Patent Publication Number: US-8978427-B2

Title: Tamper resistant security tag

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a non-provisional application claiming the benefit of U.S. Provisional Application No. 61/722,640 filed on Nov. 5, 2012, the entirely which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Statement of the Technical Field 
     The inventive arrangements relate to security tags attachable to articles of merchandise, and more particularly a security tag having an improved locking mechanism providing greater defeat resistance. 
     2. Description of the Related Art 
     Electronic article surveillance (EAS) systems are well known in the art and are used for inventory control and to prevent theft and similar unauthorized removal of articles from a controlled area. Typically, in such systems a system transmitter and a system receiver are used to establish a surveillance zone, which must be traversed by any article being removed from the controlled area. 
     An EAS tag is security tag affixed to each article and includes a marker or sensor adapted to interact with a signal being transmitted by the system transmitter into the surveillance zone. This interaction causes a further signal to be established in the surveillance zone, which further signal is received by the system receiver. Accordingly, upon movement of a tagged article through the surveillance zone, a signal will be received by the system receiver, identifying the unauthorized presence of the tagged article in the zone. The security tags are designed to be releasable only by a specially designed implement. 
     Security tags used in EAS systems often include a locking mechanism which serves to affix the tag to an article. The tag may be locked to the article itself, or the tag can be configured as mated components, which are attachable to one another with a portion of the article secured between the tag components. A common locking arrangement used in security tags is a magnetically-actuatable locking mechanism. These types of security tags use a magnet to unlock the locking mechanism. The magnet interacts with the magnetic components in the lock and actuates such magnetic components to unlock the mechanism. 
     SUMMARY OF THE INVENTION 
     The invention concerns a tamper-resistant security tag which includes a housing and a movable locking element disposed within the housing. A latch is disposed within the housing and is resiliently biased toward the movable locking element. The latch is movable responsive to application of a magnetic field between a locked position, in which movement of the locking element is prevented by the latch, and an unlocked position, in which movement of the locking element is unrestricted by the latch. A guide structure is provided within the housing and is arranged to constrain a movement of the latch. The latch and the guide structure are cooperatively arranged to facilitate engagement between at least one portion of the guide structure and a portion of the latch. These portions of the latch and the guide structure are strategically arranged to ensure that the engagement will disrupt a motion trajectory of the latch occurring when the housing is subjected to a physical impact. Consequently, the latch is selectively inhibited from moving fully from the locked position to the unlocked position when the housing is subjected to the physical impact. 
     The invention also concerns a method for preventing defeat of a security tag in a security tag as described herein. The method involves disrupting with the guide structure a motion trajectory of the latch occurring when the housing is subjected to a physical impact so that the latch is selectively inhibited from moving fully from the locked position to the unlocked position only when the housing is subjected to the physical impact. The kinetic energy of the latch associated with such motion trajectory is effectively wasted within the housing by the motion disrupting action of the guide structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures, and in which: 
         FIG. 1A  is a perspective view of a security tag with a prior art magnetic locking mechanism. 
         FIG. 1B  is a cutaway view showing internal components of the security tag in  FIG. 1A . 
         FIG. 2  is a cutaway view of a security tag with a latch in a locked position that is useful for understanding the inventive arrangements. 
         FIG. 3  is a cutaway view of the security tag in  FIG. 2 , with the latch in an unlocked position. 
         FIG. 4  is a cutaway view of a security tag, with a latch in a locked position, which is useful for understanding an alternative embodiment of the inventive arrangements. 
         FIG. 5  is a cutaway view of the security tag in  FIG. 4 , with the latch in an unlocked position. 
     
    
    
     DETAILED DESCRIPTION 
     The invention is described with reference to the attached figures. The figures are not drawn to scale and they are provided merely to illustrate the instant invention. Several aspects of the invention are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One having ordinary skill in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operation are not shown in detail to avoid obscuring the invention. The invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the invention. 
     EAS type security tags commonly include a magnetically-actuatable locking mechanism. In such locking mechanisms, the magnetic component of the lock requires a certain mass to generate a sufficient magneto-mechanical response for unlocking the tag. However, it has been found that the mechanical response generated by the unlocking magnet can be duplicated by application of external mechanical force. Application of a sufficient external force (as may be done in an attempt to defeat the tag) could result in the unlocking of the tag. A tag which can be defeated in this manner is obviously undesirable in EAS applications. It is challenging to produce a defeat resistant magnetic lock without compromising the magnetic detach or adding too much cost to the design due to added complexity. Prior solutions include the use of a stronger spring to hold the magnetic component in place. However, the use of stronger springs can cause detaching failure under conditions of authorized tag detachment, or can otherwise require a stronger and more expensive detacher device magnet. 
       FIGS. 1A and 1B  are illustrative of a conventional security tag  100  showing a prior art magnetic locking mechanism  101 . The security tag  100  includes an EAS element  112  which can be detected using conventional EAS methods. The locking mechanism  101  includes an elongated pin  102 , a latch  103  to engage the pin  102  by engagement with at least one catch  107  disposed therein. The catch can be a groove or any other suitable mechanical structure formed in the pin and which is capable of locking engagement with the latch as hereinafter described. The locking mechanism also includes a spring  104  to bias the latch  103  toward the pin  102 . A rigid plastic housing  106  can contain the locking mechanism. When the latch is in a locked position as shown, a cog or tooth  132  formed on the latch engages the catch provided in the pin. This engagement prevents the pin from moving within a pin channel  114 . The latch  103  is formed of a material that is responsive to an applied magnetic field. In this regard, the material is generally selected so as to contain iron. Accordingly, an exemplary material that can be used for this purpose is steel. In the tag shown in  FIG. 1B , detaching is accomplished with a detaching device which positions a detacher magnet (not shown) under a base portion  118  of the housing which encloses the latch. As a result of the applied magnetic field from the detacher magnet, the latch  103  experiences a downward attractive magnetic force in a direction  116  which overcomes the bias of the spring  104 . The latch  103  translates downward, disengaging the latch  103  from the pin  102  and thus unlocking the tag. Once unlocked, the pin  102  can slide within the pin channel  114  in the direction indicated by arrow  120  so that an end portion  110  of shackle  108  can clear the housing. Once the end portion  110  has cleared the housing, an item secured within the shackle can be released. 
     A drawback of the locking arrangement of  FIG. 1B  is that the action of striking the bottom of the tag against a hard surface will sometimes cause the same kind of downward translation of the latch which is normally produced by the detacher magnet described above. Accordingly, persons seeking to overcome the security measures associated with the tag have sometimes used this approach to unlock the tag from an item of merchandise. 
     The inventive arrangements disclosed herein utilize special features associated with the latch and the plastic housing to provide a low cost solution that drastically reduces the possibility for unauthorized unlocking of an EAS tag by means of mechanical impact forces. The special features provide the ability to restrict the translation of the latch as it moves away from engagement with a locking pin by incorporating an obstructive feature into the housing at strategic location. Translation movement of the latch (as opposed to rotational movement) is the primary response due to a mechanical impact forces such as may occur by swinging and hitting the security tag on a hard surface. A motion trajectory of the latch can be predicted from the orientation the tag is likely hit. One or more special structures are provided in the housing and on the latch to disrupt the rapid translational movements of the latch that may result from such mechanical impact forces, thereby preventing unauthorized unlocking of the tag. In a slower moving detaching process (as would occur in the case of authorized detaching by means of a magnetic detacher) the latch will interact with the special structures on the housing initially but it will eventually be caused to move in a way that facilitates successful detaching. In some instances, the additional required movement may be further translational movement and in other scenarios the additional required movement can be a rotational movement of the latch. 
     Referring now to  FIG. 2 , there is shown an enlarged view of a security tag  200 . The security tag  200  is similar to the security tag  100 . Accordingly, the description of the security tag  100  is generally sufficient for understanding the security tag  200 , with the exception of the locking mechanism  201  which is described below in further detail. The security tag  200  includes a housing  206  in which the locking mechanism  201  is provided. The housing is formed of a rigid plastic material and houses a detectable element  212 , such as a sensor, transponder, or electronic circuit that provides the EAS and or RFID function. 
     The housing  206  defines a latch channel  230  in which a latch  203  is movably disposed. The latch is formed of a material, such as steel, which is responsive to a magnetic field. Within the latch channel  230 , the latch  203  is resiliently biased toward a movable locking element. In this example, the locking element is an elongated pin such as locking pin  202 . As can be observed in  FIG. 2 , the locking pin  202  is slidably disposed for movement along a length of the pin channel  214 . A resilient member, such as a spring  204  is disposed between the latch  203  and a portion of the housing  206  to provide the resilient bias as described herein. 
     In  FIG. 2 , the latch  203  is shown in a locked position in which movement of the locking element (e.g. locking pin  202 ) is prevented. In other words, the locking pin  202  is unable to move along a direction indicated by arrow  220  because it is held in place by the latch. In order to provide such locking engagement, the locking pin  202  has at least one catch  207  and the latch includes at least one tooth  232  which is aligned with a catch when the locking pin is moved to a certain position within the channel. As may be observed in  FIG. 2 , the tooth is advantageously sized and shaped to engage with a catch  207  when the latch  203  is in the locked position as shown. In some embodiments, the tooth can be shaped as a cog to selectively permit movement of the locking pin in only one direction when locked. 
     The latch  203  is movable within the latch channel responsive to application of a magnetic field (not shown). More particularly, when a magnetic detacher (not shown) is placed adjacent to a base portion  218  of the housing, the latch  203  is caused to move in a direction  234 , away from the locking pin  202 . When the latch  203  has moved a certain distance away from this locked position, the tooth  232  fully disengages from the catch  207  and the locking mechanism is considered unlocked. As such, the latch is movable between a locked position shown in  FIG. 2 , in which movement of the locking element is prevented by the latch, to an unlocked position shown in  FIG. 3 . In the unlocked position shown in  FIG. 3 , movement of the locking pin  202  is unrestricted by the latch  203 . 
     A guide structure  235  is provided within or as part of the security tag housing  206  and is arranged to constrain a movement of the latch  203 . The guide structure includes one or more lateral restraints  236 ,  238 . These lateral restraints are arranged to facilitate translational movement of the latch within the latch channel  230  along a path from the locked position to the unlocked position by constraining movement of the latch in a lateral direction transverse to such path. In an exemplary arrangement shown in  FIGS. 2 and 3 , the lateral restraints  236 ,  238  can be provided in the form of side walls which generally guide the movement of the latch as it moves between the locked and unlocked positions. These side walls can define the boundaries of the latch channel  230 . A further portion of the guide structure is a stop  240 . The stop  240  is positioned adjacent to the base  218  and in some scenarios can be integrally formed with the base. The stop  240  is arranged to limit the translational movement of the latch in a direction of travel  234  toward the unlocked position. The stop functions by engaging a portion of the latch. For example, as shown in  FIGS. 2 and 3 , the latch can have a pair of legs  242   a ,  242   b . The stop  240  can function by engaging end portions  244   a ,  244   b  of the latch legs when the latch is in the fully unlocked position. In an exemplary embodiment shown in  FIGS. 2 and 3 , the stop can be formed as a channel end wall which together with the side walls (lateral restraints  236 ,  238 ) encloses the locking mechanism. As such, the guide structure  235  can effectively define a channel housing. 
     The guide structure  235  is generally arranged to prevent substantial lateral movement of the latch in direction  220 . By restricting movement of the latch in this way, the locking pin  202  is similarly prevented from moving in direction  220  within the channel  214  whenever the latch is engaged with the locking pin. From the foregoing, it will be appreciated that the guide structure (and more particularly the lateral restraints  236 ,  238 ) described herein generally restrict movement of the latch in direction  220 . Nevertheless, the lateral restraints  236 ,  238  permit latch movement in directions (e.g. direction  234 ) aligned with the length of the latch channel  230 . 
     An unauthorized person desirous of defeating a security tag will sometimes repeatedly strike the security tag on a hard surface to generate a mechanical response of the latch that is similar to the response generated by an unlocking magnet. When the security tag is abused in this way, the physical mass of latch will cause the latch to have a motion trajectory within the security tag housing that mimics the motion obtained by application of an unlocking magnet. Under certain conditions, repeated striking of the security tag in this way can cause the tag to become unlocked as the latch travels along a motion trajectory in direction  234 , away from the locking pin. A tag which can be defeated in this manner is obviously undesirable in EAS applications. In order to prevent defeat of the locking mechanism in this way, the latch  203  and the guide structure  235  are cooperatively arranged to facilitate engagement between at least one first disrupter portion of the guide structure and a second disrupter portion of the latch. These disrupter portions of the latch and the guide structure are strategically arranged to ensure that the engagement will disrupt a motion trajectory of the latch occurring when the housing is subjected to a physical impact. Consequently, the latch is selectively inhibited from moving fully from the locked position in  FIG. 2  to the unlocked position in  FIG. 3  when the housing is subjected to a physical impact as described herein. As used herein, inhibited means that the tendency of the latch to move to the unlocked position as a result of an impact is completely prevented or at least greatly suppressed as compared to conventional magnetic locking arrangements of the prior art. 
     The exact structure of the first and second disrupter portions is not critical provided that the structures are effective for accomplishing the motion disrupting action described herein. Referring once again to  FIGS. 2 and 3 , there is shown an exemplary first disrupter portion  246 ,  247  formed on the guide structure  235 , and an exemplary second disrupter portion  248  formed on the latch  203 . In some embodiments, a restricting element  247  can be included as part of the first disrupter portion to restrict a channel space in which the latch can move, and thereby urge the latch (as it moves in direction  234 ) into a position where the first disrupter portion engages the second disrupter portion. The restricting element  247  can be formed as a portion of the housing  206 , as part of the guide structure  235 , or can be attached within the latch channel by any suitable means. 
     In accordance with one embodiment of the invention, the first disrupter portion  246  comprises a bump or other protrusion extending into the latch channel  230  from the side wall of the channel housing or guide structure  235 . For example, the first disrupter portion  246  can extend in a lateral direction from a side wall (i.e. lateral restraint  238 ) of the channel housing as shown. The first disrupter portion  246  is designed to interfere with or disrupt the downward translation of the latch as it moves in direction  234  in response to an impact of the security tag on a hard surface. In some embodiments, the first disrupter portion  246  can be provided as part of a lateral wall forming the channel  230  as shown. In this regard, the first disrupter portion can be formed as a part of the housing  206  (e.g. of the same material as the housing), or otherwise can be a separate component attachable to the housing, which may be of a different material than the housing, such as a metal rivet. 
     It can be observed in  FIGS. 2 and 3  that the disrupter portion  246  is oriented or projects into the channel in a direction which is transverse to or approximately perpendicular to the direction  246 . A motion trajectory of the latch when the security tag is stuck upon a hard surface can include translation along a direction  246  as described. As a result of such movement along this direction a second disrupter portion  248  formed on the latch will engage with the first disrupter portion to disrupt the movement of the latch in direction  246 . 
     The disrupter portion  246  partially obstructs the downward translation of the latch  203  as would occur if abrupt external forces are applied to the tag, as when the tag is slammed against a hard surface in a defeat attempt. However, the second disrupter portion  248  is comprised of a contoured side of the latch  203  adjacent the first disrupter portion  246 . The contour of the second disrupter portion  248  allows the latch to move downwardly past the protrusion formed by the first disrupter portion  246  under certain conditions. In particular, such movement is facilitated when the latch is introduced to a magnetic force of sufficient strength. In the illustrated embodiment, the latch  203  the second disrupter portion  248  is essentially formed as a contoured notch which is configured to have a shape which is partially complementary to the shape of the bump forming the first disrupter portion  246 . 
     The notch formed by second disrupter portion  248  engages with the protrusion of first disrupter portion  246  when the latch is moved in direction  234 . This engagement allows the downward translation of the latch  203  only if a steady, uninterrupted force is applied to the latch. Sudden external blows to the tag will not be sufficient to permit the bump to engage with and slide past the notch. In practice, a steady uninterrupted force can only be applied to the latch by the use of the detacher magnet in the detacher device. Accordingly, to unlock the locking mechanism  201 , a detaching device is used (not shown) which is constructed and arranged to position a detacher magnet under the latch  203 . The latch  203  is pulled downward in direction  234  by the magnetic force until it overcomes the bias of the spring  204  and allows the latch to transition through the engagement of the first and second disrupter portions as described. When the latch  203  finally translates to its fully unlocked position shown in  FIG. 3 , the tooth is released from the catch so that the pin  202  can be moved. 
     Shown in  FIG. 4 , is an alternative embodiment of the invention wherein the motion of the latch necessary to effect unlocking involves a translation and rotation motion. Referring now to  FIG. 4 , there is shown an enlarged view of a security tag  400 . The security tag  400  is similar to the security tag  200 . Accordingly, the description of the security tag  200  is generally sufficient for understanding the security tag  200 , with the exception of the locking mechanism  401  which is described below in further detail. The security tag  400  includes a housing  406  in which the locking mechanism  401  is provided. The housing is formed of a rigid plastic material and houses a detectable element  412 , such as a sensor, transponder, or electronic circuit that provides the EAS and or RFID function. 
     The housing  406  defines a latch channel  430  in which a latch  403  is movably disposed. The latch is formed of a material, such as steel, which is responsive to a magnetic field. Within the latch channel  430 , the latch  403  is resiliently biased toward a movable locking element. In this example, the locking element is an elongated pin such as locking pin  402 . As can be observed in  FIG. 4 , the locking pin  402  is slidably disposed for movement along a length of the pin channel  414 . A resilient member, such as a spring  404  is disposed between the latch  403  and a portion of the housing  406  to provide the resilient bias as described herein. 
     The latch  403  is movable between a locked position and an unlocked position. In  FIG. 4 , the latch  403  is shown in the locked position in which movement of the locking element (e.g. locking pin  402 ) is prevented. In other words, the locking pin  402  is unable to move along a direction indicated by arrow  420  because it is held in place by the latch. In order to provide such locking engagement, the locking pin  402  has at least one catch  407  and the latch includes at least one tooth  432  which is aligned with the catch when the locking pin is moved to a certain position within the channel. As may be observed in  FIG. 4 , the tooth is advantageously sized and shaped to engage with catch  407  when the latch  403  is in the locked position as shown. In some embodiments, the tooth can be shaped as a cog to selectively permit movement of the locking pin in only one direction when locked. 
     The latch  403  is movable within the latch channel responsive to application of a magnetic field (not shown). More particularly, when a magnetic detacher (not shown) is placed adjacent to a base portion  418  of the housing, the latch  403  is able to translate some distance in a direction  408 . As shown in  FIG. 4 , the latch includes latch legs  442   a ,  442   b , with latch leg  442   a  being longer than latch leg  442   b . Accordingly, the latch will translate a certain distance in direction  408  until an end portion  444   a  of latch leg  442   a  engages a stop  440  associated with base portion  418 . When this happens, further translational movement of the latch along direction  408  will be inhibited. However, due to the longer length of leg  442   a  as compared to leg  442   b  the latch will pivot or rotate about end portion  444   a  to provide rotational movement in the direction indicated by arrow  434 . This rotational motion will ultimately result in the latch tooth  432  disengaging from the catch  407 , thereby releasing the locking pin. Notably, the end portion  444   a  advantageously has a rounded end to facilitate the rotational motion described herein.  FIG. 5  shows the latch in its unlocked position with the latch tooth  432  fully disengaged from the catch  407 . 
     A guide structure  435  is provided within or as part of the security tag housing  406  and is arranged to constrain a movement of the latch  403 . The guide structure includes one or more lateral restraints  436 ,  438 . These lateral restraints are arranged to facilitate translational movement of the latch within the latch channel  430  along a path from the locked position to the unlocked position. This is accomplished by generally constraining movement of the latch in a lateral direction transverse to such path. However, the lateral restraints provide a sufficient clearance space  460  to allow for the rotational movement of the latch as described herein. The clearance space can be facilitated by a beveled or chamfered edge  462  which is defined on a portion of the latch adjacent to the lateral restraint  436 . The chamfered edge  462  is formed on a portion of the latch diagonally opposed from end portion  444   a . The chamfered edge  462  provides an additional clearance space between the latch and the lateral restraint  436  to permit the rotational movement of the latch in direction  434 . Maximum rotation of the latch is reached when the chamfered edge engages the lateral restraint  436 , or when the end portion  444   b  contacts the stop  440 . 
     In an exemplary arrangement shown in  FIGS. 4 and 5 , the lateral restraints  436 ,  438  can be provided in the form of side walls which generally guide the movement of the latch as it moves between the locked and unlocked positions. These side walls can define the boundaries of the latch channel  430 . A further portion of the guide structure is the stop  440 . The stop  440  is positioned adjacent to the base  418  and in some scenarios can be integrally formed with the base. As noted above, the stop  440  is arranged to limit the translational movement of the latch in a direction of travel  408  toward the unlocked position. The stop functions by engaging a portion of the latch, such as end portion  444   a . In an exemplary embodiment shown in  FIGS. 4 and 5 , the stop can be formed as a channel end wall which together with the side walls (lateral restraints  436 ,  438 ) encloses the locking mechanism. As such, the guide structure  435  can effectively define a channel housing. 
     The guide structure  435  is generally arranged to prevent substantial lateral movement of the latch in direction  420 . By restricting movement of the latch in this way, the locking pin  402  is similarly prevented from moving in direction  420  within the channel  414  whenever the latch is engaged with the locking pin. From the foregoing, it will be appreciated that the guide structure (and more particularly the lateral restraint  438 ) described herein generally restricts movement of the latch in direction  420 . Nevertheless, the lateral restraints  436 ,  438  provide a sufficient clearance space  460  to facilitate translational latch movement in directions aligned with the length of the latch channel  430  (direction  408 ) and rotational latch movement in direction  434 . 
     As noted above, repeated striking of a conventional security tag in a certain way can cause the tag to become unlocked. In security tag  400 , the latch  403  and the guide structure  435  are cooperatively arranged to prevent defeat of the locking mechanism in this way. When the base  418  of security tag  400  is impacted upon a hard surface, the impact and the physical mass associated with latch  403  will launch the latch along a motion trajectory. This motion trajectory will generally include motion components directed along the length of the latch channel (i.e. in direction  408 ). In a conventional magnetic lock, this motion trajectory might result in the latch moving from a locked position to an unlocked position. However, in the security tag  400 , the end portion  444   a  of elongated latch leg  442   a  and stop  440  are cooperatively arranged to disrupt a motion trajectory of the latch occurring when the housing  406  is subjected to such physical impact. More particularly, after an impact, the latch may begin a motion trajectory in a direction  408 . But the stop  440  is positioned so that the motion of the latch is disrupted before the tooth  432  can disengage from the catch  407 . The stop  440  will produce a counter-acting force to re-direct the motion trajectory of the latch. The re-directed motion trajectory will include motion components directed away from the stop and toward the locking pin  402 . These motion components will cause the latch to essentially bounce back toward the locking pin. 
     Due to the longer length of leg  442   a , the impact with the stop can introduce some torque upon the latch in rotational direction  434 . However, in contrast to when there is a continuous force upon the latch exerted by an applied magnetic field, the momentary torque produced by the impact of end portion  444   a  and stop  440  is not generally sufficient to allow the locking pin to be released. Instead, it has been observed that the response of the latch after disruptive interaction of the end portion  444   a  and stop  440  involves further disruptive interaction as between the catch  407  and the tooth  432 . The disruptive interactions prevent the latch from fully rotating out of engagement with the locking pin. It has been observed that in some instances there will be a momentary disengagement of the tooth with the catch, followed by immediate re-engagement as the latch rotates back into its locked position. However, the overall resistance to unlocking is greatly improved as compared to a conventional locking arrangement. Accordingly, the latch is selectively inhibited from moving fully from the locked position to the unlocked position when the housing is subjected to the physical impact. 
     In the exemplary embodiment in  FIGS. 4 and 5 , the unequal lengths of the two legs of the latch serve to impart rotation to the latch  403  when the latch is introduced to the magnetic detacher. In other embodiments, the rotational response is achieved by configuring the latch to have a magnetic imbalance, for example, by varying the materials of different portions of the latch. When the latch is subjected to the detacher field, the latch will rotate in the direction indicated (direction  434 ) due to physical restrictions on a portion of the latch, or due to the torque introduced by the imbalance in the magnetic response. This rotation will enable the latch tooth  432  to rotate clear of the catch  407 , thereby allowing the pin to be extracted. In such a scenario, the latch and the guide structure can have a different point of engagement to facilitate the re-direction of a latch motion trajectory as described herein. In such an embodiment, all that is needed is engagement between at least one portion of the guide structure and a portion of the latch that is sufficient to disrupt a motion trajectory of the latch occurring when the housing is subjected to a physical impact. 
     The inventive arrangements have thus far been described in terms of a security tag device. However, it should be appreciated that the invention also concerns a method for preventing defeat of a security tag as described herein. As such the method involves selectively disrupting with one or more portions of a guide structure  235 ,  435  a motion trajectory of the latch occurring when the housing  206 ,  406  is subjected to a physical impact. More particularly, the method involves selectively preventing the latch  203 ,  403  from moving fully from the locked position to the unlocked position only when the housing is subjected to the physical impact. In the embodiments disclosed in  FIGS. 2-5 , the latch is capable of repeatedly and consistently moving from the locked position to the unlocked position when subjected to a continuously applied magnetic field. However, the same result cannot be produced when the security tag is subjected to a physical impact due to the motion disrupting engagement of the guide structure  235 ,  435  with the latch  203 ,  403 . In such scenarios, the kinetic energy of the latch associated with an impact produced motion trajectory is effectively re-oriented or re-directed along a different path. The re-directed energy is eventually wasted within the housing (e.g. as heat) as the kinetic energy of the latch is re-directed along various different vector that are ineffective for producing an unlocking effect. 
     All of the apparatus, methods and algorithms disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the invention has been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the apparatus, methods and sequence of steps of the method without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain components may be added to, combined with, or substituted for the components described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined.