EAS marker deactivation device having core-wound energized coils

• US 6,060,988 A
• Filed: 01/30/1998
• Issued: 05/09/2000
• Est. Priority Date: 02/03/1997
• Status: Expired due to Term

• Current Assignee: Tyco Fire & Security GmbH (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Copeland, Richard L., Coffey, Kevin R.
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US09/016,175
• Time in Patent Office: 830 Days
• Field of Search: 340/572.1, 340/572.2, 340/572.7, 340/551, 340/572.3, 335/284, 361/149, 361/267, 343/742
• US Class Current: 340/572.1
• CPC Class Codes: G08B 13/2411 Tag deactivation
• CPC Class Codes: G08B 13/242 Tag deactivation

Abstract

A device for deactivating a magnetomechanical EAS marker includes a coil and circuitry for energizing the coil to generate an alternating magnetic field. The coil is wound around a magnetic core. The core may be cruciform with four arms, on each of which a respective coil is provided. Alternatively, the core may be generally square and planar, with two coils wound around the core in different respective directions.

Claims

1. In a device for deactivating a magnetomechanical EAS marker, the device including a coil and means for energizing the coil to generate an alternating magnetic field, the improvement comprising a magnetic core around which the coil is wound, wherein said core is cruciform and has four arms, and a respective coil is positioned on each of said arms, and

wherein said means for energizing includes means for energizing the respective coils on an opposed pair of said four arms, only during a first sequence of time intervals, and for energizing the respective coils on another opposed pair of said four arms, only during a second sequence of time intervals interleaved with said first sequence of time intervals.

2. The invention according to claim 1, wherein said core is formed of a material selected from the group consisting of powdered metal, cast iron, silicon steel and carbon steel.

3. In a device for deactivating a magnetomechanical EAS marker, the device including a coil and means for energizing the coil to generate an alternating magnetic field, the improvement comprising a magnetic core around which the coil is wound, wherein said core is generally square and planar, and has two coils wound thereon, said two coils having respective axes that are orthogonal to each other.

4. The invention according to claim 3, wherein the respective axes of the coils are parallel to the plane of the core.

5. The invention according to claim 3, wherein said means for energizing includes means for energizing a first one of the two coils, only during a first sequence of time intervals, and for energizing the other of the two coils, only during a second sequence of time intervals interleaved with said first sequence of time intervals.

6. The invention according to claim 3, wherein at least one of said coils is wound in a plurality of layers around said core, said layers including an innermost layer and another layer, said innermost layer being nearer to the core than said another layer, said innermost layer being formed of a larger number of turns than said another layer.

7. The invention according to claim 6, wherein said at least one of the coils is wound in three layers consisting of an innermost layer, an intermediate layer, and an outermost layer;

said innermost layer being nearer to the core than said intermediate layer, said intermediate layer being nearer to the core than said outermost layer;

said innermost layer being formed of a larger number of turns than said intermediate layer, said intermediate layer being formed of a larger number of turns than said outermost layer.

8. In a device for deactivating a magnetomechanical EAS marker, the device including a coil and means for energizing the coil to generate an alternating magnetic field, the improvement comprising a magnetic core around which the coil is wound, wherein said coil is wound in a plurality of layers around said core, said layers including an innermost layer and another layer, said innermost layer being nearer to the core than said another layer, said innermost layer being formed of a larger number of turns than said another layer.

9. Apparatus for deactivating a magnetomechanical marker, comprising:

a magnetic core;

at least two coils wound around said magnetic core;

first means for energizing a first one of said coils only during a first sequence of time internals and not during a second sequence of time intervals interleaved with said first sequence of time intervals; and

second means for energizing a second one of said coils only during said second sequence of time intervals and not during said first sequence of time intervals.

10. Apparatus according to claim 9, wherein said first coil has an axis of winding that is perpendicular to an axis of winding of said second coil.

11. Apparatus according to claim 10, wherein said core is cruciform and has four arms, said at least two coils including four coils, each positioned on a respective one of said four arms of said core.

12. Apparatus according to claim 11, wherein, only during said first sequence of time intervals, said first means energizes two of said coils, which are respectively positioned on an opposed pair of said arms of said core;

and, only during said second sequence of time intervals, said second means energizes the coils positioned on the other arms of said core.

13. Apparatus according to claim 10, wherein said core is generally square and planar;

said first coil being wound around said core with an axis of said first coil parallel to the plane of said core, and said second coil being wound around said core with an axis of said second coil parallel to the plane of said core and perpendicular to the axis of said first coil.

14. Apparatus according to claim 10, wherein said at least two coils wound around said core include a first pair of coils energized by said first means only during said first sequence of time intervals and a second pair of coils energized by said second means only during said second sequence of time intervals.

15. Apparatus according to claim 14, wherein the coils of said first pair of coils have respective axes that are parallel to each other and the coils of said second pair of coils have respective axes that are parallel to each other and are perpendicular to the axes of the first pair of coils.

16. Apparatus according to claim 14, wherein the coils of said first pair of coils have a common axis, and the coils of said second pair of coils have a common axis that is perpendicular to the common axis of the first pair of coils.

19. A method of deactivating a magnetomechanical EAS marker, comprising the steps of:

providing a coil wound around a magnetic core, said providing including providing two coils wound around said core;

energizing said coil to generate an alternating magnetic field, said energizing including inducing respective alternating currents in said two coils such that the alternating currents are substantially 90°

out of phase with each other; and

moving said EAS marker through said alternating magnetic field to degauss a control element of said marker.

17. A method according to claim 19, wherein said energizing step further includes energizing one of said coils only during a first sequence of time intervals and energizing another of said coils during a second sequence of time intervals interleaved with said first sequence of time intervals.

18. A method according to claim 17, wherein said providing step includes providing four coils wound around said core.

20. A method of manufacturing a device for deactivating magnetomechanical EAS markers, comprising the steps of:

providing a magnetic core, said magnetic core being planar and square;

winding a first length of conductive wire on said core in a first direction to form a first coil; and

winding a second length of conductive wire on said core in a second direction to form a second coil, said second direction being perpendicular to said first direction and said second coil being wound over said first coil.

21. A method according to claim 20, wherein said core is formed of a material selected from the group consisting of powdered metal, cast iron, silicon steel and carbon steel.

22. A method of deactivating a magnetomechanical electronic article surveillance marker, comprising the steps of:

providing a first coil wound on a core;

providing a second coil wound on said core;

first energizing said first coil only on a plurality of first occasions and not during a plurality of second occasions different from said first occasions to induce in said first coil an alternating current;

second energizing said second coil only on said plurality of second occasions and not on said plurality of first occasions to induce in said second coil an alternating current; and

during a period of time that corresponds to at least one of said first occasions and at least one of said second occasions, sweeping said magnetomechanical marker in proximity to said coils to demagnetize a bias element included in said marker.

23. A method according to claim 22, wherein at least two of said first occasions and at least two of said second occasions take place within a period of one second.

24. Apparatus for deactivating an electronic article surveillance marker, comprising:

a magnetic core;

two coils wound around said magnetic core, said two coils comprising a first coil and a second coil; and

drive means for energizing said coils, said drive means operating in a first mode in a first sequence of time intervals and in a second mode in a second sequence of time intervals interleaved with said first sequence of time intervals, said drive means driving said first coil with an alternating current in said first mode and not driving said second coil in said first mode, said drive means driving said second coil with an alternating current in said second mode and not driving said first coil in said second mode.

25. Apparatus according to claim 24, further comprising a housing in which said coils are housed.

26. Apparatus according to claim 25, wherein said drive means is housed in said housing.

27. Apparatus according to claim 24, wherein a plurality of said time intervals of said first sequence and a plurality of said time intervals of said second sequence take place within a period of one second.

28. A method of deactivating a magnetomechanical electronic article surveillance marker, comprising the steps of:

providing a first coil wound on a first core;

providing a second coil wound on a second core;

first energizing said first coil only on a plurality of first occasions and not during a plurality of second occasions different from said first occasions to induce in said first coil an alternating current;

second energizing said second coil only on a plurality of second occasions and not on said plurality of first occasions to induce in said second coil an alternating current; and

during a period of time that corresponds to at lease one of said first occasions and at least one of said second occasions, sweeping said magnetomechanical marker in proximity to said coils to demagnetize a bias element included in said marker.

29. A method according to claim 28, wherein said plurality of first occasions and said plurality of second occasions take place within a period of one second.

30. Apparatus for deactivating an electronic article surveillance marker, comprising:

a first magnetic core;

a first coil wound around said first magnetic core;

a second magnetic core;

a second coil wound around said second magnetic core; and

drive means for energizing said coils, said drive means operating in a first mode in a first sequence of time intervals and in a second mode in a second sequence of time intervals interleaved with said first sequence of time intervals, said drive means driving said first coil with an alternating current in said first mode and not driving said second coil in said first mode, said drive means driving said second coil with an alternating current in said second mode and not driving said first coil in said second mode.

31. Apparatus according to claim 30, further comprising a housing in which said coils are housed.

32. Apparatus according to claim 31, wherein said drive means is housed in said housing.

33. Apparatus according to claim 30, wherein a plurality of said time intervals of said first sequence and a plurality of said time intervals of said second sequence take place within a period of one second.

34. Apparatus for deactivating an electronic article surveillance marker, comprising:

a magnetic core;

two coils wound around said magnetic core; and

drive means for energizing said coils, said drive means inducing respective alternating currents in said two coils such that the alternating currents are substantially 90°

out of phase with each other.

35. Apparatus for deactivating an electronic article surveillance marker, comprising:

a first magnetic core;

a first coil wound around said first magnetic core;

a second magnetic core;

a second coil wound around said second magnetic core; and

drive means for energizing said coils, said drive means inducing respective alternating currents in said first and second coils such that the alternating currents are substantially 90°

out of phase with each other.