US3765881A - Method of making metal-carbon brushes for electrical motors - Google Patents

Method of making metal-carbon brushes for electrical motors Download PDF

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Publication number
US3765881A
US3765881A US00265971A US3765881DA US3765881A US 3765881 A US3765881 A US 3765881A US 00265971 A US00265971 A US 00265971A US 3765881D A US3765881D A US 3765881DA US 3765881 A US3765881 A US 3765881A
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United States
Prior art keywords
graphite
bodies
weight
sifted
powder
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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US00265971A
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English (en)
Inventor
M Scholpp
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Robert Bosch GmbH
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Robert Bosch GmbH
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Publication date
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/0084—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ carbon or graphite as the main non-metallic constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
    • H01R43/00—Apparatus or processes specially adapted for manufacturing, assembling, maintaining, or repairing of line connectors or current collectors or for joining electric conductors
    • H01R43/12—Manufacture of brushes
    • 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
    • Y10T29/49117—Conductor or circuit manufacturing
    • Y10T29/49119—Brush

Definitions

  • ABSTRACT Leaf graphite is compressed to form bodies having a gross density of at least 1.5 g/cm.
  • the bodies are then comminuted in a cone-mill to obtain a raw graphite powder whose particles are of essentially ball-shaped configuration and which is then screened or sifted to have a particle size distribution between 50 and 400 microns.
  • the sifted powder is admixed with a predetermined percentage by weight of powdered copper and the mixture compressed to form a brush body, which is sintered to obtain a finished metal-carbon brush.
  • Brushes of the type here under discussion are well known and are used particularly frequently in starter motors for combustion engines. They are made from a ficient mechanical strength and to give it sufficientlyhigh electrical conductivity.
  • This percentage relationship of metal powder relative to the graphite powder applies if the graphite is natural graphite of a flake or leaf type. If the very rare type of natural graphite is used which is of the stalky or spiky characteristic rather than of the flaky or leafy type, then it is possible to reduce the metal content of the mixture from which such brushes are formed, to between 60 and 65 percent by weight. The reason for this is that this second type of graphite prevents the formation of layers without copper-copper contact or metalmetal contact, and of parallel orientation, so that despite the lesser metal content a metal penetration lattice is obtained, affording the necessary structural strength and electrical conductivity.
  • a metal-carbon brush made in this manner that is with the second type of graphite, has actually greater mechanical strength than if the leaf type of graphite is utilized; particularly it has greater cleavage strength. Due to the lesser metal content, such brushes have a higher life expectancy.
  • metal-carbon brushes in which the carbon is supplied by spiky graphite.
  • the present invention resides in a method of making metalcarbon brushes for electrical motors from leaf graphite, which briefly stated comprises the steps of compressing leaf graphite to form bodies having a gross density of at least 1.5 g/cm. Thereupon the thus formed bodies are comminuted to obtain a raw graphite powder composed of particles having essentially ball-shaped configuration. The raw graphite powder is sifted or screened in order to obtain a sifted powder having a particle size distribution between substantially 50 400 microns which is then admixed with a predetermined percentage by weight of powdered copper. The resulting mixture is compressed to form a brush body therefrom and this brush body is then sintered in order to obtain a finished metal-carbon brush.
  • the starting graphite material a leaf-type standard graphite having a carbon content 2 96 percent with a particle size of between 5 and 80 micron.
  • the pressure to which this graphite is subjected in order to compress it into the bodies which are subsequently to be comminuted is between substantially l 5 t/cm, and the maximum particle size distribution of the sifted graphite powder should be between substantially 180 and 220 micron.
  • FIGURE is a flow diagram illustrating the steps in the manufacture of brushes according to the present method.
  • flaky graphite is first compressed and compacted under pressure of approximately 3t/cm in order to obtain pressed bodies, such as tablets or the like. These bodies are then introduced into a cone mill, cone grinder or bell crusher where they are comminuted in order to obtain ground graphite powder whose particles are of substantially ball-shaped configuration.
  • the desired particle configuration can be favorably influenced by rotating the cone mill between substantially 60 and r.p.m.
  • the ground graphite powder is now sifted or screened in order to obtain a particle size distribution of between -50 and 400 micron, with a maximum or optimum of about 200 micron.
  • a quantity of it, amounting to 42 percent by weight of the mixture to be produced, may be admixed with 58 percent by weight of powdered metal, usually powdered copper.
  • the resulting mixture is then compressed to form a brush body, at a pressure of about 4 t/cm, and the resulting pressed brush body in sintered at about 750 C.
  • Another possibility is to admix the sifted powder in a ratio of 42 percent by weight with 55 percent by weight of powdered copper or metal, and 3 percent by weight of pitch, the latter serving as a binder.
  • the resulting mixture is then again compressed to form brush bodies, under a pressure of 4 t/cm and the bodies are sintered at about 500 C.
  • a standard graphite of the leaf or flake type having a carbon content of 98 percent by weight and a particle size of 5-80 micron.
  • Such graphite is commercially available.
  • When compressed to form tablets or the like it is subjected, as pointed out before, to a pressure of about 3 tlcm and the resulting tablets or bodies have a gross density of about 2 glcm
  • These tablets are then comminuted in a cone mill or hell crusher of the type well known to those skilled in the art, and described in the literature as far back as 1932 (Ullmann, Enzyklopaedie der ischen Chemie," 1932, Volume 10, pages 590 ff.).
  • the sifted or screened graphite powder which is composed largely of substantially ball-shaped particles, is then admixed with metal according to one of the two possibilities indicated in the flow sheet. It may be admixed in a ratio of 42 percent by weight of graphite powder with 58 percent by weight of powdered copper, and compressed in a press die whose internal configuration corresponds to the form of the brush body to be produced, at a pressure of 4 t/cm.
  • the compressed brush body Upon completion of the compressing the compressed brush body is removed from the die and is sintered for approximately one hour at a temperature of approximately 750 C. under a protective gas, for instance nitrogen or a gas mixture composed essentially of hydrogen, methane, and carbon monoxide.
  • a protective gas for instance nitrogen or a gas mixture composed essentially of hydrogen, methane, and carbon monoxide.
  • percent by weight of the sifted graphite powder are admixed with 55 percent by weight of powdered copper and with 3 percent by weight of pitch.
  • the latter serves as a binder.
  • the mixture is then compressed in a die at a pressure of 4 t/cm to obtain a blank or body having the configuration desired for the finished brush.
  • This blank or body is then sintered for approximately 1 hour under a protective gas (see above) and at a temperature of 500 C.
  • a protective gas see above
  • metal-carbon brushes produced in accordance with the present method have been carried out on metal-carbon brushes produced in accordance with the present method, and detailed structural examinations have been made. All of these have confirmed that, using graphite powder produced in accordance with the present invention and employing this graphite powder with the percentages of powdered copper which have been set forth herein, an integral copper penetration lattice is obtained in the finished metal-carbon brush. Furthermore, it has been established that metal-carbon brushes made in accordance with the present invention have a mechanical strength and a life expectancy, as well as an electrical conductivity, which have heretofore been impossible of achievement with other mixtures except those using the rare spike-type graphite.
  • a further advantage of the method according to the present invention, utilizing the graphite prepared in accordance with the present invention, is that the details of the mixing and compressing techniques employed are of much less significance in terms of obtaining metal-carbon brushes having the desired characteristics, than in the approaches known from the prior art.
  • the present invention thus makes it possible to produce improved metal-carbon brushes which have superior characteristics and are less expensive to make because they can be made with graphite types which are readily available, quite aside from the fact that the method eliminates the dependency upon the importation of graphite types (spiky-type natural graphite) from sources which might at any time become unavailable, for instance in the event of political crises. Moreover, the present invention permits the manufacture of metal-carbon brushes of superior characteristics in a simpler manner than heretofore possible, certainly in terms of the elimination of the necessity for previously required close control of mixing and pressing technique parameters.
  • a method of making metal-carbon brushes for electrical motors from leaf graphite comprising the steps of compressing leaf graphite to form bodies having a gross density of at least 1.5 g/cm; comminuting the thus formed bodies to obtain a raw graphite powder composed of particles having essentially ball-shaped configuration; sifting the raw graphite powder to obtain a sifted powder having a particle size distribution between substantially 50 and 400 microns; admixing the sifted graphite powder with a predetermined percentage by weight of powdered copper; compressing the resulting mixture to form a brush body therefrom; and sintering said brush body to obtain a finished metalcarbon brush.
  • step of compressing leaf graphite comprises utilizing a leaf graphite having a carbon content 2 96 percent by weight and a particle size of between substantially 5 and 80 microns.
  • a method as defined in claim 1, wherein the step of compressing leaf graphite comprises subjecting said leaf graphite to pressure of between substantially l and 5 t/cm 4.
  • a method as defined in claim 1, wherein the-step of comminuting comprises comminuting said bodies in a cone mill so as to obtain graphite powder whose particles are of said essentially ball-shaped configuration.
  • a method as defined in claim 5, wherein comminuting of said bodies in a cone mill comprises rotating the cone mill at substantially 6O RPM.
  • step of sifting comprises sifting the raw graphite powder to obtain a sifted powder having an optimum particle size distribution of between substantially and 220 microns.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Motor Or Generator Current Collectors (AREA)
  • Manufacturing Of Electrical Connectors (AREA)
  • Conductive Materials (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
US00265971A 1971-07-16 1972-06-26 Method of making metal-carbon brushes for electrical motors Expired - Lifetime US3765881A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2135537A DE2135537C3 (de) 1971-07-16 1971-07-16 Verfahren zur Herstellung von Graphit für Metallkohlebürsten

Publications (1)

Publication Number Publication Date
US3765881A true US3765881A (en) 1973-10-16

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ID=5813854

Family Applications (1)

Application Number Title Priority Date Filing Date
US00265971A Expired - Lifetime US3765881A (en) 1971-07-16 1972-06-26 Method of making metal-carbon brushes for electrical motors

Country Status (5)

Country Link
US (1) US3765881A (de)
JP (1) JPS5528194B1 (de)
DE (1) DE2135537C3 (de)
FR (1) FR2146747A5 (de)
GB (1) GB1396943A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892833A (en) * 1972-11-10 1975-07-01 Matsushita Electric Ind Co Ltd Method of making an ion-selective electrode
US4126673A (en) * 1977-05-13 1978-11-21 Cromwell Metals, Inc. Method for processing dross
US4293450A (en) * 1978-04-18 1981-10-06 Vogel F Lincoln Process for conducting electricity utilizing a specifically defined graphite intercalation compound
USRE31028E (en) * 1977-05-13 1982-09-14 Cromwell Metals, Inc. Method for processing dross
US20150307765A1 (en) * 2011-01-26 2015-10-29 Shinko Electric Industries Co., Ltd. Method of manufacturing metal composite material, metal composite material, method of manufacturing heat dissipating component, and heat dissipating component

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4220884A (en) * 1978-05-01 1980-09-02 Trw Inc. Carbon brush for motors and method of making the same

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2844544A (en) * 1955-03-08 1958-07-22 Union Carbide Corp Additive for copper graphite brush
US2974039A (en) * 1951-02-05 1961-03-07 Deventor Max Molding of metal powders
US3666688A (en) * 1968-11-27 1972-05-30 Airco Inc Tamping material

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2974039A (en) * 1951-02-05 1961-03-07 Deventor Max Molding of metal powders
US2844544A (en) * 1955-03-08 1958-07-22 Union Carbide Corp Additive for copper graphite brush
US3666688A (en) * 1968-11-27 1972-05-30 Airco Inc Tamping material

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892833A (en) * 1972-11-10 1975-07-01 Matsushita Electric Ind Co Ltd Method of making an ion-selective electrode
US4126673A (en) * 1977-05-13 1978-11-21 Cromwell Metals, Inc. Method for processing dross
USRE31028E (en) * 1977-05-13 1982-09-14 Cromwell Metals, Inc. Method for processing dross
US4293450A (en) * 1978-04-18 1981-10-06 Vogel F Lincoln Process for conducting electricity utilizing a specifically defined graphite intercalation compound
US20150307765A1 (en) * 2011-01-26 2015-10-29 Shinko Electric Industries Co., Ltd. Method of manufacturing metal composite material, metal composite material, method of manufacturing heat dissipating component, and heat dissipating component
US9920232B2 (en) * 2011-01-26 2018-03-20 Shinko Electric Industries Co., Ltd. Method of manufacturing metal composite material, metal composite material, method of manufacturing heat dissipating component, and heat dissipating component

Also Published As

Publication number Publication date
DE2135537A1 (de) 1973-02-01
JPS4820005A (de) 1973-03-13
GB1396943A (en) 1975-06-11
FR2146747A5 (de) 1973-03-02
DE2135537C3 (de) 1978-07-06
DE2135537B2 (de) 1977-11-24
JPS5528194B1 (de) 1980-07-25

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