US3791711A - Method of fabricating a three-terminal voltage surge arrester - Google Patents

Method of fabricating a three-terminal voltage surge arrester Download PDF

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Publication number
US3791711A
US3791711A US00297412A US3791711DA US3791711A US 3791711 A US3791711 A US 3791711A US 00297412 A US00297412 A US 00297412A US 3791711D A US3791711D A US 3791711DA US 3791711 A US3791711 A US 3791711A
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United States
Prior art keywords
housing
rod
side wall
pair
electrode
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Expired - Lifetime
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US00297412A
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English (en)
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G Jonassen
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TELECOMMUNICATIONS IND
TELECOMMUNICATIONS IND INC US
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TELECOMMUNICATIONS IND
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    • 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
    • H01T4/00—Overvoltage arresters using spark gaps
    • H01T4/10—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel
    • H01T4/12—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel hermetically sealed

Definitions

  • a three-terminal voltage surge arrestor is an ionization chamber formed in an electrically conductive housing wherein a pair of opposed electrodes are inserted into the chamber with a gap defined between the opposing ends of the electrodes and another gap defined between the end of each electrode and the housing side wall.
  • the two electrodes constitute the two ac tive terminals of the surge arrestor which are connected across an electrical instrument to be protected,
  • the third terminal of the arrestor is defined by the housing side wall which is grounded.
  • the pair of electrodes is positioned concentrically within the ionization chamber and in axial alignment with one another. Also, it is important to maintain a desired interelectrode gap between the opposing inner ends of the electrodes. In a true three-terminal voltage surge arrestor, such interelectrode gap should equal the gap between each electrode and the housing side wall. It will be realized that the dimensions of these gaps necessarily determine the break down characteristics of the voltage surge arrestor, i.e. the maximum voltage potential across the electrodes prior to ionization of the gas. In addition a convenient method of withdrawing air from the ionization chamber and substituting a readily ionizable gas will substantially facilitate the manufacture of the device.
  • the method of thisinvention comprises the steps of forming an electrically conductive hollow housing having a cylindrical side wall extending between opposed open ends thereof, the side wall including a longitudinally extending welding flange at each end; placing a pair of electrically insulative hollow cylindrical members within the housing adjacent opposing ends thereof and in spaced apart relation to one another to leave interiorally exposed a central part of said conductive housing; placing a pair of rod like electrodes into said ends of said housing, each electrode including means thereon for engaging its adjacent welding flange as the electrode is inserted into the housing to concentricize the rod in the housing; the confronting ends of said electrodes being spaced from one another a distance substantially equal to the distance said ends are from said exposed central part of said housing; welding one electrode rod to an end of the housing to seal it thereto; withdrawing air from the interior of the housing through the other end of the housing; injecting a noble gas into the interior of the housing through said other end of the housing; welding the other electrode rod to said other end of the housing to seal
  • the concentricizing means on each electrode rod comprises a stop having a base portion of greater outer diameter that the inner diameter'of the housing, and an inwardly tapered shoulder. If any part of the welding flange on an end of the housing engages the shoulder as the electrode rod is inserted into the housing through such end, further inward movement of the rod will cause the rod to shift laterally into concentricity with the housing, which concentricity is obtained when the base portion engages the welding flange. At this point, the rod is restrained from further inward or lateral movement thereby being maintained in concentricity with the housing.
  • FIG. 1 is a longitudinal cross-sectional view of a housing formed in accordance with the method of this invention
  • FIG. 2 is a longitudinal cross-sectional view of an insulative member --formed in accordance with the method of this invention
  • FIG. 3 is a side elevation view of a solder ring adapted to be snapped into an annular groove in the hollow member of FIG. 2;
  • FIG. 4 is a side elevational view of an electrode formed in accordance with the method of this invention.
  • FIG. 5 is a fragmentary cross-sectional view, partly in elevation, of a voltage surge arrestor of this invention shown in one stage of assembly;
  • FIG. 6 is a cross-sectional view, partly in elevation, of the arrestor of FIG. 5 shown in another stage of assembly;
  • FIG. 6A is a fragmentary view, similar to F IG. 6 but in enlarged scale, showing one end of said arrestor;
  • FIG. 7 is a cross-sectional view, partly in elevation, of the voltagesurge arrestor of FIG. 6 shown in completed form.
  • the device to be manufactured by the present method is shown in FIG. 7, wherein it is generally designated by the reference numeral 50.
  • the device or surge arrestor 50 comprises a pair of insulative tubes 22 which are in axially aligned and spaced apart relation.
  • a conductive metal segment 42 Bridging the space between the tubes 22 is a conductive metal segment 42 which is in telescoping relation with each tube 22 and its connected in hermetically sealed relation with the telescoping portions of the tube 22 by means of solder rings 30.
  • the insulative tubes 22 and the conductive central portion 42 define an outer housing which is capped at each end by an electrode assembly including an elongated electrode element 32 having a cap at its outer end, the cap being formed of flanges 36 and inwardly extending tubular metallic portions 52 welded to said flanges, the metallic portions 52 being joined in hermetically sealed relation to the tubes 3 tween said electrodes and the concentric center portion 42.
  • the interior space defined by the above described structure is filled with a readily ionizable gas such as a noble gas.
  • a readily ionizable gas such as a noble gas.
  • a first step of the method of this invention comprises forming an electrically conductive hollow housing 10 having a cylindrical side wall 12 extending between opposed open ends 14 and 16 of the housing.
  • Housing 10 is preferably metallic and most preferably made of a brazable, weldable metal such as nickel-iron alloy, brass or cooper.
  • Sidewall 12 is preferably circularly cylindrical and preferably includes an annular boss 18 formed on the inner surface 19 of the side wall boss 18 lying substantially intermediate ends 14 and 16. Boss 18 is defined by a pair of shoulders 19a and 196.
  • Housing 10 is formed with an outwardly longitudinally extending welding flange 20 at each end thereof.
  • each welding flange is annular and is tapered to a knife edge 23' (see FIG.
  • each welding flange 20 may be defined by a plurality of spaced welding protuberances (not shown) extending outwardly from each end of the housing and each terminating in a knife edge.
  • each hollow member 22 includes a cylindrical side wall 24 extending between a pair of opposed open ends 26.
  • Each hollow member 22 is fabricated of a high temperature resistant electrically insulating material such as glass or ceramic. Alumina is the preferred material for members 22.
  • Each hollow member 22 is formed with an outer diameter substantially equal to the inner diameter of .side' wall 12 of housing 10, and a length slightly less thanthe distance between each end of housing and the closest shoulder 19a or 19b of annular boss 18 to such end within the housing. In this manner, each hollow member 22 may be fitted in the housing with one end 26 of said member in contact with a shoulder 19a or 19b and the other end of said member lying near one end of the housing. This relationship is more completely described below.
  • each hollow member 22 is formed with at least one circumferential groove 28 in side wall 24.
  • each rod 32 is comprised of a solid cylindrical shaft 33 extending between opposing ends 38 and 39 thereof, and including a stop or flange 34 formed thereon.
  • stop 34 cooperates with a welding flange 20 on housing 10 to guide the rod into concentricity with the housing.
  • stop 34 comprises a circular base portion 36 and an inwardly tapered or frusto-conical shoulder 37. More specifically, shoulder 37 is tapered from a maximum diameter at base portion 36 which is less than the diameter of base portion 36, to thereby define an annular rim 39 at the outer periphery of the shoulder. Shoulder 37 tapers to a minimum diameter adjacent shaft 33 which is greater than the diameter of shaft 33. It is important that the line of intersection of shoulder 37 with base portion 36 be equal in diameter to the inner diameter of each welding flange 20 at outer edge 23 thereof.
  • end 38 of electrode shaft 33 is inserted into housing 10, such as through end 16 thereof, and in the event the electrode shaft is initially eccentric with the housing, a portion of welding flange 20 at housing end 16 will engage frusto-conical shoulder 37 to thereby direct the shaft laterally into concentric alignment with the flange edge 23 and thus with the housing, which concentricity isestablished when edge 23 of the welding flange engages base portion 36 of stop 34. Further, with edge 23 of the welding flange at the line intersection between base portion 36 and shoulder 37, the electrode rod will be restrained from further movement laterally of its axis thereby being maintained in concentric alignment with the housing.
  • solder rings 30 are snapped into associated grooves 26 in hollow members 22. Then, each hollow member is inserted into housing 10 through a distinct end thereof in the manner above described. This is followed by inserting one electrode rod 32 through the associated hollow member 22 into the interior of housing 10, the inward progression of said electrode being guided into concentricity with the housing by the cooperation of welding flange 20 with stop 34 in the manner above described.
  • the nextstep of the method of this invention comprises securing the one electrode to an associated end of the housing. This is preferably accomplished by heating such end of the housing to weld the electrode thereto. In such welding process, the rod is preferably moved further into housing 10 by applying an inward force thereto so that the welding flange will melt down and effect a hermetic seal between the flange 36 and the housing 10. This is preferably accomplished by resistance welding, although other well known welding techniques may be employed.
  • solder ring 30 closest the end of the electrode which has been welded to the housing is softened to seal the housing to the adjacent hollow member 22. It will be realized that if the application of external heat is used to weld the electrode to housing 10, the solder ring 30 in the hollow member 22 adjacent the flange 36 will be caused to melt thereby simultaneously effecting a hermetic seal between the housing side wall and such hollow member.
  • the other electrode 32 is disposed concentrically within the housing and all of the air in the interior of the housing is evacuated therefrom by a conventional vacuum assembly (not shown). (It will be recognized that the second electrode could have been so positioned earlier in the process and then held in its concentric position by suitable means.) At some point in the process up to this point, preferably at this point, the two inner solder rings 30 are softened to form second hermetic seals between hollow members 22 and metal wall 10. The purpose of this will become apparent hereinafter.
  • the housing is then preferably transferred to a conventional dry box'which typically contains dry nitrogen.
  • a noble gas such as argon
  • argon is injected into the dry box to drive out the nitrogen whereupon the noble gas passes into the interior of housing through non-welded end 14 thereof.
  • the nonwelded electrode 32 is secured to end 14, preferably in accordance with the procedure above outlined for welding the first electrode to end 16 of housing 10.
  • the assembled structure is shown in FIG. 6 wherein the pair of electrodes represent the two active terminals of a three-terminal voltage surge arrestor.
  • an interelectrode gap 40 is formed between the inner ends 38 of the pair of electrode rods, and that the gap 41 is formed between the electrode rods and boss 18 of housing side wall 12.
  • the extent of gap 40 in a direction parallelto axis 21 of the housing substantially equals the extent of gap 41 in a direction perpendicular to said axis. It has been found that such relationship between gap 40 and gap 41 optimizes the efficiency of the arrestor and, in fact, is a requirement of a true threeterminal voltage surge arrestor.
  • the side wall 12 of housing 10 contain a segment 42 thereof to be grounded and used as the third and ground terminal of the surge arrestor.
  • a segment 42 thereof to be grounded and used as the third and ground terminal of the surge arrestor.
  • boss 18 it is important that at'least a portion of such a segment include boss 18 so that when the gas is ionized, the current flow will be from the electrodes through gap 41 to ground.
  • segment 42 of housing side wall 12 it is essential 'to isolate the segment from the pair of electrode rods 32.
  • One way of accomplishing this is to remove a complete circumferential portion of housing side wall 12 near each end of the housing leaving segment 42 (FIG. 7) between the spaces formed in the housing side wall with said portions removed.
  • each such portion is removed from the housing side wall in an area between the pair of solder rings in each hollow member 22.
  • a preferred way of removing the pair of housing portions to form spaces 44 and 46 is by placing housing 10 on a lathe or the like and carving out annular rings between each of the two pairs of solder rings in the hollow members. Then, segment 42 is isolated from electrodes 32 and may serve as the third or ground electrode.
  • a three-terminal voltage surge arrestor 50 is formed, as shown in FIG. 7.
  • the operating characteristics of surge arrestor 50 will be defined by the nature and characteristics of the specific gas and electrically conductive materials used, as well as by the dimensions of gaps 40 and 41.
  • a method for fabricating a three-terminal voltage surge arrestor comprising the steps of:
  • an electrically conductive hollow housing having a cylindrical side wall extending between opposed open ends of the housing, the side wall including a welding flange at each end of the housing extending outwardly in a direction substantially parallel to the longitudinal axis of the housing;
  • the means for engaging the welding flange to concentricize said rods comprises a base on each said rod extending radially outward therefrom and a frusto-conical shoulder axially aligned with said rod and base and having a maximum radius adjacent said base and slightly smaller than the diameter of said welding flange, whereby axial movement of said electrode rods inward of said housing will laterally shift said rods when they are originally eccentric of said housing in a direction to concentricize said rods.
  • step of forming the pair of hollow members includes forming a pair of spaced apart circumferential grooves in the side wall of each hollow member, and wherein the hollow memb. positioning each solder piece in a groove in the side wall of a particular hollow member, which solder piece will melt upon the application of heat to effect a pair of spaced apart hermetic seals between said particular hollow member and the housing.

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US00297412A 1972-10-13 1972-10-13 Method of fabricating a three-terminal voltage surge arrester Expired - Lifetime US3791711A (en)

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US29741272A 1972-10-13 1972-10-13

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JP (1) JPS4973641A (enrdf_load_html_response)
CA (1) CA999421A (enrdf_load_html_response)
CH (1) CH576713A5 (enrdf_load_html_response)
DE (1) DE2346987A1 (enrdf_load_html_response)
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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3858077A (en) * 1973-11-20 1974-12-31 Gen Instrument Corp Gas tube transient voltage protector for telecommunication systems
US4156886A (en) * 1977-04-19 1979-05-29 Tii Corporation Gas tube surge arrester
US4175277A (en) * 1976-11-08 1979-11-20 Bell Telephone Laboratories, Incorporated Voltage surge protector
US4495539A (en) * 1980-09-19 1985-01-22 The M-O Valve Company Limited Excess voltage arresters
US5215478A (en) * 1992-05-29 1993-06-01 Amphenol Corporation Spark gap device
US5423694A (en) * 1993-04-12 1995-06-13 Raychem Corporation Telecommunications terminal block
US5557250A (en) * 1991-10-11 1996-09-17 Raychem Corporation Telecommunications terminal block
US5561581A (en) * 1994-01-11 1996-10-01 Hitachi, Ltd. Arrester and manufacturing method thereof
WO1997038475A1 (en) * 1996-04-09 1997-10-16 Yufeng Du A high power surge arrester
US5742223A (en) * 1995-12-07 1998-04-21 Raychem Corporation Laminar non-linear device with magnetically aligned particles
DE4444515B4 (de) * 1994-10-13 2009-10-01 Epcos Ag Gasgefüllter Drei-Elektroden-Überspannungsableiter für hohe Schaltleistungen

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3710191A (en) * 1970-12-08 1973-01-09 Siemens Ag Overvoltage arrester with several electrodes

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3710191A (en) * 1970-12-08 1973-01-09 Siemens Ag Overvoltage arrester with several electrodes

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3858077A (en) * 1973-11-20 1974-12-31 Gen Instrument Corp Gas tube transient voltage protector for telecommunication systems
US4175277A (en) * 1976-11-08 1979-11-20 Bell Telephone Laboratories, Incorporated Voltage surge protector
US4156886A (en) * 1977-04-19 1979-05-29 Tii Corporation Gas tube surge arrester
US4495539A (en) * 1980-09-19 1985-01-22 The M-O Valve Company Limited Excess voltage arresters
US5557250A (en) * 1991-10-11 1996-09-17 Raychem Corporation Telecommunications terminal block
US5215478A (en) * 1992-05-29 1993-06-01 Amphenol Corporation Spark gap device
US5423694A (en) * 1993-04-12 1995-06-13 Raychem Corporation Telecommunications terminal block
US5588869A (en) * 1993-04-12 1996-12-31 Raychem Corporation Telecommunications terminal block
US5561581A (en) * 1994-01-11 1996-10-01 Hitachi, Ltd. Arrester and manufacturing method thereof
DE4444515B4 (de) * 1994-10-13 2009-10-01 Epcos Ag Gasgefüllter Drei-Elektroden-Überspannungsableiter für hohe Schaltleistungen
US5742223A (en) * 1995-12-07 1998-04-21 Raychem Corporation Laminar non-linear device with magnetically aligned particles
WO1997038475A1 (en) * 1996-04-09 1997-10-16 Yufeng Du A high power surge arrester

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JPS4973641A (enrdf_load_html_response) 1974-07-16
DE2346987A1 (de) 1974-04-18
CH576713A5 (enrdf_load_html_response) 1976-06-15
GB1429060A (en) 1976-03-24
CA999421A (en) 1976-11-09

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