Abstract:
A safety device may be used to provide separation in the event of a side impact collision. The device may be used in a utility pole guy wire system, interposed between the guy wire and the ground anchor. The device operates in bending. A lateral force of sufficient magnitude applied to the device by the errant vehicle causes a rod within the device to break in tension, even though the tensile strength of the rod may be greater than that of the guy wire. In operation, certain massive portions of the device are tied safely to the ground, while other portions are pulled over the moving vehicle by the tension of the guy wire. The invention may be designed to tolerate axial loads, but to fail reliably when a side force exceeds a desired threshold. When installed in series with a utility pole guy wire, the invention will withstand all normal tensile and incidental loads, and will release when subjected to a high side force as from an automobile impact.

Description:
This invention was made with government support under Contract No. DTRS57-99-C-00011 awarded by the U.S. Department of Transportation. The government has certain rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to releasable connectors. More particularly, the present invention relates to a releasable connector for a guy wire system. In addition, the present invention relates to a system for releasing a guy wire from an anchor device in the event of a collision. 
     BACKGROUND OF THE INVENTION 
     The United States has between eighty million and one hundred million wooden utility poles along approximately four million miles of public roads. Approximately fifteen hundred to two thousand fatalities and about one hundred thousand injuries occur each year as a result of automotive collisions with utility poles. In an automobile crash with a utility pole guy wire, the car may roll over or it may be thrown into oncoming traffic with disastrous consequences. 
     Known techniques for reducing the number and/or severity of collisions include: providing lateral separation from the road; placing utility lines underground; shielding poles with guard rails; and providing advanced warning signs, wider shoulders, better lighting, skid resistant pavement, and better roadway alignment. The known techniques are generally too costly and/or too inconvenient for wide-scale implementation, however. Another approach has been to construct the poles in such a way as to reduce the likelihood of injury in the event of a collision. The Federal Highway Administration, for example, has developed a slip base upgrade for utility poles which reduces the likelihood of severe injury in an accident. The problems caused by guy wires, however, have not been satisfactorily resolved in the prior art. 
     A frangible guy wire device was referred to in “Safer Timber Utility Poles,” Volume I, Summary Report, Texas Transportation Institute (“TTI”) (September 1986). The device tested by TTI consisted of a six foot length of three-quarters inch galvanized steel pipe. The device relied on stress concentration as the failure mechanism. The stress concentration was formed by a rigid section connecting two pipes. Failure occurs at the pipe threads adjacent to the rigid section. There are several problems associated with the device referred to in the TTI report. One such problem is that stress concentration is not a reliable release mechanism in a guy wire system. It is difficult to control the critical dimensions at the stress concentration point, and corrosion affects the performance characteristics of the device. In addition, the device tested by TTI was unduly sensitive to the bumper height of the colliding vehicle. In particular, the device might fail to release when a car approached from “underneath” the guy wire. In addition, the long pipe itself could create a hazard during a collision, and the device could not be easily rebuilt afterward. 
     Another known device for a guy wire system is described in U.S. Pat. No. 5,529,276 (Szablya). The Szablya device relies on stress concentration and shock bending stress. As such, it is not sufficiently reliable. The release characteristics of the Szablya device would be dependent on parameters such as surface finish, corrosion, wear and manufacturing tolerances, which may be difficult to control. In general, corrosion is a problem with any outdoor system that relies on stress concentration as a release mechanism. In addition, the parts of the Szablya device that remain with the guy wire after a break could become dangerous moving objects, since they are not tied to the ground. In addition, the Szablya device would be difficult to manufacture, and it would be difficult to rebuild the device after a collision. 
     SUMMARY OF THE INVENTION 
     The disadvantages of the prior art are overcome to a great extent by the present invention. The present invention relates to a releasable connector device for providing a separation mechanism in a collision. The device may be formed of at least two elongated rigid elements and a tension member located between the rigid elements. During a side impact collision, the rigid elements pivot to amplify the axial stress applied to the tension member, such that the tension member breaks to provide the desired separation. If desired, a flexible connector or tether may be used to prevent the upper rigid element from separating from the lower element. 
     In a preferred embodiment of the invention, the rigid elements are steel pipes, and the tension element is a threaded steel rod located within the pipes. The present invention should not be limited, however, to the preferred embodiments shown and described in detail herein. 
     According to one aspect of the invention, a threaded unit is used to hold the upper pipe to the tension member. The threaded unit may be located within the upper pipe, if desired. The threaded unit may be arranged to slide out of the upper pipe along with the threaded rod during a collision. 
     According to another aspect of the invention, a threaded fixture is located within the lower pipe for connecting the tension member to the lower pipe. 
     The present invention also relates to a release system that has a connector device interposed between a guy wire and an anchor device. The connector device may be formed of elongated rigid elements in contact with each other at a break point (or at a separation plane). A flexible element may be used to secure the rigid elements together during a collision. The flexible element, which may be a cable, chain or the like, may be used to tie or tether the upper portion of the connector device to the lower portion of the device, to prevent the upper portion from causing damage and/or injury to the vehicle and/or its occupants. 
     In a preferred embodiment of the invention, a threaded rod is used as the breakable element in the connector device. When a bending stress is applied to the device, for example during a side impact collision, the threaded rod breaks in tension at a preselected break point. The tension in the guy wire causes the broken portion of the rod to be pulled out of the connector with sufficient force to minimize the possibility that the rod will come into contact with the moving vehicle or its occupants. 
     According to yet another aspect of the invention, the rigid elements are placed in an end to end relationship and a fulcrum bending point is formed between the rigid elements. During a collision, the device bends or pivots at the fulcrum point. The rigid elements themselves do not bend to the extent that any permanent deformation occurs. As a result, the pipe elements may be used in a rebuilt device, after the collision. 
     The present invention also relates to a method of operating a guy wire system, particularly during a vehicle collision. In operation, the impact force of the vehicle and tensile force in the guy wire create a bending moment in a connector device. The connector device may be interposed between the guy wire and an anchor device at approximately the height of the oncoming vehicle (i.e., the height of the bumper or other impact point of the vehicle). The bending moment causes a breakable element to break in tension. The tensile strength of the breakable element may be greater than that of the guy wire, if desired. The breakable element is broken because of the mechanical advantage applied by placing the connector device in bending. 
     As the vehicle (a car, truck, etc.) moves through the original location of the connector device, the guy wire tension causes at least a portion of the breakable element to be pulled through an upper pipe. A flexible connection keeps the upper pipe tied to a lower pipe, to reduce the amount of damage that might otherwise be done by the upper pipe. The tension of the guy wire causes the breakable rod to be cast up and over the moving vehicle. The remainder of the connector device remains anchored to the ground, where the vehicle can run over it. 
     An object of the invention is to provide a device that fails or releases reliably when subjected to a side force above a design threshold. 
     Another object of the invention is to provide a system that is actuated by automobiles, trucks and other vehicles, and that operates as intended over a wide range of vehicle speeds. 
     Another object of the invention is to provide a device that releases upon impact regardless of the direction of travel of the errant vehicle. 
     Yet another object of the invention is to provide a device that can be used in a wide variety of different size guy wire systems and in a variety of environmental conditions. 
     Another object of the invention is to provide a connector device that reliably performs a breakaway operation in bending at lateral loads smaller than those that would tend to tip a car over or allow it to ride up a guy wire. 
     Yet another object of the invention is to provide a low cost connector device that can be easily installed and repaired by utility crews. 
     In a preferred embodiment of the invention, the connector device resembles a slender rod, several feet long. The device is connected in series with the utility pole guy wire. The lower end of the device is hinged to the ground anchor. The upper end of the device is securely attached to the taught guy wire. When struck by an errant vehicle, the device is pushed out of line with the anchor and utility pole attachment points. The tension in the guy wire increases. A component of the tensile force is applied at a right angle to the axis of the device. The transverse force component creates bending moments which operate to break the device in bending, such that the guy wire is released. The tension in the guy wire causes it to snap away from the vehicle to avoid further damage to the vehicle or its occupants. Following an impact event, a utility crew only needs to replace the failed link to place the guy wire back in service. In a preferred embodiment of the invention, the guy wire system may be rebuilt or repaired with hand tools. 
     The present invention is superior to prior art designs based on stress concentrations at threads, notches or scored areas. Stress concentration devices are highly dependent on device geometry, surface finish and corrosion. Consequently, stress concentration is an unreliable failure mechanism for use in roadside environments. 
     Another object of the invention is to provide a failure mechanism that functions only in the event of a side impact. In a preferred embodiment of the invention, failure is caused by mechanical amplification of tensile force on a preloaded rod. The mechanical amplification is a function of component geometry specifically, the device diameter, and overall length. The side impact release mechanism and the ultimate tensile strength of the system are mechanically decoupled, and they can be separately engineered. 
     In a preferred embodiment of the invention, the releasable device has a higher axial tensile strength than the strongest guy wire in common use, yet the device fails reliably in a side impact with the lightest vehicle under consideration, and is not released by an impact from a slowly moving bicycle or by vandalism. Breakaway devices that rely on weaknesses caused by stress concentration, in contrast, can be separated by tension loading and by side impact loading, and therefore require a separate design for every guy wire strength. 
     These and other advantages and features of the invention will become apparent from the following detailed description which is provided in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a connector device constructed in accordance with a preferred embodiment of the present invention. 
     FIG. 2 is a partially broken away side view of the connector device of FIG.  1 . 
     FIG. 3 is an enlarged view of the portion of the connector device designated by circle  3  in FIG.  2 . 
     FIG. 4 is a partially broken away side view of the connector device located within a guy wire system. 
     FIG. 5 shows the guy wire system of FIG. 4 at a subsequent stage of operation. 
     FIGS. 6-9 illustrate the guy wire system of FIGS. 4 and 5 at sequential stages of operation. 
     FIG. 10 is a partially broken away side view of a device constructed in accordance with another preferred embodiment of the present invention. 
     FIG. 11 cross sectional view of the device of FIG. 10, taken along the line  11 — 11 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings, where like reference numerals designate like elements, there is shown in FIG. 1 a connector device  10  constructed in accordance with a preferred embodiment of the present invention. The connector device  10  has a top eye  12  for connection to a guy wire and a bottom eye  14  for connection to an anchor device. The guy wire and the anchor device are not shown in FIG.  1 . The connector device  10  includes a top tube  16 , a bottom tube  18 , and a threaded steel rod  20  (FIG.  2 ). The rod  20  is used to secure the guy wire to the bottom tube  18 . In operation, the rod  20  is broken at a break point  22  when the connector device  10  is bent sideways by an impact force  24  (FIGS.  4  and  5 ). 
     Referring again to FIG. 2, the top tube  16  may be in the form of a sturdy steel cylinder with opposite ends  26 ,  28  and a cylindrical interior space  30 . A fixture  32  is welded, bolted or otherwise rigidly secured in the top tube  16  near the second end  28 . The fixture  32  has a narrow opening  34  (FIG. 3) for receiving the rod  20 . The inner diameter of the opening  34  may be slightly greater than the outer diameter of the threaded rod  20 . The rod  20  is not threadedly connected to the fixture  32 . 
     In a preferred embodiment, the fixture  32  also has a cylindrical receiving space  36 , and a bevel portion  38  that connects the receiving space  36  to the narrow opening  34 . Providing the bevel portion  38  adjacent the narrow opening  34  avoids the formation of stress concentrations at the proximal end of the fixture  32 . 
     A threaded cylinder unit  40  is sidably received in the receiving space  36 . The unit  40  has a cylindrical exterior surface  50  and a conical surface  51 . The outer diameter of the cylindrical surface  50  is slightly less than the inner diameter of the cylindrical receiving space  36 . In a preferred embodiment of the invention, the unit  40  has interior threads along its entire length, and those threads are threadedly connected to the threaded rod  20 . The threaded cylinder unit  40  may be provided with hexagonal wrench flats  54  for rotating the unit  40  relative to the threaded rod  20 , as shown in FIG.  2 . 
     If desired, the entire unit  40  may be machined from a single piece of metal. In the illustrated embodiment, the unit  40  is made of steel. For certain applications, however, the unit  40  may be made of a different material. 
     The purpose of the cylinder unit  40  is to pull the top and bottom tubes  16 ,  18  together such that the device  10  operates as a single integral unit. The prestress applied by the unit  40  protects the rod  20  from fatigue stress in the vicinity of the break point  22 . 
     Prior to assembly, the conical surface  55  (FIG. 3) of the bevel portion  38  may diverge outwardly slightly less than the conical surface  51  of the threaded unit  40 . This ensures the contact between threaded unit  40  and bevel portion  38  occurs in a region where there is sufficient material to eliminate excessive bending in bevel portion  38  of fixture  32 . In addition, it helps minimize the gap  59  between the proximal face  61  of the threaded unit and a bottom fixture  56 , such that the rod  20  snaps at the break point  22  in tension and does not undergo excessive elongation before breaking during a side impact collision. The length of the gap  59  may be kept to a minimum to reduce the amount of elongation that occurs in the rod  20  before it breaks. In addition, the bevel portion  38  provides a gradual transition from the thick cylindrical portion of the fixture  32  to the thin edge surrounding the narrow opening  34 . 
     The bottom fixture  56  is rigidly secured within an opening of the bottom tube  18 . The bottom fixture  56  may be secured to the bottom tube  18  by a weld (not shown), a bolt or by another suitable connecting structure. The bottom fixture  56  has interior threads  60  that are aligned with the narrow opening  34  of the top fixture  32 . The threaded rod  20  is threadedly secured in the bottom fixture  56 . In operation, rotation of the threaded cylinder unit  40  causes the conical surface  51  to be forced into the bevel portion  38  of the first fixture  32 , such that the rod  20  is placed in tension at the break point  22 . 
     A tool (not shown) may be provided for tightening the threaded unit  40 . The tool may have a socket that engages the wrench flats  54 , and a head that is driven by hand or by a power tool. An extension may be located between the socket and the head. In operation, the extension extends through the top tube  16  such that the head can be rotated from outside of the tube  16  while the socket is engaged on the wrench flats  54 . The tool may be used to tighten the unit  40  to a predetermined torque. Alternatively, the tool may be used to turn the unit  40  a predetermined number of times after it has been hand-tightened on the rod  20 . 
     The tension in the rod  20  is counteracted by compression between the two tubes  16 ,  18  (or compression between the two fixtures  32 ,  56  depending on the alignment of the tube ends  28 ,  58  and the fixtures  32 ,  56 ). Thus, the rod  20  is prestressed in tension at the break point  22  before the connector device  10  is installed between the guy wire  62  (FIG. 4) and the anchor device  64 . Sufficient prestress tension should be applied to maintain the two tubes  16 ,  18  pressed together in end to end contact during installation and throughout the life of the device  10  prior to a collision. 
     In a preferred embodiment of the invention, the threaded components  20 ,  40 ,  56  of the connector device  10  are all made of steel. Making all of the connected components of the same metal material reduces the potential for galvanic corrosion. The present invention should not be limited, however, to the preferred embodiments shown and described herein in detail. Corrosion may also be prevented, for example, by providing plastic coatings or others of known art on various components and/or employing a molybdenum disulfide grease as is known in the art. 
     Referring again to FIG. 1, the rigid steel members  16 ,  18  may be connected to each other by one or more flexible chains, ropes or cables  66 . The ends of the illustrated cable  66  may be attached to the elongated pipes  16 ,  18  by welds  68 ,  70  or the like. When the connector device  10  is in its assembled pre-collision configuration (with the ends  28 ,  58  of the tubes  16 ,  18  contacting each other as shown in FIG.  1 ), the length of the cable  66  may be greater than the distance between the welds  68 ,  70 . As shown in FIG. 1, the cable  66  contains slack when the connector device  10  is in its assembled configuration. The slack may be taken up when the rod  20  is broken at the break point  22 . The cable  66  operates as an extendable tether to keep the top tube  16  attached to the bottom tube  18  when the rod  20  is broken, as discussed in more detail below. 
     The anchor device  64  (FIG. 4) may be any suitable device for securing a utility pole guy wire to the ground  72 . A shackde  73  may be connected to the anchor device  64  to permit rotation (with at least two degrees of freedom) about mutually orthogonal axes, each perpendicular to the longitudinal axis of the device  10 . The shackle  73  may be connected through the bottom eye  14 . In operation, the bottom tube  18  may remain firmly connected to the anchor device  64 , which remains connected to the ground  72 , even in the event of a high speed automotive collision. Thus, according to a preferred mode of operation, the bottom tube  18  remains connected to the ground  72  during a side impact collision. 
     The distal end of the threaded rod  20  is threaded or welded into an end socket  74 . The top eye  12  is located in the distal portion of the end socket  74 . The end socket  74  may be used to rigidly connect the threaded rod  20  to the guy wire  62 . The guy wire  62  may be a conventional steel wire for securing a utility pole against lateral forces. The tensile strength of the threaded rod  20  at the break point  22  may be greater than the tensile strength of the guy wire  62 . 
     In an alternative embodiment of the invention (not shown in the drawings), the rod  20  is threaded only in the vicinity of the bottom fixture  56 , the threaded unit  40  and the end socket  74 . The smoother the rod  20 , the easier it will slide out of the upper tube  16 , and the easier it will be snapped away from the errant automobile by the tension in the guy wire  62 . 
     In a preferred embodiment of the invention, an end cap  76  is located between the proximal end  78  of the end socket  74  and the first end  26  of the top tube  16 . The end cap  76  has a cylindrical body portion  77  that slidably overlaps the top tube  16 . The end cap  76  may be connected to the end socket  74  and/or the rod  20 . The end cap  76  is not connected to the top tube  16 . Consequently, when the end socket  74  is pulled away from the top tube  16  (by the guy wire  62 ), the end cap  76  and the upper portion of the rod  20  remain integrally connected to the end socket  74  and the guy wire  62 . As noted above, the distal end of the rod  20  is rigidly secured in the end socket  74 . 
     As shown in FIG. 2, the cylindrical portion  77  of the end cap  76  laps over the outside of the tube  16 . The overlapping construction provides superior environmental control over the interior of the tube  16 . When the tension in the guy wire  62  is applied, it tends to move the cap  76  slightly away from the distal end  26  of the top tube  16 . The movement is caused by the elongation of the rod  20  caused by the tension of the guy wire  62 . In the illustrated embodiment, the end cap  76  can move slightly away from the tube  16  and still the body portion  77  overlaps the distal portion  26  of the tube  16 . 
     In addition, the end cap  76  may be used to centralize the rod  20  within the top tube  16 . This way, the distal end  26  of the top tube  16  does not have to be moved into side contact with the rod  20  before the desired breaking action occurs at the separation plane ( 22 ). In other words, it is helpful to keep the rod  20  stationary with respect to the tube  16  during the initial moments of a collision so that there is no sideways slack in the system  10 ,  62 . 
     The end cap  76  may be used to seal off the end  26  of the top tube  16 . The end cap  76  may prevent ice, water, salt and the like from reaching the interior operative components  40 ,  22  of the device  10 . The end cap  76  may also be used to discourage vandalism and the like by providing a neat, closed construction. 
     As shown in FIG. 4, the connector device  10  may be sized to receive the impact force  24  of an oncoming automotive vehicle (not shown in FIG.  4 ). Although FIG. 4 shows the impact force  24  being applied at a location above the separation plane between the two tubes  16 ,  18 , the impact force  24  may be applied at other locations on the connector device  10 . The impact force  24  causes the connector device  10  to bend or pivot at a fulcrum point  80 . That is, the rigid elements  16 ,  18  rotate relative to each other about the fulcrum point  80 . The fulcrum point  80  is located within the plane between the two tubes  16 ,  18 . During a collision, the applied bending moment stretches the rod  20  (FIG. 4) and eventually breaks the rod  20  at the break point  22  (FIG.  5 ). The device  10  employs mechanical advantage to amplify the tension in the tension member  20  until it breaks at the break point  22 . During the collision, the tension applied to the rod  20  at the break point  22  is greater than the tension in the guy wire  62 . 
     After the break occurs at the break point  22 , the tension in the guy wire  62  causes the upper portion of the rod  20  to be snapped upwardly to a location where it is less likely to impact the automobile. That is, when the break occurs, the upper portion of the rod  20  stays with the guy wire  62 , and the top tube  16  stays with the bottom tube  18 . The cable  66  (FIG. 1) keeps the tubes  16 ,  18  flexibly connected to each other, which provides advantages as discussed in more detail below in connection with FIGS. 6-9. The guy wire  62  tends to snap upwardly and stay near the utility pole where it is less likely to damage the vehicle or injure its occupants or swing into the normal flow of traffic. 
     FIG. 6 shows the guy wire system  10 ,  62  in a pre-collision assembled configuration. The guy wire  62  is attached to a utility pole (not illustrated) in a known manner. The anchor device  64  is likewise secured to the ground  72  in a manner known in the art. The guy wire  62  should preferably be installed tight so that no slack needs to be taken up before a release occurs in a collision. In other words, the illustrated connector  10  is preferably installed in a taught guy wire system. The connector device  10  is interposed between the guy wire  62  and the ground attachment device  64 . The utility pole may be, for example, a forty foot long wooden telephone pole, and the guy wire  62  may be anchored at a desired angle (for example, sixty degrees) with respect to the ground  72 . The present invention should not be limited, however, to the specific structures and instrumentalities shown and described herein. 
     Referring now to FIG. 7, the bumper  82  of an oncoming vehicle  84  applies an impact force to the connector device  10 . The vehicle  84  may be an automobile, truck or the like. The impact force  24  causes the two pieces  16 ,  18  of the connector device  10  to pivot at the fulcrum point  80 , such that the rod  20  is broken at the break point  22  (FIG.  8 ). As the vehicle  84  continues to move through the guy wire system, the top tube  16  may be run over by the vehicle  84 . The cable  66  operates as a flexible hinge that extends between the top and bottom tubes  16 ,  18 . The top tube  16  remains attached to the ground  72  via the cable  66 , the bottom tube  18 , and the anchor device  64  (FIG.  9 ). 
     The illustrated arrangement causes the relatively massive top tube  16  to remain near the ground  72 , such that the vehicle  84  tends to run over it. The top tube  16  is prevented from flying upward where it could potentially injure the vehicle occupants. The present invention also males it easier to locate the top tube  16  after the collision so that the connector device  10  can be rebuilt with a minimum number of replacement parts. During a collision, the end socket  74  and the end cap  76  remain attached to the guy wire  62 . As a result, the end socket  74  and the end cap  76  may be reused in a rebuilt connector device  10 . In many cases, the only part that will need to be replaced to rebuild the connector device  10  will be the threaded rod  20 . 
     Referring now to FIGS. 4 and 5, according to a preferred embodiment, the tubes  16 ,  18  are sufficiently massive to ensure that they are not damaged during a high speed collision. The tubes  16 ,  18  resist bending such that the connector device  10  separates and pivots at the fulcrum point  80 . The tubes  16 ,  18  should be sufficiently strong and durable to resist degradation by vandalism, weather and the like. 
     Although the collision shown in FIGS. 7-9 involves the vehicle  84  moving toward the utility pole, the invention should not be limited to that mode of operation. The safety device  10  operates as intended regardless of the direction of movement of the oncoming vehicle  84 . When the vehicle  84  is moving away from the pole, the side impact force  24  may be applied somewhat higher up the device  10 . In a preferred embodiment of the invention, all of the operative components, including the tubes  16 ,  18 , are axially symmetrical with respect to the central axis of the threaded rod  20 . This way, the device  10  fails reliably as intended regardless of the direction of impact. 
     If desired, a plastic or metal guy wire cover (not shown), of a type known in the art, may be located over the connector device  10 . 
     Numerous structural and organizational changes may be made to the device  10  without departing from the spirit and scope of the present invention. For example, as shown in FIGS. 10 and 11, a relatively long steel cable  100  may be employed to flexibly secure the top tube  16  to the bottom tube  18 . The cable  100  may be employed instead of the cable  66  shown in FIG.  1 . The FIG. 10 cable  100  may be inserted through openings  102 ,  106 ,  108  in the two fixtures  32 ′,  56 ′. The cable  100  may form a loop such that it is prevented from passing back through the openings  106 ,  108  in the top fixture  32 ′. The middle portion  114  of the cable  100  may be looped around the bottom eye  14 . The ends of the cable  100  may be connected to each other by a suitable connection mechanism to form a closed loop. The cable  100  need not be welded or otherwise attached to the bottom tube  18 . 
     The cable  100  is slack in the pre-collision assembled position shown in FIG.  10 . When the rod  20  is broken during a collision, the flexible cable  100  prevents the top tube  16  from moving away from the bottom tube  18 , although hinged movement between the two tubes  16 ,  18  is permitted. 
     Furthermore, the present invention is not limited to use in utility pole guy wire systems. The invention may also be applicable, for example, to triple cable barrier systems. Thus, the invention may be used to prevent a car from becoming wedged under the downstream end of a triple cable barrier system where the cables extend from the last post to a buried anchor. 
     The invention may also be applicable to a wide variety of other systems. In general, the invention may be used wherever a releasable connector may be employed as part of a tension system that is released by a side impact. The invention may be used, for example, as a shunt for a patient&#39;s blood vessel, and for other surgical implants and/or other medical purposes. The invention may also be employed in the rigging of sail boats, such as offshore racing boats, rock climbing equipment, and tethers for space vehicles and other equipment. Under some design thresholds, a releasable connector may be actuated by hitting it on the side to release a sailboat rigging component in the event of an emergency, for example. 
     Reference has been made to preferred embodiments in describing the invention. However, additions, deletions, substitutions, or other modifications which would fall within the scope of the invention defined in the claims may be implemented by those skilled in the art without departing from the spirit or scope of the invention. Accordingly, the invention is not to be considered as limited by the foregoing description, but is only limited by the scope of the appended claims.