Abstract:
A new device and method for providing strain relief to a cable including a base with a tubular extension, the tubular extension having a plurality of deflectable arms, each of which are radially converged and constricted about a cable under a compression force caused by the tightening of a nut having a tapered region formed in an inner nut channel.

Description:
FIELD OF THE INVENTION 
     This invention relates to a device for providing strain relief to jacketed cables. In particular, the invention is directed to a strain relief device for securing jacketed cables of variable diameters carrying tip ring wire pairs to telephone junction boxes for distribution to telephone equipment. 
     BACKGROUND OF THE INVENTION 
     Telephone lines, which are carried by electrical conductors known as tip ring wire pairs, are generally aggregated at a particular point in a building prior to being distributed and connected to various types of telephone equipment, such as, for example, telephones, fax machines, modems etc. As the tip ring pairs enter the building as part of a multi-conductor cable, the individual tip ring wire pairs must first be broken out from the cable into individual wire pairs. This is normally accomplished in a junction box known as, for example, a building entrance protector (BEP), or network interface unit (NIU). 
     The multi-conductor cables are generally enclosed in stiff insulation jackets halving variable diameters depending upon the particular application. Because these multi-conductor cables carry the tip ring wire pairs that will be connected to various types of telephone equipment, it is necessary to provide strain relief to the cable to insure that the tip ring wire pairs do not become disconnected or loose. Loose or disconnected wires in a junction box can cause serious and hard to find malfunctions in telephone service, which requires costly repair and maintenance service. 
     Presently, however, there are no efficient means for securing multi-conductor cables of variable diameters or shapes in the BIP or NIU. Thus, there is a need for a strain relief device capable of securing multi-conductor cables of variable diameters. 
     SUMMARY OF THE INVENTION 
     The present invention is directed at overcoming shortcomings in the prior art. The present invention comprises a base mountable to a fixed object (not shown), such as a BEP or NIU. A tubular extension extends longitudinally from the base and has a compressible portion for constricting around and, thereby, securing a cable. A nut is mountable over the tubular extension and has an inner channel provided with a tapered region for constricting the compressible portion of the tubular extension. 
     The operation of mounting the nut over the tubular extension causes the tapered region of the nut to exert a compression force on the compressible portion, which deflects the compressible portion inward. In use, a cable to be strain relieved is passed through the tubular extension, and the nut is mounted onto the tubular extension to provide strain relief. As the compressible end portion is constricted an inner surface of the compressible portion contacts the cable and grippingly secures the cable in place. Because the compressible portion can be gradually compressed by the nut to a desired compression, a range of variable diameter cables can be secured by the present invention. Thus, the need to use cable fastening devices constructed for specific cable diameters is eliminated, thereby improving efficiency and reliability in cable connections. 
     In a preferred embodiment, the compressible portion is comprised of a plurality of deflectable arms having gripping ends. Under a compression force, the gripping ends radially converge and secure the cable. 
    
    
     Other objects and features of the present invention will become apparent from the following detailed description, considered in conjunction with the accompanying drawing figures. It is to be understood, however, that the drawings, which are not to scale, are designed solely for the purpose of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the figures, which are not to scale, and which are merely illustrative, and wherein like reference numerals depict like elements throughout several views: 
     FIG. 1 is a side view of a strain relief device in accordance with the present invention; 
     FIG. 2 is a side view of a second embodiment of the device of FIG. 1; 
     FIG. 3 is a perspective view of the device in FIG. 1, wherein the compressible end is in an uncompressed ate; and 
     FIG. 4 is a perspective view of the device in FIG. 1, wherein the compressible end is in a compressed state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 to  4 , there is shown a strain relief device  1  constructed in accordance with the present invention. Strain relief device  1  comprises a base  10  mountable to a fixed object and constructed for receiving therein a cable, not shown, of the type generally used in connection with telephone wiring. Strain relief device  1  further comprises a tubular extension  26  that extends longitudinally from base  10 . Tubular extension  20  has a male screw thread  26  on outer surface  24  and a compressible portion  28  for grippingly securing a cable. 
     Nut  50 , which is constructed to cause compressible portion  28  to grip a cable, has a female screw thread  58  formed on at least part of inner channel  56  located nearest first end  52 . Female screw thread  58  is constructed to threadingly engage male screw thread  26  of tubular extension  20 . Inner channel  56  is further provided with a tapered region  60  sloping inwardly towards second end  54 . One skilled in the art will recognize that the present invention is capable of being utilized in any number of applications, such as, by way of non-limiting example, securing multi-conductor cables in BEPs and NIUs. 
     With reference to FIG. 1, base  10  is constructed to mount to a fixed object, such as a BEP or NIU. Base  10  has a polygonal cross-section, such as, by way of non-limiting example, a hexagonal cross-section, to facilitate screwing base  10  into a structure as described below. 
     In a first embodiment, base  10  is provided with mounting portion  14  having a threaded portion  16  on an outer surface  17  for engaging the threaded portion of an aperture formed in a BEP or NIU, such that the tip ring wires carried within the cable can be distributed throughout the BEP or NIU or other structure. In use, a wrench or other tool is used on the hexagonal base  10  to tighten mounting portion  14  onto a structure. 
     Referring to FIG. 2, in a second embodiment, base  100  has a mounting portion  114  which is preferably disc-shaped, although one skilled in the art will recognize that the shape used is a matter of design choice and that any shape may be substituted. As depicted in FIG. 2, mounting portion  114  is provided with a plurality of mounting apertures  116 ,  116 ′. In use, a nail or screw, or any other type article commonly used to mount and object, can be driven through mounting apertures  116  to mount base  100  to a fixed object. One skilled in the art will recognize that mounting apertures are not necessary and that mounting portion  114  can be mounted if any manner known in the art, including, adhesives, welding, and the like. 
     Further, one skilled in the art will recognize, that base  10  can be mounted to a structure in any manner known in the art, including but not limited to, snap-fitting, friction fitting, adhering, or integrally forming strain relief device  1  with the BEP or NIU or other structure. 
     With further reference to FIG. 1, base  10  is provided with tubular extension  20 , which extends longitudinally from base  10  and opposite mounting portion  14 . Tubular extension  20  preferably has a male screw thread  26  formed on outer surface  24  of tubular extension  20  for matingly engaging internal female screw thread  58  of nut  50 , as discussed further below. 
     One skilled in the art will recognize, however, that mounting nut  50  over tubular extension  20  via the mating engagement of threaded regions is but one manner in which the mounting may be accomplished. Nut  50  may, by way of non-limiting example, be snap fit, friction fit, or fit in any other way to achieve the compression of tubular extension  20  and the securement of nut  50  over tubular extension  20 . 
     Tubular extension  20  preferably is formed of a durable, flexible material, such as, plastic. In a preferred embodiment, compressible portion  28  of tubular extension  20  comprises a plurality of deflectable arms  30 , which define compressible portion  28 . Each arm  30  is tapered such that each arm  30  is wider at base  32  and thinner at gripping end  34 . The taper results in ends  34  being freely spaced. Because ends  34  are freely spaced, ends  34  can be deflected inward causing gripping ends  34  to radially converge until arms  30  meet. An inner surface  35  of deflectable arms  30  collectively define a channel  40  through which a cable is passed and secured, as described further below. 
     With reference to FIG. 1, there is shown a preferred embodiment of nut  50  for use with the present invention. Nut  50  is preferably a hexagonal nut, although any type of nut generally known in the art may be utilized. Nut  50  preferably has a generally cylindrically shaped inner channel  56  provided with an internal female screw thread  58  nearest to first end  52  for connection to the corresponding male screw thread  26  of tubular extension  20 . As stated above, nut  50  may be fit over tubular extension  20  in any manner that achieves compression and securement. Inner channel  56  has a tapered region  60  nearest to second end  54  and adjacent to female screw thread  58 . Tapered region  60  slopes inwardly towards second end  54 . The particular angle of tapered region  60  is a matter of design choice and is subject to the specific application for which the present invention is utilized. 
     With reference now to FIGS. 3 and 4, there is shown nut  50  mounted onto tubular extension  20  through the mating engagement of female screw thread  58  of nut  30  with male screw thread  26  of tubular extension  20 . As depicted in FIG. 3, nut  50  is in a first position wherein the plurality of deflectable arms  30  of compressible portion  28  are in an uncompressed state. In an uncompressed state, channel  40 , which is defined by inner surfaces  35  of plurality of deflectable arms  30 , is at its maximum diameter. In this state, a cable may be slid into and through channel  40 . The operation of tightening nut  50  causes tapered region  60  to contact deflectable arms  30  forcing gripping ends  34  to converge radially inward. This inward constriction results in the gradual decrease in the diameter of channel  40 . As depicted in FIG. 4, when second nut  50  is fully tightened, deflectable arms  30  of compressible portion  28  are fully constricted and the diameter of channel  40  is at a minimum. The gradual convergence of gripping ends  14  and the reduction in diameter of channel  40  causes gripping ends  34  to make gripping contact with the inserted cable or conduit, thereby securing the cable. 
     Because the tightening of nut  50  causes compressible portion  28  to gradually compress until reaching a fully compressed state, a multitude of cable diameters can be secured by adapter  1 . The diameters of cables used with the present invention can range from the maximum diameter of channel  40  in an uncompressed state to the minimum diameter of channel  40  in a ally compressed state. One skilled in the art will recognize, however, that the respective compressed and uncompressed diameters of channel  40  are a matter of design choice and may be varied to accommodate difference ranges of cable diameters depending upon the particular application. 
     In a preferred embodiment, gripping ends  34  are formed with non-flat surfaces for enhancing gripping ends  34  frictional engagement with a cable. Gripping ends  34  may also be provided with grooves or notches, which serve the same general purpose as non-flat surfaces. One skilled in the art will recognize that gripping ends  34  may be modified in any number of ways to improve the gripping strength of gripping ends  34 . 
     Further, one skilled in the art will recognize that strain relief device  1  is not limited to the uses described herein, but may be used in applications pertaining to any field where there is a need to secure cables or other elongate members. 
     Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to preferred embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the disclosed invention may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.