Patent Publication Number: US-7906740-B2

Title: Readiness for closing indicator for circuit breakers

Description:
BACKGROUND 
     The subject invention relates to circuit breakers, and more particularly the subject invention relates to an indicator that indicates a visual and electrical indication on the status of “Readiness to close” (RTC) for circuit breakers. 
     A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. A switch mechanism of the breaker can then be thrown to open and close contacts to which the load is connected. 
     As such, a circuit breaker may be in different states, in particular a closed state with closing springs energized, a closed state with closing spring not energized, an open state with closing springs energized, an open state with closing spring not energized, an open state with any interlock applied condition, and an open state with any interlocks not applied. For a circuit breaker to close the contacts, the following conditions to be met: the closing spring should be energized, the breaker contacts should be in open state, and interlock should not be applied. 
     It is desirable to monitor this status (readiness to closing) through an indicator, which will help the customer to know the circuit breaker “ready to close” status easily. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Further exemplary embodiments include a circuit breaker system, including a circuit breaker having circuit breaker contacts and a closing spring, the closing spring operatively coupled to a charging cam assembly, a lay shaft coupled to the circuit breaker contacts, a lay shaft cam profile coupled to the lay shaft, a trip free plate coupled to lay shaft cam profile, a trip paddle coupled to the trip free plate, the trip paddle being coupled to a trip shaft and a ready to close indicator coupled to the trip free plate and a charging cam assembly. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1A  illustrates a front perspective view of a circuit breaker assembly in accordance with exemplary embodiments; 
         FIG. 1B  illustrates a front perspective view of a circuit breaker assembly in accordance with exemplary embodiments; 
         FIG. 1C  illustrates an perspective front view of an exemplary circuit breaker; 
         FIG. 1D  illustrates an perspective front view of an exemplary circuit breaker; 
         FIG. 1E  illustrates a side view of a circuit breaker assembly in accordance with exemplary embodiments; 
         FIGS. 2A-2D  illustrate multiple views of a circuit breaker in a condition of breaker charged and contacts open condition in accordance with exemplary embodiments; 
         FIGS. 3A-3C  illustrate multiple view of a circuit breaker in a condition of breaker charged, contacts open condition and trip coil activated in accordance with exemplary embodiments; 
         FIGS. 4A-C  illustrate multiple views of a circuit breaker in a condition of breaker charged and contacts closed condition in accordance with exemplary embodiments; 
         FIGS. 5A-5C  illustrate multiple views of a circuit breaker in a condition of breaker discharged and contacts open condition in accordance with exemplary embodiments; 
         FIG. 5D  illustrates a side view of an exemplary closing cam plate; 
         FIG. 6A  illustrates a side perspective view of a charging cam assembly in accordance with exemplary embodiments; 
         FIG. 6B  illustrates a side view of a ready to close cam in accordance with exemplary embodiments; 
         FIG. 7  illustrates a side view of a trip free plate in accordance with exemplary embodiments; and 
         FIG. 8  illustrates a perspective view of a lay shaft having a lay shaft cam profile in accordance with exemplary embodiments. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Exemplary embodiments provide indication of “ready to close” for a circuit breaker in response to all of the following conditions of the circuit breaker being satisfied: 1) the circuit breaker main spring is charged; 2) the shunt coil is not energized; 3) the UV coil if installed is energized; 4) the circuit breaker is not locked in OFF position by any of the provided locking/interlock means; 5) the circuit breaker is in OFF position; and 6) the mechanical lockout in the protection unit assembly is reset. If any one or more of the above conditions are not satisfied the indicator as described herein does not indicate “ready to close”. In exemplary embodiments, the indication can be a visible flag showing “Readiness to close status” or an electrical signal. The interlock application may be either through energizing shunt coils, not energizing under voltage coils, application of padlock/key lock. 
       FIG. 1A  illustrates a perspective view of a circuit breaker assembly  100  in accordance with exemplary embodiments. The assembly  100  includes a breaker housing  105 , a circuit breaker  150  disposed within the housing  105  and a lay shaft  163  disposed within the housing  105  and coupled to the circuit breaker  150 . The assembly  100  further includes a trip unit  119  shown assembled thereto. The assembly  100  is configured to allow current to flow through a circuit (not shown) in response to being in a closed configuration and to prevent current from flowing through the circuit in response to the assembly  100  being in an open configuration. In exemplary embodiments, the circuit breaker  150  further includes a “readiness to close” (RTC) indicator  151  coupled to a trip free plate  155 . In exemplary embodiments, the circuit breaker  150  further includes a charging cam assembly  170  having a RTC cam  156  coupled to the RTC indicator  151  as further described herein. As discussed above, the RTC indicator  151  can indicate a “ready to close” condition of the circuit breaker when the above-discussed criteria has been met as now described in accordance with exemplary embodiments.  FIG. 1B  illustrates a front perspective view of a circuit breaker assembly in accordance with exemplary embodiments. In this view, the circuit breaker assembly  100  includes a front cover  101  in which the RTC indicator  151  can be viewed through an RTC indicator opening  102 . 
       FIGS. 1C-1D  illustrate perspective front views of the exemplary circuit breaker  150 . In exemplary embodiments, the circuit breaker  150  includes an opening coil interface  111 , 154 , 114 , which can be referred to as a trip paddle, collectively, which is coupled to a trip shaft. The opening coil  115 ,  116 ,  118  can be either a shunt coil or a under voltage coil. Normally, a shunt coil is implemented for opening the circuit breaker  150  and an under voltage coil is implemented for checking the breaker voltage, and if the voltage is not with in the range then the under voltage coil opens the circuit breaker  150 . An interlock can also be applied via the above-described coils. For applying an interlock, the shunt coil has to be powered. The shunt coil plunger pushes the trip paddle down and keeps the circuit breaker in a not ready close condition. Normally, the under voltage coil has to be energized for keeping the circuit breaker in a ready to close condition. For applying the interlock, the under voltage coil is not energized. As such, the under voltage coil plunger pushes the trip paddle and keeps the circuit breaker in a not ready to close condition 
       FIG. 1E  illustrates a side view of a circuit breaker assembly  100  in accordance with exemplary embodiments. As illustrated the circuit breaker  150  is operatively coupled to a moving finger  132  via a coupler  124  and lay shaft  163  (described further herein). In exemplary embodiments, the moving finger is held in place by a contact spring  126 . In further exemplary embodiments a contact tip  134  disposed on the moving finger  132  is configured to engage a contact tip  142  disposed on a terminal  144 . 
       FIGS. 2A-2D  illustrate multiple views of the circuit breaker  150  in a condition of breaker charged and contacts open (with the main spring  162  charged and compressed) condition in accordance with exemplary embodiments. Furthermore, the interlock, as discussed above, is not applied. In exemplary embodiments, the breaker charged condition includes a main breaker spring  162  being charged. In exemplary embodiments, the circuit breaker includes the RTC indicator  151  coupled to the trip free plate  155  and to the RTC cam  156 . In exemplary embodiments, the RTC indicator  151  includes an RTC indicator arm  180  and cam pin  181  configured to engage a cam groove  182  disposed on the RTC cam  156 . In exemplary embodiments, the trip free plate  155  includes a trip free rear pin  160  and a trip free front pin  161 , as further illustrated in  FIG. 7 . 
     Still referring to  FIGS. 2A-2D , in the above-described condition, the RTC indicator  151  is in a ready to close indicator active condition. In exemplary embodiments, the RTC indicator  151  is biased downward via a biasing member (not shown, e.g., a spring) and the cam pin  181  engages (i.e., drops into) the RTC cam groove  182 . Furthermore, in this condition the RTC indicator  151  displays the status of “ready to close”. In exemplary embodiments, the RTC indicator is coupled to a micro-switch  152  (see  FIG. 2B ). In this condition, the RTC indicator  151  also activates the micro switch  152 , which, in turn is implemented as an electrical indication of “ready to close”. In exemplary embodiments, the micro switch  152  NO/NC contacts can be implemented as an electrical indication. At a RTC active condition, the micro switch  152  contacts are closed and vice versa for an RTC inactive condition. 
       FIGS. 3A-3C  illustrates multiple views of the circuit breaker  150  in a condition of breaker charged, contacts open (with the main spring  162  charged and compressed) condition and trip coil activated in accordance with exemplary embodiments. In this condition, the RTC indictor is in a ready to close indicator inactive condition. In exemplary embodiments, in this condition the trip paddle  154  is pushed down as indicted by directional arrow  158  as an indictor that the trip coil (not shown) has been activated. Furthermore, the interlock is applied as via the trip coil. Furthermore, the trip paddle  154  engages and pushes the trip free plate  155  via trip free front pin  161 . In exemplary embodiments, in response to the resultant movement of the trip free plate  155 , the trip free cam profile  157  (see also  FIG. 7 ) also moves, thereby engaging and rotating the RTC indicator  151 . The resultant movement of the RTC indicator  151  hides the “ready to close” insignia indication from the user. The movement of the RTC indicator  151  also prevents activation of the micro-switch  152 . Furthermore, the RTC indicator  151  is biased downward via a biasing member (not shown, e.g., a spring) and the cam pin  181  dis-engages (i.e., is raised from) the RTC cam groove  182 . 
       FIGS. 4A-4C  illustrate multiple views of a circuit breaker in a condition of breaker charged and contacts closed (with the main spring  162  charged and compressed) condition in accordance with exemplary embodiments. In this condition, the lay-shaft cam profile  159  of the lay shaft  163  engages and pushes the trip free plate  155 ) via the trip free rear pin  160 . In exemplary embodiments, due to this movement the trip free cam profile  157  rotates the RTC indicator  151  and prevents RTC indicator  151  from displaying the “ready to close” insignia and which, in turn, prevents the activation of the micro-switch  152  as described above. Furthermore, the cam pin  181  dis-engages (i.e., is raised from) the RTC cam groove  182 . However, the RTC indictor is in a ready to fall condition in which the cam pin  181  is ready to fall into the RTC cam groove  182 . However, the RTC indicator is blocked to the fall condition by the trip free cam profile  157  in which the cam pin  181  is blocked to fall in to the groove  182  by the trip free cam profile  157 . 
       FIGS. 5A-5C  illustrate multiple views of a circuit breaker in a condition of breaker discharged and contacts open (with the main spring  162  dis-charged and extended) condition in accordance with exemplary embodiments. In this condition, the RTC indictor is in a ready to close indicator in-active condition, and the interlock is not applied. In this condition, the RTC cam is rotated thereby preventing the cam pin  181  from falling into the cam groove  182 . As such, the RTC cam  156  prevents the RTC indicator  151  from showing the “ready to close” insignia and which, in turn, prevents the activation of micro-switch  152 . In exemplary embodiments, when the circuit breaker  150  closes (i.e., discharges) the charging cam assembly  170  rotates and the RTC cam groove  182  lifts the RTC indicator  151 . Thus the RTC indicator  151  is rotated.  FIG. 5C  illustrates the cam pin  181  resting on the RTC cam  156  outside the RTC cam groove  182 .  FIG. 5A  further illustrates that the charging cam assembly  170  includes a charging cam  183  and a closing cam plate  190  coupled to the charging cam assembly  170 .  FIG. 5D  illustrates a side view of an exemplary closing cam plate  190  including a closing cam plate bushing  191  a closing cam rivet pin  192  and a closing cam roller  193 . In exemplary embodiments, a charging operation of the charging cam assembly  170  includes rotating the cam shaft  164  as illustrated by arrow A counterclockwise by a handle or motor (not shown). A cam profile  184  interacts with the closing cam roller  193  when cam shaft  164  is rotated, which, in turn, rotates the closing cam plate  190  in a clockwise direction there by compressing the spring  162 . 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.