This invention relates generally to links or connectors used for mechanically linking one item to another. More particularly, the present invention relates to links or connectors designed to flex or release when exposed to a predetermined force.
Ring-type links or connectors in the form of split rings, bent wire rings, welded rings or forged chain links are well known in the art. Most of these ring-type or link connectors are intended to stay permanently closed. All of these links will open if their materials are defective, they are degraded by use or exposure to the environment or they are exposed to an excessive force. Some connecting assemblies, such as chain assemblies, are very limited in their ability to stretch and rebound in response to linear forces and fail when exposed to such forces. Other connecting assemblies, such as shock cords or bungee cords, are entirely composed of stretch materials and may not have the strength to accommodate the tension required for many applications. There is a need in the art for connecting assemblies capable of accommodating high tensions while retaining the ability to flex and rebound in response to recurring linear forces.
In some applications, the use of a non-opening link or ring-type connector is undesirable. For example, in the fishing industry, split rings, clasps, snaps, and the like are commonly used to attach fishing hooks to lures, swivels or leaders. Such devices allow the efficient replacement of hooks and the simple connection of other hardware used in the commercial and recreational fishing industries. In many applications, hooks are tied directly to the fishing line. All these methods produce a connection between the hook and the line which is much stronger than the line itself. When a hook becomes snagged on a fixed or heavy object, the most common result is failure of the fishing line at some point between where the hook is attached to the line and the fishing pole. The result is the loss of the fishing lure, the fishing line from the point of failure to the hook and the loss of all tackle including lead weights which were mounted to the lost section of line.
Such lost fishing tackle and line not only represents a financial cost to the fisherman, it also presents a significant environmental hazard. Millions of feet of fishing line and millions of lead sinkers are lost each year in streams, lakes and along the shoreline. Fishing line is typically constructed of high strength mono-filament plastic, wire, nylon and other high strength materials which do not readily decompose. Unsuspecting birds, fish, and land and marine mammals become entangled in the low visibility fishing line that is left behind beneath the water and in the trees and bushes surrounding fishing areas. Ingestion of lead is a well documented environmental problem. Lead weights that remain on the bottom of our waterways poison the food chain by contaminating the fish, waterfowl and animals that may actually ingest the lead or feed or drink close to a lead weight. There is a need in the fishing industry for an inexpensive and easily installed coupling device which will release when exposed a specified and predictable break-away force.
Another example of an application where non-release connectors are undesirable is in the sporting goods industry. Numerous sporting goods accessories are affixed to clothing or equipment by the use of permanently closed ring-type links or connectors. Examples are ski pole straps, rifle scopes, fishing reel to rod fasteners, clips holding binoculars, hardware on hip wader suspenders and the like. An accessory or attachment using a conventional device will not give way when exposed to excessive force, potentially resulting in damage to the clothing, the equipment, or the individual wearing the equipment.
Numerous other applications utilize rigid connectors which have great linear strength but lack any linear flex. Many such applications present themselves in the automotive and marine industries. Examples are the chains used for boat anchors and devices used to attach bumpers, guards, or tie down assemblies. These devices are conventionally constructed from chains, cables, ropes or other such materials which have limited linear flexibility. As a result, these devices often lack the ability to respond to changing linear forces. These devices are either tight or loose and have limited capability to achieve and maintain an appropriate tension setting. Elastic devices commonly used, such as bungee cords or rubber cords will corrode or decay over time. Such conventional rubber-based elastic products may also lack the strength and reliability required in many heavy-duty applications in the marine and automotive industries.
Briefly stated, the invention in a preferred form is a breakaway link or flexible connector for use in place of split rings, chain links, or other conventional connectors. The breakaway link or connector comprises a short coil of wireform material having known elastic and tensile properties. The coil preferably takes on a closed shape, such as an oval or a pear shape, although open shapes may also be useful. Typically, the coil will consist of no more than two complete windings around the closed shape and will be substantially planar or flat in its structure. Articles to be joined by the breakaway link are either inserted between the coils of the closed shape in the manner of a split ring, or the article is opened and secured through the breakaway link. Articles will stay linked by the breakaway connector until a pre-determined breakaway force is applied to separate the two articles. When exposed to a breakaway force, the breakaway link will uncoil, opening the closed shape and allowing the articles to separate.
The selection and use of materials having known elastic and tensile properties allows the creation of break-away links which will separate predictably in response to particular levels of force. Break-away links may be tailored to suit a wide range of potential applications. In a fishing application, for example, the break-away link can be constructed to separate at a force level slightly less than the tensile strength of the fishing line. Thus, the breakaway link will separate before the line fails, leaving only the snagged hook behind while the fishing lure, line and all the tackle attached to the line are retrieved. Breakaway links designed for use in the sporting goods industry can be tailored to separate before clothing, accessories or individuals are damaged.
The breakaway link or connector may be constructed from materials which do not return to the original closed shape following exposure to a breakaway force. Breakaway links constructed of such materials would be single use devices. Preferably, the break-away link would be constructed from known xe2x80x9csuperelasticxe2x80x9d materials such as Nickel Titanium, Copper Nickel Titanium, Iron Doped Nickel Titanium, Copper Aluminum Nickel, Copper Tin (Bronze), Copper Zinc (Brass), Copper Zinc alloyed with a few % by weight of Silicon, Tin or Aluminum, Nickel Aluminum, Iron Platinum, Manganese Copper and Iron Manganese Silicon. The Nickel Titanium based alloys have excellent strength, ductility and corrosion resistance, making them particularly attractive for a variety of uses. The term xe2x80x9csuperelasticxe2x80x9d is used to describe metal alloys having the ability to withstand much higher elastic strain than ordinary alloys before permanent distortion occurs. Superelastic wires elastically deform far more easily and recover their unstressed shape more completely over a greater range of deformation than other alloys. Superelasticity gives these materials a unique combination of rubber-like elasticity and the hardness, tensile strength, ductility and shape retention of metal.
An alternative embodiment of the invention modifies the breakaway link by crossing the windings of the short coil. Bending the tips of the ends of the material ensures the ends will not slip out. When so constructed, the coil of a breakaway link will not breakaway easily. Instead, the crossed ends engage opposing sides of the coil and resist opening of the closed shape. However, the closed shape is still flexible and will respond to force in much the same way as a breakaway link. A connector so constructed will flex, increasing the distance between the points of the closed shape exposed to the force, but not release. Such a device would be most useful in applications where items are being secured and a tension is preferably maintained but release is not desirable.
The flexible connector has the advantage of flexing in response to a known range of force while maintaining its closed shape. An example of an application where such properties would be desirable is in the lacing structure of a hiking boot. Ordinary laces and eyes or hooks have a limited ability to flex in response to the walking motion, resulting in shoes which are often either too tight or too loose. Replacing standard eyes with flexible connectors of the present invention would allow the wearer to lace the boots snugly, knowing that when walking the flexible connectors will give and spring back maintaining the proper tension on the laces. Another application would be tire chains having the ability to flex and spring back with each revolution of the tire.
Either embodiment of the invention may be produced as a separate, add on device, or incorporated into an article of manufacture. For example, break-away links may be sold as a replacement item for the split rings or snap hooks used in the fishing industry or break-away capabilities may be manufactured into fishing hooks, lures, leaders and other fishing equipment. Similarly, the flexible connector may be sold as an independent accessory or incorporated into particular assemblies, such as chain assemblies or hiking boots.
An object of the invention is to provide a new and improved breakaway link which releases at a known level of force.
Another object of the invention is to provide a new and improved breakaway link for securing articles where separation at pre-determined force levels is desirable.
A further object of the invention is to provide a new and improved breakaway link which releases at a pre-determined level of force, returns to its original shape and may be reused.
A further object of the invention is to provide a new and improved break-away link of cost effective design and manufacture which is easily installed in place of existing non-break-away links.
A yet further object of the invention is to provide a new and improved flexible connector which will expand in response to a known force and will return to its original shape, maintaining tension between articles attached to it.
Other objects and advantages of the invention will become apparent from the drawings and specification.