US3458351A - Protection of electrical contacts - Google Patents

Protection of electrical contacts Download PDF

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Publication number
US3458351A
US3458351A US376520A US3458351DA US3458351A US 3458351 A US3458351 A US 3458351A US 376520 A US376520 A US 376520A US 3458351D A US3458351D A US 3458351DA US 3458351 A US3458351 A US 3458351A
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United States
Prior art keywords
contact
contacts
substances
silicone
molecule
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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US376520A
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English (en)
Inventor
Fritz Held
Edmund Bolz
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Gesellschaft zur Foerderung der Forschung an der Eidgenoessischen Technischen Hochschule
Original Assignee
Gesellschaft zur Foerderung der Forschung an der Eidgenoessischen Technischen Hochschule
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
    • H01B3/46—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes silicones
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/60—Auxiliary means structurally associated with the switch for cleaning or lubricating contact-making surfaces

Definitions

  • the present invention is concerned with a process for the protection of electrical contacts, especially in communication and control equipment.
  • the function of electric contacts is the joining together of two electric leads at any given time or the separation of such leads or the. connection or disconnection of a source of current. After connection has been made, the touching pair of contacts forms a component part of the electrical lead which requires that the passage of current at the point of contact must not be hindered.
  • the measurable contact resistances are low and vary approximately between 5-20ai2.
  • even small increases of this contact resistance may be disturbiugly noticeable when an electric circuit requires several or many such contacts, as is outstandingly the Case in, for example, automatic telephone exchanges and many kinds of electrical control devices.
  • the greatest part of the expenditure of time for the maintenance of such devices or equipment is due to the increased contact resistances. It is, therefore, not surprising that for a very long time a great deal of attention has been paid to this problem.
  • this substance deposition exceeds thel contact surfaces by several orders of magnitude. Since this substance deposition is continuously maintained, on the one hand, by condensation and, on the other hand, by contact with synthetic resins which contain volatile components, an availability of substances is ensured. There are also to be mentioned again residues of substances which have served as auxiliaries during the production.
  • This measure of cutting off or screening the surface tension is a process which is frequently used in the horological industry and is called epilamisation.
  • This process consists in that a thin layer of, for example, a saturated, straight-chained hydrocarbon containing -20 carbon atoms which has a terminal polar group, for example a carboxylic acid group, such as stearic acid, a substance frequently used for this purpose is applied on the surface to be protected.
  • This thin layer is called epilam.
  • the protective effect is hereby twofold: the surface tensional forces are weakened by partial neutralisation by the polar groups and spaced out by the hydrocarbon chains standing vertically to the surface.
  • Liquid silicones which are finding an ever increasing use in the most varied kinds of preparations, such as mould release agents, fioor polishes, furniture polishes, hand creams and the like, exhibit, according to the molecular weight, a surface tension of 17-21 dyne cm.”l and the spreading thereof cannot be prevented by any physically-acting epilam in the described manner.
  • the solution of the problem posed was found in the process according to the present invention which essentially consists in that the surfaces surrounding the actual contact surfaces of the constructional elements having the contacts are covered with a protective layer of a solid polymeric compound which contains Si bonds.
  • a protective layer of this kind makes surfaces non-wettable by organic liquids and, at the same time, is able to chemically transform liquid silicone compounds so that they lose their mobility.
  • the protective layer can expediently be formed from a pure silicone resin or a solid organic polymeric compound containing a silicone resin, in that a thin to thinnest possible coating of a dilute solution of the polymeric compound is applied on to the surface to be treated by any of the known lacquering technics and then allowed to dry.
  • the molecules of liquid silicones are chemically bound to the cross-linked compound forming the protective layer in such a manner that they become a component part of the compound.
  • the mobility of the silicone molecule is thus removed and its transport to the contact prevented. Since the activity of the layer can be maintained over a long period of time and this protective layer is also non-wettable by non-silicone oils, the problem of the protection of contacts against contamination by liquids can be regarded as being solved by the process according to the present invention. Because of its getter action, the protective layer produced by the process according to the present invention is, in the following, referred to in this sense as a getter layer.
  • FIGURE 1 shows schematically the splitting of an Si-O bond and the exchanged combination of the parts produced by the splitting
  • FIGURE 2 shows, in principle, the same as FIGURE l but with an indication of the mechanism in the presence of a catalyst (electron-theoretical explanation);
  • FIGURES 3-5 show schematically the course of the formation of the binding of a linear, polymeric siloxane to a cross-linked polysiloxane (getter layer).
  • a silicone resin 5% of a silicone resin is dissolved in a halogenated hydrocarbon, for example, perchloroethylene.
  • a halogenated hydrocarbon for example, perchloroethylene.
  • the resultant liquid lacquer is applied, with the aid of a buckskin dipped therein, in a thin layer to the whole surface of a constructional element having contacts up to a distance of about 4 cm. from the contacts.
  • the layer is removed, by means of a fine le, from the actual contact surfaces where electric contact is to be made, but not f-rom the surfaces of the contacts and leads so that finally the lacquer-free actual contact surfaces are surrounded withmuch larger surfaces carrying a protective layer of silicone resin.
  • the protective layer may contain a catalyst.
  • a silicone resin suitable for the described use is marketed by the General Electric Company under the trade name Dri-Film 103 as a protective agent for buildings.
  • Dri-Film 103 is a solids solution in an aromatic solvent of a methylmethoxypolysiloxane resin, as described in Krantz Patent 2,810,704.
  • This is a precondensed silicone resin which, by the action of catalysts,
  • catalysts there can be -used, for example, cobalt and lead salts, preferably the naphthenates, individually or in combination.
  • cobalt and lead salts preferably the naphthenates, individually or in combination.
  • tin salts such as tin octoate and tin maleate, appear to be particularly effective.
  • FIGURE 3 the surface of a contact spring is provided with a thin layer of silicone resin 11, the getter layer, with cross-linked molecules and ernbedded molecules of catalyst 12.
  • FIGURE 3 also shows a linear, polymeric siloxane molecule 13 which acts as a contact poison. Due to the presence of the catalyst 12, a chemical reaction takes place in which an Si-O bond of a cross-linked silicone resin molecule and of a linear, polymeric siloxane molecule 13 are split (FIGURE 4) and the two resultant fragments 13a and 13b of the linear, polymeric siloxane are bound by new Si-O-Si bonds to the points of connection of the cross-linked sili- 6 cone resin layer 11 (FIGURE 5). In this manner, the substance 13 which is harmful for the electrical contact is prevented from wandering to the contact surface. Since the thermodynamic equilibrium of this reaction lies by the high molecular Weight compound, the reverse reaction can be neglected.
  • su-ch as cobalt, iron and tin salts, present on the essential metallic constructional elements can possibly act as catalysts.
  • cross-linked siloxanes such as Si-OH, Si-OR (wherein R is an alkyl, alkylene, aryl or acyl radical and Si-H, as well as organo-functional groups, can, of course, also react, according to various mechanisms, with linear, polymeric siloxanes and also with hydrocarbon compounds containing functional groups.
  • R is an alkyl, alkylene, aryl or acyl radical and Si-H
  • organo-functional groups can, of course, also react, according to various mechanisms, with linear, polymeric siloxanes and also with hydrocarbon compounds containing functional groups.
  • compositions or reaction system are the chemical stability with regard to other compounds, as well as their resistance to ageing and the impossibility of a depletion of the centres of reaction because the chemical construction of the getter layer is not altered by the grafting of linear siloxanes.
  • a process for the protection of an electrical contact, of a constructional element having an electrical contact area, against fouling by a liquid silicone contaminating material which comprises coating that portion of the surface of the constructional element entirely surrounding said electrical contact area with a thin coating of a layer of a silicone resin varnish consisting of a solution of a silicone resin, containing Si*0 bonds, in a volatile solvent for said silicone resin, allowing said solvent to evaporate and said resin to harden leaving a very thin protective film entirely surrounding said contact area, and cleaning from said electrical contact area, only, any of the coating inadvertently applied thereto, said silicone resin being a cross-linked organopolysiloxane capable of chemically combining with and inhibiting the mobility of such a liquid silicone contaminant material.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Paints Or Removers (AREA)
  • Organic Insulating Materials (AREA)
US376520A 1963-07-03 1964-06-19 Protection of electrical contacts Expired - Lifetime US3458351A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH835263A CH446544A (de) 1963-07-03 1963-07-03 Verfahren zum Schützen von elektrischen Kontakten

Publications (1)

Publication Number Publication Date
US3458351A true US3458351A (en) 1969-07-29

Family

ID=4339010

Family Applications (1)

Application Number Title Priority Date Filing Date
US376520A Expired - Lifetime US3458351A (en) 1963-07-03 1964-06-19 Protection of electrical contacts

Country Status (7)

Country Link
US (1) US3458351A (de)
AT (1) AT250485B (de)
BE (1) BE650045A (de)
CH (1) CH446544A (de)
DE (1) DE1295734B (de)
GB (1) GB1055396A (de)
SE (1) SE313375B (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928683A (en) * 1974-05-06 1975-12-23 Bell Telephone Labor Inc Corrosion inhibitor
US3947952A (en) * 1970-12-28 1976-04-06 Bell Telephone Laboratories, Incorporated Method of encapsulating beam lead semiconductor devices
US4935454A (en) * 1986-09-26 1990-06-19 Amp Incorporated Broad spectrum light and heat curable sealant composition and method of using same
US4953789A (en) * 1986-05-22 1990-09-04 Bayerische Motoren Werke Ag Arrangement for the metered supply of a fuel, especially into the combustion space of an internal combustion engine
US5395269A (en) * 1985-07-01 1995-03-07 The Whitaker Corporation Method of sealing electrical connectors using a broad spectrum light and heat curable composition

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0746541B2 (ja) * 1986-10-31 1995-05-17 東レ・ダウコーニング・シリコーン株式会社 オルガノポリシロキサンガスに起因する電気開閉接点の導電不良障害を防止する方法
DE10306106A1 (de) * 2003-02-14 2004-09-02 Braun Gmbh Verwendung von perfluorierten Polyetherölen

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1028777B (de) * 1955-04-18 1958-04-24 Dow Corning Haertungsmittel fuer harzartige Organopolysiloxane
DE1022337B (de) * 1955-08-08 1958-01-09 Licentia Gmbh Verfahren zur Herstellung von Einbrennlacken, insbesondere Drahtlacken auf Basis von Silikonharzen
DE1063735B (de) * 1956-03-12 1959-08-20 Dow Corning Lacke auf der Grundlage von Silikonharzen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3947952A (en) * 1970-12-28 1976-04-06 Bell Telephone Laboratories, Incorporated Method of encapsulating beam lead semiconductor devices
US3928683A (en) * 1974-05-06 1975-12-23 Bell Telephone Labor Inc Corrosion inhibitor
US5395269A (en) * 1985-07-01 1995-03-07 The Whitaker Corporation Method of sealing electrical connectors using a broad spectrum light and heat curable composition
US4953789A (en) * 1986-05-22 1990-09-04 Bayerische Motoren Werke Ag Arrangement for the metered supply of a fuel, especially into the combustion space of an internal combustion engine
US4935454A (en) * 1986-09-26 1990-06-19 Amp Incorporated Broad spectrum light and heat curable sealant composition and method of using same

Also Published As

Publication number Publication date
BE650045A (de) 1964-11-03
GB1055396A (en) 1967-01-18
SE313375B (de) 1969-08-11
AT250485B (de) 1966-11-10
CH446544A (de) 1967-11-15
DE1295734B (de) 1969-05-22

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