U.S. patent number 3,747,300 [Application Number 05/189,146] was granted by the patent office on 1973-07-24 for portable electrostatic air cleaner.
This patent grant is currently assigned to McGraw-Edison Company. Invention is credited to Robert F. Knudson.
United States Patent |
3,747,300 |
Knudson |
July 24, 1973 |
PORTABLE ELECTROSTATIC AIR CLEANER
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
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.
Inventors: |
Knudson; Robert F. (Concord,
MI) |
Assignee: |
McGraw-Edison Company (Elgin,
IL)
|
Family
ID: |
22696133 |
Appl.
No.: |
05/189,146 |
Filed: |
October 14, 1971 |
Current U.S.
Class: |
96/58; 96/142;
55/481; 55/485; 55/472; 55/516 |
Current CPC
Class: |
B03C
3/155 (20130101) |
Current International
Class: |
B03C
3/155 (20060101); B03C 3/04 (20060101); B03c
003/14 () |
Field of
Search: |
;55/124,126,131,132,136,137,138,139,140,141,142,143,145,146,105,149,387,472,481 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Talbert, Jr.; Dennis E.
Claims
What is claimed is:
1. 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.
Description
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.
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 4--4 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
correct orientation. The tracks are inclined 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 54, 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 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 collecting 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 11/2 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 10 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.
It 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 75 - 85
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.
* * * * *