To all whom it may concern:

Be it known that I, FOREE BAIN, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Electric Insulators, of which the following is a specification.

My invention relates to the class of insulators employed most commonly with the poles on which overhead electric wires are strung, being usually composed of glass or porcelain, and involving, as the general construction, a head circumferentially grooved to adapt it to receive the binding-wire, and having an internal threaded socket to receive the supporting-pin and a "petticoat" portion.

My improvement relates, more particularly, to the petticoat portion referred to, my object being to so construct it as to prevent the formation of a continuous film of moisture from the wire to the pin, affording a conductor that would ground the circuit.

I accomplish my object by forming the insulator circumferentially with sharp projecting lines, ridges, or corrugations.

The accompanying drawing shows an insulator of my improved construction, in broken elevation, on its supporting-pin.

A is the insulator, formed of glass, porcelain, or other suitable insulating material, and provided with the usual head portion r, having the circumferential groove n. for the binder o, with the internally- threaded socket

q for the pin p, and with the petticoat portion B.

When the insulator A, as is commonly the case in its use, is exposed, unless means be provided to prevent, a continuous film of moisture may form upon it, and thus afford a conductor from the wire o or the binder o' along the outer and inner sides of the petticoat to the pin, tending to ground the circuit, and thus lower the insulating resistance. I prevent this by forming circumferentially around both the outer and inner surfaces of the petticoat B a series of ridges m or corrugations, which should be sharp and separate, as illustrated. These break the continuity of the film, and thus prevent the formation of such a conductor as would cause the grounding of the circuit.

What I claim as new, and desire to secure by Letters Patent, is--

An insulator A, comprising, in combination, a head portion r and a petticoat portion B, with an intermediate groove n for the binder o', the petticoat portion having formed upon its outer and inner surfaces a continuous series of separate circumferential sharp ridges m, substantially as and for the purpose set forth.

                       FOREE BAIN.

In presence of--

J. W. DYRENFORTH,

M. J. FROST.