Abstract:
A removable clamp assembly for a network protector bus, the network bus having at least one opening therethrough. The clamp assembly is structured to couple the network protector bus to a vault bus. The clamp assembly includes a mounting bracket structured to be removably coupled to the network protector bus and a gripping assembly for selectively gripping the vault bus. The gripping assembly is coupled to the mounting bracket. The gripping assembly includes threaded tubes surrounding a rod with opposite threads at each end for driving the tubes, whereby the gripping fingers on the gripping assembly are movable to grip the vault buss blocks.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a network protector bus clamp and, more specifically, to a network protector having a removable bus clamp assembly that may be removed from the bus without disassembling the clamp. 
     2. Background Information 
     Secondary power distribution networks consist of interlaced grids which are supplied by two or more sources of power so that the loss of a single source of power will not result in an interruption of service. Such secondary power distribution networks provide the highest level of reliability possible with conventional power distribution and are normally used to supply high-density load areas such as a section of a city, a large building, or an industrial site. Between a power source and the network is a transformer and a network protector. The network protector consists of a circuit breaker and a control relay. The circuit breaker includes at least one set of main contacts that move between an open position and a closed position. When the main contacts are closed, electricity may flow through the network protector. The control relay senses the transformer and network voltages and line currents and executes algorithms to initiate breaker tripping or closing action. Trip determination is based on detecting an overcurrent condition or reverse power flow, that is, power flow from the network to the energy source. Network protectors are often found in dust-proof or moisture-proof housings, or vaults, which are disposed in subterranean passageways in large metropolitan areas. 
     The network protector circuit breaker has at least one line bus and a load bus. Typically, the circuit breaker is a three phase circuit breaker having three poles, each with a line bus and a load bus. The network protector busses are coupled, respectively, to a vault line bus and a vault load bus. Either the vault line bus or the vault load bus will include a fuse located on the line opposite the clamp. The network protector circuit breaker bus that is coupled to the vault bus having the fuse uses a clamp assembly to couple the network protector circuit breaker bus to the vault bus. The vault bus also terminates in a coupling block. The clamp assembly includes a plurality of gripping fingers that are structured to move between a closed position, wherein the clamp assembly engages the coupling block, and an open position, wherein the clamp assembly does not engage the coupling block. When the clamp assembly is not engaging the coupling block, and after other connections are separated the circuit breaker may be rolled out of the vault. After the repair or maintenance operations are complete, the circuit breaker is moved into the vault and the fingers are moved into the closed position, gripping the coupling block. 
     It is a priority for utility companies, and other users, to reduce the down time of the network protector during repair. One way to reduce the down time is to simply replace the network protector. The difficulty in replacing a network protector is that the replacement unit must have a clamp assembly that is structured to interact with the vault bus in the vault that houses the network protector. The shape of the vault busses vary depending on whether the bus fuse is located on network side or the transformer side of the circuit breaker. Additionally, prior art clamps were designed to be attached to five inch tubular bus sections. Current network protectors have laminated rectangular busses which are about two inches thick. Moreover, the prior art bus clamp must be completely disassembled during the removal procedure. That is, the mounting assembly for the clamp assembly must be engaging the network protector bus to hold the clamp assembly together. As such, to remove the clamp assembly, the clamp assembly must be disassembled during the removal procedure and reassembled during the installation procedure. The disassembly and reassembly of the clamp assembly causes delay in the maintenance and/or repair procedure. 
     There is, therefore, a need bus clamp assembly that is structured to engage a laminated bus. 
     There is a further need for a bus clamp assembly that can be easily removed from, and reinstalled on, a laminated bus. 
     There is a further need for a bus clamp assembly that is compatible with existing equipment. 
     SUMMARY OF THE INVENTION 
     These needs, and others, are satisfied by the invention which provides a bus clamp assembly having a mounting bracket that is structurally separate from, but coupled to, a gripping assembly. The gripping assembly provides the clamping function for attaching the network protector bus to the line conductor or the load conductor. The mounting bracket attaches the clamp assembly to the network protector bus. The bracket may be attached or removed from the network protector bus without disassembling the gripping assembly. 
     The mounting bracket is an L-shaped body having a first leg and a second leg. The first leg has a plurality of openings. The first leg openings are structured to align with openings on the network protector bus. As such, a fastening device, e.g. bolts, may be passed through the first leg openings and the network protector bus. Nuts are coupled to the bolts thereby attaching the bracket to the bus. The second leg of the bracket has one or more openings as well. The second leg opening cooperates with a fastening device to couple the bracket to the gripping assembly. The fastening device passing through the second leg and coupling the bracket to the gripping assembly remains in place as the first leg fastening devices are removed or installed. As such, the griping assembly does not have to be assembled or disassembled as the clamp assembly is coupled or de-coupled from a network protector bus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
     FIG. 1 is a front view of a network protector incorporating the invention and showing internal components schematically. 
     FIG. 2 is a side view of a network protector circuit breaker from FIG.  1 . 
     FIG. 3 is an isometric view of a network protector circuit breaker from FIG.  1 . 
     FIG. 4 is an isometric view of a clamp assembly. 
     FIG. 5 is a side view of a clamp assembly. 
     FIG. 6 is a front view of a clamp assembly. 
     FIG. 7 is a top view of a clamp assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, a network protector  10  includes a tank  12  which includes a movable door  14 . The tank  12  is structured to be placed within a vault  16 . A vault is typically made of concrete or a similar material. The two primary network protector components, a circuit breaker  20  and a relay  22  are disposed within the tank  12 . The circuit breaker includes at least one set of main contacts  24  (shown schematically) that are structured to move between a first, open position and a second closed position. When the main contacts  24  are in the second, closed, electricity may flow through the circuit breaker  20 . When the main contacts  24  are in the first, open position, electricity cannot flow through the circuit breaker  20 . The circuit breaker  20  also includes an operating mechanism  26  (shown schematically) that is structured to move the main contacts  24  between the first and second position. The main contacts  24  are coupled to one or more network protector line buses  30  and one or more network protector load buses  32 . In a preferred embodiment, shown in FIGS. 1-3, the circuit breaker  20  is a three phase circuit breaker having three poles. Each pole includes a line bus  30  and a load bus  32 . As shown in FIGS. 2 and 3, both the network protector line bus  30  and the network protector load bus  32  are each made from a plurality of laminations  30 A,  30 B,  30 C,  30 D and  32 A,  32 B,  32 C,  32 D. Each network protector line bus  30  and network protector load bus  32  has one or more sets aligned openings  36  in each lamination  30 A,  30 B,  30 C,  30 D and  32 A,  32 B,  32 C,  32 D. The network protector line bus  30  and the network protector load bus  32  are each structured to be coupled to a clamp assembly  50 , described below. The network protector line bus  30  is coupled to a vault line bus  38  and the network protector load bus  32  is coupled to a vault load bus  39 . Both the vault line bus  38  and the vault load bus  39  include a coupling block  40 . The coupling block has a generally cylindrical cavity  42  structured to engage the generally cylindrical vault line bus  38  or vault load bus  39 . The outer surfaces  44  of the coupling block  40  are generally flat. Either the vault line bus  38  or the vault load bus  39  has a fuse  46  located therein. The mounting block is located on the line,  38 ,  39  having the fuse  46 . 
     As shown in FIGS. 4-7, the clamp assembly  50  includes a mounting bracket  60  and a gripping assembly  70 . The mounting bracket  60  includes an L-shaped body  62  having a first planar leg  64  and a second planar leg  66 . The bracket first leg  64  and the bracket second leg  66  are joined at a vertex  61  and are, generally, perpendicular to each other. The bracket first leg  64  includes at least one opening  65  extending through the planar member. When there are a plurality of bracket first leg openings  65 , the openings  65  are disposed, generally, in a line extending across the planar member. The bracket first leg openings  65  are sized and spaced to align with bus lamination openings  36 . The bracket second leg  66  also includes one or more openings  67 . The bracket second leg openings  67  are aligned with medial openings  77 , described below, on the gripping assembly  70 . 
     The gripping assembly  70  includes two planar side members  72 ,  74 , a spacer  76 , a support  78 , at least one threaded rod  80 , at least one threaded shell  82 , at least one shell spring  83 , at least two hubs  84 ,  86 , and at least one set of opposed gripping fingers  88 ,  90 . The side members  72 ,  74  each have a notch  73  sized to accommodate the network protector laminated busses  30 ,  32 . The side members  72 ,  74  each have pivot openings (not shown) for pivot rods  94 ,  96 , described below, and fastener openings (not shown) for fasteners  92 , described below. The spacer  76  is a generally rectangular block disposed between the side members  72 ,  74 . The spacer  76  has threaded openings on the sides adjacent to the side members  72 ,  74 . A plurality of fasteners, such as, but not limited to, bolts  92  extend through the side member fastener openings and into the spacer threaded openings. Thus, the side members  72 ,  74  are held in a spaced relation. The spacer  76  also has one or more, preferably two, medial openings  77  extending between the faces that are, generally, parallel to threaded rod  80 . 
     Pivot rods  94 ,  96  pass through the side member pivot openings and are rotatably supported between the side members  72 ,  74 . The gripping fingers  88 ,  90  are mounted on the pivot rods  94 ,  96 , one finger  88 ,  90  on each pivot rod  94 ,  96 . As such, the gripping fingers  88 ,  90  form an opposed pair. The pair of fingers are structured to pivot between a first, closed position and a second, open position, as described below. A hub  84 ,  86  is rotatably coupled to each finger  88 ,  90 . The hub  84 ,  86  includes a generally cylindrical body  85  having a radial opening  87  therethrough. In a preferred embodiment, there are a plurality of fingers  88 A,  88 B,  88 C,  88 D,  88 E,  88 F and  90 A,  90 B,  90 C,  90 D,  90 E,  90 F. A hub  84 ,  86  is disposed between and coupled to a set of two fingers  88 ,  90 . For example, as shown in FIG. 4, hub  84 A is disposed between, and coupled to, fingers  88 A and  88 B. To rotatably couple the hub  84 A between fingers  88 A and  88 B, the fingers  88 A and  88 B may be formed each with a circular recess (not shown). The hub  84 A is rotatably disposed in the recess. When the fingers  88 A and  88 B are attached to the pivot rod  94 , as described below, the hub  84 A is secured in the recess. 
     The support  78  has, generally, an L-shape with a first leg  78 A and a second leg  78 B. The support first leg  78 A has one or more openings  79 A extending therethrough. The support first leg openings  79 A are sized and spaced to correspond to spacer medial openings  77 . The support second leg  78 B has at least one slot shaped opening  79 B extending therethrough. The support second leg opening  78 B is slot shaped to accommodate the movement of the rods  80  as the fingers  88 ,  90  move between the open and closed position. Each support second leg opening  79 B is also aligned with a hub radial opening  87 . 
     When assembled, spacer  76  holds the side members  72 ,  74  in a spaced relation. The side members  72 ,  74  rotatably support the pivot rods  94 ,  96 . The pivot rods  94 ,  96  support one or more fingers  88 ,  90 . The fingers  88 ,  90  are each rotatably coupled to a hub  84 ,  86 . Additionally, a bracket/support fastening device  100 , such as, but not limited to, a bolt  102 , couples both the mounting bracket  60  and the support  78  to the spacer  76 . The bracket/support fastening device  100  passes through the spacer medial openings  77 . The support  78  is positioned so that the support second leg opening  79 B is aligned with the hub radial openings  87 . Thus, a threaded rod  80  may pass through the hub  84  coupled to finger  88 , through the support second leg opening  79 B, and through the hub  84  coupled to finger  90 . Two threaded shells  82  engage the threaded rod  80 , one threaded shell on each side of the support  78 . The threaded shells  82  are each fixed to a hub  84 ,  86 . That is, the threaded shells  82  cannot move axially through the hub radial openings  87 . The threaded shells  82  are also coupled to the shell springs  83 , which are disposed between the threaded shells  82  and the support second leg  79 . The threaded rod  80  is structured with clockwise threads on one side of the support  78  and counter-clockwise threads on the opposite side of the support  78 . In this configuration, rotating the threaded rod  80  will cause the threaded shells  82  to move toward or away from each other. As the threaded shells  82  are fixed to the hubs  84 ,  86 , which are in turn rotatably coupled to the fingers  88 ,  90 , rotating the threaded rods  80  cause the fingers  88 ,  90  to move between the first, closed position and the second, open position. 
     As shown best in FIG. 2, the clamp assembly  50  is coupled to a circuit breaker bus  30 ,  32  using the mounting bracket  60 . That is, fasteners  110 , such as, but not limited to, a bolt  112  is passed through the bracket openings  65  (FIG. 5) and the bus openings  36  (FIG.  1 ). The bus  30 ,  32  is disposed in notch  73 . If there are multiple bracket openings  65  disposed longitudinally across the bracket first leg  64 , the clamp assembly  50  may be centered on the bus  30 ,  32 , or may be shifted to one side of the bus  30 ,  32 , as shown in FIG. 1, or the other as needed to align with the vault line bus  39  or vault load bus  39 . Moreover, because the clamp assembly fasteners  110  are not required to hold the clamp assembly  50  together, the clamp assembly  50  may be removed or installed as a unit without disassembling the gripping assembly  70 . 
     In operation, for example, the circuit breaker  20  may be moved from one network protector  10  having fuses on the vault load bus  39  to a network protector having fuses on the vault line bus  38 . In such a situation, the clamp assembly  50  must be moved from the network protector line bus  30  to the network protector load bus  32 . The method for that procedure is as follows. After power to the network protector  10  is turned off and all appropriate safety precautions are taken, the technician rotates each threaded rod  80  on the gripping assembly  70  to move the fingers  88 ,  90  into the second, open position. This action will cause the gripping fingers  88 ,  90  to move away from the coupling block  40 . The technician also uncouples the load bus  32  from the vault load bus  39  as is know in the prior art. The circuit breaker  20  is then removed from the tank  12 . The technician then removed the fasteners  110  coupling the clamp assembly  50  to the line bus  38 . The clamp assembly  50  then placed on the load bus  39  and the fasteners  110  are passed through the mounting bracket  60  and the load bus openings  36 . After the fasteners  110  are secured, the circuit breaker  20  is placed in the new tank  12 . The load bus  32  is coupled to vault load bus  39 , which terminates in a coupling block  40 , by placing the coupling block  40  between the gripping fingers  88 ,  90 . The technician rotates the threaded rod  80  to move the gripping fingers  88 ,  90  from the second open position into the first, closed position. The technician then couples the line bus  30  to the vault line bus  38  as is known in the prior art. Thus, the clamp assembly  50  is moved from the line bus  30  to the load bus  32  without disassembling the clamp assembly  50 . 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.