US2164168A - Armored electrical cable - Google Patents

Description

June 27, 1939. J. wg-rzHElSER Ef L 2,164,168

' Ammann mscnucm. cALE Original Filed May 15, 1935 fans-,e CoM/0L ana/w HaHa/var .so/vaga, ay

. B y mvmfmwff @9m-M. CWM Nm ATTORNEYS Patented June 27, 1939 UNITED lSTATES PATENT OFFIQE ARMORED ELECTRICAL CABLE tion of New Jersey original application May 15, 1935, serial No.

21,524. Divided and this application October 4, 1935, Serial No. 43,530

Z Claims.

electrical failure as for instance, due to tearing l loose during installation of any insulation on the conductors that might have adhered to the armor sheath.

Another object is to provide an armored cable of the above type, with adequate protection along 16 the entire exposed severed sharp edge of the sheath, and readily applied in installation of the cable, to preclude any possibility of cutting the insulation of the protruding outwardly turned conductors.

A feature 4of the invention is the use, preferably, of paraiiin impregnated paper, applied about the insulating conductors, preferably Iby helical winding, the heat evolved in the assembly serving to soften the wax and autogenously to bond the superposed convolutions to each other.

Another feature is the superposition of another llayer of unwaxed or unparailined paper interposed between the bonded protective paper layer and the conventional outer helically wound metal armor sheath.

This application is a division of our pending application, Serial No. 21,524, led May 15, 1935, and patented on October 29, 1935, under No. 2,018,939.

In the accompanying drawing, in which are shown one or more of the various possible embodiments of the several features of the invention,

Fig. 1 is a. perspective view of a length of the armored cable, with the protective bushing inserted,

Fig. 2 is a perspective vienr partly in longitudinal section, showing the removal of a. por

` tion of the outer protective layer,

Fig. 3 is a view similar to Fig. 2 showing one step in the application of the protective bushing,

Fig. 4 is a view similar to Fig. 3, showing the final step in the application of the bushing,

Fig, 5 is a view in longitudinal cross-section showing the bushing applied, and

Fig. 6 is a perspective view of the bushing as an article of manufacture.

Referring now to the drawing, there is shown an armored cable illustratvcly with two conductors I0 and il, each covered by conv-entional 55 insulation, illustratively braided covering i2.

The conductors are shown enclosed in an insulating protective covering, which is preferably a continuous spirally wound sheet of paper i3 impregnated with wax, preferably parafiin. The Width of the paper is illustratively three times the pitch at which it is wound, so that the coinpleted sheath will be three-ply. In the conventional process oi fabricating the armored cable by winding the protective covering simul taneously with the armor sheath, the parafln or other wax becomes suiciently softened to aiord an adequate bond of the various convolutions and to eiect a secure continuous insulating enclosure sheath, and this without the need for special application of any form of adhesive.

Irraddition to the bonded protective sheath, there is preferably employed, according to the present invention,I the further outer insulating covering i4 of paper, devoid of wax or other adhesive, which is wound about the inner protective sheath I3. About the parts thus far described, is wound the conventional metal sheath i5 comprising a strip of metal wo :ad on a pitch substantially equal to its effective width, the overlapping helical edges being crimped together at i6.

In the armored cable made as described, the outer paper layer M is free from any adhesive bond with respect to the sheath and substantially free of such bond with respect to the inner protective covering i3. Accordingly, no adhesive connection between the conductor or its protec tive covering and the outer metal sheath can occur, so that in bending and manipulating the latter, there is no possibility of tearing loose any of the protective insulation, and electric failures from this cause are not apt to occur.

In use of the device, after cutting or severing the. sheath as at il adjacent the outlet box or other terminal structure, the outer insulating layer i4 only is preferably removed down to a point slightly below the exposed end of the sheath, thereby to afford clearance for the insulating bushing Winch may be of conventional construc tion. Thus, it is seen that the insulating bushing fits snugly in said clearance thus left between the bonded protective sheath i 3 and the inner wall of the metallic armor i5. In constructions in which the entire insulating protection must be removed between the insulated conductors and the metal sheath, a simple fibre bushing may not fit with suiiicient snugness to assure its retention, while an attempt to introduce a bushing without removal of any of the insulating covering between the insulated conductors and the metal armor usually involves diiculty. While, as above noted, a conventional bushing may he employed, we have shown in Fig. 6 of the drawing one embodiment of the bushing, claimed in the parent application, of which this is a division. This bushing is shown of helical conformation and of peripheral length somewhat greater than one complete convolution. The split ends i8 and I9 of the nbre bushing B are displaced longitudinally of the bushing along a pitch such that the trailing end 20 of the leading edge I9- overlaps tie leading end 2| of the trailing edge I 8. The leading end I9' of the leading edge I 9 constitutes a guiding conformation for ready installation of the bushing and the part of the bushing adjacent said leading edge I9 becomes wedged or anchored in place in the application of the bushing, as best shown in Figs. 3 and 4. The leading rim 22 of the bushing is preferably of pitch somewhat greater than that of the outer or trail-ing rim 23, as appears from the fact that the leading split edge I9 is longer than the trailing split edge I8. Preferably, the pitch of the leading rim 22 of the bushing is substantially equal to that of the helically Wound sheath. and the trailing rim 23 which has an outwardly turned flange 24 is of somewhat lesser pitch.

The application of the bushing is quite expedl tious, since it requires nothing more than the single manipulation of introducing the leading or anchoring end I 9' with the thumb pushing it home to effect secure anchorage and then following with light pressure with the index and middle finger on the trailing rim 23 towedge it home.

The bushing thus securely wedgedl in place is effective around the entire periphery of the sharp severed edge of the armor sheath, so'that the construction avoids the objection to ordinary split insulating bushings, in which protection is substantially lacking at the region of the split. In the present construction, the split region is in fact of enhanced security, since a double layer of bre is presented thereat. y

It will thus be seen that there is herein described apparatus in which the several features oi this invention are embodied, and which in its action attains the various objects of the invention and is Well suited to meet the requirements of practical use.

As many changes could be made in the above construction, and many apparently widely difierent embodiments oi this invention could be made 4Without departing from the scope thereof, it is intended that all matter contained in the'above description or shown in the accompanying drawing shall he interpreted as illustrative and not in a limiting sense.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. An armored electric cable comprising one or more insulated conductors, paraiiin paper .strip helically wound thereabout, said strip being wax impregnated and of width several times the pitch oi the winding to present overlapping areas, the wax of said overlapping areas serving as the means for welding the saine together in a unitary flexible structure, and a second helical strip of paper, free from wax, wound about said first strip, and a metal strip helically wound about the pretectlve covering to form the armor sheath.

2. An armored electric cable comprising one or more insulated conductors, a Wax covered paper strip helically wound in overlapping relation about said conductors with the wax of said strip bonding the overlapping areas thereof together in a substantially unitary flexible insulating sheath thereabout, an outer layer of protective paper free from adhesive, encircling said first covering, a helically wound metal sheath enclosing said protected conductors, whereby a split insulating bushing frictionally may be retained in place between the armor and paraiiin paper protective covering in the space left by the removal depth of such bushing.

JOSEPH WERTZHEISER. HARRY CHARMOY,

a()A of the outer paper layer for substantially the

Images