Abstract:
A jumper cable for use with electrical meter sockets includes an improved clamp at each end. The clamp includes a substantially coaxial threaded rod, threadedly secured to a movable jaw that may move between an open position and a closed position, guided between a pair of guide surfaces that are angled in an orientation that is not parallel to the threaded rod. The movable jaw may therefore be caused to be move laterally by rotating a knob at the end of the threaded rod that is located at the end of the clamp opposite the jaws, where it will provide the best access to itself, and minimize interference with meter removal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to meter centers for electrical power distribution systems. Specifically, it relates to improvements in jumpers to assist in the removal of individual meters from the meter center without interrupting current flow. 
     2. Description of the Related Art 
     A typical meter center for metering electrical power delivered to multiple locations from a common system includes a plurality of meter compartments, with each meter compartment containing one meter corresponding to one location to which power is delivered. A supply bus, typically a three-phase bus having three line wires plus a neutral, extend from the feeder bus to the meter compartment. The feeder buses in turn extend from the utility power lines. Tenant buses connect to the meter compartment to the location wherein the electrical power is utilized. Both the supply buses and tenant buses are connected to a meter socket of the meter compartment, with the meter socket securing a meter providing an electrical connection between the supply buses and the tenant buses. This electrical connection is formed by single ended plug-in jaws on the meter socket, dimensioned and configured to engage corresponding stabs on the meter. 
     When a meter must be disconnected from the meter socket, it is desirable to provide continued electrical power to the location monitored by the meter. A typical meter socket provides a horn bypass adjacent to, and an electrical communication with, each plug-in jaw and its associated bus. The horn bypasses permit connection of a jumper from the horn bypass of the supply bus to the horn bypass of the tenant bus prior to removal of the meter from the meter socket. Some presently available jumper cables include a clamp at each end, with each clamp having a pair of jaws surrounded by insulation. Mating angled surfaces on the jaws and insulation cause the jaws to be drawn together when the insulation is rotated. However, presently available jumpers do not provide adequate clamping to the bypass horns, and also interfere with insertion and removal of the meter. 
     Accordingly, an improved jumper for connecting the supply bus with its corresponding tenant bus prior to removal of an electrical meter from its meter socket is desired. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved clamp for jumper cables for use with electrical meters. The clamp includes an electrically conductive stationary jaw, and an electrically conductive movable jaw. The opposing stationary and movable jaws are housed within an insulator sleeve. The stationary jaw and insulator sleeve define a channel therethrough, dimensioned and configured to receive a threaded rod. The threaded rod is threadedly engaged to the movable jaw at one end, and includes a knob at its opposite end. The stationary jaw and movable jaw define corresponding angled surfaces, so that turning the threaded rod to extend or retract the movable jaw will move the movable jaw parallel to these angled surfaces, thereby causing the jaw to move between an open position and a closed position. The channel containing the threaded rod is sufficiently large relative to the threaded rod to permit lateral movement of the rod, corresponding to the inward and outward movement of the movable jaw. 
     A jumper cable includes a clamp of the present invention at either end, permitting the jumper cable to be connected between a supply bus and its corresponding tenant bus within the socket for an electrical meter, by securing each clamp to the bypass horn corresponding to each bus. A typical socket for an electrical meter includes two supply buses, and two tenant buses, although the present invention is not limited to this number of corresponding supply and tenant buses. While the meter is in use, the meter forms and electrical connection between each supply bus and its corresponding tenant bus, thereby completing the current path from the utility lines, through the feeder bus, the supply bus, the meter, and the tenant bus, and finally to the consumer. This electrical connection is formed by single-ended plug-in jaws on the meter socket, with each plug-in jaw corresponding to one bus, and a stab on the meter corresponding to each jaw. 
     To remove an individual meter from its socket, one end of a jumper cable is first clamped to the bypass horn corresponding to one of the buses (which may be either a supply bus or a tenant bus), and the knob is turned to move the movable jaw from its open position to its closed position, thereby securing the bypass horn between the movable jaw and the fixed jaw. The opposite end of the jumper cable is likewise clamped to the corresponding bus. The procedure is repeated until a jumper cable connects each supply bus within the socket to its corresponding tenant bus. The meter may then be removed from the socket, with the stabs in the meter exiting the jaws. The electrical current which previously flowed from the supply buses, through the meter, to the tenant buses will now flow from the supply buses, through the jumper cables, to the tenant buses, until servicing of the meter is complete, and the meter is reattached to the socket. At this point, the jumper cables are removed from the socket. 
     A clamp of the present invention is particularly advantageous for making electrical connections because the inner clamping surfaces of the stationary and moveable jaws remain parallel to each other as the moveable jaw is moved. This maximizes the surface area contact between each jaw of the clamp and the bypass horn, maximizing the security of the clamp and minimizing electrical resistance in the connection between the clamp and bypass horn. 
     It is therefore an aspect of the present invention to provide a jumper cable for use with electrical meter sockets, having a clamp at each end providing secure clamping to the bypass horns within the meter socket. 
     It is another aspect of the present invention to provide a jumper cable for use with electrical meter sockets, wherein the clamps at each end of the jumper cable do not interfere with installation and removal of the electrical meter from the socket. 
     It is a further aspect of the present invention to provide a jumper cable for use with electrical meter sockets, wherein electrical resistance within the connection between the clamping jaws and bypass horn is minimized. 
     It is another object of the present invention to provide a jumper cable for use with electrical meter sockets, wherein the jaws of the cable&#39;s clamps remain parallel throughout movement between their open and closed positions. 
     These and other aspects of the invention will become apparent through the following description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of meter center for which a jumper of the present invention will be utilized, illustrating two jumpers of the present invention connected to the bypass horns of a meter. 
     FIG. 2 is a front view of a meter center, showing two jumpers of the present invention connected to the bypass horns of the supply buses and tenant buses of a meter socket, with the meter removed. 
     FIG. 3 is a front view of a typical meter socket for which the present invention will be used. 
     FIG. 4 is a side view of a meter socket plate with the meter disconnected, and a jumper of the present invention connected to the bypass horns. 
     FIG. 5 is a side cross-sectional view of a clamp for each end of a jumper according to the present invention, illustrating the clamp in its open position. 
     FIG. 6 is a side cross-sectional view of a clamp for each end of a jumper according to the present invention, illustrating the clamp in its closed position. 
    
    
     Like reference numbers denote like elements throughout the drawings. 
     DETAILED DESCRIPTION 
     The present invention is directed to an improved clamp for a jumper for use with electrical meter sockets. 
     A typical electrical meter center  10  is illustrated in FIGS. 1-2. The meter center  10  includes a housing  12 , having a plurality of meter socket assemblies  14 . Each meter socket assembly  14  includes a socket plate  15 , to which the various components of the socket  14  are secured. Electrical power will be supplied to the meter center by feeder buses (not shown, but well known), with a typical number of feeder buses being four. Three of the feeder buses will supply alternating current, with their phases being 120° apart, and the fourth feed bus will be a neutral bus. Each meter center will have a pair of supply buses  72 ,  74 , each supply bus  72 ,  74  being electrically connected to one of the feeder buses through phase balancers. Each supply bus will include means for forming an electrical connection to the supply bus within the meter socket  14 , typically including plug-in jaws  16 ,  18  and bypass horns  20 ,  22 . Likewise, the neutral feeder bus is electrically connected to the neutral plug-in jaws  24  within the meter socket  14 . A pair of tenant buses (not shown, but well known) leads from each meter socket assembly  14  to a location wherein electrical power will be consumed, for example, a residence or business. Each of the tenant buses is electrically connected to plug-in jaws  26 ,  28  within the meter socket assembly, and also to bypass horns  30 ,  32  within the meter socket assembly  14 . The electrical meter  34  includes a stab corresponding to each of the plug-in jaws  16 ,  18 ,  24 ,  26 , and  28  (not shown, and well known in the art). When the meter  34  is installed within the meter socket assembly  14 , the meter provides an electrical connection between the plug-in jaws for the supply buses  16 ,  18  and the plug-in jaws for the tenant buses  26 ,  28 , thereby permitting the flow of electricity from the supply buses, through the meter, to the tenant buses, and finally to the location of the consumer. 
     The use of the plug-in jaws  16 ,  18 ,  24 ,  26 , and  28  within the meter socket  14 , and corresponding stabs on the back of the meter  34 , permits the meter  34  to be removed from the socket  14  when servicing the meter  34  is desired. When servicing the meter  34 , it is desirable to provide uninterrupted flow of electricity to the consumer. This is accomplished by connecting a jumper  36  between the supply bus bypass horn  20  and tenant bus bypass horn  30 , and passing a second jumper  38  from the supply bus bypass horn  22  to the tenant bus bypass horn  32 . Current will then pass through the jumpers, permitting the meter  34  to be removed without interruption of electrical power. 
     Referring to FIGS. 4-6, each of the jumpers  36 ,  38  includes a clamp  40  at each end. Each clamp  40  includes an electrical conductive stationary jaw  42  and an electrically conductive movable jaw  44 . An example of a suitable electrically conductive material for the stationary jaw  42  and movable jaw  44  is bronze. The jaws  42 ,  44  are surrounded by insulation  46 , with an example of a suitable insulating material being plastic. A threaded rod  48  having a knob  50  at one end passes through a channel  52  defined within the insulation  46  and stationary jaw  42 . 
     The threaded rod  48  threadedly engages the movable jaw  44 , so that rotation of the threaded rod  48  causes movement of the movable jaw  44  parallel to the axis A of the clamp  40 . The stationary jaw  42  defines a pair of substantially parallel angled guide surfaces  54 ,  56  and a pair of limiting surfaces  58 ,  60  on opposing sides of the movable jaw  44 . The movable jaw  44  likewise includes a pair of substantially parallel angled bearing surfaces  60 ,  62 , corresponding to the angled surfaces  54 ,  56  of the stationary jaw  42 . The movable jaw  44  also includes limit surfaces  66 ,  68  corresponding to the limiting surfaces  58 ,  60  of the stationary jaw  42 . The angled guide and bearing surfaces  54 ,  56 ,  62 ,  64  are dimensioned and configured to cause the movable jaw  44  to move towards or away from the grasping portion  70  of the stationary jaw  42  when the threaded rod  48  is turned. In the illustrated example, turning the threaded rod  48  to move the movable jaw  44  away from the knob  50  will cause the movable jaw to move parallel to the angled guide surfaces  54 ,  56  until the limit surface  68  of the movable jaw  44  strikes the limiting surface  60  of the stationary jaw  42 , corresponding to the open position of the clamp  40 . Likewise, rotating the threaded rod  48  to move the movable jaw  44  towards the knob  50  will again cause the movable jaw  44  to move parallel to the angled guide surfaces  54 ,  56  until the limit surface  66  of the movable jaw  44  strikes the limiting surface  58  of the stationary jaw  42 , defining the closed position of the clamp  40 . The channel  52  is sufficiently wide so that the threaded rod  48  may move perpendicular to the clamp&#39;s axis A, corresponding to the movement of the movable jaw  44 . 
     Although the present example illustrates outward movements of the movable jaw  44  corresponding to opening the clamp  40 , those skilled in the art will appreciate from reading this description that rotating the angled surfaces  54 ,  56 ,  62 ,  64  approximately 90° will result in another embodiment of the clamp of the present invention wherein outward movement of the moveable jaw  44  corresponds to closing the clamp  40 . 
     When it is desired to service an electrical meter  34 , a pair of jumpers  36 ,  38 , with each jumper  36 ,  38  having a clamp  40  at each end are utilized to provide a constant flow of current to the consumer. The first jumper  36  may be connected between the supply bypass horn  20  and tenant bypass horn  30 . This connection is accomplished by first rotating the knob  50  of one clamp  40  to move the jaw  44  towards it open position, placing the bypass horn  20  between the grasping portion  70  of the stationary jaw  42  and the movable jaw  44 , and then rotating the knob  50  to move the movable jaw  44  from its open position to its closed position, thereby grasping the bypass horn  20  between the stationary jaw  42  and movable jaw  44 . Likewise, the second clamp  40  at the opposite end of the jumper  36  is opened by turning the knob  50  to move the movable jaw  44  towards its open position, and then positioned so that the movable jaw  44  and grasping portion  70  of the stationary jaw  42  are on opposing sides of the tenant bypass horn  30 . The knob  50  is then turned to move the movable jaw  40  towards the stationary jaw  42 , thereby securing the jaws  42 ,  44  around the bypass horn  30 . The second, identical jumper  38  is connected between the supply bypass horn  22  and tenant bypass horn  32  in like manner. The clamps  40  may, of course, be connected to the bypass horns  20 ,  22 ,  30 ,  32  in any order. The meter  34  may then be removed from the socket  14  without interrupting the flow of current between the supply buses and tenant buses. When servicing the meter  34  is complete, the meter  34  is reinstalled within the socket  14 , and the jumpers  36 ,  38  are removed. 
     A clamp  40  of the present invention is particularly advantageous for making electrical connections because the inner clamping surfaces of the stationary and moveable jaws  42 , 44  remain parallel to each other as the moveable jaw  44  is moved. This maximizes the surface area contact between each jaw of the clamp and the bypass horn, maximizing the security of the clamp and minimizing electrical resistance in the connection between the clamp and bypass horn. 
     While a specific embodiment of the invention has 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 the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.