US3211866A

US3211866A - Vacuum type electric circuit interrupter with plural parallel-connected contact points

Info

Publication number: US3211866A
Application number: US256295A
Authority: US
Inventors: Donald W Crouch; Thomas H Lee
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1963-02-05
Filing date: 1963-02-05
Publication date: 1965-10-12
Anticipated expiration: 1982-10-12

Description

",21 1,866 VACUUM TYPE ELECTRIC CIRCUIT INTERRUPTER WITH PLURAL Oct. 12, 1965 D. w. CROUCH ETAL PARALLEL-CONNECTED CONTACT POINTS Filed Feb. 5, 1963 INVENTORS. DONALD W. CROUCH,

THOMAS HLEE, 5y 64W ATTORNEY.

1965 0. w. CROUCH ETAL 3,211,866

VACUUM TYPE ELECTRIC CIRCUIT INTERRUPTER WITH PLURAL PARALLEL-CONNECTED CONTACT POINTS Filed Feb. 5, 1963 3 Sheets-Sheet 2 INVENTORS. DONALD l/V. CROUCH, THOMAS H. LEE,

BY $081M...

ATTORNEY.

1965 D. w. CROUCH ETAL 3,211,866

VACUUM TYPE ELECTRIC CIRCUIT INTERRUPTER WITH PLURAL PARALLEL-CONNECTED CONTACT POINTS Filed Feb. 5, 1965 s Sheets-Sheet 3 F7 6.&

32 /NVEN7'0RS.

DONALD W. CROUCH, THOMAS H. LEE, 5) j l ATTORNEY.

United States Patent 3,211,866 VACUUM TYPE ELECTRIC CIRCUIT INTERRUPT- ER WlTI-I PLURAL PARALLEL-(IONNECTED CONTACT POINTS Donald W. Crouch, Newtown Square, and Thomas H.

Lee, Media, Pa., assignors to General Electric Company, a corporation of New York Filed Feb. 5, 1963, Ser. No. 256,295 13 Claims. (Cl. 2ti0144) This invention relates to an electric circuit interrupter of the vacuum type and, more particularly, to a circuit interrupter of this type in which a plurality of movable contacts are relied upon to provide a plurality of contact points connected in parallel.

To render a circuit interrupter capable of handling high continuous and momentary currents, it is customary to provide the circuit interrupter with a plurality of movable contacts that can provide parallel-connected paths through the interrupter. The total current flowing through such an interrupter is divided between these parallel paths, thus reducing the magnetic forces and heating effects at each contact point as compared to an arrangement in which fewer or only a single contact point is present.

In a preferred form of our invention, two parallelconnected movable contacts are provided, and these contacts are surrounded by an annular electrode that is physically spaced from the two movable contacts and is electrically connected to them. The arc or arcs established by operation of the movable contacts are transferred to this annular electrode and are driven about it to aid in extinguishing them.

An object of our invention is to construct the contact structure in such a manner that the are established by operation of the movable contacts is required to move only a minimum distance to reach the annular electrode and to transfer across only the gap between the annular electrode and the movable contact nearest it.

In a vacuum-type circuit interrupter, it is customary to support any movable part located inside the evacuated envelope by means of a bearing located outside the envelope since bearings that operate in a vacuum are usually not very reliable. This ordinarily means that for each movable contact there must be a bearing outside the envelope, a rod projecting through the envelope and supporting the movable contact on the bearing, and a bellows around the rod to provide a seal that prevents leakage into the evacuated envelope.

An object of our invention is to arrange these parts in such a manner that one of the bellows is required to deflect through only a small distance, considerably less than the total opening stroke.

Another object is to arrange the contacts in such a manner that they can be readily operated by only a single mechanism of a simple construction.

In carrying out our invention in one form, we provide two movable contacts, one of which is operated by an annular rod and the other of which is operated by a second rod located internally of the annular rod. The bellows for the annular rod is located between the envelope and the annular rod, but the bellows for the second rod is located between the annular rod and the second rod. The bellows for the annular rod is flexed through the entire opening stroke, but the other bellows is flexed only through the relative movement that occurs between the two movable contacts.

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 cross sectional view through a vacuum- 3,211,866 Patented Oct. 12, 1965 type circuit interrupter embodying one form of the invention. In FIG. 1 the circuit interrupter is shown in its closed position.

FIG. 2 is a sectional view similar to that of FIG. 1 except showing the parts of the interrupter in an open position.

FIG. 3 is a sectional view along the line 33 of FIG. 2.

FIG. 4 illustrates a modified form of our invention.

FIG. 5 illustrates another modified form of our invention. The circuit interrupter of FIG. 5 is in the closed position.

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 5.

FIG. 7 is a view of a portion of the interrupter of FIG. 5 except showing the interrupter in the open position.

Referring now to FIG. 1, the circuit interrupter shown therein comprises an evacuated envelope 11 that comprises a tubular housing 12 of a suitable insulating material such as glass. At opposite ends of the housing 12 are

metallic end plates

13 and 14 that are joined in vacuum tight relationship to the glass housing 12 by means of suitable seals 15. The envelope is evacuated to a pressure of 10 mm. of mercury or even lower.

Disposed within the envelope 11 is a stationary contact structure 20 that is supported from the top plate 13 by means of a conductive rod 21 that also provides an electrical connection between the end plate 13 and the stationary contact structure 20. This stationary contact 20 is preferably in the form of a circular disk. Engageable with this stationary contact structure 20 are two

movable contacts

26 and 28, each of an annular shape. These annular

movable contacts

26 and 28 are disposed in generally concentric relationship, with the contact 26 surrounding the contact 28. The annular portion of the contact structure 20 that is engaged by inner movable contact 28 may be thought of as a first stationary contact 28a, and the annular portion of stationary contact structure 20 that is engaged by the outer movable contact 26 may be thought of as a second stationary contact 26a surrounding the first contact 28a.

The outer contact 26 is supported on a cylindrical rod 30 at the upper end of the rod. The inner contact 28 is supported on a rod 32 that is located within the cylindrical rod 30 in generally coaxial relationship thereto. Each of these

rods

30 and 32 is of a conductive material so as to enable current to be carried through the rod to or from the contacts supported thereon. The two conductive rods are electrically connected together in parallel relationship and to the lower end plate 14 by suitable means, such as the conductive

flexible braids

29, 31, 33. Thus, when the interrupter is closed, current will flow through it between an upper terminal 35 and a lower terminal 37 through the two

movable contacts

26 and 28 in parallel and the stationary contact structure 20 in series with the two movable contacts. Using two movable contacts instead of the usual one distributes the current between the two contacts, thus decreasing the amount of current that each contact point is required to conduct. This desirably reduces the magnetic forces and heating eflects at each contact point, enabling the interrupter to handle higher continuous and momentary currents.

Each of the

rods

30 and 32 is movable along its longitudinal axis to etfect circuit-controlling movement of its respective contact. For guiding the outer rod 30 during such longitudinal movement, a stationary sleeve bearing 34 is provided about the rod 30. This sleeve bearing 34 is carried by a tubular bearing support 36 that has a radially extending flange 38 suitably secured to the lower end plate 14. The cylindrical rod 30 is freely slidable in a longitudinal direction within this bearing 34.

For guiding the inner rod 32, a second sleeve bearing 40 is provided. This sleeve bearing 40 is preferably supported on the cylindrical rod 30 by means of a bearing support 42 suitably secured to the cylindrical rod 30. The

and 60, so that the two

contacts

26 and 28 move upwardly toward closed position in unison. Since the outer contact 26 projects slightly above the inner contact 28 during this interval, the outer contact will engage the stationary coninner rod 32 is freely slidable in a longitudinal direction 5 tact structure 20 first. This terminates upward movewithin this bearing 40.

For providing a seal about the outer rod 30 a flexible metallic bellows 44 is provided. This bellows 44 projects into the evacuated envelope and is secured in sealed relationship at its respective opposite ends to the. end plate 14 and the outer rod 30. For providing a seal about the inner rod 32, a second flexible metallic bellows 46 is provided. This bellows 46 is secured in sealed relationship at its respective opposite end to the cylindrical rod 30 and the inner rod 32. Each of these

bellows

44 and 46 permits movement of its respective operating rod to occur without impairing the vacuum inside the envelope 11. It will be noted that the

bearings

34 and 40 are located on the atmospheric side of the two bellows 44 and 46 and are thus disposed outside the evacuated chamber.

For imparting opening and closing movement to the

movable contacts

26 and 28, a vertically movable common operating member 50 is provided. In FIG. 1, the operating member 50 is shown in its uppermost or fully closed position, where it is held by suitable latch means (not shown). The operating member 50 is coupled to the two

contact operating rods

30 and 32 by wipe

springs

54 and 56, respectively. The wipe spring 54 is a compression spring that bears at its lower end against the common operating member 50 and at its upper end against the cylindrical operating rod 30. The other wipe spring 56 is a compression spring that bears at its lower end against the common operating member 50 and at its upper end against a shoulder 57 fixed to the inner operating rod 32. Thus, the wiper springs 54 and 56 urge their

respective contacts

30 and 32 into the closed position shown so long as the common operating member 50 is in its uppermost or fully closed position shown in FIG. 1. The basic purpose of the wipe springs is to maintain at least a predetermined amount of contact pressure on the contacts despite limited wear of the contacts that might occur after repeated operations.

Opening of the interrupter is effected by driving the common operating member 50 in a downward direction from its position of FIG. 1. Such downward motion first causes an internal shoulder 58 carried by the common operating member 50 to engage the shoulder 57 on the inner operating rod 32, thereby forcing the inner contact 28 in a downward opening direction away from the stationary contact structure 20. After a small amount of such downward opening travel has occurred, sufiicient to separate the inner contact 28 from the stationary contact structure, another shoulder 60 rigid with the inner operating rod 32 engages the part 42 that is fixed with respect to the outer contact operating rod 30. This engagement in between

parts

60 and 42 forces the cylindrical operating rod 30 in a downward opening direction to separate outer contact 26 from the stationary contact 20. After the shoulder 60 has engaged part 42, it will be apparent that the two

contacts

26 and 28 will move toward their fully open position substantially in unison. The fully-open position of the parts is illustrated in FIG. 2;

Closing of the circuit interrupter is effected by driving the common operating member 50 in an upward direction from its fully-open position of FIG. 2 into its closed position of FIG. 1. This closing operation will be discussed assuming that the

springs

54 and 56 are sufiiciently stiff that no appreciable deflection of the springs occurs until the movable contacts engage the stationary contact. Initial upward movement of member 50 applies an upward force to cylindrical operating rod 30 through the spring 54, thereby driving the operating rod 30 upwardly. Such upward movement carries the inner operating rod 32 upwardly due to the engagement between parts 42 ment of the contact 26, but the common operating member 50 continues moving upwardly compressing spring 54 and applying wiping force to the outer contact 26. The inner contact 28 also continues moving upwardly after the outer contact 26 engages the stationary contact structure due to the upward force being applied to the inner contact 28 through spring 56. After a small amount of such upwardly travel independently of the outer contact 26, the inner contact 28 engages the stationary contact structure 20. This terminates upward motion of the inner contact 28, but the common operating member 50 continues moving upwardly, compressing the lower wipe spring 56 and applying wiping force to the inner contact. Finally, upward motion of the common operating member -50 will be terminated by a suitable stop (not shown), at

which time the parts will be in the position of FIG. 1.

It will be apparent that during this closing operation, the bellows 46 was flexed only during the small amount of travel of the inner contact 28 occurring after the outer contact 26 engages the stationary contact 20 and before the inner contact 28 engages the stationary contact 20. This small amount of travel is equal to the spacing between shoulder 60 and part 42 shown in FIG. 1. Thus, the inner bellows 46 was not flexed through the whole operating stroke of either of the contacts but only through the diiference in the operating strokes of the two contacts. This is true during an opening stroke as well since relative movement between the inner contact 26 and the outer contact 28 during opening ceases as soon as shoulder 60 engages part 42.

To aid in extinguishing the are that is drawn during an opening operation, an annular arc-running electrode '70 is provided about the two

movable contacts

26 and 28. This electrode 70 is a stationary part and is supported on the lower end plate 14 by means of a tubular sleeve '72. This sleeve 72 is of a conductive material and serves to carry current to and from the electrode 70 when an arc is located thereon. Preferably, this electrode 70 is provided with spiral slots 74 of the general configuration shown and claimed in US. Patent No. 2,949,520 Schneider assigned to the assignee of this invention. These slots, which are shown in FIG. 3, are intended to provide a magnetic effect for driving any are on the electrode 70 in a circumferential direction.

It will be recalled that during an opening operation, the inner movable contact 28 moves out of engagement with the stationary contact structure 20 before the outer movable contact 26 does so. Thus, the are that is established during opening will normally be established at the outer contact 26. No arc is normally established at the inner contact 28 since the outer contact is :still in engagement with the stationary contact structure 20 when the inner contact separates from the stationary contact structure. The arc that is established as the outer contact 26 is magnetically driven radially outward as the opening stroke progresses, causing the arc to transfer across the gap between contact 26 and electrode 70. The are then moves radially outward on the electrode 70 and is then driven in a circumferential direction by the magnetic effect produced by slot 74. This motion continues until the first current Zero, at which time the arc vanishes and is prevented from restriking by the high dielectric strength of the vacuum.

The above-described radially-outward force on the are results from the fact that the current path through the arc is of a loop-shaped configuration, bowing radiallyoutward, as indicated by L in FIG. 2. As is well known, the magnetic efiect of such a path is to force the arc in a direction to lengthen the loop, which in FIG. 2 would be radially-outward. This current path is still in the form of a radially-outward bowing loop when the arc reaches the electrode 70, as illustrated at M in FIG. 2, thus causing the arc to continue traveling radially-outward toward the outer periphery of electrode 70.

A factor that is responsible for the radially-outward bowing configuration n the loop circuit L is that the current path through the contact-support 30 is located radially inwardly of any point at which the arc is normally present on the contact 26. Similarly, the current path through support 72 is located radially inwardly of the points on electrode 70 at which the arc is normally present so as to accentuate the radially-outward bowing configuration of the loop-shaped path M.

Since the outer contact 26 normally establishes the arc, rather than the inner contact 28, it will be apparent that the arc is required to move across only a single gap to reach the arc-running electrode 70. It is unnecessary to move the arc across the gap between the

contacts

28 and 26, as would be required if the arc were established at the inner contact 28.

It will be noted that the outer contact 26 will be subject to some are erosion since it is exposed to the are. But despite this are erosion, it will still be possible to obtain good contact pressure for contact 26 without interfering with the ability of the other contact 28 to engage the stationary contact 20 with the proper contact pressure. This desirable relationship is made possible by the fact that each of the

contacts

26 and 28 has its own wipe spring and by the additional fact that the wipe spring 54 permits enough movement of the common operating member 50 to allow the inner contact 28 to be forced into engagement with the stationary contact and to allow the wipe spring 56 for the inner contact 28 to be compressed.

FIG. 4 illustrates a modified embodiment having its parts shown in an open position corresponding to that depicted in FIG. 2. In the embodiment of FIG. 2, there are relatively

movable supports

38 and 42 for the

contact rods

30 and 32. But in the embodiment of FIG. 4, only-a single bearing support is relied upon for the two

contact rods

30 and 32. This single bearing support is illustrated at 80 carried by a cup-shaped member 82 having a flange 84 fixed to the lower end plate 14. The tubular contact rod 30 is guided by means of a sleeve bearing '85 carried by the stationary support 80 and disposed between the outer periphery of the support 80 and the inner periphery of the tubular contact rod 30. The inner contact rod 32 is guided by means of a sleeve bearing87 carriedv by .the stationary support 80 and disposed between the inner periphery of the stationary support and the outer periphery of the contact rod 32.

The cup-shaped support 82 for the bearing support 80 contains a series of angularly spaced holes 89. An-

gularly-spaced rods 90 fixed to the tubular contact rod 30 extend freely through these holes 89 and are secured at their lower ends to a crosshead 42a generally corresponding to the part 42 of FIG. 2. The crosshead 42a can be moved upwardly to impart closing movement to the contact rod 30 and downwardly to impart opening movement to red 30. The actuating means 50-58 of FIG.. 4 is essentially the same as the correspondingly designated means of FIG. 2 and functions in the same manner. A shoulder 42b is fixed to the tubular contact rod 30 and this bears against a shoulder 60 on the-inner contact rod 32 in the same manner as

parts

42 and 60 engage in FIG. 2.

FIGS. 5-7 illustrate still another embodiment of our invention. In this embodiment, as in the others, there are two sets of relatively movable contacts disposed in generally concentric relationship and a stationary annular arc runner surrounding the contacts of each set. The contacts of one set of these relatively movable contacts are designated 28 and 28a, respectively; and the contacts of the other set are designated 26 and 26a. The contacts 26 and 2611 are of an annular form and nated wipe spring in FIG. 1.

respectively surround the

contacts

28 and 28a. The stationary arc runners are designated 20 and 70, respectively, with are runner 20 surrounding the

upper contacts

26a and 28a and the arc runner 70 surrounding

lower contacts

26 and 28. The

outer contacts

26, 26a may be thought of as being located between the

inner contacts

28, 28a and the

stationary arc runners

20, 70.

The lower two

contacts

26 and 28 are movable contacts that are fixed relative to each other. Both of these

contacts

26 and 28 are mounted on a movable conductive rod 32.

One of the upper contacts 28a is a stationary contact that is carried by the tubular support 21 for the upper arc runner 20. Preferably, a conductive cross bar extends diametrically across the tubular support 21 and is fixed to the upper contact 28a and the tubular support 21 to provide a stationary mounting for the contact 28a.

The other upper contact 26a is formed by the lower end of a tubular flange of a cup-shaped member 102 that is mounted for limited vertical movement. This tubular flange has a pair of diametrically opposed openings 103 through Which the cross bar 100 extends with enough clearance to allow for the desired vertical movement of the cup-shaped member 102. This cup-shaped member 102 is spring-biased in a downward direction by means of a spring 104 located outside the evacuated envelope 11. This spring 104 acts against the shoulder 106 fixed to a rod 108 that is fixed to the cup-shaped member 102. A suitable bellows 110 provides a vacuum-tight seal about the movable rod 108.

The two

upper contacts

26a and 28a and upper are runner 20 are electrically connected together by means including a conductive jumper 114 located outside the envelope 11. This conductive jumper is connected at one end to the conductive rod 108 and at its other end to the upper end plate 13. End plate 13 is electrically connected to contact 28a through the cross bar 100 and the tubular support 21. The two

lower contacts

26 and 28, which are electrically connected to each other through a suitable brazed joint, are electrically connected to the lower arc runner 70 by means of a conductive jumper 33 and the conductive support 72 or the arc runner 70. When the circuit interrupter is in its closed position of FIG. 5, the two sets of

contacts

26, 26a, and 28, 28a are connected in parallel, and current may flow through the interrupter via either set of contacts. The

contacts

28 and 28a are held in engagement under pressure by means of a wipe spring 56 corresponding to a similarly desig- The

contacts

26 and 26a are held in engagement under pressure by means of the upper spring 104.

Opening of the circuit interrupter of FIG. 5 is eflected by driving the contact rod 32 downwardly. This immediately separates the inner contacts 28 and 2811, but no arcing occurs at these inner contacts since the

outer contacts

26 and 26a are still in engagement. The

outer contacts

26 and 26a continue in engagement since the upper spring 104 is capable of driving the upper contact 26a through a limited downward stroke in follow-up relationship to the downwardly moving contact 26. This engagement between

contacts

26 and 26a continues until the stationary plate 115 is engaged by the shoulder 106 on the rod 108, which is integrally connected to the contact 26a. This engagement between

parts

115 and 106 arrests the downward movement of the contact 26a, but contact 26 continues moving downward into its fully open position of FIG. 7, establishing a gap between

contacts

26 and 26a. An arc is established across this gap between contacts 26 and 2611, after which the arc moves radially outward to the

annular arc runners

20 and 70. The are

runners

20 and 70 are slotted, as in FIG. 3, to provide for rotation of the are about the arc runner until extinguished in the same manner as described in connection with FIGS. 1 and 3. It will be apparent that in FIG. 5, as well as in FIG. 1, the terminals of the are are required to jump across only 7 a single gap in order to reach the

stationary arc runners

20 and 70. This follows from the fact that the arc is initiated at the outer set of

contacts

26, 26a rather than the inner set 23, 28a.

The downward force for effecting the above described opening operation was transmitted to the contact rod 32 through a main operating rod 50 and

shoulders

58 and 57, corresponding to similarly designated parts in FIG. 1.

Closing of the interrupter is effected by driving the main operating member 50 upwardly from its open positionof FIG. 7. This action drives the operating rod 32 and

contacts

26 and 28 upwardly. After a predetermined amount of such upward motion, contact 26 engages annular contact 26a, which is then in its position of FIG. 7, forcing annular contact 26a upwardly against the wipe spring 104. After a predetermined amount of this upward motion of

contacts

26 and 26a together, the inner movable contact 28 engages the stationary contact 28a. The main operating member 50 continues moving upwardly for a slight additional distance, compressing the wipe spring 56 at the lower end of contact rod 32, thus providing contact pressure for the

contacts

28 and 28a.

It will be apparent that during closing the bellows 110 in FIG. is flexed only during the small amount of travel occurring after the

contacts

26 and 26a engage and before the

contacts

28 and 28a engage. This small amount of travel is equal to the clearance between shoulder 106 and the plate 115, as seen in FIG. 5. In view of the shortness of this travel, the bellows 110 can be only a short one. The lower bellows 44 on the other hand must be a longer one capable of being flexed through the entire operating stroke. A suitable bearing 42 is provided inside the bellows 44 for guiding the contact rod 32.

In each of the interrupters, the insulating housing is protected from the condensation of arc-generated vapors thereon by means of a suitable tubular metallic shield, such as shown at 120 in FIG. 1.

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 modification-s 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:

'1. A vacuum-type circuit interrupter comprising:

(a) generally stationary contact structure,

(b) a first movable contact engageable with said stationary contact structure when said interrupter is closed,

(0) a second movable contact of annular configuration surrounding said first movable contact and engageable with said stationary contact structure when said interrupter is closed,

(d) said second movable contact being relatively movable with respect to said first movable contact,

(e) a generally stationary arc-running electrode of annular configuration spaced from said generally stationary contact structure and surrounding said first and second movable contacts,

(f) means for electrically interconnecting said first movable contact, said second contact, and said generally stationary arc-running electrode when said interrupter is open,

(g) opening means operable during an opening operation to first separate said first movable contact from said stationary contact structure and then separate said second movable contact from said stationary contact structure,

(h) .and means for driving one terminal of an arc established by separation of said second movable contact from said stationary contact structure on to said arc-running electrode.

2. The circuit interrupter of claim 1 in combination 8 with means for driving said are in a circumferential direction about said arc-running electrode.

3. A vacuum-type circuit interrupter comprising:

(a) generally stationary contact structure,

(b) a first movable contact engageable with said sta tionary contact structure when said interrupter is closed,

(c) a generally stationary arc-running electrode of annular configuration spaced from said generally stationary contact structure and surrounding said first movable contact,

(d) a second movable contact located between said first movable contact and said stationary arc-running electrode and relatively movable with respect to said first movable contact, I

(e) means for electrically interconnecting said first movable contact, said second movable contact, and said generally stationary arc-running electrode when said interrupter is open,

(f) opening means operable during an opening operation to first separate said first movable contact from said stationary contact structure and then separate said second movable contact from said stationary contact structure,

(g) and means for driving one terminal of an arc established by separation of said second movable contact from said stationary contact structure on to said arc-running electrode.

4. The interrupter of claim 3 in combination with an evacuated envelope housing said contacts, a tubular rod coupled to said second movable contact and projecting through a wall of said envelope, an additional rod coupled to said first movable contact and projecting through a wall of said envelope, said additional rod being located within said tubular rod, tubular bearing means located between said two rods and outside said envelope for guiding said two rods, said tubular rod being slidably mounted on the exterior of said tubular bearing means and said additional rod being slidably mounted internally of said tubular bearing means.

5. The interrupter of claim 3 in combination with an evacuated envelope housing said contacts, a tubular rod coupled to said second movable contact and projecting through a wall of said envelope, an additional rod coupled to said first movable contact and projecting through a wall of said envelope, said additional rod being located within said tubular rod, a first bearing disposed externally of said tubular rod and externally of said envelope for guiding said tubular rod, a second bearing located between said tubular rod and said additional rod and located externally of said envelope for guiding said additional rod within said tubular rod.

6. The interrupter of claim 3 in combination with an evacuated envelope, a tubular rod coupled to said second movable contact and projecting through a wall of said envelope, a first flexible bellows connected between said envelope and said tubular rod and providing a seal between said envelope and said tubular rod, an additional rod coupled to said first movable contact and projecting through said envelope, said additional rod being located within said tubular rod, a second flexible bellows connected between said tubular rod and said additional rod for providing a seal between said rods.

7. The circuit interrupter of claim 6 in combination with means for transmitting opening mot-ion from said additional rod to said tubular rod after said additional rod'has moved said first contact out of engagement with said stationary contact structure during an opening operation.

8. The circuit interrupter of claim 6 in combination with an operating member for actuating said two rods and a pair of wipe springs, one of which is located between said operating member and said additional rod and the other of which is located between said operating member and said tubular rod, said wipe springs urging said movable contacts into engagement with said stationary contact structure when said contacts are closed.

9. A vacuum type circuit interrupter comprising:

(a) an evacuated envelope,

(b) a first pair of relatively movable contacts engageable with each other at a generally central location within said envelope,

(c) a generally stationary arc-running electrode of annular configuration surrounding one contact of said first pair and physically spaced from said one contact,

(d) a second pair of relatively movable contacts, one contact of said second pair being located between said annual arc-running electrode and the one contact of said first pair surrounded by said annular electrode,

(e) means for electrically connecting said annular arerunning electrode with said one contact of said first pair and said one contact of said second pair when said interrupter is open,

(f) opening means operable during an opening operation to first separate said first pair of contacts from each other and then separate said second pair of contacts from each other,

(g) and means for driving one terminal of an arc established by separation of said second pair of relatively movable contacts from said one contact of said second pair on to said stationary arc-running electrode.

10. The circuit interrupter of claim 9 in which:

(a) one contact of said first pair and one contact of said second pair are mechanically connected together for movement in unison.

(b) the other contact of said second pair being movable with respect to the other cont-act of said first pair.

11. The circuit interrupter of claim 9 in which:

(a) one contact of said first pair and one contact of said second pair are stationary contacts,

(b) and the other contacts of said first and second pair are movable contacts that are also mounted for movement with respect to each other.

12. A vacuum type circuit interrupter comprising:

(a) an evacuated enevelope,

(b) a generally stationary annular arc-running electrode,

(c) a generally stationary contact surrounded by said annular arc-running electrode,

(d) a generally annular contact surrounding said stationary contact and surrounded by said annular arcrunning electrode,

(e) means for mouting said annular contact for movement relative to said stationary contact,

(f) a pair of movable contacts for respectively engaging said stationary contact and said annular cont-act,

(g) means for mechanically connecting said movable contacts together for movement in unison,

(h) spring means for causing said annular contact to follow and thus remain in engagement with its mating movable contact during a portion of an opening operation occur-ring after said stationary contact and its mating contact have separated,

(i) means operable after said stationary contact and its mating contact have separated to block said annular contact from following its mating movable contact, thereby establishing an arcing gap between said annular contact and its mating movable contact,

(j) and means for driving the arc established at said gap on to said stationary annular arc-running electrode.

13. The vacuum type circuit interrupter of claim 12 which is further characterized by:

(a) said spring means being located outside said envelope and at one end of said envelope,

(b) force transmitting means extending through a wall of said envelope for transmitting force between said spring means and said annular contact,

(c) a bellows mounted about said force-transmitting means and providing for movement thereof without impairing the vacuum inside said envelope,

(d) additional force transmitting means for operating said movable contacts,

(c) said additional force transmitting means extending through the opposite end of said envelope,

(f) and an additional bellows about said additional force transmitting means to provide for movement thereof without impairing the vacuum inside said envelope.

References Cited by the Examiner UNITED STATES PATENTS 3/61 Lee 200-144 FOREIGN PATENTS 787,846 12/57 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner.

ROBERT S. MACON, Examiner.

Claims

1. A VACUUM-TYPE CIRCUIT INTERRUPTER COMPRISING: (A) A GENERALLY STATIONARY CONTACT STRUCTURE, (B) A FIRST MOVABLE CONTACT ENGAGEABLE WITH SAID STATIONARY CONTACT STRUCTURE WHEN SAID INTERRUPTER IS CLOSED, (C) A SECOND MOVABLE CONTACT OF ANNULAR CONFIGURATION SURROUNDING SAID FIRST MOVABLE CONTACT AND ENGAGEABLE WITH SAID STATIONARY CONTACT STRUCTURE WHEN SAID INTERRUPTER IS CLOSED, (D) SAID SECOND MOVABLE CONTACT BEING RELATIVELY MOVABLE WITH RESPECT TO SAID FIRST MOVABLE CONTACT, (E) A GENERALLY STATIONARY ARC-RUNNING ELECTRODE OF ANNULAR CONFIGURATION SPACED FROM SAID GENERALLY STATIONARY CONTACT STRUCTURE AND SURROUNDING SAID FIRST AND SECOND MOVABLE CONTACTS,