US2392201A - Electric circuit breaker - Google Patents

Description

Jan. 1, 1946. Q THUMlM ET AL 2,392,201

ELECTRI C C IRCUIT BREAKER Filed Feb. 12, 1941 5 Sheets-Sheet 1 WATER LEVEL Inventors- Car-l Thurnim,

\ David C.Pr-ince,

Herman B.Dhonau,

b Wan/p76. AMMA Then- Attorrwey.

Jan. 1, 1946. c. THuMlM ETAL 2,392,201

ELECTRIC CIRCUIT BREAKER Y Filed Feb. 12, 1941. 3 Sheets-Sheet 2 2 Carl Thumim, K David C.F r-ir1ce, Herman E .Dhor1au,

Their" Attorney.

Jan. 4 c. THUMIM ET AL 2,392,201

ELECTRIC C IRCUIT BREAKER Filed Feb. 12, 1941 3 Sheets-Sheet 3 Fig.3.

CIA/76R Fig.4.

Inventors:

Carl Thurnim, David Cfl rflnce, Herman-1 E .Dhonau.

" Their- Attorney.

Patented Jan. 1, 1946.

ELECTRIC CIRCUIT BREAKER Carl Thumim, Yeadon, Pa., David C. Prince, Q Schenectady, N. Y., and Herman B. Dhonan, Philadelphia, Pa., assignors to General Electric Company, a corporation of New York Application February 12, 1941, Serial No. 378,536

12 Claims.

Our invention relates to electric circuit breakers for interrupting high voltage power circuits, more particularly to circuit breakers having disconnecting means for electrically disconnecting or isolating the movable contacts of the breaker with respect to the power circui and has for its principal object the provision of an improved circuit breaker of the aforesaid type having disconnecting means for automatically forming an isolating gap in series with the breaker after interruption of the power circuit and for closing the circuit at said gap only after closing of the main breaker interrupting contacts so that the circuit is not made at said interrupting contacts.

The conventional oil circuit breaker operates by both making and breaking the main power circuit at the interrupting contacts. The good are extinguishing and insulating characteristics of the oil practically eliminate arcing during the making operation and so serve to protect the contacts from excessive deterioration. Also, since the oil has high dielectric strength, the contacts may remain immersed in the oil after circuit interruption without danger of voltage breakdown due to leakage currents. However, when an arc extinguishing liquid having comparatively -low dielectric strength, such as water for example, is used in place of oil the circuit making operation is frequently accompanied by excessive leakage current and arcing and failure of the breaker to close. That is, the high explosivelike pressures generated by power currents or arcing within the extinguishing liquid that may occur prior to actual engagement of the contacts tend to force the breaker open again thereby making the closing operation difficult, if not impossible. Obviously, the arcing in such cases may also be destructive to the interrupting contacts,

Also, the opening operation must be followed immediately b a separate isolating or disconnecting operation in order to prevent voltage breakdown within the interrupting chamber and reestablishment of arcing,

In accordance with our invention, these disadvantages are overcome by providing means for opening and disconnecting the breaker so as to prevent fiashover or failure after actual interruption, i. e., first, by breaking the circuit at the interrupting contacts and then opening the disconnecting contacts, preferably in air, and, for eliminating in the closing operation arc chamber pressures, first, by closing the interrupting contacts in the arc extinguishing liquid while the circuit is still open at the disconnecting contacts, and finally closing, preferably with a high speed snap action, the disconnecting contacts to complete the power circuit. By means of this arrangement, we eliminate all the prior difl'iculties at the interrupting contacts while successfully closing with minimum deterioration the disconnecting contacts to complete the power circuit.

Our invention will be more fully setforth in the following description referring to the accompanying drawings, and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawings, Fig, 1 is an elevational view, partly in section of a double-break circuit breaker embodying the present invention in a partially open circuit position prior to the closing thereof, Fig. 2 is a plan view taken along the line 2-2 of Fig. 1, Fig. 3 is an enlarged view of a part of the circuit breaker shown by Fig. 1, Fig. 4 is a view similar to Fig. 3 showing the mechanism and breaker in 'the closed circuit position, and Fig. 5 is an elevational side view of the breaker shown in Fig. 1.

Referring to Fig. 1, there is illustrated by way of example a water circuit breaker having two interrupting breaks in series arranged respectively, in the interrupting chambers l and 2. The interrupting chambers contain water as the arc extinguishing liquid and suitable baflie structure (not shown) for insuring rapid interruption of the circuit b the well-known "cross-blast"- action. It shall be understood of course that any other liquid having suitable arc extinguishing characteristics can be used without departing from the spirit of our invention, and that the term "water as used herein is intended to include any are extinguishing liquid having such dielectric properties that an additional isolating or disconnecting break in series externally of the interrupting chamber is required for the purpose of preventing leakage current and arcing within the interrupting chamber subsequent to actual breaking of the circuit and prior to actual making of the circuit.

The interrupting chambers i and 2 are preferably liquid tight so that there is no loss of liquid during an opening operation, Each chamber comprises a steel cylinder suitably lined with insulating material and closed at the upper and lower ends by members 3 and 4 which clamp between them the steel cylinder by means of tie rods 5. The steel interrupting chambers are supported on insulating bushings 6 and are connected to terminal plates 1 of the main power circuit. The steel cylinders also connect with the fixed interrupting contact structures 8 and 9 within the interrupting chambers respectively.

The movable interrupting contacts for coacting with the fixed contacts 8 and 9 comprise conducting rods l8 and l l guided through the tops of the interrupting chambers by insulating bushings l2 and I3 respectively, and rigidly secured in a manner hereinafter described to an insulating crosshead l4. A lift rod i5 is secured to the crosshead M for operating it in vertical rectilinear motion for opening and closing the circuit breaker.

For the purpose of electrically connecting and disconnecting the contact rods It and II with respect to each otherin accordance with the present invention, a bridging member It is car- I6 is supported in depending relation from the crossbar It by a T-shaped metal casting I? that is rigidly secured as indicated at I8 to the crossbar and the lift or operating rod I5. Means,

hereinafter described, are provided for locking the bridging member it so as electrically to connect the contact rods 80 and II when the breaker is closed and also during all but the final part of the opening operation, and for locking the bridging member in disconnecting position with respect to the contact rods in the fully open circuit position and also during the closing operation except for the final part thereof.

The insulating crossbar it and the bridging structure or blade I6 can be considered as a single assembly operable by the liftrod I and associated means. As will be noted by reference to Fig. 2, the crossbar It comprises a pair of spaced insulating rods which are composed of mechanically strong insulating material, such as laminated wood. The bridging blade I6 is also composed of a pair of spaced blade-like conductors, each blade being in turn composed of two closely spaced parallel sections as illustrated. The blade structure is united by a bracket I 6' as best illustrated by Fig. 5. This arrangement provides for compactness since the crossbar can nest within the bridging blade when the two are locked together in the contact-connecting position.

The crossbar it has secured at each end between the wood bars thereof an elongated metalmovable interrupting contact rods In and II respectively are mounted and secured. The outer end portions of each member I9 are formed as socket contacts for receiving coacting plug contacts 22 (Figs. 2 and 3) carried by the bridging blade It. The plug contacts 22 are mounted directly beneath the socket contacts '2! on the bridge I6 at the ends of each double-blade. As shown at the right side of Fig. 2, the plug contacts 22 are clamped as at 23 between the laminated blade,sections at each side of the bridging blade proper.

As shown, there are four sets of the disconnecting or tertiary contacts 2! and 22, although it will be apparent that two sets of such contacts are suflicient for the purposes of the present invention'. Whenthe contacts 2| and 22 are in engagement as shown by Fig. 4, there will be a continuous electrical circuit between the interrupting contacts In and II by way of the conducting supports I9, socket contacts 2|, plug contacts 22, and the conducting-bridge or blade structure IS.

The bridging blade I6 is guided for limited vertical reciprocal movement with respect to the crossbar It by means of a pair of rollers 24 'secured to opposite inner sides of the bridging blade movable within coacting vertical guides 25 formed in the supporting casting I'I (Figs.'2 and 3). Also for the purpose of guiding the bridging blade and also the assembly for vertical rectilinear movement, the bridging blade. I6 is provided withrollers 26 secured to the depending bracket It for centering the complete bridging assembly between the cams 21 that are mounted on the interrupting chambers I and 2 respectively. This arrangement is clearly shown by Figs. 3 and 4, Fig. 4 illustrating the rollers coacting with the inner'lateral cam surfaces when the breaker is closed.

In order to lock and unlock for relative movement the bridging blade IS with respect to the crossbar It, a pair of similarly arranged toggles symmetrically disposed near the opposite ends of the bridging blade interconnect the bridging blade and the casting support Ii. As more clearly shown in Fig. 3, each toggle comprises a link 28 pivotally connected at 29 to the support i1, and a link 80 pivotally connected at 3! to the bridging blade I6. The two links of the toggle are connected at 32 to form the knee joint and a .roller 33 is copivotally mounted on'the toggle knee joint. The link 30 is provided with a cam surface 38' for a purpose hereinafter described.

A toggle locking spring 85 interconnects the blade It and a flange 36" on the link 30.

In the disconnected position shown by Fig. 3, it will be noted (referring to the toggle centers 3|, 29 and 32) that thetoggle is held by the spring 3 8 in an overset locking position so that the support I1 and the blade are locked together as a unit. That is, the toggle knee 32 is past. the toggle center line defined by the pivots 29 and 3'! as clearly shown'by the drawings. In order for the blade to be unlocked with respect to the crossbar I4, it is first necessary to cause collapse of the toggle by moving the toggle knee 32 in clockwise direction until it crosses the toggle; center line. The toggle will then be free to col-x, lapse to its stretched-out position shown by Fig. 4.

Let it now be assumed that the circuit breaker is in the closed circuit connected position indicated by Fig. 4. In this position, the interrupting contacts 8-lt and 9-H (Fig. 1) are in engagement within the interrupting chambers and the, circuit is completed between the interrupting con-' tacts by the bridging blade I6 and the coacting disconnecting contacts 2I and 22. Also a current path shunting the disconnecting contacts for carrying continuous load currents in the closed position of the breaker is formed by the bridging blade. I6 and primary contacts 35 which are mounted on top of each interrupting chamber on terminals '3 directly beneath coacting contact portions 36 formed at the opposite ends of the blade. The primary contacts are electrically conv nected to the steel interrupting chambers which are in turn directly connected to the terminal conductors l and carry the load current directly through the breaker shunting both the interrupting, or secondary contacts and the disconnecting, or tertiary contacts. The primary contacts are subjected to no arcing whatever and open first, thereby shunting the current to the interrupting contacts and close after both the interrupting and disconnecting contacts have made engagement for establishing the'powercircuit.

In the closed circuit position (Fig. 4), it is essential that the toggles not only be locked but beheld in locked position for maintaining the disconnecting contacts in engagement until the circuit has been interrupted by the secondary contacts. In this position, each toggle roller 32 is held by the corresponding cam 21 in an overset position with respect to the toggle center line indicated so that the blade and crosshead are locked together in the extended position of the toggle.

Let it now be assumed that the breaker is to be tripped bpen in response to a fault or overload in the conventional manner. This actuates mechanism (not shown) for raising the lift rod l5. When the lift rod is raised to open the breaker the entire bridging assembly M-lli, including the interrupting rod contacts In and H moves upward as a unit. The primary contacts 35-35 first separate shunting the current through the interrupting contacts and when in turn the interrupting contacts separate the arc is extinguished within the interrupting chambers by suitable arc extinguishing baflies forming no part of the present invention. The disconnecting contacts 2 |-22 are still locked together during this partof the opening operation of the breaker.

After the rod contacts l and H have been raised suiiiciently to clear the circuit, it is safe to open the disconnecting contacts in series therewith so as to form isolating gaps in air exteriorly of the interrupting chambers. For this purpose, there is provided, referring to Figs. 1 and 4, a pair of toggle actuating members 31. each of which is pivotally mounted at 38 on the fixed overhead guide structure 39 and provided at its outer end with a roller 40. Guiding and spring buffer means indicated at 4| are connected to each of the pivoted members 31 and coact with stationary insulating structure 42 forming a part of the fixed structure 39. The members 31 are spring biased downward as illustrated and are positioned so that the rollers 40 are directly above the top edges of opposite portions of the bridging blade l6. Accordingly, when the blade 68 reaches the rollers 49 near the end of the opening stroke, the members 37 are rotated upwardly and the rollers 4!] slide laterally in outward directions along the top edges of the blade. The cam portions 30' of the toggle links 30 are so positioned with respect to the rollers 40 that this sidewise camming of the rollers causes them to engage the cam surfaces 30! and rotate the toggle links 30 so as to trip the toggles. That is, the toggle knee in each case is moved over the toggle center line indicated in Fig. 4 so that the toggle is free to buckle. This action is clearly indicated in dotted lines at the upper part of Fig. 4 wherein the toggle link 36 is indicated after having been rotated clockwise approximately 45.

As the toggles 28-35) collapse under the weight of the bridging blade assembly and the force exerted by spring ll acting through roller 40 against the upper edge of bridging blade it, the disconnecting contacts 2i-22 separate and assurne a disconnected position shown by Fig. 3. The toggle springs 34 continue to buckle the toggles until the knee joint is thrown over the center line again to lock the toggles. The breaker is now completely open and a pair of isolating gaps in air are in series with the open interrupting contacts in the chambers l and 2. There is therefore no danger of flashover within the interrupt ing chambers due to leakage current through the water or moisture on the chamber walls.

Let it now be assumed that the breaker is to be closed. When the lift rod I5 is lowered to initiate the closing operation, the entire bridging assembly, together with the rod contacts i0 and H moves downward. At this time, the disconnecting contacts 2l-22 are locked by the toggles in the disconnected position illustrated by Fig. 3. when the assembly nears the end of the closing stroke, the interrupting contacts 8-! D and 9-| I engage but no arcing is encountered within the interrupting chambers due to the fact that the disconnecting contacts 21-22 are still locked open. When, however, the blade l6 reaches a position where the toggle rollers 33 engage the cams 27, further downward movement of the lift rod l5 causes the rollers 33 to be cammed upwardly (in a clockwise direction in Fig. 3) so that the toggle knees 32 move over the toggle center lines and the toggles unlock. The continued downward movement of the lift rod rotates the toggle roller so as to throw the bridging blade upwardly. The configuration of the cam surface 21 coacting with toggle linkage 25-30 is such that there is an upward motion of bridging blade I6 while the toggle pin 29 and therefore the contacts 21 are moving downward. Therefore, the velocity of approach of contacts 2| and 22 is the sum of their individual velocities. This is greater than the velocity of I5 downward and results in a snap action. It will be noted that when the toggles collapse, each roller 33 rotates approximately (clockwise in Fig. 3) so as to move to the outer side of and be held by the cam 2! in overset locking position in the closed position of the breaker.

The power circuit is therefore made in air at the disconnecting contacts 2| -22, thereby eliminating any arcing difficulties within the interruptin chambers during the closing operation. The rapid and positive manner in which the power circuit is made substantially precludes material burning of the contacts, and we have found that the closing operation is not only greatly facilitated but is very eificiently performed with this arrangement.

At the final part of the stroke, the primary contacts 35-36 engage for the purpose of providing, in the manner previously "described, a shunt path for carrying the continuous power current. The breaker is now in the completely closed position shown by Fig. 4 wherein the disconnecting contacts are locked closed and the breaker is in readiness for another opening operation as previously described.

It should be understood that our invention is not, limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may occur to one skilled in the art without departing from the spirit of our invention.

What we claim as new and desire to secure by Letters Patent is:

1. An electric circuit breaker comprising an arc extinguishing chamber containing a liquid havin a dielectric strength less than oil, fixed and movable interrupting contacts separable within said liquid for extinguishing arcing, actuating means connected to said-movable contact for forming an interrupting gap within said chamher, a disconnecting contact also movable with said actuating means and electrically connected to said movable interrupting contact, a coaoting disconnecting contact mounted for limited movement on said actuating means between connecting and disconnecting positions with respect to said first-named disconnecting contact, locking means interconnectin said actuatig means and coacting disconnecting contact for locking the disconnecting contacts in connecting position during the arc extinguishing operation when the breaker is opened, means for causing unlocking and opening of said disconnecting contacts when the breaker is completely open to form a disconnecting gap in series with said interrupting gap, said locking means also locking said disconnectin contacts in disconnecting position in the open circuit position of the breaker and during the closing stroke thereof until said interrupting contacts have closed, and means for thereupon causing unlocking of said disconnecting contacts so as to make the power circuit at said disconnecting contacts.

2. An electric circuit breaker comprising an arc extinguishing chamber containing a liquid having a dielectric strength less than oil, fixed tuating means connected to said movable contact for forming an interrupting gap within said chamber, a disconnecting contact also movable with said actuating means and electrically connected to said movable interrupting contact, a coacting disconnecting contact mounted for limited reciprocal movement on said actuating means between connecting and disconnecting positions with respect to said first-named disconnecting contact, locking mean including a toggle interconnecting said actuating means and coacting disconnecting contact for locking the disconnectin contacts together in connecting position during the arc extinguishing operation when the breaker is opened, means for causing buckling and unlocking of said toggle and opening or said disconnecting contacts when the breaker is completely open to form a disconnecting gap in series with said interrupting gap, said locking t gle means also movable to another position for locking said disconnectin contacts in disconnecting position in the open circuit position of the breaker and during the closing stroke thereof until said interrupting contacts have closed, and means for thereupon causing buckling and unlocking of said toggle and closing of said disconnecting contacts so as to make the power circuit at said disconnecting contacts.

3. An electric circuit breaker comprising an arc extinguishing chamber containing a liquid having less dielectric strength than oil, fixed and movable interruptin contacts separable within said liquid for extinguishing arcing, actuating means connected to said movable contact for forming an interrupting gap within said chamber,

a disconnecting contact also mounted on said actuating means and electrically connected to said movable interrupting contact, a coacting disconnecting contact slidably mounted for limited reciprocal movement on said actuating means between conneoting and disconnecting positions with respect to said first-named disconnecting contact, a locking toggle interconnecting said actuating means and coacting disconnecting contact arranged to be overset for locking the disconnecting contacts together in connecting position during the arc extinguishing operation when.

the breaker is opened, cam means for causing buckling and unlocking of said toggle and openin of said disconnecting contacts when the breaker is completely open to form a disconnecting gap in series with said interrupting gap, said toggle also movable through its buckled position to another overset position for locking said disconnecting contacts in disconnecting position in the open circuit position of the breaker and during the closing stroke thereof until said interrupting contacts have closed, and additional cam means for thereupon causingbuckling and unlocking of said toggle for closin said disconnecting contacts substantially at the end of the breaker closing stroke so as to make the power circuit at said disconnecting contacts. I

4. An electric circuit breaker comprising an arc extinguishing chamber containing a liquid having less dielectric strength than oil, fixed and mov- 'and movable interrupting contacts separable within said liquidior extinguishing arcing, ac-

able interrupting contacts separable within said liquid for extinguishing arcing, actuating means connected to said movable contact for forming an interrupting gap within said chamber, a disconnecting contact also mounted on and movabl with said actuating means and electrically connected to said movable interrupting contact, a coacting disconnecting contact mounted for limited reciprocal movement on said actuating means between connecting and disconnecting positions with respect to said first-named disconnecting contact, a locking toggle connected at its opposite ends tosaid actuating means and coacting disconnecting contact respectively for locking the disconnecting contacts together in connecting position during the arc extinguishing apart in disconnecting position in the open circuit position of the :breaker and during the closing stroke thereof until said interrupting contacts have closed, and additional cam means for thereupon causing buckling and unlocking of said toggle, said additional cam means and the aforesaid spring means coacting to move said toggle in snap-action to the first-named locking position for closing at high speed said disconnecting contacts so as to make the power circuit at said disconnecting contacts.

5. An electric circuit breaker of the multiple chambers, an arc extinguishing liquid within said' chambers, interrupting contacts separable within said liquid in each of said chambers to form in! terrupting gaps, actuating means for separating said contacts, disconnecting contacts arranged to coact with said interrupting contacts exteriorly of said chambers to form two gaps in series relation to said interrupting gaps, means for mounting said disconnecting contacts on said actuating means so as tomove as a unit therewith for a part of its motion but with a lost-motion relation to said actuating means so as to provide for sequential openingand closing of said interrupting and disconnecting conta'cts,-means for locking said disconnecting contacts in connecting relation to said interrupting contacts in the closed circuit position of the breaker and during the arc extinguishing operation, and for locking said disconnecting contacts in disconnecting position with relation to said in errupting contacts in the open circuit position of the breaker and during the closing stroke until after engagement of said interrupting contacts, and means for unlocking said disconnecting contacts whereby the power circuit is made at said disconnecting contacts.

. 6. An electric circuit breaker or the multiple break type comprising a pair of arc extinguishing chambers, an arc extinguishingliquid within said chambers, interrupting contacts separable within said liquid in each of said chambers to form interrupting gaps, actuating means for separating said contacts, disconnecting means including a bridging blade arranged to interconnect said interrupting contacts exteriorly of said chambers and also to form two gaps in series relation to said interrupting gaps, means for mounting said bridging blade on said actuating 'means in lost motion-relation thereto for the connecting and disconnecting operations thereof, means for locking said blade in connecting relation to said interrupting contacts in the closed circuit position of the breaker and during the arc extinguishing operation, and for locking said blade in disconnecting position with relation to said interrupting contacts in the open circuit position of the breaker and during the closing stroke until after engagement of said interrupting contacts, and means operable in accordance with the position'of said actuating means for unlocking said blade at the end of said closing stroke whereby the power circuit is made at said disconnectin means, and for unlocking said blade at the end of said opening stroke.

'7. An electric circuit breaker of the multiple .break type comprising a pair of arc extinguishing chambers, an arc extinguishing liquid within said chambers, fixed and movable interrupting contacts separable within said liquid in each of said chambers to form interrupting gaps, actuating means connected to said movable contacts, disconnecting contaots also carried by said actuating means and electrically connected to said interrupting contacts, a bridging conducting blade carrying disconnecting contacts arranged to coact with the aforesaid disconnecting contacts exteriorly of said chambers to form two disconnectin gaps in series relation'to said interrupting gaps, means for mounting said bridging blade on and in lost motion relation to said actuating means providing for moving between connected and disconnected positions with respect to said firstnamed' disconnecting contacts, and means for locking said blade in connecting relation in the closed circuit position of said interrupting contacts and during the arc extinguishing operation, and for locking said blade in disconnecting position in the open circuit position of said interrupting contacts and during the closing stroke thereof until after engagement of said interrupting contacts, and means for unlocking said disconnecting contacts to form said disconnecting gaps after the power circuit has been broken and for making the power circuit at said disconnecting contacts.

8. An electric circuit breaker comprising an arc extinguishing chamber containing water, interrupting contacts separable within said water for extinguishing arcing, actuating means for separatingsaid contacts to form an interrupting gap entirely within said chamber, disconnecting contacts disposed exteriorly of said chamber arranged to form an additional isolating ap in air in series with said interrupting water gap,

, means for mounting said disconnecting contacts on said actuating means apart from said interrupting contacts so that said disconnecting contacts move as a unit with said actuating means for a portion of its operation, spring and toggle means associated with said actuating means and said disconnecting contacts arranged to cause opening of said disconnecting contacts near the end of the opening operation of said interrupting contacts, said spring and toggle means also in the initial closing operation holding said disconnecting contacts for first causing closing of said interrupting contacts Within said chamber and subsequently causing closing of said disconnecting contacts with snap action at a much higher speed than said interrupting contacts to complete the power circuit at Su disconnecting contacts.

9. An electric circuit breaker comprising an are extinguishing chamber containing a liquid having comparatively low dielectric strength, interrupting contacts separable within said liquid for extinguishing arcing, actuating means comprising :3 a movable operating rod for separating said contacts to form an interrupting gap entirely within said chamber, disconnecting contacts disposed exteriorly of said chamber arranged to form an additional isolating gap in series with said interrupting gap, means for mounting said disconnecting contacts on said operating rod so as to move as a unit therewith for a predetermined portion of its motion, locking means interconnecting said interrupting and disconnecting contacts, and means coacting with said locking means for causign separation of said disconnecting contacts subsequent to separation of said interrupting contacts, said locking means thereupon holding said interrupting contacts open during closing of said interrupting contacts within said chamber to provide for closing of the power circuit at said disconnecting contacts.

10. An electric circuit breaker of the multiple break type comprising a pair of arc interrupting contacts, a movable operating rod connected to one of said contacts for causing relative movement of said interrupting contacts in response to movement of said operating rod, a pair of disconnecting contacts serially arranged with said interrupting contacts, eachor said disconnecting contacts being mounted so as to move with said operating rod for a portion of the motion thereof while remaining fixed relative to the other disconnecting contact, and means responsive to a predetermined movement of said operating rod in one direction for causing relative movement of said disconnecting contacts.

11. An electric circuit breaker oi the multiple break type comprising a pair of arc interrupting contacts, a movable operating rod connected to one of said contacts for causing relative separation of said interrupting contacts in response to movement in one direction of said operating rod, a pair of disconnecting contacts serially arranged 45 with said interrupting contacts, each of said disconnecting contacts being mounted so as to move with said operating rod in said one direction for a portion of the motion thereof while remaining fixed relative to the other disconnecting contact, 60 and means responsive to a predetermined movement of said operating rod in a direction to separate said interrupting contacts for causing relative separation of said disconnecting contacts following separation of said interrupting contacts.

12. An electric circuit breaker of the multiple break type comprising a pair of arc interrupting contacts, a movable operating rod connected to one of said contacts for causing closing of said interrupting contacts in response to movemet in one direction of said operating rod, a pair of disconnecting contacts serially arranged with said interrupting contacts, each of said disconnecting contacts being mounted so as to move with said operating rod in said one direction for a portion of the motion thereof while remaining fixed relative to the other disconnecting contact, and means-responsive to a predetermined movement of said operating rod in a direction to close said interrupting contacts for causing closing of said 0 disconnecting contacts following closing of said interrupting contacts.

CARL THUMIM. DAVID C. PRINCE. HERMAN B. DHONAU.

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