US2751467A - High voltage, high frequency apparatus - Google Patents

Description

June 19,1956 M. R. ALEXY HIGH VOLTAGE, HIGH FREQUENCY APPARATUS 2 Sheets-Sheet 1 Filed June 30, 1955 11 TTORNE 1 M- R. ALEXY HIGH VOLTAGE, HIGH FREQUENCY APPARATUS June 19, 1956 2 Sheets5heet 2 Filed June 30, 1955 United States 2,751,467 Patented June 19, 1956 lice 2,751,467 men VOLTAGE, HIGH FREQUENCY APPARATUS Matthew R. Alexy, Philadelphia, Pa., assignor, by mesne assignments, tothe United States of America as represented by the Secretary of the Air Force Application June 30, 1953, Serial No. 365,042

4 Claims. (Cl. 200144) This invention relates to apparatus for prevention of corona discharge, and more particularly, although not necessarily exclusively, to corona prevention in high voltage switches and relay devices.

When extremely high voltages exist in an electrical conductor, the air surrounding the conductor becomes ionized. When the voltage gradient on the surface of the conductor exceeds a certain predetermined value, an electrical discharge in the form of a glow of colored light takes place. This effect is known as corona.

For average conditions, if a voltage gradient approaching 25 kv./cm. exists, corona discharge or sparking will begin to appear. If further successive layers of air surrounding the electrical elements or electrodes are ionized, arc-over or flash-over between electrodes will take place since ionized air is virtually a conductor. The voltage gradient is influenced by the design configuration. All parts in the high voltage field must be shaped to avoid disturbing the field to an extent tending to cause premature failure, i. e. parts must have rounded corners or shapes compatible with the condition of high voltage.

Spherical shapes are the best. However, certain types of electrodes are not adaptable to rounded configuration. A corona shield must then be employed. The corona shield should surround the poorly shaped electrodes in such manner as to prevent any breakdown voltage gradient in the surrounding air. Metallic elements molded in highly stressed insulators must be in intimate contact with the insulation so as to avoid internal corona.

Components in airborne equipment must approach the absolute minimum in size and weight. Internal space allotment, for example, in modern fleet aircraft is such that conventional or standard, available component parts for use with high frequency-high voltage electrical equipment cannot be used due to its cumbersome bulk and weight. Furthermore, the use of long lead lines and soldered connections with presently available electrical equipment tends to induce rather than to prevent corona discharge around such lead lines and connections.

It is, therefore, an object of the present invention to provide a miniature high-voltage, high-frequency apparatus for use with high voltage, high frequency circuits.

It is another object of the invention to provide a simple means for preventing corona discharge and for raising the break-down voltage to the maximum degree in electrical equipment operated at high frequencies.

It is a still further object of the invention to provide means for coupling and/or switching one high voltage circuit to either another high voltage circuit or to a lower voltage circuit.

A novel miniature high frequency coupling device in accordance with the present invention may comprise a switch or a relay having a central shaft and a kinematic chain of levers for transmitting the lateral motion of a solenoid plunger into the rotary motion of an insulating rotatable contact member and a high voltage contact arm. A plurality of individual contacts are disposed adjacent said rotatable contact member, said member having means disposed thereon for both low voltage and high voltage circuit connections. Corona discharge shield members in the form of domed or substantially hemispherical contact covers are disposed one over each individual contact; An elongated, hollow, cylindrical sleeve provides a corona shield and cover for the movable contact arm. Connection between the high voltage movable contact arm and the remainder of the circuit or circuits is obtained through a high-domed, fixed element disposed at one end of the central shaft and adjacent said contact arm. Kinematic motion is, or may be, initiated by a plunger type solenoid or, in the case of the multiple contact switch, by means of a rotary stepping motor.

The novel features of the invention, both as to its organization and method of operation, as well as additional objects and advantages thereof, will be understood more fully from the following description, when read in connection with the accompanying drawings in which:

Fig. l is a perspective view of a relay device utilizing the present invention;

Fig. 2 is an enlarged side view, partially in cross section, of the device of Fig. 1;

Fig. 3 is a top plan view partially in cross section, of the device of Fig. 2, the view being taken along the line 33 of Fig. 2; v

Fig. 4 is a perspective view of a rotary switch device utilizing the invention; and

Fig. 5 is a sectional view in side elevation of a portion of the device of Fig. 4, the view being taken along the line 5-5 of Fig. 4. 7

Referring to Fig. 1 of the drawing, there is shown an illustrative embodiment of the invention comprising a solenoid operated relay 10. The rotatable portion of the relay 10 consists of a coupling 12 having a shaft 14, integrally molded to one end thereof, and a threaded bushing 16 integral with the opposite end thereof (Fig. 2) The coupling member 12 is formed with a plurality of flat portions 18 and 20 thereon. One of the flat portions 18 is adapted to receive the relay contact blades 22 and 24 thereon. The relay contact members are supported on the coupling member 12 by means of bolts or screws 25 and the locking members 26, Fig. 1. The coupling member may be fabricated from any well known, highly stressed insulating material such, for example, as Mycalex glass-bonded mica. A protuberance in the form of a rim or band 28, integral with the coupling 12, is provided thereon in order to provide a longer flash-over path from the shaft 14 to the contacts 22 and 24 and the bushing 16.

An upper insulating member or shelf 30 and a lower shelf 32 are disposed to provide an operating area for the relay contact members 22 and 24. A slot 29 is provided in the upper shelf 30 to provide a longer flash-over path between the flange 81 and the contact 44 when the contact arm 54 is in engagement with the contact 48, as will be described more fully hereinafter. The shelves 30 and 32 are supported in adjacent parallel relation and separated by means of two insulating support members or posts 34. The shelves are secured to theposts by means of the screws 36 and 38. The upper insulating shelf 30, as viewed in the drawing of Fig. l, is provided with two depending insulating projections 40 and 42 integral with the shelf and adjacent one another. Each one of the projections 40 and 42 is drilled to receive a contact element therethrough. The low voltage contact 44 is provided with a conductive lead wire tab member 46. The high voltage contact 48 is not provided with a lead wire tab. A substantially hemispherical, hollow corona shield member 50 is threadedly engaged with the contact 48 to provide a high voltage corona shield for the extension of the contact 48. The contact 44 is not necessarily confinedin its function to low voltage. It can be converted to high voltage applications by using the element 50. The corona shield must have rounded corners, generous within the limits of the design, so that, even though the sharp cornered parts within the shield are somewhat exposed, they are at the same potential as the shield, thus preventing corona sparking.

A rotatable contact arm 54 is adjustably disposed immediately adjacent one end of the coupling 12 on the shaft 14. The contact arm 54 is provided with two parallel, resilient, elongated fiat contact strips 56 and 58 (Fig. 3), which are secured together by means of rivets 60 and the separating block 62 at one end thereof. Hemispherical contacts 64 and 66 are provided on the contact strips 56 and 58, respectively. A hollow metallic cylinder 67, provided with apertures 68, surrounds the contact strips 56 and 58. The contacts 64 and 66 are biased by means of the strips 56 and 58 to protrude through the apertures 68. The hollow cylinder 67 is secured to a bell-shaped member 70 by a press-fit over the area 72. The cylinder 67 thus provides a novel corona shield for the flat, sharp- edge contact strips 56 and 58. The contact arm 54 is secured to the shaft 14 by means of two set screws 74 that do not extend outside the periphery of the bell-shaped member 70.

A member 76, which may be L-shaped for convenience, is secured to the shelf 32. A series of low voltage contacts 78 are disposed on the member 76 for cooperative mating contact with the relay contacts 22 and 24.

The shaft 14 is journaled through a bearing 80 disposed in the member 82, Fig. 2. The shelf 30 is drilled to receive the member 82 which is provided with a peripheral flange 81 and which is adapted to threadedly engage a corona shield member 84. The member 82 is provided with a hollow center section 86. A member 88 is adapted to be received within the hollow section 86 and to be fixedly secured to the shaft 14 by means of a screw 90. The member 88 is thus rotatable with the shaft 14. An elongated, narrow, fiat, metallic strip 92, having a contact 94 at one end thereof, is secured to the periphery of the member 82 by means of the screw 96. A continuous wiping contact is thus provided between the strip 92 and the shaft 14. Lead wires may be disposed or secured to the member 84 through the openings 98 and 100 therethrough. The lead wires are secured Within the openings 98 by means of two set screws confined within the member 84 (Fig. 2). A high voltage path is thus provided from the contact 48 or 44 through the contact arm 67 to the lead wire openings 98 and 100. The member 84 thus provides a novel high voltage take-off or connection from the rotatable member 67 to a load (not shown).

' The threaded bushing 16, disposed at one end of the coupling 12, is drilled to threadedly receive a screw 104. The bushing is adapted to rotate within a suitable bearing 106. The bearing 106 is disposed through the shelf member 32.

, Any suitable actuating mechanism may be connected to the coupling 12. One such mechanism which has been adapted for use with the present invention is a short stroke, plunger type solenoid 108. The solenoid 108 is provided with two terminals 110 which may be connected to any suitable source of power. A kinematic chain of levers, which form no part of the present invention, may be provided for connecting the plunger 112 of the solenoid 108 with the coupling 12. The lateral motion of the solenoid plunger can thus be transformed into the rotary motion of the relay coupling 12 and its associated members. The relay 10 may be conveniently supported by means of a metallic yoke 114 and the integral straps 116 projecting therefrom. A series of fiat, projecting tabs 118, integral with the yoke 114, are also provided. The tabs 118 may be used as a further supporting means in conjunction with the leg members 120. The solenoid plunger 112 may be biased by means of a spring in the direction of the low voltage contact 44.

The relay 10, as viewed in the drawing of Fig. 1, is shown to be positioned vertically on a base member 122. However, it is within the scope of the invention to utilize the relay and associated equipment in any desired physical position.

The drawing of Fig. 4 is a perspective illustration of a rotary switch mechanism 124 utilizing the present invention. The members 126, 128 and 130 provide a bottom, middle and top supporting shelf, respectively, for the switch 124. The middle shelf 128 may be semi-elliptical in shape. A series of flat, slightly rounded contacts 132 are disposed around the periphery of the shelf 128. Each of the contacts 132 may be threadedly secured through appropriately located holes in the shelf 128 to the hollow, dome-shaped corona shields 134. A coupling member 136, substantially similar to the coupling 12 of Fig. 2, is provided with a shaft 138 and a hollow, threaded bushing 140. Both the shaft 138 and the bushing 140 may be molded integral with the coupling 136 whereby the coupling is in intimate contact with both the shaft and the bushing 140. The bushing 140 is adapted to receive the shaft 142 of a low voltage, multiple contact switch assembly 144 by means of the set screw 146 disposed in the bushing 140. The multiple contact switch assembly 144 is shown here as a multiple contact wafer switch. This type of wafer switch is widely available and is illustrated in the catalog Engineering Data Sheets, second edition, published by Oak Radio and Electric Products Company on pages 10 and 14. The shelves 126, 128 and 130 are secured in parallel relation, but separated from one another, by means of the supports or posts 148.

A rotatable contact arm 150 is secured to the shaft 138. The contact arm 150 includes an elongated, resilient, metallic strip 152 secured at one end by means of the rivets 154 and the block 155 and having a hemispherical contact member 156 secured to the opposite end thereof (Fig. 5). A hollow, cylindrical member 158, which is closed at one end, is press-fit onto a member 160. The hemispherical contact 156 projects through an opening 164 in one portion of the cylindrical member 158. The member 160 is secured to the shaft 138 by means of a set screw, not shown, disposed in an opening 162 in the member 160. As can be seen from Fig. 4, the contact arm 150 is disposed to sweep in an arc across the tops of the various contacts 132.

The shaft 138 is journaled substantially similarly to the shaft 14 in Fig. 2 and is likewise provided with a well rounded corona shield 166 substantially identical to the corona shield 84 of Fig. 2.

A rotary stepping motor 168 or other suitably actuated device is or may be provided for connection to the switch 124. A plurality of connection pins 170 is disposed peripherally of the shelf 126 for connection to the associated contacts 172 of the switch 124. The motor 168 may be energized through the leads 174 from any suitable source of potential, not shown. Since the motor 168 is actuated according to a pre-arranged program, the contact arm 150 may be caused to be advanced in a predetermined direction so as to contact each one of the contacts 132 in step-like fashion. All of the high voltage members are provided with well rounded and smoothly cornered corona shields. The flash-over path from the high voltage section to the .low voltage section has been lengthened by means of the novel configuration of the coupling members 12 and 136.

There has thus been described a high frequency switching apparatus which is capable of supporting voltages in excess of 10,000 volts at 20,000 feet altitude and at frequencies as high as those in the order of 20x10 cycles per second. The devices of the present invention have been miniaturized so that size and weight has been kept to a minimum consistent with the basic design specification and requirements of equipment adapted to operate at extremely high voltages.

What is claimed is:

1. In a miniaturized high voltage high frequency switching apparatus having a rotatable contact member, a plurality of contact elements positioned in the path of said rotatable contact member to make contact therewith, and means for rotating said rotatble contact memher so as to momentarily and conductively intercept each one of said plurality contact elements in a predetermined adjustable sequence, the combination comprising a shaft having said rotatable contact member mounted thereon, insulating coupling means integrally molded to said shaft and to said rotating means, corona discharge shielding means surrounding said rotatable contact member and each one of said plurality of contact elements, said shielding means surrounding said rotatable contact member comprising a substantially cylindrical shell having domeshaped portions at extremities thereof and apertures through which project a portion of said rotatable contact member for making contact with said contact elements, and each one of said plurality of contact elements being surrounded by corona shielding means comprising hollow dome-shaped shells.

2. A miniaturized high voltage, high frequency switching device for controlling the transfer of electrical energy between an energy source and a load associated therewith comprising a plurality of conductive members disposed between said energy source and said load, one of said conductive members being adapted to operate as a high voltage contact, a hollow, dome-shaped corona shield secured to and surrounding said high voltage con tact, movable electrical contact means adapted to be restrained in contact with a different one of said conductive members, said movable contact means comprising a plurality of elongated members, one end portion of each one of said elongated members being provided with a hemispherically shaped contact element, and a hollow, conductive sleeve providing a corona shield for said elongated members surrounding said elongated members, said sleeve being provided with apertures for said contact elements disposed adjacent said conductive members, and signal responsive energizing means connected to said movable means so as to actuate said movable means, said movable means being further adapted to come into contact with said high voltage contact upon application of a predetermined signal to said signal responsive means.

3. A miniaturized high voltage high frequency switching device for controlling the transfer of electrical energy between an energy source and a load associated therewith comprising an insulating support, at least two contact elements mounted on said insulating support, an elongated rotatable contactor, a shaft, one end of said elongated contactor mounted on said shaft, an opposite end of said elongated contactor making contact with any one of said contact elements, said elongated contactor being surrounded and substantially enclosed by a hollow conducting sleeve providing a corona shield therefor, said sleeve being provided with apertures at the end of said elongated contactor adjacent said contact elements, a contact portion of said elongated contactor projecting through said apertures, a hollow dome-shaped corona shield surrounding each one of said contact elements, said dome-shaped shell being provided with an aperture through which a contact portion of said contact element projects, an insulating coupling connecting said shaft to another shaft, said insulating coupling being intimately connected to each of said shafts thereby preventing internal corona sparking therein, and signal responsive rotating means connected to said other shaft so as to rotate said elongated contactor whereby contact is made between said energy source and said load.

4. In a high voltage high frequency switching device for controlling the transfer of electrical energy between an energy source and a load associated therewith, the combination comprising a first shaft, a second shaft, means for rotating said second shaft, coupling means of highly stressed insulating material integrally molded with and connecting said first and said second shafts thereby preventing internal corona sparking therein, said coupling member being provided with an insulating protuberance so that a longer flash-over path exists from said first shaft to said second shaft, an elongated contact member secured to and rotatable with said first shaft, a hollow conductive sleeve surrounding said elongated contact member to provide a corona shield therefor, a shielded member electrically connected to said elongated contact member to provide high voltage take-off means from said switching device to said lead, an insulating supporting structure surrounding said first shaft, at least two conductive contact elements secured to said supporting struc ture and adapted to come in contact with said elongated contact member on rotation thereof, said contact elements being electrically connected to said energy source, and said contact elements also having substantially domeshaped corona shields surrounding a substantial portion thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,751,233 Eschholz Mar. 18, 1930 2,196,008 Cole Apr. 2, 1940 2,399,430 Frese Apr. 30, 1946 2,434,572 Mankin Ian. 13, 1948 2,481,033 Nelsen Sept. 6, 1949 2,600,938 Thierfelder June 17, 1952 2,640,115 Concelman May 26, 1953

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