Patent Publication Number: US-8975548-B2

Title: Retaining structure for maintaining factory settings of gang-style linkage for high voltage dead tank breaker while operating mechanism is removed

Description:
FIELD 
     The invention relates to high voltage, dead tank circuit breakers and, more particularly, to structure for maintaining the factory pretension of a spring and thus linkage when an operating mechanism is removed from the breaker. 
     BACKGROUND 
     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 linkage so that all three poles assemblies are actuated at the same time by a single operating mechanism. 
     In shipping the circuit breaker to its installation location, it is desirable to remove the operating mechanism from the linkage so that the breaker can be shipped one truck. On such spring-open, spring-close driven circuit breakers, the pretension setting of a stand-alone open spring must be removed prior to removing the operating mechanism. This eliminates forces on a linkage which could injure the worker when removing the operating mechanism for shipping or servicing. However, when the operating mechanism is reattached, the factory pretension spring setting on the linkage is lost. 
     There is a need to provide structure to maintain factory spring pretension on a linkage of a circuit breaker when the operating mechanism is removed from the breaker. 
     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 an 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 lever and is associated with a close spring for closing the electrical contact. At least one spring structure is coupled to the lever and is constructed and arranged to open the electrical contact. The spring structure includes an open spring providing a spring force on the lever for opening the electrical contact. The open spring places the connection rod in tension. At least one retaining structure is associated with the lever and the spring structure and is constructed and arranged to ensure that the spring force of the open spring, exerted on the lever, is directed to the retaining structure so that tension on the connection rod is removed, enabling the connection rod to be serviced. 
     In accordance with another aspect of the disclosed embodiment, a method maintains pretension on linkage structure connected between an operating mechanism and at least one actuating assembly of a circuit breaker. The linkage structure includes at least one lever constructed and arranged to connect with the at least one actuating assembly for opening and closing an electrical contact of a pole assembly associated with the actuating assembly, at least one connection rod coupled to the lever and associated with a close spring for closing the electrical contact, and at least one spring structure coupled to the lever. The spring structure includes an open spring providing a spring force on the lever for opening the electrical contact. The open spring places the connection rod in tension. The method associates retaining structure with the lever and the spring structure. The retaining structure is adjusted to ensure that the spring force of the open spring, exerted on the lever, is directed to the retaining structure so that tension on the connection rod is removed, enabling the connection rod to be serviced. After servicing the connection rod, the retaining structure is further adjusted to redirect the spring force from the retaining structure back to the lever. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         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. 
         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. 
         FIG. 3  is an enlarged side view of a portion of the linkage structure associated with a pole assembly, with a lever, an open spring, and interphase connection rods. 
         FIG. 4  is a side view of a bell crank coupled to a pole assembly of circuit breaker of  FIG. 1 , with retaining structure coupled to a portion of the linkage structure of  FIG. 3 , in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT 
     With reference to  FIG. 1 , a circuit breaker is shown, generally indicated at  10 . Circuit breaker  10  is a three phase circuit breaker, and thus includes three pole assemblies  12   a ,  12   b  and  12   c . Each pole assembly  12  includes a first electrical conductor  14  carried in a first bushing  16  and a second electrical conductor  18  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. 
     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, CO2 or oil. Alternatively, a vacuum-type interrupter could be employed within the tank volume surrounded by dielectric mediums mentioned. 
     Returning to  FIG. 1 , an actuating assembly, preferably in the form of a bell crank assembly  25   a ,  25   b ,  25   c , is coupled with the movable electrical contact  24  of a respective pole assembly  12   a ,  12   b  and  12   c  for opening and closing the electrical connection between electrical conductors  14  and  18 . The bell crank assemblies are conventional and can be of the type disclosed in U.S. 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 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  29 . 
     With reference to  FIG. 3 , the linkage structure  27  includes at least one pull-pull interphase connecting rod  30  and a lever  32  coupled to one end  34  of a connection rod  30 . The other end (not shown) of the connection rod  30  is coupled to another lever  32  (not shown) at another bell crank assembly. Thus, for three pole circuit breaker, three levers  32  are provided, interconnected by two connection rods  30 . Each lever  32  is connected to linkage  36  of the associated bell crank assembly (e.g.,  25   b ) for opening and closing the electrical connection at the associated pole assembly (e.g.,  12   b ). The connecting rods  30 , interconnected via the levers  32 , are coupled to a conventional close spring  39  ( FIG. 1 ) in the operating mechanism  29  for closing the circuit breaker  10 . Each connecting rod  30  is coupled to an open spring structure, generally indicated at  40 , via end  42  of the lever  32  that is coupled to a link  44  of the spring structure  40 . The other end of the link  44  is coupled to an end of an open spring  46 . The open springs  46  provide the force opposing the close spring  39  for opening the electrical connections of the circuit breaker  10 . Spring  46  of the spring structure  40  also provides a spring force on the associated lever  32  and thus keeps the connecting rods  30  in tension. In the embodiment, three spring structures  40  are provided, one for each pole assembly  12 . However, instead of providing three separate open spring structures  40 , a single open spring  46  can be provided, for example, at pole assembly  12   a.    
     As noted above, it may be necessary to remove the operating mechanism  29  from the linkage structure  27  for service, such as maintenance or shipping. Prior to removing the operating mechanism  29  and before any factory set spring tension (via springs  46 ) is removed from the linkage structure  27 , retaining structure, generally indicated at  48 , is associated with the linkage structure  27  near at least one of the bell crank assemblies, (e.g., assembly  25   c ). With reference to  FIG. 4 , the retaining structure  48  includes an engaging member  50  associated at one end  52  with a threaded screw  54  and nut  55 . The other end  56  of the screw  54  is coupled to a housing  58  for rotation. The engaging member  50  fits over a connection pin  60  that connects the link  44  of the spring structure  40  to the associated lever  32 . The screw  54  is rotated in a first direction to tighten the screw  54  into the nut  55  and thus securing the screw with respect to the engaging member  50 . The nut  55  can be considered to be part of the engaging member  50  and thus integral therewith. As the screw  54  tightens, the force of the open springs  46  increases but the force is redirected from the levers  32  to the screw  54 . With the force off the levers  32 , which transmits force to the inter-phase connecting rods  30 , one may work on the inter-phase connecting rods  30  safely, or disconnect the connecting rods  30  from the operating mechanism  29  for shipping of the circuit breaker  10 . 
     After servicing is complete, the screw  54  is rotated in a direction opposite the first direction to loosen the screw  54  with respect to the engaging member  50 . As the screw  54  loosens, force is slowly redirected from the screw  54  to the levers  32  until the levers take all of the force of springs  46 . At that point, the factory pretension setting is back on the linkage structure  27  since no settings were changed during servicing. 
     Servicing includes maintenance, repair work, shipping, and any other act in which it would be useful to hold pretension. The retaining structure  48  is configured in an appropriate size and of appropriate material for the application. 
     Although one retaining structure  48  will simultaneously maintain the pretension on all three poles  12   a ,  12   b , and  12   c , a retaining structure  48  can be provided at each pole for increased safety at a particular pole being serviced. 
     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.