To insure the quality of products, numerous industries take significant steps to detect and remove impurities and foreign materials that may enter their product or process streams. This is especially the case in the manufacture of food products, medicine or other items that can affect the health of humans. Cable ties, like any other foreign material, are not intended to be part of a product or process stream and, therefore, it is desirable to remove them so that they do not contaminate the product and/or cause harm. However, when cable ties unintentionally enter a product or process stream, they can be very difficult to detect.
Cable ties and their accessories, such as mounting bases, have been in existence for several decades. They are quite useful in bundling wires or in tethering items to each other or to a support structure. Typically, cable ties are made of metal, plastic or a combination of the two (for example, a metal pawl in a plastic body).
The strength of a cable tie and/or its accessory is dependent on the material that is used, as well as the cross-sectional area of the tie. For most materials, a greater cross-sectional area results in a cable tie having greater strength. Accordingly, in order to maximize the strength of cable ties, great care is taken to eliminate any voids or air pockets which would decrease the cross-sectional area and weaken the ties. Therefore, one of the objectives is to maintain a certain minimum cross-sectional area along the length of cable ties and another objective is to insure that the cable ties remain intact and do not rupture or break.
Many different industries, such as the food, automotive, tobacco, pharmaceutical, rubber molding and nuclear industries, among others, employ detection equipment in order to remove any impurity or stray item that may find its way into product or process streams. Some of these systems employ X-ray equipment which identifies items having greater density. Other systems employ metal detectors that use magnetic properties to detect the foreign material. Sonar is also used to detect foreign matter as well as optics (photography) or other visual means. Obviously, the purpose of these detection systems is to scan the product or process stream to identify foreign material and remove it before harm is caused.
In the past, some cable ties have been made more detectable by the addition of small metal particles to the plastic resin prior to molding. Such metal particles are evenly distributed throughout the pre-molded material so that the metal particles are evenly distributed in the final molded product. This even distribution of the metal particles insures a fairly uniform product with only a minimal decrease in the strength of the cable tie. The ratio of plastic resin to metal particles is selected so that the cable tie can bend and flex without cracking. It is also desirable for all the metal particles to be covered by, or fully suspended within, the plastic resin so that they are not exposed to the environment. Exposure to the elements or to a corrosive environment can result in the metal particles deteriorating, which weakens cable ties and reduces their expected life. However, depending on the composition of the plastic material used to make the cable ties, it is not always possible to prevent the metal particles from being exposed on the surface of the cable ties.
The cable tie manufacturer referred to above has added metal particles to nylon cable ties so that they can be detected in the event that a tie breaks or a cut-off tail ends up where it is not wanted. The metal allows the tie or tail to be more easily detected, located and removed. These ties are sold by Hellermann-Tyton as Model No. MCT50L and described in the advertising literature as metal content ties, which can be detected by standard metal detecting equipment. Hellermann-Tyton discloses in its literature that the composition used to make the cable ties contains polyamide (nylon) 6,6 and 10% metal particles.
Increasing the amount of metal in the cable tie material increases the density of the cable tie, but it also compromises the strength of the cable tie because the additional metal replaces the nylon material in the cable tie from which the cable tie draws its strength. The strength of a cable tie is a function of its cross-sectional area and a reduction of the amount of nylon material in the cross-sectional area weakens the cable tie. Also, some of these metals may chemically react with the plastic cable tie material and cause the tie to prematurely fail. Further, such metals, if exposed to a harsh industrial environment, may quickly corrode and cause the cable tie to fail.
However, while the addition of metal particles to cable ties may suffice for some industries, it is not adequate for other industries. This is because the metal particles cannot be easily detected in the product streams of some industries. Therefore, the metal particles are oftentimes difficult to detect except by the most sensitive metal detection equipment. Also, some industries already employ X-ray equipment and so an objective of the invention is to make cable ties that are more easily detected by X-ray equipment.
Thus, it is an object of this invention to provide cable ties and accessories that are detectable without compromising their integrity or affecting their strength or operation. Yet another object of this invention is to provide a cable tie that is similar in shape to traditional cable ties so that they will be readily accepted by users. Another object of this invention is to provide a cable tie that is more easily detected than the metal cable ties that are now being sold and contains smaller amounts of metal particles. Yet another object of this invention is to add a compound that is detectable using other detection systems, such as X-ray, sonar, optics or photo/visual devices. These and other objects and advantages of the present invention will become obvious from the following disclosure.