Safety-anchored multi-conductor water-cooled electric arc furnace cable

[57] ABSTRACT

The ends of the individual conductor cable ropes of this multi-conductor water-cooled electric arc furnace cable are secured within the cup or pocket of the terminal by embedding them in solder. In order to prevent the individual conductor cable ropes from dropping out of the terminal pocket or cup when a clogging or other failure of the water cooling system causes the cable to overheat and consequently melt the solder, two of the individual conductor cables are additionally secured to the bottom wall of the terminal cup or pocket by being encased in an L-shaped tubular conductor clamp. The transverse arm of each such clamp, and the cable rope end therein are drilled for the reception of the shank of a threaded fastener, such as a bolt, the shank of which passes through a bore in the bottom or end wall of the terminal cup and receives a threaded nut on the exterior thereof.

Claims, 4 Drawing Figures

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PATENTED APR 21974

3,801,724

FIG. I

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3,801,724 1

SAFETY-ANCHORED MULTI-CONDUCTOR WATER-COOLED ELECTRIC ARC FURNACE

CABLE

In the drawing,

FIG. 1 is a side elevation, partly in central longitudinal section, of one end of a multi-conductor watercooled electric arc furnace cable, showing the safety anchorage construction, according to one form of the present invention;

FIG. 2 is a cross-section through the cable beyond the terminal, taken along the line 2—2 in FIG. 1;

FIG. 3 is a left-hand end elevation of the cable shown in FIG. 1; and

FIG. 4 is a fragmentary bottom plan view of one of the cable anchoring devices and its threaded anchoring fastener, with the conductor-securing solder and the terminal omitted, looking in the direction of the arrows 4—4 in FIG. 1.

Referring to the drawing in detail, FIG. 1 shows a safety-anchored multi-conductor water-cooled electric arc furnace cable, generally designated 10, for electrically connecting a conventional transformer (not shown) to an electric arc furnace (also not shown). Due to the three-phase electric current usually employed in such furnaces, at least three of the cables 10 are ordinarily employed, one for each phase of this current. Due to the heavy current load demand of such furnaces, a plurality Of such cables for each phase is frequently employed, especially in large electric furnaces, so that the total of six to twelve or more of such cables is employed with each furnace. As the primary voltage of such a transformer is in the neighborhood of 13,000 volts and the secondary output a current of 10,000 amperes per phase at 230 to 800 volts, the breakage of such a cable is extremely dangerous to nearby workmen, and it is such breakage that it is the purpose of the present invention to prevent.

In particular, the cable 10, of which only the furnace connection end 12 is shown, consists of a forward terminal 14 and a multi-conductor water-cooled cable unit 16 secured thereto and safety-anchored in a manner described below. The forward terminal 14 is constructed of heavy copper and has a forward connection blade 18 adapted to be connected to the furnace. The rearward terminal (not shown) at the opposite end of the cable unit 16 is of similar construction and is connected to the transformer (not shown). The forward connection blade 18 has flat opposite sides 20 (FIG. 3) and contains multiple spaced holes 22 for the reception of bolts (not shown) by which it is secured to the furnace or transformer, as the case may be. The blade 18 at its forward end 24 is provided with a threaded port 26 leading to the forward end of a cooling water passageway 28, the opposite end of which terminates in a rearward or inner port 30 opening into the cavity or cup 32 of the rearward portion or base 34 of the terminal 14.

The rearward portion or base 34 of the terminal 14 is of hollow cylindrical shape and has an outer generally cylindrical surface 36 provided with annular frustoconical ratchet teeth 38 which engage and penetrate the inner surface 40 of a hose 42 of synthetic rubber such as that known commercially by the trade name Neoprene. The forward end of the hose 42 is secured ' to the terminal 14 by multiple longitudinally-spaced hose clamps 44 which cause the annular ratchet teeth to indent and tightly grip the hose 42 in a water-tight interlocking connection.

The rearward portion or base 34 adjacent the inner or rearward port 30 is provided with a bore 46 which in turn opens into a counterbore 48 from which it is separated by an annular shoulder 50 extending therebetween and forming the bottom surface of the bottom wall or end wall 52 of the terminal base 34. Seated in the bore 46 is the outer or forward end of a riser tube • 54 which is preferably of copper, the inner or rearward end of which is seated in and snugly engages the cylindrical inner surface 56 of a fluted perforated core tube 58. The core tube 58 is of elastic deformable material, such as rubber or synthetic rubber, and has multiple perforations 60 therethrough for the flow of cooling water reaching them from the port. 26 by way of the passageway 28, port 30, riser tube 54 and core tube 58. The fluted outer surface 62 of the core tube 58 is engaged by the perforated tubular jackets 64 of a plurality ' of cable conductor ropes 66, so-called because they are composed of hair-like fine copper wires braided into a form resembling a hemp or manila rope. The perforations 68 permit cooling water to flow from the perfora tions 60 into the interiors of the jackets 64 where the water passes along the spaces or interstices between the fine wires composing the cable ropes 66.

The perforations 68 in each jacket 64 extend inwardly for a distance of approximately two feet and therebeyond each jacket 68 becomes imperforated. At this point, each jacket 64 is provided with a tubular plastic plug (not shown) held in place by suitable fasteners, such as by four brass screws.

The rearward terminal (not shown) of the cable 10 is similar to the forward terminal· 14 except that its blade which corresponds to the blade 18 is disposed at right angles to the forward blade 18. The cable unit 16 together with its hose 16 and cable conductor ropes 66 as well as the perforated jackets 64 and perforated fluted core tube 58 are conventional in construction and their details rearward, i.e. to the right of the section line 2 2 in FIG. 1, are beyond the scope of the present invention.

The outer end portion 70 of each of a plurality, preferably two, of the individual cable conductor ropes 66 is encased in the longitudinal tubular arm portion 72 of an L-shaped tubular conductor clamp 74 and extends through the transverse tubular arm 76. Both the transverse arm 76 and the conductor rope end 70 therein are drilled for the passage of the shank 78 of a threaded fastener 80, such as a bolt, having a head 82 abutting the transverse arm 76 which in turn abuts the annular shoulder 50 of the end wall 52 of the terminal 14. The shank 78 of the threaded fastener 80 passes through a 55 b°^re 84 in the end wall 52 and on its outer end is secured by means of a nut 86 threaded thereon.

The remaining conductor cables 66 are not so anchored, but, together with the anchored conductor cables 66, are secured within the counterbore 48 by a soft ₆₀ solder filling 88 which is poured into the counterbore 48 while it is in a molten condition and after the two anchored cable ropes 66 and their clamps 74 have been bolted into place. The cable ropes 66 are normally of circular cross-section (FIG. 2) but their forward por₆₅ tions 70 are passed through the tubular conductor clamps 74 while these are initially of circular crosssection. These are then swaged into rectangular crosssection after the cable rope end portions 70 have been

3,801.

inserted therein and the transverse tubular arms 76 thereof have been bent at right angles to the longitudinal tubular arm portion 72, whereupon the drilling of the bolt holes in the transverse arms 76 and cable rope ends therein are carried out. Bolting is then performed 5 by means of the threaded fasteners 80 to anchor the ends 70 of the anchored cable ropes 66 to the terminal 14, whereupon the remaining unanchored cable ends 70 are then inserted in the counterbore 48. This assembly is then placed in an upright position and the molten 10 soft solder filling 88 is then poured into the terminal base or cup 34 so as to substantially fill the counterbore 48 and also the interior of the cable hose 42 substantially back to the ends of the perforated cable rope jacket 64, ₁₅

In the operation of the invention, the rearward cable terminal (not shown) of each cable 10 is connected to the transformer, and the forward blade 18 of the forward terminal 14 is bolted to its connection at the furnace. The port 26 is connected to its corresponding 20 pipe at the furnace while the corresponding rearward terminal port is connected to a source of cooling water. Consequently, during operation of the furnace, the heat generated by the flow of electric current through each cable 10 and also by the heat of the furnace itself 25 is dissipated by the cooling water flowing through the perforated fluted core 58 and thence around the jacketed cable conductor ropes 66 by way of the perforations 60 and 68 respectively.

If, for any reason, the flow of water through the cable 30 10 is interrupted or is ended completely, the consequent rapid rise of temperature within the cable 10 causes the solder filling 88 within the terminal cup 32 to melt. Notwithstanding such melting, however, the anchored cable conductor ropes 66 are held immov- 35 ably in the terminal cup 32 by means of the cable clamps 72 and the clamping bolts 80 securing these members to the terminal cup end wall 52. The thusanchored cable conductor ropes 66 now serve mechanically as safety supporting cables so as to prevent the 40 remaining unanchored conductor cable ropes 66 from dropping out of the terminal cup 32. In this manner the present invention prevents damage to the furnace by its otherwise falling against the furnace casing and also prevents injuries to adjacent workmen, either by the 45 weight of the falling cable or by the tremendous electric current thus suddenly released, especially if water has fallen or is standing upon the floor of the furnace room.