Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1983-06-29
1987-09-15
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
29846, 333219, 428901, G08B 1324
Patent
active
046942831
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an identification device in the form of a tag-like strip affixable to an article and comprising at least one inductive member formed of flat conductor strips and one capacitive member formed of superposed conductor strip portions with a dielectric interposed therebetween, said capacitive member forming with the inductive member a closed resonant circuit.
Identification devices of this type have been known, for example, from German AS No. 2,826,861. They essentially contain an electrical parallel resonant circuit and are contemplated for generating characteristic signals permitting the identification thereof in a high frequency electromagnetic field. Such passive identification devices are used in production engineering for identifying work pieces, in analysis technololgy for identifying samples, as safeguarding means and as identifying sensors in articles' safeguarding systems, especially antitheft systems.
2. The Prior Art
If such devices are required in very large quantities the manufacturing costs are of essential significance to the economical use of the system. Conventional identification devices are manufactured, for example, by etching conductor strips out of metal foils applied on both sides of a flexible, electrically non-conductive carrier sheet, as described in the U.S. Pat. No. 3,913,219. The etched conductor strips form the required inductive member, while the capacitive member of the resonant circuit is formed by formed by opposed conductive areas and the interposed dielectric carrier sheet. In order to connect the conductor strips on the two sides of the carrier sheet so that together they cooperate to form an inductive member, contact through the carrier sheet is necessary. Furthermore, manufacturing methods requiring etching on both sides are very expensive and contacting through the carrier sheet requires a piece-by-piece check of each individual resonant unit.
SUMMARY OF THE INVENTION
It is the object of the invention to provide an identification device and a method for producing same which permit economical mass production so that the identification devices are disposable for one-time use. Furthermore, the identification devices should have close tolerances and a high degree of reliability and yet are to lend themselves to mass production at low cost.
This object is realized by an identification device of the type disclosed at the outset which, according to the invention, is characterized in that the conductor strips are arranged in at least two superposed areas formed by folding. Hence, the invention is based on the idea to arrange the windings of the inductive member in superposed relationship by so folding a conductor strip structure that the number of windings is virtually unlimited and the required distributed capacities can be provided by selective interposition of dielectric layers between conductor strip portions folded one onto the other. Since the conductor strips may be made extremely thin, a sufficiently high inductance and capacitance value can be reached and nevertheless the entire identification device is very thin. Therefore, the identification device can be made very flexible and in particular, it can be processed like a conventional paper, plastic or cardboard tag. Since the individual windings of the inductive member may be directly superposed, excellent magnetic coupling is achieved between the individual windings so that but minor leakage inductance occurs and thus precise transformation ratios of the distributed capacities contributing to the total effective resonant circuit capacitance can be maintained.
According to a preferred embodiment of the invention, the inductive and capacitive members are formed by folding together a conductor structure applied on a flexible electrically insulating carrier sheet which can be unfolded into a single plane. The structurally desired fold lines are marked by perforations, properly located and suitably located folding lines or the like. The condu
REFERENCES:
patent: 4311992 (1982-01-01), DeChant
patent: 4369557 (1983-01-01), Vandebult
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