WO1996024050A1

WO1996024050A1 - Cracks motion breakage sensor with breakage indicator

Info

Publication number: WO1996024050A1
Application number: PCT/EP1996/000370
Authority: WO
Inventors: Giuseppe Tola
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-02-02
Filing date: 1996-01-30
Publication date: 1996-08-08
Anticipated expiration: 1997-08-02
Also published as: ITSV950001A1; AU4715596A; ITSV950001A0; IT1283398B1

Abstract

A motion breakage sensor consisting of a bridge (30) of rigid and fragile material to be rigidly secured between the two edges of a crack or split to be monitored, on which sensor (35) a very thin layer of electrically conductive material (37) is laid in a continuous fashion, which is the breakage indicator capable of detecting whether the bridge (30) is intact or not through the maintenance or loss of electric continuity between the ends of the conductive track. When the bridge breaks, the electric continuity between the ends of the track (37) is interrupted. The maintenance or loss of electric continuity between the ends of the track (37) can be checked by checking and signalling devices which can consist of telltale lights and/or warning systems and/or logic units and/or data transmission systems.

Description

CRACKS MOTION BREAKAGE SENSOR WITH BREAKAGE

INDICATOR

The present invention relates to a cracks motion breakage sensor with breakage indicator.

According lo the known method, in the building industry, motion breakage sensors are employed to show the spread of a crack in the wall; they are applied to monitor any mutual motion between both edges of the crack or split, before intervening with expensive consolidation or demolition works.

According to the known method, a motion breakage sensor is made of very rigid and fragile material and consists of a fragile connection bridge between the two edges of the crack, which bridge is rigidly secured to both edges by means of cement, flange or similar other means. When the mutual splitting motion of both edges continues, the sensor breaks. These sensors need periodic checks.

A serious drawback in prior art sensors is the difficulty to check them in some instances, since the split caused by the breakage of the sensor may just be of a few tenths of millimetres and therefore not visible from a distance with the naked eye. Therefore, in order to control the breakage in the sensor, it is necessary to check it at close distance with adequate means.

For example, the above drawbacks are encountered when the sensor is placed in the ceiling of a very high room and, owing lo the presence of equipment or other things, a ladder cannot be used lo reach the area to be checked. When the sensor is located al a high elevation in the arch of a bridge or on a chimney a few lens of melers high, the situation becomes even more complex . Similar difficulties in checking the sensor are faced when it is located in the foundation, or when the sensor must not be visible from the outside and has lo be installed, for example, inside the wall and coaled with a special surface finishing. Similar problems are faced in the case of containers for gas or liquid products whose lightness must be maintained, in order to obtain accurate information on the load impact (conlained fluid or gas pressure) on crack evolution.

It is the object of this invention to solve the drawbacks mentioned above, thus permitting to check any sensor breakage even when it is not visible. For this purpose, a motion breakage sensor has been produced which can be checked not only visually, as provided by the known methods, but also by means of an electric signal. The sensor according to this invention consists of a bridge of rigid and fragile material on which a track of a very thin layer of electrically conductive material is laid in a continuous fashion. This conductive track functions as a breakage indicator capable of detecting whether the bridge is intact or not. As a matter of fact, since ihe conductive track adheres to the bridge and owing to the very thin layer of such a track, in the event the bridge breaks, the electric continuity between the two ends of the track will be interrupted.

In order to implement a sensor according to the present invention, the track of electrically conductive material needs just to be laid on the longitudinal sides of the bridge in a continuous fashion.

The main advantage with the sensor according to the present invention is essentially given by the fact that the mechanic event involved in the breaking of the bridge independently becomes a phenomenon which can be electrically recorded, by measuring the electric continuity between the two ends of the track.

Depending on the user's requirements, it will be possible to show the precious signal thus obtained at will.

The sensor according to the present invention can be advantageously connected with an electric circuit fitted with checking and signalling devices in order to check and signal by means of telltale lights, warning devices, logic units or data transmission systems the maintenance or loss of electric continuity between the ends of the conductive track.

When advisable, several sensors can also be installed, with related checking and signalling systems, which can give a general view in space and time of any changes in ihe structure under examination.

The conductive track can be laid by known methods, for example those used for printed circuit boards, or for glass decoration, or by using paint wilh conductive properties, such as silver or copper acrylic paints, which are commonly used for repairing ihe tracks of printed circuit boards or for repairing the resistance connections of rear window heating systems in cars.

The advantages discussed herein above and others will appear clear from the descriplion of the figures which are attached by way of illustration rather than limitation in which some embodiments are represented concerning the shape of the bridge, the pattern of the track and the use of the signal thus obtained: Fig. 1 - is a view of a bridge according to the prior art.

Fig. 2 - is a view of the simplest embodiment of the sensor according to this invention. Fig. 3 - is a cross-sectional view on the A-A plane of the sensor of Figure 2; Fig. 4 - is a view of the sensor according to this invention, with the track of conductive material along the four longitudinal sides of the bridge;

Fig. 5 - is a view of the sensor of figure 4 with a 180° rotation. Fig. 6 - is a cross-sectional view on the B-B plane of the sensor of figures 4 and 5. Fig. 7 - is a view of a prior art cylindrical bridge. Fig. 8 - is view of a cylindrical bridge with central weakening hole.

Fig. 9 - is a view of a bridge with a double frustrum-of-cone shape.

Fig. 10 - is a view of a conductive track layout, to be applied, according to this invention, to the bridges of figures 7, 8 and 9. Fig. 11 - is a view of a different conductive track layout, to be applied, according to this invention, to the bridges of figures 7, 8 and 9.

Fig. 12 - illustrates an installation diagram of a group of sensors.

Fig. 13 - is a wiring diagram between some sensors and a control panel.

Fig. 14 - is a view of a self-powered sensor. Figure 1 illustrates a bridge 30 according to prior art. It is tapered at the centre, with a twin dovetail shape.

Figure 2 shows the simplest embodiment of the sensor 31 according to this invention, which consists of a longitudinal track 32 of conductive material laid only on the upper side of the bridge 30. Figure 3 is a cross-sectional view on the A-A plane of sensor 31 of figure 2.

However, as shown in figure 3, should the bridge 30 in figure 2 break by bending with upward concavity, it may well happen that the break, and therefore the two edges of the bridge moving farther apart, would involve only the lower portions 33a and 33b of the bridge 30. In this case, the two upper portions 34a and 34b of the bridge, where the conductive track 32 is laid, would not move apart, with no subsequent track interruption.

In order to ensure that the conductive track is interrupted by any racture stress of the bridge, the sensor 35 was designed, which is shown in figures 4, 5 and 6, in which the conductive track 37 runs along all the longitudinal sides of the bridge 30. The figure shows an example of track 37 in a Greek fret pattern which comes back close lo the starting point.

In figure 5, sensor 35 of figure 4 has been rotated by 180° around its C-C longitudinal axis to better show the pattern of the conductive track 37.

Figure 6 is a cross-sectional view on the B-B plane, of sensor 35 illustrated in figures 4 and 5.

In the middle of sensor 35, a hole 36 can be provided aimed at further weakening the central part and facilitating the sensor break.

The cylindrical shape 40 represented in figure 7 is another shape used for prior art bridges, which can also be of a hollow type 41. One or more holes 42 may also be made in the middle of this type of bridge 40, in order to weaken the breakage area.

Figure 9 shows a bridge 50 with a double frustrum-of-cone shape and tapered towards the centre. Figure 10 and 11 show a diagram of two different conductive track layouts 43 and 44 developed on a plane, to be applied, for example, to bridges 40 and 50 illustrated in figures 7, 8, and 9.

The track 43 illustrated in figure 10 has a Greek fret pattern, whereas in figure 11 the track 44 has a spiral shape; in both cases the perimeter surface of the bridge is extensively covered, thus ensuring the immediate interruption of the conductive track 43, 44 upon the slightest breakage of the bridge 40, 50.

In order to electrically connect the conductive track 32, 37, 43, 44 with the circuit for checking electric continuity, leads 22, 23 can be placed at the ends of the track as illustrated in figures 4, 5 and 6.

The ends of these leads 22 and 23 will then be connected with the circuit for checking electric continuity or continuity interruption of the conductive track 32, 37, 43, 44. As illustrated in figure 4, said leads 22, 23 may be connected directly to the ends of the conductive track 37 and supported by the bridge 30, or they can be electrically connected by means of terminals or fastons secured on the sensor.

In order to ensure electric continuity between the leads 22, 23 and the conductive track 37, an example of the lead 22 being connected with a metal pin 24 which is passed through the bridge 35 is illustrated in figure 4. The pin 24 is then "wetted" by the conductive track 37. Conversely, the lead 23 is glued onto the bridge 35 with its sheath, its end is stripped and its internal wires are exposed and then "wetted" by the conductive track 37.

A similar procedure can be applied to terminals or fastons, since they can either be glued or secured by means of bolts or other device and their conductive appendices can then be wetted by the conductive track. Obviously enough, a similar securing system can also be used for the cylindrical and the frustrum-of-cone types of sensor.

Figure 12 shows a schematic use of one or more sensors 61, 62, 63 which are parallel connected to an electric, near or remote, power source 60. A telltale light 67, 68, 69 is series connected to each conductive track 64, 65, 66. The telltale light 67, 68, 69 is on as long as the related conductive track 64, 65, 66 remains intact. Should a sensor 61, 62, 63 break with subsequent interruption of the related conductive track 64, 65, 66, the related telltale light 67, 68, 69 is no longer supplied by power and therefore turns off. It should be pointed out that the group of sensors 61, 62, 63 is connected only by a pair of cables 70, 71 thus making the wiring very simple. This diagram can be used when the crack, although out of reach, is in any case visible, thus it is possible to check the telltale lights 67, 68, 69 with the naked eye or binoculars. Figure 13 illustrates a diagram where the signal coming from one or more sensors 80, 81, 82 is sent to a special control panel 89, where the signal can be properly processed. In each sensor 80, 81, 82, the ends of the related conductive tracks 97, 98, 99 are connected to the control panel 89 by means of pairs of cables 83 and 84, 85 and 86, 87 and 88, respectively.

This makes the installation somehow more difficult, but when the crack is out of reach or in an inconvenient position for the necessary checks, it may be advantageous to use a control panel 89 with telltale lights 90, 91, 92, each of them to be series connected with the conductive track of sensors 80, 81, 82 thus allowing to check the integrity of the related track and therefore of sensor 80, 81, 82 from a distance.

From prior art it is evident that when there are more sensors close to each other, it is possible to connect one end of the conductive track in each sensor to the same connection cable, thus using the other end to check track continuity. Therefore, in the example illustrated in figure 13, it is possible to use one single connection cable for outputs 83, 85, 87, thus saving cables and making the installation easier.

With this artifice, assuming the number of sensors to be N, N+ l cables will be enough instead of 2N. These two diagrams are illustrative examples of how the signal from the sensor can be employed, which, being detected by a logic unit in the control panel 89, can then be used in an unlimited number of ways.

With regard to the power supply of the telltale lights 67, 68, 69, batteries can be placed near the sensor series 61, 62, 63, in those cases where connection to ihe mains is not advisable. Figure 14 shows a self-powered sensor 96, which is very convenient, since it can rapidly be installed autonomously, without the need for feeding lines of any type. For this purpose, a sensor 96 is employed on which an electric power source 93 of small size is located, capable of supplying a telltale light 94, also located on the sensor 96, for a reasonably long period of time. The telltale light 94, which is visible also from a distance and indicates any interruption in the continuity of the conductive track 95, will be used to check the sensor.

The present invention comprises all the changes of details and modifications which may appear to be obvious to one skilled in the art, such as, for example, instead of a simple telltale light, the adoption of any kind of warning system, of a logic unit or of a data transmission system, or a different shape of bridge or different type of connection with the conductive track, or a different pattern of the conductive track on the bridge, but it is understood that all these variations fall within the scope of the attached claims.

Claims

1. A motion breakage sensor comprising a bridge (30, 40, 50) of rigid and fragile material to be rigidly secured between the two edges of a crack or split to be monitored, characterized by the fact that a very thin layer of electrically conductive material or conductive track (32, 37, 43, 44, 64, 65, 66, 95, 97, 98, 99) is laid on it in a continuous fashion, which is the breakage indicator capable of detecting whether the bridge is intact or not through the maintenance or loss of electric continuity between the ends of the conductive track.

2. The sensor according to claim 1, characterized by the fact that the conductive track (32, 37, 43, 44, 64, 65, 66, 95, 97, 98, 99) has its ends connected to an electric circuit (70, 71, 83, 84, 85, 86, 87, 88, 95) with which the ends have electric continuity and which is fitted with checking and signalling devices (67, 68, 69, 90, 91, 92, 94) capable of checking and signalling electric continuity at the ends of the conductive track (32, 37, 43, 44, 64, 65, 66, 95, 97, 98, 99).

3. The sensor according to claim 1, characterized by the fact that the ends of the conductive track (37) are connected with electric continuity to leads (22, 23) which can carry the continuity or continuity inlerruption signal of the conductive irack (37).

4. The sensor according to claims 1 and 2, characterized by the fact that the leads of the electric circuit (23) are directly connected to the ends of the conductive track (37) and supported by the bridge (30).

5. The sensor according lo claim 1, characterized by the fact lhal the condticlive track (32, 37, 43, 44, 64, 65, 66, 95, 97, 98, 99) is laid on the longitudinal sides of the bridge (30, 40, 50).

6. The sensor according to claim 1, characterized by the fact that the bridge has a cylindrical shape (40) and that it can possibly be of a hollow type (41).

7. The sensor according to claim 1, characterized by the fact that the conductive track laid on the side surface of the bridge has a Greek fret (43) or spiral pattern (44).

8. The sensor according to claim 1, characterized by the fact that the bridge (30, 40) has one or more weakening holes (36, 42) in the middle.

9. The sensor according to claim 1, characterized by the fact that at the ends of the conductive track (37) terminals, fastons or other devices (24) are secured for electric connection to the leads (22).

10. The sensor according to claims 1 and 2, characterized by the fact lhat the electric circuit (70, 71 , 83, 84, 85, 86, 87, 88, 95) which is fitted with checking and signalling devices (67, 68, 69, 90, 91, 92, 94) is powered by a near or remote electric power source (60, 93).

11. The sensor according to claims 1 and 2, characterized by the fact that the checking and signalling devices (67, 68, 69, 90, 91, 92, 94) for checking and signalling the electric continuity and continuity interruption of the conductive track (32, 37, 43, 44, 64, 65, 66, 95, 97, 98, 99) are consisting of telltale lights (67, 68, 69, 90, 91 , 92, 94) and/or warning systems, and/or logic units, and/or data transmission systems.

12. The sensor according to claims 1 and 2, characterized by the fact that the checking and signalling device (67, 68, 69, 94) for checking and signalling ihe electric continuity and continuity interruption of the conductive track ( 64, 65, 66, 95) is located on the sensor (61, 62, 63, 96).

13. The sensor according lo claim 1, characterized by the fact lhat one or more sensors (61, 62, 63) are parallel connected to a near or remote source of electric power (60).

14. The sensor according to claims 1 and 2, characterized by the fact thai one or more sensors (80, 81, 82) are parallel connected to a control panel (89) where one or more checking and signalling systems are mounted.

15. The sensor according to claims 1, 2 and 10, characterized by Ihe fact lhat the power source (93) is located directly on the sensor (96).