Abstract:
An asset tracking device includes a mounting bracket and a housing attached to the mounting bracket. The mounting bracket includes a magnetic portion, first apertures that receive first fasteners for attaching the mounting bracket to the asset, and second apertures that receive second fasteners. Third apertures in the housing, aligned with the second apertures in the mounting bracket, receive the second fasteners for attaching the housing to the mounting bracket. When the housing is attached to the mounting bracket, the housing makes the fasteners in the mounting bracket inaccessible so that the mounting bracket cannot be removed from the asset. When the housing is removed from the mounting bracket, a magnetic switch changes state and triggers a controller to generate a tamper alert with location information indicating the location of the tracking device. A wireless transmitter wirelessly transmits the tamper alert and location information to a central monitoring station.

Description:
RELATED APPLICATIONS 
     This invention claims all rights on and priority to U.S. provisional patent application 61/562,526 filed Nov. 22, 2011, titled APPARATUS AND METHOD FOR DETECTING UNAUTHORIZED REMOVAL OF ASSET TRACKING DEVICE. 
    
    
     FIELD 
     This invention relates to the field of determining and reporting locations of assets in transit. More particularly, this invention relates to a system for detecting unauthorized tampering with or removal of an asset tracking device from an asset, such as a shipping container or a cargo trailer. 
     BACKGROUND 
     Cargo containers, such as shipboard cargo containers and cargo trailers used in the trucking industry, are often tracked using small tracking devices attached to the containers. These tracking devices typically incorporate a GPS module for determining the location of the container and a wireless communication module, such as a cellular or satellite modem, to transmit the location information to a central monitoring station. The tracking devices are usually attached to the containers using screws or “peel and stick” adhesive pads. 
     Such tracking devices are vulnerable to unauthorized removal, such as by thieves who have stolen the cargo container to which the tracking device is attached. Typically, if a thief is aware of the presence of the tracking device, the thief will remove the device at the first opportunity and discard it to prevent tracking of the stolen container. With conventional tracking devices, removal is fairly straightforward, and may involve only removing a few screws or peeling away an adhesive pad. 
     Typically, unless the tracking device is damaged during the removal process, the device continues to transmit its location to the central monitoring station with no indication that the device has been removed from the container. In such a situation, without other independent information regarding the theft or a geofence trigger event from the tracking device, the central monitoring entity may have no indication that the container has been stolen. 
     What is needed, therefore, is a system for sensing removal of a tracking device from a container or other asset, and for transmitting a notification signal to a central monitoring station upon such removal. 
     SUMMARY 
     The above and other needs are met by an asset tracking device that includes a mounting bracket configured for secure attachment to a surface of an asset to be tracked and a housing configured to be securely attached to the mounting bracket. Within the housing are a magnetic switch, a controller, a location determination circuit, and a wireless transmitter. In a preferred embodiment, the mounting bracket includes a magnetic portion, first apertures configured to receive first fasteners for securely attaching the mounting bracket to the surface of the asset, and second apertures configured to receive second fasteners. The housing has third apertures substantially aligned with the second apertures in the mounting bracket. The third apertures are configured to receive the second fasteners for securely attaching the housing to the mounting bracket. The housing is sized and configured to make the first fasteners in the mounting bracket inaccessible when the housing is attached to the mounting bracket. With this configuration, the mounting bracket may not be removed from the surface of the asset when the housing is attached to the mounting bracket. The magnetic switch, which is disposed in or on the housing, is configured to attain a first state when the housing is attached to the mounting bracket and a second state when the housing is not attached to the mounting bracket. The controller is operable to generate tamper alert information based on the magnetic switch changing from the first state to the second state. The location determination circuit generates location information indicative of a location of the asset tracking device. The wireless transmitter is configured to wirelessly transmit the tamper alert information and the location information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages of the invention are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein: 
         FIGS. 1-3  depict an asset tracking device according to an embodiment of the present disclosure; 
         FIG. 4A  is a top view of an asset tracking device according to an embodiment of the present disclosure; 
         FIG. 4B  is a front view of the asset tracking device shown in  FIG. 4A ; 
         FIG. 4C  is a side view of the asset tracking device shown in  FIG. 4A ; and 
         FIGS. 5A and 5B  depict a functional block diagrams of the electronic components disposed within the housing of the asset tracking device according to preferred embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The figures depict an asset tracking device  10 , such as may be used to wirelessly track the location of a shipping container or cargo trailer in transit. Electrical components of the device  10  are contained within a housing  12  which may be constructed from a thermoplastic material. The electrical components are described in more detail hereinafter. 
     The device  10  includes a mounting bracket  14  having fasteners  18  for attaching the mounting bracket  14  to the asset to be tracked. In one embodiment, the fasteners  18  are screws, such as self-tapping sheet metal screws, which pass through holes  24  in the mounting bracket  14  and into a surface of the asset. Alternatively, the fasteners  18  are bolts which pass through the holes  24  and through holes in the surface of the asset, and which are secured by nuts on the opposite side of the attachment structure on the asset. One skilled in the art will appreciate that other fastening means, such as rivets, may be used in other embodiments, and that the invention is not limited by the type of fastener used to hold the mounting bracket  14  to the asset. 
     The housing  12  of the tracking device  10  is secured to the mounting bracket  14  using fasteners  16 . In an embodiment depicted in  FIGS. 1 ,  2 ,  3  and  4 A- 4 C, the fasteners  16  are screws which are driven into threaded holes  22  in the mounting bracket  14 . In another embodiment, the housing  12  may be attached to the mounting bracket  14  using a peel-and-stick adhesive pad. One skilled in the art will appreciate that other fastening means may be used in other embodiments, and that the invention is not limited by the type of fastener used to hold the housing  12  to the mounting bracket  14 . 
     As shown in  FIGS. 1 ,  2 ,  3  and  4 A- 4 C, when the housing  12  is secured to the mounting bracket  14 , the housing  12  covers the fasteners  18  that secure the mounting bracket  14  to the asset. Thus, when the housing  12  is attached to the mounting bracket  14 , the fasteners  18  are inaccessible to any tool that may be used for their removal. Accordingly, the presence of the housing  12  prevents removal of the mounting bracket  14  from the asset. In order to gain access to the fasteners  18  to remove the mounting bracket  14  from the asset, one first must remove the housing  12  from the mounting bracket  14 . 
       FIGS. 5A and 5B  depict functional block diagrams of the electronic components disposed within the housing  12  of the asset tracking device  10  according to preferred embodiments. Both embodiments preferably include a Global Positioning System (GPS) module  32  for determining location coordinates of the asset tracking device  10  based on timing signals received from GPS satellites. The device  10  includes a wireless modem  34 , such as a cellular or satellite transceiver, for transmitting the location coordinates or other information to a central monitoring station. The modem  34  may also receive communications from the central monitoring station. A controller  30 , which includes microprocessor hardware and firmware, is connected to the GPS module  32  and the wireless modem  34  and controls the operation of the tracking device  10 . A battery  36  supplies power to the GPS module  32 , controller  30 , and wireless modem  34 . 
     The embodiment depicted in  FIG. 5A  includes a magnetic switch  28  in electrical communication with the controller  30 . The magnetic switch  28  is preferably attached in close proximity to an outer wall of the housing  12 . In one embodiment, the switch  28  attains an open state when the switch  28  is in close proximity to a magnetic material. In another embodiment, the switch  28  attains a closed state when the switch  28  is in close proximity to a magnetic material. In either embodiment, the controller  30  senses the state of the magnetic switch  28  as being either open or closed. Thus, when the outer wall of the housing  12  to which the switch  28  is attached comes in close proximity to a magnetic material, the switch  28  changes state. 
     As shown in  FIG. 5A , the tracking device  10  includes a magnet  26  embedded in or otherwise attached to the mounting bracket  14  in a location which will cause the magnet  26  to be in close proximity to the magnetic switch  28  when the housing  12  is attached to the mounting bracket  14 . In this manner, when the housing  12  is attached to the mounting bracket  14 , the magnetic switch  28  is in an open (or closed) state, and when the housing  12  is not attached to the mounting bracket  14 , the magnetic switch  28  is in a closed (or open) state. Thus, when the housing  12  is removed from the mounting bracket  14 , the magnetic switch  28  transitions from an open (or closed) state to a closed (or open) state. 
     In the embodiment of  FIG. 5B , the tracking device  10  includes a pressure switch  38  in electrical communication with the controller  30 . The pressure switch  38  is preferably attached in close proximity to an outer wall of the housing  12  and adjacent to an opening  40  in the outer wall of the housing  12 . This embodiment also includes a post  42  protruding from the surface of the mounting bracket  14  in a location at which the post  42  will protrude through the opening  40  and make contact with the pressure switch  38  when the housing  12  is attached to the mounting bracket  14 . 
     When the post  42  presses against the pressure switch  38 , the switch  38  is in a closed (or open) state, and when the post  42  does not press against the switch  38 , the switch is in an open (or closed) state. In this manner, when the housing  12  is attached to the mounting bracket  14 , the pressure switch  38  is in a closed (or open) state, and when the housing  12  is not attached to the mounting bracket  14 , the pressure switch  38  is in an open (or closed) state. Thus, when the housing  12  is removed from the mounting bracket  14 , the pressure switch transitions from a closed (or open) state to an open (or closed) state. In embodiments incorporating the pressure switch  38 , a rubber O-ring gasket may be disposed around the opening  40  and between the housing  12  and the surface of bracket  14  to prevent entry of water. 
     In either of the embodiments described above, when the housing  12  of the tracking device  10  is removed from the mounting bracket  14 , the controller  30  senses the change in state of the switch  28  or  38  and triggers the wireless modem  34  to transmit a tamper alert signal indicating to the central monitoring station that the housing  12  has been removed from the mounting bracket  14 . The tamper alert signal may also include location coordinate information from the GPS module  32  indicating the location of the asset at the time the tracking device was removed. If this was an unscheduled and unauthorized removal, the central monitoring station may then take action to recover the asset, such as by notifying law enforcement. 
     In other embodiments, a separate mounting bracket  14  is not required for the tracking device  10  to transmit a tamper alert signal upon removal from the asset. For example, in the embodiment of  FIG. 5B , the post  42  protruding through the opening  40  may be a component of the pressure switch  38  rather than a part of a mounting bracket. When the housing  12  is attached to the asset, the post  42  presses against the surface of the asset thereby causing the pressure switch  38  to be in a closed (or open) state. When the housing  12  is separated from the asset, the post  42  does not press against the surface of the asset, thereby causing the pressure switch  38  to be in an open (or closed) state. 
     Similarly, in embodiments where the asset tracking device  10  is attached to an asset having a magnetic surface, a separate mounting bracket having a magnet is not needed to cause the magnetic switch  28  to change state upon removal from the asset. 
     In alternative embodiments, an optical switch, such as an infrared switch, may be used to detect when the housing  12  is attached to the mounting bracket  14  or to a surface of the asset. Those skilled in the art will be familiar with various types of photoelectric sensors that may be used for this purpose. 
     In other alternative embodiments, other types of proximity sensors may be employed to detect when the housing  12  is attached to the mounting bracket  14  or to a surface of the asset, such as capacitive or inductive sensors. 
     In yet other alternative embodiments, electrical contacts on the bottom outside surface of the housing  12  could close a circuit by contacting a conductive strip on the bracket  14 , or by contacting conductive material from which the bracket  14  is made, or by contacting conductive material on a surface of the asset being tracked. Removal of the housing  12  from the bracket  14  or surface of the asset would cause this circuit to open, which event is monitored by the controller  30 . 
     The foregoing description of embodiments for this invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.