US3920941A

US3920941A - Contact-operating mechanism for breaking vacuum interrupter contact-welds by bending action of the movable contact rod

Info

Publication number: US3920941A
Application number: US293286A
Authority: US
Inventors: Richard L Hundstad
Original assignee: Westinghouse Electric Corp
Current assignee: ABB Inc USA
Priority date: 1972-08-10
Filing date: 1972-09-28
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18

Abstract

An improved weld-breaking operating mechanism is provided for a vacuum interrupter, including various means for effecting lateral bending motion of the movable contact-operating rod.

Description

United States Patent [191 Hundstad NOV. 18, 1975 CONTACT-OPERATING MECHANISM FOR BREAKING VACUUM INTERRUPT ER CONTACT-WELDS BY BENDING ACTION OF THE MOVABLE CONTACT ROD Inventor: Richard L. Hundstad, Pittsburgh,

Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: Sept. 28, 1972 App]. No.: 293,286 7 Related U.S. Application Data Continuation-impart of Ser. No. 279,566, Aug. 10, 1972.

US. Cl 200/144 B Int. Cl. H0lh 33/66 Field of Search 200/144 B CERAMIC [56] References Cited UNITED STATES PATENTS 1.819.154 8/1931 ESchho1Z 200/144 B 3.405.245 10/1968 Toshio lto et a1 t 200/144 B 3,472,981 10/1969 McCarty et a1. 200/144 B 3,591,742 7/1971 Hundstad 200/144 B 3,591.74 7/1971 Ranheim 200/144 B Primary E.\'aminerRobert S, Macon Attorney, Agent, or FirmW. R. Crout [57] ABSTRACT An improved weld-breaking operating mechanism is provided for a vacuum interrupter, including various means for effecting lateral bending motion of the movable contact-operating rod.

12 Claims, 10 Drawing Figures U.S. Patent Nov. 18, 1975 Sheet 1 of2 3920 941 CERAMIC CERAMIC FIGS US. Patent Nov. 18, 1975 Sheet 2 of2 3,920,941

FIG.4

CERAMIC OPENING CONTACT-OPERATING MECHANISM FOR BREAKING VACUUM INTERRUPTER CONTACT-WELDS BY BENDING ACTION OF THE MOVABLE CONTACT ROD CROSS-REFERENCE TO RELATED APPLICATIONS This patent application is a continuation-in-part patent application based on my patent application filed. Aug. 10, 1972, Ser. No. 279,566.

Also attention is directed to U.S. Patent application filed May 3, 1972, Ser. No. 249,992 by Richard L. Hundstad, continued in patent application Ser. No. 416,470 filed Nov. 16, 1973.

Additional reference may be made to patent application Ser. No. 249,990, filed May 3, l972 and also reference may be made to patent application Ser. No. 249,990, filed May 3, 1972, all of said patent applications being assigned to the assignee of the instant patent application.

EMBODIMENTS OF THE INVENTION One arrangement provides a bearing means for the movable contact rod of the movable contact having a lateral clearance space therein for thereby accommodating lateral bending movement of the movable contact rod, and operating means are additionally provided for exerting combined lateral and tension-reaction forces on the movable contact rod during the opening operation to create weld-freeing stresses between the separable contacts on opening.

Another modified-type operating mechanism includes an actuating member having a forked, or bifurcated end portion carrying a pin therethrough, which pin passes through an angularly-extending slot provided in the end of the movable contact-operating rod, so that during closing, the pin is on line with the central axis of the interrupter, whereas during the pin forces, by cam action exerted on the side of the slot, an upward bending movement on the movable contact-operating rod.

Another arrangement provides double-acting bifurcated rods having an interconnecting member pinned thereto and laterally displaced therewith, so that during closing, a force may be exerted one way, and during opening, the force on the movable contact stem may be exerted in the opposite way.

Another modified-type of contact-operating mechanism includes a bifurcated actuating member having a pair of pins extending rigidly therethrough. A cooperating end portion of the contact stern extends between the furcations, and has suitably-arranged slots provided therein, so that during closing, the one pin remains on line with the center axis of the interrupter device, whereas on opening, the other pin, carried by the actuating member, engages the end of the laterally-displaced slot, and effects a lateral bending moment applied to the movable contact-operating rod.

Attention is directed to U.S. patent application filed May 3, 1972, Ser. No. 249,992, by Richard L. Hundstad, continued in application, Ser. No. 416,470, filed Nov..l6, 1973 and assigned tothe assignee of the instant application.

BACKGROUNDVOF THE INVENTION proved Weld-Break Characteristics," each separable contact of the vacuum type circuit interrupter comprises multiple contact surfaces, which are resiliently attached to the main body of the contact by contactsurface-supporting means. The contact-surface-supporting means are constructed so that if contact sur faces are welded, and if force is applied to separate the contacts, a non-uniform stress distribution is set up in any weld at the contact surfaces. This stress concentration, due to the elastic bending of the contact-surfacesupporting means, aids in breaking the weld, and allowingthe contacts to separate. Additional reference may be made to patent application Ser. No. 249,990, filing date May 3, 1972, (W. E. 42,454), which is also assigned to the same assignee as the present application.

One of the problems in the interruption of vacuumtype circuit interrupters is the welding problem, which must be overcome. All of the vacuum circuit-interrupter designs known to me have electrode stems and contact surfaces geometrically arranged, so that the welds, which are formed between the contacts, must be broken by almost pure tension. In other words, the lines of action of the forces used to pull the separable contacts apart, are concurrent with the center of the contact area. A deviation of the foregoing is my U.S. Pat. No. 3,591,742, issued July 6, 1971, and assigned to the Westinghouse Electric Corporation. In this U.S. Pat. No. 3,591,742, the separable contacts are provided with an asymmetric arrangement or configuration, which will aid in breaking welds by accomplishing a tearing, or bending action, upon the separable contacts at the initial time of contact separation during the opening operation. Reference is made herein to FIG. 2 of said U.S. Pat. No. 3,591,742 to illustrate such a tearing action.

Other patents relating to the welding problem, consider the use of low-weld-strength contact materials, involving metals, such as copper, with a small percentage ofa metal, such as bismuth. Consider, for example, patents of the type, such as Lafferty U.S. Pat. No. 2,975,225, and Lafferty et al U.S. Pat. No. 3,246,979, as examples of such patents. The materials, covered by the aforesaid patents, have a very low mechanical strength, and therefore do not have as severe a weld problem. Another partial solution to the weld problem is to choose metals, or combinations of metals, which produce brittle materials at the electrode interface. In general, the approach to the problem of contact welding has been to choose specific metals, or combinations of metals, which are mechanically weak, or which produce weak, or brittle materials at the reactive interface between the separable contacts.

'A disadvantage arises from contact surfaces, which have a low mechanical strength. Lower mechanical strength generally connotes a depressed high-voltage withstand ability. Also, lower mechanical strength materials are generally more prone to erosion.

SUMMARY OF THE INVENTION operation, to move the movable contact stem laterally through an angularly-extending slot in the end of the v contact-operating rod.

Another embodiment of the present invention includes two bifurcated members, one the actuating member and the other the contact-operating rod member, with an interposed connecting member having the pins extending therethrough in laterally-displaced relationship.

Another embodiment of the invention includes a bifurcated actuating member having two pins extending rigidly therethrough, which pass through a pair oflaterally-displaced slots provided in the end portion of the movable contact-operating rod, the arrangement being such that the one pin is on the center line of the device, and makes engagement with the end of the slot during closing, whereas during opening, the other pin engages the laterally-displaced slot first, thereby exerting an upward bending action on the movable contact-operating stem.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, partly in section, of a circuit interrupter embodying the principles of the present invention, with the contact structure being illustrated in the closed-circuit position;

FIG. .2 is a view similar to FIG. I, but illustrating the contacts during the initial portion of the opening operation;

FIG. 3 is a fragmentary detailed view illustrating the bending action exerted on the separable contacts;

' FIG. 4 is a view somewhat similar to FIG. 2, but illustrating, in an enlarged manner, the bending action and its effect upon the separable contacts;

FIG. 5 illustrates a modified form of the invention with the contacts illustrated in the closed-circuit position;

FIG. 6 is a fragmentary detailed view illustrating the bending stress exerted on the movable contact stem of FIG. 5 during the opening operation;

FIG. 6a is a detailed sectional view along the line 6A6A of FIG. 6 showing more clearly the bifurcated construction;

FIG. 7 is a view of a modified-type of arrangement illustrating bending actions exerted during the opening and closing movements; and,

FIGS. 8 and 9 illustrate, respectively, still further embodiments of the bifurcated linkage in which the bifurcated actuating member carries a pair of laterally-displaced pins fixedly secured thereto, which pass through corresponding slots provided in the end portion of the movable contact-operating stem, FIG. 8 illustrating the arrangement of the closed position with one pin on the center line of the device, and FIG. 9 illustrating the bending action exerted on the device during the opening operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1, the reference numeral 1 generally designates a vacuum-type circuit interrupter. As' well known by those skilled in the art, the vacuum interrupter 1 comprises a pair of'separable contacts 2 and 3, disposed interiorly within casing means 4; The'stationary contact 2 is'affixed to a stationary contact stem 6, the latter being affixed to an end plate 8 closing one end of the vacuum envelope 4. The cooperable movable contact 3 is affixed to a movable operating contact stem 10, the latter extending through an interrupter bearing 12 secured to the other end closure plate 14 of the interrupter, and permitting a fulcrum action to be exerted upon the movable contact stem 10.

As illustrated in FIG. I, in the closed-circuit position i of the interrupter l, as illustrated in FIG. 1, the electrical current path extends from the terminal conductor L to the contact stem 6 to the stationary contact 2, thence through the movable contact 3 through the contact stem 10, to the flexible connector 16 to the other terminal L of the interrupter.

During the opening operation, the movable contact operating stem is moved rightwardly, as viewed in FIG. 1, by an operating mechanism 18. In more detail,

. this operating mechanism 18 comprises the elongated movable operating contact stem 10, which extends' through a bearing means 20 having a clearance space provided on the top side thereof, as indicated by the reference numeral 22 in FIG. 1. The righthand end 10a of the movable contact operating stem 10 is pivotally connected, as at 24, to an angularly-extending movable thrust-rod 26, having an end cap portion 28, which is engaged by a hammer blow from a relatively heavy sleeve 30, which is biased in the opening direction by an opening spring 32. Additionally, an overtravel spring 34 is provided, seating upon the spring seat 26a, forming an integral part of the operating rod 26, and providing a desired overtravel in the closed circuit position of the device 1, as illustrated in FIG. 1.

The mechanism overtravel distance is indicated by the distance A in FIG. 1. The contact travel, in the opening direction is indicated by the distance space. 8" illustrated in FIG. 1. A suitable abutment 36 may be provided for stopping the opening travel of the cap portion 28.

Suitable operating means are provided to effect motion of the thrust sleeve 30, so that during the opening operation the thrust sleeve 30 is moved to the right, as viewed in FIG. 1 and after picking up the lost-motion, indicated by the reference numeral 38, picks up the cap portion 28, and exerts a lateral levering action upon the movable contact operating stem 10, as afforded by the fulcrum interrupter bearing 12. It will be noted, in this connection, that the bearing 20 is provided with a clearance space 22 above the electrode stem 10 when the contacts 2, 3 are closed. When the mechanism 18 starts to open, the electrode stem 10 is bent upwardly, thereby taking up the clearance 22 at the top of the bearing 20, and subjecting the electrode stem 10 to a bending movement, as illustrated more clearly in FIG. 2 of the drawings. The bending moment is resisted by the contact weld. A resulting stress concentration is thereby set up, which acts, in conjunction'with the impact loading, to aid in weld breaking. Preferably, the

- electrode operating rod, or stem 10 has sufficient strength that it can support a bending moment to be ex-' erted upon the contact surfaces.

The mechanism 18 has the important additional advantage of reducing contact resistance. As the contacts 2 and 3 are brought together, the vibrational motion,

imported to the movable electrode stem 10 by the 'function of the mechanism 18.

fways, the desired bending action movable contact operating stem.

together more intimately.

mechanism 18, will tend to make the contacts 2, 3'sea't:

FIGS. 3 and 4 illustrate, in more detail, and to 'aneh- I 'larged scale, the reaction forces between the movable contact stem and the

interrupter bearings

12, 20. It

will be noted that there-is a combined tensile and lat- .45 extending laterallytherethrough, as more clearly shown in FIG. 6a of the drawings. The pin 45 is on the center line 46 of the device so that during the closed position, the pin 45 forces the contacts 2, 3 together directly along the center line 46 of the device During the opening operation, however, as illustrated more clearly in FIG. 6, a camming action occurs, as the pin 45 moves along the angularly'extending slot 48 a distance D provided in the end portion 10a oflthe movable contact operating stem 10. The result is an upward bending action F (FIG. 6) exertedon the movable contact operating stem 10, in addition to the axial retracting force exerted thereon during the opening operation.

FIG. 7 illustrates an alternate modification in which the bifurcated actuating member 50 has a fixed pin 51 passing therethrough, which additionally passes through an interconnecting member 52, the upper portion of which is pivotally linked-at 53 to a bifurcated '.Itis'the:intention ofthe the aforesaid various means, and other alternate means, .which-will readily suggestthemselvesto those opening operation.

end portion 54 of the movable contact operating stem 55. It will be observed that during the closing operation, there is provided an upperward thrust exerted upon the movable contact operating stem 55, and during the opening operation, a downward bending action will be exerted on the movable contact operating stem 55, thereby freeing any welds formed at the separable contacts 2, 3. v

FIGS. 8 and 9 illustrate'still a further embodiment of the invention, in which both the actuating member 60 'and the movable contact operating stem 61 are provided with pin-and-slot connections such that during the closing operation, the pin 63, fixedly secured to the bifurcated end of the actuating member 60, is on the center line 46 of the device, and provides an on-line closing force at the contact structure 2, 3. During opening, however the upper pin 70, carried by the bifurcated end 61a of the actuating member 61, strikes the end of the upper slot 80, thereby creates a downward bending action exerted u ating stem 61; a

From the foregoing description, it will be apparent that there has been provided an improved operating mechanism 18 for a vacuum-type circuit interrupter 1 utilizing a pair of spaced

bearings

12, 20, one of which 20 has a lateral clearance space 22 for therein accommodating both tensile and lateral stress forces exerted upon the movable contact stem 10 by the operating pon the movable contact operjmechanism 18. Obviously, various types of operating jmechanisms may be utilized, alternately, to afford the desired travel of the movable thrust sleeve 30.

In addition, I have illustrated additional modified types of operating mechanisms, which provide, in other combination:

present application to cover skilled in the art, to effect'a lateral bending movement of the movable operating contact stem to createweld- Although there have been illustrated and described specific structures, it is to be clearly understood that Y the same were merely for the'purpose of illustration,

and that changes and modifications may readily be made therein by thoseskilled in the art, for effecting lateral bending motion of the movable contact stem, without-departing from the spirit and scope of the invention. I

I claim:

1. A vacuum-type high-power circuit-interrupter of the type in which welding occurs between the contacts in the closed-circuit position thereof, comprising, in

a. means defining an evacuatedenvelope;

b. cooperable separable contact means disposed interiorly of said evacuated envelope and including a movable contact, anda stationary contact cooperable therewith in the closed-circuit position of the device;

c. an elongated movable contact stem 10) for actuating the movable contact (3) in its opening and closing motions away from said stationary contact;

d. contact-operating means for effecting a combined lateral bending stress-force exerted laterally upon the movable-contact operating stem in addition to a tensile axial opening retracting stress-force exerted upon said movable-contact operating stem; and, I I said lateral bending stress-force being sufficient in magnitude in bending action that any welds exist- 2 ing between the closed contacts in the closed-circuit position of the device will be torn apart during the opening operation by such aforesaid adequate .bending action. I

2. The combination according to claim 1, wherein bearing means for said movable stem has a lateral clearance space (22) for accommodating lateral bendactuating member operating by the mechanism, and

the other provided at the'end portion of the movable contact operating stem, and an interconnecting member having a pairof laterally-displaced pin connections to the aforesaid two bifurcated members.

5. A vacuum-type high-power circuit-interrupter ol the type in which welding occurs between the contact:

1 in the closed-circuit position thereof, comprising ir combination,

exerted upon thev I movablecontact and a stationarycontact cooper a. means defining an evacuated envelope;

b. cooperable separable contactmeans disposed interiorly of said evacuated'envelope and including 2 able therewith in. the closed-circuit, position' of the device; t l t c.. an elongated movable contact stem for actuating the movable contact (3)lin its opening and closing motions away from said stationary contact;

d. contact operating means for effecting a combined lateral bending stress-force exerted laterally upon themovable contact operating stem in addition to a tensile axial opening retracting stress-force exerted upon said movable contact operating stem;

e. said contact-operating means comprising bearing means for said movable stem having a lateral clearancespace (22) for accommodating lateral movement of said stem (10); and,

f. said lateral bending stress-force being sufficient in magnitude in bending action that any welds existing between the closed contacts in the closed-circuit position of the device will be torn apart during the opening operation by such aforesaid adequate bending action. I

6. The combination according to claim 5, wherein an operating rod (26) is pivotally connected to one extremity of the movable contact stem (10), and exerts an off-center reaction to said movable contact stem 7. The combination according to claim 5, wherein an opening spring (32) is provided to accelerate the opening operation of the interrupter[ 8. The combination according to claim 5, wherein an additional overtravel spring (34) is provided to assist in providing a desired contact pressure in the closed-circuit position of the device.

9. The combination according to claim 1, wherein movable sleeve means provides a hammer-blow on said movable contact operating stem (10) for effecting a lateral motion thereon during the opening movement thereof.

10. The combination according to claim 9, wherein a pair of serially-related springs are provided, one of which is an opening spring and the other of which being a an overtravel spring. 11. A vacuum-type circuit interrupter comprising, in

- combination:

f. a fulcrum bearing (12) being provided adjacent one end of the vacuum envelope, and permitting a desired levering action upon the movable contact stem (l0).

12. A vacuum-type circuit interrupter comprising, in

combination:

a. means defining an evacuated envelope;

b. separable contact means disposed interiorly within said evacuated envelope and including a movable contact;

0. an elongated movable contact stem (10) for operating the movable contact (3) in its opening and closing operations; a

(1. operating means providing a lateral bending weldbreaking force upon said movable contact operating stem to exert thereby lateral and tension-reaction forces on said movable-contact stem; and,

e. two bearing means being provided, one of said bearing means being located adjacent the end of the vacuum envelope, and the other bearing means being provided adjacent the end of the movable contact operating stem.

Claims

1. A vacuum-type high-power circuit-interrupter of the type in which welding occurs between the contacts in the closed-circuit position thereof, comprising, in combination: a. means defining an evacuated envelope; b. cooperable separable contact means disposed interiorly of said evacuated envelope and including a movable contact and a stationary contact cooperable therewith in the closed-circuit position of the device; c. an elongated movable contact stem (10) for actuating the movable contact (3) in its opening and closing motions away from said stationary contact; d. contact-operating means for effecting a combined lateral bending stress-force exerted laterally upon the movable-contact operating stem in addition to a tensile axial opening retracting stress-force exerted upon said movable-contact operating stem; and, e. said lateral bending stress-force being sufficient in magnitude in bending action that any welds existing between the closed contacts in the closed-circuit position of the device will be torn apart during the opening operation by such aforesaid adequate bending action.

2. The combination according to claim 1, wherein bearing means for said movable stem has a lateral clearance space (22) for accommodating lateral bending movement of said stem.

3. The combination according to claim 1, wherein a bifurcated actuating member is provided having a pin carried therewith, and the end portion of the movable contact operating stem has an angularly-arranged slot provided therein for effecting combined bending and axial forces upon the movable contact during the opening operation.

4. The combination according to claim 1, wherein two bifurcated members are provided, one being the actuating member operating by the mechanism, and the other provided at the end portion of the movable contact operating stem, and an interconnecting member having a pair of laterally-displaced pin connections to the aforesaid two bifurcated members.

5. A vacuum-type high-power circuit-interrupter of the type in which welding occurs between the contacts in the closed-circuit position thereof, comprising, in combination, a. means defining an evacuated envelope; b. cooperable separable contact means disposed interiorly of said evacuated envelope and including a movable contact and a stationary contact cooperable therewith in the closed-circuit position of the device; c. an elongated movable contact stem (10) for actuating the movable contact (3) in its opening and closing motions away from said stationary contact; d. contact-operating means for effecting a combined lateral bending stress-force exerted laterally upon the movable contact operating stem in addition to a tensile axial opening retracting stress-force exerted upon said movable contact operating stem; e. said contact-operating means comprising bearing means for said movable stem having a lateral clearance space (22) for accommodating lateral movement of said stem (10); and, f. said lateral bending stress-force being sufficient in magnitude in bending action that any welds existing between the closed contacts in the closed-circuit position of the device will be torn apart during the opening operation by such aforesaid adequate bending action.

6. The combination according to claim 5, wherein an operating rod (26) is pivotally connected to one extremity of the movable contact stem (10), and exerts an off-center reaction to said movable contact stem (10).

7. The combination according to claim 5, wherein an opening spring (32) is provided to accelerate the opening operation of the interrupter.

8. The combination according to claim 5, wherein an additional overtravel spring (34) is provided to assist in providing a desired contact pressure in the closed-circuit position of the device.

10. The combination according to claim 9, wherein a pair of serially-related springs are provided, one of which is an opening spring and the other of which being an overtravel spring.

11. A vacuum-type circuit interrupter comprising, in combination: a. means defining an evacuated envelope; b. separable contact means disposed interiorly of said evacuated envelope including a movable contact; c. an elongated movable stem (10) for operating the movable contact (3) in its opening and closing motions; d. bearing means for said movable stem having a lateral clearance space (22) for accommodating lateral movement of said stem (10); e. operating means (18) for exerting combined lateral and tension reaction forces on said movable stem (10) during the opening operation to create weld-freeing stresses between the separable contacts on opening; and, f. a fulcrum bearing (12) being provided adjacent one end of the vacuum envelope, and permitting a desired levering action upon the movable contact stem (10).

12. A vacuum-type circuit interrupter comprising, in combination: a. means defining an evacuated envelope; b. separable contact means disposed interiorly within said evacuated envelope and including a movable contact; c. an elongated movable contact stem (10) for operating the movable contact (3) in its opening and closing operations; d. operating means providing a lateral bending weld-breaking force upon said movable contact operating stem to exert thereby lateral and tension-reaction forces on said movable-contact stem; And, e. two bearing means being provided, one of said bearing means being located adjacent the end of the vacuum envelope, and the other bearing means being provided adjacent the end of the movable contact operating stem.