US2916714A - Adjustable inductance coils - Google Patents

Description

Dec. 8, .1959 A. DONAVY ADJUSTABLE mucmcr: cons 2 Sheets-Sheet 1 Filed Oct. 23. 1956 FIG.2

FIG.

PIC-5.4

FIG. 3

Dec. 8, 1959 A. DONAVY ADJUSTABLE mnucnmca cons 2 Sheets-Sheet 2 Filed Oct. 23, 1956 FIG.6'

. "saturation The present invention relates to inductance coils, and more particularly to coils of the type comprising two series-connected windings, wherein the inductance may I be varied by modifying the direction of the magnetic flux produced by one of the windings with respect to the direction of the magnetic flux produced by the other winding. The invention more particularly relates to coils of the ftype in which the two windings are supported by two U-shaped ferro-magnetie cores arranged in such a manner that the flux produced by each winding passes into the coreof the other winding.

In such inductance devices, the two cores are usually rotatable one with respect to the other, in order to proyide a varying gap therebetween so as to vary the inductance of the coil. The construction of such inductance devices is somewhat complex and delicate, sliding contacts being needed vfor connection of the rotating winding with the outside circuits.

Therefore, it is an object of the invention to provide an inductance device of easy and dependable construction, comprising two series-connected fixedwindings and,

therefore, free of the above disadvantages.

The inductance device according to the invention comprises a pair of ferro-magnetic cores having their pole pieces secured on a flat piece of ferro-magnetic material, and magnetizing means adapted to produce magnetic of said flat piece along a varyingydirection thereof- The variationof the inductance is eifected by modifying said direction.

The invention will be better understood from the following description when read in conjunction with the aceompanying drawings, in which;

Fig. 1 shows, schematically, a side view of a coil according to the invention;

Fig. 2 is a perspective view of the essential components of the coil represented in Fig. 1 with parts broken off;

Figs. 3 and 4 illustrate the operation of the"'coil of Figs. 1 and 2;

Fig. 5 is a perspective view illustrating a modified embodiment of the invention;

Fig. 6 is a diagrammatic, partially sectional side view, of another embodiment of the invention;

Fig. 7 is a front view of certain parts of the coil illustrated in Fig. 6; and

Fig. 8 is a diagram illustrating still another embodiment of the invention.

Referring particularly now to Figs. 1 and 2, a coil is shown comprising two series-connected windings 1 and 2, wound, respectively, on two stationary cores 3 and 4 of ferro-magnetic material. In the non-limitative embodiment described, these two cores 3 and 4' are in the shape of a U with two equal branches, the end faces of which, 5 and 6, and 7 and 8 respectively, are fiat and secured to a disc 16 of ferro-magnetic material, at the respective ends of two diameters of the disc 16 perpendicular to each other, the assembly comprising the cores and the disc United States Patent 0 being supported by a frame 17, of non-magnetic material. A permanent magnet 18 is provided, the pole pieces 19 and 20 of which are applied on the periphery of the disc 16, at two directly opposed points thereof, said magnet being mounted in such a manner as to rotate about the axis YY' of the disc 16. In order not to interfere with the rotation of the magnet 18, feeding wires 22 and 23 for the winding 2 are threaded through small holes provided in the disc 16.

The magnet 18 is adapted to effect saturation of the disc 16, along a diameter joining the poles 19 and 20 of the magnet 18. Thus, when the magnet 18 is oriented as shown in Fig. 3, the disc 16 becomes saturated along diameter AB; the flux of the coil then extends over a closed path including sections 26 and 27 of the disc 16, said sections 26 and 27 having a much higher magnetic permeability than that of the saturated sections 28 and 29; under these conditions, the magnetic circuit of the coil follows the closed path illustrated by the line 3131' and, consequently, the resulting flux of the coil is the sum of the fluxes produced by windings land 2. When the magnet 18 is oriented as shown in Fig. 4, the disc 16 becomes saturated along diameter A B; the flux of the coil, which then passes through the sections 28, 29 and follows the closed path shown by line 3232' is thus the difference between the fluxes generated by both windings 1 and 2.

It is thus apparent that the resultant flux in the magnetic circuit of the coil may considerably vary. ,The range covered by the inductance is thus very wide in the case illustrated; in Fig. 3, wherein the resultant flux is maximum, the value of the inductance is maximum, whereas it is minimum in the case of Fig. 4, where the resultant flux is minimum, and it has an intermediate value if the magnet 18 is in an intermediate position between those shown in Figs. 3 and 4.

In the alternative embodiment of Fig. 5, both cores 3 and 4 are positioned on the same side of the disc 16, the magnet 18 being placed on the other side. In this embodiment, the continuous rotation of the magnet 18 is possible, without requiring any connecting Wire to pass through the disc 16.

The same result is also obtained in the embodiment illustrated in Figs. 6 and 7. In this case, the cores 3 and 4 are located on opposite sides of the disc 16, and the magnet 18 has a shape enabling it to be disposed in the plane of the disc 16. The wire 33 connecting the windings 1 and 2 then passes beyond the periphery of the magnet 18 and does not interfere with the rotation thereof.

In the modified embodiment represented in Fig. 8, instead of a rotating magnet, two stationary electro- magnets 34 and 35 are provided which have their poles applied on the periphery of the disc 16; the poles 36 and 37 of the first magnet 34 engage the ends of the diameter AB, and the poles 38 and 39 of the second magnet 35 engage the ends of the diameter A B, perpendicular to AB. Diameters AB and A B are, preferably, oriented according to the bissectrices of the angles formed by the diameters MN and M N which pass through the junctions of the cores 3 and 4 with the disc 16. The windings 41 and 42 of the electro- magnets 34 and 35 are fed by direct current supplied through an adjusting device, such as a potentiometer 43, which enables the intensity of the current to be adjusted in each of said windings. When the sliding contact 44 of the potentiometer 43 is on the end point 46, the electro-magnet 34 is in a position of maximum energization; the disc 16 is thus saturated along the diameter AB, realizing the conditions described in connection with Fig. 3. When the sliding contact 44 is on the other end point 47, the electro-magnet 35 is in a position of maximum energization, electro-magnet 35 being non energized; disc 16 will then be saturated along the direction of diameter AB, realizing the conditions illustrated in Fig. 4. With the sliding contact 44 at a position intermediate between end points. 46 and 47,21

condition intermediate between those shown in'FigS. 3 and 4 will be reached, and consequently, the coil will present an inductance intermediate betweenthernaximum value corresponding to the position shown in Fig. 3- and the minimum value corresponding to the position. shown in Fig. 4.

,It is to be understood that the invention is in no Way limited by the embodiments illustrated,, and that many modifications may be devised without departing from the scope of the invention.

For instance, the permanent'magnet 18 of theembodi- ,ment shown in Figs. 1 through 7 may be replaced by an electro-magnet; on the other hand, a ferrite material may be utilized for the cores 3 and 4 and the disc 16. Air

. gaps may also be provided in the magnetic circuit of the producing magnetic saturation of saidflat piece along a variable direction thereof.

2. A variable inductance comprising a pair. of ferro ;magnetic cores each having two pole pieces; an inductance coil wound on each of said cores; a disc of ferromagnetic material, on which said pole pieces, are. secured in quadrature, said pole pieces being perpendicular to said disc and said cores substantially spanning said disc and magnetizing means for producing magneticsaturation of said disc along a diameter thereof, thea gular position of which is variable.

3. A variable inductance device according to claim 2, in which said ferro-magnetic cores are U-shaped.

4. A variable inductance device according to claim 2, in which said ferro-magnetic cores are respectively located on the two faces of said disc.

5.. A variable inductance device according to,,claim 2, in which said ferro-magnetic cores are both located on the same face of said disc, in two planes perpendicular to said disc and at right angles one with respect to the other.

6. A variable inductance device comprising a pair of ferro-magnetic cores each having two pole pieces; an inductance coil wound on each of said cores; a disc of ferro-magnetic material on which said pole pieces are secured in quadrature, said cores substantially spanning said disc, and a permanent magnet having its pole pieces in contact with the periphery of said disc at the ends of one diameter thereof, said permanent magnet being rotatable about the axis of said disc.

7. A variable inductance'device according toclaim 6, in which two coils are respectively wound around said cores and connected to feeding wires passing through apertures provided in said disc.

8. A variable inductance device according to claim 6, in which said permanent magnet is perpendicular to the plane of said disc.

9. A variable indutance device according to claim 6, in which said permanent magnet is located in the; plane of said disc, around the periphery thereof.

10. A variable inductor comprising a pair of ferromagnetic cores each having two pole pieces; an inductance coil wound on each of said cores; a flat disc .of ferro-magnetic material On which said pole pieces are secured in quadrature, respectively at the ends of two perpendicular diameters thereof, said pole pieces being perpendicular to the surface of said flat piece and. said cores-substantially spanning said flat piece; andmagnetizing means, comprising a pair of stationary electromagnets having their pole pieces in contact with the periphery of said flat disc, respectively, at the ends of two I perpendicular diameters thereof, for producing magnetic saturation of said flat disc along a variable diameter thereof.

11. A variable inductor according to claim 10, in which said two perpendicular diameters joining the pole pieces of the electro-magnets are oriented according to the, bissectrices of said two perpendicular diameters joining the pole pieces of the cores.

12. A variable inductor according to claim 10, in which said electro-magnets comprise adjustable energizing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,126,790 Logan Aug. 16, 1938 2,617,090 Ogle Nov. 4, 1952 2,762,020 Gordon Sept. 4, 1956 2,831,157 Grayson Apr. 15, 1958 FOREIGN PATENTS 874,663 France May 18, 1942 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Alain Donavy Patent should read as corrected below.

Column 1.111% 42, 44., and 47, and. column 4, lines 1, l0, l4, and 17, strike: out "davie e", each occ'unstrcence Signed and sealed E3115 day of May 1960.,

Attest:

KARL I-JI, ROBERT C. WATSON Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,9l, l4 December 8, 1959 Alain Donavy It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, lines 42, 44., and 4.7, and column 4, lines 1, l0, l4, and 17, strike out "device", each occurrence.

Signed and sealed this day of May 1960.,

(SEAL) Attest:

KARL H, Attesting Oificer ROBERT C. WATSON Commissioner of Patents

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