Patent Publication Number: US-8124872-B2

Title: Elastomeric portable electrical outlet box

Description:
FIELD OF THE INVENTION 
     The present invention is directed to an impact resistant electrical outlet box or electrical junction box. The invention is further directed to an electrical box having an elastomeric outer layer surrounding a rigid box to provide impact resistance during use. 
     BACKGROUND OF THE INVENTION 
     Electrical boxes are commonly mounted to a stud or other support structure for supporting an electrical device and enclosing electrical wiring. The electrical boxes are often mounted in a variety of positions and locations in the wall or ceiling. 
     Portable electrical junction boxes typically are attached to an electrical cable or cord such that the boxes can be moved to a suitable location during use. The portable electrical boxes are particularly suitable for construction sites where electrical power is needed in different locations and can be moved to different locations as needed during work. The portable electrical junction box generally provides an electrical receptacle to provide electrical power to tools, lights and the like. During use, particularly on construction sites, the portable electrical junction boxes are subjected to physical abuse which can result in damage to the box. 
     Various electrical boxes have been developed for numerous purposes. One example is disclosed in U.S. Pat. No. 3,724,706 to Slocum which discloses an explosion proof junction box having a cap and a body portion. The body portion forms the junction box as a one piece molded structure. The body portion and cap are provided with an outer layer formed from a polymeric material such as polyvinyl chloride. The outer layer is formed with flexible flanges for forming a seal between the cap and the body portion. 
     Another example is disclosed in U.S. Pat. No. 5,621,189 to Dodds which discloses a conduit and a cover. The outer surfaces of the cover and the body are coated with a corrosion resistant polymeric material. The coating is disclosed as being a flexible, durable impact resistant polymer such as polyvinyl chloride. 
     U.S. Pat. No. 4,134,636 to Kleinatland et al. discloses an electrical outlet box with recesses on the outer surface and opening in a flange for receiving screws. The box includes an interior sleeve for telescopic engagement with the box. 
     U.S. Pat. No. 6,820,760 to Wegner et al. discloses an electrical outlet box extension having an interior sleeve with a plurality of ribs along its exterior surface. The interior sleeve also includes a plurality of fastening brackets for fixedly attaching the interior sleeve to an exterior ring. The exterior ring is attached to an electrical box. 
     U.S. Pat. No. 2,373,861 to Brown discloses an electrical box extension that slides within the opening of the electrical box. The upper surface of the box includes inwardly extending flanges with an opening for receiving screws to adjust the position of the sleeve. 
     Other electrical boxes are also disclosed in U.S. Pat. Nos. 2,378,861 to Peevey, U.S. Pat. No. 2,867,349 to Parker Jr., U.S. Pat. No. 3,684,819 to Wilson, U.S. Pat. No. 4,408,695 to Balkwill et al., U.S. Pat. No. 4,884,715 to Pohlmann, U.S. Pat. No. 7,038,129 to Fox and U.S. Pat. No. 6,974,295 to Anderson. 
     While each of the prior devices has been generally suitable for the intended purpose, there is a continuing need in the industry for an improved portable electrical box. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a portable electrical box for coupling directly to an electrical source and for supplying electricity to an electrical device. The invention is particularly directed to an impact resistant electrical junction box having an impact resistant outer layer and a rigid inner structure. 
     Accordingly, one aspect of the invention is to provide an impact resistant electrical junction box formed from a rigid material having an outer portion formed from an impact resistant plastic material. The outer impact resistant portion in one embodiment is made from an elastomeric material that is sufficiently flexible to protect the electrical box from damage under normal working conditions. The outer impact resistant portion is preferably a continuous outer layer formed from the elastomeric material. The outer impact resistant portion can have a non-uniform or variable thickness with the thicker portions in areas that are prone to continuous abrasion and impact. In one embodiment, the corners of the outer impact resistant portion are thicker than the middle portions. 
     Another aspect of the invention is to provide a portable electrical box that can be connected to an electrical power cord or cable to be movable to different locations as needed. In one embodiment, the portable electrical junction box is provided with a mounting structure for mounting an electrical device in the electrical box and for mounting a face plate on or over the electrical device to close an open end of the electrical box. In one embodiment, the electrical device is a duplex receptacle that can be connected to a plug of an electrical tool or light. 
     Another aspect of the invention is to provide a method of forming an electrical junction box having an impact resistant outer portion. The outer portion of the electrical junction box is made from a resilient polymeric material having sufficient flexibility to inhibit damage to the portable electrical box. The impact resistant outer portion of the electrical junction box is typically an outer layer that is molded over the electrical box in a permanent manner to prevent separation of the outer layer from the electrical box. 
     The outer layer of the electrical junction box is formed with the impact resistant outer layer molded directly on or over the outer surface of the inner electrical box. In one embodiment of the invention, the outer surface of the electrical box includes outwardly projecting members that are able to interlock with the outer layer as it is formed on the surface of the electrical box. The outer layer can be molded directly onto the outer surface of the box so that the projecting members interlock with the molded outer layer to prevent separation of the outer layer and the inner electrical box. 
     Another aspect of the invention is to provide an electrical box with an outer layer of an impact resistant polymer where the outer layer forms a skirt extending axially from the open end of the box. The skirt forms a recess for receiving a face plate to close the open end. 
     These and other aspects of the invention are basically attained by providing an electrical junction box comprising a box formed from a rigid material and having first and second side wall and end walls extending between the first and second side walls. The open front end is constructed to receive an electrical device. An outer layer made from an elastomeric polymer is adhered to the outer surface of the box. In one embodiment, a rear wall is connected to the side and end walls to form a closed bottom and an open front end. 
     The various aspects of the invention are also attained by providing an electrical junction box having an inner wall made from a rigid material and having an open end adapted for receiving an electrical device. An outer wall encloses the outer wall and is adhered to the outer surface of the inner wall. The outer wall is made from an elastomeric polymeric material. 
     The aspects of the invention are yet further attained by providing a method of producing an electrical junction box comprising the steps of positioning a rigid electrical box in a mold to define a mold cavity between an inner surface of the mold and an outer surface of the electrical box. The electrical box has first and second side wall, first and second end walls extending between the side walls, and an open front side. An elastomeric polymer is introduced into the mold cavity to mold an outer wall from the elastomeric material on the outer surface of the electrical box. The outer wall has a thickness to provide impact resistance to the electrical junction box. 
     These and other aspects and salient features of the invention will become apparent from the following detailed description of the invention, which taken in conjunction with the annexed drawings, disclose various embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following is a brief description of the drawings, in which: 
         FIG. 1  is a perspective exploded view of the electrical junction box in a first embodiment of the invention showing the electrical box and outer impact resistant layer; 
         FIG. 2  is a perspective view of the portable electrical box of the embodiment of  FIG. 1  showing the impact resistant outer layer molded onto the electrical box and the electrical cord coupled to the electrical box; 
         FIG. 3  is a perspective view of the electrical box of the embodiment of  FIG. 1  showing the inner box and the outer layer; 
         FIG. 4  is a front view of the electrical junction box of  FIG. 1 ; 
         FIG. 5  is an end view in cross-section of the electrical junction box taken along line  5 - 5  of  FIG. 1  showing the inner box and the outer layer; 
         FIG. 6  is a side view in cross-section of the electrical junction box taken along line  6 - 6  of  FIG. 1  showing the inner box, outer layer and the mounting tab for coupling with an electrical device; 
         FIG. 7  is an enlarged side view in cross-section of the mounting tab coupled to the end wall of the electrical box; 
         FIG. 8  is a perspective view of the inner electrical box showing the ribs for interlocking with the outer layer; 
         FIG. 9  is a side view of the inner electrical box of  FIG. 8 ; 
         FIG. 10  is an end view of the inner electrical box of  FIG. 8 ; 
         FIG. 11  is an end view in cross-section of the inner electrical box taken along line  11 - 11  of  FIG. 9 ; 
         FIG. 12  is a cross-sectional end view of the mold for forming the outer layer on the inner electrical box and showing the electrical box positioned in the mold cavity; 
         FIG. 13  is a cross-sectional end view of the mold showing the elastomeric polymer being injected into the mold cavity and forming the outer impact resistant layer; and 
         FIG. 14  is a perspective view showing another embodiment of the electrical junction box. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to an electrical outlet box or junction box. In particular, the invention is directed to a portable electrical outlet box having an impact resistant outer portion. The outer portion is typically in the form of an outer layer enclosing the electrical box. 
     Referring to the drawings, the portable electrical outlet box  10  of the invention includes an electrical box  12  and a molded outer portion shown as outer layer  14 .  FIG. 1  is an exploded view of the electrical outlet box  10  to illustrate the box  12  and outer layer  14 . In use, the outer layer  14  is formed on the outlet box  10  as a one piece unit. Electrical outlet box  10  which can function as an electrical junction box is designed to be portable and can be connected to an electrical cable or conduit  16  as shown in  FIG. 2 . The electrical box  12  defines an inner wall and the outer layer  14  defines an impact resistant outer wall of the electrical outlet box  10 . 
     Electrical outlet box  10  as shown in  FIG. 1  has a shape and dimension similar to a conventional electrical box for receiving an electrical device such as a duplex electrical receptacle  18 . In the embodiment illustrated, electrical box  12  is a single gang box having a substantially rectangular configuration with opposite side walls  20  and end walls  22 . In other embodiments, electrical box  12  can be a multiple gang box to support multiple electrical devices such as electrical receptacles, switches, and the like. A bottom wall  24  closes the bottom end of electrical box  12 . In one embodiment of the invention, side walls  20  and end walls  22  have a substantially uniform thickness. The walls have a thickness sufficient to provide the desired strength and structural integrity. Electrical box  12  has an open front end  26  formed by a front edge  28 . Front edge  28  is provided with a slot  30  formed in each of the end walls  22  that extend in the plane of end walls  22 . Alternatively, electrical box  12  can have mounting holes for receiving a mounting screw or other fastener member to attach an electrical device to the box. The screw holes can be provided in the front edge. 
     Electrical box  12  can be molded as a one piece member made of a rigid plastic. Typically, side walls  20  and end walls  22  have a substantially uniform thickness. 
     A mounting tab  32  is received in the respective slot  30  for supporting and mounting electrical device  18 . As shown in  FIG. 1 , mounting tabs  32  have a substantially L-shape with a first leg  34  and a second leg  36  extending substantially perpendicular to each other. First leg  34  has side edges with serrated teeth  38  for gripping the inner surface of slot  30  and permanently coupling mounting tab  32  to electrical box  12 . Second leg  36  has a threaded hole  40  for receiving mounting screws  42  for mounting electrical device  18  to mounting tabs  32 . Mounting tab  32  is preferably made of metal for grounding the electrical device and for mounting the electrical device in a secure manner. 
     Electrical box  12  has an outer surface with a plurality of interlocking members  43  extending outwardly from electrical box  12 . In the embodiment illustrated, interlocking members  43  are in the form of substantially parallel ribs  44 . The interlocking members as shown in  FIG. 1  are formed on side walls  20  and extend outwardly a distance to engage and interlock with outer layer  14 . In the embodiment illustrated, the ribs  44  have a longitudinal dimension extending from the front edge  28  to a back edge  46  of the electrical box along side walls  20 . Ribs  44  are spaced a slight distance from front edge  20  and back edge  46  as shown in  FIGS. 8 and 9 . A brace portion  48  extends perpendicular to ribs  44  to integrally connect the ribs together. As shown in  FIG. 9 , brace  48  extends substantially perpendicular to the longitudinal dimension of ribs  44  and is positioned in the center of side walls  20  of electrical box  12 . 
     In the embodiment shown, the interlocking members are in the form of parallel ribs. In other embodiments, the interlocking members can have other shapes that project outwardly from the surface of the electrical box. Alternatively, the interlocking members can be recesses. The projections and recesses can have various shapes and dimensions so long as they are able to interlock with the outer layer to resist separation. 
     Electrical outlet box  10  is formed with outer layer  14  molded directly onto and over electrical box  12  to form a one piece article. Outer layer  14  is attached to electrical box  12  to prevent separation of outer layer  14  from electrical box  12 . In one embodiment of the invention, outer layer  14  is molded directly onto the outer surfaces of electrical box  12  so that the outer layer bonds and/or adheres to the surface of the electrical box. Outer layer  14  can form an outer wall of electrical box  12 . 
     Outer layer  14  surrounds electrical box  12  to form a protective impact resistant layer to prevent damage to electrical box  12 . In a preferred embodiment, outer layer  14  is formed from an elastomeric polymer material that is sufficiently resilient and flexible to provide impact resistance to outlet box  10 . Preferably, outer layer  14  is formed from an elastomeric polymer having a hardness less than the hardness of electrical box  12  to provide impact and abrasion resistance. One example of a suitable material for forming the outer layer is a polybutylene rubber. Electrical box  12  is typically formed of a molded rigid plastic material and is formed as a one piece unit. One example of a rigid plastic material suitable for forming the electrical box is polyvinyl chloride. 
     Referring to  FIGS. 3 and 4 , outer layer  14  is formed on electrical box  12  to envelope the outer surfaces of electrical box  12 . Outer layer  14  has side portions  50  overlying side walls  20  and end portions  52  overlying end walls  22 . Side portions  50  have a middle portion  54  between the ends  56 . The middle portions  54  have a substantially uniform thickness while the side portion as a whole has a non-uniform thickness. As shown in  FIG. 4 , middle portion  54  has a thickness slightly less than the thickness of the ends  56  to define a substantially concave profile as shown in  FIG. 4 . End portions  52  have a thickness greater than middle portion  54  and substantially equal to the ends  56  of side portions  50 . 
     Side portions  50  and end portions  52  converge to define corners  58  having a rounded profile. The corners  58  have a thickness greater than a thickness of the middle portions  54  to provide a level of impact resistance greater than the side portions. Outer layer  14  includes a back portion  60  overlying bottom wall  24  of electrical box  12 . In one embodiment, outer layer  14  has a thickness greater than the thickness of the walls of electrical box  12 . As shown in  FIG. 4 , corners  58  and end portions  52  have a thickness greater than a thickness of the walls of electrical box  12 . 
     In one embodiment, end portions  52  and corners  58  have a thickness greater than a thickness of the wall of box  12  and have a thickness to provide impact resistance and to protect box  12  from damage. In the embodiment shown, middle portions  54  have a thickness substantially equal to the side wall of box  12  and end portions  52  and corners  58  have a thickness twice the thickness of the walls of box  12 . 
     Referring to  FIGS. 5 and 6 , outer layer  14  has a width greater than the width of side walls  20  and end walls  22  of electrical box  12  to define a flange shown as a skirt  62  extending from open end  26  of electrical box  12 . Skirt  62  has a length to define a recess  64  between an outer face  66  of outer layer  14  and front edge  28  of electrical box  12 . The recess  64  forms a stepped lip portion with a dimension to receive a cover face plate. Preferably, lip  64  has a depth at least equal to a thickness of the cover face plate. As shown in  FIG. 15 , side portions  50  of outer layer  14  have an inner edge  68  aligned with the outer face of side walls  20 . Ribs  44  which form the interlocking members are embedded in the side portions  50  of outer layer  14  as shown in  FIG. 5 . 
     Referring to  FIGS. 6 and 7 , skirt  62  of outer layer  14  has an inwardly extending lip  70  that extends inwardly with respect to the opening of electrical box  12  to overlie a portion of front edge  28  of side walls  22 . As shown in  FIG. 7 , lip  70  overlies a portion of mounting tab  32 . 
     In use, electrical device  18  is positioned in electrical outlet box  10  on mounting tabs  32 . A gasket member  72  having an aperture  74  is positioned over electrical device  18 . A cover plate  76  having openings  78  for receiving electrical device  18  is positioned over gasket  72 . Screws  42  are inserted through screw holes  82  in cover plate  76 , and screw holes  84  in gasket  72  and screw holes  86  in electrical device  18  are threaded into the threaded hole  40  of the respective mounting tabs  32 . As shown in  FIG. 2 , recess  64  has a depth substantially equal to the thickness of cover plate  76  so that the outer surface of cover plate  76  is substantially aligned with the outer face  66  of outer layer  14 . Electrical outlet box  10  is provided with one or more openings  88  shown in  FIG. 3 . The openings can be formed by knockouts which can be removed for receiving electrical cable  16  and a grommet  90  and cable connector as shown in  FIG. 2 . In the illustrated embodiment of the invention, the hole  88  formed by removing the knockout is formed in end wall  22  of electrical box and in end portion  52  of outer layer  14 . In alternative embodiments, a hole can be provided in other locations of the side wall or bottom wall of the electrical outlet box as desired. 
     As shown in  FIGS. 3 and 4 , outer layer  14  has thickened portions relative to the middle portion of side portion  50  of outer layer  14  to provide impact resistance to outlet box  10 . Outer layer  14  overlies the outer surfaces of electrical box  12 , thereby forming a protective outer layer to prevent damage to electrical box  12 . 
     In one embodiment of the invention, outer layer  14  of electrical outlet box  10  is formed by molding outer layer  14  directly on the outer surfaces of electrical box  12 . Referring to  FIGS. 12  and  13 , outer layer  14  is formed by positioning electrical box  12  in a mold cavity  92  of a mold  94 . Mold cavity  92  preferably has a dimension corresponding to the outer dimension of the finished outer layer  14  shown in  FIG. 1  and to define a gap  96  between the outer surface of electrical box  12  and the inner surface  98  of mold  94 . A cover  100  is placed on mold  94  to enclose the mold cavity. A polymerizable material is injected through a port  102  in mold  94  to fill the mold cavity and form outer layer  14 . After the polymerizable material is cured, outlet box  10  is removed from mold  94 . 
     Outer layer  14  is preferably formed from an elastomeric polymer that is capable of providing impact resistance to outlet box  10 . For example, outer layer  14  can be formed from a flexible polyvinyl chloride containing suitable plasticizers, a polybutylene rubber or other elastomeric polymer. 
     In the embodiment of  FIGS. 1-11 , the electrical junction box has a bottom wall with an open top end to receive one or more electrical devices. In the embodiment of  FIG. 14 , electrical junction box  110  is formed with an open front side  112  and an open rear side  114 . In the embodiment illustrated, open front side  112  and open rear side  114  are substantially the same and can support an electrical device on each side. Electrical junction box  110  is formed by an inner rigid electrical box  116  having opposite side walls  118  and opposite end walls  120  extending between open sides  112  and  114 . The outer faces  122  of end walls  120  have a slot  124  to receive a mounting tab  126  for mounting the electrical box as in the previous embodiment. 
     The electrical junction box  110  includes an impact resistant outer layer  128  that is secured to the outer surface of electrical box  116  by interlocking ribs on the outer surface of box  116 . As shown in  FIG. 14 , the outer layer  128  forms a skirt  130  around each open end of box  116  to form a lip  132 . The lip  132  receives a faceplate (not shown) to cover the electrical device in a manner substantially similar to the embodiment of  FIGS. 1-11 . The outer layer  128  preferably is formed by directly molding the resilient, impact resistant plastic material on the outer surface of box  116  so that the outer layer is bonded and adhered to the rigid electrical box  116 . The outer layer  128  is formed in a similar manner as the previous embodiment with corners  134  and end portions  136  that are thicker than middle portions  138  of side portions  140 . The thickened corners provide impact resistance to the rigid electrical box  116 . 
     While various aspects of the invention have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as defined in the appended claims.