US3185799A

US3185799A - Vacuum-type electric circuit interrupter in which a main arc is divided into series-related arcs

Info

Publication number: US3185799A
Application number: US245275A
Authority: US
Inventors: Allan N Greenwood; Joseph W Porter
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-12-17
Filing date: 1962-12-17
Publication date: 1965-05-25
Anticipated expiration: 1982-05-25
Also published as: FR1378462A; ES294372A1

Description

United States Patent O 3,185,799 VACUUM-TYPE ELECTRIC CIRCUIT INTER- RUPTER IN WHICH A MAIN ARC IS DIVIDED INTO SERIES-RELATED ARCS Allan N. Greenwood and Joseph W. Porter, Media, Pa., assignors to General Electric Company, a corporation of New York Filed Dec. 17, 1962, Ser. No. 245,275 9 Claims. (Cl. 20G- 144) This invention relates 'to an electric circuit interrupter of the vacuum type and, more particularly, to an electric circuit interrupter of this type in which a main [arc iS divided into a plurality of series-related ares in order to facilitate circuit interruption.

The usual vacuum type circuit interrupter comprises an evacuated chamber in which an arc i-s established between two relatively movable contacts. Assuming the circuit is an alternating current circuit, the arc maintains itself until about the time a natural current zero is reached, after which the arc is prevented from reigniting by the high dielectric strength of the Vacuum.

The interrupting capacity of a vacuum type interrupter can be increased by dividing the arc that is established into a plurality of series-related arcs across a -plurality of series-related gaps. After ay current zero has been reached, the total dielectric 'strength Ithat is developed across the series-related gaps exceeds that which would ybe developed across the `single gap had the arc been allowed'to persist across the single gap. The result is increased voltage interrupting ability and increased current interrupting ability as Well.

If the series-related arcs are permitted to contaminate the main arcing gap with contact vapors generated -by the series-related arcs, then there is a decreased likelihood that the main arcing gap will be able to withstand the usual recovery voltage transient that appears immediately lalter a current zero is reached. Similarly, if one of the series-related arcing gaps is contaminated by arcing products from an arc at another of the series-related gaps, then there is a decreased likelihood that the contaminated gap will -be able to withstand the recovery voltage transient. A breakdown of either the main arcing gap or a series-related arcing gap by the recovery voltage transient could interfere with the desired circuit interruption.

Accordingly, an object of our invention is to construct a vacuum circuit interruptor of this type in such a manner as to reduce the likelihood of the main arcing gap being contaminated by :arc-generated vapors from one of the series-related arcing gaps and the likelihood of one of the series-related arcing gaps being contaminated by arcgenera-ted vapors from another series-related arcing gap.

One of the factors that determines the amount of current that the interrupter can interrupt is the volume that is directly accessible to the arcing products. Generally speaking, the larger this volume becomes, the greater the interrupting capacity. In most prior interrupte-r designs, the etective volume that is directly accessible to the arcing products is determined primarily bythe diameter of the evacuated envelope and to little or no extent by the longitudinal dimension of the envelope. In these prior designs, the spaces that are typically available behind these contacts are not readily accessible to the arcing products and :in this respect are used ineiiiciently or are largely wasted. Accordingly, another object of our invention is to make more eliicient use of the spaces in the evacuated chamber that are located behind the main .arcing gap.

Another object is to vent the arcing products primarily in a direction longitudinally of the evacuated envelope into the relatively largespaces that lare present near the longitudinally-opposed ends of the envelope.

ICC

In carrying out our invention in one form, we provide a highly evacuated envelope of tubular form having longitudinally-opposed ends and a tubular wall primarily of insulating material extending between the ends. Located within the envelope are a first contact and a second contact that is engageable with the rst contact and is movable out of engagement therewith to produce a main arcing gap between the contacts located generally centrally of the length of the envelope. Also disposed within the envelope are two arc runners of a generally cupshaped configuration. The first arc runner comprises a base portion generally surrounding the -rst contact and a tubular flange at the outer periphery of the base portion projecting away from the base portion in a direction away from the main arcing ygap and toward one of the ends of the envelope. The second arc runner comprises a base portion that generally surrounds the sec-ond contact and a tubular ange at the outer periphery of this base portion projecting lfrom the base portion in a direction away yfrom the main arcing gap and toward the other end of the envelope. The first Varc runner is electrically connected to the first contact and the second arc runner to the second Contact. Also disposed within the envelope -is athird arc runner normally electrically isolated from the first and second arc runners. This third arc runner cornprises a central region of annular configuration surrounding the main arcing gap and la pair of tubular portions respectively surrounding the tubular flanges of the first and second are runners in spaced-apart relationship to thetubular anges so as to define secondary arcing gaps of annular configuration about the tubular ilanges. The tubular flanges of the first and second arc runners termi- -nate at points longitudinally spaced from the end of the envelope toward which each flange projects so that a space .is present within the envelope between the lseeondary arcing gap and this end into which Iarcing products may be freely vented. A metallic shield located between this space and the insulating walls of the envelope is provided to protect the walls from the condensation of metallic vapors thereon.

For a better understanding of our invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view partly in section showing a vacuum type circuit interrupter embodying one form of our invention. The interruptor in FIG. 1 is shown in a partially open position.

FIG. 2 shows a portion of the interrupter of FIG. l. The parts shown in FIG. 2 are in the position they occupy when the interrupter is closed.

FIG. 3 is a side elevational view of one part of the interruptor of FIG. l as viewed from a position 3 3 shown in FIG. 1.

Referring now to FIG. 1, there is shown a vacuum type circuit interrupter comprising a highly evacuated envelope 11. The envelope 11 comprises a tubular housing 12 lof a suitable insulating material such as glass and a pair of

metallic end caps

13 and 14 at the longitudinallyvopposed ends of the tubular housing. The

metallic end caps

13 and 14 are joined to the tubular housing 12 by means of suitable vacuum-tight seals 15. Preferably the tubular housing 12 is made from two coaxially disposed glass cylinders 12a and 12b between which a metallic disc 18 is disposed in a location centrally of the evacuated envelope 11. This metallic disc is joined to the two glass cylinders 12a and 12b by suitable vacuum

tight joints

20 and 21.

Disposed within the envelope 11 are a pair of relatively

movable contacts

22 and 24. Contact 22 is a stationary contactthat is supported from the top end plate 13 by means of a conductive rod 25 that serves to carry current it to and from the contact 22 when the interruptor is closed. This conductive rod 25 is suitably brazed or otherwise joined at its upper end to the upper end cap 13. At its lower end the rod 25 is brazed to the upper side of a conductive disc 28 that, in turn, is brazed to the upper side of contact 22.

The lower contact 24 is a movable Contact that is brazed to the upper end of a movable contact operating rod 3i), made from a highly conductive metal. This operating rod 3d extends through an opening in the lower end cap 14 and is freely movable in a vertical direction within this opening. A flexible metallic bellows 32 provides a seal about the operating rod 30 that permits such movement to take place without impairing the vacuum inside the envelope l1. The bellows 32 is joined in sealed relationship at its respective opposite ends to the lower end cap 14 and the operating rod 30. A suitable slide bearing 34 mounted on the lower end plate 14 provides guidance for the rod 3i) during its vertical motion.

When the interrupter is closed, the movable Contact 24 is in its uppermost position, indicated by the dotted lines 36, where it engages the stationary contact 22. This position is also depicted in FIG. 2. Current can then ow through the interrupter via a path that extends between an upper terminal 38 and a lower terminal 4t) through the upper rod 25,

contacts

22 and 24 and the conductive operating rod 3th. Opening of the interrupter is effected by driving the operating rod Sti downwardly through the solid line intermediate position shown in FIG. l into its lowermost or fully-opened position indicated by the dotted lines 41.

This opening movement separates the movable contact 24 from the stationary contact 22 and establishes an arc across the gap between the two contacts. As will soon be explained in greater detail, this larc is driven radially outward a predetermined distance, after which it is split into two series-related arcs that are spun about the longitudinal axis of the interruptor until extinguished.

To provide conductive surfaces along which the arc terminals can travel as the arc moves radially outward, a pair of cup-

shaped arc runners

50 and 52 are provided about the two

contacts

22 and 24, respectively. The cup-shaped arc runner comprises a base portion 53 generally surrounding the stationary contact 22 and a tubular flange 54- at the outer periphery of the base portion projecting from the base portion in a direction away from the main arcing gap and toward the upper end of the envelope 1li. The other arc runner 52 comprises an annular base portion 56 generally surrounding the movable contact 24 and a tubular iiange 58 at the outer periphery of the base portion 56. This ilange 58 projects from the base portion 56 in a direction away from the main arcing gap and toward the lower end of the envelope. The space between the

contacts

22 and 24 and between the base portions 53 and 56 of the two arc runners is referred to hereinafter as the main arcing gap and is designated 57.

The upper arc runner 50 is integrally joined to the central disc 28 and is thus tixedly mounted on the rod 25 in the illustrated position of FlG. l. The central disc 23 also electrically interconnects the arc runner 5t) and the stationary contact 22. The lower arc runner 52 has a central tubular portion 59 integrally joined to its annular base 56 at the inner periphery of the annular base. This tubular portion 59 is suitably joined, as by brazing, to the upper end of a conductive tubular support 6i) that is brazed at its lower end to the lower end cap 14. The lower cup-shaped arc runner 52 is therefore fixedly mounted on the lower end cap 14 and is electrically connected thereto. The movable contact 24 is movable relative to this arc runner through the central passage deiined by the tubular parts 59 and 60. The movable contact 24 and the lower cup-shaped arc runner 52 are electrically interconnected by means of an electrical connection 61 between the lower end cap 14 and the operating rod Si).

For splitting the main arc into two series-related arcs or arclets, a third arc runner 62 is provided. This third arc runner 62 has a central region 63 of annular configuration surrounding the main a-rcing gap 57 and a pair of

tubular portions

65 and 66 respectively surrounding the tubular flanges 54 and 53 of the cup-shaped

arc runners

50 and 52. These

tubular portions

65 and 66 are radiallyspaced fromthe flanges 54 and 58, and a secondary arcing gap of annular configuration is formed by the space between each pair of these tubular parts. The upper secondary arcing gap is designated 70 and the lower secondary arcing gap 72. The third arc runner 62 is supported on the centrally disposed metallic disc 18 by a suitable joint at the inner periphery of disc 18. The third arc runner 62 is normally electrically isolated from the other two

arc runners

50 and 52 and from the end caps 13 and 14. This follows from the fact that the third arc runner is spaced from the other two arc runners and its supporting disc 18 is electrically isolated from the end caps 13 and 14 by the insulating cylinders 12a and 12b that make up the envelope 12. Preferably, this isolated third arc runner is at a mid-potential with respect to the end caps when the circuit interrupter is open.

For accelerating movement of the main arc in a radially outward direction after it has been established between the

contacts

22 and 24, we force current flowing through each of the contacts to the arc-initiation point to follow a path that extends radially outward to the arcinitiation point. In this respect, note that the two

contacts

22 and 24 have annular regions near their outer peripheries where they engage each other, as shown in FIG. 2. The central portion of each contact is recessed so that engagement will not occur there. Thus, the arc is always established near the outer periphery of the contact when the contacts are separated. The bulk of the current between the contact and the rod 30 can enter or leave the contact only through its central region, as will soon be explained, and thus current iiowing through the arc and the contacts will be forced to follow a radially-outwardly bowing path as indicated by the dotted line L of FIG. 2. The magnetic effect of such a loop-shaped path is to lengthen the loop, and thus the magnetic eiiect of the loop-shaped path L will act to drive the arc radially outward.

To accentuate this magnetic effect, a ring `olf low conductivity material such as stainless steel is located behind each of the

contacts

22 and 24. These rings are designated 74 and 75. Each of these rings has a diameter considerably smaller than the diameter of the contact-making portion of its contact. Most of the current iiowing through the contact is forced to enter or leave through the restricted central region of the contact bounded by lthe rings 74, 75. Very little of this current iiows through the ring in view of its low conductivity relative to that of the contact material. Since the

rings

74 and 75 force current to enter and leave the contact through a region more centrally located than otherwise would be the case, it will be apparent that the loopshaped L is accentuated by the presence of

rings

74 and 75. Each of these rings is preferably brazed on its opposite faces to its adjacent contact and the contact support so as to impart additional mechanical strength to the contact structure.

To accelerate transfer of the lower arc terminal from the movable contact 24 to the arc runner 52, the contact 24 is provided with a tubular flange 77 that is spaced from the operating rod 3i) along the entire length of the iiange. The tubular flange 77 extends across the main arcing gap when the contacts are closed and provides an immediately available conductive path along which the lower arc terminal can run into proximity with the lower arc runner 52 as soon as the arc is initiated without waiting for any further separation of the contacts. Another factor that contributes to the speed with which the lower arc terminal is transferred to the lower arc runner 52 is the fact that as soon as the lower arc terminal reaches the tubular portion 77 of the contact 24, a downward bow is introduced into the coniiguration of the loop circuit L. For example, in FIG. 1 note that when the arc is at B the current path L includes a downward bow. This increasingly forces the lower arc terminal to move downwardly along the outer surface of tubular wall 77 toward the lower arc runner 52. The above-mentioned downward bow results from the fact that all current flowing through the contact 24 to an arc terminal on the tubular flange 77 is forced to flow through the top portion of contact 24 and is prevented from bypassing this top portion by the insulating space 78 between the flange 77 and the rod 30.

When the lower arc terminal has transferred to the lower arc runner S2, the arc moves radially outward through a position such as indicated at C. The arc then strikes the inwardly projecting annular portion 63 of the intermediate arc runner 62, which splits the arc into two series-related arclets, one between the upper arc runner 50 and the intermediate arc runner 62 and the other between the lower arc runner 52 and the intermediate arc runner 62. The two arclets are then rapidly driven through the

secondary arcing gaps

70 and 72 into positions E at the outer ends of the secondary arcing gaps. Typical positions through which the arclets pass as they move toward positions E are depicted at D. As positions E, the longitudinal axis of the arclets are substantially perpendicular to the path of contact movement and to the longitudinal dimension of the yenvelope 11. s

As the arclets approach their position E, they are subjected to a circumferentiallyacting magnetic force that spins them circumferentially about the longitudinal axis of the interrupter. This circumferentially-acting force is preferably derived from a series of angularly-spaced skewed slots 8S provided in the

tubular parts

54 and 65 and 58 and 68 at their free ends. These slots 85 are best illustrated in FIG. 3, where they are shown angularly overlapping their adjacent slot and dividing the end of tubular part 65 into a series of angularly-spaced lingers 86 respectively located between adjacent slots. Each of the slots 85 has a circumferentially-extending component that forces the current flowing to or from an arc terminal located on any one of the fingers 86 to follow a path that has a net component extending circumferentially of the tubular part. The magnetic elfect of current flowing in such a circumferentially-extending path is to drive the arclet circumferentially of the tubular part about the longitudinal axis of the interrupter.

The arclets are spun circumferentially about the axis of the interrupter until a current zero, at which time the arclets vanish and are thereafter prevented from reigniting by the high dielectric strength of the vacuum.

There are a number of different factors which determine whether or not sufficient dielectric strength will be present immediately after a current zero to prevent arcreignition. One of these factors is the amount of vapors generated prior to current zero by the arcs. Generally speaking, the greater the quantity of these vapors the more likely vapors will still be present when the recovery voltage transient stresses the gaps rimmediately after current zero and, thus, the more diincult it is to recover the dielectric strength necessary to prevent arc-reignition. By driving the arclets in a circumferential direction when they approach the positions E, the amount of metal vapors that they evaporate from the electrodes can be reduced, thereby increasing the rate at which dielectric strength is recovered immediately after current zero. Along these same lines, the rapid transfer of the arc off the

contacts

22 and 24 and its rapid motion ran Anotherfactor that determines whether or not dielectric strength willbe recovered quickly enough after current zero to prevent arc-reignition is the volume of the space directly accessible to the arc-liberated contact vapors. The larger this volume, the easier it will be for the vapors to diffuse away from the arcing regions so that they will not be present to impair dielectric strength across the stressed arcing gap after interruption. Also, the larger this volume, the less likely it will be for vapor particles to bounce yback into the high stress regions of the interrupter to trigger a dielectric breakdown.

The illustrated interrupter very effectively uses the volume available in the interrupter inasmuch as the arclets are driven away from the main gap in a direction longitudinal of the interrupter into regions E of the secondary arcing gaps adjacent the large volumes near the longitudinal ends of the interrupter. The arcing products can be expelled directly into these large volumes or spaces 80 from the

secondary arcing gaps

70 and 72. Thus, these volumes or spaces 80 behind the contacts, which in other interrupters are inefliciently used, if not altogether wasted, are used in a highly ellcient manner in our interrupter.

To condense the contact vapors that are expelled into each of these volumes 8i), a tubular metallic shield 82 of a generally L-shaped cross section is provided adjacent the walls of the interrupter in each of these volumes 80. Each of these shields 82 is suitably supported at 84 on the insulating housinglZ and is thus electrically isolated from the

adjacent end cap

13 or 14 and the intermediate arc runner 62. These shields 82 act to intercept and condense contact vapors before they can reach the insulating walls of the envelope.

By condensing the vapors, the shields 82 also serve to prevent metallic particles from bouncing back into the highly stressed regions of the interrupter to trigger a dielectric breakdown. The efficiency of these shields in condensing the hot vapors depends upon the temperature of the shields. Generally speaking, the lower this temperature, the more ellicient are the shields. This temperature can be reduced by increasing the effective spacing between the shield and the arcing region. In the illustrated arrangement, it is possible to provide an exceptionally large effective spacing between the arcing regions E and the shields 82 because the arcing vapors are expelled primarily in a direction longitudinal of the tubular envelope 11. This means that the effective spacing between the shield and the arcing region is determined primarily by the distance between the arcing region and the shield measured longitudinally of the envelope. This is in contrast to most interrupters where this effective spacing is measured radially of the envelope and can be increased only by increasing the diameter of the envelope. This is a much more expensive matter than increasing the length of the envelope, as could be done with our interrupter if it were desired to increase the spacing.

lt will be apparent from the drawing and the hereinabove description, that the upper vapor-receiving space 80 is located between the upper end cap 13 and the points at which the upwardly-extending tubular flange 54 and tubular part 65 terminate, i.e., the location E. This space 80 normally prevents an arc in the secondary gap 70 from moving upwardly past this location E. When the arc extends across the secondary arcing gap 70 while in this location E, it extends generally perpendicular to the length of the envelope, as can be seen in FIG. 1. This disposition of the arc is attributable, at least partially, to the fact that the end portions of

tubular parts

54 and 65 adjacent their upper termination points extend longitudinally of the envelope. As will be apparent from FIG. 1, substantially these same relationships are present at the lower vapor-receiving space 80 and the region E of the lower secondary gap 72.

The three

massive arc runners

50, 52 and 62 also act as vapor-condensing shields for the arc-generated contact vapors. In this regard, some of these vapors will be forced from the arcing region at E. back toward the main arcing gap 57. Vapors traveling from the arclets at E toward the main gap impinge upon the extensive surfaces of these arc runners and are thus condensed by these surfaces.

lt should be noted that substantially all straight line paths extending from the location E to the main gap region are intercepted by these arc runners t), 52, 62. vapors from the arcing region E will follow such straight line paths until they strike a condensing surface, and thus they wlil impinge upon the arc runners and most will be condensed before they can reach the rnain arcing gap. 10

This is highly advantageous in that it helps to prevent these arcing vapors from being present in the main gap region when this main gap is being highly stressed shortly after current zero, thereby reducing the chances for a breakdown across this main gap.

it should be further noted that there is no straight line communication between the two spaced-apart arcing regions E. Substantially all straight line paths extending between these two locations E are intercepted by the

arc runners

59, 52 and 62. The are runners can condense most of these vapors on their relatively cool surfaces, and thus no appreciable quantity of vapors generated at one arcing location E will reach the other arcing location to impair the dielectric strength at said other location during the critical period immediately following a current zero.

It will be noted that the annular central portion 63 of the intermediate arc runner 62 projects radially inward and thus serves as a barrier which blocks straight line communication between the two arcing regions at E. The inwardly projecting configuration of annular part 63 also contributes to the ability of the annular part to act as a barrier between the arcing regions E and the main arcing gap 57.

When the movable contact 24 of FIG. l is in its fully open position, it is Withdrawn behind the arc-running sur face of the lower arc runner 52. This provides a desirable electrostatic shielding effect since the end of the movable contact is then in a region of reduced electric stress as compared to that present above the arc-running surface. This follows from the fact that the exposed surface of the arc runner 52 is rounded with a much larger radius than the contact 24 and is essentially free of sharp protrusions. As is well known, this lessens the tendency for electric stress concentrations to be present. This shielding effect reduces the likelihood of an electrical breakdown occurring from the contact 24. The stationary contact 22 is likewise positioned behind the arc-running surface of this arc runner 50 so that the same shielding effect is present at the stationary contact structure to reduce the chances of a dielectric breakdown involving the stationary contact 22.

Another factor that helps to reduce the chances for a dielectric breakdown across the main arcing gap 57 is the presence of the radially inwardly projecting annular portion e3 on the intermediate arc runner 52. The portion 63 has curved surfaces which are generally parallel to the adjacent surfaces of the first and second arc runners, and this tends to make the electric eld more uniform across the main gap, thus reducing the chances for dielectric breakdown.

Another advantage of the illustrated interrupter is that most of the parts of the interruptor that are exposed to the arc can be made quite large and massive without necessitating the movement of large masses in opening and closing the interrupter. in this respect, note that the arc runners or electrodes Sil, 52, and 62 are quite large and massive, but there is no need to move these parts in order to control the interrupter. The only part that it is necessary to move is the relatively light movable Contact 24. The low mass of this part enables a relatively small and inexpensive operating mechanism to be relied upon for operating the interrupter and also permits higher operating speeds with less stress.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects, and we, therefore, intend in the appended claims to cover all such changes and modications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. An electric circuit interrupter of the vacuum type comprising:

(a) a highly evacuated envelope of tubular form having longitudinally opposed ends and a ltubular wall at least partially of insulating material extending longitudinally of said envelope between said ends,

(b) a first contact located within said envelope,

(c) a second contact engageable with said first contact and movable out of engagement with said first contact to produce a main arcing gap between said contacts located generally centrally or the length of said envelope,

(d) a first arc runner of a generally cup-shaped configuration comprising a base portion `generally surrounding said lirst contact and a tubular flange at the outer periphery of said base portion projecting from said base portion in a direction away from said main arcing gap and toward one of the ends of said envelope,

(e) a second arc runner of a generally cup-shaped configuration comprising a base portion generally surrounding said second contact and a tubular flange at the outer periphery of said base portion projecting from said base portion in a direction away from said main arcing gap and toward the other end of said envelope,

(f) means for electrically connecting said first arc runner to said first contact and said second arc runner to said second contact,

(g) a third arc runner normally electrically isolated from said lirst and second arc runners and comprising an annular central region surrounding said main arcing gap and a pair of tubular portions respectively projecting from said central region toward said ends of said envelope, said tubular portions respectively surrounding the tubular flanges of said first and second arc runners in spaced-apart relationship -to said tubular flanges so as to define secondary arcing gaps of annular configuration about said tubular flanges between said tubular portions and said tubular flanges,

(h) the tubular flanges of said first and second arc runners and the tubular portions of said third arc runner terminating at points longitudinally spaced from the end of said envelope toward which the flange projects so that a vapor-receiving space is present within said envelope between said secondary arcing gap and said end into which arcing products may be freely vented,

(i) each of said flanges and the tubular portion surrounding each said flange having an end portion adjacent its termination point that extends longitudinally of said envelope so that an arc located in a secondary arcing gap between an adjacent pair of said end portions extends generally perpendicular to the length of said envelope,

(i) and means including said vapor-receiving space for normally preventing an arc in said secondary arcing gap from moving past said termination points.

2. The circuit interrupter of claim l in combination with a metallic shield located between one of said spaces and the insulating walls of said envelope to protect said walls from the condensation of metallic vapors thereon.

3. The circuit interrupter of claim l in combination with means for forcing current flowing through said first or second arc runners to an arc terminal at substantially any point on said arc runner to follow a path through said arc runner that extends radially outward to said arc terminal.

4. The circuit interrupter of claim 1 in which the annular central region of said third arc runner acts as a barrier that substantially prevents straight line communication between said two secondary arcing gaps.

5. The electric circuit interrupter of claim 1 in which said three arc runners are shaped in such a manner that substantially all straight line paths between said main arcing gap and the portion of said secondary arcing gap at the outer end of said tubular iianges are intercepted by one of said arc runners.

6.y The interrupter of claim l'inwhich the annular central portion of said third arc runner projects radially inwardly between the bases of said cup-shaped arc runners, and has surfaces confronting the adjacent surfaces of said bases that are substantially parallel to said adjacent surfaces.

7. The interrupter of claim 1 in which said movable contact is spaced from said second arc runners and is movable relative thereto, said movable contact being of a cup-shaped configuration and comprising a base that is engageable with said first contact and a tubular wall that extends from said base in a direction away from said kirst contact, said tubular wall bridging said main arcing gap when the movable contact is closed, so that an arc'can run along said tubular wall to said second arc runner as soon as the arc is initiated, and means for forcing substantially all current flowing through said cup-shaped contact to an arc terminal on the tubular wall thereof to follow a path that extends through the base of said contact so that a magnetic force is available to drive said arc along said tubular wall onto said second arc runner.

8. An electric circuit interrupter as dened in claim l in which said envelope comprises a pair of end caps at longitudinally opposed ends of said tubular envelope, a first conductive rod extending between one of said end caps and said first contact, a second conductive rod projecting through the other of said end caps and carrying said movable Contact at its inner end, and a tubular conductive support for said' second arc runner surrounding said second rod and extending from said second arc runner to said scond end cap, the base of said second arc runner being of an annular configuration and said tubularconductive support being joined to said annular base at the inner periphery of said base.

9. The interrupter of claim 1 in combination with means for providing a magnetic force for driving arcs at said scondary arcing gaps around the outer periphery of said tubular flanges.

References Cited by the Examiner UNITED STATES PATENTS 2,976,382 3/61 Lee 20o- 144 FOREIGN PATENTS 389,463 3/33 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

Claims

1. AN ELECTRIC CIRCUIT INTERRUPTER OF THE VACUUM TYPE COMPRISING: (A) HIGHLY EVACUATED ENVELOPE OF TUBULAR FORM HAVING LONGITUDINALLY OPPOSED ENDS AND A TUBULAR WALL AT LEAST PARTIALLY OF INSULATING MATERIAL EXTENDING LONGITUDINALLY OF SAID ENVELOPE BETWEEN SAID ENDS, (B) A FIRST CONTACT LOCATED WITHIN SAID ENVELOPE, (C) A SECOND CONTACT ENGAGEABLE WITH SAID FIRST CONTACT AND MOVABLE OUT OF ENGAGEMENT WITH SAID FIRST CONTACT TO PRODUCE A MAIN ARCING GAP BETWEEN SAID CONTACTS LOCATED GENERALLY CENTRALLY OF THE LENGTH OF SAID ENVELOPE, (D) A FIRST ARC RUNNER OF A GENERALLY CUP-SHAPED CONFIGURATION COMPRISING A BASE PORTION GENERALLY SURROUNDING SAID FIRST CONTACT AND A TUBULAR FLANGE AT THE OUTER PERIPHERY OF SAID BASE PORTION PROJECTING FROM SAID BASE PORTION IN A DIRECTION AWAY FROM SAID MAIN ARCING GAP AND TOWARD ONE OF THE ENDS OF SAID ENVELOPE, (E) A SECOND ARC RUNNER OF A GENERALLY CUP-SHAPED CONFIGURATION COMPRISING A BASE PORTION GENERALLY SURROUNDING SAID SECOND CONTACT AND A TUBULAR FLANGE AT THE OUTER PERIPHERY OF SAID BASE PORTION PROJECTING FROM SAID BASE PORTION IN A DIRECTION AWAY FROM SAID MAIN ARCING GAP AND TOWARD THE OTHER END OF SAID ENVELOPE, (F) MEANS FOR ELECTRICALLY CONNECTING SAID FIRST ARC RUNNER TO SAID FIRST CONTACT AND SAID SECOND ARC RUNNER TO SAID SECOND CONTACT, (G) A THIRD ARC RUNNER NORMALLY ELECTRICALLY ISOLATED FROM SAID FIRST AND SECOND ARC RUNNERS AND COMPRISING AN ANNULAR CENTRAL REGION SURROUNDING SAID MAIN ARCING GAP AND A PAIR OF TUBULAR PORTIONS RESPECTIVELY PROJECTING FROM SAID CENTRAL REGION TOWARD SAID ENDS OF SAID ENVELOPE, SAID TUBULAR PORTIONS RESPECTIVELY SURROUNDING THE TUBULAR FLANGES OF SAID FIRST AND SECOND ARC RUNNERS IN SPACED-APART RELATIONSHIP TO SAID TUBULAR FLANGES SO AS TO DEFINE SECONDARY ARCING GAPS OF ANNULAR CONFIGURATION ABOUT SAID TUBULAR FLANGES BETWEEN SAID TUBULAR PORTIONS AND SAID TUBULAR FLANGES, (H) THE TUBULAR FLANGES OF SAID FIRST AND SECOND ARC RUNNERS AND THE TUBULAR PORTIONS OF SAID THIRD ARC RUNNER TERMINATING AT POINTS LONGITUDINALLY SPACED FROM THE END OF SAID ENVELOPE TOWARD WHICH THE FLANGE PROJECTS SO THAT A VAPOR-RECEIVING SPACE IS PRESENT WITHIN SAID ENVELOPE BETWEEN SAID SECONDARY ARCING GAP AND SAID END INTO WHICH ARCING PRODUCTS MAY BE FREELY VENTED, (I) EACH OF SAID FLANGES AND THE TUBULAR PORTION SURROUNDING EACH SAID FLANGE HAVING AN END PORTION ADJACENT ITS TERMINATION POINT THAT EXTENDS LONGITUDINALLY OF SAID ENVELOPE SO THAT AN ARC LOCATED IN A SECONDARY ARCING GAP BETWEEN AN ADJACENT PAIR OF SAID END PORTIONS EXTENDS GENERALLY PERPENDICULAR TO THE LENGTH OF SAID ENVELOPE, (J) AND MEANS INCLUDING SAID VAPOR-RECEIVING SPACE FOR NORMALLY PREVENTING AN ARC IN SAID SECONDARY ARCING GAP FROM MOVING PAST SAID TERMINATION POINTS.