EP0005255A1 - Löschkopf zum Löschen von Einzelspuren eines Mehrspur-Magnetbandes - Google Patents

Löschkopf zum Löschen von Einzelspuren eines Mehrspur-Magnetbandes Download PDF

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Publication number
EP0005255A1
EP0005255A1 EP79101312A EP79101312A EP0005255A1 EP 0005255 A1 EP0005255 A1 EP 0005255A1 EP 79101312 A EP79101312 A EP 79101312A EP 79101312 A EP79101312 A EP 79101312A EP 0005255 A1 EP0005255 A1 EP 0005255A1
Authority
EP
European Patent Office
Prior art keywords
pole pieces
magnetic
tape
shielding means
erase head
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.)
Withdrawn
Application number
EP79101312A
Other languages
English (en)
French (fr)
Inventor
Gerhard Dr. Rotter
Klaus Dieter Dr. Schomann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP0005255A1 publication Critical patent/EP0005255A1/de
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/90—Magnetic feature

Definitions

  • This invention relates to an erase head for erasing recorded signals from single tracks of a multi-track magnetic recording tape, comprising a pair of pole pieces having faces located for contacting a moving magnetic tape, magnetic circuit means providing a low reluctance path between said pole pieces, and magnetic shielding means arranged adjacent to the pole pieces.
  • tape recording systems typically include an erase head mounted in a leading position with respect to a recording transducer head, so that previously recorded material on the tape will be erased immediately before new material is recorded.
  • erase heads There are many types of known erase heads such as those discussed below.
  • U.S. 3,852,812 describes a tunnel erase head for data recording purposes in particular on flexible magnetic discs.
  • the tunnel erase head consists of two magnetic gaps arranged at a distance from one another and serves to erase the track edges in order to limit the track width.
  • the tunnel erase head is provided with two erase coils, each of which is allocated to one of the said gaps, the said two erase coils being energized by a direct current of opposite polarity.
  • the magnetic fields of opposite polarity which are produced effect symmetric erasure which results in the second harmonic components of a reproduced signal being minimized.
  • the erase head of the present invention effects accurate track erasure rather than erasure of the track edges.
  • U.S. 3,521,006 discloses a combined erase and record-reproduce magnetic transducer for 8-track apparatuses.
  • a dual head is provided with two three-leg type core units and the tips of the legs extend into openings in the tape-engaging face of a magnetic shield housing for the magnetic head.
  • the highly permeable metal shield housing is provided to prevent crosstalk between adjacent channels because the magnetic housing shorts out stray hum signals and signals from adjacent tracks.
  • the erase coils provide high frequency bias and thereby produce the necessary erase flux.
  • German Laid-Open Application DOS 2,317,020 describes a very similar shielded head for use in a signal recording playback system in which several tracks are recorded in the longitudinal direction on a magnetic tape. In this publication the use of the shielded head for erasing purposes is not described.
  • magnetic materials including those used to coat magnetic recording tapes, exhibit a property known as hysteresis, wherein they will retain a degree of residual magnetism after a magnetizing or magnetomotive force is removed. Accordingly, if a constant magnetic field were to be applied in a direction generally parallel to the direction of movement of the tape, each particle of magnetic material on the tape would be subjected to a gradually increasing magnetic field strength as it approached the constant field, and to a gradually decreasing magnetic field strength as it moved away from the field. However, because of the effect of hysteresis, each such particle of magnetic material would remain partially magnetized in the direction of the constant magnetic field.
  • video and audio tape recorders typically employ high-frequency, alternating-current (ac) erase heads.
  • ac alternating-current
  • the magnitude of the magnetizing force gradually diminishes, and the hysteresis loop becomes progressively smaller and smaller, until, when the particle has escaped the influence of the field, it remains in an essentially neutral magnetic condition, without any asymmetrical magnetic bias in one direction or another.
  • ac erase heads are entirely satisfactory for most purposes, they have the disadvantage of relatively high cost as compared with a comparable dc erase head. Furthermore, an ac erase head must be provided with power from a high--frequency power source, and there is a significant problem in dealing with unwanted radiation from the source. Accordingly, appropriate shielding has to be provided, at a correpondingly higher cost.
  • the present invention fulfills this need by an erase head for erasing recorded signals from single tracks of a multi--track magnetic recording tape, comprising a pair of pole pieces having faces located for contacting a moving magnetic tape,
  • the present invention resides in a magnetic recording tape erase head powered by direct current and oriented to provide a constant magnetic field substantially perpendicular to the direction of tape travel.
  • the tape erased by the erase head of the invention is left permanently magnetized in the perpendicular direction, there is no asymmetry in the longitudinal direction, parallel to the tape length, and hence no distortion, because the recording head utilizes a magnetizing field in the longitudinal direction.
  • the erase head of the invention has an arrangement of pole pieces and shields which provides a substantially uniform field over a relatively narrow portion of the tape width, corresponding to the width of a single recording track on the tape.
  • the erase head of the invention comprises a pair of relatively narrow pole pieces having end faces which engage the surface of the magnetic tape, to provide a magnetic field in a direction transverse to the direction of tape movement, and a pair of flat magnetic metal plates positioned in a generally coplanar relationship with the end faces of the pole pieces and spaced apart therefrom by approximately the width of a single recording track to be erased, to minimize the effect of stray magnetic fields which would otherwise demagnetize adjacent tracks on the recording tape.
  • the erase head device also includes a magnetic circuit coupling the two pole pieces, and means for providing a constant magnetizing force to the' magnetic circuit.
  • the relative spacing of the pole pieces, and of the shields with respect to the pole pieces, can be optimized to provide a substantially uniform magnetic field strength in the regions between the edges of the shields.
  • the constant magnetic field thereby provided still leaves particles of magnetic material residually magnetized in the direction across the width of the tape, but this has no adverse effect on the recording characteristics of the tape, since the recording and playback transducers utilize a magnetic field oriented in the direction of tape movement.
  • said magnetic shielding means includes a single flat metal plate having an aperture of approximately the same width as a single recording track, to accommodate said pole pieces.
  • said pole pieces are parallel bars of rectangular cross section, and the faces locatable in an operative relationship with the tape are rectangular end faces; said magnetic circuit means includes a generally U-shaped core joining the ends of said pole pieces opposite said rectangular end faces.
  • the erase head according to the present invention is characterized in that the source of constant magnetomotive force is a magnetizing winding on a magnetic core energized with direct current, and magnetic shielding means having planar portions located on each side of said two pole pieces, in the same plane as its end faces, whereby the horizontal component of magnetic field strength is substantially zero in the regions adjacent to said end faces and adjacent to said shielding means, the vertical component of field strength is substantially zero except in the regions adjacent to said end faces, and the resultant field strength is relatively great in the region between the portions of said shielding means but is essentially zero elsewhere.
  • said magnetic shielding means have an aperture for accommodating the faces of the pole pieces in such away that said faces do not protude beyond the surface of said shielding means.
  • the present invention provides a simple and less costly alternative to ac demagnetization of recording tapes.
  • it provides a magnetic field across a relatively small width of the tape, so that recording tracks adjacent to the one that is to be demagnetized are protected from inadvertent demagnetization.
  • each recording track may be as little as four thousandths of an inch wide, with a safety zone of an additional two thousandths of an inch between tracks.
  • direct-current erase head is oriented at right angles to the direction of travel of a recording tape 12, and is provided with a configuration of pole pieces 14 and shielding elements 16 which cooperate to provide a substantially constant magnetic field across a relatively narrow width of the tape, and only a very small magnetic field outside the desired width to be demagnetized.
  • the erase head 10 comprises two relatively narrow pole pieces 14 having flat, preferably rectangular end faces 14a oriented in a parallel relationship with each other and with the direction of movement of the recording tape 12.
  • the end faces 14a are positioned in surface contact with the tape 12, or in very close proximity to it, and there is a narrow gap between parallel adjacent edges of the end faces.
  • the magnetic field from the pole pieces 14 is oriented primarily at right-angles (x axis) to the direction of tape movement (z axis).
  • a flat magnetic shield 16 arranged in generally coplanar relationship with the end faces 14a of the pole pieces. Each shield 16 has its edge closest to the pole pieces spaced apart therefrom and also oriented generally parallel to the direction of tape travel.
  • the shields 16 operate to eliminate practically all of the fringing or leakage flux paths from the pole pieces 14, and to provide a very low level of magnetic field strength in the regions of the tape immediately adjacent to the shields.
  • Connecting the pole pieces 14 is a generally U-shaped magnetic core 17, on which is wound a magnetizing winding 18, supplied by a dc power source, indicated at 19.
  • the primary direction of the magnetic field provided by the head 10 is designated as the x axis.
  • the orthogonal directions of the y axis and z axis are defined as being perpendicular to the plane of the tape 12, and parallel to the tape movement direction, respectively.
  • the component of magnetic field strength measured in the horizontal or x-axis direction is relatively high in the region between the pole pieces 14, falls to zero in the areas across the pole pieces and shields 16, and is also relatively high in the regions between the pole pieces and shields.
  • the broken line 20 (Fig. 2) indicates the approximate magnitude, designated H xj of the horizontal component of the magnetic field strength.
  • the solid line 22 indicates the corresponding variation in the vertical component of magnetic field strength, designated Hy, measured across the same region. It will be apparent that the magnitude of the vertical component field strength H y rises from close to zero outside the pole pieces 10 to a maximum value across the faces 16a of the pole pieces, but is substantially zero between the pole pieces.
  • the resultant field strength, H is, of course, determined as the square root of the sum of the squares of the horizontal and vertical components.
  • the value of H is separately plotted as the solid line 24 in Fig. 2. It will be seen-that the field strength, H, between the edges of the shields 16 is substantially constant.
  • Fig. 2 is only an approximate illustration of the actual field strengths involved. In practice, the field strengths may vary as shown by way of example in Fig. 3, wherein the mag-' nitude of the horizontal component of field strength, H x , is indicated at 30, the magnitude of the vertical component of field strength, H y , is indicated at 32 and the resultant, H, of the horizontal and vertical components is indicated at 34.
  • the absolute spacing of the pole pieces 14 and the shields 16 will depend upon a variety of factors, such as the recording track width, the width of guard bands or safety zones between tracks, the desired field strength, and so forth. In general, however, it is a matter of relatively simple design technique to optimize the spacings between the pole pieces 24, and between the pole pieces and the shields 16, to obtain a relatively constant field strength across a desired tape width. Variations in field strength across the width the recording track are of little consequence, so long as the resultant field strength remains above a minimum level, which should be several times the value of the maximum field strength measured outside the recording track width.
  • the shields 16 may, in a variation of the embodiment of Figure 1, be formed as a single continuous shield 16', shown in Fig, la, having a single aperture 40 therein to receive the two pole pieces 14.
  • the continuous shield 16' eliminates the possibility of stray paths, through the air, between the two separate shields 16.
  • the present invention represents a significant advance in the field of nagnetic recording.
  • it provides a less costly alternative to demagnetization of recording tapes by alternating current means, and does so by obviating the disadvantages previously thought to be inherent in the use of direct current erase heads.
  • the invention is not to be limited except as by the appended claims.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Magnetic Heads (AREA)
EP79101312A 1978-05-04 1979-05-02 Löschkopf zum Löschen von Einzelspuren eines Mehrspur-Magnetbandes Withdrawn EP0005255A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US05/902,842 US4187521A (en) 1978-05-04 1978-05-04 DC erase head
US902842 1978-05-04

Publications (1)

Publication Number Publication Date
EP0005255A1 true EP0005255A1 (de) 1979-11-14

Family

ID=25416482

Family Applications (1)

Application Number Title Priority Date Filing Date
EP79101312A Withdrawn EP0005255A1 (de) 1978-05-04 1979-05-02 Löschkopf zum Löschen von Einzelspuren eines Mehrspur-Magnetbandes

Country Status (3)

Country Link
US (1) US4187521A (de)
EP (1) EP0005255A1 (de)
JP (1) JPS54149612A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8476296B2 (en) 2009-01-26 2013-07-02 Targacept, Inc. Preparation and therapeutic applications of (2S,3R)-N-2-((3-pyridinyl)methyl)-1-azabicyclo[2.2.2]OCT-3-yl)-3,5-difluorobenzamide

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4462055A (en) * 1982-01-04 1984-07-24 Ldj Electronics, Inc. Bulk tape erasing system
US4564877A (en) * 1982-04-28 1986-01-14 Tdk Corporation Magnetic recording/reproducing system with wide-gapped transducer and method for using same
JP2656733B2 (ja) * 1993-09-29 1997-09-24 インターナショナル・ビジネス・マシーンズ・コーポレイション 薄膜磁気抵抗再生ヘッドの磁気的再初期設定方法及びその装置
US5721665A (en) * 1995-08-18 1998-02-24 Data Security, Inc. Modulated magnet field bulk degaussing system
US6731491B2 (en) 2001-06-15 2004-05-04 Data Security, Inc. Bulk degausser with fixed arrays of magnet poles
US7164569B1 (en) 2004-06-30 2007-01-16 Data Security, Inc. Mechanism for automated permanent magnet degaussing
US20060018075A1 (en) * 2004-07-23 2006-01-26 Data Security, Inc. Permanent magnet bulk degausser
KR100660885B1 (ko) * 2005-11-07 2006-12-26 삼성전자주식회사 하드디스크 드라이브의 버스트 기록 방법 및 이에 적합한장치
US7715166B2 (en) * 2006-07-14 2010-05-11 Data Security, Inc. Method and reciprocating apparatus for permanent magnet erasure of magnetic storage media
US7701656B2 (en) * 2006-07-14 2010-04-20 Data Security, Inc. Method and apparatus for permanent magnet erasure of magnetic storage media
US8973824B2 (en) * 2007-12-24 2015-03-10 Dynamics Inc. Cards and devices with magnetic emulators with zoning control and advanced interiors
US20090284890A1 (en) * 2008-05-16 2009-11-19 Thiel Leroy D Mechanism and Method for Permanent Magnet Degaussing

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194894A (en) * 1961-05-30 1965-07-13 Bsr Ltd Electro-magnetic heads
US3610838A (en) * 1968-03-11 1971-10-05 Sony Corp Erasing apparatus for magnetic memory discs using two dc heads
US4071868A (en) * 1974-12-20 1978-01-31 Matsushita Electric Industrial Co., Ltd. Narrow track MR head with side shields

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2736776A (en) * 1951-06-02 1956-02-28 Armour Res Found Magnetic recorder head assembly
US3105965A (en) * 1960-04-11 1963-10-01 Honeywell Regulator Co Combined read-write and erase head assembly
US3542971A (en) * 1967-08-21 1970-11-24 Dennis Willard Magnetic transducer having positioning surfaces
US3521006A (en) * 1968-05-23 1970-07-21 Nortronics Co Multichannel combination erase and record-reproduce magnetic transducer
US3852812A (en) * 1973-07-25 1974-12-03 Potter Instrument Co Inc Symmetrical direct current tunnel erasing
JPS5751161B2 (de) * 1974-03-12 1982-10-30

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3194894A (en) * 1961-05-30 1965-07-13 Bsr Ltd Electro-magnetic heads
US3610838A (en) * 1968-03-11 1971-10-05 Sony Corp Erasing apparatus for magnetic memory discs using two dc heads
US4071868A (en) * 1974-12-20 1978-01-31 Matsushita Electric Industrial Co., Ltd. Narrow track MR head with side shields

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8476296B2 (en) 2009-01-26 2013-07-02 Targacept, Inc. Preparation and therapeutic applications of (2S,3R)-N-2-((3-pyridinyl)methyl)-1-azabicyclo[2.2.2]OCT-3-yl)-3,5-difluorobenzamide

Also Published As

Publication number Publication date
JPS54149612A (en) 1979-11-24
US4187521A (en) 1980-02-05

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Inventor name: ROTTER, GERHARD, DR.

Inventor name: SCHOMANN, KLAUS DIETER, DR.