US3284748A - Magnetic coil support having magnetic and non-magnetic flanges - Google Patents

Description

1965 HIROMI MATSUlI/IOTO 3,284,748

MAGNETIC COIL SUPPORT HAVING MAGNETIC AND NON-MAGNETIC FLANGES Filed June 25, 1964 FIG. I FIG. 2 FIG. 3

PRIOR ART INVENTOR.

M. MMID BY MnuLu. f, Mhm

United States Patent 3,284,748 MAGNETIC COIL SUPPORT HAVING MAGNETIC AND NON-MAGNETIC FLANGES Hiromi Matsumoto, Tokyo-to, Japan, assignor to Take Kabushiki Kaisha, Tokyo-to, Japan, a joint-stock company of Japan Filed June 23, 1964, Ser. No. 377,224 Claims priority, application Japan, June 24, 1963, 38/33,?)20, 38/46,895 6 Claims. (Cl. 336-233) This invention relates to inductance devices such as small-size intermediate frequency transformers to be used for transistors and various other inductance devices.

It is a principal object of the invention to provide inductance devices in which the range of inductance variation is wide, fine adjustment of the inductance value can be easily accomplished, and the construction is stable, and which can be produced by mass production technique.

Another object of the invention is to provide a magnetic core for a coil having a wide range of induction variation.

Further objects and advantages of the present invention will become apparent, and this invention will be better understood from the following description, reference being made to the accompanying drawings, in which the like parts are designated by like reference characters, and in which:

FIG. 1 is a side view of an inductance device utilizing a conventional drum core;

FIG. 2 is a diagrammatic representation of the principle of a variable inductance device;

FIG. 3 is a sectional view of one embodiment of this invention;

FIG. 4 is a sectional view of a modification of this invention;

FIG. 5 is a perspective view of the core shown in FIG. 4;

FIG. 6 is a sectional view of another modification of this invention; and 1 FIGS. 7 through 9, inclusive, are partly sectional views respectively showing further modifications of the core according to the invention.

Referring now to the accompanying drawings, there is shown in FIG. 1 a conventional drum core utilized in small size intermediate frequency transformers comprising a yoke or main body 3 and flanges 2 on the opposite ends thereof between which a coil 4 is wound around the yoke 3. These flanges and the yoke are formed or molded as a unitary structure from a suitable magnetic material. With this type of core, the range of inductance variation is increased with decrease in the diameter d or thickness t of the flange 2 to which an adjusting core of magnetic material, not shown, is to be made to approach, because when the diameter d or thickness t of the flange 2 is increased, the reluctance of the magnetic path through the magnetic path shown by dotted lines A is decreased and becomes less affected by external magnetic material.

As a result, in an extreme case, an ideal characteristic could be provided if the flange 2 on the side of the adjusting core were eliminated so as to wind a coil 4 on a T- shaped magnetic core comprising a yoke 3 and a flange 1 only, as shown in FIG. 2. In this case, the adjusting core 5 acts as a portion of the magnetic path, thus greatly increasing the sensitivity of the inductance device to the displacement of the adjusting core. With this construction, however, it is very diflicult, or impossible, to wind the coil 4 on the yoke 3.

In prior small intermediate frequency transformers, it has been the practice to securely fix the drum core and the coil mounted thereon to a base by means of an adhesive or any of various other mounting means, but such means are not advantageous from the standpoint of construction, mass production and strength of mounting.

'stituted to mount the adjusting core.

"ice

In order to overcome the various difficulties mentioned above, in accordance with this invention, there is provided a T-shaped magnetic core 6 comprising a yoke or main body-3 and a flange 1 on only one of its ends. The core is provided with a through opening 7 extending axially through the yoke and its flange. When the flange 1 is cast in a base 8 of a nonmagnetic material such as a synthetic resin, a portion of the nonmagnetic material is led through this opening 7 to form a flange 9 of nonmagnetic material on the opposite side of the core.

It is to be understood herein that the term nonmagnetic material used to form said base 8 and the flange 9 is intended not only to mean the ordinary nonmagnetic mate-' rials but also to include weak magnetic materials having relatively lower permeability than the magnetic material constituting the flange 1 and the yoke 3 as well as diamagnetic materials.

In the embodiment shown in FIG. 3, since the upper end of the yoke 3 is flat and is covered by the flange 9, the maximum value of ,u. is relatively small due to the presence of nonmagnetic material between the adjusting core 5 and the core 6. To overcome this difliculty, radial grooves 10 are cut in the end surface of the yoke 3, as shown in FIG. 5, to mold radial flanges 9 in the grooves 10, thereby to leave a portion of the end surface exposed. This is best shown in FIG. 4. In this case, the maximum value of ,u. is greatly increased because the magnetic core 6 and the adjusting core 5 can directly contact each other.

In another embodiment shown in FIG. 6, an intermediate flange 9 is also molded by forming one or more radial openings 11 through the wall of the core so as to guide a portion of the molding material contained in the through opening 7 through these radial openings.

As shown in FIG. 3, suitable terminal pins 12 are cast in the base 8 or inserted therein subsequent to its molding operation and screw threads 13 are cut to receive the adjusting core 5. It should be understood, however, that any one of a number of well known means may be sub- For example, an annular vertical rib may be formed to be spaced apart from the magnetic core, and screw threads may be cut on the inner surface of the annular rib to receive cooperating threads provided on the outer surface of the adjusting core 5.

Thus, according to this invention, as the upper flange 9 of the T-shaped magnetic core 6 is formed by the molding material which constitutes the base 8, the electromagnetic characteristic of the novel core is equivalent to a magnetic core wherein a flange on one side has been removed, thus widening the range of inductance variation, but the novel core is mechanically equivalent to the conventional configuration so that the winding operation for the coil 4 can be carried out very easily.

Moreover, as the T-shapedmagnetic core 6 is rigidly clamped between the base 8 and the flange 9, it is not required to cement or to use special mounting means. Further, as the base and the flange are made by casting operation, the novel core can be manufactured by mass production technique at low cost.

According to another embodiment of the core of this invention, as shown in FIGS. 7 to 9, inclusive, the yoke 3 and only one flange 1 thereof are formed or molded from a magnetic material, the other flange 9 and a tubular member 14 to be fitted on the yoke 3 are molded integrally from a nonmagnetic material, and the winding 4 is wound on the tubular member 14.

FIG. 7 shows one form of the core of this invention wherein both ends of the tubular member 14 are opened to expose the outer end of the yoke 3. FIG. 8 shows a modification wherein one end of the tubular member 14 is closed by the flange 9 In a still further modification 3 shown in FIG. 9, the lower end of the tubular membe 14 provided with anupper flange 9, is provided with an additional flange 9 which is placed in contact against the upper surface of the magnetic flange 1. Although a suitable adhesive and the like may be applied between the tubular member 14 and the yoke 3 and between flanges 1 and 9 even where the tubular member 14 is merely fit on the yoke 3, as the coil 4 is wound on the tubular member 14, the member 14 will be urged inwardly to be rigidly fixed upon the yoke. Thus, the tubular member 14 is prevented from disengaging, thereby to firmly secure the flange 9.

As shown in FIG. 7, when the top surface of the yoke 3 is exposed by providing a through opening in the tubular member 14, the adjustable core 5 can contact this exposed top surface to advantageously increase the maximum value of 41 While specific embodiments have been disclosed to illustrate the invention, it will be understood that many modifications and variations may be made within the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A magnetic core for a coil consisting of a yoke of magnetic material, a first flange made of magnetic material fixed to one end of said yoke, a tubular member of nonmagnetic material, said tubular member being adapted tosupport a coil, and a second flange of nonmagnetic material and connected to the other end of said tubular member remote from said first flange.

2. The magnetic core according to claim 1 wherein said first flange and said yoke are molded integrally from a magnetic material, and said tubular member and said second flange are molded integrally from a nonmagnetic material.

3. The magnetic core according to claim 1 wherein said second flange and said tubular member are provided with a through opening to expose the free end of said yoke.

4. The magnetic core according to claim 1 wherein said second flange is solid to seal the free end of said yoke.

5. An inductance device comprising a magnetic core including a cylindrical magnetic yoke, a magnetic flange combined with said yoke, and an opposite flange of said yoke; an opening extending axially through said yoke; a nonmagnetic base; said magnetic flange being cast in said base; the opposite flange being molded as an extension of said nonmagnetic base; said extension being unified with said base by nonmagnetic material filling said opening; anda coil Wound about said yoke.

6. The inductance device as defined in claim 5, wherein the yoke end opposite said magnetic flange is provided with one or more radial grooves, and part of the nonmagnetic flange is cast in said radial grooves.

References Cited by the Examiner UNITED STATES PATENTS 2,223,056 11/1940 Berthold 336212 X 2,433,207 12/ 1947 Eilenberger 336-198 X 2,905,913 9/1959 Leigh 33683 3,017,590 1/1962 Chass 336-436 FOREIGN PATENTS 907,803 3/ 1954 Germany.

LEWIS H. MYERS, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

D. J. BADER, Assistant Examiner.

Claims (1)

1. A MAGNETIC CORE FOR A COIL CONSISTING OF A YOKE OF MAGNETIC MATERIAL, A FIRST FLANGE MADE OF MAGNETIC MATERIAL FIXED TO ONE END OF SAID YOKE, A TUBULAR MEMBER OF NONMAGNETIC MATERIAL, SAID TUBULAR MEMBER BEING ADAPTED TO SUPPORT A COIL, AND A SECOND FLANGE OF NONMAGNETIC MATERIAL AND CONNECTED TO THE OTHER END OF SAID TUBULAR MEMBER REMOTE FROM SAID FIRST FLANGE.

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