US2918640A - Transformer construction - Google Patents

Description

Dec. 22, 1959 H. P. HlGGS TRANSFORMER CONSTRUCTION.

3 Sheets-Sheet 1 Filed March 23, 1956 JNVENTOR. HARQLD P. HEGGS ATTQRNEY Dec. 22, 1959 H. P. HIGGS TRANSFORMER CONSTRUCTION Filed March 23, 1956 3 Sheets-Sheet 2 INVENTOR. HAROLD P. HIGGS ATTORNEY Dec. 22, 1959 HlGGs 2,918,640

TRANSFORMER CONSTRUCTION Filed March 23, 1956 3 Sheets-Sheet 5 INVENTOR. HAROLD P. HIGGS ATTORNEY United States Patent Other:

Patented Dec. 22, 19 59 TRANSFORMER CONSTRUCTION Harold P. Higgs, Newark, N.J., assignor to General Instrument Corporation, Elizabeth, N.J., a corporation of New Jersey Application March 23, 1956, Serial No. 573,494 13 Claims. (Cl. 336-192) The present invention relates to a novel construction for a transformer particularly adapted for use in communication equipment, such as radio and television receivers.

A primary object of the present invention is to devise such a structure which'is well suited for use with printed circuit components and for assembly therewith in a manner consistent with the requirements of automatic methods of manufacture. A second primary object is the production of such a transformer which is itself susceptible to a great extent of automatic manufacture, and which may be produced on a quantity basis at a minimal cost without any sacrifice, and even with improvement, in the electrical characteristics of the unit when compared with prior art structures.

The frame of the transformer, on which appropriate circuit elements such as coils, resistors and capacitors are adapted to be mounted, is made up of a base, an essentially tubular member extending up therefrom on which the coils which make up the transformer are adapted to be mounted, and substantially rigid conductors passing through the base and extending thereabove and there below, the portions of the conductors extending below the base constituting external terminals and the portions of the conductors extending above the base constituting combined internal terminals and circuit-element mounting means.

In accordance with one aspect of the present invention, the base and the coil mounting member are integral and are formed of a moldable plastic material. The combined base and member are molded directly around the substantially rigid conductors, so that the position of the conductors relative to one another and to the other parts of the transformer structure are accurately fixed by and as a consequence of the molding operation. Consequently the downwardly extending conductor portions defining external terminals areaccurately positioned even on a mass production basis, thus facilitating the insertion of those terminals into correspondingly accurately located apertures in a panelboard at a subsequent stage of assembly of the complete receiving set. The panelboard might well be one on which printed circuits have been formed in any appropriate manner. Because of the rigid location of the external terminal portions attendant upon tightly securing the conductors within a base molded therearound, it will be appreciated that the transformer structure is exceptionally well suited for use in a fully automatic receiving set assembly line.

Another significant aspect of the present invention resides in the design of the generally tubular coil-mounting member, which extends up from the base as anopensided structure. It is preferred that in cross section it be only slightly greater than a semi-circle in circumferential length. The transformer coils are adapted to be wound onto dumbbell-shaped cores, preferably of magnetic material, and those cores are adapted to be inserted into thecoil-rnounting member via the open side thereof. Hence the spacing between the coil-carrying cores, and con sequently the spacing between'the coils themselves, can be readily and accurately controlled during assembly. It is preferred that the cores be held in .position within the open-sided member by a snap action therebetween, at least during initial assembly, but of course any suitable cement could be used if desired. The leads from the coils extend out through the open side of the mounting element, thus further facilitating electrical connection as a part of the overall assembly operation.

The ends of the coil leads are adapted ,to be secured and electrically connected to appropriate conductor p01..- tions extending up from the base, preferably at points adjacent the upper ends of those conductor portions. This permits simultaneous soldering of all of the coil leads to their respective conductor portions by a single dipping operation, means being provided to permit that dipping operation to take place without affecting the coils in the open-sided member. This means may take the form of a specially constructed dipping pot having a solder-free opening into .which the open-sided member and the coils carrier thereby are adapted to be received while the upper ends of the rigid conductor portions, with the coil leads already initially secured thereto, are dipped into the solder bath. Since the upwardly extend.- ing conductor portions are integral with the external terminals defined by the corresponding downwardly extending conductor portions, connecting of the coils to external circuitry is greatly facilitated.

In accordance with yet another aspect of the present invention the upwardly extending portions of the rigid conductors constitute supports .on which other circuit elements, such as capacitors, resistors or combinations thereof, may be mounted. These other circuit elements are preferably in the form of tubes adapted to he slid over the upwardly extending conductor portions and having conductive parts, preferably although not necessarily formed through the application of printed circuit techniques, both on the inner and outer surfaces thereof. Electrical connection between the circuit element and the conductor portion on which it is mounted is accomplished by physical contact between said conductor portion and the conductive part on the interior of the circuit element. Electrical connection to the conductive part on the exterior of the circuit element may be made by means of a conductive coil spring received around an adjacent upwardly extending conductor portion, that coil spring having an arm which resiliently engages the circuit element on an exterior conductive part thereof, thus not only accomplishing the electrical connection in question but also serving to retain the circuit element on its own conductor portion and to ensure adequate engagement, both physical and electrical, between the inner conductive part of that circuit element and the conductor portion on which it is mounted. The coil spring may be provided with a second arm which may engage the coilcarrying member for tensioning purposes or which may engage a second circuit element to secure it in place and accomplish electrical connection thereto, as the particu-' lar circuit design may dictate.

The upwardly extending conductor portions are well adapted to accomplish other connective functions. example, they may themselves be bent into engagement with appropriate portions of circuit elements mounted on adjacent conductor portions. Another connective function which is called for in almost all installations, and to which the upwardly extending conductor portions are Well adapted, is the grounding of the shield can which conventionally surrounds .a transformer unit of the type under discussion. The shield can is adapted to be telescoped over the unit and to be secured in any appropriate manner to the base thereof. An appropriate upwardly extending conductor portion can be rendered re- For silient if it is not already so and can be shaped to extend outwardly beyond the periphery of the base so as to firmly engage the inner surface of the shield can when the latter is put in place. Appropriate grounding connection can be made to the terminal extending from the base and integral with the upwardly extending conductor portion which thus engages the shield can.

The circuit constants of the circuit elements mounted on the upwardly extending conductor portions can readily be controlled during the fabrication thereof. The relative positions of the coils secured to the open-sided mounting element can be readily controlled during the assembly of the unit. Consequently the units, although manufactured on a quantity basis, will be reliably uniform in electrical characteristics, and ordinarily no adjustment of the circuit values will be required. In some specific installations, however, it is desirable to be able to modify the inductance of the coils. This can readily be done by utilizing elements of magnetic or conductive material adjustably positionable along the open-sided member relative to the respective coils so as to vary the effective inductance thereof. The positioning of these elements can be accomplished by providing the internal surface of the open-sided member with threads and by providing the outer surface of the adjustably positionable. elements with corresponding threads so that, by rotation of the individual elements, which are accessible from the ends of the open-sided mounting member, their position relative to their respective cores may be adjusted. Since the mounting element is open-sided, some means must be provided for retaining the adjustable element in engagement with the threads on the inner surface of the open-sided mounting member. The adjustable element at the upper end of the mounting member may be thus retained in threaded engagement by the use of a resilient band or the like. The adjustable element at the lower end of the open-sided mounting member may be held in position by utilizing an arm from one of the coil springs, that arm engaging the adjustable element via the open side of the mounting member and resiliently urging it against the closed and internally threaded side of that mounting element.

' To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to the structure of a transformer, as defined in the appended claims and as described in this specification, taken together with the accompanying drawings, in which:

Fig. 1 is a side elevational view of one embodiment of the transformer frame comprising a base, an upwardly extending open-sided member and a plurality of substantially rigid conductors;

Fig. 2 is a top plan view thereof;

Fig. 3 is a fragmentary cross sectional view taken along the line 3-3 of Fig. 2;

"Fig. 4 is a three-quarter perspective view of one embodiment in which condensers are adapted to be shunted across the coils (not shown), the shield can being shown in broken lines;

Fig. 5 is a view of yet another embodiment into which. a more complicated filter circuit is incorporated, the coils being shown in position and the shield can being shown in broken lines;

Fig. 6 is a side elevational view of the embodiment of Fig. 5;

Fig. 7 is a three-quarter perspective view of one of the circuit elements comprising a pair of condensers with a resistance between one pair of corresponding condenser plates;

Fig. 8 is a cross sectional view through a typical dumbbell shaped core on which a coil has been Wound;

Fig. 9 is a view similar to Fig. 5, with the coils and cores in place, means being provided for adjustably varying the inductance of each of the coils;

Fig. 10 is a three-quarter perspective view of the resilient band which engages the inductance-adjusting element at the top of the embodiment of Fig. 9;

Fig. 11 is a three-quarter perspective view of the core shown in the upper part of Fig. 9;

Fig. 12 is a three-quarter perspective exploded view of the adjustable inductance core-coil combination shown at the bottom of Fig. 9;

Fig. 13 is a diagrammatic view of the manner in which the coil leads and the upper ends of the rigid conductors may be dipped into a solder bath;

Fig. 14 is a diagram of the circuit of the embodiment of Fig. 5; and

Fig. 15 is a diagram of the circuit of the embodiment of Fig. 4.

The framework of the transformer of the present invention comprises a base generally designated 2 from which a coil mounting member generally designated 4 extends upwardly and through which a plurality of substantially rigid conductors generally designated 6 extend, portions of those conductors, designated 8, extending down from the base 2 and other portions of those conductors, designated 10, extending upwardly from the base 2. The base 2 and the coil mounting member 4 may be formed of any suitable molded plastic material, preferably thermosetting in nature. The portions of the conductors 6 which extend through the base 2 and around which the base 2 is molded may be provided with crimps or tongues 12 (see Fig. 3) so that they will be accurately, firmly and reliably held in position by the base 2 after the latter has been molded therearound. Further rigidification of the conductors 6 is accomplished by forming portions 2a and 2b of the base 2 so as to extend upwardly and downwardly respectively along the conductors 6. The conductors 6 may be formed of any suitable conductive material such as soft copper. The coil mounting member 4 is generally tubular in nature and comprises a wall 14 having an arcuate extent which is preferably slightly greater than a semi-circle. For example, the wall edges 16 may extend beyond semi-circle length for a distance of approximately .03 inch, where the inner radius of the wall 14 is on the order of .15 inch.

The transformer coils 18 and 20 are adapted to be wound within peripheral recesses 22 and 24 formed respectively in dumbbell shaped cores 26 and 28 of appropriate magnetic material. The outer diameter of the cores 26 and 28 is approximately the same as the diameter of the inner surface of the wall 14. Hence the cores 26 and 28, with the coils 18 and 20 carried thereby, are insertable into the coil mounting member 4 via the open side thereof between the edges 16, those edges snapping around the cores 26 and 28 after the latter have been inserted and thus frictionally retaining the cores in place along the coil mounting member 4. Suitable spacing jigs can be employed to ensure that the location of the cores 26 and 28 relative to one another is that which is proper for the desired electrical characteristics of the unit. The frictional or snap interengagement between the member and the cores 26 and 28 will usually be adequate for initial assembly and will often be satisfactory for final use, but cement or other attaching means may be employed to positively retain the cores 26 and 28 in proper position along the element 4. lit will be appreciated that because the cores 26 and 28 can be inserted into the element 4 in the open side thereof, assembly problems are greatly facilitated and accurate spacing between the cores can readily be accomplished.

The coil 18 is provided with leads 30 and 32, anl the coil 20 is provided with leads 34 and 36. These leads extend out from their respective coils through the open side of the coil mounting member 4 and are adapted to be wrapped around the upper ends of appropriate conductors 6. Thereafter the entire unit may be inverted (see Fig. 13) and dipped into a bath of solder so that one dip will suffice to solder the ends of all of the leads 3036 to the corresponding conductors 6. As shown in Fig. 13 the solder bath 38 may be contained within a dipping receptacle 40 having a central solder-free opening 42 into which the coil mounting member 4 and the cores and coils carried thereby are adapted to be received. In this way the dipping operation maybe carried outwithout'in any way aifecting the coils themselves.

Since the depending conductor portions 8 defining external terminals are'integral with the upwardly extending portions of the conductor 6 to which the ends of the coil leads 3036 are connected, it will be apparent that electrical connection to the coils may readily be made via said external terminals 8. As here specifically disclosed those external terminals 8 are pointed so as to facilitate plugging the unit into appropriately located apertures of sockets in a panelboard, and particularly into such a board on which circuitry has been formed through conventional printed circuit techniques. However, it will be understood that the external terminals 8 could be flattened and provided with holes so as to facilitate electrical connection thereto in a chassis utilizing conventional wire leads.

A transformer of the type under discussion is usually adapted to be enclosed within a sheet metal shield can generally designated 44 and shown in broken lines in Figs. 4 and 5, that shield can telescoping over the unit, engaging the base 2 and being secured thereto either frictionally, resiliently or positively in any appropriate manner. It is usually desired that the shield can 44 be grounded in the overall electrical circuit. To accomplish this one of the upwardly extending conductor portions 10a is rendered somewhat resilient, as by work hardening or in any othersuitable manner, and is flattened and reversely bent so that its tip extends downwardly and outwardly beyond the periphery of the base 2. When the shield can 44 is put into place, the inner surface of the shield can will be engaged by the conductor portion 10a and consequently connection of the terminal portion 8a corresponding thereto to ground in the overall circuit will accomplish the desired result.

The upwardly extending conductor portions 10 also serve as means for mounting additional circuit elements generally designated 46, such as capacitors or combined capacitors and resistors. These circuit elements 46 are preferably tubular in nature so that they may readily be received on the corresponding conductor portions 10. In the embodiment of Fig. 4 the circuit elements 46 and 46 each define a capacitor, and each is formed from a ceramic tube 48 or 48' having a conductive external coating 50 or 50 and a conductive internal coating 52 or 52', the coatings 50 and 52 and 50 and 52, defining the two plates of a capacitor separated by the dielectric ceramic 48 or 48' respectively. These coatings may be formed through the use of printed circuit techniques, or they may constitute discrete sheets of conductive material attached to the ceramic tube 48 or 48' in any appropriate manner. Capacitance valves may be controlled to a high degree of accuracy by grinding off one end of the elements 46 and 46.

The embodiment of Fig. 4 is designed to function as a first IF transformer in a receiving set. The right hand circuit element 46 in Fig. 4 is received on the upwardly extending conductor portion 10b. The upwardly extending conductor portion 100 is positioned adjacent thereto. A coil spring 54, formed of conductive material, is received over the conductor portion 10c and is provided.

with an arm 56 which extends across the conductor portion 10b. It is provided with another arm (not shown) which engages the edge 16 of the coil mounting element 4. The arrangement of the coil spring 54 is such that the arm 56 is strongly resiliently urged toward the conductor portion 10b. When the circuit element 46 is to be positioned on its conductive portion 10b the spring arm 56 is pulled away from the conductor portion 1017 so as to permit the circuit element 46 to move down against the base 2. The spring arm 56 is then released and it presses up against the circuit element 46, engaging and making electrical contact with the outer conductive surface 50 thereof. Since the spring 54 is mounted on the conductor portion 10c it will also make electrical connection therewith, and consequently the terminal portion will be electrically connected to the conductive surface50. The spring arm 56 will urge the inner conductive surface 52 of the element 46 against the conductor portion 10b on which that circuit element is mounted, so that the terminal portion 8b will be electrically connected to that inner conductive surface 52. In addition, the action of the spring arm 56 will serve to retain the circuit element 46 in position on its conductive portion 1%. A similar arrangement is employed to retain the left hand circuit element 46' inposition on the conductor portion 100. As indicated by the broken lines 30, 32, 34 and 36 at the upper ends of the conductor portions 100, 10b, 10d and 10s respectively, the leads from the coils 18 and 20 are adapted to be connected to the upper ends of the upwardly extending conductor portions 10 as shown. As a result, the circuit of Fig. 15 results.

In the embodiment of Fig. 4 only five upwardly extending conductor portions 10a-e are required. In the embodiment of Figs. 5 and 6, however, a somewhat more complex circuit is incorporated into the unit, which is designed to function as a second IF or diode stage transformer in a receiving set, and consequently seven upwardly extending conductor portions 10a, 1, g, h, i, j and k are employed. The circuit elements 46 and 46' on the conductive portions 10 and 10k are in the form of capacitors similar to those previously disclosed in connection with the embodiment of Fig. 4, having outer conductive surfaces 50 and 50" and inner conductive surfaces '52 and 52 respectively. The circuit element 46" mounted on the conductor portion 10h comprises a pair of capacitors with a resistance connected between corresponding plates. It comprises (see Fig. 7) a tubular ceramic core 585', having an inner conductive surface 59 and a pair of axially separated outer conductive surfaces 60 and 62 bridged by an outer resistive surface 64. The resistive surface may completely coat the outside of the ceramic tube 58 or it may be in the form of a narrow line, either straight or spiral. Electrical connection to the inner conductive surface 60 is made by the conductor portion 1011 on which the unit is mounted. Electrical connection to the outer conductive surface 62 is made by the arm 56 of the coil spring 54 mounted on the conductor portion 10g. Electrical connection to the other outer conductive surface 60 is made by bending the adjacent conductor portion 10i into engagement therewith and soldering the junction thus produced. The other arm 66 of the coil spring 54 visible in Fig. 5, instead of engaging the edge 16 of the coil mounting element 4, engages the conductive outer surface 50 of the circuit element 46 mounted on the conductor portion 107, the inner conductive surface 52 thereof being electrically connected to the conductive portion 10f. The circuit element 46' mounted on the conductor portion 10k constitutes a capacitor the inner conductive surface 52' of which is electrically connected to the conductor portion 10k and the outer conductive surface 50' of which is electrically connected to the conductive portion 10f by means of the arm 56 of the coil spring 54 mounted on the conductive portion 10j, the other arm 66 of that coil spring 54 engaging the edge 16 of the coil mounting element 4, as may best be seen from Fig. 6. The coil leads 30, 32, 34 and 36 are connected respectively to the upper ends of the conductor portions 10f, 10g, 10k and 107, thus producing the circuit shown in Fig. 14.

If adjustment of the individual inductances of the coils 18 and 20 is desired, elements may be provided adjustably positionable along the length of the coil mounting member 4 which are capable of afiecting the coil inductances in accordance with their proximity to the coils. In the form disclosed in Figs. 9-12, these elements, generally designated 68, are constituted by structure which, in effect, are parts of the dumbbell shaped cores 26 and 28. In the embodiment shown at the upper end of Fig. 9 and partly in Fig. 11, the core 26a has its upper end 26 of greatly reduced height. As shown a normal core 26 has inch of its upper end removed. The adjustable part 70, formed of ferrite or comparable material, has a length of approximately inch, is externally threaded, and the inner surface of the wall 14 of the coil mounting member 4 is internally threaded at 72. In order to retain the element 70 in place and ensure that it will remain in its adjusted position a resilient band 74 (see Fig. is wrapped around the upper end of the coil mounting element 4 and the exposed periphery of the element 70. In the embodiment disclosed at the bottom of Fig. 9, and in Fig. 12, the core 28 with the coil wound thereon is provided with a stub 76 extending downwardly therefrom, over which an externally threaded shell 78 is adapted to be received, the threads of the shell 78 cooperating with the threads 72 on the inner surface of the wall 14. In order to ensure proper threaded engagement and the maintenance of the shell 78 in its adjusted position, the exposed portion of the periphery of that shell is engaged by the arm 66 of the coil spring 54. The adjustably positionable elements 70 or 78 are accessible from opposite ends of the coil mounting member 4, and may be provided with kerfs 80 so that their position may be adjusted by means of a screw driver.

The desirable electrical characteristics of the transformer of the present invention can be appreciated from a consideration of the following data. When the coils 18 and 20 are wound with solid wire a Q of 100 is easily obtained on a production basis. When the wire used is 4 litz an inductance of .8 mh. and a Q of 130 can be obtained. An inductance of 6.5 mh. can be obtained by using #41 wire and a lower Q higher permeability core. This range of values is sufiicient to take care of all practical IF transformers used at 455 kc. and

265 kc. Precision control of the inductance of the coils may be attained by drilling a small hole, having, for example, a diameter of A inch, along the axis of the core. This hole will effect an inductance variation of 10%, with a consequent Q loss of about 10%. Approximately 10% inductance variation may be accomplished by means of the adjustable element 70 shown in the upper portion of Fig. 9, and approximately 15-20% variation may be accomplished with the adjustable element 78 shown in the lower portion of Fig. 9.

From the above it will be appreciated that the structure of the transformer here disclosed and claimed is exceptionally well adapted to precision manufacture, the terminal portions 8 depending from the base 2 being accurately located and therefore presenting no problems of alignment when the transformer unit is to be plugged into a socket or a printed circuit panel. Assembly of the coils and other circuit elements on the framework of the transformer is greatly facilitated, and is particularly well adapted to automatic production.

While only a limited number of embodiments of the present invention have been here disclosed, it will be appreciated that many variations may be made therein, all within the spirit of the invention as defined in the following claims.

I claim:

1. A transformer comprising a base, a member of generally tubular shape extending up therefrom and having an open side extending lengthwise thereof, said member having a coil defining a core-receiving space communicating with said open side, cores of a width not appreciably greater than the width of said open side inserted into said space via said open side and spaced from one another along the length of said space, and means for holding said cores in place within said space.

2. A transformer comprising a base, a member of generally tubular shape extending up therefrom, integral therewith, and having an open side extending lengthwise thereof said member having a wall defining a core-receiving space communicating with said open side, said base and member being formed of molded plastic material, cores of a width not appreciably greater than the width of said open side inserted into said space via said open side and spaced from one another along the length of said space, and means for holding said cores in place within said space.

3. A transformer comprising a base, a member of generally tubular shape extending up therefrom and having an open side extending lengthwise thereof, coil-carrying cores inserted into said member via the open side thereof and spaced from one another along the length of said member, said cores and said member having a snap action interengagement which, at least in part, retains said cores in place within said member.

4. A transformer comprising a base, a member of generally tubular shape extending up therefrom, integral therewith, and having an open side extending lengthwise thereof, said base and member being formed of molded plastic material, and coil-carrying cores inserted into said member via the open side thereof and spaced from one another along the length of said member, said cores and said member having a snap action interengagement which, at least in part, retains said cores in place within said member.

5. A transformer comprising a base formed of molded plastic material, elongated conductors extending through said base, the latter being molded therebetween and extending above and below said base, the portions of said conductors extending below said base defining external terminals, a winding carried by said base, a tubular circuit element surrounding one of said upwardly extending conductor portions, a coil spring mounted on one of said upwardly extending conductor portions adjacent said portion on which said circuit element is mounted, said coil spring having an arm resiliently urged against said circuit element in the direction of the conductor portion on which said circuit element is mounted, thereby retaining said circuit element in position on its conductor portion said winding, conductors and circuit element being connected together in a circuit.

6. The transformer of claim 5, in which said tubular circuit element has conductive parts on the interior and exterior thereof, said spring arm engaging said conductive part on the exterior thereof and making electrical connection therewith and said conductive part on the interior thereof engaging and making elecrical connection with its corresponding conductor portion.

7. In the transformer of claim 5, a member extending up from said base, a core mounted on said element and carrying said winding, and said coil spring having another arm resiliently urged against said element.

. In the transformer of claim 5, a member extending up from said base, a coil-carrying core mounted on said member, and said coil spring having another arm resiliently urged against said member, said tubular circuit element having conductive parts on the interior and exterior thereof, said spring arm engaging said conductive part on the exterior thereof and making electrical connection therewith and said conductive part on the interior thereof engaging and making electrical connection with its corresponding conductor portion.

9. A transformer comprising a base, elongated conductors extending through, above and below said base and out of electrically conductive relation thereto, portions of said conductors extending below said base defining external terminals, a circuit element mounted on the portion of one of said conductors extending above said base, a coil spring mounted on one of said upwardly extending conductor portions adjacent the portion on which said circuit element is mounted, said coil spring having a pair of arms extending therefrom, one of said arms being resiliently urged against said circuit elementin the direction of the conductive portion on which said circuit element is mounted so as to retain said circuit element in position, a member extending up from said base, a coilcarrying core on said member, said member being internally threaded and having an opening in its side, an externally threaded part engageable therewith and adjustably movable therealong relative to said coil to vary the inductance thereof, the other arm of said coil spring passing through the opening in the side of said member and resiliently engaging said externally threaded part.

'10. A transformer comprising a base, elongated substantially rigid conductors extending through, above and below said base and out of electrical conductive relation thereto, the portions of said conductors extending below said base defining external terminals, a winding carried by said base, a circuit element mounted on one of said upwardly extending conductor portions, and a coil spring mounted on one of said upwardly extending conductor portions adjacent said portion on which said circuit element is mounted, said coil spring having an arm resiliently urged against said circuit element in the direction of the conductor portion on which said circuit element is mounted, thereby retaining said circuit element in position on its conductor portion, said winding, conductors and circuit element being connected together in a circuit. 11. The transformer of claim 10, in which said circuit element is tubular, is received over its upwardly extending conductor portion, and has conductive parts on the interior and exterior thereof, said spring arm engaging said conductive part on the exterior thereof and making electrical connection therewith and said conductive part on the interior thereof engaging and making electrical connection with its corresponding conductor portion.

12. In the transformer of claim 10, a member extending up from said base, a core mounted on said member and carrying said winding, and said coil spring having another arm resiliently urged against said member.

13. In the transformer of claim 10, a member extending up from said base, a coil-carrying core mounted on said member, and said coil spring having another arm resiliently urged against said member, said circuit element being tubular, received over its upwardly extending conductor portion, and having conductive parts on the interior and exterior thereof, said spring arm engaging said conductive part on the exterior thereof and making electrical connection therewith, and said conductive part on the interior thereof engaging and making electrical connection with its corresponding conductor portion.

References Cited in the file of this patent UNITED STATES PATENTS 1,763,115 Wermine June 10, 1930 2,483,919 Mazzola Oct. 4, 1949 2,535,203 Guthman Dec. 26, 1950 2,569,036 Benner Sept. 25, 1951 2,590,821 Kiser Mar. 25, 1952 2,611,040 Brunetti Sept. 16, 1952 2,618,749 Altenberger Nov. 18, 1952 2,658,161 De Ano Nov. 3, 1953 2,732,529 Reid I an. 24, 1956 2,774,051 McCarthy Dec. 11, 1956 2,879,421 Broadbent et al Mar. 24, 1959 UNITED STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Patent No. $918,640 December 22 1959 Harold Pg, Higgs It is hereby certified that error appears in the above numbered patv ent requiring correction and that the said Letters Patent should read as corrected below.

Column 7 line YO 'f r "coil" read wall column 8,, line 4 for "thereof" read thereof Signed and sealed this 26th day of June 1962,

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,918,640 December 22 1959 Harold P. Higgs It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 7 line 70 for "coil" read wall column 8,, line 4 for "thereof" read thereof Signed and sealed this 26th day of June 1962,

(SEAL) Attestz' ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

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