US3909571A

US3909571A - Contact structure for high voltage gas blast circuit interrupter

Info

Publication number: US3909571A
Application number: US398871A
Authority: US
Inventors: Hansruedi Aumayer
Original assignee: ITE Imperial Corp
Current assignee: ABB Inc USA
Priority date: 1973-09-19
Filing date: 1973-09-19
Publication date: 1975-09-30
Anticipated expiration: 1992-09-30

Abstract

The cooperating stationary and movable contacts of a gas blast interrupter are each formed as elongated, tubular contacts which are slotted from one end to form contact fingers flexible at only one end. The fingers of the stationary contact engage the solid hub end of the movable contact, and the movable contact fingers slide on a stationary conductive tube.

Description

United States Patent Aumayer Sept. 30, 1975 1541 CONTACT STRUCTURE FOR HIGH 3,180,959 4/1965 MacNeill et a1. 200/148 R VOLTAGE GAS BLAST CIRCUIT 3,439,140 4/1969 Frowein 200/148 BV INTERRUPTER 3,441,692 4/1969 Cromer et a1. 200/148 R [75] Inventor: Hansruedi Aumayer, Harleysville, FOREIGN PATENTS OR APPLICATlONS Pa. 613,844 12/1948 United Kingdom 200/148 R [73] Assigneez :d-IT-E lnllperial Corporation, Spring Primary E aIm.er Robert S. Macon Ousa Attorney, Agent, or Firm-Ostrolenk, Faber, Gerb & [22] Filed: Sept. 19, 1973 Soffcn [21] Appl. No.: 398,871

[57] ABSTRACT [52] U S Cl 200/148 700/148 200/145 The cooperating stationary and movable contacts of a [51] 1 33/64 gas blast interrupter are each formed as elongated, tu- [58] Fieid B 148 E bular contacts which are slotted from one end to form 260/148 contact fingers flexible at only one end. The fingers of the stationary contact engage the solid hub end of the l 5 6] References Cited movable contact, and the movable contact fingers UNITED STATES PATENTS slide on a stationary conductive tube. 2,494,661 1/1950 Lzltour 200/148 R 7 Claims 6 Drawing Figures US. Patent Sept. 30,1975 Sheet 2 of5 3,909,571

HUI

US. Patent Sept. 30,1975

Sheet 3 of 5 l: 5-. Sb.

U.S. Patent Sept. 30,1975 Sheet 4 of 5 3,909,571

A I K a5 5' U.S. Patent Sept. 30,1975 Sheet 5 of5 3,909,57i

Ser. No. 398,870, filed Sept. CONTACT FOR HIGH VOLTAGE GAS BLAST CIR- CONTACT STRUCTURE FOR HIGH VOLTAGE GAS BLAST CIRCUIT INTERRUPTER RELATEDIAPPLICATIONS 'This application is related to copending application 19, 1973, entitled CUIT BREAKER WITH TIME-DELAYED OPEN- ING, in the name of L. J. Kucharski; Ser. No. 398,869, filed Sept. 19, 1973, entitled MECHANICAL SUP- "PORTOF TRANSIENT RECOVERY VOLTAGE CA- of G. P. Guaglione et al., all of whichare assigned to the assignee of the present invention.

' BACKGROUND OF THE INVENTION This invention relates to high voltage gas blast interrupters, and more specifically relates to a novel cooperating contactstructure for high'voltage gas blast break- 1 ers.

High voltage gas blast breakers are well known to the art, and are shown, for example, in US. Pat. 3,526,734, issued Sept. 1, 1970, entitled DEAD TANK GAS BLAST CIRCUIT BREAKER WITH INTERRUPTER STRUCTURE IMMERSED IN LOW PRESSURE OF DEAD TANK, in the name of D. H. McKeough, and in jcopending application Ser. No. 175,507, filed Aug. 27, .1971, now issued as US. Pat. No. 3,823,289, entitled INTERRUPTER STRUCTURE FOR CIRCUIT nBREAKER WITH INDIVIDUAL BLAST VALVES the sliding movablev contact. and the conductive tube' which, slidably supports the movable contact. This burning is believed to be due to bounce of the movable contact fingers on the conductive tubeat the time of A further significant advantage of the invention is that the contact fingers of both the stationary and movable contacts are relatively simply constructed and are self-biased to a given rest position. The fingers are then flexed to a greater diameter when they engage their respective solid cylindrical surfaces (the solid movable contact hub is engaged by and spreads the stationary contact fingers, and the outer surface of a stationary conductive cylinder is slidably engaged by and spreads the movable contact fingers) to cause inherent strong contact biasing forces since the contact fingers are elastically deformed and tend to return to their rest position. Therefore, contact springs are avoided and, in general, considerable economy and reliability is achieved with the use of the new contact structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIGQl is an elevational view of a circuit breaker which employs the novel contacts of the present invention where a portion of the grounded support tank of the circuit breaker has been removed to expose the various components therein;

f FIG. '2 is a cross sectional view through one of the interrupters of the circuit breaker of FIG. 1 and illustrates the novel contact structure of the present invention. v I I FIG. 2a is a top planview of the stationary contact of 2. FIG. 2b is aside plan view of the movable contact of FIG. 2. v

' FIG is a cross-sectional view of a contact structure constructedin accordance with the invention without the time delay-feature of the contact shown in FIG. 2

where thecontacts are in'the open position.

twhich incorporates'the present invention, as will be later described.,'lhe circuit breaker of FIG. 1 can, for

zexample, berated at 230,000 volts and at 63,000 amcontact separation between the movable and stationary interrupter contacts. The construction of contacts of the prior art devices is also complicated and required numerous complexly machined parts and separate contact finger biasing springs.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, both the stationary and moving contacts are formed by tubular mented fingers of the movable contact slide over the outer surface of a conductive member. It has been found than when using this arrangement, substantially no shock wave is transmitted through the movable contact fingers at the time of contact separation.

Therefore, little or no burning due to contact bounce is experienced on: the movable contact fingers or the surface of the conductive support on which they slide.

peres.jConventionally, breaker will be a threephase' breaker and two other and identical phases to the one shown in FIG. I will also be provided.

In general, the circuit breaker phase of FIG. 1 is contained within a generallyflattened spherical metallic "tank- 10 which is supported on metallic frame angle -members 1 l and '12. Angles l 1 and l2 are suitably reinforced and extend rearwardly and support additional invention is shown in adead tank configuration.

about 3 atmospheres. For purposes of the invention, any dielectric gas at any appropriate pressure could be used. For the'embodiment described herein, the gas pressure within tank will be designated a relatively low pressure. I

Each of the bushings 13 and 14 is further associated with current transformers l9 and 20, respectively, which may also be of any desired construction.

A grounded flat support platform 21 is contained within the tank 10 and is supported from the bottom of tank 10 by welded support members, such as

bolts

22 and 23 and others not shown. Platform 21 sits on leveling nuts, such as

nuts

24 and 25, respectively, of the support bolts. The platform 21 then serves as a level mount for the circuit interrupter equipment to be contained within tank 10. In the case of the breaker shown in FIG. 1, four interrupters are to be connected in series with one another to define the circuit breaker voltage rating of 230 KV. Platform 21 supports two spaced hollow tubular

insulation support members

26 and 27,

.respectively, which further serve the purpose of high pressure gas reservoirs as is more fully described in copending application Ser. No. 398,868, referred to above.

Each of the insulation support

members

26 and 27 support, at their tops, respective

blast valve housings

28 and 29 which, in turn, support series-connected interrupter units 30-31 and 3233, respectively. Each of the, interrupter units contains a pair of interrupter contacts which are simultaneously opened in the presence of a blast of gas which assists in extinguishing the arc. It is to be noted that the

tubes

26 and 27,

blast valve housings

28 and 29, and interrupters 30 to 33 are mechanically supported solely from the platform 21 and that none. of these components are supported from the bushings l3 and 14 or intermediate supports for the interrupters 31 and 32.

The top of interrupter 30 is electrically connected to the stud 35 of terminal bushing 13 through a flexible connection, which will be later described. The connectionbetween the top of interrupter 30 and stud 35 is then covered by a corona shield 36.

The bottom of interrupter 30 is then connected through housing 28 to the bottom of interrupter 31. The top of interrupter 31 is connected through flexible shunts 36a to the top of interrupter 32 with the tops of interrupters 31 and 32 and flexible connectors covered 7 by

corona shields

37 and 38, respectively.

The bottom of interrupter 32 is then connected through the blast valve housing 29 to the bottom of im terrupter 33. The top of interrupter 33 is in turn connected to the stud 39 of bushing 14 by flexible connectors, such as flexible connectors 40=and 41. The connection previously referred to between interrupter 30 and stud 35 incorporates flexible connectors, such as the connectors 40 and 41. The connection to stud 39 I is then covered by the corona shield 42.

- FIG. 1 also shows

voltage distributing impedances

43 and 44 connected across

interrupters

30 and 33, re-

' spectively. Note that any suitable arrangement of parallel-connected capacitors or resistors could be used across the various interrupters 30 to 33 in order to assure appropriate distribution of steady state and transient voltages across the series-connected breaks.

-.FIG. 1 illustrates the provision of transient

recovery voltage capacitors

50 and 51 which are to be connected from either of the line sides of thebreaker to ground.

It will be noted that the flattened elliptical shape of tank 10 makes available free space in the outer central regions of thetank so that these capacitors can be mounted within this space without interference with the operation of the breaker or Without interference with the dielectric integrity of the breaker. The mounting of these capacitors is the subject of copending application Ser. No. 398,869. a

It will be noted from FIG. 1 that the upper terminals of each of

capacitors

50 and 51 are connected by relatively

rigid conductors

52 and 53 to the tops of

interrupters

30 and 33, respectively, and are directly and solidly connected to the

bushing studs

35 and 39, respectively. The bottoms of capacitors 50 and 51'are then mechanically and electrically connected to the tank wall 10 by the support and grounding brackets54 and 55, respectively. V

The transient recovery voltage across the breaker is then controlled by the capacitors 50 and 51in the manner generally set forth in US. Pat. No. 3,383,519, it being noted that each of

capacitors

50 and 51 may have a value of approximately 0.0025 microfarads many other desired value selected by the circuit designer.

The interior of the

insulation reservoirs

26 and 27, which communicate with the

blast valve housings

28 and 29 and thence to the interrupters 30 to 33 is at a relatively high pressure, such as 15 atmospheres of the same dielectric gas which fills tank 10. I The major pressure source for the breaker is an elongated cylinder which is filled with gas at high pressure and which may be covered with a heater blanket 61 to ensure that the. gas temperature will always be sufficiently high to maintain it in a gaseous state. A protective shroud 62 covers the cylinder 60 (which may extend the full length of all of the phases of the breaker), with portholes such as porthole 63 being available to permit maintenance of the cylinder 60 and the blanket61. A suitable gas control system, 'which need not be described to understand the present invention, provides suitable gas conduits and gas controls to conduct gas from the cylinder 60 through the conduit 64 which passes through a sealing plug 65 in tube 66 which is secured to tank 10.

The high pressure conduit 64 then extends through a T-shaped member and into

conduits

67 and 68 as generally outlined by the arrows, in FIG. 1, such that high pressure gas is admitted to the interior of

insulation reservoirs

26 and 27. As willbe later described, this gas is normally sealed at the

blast valve housings

28 and 29 and high pressure gas is released through the

interrupters

30 and 33 and into low pressure tank l0'only when the contacts of the interrupters are operated.

A suitable mechanical operating mechanism (not shown herein) is provided to mechanically actuate crank arms, such as crank arm 70 associated with tube 26, which drive operating rods which extend through the center of

support tubes

26 and 27 and upwardly to blast

valve housings

28 and 29. Similar crank arms will be associated with each of the other interrupters of each phase of the breaker. Any conventional operating mechanism, such as a spring operated mechanism or hydraulically operated mechanism is then connected to each of the crank arms so that all blast valves and 6 contacts can be simultaneously operated to either open or close all interrupter contacts.

The specific details of one interrupter structure, such as the interrupter 30 of FIG. 1 and aportion of the blast valve housing 28, are shown in FIG. 2. Referring now to FIG. 2, the interrupter and blast valve are shown in cross-section and at the top of FIG. 2. Aswill be later described, interrupters 30 to 33 are subassembled units which can be easily installed when the breaker is assembled. Thus, FIG. 2 shows two

flexible shunts

80 and 81 which have

upper connectors

82 and 83 which are appropriately bolted to the stud 35 of bushing 13, while the other ends of

shunts

80 and 81 are bolted to an upper conductive adapter member 84 of the interrupter 30. Note that the stud 35 does not serve as a mechanical support for the interrupter components.

The upper adapter 84 is bolted to a second adapter portion 85 with the two

components

84 and 85 defining a volume 86 which leads to discharge ports such as the discharge port 87 which is positioned adjacent a similar port 88 in the shield 36. Note the position of port 88 in FIG. 1.

Additional ports are distributed around the periphery of shield 36 which lead to similar openings defined between

adapter members

84 and 85. Two further'ports of this general type are shown in FIG. 1 for shield 42 as the ports 89 and 90.

The adapter member 84 further serves to threadably receive a tubular arcing terminal 91. Note that arcing terminal 91 has an opening 91a therethrough which extends upwardly so that some are venting can be directly vertically upward along the axis of the opening in arcing terminal 91. i

The use of flexible shunts to make the connection from the top of interrupter 30 to the terminal bushing stud 35 is made possible since the entire mass of interrupter structure 30 is supported on top of the blast valve housing 28. In prior art arrangements, such as the arrangement shown in US. Pat. No. 3,526,734, the stationary contact structure of the interrupter is rigidly fastened to and carried by the end of the terminal bushing. This structure required careful alignment of the interrupter components during assembly of the breaker and during its operation. The structure shown in FIG. 2 eliminates the need for alignment during assembly of the circuit breaker and simple

flexible shunt members

80 and 81 are used to connect the top of the preassembled interrupter 30 to the terminal bushing stud 35. Similar advantages apply to the connection between the top of interrupter 33 of FIG. 1 and the terminal bushing stud 39.

As previously described in connection with FIG. 1 the tops of interrupters 31 and 32 are connected in series by the flexible shunt 36a. This is to be contrasted to the prior art arrangement of US. Pat.'No. 3,526,734 which required a separate support insulator extending .from the top of the housing which would physically carry the stationary contacts for interrupters 31 and 32. By supporting interrupters 31 and 32 from the

blast valve housings

28 and 29, the separate support insulator and the alignment problems which were caused by the separate mounting of the stationary contacts of these interrupters are eliminated.

The interrupter 30 of FIG. 2 contains an elongated,

generally tubular stationary contact member 100 which has an upper solid ring-shaped end 101 and slots which form segmented contact fingers, such as

fingers

102 and 103 in its other end. The segmented fingers of contact 100 are also shown in FIG. 2a which is a top end view of the contact 100. It will be further noted that the ends of the segmented contacts. such as

segmented finger contacts

102 and 103 terminate with arcing contact inserts which may have been formed as an insert ring which was brazed to the tubular contact member before the tubular member was slotted to form the segmented finger.

FIG. 20 further illustrates openings such as opening 104 in the solid flange 101 which accepts the bolts, such as bolt 105 which secures the stationary contact to adapter member 85. The bolts which pass through the openings in flange 101 of stationary contact 100 are threaded into a conductive ring which clamps the end side of flange 101 against adapter member 85. Ring 110 serves as an upper support for the insulation tube 111 which is the interrupter housing tube. Tube 111 may be made of any desired material, such as an epoxy reinforced glass tube or the like. The upper end of tube 111 is suitably secured to and sealed with respect to ring 110 as by the securing key 112 and sealing ring 1 l3.

A set of bolt openings is formed in the inner diameter of ring 110 and these bolt openings receive bolts, such as bolt 120, which threadably engage ring member 121 and hold it in position. The exterior lower portion of ring 121 is threaded and threadably receives the insulation baffle 122 which may be of a suitable arc-resistant material such as Teflon, and serves as a guide for blast gases during the opening operation of the interrupter, and as a means to protect or shield tube 111 from the hot gases created during arc interruption. Baffle 122 also contains a plurality of thin, axially directed and circumferentially spaced fins, such as fin 123. These fins then prevent the formation of a vortex in the gas blast which is guided by baffle 122.

The lower end of insulation tube 1 11 is fixed in a conductive support ring and is fixed therein and sealed thereto as by the key 131 and sealing ring 132. The ring 130 is, in turn, secured to a spider plate 133 as by bolts, such as bolt 134, where the spider plate is formed of a conductive disk 134a having radially extending web sections such as

sections

135 and 136 which are joined to a centrally extending hollow conductive shaft 137. The shaft 137 then slidably receives the segmented movable contact 138 which is slidably engaged with the outer surface of shaft 137.

The movable contact 138 consists of a generally tubularly shaped member having a solid ring-shaped end 139 which receives a solid arcing ring 140, with the lower end of contact 138 being segmented to form separate contact fingers, such as

fingers

141 and 142.

FIG. 2b shows a side plan view of the movable contact 138. The

segmented finger elements

138 and 142 along with other similar fingers are flexed outwardly from their normal relaxed position, and are therefor biased inwardly and into sliding engagement with the outer surface of shaft 137. The solid upper end 139 of movable contact 138 is movable into and out of rections through the arc, both through t'he center of stationary contact 100 and the opening in arc terminal 91, and through the central opening in contact 138 shown as opening 151.

The movable contact 138 is connected to an operating shaft 152 (which contains the opening 151) and the upper end of shaft 152 is provided with flange 153. The flange 153 is engageable with the rear surface 154 of the movable contact 138 and also receives a compression spring 155. The compression spring 155 is seated at its bottom on a ledge 156 of a spring retaining cylinder 157 which is threadably secured within the upper end of contact 138. The bottom of cylinder 157 slides within the interior of conductive tube 137 and slides on a seal 158 within the shaft 137. The operation of the interrupter contacts described above will be later described after the blast valve arrangement and support of the interrupter from the blast valve housing 28 is described.

As is shown in FIG. 1, the blast valve housing 28 supports both interrupters 30'and 31. One lateral half of the blast valve housing 28 is shown in FIG. 2 insofar as it relates to the support of interrupter 30. It will be noted,'however, that the blast valve housing 28 is symmetric so that the same structure shown in connection with interrupter 30 is provided on the opposite side of the center line 200 in FIG. 2 for the support and operation of interrupter 31.

The insulation support member 26 of FIG. 1 is partly shown in FIG. 2 and it is seen that a metal end cap 201 is fitted over and sealed to the top of insulation tube 26.

- The metal cap 201 then serves as the support for the conductive support casting 202 of the blast valve housing 26. Casting 202 is provided with a slot 203 therein for passing an arm 204 which is appropriately connected to the operating shaft 152 by the adapter fitting 205.

Cap 201 further serves to support ring 210 and circumferentially distributed posts such as posts 211 which are welded to ring 210. The posts 211 are then welded to a valve seat plate 212 which carries the cutoff valve ring 213 of the blast valve as will be later described. The valve ring 213 is then held in position by closed and a current path is formed from terminal bushing stud 35 through the flange shunts and 81 and into the

adapter members

84 and 85 and the stationary contact 100. The current then transfers from stationary contact into the movable contact 138 and the

contact fingers

141 and 142 and into the conductive tube 137. From the conductive shaft 137 the current passes through casting 202 and then to interrupter 31 which is also supported on the blast valve housing 28. The current then proceeds through the

interrupters

31, 32 and 33 in the same manner and exits at bushing 14.

While the breaker is closed, the high pressure gas from within the insulating support tube 26 fills the volume defined by the annular open gap between the bottom seal 213 and sleeve 243 and upwardly within sleeve 222 and up to the valve seat 230. The interior of interrupter 30 is at the relatively low pressure of the interior of tank 10, as contrasted to the high pressure which is held at the valve seat 230. I

In order to open the circuit breaker, the circuit breaker operating mechanism (not shown) is actuated to cause all of the operating rods, such as operating rod 220 to move simultaneously. The downward movement of rod 220 causes the sleeve 222 to move downwardly thereby to open the seal between the upper end of sleeve 222 and the valve seat 230. This permits the high pressure gas within sleeve 222 to move into the chamber.which contains spider members and 136 and upwardly through the annular channel 150 within the insulation tube 111. Thus, the pressure within the annular volume 150 begins immediately to increase.

At the same time, the downward movement of sleeve 222 causes the shaft 152 to move downwardly and, initially, the upper flanged end 153 of shaft 152 will cause the spring 155 to begin to compress. This introduces an increasing downward force on the seal sleeve 157 and thus on the movable contact 138 which is connected to sleeve 157. Initially, however, the contact 138 does not move since the frictional forces between the segmented fingers, such as

fingers

141 and 142 of the movable contact against the outer surface of shaft 137 and the frictional force between upper contact end 139 and the segmented contacts of the stationary contact 100 are sufficiently high to prevent contact motion. Ultimately, however, the spring force becomes sufficiently high as to drive the movable contact 138 downwardly, thereby causing the separation of the contact 138 from the seg- The upper end of blast valve sleeve 222 is engageable with upper blast valve seal 230 which is clamped in position by the clamping plate 231a. The ring-shaped valve seal 230 is carried on plate 231 which is generally supported by a ring 232 which is an integral portion of I It is now possible generally to describe the operation 7 of the interrupter and blast valve of FIG. 2. With the components in the position shown, the interrupter is mented fingers of the stationary contact 100 with a snap action. Note that eventually the flange 153 will pick up shoulder 260 of sleeve 157 if the movable contact does not begin to move under the force of the compression spring 155 alone.

As the contact tip separates from the arcing contact finger portions of the segmented stationary contact 100, an arc is drawn between them. Substantial gas pressure has already been established within chamber and high pressure gas may begin to flow between the separating contacts even prior to inception of the are as when the contact separation is somewhat delayed by the lost motion connection between shaft 152 and the movable contact 138.

As the

contacts

100 and 138 separate, sulfur hexafluoride or a similar interrupting gas passes rapidly through the annular region of contact separation with a portion of the gas flowing into channel 151 and another portion of the gas flowing upwardly and through i I on'the arc terminal 91 and the lower arc root will extendfrom the arcing tip 140. The are is quickly extinguishedunder the influence of the rapidly moving sulfur hexafluoride gas.

At the time the arc is extinguished; the sleeve 222 has r'noved sufficiently downward so that the shoulder 261 in the outside of the'sleeve 262 has picked up the lower sleeve 243's0 that the sleeve 243 is moved downwardly and into engagement with valve seat 213. This operation then cuts'off the further flow of high pressure gas from the interior of cap 201 toward the interrupter,

thereby'to conserve thehigh pressure gas in the reservoir.

In order to reclose the breaker, the operating rod 220 is moved upwardly so that the contact operating rod 152 moves upwardly to reclose the contacts. Little or no gas blast is necessary during the closing operation. Therefore, there is a time delay in the re-opening of the blast valve. Thus, the sleeve 243 remains sealed against seal 213 until sleeve 222 and its outwardly facing extension 241 move to a sufficiently high position that extension 241 engages the shoulder 242 of sleeve 243. At this point, the lower valve seat 213 is opened so that gas can flow for the very short time until the upper end of sleeve 222 seats against seal 230.

An important advantage of the contact structure described above is that the contact structure has few parts and no separate contact biasing springs. Thus, the contact arrangement is inexpensive and reliable. Moreover, it has been found that by arranging the contacts so that the segmented contact fingers extend from solid tubularends for both contact 100'and contact 138, a shock wave is not transmitted through the moving

contact fingers

138 and 142 at the time of contact separation. .Therefore, there is no bouncing of the

segmented contact fingers

138 and 142 on the outer surface of conductive shaft 137 so that there is no burning at this surface which burning would cause a high contact resistance.

A further advantage of the structure of FIG. 2 is that a time delay structure is easily built into the movable contact of the segmented contact configuration to ensure that gas blast action has started before the contacts separate.

A further advantage of the contact configuration [shown is that, when the contacts open, the nozzle area for allowing rapid flow of gas from annular region 150 is snapped open with the opening of the contacts, thereby allowing an extremely large passage for the flow of high pressure gas immediately after contact separation.

FIGS. 3 and 4 show a second embodiment of the contact structure of the present invention without the time delay feature of FIG. 2 which uses the sleeve 157 and spring 155. In all other respects, the structure of FIGS. 3 and 4 is similar or identical to the arrangement of FIGS. 2, 2a and 2b and similar components have been given similar identifying numerals.

FIG. 3 shows the contact structure of the invention in the open position, where the operating rod 152 has been moved downwardly. Note that the operating rod 152 is secured directly to contact 138 as by threading to the interior in the upper end of opening contact 138.

In FIGS. 3 and 4, and as was the case in FIG. 2, the stationary and moving contacts and 138, respectively, consist of a plurality of segmented contact fingers. The required contact force is, therefore, obtained by elastic deflection of the contact fingers from their rest position when the contacts engage their respective surfaces. Thus, no additional contact springs are necessary to provide the needed contact pressure. Moreover, the design of FIGS. 3 and 4 has been found to prevent the transmission of a shock wave through the movable contact fingers at the time of contact separation so that there is no bouncing of

segments

141 and 142 on the surface of shaft 137 and thus no burning at that surface.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be 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 circuit interrupter:

an integral, generally tubular stationary contact, one

end of said generally tubular contact being segmented in an axial direction to define a generally circular cluster of contact fingers;

an integral, generally tubular movable contact movable into and out of engagement with said stationary contact, one end of said generally tubular movable.contact being segmented in an axial direction to define a generally circular cluster of contact fingers, the opposite end of said movable contact being a generally solid ring; said contact fingers extending for the major length of said generally tubular movable contact from said one end of said generally tubular movable contact to said generally solid ring of said generally tubular movable contact; a

said tubular stationary and movable contacts being coaxial; said solid ring end of said movable contact being movable into engagement with surfaces of said circular cluster of contact fingers of said stationary contact and having a diameter different than the diameter defined by said surface of said cluster of stationary contact fingers when they are unflexed, thereby to create a given contact pressure when said movable and stationary contacts are in engagement;

a generally stationary conductive tube supported in insulated relation with respect to said stationary contact;

said tubular movable contact being coaxial with respect to said stationary conductive tube and being in sliding contact engagement therewith; said segmented movable contact fingers engaging a surface of said conductive tube; said conductive tube having a diameter different than the diameter defined by the engaging surfaces of said movable contact fingers when they are unflexed, thereby to create a given contact pressure when said movable contact slides relative to said conductive tube; whereby contact bounce of said movable contact fingers is substantially eliminated;

and an operating mcchanism for applying high forces over a relatively short time to said movable contact, thereby to move said movable contact into and out of engagement with said stationary contact, and wherein substantially no shock force is transmitted to the region of sliding engagment between said movable contact fingers and said stationary conductive tube when said movable contact moves out of engagement with said stationary contact; said operatingmechanism including an elongated operating shaft disposed coaxially with said movable contact and extending through the center of said stationary conductive tube, and having one end thereof fixed to said solid ring end of said movable contact 2. In the circuit interrupter of claim 1, wherein said stationary contact fingers engage and are flexed outwardly by the outer surface of said solid ring portion of said movable contact, and wherein said movable contact fingers engage and are flexed outwardly by the outer surface of said conductive tube.

3. In the circuit interrupter of claim 1, wherein said stationary contact and stationary conductive tubes are connected to respective circuit interrupter terminals.

4. In the circuit interrupter of claim 1 which further includes gas blast means operable by said operating mechanism for producing a blast of gas between said stationary and movable contacts during their movement to a disengagedposition.

5. In the circuit interrupter of claim 4 wherein the interior of said stationary contact and of said movable contact are permanently connected to a relatively low pressure region, whereby gas flows from the exterior of said stationary and movable contacts through the interiors thereof to said low pressure region during the operation of said movable contact to a disengaged position relative to said stationary contact.

. 6. In the circuit interrupter of claim 5, wherein said stationary contact fingers engage and are flexed outwardly by the outer surface of said solid ring portion of said movable contact, and wherein said movable contact fingers engage and are flexed outwardly by the outer surface of said conductive tube.

. 7. An electrical contact structure comprising:

an integral, generally tubular stationary contact,'one

circular cluster of contact fingers;

an integral, generally tubular movable contact movable into and out of engagement with said stationarylcontact, one end of said generally tubularmovable contact being segmented in an axial direction to define a generally circular cluster of contact fingers, the opposite end of said movable contact being a generally solid ring; said contact fingers extending from said one end of said generally tubular movable contact to said generally solid ring of said generally tubular movable contact; 5 said tubular stationary and movable contacts being coaxial; said solid ring end of said movable contact being movable into engagement with surfaces of said circular cluster of contact fingers of said stationary contact and having a diameter different than the diameter defined by said surfaces of said cluster of stationary contact fingers when they are unflexed, thereby to create a given contact pressure when said movable and stationary contacts are in engagement; a generally stationary conductive tube supported in insulated relation with respect to said stationary contact; I said tubular movable contact being coaxial with respect to said stationary conductive tube and being in sliding contact engagement therewith; said segmented movable contact fingers engaging a surface of said conductive tube; said conductive tube having a diameter different than the diameter defined by the engaging surfaces of said movable contact fingers when they are unflexed, thereby to create a given contact pressure when said movablev relative to said tubular movable contact and having.

j one end thereof fixed to said solid ring end of said movable contact; said operating shaft extending through and being axially movable relative to said" stationary conductive tube.

Claims

1. In a circuit interrupter: an integral, generally tubular stationary contact, one end of said generally tubular contact being segmented in an axial direction to define a generally circular cluster of contact fingers; an integral, generally tubular movable contact movable into and out of engagement with said stationary contact, one end of said generally tubular movable contact being segmented in an axial direction to define a generally circular cluster of contact fingers, the opposite end of said movable contact being a generally solid ring; said contact fingers extending for the major length of said generally tubular movable contact from said one end of said generally tubular movable contact to said generally solid ring of said generally tubular movable contact; said tubular stationary and movable contacts being coaxial; said solid ring end of said movable contact being movable into engagement with surfaces of said circular cluster of contact fingers of said stationary contact and having a diameter different than the diameter defined by said surface of said cluster of stationary contact fingers when they are unflexed, thereby to create a given contact pressure when said movable and stationary contacts are in engagement; a generally stationary conductive tube supported in insulated relation with respect to said stationary contact; said tubular movable contact being coaxial with respect to said stationary conductive tube and being in sliding contact engagement therewith; said segmented movable contact fingers engaging a surface of said conductive tube; said conductive tube having a diameter different than the diameter defined by the engaging surfaces of said movable contact fingers when they are unflexed, thereby to create a given contact pressure when said movable contact slides relative to said conductive tube; whereby contact bounce of said movable contact fingers is substantially eliminated; and an operating mechanism for applying high forces over a relatively short time to said movable contact, thereby to move said movable contact into and out of engagement with said stationary contact, and wherein substantially no shock force is transmitted to the region of sliding engagment between said movable contact fingers and said stationary conductive tube when said movable contact moves out of engagement with said stationary contact; said operating mechanism including an elongated operating shaft disposed coaxially with said movable contact and extending through the center of said stationary conductive tube, and having one end thereof fixed to said solid ring end of said movable contact.

2. In the circuit interrupter of claim 1, wherein said stationary contact fingers engage and are flexed outwardly by the outer surface of said solid ring portion of said movable contact, and wherein said movable contact fingers engage and are flexed outwardly by the outer surface of said conductive tube.

4. In the circuit interrupter of claim 1 which further includes gas blast means operable by said operating mechanism for producing a blast of gas between said stationary and movable contacts during their movement to a disengaged position.

6. In the circuit interrupter of claim 5, wherein said stationary contact fingers engage and are flexed outwardly by the outer surface of said solid ring portion of said movable contact, and wherein said movable contact fingers engage and are flexed outwardly by the outer surface of said conductive tube.

7. An electrical contact structure comprising: an integral, generally tubular stationary contact, one end of said generally tubular contact being segmented in an axial direction to define a generally circular cluster of contact fingers; an integral, generally tubular movable contact movable into and out of engagement with said stationary contact, one end of said generally tubular movable contact being segmented in an axial direction to define a generally circular cluster of contact fingers, the opposite end of said movable contact being a generally solid ring; said contact fingers extending from said one end of said generally tubular movable contact to said generally solid ring of said generally tubular movable contact; said tubular stationary and movable contacts being coaxial; said solid ring end of said movable contact being movable into engagement with surfaces of said circular cluster of contact fingers of said stationary contact and having a diameter different than the diameter defined by said surfaces of said cluster of stationary contact fingers when they are unflexed, thereby to create a given contact pressure when said movable and stationary contacts are in engagement; a generally stationary conductive tube supported in insulated relation with respect to said stationary contact; said tubular movable contact being coaxial with respect to said stationary conductive tube and being in sliding contact engagement therewith; said segmented movable contact fingers engaging a surface of said conductive tube; said conductive tube having a diameter different than the diameter defined by the engaging surfaces of said movable contact fingers when they are unflexed, thereby to create a given contact pressure when said movable contact slides relative to said conductive tube; and an elongated operating shaft coaxially disposed relative to said tubular movable contact and having one end thereof fixed to said solid ring end of said movable contact; said operating shaft extending through and being axially movable relative to said stationary conductive tube.