US3267400A

US3267400A - Variable inductance device

Info

Publication number: US3267400A
Application number: US310079A
Authority: US
Inventors: Theodore L Craige
Original assignee: United Transformer Corp
Current assignee: United Transformer Corp
Priority date: 1963-09-19
Filing date: 1963-09-19
Publication date: 1966-08-16
Anticipated expiration: 1983-08-16

Description

Aug. 16, 1966 T. L. CRAIGE 3,267,400

VARIABLE INDUCTANCE DEVICE Filed Sept. 19, 1963 2 Sheets-Sheet 1 FIG. I. FIG. 2.

FIG. 4

INVENTOR.

THEODORE L. CWA/GE' Aug. 16, 1966 Filed Sept. 19, 1963 T. L. CRAIGE VARIABLE INDUCTANCE DEVI CE 2 Sheets-Sheet 2 I! lie I if a/v /fi 2&

n z m FIG. 5.

F I INVENTOR.

THEODORE Z. CPO/6E Amt/U14 QTTOQNEYI r 3,2514% 1C6 Patented August 16, 1966 3,267,460 VARIABLE INDUCTANCE DEVICE Theodore L. Craige, Roslyn Heights, N.Y., assignor to United Transformer Corporation, New York, N.Y., a corporation of New York Filed Sept. 19, 1963, Ser. No. 310,079 6 Claims. (Cl. 336-134) the like usually include cores of magnetic material, with such cores being made up of plural laminations of various configurations. The core sections, with laminations which may be E-shaped, C-shaped, F-shaped and the like, are assembled to form a magnetic circuit having one or more air gaps therein. By adjusting the length of the air gap, there is provided a convenient means for controlling the reluctance of the magnetic core and the corresponding impedance of the inductive device.

Various techniques have been suggested in the prior art for providing a magnetic core with a variable air gap, including the constructions illustrated in US. Patent No. 2,879,489 of March 24, 1959, which is assigned to the assignee of the instant application. In said patent, the core sections of the magnetic core are arranged to include a fixed core section and a movable core section, with the core sections being retained in a relatively fixed position in relation to each other by one or more resilient clips which generate sufficient frictional holding forces to maintain the relatively fixed position despite shock, vibration, temperature variations or other environmental changes. The compressive frictional forces afforded by the interengaged core sections are sufiiciently weak to enable relative motion of the movable core section with respect to the fixed core section, for example, in response to actuation by a screw or the like which is capable of developing a sufficient actuating force to overcome the frictional forces thereby permitting adjustment of the length of the air gap. Although this construction represents a notable advance in the art and has achieved widespread commercial acceptance, there is still present the risk that high order shock or vibrational forces may cause some relative movement between the core sections and a corresponding change in the length of the air gap and the reluctance of the magnetic circuit. Even the slightest relative movements between the core sections will manifest themselves as relatively large changes in the reluctance of the magnetic circuit.

Although numerous applications require the ability to achieve large adjustments in the reluctance of the magnetic circuit and a corresponding wide range and adjustment of the inductance, there are also many applications which require a relatively narrow range of adjustment, in the order of 5 to 10% of the nominal value of the particular inductive device. For such applications, it is not necessary to provide a broad range of adjustment in the gap length, it being sufficient to have a narrow range of adjustment which would inherently limit the extent of variations in inductance inadvertently introduced by environmental changes including vibration, shock and temperature variations.- There exists a need for a magnetic core for usein inductive devices which aifords a relatively fixed gap length which cannot vary as a result of shock, vibration, temperature changes or the like, with provision for a fine or vernier adjustment of the gap length producing a corresponding adjustment in the total inductance of the ultimate inductive device.

Broadly, it is an object of the present invention to provide a magnetic core which realizes one or more of the aforesaid objectives. Specifically, it is within the contemplation of the present invention to provide a magnetic circuit in which provision is made for establishing an air gap having a major segment which is of relatively fixed length and a minor segment which is of variable length such that the overall total effective length of the air gap may be adjusted to bring about corresponding changes in the reluctance of the magnetic circuit and of the inductance of the ultimate device.

In accordance with an illustrative embodiment demonstrating objects and features of the present invention, there is provided a magnetic core which comprises plural laminations providing a magnetic circuit. The laminations are arranged relative to each other to define an air gap in a magnetic circuit. Provision is made for mounting at least one lamination for movement toward and away from an opposed lamination to permit adjustment in the effective length of the air gap thereby providing for adjustrnent of total reluctance of the magnetic circuit and inductance of the actual device.

As a further feature of the invention, provision may be made in the first instance for mounting one of two core sections for movement relative to the other of the core sections such that a course adjustment may be made in the length of the air gap, with the fine or vernier adjustment being made by provision for adjusting at least one lamination of one of the core sections in a plane parallel to the other laminations thereof and lengthwise of the air gap such that a minor segment of the air gap is of adjustable length to permit corresponding adjustment of the reluctance of the magnetic core.

The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of several presently preferred, but nonetheless illustrative embodiments in accordance with the present invention, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a front elevational view, with parts broken away and sectioned, of a variable inductor embodying features of the present invention;

FIG. 2 is a side elevational view taken from the right of FIG. 1;

FIG. 3 is a perspective view, showing plural pairs of F-shaped laminations of the type which may be employed in making up the two-section magnetic core employed in the variable inductor shown in FIGS. 1 and 2, the laminations being shown in spaced relation by pairs;

FIG. 4 is a perspective view similar to FIG. 3, but showing the laminations in assembled relation;

FIG. 5 is a perspective showing, with parts broken away, of the magnetic core embodied in the variable inductor shown in FIGS. 1 and 2;

FIG. 6 is a sectional view taken substantially along the line 6-6 of FIG. 5 and looking in the direction of the arrows;

FIG. 7 is a front elevational view, with parts broken away and sectioned for the purposes of clarity, showing a modified form of variable inductor embodying further features of the present invention;

FIG. 8 is a sectional view taken substantially along the line of 88 of FIG. 7 and looking in the direction of the arrows; and,

FIG. 9 is a top plan view, with parts broken away and sectioned to show the top of the magnetic core embodied in the device shown in FIGS. 7 and 8.

Referring now specifically to the drawings, and in particular to FIGS. 1 through 6 inclusive, there is shown an adjustable inductor, generally designated by the reference numeral 10, embodying features of the present ,segment of an air gap 38 therebetween.

invention which is of the type useful for diverse low and high frequency applications including audio and radio frequencies. Although the invention will be described in connection with this typical adjustable inductance device which is herein illustrated as incorporating a core having essentially F-shaped laminations, it will be appreciated that the invention finds applications in diverse types of inductive devices incorporating a magnetic core or circuit having one or more air gaps therein.

Specifically, the adjustable inductor includes a casing 12 having a base 14 and a cover 16. The cover 16 is secured to the upstanding flange 14a of the base 14 by soldering 18 or the like about the margins thereof to provide a hermetically sealed unit.

Disposed within the two-part casing 12 is the magnetic core 20 which basically includes two

sections

22, 24, each made up of plural laminations.

In this illustrative embodiment, the core section 22 includes a plurality of F- shaped laminations, three of which have been designated by the

reference numerals

26, 28 and 30 in FIGS. 3 and 4. In FIG. 3, alternate laminations,-such as the

laminations

26, 30 are seen to be arranged one behind the other and in coextensive relation, while the intermediate laminations, such as the lamination 28 being turned 180 into opposed relation. In a similar fashion, alternate laminations, such as the

laminations

32, 36 of the other core section 24 are arranged in coextensive relation, while the intermediate lamination 34 is likewise turned 180 and end for end into opposed relation. As may be appreciated by progressively comparing FIGS. 3 and 4, when the respectivelaminations are assembled, successive pairs of laminations of the

core sections

22, 24, such as the

laminations

28, 34 are disposed in coplanar relation and form one element of the core 20. Specifically, the F-

shaped laminations

28, 34 include

outer legs

28a, 34a, inner or intermediate legs 28b, 34b, and connecting legs 28c, 34c. The intermediate or inner legs 28b, 34b are disposed centrally of the planar core element and extend toward each other and terminate in coextensive and confronting faces which cooperate to define an elemental In similar fashion, successive pairs of laminations of the

core sections

22, 24, such as the

laminations

30, 36 cooperate to form further planar elements of the core which, when stacked,

provide further elementallsegments of the air gap 38.

It will be appreciated that other standard types of laminations may be employed in the practice of the present invention, including E-shaped laminations of the type illustrated in the several illustrative embodiments of the above-identified patent. Further, in lieu of interleaving by ones as illustrated in the drawings and as described herein, it is obvious that the core laminations can be interleaved by groups of more than one to reduce the cost of laminating.

Referring now to FIGS. 1, 2 and 5, it will be seen that the. magnetic core 20, when finally assembled, provides a closed magnetic-circuit or loop including the air gap 38. Specifically, the magnetic core 20 includes outer legs 20a, 20b composed of alternate and interleaved legs of the

respective core sections

22, 24, upper and

lower legs

20c, 20d, likewise composed of alternately interleaved legs of the

respective core sections

22, 24, and

inner legs

20e, 20 which project upwardly and downwardly from the lower and

upper legs

20c, 20d respectively and cooperate to form the air gap 38 medially of the magnetic core 20.

The laminations (i.e. 26, 28 and 30 shown in FIG. 3) of the core section 22 are secured together in stacked relation by U-shaped channel 40 which straddles the underside of the lower leg 20c and embraces the opposite faces thereof. The channel 40 is secured to the laminations by an anchoring member 42 which extends through aligned apertures formed in the connecting legs of the laminations, such as the aperture 28e shown in FIGS. 3 and 4. The anchoring member 42 may be in the form of a rivet or cold-rolled steel pin while the U-shaped channel may be secured to the base 14 as by spot welding or the like.

Frictional interengagement between the stacked laminations is achieved by the provision of U-shaped spring clips, 44, 46 which are embraced about respective outer legs 20a, 20b of the magnetic core 20, as seen best in FIGS. 1 and 2. The

clips

44, 46 contribute to the compressive frictional forces between the interleaved laminations which prevent displacement of the laminations relative to each other in response to variations in environmental conditions including shock, vibration, temperature changes and the like.

In this illustrative embodiment, one or more laminations of the core section 24 are mounted for movement relative to the other laminations of such core section such that a corresponding small segment of the air gap 38 may be adjusted in length which in turn changes the average effective length of the air gap 38 to bring about a corresponding variation in the reluctance of the magnetic circuit and in the resultant inductance of the ultimate device. Specifically, three laminations (which correspond to those designated by the

reference numerals

32, 34 and 36 in FIG. 3) are secured together for movement in planes parallel to the remaining laminations and lengthwise of the air gap 38 such that a minor segment of the air gap, designated by the reference numeral 38b, may be adjusted in relation to the major segment 38a of the gap which is defined by the remaining laminations of the to facilitate riveting of the adjustable laminations to the clamp 48. The clamp 48 is secured to an upwardly directed post 52 which in turn carries an externally threaded bolt 54 engaged within a depending internally threaded boss 56 having a slotted adjusting head 58. The boss 56 extends through a centrally disposed opening formed in the upper wall of the cover 16 of the casing 12 and is retainedtherein for rotation and against axial displacement by the provision of a spacer element or Washer 60 and a locking element or ring 62 which is received within an annular peripheral groove 56a formed on the outer surface of the depending boss 56. Upon turning of the slotted adjusting head 58, there is a corresponding axial displacement of the threaded bolt 54, serving as a lead screw, and a movement of the adjustable or floating

laminations

32, 34, 36 to bring about a corresponding change in the length of the minor or adjustable'segment 38b of the air gap 38.

The intermediate or

central legs

20c, 20 of the mag- .netic core 20 support a bobbin 64 having one or more coils 66 wound thereon. As seen best in FIG. 2, the coil terminals, for example the coil end 6611, is connected to a spade lug 68 which is mounted by an insulating grommet 70 on the base 14 of the casing 12, a similar spade lug being provided at the diametrically opposite corner of the base 14. Appropriate chassis-mounting bolts 72 are secured to the base 1.4 of the casing 12 to faciliate the mounting of the component in its operational environment. k p

In actual use, rotation of the slotted adjusting head 58 in one direction or the other serves to translate the'lead screw 54 relative to the internally threaded boss 56 and moves the one or more adjustable laminations in planes parallel to the remaining laminations and in the length direction of the adjustablesegment38b of the air gap 38.

Throughout such motion, the laminations remain in overlapping and frictional engagement with each other, such that substantially the entire reluctance variations of the core are derived from the adjustment of the air gap. Once an adjustment has been effected, the pressure exerted by the

resilient clips

44, 46 locks the laminations against further translation until an actuating force is developed which overcomes the static frictional forces. Since only a small segment or portion of the air gap is capable of adjustment, it will be appreciated that excessiVe shock or vibration which would tend to displace the movable laminations can only effect correspondingly small variations in the reluctance of the magnetic core.

Referring now to FIGS. 7 to 9 inclusive, there is shown a further embodiment of the present invention wherein provision is made for both mounting one of the two core sections for movement relative to the other of the core sections such that a gross adjustment may be made in the length of the air gap and for making a fine or vernier adjustment. Since many of the structural details of this further embodiment are similar to the embodiment shown in FIGS. 1 through 6, reference numerals have been selected as part of a 100 series to identify corresponding parts.

The adjustable inductor 110 includes a casing 112 having a base 114 and a cover 116. The cover 116 is secured to the upstanding flange 114a of the base 114 by soldering 118 about the margins thereof to provide a hermetically sealed unit. Disposed within the casing 112 is the magnetic core 120 which includes two

core sections

122, 124 made up of plural F-shaped laminations arranged in the manner previously described. The alternatively directed laminations of the lower core section 122 are secured together by the U-shaped clamp 140 which embraces the laminations and is secured thereto by a rivet or pin 142, with the bight of the clamp 140 being secured to the base 114, as by spot welding. The upper core section 124, which is adjustable toward and away from the fixed core section 122 to permit overall or gross adjustment of the air gap 138, has the laminations thereof secured together for adjustment as a unit. This is achieved by the provision of an inverted U-shaped clamp 148 which carries a rivet or pin 150 extending through all of the laminations except for the floating or adjustable laminations, herein designated by the

reference numerals

132, 134. As seen best in FIG. 8, the adjustable or floating

laminations

132, 134 which are movable in planes parallel to the remaining laminations of the core 120, afford a means for adjusting a small and minor segment 138b of the overall air gap 138 which will bring about a corresponding adjustment in the average effective length of the air gap. The

laminations

132, 134 are appropriately slotted, as indicated at 132a, 134a, to afford clearance in relation to the rivet or pin 150, with the invertedU-shaped clamp 148 being appropriately configurated, as indicated at 148a, to facilitate such adjustment.

The adjustable laminations, 132, 134 are secured together and to a common actuating head 174 which is engaged against an eccentric 176 secured to a vernier shaft 178 which is journalled in the adjacent wall of the cover 116 of the casing 112. The vernier shaft 178 has a slotted end, as indicated in FIG. 8 and designated by the reference numeral 17 8a, to faciliate adjustment thereof and may be secured in any adjusted position through the provision of a lock nut 180 threaded thereon and engaged against a washer 182. An appropriately configurated spring 184 bears against the top wall of the cover 116 of the casing 112 and against the actuating head 174 to bias the same against the peripheral surface of the eccentric 176 such that the rotational orientation of the eccentric 176 will determine the adjusted position for the laminations 132,134.

As before, a screw type actuator including a slotted head 158 is secured to an upstanding post 152 connected 6 to the channel 148. In this embodiment, the screw type actuator serves to adjust the entire movable core section 124 with respect to the stationary core section 122.

The illustrative adjustable inductor is completed by the provision of the bobbin 164 which receives one or more coils 166 wound thereon and connected to appropriate spade lugs 168 on the base 114 of the casing 112.

From the foregoing, it will be appreciated that there has been provided in accordance with the present invention a variable inductor device which comprises a core including plural laminations providing a magnetic circuit, with the laminations being arranged to define an air gap in such magnetic circuit. A first group of laminations is disposed substantially in opposed relation to a second group of laminations to provide a first and major segment for the air gap, while a third group of laminations is disposed substantially in opposed relation to a fourth group of laminations to provide a second and minor segment for the air gap. Means are provided to mount one of the third and fourth group of laminations for movement relative to the other group thereof such that a fine adjustment may be made in the effective length of the air gap. As a further feature of the invention, provision may be made in the first instance for moving all of the laminations which make up the air gap relative to each other to achieve a gross adjustment in the length of the air gap.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

What I claim is:

1. A variable inductive device comprising a core having plural laminations providing a magnetic circuit, said laminations being arranged relative to each other to define an air gap in said magnetic circuit, first groups of laminations being arranged in relation to each other to provide a relatively fixed length for a first segment of said air gap and a corresponding relatively fixed value of inductance, and means for mounting a second group of laminations for movement relative to said air gap and in planes parallel to the lamina-tions of said first group to provide an adjustable length for a second segment of said air gap and a corresponding variable inductance whereby vernier adjustment may be made in the total inductance of said device.

2. A magnetic core comprising plunal laminations, each of said laminations having at least one leg, said legs terminating in confronting faces defining an air gap therebetween, means for retaining said laminations in rela- .tively fixed relation to each other except for at least one lamination such that a major segment of said air gap is of a relatively fixed length, and means for adjusting said one lamination in a plane parallel to the other laminations and lengthwise of said gap such that a minor segment of said air gap is of adjustable length to permit vernier adjustment of the reluctance of said magnetic core.

3. A magnetic core comprising plural laminations each having an outer leg and an intermediate leg, said intermediate legs terminating in confronting faces defining an air gap therebet-ween, said outer legs being interleaved and in frictional engagement, means for retaining said laminations in relatively fixed relation to each other except for at least one lamination such that a major segment of said air gap is of a relatively fixed length, and means for adjusting said one lamination in a plane parallel to the other laminations and lengthwise of said gap such that a minor segment of said air gap is of adjustable length to permit vernier adjustment of the reluctance of said magnetic core.

4. A variable inductive device comprising a core ineluding first and second core sections each having plural laminations providing a magnetic circuit, said laminations of said first and second core sections being parallel to each other and arranged relative to each other to define an air gap in said magnetic circuit, a first group of laminations of said first core section being disposed substantially in opposed relation to a first group of laminations of said second core section to provide a first and major segment for said air gap, a second group of laminations of said first core section being disposed substantially in opposed relation to a second group of laminations of said second core section to provide a second and minor segment for said air gap, means mounting one of said core sections for lengthwise movement relative to the other of said core sections such that a gross adjustment may be made in the length of said air gap, and means mounting one of the second groups of laminations for lengthwise movement relative to the other of the second groups of laminations such that a fine adjustment may be made in the efiective length of said air gap.

5. A magnetic core comprising two core sections each including plural laminations, each of said core sect-ions having an outer leg and an intermediate leg, said intermediate legs of said core sections terminating in confronting faces defining an air gap therebetween, said outer legs of said core sections being interleaved and in frictional engagement with each other, means for retaining said core sections in relatively fixed relation to each other such that a major segment of said air gap is of a relatively fixed length, means for adjusting at least one lamination of one of said core sections in a plane parallel to the other laminations of said one core section and lengthwise of said air gap such that a minor segment of said air gap is of adjustable length to permit Vernier adjustment of the reluctance of said magnetic core, and fine adjusting means operatively connected to said one lamination for moving 8 the same against the reaction force provided by said interleaved outer legs.

6. A magnetic core comprising two core sections each including plural laminations, each of said core sections having an outer leg and an intermediate leg, said intermediate legs of said core sections terminating in confronting faces defining an air gap therebetween, said outer legs of said core sections being interleaved and in frictional engagement with each other, means for retaining said core sections in relatively fixed relation to each other such that a major segment of said air gap is of a relatively fixed length, means mounting one of said core sections for movement relative to the other of said core section such that a gross adjustment may be made in the length of said air gap, gross adjusting means operatively connected to said one core section for moving the same against the reaction force provided by said interleaved outer legs, means for adjusting at least one lamination of one of said core sections in a plane parallel to the other laminations of said one core section and lengthwise of said air gap such that a minor segment of said air gap is of adjustable length to permit Vernier adjustment of the reluctance of said magnetic core, and fine adjusting means operatively connected to said one lamination for moving the same against the reaction force provided by said interleaved outer legs.

References Cited by the Examiner UNITED STATES PATENTS 3/1959 Mitchell 336-134 3,154,756 10/1964 Bo-jarski 336l33 LARAMIE E. ASKIN, Primary Examiner.

JOHN F. BURNS, ROB-ERT K. SCHAEFER, Examiners.

C. TORRES, Assistant Examiner.

Claims

1. A VARIABLE INDUCTIVE DEVICE COMPRISING A CORE HAVING PLURAL LAMINATIONS PROVIDING A MAGNETIC CIRCUIT, SAID LAMINATIONS BEING ARRANGED RELATIVE TO EACH OTHER TO DEFINE AN AIR GAP IN SAID MAGNETIC CIRCUIT, FIRST GROUPS OF LAMINATIONS BEING ARRANGED IN RELATION TO EACH OTHER TO PROVIDE A RELATIVELY FIXED LENGTH FOR A FIRST SEGMENT OF SAID AIR GAP AND A CORRESPONDING RELATIVELY FIXED VALUE OF INDUCTANCE, AND MEANS FOR MOUNTING A SECOND GROUP OF LAMINATIONS FOR MOVEMENT RELATIVE TO SAID AIR GAP AND IN PLANES PARALLEL TO THE LAMINATIONS OF SAID FIRST GROUP TO PROVIDE AN ADJUSTABLE LENGTH FOR A SECOND SEGMENT OF SAID AIR GAP AND A CORRESPONDING VARIABLE INDUCTANCE WHEREBY VERNIER ADJUSTMENT MAY BE MADE IN THE TOTAL INDUCTANCE OF SAID DEVICE.