Patent Publication Number: US-6667681-B1

Title: Network protector fuse housing

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a fuse housing for a network protector and, more specifically, to a fuse housing that is constructed using a reduced number of parts. 
     2. Description of the Prior Art 
     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 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 the power sources and the network is a transformer and a network protector. Such network protectors are often found in dust-proof or moisture-proof housings which are disposed in subterranean passageways in large metropolitan areas. The housing, or “tank,” may be further disposed within a concrete vault. 
     The network protector consists of a circuit breaker and a control relay. The control relay senses the transformer and network voltages and line currents and executes algorithms to initiate breaker tripping or closing action. The network protector is, typically, coupled to the line and the load by a three phase bus. Network protectors often utilize fuses as a secondary means of protection. Thus, there are fuses installed on each of the phases. Because interruption of a fuse inside the network protector housing often results in damage to the circuit breaker or other components, it is often preferable to have the fuses located outside of the network protector housing. 
     The fuses are enclosed in separate watertight housings disposed on top of the network protector housing. The prior art fuse housings are made from steel or molded fiber reinforced epoxy resin. The molded fuse housings are expensive. The steel fuse housings are less expensive, but are prone to leaks around the welded joints. Moreover, because each fuse has a separate housing, there are multiple welded joints that have the potential to leak. When water penetrates the fuse housing, the fuse may be damaged or degraded, thus limiting the ability of the fuse to interrupt the circuit. 
     There is, therefore, a need for an inexpensive fuse housing that is less prone to leakage. 
     There is a further need for a new fuse housing that is compatible with existing network protectors. 
     SUMMARY OF THE INVENTION 
     These needs, and others, are satisfied by the invention which provides a network protector fuse housing that is constructed using a two clam shell halves and which is structured to enclose all fuses connected to the network protector. The clam shell halves are constructed of stamped steel and have elongated U-shaped bodies. The U-shaped bodies are welded together to form the housing. Thus, there are eight welded joints on the housing. The number of welded joints is reduced relative to the prior art fuse housings which had at least eight welded joints on each of three individual housings. 
     The fuse housing may be mounted on the tank or, if space within the vault is an issue, on a wall adjacent to the network protector. The fuse housing may also have access portals located adjacent to each fuse, or, one large portal providing access to every fuse within the housing. The portal(s) is sealed with a cover that is coupled to the housing by fasteners. 
    
    
     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. 
     FIG. 2 is an isometric view of the fuse housing first C-shaped body. 
     FIG. 3 is a front view of the fuse housing first C-shaped body. 
     FIG. 4 is a top view of the fuse housing first C-shaped body. 
     FIG. 5 is an isometric view of the fuse housing second C-shaped body. 
     FIG. 6 is a front view of the fuse housing second C-shaped body. 
     FIG. 7 is a top view of the fuse housing second C-shaped body. 
     FIG. 8 is a partially exploded isometric view of the fuse housing. 
     FIG. 9 is a partially exploded isometric view of an alternate fuse housing. 
     FIG. 10 is a isometric view of a fuse box. 
     FIG. 11 is a cross-sectional view of the fuse box. 
     FIG. 12 is a isometric view of an alternate fuse box. 
     FIG. 13 is a cross-sectional view of the alternate fuse box. 
    
    
     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 load buses  30  and one or more network protector line buses  32 . In a preferred embodiment, shown in FIG. 1, the circuit breaker  20  is a three phase circuit breaker having three poles. Each pole includes a load bus  30  and a line bus  32 . 
     Outside of the tank  12  is a fuse box  110  that includes a plurality of fuse assemblies  1  and a fuse housing assembly  40 . There is one fuse assembly  1  coupled to the cable for each pole of the circuit breaker. The fuse assemblies  1  may be coupled to the line side or the load side of the circuit breaker  20 . The fuse housing assembly  40  may be attached to the tank  12 , or spaced therefrom. As shown in FIG. 1, the fuse housing assembly  40  is coupled to the tank  12 . The coupling between the fuse housing assembly  40  and the tank  12  is watertight and may be accomplished by welding the fuse housing assembly  40  to the tank  12 . 
     As shown in FIGS. 2-8, the fuse housing assembly  40  includes a first C-shaped body  50  and a second C-shaped body  70 . Each C-shaped body  50 ,  70  is preferably formed from a single flat sheet of metal that has bent extensions as described below. As shown in FIGS. 2-4, the first C-shaped body  50  includes a generally rectangular front side  52  and first and second generally perpendicular extensions  54 ,  56 . The front side has an inner side  58  and an outer side  60 . The first and second perpendicular extensions  54 ,  56  are also generally rectangular and extend in the same direction, one each, from the shorter sides of the rectangular front side  52 . The rectangular front side  52  also includes one or more openings  62 . There are, preferably three front side openings  62 A,  62 B,  62 C, each sized to allow a network protector fuse assembly body  2  (described below) to pass therethrough. Alternatively, as shown in FIG. 9, there may be a single front side opening  62 D spanning a substantial portion of the front side  52 . Around the perimeter of the front side openings  62  are a plurality of fastener openings  64 . The fastener openings  64  may be threaded, have a nut  66  or similar device attached to the inner side  58 . Alternatively, as shown on FIG. 9, the front side opening  62 D may have a plurality of threaded rods  68  disposed along the perimeter and extending from the front side outer side  60 . 
     As shown in FIGS. 5-7, the second C-shaped body  70  has a generally rectangular back side  72  and third and fourth generally perpendicular extensions  74 ,  76 . The third and fourth perpendicular extensions  74 ,  76  each have an inner side  78  and an outer side  80 . The third and fourth perpendicular extensions  74 ,  76  are also generally rectangular and extend in the same direction, one each, from the longer sides of the generally rectangular back side  72 . The perpendicular extensions  74 ,  76  each include two or more openings  72 . The third and fourth perpendicular extension openings  82  are disposed in pairs, one opening of the pair on each of the third and fourth perpendicular extensions  74 ,  76 . The third and fourth perpendicular extension openings  82  in each pair are generally aligned. The third and fourth perpendicular extension openings  82  are sized to allow a network protector linking bus  5  (described below) to pass therethrough. Preferably, there are three pairs of third and fourth perpendicular extension openings  82 A,  82 B,  82 C,  82 D,  82 E,  82 F. Around the perimeter of the third and fourth perpendicular extension openings  82  are a plurality of fastener openings  64 . The fastener openings  64  may be threaded, have a nut  66  or similar device attached to the inner side  78 . Alternatively, as shown on FIG. 9, the third and fourth perpendicular extension openings  82  may have a plurality of threaded rods  68  disposed along the perimeter and extending from the outer side  80 . The back side  72  may also include a mounting device such as one or more mounting tabs  73 . The mounting tabs extend from the back side  72  and include an opening that allows a fastener to pass therethrough. 
     The front side  52  and the back side  72  have substantially similar dimensions and have a length sufficient to enclose more than one network protector fuse assemblies  1 . Additionally, the first and second perpendicular extensions  54 ,  56  and the third and fourth perpendicular extensions  74 ,  76  each extend from the front side  52  and the back side  72 , respectively, a substantially similar length. As such, the first C-shaped body  50  and the second C-shaped body  70  are structured to fit together in a clam-shell fashion, as shown in FIG.  8 . When the first C-shaped body  50  and the second C-shaped body  70  are fitted together, the distal ends of the first and second perpendicular extensions  54 ,  56  contact, or are immediately adjacent to, the short sides of the back side  72 . Similarly, when the first C-shaped body  50  and the second C-shaped body  70  are fitted together, the distal ends of the third and fourth perpendicular extensions  74 ,  76  contact, or are immediately adjacent to, the long sides of the front side  52 . Therefore, the first C-shaped body  50  and the second C-shaped body  70  may be welded together to form the fuse housing assembly  40 . The welded seam  41  extending along the perimeters of the first C-shaped body  50  and the second C-shaped body  70  is, essentially, watertight. 
     The fuse housing assembly  40  further includes two or more cover plates  42  structured to fit over the front side opening  62 . Thus, when there are three front side openings  62 A,  62 B,  62 C, there are also three cover plates  42 A,  42 B,  42 C. The cover plate  42  includes a seal  43  structured to engage the front side outer side  60 . The cover plate  42  further includes fastener openings  44  that are spaced to align with the front side fastener openings  62  or threaded rods  68 . The cover plates  42  are coupled to the front side  52  by a fastener device  45 , for example a bolt  46  or a nut  47  (FIG.  9 ). 
     As shown in FIGS. 10 and 11, the fuse housing assembly  40  further includes two or more cable coupling assemblies  90 . The cable coupling assemblies  90  include a collar assembly  92 , a cable interface  94 , and a fuse bus  95  (FIG.  11 ). The cable coupling assembly fuse bus  95  has a coupling device, for example, a plurality of rods, structured to cooperate and couple with the bus on the fuse assembly (described below). The collar assembly  92  includes an attachment device, such as, but not limited to, one or more bolts  96  or nuts  98 . The bolts are structured to engage the third and fourth perpendicular extension fastener openings  64  or threaded rods  68 . If the fuse housing assembly  40  is to be attached to the network protector tank, there are cable coupling assemblies  90  located on the side of the fuse housing assembly  40  opposite the network protector tank  12 . If the fuse housing assembly  40  is to be attached to a location other than the tank  12 , e.g. the vault  16  wall, there are cable coupling assemblies  90  located on both the third and fourth perpendicular extensions  74 ,  76 , as shown in FIGS. 12 and 13. 
     As stated above, the fuse housing assembly  40  may be coupled to the tank  12 , as shown in FIG. 1, or spaced from the tank  12 . When the fuse housing assembly  40  is coupled to the tank  12 , the fuse housing assembly  40  is, preferably, welded to the tank at the point where the line or load buses exit the tank  12 . That is, the line or load bus will extend in to the fuse housing assembly  40 . If the fuse housing assembly  40  is not coupled to the tank  12 , the tank  12  includes a cable coupling assembly, similar to those described above, coupled to each line or load bus. 
     Accordingly, as shown in FIGS. 11, and  13 , the fuse housing assembly  40  is structured to enclose two or more network protector fuse assemblies  1 . The network protector fuse assembly includes a body  2  that encloses the functional fuse element (not shown), a first bus  3  and a second bus  4 . The first bus  3  is structured to be coupled to, and in electrical communication with, a network protector linking bus  5 . The linking bus  5  is further coupled to the network protector bus  30 ,  32  by an attachment device, such as a plurality of cooperating rods and openings. The second bus  4  also includes an attachment device and is structured to be coupled to, and in electrical communication with, the collar assembly fuse bus  95 . If the fuse housing assembly  40  is to be attached to a location other than the tank, both the first and second fuse buses  3 ,  4  may be coupled to a collar assembly fuse bus  95  as shown in FIG.  13 . 
     Thus, as shown in FIG. 1, a fuse box  110 , which incorporates the fuse housing assembly  40  and one or more fuse assemblies  1  disposed therein, may be coupled to a tank  12  or mounted at a location other than the tank  12 . To access the fuse box  110 , a user removes the fasteners on the cover plates  42 , and then removes the cover plates  42 . The fuse assembly  1  is then placed in the fuse housing assembly  40  and coupled to the network protector bus  30 ,  32  and the collar assembly fuse bus  95 . After the fuse assembly  1  is installed, the cover plate  12  is reattached. 
     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.