Patent Document

FIELD OF THE INVENTION  
         [0001]    This invention relates to a circuit breaker, and more particularly, to a molded case circuit breaker accessory system.  
         BACKGROUND OF THE INVENTION  
         [0002]    In general the function of a circuit breaker is to electrically engage and disengage a selected circuit from an electrical power supply. This function occurs by engaging and disengaging a pair of operating contacts for each phase of the circuit breaker. The circuit breaker provides protection against persistent overcurrent conditions and against the very high currents produced by short circuits. Typically, one of each pair of the operating contacts are supported by a pivoting contact arm while the other operating contact is substantially stationary. The contact arm is pivoted by an operating mechanism such that the movable contact supported by the contact arm can be engaged and disengaged from the stationary contact.  
           [0003]    There are two modes by which the operating mechanism for the circuit breaker can disengage the operating contacts: the circuit breaker operating handle can be used to activate the operating mechanism; or a tripping mechanism, responsive to unacceptable levels of current carried by the circuit breaker, can be used to activate the operating mechanism. For many circuit breakers, the operating handle is coupled to the operating mechanism such that when the tripping mechanism activates the operating mechanism to separate the contacts, the operating handle moves to a fault or tripped position.  
           [0004]    To engage the operating contacts of the circuit breaker, the circuit breaker operating handle is used to activate the operating mechanism such that the movable contact(s) engage the stationary contact(s). A motor coupled to the circuit breaker operating handle can also be used to engage or disengage the operating contacts. The motor can be remotely operated.  
           [0005]    Various accessories are used with a circuit breaker, such as alarm, auxiliary switches, and the like. The accessories are typically mounted in the circuit breaker frame and can be serviced only by removing the circuit breaker cover thereby exposing electrically live parts. Some circuit breakers provide accessory pockets dedicated to a single type of accessory, thereby preventing other accessories from being used in that pocket. Such arrangements eliminate flexibility and increase costs since a different circuit breaker with its dedicated accessories must be used for a particular purpose.  
           [0006]    This there is a need for a molded case circuit breaker capable of using interchangeable internal accessories in the same accessory compartment in the circuit breaker cover without exposing the live electrical connections of the circuit breaker. There is also a need for a molded case circuit breaker that can be reconfigured to provide different functions without modifying the circuit breaker latching mechanism.  
         SUMMARY OF THE INVENTION  
         [0007]    One embodiment of the invention relates to the molded case circuit breaker comprising a molded housing including a main breaker cover with a first terminal and a second terminal mounted in the case. The stationary contact electrically coupled to the first terminal and a movable contact electrically coupled to the second terminal is also provided. An operating mechanism having a pivoting member movable between an ON position, an OFF position and a TRIPPED position, is coupled to the movable contact. An intermediate latching mechanism is mounted in the housing and coupled to the operating mechanism. The trip unit is coupled to the movable contact and the second terminal with the trip unit in selective operative contact with the intermediate latching mechanism. The main breaker cover is provided with an accessory compartment system comprising an accessory socket formed in the main cover on either side of an opening for the pivoting member with the accessory socket in communication with the housing and configured to accept a plurality of different types of accessories. A latching protrusion is mounted in the socket for engaging the accessory. A separate accessory cover sized to cover the accessory mounted in the accessory socket is attached to the breaker cover.  
           [0008]    Another embodiment of the present invention presents a cover for a molded case circuit breaker having an operating mechanism and an intermediate latching mechanism with the cover comprising a substantially planer member having a central opening and an accessory compartment formed in the planer member on either side of the opening with the accessory compartment configured to accept a plurality of different types of accessories and having a plurality of holes wherein a circuit breaker accessory is nested in the accessory compartment and is in contact with one of the operating mechanism and the intermediate latching mechanism.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is an isometric drawing of a molded case circuit breaker which includes an embodiment of the present bi-metal unit capable of broad rating applications.  
         [0010]    [0010]FIG. 2 is a section view of the circuit breaker shown in FIG. 1 along the lines  2 - 2  and is used to describe the operation of the circuit breaker.  
         [0011]    [0011]FIG. 3 is an exploded isometric drawing of the operating mechanism, contact structure and bi-metal trip unit of the circuit breaker shown in FIG. 1.  
         [0012]    [0012]FIG. 4 is an illustration of the circuit breaker main cover for the circuit breaker shown in FIG. 1.  
         [0013]    [0013]FIG. 5 is a top plan view of the main breaker cover illustrated in FIG. 4.  
         [0014]    [0014]FIG. 6 is a sectional side view of the breaker cover illustrated in FIG. 5 along the line  6 - 6 .  
         [0015]    [0015]FIG. 7 is an enlarged, partial sectional side view of area identified in FIG. 6 illustrating the latching protrusion engaging an accessory detent. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    [0016]FIG. 1 generally illustrates a three phase molded case circuit breaker  10  of the type which includes an operating mechanism  40  having a pivoting member  13  with a handle  14 . The pivoting member  13  and handle  14  are moveable between an ON position, an OFF position and a TRIPPED position. The exemplary circuit breaker  10  is a three pole breaker having three sets of contacts for interrupting current in each of the three respective electrical transmission phases. In the exemplary embodiment of the invention, each phase includes separate breaker contacts and a separate trip mechanism. The center pole circuit breaker includes an operating mechanism which controls the switching of all three poles of the breaker. Although an embodiment of the present invention is described in the context of the three phase circuit breaker, it is contemplated that it may be practiced in a single phase circuit breaker or in other multi-phase circuit breakers.  
         [0017]    Referring to FIG. 2., handle  14  is operable between the ON and OFF positions to enable a contact operating mechanism  40  to engage and disengage a moveable contact  42  and a stationary contact  44  for each of the three phases, such that the line terminal  18  and load terminal  16  of each phase can be electrically connected. The circuit breaker housing  12  includes three portions which are molded from an insulating material. These portions include a circuit breaker base  12 , a circuit breaker cover  20  and an accessory cover  28  with breaker cover  20  and the accessory cover  28  having an opening  29  for the handle  14  of the pivoting member  13 . The pivoting member  13  and handle  14  move within the opening  29  during the several operations of the circuit breaker  10 . FIG. 2 is a cut away view of the circuit breaker  10  along the lines  2 - 2  shown in FIG. 1. As shown in FIG. 2, the main components of the circuit breaker are a fixed line contact arm  46  and a moveable load contact arm  45 . It should be noted that another embodiment of the circuit breaker  10  has a movable line contact arm to facilitate a faster current interruption action. The load contact arms for each of the three phases of the exemplary breaker are mechanically connected together by an insulating cross bar member  55 . This cross bar member  55 , in turn, is mechanically coupled to the operating mechanism  40  so that, by moving the handle  14  from left to right, the cross bar  55  rotates in a clockwise direction and all three load contact arms  45  are concurrently moved to engage their corresponding line contact arms  46 , thereby making electrical contact between moveable contact pad  42  and stationary contact pad  44 .  
         [0018]    The operating mechanism  40  includes a cradle  41  which engages an intermediate latch  52  to hold the contacts of the circuit breaker in a closed position unless and until an over current condition occurs, which causes the circuit breaker to trip. A portion of the moveable contact arm  45  and the stationary contact bus  46  are contained in an arc chamber  56 . Each pole of the circuit breaker  10  is provided with an arc chamber  56  which is molded from an insulating material and is part of the circuit breaker  10  housing  12 . A plurality of arc plates  58  are maintained in the arc chamber  56 . The arc plates facilitate the extension and cooling of the arc formed when the circuit breaker  10  is opened while under a load and drawing current. The arc chamber  56  and arc plates  58  direct the arc away from the operating mechanism  40 .  
         [0019]    The exemplary intermediate latch  52  is generally Z-shaped having an upper leg which includes a latch surface that engages the cradle  41  and a lower leg having a latch surface which engages a trip bar  54 . The center portion of the Z-shaped intermediate latch element  52  is angled with respect to the upper and lower legs and includes two tabs which provide a pivot edge for the intermediate latch  52  when it is inserted into the mechanical frame  51 . As shown in FIG. 2, the intermediate latch  52  is coupled to a torsion spring  53  which is retained in the mechanical frame  51  by the mounting tabs of the intermediate latch  52 . The torsion spring  53  biases the upper latch surface of the intermediate latch  52  toward the cradle  41  while at the same time biasing the trip bar  54  into a position which engages the lower latch surface of the intermediate latch  52 . The trip bar  54  pivots in a counter clockwise direction about an axis  54   a , responsive to a force exerted by a bi-metallic element  62 , during, for example, a long duration over current condition. As the trip bar  54  rotates, in a counter clockwise direction, the latch surface on the upper portion of the trip bar disengages the latch surface on the lower portion of the intermediate latch  52 . When this latch surface of the intermediate latch  52  is disengaged, the intermediate latch  52  rotates in a counter clockwise direction under the force of the operating mechanism  40 , exerted through a cradle  41 . In the exemplary circuit breaker, this force is provided by a tension spring  50 . Tension is applied to the spring when the breaker toggle handle  14  is moved from the open position to the closed position. More than one tension spring  50  may be utilized.  
         [0020]    As the intermediate latch  52  rotates responsive to the upward force exerted by the cradle  41 , it releases the latch on the operating mechanism  40 , allowing the cradle  41  to rotate in a clockwise direction. When the cradle  41  rotates, the operating mechanism  40  is released and the cross bar  55  rotates in a counter clockwise direction to move the load contact arms  45  away from the line contact arms  46 .  
         [0021]    During normal operation of the circuit breaker, current flows from the line terminal  18  through the line contact arm  46  and its stationary contact pad  44  to the load contact arm  45  through its contact pad  42 . From the load contact arm  45 , the current flows through a flexible braid  48  to the bi-metallic element  62  and from the bi-metallic element  62  to the load terminal  16 . (See FIG. 3) When the current flowing through the circuit breaker exceeds the rated current for the breaker, it heats the bi-metallic element  62 , causing the element  62  to bend towards the trip bar  54 . If the over current condition persists, the bi-metallic element  62  bends sufficiently to engage the trip bar surface. As the bi-metallic element engages the trip bar surface and continues to bend, it causes the trip bar  54  to rotate in a counter clockwise direction releasing the intermediate latch  52  and thus unlatching the operating mechanism  40  of the circuit breaker.  
         [0022]    [0022]FIG. 3 is an exploded isometric drawing which illustrates the construction of a portion of the circuit breaker shown in FIG. 2. In FIG. 3 only the load contact arm  45  of the center pole of the circuit breaker is shown. This load contact arm  45  as well as the contact arms for the other two poles, are fixed in position in the cross bar element  55 . As mentioned above, additional poles, such as a four pole molded case circuit breaker can utilize the same construction as described herein, with the fourth pole allocated to a neutral. The load contact arm  45  is coupled to the bi-metallic element  62  by a flexible conductor  48  (e.g. braided copper strand). As shown in FIG. 3, current flows from the flexible conductor  48  through the bi-metallic element  62  to a connection at the top of the bi-metallic element  62  which couples the current to the load terminal  16  through the load bus  61 . The load bus  61  is supported by a load bus support  63 . It should be noted that more than one flexible conductor  48  may be utilized.  
         [0023]    In the exemplary circuit breaker  10 , the cross bar  55  is coupled to the operating mechanism  40 , which is held in place in the base or housing  12  of the molded case circuit breaker  10  by a mechanical frame  51 . The key element of the operating mechanism  40  is the cradle  41 . As shown in FIG. 3, the cradle  41  includes a latch surface  41   a  which engages the upper latch surface in the intermediate latch  52 . The intermediate latch  52  is held in place by its mounting tabs which extend through the respective openings  51   a  on either side of the mechanical frame  51 . In the exemplary embodiment of the circuit breaker, the two side members of the mechanical frame  51  support the operating mechanism  40  of the circuit breaker  10  and retain the operating mechanism  40  in the base  12  of the circuit breaker  10 .  
         [0024]    [0024]FIG. 4 illustrates the breaker cover  20 . The breaker cover  20 , in the preferred embodiment, has two accessory sockets  22  formed in the cover  20 , with one accessory socket  22  on either side of the opening  29  for the pivoting member  13  and handle  14 . The breaker cover  20  with the accessory sockets  22  or compartments can be formed, usually by well known molding techniques, as an integral unit. The accessory socket  22  can also be fabricated separately and attached to the breaker cover  20  by any suitable method such as with fasteners or adhesives. The breaker cover  20  is sized to cover the operating mechanism  40 , the moveable contact  42  and the stationary contact  44 , as well as the trip mechanism  60  of the circuit breaker  10 . The breaker cover has an opening  29  to accommodate the handle  14 .  
         [0025]    Each accessory socket or compartment  22  is provided with a plurality of openings  24 . The accessory socket openings  24  are positioned in the socket  22  to facilitate coupling of an accessory  80  with the operating mechanism  40  mounted in the housing  12 . The accessory socket openings  24  also facilitate simultaneous coupling of an accessory  80  with different parts of the operating mechanism  40  or the intermediate latching  52 . Various accessories  80  can be mounted in the accessory compartment  22  to perform various functions. Some accessories, such as a shunt trip, will trip the circuit breaker  10 , upon receiving a remote signal, by pushing the trip bar  54  in a counter clockwise direction causing release of the intermediate latch  52  of the operating mechanism  40 . The shunt trip has a member protruding through one of the openings in the accessory socket  22  and engages the operating mechanism  40  via the trip bar  54 . Another accessory, such as an auxiliary switch, provides a signal indicating the status of the circuit breaker  10 , e.g. “on” or “off”. When the auxiliary switch assembly is nested in the accessory socket  22 , a member on the switch protrudes through one of the openings  24  in the socket  22  and is in engagement with the operating mechanism  40 , typically the cross bar  55 . Multiple switches can be nested in one accessory socket  22  and each switch can engage the operating mechanism through a different opening  24  in the socket  22 .  
         [0026]    The circuit breaker cover  20  has a latching protrusion  26  mounted in each accessory socket  22 . The preferred embodiment has latching protrusion attached to the upper edge of the accessory socket  22  (See FIGS. 4, 5 and  7 ). The latching protrusion can be heat staked in place, riveted or attached with an adhesive such as epoxy. One alternative embodiment of the present breaker cover  20  has the latching protrusion molded with an accessory base  84  which engages a detent in the accessory socket  22 .  
         [0027]    Each accessory socket also has a wire channel  27  for routing signal and power wires to the individual accessory  80 . In the preferred embodiment the wires pass through the wire channel  27  in the breaker cover  20  into a separate wire channel in the housing  22  of the circuit breaker  10  and then to a remote site for further connection.  
         [0028]    While the embodiment illustrated in the Figures and described above are presently preferred, it shall be understood that these embodiments are offered by way of example only. The invention is not intended to be limited to any particular embodiment, but is intended to extend to various modifications that nevertheless fall within the scope of the appended claims. For example, other types of accessories can be nested within the accessory sockets. It is also contemplated that a resilient member on the accessory engages a detent in the accessory sockets. It is also contemplated that the trip mechanism with the bi-metal trip unit or an electronic trip unit, and load terminal be housed in a separate housing capable of mechanically and electrically connecting to a housing containing the operating mechanism and line terminal thereby providing for a quick and easy change of current ratings for an application of the circuit breaker contemplated herein. Other modifications will be evident to those with ordinary skill in the art.  
         [0029]    What is claimed is:

Technology Category: 5