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Dec. 11, 1962 A. T. SONATORE 3,058,413 PIVQT BASE SECURING METHOD AND MEANS Filed May 9, 1960 ANTHONY Z SONA TORE IN VEN TOR. United States Patent O?fice 1 3,558,413 Patented Dec. 11, 1962 2 An object of this invention is the provision of a method 3,068,413 PI‘VQT BASE SECURING METHGD AND MEANS Anthony T. Senators, Holmdel, NJ, assignor, by mesne assignments, to Daystrorn, Incorporated, Murray Hill, NJ” a corporation of Texas Filed May 53, 19%, der. No. 27,574 3 Ciairns. (Cl. 324-155) of electrically connecting ‘a coil wire end, by soldering, to a pivot base at a point intermediate the pivot base and coil. An object of this invention is the provision of a moving coil assembly comprising a pivot base secured to a mov ing coil, and means soldering the coil end to the bottom surface of the pivot base intermediate the said base and coil. This invention relates to ‘an electrical instrument and These and other objects and advantages will become more particularly to ‘a method and means for securing 10 apparent from the following description when taken with the ends of a movable coil winding to the pivot bases attached to the coil. the ‘accompanying drawings. It will be understood that the drawings are for purposes of illustration and are not Electrical instruments such as ammeters, voltmeters, to be construed as de?ning the scope or limits of the in and the like, include a wire-wound movable coil which coil may be wound upon 1a generally rectangular-shaped 15 vention, reference being had for the latter purpose to the appended claims. coil frame. Two pivot assemblies, each including a base In the drawings wherein like reference characters de and a pivot pin mounted on the base, are secured to the note like parts in the several views: outer sides of the opposite ends of the coil, with the pivot FIGURE 1 is a side elevational view of a coil assembly pins projecting outwardly ‘along an axis extending through the center of the coil. The pivots are carried in suitable 20 embodying my invention, parts being shown broken away bearings for pivotable support of the coil. In a typical moving-coil mechanism, a pair of spiral springs are employed to provide a calibrated force 0p— posing the moving coil torque; one spring surrounding each pivot base and connected thereto through suitable spring abutment members secured to the said pivot bases. The outer ends of the spiral springs ‘are secured to outer abutments and, in accordance with established practice, the springs not only bias the moving coil to a predeter mined zero position, but also are employed to conduct current to the coil; the ends of the coil windings being electrically connected to the pivot base to provide an electrical connection from the coil through the said spiral springs to the outer spring abutments. My invention in cludes a novel method and means of securing the ends of the movable coil windings to the pivot bases. In ac cordance with my invention, the end of the coil winding is secured to the pivot base simultaneously with the attach ment of the pivot base to the coil. Further, in accord ance with my invention, the end of the coil winding, or ‘ for clarity; FIGURE 2 is an exploded fragmentary sectional view showing the connection between one end of a coil wire and a pivot base; and FIGURE 3 is a fragmentary, semi-diagramm-atical view of a positioning ?xture with a coil assembly mounted thereon, which ?xture may be used in the method and means of soldering the end of the coil winding to the pivot base in accordance with my invention. Reference is now made to FIGURE 1 of the drawings wherein there is shown a coil assembly comprising a generally rectangular-shaped coil frame lil with a wire wound movable coil 11 wound thereon. A pivot assembly comprising a pivot base 12 and ‘a pointed pivot 13 is mounted at each end of the coil, which pivots are shown rotatably supported in jewel bearings 14. The pivot base may comprise a ?at base portion 16, an upstanding rectangular boss 17 and an externally-threaded cylindrical portion 18, the latter having an axial bore, not shown in FIGURE 1 for accommodation of the pointed pivot 13. A piece of insulating material 19, of cloth or paper, or the like, is positioned between the coil 11 and coil lead, is secured to the bottom surface of the pivot base intermediate the pivot base and coil end turns. In base portion 16 of the pivot base to serve as insulation a co-pending patent application Serial Number 23,228, therebetween. Suitable cement secures the pivot base now abandoned, of Raymond G. Drewes and Wallace W. Macintosh, ?led April 19, 1960, and assigned to the same 45 and insulating member to the coil winding, ‘as described in detail hereinbelow. assignee as the present application, a method and means A conventional pointer 21 with a hub portion having for securing a pivot base to an instrument coil are shown, a hole therein is mounted on the pivot base, the cylin which may be employed in the practice of this inven drical portion 1% of the base extending through the hole tion. The disclosure of such co-pending application is with the pointer hub resting on the boss 17. A washer incorporated herein“ by reference thereto. Disclosed 22 is located between the pointer 21 and an inner spring therein is a resistance heating method wherein an elec~ abutment 23. At the lower end of the coil assembly the trical current is passed through the pivot base to heat spring abutment 23 abuts the boss 17; no pointer being the pivot base and adjacent cement used in securing the included at that end. Nuts 24 threaded on the externally base to the coil thereby at least partially curing or polym~ erizing the cement. With my invention, the bottom sur 55 threaded portion 18 of the bases secure the pointer and inner abutment thereto. faces of the pivot bases and the ends of the coil winding The inner ends of spiral springs 26 are secured to the are pre~tinned prior to securing the pivot base on the abutments23, while the outer ends of the spiral springs coil. The end of the coil is placed beneath the pivot base are mounted on relatively ?xed outer abutments 27 frag in contact therewith and the subsequent heating of the pivot base in securing the same to the coil also functions 60 mentarily shown in FIGURE 1. In ‘accordance with established practice, the spiral springs not only bias the to solder together the pre-tinned base and coil lead. coil to ‘a predetermined position, but also provide a con An object of this invention is the provision of a method ducting current path to the coil. Lead wires: 28 are shown of soldering the end of a coil winding to a pivot base secured to the abutments 27 for connection to a source, which method includes placing the pro-tinned winding end under the pre-tinned bottom of the pivot base and 65 not shown, to be measured. The current path from the lead wires 23 may be traced through the spiral springs heating the pivot base to thereby solder the coil wire to 26, ‘abutments 23, and pivot bases 12 to the ends of the the base. coil winding which are soldered to the pivot bases in a An object of this invention is the provision of a mov novel manner in accordance with my invention. ing coil assembly comprising a wire wound coil and a pivot base ‘assembly secured thereto, and means soldering 70 Reference is now also made to FIGURE 2 of t -e draw the coil wire end to the bottom side of the pivot base ings showing an exploded view of a joint between a coil intermediate the pivot base ‘and coil. and pivot base. For clarity, the parts and elements‘of 3,068,413 3 A thermoplastic ‘or thermosetting type. ‘V‘Jith certain heat reactive cements and with sufficient heat provided by the current ?ow through the pivot base, the cement may be ?nally gelled or cured without further baking. With (A the connection have not been shown in proper relative size; the drawing being intended merely to aid in an understanding of the invention. ‘in securing the pivot base to the coil, a thin layer of suitable cement 33’ is first brushed onto the end turns of the coil 11 and the in UK sulating member 1% is placed in position thereon. A thin coating of cement, designated 32, is then spread other cements, a further oven baking subsequent to the above-described resistance heating process may be re quired. Obviously, both pivot bases may be simul over the insulating member. The end of the coil wire, taneously secured to the movable coil, at the same time both coil leads ‘are being soldered to the pivot bases. designated 11', which who has been pro-tinned as at 33, is then placed on the insulating member 13 upon which 10 Since the soldering of the coil lead to the pivot base and the securing of the said pivot base to the coil are simul— the cement 32 has been spread. In accordance with my taneously e?ected, it will be apparent that the prior art invention, the bottom surface of the pivot base is tinned, step of soldering the coil leads to the pivot bases after as at 34., before the base is placed on the insulating mem the pivot bases are secured to the coil is eliminated. ber 19 upon which the cement 32 and tinned wire end 1i.’ have been placed. With the pivot base positioned on 15 Further, the resulting soldered connection is superior to prior art arrangements since the contact is embedded in the insulating member 19, in contact with t‘nc tinned the cement and no corrosive effects of the ‘atmosphere wire end, heat is applied to the pivot base to simultaneous therein take place. ly solder the coil lead to the pivot base and to set the Having now described my invention in detail in ac cement. A suitable method and apparatus for properly locating the pivot base on the coil and of heating the pivot 20 cordance with the requirements or" the patent statutes, various other changes and modi?cations will suggest them base to set the cement and solder the coil wire to the base are shown and described in the above-mentioned co pending patent application Serial Number 23,228. selves to those skilled in this art and it is intended that A such changes and modi?cations may be made without de parting from the scope and spirit of the invention as set fragmentary, semi-diagrammatical, view of a means for locating the pivot base on the coil and including means 25 forth in the following claims. I claim: for passing an electrical current through the base to heat 1. A method of manufacturing a movable coil as— the same is shown in FIGURE 3. In FIGURE 3, the sembly of an electrical instrument of the movable coil coil 1% is shown positioned upon a pedestal 36 or" a posi type and which includes a wire-wound movable coil with tioning ?xture. A plunger element 38, spring biased in the direction of the arrow designated 39 and comprising7 loads and a pivot base secured to the coil, the said method including tinning the coil leads and the bottom surface a portion of the positioning ?xture, accurately locates the A pair of of the pivot base, spreading a heat reactive cement on the electrodes 41, 41 are shown in contact with the pivot coil, placing an insulating member on the cement, spread pivot base 12 on the end turns of the coil. ing a heat reactive cement over the insulating member, base at spaced points thereon, the said electrodes being connected through lead wires 42, 42 to the secondary 35 placing the bottom surface of the pivot base on the cement spread on the insulating member with the tinned Wire winding 43 of a transformer $4. The transformer pri mary winding 46 is connected to a suitable A.-C. source lead in contact with the tinned bottom surface of. the 47 through a switch 4-3. As described above, a thin layer pivot base, and heating the pivot base thereby gelling the cement and soldering the coil lead to the pivot base. of suitable cement is applied to the coil, the insulating 2. The invention as recited in claim 1 wherein the pivot member 19 is placed thereon, a thin layer of suitable base is heated by passing an electric current therethrough. cement is applied to the insulating member and the tinned 3. A method of manufacturing a movable coil assembly pivot base is placed thereon with the tinned coil lead in of an electrical instrument of the movable coil type and contact with the pivot base. The coil assembly is then which includes a wire-Wound movable coil With leads and placed in the positioning ?xture to properly locate the pivot base (or both bases simultaneously) on the coil. 45 a pivot base secured to the coil, the said method includ—~ ing tinning the coil leads and the bottom surface of the With the electrodes 41, 41 in place on the pivot base, the switch 48 is closed and an electric current is passed pivot base, spreading a heat reactive cement on the coil, placing the bottom surface of the pivot base on the cement through the said pivot base. A current ilow of 20 spread on the coil with the tinned wire lead in contact amperes for about 0.5 second has been found to provide with the tinned bottom surface of the pivot base, and the necessary amount of heat to properly gel one par- ' heating the pivot base thereby gelling the cement and ticular epoxy resin type cement. The heat thus provided soldering the coil lead to the pivot base. simultaneously solders the tinned wire end 11’ to the bot tom tinned surface of the pivot base and gels, or cures, the cement su?iciently to keep the pivot base in place on the coil. With the coil lead ‘11’ positioned beneath the pivot base, my invention is particularly applicable to an ar rangement wherein the coil wire is of a small size since a large wire would possibly permit “rocking” of the pivot base thereon. In one application, a coil wire of .061" 60 diameter is used with an insulating member 1? having a thickness of .003”, which Wire is sufficiently small to embed in the cement and insulating member to thereby permit a stable mounting of the pivot base on the coil. It will be understood that my invention is not limited to any particular type cement since any suitable heat re active cement may be used. The cement may be of the References Cited in the ?le ‘6r this patent UNITED STATES PATENTS 2,425,443 So-reng _______________ __ Aug. l2, 1%! 2,735,068 2,890,416 Wolferz ______________ __ Feb. 14, 1956 Walker _______________ __ June 9, 1959 2,953,673 Bouton ______________ __ Sept. 20, 1960 576,801 Great Britain _________ __ Apr. 18, 1946 FOREIGN PATENTS OTHER REFERENCES Publication, Selectacon, Engineering Bulletin No. 9, by Tape Cable Corp, Rochester, N.Y., November 1958.