Abstract:
A circuit interrupting device has a circuit interrupter with a stationary contact and a moveable contact. The movable contact is movable relative to the stationary contact between a closed position that allows current to pass through the circuit interrupter and an open position separating the contacts and preventing current from passing through the circuit interrupter. The movable contact is controlled by a solenoid assembly. The movable contact is connected to a plunger of the solenoid assembly by a turnbuckle and weld break assembly. The turnbuckle and weld break assembly permits adjusting the contact wipe distance and generates a hammer force to break any welds between the contacts of the vacuum interrupter.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of prior application Ser. No. 10/759,086, filed Jan. 20, 2004, now U.S. Pat. No. 6,852,939 and 10/759,087, filed Jan. 20, 2004; now U.S. Pat. No. 6,794,596 which are both divisionals of application Ser. No. 10/117,338, filed Apr. 8, 2002, now U.S. Pat. No. 6,753,493; which claims the benefit of U.S. Provisional Application No. 60/294,581, filed Jun. 1, 2001. The subject matter of each of these applications is incorporated herein by reference in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to a device for interrupting an electrical circuit. More specifically, the present invention relates to a vacuum interrupter driven by a magnetic solenoid. 
   BACKGROUND OF THE INVENTION 
   Conventional circuit interrupting devices, such as circuit breakers, sectionalizers, and reclosers, provide protection for power distribution systems and the various apparatus on those power distribution systems by isolating a faulted section from the main part of the system. A fault current in the system can occur under various conditions, including lightning, an animal or tree shorting the power lines, or different power lines contacting each other. 
   Conventional circuit interrupting devices sense a fault and interrupt the current path. Conventional reclosers also re-close the current path and monitor continued fault conditions, thereby re-energizing the utility line upon termination of the fault. This provides maximum continuity of electrical service. If a fault is permanent, the recloser remains open after a certain pre-set number of reclosing operations. 
   Conventional circuit interrupters typically have opposing contacts. The opposing contacts move from an open position where the contacts are separated and no current passes between them to a closed position where the contacts abut one another, allowing current to pass between them. The contacts are usually sealed into a vacuum bottle to minimize the arcing that occurs when the contacts are opened and closed. Arcing is undesirable because it causes erosion of the contacts. Arcing can also weld the opposing contacts together, effectively preventing operation of the circuit interrupter. 
   Examples of conventional circuit interrupting devices include U.S. Pat. No. 6,242,708 to Marchand et al.; U.S. Pat. No. 5,663,712 to Kamp; U.S. Pat. No. 5,175,403 to Hamm et al.; U.S. Pat. No. 5,103,364 to Kamp; U.S. Pat. No. 5,099,382 to Eppinger; U.S. Pat. No. 4,568,804 to Luehring and U.S. Pat. No. 4,323,871 to Kamp et al. The subject matter of each of these patents is incorporated herein by reference in its entirety. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a circuit interrupting device that is actuated by a solenoid. 
   Another object of the present invention is to provide a circuit interrupting device that can break welds between contacts in the circuit interrupting device. 
   A further object of the present invention is to provide a circuit interrupting device that compensates for erosion of the contacts that occurs during operation. 
   These objects are basically attained by a circuit interrupting device that has a circuit interrupter with a stationary contact and a moveable contact. The movable contact is actuated by a solenoid assembly and is movable between a closed position and an open position. In the closed position, the contacts abut one another and allow current to pass through the circuit interrupter. In the open position, the contacts are separated by a gap, preventing current from passing through the circuit interrupter. The movable contact is connected to a plunger of the solenoid assembly by a turnbuckle and weld break assembly. The turnbuckle and weld break assembly functions as a turnbuckle and thereby provides the ability to adjust the wipe distance of the contacts. The turnbuckle and weld break assembly also generates a hammer force to break any welds between the contacts. 
   Other objects, advantages, and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings which form a part of this disclosure: 
       FIG. 1  is a side elevational view of a circuit interrupting device in accordance with an embodiment of the present invention; 
       FIG. 2  is a side elevational view in section of the circuit interrupting device illustrated in  FIG. 1 ; 
       FIG. 3  is an enlarged side elevational view of the solenoid assembly of the circuit interrupting device illustrated in  FIG. 1 ; 
       FIG. 4  is an enlarged side elevational view of the vacuum interrupter and shunt assembly of the circuit interrupting device illustrated in  FIG. 1 ; 
       FIG. 5  is an enlarged side elevational view of the turnbuckle and weld break assembly of the circuit interrupting device illustrated in  FIG. 1 ; 
       FIG. 6  is a side elevational view in section of the turnbuckle and weld break assembly illustrated in  FIG. 5 ; and 
       FIG. 7  is an enlarged side elevational view in section of the actuator block and plunger of the solenoid assembly illustrated in  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1–7 , a circuit interrupting device  10  in accordance with an embodiment of the invention has a vacuum interrupter  12  connected to a solenoid assembly  14  by a turnbuckle and weld break assembly  16 . 
   The vacuum interrupter  12  is conventional and therefore is only described in sufficient detail to allow one of ordinary skill in the art to make and use the present invention. The vacuum interrupter  12  provides voltage switching and includes a vacuum bottle  18  having a ceramic outer shell  20  with a first end  22  and a second opposing end  24 . A stationary or primary contact  26  is fixed at the first end  22  and a movable contact  28  is slidably supported in an opening  30  at the second end  24 . A seal (not shown) can be provided to ensure a vacuum is maintained in the vacuum bottle  18 . The contacts  26 ,  28  are preferably made of a conductive material, such as copper. The movable contact  28  is connected to and operated by the solenoid assembly  14 . When the stationary contact  26  and movable contact  28  are in contact, the vacuum interrupter is in the closed position and the circuit interrupting device  10  is operating and conducting electrical power under normal conditions. During a fault, the movable contact  28  is separated from the stationary contact  26 , typically by about a fraction of an inch, e.g. about 9 mm, to an open position, thereby interrupting the current path and isolating a fault current. 
   The vacuum interrupter  12  should meet certain minimum requirements for industry standards. For example, when used in a recloser application, the vacuum interrupter should meet industry standards outlined in for example ANSI/IEEE C37.60 for reclosers. 
   The vacuum interrupter  12  is supported by a dielectric housing  32  preferably made of a glass filled polyester. The housing  32  is a unitary one-piece member that is hollow and generally cylindrical in shape to accommodate the vacuum interrupter  12 . A first end  34  of the housing  32  includes an opening  36  for receiving a conductive insert or first terminal  38  molded into the opening  36  of the housing  32 . A bolt  40  extends through the insert  38  into the vacuum interrupter stationary contact  26  thereby connecting the insert  38  to the vacuum interrupter  12 . The insert  38  provides a mechanism for electrically connecting the stationary contact  26  and the vacuum interrupter  12  directly or indirectly to a power distribution system. 
   Between the vacuum bottle  18  and the dielectric housing  32  is a dielectric filler  42  that fills the space therebetween, thereby replacing the lower dielectric strength air with a higher dielectric material. In particular, the filler  42  is a dielectric material that bonds to all contact surfaces ensuring an arc track resistant surface interface. The filler can be any dielectric material such as a dielectric epoxy, polyurethane, a silicone grease or solid. Preferably, the filler  42  is room temperature curable and has an acceptable pot life to allow ease in manufacturing. The filler preferably has a very low viscosity to enable the manufacturing and assembly process to be done without using a vacuum. 
   Weathershed insulation  44  is disposed around the outside of the dielectric housing  32  to provide dielectric strength and weatherability to the vacuum interrupter  12 . Preferably, the weathershed insulation  44  is made of a rubber material, such as rubber, EPDM, silicone or any other known material. Alternatively, the weathershed  44  and the dielectric housing  32  can be formed as a unitary housing made of a dielectric epoxy material. 
   A flexible shunt  46  is rigidly attached to the movable contact  28  using a stud bolt  48 . Preferably, the shunt  46  is made of sheets of thin copper material. The flexible shunt  46  is connected to a current ring  50  to allow current to transfer from the movable contact  28  to the current ring  50 . Preferably, the flexible shunt  46  has two connections to the current ring  50  so that any current traveling through the shunt is split between the connections. This allows less copper to be used and maintains a balanced mechanical load on the moving contact and drive parts. 
   The solenoid assembly  14  is a latching or bistable mechanism that moves the movable contact  28  between and holds it in the open and closed positions with respect to the stationary contact  26 . The solenoid assembly  14  includes a generally cylindrical housing  52  with a first end  54  and a second, opposing end  56 . A spring guide  58  is connected to the first end  54  of the solenoid assembly  14 . Preferably, the connection is made with three  10-32  screws  60 . The solenoid assembly  14  has a longitudinal plunger  62  received therein. The plunger  62  has a first connection end  64  for connecting to the turnbuckle and weld break assembly  16  and a second, opposing end  66  without any insulation therebetween. Also received within the cylindrical housing  52  is an actuator block  68  that is generally cylindrical. The end  66  of the plunger  62  extends through an opening  70  in the actuator block  68  into an inner bore  72  in the actuator block  68 . A preload adjustment screw  76  extends through an actuator cover  78  and into the inner bore  72  of the actuator block  68 . A biasing member  80  is disposed in the inner bore  72  between the end  66  of the plunger  62  and the end  74  of the preload adjustment screw  76 . The biasing member  80  is preferably a plurality of Belleville washers. The preload adjustment screw  76  is threadably connected to the actuator cover  78  so that the load applied by the biasing member  80  on the plunger  62  can be increased or decreased by adjusting the screw  76 . This allows selection of the appropriate amount of load to ensure the proper connection between the stationary contact  26  and the movable contact  28  in the vacuum interrupter  12 . Preferably, the preload adjustment screw  76  is turned so that the biasing member applies a force of 130 lbs. This ensures that the holding force is at least 130 lbs the instant the contacts touch when they are closing. 
   An adjustment nut  82  is threaded onto the connection end  64  of the plunger  62  so that a drive disk  126  may be slid onto the plunger  62  and placed adjacent to the nut  82  ( FIG. 3 ). A biasing member  84 , preferably a coil spring, is located between the drive disk  126  and a radial spring seat  86  of the spring guide  58 . In this manner, the force generated by the biasing member  84  is applied to the plunger  62 . 
   A permanent magnet  88 , preferably any rare earth magnet, abuts the first end  90  of the actuating block  68 , and holds the actuating block  68  toward the magnet  88 , forcing the movable contact  28  against the stationary contact  26  in the vacuum interrupter  12  closed position. The permanent magnet  88  and flux concentrator  92  allow the solenoid assembly  14  to hold the vacuum interrupter contacts  26 ,  28  closed without power. An energy coil  94  surrounds the actuator block  68 . The coil  94  creates an opposing magnetic force, opposite to the magnet, releasing the actuator block  68  away from the magnet  88  when energized in a first direction. In this manner, the biasing member  84  forces the actuator block  68  away from the magnet  88 , thereby moving the movable contact  28  away from the stationary contact  26  to the open position. The coil  94  can also create a magnetic force in the same direction as the magnet  88 . This overcomes the force of the biasing member  84  and moves the movable contact  28  back into the closed position. 
   The biasing member  84  also controls the vacuum interrupter contact bounce when the vacuum interrupter is closed. The biasing member  84  applies pressure to the plunger  62 , rather than applying pressure directly to the actuator block  68 . This arrangement allows pressure to be maintained on the plunger  62  throughout the closing stroke. The spring also assists in the prevention of contact bounce by opposing the forces generated by the biasing member  80  located in the actuator block  68 . This arrangement allows a higher preload on the biasing member  80 . The forces generated by the biasing member  80  oppose any recoil of the movable contact  28  at the moment the movable impacts the stationary contact  26  during a close operation. 
   The stud bolt  48  in the movable contact  28  is connected to the plunger  62  of the solenoid assembly  14  by a turnbuckle and weld break assembly  16 . As seen most clearly in  FIGS. 5 and 6 , the turnbuckle and weld break assembly  16  has an outer slide body  96  attached to the stud bolt  48  by a first set of threads  98 . The pitch of the first set of threads is preferably 18 threads per inch. An inner slide member  100  is slidably received within the outer slide body  96  and is attached to the plunger  62  by a second set of threads  102 . The pitch of the second set of threads is different than the pitch of the first set of threads and is preferably 24 threads per inch. The first and second set of threads preferably face the same direction (e.g. both are right-handed threads), but may face opposite directions. A groove pin  104  extends through a hole  106  in the inner slide member  100  and rests in slots  108  located in the outer slide body  96 . This allows the outer and inner slide members  96 ,  100  to slide relative to one another for a predetermined length that is the length of the slots  108 , which length is greater than the transverse diameter of the groove pin  104 . A washer  110  encircles the outer slide body  96  and abuts the groove pin  104 . A coil spring  112  is located between the washer  110  and a shoulder  114  on the outer slide body  96  and biases the groove pin  104  toward one end  116  of the slot  108 . In operation, if the stationary contact  26  is welded to the movable contact  28 , the plunger  62  may begin moving the length of the slot  108 . When the groove pin  102  reaches the second end  118  of the slot  108 , it creates a hammer force on the movable contact  28 , breaking any welds between the contacts  26 ,  28 . Further, when the plunger reaches the end of its travel, the spring  112 , which was compressed at the start of the travel of the actuator, biases the groove pin  104  back toward its original position at the first end  116  of the slot  108 . The movable contact  28  therefore moves the same distance as the plunger  62 . Without the spring  112 , the movable contact  28  would move the length of the travel of the plunger  62  minus the length of the slot  108 . The compression force of the spring  112  should be greater than the inherent contact force of the vacuum interrupter  12  when the vacuum interrupter is fully open (e.g. about 9 mm). 
   Assembly of the Circuit Interrupting Device 
   Referring to  FIGS. 3 and 4 , the circuit interrupting device  10  is preferably assembled by building the solenoid assembly  14 , building a vacuum interrupter and shunt assembly  128 , and then connecting the two assemblies together. To build the solenoid assembly  14 , the preload adjustment screw  76  is threaded into the actuator cover  78 . The screw  76  is turned to apply six turns of pressure on the biasing members  80 . Preferably, six turns on the screw  76  apply around 130 lbs. of preload pressure. Next, the adjustment nut  82  is threaded onto the connection end  64  of the plunger  62 . The biasing member  84  and drive disk  126  are then slid onto the plunger  62 . The spring guide  58  is attached to the solenoid housing  52 . The spring guide  58  is attached using a holding fixture such as a vice because the biasing member  84  is under pressure when assembled. The adjustment nut  82  is adjusted to apply an appropriate preload force on the biasing member  84 . Preferably, the compressed length of the biasing member  84  is 1⅛ inches. 
   To build the vacuum interrupter and shunt assembly  128 , the flexible shunt  46  is fastened to the current ring  50 . The flexible shunt  46  is then attached to the vacuum interrupter by threading the stud bolt  48  into the moving contact  28  of the vacuum interrupter  12 . Preferably, a flat washer and a serrated Belleville washer (not illustrated here) are placed between the bolt  48  and the shunt  56  to prevent loosening of the connection between the bolt  48  and the moving contact  28 . The turnbuckle and weld break assembly  16  is threaded as far as it will go onto the stud bolt  48 . 
   The solenoid assembly  14  is then attached to the vacuum interrupter and shunt assembly  128  by threading the plunger  62  of the solenoid assembly  14  into the turnbuckle and weld break assembly  16 . The plunger  62  is threaded into the turnbuckle and weld break assembly  16  until there is no gap between the spring guide  58  and the current ring  50 . At this point, continuing to thread the plunger  62  into the turnbuckle assembly  16  will begin to separate the vacuum interrupter contacts  26 ,  28 . The threading operation should be stopped just before the contacts separate. Three  10-32  screws  130  are used to attach the spring guide  58  and the current ring  50  to the dielectric housing  32 . 
   Setup of the Circuit Interrupting Device 
   Before the circuit interrupter device  10  will function properly, the turnbuckle and weld break assembly  16 , the adjustment nut  82 , and the preload adjustment screw  76  must all be adjusted. Starting with the turnbuckle and weld break assembly  16 , due to the different pitches of the first and second set of threads  98 ,  102 , when the turnbuckle is turned counter clockwise it has the effect of pushing the plunger  62  backwards against the biasing member  80 . As seen most clearly in  FIG. 7 , this creates a gap  120  between the plunger  62  and the bottom  122  of the inner bore  72  of the actuator block  68 . The gap  102  is the contact wipe distance, and it allows the contacts  26 ,  28  of the vacuum interrupter  12  to erode without losing the contact pressure generated by the biasing member  80  in the solenoid assembly  14 . The turnbuckle is turned counter-clockwise 3 full turns, which preferably creates a wipe distance of approximately 1 mm. The gap  120  is lost motion—i.e. the gap requires that the actuator block  68  move 10 mm from closed to open to obtain a 9 mm gap between the contacts  26 ,  28  of the vacuum interrupter  12 . 
   The adjustment nut  82  is adjusted for more or less compression on the biasing member  84  as needed. The adjustment nut  82  is adjusted properly when the actuator block  68  moves the full distance (preferably 10 mm) when actuated and also maintains a small preload when the contacts are fully open. In other words, the adjustment nut  82  is adjusted so that the actuator block  68  cannot be pushed and stopped at some point in the stroke less then fully open or fully closed. 
   The preload adjustment screw  76  is adjusted by increasing the pressure applied to the biasing member  80  until the unit just barely opens when 52 volts is applied to the coil  94  from a 1000 uF capacitor. If the unit opens below this value, the preload adjustment screw is adjusted to apply less pressure. Further, the unit should close and latch with 50 volts applied by a 1000 uF capacitor. If too much pressure is applied by the preload adjustment screw  76 , the actuator block  68  will close but will not latch. If this occurs, the pressure can be decreased by turning the set screw back by ½ a turn counter-clockwise or any other suitable amount. 
   After performing these adjustments, the unit should be checked for bounce free closure by using an oscilloscope. 
   While one embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.