US2796144A - Electrical filtration - Google Patents

Description

June 18, 1957 w. K. HALL v 2,796,144v

' ELECTRICAL FILTRATION Filed March l0, 1954 2 Sheets-Sheet 1 June 18, 1957 w. K. HALL 2,796,144 ELECTRICAL FILTRATION v Filed March 1o, 1954 2 Sheets-Sheet 2 nLncrnrcAL Yisrnrnarron Willis K. Hall, Blissteld, Mich., assigner of one-half to Donald B. Bennet-t, Millbury, Ohio Application March 1o, 1954, serial N0.415,3s6

4 Claims. (Cl. 18S- 7) This invention relates to an electrostatic precipitator Vfor removing small foreign particles suchas dust and pollen from gases such as air. More particularly, it deals with a portable electrostatic precipitator which may be used in combination with an air conditioning unit for a room in a home for purifying the air circulated through it by means of a blower incorporated therein.

States atentO It is an object of this invention to produce asirnple,

eiiicient, effective, compact, lightweight, healthy, economic and self-contained electrostatic precipitator.

Another object is to produce such a precipitator having simple ionizing and collecting sections in which the nondischarging ionizing electrodes and collector plates are combined, 'and which precipitator may be readily cleaned by removal of the collector plates without touching or changing any electrical connections.

Another object is to produce an electrostatic precipitator adapted for producing an effective high D. C. voltage from a standard 110 volt house current source by means of a light weight electronic :apparatus including a high frequency -thermionic tube oscillator and an air transformer.

Another object is to produce such .a precipitator in which the velocity of the gas 'passing through it is successively increased and decreased to provide a turbulence and thereby increase the agitation ofthe gas so that more particles will be able to come close to the charging electrode, and so that blow-olf of the particles from the collector plate will be reduced.

Another object is to produce such a precipitator in which the charging electrode comprises one continuous wire with a purality of parallel sections all having the same charge, and a plurality of collector plates all of which are connected together and have the same oppo-A site charge.

Another object is to produce such an electrical precipitator in which the electrodes have substantially no connections which produce discharges .and ozone, since the production of too much ozone in such a portable precipitator is detrimental to health.

Another object is to produce such an electronic precipitator in which the charging electrodes are so shaped and arranged as to produce successive repelling lines of llux so that there are spaced successive areas of increased and decreased flux density for the gas passing through the precipitator for clariication.

Another object is to produce an electrostatic precipitator in which such a high frequency charge is employed that the off-time of `each cycle is so short lthat the particles being charged have no time to lose their charge before being collected. t

Generally speaking, the electrostatic precipitator of this invention comprises :a housing in which is provided a series of ducts through which the gas to be purified is drawn by means of a blower or fan communicating with a chamber at one end of said ducts. These ducts are preferably parallel and contain a plurality of parallel ridges ICC Patented June 18, 1957 transverse of 1the ow of the gas stream through them,

and charging electrodes extending between the plates in .alignment with said ridges, whereby the ridges not only form Venturi-type narrow channels for intermittent increases in the velocity of the gas through the apparatus,

but'also increase the flux density adjacent the charging electrodes. This increase in ilux density adjacent each charging electrode is caused both by the fact that the .ridges have concave curved surfaces to form rconverging ilux density lines, and that adjacent similarly charging electrodes are so successively spaced that in the ducts in Vthe direction of the flow of the gas therein. Thus there is produced a zone of low ux density by the opposition of the like charges applied to said adjacent charging electrodes. The wires and plates are so arranged that the plates may be easily removed from the precipitator for cleaning Awithout touching or changing any of the electrical connections, or removing any of the charging lelectrodes or their terminals. The charging electrodes which comprise a parallel ygroup of wires arranged between the collector electrode plates, which wires may be formed from sections of one continuous wire, avoid many ozone producing terminals at each 'end of each section.

In the housingfortthe precipitator there may ybe provided a separate chamber for the electrical circuit for producing the high D. C. voltage required for charging the electrodes of the precipitator, from a normal volt 60 cycle A. C. household current supply source. This circuit may comprise electronic tubes, rectiliers, oscilla `tors and air transformers, with which equipment it is possible to produce the high voltage required at an increased frequency, thereby reducing the size, weight and complexity of the precipitator unit.

The above mentioned and other features and objects of this invention and the manner .of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the `accompanying drawings, wherein: Pig. 1 is a perspective View, with parts broken away, of a portable air cleaner electrostatic precipitator unit according to this invention as adapted for household room use;

Fig. 2 is an enlarged horizontal section taken along line Il-II of Fig. l showing the path of the air through the unit; i

Fig. 3 is a vertical section taken along line III- III of Fig. 2 through the parallel air ducts of the electrostatic charging and collecting section of the precipitator unit;

Fig. 4 is a schematic Vertical section taken along line IV-IV of Fig. 3 lengthwise of the parallel ducts, showing the ribs or ridges on the collecting electrode plates directly opposite the spaced charging electrode wires parallel with said ridges; and

Fig. 5 is a schematic wiring diagram of an electrical circuit for an electrostatic precipitator as disclosed in Figs. l through 4,

A housing 1 is mounted on casters 2 with an air-intake port or window 3 and an exhaust or discharge port 4. Electric power supply, as from a flexible Wire pair, may be 110 volt 60 cycle, connected through a complementary fitting to two-prong receiver or socket 5 in proximity to a toggle switch 6. The port 3 is to a chamber section 7 at one end of the housing 1. The opposite end of the housing 1 has a chamber section 8 with a floor 9 having an intake port 1t) forming the intake to a blower 11 providing fair` supply to the discharge port 4. A power supply housing 12 is carried by the housing 1 for the unit below floor 13 for the chamber section 7.

Electrical power conductors 14, 15, from the switch 6 (Fig. 5) extend to a motor 16 to drive the centrifugal type of air pump or blower 11. Conductors 17, 18, from the switch 6 extend to a transformer 19.

The specific illustration has to do with the handling of a fluid medium of high resistance to conducting electricity. Particles in such a medium, as air, have response to taking on electrical charges from an oscillating high potential electric current supply. Having in mind ready portability for the unit, and extreme high voltage with low amperage in the direct current supply needed in the unit, there is compactness achieved through an electrical conversion means and circuit shown in Fig. 5. This circuit extends from the transformer 19 for current voltage stepup to a thermionic full wave rectifier tube 20.Y Connected to the tube 20 is a low voltage filter capacitor 21 say of 400 mfd. at 600 volts. Line 22 from the tube 20 has rectiied or direct current of say 350 volts, as the power source for the operation of a pentode 24. A circuit 23 furnishes heat for an indirectly heated cathode at the 'pentode oscillator tube 24. The filament heating circuit 23 for the cathode thereof is from the transformer 19. Cathode bias resistor 25, of say 200 ohms at 1 watt, is in parallel to a ground with cathode bias capacitor 26, of say .05 mfd. at 50 volts. A screen grid bypass capacitor 27, say of .0005 mfd. at 600 volts, is between the cathode bias resistor and screen grid voltage dropping resistor 28, say of 5600 ohms at l watt, fromthe pentode 24. The resistor 28 has connection to the 350 volt D. C. supply line 22 from the rectifier tube 20, and connection 29 to a tuned plate capacitor 30 of range for capacitance of 300 to 800 mmfd. at 600 volts, and in parallel therewith to an inductance 37 then connected back to the plate of the pentode 24 through conductor 31. From the pentode oscillator tube 24 is a conductor 32 to a grid inductance 33 and tuned grid capacitor 34, of say 680 mmfd. at 200 volts.

Between the capacitor 34 and ground is a grid leak capacitor 35, of rating say .0005 mfd. at 50 volts, in parallel with a grid leak or grid bias resistor 36 of say 470 kiloohms at 1/2 watt.

From the inductance winding 37, there is step up winding 38 of an air core transformer to the range of say 15,000 volts to a diode rectifier tube 39. This tube 39 may have a heater circuit 40 from the winding or coil 37 Take-off line 41 may, at some output conditions, not be required as to capacitor or condenser 42, say of 500 mmfd. at 20 kilovolts. By choosing the values of inductances 33 and 37 so that the tube 39 operates as an oscillator at a frequency of say 100 kilocycles, the voltage and thereby the electric power consumption for a given performance of the unit may be materially reduced and the overall efficiency of the unit increased.

The housing 1 has insulation wall front 43, and parallel thereto an insulation wall back 44. Connecting the floors 9, 13, is a wall 4S, parallel to a top 46 for the housing 1. These parallel walls 43, 44, and 45, 46, form a tube section 47 or all of that portion of Fig. 2 shown in Fig. 4, connecting the chamber sections 13, 9. Sub-duct sections are formed by collector electrodes or electrical conductor intermediate plates 48 and outer plates 49. Electrical conductive channel guides 50 provide slide seats for edges of the plates 48, 49, to direct such in symmetrical spacing in parallel and electrical connection to ground 55. Insulated packing or baffles S1 (see Fig. 3) space the plates 49 from the walls 45, 46, and direct air ow to be confined between the plates or collecting electrodes 48, 49, from the chamber section 13 to the chamber section 9, shown as in four sub-ducts 52.

At a capacity of 170 cu. ft. per min. to be handled by the blower 11, with the housing in the range of 14 in. wide and 28 in. long, 8 in. at each end for the Vchambers 13, 9, leaves about l2 in. for the length of tube section 47 divided into the sectional ducts 52, of 14 in. wide and say 2%, in. spacing. between the collector electrodes 48, 49.V 'These collector plate electrodes 48 and 49 have opposing parallel ridges or ribs 53 with at eddy-receiving spaces 54 therebetween. These plates 48, 49, have an electrical ground 55, shown as negative in the circuit of Fig. 5 from the electrostatic charge of positive through the wire 41 having at the front housing side 43 crossovers or conductor wire sections 56 (see Figs. 1 and 2) connected to the other or back side 44 cross-overs or conductor Wire sections 57 through the discharge or charging electrodes or wires 58 (Fig. 5). Drop connections 59 at the wall 43 connect the different levels of the discharge electrode wires 58. These cross-overs are arranged for easy removal of the collector plates 48 and 49 without touching the connections between the parallel charging sections of the charging electrodes 58 or their continuously connected wire conductor from which they are formed.

ln the insulation wall back side 44 are slots or ports 60 with which register slightly projecting ends of the plate or collector electrodes 48, 49, to the end that, as particles accumulate thereon, these plates may be withdrawn, without disturbing the electrical circuit connections, for the particles to be brushed off or otherwise action taken to clear such of particle accumulation thereon from deposit due to positive electrical charging action from the charging electrodes 58 parallel to the ribs 53. With the embodiment for the charging electrodes 58 to extend horizontally, the location of the charging electrodes is in line with the common diameter connecting the ribs 53 of adjacent plates, thereby providing location for minimum distance flux lines 69. Along this range and in proximity thereto, suspension particles, in the uniform velocity flowing medium or air to be purified, are acted upon by the positive flux from the charging electrodes 58, Electrical charges thus taken on by such particles have conductive reaction in being ung to impact the negative plate area of the duct wall collecting electrodes or plates 48, 49, being grounded by way of the connection 55. The experience has been that gravity is a minor, if not negligible factor in this electrical precipitator operation, for particle accumulation upon the downward facing or undersides of the collector electrode plates 49, 48, approaches, if not exceeds that of the deposit upon the upper sides.

The specific construction of the plates, the ridges or ribs therealong and the location of the charging electrode wires parallel to and between the parallel ridges of adjacent plates, produce successive Venturi effects at each adjacent ridge pair for the gas passing through the ducts 52. These ridges thereby also cause turbulence around their corners agitating the particles in the gas so that more of them will pass close to a subsequently passed charging electrode 58, if they missed passing close to a formerly passed electrode 58, so that all of the particles have a better chance of obtaining a charge and being collected on the collecting electrode plates 48, 49. The crevices 54 which occur at the bases of opposite sides of the ridges 53, and particularly those on the leeward side of the ridges, provide deader air spaces which are conducive to the settling and collection of particles, preventing them from being blown off of the plates. Thus, the successive opposing pairs of ridges 53 through which the gas to be purified must pass between each of the plates 48, 49, gives a pulsating velocity action to the gas, increasing its turbulence. Y

Another important advantage of the structure of the precipitator of this invention is illustrated by the flux lines 69 and 70 in Fig. 4, which show that the convex curved surfaces of the ridges 53 have a tendency -to produce converging lines of flux to increase the flux density yadjacent them, and also the fact that the successive charging electrodes 58 in any one duct 52 carrying the same charge, produce repelling fields halfway between adjacent electrodes 58, which fields further concentrate the flux lines 70 adjacent the ridges 53 and charging electrodes 58, This effect produces a variably charged field through which the gas passes, which has an additional effect of agitating the particles in the gas, so that more of them will be moved into the close region of at least one of successively arranged charging electrodes.

Furthermore, the high frequency of the oscillation used in producing the D. C. charging current which is applied to the positive charging electrodes 58, permits a lower D. C. charging voltage than otherwise would be necessary for the transformation of just a 60 cycle 110 volt current; since the higher frequency is sufficiently rapid that the particles which may be charged thereby will not have time to discharge during the short interval of time that the oscillations are at a zero or low potential.

Connecting and disconnecting the power supply to this portable electrical filtration unit at the fitting 5 and noting whether or not the blower operates, provides an indication of energization of the precipitator. A further check is provided by a milliampere neon bulb 71 (Fig. 5) in the high potential electrical circuit connected in line 55 between the slide guides 50 and ground, for instance.

Demonstration of eifective electrical `filtration of the present invention has been demonstrated by hte following test: A unit of the dimension suggested herein with an induced air ow in the range of 170 cu. ft. per min. was operated continuously for an interval of 12 hours to purify the normal living room air in a residence, and thereafter the deposit from the collector electrode plates was cleared and collected over a 3 in. diameter area of white lter paper to disclose a definitely perceptible gray*not solid black stain or coloring of the paper. Simultaneous check of this performance was made by conducting the exhaust from this unit directly through a similar unit. Cleaning of the collector electrode plates of the second or follower unit developed such minor particle collection volume as to be hardly perceptible on a 3 in. diameter area of filter paper. From this it follows the particle removal in passing contaminated air once through a unit is in the range of 99 percent. The perodic cleaning of the collector electrode plates 48, 49, or par- What is claimed and it is desired to secure by Letters Patent is:

l. An electrostatic precipitator apparatus comprising: a housing, means for conducting a gas containing suspendcd particles to be precipitated through said housing, a plurality of spaced horizontal electrode plates in said housing with parallel ridges on said plates, said plates being parallel to the flow of the gas through said housing but with said ridges being transverse of said ow and with adjacent ridges on adjacent plates being directly opposite and parallel to each other, a plurality of electrode ywire section suspended between and parallel to each opposing pair of ridges on adjacent spaced plates, and means for removing said electrode plates from said housing for cleaning purposes without disturbing said wires.

2. An apparatus according to claim 1 including means connected to one of said electrodes for visually indicating the energization of said apparatus.

3. An apparatus according to claim l wherein said wire sections comprise one continuous wire.

4. An apparatus according to claim 1 including means for introducing the gas into said housing transverse to the flow of said gas between said plates.

References Cited in the file of this patent UNITED STATES PATENTS 1,541,677 Anderson June 8, 1925 1,965,924 Heinrich July 10, 1934 2,462,890 Newman Mar. l, 1949 2,632,522 Fields Mar. 24, 1953 2,640,559 Hills June 2, 1953 2,650,672 Barr et al. Sept. 1, 1953 FOREIGN PATENTS 360,119 Germany Sept. 29, 1922 383,547 Great Britain Nov. 17, 1932l 684,342 Germany Nov. 27, 1939

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