Patent Publication Number: US-6903635-B2

Title: Circuit breaker interface mechanism for auxiliary switch accessory

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to circuit breakers, and, more particularly to a circuit breaker interface mechanism for an auxiliary switch accessory. 
   It is generally well known in the art of circuit breakers to provide a reset mechanism to reset a tripping device such as an accessory shunt trip or under voltage device. During quiescent operation, (i.e. when the circuit breaker contacts are closed to allow the flow of electrical current) the operating handle of an operating mechanism is in the “ON” position. To stop the current flow manually, the handle may be shifted to the “OFF” position thereby opening the electrical contacts. Upon attainment of a pre-determined condition (trip event), such as ground fault or overload, the operating mechanism of the circuit breaker will release the forces of the mechanism operating springs and release the operating handle to a tripped position between the “ON” position and the “OFF” position. Before the circuit breaker may be turned “ON”, the operating mechanism must be manually reset. This is accomplished by rotating the operating handle beyond the “OFF” position against the bias of the operating mechanism springs, thereby locking the operating mechanism in position. 
   The same mechanical forces used to direct the operating mechanism from the tripped position to the reset position are used to reset any attached accessories, such as a shunt trip actuator, auxiliary switch accessory, bell alarm or other type of accessory unit. However, as accessories are generally separate components mounted proximate to the operating mechanism, positional variations at the interface of the accessory and the circuit breaker operating mechanism are possible due to manufacturing tolerances. These positional variations can affect the resetting motion translated to the bell alarm switch or its components by not compensating for any over-travel resulting from the possible tolerance variations. Furthermore, a reliable interface mechanism between the circuit breaker and internal accessories is desired that will provide reliable actuation of the accessory switch to change a state thereof when the breaker changes state in either an “on”, “off”, or “trip” operation without robbing energy from the operating mechanism during the “off” to “on” operation, which is common with conventional accessory interface systems. Conventional accessory interface systems between the operating mechanism and accessories presently rely only on limited “take up” provided by the accessory switch. It is further desired that the switch also be field installable by the customer without violating UL requirements. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by an assembly for interacting with a circuit breaker operating mechanism of a circuit breaker including a housing and a pair of contacts within the housing, the operating mechanism arranged to separate the pair of contacts upon the occurrence of a trip event. The assembly includes a plurality of linkages arranged to transmit mechanical energy from the operating mechanism to a plunger of an accessory device for changing a state thereof. The system of linkages is configured to compensate for any over-travel resulting from possible tolerance variations. 
   In an exemplary embodiment of the invention, an assembly for interacting with a circuit breaker operating mechanism of a circuit breaker, the assembly includes an accessory device disposed in the housing including a plunger configured for movement between a retracted position and a protruded position. A crank link having operable communication with the operating mechanism is in further mechanical cooperation with a first link that in turn is in mechanical cooperation with a second link. The second link is in further mechanical cooperation with the plunger. When the operating mechanism applies a force to the crank link, the force changes a state of the accessory device by being transmitted from the operating mechanism to the crank link, from the crank link to the first link, from the first link to the second link, and from the second link to the plunger for changing a position of the plunger from either the protruded position or the retracted position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
       FIG. 1  is a top perspective view of a molded case circuit breaker; 
       FIG. 2  is an exploded perspective view of a molded case circuit breaker; 
       FIG. 3  is a side perspective view of the circuit breaker of  FIG. 2  with the top cover removed and an actuator and an auxiliary switch in an assembly view; 
       FIG. 4  is a partial sectional view of a rotary contact structure and operating mechanism embodied by the present invention in the “off” position; 
       FIG. 5  is a partial sectional view of the rotary contact structure and operating mechanism of  FIG. 3  in the “on” position; 
       FIG. 6  is a partial sectional view of the rotary contact structure and operating mechanism of  FIGS. 3 and 4  in the “tripped” position; 
       FIG. 7  is a side view of the operating mechanism in a closed/“on” position and the auxiliary switch in an inactivated position; and 
       FIG. 8  is a side view of the operating mechanism in an open/“off” position and the auxiliary switch in an activated position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a top perspective view of a molded case circuit breaker  10  is generally shown. Molded case circuit breaker  10  is generally interconnected within a protected circuit between multiple phases of a power source (not shown) at line end  14  and a load to be protected (not shown) at load end  12 . Molded case circuit breaker  10  includes a base  18 , a mid cover  20  and a top cover  22  having a toggle handle (operating handle) extending through an opening  24 . Toggle handle  44  is interconnected with a circuit breaker operating mechanism  38  ( FIG. 2 ) and allows for external operation of cassettes  32 ,  34  and  36 . An accessory (e.g., a bell alarm switch)  26  is positioned within the mid cover  20  as shown in phantom, and interfaces with circuit breaker operating mechanism  38 . In an exemplary embodiment, the accessory  26  is a bell alarm switch (switch), however, other auxiliary switch accessories are contemplated. 
   Referring now to  FIG. 2 , an exploded view of molded case circuit breaker  10  is provided. A series of circuit breaker cassettes  32 ,  34 ,  36  are generally well known and may be, for example, of the rotary type. Examples of rotary contact structures that may be operated by operating mechanism  38  are described in more detail in U.S. Pat. Nos. 6,114,641 and 6,396,369, both entitled “Rotary Contact Assembly For High-Ampere Rated Circuit Breakers”, and U.S. Pat. No. 6,175,288, entitled “Supplemental Trip Unit For Rotary Circuit Interrupters”. 
   Circuit breaker cassettes  32 ,  34 ,  36  are seated approximately upstanding within base  18 , and the cassette  34  includes operating mechanism  38  positioned thereon. The individual phases of current are divided into three phases, wherein each phase passes through one of the circuit breaker cassettes  32 ,  34 ,  36 . Each of cassettes  32 ,  34 ,  36  includes one or more contact pairs therein for passage of current when the contacts are closed and for preventing passage of current when the contact pairs are opened. It is contemplated that the number of phases, or specific type of cassette utilized, can vary according to factors including, but not limited to, the type of load circuit being protected and the type of line input being provided to the circuit breaker  10 . 
   Still referring to  FIG. 2 , each cassette  32 ,  34 ,  36  is commonly operated by a cross bar (cross pin)  40  that interfaces with the internal mechanisms of cassettes  32 ,  34 ,  36  such that when one of cassettes  32 ,  34 ,  36  are opened or closed, the other cassettes  32 ,  34 ,  36  will operate cooperatively. It will be recognized by one skilled in the pertinent art that only one cross bar may be used to interface with the internal mechanisms of cassettes  32 ,  34 ,  36  such that when one of cassettes  32 ,  34 ,  36  are opened or closed, the other cassettes  32 ,  34 ,  36  will operate cooperatively. Positioning rods  31  are also employed to position the cassettes  32 ,  34 ,  36  adjacent to each other. Operating mechanism  38  is positioned and configured atop cassette  34 , which is generally disposed intermediate to cassettes  32  and  36 . Operating mechanism  38  operates substantially as described herein and as described in U.S. patent application Ser. No. 6,218,919, entitled “Circuit Breaker Latch Mechanism with Decreased Trip Time”. However, it is contemplated that other operating mechanisms may be employed, as well. The cassettes  32 ,  34 ,  36  are typically formed of high strength plastic material and each include opposing sidewalls. 
   Referring to  FIG. 3 , an isometric view of the circuit breaker  10  is shown, showing accessory  26  and a portion of an interface mechanism is shown generally in an exploded view with the top cover  22  ( FIG. 1 ) removed. The accessory  26  is shown removed from a cavity  50  located within the mid cover  20  for clarity. 
   The cavity  50  is formed integral with the mid cover  20  and comprises a front mounting surface  54 , a rear mounting surface  60  and a bottom surface connecting the rear and front mounting surfaces  60  and  54 , respectively. The bottom surface of the cavity  50  is perpendicular to the front and rear mounting surfaces  54 ,  60 . Located intermediate the rear mounting surface  60  and the front mounting surface  54  is a shelf  80 . The shelf  71  and shelf  80  are integrally molded within the cavity  50 . 
   The accessory  26  (e.g., an auxiliary switch accessory) is mounted within cavity  50  located within the mid cover  20 . The switch  26  comprises a front surface  254  and a rear surface  256  and a connecting bottom surface  264 . The front surface  254  having a tab  258  disposed thereon. Extending upward from the rear surface  256  is a mounting prong  260 . A first end  262  of the mounting prong  260  is attached to the accessory  26  at a point just above the bottom surface  264 . The mounting prong  260  is thin and flexible in comparison with the switch  26 . The mounting prong  260  extends upward from the first end  262 , it angles slightly away from the rear surface  256  of the switch  26 . A second end  259  of the mounting prong  260  is separated a distance from the rear surface  256  of the accessory  26 . 
   The accessory  26  also includes a push button plunger (plunger)  266  that is spring mounted from the bottom surface  264  of the accessory  26 . The plunger  266  is spring loaded to permit the plunger  266  to be depressed closing contacts within the switch  26  and also to be released back outward opening the contacts within the switch  26 . When the switch  26  is installed within the cavity  50  as described herein below, the plunger  266  extends downward and is positioned to align with an arm or compliant member shown generally at  316 . The accessory  26  may then be connected with a remote bell alarm, for example, by means of a pair of wires  268  that extend from the accessory  26 . 
   The accessory  26  is installed into the cavity  50  by the end user. When installing the accessory  26  into the cavity  50 , the tab  258  of the accessory  26  is arranged so as to be inserted under the shelf  71 . Then, the mounting prong  260  is flexed so that a tab  270  on the mounting prong  260  can snap into place under the shelf  80 . Thus, the accessory  26  is held in position within the cavity  50  by the interaction of the tab  258  and the mounting prong  260  of the switch  26  with the shelf  71  and shelf  80 , respectively. When the accessory  26  is installed in the mid cover  20  of the circuit breaker  10 , the plunger  266  aligns with and is located proximate to the arm or compliant member  316 . 
   Referring now to  FIGS. 4 ,  5 , and  6 , the operating mechanism  38  will now be detailed. An exemplary rotary contact assembly  56  is shown disposed within each cassette  32 ,  34 ,  36  and shown in the “off”, “on” and “tripped” conditions, respectively. Also depicted are partial side views of operating mechanism  38 , the components of which are described in greater detail further herein. Rotary contact assembly  56  includes a load side contact strap  58  and line side contact strap  62  for connection with a power source and a protected circuit (not shown), respectively. Load side contact strap  58  includes a stationary contact  64  and line side contact strap  62  includes a stationary contact  66 . Rotary contact assembly  56  further includes a movable contact arm  68  having a set of contacts  72  and  74  that mate with stationary contacts  64  and  66 , respectively. In the “off” position ( FIG. 4 ) of operating mechanism  38 , wherein toggle handle  44  is oriented to the right (e.g., via a manual or mechanical force), contacts  72  and  74  are separated from stationary contacts  64  and  66 , thereby preventing current from flowing through contact arm  68 . 
   In the “on” position ( FIG. 5 ) of operating mechanism  38 , wherein toggle handle  44  is oriented to the left as depicted in  FIG. 4  (e.g., via a manual or mechanical force), contacts  72  and  74  are mated with stationary contacts  64  and  66 , thereby allowing current to flow through contact arm  68 . In the “tripped” position ( FIG. 6 ) of operating mechanism  38 , toggle handle  44  is oriented between the “on” position and the “off” position (typically by the release of mechanism springs within operating mechanism  38 , described in greater detail herein). In this “tripped” position, contacts  72  and  74  are separated from stationary contacts  64  and  66  by the action of operating mechanism  38 , thereby preventing current from flowing through contact arm  68 . When operating mechanism  38  is in the “tripped” position, it must ultimately be returned to the “on” position for operation. This is effectuated by applying a reset force to move toggle handle  44  to a “reset” condition, which is beyond the “off” position (i.e., further to the right of the “off” position in FIG.  4 ), and then back to the “on” position. This reset force must be high enough to overcome the mechanism springs, described herein. 
   Contact arm  68  is mounted on a rotor structure  76  that houses one or more sets of contact springs (not shown). Contact arm  68  and rotor structure  76  pivot about a common center  78 . Cross pin  40  interfaces through an opening  82  within rotor structure  76  generally to cause contact arm  68  to be moved from the “on”, “off” and “tripped” position. 
   Referring now to  FIGS. 7 and 8 , the components of operating mechanism  38  will now be detailed in relation to interfacing with accessory  26 . As viewed in  FIG. 7 , operating mechanism  38  is in the closed or “on” position. Operating mechanism  38  has operating mechanism side frames  86  configured and positioned to straddle sidewalls  46 ,  48  of cassette  34  (FIG.  2 ). 
   Toggle handle  44  ( FIG. 2 ) is rigidly interconnected with a drive member or handle yoke  88 . Handle yoke  88  includes opposing side portions (only one shown)  89 . Each side portion  89  includes a U-shaped portion  92  at the bottom portion of each side portion  89 . U-shaped portions  92  are rotatably positioned on a pair of bearing portions (not shown) protruding outwardly from side frames  86 . 
   Operating mechanism  38  has a pair of cranks  208  each operably connected to a corresponding cradle  210 . Examples of rotary contact structures having such cradles that may be operated by operating mechanism  38  are described in more detail in U.S. patent application Ser. No. 09/795,017 Each crank  208  pivots about a center  78 . Crank  208  has an opening  212  where cross pin  40  ( FIG. 2 ) passes through into arcuate passage  52  of cassettes  32 ,  34  and  36  ( FIG. 2 ) and a complementary set of arcuate passages  214  on each side frame  86 . 
   Crank  208  includes a crank link  300  extending from crank  208 . Crank link  300  is in operable communication with a first link shown generally at  302  that is pivotally mounted to the adjacent cassettes via a first pin  304 . In an exemplary embodiment with reference to  FIGS. 2 and 8 , first pin  304  includes one of the two positioning rods  31 , such that first link  302  pivots about positioning rod  31  disposed between each cassette  32 ,  34 ,  36 . First link  302  includes a first arm  306  disposed at one end of link  302  and a contact member  308  disposed at an opposite end thereof. One end of first arm  306  extends from first pin  304  while an opposite end is in operable communication with crank link  300  discussed more fully below. 
   Contact member  308  pivots about pin  304  in tandem with first arm  306  at an opposite end thereto. Contact member  308  in turn is in operable communication with a second link shown generally at  312  that is pivotally mounted in a pocket of mid cover  20  via a second pin  314 . Second link  312  includes a second arm  316  depending at one end from link  312  and is in operable communication with an end surface of plunger  266  defining plunger  266 . Plunger  266  is preferably biased toward first link  302  providing a bias on second arm  316  to bias second link  312  to pivot in a clockwise direction indicated by arrow  320  around pin  314 . The bias of second link  312  in the direction indicated by arrow  320  causes first link  302  to be biased in a counter clockwise direction indicated by arrow  321 , which causes crank link  300  to rotate clockwise. In this manner, the bias on crank link  300  is in the same clockwise direction that a bias on crank  208  is urging the pair of contacts in the “on” position. 
   Referring now to  FIGS. 7 and 8 , operation of an exemplary embodiment of an auxiliary switch accessory interface mechanism will be described shown generally at  272 .  FIG. 8  depicts the breaker contacts in the open or “off” position.  FIGS. 7 and 8  also illustrate accessory  26  shown in the inactivated position and the activated position, respectively, via translation of plunger  266 . The interface mechanism  272  includes a set of linkages comprising crank link  300 , first link  302 , and second link  312  in mechanical cooperation with each other and with crank  208  and plunger  266  of accessory  26  to change the state of accessory  26 . 
     FIG. 7  depicts the closed or “on” position when the contacts are closed and the accessory  26  biases plunger  266  away therefrom to indicate a first state. The first state in this embodiment is indicative of the “on” position and accessory  26  is considered inactivated. When accessory  26  and interface mechanism are employed together a mechanical auxiliary switch assembly (assembly)  274 , for example, assembly  274  is employed to provide indication when the operating mechanism  38  is discharged as is the case when the circuit breaker  10  ( FIG. 1 ) is in the tripped condition or manually placed in the “off” condition and accessory  26  is considered activated. 
   In operation, as the breaker contacts begin to open from the closed position depicted in  FIG. 7 , crank  208  and crank link  300  rotate counter clockwise indicated by direction arrow  322  which causes a tapered portion  324  of link  300  to first engage and rotate first link  302  in a clockwise direction indicated by arrow  326 . Tapered portion  324  engages first arm  306  of first link  302  causing clockwise rotation thereof (arrow  326  in  FIG. 7 ) which causes contact member  308  to also engage and rotate second link  312  in a counter clockwise direction indicated by arrow  328  in FIG.  8 . When second link  312  turns counter clockwise shown by arrow  328 , second arm  316  extending from second link  312  also turns counter clockwise and urges plunger  266  into accessory  26  to a retracted position. When plunger  266  illustrated in phantom in  FIG. 8  is in the retracted position, accessory  26  changes state, such that the first state is changed to a second state indicative that the circuit breaker contacts are no longer closed. 
   Second arm  316  as shown in  FIGS. 7 and 8  is configured as a stepped or offset compliant member, such that one side of the offset is in mechanical cooperation with contact member  308  of first link  302  while an opposite side of the offset is in mechanical cooperation with the end of the plunger  266 . The size of the offset in second arm  316  is configured based on the distances between plunger  266 , second link  312 , and pivot pin  314 , as well as the angle created therebetween. 
   Second arm  316  is preferably configured as a compliant member such that it allows flexible motion to “take up” variable gaps to compensate for any over travel resulting from possible tolerance variations of the interface mechanism or variations in actuation stroke of the plunger  266 . More specifically, the compliant member is configured to flex providing “take up” for any over-travel as a result of positional variations at an interface of the accessory device and the circuit breaker operating mechanism due to manufacturing tolerances, assembly tolerances, accessory device installation, or extreme variations in actuation stroke of the plunger. The second link  312 , and in particular the second arm  316 , is employed to provide mechanical cooperation between the interfaced members, (the crank  208  and accessory  26 ), While adding compliancy to absorb forces in excess of those required to change the state of the accessory  26 . 
   In an exemplary embodiment, second arm  316  is preferably fabricated as a thin strip of stainless steel that is designed to flex when the force to operate the switch or accessory is exceeded, providing the “take-up” for any remaining over-travel as a result of variations due to part and assembly tolerances and accessory installation. However, other suitable materials are contemplated that provide the required “take up” and is not limited to stainless steel. 
   When the circuit breaker  10  is tripped, for example due to an overcurrent condition or a mechanical trip, toggle handle  44  is between the “ON” position ( FIG. 7 ) and the “OFF” position (FIG.  8 ). Upon the occurrence of such an overcurrent condition and simultaneous articulation of the operating mechanism  38  to separate the contacts, the assembly  274  is activated consistent with the circuit breaker  10  being in the uncharged state. The activation of the accessory  26  whereby the plunger  266  is urged to a retracted position, as shown in  FIG. 8 , provides an indication to a remote operator, for example, that such a tripped condition has occurred and that the operating mechanism  38  has responded to interrupt the circuit current. 
   In order to reengage the operating mechanism  38  to the “ON” position, so as to return to quiescent condition, both operating mechanism  38  and assembly  274 , or more particularly, the switch  26  must be reset. 
   Before toggle handle  44  may be returned to the quiescent operation position, i.e., “ON”, circuit breaker operating mechanism  38  must be reset. This is accomplished by manually rotating toggle handle  44  in the counter-clockwise direction against the forces of one or more springs (not shown), thereby resetting latch  138  of operating mechanism  38  from the “Tripped” position to the “Latched” position. 
   A compliant member, and in particular the second arm  316 , is employed to provide mechanical cooperation between the interfaced members, (the crank  208  and the accessory  26 ), while adding compliancy to absorb forces in excess of those required to reset the accessory  26 . 
   It will also be recognized by one skilled in the pertinent art that the first link  302  and the second link  312  are pivotally disposed such that the accessory device  26  uses energy from the operating mechanism in moving the pair of contacts from the “on” to “off” position. In this manner, robbing energy from the operating mechanism during the critical “off” to “on” operation that is typical in conventional systems is avoided. 
   Thus, interface mechanism  272  disposable between the circuit breaker and internal accessories is provided which easily provides actuation of variably configured auxiliary switches or accessories when the circuit breaker changes state in either an overload “trip” condition or an “on” to “off” manual operation. The interface mechanism stores energy from the operating mechanism when going from the “on” to “off” operation of the circuit breaker, thereby using only the stored energy during the more critical “off” to “on” operation, without robbing the operating mechanism of any energy during this critical “off” to “on” operation. Accessory  26  is easily installed and is contained within the space available within the mid cover  20 . The relevant UL requirement allows the customer to remove the top cover  14  ( FIG. 2 ) and install the accessories since the operating mechanism and all other exposed metal parts are electrically isolated from the live parts within the cassettes. Also, the end user can easily utilize the interface mechanism  272  with the accessory  26  that is easily engaged within the mid cover  20 . Additionally, any manufacturing variances as to the precise location of the accessory  26  or variably dimensioned accessories  26  within mid cover  20 , and relative to the cradle  106  of the operating mechanism  38  are tolerated, as are field or installation imperfections that may jolt or otherwise shift the locations of the accessory  26  relative to the cradle  106 . The interface mechanism  272  has the ability to compensate for manufacturing tolerances to ensure that the accessory  26  provides accurate status indications of the operating mechanism  38  through the set of linkages employed in the interface mechanism  272 . 
   While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.