Patent Publication Number: US-7714716-B2

Title: Coded security sensor for a door

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to surveillance system sensors, and, more particularly, to surveillance system sensors for detecting the opening of a door or window. 
   2. Description of the Related Art 
   Surveillance systems, also known as security systems, are known to include door sensors for monitoring the opening and closing of a door. Door sensors are known to be in the form of a pushbutton that is held in a depressed state by the door when the door is in a closed position. When opening, the door moves away from the pushbutton, thereby releasing the pushbutton from the depressed state. A controller monitors the state of the pushbutton, and may issue an alarm signal if the door is opened without authorization. A problem with this type of sensor is that an intruder can defeat it by inserting a thin object, such as a piece of sheet metal, between the door and the pushbutton such that the object holds the pushbutton in a depressed state when the door is opened. Thus, the controller cannot detect that the door has been opened. 
   Another type of door sensor is the magnetic reed switch type that includes a reed switch sensor mounted on the door frame. The sensor detects and monitors the presence of a magnet that is mounted on the door at a location that is adjacent to the sensor when the door is in the closed position. Thus, the magnet may be detected by the sensor only when the door is closed. A problem with this type of sensor is that it too may be defeated by an intruder. For example, the intruder may attach another magnet adjacent to the reed switch sensor before opening the door such that the sensor&#39;s detection of the presence of a magnet is uninterrupted. Here too, the sensor, and a controller connected to the sensor, cannot detect that the door has been opened. 
   What is needed in the art is a door/window sensor that cannot be easily defeated by an intruder and that can be incorporated into a security system. 
   SUMMARY OF THE INVENTION 
   The present invention provides a door sensor having a first part that may be mounted on a door frame or on a door, and that includes an optical or magnetic code reader. A second part of the door sensor may be mounted on the other one of the door frame and the door, and includes a multi-bit code which may be read by the code reader. 
   The invention comprises, in one form thereof, a method of detecting a position of a movable building structure. A readable code is mounted in association with a first surface of the movable building structure or with a second surface of a second structure. A code reader is mounted in association with the other of the first surface and the second surface. The readable code is read by the code reader to thereby verify that the first surface of the movable building structure is disposed in opposition to the second surface of the second structure. 
   The invention comprises, in another form thereof, a security assembly including a first building structure at least partially defining a building opening. The first building structure has a first surface. A movable building structure is movable between a closed position in which the movable building structure covers the opening and an open position in which the movable building structure uncovers the opening. The movable building structure has a perimeter with a second surface disposed in opposition to the first surface when the movable building structure is in the closed position. A sensor apparatus includes an optical scanner mounted in the first surface or the second surface. The optical scanner scans a pattern printed in association with the other of the first surface and the second surface and produces a signal dependent upon the pattern. A decoder is in communication with the scanner. The decoder receives the signal and verifies therefrom that the movable building structure is disposed in opposition to the first building structure. 
   The invention comprises, in yet another form thereof, a security assembly including a first building structure at least partially defining a building opening. The first building structure has a first surface. A movable building structure is movable between a closed position in which the movable building structure covers the opening and an open position in which the movable building structure uncovers the opening. The movable building structure has a perimeter with a second surface disposed in opposition to the first surface when the movable building structure is in the closed position. A sensor apparatus includes a plurality of magnetic field sensors mounted in the first surface or the second surface. Each of the sensors senses whether a respective magnetic element is disposed opposite the sensor on the other of the first surface and the second surface, and produces a signal indicative thereof. A decoder device, which is in communication with the sensors, receives the signals and verifies therefrom that the movable building structure is disposed in opposition to the first building structure. 
   The invention comprises, in still another form thereof, a security assembly including a first object having a first surface and a second object having a second surface. The second object is movable between a first position in which the first surface is adjacent to the second surface and a second position in which the first surface is non-adjacent to the second surface. A sensor apparatus includes a plurality of magnetic field sensors mounted in the first surface or the second surface. Each of the sensors senses whether a respective magnetic element is disposed opposite the sensor on the other of the first surface and the second surface, and produces a signal indicative thereof. A decoder device is in communication with the sensors. The decoder device receives the signals and determines therefrom whether the second object is in the first position or the second position. 
   An advantage of the present invention is that it is difficult for a would-be intruder to defeat. Because the code or pattern read by the sensor is unique and is not visible, it is difficult for a would-be intruder to replicate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a plan view of one embodiment of a door assembly including a security sensor apparatus of the present invention. 
       FIG. 2  is a block diagram of one embodiment of the sensor apparatus of  FIG. 1 . 
       FIG. 3  is a block diagram of another embodiment of the sensor apparatus of  FIG. 1 . 
       FIG. 4  is a plan view of one embodiment of a window assembly including a security sensor apparatus of the present invention. 
       FIG. 5  is a flow chart of one embodiment of a method of the present invention for detecting a position of a movable building structure. 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates embodiments of the invention, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed. 
   DESCRIPTION OF THE PRESENT INVENTION 
   Referring now to the drawings and particularly to  FIG. 1 , there is shown one embodiment of a security assembly, in particular a door assembly  10 , of the present invention for incorporation into a structure  12  such as a building, or, more particularly, a wall of a building. Door assembly  10  includes a movable building structure in the form of a door  14 , which is surrounded by portions of structure  12 , such as a door frame  16  and a floor surface  18 . Door frame  16  and a floor surface  18  define a building opening  19  in the form of a doorway that door  14  covers when door  14  is in a closed position and that door  14  uncovers when door  14  is in an open position. A security sensor apparatus  20  is mounted partially within door  14  and partially within door frame  16 . Security sensor apparatus  20  includes a readable code arrangement  22  and a code reader  24 . Readable code arrangement  22  and code reader  24  may be mounted in opposing locations within door  14  and door frame  16 , respectively. 
   Door  14  may be opened by manually grasping knob  26  and rotating door  14  about hinges  28   a,    28   b,  i.e., about an axis  30  defined by hinges  28 , as is well known. If door  14  is locked, i.e., if a latch  32  of door  14  is locked in a coupled state with frame  16 , an intruder may nevertheless open door  14  by breaking hinges  28  and/or latch  32  away from frame  16 , thereby allowing door  14  to be moved away from frame  16 , as is also well known. 
   Readable code arrangement  22  may be mounted in or on a surface of door  14  at a location that is along a perimeter  34  of door  14 . Perimeter  34  may be defined as an outer section of door  14  that is between outer edges  36  of door  14  and locations indicated generally by dashed line  38 . Readable code arrangement  22  is shown mounted in a surface of perimeter  34  that is disposed opposite from hinges  28 . However, readable code arrangement  22  could alternatively be mounted in a surface of perimeter  34  that is adjacent to hinges  28 , as indicated at  40 . Moreover, readable code arrangement  22  could be mounted not in a jamb, but rather in a surface of an upper portion of perimeter  34 , as indicated at  42 . 
   Regardless of in which location in the surface of perimeter  34  readable code arrangement  22  is mounted, code reader  24  may be mounted in a surface of door frame  16  at a location that opposes the mounting location of readable code arrangement  22 . 
   As shown in  FIG. 2 , code reader  24  may be electrically connected to a controller  48 , such as through line  54 . Controller  48  may be in the form of a decoder that receives on line  54  a signal from code reader  24  that is indicative of a code read by code reader  24 . Controller  48  may compare the code read by code reader  24  to an expected code which may be pre-programmed into controller  48 . If controller  48  determines that there is a sufficient match between the code read by code reader  24  and the expected code, then controller  48  may thereby verify that door  14  is disposed in opposition to, or adjacent to, door frame  16 , i.e., that door  14  is in the closed position. 
   Although controller  48  is shown in  FIG. 2  as being disposed outside of door frame  16 , controller  48  may alternatively be disposed within door frame  16 . In a particular embodiment, controller  48  is disposed within a control panel (not shown) or within some other centralized device that is capable of causing some type of alarm signal or tamper signal to be issued in response to controller  48  determining that door  14  has been opened without authorization. A determination that door  14  has been opened may be made by controller  48  as a result of code reader  24  no longer reading a code that matches the expected code that may be programmed into controller  48 . Code reader  24  may attempt to read the code continuously or periodically with a frequency that may depend upon the requirements of a particular application. 
   Code reader  24  may be in the form of a bar code reader that reads a readable code arrangement  22  in the form of a bar code that is printed in association with a surface  56  of outer edge  36  of door  14 . The bar code may be printed directly on surface  56 , or may be printed on a label or sticker that is affixed to surface  56 , for example. 
   Code reader  24  may scan the code on surface  56  by using light in the infrared range. In order to prevent a bystander from visually reading the code on surface  56  and replicating the code on a portable surface for use in defeating the system, the code may be covered by a substrate  58  that is visually opaque. Substrate  58  may also be transparent to infrared light in order to allow code reader  24  to read the code through substrate  58 . Substrate  58  may be attached to surface  56  via adhesive or any conventional fastening devices, such as screws (not shown). Code reader  24  may include an emitter (not shown) that produces optical energy having a wavelength in the infrared range. Code reader  24  may also include a photodiode (not shown) or any other type of optical receiver that is capable of detecting optical energy of the infrared frequency range. 
   In order to prevent a would-be intruder from removing substrate  58  so that he may visually read the code, substrate  58  and the code may be configured such that attempting to remove substrate  58  from surface  56  results in the code becoming unreadable. For example, the code could be laminated or molded underneath or into substrate  58 . Substrate  58  may be designed to break, disintegrate, or otherwise self-destruct along with the code in the event that an attempt is made to remove substrate  58  from surface  56 . Particularly, the code could be formed of thin, fragile material that is molded into substrate  58  such that the code breaks apart and becomes unreadable if substrate  58  is tampered with. 
   As shown in  FIG. 2 , the code is deposited on a substantially planar surface  56 , and substrate  58  is attached to the planar surface  56 . However, in another embodiment, surface  56  is provided with a recess  60 , indicated in dashed lines in  FIG. 2 , sized to receive substrate  58  therein. Recess  60  may be provided with a depth such that an outer surface  62  of substrate  58  is coplanar with the remainder of surface  56  that is not included in recess  60 . Such a configuration has the advantages of substrate  58  being more difficult to remove from door  14 , and of outer surface  62  and surface  56  conjointly forming a continuous smooth surface that is less subject to being damaged and causing damage. 
   It is to be understood that when code reader  24  is in the form of an optical scanner, the code that is read is not limited to a bar code or any type of binary code. It is possible within the scope of the invention for code reader  24  to optically read or recognize a unique pattern that is printed or otherwise deposited in association with surface  56 . Code reader  24  may read or recognize the pattern digitally or through other techniques. 
     FIG. 3  illustrates another embodiment of a sensor apparatus  120  suitable for use in the application depicted in  FIG. 1 . In this embodiment, a readable code arrangement  122  is in the form of locations  64   a - h  each having a respective presence or absence of a magnet  66  therein. In the example shown, locations  64   a, b, e, f  and  h  each have a respective magnet  66  present therein; and a magnet is absent in each of locations  64   c, d  and  g . Considering location  64   a  to represent a least significant bit, and location  64   h  to represent a most significant bit, the placement of the five magnets  66  in  FIG. 3  may be represented by the binary code 1011 0011. A visually opaque but magnetically transparent shield  68  may cover each of locations  64  in order to prevent a would-be intruder from seeing in which locations  64  that magnets  66  are present. 
   In the embodiment of  FIG. 3 , a code reader  124  is in the form of magnetic field sensors  70   a - h  that are electrically connected to a decoder device in the form of a controller  148 . Magnetic field sensors  70  may be in the form of reed switches that each sense whether a magnet  66  is disposed opposite the sensor, and that each produce a signal indicative of whether the magnet is sensed. Each of the signals may be transmitted by the respective reed switches to controller  148 . 
   During use, after installation of security sensor apparatus  20  or  120 , door  14  is moved to a closed position and sensor apparatus  20 ,  120  is armed, such as by a user via a control panel (not shown). In the armed state, sensor apparatus  20 ,  120  may continually or periodically monitor the status of door  14 . The user may disarm sensor apparatus  20 ,  120  by entering a security code into the control panel, for example, perhaps within a grace time period after door  14  is opened. In the disarmed state, sensor apparatus  20 ,  120  may no longer monitor door  14 , or may refrain from issuing an alarm signal or tamper signal if door  14  is opened. 
   In the armed state, if door  14  is opened, such as by an intruder, then code reader  24  or  124  is no longer in position to read the readable code of arrangement  22 ,  122 . A determination that door  14  has been opened may be made by controller  48  or  148  based upon a code reader  24 ,  124  no longer reading a code that matches an expected code that may be pre-programmed into controller  48 ,  148 . That is, controller  48 ,  148  compares a code that is read (or not read) by code reader  24 ,  124  to the expected code in order to determine whether there is a sufficient match between the two. The read code and the expected code may both be binary. Controller  48 ,  148  may issue an alarm signal in response to the determination that door  14  has been opened without authorization. 
   If controller  48 ,  148  determines that some code is being read by code reader  24 ,  124 , but it is not the expected code, then controller  48 ,  148  may conclude that someone may be tampering with sensor apparatus  20 ,  120 . That is, then controller  48 ,  148  may conclude that someone may be unsuccessfully trying to defeat sensor apparatus  20 ,  120  by attempting to place a counterfeit readable code arrangement such that it may be read by code reader  24 ,  124 . Controller  48 ,  148  may then issue a tamper signal, which may be, for example, in the form of a beeping sound that indicates to the user that investigation or maintenance may be needed. 
   The present invention has been described herein as being applied to detecting the opening and closing of a hinged door that swings between an open position and a closed position. However, the present invention may be used to monitor any movable building structure that is movable between a closed position in which the movable building structure covers a building opening and an open position in which the movable building structure uncovers the building opening. 
   In  FIG. 4 , there is shown another embodiment of a security assembly of the present invention in the form of a window assembly  210  for incorporation into a structure  212  such as a building, or, more particularly, a wall of a building. Window assembly  210  includes a movable building structure in the form of a movable window sash  214 , which is surrounded by portions of structure  212 , such as a wall, a window frame  216  and a fixed window sash  218 . Window frame  216  and a fixed window sash  218  define a building opening  219  in the form of a window opening that sash  214  covers when sash  214  is in a closed position and that sash  214  uncovers when sash  214  is in an open position. A security sensor apparatus  220  is mounted partially within sash  214  and partially within window frame  216 . More particularly, sensor apparatus  220  includes a readable code arrangement  222  and a code reader  224  which may be mounted in opposing locations within sash  214  and window frame  216 , respectively. 
   Sash  214  may be opened by manually grasping sash  214  and sliding sash  214  in an upward direction  225 , as is well known. Imaginary planes defined by sashes  214 ,  218  may be parallel to each other and displaced from each other in a direction into the page of  FIG. 4 . To at least partially open sash  214 , and thereby at least partially uncover opening  219 , sash  214  may be slid in direction  225  in tracks (not shown) in frame  216  such that sash  214  at least partially overlaps sash  218  in a direction into the page of  FIG. 4 , as is also well known. 
   Readable code arrangement  222  may be mounted in a surface of sash  214  at a location that is along a perimeter  234  of sash  214 . Perimeter  234  may be defined as an outer section of sash  214  that is between outer edges  236  of sash  214  and locations indicated generally by dashed line  238 . Readable code arrangement  222  is shown mounted in a vertically-oriented surface of perimeter  234 . However, readable code arrangement  222  could alternatively be mounted in the portion of the surface of perimeter  234  that is on the other end of sash  214 , as indicated at  240 . Moreover, readable code arrangement  222  could be mounted not in a vertically-oriented surface, but rather in a horizontally-oriented surface of perimeter  234  that is disposed opposite the window sill, as indicated at  242 . Regardless of in which location in the surface of perimeter  234  readable code arrangement  222  is mounted, code reader  224  may be mounted in a surface of window frame  216  at a location that opposes the mounting location of readable code arrangement  222 . 
     FIG. 5  illustrates one embodiment of a method  500  of the present invention for detecting a position of a movable building structure. In a first step  502 , a readable code is mounted in association with a first surface of a movable building structure or with a second surface of a second structure. For example, a bar code may be mounted on a surface  56  of door  14 , or may be mounted on a surface of door frame  16 . As another example, magnets  66  may be mounted in a subset of locations  64  on the surface of door  14 , or may be mounted in a subset of locations on a surface of door frame  16 . In a next step  504 , a code reader is mounted in association with the other of the first surface and the second surface. In particular, if a bar code or magnets  66  are mounted on a surface  56  of door  14 , then a bar code scanner or magnetic field sensors  70  may be mounted on a surface of door frame  16 . Alternatively, if a bar code or magnets  66  are mounted on a surface of door frame  16 , then a bar code scanner or magnetic field sensors may be mounted on a surface  56  of door  14 . In final step  506 , the readable code is read by the code reader to thereby verify that the first surface of the movable building structure is disposed in opposition to the second surface of the second structure. For example, the bar code may be read by the bar code scanner, or the locations of magnets  66  may be detected by magnetic field sensors  70 , to thereby verify that door  14  is disposed in opposition to door frame  16 , e.g., that door  14  is in the closed position. Although method  500  has been described above as applying to a door, it is to be understood that method  500  is equally applicable to a window. 
   The present invention has been primarily described herein in connection with sensing the opening of a hinged door that swings between an open position and a closed position. However, it is to be understood that the features of the present invention described herein may be equally applicable to sensing the opening of any movable building structure (such as a window or a sliding door) that translates between an open position and a closed position. Further, the features of the present invention described herein may be applicable to sensing the movement of any object, including an object that is not part of a building. 
   The present invention has been described herein as including a readable code arrangement and a code reader mounted at opposing locations within the door and the door frame, respectively. However, it is to be understood that it is within the scope of the present invention for the readable code arrangement to be mounted within the door frame and the code reader to be mounted within the door. Moreover, it is also within the scope of the present invention for one of the readable code arrangement and the code reader to be mounted within a bottom edge of the door and the other to be mounted at an opposing location within the floor surface. 
   The readable code arrangement of the present invention has been described herein as being mounted in an outer edge of a door so as to be sensed by a code reader that is opposingly positioned in the door frame. However, it is also possible for the readable code arrangement to be mounted within or on one of the two large opposite surfaces of the door, albeit along the perimeter of the door such that the readable code arrangement is covered, when the door is closed, by a portion of the door frame that is parallel to the plane defined by the door. In this case, the code reader may be mounted in or on the opposing surface of the door frame that is parallel to a plane defined by the door when the door is closed. 
   The code reader of the present invention has been described herein as being disposed in a fixed building structure, such as a door frame or a window frame. However, it is to be understood that it is also possible within the scope of the invention for both the code reader and the readable code arrangement to be disposed in opposing surfaces of two movable structures. For example, the code reader and the readable code arrangement may be disposed in opposing surfaces of a pair of French doors or a pair of French windows, both of which are hinged at opposite outside edges, and which open in the middle between the two movable structures. 
   While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.