Abstract:
A method for measuring a vibration from four or more equidistant points in a chamber, comprising centering a chamber surface around a center point, containing a fluid within the chamber surface, measuring a fluid vibration from at least four measuring points in juxtaposition with the chamber surface, wherein at least two measuring points are located along a first axis passing through the center point and at least two measuring points are located along a second axis passing through the center point.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a vibration sensor having multiple transducers in contact with fluid contained within a sensor chamber. 
       BACKGROUND OF THE INVENTION 
       [0002]    Determining the direction and/or intensity of vibrations provides valuable information in many diverse technological fields, for example, seismic plotting of an earthquake, locating tunnel activity, and intrusion event detection. 
         [0003]    A common prior art vibration sensor comprises a transducer in contact with fluid in a chamber. As the fluid vibrates in response to vibrations that contact the chamber, the transducer produces a signal that is received by a signal interpreter. The interpreter uses the signal to characterize vibrations in magnitude, frequency or vector along an axis passing through the fluid. 
         [0004]    To characterize a vibration in multiple axes, multiple sensors, each having a different axis, for example, are coupled together or alternatively, the sensor is rotated and/or moved with respect to the vibration; as seen in the following exemplary patents: 
         [0005]    In U.S. Pat. No. 4,525,819, Hartley, John Edward teaches a geophone transducer that is partially submerged in a fluid and detects horizontal seismic waves. 
         [0006]    In U.S. Pat. No. 4,334,296, Hall Jr., Ernest M. teaches a geophone comprising a fluid filled chamber having transducers in flexible top and bottom walls. Multiple geophones are used to provide output signals relating to the direction of the earth&#39;s motion. 
       SUMMARY OF THE INVENTION 
       [0007]    An aspect of an embodiment of the present invention comprises a vibration sensor that simultaneously provides output signals along multiple axes of a vibration, the sensor having a vibration-transmitting housing surrounding a chamber, the chamber containing a fluid and having a surface substantially in contact with the fluid. 
         [0008]    In an exemplary embodiment, the sensor further includes two or more paired vibration transducers positioned around the chamber, each transducer having a body including a first end; a second end; and a central axis segment between the first and second ends that passes through the center of the body, each body including a port adapted to communicate with a signal interpreter. 
         [0009]    Each first transducer end is operatively associated with the housing. Each second transducer end includes a transducing element operatively associated with the chamber fluid. 
         [0010]    In an exemplary embodiment, a first transducer pair and a second transducer pair are paired around the chamber so that a first axis passes through a first transducer of each pair, the center of the chamber and through a second transducer of each pair; the first and second transducer pairs providing vibration information from the center of the chamber. 
         [0011]    In an exemplary embodiment, the axes passing through the first and second transducer pairs are planar and perpendicular to each other. Planar axes, as used herein, refer to axes that lie along a single flat plane. 
         [0012]    In an exemplary embodiment, the sensor includes at least a third axis containing a transducer pair similarly paired in the manner of the first and second transducer pairs. 
         [0013]    Optionally, at least three of the three axes passing through the transducer pairs are perpendicular to each other and thereby characterize vibrations in the X-, Y-, and Z-axes. 
         [0014]    In an alternative exemplary embodiment, each transducer in at least one pair of transducers includes an amplification housing to amplify the vibrations. 
         [0015]    A further aspect of the present invention comprises a method for measuring a vibration, using at least one first pair and at least one second pair of transducers. 
         [0016]    As used herein, the word “fluid” designates “a continuous amorphous substance that tends to flow and to conform to the outline of its container” (Word Web© 2005) and includes any liquid or powder suspended in liquid comprising an inertial mass that is responsive to vibrations. 
         [0017]    As used herein, “vibration” refers to the response of the chamber fluid to motion or oscillations outside the chamber originating in, inter alia, mechanical or geological systems; the chamber fluid vibration pressure being measurable in frequency and amplitude. (“Harris&#39; Shock and Vibration Handbook”, Fifth Edition; Edited by Cyril M. Harris and Allan G. Piersol) 
         [0018]    As used herein, “transducer” refers to a device that converts the pressure of a shock or a vibratory motion into an optical, mechanical or electrical signal that is proportional to one or more motion parameters. 
         [0019]    As used herein, “transducing element” refers to the portion of the transducer that converts the pressure of the vibration motion into a signal. (ibid) 
         [0020]    There is thus provided a vibration sensor and method for measuring vibrations, the sensor having two or more paired transducers, the sensor comprising a chamber within a housing, the chamber including a center, a surface in which all portions of the surface are substantially equidistant from the chamber center and a volume of a vibration-sensitive fluid substantially in contact with the surface. 
         [0021]    The sensor further includes two or more pairs of vibration-sensitive transducers, wherein each transducer of each of the two or more pairs is adapted to communicate with at least one signal interpreter. Each transducer has a body including a first end portion, a second end portion and a central axis segment passing axially through the center of the body, between the first end portion and the second end portion. 
         [0022]    The first end portion is operatively associated with the chamber surface and includes a transducing element receptor portion, at least a portion of the transducing element portion being substantially in contact with the fluid. The second end portion is in operative association with the housing and each transducer pair of the two or more transducer pairs includes an axis passing through the central segment of a first transducer, the chamber center, and the central segment of a second transducer. 
         [0023]    Optionally, the signal interpreter provides at least one of adding and subtracting the signals generated by each of the at least two pairs of transducers. 
         [0024]    In an exemplary embodiment, the axes of the two or more transducer pairs are planar and at least one first axis passing through at least one first transducer pair is at least one of perpendicular and obliquely angled, with respect to at least one second axis passing through at least one second transducer pair. 
         [0025]    Alternatively, the at least two transducer pairs comprise at least three transducer pairs, and the at least one third transducer pair that is at least one of: 
         [0026]    Planar, and oblique with respect to the plane of the at least two planar transducer pairs and the at least one third transducer pair axis is perpendicular to the plane of the at least two transducer pairs. 
         [0027]    Optionally, the at least three transducer pairs comprise at least four transducer pairs, and include at least one fourth transducer pair angled 45 degrees to the two or more planar axes. 
         [0028]    Optionally, each transducer of at least one transducer pair includes an amplification housing. 
         [0029]    An aspect of an embodiment of the present invention comprises a vibration sensor having one or more paired transducers, the sensor comprising a chamber within a housing, the chamber including a center, a surface in which all portions of the surface are substantially equidistant from the chamber center and a volume of a vibration-sensitive fluid substantially in contact with the surface. 
         [0030]    In an exemplary embodiment, the present invention further includes one or more pairs of vibration-sensitive transducers, wherein each transducer is adapted to communicate with at least one signal interpreter, each transducer further having a body that includes a first end portion with a cross sectional area, a second end portion, and a central axis segment passing axially through the center of the body between the first end portion and the second end portion. 
         [0031]    The first end portion, including a transducing element receptor portion and an amplification housing, comprises a support element projecting from the body and beyond the transducing element, the support including one or more walls that surround an amplification fluid and a membrane attached to the support element and enclosing the amplification fluid, the membrane further including an area in contact with the chamber fluid, the contact area being substantially greater than the first end portion cross section. 
         [0032]    The second end portion is in operative association with the housing and each transducer pair of the one or more transducer pairs includes an axis passing through the central segment of a first transducer, the chamber center and the central segment of a second transducer. 
         [0033]    An aspect of the present invention further includes a method for measuring a vibration from four or more equidistant points, comprising centering a chamber surface around a center point, filling the chamber with fluid, measuring a fluid vibration from at least four measuring points juxtaposed against the chamber surface, wherein at least two measuring points are located along a first axis passing through the center point and at least two measuring points are located along a second axis passing through the center point. Optionally, two or more of the at least four measuring points comprise transducers having amplification housings. 
         [0034]    An aspect of the present invention includes a method for measuring a vibration from two or more equidistant points, comprising centering a chamber surface around a center point, containing a fluid within the surface, juxtaposing two or more vibration measuring elements in juxtaposition with the surface, placing an amplification housing over the two or more vibration measuring elements and measuring a fluid vibration from at least two measuring points juxtaposed against the chamber surface; wherein at least two measuring points are located along an axis passing through the center point. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    Exemplary non-limiting embodiments of the invention are described in the following description, read with reference to the figures attached hereto. In the figures, identical and similar structures, elements or parts thereof that appear in more than one figure are generally labeled with the same or similar references in the figures in which they appear. Dimensions of components and features shown in the figures are chosen primarily for convenience and clarity of presentation and are not necessarily to scale. 
           [0036]    The attached figures are: 
           [0037]      FIG. 1  shows a schematic view of a vibration sensor system, in accordance with an embodiment of the present invention; 
           [0038]      FIG. 2  shows a detailed exploded view of the vibration sensor of  FIG. 1 , in accordance with an embodiment of the present invention; and 
           [0039]      FIG. 3  shows a pressure transducer having an amplification diaphragm, in accordance with an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Vibration Sensor Operation 
       [0040]      FIG. 1  shows a schematic view of an exemplary embodiment of a vibration sensor  100  having a central, substantially spherical chamber  150 , including a spherical surface  154  and a center  156 . Chamber  150  contains a volume of fluid  152  and is surrounded by a housing  100  comprising a material adapted to transmit vibrations from an outside volume  112  to fluid  152 , comprising, for example, a material including metal and/or plastic. 
         [0041]    In an exemplary embodiment, chamber  150  includes six bores arranged into three pairs aligned with each of three axes  172 ,  182 , and  192 . A first bore  170  and a second bore  176  each have a central axis segment substantially aligned with an X-axis  172  that passes through center  156 . A third bore  180  and a fourth bore  186  each have a central axis segment substantially aligned with a Y-axis  182  that passes through center  156 . A fifth bore  190  and a sixth bore  196  each have a central axis segment substantially aligned with a Z-axis  192  that passes through center  156 . 
         [0042]    A vibration pressure transducer  160  is affixed, for example, with glue in each of bores  170 ,  176 ,  180 ,  186 ,  190  and  196 , and includes a transducing element  162  substantially in contact with, and responsive to, the pressure of fluid  152  vibrations passing through chamber  150 . 
         [0043]    In an exemplary embodiment, a signal interpreter  102  is connected to each transducer  160  via paired cables  174 ,  184  and  194 . X-axis paired cables  174  connect interpreter  102  to transducers  160  in bores  170  and  176 . Y-axis cables  184  connect interpreter  102  to transducers  160  in bores  180  and  186 . Z-axis cable  194  connect interpreter  102  to transducers  160  in bore  190  and  196 . 
         [0044]    Optionally, cables  174 ,  184  and  194 , for example, comprise four electrical wires, two wires connecting to each transducer  160 . 
         [0045]    As used herein, the term “transducer  160 ” refers to any active or passive transducer  160 , whose signal can be characterized by voltage, current amplitude, frequency, or phase. Active transducers  160  generate electrical signals from energy taken from the physical phenomenon being measured and include piezoelectric and inductive transducers  160 . Passive transducers  160  measure the effect of the physical phenomenon on resistivity, capacity, or inductivity of an electric current and include resistive, capacitive, inductive, and optoelectronic transducers  160 ; some examples being Electret Condensers and coiled wire and magnet arrangements. 
         [0046]    Alternatively, cables  174 ,  184  and  194  include wave guides and transducers  160  that transmit wave signals, for example, in infra red frequencies. In still other embodiments, each transducer provides a wireless signal that is received by receptor  102 . 
         [0047]    In an exemplary embodiment, signal interpreter  102  records information provided by the output of each transducer  160  individually and processes and/or analyzes the signal either during or following recording; using any one of the many signal analysis processes known in the art. 
         [0048]    By way of example, interpreter  102  adds or subtracts signals from each set of two transducers  160  located on the X-172, Y-182 and/or Z-192 axes, thereby amplifying or attenuating signals and/or eliminating extraneous diffuse vibration noise; diffuse vibration noise referring to vibrations with the same amplitude and phase coming from all directions. 
         [0049]    The resultant signal information from X-172, Y-182 and Z-192 axes is then processed by interpreter  102  to characterize a three-dimensional state of energy state of fluid  152  at center  156  along the X-172, Y-182 and/or Z-192 axes. This characterization, for example, provides frequency and magnitude information so that one sensor  100  can be used in place of multiple prior art sensors that each record along a single axis. 
         [0050]      FIG. 3  shows an exemplary embodiment in which transducer  160  is modified to be responsive to weak signals. Modified transducer  160  includes an amplification housing  200  comprising a substantially rigid conical wall  230  having a vibration amplification membrane  220  that includes a large surface area. Wall  230 , membrane  220 , and a transducing element  262  enclose a volume of compressible amplification fluid  210 , for example, a gas. 
         [0051]    The pressure of each vibration against membrane  220  causes membrane  220  to deform wherein the pressure of fluid  210  is inversely proportional to volumetric changes according to the following formula: 
         [0000]    
       
         
           
             
               
                 P 
                 1 
               
               - 
               
                 
                   P 
                   o 
                 
                 · 
                 
                   
                     V 
                     o 
                   
                   
                     V 
                     1 
                   
                 
               
             
             ; 
             
               wherein 
                
               
                 : 
               
             
           
         
       
       
         
           
             P o =the pressure variation applied on membrane  220 ; 
             P l =the pressure variation measured by transducing element  262 ; 
             V o =the volume of fluid  210  before pressure Po is applied; and 
             V l =the volume of fluid  210  after pressure variation Po is applied. 
           
         
       
     
         [0056]    Based upon the above formula, vibration pressure on membrane  220  results in an elevated vibration pressure on transducing element  262 ; the resultant signal, for example, aiding interpreter  102  in distinguishing weak signals from background noise. 
       Vibration Sensor Variations 
       [0057]    Vibration sensor  100  is not limited to the embodiments presented, but may be modified in many diverse ways, for example, providing unique configurations of sensor  100  for the many applications that are known to those familiar with the art. By way of example, only a few modifications of sensor  100  will now be presented. 
         [0058]    In an exemplary embodiment, housing  110  comprises an upper section  142 , a lower section  144  and a middle section  140 . Alternatively, housing  110  is manufactured in one piece, for example using injection molding techniques. 
         [0059]    As shown, X bores  170  and  176  and Y bores  180  and  186 , are located in middle section  140  while Z bore  190  is located in upper section and Z bore  196  is located in lower section  144 . 
         [0060]    Additional pairs of bores (not shown) provide additional signal information to signal interpreter  102   
         [0061]    Additionally or alternatively, three or more axes  172 ,  182  and  192  may pass through bores  170 , 176 ,  180 ,  186 ,  190  and  106  at different angles for specific uses. To detect vibrations emitted from a distance, for example in detecting buried pipes supplying water, sensor  100  is optimally configured with multiple axes passing from upper section  142  to lower section  144  each at angles of between 0 and 90 degrees. 
         [0062]    Alternatively, sensor  100  may include two pairs of transducers  160  along X-axis  172  and Y-axis  182  axes, accruing greater sensitivity to the signal information provided to signal interpreter  102 . 
         [0063]    Bores  170 , 176 ,  180 ,  186 ,  190 , and  196  along with their respective transducers  160  communicate with outside volume  112 , and, together with the glue mentioned above, seal chamber  150 . Alternatively, transducers  160  are mounted upon the inner surface of chamber  150  or embedded in housing  110  so that transducing elements  162  are recessed into surface  154 . 
         [0064]    Proceeding to  FIG. 2 , sensor  100  is shown in an exploded view and includes an upper compressible gasket  132  between upper  142  and middle  140  sections; and a lower compressible gasket  134  between middle  140  and lowers  144  sections. 
         [0065]    Gaskets  152  and  154 , for example, comprise a compressible and/or flexible rubber material so that when bolts (not shown) extend vertically through the corners of sections  140 ,  142  and  144 , gaskets  152  and  154  are compressed to seal chamber fluid  152  from outside volume  112 . 
         [0066]    Additionally or alternatively, gaskets  152  and  154  include upper and lower surfaces that adhere to adjacent surfaces of sections  140 ,  142  and  144 , thereby aiding in sealing chamber  150 . 
         [0067]    Transducers  160  are shown having a cylindrical cross-section. Alternatively, transducers  160  have a rectangular cross-section, an elliptical cross-section, or other cross sectional shapes depending, for example, on the type of transducer  160  and/or application. 
         [0068]    Additionally, the composition of fluid  152  varies depending upon the inertial mass characteristics required for a given application. For example, a high density fluid  152  such as liquid mercury may be required in some applications. Other applications are best served by particles, for example, a powdered metal alone or, for example, suspended in fluid  152 ; the many options for fluid  152  having specific characteristics being well know to those familiar with the art 
         [0069]    In some embodiments, fluid  152  substantially fills chamber  150  while in other embodiments, chamber  150  is partially filled. For example, in some embodiments, fluid fills 90% of chamber  150  to allow fluid  152  to expand due to anticipated temperature fluctuation. 
         [0070]    In some embodiments, chamber  150  has a surface  154  that is substantially spherical while in other embodiments, surface  154  comprises several flat, intersecting planes, for example comprising a tetrahedron. 
         [0071]    The many uses and embodiments of sensor  100 , whether detection of seismic reflections, energy reaching a space station, or locating tunnel activity, are well known to those familiar with the art. 
       EPILOGUE 
       [0072]    While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. 
         [0073]    Also, combinations of elements and/or variations in elements may be combined and single elements may be used, such variations and modifications, as well as others that may become apparent to those skilled in the art, are intended to be included within the scope of the invention, as defined by the appended claims. 
         [0074]    The terms “include”, “comprise” and “have” and their conjugates as used herein mean “including but not necessarily limited to.” 
         [0075]    It will be appreciated by a person skilled in the art that the present invention is not limited by what has thus far been described. Rather, the scope of the present invention is limited only by the following claims.