Patent Application
20070234525
The present invention relates to cable ties that can be easily found in the event that they unintentionally enter a product or a process stream. The cable ties are made from compositions that include plastic resins and detectable materials. These detectable materials are metal particles and compounds, which allow the cable ties to be easily detected using different types of detection equipment. Typically, the metal particles and compounds are mixed with the plastic resins to provide a composition which is then formed into a cable tie using processes well know to those of ordinary skill in the art.
Detection of failed cable ties or their severed components is an important issue in various industries and the present invention addresses this issue by providing a cable tie made from compositions with density and X-ray identifiable characteristics that make it easier to detect the cable tie. These characteristic are present in the cable tie materials and do not come from a device attached to the cable tie. This reduces the manufacturing costs and assembly time to a minimum. This also allows portions of a cable tie to be detected since all of the material in the cable tie is made from the detectable composition. Thus, even relatively small portions of the cable tie can be detected in a product stream.
As used in the disclosure of the present invention, metal detection means include devices that measure or sense magnetism, whereas, X-ray devices include those that detect irregularities in density in the product stream. The purpose of the present invention is to devise a cable tie composition that includes components that can be readily detected and located by either system.
As used in the present application, the term “cable tie” is intended to include cable ties as well as cable tie accessories, such as mounting bases, identification tags, markers, and other clamps, clips and retainers normally associated with cables or cable ties. Such cable ties and cable tie accessories are sold by Thomas & Betts Corporation under its TY-RAP® brand name. Moreover, the term “cable tie” as used herein is not limited to ties that are used with bundled wires and cables, but also refers to any type of plastic tie which includes a strap and a locking head on opposing ends or which has opposing ends that can be attached together to form a closed loop. Examples of such ties are found in U.S. Pat. No. 3,186,047 to Schwester et al.; U.S. Pat. Nos. 5,621,949 and 5,630,252 to Wells; U.S. Pat. Nos. 6,076,235; 6,128,809; and 6,185,791 to Khokhar; U.S. Pat. No. 7,017,237 to Magno, Jr. et al.; and U.S. Des. 205,940 to Miller. All of which are incorporated herein in their entirety. However, the examples in these patents are not intended to limit the construction of the term “cable tie” as used herein in any way.
The cable ties of the present invention are formed from plastic materials, as well as metal particles and one or more X-ray detectable compounds. The addition of metal particles and a compound to the plastic materials provides a cable tie that can be easily detected using either X-ray, metal detection devices, sonar, optics, visually or other like systems. Preferably, the metal particles and compounds are blended with the plastic material so that, when the cable ties are formed, the metal particles and compounds are fully disbursed or distributed throughout the cable tie. In preferred embodiments, the metal particles make up at least 0.3% by weight of the composition and as much as 25% by weight of the composition, and the one or more compounds make up at least 0.5% by weight of the composition and as much as 15% by weight of the composition. In more preferred embodiments, the metal particles make up from about 2% to about 15% by weight of the composition and the one or more compounds make up from 1% to about 10% by weight of the composition.
Ideally, the metal particles and the compound are combined with one or more plastic resins to form the composition prior to forming the cable tie. The composition is heated to a temperature high enough to allow the cable ties to be formed using extrusion or molding processes. Typically, the temperature corresponds to the melting temperature of the plastic resin or the blend of plastic resins that make up the composition. Those of ordinary skill in the art relating to extrusion or molding processes are familiar with the required processing temperatures of different plastic materials.
The plastic resins that can be used in the compositions of the present invention are polypropylene, polycarbonate, polyethylene terephthalate (PET), polyethylene, fluoropolymers and polyamide, preferably nylon and most preferably nylon 6,6, nylon 6,12 or nylon 11. Polypropylene and polyamide resins are preferred, polypropylenes because they can be easily mixed with metal particles and compounds and polyamides because they form particularly strong and durable cable ties.
Cable ties formed from plastic resins, whether they are of one-piece or two-piece construction, are generally identified or referred to in the industry as nylon or plastic cable ties (for any plastic material other than nylon). Depending on the plastic resin that is used, the density of the cable ties formed from the resins can vary widely and have different properties and performance characteristics. Consequently, cable ties, or portions of cable ties, that inadvertently enter a product stream can sink to different depths in the stream depending in part on the density of the cable tie materials and the density of the process stream material.
The metal particles can be ferrous, implying some iron therein, or non-ferrous, which would include such materials as stainless steel, aluminum or copper. Where magnetism is the method used to detect the foreign material, ferrous metals are preferred. Preferred metal particles are resistant to rusting or corrosion due to the environment in which the cable tie is used. Such corrosion is more likely to occur in extreme wash-down areas. Therefore, the materials used in the cable ties and the method used to form the cable ties are selected to minimize or avoid deterioration due to such applications. The metal and plastic materials should be selected to provide maximum resistance to corrosion and/or deterioration due to vapors, fumes or exposure to certain chemical or other conditions found at a facility. Thus, the composition of the detectable cable ties is dictated by the specific applications to insure optimal performance.
The metal particles should be no more than about 25% by weight of the cable tie, more preferably less than about 15% by weight, to minimize the occurrence of cracking when the cable tie is wrapped around a bundle of wires. At the same time, a sufficient amount of the metal particles must be added to the plastic resin so that the cable ties can be easily detected. It has been found that the cable ties must contain at least 0.3% by weight metal particles in order to be easily detectable, preferably at least 2% by weight and most preferably at least 5% by weight. Thus, a cable tie containing metal particles dispersed in the cable tie material in a range of 0.3% to 25% by weight is contemplated by this invention, and preferably in the range of 2% to 15% by weight. Other ranges within these limits are also suitable. Coated and or encapsulated metal particles are well known in the art and are disclosed in U.S. Pat. No. 5,198,137 to Rutz et al.; U.S. Pat. No. 5,395,695 to Shain et al.; U.S. Pat. Nos. 5,472,661 and 5,629,092 to Gay; and U.S. Pat. No. 5,679,402 to Lee. All of these references with respect to their teachings of plastic coated metal particles are incorporated herein in their entirety.
The compounds of the present invention are contrast agents, i.e. materials which strongly absorb X-ray radiation and, therefore, can be easily detected by X-rays. The contrasting compounds should be no more than about 15% by weight of the cable tie, more preferably less than about 10% by weight. X-rays are a form of electromagnetic radiation with a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 to 30,000 PHz (1015 hertz). X-rays are primarily used for diagnostic radiography and crystallography. However, it has been found that a small amount of particular compounds added to plastic cable tie material prior to molding acts as a contrast agent for X-ray detection. This allows cable ties formed in this manner to be easily detected using X-ray detection devices.
The contrasting compounds of the present invention are used as a marker in the plastic cable tie material so that the ties can be easily detected and located in a product or process stream. Every metal absorbs X-rays to some extent depending on the atomic number and the thickness. The contrasting compounds are selected for their ability to be easily detected by X-ray detection devices when present in small amounts. Thus, the ability to detect cable ties containing these contrasting compounds using X-ray equipment is greatly enhanced. It has been found that only a slight amount of a contrasting compound is required to increase the detectability of the cable tie using X-ray devices. Preferred contrasting compounds include iodine and barium compounds, which are easy to detect using X-ray equipment and are widely used in the medical field. The most preferred compound is barium sulfate, which typically is provided in the form of an insoluble white powder. The more barium sulfate in a composition, the more “dense” the X-ray effect, i.e. the greater the X-ray signature. It has been found that adding barium sulfate in an amount of at least 0.5% by weight of the cable tie material increases the detectability of the cable tie and, when barium sulfate is added in an amount of at least 3% by weight of the cable tie material, the cable ties can be easily detected.
The compound and the metal particles are combined with the plastic resin (or resins) prior to molding the cable tie to ensure even distribution of the component materials. The amount of compound and the amount of metal particles added to a plastic cable tie material can vary provided that the strength and flexibility of the cable tie is not compromised. Accordingly, the amounts of compound and the amount of metal particles added are particularly dependent upon the properties and processing characteristics of the specific plastic resins that are used.
The preferred method for forming the cable ties of the present invention includes combining metal particles, a compound and plastic material to form a composition. The composition is then heated to melt the plastic material. Because different plastic materials have different melt temperatures, the temperature to which the composition is heated will vary according to the plastic (or plastics) that are being used. The heated composition is then formed into cable ties using any of the well known methods for forming cable ties. In preferred embodiments, the formation of the cable ties includes either extrusion or molding steps. After the cable ties are formed, they are cooled, preferably to room temperature.
The metal particles are preferably metal flakes and most preferably metal flakes in a plastic carrier. The metal flakes are added to a plastic carrier so that they can be more easily processed with the plastic material in conventional plastic processing equipment, such as extruders and molding machines. Any plastic that is compatible with the plastic material used to form the cable ties can be used as the plastic carrier. The preferred plastic carriers are polyamides, polyethylenes and polypropylenes. In the most preferred embodiments, the melting temperature of the plastic carrier is greater than the melting temperature of the plastic material. When the cable ties are formed, the composition is heated to a temperature greater than the melting temperature of the plastic material, but lower than or equal to the melting temperature of the plastic carrier. In preferred embodiments, the melting temperature of the plastic material is lower than the melting temperature of the plastic carrier. This keeps the metal particles entrained in the plastic carrier and prevents them from falling to the bottom of the composition during processing.
While select preferred embodiments of this invention are illustrated, various modifications may occur to those skilled in the art. Therefore, it is to be understood that these modifications are incorporated within the embodiments of the present invention as if they were fully illustrated and described herein.
The examples set forth below serve to provide further appreciation of the invention but are not meant in any way to restrict the scope of the invention.
In this example, a formulation was prepared that contained:
After the cable ties cooled, one of the ties was placed on a table and scanned with a metal detecting device manufactured by Thermo Electron Corporation, Waltham, Mass., which was set to detect metal particles at 0.170 cm/ferrous sphere. The metal detector indicated that the cable tie contained metal. This confirmed that the cable ties could be detected using a metal detecting device. The cable tie was then X-rayed with an X-ray device manufactured by Smith-Heimann, Eagle FA detector. The X-ray showed that the cable tie provided a clear X-ray image.
Thus, while there have been described the preferred embodiments of the present invention, those skilled in the art will realize that other embodiments can be made without departing from the spirit of the invention, and it is intended to include all such further modifications and changes as come within the true scope of the claims set forth herein.
This application claims priority from provisional application Ser. No. 60/789,361, filed on Apr. 5, 2006, which is incorporated herein in its entirety. This application also incorporates in their entirety U.S. application Ser. No. ______, filed on December ______, 2006 titled “Buoyant Detectable Cable Tie” and U.S. application Ser. No. ______, filed on Dec. 13, 2006 titled “Cable Ties Authentically Verifiable.”
| Number | Date | Country | |
|---|---|---|---|
| 60789361 | Apr 2006 | US |
