US1715888A

US1715888A - Insulator

Info

Publication number: US1715888A
Application number: US747891A
Authority: US
Inventors: Arthur O Austin
Original assignee: Ohio Brass Co
Current assignee: Ohio Brass Co
Priority date: 1920-12-06
Filing date: 1924-11-05
Publication date: 1929-06-04
Anticipated expiration: 1946-06-04

Description

Jung: 4, 1929. A. o. AUSTIN 1,715,888

INSULATOR Original Filed Dec. 6, 1920 2 sh et -sh t 1 INVENTOR M4 4Q m By i mwg June 4, 1929. v A. o. AUSTIN 1,715,888

INSULATOR "Original Filed Dec. 6, 1920 2 Sheets-Sheet 2 I/Vl/E/VTW M cm-L Patented June 4, 1929.

UNITED STATES PATENT OFFICE.

ARTHUR O. AUSTIN, 0F BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY.

INSULATOR.

Original application filed December 6, 1920, Serial No. 428,437. Divided and this application filed November 5, 1924.

This invention relates to electrical insulators, and especially to insulators of high potentials, and has for its object the provision of insulators which shall be of improved construction and operation.

' The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawings and described in the following specification, and it is more particularly pointed out in the appended claims.

The present application is a division of my prior application Serial No. 428,437, filed Dec. 6, 19:20, which application has matured into Patent No. 1,516,585, dated Nov. 25, 1924.

In the drawings,

Fig. 1 is an elevation with parts in section, showing an insulator having one embodiment of the present invention applied thereto.

Figs. 2 and 3 are elevations partly sectioned, showing other embodiments of the invention.

In high tension insulators Where two conductors of different potentials are separated from one another by an insulating member, it is well known that an electrostatic field is present in which the lines of force extend through the insulator and the surrounding medium from one of the conductors to the other. These lines of force are most closely concentrated at the portions of the insulated conductors which are nearest to one another. The lines of force also tend to emanate from any restricted projections or points formed upon the conductors so that such points are surrounded by a concentrated field.

\Vhen insulators or dielectrics are worked at high pressures or potentials there is a tendency to produce a concentration of electrostatic flux. static flux may set up a stress of such magnitude that it will damage the dielectric. This stress may be set up around a conductor imbedded in a solid dielectric or around a con ducting surface which operates in a medium such asair, oil, wax, or other medium. When the conducting surface operates in air, corona or brush discharge may occur at a fairly low voltage, particularly where the conductor has a sharp edge or point. If corona or brush discharge occurs at normal frequency, say cycles, and an electrical stress at high frequency is impressed on the electrode, the current will be increased in the further from the electrode.

This concentration of electro- Serial No. 747,891.

streamer or brush discharge. Since the resistance of the streamer drops off very rapidly with an increase in the current, it is seen that where the frequency is high the current may be very materially increased. This increase in current lowers the resistance in the streamer, permitting the streamer to flow out This increase in distance increases the capacitance of the streamer and-permits more current to flow. The increased current in turn still further lowers the resistance in the streamer so that it extends still further. IVhere a persistent wave at high frequency is applied, such as in wireless work, a com 'iaratively small voltage will cause the streamer to build out several feet once it is started. This streamer may arc to ground or absorb considerable energy or damage any insulator which may be near the surface which discharges.

In wireless work where a high frequency generator is used, or the equivalent, the point of brush discharge from a conducting surface limits the voltage which may be used. If this discharging surface is covered by a dielectric having greater strength than air, it may be possible to operate at a higher voltage or stress as a streamer which will grow to serious proportions is prevented. It will be seen that where this is the condition and dielectric material having strong insulating properties is used to cover the surface which as greatest tendency to discharge, a higher operating voltage may be used.

Fig. 1 shows an insulator 7 6 having chambers 7 7 atboth ends formed by bafile-plates 78 and lined with metallic coating 79 to produce an insulated flux screen or shield. The screen or shield 79 constitutes a radiating surface for the electrostatic flux and is covered by the dielectric material of the insulator so that danger of electrical discharge along the lines of force emanating from the screen 79 is avoided. A weather shield 80 may be used with this construction and petticoats 81 are separately formed and secured to the in sulator by cement 82. The cement 82 should be of insulating material to force any leakage currents over the petticoats 81. I

In Fig. 2 a tubular insulator 83 is shown provided with an end cap 84, and an internal insulating thimble 85 is supported on a plug 86 secured to the interior of the end cap 84. The plug 86 may be provided with openings 87 to facilitate circulation of air through the interior of the tube 83. The thimble 85 has its inner surface coated with a metallic coating 88 to provide a flux distributing member insulated by the thimble 85. The coating 88 is, of course, electrically connected with the end cap 84. For high potentials the cement will furnish sutlicient conductivity for this purpose.

The form of the invention shown in Fig. 3 is similar to that of Fig. 2, with the addition of an external non-insulated round metal portion 91 from which lines of force may emanate toward the opposite conductor and thus cooperate with the internal flux member 88 in preventing concentration of lines of force.

Insulators constructed according to the present invention are particularly adapted for operators at radio frequencies and for operation in oil or gas, or in other insulating mediums where the heating from charging currents starting from terminals may cause trouble. The flux distributing medium forms a low resistance path for the charging currents adjacent the terminals and provides good Contact between the terminal members and dielectric, thus avoiding heating due to charging currents at the junction of the terminal with the dielectric. This is especially true where the flux distributing medium is in the form of a metallic coating.

For many purposes hollow insulators have great advantages over those made of solid dielectric material. lhe mechanical strength of such an insulator for a given weight is, or" course, far greater than that of an insulator made of a solid bar. Heretofore the use of tubular insulators having fittings at opposite ends has been greatly restricted because of the danger of discharge through the center of the insulator. A discharge over the outer surface of an insulator usually interferes only temporarily with the operation of the line, but discharge through a tubular insulator is commonly attended by an explosion of the insulator or other injury, because of the heating eliect of the discharge within a confined space. Where an insulator is made of solid material a simple metallic flux screen may be imbedded in the material of the insulator, as shown in my prior Patent No. 1,516,585, granted November 25, 192 1, but it is apparent that it such a member were used in a hollow insulator it would increase rather than decrease the danger of discharge through the center of the tube. By provid ing an insulated pocket within the interior of the tubular insulator I am able to secure the benefits of the flux screen without increasing the hazard of discharge through the tubular opening. The metallic coating on the inside of the pocket will cause the lines of force to emanate through the insulating material of which the pocket is made and this material will prevent discharge along these lines of force, thus decreasing the danger of discharge from the fitting through the center of the insulator. By supplementing the internal flux screen by an external screen, as shown in Fig. 3, the danger of discharge through the tubular member is still further decreased and by thus providing two paths for the lines of force, one on the outside and one on the inside of the insulator, each sup plements the other so that there is not an excessive concentration of flux emanating fro 2. either of the flux screens;

I claim:

1. An insulator comprising a hollow dielectric body, a supportsecured to said body, a flux distributing screen having electrical connection with said support and extending beyond said support into the interior of said body, and a dielectric covering for said screen separating said screen from a portion of the opening within said body.

2. An insulator comprising a hollow dielectric body, a support connected with said body, said body having a pocket therein adjacent said support, and a conductor lining for the interior of saidpoclret, said pocket being closed by dielectric material at the end thereof opposite said support to separate said conductor lining from a portion or the open space within said insulator.

3. An insulator comprising a hollow dielectric body having a battle of dielectric material separating the opening within said body into sections and founing a pocket adjacent one end of said body, a support for the insulator connected with said body at the end thereof adjacent said pocket, and a coating of conducting material on the interior of said pocket.

4:. An insulator comprising a hollow dielectric member, a battle disposed within said member and separating the interior thereof into sections and forming a pocketadjacent one end of said insulator, a support connected with said insulator at the end thereof adjacent said pocket, a coating of conducting material disposed on the interior of said pocket and electrically connected with said support, and a flux screen of conducting material connected with said support and arranged on the outside of said insulator.

5. An insulator comprising a dielectric member having an opening adjacent one end thereof, the interior of said opening being coated with conducting material, a support secured to the end of said insulator adjacent said opening, and an external flux screen carried by said support.

6. In combination, a tubular dielectric member, a support connected with one end of said tubular member, a cup-shaped dielectric member extending into said tubular member and having its open end connected with said support, and a flux screen of conducting material extending into said cupshaped member.

7. An insulator comprising a tubular dielectric member, a support connected with one end of said member, a cup-shaped dielectric member having its open end connected with said support and having its closed end projecting into the opening in said tubular member, and a coating of conducting material on the interior of said cup-shaped member.

8. An insulator comprising a tubular dielectric member, a support connected with one end of said member, a cup-shaped member of dielectric material extending into the opening in said tubular member and having its closed end directed into said opening, said cup-shaped member being mounted on said support, independently of said tubular member, and a coating of conducting material on the interior of said cup-shaped dielectric member.

9. An insulator comprising a tubular dielectric member, a metallic cap secured to one end of said member, a metal plug threaded in to said cap, a dielectric member mounted on said plug and having a pocket therein, the closed end of said pocket being directed into the opening in said tubular member, said dielectric member being disposed within the opening of said tubular dielectric member and having a coating of conducting material on the inner face thereof.

10. An insulator comprising a tubular dielectric member, a cap secured to one end of said dielectric member, said cap having a supporting projection extending into said member, a dielectric member having a pocket therein closed at one end and open at the other, the open end of said last-named dielectric member being secured to said projection while the closed end thereof extends into the opening in said tubular dielectric member, and a coating of conducting material disposed on the inner surface of said pocket.

11. An insulator comprising a tubular dielectric member, a cap secured to one end of said member, a flux screen of conducting material mounted on said cap and disposed outside of said tubular member, a plug threaded into said cap and extending into said tubular member, a cup-shaped member of dielectric material having the open end thereof secured to said plug and having the closed end thereof disposed within the opening in said tubular member, and a coating of conducting material disposed on the interior surface of said cup-shaped dielectric member.

12. An insulator comprising a tubular dielectric member, a cap secured to one end of said member, an external flux screen mounted on said cap and extending in the direction of said insulator beyond the connection between said cap and said dielectric member, a cup-shaped member of dielectric material supported by said cap within the interior of said tubular dielectric member and having its closed end directed into the opening in said tubular member, and a coating of conducting material on the interior of said cupshaped member, said coating extending into the opening in said tubular dielectric member beyond the extreme point of connection between said tubular member and said cap.

In testimon; whereof I have signed my name to this specification on this 31st day of Oct. A. D. 1924.

ARTHUR O. AUSTIN.