Abstract:
Improved, magnetic high security switch apparatus is provided for use in detecting relative movement between first and second members such as a door frame and door from a close position, wherein the members are proximal, and an open position, where the members are separated. The switch apparatus includes a magnetic shiftable ball switch assembly having an elongated housing and a shiftable ball therein, which traverses an oblique path of travel between respective switch states in response to relative movement between the first and second members. Preferably, the housing is oriented at an oblique angle relative to the horizontal in order to prevent defeat of the switch apparatus through use of an external defeat magnet.

Description:
CROSS-RELATED APPLICATIONS 
     This application claims the benefit of Provisional Patent Application No. 61/456,611, filed Nov. 10, 2010, and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is broadly concerned with improved, high security switch apparatus, which can be used as a part of an alarm system responsive to unauthorized opening of a door or the like. More particularly, the invention is concerned with such apparatus which makes use of a ball-type magnetic switch assembly having an elongated housing and a magnetically shiftable ball therein. The ball traverses a path of travel between respective switch states which is oriented at an oblique angle relative to the horizontal, in order to prevent defeat of the alarm system through use of an external defeat magnet. 
     2. Description of the Prior Art 
     Prior art security alarm systems often make use of magnetic switches attached to doors and windows and integrated with the system for detecting unauthorized openings. One common type of magnetic switch used in these situations is a so-called reed switch. It has been found that reed switches are subject to unauthorized manipulation through use of an external magnet. Specifically, an intruder can hold a relatively strong magnet adjacent the reed switch which will then be operated (to either, open or close depending on the control scheme). With this accomplished, an intruder can open the door or window without triggering the alarm system. 
     A number of magnetic switches have been proposed in the past to overcome the inherent deficiencies of reed switches. U.S. Pat. Nos. 5,332,992, 5,530,428, 5,673,021, 5,880,659, 5,977,873, 6,506,987, 6,603,378, 7,023,308, 7,291,794, and 7,825,801 describe switches of this type. These switches typically include a pair of spaced apart switch elements with a shiftable body (e.g., a spherical ball) vertically movable within an upright housing between a first position where the ball is in simultaneous contact with both elements and a second position out of such simultaneous contact. An alarm circuit is operatively coupled with the switch elements so as to detect movement of the body. These switches represent a very significant advance in the art. The Magnasphere Corporation of Waukesha, Wis., has commercialized a series of magnetic switches of this type. 
     While magnetic ball switches of this type are greatly superior to reed switches, instances can arise when a very strong defeat magnet can be successfully used against alarm systems containing conventional magnetic ball switches. This may occur when the strong magnet is strategically placed so as to maintain the ball in its non-alarm switch state during the course of an illegal entry. There is accordingly a need in the art for an improved magnetic ball switch which makes it virtually impossible to defeat the switch using an external defeat magnet. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems outlined above, and provides high-security magnetic switch apparatus for detecting relative movement between first and second members from a close position wherein the members are proximal, and an open position where the members are separated. The apparatus broadly comprises a switch assembly for mounting on one of the members and including a housing configured and presenting a central axis and having first and second, spaced apart, electrically conductive switch elements, together with a shiftable, electrically conductive body within the housing and movable between a first switch state wherein the body is in simultaneous contact with the first and second switch elements, and a second switch state wherein the body is not in simultaneous contact with the first and second switch elements. The overall switch assembly also includes a biasing member proximal to the switch housing. The biasing member and the shiftable body of the switch are magnetically correlated such that when the first and second members are in the open position, the biasing member magnetically maintains the body in one of the switch states. 
     The overall apparatus also has an operating magnet configured for mounting on the other of the members. The operating magnet and the switch assembly are magnetically correlated such that when the first and second members are in the close position, the operating magnet magnetically maintains the body in the other of the switch states against the magnetic correlation between the body and the biasing means. 
     As used herein, “magnetically correlated” refers to the fact that the respective components of the switch apparatus are selected in terms of the material makeup thereof, size, location, and relative orientation so as to provide the requisite magnetic functionality for the components. 
     In order to increase the security of the switch apparatus, the switch assembly is oriented so that the movable body traverses a path of travel between the first and second switch states which is oblique relative to the horizontal, so that, if a defeat magnet is placed adjacent the switch assembly when the first and second members are in the close position, the defeat magnet will magnetically move the body to the one switch state notwithstanding the close position of the first and second members. In preferred forms, the housing is oriented with the central axis thereof at an oblique angle relative to the horizontal. 
     Preferably, the shiftable switch body is in the form of a spherical ball formed of magnetic material, whereas the biasing member is formed of a ferromagnetic material, such as steel. The switch assembly housing is oriented with the central axis thereof at an angle of from about 15-80° relative to the horizontal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a preferred magnetic switch apparatus in accordance with the invention, shown mounted and in use with a door frame and door; 
         FIG. 2  is a fragmentary sectional view illustrating the components of the apparatus including a switch assembly, with the apparatus mounted on the door frame and door, and with the switch assembly in a first switch state; 
         FIG. 3  is a view similar to that of  FIG. 2 , but depicting the switch assembly in a second switch state; 
         FIG. 4  is a view similar to that of  FIG. 1 , but depicting the alarm operation of the switch apparatus in the event that a defeat magnet is used in an attempted unauthorized opening of the door; 
         FIG. 5  is another switch apparatus embodiment in accordance with the invention, mounted on a door frame and door, with the switch assembly thereof in a switch open state; 
         FIG. 6  is a still further switch apparatus embodiment in accordance with the invention, mounted on a door frame and door, with the switch assembly thereof in a switch closed state; 
         FIG. 7  is a view similar to that of  FIG. 5 , but illustrating the switch assembly in the switch state closed; and 
         FIG. 8  is a view similar to that of  FIG. 6 , but depicting the alarm operation of the switch apparatus in the event that a defeat magnet is used in an attempted unauthorized opening of the door. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiment of FIGS.  1 - 4   
     Turning now to the drawings, a switch apparatus  10  is illustrated in  FIG. 1 , with components thereof mounted on a door frame  12  and door  14 . Although not shown, it will be understood that the switch assembly  10  is operatively connected with an alarm system which will produce a discernable alarm in the event of a forced entry through door  14 . The switch apparatus  10  broadly includes a switch assembly  16  normally mounted on frame  12 , and a operating magnet assembly  18  mounted on door  14 . As illustrated, when the door  14  is closed, the assemblies  16  and  18  are in close proximity, and when the door  14  is opened, the assemblies  16  and  18  are separated. 
     In more detail, the switch assembly  16  includes an outer enclosure  20  in the form of a generally rectangular box-like structure having inner and outer sidewalls  22 ,  24 . As seen, the inner sidewall  22  abuts frame  12  and screws  26  are employed to secure the enclosure  20 . The switch assembly  16  further includes a magnetic switch  28  and a biasing member  30  within enclosure  20 . The switch  28  is in the form of a Magnasphere® magnetic switch and has an elongated metallic housing  32  with a non-conductive closure disk  34  at the lower end thereof. An elongated, rod-like first switch element  36  extends centrally through the closure disk  34  and is coupled with an external electrical lead  38 . The conductive housing  32  serves as the second switch element, and an external lead  40  is coupled to the housing for this purpose. 
     A spherical magnetic body in the form of a spherical ball  42  is located within housing  32 . The ball is shiftable within the housing  32  between a first switch state (see  FIG. 2 ), wherein the ball  42  is in simultaneous electrical contact with the switch element  36  and housing  32  (in this instance, the closed switch state), and a second switch state (see  FIG. 3 ), wherein the ball  42  is not in simultaneous contact with switch element  36  and housing  32  (in this instance, the open switch state). 
     The biasing member  30  comprises an elongated ferromagnetic (e.g., steel) component  44  of cylindrical shape. As illustrated, the component  44  is axially aligned with housing  32  and is spaced therefrom. 
     The switch  28  and biasing component  44  are magnetically correlated, such that when the  14  and frame  12  are in the open position ( FIG. 3 ), the biasing component serves to magnetically shift and maintain the ball  42  in the second switch state wherein the ball  42  is out of simultaneous contact with the switch elements. In this embodiment, the ball  42  is formed of magnetic material, whereas the component  44  is ferromagnetic; of course, this arrangement could be reversed. The only important feature is that there be an appropriate magnetic correlation between the ball  42  and component  44 . 
     In preferred manufacturing practice, the switch  28  and biasing component  44  are properly located within enclosure  20  and are tested for the appropriate magnetic correlation between the ball  42  and component  44 . At this point, the enclosure  20  is filled with a potting material  45 , such as epoxy, which surrounds the switch assembly  28  and component  44 , permanently maintaining them in the desired orientation. 
     The overall switch apparatus  10  also includes an operating magnet  46  mounted to door frame  14 . In detail, the magnet  46  is housed within a metallic enclosure  48  secured to door  14  by means of screws  50 . The internal operating magnet  46  is magnetically correlated with the switch  28  so that, when the door  14  and frame  12  are in the close position, the operating magnet magnetically shifts and maintains the ball  42  in the other of the switch states (in this instance, the closed switch state) against the magnetic correlation between the ball  42  and biasing component  44 . If desired, the enclosure  48  may be filled with potting material in the same manner as enclosure  20 . 
     Importantly, the housing  32  is oriented at an oblique angle within enclosure  20 . Referring to  FIG. 2 , it will be observed that the central axis A of the housing  32  is at an oblique angle θ relative to the horizontal H. As used herein, an “oblique” angle is an acute or obtuse angle, but not a right angle, a straight angle, or a full angle. Preferably, the angle θ broadly ranges from about 15-80°, and, in this embodiment, from about 50-75°, relative to the horizontal. Also, the housing  32  is oriented such that an upwardly extending vector coincident with the central axis A may be resolved into orthogonal vector components, a an upwardly extending vertical component and a horizontal component directed away from the door frame  12 . The inclination of housing  32  (and preferably the magnetic component  44  as well) makes it virtually impossible to defeat the switch apparatus  10  through the use of a defeat magnet (see  FIG. 4 ), as explained below. 
     The operation of switch apparatus  10  can be readily understood from a sequential consideration of  FIGS. 2 and 3 . When the door  14  is closed, the operating magnet  46  comes into play to magnetically move and hold the ball  42  in the first switch state with the body  44  in simultaneous contact with rod-like first switch element  36  and the conductive housing  32  ( FIG. 2 ). However, when the door  14  is in the open position ( FIG. 3 ), the magnetic correlation between component  44  and ball  42  serves to magnetically move and maintain the ball  42  in the second switch state where the ball  42  is out of contact with the switch element  36 . Of course, during normal business hours, the alarm coupled with the switch apparatus  10  is disarmed, and thus authorized opening of the door  14  does not trigger any alarm, even though the switch  28  changes states during opening and closing of door  14 . During non-business hours, the alarm is armed so that if the door  14  is forced open in the course of an illegal entry, the movement of the ball  42  from the first switch state ( FIG. 2 ), to the second switch state ( FIG. 3 ) triggers the alarm. 
     It will be appreciated that the ball  42  traverses a path of travel between switch states which is oblique relative to the horizontal. This is preferably accomplished by the inclination of housing  32  and, preferably, component  44 . In such an orientation, it is virtually impossible to defeat the apparatus  10  through the use of a defeat magnet  52 . That is, as seen in  FIG. 4 , if a defeat magnet  52  is placed adjacent the outer sidewall  24  of enclosure  20  while the system is armed, the defeat magnet itself will magnetically move ball  42  along an oblique path of travel to the second switch state, thereby triggering the alarm. This is to be contrasted with certain situations where a fully upright switch housing (i.e., oriented at a right angle to the horizontal H) could be defeated by a defeat magnet, i.e., the defeat magnet is of sufficient strength to maintain the ball  42  in the first switch state thereof, notwithstanding the opening of door  14 . It will be appreciated that the inclination of the switch assembly  28  will necessarily cause ball movement to the second switch state in the presence of the defeat magnet  52 ; indeed, the stronger the defeat magnet, the more positively will it magnetically move the ball  42  to the alarm-giving second switch state. 
     Embodiments of FIGS.  5 - 8   
       FIGS. 5 ,  7 , and  8  illustrate another embodiment in accordance with the invention in the form of a switch apparatus  54 , broadly including a switch assembly  56  and an operating magnet assembly  58  respectively secured to door frame  12  and door  14 . 
     The assembly  56  includes an outer enclosure  60  with a switch  62  therein, and filled with potting material  64 . The switch  62  includes an elongated, metallic, electrically conductive switch housing  66  with an endmost closure disk  68  formed of a non-conducting material, such as synthetic resin. An annular biasing element  69  formed of ferromagnetic material surrounds the upper end of housing  66  adjacent the disk  68 . A rod-like, electrically conductive first switch element  70  extends centrally through the disk  68  and into the confines of housing  66 , the latter serving as a second switch element. Leads  71  are operatively coupled to the switch element  70  and housing  66  to allow the switch assembly to be coupled to an alarm system (not shown). A magnetic spherical ball  72  is located within the housing  66  and is shiftable between a second state or open switch position ( FIG. 5 ), wherein the ball  72  is out of contact with the switch element  70 , and a first state or closed switch position ( FIG. 7 ), where the ball  72  is in simultaneous contact with the first switch element  70  and metallic housing  66 . 
     The operating magnet assembly  58  includes a housing  74  with an operating magnet  76  strategically located therein. Again, the housing  74  is filled with potting material  64 . 
     The operation of switch apparatus  54  is substantially identical to that previously described with respect to apparatus  10 , except that the switch states are reversed. That is, when the door  14  is closed ( FIG. 5 ), the operating magnet  76  serves to shift and maintain the ball  72  in the second switch state corresponding to the switch open position. When the door  14  is opened, the biasing element  69  serves to magnetically move and maintain the ball in the first switch state corresponding to the switch closed position ( FIG. 7 ). The anti-defeat function of the switch apparatus  56  is also identical to that described above, in that the defeat magnet  52  serves to move the ball  72  to an alarm-giving first switch state, wherein the ball  72  is in simultaneous contact with switch element  70  and housing  66 . In this embodiment, the central axis of housing  66  is at an angle of from about 15-60°. 
       FIG. 6  illustrates a switch apparatus  54   a  very similar to the apparatus  54 , and accordingly identical components are identically numbered, with the  FIG. 6  component reference numbers including the subscript “a.” The only differences in the assembly  54   a  are that the switch  62   a  is reversed, and the biasing element  69   a  is positioned on the housing  66   a  at a position remote from disk  68   a . It will be appreciated that the apparatus  54   a  operates identically to the apparatus  10  insofar as the switch states are concerned. In both of these embodiments, when the door  14  is closed, the switches  28  and  62   a  assume a switch state wherein the spherical ball  42  or  72   a  are in simultaneous contact with the switch elements; and when the door  14  is opened, the switch states are changed. It will further be appreciated that the anti-defeat operation of the switch apparatus  54   a  is identical to that of the apparatus  54 . 
     While the first switch state has been described herein as a state where the shiftable balls  42 ,  72 , and  72   a  are in simultaneous contact with the switch elements, and conversely the second switch state is described where the balls are out of such simultaneous contact, it will be appreciated that such designations are for convenience only, and that such designations could be reversed if desired. 
     Also, while the switch apparatuses hereof have been described in the context of doors and door frames, the invention could equally be used with any system utilizing relatively shiftable members, such as windows and window frames.