EP0123475A1 - Method of joining a contact to an electrode - Google Patents
Method of joining a contact to an electrode Download PDFInfo
- Publication number
- EP0123475A1 EP0123475A1 EP84302428A EP84302428A EP0123475A1 EP 0123475 A1 EP0123475 A1 EP 0123475A1 EP 84302428 A EP84302428 A EP 84302428A EP 84302428 A EP84302428 A EP 84302428A EP 0123475 A1 EP0123475 A1 EP 0123475A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrode
- contact
- stem
- bore
- vacuum
- 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.)
- Withdrawn
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
- H01H33/60—Switches wherein the means for extinguishing or preventing the arc do not include separate means for obtaining or increasing flow of arc-extinguishing fluid
- H01H33/66—Vacuum switches
- H01H33/664—Contacts; Arc-extinguishing means, e.g. arcing rings
Definitions
- the annular bushing 28 is preferably an insulating member and includes a cylindrical portion 56 which extends coaxially within the bellows 32.
- the guide bushing 28 can also include an axially extending flange 58 by which the guide bushing 28 is radially aligned and seated within the end plate 14 aperture 26.
- the guide bushing 28 is secured to the end plate 14 by a retainer member 60 disposed over the bushing and engaged with the outer edge 62 of the end plate 14.
Landscapes
- High-Tension Arc-Extinguishing Switches Without Spraying Means (AREA)
Abstract
@ Method of joining an electrode to a contact having a material constituent with high vapor pressure in a final assembly stage of a vacuum device such as a vacuum interrupter. Attachment is effected during the vacuum-exhaust operation by providing an axially extending stem of a contact that is inserted into an axial bore in an electrode. A low vapor pressure, low melting point material such as tin (SN) or the like is placed in the bore prior to the insertion of the stem. Venting means in the electrode purge the bore during the vacuum exhaust stage which provides sufficient heat to liquefy the conductive material which flows between the stem and electrode, bore wall where it eventually solidifies upon cooling.
Description
- This invention relates to a method of joining a contact to an electrode. More particularly, this invention provides a technique for the low temperature fabrication of electrode to contact bonds. This technique is particularly useful in the manufacture of vacuum devices, such as vacuum circuit interrupters.
- Vacuum circuit interrupters are used to interrupt electric currents in electric power transmission and distribution systems. A conventional interrupter includes a generally cylindrical insulating envelope portion with a pair of contacts hermetically sealed through end plates sealed to the insulating envelope, with the device being evacuated. One of the contacts is movable along the device axis to make and break contact with the other, fixed contact from a mating closed contact, current carrying position, to an open contact, spaced apart circuit interrupting position.
- The conventional structure for permitting contact movement is a generally cylindrical bellows which is hermetically sealed at one end to an end plate, and at the other end to the contact support rod or electrode which extends slidably through a guide bushing in the end plate.
- It is the conventional practice to firmly attach the metal contact to the electrode by means of high temperature'vacuum brazing. This technique is illustrated in U.S.' Patent Specification Nos. 4,053,728 and 2,406,327. The electrode is usually copper while the contact may be copper, chromium, tungsten or a desired alloy thereof. Because a copper electrode is often being joined to a contact formed from a different material, the high temperature process of vacuum brazing makes a contact to electrode joint possible regardless of the disparity of the materials being joined.
- Another technique for joining the contact to an electrode is disclosed in U.S. Patent Specification Nos. 4,272,661 and 2,406,327 whereby the contact is attached to the electrode with a threaded member such as a screw or bolt..
- The type of material used in the contact is determined by the performance requirements of the particular vacuum interrupter device in which the contact is employed. As discussed above, vacuum brazing is routinely used in most vacuum interrupters and the completed contact-electrode junction is preserved for other subsequent tube assembly operations in' a vacuum environment. In certain cases, however, a contact is used in a vacuum interrupter which is necessary to obtain desired vacuum interrupter performance, but which is not compatible with high temperature-vacuum processing. For example, a contact heavily loaded with a material which has a low melting temperature and a high vapor pressure and which expands during solidification, such as bismuth (Bi), is disposed to failure. This failure is certain if the contact is present in an evacuated bottle that is brazed at high temperature because the bismuth, or a material with similar properties, generates a vapor which penetrates the braze joints rendering them brittle and full of voids. As a result the joint is not vacuum tight.
- It is therefore an object of this invention to provide a technique for the assembly of an electrode and contact by means of a liquid-mechanical attachment.
- It is another object of this invention to provide a method for forming a low resistance joint which bonds the electrode and contact of a vacuum device.
- It is yet another object of this invention to provide a technique for the attachment of a contact heavily loaded with a metal having a low melting temperature and high vapor pressure to an electrode.
- Accordingly, the present invention resides in a method of joining a contact to an electrode which comprises the steps of joining an electrically conductive stem to the contact; inserting said stem into an electrode having a bore therein adapted to receive said stem; providing a low vapor pressure, low melting point temperature conductive material in said bore; heating said electrode and conductor under a vacuum to at least a temperature sufficient to liquefy said conductive material whereby said material flows between said stem and said electrode bore; and cooling said conductor and electrode, solidifying said liquefied conductive material, forming a conductor joint between said electrode and said conductor.
- Desirably, the electrode has a vent therein permitting purging of the bore during the final vacuum stage of assembly. The stem and bore may have complementing threads whereby a mechanical joint is formed when the contact mounted stem is threaded into the bore in the electrode.
- In order that the invention can be more clearly understood, convenient embodiments thereof will now be described, by way of example, with reference to the accompanying drawing, which is an elevational view, partly in cross section, of a vacuum interrupter.
- Vacuum circuit interrupter 10 includes a gener- .ally cylindrical,
insulating envelope 12 withend plate closures end plate 14 is at the movable contact end, whileend plate 16 is at the fixed contact end. - The fixed
end plate 16 is an inwardly dished member with a cylindrical conductivesupport rod electrode 22 sealed through acentral aperture 24 provided through theend plate 16. - - The
movable end plate 14 is a planar member with acentral aperture 26 therethrough. An annularguide bushing member 28 is disposed within theaperture 26 and a movable contactsupport rod electrode 30 is slidably fitted through theguide bushing member 28. A generally cylindricalbellows seal member 32 is hermetically sealed at oneend 34 to theend plate 14, while the other end of thebellows seal member 32 is hermetically sealed to thecontact support rod 30 at an axially inwardly extendingportion 38. - The
contacts 4C and 42 which are disposed at the extending ends of respective contact support rod orelectrode cylindrical center shield 48 is closely spaced from the insulatingenvelope 12, whileannular end shields respective end seals shaped bellows shield 54 which is mounted from movablesupport rod electrode 30, extends about thebellows 32. - The
annular bushing 28 is preferably an insulating member and includes acylindrical portion 56 which extends coaxially within thebellows 32. The guide bushing 28 can also include an axially extendingflange 58 by which the guide bushing 28 is radially aligned and seated within theend plate 14aperture 26. Theguide bushing 28 is secured to theend plate 14 by aretainer member 60 disposed over the bushing and engaged with theouter edge 62 of theend plate 14. - The present invention is directed to a technique r for the attachment of each
contact support rod electrodes envelope 12 at high enough temperature and vacuum to obtain desirable vacuum tube performance and yet maintains low enough bismuth vapor pressure that contact fall off and other disattach- ment problems are substantially eliminated. - The contact assembly includes the contact 40 (or 42) and a threaded
stem 64. The threadedstems 64 consist of an electrically conductive material such as copper or the like which may be threaded at only one end as indicated at 66 or at both ends (not illustrated). The threadedstem 64 can include a flangedportion 68 which mechanically retains the contact 40 (or 42) against the electrode 22 (or 30). Additionally, each contact 40 (42) can be mounted on a stainless steel substrate, one of which is illustrated at 70 as an example thereof. Alternatively, the threadedstem 64 can be attached to the contact 40 (or 42) prior to the assembly of the vacuum tube by means of a braze joint or as will be explained below, by an adaptation of the method of this invention. Theelectrodes axial bore 72 having a threadedwall portion 74 adapted to receive the threadedportion 68 of the stem 66 axially extending from the contact. Thebore 72 also includes a wellportion 76 containing asupply 78 of a low vapor pressure, low melting point conductor, such as tin (Sn) a tin alloy, or the .like. A vent, such as thevent hole 80 is provided in each of theelectrodes Venting hole 80 provides communication between theelectrode bore wells 76 and the environment exterior thereto which is the evacuatedenvelope 12 of the vacuum tube assembly 10. During the assembly of the vacuum tube, air is purged from the threaded surfaces of the stem and electrode bore which purging in turn facilitates the migration of thetin 78 along the threaded surfaces. - During final assembly of the vacuum interrupter structure 10, the contact and stem are joined together by brazing, in a hydrogen atmosphere, a brazed threaded joint or by means of a thin strip of tin (Sn), a tin alloy or the like characterized by low vapor pressure and a low melting point disposed between the stem and the contact, or the stem, substrate and contact as at 82. When the thin strip of tin is utilized, the joint between the contact and the stem is formed during vacuum exhaust. The electrode bore well 76 is filled with tin and the contact stem screwed tightly into the electrode bore well 76. Subsequent exhaust in vacuum heats the vacuum interrupter structure 10 to a temperature of about 450°C In reaching this temperature, the exhaust cycle passes through the melting point of tin, 231°C. The liquid tin wicks into the purged, mated threads, but does not evaporate because of its low vapor pressure. Moreover, the mated threads of the stem and electrode bore function as a mechanical stop which captures the melted tin. In addition, it is possible to provide other mechanical means such as a flute, wedge or step associated with the electrode to effect the mechanical capture of the tin and inhibit further migration either in addition to or in lieu of threads. The tin freezes in situ upon cooling to room temperature and is not attacked by corrosive bismuth vapor while in the liquid state. Alternatively, rather than providing tin, a tin alloy or the like in the electrode well, the stem and/or the electrode bore can be plated with the low vapor pressure, low melting point conductive material prior to the mechanical connection of the contact to the electrode.
- During operation of the vacuum interrupter at appropriate current and temperature ranges the contact electrode joint formed according to the present technique has been found to be compatible with, and imperceptible as, a resistive element in series with the electrode.
Claims (6)
1. A method of joining a contact to an electrode characterized by the steps of joining an electrically conductive stem to the contact; inserting said stem into an electrode having a bore therein adapted to receive said stem; providing a low vapor pressure, low melting point temperature conductive material in said bore; heating said electrode and conductor under a vacuum to at least a temperature sufficient to liquefy said conductive material whereby said material flows between said stem and said electrode bore; and cooling said conductor and electrode, solidifying said liquefied conductive material, forming a conductor joint between said electrode and said conductor.
2. A method according to claim 1, characterized in that the conductive material is tin or a tin alloy.
3. A method according to claim 1 or 2, characterized in that the electrode bore adapted to receive the stem therein has threaded sidewalls and the stem is provided with complementary threads and is threadedly received in the bore whereby the liquefied material flows between said threads.
4. A method according to claim 1, 2 or 3, characterized in that the electrode bore is purged through a vent in the electrode as the contact and electrode are heated in the vacuum.
5. A method according to any of claims 1 to 4, characterized in that the electrically conductive stem is joined to the contact by providing a low vapor pressure, low melting point temperature conductive material between the stem and the contact, liquefying said material and then solidifying the latter.
6. A method according to any of claims 1 to 5, characterized in that the contact consists of an alloy which includes bismuth.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US48478883A | 1983-04-14 | 1983-04-14 | |
US484788 | 1983-04-14 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0123475A1 true EP0123475A1 (en) | 1984-10-31 |
Family
ID=23925601
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP84302428A Withdrawn EP0123475A1 (en) | 1983-04-14 | 1984-04-10 | Method of joining a contact to an electrode |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0123475A1 (en) |
JP (1) | JPS59198625A (en) |
ZA (1) | ZA842116B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0763841A2 (en) * | 1995-09-16 | 1997-03-19 | ABBPATENT GmbH | Contact arrangement for vacuum switch |
WO2014031428A1 (en) * | 2012-08-20 | 2014-02-27 | Eaton Corporation | Contact assembly and vacuum switch including the same |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1437162A (en) * | 1964-11-19 | 1966-04-29 | Improvements to electrical vacuum switches | |
US3265840A (en) * | 1963-12-12 | 1966-08-09 | Joslyn Mfg & Supply Co | Vacuum type circuit interrupter device |
FR1529344A (en) * | 1967-06-28 | 1968-06-14 | Ass Elect Ind | Hermetically sealed switches |
US3430015A (en) * | 1966-03-28 | 1969-02-25 | Gen Electric | Vacuum-type circuit interrupter having brazed joints protected from weld-inhibiting constitutent in contact structure |
DE1957812A1 (en) * | 1969-04-24 | 1970-11-05 | Elektro App Werke Berlin Trept | Switching capsule for vacuum switches and contactors |
CH531248A (en) * | 1971-05-17 | 1972-11-30 | Siemens Ag | Vacuum switch |
-
1984
- 1984-03-21 ZA ZA842116A patent/ZA842116B/en unknown
- 1984-04-10 EP EP84302428A patent/EP0123475A1/en not_active Withdrawn
- 1984-04-12 JP JP59074834A patent/JPS59198625A/en active Pending
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3265840A (en) * | 1963-12-12 | 1966-08-09 | Joslyn Mfg & Supply Co | Vacuum type circuit interrupter device |
FR1437162A (en) * | 1964-11-19 | 1966-04-29 | Improvements to electrical vacuum switches | |
US3430015A (en) * | 1966-03-28 | 1969-02-25 | Gen Electric | Vacuum-type circuit interrupter having brazed joints protected from weld-inhibiting constitutent in contact structure |
FR1529344A (en) * | 1967-06-28 | 1968-06-14 | Ass Elect Ind | Hermetically sealed switches |
DE1957812A1 (en) * | 1969-04-24 | 1970-11-05 | Elektro App Werke Berlin Trept | Switching capsule for vacuum switches and contactors |
CH531248A (en) * | 1971-05-17 | 1972-11-30 | Siemens Ag | Vacuum switch |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0763841A2 (en) * | 1995-09-16 | 1997-03-19 | ABBPATENT GmbH | Contact arrangement for vacuum switch |
EP0763841A3 (en) * | 1995-09-16 | 1998-05-20 | ABBPATENT GmbH | Contact arrangement for vacuum switch |
WO2014031428A1 (en) * | 2012-08-20 | 2014-02-27 | Eaton Corporation | Contact assembly and vacuum switch including the same |
Also Published As
Publication number | Publication date |
---|---|
JPS59198625A (en) | 1984-11-10 |
ZA842116B (en) | 1984-10-31 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Designated state(s): CH DE GB IT LI NL |
|
17P | Request for examination filed |
Effective date: 19850429 |
|
17Q | First examination report despatched |
Effective date: 19860407 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
18D | Application deemed to be withdrawn |
Effective date: 19860819 |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: SANTILLI, VINCENT JOSEPH |