US3430015A - Vacuum-type circuit interrupter having brazed joints protected from weld-inhibiting constitutent in contact structure - Google Patents

Vacuum-type circuit interrupter having brazed joints protected from weld-inhibiting constitutent in contact structure Download PDF

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Publication number
US3430015A
US3430015A US537979A US3430015DA US3430015A US 3430015 A US3430015 A US 3430015A US 537979 A US537979 A US 537979A US 3430015D A US3430015D A US 3430015DA US 3430015 A US3430015 A US 3430015A
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United States
Prior art keywords
contact
weld
vacuum
inhibiting
brazed
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Expired - Lifetime
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US537979A
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English (en)
Inventor
Donald W Crouch
Robert Crowell
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General Electric Co
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General Electric Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/0203—Contacts characterised by the material thereof specially adapted for vacuum switches
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H1/00—Contacts
    • H01H1/02—Contacts characterised by the material thereof
    • H01H1/0203—Contacts characterised by the material thereof specially adapted for vacuum switches
    • H01H2001/0205—Conditioning of the contact material through arcing during manufacturing, e.g. vacuum-depositing of layer on contact surface

Definitions

  • a vacuum-type circuit interrupter comprising a brazed joint in its envelope located immediately adjacent one of the contacts of the interrupter and remote from the other contact.
  • a weld-inhibiting constituent for preventing contact welding is incorporated in the metal of the contacts but is confined to the contact remote from said brazed joint. The contact immediately adjacent the brazed joint is essentially free of the weld-inhibiting constituent.
  • This invention relates to a vacuum-type electric circuit interrupter that comprises relatively movable contacts and, more particularly, relates to an interrupter of this type in which objectionable contact-welding is prevented by the presence of a weld-inhibiting constituent in the metal of the contacts.
  • a vacuum-type circuit interrupter must have contacts that are extremely clean and devoid of oxide and other contaminating films on their surfaces. This cleanliness is required in order to impart high dielectric strength and current-interrupting capacity to the interrupter, but unfortunately the clean surface conditions are conducive to the formation of strong welds between the contacts. For preventing the formation of such welds, it is proposed in application Ser. No. 186,127 Lafierty et al., filed June 3, 1963, now Patent No. 3,246,979, and assigned to the assignee of the present invention, that a Weld-inhibiting metal be incorporated as a minor constituent in the contact metaL.
  • This weldrinhibiting minor constituent has a low solid-state solubility in the major constituent and acts to ernbrittle any welds that are formed between the contacts so that they can be easily broken with relatively small contact-separating force.
  • the weld-inhibiting constituent also has a lower effective freezing temperature than that of the major constituent.
  • An example of a metal suitable for use as a weld-inhibiting minor constituent is bismuth when the major con stituent is copper or silver. Another example is lead when the major constituent is copper or silver. Other examples are set forth in the aforementioned Laiferty et al. application.
  • An object of our invention is to prevent the brazed 3,430,015 Patented Feb. 25, 1969 joints of the interrupter from being impaired by the presence of a weld-inhibiting minor constituent in the contact metal, while still retaining a high resistance to contact-welding.
  • the other contact is made of a metal that 's essentially free of the weld-inhibiting constituent prior to interrupter operation.
  • the interrupter includes brazed vacuum-tight joints, but none of these joints is located close to the contact containing the weld-inhibiting constituent. Any brazed vacuum-tight joint that is located near a contact is located near the contact that is free of the weld-inhibiting constituent. This joint, as well as the other brazed vacuum-tight joints, is remote from the contact containing the weld-inhibiting constituent.
  • the illustrated vacuumtype circuit interrupter comprises a sealed envelope 11 that is evacuated to a pressure of 10- millimeters of mercury or lower.
  • This envelope 11 comprises a tubular ceramic housing 12 and a pair of metal end caps 13 and 14 joined to the housing 12 in vacuum-tight relationship at its respective opposite ends. Suitable ceramic-tometal joints 15 are used for joining the end caps 13 and 14 to the ceramic housing 12.
  • the upper electrode 20 is a stationary electrode that is joined to the upper end cap 13 by means of a vacuum-tight brazed joint 23, which will soon be referred to in greater detail.
  • the lower electrode 21 is a movable electrode that projects freely through a central opening 24 in the lower end cap 14.
  • a flexible tubular metal bellows 25 surrounding the electrode 21 is provided.
  • This bellows 25 has its lower end joined to the lower end cap 14 by a suitable vacuum-tight seal 26 and its upper end joined to the movable electrode 21 by a suitable vacuum tight brazed joint 28.
  • the upper electrode 20 is constituted by a circuitmaking portion, or contact, 30 and a contact-supporting rod 32 carrying the contact 30 at its lower end.
  • the contact 30 is suitably joined to the rod 32 by a joint 34.
  • This joint 34 is formed by providing the contact 30 with a plug portion 35 fitting into a socket 36 in the lower end of rod 32.
  • the walls of the socket are crimped to form dimples 37 tightly fitting into an annular groove in the plug 35.
  • the lower electrode 21 is of essentially the same construction and comprises a circuit-making portion, or contact, 40 and a contact-supporting rod 42 carrying the contact 40 at its upper end.
  • the contact 40 and its supporting rod 42 are shown joined together in the same manner as contact 30 and its supporting rod 32.
  • the lower electrode 21 When the interrupter is to be closed, the lower electrode 21 is driven in an upward direction to move its contact 40 into engagement with the contact 30 of the upper electrode.
  • the dotted line 40a indicates the position of the lower contact 40 when it engages the upper contact. This engagement permits current to flow through the interrupter via the electrodes 20 and 21 through the contacts 30 and 40.
  • the lower electrode 21 Assuming that the contacts are engaged, when an interrupting operation is to take place, the lower electrode 21 is driven downwardly to separate lower contact 40 from upper contact 30. This establishes an are between the two contacts. Assuming an alternating current circuit, the arc persists until about the time of the first natural current zero, at which time the arc vanishes and the vacuum recovers its dielectric strength, thereby preventing the are from reestablishing.
  • a tubular metal shield 50 is provided. This shield 50 surrounds the contacts 30 and 40 and is spaced therefrom. It is shown supported from the lower end cap 14.
  • a cup-shaped auxiliary shield 52 surrounds the upper end of the shield 50 to provide additional means for condensing any vapors generated by the arc and traveling toward the insulating housing 12.
  • This cup-shaped shield 52 has a central opening surrounding the upper electrode 20 and is joined thereto by means of the brazed vacuum-tight joint 23.
  • This shield is an annular metal disc which protects the bellows 25 from damage by the hot arcing products. This shield is joined to the electrode 21 at the brazed joint 28.
  • the contacts 30 and 40 have clean surfaces that are essentially free of oxide and other contaminating films.
  • the contacts are driven together, there is a tendency for a weld to form between the surfaces in view of their cleanliness, the high pressures involved, and the arcing which occasionally occurs on closing.
  • weld-inhibiting metal be incorporated as a minor constituent in the contact metal.
  • This weldinhibiting minor constituent has a low solid state solubility in the major constituent and acts to drastically weaken through embrittlement any Welds that are formed between the contacts so that they can be easily and cleanly broken with a relatively small contact-separating force.
  • metals suitable for use as weld-inhibiting minor constituents are bismuth and lead when the major constituent is either copper or silver. In other words, alloys such as copper-bismuth, copper-lead, silverbismuth, and silver-lead can be used for the contacts 30 and 40 to prevent objectionable contact-welding.
  • the minor constituent is listed second in each of these alloys.
  • the joints 23 and 28 are formed by placing shims or rings of brazing material between or near the parts to be joined and by heating the entire interrupter to a temperature in excess of the melting point of the brazing alloy.
  • a typical brazing alloy is a coppersilver eutectic, which has a melting point of 780 C.
  • the temperature of the interrupter is raised to slightly over 800 0., thereby melting the brazing alloy and causing it to flow into all openings in the joint. Thereafter, the temperature is reduced to solidify the molten metal and form the vacuum-tight seal.
  • weld inhibitors such as bismuth and lead have very little solid-state solubility in the copper or silver of the brazed metal, there is appreciable liquidstate solubility, and it is believed that some of the bismuth or lead dissolves in the molten brazed metal.
  • the brazed metal solidifies upon cooling, the bismuth or lead comes out of solution and enters the grain boundaries of the brazed metal, and for some reason, not fully understood, produces pores in the brazed metal. This joint-impairment has been observed even when the joint is located at a point spaced from the contact.
  • One of these cooperating features is that we incorporate the weld-inhibiting minor constituent in only the contact 30.
  • the other contact 40 is maintained essentially free of the weld-inhibiting minor constituent, at least prior to an interrupting operation.
  • the bismuth content of the copper-bismuth alloy is held below a few percent by weight.
  • a second one of these cooperating features is that the brazed joints (23 and 28) are located remote from the particular contact (30) that contains the weld-inhibiting constituent.
  • the antiweld constituent is provided in only one of the two contacts, it is still capable of effectively preventing a strong weld from forming between the contacts when the contacts are engaged.
  • the brazed joints 28 and .23 can be of any suitable conventional form. In the illustrated interrupter, they are of the form disclosed and claimed in application Ser. No. 342,757, Crouch, filed Jan. 31, 1964, now Patent No. 3,290,772, and assigned to the assignee of the present invention.
  • the upper joint 23 comprises a pair of spaced-apart positioning rings 60 surroundings the electrode 20 and disposed at opposite sides of the plate structure 13, 52. Before the joint is formed, shims or rings of brazed metal are disposed adjacent or between the parts of the joint. Then the entire interrupter, including the joint 23, is heated to melt the braze metal and cause it to fill all openings in the joint. Upon subsequent cooling, the braze metal solidifies, forming a bond with the adjacent parts and a vacuum-tight seal between the parts.
  • the lower joint 28 is made in the same manner during the aforementioned heating operation.
  • the aforementioned heating operation is also used as a bake-out for removing contaminants from the surfaces of the interrupter parts.
  • the envelope 11 is suitably evacuated during or immediately following this heating operation.
  • a vacuum-type circuit interrupter comprising:
  • said first brazed joint being located immediately adjacent the contact of said first electrode but remote from the contact of said second electrode
  • the contact of said second electrode being formed of an alloy containing a small percentage of a weldinhibiting metal constituent that em-brittles any welds formed between said contacts when engaged,
  • said first brazed joint including brazing metal in which said weld-inhibiting metal has appreciable liquid-state solubility but is substantially insoluble in the solid state.
  • said alloy is selected from a group consisting essentially of copper-bismuth, copper-lead, silverbismuth and silver-lead, and
  • the material of the contact of said first electrode is selected from a group consisting essentially of copper and silver.

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  • High-Tension Arc-Extinguishing Switches Without Spraying Means (AREA)
US537979A 1966-03-28 1966-03-28 Vacuum-type circuit interrupter having brazed joints protected from weld-inhibiting constitutent in contact structure Expired - Lifetime US3430015A (en)

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US53797966A 1966-03-28 1966-03-28

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US3430015A true US3430015A (en) 1969-02-25

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US (1) US3430015A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
JP (1) JPS451489B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE1640211A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
GB (1) GB1103619A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3541284A (en) * 1967-12-14 1970-11-17 Allis Chalmers Mfg Co Combined vacuum circuit interrupter and impedance means
US3576960A (en) * 1968-03-08 1971-05-04 Gen Electric Flange fastening means for a contact button for a vacuum-type circuit interrupter
JPS4897060A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1972-02-14 1973-12-11
JPS496472A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1972-05-09 1974-01-21
US3789256A (en) * 1972-05-03 1974-01-29 Westinghouse Electric Corp Shielded spark gap device
JPS49131567U (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1973-03-10 1974-11-12
US3857005A (en) * 1970-11-25 1974-12-24 Siemens Ag Vacuum switch assembly
US3996437A (en) * 1973-12-03 1976-12-07 Cutler-Hammer, Inc. Vacuum contactor for motor control and method of making
US4077114A (en) * 1975-03-22 1978-03-07 Kabushiki Kaisha Meidensha Vacuum power interrupter
US4478347A (en) * 1981-01-23 1984-10-23 Westinghouse Electric Corp. Unitary end closure and seal shield member for vacuum interrupter
EP0123475A1 (en) * 1983-04-14 1984-10-31 Westinghouse Electric Corporation Method of joining a contact to an electrode
US4481390A (en) * 1980-07-01 1984-11-06 Kabushiki Kaisha Meidensha Vacuum circuit interrupter
US5594224A (en) * 1993-12-24 1997-01-14 Hitachi, Ltd. Vacuum circuit interrupter
US11756756B2 (en) * 2021-02-25 2023-09-12 S&C Electric Company Vacuum interrupter with double live shield

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6059691B2 (ja) * 1979-02-23 1985-12-26 三菱電機株式会社 真空しや断器用接点及びその製造方法
GB2323213B (en) * 1997-03-10 2001-10-17 Gec Alsthom Ltd Vacuum switching device

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975256A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum type circuit interrupter
US2979587A (en) * 1958-10-28 1961-04-11 Jennings Radio Mfg Corp Vacuum electric switch
US3082307A (en) * 1959-04-30 1963-03-19 Gen Electric Vacuum type circuit interrupter
US3185800A (en) * 1963-02-18 1965-05-25 Gen Electric Vacuum type circuit interrupter with improved vapor-condensing shielding
US3246979A (en) * 1961-11-10 1966-04-19 Gen Electric Vacuum circuit interrupter contacts
US3280286A (en) * 1964-07-03 1966-10-18 Mc Graw Edison Co Vacuum-type circuit interrupter
US3321599A (en) * 1966-04-20 1967-05-23 Gen Electric Vacuum-type circuit interrupter with means for reducing arc voltage during high instantaneous currents

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975256A (en) * 1958-07-24 1961-03-14 Gen Electric Vacuum type circuit interrupter
US2979587A (en) * 1958-10-28 1961-04-11 Jennings Radio Mfg Corp Vacuum electric switch
US3082307A (en) * 1959-04-30 1963-03-19 Gen Electric Vacuum type circuit interrupter
US3246979A (en) * 1961-11-10 1966-04-19 Gen Electric Vacuum circuit interrupter contacts
US3185800A (en) * 1963-02-18 1965-05-25 Gen Electric Vacuum type circuit interrupter with improved vapor-condensing shielding
US3280286A (en) * 1964-07-03 1966-10-18 Mc Graw Edison Co Vacuum-type circuit interrupter
US3321599A (en) * 1966-04-20 1967-05-23 Gen Electric Vacuum-type circuit interrupter with means for reducing arc voltage during high instantaneous currents

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3541284A (en) * 1967-12-14 1970-11-17 Allis Chalmers Mfg Co Combined vacuum circuit interrupter and impedance means
US3576960A (en) * 1968-03-08 1971-05-04 Gen Electric Flange fastening means for a contact button for a vacuum-type circuit interrupter
US3857005A (en) * 1970-11-25 1974-12-24 Siemens Ag Vacuum switch assembly
JPS4897060A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1972-02-14 1973-12-11
US3789256A (en) * 1972-05-03 1974-01-29 Westinghouse Electric Corp Shielded spark gap device
JPS496472A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1972-05-09 1974-01-21
JPS49131567U (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1973-03-10 1974-11-12
US3996437A (en) * 1973-12-03 1976-12-07 Cutler-Hammer, Inc. Vacuum contactor for motor control and method of making
US4077114A (en) * 1975-03-22 1978-03-07 Kabushiki Kaisha Meidensha Vacuum power interrupter
US4481390A (en) * 1980-07-01 1984-11-06 Kabushiki Kaisha Meidensha Vacuum circuit interrupter
US4478347A (en) * 1981-01-23 1984-10-23 Westinghouse Electric Corp. Unitary end closure and seal shield member for vacuum interrupter
EP0123475A1 (en) * 1983-04-14 1984-10-31 Westinghouse Electric Corporation Method of joining a contact to an electrode
US5594224A (en) * 1993-12-24 1997-01-14 Hitachi, Ltd. Vacuum circuit interrupter
US11756756B2 (en) * 2021-02-25 2023-09-12 S&C Electric Company Vacuum interrupter with double live shield

Also Published As

Publication number Publication date
JPS451489B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1970-01-19
GB1103619A (en) 1968-02-21
DE1640211A1 (de) 1970-06-04

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