US3745498A

US3745498A - Coil form

Info

Publication number: US3745498A
Application number: US00268420A
Authority: US
Inventors: R Hagood
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1972-07-03
Filing date: 1972-07-03
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10
Also published as: CA993062A; DE2333815A1; GB1401402A; IL42657A; JPS4946361A; IL42657A0; AU5765073A

Abstract

A molded plastic tubular body having a copper sleeve fixedly engaged about one end thereof adapted to be inserted into a printed circuit board and soldered thereto for electrical contact and mechanical bond. An integrally formed positioning shoulder adjacent the one end for positioning the body relative to the printed circuit board, integrally formed longitudinally extending ribs within the central opening of the body for threadedly receiving a cylindrical tuning core with threads in the outer periphery thereof and a resilient contact affixed to the opposite end of the body so as to extend axially outwardly therefrom to electrically engage an antenna.

Description

United States Patent 1 [451 July 10, 1973 Hagood COIL FORM [75] Inventor: Ray E. Hagood, Fort Lauderdale,

Fla.

[73] Assignee: Motorola, Inc., Franklin Park, Ill.

[22] Filed: July 3, 1972 [211 App]. No.: 268,420

[52] US. Cl 336/65, 336/136, 336/192 [51] Int. Cl. 1101f 15/02 [58] Field of Search 336/65, 136, 192

[56] References Cited UNITED STATES PATENTS 2,914,276 11/1959 Antalek et a1. 336/65 X 3,130,381 4/1964 Oeler et a1. 336/65 X 3,355,687 11/1967 Adams 336/192 X Primary Examiner-James D. Trammell Altorney-Vincent]. Rauner and Eugene A. Parson [57] ABSTRACT A molded plastic tubular body having a copper sleeve fixedly engaged about one end thereof adapted to be inserted into a printed circuit board and soldered thereto for electrical contact and mechanical bond An integrally formed positioning shoulder adjacent the one end for positioning the body relative to the printed circuit board, integrally formed longitudinally extending ribs within the central opening of the body for threadedly receiving a cylindrical tuning core with threads in the outer periphery thereof and a resilient contact affixed to the opposite end of the body so as to extend axially outwardly therefrom to electrically engage an antenna.

10 Claims, 3 Drawing Figures con. FORM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to a coil form for receiving coils thereon and mounting said coil form in mechanical engagement with a printed circuit board. Electronic circuits, such as radio receivers and transmitters and the like, utilize a number of fixed and variable or tunable coils and inductances. These coils must be wound 1 on a form and mechanically mounted on a base or the like. In many instances, the base is a printed circuit board and mechanical connection thereto may be somewhat difficult.

2. Description of the Prior Art In all prior art coil forms, one end of the form and/or some relatively complicated mechanism attached thereto is utilized to physically mount the coil form while separate apparatus, such as terminals and the like, are affixed to the coil form to electrically connect the coil to the remaining circuitry. Coil forms that are not mounted by complicated mechanisms are mounted by glue, epoxy resins, or the like. This material requires additional time to dry or set and is generally difficult to apply. Thus, additional time and steps are required in assembly and mounting of the prior art coil forms which increases the installation time and cost and also increases the chances of poor mechanical connections.

SUMMARY OF THE INVENTION It is a further object of the present invention to provide a coil form which is simpler to install and has increased reliability.

It is a further object of the present invention to provide a coil form which may be mounted mechanically in a single wave soldering step.

It is a further object of the present invention to provide a coil form in which an antenna contact may be affixed easily by means of a snap in lock feature provided in this invention for simplified contact with the antenna.

These and other objects of this invention will become apparent to those skilled in the art upon consideration of the accompanying specification, claims and draw mgs.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings, wherein like characters indicate like parts throughout the Figures:

FIG. I is a view in side elevation illustrating the coil form positioned in a printed circuit board, portions thereof broken away and shown in sections;

FIG. 2 is an enlarged view in top plan of the structure illustrated in FIG. land FIG. 3 is an enlarged view in bottom plan of the structure illustrated in FIG. 1, with the printed circuit board removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the Figures, the numeral 10 generally designates an elongated tubular body formed of electrically insulating material, such as by molding plastic or O the like. The body 10 includes a first end portion 11,

a central portion 12 and a second or opposite end portion 13. The central portion 12 has a circular cross section with the desired diameter and length to receive thereon coil means, such as antenna coils or the like. The thickness of the walls of the body 10 are sufficient to provide the desired strength without introducing unnecessary weight or use of material.

The first end 1 1 has a generally circular cross section, although it should be understood that any desired shape might be utilized, and is separated from the central portion 12 by a radially outwardly extending collar 15. The first end 11 is inserted through an opening defined by a printed circuit board 16 and the collar 15 positions the body 10 relative to the printed circuit board 16. In this embodiment, the collar 15 is formed as an integral part of the body 10 but it should be understood that other positioning means might be affixed to the body 10 after the formation thereof, if desired.

A thin sleeve 20 of solderable material, in this embodiment nickel silver or other corrosive resistant, solderable material, is affixed in coaxial engagement over the outer periphery of the first end 11 of body 10. The material may, in addition, be an electrical conductor for contact between a coil and the printed circuit board 16, as will be described presently. The sleeve 20 may be affixed to the first end 11 by molding the body 10 onto the sleeve 20 or by forming the sleeve 20 as a snap-ring which can be firmly and fixedly snapped onto the first end 11. The combined diameter of the first end 11 with the sleeve 20 affixed thereover is such that it mates snuggly with the opening in the printed circuit board 16. Conductors 21 printed on the board 16 so as to overlie at least portions of the periphery of the opening through the board 16 can be mechanically attached to the sleeve 20 by some convenient method, such as wave soldering or the like. Thus, the coil form is relatively simple to construct and is much easier to install than any of the prior art devices, since the coil form can be mechanically mounted and fixed to the printed circuit board when other wave soldering on the board is accomplished.

In the present embodiment, a longitudinally extending slit 22 is formed in the sleeve 20 to prevent the sleeve20 from acting as a shorted turn on the coil form. While it has been found through experimentation that the sleeve .20, even if completely encircling the end 11, does not detract from'the operation of a coil 23 wound on the central portion 12 of the form 10 if the coil 23 is positioned sufficiently distant on the form from the sleeve 20, it may be desirable in some instances to provide one or more slits 22 therein. In the present embodiment the coil 23 is wound around the central portion 12 and the ends are adapted to be connected to the associated circuitry. It should be understood that in certain embodiments it may be desirable to connect one end of the coil directly to the sleeve 20 and connect the sleeve 20 to the associated circuitry through the conductors 21 on the printed circuit board 16. When this is done the sleeve 20 may add some inductance to the coil, which can be determined during initial design.

In addition to the above described positioning devices, a longitudinally extending key or ridge 40 extends radially outward from the lower portion 1 1 of the form through the slit 22. The ridge 40 is utilized to orient the coil form in rotational position within the hole in the printed circuit board 16, during assembly. In some instances the rotational orientation of the coil form is not essential and the ridge 40 may be eliminated. Also, in some instances additional longitudinally extending ridges may be desirable.

The opposite end portion 13, which in this embodiment also has a circular cross section and a longitudinally extending slit therein, is constructed to receive a resilient antenna contact 25. The antenna 25 has a semicircular portion adapted to be coaxiallyengaged within the opposite end portion 13. One end of the semicircular portion is bent radially outwardly to be engaged in the slit in the coil form to prevent relative rotation of the antenna contact 25. In the present embodiment the antenna contact 25 is formed from a single piece of resilient material, such as berylco or the like, and an irregularly shaped elongated piece thereof, which extends longitudinally from the outer end of the semicircular piece, is bent so as to extend over the end of the body 10 in axially spaced relationship therefrom. The portion of the contact 25 extending laterally across the end of the body 10 is resiliently affixed at one end so that the portion is springable in an axial direction. This axially extending portion of the contact 25 extends through an opening in a housing 30 and is designed to frictionally engage an antenna external of the housing 30 to provide an electrical contact therewith. While it should be understood that the coil form described may be utilized for coils other than antenna coils, in which case the antenna contact 25 will not be utilized, when the coil form is utilized for an antenna coil and the antenna contact 25 is affixed to one end thereof, one end of the coil 23 may be attached directly to the antenna contact 25. r

In many instances, it may be desirable to provide a core 35 of magnetic material for tuning the coil 23 wound on the body 10. The central opening through the body 10 has a plurality of longitudinally extending, inwardly directed ridges 36, which in this embodiment have a generally triangularly shaped cross section. While it should be understood that the ridges 36 might have substantially any configuration, they should be constructed so as to be relatively easily deformed. The core 35 is generally cylindrically shaped with external threads thereon and upon a slight initial forcing thereof, may be threadedly engaged in the opening through the body 10. The ridges 36 deform to form internal threads for receiving the core 35 therebetween and for allowing longitudinal movement thereof for tuning the coil 23 wrapped around the body 10. It should be understood that double tuned coils might be provided on the body 10 by eliminating the antenna contact 25 and threading a second core into the opposite end of the body 10.

Thus, an improved coil form is disclosed which can be easily constructed and installed by soldering to a printed circuit board or the like. Some form of resilient contact may be provided at one end thereof, if desired,

for providing an electrical connection to an antenna or the like. Further, tuning cores may be threadedly engaged in a central opening therethrough to render tunable any coils wound thereon. In addition to the above, positioning devices may be incorporated to orient the coil form relative to a printed circuit board, both in heighth and in rotational position: The installation of the coil form is greatly simplified because it is mechanically mounted by a simple wave soldering step, or the like, and does not require any additional application of adhesives, epoxies, etc., or the consequent drying or curing thereof. Further, in some instances the mechanical and electrical connections can be made simultaneously.

While I have shown and described a specific embodiment of this invention, further modifications and improvements will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular form shown and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.

I claim:

1. An improved coil form adapted to be mounted in an opening defined by a printed circuit board or the like, said coil form comprising:

a. a tubular body of electrically insulating material having one end formed to mate with the opening;

b. positioning means affixed to said body and extending outwardly from the outer surface thereof for positioning said body relative to the printed circuit board; and

c. solderable means affixed to the outer surface of said body adjacent the one end for engaging conducting portions of the printed circuit board to mechanically mount the coil form.

2. An improved coil form as set forth in claim 1 wherein the solderable means includes a sleeve of c0nducting material at least partially encircling the body at one end.

3. An improved coil form as set forth in claim I wherein the tubular body is molded from plastic.

4. An improved coil form as set forth in claim 3 wherein the positioning means includes an integrally formed collar.

5. An improved coil form as set forth in claim 4 wherein the positioning means further includes an axially extending ridge for orienting the rotational position of the body relative to the printed circuit board.

6. An improved coil form as set forth in claim I having in addition axially extending ridges affixed to the inner surface of the body in radially inwardly extending relationship, said ridges being formed of material which will form threads upon the insertion of an externally threaded, cylindrical core therein.

7. An improved coil form as set forth in claim I having in addition an antenna contact affixed to the end opposite the one end.

8. An improved coil form as set forth in claim 7 wherein the antenna contact includes electrically conducting resilient material affixed to the opposite end of the body for electrical contact with a coil wound on the body and extending generally axially outward from the body for resilient electrical contact with an antenna.

9. In a radio incorporating a printed circuit board and having an antenna, an improved tunable antenna coil form therefor comprising:

a. A tubular molded plastic body having one end thereof engaged in an opening defined within the printed circuit board;

b. a sleeve formed of solderable material affixed to the outer surface of said body in coaxial alignment adjacent the one end thereof and soldered to conductors on the printed circuit board for mechanical and electrical contact therewith;

c. an integrally formed, outwardly extending collar in the outer periphery of said body adjacent the one end, said collar butting against the printed circuit board adjacent the opening therethrough for positioning said body relative to the printed circuit board;

d. integrally formed, longitudinally oriented, radially inwardly extending ribs in the inner periphery of said body threadedly engaged with a cylindrical externally threaded core;

e. resilient antenna contact means affixed to said body adjacent the end opposite the one end and extending generally axially outwardly therefrom into electrical contact with the antenna; and

f. coil means wrapped around said body and electrically contacting said sleeve and said antenna contact.

10. A method of mechanically mounting a coil form to a printed circuit board comprising the steps of:

to the conductors of the printed circuit board.

Claims

1. An improved coil form adapted to be mounted in an opening defined by a printed circuit board or the like, said coil form comprising: a. a tubular body of electrically insulating material having one end formed to mate with the opening; b. positioning means affixed to said body and extending outwardly from the outer surface thereof for positioning said body relative to the printed circuit board; and c. solderable means affixed to the outer surface of said body adjacent the one end for engaging conducting portions of the printed circuit board to mechanically mount the coil form.

2. An improved coil form as set forth in claim 1 wherein the solderable means includes a sleeve of conducting material at least partially encircling the body at one end.

3. An improved coil form as set forth in claim 1 wherein the tubular body is molded from plastic.

6. An improved coil form as set forth in claim 1 having in addition axially extending ridges affixed to the inner surface of the body in radially inwardly extending relationship, said ridges being formed of material which will form threads upon the insertion of an externally threaded, cylindrical core therein.

7. An improved coil form as set forth in claim 1 having in addition an antenna contact affixed to the end opposite the one end.

9. In a radio incorporating a printed circuit board and having an antenna, an improved tunable antenna coil form therefor comprising: a. A tubular molded plastic body having one end thereof engaged in an opening defined within the printed circuit board; b. a sleeve formed of solderable material affixed to the outer surface of said body in coaxial alignment adjacent the one end thereof and soldered to conductors on the printed circuit board for mechanical and electrical contact therewith; c. an integrally formed, outwardly extending collar in the outer periphery of said body adjacent the one end, said collar butting against the printed circuit board adjacent the opening therethrough for positioning said body relative to the printed circuit board; d. integrally formed, longitudinally oriented, radially inwardly extending ribs in the inner periphery of said body threadedly engaged with a cylindrical externally threaded core; e. resilient antenna contact means affixed to said body adjacent the end opposite the one end and extending generally axially outwardly therefrom into electrical contact with the antenna; and f. coil means wrapped around said body and electrically contacting said sleeve and said antenna contact.

10. A method of mechanically mounting a coil form to a printed circuit board comprising the steps of: a. providing a tubular coil form having a solderable ring coaxially affixed to one end thereof in at least partially encircling engagement; b. inserting the one end of the coil form in a mating opening defined by the printed circuit board, said printed circuit board having conductors overlapping at least a portion of the periphery of the opening; and c. wave soldering the solderable ring of the coil form to the conductors of the printed circuit board.