Abstract:
A circuit breaker assembly includes first and second rotary contact assemblies mountable to a base member, a circuit breaker operating mechanism mounted to the first rotary contact assembly, and a trip bar in mechanical communication with the first rotary contact assembly and the circuit breaker operating mechanism. The rotary contact assemblies each include rotors rotatable about axes therethrough and movable contact arms pivotally mounted within the rotors. The circuit breaker operating mechanism serves to position the rotors to separate movable contacts thereon from fixed contacts. A trip override device includes spring links operably connected via springs to each of the rotors of the rotary contact assemblies and the trip bar. The trip bar comprises trip levers protruding radially therefrom and being in mechanical communication with the rotary contact assemblies.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to circuit breakers, and, more particularly, to a trip system for a high-level interruption of current that functions as a result of the rotor system of a rotary circuit breaker. 
     Override systems of the prior art typically use electronic trip units to respond to high-level fault conditions and initiate the separation of all of the contacts in a plurality of rotary circuit poles ganged together to form a multi-pole circuit breaker. For example, in U.S. Pat. No. 4,616,198 entitled “Contact Arrangement for a Current Limiting Circuit Breaker”, separate electrodynamic forces may be generated in any of the poles of the circuit breaker causing the contact arms to pivot upon an overcurrent condition. As the contact arms are pivoted, the contacts secured to the arms are separated from the stationary contacts mounted within the circuit breaker, thereby stopping the flow of electric current through the contacts. In that invention, a contact arm associated with one pole of the circuit breaker can open independently of the contact arms associated with the other poles of the circuit breaker. Therefore, the current in only one pole is interrupted upon an overcurrent condition. The override system serves to avoid the occurrence of such “single phasing”, where one of the phases interrupts independently of the remaining phases. 
     Another use of electronic trip units is recited in U.S. Pat. No. 4,672,501 entitled “Circuit Breaker and Protective Relay Unit”, which describes the use of electronic circuitry to determine the occurrence of an overcurrent and the use of a current transformer to sense circuit current. However, when using such circuitry in conjunction with rotary contact arrangements, the current transformer cores can become saturated upon occurrence of a short circuit overcurrent and an auxiliary trip unit must be employed to ensure short circuit overcurrent protection. 
     Short circuit overcurrent protection in rotary contact circuit breakers is also described in U.S. Pat. No. 5,103,198 entitled “Instantaneous Trip Device of a Circuit Breaker”, wherein the overpressure developed within a circuit breaker arc chamber upon contact separation in one pole drives a piston against an operating mechanism trip bar to actuate contact separation in the remaining circuit breaker poles. However, it has since been determined that the overpressure response is sensitive to voltage levels upon arc occurrence and that it is less sensitive to short circuit current values. 
     Electronic methods of contact separation, especially those that operate as the result of magnetic repulsive forces, are slower to respond and thereby increase the time required for a circuit breaker operating mechanism to respond to an overcurrent. 
     SUMMARY OF THE INVENTION 
     In the present invention, a circuit breaker assembly includes first and second rotary contact assemblies mountable to a base member, a circuit breaker operating mechanism mounted to the first rotary contact assembly, and a trip bar in mechanical communication with the first rotary contact assembly and the circuit breaker operating mechanism. The rotary contact assemblies each include rotors rotatable about axes therethrough and movable contact arms pivotally mounted within the rotors. The circuit breaker operating mechanism serves to position the rotors to separate movable contacts thereon from fixed contacts. A trip override device includes spring links operably connected via springs to each of the rotors of the rotary contact assemblies and the trip bar. The trip bar comprises a trip rod having trip levers protruding radially therefrom and being in mechanical communication with the rotary contact assemblies. 
     The above trip override system allows contact separation in one pole to actuate the operating mechanism in all other poles in the circuit breaker. The system has many advantages over the prior art, including that it functions independently of the system voltage by working off the mechanics of the rotor system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a rotary contact assembly; 
     FIG. 2 is a side elevation view of the rotary contact assembly embodying a trip override device, of the present invention, showing the contacts in a closed position; 
     FIG. 3 is a side elevation view of the rotary contact assembly embodying the trip override device, of the present invention, showing the contacts in a tripped position; 
     FIG. 4 is a perspective view of the rotary contact assembly embodying the trip override device, of the present invention, showing the contacts in a tripped position; 
     FIG. 5 is a perspective view of a spring link, of the present invention, attached to a contact arm and engaging a trip lever, of the present invention, on a trip bar, of the present invention; 
     FIG. 6 is a perspective view of the trip bar, of the present invention, relative to a rotary contact assembly and a latching mechanism; and 
     FIG. 7 is an exploded perspective view of three rotary contact assemblies, a circuit breaker operating mechanism, and a trip bar, of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a circuit breaker cassette, shown generally at  10 , comprises a rotary contact assembly, shown generally at  12 , in an electrically-insulative housing  14  intermediate a line-side contact strap  16 , and a load-side contact strap  18 . Line-side contact strap  16  is electrically connectable to line-side wiring (not shown) in an electrical distribution circuit, and load-side contact strap  18  is electrically connectable to load-side wiring (not shown) via a lug (not shown) or a device such as a bimetallic element or current sensor (not shown). Although only a single cassette  10  is shown, a separate cassette  10  is employed for each pole of a multi-pole circuit breaker and operated in a manner similar to that of cassette  10 . 
     Electrical transport through rotary contact assembly  12  of cassette  10  occurs from line-side contact strap  16  to an associated fixed contact  24 , through movable contacts  26 ,  28  secured to the ends of a movable contact arm shown generally at  30 , and to an associated fixed contact  32  on load-side contact strap  18 . Movable contact arm  30  is pivotally arranged between two halves of a rotor  34  and moves in conjunction with rotor  34  upon manual articulation of rotor  34 . Rotor  34  is rotatably positioned on a rotor pivot axle (shown below with reference to FIGS.  2  and  3 ), the ends of which are supported by inner parallel walls of electrically-insulative housing  14 . 
     Referring now to FIG. 2, rotary contact assembly  12  is shown in an “untripped” or “on” position. An inventive spring link is shown generally at  36 . Spring link  36  comprises two substantially flat L-shaped members  38  connected at the first ends thereof by a pivot pin  40 . Each L-shaped member  38  is pivotally mounted to opposing sides of contact arm  30  using pivot pin  40  and is fixed in a parallel planar relationship with the other by a spring pin  42  and a trip pin  44 . Trip pin  44  is fixedly connected to and between the second ends of each L-shaped member  38  and is mechanically communicable with a trip bar  54 . Spring pin  42  is positioned intermediate the ends of L-shaped member  38  and extends normally through each L-shaped member  38 . Spring pin  42  is captured within rotor  34  via an elongated clearance slot  46  cut into the face of rotor  34  thereby allowing spring link  36  to rotate and translate relative to rotor  34  in the manner described with reference to FIGS. 3 and 4. 
     A first contact spring  35  stretches across the face of rotor  34 . First contact spring is supported on one end by the protrusion of spring pin  42  through slot  46  on the face of rotor  34  and is supported on the other end by a support pin (not shown) on the same face of rotor  34  and located on the perimeter of rotor  34  opposite slot  46 . A second contact spring (not shown) is likewise supported on the same face of rotor  34  and is positioned to extend parallel to the first contact spring  35 . A third contact spring (not shown) is positioned on the opposing face of rotor  34 , is supported by the protrusion of spring pin  42  and the support pin, and functions in the same manner as the first contact spring. A fourth contact spring (not shown) is supported on the opposing face of rotor  34  parallel to the third contact spring. The contact springs are connected to both rotor  34  and contact arm  30  in such a manner so as to bias contact arm  30  into a closed position relative to rotor  34 , thereby ensuring an electrically sound connection between fixed contacts  24 ,  32  and movable contacts  26 ,  28 . 
     A spring force F is exerted by the first contact spring  35  and the third contact spring to draw spring pin  42  toward the support pin. Force F is transferable to movable contact arm  30  via spring pin  42 , spring link  36 , and pivot pin  40 . If pivot pin  40  is rotated in a clockwise direction about a rotor pivot axle  50 , force F causes the rotation of movable contact arm  30  and urges movable contacts  26 ,  28  toward fixed contacts  24 ,  32 . A second spring force (not shown) is exerted by the second-and fourth contact springs to assist in biasing contact arm  30  such that fixed contacts  24 ,  32  and movable contacts  26 ,  28  are engaged. 
     Referring now to FIGS. 3 and 4, rotary contact assembly  12  is shown with contact arm  30  in the “forced open” position as a result of an encountered overcurrent condition. As a result of this overcurrent condition, movable contacts  26 ,  28  and fixed contacts  24 ,  32  are separated by magnetic repulsive forces that occur between fixed contacts  24 ,  32  and movable contacts  26 ,  28 . The forces caused by magnetic repulsion act against the forces created by the contact springs, which tend to maintain fixed contacts  24 ,  32  and movable contacts  26 ,  28  in a closed position. If the repulsive force exceeds the closing force created by the contact springs, contact arm  30  rotates in the direction of an arrow  48  while rotor  24  remains in a closed stationary or “on”position. The rotation of contact arm  30  moves pivot pin  40  in the direction of an arrow  49  around rotor pivot axle  50  in an arcuate path. As pivot pin  40  begins to move, the motion of pivot pin  40  along the arcuate path relative to slot  46  is transferred to spring pin  42 , which translates along slot  46  toward an outer perimeter of rotor  34 . Simultaneous with the arcuate movement of pivot pin  40  and the translation of spring pin  42  along slot  46 , the second ends of L-shaped members  38  between which trip pin  44  is positioned pivot about pivot pin  40 . As trip pin  44  pivots, it engages a trip lever  52  on a trip bar  54  that unarmes a circuit breaker operating mechanism  13  via a trip mechanism arm  55  or arm extending from the trip bar  54 . The operating mechanism  13  opens all contacts in the circuit breaker and thereby stops the flow of electrical current through the circuit breaker for all poles disposed therein. 
     Referring now to FIG. 5, a trip bar is shown generally at  54  and as it would be positioned relative to contact arm  30 . Trip bar  54  comprises an elongated rod  56  having a plurality of trip levers  52  protruding radially therefrom. Trip rod  56  is rotatable about a longitudinal axis thereof such that each trip lever  52  pivots about the longitudinal axis of trip rod  56  and is engageable by a corresponding trip pin  44  associated with a corresponding rotary contact assembly. In an overcurrent condition associated with a single rotary contact assembly  12 , trip pin  44  will engage trip lever  52 , which will in turn axially rotate trip rod  56 , thereby pivoting the trip mechanism arm  55  extending from trip rod  56 . 
     In FIG. 6, rotary contact assembly  12  having a circuit breaker operating mechanism  13  located thereon is shown. Circuit breaker operating mechanism  13  has an arm assembly  68 . Rotary contact assembly  12  having circuit breaker operating mechanism  13  located thereon may be ganged together with other rotary contact assemblies. Arm assembly  68  is actuatable by the trip mechanism  58 . In the event of a fault condition, such as an overcurrent in only a single pole of circuit breaker  10 , trip mechanism  58  causes the tripping of all other poles of the circuit. Trip mechanism  58  is shown positioned on a side of rotary contact assembly  12 . During operation of the circuit under a fault condition, trip bar  54  rotates causing trip mechanism arm  55  to pivot downward about trip bar  54 . Trip mechanism arm  55  is pivotally engaged with a linkage element  60  of trip mechanism  58 , which in turn causes a trip element  62  to pivot about a pivot point  64  and move a trip arm  66  of arm assembly  68 . Movement of arm assembly  68  unarmes the operating mechanism  13 , which causes the contacts associated with other poles of the circuit breaker to open and stop the flow of electrical current through that pole of the circuit breaker. 
     Referring now to FIG. 7, trip bar  54  is shown as it would be positioned relative to a plurality of cassettes  14  containing rotary contact assemblies  12  and circuit breaker operating mechanism  13  positioned atop one of cassettes  14 . Rods  72  are disposed through holes  73  in rotary contact assemblies  12  to link rotors  34  to circuit breaker operating mechanism  13 . It can be seen that when any one of the contact arms is forced open due to repulsive forces generated during an overcurrent condition, trip lever  52  is thrown, thereby causing trip bar  54  to rotate, which in turn causes circuit breaker operating mechanism  13  to unlatch. Because all rotors  34  are attached by rods  72 , the pivoting of rods  72  about the pivot point of rotor  34  causes all rotors  34  to rotate and move the contacts in each pole from a closed position to an open position. 
     Trip bar  54 , which comprises trip rod  56  and trip lever  52  depending from trip rod  56 , is a part of a trip override system for circuit breaker operating mechanism  13 , which allows contact separation in one pole to actuate the operating mechanism in all other poles in the circuit breaker. The above system has many advantages over the prior art, including that it functions independently of the system voltage by working off the mechanics of the rotor system. 
     While this 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.