US3660791A

US3660791A - Electrical coil

Info

Publication number: US3660791A
Application number: US71096A
Authority: US
Inventors: Dhu Aine J Davis
Original assignee: Hermetic Coil Co Inc
Current assignee: Hermetic Coil Co Inc
Priority date: 1970-09-10
Filing date: 1970-09-10
Publication date: 1972-05-02
Anticipated expiration: 1989-05-02

Abstract

An electrical coil having a bobbin configuration with a coil receiving a central portion and a pair of end discs at opposite ends of the central portion, and a coil would on the central portion with end wires for connection to appropriate flexible wire-like terminal leads. A pair of elongated troughs are formed on the outside face of one of the bobbin end discs for receiving and positioning the terminal leads for connection to the winding end wires. Apertures are formed through the one end disc at the ends of the troughs so that the winding end wires may be inserted therethrough for connection to the terminal leads. An encapsulating casing for the coil covers a portion of the flexible terminals leads and, after encapsulation, the leads are bent outwardly from the one end disc generally perpendicular thereto for connection in an appropriate circuit. A heat flangible fuse is joined in one of the innermost turns of the coil and is positioned on and spans a pair of spaced raised ribs formed on the bobbin central portion so that the space between the ribs forms a recess to receive the fuse in a molten state to insure a positive fuse break. At least one elongated raised rib is formed on the central portion and extends between the end discs to provide insulating air spaces on opposite sides of the rib, between the wound coil and the bobbin central portion.

Description

United States Patent Davis 51 May 2,1972

[54] ELECTRICAL COIL Dhu Aine J. Davis, Wheaton, ll].

[73] Assignee: Hermetic Coil Co., Inc.

[22] Filed: Sept. 10, 1970 [21] Appl. No.: 71,096

[72] Inventor:

[ 52] U.S. Cl... ..336/l92, 336/96, 336/205 Primary E.\'aminerE. A. Goldberg Att0rney-Hofgren, Wegner, Allen, Stellman & McCord [57] ABSTRACT An electrical coil having a bobbin configuration with a coil receiving a central portion and a pair of end discs at opposite ends of the central portion, and a coil would on the central portion with end wires for connection to appropriate flexible wire-like terminal leads. A pair of elongated troughs are formed on the outside face of one of the bobbin end discs for receiving and positioning the terminal leads for connection to the winding end wires. Apertures are formed through the one end disc at the ends of the troughs so that the winding end wires may be inserted therethrough for connection to the terminal leads. An encapsulating casing for the coil covers a portion of the flexible terminals leads and. after encapsulation. the leads are bent outwardly from the one end disc generally perpendicular thereto for connection in an appropriate circuit. A heat flangible fuse is joined in one of the innermost turns of the coil and is positioned on and spans a pair of spaced raised ribs formed on the bobbin central portion so that the space between the ribs forms a recess to receive the fuse in a molten state to insure a positive fuse break. At least one elongated raised rib is formed on the central portion and extends between the end discs to provide insulating air spaces on opposite sides of the rib, between the wound coil and the bobbin central portion.

5 Claims, 10 Drawing Figures PATENTEBMM 2|972 3.660.791 SHEET 16F 2 /V 27 T 22 25 22 22 4 I ATTORNEYS ELECTRICAL con.

BAC KGROUNDAND SUMMARY OF THE INVENTION This invention is concerned primarily with electrical coils of many turns of wire'wound on a spool-like bobbin of a molded is quite difficult to manipulate and connectto the terminals,

particularly insulated covered wire-like terminal leads.

Therefore, an object of this invention is to provide an improved electricalcoilwhich is simple and easy to manufacture and provides for easy manipulation of the winding end wires for connection to the terminal leads.

In certain instances, it would be desirable to provide an electrical coil of the character described which has an encapsulating casing, with terminal leads extending outwardly from the coil generally perpendicular to one of the bobbin end discs, without the terminal leads protruding beyond the periphery of the end disc. In the coil disclosed herein, a pair of elongated troughs are formed on the outside face of one of the bobbin end discs for receivingand positioning elongated wirelike flexible terminal leads, with a conductor portion at one end of each of theterminal leads disposed generally at the end of its respective positioning trough. A pair of apertures are formed through the one end disc, one aperture extending through the bottom of each of the troughs at the end thereof adjacent the exposed conductor portionsof the terminal leads, whereby the winding end wires may be inserted through the apertures to the outside of the one end disc for connection to the terminal leads. An encapsulating casing is provided for the coil, with the casing covering only a portion of the flexible terminal leads, but at least the connection between the terminal leads and the winding end wires, thereby permitting the terminal leads to be bent outwardly from the one end disc, generally perpendicular thereto, after encapsulation, without the terminal leads protruding beyond the periphery of the end disc.

assembling the electrical coil set forth in the preceding para- Another object of the' invention is to provide a method of graph, comprising the steps of winding a coil on the central portion of the bobbin with the winding end wires protruding from the coil for connectionto the flexible wire-like terminal leads, positioning the terminal leads in said troughs, connecting the winding end wires to the terminal leads after the leads have been inserted through said apertures, applying an encapsulating casing over at least a portion of the coil and over the connection between the winding end wires and the terminal leads, and bending the terminal leads outwardly from the one bobbin end disc generally perpendicular thereto for connection in an appropriatecircuit. Preferably, the terminal leads are held in the trough against the walls thereof during the application of the encapsulating casing.

' It has also been desirous to provide heat frangible fuses in coils of the character described, whereby the fuses will burn out when the coil reaches a predetermined high temperature. Such fuses normally have taken the form of a section of solder joined in one of the turns of the coil whereby the solder will melt at thepredetermined temperature and breaking the connection with the adjoining wire of the coil. However, heretofore the problem with electrical coils of the character described herein was that when the fuse would become molten, the solder had no place to flow and oftentimes the molten solder still would conduct electricity without forming a break between the adjoining wires of the coil.

Therefore, another object of the present invention is to provide an electrical coil having an improved arrangement for receiving a heat frangible fuse, particularly a solder link fuse, to insure a positive fuse break.

A further object of the invention is to provide an electrical coil of the character described wherein a heat frangible fuse is joined in the coil adjacent the outer surface of the bobbin central portion, with a recess formed in the central portion beneath the fuse to receive the fuse in a molten state to insure a positive fuse break from the adjoining wires of the coil.

In a preferred embodiment of the invention, a pair of spaced raised ribs are formed on the central portion of the bobbin beneath the fuse, with the fuse resting on and spanning the ribs when inthe wound coil. The space between the ribs forms a recess or air pocket to receive the fuse in a molten state to insure a positive fuse break. The ribs are formed on the bobbin central portion adjacent the juncture of the central portion and one of the bobbin end discs so that theinside face of the end disc facilitates positioning and holding the fuse on the ribs. Y

Another feature of the invention is the provision of elongated raised ribs on the central portion of thebobbin extending between the bobbin end discs to provide insulating air spaces on opposite sides of theelongated ribs and between the wound coil and't'he bobbin central portion.

Other objects, features and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings.

DESCRIPT ION OF THE DRAWINGS FIG. 1 is a side elevational view looking at the outside face of oneof the bobbin end discs, with the terminal leads positioned in connection with the winding end wires, prior to encapsulation;

FIG. 2 is a side elevationalview looking in the direction of line 2-2 in FIG. 1,: with a portion of the coil cut away to illus trate the fuse-positioning ribs on the outside of the central portion of the bobbin; FIG. 3 is a section taken generally alongthe line 3-3 of FIG. 2, with a portion of the coil cut away to illustrate the fuse-positioning ribs and the disposition of the winding end wires in the apertures in one of the bobbin end discs, and with a core positioned in the coil;

FIG. 4 is a partial section taken generally along the line 4 4ofFIG.3; I

FIG. 5 is a partial section taken generally along the line 5- -5 of FIG. 2, illustrating-the heat frangible fuse in position of the bobbin;

FIG. 6 isa view similar to that of FIG. 5 showinga'break in the fuse, with the fusebeginningto melt and flowing intothe recesses formed: between the ribs on the central portion of the bobbin; l

FIG. 7 is aperspective view ,of a completely encapsulated electrical coil embodying the concepts of the present invention, with the core of the coil removed to facilitate the illustration;

FIG. 8 is a side elevational view, on a reduced scale, looking at the left-hand side of the coil shown in FIG. 7;

FIG. 9 is a partial section-taken generally along the line 9- 9 of-FIG. 7; and

FIG. 10 is a section taken generally along the line l0-l0 of FIG. 3, with the ends of the core cut away.

spanning the ribs formed on the outside of the central portion DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings in greaterdetail, an electrical coil is provided with a bobbin configuration having a coil-receiving barrel or central portion 12 (FIG. 10), with a pair of generally parallel end discs, 14a, 14b at opposite ends of the central portion, defining a coil-receiving channel. A coil 16 is wound on :the central portion of the bobbin within the channel and has winding

end wires

18a, 18b for connection to flexible, insulated wires or terminal leads 20a, 20b, respectively as best seen in FIGS. 1 and 2.

Referring particularly to FIGS. 1, 2 and 4, a pair of elongated

concave troughs

22a, 22b are formed on the outside face of the end disc 14a for receiving and positioning the flexible terminal leads 20a, 20b, respectively, generally flush with the outside of the end disc 14a for connection to the winding

end wires

18a, 18 b. A pair of elongated slots or apertures 24a, 2412 are formed through the end disc 14a through which the winding end wires are inserted for connection to exposed conductor portions from the terminal leads 20a, 20b on the outside of the end disc 14a. The winding end wire 18b comprises the inner-end of the wound coil, that is the end adjacent the central portion 14 of the bobbin, and is inserted through the innermost aperture 24b for connection to the exposed conductor portion of the terminal lead 20b. The winding end wire 18a comprises the outer end of the wound coil extending from the last turn of the coil and is inserted through the aperture 24a.for connection to the exposed conductor portion of the terminal lead 20a. p

Preferably, the

apertures

24a, 24b are formed at one end of the

troughs

22a, 22b for connection to the terminal leads. In the embodiment of the invention shown in the drawings,.the apertures actually extend through the bottom of the troughs. For purposes to be described hereinafter, the

troughs

22a, 22b are interrupted intermediate the ends thereof, as is best seen in FIG. 1, forming arecess 25.

Before going into the encapsulation of the above described electrical coil and the method of assembling the coil, it should be pointed out that the

troughs

22a, 22b and the

apertures

24a, 24b not only facilitate manipulating and connecting the winding end wires and the terminal leads, but such a structure permits the terminal leads to be bent outwardly from the end disc 14a generally perpendicular thereto for connection in an appropriate circuit, without the terminal leads protruding beyond the periphery of the end disc. The outwardly bent flexible terminal leads are shown in FIG. 7 (where a fully encapsulated coil is shown), the initial position of the terminal leads being shown by the dot-dash lines.

A molded encapsulating casing, generally designated 28, is provided for at least a portion of the coil, with the casing covering only a portion of the flexible terminal leads 20a, 20b, as best seen in FIG. 7. The encapsulating casing should at least cover the connection between the terminal leads and the winding end wires to insulate the connection and to facilitate maintaining a sound connection. With the encapsulating casing covering only a portion of the flexible terminal leads, the leads may be bent outwardly from the end disc 14a without protruding beyond the periphery of the end disc, as described above. It should be pointed out that by providing the interruption or recess 25 in the

troughs

22a, 22b, the encapsulating material is permitted to flow about the terminal 2 about 4 terminal leads 20a, 20b, to aid in holding the terminal leads in position. Furthermore, as best seen in FIG. 7, a portion of the trough structure, as well as a portion of the outer face of the end disc 14a of the bobbin, are exposed after the encapsulating casing is molded about the bobbin. This portion of the trough structure forms part of the mold during the molding process whereby the terminal leads are held in the trough against the walls thereof during the application of the encapsulating casing and none of the encapsulant will flow about the adjacent portions of the terminal leads, to permit the leads to be bent outwardly as shown in FIG. 7.

The method of assembling the electrical coil described above is as follows. The coil first is wound on the central portion '12 of the bobbin within the channel formed by the bobbin, with the inner and outer ends of the coil protruding therefrom, preferably adjacent the

apertures

24a, 24b for insertion therethrough. The flexible terminal leads 20a, 20b then are positioned generally flush with the outside face of the end disc 14, (namely, within the

troughs

22a, 22b respectively). The winding end wires may be connected to the exposed conductor portions of the terminal leads either before or after the terminal leads are positioned within the troughs. Preferably, the end wires are inserted through the

apertures

24a, 24b before positioning the terminal leads. An encapsulating casing is applied over at least a portion of the coil, bobbin and terminal leads, as best illustrated in FIG. 7. The terminal leads then are bent outwardly from the end disc 14a generally perpendicular thereto for connection in an. appropriate circuit. During the encapsulating process, the terminal leads are held within the trough against the walls thereof.

As stated above, problems have been encountered in providing a heat frangible fuse, normally a solder link fuse, in a wound coil. The fuse would become molten and still conduct electricity without breaking the circuit because the molten solder had no place to flow. Means are provided in the coil of the present invention for providing a positive break for such a heat frangible fuse. As best seen in FIGS. ,5 and 6, an elongated heat frangible fuse 32, preferably a solder link .fuse, is joined in the coil in one of the innermost turns of the coil adjacent the outer surface of the central portion 12 of the bobbin. In the form of the invention shown in the drawings, the central portion 12 of the bobbin is generally rectangular in cross section and has three spaced raised ribs 34 protruding outwardly from one of the flat faces thereof. The elongated fuse 32 rests on and spans the ribs 34 in the wound coil as best seen in FIG. 5. The spacing between the ribs 34 form recesses 36 (FIG. 5) beneath the fuse to receive the fuse in a molten state (FIG. 6) to insure a positive fuse break from the adjoining wire portions 37 of one of the inner turns of the wound coil. The preferred form of the invention includes three ribs so as to provide a barrier between the recesses to further insure a positive fuse break. Referring particularly to FIG. 2, the ribs 34 preferably are formed at the juncture of the central portion 12 and one of the end discs (end disc 14a in the drawings) so that the inside face of the disc 14a facilitates positioning and maintaining the fuse 32 on top of and spanning the ribs 34. In essence, the fuse will be sandwiched between the inner face of the end disc 14a and the adjacent turns of the wound coil so as to hold the fuse on the ribs 34.

In use, the coil includes a hot iron core C within the bobbin central portion 12. As seen in FIGS. 2 and 3, a pair of elongated raised ribs 38 are formed on at least two opposite flat sides of the bobbin central portion 12 and extending between the end discs 14a,.14b. These raised ribs form insulating air spaces 40 (FIG. 3) on each side of the ribs 38 between the wound coil and the bobbin central portion to aid in insulating the coil from the heat generated in the core C. The core shown in the drawings is laminated and held together by rivets 42 (FIG. 10). The rivets are disposed in grooves 44 recessed on the inside of the bobbin central portion 12. The grooves 44 also perform an insulating function and preferrably are disposed in the bobbin central portion from the ribs 38.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom as some modifications will be obvious to those skilled in the art.

I claim:

1. In an electrical coil having a bobbin configuration with a coil receiving central portion and at least one disc at one end of the central portion, a coil wound on the central portion and having two end wires for connection to appropriate terminal leads, the improvement comprising:

first and second flexible terminal leads one connected with each of said coil end wires;

means on said one end disc to position one of said flexible terminal leads generally flush with the outside face of the one end disc and to permit the terminal lead to be bent outwardly from said one end disc generally perpendicular thereto for connection in an appropriate circuit without the terminal lead protruding beyond the periphery of the end disc; and

a molded encapsulating casing for at least a portion of said coil, said encapsulating casing covering only a portion of said flexible terminal lead, said portion including the connection between the terminal lead and the winding end wire to hold the terminal lead connected to the winding end wire and the disc, the positioning means having a wall surface which supports the terminal lead during encapsulation, sealing off the flow of encapsulating material, the encapsulating casing terminating inside the periphery of the end disc to permit the terminal lead to be bent outwardly from said one end disc and extend generally axially thereof, without protruding beyond the periphery of the end disc.

2. The electrical coil of claim 1 wherein said means for positioning said terminal lead comprises an elongated trough on the outside face of said one end disc for receiving and positioning an elongated wire-like flexible tenninal lead, with a conductor portion at one end of the terminal lead connected to said one winding end wire.

3. The electrical coil of claim 2 including an aperture in the one end disc and the bottom of said trough at one end thereof and through which said one winding end wire extends for connection to the conductor portion at said one end of the terminal lead. 1

4. The electrical coil of claim 3 including a pair of said elongated troughs formed generally parallel to each other on the outside face of said one end disc, and a pair of said apertures in said one disc, one aperture in the bottom of each of said troughs at adjacent ends thereof whereby the innermost aperture receives the winding end wire from the inner end of the coil and the outermost aperture receives the winding end wire from the last turn of the coil.

5. The electrical coil of claim 1 including an aperture in said one end disc through which said one winding end wire extends whereby the end wire is exposed on the outside of said one end disc for connection to said terminal lead.

Claims

1. In an electrical coil having a bobbin configuration with a coil receiving central portion and at least one disc at one end of the central portion, a coil wound on the central portion and having two end wires for connection to appropriate terminal leads, the improvement comprising: first and second flexible terminal leads, one connected with each of said coil end wires; means on said one end disc to position one of said flexible terminal leads generally flush with the outside face of the one end disc and to permit the terminal lead to be bent outwardly from said one end disc generally perpendicular thereto for connection in an appropriate circuit without the terminal lead protruding beyond the periphery of the end disc; and a molded encapsulating casing for at least a portion of said coil, said encapsulating casing covering only a portion of said flexible terminal lead, said portion including the connection between the terminal lead and the winding end wire to hold the terminal lead connected to the winding end wire and the disc, the positioning means having a wall surface which supports the terminal lead during encapsulation, sealing off the flow of encapsulating material, the encapsulating casing terminating inside the periphery of the end disc to permit the terminal lead to be bent outwardly from said one end disc and extend generally axially thereof, without protruding beyond the periphery of the end disc.

2. The electrical coil of claim 1 wherein said means for positioning said terminal lead comprises an elongated trough on the outside face of said one end disc for receiving and positioning an elongated wire-like flexible terminal lead, with a conductor portion at one end of the terminal lead connected to said one winding end wire.

3. The electrical coil of claim 2 including an aperture in the one end disc and the bottom of said trough at one end thereof and through which said one winding end wire extends for connection to the conductor portion at said one end of the terminal lead.