US1828614A - Electric conductor - Google Patents

Description

Oct. 20, 1931.. c. F. OBERMAIER 1,828,614

ELECTRI C CONDUCTOR Filed March 10, 1926 rn/ent or Carl F Obermaie l H is Attorn ey.

. tion.

Patented Oct. 20, 1931 UNITED STATES PATENT OFFICE CARL F. OBERMAIER, OF YORK, PENNSYLVANIA, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC CONDUCTOR Application filed March 10, 1926. Serial No. 93,712.

My invention relates to electric conductors,

and has for its object the provision of a flexible multiple electric conductor.

My invention relates in particular to the multiple conductor cords used with electrically heated appliances, such as flatirons, and the like. Such multiple conductor cords consist of a plurality of insulated conductors, usually two, which may be and usually are twisted, and bound together by an outer fabric sleeve. NVhen the insulated conductors are thus secured together it will be ob; served that there is substantially continuous linear contact between them, which comparatively large area of contact gives a very appreciable amount of friction thereby offering a considerable impediment to slippage of the conductors with relation to each other when the cord is bent. This results in impairment of the flexibility of the multiple conductor cord as a whole. Furthermore, if the conductors be twisted together tightly or the outer fabric sleeve applied tightly the friction between the conductors will be increased and the flexibility of the cord corres ondingly impaired.

11 carrying out my invention, I wrap a cord lielically around one of the insulated conductors throughout its full length, the turns of this cord being widely spaced, whereby point contact is provided between the conductors. This decreases the friction between the conductors and provides for a corresponding increase in flexibility of the multiple conductor cord.

For a more complete understanding of my invention reference should be had to the accompanying drawing, the single figure of which is a fragmentary view of an insulated electrical conductor embodying my inven- Referring to the drawing, I have shown my invention in one form as embodied in a twisted twin conductor cord, such as often used for electrical appliances and thelike, although it will be understood that my invention has applicationto various kinds of electrical conductor cords. The conducting cord comprises two copper conducting wires 10 and 11 which for the purpose of giving them greater flexibility are made up of a plurality of small copper wirs either bunched, stranded or braided. Various flexible insulations may be used for the con ductors 10 and 11, although as shown an electrically insulating layer or wrapping 12 of asbestos cords or threads is first applied directly to the copper conductor. This layer consists of a plurality of tightly twisted asbestos cords 13 which are wrapped together around the wire and lie side by side. As shown, several of these threads or cords are wound on the conductor simultaneously, the cords, it will be understood, passing around and around the conductor in helical formation, as shown in the drawing. The cords, lying side by side, form in effect a band which is Wrapped on the conductor. This wrapping of asbestos cords is secured to the conductor and the turns of the cords held rigidly in place by means of an outer layer of felted asbestos 14 which is applied directly over the cords.

Any suitable apparatus may be used for apsulating covering. This cord passes around the insulated conductor in an open helix, the turns being spaced a suitable distance apart and as shown are quite widely separated. As shown the cord 15 consists of a pair of strands lying side by side. The two insulated conductors may be and usually are twisted together and secured in this relation by means of an outer sleeve 16 of braided fabric threads, such as cotton or silk.

It will be observed that the two insulated conductors are twisted together in such man- 0 ner that the insulated conductor lI passes around the insulated conductor 10 in a direction opposite to the cord 15. It will also be observed that the spacing of the turns of the cord 15 is approximately half the spacing of the .turns of the conductors 10 and 11 so there are two turns of the cords 15 to every turn of the conductors 10 and 11.

The cord 15 has the effect of slightly separating the two insulated conductors so that the otherwise continuous linear contact between the two conductors is broken up into a plurality of point contacts with the cord 15. The point contacts result in much less friction between the two conductors and consequently reduce the impediment to relative slippage of the conductors when the twin conductor cord is bent. The flexibility of the cord as a whole is thereby increased.

'While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from-the spirit of my invention, the scope of which is set forth in the annexed claims.

What I claim as new, and desire to secure .by Letters Patent of the United States, is:

l. The combination with a multiple conductor cord comprising a plurality of insulated conductors, of an attenuated flexible mernber wrapped around one of said conductors so as to reduce the friction between said conductors and thereby increase the-flexibility of the cord, and an outer covering surrounding said conductors.

2. The combination with a plurality of insulated conductors, of a cord of fibrous material wrapped helically around one of said conductors so as to reduce the contact area between said conductors and thereby increase their flexibility, and an outer fibrous cover-- ing surrounding said conductors.

3. A flexible electric heater cord comprising a pair of insulated conductors twisted together, an outer fibrous covering securing said conductors together, and a cord of fibrous material wound helically around one of said conductors.

4:. A flexible heater cord comprising a pair of stranded conductors, electrical insulation on each of said conductors, said conductors being twisted together, a cord of fibrous material wound helically around one of said conductors, and an outer fibrous covering surrounding said conductors so as to secure them together.

In witness whereof, I have hereunto set my hand this 8th day of March, 19:26.

CARL F. OBERMATER.

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