US2751525A - Permanent magnet - Google Patents

Permanent magnet Download PDF

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Publication number
US2751525A
US2751525A US441549A US44154954A US2751525A US 2751525 A US2751525 A US 2751525A US 441549 A US441549 A US 441549A US 44154954 A US44154954 A US 44154954A US 2751525 A US2751525 A US 2751525A
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US
United States
Prior art keywords
magnet
shaft
cement
permanent magnet
sleeve
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
Application number
US441549A
Inventor
Hekelaar Maarten
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.)
Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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.)
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Publication date
Application filed by Hartford National Bank and Trust Co filed Critical Hartford National Bank and Trust Co
Application granted granted Critical
Publication of US2751525A publication Critical patent/US2751525A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/27—Rotor cores with permanent magnets
    • H02K1/2706—Inner rotors
    • H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
    • H02K1/2726—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of a single magnet or two or more axially juxtaposed single magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/10—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure
    • 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
    • Y10T29/49075—Electromagnet, transformer or inductor including permanent magnet or core

Definitions

  • the invention relates to a bored permanent magnet consisting of magnetic oxidic material having a high retentivity and a high coercivity of the formula MFemOrs, where M represents one or more of the metals Ba, Sr or Pb, a shaft being secured in the bore provided in the permanent magnet by means of a cement.
  • the space between the magnet and the shaft is completely filled by the cement.
  • the cement may be provided with a filler to enable undue hollow spaces of the bore to be filled.
  • a sleeve is arranged in the bore so as to surround the shaft, which sleeve is made of non-porous material and is secured to the permanent magnet and to the shaft with the aid of a cement.
  • the advantage is obtained that the cement provided between the shaft and the sleeve is protected from the action of detrimental substances by the sleeve made of non-porous material so that in this event the cementing properties are completely maintained.
  • this attachment is very important, since in the loaded condition the greatest stresses are produced at this point. It is true that the cement layer provided between the sleeve and the permanent magnet according to the invention are not protected from detrimental substances, however, this is not inconvenient since at this point the attachment is effected at a much larger diameter with the result that in the loaded condition the stresses produced at this point are much smaller than in the cement layer provided between the shaft and the sleeve. For the same reason the absorption of the cement by the porous magnetic material which may occur does not inconveniently aifect the attachment of the magnet to the sleeve.
  • the diameter of the bore formed in the permanent magnet may be made such that any stresses which may be produced in the cement layer provided between the shaft and the magnet do not exceed the maximum stress which nited States Patent Patenteddune 19, 1956 the cement is able to absorb after the absorption of substances detrimentally affecting the cementing properties and/or after the absorption of the cement by the magnetic material.
  • the sleeve may be made of a non-porous ceramic material, since this material is very cheap and a cement readily adheres to it.
  • the cement consists of a synthetic resin, for example the one known under the name of Araldite.
  • the difference in diameter between the magnet and the sleeve and between the sleeve and the shaft is about 0.3 mm. while the diameter of the bore formed in the magnet is about two times the diameter of the shaft.
  • a permanent magnet 1 of the kind to which the invention relates is provided with a bore 2.
  • a sleeve 3 made of non-porous ceramic material is secured in the bore 2 by means of a layer 4 of ethoxyline resin arranged between the sleeve 3 and the permanent magnet 1.
  • a shaft 5 preferably made of metal is secured in the sleeve 3 also by means of a layer 6 of ethoxyline resin.
  • Ferroxdure The material known under the name of Ferroxdure is fully described in Philips Technical Review, vol. 13, No. 7, pages 194-208. It is an oxidic material composed of hexagonal crystals having a composition MFeizOis in which M is one or more of the metals barium, strontium or lead and in which a portion of one of those latter metals may be replaced by calcium.
  • a cement known under the name of Araldite is a condensation product 2,2'-diphenylolpropane and epichlorohydrin.
  • compositions of suitable ceramic materials for the sleeve are e. g.
  • the permanent magnets in accordance with the invention may, for example, be used in electric motors or electric generators in which permanent magnets rotate.
  • the magnets in accordance with the invention may also be used for magnetic couplings.
  • a hollow cylindrical permanent magnet defining a central bore, said magnet consisting essentially of a composition MFerzOrs, M being a metal selected from the group consisting of barium, strontium, and lead, said magnet having a high retentivity and coercivity, a shaft centrally disposed within said bore and extending substantially parallel to the central axis of said magnet, and a cylindrical sleeve of a dense non-porous ceramic material disposed between and secured to the shaft and the magnet by cement.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)

Description

June 19, 1956 M. HEKELAAR 2,751,525
PERMANENT MAGNET Filed July 6, 1954 INVENT MAARTEN H LAAR BY W MW PERMANENT MAGNET Maarten Hekelaar, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 6, 1954, Serial No. 441,549
tllaims priority, application Netherlands July 24, 1953 4 Claims. (Cl. 317-201) The invention relates to a bored permanent magnet consisting of magnetic oxidic material having a high retentivity and a high coercivity of the formula MFemOrs, where M represents one or more of the metals Ba, Sr or Pb, a shaft being secured in the bore provided in the permanent magnet by means of a cement.
In a known manner of securing a permanent magnet to a shaft the space between the magnet and the shaft is completely filled by the cement. If required, the cement may be provided with a filler to enable undue hollow spaces of the bore to be filled.
It has been found that the known attachment for a permanent magnetic material of the kind to which the invention relates does not fulfill the requirements which this attachment must satisfy. This is due to the fact that the above-mentioned permanent magnetic material is porous with the result that during the securing process a large part of the cement is absorbed by the permanent magnetic material. Consequently the magnets will work loose from the shaft in course of time. In addition the cement will be able via the porous magnetic material to absorb substances from its surroundings, for example, moisture or oil, with the result that the cementing properties will be detrimentally affected. These detrimental effects will be more important as the diameter of the shaft is smaller, since when a load is imposed the stresses produced in the attachment of the shaft to the magnet will be greatest at the smallest diameter, that is at the point at which the cement is secured to the shaft.
According to the invention, in order to obviate the above difficulties, a sleeve is arranged in the bore so as to surround the shaft, which sleeve is made of non-porous material and is secured to the permanent magnet and to the shaft with the aid of a cement.
Thus, the advantage is obtained that the cement provided between the shaft and the sleeve is protected from the action of detrimental substances by the sleeve made of non-porous material so that in this event the cementing properties are completely maintained. As has been explained hereinbefore, this attachment is very important, since in the loaded condition the greatest stresses are produced at this point. It is true that the cement layer provided between the sleeve and the permanent magnet according to the invention are not protected from detrimental substances, however, this is not inconvenient since at this point the attachment is effected at a much larger diameter with the result that in the loaded condition the stresses produced at this point are much smaller than in the cement layer provided between the shaft and the sleeve. For the same reason the absorption of the cement by the porous magnetic material which may occur does not inconveniently aifect the attachment of the magnet to the sleeve.
The diameter of the bore formed in the permanent magnet may be made such that any stresses which may be produced in the cement layer provided between the shaft and the magnet do not exceed the maximum stress which nited States Patent Patenteddune 19, 1956 the cement is able to absorb after the absorption of substances detrimentally affecting the cementing properties and/or after the absorption of the cement by the magnetic material.
The sleeve may be made of a non-porous ceramic material, since this material is very cheap and a cement readily adheres to it. Preferably the cement consists of a synthetic resin, for example the one known under the name of Araldite. In a preferred embodiment the difference in diameter between the magnet and the sleeve and between the sleeve and the shaft is about 0.3 mm. while the diameter of the bore formed in the magnet is about two times the diameter of the shaft.
The invention will now be described with reference to the accompanying drawing in which a sectional view of one embodiment of a permanent magnet secured to a shaft is shown diagrammatically. A permanent magnet 1 of the kind to which the invention relates is provided with a bore 2. A sleeve 3 made of non-porous ceramic material is secured in the bore 2 by means of a layer 4 of ethoxyline resin arranged between the sleeve 3 and the permanent magnet 1. A shaft 5 preferably made of metal is secured in the sleeve 3 also by means of a layer 6 of ethoxyline resin. In one embodiment in which the attachment of a permanent magnet made of a material known under the name of Ferroxdure to a metal shaft of a bicycle dynamo is constituted in accordance with the invention by a sleeve made of ceramic material sintered to compactness and by a cement known under the name of Araldite, it was found that this attachment collapsed only after a load of 1 /2 tons was imposed on it.
The material known under the name of Ferroxdure is fully described in Philips Technical Review, vol. 13, No. 7, pages 194-208. It is an oxidic material composed of hexagonal crystals having a composition MFeizOis in which M is one or more of the metals barium, strontium or lead and in which a portion of one of those latter metals may be replaced by calcium.
A cement known under the name of Araldite is a condensation product 2,2'-diphenylolpropane and epichlorohydrin.
Compositions of suitable ceramic materials for the sleeve are e. g.
76.2% powdered steatite 12.6% clay 7.9% barium carbonate 3.3% magnesite sintered at 1320 C., and
47.9% kaolin 15.9% clay 18.3% feldspar 17.9% quartz sintered at 1320 C.
The permanent magnets in accordance with the invention may, for example, be used in electric motors or electric generators in which permanent magnets rotate. The magnets in accordance with the invention may also be used for magnetic couplings.
What is claimed is:
1. In combination, a hollow cylindrical permanent magnet defining a central bore, said magnet consisting essentially of a composition MFerzOrs, M being a metal selected from the group consisting of barium, strontium, and lead, said magnet having a high retentivity and coercivity, a shaft centrally disposed within said bore and extending substantially parallel to the central axis of said magnet, and a cylindrical sleeve of a dense non-porous ceramic material disposed between and secured to the shaft and the magnet by cement.
2. The combination as claimed in claim 1 in which the diameter of the bore provided in the magnet is apthe cement consists of a synthetic resin. proximately 2 times the diameter of the shaft.
3. The combination as claimed in claim 1 in which the difference in diameter between the magnet and the References Cited 111 the file of thls patent sleeve and between the sleeve and the shaft is approxi- 5 UNITED STATES PATENTS infeterlgsgf min, the cement being constltuted by ethoxy- 2,475,321 Horn July 5, 1949 4. The combination as claimed in claim 1 in which 2543551 Krug 1951

Claims (1)

1. IN COMBINATION, A HOLLOW CYLINDRICAL PERMANENT MAGNET DEFINING A CENTRAL BORE, SAID MAGNET CONSISTING ESSENTIALLY OF A COMPOSITION MFE12O19, M BEING A METAL SELECTED FROM THE GROUP CONSISTING OF BARIUM, STRONTIUM, AND LEAD, SAID MAGNET HAVING A HIGH RETENTIVITY AND COERCIVITY, A SHAFT CENTRALLY DISPOSED WITHIN SAID BORE AND EXTENDING SUBSTANTIALLY PARALLEL TO THE CENTRAL AXIS OF SAID MAGNET, AND A CYLINDRICAL SLEEVE OF A DENSE NON-POROUS
US441549A 1953-07-24 1954-07-06 Permanent magnet Expired - Lifetime US2751525A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL2751525X 1953-07-24

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2972784A (en) * 1958-03-04 1961-02-28 Arthur S La Pine & Company Method of encapsulating a magnet with polytetrafluoroethylene
US2999275A (en) * 1958-07-15 1961-09-12 Leyman Corp Mechanical orientation of magnetically anisotropic particles
US3014751A (en) * 1958-01-27 1961-12-26 Cloyd D Smith Magnetic device
US3029824A (en) * 1957-07-26 1962-04-17 Standard Packaging Corp Smoker's article
US3090107A (en) * 1958-07-24 1963-05-21 Sylvania Electric Prod Method of making a permanent magnet
US3737987A (en) * 1969-11-21 1973-06-12 Black & Decker Mfg Co Method of making an insulated armature
US3737988A (en) * 1969-11-21 1973-06-12 Black & Decker Mfg Co Method of bonding armature sub-assemblies
US3778892A (en) * 1972-08-04 1973-12-18 Black & Decker Mfg Co Method of producing double-insulated armature sub-assemblies
US4264683A (en) * 1978-07-26 1981-04-28 Permacoraltair, Inc. Metallic inductor cores

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2475321A (en) * 1943-06-22 1949-07-05 Henry L Crowley Molded core
US2543551A (en) * 1948-06-10 1951-02-27 Stackpole Carbon Co Variable inductance core structure

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2475321A (en) * 1943-06-22 1949-07-05 Henry L Crowley Molded core
US2543551A (en) * 1948-06-10 1951-02-27 Stackpole Carbon Co Variable inductance core structure

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3029824A (en) * 1957-07-26 1962-04-17 Standard Packaging Corp Smoker's article
US3014751A (en) * 1958-01-27 1961-12-26 Cloyd D Smith Magnetic device
US2972784A (en) * 1958-03-04 1961-02-28 Arthur S La Pine & Company Method of encapsulating a magnet with polytetrafluoroethylene
US2999275A (en) * 1958-07-15 1961-09-12 Leyman Corp Mechanical orientation of magnetically anisotropic particles
US3090107A (en) * 1958-07-24 1963-05-21 Sylvania Electric Prod Method of making a permanent magnet
US3737987A (en) * 1969-11-21 1973-06-12 Black & Decker Mfg Co Method of making an insulated armature
US3737988A (en) * 1969-11-21 1973-06-12 Black & Decker Mfg Co Method of bonding armature sub-assemblies
US3778892A (en) * 1972-08-04 1973-12-18 Black & Decker Mfg Co Method of producing double-insulated armature sub-assemblies
US4264683A (en) * 1978-07-26 1981-04-28 Permacoraltair, Inc. Metallic inductor cores

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