US3467767A - Electrically conductive cable rope - Google Patents

Description

Sept. 16, 1969 w. TOTO ELECTRICALLY CONDUCTIVE CABLE ROPE Original Fil ed April 23, 1965 2 Sheets-Sheet 1 INVENTOR WILLIAM A. TOTO .rLli W am: 023:

ATTORNEY Sept. 16, 1969- w. 'ro'ro 3,467,767

ELECTRICALLY CONDUCTIVE CABLE ROPE Original Filed April 23, 1965 2 Sheets-Sheet 2 MILQQ', I

INVENTOR WILLIAM A TOTO ATTORNEY United States Patent 3,467,767 Y ELECTRICALLY CONDUCTIVE'CABLE ROPE William Toto, 3645 Warrensville Center Road, r Cleveland, Ohio 44122 g Original application Apr. 23, 1965, SenNo. 450,421, now Patent No. 3,333,044, dated Aug. 25, 1967. Divided and this application May 23, 1967, Ser. No. 640,587 The portion of the term of the patent subsequent to July 25, 1984, has been disclaimed Int. Cl. H01b 11/02 U.S. Cl. 174113 1 Claim ABSTRACT OF THE DISCLOSURE A special welding cable rope consisting essentially of 14 groups of strands of elliptical cross-section wherein 4 groups form a core section and groups form a peripheral section providing minimum wear points in the passage of alternating current through .the cable- SPECIFICATION The present application is a division of copending Ser. No. 450,421, filed Apr. 23, 1965, now -U.S. Patent No. 3,333,044, issued July 25, 1967.

This invention relates to a cable terminal unit and more particularly to an alternate polarity multiple conductor terminal unit having a greatly extended operating life due to a novel end structure which reduces fatigue chafing of the fine wires induced by kick and twisting of the wire and which greatly facilitates the problem of dissipating large quantities of internally generated heat.

The cable terminal of this invention is specifically intended to be used in connection with the kickless cable of the type described and claimed in U.S. Patent No. 2,320,470 to M. G. Rees and No. 2,308,673 to L. S.

Burgett. 1

According to the invention there is provided for an alternating polarity, kickless electric water-cooled cable, internal and circumferential bearing surfaces acting together to provide sliding surfaces for the rope conductors at the welding gun end of the cable. ,Theseg surfaces permit free movement of the ropes and prevent chafing of the fine wires while maintaining the ropes in spaced apart relation, thus maintaining open the the coolant flow passageways when .theacablerisbent at-=thewelding gun end. A spiralingshaped swagedv connector is provided for connecting the ropes of one polarity :to the welding gun. The connectors shape approximates the helix of the rope lay, mating in overlapping relation with an" opposite polarity connector containing .an aperture for passageof coolant flow.

At each end the cable consists of two leads wound about a perforated resilient sleeve containinga-collapsible hollow core element such, as-. a helical spring-. The end of the core has a helically shaped semirigid spacer located six to eight inches beyond,the terminal at the transformer .endfof the cable, enabling the cool-. ant to be conveyed directly to this region, .thereby forming-a coolant pocket between the spacer and "the end of the connector. -.This' arrangement assures :that coolant is always accessible to the rope conductors at the hottest portion ofthe cable. Coolantv flow is distrib- 3,467,767 Patented Sept. 16, 1969 Thereis provided a 14 bunch rope construction of fine stranded wire composed of a core of 4 bunches surrounded by a peripheral layer of 10 bunches. The twist direction of each bunch is opposite to its adjacent bunch in the outer and inner core groups. Each bunch in the core group has an eccentric transverse cross section to establish points of physical contact with bunches of the outer group. The closing helix of both the outer and core groupings is the same and has the same direction to maintain, the direction of the helix angle of the formed negative connector. Thus, wear caused by induced magnetic fields, as well as by physical contact of the bunches,

in each rope is reduced.

For an introductory discussion of prior art arrangements relating to welding cable assemblies, reference to applicants U.S. Patent No. 3,127,467 may be made. The kickless cable referred to in this disclosure has alternating polarity configuration wherein multiple strand cable lead conductors are alternately spaced on a circle about the longitudinal axis and spirally wound about a core, and incorporating inner and outer nonconductive sheaths adapted to internally separate the conductors of opposite polarity, both leads of which are jacketed by a flexible hose capable of carrying coolant water.

Perhaps the most important practical consideration for efiicient cable usage is the problem of removing the heat generated by the cables resistance. The basic heat equation W=I RD where W=watts, heat I=current, amps R=total resistance D=duty cycle or on time very neatly illustrates the large quantities of energy dissipated in ohmic heating and must be removed by the coolant flow in order to achieve the maximum potential of the cables MCM size and to prevent the premature deterioration of the cable.

It should be noted here that the I term commonly varies between 10 to 4x10 and that the resistance value (R) increases 3.5% with each 10 F. rise in temperature of the copper. This increase in coppers resistance, of course, aggravates the problem by completing the viciously ascending heat generating cycle.

,Ih. -P 9 1 ni$ fur he mpli at d whenthe welding gun operator'severely bends or twists the welding gun and cable assernblyin order to perform his spot-welding operations on a moving auto body. These bends will restrict the flowat'thekinked cable areas, thereby causing localizedv heat spots. An alternately wound kickless cable is divided into two concentric groups of ropes by a thin rubber tube. The tube serves as a separator and insulator for the'two cable leads; It has been an undesirable characteristic of this cable to exhibit a major unbalance division of flow between the central flow through. the inside of the separator when compared to the external flow outside of the separator. The conductors inside the separa tor will always receive less than half of the flow. This imbalance is caused by the twisting and tightening action of the helix on the cable assembly. The inner group of uted over the outer rope conductors-of the .cable..by-

conductors are" forced to hug the solid core. Similarly,

the separator becomes tightlyv wound about the inner group of conductors, with the net result of closing up the. inner or positive flow passageways, while increasing thesize of the outer or negative flow passageways. When the assembled cable. is, subjected to line pressure, the cables outer hose or jacket will expand and further open up the outer negative flow passageways about the outer group of cables, thereby causing an even greater unbalance flow condition.

This condition, as well as the others previously described, will produce localized cable hot spots along the inner group of rope conductors that will seriously damage the separator and cause the two leads to short out causing the cable to quickly destroy itself.

It now becomes apparent that the major cause of cable failures are either of two types: 1) separator failure or burnout caused by hot-spot 6 to 8 inches beyond the terminal at the transformer end of the cable; (2) mechanical breakage of the fine wires 6 to 8 inches beyond the terminal at the gun welder end of the cable.

Separator failures are common when the surface temperatures of the strands exceed 250 F. during continuous operations. The separators generally extruded from the Buna-N compounds can be expected to rapidly deteriorate and flake away. Their residues can be found as deposits on the coolant stream passageways of the cable and its terminals, and they will further impede the flow and accelerate cable failures. The cable area 6 to 8 inches beyond the terminal lugs at the transformer connection is most detrimentally affected by the high temperatures of the coolant flow, since at this point a balance is reached between the heat dissipated into the transformer lugs and the high point of the longitudinal temperature gradient along the cables length. It is at this point that many cables fail because of the insuflicient heat transfer rate due to the large amount of accumulated heat in the coolant flow stream by the time it reaches its area coming up from the gun end of the cable.

The other equally serious problem causing failures in cables is broughtabout by mechanical fracturing of wires also in the area 6 to 8 inches beyond the terminal at the gun end previously described in applicants US. Patent No. 3,127,467. This type of breakdown is caused by the mechanical bending stresses imparted to the wires as the cable is kicked or bent by the operator. When the cable is sharply bent the three inner conductors are unable to realign themselves into compensating positions because of high frictional forces, and thereby restrict the water flow at this area which further accelerates the breakage to the fine wires.

It is the object of this invention to provide a highly efilcient heat transfer system immediately beyond the terminals of six rope configuration welding cable, particularly in the area beyond the terminal at the transformer end of the cable.

Another object of this invention is to provide internal and circumferential bearing surfaces for each of the six rope conductors at the area to the rear of the terminals at the gun end of the cable in order to overcome wire fracturing at this point, when the cable is severely kinked.

Another object of this invention is to provide a terminal connector to position the inner and outer conductors so that they are free to align themselves behind the terminals during severe bending of the cable.

'Other objects of the inevntion will be in part be obvious for a fuller understanding of the nature and objects of the invention. Reference is made to the following detailed description taken together with the accompanying drawings in which:

FIG. 1 is a fragmentary diagrammatic view of the flexible liquid cooled cable of the present invention;

FIG. 2 is a fragmentary isometric view of a preferred embodiment of the flexible cable showing the positive connector lead removed from the terminal assembly;

FIG. 3 is a fragmentary plan view of FIG. 2 taken substantially on line 3-3;

FIG. 4 is a vertical sectional view taken substantially on line 44 of FIG. 1;

FIG. 5 is avertical sectional view taken substantially on line 5-5 of FIG. 2; and

FIGS. 6, 7 and 8 are transverse cross sectional views of the cable assembly of the invention along the cuts 6-6, 7-7 and 8-8 of FIG. 3.

Referring to FIGS. 1, 2 and 3, the flexible water-cooled electric welding cable assembly embodying the present invention is generally designated by numeral 10. The cable assembly 10 is shown extending between transformer T and welding gun W. Connecting the cable assembly 10 to the transformer and welding guns are shown two terminals each composed of two conductive elements 11 and 12, positive and negative respectively, insulatingly separated by a conductive block 11a. Bolts 13 passing through a hole in terminals 14 and insulators 15 secure the elements to the terminals. The conductive elements 11 and 12 may be a flexible lamination of copper strips composed of a pair of identical semicylindrical sections, generally machined from round copperstock and sawed into two semicyclindrical lengths. The shape of the elements 11 and 12 can be made to suit most any application. A relatively thin flat insulating element 16 insulates conductive block 11a from element 12 along their joint faces. Threaded holes 18, shown in the negative conductive block 11a, are used for fastening the conductive element 11 to the terminal. Coolant ports 19 and 20, located in the block 11a in each terminal assembly, are threaded to receive hose fittings carrying coolant to the cable. The coolant is introduced at the welding gun end which is usually the lowest point in the suspended cable so as to flow upward through the cable and emerging from port 20 in the top terminal that is attached to the transformer overhead.

In the preferred embodiment as shown in FIGS. 2 and 3, the rearward end of each terminal conductor 11 and 12 is radially undercut to form axially projected, doubly beveled tangs 21 and 22 that are integral with the body of the conductive elements, and are each adapted to receive in mating arrangement forming a strong lap joint a cable lead connector whose outer surface 23 is generally conical in form in order to snugly fit within the internal diameter of the cable hose 5. The negative connector 26 and positive connector 24 are bolted to the tangs 21 and 22 using 18-8 stainless steel bolts 25. This lap joint can further be secured by silver soldering the mating surfaces together.

As best seen in FIGS. 2, 3 and 7, the interior faces of the terminal conductors 11 and 12 may be provided with axial grooves or channels 27 and the insulating sheet 16 is slotted in this area to match the channel opening in order to facilitate the coolant flow through the channel. The channel then becomes the common distribution point for the division of flow for the positive and the negative coolant flow passageways. Coolant ports 19 and 20 located in each negative conductor block 11 are similarly located but not shown in the positive conductor elements 12. It will be noted (see FIG. 7) that when the terminal is assembled, inward facing surfaces 28 of the tangs 21 and-22 are spaced apart to form a space 29 which functions as a coolant portioning port for controlling the coolant flow to the negative outer group of 3 ropes. The flow to the negative lead can be varied by tapering the sides of the tangs 21 and 22 accordingly when a greater quantity of water is desired to be passed over the outer strands. Another method of varying the flow to the negative or outer strands is to vary the crosswise length of the dividing insulated strip 16 at point 30. Increasing the length will tend to decrease the flow and vice versa.

As shown in FIG. 2, it should be noted that the positive connector 24 has been shown disconnected from the positive terminal tang 21. Two bolts 25 pass through the connector clearance holes 31 and are threaded into the tangs. This better illustrates the construction details of each of the connectors. Similarly, negative connector 26 can be disconnected from the negative tang 22 by removing the threaded bolts 25. The negative connector 26 ties together as a conductive unit. The terminal end portions of each group of 3 negative core conductors 32 of like polarity are inserted into a preformed conductive metal sleeve 33 and swagged together in a heavy press using a progressive type die in order to achieve an in tricately contoured shape. This connector 26 transpositions the 3 ropes and from their outer circumferential positions into a common semicircular cross section. The connectors in this description are twice the length as those set forth in applicants US. Patent No. 3,127,467 and contain two helical fluted recesses on a circumferential surface and are shown as 33a. The fluted recesses 3311 act as flow channels to convey coolant flow passing through the tang vow proportioning port 29 and hence around a manifold flow groove 34 which in turn feeds the two spiraling fluted grooves 33. The coolait flow can now flow evenly distributed along the 3 outer negative strands for efficient removal of heat generated. The helix angle in the connector is approximately 30. The strands thusly maintain the same helix angle through the connector collar as they have throughout the length of the cable.

The present conductor construction comprises a novel 4-in. core and peripheral conductor bunches to form a stable configuration in which elliptically shaped bunches arepresent in the core to support the outer bunches. This elliptical core configuration, allowing 6 crossover points, is new in the welding cable field.

In contrast to 35 Chafing points for the concentric 7 x 9 rope, the 14 bunch herringbone herein reduces wire fracture by providing greater lateral contact surface areas than in the 35 crossover point of the prior art cable. As the contact areas become greater, the wearing pressures become smaller.

It has been verified by extensive testing (to be described later) that it is important to the life of the cable, particularly in the area behind the terminal, that the strand approaching angle ino the connector collar should be the same as the outer helix angle of the strands. All presently marketed kickess cables make no provision for attaching the rope strands to the terminals so that the helix angle is maintained at the entrance to the rear of the terminals. Unless this is done severe bending stresses are imposed on the strands because they are caused to turn a sharp corner upon entering the terminals.

In the present invention the connector section as the manifold groove line makes a smooth transition from the helix angle to one that is parallel to the longitudinal axis of the cable. Since this transition is carried out at a rigid section of the cable, no bending stresses are imparted to the strands. Further, applicant has designed the connector openings with a generous tapered and flared entry portion 35 to'permit additional freedom of wire movement" while the cable is being bent.

As stated at the outset, cable conductors attached to terminals at the Welding gun end of the cable have a tendency to fail in the immediate area of the cable to terminal connection. This failure is attributed in large measure to the repeated subjection of the cable conductors to severe bending stresses in this area since the cables are acutely bent by the welding gun operator. In order to. overcome this difficulty, a .060 inch wall nylon sleeve 36 is fastened over both connectors and extends beyond them for at least 1 /2 times the cables diameter. The sleeve serves two purposes: (1) It provides a better bearing surface over which the outer 3 strands are able to slide. (The coefficient of friction of nylon is considerably less than that of rubber.) (2) The nylon sleeve offers just the proper amount of semirigidity to the area so as to increase the radius of curvature of the cable while it is being kinked so that the outer strands are not subjected to the high localized bending stresses.

The'sleeve also serves the function of covering the spiraling flutes or channels 33 of the negative connectors preventing the rubber hose from closing in on them and thereby becoming coolant tunnels for the negative flow.

In FIG. 2 an exploded fragmentary view depicts the cables outer jacket or hose-5 cut away and the positive connector lead 24 disconnected from the rear portion of the positive element 12 of the terminal. An inner resilient sheath 37 (FIG. 8) is used as the insulator enclosing one set of positive conductors strand 38, wound about a central core assembly. The negative conductor strands 32 are helically wound and in alternating positions with the positive strands. Both groups are insulated from each other by the insulating sheath 37. Sheath 37 has been pulled away from the cable and is shown in FIG. 2 in a relation which illustrates the structural interrelation of the helically grooved or fluted nylon conductor bearing 39 and the core assembly that is composed of a loosely wound brass spring 40 inserted into an oversized perforated resilient tubing 41. The inner nylon hearing has a central bore and is approximately .75 inch long with 6 arms .375 inch long and located .25 of an inch beyond the end of the circumferential bearing sleeve 36.

The bearing 39 has inner helical flutes 42, is shaped to snugly fit the 3 positive conductor strands and is held in contact with the positive condutcors by the spring 40 which passes through its control bore. The bearing is restricted from moving either down the length of the cable by the perforated resilient tubing 41, and it cannot move towards the positive connector because the conductors 38 are brought together in tight relation as they enter the connector 24. It can now be appreciated that as the cable is severely bent beyond the terminal, the negative or outer group of 3 ropes will slide along the inner surface of the nylon sleeve 36 and concurrently the inner or positive group of 3 ropes 38 will slide along the fluted grooves 42. The combined action of the nylon collar 36 and the nylon wheel 39 imparts universal bearing action to each of the 6 ropes of the cable. This results in even sliding action overcoming the concentration of bending stresses on the strands by allowing for their mutual movement and realignment throughout the cables bending cycle.

The conductor portion immediately forward of the internal nylon bearing 39 of the positive lead is most adversely affected by high temperatures generated by the heavy current flows, and for eflicient operation according to the invention, coolant reaches this portion in plentiful quantities about the congested conductors, particularly when the cable is bent. It can be seen in FIG. 3 that in the vicinity of the loosely wound spring 40 and the bearing 39, there is created a space providing reservoir pocket for free-flowing coolant that may intimately flush the major portion of the conductors in this area, thereby providing an ideal turbulent flow condition for good heat transfer action.

The loosely wound spring is inserted into a flow metering port axially located in the connector 24. This port 43 may be drilled after the connector has been formed by swaging. The diameter of the hole is varied to balance out the systems distribution of flow.

The spring core 40 continues through the internal bearing 39 and acts as a core, jacketed by a perforated resilient tube whose internal diameter is 35% greater than the springs outside diameter. The other end of the cable, i.e., the transformer end, is identical to that shown in FIG. 3 except the ports in the terminals become outlets instead of inlet ports.

Further reduction in the wear of the cable is provided by the strand grouping, shown in FIGS. 4, 5 and 6, whereby, as designated in FIG. 4, each rope consists of 14 strand groups arranged in an outer or peripheral group 51 of 10 strand groups 51a, 51b, 51c, 51d, 51e, 511, 51g, 51h, 511' and 51] and an inner or core group 53 of 4 strand groups 53a, 53b, 53c and 53d. The sense of the twisting of each one of the strand groups is indicated by an arrow, it being noted that each outer group of strands 51 is twisted oppositely from its adjacent strand group, group 51a being opposite to 51b-51j being opposite to 51a.

The groups 53a-53d of core groups 53 are also twisted oppositely in the same manner as those of the outer group. The groups of the core 53 are elliptical in cross section so that as a result the wear points due to induced magrietic fields dccur only at the six points 55. This reduces chafing.

The functionof the perforated resilient core assembly in the alternate polarity type cable of this disclosure is similar to that given in applicants U.S. Patent No. 3,143,- 593 for a pulsating'flow core of a diametrically opposite type cable, whereby the kicking 'or pulsating action of the conductorsdue to their reactive forces alternately squeeze into and away from the loosely fitting elastic tubing causing a lateral displacement of water from the control core in a flushing eddy current manner. The cor rect proportions of each of the negative and positive metering ports result in the desired optimum balance of 55% of total flow passing through the passageways among the positive ropes and 45 along the passageways among the negative outer ropes. As the hose ages, it will expand andtheifiow balance will change to a 5 0-5 0%.

" The cable described in this invention and noted as cable C has been competitively tested along with the type of cables described in' US. Patent No. 2,504,777 and U.S. Patent No. 2,691,691 called cable A, and U.S. Patent No. 2,702,311 called cable B. The results have been summarized and are tabulated below:

Cable Type Electrical Cycles Mechanical Cycles The results show conclusively that the cable "of type C of this disclosure has three times the potential life of either "of the other two types of cables that are now commercially available ancl'previously identified as A and B cables.'It should be noted eagles C and C were still functioningwhentheywere removed from the test stand.' Upon their examination, it was estimated that the ex-- pected life span approaches 15,000,000 electrical cycles. The test simulated actual autom-otive production line coriditions by using a-specialmachine that can repetitively duplicate the many mechanical motions performed by the welding gun operator while using a portable welding tool to spot-weld auto body components along. a moving as-- sembliy linesThe electrical, testing was concurrentlyper formed on the cables while they were subjected to mechanical flexing motions.'A constant load of 18,000 amps necessary at the gun end for achieving (1) mechanical Was maintained at 200 times per minute consisting of 4 weld cycles or 22.2 duty cycle. A suflicient water pressure differential was chosen at the beginning of the test in order to permit 2 g.p.m. of coolant flow and thereafter main:

tained at this level. Inlet flow temperature was maintained at and the conductivity and water flows allowed to vary decreasingly in accordance with the cables rate of deterioration until totalfailure resulted.

/ Although the novel cable of the present invention has: identical c-onstructionlboth at the gun end and transformer end, these respective ends have diiferent types of failures and, in practice, there is no system for confining the cablets usage to a transformer end or a gun end. It must be interchangeable for both ends, and must be used by" unskilled personnel.

It will be apparentfrom the foregoing description that the nylon collar and the manifold connector grooves are not important at the transformer end, but become vitally ductive strands consisting of 4 groups forming a core sec-' tion and 10 groups forming a peripheral section surrounding said core section, said core strand groups being essentially elliptical in transverse cross section, adjacent strand groups of both said peripheral and core sections being alternately oppositely twisted, whereby there are provided six wear points in each of said groups, said core section being structurally stable to support the peripheral groups.

References Cited UNITED STATES PATENTS 3,333,044 7/1967V Toto 174--is.

LEWIS n. MYERS, Primary Examine; A.-T. GRIMLEY, Assistant Examiner I US. 01. X.R.

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