US1701562A - Insulator - Google Patents

Description

Feb. 12, 1929.

c. s GORDON INSUL'ATOR Filed July l, 1925 INVENTOR 6'. (5' 00111010 1 ATTORNEY h UNITED" STATES I onnsmins. oonnon, or raw Yonx, N. Y., assrcnon -PV.:ATEN 'IAOFFICEI.I I

TO AMERICAN TELEPHONE-AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

- msum'ron.

' Application filedluly 1,

1 This invention relates improvements in insulators, and more particularly to a construction of insulator adapted to stabihze the leakage loss under diflerent weather condif With the developmentof methods of transmitting telephonic and telegraphic s gnals by means of carrier currents propagated alon' open wire lines, new transm ssion prob ems have been introduced. Owing to the fact that the carrier currents employed are relatively high in frequ as compared if with the voice currents or orse currents utilized in the ordinary methods of communication, it has been found that the attenuation is ver 'markedly increased, so much so, in fact, t at repeaters for amplifying the transmitted currents mustbe separated by much shorter distances, thereby adding tothe ex-- pense of the plant outside the 'terminalstations at which" the carrier apparatus is applied, 1 A ver material part of this attenuation is 1 due to eakage loss through the insulators comprising the other plate.

thus formed introduces a leakage loss due to which are customarily employed upon open wire lines, and this loss varies through a very wide range under difierentweather conditions. The insulator acts like a condenser, the glass of the insulator constituting the dielectric, the line wire and tie-wire on the outside of the insulator comprising one'plate, and the wooden pin upon which the insulator is supported The condenser so-called dielectric hysteresis and this loss varies with the capacity of the condenser.

In dry weather, the outer plate of the condenser, that is, the portion of the line wire adjacent to the insulator and its associated tie wire, constitutes a'plate of relatively small. area so that the capacity is relatively small and hence the leakage loss, even at carrier fre- 'quencies, is small'as compared with the total attenuation of the, circuit. Durin wet weather, however, the entire outer sur ace of the insulator becomes wet, with the result that the conductive area external to the insulator is very much increased. As a result the capacity, and consequentl the leakage loss, is very much increased. uring the extremes of wet and dry weather the attenuation of the system varies through a wide range due to -the position of the pin in Figure 1925.; Serial No. 40,893.

this cause alone, and this vision of special regul ting apparatus for maintaining the transmission equivalent'of the circuit constant under all weather conditions. 1

In order to avoidlthe expense ofthe regu lating arrangements it becomes desirable to devise some method for stabilizing the capacity of the insulator and hence its dielectricloss represent two embodiments of the invention,

and Fig. 1* represents the supporting pinto be used in connection with the insulators of Fi s. 1 and 2.

eferring to Fig. l, A designates a body of dielectric material having an internall screw-threaded opening 11 by means of whic the body may be screwed upon asupporting in. A petticoat l2extendsdownwardly from v the body A and surrounds the supporting pinv ecessitates the prosome little distance away from its outer sur- I face as shown by the dotted line representing 1. The in- ,ner surface of the petticoat is corru ated, as shown at 13, to increase the lengt dry ath formed by 7 crab these corrugationswill be made in the form of a screw thread of the same pitch as the internal threads of the openin 11 so that the mold or core which is used in Eorming the entire body'may be screwed out after the plastic material has hardened.

Instead of securing the line conductor and of the said 1nner surface. Preftie wire about the outer margin of the dielectric body A, as in the usual type of insulator, a small knob 14.- is formed on the top of the insulator so that the line conductor and tie wire may be, seated in .the'peripheral groove 15 of the knob. A laterally extending, umbrellalike structure 16 is provided near the upper edge of the dielectric body A to maintain the outer surface of the dielectric body dry bescrew -threaded opening 11.

- {principal existing. capacity neath the structure 16 downto a point substantially opposite the lower edge of' the In order to fix or stabilize the leakage loss, which'is proportionate to the capacity, a coa mg -"outer surface of the petticoat 12 will not materially increase the'capacity .as this conductive area is-isolate'd from the line conductor and tie wire and theassociated, conductive material 17 by a'dry path due to the corrugations 18 on the under side of the umbrella-like struc- -ture 18, and is likewise isolated from the supportlng pin by the dry path'due tp the corrugations 13. 5

'Obviousl therefore, thecapacity of the insulator and hence the'dielectric loss (which is proportionate to the capacity) isfixed and stablllzed at a value somewhat greater than the dry weather value which would exist if there were no conductive layer 17, but yet materially smaller than the value that would,

exist duringwet weather if it were possible for the whole-external surface of the insulater to become wet.. Also, the direct cur-l rent leakage is stabilized at a low value condition by the provision of the long dry path under the petticoat of1the insulator. It is unnecessary to provide any additional repeaters by reason of the useof the outer metallic' shell, as repeaters "must be provided even with existing insulators to give sufiivcient gain for the worst transmission conditions. By stabilizing the insulator-at an intermediate condition, however, some saving in the number of repeaters may be possible, but, what is more important, the equipment for 'maintaining the transmission constant maybe eliminated and the expense propo-r-' tlonately cut down.

Fig. 2 shows a slight modification of the arrangement of Fig. 1. I In this instance the knob or button 1%, instead of being coated or covered with aconductive material, is 1tself formed of conductive material-which may be welded, soldered, riveted or otherwisesecured to the conductive layer 17. The

underlying principles of this structure are, however, the same as in the case of Fig. 1 and no further discussion is necessary.

It will be obvious that the general prinof conductive material 17 is applied to the I outer surface of the dielectric over the knob 14 and over the parts of the umbrella-like. -structure 16' which are exposed to the weather.

Owing to the shape of the structure 16, the

surfaceand the pin,

ciplesherein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:.

1. An insulator comprising a body of dielectric material havingan inner opening to receive a supporting pin, a relatively small button like structure on the top of said body having a grooved portion ,to which the line conductor and tie wire may be secured, said grooved portion being of a diameter not materially greater than the supporting pin, an umbrella-like structure at the upper side of said dielectric body for protecting a ortion of the outerasurface of said bo y om moisture, and a surface of conductive material extending from'the outer edgesof said umbrella-like structure to and over said button, the umbrella-like structure with its ,metallic surface extending; horizontally utthe top of cured, said grooved" portion being of a diam eter not materially greater than the supporting pin, "an umbrella-like structure at the upper side of said dielectric body for protecting a portion ofthe outer surface of said body from moisture, anda surface of conductive material extending. from thenuter edges of said umbrella-like structure toand over said button, the umbrella-likev structure with its metallic surface extending horizontally outward and away to reduce the capacity-between the metallic surface and the pin, and the underside of said umbrella-like structure being corrugated to lengthenthe dry'path formed thereby.

3. An insulator comprising a body of dielectric material havingan inner opening to receive a supporting pin, a relatively small button-like structure on the top of said body the line conductor-and tie wire may be secured, said grooved portion being of a diameter not materially greater than the supporting pin, an umbrella-like structure at the upper side of said dielectric body for-protecting a portion of the outer surface of said body from moisture, a surface of conductive material extending from the outer edges of said umbrella-like structure to and over sald from the supporting pm '11s having a grooved portion to which button, the umbrella-like structure with its metallic surface extending horizontally outward and away, fromthe supporting pin to reduce the capacity between the metallic and a petticoa't extendthe supporting pin.

' from said ing downwardly .from said dielectric and surrounding but spaced away from the threadedopening to receive a supporting pin and a tticoat extending downwardly &(ly and surrounding the-pin,

the inner surface of said Petticoat having screw-threaded corrugations of i the same pitch but of larger diameter than the threads of the pin, whereby an integral mold may 15 be used to form-thetwo sets of threads on the inner'surface of the insulator and the moldmaybe unscrewed from the interior of the insulator.

In testimony whereof, I have signed my 20 name to this specification this 25th day of June, 1925.

CHESTER s. :GORDON.

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