US3261957A - Reed-type switching device - Google Patents

Reed-type switching device Download PDF

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Publication number
US3261957A
US3261957A US398448A US39844864A US3261957A US 3261957 A US3261957 A US 3261957A US 398448 A US398448 A US 398448A US 39844864 A US39844864 A US 39844864A US 3261957 A US3261957 A US 3261957A
Authority
US
United States
Prior art keywords
oxygen
envelope
contact
switching device
reed
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
US398448A
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English (en)
Inventor
Theobald Hermann Theodor
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.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
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 Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Application granted granted Critical
Publication of US3261957A publication Critical patent/US3261957A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
    • H01T1/00—Details of spark gaps
    • H01T1/24—Selection of materials for electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/0201—Materials for reed contacts
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/64—Protective enclosures, baffle plates, or screens for contacts
    • H01H1/66—Contacts sealed in an evacuated or gas-filled envelope, e.g. magnetic dry-reed contacts

Definitions

  • the present invention refers to a dry reed switch, such as a reed switch in a sealed protective tube.
  • a reed switch of a known type is shown in the enclosed drawing.
  • Two reeds 1 and 2 of magnetic material extend hermetically sealed through the ends of a protective tube 3.
  • the inner ends of the reeds overlap each other, spaced apart.
  • the protective tube is normally filled with an inert gas, for instance nitrogen, often with an addition of hydrogen.
  • the object of the gas is to avoid corrosion of the contact surfaces, so that the contact resistance remains low, the hydrogen neutralizing possible rests of oxygen.
  • These contact devices ordinarily have a sufliciently long life at normal use in telephone equipment.
  • the contacts are used for heavy work, for instance for digit impulsing, the contacts do serve satisfactorily only for a limited time.
  • the defects appearing on the contacts principally consist in sticking of the two contact parts. Such a sticking appears because of material propagation between the contact parts, whereby roughness appears on the surfaces of the contact parts so that they may stick together. This sticking appears the earlier, the heavier the current is that is closed and interrupted by the contact, and with certain uses entailing a great number of makes and breaks the life duration of these contacts is highly unsatisfactory.
  • the tube contains, besides the inert gas, an amount of oxygen per volume unit that is smaller or at the most equal to that present in ambient air.
  • the concentration of oxygen In tubes with a small volume a higher concentration of oxygen may be used, and conversely, in tubes having a large volume the concentration of oxygen must be lower.
  • the oxygen present in the tube is to a certain extent consumed by oxidization of iron and nickel from the contacts, the quantity of oxygen chemically bound thereby being proportionally bigger the smaller the tube volume is, so that in a smaller tube the concentration of free oxygen is reduced more quickly than in a bigger tube, where the concentration is already lower from the beginning.
  • the contact surfaces of used reed contacts of the conventional design are determined by means of a microscope and compared with reed contacts used in presence of oxygen, considerable differences are found between them.
  • the former show a substantial surface roughness while the latter are comparatively smooth. This depends upon the influence of the oxygen and may be explained in the following way.
  • the reed contacts are made of an alloy of iron and nickel and have at the contact surfaces a thin layer of some precious metal.
  • a material propagation occurs between the contact parts, said material propaga- .tion forming p qjt sltions on the one surface and cavities on the other surface. In the known devices these projections and cavities are slowly increasing and finally become so pronounced as to cause sticking by the roughness of the contact parts hooking together.
  • the oxygen concentration is not too high. With a weak concentration of oxygen FeO and NiO are formed, and with higher concentration Fe O and Ni O are formed which latter oxides produce a higher contact consistence. Provided the air had free access a complete contact interruption would soon occur. Tests carried out show that the appropriate oxygen concentration is different for different contact materials. Thus it has been found convenient to use a higher oxygen concentration with gold cont-acts than, for instance, with rhodium contacts. A content of 1% oxygen and 99% inert gas seems to give a good increase of the life duration and so does also a concentration of oxygen of 20% (the concentration of oxygen in air) with inert gas, which however as already mentioned gives a relatively high contact resistance. An oxygen content of up to 5% seems to give the best result.
  • a switching device of the kind including a closed tubular envelope, a pair of resilient contact reeds of magnetizable material extending into said envelope gas-tight sealed thereto and having parts within the envelope overlapping each other in spaced-apart relationship, and a coil disposed outside said envelope to flex said contact reeds into contact-making engagement upon excitation of the coil, the improvement comprising a gas mixture of an inert gas and oxygen contained in said envelope, the oxygen component in said mixture being less per volume unit than the oxygen content of atmospheric air.
  • a switching device wherein the oxygen component in said mixture is between 1% to 20% per volume unit.
  • a switching device wherein the oxygen component in said mixture is between 1% to 5% per volume unit.
  • a switching device according to claim 1, wherein the inert gas component in said mixture is nitrogen.
  • a switching device wherein the engageable parts of said reeds are coated with a precious metal.
  • a switching device wherein said contact reeds extend into said envelope from opposite ends thereof in mutually parallel relationship, the inner ends of said reeds overlapping each other.

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  • Contacts (AREA)
US398448A 1963-09-24 1964-09-22 Reed-type switching device Expired - Lifetime US3261957A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE1041263 1963-09-24

Publications (1)

Publication Number Publication Date
US3261957A true US3261957A (en) 1966-07-19

Family

ID=20292266

Family Applications (1)

Application Number Title Priority Date Filing Date
US398448A Expired - Lifetime US3261957A (en) 1963-09-24 1964-09-22 Reed-type switching device

Country Status (9)

Country Link
US (1) US3261957A (OSRAM)
BE (1) BE652611A (OSRAM)
BR (1) BR6462139D0 (OSRAM)
DE (1) DE1244296B (OSRAM)
DK (1) DK111627C (OSRAM)
FI (1) FI40917B (OSRAM)
FR (1) FR1408691A (OSRAM)
GB (1) GB1078277A (OSRAM)
NL (1) NL146634B (OSRAM)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11309140B2 (en) * 2019-01-04 2022-04-19 Littelfuse, Inc. Contact switch coating

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1517702A (en) * 1974-09-19 1978-07-12 Fujitsu Ltd Electrical contact

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2289830A (en) * 1938-03-29 1942-07-14 Bell Telephone Labor Inc Circuit closing device
US2696543A (en) * 1948-12-18 1954-12-07 Bell Telephone Labor Inc Electric switch

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2289830A (en) * 1938-03-29 1942-07-14 Bell Telephone Labor Inc Circuit closing device
US2696543A (en) * 1948-12-18 1954-12-07 Bell Telephone Labor Inc Electric switch

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11309140B2 (en) * 2019-01-04 2022-04-19 Littelfuse, Inc. Contact switch coating
US20220122784A1 (en) * 2019-01-04 2022-04-21 Littelfuse, Inc. Contact switch coating

Also Published As

Publication number Publication date
BE652611A (OSRAM) 1964-12-31
GB1078277A (en) 1967-08-09
DK111627B (OSRAM) 1968-09-23
BR6462139D0 (pt) 1973-08-09
FI40917B (OSRAM) 1969-03-31
NL146634B (nl) 1975-07-15
DE1244296B (de) 1967-07-13
NL6409819A (OSRAM) 1965-03-25
FR1408691A (fr) 1965-08-13
DK111627C (da) 1968-09-23

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