US 2440668 A
Description (OCR text may contain errors)
April 27, 1948.
J. P. TARBOX CABLE GONSTRUCTION Filed Aug. 18, 1943 I/A y -I IlV// I N VEN TOR FIG 6 Patented Apr. 27, 1948 CABLE CONSTRUCTION John P. Tarbox, Philadelphia, Pa., assigner to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Application August 18, 1943, Serial No. 499,058
3 Claims. l
This invention relates to electric bus bars, cables, and the like and has particular applicalbility to conductors for transfer of heavy currents. In certain industrial fields, asin the welding art, currents are employed of values often exceeding 1000 amperes and consequently it'becomes of considerable importance that the conductors are capable of carrying these currents without overheating with resulting loss in voltage and power.
While numerous factors in conductor construction should be considered applicant has ascertained the following to be of outstanding importance: (a) strand formation of the conductor, (b) proximity of in and out conductors, (c) direct cooling of conductor-s by a coolant. Strand formation has utility in tending to eonne the current in individual strands since oxidation of the strand surface develops a current resistant iilm. To the extent that this surface resistance develops skin elect in each strand, losses due to alternating currents are reduced. Moreover. strand formation facilitates easy fiexure of the bar or cable, this feature being of particular importance in the welding art.
Proximity of in and out conductor sections is of importance primarily in reducing the reactance oi the conductors, thereby permitting a larger current now as ci a given temperature and re-n ducing iateral stress or hielt. Reduction ci reactance arises from the pure inductive action of one section on the other as well as the inductive interaction due to the physical connection of the two sections and known as proximity effect. The result ci both inductions 'ls to reduce the reactance on adjacent conductor surface thus increas ing current lnow..
Direct cooling supplements the other two factors by providing a certain means for abstracting heat from 'the conductor. By so doing the heat developed by the current is prevented from accumulating in the conductor and hence for a given temperature the current output may be increased.
Having the above factors under consideration the objects of the invention.` may be thus summarized: to provide a cable construction wherein stranded conductors are effectively employed; to provide a conductor having increased current capacity due to diminished reactance; to provide effective means for introducing and applying a coolant in direct relation to the conductor; to provide structure permitting ready iiexure of the conductor; to provide c. conductor resistant to short circuit stresses; to provide terminal connections for the conductors; and to provide in general a compact, flexible conductor construction -capable of use with highest eiiiciency.
With these objects in mindrreference is now made to the disclosure including the description of certain embodiments of the invention, which may be preferred, and the accompanying drawings in which:
Figure i is a sectional view of a bus bar cable illustrating one form of a conductor;
Figure 2 is a view illustrating a modied form of the bus bar construction; y
Figures 3 and 4 illustrate further conductor modiiications;
Figure 5 is a sectional view of a connection between general bus bars and the conductor unit of the invention; and
Figure 6 is a section taken along lines 6-6 of Figure 5.
Referring to Figure 1 there is indicated an insulation support for the cable or conductor indicated generally by the numeral iii, this support including a flattened nexible strip ii attached to extend the full width oi the conductor and beyond the same. Atreither edge of this strip is secured enlarged sections i2 having duplex flaps i3 with diagonal edges lli extending from opposite sides thereof. The flap width is such that when folded with the edges ld in engaging relationship a tubular conduit i5 is formed on either side of the central strip partition li.
Adapted to be positioned within the tubular conduits it as above described are a plurality of cables I6 each of which is formed of multiple intertwisted strands l1. These cables overlie and underlie the partition il to which they are attached as by vulcanization. The strip edge and flap material may be a homogeneou-s substance such as rubber or rubber containing composition possesing sucient strength and rigidity to maintain normally the indicated form but also having suflicient elasticity to permit a degree of flexing under iniiuence of torsional stresses. The material also preferably should be such as to permit sealing or bonding so that the cables I6 may be welded securely in place and the juncture of the end flap oiler adequate resistance to strain.
In assembling the conductor in accordance with the above described structure with the aps I3 open, the cables I6 are placed into position on 5 either side of the strip I I and vulcanized or otherwise secured in place. The adjoining edges I4 of the adjacent flaps are then brought together and bonded by an appropriate means so 'as to be waterproof. Itis pointed out that the dimensions of the ilaps I3 are such that when bonded there exists a conduit I5 of cross sectional area substantially in excess of the total cross sectional area of the cables I6, this being for the purpose of providing a channel for cooling liquid such as water whereby the conductors may be subjected to a constant cooling during periods of current conduction.
Figure 2 illustrates the modication oi the invention wherein the supporting unit 29, including the cross strip ZI, end sections 22 and side ilaps 23 are similar to corresponding parts of the support II) of Figure 1. The change over the described modiication lies in the employment of multiple cables 2d, the same being in rectangular 25 cross section and being formed of a plurality of individual strands 25 twisted together. In assembiing the conductor according to this modiiication the cables 24 are somewhat displaced from each other so as to provide space for entry l of bonding material so that when sealed or vulcanized the cables are securely fastened not only to the strip 2i but to each other thus imparting an increased rigidity to the whole structure. Conduits 26 are formed in the completed assem- 35 bly.
In Figure 3 is illustrated a modification of the invention employing supporting elements frictionally related to each other'instead of integral.
In this modification the cables 30 are cylindrical 40 and formed of inter-twisted strands 3i, one cable being above and another below an insulating partition 32, in which grooves 33 form supporting channels. A sheath 34 forms a casing around the conductors and insulator 32, the sheath being 45 of insulating and iiexible material which is impervious to Water. As shown the sheath 3d is taut, frictional contact with the squared ends 35 of the insulator strip 32 serving to hold them in place. Channels 36 above and below the strip 50 32 and on either side of the conductors are formed by this construction.
The modication of Figure 4 also utilizes frictional holding means between the central partition and casing. There is illustrated a central 55 strip `4I) with enlarged edge members 4I and having vertical inner surfaces l42 deilning shallow channels in which the conductor is positioned.
In this form of the invention the conductor is illustrated as a bus bar 43 although cables, strand-I 60 or single, may also be employed. The outer surface of the edge sections are curved to form a curvilinear surface for engagement with ythe inner surface of the enclosing sheath or casing 44.
It is observed that this sheath is oversized so that 65 normally spaces forming conduits 45 exist for conductor of water or other coolant.
There is illustrated in Figures 5 and 6 means by which the conductors as hereinabove described may be attached to a pane1 bus bar for example 70 and to the coolant source. The panel bus bars are indicated at 50, the same being attached to the cable or bus bar 5I of the conductorby any appropriate means such as the rivets 52. Interposed between the bus bars is an insulation 75 member 53 which is of a thickness suiiicient to overlie the ends of the bus bars 5l of the conductor. f On the other side of the bus bars 50 are positioned the ferrule connections -li to the water pipe lines 55. These ferrules take the form of circular segments 56 having a :dat side 5I and an upper curved side 58 through the center of which a conduit 53 extends. A tube 6@ connects one end of this conduit to the pipe line thus establishing a pipe connection to the conductor bus bars or cables 5I. The casing or sheath 6I of the conductor is extended to overlie the ferrules iid and the insulation block 53, contact of the sheath with the ferrule and insulation being made watertight by means of the clamp t2.
In connection with the modification of the inf vention herein disclosed itis pointed out that the intervening partition forming part of the support Within the conductor separating and s upporting the conductors has a thickness of such value that the cables on one side of the partition inductively aiect the cables on the other side. In order to make this action the more positive preferably the thickness of this partition should not be cut over Va" and desirably ils". With this limited separation of the cables, the same carrying current in opposite directions, the eect oil induction is made pronounced thus reducing the reactance on the adjacent surfaces of the cables and permitting a larger ow of current than would otherwise ow. This factor is of consider= able importance inalternating current circuits where the cables carry large amounts ot current as is the case when employed in connection with welding apparatus. Itis pointed out further that the employment of strands in each cable increases the exibility of the conductor as a Whole so that the cable may be readily employed in shops and among machines. Stranding also increases the overall surface area of the cables and where the strand surface is subject to oxidation.
as is generally the case, the interstrand resistance is increased thus tending to conne the skin eiect current to the individual strands rather than to the cable as a whole. In this way the overall resistance of the cable may be decreased when utilized in connection with alternating currents. l
In each modication as disclosed a cross section of the conduit for current is materially greater than that of the enclosed conductor so that ample passageway is maintained for the cooling liquid. The value of the coolant resides in the overall reduction of heat due to coolant i'low so that for a given temperature the amount of current is considerably increased. Thus the utilization of the cooling medium combines with the reductionvof reactance and the increase in edective surface area of the conductor to augment appreciably the currentcarrying capacity of the conductor, over conductors of the same cross section not embodying the described inventive concepts.
For illustrative purposes the invention has been described 'as applied to dual cable oonductors. However, three or more conductors in separate coolant conduits may be employed under certain condition. Other modifications may :be made, the scope of the invention being determined by thevclaims hereto appended.
Whatisclaimedis: 1. A process 0f making electrical conductors which comprises forming a strip of insulation material with exible, divided, strip extensions on each edge, thereof, positioning electrical conducting units on each side of said strip, folding over adjacent 'opposite edge extensions to form conducting unit enclosing tubes of greater cross sectional area than the enclosed conducting unit and sealing together the folded edges of 5 said edge extensions.
2. A cable blank for electric conductors comprising a strip of insulation material having -exible reversely extended strip extensions at each edge on each side thereof, the width of each 10 extension being greater than one-half lof the strip width whereby the extensions on one side of the strip may be edge joined to form a tube adapted to receive a conductor.
3. A cable blank for electric conductors coni-= 15 132mg@ :arising a strip of insulation material adapted to be placed between said conductors and having flexible reversely extended strip extensions at 'ee-ch edge on each side thereof, the sum ef the Widths from edge to edge of the strip extensions 2@ on, each side exceeding the Width of said strip.
JOHN P. TARBO/X.
6 REFERENCES CITED The following references are of record in the file of this patent:
U'NII'ED STATES PATENTS Number Name Date 1,393,750 Carter Oct. 18, 19.21 1,883,269 Yonkers Oct. 18, 1932 2,066,242 Abbott Dec. 29, 1936 2,139,888 Fausek Dec. 13, 1938 2,191,544 Ruskin Feb, 27, 1940 2,218,979 Arutunofi Oct. 22, 1940 2,247,133 Reese June 24, 1941 2,26%,439 Gnyatt Deo. 2, 1941 Rees -..f June 1, 1943 FUREiGN Number Connty Hate 11,692 Switzerland 1395 92,4@1 Gemnany 6, 1995 @84,9541 Germany Non., 27, i939 914,997 France 22, 1937 834,955 France Sept., 12, 1938