Title of Invention	"METHOD AND APPARATUS FOR MOUNTING VAPOR SHIELD IN VACUUM INTERRUPTER AND VACUUM INTERRUPTER INCORPORATING SAME"
Abstract	A vacuum interrupter which comprises a single piece ceramic tube having end members secured to each end thereof to form therewith a vacuum envelope, a fixed contact mounted on a fixed electrode extending through one end member,a moveable contact mounted on a moveable electrode extending through the other end member and axially reciprocating into and out of contact with the fixed contact, a tubular shield inside the ceramic tube and surrounding the fixed contact and moveable contact, characterised in that a shield mount comprises a split ring which is installed in a circumferential groove in an inner surface of said ceramic tube and projects radially inwards into said vacuum envelope, a connection connecting said tubular shield to said split ring.

Title of Invention

"METHOD AND APPARATUS FOR MOUNTING VAPOR SHIELD IN VACUUM INTERRUPTER AND VACUUM INTERRUPTER INCORPORATING SAME"

Abstract

A vacuum interrupter which comprises a single piece ceramic tube having end members secured to each end thereof to form therewith a vacuum envelope, a fixed contact mounted on a fixed electrode extending through one end member,a moveable contact mounted on a moveable electrode extending through the other end member and axially reciprocating into and out of contact with the fixed contact, a tubular shield inside the ceramic tube and surrounding the fixed contact and moveable contact, characterised in that a shield mount comprises a split ring which is installed in a circumferential groove in an inner surface of said ceramic tube and projects radially inwards into said vacuum envelope, a connection connecting said tubular shield to said split ring.

Full Text	METHOD AND APPARATUS FOR MOUNTING VAPOR SHIELD W. VACUUM IKTEBBXPTER AND VACUUM INTERRUPTER INCORPORATING, S AMK BACKGROUND. OF THEJMyENTIQN Field of the fa-venttoft This invention relates to vacuum interrupters which provide protection in^ electric power circuits. More particularly, it relates to an arrangement and method for TTimwitino a vapor shield inside the ceramic- insulator forming the vacuum envelope of the interrupter. Background Information Vacuum intectuptets. typically haYe^tubulaE ceramic capped by endplatesto. form a vacuum envelope. A fixed contact mounted in the vacuum envelope on a first electrode extending through one end cap, and a moveable contact mounted on a moveable electcodeaxially slidj^blfetibrxaj^htheotiiex end. plate-form, a pair, of separable, contacts, which, are opened and closed by movement of the moveable electrode by a mechanism located outside of the vacuum envelope. When the separable contacts are opened with current flowing through,the, vacuum interrupter, ametalrvapor arc, is.struck between, the.contact surfaces. This arc continues until the current is interrupted, typically as the ac current goes through a zero crossing. In order to prevent the metal vapor from condensing on the ceramic insulator, ^generally cvJindrical metal vapor shield i&tvpically provided, between the contacts, and the ceramic inside the vacuum envelope. One type of vapor shield, the fixed shield, is electrically tied to one electrode, e.g., the fixed electrode, and therefore, can be physically supported by that electrode. The second common type, of vapor shield is. the floating, shield. which is electrically isolated from both electrodes. While it is widely known that the floating shield performs better at high voltages than the fixed shield designs, it is more difficult to mount. One common arrangement for mounting a floating vapor shield requires that the. ceramic be. formed, in. two cylindrical parts- wiJh. aLtnstal mojunjjng tiug. sand wictaed-between. The vapor shield is men secured to this mounting ring, typically by discrete flanges brazed to the shield and the mounting ring. While functionally adequate, this arrangement 1 can have several disadvantages. First attaching the shield in this manner requires two braze joints, which haxe. vacuum, on one side. and air on the, other, thereby providing two. potential leak paths. Second, the two cylindrical ceramics must be metal 1 zed at both ends, which leads to an increased cost. Lastly, the support mechanism exposes a conductor to the air leading to the need, fox external insulation for high, voltage, applications,. For these reasons, it is highly desirable to attach a floating shield inside a single ceramic. One approach has been to crimp the shield around a feature such as a ridge molded, as. part of the. cexamic Tbis_ is_ turn consuruing aad adds.a. feir amount of cost to. the. ceramic. Various other approaches to attaching the floating shield to a single piece ceramic have required specialized components which add complexity and cost There is. a need, therefore, for an improved arrangement and method for securing a floating vapor shield in a vacuum interrupter. There is a general need for such an improved mount and method of mounting which, do not require complex specialized parts, or tej&niques. More particularly, there is also a need for such an improved mount and method which can be used with a single piece ceramic. SUMMARY OF THE INVENTION This myentioa ^isfies. &&& needs, and otters, by providing a. vacum" interrupter with a single piece ceramic tube having a circumferential groove in an inner surface. A pair of end members form with this single piece ceramic tube a vacuum enclosure. A fixed contact is. mounted, oa a fixed electrode extending tbj"^ A moveable contact is mounted on a moveable electrode extending through the other end member and axially reciprocal into and out of contact with the fixed contact. A tubular shield is. supported inside, the ceramic tube and surrounding the. fixed and moveab Le contacts, by a shield mount. This shield mount includes a split ring seated in the circumferential groove in the ceramic tube and projecting radially inward from the inner surface of the ceramic tube into the. vacuum envelope where a coiraeetJon. coHnecis the shield to the split ting. The connection between the split ring and the vacuum shield can take several forms. In a preferred form of the invention, this connection includes a flange fixed to the outer surface, of the.tubiUar shield and a braze ring fixing the.flange.to.the.split ring. Also, preferably, the flange forms a gap with the outer surface of the tubular shield and the braze is formed from a braze ring positioned in the gap where it fixes the split ring to the flange in the outer surface of the tubular shield- In one embodiment of the iavenUocu the flange has a 2 radially extending terminal section which seats on the split ring. Also preferably, the flange extends, substantially fully around, the. tubular shield. In another aspect of the invention, the connection connecting the vapor shield to the split ring includes a circumferential shield groove in an outer surface of the shield, and an. additional split ring installed in the. groove in the shield, and projecting radially ojuiwanL A braze connection fixes the additional split ring in the groove in the shield to the split ring seated in the ceramic tube. In accordance with another aspect of the. invention, the connection connecting the split ring seated in the ceramic tube to the shield comprises an additional circumferential groove in the outer surface of the vapor shield m which the split ring seats directiy. This connection can, be further augmented by including a brazering to- fix thesplit ring t& the shield. The invention also is directed to a method of securing a floating vapor shield in a. vacuum interrupter which includes, the steps of forming acircumfexential groove in the ceramic tube, installing a split ring in the groove, and fastening the vapor shield to the split ring. The preferred form of fastening is implemented by providing a flange on the outer surface of the shield and fixing the flange, to the split ring, preferably by brazing. In a preferred method, the flange is formed with a gap between the flange and the shield and a braze ring is seated in this gap. The shield is then positioned in the ceramic tube with the flange engaging the split ring Heat is. applied, preferably in a. vacuum, to. melt the braze ring-In accordance with another aspect of the invention, the shield is fastened to the split ring by forming a shield groove in the outer surface of the tubular shield, installing an additional split ring in this, shield groove, and then brazing the additional split ring to. the split ring installed in the ceramic tube. Preferably, the brazing is accomplished by placing the braze ring on top of the additional split ring, inserting the shield into the ceramic tube with the additional sp^t ring "=p?"ed on fof q*Witional split ring qn In still another aspect of the invention, the tubular shield is fastened to the split ring by providing the tubular shield with a shield groove in an outer surface and installing the split ring in this shield groove as well as in the groove in the ceramic tube. Preferably, the split ring is brazed to the tube shield. The split ring is. installed in the ceramic, tube, by compressing it to. reduce its. outside diameter to an outer dimension which is less than the inner diameter of the ceramic 3 tube, aligning the compressed split ring with the groove in the ceramic tube and releasing the split ring to. radially expand into, the groove. BRIEF DESCRIPTION OF THE DRAWINGS A. full understanding nf ttie iav^njion, cm be gamed from tbe following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: Figure 1 is a longitudinal sectional view through a vacuum interrupter incorporating the invention. Figure 2 is a fragmentary view in enlarged scale of a section of Figure 1. Figure 3. is. a plane, view of one type, of split ring which forms part of the arrangement shown in Figure 2. Figure 4 is a view similar to Figure 2 of another embodiment of the invention- Figure 5 is a view similar to Figure 2 of an additional embodiment of the invention. Figure 6 illustrates a variation of the embodiment of the invention illustrated in Figure 5. Figure 7 is_ a. view, similar to Figure 2 of yet another embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure I illustrates a vacuum, ijiterrujjter 1... Tbe va.cu.urn. in;terruptet 1 includes a ceramic tube 3 which with end plates 5 and 7 forms a vacuum envelope 9. A fixed contact 11 is mounted on a fixed electrode 13 which extends through the end plate 5. A moveable.contact 15 is-carried by a maveable electrode. 17 and extends through the end plate 7. A bellows 19 forms a seal between the end plate 7 and the moveable electrode 17 while allowing axial movement of the moveable electrode 17 to bring the moveable contact 15 into and out of contact with the fixed, contact 11. The fixed contact 11 and moveable contact 15 form separable contacts 21 which when closed, complete an electrical circuit between trie fixed electrode 13. and maveable electrode 17, and when opened by axial movement of the moveable electrode 17 interrupt current flowing through the vacuum interrupter. The moveable electrode 17 is moved axially to open and dose the separable contacts by an 4 operating mechanism (not shown) connected to the moveable electrode outside of the vacuum envelop.e 9. As has been discussed, when the separable contacts 21 are opened with current flowing through the vacuum interrupter, an arc is struck between the fixed contact 11 and the raoveahle contact 15. These contacts, are configured, ta aid in extinguishing the arc which is necessary to interrupt the current flowing through the vacuum interrupter, as is well known. As was also mentioned above, the arc vaporizes metal from the contacts 11 and 15 which, could be deposited on the inner surface 23 of the ceramic 3 which serves, as an electrical insulator, as well as defining the vacuum envelope 9. In order to prevent such deposits, it is well known to provide a tubular vapor shield 25 between the separable contacts 21 and the.ceramic 3. This tubular vapor shield 25. isgeneraUy cylindrical, and as shown in Figure 1, is necked down to a degree at each end to extend its protection of the inner surface 23 of the ceramic 3. It is common to also provide an end shield 27 mounted on the moveable electrode 17 to. protect the bellows 19 from metal-vapor deposits. The vapor shield 25 is a floating shield. That is, it is not electrically connected to either electrode so that its potential floats. To provide this electrical isolation, the. vapor shield 25. is. supported by the ceramic 3. which, as. mentioned, is. an electrical insulator. In accordance with the invention and as more clearly seen in Figure 2, the tubular shield25 is. secured to. the ceramic 3 by a shield mount 31 which includes, aradially extending, circumferential groove 33 which is machined in the inner surface 23 of the ceramic 3 and a ring such as the split ring 35 which is installed in the groove 33. As shown in Figure X the exemplary split ring 3 5 has. agap_ 37 which permits, the split ring to. be radially compressed for insertion within the ceramic 3. Holes 39 accommodate pins on a conventional tool (not shown) used to manipulate the split ring. One of the advantages of the invention is that the. split ring 35 may be a conventional "snap, ring" or "retainer ring" which, are widely used and therefore inexpensive. The split ring 35 is seated in the groove 33 in the ceramic 3 and is sized so that it projects radially inward from the inner surface 23 of the ceramic 3. The gan 3 7 in the, spJit ring 35 is. sized to permit the ring to. be compressed sufficiently fox insertion inside the ceramic tube 3. In ihe exemplary split ring, the gap 37 subtends an angle V of about 15°. Th&tuhular. vapor shield 25 is then secured to. the, split ring 35 by a connection 41. In the embodiment of the invention illustrated in Figures 1 and 2, this connection 41 includes a flange 43 with a cylindrical section 45 at one end which is secured 5 to the outer surface of the tubular vapor shield 25 such as by brazing. Preferably, this flange 43- is, continuous, around the tubular vapor shield 25. The. other end 47 of the. flange 43. is. also, cylindrical but of larger diameter to form a gap 49 with the tubular shield 25. A tapered section 51 joins the cylindrical sections 45 and 47. A radial lip 53 on the cylindrical section 47 seMs OIL the split ring 35, The.connection 41 fur^exuidudes.abrazefoxrjie!4bya.braze. ring 55 which is seated in the gap 49. The method for securing the arc shield 25 to the ceramic tube using the shield mount 3_ 1 shown in Figures I and 3_ includes; forming, such as_ by machining, the groove 3_3- in the inner surface 23 of the ceramic 3, installing a ring, such as the split ring 35 in this groove 33 by radially compressing the split ring 35 using a tool (not shown) which engages the holes 3.9, aligning the compressed split ring 35 with the groove 33. and releasing the split ring, allowing it to expand into the groove but still projecting radially into the vacuum envelope 9. Next the flange 43 is secured to the arc shield 25 such as by brazing and the braze_ringS5 is.wedgejiui!o.thegap49heiw^e^ Thearc shield is then axially inserted into the ceramic 3 to seat the lip or rim 51 of the flange 43 against the split ring 35. The ceramic and arc shield are then placed in a vacuum oven which melts, the braze, ring 5.5. allowing the braze, material to. flow between the split ring 3.5 and the rim5I of the flange 43 and between the split ring and the arc shield 25. Finally, the braze is allowed to cool to solidify the connection. Figure 4 illustrates another embodiment of the. invention in which me. shield mount 31' uses a connection 41' in which the flange 43' has a cylindrical end section 45' brazed to the arc shield 25 and the other end section 47' is flared outward to form a gap 49. Again, a braze ring 55- is. wedged into this gap 49 between, the flange 43/ and the arc shield 25. As in the case of the first embodiment, the braze ring 55 melts when placed in a vacuum oven and forms a braze connection between tire split ring 35, the arc shield 25 and the flange 43'. An additional embodiment of the invention is.illustrated in. Figure 5 where, the shield mount 31" has a connection 41" which includes a circumferential shield groove 57 formed, such as by machining, in the outer surface 59 of the shield 25 in which the inner edge of the split ring 35 is. seated. Tnis connection. 41" also mcludes-a braze ring 55 which is dropped down on top of the split ring 35 and which melts to braze the split ring to the arc shield 25 when heated in the vacuum oven. In this embodiment, the split ring 35 is slightly compressed.radially and snapped into fee groove 3.3 in. the ceramic 3. The vapor shield25 is. then pressed into the split ring 35 causing it to expand within the groove 33 in the ceramic 3 until the shield groove 57 becomes aligned with the split ring 35 which then springs inward to 6 engage the shield groove. In a variation of this embodiment of the invention, the braze inset can be eliminated, as. shown in Figure 6. Yet another embodiment of the invention is illustrated in Figure 7. Here, the shield mount 31'" has a connection 41'" which includes an additional circumferential groove 61 formed, such as by machining, in the. outer surface. 5 9 of the arc shield and in which is. seated an additional split ring 63. In mis arrangement, the braze ring 55 is dropped down on top of the split ring 35.. and the arc shield is then inserted in the ceramic until the additional split ring 63 seats OJI top ctfthebrjazering 53, whi^ split ring 35 to the arc shield 25 and to the additional split ring 63. Typically, the ceramic is AI2O3 material, the arc shield 25 is copper or steel, the split ring 35 and the additional split ring 6i are 3.16. stainless, steel and the flanges.43. and 43' are 304 stainless steel. The invention provides a mount for the tubular arc shield in a vacuum interrupter and a method of securing it within the cecamic which, uses commonly available, split rings and other simple parts which are easily assembled to provide a secure mount for the arc shield. In addition, a single piece ceramic can be used so mat it is not necessary to form the ceramic in two. pieces, and rae£auze_ both ends of each piece. Therefore, it also, eliminates, the electrical isolation problem of the prior art technique of having a metal ring exposed at the outer surface of the ceramic, and consequently also eliminates the need for electrically isolating this ring.. The result is. a less, expensive and easier to implement arrangement While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those detailscould be developed in. light of ^ o.vecdl t®d3ings. of fe oj^ctoajre.. Accordingly^ the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents.thereof 7 WE CLAIM: 1. A vacuum interrupter (1) comprising: a single piece ceramic tube (3) having end members (5, 7) secured to each end thereof to form therewith a vacuum envelope (9); a fixed contact (11) mounted on a fixed electrode (13) extending through one end member (5); a moveable contact (15) mounted on a moveable electrode (17) extending through the other end member (7) and axially reciprocating into and out of contact with the fixed contact (11); a tubular shield (25) inside the ceramic tube (3) and surrounding the fixed contact (11) and moveable contact (15); characterised in that a shield mount (31) comprises a split ring (35) which is installed in a circumferential groove (33) in an inner surface (23) of said ceramic tube (3) and projects radially inwards into said vacuum envelope (9), a connection (41) connecting said tubular shield (25) to said split ring (35). 8 2. The vacuum interrupter as claimed in Claim 1 wherein the connection comprises a flange fixed to an outer surface of the tubular shield and a braze connection fixing the flange to the split ring. 3. The vacuum interrupter as claimed in Claim 2 wherein the flange forms a radial gap (49) with the outer surface of the tubular arc shield and the braze connection comprises a braze ring seated in the gap and which melts to fix the flange to the split ring. 4. The vacuum interrupter as claimed in Claim 3 wherein the flange has a radially extending terminal lip which abuts the split ring. 5. The vacuum interrupter as claimed in Claim 3 wherein the flange extends substantially fully around the tubular shield. 6. The vacuum interrupter as claimed in Claim 1 wherein the connection comprises a circumferential shield groove in an outer surface of the tubular shield, an additional split ring installed in the shield groove and projecting radially outward, and a braze connection fixing the additional split ring to the split ring installed in the ceramic tube. 9 7. The vacuum interrupter as claimed in Claim 1 wherein the connection comprises a circumferential shield groove in an outer surface of the tubular shield in which the split ring is seated. 8. The vacuum interrupter as claimed in Claim 7 wherein the connection further includes a braze connection fixing the split ring to the tubular shield. 9. A method of securing a tubular shield within a ceramic tube of a vacuum interrupter comprising the steps of: forming a circumferential groove on an inner surface of the ceramic tube; installing a split ring in the circumferential groove with the split ring projecting radially inward from the inner surface of the ceramic tube; and fastening the tubular shield to the split ring. 10. The method as claimed in Claim 9 wherein the fastening step comprises providing a flange on an outer surface of the tubular shield, and fixing the flange to the split ring. 10 11. The method as claimed in Claim 10 wherein the step of fixing comprises brazing. 12. The method as claimed in Claim 11 including forming the flange with a gap between the flange and the outer surface of the tubular shield, seating a braze ring in the gap, positioning the tubular shield within the ceramic tube with the flange engaging the split ring, applying heat to melt the braze ring, and cooling the melted braze. 13. The method as claimed in Claim 12 wherein the heat is applied in a vacuum. 14. The method as claimed in Claim 1 wherein the tubular shield is fastened to the split ring by providing a circumferential shield groove in an outer surface of the tubular shield, installing an additional split ring in the shield groove, and brazing the additional split ring to the split ring installed in the ceramic tube. 15. The method as claimed in Claim 14 wherein the brazing comprises placing a braze ring on the top of the split ring installed in the ceramic tube, inserting the tubular shield into the ceramic tube with the additional split ring seated on the braze ring, and applying heat to melt the braze ring. 11 16. The method as claimed in Claim 9 wherein the fastening comprises providing the tubular shield with a shield groove in an outer surface, installing the split ring in the shield groove also. 17. The method as claimed in Claim 16 further including brazing the split ring to the tubular shield. 18. The method as claimed in Claim 9 wherein installing the split ring comprises compressing the split ring to reduce its outside diameter to less than an inside diameter of the ceramic tube, aligning the compressed split ring with the groove, and releasing the split ring to radially expand into the groove. 19. A vacuum interrupter having a ceramic tube within which a tubular shield is secured by the method as claimed in any one of Claims 9 to 18. 20. A vacuum interrupter as claimed in Claim 1 and substantially as described herein with particular reference to Figures 1 to 3 or Figure 4 or Figure 5 or Figure 6 or Figure 7 of the accompanying drawings. A vacuum interrupter which comprises a single piece ceramic tube having end members secured to each end thereof to form therewith a vacuum envelope, a fixed contact mounted on a fixed electrode extending through one end member,a moveable contact mounted on a moveable electrode extending through the other end member and axially reciprocating into and out of contact with the fixed contact, a tubular shield inside the ceramic tube and surrounding the fixed contact and moveable contact, characterised in that a shield mount comprises a split ring which is installed in a circumferential groove in an inner surface of said ceramic tube and projects radially inwards into said vacuum envelope, a connection connecting said tubular shield to said split ring.

Full Text

METHOD AND APPARATUS FOR MOUNTING VAPOR SHIELD W. VACUUM IKTEBBXPTER
AND VACUUM INTERRUPTER INCORPORATING, S AMK
BACKGROUND. OF THEJMyENTIQN
Field of the fa-venttoft
This invention relates to vacuum interrupters which provide protection in^ electric power circuits. More particularly, it relates to an arrangement and method for TTimwitino a vapor shield inside the ceramic- insulator forming the vacuum envelope of the interrupter.
Background Information
Vacuum intectuptets. typically haYe^tubulaE ceramic capped by endplatesto. form a vacuum envelope. A fixed contact mounted in the vacuum envelope on a first electrode extending through one end cap, and a moveable contact mounted on a moveable electcodeaxially slidj^blfetibrxaj^htheotiiex end. plate-form, a pair, of separable, contacts, which, are opened and closed by movement of the moveable electrode by a mechanism located outside of the vacuum envelope. When the separable contacts are opened with current flowing through,the, vacuum interrupter, ametalrvapor arc, is.struck between, the.contact surfaces. This arc continues until the current is interrupted, typically as the ac current goes through a zero crossing. In order to prevent the metal vapor from condensing on the ceramic insulator, ^generally cvJindrical metal vapor shield i&tvpically provided, between the contacts, and the ceramic inside the vacuum envelope. One type of vapor shield, the fixed shield, is electrically tied to one electrode, e.g., the fixed electrode, and therefore, can be physically supported by that electrode. The second common type, of vapor shield is. the floating, shield. which is electrically isolated from both electrodes. While it is widely known that the floating shield performs better at high voltages than the fixed shield designs, it is more difficult to mount.
One common arrangement for mounting a floating vapor shield requires that the. ceramic be. formed, in. two cylindrical parts- wiJh. aLtnstal mojunjjng tiug. sand wictaed-between. The vapor shield is men secured to this mounting ring, typically by discrete flanges brazed to the shield and the mounting ring. While functionally adequate, this arrangement
1

can have several disadvantages. First attaching the shield in this manner requires two braze joints, which haxe. vacuum, on one side. and air on the, other, thereby providing two. potential leak paths. Second, the two cylindrical ceramics must be metal 1 zed at both ends, which leads to an increased cost. Lastly, the support mechanism exposes a conductor to the air leading to the need, fox external insulation for high, voltage, applications,.
For these reasons, it is highly desirable to attach a floating shield inside a single ceramic. One approach has been to crimp the shield around a feature such as a ridge molded, as. part of the. cexamic Tbis_ is_ turn consuruing aad adds.a. feir amount of cost to. the. ceramic. Various other approaches to attaching the floating shield to a single piece ceramic have required specialized components which add complexity and cost
There is. a need, therefore, for an improved arrangement and method for securing a floating vapor shield in a vacuum interrupter.
There is a general need for such an improved mount and method of mounting which, do not require complex specialized parts, or tej&niques.
More particularly, there is also a need for such an improved mount and method which can be used with a single piece ceramic.
SUMMARY OF THE INVENTION
This myentioa ^isfies. &&& needs, and otters, by providing a. vacum"
interrupter with a single piece ceramic tube having a circumferential groove in an inner
surface. A pair of end members form with this single piece ceramic tube a vacuum enclosure.
A fixed contact is. mounted, oa a fixed electrode extending tbj"^ A
moveable contact is mounted on a moveable electrode extending through the other end member and axially reciprocal into and out of contact with the fixed contact. A tubular shield is. supported inside, the ceramic tube and surrounding the. fixed and moveab Le contacts, by a shield mount. This shield mount includes a split ring seated in the circumferential groove in the ceramic tube and projecting radially inward from the inner surface of the ceramic tube into the. vacuum envelope where a coiraeetJon. coHnecis the shield to the split ting.
The connection between the split ring and the vacuum shield can take several forms. In a preferred form of the invention, this connection includes a flange fixed to the outer surface, of the.tubiUar shield and a braze ring fixing the.flange.to.the.split ring. Also, preferably, the flange forms a gap with the outer surface of the tubular shield and the braze is formed from a braze ring positioned in the gap where it fixes the split ring to the flange in the outer surface of the tubular shield- In one embodiment of the iavenUocu the flange has a
2

radially extending terminal section which seats on the split ring. Also preferably, the flange extends, substantially fully around, the. tubular shield.
In another aspect of the invention, the connection connecting the vapor shield to the split ring includes a circumferential shield groove in an outer surface of the shield, and an. additional split ring installed in the. groove in the shield, and projecting radially ojuiwanL A braze connection fixes the additional split ring in the groove in the shield to the split ring seated in the ceramic tube.
In accordance with another aspect of the. invention, the connection connecting the split ring seated in the ceramic tube to the shield comprises an additional circumferential groove in the outer surface of the vapor shield m which the split ring seats directiy. This connection can, be further augmented by including a brazering to- fix thesplit ring t& the shield.
The invention also is directed to a method of securing a floating vapor shield in a. vacuum interrupter which includes, the steps of forming acircumfexential groove in the ceramic tube, installing a split ring in the groove, and fastening the vapor shield to the split ring. The preferred form of fastening is implemented by providing a flange on the outer surface of the shield and fixing the flange, to the split ring, preferably by brazing. In a preferred method, the flange is formed with a gap between the flange and the shield and a braze ring is seated in this gap. The shield is then positioned in the ceramic tube with the flange engaging the split ring Heat is. applied, preferably in a. vacuum, to. melt the braze ring-In accordance with another aspect of the invention, the shield is fastened to the split ring by forming a shield groove in the outer surface of the tubular shield, installing an additional split ring in this, shield groove, and then brazing the additional split ring to. the split ring installed in the ceramic tube. Preferably, the brazing is accomplished by placing the braze ring on top of the additional split ring, inserting the shield into the ceramic tube with the additional sp^t ring "=p?"ed on fof q*Witional split ring qn In still another aspect of the invention, the tubular shield is fastened to the split ring by providing the tubular shield with a shield groove in an outer surface and installing the split ring in this shield groove as well as in the groove in the ceramic tube. Preferably, the split ring is brazed to the tube shield.
The split ring is. installed in the ceramic, tube, by compressing it to. reduce its. outside diameter to an outer dimension which is less than the inner diameter of the ceramic
3

tube, aligning the compressed split ring with the groove in the ceramic tube and releasing the split ring to. radially expand into, the groove.
BRIEF DESCRIPTION OF THE DRAWINGS
A. full understanding nf ttie iav^njion, cm be gamed from tbe following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
Figure 1 is a longitudinal sectional view through a vacuum interrupter incorporating the invention.
Figure 2 is a fragmentary view in enlarged scale of a section of Figure 1.
Figure 3. is. a plane, view of one type, of split ring which forms part of the arrangement shown in Figure 2.
Figure 4 is a view similar to Figure 2 of another embodiment of the invention-
Figure 5 is a view similar to Figure 2 of an additional embodiment of the invention.
Figure 6 illustrates a variation of the embodiment of the invention illustrated in Figure 5.
Figure 7 is_ a. view, similar to Figure 2 of yet another embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure I illustrates a vacuum, ijiterrujjter 1... Tbe va.cu.urn. in;terruptet 1
includes a ceramic tube 3 which with end plates 5 and 7 forms a vacuum envelope 9. A fixed contact 11 is mounted on a fixed electrode 13 which extends through the end plate 5. A moveable.contact 15 is-carried by a maveable electrode. 17 and extends through the end plate 7. A bellows 19 forms a seal between the end plate 7 and the moveable electrode 17 while allowing axial movement of the moveable electrode 17 to bring the moveable contact 15 into and out of contact with the fixed, contact 11. The fixed contact 11 and moveable contact 15 form separable contacts 21 which when closed, complete an electrical circuit between trie fixed electrode 13. and maveable electrode 17, and when opened by axial movement of the moveable electrode 17 interrupt current flowing through the vacuum interrupter. The moveable electrode 17 is moved axially to open and dose the separable contacts by an
4

operating mechanism (not shown) connected to the moveable electrode outside of the vacuum envelop.e 9.
As has been discussed, when the separable contacts 21 are opened with current flowing through the vacuum interrupter, an arc is struck between the fixed contact 11 and the raoveahle contact 15. These contacts, are configured, ta aid in extinguishing the arc which is necessary to interrupt the current flowing through the vacuum interrupter, as is well known. As was also mentioned above, the arc vaporizes metal from the contacts 11 and 15 which, could be deposited on the inner surface 23 of the ceramic 3 which serves, as an electrical insulator, as well as defining the vacuum envelope 9. In order to prevent such deposits, it is well known to provide a tubular vapor shield 25 between the separable contacts 21 and the.ceramic 3. This tubular vapor shield 25. isgeneraUy cylindrical, and as shown in Figure 1, is necked down to a degree at each end to extend its protection of the inner surface 23 of the ceramic 3. It is common to also provide an end shield 27 mounted on the moveable electrode 17 to. protect the bellows 19 from metal-vapor deposits.
The vapor shield 25 is a floating shield. That is, it is not electrically connected to either electrode so that its potential floats. To provide this electrical isolation, the. vapor shield 25. is. supported by the ceramic 3. which, as. mentioned, is. an electrical insulator.
In accordance with the invention and as more clearly seen in Figure 2, the tubular shield25 is. secured to. the ceramic 3 by a shield mount 31 which includes, aradially extending, circumferential groove 33 which is machined in the inner surface 23 of the ceramic 3 and a ring such as the split ring 35 which is installed in the groove 33. As shown in Figure X the exemplary split ring 3 5 has. agap_ 37 which permits, the split ring to. be radially compressed for insertion within the ceramic 3. Holes 39 accommodate pins on a conventional tool (not shown) used to manipulate the split ring. One of the advantages of the invention is that the. split ring 35 may be a conventional "snap, ring" or "retainer ring" which, are widely used and therefore inexpensive. The split ring 35 is seated in the groove 33 in the ceramic 3 and is sized so that it projects radially inward from the inner surface 23 of the ceramic 3. The gan 3 7 in the, spJit ring 35 is. sized to permit the ring to. be compressed sufficiently fox insertion inside the ceramic tube 3. In ihe exemplary split ring, the gap 37 subtends an angle V of about 15°.
Th&tuhular. vapor shield 25 is then secured to. the, split ring 35 by a connection 41. In the embodiment of the invention illustrated in Figures 1 and 2, this connection 41 includes a flange 43 with a cylindrical section 45 at one end which is secured
5

to the outer surface of the tubular vapor shield 25 such as by brazing. Preferably, this flange 43- is, continuous, around the tubular vapor shield 25. The. other end 47 of the. flange 43. is. also, cylindrical but of larger diameter to form a gap 49 with the tubular shield 25. A tapered section 51 joins the cylindrical sections 45 and 47. A radial lip 53 on the cylindrical section 47 seMs OIL the split ring 35, The.connection 41 fur^exuidudes.abrazefoxrjie!4bya.braze. ring 55 which is seated in the gap 49.
The method for securing the arc shield 25 to the ceramic tube using the shield
mount 3_ 1 shown in Figures I and 3_ includes; forming, such as_ by machining, the groove 3_3-
in the inner surface 23 of the ceramic 3, installing a ring, such as the split ring 35 in this
groove 33 by radially compressing the split ring 35 using a tool (not shown) which engages
the holes 3.9, aligning the compressed split ring 35 with the groove 33. and releasing the split
ring, allowing it to expand into the groove but still projecting radially into the vacuum
envelope 9. Next the flange 43 is secured to the arc shield 25 such as by brazing and the
braze_ringS5 is.wedgejiui!o.thegap49heiw^e^ Thearc
shield is then axially inserted into the ceramic 3 to seat the lip or rim 51 of the flange 43 against the split ring 35. The ceramic and arc shield are then placed in a vacuum oven which melts, the braze, ring 5.5. allowing the braze, material to. flow between the split ring 3.5 and the rim5I of the flange 43 and between the split ring and the arc shield 25. Finally, the braze is allowed to cool to solidify the connection.
Figure 4 illustrates another embodiment of the. invention in which me. shield mount 31' uses a connection 41' in which the flange 43' has a cylindrical end section 45' brazed to the arc shield 25 and the other end section 47' is flared outward to form a gap 49. Again, a braze ring 55- is. wedged into this gap 49 between, the flange 43/ and the arc shield 25. As in the case of the first embodiment, the braze ring 55 melts when placed in a vacuum oven and forms a braze connection between tire split ring 35, the arc shield 25 and the flange 43'.
An additional embodiment of the invention is.illustrated in. Figure 5 where, the shield mount 31" has a connection 41" which includes a circumferential shield groove 57 formed, such as by machining, in the outer surface 59 of the shield 25 in which the inner edge of the split ring 35 is. seated. Tnis connection. 41" also mcludes-a braze ring 55 which is dropped down on top of the split ring 35 and which melts to braze the split ring to the arc shield 25 when heated in the vacuum oven. In this embodiment, the split ring 35 is slightly compressed.radially and snapped into fee groove 3.3 in. the ceramic 3. The vapor shield25 is. then pressed into the split ring 35 causing it to expand within the groove 33 in the ceramic 3
until the shield groove 57 becomes aligned with the split ring 35 which then springs inward to
6

engage the shield groove. In a variation of this embodiment of the invention, the braze inset can be eliminated, as. shown in Figure 6.
Yet another embodiment of the invention is illustrated in Figure 7. Here, the shield mount 31'" has a connection 41'" which includes an additional circumferential groove 61 formed, such as by machining, in the. outer surface. 5 9 of the arc shield and in which is. seated an additional split ring 63. In mis arrangement, the braze ring 55 is dropped down on top of the split ring 35.. and the arc shield is then inserted in the ceramic until the additional split ring 63 seats OJI top ctfthebrjazering 53, whi^ split ring 35 to the arc shield 25 and to the additional split ring 63.
Typically, the ceramic is AI2O3 material, the arc shield 25 is copper or steel, the split ring 35 and the additional split ring 6i are 3.16. stainless, steel and the flanges.43. and 43' are 304 stainless steel.
The invention provides a mount for the tubular arc shield in a vacuum interrupter and a method of securing it within the cecamic which, uses commonly available, split rings and other simple parts which are easily assembled to provide a secure mount for the arc shield. In addition, a single piece ceramic can be used so mat it is not necessary to form the ceramic in two. pieces, and rae£auze_ both ends of each piece. Therefore, it also, eliminates, the electrical isolation problem of the prior art technique of having a metal ring exposed at the outer surface of the ceramic, and consequently also eliminates the need for electrically isolating this ring.. The result is. a less, expensive and easier to implement arrangement
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those detailscould be developed in. light of ^ o.vecdl t®d3ings. of fe oj^ctoajre.. Accordingly^ the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents.thereof
7

WE CLAIM:
1. A vacuum interrupter (1) comprising:
a single piece ceramic tube (3) having end members (5, 7) secured to each end thereof to form therewith a vacuum envelope (9);
a fixed contact (11) mounted on a fixed electrode (13) extending through one end member (5);
a moveable contact (15) mounted on a moveable electrode (17) extending through the other end member (7) and axially reciprocating into and out of contact with the fixed contact (11);
a tubular shield (25) inside the ceramic tube (3) and surrounding the fixed contact (11) and moveable contact (15);
characterised in that a shield mount (31) comprises a split ring (35) which is installed in a circumferential groove (33) in an inner surface (23) of said ceramic tube (3) and projects radially inwards into said vacuum envelope (9), a connection (41) connecting said tubular shield (25) to said split ring (35).
8

2. The vacuum interrupter as claimed in Claim 1 wherein the
connection comprises a flange fixed to an outer surface of the tubular shield
and a braze connection fixing the flange to the split ring.
3. The vacuum interrupter as claimed in Claim 2 wherein the flange
forms a radial gap (49) with the outer surface of the tubular arc shield and
the braze connection comprises a braze ring seated in the gap and which
melts to fix the flange to the split ring.
4. The vacuum interrupter as claimed in Claim 3 wherein the flange
has a radially extending terminal lip which abuts the split ring.
5. The vacuum interrupter as claimed in Claim 3 wherein the flange
extends substantially fully around the tubular shield.
6. The vacuum interrupter as claimed in Claim 1 wherein the
connection comprises a circumferential shield groove in an outer surface of
the tubular shield, an additional split ring installed in the shield groove and
projecting radially outward, and a braze connection fixing the additional
split ring to the split ring installed in the ceramic tube.
9

7. The vacuum interrupter as claimed in Claim 1 wherein the
connection comprises a circumferential shield groove in an outer surface of
the tubular shield in which the split ring is seated.
8. The vacuum interrupter as claimed in Claim 7 wherein the
connection further includes a braze connection fixing the split ring to the
tubular shield.
9. A method of securing a tubular shield within a ceramic tube of a
vacuum interrupter comprising the steps of:
forming a circumferential groove on an inner surface of the ceramic
tube;
installing a split ring in the circumferential groove with the split ring projecting radially inward from the inner surface of the ceramic tube; and
fastening the tubular shield to the split ring.
10. The method as claimed in Claim 9 wherein the fastening step
comprises providing a flange on an outer surface of the tubular shield, and
fixing the flange to the split ring.
10

11. The method as claimed in Claim 10 wherein the step of fixing
comprises brazing.
12. The method as claimed in Claim 11 including forming the flange
with a gap between the flange and the outer surface of the tubular shield,
seating a braze ring in the gap, positioning the tubular shield within the
ceramic tube with the flange engaging the split ring, applying heat to melt
the braze ring, and cooling the melted braze.
13. The method as claimed in Claim 12 wherein the heat is applied in a
vacuum.
14. The method as claimed in Claim 1 wherein the tubular shield is
fastened to the split ring by providing a circumferential shield groove in an
outer surface of the tubular shield, installing an additional split ring in the
shield groove, and brazing the additional split ring to the split ring installed
in the ceramic tube.
15. The method as claimed in Claim 14 wherein the brazing comprises
placing a braze ring on the top of the split ring installed in the ceramic tube,
inserting the tubular shield into the ceramic tube with the additional split
ring seated on the braze ring, and applying heat to melt the braze ring.
11

16. The method as claimed in Claim 9 wherein the fastening comprises
providing the tubular shield with a shield groove in an outer surface,
installing the split ring in the shield groove also.
17. The method as claimed in Claim 16 further including brazing the
split ring to the tubular shield.
18. The method as claimed in Claim 9 wherein installing the split ring
comprises compressing the split ring to reduce its outside diameter to less
than an inside diameter of the ceramic tube, aligning the compressed split
ring with the groove, and releasing the split ring to radially expand into the
groove.
19. A vacuum interrupter having a ceramic tube within which a tubular
shield is secured by the method as claimed in any one of Claims 9 to 18.
20. A vacuum interrupter as claimed in Claim 1 and substantially as
described herein with particular reference to Figures 1 to 3 or Figure 4 or
Figure 5 or Figure 6 or Figure 7 of the accompanying drawings.
A vacuum interrupter which comprises a single piece ceramic tube having end members secured to each end thereof to form therewith a vacuum envelope, a fixed contact mounted on a fixed electrode extending through one end member,a moveable contact mounted on a moveable electrode extending through the other end member and axially reciprocating into and out of contact with the fixed contact, a tubular shield inside the ceramic tube and surrounding the fixed contact and moveable contact, characterised in that a shield mount comprises a split ring which is installed in a circumferential groove in an inner surface of said ceramic tube and projects radially inwards into said vacuum envelope, a connection connecting said tubular shield to said split ring.

Documents:

00390-cal-2001 abstract.pdf

00390-cal-2001 claims.pdf

00390-cal-2001 correspondence.pdf

00390-cal-2001 description(complete).pdf

00390-cal-2001 drawings.pdf

00390-cal-2001 form-1.pdf

00390-cal-2001 form-18.pdf

00390-cal-2001 form-2.pdf

00390-cal-2001 form-3.pdf

00390-cal-2001 form-5.pdf

00390-cal-2001 g.p.a.pdf

00390-cal-2001 letters patent.pdf

00390-cal-2001 priority document.pdf

390-CAL-2001-FORM-27.pdf

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Patent Number

205516

Indian Patent Application Number

390/CAL/2001

PG Journal Number

14/2007

Publication Date

06-Apr-2007

Grant Date

05-Apr-2007

Date of Filing

11-Jul-2001

Name of Patentee

EATON CORPORATION

Applicant Address

EATON CENTER, 1111 SUPERIOR AVENUE, CLEVELAND, OHIO 441114

Inventors:

#	Inventor's Name	Inventor's Address
1	MAYO STEPHEN DAVID	293 ORIOLE DRIVE, HORSEHEADS NY 14844
2	SLADE PAUL GRAHAM	176 OAKWOOD LANE, ITHACA, NY 14850
3	ROSKRANS BENJAMIN ALEX	607 W. WATER STREET, ELIMIRA, NY 14905
4	BURMINGHAM DALE LOWELL	103 SHULTZ DR., NEWFIELD, NY 14867
5	DUNHAM BRADLEY EUGENE	90 SQUEDUNK ROAD, LISLE, NY 13797,

PCT International Classification Number

H01H 33/66

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	09/616.484	2000-07-14	U.S.A.