US1787629A - Nonsticky water and flame resistant insulated conductor, conduit, etc., and method of making - Google Patents

Description

Jan 931; .J. A. KENNEDY 1,737,629

NONSTICKY WATER AND FLAME RESISTANT INSULATED CONDUCTOR,

CONDUIT, ETC. AND METHOD OF MAKING Filed Oct. 2. 1928 Patented Jan. 1931 UNITED STATES PATENT OFFICE JOSEPH A. KENNEDY, 0] PAWTUCKET, RHODE'ISLAND, ASSIGNOB, BY MESNE ASSIGN- IENTS, T0 ANACONDA WARE nonsrrcxx warm m m AND CABLE COMPANY, A CORPORATION 01' DELA- IILAIE RESISTANT INSULATEl) CONDUCTOR, CONDUI'I, E'I'C.,

AND METHOD 0! MAKING Application fled October 2, 1928. Serial No. 309,502.

' This invention relates to the art of waterresistant and flame-proofed insulated electrical cable and other conductors, non-metallic flexible conduit for receiving and protecting electrical conductors, and other manufa'ctures of similar character. It is concerned with methods of treating such manufactures to make them not only water-proof and flameproof within the limits of established practice, but also non-sticky on the surface.

' Such goods are treated with compounds to render them water-proof and flame-proof, conforming to the standards established by the National Board of Fire Underwriters. Heretofore asphaltum has been commonly used as the water-proofing compound, and stearin itch as the flame-proofing compound, the asp alt being first applied and caused to penetrate and impregnate to a greater or less extent the sheathing of the conductor cable or the structure of the conduit, and the stearin pitch being subsequently applied as an outer coating. While these substances are satisfactory from the point of view of the underwriters requirements and cost considerations, the stearin pitch coating has the objectionable quality of being sticky. It is a semi-solid amorphous substance when cold,

and is liquefiable by heat. It is applied to the goods by passing the latter through a body of the stearin pitch contained in liquid condition in a heated tank. After heating and application in this manner, its sticky condition persists even after cooling, so that when the coated goods have been rolled into a coil for storage and shipment, the ,turns of the coil adhere together and the coating is liable to be more or less stripped oif when uncoiled; and also the sticky material soils the hands of users and anything else with.

which it may come in contact. In the efiort to overcome this sticky quality, the practice has been commonly followed of passing the coated goods, after leaving the tank of melted stearin pitch, through a loose mass of mica flakes or powdered talc, some of which will adhere more or less firmly tokthe sticky coat= ing. But the protection given'by this means is not complete andsatisfa'ctory. Another efiort in the same direction, which consists in'applying an additional coat of paraflin or other wa substance over the stearin pitch has met with greater success. Both of these treatments, however, involve material, and a step in the process, additional to the commonly used asphaltum and stearin pitch, and to the processes followed in applying these substances.

Accordin to the present invention, I obtain the desired effect of water-proofing and flame-proofing the goods, and overcoming the stickiness of the flame-proofing coat, by successive treatments with wax and stearin pitch, eliminating the use of asphaltum altogether and the step of applying powdered mineral or melted wax on the surface ofthe flameproofing compound. In this new treatment the wax impregnation takes the place of asphalt impregnation and obtains an equally.

successful water-proofingefl'ect. It likewise neutralizes or overcomes the surface stickiness of the stearin pitch coat. The last named effect is due to the fact, which I have discovered and utilized industrially for the first time, I believe, that when wax of lower meltadhesive quality of the external surface of the stearin itch coating and produce a waxy feeling to t e touch, but is insufiicient to increase the infiammability of the stearin pitch coat appreciably. It does not exist on the slfirface of the pitch coating as a distinct film o wax.

The steps of the process and characteris:

tics of theproduct in which this invention resides are more fully described in the following specification, in connection with the drawings. In the latter,-

I Figs. 1, 2 and 3 are diagrammatic views illustrating the nature of the steps performed in impregnating a cable or electrical conduc- 'torsaccording to this invention but without attempting-to show the details of the commercial apparatusen ployed; v p

Fig. 4 is a fragmentary elevation of a partially dismembered cable embodying this invention;

Fig. 5 is a fragmetary partial elevation and partial section of a conduit for electrical purposes embodying the same invention.

The invention may be applied to the treatment of all types of flexible insulated electrical conductors or cables, and flexible nonmetallic conduit designed to receive electrical conductors and for like uses. In Fig. 4 I have shown illustratively a cable consisting of two insulated wiresaand bwhich are Wrapped about with strands of twisted paper or other equivalent cords in order to preserve and maintain a prescribed distance between the metallic cores of the individual conductors, and are laid side by side, in conjunction with thick filler cords (Z, (Z, into a cable which is covered by a sheath 6 constructed of interwoven or braided strands. In Fig. 5 I have shown a flexible non-metallic conduit of the typp shown in the Smith Patent No. 1,016,527, Fe ruary 6, 1912, as illustrative of another class of goods in which the invention may be embodied, such conduit being constructed of lon itudinal warp strands and helical weft or lling strands.

In applying the treatment of this invention to a cable, the separate wires, with their surrounding strands 0, are passed through a tank It containing a body of melted waxand heated .by gas flames 2' or otherwise to a temperature high enough to keep the wax in melted condition. After the wax thus applied has be-.

come solid, the wires are combined in a cable and covered with the woven or braided sheath 6. The entire cable is then passed through a similar heated tank j containing wax in melted condition; The wax is sufficiently fluid and the cable is passed through the tank slowly enough to permit a substantiall complete impregnation of the sheath and the component "strands thereof by thewax. As the cable emerges from the tank the surplus wax adhering to its surface is wiped off by means well understood in the art.

In these treatments I may use any wax which has a melting point lower than that of stearin pitch and is sufiiciently thin when melted to penetrate into and between the strands of the sheath, as above set forth. Paraffin wax is suitable for this purpose and may serve as an illustration of a large class of equivalent waxes having the desired properties.

The procedure above described, so far as concerns the preliminary treatment of the wires before being covered with the sheath 0, may be modified or omitted "without departure from the invention. Thus, in the case of cables containing two or more wires differently colored to designate different polarity, the light colored wire or wires may be treated with a clear wax, and black or other; dark colored wires treated with a different suitable compound, if desired, to reduce expense or for other reasons. Or indeed the preliminary wax treating ma be omitted altogether and the treatment a ter application of the sheath relied on to permeate the covering strands 0, and 'even the braided jackets of the individual Wires.

Finally the wax impregnated cable, after cooling, is passed through a tank In containing a body of melted stearin pitch maintained in a sufliciently fluid condition, by-the heat of gas flames under the tank or othersuitable means, to permit immersion and passage of the cable through it, In leaving the tank the cable passes through a die or wiper which removes the excess of stearin pitch. A second coat of stearin pitchmay be applied if desired by a repetition of the step last described.

The heat of the stearin pitch bath melts the previously applied Wax; and the free melted wax, that is, so much of it as-is not retained in the sheath by capillarity, percolates through the enveloping coat or coats of stearin pitch and appearson the surface of the outer coat in suflicient quantity to give it a slightly waxy feeling to the touch and make it completely nonadhesive either to adjacent bodies of the same material, to the hands of the user, or to other objects with which it may come in contact. But the wax does not make a perceptible film on the surface, neither is it present in suflicient quantity to burn when subjeced to the flame test, or to impair the ability of the stearin pitch coating to conform to the established flame-proofing standards. It leaves the sheath highly flexible and avoids deposit of a black sticky compound on the inside of the sheath and on the individual wires. As the result of using wax in this connection the stearin pitch coating does not y penetrate through the meshes of the sheath goods are treated by impregnation first in melted asphaltum and then in melted stearin pitch, the black compounds usually penetrate the sheath more or less, leaving a sticky deposit on the inside of the sheath which soils the hands of the workman when removing the sheath preparatory to connecting up the wires,

and also discoloring those wires which aregiven a light color forpolarity distinction.

Conduits are treated according to this invention in the same way as above described with respect to cable. Indeed an 0 en conduit of woven construction is essentially the same as the outer sheath of a cable or other insulated conductor, so far as the invention is concerned. It differs in having an :open interior instead of being filled with wires, etc, but it is so passed through the baths of wax and stearin pitch that these materials are applied to it on the outside only and penetrate only to the extent that they can soak into the interstices during the time that a given point in the length of the conduit remains in the bath. The same qualities are given to the conduit by this treatment as are given to the cable. For the purpose of generic definition I have adopted the term covering for electrical conductors to designate both the conduit as a separate article of o manufacture, and the outer sheath which receives the impregnating and coating treatment as a component of an electrical cable I or single insulated conductor which may be treated by this method. 4 It will be noted that in the treatment of both described'embodiments of such coverings, according to this invention, the usual coating or impregnation by 'a sphaltum is omitted, and the water-proofing effect is g fully and adequately obtained by the substituted wax treatment. Thus the wax performs the double function of water-proofing the article and mitigating the stickiness of the flame-proofing compound. And, in ap- 5 plication according to my discovery and in- 'vention, it performs these'functions without creating a fire hazard.

What I claim and desire to secure by Letters Patent is: I so 1. The method of water-proofing and flame-proofing coverings for'electrical conductors which consists in fir t. impregnatingv such covering withwax of a lower melting point than the after-mentioned flame proof- '35 ing compound, and then enveloping said covering with a coat of flame-proofing com- Jpound which is liquefiable by heat and is applied at a temperature higher than the melting point of the wax.

2. The method of water-proofing and flame-proofing coverings for electrical conductors, and mitigating the stickiness of the flame-proofing substance, which consists in first applying to the covering a waxy substance which is liquefiable at a temperature the atmospheric temperatures, but insufli cient to create a 'fire hazard.

i. A covering for electrical conductors having a water-proofing content of wax on and adjacent to its outer surface, and an enveloping coating of flame-proofing material interpenetrated to a certain extent by such wax.

5. A covering for electrical conductors constructed of interconnected fibrous strands having material which in itself is more or less sticky at ordinary temperatures, and having a content of wax within its structure inside of said coating and penetrating the latter to the outer 'surface in suflicient measure to render such surface substantially non-sticky.

6. A covering for electrical conductors of textile construction, combined with a wax impregnation and a flame-proofing coat ng of stearin pitch, a portion of the wax being interspersed through said coating to the outer surface thereof in sufficient measure to render such surface substantially non-sticky, but insufiicient to create a fire hazard.

In testimony whereof I have aflixed my signature.

\ JOSEPH A. KENNEDY.

lower than that to which the flame-proofing substance is brought when applied to the covering, and also has the'property of penetrat' ing the flame-proofing substance when both are in the liquid condition; and then applying' to the article thus treated a coating of flame-proofing composition at a temperature high enough to'melt the waxy substance.

penetrate through such stearin pitch coating in suflicient quantity to mitigate the sures face stickiness ofjthe latter, when cooled to 3. The method of water-proofing and i

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