Tamper switch arrangement

A tamper switch arrangement detects tampering with a device, and includes a tamper switch assembly having a tamper switch with a first part and a second part. The first and second parts are movable relative to each other between an open switch position and a closed switch position. The tamper switch is biased into one of the open and closed switch positions. An enclosure substantially encloses the tamper switch assembly and the device. The enclosure includes a door and an opening disposed opposite the door. The enclosure is sized such that the tamper switch assembly may be compressed between an inner surface of the door and a second surface via the opening to thereby overcome the bias and actuate the tamper switch into an other of the open and closed switch positions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems for detecting unauthorized tampering with a device, and, more particularly, to systems for detecting unauthorized tampering with a device that is disposed within an enclosure.

2. Description of the Related Art

Many devices must be placed in locations where they may be exposed to unauthorized tampering or theft. Such devices include controllers for telephone systems, alarm systems, cable television systems, firearms, art work and other valuables, for example. In order to protect the devices from tampering and other forms of physical harm, they may be placed within security system enclosures in the form of boxes that are attached to fixed structures such as ceilings, walls, floors and posts. The boxes may have hinged covers for enabling authorized access to the devices within the boxes, and theses doors may be locked shut.

The security system enclosures commonly employ tamper switches for detecting that the cover of the enclosure has been opened, or that the enclosure has been removed from the fixed structure to which it was attached. A typical tamper switch has a pair of contacts that may be opened or closed as a result of the enclosure door being opened, or as a result of the enclosure being removed from the fixed structure. A problem, however, is that separate switches must be used for detecting the opening of the door and the removal of the enclosure from the fixed structure. That is, one tamper switch may detect the opening of the door, and a separate tamper switch may be required to detect the removal of the enclosure from the wall. The use of two separate switches adds to the cost and increases the size of the tamper detection system.

What is needed in the art is a tamper switch arrangement that utilizes a single tamper switch to detect both the opening of a door of the security system enclosure and the removal of the enclosure from the fixed structure on which it is mounted.

SUMMARY OF THE INVENTION

The present invention provides a tamper switch arrangement including an enclosure containing a tamper switch assembly having only a single tamper switch. The tamper switch assembly may be compressed between a front door of the enclosure and a fixed structure to which the arrangement is mounted through an opening in the rear of the enclosure. If the door is opened or if the enclosure is removed from the fixed structure, the tamper switch will be actuated from a closed switch position to an open switch position, or vice versa, thereby enabling the transmission of an alarm signal indicative of the tampering.

The invention comprises, in one form thereof, a tamper switch arrangement for detecting tampering with a device. The tamper switch arrangement includes a tamper switch assembly having a tamper switch with a first part and a second part. The first and second parts are movable relative to each other between an open switch position and a closed switch position. The tamper switch is biased into one of the open and closed switch positions. An enclosure substantially encloses the tamper switch assembly and the device. The enclosure includes a door and an opening disposed opposite the door. The enclosure is sized such that the tamper switch assembly may be compressed between an inner surface of the door and a second surface via the opening to thereby overcome the bias and actuate the tamper switch into an other of the open and closed switch positions.

In another form, the invention comprises a tamper detection assembly for placement within an enclosure. The assembly includes a tamper switch having a first part and a second part. The first and second parts are movable relative to each other between an open switch position and a closed switch position. The tamper switch is biased into one of the open and closed switch positions. The tamper switch is compressed between an inner surface of a front door of the enclosure and a second surface via a rear opening of the enclosure such that the bias is overcome and the tamper switch is actuated into an other of the open and closed switch positions. A spring is operably coupled between the tamper switch and one of the opening and the door of the enclosure. The spring is configured to be compressed upon closing of the door after the tamper switch has been actuated into the other of the open and closed switch positions.

In yet another form, the invention comprises a tamper detection assembly for placement within an enclosure. The assembly includes a tamper switch having a first part and a second part. The first and second parts are movable relative to each other between an open switch position and a closed switch position. The tamper switch is biased into one of the open and closed switch positions. A switch actuator is operably coupled to the tamper switch and actuates the tamper switch into an other of the open and closed switch positions in response to the tamper detection assembly being compressed between an inner surface of a front door of the enclosure and a second surface via a rear opening of the enclosure.

An advantage of the present invention is that a single tamper switch may be used to detect both the opening the enclosure door and the removal of the enclosure from the fixed structure to which it is mounted.

Another advantage is that the tamper switch assembly has an adjustable length and includes a compressible spring in order to accommodate enclosures of different depths.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplifications set out herein illustrate the invention, in one form, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed.

DESCRIPTION OF THE PRESENT INVENTION

Referring now to the drawings, and particularly toFIG. 1, there is shown one embodiment of a tamper switch arrangement10of the present invention attached to a wall12. Arrangement10includes an enclosure14, a tamper switch assembly or “tamper detection assembly”16, a rail18and a plug assembly20.

As best illustrated inFIG. 2, tamper switch assembly16includes a tamper switch22disposed within a housing24having a bottom housing half26and a top housing half28. Tamper switch22includes two parts that are movable relative to each other. More particularly, tamper switch22includes a rod30that is slidable or otherwise movable relative to a switch body32to thereby toggle switch22between a closed switch position in which a pair of switch contacts74,76are electrically connected together and an open switch position in which contacts74,76are electrically disconnected from one another.

A switch actuator38includes a coil spring40and a plunger42. A first end44of rod30is securely received in first end46of spring40. A second end48of spring40is received in a spring retainer cup50of plunger42. A shaft52extends from a closed end of cup50.

Bottom housing half26includes a groove54for slidingly receiving rail18, as best illustrated inFIG. 3. A pair of posts56,58may be received in respective throughholes60,62of a printed circuit board (PCB)64to thereby mechanically support PCB64on bottom housing half26, as best shown inFIG. 4. Although only two posts56,58and only two throughholes60,62are shown in the drawings, four posts and four throughholes may be provided for additional support. That is, a respective post may be provided on each of the four corners of bottom housing half26, and a respective throughhole may be provided in each of the four corners of PCB64. PCB64includes a pair of throughholes66,68for receiving respective mounting supports34,36for switch22. PCB64also includes a pair of plated throughholes70,72for receiving respective contacts74,76of tamper switch22. Contacts74,76may be soldered to PCB64and to respective wires (not shown) that lead out of housing24. Opposing notches78,80on bottom housing half26and top housing half28, respectively, conjointly form channels through which the wires may lead out of housing24.

Bottom housing half26includes an end wall82that limits the movement of cup50away from switch22due to the force of spring40. As can be seen inFIGS. 1,3and4, cup50may abut end wall82. Similarly, top housing half28includes an end wall84against which cup50may also abut, as shown inFIG. 1, and which also limits the movement of cup50. Opposing notches86,88in respective end walls82,84conjointly form a channel through which shaft52may slide.

Top housing half28includes an elongate element in the form of a cantilever90having aligned, angled teeth92along its length. Another elongate element in the form of a door strike94includes a slot96in which cantilever90may be retainingly received. At the front end of slot96is a flexible pawl98having wings99a,99bwhich may be gripped and rotated in the direction of arrow100to allow cantilever90to be inserted into slot96. When door strike94is at a desired point along the length of cantilever90, wings99may be released in order to allow pawl98to settle into one of the notches between teeth92. Thus, door strike94is selectively couplable to cantilever90at a plurality of points along the length of cantilever90. Cantilever90and door strike94conjointly form an elongate device having an adjustable length in the longitudinal directions indicated by double arrow102.

Enclosure14may substantially enclose tamper switch assembly16and the device (not shown), such as an alarm system, that enclosure14is to protect from tampering. As best illustrated inFIG. 5, enclosure14may be in the form of a rectangular box having a hinged front door104and a rear opening106disposed opposite door104. In the embodiment shown, opening106is in the form of a circular throughhole. Enclosure14may be sized, e.g., may have a length in directions102, such that tamper switch assembly16may be compressed between an inner surface108(FIG. 6) of door104and a surface110of plug assembly20that extends into enclosure14via opening106. An inner surface of a wall of enclosure14, such as inner surface107of bottom wall109, may be attached to rail18via an anchoring device111. Enclosure14may also include a channel (not shown) for carrying one or more wires (not shown) leading from tamper switch22to a device, such as an alarm (not shown), disposed outside of enclosure14. Via the wires and switch22, the alarm may be activated by an alarm system protected within enclosure14.

Plug assembly20includes a plug112having a disc-shaped base114and a toroidal main part116. Plug112has a fastener hole118extending therethrough for receiving a fastener120for fastening plug112to wall12. Fastener120is shown in the drawings as a screw. However, it is also possible for fastener120to be in the form of a nail, wall anchor, etc. An outer surface122of main part116and an exposed outer surface124(FIG. 6) of fastener120conjointly form surface110of plug assembly20. Fastener120may immovably fasten plug112to wall12such that plug assembly20is a fixed structure. However, it is also possible for fastener120to rotatably fasten plug112to wall12such that plug112may rotate about fastener120. Main part116may extend from base114at a right angle to thereby provide an annular shoulder that is sized to be snugly received in opening106. That is, a width of main part116may closely match the width of opening106.

In operation, enclosure14is moved toward wall12such that opening106is placed over main part116of plug112. Movement of enclosure14toward wall12is continued until enclosure14abuts base114of plug112, as shown inFIG. 6. Enclosure14may then be attached to wall12via some attachment apparatus (not shown), such as brackets that are attached to both wall12and enclosure14via bolts, for example.

Tamper switch assembly16may be inserted into enclosure14through an open door104. Groove54of housing24may be aligned with rail18such that rail18is received in groove54as tamper switch assembly16is inserted into enclosure14. Tamper switch assembly16may be slid along rail18in directions102generally aligned with door104and opening106. Tamper switch assembly16may be slid along rail18until a distal end126(FIG. 1) of shaft52abuts surface110of plug assembly20, as shown inFIG. 1. In this uncompressed state of tamper switch assembly16, the relative positions of rod30and body32of tamper switch22are as shown inFIG. 1. In one embodiment, this relative positioning of rod30and body32places switch22in an open switch position. That is, there is no electrical connection between contacts74,76. Tamper switch22may include a biasing device (not shown) that biases rod30and body32into their relative positions as shown inFIG. 1, i.e., that biases switch22into the open switch position. The biasing device of tamper switch22may be a leaf spring or some other type of spring, for example.

Door strike94may now be coupled to top housing half28at a desired one of the plurality of points along the length of cantilever90. More particularly, wings99may be gripped and pawl98may be rotated in direction100away from teeth92. Door strike94may then be slid freely along the length of cantilever90until strike94reaches the desired position. Wings99may then be released to thereby allow pawl98to releaseably lock into a notch between a desired pair of adjacent teeth92. In one embodiment, door strike94is positioned on cantilever90such that door strike94extends a desired distance past the end of an enclosure wall, such as wall109. Further, door strike94may be positioned on cantilever90such that door strike94extends a predetermined distance past the end of an enclosure wall. In order to facilitate such positioning, door strike94may be provided with a mark128that may be aligned with the end of a wall, such as wall109. The farther door strike94extends past the ends of the enclosure walls, the greater the level of compression of switch assembly16when door104is closed. Thus, the elongate device formed by cantilever90and door strike94has a length that is adjustable to set a level of compression of switch assembly16.

Next, door104of enclosure14may be closed as shown inFIG. 6such that tamper switch assembly16is compressed between inner surface108of door104and surface110of plug assembly20via opening106. In response to this compression of tamper switch assembly16, switch actuator38may actuate tamper switch22into an other position, i.e., a closed position in which contacts74,76are electrically connected together. More particularly, as tamper switch assembly16is compressed, housing24may slide along rail18toward wall12. Plunger42, which abuts plug assembly20, remains fixed during the compression. Thus, spring40is compressed between plunger42and rod30and thereby increases the force that it exerts on rod30. The increased force on rod30overcomes the bias of the biasing device of switch22and causes rod30to slide into a position as shown inFIG. 6relative to body32. In one embodiment, this relative positioning of rod30and body32places switch22in a closed switch position. That is, there is an electrical connection, i.e., an electrical short, between contacts74,76. Cover104may be latched and possibly locked in the closed door position via use of latching mechanism130or any other suitable latching mechanism. A continuous electrical signal may be applied to one of contacts74,76and may be carried through the other one of contacts74,76to an alarm system. In this condition, tamper switch arrangement10is set to detect tampering with a device disposed within enclosure14.

If someone does tamper with the device, such as by first opening door104in order to gain access to the device, then the force of spring40may push housing24, via rod30, in a direction132away from wall12. With spring40expanding and exerting less force on rod30, the biasing device of switch22may again overcome the force of spring40and return rod30and body32to their positions as shown inFIG. 1, i.e., the open switch position. The force of spring40causes housing24to move still farther in direction132until cup50abuts end walls82,84and the entire tamper switch arrangement10has returned to its position as shown inFIG. 1. The loss of electrical connection between contacts74,76terminates the transmission of the electrical signal to the alarm system and signifies to the alarm system that someone may have gained access to the device within enclosure14.

If someone tries to gain access to the device by pulling enclosure14off of wall12such that plug assembly20no longer occupies opening106, then the force of spring40may push plunger42in a direction134toward opening106. With spring40expanding and exerting less force on rod30, the biasing device of switch22may again overcome the force of spring40and return rod30and body32to their former relative positions as shown inFIG. 1, i.e., the open switch position. The force of spring40causes plunger42to move still farther in direction134until cup50abuts end walls82,84and the entire tamper switch arrangement10is in the position as shown inFIG. 7. With plug assembly20no longer occupying opening106, distal end126of shaft52may extend into or through opening106. The loss of electrical connection between contacts74,76terminates the transmission of the electrical signal to the alarm system and signifies to the alarm system that someone may have gained access to the device within enclosure14.

As described above, tamper switch22may be biased back into the open switch position when door104is opened and/or enclosure14is moved away from surface110of plug assembly20. Thus, tamper switch arrangement10of the present invention enables a single tamper switch to be used to detect both the opening of a door of an enclosure and the removal of the enclosure from a wall, floor, ceiling or post to which the enclosure is mounted.

Switch actuator38and spring40have been described herein as being operably coupled between tamper switch22and opening106. Moreover, the elongate device formed by cantilever90and door strike94has been described herein as being operably coupled between tamper switch22and door104. However, it is to be understood that it is within the scope of the present invention for a switch actuator and/or spring to be operably coupled between a tamper switch and an enclosure door, and for an elongate device to be operably coupled between the tamper switch and an enclosure opening.

Rail18has been disclosed herein as being separate from and attached to wall109of enclosure14. However, it is also possible for the rail to be formed unitarily with the enclosure wall such that the wall itself includes a rail on which the tamper switch assembly may be slid to and fro.