US3259726A

US3259726A - Telescoping type circuit breaker having isolator contact with arc snuffing means

Info

Publication number: US3259726A
Application number: US348749A
Authority: US
Inventors: Raymond L Rueffer
Original assignee: Kearney National Inc
Current assignee: Kearney National Inc
Priority date: 1964-03-02
Filing date: 1964-03-02
Publication date: 1966-07-05
Anticipated expiration: 1983-07-05

Description

July 5, 1966 R. L. RUEFFER 3,259,726

TELESCOPING TYPE CIRCUIT BREAKER HAVING ISOLATOR CONTACT WITH ARC SNUFFING MEANS Filed March 2, 1964 5 Sheets-Sheet 1 INVENTOR. RAYMOND L. RUEF'FER BY r ATTORNEY July 5, 1966 R. L. RUEFFER 3,259,726

TELESCOPING TYPE CIRCUIT BREAKER HAVING ISOLATOR CONTACT WITH ARC SNUFFING MEANS Filed March 2, 1964 5 Sheets-Sheet 5 all!!! same.

F G 6' 357 379 INVENTOR.

RAYMOND L. RUEFFER United States Patent 3,259,726 TELESCOPING TYPE CIRCUIT BREAKER HAVING ISOLATOR CONTACT WITH ARC SNUFFING MEANS Raymond L. Ruelfer, Alfton, Mo., assignor to Kearney- National Inc., St. Louis, Mo., a corporation of Delaware Filed Mar. 2, 1964, Ser. No. 348,749 6 Claims. (Cl. 200-151) This invention relates to a telescoping type of disconnect unit for an electric circuit isolator such as shown in my prior United States application for patent, Serial No. 318,637, filed October 24, 1963, and entitled Electric Circuit isolator. The disconnect unit constructed in accordance with the teachings of this disclosure may be substituted for the units 140, 141 and 142 shown in my prior application for patent.

As explained in this prior application, an electric circuit isolator is a disconnect often used for installations, such as public buildings or other commercial users of large amounts of electric power. These installations usually carry a heavy current which may be one or more hundreds of amps at anywhere from several hundred to several thousand volts.

A circuit isolator must effectively isolate a service circuit for safety reasons and, in using my prior machine, it is preferable to disconnect all of the power from, or to, a service circuit before opening the circuit isolator which, when open, isolates this particular service circuit to which it is connected even tho-ugh other service circuits may be re-energized.

With the substitution of my improved units disclosed herein, it is unnecessary to disconnect the power supply before opening the isolator because these improved units include arc suppressing devices so that the isolator may be opened under load in perfect safety and without the risk of damage due to arcing.

Accordingly, it is one of the objects of this invention to provide an improved disconnect unit of the telescoping type which has the added advantage of safe operation under heavy electric load.

It is still another object of the invention to provide an improved disconnect unit of the telescoping type which has self-aligning contact structure including the added advantage of safe operation by eliminating arcing danger.

This improved unit has separable contacts to open an electric circuit and an insulator housing in which the contacts are totally enclosed when connected. The insulator housing opens when the contacts open so as to indicate the open relation of the contacts visually. The housing, when open, still conceals the contacts making them inaccessible to touch.

One of these contacts includes an arc suppressing device operated sequentially on opening to suppress any are which might be struck due to contact separation. The incorporation in the device of the arc suppressor in no way changes or detracts from the self-aligning features built into the unit as described in detail in my prior patent application or eliminates other features contributing to reliability and simplicity in its operation or design.

Other objects and advantages of this invention will appear from the following detailed description which is in such clear, concise and exact terms, as will enable any person skilled in the art to make and use the same when taken in conjunction with the accompanying drawings, forming a part thereof, and in which:

FIG. 1 is an environmental view illustrating a circuit isolator constructed in accordance with this invention;

FIG. 2 is a perspective view with parts broken away 3,259,726 Patented July 5, 1966 "ice and in section illustrating an embodiment of one unit of this invention such as shown in FIG. 1;

FIG. 3 is a fragmentary sectional view of the upper contact and are suppressor shown in FIG. 2;

FIG. 4 is a perspective view with parts broken away and in section illustrating another embodiment of this invention such as used in FIG. 1;

FIG. 5 is a fragmentary sectional view of the upper contact and load interrupter shown in FIG. 4; and

FIG. 6 is a side view of the internal mechanism within an arc suppressor showing a modified form of brush.

One mechanism in which a unit, or units, constructed in accordance with this invention may be mounted for operation is depicted in FIG. 1, which mechanism is described in detail in my prior patent application herein identified. This description will be restricted to only so much of this prior structure as required for an understanding of the improvement in the unit itself.

The open box-like frame 1, shown in FIG. 1, is closed at its opposite ends 2 and 3 and at its top 4 and bottom 5. Mounting bracket 6 provides for attachment of frame 1 to a support. The inner sides of ends 2 and 3 carry vertical guide-s 9 and 11, respectively. A subframe 13 within the box-like frame 1 has protruding guide pins 14 and 16 in the guides 9 and 11 so that subframe 13 is confined to vertical movement between the closed sides 4 and 5. Handle 18 rocks a crank shaft 19 and cranks 20 and 21. Links 22 and 23 connect between the cranks and pins 14 and 16 and raise and lower the subframe 13 as handle 18 moves.

There are three units, such as ABC, in the illustrated mechanism. Each unit is the same and all have fixed insulated parts, such as 24 and 25, received in aligned holes in the top and bottom walls 4 and 5, which parts are held therein by screws 27 in apertured flanges 28 and screws 29 in apertured flanges 30. All of these units AB-C have intermediate movable insulator sections 32 straddled by spaced side members in sub frame 13- and attached to the subframe by screws in flanges on the movable sections 32. The

parts

24, 25 and 32 are hollow insulators and the intermediate sections 32 telescope with fixed

parts

24 and 25 as will be later described. Projecting through the fixed

parts

24 and 25 are threaded

electric terminals

33 and 34, respectively. Power feeders are connected to one set of terminals, such as 34, and a service circuit is connected to the other set of terminals 33. Operation of handle 18 upwardly to the position shown in FIG. 1 connects the service circuit to power. When the handle 18 is moved downward to its lowest position, the units open the connection between the feeders and the service circuit to isolate the service circuit from its power supply.

The description so far has been limited to the mechanism described in my .prior application for patent above identified. This invention is primarily concerned with the construction for the units ABC which are described hereinafter in detail.

FIG. 2 illustrates a construction for a unit, such as ABC shown in FIG. 1. One of the fixed parts 25 is a cup-shaped insulator surrounded by a flange, such as 30, for supporting the cup-shaped insulator 25 within an aperture in the side 5 of the box-like structure 1. The closed end of the cup-shaped insulator 25 is apertured and this aperture has secured therein the terminal 34 which projects from the outside of the insulator and has formed thereon an electrode 36 projecting axially of of the cup-shaped insulator 25. Slidable on the electrode 36 is tubular contact 38. On the lower internal wall of the sleeve contact 38 is an annular head 39 slidably gripping the external surface of the electrode 36. The lower end of the sleeve contact 38 is split to provide a plurality of spring fingers which are held in engagement with the electrode 36 by a surrounding garter spring 40.

Intermediate telescoping section 32 is surrounded by an external flange 42 forming the support for the intermediate telescoping sleeve 32 in the subfraime 13. As heretofore pointed out, the flange 42 may be secured to the s-ubfrarne 13 by screws, or clamps, so as to move with the subfra me from the open position of the isolator parts as depicted in FIG. 2. Internally of the telescoping intermediate insulator part 32 is a supporting flange 43. Contact sleeve 38 projects through the flange 43 and is loosely received therein. A spring ring 45 seated in a groove surrounding the contact sleeve 38 loosely abuts the lower side of the flange 43. The upper side of the flange 43 projects beneath head 46 of a plug part 47 brazed or otherwise suitably secured in the upper end of the sleeve contact 38. Integral with the head 46 is a blade type of electrode 49 provided with a spear end 50. The

blade type contacts

51 and 52, shown on opposite sides of the electrode 49, have a bight portion 54 slotted at 55 for the electrode 49. The bight portion 54 is brazed or otherwise suitably secured to the head 46.

The intermediate telescoping sleeve insulator 32 has an upwardly projecting skirt part 57 concealing the electrode 49 and the

blade contacts

51 and 52. The skirt 57 also has an external size so as to telescope within the cup-shaped fixed part 24 on closing of the contacts within the isolator unit. When the contacts are open, this is visibly indicated by separation of the skirt 57 from the cup-shaped part 2.4. Protruding downwardly from the flange 42 is a lower skirt 59 which is dimensioned to telescope within the cup-shaped part 25.

The upper insulator part 24 is inverted cup-shaped and surrounded by a flange 28 by which it is supported in an aperture in top wall 4. The closed end of the cup 24 is aperturcd to receive the terminal 33. This teraninal 33 is hollow as will be pointed out hereinafter and contains an arc suppressing device 60 which includes a socket 61 of insulating material into which electrode 49 moves when the isolator unit is closed. Externally of the insulator socket 61 are a pair of flat fixed contacts such as 62 with diagonal ribs 63 (one of which is shown in FIG. 2).

Blades

51 and 52 move into face to face contact with the ribs 63 to form the electric load carrying circuit when the isolator is closed. The are suppressing device 60 has apertured flanges which mate with similar apertured flanges at the lower end of the terminal 33 where it projects within the cup-shaped insulator 24. Bolts, such as 65, secure the flanges together and the arc suppressing device within the terminal 33. Terminal 33 is externally threaded and clamped in place within the cup 24 by nuts, such as 66 and 67, all as shown in FIG. 3.

Turning now to FIG. 3, the [metal ferrule part 62 of the arc break device which carries the flanges and contact surfaces 63 has a rabbeted portion 95 holding a tubular extension 96. The tubular extension 96 is of metal and is stepped externally at 97 to fonm a reduced tubular diameter extension 98. Metal casing 100 which surrounds the tubular extension 96 has a press fit in the rabbeted portion 95 and has a cap 102 closing its upper end. An O-ring of rubber-like material 104 forms a cushion support on the cap 102 for a disk 105. Anchored in the the disk is a plunger 106 formed of a plurality of flat strips of copper or conductor material, all of which are secured together intermediate their ends by a rivet 107. Two of the strips forming the plunger 106 and indicated as 108 and 109 form a socket-like contact electrically connected with plunger 106. A pair of spring pressed brushes 110 bear against opposite edges of the flat plunger 106 and also against the cylindrical casing 96 so as to form an electrical connection between the plunger and the metal casing. The screw 111 supports a pair of

spring fingers

116 and 117 which are anchored at their lower ends in opposite

snulfer elements

120 and 121. A coil spring 123 is compressed between the shoulder 97 and disk and tends to hold the

contacts

108 and 109 in the position shown in FIG. 3.

The flat electrode 49 passes between the

snulfer elements

120 and 121 as the contacts are closed in the isolator. The spear end 50 protrudes beyond the snuffer element into the arc suppressor 60 and is gripped between the

contacts

108 and 109 of the socket type contact therein. This forms an electric connection between the electrode 49,

sockets

108, 109, plunger 106, brushes and metal sleeve 95 to the ferrule 62. The ferrule in turn is an integral part of the flange connection secured by the bolts 65 to terminal 33. Contact ribs 63 also on the ferrule 62 are electrically connected to the terminal 33.

If the contacts of the unit are opened as shown in FIG. 2 and handle 18 is moved to the closed position, the intermediate section 32 moves upwardly from the position shown in FIG. 2 along with the subfrarne 13. Sleeve 32 carries tubular contact 38 and

blade contacts

51, 52 as well as electrode 49. Electric contact is maintained between the sleeve type contact 38 and the electrode 36 as the intermediate section 32 moves upwardly. As the handle 18 continues to move, blades 51'and 52 make con tact with the ribs 63 thereby completing the circuit through the isolator. Still further movement of the handle 18 forces the spear end 50 into the socket formed by the

contacts

108 and 109, thus, at the same time, completing a circuit through the arc suppressing device.

Blade contacts

51 and 52 and sleeve con-tact 38 with the electrode 36 form the load carrying electric connection from terminal 33 to terminal 34, after the handle has moved to its full up position.

To isolate the service circuit, handle 18 is moved downwardly. Initial downward movement of the handle separates

blade contacts

51 and 52 from the ribs 63 so that the load is now carried to the terminal 33 through the flat electrode 49 and its connection between

electric contacts

108 and 109. As the movement of the handle 18 continues downwardly, the grip of the

contacts

108 and 109 on the spear end 50 is maintained so as to draw plunger 106 downwardly compressing the spring 123. This downward movement not only moves the

contacts

108 and 109, but also carries along with it the snutfers and 121 until the washer, or disk, 105 contacts the end of sleeve 96. At this point, the snutfers have been withdrawn from the arc suppressor as they follow the electrode 49.

Contacts

108 and 109 release their grip on the spear end 50 after they have reached their limit of downward travel. On release, spring 123 expands retracting the contacts and the snuffers from the electrode 49. The circuit is broken through the unit from the terminal 33 to the terminal 34 and at the same time the snulfers retract within the arc suppressor coming together as shown in FIG. 3. Any are which has formed between the end of the electrode 50 and the

contacts

108 and 109 is immediately extinguished by the snuffers whichform a barrier to arc travel between the

contacts

108 and 109 and the end of electrode 49. The

snuifers may be made of a resin material which will give added.

With reference to FIG. 4, the cup-shaped insulator of a fixed part 230 is apertured at its closed end and, the

threaded end of terminal 234 is secured in this aperture by suitable nuts. The terminal 234 has an electrode part 236 which projects axially within the cup-shaped insulator 230. Flange 229 around the cup-shaped insulator 230 forms the means to support the fixed part 230 in an opening in the bottom wall 5 of the frame 1.

The movable insulator part 232 has one end in telescoping relation with respect to the cup-shaped insulator part 230 and its opposite end constructed and arranged to telescope within the cup-shaped insulator part 224. Flange 242 around the insulator is a support for the movable insulator part 232 in the subfra-me 13. Internal shoulder 243 on insulator 232 is arranged to support the external annular flange 246 on the metal bushing 247. There is an annular depending skirt 253 on the bushing 247. A contact sleeve 238 is secured on the skirt 253 by brazing and telescopes with the electrode 236. Contact is made through an annular rib 239 within the contact sleeve 238 and the end of this sleeve is split to form spring fingers, all as described in my prior patent application above identified. Garter spring 240 is seated in an annular groove around the sleeve contact 238.

The bushing 247 is centrally apertured for slidably holding an electrode rod 254. A spring 255 surrounds the rod 254 and is compressed between a seat on the skirt 253 and a washer 256 held on the threaded end of the rod 254. The upper end of the rod 254 is slotted and the slot receives the end of a flat blade type electrode 249 securely anchored to the rod 254 within the slot. Since the blade 249 is wider than the diameter of the rod 254, it has protruding edges which act as stops to prevent further expansion of spring 255. The edges contact the upper surface of the bushing 247. Brushes 259 on the bushing 247 form an electric connection to the rod 254 and from the rod 254 to blade 249. A sleeve contact 252 is brazed to the bushing 247 and surrounds electrode blade 249. The internal annular rib 251 forms the electric contact surface when telescoped with the tubular contact 262 which is a stationary electrode and part of an assembly including terminal 233 in cup 224. The end of the tubular contact 252 may be slotted to form spring fingers as described in my prior application. Garter spring 293 is seated in the groove around the end of contact sleeve 252.

The flange 246 is suitably secured by pins 241 to internal shoulder 243 so that both

sleeve contacts

238 and 252 move with movable insulator part 232. Pins 241, above-mentioned, may be received in slots within the flange 246 to provide for some floating movement of the bushing 247 with respect to the supporting shoulder 243. Flexibility of this kind is a distinct benefit during engagement of the contacts of the isolator. Regardless of how the flange 246 is secured on the shoulder 243, blade 249 is positively moved by the shoulder with the intermediate movable insulator part 232 in a direction to telescope within contact 262. On reverse movement of the insulator part 232, spring 255 is a yielding connection for moving the electrode 249. As will be pointed out hereinafter, the spring 255 is so selected that movement of the electrode 249 is not compelled until the spring 255 is compressed solid. This is due to the fact that the spear end 250 has a tendency to hang in the are suppressor device 260 as hereinafter described.

Sleeve contacts

238 and 252 are electrically connected through bushing 247 and both are electrically connected with electrode 249 through brushes 259. When the sleeve contact 252 is telescoped with electrode 262 an electric circuit is completed from terminal 233 to terminal 234 through electrode 262, sleeve 252, bushing 247, sl'eeve contact 238 to electrode 236 and terminal 234.

Details of the second circuit from the blade electrode 249 through the arc suppressor 260 are more clearly shown in FIG. 5. Turning now to FIG. 5, it will be observed that terminal 233 has a threaded socket 270 as well as an externally threaded end. Arc suppressor 260 has a tubular casing 272 externally threaded to mate with threads 271 on the inside of socket 270. Nut 273 internally of the insulator cup 224 forms a rigid connection mounting the terminal 233 and the arc suppressing device 260 in the end of the insulator cup 224.

Internal threads 274 in the end of the casing of the are suppressor 260 form a connection with external threads 275 on the end of electrode 262. There is a reduced tubular extension 276 on electrode 262 and an internal shoulder 277 at the junction between the part with threads 275, and the extension thereon 276.

Electrode 262 is electrically connected with a metal plunger 280 by brushes 279 which have a free end biased against one side of plunger 280 and the opposite end clamped between shoulder 277 and an end of an insulated tubular guide 282 which projects from within electrode 262. Plunger 280 is in turn electrically and mechanically connected with socket members 285 which are spring fingers gripping the spear end 250, or blade electrode 249. A pair of leaf springs 287 are secured at one end to opposite sides of the plunger 280 by connector 289 and carry a pair of snufi'ers 290 on their free ends. The snuflers are pressed against opposite sides of blades 249.

The plunger 280 has one end anchored in a disk 292 which is held against O-ring 294 forming a cushion between disk 292 and a plug 295 closing the casing 272. A spring 296 is compressed between the disk 292 and the threaded part 275 of electrode 262.

When the isolator unit is closed, the electric circuit is completed not only between the

contacts

252 and 238 with

electrodes

262 and 236 as described, but also through the arc suppressor 260 from blade 249 to socket 285, plunger 280, brushes 279, casing 272 and terminal 233. During the opening operation of the unit, movable insulator 232 travels in a direction from within cup insulator 224. The sleeve contact 252 separates from electrode 262, but there will be no arc since a parallel circuit through the arc suppressor from blade 249 to socket 285 is still operative. As the movement of movable insulator 232 continues, spring 255 is compressed because the spear end 250, or blade 249, is frictionally held in the socket 285. After a predetermined separation, but preferably while the end of insualtor 232 is still within the cup insulator 224, spring 2255 becomes solid and, thereafter, continued movement draws socket 285 and snuffers 290 toward the end of tube 282, compressing spring 296. When disk 292 contacts the end of extension 276, blade 249 is freed from socket 285. Spring 289 expands retracting socket 285 and withdrawing snuifers 290 which come together as they move into tube 282 and form a bar rier to arc travel from the socket 285 to electrode 249. Both snuifers 290 and tube 282 may be formed of a resin which gives off a gas when an arc is formed. At the same time that spring 296 is retracting socket 285, spring 296expands withdrawing the blade 249 away from the arc suppressor 269. These events all take place after the end of movable insulator 232 has withdrawn from cup 224 so that the action is observable to the operator. When the handle 18 reaches the end of its travel, electrode 249 has withdrawn into movable insulator 232.

Turning now to FIG. 6, therein shown is a sub-assembly of parts for an arc suppressor such as heretofore described and as shown specifically in FIG. 5. Corresponding parts in FIG. 6 are indicated by the same reference characters used in FIG. 5 with added.

As in FIG. 5, the snutfers 390 are mounted on leaf springs 387 and fastened to the plunger 380 by connector 389. The electric socket, or gripper contact, 385 is formed at one end of the plunger 380' and the opposite end of the plunger is notched to hold a disk, such as 292 shown in FIG. 5 on the end of the plunger 280. As also shown in FIG. 5, the plunger 380 of FIG. 6 comprises two strips Of metal side by side held together by rivets A and B. In this modification, the electric connection is made between the plunger 380 and the casing 372 by a brush in the form of a wire bail 379 frictionally clamped between the strips of the plunger 380 at points on opposite sides of the rivets A and B. The ends of the bail 379 are left open to permit expansion and traction.

Each leg of the bail 379 makes sliding contact with the inner surface of the casing 372 on the outside of the spring 396 so as to electrically connect the plunger 380 and the socket 385 with the casing 372. The brush 379 can be made of a suitable metal which is springy, such as Phosphorbronze. As will be apparent from a comparison of FIGS. and 6, the bail 379 is a full-floating electric brush and replaces the pair of fixed brushes 279 in FIG. 5.

Changes in and modifications of the structure described may be made Without departing from the spirit of my invention or sacrificing its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In an electric circuit isolator having a first fixed contact member; a second fixed contact member;

means mounting said contact members in substantial alignment and spaced a substantial distance apart; and a bridging member mounted for rectilinear movement between said contact members to make and break a circuit therebetween, said bridging member being continuously electrically connected to said first fixed contact member but movable relative thereto, and being selectively electrically connected to and disconnected from said second fixed contact member, the improvement which comprises: said bridging member having:

(a) a main contact selectively engageable with said second fixed contact member,

(b) a spear contact permanently electrically and mechanically connected to said main contact and continuously electrically connected with said first fixed contact member,

said second fixed contact member having electrically connected thereto, a gripper contact member, said gripper contact member:

(c) being spring mounted for limited rectilinear movement toward and away from said first fixed contact member,

(d) being constantly spring biased in a direction away from said first fixed contact member,

(e) having means for receiving and resiliently gripping said spear contact when said main contact and said second fixed contact are engaged; and

(f) having an arc snuffer mounted thereon, movable therewith and projecting therefrom for a substantial distance toward said first fixed contact, said are snuffer providing a channel for traverse by said spear contact to and from said means (e),

the gripping force exerted by said means (e) upon said spear contact being so coordinated with the spring bias on said gripper contact member that during circuit interruption the gripper contact member moves with said spear contact until said main contact has separated from said second fixed contact.

2. The improvement of claim 1 wherein the gripper contact member is disposed within an electrically conductive tube electrically and mechanically connected with said second fixed contact member, the axis of said tube being parallel with said rectilinear movement, and a spring-biased brush for maintaining said gripper contact member in electrical connection with said tube. 3. The improvement of claim 2 wherein the springbiased brush is a hair-pin spring movable with said gripper contact member, the legs of said hair-pin spring being biasedinto electrical contact with the interior of said tube at substantially diametrically opposite points.

4. The improvement of claim 1 wherein said arc snuffer is composed of a plurality of elementstormed of gasemitting material, and said elements are connected to said gripper contact member, by spring'fingers.

5. The improvement of claim 1 wherein said gripper contact member is mounted upon a plunger disposed within a tubular casing fixed relative to said second fixed contact and whose axis is substantially parallel with said rectilinear movement, said plunger being anchored to disk whose outside diameter corresponds substantially with the inside diameter of said tubular casing, said disk being free to move axially of said tubular casing and being References Cited by the Examiner UNITED STATES PATENTS 2,267,399 12/1941 Farrer et'al. 200-146 X 2,841,672 7/1958 Hoye 200l63' 3,060,285 10/1962 Steinbruner 20077 X ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner.

P. E. CRAWFORD, Assistant Examiner.

Claims

1. IN AN ELECTRIC CIRCUIT ISOLATOR HAVING A FIRST FIXED CONTACT MEMBER; A SECOND FIXED CONTACT MEMBER; MEANS MOUNTING SAID CONTACT MEMBERS IN SUBSTANTIAL ALIGNMENT AND SPACED A SUBSTANTIAL DISTANCE APART; AND A BRIDGING MEMBER MOUNTED FOR RECTILINEAR MOVEMENT BETWEEN SAID CONTACT MEMBERS TO MAKE AND BREAK A CIRCUIT THEREBETWEEN, SAID BRIDGING MEMBER BEING CONTINUOUSLY ELECTRICALLY CONNECTED TO SAID FIRST FIXED CONTACT MEMBER BUT MOVABLE RELATIVE THERETO, AND BEING SELECTIVELY ELECTRICALLY CONNECTED TO AND DISCONNECTED FROM SAID SECOND FIXED CONTACT MEMBER, THE IMPROVEMENT WITH COMPRISES: SAID BRIDGING MEMBER HAVING: (A) A MAIN CONTACT SELECTIVELY ENGAGEABLE WITH SAID SECOND FIXED CONTACT MEMBER, (B) A SPEAR CONTACT PERMANENTLY ELECTRICALLY AND MECHANICALLY CONNECTED TO SAID MAIN CONTACT AND CONTINUOUSLY ELECTRICALLY CONNECTED WITH SAID FIRST FIXED CONTACT MEMBER, SAID SECOND FIXED CONTACT MEMBER HAVING ELECTRICALLY CONNECTED THERETO, A GRIPPER CONTACT MEMBER, SAID GRIPPER CONTACT MEMBER: (C) BEING SPRING MOUNTED FOR LIMITED RECTILINEAR MOVEMENT TOWARD AND AWAY FROM SAID FIRST FIXED CONTACT MEMBER, (D) BEING CONSTANTLY SPRING BIASED IN A DIRECTION AWAY FROM SAID FIRST FIXED CONTACT MEMBER, (E) HAVING MEANS FOR RECEIVING AND RESILIENTLY GRIPPING SAID SPEAR CONTACT WHEN SAID MAIN CONTACT AND SAID SECOND FIXED CONTACT ARE ENGAGED; AND (F) HAVING AN ARC SNUFFER MOUNTED THEREON, MOVABLE THEREWITH AND PROJECTING THEREFROM FOR A SUBSTANTIAL DISTANCE FORWARD SAID FIRST FIXED CONTACT, SAID ARC SNUFFER PROVIDING A CHANNEL FOR TRAVERSE BY SAID SPEAR CONTACT TO AND FROM SAID MEANS (E), THE GRIPPING FORCE EXERTED BY SAID MEANS (E) UPON SAID SPEAR CONTACT BEING SO COORDINATED WITH THE SPRING BIAS ON SAID GRIPPER CONTACT MEMBER THAT DURING CIRCUIT INTERRUPTION THE GRIPPER CONTACT MEMBER MOVES WITH SAID SPEAR CONTACT UNTIL SAID MAIN CONTACT HAS SEPARATED FROM SAID SECOND FIXED CONTACT.