n/a
The present invention relates generally to a detachment method and magnetic detacher for electronic article surveillance (“EAS”) tags and more specifically to a method and system for optimizing the field profile of a high strength magnetic detacher.
Electronic Article Surveillance (“EAS”) systems are designed to prevent unauthorized removal of an item from a controlled area. A typical EAS system may include 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. A security tag is deactivated before a tagged item can leave the controlled area without triggering the alarm.
As is known in the art, security tags (also referred to as labels) for EAS systems can be constructed in any number of configurations. The desired configuration of the tag or label is often dictated by the nature of the article to be protected. For example, an EAS label may be enclosed in a rigid housing which can be secured to the monitored item, such as hard tags containing EAS labels which are commonly attached to clothing in retail stores. Some EAS hard tags typically include a plastic tag body which houses 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. Generally, theses tags require a detacher unit to remove the tack from the tag body and allow the item to be separated from the 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.
As is shown in
The high field strength magnet assembly 32 includes a cylindrical core magnet 34 and an oppositely magnetized ring magnet 36 stacked on top of the cylindrical core magnet 34 in order to maximize the axial magnetic field in proximity of a cavity 38 of the ring magnet 36. To permit the removal of the tack 18, the protrusion 24 of the EAS tag 10 or other magnetic securing device is inserted into the cavity 38 to take advantage of the strong field inside the ring magnet 36. The magnet assembly 32 provides a substantially vertical magnetic field in the cavity 38 sufficient to force the clamping mechanism 22 to disengage and allow removal of the tack 18 from the tag body 12.
Many different types of magnetic clamping mechanisms 22 are used in a variety of EAS tags and other magnetic securing devices. For example, one such clamping mechanism 22 is shown in
Other magnetic clamping mechanisms 22 may use different locking devices, but the principle operation of the magnetic detacher unit 26 remains the same as described above. To disengage a particular EAS tag 10 or other magnetic securing device, the high field strength magnet assembly 32 must present the needed magnetic field strength at the exact location of the implemented clutch 40. Because the field strength of the magnet assembly 32 decreases quite rapidly as the distance away from the magnet assembly increases, much stronger magnets than needed are often used in constructing the magnetic detacher unit 26. Stronger magnets introduce additional cost into manufacturing the magnetic detacher unit 26.
Additionally, the security tags used in an EAS system are replaced over time due to theft, loss, or normal wear and tear. For example, a sales clerk may forget to remove the EAS tag 10 from a purchased item. The security tags designed to be used in conjunction with a specific EAS system having a particular magnetic detacher unit 26 may be replaced with cheaper, “knock-off” EAS tags often provided by sub-standard manufacturers. These “knock-off” tags may not meet the requirements of the EAS system, provide a risk of unauthorized removal and do not, necessarily, have the magnetic clamping mechanism 22 at the same position of the original manufacturer's EAS tag 10. Often these “knock-off” tags may be easily detached using a single magnet, essentially rendering the protection offered by the EAS system practically worthless.
Therefore, what is needed is a system and method for optimizing the field profile of a high strength magnetic detacher in order to achieve maximum field strength at particular location.
The present invention advantageously provides a method and system for optimizing the field profile of a high strength magnetic detacher in order to achieve maximum field strength at particular location.
In accordance with one aspect, the present invention provides a magnetic detacher in which a housing defines an inner volume in which is positioned a core magnet and a ring magnet. The core magnet has a body with a top surface and a bottom surface opposite the top surface. The core magnet produces a first magnetic field. The ring magnet defines a cavity having a first diameter. The ring magnet has a top surface, a bottom surface opposite the top surface. The ring magnet produces a second magnetic field and is axially aligned with the core magnet such that the first magnetic field opposes the second magnetic field along the bodies of the respective magnets and enhances the second magnetic field within the cavity. The top surface of the core magnet is separated from the bottom surface of the ring magnet by a predetermined distance to produce a resultant magnetic field having a first resultant field strength at a specific position that is greater than a second resultant field strength produced at the same position when the top surface of the core magnet abuts the bottom surface of the ring magnet.
In accordance with another aspect, the present invention provides a magnet assembly for use in a magnetic detacher in which the magnet assembly has a core magnet has a body with a top surface and a bottom surface opposite the top surface. The core magnet produces a first magnetic field. A ring magnet defines a cavity having a first diameter. The ring magnet has a body with a top surface and a bottom surface opposite the top surface. The ring magnet produces a second magnetic field and is axially aligned with the core magnet such that the first magnetic field opposes the second magnetic field along the bodies of the respective magnets and enhances the second magnetic field within the cavity. The top surface of the core magnet is separated from the bottom surface of the ring magnet by a predetermined distance to produce a resultant magnetic field having a first field strength at a specific position that is greater than a second field strength produced at the same position when the top surface of the core magnet abuts the bottom surface of the ring magnet.
In accordance with yet another aspect, the present invention provides a method for detaching a magnetic securing device from an item. The magnetic securing device is secured by a clutch mechanism engaging a magnetic locking mechanism. The magnetic securing device is received in a magnetic electronic article surveillance tag detacher in which the magnetic electronic article surveillance tag detacher includes a core magnet and a ring magnet. The core magnet has a body with a top surface and a bottom surface opposite the top surface. The core magnet produces a first magnetic field. The ring magnet defines a cavity having a first diameter. The ring magnet has a body with a top surface and a bottom surface opposite the top surface. The ring magnet produces a second magnetic field and is axially aligned with the core magnet such that the first magnetic field opposes the second magnetic field along the bodies of the respective magnets and enhances the second magnetic field within the cavity. The top surface of the core magnet is separated from the bottom surface of the ring magnet by a predetermined distance to produce a resultant magnetic field having a first resultant field strength at a specific position that is greater than a second resultant field strength produced at the same position when the top surface of the core magnet abuts the bottom surface of the ring magnet. The field strength at the specific position disengages the clutch mechanism to release the magnetic locking mechanism.
A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
Before describing in detail exemplary embodiments that are in accordance with the present invention, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to implementing a system and method for optimizing the field profile of a high strength magnetic detacher. Accordingly, the system and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.
One embodiment of the present invention advantageously provides a method and system for fine-tuning the magnetic field profile of a magnetic assembly in a magnetic detacher unit in order to use the magnetic detacher with a specific mechanical tag design. The use of a spacer element enhances the magnetic field produced within the zone of interest (detaching zone). Additionally, a booster element constructed from, for example, soft ferromagnetic material, aids in enhancing the magnetic field further out into the detaching zone.
In another embodiment, a magnetic shield element with a similar foot print as the ring magnet may also help condense the field into the cavity of the detacher unit. A shield element with a thickness of only a fraction of millimeter also effectively reduces the stray field to the outside environment. This shielding minimizes the possibility of destroying magnetic cards (such as credit card, gift card, etc.) or attracting other ferrous objects, such as tools, cook wares, etc.
Referring now to the drawing figures in which like reference designators refer to like elements, there is shown in
The spacer 56 may be constructed preferably from non-ferrous materials, for example, plastic, cloth, etc. Alternatively, the ring magnet 54 and the core magnet 52 may be secured in the magnetic detacher unit such that they are separated from each other by an air gap. The spacer 56 may include a cavity (not shown) having a diameter equal to the diameter of the cavity 58 in the ring magnet 54 in order to accommodate insertion of the protrusion 24 on EAS tag 10 (see
In accordance with the present invention, for any specific magnetic EAS tag 10 or other magnetic securing device, a spring 40 (
Referring now to
In
As can be seen from
Another added benefit for providing a space between the core magnet 52 and the ring magnet 54 is the reduction of the magnetic instability due to the opposing field configuration. A 1 mm spacing reduces the surface magnetic field by about six hundred Oersted, e.g., from 5.5 kOe to about 4.9 kOe seen at the ring magnet 54 surface.
The present invention advantageously tunes the resultant magnetic field strength of magnetic assembly having a combination of a ring magnet and a cylindrical core magnet to provide an optimal magnetic field strength at a predetermined distance away from the surface, e.g., at substantially the location of clutch of the EAS tag or other magnetic securing devices. This feature allows a magnetic assembly of a magnetic detacher e.g., the clutch location, to be tuned to operate only with specifically designed EAS tags or other magnetic securing devices.
Additionally, because the magnetic field strength of the magnet assembly is increased in comparison to prior art magnets, a weaker core magnet may be used to achieve the same field strength previously requiring stronger magnets, thereby reducing the overall cost of the magnet assembly.
Unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Significantly, this invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be had to the following claims, rather than to the foregoing specification, as indicating the scope of the invention.
This application is related to and claims priority to U.S. Provisional Patent Application No. 61/203,060, entitled “OPTIMIZATION OF THE FIELD PROFILE ON A HIGH FIELD STRENGTH MAGNETIC DETACHER,” filed Dec. 17, 2008, the entire contents of which is incorporated herein by reference.
Number | Date | Country | |
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61203060 | Dec 2008 | US |