Abstract:
A permanently installed manual trip mechanism is mounted internally to a circuit breaker with a user operated handle extending to the outside of the enclosure. The mechanism converts a relatively small operator input to larger spring charge. Upon triggering, the mechanism provides the required operating velocity of the circuit breaker during the opening stroke for load break operation.

Description:
CLAIM OF PRIORITY 
     This application claims priority to U.S. Provisional Application No. 61/153,007 filed on Feb. 17, 2009 and entitled Manual Tripping Device for Circuit Breaker, the contents of which are incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     Circuit breakers are commonly found in substations and are operable to selectively open and close electrical connections. Modern medium to high voltage circuit breakers include automatic, electronically controlled actuating systems that recognize fault conditions and initiate trip sequences. These electronically controlled breakers may also be remotely actuated from an off-site location, such as a power utility operational control room. 
     Despite the highly automated nature of modern circuit breakers, the need still exists for reliable and safe means to manually actuate (open) the breaker. Manual tripping (opening) of a circuit breaker must follow through the stroke of the actuation with enough force to achieve proper contact velocities (i.e. the velocity the two contacts are drawn apart) regardless of the amount of energy remaining in the “wipe” contact springs. As the contacts erode, the amount of force and stored energy in the circuit breaker decreases and the force and energy required by the manual tripping device to open the circuit breaker increases. The design of the manual tripping device is such that it functions properly with the minimum amount of contact wipe spring compression on all phases (or worst case condition). Forces that must be overcome by a manual actuation mechanism include: the magnetic holding force of the magnetic actuators (from installed permanent magnets), weld break of any contacts if needed, operating friction and acceleration of mass in various parts. In medium voltage outdoor circuit breakers (i.e. 5 kV through 38 kV), the magnetic holding force of the actuator is based on the interrupting rating and requires enough holding force to withstand the forces generated by approximately 12 to 50 kA rms, asym fault current and possibly higher. This force is counteracted by the total “wipe” spring contact force acting on the actuator. The wiping spring contact force reduces the manual tripping force requirement, but the holding force of the actuator remains a significant value, and the resulting net latching force (manual tripping force required) can be over 1000 lbs in a circuit breaker with a high short circuit rating. In addition, the human operator should not be required to apply greater than a 50 lb force to a lever or handle to manually trip the unit. 
     Some prior art manual actuation devices incorporate an automatic spring charged mechanism for opening and closing operations. According to these designs, energy is transferred from a power device, such as an electric motor, and stored in a spring system which holds the charge indefinitely, even in the absence of control power to the motor. When triggered manually, the mechanism provides the tripping (opening) energy and operation of the circuit breaker. Such solutions are relatively more expensive, as they require an internal source of input power (electric motor). Further, if the spring charge is exhausted, no further operation is possible unless power is available to the input power source. Further, such mechanisms typically require a regular maintenance cycle, due to the use of the older electric motor and an excessive amount of small parts in the mechanism. Such maintenance cycles are disadvantageous, as operators prefer maintenance free equipment wherever possible. 
     Thus, there is a need in the art for a manual tripping mechanism that can initiate and complete the manual tripping operation without any motorized spring charging mechanism and is operable with reduced input force applied by an operator on the lever. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention a manual operating mechanism is provided for a circuit breaker having a breaker shaft operatively connected to one or more poles. The manual operating mechanism includes an operating shaft having a handle secured thereto. A charging assembly is operatively engaged with the operating shaft through a radially offset linkage. The charging assembly carries a main spring. A trigger assembly engages and selectively supports a first end of the main spring. Rotation of the operating shaft in a first direction causes the main spring to compress against the trigger assembly until a trigger point is reached. When the trigger point is reached, the trigger assembly stops supporting the first end of the main spring and the main spring operatively engages the breaker shaft to cause movement thereof. 
     According to another aspect of the present invention a manual operating mechanism is provided for a circuit breaker having a breaker shaft operatively connected to one or more poles. The manual operating mechanism includes an operating shaft having a handle secured thereto. A charging assembly is operatively engaged with the operating shaft. The charging assembly carries a main spring. A trigger assembly engages and selectively supports a first end of the main spring. The trigger assembly includes a trigger. A toggle assembly is operatively connected to the operating shaft and alternately aids or resists rotation of the operating shaft depending on the angular position of the operating shaft. Rotation of the operating shaft in a first direction causes the main spring to compress against the trigger assembly until the toggle assembly contacts the trigger, at which time, the trigger assembly stops supporting the first end of the main spring and the main spring operatively engages the breaker shaft to cause movement thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevated view of a breaker having a manual actuator according to the present invention; 
         FIG. 2  shows an elevated rear view of a breaker according to  FIG. 1 ; 
         FIG. 3  shows a partially schematic view of the interior of a pole as shown in  FIG. 1  wherein the internal contacts are open; 
         FIG. 4  shows a partially schematic view of the interior of a pole as shown in  FIG. 1  wherein the internal contacts are closed; 
         FIG. 5  shows a rear view of the breaker of  FIG. 1  with the housing and poles removed for clarity; 
         FIG. 6  shows a side profile view of the manual actuator in a first, steady state position according to the present invention wherein the housing, poles and magnetic actuator are removed for clarity; 
         FIG. 7  is a rear view of a of the manual actuator of  FIG. 6 ; 
         FIG. 8  is a rear and right side view of the manual actuator of  FIG. 6 : 
         FIG. 9  is a rear and left side view of the manual actuator of  FIG. 6 ; 
         FIG. 10  is a side profile view of the manual actuator in a second position wherein the housing, poles, magnetic actuator, and crank shaft are removed for clarity. 
         FIG. 11  is a rear and right side view of the manual actuator of  FIG. 10 ; 
         FIG. 12  is a rear and left side view of the manual actuator of  FIG. 10 ; 
         FIG. 13  is a side profile view of the manual actuator in a third position just before triggering, wherein the housing, poles, magnetic actuator, and crank shaft are removed for clarity. 
         FIG. 14  is a rear and right side view of the manual actuator of  FIG. 13 ; 
         FIG. 15  is a rear and left side view of the manual actuator of  FIG. 13 ; 
         FIG. 16  is a side profile view of the manual actuator in a fourth position after triggering, wherein the housing, poles, magnetic actuator, and crank shaft are removed for clarity. 
         FIG. 17  is a rear and right side view of the manual actuator of  FIG. 16 ; 
         FIG. 18  is a rear and left side view of the manual actuator of  FIG. 16 ; and 
         FIG. 19  is a rear and right side view of the manual actuator of  FIG. 16  showing the crank shaft. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With Reference now to  FIGS. 1 and 2 , a circuit breaker is shown and generally indicated with the numeral  10 . Circuit breaker  10  is a three phase circuit breaker, and thus includes three poles  12   a,    12   b  and  12   c.  Each pole includes a first exterior electrical connection  14  and a second exterior electrical connection  16 . As is known in the art, electrical power lines are coupled to first exterior connection  14  and second exterior connection  16  and breaker  10  selectively opens or closes the electrical connection therebetween. 
     With reference to  FIGS. 3 and 4 , a simplified view of the interior of the poles  12  is shown, wherein first exterior electrical connection  14  is electrically connected to a stationary contact  18  which is immovably secured within pole  12 . Second exterior electrical connection  16  is electrically connected to a movable contact  20  which is carried within pole  12  in a manner allowing longitudinal movement therein. Thus, in a first position, the movable contact  20  may be positioned to break the electrical connection between first exterior electrical connection  14  and second exterior electrical connection  16  (see  FIG. 3 ). In a second position, the movable contact  20  may be brought into contact with stationary contact  18  to electrically connect the first exterior electrical connection  14  and the second exterior electrical connection  16  (see  FIG. 4 ). In one or more embodiments, poles  12  may contain isolative materials such as oils or inert gasses. In other embodiments, the interior of poles  12  may be devoid of gasses or liquids (i.e. vacuum). Each pole  12  may further include wipe springs (not shown) that are positioned to maintain contact pressure between stationary and movable contacts  18  and  20  when they are in the second, engaged position. 
     With reference to  FIG. 2 , an actuating rod  22  extends into each pole  12  and is mechanically, connected to the movable contact  20  in each pole. Thus, the longitudinal movement of actuating rod  22  causes the movement of movable contact  20  as discussed above. The actuating rod  22  for each of the three poles  12  extends into a housing  24  (shown with the rear and side covers removed for clarity). Within housing  24 , a crank shaft  26  is positioned, having an axis of rotation perpendicular to the longitudinal movement of actuating rods  22 . All three actuating rods  22  are coupled to crank shaft  26  through brackets  28 . In this manner, it can be seen that rotation of crank shaft  26  causes predominately longitudinal movement of actuating rods  22 . Thus, rotation of crank shaft  26  causes the movement of movable contact  20 , which consequently opens or closes the electrical connection between first and second exterior electrical connections  14  and  16 . 
     As discussed above, normal opening and closing of the circuit breaker is performed automatically by a magnetic actuator  30 . Reference is now made to  FIG. 5 , which shows breaker  10  with poles  12  and housing  24  removed for clarity. Magnetic actuator  30  includes a driving shaft  32  that is coupled to crank shaft  26  through a bracket  34 . Driving shaft  32  is selectively driven upward or downward by electrically powered coils. Upward or downward movement causes rotation of crank shaft  26 . When in the open or closed position, internal magnets then hold the driving shaft  32  in position. Magnetic actuator  30  may be triggered by on-board electronics reacting to a sensed fault or other condition. Magnetic actuator  30  may also be triggered remotely upon receipt of a trip command from a utility control room operator. 
     Though the magnetic actuator  30  provides the normal actuation of breaker  10 , in many instances, manual actuation of the breaker is required. For example, manual actuation may be required if magnetic actuator power is lost, if the magnetic actuator malfunctions or is damaged, if there was a system failure electrically or mechanically, or if local ground personnel wish to manually block the operation of the breaker during maintenance. In such situations, a manual actuator  40  according to the present invention is provided to allow a local, human operator to manually operate breaker  10 . 
     With reference now to  FIGS. 2 , and  6 - 9 , manual actuator  40  includes an exterior handle  42  that is provided for a human operator to impart a force. Exterior handle  42  is secured to an operating shaft  44  positioned within housing  24 , such that, when a force is applied to handle  42  by a utility service person, operating shaft  44  will rotate. The axis of rotation of crank shaft  26  and operating shaft  44  are parallel and vertically offset. Operating shaft  44  is carried at one end on a housing bushing (not shown) and at the opposed end, by a bushing (not shown) in a support bracket  46 . 
     A toggle assembly  47  is provided proximate to support bracket  46 . As will be hereinafter discussed, toggle assembly  47  provides a holding force on operating shaft  44  when in the unactuated position. Further, during operation, once an over-toggle point is reached, the toggle assembly  47  aids the human operator in rotating the operating shaft  44 . Toggle assembly  47  includes a pair of spaced flanges  48 , a T-shaped pin  50 , a trunion  52  and a toggle spring  54 . Flanges  48  are secured to operating shaft  44  and rotatable therewith. The spaced flanges  48  extend radially outwardly from operating shaft  44  and are coupled to T-shaped pin  50  which is itself slidably mounted to trunion  52 . The trunion  52  is rotatably carried in support bracket  46 . Toggle spring  54  is carried between trunion  52  and the outwardly extending arms  56  of T-shaped pin  50 . Because T-shaped pin  50  is secured to flanges  48  and is also slidably received in trunion  52 , toggle spring  54  will variably compress or expand based on the rotational position of operating shaft  44 . In other words, as will be discussed in greater detail below, toggle spring  54  either resists or aids rotation of operating shaft  44  depending upon the direction of rotation and angular position of operating shaft  44 . 
     Flanges  48  are coupled to a transfer shaft  58  at a location angularly offset (with respect to operating shaft  44 ) from T-shaped pin  54 . Transfer shaft  58  is spaced from, and extends parallel to operating shaft  44 , through a first arc shaped slot  59  in support bracket  46 . As can be seen, rotation of operating shaft  44  draws transfer shaft  58  through an arcing, semi-circular path. 
     A charging assembly  49  is provided on the opposed side of support bracket  46 . As will be hereinafter discussed, charging assembly  49  acts to compress a main spring  76  when operating shaft  44  is rotated. In this manner, main spring  76  stores the energy necessary to manually operate the breaker  10 . Charging assembly  49  includes a main spring arm  60  which is rotatably coupled to transfer shaft  58  at the opposed end from flanges  48 . Main spring arm  60  includes a generally J-shaped bottom portion  62  that wraps around, but is not coupled to, a pivot shaft  63  that extends from support bracket  46  and is axially aligned with operating shaft  44 . Main spring arm  60  extends upwardly from J-shaped portion  62  and terminates at the top at a T-shaped mounting area  64 . 
     Charging assembly  49  further includes a pair of pivot arms  66  and a bracket  68 . Each arm of the T-shaped mounting area  64  is coupled to one of the pivot arms  66 , which are each rotatably secured to bracket  68 . Thus, main spring arm  60  is carried at the top by a pair of pivoting arms  66  and carried on the bottom on transfer shaft  58 . As will be discussed in greater detail below, main spring arm  60  moves up or down (relative to pivot shaft  63 ), in a generally arcing motion, when operating shaft  44  rotates. For example, from a starting point of the configuration of  FIGS. 6-9 , if operating shaft  44  rotates clockwise (hereinafter rotational direction is taken from the reference point of the handle end of operating shaft  44 ), transfer shaft  58  will travel downward in an arcing fashion. Because main spring arm  60  is pivotally secured to transfer shaft  58 , and because pivot arms  66  allow downward movement, main spring arm  60  will thus move downward, relative to pivot shaft  63 . 
     Main spring arm  60  further includes a generally flat, landing surface  70  and a spring receiving portion  72  that extends between landing surface  70  and the T-shaped mounting area  64 . A base plate  74  is received on the spring receiving portion  72  and is slidable on spring receiving portion  72  until reaching landing surface  70 , wherein further sliding movement is prevented. A main spring  76  is positioned on spring receiving portion and is secured between T-shaped mounting area  64  and base plate  74 . Thus, main spring  76  is compressible between T-shaped mounting area and base plate  74 . 
     The pivot shaft  63  carries a trigger assembly  78  that, as will be discussed below, enables the spring charge on main spring  76  to grow, and ultimately release, allowing main spring  76  to rotate crank shaft  26 . Trigger assembly  78  includes a pair of bottom linkages  80  and a pair of top linkages  82 . Bottom linkages  80  are positioned on each side of main spring arm  60  and are secured to pivot shaft  63  in a manner allowing rotation thereon. Bottom linkages  80  extend upwardly and are secured to top linkages  82  by a fastener  84  that allows for relative pivoting motion therebetween. The opposed ends of top linkages  82  are coupled together by a guide pin  86  which is received in a guide channel  88  running longitudinally on main spring arm  60 . Guide channel  88  extends downwardly from proximate to landing surface  70  into spring receiving portion  72 . 
     A foot extends rearwardly from bottom linkage  80   a  and attaches to a tension spring  92 , which is secured to a bracket  94 . In this manner, bottom linkages  80  are biased in the counterclockwise direction. The bottom linkage  80   b  closest to support bracket  46  further includes a trigger  96  that extends through a second arced slot  98  in support bracket  46 . As will be discussed in greater detail below, trigger  96  is positioned to contact a leading edge of flange  48  when operating shaft  44  is rotated to a predetermined position. 
     Slot  98  is semi-circular and includes a stop edge  99  trigger  96  is freely movable through slot  98  until engaging stop edge  99 , which thereafter prevents relative rotation between top and bottom linkages  82  and  80  beyond a predefined angle. According to one embodiment, the predefined angle is about 185 degrees. In this or other embodiments, range could be from about 182 to about 185 degrees. Thus, without any other forces acting on trigger assembly  78 , spring  92  pulls bottom linkages  80  rearward until further relative rotation between bottom and top linkage is prevented by the trigger  96  contacting stop edge  99  and rotation of the trigger assembly  78  as a whole is prevented by guide pin  86  contacting the walls of guide channel  88 . In this support configuration, bottom linkages  80  are oriented at approximately 185 degrees relative to top linkages  82 . Hereinafter, this configuration is referred to as the first or steady state configuration. It should further be appreciated that trigger assembly, when in this first configuration, is capable of supporting a downward directed force at the top of top linkage  82 . 
     Manual actuator  40  may also include an electrical interlock switch  100  (see  FIG. 9 ) which is positioned to sense when operating shaft  44  rotates. If rotation (indicating manual actuation) is sensed, operation of the magnetic actuator  30  is prevented, even if normal operating power is available. 
     During normal automatic operation, manual actuator  40  remains in the first, steady state configuration as shown in  FIGS. 1-9 . When in the steady state configuration, toggle spring  54  imparts a force on flanges  48  urging operating shaft  44  in the counterclockwise direction. However, rotation is prevented because counterclockwise rotation of flanges  48  would cause upward movement of main spring arm  60 , which is prevented from doing so because J-shaped portion  62  engages pivot shaft  63 . Thus, toggle spring  54  holds operating shaft  44 , and consequently handle  42  in a first operating position. 
     When handle  42  is in the first operating position, trigger assembly  78  is in a holding, weight bearing position, wherein, the top linkages  82  are angled slightly and trigger  96  rests against stop edge  99 . When in this configuration, the manual actuator  40  does not affect or inhibit the operation of breaker  10 . Specifically, base plate  74  is held above, but do not contact, a pair of lever arms  104  coupled to crank shaft  26 . 
     When in the first, steady state position, base plate  74  is supported by landing surface  70  and the top edge of top linkage  82  is proximate too, but does not contact base plate  74 . As will be discussed below in greater detail, such a configuration allows the manual actuator to properly reset (i.e. allows trigger assembly to reposition in the steady state position) after manually actuating breaker  10 . 
     If manual actuation of breaker  10  is required, a human operator grips exterior handle and causes operating shaft  44  to rotate clockwise. With reference now to  FIGS. 10-12 , a second operating shaft position is shown representing the initiation of a manual actuation when a human operator pulls on handle  42 . As can be seen, as the operating shaft  44  rotates, the rotation is resisted by toggle spring  54 , which is in compression and is acting on flanges  48 . 
     Clockwise rotation of operating shaft  44  causes main spring to  76  to begin charging. Specifically, because main spring arm  60  is connected to flanges  48  via transfer shaft  58 , rotation of flange  48  causes main spring arm  60  to lower. As main spring arm  60  is lowered, trigger assembly  78  contacts base plate  74  and landing surface  70  is drawn away from base plate  74  which is held in place by top linkage  82 . In this manner, trigger assembly  78  takes up the force of the main spring  76  as landing surface  70  moves away. According to one embodiment, main spring  76  may be selected and positioned so that, when in the steady state position, the spring is pre-compressed. 
     As discussed above, main spring  76  is secured between T-shaped mounting area  64  of main spring arm  60  and base plate  74 . Thus, as main spring arm  60  is lowered, main spring  76  is compressed because T-shaped mounting area  64  is dawn lower and base plate  74  is held in place by trigger assembly  78 . In this manner, rotation of operating shaft  44  causes main spring  76  to charge. 
     Further rotation of operating shaft  44  causes toggle spring  54  to compress and trunion  52  to pivot until the trunion  52  reaches a toggle point, wherein the longitudinal axis of toggle spring  54  is radially aligned with operating shaft  44 . After reaching the toggle point, further clockwise movement, as shown in  FIGS. 13-15  is aided by toggle spring  54 . Thus, as compression on main spring  76  increases (thereby increasing the resistance against further clockwise movement), toggle spring  54  begins to aid clockwise motion of operating shaft  44 . As operating shaft  44  continues to rotate, trigger assembly  78  continues to support main spring  76  while main spring arm  60  continues to move downward, compressing spring  76 . 
     As the operating shaft  44  continues to rotate, main spring arm  60  continues to move downwardly relative to base plate  74 . However, because transfer shaft  58  moves in an arcing motion, as operating shaft  44  rotates, the component of the main spring force resisting rotation grows smaller. In other words, as the charge on the main spring grows, the effective moment arm is reduced. In this manner, the required input torque by the human operator is reduced and held within an acceptable range throughout the rotation of the operating handle  42 . 
     With reference now to  FIGS. 13-15 , an initial trip configuration or trigger point is shown, wherein the leading edge of flange  48  contacts trigger  96 . At this time, main spring  76  is substantially fully charged. According to one embodiment, when in the initial trip position, the transfer shaft  58  is proximate to the lowest point in its arced travel path. In other words, when in the initial trip configuration, the main spring  76  is at or near its maximum compression. 
     When flange  48  contacts trigger  96 , bottom linkage  80  is forced in a clockwise motion, causing the relative angle between top linkages  82  and bottom linkages  80  to rotate to less than 180 degrees. This causes trigger assembly  78  to destabilize. With the base plate  74  no longer supported by trigger assembly  78 , main spring  76  rapidly forces base plate  74  downward and into contact with crank shaft arms  104  which are positioned below base plate  74  (see  FIGS. 7 ,  8 , and  19 ). 
     With reference now to  FIGS. 16-19 , it can be seen that main spring  76 , acting through base plate  74 , contacts crank shaft arms  104 , thereby rotating crank shaft  26 . The force of main spring  76  is sufficient to overcome the actuator magnet resistance, contact welding, and any other system resistance so that rotation of crank shaft  26  causes the contacts within poles  12  to separate at the appropriate speed. After triggering, it can be seen that the destabilized trigger assembly  78  collapsed and is in a tripped configuration, however, top linkage  82  is still held against base plate  74  by tension spring  92 . 
     Manual actuator  40  may be reset by simply reversing the above disclosed steps. Specifically, counterclockwise rotation of operating shaft  44  causes landing surface  70  to move upwardly, consequently pushing base plate  74  upwardly. Top linkage  80 , urged by tension spring  92 , follows the movement of base plate  74  until landing surface  70  moves high enough for top linkage  80  to move beyond 180 degrees relative to bottom linkages  80 . The steady state position is again reached when trigger  96  contacts stop edge  99 . Thereafter, as discussed above, trigger assembly  78  is capable of maintaining the force of main spring  76  during manual actuation until trigger  96  is contacted by flange  48 . Further, as discussed above, once in the steady state configuration, toggle spring  54  maintains exterior handle  42  in position. It should be appreciated that, though the manual actuator is reset according to the above described steps, resetting of the manual actuator does not cause rotation of crank shaft  24 . Thus, resetting of the manual actuator does not cause the contacts in poles  12  to close. 
     In this manner, manual actuator  40  provides an internal spring charged, over-toggle mechanism which uses a combination of springs, a trigger mechanism and an external operating handle. According to one embodiment, the manual actuator  40  of the present invention develops approximately 1000 lbs of stored energy in main spring  76  which, when triggered, acts on lever arms  104  attached to the breaker main crankshaft  26 . As the manual trip lever is rotated, the mechanism distributes the input force over distance, reducing the maximum force applied by hand at the lever to about 50 lbs. 
     It should be appreciated that, though the above described circuit breaker is operable via a crank shaft, the manual actuator of the present invention may be incorporated in breakers actuated by other means. For example, the manual actuator may be incorporated in breakers that are actuated via a linear main shaft, which operates the circuit breaker poles by movement along its axis and not by rotation. In such a configuration, the manual actuator may apply the actuating force in the direction of that axis. 
     It is to be understood that the description of the foregoing exemplary embodiment(s) is (are) intended to be only illustrative, rather than exhaustive, of the present invention. Those of ordinary skill will be able to make certain additions, deletions, and/or modifications to the embodiment(s) of the disclosed subject matter without departing from the spirit of the invention or its scope, as defined by the appended claims.