In-line strain relief

[0002] This is a §111(a) application relating to U.S. Appln. Ser. No. 60/122,816 filed Mar. 4, 1999.

[0003] The present invention relates to strain reliefs in general, and more particularly, to an in-line strain relief used on an electrical cord.

[0004] A known method of providing strain relief in electrical cords, e.g., when used in lamps, has been the Underwriters' 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.

[0005] 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.

[0006] 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:

[0007] FIG. 1 shows the step-by-step method of tying a strain relief knot known in the prior art;

[0008] FIG. 2 is a perspective view of an in-line strain relief apparatus constructed in accordance with the present invention;

[0009] FIG. 3 is an end view of the strain relief shown in FIG. 2;

[0010] FIGS. 4a-4dare sequential side views of the steps of attaching the strain relief shown in FIG. 2 to an electrical cord;

[0011] FIG. 5 is a perspective view of a first alternate embodiment of the strain relief shown in FIG. 2;

[0012] FIG. 6 is a perspective view of a second alternate embodiment of the strain relief shown in FIG. 2;

[0013] FIG. 7 is a perspective view of a third alternate embodiment of the strain relief shown in FIG. 2;

[0014] FIG. 8 is a perspective view of a fourth alternate embodiment of the strain relief shown in FIG. 2;

[0015] FIG. 9 is a perspective view of a fifth alternate embodiment of a strain relief constructed in accordance with the present invention; and

[0016] FIG. 10 is a perspective view of a sixth alternate embodiment of a strain relief constructed in accordance with the present invention.

[0017] FIG. 1 shows the known, Underwriters' 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.

[0018] 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.

[0019] 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.

[0020] FIGS. 4athrough 4dshow the sequence involved in attaching an electrical cord 36 to the strain relief 10. As shown in FIG. 4a, 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. 4b, 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. 4c, the loop 38 is pulled down against the bridge pin 34. Lastly, as shown in FIG. 4d, 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.