Abstract:
A solid-dielectric switch includes a visible disconnect assembly having an open state and a closed state. A molded housing at least partially encases the visible disconnect assembly. At least a portion of the molded housing forms a molded one-piece wall having an inner surface and an outer surface. An aperture in the molded one-piece wall extends between the inner surface and the outer surface of the wall. A viewing window is disposed in the aperture and molded into the molded wall. The viewing window includes a lens, wherein the viewing window has an outer edge that is embedded within the molded one-piece wall with the outer edge extending into the molded one-piece wall between the inner surface and the outer surface of the molded one-piece wall.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Non-Provisional application Ser. No. 13/476,489, filed May 21, 2012 and U.S. Provisional Application No. 61/633,429, filed Feb. 9, 2012, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Integral visible disconnects in oil-based and gas-based switches provide an operator with visual verification of an open circuit. However, the size of these switches is often constrained based on the cost and supply of the oil or gas. Furthermore, the gasses and oils used in these types of switches are often flammable, which creates safety concerns. In addition, the gasses and oils used in the switches have an environmental impact that must be considered when determining whether it is cost-effective and environmentally safe to place a switch in a particular location, such as underground. 
       SUMMARY 
       [0003]    Solid-dielectric switches solve many of the concerns described above relating to oil-based and gas-based switches, and can be safely placed in underground environments. To provide a visible disconnect, existing solid-dielectric switches rely on external devices (e.g., load break elbows). However, safety practices of utilities often require extensive use of personal protective equipment to operate external devices in confined spaces, and some utilities disallow the practice altogether for safety concerns. Therefore, solid-dielectric switches are typically not as regularly used as oil-based or gas-based switches because such switches do not provide an integral visible disconnect. 
         [0004]    Accordingly, embodiments of the present invention provide an integral visible disconnect as part of a solid-dielectric switch. The integral disconnect eliminates the need for dangerous external devices, such as load break elbows, to provide a visible disconnect of the distribution circuit. Therefore, one embodiment of the invention provides a solid-dielectric switch including a visible disconnect assembly having an open state and a closed state, a molded housing at least partially encasing the visible disconnect assembly, and a viewing window molded into the molded housing, wherein the visible disconnect is visible through the viewing window. 
         [0005]    Another embodiment of the invention provides a method of molding a housing for a solid-dielectric switch. The method includes providing a mold including an external shell and an internal mandrel, the external shell defining external dimensions of a housing of the switch and the internal mandrel defining internal dimensions of the housing. The method also includes providing a viewing window, sealing the viewing window between the external shell and the inner mandrel, and filling the mold with epoxy to mold the lens into the housing. 
         [0006]    In another embodiment, a solid-dielectric switch includes a visible disconnect assembly having an open state and a closed state. A molded housing at least partially encases the visible disconnect assembly. At least a portion of the molded housing forms a molded one-piece wall having an inner surface and an outer surface. An aperture in the molded one-piece wall extends between the inner surface and the outer surface of the wall. A viewing window is disposed in the aperture and molded into the molded wall. The viewing window includes a lens, wherein the viewing window has an outer edge that is embedded within the molded one-piece wall with the outer edge extending into the molded one-piece wall between the inner surface and the outer surface of the molded one-piece wall. 
         [0007]    In another embodiment, a housing for a solid-dielectric switch with a visible disconnect assembly has an open state and a closed state. The housing includes a molded one-piece wall having an inner surface and an outer surface. An aperture in the molded one-piece wall extends between the inner surface and the outer surface of the wall. A viewing window disposed in the aperture includes a lens. The viewing window has an outer edge that is embedded in the molded one-piece wall with the outer edge extending into the molded one-piece wall between the inner surface and the outer surface of the wall. 
         [0008]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a cross-sectional view of a solid-dielectric switch including a visible disconnect assembly and a load-breaking device, with the load-breaking device and the visible disconnect assembly in a closed state. 
           [0010]      FIG. 2  is a cross-sectional view of the solid-dielectric switch of  FIG. 1 , with the load-breaking device in an open state and the visible disconnect assembly in a closed state. 
           [0011]      FIG. 3  is a cross-sectional view of the solid-dielectric switch of  FIG. 1 , with the load-breaking device and the visible disconnect assembly in an open state. 
           [0012]      FIG. 4  is a flow chart illustrating a method of molding a housing of the switch of  FIG. 1 . 
           [0013]      FIGS. 5A-5E ,  6 A- 6 D,  7 ,  8 , and  9  are views of the switch of  FIG. 1  during the molding process of  FIG. 4 . 
           [0014]      FIGS. 5F-5H  illustrate the viewing window of the switch of  FIG. 1 . 
           [0015]      FIG. 10  is a perspective view of the switch of  FIG. 1 , with the visible disconnect assembly in a closed state as viewed through the viewing window. 
           [0016]      FIG. 11  is a perspective view of the switch of  FIG. 1 , with the visible disconnect assembly in an open state as viewed through the viewing window. 
           [0017]      FIG. 12  are front views of the switch of  FIG. 1 , with the visible disconnect assembly in an open state and a closed state as viewed through the viewing window. 
           [0018]      FIG. 13  is a side view of the switch of  FIG. 1 . 
           [0019]      FIG. 14  is a perspective view of the switch of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0021]      FIG. 1  illustrates a solid-dielectric switch  10 . The switch  10  includes one or more internal components, such as a load breaking device  12  (e.g., a vacuum interrupter) and an integral visible disconnect assembly  14 . The switch  10  also includes a molded housing  16  and a generally transparent or translucent viewing window  18  molded into the housing  16 . The housing  16  at least partially encases the internal components of the switch  10  (e.g., the vacuum interrupter  12  and the visible disconnect assembly  14 ). The housing  16  is molded using a rigid material, such as an epoxy. The vacuum interrupter  12  includes two contacts  19   a  and  19   b . When the contacts  19   a  and  19   b  are connected (see  FIG. 1 ), the vacuum interrupter  12  is in a closed state and the circuit is closed. When the contacts  19   a  and  19   b  are not connected (see  FIGS. 2 and 3 ), the vacuum interrupter  12  is in an open state and the circuit is open. The state of the vacuum interrupter  12  can be changed using a drive mechanism  20  (e.g., an actuator). The drive mechanism  20  can be operated manually or in an automated fashion. 
         [0022]    The visible disconnect assembly  14  is connected in series with the vacuum interrupter  12 . The visible disconnect assembly  14  illustrated in  FIG. 1  includes a knife blade assembly that includes a blade  21  and a lever  22 . The lever  22  can be operated manually or in an automated fashion to move the blade  21  between a closed state (see  FIG. 1 ) and an open state (see  FIG. 3 ). For example, in some embodiments, the lever  22  pivots the blade  21  on a pin  23  or other pivoting mechanism between the two states. In the closed state, the blade  21  physically and electrically connects the vacuum interrupter  12  with a source conductor  24 . In the open state, the blade  21  physically and electrically disconnects the vacuum interrupter  12  from the source conductor  24 . Therefore, the physical position of the blade  21  can be used to visually inspect whether the vacuum interrupter  12  is physically and, consequently, electrically connected to the source conductor  24 . Therefore, the physical position of the blade  21  provides visual verification to an operator regarding whether current is flowing through the switch  10 . 
         [0023]    In some embodiments, external operating handles (not shown) on the switch  10  allow an operator or an automated controller to operate the drive mechanism  20  and the lever  22 . To prevent unsafe arcing, an interlock (not shown) between the drive mechanism  20  and the lever  22  allows the visible disconnect to be opened or closed only if the vacuum interrupter  12  is in the open state. For example, the external operating handles associated with the drive mechanism  20  and the lever  22  can be arranged such that the lever  22  can only be operated using the external operating handle (e.g., rotated) when the vacuum interrupter  12  is in the open state. 
         [0024]    Therefore, before the visible disconnect assembly  14  can be opened, the vacuum interrupter  12  is opened using the drive mechanism  20  (see  FIG. 2 ). After the vacuum interrupter  12  has been opened, the circuit defined by the switch has been interrupted and the state of the visible disconnect assembly  14  can be safely changed. In particular, with the vacuum interrupter  12  open, the visible disconnect assembly  14  can be opened, as shown in  FIG. 3 , and the open state of the visible disconnect assembly  14  is observable through the viewing window  18 . 
         [0025]    As noted above, although visible disconnect assemblies and associated viewing windows have been used in gas and oil based switches, solid-dielectric switches have historically not included visible disconnect assemblies as it was unknown how to successfully mold a viewing window into the epoxy housing of a solid-dielectric switch. One difficulty with such molding is that the material of the viewing window must be able to withstand the molding temperatures encountered in epoxy molding. These temperatures can approach approximately 170° Celsius, which is well above the melting point of plastics that are optically clear. Also, the material of the viewing window  18  must also be able to withstand compressions and contractions occurring during the molding process. In addition, the epoxy must be kept off of viewing surfaces of the window, which complicates the molding process. Furthermore, the edge of the viewing window must form a hermetic seal with the epoxy that is also flexible enough to withstand thermal expansions and contractions caused by environmental temperature swings experienced by the switch  10  during use. 
         [0026]    In addition, although clear epoxies exist that could be used to form transparent housings, these materials contain pure resin or hardeners and do not contain any filler. The fillers (e.g., silica or alumina), however, are what gives epoxies its strength (e.g., fillers are typically make up approximately 65% to approximately 85% of the material content of an epoxy). Without the fillers, a transparent epoxy lacks the strength necessary for molding a housing of a solid dielectric switch. Similarly, rigid materials, such as an epoxy, do not accommodate the insertion of components into the material after the materials have cured. Therefore, unlike flexible materials (e.g., ethylene propylene diene monomer rubber), a viewing window cannot be inserted into a molded housing constructed from a rigid epoxy after the housing has been formed. 
         [0027]      FIG. 4  is a flow chart illustrating a method  40  of molding the housing  16  of the switch  10  to account for the above problems associated with molding the viewing window  18  into the housing  16 . Accordingly, as shown in  FIG. 4 , the method  40  includes providing a generally transparent or translucent viewing window  18  that can withstand high molding temperatures (at  41 ). In some embodiments, a glass is used as the viewing window  18  because glass can withstand high molding temperature. However, other generally transparent materials that can withstand the molding temperatures (e.g., approximately 170° Celsius or greater) can be used as the viewing window  18 . 
         [0028]    A mold is also provided that includes an external shell  52  and an internal mandrel  50  (see  FIGS. 5A-5E ) (at  43 ). The external shell  52  defines the outside dimensions of the housing  16 , and the internal mandrel  50  defines the inner surface of the housing  16 . Typically, the external shell  52  and a complementary shell (e.g. a mirror image of the shell  52 ) are brought together to form the mold with the mandrel  50  and other components inside. To prevent epoxy from covering the viewing surfaces of the viewing window  18 , the viewing window  18  is held and sealed between the external shell  52  and the mandrel  50  (at  44 ). To seal the window  18  against these components, a flexible seal can be provided on the mandrel and on the external shell using an elastomer that can withstand the molding temperatures, such as silicone. The seal can include a band  56  that has a circular cross-section like an o-ring and is held in a mating groove in the mandrel  50  and in the external shell  52  (see  FIGS. 5A-5E ). When the mandrel  50  is placed inside the external shell  52 , the viewing window  18  is positioned between the elastomeric bands  56  in the mandrel  50  and the external shell  52 , and the bands  56  are compressed and seal against the inner and outer surface of the window  18 . Therefore, the bands  56  form a flexible “shutoff” between the mold and the viewing window  18 , which prevents epoxy from covering the viewing surfaces of the window  18 . The compressible nature of the bands  56  also accommodates the manufacturing tolerances of the window  18  during the molding process. 
         [0029]    Also, to ensure a strong yet flexible hermetic seal between the viewing window  18  and the epoxy, the non-viewing surfaces of the window  18  can optionally be coated with an elastomeric material (at  42 ), such as neoprene or ethylene propylene diene monomer (“EPDM”). The coating of elastomeric material  80  (illustrated in  FIG. 5C , for example) bonds to the epoxy and forms a cushion that accommodates the difference in thermal expansions and contractions between the cured epoxy and the viewing window  18 . 
         [0030]    In some embodiments, the window  18  includes a protrusion  82  near one or both edges (see  FIG. 5C-5E ). The protrusion  82  mates with a recess  84  in the external shell  52  (see  FIG. 5B ). The protrusion  82  can be formed as part of the coating  80  or can be formed as a separate component (e.g., formed from an elastomeric material or other material capable of withstanding the molding process) and coupled to the window  18  before or after the coating  80  is applied. 
         [0031]    In some embodiments, a ridge  90  is formed along the inside and outside perimeter of the viewing surfaces of the glass lens forming the window  18  (see  FIGS. 5F-5H ). The ridge  90  can be formed in the glass lens, and the ridge  90  increases the length of the bond line between the viewing window  18  and the epoxy forming the housing  16 . Therefore, the ridge  90  provides a greater sealing distance and greater dielectric distance and also helps lock the window  18  in place within the epoxy molding. It should be understood, however, that the ridge  90  is optional and, in some embodiments, the window  18  can include a straight line bond with the epoxy. 
         [0032]    Another method of holding the viewing window  18  between the mandrel  50  and the external shell  52  (at  44 ) includes using an inflatable elastomeric bladder  60  on the mandrel  50  and using an elastomeric band  56  on the shell  52  (see  FIGS. 6A-6D ). After the mandrel  50  is inserted into the outer shell  52 , the bladder  60  is inflated (e.g., with water, air, or fluid pressure), which presses the viewing window  18  against the band  56  on the shell  52 . In some embodiments, the bladder  60  is filled with a liquid, such as polyethylene glycol, that can inflate the bladder  60  and does not harm the epoxy if the liquid leaks from the bladder  60  during the molding process. The band  56  forms a seal between the outer surface of the window  18  and the external shell  52 , and the bladder  60  forms a seal between the inner surface of the window  18  and the mandrel  50  to help keep epoxy from covering the viewing surface of the window  18 . Once the epoxy has cured in the mold, the pressure in the bladder  60  can be released (i.e., the bladder  60  can be deflated), which allows the mandrel  50  to be removed. Use of the bladder  60  helps to control the amount of pressure on the viewing window  18 , otherwise the pressure may cause the window  18  to break or become dislodged. 
         [0033]    After the window  18  is sealed in place between the external shell  52  and the mandrel  50  (at  44 ), the internal components of the switch  10  (e.g., the vacuum interrupter  12  and the visible disconnect assembly  14 ) are placed in the mold (see  FIGS. 7-9 ) (at  45 ). The mold can then be filled with epoxy (i.e., the area between the external shell  52  and the mandrel  50  is filled with epoxy) (at  46 ), and the epoxy is allowed to cure (at  47 ). After the epoxy has cured, the switch  10  can be removed from the mold (at  48 ), and the switch  10  can be assembled with other components (e.g., external operating handles for operating the drive mechanism  20  and the lever  22 , interlocks for the operating handles, etc.). 
         [0034]    As shown in  FIGS. 10-14 , the visible disconnect assembly  14  is viewable through the viewing window  18 . In particular,  FIG. 10  illustrates the visible disconnect assembly  14  as viewed through the viewing window  18  when the assembly  14  is in an open state. In contrast,  FIG. 11  illustrates the visible disconnect assembly  14  as viewed through the viewing window  18  when the assembly  14  is in a closed state. Therefore, as illustrated in  FIG. 12 , an operator can view the visible disconnect assembly  14  through the viewing window  18  to visually determine whether the assembly  14  is in an open state (i.e., the switch on the left in  FIG. 12 ) or a closed state (i.e., the switch on the right in  FIG. 12 ). 
         [0035]    In some embodiments, as illustrated in  FIGS. 10-14 , the viewing window  18  at least partially covers a front side of the switch  10  and one or more sides of the switch  10 . Thus, the viewing window  18  can provide a wide angle for viewing the visible disconnect assembly  14  inside the housing  16 . The viewing window  18  can also be curved, as illustrated in  FIGS. 10-14 , which prevents distortions that may be caused by straight edges in the window  18 . Also, it should be understood that although only a single viewing window  18  is illustrated in  FIGS. 10-14  for each switch  10 , the switch  10  can include multiple viewing windows  18 , which allow multiple vantage points for viewing the visible disconnect assembly  14  or other components contained in the switch  10 . For example, in some embodiments, regardless of whether the switch  10  includes an integral visible disconnect assembly  14 , the solid-dielectric switch  10  can include a viewing window  18  as described above to allow an operator to view any internal area or component of the switch  10 . Furthermore, it should be understood that the viewing window  18  and the method of molding the same can be used with any solid-dielectric switch that includes more, fewer, or different internal components than those illustrated in  FIGS. 1-3 . For example, the viewing window  18  can be used with other types of visible disconnect assemblies than just the knife blade assembly illustrated in  FIGS. 1-3 . 
         [0036]    In some embodiments, the housing  16  also defines one or more connectors for connecting cables to the switch  16 . For example, as illustrated in  FIG. 13 , in some embodiments, the housing  16  defines a first connector  70   a  and a second connector  70   b . The first connector  70   a  can be positioned in a first plane P 1  and the second connector  70   b  can be positioned in a second plane P 2 . The first plane P 1  and the second plane P 2  are different planes and are separated by an offset distance D. For example, in some embodiments, the offset distance D is approximately 5.0 inches. However, it should be understood that the offset distance D can vary depending on the configuration of the switch, the connectors, cables connected to the connectors, and the environment where the switch is located. Offsetting the connectors  70   a  and  70   b  allows for easier connection of cables to the connectors  70   a  and  70   b . In particular, depending on the size of the cables and the size of the connectors  70   a  and  70   b , the cables, when connected, may form a tight configuration that makes it difficult to access and remove a single cable. Therefore, offsetting the connectors  70   a  and  70   b  makes it easier to manage the cables connected to the connectors  70   a  and  70   b.    
         [0037]    While the invention is described in terms of several preferred embodiments of circuit or fault interrupting devices, it will be appreciated that the invention is not limited to circuit interrupting and disconnect devices. The inventive concepts may be employed in connection with any number of devices including circuit breakers, reclosers, and the like. Also, it should be understood that the switch  10  can include a single-phase interrupting device or a multi-phase (e.g., a three phase) interrupting device, as illustrated in  FIGS. 13 and 14 . When a multi-phase interrupting device is used, each vacuum interrupter  12  can be associated with a separate visible disconnect assembly  14  and a separate viewing window  18 . In other embodiments, the multiple vacuum interrupters  12  in a multi-phase interrupting device can be associated with one or more shared visible disconnect assemblies  14  and one or more shared viewing windows  18 . 
         [0038]    Various features and advantages of the invention are set forth in the following claims.