Abstract:
A rotor assembly may include first rotor half, a first spring supported with the first rotor half, a second rotor half, and a second spring supported within the second rotor half, wherein the first rotor half and the second rotor half are adjoined to enclose the first and second springs. A coiled section of each spring may surround a rotor center pin. A contact arm positioned between the springs may include a non-circular opening. A method for assembling such a rotor assembly is further described.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present disclosure relates generally to a contact assembly, and particularly to a rotor assembly for a contact assembly.  
         [0002]     Contact pairs are commonly arranged upon one movable rotary contact arm. When an overcurrent condition exists, electromagnetic forces cause the rotary contact arm to separate from fixed contacts against the closing force of one or more contact springs.  
         [0003]     The rotary contact arm is typically connected to the contact springs via pivotal links. During quiescent operation, the contact springs provide a force to the rotary contact arm via the links in a direction as to drive the rotary contact arm into the fixed contacts. Upon short circuit condition, for example, current levels at or above the “withstand level” of the interrupter, the electromagnetic forces generated between the fixed contacts and the rotary contact arm causes the rotary contact arm to rotate away from the fixed contacts. If the overcurrent level reaches or exceeds the “let-through level”, the spring force passes a point commonly referred to as the “overcenter” position and the rotational direction of the contact spring force changes, i.e., the contact springs provide a force to the rotary contact arm via the links in a direction as to drive the rotary contact arm apart from the fixed contacts.  
         [0004]     The rotary assemblies of prior systems use compression springs to provide the spring force. Compression springs are coiled helical springs that resist a compressive force applied axially. Such rotary assemblies are designed such that assembly time is high, and does not meet top-down assembly criteria. Furthermore, these systems require complex assembly jigs and fixtures.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     Embodiments of the invention include a rotor assembly including a first rotor half, a first spring supported with the first rotor half, a second rotor half, and a second spring supported within the second rotor half, wherein the first rotor half and the second rotor half are adjoined to enclose the first and second springs.  
         [0006]     Other embodiments include a method for assembling a rotor assembly, the method including arranging a first rotor half with an inner side exposing a central recess, placing a coiled section of a first spring within the central recess, inserting a rotor center pin within the central recess and through the coiled section of the first spring, threading an opening of a contact arm over the rotor center pin, threading a coiled section of a second spring over the rotor center pin, and placing a central recess of the second rotor half over the rotor center pin.  
         [0007]     Other embodiments include a contact assembly including a first fixed contact, a second fixed contact, a contact arm having a first end, a second end, and a central portion, a first movable contact attached to the first end of the contact arm and movable in and out of engagement with the first fixed contact, a second movable contact attached to the second end of the contact arm and movable in and out of engagement with the second fixed contact, an opening within the central portion of the contact arm, wherein the opening has a length that is longer than its width, and a center rotor pin passing through the opening, wherein the contact arm is rotatable about the center rotor pin, wherein, when non-uniform erosion of any of the fixed or movable contacts occurs, the opening allows for re-alignment of the contact arm about the center rotor pin for ensuring uniform contact pressure between the first fixed and movable contacts and between the second fixed and movable contacts. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     Referring to the exemplary drawings wherein like elements are numbered alike in the accompanying FIGS.:  
         [0009]      FIG. 1  depicts a front perspective view of an exemplary circuit breaker rotary contact assembly for employing the split rotor system with springs;  
         [0010]      FIG. 2  depicts a front perspective view of an exemplary assembled rotor system;  
         [0011]      FIG. 3  depicts an exploded view of the rotor system of  FIG. 1 ;  
         [0012]      FIG. 4  depicts an exemplary rotor half;  
         [0013]      FIG. 5  depicts the rotor half of  FIG. 4  with a spring;  
         [0014]      FIG. 6  depicts the rotor half and spring of  FIG. 5  with a rotor center pin;  
         [0015]      FIG. 7  depicts an exemplary contact arm installed upon the assembly of  FIG. 6 ;  
         [0016]      FIG. 8  depicts another spring installed upon the assembly of  FIG. 7 ;  
         [0017]      FIG. 9  depicts an exemplary second rotor half, in phantom, disposed upon the assembly of  FIG. 8 ; and,  
         [0018]      FIG. 10  shows the rotor assembly of  FIG. 9  positioned with an exemplary contact assembly. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     An embodiment of the invention provides a split rotor with spring, to reduce friction, in a double break arrangement and having a top down assembly in the manufacturing which, in result, will reduce the assembly time in an automated system. This system is accomplished through the development of a contact arrangement for a frame breaker, with fewer components and less assembly time to reduce the cost of the breaker. Thus, a double contact rotor system is provided that will deliver equal contact force regardless of contact wear, electrical isolation from adjacent electrical phases and few parts for ease of manufacture. In result, the whole pole enclosure assembly is a top down assembly.  
         [0020]      FIG. 1  shows an exemplary circuit breaker rotary contact assembly  10  that may employ the split rotor with spring. While only one embodiment of a circuit breaker rotary contact assembly  9  is shown, it should be understood that the split rotor with spring may be utilized in alternate embodiments of a circuit breaker rotary contact assembly. The circuit breaker rotary contact assembly  9  may include opposing line and load straps  23 ,  31  adapted for connection with an associated electrical distribution system and a protected electric circuit. Fixed contacts  27 ,  27 B′ connect with the line and the load straps while the moveable contacts  28 ,  28 B′ are attached to the ends  30  of moveable contact arms  32  for making moveable connection with the associated fixed contacts to complete the circuit connection with the line and load straps  23 ,  31 . The movable contact arms  32  may be of unitary structure and rotate within the rotor and contact arm assembly  19  about the contact arm pivot  29  when rotated upon response to the circuit breaker operating mechanism (not shown) by connection via the pins  38  and the pair of opposing levers  36 ,  37 , shown generally by item  35 . The arcs generated when the contacts  27 B′,  28 B′ and  27 ,  28  are separated upon overload circuit current conditions are cooled and quenched within the arc chambers  33 ,  34  to interrupt current through the protected circuit. It should be noted that other conditions may also cause the contacts to separate other than overload conditions. The rotor  19  may rotate about a rotor pivot in response to the circuit breaker operating mechanism and interacts with the moveable contact arms  32 .  
         [0021]     Turning now to  FIG. 2 , an assembled rotor assembly  50  is shown. The rotor assembly  50  may be used within a contact assembly such as shown in  FIG. 1  or within any contact assembly or other mechanism that utilizes a rotor assembly having a double break contact arm, that is, a contact arm having a movable contact on each arm end. The rotor assembly  50  may include a first rotor half  52  and a second rotor half  54 . The first rotor half  52  and the second rotor half  54  support the contact arm  56  therebetween.  
         [0022]     With further reference to  FIG. 3 , the contact arm  56  may include a first end  58  that supports a first movable contact  60 , and a second end  62  that supports a second movable contact  64 . By a “movable contact”, it should be understood that the contacts  60 ,  64  are not movable with respect to the contact arm  56 , but instead move with the contact arm  56  as the contact arm  56  is moved to engage the contacts  60 ,  64  with a respective pair of fixed contacts within a circuit breaker or as the contact arm  56  is moved to separate the contacts  60 ,  64  from the fixed contacts. The contact arm  56  may further include a central portion that connects the first end  58  to the second end  62 . Within the central portion  66 , there may be an opening  68  which may be oblong in shape. Although an oblong shape is described, it should be understood that various other shapes may also successfully achieve the below-described functions, such as rectangular, elliptical, or diamond shapes. The opening  68  is shaped so that the contact arm  56  shares an axis of rotation  70  with a longitudinal axis  72  of a rotor center pin  74 . Also, the opening  68  may be shaped to have a length L which is measured to be parallel to a line that perpendicularly intersects a contacting face of the movable contacts  60 ,  64 , and a width W which is measured to be parallel to a line that is parallel with a contacting face of the movable contacts  60 ,  64 . The width W may be smaller than the length L, where the width W of the opening  68  is the distance from a first side of the opening  68  closest to the first end  58  to a second side of the opening  68  closest to the second end  62 . Thus, the length L of the opening  68  is the distance from a third side of the opening  68  that connects one end of the first side of the opening  68  to one end of the second side of the opening  68  to a fourth side of the opening  68  that connects another end of the first side of the opening  68  to another end of the second side of the opening  68 . By “side” of an opening  68 , it should be understood that such a side may be curved, pointed, straight, etc., depending on the shape of the opening  68 .  
         [0023]     The first rotor half  52  and second rotor half  54  may each include a protrusion  76 , each protrusion including a longitudinal aperture  78 , where each longitudinal aperture  78  has a longitudinal axis that is parallel with the longitudinal axis of the rotor center pin  74 . The first rotor half  52  and the second rotor half  54  may also each include a receiving portion  80 , each receiving portion  80  including a longitudinal aperture  82 , where each longitudinal aperture  82  may have a longitudinal axis that is parallel with the longitudinal axis of the rotor center pin  74 . When assembled, the protrusion  76  of the first rotor half  52  may be received within the receiving portion  80  of the second rotor half  54 , and the protrusion  76  of the second rotor half  54  may be received within the receiving portion  80  of the first rotor half  52 . Thus, the longitudinal apertures  78  may combine with the longitudinal apertures  82  to form a pair of passageways through the rotor assembly  50 . Such passageways may be used for allowing for a link connection by means of an extended rotor pin or driving pin (not shown) with the circuit breaker operating mechanism, via mechanism links, to allow manual intervention for opening and closing the circuit breaker contacts. These pins may also be used to connect adjacent rotor assemblies, and to connect the contact assembly with the operating mechanism for normal operations. The passageways, and thus the protrusions  76  and receiving portions  80 , may be diametrically opposed, although other configurations that are found useful within a circuit breaker would also be within the scope of this rotor assembly. Also, it should be noted that the rotor halves  52 ,  54  may be identical in shape, for reducing manufacturing expenses related to component parts, however altering designs of the rotor halves  52 ,  54  are within the scope of this rotor assembly  50 .  
         [0024]     The first rotor half  52  and the second rotor half  54  may also each include a central recess  84  for receiving first and second ends of the center rotor pin  74 . Also partially positioned within each recess  84  may be a spring  86 ,  88 . The springs  86 ,  88  shown in  FIG. 3  are torsion type springs. A torsion spring is made to offer resistance to applied torque. When deflected, a torsion spring may reduce in coil diameter, and extend in overall length. In a torsion spring, torque is the twisting action which tends to produce rotation. While torsion springs are demonstrated in  FIG. 3 , alternate spring assemblies would be within the scope of this rotor assembly  50 . Such alternate spring assemblies may include, but are not limited to, springs that are not compression springs, such as torsion springs, extension springs, tension springs, etc. An extension spring, also known as a tension spring, is wound with initial tension which hold the coils together and offers resistance to a pulling force. Extension springs may have many different styles of ends, such as hooked, looped, or bent ends. In yet another alternate embodiment, the rotor assembly  50 , which utilizes a split rotor, may even utilize a compression spring.  
         [0025]     The torsion springs  86 ,  88  may be identical in shape, but are positioned in opposite directions during assembly as shown. Although identical torsion springs  86 ,  88  simplify the manufacture of the rotor assembly  50 , it would be within the scope of this rotor assembly to include torsion springs of altering designs. Each torsion spring  86 ,  88  may include an uncoiled first end  90  that is seated furthest into the central recess  84 . From the first end  90 , the torsion spring may then include a tightly coiled section  92 , such as of spiraled wire, and then an uncoiled second end  94 . The uncoiled second end  94  may engage one end  58  or  62  of the contact arm  56 . The contact arm  56  may be molded or otherwise formed to include a first groove  96  on the first end  56  of the contact arm  56  and a second groove  98  on the second end  62  of the contact arm  56 . The second end  94  of the first torsion spring  86  may engage with groove  96  of the contact arm  56  and the second end  94  of the second torsion spring  88  may engage with the groove  98  of the contact arm  56 . The engagement between the torsion springs and the grooves may include a straight portion  100  of the second end  94  lying flush with a surface of the grooves  96 ,  98 . Alternatively, the second end  94  may hook onto or otherwise engage with the grooves  96 ,  98 .  
         [0026]     Thus, a rotor assembly  50  has been described that is capable of “top down” assembly. A procedure that is capable of top down assembly will show a reduction in assembly time of a product, and may also be manufactured using an automated system.  FIGS. 4-9  demonstrate how the rotor assembly  50  may be assembled using such a top down assembly process.  FIG. 4  shows the first rotor half  52  positioned such that protrusion  78  extends outwardly and recess  84  is made available.  
         [0027]      FIG. 5  shows the first torsion spring  86  inserted within the recess  84 , such that the first end  90  may be situated within a groove  102  in the first rotor half  52  extending from the recess  84 . The coiled section  92  may be completely seated within the recess  84 , and the uncoiled second end  94  may extend outside of the recess, and flush with an inner side  104  of the first rotor half  52 . While the first end  90  of the first torsion spring  86  is restricted from movement, the second end  94  may be partially movable, and may move along with the contact arm  56 .  
         [0028]      FIG. 6  shows the insertion of the rotor center pin  74  within the recess  84  such that the rotor center pin  74  is seated within the coiled section  92  of the first torsion spring  86 .  
         [0029]      FIG. 7  shows the contact arm  56  threaded onto the rotor center pin  74  by placing the opening  68  over the rotor center pin  74 . It can be seen that the opening  68  has a length L that is larger than a diameter of the rotor center pin  74 . Even after a few electrical operations, there may be non-uniform erosion of the contacts. Because of the oblong shape of the opening  68 , or a similar shape as previously described, the contact arm  56  can re-align itself to give uniform contact pressure on both sides of the contact arm  56 . It should also be noted that the contact arm  56  is wrapped about the protrusion  78  and the receiving portion  80  such that, when fully assembled, the contact arm  56  has a limited degree of circular movement about the longitudinal axis  70 .  FIG. 7  also demonstrates how the straight portion  100  of the second end  94  of the first torsion spring  86  is seated up against the second contact arm  62  within the groove  98 . It is noted that although this configuration is the reverse of what is shown in  FIG. 2 , it should be understood that either configuration would function in the same manner. That is, whether the first torsion spring  86  engages with groove  98  or groove  96  does not matter, as long as the second torsion spring  88  engages with the other of the groove  98  or groove  96 , thus having one second end  94  per groove.  
         [0030]      FIG. 8  shows the second torsion spring  88  being added to the assembly  50 . The second torsion spring  88  is threaded over the rotor center pin  74  by passing the end of the rotor center pin  74  into the coiled section  92  of the second torsion spring  88 . The straight portion  100  of the second end  94  of the second torsion spring  88  is seated within the groove  96 .  
         [0031]      FIG. 9  shows how the second rotor half  54  (shown in phantom) may be placed over the assembly of the first rotor half  54 , first torsion spring  86 , rotor center pin  74 , contact arm  56 , and second torsion spring  88 . As previously described, the protrusion  78  of the first rotor half  52  is received in the receiving portion  80  of the second rotor half  54 , and the protrusion  78  of the second rotor half  54  is received in the receiving portion  80  of the first rotor half  52 . The rotor center pin  74  is seated within the recess  84  of the second rotor half  54 , as is the coiled portion  92  of the second torsion spring  88 . It should also be noted that the first end  90  of the second torsion spring  88  may be seated within a groove  102  extending from the recess  84  as similarly shown in  FIG. 5  with respect to the first torsion spring  86  and the first rotor half  52 . Also, while the first end  90  of the second torsion spring  88  may be held stationary within the second rotor half  54 , the second end  94  of the second torsion spring  88  may be movable with respect to the second rotor half  54 , as it moves with the contact arm  56 , via the flat portion  100  engaged with the groove  96  of the contact arm  56 .  
         [0032]      FIG. 10  shows the rotor assembly  50  positioned within a circuit breaker  150 . The second rotor half  54  is again shown in phantom to reveal the second torsion spring  88 , contact arm  56 , and first rotor half  52 .  
         [0033]     Thus, a double break contact bridge located at the center of a two piece rotor, such as left and right side rotor halves, has been described. The center pin may be located in the oblong hole in the contact bridge and both sides in left half and right half of the rotor. The advantage of the oblong hole is, even after a few electrical operations, if there is non-uniform erosion of the contact tip, the contact bridge can re-align itself to give uniform contact pressure of both side of the bridge. The contact bridge may be loaded with the pre-determined force of a pair of springs located on both sides of the contact bridge. These springs may be located in the perpendicular direction to the axis of the center pin. The whole rotor assembly may be located in the bearing axis of the pole enclosure.  
         [0034]     While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best or only mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.