[0001] FIELD

[0002] The invention relates to high voltage, dead tank circuit breakers and, more particularly, to linkage structure for transmitting energy from an operating mechanism simultaneously to poles of the circuit breaker while maintaining the linkage structure in tension.

[0003] BACKGROUND

[0004] Circuit breakers are commonly found in substations and are operable to selectively open and close electrical connections. Typical dead tank circuit breakers have pole assemblies that include first and second electrical conductors in associated bushings. As is known in the art, electrical power lines are coupled to first and second electrical conductors, and the circuit breaker selectively opens or closes the electrical connection there-between. A bell crank or other actuating assembly is associated with a respective pole assembly. The bell cranks are interconnected by a gang-style rotary or push- pull linkage so that all three poles assemblies are actuated at the same time by a single operating mechanism.

[0005] As voltage ratings for three pole operated, dead tank circuit breakers become larger, the pole spread gets larger. As a result, conventional rotary or push-pull inter-phase linkage introduce lag into the breaker operation. To prevent lag, the linkage must be made larger, increasing weight and the energy required of the operating mechanism. In push-pull configurations, the rod of the linkage must stand up to compression over a long time span, which can lead to buckling.

[0006] Thus, there is a need to provide circuit breaker linkage structure that uses a pull- pull configuration where the inter-phase connection rods are always in tension. SUMMARY

An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is obtained by providing linkage structure for connection between an operating mechanism and at least one actuating assembly of a circuit breaker for opening and closing a movable electrical contact of a pole assembly associated with the actuating assembly. The linkage structure includes at least one lever constructed and arranged to connect with the at least one actuating assembly. At least one connection rod is coupled to the lever and is associated with a close spring for closing the electrical contact. At least one spring structure is coupled to the lever. The spring structure includes at least one open spring providing a spring force on the lever for opening the electrical contact while maintaining the connection rod in tension.

In accordance with another aspect of the disclosed embodiment, a method is provided for maintaining pretension on linkage structure connected between an operating mechanism and at least one actuating assembly of a circuit breaker. The method couples at least one lever with the at least one actuating assembly for opening and closing a movable electrical contact of a pole assembly associated with the actuating assembly. At least one connection rod is coupled to the lever. The connection rod is associated with a close spring for closing the electrical contact. At least one spring structure is coupled to the lever. The spring structure includes at least one open spring providing a spring force on the lever for opening the electrical contact while maintaining the connection rod in tension.

Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. [0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:

[0013] FIG. 1 is a front view of a high voltage, three pole operated dead tank circuit breaker having an interphase linkage structure in accordance with an embodiment.

[0014] FIG. 2 is a schematic view of an interior of a breaker pole of the circuit breaker of

FIG. 1 , wherein the electrical contacts are open.

[0015] FIG. 3 is a side view of the linkage structure of the circuit breaker of FIG. 2 with housings removed.

[0016] FIG. 4 is an enlarged side view of the portion of the linkage structure encircled at

A in FIG. 3, showing a lever, an open spring, and interphase connection rods.

[0017] DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0018] With reference to FIG. 1 , a circuit breaker is shown , generally indicated at

10. Circuit breaker 1 0 is preferably a three phase circuit breaker and thus includes three pole assemblies 1 2a, 1 2b and 1 2c. Each pole assembly 12 includes a first electrical conductor 14 carried in a first bushing 1 6 and a second electrical conductor 1 8 carried in a second bushing 20. Electrical power lines are coupled to the first and second electrical conductors 14 and 18, and the circuit breaker 10 selectively opens or closes the electrical connection there-between.

[0019] With reference to FIG. 2, a simplified view of an interior of pole assembly 12 is shown, wherein first electrical conductor 14 is electrically connected to a stationary contact 22 which is immovably secured within pole assembly 12. Second electrical conductor 18 is electrically connected to a movable contact 24 which is carried within pole assembly 12 in a manner allowing longitudinal movement therein. Thus, in a first position, the movable contact 24 may be positioned to break the electrical connection between first the electrical conductor 14 and second electrical conductor 18 (FIG. 2). In a second position, the movable contact 24 may be brought into contact with stationary contact 22 to electrically connect the first electrical conductor 14 and the second electrical conductor 18. The interior space of pole assemblies 12 are sealed and generally adapted to minimize arcing between stationary contact 22 and movable contact 24. The interior volume of pole assembly 12 may be filled with dielectric mediums that include SF6, dry air, dry nitrogen, C0 ₂ or oil. Alternatively, a vacuum-type interrupter could be employed within the tank volume surrounded by dielectric mediums mentioned.

[0020] With reference to FIG. 3, an actuating assembly, preferably in the form of a bell crank assembly 25a, 25b, 25c, is coupled with the movable electrical contact 24 of a respective pole assembly 12a, 12b and 12c for opening and closing the electrical connection between conductors 14 and 18. The bell crank assemblies are conventional and can be of the type disclosed in U.S. Patent Application Publication No. 20100270136 A1 , the content of which is hereby incorporated by reference into this specification. The bell crank assemblies are interconnected by a gang-style, non-rotary, pull-pull linkage structure, generally indicated at 27, so that all three poles assemblies are actuated at the same time by a single, electrically controlled operating mechanism 30.

[0021 ] With reference to FIG. 3, the linkage structure 27 includes a lever 32a, 32b and

32c coupled with a respective bell crank assembly 25a, 25b and 25c for opening and closing the electrical connection at the associated pole assembly (e.g., 12b). In particular and as best shown in FIG. 4, each lever (e.g., lever 32b) is coupled via a crank link 34 with the associated bell crank assembly (e.g., bell crank assembly 25b). An interphase connecting rod 36 is coupled to the lever 32b at pin connection 38. The other end (not shown in FIG. 4) of the connection rod 36 is coupled lever 32c. Connection rod 36' is coupled between levers 32b and 32a. Thus, for three pole circuit breaker, three levers 32a, 32b and 32c are provided, interconnected by two connection rods 36 and 36'. Rod 37 (FIG. 1 ) is coupled to lever 32c and to a close spring 39 in the operating mechanism 29 for closing the circuit breaker 1 0. Since the levers 32a, 32b and 32c are interconnected via the connection rods 36, 36' and rod 37, the levers move simultaneously upon actuating of the mechanism 30 to operate the bell crank assemblies simultaneously.

[0022] As shown in FIGs. 3 and 4, an open spring structure 40a, 40b and 40c is coupled to a respective lever 32a, 32b and 32c. For example, an end of link 42 of the spring structure 40 is coupled by a pin connection 44 to the lever 32b. The other end of the link 42 is coupled to an end of an open coil spring 46. The open springs 46 provide the force opposing the close spring 39 for opening electrical the electrical conductors 14, 18 of the circuit breaker 10. Spring 46 of the spring structure 40 also provides a spring force on the associated lever 32 and thus maintains the connecting rods 36, 36' in tension. In the embodiment, three spring structures 40 are provided, one for each pole assembly 12 with the total spring force of the open springs 46 opposing the spring force of the close spring 39. However, instead of providing three separate open springs 46, a single open spring 46 can be provided, for example, at only pole assembly 12a that opposes the force of the close spring 39.

[0023] Since the connection rods 36, 36 are always in tension, the size thereof can be is minimized since buckling and torsion are not present. The pull-pull configuration as compared to the rotary and push-pull systems requires the smallest interphase connection rods, which ensures a compact configuration requiring less energy for operation, reduces shipping weight of the breaker 10, and reduces lag time.

[0024] The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.