Laminated magnetic core for induction devices and laminations for forming such magnetic core

[57] ABSTRACT

A laminated magnetic core for electric induction devices comprising a shell formed of laminations. Each of said laminations comprising two parallel yoke legs and two outer legs arranged between and perpendicular to such parallel yoke legs. A central leg is disposed parallel to the outer legs and forms with one of said parallel yoke legs an air gap. Each of the laminations of the shell embodying similar U-shaped lamination elements comprising a respective outer leg and unequal length yoke leg sections protruding from the ends of such respective outer legs. These lamination elements bear against one another at the end faces of their longer yoke leg sections to form a shell lamination for the magnetic core. Further, such lamination elements bear at the end faces of their shorter yoke leg sections against a central web forming the central leg and arranged between such shorter yoke leg sections.

Claims, 6 Drawing Figures

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LAMINATED MAGNETIC CORE FOR INDUCTION DEVICES AND LAMINATIONS FOR FORMING SUCH MAGNETIC CORE

BACKGROUND OF THE INVENTION

The present invention broadly relates to improvements in laminated magnetic cores for electric induction devices and also pertains to new and improved punched magnetic core laminations for such cores, such magnetic core comprising a shell formed of two yoke legs which are parallel to one another, two outer legs disposed between and extending perpendicular to such parallel yoke legs and a central leg which is parallel to the outer legs, which central leg together with one of the yoke legs forms an air gap.

Laminated shell cores for electric induction devices are known to the art which possess an E-shaped component with equal length legs which are interconnected with one another through the agency of an l-shaped portion serving as a yoke. The individual laminations of such laminated magnetic core are stamped-out of a sheet metal member without waste by means of the socalled DIN-cut, wherein in each case two E-shaped portions having their legs abutting one another at their ends are simultaneously stamped-out and from the windows formed by the abutting legs there are stamped-out two l-shaped portions.

However, if it is desired to form for such shell core an air gap between the central leg of the E-shaped portions and the l-shaped portion, then, the l-shaped portion must be appropriately spaced from the E-shaped portion, so that air gaps appear also between the outer legs and the l-shaped portion, something which is undesired because of the occurring stray or leakage flux.

Now, in British Pat. 671,823 there is described a laminated magnetic core which is constructed similar to the previously described shell core, and wherein the last-mentioned drawbacks are overcome in that an essentially l-shaped yoke leg constructed widened at its ends bears against the outer legs of the equal length legs of the E-shaped portion, whereas between the central leg and the central portion of the yoke leg which is narrow in contrast to the ends there is formed an air gap.

However, this air gap cannot be changed in size, since when the magnetic core is assembled together the spacing between the central leg and the yoke leg cannot be altered.

Additionally, if the individual laminations are stamped-out without waste similar to the previously described DIN-cut, then, apart from the l-shaped portion also the legs of the E-shaped portion possess unequal width.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide a new and improved construction of laminated magnetic core for induction devices which overcomes the previously mentioned drawbacks, the inventive magnetic core being formed of novel punched laminations.

Another objective of this invention is to provide a laminated magnetic core, the air gap between the central or middle leg and one yoke leg of which can be varied and the laminations of which additionally can be stamped-out from sheet metal without waste.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the laminated magnet core of the present invention is manifested by the features that shell possesses similar U-shaped shell or lamination elements formed from a respective outer leg and unequal length yoke leg sections or portions which protrude from the ends of such outer legs. The U-shaped shell or lamination elements bear against one another at the free end faces of their longer yoke leg sections and the end faces of their shorter yoke leg sections abut against a central web arranged between the shorter yoke leg sections and embodying the central leg.

U.S. Pat. No. 3,201,731 teaches to the art forming the laminations from U-shaped shell portions with different length legs by punching such out from a strip of constant width, wherein, in each case, two laminations which mutually interengage with one another with their shorter legs between the legs of the other lamination so as to form a gapless rectangle are conjointly punchedout. With a shell core as illustrated in the previously mentioned United States Patent and formed of such type punched-out laminations and in contrast to the inventive magnet core, it is necessary that four such laminations be assembled together in order to form a shell core cross-section. Additionally, such shell core does not possess at its central leg any adjustable air gap.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawing wherein:

FIG. 1 is a plan view of a first embodiment of magnetic core for electric induction devices formed of sheet metal laminations constructed according to the teachings of the present invention;

FIG. la and lb illustrate the punching cuts used for fabricating the sheet metal laminations for the magnetic core of FIG. 1;

FIG. 2 is a plan view of a second embodiment of magnet core for an electric induction device formed of sheet metal laminations; and

FIGS. 2α and 2b illustrate the punching cuts used for fabricating the sheet metal laminations for producing the magnetic core of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Describing now the drawings, each of the laminated magnet cores 50 (FIG. 1) and 60 (FIG. 2) as illustrated in the drawings will be seen to respectively embody a central or middle leg 13 and 23 and a respective shell 51 and 61 surrounding such legs consisting of two outer legs 11α, 12α and 21α, 22α respectively and two yoke legs lift, 12b and 11c, 12c and 21b, 22b and 21c, 22c respectively and forming the magnetic short-circuit path. The cross-section of the relevant central leg is essentially twice as large as that of the shell, since the total magnetic flux in the central leg is subdivided in such a manner that only one half of the flux flows through the shell. Consequently, with constant thickness of the magnetic core the central leg can be twice as wide as the jacket.

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Now referring more specifically to the embodiment of laminated or stacked magnetic core as depicted in FIG. 1, each shell 51 embodies a stack of laminations each formed of two similar U-shaped lamination or shell elements 11 and 12. Each such lamination ele- 5 ment 11 and 12 comprises a respective outer leg 11α and 12α and two yoke leg portions or sections 11b, 11c and 12b, 12c respectively, extending perpendicular to the associated outer leg 11α and 12α respectively and protruding from the ends of such outer legs, as shown. ¹⁰Both of the lamination elements 11 and 12 abut against one another at the free ends of their longer yoke leg sections 11b and 12b. In the intermediate space formed by both shorter yoke leg sections 11c and 12c there is accommodated a central web 13 which is disposed ¹⁵parallel to the outer legs 11α and 12α, this central web 13 embodying the central leg and simultaneously filling-out the intermediate compartment or space formed at the lamination and which is located between the shorter yoke leg sections 11c and 12c. A respective ²⁰window opening 14 is formed between the central web or leg 13 and each of the outer legs 11α anti 12α, as shown.

The central web or leg 13 together with the yoke leg 25 formed from the longer yoke leg sections 11b and 12b forms an air gap 16. For the purpose of adjusting the size of this air gap 16 the central web 13 can be displaceably guided in its lengthwise direction by means of the shorter yoke leg sections 11c and 12c. ₃₀

The dimensions of the laminated magnet core 50 are chosen in such a manner that the laminations thereof can be fabricated by means of a punching or stampingcut to be described more fully in conjunction with the showing thereof depicted in FIGS, la and lb. With a 35 lamination width of dimension a and a central web width of 2α, there is obtained a magnet core having the outside dimensions 4α to 6α and with window opening openings 14, the height of which amounts to 2α and the width of which amounts to a. The length of the shorter 40 yoke leg sections 11c and 12c amounts to 2α and is smaller by the amount a than the length of the longer yoke leg sections 11b and 12b.

FIGS, la and lb illustrate the manner in which the lamellae of the lamination or shell elements 11 and 12 45 with their unequal length yoke leg sections 11b and 12c and 11c and 12b bearing against one another, together with a lamellae of the central web 13, can be assembled together into a gapless rectangle with the side lengths possessing the dimensions 4α and 5α. The individual ⁵⁰rectangles can be lined up adjacent one another into a strip 15 of constant width, possessing the dimension 5α in FIG. la and the dimension 4α in FIG. lb. The individual sheet metal laminations of the laminated magnetic core importantly can be punched-out of such ⁵⁵sheet metal strips 15 without waste when there is provided the rectangular arrangements depicted in FIGS, la and lb.

The laminations forming the shell 61 of the magnet core 60 illustrated in FIG. 2, similar to the magnetic core illustrated in FIG. 1, each consist of two similar Ushaped lamination or shell elements 21 and 22, each of which possesses a respective outer leg 21α and 22α equipped with a respective yoke leg section 21b, 21c and 22b, 22c which protrude from and extend perpendicular to the associated outer legs 21α and 22α. The lamination elements 21 and 22 which abut one another by means of the free ends of both of their longer yoke leg sections or portions 21b and 22b form a lamination 61 which possesses an intermediate space between the shorter yoke leg sections 21c and 22b, as shown. This intermediate space is filled by a central or middle web 23 which is disposed parallel to the outer legs 21α and 22α and embodies the central leg. This central web 23, similar to the central web 13 of FIG. 1, can be displaced in its lengthwise direction, so that there is obtained an adjustment of the air gap 26 at the central or middle leg. Between the central leg 23 and outer legs 21α and 22α there are formed window openings 24.

With a lamination width of dimension a and a central web width of 2α this magnet core possesses a height of the window openings 24 of a. The width b of this window opening 24, on the otherhand, can be freely selected. The shorter yoke leg sections 21c and 22c are shorter by the amount a than the longer yoke leg sections 21b and 22b respectively. It is thus possible to form magnetic cores which possess outside dimensions of 3α and 4α + 2b.

In FIGS. 2α and 2b there is illustrated the manner in which two respective lamellae of the lamination elements 21 and 22 can be interleaved or interfitted in pairs with one another. The respective shorter yoke leg sections 21c or 22c of the one lamination element 21 or 22 always engages between the yoke leg sections 22c, 22b or 21b, 21c of the other jacket element and fills the space forming the window openings 24. Each two lamellae of the lamination elements 21 and 22 form a gapless rectangle with the sides having the dimensions 4aand2a + b.

The lamellae of the lamination or shell elements 21 and 22 can be punched-out in the form of such abutting rectangles from a strip 25 of constant width, possessing the dimension 2α + b (FIG. 2α) and the dimension 4α (FIG. 2b). The central webs or legs 23, which possesses a square cross-section with a side length dimension of 2α, are likewise punched-out free of waste from a second sheet metal strip (not illustrated) having a width possessing the dimension 2α.

With the laminated magnet core of the type illustrated in FIGS. 1 and 2 the respective air gap 16 or 26 at the relevant central web or leg 13 or 23 can be easily adjusted without having to tolerate any undesired air gap at the lamination 51 or 61 respectively.

The described magnetic cores 50 and 60 are preferably used for inductance or choke coils for the operation of fluorescent tubes. In so doing, it is important to dimension the magnet core in such a fashion that without economical or technological drawbacks there is obtained a low constructional height of the series connected devices. Above all it has been found that the magnetic core of FIG. 1, owing to its cross-sectional dimensions of 4α and 6α is particularly suitable for series connected devices. The height of this magnetic core in relation to its width is in a ratio of 1:1.5, rendering possible the economical construction of series connected devices of low structural height, whereby material can be saved at the socket of the fluorescent tubes, also bringing with it advantages as concerns lighting technology and aesthetic effect.

If with the embodiment of FIG. 1 there is selected for the dimension a the value of 6.4 cm., then, there is obtained a magnetic core with the particularly favorable cross-sectional dimensions of 38.4 X 25.6 cm.

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If the magnetic cores are arranged in a housing formed of sheet iron, then, in certain cases it is desired to incorporate such iron sheet metal housing as active component in the magnetic circuit. In this case the lamination elements are reduced in their width by an amount corresponding to the thickness of the sheet iron used for the housing, so that the width thereof is a little smaller than half the width of the central web.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,