US2717292A

US2717292A - Air circuit breaker

Info

Publication number: US2717292A
Application number: US283038A
Authority: US
Inventors: Russell E Frink; Olsson Paul
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1952-04-18
Filing date: 1952-04-18
Publication date: 1955-09-06
Anticipated expiration: 1972-09-06
Also published as: BE519241A

Description

R E. FRINK ET AL Sept. 6, 1955 AIR CIRCUIT BREAKER 4 Sheets-Sheet 1 Filed April 18, 1952 Fig. l.

n O H G U S n 3 INVENTORS Russeii E. Fvink and Paui Oisson.

o AMM AT ORNE YV WiTNESSES:

R. E. FRINK ET AL AIR CIRCUIT BREAKER Sept. 6, 1955 4 Sheets-Sheet 2 Filed April 18, 1952 Fig. 3.

QNVENTORS Russell E. Frink and Paul Qisson. QJ Aim;

A u ATTORNEQ WITNESSES: 21x2 4 Sepia 1955 F2. E. FRENK ET AL AIR CIRCUIT BREAKER 4 Sheets-Sheet I5 Filed April 18 Frink and WETNESSES: gi a 44m Sept. 6, 1955 R. E. FRINK ET AL AIR CIRCUIT BREAKER 4 Sheets-Sheet 4 Filed April 18, 1952 INVENTORS Russell E. Frink and Paul Olsson. a BYl/ Z ATTORNE F lg 7 WITNESSES: 94 I. W.

United States Patent AIR CIRCUIT BREAKER Russell E. Frink and Paul Olsson, Pittsburgh, Pa., .as-

signors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 18, 1952, Serial No. 283,038

8 Claims. (Cl. 200-144) This invention relates to circuit breakers and, more particularly, to contact structures for air circuit breakers.

An object of the invention is to provide a circuit breaker with an improved contact structure which fits into a relatively small space and has high current-carrying capacity.

Another object of the invention is to provide a circuit breaker with an improved contact structure having high interrupting and current-carrying capacities Which is rugged and durable in construction.

Another object of the invention is to provide a circuit breaker with an improved contact arrangement according to the preceding paragraphs wherein the magnetic forces induced by the current flow are utilized to increase the contact pressure.

Other objects and advantages of the invention will be pointed out in the following description and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In said drawings:

Figure l is a side elevational view, partly in section, of r a circuit breaker embodying the principles of the invention;

Fig. 2 is a detail view of the latch mechanism;

Fig. 3 is an enlarged side elevational view, partly in section, showing the improved contact structure in the closedcontact position;

Fig. 4 is an enlarged elevational View of the stationary contact structure taken along line IV-IV of Fig. 3 and looking in the direction of the arrows;

Fig. 5 is a bottom view, partly in section, of the stationary contact structure shown in Fig. 4;

Fig. 6 is a vertical sectional view of the contact structure taken on line VI-VI of Fig. 4, showing the contacts in full lines in the closed position, and in dot-and-dash lines in the position at which the main contacts are about to separate; and

Fig. 7 is a view similar to Fig. 6 but showing the contacts in full lines in the position at which the intermediate contacts are about to separate and in dot-and-dash lines in the position at which the arcing contacts are about to separate.

Referring to Fig. 1 of the drawings, the circuit breaker is of the roll-out type and is mounted on a truck comprising a pair of side plates 11 (only one being shown) which are rigidly joined by

cross members

13, 15, 17, and 19 to form a rigid frame for supporting the circuit breaker. The truck is mounted on wheels 20 to facilitate rolling the breaker into and out of a cubicle in order to connect and disconnect the breaker in an electrical circuit.

The circuit breaker is of the multi-pole type (only one pole being shown) and comprises generally a plurality of sets of separable contact means 21, a common operating mechanism 23, a trip device 25, and a closing means 27.

The contact means consists generally of

stationary contact blocks

29 and 31 mounted respectively on upper and

lower terminal members

33 and 35 which, in turn, are

rigidly supported on a back plate 37. The back plate 37- is rigidly supported by angular brackets 39 (only one being shown) rigidly secured to the side plates 11 of the frame. The detailed description of the improved contact structure will be fully described hereinafter.

The specific structures of the operating mechanism, trip mechanism and the closing means shown are fully disclosed in Patent No. 2,515,994, issued July 18, 1950, to Joseph D. Findley, Alvin W. Ogg, and Fritz E. Florschutz and assigned to the assignee of the instant invention, for which reason only a brief description of these mechanisms is given herein.

A switch arm 41 for operating the movable contacts (there being a switch arm 41 for each pole of the breaker) is pivotally mounted by a pivot pin 43 on the lower terminal member 35 and is operatively connected by means of an insulating operating rod 51 to the operating mechanism 23. The upper ends of the operating rods 51 are pivotally connected by pivot pins 53 to the corresponding switch arms 41, and the lower ends of the operating rods are connected by suitable means to an angular crossbar 59 which is common to all of the poles of the breaker. The crossbar 59 is pivotally connected at its ends by pivot pins 55 (only one being shown) to an operating lever 61 which is pivotally mounted on a shaft 67 supported in the side members of a generally U-shaped frame 69. The frame 69 is supported on the

cross members

13, 15, and 17 and is shown partly broken away more clearly to show the operating mechanism.

In addition to the operating lever 61, the operating mechanism consists of a closing lever also mounted on the shaft 67 and connected by means of a link 81 to the movable armature 85 of the closing solenoid 27 The operating lever 61 and the closing lever 75 are connected by means of an underset thrust-transmitting toggle comprising toggle links 87 and 89 pivotally connected together by a knee pivot pin 91. The toggle link 87 is pivotally connected to the operating lever 61 and the toggle link 89 is pivotally connected to the closing lever 75.

The closing lever 75 is held in the closed position by a spring-biased latch which normally engages a roller 101 on the closing lever and holds the latter in the position shown.

The toggle 87-89 is releasably held in a slightly underset position by a latch member 103 mounted on the shaft 67 for movement relative thereto. A link 105 connects the knee of the toggle 87-89 to the latch member 103 which is normally releasably held in latching position by the latching and tripping mechanism shown in Fig. 2. This mechanism comprises a trip member 109 carrying a latch roller 119 which is biased by a spring 123 into latching engagement with a shoulder on the latch member 103 to releasably restrain the latter and the toggle 87-89 in thrust-transmitting position.

The latch 109 is of the slip-off type, and a trigger latch 127 is provided to releasably restrain the latch member 109 and the latch roller 119 in latching position. The latch 127 has a projection 131 normally engaging a latching projection 133 on the trip member 109 and is biased to latching position by a spring 135. A tripping electromagnet 137 is provided to operate the latch mechanism and effect release of the operating mechanism and opening of the circuit breaker.

When an overload current occurs, the tripping electromagnet 137 is energized and operates the latch mechanism to eifect release of the latch 109 which, in turn, releases the latch member 103. Upon release of the latch member 103, the toggle 87-89 immediately collapses, permitting clockwise rotation of the operating lever 61 and operating movement of the switch arms 41 for the several poles of the breaker.

The toggle 87-89 is reset to its thrust-transmitting position, and the latch member 103 is reset and relatched automatically during the opening operation. This is effected by a pair of springs 169 (only one being shown) connected under tension between the armature 85 and the closing lever 75 at a point near the shaft 67. When the toggle 87-89 collapses, a roller 175 on the toggle link 89 engages and moves the latch 95 to disengage the latter from the roller 101, thus releasing the closing lever 75 whereupon the springs 169 move the armature 85 and through the link 81 rotate the closing lever 75 clockwise. This movement extends the toggle 8789 to its underset position and through the link 105 rotates the latch member 103 clockwise to its latching position, ermitting resetting of the latching mechanism to latching position. Thereafter, the circuit breaker is closed by energization of the closing solenoid 27 from any suitable source. When energized, the solenoid 27 attracts its armature 85 and through the link 81 rotates the closing lever 75 counterclockwise. Since the toggle 87-439 is held in thrust-transmitting position, the movement of the closing lever is transmitted therethrough and actuates the operating lever 61 and the rods 51 to close the contact means 21. As the mechanism reaches the closed position, the latch 95 reengages the roller 101 and restrains the breaker mechanism in the closed circuit position.

Referring now to Fig. 3 of the drawings, the switch arm 41 is channel-shaped and has rigidly mounted thereon a pair of laterally spaced main movable contacts 177, an intermediate contact 179 and an arcing contact 181. The main movable contacts 177 cooperate with spaced main stationary contacts 183. The movable intermediate contacts 179 cooperate with a stationary intermediate contact 185, and the movable arcing contact 181 cooperates with a stationary arcing contact 187. The stationary intermediate contact 185 and the stationary arcing contact 187 are mounted on a contact platform 205 (see also Figs. 4, 5, 6, and 7) mounted on the upper contact block 29 for limited movement relative thereto by means of a pair of spaced plates 207 disposed one on each side of the contact block 29. The plates 207 are supported on bolts 209, extending through openings in the contact block 29 and threaded at both ends to receive nuts 210. Springs 212 are compressed between the nuts 210 and the plates 207 to provide good contact pressure between the plates 207 and the contact block 29. The plates 207 are provided with elongated slots 214 surrounding the lower bolt 209 to permit limited pivotal movement of the plates about the upper bolt 209.

The platform 205 is provided with laterally extending studs 211 disposed adjacent the lower end theerof and extending into elongated slots 213 in the plates 207 for supporting the platform for limited movement relative to the plates 207. Ears 215 extend laterally from the sides of the platform 205 into openings 217 in the plates to limit the movement of the platform.

The platform 205 is biased outwardly away from the contact block 29 by means of a coil spring 219 (Figs. 3, 6, and 7) disposed adjacent the upper end of the platform 205 and a pair of coil springs 221 (Figs. 3 to 7) located near the lower end of the platform. The spring 219 is compressed between the contact block 29 and the contact platform 205 and is provided with a guide stud 223 secured to the contact block 29. The springs 221 are compressed between the ends of a U-shaped flexible conductor 225 (Fig. 3) which serves to electrically connect the contact platform 205 to the contact block 29. A flexible conductor 227 electrically connects the lower end of the switch arm 41 to the lower contact block 31.

The main stationary contacts 183 are formed on the lower corners of the plates 207 (Figs. 3, 4, and and extend inwardly toward each other. A connecting bar 229 is supported on pins 231 mounted in the bar 229 and supported in openings in the main contacts 183. Springs 233 compressed between the bar 229 and a bar 235 secured to the contact block 29 bias the plates 207 in a clockwise direction about the upper bolt 209 and provide contact pressure between the main stationary contacts 183 and the main movable contacts 177 in the closed position of the switch arm 41. The purpose of the connecting bar 229 is to tie the plates 207 together laterally while permitting a slight independent pivotal movement of each of the plates.

When the trip device 25 (Fig. 1) is energized and effects collapse of the toggle 8789, the operating lever 61 starts to rotate clockwise, permitting downward movement of the rod 51 and movement of the switch arm 41 about its pivot 43 in opening direction. As the switch arm 41 moves in opening direction, the

stationary contacts

183, and 187 remain in contact, respectively, with the moving

contacts

177, 179 and 181 until the slot 214 in the plates 207 engages the lower bolt 209, the plates 207 pivoting about the upper bolt 209 by the pressure of the springs 233. The contact structure is shown in full lines in Fig. 6 in the closed position and in dot-anddash lines at 214a in the position in which the slots 214 have engaged the bolt 209, and the main contacts 177-183 are about to separate. In this position the switch arm 41 has moved to the position shown at 41a but the contact platform 205 has followed the switch arm under the pressure of

springs

219 and 221. It will be noticed by reference to Fig. 6 that the slots 213 in the plates 207 have moved to the dot-and-dash position 213a and that the studs 211 on the platform have moved to the position shown at 211a but are not yet in contact with the left-hand walls of the slots 213. The plates 207 do not move farther during an opening operation, but upon continued movement of the switch arm 41 in opening direction, the platform 205 follows until the studs 211 engage the left-hand ends of the now stationary slots 213 in the plates 207. At this time the main contacts have separated slightly as shown at 183a and the intermediate and arcing contacts are still engaged in the position shown at 185a. The parts are shown in this position in full lines in Fig. 7.

As the opening movement of the switch arm 41 continues, the platform 205 pivots about the studs 211 and the upper end thereof follows the switch arm with the arcing contact 187 maintaining contact with the moving arcing contact 181 until the ears 215 are stopped by striking the walls of the openings 217 in the contact plates 207. In this position of the parts, shown by dot-and-dash lines in Fig. 7, the main and intermediate movable contacts have opened to the positions shown, respectively, at 177b and 179k and the arcing contacts are about to separate.

Upon continued opening movement of the moving switch arm 41 from the position 4112 (Fig. 7) the arcing contacts separate and the switch arm will move to the open position without further movement of the contact platform 205 or the contact plates 207, drawing an are between the arcing contacts. The are is drawn into an arc-extinguishing structure, indicated generally 237 (Fig. 1), where it is quickly extinguished.

The contacts close in the reverse sequence when the switch arm 41 is operated to the closed position, that is, the arcing contacts close first, then the intermediate contacts, and finally the main contacts close.

In the type of circuit breaker illustrated, the arc will usually be extinguished when the arcing contacts have separated approximately two inches. When interrupting capacitor banks or are furnaces and under certain conditions when the circuit constants give a low damping factor and the current is of sufficient magnitude, a switching surge may be produced which will cause the arc to restrike across a gap of this dimension or larger. Such restrikes may even occur outside the arc chute between live or grounded parts such, for instance, as between the main stationary contacts and the switch arm 41 at a point below the main movable contacts. The latter is prevented by providing the switch arm with an insulating sleeve 239.

The contact structure provides increased momentary and continuous current-carrying capacity in a small compact arrangement which permits placing the entire separating contact structure inside the arc chute; hence, any restriking of the arc will occur between the interrupting contact structure and will be confined within the arc extinguisher.

While there has been shown and described and pointed out the novel features of the invention as applied to a single modification, it will be understood that various omissions and substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing from the spirit of the invention.

We claim as our invention:

1. In a circuit breaker, stationary contacts comprising a fixed contact member, a pair of spaced movable contact carrying plates disposed one on each side of said fixed contact member and mounted on said fixed contact member for limited movement relative thereto, springs providing pressure contact between said contact carrying plates and said fixed contact member, main stationary contacts on said movable contact carrying plates, a contact member disposed between said contact carrying plates and supported between said movable contact carrying plates for limited movement relative thereto, intermediate and arcing contacts on said contact member, and a movable switch member having movable main, intermediate and arcing contacts thereon for cooperating, respectively, with said stationary main, intermediate and arcing contacts to open and close the circuit.

2. In a circuit breaker, stationary contacts comprising a fixed contact support member, a pair of movable c0ntact carrying plates disposed one on each side of said fixed contact support member and pivotally mounted on said fixed contact support member for limited pivotal movement relative thereto, a plurality of springs biasing said movable contact carrying plates into pressure contact with said fixed contact support member, main stationary contacts mounted on said movable contact carrying plates, a contact-carrying member supported between said movable contact carrying plates for limited movement relative to said contact carrying plates, intermediate and arcing contacts mounted on said contact-carrying member, and a movable switch member having movable main, intermediate and arcing contacts mounted thereon for cooperating, respectively, with said stationary main, intermediate and arcing contacts to open and close said circuit.

3. In a circuit breaker, a pair of spaced terminals, a stationary contact structure comprising a conducting member rigidly mounted on one of said terminals, a pair of movable contact plates pivotally mounted one on each side of said conducting member for limited sliding movement relative thereto, main stationary contacts rigid with said movable contact plates, springs biasing said movable contact plates for pivotally moving said main stationary contacts away from said conducting member, spring means biasing said movable contact plates into pressure engagement with said conducting member, a rigid contact member having stationary intermediate and arcing contacts thereon, said rigid contact member being mounted on said movable contact plates and biased for limited movement relative to said movable contact plates and said conducting member, and a movable switch member pivotally mounted on the other of said terminals and having movable main, intermediate and arcing contacts rigid therewith for cooperating with said stationary contact structure to open and close the circuit.

4. In a circuit breaker, a pair of spaced terminals, a stationary contact structure supported on one of said terminals comprising a member of conducting material rigidly secured to one of said terminals, a pair of spaced movable contact-carrying members mounted on said conducting member, said contact-carrying members being pivotally mounted one on each side of said conducting member for limited movement relative thereto, main stationary contacts rigidly mounted on said spaced movable contact-carrying members, said contact-carrying members having openings therein, a rigid contact member having stationary intermediate and arcing contacts rigid therewith, said rigid contact member having projections thereon engaging in said openings in said spaced movable contact-carrying members to support said rigid contact member for limited movement relative to said spaced movable contact-carrying members, and a switch arm having main, intermediate and arcing contacts thereon and pivotally mounted on the other of said terminals for movement into and out of engagement with said stationary contact structure to open and close said circuit.

5. In a circuit breaker, a pair of spaced terminals, a stationary contact assemblage mounted on one of said terminals comprising a pair of spaced contact-carrying members having openings therein and pivotally mounted one on each side of said terminal for limited movement relative to said terminal, each of said contact-carrying members being biased away from said terminal and having a main stationary contact thereon, spring means biasing said contact-carrying members against opposite sides of said terminal to provide pressure contact therebetween, a rigid contact member having stationary intermediate and arcing contacts rigid therewith and having projections thereon engaging in the openings in said spaced contact-carrying members to support said rigid contact member for limited movement relative to said spaced contact-carrying members, spring means biasing said rigid contact member away from said terminal, a movable switch arm having a movable contact assemblage rigid therewith comprising movable main, intermediate and arcing contacts, and said movable switch arm being pivotally mounted on the other one of said terminals and movable to an open position and to a closed position to cause engagement and disengagement of said movable contact assemblage with said stationary contact assemblage.

6. In a circuit breaker, a pair of spaced terminals, a member of conducting material mounted on one of said terminals, a pair of spaced contact-carrying members having a plurality of openings therein and disposed one on each side of said conducting member, each of said contact-carrying members having a main contact rigid therewith, pivot means pivotally mounting said contact-carrying members on said conducting member for movement relative thereto, stop members for limiting the movement of said contact-carrying members relative to said conducting member, springs biasing said contact-carrying members into close engagement with said conducting member, a rigid contact member disposed between said spaced contact-carrying members and having intermediate and arcing contacts rigid therewith, a plurality of projections on said rigid contact member engaging said openings to support said rigid contact member between said contact-carrying members for movement relative thereto and for limiting said movement, a pivoted switch arm pivotally supported on the other of said terminals and having movable main, intermediate and arcing contacts rigid therewith, said switch arm being movable to an open position and to a closed position to effect engagement and disengagement of said movable contacts with the corresponding stationary contacts.

7. In a circuit breaker, a pair of spaced terminals, a stationary contact structure comprising main, intermediate and arcing contacts mounted on one of said terminals, a movable switch arm pivotally mounted on the other of said terminals and having a movable contact assemblage thereon comprising main, intermediate and arcing contacts for cooperating with the corresponding stationary contacts of the stationary contact structure for establishing an arc, an arc chute structure having arc-extinguishing means therein, said stationary contact structure and said co- 7 operating movable contact assemblage being compactly arranged and disposed entirely within said arc chute so that any are or restrike will occur within said are chute,-

and insulating means surrounding a portion of said movable switch arm adjacent said are chute to' prevent the arc from striking said switch arm outside said are chute.

8. In a circuit breaker, a pair of terminals, a stationary contact structure mounted on one of said terminals comprising stationary main, intermediate and arcing contacts, a movable switch member pivotally mounted on the other of said terminals, a flexible conductor electrically connecting said movable switch arm to said other terminal, a movable contact assemblage mounted on said movable switch member comprising movable main, intermediate and arcing contacts, said movable contact assemblage cooperating with said stationary contact structure to establish an arc, an arc chute structure having arc-extinguishing 8 means therein, said stationary contact structure and said cooperating movable contact assemblage being arranged compactly and disposed entirely Within said are chute so that any arc or restrike of the arc will occur within said are chute, and an insulating sleeve surrounding a portion of said movable switch member adjacent said arc chute.

References Cited in the file of this patent UNITED STATES PATENTS 1,074,431 Hewlett Sept. 30, 1913 2,259,971 Cumming et al Oct. 21, 1941 2,462,283 Rathert Feb. 22, 1949 2,477,189 Lerstrup July 26, 1949 2,492,762 Palme Dec. 27, 1949 2,571,933 Olsson et al Oct. 16, 1951