Communications: electrical – Condition responsive indicating system – Specific condition
Utility Patent
1999-04-12
2001-01-02
Trieu, Van T. (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S551000, C340S676000, C156S064000, C324S207240
Utility Patent
active
06169481
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to systems and materials for presence sensing, and in particular, to a low cost material with magnetizable filaments whose presence may be sensed remotely by an industrial control system.
In the manufacture of a multi-component product, for example, packaged pharmaceuticals intended for over-the-counter sale, it is important to verify that the package includes a paper insert listing the characteristics of the drug and instructions for safe use. While considerable care is taken in placing the insert into the package, ideally, its presence in the package could be verified after the package is sealed. One way of doing this is by weighing the package to detect the additional weight of the insert. For light inserts or products that vary in weight, such an approach is unreliable.
What is needed is a low cost method of sensing the presence of an insert or similar component of a product, after the product is sealed in a package.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a material incorporating a small percentage of filamentized magnetic material whose presence may be detectable at a distance. The material is versatile and of low cost and may be used for a wide variety of presence sensing applications including detection of critical product components in manufacture multi-component products such as packages as described above.
Specifically the material is formed of a non-magnetic matrix material in which is dispersed a plurality of magnetizable filaments. The filaments may represent a relatively low volume percentage of the matrix (for example, 0.1%) and the matrix material may be selected from a wide variety of non-magnetic materials including paper and plastic.
Thus it is one object of the invention to provide a method of remote sensing in which the material to be sensed is modified and an external tag is not needed. The low percentage of fibers and low cost of the fibers allow them to be directly incorporated into a variety of raw materials.
The filaments preferably have an aspect ratio that is quite large and, for example, may have a length of 3-6 mm and a diameter of 2-16 microns.
Thus it is another object of the invention to minimize the demagnetization effect, a bulk property of magnetic materials that resists their magnetization. The high aspect ratio allows the filaments to be easily magnetized by an external magnetic field, increasing the distance at which their presence may be sensed. This is in contrast to magnetic inks using granular magnetic materials which can only be detected at short range.
The filaments may be formed of a magnetically “soft” material with high permeability.
Thus it is another object of the invention to permit remote sensing of the filaments by detection of a distortion of magnetization field caused by magnetization of the filaments and/or their saturation. Measurement of distortion of an applied oscillating magnetic field provides an extremely sensitive detection technique.
A detection system for the material may include an oscillator producing a waveform at a fundamental frequency and any antenna structure connected to the oscillator for transmitting the waveform as a magnetic field to envelop the sensed material. An electronic detector connected to the antenna structure may detect a distortion in the waveform caused by the magnetization or saturation of the filaments in the applied field.
Thus it is another object of the invention to provide a sensing scheme that may work at considerable distance from the filaments, and that is indifferent to absolute magnetic signal strength which may vary depending on the distance between the sensed material and the antenna structure and the orientation of the sensed material. Because of their high permeability, the signal from the filaments is uniquely different from signals that could arise from other materials of lower permeability material such as from a conveyor belt or other incidental metal. Due to different frequencies being used, the signal is also different from power line fields and the like.
The antenna structure may be a Helmholtz coil pair positioned about the sensing target.
Thus it is another object of the invention to provide a simple antenna structure that transmits and receives electromagnetic signals uniformly over a volume. Sensitivity of the detector to variation in the location of the sensed object with respect to the antenna is thus reduced.
The detector may analyze the harmonic distortion of the waveform and may be phase sensitive to detect only distortion in phase with the driving waveform.
Thus it is another object of the invention to employ detection techniques that provide improved signal-to-noise ratio in the detected signal so to provide increased distance between the sensed material and the antenna structure of the detector.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessary represent the full scope of the invention, however, and reference must be made to the claims herein for interpreting the scope of the invention.
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Bradford Jonathan D.
Fooks Elik I.
Goldberg Ira B.
Hollingsworth Charles S.
Lucak Mark A.
Baxter Keith M.
Horn John J.
Rockwell Technologies LLC
Trieu Van T.
Walbrun William R.
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