United States Patent Office   

2,734,098 

Patented Feb. 7, 1956


2,734,098

 TRANSPOSITION INSULATORS

 Elmer Johannes Bonnesen, West Orange, N.J., assignor to American Telephone and Telegraph Company. A corporation of New York

Application November 30, 1950, Serial No. 198,421

4 Claims. (Cl. 174-194)


This invention relates to insulators for telephone transmission lines and more particularly to a multiple groove composite type insulator for use in transposing open wire lines in high quality circuits.

One object of this invention is the provision of a multiple groove composite type transposition insulator which will have greater mechanical strength than presently known insulators.

Another object of the invention is to facilitate the manufacture of multiple groove transposition insulators.

In the construction of high quality open wire telephone circuits, it is a well established practice to transpose the wires in a pair at predetermined intervals along the spans to avoid interference between adjacent pairs and eliminate cross-talk.  At present various devices and structures are used to accomplish these transpositions; for example point-type transposition at cross-arms or pole supported fixtures are provided; also brackets having insulators mounted thereon are positioned in mid-span and multiple-groove insulators which may be supported on brackets or suitable supports at the required transposition position are also provided.

It has been common practice to use a multiple groove two-piece insulator of glass or other vitreous material. This particular structure was necessary to facilitate manufacture of an all glass or vitreous insulator since to provide multiple-grooves therein with a suitable skirt between the grooves to provide a long leakage path, which is mandatory on high quality open wire lines, was not feasible or practicable inasmuch as the extending skirt prevented the use of known molding methods and to devise new methods would be prohibitive due to the cost involved.  It has been known that two-piece multiple grooved glass insulators have an inherent weakness where they are joined but since no other structures were available they have been used but maintenance has been high due to failure of the insulators.

This invention provides a multiple groove transposition insulator which is as strong mechanically as a one-piece insulator and has a long leakage path between the conductors in the grooves, and furthermore is relatively inexpensive to manufacture.

In accordance with the preferred form of my invention, I have provided a multiple groove vitreous insulator which has a composite structure, that is, the main body portion is constructed from a suitable vitreous insulating material, and the skirt portion which separates the wire grooves and assures a long leakage path there between is constructed from a non-vitreous material, for example wax impregnated rubber.

The invention will be understood more clearly from the following detailed description when read in connection with the accompanying drawing in which:

Fig. 1 is an elevational view partly in section of one embodiment of this invention, showing the structure of the skirt and its location with respect to the wire receiving grooves; and

Fig. 2 is a fragmentary view of a portion of a transmission line illustrating one method of utilizing the insulator of this invention.

As shown in Fig. 1, the insulator comprises a body member 10 of suitable insulating material, preferably of glass or other vitreous material, having on its periphery the circumferential wire receiving grooves 11 and 12. The bottom of the member 10 is provided with the usual skirt 13 to provide a long leakage path between the insulator pin and the wires located in the grooves on the insulators.  Located between the grooves 11 and 12 is a circumferential groove 14 in which is positioned a skirt member 15 which is constricted from a non-vitreous material such as wax impregnated rubber.  Since the inside of the skirt member 15 has a diameter less than the diameter of

 

the insulator at the groove 14, the skirt 15 will be firmly positioned in this groove and cannot readily be displaced.

Due to the cross-section structure at the skirt 15 and the adjacent groove 16, a long leakage path is provided between the wires positioned in the wire receiving grooves 11 and 12. The interior of the body member 10 is provided with suitable internal threads 17 which are adapted to engage the external threads of an insulator supporting pin 18, such as shown in Fig. 2, which may be of wood or metal.

While I have shown and described a preferred embodiment of my invention, it is to be understood that various changes and modifications may be made therein without departing from the scope and spirit of the invention.

What is claimed is:

1. A transposition insulator for electrical circuits comprising a body member of insulating maternal having its lower portion outwardly flared, said body member having therein a pin receiving recess which extends from said lower portion only partially into the body member to provide an unbroken upper surface at the top of said body member, said body member having on its outer surface, a pair of spaced apart circumferential wire receiving grooves, a third groove intermediate said wire receiving grooves, and a downwardly depending skirt of elastic Insulating material positioned in said third groove and extending beyond the periphery of the outwardly flared lower portion of the body member.

2. A transposition insulator for electrical circuits comprising a body member of insulating material having its lower portion outwardly flared, said body member having therein a pin receiving recess which extends from said lower portion only partially into the body member to provide an unbroken upper surface at the top of said body member, said body member having on its outer surface a pair of spaced apart circumferential wire receiving grooves one adjacent the top portion of said member and the other adjacent the flared lower portion, a third groove intermediate the upper and lower wire receiving grooves, and a downwardly depending skirt of elastic insulating maternal positioned in said third groove and extending beyond the periphery of the outwardly flared lower portion of the body member.

3. A transposition insulator for electrical circuits comprising a body member of insulating material having its lower portion outwardly flared, said body member having therein a threaded pin receiving recess which extends only partially from said lower portion into the body men her to provide an unbroken upper surface at the top of said body member, said body member having on its outer surface, a pair of spaced apart circumferential wire receiving grooves, a third groove intermediate said wire receiving grooves, and a downwardly depending skirt of wax impregnated elastic insulating material positioned in said third groove and extending beyond the periphery of the outwardly flared lower portion of the body member.

4. A transposition insulator for electrical circuits comprising a body member of insulating material having its lower portion outwardly flared, said body member having therein a threaded pin receiving recess which extends from said lower portion only partially into the body member to provide an unbroken upper surface at the top of the insulator, said body member having on its outer surface a pair of spaced apart circumferential wire receiving grooves, one adjacent the top portion of the insulator and the other adjacent the flared lower portion,  third groove intermediate said wire receiving groove, and a downwardly depending skirt of wax impregnated elastic insulating maternal positioned in said third groove and extending beyond the periphery of the outwardly flared lower portion of the body member.

References Cited in the file of this patent:

UNITED STATES PATENTS

1,065,737  Slonecker - - - June 24, 1913

1,795,638  Champion - - - Mar. 10, 1931

2,135,558  Bott - - - - - - - Nov.   8, 1938

2,138,571  Dehmel- - - - - Nov. 29, 1938

2,266,400  Reed  - - - - - - Dec. 16, 1941

2,304,483  Smith et al.  - - Dec.   8, 1942

2,31l,779   Shilling- - - - - Feb.  23, 1943

 

FOREIGN PATENTS

146,911  Germany - - - - Dec. 19, 1903

  28,141  Denmark - - - - July   23, 1921

414,535  Germany - - - - May  30, 1925