US2191393A - Transformer - Google Patents

Description

F 1940. M. w. HUMPHREYS 2,191,393

TRANSFORMER Filed Nov. 23, 1937 IN VEN'IFOR. M/Q/P/O/Y M #(MPH/PE n5 fate f/mm f/ ATTORNEYfi Patented Feb. 20, 1940 UNITED STATES PATENT .OFFICE 3Claims.

This invention relates to electric transformers, and has particular reference to the transformer core and to the method of making the same.

The principal object of the invention is to eliminate the necessity for making core stampings, to avoid the loss by way of scrap incident to the punching of the stampings or laminae, to eliminate the expense incident to the assembly of stamped laminations, and to provide a transformer having a core which is so formed as to provide improvement in the magnetic path and increased efliciency.

In accordance with the present invention, the core, instead of being built up of a large number of iron stampings, as is customary, is made from strip material which is wound in superposed layers and generally from one continuous iron strip. Preferably the core is wound from strip material through the coils until an annulus of proper thickness is built up, and subsequently the initial annular shape of the core may be changed by bending the core in a press or by other suitable means to a relatively flat or oblong shape.

The invention may be further briefly summarized as consisting in certain steps of the improved method and in the improved transformer which will be described in the specification and set forth in the appended claims.

In the drawing which illustrates the principle of the invention.

Fig. 1 is a view illustrating the manner in which the core is initially produced in the form of an annulus from core-forming material in the form of a continuous strip;

36 Fig. 2 is a side view of a transformer with parts in section, illustrating by way of example a form in which the transformer core may be eventually shaped;

Fig. 3 is a sectional view substantially along the line 3--3 of Fig. 2; and

Fig. 4 is a sectional view substantially along the line 4-4 of Fig. 2.

As is well known, transformers require laminated cores built up from stampings punched from sheet iron or other suitable sheet metal,

with considerable loss by reason of scrap material, and these punchings or stamped laminations are subsequently assembled to the desired core shape with the primary and secondary coils or coil sections in proper relation on portions of the core. In accordance with the present invention, the use of stampings is entirely eliminated and the laminated core is built up by winding a coreforming strip through the coils into the form of so an annulus, the winding being continued until there are sufiicient superposed layers to form a laminated core having the required cross-section. Although the core may, if desired, be retained in the shape of an annulus, it is generally flattened to oblong shape, leaving straight legs to accom- 6 modate the coils and more or less semi-circular ends.

The particular design of the transformer so far as insulation and coils are concerned is quite immaterial to the invention, but in Figs. 2, 3, and 10 4 I have shown a transformer produced by my improved method. This transformer has a core formed in accordance with the present invention, and, in addition, one primary and two secondaries and two magnetic chokes or shunts. How- 15 ever, it is to be understood that these features and the transformer design so far as the coils and chokes are concerned are not essential to the present invention. The transformer illustrated has an elongated core it which is continuous in the respect that it is built up of a continuous strip of core-forming material, such as soft iron. This core, as illustrated, has two parallel legs and rounded ends. On one of the legs is positioned a primary coil II and two secondary coils II but, 25 of course, in some instances there may be a single secondary as well as a single primary, or the primary and secondary windings may be otherwise made sectional. In this instance also the transformer has two magnetic shunts I3 30 formed from substantially c-shaped stampings which are hooked over the parallel legs of the core and extend down along one side thrreof. The shunts and coils are provided with suitable insulation which per se is immaterial to the pres- 35 cut invention, the principal feature of which is the method by which the core is formed.

As previously stated, the core is formed from a continuous strip of iron or other core-forming material which is wound in the form of an annulus through the coils. In Fig. 1 I have shown in simplified manner a fixture in which this can be done. In this view the strip of core-forming material is indicated at I4. It iswoundin the form of an annulus l5 through the previously formed 45 primary and secondary coils of which there may be two or more. The coils may be supported in a suitable stationary part It of the fixture which includes. a standard II, the coils being held stationary while the annulus is rotated through the 50 coils while the strip is fed thereon until the annulus has assumed the desired thickness. In this instance the annulus is supported at its inner periphery by rollers ll which may be rotatably supported in fixed position on suitable arms ll of the fixture. The annulus may be rotated in move outwardly to accommodate the constantly increasing thickness of the annulus. There may be as many of these supporting and driving rollers as desired, and power may beapplied to them in any suitable fashion, but preferably a from a single driving member from which power may be transmitted to the rollers 20 by shafts made flexible lay-universal joints or otherwise.

The mechanical driving means for this purpose is not illustratedss it may assume various forms and per se constitutes no part of the present invention.

To start the core, the strip may be strung through the primary and secondary coils or coil sections until the first layer is completed and the inner end may then be fastened to the innermost complete convolution by spot-welding or soldering, the band so formed then resting upon the inner rollers l8 and being engaged by the outer radially movable driving rollers 20. Then the rotation of the rollers III is started and this band is thereby rotated, feeding the strip H thereon and gradually building it up until, as before stated, an annulus of proper thickness is formed, whereupon the rotation is stopped. The strip, I4 will be held under any desired tension so that the superposed convolutions will be in close engagement. After the core is built up to the proper thickness and the rotation of the driving rollers is stopped, the outer layer .or convolution is cut from the strip l4 and the outer free end may be fastened to the outermost complete convolution by spot-welding or soldering. Next the core in the shape of an annulus with the coils is removed from the fixture.

It is unnecessary in all instances to change the shape of the core, but in case it is desired to change its shape, for example, to the oblong or flattened shape illustrated in Fig. 2, this can be done in a suitable press or byother suitable pressing means, the coils of course being first suitably arranged with respect to each" other. Then, if magnetic chokes such as those-illustrated are desired in any particular transformer, these can be added without difficulty.

I regard the transformer core formed of a continuous strip or from strip material wound through the coils in superposed convolutions or layers as being more suitable from the standpoint of emciency than a core formed from eeparate stampings, and, additionally, the expense incident to producing the stampings, the loss in scrap, and the expense incident to assembling the stampings are avoided. It will be seen therefore that the objects stated at the beginning of the specification are accomplished very eifectively.. I do not desire to be confined to either the transformer design or the precise steps of the method herein illustrated, butaim in my claims to cover all modifications which do not involve a departure from the spirit and scope of the invention. Y

Having thus described my invention, I claim:

1. The method of forming a transformer composed of coils and a core which consists in feeding a strip of core-forming material through the coils thus forming an annulus, supporting the annulus interiorly thereof at a plurality of circumferentially spaced points and at the same time holding the coils in definite position, and applying friction driving means to the annulus at a plurality of circumferentially spaced points thereby rotating the annulus and causing a predetermined number of convolutions to be built up withthe strip being fed onto the outer periphery of the annulus.

2. The method of forming a transformer composed of primary and secondary coils and a core, which comprises supporting the coils in fixed and spaced relation around a central point, feeding core-forming material in the form of a substantially flat strip successively through the openings of the coils so as to form an annulus with the strip extending crosswise of the coil openings over the inner edges thereof, and retating the annulus to wind the strip thereon so as to build it up toward the outer edges of the coil openings with the convolutions superposed upon each other in a radial direction until a core of the desired thickness is obtained.

3. The method of forming a transformer composed of primary and secondary coils and a core, which comprises supporting the coils in fixed and spaced relation around a central point, feeding core-forming material in the form of a substantially flat strip successively through the openings of the coils so as to form an annulus with the strip extending crosswise of the coil openings over the inner edges thereof, supporting the annulus at its inner periphery, and rotating the annulus to wind the strip thereon so as to build it up toward the outer edges of the coil openings with the convolutions superposed upon each other in a radial direction until a core of the desired thickness is obtained.

MARION W.

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