Patent Publication Number: US-4060305-A

Title: Loop forming gauge and method of forming a loop

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electrical wiring device having a terminal screw and incorporating a stripping gauge, a loop-forming gauge and a wire-restraint each of which functions in coordination with the other. It also relates to a method of forming a loop at a predetermined location in a bare end of an insulated electrical conductor wire. 
     The invention relates, more paricularly, to an electrical wiring device having a terminal plate carrying a binding screw which combines a strip gauge, and a gauge for forming a loop in a bare end of an insulated conductor wire for engagement with the binding screw and a wire-restraint engaging with insulation on the wire when the loop in wire is held under the binding screw. 
     The invention also relates to a method of forming a loop in a bare end of an insulated conductor wire at a location where insulation on the wire extends into a wire-restaint when said loop is in engagement with a binding screw. 
     DESCRIPTION OF THE PRIOR ART 
     It has been customary to provide a strip gauge on an electrical wiring device to indicate the length of insulation which is removed from an insulated conductor wire for purpose of connecting the wire to a terminal screw or the like. In accordance with applicants&#39; invention, provision is made to form a loop in the bare end of wire at a location coordinated lengthwise so that a wire-restraint on the device enters into engagement with insulation on the wire when the looped bare end thereof is secured to a binding screw. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an electrical wiring device with a gauge for correctly forming a loop in a bare end of a conductor wire which is electrically secured in place under a terminal screw and with insulation on the wire extending into a wire-restraint passageway. 
     An object of the present invention is to provide an electrical wiring device combining a strip gauge and a loop-forming gauge dimensioned to insure that insulation adjoining a bare end of an insulated conductor wire enters a wire-restaint when a loop formed in a bare end of the wire is secured to a binding screw terminal. 
     A further object of the invention is to provide a simple and effective procedure for forming a loop of proper dimension and size in a bare end of an insulated electrical conductor wire. 
     Other advantages and objects of the invention will be better understood from the following description and the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a fragmentary bottom view of one end of an electrical wiring device embodying the present invention with a looped bare end of an insulated conductor wire attached to a binding screw thereof; 
     FIG. 2 is a fragmentary side view of the wiring device shown in FIG. 1 as seen from lines 2--2; 
     FIG. 3 is a fragmentary view in vertical section taken along line 3--3 of FIG. 2 with a bare end of a conductor wire, as shown by dot and dash lines, inserted into loop forming position; and 
     FIG. 4 is a fragmentary view corresponding to FIG. 3 after a loop has been formed in the bare end of the conductor wire. 
    
    
     DETAILED DESCRIPTION OF THE DRAWING 
     Referring now to FIG. 1, there is an end portion of a wiring device 10 having a rigid base 11 molded of plastic insulating material. The wiring device 10 may be of conventional contruction and hence, need not be described in detail here. 
     A terminal plate 12 of conductive material extends along one side of the wiring device 10 and carries a headed terminal screw 13. The screw 13 threadably engages with the plate 12 for movement of a head 13a thereof toward and away from the plate 12. As shown in FIGS. 1 &amp; 2, a bare end 14 of an insulated conductor wire 15 is looped around the terminal screw 13 and is secured against the terminal plate 12 by the head 13a of the screw 13 which holds the wire in electrical contact with the plate 12. The particular wire 15 illustrated is a solid type of wire. 
     In order to establish good electrical contact between the looped bare end 14 of the wire 15 and the plate 12, the looped end 14 should rest flat against the terminal plate 12 and the loop should extend approximately three-quarters of a turn around the screw 13, in a clockwise direction (for a right hand screw). As shown in FIGS. 1 &amp; 2, the conductor wire 15 enters a wire-restraint 16 at one end of the device 10 while the free end extends rearwardly into a second wire-restraint 17 which extends parallel the restraint 16. As shown in FIG. 2, the insulation on the entering of the end of the conductor wire 15 extends into the restraint 16 for a short distance when the bare end 14 is looped around the binding screw 13. This requires that the loop in the end 14 be formed at a proper distance from the end of the wire. The restraint passgeways 16 and 17 are formed by a central rib 16a with side ribs 16b extending along opposite sides of the base 11. 
     As shown in FIG. 1, a strip gauge 18 is molded in the base 11 of the device 10. The strip gauge 18 determines the proper length of the wire 15 from which the insulation is removed to expose the bare end 14 of the wire in which the loop is formed. The insulation is removed by cutting or slicing through the insulation and sliding the severed insulation from the bare end 14 of the wire 15. 
     Once the insulation is removed to expose the bare end 14 of the wire, a loop is then formed therein. The loop is formed by inserting the bare end 14 of the wire 15 vertically, as shown in FIG. 3, into a cavity 19 and seating the end of the wire at a base or bottom 20 of the cavity 19. As shown, the bottom 20 of the cavity 19 is stepped to receive wires of different sizes namely, #10 AWG, #12 AWG or #14 AWG. As shown, the end of the #10 wire will be seated on the first step, the end of the #12 wire (not shown) will be seated on the second step, and the end of the #14 wire (not shown) will be seated on the third or last step. 
     After the bare end 14 of the wire has been inserted in the cavity 19 and the end is seated at the bottom 20 thereof, the bare end 14 of the wire which is held or confined by the side walls of the cavity 19 and is then bent at a location intermediate its length over a rounded shoulder 21 formed at an upper end of one of the side walls defining the cavity 19 to a looped configuration as shown in FIG. 4. This procedure forms a loop in the bare end 14 of the conductor wire at a location where insulation on the wire 15 enters into the wire-restraint 16 when the loop extends around and is secured under the terminal screw 13. 
     More specifically, the cavity 19 has a diameter of 0.109 inch and a depth of 0.285 inch for #10 AWG wire. The diameter at the bottom of the cavity decreases to 0.88 inch and the overall depth of the cavity increases to 0.325 inch for the #12 wire. At the third step, the diameter of the cavity decreases to 0.72 inch and the depth increases to 0.365 inch for the #14 AWG wire. The stepped down dimensions at the bottom of the cavity 19 permit the cavity to accomodate three different sizes of wire. In each case, the insulation on the wire 15 will enter into and be protected by the wire-restraint 16. 
     SUMMARY 
     Briefly, the present invention relates to an electrical wiring device which incorporates both a loop forming gauge, a stripping gauge and a wire-restaint. The stripping gauge determines the length of wire from which insulation is to be removed and also, the location in the bare end of the wire where the loop is formed by the loop forming gauge. The loop forming gauge forms the loop in a bare end of a solid wire which fits snugly around a binding screw and under a headed end of the screw for convenient use in electrically attaching the bare end of the wire to the wiring device with the insulation on the wire extending into the wire-restraint. 
     The loop in the bare end of the wire can be readily and accurately formed by unskilled persons and without the use of tools. 
     It will be understood that various changes and modifications may be made by those skilled in the art in the embodiment of the invention illustrated and described herein without departing from the spirit or scope of the invention.