaminants in the air stream.

The next stage of the air purifier of the present invention is disposed below the lamps 40 and 42. The next stage namely the third filter means, is comprised of a high efficiency particulate air filter in the form of a pleated filter member 44. Non-charged particles will enter the filter member 44 and be trapped therein with the usual efficiency of the medium. However, charged particles even with one electron missing, will be trapped with a greater efficiency. This is accomplished by an electrostatic field which causes the charged particles to travel in a zig-zag path through the filter member 44. The increased path length causes the particles to make many more encounters or impacts with the filter member 44.

The filter member 44 is preferably a high efficiency air filter media such as DEXIGLAS sold commercially. Said air filter media may be manufactured by laminating two or more separate and distinct media together forming a multiply filter. The plies of the filter are constructed entirely of synthetic fibers chemically bonded together with a moisture-resistant, fire-retarding bonding agent and coated with a mildew inhibitor. Tough filter media with temperate resistance up to 300.degree.C may be microglass or microglass and cellulosic fibers treated with plastic resins. Said air filter member 44 does not interfere with the ability of the air to flow through the air purifier 10 of the present invention with substantially laminar flow and a maximum pressure drop of 0.3 inches of water.

The pleated filter member 44 is supported between charged electrode plates 46 and 48 electrically insulated from the housing and coupled to a power supply 50 by conductors 56 and 54, respectively. The filter member 44 and the plates are part of a subassembly installed as a unit with non-conductive walls 47 and 49. The plates 46 and 48 are the end walls of a topless, bottomless unit. If desired, plates 46 and 48 may be the side walls of the unit if the filter member 44 is rotated 90.degree. from the position shown. Hence, plates 46 and 48 may be positioned to be parallel to walls 12 and 14, if desired. The power supply 50 is disposed within chamber 52. Chamber 52 is likewise defined by the side wall 18 and wall panel 38 so as to be below chamber 36. Suitable door means is provided to facilitate access to chamber 52.

One or more blowers are provided to create an air stream through the air purifier 10 and return the air stream to the room surrounding the purifier 10. As shown more clearly in FIG. 1, there is provided a pair of blowers. The first blower 58 has a motor 60 at its bottom and an air intake at its upper end. The outlet of the blower 58 is connected to an outlet conduit 62 aligned with a grille 64 in side wall 16.

A blower 66 has a motor 68 and an intake at its upper end. The outlet of blower 66 is connected to an outlet conduit 70 aligned with an outlet grille 72 in side wall 18. Suitable controls such as an on-off switch, speed control, and pilot light may be provided on the housing wherever desired. As illustrated in FIG. 2, the controls 74 are provided on the front wall 12. An electrical distribution block 76 may be provided within the housing and connected to a source of potential by electrical cord 80. The distribution box 76 is coupled to the motors 60 and 68 as well as the power supply 50 by conductors, not shown.

In FIG. 3, there is illustrated a schematic diagram of the power supply 50 which is a multi-vibrator network for generating a square wave potential applied to plates 46 and 48. The power supply includes a full wave bridge rectifier 82 and multi-vibrator 83 whose output is coupled to conductors 54 and 56. A capacitor 86, such as a two microfarad capacitor, is coupled across the conductors 84 and 86. A resistor 88, such as a 100K ohm resistor, is connected in series with a neon tube 90 across the conductors 84 and 86. A similar resistor 92 is connected in series with a similar neon tube 94 across conductors 84 and 86.

A capacitor 96 such as 0.3uf is coupled across the junction 98 and 99 as shown more clearly in FIG. 3. The conductor 56 is coupled to junction 99. Those skilled in the art should recognize that multi-vibrator circuit 83 generates a square wave such as illustrated just below conductor 54. Submicron particles are influenced most by the small voltages applied to the plates 46 and 48 such as 100 to 170 volts. The square wave signal applied to the plates at a frequency of about 8 cycles per second causes particles of 0.05 micron size travelling at the rate of 200 fpm to make at least seven encounters with the filter member 44.

The velocity of the air stream is in the range of 100 to 500 fpm with the frequency of the square wave signal varying from 4 to 20 cps in accordance with a straight line graph of velocity versus frequency.

In view of the above description, a detailed description of operation is not deemed necessary. Air from a room is sucked in through the intake grille 26 and returned to the room through the grilles 64 and 72 by means of the blowers 68 and 66. The air flow is essentially laminar and indicated diagrammatically by the arrows in FIG. 1. The air sequentially is subjected to a roughing filter, an oxidation process for odor removal, ultraviolet rays, and then passes through a high efficiency filter. The air returned to the room by way of the grilles 72 and 64 is free of odors, bacteria, viruses, and particulates greater than 0.3 microns.

The air purifier may be utilized in industrial applications, for hospital applications wherein health of a patient requires a purified atmosphere, as well as in the home as a supplement to air conditioning systems which essentially cool the air and remove only gross particulates. The air purifier 10 is a compact integrated unit which in order to use merely requires that the plug on cord 80 be plugged into the conventional household electrical circuit. As soon as the on switch of control 74 is turned, the blowers will start, the power supply 50 will be connected to the source of potential and the lamps 40 and 42 will be turned on. Periodically, it will be necessary to check the level of the oxidizing agent in container 34 and refill the same. Otherwise, the air purifier 10 requires little or no maintenance, except for replacement of elements 28 and 44 as needed.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

Claims

I claim:

1. An air purifier comprising a housing containing an inlet and an outlet, blower means for causing air to flow through the housing from the inlet to the outlet, two filter means in series in said housing between said inlet and outlet for filtering the air flowing between the inlet and outlet, one of said filter means being a pleated member, means defining a low voltage electrostatic field in said housing for causing particles to travel in a zig-zag path through the filter member, said last-mentioned means including spaced electrode plates coupled to a power supply, said filter member being disposed between said plates, an odor oxidizing means including an air-permeable substrate, and an ultraviolet lamp means for sequentially treating air at a location in the housing between said two filter means.

2. An air purifier in accordance with claim 1 including a pair of oppositely disposed germicidal lamps facing towards each other and positioned between said two filter means.

3. An air purifier comprising a housing containing an inlet and an outlet, blower means for causing air to flow through the housing from the inlet to the outlet, two filter means in series in said housing between said inlet and outlet for filtering the air flowing between the inlet and outlet, one of said filter means being a pleated member, means defining a low voltage electrostatic field in said housing for causing particles to travel in a zig-zag path through the filter member, said last-mentioned means including spaced electrode plates coupled to a power supply, said filter member being disposed between said plates, an odor oxidizing means having a substrate connected to a source of an oxidizing agent, and said substrate being disposed between said two filter means.

4. An air purifier in accordance with claim 3 wherein said housing includes a chamber, a container for an oxidizing agent within said chamber, and wick means connecting said substrate to said container.

5. An air purifier comprising a housing containing an inlet and an outlet, blower means for causing air to flow through the housing from the inlet to the outlet, two filter means in series in said housing between said inlet and outlet for filtering the air flowing between the inlet and outlet, one of said filter means being a pleated member, means defining a low voltage electrostatic field in said housing for causing particles to travel in a zig-zag path through the filter member, said last-mentioned means including spaced electrode plates coupled to a power supply, said filter member being disposed between said plates, said last-mentioned means including a rectifier multi-vibrator circuit for producing a square wave signal at said spaced electroplates between which said filter member is disposed.

6. An air purifier in accordance with claim 5 wherein said circuit is an AC circuit with a square wave signal frequency of about 4 to 20 cycles per second.

7. An air purifier comprising a housing containing an inlet and an outlet, blower means for causing air to flow through the housing from the inlet to the outlet, filter means in series in said housing between said inlet and outlet for filtering the air flowing between the inlet and outlet, one of said filter means being a pleated filter member, means defining a low voltage electrostatic field in said housing for causing particles to travel in a zig-zag path through the pleated filter member, said last-mentioned means including spaced electrode plates coupled to a power supply, said pleated filter member being disposed between said plates, oxidizing means upstream from said one filter means for chemically oxidizing odors, said odor oxidizing means including a substrate through which air can flow, a source of an oxidizing agent, and wick means connecting said substrate to said source of oxidizing agent.

8. An air purifier in accordance with claim 7 wherein said power supply includes a rectifier multi-vibrator circuit for producing a square wave signal at spaced electrode plates between said pleated filter member is disposed, said circuit being an AC circuit, and the square wave signal having a frequency of about 4 to 20 cycles per second.