Abstract:
An apparatus for monitoring level variations in a given orientation of a structure, comprises a support portion secured to a structure to be monitored as a function of the given orientation in an adjustable position with respect to the horizon. A balancing arm hangs from the support portion in a resting position with respect to the horizon with one rotational degree of freedom being provided between the support portion and the balancing arm, such that a level variation in the given orientation of the structure causes the balancing arm to tend toward the resting position due to gravitational force A retaining member interrelates the balancing arm to the support portion, the retaining member retaining the balancing arm in the resting position. Sensors are positioned on the retaining member and are wired to a control system to measure strain of the retaining member resulting from the balancing arm tending toward the resting position, to quantify the level variation in the given orientation.

Description:
TECHNICAL FIELD 
   The present invention generally relates to sensors used on structures to monitor, particularly but not exclusively, level variations in magnitude, orientation, and deformation resulting from, for example, deflection or tilt. 
   BACKGROUND ART 
   Sensors of all types are installed on large-scale structures to measure parameters such as level variation, deformation and tilt resulting from a plurality of internal factors, e.g., material quality, foundations, and external factors, e.g., wind, temperature variations, earthquakes, landslides, ice and snow build-up. The sensors are provided to ensure the safety of occupants or users of the large-scale structures, by monitoring unusual variations in the above-described parameters, which could cause severe damage. Such monitoring would indicate when corrective action needs to be taken to prevent failure of such monitored structures. 
   It would be desirable to provide various sensor apparatuses that could be installed on existing older structures, e.g., without sensor apparatuses, or new structures, that isolate the various parameters by their configuration. 
   SUMMARY OF INVENTION 
   It is a feature of the present invention to provide a novel sensor apparatus for monitoring a level variation in a given orientation of structures. 
   It is a further feature of the present invention to provide a novel sensor apparatus for measuring deformation of structures so as to prevent cracks. 
   It is a still further feature of the present invention to provide a novel sensor apparatus for monitoring magnitude and orientation of level variations of structures. 
   According to the above features of the present invention, from a broad aspect, there is provided an apparatus for monitoring level variations in a given orientation of a structure, comprising: a support portion, adapted to be secured to a structure to be monitored as a function of said given orientation in an adjustable position with respect to the horizon; a balancing arm hanging from the support portion in a resting position with respect to the horizon with one rotational degree of freedom being provided between the support portion and the balancing arm, such that a level variation in said given orientation of the structure causes the balancing arm to tend toward said resting position due to gravitational force; a retaining member interrelating the balancing arm to the support portion, the retaining member retaining the balancing arm in said resting position; and at least one sensor positioned on the retaining member and adapted to be wired to a control system to measure strain of the retaining member resulting from the balancing arm tending toward the resting position, to quantify the level variation in said given orientation. 
   According to a further broad aspect of the present invention, there is provided an apparatus for monitoring deformation and stress in a given orientation of a structure, comprising: a first post and a second post each having a connection end adapted to be secured to a structure to be monitored, and a free support end, the free support ends of the first post and the second post being separated by a gap, the gap being oriented as a function of said given orientation; a sensor portion having a first leg and a second leg, the first leg and the second leg being interconnected at a first end, and each connected to a respective one of the free support ends at a second end so as to bridge the gap such that a deformation and stress of the structure causes strain of the first leg and the second leg of the sensor portion; and at least one sensor on a surface of at least one of the legs, the at least one sensor adapted to be wired to a control system to quantify a deformation of the structure as a function of said strain. 
   According to a still further broad aspect of the present invention, there is provided an apparatus for monitoring a level variation and an orientation thereof of a structure, comprising: a support portion adapted to be secured to a structure to be monitored in an adjustable position with respect to the horizon; a pendulum hanging freely from the support portion in a resting position with respect to the support portion, the wire of the pendulum adapted to be wired to a control system; an orientation ring supported by the support portion so as to be concentrically disposed with respect to the pendulum in the resting position, the orientation ring being segmented in ring portions each identified to an orientation value and each adapted to be wired to the control system; and at least one amplitude ring supported by the support portion so as to be concentrically disposed with respect to the pendulum in the resting position, the at least one amplitude ring being adapted to be wired to the control system; wherein a level variation of a given amplitude of the structure causes a displacement of the pendulum with respect to the resting position such that the pendulum closes contact with said at least one amplitude ring to signal a level variation of at least said given amplitude, and with at least one of said ring portions to indicate an orientation of said level variation. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which: 
       FIG. 1  is a schematic front elevational view of a level monitoring sensor apparatus in accordance with the present invention; 
       FIG. 2A  is a bottom plan view of a sensor mechanism of the level monitoring sensor apparatus of the present invention; 
       FIG. 2B  is a side elevational view of a finger of the sensor mechanism of the level monitoring sensor apparatus; 
       FIG. 3  is a perspective view of the level monitoring sensor apparatus in accordance with a first embodiment of the present invention; 
       FIG. 4A  is a side elevational view of a solid structure sensor apparatus in accordance with the present invention; 
       FIG. 4B  is a side elevational view of an alternative embodiment of a connection end of the solid structure sensor apparatus; 
       FIG. 5  is a front elevational view of a sensor portion of the solid structure sensor apparatus of the present invention, illustrating a preferred positioning of strain gauges; 
       FIG. 6  is a schematic cross-sectional view of a multicontact pendulum sensor in accordance with the present invention; 
       FIG. 7  is a top plan view of an orientation ring of the multicontact pendulum sensor apparatus of the present invention to indicate the direction of the tilting; 
       FIG. 8  is a top plan view of a monitoring board of the multicontact pendulum sensor apparatus of the present invention; 
       FIG. 9  is a side, elevational view of the orientation ring to indicate the direction of the tilting; 
       FIG. 10A  is a schematic side elevation view of a bridge equipped with sensor apparatuses of the present invention; and 
       FIG. 10B  is a schematic top plan view of a monitoring board of the bridge of FIG.  10 A. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring to the drawings, and more particularly to  FIG. 1 , a level monitoring sensor apparatus is generally shown at  10 . The apparatus  10  generally consists of a support structure  12  and a sensor mechanism  14 . A casing (not shown) may also be provided in order to conceal the apparatus  10 . 
   The structure  12  has a base  20  from which a pair of posts  21  project upwardly. The structure  12  stands on a surface G to be monitored by a plurality of legs  22  (e.g., three legs  22 ). The legs  22  are preferably vertically adjustable (e.g., telescopic legs, bolt-and-nut legs) so as to level the apparatus  10  with respect to the horizon, by way of level  23 . A support beam  24  extends horizontally between free ends of the posts  21  and is fixed thereto. A fixed arm of the support structure  12  is fixed to the support beam  24 . 
   The fixed arm  40  has a weight  41  at a free end thereof, and a finger  42  projecting from the weight  41  towards the balancing arm  50 . The finger  42  is best shown in  FIG. 2A and 2B . The finger  42  has in a preferred configuration a free end  43 , and a retaining wall  44  is provided in a throat portion of the finger  42 . Strain gauges  45  are positioned on the retaining wall  44  with opposed gauging surfaces, and are wired so as to measure the strain that will be sustained by the finger  42 , for instance, at the free end  43 . 
   The sensor mechanism  14  has a balancing arm  50  that hangs from the support beam  24 . The balancing arm  50  can pivot about the support beam  24 . The balancing arm  50  thus moves in a swinging motion, as best shown by arrows A 1  and A 2  of FIG.  2 A. In other words, when contemplating  FIG. 1 , the balancing arm  50 , if displaced, would come out of the page. 
   The balancing arm  50  has a weight  51  at a free end thereof, with an arch  52  connected to a bottom surface of the weight  51 , which will cooperate with the finger  42 . More specifically, the cooperation between the finger  42  and the arch  52  is shown in greater detail in FIG.  2 A. The arch  52  defines an opening  53  in which the free end  43  of the finger is received. The opening  53  is substantially of the same size as the thickness of the free end  43  of the finger  42 , such that there is no play therebetween. 
   The apparatus  10  is mounted to a surface whose level needs to be monitored. The base  20  is positioned so as to be horizontal with respect to the ground, in which case the fixed arm  40  and the balancing arm  50  are aligned with respect to one another, with the arms  40  and  50  being normal with respect to the horizon. In such a position, the balancing arm  50  does not exert any pressure on the fixed arm  40  through the arch  52 /finger  42  cooperation. The apparatus  10  will be subjected to level variations of the supporting surface G, and this will unbalance the balancing arm  50 , resulting in the balancing arm  50  being normal with respect to the horizon. A bending of the retaining wall  44  will result from this unbalance, and will be measured by the strain gauge  45 . 
   On the other hand, the fixed arm  40  will not pivot due to its rigid connection with the support beam  24 . The pivoting of the balancing arm  50  will be transmitted to the finger  42  by the arch  52  of the balancing arm  50 . The displacement of the balancing arm  50  with respect to the fixed arm  40  will cause opposing effects of tension/compression on the opposed gauging surfaces of the retaining wall  44 . This will be picked up by the strain gauges  45 , and the signal will be interpreted as a function of the level of the element that is measured, to indicate a level of the surface G of the element being measured. Circuit configurations for the strain gauges  45  will be discussed hereinafter. 
   The apparatus  10  is strategically positioned in view of level variations of the surface G. For instance, it is preferred to position the apparatus  10  such that the plane of rotation of the balancing arm  50  is superposed on the plane of the level variation of the greatest magnitude. The sensor apparatus  10  is preferably used to isolate a level variation in a single orientation of a structure. For instance, it may be unnecessary to measure the level variation in every orientation on structures that are elongated. For instance, a span of a bridge can be equipped with the sensor apparatus  10  adequately positioned such that the level variation in a longitudinal dimension of the span, i.e., from pier to pier, is measured. 
   The longer the fixed arm  40  and the balancing arm  50  are, the greater the balancing effect will be therebetween. Moreover, the weight  51  of the balancing arm  50  accentuates the strain picked up by the strain gauges  45 . On the other hand, the weight  41  stabilizes the fixed arm  40 . 
   It is advantageous to have a single rotational degree of freedom between the balancing arm  50  and the fixed arm  40 , as this will cause a direction of level variation to be isolated. The fixed arm  40  and the balancing arm  50  are preferably identical (i.e., in length and in cross-section), such that thermal expansion/contraction of the arms  40  and  50  will not have an effect on the strain measurement. 
   Referring to  FIG. 3 , a preferred configuration of the level monitoring sensor apparatus  10  is shown. The support beam  24  is provided with a trough  25 , and the balancing arm  50  defines a channel  54  in which a triangular cross-section pivot  55  is positioned so as to be received in the trough  25 . The fixed arm  40  and the balancing arm  50  are shown having a throat portion  46  and  56 , respectively, at a bottom of which weights  41  and  51 , respectively, are located. As mentioned previously, the fixed arm  40  is fixed to the support beam  24 . Alternatively, the balancing arm  50  can be mounted to the support beam  24  by a bearing, as schematically shown in FIG.  1 . The support beam  24  is also illustrated as being supported by bearings, whereby a locking system  24 ′ is required to set the support beam  24  once the fixed arm  40  is vertically aligned. 
   The level monitoring sensor apparatus  10  is designed to monitor the slightest level variation in any structure standing, hanging, held from one or multiple corners, held from the center, or resting flat on the ground. This movement can be caused by various factors such as time, wind, earthquake, load supported by the structure, pressure, landslide, defects in the material of the structure, loose joints, and poor support or poor foundation. It is contemplated to set threshold values of strain sustained by the finger  42  (e.g., at the free end  43 ), at which an alarm would sound to indicate abnormally high level variations. The sensor apparatus  10  can readily be installed on existing structures. 
   As mentioned previously, the greater the length of the arms  40  and  50  is, the smaller the level variation measured can be, as the length of the arms  40  and  50  is proportional to the strain of the finger  42 . It is also possible to reduce the height and the width of the retaining wall  44  so as to increase the signal picked up by the strain gauges  45 . A thinner and shorter retaining wall  44  will be more sensitive to the pressure exerted by the balancing arm  50 . 
   Referring to the drawings, and more particularly to  FIG. 4A , a solid structure sensor apparatus in accordance with the present invention is generally shown at  100 . The solid structure sensor apparatus  100 , hereinafter “sensor apparatus  100 ,” is shown secured to a solid structure S to be monitored. 
   The sensor apparatus  100  has a mount portion  102  and a sensor portion  104 . The mount portion  102  has a pair of upstanding posts  120 . Each post  120  has at a bottom end thereof connection ends  121  so as to be fixed to the solid structure S. The connection ends  121  are illustrated nonrestrictively as perpendicularly disposed plates used in combination with bolts  122  to secure the sensor apparatus  100  to the solid structure S. The free end of each post  120  has a horizontal support portion  123 , which consists of perpendicularly disposed flanges. The horizontal support portions  123  of the posts  120  are separated by a gap  124 . In another embodiment of the sensor apparatus  100 , illustrated in  FIG. 4B , a plurality of threaded rods  126  are welded, inserted, glued or cemented to the solid structure S. The connection ends  121  are sandwiched between nuts  125 , threadingly engaged with the threaded rods  126 , such that the sensor apparatus  100  can be leveled. 
   Referring to  FIG. 4A , the sensor portion  104  has an inverted U-shaped body  140 , whose opposed ends sit on the horizontal support portions  123  of the posts  120 . The sensor portion  104  is fixed to the mount portion  102 . The inverted U-shaped body  140  defines a pair of gauging surfaces  141  upon which strain gauges  142  are bonded. Referring to  FIG. 5 , a preferred positioning of the strain gauges  142  is shown. One of the two gauging surfaces  141  is shown in  FIG. 5 , with the other of the gauging surfaces  141  having a similar strain gauge configuration. Accordingly, each gauging surface  141  has a pair of strain gauges  142  thereon, with the strain gauges  142  being perpendicularly disposed with respect to one another, such that one of the strain gauges  142  of each gauging surface  141  reacts in compression, while the other one of the strain gauges  142  reacts in tension, or vice versa. As will be described hereinafter, the four strain gauges  142  are wired in a bridge configuration so as to obtain precise strain measurement of the solid structure S. 
   The posts  120  of the mount portion  102  amplify bending deformation of the solid structure S. The posts  120  are preferably made of the same material and have a similar configuration (i.e., length, cross-section, dimension of the support portions  123 ), such that thermal changes have negligible effect on the strain measurement performed by the sensor apparatus  100 . The surface of contact between the apparatus  100  and the solid structure S is relatively small to limit friction therebetween for more accurate measurement. 
   A casing (not shown) is typically provided to conceal the sensor apparatus  100 . The sensor apparatus  100  can be installed on existing structures. The sensor portion  104  is preferably bolted (but may also be welded thereto) to the mount portion  102  once the mount portion  102  has been secured to the solid structure S. The sensor apparatus  100  is designed to monitor the pressure, the strain, the stress, the overload, the fatigue level, and the strength of any solid structure. The solid structure S can be resting on the ground or can be supported in another way, and may be of any solid material. Any suitable transducer configuration can be used for the interpretation of the strain picked up by the strain gauges. 
   Referring to the drawings, and more particularly to  FIG. 6 , a multicontact pendulum sensor apparatus is generally shown at  200 , and will be referred to hereinafter as “sensor apparatus  200 .” The sensor apparatus  200  has a mount portion  202  and a sensor mechanism  204 . 
   The mount portion  202  has a casing  220 , having legs  221  by which the sensor apparatus  200  is supported on a surface S of an element to be monitored. The legs  221  are adjustable in height and are used in combination with a spherical level  223  on top of the casing  220  to set the sensor apparatus  200  horizontally. The casing  220  also has a compass  224 , which will be used to orient the sensor apparatus  200 . 
   The casing  220  defines an inner cavity  222  adapted to receive the sensor mechanism  204  therein. The casing  220  has, for instance, a removable cover so as to provide access to the inner cavity  222 . A support plate  225  is horizontally disposed in the inner cavity  222 , and defines a circular opening  226  by which the sensor mechanism  204  will hang freely in the inner cavity  222 . The casing  220  and the support plate  225  of the casing  220  mostly consist of nonconductive materials. 
   The sensor mechanism  204  has a bucket-type housing  240 , having an inner cavity. The housing  240  has a removable cover  241 . The cover  241  has a concentrically disposed tube  242  with a ball connector  243  at a free end of the tube  242 . The center of the ball connector  243  is aligned with a center of the cover  241  and a central axis of the tube  242 . The housing  240  hangs freely in the inner cavity  222  of the casing  220  by the ball connector  243  being supported by the support plate  225  and the tube  242  passing through the opening  226 . The cooperation between the circular opening  226  and the ball connector  243  allows free movement of the sensor mechanism  204  in three rotational degrees of freedom with respect to the mount portion  202 . 
   An orientation ring  244  and amplitude rings  245  are supported by nonconductive support arms  258  so as to be concentrically disposed with respect to the central axis of the housing  240 . This central axis of the housing  240  passes through the center of the cover  241  and of the ball connector  243 , and is coincident with the axis of the tube  242 . The orientation ring  244  is positioned above the amplitude rings  245 . Thereafter, amplitude rings  245 A,  245 B,  245 C and  245 D sequentially increase in diameter from top to bottom. The orientation ring  244  is connected to a monitoring board by a plurality of orientation output wires  250 . Similarly, each of the amplitude rings  245  has a respective amplitude output wire  251 , so as to be connected to the monitoring board. 
   A pendulum  247  hangs freely from a center of the ball connector  243  and passes through each of the rings  244  and  245 . The pendulum  247  has a weight  248  at a bottom end thereof. The wire  246  of the pendulum  247  is conductive, and is connected to input wire  249  such that an input signal can be fed to the pendulum  247 . Preferably, a liquid is provided in the housing  240  to dampen movement of the weight  248  of the pendulum  247 . Typically, the liquid is a nonconductive antifreeze oil. 
   As the pendulum  247  hangs freely in the inner cavity of the housing  240 , it is free to swing in any direction. The amplitude rings  245  are sized such that the wire  246  of the pendulum  247  comes into contact with the smaller ring (i.e.,  245 A) and gradually with the following ring in diameter. The orientation ring  244  is smaller than the amplitude rings  245 , whereby contact between the wire  246  and the orientation ring  244  will precede or accompany contact between the wire  246  and any one of the amplitude rings  245 . 
   Referring to  FIG. 7 , the orientation ring  244  is shown consisting of eight annular segments  254 . The annular segments  254  are separated by nonconductive spacers  254 ′. As shown in  FIG. 9 , ends of the annular segment  254  overlap one another. Each of the annular segments  254  is wired such that, when the wire  246  of the pendulum  247  comes into contact with one of the annular segments  254  (or two, in the case of overlapping annular segments  254 ), current from the input wire  249  is conducted to the appropriate orientation output wire  250 . Each of the annular segments  254  is given an orientation such that transmission of current from the pendulum  247  to the orientation ring  244  will be identified as an orientation. Accordingly, a displacement of the pendulum  247  will have an orientation. It is pointed that, although the orientation ring  244  is shown having eight annular segments  254 , more or fewer annular segments  254  may be provided for the orientation ring  244 . 
   The increasing diameter of the amplitude rings  245  from top to bottom ensures that the wire  246  of the pendulum  247  will come into contact with the smallest amplitude ring, namely amplitude ring  245 A. Once more, the contact between the wire  246  and the amplitude rings form a loop, whereby the amplitude output wire  251  will send a signal with regard to the amplitude ring  245  in which contact has occurred between the pendulum  247  and the amplitude ring  245 . 
   The fluid  252  is provided to reduce unwanted negligible oscillations of the pendulum  247 . Referring to  FIG. 9 , a monitoring board to be used in conjunction with the sensor apparatus  200  is generally shown at  260 . The monitoring board  260  of this embodiment has orientation indicators  261  and amplitude indicators  262 , and is wired to the orientation output wires  250  and the amplitude output wires  251 . The orientation indicators  261  are each combined to one of the annular segments  254  of the orientation ring  244  via the respective orientation output wires  250 . The orientation indicators  261  are combined with orientation indicia, as illustrated in  FIG. 9 , to indicate the direction of the tilting of the element under study. Similarly, the amplitude indicators  262  are each combined to a respective amplitude ring  245  to give, e.g., a schematic illustration of the amplitude. For instance, an amplitude level of 3 may indicate a warning of strong amplitudes, whereas an amplitude level of 4 can trigger an alarm. 
   The sensor apparatus  200  must be calibrated in order to match the orientation of the respective annular segments  254  with the actual cardinal points. A cardinal point indicator  255  (e.g., north) is provided on the housing  240  such that the housing  240  can be rotated to match the actual orientation provided by the compass  224 . The ball connector  243 /circular opening  226  configuration enables rotation of the sensor mechanism  204  in accordance with the appropriate orientation. A weight  256  ensures that the sensor mechanism  204  is aligned vertically prior to the orientation. The weight  256  may be removed thereafter for normal operation of the sensor apparatus  200 . A fixing mechanism  257  is also used to prevent movement between the sensor mechanism  204  and the mount portion  202 , once the orientation is set and the sensor mechanism  204  is vertically positioned. Accordingly, the pendulum  247  will be the only movable portion of the sensor apparatus  200 , whereby level variation of the surface S can be qualified in magnitude and orientation. 
   The sensor apparatus  200  can be used to indicate the tilting progress of structures against time, wind, earthquake, loads, landslide, defects in material, and weak support or foundation. The longer the wire of the pendulum  247  is, the more sensitive the apparatus will be to small degrees of tilting. Similarly, the smaller the amplitude rings  245  are, the more sensitive the sensor apparatus  200  will be to small degrees of inclination. Obviously, more or fewer amplitude rings  245  can be provided. 
   The sensor apparatuses  10 ,  100  and  200  can be used individually or simultaneously in a plurality of structures. More particularly, but not exclusively, bridges, tunnels, dams, earthquake detection systems, landslide detection systems, silos, tanks, reservoirs, roofs, railways, subways, foundations, floors, walls, nuclear plants, industrial chimneys, high-rise buildings and towers, industrial signs, cranes, high-rise posts for cable carts, power lines and amusement parks, and involve the sensor apparatuses of the present invention. 
   For instance,  FIG. 10A  illustrates a bridge B. The level monitoring sensor apparatuses  10  are installed on the spans of the bridge, along with the solid structure sensor apparatus  100 , to monitor any unusual activity (e.g., level and deflection) of the bridge B. The multicontact pendulum sensor apparatuses  200  are installed in the piers P to monitor the tilt. 
   The group of sensor apparatuses  10 ,  100  and  200  on the bridge B can be powered by solar energy. A solar panel is shown at  302 . A control station positioned remotely from the bridge B can receive sensor apparatus data through a communication system such as wireless communication antenna  304 . A monitoring board  300  is illustrated in  FIG. 10B , and can be provided as an intensity indicator to indicate to a bridge traffic operator whether the bridge B can be used. 
   For instance, each of the sensors  10 ,  100  and  200  installed on the bridge B can be connected to three lights on the monitoring board  300 , with a red light indicating hazardous unusual activity, that could prompt the operator to close the bridge B. 
   It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims.