Abstract:
A circuit breaker rotary contact assembly employs a common pivot between the rotor assembly and the rotary contact arm. A pair of off-center expansion springs directly engage the rotor at one end and engage the rotary contact arm via a linkage arrangement at an opposite end thereof.

Description:
CROSS REFERENCE OF RELATED APPLICATIONS 
     This is a continuation-in-part of application Ser. No. 09/087038, filed May 29, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 4,616,198 entitled “Contact Arrangement for a Current Limiting Circuit Breaker” describes the early use of a first and second pair of circuit breaker contacts arranged in series to substantially reduce the amount of current let through upon the occurrence of an overcurrent condition. 
     When the contact pairs are arranged upon one movable contact arm such as described within U.S. Pat. No. 4,910,485 entitled “Multiple Circuit Breaker with Double Break Rotary Contact”, some means must be provided to insure that the opposing contact pairs exhibit the same contact pressure to reduce contact wear and erosion. 
     One arrangement for providing uniform contact wear is described within U.S. Pat. No. 4,649,247 entitled “Contact Assembly for Low-voltage Circuit Breakers with a Two-Arm Contact Lever”. This arrangement includes an elongate slot formed perpendicular to the contact travel to provide uniform contact closure force on both pairs of contacts. 
     U.S. Pat. No. 5,030,804 entitled “Contact Arrangement for Electrical Switching Devices” describes providing a pair of cylindrical plates on either side of the contact arms and forming elongated slots within each of the cylindrical plates. 
     Other examples of circuit breakers employing rotary contacts are found in U.S. Pat. No. 5, 281,776 entitled “Multipole Circuit Breaker with Single Pole Units; U.S. Pat. No. 5,310,971 entitled “Molded Case Circuit Breaker with Contact Bridge Slowed Down at the End of Repulsion Travel”; and U.S. Pat. No. 5,357,066 entitled “Operating Mechanism for a Four-Pole Circuit Breaker”. 
     State of the art circuit breakers employing a rotary contact arrangement employ a rotor assembly and pair of powerful expansion springs to maintain contact between the rotor assembly and the rotary contact arm as well as to maintain good electrical connection between the contacts, per se. The added compression forces provided by the powerful expansion springs must be overcome when the contacts become separated by the contact “blow open” forces of magnetic repulsion that occur upon extreme overcurrent conditions within the protected circuit before the circuit breaker operating mechanism has time to respond. 
     Accordingly, it is believed advantageous to have a rotary contact arrangement with expansion springs arranged between the rotary assembly and the rotary contact arm that maintain good electrical connection between the contacts during quiescent operating current conditions while enhancing contact separation upon occurrence of extreme overcurrent conditions. 
     SUMMARY OF THE INVENTION 
     A circuit breaker rotary contact assembly employs a common pivot between the rotor assembly and a two piece rotary contact arm assembly. A pair of off-center expansion springs directly engages the rotor at one end and engages the rotary contact arm assembly via a linkage arrangement at an opposite end thereof. The rotary contact arm assembly is slotted at a central portion for tolerance compensation between the rotary contact assembly components as well as to reduce contact wear and contact erosion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective view of a circuit breaker employing a rotary contact assembly according to the invention; 
     FIG. 2 is a top perspective view of the complete contact assembly contained within the circuit breaker of FIG. 1; 
     FIG. 3 is an enlarged top perspective view of the rotor in isometric projection with the contact arm assembly of FIG. 2; 
     FIG. 4 is an enlarged front plan view of the rotary contact arm assembly according to the invention with the contacts in the CLOSED position; 
     FIG. 5 is an enlarged front plan view of the rotary contact arm assembly according to the invention with the contacts in the OPEN position; and 
     FIG. 6 is an alternate embodiment of the rotary contact arm assembly according to the invention. 
     FIG. 7 is a perspective view of the rotor assembly with a two piece contact arm assembly. 
     FIG. 8 s a perspective view of one of the contact arms shown in FIG.  7 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A multi-pole circuit breaker  10  is shown in FIG. 1 consisting of a case  14  and cover  15  with an operating handle  16  projecting from the cover through an aperture  17 . The operating handle interacts with the circuit breaker operating mechanism  18  to control the ON and OFF positions of the central rotary contact arm  30 , and central rotary contact arm assembly  32  within the circuit breaker operating mechanism. The contact arm assembly  32  being formed within the central pole  11 . A first rotary contact arm  22  and first rotary contact arm assembly  20  within a first pole  12 , on one side of the operating mechanism  18  within the central pole  11 , and a second rotary contact arm  24  and second rotary contact arm assembly  21  within a second pole  13  on the opposite side of the central pole, move in unison to provide complete multi-pole circuit interruption. An elongated pin  38  interconnects the operating mechanism  18  with the center, first and second rotary contact arm assemblies  32 ,  20 ,  21 . As described within the aforementioned U.S. Pat. No. 4,649,247 a rotor  19  interconnects each of the rotary contact arms  22 ,  24 ,  30  with the corresponding pairs affixed contacts  27 ,  27 ′ and, movable contacts  28 ,  28 ′. 
     The rotor  19  in the circuit breaker assembly  9  is depicted FIG. 2 intermediate the line strap  23  and load strap  31  and the associated arc chutes  33 ,  34 . The first rotary contact arm assembly  20  and second rotary contact arm assembly  21  of FIG. 1 are not shown herein but are mirror images of the central rotary contact arm assembly  32  and operate in a similar manner. The arc chutes  33 ,  34  are similar to that described within U.S. Pat. No. 4,375,021 entitled “Rapid Electric Arc Extinguishing Assembly in Circuit Breaking Devices Such as Electric Circuit Breakers”. The central rotary contact arm  30  moves in unison with the rotor  19  that, in turn, connects with the circuit breaker operating mechanism  18  of FIG. 1 by means of the elongated pin  38  to move the movable contacts  28 ,  28 ′ between the CLOSED position depicted in solid lines in FIG.  4  and the OPEN position. The clevis  35  consisting of the extending sidearms  36 ,  37  attach the rotor  19  with the circuit breaker operating mechanism  18  and the operating handle  16  of FIG. 1 to allow both automatic as well as manual intervention for opening and closing the circuit breaker contacts  27 ,  27 ′ and  28 ,  28 ′. The rotor  19  is positioned between the line and load straps  23 ,  31  along with one of the contact pairs  27 ,  28 ,  27 ′,  28 ′ to hold the contacts in close abutment to promote electrical transfer between the fixed and moveable contacts during quiescent circuit current conditions. The operating pivot pin  29  of the central rotary contact arm  30  extends through the rotor  19  and responds to the rotational movement of the rotor to effect the contact closing and opening function in the manner described within the U.S. patent application Ser. No. 09/108684, filed Jul. 1, 1998 entitled “Rotary Contact Assembly for High Ampere-Rated Circuit Breakers” which is incorporated herein by reference. 
     In accordance with the teachings of the invention, a hinged attachment between the slotted rotor surfaces  19 A,  19 B arranged on opposite sides of the slotted movable contact arm  30  within the rotor assembly  39  as now shown in FIG. 3 provides for automatic tolerance compensation between the slotted rotors and the slotted movable contact arms within all three poles  11 - 13  of the circuit breaker  10  of FIG.  1 . The slotted contact arm  30  includes a slotted pivot aperture  46  for receiving the pivot pin  29  and a pair of top and bottom links  48 ,  49  attached to the slotted movable contact arm by means of pins  52 ,  53  and apertures  54 ,  55  arranged within the V-shaped slots  50 ,  51 . The slotted rotor  19  defines a pair of outer surfaces  19 A,  19 B each include central apertures, one of which is shown at  60  for receiving the pivot pin  29 , along with opposing shallow slots  44 A,  44 B and opposing deep slots  45 A,  45 B, as indicated. A first expansion spring  40  is attached to the slotted rotors by means of first pins  42 A,  42 B. The slotted contact arm  30  is inserted within the slot  63  formed within the slotted rotor intermediate the rotor outer surfaces  19 A,  19 B. The first pin  42 A extends through the shallow slot  44 A and the second pin  42 B extends through the deep slot  45 B. The first pin  42 A extends under the surface  61  defined under the movable contact arm  30 A and then through one end of an opposing expansion spring  58  on the rotor outer surface  19 B. The second pin  42 B extends through the deep slot  45 B, through the aperture  56  in the top link  48 , and then through the other end of the expansion spring  58  on the rotor outer surface  19 B. A second expansion spring  41  is attached to the slotted rotor by means of second pins  43 A,  43 B. The second pin  43 A extends through the deep slot  45 A, through the aperture  57  in the bottom link  49 , and then through one end of an opposing expansion spring  59  on the rotor outer surface  19 B. The second pin  43 B extends through the shallow slot  44 B, over the surface  62  defined on the movable contact arm  30 B and then through the other end of the expansion spring  59  on the rotor outer surface  19 B. 
     The slotted rotor assembly  39  is depicted in FIG. 4 with the movable contacts  28 ,  28 ′ on the opposite ends of the contact arms  30 A,  30 B in the CLOSED condition relative to the fixed contacts  27 ,  27 ′ (shown in FIG.  1 ). The top and bottom links  48 ,  49  are arranged on the top and bottom parts of the slotted contact arm  30  within the V-shaped slots  50 ,  51  and within the associated slots  45 A,  45 B on the slotted rotor  19  as viewed from the rotor surface  19 A. The expansion spring  41  is shown arranged between the pins  43 A,  43 B and the expansion spring  40  between the pin  42 B in the top link  48  and the pin  42 A is omitted to show the positional relationship between the line of force F 1 , directed through the pins  42 B,  52  in the top link  48 . This arrangement provides optimum contact pressure between the movable and fixed contacts  28 ,  27 ,  28 ′,  27 ′ while allowing for contact wear compensation and tolerance adjustment between the components within the rotor assemblies  39  within the individual poles within the circuit breaker of FIG.  1 . 
     Upon occurrence of a large overcurrent condition within the circuit breaker assembly of FIG. 2 containing the slotted rotor assembly  39  of FIG. 5, the magnetic repulsion forces generated between the movable and fixed contacts  28 ,  27 , 27 ′ (shown in FIG. 1) within the circuit breaker assembly drive the movable contact arms  30 A,  30 B and the associated movable contacts  28 ,  28 ′ in the counterclockwise direction about the pivot pin  29  to the OPEN position shown in FIG.  5 . The rotation of the upper link  48  moves the link pin  52  to the position indicated in FIG. 5 such that the line of force exerted by the expansion springs  40 ,  41  (FIG. 3) is now directed through the pins  42 B,  52  in the top link  48  as indicated at F 2 , locking the slotted contact arm  30  in the OPEN position to prevent re-closure of associated the movable and fixed contacts  28 ,  27 ,  28 ′,  27 ′ until the circuit breaker operating mechanism  18  shown in FIG. 1 has responded to separate the movable and fixed contacts  28 ,  27 ,  28 ′,  27 ′ within each of the circuit breaker poles  11 - 13 . Upon movement of the circuit breaker operating handle  16  to reset the circuit breaker operating mechanism, the slotted contact arm  30  rotates in the clockwise direction about the pivot  29  to return the contact arms  30 A,  30 B to the CLOSED position shown in FIG.  4 . It has been determined that the automatic expansion and contraction of the springs  40 ,  41 , 58 ,  59 , the top and bottom links  48 ,  49  and the provision of the slots  44 A,  44 B,  45 A,  45 B of FIG. 3 results in the best tolerance adjustment between the rotor assembly  39  than has ever heretofore been attainable in so-called rotary contact arrangements with self locking contact arm capabilities within circuit breakers. 
     U.S. Pat. No. 4,616,198 entitled “Contact Arrangement for a Current Limiting Circuit Breaker” describes a circuit interruption arrangement having a single pair of fixed and movable contacts that become separated by rotation of a single contact arm to which the movable contact is attached at one end. 
     In further accordance with the teachings of the invention, a semi-rotor assembly  64  is depicted in FIG. 6 to include a semi-rotor  65  having a circular forward surface as indicated at  65 A and a planar rear surface as indicated at  65 B. The movable contact  69  is positioned at one end of the contact arm and the pivot pin  70  attaches the contact arm to the semi-rotor  65  at the opposite end thereof. A contact braid  72  is fixedly attached to the movable contact arm as indicated at  73  at one end, and to the load strap  74  at the opposite end as indicated at  80 . In a similar manner as described with respect to FIGS. 3-5, a link  75  connects with the contact arm  68  at one end by means of the pin  77  and is positioned within the slot  65 C within the semi-rotor  65  and is retained therein by means of the extended pin  79 . A similar expansion spring  81  extends between the pin  79  at one end of the expansion spring as indicated at  78  and the extended pin  82  within the slot  67  at the opposite end of the expansion spring as indicated at  83 . An opposing expansion spring (not shown) extends between the pin  79  and the extended spring pin  82  on the other side of the semi-rotor assembly  64 . The link  75  is arranged such that the force line F 3  exhibited by the expansion spring between the semi-rotor and the contact arm is directed along the link pins  77 ,  79  resulting in the maximum contact pressure exhibited between the movable and fixed contacts  69 ,  71  when the contacts are in the CLOSED position indicated in solid lines. Upon occurrence of a large overcurrent condition within the circuit breaker assembly of FIG. 2 containing the semi-rotor assembly  64  of FIG. 6, the magnetic repulsion forces generated between the movable and fixed contacts  69 ,  71  within the circuit breaker assembly drive the movable contact arm  68  and the associated movable contact  69  in the counterclockwise direction about the pivot pin  70  to the OPEN position indicated in dashed lines. The force line F 4  exhibited by the expansion spring between the semi-rotor and the contact arm is now directed along the link pins  77 ,  79  in such a manner that the movable contact arm  68  is locked in the OPEN position to prevent re-closure of associated the movable and fixed contacts  69 ,  71  until the circuit breaker operating mechanism  18  shown in FIG. 1 has responded to separate the movable and fixed contacts  28 ,  27  within each of the circuit breaker poles  11 - 13 . Upon movement of the circuit breaker operating handle  16  to reset the circuit breaker operating mechanism, the movable contact arm  68  rotates in the clockwise indicate direction about the pivot  70  to return the contact  69  to the CLOSED position in the manner described earlier. 
     The provision of a link connection between a rotor assembly and a movable contact arm has been shown herein to improve performance of a circuit breaker during contact separation as well as contact closure. The arrangement of at least one expansion spring between the link and the associated rotor provides optimum contact force by compensating for component tolerance and contact erosion and wear while still maintaining a reliable means for locking the contact arm  30  open in the event of an over current condition. 
     An another alternate embodiment is the rotor assembly  39 ′ shown in FIG.  7 . In this embodiment, the contact arm  30  of assembly  39  is replaced by a two piece contact arm assembly  86 . The contact arm assembly  86  is made from two contact arm halves  88 ,  90 . These contact arm halves  88 ,  90  are held together by the braze joint  87 , 87 ′ that also secures the movable contacts  28 ,  28 ′ to the contact arm assembly  86 . Each contact arm half  88 ,  90  has a slot  91 ,  91 ′,  92 ,  92 ′ which when assembled defines the slots  93 ,  94  which are sized to receive a single linkage  95 ,  96 . The single linkage  95 ,  96  takes the place of and performs the same function as the pair of linkages  48 ,  49  in rotor assembly  39 . By replacing the pair of linkages  48 ,  49  with the single linkage  95 ,  96 , less parts are required, reducing manufacturing costs and making it easier to assemble than is possible with the rotor assembly  39 . Additionally, by eliminating the thickness of one of one linkage in the contact arm/linkage assembly, more material can be added to the rotor and thus increase the manufacturability of the rotor  19 . 
     The contact arm assembly  86  is inserted into slot  63  and is held in the rotor by pins  42 B,  43 B which are inserted into the apertures  97 ,  98  in the linkages  95 , 96  and the expansion springs  40 ,  41 ,  58 ,  59 . The pin  29  is inserted into the central opening  60  in the rotor  19  and through the slot  99  in the contact arm assembly  86  in a similar manner to that described above for rotor assembly  39 . The function and operation of the rotor assembly  39 ′ is identical to that described above for rotor assembly  39 . 
     The contact arm half  88  is shown in FIG.  8 . The slots  91 ,  92  may be formed in the contact arm half  88  by any method conducive to effective manufacturing, such as machining or coining. The slot  99 A along with the respective slot  99 B in the adjoining contact arm half  90  for the slot  99  in the contact arm assembly  86 . Note, the contact arm half  90  is a mirror image of the contact arm half  88 .