IL115427A

IL115427A - Security apparatus particularly for protecting the perimeters of sites

Info

Publication number: IL115427A
Application number: IL11542795A
Authority: IL
Original assignee: Tonelli Augusto; Tonelli Aldo; Tonelli Giorgio
Priority date: 1994-09-27
Filing date: 1995-09-27
Publication date: 1998-08-16
Also published as: AU3698495A; IL115427A0; ITMI941966A1; WO1996010195A1; IT1271219B; ITMI941966A0

Description

SECURITY APPARATUS, PARTICULARLY FOR PROTECTING THE PERIMETERS OF SITES SECURITY APPARATUS, PARTICULARLY FOR PROTECTING THE PERIMETERS OF SITES The present invention relates to security apparatus, particularly for the protection of site perimeters, operable to indicate approaches, intrusions and the like, comprising a detector extending around the perimeter of the site to be protected, and a supply and control unit.

As is known, the requirement for perimetral protection of sites is currently particularly felt, with the need for immediate indication of possible intrusion of a stranger, or of an unauthorized person or even only of his approach, indicated by suitable emission of alarm signals.

In one known apparatus currently utilised, a detector constituted by a cable containing optical fibres is buried along the perimeter of the site to be protected. A supply and control unit is operable to transmit appropriate light radiation through the optical fibres and to receive the modifications to which the radiation is subjected as a result of mechanical stress such as compression which is exerted on the fibre by the intruder via vibrations induced in the ground by his approach.

This apparatus does not have a high degree of sensitivity because the cable must be buried close to the surface, lying between 10 and 30 cm, with the disadvantage of leaving the cable to the risk of damage resulting from operations on the ground such as hoeing, turfing or renewing the grass cover. Moreover this apparatus requires a sophisticated and expensive electronic circuit .

Apparatus is also known in which the detector is constituted by a pair of split cables which run alongside one another, one being a radio frequency emitter and the other being the receiver. The disturbance caused to the radio frequency transmission by an intruder is captured by the control unit. Apparatus based on these detectors are disturbed by water; in the case of heavy rain they tend to be activated incorrectly so as to give false alarm signals.

Apparatus has been suggested with a detector comprising two tubes running parallel to one another at a certain distance along the perimeter of the area to be protected, and filled with a pressure liquid. A pressure transducer detects possible pressure differences between the two tubes, induced upon approach by an intruder. These detectors are practically insensitive to water but have various disadvantages. Upon burying they are rather labourious to put into operation. Moreover, rather delicate adjustments are needed at the installation site and subsequent periodic recalibrations are necessary.

The problem on which the present invention is based is that of making available apparatus of the specified type which will have structural and functional characteristics such as to satisfy the said requirements, at the same time overcoming the disadvantages of the prior art.

This problem is resolved by apparatus of the specified type which is characterised in that the said detector comprises a plurality of piezo-electric transducers intended to be buried underground.

Further characteristics and advantages of the apparatus according to the present invention will become apparent from the following description of a preferred embodiment, given by way of indicative and non-limitative example, with reference to the attached drawings, in which: Figure 1 is a schematic view of the apparatus according to the invention; Figure 2 is a side view of a detail of the apparatus according to the invention; Figure 3 is a side view, partly exploded and partly in section, of the detail of Figure 2; Figure 4 is a schematic, partially sectioned view of another detail of the apparatus of Figure 1; Figure 5 is a schematic view of another detail of the apparatus of Figure 1; and Figure 6 is a highly schematic view of the apparatus of Figure 1 in operation.

With reference to the attached drawings, the reference numeral 1 generally indicates security apparatus, particularly for the protection of site perimeters, operable to indicate approaches, intrusions and the like.

The apparatus 1 comprises a detector 2 intended to extend along the perimeter of the site to be protected, and a supply and control unit 3.

The detector 2, which is intended to be buried about 40-50 cm underground, comprises a plurality P of piezoelectric transducers 4 regularly spaced along a line 5 leading to the unit 3, with a spacing of, for example, 1.5 m.

Each piezo-electric transducer 4 comprises a cup-shape body 6 having a vertical axis X-X. The cup-shape body 6 comprises a bottom 7, a cylindrical wall 8 and a free edge 9.

A plate-like piezo-electric sensor 10, having a peripheral portion 11a, is fixed in the cup-shape body 6 to define a chamber 12 between the bottom 7 and the plate-like piezo-electric sensor 10 itself.

In particular, the peripheral portion 11a is fixed, for example by means of appropriate adhesive, to an annular step 13 formed internally of the side wall 8.

The plate-like piezo-electric sensor 10 may be made of a metal plate 14, for example copper, and a ceramic plate 15 which is adhered to the plate 14 by means of a layer 16 of insulating material.

From the sensor 10, or rather from the plate 14 and the plate 15, extend respective conductor wires 17 and 18 which lead out from the cup-shape body 6 to the line 5.

The cup-shape body 6 also includes a spike 19 associated with the bottom 7 and extending from this downwardly and coaxially of the axis X-X.

The spike 19 has a predetermined length, for example about 8-10 cm, sufficient to couple the cup shape body 6 and therefore the peripheral portion 11a of the sensor 10 securely with a deeper layer, indicated A, of the ground, which in general is not digged.

The piezo-electric transducer 4 includes a receptor element 20 which is associated with the piezo-electric sensor 10 on the opposite side from the chamber 12.

The receptor element 20 includes a layer 21 of appropriate plastics material, for example a two-part epoxy resin. The layer 21 is located in the cup-shape body 6 above a central portion lib of the sensor and preferably occupies almost the whole of the cup-shape body above the sensor.

The receptor element further includes a tower-shape body 22 having an axis X-X, rising from the layer 21 in correspondence with the central portion lib of the sensor and seated in it by means of a spigot 22a.

The tower-like body 22 has a predetermined height, for example 8-10 cm sufficient to couple the receptor element 20 and therefore the central portion lib of the sensor with a less deep layer, indicated B, of ground which is digged because the sensor has been buried in it.

The body of the tower 22 is preferably formed by a lower, frusto-conical portion 23 and by an upper, cylindrical portion 24. The tower body 22 is provided with outer fins 25 which are orientated in a radial sense with respect to the axis X-X.

The transducer 4 further includes a screen 26 extending a short distance from the top of the tower body. The screen 26 has the form of a disc on the X-X axis and is fixed, by means of thin columns 27 to the cup-shape body 6 and in particular to its free edge 9.

It is to be noted that in the security apparatus 1 the plurality of piezo-electric transducers P alternate along the line 5, according to a first plurality PI and a second plurality P2. The two sets of transducers PI and P2 are joined to the unit 3 by respective lines, indicated 28 and 29. The two lines 28 and 29, which are bi-polar with conductors 30 and 31, and a ground conductor 32, constitute the line 5 as a whole.

The conductive wires 17 and 18 of the individual sensors are connected to the conductors 30 and 31 respectively.

The supply and control unit 3 comprises a first comparator node 33 and a second comparator node 34 to which the line 28 leads, and a first comparator node 35 and a second comparator node 36 to which the line 29 leads .

The comparator nodes 33 and 35 also have respective reference inputs 37 and 38 which are calibrated at a high threshold value.

The comparators 34 and 36 also have reference inputs 39 and 40 calibrated at a low threshold value.

Lines 41 and 42 respectively, lead from the comparator nodes 33 and 35 to an alarm emitter 43.

Lines 44 and 45 lead to an AND node 46 from which a line 47 leads from the comparator nodes 34 and 36 to the alarm emitter 43.

In operation, any possible approach of an intruder induces a vibration in the ground, above all at low frequency, which propagates through the ground surface down to the less deep layer B with a given amplitude and down to the deeper layer A with a reduced amplitude.

As a result of the greater amplitude of the vibrations in the less deep layer with respect to the amplitude of the vibrations in the deeper layer of the ground the receptor element 20 is subjected to relative movements in relation to the cup shape body 6 and the spike 19. As a consequence of these relative movements the sensor 10 is stressed predominantly in flexing, and emits relatively strong signals, indicated in the drawings with S, if the intruder approaches the perimeter in correspondence with a transducer, or relatively weak signals, indicated T, if the intruder approaches the perimeter in a position substantially equidistant between two adjacent transducers in the line 5.

The signal S is passed directly to the alarm emitter 43 if its magnitude exceeds the high threshold value to which the comparator nodes 33 and 35 are calibrated.

Signal T activates the alarm emitter 43 only when for both the adjacent transducers affected by the intrusion its magnitude, independently of the phase, exceeds the low threshold value to which the comparator nodes 34 and 36 are calibrated.

It is to be noted that, thanks to the screen 26, the sensor is protected from over-stressing to which it could be subject from directly above as a result of an intrusion which manifests itself exactly on its vertical.

The principal advantage of the security apparatus according to the present invention lies in its unusual sensitivity, above all in comparison with the low frequency stresses which reach it.

Thanks to the close, intimate coupling of the receptor body, on the one hand, with the less deep layer of ground and, on the other hand, the cup-shape body and the spike with the deeper layer of the ground, the difference in the amplitude of the vibrations induced by the intruder in the two layers nevertheless converts into a deflection which is immediately detected by the sensor.

The security apparatus according to the present invention is also reliable in that it is insensitive to atmospheric agents and in particular to water, and can be buried relatively deeply, such as 40-50 cm, so as not to be damaged by operations to the soil.

Not the least advantage of the apparatus according to the invention is that of guaranteeing an improved operation on the one hand by avoiding false alarms due to the passage of small animals even stepping on the ground immediately above a transducer, since this does not imply the achievement of the high threshold value, and on the other hand by nevertheless detecting the passage of a person even at a position equidistant between two adjacent transducers.

Obviously, the apparatus described above can have numerous modifications and variations introduced thereto by a man skilled in the art for the purpose of satisfying contingent and specific requirements, all however lying within the protective ambit of the invention as defined in the following claims. 11 115427/2

Claims

1. Security apparatus (1), particularly for protecting the perimeter of a site, operable to indicate approaches, intrusions and the like, of the type comprising a detector (2) extending along the perimeter of the site to be protected and a supply and control unit (3) , the said detector (2) comprising a plurality (P) of piezo-electric transducers (4) intended to be buried underground, characterized in that each piezo-electric transducer (4) comprises a cup-shape body (6) having a vertical axis (X-X) and comprising a bottom (7) and a side wall (8), and a plate-like piezo-electric sensor (10) having a peripheral portion (11a) fixed to the side wall (8) to define a chamber (12) with the bottom (7) and a central portion (lib) intended to be coupled with a less deep layer (B) of the ground, a spike (19) being coaxially associated with the bottom (7) and having a predetermined length sufficient to couple the cup-shape body (6) intimately with a deeper layer (A) of the ground, and a receptor element (20) being associated with the plate-like piezoelectric sensor (10) on the opposite side from the chamber ( 12 ) .

2. Security apparatus (1) according to Claim 1, characterized in that the receptor element (20) includes a layer (21) of suitable plastics material. 12 115427/2

3. Security apparatus (1) according to Claim 2, characterized in that the receptor element (20) includes a tower-shape body (22) rising the said layer (21) and having a predetermined height sufficient to couple a central portion (115) of the plate-like piezoelectric sensor (10) intimately with a less deep layer (B) of the ground .

4. Security apparatus (1) according to Claim 3, characterized in that the tower-shape body (22) has a lower frusto-conical portion (23) and an upper cylindrical portion (24).

5. Security apparatus (1) according to Claim 4, characterized in that the tower-shape body (22) is provided with fins (25) .

6. Security apparatus (1) according to Claim 5, characterized in that the piezoelectric transducer (4) includes a screen (26) extending a short distance above the summit of the tower-shape body (22) and fixed by means of columns (27) to the cup shape body (6) .

7. Security apparatus (1) according to Claim 1, characterized in that the piezoelectric transducers (4) 13 115427/2 of the said plurality (P) of transducers alternate along the perimeter of the site to be protected as a first and a second plurality (PI, P2) connected to the supply and control unit (3) by means of respective lines (28, 29) and in that the supply and control unit (3) includes, for each line (28, 29) a first comparator node (33, 35) and a second comparator node (34, 36) respectively calibrated to a high threshold level and a low threshold level, the first comparator nodes (33, 35) being individually connected to an alarm emitter (43) and the second comparator nodes (34, 36) being connected to an AND node (46) in turn connected to the alarm emitter (43) .

8. A piezoelectric transducer (4) for security apparatus (1), particularly for protecting the perimeter of a site, operable to indicate approaches, intrusions and the like, according to claims 1 to 7.