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US5580664A
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Dual status thin-film eas marker having multiple magnetic layers
Assignee: 3M Co
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Filing: 1995-01-04
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Granted: 1996-12-03
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Expires: 2015-01-04
Abstract
Abstract A dual status marker for use with a magnetic-type EAS system has a signal-producing layer including at least one magnetic thin-film of high permeability and low coercive force such as permalloy, and a signal-blocking layer including at least one remanently magnetizable thin-film such as an Fe-Cr alloy. The remanently magnetizable thin-film or thin-films should have a total thickness at least equal to, and preferably at least twice, the total thickness of the magnetic thin-film or thin-films of high permeability. By doing so, the marker is more reliably deactivated when the signal-blocking layer is magnetized. For even greater assurance of deactivation, the signal-blocking layer should include more than one remanently magnetizable thin-film, thus giving it a squarer B-H loop and greater assurance against false alarms.
Inventors
- 👤 Ching-Long Tsai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 18:38
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2408; G08B13/2411; G08B13/2428; G08B13/2437; G08B13/2442; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/12; Y10T428/12465; Y10T428/12493; Y10T428/12535; Y10T428/31504; Y10T428/31678
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
146 words
A dual status marker for use with a magnetic electronic article surveillance system, which system produces in an interrogation zone alternating magnetic fields having average peak intensities of less than 20 Oersteds, the dual status marker comprising: a signal-producing layer having a differential permeability above 5000 and a coercive force less than the average peak intensities encountered in the interrogation zone, such that upon exposure to the alternating magnetic fields, the magnetization state of the signal-producing layer is periodically reversed thus producing an alarm signal; and a signal-blocking layer in substantial contact with the signal-producing layer, the signal-blocking layer comprised of a plurality of remanently magnetizable deposition film layer, the signal blocking layer further having a coercivity above 25 Oe and providing magnetic flux such that the signal-producing layer is prevented from producing the alarm signal in the interrogation zone when the signal-blocking layer is magnetized.
Claim 2
Dependent Claim
146 words
A dual status marker for use with a magnetic electronic article surveillance system, which system produces in an interrogation zone alternating magnetic fields having average peak intensities of less than 20 Oersteds, the dual status marker comprising: a signal-producing layer having a differential permeability above 5000 and a coercive force less than the average peak intensities encountered in the interrogation zone, such that upon exposure to the alternating magnetic fields, the magnetization state of the signal-producing layer is periodically reversed thus producing an alarm signal; and a signal-blocking layer in substantial contact with the signal-producing layer, the signal-blocking layer comprised of a plurality of remanently magnetizable deposition film layer, the signal blocking layer further having a coercivity above 25 Oe and providing magnetic flux such that the signal-producing layer is prevented from producing the alarm signal in the interrogation zone when the signal-blocking layer is magnetized.
Claim 3
Dependent Claim
31 words
A dual status marker as defined in claim 1 wherein said plurality of remanently magnetizable deposition films comprises an Fe-Cr alloy having a Cr content up to about 20 atomic percent.
Claim 4
Dependent Claim
28 words
A dual status marker as defined in claim 2 wherein the Cr content of said plurality of remanently magnetizable deposition films is from 1 to 15 atomic %.
Claim 5
Dependent Claim
33 words
A dual status marker as defined in claim 1 wherein said plurality of remanently magnetizable deposition films has a total thickness from 2 to 5 times the total thickness of the signal-producing layer.
Claim 6
Dependent Claim
27 words
A dual status marker as defined in claim 1 wherein the total thickness of the plurality of remanently magnetizable deposition films is from 0.8 to 1.2 μm.
Claim 7
Dependent Claim
17 words
A dual status marker as defined in claim 1 wherein the remanently magnetizable deposition films are discontinuous.
Claim 8
Dependent Claim
92 words
A control element which affords dual status to a marker having a signal-producing layer that produces an alarm signal when the marker is passed through an interrogation zone of a magnetic electronic article surveillance system, the control element comprising: a plurality of remanently magnetizable deposition film layer having a coercivity above 25 Oe and providing magnetic flux such that, when placed in substantial contact with the signal-producing layer, the signal-producing layer is prevented from producing the alarm signal in the interrogation zone when the plurality of remanently magnetizable deposition films are magnetized.
Claim 9
Dependent Claim
92 words
A control element which affords dual status to a marker having a signal-producing layer that produces an alarm signal when the marker is passed through an interrogation zone of a magnetic electronic article surveillance system, the control element comprising: a plurality of remanently magnetizable deposition film layer having a coercivity above 25 Oe and providing magnetic flux such that, when placed in substantial contact with the signal-producing layer, the signal-producing layer is prevented from producing the alarm signal in the interrogation zone when the plurality of remanently magnetizable deposition films are magnetized.
Claim 10
Dependent Claim
25 words
A marker-deactivating product as defined in claim 7 wherein said plurality of remanently magnetizable thin-films have a total thickness of from 0.8 to 1.2 μm.
Claim 11
Dependent Claim
26 words
A dual status marker as defined in claim 1 wherein the signal-blocking layer further comprises alternating layers of remanently magnetizable deposition films and non-magnetic deposition films.
Claim 12
Dependent Claim
28 words
A dual status marker as defined in claim 9 wherein discontinuities of the at least one remanently magnetizable deposition film are segments of substantially uniform size and shape.
Claim 13
Dependent Claim
25 words
A dual status marker as defined in claim 10 wherein each of the segments has an area of from 1 to 100 mm 2 .
Claim 14
Dependent Claim
23 words
A dual status marker as defined in claim 1 further including a substrate adapted to support the signal-producing layer and the signal-blocking layer.
Claim 15
Dependent Claim
16 words
A dual status marker as defined in claim 12 wherein the substrate is a flexible web.
Claim 16
Dependent Claim
22 words
A dual status marker as defined in claim 12 wherein the substrate comprises an article that is to be protected against theft.
Claim 17
Dependent Claim
23 words
A dual status marker as defined in claim 1 wherein the marker has an area of from 2 to 10 cm 2 .
Claim 18
Dependent Claim
24 words
A dual status marker as defined in claim 12 wherein each of the nonmagnetic deposition films is no greater than 20 nm in thickness.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-12-03 | 2000-06-03 | 2000-12-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-12-03 | 2004-06-03 | 2004-12-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-12-03 | 2008-06-03 | 2008-12-03 | $7700.00 | Window Closed / Lapsed |