Inductance tuning means and methods of manufacture

• US 4,511,872 A
• Filed: 11/05/1982
• Issued: 04/16/1985
• Est. Priority Date: 11/05/1982
• Status: Expired due to Fees

• Current Assignee: Spang & Company
• Original Assignee: Spang Industries, Inc.
• Inventors: Huth, Joseph F. III, Olmsted, Robert W.
• Primary Examiner(s): Kozma, Thomas J.
• Application Number:
  US06/439,372
• Time in Patent Office: 893 Days
• Field of Search: 29/602 R, 29/607, 29/608, 29/606, 264/67, 264/DIG. 58, 336/83, 336/212, 336/130, 336/132, 336/134, 336/135, 336/136, 336/233, 338/87
• US Class Current: 336/83
• CPC Class Codes: H01F 21/06 by movement of core or part of core relative to the windings as a whole
• CPC Class Codes: H01F 41/0246 Manufacturing of magnetic circuits by moulding or by pressing powder magnetic cores made by moulding or by pressing powder H01F27/255; soft magnetic particles H01F1/20, H01F1/36
• CPC Class Codes: Y10S 264/58 Processes of forming magnets
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor
• CPC Class Codes: Y10T 29/49076 From comminuted material

Abstract

New ferrite pot core type products and fabrication methods are disclosed for production and assembly of tunable-inductance magnetically-soft ferrite devices. Unitary helical threads formed within the central opening of a ferrite pot core element provide controlled axial movement of a non-threaded male tuning member, carrying a ferrite rod, to adjust the air gap between spaced center posts of an assembled pair of pot core elements. Thread matching and registry requirements are eliminated by such unitary thread means which present either helical path die means, for cutting threads in a cylindrical nonmagnetic portion of a male tuning member or, circumferentially continuous helical threads, which deform nonmagnetic protrusions uniformly distributed about the periphery of a noncircular cross section nonmagnetic portion of a male tuning member during rotation of a male tuning member within a core element central opening.

Claims

1. Method for manufacturing a magnetically-soft ferrite pot core element to provide unitary means for adjusting the air gap presented by a pair of ferrite pot core elements assembled to form a ferrite pot core in which coil windings are positioned, comprising

providing a substantially homogeneous mass of particulate ferrite-forming material which is reactive when treated at elevated temperature to form a magnetically-soft ceramic ferrite,

molding such ferrite-forming material at elevated pressure to form a unitary part compacted in a green state for conversion to a ceramic-state ferrite pot core element including

an elongated center post symmetrically distributed about a centrally located longitudinal axis,

such center post terminating in a distal end surface, lying in a plane which is transverse to the centrally located longitudinal axis, for use in defining an air gap in such assembled electrical inductance device,

a web portion extending in transverse relationship to such centrally located axis at the remaining end of such center post longitudinally opposite to such distal end surface, and

a skirt portion extending from such web in space relationship from such center post and extending in an axial direction to define a space for positioning coil windings between such center post and such skirt portion,

such center post presenting an inner wall surface defining a central opening extending longitudinally with and substantially symmetrically about the centrally located longitudinal axis,

such inner wall surface including axially-directed reentrant portions separated by axially-directed non-reentrant portions,

establishing unitary die means within such center post central opening for acting on a thread-free nonmagnetic portion of an elongated air gap adjustor member,

such die means including

helically-oriented screw thread means for providing axial movement of an air gap adjustor member upon rotation within such central opening of a ferrite pot core element,

such helically-oriented screw thread means consisting of discontinuous helically-oriented threads established on such axially-directed non-reentrant portions of such center post inner wall surface,

such helically-oriented threads being interrupted along such inner wall surface by such axially-directed reentrant portions,

such axially-directed reentrant portions defining thread-free longitudinally-open flute means which remain longitudinally open after insertion of such elongated adjustor member into such central opening,

such discontinuous helically-oriented screw threads being formed in such non-reentrant portions of the inner wall surface of the central opening of the unitary part compacted from ferrite-forming material while such unitary part is in a green state after pressure compaction, and

following forming of such discontinuous screw threads,

sintering such core part utilizing an elevated temperature to convert such compacted part from such green state to a ceramic state.

2. A magnetically-soft ferrite pot core element providing unitary means for adjusting the air gap presented by a pair of ferrite pot core elements assembled to form a ferrite pot core in which coil windings are positioned, such pot core element comprising

an elongated center post symmetrical about a central longitudinal axis,

such center post terminating in a distal end surface, lying in a plane which is transverse to such centrally located axis, for use in defining an air gap in such assembled ferrite pot core,

a web extending in a direction transverse to such centrally located axis from the remaining longitudinal end of the center post opposite to such distal end surface, and

a skirt portion extending from such web in an axial direction to define a space for positioning coil windings between the exterior surface of such center post and such skirt portion,

such center post having an axially-extending inner wall surface defining a central opening for receiving an elongated adjustor member for adjusting the air gap of such assembled ferrite pot core,

such central opening wall surface presenting axially-directed reentrant portions separated by axially-directed non-reentrant portions,

unitary die means presenting helically-oriented screw threads in the ferrite material of such axially-directed non-reentrant portions for axial-location adjustment of a thread-free elongated adjustor member upon rotation of such member in contact with such die means within such central opening,

such helically-oriented thread means being interrupted about periphery of such central opening wall surface by such axially-directed reentrant portions which define flute means,

such flute means presenting axially-directed elongated thread-free passage means along such wall surface within such central opening.

3. Adjustable air gap ferrite pot core assembly comprising, in combination,

a pair of magnetically-soft ferrite pot core elements,

each such core element including an elongated center post symmetrical about a centrally located longitudinal axis, a web extending in transverse relation to such axis contiguous to one longtudinal end of the center post, and a skirt extending from the web generally parallel to and in spaced relation from the center post defining a space for coil windings between the center post and the skirt,

each core element skirt terminating in a mating surface for contacting the corresponding mating surface on the remaining core element skirt when in assembled relationship,

the center post of each core element terminating in a distal end surface, lying in a plane which is transverse to such centrally located longitudinal axis, with such distal end surfaces being spaced axially from one another when the mating surfaces on the skirts of the pair of core elements are in contacting relationships so as to define an air gap between such distal end surfaces,

each core element center post defining a central opening presenting a wall surface which is symmetrically disposed about such centrally located longitudinal axis,

such central openings beings in axial alignment when the pair of core elements are assembled for receiving an elongated air gap adjustor member for axially-directed movement within such center openings,

such elongated adjustor member presenting a thread-free non-magnetic cylindrical peripheral surface having a predetermined transverse dimension enabling it to be cooperatively received within a central opening of a core element center post,

such central opening wall surface of at least one of such pair of core elements presenting axially-directed reentrant portions separated by axially-directed non-reentrant portions, and

central opening die means presenting unitary helically-oriented threads located in the ferrite material of such non-reentrant portions of such central opening wall surface of such at least one of such pair of core elements for acting on at least a portion of such thread-free nonmagnetic external peripheral surface of the elongated adjustor member to cause longitudinal movement of such adjustor member along such centrally located axis upon rotation of such adjustor member within such central opening,

such helically-oriented threads being interrupted about the periphery of such central opening wall surface by such axially-directed reentrant portions which define thread-free longitudinally-open flute means which remain open after insertion of such elongated adjustor member within such central opening,

the nonmagnetic external peripheral surface of such adjustor member engaging and cooperating with such interrupted helically-oriented threads for control of axial positioning of such adjustor member,

such adjustor member carrying magnetic material for adjusting the air gap ferrite pot core assembly upon axial movement of such adjustor member within such aligned central openings.

4. The ferrite pot core assembly of claim 3 in which such pair of ferrite pot core elements are substantially identical with die means in respective central opening wall surfaces contiguous to the distal end surfaces of the center post of each core element, and

a non-threaded uniform-diameter cylindrical-configuration counterbore portion in each respective central opening wall surface leading to such die means for receiving such adjustor member.

5. Adjustable air gap ferrite pot core assembly comprising, in combination,

a pair of magnetically-soft ferrite pot core elements each including a center post symmetrical about a centrally located axis, a web extending from one end of the center post in transverse relation to such axis, and a skirt extending from the web in generally parallel spaced relation from the center post and defining a space for coil windings between the center post and the skirt,

each core element skirt terminating in a mating surface for contacting the corresponding mating surface on the other core element skirt in assembled relationship,

the center post of each core element terminating in a distal end surface lying in a plane disposed in transverse relationship to such central longitudinal axis with such end surfaces being spaced axially from one another so as to define an air gap therebetween when the mating surfaces on the skirts of the pair of core elements are in contacting relationship,

each core element center post defining a central opening presenting a wall surface having axially-directed reentrant portions and axially-directed non-reentrant portions,

respective axially-directed reentrant and non-reentrant portions of each core element being in axial alignment when the pair of core elements are assembled for receiving an elongated air gap adjustor member for axially-directed movement within such central openings,

central opening die means consisting of unitary helically-oriented threads in the ferrite material of the axially-directed non-reentrant wall surface portions of the central opening of such core elements for providing axial direction movement of an elongated air gap adjustor member upon rotation of such adjustor member in contact with such die means within the central opening of a core element,

such helically-oriented threads being interrupted about the periphery of such central opening wall surface by such axially-directed reentrant portions which define flute means,

such flute means comprising thread-free longitudinally-open passage means, within such central openings of both core elements, which remain longitudinally open after insertion of such elongated adjustor member,

such unitary die means being located along the wall surface of each core element contiguous to the respective distal end surface of each such core element center post,

the central opening wall surface of each core element further including a non-threaded uniform-diameter cylindrical-configuration counterbore portion between such die means of each respective core element and its remaining longitudinal end of such central opening which is opposite to its distal end surface,

such counterbore portion having a diameter which is no less than the maximum diameter presented by such discontinuous threads and approximates the maximum diameter presented by such non-threaded flute means passages, and

an elongated air gap adjustor member adapted to be received within such aligned central openings by insertion along such centrally located axis, through such counterbore portion of one of such pair of core elements selected for insertion of such adjustor member, in a direction toward the die means of such selected core element,

such adjustor member including

a head portion located at one longitudinal end of such male member,

such head portion presenting a thread-free external periphery cylindrical surface of soft plastic nonmagnetic material for engaging and cooperating with such die means of such one core element selected for insertion of such adjustor member,

magnetic material for adjusting such assembled ferrite pot core air gap upon axial movement of such adjustor member within such aligned central openings,

an extension means supporting such magnetic material between such head portion and such remaining longitudinal end of such adjustor member, and

a flat resilient washer of soft plastic non-magnetic material secured to such extension means contiguous to such remaining longitudinal end of such adjustor member,

such head portion nonmagnetic material having a maximum cross-sectional dimension providing contact about at least a portion of its external periphery with such die means in such core element selected for insertion of such adjustor member so as to cause axial movement of such adjustor member upon rotation of such adjustor member within such central opening,

such plastic washer having a cross-sectional dimension corresponding to such maximum cross-sectional dimension of such head portion so as to support such remaining longitudinal end of such adjustor member in the die means of the remaining core element of such pair of ferrite pot core elements.