Abstract:
Tamper-resistant alarm switch assemblies ( 22, 100, 124, 148 ) are provided which include a first movement-sensing switch ( 24 ) and a second tamper-sensing switch assembly ( 25 ) including a switchable component ( 26 ) and an actuating component ( 74, 136, 166 ), mounted on a member ( 30 ) and each being switchable between respective first and second movement-sensing and tamper-sensing switch states in response to relative movement between first and second members ( 30, 32 ), and relative shifting between the switch ( 26 ) and actuating component ( 74, 136, 166 ). Mounting structure ( 28, 106, 138 ) is provided to attach the first switch ( 24 ) and second switch assembly ( 25 ) to the member ( 30 ) in a normal operating position wherein the first switch ( 24 ) will sense relative movement between the first and second members ( 30, 32 ), with relative shifting between the switchable component ( 26 ) and the actuating component ( 74, 136, 166 ) in the event of an attempted detachment of at least one of the components ( 26, 74, 136, 166 ) of the tamper switch assembly ( 25 ), or the first switch ( 24 ), or both thereof, from the member ( 30 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with improved tamper-resistant switch assemblies operable to detect relative movement between first and second relatively shiftable members while providing a reliable anti-tampering feature. More particularly, the invention is concerned with such switch assemblies which are specifically designed for use in high security contexts, while permitting interior mounting of the components thereof within standard hollow door frames or the like. 
     2. Description of the Prior Art 
     In recent years the Magnasphere Corp. of Brookfield, Wis. has introduced a series of innovative and highly reliable switch products useful as a part of alarm systems or as proximity sensors. Such Magnasphere switches in general include a hollow housing typically (though not necessarily) formed of electrically conductive material and with one or more conductive electrodes extending into the housing. A shiftable conductive ball is also located within the housing. The ball moves under the influence of magnetic conditions between respective switch states, usually from a position of simultaneous contact with the switch electrodes to a position out of such simultaneous contact. Such switches are referred to herein as “magnetic ball” switches. U.S. Pat. Nos. 7,291,794; 5,977,873; 6,506,987; 6,603,378; 6,803,845; 7,023,308; and 5,332,992 illustrate various types of magnetic ball switches. 
     Harco Laboratories, Inc. of Bramford, Conn. has also commercialized a series of high-security switch products using multiple Magnasphere switches. See, e.g., U.S. Pat. Nos. 7,187,259; 7,218,194; and 7,248,136. High security switches of this type are almost always mounted externally, e.g., external assemblies are mounted in adjacent relationship on a door and door frame. These external switches may also include anti-tamper switch components, see U.S. Pat. No. 5,633,626. 
     However, externally mounted high security switches tend to be very unsightly and make easy access for potential tamperers. A particular problem in this regard is that putatively loyal employees may during business hours or other time when an alarm system is not operational attempt to tamper with inactive external switch components, so as to permit unauthorized entry during non-business hours when the alarm system is supposed to provide security. 
     Accordingly, there is a real unsatisfied need in the art for improved high security and other alarm switch assemblies which can if desired by mounted internally within hollow structures such as metallic door frames, and which provide reliable motion sensing and tamper sensing as required. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems outlined above and provides improved tamper-resistant switch assemblies operable to detect relative movement between first and second members, while also providing a secure and reliable anti-tamper feature. The switch assemblies of the invention are particularly suited to be a part of high security switches which may be mounted internally within the door frame or the like. Broadly speaking, the switch assemblies include a first movement-sensing switch mounted on one of the members and operable to switch between first and second separate movement-sensing states in response to relative movement between the first and second members, together with a second tamper switch assembly mounted on the one member and including a switchable component and an actuating component. The switchable component and actuating component are relatively shiftable, and the switchable component is switchable between first and second tamper-sensing states in response to the relative shifting between the switchable and actuating components. Finally, the overall assemblies include mounting structure operable to attach the first switch and the second switches to the one member in a normal operating position wherein the first switch will sense relative movement between the first and second members, and to cause relative shifting between the switchable component and the actuating component of the tamper-sensing switch assembly, in the event of attempted detachment of at least one of the components of the second switch assembly, the first switch, or both thereof, from the normal operating position. 
     Preferably, both the movement-sensing and the tamper-sensing switches are magnetically actuatable switches operable to switch between first and second separate switch states in response to a change in magnetic field conditions adjacent the switches. Especially preferred are magnetic ball or Magnasphere switches having a housing, at least one elongated, electrically conductive switch element extending into the housing, a shiftable body located within the housing and formed of electrically conductive material, and a second electrically conductive switch element, the body being shiftable within the housing between a first position wherein the body is in electrical contact with both the first and second switch elements, and a second position wherein the body is not in contact with both the first and second switch elements. 
     The mounting structure may be variable, depending upon the type of mounting member being used, and whether the switch assemblies are being retrofitted as replacements. For example, in certain cases the mounting structure comprises a first plate supporting the first movement-sensing switch, a second plate supporting one of the tamper-sensing switch assembly components, wherein the first and second plates secured to the one member. Typically threaded fasteners are used to attach the first and second plates to the one member. In such embodiments, the first and second switches are located within the first member and are cooperatively configured such that detachment of the first or second plate, or both thereof, causes alarm-triggering relative shifting movement between the switchable component and the actuating component of the tamper switch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a door mounted within a door frame and wherein the door and door frame are equipped with an alarm switch assembly in accordance with the invention; 
         FIG. 2  is a fragmentary, perspective, exploded view illustrating a portion of the door frame of  FIG. 1 , and with a first tamper-resistant alarm switch assembly embodiment; 
         FIG. 3  is a schematic view illustrating the configuration of a preferred movement-sensing switch in accordance with the invention, and illustrating the two switch states thereof; 
         FIG. 4  is a schematic view illustrating the configuration of a preferred switchable component forming a part of a tamper switch assembly in accordance with the invention; 
         FIG. 5  is a fragmentary vertical sectional view with parts broken away of the door and door frame-mounted alarm assembly of  FIG. 1 , shown with the door in its closed position and the movement-sensing switch in its first state; 
         FIG. 6  is a view similar to that of  FIG. 5 , but illustrating the door in its opened positioned and with the movement-sensing switch in its second state; 
         FIG. 7  is a view similar to that of  FIG. 6 , but illustrating operation of the tamper switch assembly in the event of an attempt to detach the switch assembly from the door frame; 
         FIG. 8  is a view similar to that of  FIG. 6 , but illustrating a second alarm switch assembly embodiment, wherein the door is closed and the movement-sensing switch thereof is in its first state; 
         FIG. 9  is a view similar to that of  FIG. 8 , but illustrating the door in its open position and with the movement-sensing switch in its second state; 
         FIG. 10  is a view similar to that of  FIG. 9 , but illustrating operation of the tamper switch assembly in the event of an attempt to detach the movement-sensing switch from the door frame; 
         FIG. 11  is a view similar to that of  FIG. 10 , but illustrating the operation of the tamper switch assembly in the event of an attempt to detach the tamper switch assembly from the door frame; 
         FIG. 12  is a perspective view with parts broken away of a third alarm assembly embodiment in accordance with the invention; 
         FIG. 13  is a view similar to that of  FIG. 6  and illustrating the  FIG. 13  embodiment with the door in its closed position and the movement-sensing switch in its first state; 
         FIG. 14  is a view similar to that of  FIG. 13 , but depicting the door opened and the movement-sensing switch in its second state; 
         FIG. 15  is an exploded perspective view of components of a fourth alarm switch assembly embodiment; 
         FIG. 16  is a vertical sectional view illustrating the fourth embodiment installed on a door/door frame; and 
         FIG. 17  is a vertical sectional exploded view illustrating the steps involved in construction of the switch assembly of the fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, a protected door and door frame assembly  20  illustrated in  FIG. 1 , with a tamper-resistant alarm switch assembly  22  in accordance with the invention operatively mounted on the door/door frame assembly  20 . Although not shown, it will be understood that the assembly  20  is operatively coupled with an alarm controller and alarm bell or other perceptible alarm-indicating device. A complete system of this type is illustrated in U.S. Pat. No. 7,291,794 ( FIG. 3 ), and such system disclosure is incorporated by reference herein. 
     The assembly  22  includes a first movement-sensing switch  24  ( FIG. 3 ), as well as a second tamper-sensing switch assembly  25  including a switchable component in the form of a switch  26 . Mounting structure  28  is also provided for securing the switches  24  and  26  onto the door or door frame of assembly  20 . Preferably, the switches  24 ,  26  are mounted on a door frame  30  such that the operative components are internally located within the confines of the door frame, with other components of the overall assembly  22  mounted on door  32 , as will be explained. In use, the assembly  22  is designed to initiate an alarm in the event of an unauthorized opening of door  32  when the alarm system is armed. Moreover, the assembly  22  is especially designed to provide a secure and reliable anti-tamper function when the door  32  is properly open, for example during normal business hours where the switch  24  is disarmed, thus exposing the assembly  22  to tampering. 
     In greater detail, the preferred movement-sensing switch  24  is a magnetic ball switch of the type commercialized by Magnasphere, Inc. of Brookfield, Wis. Such an exemplary switch is illustrated in  FIG. 3  and includes a metallic can-like housing  34  presenting a terminal flange  36 . The open end of housing  34  is closed by a cover  38  comprising a peripheral metallic wall  40  supporting a non-metallic plug  42 . An elongated, electrically conductive electrode  44  extends through plug  42  as shown, into the confines of housing  34 . A second electrode  46  is electrically coupled with metallic housing  34 . The switch  24  further includes a shiftable ball  48  located within housing  34 . Preferably, the ball is formed of magnetic material such as a ferromagnetic metal, or comprises a non-metallic ball coated with such a ferromagnetic material. A biasing magnet  50  is located adjacent the end of housing  34  remote from plug  42  and is magnetically coupled with ball  48 . As further shown in  FIG. 3 , the ball  48  may assume a first position (shown in full lines), corresponding to a first switch state, wherein the ball is magnetically biased towards the adjacent wall of housing  34 , and is out of contact with electrode  44  (and thus out of simultaneous contact with both electrodes  44  and housing  34 ). The ball  48  may alternately be shifted to a second position (shown in phantom), corresponding to a second switch state, wherein the ball is magnetically biased to a position in simultaneous contact with electrode  44  and the wall of housing  34 , the latter being electrically connected with electrode  46 . The preferred switch  24  also includes a separate operating magnet  52  which in the illustrated embodiment is mounted on door  32 . 
     Again referring to  FIG. 1 , it will be appreciated that when door  32  is closed operating magnet  52  is closely adjacent the switch  24 . As such, the magnetic field conditions adjacent the switch  24  induced by magnet  52  serve to move the ball  48  to the second position described above. However, in the event that the door  32  is opened while the assembly  22  is active, the magnet  52  moves away from the switch  24 , thereby allowing bias magnet  50  to magnetically shift ball  48  to the first position. This change in switch state is read by the alarm controller, and an alarm is actuated. 
     The preferred tamper-sensing switch  26  is illustrated in  FIG. 4  and is likewise of the magnetic ball variety. Specifically, the switch  26  includes a metallic housing  54 , and a cover  56  made up of peripheral wall  58  and non-conductive central plug  60 . A first electrode  62  extends through plug  60  and into the confines of housing  54 . A second electrode  64  is operatively secured to conductive housing  54 . A shiftable ball  66  is located within housing  54  and is shiftable between a first position (shown in full lines) corresponding to a first switch state, which is out of simultaneous contact with the electrode  62  and housing  54 . A magnetic biasing ring  68  is located about housing  54  and serves to bias ball  66  to the  FIG. 4  position. In the event that the switch  26  experiences magnetic field conditions of sufficient magnitude, the ball  66  is magnetically shifted to a second position in simultaneous contact with electrode  62  and housing  54 . 
     Attention is next directed to  FIGS. 2 and 5 , which illustrate in detail the assembly  22  and the preferred mounting thereof to door frame  30 . The switch  24  is located within a circular housing  70  which is filled with an epoxy or other suitable encapsulant  72  (the Figures illustrate only a portion of the encapsulant to facilitate an understanding of the invention). The electrodes  44  and  46  extend out of housing  70  for attachment to the overall alarm system. In addition, it will be observed that a tamper switch operating magnet  74  forming a part of tamper switch assembly  25  is also encased within encapsulant  72  in spaced relationship to the switch  24 . The tamper-sensing switch  26  is likewise located within a separate encapsulant-filled housing  76 , with the electrodes  62  and  64  extending out of the housing  76  for connection to the alarm system. 
     The switches  24  and  26  must be located in proper relative positions in order to operate effectively. Accordingly, the mounting structure  28  is especially designed for this purpose. The structure  28  includes a first apertured plate  78  supporting housing  70  and having a pair of spaced apart fastener-receiving openings  80 . Further, the structure  28  includes a second, generally L-shaped plate  82  supporting housing  76  and having a fastener-receiving opening  84 . In order to mount the assembly  22  within door frame  30 , a previously existing (in the case of a retrofit) or freshly drilled hole  86  is provided in door frame  30 , along with threaded fastener bores  88 ; as depicted, the hole  86  is closely dimensioned relative to the housing  70  so as to have only a minimum of side play. The structure  28  is completed by provision of two mounting screws  90 . 
     In order to install assembly  22  within door frame  30 , the upright leg of second plate  82  and attached housing  76  are passed through hole  86 , followed by insertion of the housing  70 . The opening  84  of plate  82  is then moved in registry with one of the openings  80  of plate  78 , and these aligned openings are located in registry with the adjacent bore  88 . Such positioning also serves to align the other opening  80  with the remaining bore  88 . Next, the screws  90  are passed through the openings and are threaded into the bores  88  in order to complete the construction. As installed, it will be seen that the switch  24  is located adjacent the bottom of housing  70 , whereas magnet  74  is located near the top of the housing and proximal to the sidewall thereof. Moreover, the switch  26  is located in close relationship to the magnet  74 , owing to the configuration of plate  82 . 
     The door  32  is equipped with a magnet  52  as previously described. In detail, the magnet  52  is positioned within an opening  92  of door  32  with a lower epoxy or similar plug  94 . The magnet  52  plug  94  are attached to door  30  by means of apertured plate  96  having a depending tubular section  96   a , with the plate  96  secured to the upper edge of door  32  by means of screws  98 . 
       FIG. 5  illustrates the door  32  closed against door frame  30 , in the normal security condition of assembly  22 . As seen, the magnet  52  is directly below switch  24 , and the influence of the magnet  52  serves to move switch ball  48  to the second position thereof with the ball is in simultaneous contact with electrode  44  and housing  34 . At the same time, the proximity of magnet  74  and tamper-sensing switch  26  causes the switch ball  66  of the latter to be moved to the second position thereof in simultaneous contact with electrode  62  and housing  54 . 
     If the door  32  is opened without disarming the alarm system, the movement of magnet  52  away from switch  24  allows biasing magnet  50  to move ball  48  to its first position as illustrated in  FIG. 6 . This change in switch state is then read by the alarm system and an alarm is triggered. It will be appreciated that during this operational sequence the tamper switch  26  does not come in to play. 
     However, in high security situations a tamper-resistant alarm switch assembly is desirable in order to prevent tampering with the switch assembly when the door  32  is open during normal business hours or the like.  FIG. 7  illustrates the operation of assembly  22  in such an event. Specifically, in order to disarm or otherwise deactivate the assembly  22 , the screws  90  would be removed as shown, and the plates  78  and  82  would be grasped and pulled away from door frame  30 . This immediately creates a situation where the tamper-sensing switch  26  is moved away from operating magnet  74 . This may occur owing to slippage between the housing  70  and plate  82 , or when the housing  76  engages the inner surface of door frame  30 . In any case, such relative movement between magnet  74  and tamper-sensing switch  26  immediately causes the switch ball  66  to move under the influence of biasing ring  68  to the first position thereof wherein the ball  66  is out of simultaneous contact with the electrode  62  and housing  54 . In this condition the alarm system is actuated. In this connection, it will be appreciated that in this tamper-sensing mode the movement-sensing switch  24  would normally be deactivated, because of the fact that the premises would be normally open, and door  32  could thus be opened and closed without triggering the alarm system. However, in the tamper-sensing mode, the tamper-sensing switch  26  would be armed to trigger an alarm if the assembly  22  is subjected to tampering. 
       FIGS. 8-11  illustrate another alarm switch assembly  100  which is designed for use with a door frame  30  having a relatively large, typically rectangular opening  104  therein. Such an opening  104  would commonly be found with certain types of conventional alarm switch assemblies currently in use. The assembly  100  and some of the remaining embodiments described herein preferably use the same door frame mounted movement-sensing switch  24  and associated operating magnet  52  within door  32 , and the same tamper-sensing switch assembly  25  including switch  26  and proximal operating magnet  74 . Accordingly, such like parts are identically numbered. 
     The assembly  100  makes use of mounting structure  106  which takes into account the rectangular opening  104 . In particular, the mounting structure  106  includes a relatively large first plate  108  having lateral opening  110  therein and which supports the housing  70 , much in the manner of plate  78 . The first plate  108  is secured to door frame  30  by means of screws  112  extending through openings  110  and into threaded bores provided in door frame  30 . The structure  106  further includes a somewhat Z-shaped bracket or second plate  114  which includes a bored connection leg  116 , a lateral stretch  118 , and an upright leg  120  supporting housing  76 . The second plate  114  is secured in place by means of a screw  122  extending through door frame  30  and into connection leg  116 . 
     The normal operating condition of assembly  100  ( FIG. 8 ) is the same of that for assembly  22 , such that when door  32  is opened, the movement-sensing switch  24  changes state to actuate an alarm. In the tamper-sensing condition ( FIG. 9 ), detachment of the first plate  108  by removal of the screws  112  causes the attached housing  76  to move out of opening  104 , thereby creating a relative movement between operating magnet  74  and tamper-sensing switch  26 . This in turn causes the tamper switch ball  66  to be shifted under the influence of biasing ring  68  to the first switch position, with resultant alarm triggering. Alternately, if an attempt is made to tamper with assembly  100  by removing screw  122 , the detached second plate  114  tilts or dislodges as illustrated in  FIG. 11  to again cause relative movement between magnet  74  and tamper-sensing switch  26 , which also triggers the alarm. 
       FIGS. 12-14  depict a still further embodiment of the invention, in the form of an alarm switch assembly  124 . The switch  24  is located within an encapsulant-filled housing  126  without provision of an operating magnet for tamper-sensing switch  26 . Rather, the tamper-sensing switch  26  is provided with a mount  128  including an upright tubular column  130  supported by a base plate  132 , the latter having an opening  134  in registry with the column  130 . A magnetic ball  136  is located within column  130  and is vertically moveable therein. The mounting structure  138  for assembly  124  is in the form of a simple plate  140  supporting housing  126  and base plate  132 . Connection openings  142  are provided adjacent the ends of plate  140  with one of such openings in registry with opening  134 , and receive and attachment screws  144  and  146 . It will be seen that screw  146  is considerably longer than the other screw  144 . 
       FIG. 13  illustrates the normal armed condition of the assembly  124 , with the door-mounted magnet  52  directly beneath movement-sensing switch  24 . Moreover, the longer screw  146  extends upwardly through openings  142  and  134 , and serves to elevate ball  136  to a point closely adjacent the tamper-sensing switch  26 . This relative location between the ball  136  and switch  26  serves to maintain tamper switch ball  66  in its second position in simultaneous contact with electrode  62  and housing  54 . 
     In the event of an attempted tamper, the removal of screw  146  ( FIG. 14 ) allows ball  136  to move downwardly within column  130 , with result that biasing ring  68  of tamper-sensing switch  26  moves ball  66  to its second position out of simultaneous contact with housing  54  and electrode  62 , thereby triggering an alarm. 
     It will be appreciated that in lieu of screw  146  an unthreaded upright positioning post or element could be used, with separate conventional mounting screws. 
       FIGS. 15 and 16  illustrate another alarm switch assembly  148 , which again makes use of the previously described movement-sensing switch  24  and tamper-sensing switch  26 . In this configuration, the assembly  148  is designed to fit within a circular opening  150  provided in door frame  30 . The switches  24  and  26  are both mounted within a encapsulated-filled housing  152 , with the switch  24  adjacent the base of the housing while the switch  26  is located near the upper end thereof. The housing  152  is also equipped with a counter sunk screw passageway  154  extending from the base to the upper end of the housing. The housing  152  fits within a complemental tubular bushing  156  having a lowermost abutment flange  158  and a pair of opposed side slots  160 . The top plate  162  of the housing includes a threaded ferrule  164  in alignment with passageway  154 , and an operating magnet  166 . 
     The mounting structure for assembly  148  includes the flange  158 , a connection screw  170  extending through passageway  154  and threaded into ferrule  164 , and a pair of spring clips  172 . The latter have a compressible bent section  174  and an upright section  176 . In use, the bushing  156  is installed within opening  150 , followed by positioning of clips  172  such that sections  174  thereof protrude through slots  160 . Next, the housing  152  is inserted into bushing  156 , thereby captively retaining the legs  176  of the clips  172  between the outer wall of the housing  152  and the inner wall of bushing  156 . The inherent spring qualities of the clips  172  serves to bias the flange  158  upwardly against the surface of door frame  30 . The screw  170  is then inserted through bore  154  by threading the end thereof into ferrule  164 . 
     The normal operation of assembly  148  is exactly that as described in connection with the earlier embodiment, it being understood that door-mounted magnet  152  is located directly below movement-sensing switch  24 , and that bushing-mounted magnet  166  is directly adjacent the tamper-sensing switch  26 . In the event of a tamper attempt wherein screw  170  is removed and housing  152  is removed from bushing  156 , the relative shifting of the switch  26  and magnet  166  serves to trigger an alarm. 
     It will thus be seen that the present invention provides tamper-resistant switch assemblies which retain full functionality during normal alarm operations, but which also have a significant tamper resistance. While the invention has been illustrated in the context of a system for protecting a door, it will be understood that the switch assemblies hereof can be used in a wide variety of situations, such as in the protection of windows or as proximity sensors. In this environment, the switch assemblies would signal the presence of a ferromagnetic body so that if such a body comes into proximity with the switch assemblies, the magnetic attraction is effected and a change in switch state occurs. 
     It will also be appreciated that the switch assemblies can be reversed, in the sense that the switch assemblies may be mounted on doors, rather than door frames. The same of course would be true in other uses. Further, while in the preferred magnetic ball switches use is made of external biasing and operating magnets, and a corresponding ferromagnetic ball, it is only necessary that these components be fabricated from appropriate materials which make possible the desired magnetic operation. Thus, the switch balls could be made of magnetic material, whereas the external components could be fabricated from a ferromagnetic material such as steel. Broadly speaking, it is only necessary that there be an adequate magnetic attraction or coupling between the switch balls and the associated components outside of the ball housings. 
     It should also be clear that while magnetic ball switches are preferred, the invention can utilize different types of switches as movement-sensing and/or tamper-sensing switches. Thus, these switches may be individually selected from the group consisting of a reed switch, a Hall effect switch, a micro switch, a magnetic slide switch of the type disclosed in U.S. Pat. No. 5,668,533 fully incorporated by reference herein, or a magnetic ball switch. Again, the only requisite is that a switch be provided which will change state for motion and/or tamper sensing.