Patent Publication Number: US-2016240335-A1

Title: Circuit breaker crossbar assembly and method

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to circuit breakers and, more particularly to a circuit breaker crossbar assembly. 
     Multi-phase industrial electrical power distribution systems are protected against damage from overcurrent circuit conditions by corresponding single or multi-pole circuit breakers wherein each phase of the power distribution circuit is directed through a separate pole within the circuit breaker assembly. The overcurrent situations may be caused, for example, by short circuits or ground faults in or near such equipment. A circuit breaker may be manually switched from an “ON” condition to an “OFF” condition and vice versa. Additionally, the circuit breaker typically includes a mechanism that is configured to automatically switch the circuit breaker to an “OFF” (e.g., “TRIP”) condition in response to an undesirable operating situation, such as a short circuit, for example. 
     Circuit breakers typically include at least one pair of separable main contacts housed within a housing which typically comprises a base and a corresponding cover. The separable contacts may be operated either manually by way of an operating handle disposed on the outside of the circuit breaker housing and in operative communication with an operating mechanism disposed within the circuit breaker housing, or automatically in response to an overcurrent condition. In the automatic mode of operation, the contacts may be opened by an operating mechanism, controlled by a trip unit, or by magnetic repulsion forces generated between the stationary and movable contacts during relatively high levels of over current. Because of the potential for damage caused by the overcurrent conditions, it is desirable to trip the circuit breaker as rapidly as possible to interrupt the current flow through the circuit breaker. 
     Typically, the at least one pair of separable main contacts comprise a moveable contact and a stationary contact, wherein the moveable contact is selectively moved by the operating mechanism between the ON condition in contact with the stationary contact, and the OFF position separate from the stationary contact, and vice versa. The circuit breaker operating mechanism often includes a crossbar unit that is operatively coupled to the movable contact and arranged to rotate or otherwise move the moveable contacts between the ON and OFF conditions. 
     Various components are employed to convert the manual input or the automatic initiation of condition switching to rotation of moveable contact arm assemblies that determine a condition of the circuit breaker. Conventionally, the circuit breaker is in an “ON” or closed condition when one or more moveable contacts coupled to corresponding moveable contact arms are engaged with a respective stationary contact. Conversely, the circuit breaker is in an open, OFF or TRIP condition when the one or more moveable contacts are disengaged from the respective stationary contact. One conventional component that may rotate the moveable contact arm assemblies is a common crossbar that is rotatably coupled to the moveable contact arm assemblies. 
     Different circuit breakers require moveable contact arm assemblies that are of distinct configurations. For example, the moveable contact arm assemblies will vary in size and shape, to provide desired performance characteristics, or to obtain a desired rating for a circuit breaker. Based on the various geometries of the moveable contact arm assemblies in circuit breakers of different ratings, a custom or specifically configured crossbar is required to enable proper operation of the contact arm assembly in circuit breakers of a given rating. This requires manufacturing different crossbars, corresponding to specific contact arm assemblies and circuit breaker ratings, thereby adding time, cost and complexity to the manufacturing process. It would be desirable to provide a circuit breaker capable of using a standard crossbar that is configured to perform across a range of circuit breaker ratings, and with a variety of moveable contact arm assemblies. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, a circuit breaker crossbar assembly is provided and includes a crossbar rotatable between a first rotational position and a second rotational position, the crossbar operably coupleable to at least one moveable contact arm of the circuit breaker. The circuit breaker crossbar assembly also includes an insert member disposed in communication with the crossbar and the at least one moveable contact arm assembly to exert a force on the at least one moveable contact arm. 
     According to another aspect of the invention, a circuit breaker is provided and includes a plurality of moveable contact arm assemblies configured to conduct current through the circuit breaker. Also included is a crossbar operatively coupled to the plurality of moveable contact arm assemblies, rotatable between a first rotational position and a second rotational position. Further included a mechanism configured to selectively rotate the crossbar between the first and second rotational positions. Yet further included is a plurality of insert members, each of the plurality of insert members coupled there between the crossbar and a respective moveable contact arm assembly, and arranged to exert a force on the respective moveable contact arm assembly. 
     According to yet another aspect of the invention, a method of assembling a crossbar assembly for a circuit breaker is provided. The method includes operably coupling a portion of a moveable contact arm assembly to a crossbar, the moveable contact arm assembly selected from a plurality of distinct configurations of moveable contact arm assemblies. The method also includes manufacturing an insert member having a customized configuration that is determined by a configuration of the moveable contact arm assembly operably coupled to the crossbar. The method further includes disposing the insert member between, and into communication with, the crossbar and the moveable contact arm assembly to exert a force on the moveable contact arm. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a mechanism assembly and a crossbar assembly of a circuit breaker; 
         FIG. 2  is a perspective disassembled view of a crossbar and insert member of the circuit breaker; 
         FIG. 3  is a perspective assembled view of the crossbar coupled to a plurality of moveable contact arm assemblies and the insert member; 
         FIG. 4  is a perspective, sectional view of the crossbar assembly having an insert member according to a first embodiment to accommodate a first configuration of a moveable contact arm; and 
         FIG. 5  is a perspective, sectional view of the crossbar assembly having an insert member according to a second embodiment to accommodate a second configuration of a moveable contact arm. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a circuit breaker  10  of the multi-pole variety is partially illustrated. The circuit breaker  10  has a cover and housing removed to better illustrate various components of the circuit breaker  10  that are relevant to the embodiments of the invention described herein. The circuit breaker  10  includes a mechanism  12  that is generally referenced with numeral  12 . The mechanism  12  is configured to enable a selective switching of the circuit breaker  10  between an open and a closed state. For example, the mechanism  12  may include a number of components configured to detect a hazardous or undesirable operating condition and to initiate switching the circuit breaker  12  from a closed condition, to a tripped or open condition. Additionally, manual manipulation of the condition of the circuit breaker mechanism  12  may be selectively facilitated with a handle  14  that may be actuated by an operator. This gives the operator the ability to turn the circuit breaker  10  “ON” to energize a protected circuit, turn the circuit breaker “OFF” to disconnect the protected circuit, or reset the circuit breaker  10  from a tripped condition. Overall, the mechanism  12  converts movement of the handle  14  into mechanical force to operate the circuit breaker  10 . 
     The circuit breaker  10  illustrated depicts a three-phase configuration, however, the embodiments disclosed herein are not limited to this configuration, such that alternative phase configurations (e.g., one-phase, two-phase, four-phase, etc.) may be employed. Specifically, three moveable contact arm assemblies  16  are illustrated. For example, in the depicted embodiment, each of the moveable contact assemblies  16  may be associated with a corresponding phase of a protected circuit. The moveable contact arm assemblies  16  may comprise one or more conductive individual moveable contact arms  9 . The moveable contact arm assemblies  16  are coupled to the crossbar  19  and are selectively rotatable in response to rotation of the crossbar  19 . In an embodiment, the moveable contact arms  9  may be disposed, at least partially, within a crossbar assembly  18  that includes a crossbar  19 . The crossbar  19  extends from a first end  20  to a second end  22 . The first end  20  of the crossbar  19  is operatively rotatably coupled to a first bracket  24  disposed on a first side  26  of the circuit breaker  10 . Similarly, the second end  22  of the crossbar  19  is operatively rotatably coupled to a second bracket  28  located on a second side  30  of the circuit breaker  10 . The coupling of the crossbar to the respective first and second brackets  24 ,  28  may be made with any suitable coupling that allows selective rotation of the crossbar  19 , such as with pin joint connections. 
     In operation, the crossbar  19  rotates upon actuation from the mechanism  12  to selectively drive the moveable contact arm assemblies  16  into a position that either renders the circuit breaker  10  in the “ON” condition, the “OFF” condition, or the “TRIP” condition. Specifically, in the event an operator manually operates mechanism  12  turns the circuit breaker  10  toward the ON condition, the mechanism  12  interacts with the crossbar  19 , which in turn drives the moveable contact arm assemblies  16  toward a closed position. In the event an operator manually actuates the mechanism  12  to switch the circuit breaker  10  from an ON condition toward an OFF condition, or in the alternative, if the mechanism automatically initiates a tripping sequence, the mechanism  12  interacts with the crossbar  19 , causing it to rotate, which in turn rotates the moveable contact arm assemblies  16  toward an open position. 
     In an embodiment, the crossbar  19  includes multiple segments that are operatively coupled to the moveable contact arm assemblies  16 . In the illustrated embodiment with three moveable contact arm assemblies, a first segment  32 , a second segment  34  and a third segment  36  are included to correspond to the number of moveable contact arm assemblies. In such an embodiment, the first segment  32  is associated with a first moveable contact arm assembly  38 , the second segment  34  is associated with a second moveable contact arm assembly  40 , and the third segment  36  is associated with a third moveable contact arm assembly  42 . Disposed between each pair of segments is at least one coupling segment of the crossbar  19 . In the illustrated embodiment, a first coupling segment  44  is disposed between the first segment  32  and the second segment  34  of the crossbar  19 , and therefore between the first moveable contact arm assembly  38  and the second moveable contact arm assembly  40 . Similarly, a second coupling segment  46  is disposed between the second segment  34  and the third segment  36  of the crossbar  19 , and therefore between the second moveable contact arm assembly  40  and the third moveable contact arm assembly  42 . As noted above, the number of segments and moveable contact arm assemblies may vary depending upon the particular circuit breaker, and as a result it is to be appreciated that the number of associated coupling segments may vary as well. 
     Referring now to  FIGS. 2 and 3 , the crossbar assembly  18  is illustrated in greater detail.  FIG. 2  depicts the crossbar assembly  18  in a disassembled condition. In particular, the crossbar  19  is shown without the moveable contact arm assemblies  16  operatively coupled thereto. Additionally, a plurality of insert members  50  are shown in a pre-assembly condition. As will be appreciated from the description herein, the insert members  50  are customizable components that are manufactured to have an overall configuration, including size and shape, that is dependent upon the particular configuration of the moveable contact arm assemblies  16 . This is advantageous based on the need for distinct moveable contact arm assembly configurations and quantities in different types of circuit breakers. Rather than requiring a unique crossbar for each type of moveable contact arm, use of the insert members  50  facilitate the manufacture of a single standard crossbar that is well-suited to accommodate multiple configurations of moveable contact arm assemblies. For example, it may be less costly for a manufacturer of circuit breakers to provide a line a circuit breakers having several models or frames, each model or frame having a different current rating associated with different moveable contact arm assembly  16 , by using a common or standard crossbar  19 , in conjunction with a less costly customized insert member  50 , rather than using a customized crossbar for each rating without an insert member as in the prior art.. The insert members  50  may be formed of any suitable manufacturing process. In one embodiment, the insert members  50  are molded components. Alternatively, the insert members  50  may be formed by a machining process. 
     As shown in  FIG. 3 , the insert members  50  are disposed between, and coupled to, the crossbar  19  and the moveable contact arm assemblies  16 . Specifically, each insert member  50  is sandwiched between the crossbar  19  and a corresponding moveable contact arm  16 . As discussed above, the insert member  50  is sized and shaped in a customizable manner that is dependent upon the configuration of the moveable contact arm assemblies. In this way, a common or standard crossbar is able to function with a variety of moveable contact arm assemblies in cooperation with a customized insert member  50 . 
     Referring to  FIG. 4 , the insert member  50  is illustrated according to a first embodiment. To facilitate a better understanding of the insert member  50 , a portion of the crossbar assembly  18  has been cut-away to better illustrate features of the insert member  50 . As described above, the insert member  50  is disposed between the crossbar  19  and a corresponding moveable contact arm assembly  16  in a sandwiched manner. For example, in an embodiment, each of the crossbar segments  32 ,  34 ,  36  defines a respective aperture  62 ,  64 ,  66  defined thereon. The aperture  62 ,  64 ,  66  is sized and disposed to operatively receive a respective moveable contact arm assembly  16  there through. In an embodiment, each of the crossbar segments  32 ,  34 ,  36  may further define a cavity  72 ,  74 ,  76  therein. Each cavity  72 ,  74 ,  76  extends to the corresponding aperture  62 ,  64 ,  66  and is sized and arranged to receive the corresponding insert member  50  therein. Further, each cavity  72 ,  74 ,  76  is sized to operatively receive a corresponding insert member therein. 
     It is contemplated that one or more components are disposed between the insert member  50  and the crossbar  19  and/or the moveable contact arm assemblies  16 , such that the insert member  50  may be coupled in indirect contact with the components. The insert member  50  may simply be sandwiched in the space between the crossbar  19  and the moveable contact arm assembly  16 , as described above, or may be mechanically fastened thereto with one or more mechanical fasteners, such as pins or threaded fasteners, for example. 
     In the fully assembled condition, the insert member  50  is configured to exert a force on the moveable contact arm assembly to ensure that an appropriate connection is made between the moveable contact arm assembly and a fixed contact (not shown) to complete a circuit, when desired. In an embodiment, the force is facilitated by a biasing member  51 . In various embodiments, the biasing member may be integrally formed with, or operatively coupled to, the insert member  50 . In the illustrated embodiment of  FIG. 4 , the insert member includes a plunger  52  that is coupled to the moveable contact arm assembly  16  at a first end  54  of the plunger  52 . In the illustrated embodiment, the biasing member  51  coupled in mechanical communication with the plunger  52  at a second end  56  of the plunger and comprises any suitable resilient element configured to bias the plunger  52  in order to exert the force on the moveable contact  16  arm. 
     Referring to  FIG. 5 , the insert member  50  is illustrated according to a second embodiment. As with the embodiment of  FIG. 4 , to facilitate a better understanding of the insert member  50 , a portion of the crossbar assembly  18  has been cut-away to better illustrate features of the insert member  50 . The insert member  50  is situated between the crossbar  19  and the moveable contact arm assemblies  16  in a manner similar to the insert member described above in conjunction with  FIG. 4 , however, the biasing member  51  differs in this embodiment. In the illustrated embodiment, the biasing member  51  comprises a spring that is operatively coupled to the moveable contact arm assembly  16  at a first end  58  of the spring and operatively coupled to the insert member  50  at a second end  60  of the spring, thereby exerting the biasing force on the moveable contact arm assembly  16 . 
     Advantageously, a single configuration of a crossbar  19  may be utilized with distinct types of moveable contact arm assemblies  16  with the use of the insert members  50  described herein. This beneficially reduces or eliminates the need for manufacture of distinct configurations of crossbars to match unique types of moveable contact arm assemblies, thereby reducing manufacturing time, cost and complexity. The insert members  50  are much less expensive and easier to manufacture on a customizable basis, when compared to the larger and more complex crossbars. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.