EP1957735B1

EP1957735B1 - Magnetic detacher with open access

Info

Publication number: EP1957735B1
Application number: EP05852995A
Authority: EP
Inventors: Wing K. Ho
Original assignee: Sensormatic Electronics Corp
Current assignee: Sensormatic Electronics LLC
Priority date: 2005-12-01
Filing date: 2005-12-01
Publication date: 2011-03-23
Anticipated expiration: 2025-12-01
Also published as: CN101356331B; DE602005027133D1; CN101356331A; JP2009517771A; WO2007064339A1; CA2630681C; AU2005338679A1; HK1125985A1; JP5397803B2; ES2359324T3; EP1957735A1; AU2005338679B2; HK1161859A1; CA2630681A1; ATE503067T1

Abstract

Various embodiments of a magnetic detacher with open access are described. In one embodiment, the magnetic detacher may include a magnet assembly to provide open access to a hard tag and a magnetic field sufficient to disengage a clamping mechanism of the hard tag.

Description

BACKGROUND

An Electronic Article Surveillance (EAS) system is designed to prevent unauthorized removal of an item from a controlled area. A typical EAS system may comprise a monitoring system and one or more security tags. The monitoring system may create an interrogation zone at an access point for the controlled area. A security tag may be fastened to an item, such as an article of clothing. If the tagged item enters the interrogation zone, an alarm may be triggered indicating unauthorized removal of the tagged item from the controlled area. In general, the security tag must be deactivated before a tagged item can leave the controlled area without triggering the alarm.
Security tags may take a variety of forms including soft tags and hard tags. In general, soft tags are disposable and used only once, while hard tags are reusable. An example of a soft tag is an adhesive-backed security label. A soft tag may be deactivated by a deactivator unit, such as a scanner that uses a specific field to deactivate the soft tag when it touches or comes in close proximity to the soft tag.
Hard tags typically comprise a plastic tag body housing an EAS sensor and a locking mechanism including a pin or tack which passes through the item and is clamped to the tag body to secure the item and tag together. In general, a hard tag requires a detacher unit to remove the tack from the tag body and allow the item to be separated from the hard tag. In some applications, a detacher unit may include a magnet assembly which applies a magnetic field to the tag body for releasing the tack.

FIG. 1 illustrates a conventional hard tag 10 having a plastic tag body 11 formed with a protrusion 12. The tag body 11 houses an EAS sensor 13 for triggering an alarm. The hard tag 10 includes a tack 14 with an enlarged head 15. As shown, the tack 14 is securely held by a clamping mechanism 16 within the tag body 11.
FIG. 2 illustrates a conventional magnet assembly 20 for a detacher unit. The magnet assembly 20 includes a cylindrical magnet 21 and an oppositely magnetized ring magnet 22 stacked on top of the cylindrical magnet 21. As shown, the magnet assembly 20 includes a cavity 23 of approximately 6 to 7mm in depth. This configuration is well-suited for a conventional hard tag, such as hard tag 10, where the cavity 23 of the magnet assembly 20 is compatible with the protrusion 12 of the tag body 11. To permit the removal of the tack 14, the protrusion 12 is inserted into the cavity 23 to take advantage of the strong field inside the ring magnet 22. The magnet assembly 20 provides a substantially vertical magnetic field in the cavity 23 sufficient to force the clamping mechanism 16 to disengage and allow removal of the tack 14 from the tag body 11.

US 6,084,498 disclose a magnetic decoupler with a magnetic field shape, strength and gradient optimized for releasing security tags. The detacher disclosed in D1 comprises a magnet assembly for accessing a hard tag comprising a clamping mechanism and to provide a magnetic field sufficient to disengage said clamping mechanism of the tag, wherein the magnet assembly includes a quadrature magnet assembly and a ring magnet, arranged on top of the quadrature magnet assembly. Together with a steel cup covering both, the ring magnet and the quadrature magnet assembly, a closed magnetic detacher is provided which includes a cavity into which a nipple of a tag may be inserted.
US 5,063,934 discloses a permanent magnet assembly for creating a uniform magnetic field across a portion of an air gap. The magnet assembly includes a first principle magnet, a pole piece contacting said principal magnet and a set of auxiliary magnets extending about the periphery of the pole piece. The teaching includes the positioning of two such magnet groups in a test chamber. No use of such a device in combination with a magnetic detacher is disclosed.
In many tagging applications, such as tagging of bottles and compact discs, for example, the clamping mechanism of a hard tag may be embedded in the existing packaging of an item or may have a low profile to minimize vulnerability of defeats and facilitate shelving of items. For such applications and packaging requirements, a different detacher design is required to provide open access to the embedded or low profile clamping mechanism and, at the same time, providing a sufficient magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: illustrates a conventional hard tag.
FIG. 2: illustrates a conventional magnet assembly for a detacher unit.
FIG. 3: illustrates a magnetic detacher in accordance with one embodiment.
FIG. 4: illustrates a graph in accordance with one embodiment.
FIG. 5: illustrates a graph in accordance with one embodiment.

DETAILED DESCRIPTION

Numerous specific details may be set forth herein to provide a thorough understanding of the embodiments of the invention. It will be understood by those skilled in the art, however, that the embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the embodiments of the invention. It can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the invention.
It is worthy to note that any reference in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.
FIG. 3 illustrates one embodiment of a magnetic detacher 30. In this embodiment, the magnetic detacher 30 comprises a magnet assembly 31 including a cylindrical magnet 32 and a ring magnet 33. In various implementations, the cylindrical magnet 32 and the ring magnet 33 may comprise one or more permanent magnets. In general, permanent magnets have a defined magnetization axis dependent upon the magnetization process, orientation of the material, the geometry, and other material properties.
In various embodiments, the permanent magnets may comprise paramagnetic components such as samarium (Sm) and neodymium (Nd) and ferromagnetic components such as iron (Fe) and cobalt (Co). During the fabrication of permanent magnets, a crystalline domain structure may be created which exhibits oriented intra-domain magnetization known as magneto-crystalline anisotropy, which is the mechanism that produces strong magnetic fields. The permanent magnet may undergo processing including, for example, compression of components in the presence of an ambient magnetic field, sintering of the compressed material, and remagnetization.
Examples of permanent magnets include but are not limited Neodymium Iron Boron (NdFeB) magnets, hard ferrite magnets, and cobalt magnets such as Samarium Cobalt (SmCo) magnets and Aluminum Nickel Cobalt (AlNiCo) magnets. The permanent magnets may comprise sintered and/or bonded magnets. The permanent magnets also may include a variety of coatings to deter corrosion.
In various embodiments, the magnetic detacher 30 is structured and arranged to provide open access to various magnetic clamping mechanisms. As such, the magnetic detacher 30 is capable of disengaging the clamping mechanism of a hard tag placed at any angular position relative to its axis. In various implementations, the magnetic detacher 30 is configured to provide a relatively symmetric field about its axis making it usable for hard tag placed at any angular position.
In the embodiment shown in FIG. 3, for example, a top surface 34 of the cylindrical magnet 32 is substantially coplanar and concentric with a top surface 35 of the ring magnet 33. As shown, the cylindrical magnet 32 and the ring magnet 33 are substantially flush allowing a hard tag to be received in any direction. The magnetic detacher 30 thus provides open access to various magnetic clamping devices in hard tags. The embodiments are not limited in this context.
In some embodiments, the top surface 34 of the cylindrical magnet 32 may be slightly offset upwardly or downwardly from the top surface 35 of the ring magnet 33. For example, the top surface 34 of the cylindrical magnet 32 may offset by 2 to 3 mm higher or lower from the top surface 35 of the ring magnet 33. The embodiments are not limited in this context.
In various embodiment, the magnet assembly 31 comprises a ring magnet 33 that is magnetised radially. The ring magnet 33 may comprise, for example, multiple sections 36-1-n, where n represents a positive integer value and each of the multiple sections 36-1-n is magnetized in a direction pointing to the center of the ring magnet 33. In the embodiment shown in FIG. 3, for example, the ring magnet 33 is quartered into a first section 36-1, second section 36-2, third section 36-3, and fourth section 36-4. In FIG. 3, the white arrows indicate the orientation of magnetization. In this embodiment, for the top half of the ring magnet 33, magnetic flux is directed inwardly toward the center of the ring magnet 33 and bent upwardly and out of the ring magnet 33. The magnetic field of the ring magnet 33 adds to the upwardly pointing magnetic field generated by the core cylindrical magnet 32 resulting in a very strong magnetic field. In various implementations, the magnet assembly 31 provides a relatively symmetric field about its axis making the magnetic detacher 30 usable for a hard tag placed at any angular position. In some embodiments, soft iron material can be placed at the bottom of the magnet assembly 31 to achieve keeper effect and enhance the surface field.
In various embodiments, the ring magnet 33 may be divided into four or more sections with each magnet section magnetized in a direction pointing to the center of the ring magnet 33. It can be appreciated that with less than four sections, the ring magnet 33 may have substantial field variation so that the clamping mechanism can only be disengaged at specific angular positions.

TABLE 1 illustrates a comparison of magnetic surface fields in kilo-Gauss (kG) at the center on a cylindrical magnet for various magnet detacher configurations. The configurations may include a ring magnet having an inner diameter (ID), an outer diameter (OD), and height (h).

Magnetic Detacher Configuration	Ring Magnet Dimensions (mm)	Ring Magnet Volume (cc)	Surface Field (kG)
1. Cylindrical magnet only	NA	0 cc	5.424 kG
2. Ring magnet on cylindrical magnet	ID=15, OD=30, h=7	3.68 cc	7.068 kG
3. Ring magnet flush with cylindrical magnet	ID=24, OD=44, h=10	10.68 cc	6.426 kG
4. Ring magnet-flush with cylindrical magnet	ID=24, OD=44, h=12	12.82 cc	7.115 kG
5. Ring magnet flush with cylindrical magnet	ID=24, OD=59, h=10	22.82 cc	7.071 kG
6. Half ring magnet on cylindrical magnet	ID=15, OD=30, h=12	3.180 cc	6.161 kG

TABLE 1

As shown in TABLE 1, the detacher configuration using only a single cylindrical magnet provides a much lower surface field than the detacher configurations using a magnet assembly. To achieve open access with a single magnet configuration would require employing only a cylindrical magnet, for example, by removing the ring magnet 22 from the conventional magnet assembly 20. Such approach compromises the detaching field as the clamping mechanism must be designed to be opened by a weaker magnet and thus made more susceptible to defeat by a "street" magnet.
As also shown in TABLE 1, a similar field to that provided by the conventional detacher configuration using a ring magnet on a cylindrical magnet can be achieved with the appropriate choice of dimensions for a ring magnet that can fit over a cylindrical magnet. As such, the detacher configurations using a ring magnet flush with a cylindrical magnet provide open access and a sufficient field with the appropriate choice of magnet dimensions. For example, the height of the ring magnet (e.g., ring magnet 33) can be increased to 12 mm, or alternately, the outer diameter can be increased to about 60 mm to achieve a magnetic field level of about 7.1kG for such detacher configurations. In addition, the detacher configuration using a half ring magnet having a height of about 12 mm stacked on a cylindrical magnet also may provide a sufficient magnetic field while allowing open access from one side of the magnet assembly. The embodiments are not limited in this context.
FIG. 4 illustrates one embodiment of a graph 60 illustrating magnetic field level as a function of ring magnet height for various magnetic detacher configurations using a ring magnet flush with a cylindrical magnet. As shown, further field enhancement is possible with a larger magnet. The embodiments are not limited in this context.
FIG. 5 illustrates one embodiment of a graph 70 illustrating magnetic field level as a function of distance from the center of the magnet surface. As shown in the plot, various embodiments of the magnetic detacher have enhanced field projection as compared to the conventional magnet assembly. In such embodiments, the magnetic detachers have a longer field projection allowing the magnetic detachers to disengage the clamping mechanism of a hard tag at greater distances as compared to the conventional magnet assembly. The embodiments are not limited in this context.
The discussion and field values above are based on using grade 35 NdFeB magnets. If a higher grade of magnet such as a grade 50 NdFeB magnet is used, the magnetic field levels typically will increase by 10-15%. The embodiments are not limited in this context.
In various implementations, the described embodiments comprise a magnetic detacher to provide open access to various hard tags and a sufficiently strong magnetic field level for disengaging the clamping mechanism of such hard tags. The described embodiments may be employed in a variety of tagging applications, such as tagging of bottles and compact discs, for example, where the clamping mechanism of a hard tag is embedded in the existing packaging of an item or may have a low profile to minimize vulnerability of defeats and facilitate shelving of items.
In various implementations, the described embodiments avoid the need to use a high profile or protruding design in tagging applications such as tagging bottles and compact discs. The use of a protruding clamp on a slender package such as that of a compact disc, jewel case, or eyeglass wear is often problematic since the protruding clamp is prone to being snapped off or other tampering. The use of a protruding clamp also hinders efficient use of shelf space since the protrusion consumes space and makes stacking or arranging merchandise difficult.
In various implementations, the described embodiments comprise a magnetic detacher using a magnet assembly that provides a higher magnetic field level than a detacher configuration using only a single magnet. Such embodiments avoid the need to design the clamping mechanism of a hard tag to work with a weaker magnet which would lower defeat resistance.

LIST OF REFERENCE NUMBERS

10: hard tag
11: tag body
12: protrusion
13: EAS sensor
14: tack
15: head
16: clamping mechanism

20: magnet assembly
21: cylindrical magnet
22: ring magnet
23: cavity

30: magnetic detacher
31: magnet assembly
32: cylindrical magnet
33: ring magnet
34: top surface (cylindrical magnet)
35: top surface (ring magnet)

Claims

A magnetic detacher (30) comprising:
a magnet assembly (20) for accessing a hard tag (10) comprising a clamping mechanism (16) and to provide a magnetic field sufficient to disengage said clamping mechanism (16) of said hard tag (10), said detacher (30) comprising a ring magnet (22),
characterized in that
- a cylindrical magnet (21); and

- said ring magnet (22)
- - halving a top surface (35) coplanar with a top surface (34) of said cylindrical magnet (21) or

- - having a top surface with an offset up to 3 mm higher or lower from a top surface (34) of said cylindrical magnet (21);

- said ring magnet (22) is radially magnetized and comprises multiple sections and

- wherein each of said multiple sections is magnetized in a direction pointing to a center of said ring magnet (22).
The magnetic detacher (30) of claim 1, said ring magnet (22) comprising four or more sections.
The magnetic detacher (30) of claim 1, wherein magnet flux generated by said ring magnet (22) is directed inwardly toward a center of said ring magnet (22) and bent upwardly and out of said ring magnet (22).
The magnetic detacher (30) of claim 1, wherein a magnet field generated by said ring magnet (22) adds to a vertically pointing magnetic field generated by said cylindrical magnet (21).
The magnetic detacher (30) of claim 1, wherein said magnet assembly (20) provides a symmetric radial field about an axis of the magnet assembly.
The magnetic detacher (30) of claim 1, further comprising soft iron material placed at a bottom of said magnet assembly (20) to enhance the magnetic field.
The magnetic detacher (30) of claim 1, wherein said magnet assembly (20) comprises one or more permanent magnets.
The magnetic detacher (30) or claim 7, wherein said one or more permanent magnets comprises at least one of a NdFeB magnet, a hard ferrite magnet, a SmCo magnet, and a AINiCo magnet.
The magnetic detacher (30) of claim 1, wherein said ring magnet (22) comprises a height dimension greater than or equal to 10 mm.
The magnetic detacher (30) of claim 1, wherein said ring magnet (22) comprises an outer diameter dimension greater than or equal to 44 mm.
The magnetic detacher (30) of claim 1, wherein said magnet assembly (20) provides field projection.