Abstract:
An electrical outlet box extension comprising a perimetrical side wall with an inner surface and an outer surface having an open front face and an open rear face and defining an interior space, and having at least one outwardly protruding resilient tab located on the side wall outer surface. The box extension is designed for adjustable insertable receipt within an electrical outlet box for increasing the depth of the box.

Description:
CROSS-REFERENCE TO RELATED APPLICATION:  
       [0001]     This application claims priority to U.S. Provisional Patent Application No. 60/713,121, filed on Aug. 31, 2005, which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to a pull out extension contained in an electrical outlet box for housing electrical fixtures such as a switch or a receptacle. More particularly, the present invention relates to an extension for increasing the depth of an electrical box in certain applications such as for use on a concrete wall.  
       BACKGROUND OF THE INVENTION  
       [0003]     It has long been known to house electrical fixtures such as switches and receptacles in an electrical outlet box. The outlet box permits the insertion of electrical wires into the box which are terminated to electrical fixtures. The fixtures then may be mounted to the box which provides protection to the fixtures as well as the wires terminated therein. The outlet box is then mounted to a wall at a convenient location to provide access. Most outlet boxes accommodate one or more electrical fixtures, which terminate standard 110 volt electrical wires.  
         [0004]     Outlet boxes are available in a variety of configurations and sizes. The selection of which type of box to use is dependant upon the specifics of the application. The most commonly employed box is a single-gang outlet box, also referred to as a standard outlet box. The single-gang box is ideal for applications in which only one receptacle is required for the application. Standard outlet boxes have opening dimensions of approximately 3″×2¼″ and are available in a variety of depths. Double-gang and triple-gang boxes are also available, and they typically have the capacity to hold two and three receptacles respectively. A four inch (4″) square box is also commonly employed for multiple receptacle applications.  
         [0005]     Typically, outlet boxes are mounted by affixing mounting ears to a wall stud or other structural member. In the usual application, the installer will offset the electrical box when installed on the wall studs in order to compensate for the thickness of any finishing material to be installed. The offset is intended to ensure the open face of the box is aligned flush with the finish material to conform to electrical codes. In addition, for some applications, such as exterior uses, there is a requirement to install electrical boxes on poured concrete walls, wherein the outlet box, may be mounted within a concrete structure. This is accomplished by attaching the box to a form in the desired location. The form is usually a wooden temporary structure used to contain the poured concrete in the desired shape that is removed after the concrete has hardened. The outlet box remains in the concrete after removal of the form.  
         [0006]     However, in some applications the offset is insufficient to bring the open face of the box flush with the finish material. In these cases extensions must be installed by the electrician to bridge the gap between the box opening and the surface of the finish material. This can occur, for example, when ceramic or stone tile are added to the sheet rock wall material. the prior art methods for providing an extension after the finish materials are installed involve squeezing the extension between the box and the wall finishing material and using longer than normal screws to install the electrical device such as a switch or receptacle. Alternately, the box may provide additional pretapped holes for affixing an extension which the installer may use for attaching the extension before installing the electrical device. In either case additional time consuming labor is needed to adapt the box for use and compliance with electrical codes.  
         [0007]     Therefore, it would be desirable to have an extension for an electrical box that can be easily installed to extend the open front perimeter of the box after the finishing materials are installed such that the perimeter will be flush with the finished wall surface to conform to electrical code requirements.  
       SUMMARY OF THE INVENTION  
       [0008]     Applicant has overcome the shortcomings of prior art electrical outlet boxes by providing an extension device that can be installed within the electrical box and pulled out from the front of the box to increase the depth of the box, once it is set in place without the need for attaching a separate extension.  
         [0009]     The present invention therefore provides an electrical outlet box extension comprising a generally rectangular perimetrical side wall with an inner surface and an outer surface having an open front face and an open rear face and defining an interior space. The extension includes at least one outwardly protruding resilient tab located on the side wall outer surface.  
         [0010]     More specifically, the present invention provides an electrical outlet box assembly. The assembly includes an electrical outlet box having a back wall, a perimetrical side wall surrounding the back wall, an open front face and a box interior. The side wall includes at least one cavity thereon. An extension includes a perimetrical side wall with an inner surface and an outer surface. The side wall of the extension includes at least one resilient tab. The resilient tab has an outwardly protruding lip adapted for cooperative engagement with the cavity of the outlet box for insertably accommodating the extension in the box.  
         [0011]     The box side wall may include a plurality of spaced apart cavities thereon. The resilient tab of the extension is resiliently positionable within one of the pluralities of cavities for adjustably positioning the extension with respect to the box. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a perspective view of the assembled electrical box extension according to the present invention.  
         [0013]      FIG. 2  is a perspective view of the partially assembled electrical box extension according to the present invention in an unfolded position.  
         [0014]      FIG. 3  is a front plan view of the electrical box extension according to the present invention.  
         [0015]      FIG. 4  is a side plan view of the electrical box extension according to the present invention.  
         [0016]      FIG. 5  is a partial cross sectional view of the electrical box extension according to the present invention along section A-A of  FIG. 3  with the extension in the retracted position.  
         [0017]      FIG. 6  is a partial cross sectional view of the electrical box extension according to the present invention along section A-A of  FIG. 3  with the extension in the extended position.  
         [0018]      FIG. 7  is a perspective view of an alternate embodiment of the electrical box extension according to the present invention.  
         [0019]      FIG. 8  is a perspective view of an alternate embodiment of a feature of the electrical box extension according to the present invention.  
         [0020]      FIG. 9  is a front view of an alternate embodiment of the electrical box extension according to the present invention.  
         [0021]      FIG. 10  is a side view of an alternate embodiment of the electrical box extension according to the present invention.  
         [0022]      FIG. 11  is a cross sectional view of an alternate embodiment of the electrical box extension according to the present invention along section B-B of  FIG. 9  with the extension in the retracted position.  
         [0023]      FIG. 12  is a cross sectional view of an alternate embodiment of the electrical box extension according to the present invention along section B-B of  FIG. 9  with the extension in the extended position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     There will be detailed below the preferred embodiments of the present invention with reference to the accompanying drawings. Like members are designated by like reference characters in all figures.  
         [0025]     Turning now to  FIGS. 1 and 2 , there is shown a perspective view of the outlet box extension according to the present invention. The extension, which is a generally rectangular frame  100 , typically made of a metallic material, which may be a folded sheet metal. The extension has ears  102  located on the top  104  and bottom walls  106 , each having tapped holes  108  for mounting an electrical device within the electrical box. Because the ears  102  and holes  108  are mounted on the extension frame  100  the holes  108  are closer to the device that will be installed in the extension allowing the use of shorter screws which provide a stronger and more stable mounting within the electrical box. The extension is held in place by tabs  110 , which are resilient deformable structures that protrude from the side wall  112  and  114  of frame  100 . The tabs  110  are snapped into cavities in the electrical box as will be shown in  FIG. 3-6 . Also shown in  FIG. 1  are generally hemispherical notches  116 , which are placed to clear the space in the box adjacent to knockouts and therefore allow penetration and insertion of conduit and connectors within the box.  
         [0026]     Referring specifically to  FIG. 2 , there is shown the extension according to the present invention wherein the extension frame  100  is depicted in an unfolded view in order to more clearly show the locking mechanism for holding together the folded sheet metal material. As shown the locking system is made up of teeth  120  and notches  122  for cooperatively engaging each other. This locking system provides a secure attachment that will withstand the pull force during extension but not require a welding operation.  
         [0027]     Turning now to  FIGS. 3-6 , the extension frame  100  according to the present invention is shown. In the view of  FIG. 3 , tabs  110  are visible extending from the exterior of sidewall  112  and  114 . As more clearly depicted in  FIG. 4 , the tab  110  is made up of components having an elastic resilient support portion  202  a locking lip  204  for cooperatively engaging a cavity in the electrical box and an embossed opening  206 , which may be used by the installer to change the position of locking lip  204  by bending the resilient support portion  202  with a long nose pliers or screw driver.  
         [0028]     Referring to  FIGS. 5 and 6 , the extension frame  100  is shown in position with respect to an electrical box  208 . Box  208  may be an assembled outlet box having a back wall  208   a , a perimetrical side wall  208   b , and a box interior  208   c  opening to a front face  208   d . Electrical box  208  includes cavities  210 ,  212  and  214 . The cavities are located on the inner surface of the box wall. Once the box has been installed with the extension frame  100  nested within the box such that the extension is flush with the box opening, the extension can be pulled outside the box until tab  110  and particularly lip  204  snap into cavities  210 ,  212  or  214  in the inner surface of the electrical box. By providing several cavities on the inside box wall, the extension can be snapped and adjusted in different positions. Therefore the extension according to the present invention can be used for different thickness finishing material.  
         [0029]     In  FIG. 5 , locking lip  204  is cooperatively engaged in cavity  214 , wherein the extension is flush with the electrical box opening. By resiliently deforming resilient support portion  202 , lip  204  is disengaged from cavity  214  and extension frame  100  is free to translate with respect to box  208 . While not shown in the cross section depicted, it should be understood by one skilled in the art that a complementary tab and cavity are located on the adjacent side wall of electrical box  208  to provide a secure and stable lock.  
         [0030]     With reference to  FIG. 6 , the extension shown is fully extended. The locking lip  204  is cooperatively engaged in cavity  210 , wherein the extension is in the fully extended position such that the extension front edge  216  is extended a distance  218  from the front edge  220  of the electrical box. By resiliently deforming resilient support portion  202 , lip  204  is disengaged from cavity  214  and extension frame  100  is free to translate with respect to box  208 .  
         [0031]     While not shown in the cross section depicted, it should be understood by one skilled in the art that a complementary tab and cavity are located on the adjacent side wall of electrical box  208  to provide a secure and stable lock. It should be further noted that an intermediate position exists wherein lip  208  would engage cavity  214 .  
         [0032]     Turning to  FIG. 7 , there is shown an alternate embodiment of the pull out extension according to the present invention, designed to be used for electrical boxes in concrete wall. In this embodiment, the extension  300  is provided with protrusions  310 . In this embodiment, the extension must be flush with the electrical box when the box is fastened to a form prior to pouring concrete. After the concrete has hardened and the form removed the box will be flush with the concrete wall. In cases where a finishing material is added to the concrete wall such as ceramic tile or stone, the extension can be pulled out of the box to correspond to the additional depth of the finishing material. The extension  300  according to the present embodiment is held in place by the friction between protrusions  310  and the interior of the box wall. No cavity is provided in the box for the initial nested position, but only for the extended position. This embodiment can be typically used, for example when the thickness of the finishing material is known prior to the installation of the box.  
         [0033]     Turning to  FIG. 8  there is shown an alternate embodiment of the locking attachment for holding extension frame in the generally rectangular shape. In  FIG. 8 , there is shown a portion of the extension according to the present invention wherein the extension frame  100  depicted has interwoven locking tabs  400  that cooperatively engage each other at the outside wall the extension frame  100 . This locking system provides a secure attachment that will withstand the pull force during extension but not require a welding operation. However, it should be noted that the locking system as depicted could be welded, wherein the locking system can be located in the corner of the extension or on one of the side walls.  
         [0034]     Another alternate embodiment of the present invention is shown  FIGS. 9-12 . In this embodiment the extension is made of a single unitary plastic part. As shown in  FIG. 9 , tab  110  extends beyond the outside wall of extension frame  500 , and also incorporates a flange  502  on the interior of tab  110 . Holes  504  are provided on the flange  502  for use by the installer to resiliently bend the tab  100  to change its position. This can be done with a screw driver or long nose pliers.  
         [0035]     As more clearly depicted in  FIG. 10 , the tab  501  is made up of components having an elastic resilient support portion  506  a locking lip  505  for cooperatively engaging a cavity in the electrical box.  
         [0036]     Referring to  FIGS. 11 and 12 , the extension frame  500  is shown in position with respect to electrical box  518  (shown in phantom). Box  518  may be an assembled electrical box having a back wall  518   a , a permetrical side wall  518   b , a box interior  518   c , opening to a front face  518   d . Electrical box  518  only includes cavities  510 ,  512  and  514 . The cavities are located on the inner surface of the box wall. Once the box has been installed with the extension frame  500  nested within the box such that the extension is flush with the box opening, the extension can be pulled outside the box until lip  508  snap into cavities  510 ,  512  or  514  in the inner surface of the electrical box  518 . By providing several cavities on the inside box wall, the extension can be snapped and adjusted in different positions. Therefore the extension according to the present invention can be used for different thickness finishing material  
         [0037]     In  FIG. 11 , locking lip  505  is cooperatively engaged in cavity  514 , wherein the extension is flush with the electrical box opening. By resiliently deforming resilient support portion  506 , lip  508  is disengaged from cavity  514  and extension frame  500  is free to translate with respect to box. While not shown in the cross section depicted, it should be understood by one skilled in the art that a complementary tab and cavity are located on the adjacent side wall of electrical box  518  to provide a secure and stable lock.  
         [0038]     With reference to  FIG. 12 , the extension shown is fully extended. The locking lip  508  is cooperatively engaged in cavity  510 , wherein the extension is in the fully extended position such that the extension front edge  520  is extended a distance  522  from the front edge  524  of the electrical box  518 . By resiliently deforming resilient support portion  506 , lip  508  is disengaged from cavity  514  and extension frame  500  is free to translate with respect to box  518 . While not shown in the cross section depicted, it should be understood by one skilled in the art that a complementary tab and cavity are located on the adjacent side wall of electrical box  518  to provide a secure and stable lock. It should be further noted that an intermediate position exists wherein lip  508  would engage cavity  514 .  
         [0039]     Various changes to the foregoing described and shown structures would now be evident to those skilled in the art. Accordingly, the particularly disclosed scope of the invention is set forth in the following claims.