Abstract:
The present invention relates to the field of microsensors, and particularly to a passive and reversible deformation sensor, specifically cycles of deformations in a direction OX of a structure, specifically during cycles of temperatures or mechanical stresses to which the structure is subjected, this sensor including elements ( 4, 5, 6 ) for detecting and, preferably, counting cycles of variations in the distance between two points or areas of a structure, these elements including a support having first and second portions ( 41, 44 ) attachable to, respectively, either of the two points or areas of the structure, wherein the detecting elements are associated with each of the first and second portions of the support, sensor characterized by in that the detecting elements include elements ( 54   1   , 54   2   , 54   3   , 55   1   , 55   2   , 55   3   , 56   1   , 56   2   , 56   3 ) for distinguishing between at least two different thresholds of cycles of variations in distance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/FR2012/000155, filed Apr. 20, 2012, which claims priority of French patent application no. 1101274 filed on Apr. 22, 2011. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of microsensors, and particularly to a microsensor able to detect, and preferably also to count, cycles of variations in the distance between two points or areas of a structure subjected to a repeated external action, for example cycles of temperatures or mechanical stresses as for example the number of passes of vehicles across a bridge, generating a known stress level in the structure. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    In this respect, patent U.S. Pat. No. 5,452,335 is known, which describes several examples of sensor of cycles of temperature, of which, on one hand, a first example, shown in  FIGS. 1 and 2  and in column  4 , of a passive sensor able to detect and count cycles of temperature in relation to a preset temperature threshold and, on the other hand, a second example, shown in columns  10  and  11  with respect to  FIGS. 10 to 12  and which relates to an electronic sensor for detecting and counting cycles of temperature in relation to two temperature thresholds, wherein this sensor comprises an electrical power supply and a preprogrammed microprocessor. 
         [0004]    In the field of road infrastructures, such as for example a bridge, in order to determine the structural evolution it is important to know the number of vehicles that have crossed it. 
         [0005]    In this respect, patent FR2875324 is known, which describes a vehicle pass counter comprising essentially a microphone arranged in an acoustic cavity and connected to means for processing signals emitted from the microphone. The signal characteristic of a motor vehicle is thus detected by such a device. 
         [0006]    Other devices are known, operating with ultrasounds, pressure sensors or image sensors and to which processing means are associated. 
         [0007]    These devices have, as the second above-mentioned example, several disadvantages: 
         [0008]    The first one relates to their service life: it is limited, at most, to the service life of the supply means, namely batteries, that is about one or two years. 
         [0009]    The second one relates to the impossibility to use them with a complete pyrotechnic security. Indeed, the presence of a potential difference, and thus of an electrical current, creates a risk of spark formation or short circuit which could generate a fire or even an explosion in presence of explosive material. 
         [0010]    The third one relates to their sensitivity to magnetic fields, particularly because of the generation of induced currents in the electrical circuits and of the degradation of the electronic components resulting therefrom. In addition, in most cases, these sensors and associated processing means have a large size, typically of several tens centimeters, thus making them very visible and which explains why they are subject to acts of vandalism. 
         [0011]    To solve these problems, patent application EP1998145 describes a reversible and passive microsensor for counting the number of cycles of loads to which a structure is subjected, which could for example correspond to the number of cycles of temperature, mechanical tensile, compression and/or bending loads generated, for example, by the crossing of movable vehicles on this structure, the size of which advantageously does not exceed 5 cm, and preferably 2 cm, for its largest dimension, and having an almost unlimited service life, which could be used in pyrotechnic security, having no sensitivity to electromagnetic fields and enabling a fault-free counting of this number of cycles or passes. 
         [0012]    Reversible sensor refers to a sensor able to detect a cycle of variations in the distance without deteriorating itself, thus able to then detect another cycle. 
         [0013]    Passive means refer to means operating without any power source, contrary to so-called active means used in the above-mentioned patent applications and which use a power source, namely an electrical power supply. 
         [0014]    This microsensor is provided with means for detecting and counting cycles of variations in the distance between two points or areas of a structure, these means comprising a support having a first portion and a second portion, each having an anchor area, wherein these anchor areas are attachable to, respectively, either of said two points of areas of the structure and consist in blocks, notches and/or bores and have smaller dimensions than the first and second portions, the counting means being associated with each of said first and second portions of the support. 
         [0015]    More specifically, and as shown in  FIGS. 1   a  and  1   b,  this passive microsensor for detecting and counting the number of passes of vehicles comprises a support  101 , essentially with a U shape, comprising thus a first portion  102  and a second portion  103  connected to each other by a third portion  104  forming the base of the U, and counting means  105  arranged on the support and comprising at least a first teethed wheel  106  disposed on said first portion  102  of the support  101  and, on one hand, a beam  107  for driving this first teethed wheel  106 , attached, at one end  108  of the ends  108 ,  109  thereof, to said second portion  103  and provided, at the other end  109  thereof, with a tooth  110 , shown in  FIG. 10  and able to form a gearing  111  with the teeth  112  of the first teethed wheel  106 , and, on the other hand, a reverse running stop device  113  for the first teethed wheel  106  and such that the first portion  102  becoming closer to the second portion  103  of the support  101  causes the teethed wheel  106  to be driven by the driving tooth  110  of the driving beam  107  while the distancing of these two portions causes the first teethed wheel  106  to be held by the reverse running stop device  113  and the tooth  110  of the driving beam to be retracted on a tooth  112  of the first teethed wheel  106 . 
         [0016]    As shown in  FIG. 1   a,  the first and second portions are provided with first and second anchor areas, respectively  224  and  225 , formed by bores, in each of which a screw can be inserted for attaching the microsensor on the structure to be analysed, such as for example the parapet of a bridge. The bores  224  and  225  have a diameter slightly larger than that of said screws. 
         [0017]    In this exemplary embodiment, the first and second anchor areas  224 ,  225  are disposed respectively according to a first axis Y 1  and a second axis Y 2  parallel to each other and separated by a distance L. In a preferred manner enabling to minimize the size of the sensor, these anchor areas are arranged such that the length L is as long as possible and such that the deformation of the structure between the axes Y 1  and Y 2  is at least equal to the pitch P of the teeth of the counting wheel. Indeed, when the microsensor is attached to a structure which is subjected to a deformation, the variation in the distance between these two anchor areas  224  and  225 , thus between the axes Y 1  and Y 2 , is proportional to this length L. As a result, for a given pitch P of the teeth of the counting wheel, and in case of the use of only one driving beam, the deformation of the structure between the axes Y 1  and Y 2  must at least be equal to P and preferably lower than or equal to 1.5×P. 
         [0018]    As shown in  FIG. 1   b,  faces  113 ,  134  and  135  of respective portions  102 ,  103  and  104  of the support  101  are planar and arranged in the same plane and adapted to be pressed against the structure to be analysed via said screws. 
         [0019]    In this exemplary embodiment, the third portion  104  of the support has itself a reversed U-shape with a thick base  136 . This shape enables to have smaller sections at the legs of the U of this beam than at the base  136 , and a break would occur at one of the legs, and thus in a direction parallel to that of the normal movement of the first and second portions, in case of a significant force is applied at this third portion, thus avoiding any relative movement between these portions in the normal direction of the movement and avoiding a potential offset between the teethed wheel  106  and the tooth  110  of the driving beam  107 . In this type of microsensor, the axis of the counting wheel is arranged on the axis Y 1  of the first portion  102 , and the driving beam  107  is integral with the second portion  103 . 
         [0020]    When a structure is subjected to different types of stresses which can generate variable deformations, it may be interesting to distinguish several deformation categories corresponding to different detection thresholds. On a bridge, several microsensors, such as the microsensor of  FIGS. 1   a  and  1   b,  can be attached, each comprising a counting wheel with a tooth pitch different from that of the others. Thus, one of them can count only the passes of trucks of more than 20 tons, another can count only vehicles of more than 3.5 tons and a third one can count all vehicles of more than one ton. Several identical sensors can also be used: indeed, a bridge being subjected to bending, these sensors can be arranged at distances different from the neutral fiber of the bridge so as to detect different events. 
         [0021]    However, where the structure subjected to these deformations is of a small size or has a reduced potential implantation area, and where several detection thresholds must be performed, its surface may not be sufficiently large to arrange as many different microsensors as different thresholds to be detected. 
         [0022]    The invention intends to solve this disadvantage by providing a microsensor having all the above-mentioned advantages described in the application EP1998145 as well as the advantage of detecting several thresholds. 
       BRIEF SUMMARY OF THE INVENTION 
       [0023]    The solution which is provided is a reversible and passive deformation sensor, specifically for cycles of deformations in a direction OX of a structure, specifically during cycles of temperature or mechanical stresses to which said structure is subjected, this sensor comprising:
   means for detecting and, preferably also means for counting, cycles of variations in the distance between two points or areas of a structure,   a support having first and second portions attachable to, respectively, either of said two points or areas of the structure, wherein the detecting means are associated with each of said first and second portions of the support,
 
and this sensor being characterized in that the detecting means comprise means for distinguishing between at least two different thresholds of cycles of variations in distance.
   
 
         [0026]    According to a particular feature, the detecting means comprise at least a first and a second detecting assembly, each comprising at least a first teethed wheel integral with one of the first and second portions and, on one hand, a beam for driving this teethed wheel made integral, directly or indirectly, at one of the end of the beam, with the other of the first and second portions and comprising, at the other end of the beam, a tooth able to form a gearing with the teeth of this first teethed wheel, wherein the tooth pitch of the first teethed wheel of the first assembly being different from the pitch of the first teethed wheel of the second assembly. 
         [0027]    According to an additional feature enabling to obtain a sensor with a low surface footprint, characterized in that the first and second assemblies are superimposed. 
         [0028]    According to a feature, the first and second assemblies are juxtaposed. 
         [0029]    According to a preferred feature, said first and second portions of the support have a L shape and are arranged head-to-foot, the bases of the Ls forming an anchor area and one of them being located at one side of the support and the other at the opposite side of the support. 
         [0030]    According to a feature facilitating the positioning of the support on a structure, the ends ( 37 ,  38 ) of said first and second portions of the support are connected to each other by an elastic element. 
         [0031]    According to a particular feature, a sensor according to the invention comprises sequentially, in a direction OX, a first anchor area integral with one of said first and second portions of the support, a first detecting assembly, a second detecting assembly, even a third, a fourth, etc. assembly, and finally a second anchor area integral with the other portion. 
         [0032]    According to another feature enabling to detect and count cycles of deformations, a sensor according to the invention is provided with a reverse running stop device associated with the first teethed wheel, comprising for example a beam integral, at one of the ends of the beam, with the first support or with the first portion of the support and comprising, at the other end of the beam, at least one tooth able to mesh with the teeth of the teethed wheel and, preferably, the reverse running stop device comprises a tooth able to mesh with said first teethed wheel, this tooth as well as the one of the driving beam and these of the first teethed wheel each comprising a radial surface and a tilted surface connecting the end of the radial surface of this tooth to the base of the radial surface of the next tooth. 
         [0033]    According to a particular feature, each assembly is provided with 9-shaped driving means, having a first O-shaped rigid portion attached to the second portion of the support, a second elastic portion one end of which is integral with the first portion while the opposite end is integral with a third portion provided with a primary beam and a secondary beam, this latter being provided with a tooth at its free end, and, preferably, the first portion of the support is provided with a stop able to restrict, directly or indirectly, the stroke of said secondary beam. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0034]    Other advantages and features of the invention will become apparent in the description of several alternative embodiments of the invention with reference to the appended drawings, in which: 
           [0035]      FIG. 2  shows a diagram of a first alternative embodiment of a support  9  usable in a reversible and passive sensor for deformations in a direction OX of a structure according to the invention. 
           [0036]      FIG. 3  shows a diagram of a second alternative embodiment of a support  9  usable in a reversible and passive sensor for deformations in a direction OX of a structure according to the invention. 
           [0037]      FIG. 4   a  shows a perspective view of the support of  FIG. 3  on which detecting and counting means have been arranged. 
           [0038]      FIG. 4   b  shows a sectional view of the sensor along axis BB′ in  FIG. 4   a , this sensor being attached on a structure to be monitored. 
           [0039]      FIG. 4   c  shows an enlarged view of one of the detecting and counting assemblies. 
           [0040]      FIG. 5  shows a partial detailed diagram of one of the assemblies. 
           [0041]      FIGS. 6   a  and  6   b  show the operating principle of the microsensor according to the invention. 
           [0042]      FIG. 7  shows a diagram of a first exemplary embodiment of the means for counting the number of detections. 
           [0043]      FIG. 8  shows a diagram of a second exemplary embodiment of the means for counting the number of detections. 
           [0044]      FIGS. 9   a  and  9   b  show another alternative embodiment of the invention, wherein  FIG. 9   a  is a longitudinal sectional view along OX passing through the main axis of the teethed wheels while  FIG. 9   b  is a side view. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]      FIG. 2  shows a diagram of a first alternative embodiment of a support  9  usable in a reversible and passive sensor of deformations in a direction OX of a structure according to the invention. 
         [0046]    This support  9  is provided with two L-shaped sub-assemblies  10 ,  11 , arranged head-to-foot and separated by a gap  12  and respective bases  13 ,  14  of which are, in part, anchor areas for anchoring the support  9  on the structure to be monitored. 
         [0047]    In this exemplary embodiment, these bases  13 ,  14  each comprise two bores  15 ,  16  and  17 ,  18 . The axes Y 1  and Y 2  passing respectively through the centers of the bores  15 ,  16  and  17 ,  18  are perpendicular to the axis OX while the axes X 1  and X 2  passing respectively through the centers of the bores  15 ,  17  and  16 ,  18  are parallel to the axis OX. 
         [0048]    The second portions  21 ,  23  of the Ls perpendicular to the respective bases  13  and  14  are positioned along the axis OX. 
         [0049]    The second portion  21  of the first sub-assembly  10  is provided with three bores  19  evenly distributed along the axis OX as well as three pairs of bores  20 , wherein the axis passing through the centers of a pair of bores is parallel to the axis Y 1  and wherein each of the pairs is associated with one of the bores  19 . Each bore  20  is adapted to accommodate a pin protruding from the support and capable of enabling a prepositioning of reverse running stop means. 
         [0050]    The second portion  23  of the second sub-assembly  11  is provided with three pairs of bores  22  also distributed along the axis OX, wherein each of the pairs  22  is associated to one of the bores  19 . Each bore  22  is adapted to accommodate a pin protruding from the support and capable of enabling a prepositioning of driving means. 
         [0051]    When such a support is attached to a structure, for example by bonding or by screws, it is preferable to insert shims in the gap  12  to allow an accurate positioning of the sub-assemblies  10 ,  11  with respect to each other. 
         [0052]      FIG. 3  shows a diagram of a second alternative embodiment of a support  29  usable in a reversible and passive sensor for deformations in a direction OX of a structure according to the invention. 
         [0053]    This support  29  is provided with first and second L-shaped sub-assemblies  30 ,  31  arranged head-to-foot and separated essentially longitudinally along the axis OX by a gap  32 , respective bases  33 ,  34  of which are, in part, anchor areas for anchoring the support  29  on the structure to be monitored. 
         [0054]    As in the above example, these bases  33 ,  34  each comprises two bores  15 ,  16  and  17 ,  18 . The axes Y 1  and Y 2  passing respectively through the centers of the bores  15 ,  16  and  17 ,  18  are perpendicular to the axis OX while the axes X 1  and X 2  passing respectively through the centers of the bores  15 ,  17  and  16 ,  18  are parallel to the axis OX. 
         [0055]    Furthermore, these first and second longitudinal portions  41 ;  44  are connected to each other, at the ends  37 ,  38  thereof, by an elastic element, in this case a material strand  35  and  36 . 
         [0056]    The second portion  41  of the first sub-assembly  30  is provided with three bores  19  evenly distributed along the axis OX as well as three pairs of bores  20 , wherein the axis passing through the centers of a pair of bores is parallel to the axis Y 1  and wherein each of the pairs is associated with one of the bores  19 . Each bore  20  is adapted to accommodate a pin protruding from the support and capable of enabling a prepositioning of reverse running stop means. 
         [0057]    This second portion  41  comprises as many substantially square-shaped recesses  42  as bores  19 , each recess being centered about one of the bores  19 . It also comprises three crenels  43  protruding from the lateral surface of the second portion  41  of the first sub-assembly  30  opposite to the second portion  44  of the second sub-assembly  31 . For each of the bores  19 , the axis passing through its center and parallel to the axis Y 1  is also an axis of symmetry of one of the crenels  43 . Each of these crenels comprises, in the median portion thereof, a bore  48 . 
         [0058]    The second portion  44  of the second sub-assembly  31  is provided with three pairs of bores  22  distributed as the bores  19  along the axis OX, each of the pairs  22  being associated with one of the bores  19 . Each bore  22  is adapted to accommodate a pin protruding from the support and capable of enabling a prepositioning of reverse running stop means. 
         [0059]    In addition, the lateral surface of the second portion  44  of the second sub-assembly  31  opposite to the second portion  41  of the first sub-assembly  30  comprises notches  45  which have dimensions larger than that of the crenels  43  and adapted to allow the insertion of crenels therein. 
         [0060]    Each of the bases  33 ,  34  is partially separated from the corresponding second portion of the L by two notches  46 ,  47  which are coaxial and facing to each other. 
         [0061]    The small notches  46  are not absolutely necessary, but they have the following advantages:
   facilitating the rotation of the 2 anchor areas in relation to each other. Indeed, when the monitor is installed on a structure which is subjected to bending, the right sections are rotating. Such an arrangement, by providing an elasticity (compliance), therefor allows to avoid an unnecessary increase of the stresses.   centering of the base with respect to the second corresponding movable portion of the support,   leaving, at the bases, only the material necessary to support the tensile or compression loads.   
 
         [0065]    The large notches  47  enable to create the elastic elements, namely material strands  35 ,  36  for making the sub-assemblies  30 ,  31  integral to each other. 
         [0066]      FIG. 4   a  shows a perspective view of the support of  FIG. 3  on which detecting and counting means have been disposed, while  FIG. 4   b  shows a sectional view of the sensor along the axis BB′ of  FIG. 4   a , this sensor being attached on a structure to be monitored, and  FIG. 4   c  shows an enlarged view of one of the detecting and counting sub-assemblies. 
         [0067]    On the support  29  in  FIG. 3 , three assemblies  4 ,  5 ,  6  are arranged, each comprising:
   pins  50 ,  51 ,  52 ,  53  press fitted in the bores  19 ,  20 ,  48  and  22  and protruding from the support  29  and serving as stop or rotation axis.   a teethed wheel  54   1 ,  54   2  or  54   3 ,   reverse running stop means  55   1 ,  55   2  or  55   3      driving means  56   1 ,  56   2  or  56   3 .   
 
         [0072]    In order to allow the detection of several different deformation thresholds, the teethed wheels  54   1 ,  54   2  or  54   3  have a tooth pitch different from a wheel to another. 
         [0073]      FIG. 4   c  shows an enlarged view of the assembly  5 . This latter comprises:
   pins  50 ,  51 ,  52 ,  53  press fitted in the bores  19 ,  20 ,  48  and  22  and protruding from the support  29  and serving as stop or rotation axis.   a teethed wheel  54   2  with a tooth pitch equal to p 2 ,   reverse running stop means  55   2 ,   driving means  56   2 .     
         [0078]    The driving means  56   2  comprise a 9-shaped plate, comprising:
   a first O-shaped rigid portion  60  attached to the second portion  44  of the second sub-assembly  31  of the support  29 , the central opening of this first portion being formed by a slotted hole,   a second elastic portion  61 , one end of which is integral with the first portion while the opposite end is integral with a third portion  62 ,   the third portion  62 , comprising a primary L-shaped beam  63 , one of the lateral faces of which is attached to said second portion  61  while the base is integral with a secondary beam  64  with substantially the same length as the primary beam and parallel to this latter, but being thinner and comprising, as shown in  FIG. 5 , a tooth  71  at the end thereof, this tooth being able, as shown in  FIG. 5 , to form a pawl-type gearing with the teethed wheel  54   2 . This third portion  62  thus forms a U, main legs of which are formed by said primary and secondary beams  63  and  64 .   
 
         [0082]    Furthermore, the lateral face  65  of the first portion  60 , a part of which is integral with the second elastic portion  61 , is provided with a notch with substantially the same length as the pins  52 , and the shape of this first portion as well as the positioning of the pins  52  on the support enable to perfectly preposition these driving means before attaching them, for example by bonding or screwing, on the support  29 . 
         [0083]    The reverse running stop means  55   2  have a plate shape and comprise:
   a first O-shaped rigid portion  66  attached to the second portion  41  of the first sub-assembly  30  of the support, the central opening of this first portion being formed by a slotted hole,   a second portion  67  with smaller dimensions than that of the first portion and comprising a primary L-shaped beam  38 , one lateral face of which is attached to said first portion  66  while the base is integral with a secondary beam  69  with substantially the same length as the primary beam and parallel to this latter, but being thinner and comprising, as shown in  FIG. 5 , a tooth  72  at the end thereof, this tooth being able, as shown in  FIG. 5 , to form a pawl-type gearing with the teethed wheel  54   2 . This second portion thus forms a U, main legs of which are formed by said primary and secondary beams  68  and  69 .   
 
         [0086]    Furthermore, the lateral face  70  of the first portion  66 , a part of which is integral with the second portion  37 , is provided with a notch  70  with substantially the same dimension as the diameter of the pins  51 , and the shape of this lateral face  70  as well as the positioning of the pins  52  on the support enable to perfectly preposition these driving means before attaching them, for example by bonding or screwing, on the support  29 . 
         [0087]    In this exemplary embodiment, the first and second anchor areas  33 ,  34  are respectively arranged along a first axis Y 1  and a second axis Y 2  parallel to each other and separated by a distance L. In a preferred manner enabling to minimize the size of the sensor, these anchor areas are arranged such that the length L is as long as possible and such that the deformation of the structure between the axes Y 1  and Y 2  is at least equal to the pitch p of the teeth of the teethed wheel. Indeed, when the microsensor is attached on a structure subjected to a deformation, the variation in the distance between the two anchor areas  33  and  34 , thus between the axes Y 1  and Y 2 , is proportional to this length L. As a result, for a given pitch p of the teeth of the teethed wheel, and in case of the use of only one driving beam associated with this wheel, the deformation of the structure between the axes Y 1  and Y 2  must be at least equal to p. Furthermore, the function of the pin  53  inserted in the bore  48  of the crenel  43  is to restrict, in the OX direction, the stroke of the primary beam  63  at a value equal to about 1.5 times the pitch p of the teeth of the associated teethed wheel. As the secondary driving beam of the wheel is integral with and parallel to the primary beam, the movement thereof in the OX direction will also be restricted to 1.5 times the pitch p of the teeth of the associated teethed wheel. As a result, with this pin  53  forming a restriction device, any movement in the OX direction greater than said tooth pitch will cause the teethed wheel to rotate of an angle corresponding to only one tooth. Without this pin  53 , any movement Δx (spacing between the anchor areas of Δx) of the structure in the OX direction greater than p would cause the tooth  71  of the secondary beam to move of Δx and the wheel to be rotated of an angle equal to the integer part of the ratio: 
         [0000]      (Δx/p)
 
         [0088]    Finally, the function of the pin  53  is, indirectly, to restrict the movement of the driving beam  64  toward the base  33  of the first sub-assembly  30  of the support  29 , with a calibrated value and substantially corresponding to the value of one pitch and a half of the teeth of the first teethed wheel. This pin  53  thus forms means for restricting the stroke of the tooth  71  of the secondary driving beam  64  or, in other words, stop means. 
         [0089]    Each of the teeth wheels is provided with a mark  91 , formed for example by a straight engraving disposed for example in front of the tooth  71  of the secondary driving beam  64  during the implantation of the sensor and enabling to count the number of cycles of deformations to which the structure is subjected simply by counting the teeth of the teethed wheel located between the mark  97  and the tooth  71  and in the opposite direction of the rotation direction of the wheel. 
         [0090]    As shown in  FIG. 5 , this teethed wheel  54   2  is provided with teeth  16  on the external peripheral surface  17  thereof and an internal peripheral surface  95 , preferably rough, for cooperating with a sleeve  12  integral with the pin  50  in order to create a resistive torque and prevent an autorotation of the teethed wheel. 
         [0091]    The secondary beam  64  of the driving means, referred to as driving beam  64  thereafter, is provided with a tooth  71  at the free end  73  thereof, this tooth  71  being able to form a pawl-type gearing with the teeth  16  of said wheel  54   2 . 
         [0092]    On this figure, the OX direction indicates the direction of the deformations that can be detected by this sensor while the arrow indicates the normal rotation direction of the counting wheel  54   2 . Along this direction, each of the teeth  16  of this teethed wheel  54   2  comprises a first radial surface  23  and a tilted surface  24  connecting the upper end  25  of said first radial surface to the base  26  of the radial surface of the next tooth. Still along this direction, the tooth  71  integral with the driving beam  64  comprises a tilted surface  28  and a radial surface  27 , this latter being opposite to said first radial surface  23  of a tooth  16  of the wheel  54   2.    
         [0093]    Thus, the tooth  71  of the driving beam has a driving face which comes into contact with a tooth of the teethed wheel so as to rotate this wheel during a movement in one direction of the driving element and a guide face enabling sliding, and thus retraction, of the driving element on the tooth of the teethed wheel during a movement of the driving element in the direction opposite to the above-mentioned one since the teethed wheel is then blocked by the reverse running stop means. 
         [0094]    The driving beam has an elasticity sufficient to retract a tooth  16  without deteriorating it. In addition, the driving beam and the reverse running stop beam have a deflection when they are against the wheel. This initial deformation enables to ensure the contact and thus the meshing, despite manufacturing/assembly defects and uncertainties. 
         [0095]      FIGS. 6   a  and  6   b  show the operating principle of the microsensor according to the invention. 
         [0096]    As shown in these figures, when such a sensor is attached, by both anchor areas  33 ,  34  thereof, for example by adhesive blocks inserted in the bores  15 ,  16 ,  17  and  18 , on a structure  49  subjected to a load generating a deformation, for example an elongation only in the OX direction, this deformation of the structure will generate a variation in the spacing between these blocks and thus of the respective centers thereof. Let A and B be the respective centers of the blocks in their initial or normal position and xA and xB the coordinates thereof in the axis OX. When the structure  49  is subjected to a load, spacing between the blocks varies and the points A and B are in the extreme positions A′ and B′, their coordinates being then xA′ and xB′ while the blocks come back to their initial position, or a slightly different one, when the load ends or after some time. 
         [0097]    The coordinate difference between the initial position and the extreme position is expressed by the following expression: 
         [0000]      Δ x =( xA′−xA )−( xB′−xB )
   Δy=0 according to the above-mentioned hypothesis.   
 
         [0099]    This spacing difference between the blocks causes a variation in the positioning between the second portions  41 ,  44  of the first and second sub-assemblies, respectively  30  and  31 . As the teethed wheels  54   1 ,  54   2  and  54   3  are integral with the second portion  41  of the first sub-assembly  30  and as each of the driving beams  64  comprises a tooth  71  meshed with one of the teethed wheels, said variation in the positioning generates a corresponding drive of the teethed wheels by said driving beams  64  in the direction of the arrow. 
         [0100]    As the teethed wheels  54   1 ,  54   2  and  54   3  have different tooth pitches p 1 , p 2 , p 3 , for example with p 1 &lt;p 2 &lt;p 3 , the deformation Δx to which the structure  49  is subjected will be detected or not detected depending on the value thereof and the value of the pitches as indicated in the following table. 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 Included 
                 Included 
                   
               
               
                   
                   
                 between p1 and 
                 between 
                 Greater 
               
               
                 Deformation Δ 
                 Lower than p1 
                 p2 
                 p2 and p3 
                 than p3 
               
               
                   
               
             
             
               
                 Wheel 54 1   
                 Non-detection 
                 Detection 
                 Detection 
                 Detection 
               
               
                 Wheel 54 2   
                 Non-detection 
                 Non-detection 
                 Detection 
                 Detection 
               
               
                 Wheel 54 3   
                 Non-detection 
                 Non-detection 
                 Non- 
                 Detection 
               
               
                   
                   
                   
                 detection 
               
               
                   
               
             
          
         
       
     
         [0101]      FIG. 7  shows a diagram of a first exemplary embodiment of means for counting the number of detections, wherein they simply consists in marks, for example engraved on the visible face of the wheel, with a main mark  91  above which the tooth  71  of the secondary driving beam  64  is arranged during the implantation of the sensor and with secondary marks  96  evenly distributed, for example every 50 teeth, on the periphery of the teethed wheel  56   i.    
         [0102]    However, these counting means do not enable to count a number of successive cycles of deformations greater than the number of teeth of the wheel. 
         [0103]      FIG. 8  shows a diagram of a second exemplary embodiment of means for counting the number of detections enabling to solve the above-mentioned drawback. These counting means comprise:
   a main mark  97  above which the tooth  71  of the secondary driving beam  64  is arranged during the implantation of the sensor,   a wheel,   a second teethed wheel  150   i  coaxially attached on the teethed wheel  54   i  and comprising only one tooth  151 ,   a third teethed wheel comprising for example 20 teeth and capable of being driven of an angle equal to 2n/20 by the tooth  151  at each turn of the teethed wheel  54   i.      
 
         [0108]    These means enable to count a number of cycles of deformations between 0 and 20 times the number of teeth on the teethed wheel  54   i.    
         [0109]    Furthermore, counting optical means can be used for example as those described in the patent application FR2875324. 
         [0110]      FIGS. 9   a  and  9   b  show another alternative embodiment of the invention,  FIG. 9   a  being a longitudinal sectional view in the OX direction, passing through the main axis of the teethed wheels while  FIG. 9   b  is a side view. 
         [0111]    In this exemplary embodiment, the support is similar to but shorter than that of  FIG. 3 . It comprises two opposite anchor areas  233  and  234  partially delimited by notches  46 ,  47  and first and second longitudinal portions  241 ,  244  separated by a gap  12 . Furthermore, these first and second longitudinal portions  241 ,  244  are connected to each other, at the ends thereof, by an elastic element, in this case a material strand  35  and  36 . 
         [0112]    The detecting means comprise three superimposed assemblies, each comprising:
   a teethed wheel  54   i ,   reverse running stop means  55   i ,   driving means  56   i .   
 
         [0116]    The teethed wheels  54   1 ,  54   2  or  54   3  are moveable about a same pin  250  integral with the support  229  and have different tooth pitches p 1 , p 2  and p 3  (with p 1 &gt;p 2 &gt;p 3 ), thus enabling to detect three different deformation thresholds. In this exemplary embodiment, they comprise the same number of teeth, that is 1000; thus, the diameters thereof are different, and the one  54   i  having the largest diameter and a tooth pitch p 1  is arranged first on the pin  250 , and then are arranged respectively on the pin  250  the teethed wheel  54   2  and the teethed wheel  54   3 , all of these wheels having an overall frustoconical shape, the base of which is facing the first longitudinal portion  241 . 
         [0117]    The reverse running stop means  55   1 ,  55   2  or  55   3  are identical, except for the driving tooth which is adapted to the pitch of the corresponding wheel, and are attached one above the other, with an offset such that the tooth of each of them is in contact with a tooth of the corresponding wheel. An O-shaped spacer separates them. These means are identical to those described in  FIGS. 4   a  to  5 . 
         [0118]    The driving means  56   1 ,  56   2  or  56   3  are identical, except for the driving tooth which is adapted to the pitch of the corresponding wheel, and attached one above the other, an O-shaped spacer separating them, but they are offset in the OX direction such that, without any deformation, the distance separating the end of the primary beam thereof and the stop  253  is respectively equal to about: 
         [0119]    1.5×p 1  for means  56   1    
         [0120]    1.5×p 2  for means  56   2    
         [0121]    1.5×3 for means  56   3    
         [0122]    For the counting of cycles of deformation, each teethed wheel is provided at the periphery thereof with a dialing from 0 to 980, with an increment of 20 teeth, and the first longitudinal portion  241  is provided with a straight engraving arranged along the radius of the wheels and at which the number 0 is placed, for each of the wheels, during the insertion of these wheels on the pin  250 . In use, as the wheels have different diameters, it is just necessary to perform a visual reading, for each wheel, of the number present at the straight engraving. 
         [0123]    The above-described embodiments have, with respect to the prior art, numerous advantages. Thus, the microsensor is entirely passive, and it is the event itself (action of an object able to bend a structure) that provides the power necessary for the operation of the detecting and counting functions. 
         [0124]    In this case, the microsensor is operated for a period which is not restricted by the service life of the power supply. Given the very nature of the materials which are used, in this case silicon, the service life of the sensor is in every instance highly greater than that of all weapon systems, including for passive systems stored for very long periods. 
         [0125]    In this case, the inert characteristic of the counter enables to contemplate its application to a system operating in pyrotechnic security, which provides a significant progress with respect to current capacities. In addition, a microsensor according to the invention is entirely insensitive to electromagnetic fields. 
         [0126]    In addition, it enables to simplify the assembly: less installations (number of tapped holes, bondings, flanges), reduce the cost and increase the discretion. 
         [0127]    Furthermore, the proposed solution is very simple to implement and has a highly reliable operating. It is independent from a power supply, discreet and has a low unit cost. 
         [0128]    Furthermore, the tooth of the reverse running stop beam can be replaced by a friction pad capable of applying a friction force on the counting teethed wheel. It has a double function. In both cases, it is the friction force of the pad on the wheel that enables it to perform its function. This friction force is determined by the preload of the pad beam. On one hand, it restricts an excessive rotation due to inertial effects of the counting wheel in the normal rotation direction. On the other hand, it prevents a rotation of the counting wheel in the direction opposite to the normal direction during return of the driving tooth, provided that the friction force of the pad is higher than that of the driving beam on the wheel. 
         [0129]    Furthermore, in case where one wishes that thermal expansion differences between the sensor and the structure be compensated for, it is preferable, on one hand, to make the supports of the sensor in one material the thermal expansion coefficient of which is close to that of the material of the structure, and, on the other hand, to geometrically compensate this thermal expansion via the shape of said first and second portions of the support and the positioning of the counting wheel. 
         [0130]    Furthermore, within the framework of  FIG. 5 , the connection between the pin  50  and the teethed wheel could be of a pivot type, for example pin/hub type, pin+2 roll bearings, pin+2 plain bearings or pin+2 jewel bearings and the resistive torque could also be ensured by the reverse running stop module.