Abstract:
A strain relief for an electrical cord has a body with an opening extending therethrough for accommodating an electrical cord therein. The strain relief replaces a UL knot and establishes a frictional interaction with the cord to prevent sliding relative to the cord. The cord threads through the strain relief with the strain relief forcing the cord to change directions at least once. In one embodiment, a movable bridging member extends from the body proximate to a central opening in the body. In its closed position, the bridging member provides the support around which the electrical cord is looped to change direction. A pair of opposed grippers hold the electrical cord at 90 degrees relative to the axis of the body opening.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a §111(a) application relating to U.S. Appln. Ser. No. 60/122,816 filed Mar. 4, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to strain reliefs in general, and more particularly, to an in-line strain relief used on an electrical cord. 
     BACKGROUND OF THE INVENTION 
     A known method of providing strain relief in electrical cords, e.g., when used in lamps, has been the Underwriters&#39; Laboratories approved knot “U.L. knot” (see FIG.  1 ). Such a knot is used to prevent the electrical cord from becoming detached from the internal terminals of an electrical device, e.g., the light bulb socket of a lamp, when the portion of the cord that is exterior to the device is pulled. The strain relief provided by the knot is achieved by tying the knot inside the electrical device such that the knot rests against a hole in the device through which the cord passes. When the cord is pulled on, the knot abuts the hole, thereby preventing further pulling of the wire. While the U.L. knot is effective for relatively thin wires, it is not very effective when used with thicker wires that are now a required standard in electrical devices such as lamps. 
     SUMMARY OF THE INVENTION 
     A strain relief for an electrical cord has a body with an opening extending therethrough from a first side to a second side thereof. The opening accommodates an electrical cord therein. A bridging member extends from the body proximate to the second side, bridging the opening. The bridging member is capable of supporting a loop in the electrical cord disposed in the opening, preventing the loop from passing through the opening. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following detailed description of an exemplary embodiment considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 shows the step-by-step method of tying a strain relief knot known in the prior art; 
     FIG. 2 is a perspective view of an in-line strain relief apparatus constructed in accordance with the present invention; 
     FIG. 3 is an end view of the strain relief shown in FIG. 2; 
     FIGS. 4 a - 4   d  are sequential side views of the steps of attaching the strain relief shown in FIG. 2 to an electrical cord; 
     FIG. 5 is a perspective view of a first alternate embodiment of the strain relief shown in FIG. 2; 
     FIG. 6 is a perspective view of a second alternate embodiment of the strain relief shown in FIG. 2; 
     FIG. 7 is a perspective view of a third alternate embodiment of the strain relief shown in FIG. 2; 
     FIG. 8 is a perspective view of a fourth alternate embodiment of the strain relief shown in FIG. 2; 
     FIG. 9 is a perspective view of a fifth alternate embodiment of a strain relief constructed in accordance with the present invention; and 
     FIG. 10 is a perspective view of a sixth alternate embodiment of a strain relief constructed in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows the known, Underwriters&#39; Laboratories approved method of tying a knot in an electrical cord to provide strain relief progressing through sequential steps labeled A, B, C, and D. 
     Referring now to FIGS. 2 and 3, a strain relief  10  includes a hollow rectangular body  12  having an upper end  14  and a lower end  16 . The body  12  includes a first side  18  having a slot  20  and a second side  22  having a slot  24 , the first side  18  being parallel to the second side  22 . The slots  20 ,  24  extend from the upper end  14  to approximately midway between the upper end  14  and the lower end  16 . Two arches  26 , 28  connect the first side  18  to the second side  22 . Four retaining tabs or grippers  30  project inward from the lower end  16 , with two tabs  30  located underneath each of the arches  26 , 28 . 
     A living hinge  32  connects a bridge pin  34  to the first side  18 , below the slot  20 . As will be explained in greater detail below, when the bridge pin  34  is moved into its closed position, it first enters slot  20  and then slot  24 , bridging the gap between the first side  18  and the second side  22 . 
     FIGS. 4 a  through  4   d  show the sequence involved in attaching an electrical cord  36  to the strain relief  10 . As shown in FIG. 4 a , a loop  38  is made in the cord  36 . The loop  38  is then passed into the strain relief  10  through the lower end  16  of the body  12 . Referring to FIG. 4 b , the loop  38  is large enough for the bridge pin  34  to pass therethrough. The bridge pin  34  is folded into its closed position such that it rests in the slots  20 ,  24 . In FIG. 4 c , the loop  38  is pulled down against the bridge pin  34 . Lastly, as shown in FIG. 4 d , the free ends of the cord  36  are bent towards the arches  26 ,  28  and secured in the position shown by the retaining tabs  30 . The retaining tabs  30  may be dimensioned and positioned to impress themselves into the cord insulation. 
     The strain relief  10  is positioned on a portion of the cord  36  internal to a corresponding electrical device (not shown), such that the strain relief  10  rests against a hole in the electrical device through which the cord  36  passes. If the cord  36  is pulled on, the strain relief  10  abuts the hole, preventing the cord  36  from being pulled out of the electrical device and from becoming detached from the internal terminals of the electrical device. 
     Four other exemplary embodiments of a strain relief constructed in accordance with the present invention are illustrated in FIGS. 5,  6 ,  7 , and  8 , respectively. Elements illustrated in FIGS. 5,  6 ,  7 , and  8  which correspond to the elements described above with respect to FIGS. 2-4 have been designated by corresponding reference numerals increased by one hundred, two hundred, three hundred, and four hundred respectively. The embodiments of FIGS. 5,  6 ,  7 , and  8  are designed for use in the same manner as the embodiment of FIGS. 2-4 unless otherwise stated. 
     As shown in FIG. 5, a strain relief  110  includes a hollow rectangular body  112  having an upper end  114  and a lower end  116 . The body  112  includes a first side  118  having a slot  120  and a second side  122  having a slot  124 , the first side  118  being parallel to the second side  122 . The slots  120 ,  124  extend from the upper end  114  to approximately midway between the upper end  114  and the lower end  116 . Two arches  126 ,  128  connect the first side  118  to the second side  122 . Four retaining tabs  130  project inward from the lower end  116 , with two tabs  130  located underneath each of the arches  126 ,  128 . A living hinge  132  connects a bridge pin  134  to the first side  118 , below the slot  120 . A thumb tab  140  extends from the bridge pin  134  to allow for easy gripping of the bridge pin  134  to move it between its open and closed positions. 
     Referring now to FIG. 6, a strain relief  210  includes a hollow rectangular body  212  having an upper end  214  and a lower end  216 . The body  212  includes a first side  218  having a slot  220  and a second side  222  having a slot  224 , the first side  218  being parallel to the second side  222 . The slots  220 ,  224  extend from the upper end  214  to approximately midway between the upper end  214  and the lower end  216 . Two arches  226 ,  228  connect the first side  218  to the second side  222 . Four retaining tabs  230  project inward from the lower end  216 , with two tabs  230  located underneath each of the arches  226 ,  228 . 
     A living hinge  232  connects a bridge pin  234  to the first side  218 , below the slot  220 . The bridge pin  234  includes a flat section  250 , which is located between two centering ears  252 . This embodiment of the bridge pin  234  holds an electrical cord (not shown) in the center of the bridge pin  234 , and lowers the cord height relative to the upper end  214 , e.g., to allow the cord to be flush with the upper end  214  of the body  212  when the cord is secured to the strain relief  210 . 
     As shown in FIG. 7, a strain relief  310  includes a hollow rectangular body  312  having an upper end  314  and a lower end  316 . The body  312  includes a first side  318  having a slot  320  and a second side  322  having a slot  324 , the first side  318  being parallel to the second side  322 . The slots  320 ,  324  extend from the upper end  314  to approximately midway between the upper end  314  and the lower end  316 . Two arches  326 ,  328  connect the first side  318  to the second side  322 . Four retaining tabs  330  project inward from the lower end  316 , with two tabs  330  located underneath each of the arches  326 ,  328 . 
     A living hinge  332  connects a bridge pin  334  to the first side  318 , below the slot  320 . The bridge pin  334  includes a hook  360  which is designed to engage a corresponding catch  362  which is positioned on the interior of the second side  322  below the slot  324 . When the bridge pin  334  is moved to its closed position, the hook  360  engages the catch  362 , thereby securing the bridge pin  334  in the closed position. Alternatively, the bridge pin  334  can be retained in the slots  320 ,  324  by detents extending from the side surfaces of the slots  320 ,  324  that engage depressions formed in the bridge pin  334  or vice versa. 
     As shown in FIG. 8, a strain relief  410  includes a hollow rectangular body  412  having an upper end  414  and a lower end  416 . The body  412  includes a first side  418  having a slot  420  and a second side  422  having a slot  424 , the first side  418  being parallel to the second side  422 . The slots  420 ,  424  extend from the upper end  414  to approximately midway between the upper end  414  and the lower end  416 . Two arches  426 ,  428  connect the first side  418  to the second side  422 . Four retaining tabs  430  project inward from the lower end  416 , with two tabs  430  located underneath each of the arches  426 ,  428 . A living hinge  432  connects a bridge pin  434  to the first side  418 , below the slot  420 . 
     The arch  428  includes a central finger  470 , located adjacent to the upper end  414 , and two outwardly directed fingers  472 , located adjacent to the lower end  416 . The fingers  470 ,  472  are used to secure the strain relief  410  in a hole, e.g., formed in sheet metal through which the cord controlled by the strain relief  410  passes. 
     FIGS. 9 and 10 show two additional exemplary embodiments of a strain relief constructed in accordance with the present invention. The embodiments of FIGS. 9 and 10 are designed for use in the same manner as the embodiment of FIGS. 2-4 unless otherwise stated. 
     As shown in FIG. 9, a strain relief  510  has a hollow rectangular body  512  with a first wall  514  and a second wall  516 . The walls  514 ,  516  are parallel to each other and are connected at opposite ends thereof by a first arch  518  and a second arch  520 . An integral bridge  522  is centrally located between the arches  518 ,  520  and connects the walls  514 ,  516 . A first opening  524  is formed between the first arch  518  and the bridge  522 . A second opening  526  is formed between the bridge  522  and the second arch  520 . Two retaining tabs  528  are located underneath each of the arches  518 ,  520 . 
     To install the strain relief  510  on an electrical cord (not shown), the cord is passed under the first arch  518  and up through the first opening  524 . The cord is then passed over the bridge  522 , down through the second opening  526 , and under the second arch  520 . The cord is pulled tightly around the bridge  522 , taking up any slack in the cord. The free ends of the cord are locked between the arches  518 ,  520  and the retaining tabs  528 , thereby securing the cord to the strain relief  510 . 
     Referring now to FIG. 10, a strain relief  610  includes an S-shaped body  612  having a first foot  614  with a retaining tab  616 . A first arch  618  connects the first foot  614  with a first wall  620 , which has a retaining tab  622  (shown in phantom) located opposite the retaining tab  616  on the first foot  614 . An integral bridge  624  extends from the first wall  620  parallel to the first arch  618 , forming a first U-shaped channel  626  therebetween. The bridge  624  ends at a second wall  628  which has a retaining tab  630 . A second arch  632  extends from the second wall  628  parallel to the bridge  624 , forming a second U-shaped channel  634  therebetween. The second arch  632  ends at a second foot  636  which has a retaining tab  638  (shown in phantom) located opposite the retaining tab  630  on the second wall  628 . 
     To install the strain relief  610  on an electrical cord (not shown), the cord is passed under the first arch  618  and into the first channel  626 . The cord is then passed over the bridge  624 , into the second channel  634 , and under the second arch  632 . The cord is pulled tightly around the bridge  624 , taking up any slack in the cord. The free ends of the cord are locked between the first arch  618  and the retaining tabs  616 ,  622 , and between the second arch  632  and the retaining tabs  630 ,  638 , respectively. 
     Another method for attaching the strain relief  610  to an electrical cord begins with forming a loop with the cord, the loop having a bend at the top and left and right branches depending from the bend. The first channel  626  is positioned such that it surrounds the left branch of the cord below the bend. The right branch of the cord is placed in the second channel  634  and the loop is then pulled tightly against the top of the bridge  624 . The free ends of the cord are locked between the first arch  618  and the retaining tabs  616 ,  622 , and between the second arch  632  and the retaining tabs  630 ,  638 , respectively. 
     It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the present invention. For instance, different locking mechanisms can be used to lock the bridge pin  34  in the closed position onto the body  12 . The width of the body  12  (i.e., the distance between the first side  18  and the second side  22 ) can be varied to accommodate electrical cords of any thickness. Varying the distance between the first side  18  and the second side  22  would also necessitate varying the size of the arches  26 ,  28  and the bridge pin  34 . Accordingly, all such variations and modifications are intended to be included within the scope of the invention as defined in the appended claims.