US 1589438 A
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H. M. SHORT FLEXIBLE NONMETALLIC ELECTRIC CONDUIT June 22 1926. 1,589,438
Filed June 17, 1922 8141mm to;
Patented June 22, 1926.
UNITED STATES HENRY M. SHORT, 0F PENN YAN, NEW YORK.
FLEXIBLE NONMETALLIC ELECTRIC COND'UIT.
Application filed June 17, 1922. Serial No. 569,089.
The main object of my invention is to provide a conduit of this type which will fulfill the underwriters requirements at a minimum of expense.
Another object is to provide in such a conduit a smooth interior so that it may be readily fished.
Another object is to construct a conduit which is comparatively light in weight and yet sufliciently rigid to withstand crushing under normal conditions.
Another object is to so construct a conduit that it may have substantial longitudinal strength and yet be capable of flexure without buckling.
In carrying out the invention, I construct the conduit of a comparatively rigid helical member, flexible longitudinal strands on the outside of the helical member, and a knitted binder, and impregnate the outside with a suitable compound which is substantially waterproof and fireproof.
Fig. 1 is a fragmentary view of a piece of conduit embodying my invention showing part of it coated and part of it uncoated and split open.
Fig. 2 is a fragmentary very much enlarged view partly in section on the plane of the line 2-2 of Fig. 3.
Fig. 3 is a fragmentary longitudinal sectional view on the plane of the line 3-3 of The helical member 5 is preferably of a comparatively hard twisted paper, such'as a paper string which has considerable rigidity as well as tensile strength. I
The longitudinal strands 6 are preferably of some softer material, such as yarn or cotton threads which are flexible and yet of substantial tensile strength.
The knitted fabric is preferably of a comparatively soft flexible material such as yarn or cotton thread which may be readily handled in a knitting machine.
The longitudinal tension strands are preferably laid on the outside of the helical member 5 and the knitting so arranged as to bring the chain stitch portion 7 on the inside and the binder loops 8 on the outside. The chain loops 9 come between adjacent coils of the helix near the inside and the tension is so arranged as to draw the strands 6 somewhat in between the helices. This not only provides a smooth interior for the conduit but it artially fills up the spaces between the coi s of the helix and uts just enough crimp into the longitudinal strands to make the conduit flexible.
After the conduit is finished it is impregnated from the outside with a composition which forms a coating 10 and fills in the spaces between the various elements of the conduit. Although none of the elements of the conduit in themselves have sufficient strength to afford the necessary longitudinal tensile strength, all the necessary resistance to crushing even when combined, the finished product when impregnated constitutes what may be considered as a oneiece tube of substantial strength and flexibility.
It will be obvious that the interior may be coated with anti-friction material if desired, and that the exterior may be provided with additional coating or covering for special purposes when necessary.
1. A flexible single-wall non-metallic electric conduit comprising a helical member formed of hard paper string, flexible longitudinal strands of softer material than the helical member, a knitted binder of comparatively soft cotton yarn having looped portions embracingsaid longitudinal strands and holding them in between the adjacent turns of the paper string, and a fireproof and waterproof composition covering the outside of the conduit, impregnating the outer part of the cotton yarn and filling up the spaces between the adjacent strings, yarns and strands, and stiffening the conduit to prevent collapse and leaving the interior smooth and capable of being readily fished.
2. A flexible non-metallic conduit comprising, a helical paper cord, flexible lon itudinal strands, and a knitted cotton bin er having a chain stitch portion forming the interior surface and having the loop portions on the outside, and a composition impregnating the loop portion and filling between the adjacent coils of the helix and the chain stitch portion of the binder and securing the inner chain stitch portion to the helix.
HENRY M. SHORT.