Wiring device with ground clamping plate

Abstract

The present invention relates to electrical wiring devices such as electrical receptacles, switches, and the like, and more particularly to wiring devices with a clamp for the ground connections to such devices. The present invention includes a pressure plate which engages the ground plate of a receptacle with legs of a pressure plate disposed within correspondingly shaped recesses adjacent the ground plate of the receptacle, so that the pressure plate is substantially constrained from rotation relative to the ground plate so that a wire can be received between the ground plate and the pressure plate when the screw is backed out a sufficient distance.

We claim:  
     
       1. A wiring device comprising: 
       (a) a ground plate to which a ground connection is to be made;  
       (b) a threaded opening in the ground plate;  
       (c) a screw engaged with the threaded opening and having an enlarged head;  
       (d) a pressure plate having an opening therethrough and engaging the screw between the enlarged head and the ground plate; and  
       (e) a recess on one of the ground plate and the pressure plate and a corresponding leg on the other of the ground plate and the pressure plate for substantially preventing rotation of the pressure plate relative to the ground plate when the screw is engaged with the pressure plate.  
     
     
       2. The wiring device as defined in  claim 1  in which the pressure plate includes a bull nose for guiding a wire attached to the wiring device into a fixed location relative to the pressure plate. 
     
     
       3. The wiring device as defined in  claim 2  in which the bull nose is concave. 
     
     
       4. The wiring device as defined in  claim 1  in which the pressure plate includes a cut-away region for substantially preventing two wires from being simultaneously engaged by the pressure plate, one on each side of the screw. 
     
     
       5. The wiring device as defined in  claim 4  in which the screw includes a deformed end opposite the enlarged head for preventing the screw from being withdrawn from the threaded opening while still permitting the screw to be turned. 
     
     
       6. The wiring device as defined in  claim 4  in which the ground plate, the screw, and the pressure plate comprise a conducting material. 
     
     
       7. The wiring device as defined in  claim 4  in which the pressure plate includes a bull nose for guiding one of the wires attached to the wiring device into a fixed location relative to the pressure plate. 
     
     
       8. The wiring device as defined in  claim 7  in which the bull nose is concave. 
     
     
       9. The wiring device as defined in  claim 1  in which the screw includes a deformed end opposite the enlarged head for preventing the screw from being withdrawn from the threaded opening, while still permitting the screw to be turned. 
     
     
       10. The wiring device as defined in  claim 1  in which the recess is on the ground plate and the corresponding leg is on the pressure plate. 
     
     
       11. The wiring device as defined in  claim 1  in which the ground plate, the screw, and the pressure plate comprise a conducting material. 
     
     
       12. A wiring device comprising: 
       (a) a ground plate to which ground connection is to be made;  
       (b) a threaded opening in the ground plate;  
       (c) a screw engaged with the threaded opening and having an enlarged head;  
       (d) a pressure plate having an opening therethrough and engaging the screw between the enlarged head and the ground plate, and having a cut away region; and,  
       (e) a ground wire electrically entrapped between the pressure plate and the ground plate.  
     
     
       13. The wiring device as defined in  claim 12  in which the pressure plate includes a bull nose tapered towards the threaded opening for guiding the ground wire attached to the wiring device towards the threaded opening and into a fixed location between the pressure plate and the ground plate. 
     
     
       14. The wiring device as defined in  claim 12  in which the screw includes a deformed end opposite the enlarged head for preventing the screw from being withdrawn from the threaded opening while still permitting the screw to be turned. 
     
     
       15. The wiring device as defined in  claim 12  comprising a recess on one of the ground plate and the pressure plate, and a corresponding leg on the other of the ground plate and the pressure plate for substantially preventing rotation of the pressure plate relative to the ground plate, when the screw is engaged with the pressure plate. 
     
     
       16. A pressure plate for electrically entrapping a ground wire against a ground plate, the pressure plate comprising: 
       a generally rectangular front plate;  
       a screw opening in a central location of the front plate;  
       a bull nose positioned near a first corner of the front plate, the bull nose tapered towards the screw opening; and  
       wherein a second corner of the front plate, adjacent the first corner, is cut-away from the front plate to define a cut-away region for substantially preventing two wires from being simultaneously engaged by the pressure plate, one on each side of the screw opening.  
     
     
       17. The pressure plate as defined in  claim 16  further comprising a leg, generally perpendicular to the front plate, and extending from between the cut-away region and a third corner, the third corner being diagonally opposite the first corner. 
     
     
       18. The pressure plate as defined in  claim 17  further comprising a second leg, generally perpendicular to the front plate, extending from between the first corner and a fourth corner of the front plate. 
     
     
       19. A wiring device comprising: 
       (a) a ground plate to which ground connection is to be made;  
       (b) a threaded opening in the ground plate;  
       (c) a screw engaged with the threaded opening and having an enlarged head;  
       (d) a pressure plate having an opening therethrough and engaging the screw between the enlarged head and the ground plate, and having a cut away region for discouraging an installer from placing two wires, one on each side of the screw, between the pressure plate and the ground plate; and,  
       (e) a ground wire electrically entrapped between the pressure plate and the ground plate.  
     
     
       20. A wiring device, comprising: 
       
         a ground plate to which a ground connection is to be made;  
       
       
         a threaded opening in said ground plate;  
       
       
         a screw engaged with said threaded opening and having an enlarged head;  
       
       
         a pressure plate having an opening therethrough and engaging said screw between said enlarged head and said ground plate of the wiring device; and  
       
       
         cooperating means on said ground plate and said pressure plate for substantially preventing rotation of said pressure plate relative to said ground plate when said screw is engaged with said pressure plate;  
       
       
         wherein said cooperating means includes a recess on said ground plate and a corresponding leg on said pressure plate.  
       
     
     
       21. A wiring device according to  claim 20 , wherein said ground plate includes a base plate, said opening for said screw extends through said base plate, and said leg is arranged at an approximately  90  degree angle with respect to said base plate.  
     
     
       22. A wiring device, comprising: 
       
         a ground plate to which a ground connection is to be made;  
       
       
         a threaded opening in said ground plate;  
       
       
         a screw engaged with said threaded opening and having an enlarged head;  
       
       
         a pressure plate having an opening therethrough and engaging said screw between said enlarged head and said ground plate of the wiring device; and  
       
       
         cooperating means on said ground plate and said pressure plate for substantially preventing rotation of said pressure plate relative to said ground plate when said screw is engaged with said pressure plate;  
       
       
         wherein said cooperating means includes a leg of said pressure plate which extends at approximately a  90  degree angle from said pressure plate, said leg extending past a portion of said ground plate which entraps said ground connection when said screw is tightened.  
       
     
     
       23. A wiring device, comprising: 
       
         a ground plate to which a ground connection is to be made;  
       
       
         a threaded opening in said ground plate;  
       
       
         a screw engaged with said threaded opening and having an enlarged head;  
       
       
         a pressure plate having an opening therethrough and engaging said screw between said enlarged head and said ground plate of the wiring device;  
       
       
         cooperating means on said ground plate and said pressure plate for substantially preventing rotation of said pressure plate relative to said ground plate when said screw is engaged with said pressure plate;  
       
       
         wherein said cooperating means includes a hole on said ground plate and a corresponding leg on said pressure plate which extends through said hole when said screw is tightened to bring said pressure plate and said ground plate into electrical contact with said ground connection.  
       
     
     
       24. A wiring device according to  claim 23 , wherein said ground plate includes a base plate, said opening for said screw extends through said base plate, and said leg is arranged at an approximately  90  degree angle with respect to said base plate.  
     
     
       25. A wiring device, comprising: 
       
         a ground plate to which a ground connection is to be made;  
       
       
         a threaded opening in said ground plate;  
       
       
         a screw engaged with said threaded opening and having an enlarged head;  
       
       
         a pressure plate having an opening therethrough and engaging said screw between said enlarged head and said ground plate of the wiring device;  
       
       
         means for discouraging an installer from placing two wires, one on each side of said screw, between said pressure plate and said ground plate; and  
       
       
         a ground wire electrically entrapped between said pressure plate and said ground plate.  
       
     
     
       26. A wiring device according to  claim 25 , wherein said pressure plate includes a generally rectangular portion and said means for discouraging includes said opening in said pressure plate being off- center in said generally rectangular portion.    
     
     
       27. A wiring device according to  claim 25 , wherein said pressure plate includes a generally rectangular portion and said means for discouraging includes a side of said rectangular portion being substantially cut away.