Electrical terminal having pyramid teeth thereon

[57] ABSTRACT

This invention relates to a stamped and formed generally U-shaped electrical terminal useful for terminating magnet or electromagnetic coil wire. More particularly this invention provides a U-shaped terminal stamped and formed from a conductive material wherein a leg has a slot or an opening and a shank which contains a locking tab extending normal thereto such that the locking tab may protrude through the slot or opening and be bent against the leg so as to bias that leg against the shank. The inside surface of the shank leg may contain a plurality of elongated pyramidal shaped teeth or groups of such teeth. When a wire is passed between the shank and leg and both are closed and locked one against the other via the locking tab, the teeth bite through the insulation and into the conductor making electrical contact therewith.

Claims, 6 Drawing Figures

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PATENTEE DEC 31974

SHEET 1 OF 2

3.852,702

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PATENTED DEC 31974

SHEET 2 OF 2

3,852,702

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3,852,

ELECTRICAL TERMINAL HAVING PYRAMID TEETH THEREON

BACKGROUND OF THE INVENTION ₅The problem which led to the development of the present invention was that of attempting to terminate or electrically connect very fine film-insulated wire coming from small electromagnetic coils. As is apparent to those skilled in the art, stripping and soldering 10 such fine wire is difficult, costly, and sometimes unsatisfactory. In view of the type of apparatus where such coils are used, a type of connection where soldering could be omitted was desired. To this end an S-shaped clip was developed with one curved portion of the clip 15 being fastened onto the flange of the electromagnetic coil. The escond curve of the clip received the fine wire and then was bent or squeezed together traping the wire between the two legs of the S-shaped clip. This device for terminating the fine wire worked satisfactorily 20 but only temporarily. It was soon discovered that the resiliency of the S-shaped clip and its memory resulted in the relaxation or opening of the squeezed together portion of the clip so that electrical contact was lost or at est was characterized by an on again off again situa- 25 tion. Obviously this type of connection would not suffice in devices which were hermetically sealed; that is, the connection must be reliable for the life of the device utilizing such connection. The unsatisfactory results of the S-shaped clip resulted in thinking of various means to lock the two legs of the curve together. Thus, the conception was developed of having a tab extending from one leg through an opening in the second leg and bending the tab down against the second leg pressing it tightly and holding it against the first leg. Tests show that this device resulted in a permanent electrical connection; that is, one wherein the legs could not open up again.

As the fine wire in such electromagnetic coils are coated with insulating varnish it was necessary early in the development of the electrical connection to strip such insulating varnish away therefrom. Two conventional methods were used, the first using chemical means and the second using abrasive means. Both methods of stripping the varnish away from the wire proved unsatisfactory for a number of reasons. It was therefore desirable to devse means to terminate the wire without first removing the insulating varnish. This led to the development of a plurality of teeth extending along the inner surface of one leg where such teeth would bite through the insulating varnish as the tab pressed one leg against the other. Further developmental work resulted in providing two sets of a plurality of elongated teeth on one of the legs. Each set contained teeth of different height, the smallest tooth being nearest the outer edge of the leg surface and the tooth having the highest elevation being nearest the inside of the leg. The plurality of teeth of varying heights were to bite into and through the insulating varnish to varying degrees thereby establishing good electrical connection and further a mechanical grip.

Accordingly the present invention provides a generally U-shaped electrical terminal stamped and formed from a sheet of conductive material and comprising a leg having a generally concave portion thereon and an opening therethrough and a shank which is parallel to the leg and contains a locking tab which extends nor702 mal to the axis of the leg. The tab is adapted to extend through the opening of the leg so that it may be bent parallel to the leg to press it up against the shank. Further the shank contains on its surface facing the leg a plurality of teeth where each tooth is of a different height. These teeth bite into an insulated electrical wire placed across the teeth when the leg is biased against the shank. The terminal has a bight which hinges the shank and the leg together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the preferred embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along the longitudinal axis of the embodiment of FIG. 1;

FIG. 3 is the embodiment of FIG. 1 after it has been crimped onto an insulated electrical wire;

FIG. 4 is a perspective view of the embodiment of FIG. 1 showing a conventional ring tongue at one end; and

FIGS. 5 and 6 are taken along lines 5—5 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1 the electrical terminal 10 of the present invention is illustrated. Terminal 10 consists of a leg 12, a shank 14 and a bight 16 which is the hinge for terminal 10. As FIG. 1 shows the leg, shank and bight are quite wide relative to the thickness. The width of course is a matter of preference.

Referring now to both FIGS. 1 and 2, leg 12 is preferably concave, generally designated by the reference numeral 18, beginning with the junction of the leg with ³⁵ bight 16 and terminating at free end 20. In addition to having a concave portion leg 12 contains a slot 22. This slot extends from about half way along leg 12 through bight 16 and into shank 14.

Shank 14, the other half of the U-shaped terminal, ⁴⁰ parallels leg 12 and is connected thereto by bight 16.

The material removed to form slot 22 remains attached to shank 14 at the end of the slot to form a locking tab 24. This tab is bent to project from the shank outwardly through the slot in leg 12 as the drawing indicates.

⁴⁵ In addition to having locking tab 24, shank 14 has on its inner surface 30; i.e., the surface facing leg 12, a plurality of teeth 26 which extend along and on either side of the longitudinal axis of the shank. Each sets, herein designated by reference numeral 28, contains a number ⁵⁰ of teeth of varying height, the highest tooth being on the inside of the set and the lowest tooth being adjacent the side of the shank. As FIGS. 1, 5 and 6 show, each tooth is triangular or pyramidal in shape, the apex ₅₅ thereof being rather sharp.

METHOD OF USE OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 2 through 6 the method of ₆₀ use of the present invention will now be described. FIG.

shows a magnet wire 32 positioned across the width of electrical terminal 10, the wire preferably being positioned immediately adjacent to the inside portion 34 of locking tab 24. Locking tab 24 is now bent down ₆₅ against leg 12 pressing that leg against teeth 26. This biasing action pushes wire 32 onto the teeth so that, the sharp points cut into the insulation 38 as shown in FIG.

5. In the case of a small wire 32 the larger teeth may

3,852,702 actually cut completely through the wire. FIGS. 3 and 4 show the completed termination of magnet wire 32. FIG. 4 also shows a ring tongue 36 integral with and extending from shank 14. Ring tongue 36 represents only one of a number of standard tongue styles which may be formed with electrical terminal 10.

Referring now to FIG. 5, where wire 32 is of small diameter the inner most teeth of each tooth set 28 will completely cut through the wire. As the height of the teeth decrease towards either side of shank 14 the depth of penetration into wire 32 by the teeth decreases. The result of the varying depths of penetration into wire 32 is an extremely good electrical contact and an extremely good mechanical grip on the wire. FIG. 6 illustrates the situation where a wire of larger diameter, herein designated as 32, is terminated in electrical terminal 10. As is clearly seen in the drawing the teeth penetrate into but do not sever the wire as happened with wire 32. Not withstanding this the termination provides an extremely good electrical contact. Further, it is to be noted that the teeth cut through insulation 38 so that stripping of the wire is not required. In addition to illustrating how teeth 26 cut through the insulation on wire 32 prime, FIG. 6 also shows the ability of electrical terminal 10 to accomodate a wide range of wire sizes and insulation thicknesses.

As is now apparent the present invention contains a novel feature in the locking tab which biases the leg against the shank and further which locks the two together. Another novel feature is the pyramidal or triangular shaped teeth which increase in height from the outside in. Yet another feature is that as the leg is forced down onto the wire, the flattening of the concave section 18 imparts a rolling action to the wire which enhances the penetrating ability of teeth 26. Another feature is that the wire being crimped is automatically and properly positioned in the terminal when it is bearing up against inside portion 34 (FIG. 2). Still another novel feature of the present invention is that the wire being terminated is subjected to two compressive force vectors; one is parallel to the apex of the teeth and the second is at about a right angle thereto as the wire is pushed down the sides of the triangular shaped teeth. As FIGS. 5 and 6 show, a mass of wire equal to the distance between the apex of adjacent teeth is squeezed into the decreasingly smaller area etween the apex of the teeth and the surface of the shank.

Although the present invention was developed initially for electromagnet coil wire, it should now be apparent that the terminal can crimp any kind of wire including aluminum, and that the novel features disclosed above would be present in any size terminal built in accordance with this disclosure.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom. Modifications to the electrical terminal disclosed herein will be obvious'to those skilled in the art. For example, a terminal may be constructed in which the shank contains one set of teeth progressing in size from one side to the other. A terminal of this type lends itself readily to a sutomatic wire cutting in bobbin construction.