US 3747300 A
A portable electrostatic air cleaner having a case with an air inlet and an air outlet and fan means for moving air through the case from the inlet to the outlet, three tracks formed on inner case walls and extended diagonally across the case from an access opening on the rear case wall and being of different sizes, three filter elements likewise of different sizes corresponding to the tracks and received and supported thereby in a series flow sequence between the inlet and outlet specifically where the upstream filter element is a mechanical filter, the second filter element is an electrostatic air precipitator, and the downstream filter element an activated charcoal filter, the filter elements being inserted into and/or removed from the tracks through the access opening, a panel to selectively close the access opening, operating controls including a panel with normally adjustable knobs and including safety controls requiring the charcoal filter element to be in place and the panel to close the access opening before the cleaner can operate, and a screen cover on the case overlying the air outlet and all control knobs.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Knudson 1 PORTABLE ELECTROSTATIC AIR CLEANER  inventor: Robert F. Knudson, Concord, Mich. [731 Assignee: McGraw-Edison Company, Elgin, 111.  Filed: Oct. 14, 1971 211 Appl. No.: 189,146
 U.S. Cl....'. 55/126, 55/138, 55/139, 55/141, 55/149, 55/387, 55/472, 55/481,
 Int. Cl. 1103c 3/14  Field of Search... .[55/124, 126, 131,
[4 1 July 24,1973
Primary Examiner-Dennis E. Talbert, Jr. Attorney-Charles F. Lind 51 ABSTRACT A portable electrostatic air cleaner having a case with an air inlet and an air outlet and fan means for moving air through the case from the inlet to the outlet, three tracks formed on inner case walls and extended diagonally across the case from an access opening on the rear case wall and being of different sizes, three filter elements likewise of different sizes corresponding to the tracks and received and supported thereby in a series flow sequence between the inlet and outlet specifically where the upstream filter element is a mechanical filter, the second filter element is an electrostatic air precipitator, and the downstream filter element anactivated charcoal filter, the filter elements being inserted into and/or removed from the tracks through the access opening, a panel to selectively close the access opening, operating controls including a panel with normally adjustable knobs and, including safety controls requiring the charcoal filter element to be in place and the panel to close the access opening before the cleaner can operate, and a screen cover on the case overlying the air outlet and all control knobs.
7 Claims, 6 Drawing Figures PATENTED JUL24|975 3. 747. 300
SHEET 1 BF 2 aari naaisvn @fw 1 PORTABLE ELECTROSTATIC AIR CLEANER An electrostatic air precipitator typically provides a plurality of charging and collecting electrodes located in an air stream, where air particles are electrically charged as they pass the high voltage charging electrodes and are drawn then by electrostatic attraction to the collecting electrodes which are grounded or at the oppositely charged potential. The electrostatic attraction effectively removes extremely small particles much too small for mechanical filtering. Once drawn to the collecting electrodes, the particles typically are held there by smudge or other contaminants which build up to reduce the efficiency. Consequently the precipitator must be cleaned frequently by removing it from the unit and washing it with a soapy solution or other cleaning solvent.
This invention relates to, and an object of this invention is to provide, an air cleaning device having an electrostatic air precipitator which can be removed for servicing and thereafter replaced with minimum technical expertise required and with minimum chance of harm to the person or equipment.
Another object of this invention is to provide an electrostatic air cleaner having a mechanical filter and an activated charcoal filter located in sandwiching relation to the precipitator, and further having mountings for the filters that include structure separated from the exterior case walls which tend to muffle arcing sounds that might eminate from the precipitator during operation. 9
These and other objects of this invention will be more fully understood and appreciated after reviewing the following specification, the accompanying drawings forming a part thereof, wherein:
FIG. 1 is a front elevational view of the subject air cleaner, with part of the unit being broken away for clarity of disclosure;
FIG. 2 is a top plan view of the unit shown in FIG. 1 again with part of the unit broken away for clarity of disclosure,
FIGS. 3 and 4, are sectional views as seen generally from line 3-3 in FIG. 1 and line 44 in FIG. 3, respectively;
FIG. 5 is a sectional view as seen generally from line 5-5 in FIG. 4;
FIG. 6 is an enlarged frontal view of the filter element as seen generally in FIG. 5.
The disclosed air cleaner utilizes three filter elements in series flow including a mechanical filter, the electrostatic air precipitator downstream of the mechanical filter, and an activated charcoal filter downstream of the precipitator. The filters are sized of different thicknesses, and appropriately sized tracks on the case walls receive and mount the filters but only in the noted correctorientation. The tracks areinclined crosswise to the air flow and line up with an access opening in the rear case wall so that the filters can be inserted into or removed from the tracks through the access opening while yet not requiring any moving filter mounting parts. Electric contacts on a case wall cooperate with precipitator contacts so that electric connection is made automatically upon proper insertion of the precipitator. Handles on the precipitator preclude electrical shorting should the precipitator be improperly positioned in its track. The filter mounting tracks are on walls separated from the exterior case walls so that possible high voltage arcing sounds of the precipitator is not transmitted as readily outside of the case. The specific sandwiching mechanical and charcoal filter elements about the precipitator always provides sound baffling for quiet operation.
As shown in the drawings, the air cleaner 10 has a case 12 formed of a sheet metal, plastic or the like and is portable adapted to be rolled about on casters 11. The case exterior includes a front wall 13, opposed end walls 14, a rear wall 15 and a bottom wall 16. An interior wall 18 is connected crosswise between the vertical case walls and has an opening 20 therein communicating with a lower defined enclosure 21. An exterior top wall is located across the case and includes a control panel 22 and an open mesh screen 23 which isolates the interior wall 18 while allows free air circulation through the screen. A cover is further hinged at 26 to the rear wall and has a peripheral frame 27 and an open mesh screen 28 for allowing free air transfer through the screen.
The lower part of rear wall 15 has louvered openings 32 to the case enclosure 21. A fan 33 supported by brackets 31 from the interior wall 18 is located centrally within the opening 20 operable to draw air in the louvered openings 32 and discharge the same from the case through the screens 23 and 28. An access opening 34 is defined in rear wall 15 above the louvered openings 32, and a closure panel 35 is pivoted about hinge 36 to selectively close and/or open the access opening 34. A pair of locks 38 are provided on the panel to underlie the rear wall to hold the panel in the closed secured position when appropriate.
An inner end wall 39 extends between the front wall 13, rear wall 15, and interior wall 18 and has a rear edge that is abutted by the closed closure panel 35. An opposing inner end wall 40 is defined parallel to the wall 39 and is connected likewise between the front, rear and interior walls. Formed on the inner end walls 39 and 40 are sets of tracks which incline generally downwardly and forwardly from alignment with the access opening to a base wall 42 connected between the spaced inner end walls 39 and 40.
Specifically, the tracks include a lower track 45 adjacent the louvered openings 32, an intermediate track 46, and an upper track 47 adjacent the fan opening 20, and the tracks are of different widths or size. The inner end walls 39 and 40 terminate just below the lower track 45, while they extend upwardly to and are connected with cross wall 18. Base wall 42 extends to and is connected with the front wall 13 as along corner 49. The lower track 45 is in line slightly above the lower edge of the access opening, and the upper track 47 is slightly below the upper edge of the access opening. In the preferred embodiment disclosed, the, three filter elements are supported by the tracks in series with the air flow through the enclosure. The filter elements include a mechanical filter 52, an electrostatic precipitator, and an activated charcoal filter 56.
The mechanical filter 52 shown includes an annular frame 60 which holds in place a plurality of separate sheets 61, typically of aluminum, stamped with a honeycomb pattern of expanded openings. With the openings of the separate sheets randomly misaligning, the labrinth flow paths through the misaligned openings is effective for filtering out larger particles from the air stream while providing a durable easily washable filter.
The precipitator 54 used herein has a tubular frame I 64 and a pair of protective grids or screens 65 are connected across the open ends of the frame. Confined between the protective grids within the frame are located a charging section 66 and a collecting section 67. The charging section 66 includes one or more elongated wires or electrode 68 each of which is disposed between separated plates 69 and where both plates and wire are supported by appropriate insulators. The col lecting section 67 of the precipitator includes a plurality of insulator supported parallel plates 71 separated by approximately one-fourth inch and extended in the direction of the air flow perhaps 1% or 2 inches.
An electrical connection to the precipitator electrodes is made through spring loaded contacts 79 located at the base wall 42 cooperating with stationary contacts 76 on the precipitator frame 64, the latter contacts being in turn through appropriate conductors (not shown) connected in circuit with the electrodes and collecting plates as noted. An appropriate power pack and circuit connection imposes a high voltage direct current potential on the charging electrodes 68 and a ground to the adjacent plates 69, and imposes a high voltage opposite direct current charge on alternate collecting plates 71 and a ground on the remaining alternate collecting plates 71. The high voltage charge on the charging electrodes 68 might be 5,000 to 6,000 volts while a moderately lesser voltage of 2,000 to 4,000 volts might be imposed on the charged collecting plates 71.
It should be noted that the precipitator can only be inserted into the intermediate track 46 oriented where the air flow is initially through the charging section 66 and subsequently through the collecting section 67 because the precipitator frame 64 has off set ridges 85 which can only fit into appropriately located recesses 86 on the track 46. Moreover, a pair of handles 87 located on the precipitator frame opposite from the contacts 76 preclude the precipitator shorting against the base wall contacts 79 even if it should be put in upside down, as it were, with the handles against the base wall 42. In this orientation, the panel 35 hits the precipitator and thus cannot be closed.
The charcoal filter element 56 likewise has an annular frame 89 which can be of metal and has two opposing fine screens 88 which are staked to the frame. Confined between the opposing screens is a honeycomb structure of bonded or pressed board defining many honeycomb cells 90 that extend between the screens in the direction of air flow. Small charcoal granulars 91 occupying some to 30 percent of the total cell area are located in each cell so that air can move freely through the cells in close proximity to the charcoal but without creating undue air flow resistance.
lt is understood of course that the mechanical filter 52 is confined in the lower track 45, the electrostatic filter 54 is confined in the intermediate track 46, and the charcoal filter 56 is confined in the upper track 47, and each filter extends completely across the case on a downwardly and forwardly inclined manner. To minimize any leakage past the filters as noted above, there is a resilient sealing element located around the periphery of the access door which overlaps the underlying rear wall and likewise sealing element is secured to the door to cooperate with the corner of the mechanical filter 52. Consequently, all the air circulated through the unit is passed in series flow initially through the mechanical filter 52, subsequently through the precipitator 54, and lastly through the charcoal filter 56.
The diagonal orientation of the filters crosswise to the case allows the filters to be large compared to the given height and front to rear dimensions of the case and allows the filters to be inserted in or removed from the case through the access opening while having the stationary filter mounting tracks.
The specific filter mounting arrangement further virtually surrounded all sides of the electrostatic precipitator 54 with sound muffling structure for quiet operation. In this regard, the tracks are on inner end walls 39 and 40 separated from the exterior end case walls 14, the access closure door 35 is located at the rear of the precipitator, the base wall 42 is provided at the front of the precipitator again mostly separated from the front case wall 13, and the charcoal filter 56 and mechanical filter 52 sandwich the two sides of the precipitator. Moreover, the air inlet is on the rear side of the unit and the air outlet opening on the top wall so that any sound waves from the openings in the unit must be deflected or bent before reaching an occupant of the room typically laterally spaced forwardly or sidewardly from the unit.
An on-off control 93 is located on the control panel 22, and this would also provide a particular drying cycle for operating the fan only and with no potential at the base wall, which would be used immediately after washing the precipitator. Another control 94 varies the speed of the fan, by for example, an infinite speed control so that the fan motor can be operated at low speeds for smaller rooms or at fast speeds for larger rooms.
The unit further has a number of safety controls which must be completed before operation can begin. One safety control switch 96 is mounted adjacent the track 56 which necessitates that a charcoal filter must be located in place before either the fan or precipitator can be operated. Likewise, normally open switch 97 located adjacent the access door requires that the access door be closed before the unit will operate.
Noting the operation of the device, as air is moved through the precipitator, particles in the air are charged by the high voltage electrodes 68 and are then collected on the collecting electrodes 71. The force of attraction or repulsion on any one particle depends upon the differential charge on the particle and on the collecting plates and upon the space between the plates. Slow air speeds allow more particles to be removed per unit volume of air but then only a small total volume of air is handled, while the faster air speeds might not have the high per unit volume of entrapment but more overall air volume is handled.
It should be appreciated that the mechanical filter tends to separate the larger particles from the air flow while the electrostatic air precipitator is effective on the particles much too small for entrapment in the mechanical filter. The charcoal filter'minimizes the passage of odors through the unit, where ozone might typically be generated by the precipitator, and this and most any normal room odor would be eliminated or at least reduced.
Preferably, the filter elements have comparable resistance to air flow through them, and the overall air flow through the clean filter elements should be no less than approximately percent of the air flow when no filters are in place. The disclosed cleaner has approximately 400 to 500 cubic feet per minute air flow, which is quite acceptable for domestic use.
What is claimed is:
l. A portable electrostatic air cleaner, comprising a case having walls connected together defining an enclosure and defining an air inlet to and an air outlet from the enclosure, fan means supported by the case for drawing air through the inlet and enclosure and for discharging the same from the outlet, one case wall having an access opening to the enclosure and a closure panel for selectively closing the access opening, a pair of opposing track walls and inclined in line from the access opening downwardly across the enclosure with the air inlet and air outlet being on opposite sides thereof, a mechanical filter element adapted to be received in the track adjacent the air inlet, an activated charcoal filter element adapted to be received in the track adjacent the air outlet, and an electrostatic air precipitator filter element adapted to be received in the intermediate track between the mechanical and charcoal filter elements, the filter elements extending across the enclosure in series air flow between the air inlet and the air outlet, means between the track walls and the case and the filter elements and case operable to preclude air movement from the air inlet through the enclosure and out the air outlet other than in series through the filter elements, the track walls being spaced inwardly of adjacent opposing case walls, a base wall also spaced from a case wall extended between the track walls, electrical contact means defined on said base wall, said precipitator having an annular frame and having exposed contacts on one face of the frame suited to engage the base wall contact means with the precipitator positioned properly in the intermediate track, and the precipitator also having handles projected from the frame face opposite from the contacts for engaging the base wall upon improper positioning of the precipitator within the intermediate track to preclude electrical shorting across the base wall contact means.
2. An air cleaner according to claim 1, wherein the filter elements are of different thicknesses and the various pairs of tracks are of specific widths to receive the filter elements only in said assembled relation.
3. An air cleaner, according to claim 1, wherein the precipitator frame has at least one ridge nonsymmetrically located thereon, and wherein the intermediate track is provided with a recess adapted to receive the ridge only in proper orientation of the precipitator in the intermediate track.
4. An air cleaner, according to claim 3, wherein a safety control is provided associated with the charcoal filter element track and requires the presence of the charcoal filter in the track before operation of the fan means and precipitator can occur.
5. An air cleaner, according to claim 3, wherein the filter elements are of different thicknesses and the various tracks are of specific widths suitable to receive the filter elements only in said assembled relation.
6. An air cleaner, according to claim 1, wherein the access opening and the air inlet are located on the rear wall of the case with the access opening being vertically above the air inlet.
7. An air cleaner, according to claim 6, further including a top case wall having open grill means covering the fan means and a panel having control elements mounted thereon, a cover overlying the top case wall and having a screen construction, and the air outlet being through the open grill means and screen construction.