Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2001-05-09
2003-06-24
Trieu, Van (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S541000, C340S550000
Reexamination Certificate
active
06583721
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to intrusion detection system in general, and specifically to fencing systems utilizing taut wires and detector devices to detect intrusion.
BACKGROUND OF THE INVENTION
Numerous types of intrusion detection fences have been developed in order to successfully detect attempts of intruders to circumvent the system. Reference is now made to
FIG. 1
which illustrate a typical prior art system such as U.S. Pat. No. 4,367,459 to Amir which consists of a fence having a plurality of trip wires
12
secured between two anchored posts
14
and a detector post
16
located between the anchored posts
14
. A detecting device
18
such as a transducer is fixed to the intermediate detector post
16
. Typically, the anchor posts
14
are located between 30 and 60 meters apart, that is the detector post
16
is approximately 15-30 meters away from an anchor post
14
. The plurality of trip wires
12
are connected to a common actuator
20
, which is supported by detector post
16
. Any change in the lateral tension of wire
12
due to bending or cutting of the wire, for example, is ‘received’ by the common actuator
20
and transmitted to the transducer (detecting device
18
).
The larger the distance between detector post
16
and anchor posts
14
, the less sensitive the detection system. This is especially so in the vicinity of the anchor posts
14
further away from a common actuator
20
, since as a result of the lateral movement of the wire deflection adjacent to the anchor post
14
is at a minimum near the common actuator.
In order to overcome these disadvantages, wire guiding posts
22
are placed between the detector posts
16
and between the anchor post
14
and the detector posts
16
to guide the wires
12
which slide through them without being held by them (the wires are not secured to the guiding post
22
).
In a further variation as illustrated in
FIG. 2
, it is known to use one or more helical wire supports
24
between the common actuators
20
(in place of or in addition to wire guiding poles of FIG.
1
). These helical wire supports
24
also act as sliding supports which translate the vertical motion of the wires, which have been bent or cut, into a lateral movement which can be sensed by the common actuator
20
and detected by the detecting device
18
connected to the common actuator
20
.
However, these helical wire supports
24
(as shown in
FIG. 2
) or wire guiding posts
22
(as shown in
FIG. 1
) have the disadvantage that they can be easily mechanically cut, broken or removed by the intruder, actions which may not trigger the alarm. Thus, if an intruder has enough time, the removing or cutting of the helical wire cases the fence to lose its sensitivity. Thereafter, the intruder can, in some situations, move the taut wires apart without triggering the detecting device
18
.
U.S. Pat. No. 4,829,287 to Kerr, schematically illustrated in
FIG. 3
to which reference is now made, utilizes a plurality of detector posts
30
between anchor posts (not shown) and a plurality of sensors
32
which are mounted on each detector post
30
. Each of the parallel taut wires
34
, anchored to the anchor posts, engage a single sensor. Between horizontally consecutive sensors, wire guiding devices comprising a rod and helical coil support members
36
(similar to
FIG. 2
) are placed to guide the taut wires
34
, keep them apart and translate the bending movement of the wire into a lateral motion through the helical coil supports.
Intrusion detection systems having a sensor fitted to each taut wire are much more expensive, since they require a sensor for each strand of wire, and consequently also require a great deal more maintenance. Eventually, the sensor parts of the taut wire system which are relatively costly and the most vulnerable parts of the system lose their sensitivity especially if not properly maintained. Therefore, these “sensor for each wire” type systems are much more expensive in comparison to the “common actuator” type of fences mentioned above.
While the “common actuator” type fences are less expensive are generally less sensitive especially when the intruder removes or breaks the helical or guiding posts and thereby reducing the fence's sensitivity and causing the fence to deteriorate and become less effective.
SUMMARY OF THE PRESENT INVENTION
It is an object of the present invention to provide an improved intrusion detection fence utilizing a plurality of tensioned taut wires, which overcomes the limitations and disadvantages of prior art systems.
It is a further object of the present invention to improve the sensitivity of the system by reducing the opportunity for intrusion even when the intruder tries to reduce its sensitivity by removing or braking one or more of the guiding posts or helical supports. In the preferred embodiment, the intrusion detection system includes a plurality of active sensor devices each connected to a common actuator. The active sensor devices are placed between anchor posts which tautly restrain the taut wires.
There is therefore provided, in accordance with a preferred embodiment of the present invention, an intrusion detection fence, which includes a plurality of trip wires secured between a pair of anchor posts, a plurality of detector posts anchored in the ground, located between the anchor posts, at least one actuator attached to each of the detector posts, the actuator also being coupled to each of the plurality of trip wires; and a detecting device attached to the actuator and secured to each of the detector posts. The deflection or cutting of any of the plurality of trip wires activates at least one of the detecting devices adjacent to the activated trip wires.
Furthermore, in accordance with a preferred embodiment of the present invention, deflection of any of the plurality of trip wires activates each of the detecting devices either side of the activated trip wires.
Furthermore, in accordance with a preferred embodiment of the present invention, the actuator is an actuating wire tensioned between the ends of the detector post. The actuator is an actuator bar or flange.
Additionally, in accordance with a preferred embodiment of the present invention, the fence further includes a passive wire attached to each of the detecting device, the passive wire being parallel to the actuator wire.
In addition, in accordance with a preferred embodiment of the present invention, The detecting device is housed within a central leg of a generally “I” shaped housing, the housing further includes a bottom leg and a top leg attached to the central leg. The housing further includes a pair of clamps attached to the top leg for clamping common actuator wire and passive wire to the detecting device.
In addition there is also provided, in accordance with a preferred embodiment of the present invention, an intrusion detection system which includes a fence having a plurality of trip wires secured between a pair of anchor posts, a plurality of detector posts anchored in the ground, located between the anchor posts, at least one actuator attached to each of the detector posts, the actuator also being coupled to each of the plurality of trip wires, a detecting device attached to the at least one actuator and secured to each of the detector posts: and a control center coupled to each of the detecting devices. The control center includes a processor for determining and indicating the location of detecting device activated by the deflection of any of the trip wires.
In a second embodiment, in accordance with a preferred embodiment of the present invention, the system and fence further include a plurality of guiding posts, each guiding post being located between each pair of detecting posts or between a anchor post and a detecting post. The actuating wire is tensioned between the top of one of the guiding posts and the bottom of the adjacent guiding post. Alternatively, the actuating wire is tensioned between one end of one of the guiding posts and the end of one of the anchor posts.
Furthermore
Dank Hersh Yaakov
Zilberstein Moshe
Eitan, Pearl, Latzer & Cohen Zedek LLP.
Magal Security Systems Ltd.
Trieu Van
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