US1955337A - Circuit breaker - Google Patents

Description

April 17, 1934. w M, LEEDS ET AL 1,955,337

CIRCUIT BREAKER Filed Jan. 2, 1932 3 Sheds-Sheet l A? /a z WITNESSES: INVENTORS Mh/brop A4. leads I 9' d0a EoJn///0. /5r1.57bA"/e A OLA/ .m I BY 'ATTORNEY April 17, 1934.

w. M, LEEDS ET! AL 1,955,337

CIRCUIT BREAKER Filed Jan. 2, 1952 3 Sheets-Sheet 2 5/ 5:2 WITNESS s; INVENTORS M'n rhrapM Leeds 5o andEaawel/C/nfibF/a.

Mm" BY ATTORNEY Patented Apr. 11, 1934 cmourr BREAKER Winthrop M. Leeds and Roswell C. Van Sickle, Wilkinsburg, Pa., assignors to Westinghouse Electric and Manufacturing Company, a corporation of Pennsylvania Application January 2, 1932, Serial No. 584,388

17 Claims. (01. 200-146) Our invention relates to circuit breakers and. particularly to a heavy current contact structure therefor.

One object of our invention is to provide a contact structure which shall be simple and rugged in construction and which shall maintain low contact resistance between the moving and the fixed members, despite any pitting or roughening of the contact surfaces due to arcing.

A second object of our invention is to provide a circuit breaker contact structure within which the arc resulting from an interruption of the circuit is drawn between other surfaces than those normally used for contact purposes.

A further object of our invention is to provide a circuit interrupter having main contacts, auxiliary contact membersand arc-extinguishing structures associated with the auxiliary contact members, in which the circuit is first es tablished and finally interrupted by the auxiliary contacts.

A still further object of our invention is to provide a circuit interrupter having main and auxiliary contact members, in which the contact resistance of the auxiliary contacts--between which the circuit is established and interruptedis maintained at a sufiiciently low value to permit the .opening of the main contact elements without appreciable arcing action therebetween.

In the interruption of power circuits by the use of fluid-break type switches, the arc may be established between the same surfaces that are used for current carrying purposes. This, however, creates a very undesirable condition; the contact surfaces become roughened and pitted, and often become coated with high resistance oxide films as a result of the action of the arc, and in order to maintain satisfactory operation of the interrupter it is necessary to frequently renew the contacts-at best a most unsatisfactory solution.

Numerous expedients have been tried with a view toward eliminating these difficulties. For example, two sets of contacts have been supplied-an auxiliary set for establishing and for interrupting the circuit, and main contacts for carrying the normal current in the circuit. Even with this arrangement the operation is not satisfactory, because the constantly increasing re- 9 sistance of the auxiliary contactsas the number of operations increases-often becomes sufii ciently large to cause arcing during the opening of the main contacts. This last is especially undesirable because the main contacts, due to their relatively large cross section, are very rarely provided with arc extinguishing structures, and any arc established therebetween continues for a considerable time and may cause serious damage not only to the contact but to the interrupter itself.

Our invention; however, obviates all of these difficulties by providing means whereby separate surfaces are provided for contact and for arcing purposes. Furthermore, our invention is equally applicable to interrupters having one or-two sets of contacts.

The features of our invention which we believe to be new are particularly pointed out in the appended claims. For full understanding of the principles of our invention and the best mode of applying the same, reference may be had to the accompanying drawings, in which:

Figure 1 is a cross sectional view, partly in elevation, of an oil circuit breaker embodying our invention;

Fig. 2 is an enlarged side elevation of the contact structure;

Fig. 3 is an enlarged end elevation of the con tact structure;

Fig. 4 is an enlarged side elevation of the auxiliary contact structure;

Fig. 5 is a cross sectional view, of the auxiliary contact structure taken along the line V-V of Fig. 4;

Fig. 6 is a side'elevaticnal view showing the elements of our invention;

Fig. 7 is a sectional view, taken on the line VII-VII of Fig. 6, which shows the auxiliary contacts in the closed position;

Fig. 8 is a similar sectional view showing the auxiliary contacts in the partiallyv open position;

Fig. 9 is a cross sectional view of the are extinguishing structure taken on the line IX-IX of Fig. 6, and

Figs. 10 to 14, inclusive, are plan views of the various plates used in the arc extinguishing structure shown in Fig. 9. I

In carrying out this particular embodiment of our invention, we employ the customary circuit breaker construction which includes a tank 1 having a cover 2, insulating lead-in bushings 3 extending therethrough, stationary contact structures 4, a body of liquid 5, a movable contact member 7 having contact tips 9, a pull rod 10 for operating the movable contact element, and a mechanism (not shown) for actuating the pull rod.

The contact structures 4 shown in Figs. 1, 2, and 3 each include a stationary contact member 6 fastened by bolts 8 to the conductor of the insulated lead in bushings 3. Integral with the stationary contact member 6 is a supporting frame 12, which has attached thereto an arc extinguishing structure 13 and the main contact brushes 15. The through bolts 50 which fasten the arc extinguishing structure to the supporting frame pass through suitable spacing sleeves 60. As shown in Fig. 3, the main contact brushes are divided into segments, three on each side of the contact structure; the bolts 16 serve to fasten the individual segments to the frame 12.

The movable contact member 7 comprises two main contact members 17 .disposed on opposite sides of an auxiliary contact bridging bar 18; the main contact members 17 are adapted to engage the main contact brushes 15 only when the breaker is in the fully closed position. The bridging bar 18 has contact tips 9 which are formed of an arc resisting, conducting material; we prefer to make these tips of an alloy composed of 60% tungsten and 40% silver, but there are numerous other suitable materials available. As will be more fully pointed out later, the electrical circuit through the interrupter is established and broken by the contact tips 9 of the auxiliary contact bridging bar 18. Suitable means such as bolts 19 fasten the bridging element to the pull rod 10.

We shall now point out the elements of our invention as shown diagrammatically in Figs. 6, 7, and 8 in order that the detail structure shown in Figs. 5 and 6 may be more easily understood. Fig. 6 is a side elevation wherein is shown a movable contact member 7 having contact tips 9 and a pull rod 10, are extinguishing structures 13 having an open slot wherein said contact tips 9 move, and a contact structure 4.

The contact structures 4 include a pivoted contact element 35 biased downwardly by the spring 37, and pivoted opposing contact fingers 23 pivoted about pin 24 and biased toward each other by the springs 31. The pivoted contact element 35 is wedge shaped on its free end 40 and is so disposedthat this wedge shaped end is engaged by the pivoted opposing contact fingers 23. Surfaces 42 are provided on these opposing fingers which coact with the surfaces 41 on the wedge shaped end 40 to keep the fingers separated. Also, there are other surfaces such as the ridges 26, on the ends of the pivoted opposing contact fingers, which engage the contact surfaces 43 in the sides of the bridging bar 18 when the interrupter is in the closed position.

In the open position, as shown in Fig. 8, the opposed fingers 23 are held separated by this wedge shaped end 40, and a suitable protuberance 45 of arc resisting conducting material, on the bottom of the pivoted contact element 35 extends from between the fingers down into the are extinguishing structure 13. As the breaker closes, the contact tip 9 abuts against this protuberance 45 and upon further movement forces the pivoted contact element 35 up out of engagement with the fingers whereupon the ridges 26 on the pivoted opposing fingers engage the sides 43 of the bridging bar 18. It should be noted that the final current carrying contact is between the ridges 26 and the sides 43 of the bridging bar 18, and that the opposing contact fingers do not grip the sides of the bridging bar until the breaker is nearly closed. This action may be varied by changing the surfaces 42 which coact with surfaces 41 on the wedge shaped end 40 of the pivoted contact element. During the opening of the breaker the process is reversed; the projection 45 of the pivoted contact element 35 is held in abutting contact with the downwardly moving contact tip 9 by its biasing means 37, as shown in Fig. 7, and, as the opening movement progresses, the fingers 23 are separated by the wedge action of the pivoted contact element, thus interrupting the electrical circuit between the fingers and the sides 43 of the bridging bar 18; finally, the pivoted contact element engages the top plate 57 of the arc extinguishing structure 13, its downward movement is stopped, and the arc is established. At this point, however, the protuberance 45 has moved between the opposing fingers and extends downwardly into the arc extinguishing structure. Thus, when the abutting contact between the contact tip and the moving contact element is broken, .the arc is established between the tip 9 of the bridging bar 18 and the protuberance 45 on the moving contact element,neither of which are the contact surfaces depended upon to carry the circuit current when the breaker is fully closed, and both of which are composed of arc resisting, conducting material.

The stationary contact structure 4 shown in Figs. 4 and 5 embodies all of the elements shown in Figs. 6, 7, and 8 and operates insubstantially the same manner. Both views show the breaker contacts in the closed position. The supporting frame 12 of the stationary contact member 6 has as integral parts thereof the lugs 20 and 21, the projecting arms 22, and the supporting structure for the main contact brushes 15. The two pivoted opposing contact fingers 23 are pivoted on the pin 24 which extends through suitable aligned openings in the lugs 20 and 21; the cotter pins 25 prevent sidewise displacement of the pin 24. The springs 31 which are held in position by the recesses 46 and 47 in the supporting frame 12 and in the pivoted fingers 23, respectively, bias the fingers toward each other. The shunts 32, fastened by bolts 33 and 34, electrically connect the pivoted fingers with the stationary contact. The ridges 26 on the opposing surfaces of the contact fingers provide suitable contact surfaces for engaging the sides 43 of the bridging bar 18.

The pivoted contact element 35 comprises an arm member pivoted on one end by the pin 36 to the projecting arms 22 of the supporting frame. The other end 40 of the arm member is substantially wedge shaped and is adapted to move between the pivoted opposing contact fingers 23. The springs 37, which are held in position by the recesses 48 and 49, bias the pivoted contact element downwardly. Suitable opposing surfaces 42 on the contact fingers coact with the surfaces 41 on the wedge shaped end 40 in such manner that when the breaker is in the open position, the fingers 23 are held separated against their bias and the projection 45 on the lower part of the pivoted contact element 35 protrudes downwardly into the arc extinguishing structure. As stated before, the downward movement of this wedge shaped end 40 is limited by the engagement of the surfaces 41 with the projections 26 on the opposing fingers. The electrical circuit from the stationary contact frame 12 to the pivoted contact element 35 is completed by the shunt 38 which is maintained in position by the bolt 39.

The are extinguishing structure 13 in combination with the structure of our invention gives particularly satisfactory results. This structure comprises, in general, a chamber having an open slot and slotted plates of magnetic material arranged transverse to the arc path at spaced intervals. The are is drawn within the slot and is moved into the structure by the magnetic action of the plates. During this inward movement of the are. considerable volumes of gas are formed; this gas flows outwardly, transverse to the arc, and is vented at the sides of the structure. The cxtinguishment of the are results from the cooling action of this outward, transverse flow of gas.

The form of arc extinguishing structure which we prefer to use is shown in detail in Figs. 6 to 14, inclusive. This structure comprises a plurality of plate elements that are assembled on through bolts to 'form a complete are extinguishing device. The respective elements are shown in Figs. 10 to 14, inclusive, these elements are combined into unit group assemblages, and the complete structure contains a plurality of these unit groups.

Each unit group assemblageincludes two fiber insulating plates 54, shown in Fig. 11, each having the slots 53 and 63 which connect with the flared opening 59, assembled on opposite sides of a magnetic plate 52 and a lining plate 51, both last mentioned plates being shown in Fig. 12. The magnetic plate 52 contains a large open slot that is lined by the insulating plate 51 which contains the slots 53 and 63, and the flared opening 59-simi1ar to the slots 53 and 63 and the flared opening 59 in plates 54. In addition to the above, each unit group includes a plurality of insulating plates 55, shown in Fig. 13, assembled between the fiber plate magnetic plate-fiber plate assemblages of the adjacent units.

'These insulating plates 55 also have the common slots 53 and 63, and the flared opening 59. In addition they have a plurality of recesses 56, for retaining the arc extinguishing fluid, which open into the slots 63. The flared openings 59 serve to form vents for the gases generated during the extinguishing of the arc.

The complete are extinguishing structure 13 includes a top insulating plate 57, as shown in Fig. 10, which is provided with the common slots 53 and 63; a plurality of the unit group assemblages; a plate unit, adjacent to the bottom plate, comprising a fiber plate-magnetic plate-- fiber plate assemblage; and a bottom plate 58. as shown in Fig. 14, which has the common slot 53 and the flared vent 59. The common slot 53, which exists in all of the insulating plates aligns on assembly to form a continuous passage, open at each end and vented transverse to its longitudinal axis by the openings 59. It is within this passage that the contact tips 9 move, and the arc is established and interrupted. The operation and theory of this type of arc extinguishing structure is more fully pointed out in Patent Number 1,899,605, issued to B. P. Baker and E. G. Kees on February 28, 1933, and assigned to the assignee of this invention.

The operation of this complete embodiment of our invention is substantially the same as the operation of the structures shown in Figs. 6, 7, and 8. In the open position, the contactflngers 23 are held separated by the wedge shaped end 40 of the pivoted contact element 35, and the protuberance 45 on the lower side of the pivoted contact element extends from between the fingers downwardly toward the movable contact member '7. As the interrupter closes, the movable contact member. moves upwardly and first establishes the circuit between the contact tips 9 and the protuberances 45 of the pivoted contact elements. Later, the sides 43 of the bridging bar 18-are engaged by the ridges 26 on the pivoted contact fingers 23-the wedge shaped ends 40 of the pivoted contact elements 35 having been displaced upwardly from between the opposed fingers-and the main contact members 17 engage the main contact brushes 15. On opening, the sequence is reversed. The main contacts are opened, the pivotedcontact elements move downwardly in abutting engagement with the contact tips of the bridging bar, the pivoted fingers break contact with the sides of the bridging bar, and finally, as the pivoted contact elements engage the limiting stops associated with the fingers, the circuit is interrupted and the are is drawn between the ends of the contact tips and the protruding lower surfaces of the pivoted contact elements. This is most important, because the arc is thus drawn between other surfaces than those used for carrying current when the breaker is in the fully closed position; and, as pointed out previously, the tips 9 and the protuberances 45 are of arc resisting material.

While, in accordance with the patent statutes, we have given the foregoing details of a practical embodiment of our invention, it is to be understood that many of these are merely illustrative and that many variations are possible without departing from the broad idea involved. For example, the arc extinguishing structures and the main contacts, while very desirable, are not essential parts of our invention. Neither is it necessary that a double break interrupter be employed. Other modifications will suggest themselves to those skilled in the art, and it is our desire to be limited only .as set forth in the following claims.

We claim as our invention:

1. A contact structure for circuit interrupters including a movable contact member, a movable contact element. a contact finger biased toward said movable contact member, and means for biasing said movable contact element toward said movable contact member; said movable contact element having camming means associated therewith for causing said contact finger to engage said movable contact member only when said movable contact member is in a predetermined position, said movable contact member remaining in engagement with said contact element after breaking contact with said contact finger.

2. A contact structure for circuit interrupters including a movable contact member, a movable contact element, a plurality of opposing contact fingers biased toward each other, means for biasing said movable Contact element toward said I movable contact member, and means for limiting the motion of said movable contact element; said movable contact element and at least one of said contact fingers having engaging camming sur-' faces for causing said fingers to engage said movable contact member only when said movable contact member is in a predetermined position during the opening process, said movable contact member remaining in engagement with said contact element after breaking contact with said contact fingers until said contact element is restrained from further movement by said limiting means.

3. A contact structure for circuit interrupters including a movable contact element, a plurality of opposing contact fingers biased toward each other by resilient means, resilient means for biasing one end of said movable contact element into a position between said opposing contact fingers, and a movable contact member, which engages said movable contact element during the opening and the closing of said interrupter, said movable contact element and at least one of said contact fingers having means associated therewith for holding said fingers away from each other against said biasing means except when said movable contact member is in a predeter-' mined position, said fingers then engaging said movable contact member.

4. A contact structure for circuit interrupters including a supporting frame, a movable contact element supported on said frame and having a camming portion, a plurality of opposing contact fingers, at least some of which have camming surfaces, supported on said frame and biased toward each other by resilient means, means for defining the movement of said movable contact element, resilient means for biasing said camming portion of said contact element into a position between said contact fingers to engage said cam ming surfaces, and a movable contact member which abuts against said contact element during the opening and closing of the interrupter; the camming action of said portion and said surfaces causing said movable contact member to engage said fingers only when substantially in the closed position, and, during the opening process, causing said fingers to break contact with said movable contact member before the contacting end of said member has moved entirely from the space between said opposing fingers and before the abutting contact with said movable contact element is broken.

5. A contact structure for circuit interrupters including a movable contact member, a contact element comprising an arm which is wedge shaped at one end and is pivoted at the other end, a plurality of opposing contact fingers biased toward each other, means for biasing the wedge shaped end of said contact arm into a position between said opposing contact fingers, and means for limiting the movement of said wedge shaped end; said movable contact member engaging said opposing fingers when in the closed position and, when moving to the open position, remaining in engagement with saidv wedge shaped end, after breaking contact with said opposing fingers, until said wedge shaped end is restrained from further movement towards said movable contact by said limiting means.

6. A contact structure for circuit interrupters including a supporting frame, a contact element comprising an arm which is wedge shaped at one end and pivoted at the other end to said supporting frame, said wedge shaped end having a portion of arc resisting conducting material, a plurality of opposing contact fingers pivoted to said supporting frame and biased toward each other by resilient means, means for limiting the movement of said pivoted contact arm, resilient means for biasing the wedge shaped end of said pivoted contact arm into a position between said contact fingers and into engagement with said limiting means, and a movable contact member having an arc resisting portion which abuts against the arc resisting portion of said wedge shaped end during the opening and the closing of the interrupter, and having a current carrying portion of greater conductivity than said arc resisting portion which engages said pivoted fingers when in the closed position.

7. A contact structure for circuit interrupters including a supporting frame, a movable contact member, a contact element comprising an arm which is wedge shaped at one end, pivoted at the other end to the supporting member, and having a resilient biasing means associated therewith,

surfaces of said opposing contact fingers coacting with said wedge shaped end and thus maintaining a sufficient separation therebetween to permit the protuberance therethrough of a narrower section of the wedge shaped end of said contact arm, said movable contact member first abutting against this narrower section of the wedge shaped end during the closing of said interrupter, and engaging said pivoted contact fingers when in the fully closed position; said movable contact, during the opening of said interrupter, establishing the are between said abutting surfaces and thereby preventing burning and pitting of the closed contact surfaces.

8. In combination in a circuit interrupter, separable main contact members, an auxiliary contact structure including a movable contact member, a movable contact element having a camming portion, a plurality of opposing contact fingers biased toward each other, means for biasing said movable contact element toward said movable contact member, said camming portion cooperating with camming surfaces on at least some of said fingers to cause said movable contact member to engage said fingers when in the closed position and to disengage said contact fingers during the opening process before breaking contact with said movable element, and means for opening said separable main contact members prior to said breaking of contact between said movable contact member and said auxiliary contact structure.

9. In combination in a circuit interrupter, separable main contact members, an auxiliary contact structure, a movable contact member, and means for initially establishing and finally interrupting the circuit through said auxiliary contact structure; said auxiliary contact structure includinga supporting frame, a contact element comprising an arm which is wedge shaped at one end and is pivoted at the other end to said sup porting frame, said wedge shaped end having a portion of arc resisting conducting material, a. plurality of opposing contact fingers pivoted to said supporting frame and biased toward each other by resilient means, means for limiting the movement of said pivoted contact arm, and resilient means for biasing the wedge shaped end of said pivoted contact arm into a position between said contact fingers and into engagement with said limiting means; said movable contact member abutting against the arc resisting conducting portion of said wedge shaped end during the opening and the closing of the interrupter, engaging said pivoted fingers when in the closed position, and, during the opening process, breaking contact with said pivoted fingers before the abutting contact with said wedge shaped end is broken.

10. In combination in a circuit interrupter, separable main contact members, and an auxiliary contact structure which includes a movable contact member, a movable contact element, a plurality of opposing contact fingers, means bias- .ing said fingers toward each other, means for biasing said movable contact element toward said movable contact member, and means for holding closing the circuit, said contact assemblage in cluding a contact finger biased toward said movable contact member, and means, electrically connected to said contact assemblage, for causing said contact finger to move away from the axis of the path of movement of said movable contact member when said movable contact member has reached a predetermined position during the opening process.

' 12. In a circuit interrupter, a stationary contact assemblage and a cooperating contact member movable longitudinally, in a substantially fixed path, to open and to close the circuit, said contact assemblage including a pair of opposed contact fingers biased toward each other and adaptedto engage said movable contact member when said circuit interrupter is in the closcd position, and means including a single cam member for causing said fingersto move laterally away from the axis of the path of movement of said movable contact member and thereby disengage said movable contact member when said contact member has reached a predetermined position during the opening process.

13. In a circuit interrupter,'a contact assemblage, and a cooperating movable contact member for opening and closing the circuit, said contact assemblage including a contact finger, having a camming surface on the current carrying portion thereof biased toward said movable contact member and camming means for coopcrating with said camming surface to prevent said contact finger from engaging said movable contact member except when said movable contact member is in a predetermined position.

14. In a circuit interrupter, a stationary contact assemblage, and a longitudinally movable contact member for cooperating therewith to open and to close the circuit, said stationary contact assemblage including a pair of opposed contact fingers biased toward each other and adapted to engage said movable contact member when said circuit interrupter is in the closed position, and camming means for causing said opposed fingers to disengage said movable contact member when said contact member reaches a predetermined position in the space between said opposing fingers during the opening operation of said interrupter.

15. In a circuit interrupter, a stationary contact assemblage, and a cooperating movable contact member for opening and closing the circuit, said stationary contact assemblage including a pair of opposed contact fingers biased toward each other and adapted to engage said movable contact member when said circuit interrupter is in the closed position, and camming means for causing said opposed contact fingers to separate and thereby disengage said movable contact member at a predetermined point during the opening operation of the interrupter, said camming means including a member movable between said opposed contact fingers.

16. In a circuit interrupter, a stationary contact assemblage, and a cooperating movable con-. tact member for opening and closing the circuit,

said stationary contact assemblage including --a pair of opposed contact fingers biased toward each other and adapted to engage said movable contact member when said circuit breaker is in the closed position, and camming means for causing said opposed contact fingers to separate and thereby disengage said movable contact member at a predetermined point during the opening operation of the interrupter, said camming means including a member having at least one camming surface which is adapted to move between said opposed contact fingers, at least one of the opposing surfaces of said fingers having a camming surface for coacting with the corresponding surface on said movable member.

17. In a circuit interrupter, a contact assemblage, and a cooperating contact member movaway from the path of movement of said movable contact member and thereby disengage said movable contact when said movable contact member has reached a predetermined position during the opening operation.

' WINTHROP M. LEEDS.

ROSWELL C. VAN SICKLE.

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