Patent Publication Number: US-6903636-B2

Title: Shock resistant auxiliary switch mechanism and circuit breaker

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is related to commonly assigned, concurrently filed U.S. patent application Ser. No. 10/463,989, filed Jun. 18, 2003, entitled “Shock Resistant Bell Alarm Switch Mechanism And Circuit Breaker”. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to circuit breakers and, more particularly, to a shock resistant auxiliary switch mechanism for a circuit breaker. 
   2. Description of the Related Art 
   Circuit breakers are used for numerous purposes in power distribution systems. Among such purposes is the interruption of current in a protected system during specified conditions. 
   Each pole of a circuit breaker includes a stationary contact and a movable contact, with the movable contact typically being mounted on an arm that can pivot the movable contact into and out of the electrical engagement with the stationary contact. A multi-pole circuit breaker typically includes a single operating mechanism for all of the poles, with the operating mechanism including a single crossbar and a single cradle. The crossbar extends between all of the poles and synchronizes the operation thereof. The cradle is operable to pivot the crossbar in order to separate the movable contacts from the stationary contacts in the event of a trip situation. 
   A circuit breaker can be in any one of an ON position, an OFF position, and a TRIPPED position. The movable contacts are connected with the stationary contacts when the circuit breaker is in the ON position. The cradle is a mechanism, usually spring-operated, that is operable to switch the circuit breaker from the ON position to the TRIPPED position by pivoting the crossbar to separate the movable contacts from the stationary contacts. When the cradle is mechanically energized, such as loading the springs thereof, a handle of the circuit breaker can be employed to switch the circuit breaker between the ON position and the OFF position by pivoting the crossbar such that the movable contacts are moved into and out of engagement with the stationary contacts. 
   While the specific condition of a circuit breaker often is plain to an observer, it is nevertheless often desirable to provide additional apparatuses to indicate to a technician the condition of the circuit breaker. For instance, some circuit breakers include an auxiliary switch that is operated by the crossbar and indicates the condition of the contacts as either being connected or disconnected, meaning that it indicates whether the circuit breaker is in the ON position or is in either of the OFF and TRIPPED positions. Alternatively, or in addition thereto, a circuit breaker may include a bell alarm switch that is operated by the cradle to indicate whether the circuit breaker is in the TRIPPED position or in one of the ON and OFF positions. While such auxiliary switches and bell alarm switches have been generally effective for their intended purposes, such switches have not, however, been without limitations. 
   Depending upon the application, a circuit breaker may be subjected to shock loading. Different applications have different requirements for the continued operation of circuit breakers during shock loading. Known auxiliary switches typically include a microswitch having a common conductor that is pivotable about an axis, with the pivotable portion having a asymmetric distribution of mass about the pivot point. Such asymmetry can result in unintended rotation of the common conductor in the event of a shock loading, which can undesirably result in an incorrect indication of the condition of the contacts and/or cradle. It is thus desired to provide an improved auxiliary switch mechanism and resulting circuit breaker that are configured to resist the effect of shock loading. 
   SUMMARY OF THE INVENTION 
   An improved shock resistant auxiliary switch mechanism and resulting circuit breaker in accordance with the present invention meet these and other needs. An improved shock resistant auxiliary switch mechanism for a circuit breaker includes a common conductor having a conduction plate that is slidably translatable between electrically conductive contact with first and second conductors. The conduction plate is biased by a spring in a direction toward contact with the first conductor. An improved shock resistant circuit breaker including the improved auxiliary switch mechanism includes a crossbar that is operatively engageable with the conduction plate to releasably retain the conduction plate in a position in contact with the second conductor. When the circuit breaker is in an ON position, the conduction plate is operatively interposed between the crossbar and the bias of the spring. 
   Accordingly, an aspect of the present invention is to provide an auxiliary switch mechanism and a resulting circuit breaker that are resistant to shock loading. 
   Another aspect of the present invention is to provide a shock resistant auxiliary switch mechanism for use in a circuit breaker, with the auxiliary switch mechanism including a first conductor, a second conductor, and a common conductor, and with the common conductor including a slidably translatable conduction plate that is alternately connectable with the first and second conductors. 
   Another aspect of the present invention is to provide a shock resistant auxiliary switch mechanism for use in a shock resistant circuit breaker having a crossbar, with the auxiliary switch mechanism including a common conductor having a conduction plate that is movable between a first position and a second position and that is biased by a spring toward the first position, with the crossbar being operatively engageable with the conduction plate to releasably retain the conduction plate in the second position, whereby the conduction plate is operatively interposed between the crossbar and the bias of the spring. 
   Accordingly, an aspect of the present invention is to provide an improved shock resistant auxiliary switch mechanism for use in a circuit breaker, with the circuit breaker including a set of separable contacts, and with the auxiliary switch mechanism being structured to indicate a disconnected state of the set of contacts, in which the general nature of the auxiliary switch mechanism can be stated as including a frame, a switch assembly, and a biasing member. The switch assembly is mounted on the frame and includes a first conductor, a second conductor, a common conductor, and an actuator. The actuator is operatively engaged with the common conductor to slidably move at least a portion of the common conductor between a first position in which the common conductor is connected with the first conductor and a second position in which the common conductor is connected with the second conductor. The biasing member biases the actuator toward the first position. The actuator is structured to be engaged by a movable member of the circuit breaker to releasably retain the actuator in the second position whereby the actuator is operationally interposed between the bias of the biasing member and the movable member of the circuit breaker to resist unintended movement of the at least portion of the common conductor due to a shock event. 
   Another aspect of the present invention it to provide an improved shock resistant auxiliary switch mechanism for use in a circuit breaker, with the circuit breaker including a set of separable contacts, and with the auxiliary switch mechanism being structured to indicate a disconnected state of the set of contacts, in which the general nature of the auxiliary switch mechanism can be stated as including a frame, a switch assembly, and a biasing member. The switch assembly is mounted on the frame and includes a first conductor, a second conductor, a common conductor, and an actuator. The common conductor includes a slidably translatable conduction plate. The actuator is operatively engaged with the conduction plate to slidably translate the conduction plate between a first position connected with the first conductor and a second position connected with the second conductor. The biasing member biases the actuator toward the first position, and the actuator is structured to be operatively engaged by a movable member of the circuit breaker. 
   Another aspect of the present invention is to provide an improved shock resistant circuit breaker, the general nature of which can be stated as including a line conductor, a load conductor, and a set of separable contacts interposed between the line and load conductors. The set of separable contacts includes a movable contact and a stationary contact, and a movable member is operatively connected with the movable contact. The circuit breaker further includes a shock resistant auxiliary switch mechanism, with the auxiliary switch mechanism including a frame, a switch assembly, and a biasing member. The switch assembly is mounted on the frame. The switch assembly includes a first conductor, a second conductor, a common conductor, and an actuator. The actuator is operatively engaged with the common conductor to slidably move at least a portion of the common conductor between a first position in which the common conductor is connected with the first conductor and a second position in which the common conductor is connected with the second conductor. The biasing member biases the actuator toward the first position. The movable member is operatively engageable with the actuator to releasably retain the actuator in the second position whereby the actuator is operationally interposed between the movable member and the bias of the biasing member to resist unintended movement of the at least portion of the common conductor due to a shock event. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A further understanding of the invention can be gained from the following Description of the Preferred Embodiment when read in conjunction with the accompanying drawings in which: 
     FIG.  1 . is a schematic view of an improved circuit breaker in accordance with the present invention that includes an improved auxiliary switch mechanism in accordance with the present invention; 
       FIG. 2  is an exploded isometric view of the auxiliary switch mechanism; 
       FIG. 3  is an assembled isometric view of the auxiliary switch mechanism from a different perspective than that of  FIG. 2 ; 
       FIG. 4  is a schematic view of the auxiliary switch mechanism and a crossbar of the circuit breaker, with the auxiliary switch mechanism being in a first position; and 
       FIG. 5  is a view similar to  FIG. 4 , except depicting the auxiliary switch mechanism being in a second position. 
   

   Similar numerals refer to similar parts throughout the specification. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   An improved circuit breaker  4  in accordance with the present invention is depicted schematically in FIG.  1 . As will be set forth in greater detail below, the circuit breaker  4  includes an improved auxiliary switch mechanism  8  in accordance with the present invention, with the auxiliary switch mechanism  8  being depicted schematically in FIG.  1 . The improved circuit breaker  4  and the improved auxiliary switch mechanism  8  advantageously are both configured to resist malfunction due to shock events. 
   The schematically depicted circuit breaker  4  additionally includes a line conductor  12 , a load conductor  16 , a movable arm  20 , a stationary contact  24 , a movable contact  28 , a handle  32 , an operating mechanism  36 , and a case  40 . The case  40  provides the support for all of the other components of the circuit breaker  4 . 
   The operating mechanism  36  includes a cradle  44  and a crossbar  48 . The crossbar  48  is operatively connected with the movable arm  20  to move the movable contact  28  into and out of engagement with the stationary contact  24 , such as when the circuit breaker  4  is moved between the ON position and the OFF or TRIPPED positions. The cradle  44  is operatively connected with the crossbar  48  to move the circuit breaker  4  from the ON position to the TRIPPED position. The handle  32  is operatively connected with the crossbar  48  to move the circuit breaker  4  between the ON position and the OFF position. While it is understood that the handle  32  is operatively connected with the cradle  44  to load the springs of the cradle  44  in a known fashion after the circuit breaker  4  has been tripped, for purposes of clarity such relationship is not explicitly depicted in FIG.  1 . It is also understood that the circuit breaker  4  is a multi-pole circuit breaker even though only a single pole is depicted, and it is further understood that the teachings herein can be applied to a single pole circuit breaker without departing from the concept of the present invention. 
   It can also be seen from  FIG. 1  that the crossbar  48  is operatively connected with the auxiliary switch mechanism  8 . Such operative engagement is schematically depicted in  FIGS. 4 and 5  and will be discussed in greater detail below. 
   The auxiliary switch mechanism  8  is depicted in an exploded fashion in FIG.  2 . The auxiliary switch mechanism  8  generally includes a switch assembly  52 , a frame  56 , and a biasing member  60  which, in the depicted embodiment, is a helical compression spring. The switch assembly  52  and the spring  60  are both mounted on the frame  56 , and the frame  56  is in turn disposed on the case  40  of the circuit breaker  4 . 
   The frame  56  more specifically includes a first member  64  upon which are mounted a second member  68 , and a third member  72 . The second and third members  68  and  72  are attached to the first member  64  with a number of fasteners  76  which are depicted in the exemplary embodiment as being screws in combination with nuts and lock washers. The second member  68  includes a mounting hole  80  within which the switch assembly  52  is received. The third member  72  includes a tab  84  for mounting of the spring  60 . 
   As can be understood from  FIGS. 2-5 , the switch assembly  52  includes a housing  88 , a toggle  92 , a first conductor  96 , a second conductor  100 , and a common conductor  104 . The toggle  92  includes a connector  108  for attachment of the spring  60 , and  FIG. 3  depicts the spring  60  as extending between the connector  108  and the tab  84 . The spring  60  is disposed at the exterior of the housing  88 . 
   As can be seen from  FIGS. 4 and 5 , the common conductor  104  includes a conduction plate  112  that is slidably translatable on a support surface  116  of the housing  88 . The toggle  92  is pivotably disposed on the housing  88 , with one end of the toggle  92  being operatively connected with the conduction plate  112  and with a second opposite end of the toggle  92  being operatively connected with the spring  60 . The spring  60  thus can be said to be operatively connected with the conduction plate  112  and to operatively extend between the frame  56  and the common conductor  104 . 
   The toggle  92  and the conduction plate  112  are movable between a first position ( FIG. 4 ) and a second position (FIG.  5 ). In the first position (FIG.  4 ), the conduction plate  112  is connected with the first conductor  96 , whereby the common conductor  104  and the first conductor  96  are electrically conductively connected with one another. In the second position (FIG.  5 ), the conduction plate  112  is connected with the second conductor  100 , whereby the second conductor  100  and the common conductor  104  are electrically conductively connected with one another. 
   The spring  60  biases the toggle  92  and the conduction plate  112  toward the first position. The toggle  92  and the conduction plate  112  thus are in the first position when the crossbar  48  is disengaged from the toggle  92  ( FIG. 4 ) such as when the circuit breaker  4  is in either the OFF position or the TRIPPED position. In switching the circuit breaker  4  to the ON position (FIG.  5 ), however, a lobe  120  of the crossbar  48  engages the toggle  92  and overcomes the bias of the spring  60  to move the toggle  92  and the conduction plate  112  to the second position. In such a condition, the crossbar  48  releasably retains the toggle  92  and the conduction plate  112  in the second position while the spring  60  still biases the toggle  92  and the conduction plate  112  toward the first position. When the circuit breaker  4  is in the ON position, therefore, the toggle  92  and the conduction plate  112  are operatively interposed between the crossbar  48  and the bias of the spring  60 . 
   Such operative interposition of the toggle  92  and the conduction plate  112  between the crossbar  48  and the spring  60  resists unintended movement of the toggle  92  and/or the conduction plate  112  away from the second position upon the occurrence of a shock event. The toggle  92  and the conduction plate  112  cannot move away from the second position when the circuit breaker  4  is in the ON position ( FIG. 5 ) unless the crossbar  48  somehow becomes disengaged with the toggle  92 , which generally could happen only upon at least partial destruction of the circuit breaker  4 . While previously known switches may have included a spring or other biasing system, such springs or biasing systems have previously been configured only to retain the switches in a given position in a static environment and have not been configured to retain the switches in given positions during shock loading. 
   Additional shock resistance results from the conduction plate  112  being slidably translatable on the support surface  116 . Many previously known switches have employed conduction members that are pivotable about an axis and that have an asymmetric weight distribution about the axis, such that in the event of a shock load the asymmetry of the weight distribution can cause the conduction member to pivot slightly and break contact with other conductors in the switch, which is undesirable. Since the conduction plate  112  is translatable, no combination of events could cause an unintended pivoting of the conduction plate  112 . As set forth above, the only way in which the conduction plate  112  can move from the second position when the circuit breaker  4  is in the ON condition is for the toggle  92  and the conduction plate  112  to overcome the bias of the spring  60  which, in the ON position, is already compressed to a significant extent. 
   As can further be understood from  FIG. 5 , the lobe  120  is engageable with the connector  108  of the toggle  92  when the crossbar  48  and the toggle  92  are engaged with one another. Depending upon the specific selection of materials employed, the bearing of the lobe  120  on the connector  108  instead of on other portions of the toggle  92  can resist frictional wear of the auxiliary switch mechanism  8 . 
   While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.