US3480896A - Adjustable inductor - Google Patents

Adjustable inductor Download PDF

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Publication number
US3480896A
US3480896A US679798A US3480896DA US3480896A US 3480896 A US3480896 A US 3480896A US 679798 A US679798 A US 679798A US 3480896D A US3480896D A US 3480896DA US 3480896 A US3480896 A US 3480896A
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Prior art keywords
slug
cores
inductor
cup
core
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US679798A
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Werner E Neuman
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Components Corp
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Components Corp
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F17/00Fixed inductances of the signal type 
    • H01F17/04Fixed inductances of the signal type  with magnetic core
    • H01F17/043Fixed inductances of the signal type  with magnetic core with two, usually identical or nearly identical parts enclosing completely the coil (pot cores)

Definitions

  • Inductors of this character must be assembled with great care.
  • the gap between the inner rings is critical and the avoidance of stresses within the core structure is critical.
  • the permeability of the core will drift and vary over a period of time.
  • the inductors must be proof against a certain amount of shock incident to handling, use in mobile equipment, etc. Consequently, a problem resides in the simple assembly of an inductor of this character whereby the parts are secured firmly and accurately together without the imposition of distorting stresses.
  • the tuning slug when once adjusted, remain in its adjusted position and not be subject to displacement therefrom by vibration or shock. As a part of this same consideration, it is desirable that the tuning slug be periodically adjustable from one position to another and retain its same resistance to accidental dislocation between such changes.
  • the clearance of the slug is such as to preclude the existence of any intervening material between the slug and the inside sleeve.
  • the invention here is directed to a shockproof tunable inductor of the type described including a novel form of assembly and a novel provision for tuning slug adjustment, the latter of which is not only proof against shock but capable of unlimited readjustment without losing its strong frictional drag characteristics which maintain the tuning slug in position.
  • FIG. 1 is a perspective view of an inductor embodying my invention
  • FIG. 2 is a vertical section through the inductor of FIG. 1 taken along line 2-2 of that figure looking in the direction of the arrows;
  • FIG. 3 is a transverse section taken along the line 33 of FIG. 2 looking in the direction of the arrows.
  • the inductor considered includes two substantially identical annular cup cores 10 and 12 desirably formed of a ceramic ferrite sufficiently dense and solid as to have negligible or no water absorbing capability, although, for some purposes, sintered iron is suitable.
  • the cores include an annular base 14 and inner and outer cylindrical walls 16 and 18 extending alike from the inner and outer peripheries of the base 14 respectively. The inner walls are shorter than the outer walls.
  • the lower core 10 will have its base notched out as at 20 at one or more discrete points through the outer periphery inwardly beyond the outer wall 18.
  • a winding 22 on a spool or bobbin 24 is inserted into the annular cavity of the lower cup core 10 to surround and stand above the inner wall thereof.
  • the upper cup core is inverted and inserted into the upper end of the spool with the inner wall contained within the axial aperture of the spool.
  • the relationship of the cores to the spool is such that the outer walls of the cores contact each other and the inner walls stand somewhat spaced from each other defining an annular gap 26.
  • the leads 28 of the coil 22 are passed through the notches 20 for appropriate electrical connection.
  • the lower core rests on the rim 30 of a shallow, cuplike base formed of molded or machined plastic 32.
  • the diameter of the rim is equal to that of the core and the wall thickness of the rim is approximately equal to that of the outer wall of the core.
  • the base has terminal pins 34 molded or assembled therein extending above and below the bottom 36 thereof to which the coil leads 28 are soldered within the cup. Externally, the base has a peripheral recess formed above its lower edge to define an annular ledge 38 parallel to the rim 30 of the base.
  • the inductor is bound together as a unit by a can 40
  • An 0 ring 42 of synthetic rubber having a diameter equal to the outside diameter of the cup cores 10 and 12 is placed on the top cup core and the inverted can 40 placed over the entire, stacked assembly of the tWo cup cores and the base, with the bottom 44 thereof bearing against the O ring and the cylindrical sides 46 extending down beyond the ledge 38 of the base.
  • the free edge 48 of the can is rolled inwardly as by spinning or the like to engage the ledge 38 and exert a compressive force against the outer edges of the cup cores and the base through the resilient medium of the O ring 42 to contain the whole structure firmly together.
  • the O ring in this assembly contributes several desirable effects: it holds the two cup cores tightly together in straight compression along their outer edges for optimum magnetic coupling; it loads resiliently the engagement of the spun edge 48 against the ledge 38 for optimum tightness; it makes the assembly shake-proof; and it achieves all this without the application of pressure on the cup cores inwardly of the outer edges which might tend to distort the cores and interfere with the predictable values of the inductor.
  • a tuning slug 50 of ceramic or sintered iron is employed which fits very closely within the sleeve defined by the inside walls 16 of the cup cores for optimum coupling and a maximum range of values. This exceedingly close fit prohibits the use of material intervening between the inside wall of the cup core and the tuning slug, and imposes the requirement that adjusting engagement between core and slug be made axially away from the slug.
  • the tuning slug 50 is a tubular member having a central aperture 52 therethrough.
  • a fibre glass rod 54 is machined to have a threaded lower end 56, a flange 58 upwardly of the threaded portion, and a small diameter stem 60 receivable closely within the bore 52 of the slug 50.
  • the stem extends upwardly above the slug.
  • a brass cap 62 is press-fitted on the upwardly extending end of the stern above the slug, and desirably cemented thereto, in tight contact with the slug so that the slug is confined between it and the flange 58.
  • the cap is cross slotted at its top end as at 64 for adjustment by a screwdriver blade.
  • the can 40 has an aperture 66 in the center of the base thereof through which screwdriver access to the cap is provided.
  • the aperture 66 is smaller than the cap 62 so that the can constitutes a stop for the adjustment of the slug when the slug is wholly withdrawn from the gap.
  • a tubular, flanged nylon nut 68 is press-fitted and ad hesively secured within the lower end of the aperture of the lower cup core with the flange 70 thereof bearing against the base of the cup core.
  • the threaded end 56 of the stem 54 is engaged in the nut.
  • the nut need not be threaded.
  • the fibre glass is sufficiently hard to impress its own threads into the softer nylon material. The engagement of the fibre glass threads with the nylon nut provides a high component of frictional resistance to accidental movement of the stem within the nut, and thus anchors the slug against accidental displacement while permitting an unlimited number of adjustments without lessening frictional holding.
  • the inside diameter of the sleeve will be about .122 inch and the outside diameter of the tuning slug will be about .115 inch.
  • the aperture therefore through which the stem must extend is exceedingly small, about .038 inch, and with the frictional engagement sufficient to hold the slug in its adjusted position to meet the vibration resistant qualifications, a substantial torsional force of adjustment must be transmitted through the very small diameter stem.
  • Fibre glass possesses the requisite torsional strength, is easily machinable, is nonmetallic, and is a unique and practical answer to the problem.
  • a machined brass equivalent to the fibre glass stem has been employed successfully in the practice of this invention. The strength of the brass may be superior to the fibre glass. However such substitution results in a 10 to 20% increase in the loss of the inductor at some frequencies.
  • a tunable inductor comprising a pair of annular cup cores, each having an outer wall and a shorter inner wall extending alike from the outside edge and the inside edge respectively of an annular base, the free edges of said outer walls meeting, a winding contained in the annular space between said inner and outer walls, means securing said cores together in said relationship, a cylindrical tuning slug having an axial bore therethrough within said inner walls, and means for moving said slug variably across the gap between the inner walls of said cores including-a shaft of a material strong in torsion extending through said slug bore and providing a shoulder, means anchoring said slug against said shoulder, said shaft extending beyond said shoulder in a threaded extension, and a nut in one of said inner walls beyond said gap engaging said threaded extension with high frictional resistance to rotation, said shaft having means at the free end thereof for effecting rotation thereof.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Coils Or Transformers For Communication (AREA)

Description

Nov. 25, 1969 w. E. NEUMAN ADJUSTABLE INDUCTOR Filed Nov. 1, 1967 United States Patent 3,480,896 ADJUSTABLE INDUCTOR Werner E. Neuman, Deerfield, Ill., assignor to Components Corporation, Chicago, Ill., a corporation of Illinois Filed Nov. 1, 1967, Ser. No. 679,798 Int. Cl. H01f /02, 21/06, 27/02 US. Cl. 336-83 3 Claims ABSTRACT OF THE DISCLOSURE Background of the invention High Q coils of the type under consideration here are formed of two, facing, annular, cup cores wherein the outside rings or walls abut and the inside rings or walls stand somewhat apart. A winding is contained in the an nular space between the inner and outer walls. A tuning slug fits closely within the sleeve defined by the inner rings and is adjustable to span the gap between the inner rings or to be variably displaced from such spanning position.
Inductors of this character must be assembled with great care. The gap between the inner rings is critical and the avoidance of stresses within the core structure is critical. Else, the permeability of the core will drift and vary over a period of time. At the same time, the inductors must be proof against a certain amount of shock incident to handling, use in mobile equipment, etc. Consequently, a problem resides in the simple assembly of an inductor of this character whereby the parts are secured firmly and accurately together without the imposition of distorting stresses.
Likewise, of course, it is highly important that the tuning slug, when once adjusted, remain in its adjusted position and not be subject to displacement therefrom by vibration or shock. As a part of this same consideration, it is desirable that the tuning slug be periodically adjustable from one position to another and retain its same resistance to accidental dislocation between such changes.
With regard to the latter consideration, it should be appreciated that for maximum reactance and maximum variation, the clearance of the slug is such as to preclude the existence of any intervening material between the slug and the inside sleeve.
Summary of the invention The invention here is directed to a shockproof tunable inductor of the type described including a novel form of assembly and a novel provision for tuning slug adjustment, the latter of which is not only proof against shock but capable of unlimited readjustment without losing its strong frictional drag characteristics which maintain the tuning slug in position.
Brief description of the drawings FIG. 1 is a perspective view of an inductor embodying my invention;
FIG. 2 is a vertical section through the inductor of FIG. 1 taken along line 2-2 of that figure looking in the direction of the arrows; and
FIG. 3 is a transverse section taken along the line 33 of FIG. 2 looking in the direction of the arrows.
Description of the preferred embodiment The inductor considered includes two substantially identical annular cup cores 10 and 12 desirably formed of a ceramic ferrite sufficiently dense and solid as to have negligible or no water absorbing capability, although, for some purposes, sintered iron is suitable. The cores include an annular base 14 and inner and outer cylindrical walls 16 and 18 extending alike from the inner and outer peripheries of the base 14 respectively. The inner walls are shorter than the outer walls. The lower core 10 will have its base notched out as at 20 at one or more discrete points through the outer periphery inwardly beyond the outer wall 18. A winding 22 on a spool or bobbin 24 is inserted into the annular cavity of the lower cup core 10 to surround and stand above the inner wall thereof. The upper cup core is inverted and inserted into the upper end of the spool with the inner wall contained within the axial aperture of the spool. The relationship of the cores to the spool is such that the outer walls of the cores contact each other and the inner walls stand somewhat spaced from each other defining an annular gap 26. The leads 28 of the coil 22 are passed through the notches 20 for appropriate electrical connection.
The lower core rests on the rim 30 of a shallow, cuplike base formed of molded or machined plastic 32. The diameter of the rim is equal to that of the core and the wall thickness of the rim is approximately equal to that of the outer wall of the core. The base has terminal pins 34 molded or assembled therein extending above and below the bottom 36 thereof to which the coil leads 28 are soldered within the cup. Externally, the base has a peripheral recess formed above its lower edge to define an annular ledge 38 parallel to the rim 30 of the base.
The inductor is bound together as a unit by a can 40 An 0 ring 42 of synthetic rubber having a diameter equal to the outside diameter of the cup cores 10 and 12 is placed on the top cup core and the inverted can 40 placed over the entire, stacked assembly of the tWo cup cores and the base, with the bottom 44 thereof bearing against the O ring and the cylindrical sides 46 extending down beyond the ledge 38 of the base. Thereafter the free edge 48 of the can is rolled inwardly as by spinning or the like to engage the ledge 38 and exert a compressive force against the outer edges of the cup cores and the base through the resilient medium of the O ring 42 to contain the whole structure firmly together. The O ring in this assembly contributes several desirable effects: it holds the two cup cores tightly together in straight compression along their outer edges for optimum magnetic coupling; it loads resiliently the engagement of the spun edge 48 against the ledge 38 for optimum tightness; it makes the assembly shake-proof; and it achieves all this without the application of pressure on the cup cores inwardly of the outer edges which might tend to distort the cores and interfere with the predictable values of the inductor.
In the illustrated inductor, a tuning slug 50 of ceramic or sintered iron is employed which fits very closely within the sleeve defined by the inside walls 16 of the cup cores for optimum coupling and a maximum range of values. This exceedingly close fit prohibits the use of material intervening between the inside wall of the cup core and the tuning slug, and imposes the requirement that adjusting engagement between core and slug be made axially away from the slug.
As shown here, the tuning slug 50 is a tubular member having a central aperture 52 therethrough. A fibre glass rod 54 is machined to have a threaded lower end 56, a flange 58 upwardly of the threaded portion, and a small diameter stem 60 receivable closely within the bore 52 of the slug 50. The stem extends upwardly above the slug. A brass cap 62 is press-fitted on the upwardly extending end of the stern above the slug, and desirably cemented thereto, in tight contact with the slug so that the slug is confined between it and the flange 58. The cap is cross slotted at its top end as at 64 for adjustment by a screwdriver blade. The can 40 has an aperture 66 in the center of the base thereof through which screwdriver access to the cap is provided. The aperture 66 is smaller than the cap 62 so that the can constitutes a stop for the adjustment of the slug when the slug is wholly withdrawn from the gap.
A tubular, flanged nylon nut 68 is press-fitted and ad hesively secured within the lower end of the aperture of the lower cup core with the flange 70 thereof bearing against the base of the cup core. The threaded end 56 of the stem 54 is engaged in the nut. The nut need not be threaded. The fibre glass is sufficiently hard to impress its own threads into the softer nylon material. The engagement of the fibre glass threads with the nylon nut provides a high component of frictional resistance to accidental movement of the stem within the nut, and thus anchors the slug against accidental displacement while permitting an unlimited number of adjustments without lessening frictional holding.
This effect is attainable through the employment of the fibre glass stem. In a characteristic embodiment of this invention, the inside diameter of the sleeve will be about .122 inch and the outside diameter of the tuning slug will be about .115 inch. The aperture therefore through which the stem must extend is exceedingly small, about .038 inch, and with the frictional engagement sufficient to hold the slug in its adjusted position to meet the vibration resistant qualifications, a substantial torsional force of adjustment must be transmitted through the very small diameter stem. Fibre glass possesses the requisite torsional strength, is easily machinable, is nonmetallic, and is a unique and practical answer to the problem. A machined brass equivalent to the fibre glass stem has been employed successfully in the practice of this invention. The strength of the brass may be superior to the fibre glass. However such substitution results in a 10 to 20% increase in the loss of the inductor at some frequencies.
Although a single embodiment only has been described of this invention it should be appreciated that this embodiment is set forth only by way of illustration and not .4 by way of limitation and that this invention should be regarded as being limited only as set forth in the fo1- lowing claims.
I claim:
1. A tunable inductor comprising a pair of annular cup cores, each having an outer wall and a shorter inner wall extending alike from the outside edge and the inside edge respectively of an annular base, the free edges of said outer walls meeting, a winding contained in the annular space between said inner and outer walls, means securing said cores together in said relationship, a cylindrical tuning slug having an axial bore therethrough within said inner walls, and means for moving said slug variably across the gap between the inner walls of said cores including-a shaft of a material strong in torsion extending through said slug bore and providing a shoulder, means anchoring said slug against said shoulder, said shaft extending beyond said shoulder in a threaded extension, and a nut in one of said inner walls beyond said gap engaging said threaded extension with high frictional resistance to rotation, said shaft having means at the free end thereof for effecting rotation thereof.
2. The combination as set forth in claim 1 wherein said nut is an unthreaded, relatively soft, deformable polymer, impressible by said extension to define matching threads.
3. The combination as set forth in claim 1 wherein said shaft is machined fibre glass.
References Cited UNITED STATES PATENTS 2,221,217 11/1940 Kink et a1. 336136 XR 2,608,610 8/1952 Thulin 336-83 XR 2,669,700 2/1954 Ranch 336-83 XR 2,946,029 7/1960 Abrams et al. 33683 XR 3,027,527 3/1962 West 336-- 3,162,829 12/1964 Wildy et al. 336-83 3,197,167 7/1965 Stungis 336-83 LEWIS M. MYERS, Primary Examiner T. J. KOZMA, Assistant Examiner U.S. C1. X.R. 336136, 92
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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3671759A (en) * 1970-09-02 1972-06-20 Northern Electric Co Magnetic sensor
US3898601A (en) * 1972-07-27 1975-08-05 Siemens Ag Core
DE2619912A1 (en) * 1975-05-06 1976-11-18 Volvo Ab TOWING DEVICE FOR MOTOR VEHICLES
US4054855A (en) * 1975-03-20 1977-10-18 Siemens Aktiengesellschaft Adjustable-inductance electric coil
US4149133A (en) * 1977-10-14 1979-04-10 Johnson Controls, Inc. Variable differential transformer apparatus
US4498067A (en) * 1981-04-20 1985-02-05 Murata Manufacturing Co., Ltd. Small-size inductor
EP0142207A1 (en) * 1983-11-10 1985-05-22 N.V. Nederlandsche Apparatenfabriek NEDAP Leakage transformer with small stray field
US4529956A (en) * 1984-08-16 1985-07-16 Honeywell Inc. Combined transformer and variable inductor
DE4120097A1 (en) * 1990-06-20 1992-01-09 Toko Inc HF coil assembly with thin walled core - having recess to prevent fracture by force applied by burr formed on cover during mfr.
US5345209A (en) * 1992-07-30 1994-09-06 Tdk Corporation Adjustment system for a coil device
US6392521B1 (en) * 2000-10-12 2002-05-21 Clinton Instrument Company Variable inductance transformer with electronic control
US8299879B2 (en) 2011-02-10 2012-10-30 Leco Corporation Transformer assembly using an internal load and method for forming same
US20120299685A1 (en) * 2010-06-22 2012-11-29 Toyota Jidosha Kabushiki Kaisha Reactor and reactor manufacturing method

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2221217A (en) * 1938-03-14 1940-11-12 Johnson Lab Inc Permeability tuned coupling device
US2608610A (en) * 1950-01-28 1952-08-26 Bell Telephone Labor Inc Transformer
US2669700A (en) * 1952-02-04 1954-02-16 Rauch Alexander Cup-core assembly for inductors
US2946029A (en) * 1955-12-22 1960-07-19 Cambridge Thermionic Corp Impedance assembly
US3027527A (en) * 1959-06-17 1962-03-27 Cambridge Thermionic Corp Sealed variable impedance device
US3162829A (en) * 1958-11-14 1964-12-22 Philips Corp Ferromagnetic pot-core assembles
US3197167A (en) * 1963-04-01 1965-07-27 Gen Electric Mounting clip for pot core

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2221217A (en) * 1938-03-14 1940-11-12 Johnson Lab Inc Permeability tuned coupling device
US2608610A (en) * 1950-01-28 1952-08-26 Bell Telephone Labor Inc Transformer
US2669700A (en) * 1952-02-04 1954-02-16 Rauch Alexander Cup-core assembly for inductors
US2946029A (en) * 1955-12-22 1960-07-19 Cambridge Thermionic Corp Impedance assembly
US3162829A (en) * 1958-11-14 1964-12-22 Philips Corp Ferromagnetic pot-core assembles
US3027527A (en) * 1959-06-17 1962-03-27 Cambridge Thermionic Corp Sealed variable impedance device
US3197167A (en) * 1963-04-01 1965-07-27 Gen Electric Mounting clip for pot core

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3671759A (en) * 1970-09-02 1972-06-20 Northern Electric Co Magnetic sensor
US3898601A (en) * 1972-07-27 1975-08-05 Siemens Ag Core
US4054855A (en) * 1975-03-20 1977-10-18 Siemens Aktiengesellschaft Adjustable-inductance electric coil
DE2619912A1 (en) * 1975-05-06 1976-11-18 Volvo Ab TOWING DEVICE FOR MOTOR VEHICLES
US4149133A (en) * 1977-10-14 1979-04-10 Johnson Controls, Inc. Variable differential transformer apparatus
US4498067A (en) * 1981-04-20 1985-02-05 Murata Manufacturing Co., Ltd. Small-size inductor
EP0142207A1 (en) * 1983-11-10 1985-05-22 N.V. Nederlandsche Apparatenfabriek NEDAP Leakage transformer with small stray field
US4529956A (en) * 1984-08-16 1985-07-16 Honeywell Inc. Combined transformer and variable inductor
DE4120097A1 (en) * 1990-06-20 1992-01-09 Toko Inc HF coil assembly with thin walled core - having recess to prevent fracture by force applied by burr formed on cover during mfr.
US5345209A (en) * 1992-07-30 1994-09-06 Tdk Corporation Adjustment system for a coil device
US5572788A (en) * 1992-07-30 1996-11-12 Tdk Corporation Coil device
US6392521B1 (en) * 2000-10-12 2002-05-21 Clinton Instrument Company Variable inductance transformer with electronic control
US20120299685A1 (en) * 2010-06-22 2012-11-29 Toyota Jidosha Kabushiki Kaisha Reactor and reactor manufacturing method
US8461955B2 (en) * 2010-06-22 2013-06-11 Toyota Jidosha Kabushiki Kaisha Reactor and reactor manufacturing method
US8299879B2 (en) 2011-02-10 2012-10-30 Leco Corporation Transformer assembly using an internal load and method for forming same

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