EP1738335B1

EP1738335B1 - Intrusion preventing apparatus for fences or the like

Info

Publication number: EP1738335B1
Application number: EP04727093A
Authority: EP
Inventors: Federico Ciordinik
Original assignee: Doni Roberto
Current assignee: Doni Roberto
Priority date: 2004-04-13
Filing date: 2004-04-13
Publication date: 2007-12-05
Anticipated expiration: 2024-04-13
Also published as: WO2005101340A1; DE602004010551T2; EP1738335A1; DE602004010551D1; ATE380377T1

Abstract

The invention relates to an intrusion preventing apparatus for fences (1, 2) comprising one or more cables (3) composed of a fiber optic bundle (103) and an outer protective sheath (203), which longitudinally subtend a perimeter to be protected and are supported at a plurality of vertical spaced posts (4) and wherein, at least at some of said posts (4), means (8, 9) are provided for deforming the cables (3), which may be moved from an idle position to an operating cable (3) deforming position in which an optical signal is attenuated below a threshold value, which means (8, 9) are operated as the tension of the cable (3) is increased. According to the invention, said deforming means are a pair of clamping jaws (8, 9) facing toward each other on opposite sides of the cable (3) and freely pivoting on pins (10) along the axis of the cable (3), which jaws, in the idle position, engage the outer sheath (203) of the cable (3) with a predetermined force without deforming it whereas, as the tension of the cable (3) increases, they are urged by the cable (3) into an arc-shaped pivotal motion, thereby causing the cable (3) to be pinched. The invention further addresses tamper preventing means (12, 13) for the apparatus. Said deforming and/or pinching means are disposed in a housing which is formed by two separable parts and has tamper indicating means composed of second fiber optic cable deforming and/or pinching means.

Description

The invention addresses an intrusion preventing apparatus for fences or the like, comprising at least one, preferably two or more cables, each composed of at least one or a bundle of optical fibers and an outer protective sheath, which fiber optic cables subtend substantially longitudinally a length or a perimeter to be protected and are held or supported, each at a different height, at a plurality of spaced support locations and wherein, at least at some of said support locations, first deforming and/or pinching means are provided for each fiber optic cable, which first deforming/pinching means may be moved from an idle position in which they do not interfere with the fiber optic cable to an operating fiber optic cable deforming and/or pinching position, in which an optical signal transmitted through the cable is attenuated below a predetermined threshold value or anyway modified, and which first deforming and/or pinching means are automatically operated upon increase of the fiber optic cable tension, for example caused by a pulling/bending action on said fiber optic cable.
An apparatus of this type is disclosed in US 5,434,557 .
Apparatuses of this type are known, which are used for protecting high-risk zones, such as airports and the like, generally in combination with conventional fences, e.g. made of an electrically welded mesh supported by piles. A first type of such intrusion preventing apparatuses includes, at an axial end junction point between two fiber optic cables, a connector which is used to disconnect the junction between the two fiber optic cables in case of an intrusion attempt, thereby causing a total interruption of the signal. However, these connectors should be constructed with great precision, whereby their mechanical fabrication is considerably expensive. Furthermore, the signal interruption effect is not automatically reversible. A second known type of such intrusion preventing apparatus provides the use of three different components, the first being the actual intrusion preventing means which acts on a cable, for example made of steel, that is laid horizontally outside the actual fence mesh. Upon tension increase or cut of said metal cable, one of two cusps pinches a fiber optic cable which is placed vertically on a fence supporting post. An apparatus protecting case is further provided, with a tamper indicating device, which is triggered when the case is opened. Said second element acts on a further fiber optic cable which is laid horizontally outside the fence mesh by a spring-operated cusp. The third component is a fastener block for securing the horizontally laid metal wires and fiber optic cables on some posts of the enclosure. The above apparatus is apparently very complex and costly, as it requires the use of both an actual intrusion preventing device and of a tamper indicating device, as well as the presence of at least two separate fiber optic cables to accomplish both tasks and the use of elastic opposing members such as springs or the like, which can be exposed to failures caused, for example, by weather deterioration. In fact, the intrusion signal is provided by the deformation of the optical fibers subtended between the posts, whereas the deforming and/or pinching means tamper attempt signal is generated by tamper preventing means which act on an additional different fiber optic cable.
This prior art arrangement requires greater amounts of optical fibers, as different optical fibers to be associated to the tamper preventing device are needed. Also, the tamper preventing means increase the complexity and costs of the construction, in terms of both time and difficulty of installation.
Therefore, the present invention has the object of obviating the above drawbacks and providing, by simple and inexpensive means, an intrusion preventing apparatus like the one described hereinbefore, which provides an effective protection of fences or the like by causing, upon an intrusion attempt, the optical signal transmitted by a fiber optic cable to be lowered below a predetermined threshold, due to an at least one reversible deformation of said cable, without requiring fiber optic interruption and allowing for multiple passages between signal conduction and interruption or attenuation states. A further object is of combining the intrusion preventing function and the apparatus tamper preventing function in a single fiber optic cable, without requiring any complex mechanism, and particularly the use of elastic means such as springs or the like.
The invention fulfils the above objects by providing an apparatus of the type described hereinbefore, in which each of said first deforming and/or pinching means is housed in a case which has two separable and joinable parts, the case further including tamper preventing and open-case condition indicating means, which are triggered to deform and/or pinch the fiber optic cable in response to a relative separating motion of said two parts of the housing case.
Advantageously, the means to prevent tampering of the case that houses the first deforming and/or pinching means are second fiber optic cable deforming and/or pinching means which are triggered to deform and/or pinch the fiber optic cable by the relative separating motion of said two parts of the case.
The second fiber optic cable deforming and/or pinching means are formed by two pinching members, which are secured to one part and the other of the case respectively, and have fiber optic cable deforming or pinching surfaces oriented at least partly transverse to the separation direction of the two parts of the case, and are moved from a closed-case condition in which they do not interfere with the fiber optic cable, to a fiber optic cable deforming and/or pinching condition, which occurs when said two parts of the case are in an intermediate spaced-apart position.
According to a further improvement, the two parts of the case have intermediate end-of-separation-stroke means, which end-of-separation-stroke means are designed in such a manner that they can be defeated by a predetermined pulling force in the separation direction, and which end-of-stroke means lock, with said predetermined force, the two parts of the case at such a relative distance that the second deforming and/or pinching means which form the case tamper preventing means are in the operating fiber optic cable deforming and/or pinching position.
Advantageously, said end-of-stroke means are provided in an intermediate position of cooperating connection/disconnection guide means, which are associated to the one and the other of the two case parts respectively.
In accordance with an advantageous improvement, case tamper preventing and case-open condition indicating means may be provided, whose action is to deform and/or pinch the same fiber optic cable which is subjected to the action of the two forked pivoting jaws. Hence, the fabrication and operation of the apparatus are considerably simplified as compared with prior art apparatuses which, as mentioned above, require two distinct members to separately act on two different fiber optic cables.
The above description shows how the invention achieves savings in high-cost materials, such as optical fibers, and a much simpler construction which allows to shorten installation times.
According to one embodiment, the first fiber optic cable deforming and/or pinching means consist of two jaws facing toward each other and mounted on opposite sides of the fiber optic cable, to pivot freely along the fiber optic cable axis. In the idle condition, these jaws engage with a predetermined force two opposite portions of the outer sheath of the fiber optic cable without causing any deformation thereof whereas, as the fiber optic cable tension increases, the jaws are urged by the cable into an arc-shaped pivotal motion in the fiber optic cable puling direction, thereby causing the fiber optic cable to be pinched and/or deformed, which results in a change in the optical signal being transmitted. As the tension increase ceases, the elastic return force of the fiber optic cable causes the clamping jaws to pivot back in the opposite direction, and restores the conduction condition, in which the signal is brought back to substantially the original level. Obviously, the cut of the fiber optic cable causes a total signal interruption.
According to this embodiment, to be described in greater detail in the description of the drawings, each of the two clamping jaws may be a forked member, which is freely pivotable at its apex on a cylindrical pin. The two pins may be situated on opposite sides of the fiber optic cable and perpendicularly to the post axis and to the fiber optic cable axis. The two forked jaws are disposed on a common plane, parallel to the post axis and coplanar with the fiber optic cable, symmetrically with respect to the fiber optic cable and with apertures that face toward each other. The ends of the forked jaws, when the latter are in the idle position, are in contact with the outer sheath of the fiber optic cable to obtain at least a friction engagement with or a slight compression of the cable sheath only. In this regard, it shall be noted that said protective sheaths are typically made of a relatively soft and deformable material, such as plastic or the like.
Each end of a first pivoting forked jaw may be pointed, whereas each end of the second pivoting forked jaw may have two adjacent points which form a V-shaped recess substantially complementary to each of the points of the first forked jaw. Each point of the first forked jaw is at such a distance from the corresponding double point of the other forked jaw as to engage in a substantially snug manner and/or to slightly compress the outer sheath only of the fiber optic cable with no deformation thereof, when the pivoting forked jaws are in the idle condition.
As the tension of the fiber optic cable increases, the vertexes of the points of the first forked jaw and the vertexes of the double points of the second forked jaw move toward said tension increase along arc-shaped paths, which are at least tangent, particularly slightly intersected. Thanks to this arrangement, a fiber optic cable segment interposed between the two jaws is deformed and/or pinched between the point of the first jaw and the opposed double point of the second jaw, which jaws are farthest from the point in which the pulling force is exerted on the fiber optic cable.
Nevertheless, in the above preferred embodiment of the invention, the pairs of opposed fiber optic cable pinching and/or deforming jaws may be housed in a case-like element, including a bottom wall, which can be secured to the fiber optic cable supporting post and a cover part, which can be engaged with said bottom wall. The two pins about which the two forked jaws pivot may be integral with said bottom wall of the case, whereas the cover part may advantageously have side apertures for snug passage of the fiber optic cable.
The cover part and the bottom wall of the case may have each one of two members which cooperate to perform a fiber optic cable deforming and/or compressing action, upon separation of the cover from the bottom wall in a predetermined uniquely possible direction.
Such unique cover separation direction may be orthogonal to the bottom wall of the case and to the inner face of the cover. To this end, the bottom wall of the case and the cover part may have complementary guides for mutual connection/disconnection which are oriented perpendicular to the bottom wall of the case and to the inner face of the cover.
Said connection/disconnection guides include at least two cylindrical pins which perpendicularly branch off the inner face of the cover part, each of which two pins is disposed in such position as to correspond to one of the two pivots of the forked jaws on the bottom wall of the case, said pivots having a tubular shape, i.e. with a central axial hole so that, when the cover part is brought closer to the bottom wall for closing the case, each of the two pins of the cover engages in an axially slideable manner in the corresponding pin of the bottom wall.
Advantageously, complementary removable engagement means may be provided, e.g. having a snap fit, force fit or similar action between each pin of the cover part and its respective pin of the bottom wall of the case which form end-of-stroke means in an intermediate separation position between the bottom wall and the cover part of the case.
Said means may include at least one radially widened, particularly annular portion, of the outer cylindrical wall of each pin of the cover part and/or at least one radially narrowed, particularly annular portion, of the inner cylindrical wall of each of the two pins of the bottom wall of the case, said radially widened and narrowed portions having such sizes that, when combined with a predetermined resilience and/or deformability of the material, allow to defeat the end-of-stroke position by a predetermined pulling force.
The tamper preventing, open-case condition indicating means may include at least one first deforming member which protrudes from the bottom wall of the case and a second deforming member which protrudes from the inner face of the cover, opposite said bottom wall of the case. These two deforming members may have their longitudinal axis contained in a plane parallel to the direction of separation between the two case parts, which two deforming members (12, 13) advantageously have different inclinations with respect to the axis orthogonal to said bottom wall and to said inner face of the cover so that, when the case is closed, said deforming members form a corner area in which the fiber optic cable is housed in an undeformed and/or unpinched condition whereas, as the cover is removed along the unique extraction direction, said deforming members slide mutually thereby generating a progressive fiber optic cable deforming and/or pinching action by wedging the cable between said two deforming members (12, 13). It shall be noted that the pinching action is facilitated by the fact that the mutual engagement means of the cover and the bottom wall oppose the cover removal action, so that the latter may be only accomplished abruptly and quickly, and this assists the wedging of the cable between the two deforming members.
According to an improvement, the edge of the first deforming member facing toward the second deforming member may have a cusp section extending all along said first member, whereas the opposed side of the second deforming member may have a bicuspid section, which also extends all along said second deforming member. The two longitudinal cusps may be parallel and form a longitudinal V-shaped recess substantially complementary to the cusp of the first deforming member, or vice versa, so as to generate a progressive wedging action, thereby causing the fiber optic cable to be deformed and/or pinched between the two deforming members as the cover is abruptly removed from the bottom wall of the case.
According to a further improvement, means may be provided for retaining the fiber optic cable and preventing it from slideably moving away from the bottom wall of the case upon removal of the cover.
To this end, the cusp-shaped edge of the deforming member associated to the bottom wall of the case may have a substantially semicircular or U-shaped aperture for housing and retaining the fiber optic cable and preventing it from slideably moving away from the bottom wall of the case upon removal of the cover. An additional semicircular aperture may be provided for further retaining the fiber optic cable in an appropriate position on the bicuspid edge of the deforming member associated to the inner wall of the cover.
The deforming and/or pinching means and the open-case condition and any other tamper indicating means of the above mentioned means may be provided at the cable fastening locations of some of the posts, there being provided at least one post without said deforming and/or pinching means interposed between two posts having said means. On the posts that have no such deforming and/or pinching means simple means may be provided for securing the fiber optic cable to said posts and for preventing it from sliding off. Such fastener means may be housed in an openable case, whose external aspect is substantially identical to that of the case for housing the deforming and/or pinching means, so as to prevent undesired detection of the case that contains said means.
Here again, said fastener means containing case may have a bottom wall and a cover part that may be removably connected, open-case and/or tamper indicating means being provided between the cover and the bottom wall, particularly of the same type as described above.
While this disclosure relates to the most frequent condition, with a plurality of vertical posts supporting horizontally laid fiber optic cables, said posts may be inclined inwardly or outwardly from the perimeter to be protected, or alternatively the fiber optic cables may be arranged vertically, while the support posts are laid horizontally. As a further alternative, any other orientation may be provided for both, intermediate between the horizontal and the vertical orientations.
The advantages of this invention are apparent from the above description and mainly consist in that it provides a very simple construction and installation of the apparatus. In fact, both the intrusion preventing and the system tamper preventing functions are combined in a single apparatus, which operates on a single fiber optic cable. This avoids the provision of a second fiber optic cable which is known to be very costly. Also, the invention requires no movable opposing members, such as springs or the like, which are exposed to deterioration, particularly due to weather conditions. Finally, the apparatus does not require the total interruption of the fiber optic cable, whereby the normal signal conduction condition may be restored in a substantially automatic manner.
Further characteristics and improvements will form the subject of the dependent claims.
The characteristics of the invention and the advantages derived therefrom will be more apparent from the following detailed description of the annexed drawings , in which:

Fig. 1 is a perspective view of an intrusion preventing apparatus of the present invention combined with a conventional fence segment.
Fig. 2 is a perspective view of a post with two cases fitted thereon, the one containing the fiber optic cable deforming/pinching means and the other containing the fiber optic fastening means, the covers of the two cases being in the open condition.
Fig. 3 is a top, partly cross sectional view, of the bottom wall of the case designed for containing the cable deforming/pinching means, fitted on the post, the deforming/pinching means being omitted.
Fig. 4 is a front view of the two intrusion preventing deforming/pinching jaws and the two tamper preventing deforming members, combined with a length of fiber optic cable which is shown in an unpinched and undeformed condition. The cusp-shaped deforming member is shown in a sectional view, taken along line I-I of Fig. 7.
Figures 5A and 5B are partly sectional side view of the case for housing the intrusion preventing jaws and the tamper preventing deforming members, respectively with the cover in the open condition and in the closed condition.
Figs. 6 and 7 are side views of the tamper preventing deforming members associated to the bottom wall of the case in the idle condition (Fig. 6) and in the fiber optic cable deforming condition (Fig. 7).
Fig. 8 is an exploded perspective view of the case containing the fiber optic cable fastening means, with the cover in the open condition.
Fig. 9 is a cross sectional view of the fiber optic cable combined with a covering and protective element.

Referring to the Figures, a preferred embodiment of the intrusion preventing apparatus of the invention is shown, which is designed for protecting a conventional fence formed by a vertical metal mesh 2 and supported by a plurality of vertical piles 1. The intrusion preventing apparatus is formed by a plurality of fiber optic cables 3 which longitudinally subtend a length or the whole of the fence perimeter to be protected. These fiber optic cables 3 are held or supported, each at a different height from the ground and in parallel arrangements, at a plurality of vertical posts 4. In the embodiment of the figures, each post 4 is secured on the outer side of a corresponding pile 1 of the fence. By this arrangement, the post 4 need not be anchored to the ground, but arrangements other than the one of the figures are feasible. For example, the posts 4 may be placed in positions that do not correspond to the piles 1, and be anchored to the ground independently thereof, otherwise the fence piles 1 might be avoided and the metal mesh 2 may be secured directly to the inner side of the posts 4. In a particularly simple arrangement, the inner fence formed by the piles 1 and the metal mesh 2 may be completely avoided, and the protection action may be solely performed by the apparatus of the invention. Each cable 3 is composed of a fiber optic bundle 103 and an outer protective sheath 203, made of a relatively soft and deformable material. As mentioned above, there are provided means for preventing the cable 3 from being broken and means for preventing the actual apparatus from being tampered. These means are contained in a case, e.g. made of metal or plastic, which is formed by a substantially rectangular bottom wall 5 and a cover part 6, having larger sidewalls 106 and smaller sidewalls 206. Obviously, the container embodiment described above shall be intended by way of a non limiting example, as the case may be manufactured in any other desired and suitable shape. In an intermediate position of each of the two larger sidewalls 106 a recess 306 is provided for snug passage of the fiber optic cable 3.
The bottom wall 5 of the case is secured on the outer face of the post 4, which is formed by a tubular pile. The bottom wall 5 has a backplate 105 with dove-tail or similar shape, which forms a slide, slideably engaged in a complementary guide 104 on the outer side of the post 4. Hence, the bottom wall 5 may be slideably engaged in the guide, to be easily brought into the ideal position of the post, and to be easily secured on the post 4 at the desired height from the ground by a screw 7 of such a length that, in the fastened condition, it does not protrude out of the surface of the button wall 5, and does not interfere with the moving parts of the apparatus. As better shown hereafter, said fastening screw 7 is covered by said moving parts, i.e. by the case cover, so that the case cannot be removed from the post 4 without generating an alarm. In fact, the screw 7 may be only removed by opening the case, thereby triggering the tamper preventing means.
It shall be further noted that, even when a case were slideably released from the post without causing an alarm, i.e. even when the case could be removed from its fastened position without being opened, the case might only be separated from the post by being slid along the guide 104 to the free end opening. This requires all the cases on the post to be separated from the post, and increases the probability that one of the abusive removal operations might generate an alarm, as well as the time required for such operations.
In the embodiment that is shown in the figures, the post has a tubular shape and has on one side, i.e. on the side for attachment of the cable fastener case and/or the deforming and/or pinching member and tamper-preventing sensor containing case, a tubular C-shaped guide which opens by a longitudinal median slot along the wall which adheres to such cases. On the other hand, the cases have a rear appendage which is formed by a plate-like slide which is supported in a cantilever fashion and at a predetermined distance from the rear wall of the case, by a rib or a rear extension. The slide is formed by a plate that is wider than the longitudinal slot and has surfaces for abutment against the inner side of the two wall parts on the two sides of the slot. The rear rib or extension have such a thickness that they are able to pass through the longitudinal slot. Furthermore, the bottom side of the case, the slide and the rib form two grooves for slideable engagement of the two wall strips that laterally delimit the slot and the facing surfaces of the slide and the bottom wall of the case are at such a distance from each other that at least one screw engaged in a threaded through hole of the bottom wall of the case might be brought to contact with the corresponding wall strip of the guide that delimits on at least one side the longitudinal strip of the guide that delimits on at least one side the longitudinal slot of the guide, thereby acting to clamp said wall strip between the screw and the slide, whereby the case and slide assembly are locked in position in the longitudinal guide. The post or at least the longitudinal guide are open on at least one end side.
In addition to the above functional advantages, the construction with an open longitudinal guide allows the posts to be fabricated by extrusion, for instance by cutting tubular aluminum sections. The only processing step required after extrusion is cutting the sections to the appropriate length, whereas the guide with longitudinal slot on the side by which the case is secured to the post may be formed at the same time as the extrusion of the sections. The above allows to considerably reduce the operational steps required for securing the cases containing the fastener devices and the deforming and/or pinching means to the posts, thereby dramatically reducing the number and types of assembly parts to be kept in stock.
The apparatus further includes a pair of forked jaws 8, 9, which face toward each other and are mounted on opposite sides of the fiber optic cable 3, each being pivoted in the apex zone to swing freely on a cylindrical pin 10, 11 along the axis of the fiber optic cable 3. The two pins respectively 10 and 11 are provided on opposite sides of the fiber optic cable 3 and perpendicularly branch off the bottom wall 5 and the inner face of the cover 6 respectively. The two forked jaws 8, 9 are situated on a common plane, parallel to the bottom wall 5 and coplanar with the axis of the fiber optic cable 3. The two forked jaws 8, 9 are disposed symmetrically with respect to the fiber optic cable 3 and with apertures that face toward each other. Each end of a pivoting jaw 9 has one point 109, whereas each end of the other pivoting forked jaw 8 has two adjacent points 108 which form a V-shaped recess substantially complementary to each of the points 109 of the forked jaw 9. Each point 109 of the first forked jaw 9 is at such a distance from the corresponding double point 108 of the other forked jaw 8 as to engage in a substantially snug manner and/or to slightly compress the outer sheath 203 of the fiber optic cable 3 with no deformation thereof, when the pivoting forked jaws 8, 9 are in the idle condition. As the tension of the fiber optic cable 3 increases, for instance due to a pulling/bending action thereon, the two forked jaws 8, 9 are urged by the cable to pivot along an arc of a circle in the direction of the tension increase, thanks to a slight engagement of the points 109 and the double points 108 with the outer sheath 203 of the cable 3. The vertexes of the points 109 of the first forked jaw 9 and the vertexes of the double points 108 of the second forked jaw 8 move in the direction of the tension increase along slightly intersecting circular arc paths, and move closer to each other to the central area, so that a segment of the fiber optic cable 3 is deformed and/or pinched between the point 109 of the first jaw 9 and the opposed double point 108 of the second jaw which are farthest from the point in which the pulling force is exerted on the fiber optic cable 3. By this arrangement, the optical signal transmitted by the fiber optic cable 3 is attenuated below a predetermined threshold value, and an intrusion attempt is detected. It shall be noted that the arrangement of the jaws 8, 9 may be different from that described above, i.e. the jaws may have inverted positions. Optionally, a greater number of jaw pairs 8, 9 may be provided, still disposed on opposite sides of the fiber optic cable 3, for simultaneously deforming/pinching the cable 3 in response to an increase of the tension thereof. It shall be further noted that the two jaws 8, 9 are constructed in such a manner as to allow the cable deforming/pinching action to be performed in either direction parallel to the cable axis, depending on the tension application point thereon.
Two cylindrical pins are further provided, which perpendicularly branch off the inner face of the cover part 6, each of which two pins 11 has a position that corresponds to that of one of the two pins 10 of the forked jaws 8, 9 on the bottom wall of the case. The two pins 10 have a tubular shape and the inner hole thereof is substantially complementary in shape to the two pins on the cover part 6. As the cover part 6 is moved closer to the bottom wall 5 for closing the case, each of the two pins 11 of the cover 6 engages in an axially slideable manner in the corresponding pin 10 of the bottom wall 5. To this end, each of said pins 10 has a hollow cylindrical shape, corresponding to each of the two pins 11 of the cover 5. Thus, the case may be opened/closed by moving the cover part 6 away and toward the bottom wall 5 in a uniquely possible direction which, in a preferred embodiment, is perpendicular to said bottom wall 5. Each of the pins 11 of the cover 6 has a radially widened portion 111. The hole in the pivots 10 substantially corresponds to the radial widened portion whereas, in a predetermined location with reference to the axial extension of the hole, an inner shoulder is provided for abutment against the radial enlargement, which forms an end-of-stroke pawl in the direction of removal of the pins 11 from the corresponding holes in the pivots 10. The abutment position with reference to the separation stroke of the cover 6 is selected in such a manner that, when the radial widened portion 111 on the pins 11 abuts against the radial narrowed portion 110, i.e. the radial shoulder in the corresponding holes of the pivots 10, the tamper preventing means are in the operating indication position. The cooperating radially widened portions 111 of the guide pins 11 and the radial shoulders in the holes of the pivots 10 have such a shape and size that, in combination with the elastic deformability properties of the material which constitutes said pins 10, 11, the abutment position may be defeated by exerting a pulling force exceeding a predetermined pulling force. Thanks to this arrangement, the action of removing the cover 6 may solely be an abrupt and quick action. The usefulness of these arrangements shall be considered in relation to the proper operation of the tamper preventing means and open case condition indicating means that are provided in the apparatus. These include a first deforming member 12 protruding from the bottom wall 5 and a second deforming member 13 protruding from the inner face of the cover 6 opposed to said bottom wall 5 of the case. These two deforming members 12, 13 have different inclinations with respect to the axis orthogonal to the said bottom wall 5 and to the inner face of the cover 6. The edge of the first deforming member 12 facing toward the second deforming member 13 has a cusp section 112 extending all along said first deforming member 12, whereas the opposed side of the second deforming member 13 has a bicuspid section 113, which also extends all along said second deforming member 13. The two longitudinal cusps 113 are parallel and form a V-shaped longitudinal recess which is substantially complementary to the cusp 112 of the first deforming member 12. The cusp-shaped edge 112 of the deforming member 12 associated to the bottom wall 5 of the case has a substantially semicircular aperture 212 for housing and retaining the fiber optic cable 3 and preventing it from slideably moving away from the bottom wall 5. Upon removal of the cover 6 along the only possible removal direction, the deforming member 13 associated to the cover 6 moves parallel to itself and to the deforming member 12 associated to the bottom wall 5, thereby causing the fiber optic cable 3 to be progressively wedged between the cusp 112 and the opposed two cusps 113 of the deforming member 13 and to be consequently deformed/pinched thereby attenuating the signal below a predetermined threshold value. Such condition occurs as soon as the radially widened portions 111 of the guide pins 11 abut against the cooperating inner radial shoulders 110 in the pivots 10. This provides an advantageous effect. Whenever someone should try to separate the cover part 6 from the rest of the case, they would first encounter no hindrance to the motion of the cover in the separation direction defined by the cooperating guide pins 11 and by the pivots 10, wherein the former slide. However, such sliding motion would suddenly be stopped by the abutment of the radially enlarged portions 111 against the radial inner shoulders 11, whereby the cover separation action would be suddenly stopped. This occurs in the relative position of the two case parts, in which the deforming and/or pinching means 12, 13 which have the function of tamper preventing means are in the operating fiber optic cable deforming and/or pinching position, hence in the case tamper indicating condition. As the continuous separation movement of the two case parts is stopped, the intruder would encounter a resistance and stop the movement to repeat the pulling action, and exert a higher separation force. This causes the two case parts to remain in the intermediate abutment position of the separation stroke, which is an optimal deformation condition for tamper indication for a certain time, such as to ensure a safe open case condition indicating action.
Thanks to the longer operation time of the deforming/pinching means 12, 13 which act as tamper preventing means, the light signal change generated by said deforming/pinching means may be effectively differentiated from fast light signal change transients which are typically not caused by tamper or intrusion actions, which increases the system operation safety against false alarms.
It shall be noted that the deforming/pinching means, combined with the tamper preventing means described above are only provided at the fiber optic cable 3 fastening locations of some of the posts 4, the fiber optic cable 3 being provided with simple means for securing it to the posts 4 only at some of said posts 4. These fastener means are housed in an openable case, whose external aspect is identical to that of the case for housing the pinching jaws 8, 9, and may be secured to the post 4 in a similar fashion. The fastener means include a cable grip clamp 14 which uses screws 15 to secure the cable 3 to the bottom wall 5' without causing any significant deformation of the cable 3. A longitudinal member 16 may be further provided for covering and protecting the fiber optic cable 3 in the lengths between two adjacent posts 4, in such a manner as to prevent the cable 3 from being damaged, for instance by rodents or the like. This protective member 16 is a C-shaped member whose diameter substantially corresponds to that of the fiber optic cable 3. The latter is open on one side to allow application thereof on the fiber optic cable 3. The two stems of the C shape of the member 16 extend in parallel directions to such an extent as to prevent easy access to the cable 3 from the open portion of the cover member 16.
All the above members that form the intrusion preventing apparatus of the invention may be made of any suitable material, particularly plastic or metal.
In order to achieve an optimized detection functionality, slipping between the cable parts shall be minimized. Typically, the cable is formed by an optical fiber or a fiber optic bundle, enclosed in a first inner coating, composed of a plurality of resilient strands, made of a material named Kevlar and this assembly is in turn enclosed in an additional outer tubular sheath made of plastic, particularly polyurethane. The inner Kevlar coating and the outer sheath are applied to the cable by extrusion or coextrusion.
A special kind of cable has an outer polyurethane sheath, which is attached to the inner Kevlar coating layer by physico-chemical bonding and/or by embedding at least some of the strands of the inner covering of the optical fiber in the material of the outer sheath.
The inner Kevlar coating and the external polyurethane sheath are provided by coextrusion and simultaneous direct application on the core formed by at least one optical fiber or a fiber bundle. The process for obtaining a physico-chemical bonding between the inner coating and the outer sheath and/or for at least partially embedding the strands of the inner coating in the outer sheath material adds a delay for sheath cooling, with reference to the moment in which the sheath is brought to contact with the strands of the inner coating layer. This is achieved, for instance, by decreasing the extrusion rate to a predetermined extent. This arrangement causes the extruded polyurethane sheath to be still warm enough when it contacts the Kevlar strands of the inner lining, to generate a physico-chemical bonding and/or a partial embedding thereof in the mutual contact area as described above. Extrusion rate adjustment allows to adjust the physico-chemical bonding and/or at least partial embedding effect as described above, depending on the mechanical features being requested.
Thanks to the above, the Kevlar strands generate, with the outer sheath, a sort of fiber reinforced plastic coating connected thereto. The advantages consist in avoiding any relative slipping motion between the components of the fiber optic cable and in achieving a stronger fiber optic cable.

Claims

An intrusion preventing apparatus for fences (1, 2) or the like, comprising at least one, preferably two or more cables (3), each composed of at least one or a bundle of optical fibers (103) and an outer protective sheath (203), which fiber optic cables (3) subtend substantially longitudinally a length or a perimeter to be protected and are held or supported, each at a different height, at a plurality of spaced support locations (4) and wherein, at least at some of said support locations (4), first deforming and/or pinching means (8, 9) are provided for each fiber optic cable (3), which first deforming/pinching means (8, 9) may be moved from an idle position in which they do not interfere with the fiber optic cable (3) to an operating fiber optic cable (3) deforming and/or pinching position, in which an optical signal transmitted through the cable is attenuated below a predetermined threshold value or anyway modified, and which first deforming and/or pinching means (8, 9) are automatically operated upon increase of the tension of the fiber optic cable (3), for example caused by a pulling/bending action on said fiber optic cable (3), characterized in that each of said first deforming and/or pinching means is housed in a case having two separable and joinable case parts, said case further containing tamper preventing and open-case condition indicating means (11, 12), which are triggered to deform and/or pinch the fiber optic cable in response to a relative separating motion of said two parts of the housing case.
An apparatus as claimed in claim 1, characterized in that the means to prevent tampering of the case that houses the first deforming and/or pinching means are second fiber optic cable deforming and/or pinching means which are triggered to deform and/or pinch the fiber optic cable by the relative separating motion of said two parts of the case.
An apparatus as claimed in claim 2, characterized in that the second fiber optic cable deforming and/or pinching means are formed by two pinching members, which are secured to one part and the other of the case respectively, and have fiber optic cable deforming or pinching surfaces oriented at least partly transverse to the separation direction of the two parts of the case, and are moved from a closed-case condition in which they do not interfere with the fiber optic cable, to a fiber optic cable deforming and/or pinching condition, which occurs when said two parts of the case are in an intermediate spaced-apart position.
An apparatus as claimed in one or more of the preceding claims, characterized in that the two parts of the case have intermediate end-of-separation-stroke means, which end-of-separation-stroke means are designed in such a manner that they can be defeated by a predetermined pulling force in the separation direction, and which end-of-stroke means lock, with said predetermined force, the two parts of the case at such a relative distance that the second deforming and/or pinching means which form the case tamper preventing means are in the operating fiber optic cable deforming and/or pinching position.
An apparatus as claimed in claim 4, characterized in that said end-of-stroke means are provided in an intermediate position of cooperating connection/disconnection guide means, which are associated to the one and the other of the two case parts respectively.
An apparatus as claimed in one or more of the preceding claims, characterized in that the first deforming/pinching means are a pair of clamping jaws (8, 9) facing toward each other on opposite sides of the fiber optic cable (3) and freely pivoting on pins (10) along the axis of the fiber optic cable (3), which jaws (8, 9), in the idle position, engage the outer sheath (203) of the fiber optic cable (3) with a predetermined force without deforming it whereas, as the tension of the fiber optic cable (3) increases, they are urged by the cable (3) into an arc-shaped pivotal motion in the direction of the pulling/bending action exerted on the fiber optic cable (3), thereby causing the fiber optic cable (3) to be pinched and/or deformed, which involves a change in the optical signal being transmitted.
An apparatus as claimed in one or more of the preceding claims, characterized in that the fiber optic cable/s are secured or held, each at a different height, at a plurality of vertical or substantially vertical posts (4), such as piles or the like, which are arranged at a distance from each other and wherein first deforming and/or pinching means (8, 9) are provided at least at some of said vertical posts (4).
An apparatus as claimed in one or more of the preceding claims, characterized in that each of the two clamping jaws (8, 9) is a forked member, which is freely pivotable at its apex on a cylindrical pin (10), the two pins (10) being situated on opposite sides of the fiber optic cable (3) and perpendicularly to the axis of the post (4) and to the axis of the fiber optic cable (3), the two forked jaws (8, 9) being disposed on a common plane, parallel to the post axis (4) and coplanar with the fiber optic cable (3), and the two forked jaws (8, 9) being disposed symmetrically with respect to the fiber optic cable (3) and with apertures that face toward each other, and the ends (108, 109) of the forked jaws (8, 9), in the idle position of said forked jaws (8, 9), being in contact with the outer sheath (203) of the fiber optic cable (3) to obtain at least a friction engagement with or a slight compression of the sheath (203) of the cable (3).
An apparatus as claimed in one or more of the preceding claims, characterized in that each end of a first pivoting forked jaw (9) has one point (109), whereas each end of the second pivoting forked jaw (8) has two adjacent points (108) which form a V-shaped recess substantially complementary to each of the points (109) of the first forked jaw (9), each point (109) of the first forked jaw (9) being at such a distance from the corresponding double point (108) of the other forked jaw (8) as to engage in a substantially snug manner and/or to slightly compress the outer sheath (203) only of the fiber optic cable (3) with no deformation thereof, when the pivoting forked jaws (8, 9) are in the idle condition.
An apparatus as claimed in one or more of the preceding claims, characterized in that, as the tension of the fiber optic cable (3) increases, the vertexes of the points (109) of the first forked jaw (9) and the vertexes of the double points (108) of the second forked jaw (8) move in the direction of the tension increase along arc-shaped paths that are at least tangent, particularly slightly intersected, so that a segment of the fiber optic cable (3) is deformed and/or pinched between the point (109) of the first jaw (9) and the opposed double point (108) of the second jaw (8) which are farthest from the point in which the pulling force is exerted on the fiber optic cable (3).
An apparatus as claimed in one or more of the preceding claims, characterized in that the two pins (10) about which the two forked jaws (8, 9) pivot are made of one piece with the surface of the post (4) that holds or supports the fiber optic cable (3).
An apparatus as claimed in one or more of the preceding claims, characterized in that the pairs of opposed jaws (8, 9) for pinching and/or deforming the fiber optic cable (3) are housed in a case-like enclosure element, including a bottom wall (5), which can be secured to a corresponding post (4) for supporting the fiber optic cable (3) and a cover part (6), which can be engaged with said bottom wall (5), the two pins (10) about which the two forked jaws (8, 9) pivot being made of one piece with said bottom wall (5) of the case, and the cover part (6) having apertures (306) for snug passage of the fiber optic cable (3).
An apparatus as claimed in one or more of the preceding claims, characterized in that the case tamper preventing and case-open condition indicating means (12, 13) act to deform and/or pinch the same fiber optic cable (3) which is subjected to the action of the two forked pivoting jaws (8, 9).
An apparatus as claimed in one or more of the preceding claims, characterized in that the cover part (6) and the bottom wall (5) of the case have each one of two members (13, 12) which cooperate to perform a fiber optic cable (3) deforming and/or compressing action, upon separation of the cover (6) from the bottom wall (5) in a predetermined uniquely possible direction.
An apparatus as claimed in one or more of the preceding claims, characterized in that said unique direction of separation of the cover part (6) is orthogonal to the bottom wall (5) of the case and to the inner face of the cover (6), the bottom wall (5) of the case and the cover part (6) having complementary connection/disconnection guides (10, 11) which are oriented perpendicular to the bottom wall (5) of the case and to the inner face of the cover (6).
An apparatus as claimed in one or more of the preceding claims, characterized in that said connection/disconnection guides include at least two cylindrical pins (11) which perpendicularly branch off the inner face of the cover part (6), each of which two pins (11) is disposed in such position as to correspond to one of the two pins pivots (10) of the forked jaws (8, 9) on the bottom wall (5) of the case, said pivots (10) having a tubular shape, i.e. with a central axial hole so that, when the cover part (6) is brought closer to the bottom wall (5) for closing the case, each of the two pins (11) of the cover (6) engages in an axially slideable manner in the corresponding pin (10) of the bottom wall (5).
Advantageously, complementary removable engagement means (111) are provided, e.g. having a snap fit, force fit or similar action between each pin (11) of the cover part (6) and its respective pin (10) of the bottom wall (5) of the case which form end-of-stroke means in an intermediate separation position between the bottom wall and the cover part of the case.
An apparatus as claimed in one or more of the preceding claims, characterized in that said removable engagement means include at least one radially widened, particularly annular portion (111), of the outer cylindrical wall of each pin (11) of the cover part (6) and/or at least one radially narrowed, particularly annular portion, of the inner cylindrical wall of each of the two pins (10) of the bottom wall (5) of the case, said radially widened and narrowed portions having such sizes that, when combined with a predetermined resilience and/or deformability of the material, allow to defeat the end-of-stroke position by a predetermined pulling force.
An apparatus as claimed in one or more of the preceding claims, characterized in that the tamper preventing and open-case condition indicating means include at least one first deforming member (12) protruding from the bottom wall (5) of the case and a second deforming member (13) protruding from the inner face of the cover (6) opposed to said bottom wall (5) of the case, which two deforming members (12, 13) have their longitudinal axis contained in a plane parallel to the direction of separation between the two case parts, which two deforming members (12, 13) have different inclinations with respect to the axis orthogonal to said bottom wall (5) and to said inner face of the cover (6) so that, when the case is closed, said deforming members (12, 13) form a corner area in which the fiber optic cable (3) is housed in an undeformed and/or unpinched condition whereas, as the cover part (6) is removed along the unique extraction direction, said deforming members (12, 13) slide mutually thereby generating a progressive deforming and/or pinching action on the fiber optic cable (3) by wedging thereof between said two deforming members (12, 13).
An apparatus as claimed in one or more of the preceding claims, characterized in that the edge of the first deforming member (12) facing toward the second deforming member (13) has a cusp section (112) extending all along said first deforming member (12), whereas the opposed side of the second deforming member (13) has a bicuspid section (113), which also extends all along said second deforming member (13) the two longitudinal cusps (113) being parallel and forming a longitudinal V-shaped recess substantially complementary to the cusp (112) of the first deforming member (12), or vice versa, so as to generate a progressive wedging action, thereby causing the fiber optic cable (3) to be deformed and/or pinched between the two deforming members (12, 13) as the cover (6) is removed from the bottom wall (5) of the case.
An apparatus as claimed in one or more of the preceding claims, characterized in that means (212) are provided for retaining the fiber optic cable (3) and preventing it from slideably moving away from the bottom wall (5) of the case upon removal of the cover (6).
An apparatus as claimed in one or more of the preceding claims, characterized in that the cusp-shaped edge (112) of the deforming member (12) associated to the bottom wall (5) of the case has a substantially semicircular or U-shaped aperture (212) for housing and retaining the fiber optic cable (3) and preventing it from slideably moving away from the bottom wall (5) of the case upon removal of the cover (6).
An apparatus as claimed in one or more of the preceding claims, comprising a plurality of posts (4) and at least one fiber optic cable (3) which is secured to said posts (4), characterized in that the deforming/pinching means (8, 9), combined with the means (12, 13) for indicating the opening or tamper of said deforming/pinching means (8, 9) are only provided at the fiber optic cable (3) fastening locations of some of the posts (4), there being provided at least one post (4) without said deforming/pinching means (8, 9) interposed between two posts (4) having said means (8, 9), whereas on said posts (4) that have no such deforming and/or pinching means (8, 9) simple means (14, 15) are provided for fastening the fiber optic cable (3) to said posts (4), which fastener means (14, 15) are housed in an openable case, whose external aspect is substantially identical to that of the case for housing the first deforming/pinching means (8, 9).
An apparatus as claimed in claim 23, characterized in that the case containing the fastener means (14, 15) has a bottom wall (5') and a cover part that may be removably connected, open-case and/or tamper indicating means being provided between the cover and the bottom wall (5').
An apparatus as claimed in one or more of the preceding claims, characterized in that the fiber optic cables (3) are laid horizontally, whereas the piles or posts (4) for supporting the latter are inclined inwardly or outwardly from the perimeter to be protected.
An apparatus as claimed in one or more of the preceding claims, characterized in that the fiber optic cables (3) are arranged vertically, whereas the support posts (4) are laid horizontally.
An apparatus as claimed in one or more of the preceding claims, characterized in that both the cases or enclosures for the deforming and/or pinching means and the cases or enclosures for the fastener means are engaged on the posts by means that allow said cases or enclosures to slide along said posts (4), there being provided position lock means for said sliding cases or enclosures, which means are solely accessible from inside said cases or enclosures.
An apparatus as claimed in claim 27, characterized in that, on the side of each post (4) designed for attachment of said cases or enclosures, each post (4) has a longitudinal guide, which guide has a tubular section all along it which opens by a longitudinal slot at the center of the surface upon which the enclosures and/or cases are fixed to said post, whereas said bottom of the enclosures or cases has a slide-like appendage which is formed by a widened member whose transverse extension is greater than the width of the slot and which is connected to said bottom of the case or enclosure by means of a rib that is slightly thinner than said longitudinal slot and holds the widened member at a distance from the bottom wall that is slightly greater than the thickness of the wall of the tubular guide.
An apparatus as claimed in claim 28 or 29, characterized in that the removable means for locking the housing cases or enclosures in position are means for clamping the wall of the guide upon which the bottom of the case or enclosure rest, such as screw-operated clamps.
An apparatus as claimed in claim 29, characterized in that the bottom of the case has, at the side of the longitudinal slot of the guide, at least one threaded through hole, for engagement of a screw or bolt fastener.
An apparatus as claimed in claim 30, characterized in that the bottom of the case has at least two or more threaded through holes, arranged on the bottom of the case or enclosure on the two sides of the longitudinal slot of the guide, the screws or bolts being only accessible from inside the case or enclosure.
An apparatus as claimed in one or more of the preceding claims, characterized in that the posts and the guides thereon for the sliding enclosures or cases are made from one piece.
An apparatus as claimed in claim 32, characterized in that the posts are made from extruded aluminum bars or the like that are cut to length.