Abstract:
An auxiliary switch activation mechanism is provided for use with a circuit breaker having an auxiliary switch and an operating mechanism for opening and closing main electrical contacts. The auxiliary switch activation mechanism includes a lever having a first end removably connectable to the operating mechanism, a second end of said lever removably connectable to the auxiliary switch, and a spring, mechanically coupled to the lever, which imparts a rotational bias on the lever. The lever provides an assisting force to the operating mechanism for opening the main electrical contacts.

Description:
BACKGROUND  
         [0001]    Electrical circuit breakers are utilized throughout electrical power transmission and distribution systems to interrupt the flow of electric current to a protected load. A conventional circuit breaker includes a pair of separable (main) contacts that open in response to a fault condition (e.g., overcurrent or ground fault) to interrupt the current flow. Auxiliary position switches are typically mounted to the frame of the circuit breaker to provide an electrical signal indicative of the position of the main contacts.  
           [0002]    A typical auxiliary switch includes a separable contact structure in which one contact is disposed on a stationary contact arm, while the other contact is disposed on a movable contact arm. A spring generally urges the movable contact arm about a pivot to position the contacts in a normally open or normally closed state. A plunger engages the movable contact arm for opening the separable contacts in the normally closed configuration or for closing the separable contacts in the normally open configuration. When the plunger is depressed, it moves the movable contact arm to open or close the contacts accordingly.  
           [0003]    Typically, the plunger of the auxiliary switch is actuated by a solid mechanical link to an operating mechanism in the circuit breaker, which acts to separate the main contacts of the circuit breaker. The plunger is displaced upon rotation or displacement of the movable contact arm. The displacement of the auxiliary switch plunger separates (or joins) the contacts in the auxiliary switch, which causes an electrical signal to be sent to a local or remote alarm, light or other monitoring device, thereby indicating the position of the separable contacts in the circuit breaker.  
           [0004]    The force used to overcome the auxiliary switch spring and actuate the auxiliary switch is the same force used to separate the contacts in the circuit breaker. This force is typically provided by main springs in the operating mechanism of the circuit breaker. However, the use of the force provided by the main springs to actuate the auxiliary switch reduces the amount of force available to separate the contacts. Increasing the size of the main springs can compensate for the reduced force. However, increasing the size of the springs may not be desirable, since a corresponding increase in the size of the circuit breaker housing may result.  
         BRIEF SUMMARY  
         [0005]    The above discussed and other drawbacks and deficiencies are overcome or alleviated by an auxiliary switch activation mechanism provided for use with a circuit breaker having an auxiliary switch and an operating mechanism for opening and closing main electrical contacts. In an exemplary embodiment of the present invention, the auxiliary switch activation mechanism includes a lever having a first end removably connectable to the operating mechanism, a second end of said lever removably connectable to the auxiliary switch, and a spring, mechanically coupled to the lever, which imparts a rotational bias on the lever. The lever provides an assisting force to the operating mechanism for opening the main electrical contacts.  
           [0006]    In another embodiment, first end of the lever is removably connectable to a crank in the operating mechanism. The lever further comprises a foot which is slidingly engageable with a nose surface on the crank. The foot remains in contact with the nose surface when the circuit breaker main electrical contacts are in a closed position. Further, the foot is slidingly engageable with a bottom surface of the crank, and is removably engageable with the bottom surface when the circuit breaker main contacts are in an open or tripped position.  
           [0007]    In yet another embodiment, the lever is substantially L-shaped and further includes a lip, which is removingly engageable with the auxiliary switch. The lever imparts a rotational force on the crank when the circuit breaker main electrical contacts are caused to be opened or tripped from a closed position.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    Referring to the exemplary drawings wherein like elements are numbered alike in the several Figures:  
         [0009]    [0009]FIG. 1 is a partially exploded, perspective view of a circuit breaker including an auxiliary switch;  
         [0010]    [0010]FIG. 2 is a partially exploded perspective view of three cassettes contained in the circuit breaker shown in FIG. 1, depicting the auxiliary switch actuation mechanism;  
         [0011]    [0011]FIG. 3 is a perspective view of the cassettes and auxiliary switch actuation mechanism shown in FIG. 2;  
         [0012]    [0012]FIG. 4 is a side view of a circuit breaker operating mechanism shown mounted on a rotary contact assembly, illustrating the contacts in a closed position;  
         [0013]    [0013]FIG. 5 is another side view of the operating mechanism shown mounted on a rotary contact assembly, illustrating the contacts in an open position;  
         [0014]    [0014]FIG. 6 is a cross-sectional, side elevational view of the circuit breaker of FIG. 1, taken along line  6 - 6 , which generally illustrates the interconnection of the operating mechanism and the auxiliary switch actuation mechanism when the operating mechanism is tripped; and  
         [0015]    [0015]FIG. 7 is another partial cross-sectional, side elevational view of the circuit breaker of FIG. 1, taken along line  6 - 6 , which illustrates the interconnection of the operating mechanism and the auxiliary switch actuation mechanism when the operating mechanism is closed.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Referring initially to FIG. 1, there is shown a typical circuit breaker  10  having a base  12 , a midcover  14 , auxiliary switch sockets  16  formed within the midcover  14  and an exemplary auxiliary switch  18  positioned over its intended final installed position within the circuit breaker base  12 . In a  3 -pole system (i.e., corresponding with three phases of current), three rotary cassettes (outboard cassettes  28  and center cassette  22 ) are concurrently operated by an operating mechanism, as described hereinafter. A toggle handle  11  allows for the manual operation of cassettes  22 ,  28 . Auxiliary switch  18  includes a pair of electrical contacts (not shown) for external connection to a control/monitoring circuit (not shown) and a depressible plunger  66 , which opens and closes the auxiliary switch contacts. Sockets  16  include an aperture  15 , through which plunger  66  extends, and a ledge  17  upon which the bottom of auxiliary switch  18  rests.  
         [0017]    Referring now to FIGS. 2 and 3, a circuit breaker operating mechanism  20  is shown positioned over center cassette  22  by rods  24  and  26 . Rods  24  and  26  also position outboard cassettes  28  adjacent to center cassette  22 . FIG. 2 also illustrates an auxiliary switch actuation mechanism  50 . The auxiliary switch actuation mechanisms  50  feature a pair of pivotally mounted levers  52 , which fit over the outboard cassettes  28  and pivot about rod  24 . Each actuation mechanism  50  includes an activation spring  54 , which is secured about post  55  and positioned on the outside surfaces of center cassette  22 . Each lever  52  is generally L-shaped and further includes a lip  60  located along a horizontal section  62  thereon. The function of the lip  60  will be described in greater detail later. Lever  52  also has a foot  64  located at the end of its vertical section  58  and adjacent the lobe  56 .  
         [0018]    Referring now to FIGS. 4 and 5, center cassette  22  includes a rotary contact assembly  27  including a rotary contact arm  30  rotatably mounted therewithin. It should be noted that each cassette, including outboard cassettes  28 , feature rotary contact assemblies  27 . However, for ease of description, rotary contact assembly  27  in FIGS. 4 and 5 is the one included in center cassette  22 . Rotary contact assembly  27  of center cassette  22  further includes a crank  69  on each side of center cassette  22 . Each crank  69  is connected to a lower link  71  in operating mechanism  20  through a rivet  73  and pivots (in unison with rotary contact arm  30 ) about a center point  75 .  
         [0019]    An electrical contact  32  is secured to one end of a rotary contact arm  30 , which is maintained between cranks  69 , while another electrical contact  34  is secured to the opposite end of the rotary contact arm  30 . Rotary contact assembly  27  also includes a current carrying strap  36  extending from a load side of the cassette  22  and a current carrying strap  38  extending from a line side of the cassette  22 . A fixed contact  40  arranged proximate to contact  34  is electrically connected to the line side current carrying strap  38 . A fixed contact  42  arranged proximate to contact  32  is electrically connected to the load side current carrying strap  36 . The rotary contact arm  30  rotates to bring the contacts mounted on the rotary contact arm (movable contacts)  32  and  34  into and out of electrical connection with their associated fixed contacts  42  and  40 , respectively. When the fixed and movable contacts  32  and  42 , and  34  and  40  are touching (closed), electrical current passes from the line side current carrying strap  38  to the load side current carrying strap  36  via the closed contacts. When contacts  32  and  42 , and contacts  34  and  40  are separated (opened), the flow of electrical current from the line side current carrying strap  38  to the load side current carrying strap  36  is interrupted.  
         [0020]    [0020]FIG. 4 illustrates the rotary contact assembly  27  in the closed position. Toggle handle  11  is shown positioned to the right. The toggle handle  11  is rigidly connected to a handle yoke  51  which, in turn, is connected to a set of powerful mechanism springs  53  linked by a drive connector (not shown). The drive connector connects springs  53  to other components in the operating mechanism  20 , including rotary contact assembly  27 . FIG. 5 illustrates the rotary contact assembly  27  in the open position, with the toggle handle  11  shown positioned to the left.  
         [0021]    Referring now to FIGS. 6 and 7, the auxiliary switch actuation mechanism  50  is shown in operation with crank  69  of rotary contact assembly  27 . For ease of description, only one of two actuation mechanisms  50  will be described in operational detail. However, it should be understood that each actuation mechanism  50  functions identical to, and simultaneously with, the other actuation mechanism.  
         [0022]    When the circuit breaker  10  is in the open position, as depicted in FIG. 6, the lever  52  is biased in a clockwise direction by activation spring  54 , which engages lobe  56 , located along a vertical section  58  (FIG. 2) on lever  52 . The biasing force of spring  54  pivots the lever  52  in a clockwise direction (with respect to the views in FIGS. 6 and 7), thereby causing the lip  60  to completely engage and depress plunger  66  into auxiliary switch  18 . When depressed, plunger  66  either opens or closes contacts (not shown) in auxiliary switch  18 , as the case may be, and provides an appropriate indication as to the status of the main circuit breaker contacts. In the open position, lever  52  is completely disengaged from crank  69 .  
         [0023]    [0023]FIG. 7 illustrates the arrangement of the operating mechanism and the lever  52  when the main circuit breaker contacts are in the closed position. As the main breaker contacts are closed, the operating mechanism  20  is rotated clockwise, causing a bottom surface  68  of crank  69  to initially engage the foot  64  of lever  52 . This action then causes lever  52  to rotate in a counterclockwise direction, opposite to the biasing force of spring  54 . As the lever  52  is rotated counterclockwise, its foot  64  slides along the bottom surface  68  of crank  69  until it finally comes into contact with a nose surface  70  of crank  69 . When the operating mechanism  20  has completed its rotational motion to the closed position, it can be seen that the lip  60  of lever  52  has sufficiently rotated counterclockwise such that it has disengaged from and released plunger  66 . When released, the plunger  66  correspondingly closes or opens the auxiliary switch  18  contacts.  
         [0024]    The nose surface  70  of crank  69  requires very little force to bias the foot  64  of lever  52  in a counterclockwise direction. Once the main breaker contacts are in the closed position, they may be subsequently opened manually or tripped open during a fault or overcurrent condition. In such a case, the crank  69  begins to rotate counterclockwise, back toward the position shown in FIG. 6. During this counterclockwise rotation, the nose surface  70  of crank  69  slides across the foot  64  of lever  52  (in the opposite direction of that during the closing sequence). As soon as the nose surface  70  is clear of the foot  64 , the lever  52  is released and caused to be rotated in a clockwise direction by activation spring  54 . The foot  64 , being rotated clockwise in this manner, then catches the bottom surface  68  of crank  69  and imparts an additional counterclockwise force on the crank  69 , thereby assisting the main springs in the operating mechanism  20  to rotate the contact arm and separate the main contacts. Finally, the crank  69  and lever  52  return to their original positions as depicted in FIG. 4 with the plunger  66  once again completely depressed by lip  60 .  
         [0025]    The embodiments as described hereinbefore provide a reliable actuation arrangement for actuating contacts in a circuit breaker auxiliary switch while requiring a minimal amount of energy from the operating mechanism. Further, the actuation arrangement assists the operating mechanism during that part of the opening cycle when the energy of the operating mechanism is at its lowest.  
         [0026]    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 the 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.