US3114811A - Reduction of sticking of mercury-wetted contacts - Google Patents

Reduction of sticking of mercury-wetted contacts Download PDF

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Publication number
US3114811A
US3114811A US152776A US15277661A US3114811A US 3114811 A US3114811 A US 3114811A US 152776 A US152776 A US 152776A US 15277661 A US15277661 A US 15277661A US 3114811 A US3114811 A US 3114811A
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United States
Prior art keywords
mercury
contacts
contact
wetted
sticking
Prior art date
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Expired - Lifetime
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US152776A
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English (en)
Inventor
Girard T Kohman
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.)
AT&T Corp
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Bell Telephone Laboratories Inc
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Filing date
Publication date
Priority to BE624902D priority Critical patent/BE624902A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US152776A priority patent/US3114811A/en
Priority to FR915105A priority patent/FR1339163A/fr
Priority to JP5015962A priority patent/JPS4013100B1/ja
Application granted granted Critical
Publication of US3114811A publication Critical patent/US3114811A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/06—Contacts characterised by the shape or structure of the contact-making surface, e.g. grooved
    • H01H1/08—Contacts characterised by the shape or structure of the contact-making surface, e.g. grooved wetted with mercury
    • 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

Definitions

  • FIG. 2 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 2 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • This invention relates to switches; more particularly it relates to switches which employ mercury-wetted contacts.
  • the above described difficulty is substantially eliminated *by the provision of an array of inert members, hereinunder designated spacers, on one of the contacting surfaces of each pair of contacts.
  • the spacers are chemically inert insofar as any interaction with mercury is concerned. They are proportioned and arranged so that a film of liquid mercury covers the entire surface of the contact, preferably including also the surfaces of the spacers. Such contacts have appreciably less tendency to stick when normal operation to break the electrical connection, that is, to open the switch, is initiated.
  • the array of spacers can be a plurality of closely spaced linear'elements or it can be a plurality of particles liberally distributed over the surface of the contact.
  • the pairs of contacting surfaces comprise one surface essentially of iron with a very thin oxide layer thereon, and a second surface of a noble metal.
  • a noble metal such as gold, silver, ruthenium, rhodium, palladium, osmium, iridium or platinum.
  • platinum is preferred because of its low solubility in mercury.
  • the higher solubility of gold and silver, for example, if these metals are employed for the other contact, could, under certain conditions, result in limiting the fault-free life of the switch in that it could cause sticking difficulties as a result of the formamaking the other contact of the pair of a noble metal i'lce tion of too large a quantity of amalgam.
  • such contacts by a continuation of the formation of amalgam are likely to disintegrate.
  • a novel surface treatment of contact carrying springs or armature members is proposed, which treatment facilitates wetting of the surface so treated with liquid mercury.
  • the treatment results in providing a surface covered with finely divided particles of metallic nickel.
  • Such a granular surface has been found to have a pronounced wick action with liquid mercury in. that it is effective in drawing liquid mercury from a reservoir to wet contacts at the upper end of a vertical spring or armature member, the lower end of which extends into a liquid mercury reservoir.
  • a principal object of the invention is, accordingly, to substantially reduce the difliculties resulting from the sticking of mercury-wetted contacts in relays and similar switching devices.
  • Another object is to provide pairs of contact surfaces for switching devices in which the contact surfaces are meroury-wetted which have a minimum tendency to stick.
  • a further object is to impart wick action to surfaces of metallic members employed in switching devices which have mercury-'wetted contacts.
  • FIG. 1 illustrates a typical prior art switching device employing mercury-wetted contacts
  • FIG. 2 is a front View of a spring or armature member embodying certain principles of the invention and suitable for use in the device of FIG. 1; I
  • FIG. 3 is a side view of the member of FIG. 2;
  • FIG. 4 illustrates an alternative form of Contact of the invention.
  • FIG. 1 a typical mercury-wetted contact switching device is shown to an enlarged scale. Normally, for example, the over-all length of glass envelope 10 is made one inch and other parts of the assembly'are of correspondingly reduced dimensions.
  • This specific device is, with exceptions to be described in detail hereinbelow, similar to the switching devices disclosed, described in detail, and claimed in Patent No. 2,609,464, granted September 2, 1952, to J. T. L. Brown and C. E. Pollard, Jr, and Patent No. 2,868,926, granted January 13, 1959, to C. E. Pollard, J12, both of which patents are assigned to applicants assignee. Accordingly, Patents 2,609,464 and 2,868,926 are incorporated by reference and, insofar as they are pertinent, are made an integral portion of the disclosure of the present application.
  • the principal parts of the device of FIG. 1 are a glass envelope 10, enclosing a mercury reservoir 14 at its lower end, a contact bearing armature 12 held on a metal pedestal member 22 embedded in the lower end of envelope 10, a pair of contact bearing metal stud members 18and 12, likewise embedded in envelope 10 but at its upper end, and a solenoidal electrical winding 16 encircling the central portion of envelope 10 Envelope 10 is sealed and may be substantially evacuated or it may be filled with a chemically inert gas in accordance with practices well known and widely used in the art.
  • a direct current passed through winding 16 in one direction (or polarity) willcause the upper end of armature 12 to move to the right bringing its right contact 26 into contact with contact 24 on the lower end of stud 11 8.
  • a direct current'of the opposite direction (or polarity) through winding 16 will cause the upper end of armature 12 plated with metallic nickel.
  • contacts 26 on opposite sides of armature 12 are preferably of iron (or an iron alloy) having a very thin oxide coating thereon.
  • This oxide coating should be, for example, approximately ten Angstroms or less in thickness.
  • each of the contact surfaces should be of a noble metal and should not be permitted to become oxidized.
  • Contacts 24 on supports 18 and 20, respectively are of a noble metal, and more particularly, a metal such as platinum which is readily wet by mercury but with a minimum of amalgam formation. It is common practice to alloy a small amount of nickel (ten or twelve percent by weight) with the platinum which [further facilitates wetting its surface with mer cury.
  • the glass envelope is normally sealed so as to be -gas-tight, it is entirely feasible and often the practice to seal it off with an inert or nonoxidizing gas, such as nitrogen, filling it so that further oxidation of the contacts will not occur after envelope 10 is sealed.
  • Contacts 26 may, of course, be introduced into envelope 10 with an appropriately thin oxide coating.
  • the thickness of the oxide coating on the iron may be reduced after it is assembled in the glass envelope by treatment in a reducing atmosphere such as hydrogen prior to filling the envelope with an inert atmosphere and sealing it.
  • a thinly oxidized iron contact paired with one of platinum will freely pass electrical current but will form negligible coatings of amalgam with mercury. so that the problem of the contacts sticking is substantially eliminated.
  • the surface of the member from a point below the surface of liquid mercury in the reservoir up to the upper end of the contacts is Alternatively, the member may be fabricated from a nickel strip of appropriate size. The surface is then wetted with mercury and allowed to form a layer of amalgam (of mercury and nickel, obviously). Such a surface will form a thin layer of amalgam at room temperature in a few hours.
  • the nickel in order to thicken the layer of porous nickel amalgam so as to increase the capillary action, it is preferable to subject the nickel to several temperature cycles between room temperature and an elevated temperature (100 degrees centigrade or higher), maintaining the higher temperature for an hour or more during each cycle. After this treatment the nickel surface when wet with mercury will have a granular, bright tinny appearance. Upon heating again, but in a vacuum, the excess mercury can be distilled from the surface exposing a grey film of amalgam crystals.
  • amalgam crystals can be decomposed, the mercury being distilled off, leaving behind a black granular deposit consisting of a finely divided layer of metallic nickel.
  • This layer is porous and readily wet by mercury.
  • a member with such a surface will exhibit a pronounced wick action, that is, if held in a vertical position with its lower end dipped in liquid mercury, capillary action readily draws mercury to the upper end of the member.
  • the surface of one contact of each pair of mercurywetted contacts is provided with an array of thin, closely spaced members, which are chemically inert to mercury.
  • these members may be parallel, elongated bar-like members, as illustrated to a further enlarged scale in FIGS. 2 and 3 by members 114, extending vertically across the surface of contacts 126 on armature 112.
  • Armature 112 may be otherwise identical with armature 12 of FIG. 1 and may be substituted for the latter in the assembly of FIG. 1.
  • Contacts 126 are, for example, as mentioned above, preferably platinum.
  • spacers 114 of FIGS. 2 and 3 can be obtained by spraying a thin layer (approximately .001 inch) of a ceramic glaze or glassy material on the surface of a contact 126, after which the bars 114 are formed by the mechanical removal (as by milling) of those parts of the film not required to form the bars 114.
  • Each bar can, for example, be approximately a mil (.001 inch) wide and the spacing between bars 114- can be of similar width.
  • the thickness of the film should be somewhat less than the thickness of the mercury film between spacers which normally will be of substantially a mil, but since glass or ceramic glaze if meticulously cleaned will be wetted by mercury, it can be somewhat thicker in some cases.
  • the thickness of bars 114 should be restricted to not more than the thickness of the mercury film between spacers (one mil) and the intervals between bars should be several mils so that the mercury wetting of the contact surface between spacers will provide a layer of liquid mercury of equal or greater maximum thickness than that of the bars.
  • an array of randomly distribued, closely spaced granular particles 132 may be affixed to the surface of the contact member 130 in lieu of the bars 114 of FIGS. 2 and 3.
  • These can, for example, be of clean silica or of a semiconductor such as silicon carbide and may be embedded in the contact surface during fabrication when the surface is in a partially molten state or by powder metallurgy techniques. The surface upon solidification can then be etched to expose portions of the particles to a depth in the order of .001 inch.
  • Either the bars 114 of FIGS. 2 and 3 or the particles 132 of FIG. 4 will act as spacers so that contact is made through a film of liquid mercury. A contact provided with such spacing elements will have a negligible tendency to stick to a conventional contact of noble metal.
  • a switching device of the type which employs a pair of solid metallic mercury-wetted contacts for making and breaking an electrical circuit, one of said contacts having an array of a plurality of thin spacing members of a chemically inert and electrically nonconductive substance on its surface.
  • a pair of solid metallic mercury-wetted contacts for making and breaking an electrical circuit, one of said contacts comprising a member of iron having a thin layer of oxide thereon, the other contact comprising a member of a noble metal.
  • a pair of solid metallic mercury-Wetted contacts for making and breaking an electrical circuit, one of said contacts including thin spacing members of a chemically inert and electrically nonconductive substance on its surface, the spacing members being adapted to hold a fluid mercury film n the contact surface.
  • a switching device of the type which employs a reservoir of mercury and a pair of solid metallic mer cury-wetted contacts for making and breaking an electrical circuit, at least one of said contacts being supported on a first end of a movable supporting member, the other end of the member being in contact with the mercury in the reservoir of mercury, the surface of the supporting member between the mercury in the reservoir and the contact surface being covered with a granular layer of finely divided metallic nickel.
  • a pair of solid metallic mercury-wetted contacts for making and breaking an electrical circuit, one of said contacts containing a granular, chemically inert material incorporated in the surface of the contact, portions of the grains of said material protruding above the surface of the contact for a distance of approximately .001 inch.
  • a pair of solid metallic mercury-wetted contacts for making and breaking an electrical circuit, one of the contacts containing elongated spacers arranged in parallel array, the spacers being of a material chemically inert with respect to mercury and electrically nonconductive.
  • a pair of solid metallic mercury-wetted contacts for making and breaking an electrical circuit, one of said contacts containing chemically inert and electrically nonconductive spacers distributed over its surface in a manner permitting the contact surface to be readily wetted by a fluid film of mercury of sufiicient thickness to make contact with the other contact.
  • a pair of solid metallic mercury-wetted contacts for making or breaking an electrical circuit, one of said contacts containing a discontinuous thin layer of a vitreous enamel or glaze as a spacer arranged to permit the formation by surface tension forces of a fluid film of mercury over the contact surface.

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US152776A 1961-11-16 1961-11-16 Reduction of sticking of mercury-wetted contacts Expired - Lifetime US3114811A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE624902D BE624902A (xx) 1961-11-16
US152776A US3114811A (en) 1961-11-16 1961-11-16 Reduction of sticking of mercury-wetted contacts
FR915105A FR1339163A (fr) 1961-11-16 1962-11-12 Dispositif de réduction du collage entre des contacts mouillés de mercure
JP5015962A JPS4013100B1 (xx) 1961-11-16 1962-11-16

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US152776A US3114811A (en) 1961-11-16 1961-11-16 Reduction of sticking of mercury-wetted contacts

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US3114811A true US3114811A (en) 1963-12-17

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JP (1) JPS4013100B1 (xx)
BE (1) BE624902A (xx)
FR (1) FR1339163A (xx)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3331037A (en) * 1964-07-09 1967-07-11 C P Claire & Company Spherical contact structure for sealed mercury switches
US3431377A (en) * 1967-03-03 1969-03-04 Bell Telephone Labor Inc Mercury contact switch having an alloy contact
US3463119A (en) * 1968-01-30 1969-08-26 United Aircraft Corp Nickel-mercury amalgam seal
US3831118A (en) * 1970-08-24 1974-08-20 Fifth Dimension Inc Mercury switch
US4085392A (en) * 1976-01-14 1978-04-18 Gordos Corporation Reed switch construction
FR2389220A1 (fr) * 1977-04-29 1978-11-24 Clare Int Nv C P Commutateur a lamelles de contact mouillees par du mercure
US4236129A (en) * 1979-06-20 1980-11-25 Gordos Corporation Mercury contact switch
EP0019516A1 (fr) * 1979-05-10 1980-11-26 ETAT FRANCAIS repr. par le Secrétaire d'Etat aux Postes & Télécommunications (Centre National d'Etudes des Télécommunications) Dispositifs de contact électrique à liquide conducteur
FR2456379A2 (fr) * 1977-03-22 1980-12-05 France Etat Dispositifs de contact electrique a liquide conducteur
US4311769A (en) * 1979-02-21 1982-01-19 Andreev Oleg M Mercury contact
US4617542A (en) * 1983-10-17 1986-10-14 Imcs Corporation High voltage switching device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2147506A (en) * 1936-11-03 1939-02-14 Brown Brockmeyer Company Floating weight electric switch
US2769875A (en) * 1953-09-25 1956-11-06 Bell Telephone Labor Inc Mercury contact switch
US2868926A (en) * 1957-06-25 1959-01-13 Bell Telephone Labor Inc Switch
US3018354A (en) * 1959-10-22 1962-01-23 Bell Telephone Labor Inc Means for preventing contact sticking in mercury contact switches

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2147506A (en) * 1936-11-03 1939-02-14 Brown Brockmeyer Company Floating weight electric switch
US2769875A (en) * 1953-09-25 1956-11-06 Bell Telephone Labor Inc Mercury contact switch
US2868926A (en) * 1957-06-25 1959-01-13 Bell Telephone Labor Inc Switch
US3018354A (en) * 1959-10-22 1962-01-23 Bell Telephone Labor Inc Means for preventing contact sticking in mercury contact switches

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3331037A (en) * 1964-07-09 1967-07-11 C P Claire & Company Spherical contact structure for sealed mercury switches
US3431377A (en) * 1967-03-03 1969-03-04 Bell Telephone Labor Inc Mercury contact switch having an alloy contact
US3463119A (en) * 1968-01-30 1969-08-26 United Aircraft Corp Nickel-mercury amalgam seal
US3831118A (en) * 1970-08-24 1974-08-20 Fifth Dimension Inc Mercury switch
US4085392A (en) * 1976-01-14 1978-04-18 Gordos Corporation Reed switch construction
US4148000A (en) * 1976-01-14 1979-04-03 Gordos Corporation Reed switch construction
FR2456379A2 (fr) * 1977-03-22 1980-12-05 France Etat Dispositifs de contact electrique a liquide conducteur
FR2389220A1 (fr) * 1977-04-29 1978-11-24 Clare Int Nv C P Commutateur a lamelles de contact mouillees par du mercure
US4311769A (en) * 1979-02-21 1982-01-19 Andreev Oleg M Mercury contact
EP0019516A1 (fr) * 1979-05-10 1980-11-26 ETAT FRANCAIS repr. par le Secrétaire d'Etat aux Postes & Télécommunications (Centre National d'Etudes des Télécommunications) Dispositifs de contact électrique à liquide conducteur
US4236129A (en) * 1979-06-20 1980-11-25 Gordos Corporation Mercury contact switch
US4617542A (en) * 1983-10-17 1986-10-14 Imcs Corporation High voltage switching device

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Publication number Publication date
BE624902A (xx)
JPS4013100B1 (xx) 1965-06-25
FR1339163A (fr) 1963-10-04

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