US3614356A

US3614356A - Shield assembly for high-voltage gas circuit breaker

Info

Publication number: US3614356A
Application number: US852535A
Authority: US
Inventors: Henry G Meier; James R Mccloud
Original assignee: ITE Imperial Corp
Current assignee: ABB Inc USA
Priority date: 1969-08-25
Filing date: 1969-08-25
Publication date: 1971-10-19
Anticipated expiration: 1988-10-19
Also published as: CH533352A

Abstract

A high voltage gas circuit breaker has a plurality of interrupter structures, each of which contain an upper stationary contact and corona shield which surrounds the upper contact. The corona shield has openings in a lower rim disposed to direct the gas blast during interruption downwardly and at an angle outwardly from the external surface of its respective interrupter structure from the external surface of its respective interrupter structure to prevent contamination of the insulation surface of the interrupter structure by arc products.

Description

United States Patent Inventors Henry G. Meier Glendale;

James R. McCloud, Burbank, both of Calif. Appl. No. 852,535 Filed Aug. 25, I969v Patented Oct. 19, 1971 Assignee I-T-E Imperial Corporation Philadelphia, Pa.

SHIELD ASSEMBLY FOR HIGH-VOLTAGE GAS CIRCUIT BREAKER 7 Claims, 6 Drawing Figs.

0.8. CI 200/148 R, 200/ 148 IV Int. Cl HOIh 33/82 Field of Search ZOO/148.2, 148 B, 148

[5 6] References Cited UNITED STATES PATENTS 3,040,149 6/1962 Easley et al 200/148 B 3,495,057 2/l970 Golota 200/148 B Primary Examiner-Robert S. Macon Attorney-0strolenk, Faber, Gerb & Soffen ABSTRACT: A high voltage gas circuit breaker has a plurality of interrupter structures, each of which contain an upper stationary contact and corona shield which surrounds the upper contact. The corona shield has openings in a lower rim disposed to direct the gas blast during interruption downwardly and at an angle outwardly from the external surface of its respective interrupter structure from the external surface of its respective interrupter structure to prevent contamination of the insulation surface of the interrupter structure by are products.

PATENTEUHBT 19 ml 3.614.356

- SHEET 5 [IF 5 SHIELD ASSEMBLY FOR HIGH-VOLTAGE GAS CIRCUIT BREAKER RELATED APPLICATIONS This application is an improvement of the structure shown in copending application Ser. No. 680,778, filed Nov. 6, 1967, in the name of John H. Golota, and assigned to the assignee of the present invention. This application is related to copending application Ser. No. 845,375, filed July 28, I969, in the name of Henry G. Meier and James R. McCloud, and assigned to the assignee of the present invention.

THE PRIOR ART Circuit interrupters of the type to which the invention applies are known and are typically shown in the above-noted application. Such interrupters are provided with a stationary nozzle contact and a movable contact which is surrounded by a movable baffle which can engage the stationary nozzle contact to define a confined gas blast path through an arc drawn between the movable and stationary contacts during their separation. A blast valve which is upstream of the contacts is opened just prior to the opening of the contacts. The baffle is adapted to be withdrawn when the contacts are fully opened and the gas blast is turned off to bring it out of the high electrostatic stress region between the opened contacts.

In the past, the gas blast has been directed downwardly and over the outer surface of the insulation members forming the interruption chamber. It has been found that this can cause the coating of these insulating surfaces with conductive contamination products, thereby reducing the ability of the interrupter to withstand high voltage when the interrupter is open.

The present invention forces the gas blast during arcing to be directed downwardly, but angled away from these insulation surfaces so that the high voltage withstanding ability of the interrupter is not affected after prolonged operation.

SUMMARY OF INVENTION Inaccordance with the present invention, the corona shield for each of the interrupters is provided with one or more openings along a bottom inwardly turned lip thereof, with the interior of the shield being in communication with the interior of the nozzle of the stationary contact. The openings in the shield are spaced outwardly from its interior diameter so that gas during interruption is forced to take a path downward but flaring outward at an angle of, for example, 30 from the axis of the interrupter chamber, whereby the gas during interrup tion is not applied directly onto the outer surface of the interrupter chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a circuit breaker of the type to which the invention applies, and is partly in cross section.

FIG. 2 is a cross-sectional view of tone of the interrupters of FIG. 1.

FIG. 3 is a cross-sectional view of the novel structure of the present invention.

FIG. 4 is a cross-sectional view of a portion of one interrupter of the type shown in FIG. 3 along with a corona shield providing discharge openings in accordance with the invention.

FIG. 5 is a cross'sectional view of FIG. 4 with the left-hand side of FIG. 5 being taken across the section lines 5a-5a in FIG. 4 and with the right-hand side of FIG. 5 being taken across the section lines 5b-5b in FIG. 4.

FIG. 6 schematically shows a schematic diagram of a complete circuit interrupter in cross-sectional view and illustrates the gas blast patterns for each interrupter in accordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS a. Background of the Invention FIGS. 1 and 2 show a typical prior art interrupter structure to which the present invention is applied. The device of FIGS. 1 and 2 is shown in copending application Ser. No. 680,778, and the disclosure of that application is incorporated herein by reference to show the entire circuit breaker assembly which would be used with the present invention.

FIG. I shows the assembly of a prior art interrupter assembly, and illustrates two series connected interrupters l0 and 11. Interrupters l0 and 11 are identical and will be described in detail hereinafter. The interrupters I0 and II are controlled by an operating mechanism, generally indicated by numeral 12, which is supported on a tank housing 13. Tank housing 13 is, in turn, carried on an elongated insulation pedestal 14 which may be carried on a high-pressure gas supply at ground potential.

Each of

interrupters

10 and 11 are connected at their tops to conductors which are connected in series with the circuit to be protected. The connection surrounding the topsof interrupters l0 and 11 and the insulator bushings are covered with corona shields l5 and 16. FIG. 2 shows the connection of interrupter 10 to a lower portion 17 of an insulator bushing connected thereto.

An upper adapter plate 18 is provided which has a series of tapped openings therein, and alternate through-openings (not shown). The upper surface of adapter 18 then has a conical surface 31 which engages the conical lower surface 32 of insu lator 17 to permit angular adjustment of insulator 17, as shown by arrow 17a in FIG. 2. A series of bolts, such as bolt 33 having washer 34, then extend through openings, such as through-opening 28, to secure upper adapter 18 to insulator I7.

A lower adapter 35 is then provided which has a plurality of extending ears containing through-openings such as opening 36 extending from a central web 42. An annular groove 43 is cut through the web 42 so that it is held by the material of the extending cars. A plurality of through-holes and aligned tapped openings such as opening 44 are then formed in the web 42, and the interior web surface is threaded by thread 50. The through-openings in lower adapter 35 are then aligned with tapped openings in upper adapter 18 and suitable bolts and washers, such as bolt 51 and washer 52, shown in FIG. 1, secure shield 15 and

adapter plates

18 and 35 together.

The interior thread 50 of web 42 of lower adapter 35 receives the stationary contact 53 of the interrupter. Contact 53 comprises a main body 54 having a central opening 55 which tapers outwardly to define a blast orifice. The outer diameter of body 54 is threaded with a thread 56, and an arcresistant insert 57. Thread 56 of contact 53 is then threaded into thread 50 of lower adapter 35 and is secured therein by tightening a plurality of bolts, such as bolt 570, shown in FIG. 2, which pass through the through-openings in the lower part of web 42 and into the threaded opening 44. As these bolts are tightened, the upper and lower interior portions of web 42 tighten on thread 56 to hold contact 53 securely. Note that the axial contact position is easily controlled by threading contact 53 more or less into thread 50, as shown by arrow 58 in FIG. 2. Moreover, by providing clearance between the outer diameter of the bolts, such as bolt 51, which secure lower adapter 35 to upper adapter 18 and the corresponding through-openings, such as opening 36, lateral adjustment can be obtained for contact 53, as shown by arrow 59 in FIG. 2.

The movable contact assembly is shown in FIG. 2 and is composed of a circular cluster of contact fingers, such as fingers 60 and 66, each having generally rectangular shape. Each of the contact fingers have arc-resistant inserts secured thereto, such as inserts 72 and 73, secured to contacts 60 and 66, respectively. Each of the contact fingers have two projections, such as

projections

74 and 75, for finger 60, which receive biasing leaf springs shown as

leaf springs

76 and 77 for contacts 60 and 66 which bear on insulation buttons 78 and 79, respectively.

The contact fingers are-laid on the outer notches in a contact retainer 80, and are held on the retainer 80 by a spring and to provide commutation of the are from insert 72 to contact 85 during opening. The interior of arcing contact 85 is threaded and threadably receives the end of operating shaft 86 and is secured thereon by a suitable locking nut.

An interrupter support 88 is then provided for slidably holding the movable contact assembly. Support 88 contains a central stationary contact portion 89, the outer end of which slidably receives the lower ends of contact fingers, such as fingers 60 and 66, in slidable engagement. Central portion 89 is connected to base portion 90 by suitable webs (not shown). Two rings 107 and 108 of insulating material, shown in FIG. 2, are contained in internal grooves in the central opening 111 of central portion 89 to seal around the operating rod 86 and to provide electrical insulation between rod 86 and base 90, as shown in FIG. 2. Support 88 is then fastened to support casting sections 112 and 113 (which are parts of a common casting) of FIGS. 1 and 2, as by bolts which thread into appropriate tapped openings in casting

sections

112 and 113, partly shown in FIG. 1 by bolts 114 and 115. Note that the operating rod 86 passes through a suitable opening, which may be sealed, in casting section 112. I

An interrupter tube assembly, arranged above the support 88 and enclosing the contact area is carried on a flange 116. Flange 116 comprises an extending cylindrical portion 117 secured to support 88 beneath it by bolts (not shown) extending through openings in flange 116 and respective openings in support 88, which bolts are threaded into the

castings

112 and 113.

An interrupter tube 122 is then secured to extension 117 in any suitable manner, where tube 122 is of glass fiber, or the like. Tube 122 then slidably receives the movable interrupter tube portion (or baffle) 123, which is movable in the direction of arrow 124, with a gasket 125a between the surfaces of tube 122 and sliding portion 123.

The movable interrupter tube or baffle 123 comprises an outerv insulation cylinder 125 and an inner lining cylinder 126 which secure, between them, an insulation lining disk 127 and baffle ring 128. The bottom of the cylinders are secured by ring 129 which has a lower lip extending below liner 126 and a plurality of pins, such as pin 130, which extend into cylinder 125.

Four pins, two of which are shown as

pins

131 and 133, then extend into openings in ring 129 and are locked therein by suitable locking pins.

Pins

131 and 133 are seen in FIG. 2 with the four pins disposed 90 from one another. Each of the pins have enlarged heads, such as head 135 of pin 133, which are captured in housings, such as housing 138 for pin 133. A split retainer spring disk 139 has suitable openings for receiving the four spring housings, including housing 138. Internal springs, such as spring 145 of housing 138, then bias the housings toward the ring 129 and external springs, such as spring 148, bias plate 139 toward the ring 129.

In assembling the movable interrupter tube, it will be noted in FIG. 2 that the periphery. of plate 139 is captured between adapter 116 and support 88, with ring 129 beneath shoulder 150 in stationary tube portion 122. Also, it is seen that the baffle ring lies just adjacent the lower tapered surface of contact 53.

The operating mechanism for moving operating rod 86 is best shown in FIG. 1 where it is seen that the casting

sections

112 and 113 have a downwardly extending portion 151. For tion 151 has two slots for passing

ears

152 and 153 of a cylindrical blast valve. The

cars

152 and 153 are then connected to

links

154 and 155, respectively, which are, in turn, pivotally connected to operating rods 86 for

interrupters

10 and 11 through

suitable couplings

156 and 157, respectively.

The blast valve comprises a cylindrical body 158 connected to a central hub 159 by streamlined arms, such as arm 160. The ends of cylindrical body 158 are formed with annular valve disk engaging sections. The interior opening in hub 159 is provided with a thread 166. The two

ears

152 and 153 then extend outward from cylindrical body 158.

Cylindrical valve body 158 then moves between an upper and lower valve seat. The upper valve seat is composed of an upper disk 167 which is secured to casting section 113 and a lower disk 168 which is bolted to disk 167 as by bolts, such as bolt 169. Disk 168 is sealed with respect to casting section 113 by seal ring 170 and carries a main valve seat ring 171 which cooperates with the upper end of cylindrical valve body 158. A valve retaining disk 172 is bolted to disk 168 as by bolt 173 and securely holds ring 171 in position. Disk 172 also has a buffer disk 174 bolted thereto as by bolt 175 which engages nut 176 when the valve 158 is moved upwardly.

Hub 159 is threaded on operating shaft 177 and is locked in place by nut 176 which is also threaded on shaft 177. Note that an annular seal 178 is contained in casting portion 112 and seals around cylinder 158 and guides the motion of cylinder 158.

A ring 180 is then secured to the bottom of casting 112, and downwardly projecting members 181 are welded to ring 180.

-Members 181 then support the lower valve seal for valve 158.

Note that a ring 182 having a sealing ring 183 engaging ring 182 is provided with a sliding seal ring which surrounds the lower portion of cylinder 158.

The bottom of members 181 carries a ring 185. Ring 185 is connected to valve disk 186 and valve disk 187 by bolt means, such as bolt 188. Sealing rings 189 and 190 prevent leakage between

rings

185 and 186. Ring 186 carries a main valve seat 191 which cooperates with the bottom of cylinder 158. Note that a sliding seal 192 is formed between disk 186 and shaft 177, and that a buffer 193 is connected to the top of disk 187 to receive the bottom of hub 159 when valve 158 moves down.

The ring 180 is welded to high-pressure tank 13 which is composed of welded upper and

lower halves

200 and 201, respectively. High-pressure gas, such as air and preferably sulfur hexafluoride, is then supplied to the interior of tank 13 from the central channel through insulator 14 which is appropriately connected at its bottom to a high-pressure gas source, as will be later described.

' An elongated operating shaft 203, which extends coaxially with insulator 14, can be moved up and down by operating means, to be later described, which may be carried at ground, and is connected to shaft 177 by a shock-absorbing coupling.

FIG. 1 further shows a small tubular member extending downwardly and into the annular space between pedestal 14 and rod 203, and arranged so that any gas which condenses on the surface of housing 13 will flow downwardly and freely through the annular space without impinging on the insulating surfaces of

members

14 and 203.

The coupling as shown in FIG. 1 is comprised of a spring 204 captured between

rings

205 and 206 at its top and bottom, and an outer cylinder 207 on its outer periphery. Ring 205 is captured beneath a shoulder in shaft 177 as shown, while ring 206 is held by nuts 208 and'209 which are threaded on the threaded'bottom of shaft 177.

Outer shells

210 and 211 each have threaded interiors, threaded on the outer threaded surface of cylinder 207 with extension 212 of shell 210 bearing on ring 205, while ring 206 seats under the interior shoulder in cylinder 207. Operating shaft 203 is then connected to shell 211 by connection ring 213. When shaft 203 moves down, it will be seen that downward force is exerted through

shells

211, 210, ring 205, and spring 204 on ring 206. Similarly, upward movement of shaft 203 is transmitted through cylinder 207, ring 206, spring 204 and ring 205. Thus,

. both upward and downward movement of shaft 203 is transmitted to shaft 177 through shock-absorbing spring 204. This also makes the mechanism relatively insensitive to small dimensional changes such as produced by misalignment and temperature changes.

OPERATION OF PRIOR ART DEVICE OF FIGS. 1 AND 2 The prior art device of FIGS. 1 and 2 operates such that interrupter tube 123 is biased downwardly to an open position by spring 145 when the movable contact structure is open. When the circuit breaker is closed, the movable contact moves up and the upper end of insert 72 picks up the movable tube or-baffle 123 at liner 127 and drives the baffle against and around the stationary contact 53. This then defines a channel for movement of high-pressure gas through the interior of baffle 123 and out through the opening 55 in contact 53, and thus through the separating contacts.

When the circuit breaker is to be opened, operating rod 203 moves down to open valve 158, permitting the flow of highpressure gas into the interior of the interrupter and the interior of baffle 123. Note that the pressure of this gas holds the baffle 123 closed against the force of its opening biasing springs even though the movable contact moves down and away from baffie 123. Thus, the desired gas passage for moving gas through the orifice 55 is maintained by baffle 123.

Once the valve 158 reaches valve 191, the contacts are fully open and the arc extinguished. The gas pressure is removed from baffle 123 so that it is moved downward to an open" position by its biasing springs so that it removed from the high stress of the electrostatic field in the region between the open contacts.

It is seen that the baffle 123 is driven closed by the movable contact (or is closely followed by the movable contact) when this contact is closed, and is held in its closed position. It has been found that the high-impact forces on the baffle from the movable contact can break the baffle 123.

THE STRUCTURE SHOWN IN FIG. 3

The present invention provides an improved drive for baffle 123 in which it is operated solely by differential pressure operating against the biasing force of the baffle opening springs so that the baffle 123 is not subject to breakage due to impact with the movable contact. The invention is shown-in FIG. 3 in which parts similar to those of FIGS. 1 and 2 have similar identifying numerals. A few further differences, besides the change in the essential baffle structure are also shown in FIG. 3, and will be discussed. In FIG. 3, the structure to the left of the centerline is shown in section with the baffle 123 open and the contacts closed. The movable contact is shown in plan view to the right of the centerline with the movable contact in its open position.

The interrupter of FIG. 3 corresponds to interrupter of FIGS. 1 and 2, and it is seen that lower adapter plate 35 receives contact 53. The movable contact assembly 300 is similar to that of FIG. 2, but is modified in a few respects. Thus, typical contact 301, corresponding to contact 66 of FIG. 1 has an integral arcing surface 302 for engaging contact 53. Note that

finger contacts

303, 304 and 305 are partly shown, in the open position to the right of the centerline in FIG. 3. In addition, a circular conductive shield 306 is secured to the various contact finger biasing springs and cooperates with member 81 in FIG. 2. Arcing contact 85 is attached to rod 86 by a modified flanged body 310 in FIG. 3. In addition, a modified buffer 311 is secured to member 89 to receive the bottom of member 310 when the movable contact reaches the open position.

In FIG. 3, a unitary sleeve 312 bolted to body 88 replaces flange 117 and member 122 of FIG. 2, where sleeve 312 has a larger diameter than member 122 of FIG. 2 to accommodate a larger diameter baffle 123.

Baffle 123 has a shortened inwardly turned lip 313, the interior diameter of which is greater than the outer diameter of contact shield 306. Thus, as contrasted to the arrangement of 7 FIG. 2, the movable contact assembly will not engage baffle 123. Baffle 123 then has in interior liner 314, and the baffleis secured to a lower plate 315 by a clamp 316. Plate 315 receives a plurality of bolts, such as bolt 317, about its periphery which have extending heads such as head 318. Spring housings, such as housing 311 in FIG. 3, are pressed against plate 315 by springs, such as spring 320, partly shown in FIG. 3, which presses between head 318 and the top of the tube 311. Tube 311 is then biased against fixed plate 321 by spring 322 contained in spring guide tube 323. As in the case of FIG. 2, a plurality of such spring support elements are disposed around the periphery of plate 315, and operate normally to bias baffle 123 downward to the open position shown in FIG. 3 (through compression springs such as spring 320).

OPERATION OF DEVICE OF FIG. 3

In operation, when the contacts are closed, as shown to the left in FIG. 3, the baffle 123 will be open due to the biasing springs, such as spring 320, which bias baffle 123 downwardly. If the breaker is to be opened, rod 86 is moved down, and, as shown in FIGS. 1 and 2, the blast valve 158 is opened. A highpressure gas then flows upwardly in the direction of arrow 330, thereby applying a differential force to baffle 123 which moves the baffle upward and against springs such as spring 320. The baffle 123 then closes against a seal 331 formed in contact 53, thereby defining a gas flow channel through orifice 55. The contacts subsequently separate and this gas flows in the region of the arc to cool and deionize the arc. When the movable contact reaches its fully open position shown to the right of the centerline in FIG. 3, the blast valve closes and the high-pressure gas is cut off. Thus, baffle 123 retracts to its open position and away from the gap between the open contacts.

When the breaker is to be closed, rod 86 is moved upward and the blast valve is again opened. High-pressure gas thus flows to temporarily close baffle 123 to form the desired gas channel through orifice 55. After the contacts are closed, the blast valve closes, and baffle 123 retracts to its open position. Note that in the above operation, the movable contact does not engage baffle 123 and any overtravel of the movable contact will not affect the baffle 123. Moreover, and as shown in FIG. 3 to the right of the centerline, the baffle 123 is disposed in its most favorable dielectric position when the contacts are open with its inwardly facing lip 313 generally parallel to the end of arcing contact 57. Thus, the baffle 123 generally follows an equipotential line in the open contact gap, and is subject to minimum dielectric stress.

THE INVENTION SHOWN IN FIGS. 4, 5 AND 6 The invention is shown in connection with the interrupter structure of the type described in FIG. 3, and consists of the modified corona shield structure 401 shown in FIGS. 4 and 5. Corona shield 401 is suitably connected to adapter 402 (which may be similar to adapter 18 of FIG. 1) through a spider plate 399. The spider plate 399 is provided with spider sections such as

sections

403, 404, 405 and 406, as shown in FIG. 5. The spider plate 399 is connected to adapter 402 as by volts, such as bolt 407, and is also connected to the stationary contact by bolts, such as

bolts

408 and 409.

In accordance with the present invention, corona shield 401 has an inwardly turned bottom section 398 which contains a plurality of openings, such as

openings

410, 411, $12, 413 and 414; opening 413 being shown in both FIGS. 4 and 5. Each of the openings such as 410 to 414 lie on a circle having a diameter greater than the outer diameter of member 312 and are angled outwardly from the centerline of the interrupter. Accordingly, during interruption, gas will flow as indicated by

arrows

420 and 421, where the gas emerging from the shield the interrupters and capacitors. It will be noted that this is a distinct advantage from the arrangement shown in FIG. 1, for example, where the are products are discharged from

shields

15 and 16 directly down and over the exterior of interrupters l and 11. FIG. 6 schematically illustrates the blast pattern for an entire circuit breaker. Thus, in FIG. 6 there is schematically illustrated four

corona shields

430, 431, 432 and 433 of four series-connected interrupters contained within a comand orifices 433a and 433 b for shield 433. It will be seen that the orifice lengths (of the equivalent orifice fonned by a plurality of individual openings) is such that the blast from one interrupter is not discharged against the exterior surface of an adjacent interrupter. Thus, in FIG. 6 the orifices are so dimensioned that the blast is downward and at about 30 from the center line of the respective interrupters. In this manner, the discharge gas of the interrupters cannot cause flashover to the grounded tank during interruption or adversely'coat the interior of the tank walls which are sufficiently spaced from the interrupters.

Shields

430 and 433 are of the type shown for interrupter 11 in FIG. 1 and for the interrupter shown in FIGS. 4 and 5. Shields 431 and.432 are modifications of the shield shown in shield in FIG. 1.

In the event that voltage grading capacitors are connected across the various interrupter contacts, these capacitors can be so located on the exteriorof the interrupter that they are out of the path of the blast gas. Thus, capacitors can be located alongside each interrupter at locations schematically shown in FIGS. 5 and 6 by pairs of grading capacitors 500-501 (FIG. 5); and 502-503, 504-505, 506-507 and 508-509 for the four interrupters of FIG. 6. Note that the coating of these capacitors by blast products would short circuit the interrupter so that they must be out of the blast gas path.

'Although this invention has been described with respect to particular embodiments, it should be understood that many" variations and modifications will now be obvious to those ,skilled in the art, and, therefore, the scope of this invention is limited not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention. in which an exclusive privilege or property is claimed are defined as follows:

1. In a gas blast circuit interrupter; said gas blast circuit interrupter comprising a stationary contact having a central channel therethrough, a movable contact movable into and out of engagement with respect to said stationary contact, a'

source of high-pressure gas, a hollow cylindrical valve of insulation material surrounding said movable contact'and being movable into and out of sealing relation with an annular area surrounding said central channel, means connecting said source of high-pressure gas to the interior of said hollow cylindrical valve, means for moving said hollow cylindrical valve out of sealing relation with said annular area when said movable contact moves out of engagement with said stationary contact, whereby a blast of gas is directed between said movable and stationary contacts and through said central channel in said stationary contact, and a corona shield comprising a smoothly curved, generally hollow cylindrical conductive body surrounding said stationary contact, one end of said corona shield being in a plane generally adjacent the end of said stationary contact and having an inwardly turned rim portion; the improvement which comprises gasdischarge opening means in said inwardly turned rim portion which are disposed outwardly from the interior diameter of said rim portion and gas channel means for connecting said central channel in said stationary contact to said discharge opening means; the discharge path of all 'gas discharged through said discharge opening means extending at an angle to the axis of said hollow cylindrical valve and being directed away from the outer surface of said hollow cylindrical valve.

2. The interrupter of claim 1 wherein the outer diameter of said hollow cylindrical valve is about equal to the internal diameter of said inwardly turned rim portion of said shield.

3. The interrupter of claim 2 wherein said discharge opening means consists of a plurality of spaced openings in said rim.

4. The interrupter of claim 2 which includes a second interrupter of similar construction positioned adjacent thereto, and a tank for receiving said interrupter and said second interrupter; said discharge opening means of the corona shields of said interrupters defining blast patterns extending generally laterally of a line joining said interrupters to prevent the application of the gas blast of one of said interrupters to the hollow movable valve of the other.

5. In a high-voltage gas blast interrupter;

" a. a stationaryv contact assembly having a gas discharge channel therethrough;

b. a tubular interrupter assembly presenting an outer insulation surface which is coaxial with said gas discharge channel in said stationary contact assembly and which is disposed adjacent one end of said stationary contact assembly;

c. a corona shield surrounding said stationary contact assembly and having an inwardly turned rim at one end thereof which is disposed in a plane which generally includes said one end of said stationarycontact assembly, the inner diameter of said inwardly turned rim being approximately equal to the outer diameter of said tubular interrupter assembly, and gas discharge opening means in said inwardly turned rim which are radially removed from its said inner diameter;

d. and a high-pressure gas source and conduit means for moving high-pressure gas through a generally reentrant path which has a first leg including said tubular interrupter assembly and said gas discharge channel in said stationary contact, and a second, and reentrant leg including said gas discharge opening means in said corona shield; the discharge of all gas from said gas discharge opening means being directeddown and away from said outer insulation surface of said tubular interrupter assembly.

6. The interrupter of claim 5 wherein said discharge opening means consists of a plurality of spaced openings in said

Claims

1. In a gas blast circuit interrupter; said gas blast circuit interrupter comprising a stationary contact having a central channel therethrough, a movable contact movable into and out of engagement with respect to said stationary contact, a source of high-pressure gas, a hollow cylindrical valve of insulation material surrounding said movable contact and being movable into and out of sealing relation with an annular area surrounding said central channel, means connecting said source of high-pressure gas to the interior of said hollow cylindrical valve, means for moving said hollow cylindrical valve out of sealing relation with said annular area when said movable contact moves out of engagement with said stationary contact, whereby a blast of gas is directed between said movable and stationary contacts and through said central channel in said stationary contact, and a corona shield comprising a smoothly curved, generally hollow cylindrical conductive body surrounding said stationary contact, one end of said corona shield being in a plane generally adjacent the end of said stationary contact and having an inwardly turned rim portion; the improvement which comprises gas discharge opening means in said inwardly turned rim portion which are disposed outwardly from the interior diameter of said rim portion and gas channel means for connecting said central channel in said stationary contact to said discharge opening means; the discharge path of all gas discharged through said discharge opening means extending at an angle to the axis of said hollow cylindrical valve and being directed away from the outer surface of said hollow cylindrical valve.

5. In a high-voltage gas blast interrupter; a. a stationary contact assembly having a gas discharge channel therethrough; b. a tubular interrupter assembly presenting an outer insulation surface which is coaxial with said gas discharge channel in said stationary contact assembly and which is disposed adjacent one end of said stationary contact assembly; c. a corona shield surrounding said stationary contact assembly and having an inwardly turned rim at one end thereof which is disposed in a plane which generally includes said one end of said stationary contact assembly, the inner diameter of said inwardly turned rim being approximately equal to the outer diameter of said tubular interrupter assembly, and gas discharge opening means in said inwardly turned rim which are radially removed from its said inner diameter; d. and a high-pressure gas source and conduit means for moving high-pressure gas through a generally reentrant path which has a first leg including said tubular interrupter assembly and said gas discharge channel in said stationary contact, and a second, and rEentrant leg including said gas discharge opening means in said corona shield; the discharge of all gas from said gas discharge opening means being directed down and away from said outer insulation surface of said tubular interrupter assembly.

6. The interrupter of claim 5 wherein said discharge opening means consists of a plurality of spaced openings in said rim.

7. The interrupter of claim 5 which includes a second interrupter of similar construction positioned adjacent thereto, and a tank for receiving said interrupter and said second interrupter; said discharge opening means of the corona shields of said interrupters defining blast patterns extending generally laterally of a line joining said interrupters to prevent the application of the gas blast of one of said interrupters to the hollow movable valve of the other.