US2462890A - Electrostatic precipitator system - Google Patents

Description

March 1, 1949; M, NEWMAN 2,462,890

ELECTROSTATI G PRECIPITATOR SYSTEM Filed Oct. 30, 1943 Y 3 Sheets-Sheet l 3G 37 24 2G 3G PREC/PHHTING /8 Z 3 333 PLATES H H I' M QM'Q :4

PREC/P/TAT/NG ZONE l6 l5 ..!.m. 42 44 ION/ZING 4 4/ 45 41 4! ZONE [VVENTOE M02215 NEWMAN Patented Mar. 1, 1949' znozpuu UNITED STATES PATENT OFFICE ELECTROSTATIC PRECIPITATOR SYSTEM Morris Newman, Minneapolis, Minn.

Application October 30, 1943, Serial No. 508,336

14 Claims.

This invention relates to electrostatic precipitator systems and particularly to systems wherein ionization is produced under different potentials than that employed for precipitation of the ionized particles. It has been discovered that ionization may be produced by an alternating current having a frequency in the range from high audio frequencies to slightly below the low radio frequencies and having a unidirectional voltage component and that the degree of ionization may be conveniently and readily controlled automatically in such a system.

It is accordingly an object of the invention to provide an improved electrostatic precipitating apparatus and system wherein dust and microbiological particles in the air and gas stream are charged by a high voltage alternating potential having a frequency in the range extending from high audio frequencies to a frequency slightly lower than the low r-adio frequencies, and a high voltage unidirectional component. It is also an object of the invention to provide an improved electrostatic precipitating system including a. power source therefor, and more particularly to provide a system wherein the degree of ionization is automatically and conveniently regulated so as to prevent excessive ionization with resultant ozoneand nitrous oxide formation.

It is also a purpose of the invention to provide safe electrostatic precipitator systems which are free from dangerous capacitators which have heretofore been used, and to provide safe electrostatic precipitator systems wherein the precipitator plates have -a dual function. It is also an object to provide in such systems a safe high v frequency energization obviating danger.

It is also an object of the invention to provide an electrostatic precipitating apparatus and system-o'fportable nature, including a convenient, low-weight power pack for the apparatus.

Other and further objects are those inherent in the apparatus illustrated, described and claimed.

The invention is illustrated with reference to the drawings in which Figure 1 is a sectional view through an electrostatic precipitating apparatus;

Figures 2, 3, 4 and 5 are wiring diagrams of varying forms of electrical circuit arrangements for supplying electrical power as a portion of the electrostatic precipitating apparatus and system of the invention;

Figures 6 and 7 are graphs illustrating the operation of the invention;

Fi ures 8 and 9 are schematic illustrations of Throughout the drawings corresponding numerals refer to the same parts.

Referring to Figure 1, there is illustrated a cross section through a. precipitating apparatus wherein the outer framework of container i0 is a rectangular cross section and may conveniently be composed of sheet metal. Upon the side walls H and I2 of the container are mounted oppositely 3 spaced pairs of insulators l3 and I4 and I5 and Hi. The pair of insulators i3 and it serve to support a rod l8 and similarly insulators i5 and I6 support a rod i9. Extending in parallel relation to rods l8 and i9, and mounted upon the side walls II and I! there are positioned a pair of rods 20 and 2!. Within the container there are positioned a plurality of uniformly spaced plates 23, 24, 25, 26, 21, 28, 29, 30, 3|, 32, 33, 34, 35. The evenly numbered plates are mounted upon rods yond either end of the even numbered plates 0 and are mechanically supported by and electrihence to the odd numbered plates.

plates.

ure 1.

Beneath the precipitating plates as illustrated in Figure 1 there is an ionizing zone indicated by the bracket shown at the right in Figure 1. The ionizing zone in this instance is composed of a plurality of wires 40 which are spaced between a plurality of short plates 4|, which may be solid or open construction such as a screen, or per- 5 forated material, or a grid of wires held in a 20 and 2i, and hence are mechanically supported cally connected to the rods I8 and 19, but by virtue of insulators I3--l8 the odd numbered plates are electrically insulated from the container ID. The odd numbered plates are electrically charged by a conductor 36 which passes through an insulating bushing 31 in the side wall of container i0, and is electrically connected to the rod l8, and The opposite side of the electrical circuit is represented by conductor 38 which is electrically connected to the container Ill, and hence to the evenly numbered and thence through line 1| cordingly mechanically supported by and electrically connected to the container l0, which is preferably grounded. I

The plates 4| are mounted upon rod or rods 43 which in turn support upon spaced insulators 44 attached to the container I0. The plates 4| are accordingly mechanically supported by, but

, are electrically insulated from the container l and also electrically insulated from the even numbered plates of the precipitating zone. Electrical potential is applied to the plates 4| by means of a conductor 45 which passes through an insulating bushing 46 in the side wall H, the conductor being attached to the rod 43.

A source of alternatin current having a frequency in the range from high audio frequencies to slightly lower than the low radio frequencies and having a unidirectional component is applied between conductor 38, which is attached to the container (and hence electrically connected to Wires 40) and conductor 45 extending to the ionizing plates 4|. The apparatus for generating and applying said potential to the common wire 38, the precipitating plate conductor 36 and, the ionizing zone conductor 45 may be any one of those illustrated in Figures 3, 4 and 5, with or without variations such as illustrated in Figures 8 or 9.

Referring to Figure 2, there is illustrated one form of power pack constituting a portion of the electrostatic apparatus and system of the present invention. In Figure 2 low voltage commercial frequency alternating current is sup lied to feeders L1 and L2, feeder L1 being grounded as illustrated at 50. The apparatus includes a full wave rectifier generally designated having cathodes 52 and 54 and anodes 53 and 55. The cathodes 52 and 54 are indirectly heated by filaments' 56 and 51 which are connected in series as illustrated. Feeder L2 is connected by conductor 58 to anode 53 and by conductor 59 to the cathode 54. Cathode 52 is connected by conductor 60 through junction 6| and line 62 to one terminal of condenser 63 and thence through the condenser, line 64, junction 65 and line 66 through condenser 61, line 68 to junction 69 and through line to the anode 55. Junction 65 is connected by line 1| to junction 12 on feeder L1. It will thus be observed that when the alternating current potential is such that L2 is positive in respect to L1, current will flow from L2 through line 58, anode 53, cathode 52, line 60, junction 6|, line 62, through condenser 63, line 64 to junction 65 and thence through line 1| to junction 12 on L1. During the next half cycle when L1 is positive with respect to Le, current will flow from L1 to junction 12 to junction 65, line 86, condenser 61, junction 69, line 10 through tube 5| via anode 55 and cathode 54 through line 59 to L2. Condensers 63 and 61 are accordingly charged in the same direction by alternate half cycles of the alternating potential applied to feeders Li and L2 and therefore the potential existing between junctions 6| and 69 reaches twice the crest value of the alternating potential of the supply lines, when there is no load. and is slightly less than this when loaded by the load of oscillator tube 15. The potential across junctions 6| and 69 serves as the direct current supply for the remainder of the apparatus.

An oscillator tube is illustrated at 15 and includes cathode 16, which is indirectly heated by filament 11, a control grid 18, screen grid 19, grid 80'and anode 8|. Line 82 extends from junction 69 to junction 83 on the cathode connection 84 of tube 15. The cathode 16 is connected to grid 80 by an internal connection 85 of the tube, and the screen grid is connected to junction 65 by means of line 86. The screen grid is accordingly maintained at an intermediate direct current potential which is half the potential existing between junctions 6| and 69.

At 90 there is illustrated a transformer having a primary winding 9|, a high voltage secondary winding 92, a low voltage oscillator feed back secondary 93 which may be air coupled, but preferably has a complete or nearly complete iron circuit 94. The core 94 is preferably composed of high grade transformer steel of .003 inch or less in thickness and may be either an open or closed iron core. One terminal of the primary winding 9| is connected by wire 96 to junction 6|, the opposite end of the primary winding being connected by wire 91 to the anode 8| of the oscillator tube 15. Junction 83, which is connected to the cathode of the oscillator tube is electrically connected through line 98 and through resistance 99 and capacitance H10 (in parallel) to junction I02, which serves as one of the terminals from which direct current at high voltage is supplied by the apparatus through the common line 38 (see Figure 1). The oscillator feed back secondary 93 may be connected directly to junction I02, or, alternatively. may be connected through line 93 to line H4, in which case the connection to junction I02 is broken. The opposite terminal of the feed back winding I03 is connected through line I03 and through the grid bias resistor I04, and grid bias condenser I05 (in parallel) to the control grid 18 of the oscillator tube 15. It is sometimes desirable to connect a variable condenser 16 across the primary 9| of the transformer so as to allow tuning of the circuits for achieving the most desirable frequency of oscillation of tube 15, although in instances the inherent capacitance of the transformer and related connections is suflicient to establish the necessary oscillatory relationship in the circuit, and condenser l06may therefore be considered as'optional.

The net effect of oscillator tube 15 is therefore to impress upon primary winding 9| and oscillating current of a frequency in the range from the high audio frequencies to slightly below the low radio frequencies, viz. from about 5,000 to about 30,000 cycles per second or somewhat higher, and this causes voltages to be induced in secondary windings 92 and 93. I

An energizing potential of the frequency range stated has the attributes such that when the ionizing potential is applied to the ionizing zone (Figure 1) or to other appropriate precipitating apparatus, no dust particle may move through ,the length of the ionizing zone without having impressed thereon at least one cycle crest of ionizing potential. At the same time, the frequency is sufiiciently low so as not to be in the radio frequency range so as not to cause disturbance therein. The frequency range stated also permits heretofore been used in electrostatic precipitating apparatus.

The secondary winding 93 serves as the feed back circuit for controlling the oscillation of tube 18 through the voltage applied upon control grid 18. The grid bias resistor I04 and condenser I05 operate in the usual manner to establish a grid bias upon the grid 18.

The number of turns in secondary winding 92 is large as compared to the number of turns in winding 9|, and a high voltage is therefore induced between terminal 38 and the opposite end of the winding. The winding is preferably provided with an intermediate variable tap I01 which is connected by line I08 to the anode Ill of the rectifier tube generally designated I I0. The rectifier tube is provided with a cathode III which is connected by line I I4 to junction 88, and hence through line 98, and through resistor 99 and capacitor I00 (in parallel) to Junction I02 and thus. Cathode III is indirectly heated by filament I I2.

to the common line 38.

the event specially designed tubes are utilized, the

filaments 58, 51, 11 and H2 may be designed so as to utilize entire voltage between feeders L1 and La, and the resistance II1 may thereby be eliminated.

' As a result of the voltage induced in the winding 92, between terminal 38 and tap I01, there is provided across lines 88 and 38 a unidirectional high voltage through a circuit as follows: From the common line '38, terminal I02, through resistor 99 and condenser I00 (in parallel), line 98, junction 83, line [I4 to cathode III of the rectifier I I0, thence to anode H3, through line I08 to tap I01 and through the winding 92 to terrhinal 88. This unidirectional high voltage is applied between the corresponding terminals 38 and 88 of -a precipitating apparatus, for example that illustrated in Figure 1. I

The transformer winding 92 is also provided with another variable tap I 2| to which line 45 is attached. The voltage at tap I2I may be less than, equal to or greater than the voltage at tap I01, according to'the mode of operation of the electrostatic precipitator, but it is preferably made greater than the voltage at tap I01 for a purpose hereinafter to be described. As a result of this mode ofconnection, a voltage is produced between lines 38 and 45 having a frequency in the range from high audio frequencies to slightly lower than the low radio frequencies and having a high voltage unidirectional component. The circuit producing this complex potential extends from the common-line 38, tap I02, thence through resistor 99 and condenser I00 (in parallel) through line 98 to junction 83, and thence through line II4 to cathode III of rectifier tube I I0, and to the anode H3 through line I08 to tap I01 through the portions of the winding 92 between taps I01 and I2I to line 45. The line 45 is connected to the corresponding numbered line of the precipitating apparatus, for example as shown in Figure 1, leading to the ionizing zone of the apparatus.

Referring to Figure 6, there is shown a graph illustrating the voltage on the precipitating plates of the electrostatic precipitator and the voltage existing between the ionizing wires 40 and the plates M of the ionizing zone. In Figure 6 the line I28--I24 represents the unidirectional voltage applied between the precipitating plates 23-85 of the apparatus shown in Figure 1, the voltage E being preferably in the range of 3,000 to 50,000 volts, depending upon the spacing of the plates and other factors. The voltage existing between the ionizing wires 40 and the plates 4| includes the unidirectional component E and upon this there is superimposed an alternating current voltage having a crest value of E, which is preferably greater than the voltage E with the result that as the voltage E becomes negative, a negative voltage E'--E occurs at each half cycle between the wires 40 and plates 4|. If the voltages E and E are adjusted to appropriate values, in relation to the size of wire used for the wires 40, ionization will not occur until the total voltage between the wires 40 and plates reaches another value Ec (voltage at which ionization occurs). Where the precipitating apparatus is utilized for the purification of air used for respiratory purposes, it is undesirable that any extensive ionization should occur in the apparatus,

7 in as much as ionization causes the formation of ozone and oxides of nitrogen.

In order that the ionization phenomena may be limited despite the variations in line voltage occurring between lines L1 and L2, the power pack includes a regulator apparatus which, in the illustrated embodiment, consists of resist ance 99 and condenser I00 (in parallel) in cooperaiion with the remaining portions of the apparatus. The operation of the apparatus is such that when ionization begins to occur, the increased current, due to the corona formation, causes the amplitude of the oscillating currents through tube 15 to be decreased thereby decreasing the voltage to a point suflicient that the ionization is held at a pre-adjusted small but sufficient value.

Figure. '7 is a graph illustrating the corona current for a wire of given size plotted against the potential applied to the wire. In Figure '7 the curve I25-I28 illustrates the corona loss for ionizing wires 40 which are of given size, for example, as in Patent 1,343,285. When the voltage applied to wires40 is below the amount E1, no corona occurs and the current I is accordingly zero; As the voltage reaches'the amount E1, corona begins. As the rate of increase of corona current increases for each added increment of voltage, curve I25, I26, I21, I28 has an increasingly rising slope. By suitable adjustment (or selection of the circuit constants) of the apparatus illustrated in Figure 3, the magnitude of the voltage supplied between lines 38 and can be caused to be at or slightly above the voltage E1 on the curve shown in Figure 7 or at any selected point on the curve. If, due to an increase in line voltage applied between lines L1 and L2, there is a reflected-increase in the voltage between the ioniz ng wires 40 and plates M, the current drawn through resistor 99 and the condenser I00 (in parallel) increases as shown by 7 at nearly the same or at only a negligibly increased value, and consequently the voltage across the ionizing wires 40 and plates M (and also across the precipitating plates) is held at a value closely approximating the values existing before an increase occurred in the voltage across lines Li and L2. In this manner the ionization on the wires 40'may be closely controlled to a regulated amount such that deleterious formation of ozone and nitrogen oxides does not occur in the air or other gas circulated through the purification apparatus.

It will readily be observed that the oscillator tube 15 may be adjusted so as to permit an operation at any point along the curve I25 l28, and thus any degree of corona current, consistent with acceptable operation of the precipitator, may be permitted.

The secondary 93 may optionally be connected directly to line II4, as shown by line 93', rather than to junction I02 (which is in such case disconnected), and grid 19 is then connected through line 86' to junction I02 rather than. to

junction 65. These variations in the connections.

are illustrated in lines at 93' and 86' in Figure 3. If connections 86 and 93' are not used, Winding 33 is simply connected directly to junction I02, with favorable results as aforestated. Or, a tube having four grids may be used and the fourth grid connected to junction I02, the remaining grids being as illustrated. A four-grid tube is illustrated in Figure 3, hereinafter discussed. By this manner of connecting secondary 93 directly to line II4 (rather than through the resistor 99 and condenser I), the feed back voltages controlling oscillation of the tube are isolated from the control voltage bias across resistor 93-condenser I 00, which serve to maintain the output voltage at a closely regulated value.

In the apparatus of Figure 2, the full wave rectifier tube 5i, together with the condensers 63 and 61 serves as a voltage doubler circuit so that the apparatus may conveniently be powered from low voltage alternating current circuits such as 110-volt circuits. Ordinary oscillator tubes, such as the tube 15, have a working internal voltage drop such that the input voltage of the tube, for most eflicient operation; must be in excess of ordinary 110-volt supply line voltages. By utilizing the rectifier tube 5| and condensers 63 and 61, there is provided an exceptionally low weight apparatus for supplying the relatively high voltage between lines 82 and 96, which constitute the input of the oscillator tube.

The apparatus in Figure 2 is illustrated as utilizing an oscillator tube of the pentode type, but there may likewise be utilized an ordinary triode by dispensing with grids 19 and 80 and connections 85 and 86.

Referring to Figure 3, there is illustrated a somewhat modified form of power pack in which the osc llator and rectifier portions of the apparatus illustrated under the bracket I are the same as the corresponding portion of the apparatus illustrated in Figure 2. However, in the apparatus of Figure 3 two full Wave rectifiers generally designated I3I and I32 are illustrated, and these cooperate with a series of four con densers I33, I34, I and I36 to produce across lines 82 and 96 a voltage equal to four times the crest value of the alternating voltage on feeders L1 and L2, when the oscillator tube 15 is disconnected.

The full wave rectifier I3I includes a cathode I33 which is indirectly heated by filament I34 and a second cathode I35 indirectly heated by filament I36. Cathode I33 cooperates with anode I31, and cathode I35 cooperates with a similar anode I38. The full wave rectifier I32 is preferably identical with the rectifier I3I and includes a cathode I40 which is indirectly heated by filament MI, and a cathode I42 indirectly heated by filament I43. Cathode I40 cooperates with an anode I44, and cathode I42 cooperates with an anode I45. The rectifiers I3I and I32 and the condensers I29, I34, I35 and I36 are connected as follows: Feeder L1 is connected directly to one terminal of condenser I29, the other terminal of the condenser being connected through line I41 to one terminal of condenser I35. The opposite terminal of condenser I35 is connected through line I48 to anode I45 of rectifier tube I32. From junction I49 on line I41 there extends a line I50 leading to anode I38, cathode I33 being connected to junction I5I on line I50. Cathode I40 is similarly connected to junction I53 on line I40. Feeder L2 is connected directly to anode I31 of tube I 3I and to one terminal of condenser I33, the opposite terminal of condenser I33 being connected by line I55 to one terminal of condenser I34, the opposite terminal of which is connected by line I56 to junction I51, which constitutes one of the output voltage terminals of the voltage multiplier'portion of the apparatus. Junction I51 is connected directly to cathode I42 of the rectifier tube I32. Junction. I51 is connected to line 96 of the oscillator in a manner analogous to the connection of line 96 to junction 6| in Figure 2. Line 82 of the oscillator (Figure 3) is connected to junction I58 0n feeder L1, which constitutes another output terminal of the voltage multiplier. From junction I59 on line I55 a circuit I60 extends directly to cathode I35 of tube I3I and from junction I 6| on line I60 there extends circuit I62 leading to junction I63, which is connected to anode I44 and is also connected by line 86 to grid 19 of the oscillator tube 15. All of the filaments of full wave rectifier tubes I3I and I32, oscillator tube 15 and rectifier tube IIO are connected in series directly across feeders L1 and L2. Thus a circuit extends from junction I65 on feeder L2 (which corresponds to the similar junction II5 on line L2 in Figure 2), through line I66, filaments I34 and I36 of the tube I3I, thence through line I61 and filaments I 4| and I43 of tube I 32, through line II9, filament 11, oscillator tube 15, line I20, filament II2 of the half wave rectifier H0, through line I68, to junction I69 and thence through line 82 to junction I 58 on feeder L1.

When alternating current is applied to feeders L1 and Li, a unidirectional voltage will appear upon lines 82 and 96, the magnitude of the voltage being four times the crest value of the alternating current applied to feeders Ll and L2, when the oscillator tube 15 is disconnected and slightly less when the oscillator is connected. As a consequence tube 15 operates eificiently. At the same time it .will be observed that the apparatus for accomplishing the multiplication of the line voltage consists only of the full wave rectifier and four condensers, together with the necessary connections and these are extremely light in weight as compared with ordinary transformerrectifier construction.

The oscillator tube 15 of Figure 3 and rectifier tube H0, together with the transformer shown under bracket I30 of Figure 3, operate in exactly the same manner as that described above with reference to Figure 2 (and shown under the bracket I29). Therefore these parts of the apparatus of Figure 3 need not be further described in detail.

In the apparatus of Figure 3, as in that of Figure 2, the feed back and voltage regulation control voltages supplied to grid 18 may be separated and each applied separately to grids of tube 15. To accomplish this end, winding 93 is disconnected from junction I02 and is connected to line I88 as illustrated by the line 93", and a fourth grid 81 which is then used in such alternative form is connected to Junction I02 as shown by the line 86'. Also grid 19 may be disconnected from junction I83 and reconnected to junction I02, where it is desired to use a three-grid oscillator tube, as shown, rather than a four-grid tube. In this way the rise in output current in line 38 produces a biasing voltage which is applied to achieve regulation via grid 81 (or grid 19), whereas the feed back voltage maintaining oscillation is applied via grid 18. It will be understood that in Figure 3, when the changed connections illustrated by the lines 86' and 93' are not used, winding 93 is then connected directly to junction I02, and the feed back oscillation control voltage and also the output voltage regulation control voltages are accordingly combined and applied on the one grid, viz. grid 18.

The devices of Figures 2 and 3 are of exceptional utility wherein low weight and low cost are of importance in as much as sufiiciently high voltage for efiicient operation of electrostatic precipitators, viz. 3,000 to 50,000 volts, is conveniently supplied, and suillcient current is available without the use of the cumbersome apparatus customarily used. The transformer 80'is of low weight and indeed the entire apparatus of Figures 2 and 3 weighs only a few pounds and may be housed in a space from 2-3 inches wide, 4-6

inches long and 3-4 inches high. The apparatus. a

is accordingly admirably suited for portable electrostatic precipitator installations, and where low cost is a factor.

In Figure 4 there is illustrated an apparatus suitable for use where the power source is a low voltage direct current, for example an automobile battery of 6-12 volts. In the apparatus of Figure 4 there is utilized a vibrator, generally designated "I, of conventional design customarily used in automobile radio apparatus and includes vibrator magnet I13 and contacts I14 and I15 together with the main vibrator reed I12 and its cooperating contacts I16 and I11. Contacts I16 and I11 are connected by lines I18 and I19 respectively to the opposite terminals of a primary transformer winding I80 of transformer generally designated I8I. To a mid-point tap I82 on the transformer winding there is connected a condenser I83, the opposite terminal of which is connected to junction I84 and thence to the vibrator reed I12. Junction I84 is connected by line I85, namely, to the negative low voltage sup ply line I86 and the mid-point tap I82 of winding I80 is connected to positive line I 81. The positive voltage supply line I81 is connected by line I88 to one terminal of the vibrator magnet I13 of the vibrator assembly. Contacts I14 and I15 are in engagement when the vibrator I1I is deenergized, and when energized, the magnet I18 draws the magnetic reed I12 downwardly as illustrated in Figure 4, thus breaking contacts I14-I15. Reed I12 vibrates and alternately engages contacts I16 and I11 and as a result a pulsating direct current is applied alternately in opposite directions to the two halves of the primary winding I80 oi the transformer I8I. As a result a much higher voltage is induced in the secondary winding I88.

Mid-point I90 of the secondary winding I89 is connected by line I88 to junction I99 on the low voltage power supply line I86, and the end terminals of winding I89 are connected by lines I9I and I92 to the anodes I93 and I94, respectively, of the full wave rectifier generally desig nated I95. The full wave rectifier tube I85 is provided with a cathode I96 which is indirectly heated by the filament I91, the latter being directly connected across the low voltage leads of supply lines I81 and I86. The vibrator I1I, transformer I8I and rectifier tube I95, which are indicated generally under the bracket I98 serve as a high voltage direct current supply for the input of the oscillator 15, this supply being applied across conductors 86 and 96. A condenser 201 connected between junction 208 on line 96 and junction 209 on line I86 serves to smooth out ripples in the direct current supply of tube 15.

The high frequency oscillator 15, transformer 94 and rectifier IIO of the apparatus, shown generally under the bracket 200, are similar to those shown in Figures 2 and 3, suitable changes in the wiring being made to accommodate the low voltage supply source. Thus, the oscillator 15 is provided with an indirectly heated cathode 16 which is connected to one terminal of the heating filament 11, the filament being connected directly across the low voltage supply leads I86 and I81. The grid 80 is connected externally or internally of the tube by line 85' to the terminal of filament ll 11 which is in turn connected to line i86. One

terminal of the transformer primary winding BI is connected by line 91 directly to the anode 8| of the oscillator tube, the other terminal of the primary 9i being connected to line 96. The feed back secondary winding of the transformer is shown at 93, one terminal of such winding being connected through a grid bias resistor I04 and condenser I03 (in parallel) to the grid 18. The other terminal of the feed back winding is connected to junction I02 to which the common output line 38 is also connected. To the junction I02 there is connected (in parallel) the voltage regulator resistor 99 and condenser I00, the opposite terminals of these elements being connected by line to the cathode 16 and to the low voltage power supply line I86. If desired, the winding 93 may be connected directly to line I86 and a connection run from terminal I02 to grid 19, or a fourth grid, as explained with reference to Figures 2 and 3.

Th half wave rectifier tube is shown at N0, the cathode II I being connected to one terminal of the indirect heater filament II2, the latter being in turn connected directly to the low voltage supply lines I86 and I81. The anode II3 of the half wave rectifier is connected to tap I01 on the transformer secondary winding 92. Output line 36 constitutes one of the terminals of the unidirectional high voltage supply. From variable tap I2I on the winding 92 there extends line 45 which supplies the ionizing potential, namely a high voltage alternating potential having a frequency in the range from high audio frequencies, slightly below the low radio frequencies, and a unidirectional high voltage component.

Grid 19 of the oscillator tube is connected by line 86 to junction 202 which is in turn connected through a resistor 203 to junction 20I on line 88. A condenser 204 is connected between junction tube 15.

11 ,202 on line 86 and junction 205 on low voltage supplyline I86. I

Assuming that low voltage direct current is supplied to lines I86 and I81, the filaments of ,all of the thermionic tubes I95, I5 and H are ,iliuminated andthe tubes are in condition for operation. At the same time, the operation of .the automotive type radio vibrator I'II supplies .a pulsating direct current to the winding I80 and transformer I8I, and there is accordingly induced in winding I89 a relatively high voltage alternating current which is rectified by tube I95. Under such conditions of operation the oscillator tube I will oscillate through a circuit as follows: Beginning at low voltage supply line I86 current ,fiows from junction I99 to mid-point I90 on transformer secondary I89 and thence alternately through the upper and lower halves of the winding I89 and alternately to the anodes I 93 and I94, thence through the full wave rectifier tube I95 to cathode I96 and through line 96 to transformer primary 9|, line 91, anode 8I of the oscillator tube I5, cathode I6, through the lead of filament II to the low voltage supply line I86 and through the latter to junction I99. The oscillator tube I5 oscillates at a frequency from 5,000 to 30,000 cycles per second or somewhat higher as determined by the inductance and inherent capacitance of transformer 94 and the circuits associated therewith (or due to optional,

condenser I06 when used), whereby an oscillating current flows through the primary 9I. Through transformer action a high voltage range from 3,000 to 50,000 volts (according to the.de-

sign of the dust precipitator apparatus) is in-.

duced in winding 92. A relatively low voltage is induced in winding 93, and controls the oscillator The voltage induced in winding 92 is rectified by half wave rectifier III] as described with reference to Figure 3 and as a result, a high voltage direct current is supplied across leads 36 and 38, and a high'voltage direct current together with an alternating current component is supplied between leads 38 and 45. These leads are connected to correspondingly numbered leads of the precipitator apparatus illustrated in Figure 1 or a similar precipitator.

The voltage regulation of the high voltage output between lines 38 and 45 (and also between lines 38 and 36) is achieved by the action of resistor 99 and condenser I00 as described with reference to Figure 2. Therefore, a substantially constant high voltage is applied to the ionizing zone (wires 40 and plates 4|) and also on the precipitating zone (plates 2335) and is achieved regardless of voltage variations of the low voltage supply on lines I86 and I81.

In Figure 5 there is illustrated a modified form of the invention which is similar to that illustrated in Figure 4, except that the primary I8I of the transformer generally designated I8I is energized from a suitable source of alternating current illustrated by the alternating current lines L1 and L2, rather than being energized with pulsating direct current as illustrated in Figure 4. In Figure 5 the filament current supply is provided by transformer secondary 2I0, which is connected across the low voltage supply lines I86 and I8! which in this case are energized with alternating current rather than direct current. In all other respects the apparatus of Figure 5 is similar to that shown in Figure 4.

1 Referring again to Figure 7, the corona current curve I25-I28 is determined by the physical characteristics of the surface from which i2 corona is emitted, in this instance the round ion ization wires 40, and by the characteristics of the surrounding atmosphere, viz. atmosphericpressure, temperature, and humidity.

At this juncture it may be noted that corona varies very appreciably with respect to atmospheric pressure, a ten percent fall in the barometer reading being roughly equal in corona-producing effect to a ten percent increase in voltage on the corona-producing surface. As the corona increases roughly as the square of the applied voltage, very serious corona increase may accompany a fall in atmospheric pressure or rise in line voltage in any unregulated precipitation system. Likewise a 10% increase in voltage, whichis not at all unusual in secondary distribution systems, occasions a 50% increase in corona in an unregulated system. Where the apparatus is used for the purification of air for respiratory purposes, such an increase in corona causes a disagreeable and harmful increase in ozone and nitrogen oxides.

In Figure 7 there is illustrated a second curve 2 I 3-2 I4 displaced from curve I25i 28, illustrating the corona current of corona control wire 40' which is energized from the same supply source as that corresponding to the curve I25I 29. The only variation between wire and wire 40' is that the latter is somewhat larger in diameter and hence corona does not begin on wire 00' until voltage E2 is reached, and then it increases with increased voltage as shown by curve 243-?- 2I4. As a result corona does not occur for the wire 40' (curve 2I3-2I4) until the voltage has risen to a value of E2, at which time corona, in an amount corresponding to point I26, is present on wire 40 (corresponding to curve I25-I28). Precise regulation of the corona discharge of the wire 40 may be achieved by utilizing an apparatus such as that illustrated'in Figures 8 or 9 in which a second wire 40' is used for corona control regulation.

Referring to Figure 8, there is illustrated a portion of the wiring diagram of the apparatus shown in Figures 2, 3, 4 or 5, this portion being transformer 90 and the regulator portion of the circuits, namely resistor 99 and capacitor I00. In addition to Figure 8 there is schematically illustrated the electrostatic precipitator apparatus of Figure 1, wherein the precipitating plates 2335 are shown in uniformly spaced relationship, alternate plates being connected respectively to the common conductor 38 and to the high voltage direct current conductor 36. The precipitating apparatus also includes the working ionizing wire 40 together with its cooperating plates 4 I, the wire 40 being connected to the common conductor 38, and the plates 4| to the high voltage conductor 45 which supplies high voltage direct current having a high frequency alternating component. In addition in Figure 8 there is provided a control ionizing wire 40' together with cooperating, spaced plates 4 I In the normal dust precipitating system such as that illustrated in Patent 1,343,285, it is desired to operate the ionizing wire at a condition of slight corona formation such that the corona, produces the ionization sufiicient for dust precipitation, but not enough to render the dust-freed air objectionable for human respiration. Accordingly, wire 40 is operated as in Patent 1,343,285 at a voltage such as will produe a slight corona, the corona current begins, for example in the region I 26-I 21 of the curve shown in Figure 7. Wire 40 is of a size selected such that corona The ionizing current for the working ionizing wire 40 and plates 4| and the control ionizing wire and plates 40' and 4| are drawn in parallel through resistor 99 and capacitor I (Figure 8), and the electrical constants of these elements of the circuit are appropriately selected so as to permit oscillator tube 15 (Figures 2-5) to operate at a magnitude of oscillation sufficient to allow the voltage applied to wire 00 and plate 4| to rise to the value E2 when the total corona current drawn by wires 40 and 40' corresponds to point I20 (Figure 7). However, any increase in voltage occasioned by an increase in. voltage across lines L1 and L2 will cause wire 40' to begin to manifest corona at the zero point 2I3 on the curve 2I3--2I4. Accordingly, any rise in voltage beyond E: (Figure 7) will effect the regulating resistor 99 and capacitor I00, and will suppress any corresponding increase in value of the oscillating current flowing through oscillator tube I5. Thus, by utilizing the control ionizing wire 40' and its associated plates 4 I in parallel with working wire it is possible very sharply to control the ionizing voltage applied to the working ionizing wire 40, and by appropriate choice of size of the wire 40, it is thus possible to work at any established voltage E2 on both wires, In this way it is possible to allow a controlled degree of ionization on wire 40 without the hazard of undue ionization which would otherwise be occasioned by a rise in voltage on the supply lines L1 and L2.

Atmospheric changes such as variations in barometer, humidity and temperature, or variations in latent ionization such as cause an increase in ionization, serve automatically to achieve selfregulation. Any corona-increasing atmospheric disturbance in effect shifts both of the curves I25I28 and 2I3--2I4 to the left, parallel to their illustrated positions. Assuming the power supply voltage conditions to be constant, such a leftward shift has the effect of an increase in the applied voltage, and causes corona current to increase on wire 40 and to start on wire 40, the voltage regulation bias voltage across resistor 99 and condenser I00. immediately effects tube I5, and reduces the magnitude of the oscillations until the corona is again decreased. This functioning is characteristic not only of the apparatus of Figures 8 and 9, but also is characteristic, to a lesser degree, of the systems of Figures 2-5.

It will thus be observed that one may utilize the manifested function (corona current) as the direct agent for controlling the voltage of the power supply feeding the corona producing system. This is one of several very useful features of the invention.

In Figure 9 there is illustrated a modified form of regulating apparatus utilizing a working ionizing wire 00 and a control ionizing wire 40' of the type illustrated in Figure 8, except that the control ionizing wire is connected to a tap on resistor 99 so that the current drawn by the control ionizing wire 40' traverses the entire resistor '99 whereas the current drawn by the working ionizing wire traverses only portion 99a. By suitable choice of circuit constants of resistor 99 and condenser I00 and wire diameter of the control ionizing wire 40 and working ionizing wire 40, the system may be caused to operate in the voltage I20 (curve, Figure 7) due to the regulating action of the control ionizing wire. The portion 99a of resistor 99 may be very small, as compared with the whole of resistor 99, since the regulating effect is achieved by the ionizing current of wire 40' which is drawn through the entire resistor 99 (and condenser I00). However, should a flashover occur between the working ionizing wire 40 and its associated plates ll or between the alternately charged precipitating plates 23--35, the flash-over current is suflicient, when drawn through the relatively low value of resistor 99a to cause the oscillator tube to be biased to cutoff, thereby extinguishing the flash-over are. In this manner the large increase in current due to flash-over is utilized, through the relatively small portion 99a of the regulator resistor, to achieve an equal or greater regulatory effect than ordinarily occurs during working due to small increases of ionizing current for control wire 40', drawn through the whole of resistor 99 and condenser I00. Thus resistor 99a may be chosen of a size such that a current of flash-over proportions flowing therethrough is sufficient completely to block oscillation of tube I5, and thus simply interrupt the high voltage supply.

In the apparatus of Figures 8 and 9, the winding 93 may be alternatively, the connections to I02 may be broken and winding 93 connected to junction I02, or connected by the circuit 93' to the lead corresponding to line II4 of Figure 2, I68 of Figure 3 or 85 of Figures 4or 5. When so connected junction I02 is connected as by line 88' (Figure 3) to a fourth grid of the oscillator tube I5, or grid I9 may be utilized as the voltage regulation grid, rather than being connected to a constant voltage point of the power supply.

In any of the circuits heretofore described, the type of oscillator tube I5 should be chosen so as to be capable of regulation by the ionizing currents flowing in the apparatus. Alternatively, the voltage regulating potential which is available at junction I02 may be amplified through a simple single or multiple stage amplifier before being applied to the voltage regulating grid of the oscillator tube. Thus, using the. potential at junction I02 as the input to an amplifier, the output thereof may be applied conveniently to line 86'. Also'an adequately controlled small power unit,.as described above, may be used to drive a large power oscillator where large output is desired.

be housed in an air-filled tube 205, such as that shown in Figure 10, which is open to the atmosphere or separated therefrom by a screen, porous plate etc., as illustrated by the dotted line 290, for allowing ready change of pressure within the tube when the atmospheric pressure changes. Or the tube 265 may be sealed and provided with a sylphon bellows diaphragm 261 at an end or side wall so as to allow the pressure of the air within the tube to equalize to atmospheric pressure by fiexure of said bellows. For convenience, the tube is provided with a socket 268 which serves to carry the plate 4| and wire 40' by means of a squash 269. Wire 40 and plate ll are thus protected and are removed from the flow of gases undergoing precipitation and yet are subjected to the same atmospheric conditions as the air being precipitated.

Other and further modifications will be apparent to those skilled in the art without departing from the spirit of the invention illustrated, described and claimed.

15 What I claim is:

1. An electrostatic precipitator system comprising spaced precipitating plates, spaced ionizing electrodes adjacent the precipitating plates, and electrical means, adapted to be energized from a low voltage source for supplying a unidirectional high voltage to said precipitating plates and ionizing electrodes, and means responsive to variations in the'flow of ionizing current to said ionizing electrodes occurring at-voltages below those at which momentary or transient flash-over occurs for maintaining the ionizing current substantially constant.

2. An electrostatic precipitator system comprising spaced precipitating plates, an ionizing electrode adjacent the precipitating plates, and electrical means-including a low voltage oscillator, a step-up transformer and a rectifier for supplying a unidirectional high voltage to said precipitating plates and ionizing electrode, and means responsive to an increase in ionizing current output of said electrical means occurring at voltages below those at which momentary or transient flash-over occurs for biasing the oscillator to decrease the current output thereof.

3. An electrostatic precipitator system com prising spaced precipitating plates, an ionizing electrode adjacent the precipitating plates, and electrical means including a low voltage grid controlled oscillator tube, a step-up transformer and a rectifier for supplying a high voltage having a unidirectional component to said precipitating plates and ionizing electrode, and means, including a resistor connected in series with the circuit to said ionizing electrode and connected to said oscillator tube for decreasing the voltage of oscillator tube output when the current flowing to said ionizing electrode increases beyond a predetermined value.

4. The apparatus of claim 3 further characterized in that an amplifier is interposed between said resistor and the control grid of said oscillator tube for amplifying the potential of said resistor for application in controlling relation to said control grid.

5. An electrostatic precipitator system comprising spaced precipitating plates, an ionizing electrode adjacent the precipitating plates and electrical means adapted to be energized from a low voltage source for supplying a high voltage having a unidirectional component to said precipitating plates and ionizing electrode, said electrical means including a low voltage oscillator tube energized from the low voltage source and capable of oscillating at a frequency of 5,000 to 30,000 cycles per second, an iron core transformer having a low voltage primary winding connected to the oscillator tube and a high voltage secondary winding, a rectifier tube, said rectifier tube being connected in series with said secondary winding and to the precipitatng plates and ionizing electrode, and a resistor also connected in series with the circuit to said ionizing electrode and to the oscillator tube for maintaining the for limiting the voltage appiied to the precipitating plates and working ionizing electrode.

7. The apparatus of claim 6 further characterized in that the control ionizing electrode is housed in a separate chamber maintained under atmospheric pressure.

8. An electrostatic precipitator system comprising spaced precipitating plates, a working ionizing electrode capable of emitting a corona discharge at a predetermined desired voltage, a control ionizing electrode incapable of emitting a corona discharge at said predetermined voltage but capable of emitting such discharge at an increased voltage, means for supplying the same high voltage to said plates and ionizing electrodes, and means responsive to a flow of corona discharge current to the control ionizing surface for regulating the value of said high voltage.

9. An electrostatic precipitator system comprising spaced precipitating plates, a working ionizing wire and associated conductive surfaces constituting a working ionizing zone adjacent the precipitating plates, a control ionizing wire of slightly larger guage than the working ionizing wire and associated conductive surfaces adjacent thereto, means for supplying a high voltage to the spaced precipitating plates and ionizing wires, and means responsive to the flow of corona current to said control ionizing wire for regulating the voltage applied to both ionizing wires and the precipitating plates.

10. An electrostatic precipitator system comprising spaced precipitating plates, a working ionizing wire and associated conductive surfaces constituting a working ionizing zone adjacent the precipitating plates, a control ionizing wire of slightly'larger guage than the working ionizing wire and associated conductive surfaces adjacent thereto, means for supplying a high voltage to 40 the spaced precipitating plates and ionizing wires,

voltage output of said oscillator tube at a level and means responsive to the flow of corona current to said control ionizing wire for regulating the voltage applied to both ionizing wires, and responsive to the flow of arc-over current between said precipitating plates or between said working ionizing wire 'and its associated conductive surface for substantially reducing said voltage.

11. An electrostatic precipitator system comprising spaced precipitating plates, a working ionizing surface capable of emitting a corona discharge at a predetermined desired voltage, a control ionizing surface incapable of emitting a corona discharge at said predetermined voltage but capable of emitting such discharge at an increased voltage, means for supplying a high voltage to said plates and ionizing surfaces and resistor means in series with a conductor supplying current to said control ionizing surface and connected to said means for supplying high voltage for regulating the high voltage supplied to said plates and surfaces, for maintaining substantially constant said corona discharge from the working ionizing surface.

12. An electrostatic precipitator system comprising spaced precipitating plates, a working ionizing wire and associated conductive surfaces constituting a working ionizing zone adjacent the precipitating plates, a control ionizing wire of slightly larger guage than the working ionizing wire and associated conductive surfaces adjacent thereto, means for supplying a high voltage to the spaced precipitating plates and ionizing wires, resistor means connected in series relation with said control ionizing wire and connected to said 17 means for supplying high voltage for regulating the high voltage.

13. An electrostatic precipitator system comprising spaced precipitating plates, a working ionizing wire and associated conductive surfaces constituting a working ionizing zone adjacent the precipitating plates, a control ionizing wire of slightly larger guage than the working ionizing wire and associated conductive surfaces adjacent thereto, means for supplying high voltage to the spaced precipitating plates and ionizing wires comprising a relatively low voltage oscillator tube, a transformer having a low voltage primary and a high voltage secondary, a rectifier tube, the output of said oscillator tube being connected to said primary and the secondary being connected through said rectifier to the spaced precipitating plates and ionizing wires, and resistor means in series connection with said control ionizing wire and connected to said oscillating tube for regulating the voltage applied to the plates and ionizing wires.

14. An electrostatic precipitator system comprising spaced precipitating plates, a working ionizing wire and associated conductive surfaces constituting a working ionizing zone adjacent the precipitating plates, a control ionizing wire of slightly larger guage than the working ionizing wire and associated conductive surfaces adjacentthereto, means for supplying high voltage to the spaced precipitating plates and ionizing wires comprising a relatively low voltage oscillator tube, a transformer having a low voltage primary and a high voltage secondary, a rectifier tube, the output of said oscillator tube being connected to said primary and the secondary being connected through said rectifier to the spaced precipitating plates and ionizing wires, and resistor means in series connection with said control ionizing wire and connected to said oscillating tube for regulat-.

ing the voltage output applied to the plates and ionizing wires, a portion of said resistor means being connected in series relation to said working ionizing wire and precipitating plates for reducing the voltage output during fiashover.

MORRIS NEWMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,558,991 Lewers; Oct. 27, 1925 1,878,024 Strigel Sept. 20, 1932 1,946,563 Barrett Feb. 13, 1934 1,979,422 Tholstrup Nov. 6, 1934 2,000,654 Wintermute May 7, 1935 2,010,600 Levy Aug. 6, 1935 2,042,181 Knowles May 26, 1936 2,086,063 Brion et al. July 6, 1937 2,101,168 Deutsch Dec. 7, 1937 2,114,682 Gumaer Apr. 19, 1938 2,129,783 Penney Sept. 13, 1938 2,233,639 Pegg Mar. 4, 1941 2,251,451 Heinrich Aug. 5, 1941 2,297,740 Brown Oct. 6, 1942 2,297,841 MacKenzie Oct. 6, 1942 2,336,625 Milton Dec. 14, 1946 FOREIGN PATENTS Number Country Date 523,690 Germany Apr. 25, 1931 371,859 Great Britain Apr. 2, 1932 657,376 Germany Mar. 3, 1938 546,617 Great Britain July 22, 1942 OTHER REFERENCES Publication: Electrical PrecipitationTheory of the Removal of Suspended Matter from Fluids, by W. W. Strong; A.I.E.E., Feb. 19, 1915.

Certificate of Correction Patent No. 2,462,890. March 1, 1949.

MORRIS NEWMAN It is hereby certified that errors appear in the printed specification of the above numbered patent requirmg correction as follows:

Column 14, line 29, after the numeral 93 strike out connected to junction 102, or and insert the same before alternatively in line 28, same column;

and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Office,

Signed and sealed this 6th day of December, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,462,890. March 1, 1949. MORRIS NEWMAN It is hereby certified that errors appear in the printed specification of the above numbered patent requirmg correction as follows:

Column 14, line 29, after the numeral 93 strike out connected to junction 102, or and lnsert the same before alternatively 1n hne 28, same column;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office,

Signed and sealed this 6th day of December, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gommz'ssioner of Patents.

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