Oct. 20, 1970 E. b. BELANGER 3,535,665

LAMINATED CORE TRANSFORMER Filed April 14, 1969 United States Patent 3,535,665 LAMINATED CORE TRANSFORMER Ernest Donald Belanger, Bloomsbury, N.J., assignor to Nytronics, Inc., Pelham Manor, N.Y., a corporation of Delaware Filed Apr. 14, 1969, Ser. No. 815,845 Int. Cl. H01f 27/24 US. Cl. 336-178 Claims ABSTRACT OF THE DISCLOSURE This invention comprises a laminated core transformer FIELD OF INVENTION This invention relates to a laminated core transformer. More particularly this invention relates to a transformer having a stacked core comprising sets of shaped laminations which complete a magnetic circuit.

DESCRIPTION OF PRIOR ART Prior laminations in transformers have been stamped in E-I, E-E, D-U, F, L, U-I shapes as well as in special configurations for special applications. For transformer use, all are designed to be inserted into a previous wound coil. These coils may be wound on a bobbin or on a supporting tube with a material such as paper or other insulating material between the layers of wire for support of the winding. In some cases, wire with a bondable coating is used to make a self-supporting coil. In each case, the coil has to be wound with clearances so that the laminations can be inserted without damaging the coil.

When miniature transformers are designed around these standard shapes, the clearances and/or bobbins occupy a much larger percentage of the winding area available resulting in a very inefiicient transformer.

OBJECTS An object of this invention is to provide an eificient transformer utilizing more effectively, available winding space.

A further object of this invention is to provide a core having sets of laminations, each set comprising an H shaped and an I shaped element.

A still further object of this invention is to provide a laminated core transformer having H and I shaped elements in which a coil is wound around the cross-bar of the H element.

Yet another object of this invention is to provide a laminated core transformer having H and I shaped elements occupying minimum space in which the ends of the elements are tapered providing easy insertion and providing a complete magnetic core circuit.

A still further object of this invention is to provide H and I shaped elements stacked respectively together to provide a laminated core, in which the effective reactance is easily controlled and varied by the manner in which the elements are stacked.

Another object of this invention is to provide a method for assembling a transformer in which a winding may be placed directly around the cross-bar of an H shaped laminate to efficiently occupy the available air space, and to complete the transformer with mating I shaped elements.

The above-mentioned and other features and objects ice of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompaying drawing, wherein:

FIG. 1 is a perspective view of the laminated core transformer of my invention;

FIG. 2 is a top view of an H shaped element used in the stacked lamination of FIG. 1;

FIG. 2A is a top view of the I shaped element;

FIG. 3 is a top view of another embodiment of the H shaped core piece;

FIG. 3A is a top view of the I shaped element used with the H of FIG. 3;

FIG. 4 is a diagram illustrating the position of the coil around the H shaped core piece and the insertion of the I core piece; and

FIG. 5 is a diagram similar to FIG. 4 illustrating the removal of the I shaped core piece.

Referring now to FIG. 1, there is shown a transformer 10 having a laminated core 20 and winding 11. One embodiment of the core construction may be understood by referring to FIGS. 2 and 2A. In FIG. 2 there is shown a core piece shown as generally H shaped having a right leg 21, a left leg 14, and a cross-bar 28.

As an aspect of novelty in this invention, the H pieces may be stacked one above the other and the coil may be wound around the cross-bar to extend almost and very close to the outer extremity of the coil space which is defined by the end or top surface of the right leg portion 23 and the end surface of the lower left leg portion 25.

In providing the stackings, the H pieces are preferably alternately arranged so that the left leg 24 becomes the right leg in the next successive layer and vice versa. The left and right legs are preferably each of the dimension L. It will be noted that the staggering results in the upper right leg portion 23 being shorter than the upper left leg portion 26 while the lower right leg portion 22 is longer than the lower left leg portion 25. The differential in height resulting from the staggering is an amount equal to W, which is the width of the I piece 29, as will be understood later. In this way, a shape is provided in each laminate or layer of which the I shaped element may fit into and yet be supported on its bottom surface by both the underlying I shaped element as well as an extending portion of the respective leg. The core is completed by the I shaped element 29, as illustrated.

Referring now to FIGS. 3 and 3A, there is shown my preferred embodiment. The H shaped piece 30 has a right leg 31, a left leg 34, and a cross-bar 38. The legs are again staggered so that the outer lengths of the legs are the same as those of FIG. 2. As illustrated, the upper right leg 33 and the lower left leg 35 are formed in the same manner as legs 23 and 25 of FIG. 2. The lower right leg portion 32 and the upper left leg portion 36 are cut to provide angled ends 41 and 42, respectively. The I shaped element 39 of FIG. 3 is also cut to provide an angled end 40. It will be noted that I piece 39 has an upper surface (inner with respect to the entire core) of length L, but a lower (or outside) surface which is greater. Because of the angular cut to the end, the said lower surface has a length preferably equal to L+ W.

The manner of making the transformer will now be considered in greater detail. The H pieces are arranged in stack formation so that the leftv and right legs have respective layers preferably alternating. The H laminations are pre-assembled to the required stack height and held together with suitable means such as with a thin piece of tape or with cement or by painting an adhesive on any or all of the exposed edges, or by using a thin heat shrinkable tubing over the cross-bar and/or the legs and .then applying heat such as hot air for a few seconds. The hot air shrinks the tubing tight against the laminations. The assembled stack is then attached to the winding machine and the coil wound directly on the-lamination stack around the cross-bar of the H. The advantages are now obvious. No tube or margin clearances are required.

In miniature transformers, the working voltages are usually low enough so that the normal insulation on the wire is enough protection. In some cases, it may be desirable to paint the winding area of the lamination stack with a thin insulating coat or wrap the legs with a thin piece of tape, or a piece of heat shrinkable tubing and shrinking it tight with the application of heat.

After the coil is wound, the I pieces are inserted to complete the magnetic circuit. It should be noted that the H stack can be arranged in any of several different ways, depending on the magnetic properties desired; they can be stacked alternately so that all joints are covered (used when maximum permeability is required) or they can be stacked all in the same direction and an air gap introduced between the H stack and the I stack if desired (used in DC bias current applications, such as reactors or transformers with DC current in one or more windings). They can also be stacked in alternate sets of 2 or 3 or 4 etc. to achieve whatever magnetic properties desired.

The manner by which the end I pieces 39 are inserted and removed are illustrated ni FIGS. 4 and 5, the arrows suggesting insertion and removal forces respectively. The alternate stacking of the H pieces is illustrated showing respective left and right legs of such H pieces are arranged on respective opposite right and left sides of the core. The I piece 39 is inserted and the left end thereof fits over the angled end 41 of the next lower H piece. It will be noted that the angled end 40 makes in and out adjustment possible without access to the coil space occupied almost in total by coil 11. The angled end 40 mates with angled end 41 of leg 31 and provides complementary angular relationship. Typically, such angles may be 45 degrees. In this way the H and I pieces can lie flat in a plane. The angles formed are preferably complementary. If they are not exactly complementary, but so long as their total is 90 degrees or less, the coil pieces may still lie flat and be coplanar, although some air space will appear in the space between the angled surfaces.

In summary, there has been provided a laminated core transformer having a stack of magnetic elements providing a laminated core in a transformer assembly, having H shaped and I shaped flat core pieces-and a coil wound around and supported over the cross-bar of the H piece. The I pieces are positioned to bridge the gap between the upper and lower ends of the legs of the H. The width of the I piece is W, and the legs of the H are staggered by an amount substantially equal to W, to provide a square core. The side dimension is L+ W. The legs of the H may be staggered, and the extending ends of the" legs maybe formed at an acute angle, along with the endof the I piece. The core pieces are arranged so that the said acute angles are additive, the acute angles in total being not more than 90 degrees to allow the H and I pieces to lie flat. The H and I pieces may be optimally stacked to provide a core substantially devoid of air space between the core pieces or the ends of the H and I pieces may overlap to provide a core having air spaces between the respective laminates. The coil therefore substantially occupies the space between. the crossbar of the H and the inner side of the I piece.

While the foregoing description sets forth the principles of the invention in connection with specific apparatus, it is to be understood that this description is made only by way of example and not as a limitation of the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A laminated core transformer comprising:

a stack of magnetic elements providing a laminated core in a transformer assembly;

said stack comprising sets of substantially H shaped and I shaped flat core pieces;

a coil wound around and supported over the cross-bar of the H piece;

the I pieces being positioned to bridge the gap between the upper and lower ends of the legs of the H.

2. The core transformer of claim 1, in which the width of the I piece is W, and in which the legs of the H are staggered by an amount substantially equal to W, whereby a square core is provided having a side substantially equal to L+ W.

3. The core transformer of claim 1 in which legs of the H are staggered, and in which the extending ends of the legs are formed at an acute angle, and in which at least one end of the I piece is formed at an acute angle.

4. The core transformer of claim 3, in which said core pieces are arranged so that the said acute angles are additive said acute angles in total being not more than 90 degrees to allow the H and I pieces to lie flat.

5. The core transformer of claim 1 in which the extending leg ends of the legs of H are formed at an acute angle and in which the end of the I piece is formed at an acute angle.

6. The core transformer of claim in which the I pieces are arranged so that the angles are additive,

said acute angles being, in total, not more than 90 degrees to allow the H and I pieces to lie flat.

7. The core transformer of claim 5 in which the ends of the H and I pieces overlap whereby a core is provided having air spaces therein.

8. The core transformer of claim 5 in which the coil substantially occupies the space between the cross-bar of the H and the inner side of the I piece.

9. The core transformer of claim 1 in which the H pieces are uniformly stacked with respect to left and right sides of the core.

50 10. The core transformer of claim 1 in which at least some of the H pieces are alternately stacked with respective left and right legs of such H pieces being arranged in respective opposite right and left sides of the core.

References Cited US. Cl. X.R.