US3233308A - Method of manufacturing magnetic heads having very short gap lengths - Google Patents

Method of manufacturing magnetic heads having very short gap lengths Download PDF

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Publication number
US3233308A
US3233308A US175536A US17553662A US3233308A US 3233308 A US3233308 A US 3233308A US 175536 A US175536 A US 175536A US 17553662 A US17553662 A US 17553662A US 3233308 A US3233308 A US 3233308A
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US
United States
Prior art keywords
edge
gap
plate
grinding
melting point
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US175536A
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English (en)
Inventor
Simon Duinker
Marinus Josephus Johannes Schoones
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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Filing date
Publication date
Application filed by US Philips Corp filed Critical US Philips Corp
Application granted granted Critical
Publication of US3233308A publication Critical patent/US3233308A/en
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/127—Structure or manufacture of heads, e.g. inductive
    • G11B5/187—Structure or manufacture of the surface of the head in physical contact with, or immediately adjacent to the recording medium; Pole pieces; Gap features
    • G11B5/1871—Shaping or contouring of the transducing or guiding surface
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/127—Structure or manufacture of heads, e.g. inductive
    • G11B5/187—Structure or manufacture of the surface of the head in physical contact with, or immediately adjacent to the recording medium; Pole pieces; Gap features
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/4902—Electromagnet, transformer or inductor
    • Y10T29/49021—Magnetic recording reproducing transducer [e.g., tape head, core, etc.]
    • Y10T29/49032—Fabricating head structure or component thereof
    • Y10T29/49048—Machining magnetic material [e.g., grinding, etching, polishing]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/4902—Electromagnet, transformer or inductor
    • Y10T29/49021—Magnetic recording reproducing transducer [e.g., tape head, core, etc.]
    • Y10T29/49032—Fabricating head structure or component thereof
    • Y10T29/49055—Fabricating head structure or component thereof with bond/laminating preformed parts, at least two magnetic

Definitions

  • This invention relates to a method of manufacturing magnetic heads. More particularly, it relates to a method of manufacture of such heads which have very short gap lengths, the method providing a head which is mechanically strong and magnetically efficient.
  • the recording density required of some magnetic recordings has become such that they can only be recorded and reproduced with the aid of heads having very short gap lengths, for example from 1 to 2 microns.
  • their depth, corresponding to the height of the gap has to be at least 150 microns. If both walls consist of a material having a high magnetic reluctance which is generally used in manufacturing heads of the type under consideration, for example ferrite, the efiiciency of the head is appreciably lower than that of heads having longer gap lengths.
  • the magnetic reluctance of the useful path of the lines of magnetic flux i.e., the path through the magnetic record carrier
  • the gap height consequently has to be limited to about microns; this value of gap height, however, is only a fraction of the value required in order to give the head sufiicient mechanical strength, the latter value being at least 150 microns.
  • one of the two plates from which the pole pieces of the head are made is scored by grinding for part of the surface by which it engages the other plate; the depth of scoring appreciably exceeds the desired gap length of the finished head, and the recess formed by scoring is filled with a strengthening material having a comparatively high melting point, for example glass, after which the said surface is ground and polished; after the other plate has been ground and polished, it is pressed against the first plate with the interposition of a thin layer of non-magnetic filling material having a lower melting point than the strengthening material and having a thickness equal to the desired gap length; finally the poleface of the head is given the desired outline and the gap height is given the desired value by grinding and polishing.
  • the gap length is to be understood as the dimension indicated in the drawing; the gap height is the dimension of the gap in the vertical direction of the plane of the drawing.
  • This dimensional nomenclature is that employed and shown in an article by S. Duinker, Durable High-Resolution Ferrite Transducer Heads Employing Bonding Glass Spacers in Philips Research Reports, vol. 15, 1960, pages 342-367; see especially FIG. 1 of this article.
  • the above mentioned recess provided by grinding the surface of one plate is preferably shaped so as to be rounded at the end nearer the future poleface of the head, the radius of the rounded end preferably being a few times greater than that corresponding to the depth of the recess in the said surface.
  • the figure shows two ferrite plates 1 and 2, the lefthand plate 1 being recessed as shown generally by reference numeral 4 by grinding to a depth of about microns.
  • this recess 4 terminates in a rounded part 5 through a distance exceeding the desired gap height, for example through a distance of from 100 to 200 microns.
  • the rounded part 5 serves to limit the magnetic reluctance of the flux lines traversing the gap 9 to a value which is not unnecessarily large.
  • the recess 4 is filled with a layer 6 of glass or other non-magnetic strengthening material having a high melting point.
  • the surface of the plate 1 to be engaged by the plate 2, which surface consequently largely consists of glass, now is ground fiat and polished and then coated with a film It of enamel or other suitable filling material for the future gap having substantially the thickness of the desired gap length, the melting point of this material being lower than that of the above mentioned strengthening material.
  • the plate 2 After the plate 2 has been ground flat and polished it is pressed against the plate 1 while heating until it firmly adheres thereto.
  • the pressure employed is not so great as to force any appreciable amount of the gap forming material from between the plates.
  • the poleface of the head is then given the desired outline and the gap is given the desired height of, for example, 25 microns by grinding and polishing, during which process the glass or other strengthening material 6 prevents the tapering part of the plate 1 from collapsing under the mechanical pressure inevitable in grinding and polishing. Owing to its high melting point the glass 6 retains the required strength during this operation.
  • the coetficient of expansion of the enamel in the gap 9 has to be matched to that of the ferrite.
  • the plates may be firmly secured, with the poleface down, in a jig which is shaped in accordance with the pole-face, after which with the aid of asuitable grinding tool capable of being lowered in the plane of the gap so much material is removed by grinding as to produce the outline shown in the figure. It should be ensured that at the gap end a part of the plate 2 of at least microns high is left and that at this point the two plates are kept together by the portion 6 of the strengthening material which is not removed by grinding.
  • the poleface outlines may be produced by any convenient method and they may alternatively be produced before the parts 1 and 2 are secured to one another. Between the extending legs 7 and 8 of the plates an amount of space is thus produced sufiicient to accommodate the windings of the head.
  • a method of manufacturing a magnetic head having a very short gap length and composed of at least two magnetic plates forming the head pole pieces each having a surface and an adjoining edge comprising: grinding a recess in the part of the edge of one of said plates which is adapted to confront the edge of the other plate to form the gap, said recess being ground to a depth substantially exceeding the desired gap length of the completed head and being located at a portion of said plate remote from where the surface and edge are joined, said grinding leaving intact a conjoining portion of said edge where the surface and edge are joined, filling said recess with a non-magnetic strengtheing material having a comparatively high melting point, said filling being done at said high melting point such that said strengthening material is fusion bonded to the plate and has an exposed part in approximate alignment with said conjoining portion, grinding and polishing said conjoining part of said one edge and said exposed part of the strengthening material, grinding and polishing said edge of said other plate, interposing a thin layer of gap filler material between
  • a method of manufacturing a magnetic head having a very short gap length and composed of at least two magnetic plates forming the head pole pieces each having a surface and an adjoining edge comprising: grinding a rounded recess in the part of the edge of one of said plates which is adapted to confront the edge of the other plate to form the gap, said recess being ground to a depth substantially exceeding the desired gap length of the completed head and being located at a portion of said plate remote from where the surface and edge are joined, said grinding leaving intact a conjoining portion of said edge where the surface and edge are joined and being rounded at the portion remote from the edge, filling said recess with a non-magnetic strengthening material having a comparatively high melting point, said filling being done at said high melting point such that said strengthening material is fusion bonded to the plate and has an exposed part in approximate alignment with said conjoining portion, grinding and polishing said conjoining part of said one edge and said exposed part of the strengthening material, grinding and polishing said edge of said other plate, interposing
  • a method of manufacturing a magnetic head having a very short gap length and composed of at least two ferrite plates forming the head pole pieces each having a surface and an adjoining edge comprising: grinding a rounded recess in the part of the edge of one of said plates which is adapted to confront the edge of the other plate to form the gap, said recess being ground to a depth substantially exceeding the desired gap length of the completed head and being located at a portion of said plate remote from where the surface and edge are joined, said grinding leaving intact a conjoining portion of said edge where the surface and edge are joined and being rounded at the portion remote from the edge, filling said recess with glass having a comparatively high melting point, said filling being done at said high melting point such that said glass is fusion bonded to the plate and has an exposed part in approximate alignment with said conjoining portion, grinding and polishing said conjoining part of said one edge and said exposed part of the glass, grinding and polishing said edge of said other plate, interposing a thin layer of gap filler material

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Magnetic Heads (AREA)
US175536A 1961-03-30 1962-02-26 Method of manufacturing magnetic heads having very short gap lengths Expired - Lifetime US3233308A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL263099 1961-03-30

Publications (1)

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US3233308A true US3233308A (en) 1966-02-08

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US175536A Expired - Lifetime US3233308A (en) 1961-03-30 1962-02-26 Method of manufacturing magnetic heads having very short gap lengths

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US (1) US3233308A (enrdf_load_html_response)
AT (1) AT242389B (enrdf_load_html_response)
CH (1) CH415091A (enrdf_load_html_response)
DK (1) DK104577C (enrdf_load_html_response)
ES (1) ES275904A1 (enrdf_load_html_response)
GB (1) GB996957A (enrdf_load_html_response)
NL (1) NL263099A (enrdf_load_html_response)
SE (1) SE323818C (enrdf_load_html_response)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3435155A (en) * 1963-03-01 1969-03-25 Philips Corp Pole pieces for magnetic heads with accurately determined gap heights

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8200531A (nl) * 1982-02-12 1983-09-01 Philips Nv Magneetkop met gedeeltelijk uitgeetste wikkelopening.

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1031020B (de) * 1953-09-07 1958-05-29 Telefunken Gmbh Magnetisierungskopf fuer Magnettongeraete
US2915812A (en) * 1953-04-21 1959-12-08 Rca Corp Method of constructing magnetic heads
GB827335A (en) * 1957-07-26 1960-02-03 British Broadcasting Corp Improvements in magnetic recording and reproducing heads
US2933565A (en) * 1953-04-15 1960-04-19 Siemens Ag Magnetic transducers
GB852533A (en) * 1956-07-26 1960-10-26 Philips Electrical Ind Ltd Improvements relating to magnetic recording and reproducing heads
US3079470A (en) * 1959-12-21 1963-02-26 Armour Res Found Magnetic transducer head
US3094772A (en) * 1956-07-26 1963-06-25 Philips Corp Method of producing magnetic heads with accurately predetermined gap heights
US3104455A (en) * 1959-08-10 1963-09-24 Clevite Corp Method of manufacturing magnetic transducer head

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2933565A (en) * 1953-04-15 1960-04-19 Siemens Ag Magnetic transducers
US2915812A (en) * 1953-04-21 1959-12-08 Rca Corp Method of constructing magnetic heads
DE1031020B (de) * 1953-09-07 1958-05-29 Telefunken Gmbh Magnetisierungskopf fuer Magnettongeraete
GB852533A (en) * 1956-07-26 1960-10-26 Philips Electrical Ind Ltd Improvements relating to magnetic recording and reproducing heads
US3094772A (en) * 1956-07-26 1963-06-25 Philips Corp Method of producing magnetic heads with accurately predetermined gap heights
GB827335A (en) * 1957-07-26 1960-02-03 British Broadcasting Corp Improvements in magnetic recording and reproducing heads
US3104455A (en) * 1959-08-10 1963-09-24 Clevite Corp Method of manufacturing magnetic transducer head
US3079470A (en) * 1959-12-21 1963-02-26 Armour Res Found Magnetic transducer head

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3435155A (en) * 1963-03-01 1969-03-25 Philips Corp Pole pieces for magnetic heads with accurately determined gap heights

Also Published As

Publication number Publication date
AT242389B (de) 1965-09-10
GB996957A (en) 1965-06-30
NL263099A (enrdf_load_html_response)
ES275904A1 (es) 1963-01-01
SE323818B (sv) 1970-05-11
DK104577C (da) 1966-06-06
CH415091A (de) 1966-06-15
SE323818C (sv) 1972-05-23

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