Patent Publication Number: US-6657144-B2

Title: Through strap for switch

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates in general to electrical switches and more specifically to a switch which includes an internal through-strap which does not require a separate component which acts as a barrier to isolate the strap from the switch terminals. 
     The following patents illustrate a variety of electrical switching devices which exemplify the state of the art with respect to through-straps or equivalent components. 
     U.S. Pat. No. 4,255,637 (Matsuda) discloses a switch assembly which includes a case  12  containing light control components, a front panel  16  furnished with a control knob, and a radiating plate  14  (a through-strap) for attaching the assembly to a switch box  21  and mounted between the case and the front panel. The assembly requires an insulating plate  50 . 
     U.S. Pat. No. 5,213,204 (Sommer) discloses an electrical switch assembly including a cover  30  for mounting a rocker switch  16  and a base  28  for mounting a switch unit  14 . No strap is disclosed, but the cover  30 , which is external, also performs many of the functions of a through-strap. 
     U.S. Pat. No. 5,783,787 (Data) discloses a switch assembly including a front housing  12  in which four rocker actuators  30  are mounted, and a rear wiring module  42  in which terminals  44  are mounted. A front plate  40 , which is similar to an external through-strap, is mounted between the housing and the module. 
     U.S. Pat. No. 6,005,308 (Bryde et al.) discloses a switch and dimmer device that is interposed between a bezel housing  17  and a back cover  12 . Yoke  20  is an external through-strap 
     U.S. Pat. No. Des. 430,497 (Michaels) discloses an external yoke sandwiched between a cover member mounting a switch and a body member mounting the switch terminals. 
     The only internal through strap in the above cited prior art requires an insulating component to isolate the strap from the terminal. Where the through-strap is external, it does not provide for any significant reinforcement of the device 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an internal through-strap for an electrical device which overcomes the shortcomings of the prior art described above. 
     It is another object of the present invention to provide an internal through-strap for an electrical device which eliminates the need for a separate electrical barrier component. 
     It is a further object of the present invention to provide an internal through-strap which contributes to a rugged switch assembly by providing reinforcement for the device. 
     The present invention is directed to an electrical switch assembly which includes an internal metal strap or through-strap which functions to provide attachment means to an electrical enclosure. A top enclosure functions to captivate and holds a planar through-strap in a fixed, nesting engagement by contact between the bottom surface of the top enclosure and the top surface of the through strap. A body or bottom enclosure captivates and holds the through-strap in a fixed, nesting engagement by contact between the top surface the body and the bottom surface of the through-strap. The strap includes a vertically disposed tab which is designed and positioned to be received in a notch or well contained in the top enclosure which functions to orient and captivate the through-strap in a predetermined location during and after assembly. A corresponding notch is also included in the body which also functions to orient and captivate the through strap. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a further understanding of these and objects of the invention, reference will be made to the following detailed description of the invention which is to be read in connection with the accompanying drawings, wherein: 
     FIG. 1 is an exploded view of a switch assembly which incorporates the internal through strap of the present invention. 
     FIG. 2 is a front view of the through-strap of the present invention. 
     FIG. 3 is a side view of the through-strap of the present invention. 
     FIG. 4 is a back view of the frame or top enclosure of the switch assembly. 
     FIG. 5 is partial front view of the assembly with the frame and ground strap in assembled position. 
     FIG. 6 is a side view of the assembled switch assembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is more completely understood with reference to FIG. 1 of the drawings which is an exploded view of the switch assembly  10  of the present invention. The invention includes a paddle or rocker  12 , and associated spring  14  and moveable terminal  16 . The paddle rocker and associated parts are connected to frame  18  along with the through strap  26  of the present invention. Through strap  26  contains mounting screws  28 , ground screw  23  and ground tab  30 . The strap further contains a mounting flange at either end which contains holes  34  to receive mounting screws  28  for fastening the assembly to a wall plate. Holes  36  are located at each end for receiving mounting screws for mounting the assembly to a wall box. Holes  38  are optionally used for fastening the assembly to a wallboard and can be easily broken away if not required for use. The assembly further contains a pivot terminal  44 , stationary terminals  46  and  47 , both terminals having a trip plate  48  and wire binding screw  50  which form a part of body  42 . 
     FIG. 2 is a front view of the through strap of the present invention. The through strap  26  is basically rectangular in configuration having an open central portion  33  formed by a pair of elongated side members  31  which contain reinforcing ribs  32  and holes  37  which accommodate plastic tabs  24  contained on the frame which are used in heat sealing the device together in final assembly. Two holes  35  are also positioned to accommodate corresponding plastic sealing tabs  52  contained on body  42 . As will be described in greater detail later, the reenforcing ribs  32  have a protruding or dimpled side as shown in FIG. 2, and a corresponding recessed back side. The protruding ribs allow for placement and nesting within corresponding recesses  20  (FIG. 4) contained in the edges of frame  18 . The strap further contains a slight recess or bend near each end which forms a shoulder  39  to facilitate placement in body  42 . Shoulders  39  aid in orienting and captivating the through strap with the vertical shoulder  54  formed at each end of body  42  (FIG.  6 ). 
     FIG. 3 is the side view of the through strap of the present invention which shows vertically attached ground tab  30 , reinforcement ribs  32 , and shoulders  39 . The flat planar configuration of the through strap is designed to nest in fixed engagement and form a tight seal between the top frame  18  and bottom body portion  42 . 
     FIG. 4 is a back view of the frame or top enclosure which shows recesses  20  which accommodate the raised portions of the reinforcing ribs  32  of the through strap when the components are assembled. The frame further contains a plurality of vertical disposed plastic tabs  24  which pass through holes in the sides of the through strap and when heated, bond with holes in the body or bottom enclosure  42  to seal the assembly together. Notch  22  is designed to index and hold the through strap in place by contact with ground tab  30 . 
     FIG. 5 illustrates the through strap in assembled or nesting position against the underside of frame  18  with the ground tab  30  of the through strap contained in notch  22  of the frame. Notch  22  is formed at a predetermined location to allow for placement and indexing of the base of the ground tab to hold it in place and to ensure an accurate assembly of the two parts. In this view the protruding ribs  32  of the through strap are nesting in recesses  20  of frame  18 . 
     FIG. 6 shows the switch assembly in its final assembled form in which the frame  18  and body  42  form a tight seal along the side edges of the through strap with the through strap providing for physical reinforcement of the switch assembly and where the frame through its recesses  20  allows the reinforcing ribs  32  of the strap to nest in said recesses which functions to position and isolate the metal strap away from the switch components when the assembly is sealed. Correspondingly, the body or bottom portion  42  of the assembly also has recessed surfaces which similarly function to isolate and segregate the strap from the switch components as in the frame described above. The strap also has been sized such that its outer edges basically conform to the outside dimensions of the frame and body. For example, in a switch having a width of approximately 1.75 inches, the strap is configured such that its width will be no greater than {fraction (1/32)} inch more than the overall switch width. This feature becomes important when switches are used in a multigang arrangement and the overall width of the gang arrangement is critical with respect to space. 
     While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawing, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the spirit and scope of the invention as defined by the claims.