EP0096182B1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Coded surveillance system having magnetomechanical marker
Assignee: IDENTITECH Corp
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Filing: 1983-04-09
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Granted: 1989-03-15
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Expires: 2003-04-09
Abstract
Abstract A magnetic article surveillance system marker is adapted, when armed, to resonate at preselected frequencies provided by an incident magnetic field applied within an interrogation zone. The marker is a pluraliry of elongated ductile strips of magnetostrictive ferromagnetic material each of the strips being disposed adjacent to a ferromagnetic element which, upon being magnetized, magnetically biases the strips and arms them to resonate at the preselected frequencies. A substantial change in effective magnetic permeability of the marker at the preselected frequencies provides the marker with signal identity.
Inventors
- 👤 Philip Marron Anderson Iii
- 👤 James Edward Kearney
- 👤 Gerald Robert Bretts
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 13:17
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2408; G01; G01V; G01V15/00; G06; G06K; G06K19/00; G06K19/06; G06K19/067; G06K19/0672; G06K7/00; G06K7/08; G06K7/082; G06K7/083; G06K7/086; G08B13/2428; G08B13/2437; G08B13/2442; G08B13/2465; G08B13/2482; G08B13/2488
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
153 words
A marker (16) for use in a magnetic article surveillance system, said marker (16) comprising an elongated ductile strip (18) of ferromagnetic material to be subjected to an incident alternating magnetic field applied within an interrogation zone (12), in response to which magnetic field said marker (16) is adapted to generate a signal to be detected to indicate the presence of said marker (16) within said interrogation zone (12), characterized by said marker (16) comprising a plurality of elongated ductile strips (18) of magnetostrictive material adapted to be magnetically biased and thereby armed to resonate mechanically at preselected frequencies provided by said incident magnetic field, and to undergo a substantial change in effective magnetic permeability at said preselected frequencies that provides said marker with signal identity, each of said strips (18) having a magnetomechanical coupling factor, k, greater than 0, where f r and f a being the resonant and anti-resonant frequencies, respectively.
Claim 2
Dependent Claim
153 words
A marker (16) for use in a magnetic article surveillance system, said marker (16) comprising an elongated ductile strip (18) of ferromagnetic material to be subjected to an incident alternating magnetic field applied within an interrogation zone (12), in response to which magnetic field said marker (16) is adapted to generate a signal to be detected to indicate the presence of said marker (16) within said interrogation zone (12), characterized by said marker (16) comprising a plurality of elongated ductile strips (18) of magnetostrictive material adapted to be magnetically biased and thereby armed to resonate mechanically at preselected frequencies provided by said incident magnetic field, and to undergo a substantial change in effective magnetic permeability at said preselected frequencies that provides said marker with signal identity, each of said strips (18) having a magnetomechanical coupling factor, k, greater than 0, where f r and f a being the resonant and anti-resonant frequencies, respectively.
Claim 3
Dependent Claim
42 words
A marker as recited in claim 1, characterized in that each of said strips (18, 18') is disposed adjacent to a ferromagnetic element (44) which, upon being magnetized, magnetically biases said strips (18,18') and arms them to resonate at said preselected frequencies.
Claim 4
Dependent Claim
22 words
A marker as recited in claim 1 or 2, characterized in that said magnetostrictive ferromagnetic material is at least 50 percent amorphous.
Claim 5
Dependent Claim
119 words
A marker as recited in one of claims 1 to 3, characterized in that said material has a composition consisting ssentialy of the formula MgN b O e X d Y e Z,, where M is at least one of iron and cobalt, N is nickel, 0 is at least one of chromium and molybdenum, X is at least one of boron and phosphorous, Y is silicon, Z is carbon, "a""f"' are in atom percent, "a" ranges from about 35-85, "b" ranges from about 0-45, "c" ranges from about 0-7, "d" ranges from about 5-22, "e" ranges from about 0-15 and "f" ranges from about 0-2, and the sum of d + e + f ranges from about 15-25.
Claim 6
Dependent Claim
68 words
A marker as recited in one of the claims 1 to 4, characterized in that said strips (18, 18') are sandwiched betwee the faces of two pieces of fabric (75), each of said pieces of fabric (75) having planar dimensions greater than the corresponding aggregate dimensions of said strips (18, 18'), said pieces of fabric (75) being joined together at the edges thereof to form fabric sandwiched strips.
Claim 7
Dependent Claim
23 words
A marker as recited in claim 5, characterized in that said fabric sandwiched strips are disposed within an air-tight casing of polymeric film.
Claim 8
Dependent Claim
101 words
An article surveillance system responsive to the presence of at least one of a plurality of markers (16) within an interrogation zone (12), comprising: a) means (24, 22) for defining an interrogation zone (12); b) generating means (14) for generating a magnetic field having a frequency band within said interrogation zone (12) said generating means (14) including an interrogating coil (24); characterized by c) a plurality of markers (16) as recited in one of the claims 1 to 6; d) detecting means (22, 170) for detecting resonances of said markers (16) within said interrogation zone (12) at each different preselected frequency.
Claim 9
Dependent Claim
94 words
An article surveillance system as recited in claim 7, characterized in that said generating means (14) includes energizing means (201) for providing said interrogating coil (24) with an engerizing signal, said detecting means includes receiving means (202) for distinguishing a resonant frequency for each of said markers (16) detected by said receiving coil (22) from other frequencies induced therein and said system further includes synchronizing means (200) associated with said energizing means (201) and said receiving means (202) for sequentially activating and deactivating each of said energizing means (201) and said receiving means (202).
Claim 10
Dependent Claim
40 words
An article surveillance system as recited in claim 8, characterized in that said synchronizing means (200) is adapted to prevent activation of said receiving means (202) for substantially the entire period of time that said energizing means (201) is activated.
Claim 11
Dependent Claim
42 words
An article surveillance system as recited in claim 8 or 9, characterized in that said receiving means (202) is adapted to distinguish all resonant frequencies for each of said markers (16) detected by said receiving coil (22) from other frequencies induced therein.
References Cited (Backward Citations)
No citation records indexed.
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