Dec. 24, 1946. c. J. GANCI 2,413,043 RESISTIVE DEVICE AND METHOD OF MAKING Filed Aug. 14, 1943 INVENTOR. w 07-709mm’ Patented Dec. 24, 1946 2,413,043 UNITED STATES PATENT OFFICE . 2,413,043 RESISTIVE DEVICE AND METHOD OF MAKING Charles J. Ganci, Rldgewood, N. Y., assignor to Ward Leonard Electric Company, a corpora tion of New York 1 Application August 14, 1943, Serial No. 498,651 6 Claims. (01. 201-63) This invention relates to‘improvements in re sistive devices such as tubular resistive units and other forms. _ In making resistive units, such as of tubular form, in which a solid conductor, usually in the form of a wire or ribbon, or a conductor of vari 2 obtain a, device which will have a uniform and smooth surface throughout its length and sub stantially overcome rejects in the process of manufacture due to failure of the connection be tween the conductor and the stranded lead wires. A further object is to produce a process of manu ous forms and cross-sections, is utilized as the facture which may be conveniently accomplished resistive conductor, it is desirable to provide and carried out with assurance of dependability stranded wire connections thereto, or so-called and durability. Other objects and advantages pigtail leads, owing to their ?exibility and con 10 will be understood from the following description venience in making connections to the circuit in which the device is to be used and owing to their comparative freedom from breaking after re peated bending and twisting. It has been com mon to twist the stranded wire around the solid wire and solder the connection but this forms an objectionably enlarged joint; and particularly in and accompanying: drawing which illustrate em bodiments of the invention and the steps in the method of making. P18‘. 1 is a side view of a resistive device of tubular form showing the tubular support and , the conductor applied thereto before the applica tion of the insulating coating; Fig. 2 is a side view of the completed unit; Fig. 3 is a diagram show ing a step in the process of preparing the strand joint is objectionable not only in increasing the 20 ed conductor for welding; Fig. 4 is a diagram outside dimension of the unit but in the difficulty showing a further step in the process; Fig. 5 is of properly covering and embedding the joint a similar diagram showing the ?nal step in the with the insulating coating. process; and Figs. 6, 7 and 8 are side views of According to the'present invention, the ends joined conductors as illustrative examples. of the conductors are butt welded together to pro Referring to Fig. 1, the main support is a tube duce a joint not appreciably larger than the size i of insulating material such as porcelain. On of the conductors and give the joined conductors this is wound a solid conductor 2 forming the re the appearance of a continuous conductor. When sistive conductor. This is of a proper size, length a resistive conductor with such welded terminal and. number of turns to give the desired resistance leads of stranded wire is utilized in a resistive to the unit. It may be of any suitable metal or device, there are no enlarged joints to contend alloy, such as Nichrome composed of nickel, chro with in applying the insulating coating, result mium and iron, or may be an alloy of nickel and ing in a final product having a uniform and copper, or of nickel and chromium, various al~ smooth appearance throughout. But the butt loys of iron, or any other metal or alloy accord welding of the end of a stranded wire cannot be ing to particular requirements. accomplished properly if it be attempted to weld At each end of the resistive conductor 2 is a by joining the ends of the stranded wire to the joint 3 between it and the stranded wires 4 and end of a conductor; because some of the strands 5 forming the ?exible terminal connections. The may be welded while others will not. This results lead 4 continues from its joint 3 around the tube in a poor electrical connection and in the spread 40 and then passes within the tube through a hole ing out of the unwelded strands or of some of 6 and then out from the end of the tube to form them, giving an awkward joint to properly and the outside lead. The lead 5 continues from its fully cover by the insulating coating. It also re joint 3 around the tube and then passes within sults in a portion protruding from the unit at the tube through a notch l and through the length the joint. Furthermore, during the maturing of, of the tube to form the other outside lead. the insulating coating, as by firing in a furnace, As to the joint 3, it is shown as a solid con the strains imposed on the few welded strands are nection between the solid conductor 2 and the likely to- rupture the connection, giving an open stranded wire leads 4 and 5; and this joint is no circuit in the completed article. The number of larger than the conductor 2 or the leads, giving rejects from this cause alone may be considerable. .50 the appearance of a continuous conductor of uni Even if the opening of the circuit does not occur, form size having no protruding portions or ob the few strands remaining connected will, dur jectionable enlargement. It therefore forms a‘ ing use of the device, cause excessive heating local joint which may be readily and conveniently cov-' ized at the joint which is likely to cause a break ered by the insulating coating. In fact it is just down of the device after a short period of use. as easily and fully covered as any other portions of The present invention overcomes these various the conductor. The device as shown in Fig. 1 difllculties. . is ready for the application of the insulating One object of the invention is to produce a re coating which may be of any suitable mate sistive device which will be durable and depend rial but is preferably of vitreous enamel mate able in long continued use. Another object is to 60 rial. The coating is matured by flring in a fur resistive units wherein the resistive conductor is coated with an insulating coating, the enlarged 4 gether and fused in the manner described with nace if vof vitreous‘ enamel, and by drying or reference to Fig. 5. other'wiseaccording to the character of the coat ing material. A stranded wire 35' thus fused to a larger braided wire 20 is'shown as an ' ~ example in Fig. 8 at the solid joint 2 I. All strands Fig. 2 shows the completed unit with the in-,' of each of the two conductors are thus fused to the common joint and insure complete electrical connection between all strands of both conduc sulating coating 8; and it is obvious that the de vice is of uniform size throughout with a smooth Y surface and no objectionable protruding portions. This particular resistive unit was for an immen _ Although preferred embodiments have been de ' sion heater and was adapted to slide into a quite ' closely ?tted tube or casing; any projection from 10 scribed as illustrative examples, the invention tors. - ‘ may be embodied in other typesvand forms of re- . the unit due to enlarged. joints or connections between the conductor and leads would prevent it sistive devices and modi?cations made without vdeparting from the scope of the invention. from ?ttingwithinthe tubular casing. In mak- , ing the unit, the resistive conductor is ?rst made ' of proper length and then-the stranded wire ter minals-Pare joined'fthereto'_ in ‘the manner later described;?Thee-freeei‘id‘of the lead 6 is passed ‘ I claim: l5 _ e . - 1. A resistive device comprising an insulating‘ . ' support, a‘ solid resistive conductor carried there by, and a lead of a stranded conductorjoined _ thereto, the end of the stranded conductor hav ing a fused solid end butting against the end of the lead 4 and the conductor;’ is wound around solid conductor and fused thereto in a solid the tube and also a portion of the lead 5. The 20 the joint of a size approximately equal to that of remaining portion of the lead 5 is then-passed the larger of the two conductors. through the length of the tube and held in place 2-. A resistive device comprising an insulating by being drawn into the notch l. The insulat-__ : ,._'support;, _a,-s,olid gresistiveiconductor carried there ing' coating is thenapplied. _ r ~ ' through thehole s and then the inner portion of As to-the making of?the"joint,‘fE‘ig'.'3‘shows' 25' the ?rst step. A length of stranded wire 9 is clampedbetween the jaws 10. of .a butt welder,‘ ' a portion of the‘ wire extending vbetween the two by,‘ ‘and a"l'e"ad"'of""a stranded conductor joined thereto, the end?of; each strand of the stranded > oonductoribeing =fused'into1a:solidsend, and the 'said solid end beingfusedlto the" end of the solid pairs of fljaws.‘ conductor; The Ewelder ‘is supplied with cur- rent from a suitable source, such as ‘from the " ' ' a ' 1" . .._\ 3; A resistive ‘device vcomprising ;__an insulating support, a vsolid resistive’conductor ‘carried there-_ secondary‘!l‘oféatransformer l2. The heating by, a lead of a stranded conductor joined there~ is concentrated at the midportion of the stranded to, the fused solid end of the stranded conductor ' wire and fused there, resulting in the separation '_ butting against they end of the‘ solid conductor of the wire to-form two. separate leads and in a and fused thereto in a solid joint of a"'jsize-ap fused solid end [3 on each-of the leads, as shown .35 . proximately equal to that of theilargeii of the in Fig. 4'; This solid fused end is not materially two conductors, and an insulating coating cov larger or smaller than thejsize or diameter of \ - ering said resistive conductor and'sla'eid joint. the stranded wire and all of the strands areipers ' . 4. A resistive'device comprising; an insulating manently fused andiconnected to this solid end. 40 support, a solid resistive conductor-1 carried there‘, The next step isshown in 5. Here one of there- ' by, a lead of a‘stranded conduct " 'oine'd I the stranded wires or leads ‘9 having the fused to,'thejend of each strand of ‘the stranded con solid end-is-zf'placed in one of‘ the jaws of' the ' ductor being fused into a solid end, andjjthe said welder' and ‘the solidhresist‘ive conductor 2 is " solid end being. fused to the end oft-the solid con.‘ placed in. the other jaw. 'One of the vjaws is then ductor, and an insulating .coating'fcoverihg said moved towards the-"other toi brlngtogether the resistive conductor and said joint. solid end-[l3 of the lead and the end-of the solid‘ 55: r .5. A resistive vdevice comprising-1 an insulating conductor. . Thiscauses. the fusing-of the meeting ._ supporting tube, a solid resistive conductor wound f ends givinga solidjointZ Messhown :in-Flgg?? : ' thereon, aleadrofastrandedrconductor joined to and the (:onnection of :all-o?thé-strands'tojithe ' mt or: ' each end -'of said solid conductor respectively, the solid conductor-is insured with ‘fai'sdlid'j Ifuséadsolidjehds of thesai’dis'tranded conductor about the ~ ‘same "size "as xii-emerges 'or‘thé tea, v-buttingagainst the, ends'of 'said‘sdlid conductor and fused thereto in solid joints of ‘a ‘size'fdpprox imately' equal to the size of theilarger ofjthe con wires. Another stranded leadis "in'i'il'a?y Q0111 . nect-ed td't'h‘e other end'iioffthehlsolid conductor, 2; and thevlj-combined conductor is ,then readyv for applieationj to the tube 1 , :the device ‘being; completed m'the’mannerza‘lready-described; " This method of forming- the joint is applicable, ‘I Eductors, and an insulatingicoatinggcovering said 'solidconductor and coveringsaidéjeints por 'ftion's of each ofv said stranded conductors; jii;v A resistive} device comprising an insulating to the joining-of- strandisdcondirctois, or'xnulé/ supporting §~tub_e»,;§ a - solid;- ‘resistive , , _ conductor tiple condactors. ‘of different‘; sizes/"toI solidIcpn-j" “ Y iwoundth'erjeo'n; a lead'i'of Estrandedé conductor ductors of" "jdi?erent sizes massages‘ shows a stranded conductor} . . . . . Fig. 265 . bonnected..to...a,,n Solid wire’ll'? let the. joint H5. the,..wire; is being: “joined to each-end ‘of jsaid‘solid i: lductor respec -'-tively;:"tj_he ends of the ‘leaf "s't Ii rd wire being . ., .. said: Lie fusedjtq solid"; ends,; and mis butting of much larger size ‘than thes‘trandedwir'ei Fig.3 "lagairist‘?hé' "é‘n‘dswof vsaid solid conductor and '7 shows the stranded wire l5 connected at the joint 18 to a solid wire ld‘of smaller size. This method of forming the joint is applicable like- v_ I wise to the joining of two stranded or braided wires or conductors. In. that'case a solid end'i ?rst formed on the ends of each of such con ductors in the manner described with reference _ to Figs. 3 and 4. The fused ends of the two conductors to be joined are then brought to fused thereto in solid joints of a size approxi mately equal to the size of the larger of the con ductors, and an insulating coating covering said [solid conductor and covering said joints and por Itions of each of said stranded conductors, the uncovered ends of said stranded conductors being passed through openings in said tube to form ex ternal leads. CHARLES J. GANCI.