1. Field of the Invention
The present invention is broadly concerned with security assemblies adapted for connection to doors or similar movable objects, in order to provide an alarm function in the event of unauthorized opening of the doors. More particularly, it is concerned with such security assemblies, as well as switch assemblies forming a part thereof wherein the security assemblies have one or more switch assemblies each having a magnetically operated switch member.
2. Description of the Prior Art
Prior art security alarm systems often make use of magnetic switches attached to doors and windows which are integrated within a system for detecting unauthorized openings. One common type of magnetic switch used in these situations is a so-called reed switch. Reed switches are subject to unauthorized manipulation through use of an external magnet, allowing an intruder to open a door or window without triggering the alarm system.
A number of magnetic switches have been proposed in the past to overcome deficiencies of reed switches. U.S. Pat. Nos. 5,997,873, 5,530,428, 5,332,992, 5,673,021, and 6,603,378 describe switches having a pair of spaced apart switch elements with a shiftable body (e.g., a spherical ball) movable between a first position where the ball is in simultaneous contact with both switch elements, and a second position out of such simultaneous contact. An alarm circuit is operatively coupled with the switch element so as to detect movement of the body and a corresponding change in electrical state of the switch element, which in turn triggers an alarm function.
Cargo containers which are moved or shipped over long distances present a significant security problem. For example, unless properly protected, such containers may be opened en route and the contents thereof stolen. Also, such containers could be opened and a bomb or other terrorist device inserted therein. Accordingly, it is very important that such containers be secured against unauthorized access. One problem in this regard is that most prior security systems require a source of AC power, which is not feasible when seeking to protect shipping containers.
The present invention overcomes the problems outlined above and provides security assemblies especially adapted for use with shipping containers having a cargo enclosure presenting a doorway, and with an door operably coupled adjacent the doorway. Broadly speaking, such security assemblies include at least one switch assembly mounted on either the door or the doorway. The switch assembly includes a switch member having a first switch element, a second switch element in spaced relationship to the first element, and an electrically conductive body shiftable between a first body position in contact with the first and second switch elements and defining a first switch state, and a second body position out of the simultaneous contact with the first and second switch elements and defining a second switch state. A shiftable component is located proximal to the switch member and is movable between first and second component positions. The shiftable component and proximal switch member body are being magnetically coupled such that movement of the component between the first and second component positions effects corresponding movement of the body between the first and second body positions in order to change the state of the switch member. The overall security assembly also has an alarm controller and circuitry operably coupling the at least one switch member and the alarm controller in order to initiate an alarm upon unauthorized opening of the door. The switch member is oriented such that upon the unauthorized opening of the door, the component is shifted between the component positions thereof, and the switch member changes state, thereby actuating the alarm controller.
In preferred forms, each switch member body comprises a substantially spherical ball, which is located within a metallic switch housing. The first switch element is in the form of an electrode extending into the housing, while the second switch element comprises at least a portion of the conductive housing. The shiftable component preferably is in the form of a spring-biased plunger.
In order to provide the magnet coupling between the shiftable body and component, one of the body or component is permanently magnetized while the other is formed of a complemental permanently magnetized material or an appropriate material which is magnetically susceptible.
The security assemblies of the invention are normally self-contained, and include a battery for actuation of the alarm controller. An antenna may also be provided with the controller in order to transmit alarm signals to a remote location. If desired, after such a signal is received, the container could be tracked using conventional GPS technology.
Turning now to the drawings, a security assembly 20 in accordance with the invention is illustrated in
In more detail, the switch assemblies 26, 28 are in most respects identical, each including a switch member 44 and a shiftable component 46. Each switch member 44 has a small, preferably metallic switch housing 48 with a pair of switch elements 50, 52 and an electrically conductive body 54 located within the housing 48. The housing 48 also has an insulative cover 56 disposed over the open end thereof. These switch members are similar to the magnetic switch units described in U.S. Pat. No. 6,603,378.
In the form shown, the switch element 50 of each member 44 is an elongated, electrically conductive electrode which extends through cover 56 and into the confines of switch housing 48, whereas the element 52 is a portion or all of the conductive housing 48. In order to allow electrical connection of the switch assembly to controller 30, leads 50a and 52a are provided. In preferred forms, the body 54 is substantially spherical and is formed of ferromagnetic or other magnetically susceptible material.
Each component 46 is in the form of a shiftable plunger 58 having a base 60 and a rounded, outboard plunger end 62. Each plunger 58 is shiftable within a bore 64 in housing 22 adjacent the associated switch member 44. The plungers 58 are biased upwardly by means of a coil spring 66 situated beneath each base 60 and a stop 68 threaded into housing 22. Each plunger base 60 carries a small permanent magnet 70 therein at a location closely adjacent to the associated switch housing 48. In this manner, and as more fully described below, each magnet 70 and adjacent body 54 are magnetically coupled so that the movement of the plunger magnet 70 effects corresponding movement of the body 54 within the associated switch housing 48. It will be observed in this respect that the magnet 70 forming a part of switch assembly 26 is located adjacent the bottom of base 60, whereas the magnet 70 forming apart of switch assembly 28 is placed above the bottom of the base 60. The importance of this relative offset between the positions of the magnets 70 will be made clear hereafter.
The circuitry 36 is designed to operably connect the switch assemblies 26 and 28 with controller 30. To this end, the circuitry 36 includes a common conductor 72 leading from controller 30 and electrically connected with the leads 52a forming a part of the switch assemblies 26 and 28. Additionally, a conductor 74 is provided, extending from controller 30 and electrically connected with the leads 50a. In this fashion, the switch assemblies are coupled in parallel, but a variety of other wiring schemes could also be employed.
Attention is next directed to
During opening of door 38 (
In the door-closed position of
As explained, in the preferred embodiments of the invention, the plungers 58 carry permanent magnets 70, and the shiftable bodies 54 are formed of a material which is magnetically susceptible (e.g., steel). However, this arrangement is not essential, and it is only required that the shiftable component and the shiftable body be magnetically coupled. As such, both of these parts could be formed from permanently magnetic material, or the bodies may be permanent magnets while the associated shiftable components could be formed of magnetically susceptible material.
In the preferred forms, the first switch assembly positions where the bodies 54 are in simultaneous contact with the switch elements are “switch-closed” positions, while the second switch assembly positions where the bodies 54 are out of simultaneous contact with the switch elements are “switch-open” positions. This arrangement is not essential, though, and those skilled in the art will appreciate that the switch assemblies can be configured so that the switch positions correspond to different electrical states.
Additionally, while in the depicted embodiments, the switch assemblies of the invention are mounted on a movable door, these door-mounted configurations are not essential. For example, the switch assemblies could be fixedly mounted on a cargo enclosure adjacent the doorway, whereas an actuating bracket is carried by the door. In one such embodiment, and referring to the dual-switch design of
This application is a division of identically-titled application Ser. No. 11/372,165, filed Mar. 9, 2006, and incorporated herein by reference in its entirety.
Number | Date | Country | |
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Parent | 11372165 | Mar 2006 | US |
Child | 12876600 | US |