Note: Descriptions are shown in the official language in which they were submitted.
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MAGNETOMECHANICAL TAG USED IN
ELECTRONIC ARTICLE SURVEILLANCE AND
METHOD OF MANUFACTURING A
MAGNETOMECHANICAL TAG
Field of the Invention
This invention relates generally to magnetomechanical tags used in electronic
article surveillance (EAS) systems, and more particularly, to methods for
manufacturing
EAS tags.
BACKGROUND OF THE INVENTION
Description of the Related Art
In acoustomagnetic or magnetomechanical electronic article surveillance, or
a detection system may excite an EAS tag by transmitting an electromagnetic
burst at a resonance frequency of the tag. When the tag is present within an
interrogation
zone defined by the electromagnetic field generated by the burst transmitter,
the tag
resonates with an acoustomagnetic or magnetomechanical response frequency that
is
detectable by a receiver in the detection system.
EAS systems may be provided to prevent or deter theft of merchandise from
retail establishments. In a typical EAS system, EAS tags configured to
interact with an
electromagnetic or magnetic field generated by equipment placed, for example,
at an exit
of a store are utilized. Removable EAS tags that may be configured as labels
are
typically placed on the article at the store or at an intermediate location.
Alternatively,
EAS tags or labels may be integrated into the article during manufacture in a
process
known as "source tagging."
If an EAS tag is brought into the field or interrogation zone of the field
generating equipment, the presence of the tag is detected and an alarm may be
generated,
such as a visual or audible alarm. Removable EAS tags are typically removed at
the
checkout counter upon payment for the merchandise. Other types of EAS tags,
such as
EAS tags integrated with the article, are deactivated at the checkout counter,
for example,
by a deactivation device that changes an electromagnetic or magnetic
characteristic of the
EAS tag such that the presence of the EAS tag will no longer be detected
within the
interrogation zone.
EAS tags are typically assembled in a stacking or layering process wherein the
various component parts are attached and sealed together. During the assembly
process, a
powder lubricant is applied to reduce the friction between some of the
component parts
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(e.g., between a resonator and substrate). The applied powder lubricant is
typically not
applied in a controlled process and may affect the heat sealing of the EAS
tag, for
example, not allow proper or complete sealing of the EAS tag because too much
powder
lubricant is applied. Also, because the applied powder lubricant process is
not controlled,
too little powder lubricant may be applied resulting in increased friction
within the EAS
tag and a potential reduction of tag signal amplitude. Thus, the addition of
too little or
too much powder lubricant affects the assembly and operation of the EAS tags.
BRIEF DESCRIPTION OF THE INVENTION
An electronic article surveillance (EAS) tag may be provided that may include
at
least one resonator, a housing configured to allow vibration therein of the at
least one
resonator and a cover heat sealed to the housing at a heat sealing
temperature. The EAS
tag further may include a powder lubricant within the housing. The powder
lubricant
may have a melting temperature less than the heat sealing temperature.
A method for sealing an electronic article surveillance (EAS) tag also may be
provided. The method may include applying a powder lubricant to a sealing
portion of
the EAS tag and heat sealing the sealing portion by melting the powder
lubricant.
A method for assembling an electronic article surveillance (EAS) tag further
may be provided. The method may include positioning a lidstock cover over a
coverstock
housing such that an edge of the lidstock cover aligns with an edge of a
flange of the
coverstock housing. The method also may include heating the flange of the
coverstock
housing wherein a bonding layer comprising a powder lubricant melts to seal
the lidstock
cover and the coverstock housing.
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According to one aspect of the present invention, there is provided an
electronic article surveillance (EAS) tag comprising: at least one resonator;
a housing
having a sealing portion, the housing being configured to allow vibration
therein of the
at least one resonator; a cover heat sealed to the sealing portion of the
housing at a
According to another aspect of the present invention, there is provided
15 According to still another aspect of the present invention, there
is
provided a method for assembling an electronic article surveillance (EAS) tag,
the
method comprising: positioning a lidstock cover over a coverstock housing such
that
an edge of the lidstock cover aligns with an edge of a flange of the
coverstock
housing; applying a powder lubricant to the flange of the coverstock housing
and to at
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BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of various embodiments of the invention, reference
should be made to the following detailed description that should be read in
conjunction
with the following figures wherein like numerals represent like parts.
Figure 1 is a diagram of an electronic article surveillance system
illustrating a
magnetomechanical label within a field of interrogation generated by the
system.
Figure 2 is a diagram of an EAS tag formed in accordance with an embodiment
of the invention.
Figure 3 is a side elevation view of an EAS tag formed in accordance with an
embodiment of the invention in an unsealed state.
Figure 4 is a side elevation view of an EAS tag formed in accordance with an
embodiment of the invention in a sealed state.
Figure 5 is a side elevation view of an EAS tag formed in accordance with an
embodiment of the invention illustrating a lubricant dispenser dispensing
powder
lubricant in the EAS tag.
Figure 6 is a side elevation view of an EAS tag formed in accordance with
another embodiment of the invention in a sealed state.
Figure 7 is a flowchart of method for sealing an EAS tag in accordance with an
embodiment of the invention.
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DETAILED DESCRIPTION OF THE INVENTION
For simplicity and ease of explanation, the invention will be described herein
in
connection with various embodiments thereof. Those skilled in the art will
recognize,
however, that the features and advantages of the various embodiments may be
implemented in a variety of configurations. It is to be understood, therefore,
that the
embodiments described herein are presented by way of illustration, not of
limitation.
In general, various embodiments of the present invention provide an electronic
article surveillance (EAS) tag for use in connection with an EAS system. It
should be
noted that when reference is made herein to an EAS tag, this includes any type
of EAS
marker or label, whether removably attached or integrated with an object and
that
generally includes a magnetomechanical structure that includes one or more
magnetostrictive resonating elements. Further, an EAS tag formed in accordance
with
various embodiments of the invention may used in different types of EAS
systems,
including, for example, any mechanical resonance type EAS system, among
others.
Figure 1 illustrates an EAS system 10 that may include a first antenna
pedestal
12 and a second antenna pedestal 14. The antenna pedestals 12 and 14 may be
connected
to a control unit 16 that may include a transmitter 18 and a receiver 20. The
control unit
16 may be configured for communication with an external device, for example, a
computer system controlling or monitoring operation of a number of EAS
systems. In
addition, the control unit 16 may be configured to control transmissions from
the
transmitter 18 and receptions at the receiver 20 such that the antenna
pedestals 12 and 14
can be utilized for both transmission of signals for reception by an EAS tag
30 and
reception of signals generated by the excitation of EAS tag 30. Specifically,
such
receptions typically occur when the EAS tags 30 are within an interrogation
zone 32,
which is generally between the antenna pedestals 12 and 14.
The system 10 is representative of many EAS system embodiments and is
provided as an example only. For example, in an alternative embodiment, the
control unit
16 may be located within one of the antenna pedestals 12 and 14. In still
another
embodiment, additional antennas that only receive signals from the EAS tags 30
may be
utilized as part of the EAS system. Also, a single control unit 16, either
within a pedestal
or located separately, may be configured to control multiple sets of antenna
pedestals. As
is known, a deactivation device 40, for example, incorporated into the
checkout counter
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of a retailer, may be utilized to degauss the EAS tags 30 upon purchase of the
item to
which, or into which, the EAS tag 30 is attached or integrated.
Figure 2 is an illustration of an embodiment of a magnetomechanical EAS tag
50, which is also sometimes referred to as an EAS label. The EAS tag 50 may
include a
housing 52 having a cavity 54 formed therein and a flange 56 extending around
an upper
surface of the housing 52. The flange 56 may extend generally around an upper
edge of
the housing 52 and may form a lip extending perpendicular to the top edge. The
EAS tag
50 further may include one or more magnetostrictive resonators 58 (only one
shown in
Figure 2) that may be located in the cavity 54. The cavity 54 may be sized and
shaped to
provide sufficient space for the one or more resonators 58 to vibrate at a
resonant
frequency. The resonant frequency of the one or more resonators 58 may be
determined,
at least in part, by a length and width of the one or more resonators 58 and a
strength of a
magnetic field near the one or more resonators 58. A cover 60, commonly
referred to as a
lidstock layer, may be positioned on the housing 52, and more particularly,
abutting
against the flange 56 and sealed (e.g., heat sealed) thereto as described in
more detail
herein.
A biasing element 62 may be provided on top of the cover 60 and attached
thereto (e.g., adhesively bonded thereto) using an adhesive layer 64, which
may be a
double-sided adhesive layer. The biasing element 62 may be formed of any hard
or semi-
hard metallic element that biases the one or more resonators 58.
In operation, after fully saturating the biasing element 62 through
magnetization,
the EAS tag 50 is in the active state. The resonant frequency and amplitude of
the
resonant frequency generated within EAS tag 50 may be optimized for a
particular
detection algorithm based on a field strength provided by the biasing element
62. The
EAS tag 50 may be attached to an object using various methods, for example,
with one
side of the adhesive layer 64. The EAS tag 50 alternatively may be contained
within the
packaging of other objects or items. Also, the EAS tags 50 may be permanently
embedded within certain objects (e.g., molded within the object) during
production of the
object.
Figure 3 is an illustration of an embodiment of an EAS tag 50 that may include
a
powder lubricant 70 applied thereto. For example, the powder lubricant 70 may
be
applied to coat or partially coat a portion of the EAS tag 50. The powder
lubricant 70
may be applied in an even pattern or an uneven pattern. Additionally, the
powder
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lubricant 70 may be provided within the cavity 54 and in contact with the one
or more
resonators 58. The powder lubricant 70 may be applied during an assembly stage
of the
EAS tag 50 as described in more detail below or during the manufacture of the
cover 60.
The powder lubricant 70 may be formed from a low melting temperature powder
lubricant, for example, having a melting temperature of less than 110 degrees
Celsius, and
more particularly, less than a sealing temperature for sealing the EAS tag 50.
For
example, the powder lubricant 70 may be formed from a low density polyethylene
(LDPE) material having a melting point at or below a heat sealing temperature
for the
EAS label 50, for example, at or below 110 degrees Celsius. In general, the
powder
lubricant 70 may be formed from different powder materials having different
particle
sizes, for example, based on the application or type of use. In various
embodiments, and
for example, the powder lubricant 70 may be formed from the following
materials:
1. High Density Polyethylene (HDPE).
(approximate particle size of 60 microns)
2. Medium Density Polyethylene (MDPE).
(approximate particle size of 60 microns)
3. Low Density Polyethylene (LDPE).
(approximate particle size of 20 microns)
4. Polyethylene (PE) Oxide (approximate particle size less than 45
microns).
5. Oxy-Dry powder (approximate particle size of 26 microns) available from
Oxy-Dry Corporation.
Other materials may be used to form the powder lubricant 70 as needed or
desired, for
example, based on the particular application or type of EAS system 10 or EAS
tag 50.
The housing 52 may be formed from a coverstock material that may be
configured as a multi-ply arrangement. The coverstock material may comprise,
for
example, a polystyrene material. A coverstock bonding layer 72 also may be
provided on
a top surface of the housing 52 including within the cavity 54 and on the
flange 56. The
coverstock bonding layer 72 may be formed from, for example, an LDPE material
having
a melting point close to the sealing temperature (e.g., 110 degrees Celsius).
The
coverstock bonding layer 72 may provide a bonding layer during a heat sealing
stage at a
temperature slightly higher than 110 degrees Celsius, for example, 112 degrees
Celsius.
The cover 60 may be formed from a lidstock material that may be configured as
a multi-
ply arrangement. The lidstock material may comprise, for example, a
polyethylene
terephthalate (PET) material. A lidstock bonding layer 74 also may be provided
on a
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bottom surface of the housing 60 and formed from an LDPE material having
similar
properties to the coverstock bonding layer 72.
Accordingly, when sealing the EAS tag 50 using any known process, for
example, applying heat to the flange 56 areas as illustrated by the arrows in
Figure 4, the
powder lubricant 70 located on the flange 56 melts, and together with the
coverstock
bonding layer 72 and the lidstock bonding layer 74 that also melt, seals the
cover 60 to
the housing 52 (e.g., powder lubricant 70 forms a sealing layer with the
coverstock
bonding layer 72 and the lidstock bonding layer 74). This sealing engagement
also may
seal the one or more resonators 58 within the cavity 54.
In an alternative embodiment shown in Figures 5 and 6, the coverstock bonding
layer 72 and the lidstock bonding layer 74 may be removed from the EAS tag 50
and the
powder lubricant 70 may form the seal between the cover 60 and the housing 52
along the
flange 56. In this embodiment, the powder lubricant 70 may be applied during
the
assembly stage, for example, by a lubricant dispenser 80. For example, the
lubricant
dispenser 80 may dispense powder lubricant 70 through openings (not shown) for
a
predetermined period of time for each EAS tag 50. However, the dispensing of
the
powder lubricant 70 by the lubricant dispenser 80 may be provided in any
manner using
any dispensing means. The lubricant dispenser 80 may be provided on top of a
sheet of
the coverstock to apply the powder lubricant 70, for example, evenly apply the
powder
lubricant 70 on the flange 56 and within the cavity 54 having the one or more
resonators
58 therein. Again, the powder lubricant 70 may be an LDPE material that melts
at the
surface of the flange 58 during the sealing process and as shown in Figure 6.
The powder
lubricant 70 may form the seal or bond between the cover 60 and the flange 58
sealing the
one or more resonators 58 within the cavity 54. Thus, the powder lubricant 70
provides
friction reduction within the cavity 54 and sealing of the cover 60 to the
flange 56.
A method 100 for sealing an EAS tag 50 is illustrated in Figure 7. At 102 a
powder lubricant may be applied to the EAS tag 50. For example, the powder
lubricant
70 may be dispensed on the EAS tag 50, and more particularly, at least within
the cavity
54 and along the flange 56. The powder lubricant 70 may be applied in an
evenly
distributed manner or unevenly/randomly. The application of the powder
lubricant 70
may be provided in any known manner, for example, by spraying, blowing,
dropping,
spreading, dusting, etc. the powder lubricant 70 to the surfaces of the cavity
54 and the
flange 56. During the powder lubricant application process powder lubricant 70
also may
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be applied to other surfaces of the EAS tag 50 either intentionally or
unintentionally. The
amount of powder lubricant 70 applied may be controlled, for example, by
timing the
duration of the powder lubricant application, measuring the amount of powder
lubricant
70 to be applied, etc. However, in an alternative embodiment, the powder
lubricant 70 is
not applied in a controlled process, but manually, for example, by hand using
a shaker
bottle containing the powder lubricant 70. The amount applied may be based on,
for
example, the type of powder lubricant 70 or the application or use for the EAS
tag 50.
In another embodiment, in addition to or instead of applying the powder
lubricant 70 to the flange 56 of the housing 52, bonding layers may be
provided, for
example, the coverstock bonding layer 72 and the lidstock bonding layer 74. In
this
embodiment, the powder lubricant 70 may (i) not be applied, (ii) applied
within the cavity
58 with any excess coating the bonding layers and/or (iii) applied to one or
more of the
bonding layers.
The powder lubricant 70 may be formed of a material that melts during a
sealing
process of the EAS tag 50. For example, the powder lubricant 70 may be formed
from a
low melting temperature powder lubricant 70, for example, having a melting
temperature
of less than the sealing temperature for the EAS tag 50 (e.g., 110 degrees
Celsius). For
example, the powder lubricant 70 may be formed from a low density polyethylene
(LDPE) material having a melting point at or below a heat sealing temperature
for the
EAS label 50, such as a polyethylene composite material or a PE oxide
material.
Thereafter, at 104 the components of the unassembled EAS tag 50 including the
powder lubricant coated components may be aligned. For example, the cover 60
may be
aligned on top of the housing 52 having the one or more resonators 58 therein.
The
alignment may include aligning the edges of the cover 60 with the edges of the
flange 56.
Once the components are aligned, a heat source may apply heat at 106 to the
aligned
components to heat seal the components, for example, heat seal the cover 60 to
the
housing 52. This sealing engagement also may seal the one or more resonators
58 within
the cavity 54. The heat source may be any type of heating device capable of
applying
directed heat to the components or portions of the components of the EAS tag
50. The
heat source may direct heat only to portions of the components to be sealed,
for example,
along the flange 56. The portions having one of the powder lubricant 70 and
the bonding
layers therebetween that are heated are bonded or sealed together. More
particularly, the
application of the heat from the heat source melts either the powder lubricant
70, the
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bonding layers, or both depending on which of these materials is provided
between the
portions of the components to be sealed. In one embodiment, the heat level is
provided
such that the temperature is above the melting point of one of the powder
lubricant and
the bonding layers. For example, the melting point of the powder lubricant 70
may be
lower than the melting point of the bonding layers such that any powder
lubricant 70
present with the bonding layers also melts upon or before reaching the melting
point of
the bonding layers. In another embodiment, wherein only the powder lubricant
70 may
be melted during the sealing process (e.g., when no bonding layers are
present), the
powder lubricant 70 may be formed of a material that has a melting point
either less than
the melting point of the bonding layer (such that the same heating source may
be used if
the bonding layers are present) and/or less than a temperature that would
caused damage
to the material forming the housing 54 (e.g., causing the housing 54 to deform
or melt).
Once sealed, for example, once the cover 60 is sealed to the flange 56 of the
housing 52, at 108 additional components may be added to the EAS tag 50. For
example,
a bias member 62 may be adhered to the top of the cover 60 using an adhesive
layer 64,
which may be a double-sided adhesive layer.
Thus, various embodiments provide a powder lubricant that may be used to seal
an EAS tag. The powder lubricant may be used in combination with other bonding
materials or may be used alone to seal, for example, one or more resonators
within a
housing of the EAS tag.
While the invention has been described in terms of various specific
embodiments, those skilled in the art will recognize that the various
embodiments of the
invention can be practiced with modification within the spirit and scope of
the claims.
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