Patent Publication Number: US-7718908-B2

Title: Contact arm assembly and method for assembling the contact arm assembly

Description:
FIELD OF INVENTION 
   This application relates to a contact arm assembly and a method for assembling the contact arm assembly. 
   BACKGROUND 
   Circuit breakers have been utilized to protect electrical equipment from overcurrent conditions. However, the circuit breakers generally have contact arms with a multitude of components that are relatively expensive to manufacture. 
   Further, double break breakers have been developed. However, designers have not been able to convert the double break breaker into a single break breaker within a similar housing configuration, resulting in increased manufacturing costs. 
   Accordingly, the inventors herein have recognized a need for an improved contact arm assembly that minimizes and/or eliminates the above-mentioned deficiency. 
   BRIEF DESCRIPTION 
   A contact arm assembly in accordance with the exemplary embodiment is provided. The contact arm assembly includes a first contact arm having a first end portion and a second end portion. The first end portion has a first contact disposed thereon and a first spring holder portion disposed thereon. The second end portion has a first tab member for coupling a first braided strap thereto. The first contact arm has a first pivot aperture extending therethrough. The contact arm assembly further includes first and second side plates. The first side plate is disposed proximate to a first side of the first contact arm and the second side plate is disposed proximate to a second side of the first contact arm. The first side plate has a first spring support groove thereon and a first aperture extending therethrough. The second side plate has a second spring support groove thereon and a second aperture extending therethrough. The contact arm assembly further includes a first spring support pin disposed in the first and second spring support grooves of the first and second side plates, respectively. The contact arm assembly further includes a pivot pin disposed through the first circular pivot aperture of the first contact arm and into the first and second apertures of the first and second side plates, respectively. The contact arm assembly further includes a first spring disposed between the first spring holder portion of the first contact arm and the first spring support pin. 
   An advantage of the contact arm assembly is that it can be utilized in a single break breaker housing that is similar to a housing of a double break breaker. 
   A method for assembling a contact arm assembly in accordance with another exemplary embodiment is provided. The method includes coupling a first contact on a first end portion of a first contact arm. The method further includes coupling a first braided strap on a first tab member of a second end portion of the first contact arm. The method further includes disposing a pivot pin through a first pivot aperture of the first contact arm. The method further includes disposing a first side plate proximate to a first side of the first contact arm. The method further includes disposing a second side plate proximate to a second side of the first contact arm such that the pivot pin extends into first and second apertures of the first and second side plates, respectively to form a first assembly. The method further includes disposing the first assembly in a cavity of a rotor housing. The method further includes disposing a first spring support pin in first and second spring support grooves of the first and second side plates, respectively. The method further includes attaching a first spring between a first spring holder portion of the first contact arm and the first spring support pin to obtain the contact arm assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic of a circuit breaker in accordance with an exemplary embodiment; 
       FIG. 2  is a schematic of contact arm assemblies utilized in the circuit breaker of  FIG. 1 ; 
       FIG. 3  is a schematic of a contact arm assembly of  FIG. 2 ; 
       FIG. 4  is a schematic of a rotor utilized in the contact arm assembly of  FIG. 3 ; 
       FIG. 5  is a schematic of another contact arm assembly utilized in the circuit breaker of  FIG. 1 ; 
       FIG. 6  is a schematic of a spring assembly utilized in the contact arm assembly of  FIG. 3 ; 
       FIG. 7  is a schematic of a spring guide plate utilized in the spring assembly of  FIG. 6 ; 
       FIG. 8  is a schematic of a spring retainer utilized in the spring assembly of  FIG. 6 ; 
       FIG. 9  is a schematic of the circuit breaker of  FIG. 1  in a blow open operational state; 
       FIG. 10  is a schematic of the circuit breaker of  FIG. 1  in a tripped operational state; 
       FIG. 11  is a schematic of the circuit breaker of  FIG. 1  in an off operational state; and 
       FIGS. 12-13  are flowcharts of a method for assembling the contact arm assembly of  FIG. 3 . 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1 and 2 , a circuit breaker  10  in accordance with an exemplary embodiment is illustrated. The circuit breaker  10  includes contact arm assemblies  30 ,  32 ,  34 , and a switching assembly  38 . The circuit breaker  10  is a single break circuit breaker. As shown in  FIG. 1 , the contact arm assembly  30  has a closed operational position in which electrical current can flow therethough. 
   Since the contact arm assemblies  30 ,  32 ,  34  have a substantially similar configuration, only the contact arm assembly  30  will be discussed in greater detail below. Referring to  FIGS. 1 ,  2  and  3 , the contact arm assembly  30  includes contact arms  50 ,  52 ,  54 ,  56 , contacts  70 ,  72 ,  74 ,  76 , side plates  80 ,  82 , a pivot pin  86 , a pin  88 , spring assemblies  90 ,  92 ,  94 ,  96 , a rotor  97 , a stationary contact  98  and three other stationary contacts (not shown), a line strap  99 , braided straps  100 ,  102 ,  104 ,  106 , and a load strap  108 . 
   The contact arms  50 ,  52 ,  54 ,  56  are sandwiched between the side plates  80 ,  82  and when rotated to the closed operational state, conduct an electrical current from the line strap  99  to the load strap  108 —via the stationary contact  98  and three additional stationary contacts (not shown), the contacts  70 ,  72 ,  74 ,  76 , and the braided straps  100 ,  102 ,  104 ,  106 . Since the contact arms  50 ,  52 ,  54 ,  56  have a substantially similar configuration, only the contact arms  50 ,  56  will be explained in greater detail below. 
   Referring to  FIGS. 1 and 3 , the contact arm  50  has an end portion  120 , an end portion  122 , and a circular pivot aperture  124 . The end portion  120  includes a spring holder portion  128  having a groove  129  for holding an end of the spring assembly  90  thereon. The contact  70  is disposed on the end portion  120  opposite to the spring holder portion  128 . The end portion  122  has a tab portion  130  that is coupled to the braided strap  100 . The contact arm  50  is disposed between the side plate  80  and the contact arm  52  and the pivot pin  86  extends through the circular pivot aperture  124  of the contact arm  50  and into an aperture of the side plate  80 . It can be noted that the pivot pin  86  further extends through circular pivot apertures in each of the contact arms  50 ,  52 ,  54 ,  56  such that the contact arms can rotate about the pivot pin  86 . 
   Referring to  FIGS. 3 and 5 , the contact arm  56  has an end portion  140 , an end portion  142 , and a circular pivot aperture  144 . The end portion  140  includes a spring holder portion  148  having a groove  149  for holding an end of the spring assembly  96  thereon. The contact  76  is disposed on the end portion  140  opposite to the spring holder portion  148 . The end portion  142  has a tab portion  150  configured to be coupled to the braided strap  106 . The contact arm  56  is disposed between the side plate  82  and the contact arm  54  and the pivot pin  86  extends through the circular pivot aperture  144  of the contact arm  56  and into an aperture of the side plate  82 . 
   Referring to  FIGS. 1 ,  3  and  4 , the side plates  80 ,  82  are disposed on opposite sides of the contact arms  50 ,  52 ,  54 ,  56  and are configured to be disposed within grooves  238 ,  236 , respectively, of the housing  220  of the rotor  97 . Accordingly, the side plates  80 ,  82  rotate with the rotor  97 . 
   The side plate  80  includes a spring support groove  162  for receiving a pin  88  that holds an end of the spring assembly  90 . Thus, the spring assembly  90  is disposed between the pin  88  and the spring holder portion  128  of the contact arm  50 . The spring assembly  90  biases the contact arm  50  in a counter-clockwise direction toward the stationary contact  98 . The side plate  80  further includes an aperture  160  extending therethrough for receiving the pivot pin  86  therein. 
   Referring to  FIGS. 4 and 5 , the side plate  82  includes a spring support groove  172  for receiving the pin  88  that holds an end of the spring assembly  96 . Thus, the spring assembly  96  is disposed between the pin  88  and the spring holder portion  148  of the contact arm  56 . The spring assembly  96  biases the contact arm  56  in a counter-clockwise direction toward a respective stationary contact. The side plate  82  further includes an aperture  170  extending therethrough for receiving the pivot pin  86  therein. It should be noted that the spring assemblies  92 ,  96  are disposed between the pin  88  and spring hold portions on the contact arms  52 ,  54 , respectively. 
   Referring to  FIG. 3 , the spring assemblies  90 ,  92 ,  94 ,  96  are configured to bias the contact arms  50 ,  52 ,  54 ,  56  in a counter-clockwise direction toward respective stationary contacts. Since the spring assemblies  90 ,  92 ,  94 ,  96  having a substantially similar structure, only the spring assembly  90  will discussed in greater detail below. 
   Referring to  FIGS. 6-8 , the spring assembly  90  includes a spring guide plate  190 , a spring  192 , and a spring retainer  194 . The spring guide plate  190  is configured to receive the spring  190  thereon and supports the spring  192 . The spring guide plate  190  includes a slot  196  for receiving a portion of the spring retainer  194  therein. The spring guide plate  190  further includes flange portions  198 ,  200  configured to hold an end of the spring  90  thereon. The spring guide plate  190  further includes a mating surface  202  configured to receive the pin  88  (shown in  FIG. 3 ) therein. The spring retainer  194  is configured to be disposed with the slot  196  of the spring guide plate  190  such that the spring  192  is held between the spring retainer  194  and the flange portions  198 ,  200  of the spring guide plate  190 . 
   Referring to  FIGS. 1 ,  2  and  4 , the rotor  97  is provided to rotate and to hold the contact arms in a tripped (i.e., open) operational state when an over-current condition has been detected through the contact arm assemblies. The rotor  97  includes housings  220 ,  222 ,  224 . 
   The housing  220  holds a first set of contact arms  225  including the contact arms  50 ,  52 ,  54 ,  56  therein. In particular, the housing  220  includes a cavity  230  for holding the contact arms  50 ,  52 ,  54 ,  56  therein. Further, the housing  220  includes side walls  232 ,  234  having grooves  236 ,  238 , respectively, for receiving the side plates  82 ,  80 , respectively, therein. 
   The housing  222  holds a second set of contact arms  226  therein. In particular, the housing  222  includes a cavity  240  for holding the second set of contact arms  226  therein. Further, the housing  220  includes side walls  242 ,  244  having grooves  246 ,  248 , respectively, for receiving the two side plates therein. 
   The housing  224  holds a third set of contact arms  228  therein. In particular, the housing  224  includes a cavity  250  for holding the third set of contact arms  228  therein. Further, the housing  224  includes side walls  252 ,  254  having grooves  256 ,  258 , respectively, for receiving the two side plates therein. 
   Referring to  FIG. 3 , the braided straps  100 ,  102 ,  104 ,  106  are electrically coupled to the contact arms  50 ,  52 ,  54 ,  56 , respectively. Further, the braided straps  100 ,  102 ,  104 ,  106  are electrically coupled to the load strap  108 . 
   A general overview of the operation of the contact arm assembly  30  with respect to the contact arm  50  will now be provided. It should be understood that the other contact arms in contact arm assembly  30  operate in a similar manner as contact arm  50 . Referring to  FIG. 1 , the contact arm assembly  30  has a closed operational state such that the contact  70  on the contact arm  50  contacts the stationary contact  98 . Further, the contact arm assembly  30  allows electrical current to flow through the lines strap  99 , the stationary contact  98 , the contact  70 , the contact arm  50 , the braided strap  100 , and the load strap  108 . 
   Referring to  FIG. 9 , when an overcurrent condition occurs, repulsive forces between the contact arm  50  and the stationary contact  98  urge the contact arm  50  away from the stationary contact  98  in a clockwise direction such that contact  70  on the contact arm  50  no longer contacts the stationary contact  98  and the contact arm  50  has a blow open operational state. 
   Referring to  FIG. 10 , after the overcurrent condition occurs, the rotor  97  is rotated in a clockwise direction by the switching assembly  38  such that a surface  260  of the rotor  96  contacts the contact arm  50  to hold the contact arm  50  in a tripped (i.e., open) operational state such that no electrical current flows through the contact arm  50 . 
   Referring to  FIG. 11 , when a user rotates the handle  300  of the switching assembly  38  in a clockwise direction, the switching assembly  38  urges the rotor  97  to rotate in a clockwise direction. As a result, the surface  260  of the rotor  96  contacts the contact arm  50  and moves the contact arm  50  to an off operational state such that no electrical current flows through the contact arm  50 . 
   Referring to  FIGS. 12 and 13 , a flowchart of a method for assembling the contact arm assembly  30  will now be explained. For purposes of simplicity, the method will include steps for assembling the contact arm assembly  30  with only the contact arms  50 ,  56 . However, it should be understood that the method could alternately be adapted to assemble a contact arm assembly with a single contact arm or with a plurality of contact arms such as contact arms  50 ,  52 ,  54 ,  56 . It should be further noted that in the non-limiting exemplary flowchart some of the following steps are performed by a person. However, the following steps could be alternatively be performed by one or more machines in an automated process instead of by the person. 
   At step  270 , a person couples the first contact  70  on the first end portion  120  of the first contact arm  50 . 
   At step  272 , the person couples the first braided strap  100  on the first tab member  130  of the second end portion  122  of the first contact arm  50 . 
   At step  274 , the person couples the second contact  76  on the third end portion  140  of the second contact arm  56 . 
   At step  276 , the person couples the second braided strap  106  on the second tab member  150  of the fourth end portion  142  of the second contact arm  56 . 
   At step  278 , a person disposes the pivot pin  86  through first and second circular pivot apertures of the first and second contact arms  50 ,  56 , respectively. 
   At step  280 , the person disposes the first side plate  80  against a side of the first contact arm  50 . 
   At step  282 , the person disposes the second side plate  82  proximate to a side of the second contact arm  56  such that the pivot pin  86  extends through the first and second circular pivot apertures of the first and second contact arms  50 ,  56 , respectively, and into first and second apertures of the first and second side plates  80 ,  82 , respectively, to form a first assembly. 
   At step  284 , the person disposes the first assembly in that cavity  230  of the rotor housing  220 . 
   At step  286 , the person disposes a first spring support pin  88  in first and second spring support grooves of the first and second side plates  80 ,  82 , respectively. 
   At step  288 , the person attaches a first spring between a first spring holder portion of the first contact arm  50  and the first spring support pin  88 . 
   At step  290 , the person attaches a second spring between a second spring holder portion of the second contact arm  56  and the first spring support pin  88 . 
   At step  292 , the person disposes a portion of a first line strap  99  proximate to the first contact  98  on the first contact arm  50 . 
   At step  294 , the person couples the first braided strap  100  to the first load strap  108 . 
   At step  296 , the person disposes a portion of a second line strap proximate to the second contact  76  on the second contact arm  56 . 
   At step  298 , the person couples the second braided strap  106  to the first load strap  108 . 
   Referring to  FIG. 1 , the switching assembly  38  will now be explained. The switching assembly  38  is provided to transition the contact arm assemblies  30 ,  32 ,  34  from a closed operational state in which electrical current is conducted through the contact arm assemblies to an off (i.e., open) operational state in which no electrical current is conducted through the contact arm assemblies, and vice versa. For purposes of simplicity, the following discussion, will focus on the operation of the switching assembly  38  on the contact arm assembly  30 . 
   The switching assembly  38  includes a handle  300 , an upper link  302 , a hinge pin  303 , a lower link  304 , a toggle pin  306 , a spring support  308 , a spring  310 , a cradle  312 , a housing portion  314 , a handlebar  316 , a pin  318 , a primary latch  320 , a pin  322 , a secondary latch  324 , a pin  326 , a trip bar  328 , and a pin  329   
   The handle  300  is coupled to the upper link  302 . The upper link  302  is rotatably coupled to the lower link  304  via the toggle pin  306 . The toggle pin  306  is further coupled to the cradle  312  and an end of the spring support  308 . The lower link  304  is further coupled to the rotor  97 . 
   The spring  310  is disposed on the spring support  308  that extends between the handle  300  and the toggle pin  306 . The spring  310  is configured to bias the upper link  300  and the lower link  304  such that the lower link  304  pushes the contact arm  54  toward the stationary contact  98  when the handle  300  is at a maximum leftward position. 
   When a user rotates the handle  300  in a clockwise direction to transition the contact arm assembly  30  from the closed operational state to an off (i.e., open) operational state, the upper link  302  moves the lower link  300  such that the lower link  304  rotates the rotor  97  in a clockwise direction to move the contact  70  away from the stationary contact  98 . 
   The cradle  312  is rotatably coupled to the housing portion  314  via the pin  313 . Further, the cradle  312  is coupled to the upper link  302  via the hinge pin  303  of the upper link  302 . The cradle  312  is further detachably coupled to the primary latch  320 . The primary latch  320  rotates about the pin  322 . The primary latch  320  is further rotatably coupled to the secondary latch  324 . The secondary latch  324  rotates about the pin  326 . The secondary latch  324  is further rotatably coupled to the trip bar  328 . The trip bar  320  rotates about the pin  329 . 
   Referring to  FIGS. 9 and 10 , during operation when an overcurrent condition occurs through the contact arm assembly  30  and the contact arm assembly  30  has a blow open operational state, the trip bar  328  rotates in a counterclockwise direction. In response to the trip bar  328  rotating in a counterclockwise direction, the secondary latch  324  rotates in a clockwise direction. Further, the secondary latch  324  induces the primary latch  320  to rotate in a clockwise direction. As result, the cradle  312  moves in a counterclockwise direction which urges the lower link  304  to move upwardly which rotates the rotor  97  in a clockwise direction. Further, rotation of the rotor  97  in the clockwise direction causes the surface  260  of the rotor  97  to contact the contact arm  50  for maintaining the contact arm  50  at an open position away from the stationary contact  98  and the contact arm assembly has a tripped operational state. 
   Referring to  FIGS. 10 and 11 , after the contact arm assembly  30  has the tripped operational state, a user can reset the contact arm assembly  30  to an off operational state by rotating the handle  300  in a clockwise direction. In particular, the handle  300  is coupled to the handle bar  316  that rotates about the pin  318 . The handle bar  316  further includes a pin  319 . During rotation of both the handle  300  and the handle bar  316  in a clockwise direction, the pin  319  contacts the cradle  312  and moves the cradle rightwardly such that the cradle  312  is latched by the primary latch  320 . 
   The contact arm assembly and the method for assembling the contact arm assembly provide a substantial advantage over other assemblies and methods. In particular, the contact arm assembly and method provide a technical effect of utilizing a relatively small number of components that substantially reduces manufacturing costs as compared to other assemblies. 
   While the invention is described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalence may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to the teachings of the invention to adapt to a particular situation without departing from the scope thereof. Therefore, it is intended that the invention not be limited to the embodiments disclosed for carrying out this invention, but that the invention includes all embodiments falling with the scope of the appended claims. Moreover, the use of the terms first, second, etc. does not denote any order of importance, but rather the terms first, second, etc. are used to distinguish one element from another.