US3628090A

US3628090A - Static discharge apparatus

Info

Publication number: US3628090A
Application number: US25155A
Authority: US
Inventors: William K Mclain
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-04-02
Filing date: 1970-04-02
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14

Abstract

Apparatus to discharge static electrical charges on the body of an aircraft, having an extended discharge range. Both a lowpotential discharge path and a parallel high-potential discharge path are provided for discharge of accumulated static charge.

Description

United States Patent [72] Inventor William K. McLaln Orange, Calif.

[21] Appl. No. 25,155

[22] Filed Apr. 2, 1970 [45] Patented Dec. 14, 1971 [73] Assignee Alice Richmond McLaln Orange County, Calif.

[54] STATIC DISCHARGE APPARATUS 4 Claims, 3 Drawing Figs.

[52] U.S.Cl 317/2 E, 174/4 R [51] Int. Cl v; B64d 45/02 [50] Field of Search 317/2 R, 2

E; 217/2 E; 174/3, 4 R; 343/899 [56] References Cited UNITED STATES PATENTS 2,933,732 4/1960 Tanner 343/899 3,106,663 10/1963 Tanner... 317/2E 3,131,391 4/1964 Boswell et al. 343/899 3,528,629 9/1970 Cooper 317/2 E 3,034,020 5/1962 Benkoczy et al.. 317/2 E 3,170,087 2/1965 Tanner et al 317/2 E Primary Examiner-L. T. Hix

Atlorneys'George .I. Netter and Kendrick and Subkow ABSTRACT: Apparatus to discharge static electrical charges on the body of an aircraft, having an extended discharge range. Both a low-potential discharge path and a parallel highpotential discharge path are provided for discharge of accumulated static charge.

The present invention relates generally to static discharge apparatus, and, more particularly, to such static discharge apparatus having an extended discharge range without deleteri-' ous effects on the apparatus.

An ever present problem with aircraft is the accumulation of static electric charge on the aircraft during flight, which charge can, if not dissipated otherwise, discharge suddenly in the form of lightning and destroy a part of the craft. Even'if charge dissipation means are adopted to prevent such lightning damage, they can create an undesirably large amount of radio noise, interfering with communications systems of the aircraft.

In the past static charge removal has been conventionally accomplished by using low-potential discharge electrodes having sharp or pointed ends which ionize the adjacent air to produce a charge dissipation path. However, in removing charge by such electrodes, high fronts are developed and radio communications arefrequently impaired. For this reason, an alternate approach in the past has been to construct static dischargers of brushlike electrodes consisting of a plurality of small filamentlike elements which effect discharge of lower levels of accumulated charge, thereby preventing accumulation of charge to that state at which its discharge would either be deleterious to the aircraft or interfere with radio communication. The brush electrodes, however, although excellent for low-charge, ranges (i.e., 25 kilovolts or under), can be destroyed or substantially impaired very quickly if a higher magnitude of charge is developed on the aircraft.

SUMMARY OF THE INVENTION In accordance with the practice of this invention, there is provided a rodlike, low-resistance element, one end of which is connected to an external part of the aircraft and its outer end terminates in a spherical electrode of predetermined dimensions. Spaced from the spherical electrode there is provided a brushlike electrode affixed to the rodlike element the brush element parts of which are arranged in surrounding relationship to the rodlike element. Thedimensions and spacing of the spherical electrode and the brush electrode are such that the brush electrode will afford dissipation of lower-charge ranges of accumulation, whereas on high-charge accumulation, dissipation will be effected via the spherical electrode, thereby preventing damage to the brush electrode.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the static discharger of the present invention.

can be considered as having zero resistance. Similarly, the ball electrode 12 afiixed to the end of the rod 11 is constructed of a low-resistance metal. In a practical construction of the invention, the rod 11 was approximately 5 inches in length and FIG. 2 is a longitudinal sectional view of the static discharger of FIG. I, taken along the line 2-2 of FIG. 1.

FIG. 3 depicts the static discharger in disassembly.

DESCRIPTION OF A PREFERRED EMBODIMENT Turning now to the drawings and particularly FIG. 1, the static discharger device of the present invention is identified generally by the reference numeral 10 and is seen to include a rodlike element 11 terminating at its outer end in a spherical ball electrode 12, the other end of which is received within a mounting means 13 to be afiixed to the aircraft. The rod 11 and spherical electrode 12 generally comprise the high-voltage discharge member, that is, the means by which accumulated charge on the aircraft in excess of approximately 25 kilovolts is dissipated.

Additionally, a brushlike low-voltage electrode means 14 is affixed to the member 11 at a point spaced from the spherical electrode 12 with the brushes flaring outwardly toward the ball end.

As to details of construction, the rod 11 consists of a good conductive metal such that its total resistance measured from one end to the other is very low, and, for all practical purposes had a diameter of about 0.050 inches. The spherical electrode 12, affixed to the outer end of the rod 11, had a diameter of approximately 0.250 inches. The relative dimensions specified for the members 1 l and 12 are important in that the discharge effect to be achieved via the rod 11 and the electrode 12 into the surrounding air is for relatively high levels of static charge accumulated on the aircraft, i.e., in excess of approximately 25 kilovolts. If the ball member 12, for example, has a substantially smaller diameter, it will tend to discharge lower levels of accumulated charge, thereby making it inherently subject to damage in the event that it would have to dissipate a much higher level of voltage. ON the other hand, if the diameter of the ball 12 is made substantially larger, although it will then easily accommodate discharges of higher-levelvoltages, this will permit an undue accumulation of high voltage on the aircraft which could discharge via the low-voltage electrode means to be described later herein and damage it.

More particularly, the potential difference at which corona will developor discharge of an accumulated charge on a conductor to, say, a surrounding air environment, is directly related to the surface condition of the conductor. That is, wherever a sharp point or edge exists, corona and its discharge will take place at a relatively low potential, whereas for very smooth flat or slightly curved surfaces, the charge potential necessary to achieve corona is much higher. For example, in the specific embodiment given above for a 0.250 metal sphere, breakdown to achieve discharge requires approximately 25 kilovolts. Also, the materials used are important in that the work function of the material determines the number of electrons that can be provided by the material for producing corona.

The low-voltage discharge electrode 14 includes a connecting collar 15 affixed onto the rod 11 at a point spaced inwardly of the ball electrode 12. A plurality of flexible conductive brushes I6,one end of each being secured in the collar and the other end extending toward the ball electrode; as depicted in FIGS. -1 and 2, the brushes l6 flare outwardly in a cone, which is the shape they will assume during charge dissipation due to mutual repulsion of the like charges carried by the brushes. However, when in an uncharged condition the flexible brushes will tend to be relaxed and extend randomly about the rod 11.

The holder or attachment means 13, as shown best in FIG. 3, comprises a pair of cast body halves l7 and I8 with as included slot 19, into which the rod II is fittingly received when assembled. Although other materials may be found satisfactory, best results to date have been obtained by constructing the body halves l7 and 18 from plastic and plating the outer surfaces of the halves with a good conductor such as nickel or gold, for example.

As seen best in FIG. 2, the end of the rod 11, received I within slots 19 of the body halves l7 and 18, is slightly enlarged as at 20. Moreover, the slots 19 include a quantity 21 of an epoxy material, for example, filled with a conductive powder such as silver. The material 21 not only serves to anchor the rod within the slots 19, but also insures good electrical contact between the rod 11, the plating of the body halves l7 and 18, and the aircraft. The means 13 may be connected to the aircraft by any conventional technique, a threaded member 22 being illustrated as exemplary of but one such means. I claim: 1. Apparatus for discharging static electric charge from a body into a gaseous environment, comprising:

a metal rod; electrically conductive means connecting one end of the rod to the body and disposing the other rod end in the gaseous environment; a smooth surfaced metal ball affixed to the other rod end;

and

a plurality of metallic filament means, each having one end mounting means providing a low-ohmic connection electrically connected to the rod inwardly of the ball and I between said wing and said rod; extending away from aid rod to terminate in the atan electrode connected to the other end of said rod having a mosphere. smooth curved outer surface; and 2. Apparatus as in claim 1. in which metallic collar means 5 a p ity of elongated elements. h h ing ne en are received onto said r d d fi' d thereto at a point physically and electrically connected to said rod and the spaced inwardly of the metal ball, said metallic filament means Othef end "8 Pointed and extending y from Said being secured to said collar means. Int he an:-

3. A static electric charge discharger for attachment to the A Stat": deem: charge dlschal'ger as clalm which wing f aifcrafl'comprisingz 10 the mounting means includes a pair of parts that are fitted a l i together about the rod end, the surfaces of said parts being mounting means affixed to the aircraft wing having parts for coated wnh a conductwe securingly receiving one end of the rod therein, said

Claims

1. Apparatus for discharging static electric charge from a body into a gaseous environment, comprising: a metal rod; electrically conductive means connecting one end of the rod to the body and disposing the other rod end in the gaseous environment; a smooth surfaced metal ball affixed to the other rod end; and a plurality of metallic filament means, each having one end electrically connected to the rod inwardly of the ball and extending away from said rod to terminate in the atmosphere.

2. Apparatus as in claim 1, in which metallic collar means are received onto said rod and affixed thereto at a point spaced inwardly of the metal ball, said metallic filament means being secured to said collar means.

3. A static electric charge discharger for attachment to the wing of an aircraft, comprising: a metallic rod; mounting means affixed to the aircraft wing having parts for securingly receiving one end of the rod therein, said mounting means providing a low-ohmic connection between said wing and said rod; an electrode connected to the other end of said rod having a smooth curved outer surface; and a plurality of elongated elements, each having one end physically and electrically connected to said rod and the other end being pointed and extending away from said rod into the air.

4. A static electric charge discharger as in claim 3, in which the mounting means includes a pair of parts that are fitted together about the rod end, the surfaces of said parts being coated with a conductive material.