Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1989-02-13
1991-03-19
Orsino, Joseph A.
Communications: electrical
Condition responsive indicating system
Specific condition
340572, G08B 1324
Patent
active
050014587
DESCRIPTION:
BRIEF SUMMARY
The problem of remote detecting of articles and objects has been the subject of numerous technical solutions, the best of which correspond to the capacity of the human eye.
One method of improving the reliability of prior art detecting systems comprises the steps of providing on each article or object a marker or label which is more readily detected than the object itself. Such a system is utilized in stores where articles provided with bar code labels automatically are detected and entered in the recording counter when passed one by one in front of a detecting unit. Similar methods are utilized in factories where products are assembled in different parts of the premises and transported therebetween by means of conveyers and the like. Markers on the products make it possible to direct them automatically through the factory to desired locations therein.
One of the problems with systems utilizing bar code labels is the necessity of bringing an intact and completly visiable label within a narrow field of a vision of the detecting device.
New developments in this technical field, see EP-A2-0 096 182, have brought forth a system responsive to the presence of at least one of a plurality of markers within an interrogation zone, comprising: within said interrogating zone; zone, each of said markers being characterized by a substantial change in its effective magnetic permeability at a different preselected frequency within said frequency band that provides each of said markers with signal identity; and interrogation zone at each different preselected frequency.
The markers of this system comprise a plurality of elongated ductile strips of magnetostrictive ferromagnetic material each of said strips being disposed adjacent to a ferromagnetic element which, upon being magnetized, magnetically biases said strips and arms them to resonate at said preselected frequencies, each of said strips having a magnetomechanical coupling factor, k greater than 0, where k=(1-f.sub.r.sup.2 /f.sub.a.sup.2), fr and fa being the resonant and anti-resonant frequencies, respectively.
A major problem of the system disclosed in EP--A2-0 096 182 is the difficulty of detecting and identifying several markers provided with a plurality of strips, the strips beeing taken from a finite number of such strips without mismatching strips belonging to different markers. This problem does not occur when the system is used with a highly limited number of different markers and no attention is paid to the case when two or more identical markers occur at the same time in the interrogation zone.
In the EP-A2-0 096 182 the bias field is provided by a hard ferromagnetic material, i.e. a permanent magnet, located proximate the strips so as to make possible deactivation of the marker by demagnetization of the magnet, thus altering the resonant frequencies and preventing detection.
A subject of the present invention is to make possible automatic remote identification of a practically indefinite number of separate objects in a set of objects without placing restrictions on the location and visibility of the individual objects. In this aspect the identification capacity is superior to the capacity of the human eye.
Accordingly the method according to the invention has been given the characteristics appearing from claim 1.
In order to explain the invention in more detail reference is made to the accompanying drawings, in which
FIG. 1 is a plan view of a marker comprising three strips of magnetostrictive material,
FIG. 2A is a perspective view of a detecting system for using the method according to the invention,
FIG. 2B is a perspective view of a cashier desk for use with the detecting system shown in FIG. 2A for using the method according to the invention,
FIG. 3 is a graph showing an interrogation signal applied to the interrogation zone,
FIG. 4 is a graph showing the detected signal over a preselected frequency range,
FIG. 5 is a graph depicting the magnetic field dependency of the resonant frequency for a strip containing an amorphous metal alloy,
FIG. 6 is a
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Persson Leif A.
Tyren Carl H.
Orsino Joseph A.
Sutcliffe Geoff
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