Abstract:
Cluster assemblies for both low and medium voltage applications which allow a movable circuit breaker to connect to a fixed part of the switchgear. The assembly apparatus comprises a plurality of conducting bridge elements consisting of resilient finger springs held in a predetermined geometrical configuration by a guide plate and a locator plate, wherein the locator plate is fixedly attached to a conductor. The resilient finger springs act to engage and hold a second conductor, thus making the electrical connection. The apparatus is scalably configured to address any range of low and medium voltage current necessary to be carried by the switchgear using simple and easily manufactured components.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     REFERENCE TO A MICRO-FICHE APPENDIX 
     None. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates generally to the field of contact assemblies for switchgear apparatus, and more specifically to cluster assemblies for both low and medium voltage applications which allow a movable circuit breaker to connect to a fixed part of the switchgear. 
     BRIEF SUMMARY OF THE INVENTION 
     Switchgear assemblies for both low and medium voltage applications use contact assemblies that allow a movable circuit breaker to connect to a fixed part of the switchgear. The means of making this connection is accomplished by copper fingers that are spring loaded and which bridge between conductors of uniform geometrical shape including, but not limited to round and rectangular conductors. Many different types of springs are used in these assemblies including compression, tension and leaf styles. For each embodiment of the present invention, the means of retaining the fingers and springs has varied widely as required to satisfy the particular size and geometry of conductor. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a perspective view of a finger element of an embodiment of the present invention. 
     FIG. 2 is a perspective view of a finger spring element of an embodiment of the present invention. 
     FIG. 3 is a perspective view of a resilient finger spring assembly of the finger element depicted in FIG.  1  and the spring element depicted in FIG.  2 . 
     FIG. 4 is a perspective view of a partial assembly of the finger and spring assembly, locator, and guide of an embodiment of the present invention. 
     FIG. 5 is a side view of disconnected cluster assembly of an embodiment of the present invention. 
     FIG. 6 is a side view of connected cluster assembly of an embodiment of the present invention. 
     FIG. 7A is a perspective view of a 12 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 7B is an end view of typical locator plate for a 12 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 7C is an end view of typical guide plate for a 12 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 8A is a perspective view of a 24 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 8B is an end view of typical locator plate for a 24 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 8C is an end view of typical guide plate for a 24 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 9A is a perspective view of a 58 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 9B is an end view of typical locator plate for a 58 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 9C is an end view of typical guide plate for a 58 finger rectangular cluster assembly of an embodiment of the present invention. 
     FIG. 10A is a perspective view of a 20 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 10B is an end view of typical locator plate for a 20 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 10C is an end view of typical guide plate for a 20 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 11A is a perspective view of a 36 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 11B is an end view of typical locator plate for a 36 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 11C is an end view of typical guide plate for a 36 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 12A is a perspective view of a 54 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 12B is an end view of typical locator plate for a 54 finger circular cluster assembly of an embodiment of the present invention. 
     FIG. 12C is an end view of typical guide plate for a 54 finger circular cluster assembly of an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The apparatus of the present invention comprises a primary finger  10  as depicted in FIG.  1 . The primary finger  10  is produced by stamping or similar high volume process from high conductivity copper. The primary finger  10  is common to all designs or embodiments of the present invention so that economical high volume production methods can be employed. The primary finger  10  further comprises a predetermined width, a predetermined length, a center point midway along the finger length, two ends, a top side comprising a circular spring locator  12  located at one end of the finger top side, and a bottom side comprising a locator slot  14  located at the end of the bottom side opposite from the end of the finger having the circular spring locator  12  and a guide slot  16  located on the finger bottom at a point slightly off the center point of the finger towards the locator slot  14 . The preferred embodiment of finger  10  is 0.155 inches thick; however a specific thickness is not necessarily determinative of how the finger functions. As shown, for example in FIG. 7C, the slot width  150  in which one or more fingers  10  will be inserted is sized to accommodate the number of fingers desired per slot and the total finger width. The finger end opposite the end of the locator slot  14  is angled at 45 degrees to form a conical or ramped shaped tip  19 , FIGS. 1 and 5. 
     A finger spring  20 , FIG. 2, of an embodiment of the present invention comprises a formed circular end  22 , a deformed convex top side  24 , a deformed concave bottom side  26 , and a foot end  28 , wherein the deformed top and bottom sides define a leaf spring mechanism. The preferred embodiment of finger spring  20  is made of spring steel and is 18 gauge thick, 0.150 inches wide, and about 2 inches long to provide the requisite load contact force in the deformed state. The finger spring  20  is also common to all designs or embodiments of the present invention and again high volume production methods allow for an economical part. 
     As shown in FIG. 3, the finger  10  and spring  20  are assembled by locating the formed circular end  22  of the spring  20  into the circular spring locator  12  of the finger  10 , aligning the spring leaf so that the spring convex top side  24  bows above the finger top side, and the spring foot  28  rests on the finger top side providing the resilient finger spring assembly  30 . 
     In order to retain the finger spring assembly  30  and have it cooperate with the fixed side of a conductor, two flat metal plates constructed from non-magnetic steel are used, FIGS. 4-6. Both plates comprise front and back surfaces which are identically sized by width and length and which have identical geometries. Both plate surfaces further comprise plate edges of a predetermined plate thickness, and have an array of identically sized and located slots  150 . One of the two plates is a locator plate  60  and the other plate is a guide plate  70 . The locator plate comprises means by which it can be fixedly connected to the fixed part of the conductor  400 . 
     The locator plate  60  further comprises means to attach to the guide plate  70  other than the resilient finger spring assemblies on certain embodiments of the present invention. For example, where locator and guide plate geometries are rectangular, the means by which the locator plate  60  cooperates with the guide plate  70  further comprises two fixed arms  67  extending at right angles from the locator plate  60  front surface for a predetermined length such that it extends past the guide plate  70 . The guide plate  70  further comprises two notches on each side that the locator plate fixed arms  67  pass through. The dimension between the fixed arms  67  is larger than the distance between the vertical surfaces of the two notches of the guide plate  70 . The clearance resulting from the difference between the two dimensions limits the side-to-side motion of the guide plate  70  and thus the outer ends of each finger  10 . The dimensional height of the fixed arms  67  is also slightly smaller than the dimensional height of the guide plate side notches. Again the clearance between these corresponding elements limits the up and down motion of the guide plate and thus the outer, tapered tips  19  of the fingers  10 . Limiting the side-to-side and up and down motions of each finger  10  is critical to ensure that each finger  10  aligns with the conductor  200  so that each finger  10  properly engages with the conductor  200  but the clearance also allows for some misalignment between conductors  200  and  400 . 
     The cluster assembly is held together by the location of the finger slots  14  and  16  in each of the locator plate  60  and the guide plate  70 , respectively, and the action of the finger spring  20  holding them in place. The resilient finger spring assembly position allows sufficient movement of the oppositely opposed resilient finger spring assembly to receive and engage the movable conductor element tapered tip and full element width, and wherein such oppositely opposed pair of resilient finger spring assemblies for rectangular locator and guide plate geometries define a gap distance between the tapered finger assembly edges which is smaller than the width of the movable conductor element. In the case of the circular cluster assemblies and locator/guide plate geometries, FIGS. 10A-12C, the circular array of the resilient finger spring assemblies and the dimensions of the parts both limit the total motion of the fingers relative to the centerline of the assembly but allow for misalignment of the conductor centerlines. 
     In an embodiment of the present invention, FIGS. 4,  5 ,  8 B, and  8 C, the locator plate  60  and the guide plate  70  are each 10 gauge thick, and the means by which the locator plate can be fixedly connected to the fixed part of the conductor further comprises locator plate openings  65  and guide plate openings  69  for receiving means to bolt the plate to the conductor  400 . In an embodiment of the present invention using rectangular locator and guide plate geometries, the means by which the locator plate  60  connects to the guide plate  70  further comprises two fixed arms  67  extending at a right angles from the locator plate  60  front surface for a predetermined length towards the locator plate  60  rear surface and beyond, and terminating in connection with the guide plate  70  notched edges. The predetermined length of the fixed arms  67  corresponds to the distance between the finger locator slot  14  and the finger guide slot  16  so that when the locator plate  60  is attached to the guide plate  70 , each finger slot can receive its respective plate when the finger is positioned into one of the array of corresponding plate slots. These locator and guide plates can be manufactured using numerically controlled laser cutting equipment known in the art. This production process easily can vary the plate sizes and shapes to economically produce smaller numbers of parts. 
     As shown in the partial assembly of an embodiment of the present invention using rectangular locator/guide plate geometries, FIGS. 4,  8 B, and  8 C, after the locator plate  60  has been attached to the guide plate  70  by means of securing the locator plate arms  67  into the guide plate notches  69 , one finger spring assembly  30  is located in the first slot in the array of plate slots of a partial assembly. The locator slot  14  in the finger bottom is positioned such that the locator plate  60  fits in to the locator slot  14  and holds the spring assembly  30  in place, FIGS. 4-6. As depicted in FIGS. 4 and 5, the leaf spring contacts the guide plate  70  at the top of the respective guide plate slot while the finger guide slot  16  receives the guide plate, wherein the guide plate also secures the spring assembly  30 . The finger guide slot  16  depth is such that the leaf spring is deformed from its free state and therefore holds the finger  10  against the bottom of the respective guide plate slot. With this configuration, FIG. 5, the finger  10  is held so that it is at an approximate 4 degree angle of declination measured from the centerline of the conductor  200  in a disconnected state. In the disconnected state, the conductor centerlines are misaligned. The conductor cross-sections are either round or rectangular; however the cross-section of the conductor  400  to which the locator plate  70  is fixedly attached is the same as the cross-section of the conductor  200  to which the cluster assembly engages. As further depicted in FIG. 5, at this 4 degree angle of declination, the gap between the two fingers is smaller than the width of the conductor  200  to be received. Once the cluster assembly engages the conductor  200  and is connected, the finger spring  20  further deforms and the finger  10  angle becomes nearly parallel to the centerline of the conductor  200 , FIG. 6, and the conductor centerlines are then aligned. 
     The tip of the conductor  200  to be received is shaped with corresponding 45 degree angles so that each finger end  19  engages the conductor  200  first at this angled tip, FIG.  5 . Once the cluster  40  is connected to the conductor  200 , FIG. 6, the corresponding finger  10  of the finger spring assemblies  30  moves to a parallel position relative to the conductor  200  centerline. The top of the corresponding guide plate  70  slot further causes deformation of the resilient finger spring  20  and each finger  10  now contacts both conductors. The force on each conductor is equal since the guide plate  70  is midway between the raised contact sections of the fingers. The force exerted in the connected cluster is sufficient to ensure good contact between the fingers and the conductors and to allow transfer of electrical current between the two conductors. 
     Low and medium switchgear require differing levels of rated normal current be carried. These rated currents range from 600 amps to as much as 6,000 amps. The sizes and shapes of conductors to adequately carry this range of current vary and no single design is possible. A number of possible embodiments are depicted in FIGS. 7A-12C. All of these embodiments use the same primary finger and finger spring components which can be produced in high volume and low cost. Each of the corresponding locator plates and guide plates are shaped and sized to suit the conductor profile employed for the specific current rating and type of circuit breaker. The locator plates and guide plates are manufactured by a process which easily and economically can produce the lower volume variable parts. As depicted in FIGS. 7A-12C, it is possible to install more than one resilient finger spring assembly in each plate slot. Up to four resilient finger spring assemblies per slot have been successfully used, though four is by no means a limit. As depicted in FIGS. 10A-12C, the circular locator and guide plates do not require attachment means between the plates other than the resilient finger spring assemblies, and the circular guide plates do not require access means to bolt the plate assemblies to the fixed conductor since the guide plate opening itself provides this access. The suitable array of locator/guide plate slots and the number of resilient finger spring assemblies per slot are determined by the current rating desired. 
     Therefore, the disclosed invention provides cluster assemblies for switchgear which are uncomplicated, use few and easily manufactured parts, achieve a high degree of precision location and orientation, and eliminate design complexity and tedious assembly procedures. It will be understood that, while presently preferred embodiments of the invention have been illustrated and described, the invention is not limited thereto, but may be otherwise variously embodied within the scope of the following claims.