Abstract:
The present invention relates to an installation of a wiring device configured to receive a cover plate which snaps on to a wiring device such as a switch or receptacle. With this invention, openings for threaded fasteners in the face of the cover plate are eliminated. In an embodiment, the cover plate has an opening sized to accommodate a wiring device and supports, on opposing side walls of the opening, at least one protrusion. The protrusions on the cover plate are located to detachably engage corresponding protrusions on the wiring device as the cover plate is pressed onto the wiring device.

Description:
[0001]    This application claims priority pursuant to 35 U.S.C. 119(e) from U.S. Provisional Application having Application No. 60/807,686 filed Jul. 18, 2006. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to an assembly of flush mounted wiring devices and more particularly to a wiring devices configured to receive a cover plate. 
         [0004]    2. Description of the Prior Art 
         [0005]    Prior art cover plates are usually in the form of a substantially flat plate having one or more openings which provide access to a wiring device within a wall box. The purpose of the cover plate is to provide a protective cover for the electrical box installation while preventing exposure of a user to the electrical wires in the interior of the electrical box. The term wiring device refers to, but is not limited to on-off switches, receptacles, outlets, dimmers motor speed control switches and the like. Wiring devices include a metal ground/mounting strap having two openings at each end, one being an oversize mounting opening for mounting the wiring device to an electrical box and the other a threaded opening for fastening the cover plate to the ground/mounting strap with screw fasteners. The oversize mounting openings permit the wiring device to be horizontally positioned while being mounted to a wall box. 
         [0006]    The use of screws to attach a plate to a wiring device requires the installer to first align the openings in the cover plate with the threaded openings in the ground/mounting strap, then insert small screws through the cover plate and tighten the screws with a screw driver. The heads of the screws used to attach the cover plate to the wiring device are exposed and, therefore, may detract from the overall appearance of the cover plate. Currently, cover plates which are composed of plastic material are in widespread use. Thus, the use of screws to attach a plastic wall plate to the ground/mounting strap of a wiring device may cause the cover plate to fracture if the screws be over tightened. 
         [0007]    What is needed is a wiring device having a frame, or housing which can be quickly and easily coupled to a cover plate by an installer without the use of screws. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention relates to an assembly of wiring devices configured to receive a cover plate which snaps on to the frame of a wiring device such as a switch or receptacle. With this invention, openings for threaded fasteners in the face of the cover plate are eliminated. In an embodiment, the cover plate has an opening sized to accommodate a wiring device and supports, on opposing side walls of the opening, at least one protrusion. The protrusions on the cover plate are located to detachably engage corresponding protrusions on the wiring device as the cover plate is pressed onto the wiring device. 
         [0009]    The foregoing has outlined, rather broadly, the preferred feature of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention and that such other structures do not depart from the spirit and scope of the invention in its broadest form. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Other aspects, feature and advantages of the present invention will become more fully apparent from the following detailed description, the appended claim and the accompanying drawings in which similar elements are given similar reference numerals where: 
           [0011]      FIG. 1  is a perspective view of an on-off switch coupled to a cover plate in accordance with the principles of the invention; 
           [0012]      FIG. 2  is a perspective view of the cover plate of  FIG. 1 ; 
           [0013]      FIG. 3  is a detailed view of an inside corner of the opening in the cover plate of  FIG. 2  showing a protrusion for engaging a protrusion on a wiring device; 
           [0014]      FIG. 4  is a perspective view of a wiring device showing a series of protrusions for engaging the protrusion on the cover plate; 
           [0015]      FIG. 5  is a detailed view of a corner portion of  FIG. 4  showing the protrusions on the wiring device; 
           [0016]      FIG. 6  is a perspective partial cut-away sectional view along line  6 - 6  of  FIG. 1  showing the cover plate coupled to the wiring device; 
           [0017]      FIG. 6A  is an exploded perspective view of circled section  61  of  FIG. 6 ; 
           [0018]      FIG. 7  is a detailed view showing the protrusion on the cover plate engaging the protrusion on the wiring device; and 
           [0019]      FIG. 8  is a front perspective view of a receptacle coupled to a cover plate in accordance with the principles of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]      FIG. 1  shows an electrical wiring device and cover plate assemblage  10  in accordance with an embodiment of the invention. As described below, cover plate  12  is securely coupled to the wiring device  14  without requiring either threaded fasteners or openings in the face of the cover plate. Referring to  FIGS. 2 and 3 , cover plate  12  has a rectangular aperture  37  defined by vertical wall  21 ,  25  and horizontal walls  17 ,  19 . Vertical wall  21  supports a first shaped protrusion  22  and vertical wall  25  supports a second shaped protrusion (not shown). A wiring device, which can be an on-off switch  14  (see  FIGS. 4 and 5 ) having a rocker paddle  16  located within a frame  18  for example, supports protrusions  24 ,  26 ,  28  disposed on upper and lower ends on the left side wall  32  of the frame  18  of the wiring device and similar structure on the right side wall  36  of the frame  18 . The protrusion  22  (see  FIGS. 6 ,  6 A and  7 ) on the right side wall  21  of the aperture in cover plate  12  is positioned to mate with frame protrusions  24 ,  26 ,  28  on the right side wall  36  of the frame  18  of the on-off switch  14  and, in a similar manner, the cover plate protrusion  23  on the left side wall  25  of the aperture in cover plate  12  is positioned to mate with the frame protrusions  24 ,  26 ,  28  on the left side wall  32  of the frame  18  of the on-off switch. 
         [0021]    Referring to  FIG. 1 , in a typical application, the on-off switch  14  electrically couples a power source to a load to control the power to the load. The switch  14  includes a frame  18 , a switch paddle actuator  16  and a switch housing  20 . The housing  20 , which includes a ground/mounting strap, supports wiring contact assemblies (e.g., screws) for connection to power conductors (e.g., phase, neutral and ground) of an electrical wiring system such as a standard alternating current (AC) 120 Volts, 60 Hz power source, typically found in residential homes and commercial buildings. Although a rocker type of switch paddle actuator  16  is shown, another type of actuator such as a slider, rotatable knob etc. can be used. In addition, while the electrical wiring device  14  is shown as a switch, the invention here disclosed can be equally applied to a receptacle, a dimmer or other type of wiring device. 
         [0022]      FIG. 3  shows a more detailed view of the protrusion on the vertical wall of the aperture of the cover plate  12 , and  FIG. 5  shows a more detailed view of the protrusions  24 ,  26  and  28  on the left side wall of the frame  18  of the switch  14 . Referring to  FIGS. 2 and 3 , the cover plate  12  of the present embodiment has a front face surface  15  with a generally rectangular shaped central aperture  37  having vertical and horizontal walls. The aperture is sized to be positioned around the frame  18  ( FIGS. 4 and 5 ) of the switch  14 . The aperture in the cover plate  12  has a top wall  17 , a bottom wall  19 , a left side wall  21  and a right side wall  25 . These walls are generally perpendicular to the front surface  15  of the cover plate and extend back from the front face surface of the cover plate. A cover plate protrusion  22  is disposed on the left side wall  21  along the vertical (longitudinal) axis of the cover plate  12  and a second protrusion  23  (not shown) is disposed in a similar manner on the right side wall  25  of the cover plate. Each protrusion  22  and  23  can be a strip of plastic having a cross section which is substantially triangular, half circular, triangular, equilateral triangular, or another suitable cross section. 
         [0023]    Referring to  FIGS. 4 and 5 , the switch assembly  14  includes a ground/mounting strap  30  located between the housing  20  and the switch frame  18 . The frame  18  of the present embodiment has a generally rectangular shape defined by a top wall, a bottom wall and two side walls. Each side wall supports two sets of frame protrusions  24 ,  26 ,  28 , one set being located on the upper end of the side wall and the second set being located on the lower end of the side wall  36 . Each frame protrusion  24 ,  26 ,  28  can have a horizontal wall  27 , an angled ramp shaped wall  29  and a vertical wall  31 . Each protrusion can have a cross section which is trapezium, semicircular, trapezoid, or another suitable cross section. The sets of frame protrusions are arranged along the side walls  32 ,  36  of the frame  18  to engage respective wall plate protrusions  22 ,  23  ( FIGS. 2 and 3 ) on the cover plate. The frame protrusion  24 ,  26 ,  28  are shown arranged in a stair or off set step like fashion, but can be arranged in another configuration such as in an aligned arrangement. The triangular shaped cover plate protrusions  22 ,  23  ( FIGS. 2 and 3 ), which are shown being disposed on the side walls  21 ,  25  can be repositioned to be disposed on the top and bottom walls  17 ,  19  of the cover plate and the sets of frame protrusions can be located on the top and bottom wall of the wiring device. The protrusion  22  on the cover plate  12  ( FIGS. 2 and 3 ) is shown as a single linear triangular shaped members located to engage frame protrusions  24 ,  26 ,  28  on right side wall  36 . However, it is understood that protrusion  22  can be two or more separate segments as long as they are located to engage the frame protrusions  24 ,  26 ,  28 . The cover plate  12 , the housing  20  and the switch frame  18  are normally made of non-conductive material such as plastic or other material, and the ground/mounting strap  30  is made of conductive material such as cold rolled steel, aluminum or other material. 
         [0024]      FIGS. 6 and 7  show detailed views of the cover plate  12  coupled to the switch frame assembly  14 . A description of the coupling of the left side of the cover plate to the frame protrusions  24 ,  26 ,  28  on the left side wall  32  of the switch is provided. The coupling between the right side of the cover plate to the frame protrusion  24 ,  26 ,  28  on right side wall  36  of the switch is similar and, therefore, is not described. The side walls  21 ,  25  of the cover plate  12  are slightly flexible whereas the side walls  32 ,  36  of the frame  18  are rigid. Therefore, as the cover plate is pushed onto the switch, the protrusions  22 ,  23  on the cover plate  12  first make contact with the angled ramp shaped wall  29  of the first protrusion  24  of each set of protrusions on the frame  18 . As the cover plate is pushed further, protrusions  22 ,  23  on the respective side walls  21 ,  25  of the cover plate yield slightly to pass over protrusions  24  and then spring back to their original position. The cover plate protrusions  22 ,  23  are shown having an angled ramp shaped wall on the front and a horizontal wall on the back, but another shape can be employed. The cover plate protrusions  22 ,  23  may be of the same material as the cover plate and can be formed with the cover plate or can be attached to the cover plate. The protrusions  24 ,  26 ,  28  on side walls  32 ,  36  of the switch are shown having a ramp shape wall on the front surface and a vertical wall on the back surface, but other shapes can be employed. Similar to the cover plate protrusions  22 ,  23 , the switch protrusions  24 ,  26 ,  28  can be an integral part of the switch by molding the protrusion to the switch frame during the molding step. However, in some instances it may be desirable that the cover plate protrusions  22 ,  23  and the frame protrusions  24 ,  26 ,  28  are made from a more flexible material such as a yieldable plastic or rubber or the like so that they flex as they contact each other. 
         [0025]    Referring to  FIG. 7 , a description is now provided of the coupling mechanism between the cover plate  12  and the switch assembly  14 . In the description which follows, it is assumed that the switch assembly  14 , and therefore the switch frame  18  is securely mounted to an electrical junction box and that a user wishes to attach or mount the cover plate  12  to the switch assembly. The opening  37  of the cover plate  12  is placed over the switch assembly  14  so that rear surface of the cover plate faces the front face of the switch assembly and the opening in the cover plate is aligned with the front face of the switch assembly. The cover plate  12  is then advanced towards the switch assembly  14  so that the rear surface of the cover plate protrusion  23  is brought into contact with the angled ramp shaped wall of the first frame protrusion  24 . As noted above, the side wall of the cover plate  12 , or the protrusion itself is slightly flexible and the side wall of the frame  18  is comparatively rigid. Therefore, in one embodiment, as the cover plate  12  is urged further towards the frame, the side wall of the cover plate or the protrusion on the cover plate yields by flexing and/or bending slightly to allow the cover plate protrusion  23  to pass over the first frame protrusion  24 . Once the cover plate protrusion  23  passes over the first frame protrusion  24 , the cover plate protrusion  23  ends up behind protrusion  24  and in front of the angled ramp shaped wall of the second frame protrusion  26 . 
         [0026]    At this time the cover plate is securely coupled to the switch frame assembly without the need for openings in the cover plate and threaded fasteners such as screws. Depending upon the position of the wall surface relative to the face of the switch, the cover plate  12 , it may be possible to urged the cover plate further towards the frame to cause the cover plate protrusion  23  to pass over the second frame protrusion  26  and rest between the second frame protrusion  26  and the third frame protrusion  28 . In either instance, the front surface of the cover plate will be parallel with the front surface of the switch frame. Although not shown, if desired the cover plate can be mounted to the frame at an angle (i.e., not parallel) by urging one end portion of the cover plate towards the frame while holding the opposite end of the cover plate fixed. This feature is can be used when the wall upon which the switch assembly  14  is installed is not parallel with the front surface of the frame. 
         [0027]    To further illustrate the present invention, it will now be assumed that a user wants to remove the cover plate  12  from the switch assembly  14  and that the cover plate protrusions are located between the first and second frame protrusions  24 ,  26 . To remove the cover plate, the user first grasps the cover plate  12 , usually at the bottom or the top, and urges the end away from the assembly. This will cause the front surface of the cover plate protrusion  23  to move away from the second protrusion  26  and towards the rear surface of the first frame protrusion  24 . As noted above, the side wall of the frame  18  is comparatively rigid and the side wall of the cover plate  12  and/or the cover plate protrusion can flex. As the cover plate  12  is pulled away from the wall, the side wall of the cover plate flexes slightly allowing the cover plate protrusion  23  to pass over the first frame protrusion  24 . As the cover plate protrusion  23  passes over the first frame protrusion  24  the cover plate becomes detached from the switch assembly  14 . 
         [0028]      FIG. 8  shows a cover plate and receptacle assembly  100  in accordance with an embodiment of the invention. The assembly  100  is similar to the assembly  10  of  FIG. 1  except that the wiring device is a receptacle. The receptacle  114  shown as a duplex receptacle having openings for accepting the blades (phase and neutral) and ground pins of two plugs. The assembly  100  is a receptacle frame and cover plate snap-on assembly which does not have openings in the front face of cover plate or fasteners such as screws to hold the cover plate to the receptacle. The assembly  100  incorporates the techniques of the present invention as described above and, therefore, is not repeated here. 
         [0029]    Although a rocker switch and a receptacle are shown in the figures, this invention would apply equally well to any wiring device and cover plate assembly including but not limited to a toggle switch, a standard duplex receptacle, a dimmer, a timer, etc. In addition, while a rocker switch is described in detail with a frame around the rocker, such a separate frame is not needed and the edge of any wiring device can be used and a frame is not required as a distinct element. 
         [0030]    While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and changes of the form and details of the apparatus illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention.