US3590329A

US3590329A - Coil assembly and method of making the same

Info

Publication number: US3590329A
Application number: US821837A
Authority: US
Inventors: James E Krepps Jr
Original assignee: Sarkes Tarzian Inc
Current assignee: TARZIAN MARY; TARZIAN SARKES
Priority date: 1969-05-05
Filing date: 1969-05-05
Publication date: 1971-06-29
Anticipated expiration: 1988-06-29

Abstract

A coil assembly and method of making the same comprising an elongated coil form of insulating material, a first coil on the form having a plurality of coaxial turns with selected spacing between adjacent turns, and a second coil having a single turn or less mounted on the coil form in coaxial relation with and spaced between a pair of adjacent turns on the first coil. The second coil includes a pair of integral connector leads at opposite ends of the turn which leads extend outwardly of the coil form from between spaced adjacent turns of the first coil. Integral connector leads of the first and/or second coil support the coils in a mold forming member during and after fabrication of the coil form, which is integrally molded to support the coils in fixed mutual inductive relationship.

Description

United States Patent Inventor [72] JamesE.Krepps,Jr. 2,771,585 11/1956 De Long 336/183 X Bloomiugton, lud- 2,899,631 8/1959 Cushmanm. 336/192 X 211 Appl. No 821,837 2,910,529 10/1959 Splitt 336/183 x [22] Filed May 5,1969 2,937,350 5/1960 Sasaki 336/183 [45] Patented June 29, 1971 3,169,234 2/1965 Renskersm. 336/208 X [73] Assignee Sarkes Tarzian Inc. 3,443,257 5/1969 Mollman 317/101 (CC) Bloomington, 1nd- 3,486,224 12/1969 Chaney 317/101 CC Primary Examiner-T. J. Kozma s4 COIL ASSEMBLY AND METHOD or MAKING THE Mme-Mason, Kolehmainfin, Rathburn & y

SAME 9 Claims 10 Drawmg Figs ABSTRACT: A coil assembly and method of making the same U.S.Cl comprising an elongated coil form of insulating material a 29/626, 336/651 336/183, first coil on the form having a plurality of coaxial turns with 336/ l92,336/2 8 selected spacing between adjacent turns, and a second coil [51 1 Int. Cl 1/04, having a ingle turn or less mounted on the coil form in coaxial H011 15/02, HOIfH/O2 relation with and spaced between a pair of adjacent turns on 0 Search the first coll The econd coll includes a pair of integral con. I98, 208, 192, 65, 205; 317/ 101 CC; 2 nector leads at opposite ends of the turn which leads extend 6215;264/272 outwardly of the coil form from between spaced adjacent turns of the first coil. Integral connector leads of the first [56] References C'ted and/or second coil support the coils in a mold forming UNITED STATES PATENTS member during and after fabrication of the coil form, which is 1,713,462 5/1929 Blatterman 336/183 integrally molded to support the coils in fixed mutual induc- 2,729,796 H1956 Hulst 336/183 X tive relationship.

PATENTED JUN29 |97| SHEET 2 OF 2 FIG. 7

FIG. 6

v INVENTOR JAMES E. KREPP5,JR war/( A,

F I 6. I0

Attorneys COIL ASSEMBLY AND METHOD OF MAKING THE SAME The present invention relates to a new and improved coil assembly and a method of making the same. More particularly, the coil assembly of the present invention is especially adapted for use as an antenna coil, oscillator coil, IF transformer, choke, and the like, as commonly used in television, FM and other radio and radar equipment.

In VHF and UHF television, radio, and FM equipment, often the inductance values of the coils used require only a single turn or less of relatively small diameter mounted on an air core coil form. The dimensional tolerances of the coils and the spacing or placement of the turns in relation to one another is relatively critical and, if close dimensional tolerances are not maintained, the inductances are not usable for their intended purposes.

It is an object of the present invention to provide a new and improved electrical coil assembly and method of making the same.

Another object of the present invention is to provide a new and improved coil assembly of the character described for use at VHF and UHF frequencies which may be readily manufactured on a mass production basis, at low unit cost, at relatively low reject rate, and 'with uniform electrical characteristics.

Still another object of the present invention is to provide a new and improved coil assembly which is especially adapted to be mounted on and connected to a printed circuit board.

Another object of the present invention is to provide a new and improved coil assembly including a first winding having a plurality of coaxial turns and a pair of separate coils, each having a single turn or less and disposed between adjacent turns of the first winding, said separate coils being adapted to be connected together through a printed circuit board connection to form a precisely balanced, center tapped winding inductively coupled to the first winding.

The foregoing and other objects and advantages of the present invention are accomplished in an illustrated embodiment thereof comprising a new and improved coil assembly having an elongated coil form of molded insulating material and a first coil thereon having a plurality of helical, coaxially aligned turns with selected pitch or spacing between adjacent turns of the coil. A second coil having a single tum or less is mounted on the coil form in coaxial relation with and spaced between a pair of adjacent turns on the first coil, and the second coil includes a pair of integrally formed connector leads at opposite ends extending outwardly of the coil form from between spaced adjacent turns of the first coil. The coil assembly is especially adapted for mounting on a printed circuit board and the coil leads are adapted to physically support and secure the coil assembly in place as well as provide electrical connection with the circuitry on the printed circuit board.

In constructing a coil assembly in accordance with the present invention, preformed first and second coils are positioned in a first coil form molding member and are self-supported therein by the coil leads. A second molding member is then closed with the first member over the first and second coils to accurately position and align the coils in place and provide accurate spacing between the mutually inductive turns. After the mold is closed, a core pin is inserted into the mold and plastic material is introduced into the mold cavity, preferably in an injection molding process. When the molded coil form hardens or cures, the mold is opened and the finished coil form positively secures the turns of the first and second coils in proper relation with one another.

For a better understanding of the present invention, reference should be had to the following detailed description taken in conjunction with the claims and drawings in which:

FIG. 1 is a side elevation of a new and improved coil assembly constructed in accordance with the features of the present invention;

FIG. 2 is a bottom elevational view looking upwardly in the direction of the arrows 2-2 of FIG. 1;

FIG. 3 is a transverse cross-sectional view taken substantially along line 3-3 ofFlG. 1;

FIG. 4 is a perspective view illustrating the coil assembly mounted on a printed circuit board;

FIG. 5 is a perspective view similar to FIG. 4 but illustrating the opposite side of the circuit board and the connection between the leads of the coil assembly and the circuitry of the circuit board;

FIG. 6 and 7 are schematic, electrical circuit diagrams of coil assemblies in accordance with the present invention;

FIG. 8 is a perspective view illustrating a step in the method of making a coil assembly inductance in accordance with the present invention;

FIG. 9 is a transverse cross-sectional view taken substantially along line 9-9 of FIG. 8 and illustrating in dotted lines an upper member as it is moved downwardly into a mold closing position; and

FIG. 10 is a transverse cross-sectional view similar to FIG. 9 illustrating both members of the mold in a closed position with V a core pin inserted on the coil form as molded therein.

Referring now, more particularly, to the drawings, therein is illustrated a new and improved coil assembly constructed in accordance with the features of the present invention and illustrated as a whole in FIGS. 1, 2, 4, and 5 and referred to generally by the reference numeral 20. The coil assembly 20 includes a hollow, generally cylindrical coil form 22 formed of integrally molded insulating material and provided with outwardly projecting supporting foot portions 22a at opposite ends thereof.

The coil assembly 20 includes a first winding 24 having a plurality of helical, coaxial turns 25, and the winding 24 may serve as the primary winding of an antenna coil suitable for use in television or FM tuners. The coil 24 is provided with a pair of integrally formed connector leads 26 at the opposite ends thereof and the leads 26 project outwardly of the longitudinal axis of the coil form 22 in the same general direction and parallel with the mounting foot portions 221: of the coil form. The connector leads, as shown in FIG. I, extend outwardly beyond the outer end surfaces of the mounting foot portions 22a.

in addition to the multitum coil 24, the coil assembly 20 also includes two separate, single-turn loops or

coils

28 and 30, each of which is in coaxial alignment with the turns of the coil 24 and is disposed between a pair of adjacent turns thereof. As best shown in FIGS. 3, 9, and 10, the single-

turn coils

28 and 30 each comprise a single circular loop of wire with a pair of connector leads 29 and 31, respectively, projecting outwardly from the ends of the loops in a direction generally perpendicular to the longitudinal axis of the coil form 22 and generally parallel with the leads 26 of the multiturn winding 24. The single turns or loops of the

coils

28 and 30 are disposed to lie on planes angularly intersecting the coil form 22 and are spaced between adjacent turns or convolutions 25 of the multiturn coil winding 24. The single-

turn coils

28 and 30 preferably are equal in diameter to the turns 25.

In FIG. 3 is illustrated the single-turn winding 28 which comprises a substantially circular loop of wire and at opposite ends of the loop are integrally formed the connecting and supporting end leads 29 which are spaced apart and parallel. The leads 29 extend outwardly and generally normal of the coil form 22 from points spaced between adjacent pairs of turns or loops 25 of the multitum winding 24, and thus there is no interference or contact between the coil leads 29 and the helical turns 25, even though the single-

turn coils

28 and 30 are positioned directly between adjacent turns or convolutions 25 of the multitum coil 24.

FIGS. 6 and 7 are schematic diagrams of typical coil assemblies provided in accordance with the present invention. In FIG. 6 a pair of single-

turn coils

28 and 30 are provided which are inductively coupled with a multitum winding 24 on the common coil form 22. The single-

turn coils

28 and 30 are interconnected together externally of the coil form 22 (for example, on a printed circuit board, (FIGS. 4 and 5) to form a two-turn primary winding with a center tap for balanced line input and a multitum coil 24 comprises a'secondary winding of the coil assembly. Since the

coils

28 and 30 may be precisely identical, as described in detail hereinafter, and the coupling of each coil to the secondary is exactly the same, the center-tapped primary thus formed is exactly balanced for coupling to a conventional 300 'ohm twin lead antenna input. Also, either one of the

coils

28 or 30 may be used separately as the sole input coil to match a 75 ohm input, if desired.

In FIG. 7, the single-turn coil 28 is the primary winding, and the multitum coil 24 and single-turn coil 30 are secondary windings. The schematic diagrams shown in FIGS. 6 and 7 indicate typical VHF-UHF coupling arrangements in which the coil assembly 20 constructed in accordance with the present invention may be employed.

, Referring to FIG. 8, in fabricating a coil assembly 20 in accordance with the invention, each

separate coil

24, 28, and 30 is formed with its respective connecting and supporting

leads

26, 29 and 31, as described. The preformed coils are then placed in a free-standing position supported on the lower half or drag portion of a coil form mold member 32, which is to be used for the injection molding of the coil form 22. As best shown in FIG. 8, the mold member 32 includes an elongated, substantially semicylindrical recess or cavity portion 32a for forming the main cylindrical, hollow body portion of the coil form 22, and at each end of the cavity 320 is formed a transverse slot or depression 32b for molding of the feet portion 22a. The mold member 32 includes semicylindrical recesses 34 at opposite ends of the elongated cavity 32a and slots 32b for supporting opposite ends of a cylindrical central core pin 36 (FIG. inserted into the closed mold for forming the hollow center bore of the coil form. The semicylindrical recess or cavity 320 is provided with a plurality of longitudinally spaced, helically shaped, transverse grooves 37 adapted to receive and support the turns or convolutions 25 of the winding 24 and lower portions of the single turn or loop of the

coils

28 and 30 disposed between the turns 25.

coil turns is established. As best shown in FIGS. 9 and 10, when the upper mold member 40 is moved downwardly into mold closed position (FIG. 10), the single-

turn coils

28 and 30 are compressed radially and then held with precise longitudinal spacing between the turns and coils by the

grooves

41 and 37 in the

respective mold members

32 and 40.

After the

mold members

32 and 40 are closed together, an elongated core pin 36 is inserted coaxially through the central portion of the cylindrical mold cavity formed by the

cooperating recesses

32a and 40a, so that the coil form 22 will be hollow to provide an air core for the coil assembly. The mold cavity is filled with insulating plastic material, preferably in an injecting molding process, and after the material sets or hardens the mold is opened and the finished coil assembly is removed.

The diameter of the

mold cavities

32a and 40a is substantially equal to the mean diameters of the coil convolutions 25 The coil leads 26, 29, and 31 support the

respective coils

24, 28, and 30 in a free, standing position on the lower mold member 32 (FIG. 8) with the turn portions of the coils seated in the grooves 37 in the cavity 320. To this end, the mold member 32 is formed with a plurality of spaced apart, downwardly extending bores or holes 39 (FIGS. 9 and 10) for receiving the respective coil leads 26, 29, and 31. At the upper ends adjacent the cavity 32a the bores 39 are enlarged as at 390 to form integral bosses 40 of molded insulating material for firmly holding the respective leads 27, 29, and 31 of the coils in precise outwardly extending parallel alignment generally normal to the main cylindrical body of the coil form. The drilled bores 39 in the mold member 32 are slightly larger in diameter than the respective leads 26, 29, and 31, of the coils so that the coils can be easily inserted into a free standing position as shown in FIG. 8, preferably with an automatic feeding device. When the upper surface of the lower mold member 32 is exposed as shown, with

cavities

32a and 32b and recesses 39a and bores 39 readily accessible, the preformed coils 24, 28, and 30 may be rapidly placed in a precise alignment on the mold member with the

leads

26, 29, and 31 seated in the aligning bores 39. After the

coils

24, 28, and 30 have thus been positioned in free standing position on the open mold member 32, a top half of the mold or mating portion 40 is moved downwardly against the lower member 32 (as indicated in FIG. 9 by the arrows) to a mold-closed position, as shown in FIG. 10. The upper mold member 40 has an elongated, substantially semicylindrical cavity 400 therein for forming the upper portion of the body of the coil form 22 and v a plurality of longitudinally spaced, helically shaped, transverse grooves 41 are provided for receiving the upper half portions of the turns 25 of the multitum coil 24 and the upper half portions of the single-turn coils 28 and 30. The

cavities

32a and 40a cooperate to form the main body of the coil form 22 and pairs of the

respective grooves

37 and 41 cooperate to hold the turns of the

coils

24, 28, and 30 in a precisely spaced relation so that the desired mutual inductance between the and the circular loops of the single-turn coils 28 and 30 so that when the plastic material sets, the coils are firmly held in place with the desired coil diameter and spacing or pitch between turns. Each of the single-turn coils 28 and 30 and its

respective leads

29 and 31 is constructed with the loop portion of the coil and the leads substantially on a common plane, which bisects the longitudinal axis of the coil form at an angle approximately equal to the pitch angle or helix generation angle of the turns 25 on the multiturn winding 24. The turns 25 of the multitum coil 24 are arranged in helical configuration and the individual single-turn coils 28 and 30 lie in parallel planes which are spaced approximately midway between adjacent pairs of the turns 25. Because of this arrangement, there is no interference between the outwardly extending leads 29 and 31 of the single-turn coils 28 and 30 and the helical convolutions 25 of the multitum coil 24, as the leads project outwardly from the coil from points spaced between pairs of adjacent coil turns 25 thereon.

The body of the molded coil form 27 maintains accurate coil diameter and turn spacing between the coils of the coil assembly, and, in addition, integrally molded nub portions 42 (FIGS. 1, 4 and 5) are provided to more firmly hold the adjacent turns or convolutions of the coils in the desired pitch spacing outwardly of the outer surface of the main body of the coil form. The nub portions 42 are formed by recesses 40b (FIGS. 9 and 10) provided in the upper mold member 40 and serve to prevent the turns of the coils from expanding in diameter.

VA finished coil assembly 20 appears substantially as shown in FIGS. 1,2, and 3, with a plurality of connecting and supporting coil leads 26, 29, and 31 projecting downwardly in the same general or common direction as the supporting foot portions 220 at opposite ends of the coil form 22. The completed coil assembly is especially adapted, as shown in FIGS. 4 and 5, for mounting on and electrical connection with circuitry on a printed circuit board 44. The circuit board 44 includes a pluraLity of circuit forming conducting strips 45, etc., on at least one face thereof, and a plurality of preciselyspaced holes 46 for receiving the respective leads 26, 29 and 31 of the coil assembly 20 mounted thereon. The coil leads provide means for positively keying the coil assembly in place on the circuit board 44 and the foot portions 22a of the coil form bear against the surface of the circuit board to maintain proper spacing of the coil axis in parallel relation to the circuit board. The coil leads 26, 29, and 31, extend through the holes 46 in the board and are soldered to various conducting strips 45 thereon to complete the electrical and mechanical connection of the coil assembly 20 with the circuit board. The coil leads serve a dual purpose in properly aligning a mechanically supporting the coil assembly 20 on the circuit board. The coil leads serve a dual purpose in properly aligning and mechanically supporting the coil assembly 20 on the circuit board 44 and in electrically interconnecting the

coils

24, 28, 30, etc., of the coil assembly with the circuitry on the board. As shown in FIG. 5, the adjacent pair of coil leads 29 and 31 of the respective single-turn coils 28 and 30 project through a common conducting strip 47 on the printed circuit board 44 and are soldered thereto to produce the circuit configuration shown schematically in FIG. 6, wherein each of the single-turn coils 28 and 30 comprises a portion of a multiturn winding. The soldered connection 47 between the adjacent supporting coil leads 29 and 31 of the

coils

28 and 30 connects the two coils in series to form a single winding which is in a mutual inductive relation with the turns 25 of the multitum coil 24. However, the above-described method of assembly of, the

coils

28 and 30 is considerably simpler than an arrangement wherein two multitum coils must be threaded into one another before they are supported in the bottom mold member. Furthermore, use of the soldered connection 47 as a center tap provides a precisely balanced input for coupling to 300-ohm antenna input circuits, as described heretofore.

While but a single embodiment of the present invention has been here specifically disclosed, it will be apparent that many variations may be made therein, all within the scope and spirit of the invention.

What I claim as new and desired to be secured by Letters Patent of the United States is:

l. A coil assembly comprising an elongated coil form having a body of molded insulating material, a first coil molded in place on said coil form having a plurality of turns with a selected spacing between adjacent turns, a second coil having a single turn-or less molded in place on said coil form in coaxial relation with and spaced between a pair of adjacent turns of said first coil, said second coil including a pair of integral connector leads at opposite ends of said single turn extending outwardly of said coil from between spaced adjacent turns of said first coil, and insulating support means integrally molded on said coil form body around said connector leads for securing said second coil in spaced apart relation between said adjacent turns of said first coil, said connector leads projecting outwardly beyond said support means for making external electrical connections.

2. The coil assembly of claim 1 including a third coil having a single turn or less mounted on said coil form in coaxial relation with and spaced between a pair of adjacent turns of said first coil, said third coil including a pair of integral connector leads at opposite ends of said single turn extending outwardly of said coil form between spaced adjacent turns of said first coil, and connector means remote from said coil form for interconnecting adjacent connector leads from second and third coils whereby said coils form a tapped common winding of said inductance.

.3. The coil assembly of claim 1 in combination with a printed circuit board having circuit conductors thereon connected with said connector leads for supporting said inductance on said circuit board, said support means having end surfaces in spacing contact against said circuit board.

4. The coil assembly of claim 2 wherein said connector means comprises a printed circuit board having circuit eon- 6 ductors thereon, said coil connector leads extending generally in a common direction toward said circuit board and connected to 'said' conductors thereon for supporting said inductance on said circuit board, said support means including end surfaces for contact against said circuit board to maintain a selected spacing between said board and said coil form body.

5. The coil assembly of claim 1 wherein said connector leads of said second coil are parallel and said single turn or less and said connector leads lie in a common plane angularly intersecting the longitudinal axis of said coil form.

6. A coil assembly comprising an elongated coil form having a body of molded insulating material, a first coil molded in place on said form including a plurality of turns with a selected pitch distance between adjacent turns, a second coil having a single loop and molded in place on said coil form spaced between a pair of adjacent turns of said first coil, said second coil having a pair of end leads extending outwardly of said form from between adjacent turns of said first coil, insulating support means integrally molded on said form body around said leads for holding said second coil in said spaced apart relation between adjacent turns of said first coil, a third coil having a single loop and molded in place on said coil form spaced between a pair of adjacent turns of said first coil and including a pair of end leads extending outwardly of said form from between adjacent turns of said first coil, insulting support means integrally molded on said form body around the end leads of said third coil for holding said third coil in spaced apart relation between adjacent turns of said first coil, said end leads of said second and third coils extending, respectively, outwardly of said support means for making external electrical connections.

7. A method of making a coil assembly comprising the steps of forming a first coil with a plurality of coaxial, spaced turns and a pair of parallel connector leads at opposite ends extending outwardly of the coiling axis of said turns, forming a second coil having a single turn or less and a pair of parallel connector leads extending outwardly from the ends of said turn, placing said first coil on a mold forming member with said leads in a coil supporting upstanding position thereon, placing said second coil on said mold forming member with said leads in a coil supporting upstanding position and said single turn in coaxial alignment spaced between a pair of turns in said first coil, and molding a coil form in said member for holding said first and second coils in fixed position relative to each other.

8. The method of claim 7 wherein coaxial alignment between the turns of said first and second coils is obtained by moving a second mold forming member into a closed position forming a cavity for said coil form.

9. The method of claim 8 wherein said turns are compressed radially inwardly during coaxial alignment by moving said second mold forming member into said closed position.

Claims

1. A coil assembly comprising an elongated coil form having a body of molded insulating material, a first coil molded in place oN said coil form having a plurality of turns with a selected spacing between adjacent turns, a second coil having a single turn or less molded in place on said coil form in coaxial relation with and spaced between a pair of adjacent turns of said first coil, said second coil including a pair of integral connector leads at opposite ends of said single turn extending outwardly of said coil form between spaced adjacent turns of said first coil, and insulating support means integrally molded on said coil form body around said connector leads for securing said second coil in spaced apart relation between said adjacent turns of said first coil, said connector leads projecting outwardly beyond said support means for making external electrical connections.

2. The coil assembly of claim 1 including a third coil having a single turn or less mounted on said coil form in coaxial relation with and spaced between a pair of adjacent turns of said first coil, said third coil including a pair of integral connector leads at opposite ends of said single turn extending outwardly of said coil form between spaced adjacent turns of said first coil, and connector means remote from said coil form for interconnecting adjacent connector leads from said second and third coils whereby said coils form a tapped common winding of said inductance.

3. The coil assembly of claim 1 in combination with a printed circuit board having circuit conductors thereon connected with said connector leads for supporting said inductance on said circuit board, said support means having end surfaces in spacing contact against said circuit board.

4. The coil assembly of claim 2 wherein said connector means comprises a printed circuit board having circuit conductors thereon, said coil connector leads extending generally in a common direction toward said circuit board and connected to said conductors thereon for supporting said inductance on said circuit board, said support means including end surfaces for contact against said circuit board to maintain a selected spacing between said board and said coil form body.

6. A coil assembly comprising an elongated coil form having a body of molded insulating material, a first coil molded in place on said form including a plurality of turns with a selected pitch distance between adjacent turns, a second coil having a single loop and molded in place on said coil form spaced between a pair of adjacent turns of said first coil, said second coil having a pair of end leads extending outwardly of said form from between adjacent turns of said first coil, insulating support means integrally molded on said form body around said leads for holding said second coil in said spaced apart relation between adjacent turns of said first coil, a third coil having a single loop and molded in place on said coil form spaced between a pair of adjacent turns of said first coil and including a pair of end leads extending outwardly of said form from between adjacent turns of said first coil, insulating support means integrally molded on said form body around the end leads of said third coil for holding said third coil in spaced apart relation between adjacent turns of said first coil, said end leads of said second and third coils extending, respectively, outwardly of said support means for making external electrical connections.