US3394331A - Winding having a two turn conductive strip therearound - Google Patents

Description

July 23, 1968 R, w, AIKEN (ET AL 3,394,331

WINDING HAVING A TWO TURN CONDUCTIVE STRIP THEREAROUND Filed June :1, 1966 United States Patent 3,394,331 WINDING HAVING A TWO TURN CONDUCTIVE STRIP THEREAROUND Robert W. Aiken and Robert E. Canup, Richmond, Va.,

assignors, by mesne assignments, to Texaco, Inc., New

York, N.Y.

Filed June 2, 1966, Ser. No. 554,785 3 Claims. (Cl. 336-70) ABSTRACT OF THE DISCLOSURE High voltage coil structure for a transformer or the like. Individual turns of winding layers are spaced apart and the outermost two winding layers are strips that extend the full width of the next outermost layer of winding turns.

BACKGROUND OF THE INVENTION It has been recognized in high voltage induction equipment, especially transformers and the like, that there is insulation difiiculty with respect to the outer layers or windings of induction coils. Such difliculty stems from the tendency for concentration of voltage especially where a transient or rapidly changing voltage is applied. The concentration arises in the outermost layers of a high voltage winding so that the insulation tends to break down and cause short circuiting between turns of the coil. An obvious solution that has been applied is increased insulation thickness, and/or added spacing between turns of the coil on the outer layers. However, it has long been recognized that such solution entails suflicient added bulk and expense so as to leave much to be desired.

Some previous solutions have included the use of shielding layers such as to provide capacitive effects and thus avoid the excess high tension conditions. However, such attempts have been applied only to large size power transformers and the like; and .on account of the complications in manufacture and the bulk of the structure involved such structure is not applicable to a relatively small sized transformer such as the type employed with an internal combustion engine ignition system.

In addition, the known previous structures that provide shielding against high tension concentration effects have employed structure such that the shielding layers are applied in an electrically floating manner which fails to obtain the dual function quality that is obtained with structure according to this invention.

DESCRIPTION OF THE INVENTION It is an object of this invention to provide improved winding structure for a high voltage coil such that the outermost turns of the coil take the form of a conductive material strip that is at least as wide as the length of the coil winding layer thereunder.

Briefly, the invention concerns high voltage induction machinery. Specifically it deals with the combination of an improved high voltage coil that comprises a plurality of winding layers having predetermined axial dimensions. And it comprises at least .one turn of a conducting material strip that surrounds the outermost of said winding layers. The said strip covers said winding layers and forms a corona shield therefor.

The foregoing and other objects and benefits of the invention will be described in greater detail hereafter in accordance with the best mode contemplated for carrying out the invention, and in connection with which there are the illustrations of the drawings, wherein:

The figure of drawing shows a schematic elevation partly in cross-section, illustrating a high voltage winding 3,394,331 Patented July 23, 1968 for a transformer or the like, in accordance with the invention.

A preferred embodiment according to this invention relates to the high voltage coil of transformers. The transformer being one especially intended for use in internal combustion engine ignition systems.

Referring to the figure of drawing, it will be observed that there is a core element 11. This may take various forms, but as schematically indicated by the dashed lines it could be a closed rectangular shape. In such cases the primary winding or low voltage winding (not shown) of the transformer would be located on another leg (not shown) of the core parallel to that illustrated.

Core member 11 is preferably constructed of magnetically permeable material, such as soft iron or the like, and as indicated in the drawings is preferably laminated in order to reduce eddy current elfects, as is standard practice for core materials. Surrounding the core 11 there is a coil form 12 that is constructed of insulating material.

As schematically indicated, the total coil of the illustrated transformer is made up by winding a conducting material wire 15 around the coil form 12 so as to form a plurality of layers 16-20 illustrated. It will be observed that these winding layers 16-20 are tapered in axial length as they progress outward from the coil form 12. This is done in order to provide a decrease in voltage per layer as the layers progress outwardly toward the outside of the coil. The individual turns of the winding layers are separated by two diameter spacing (center to center) of the wire 15 as the turns are laid on. Each layer of turns is separated from the next successive layer by a thin sheet of insulating material 23. This is preferably a material such as that known by the trade name Mylar.

Outside of the last layer of turns 20 there is a double thickness sheet of insulating material 24, and on top of sheet 24 there is a complete first turn of a conducting material strip 25. Strip 25 is wrapped for two turns so that there is another layer of the insulating material sheet 26 that separates the first turn from the second or outermost turn.

It will be observed that the two turns of strip 25 are electrically connected in series with the coils (wrapped in layers 1620) so as to form the last two turns of the total coil. This is accomplished in any feasible manner such as by carrying the end .of the last turn on outer layer 20 around one edge of the strip or sheet 24, as illustrated, by a short connecting wire 30. The outermost or free end of strip 25 is then connected to a terminal wire 31. The other end of the complete coil is brought out from the coil structure via a terminal wire or connecter 32, as illustrated.

The outermost or covering layer for the coil is preferably a triple thickness sheet 35. This is preferably constructed of the same insulating material as that employed in the inner separating sheets 23 and 24 and 26.

It will be observed that by use of the illustrated structure for a high voltage inductive coil, substantially higher voltage may be applied without damage to the coil than was heretofore possible, in the absence of known techniques such as increasing insulation on the outer layers by large increases in thickness and/or very wide spacing and the like. Consequently, the high voltage results obtained are obtainable with compact and inexpensive structure so that a transformer using the structure of this invention is applicable to extra high voltage internal combustion engine ignition systems.

It will be noted also that with structure according to this invention even in the event that corona discharge should cause deterioration of the insulation to the point where it becomes punctured, there is insuflicient voltage between layers (since the outer two layers consist of a single turn each) to cause arc-over and perforce shorting between layers or turns.

While a particular embodiment'of the invention has been described above in considerable detail in accordance with the applicable statutes, this is not to be taken as in any way limiting the invention but merely as being descriptive thereof.

We claim:

1. In high voltage induction machinery, in combination an improved high voltage coil comprising a plurality of winding layers having predetermined axial dimensions,

said winding layers being tapered in axial length thereof as they progress outward from the axis of the coil in order to reduce the voltage per layer, and a conducting material winding comprising a strip surrounding the outermost of said winding layers,

said conducting material winding strip having at least two turns and being connected in series with the end of said outermost winding layer,

said strip covering said winding layers and forming a corona shield therefor.

2. A high voltage coil according to claim 1 wherein the turns of said winding layers are spaced mutually apart by a distance of two diameters center to center.

3. A high voltage coil according to claim 2 wherein said strip is wider than the axial dimension of said outermost layer, and

further including a terminal connection electrically connected to the outermost end of said strip.

References Cited LARAMIE E. ASKIN, Primary Examiner.

T. J. KOZMA, Assistawt Examiner.

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