Патент USA US2407171код для вставки
Sept. 3, 1946. |_, E, McFARREN 2,407,171 FIXED RES IS TOR Filed llay 16, 1944' > .21 —$5.9~Z~ “m \ \ I 10 I %£5“ I 19 gwawawy??mlwmv 21 12 i3 is ....... 21 12 16. 11* it mmvron LAWRENCE EMcF??/FEN BY ‘ Chm-7% Arroawsr Patented Sept. 3, 1946 ' 2,407,171 UNITED STATES PATENT OFFICE 2,407,171. FIXED RESISTOR Lawrence McFarren, Indianapolis, Ind., assign. or to P. R- Mallory & 00-, Inc-J Indianapolis, Ind., a corporation of Delaware Application May 16, 1944, Serial No. 535,788 1 claim- (Cl- 201-67) 2 1 The. present invention relates to resistors, and, moreparticularly, to wire-wound resistors of the type employed in connection with electrical measuring instruments for extending the range of measurement. As those skilled in the art know, precision ex ternal meter resistors of the described character essentially comprise a glass or ceramic enclosure with ferrules at the ends thereof. Within the en: closure the, windings of resistance wire are pro external meter resistor which is. simple in struc ture, is capable of passing the most severe test, and which may be readily manufactured and sold on a practical and commercial scale at a low cost. Other and further objects and advantages of the. invention will become apparent from the fol-. lowing description, taken in conjunction with the accompanying drawing; in which Fig. 1 illustrates a side elevational view of a vided on a suitable base likewise constituted of ferrule type resistor embodying the principles of the present invention; glass or of ceramic material. These units are very di?icult to make since their resistance has the unitary resistor; to be. within very close tolerances, they. have to Fig. 2 depicts a longitudinal sectional View. of Fig. 3 shows a similar sectional view of one of be non-inductively. wound and in addition have 15 the resistance elements or units which maybe to pass severe tests. Another practical difficulty experienced in connection with these resistors employed in the preferred form of the invention; and was that they had to be manufactured in a large Fig. 4 is a longitudinal sectional view of a mod number. of different sizes and resistance values in i?ed form of the resistance element or unit which accordance with the, speci?c application contem may be incorporated into the resistor of the in plated. Of course, manufacturing and carrying vention. in stock a large number of different resistance While a preferred embodiment of the inven values was connected with considerable incon tion is described herein, it is contemplated that venience as it necessitated tying up a great deal considerable variation may be made in the meth of capital and raw material in the form of resis 25 od of procedure and the construction of parts tors of different values including such values for without departing from the spirit of the inven which there was very little demand. Various. tion. In the following description and in the suggestions and proposals have been made to eliminate this. difficulty but, as far as is known, none of these suggestions and proposals, was com pletely satisfactory. and successful when carried into practice. on a practical and commercial scale. It is an object of the present invention to pro vide a precision meter resistor which completely eliminates the foregoing difficulties, It is another object of the present invention to provide a resistor of novel and improved charac ter which permits building up any practically desirable resistance value from a plurality of claims, parts will be identi?ed by speci?c names, for convenience, but they are intended to be asv generic in their application to similar parts as the art will permit. Referring now more particularly to Figs. 1 to 3 of the drawing, reference character It] denotes a cylindrical casing constituted of moisture and heat-resistant insulating material such as, for example, glazed porcelain, “Isolantite,” “Pyrex,” and the like. The ends of casing Ii] are closed by means of ferrules ll of brass, bronze, or some other metal. Within casing 10 there are disposed end to end standard values. a plurality of resistance elements or units. Each It is a further object of the present invention of these comprises a cylindrical spool 12 with in tegrally formed barriers l3 de?ning winding to provide an external meter resistor of the fer rule type comprising an insulative enclosure with spaces I4 within which there are disposed wind ferrules at the ends thereof, within which there 45 ings l5 of resistance wire. In accordance with are disposed a plurality of serially connected uni the usual practice, an even number of winding tary resistors selected from a few standard val spaces is provided for one unit and the direction ues in accordance with the desired application. of Winding is reversed for adjoining winding It is also within the contemplation of the in spaces in order to make the ?nished resistance vention to provide a ferrule type meter resistor 50 substantially non-inductive. Barriers l3 are also. which may be assembled from appropriately se provided with the usual radial slots for the pas lected standard elements to constitute a preci sage of the interconnecting portions l6 of the re sistance wire. Cylindrical spools [2 may be con sion resistance of any desired value within a wide range. stituted of the same materials as casing [0, such The invention also contemplates a precision 55 ar particularly “Isolantite.” 2,407,171 4 The end faces of spools I2 may be provided with a metalized layer I‘! to which the ends of the resistance wire may be soldered. Electrical connection between the adjoining ends of the Fig. 3 is a longitudinal sectional view of a resistance unit which is in every respect identical with the units shown in Fig. 2 with the only dif several spools may be established by brazing or ference that four Winding spaces I4 are de?ned therein by means of a corresponding number of soldering the silvered ends of the spools together. As an alternative, jumpers (not shown) may be barriers I3. The structure and the operation of the resistance unit should be self-explanatory. soldered across from one spool to the next one in a manner well understood. Fig. 4 is a similar view of a modified form of re be readily assembled with considerable savings said tube, a plurality of stacked unitary resist sistance unit which is also practically identical Electrical connection between the serially con 10 with the structures shown in Figs. 2 and 3, similar nected resistance units and the end ferrules II reference characters being used to denote corre may be secured in a great variety of ways. One sponding parts. The difference resides in that form of construction which was found satisfac one end of spool I2 is provided with a head 30 of tory comprises an apertured disc or spider I8 of conical shape while the other end of the spool is spring metal having an opening I9 in the center provided with a conical depression 3| of conform thereof and having its circumferential edges 20 ing shape. Both head 30 and depression 3I are clamped between the ends of casing I0 and coated with a metalized layer 32 to which the ends ?anges 2I' of the ferrules. Disc or spider I8 will of the resistance wire are electrically connected. resiliently hold the stacked resistance units A plurality of such resistance elements or units within tubular casing it). A conductor 22 has 20 may be readily stacked or mounted end to end by one of its ends extending through opening I9 in inserting the conical head of one unit into the disc I8 and soldered to metallic layer I‘! at the corresponding depression of the next one. Elec end of the spool at 23 while its other end extends trical connection between the several stacked through a corresponding opening 24 in ferrule units may be made by brazing metalized layers I I and is soldered thereto at 25. Ferrules I I may 25 32 together or by means of soldered jumpers, as be secured to the ends of easing II! in various it is set forth more fully in the foregoing. ways such as by cementing or by silvering the While the present invention, as to its objects ends of the casing tube and soldering the flanges and advantages, has been described herein as of the ferrules thereto. carried out by speci?c embodiments thereof, it is From the foregoing description the operation 30 not desired to be limited thereby but it is in of the resistor of the invention and its advan tended to cover the invention broadly within the tages will be readily understood by those skilled spirit and scope of the appended claims. in the art. Obviously, by manufacturing re What is claimed is: sistance elements orunits in a few standard val~ An electrical resistor comprising in combina ues, a very large number of resistor values may 35 tion an insulative tube, a ferrule at each end of in manufacturing cost. ance values which have greatly reduced and at sired value within the The number of resist ance elements mounted Within said tube, each of to be carried in stock is said resistance elements including an insulative the same time any de spool with windings of resistance Wire thereon practical range is in 40 having one of its ends formed with an external stantaneously available. conical surface and its other end formed with a The advantages of the present invention are corresponding internal conical surface and a particularly accentuated by recent efforts in the metalized layer on each of said surfaces consti direction of standardizing meter resistors. Thus, the American Standards Association has issued speci?cations for ferrule type meter resistors covering three mechanical sizes and thirteen re sistance values from 0.5 to 6 megohms. Each tuting terminals for said windings, the external and internal conical surfaces of adjoining spools being adapted to mate with each other to main tain the relative position of the spools in the stack, means including a fused metallic bond be tween each pair of adjoining metalized layers for megohm, 0.5 megohm and 1.0 mego‘nm. The re connecting all of said windings in series, and means for connecting the terminals of said seri sistor of the present invention, of course, is ex~ cellently adaptable for the manufacture of such ally connected Windings to said ferrules. standard resistors since by carrying in stock only resistance units of three different values, any LAWRENCE E. MCFARREN. resistance within the standard range may be 55 standard resistance value is a multiple of 0.3 immediately assembled.