US3889138A

US3889138A - Electrostatic generator

Info

Publication number: US3889138A
Application number: US446954A
Authority: US
Inventors: William Douglas Allen; Michael Morris
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1971-10-28
Filing date: 1974-02-28
Publication date: 1975-06-10
Anticipated expiration: 1992-06-10

Abstract

An electrostatic generator comprises a pair of side by side disposed endless chains, each chain comprising metal pellets insulated from one another, with metal strips interconnecting the pellets of one chain with oppositely-disposed pellets of the other chain. Induction electrodes are provided for charging the pellets and strips as the chains are made to rotate together, and for transferring the charges to a high voltage terminal.

Description

United States Patent Allen et al. June 10, 1975 ELECTROSTATIC GENERATOR [75] Inventors: William Douglas Allen, Quirang [56] References C'ted Burcot, near Abingdon; Michael UNITED STATES PATENTS Morris, Fro both of England 3,048,720 8/1962 Cloud 310/5 Assigneez United Kingdom Atomic gy 3,469,118 9/1969 Herb et al 310/6 Authority London England Primary ExaminerDonovan F. Duggan [22] Filed: Feb- 28, 1974 Attorney, Agent, or Firm-Larson, Taylor & Hinds 21 Appl. No.2 446,954

[57] ABSTRACT Relted Apphcanon Data An electrostatic generator comprises a pair of side by [63] Commuauo of 2971838 Oct 16, 1972, side disposed endless chains, each chain comprising abandonedmetal pellets insulated from one another, with metal strips interconnecting the pellets of one chain with [30] Fore'gn Data oppositely-disposed pellets of the other chain.

Oct. 28, 1971 Umted Kmgdom 50287/71 Induction eectrodes are provided for g g the pellets and strips as the chains are made to rotate together, and for transferring the Charges to a g 58 Field of Search 310/5, 6, 7; 322/2; Mtage termmal' 317/2 5 4 Claims, 3 Drawing Figures PATENTEDJUN 1 0 I975 SHEET ELECTROSTATIC GENERATOR This is a continuation of application Ser. No. 297,838 filed Oct. I6, 1972, now abandoned.

This invention relates to electrostatic generators.

In the Van de Graff type of electrostatic generator electrical charges are conveyed to a high voltage terminal by way of a rapidly moving endless belt of insulating material. The charges are sprayed at earth potential from sharp corona points and collected at high potential from other corona points.

This arrangement has several disadvantages however. For example, the arrangement results in the formation of belt dust, the formation of corrosive products from the corona discharges and, in particular. it results in a tendency for surge propagation along the belt.

An improved method of conveying electrical charges to a high voltage terminal has been proposed by R. G. Herb et al. (See British Patent Specification No. 1,254,878 and corresponding US. Pat. No. 3,469,l l8 Here an endless chain of cylindrical metal pellets insulated from each other is provided. The chain is supported by and runs between a pair of electro conductive pulleys and the pellets of the chain are charged by induction. For example, that pulley remote from the high voltage terminal is maintained at earth potential and as each pellet is about to leave that pulley it enters a high voltage field imposed by an induction electrode adjacent the pulley and at a high negative voltage relative to it. This electrode induces a positive charge on the pellet, which charge is conveyed to the high voltage terminal via the other pulley and a discharge electrode adjacent thereto. The Herb et a1 method offers several advantages over Van de Graff-type generators. For example, the Herb et al method offers freedom from the effects of corona, from belt dust and, in particular, from surge breakdown, since the breakdown travels by way of the metal beads. However, its one significant limitation is that its current carrying capacity is limited to currents of approximately 100 micro amperes.

On the other hand, an electrostatic generator according to the present invention is believed to be capable of carrying currents which are substantially more than 100 micro amperes.

According to the present invention, an electrostatic generator comprises a high voltage terminal, a pair of side by side disposed endless chains with their bights rotatable about common axes, each of said chains being formed by a plurality of electrically conductive pellets insulated from each other, laterally disposed electrically conductive members interconnecting the pellets of one chain with the pellets of the other chain, means for rotating the chains, means for charging the pellets and the members as the chains rotate and means for transferring the charges to the high voltage terminal.

An embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, wherein:

FIG. 1 is a side view of an electrostatic generator,

FIG. 2 is a section, to an enlarged scale, taken on the lines I] ll of FIG. 1, and FIG. 3 is a side view of a modified form of generator.

With reference to FIGS. 1 and 2, a high voltage electrostatic generator 1 forming part of a particle accelerator comprises a high voltage terminal 2, and a pair of side by side disposed endless chains 3 with their bights rotatable about common axes provided by shafts 4, 5.

i on the other pulley 13 is pulled around by the lateral i Each chain 3 is formed by a plurality of electrically conductive pellets 6 insulated from each other by nylon links 7. Laterally disposed electrically conductive members 8 interconnect the pellets 6 of one chain 3 with the pellets of the other chain 3 by interconnecting oppositely facing pellets 6 of the chains 3. The chains 3 are rotated by an electrical drive unit 9. Charging means 10 are provided for charging the pellets 6 as the chains 3 rotate, and discharging means 11 are provided for transferring the charges to the high voltage terminal 2.

In further detail, the generator 1 is housed in a pressure vessel 12 filled with a high density insulating gas,

Each chain 3 is identical. The pellets 6 are of stainless steel and the lateral members 8 are of aluminium. The chains 3 are each supported by and run between grooved metal pulleys l3, 14. The electrical drive unit 9 rotates one ofthe pulleys l3 and the chain 3 mounted members 8. Thus one chain 3 drives the other.

The pellets 6 are of tubular form and the lateral members 8 comprise strips of aluminum. A pair of vertically spaced lateral members 8 interconnect each oppositely facing pair of pellets 6. ln plan view the chains 3 and the lateral members 8 therebetween have a ladder-like form.

The chains 3 and lateral members 8 run through apertures formed in a horizontally disposed insulator stack" 15 comprising glass insulator plates 16 sandwiched between metal shielding plates 17. The insulator stack 15 is used to support the high voltage terminal 2 within and to insulate it from the pressure vessel 12.

The charging means 10 comprise upper and lower induction electrodes 20, 21, disposed above and below the pairs of lateral members 8 and in close proximity to the pulleys 13. A power supply 22 is used to apply a negative voltage between the cooperating pairs of induction electrodes 20, 21 and the pulleys 13, which pulleys are earthed through their common shaft 4. The surfaces of the electrodes 20, 21 adjacent the pellets 6 and members 8 are made smooth so as to substantially eliminate sparking. Similarly, the surfaces of the pellets 6 and members 8 are rendered smooth.

The discharging means 11 comprises a pair of cooperating induction electrodes identical in form to the electrodes 20, 21 and these electrodes are also disposed in close proximity to the pulleys 5. The common shaft 5 of the pulleys 5 is electrically connected to the high voltage terminal 2 by a conductor 23 and the discharging means 11 is negatively charged, relative to the terminal 2.

The charging and discharging means 10, 11 are disposed so that the upper runs of the chains 3 pass between their cooperating electrodes. Similar cooperating pairs of electrodes, shown at 24 and 25, are disposed so that the lower runs of the chains 3 pass between them. The electrodes 24 are disposed in close proximity to the pulleys l3 and the electrodes 25 are disposed in close proximity to the pulleys 14. A power supply 26 is used to apply a positive voltage between the electrodes 24 and the pulleys 13. The electrodes 25 are positively charged, relative to the high voltage terminal 2.

One way of charging the means 11 negatively, and the electrodes 25 positively, both relative to the high voltage terminal 2, is disclosed in either of the aforementioned British Patent Specification No. 1,254,878

3 or corresponding US. Pat. No. 3,469,l l8 (Herb et al). (See particularly FIG. 8 of that specification).

In operation, the drive unit 9 is used to rotate the assembly of chains 3 and lateral members 8 around the pulleys l3, l4 and in the direction shown by the arrow adjacent pulley 13.

The charging means 10 serve to draw positive charges in a smooth manner into the pellets 6 and interconnecting lateral members 8 before they break contact with the pulleys 13. These charges are bound on the pellets 6 and members 8 before they break contact with the pulleys 13 so that there is no substantial sparking on termination of contact.

As the positively charged pellets 6 and members 8 enter the negatively charged discharging means 11 the former give up their charges which pass to the high voltage terminal 2, by way of the pulleys 14, where the charges accumulate on the surface of the terminal 2. Again, the arrangement is such that the charges flow smoothly from the pellets 6 and members 8, with no substantial sparking.

As the pellets 6 and members 8 leave the pulleys 14, negative charges are bound on them by means of the electrodes 25. They then move along to pass between the electrodes 24 where a positive voltage binds the negative charges on the pellets 6 and members 8 until after they contact the pulleys 13. Thus sparking is substantially eliminated.

The pellets 6 and members 8 then pass around the peripheries of the pulleys 13 to be recharged and the above-described cycle is repeated.

The invention is believed to provide an electrostatic generator of increased current-carrying capacity, which current can be measured in milliamperes, rather than I microamperes or so.

This is because the areas of the pellets 6 and lateral members 8 therebetween are considerably greater than the pellets per se. Thus, the current carrying capacity of generators according to the invention may be greater by a factor of at least compared with the capacity of generators using pellets only.

Furthermore, compared with arrangements using only endless chains of pellets and not lateral members therebetween as well, vibration in planes parallel to the axes of the pulleys is substantially reduced and vibration normal to the planes should be effectively damped by the dense insulating gas in the pressure vessel 12. In addition, as twisting of the chains 2 is substantially re duced, wear on the insulating links is reduced correspondingly.

FIG. 3 illustrates a modification, rather similar to socalled tandem accelerator systems, wherein double charging is employed.

In FIG. 3, the generator 1a uses first and second charging means 10a and 10b. The positive charges on the pellets 6 and lateral members 8 (the latter are not shown in this figure) are given up to a central high voltage terminal 2a, by way of pulleys 14a and conductors 23a. The terminal 2a is disposed between and is supported by insulator stack portions 15a, 15!). First and second discharging and sign-reversing means, identical to the electrodes 11, 25 ofFIG. l are not shown in FIG. 3 for the sake of clarity. However, it will be understood that such means are in fact disposed adjacent the pulleys 14a. 7

In FIG. 3, the bights of the chains 3 are supported by two pulleys 13, each of which is earthed. Thus in operation, the pellets 6 and lateral members 8 receive positive charges at the charging means 10 and these charges are then given up to the high voltage terminal 2a via the upper pulley 14a. The pellets 6 and lateral members 8 receive negative chargesas they leave the upper pulley 14a, which charges are bound on them by the electrodes 24b. They are then recharged positively by the charging means 10b.

They then give up their charges once again to the high voltage terminal 2a, but this time by way of the lower pulley 14a. As they leave this pulley they receive negative charges, which charges are bound on them by the electrodes 24a. The cycle is then repeated.

Thus, the current-carrying capacity of the generator la of FIG. 3 is twice that of the generator 1 of FIGS. 1 and 2.

We claim:

I. For electrically charging a high voltage terminal, the combination comprising a series of electrically conducting members of elongated form having smooth uncovered external surfaces, mechanical linkages interconnecting and electrically insulating adjacent members from one another thereby to arrange the members in substantially parallel side-by-side array in an endless chain, a charging station and discharging station of which at least the former comprises induction electrode means disposed on both sides of the elongated members, the discharging station being arranged for the transfer of charge from the members to the high voltage terminal, and means for driving the endless chain along a path of travel from the charging station to the discharging station.

2. The combination as claimed in claim I, wherein the mechanical linkages interconnecting adjacent elongated members comprise link means spaced apart transversely of the path of travel.

3. The combination as claimed in claim 2, wherein the link means comprises a laterally spaced pair of endless chain structures each of which is formed by a plurality of electrically conductive bodies connected to each other by links of insulating material, each said elongated member being attached to and extending between one electrically conductive body of one said chain structure and on oppositely disposed electrically conductive body of the other chain structure.

4. The combination as claimed in claim 3, provided with spaced pairs of pulleys, the said chain structures moving around the said spaced pairs of pulleys which are electrically conducting for carrying electrical charge to or from a said charging station or discharging station.

P511050 UNITED STATES PATENT OFFICE 569 CERTIFICATE OF CORRECTION Patent No. 3,889,138 Dated June 10, 1975 Inventor(s) ALLEN ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The Assignee appearing in the heading of the patent should be Science Research Council, State House, High Holborn, London Signed and Scaled this seventeenth D 3) Of February 1976 [SEAL] Attest:

RUTH- C. MASON C. MARSHALL DANN Al sllllg ()jfl've Commissioner of Parents and Trademarks P611050 UNITED STATES PATENT OFFICE 569 CERTIFICATE OF CORREC Patent No. 3'889'l38 Dated une 1 975 Inventor(s LEN ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The Assignee appearing in the heading of the patent should be Science Research Council, State House, High Holborn, London Signed and Sealed this seventeenth D3) of February 1976 [SEAL] Attest:

' RUTH c. M ssoN c. MARSHALL DANN Arresting Officer v Commissioner ufPatenls and Trademarks

Claims

1. For electrically charging a high voltage terminal, the combination comprising a series of electrically conducting members of elongated form having smooth uncovered external surfaces, mechanical linkages interconnecting and electrically insulating adjacent members from one another thereby to arrange the members in substantially parallel side-by-side array in an endless chain, a charging station and discharging station of which at least the former comprises induction electrode means disposed on both sides of the elongated members, the discharging station being arranged for the transfer of charge from the members to the high voltage terminal, and means for driving the endless chain along a path of travel from the charging station to the discharging station.

2. The combination as claimed in claim 1, wherein the mechanical linkages interconnecting adjacent elongated members comprise link means spaced apart transversely of the path of travel.