EP0535902A2 - Aimant anisotrope à circuit magnétique interne fermé et procédé - Google Patents

Aimant anisotrope à circuit magnétique interne fermé et procédé Download PDF

Info

Publication number
EP0535902A2
EP0535902A2 EP92308844A EP92308844A EP0535902A2 EP 0535902 A2 EP0535902 A2 EP 0535902A2 EP 92308844 A EP92308844 A EP 92308844A EP 92308844 A EP92308844 A EP 92308844A EP 0535902 A2 EP0535902 A2 EP 0535902A2
Authority
EP
European Patent Office
Prior art keywords
magnet
magnetic
magnetic particles
orientation
internal closed
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Withdrawn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
EP92308844A
Other languages
German (de)
English (en)
Other versions
EP0535902A3 (en
Inventor
Satoshi Tokyo Head Office Nakatsuka
Akira Tokyo Head Office Yasuda
Itsuo c/o Technical Research Division Tanaka
Koichi c/o Technical Research Division Nushiro
Takahiro C/O Technical Research Division Kikuchi
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.)
JFE Steel Corp
Original Assignee
Kawasaki Steel Corp
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
Priority claimed from JP30631091A external-priority patent/JPH05144650A/ja
Application filed by Kawasaki Steel Corp filed Critical Kawasaki Steel Corp
Publication of EP0535902A2 publication Critical patent/EP0535902A2/fr
Publication of EP0535902A3 publication Critical patent/EP0535902A3/en
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0273—Imparting anisotropy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0205—Magnetic circuits with PM in general
    • H01F7/021—Construction of PM

Definitions

  • the present invention relates to an anisotropic magnet, and particularly to means for improvement of the surface magnetic field of a working surface of an anisotropic magnet after magnetization. It further relates to a novel method of making such a magnet.
  • the present invention can be effectively used for applications which require strong surface magnetic field and long lines of magnetic force.
  • the application of the present invention is not limited, although it is preferably used forsignal magnets, magnets forfixed displays such as paper, notes and the like, attractive display boards, heath apparatus and the like.
  • Rare earth or ferrite sintered magnets and plastic magnets are generally used for attraction fixing.
  • the magnetic particles in such magnets are oriented in the direction of the magnet thickness, and the magnetic characteristics depend upon the type of raw materials used and the content of the magnetic particles.
  • An anisotropic permanent magnet has been proposed as an improved magnet in Japanese Patent Publication No. 63-59243 in which consideration was given to the direction of orientation of the magnetic particles to improve magnetic characteristics.
  • this magnet the directions of the axes of easy magnetization are focused on and oriented to a working surface from the non-working surfaces.
  • the magnet permits an increase of magnetic flux density (or magnetic flux per unit segment), as compared with previous magnets.
  • the focusing orientation type anisotropic magnet has a greater surface magnetic field than that of an anisotropic magnet, the magnet cannot be satisfactorily used for some applications.
  • the present invention seeks to provide an anisotropic magnet having increased surface magnetic flux density, further to provide a superior magnet at lower cost and still further to provide a novel method of producing a magnet in accordance with the present invention.
  • Other aims of the invention will be understood from the description the present invention below.
  • the present invention provides an internal closed magnetic circuit-type anisotropic magnet comprising a permanent magnet having at least one orientation region of magnetic particles on a working surface comprising a flat or curved surface, wherein the axes of easy magnetization of magnetic particles in the orientation region are passed through the magnet from the edge portion of the orientation region and focused on and oriented to the central portion of the orientation region.
  • the present invention also provides a method of effectively producing such a superior magnet.
  • Fig. 1 shows the lines of magnetic force radiated when a magnet (internal closed magnetic circuit type anisotropic magnet) in accordance with the present invention is attached to a ferromagnetic substance.
  • the magnet of the present invention may have a flat or a curved working surface. This enables the magnet to attract any desired surface and allows the magnet to be applied to a rotor of a precision motor, for example.
  • an orientation region of magnetic particles is formed on the working surface, and the number of orientation regions may be one when the magnet is used simply for attraction.
  • a plurality of orientation regions of magnetic particles may be arranged at constant intervals.
  • the orientation regions may be appropriately physically arranged in accordance with the desired applications.
  • An important characteristic of the present invention is the arrangement of the axes of easy magnetization of the magnetic particles in the orientation region.
  • the axes of easy magnetization of the magnetic particles in magnet 2 of Fig. 1 are oriented along lines which pass through the body of the magnet in direction extending substantially from the edge portion of the orientation region of the magnetic particles to a substantially central portion thereof. This is shown by the dotted lines 1 in Fig 1.
  • the axes of easy magnetization are arranged as substantially concentric rings as if they were arranged along "growth rings" as viewed in a cross section vertical to the working or attracting surface of the magnet.
  • the distribution of the lines of magnetic force in the orientation region shows a pattern of substantially annular rings in correspondence with the axes of easy magnetization, and useless radiation of the lines of magnetic force to the outside is substantially completely prevented.
  • the pattern of the surface magnetic flux density on the working surface of the magnet of the present invention thus has an angularform, which is sharper than that of a conventional axial magnet as shown in Fig. 2(b) and that of a conventional focusing orientation type magnet as shown in Fig. 2(c).
  • Astron- ger surface magnetic flux density can thus be obtained, and the range of the lines of magnetic force is increased.
  • the present invention can be applied to a usual substantially disk-like magnet and to other magnets having various forms including the following:
  • Orientation regions 4 are regularly arranged on the working surface of a substantially annular magnet 2.
  • the orientations of axes of easy magnetization in sections along line A-Aand line B-B in the peripheral direction are as shown in Figs. 3(b) and 3(c), respectively.
  • This arrangement permits the magnet to be advantageously used for a signal.
  • Orientation regions 4 of magnetic particles are provided on the external peripheral surface (Fig. 4(a)) or the internal peripheral surface (Fig. 4(b)) of a substantially cylindrical magnet 2 at a constant pitch in accordance with one form of the present invention.
  • This arrangement permits the magnet to be used advantageously for a signal or a small precision motor, for example.
  • Orientation regions of magnetic particles are provided at a constant pitch or in a geometrical pattern on the upper or lower surface of a plate magnet, which serves as a working surface.
  • the present invention can be preferably applied to general types of plate magnets and to disk-like magnets. This magnet is used forfixing paper or sheet.
  • Orientation regions of magnetic particles are provided on a substantially spherical surface serving as a working surface of a magnet along the longitude lines or parallels thereof, at a constant pitch.
  • This type and arrangement of magnet is preferably used for health improving appliances, for example.
  • orientation regions of magnetic particles can be provided on the projections formed on the spherical surface.
  • the present invention can be applied to either a plastic magnet or a sintered magnet, for example.
  • ferrite magnetic particles such as ferrite magnetic particles, Alnico magnetic particles, rare earth-type magnetic particles such as samarium-cobalt magnetic particles, neodymium-iron-boron magnetic particles and the like can be used as magnetic particles in a plastic magnet or a sintered magnet.
  • the particle size of ferrite magnetic particles is preferably about 1.5 f..lm, as one example, and the particle size of other magnetic particles is preferably about 5 to 50 ⁇ m.
  • resins can be used.
  • Typical examples of such resins include polyamide resins such as polyamide-6, polyamide-12 and the like; vinyl homopolymer or copolymer resins such as polyinyl chloride, vinyl chloride-vinyl acetate copolymers, polyethyl methacrylate, polystyrene, polyethylene, polypropylene and the like; synthetic resins such as polyurethane, silicone, polycarbonate, PBT, PET, polyether ether ketone, PPS, chlorinated polyethylene, Hypalon and the like; synthetic rubbers such as propylene-ethylene rubber, Neoprene, styrene-butadiene rubber, acrylonitrile-butadiene rubber and the like; epoxy resins, and phenolic resins; natural resins such as natural rubber, rosin and coumarone-indene resin.
  • the mix ratio between the magnetic particles and the resin used as a binder is quite variable and depends upon application, the ratio of the magnetic particles is preferably about 40 to 70 vol%.
  • the surface magnetic field is improved by controlling in a novel arrangement the orientation of a magnetic particles in a magnet.
  • FIG. 7 shows a substantially disk-like or square magnet as an example.
  • reference numeral 11 denotes a cavity provided on a magnetic orientation mold
  • reference numeral 12 is a main pole
  • reference numeral 14 is a counter pole
  • reference numeral 15 is a yoke.
  • a the main pole 12 and the counter pole 13 are permanent magnets.
  • electromagnets may be used instead.
  • a plastic magnet may be used consisting magnetic particles and a resin, mixed in a predetermined ratio. The mix is placed in the cavity 11, and the magnetic poles are then disposed at predetermined positions to orientthe axes of easy magnetization of the magnetic particles along the lines of magnetic force 15, as shown by the arrows in Figs. 7(a) and 7(b).
  • a substantially disk-like magnet or a substantially square magnet having a diameter or side of 30 mm and a height of 10 mm was formed by magnetic orientation injection molding or magnetic orientation compression molding.
  • a mold was used having each of the magnetic circuits shown in Figs. 7(a) and 7(b), and 8(a) and 8(b) (which are Comparative Examples).
  • Magnetic particle A ferrite magnetic particle (magneto-plumbite type strontium ferrite with an average particle size of 1.5 ⁇ m)
  • Magnetic particle B samarium-cobalt magnetic particle (Sm 2 Co 17 , average particle size 10 ⁇ m)
  • Synthetic resin polyamide 12
  • TTS isopropyltriisostearoyl titanate
  • Composition P plastic magnet
  • composition S sintered magnet
  • the disk-like magnet formed by the above method was examined with respect to its surface magnetic flux density (peak value) after magnetization and the linear magnetic flux when it was attached to an iron plate. The results obtained are shown in Table 1.
  • linear magnetic flux corresponds to the integral of the magnetic flux distribution at a line on the working surface of a magnet, as illustrated in Fig. 9, and expressed by the following equation:
  • an all internal closed magnetic circuit type anisotropic magnets obtained in accordance with the present invention the surface magnetic flux density on the working surface and the linear magnetic flux on the attraction surface when the magnets are attached to an iron plate are significantly improved, as compared with axial type magnets and focusing orientation type magnets, which are obtained in accordance with conventional methods.
  • the internal closed magnetic circuit anisotropic magnet of the present invention has the advantage with of excellent attraction, as compared with conventional magnets.
  • the internal closed magnetic circuit anisotropic magnet of the present invention has the excellent advantage that substantially no line of magnetic force leaks to the outside and that the peak value of the surface magnetic flux density is extremely high.
  • the magnet of the present invention can also easily be produced.
  • the magnet raw material is provided with fluidity by dispersing magnetic particles therein and is supplied to a magnetic orientation molding machine, and is then molded while a magnetic field is being applied, so that the magnetic particles are oriented along the axes of easy magnetization.
  • a pulsed strong magnetic field may be generated by pulsatively passing a large current through an exciting coil. It is applied to the magnet raw material before the orienting magnetic field is applied for orienting the magnetic particles.
  • a strong magnetic field is applied to a magnet raw material for a short time so as to change only the magnetic direction of each of the magnetic particles with substantially no rotation of the magnetic particles (in the case of a ferrite magnet), or generate a magnetic moment (in the case of a rare earth magnet), thereby arranging the axes of easy magnetization of the magnetic particles within 90° from a direction desirable for the final product (Fig. 10(b)).
  • a different static magnetic field is applied which differs from the pulsed strong magnetic field of the previous step has an intensity that is effective for rotating and moving the magnetic particles.
  • This step-wise method thus enables the production of a magnet containing magnetic particles having small deviations from a desired direction with small required energy because rotation and movement of the magnetic particles in a plastic or in a slurry are very small.
  • Fig. 10(a) is shown immediately after a pulsed strong magnetic field is applied in (Fig. 10(b)), and is shown after an orientation magnetic field is applied in Fig. 10(c).
  • Figs. 10(d) 10(f) schematically show the orientations of the magnetic particles before a magnetic field is applied (Figs. 10(d) and 10 (e)) and after an orientation magnetic field is applied (Fig. 10(f)) when no pulsed strong magnetic field is applied. There is some orientation, but it is not nearly as uniform as it is in Fig. 10(c).
  • Figs. 11(a) - 11(c) also schematically show orientations of magnetic particles before a magnetic field is applied (Fig. 10(a)), immediately after a pulsed strong magnetic field is applied (Fig. 10(b)), and after an orientation magnetic field is applied (Fig. 1 0(c)) when the production method of the present invention is applied to rare earth magnetic particles.
  • Figs. 10(a) - 10(c) schematically show orientations of magnetic particles before a magnetic field is applied (Figs. 10(d) and 10 (e)) and after an orientation magnetic field is applied (Fig. 10(f)) when no pulsed strong magnetic field is applied.
  • the ferrite magnetic particle 21 a shown in Fig. 10(a) has a single magnetic domain structure and manifests the direction of a magnetic moment before the magnetic field is applied.
  • the rare earth magnetic particle 21 b shown in Fig. 11 (a) displays no magnetic moment before the magnetic field is applied because equal magnetic moments in opposite directions are canceled in the particle.
  • a pulsed strong magnetic field is applied to the rare earth magnetic particles in accordance with the present invention, the magnetic moment is manifested.
  • the magnetic moments of the magnetic particles are then easily arranged in the orientation direction by applying the orientation magnetic field is applied thereto.
  • the present invention is thus useful for the case where rare earth magnetic particles having an intrinsic coercive force of at least 5000 oersted is used.
  • compositions may be used as the binder composition for a plastic magnet and the slurry composition for a sintered magnet in order to impart fluidity by dispersing the magnetic particles. Additives may be also appropriately added.
  • the pulsed strong magnetic field is preferably generated by pulsatively passing a large current through an exciting coil.
  • the optimum value of the large current supplied to the exciting coil depends upon the desired orientation direction and the number of turns of the exciting coil. However, the value of the large current is generally at least 100 A, preferably at least 1000 A, and more preferably, in the case of the exciting coil with a small number of turns, it is at least 10000 A.
  • the standard of the magnetomotive force of the exciting coil is 5000 ampere-turn, preferably 15000 ampere-turn.
  • the intensity of the magnetic field generated in the mold by the above large current is preferably 5000 to 15000 oersted.
  • a magnetic field of at least 12000 oersted, preferably at least 15000 oersted, more preferably at least 18000 oersted must be applied for a moment.
  • the direction of application of the pulsed strong magnetic field is preferably the same as that of the subsequent application of the magnetic field for orienting the magnetic particles.
  • the application direction is not necessarily limited.
  • the magnetic field then applied for orienting the magnetic particles is also preferably generated by supplying a current to an exciting coil.
  • the current value is about 30 A which is generally used. It is important to continue the application of the magnetic field until the magnetic particles are solidified in accordance with the shape of the product, the temperature of the heating cylinder of the molding machine used and the temperature of the mold. In a wet sintering method, it is also necessary to continue the application of the magnetic field until a predetermined amount of water has been discharged.
  • the application time of the magnetic field is generally 30 seconds, and at longest 2 minutes, in accordance with the molding method.
  • the combination of a pulse power source and a constant current power source, both of which are separately disposed, is preferably used as the exciting power source because there are differences in the characteristics of the magnetic field applied.
  • Known devices can be used as the power sources.
  • the pulse generating section of the pulse power source may have a voltage up to 2000 V and an electric capacity of 2000 f..lF.
  • Magnetic particle A ferrite magnetic particle
  • magneto-plumbite type strontium ferrite within average particle size of 1.5 ⁇ m, intrinsic coercive force: 3000 oersted
  • Magnetic particle B samarium-cobalt magnetic particle
  • the raw materials for a plastic magnet and a sintered magnet respectively had the following compositions:
  • the molding conditions for the plastic magnet and the sintered magnet were the following:
  • Molding condition B sintered magnet
  • An exciting power source of 2000 V and 1500 mF was used for applying a pulsed strong magnetic field, and a thick exciting coil of 2 turns was used, various values of currents being applied thereto.
  • An exciting power source for then applying an orientation magnetic field was separately provided, and a current of 30 Awas supplied to an exciting coil of 300 turns.
  • a forced cooling jacket was provided on each of the exciting coils so as to cool it with cooling water at 10°C.
  • the surface magnetic flux density of each of the magnets obtained is shown in Table 2 together with the pulsed magnetic field application conditions.
  • a magnet raw material which was provided with fluidity by dispersing magnetic particles therein was supplied to the magnetic orientation molding machine, and a pulsed strong magnetic field generated by pulsatively passing a large current through the exciting coil was applied to the magnet raw material before the magnetic particles were oriented along the axes of easy magnetization thereof by molding the raw material while applying a magnetic field thereto. It was thus possible to easily orient the axes of easy magnetization of the magnetic particles in a predetermined direction and to improve the magnetic characteristics of the magnet produced.
  • the application of the method is not limited to the internal closed magnetic circuit type magnet to which the present invention relates. It is a matter of course that the method can be widely applied to production of various anisotropic magnets.
  • the present invention thus permits significant improvement in the surface magnetic flux density on the working surface of a magnet, the range of lines of magnetic force and the linear magnetic flux thereof.
  • the present invention also permits the formation of an excellent surface magnetic field even in a ferrite synthetic magnet, as compared with that of a conventional sintered magnet.
EP19920308844 1991-09-30 1992-09-29 Internal closed magnetic circuit anisotropic magnet and method Withdrawn EP0535902A3 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
JP25161091 1991-09-30
JP251610/91 1991-09-30
JP30631091A JPH05144650A (ja) 1991-11-21 1991-11-21 磁石の製造方法
JP306310/91 1991-11-21
JP11172192 1992-04-30
JP111721/92 1992-04-30

Publications (2)

Publication Number Publication Date
EP0535902A2 true EP0535902A2 (fr) 1993-04-07
EP0535902A3 EP0535902A3 (en) 1993-11-03

Family

ID=27312027

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920308844 Withdrawn EP0535902A3 (en) 1991-09-30 1992-09-29 Internal closed magnetic circuit anisotropic magnet and method

Country Status (1)

Country Link
EP (1) EP0535902A3 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1063659A2 (fr) * 1999-06-22 2000-12-27 Toda Kogyo Corporation Aimant permanent anisotropique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2833517A1 (de) * 1977-08-01 1979-02-08 Matsushita Electric Ind Co Ltd Magnetsystem
JPS5613705A (en) * 1979-07-16 1981-02-10 Matsushita Electric Ind Co Ltd Magnetic circuit using anisotropic magnet
JPS6427208A (en) * 1987-04-07 1989-01-30 Hitachi Metals Ltd Cylindrical permanent magnet, motor using same and manufacture thereof
US4954800A (en) * 1986-05-20 1990-09-04 Canon Kabushiki Kaisha Magnet and method of manufacturing the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2833517A1 (de) * 1977-08-01 1979-02-08 Matsushita Electric Ind Co Ltd Magnetsystem
JPS5613705A (en) * 1979-07-16 1981-02-10 Matsushita Electric Ind Co Ltd Magnetic circuit using anisotropic magnet
US4954800A (en) * 1986-05-20 1990-09-04 Canon Kabushiki Kaisha Magnet and method of manufacturing the same
JPS6427208A (en) * 1987-04-07 1989-01-30 Hitachi Metals Ltd Cylindrical permanent magnet, motor using same and manufacture thereof

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 13, no. 216 (E-760)19 May 1989 & JP-A-01 027 208 ( HITACHI METALS LTD. ) 30 January 1989 *
PATENT ABSTRACTS OF JAPAN vol. 5, no. 63 (E-54)(735) 28 April 1981 & JP-A-56 013 705 ( MATSUSHITA DENKI SANGYO K.K. ) 10 February 1981 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1063659A2 (fr) * 1999-06-22 2000-12-27 Toda Kogyo Corporation Aimant permanent anisotropique
EP1063659A3 (fr) * 1999-06-22 2001-04-18 Toda Kogyo Corporation Aimant permanent anisotropique

Also Published As

Publication number Publication date
EP0535902A3 (en) 1993-11-03

Similar Documents

Publication Publication Date Title
EP0535901A2 (fr) Aimant anisotropique à orientation latérale
EP0181597B1 (fr) Procédé de fabrication d'un aimant permanent
JPS6427208A (en) Cylindrical permanent magnet, motor using same and manufacture thereof
US3985588A (en) Spinning mold method for making permanent magnets
JP3007491B2 (ja) 側面配向型異方性磁石
US4702852A (en) Multipolarly magnetized magnet
EP0535902A2 (fr) Aimant anisotrope à circuit magnétique interne fermé et procédé
JP2769061B2 (ja) 極異方配向磁石
GB1447264A (en) Polymer bonded magnets
Gardocki et al. Improvement of the filler orientability during injection molding of multi-polar SmCo-magnets by premagnetization
EP0295744B1 (fr) Rotor multipolaire
JP3007492B2 (ja) 内面閉磁路型異方性磁石
KR100385597B1 (ko) 소형모터및그에사용되는로터본체의제조방법
JP7381851B2 (ja) 円筒状ボンド磁石の製造方法、円筒状ボンド磁石成形用金型、および円筒状ボンド磁石
GB2069766A (en) Improvements in or relating to methods of producing anisotropic permanent magnets and magnets produced by such methods
JP2001167963A (ja) 磁石の製造方法及び磁石成形金型
JPH06349630A (ja) 異方性磁石
JP2002030304A (ja) ラジアル磁場成形方法とその成形装置
JPH01124208A (ja) 径方向２極磁石の製造方法
JPH0624176B2 (ja) 極異方性長尺成形品の製造方法
JP2002198216A (ja) シート磁石及びその着磁方法
JPS6037112A (ja) 異方性複合磁石の製造方法
JPS60931B2 (ja) 異方性磁石の製造方法及び製造装置
CN1627094A (zh) 具有相对永磁体的磁路及调整其磁场的方法
JPS62232107A (ja) 異方性樹脂磁石およびその製造方法

Legal Events

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

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): DE FR NL

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): DE FR NL

17P Request for examination filed

Effective date: 19940208

18W Application withdrawn

Withdrawal date: 19950505

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

R18W Application withdrawn (corrected)

Effective date: 19950505