US2171242A - High-voltage generator - Google Patents

Description

Aug. 29, 1939. N. E. LINDENBLAD 2,171,242

' HIGH VOLTAGE GENERATOR Original Filed Au -9, 193s THIRD ION/ZER I an. wall/"#111114 INDUCTION i -44 \BRUSH SEcoNo 53 5 /ONIZER COLLECTOR 58 3 14 1 W0 20 14 l -o INVENTOR NILS E. LINDENBLAD ATTORN EY Patented Aug. 29, 1939 HIGH-VOLTAGE GENERATOR Nils E. Lindenblad, Port Jefferson, N. Y., assignor to Radio Corporation of America, a. corporation of Delaware Original application August 9, 1933, Serial No. 684,328. Divided and this application May 23, 1936, Serial No. 81,360

4 Claims. (Cl. 171-329) My present invention has as its main object the provision of methods and means for generating very high potentials or voltages at high energy levels.

In one way of carrying out my invention for the generation of high direct current voltages, I charge metallic units, preferably particles of metal, by actual conductive contact with a direct current source. Then, by moving the particles away from the source, the voltages of the charges thereon are increased, in a manner which shall be explained more fully hereinafter, and the charges are ultimately deposited upon a low volt age gradient-section of a charge-storing device or container.

This application is a division of application Ser.

' No. 684,328, filed August 9, 1933, by Nils E. Lindenblad, for improvements in high voltage generators,

In another arrangement for producing high voltages according to my present invention, an induction electrode, either grounded or preferably maintained at a high voltage, is insulatingly separated from a chargeable medium which may be a solid, a liquid or a gas, and by the use of a point discharge electrode system connected to a direct current source or preferably to ground, ionization or corona is caused to take place through and/or about the chargeable medium. The charged medium is then moved or carried to a low gradient area on a chargeable element the high voltage surface of which is brought up to an exceedingly high voltage by the continued deposits from the charged medium. In a further modification of my present invention both my contact and induction principles, about which more will be said later, are utilized.

A further and more specific object of my present invention is to provide systems which utilize my improved contact and induction principles for charging solid mediums such as belts and disks, for charging liquids such as oil and oil containing metallic particles in suspension and for charg ing gases.

In some instances, in carrying into effect the purposes of my present invention, rather high initial excitation voltages are required. If it is attempted to cascade alternating current transformers to build up a high alternating current voltage, which voltage may be used directly in some forms of my present invention, or if it is attempted to use the cascaded transformer system so that the high alternating current voltage developed may be rectified so as to obtain a high direct current voltage, it will be found that insulation difficulties in the final transformer stage will prove practically insurmountable. That is to say, if the core of the final transformer is grounded, the high voltage generated in the coils will require exceedingly heavy insulation,

and for all practical purposes it will be found almost impossible to provide the needed insulation. Accordingly, a further object of my present invention is to provide an improved cascaded system of transformers for developing an exceedingly high alternating current or direct current voltage in which the core of each stage will be subjected to no more than the voltage developed by any particular stage, rather than as explained before, be subject to the accumulated voltage up to the voltage of that stage.

My invention further contemplates in connection with the cascaded. transformer system, the rectification of the voltage of each stage. As it is desirable to make the voltage of each stage as high as possible, it will be found that ordinary tube rectifiers subjected to high alternating current voltages for rectification, will have their filaments subjected to high electrostatic stresses leading'to their rapid destruction. Consequently, a further object of my present invention is to provide an improved tube rectifier circuit.- For this purpose, I provide an arrangement wherein the cathodes or filaments are protected from subjection to high electrostatic forces by suitably connecting a protective grid about the cathode directly, or through a bias source, to the cathode.

This invention will be given in greater detail by the aid of the accompanying drawing which, however, is not to be considered in any way limitative of my present invention but is to be considered only illustrative. Turning to it:

Fig. 1 diagrammatically illustrates one form of my invention whereinmy improved belt system is cascaded with a plurality of disk arrangements for producing a high direct current voltage;

Fig. 2 is a cross-sectional diagrammatic view. of the belt exciter of Fig. 1;

Fig. 2a is a cross-sectional view of the schematic arrangement shown in Fig. 2 along the plane 3-3; while Fig. 3 illustrates a high voltage rectifier which may be utilized in place of the belt exciter unit of Fig. 1.

Fig. 4 illustrates'a cascaded disc arrangement having incorporated therein various features of my present invention for producing an exceedingly high direct current voltage.

Referring to Fig. 1, a motor 2, through shaft 4, drives a direct current high voltage generator 6 and pulley'8. The'pulley 8 in turn drives a belt Ill, I2 (see also Figs. 2 and 3) which at its other end rides within a collector I4 in the form of a metallic sphere or cylinder. The collector is suitably insulated from ground by means of an. insulating supporting I6. The pulley I8 within the shell I4 may be supported in any suitable way as for example by means of a bearing (not shown) fastened to the interior of the collector shell I4. As shown in Fig. 2a, the belt I0, I2 rides into the shell by virtue of elliptical or other smoothly curved orifices 14a and 14b.

The belt I6, I2 is preferably made of varnished silk. However, for use with my present invention, it is revarnished with a suitable varnish resinous or nitrocellulose compound, or similar substance such as an oven baking varnish, and when this layer of resinous material is almost dry, a metallic powder such as aluminum dust is rubbed into the surface which does not come into contact with the metallic pulleys 8, I8. The belt is then allowed to dry and another layer or coating of varnish is applied and the belt with the sandwich of varnish layers and metallic powder is thoroughly baked. The belt is then placed upon the two pulleys 8, I8 and driven by the motor 2. At a point where the belt straightens out leaving the pulley 8, a soft metallic brush 20 is allowed to drag over the metallized surface of the belt. After a little use the top coating of the varnish is worn through sufliciently to allow actual conductive contact of the 'softmetallic brush 20 and the metallic particlesinsulatingly supported upon the belt. These metallic particles or units then form one side or effective plates of a condenser and the metallic pulley 8 the other.

Now, with the generator 6 switched into action so as to apply a moderately high voltage, say 500 volts to the brush 20, the particles or units carried by the supporting member or belt III, I2 will be charged up as they contact with the metallic brush 26. As the belt straightens out and is moved away from the brush, the charged units (which have become charged by actual contact), because of their relative motion and increased distance. between themselves and their effective other condenser plate or electrode, namely, pulley 8, will have their capacities decreased. Because of this decrease in effective capacity, the voltage on the particles will rise to several thousand volts, If there are some particles which did not happen to get charged under the brush, they will receive' a charge through leakage from their contiguous charged brethren. As the particles or units move within the collector shell I4 and approach the discharge points 22 which preferably are not in direct contact with the outer surface of the belt, it will be found that the voltage on the metallic particles is sufficiently high to arc across the air gap between the metallic points 22 and the belt. This arcing is in the form of corona.- The various charges deposited on the internal low voltage gradient area of the collector shell then scamper to the outer surface of the collector shell I4 building up a large uni-directional potential thereon. The leakage throughout the length of the belt is too small to cause any drainage of the built-up charge on the collector.

The charge accumulated upon the outer surface of the collector shell I4 may then be utilized in any desired way. As shown in Fig. 1, I use the charge on the collector shell to excite the preferred form of my high voltage disk type of generator.

As shown in Fig. 1, the charge on the outer 'The surface 28 of the induction electrode 26 may be made fiat and parallel to the disk or it may be made elliptical, spherical, parabolic, hyperbolic, or may be made to curve in accordance with any law which will give small corona loss. Because of the high voltages developed on the induction electrode, and to prevent corona arc-over due to, among other things, ionization of the air between the induction electrode and the insulating disk 30 which, incidentally, may be made of a suitable material suchjas Micarta, a sheet of insulating material 32 is placed between the induction electrode 26 and the disk 3i].

On the opposite side of the disk 30 I place a charging electrode 34 having metallic discharge points '36. The charging electrode 34 or the brush ionization system 34, 36 is connected by to ground 46. As illustrated, the charging system faces a section of the disk 30 opposite the.

induction electrode 26 or opposite the projected area of the induction electrode upon the disk 30.

Assuming that the generator 6 has impressed a positive charge upon the particles riding upon the belt I0, I2, the outer surface of the collector shell I4 will become charged to a high positive potential. So also the induction electrode 26 will become at a high positive potential and will tend to attract to it charges from the charging system or brush ionization system 34, 36. The discharge from the points 36, however, cannot reach the induction electrode 26 because of the interposition of the disk 36, as a result of which negative charges settle upon the sectionof the disk 36 between the discharge points 36 and the induction electrode 26. Because of the preferably high insulating qualities of the disk 30, the charges do not leak or distribute themselves all over the surface of the disk but remain carried sult of which more and more ions will be drawn from the points 36 and settle on the disk.- Hence,

greater speeds of rotation will causea greater number of charges per unit of time to be de posited on the disk giving, as a consequence, a current fed into the second collector 46 proportional to the rotative speed of the disk 30. Therefore, an appreciable amount of current may be fed into the second collector 46 which is limited, in generaL'only by the rotative speed of disk 36. However, inasmuch as the second collector 46 is of opposite polarity to that of the induction electrode 26, there will be a very high voltage gradient between these two bodies which will on the smaller models with small diameter disks tend to cause undesirable loss in the form negative and of opposite polarity to the induction electrode 26 will tend to produce a neutralizing 1 action on the desired corona between the brush points 36 and the disk 30. These disad- -of corona. Moreover, the second electrode being vantages, however, can be avoided by making the disk 3|! of large diameter and secondly by shielding those elements from each other, by means of grounded metallic shields spaced from the second collector and also from the induction electrode. The part of the shield around shaft 42 would take the form of a cylinder about the same and suitably connected to the rest oi the shield and grounded and spaced from the various elements to prevent discharge to it.

.'As a further precaution, the induction electrode 26 may be made mounted within a glass envelope, the same being evacuated to a very high degree, or a double walled glass spacer may be used, the space between the walls being highly evacuated. The high vacuum will then afford exceedingly good insulation against undesired corona loss from the induction electrode.

At this point it may be well to point out that the polarity'assumed for the generator has been taken arbitrarily to impress a positive potential upon the metallic brush 20. If desired, the brush 20 may be connected to the negative terminal of the generator 6 in which case the polarities throughout the system would be reversed.

Als0,' in order to avoid the high potential gradient between the induction electrode 26 and the second collector 46, the induction electrode. 26 with the extra insulating sheet 32 and charging electrode 34 may be reversed in position so that the induction electrode is grounded and the charging electrode 34 is connected to shell [4. However, in this case there will not be an unlimited amount of ions produced upon the brush tips 36 since the output or charges placed upon the disk 30 will be limited by the charge delivered from the first collector shell I4. is so since the charge on the disk can only be derived from the discharging points 36 and as their source now will drop in potential due to actual discharge at points 36 the amount 01' charge which can be deposited upon the disk will be limited by the charge on collector shell l4. The faster the disk is rotated, the faster will collector 14 be drained and the lower will its voltage be. In the first mentioned connection, the faster the disk is rotated the faster is the deposit of charge at constant voltage since there is no drainage of the source.

"However, despite this, there is in the second 'case an appreciable gain in voltage due to the movement of the charges away from the char ing system and in addition, with a reversal of. the electrodes 26, 34 shown in Fig. 1, since the second collector 46 and the charging electrode or brush ionizer 34 are oithe same polarity, there will be no exceedingly high voltage gradient between the charging electrode and the collector, as aconsequence of which there will be no bad corona losses. Moreover, the neutralizing action adverted to will not take place. However, this reversal will not be necessary on a large machine where there is ample room for grounded metallic shieldsbetween the second collector and the induction electrode, as well as first collector l4.

Turning back now to the arrangement as illustr'ated in Fig. l, the negative charge on the U-s'haped, curved, second collector 48 is then conductively brought by means of tubular metallic pipe 43 to a second brush ionizer or charging electrode 50 carrying the metallic discharge points 52. On the opposite side or the charging electrode 5B is connected an induction electrode- 53 similar in structure to induction electrode 26 but grounded through- conductors 54, 54. Here This duction electrode and the second rotating disk 60, also of an insulating material of high tensile strength. As the disk 60 rotates, the negative charge on the second collector is deposited through the discharge points 52 thereon. Movement of the charge away from the electrode 50 causes it to increase in potential and the increased potential charge is deposited on a third collector 62 which picks up the charge by means of the metallic pickup points 64. In connection with the third collector system the charge de-- posited upon the disk is limited by the amount of energy fed into the second collector 46 since the induction electrode is connected to ground.

As in connection with the belt system, the disk may contain metallic particles by rubbing the same into the surfaces of the disk and then fixing them thereon by suitable insulating compounds With the metallic particles on the surfaces of the disk, the various brush points such as 35, 44 and 64 may, if desired, make actual contact with the particles carried by the disks as do the metallic hairs or filaments of the metallic brush 20 riding upon the belt l0, I2.

Charging of the belt system shown in Fig. 1 is not, however, limited to the contact method and means which I have described. On the other hand, the induction arrangement such as used for the disks 3!], Bi! of Fig. 1 may be applied equally as well to the belt.

It should be clear, in connection with Fig. 1, that additional collector stages may be cascaded to the third system. For example, an additional disk may be placed still further to' the left on shaft 42 and a brush ionizer system or an induction electrode such as 48, 50 connected to the third collector 62 to charge up the disk, a suitable induction electrode or brush ionizer being connected to the opposite side of the disk to ground, and so on. Moreover, while the system shown in Fig. 1 indicates various rotating elements or disks mounted on a common shaft, this is not at all necessary since the rotating e.e-

ments may be mounted independently arid, if de-;

supply source 18. The second transformer Iii is also connected to the power supply line 18 and applies the high voltage developed in the secondary across the cathode l4 and anode 32 of the rectifier. A condenser 84 may be connected between the anode and ground as shown in Fig. 3 to smooth out the potentials applied through conductor 10 to the induction electrode 26. It is to be clear also that if desired the conductor 10 and the rectifier system may be used to replace the generator 6 and supply suitable potential to the brush 20. As shown in Fig. 3, the conductor I0 will apply a negative potential to the induction electrode 26 it connected thereto, but which potential should be sufliciently high to cause corona between the brush tips 36 and the rotating disk 30. .On the other hand, if it is desired to'apply a positive potential to the induction electrode, the conductor Ill should be grounded and the conductor 86 of Fig. 8 connected to the induction electrode 2% or the brush 20, as the case may be, rather than as illustrated in Fig. 3 to ground- The grid is connected to the filament either directly as shown, or through suitable bias; the purpose of the grid in this special rectifier is to protect the filament from mechanical destruction by electrostatic forces.

I have already pointed out that it is not necessary, as shown in Fig. 1, to mount the disk systerms on a common shaft. As illustrated in Fig. 4 a plurality of shafts 86, 88, 90 driven by any suitable means (not shown) at the same or different speeds are provided. By means of an alternating current rectifier system 92,. the first induction electrode as is charged to a negative potential causing positive ions to be drawn from the charging electrode 96 upon the rotating disk 98. These positive ions in turn jump on to the first collector sec charging the same up to a high potential. The-charge on the first collector lfifi is then fed from charging electrode M2 to the second disk liid'which carries the charge over to the second collector Hi6 which, from what has gone on before, will be charged to a positive potential. The positive potential on the collector W6 is then fed by means of charging conductor )8 to a third disc ill! and thence to a third collector M2, the high positive voltage on which may be fed by means of a suitable conductor lid to any suitable utilization means. The back connection I is employed to reduce the potential difference between adjacent elements. It is natural that the output of one stage may be fed either to the induction electrode or to the brush ionizer of the next stage. When a sufficiently high voltage is reached in any stage and because of the high voltages involved, the charge will jump from charging electrode are, for example, to its cooperating disc i it, without requiring the presence of the induction electrode M8, hence, in the higher voltage stage the induction electrodes H6, H8, and the back connection 926 to previous stages will be found unnecessary as a consequence of which the insulating'sheets I22 may also bedispensed with although in connection with the first induction electrode 965 it is preferred that an insulating sheet 124 be provided. One idea being that, at the extra high potentials involved in this embodiment, there will be sufficient gradient around the brushes I92 and M8 to cause corona without the presence of an induction electrode.

As in connection with the belt, movement of the charged sections of the disk away from the induction and charging electrodes will cause, by virtue of the work done upon the disk, a rise in potential of the sections or, where the disks carry particles, a rise in potential on the charges of the particles. Consequently, the disk system also serves to increase voltage as well as, as shown in connection with, for example, the first disk system 30, 46, 34, 26 of Fig. 1, current or power.

While a collector system may have regions,

- such as the inside of a sphere or acylinder, where there is novoltage gradient present due to charge on'the outside of the system, there is always a field outside the system which must be traversed before the inside may be reached. A charge to be transported to the sphere must therefore traverse this field. The higher the potential of the; collector system becomes, due to accumulating charges, the greater will the expenditure of efforts to transfer an additional charge have to be.

A certain confusion in conception of this phenomena has been noticed at times. It has been noticed that the conception has at times arisen that since the gradient of the inside of a sphere is zero, it would be possible to connect a conductor from a source of moderate potential to the inside of a sphere and thus, since there is no gradient inside, the sphere could becharged up indefinitely in this way. This is of course erroneous; in fact, ridiculous-but why after all is this not possible? The answer is of course that though the gradient inside is zero, this zero space is elevated to the same potential asthe rest of the system and cannot be reached without going through the outside gradient of the system. Any charge in order to accomplish a journey towards the system must therefore have enough force behind it to move it forward. The work spent on a charge in this way is simply the elevation of its potential to such a value that it'can join the charges already in the system. In depositing a charge it is, therefore, really not necessary that itbe deposited inside the system. Due to inherent difficulties in most cases this is however advisable. A conveying system such as a belt or a disk has sections arriving at the same rate as it has sections leaving the collector system.

If for instance the collector system has the form of a pulley, the charges coming with a belt may very well be deposited directly on the outside of the same, but-it would also carry charge away from the same. This example can be applied in innumerable variations.

In connection with the rectifier shown in Fig. 3, a three-element tube may be used, in which case the grid and filament may be used as the rectifier elements and the plate left disconnected or floating. Or, the grid and plate may be connected together and used as a common cold electrode element. Preferably, as illustrated, the grid is connected to the filament whereby it shields and protects the filament from breakage due to electrostatic forces when very high potentials are applied across the plate and cathode.

Also, it has been pointed out that where the disks carry metallic particles substantially insulatedfrom each other, actual metallic contact maybe made with them'by means of the points or soft metallic hairs carried by the brush ionization or charging electrodes. However, even with the metallic particles carried by the disks, mew

that' the charge, while not leaking substantially over the surface of the disk will pass sometimes to quite an extent through it since the disk is relatively thin.

When using the rectifier for charging the induction electrode, the rectifier output should produce a voltage of, for example, 15,000 volts, or any voltage sumcient to produce the desired ionization from the charging electrode. When used to charge the belt, a more moderate voltage such as 500 volts may be applied to the charging brushalthough when using my induction apparatus to charge the belt, the exciting voltage should be highenough to cause ionization or corona.

Various changes will readily suggest themselves in carrying out the principles of my present invention. Thus,'for example,'in connection with the belt machines, a charging pulley and brush system can be placed at each end of the belt and the collector system half way between. In this way, the belt will be doubled in capacity. Accordingly, my present invention is not to be considered limited by the various illustrations given but on the other hand is to be given the full scope indicated in the appended claims.

-What is claimed is: 1. Apparatus for generating high voltages comprising an alternating current source, an electron discharge rectifier device having an anode grid and cathode, a transformer system connected to said alternating current source, at least one transformer of said system being connected to the grid of said electron discharge device, and at least one other transformer of said system being connected to the cathode of said electron discharge device, a chargeable medium, an induction electrode coupled to the anode of said rectifier device, an insulating medium separating the induction electrode from the charge-- able medium, a charging electrode for charging said chargeable medium under the influence of said induction electrode,-and means for discharging the charged medium into a utilization circuit.

2. Apparatus for generating high voltages comprising an alternating current source, an electron discharge rectifier device having an anode grid and cathode, a transformer system connected to said alternating current source, at least one transformer of said system being connected to the grid of said electron discharge device, and-at least one other transformer of said system being connected to the cathode of said electron discharge'device, and a condenser connected to the anode of said electron discharge device for smoothing out the rectified potential, a chargeable medium, an induction electrode coupled to the anode of said rectifier device, an

insulating medium separating the induction electrode from the chargeable medium, a charging electrode for charging said chargeable medium under the influence of said induction electrode,

and means for discharging the-charged medium into a utilization circuit.

3. Apparatus for generating high voltages comprising an alternating current source, an electron discharge rectifier device having an anode grid and cathode, a. transformer system connected to the input grid of said electron discharge device and said cathode, means connected to said transformer system whereby the filament of said rectifier is controlled by the grid of said electron discharge device, a chargeable medium, an induction electrode coupled to the anode of said rectifier device, an insulating medium separating the induction electrode from the chargeable, medium, a charging electrode for charging said chargeable medium under the influence of said induction electrode, and means for dischar ing the charged medium into a utilization circuit.

4. Apparatus for generating high voltages comprising an alternating current source, an electron discharge rectifier device having an anode, grid and cathode, a transformer system connected to said alternating current source and the grid of said electron discharge device and said cathode, a chargeable medium, an induction electrode, an insulating medium separating the induction electrode from the chargeable medium, a charging electrode for charging said chargeable medium under the influence of said induction electrode, the anode of said rectifier device coupled to said induction electrode, and means for discharging the charged medium into a utilization circuit.

NILS E. LINDENBLAD.

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