Abstract:
A method and apparatus for controlling a force applied to a pantograph. A bidirectional snubber and a velocity controller are used to dampen the applied force. Linkages between a shaft and the bidirectional snubber and between the bidirectional snubber and the velocity controller are used to rotationally translate the applied force.

Description:
CLAIM OF PRIORITY 
   This application claims priority to, and incorporates by reference herein in its entirety, pending United States Provisional Patent Application Ser. No. 60/568,005 filed May 4, 2004. 

   FIELD OF THE INVENTION 
   The invention is directed to an assembly for controlling a force applied to a MOC (mechanism operated contact) assembly in an electrical switching apparatus such as in a circuit breaker wherein a mechanism within the circuit breaker engages an MOC assembly and applies a force. 
   BACKGROUND OF THE INVENTION 
   The opening and closing of contacts within electrical switching equipment has traditionally been done through the use of mechanical switches in electrical components such as circuit breakers, contactors, motor starters, motor controllers and other load controllers. Exemplar switches are disclosed in U.S. Pat. No. 5,856,643, U.S. Pat. No. 4,176,262, and U.S. Pat. No. 4,743,876 and are incorporated herein by reference. Circuit breakers contain separable primary contacts as well as an MOC operator that controls the MOC assembly. In particular, control of the MOC assembly has traditionally been accomplished through mechanical means, and has utilized an interface mechanism such as a pantograph assembly and an MOC operator on the circuit breaker. As originally designed, the MOC operator engages and applies a generally downward force when the circuit breaker closes and upward force when the circuit breaker opens on the MOC assembly. The application of these forces on the MOC assembly causes an MOC rod connected to the MOC assembly to move in corresponding directions and thereby change the status of the MOC assembly. 
   Due to the various designs employed by various electrical equipment manufacturers, replacement of electrical components such as vacuum circuit breakers which utilize the MOC assembly is often difficult. In particular, pantograph coupling or engagement to the MOC operator is often a dynamic mismatch. The force applied by a new MOC operator to the existing MOC assembly is often significantly higher than that originally designed—in some instances as large as 16 times the force applied by the original MOC operator. Under such circumstances, premature wear, or failure of the MOC assembly is likely. Moreover, the excessive force on the MOC assembly may cause significant contact bounce. Also, the force requirements placed on the circuit breaker can cause stalling of the circuit breaker. Accordingly, there is a need for a method and apparatus for controlling the forces applied to the MOC assembly and which may be readily used and applied to the myriad of brands and types of electrical switching equipment. 
   SUMMARY OF THE INVENTION 
   The invention controls the application of a force applied to a pantograph. A bidirectional snubber member is coupled to a shaft within a circuit breaker mechanism to oppose the force transferred to an MOC operator. The snubber opposes the applied force by compressing a spring within the snubber housing and then uncoiling the compressed spring. A velocity controller is used to further augment the opposition forces necessary to dampen the applied force to the pantograph. Rotational linkages between the shaft and the bidirectional snubber and between the bidirectional snubber and the velocity controller are used to translate the force. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A wide variety of potential embodiments will be more readily understood through the following detailed description, with reference to the accompanying drawings in which: 
       FIG. 1  is an operational side view of the present invention in an open position as applied to an existing bank of auxiliary switches; 
       FIG. 2  is an operational side view of the present invention in a closed position as applied to an existing bank of auxiliary switches; 
       FIG. 3  is an operational frontal view of the present invention in an open position as applied to an existing bank of auxiliary switches; 
       FIG. 4  is an operational frontal view of the present invention in a closed position as applied to an existing bank of auxiliary switches; 
       FIG. 5  is a top view of the bidirectional snubber (BDS); 
       FIG. 6  is a side view of the (BDS); and 
       FIG. 7  is a side view of the bidirectional velocity controller (BVC). 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   NUMERIC REFERENCE 
   
       
         1 . Circuit Breaker Mechanism 
         6  Closing Compression Spring 
         7 A Top Plunger Pin 
         7 B Bottom Plunger Pin 
         8  Opening Compression Spring 
         10 . Main Shaft 
         11  BDS Plunger bottom 
         13  BDS Tube 
         14  BDS Plunger rod 
         19  BDS plunger top 
         25 . MOC Assembly 
         30  Clamp Block 
         34  BVC lever arm 
         36  BVC Plunger rod 
         38  Bidirectional Velocity Controller (BVC) 
         44  BDS Lever Arm 
         50  BDS Linkage Plate 
         51  BDS Linkage Rod 
         52  Bidirectional Snubber (BDS) member 
         56  MOC Actuator Lever 
         57  MOC pin 
         58  Pantograph 
         60  MOC actuator rod 
         72  Adjustment Knob (Compression) 
         74  Adjustment Knob (Extension) 
     
  
     FIG. 1  illustrates a portion of a circuit breaker in which an assembly is shown in an open position and is in accordance with the present invention. Within the circuit breaker, main shaft  10  of the circuit breaker operator mechanism  1  is shown. Main shaft  10  rotates in a counterclockwise (CCW) direction when the circuit breaker operates to close its main contacts and main shaft  10  rotates in a clockwise (CW) direction when the circuit breaker operates to open its main contacts. The rotation of main shaft  10  also operates the cubicle mounted MOC assembly  25 . (See  FIGS. 3 &amp; 4 ) 
   The main shaft  10  and clamp block  30  rotate with substantially the same rotational velocity. Clamp block  30  connects to bidirectional snubber (BDS) linkage rod  51  of BDS  52  ( FIGS. 5 &amp; 6 ) and is moved in substantially a downward direction during a circuit breaker close operation. BDS linkage rod  51  is connected to a rotatable BDS lever arm  44 . The assembly shown in  FIG. 1  includes BDS lever arm  44 , however this is only representative of this particular embodiment and is not required for all circuit breaker assemblies. The BDS lever arm  44  is provided in this embodiment as a means of achieving a translation or a reversal of directional movement and may be substituted with other means known to those skilled in the art. As shown in  FIG. 1 , BDS lever arm  44  is connected at one end to BDS linkage rod  51  and on the other end to BDS plunger rod  14 . The BDS plunger rod  14  is connected to the bidirectional snubber (BDS) member  52  at BDS plunger top  19 . BDS member  52  is connected to BDS linkage plate  50 . The BDS plunger rod  51 , BDS plunger top  19 , BDS plunger bottom  11 , springs  8  and  6 , and BDS tube  13  comprise BDS member  52 . BDS linkage plate  50  is connected to rotatable bidirectional velocity controller (BVC) lever arm  34  which also connects to the MOC actuator lever  56 . BVC lever arm  34  is connected to the bi-directional velocity controller (BVC)  38 . The bottom end of the BVC  38  is mounted to the circuit breaker frame. Rotation of the BVC lever arm  34  also rotates MOC actuator lever  56 . The MOC pin  57  of the MOC actuator lever  56  engages the cubicle mounted pantograph  58 . The use of a pantograph  58  is only one of a myriad of possible solutions (linkages) used by original equipment manufacturers such as Westinghouse Electric. Other linkages were provided by various other original equipment manufacturers. The pantograph  58  is connected to the MOC actuator rod  60 . MOC actuator rod  60  connects to cubicle mounted MOC switch assemblies  25   
   Circuit breaker operation from an open position to a closed position is shown in  FIG. 1 , requires the rotation of main shaft  10  and clamp block  30  in a counter-clockwise (CCW) direction. Main shaft  10  and clamp block  30  are connected to BDS linkage rod  51 . Closing the circuit breaker moves BDS linkage rod  51  in substantially an upward direction. Upward movement of BDS linkage rod  51  rotates BDS lever arm  44  in CCW direction. CCW rotation of BDS lever arm  44  moves the BDS plunger rod  14  and BDS plunger top  19  in substantially a downward direction. The top plunger pin  7 A (right hand pin in  FIG. 5 ) pushes against a slot and moves BDS tube  13  substantially downward. The movement of BDS tube  13  substantially downward stores energy in the closing compression spring  6 . After the energy is stored in the close spring  6  and the substantially downward movement of the BDS tube  13  has stopped, the energy in the close spring  6  is discharged so as to move the BDS plunger bottom  11  substantially downward. The velocity of movement of the BDS plunger bottom  11  is controlled by BVC  38 . The downward movement of the BDS plunger bottom  11  moves the BDS linkage plate  50  downward. Downward movement of the BDS linkage plate  50  rotates the BVC lever arm  34  CCW. CCW rotation of the BVC lever arm  34  pulls tension on the BVC plunger rod  36  of BVC  38 . The BVC  38  controls and reduces the rotational velocity of the BVC lever arm  34 . 
   The CCW rotation of the BVC lever arm  34  causes CCW rotation of the MOC actuator lever  56 . The MOC pin  57  of MOC actuator lever  56  moves the cubicle mounted pantograph  58  substantially downward. The downward movement of the pantograph  58  moves the MOC actuator rod  60  substantially downward to operate the cubicle mounted MOC auxiliary assembly  25  (not shown). 
   Circuit breaker operation from a closed position to an open position is shown in  FIG. 2 . Main shaft  10  and clamp block  30  rotate clockwise (CW). Main shaft  10  and clamp block  30  are connected to BDS linkage rod  51 . Opening the circuit breaker moves BDS linkage rod  51  in substantially a downward direction. Downward movement of BDS linkage rod  51  rotates BDS lever arm  44  in CW direction. CW rotation of the BDS lever arm  44  moves BDS plunger rod  14  in substantially an upward direction. The BDS plunger  14  is pulled and energy is stored in the opening compression spring  8 . After the energy is stored in the opening spring  8  and the upward movement of BDS tube  13  has stopped, the energy in the opening spring  8  is discharged so as to move BDS tube  13  substantially upward. The upward movement of BDS tube  13  pulls against bottom plunger pin  7 B (LH in  FIG. 5 ) which rides against the end of the slot in the BDS tube  13 . The bottom plunger pin  7 B is connected through the BDS plunger bottom  11 . Discharge of the opening compression spring  8  results in substantially an upward movement of the BDS plunger bottom item  11 . The velocity of the movement of the BDS plunger bottom  11  is controlled by the BVC  38 . The upward movement of the BDS plunger bottom  11  moves the BDS linkage plate  50  upward. Upward movement of the BDS linkage plate  50  rotates the BVC lever arm  34  CW. CW rotation of the BVC lever arm  34  pushes compression on the BVC plunger rod  36 . The BVC  38  controls and reduces the velocity of the BVC lever arm  34 . 
   The CW rotation of the BVC lever arm  34  causes CW rotation of the MOC actuator lever  56 . The MOC pin  57  of the MOC actuator lever  56  moves the cubicle mounted pantograph  58  substantially upward The upward movement of the pantograph  58  moves the MOC actuator rod  60  substantially upward to operate the cubicle mounted MOC assembly  25  (not shown). 
   The BVC plunger rod  36  is preferably coupled to BVC  38  in a slidable, bidirectional, controllable and resistive manner. The BVC  38  is preferably a hydraulic speed or feed controller (See  FIG. 7 ). However, other types of velocity and feed controllers as known to one skilled in the art, may be used. In the embodiment shown in  FIG. 1 , the BVC  38  is a dual and bi-directional feed velocity controller. Both tension and compression regulation is provided by BVC  38 . Operationally, BVC  38  provides a tension and compression force, ranging from 9.5 lbs (min) to 450 lbs (max). The regulation of tension or compression forces may be adjustable or fixed. The other end of BVC  38  is attached to the circuit breaker frame. 
   In the embodiment shown in  FIGS. 1 &amp; 2 , BDS member  52  comprises an BDS tube  13  having an upper and lower region. The arrangement of springs may be reversed for different embodiments. BDS member  52  has an opening compression spring  8  in the upper region within an inner chamber. When, the BDS member  52  is subjected to a circuit breaker opening operation, the BDS plunger top  19  is forced into the BDS member  52 , so as to compress the opening compression spring  8 . In this position, opening compression spring  8  is compressed while a closing compressing spring  6  remains unaffected by the compression of the opening compression spring  8 . 
   When the BDS member  52  is subjected to a circuit breaker closing operation, the BDS plunger bottom  11  is forced into the BDS member  52 , so as to compress the closing compression spring  6 . In this position, closing compression spring  6  is compressed while the opening compression spring  8  remains unaffected by the compression of the closing spring  6 . The closing and opening compression springs  6 ,  8  are set apart from each other. 
   Operationally, an external signal, such as a protective relay senses an over current condition, operates (trips) the circuit breaker to open both the primary contacts and the MOC assembly auxiliary contacts  25 . From a closed position, the tripping of the circuit breaker causes the main shaft  10  to rotate clockwise an estimated 60 degrees. The rotation of the main shaft  10  causes the clamp block  30  to also rotate in a clockwise direction. The rotation of the clamp block  30  and the main shaft  10  has the direct effect of pulling the BDS linkage rod  14  substantially upward and the BVC rod  36  downward. The clockwise rotation of clamp block  30  causes the BVC lever arm  34  to rotate in a clockwise direction about its pivot pin. The clockwise movement of the BVC lever arm  34  also causes the downward application of a force on BVC rod  36  so as to cause BVC rod  36  to travel in the inward direction within BVC  38 . In the embodiment shown in  FIGS. 1 &amp; 2 , the BVC  38  is a hydraulic feed controller containing automatic transmission fluid (ATF). However it should be understood that the BVC  38  ( FIG. 7 ) may contain other fluids, gases and/or solids alone or in combination capable of resisting compression in a controllable manner. The BVC&#39;s  38  resistance to compression controls the velocity at which the MOC pin  57  moves the pantograph  58 . 
   The foregoing Detailed Description of the Preferred Embodiment is to be understood as being in every respect illustrative and exemplary. The scope of the invention disclosed herein is not to be determined from the description of the invention, but rather from the Claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention.