US3612918A

US3612918A - Electrostatic high-tension belt generator

Info

Publication number: US3612918A
Application number: US791374*A
Authority: US
Inventors: Kurt Willutzki
Original assignee: ITF INDUKTIVE TECH FORCHUNG GM
Current assignee: ITF INDUKTIVE TECH FORCHUNG GM; ITF INDUKTIVE TECHNISCHE FORCHUNG GmbH
Priority date: 1968-01-19
Filing date: 1969-01-15
Publication date: 1971-10-12
Anticipated expiration: 1988-10-12
Also published as: ES362647A1; GB1235214A; CH484552A; BE727008A; DK121564B; NO123435B; FR1598709A; JPS4811852B1; SE355906B; NL6900547A

Abstract

An endless running belt or insulating thread of an electrostatic high-tension belt generator forms a belt or insulating thread wall of plural parallel coils over a path between guide rollers and diverting rollers with respect to which opposite charging roller means and diffusion electrodes are provided. An insulating wall interconnects the guide rollers in an exchangeable construction unit and potential rings are formed of hard foam material having a metallic conductive cover particularly of a wrapping of aluminum foil. Annular plate-formed supports are engaged centrally by sparking distance spacer means and peripherally engage the potential rings like a clamp to avoid damage of potential ring surface in case of disturbance. A particle accelerator exemplified by a discharge tube is provided in passages with the generator and a tubular insulating lining means is provided in said passages to form rigid machine frame connecting elements between the generator socket and a removable high-tension electrode on opposite ends of an airtight liner having beaded edges and filled with pressurized gaseous medium of high dielectric strength.

Description

United States Patent [72] Inventor Kurt Willutzki Tubingen, Germany [21] Appl. No. 791,374

[22] Filed Jan. 15,1969

[45] Patented Oct. 12, 1971 [73] Assignee ITF lnduktive Technische Forchung Gmbl-l Dusseldorf, Germany [32] Priority Jan. 19, 1968 [33] Germany [54] ELECTROSTATIC HIGH-TENSION BELT GENERATOR 24 Claims, 7 Drawing Figs.

[52] US. Cl... 310/6 [51] Int. Cl H02n 1/12 [50] Field of Search 310/5, 6; 322/2 [5 6] References Cited UNITED STATES PATENTS 1,991,236 2/1935 Van De Graaff 310/5 3,028,685 4/1902 Silverman 310/6 3,024,407 3/1962 Bergan et al. 310/5 X 2,810,077 10/1957 Gale 250/93 2,697,793 12/1954 Trump et al. 310/5 2,858,460 10/1958 Wilson 310/5 3,256,450 6/1966 Gartner 310/5 X Primary ExaminerWarren E. Ray Assistant ExaminerB. A. Reynolds Att0rneyWalter Becker exchangeable construction unit and potential rings are formed of hard foam material having a metallic conductive cover particularly of a wrapping of aluminum foil. Annular plateformed supports are engaged centrally by sparking distance spacer means and peripherally engage the potential rings like a clamp to avoid damage of potential ring surface in case of disturbance. A particle accelerator exemplified by a discharge tube is provided in passages with the generator and a tubular insulating lining means is provided in said passages to form rigid machine frame connecting elements between the generator socket and a removable high-tension electrode on opposite ends of an airtight liner having beaded edges and filled with pressurized gaseous medium of high dielectric strength.

1 i 8 g k l m re i l g l E l l g m I Z: l l m g I m 1 I I g 3! I g m l g I m I r a m 1 l a?? PAIENTEnnm 12 zen 8,612,918

sum 1 OF 3 lnren/an Ku 27 WILL urzK/ ELECTROSTATIC HIGH-TENSION BELT GENERATOR The invention concerns an electrostatic belt generator according to Van de Graaff with an endless running belt which is being led between the electrode of a charging plant continuously loaded with the charging tension and which will transmit the charge hereby received to the generator electrode by corona discharge.

Electrostatic belt generators according to Van de Graaff are mainly used for research purposes in combination with a particle accelerator tube as source for electrons and ions of high energy as well as their secondary products like X-rays and neutrons. For commercial application, however, these appliances are not suitable for the following reasons:

The first disadvantage is the fact that the maximum current of wellknown belt generators is about some 100 yA, according to a power of only some 100 W., whereas an'appliance for commercial use with a tension of about 1.5 MV must yield a current of some mA, in order to be able to compete with already experienced installations Co- 60, which are, however, too expensive for most of the applications. Commercial applications are for example: Improvement and purifying of textile products by irradiation of textile fibers and fabrics, improvement of the mechanic properties .of chemical and technical products, sterilization of all medical lines and in the food industry, etc.

As on the electrostatic belt generators known previously, the belt had been kept nonpositively on the guide rollers; an enlargement of the generators power by extension of the belt increase of the belt running speed over a limit of 12 to 15 m./sec., is not possible regarding the running stability of the belt, the spreading of the electrical tension over the whole width of the belt and the belts tendency to flutter.

The object of the present invention is, therefore, to create an improved electrostatic high-voltage generator which can yield a considerably higher capacity at relatively little construction expense or cost.

In order to solve this problem, the present invention provides a charging transport means or carrier in the form of an unlimited belt or insulated thread which is conducted back from the running end of the guide roller as far as the running end with many coils placed side by side spaced apart a little distance, over two guide rollers which are situated axially parallel and correspondingly grooved, and over derivation or following rolls positioned beside the conducting roll.

The advantage of an endless belt or insulated thread which forms a thread surface or thread wall by means of its coils, is the fact that instead of a nonpositive conduction there is a clamping conduction applied so that the belt generator can run with a considerably higher speed.

Between the different parallel running belt or insulated thread parts there will automatically result a compensating tension. There can practically be also be no fluttering or vibration as the different belts or insulated threads have the tendency to have different vibrations which compensate ans damp each other over the air existing between them.

As a charging plant there is provided a charging roller touching the belt or thread wall and situated at the corresponding discharge electrode beside the guide roller lying on ground potential. The charging roller can be provided with an insulating coat and preferably has semicircular guide slots which correspond in their diameter to the belt or insulated thread thickness and the division of which corresponds to the division of the guide roller. It would be very favorable if the charging roller could be placed so near to the belt or thread wall that the wall will be deflected a small amount in an angle of contact of about 10 to A further characteristic of the invention is that the placement of the belts or threads or eventually several belt or thread arrangements connected in parallel with their guide rollers and the separating wall connecting and insulating the guide rollers form a closed and removable construction unit. By this means the generator having belt or thread failure can quickly be repaired by replacing the defective belt or thread arrangement by a new one which has been kept outside of the generator or eventually by a newly wound arrangement which has been covered just before being installed. Another object of this invention is the special construction of potential rings between the hightension'electrode and the generator socket lying on ground potential where one or more continuous shafts are'provided for the belt or thread arrangements and eventually for the receipt of the high-voltage consumer which operates with the generator. These potential rings preferably consist of hard plastic foam which iscovered by an aluminum foil. In order to journal the potential rings there are provided two bore holes which are aligned one with respect to another, where, from the two sides thereon, plate-formed supports consisting of conducting material are placed, the insides of which lying one on another are supported in the distance parts, and the edge parts of which surround or encompass the next potential ring edges like a clamp. If the clamplike parts of these supports extend above the surfaces of the potential rings, they form or provide between two adjacent potential rings, nominal spark distances which react in case of disturbance and protect the potential rings. Conceming the distance parts, one of them, which lies between two potential rings, can be developed as ohmic voltage divider.

In contrast to the previously known electrostatic belt generators which are mostly placed in a 15 to 25 atm.-pressure tank that is very inconvenient because of large mounting requirements and because of the difficult filling of the tank, the belt generator in this invention can work without such a pressure tank. It is however, advantageous inventively to place a hermetically sealed cover of plastic foil and spark-resistant material which surrounds the potential ring part between the generator socket and the high voltage electrode. This hennetically sealed cover is kept inflated with compressed air and this facilitates an enlargement of the surrounding space with gas of high dielectric strength.

Further details and characteristics of the invention are apparent from the following description and from the accompanying drawings, wherein a preferred embodiment of an electrostatic belt generator with particle accelerator tube is shown.

The drawings show:

FIG. 1 shows a partially sectioned diagrammatic side view of the electrostatic generator of the present invention;

F IG.'2 shows a diagrammatic perspective view of the belt or thread guide; 1

FIG. 3 shows a sectional fragmentary view through the charging planton an enlarged scale;

FIG. 4 shows a section taken along line lVlV of FIG. 3; FIG. 5 shows a partial sectional view through the high-voltage electrode and the potential rings placed under it, which is enlarged in relation to FIG. 1; FIG. 6 shows a section taken along line VIVI of FIG. 1 and "FIG. 7 shows a horizontal cross section through the belt generator'of this invention which is provided with a plurality of belt or thread arrangements.

The belt generator shown in FIG. 1 consists of a generator socket l carrying a plurality of potential rings 2, which will be described subsequently and which are closed at the upper end voltage electrode 3. The discharging tube 8, the electron optic means 9, the diffusion pump 10 and the target 11 constructed as a Lenard window, belong to this particle accelerator, which, however, is not the subject of this invention. In the belt or thread shaft 4 there is a belt or thread arrangement 12 as a closed and exchangeable construction unit, which is described further with reference to FIG. 2.

A well insulated, monofile, endless belt or insulating thread 13 of circular form and of high resistance to extension belongs to the belt or thread arrangement 12. The belt or thread can be made of polyamid or polyester, for example. The belt or thread 13 is guided in a plurality of parallel coils (FIG. 2 is only diagrammatic) over the guide rollers provided with circulation grooves. From the upper end of the guide roller 15 the belt or thread is led back over the

diverting rollers

16 and 17 as far as the running end of the guide roller 15. The two

guide rollers

14 and 15 are exactly parallel axially relative to each other and are connected to each other with their joumaling support by means of the separating wall 18 shown in FIG. 1, so that the collective construction unit itself shown in FIG. 2 can be readily interchanged. The possibility of exchanging the belt or thread arrangement 12 and the particle accelerator 7 can be facilitated by the fact that the high-voltage electrode 3 can be revolved.

Concerning the belt or thread arrangement 12, the parallel or adjoining wires form a belt or thread wall which is movable analogous with a belt over the two

guide rollers

14 and 15, where, however, the different belt or thread coils are closely led through the guide grooves. A smooth running of the belts or threads is guaranteed, even at very high speeds, for the following reason: The single belts or thread dependent upon mass and prestress is a structure capable of vibration. By the air gap existing therebetween, each belt or thread is closely coupled with the adjoining belts or threads which always have different self-vibration and damp the other belts or threads.

ln order to energize the belt or thread arrangement 12, the electromotor 19 is provided and placed in the generator socket 1; the electromotor 19, for example, can have a capacity of 4 kw, at a nominal r.p.m. of 2,850.

This electromotor 19 is connected with the lower guide roller means 14 by means of a tooth belt transmission 20. The energizing of the belt or thread wall in the region of the lower guide roller 14 will be executed by a charging roller 21 which is placed axially parallel to the guide roller 14 in the vicinity of this roller, and which is preferably shifted against the belt or thread wall, so that this wall will extend a small amount according to the closing angle of from to 20. At the opposite side of this charging roller 21 there is a diffusion electrode 22.

In corresponding manner, there can also be placed a charging roller 21' working with opposite polarity with a diffusion electrode 22, adjoining the upper guide roller 15, so the starting capacity of the generator can be increased by about 50 percent-as the tests have shown. Details of this charging unit can be taken from FIGS. 3 and 4.

Whereas the belt or thread guide rollers 14 and consist entirely of metal, the charging roller 21 charged with the charging tension is provided with an insulating cover 23, the dielectric constant of which must, if possible, approach that of the belt or thread material. This cover 23 is also provided with running grooves, the profile of which corresponds to the half belt or thread cross section. It is to be understood that the division of the grooves of the charging roller 21 corresponds to the division of the grooves of the

guide rollers

14 and 15. If a charging tension is applied between the metal core of the charging roller 21 and the diffusion electrode 22, the gas which has been ionized by the diffusion electrode 22 and which is now conducting, and the metal core of the charging roller 23 form the components of a condenser, the dielectric parts of which are the insulating cover 23 and the belt or thread 13. The condenser will now be charged according to the magnitude of the potential and the intermediate dielectric strength. The belt or thread 13 running thereover picks up the portion of the condenser charge according to its volume. The experiences have shown that at a sufi'lcient diffusion tension, this portion of the condenser charge is greater than the charging density given by which amounts to 8 CGS units/cm.*=22.5 pa.sec./m..

When taking from the charging roller 21, the surplus charge sputters or disperses from the belt or thread wall into the surrounding region which transports then its maximal charge to the high-voltage electrode 3, wherein contrary to the usual belt generator-both sides of the belt or thread wall are charged. At a belt or thread wall breadth of 0.7 m. and at a speed of 40 m./sec. which is absolutely possible, the theoretic limit of the current is 0.7X2X40X22.5=l,260 uA.=l.26 m/A.

Practically attainable is about 0.7 of this theoretical limit that is 1.26X0.7=0.88 m/A. This value applies only for the simple charge.

If as shown'in FIG. 1, the transversed belt or thread wall is also charged with opposite polarity this value will be increased by about 50 percent to 1.3 m/A. At a starting potential of 1.5 MV, a belt generator with the above-mentioned dimension has a power of l.5Xl0Xl.3 l0=l.95 X103 W, that is nearly 2 kw. According to FIG 7, it is absolutely possible to equip a generator with a plurality of belt or thread arrangements 12 (eventually together with a common particle accelerator 7), and the above-mentioned power can be multiplied by the number of its belt or thread arrangements.

The belt or thread 13 which consists of organic material, is mechanically and chemically highly stressed by the ionized atmosphere, so that it must be exchanged at certain periods of time. This can easily be done with very little expense in cost and time, according to the above-mentioned construction.

As the generator according to this invention and as before mentioned can easily attain a considerable power, it does not require a special pressure vessel, as by an increase of the pressure up to from 15 to 25 atm, the generator voltage increases only by 2 to 2.5. The open construction of this invention is therefore more inexpensive because the linear dimensions of the generator increase proportionally to the tension and because in this case a light construction is possible.

The boundary voltage of the generator is determined by the radius of curvature of the high-voltage electrode 3 which must amount to 0.6 to 0.7 m. approximately at 1.5 MW, and otherwise by the field relations between the high-voltage electrode 3 and the generator socket 1 lying on ground potential. It would be suitable if the space between the two electrodes of the generator would be divided into a certain number of identical potential steps or stages where the tension stages are formed by means of guiding bodies, the previously mentioned potential rings 2. The voltage drop between the potential rings 2 is defined by interconnected ohmic potential dividers which are not described in detail and which can be realized in each of plural spacer parts.

It has proved advantageous to take potential rings 2 of a strength and mutual spacing of 20 mm. These dimensions make it possible to build an inexpensive lightweight construction and an increase of voltage from ring to ring of 30 kv. which can easily be controlled. This voltage drop of 30 kv./40 mm. ring distance, is as shown by experience in a more favorable proportion to the voltage stability of the belt or thread wall surface.

As it is shown in FIG, 5, the potentialrings 2 consist of hard plastic foam plates with edges according to the Rogowski profile, in order to equalize the field line distribution. The potential rings 2 are at each side covered by an aluminum foil. in the potential rings 2 there are breaks for the previously mentioned quadrilateral belt or thread shaft 4, as well as for the cylindrical shaft 5, for the discharging tube 8 and for the borings 24 for seating the supports 25. As shown in FIG. 5, these supports have the form of plates and the flat inner parts 26 line one on the other and the annular toruslike outer edge part 27 surround the adjoining edges of the potential rings 2 like a clamp. Between these outer parts 27, the potential rings have a decreased spacing, so that required are or sparking distances occur which in case of disturbance avoid damage of the potential ring surface and which indicate a possible loss of one voltage divider stage by the sparking distance, maintained by spacer means 28.

The considerable mechanical stress of the high-voltage electrode 3 forms in addition to the unavoidable remaining unbalance of the upper guide rollers, a belt or thread tension which can amount to 1,000 kg. approximately at a roller length of 70 cm. This belt or thread tension or pull is taken by the wire shaft 4 and shafts 5 for the discharging tube which are preferably equipped with a strengthened insulating cover 29. The two mentioned shafts are, as shown in FIG. 5, reinforced at their ends with the generator socket 1, as well as screwed in with the high-voltage electrode flat sheet 30.

As construction material for the shaft lining 29, acrylic resin has proved advantageous as this material possesses sufficient mechanical properties and can easily be finished, and furthermore has high resistance therethrough and, in this case, a very important high surface resistance.

Since open generators are very sensitive to dust at high voltages, it is necessary to operate the construction parts, which are charged with voltage, especially the charging transport belt or thread 13, and a potential rings 2, in a separate, climatized (air-conditioned) atmosphere. For this purpose, as shown in FIGS. 1 and 5, there is provided a foil lining 31 which is cylindrical in its middle and annular toruslike in form at its upper edge parts (and likewise in the lower parts also). The lower part of the foil lining 13 is hermetically connected in airtight relationship with the generator socket 1, whereas the upper annular toruslike part is kept between the correspondingly profiled high-voltage electrode flat sheet 30 and the high-voltage electrode semicircle. The profiling of the clamping parts and the construction of these clamping parts which are provided with a Rogowski profile, avoid the settling of sliding discharges on the foil cover 31.

The volume enclosed by the foil cover 31, the high voltage electrode 3 and the caselike generator socket, can be filled by a blower or fan motor with dust free filtered air. If necessary, this air can be dried and, in order to increase the dielectric strength, there can be added suitable gas like C Cl C CI F or S F What I claim is:

1. An electrostatic high-tension belt generator with an endless running belt which is fed between an electrode of a charging plant continuously loaded with the charging tension and which also transmits the charge hereby received to the generator electrode by corona discharge, comprising: an endless insulating thread provided for charge transmission and including a plurality of parallel coils, a pair of axially parallel guide rollers associated with said generator and grooved correspondingly to circulate said thread coils, and diverting roller means adjoining said guide rollers from the running off end of which there is return of said insulating thread onto said roller means.

2. A generator according to claim 1, in which a charging roller serves as a loading device for an insulating thread wall formed of insulating thread coils engaging said charging roller, and a diffusion electrode associated with said charging roller and located axially parallel adjoining at least one grounded guide roller.

3. A generator according to claim 2, in which an insulating material cover is provided additionally on said charging roller.

4. A generator according to claim 2, in which semicircular guide slots are provided on said charging roller and correspond to the thread strength and coincide divisionally with division of said guide rollers.

5. A generator according to claim 2, in which said charging roller is adjustable in a direction perpendicular to said insulating thread wall.

6. A generator according to claim 2, in which said charging roller is advanced against said insulating thread wall deflected by a small amount corresponding to a coil angle of from to 20.

7. A generator according to claim 6, in which said diffusion electrode particularly lies across from approximately the middle of the insulating thread coil surrounded portion of said charging roller.

8. A generator according to claim 2, in which an opposite polarity charging roller and corresponding diffusion electrode additionally exist collectively in scope of high-tension potential of one guide roller.

9. A generator according to claim 1, in which there are several parallel connected insulating thread arrangements.

10. A generator according to claim 1, in which an insulating separating wall interconnects said guide rollers for insulating thread arrangement inclusive as an exchangeable construction unit.

11. A generator according to claim 1, in which between a high-tension electrode and grounded generator socket, there are plural disc-shaped potential rings having at least one through passage for receiving the insulating thread arrangement and high-resistance potential divider means connected in alignment with said potential rings.

12. A generator according to claim 11, in which a particle accelerator exemplified by a discharge tube is provided in an additional through passage for generator driven receipt thereof.

13. A generator according to claim 12, in which tubular insulating lining means provided in said passages form rigid machine frame connecting elements between said generator socket and said high-tension electrode.

14. A generator according to claim 11, in which said potential rings consist of hard foam material having a metallic con ductive cover particularly of a wrapping of aluminum foil.

15. A generator according to claim 11, in which edges of said potential rings corresponding to equalization of field line distribution are provided with a Rogowski profile.

16. A generator according to claim 1 l, in which plate-forming supports of conductive material having bores directed toward each other on both sides of said potential rings, and spacer means centrally between said supports of adjoining potential rings, said supports peripherally clamping adjoining potential ring edges.

17. A generator according to claim 16, in which said supports in peripherally clamping upper surfaces of said potential rings thereby form a preset sparking distance between two adjoining potential rings in case of disturbance.

18. A generator according to claim 16, in which said spacer means each is formed as an ohmic potential divider between two said potential rings.

19. A generator according to claim 11, in which an airtight liner is provided between said generator socket and said hightension electrode, said liner enclosing said potential rings with a slide dischargeproof synthetic spark-resistant material foil.

20. A generator according to claim 19, in which both upper and lower edge portions of said foil liner are formed as annular beading.

21. A generator according to claim 20, in which said upper edging of said foil liner is restrained between two Rogowski profile formed edges of said high-tension electrodes.

22. A generator according to claim 19, in which a pressurized gaseous source is connected to space enclosed by said foil liner.

23. A generator according to claim 19, in which space enclosed by said foil liner is hermetically sealed and enriched with an inflating gas of high dielectric strength.

24. A generator according to claim 11, in which said hightension electrode is removable.

Claims

6. A generator according to claim 2, in which said charging roller is advanced against said insulating thread wall deflected by a small amount corresponding to a coil angle of from 10* to 20*.

14. A generator according to claim 11, in which said potential rings consist of hard foam material having a metallic conductive cover particularly of a wrapping of aluminum foil.

16. A generator according to claim 11, in which plate-forming supports of conductive material having bores directed toward each other on both sides of said potential rings, and spacer means centrally between said supports of adjoining potential rings, said supports peripherally clamping adjoining potential ring edges.

19. A generator according to claim 11, in which an airtight liner is provided between said generator socket and said high-tension electrode, said liner enclosing said potential rings with a slide dischargeproof synthetic spark-resistant material foil.

24. A generator according to claim 11, in which said high-tension electrode is removable.