Abstract:
An optical soil sensor for mobilized measurements of in-situ soil characteristics has a shank assembly, which creates a furrow in which a soil sample is exposed, and a window plate assembly including a window through which emitted and reflected light pass. The sensor window, formed of a hard and durable material, is positioned in intimate contact with the soil sample as the sensor moves across the ground or field and is continually scoured by the soil to greatly reduce or eliminate window buildup and contamination. The intimate contact between the window and soil also eliminates the sample distance or air gap through which light must pass, thereby reducing measurement distortion and error. The soil sensor provides a structural platform compatible with a wide variety of light sources, light detectors, signal conditioners, and other devices.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0001] Not Applicable. 
     
    
     
       CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0002]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    This invention relates generally to soil sensors, and more particularly to an optical soil sensor for mobilized measurements of in-situ soil characteristics. Various optical methods and devices are available for the measurement of soil constituents such as organic matter. Generally, these methods involve illuminating the soil with an artificial light source and then measuring the light reflected from the soil or the light resulting from the fluorescence of soil constituents.  
           [0004]    U.S. Pat. No. 5,044,756 to Gaultney et al. and U.S. Pat. No. 5,038,040 to Funk et al. disclose in-situ soil testing devices that are used while the device moves across ground such as an agricultural field. However, both Gaultney et al. and Funk et al. disclose devices requiring a sample distance or gap between the sensor window and the soil being sampled. These devices have several important drawbacks. First, neither the Gaultney et al. or Funk et al. device provide a method for keeping clean the window through which light travels in and out. Given the harsh operating environment in which these soil sensors operate, materials such as dirt, dust, mud, debris, and moisture will invariably adhere to and contaminate the window, impede the passage of light through the window, and detrimentally affect the performance of the sensor.  
           [0005]    Second, dust and other airborne material in the sample distance or gap through which the emitted and reflected light must travel will scatter and interact with the light and cause measurement distortion or error. Consequently, it is desirable to minimize or completely eliminate any sample distance or air gap between the window and soil sample in order to improve the quality and integrity of the measurements.  
           [0006]    U.S. Pat. No. 5,739,536 to Bucholtz et al. discloses a probe, or “penetrometer,” for penetrating the soil to obtain information on chemicals present at various depths of the soil. While the window of the Bucholtz et al. device is in intimate contact with the soil being sampled, the Bucholtz et al. reference does not allow for mobilized measurement of soil characteristics as the soil sensor moves horizontally across the ground or field. Similarly, U.S. Pat. No. 5,887,491 to Monson et al. discloses a soil probe which is inserted into the soil for determining various soil characteristics, but does not allow for mobilized measurements.  
           [0007]    There is a therefore a need for an optical soil sensor device with an inherently self-cleaning window that provides for mobilized measurement of in-situ soil characteristics as the device moves across a field or other ground, and which maintains measurement quality and integrity by eliminating the sample distance or gap between the window and the soil being sampled.  
         SUMMARY OF THE INVENTION  
         [0008]    Accordingly, it is an object of the present invention to provide an optical soil sensor for measurement of in-situ soil characteristics as the sensor moves across ground such as an agricultural field.  
           [0009]    It is a further object of the present invention to eliminate the sample distance or gap between the window of the device and the soil being sampled and to provide for intimate contact between the window and the soil.  
           [0010]    Another object of the present invention is to provide an inherently self-cleaning, self-scouring window that eliminates or greatly reduces buildup on and contamination of the window in a harsh operating environment such as an agricultural field.  
           [0011]    Another object of the present invention is to provide a substantially flat and uniform soil surface on which the soil sensor and window operates.  
           [0012]    Another object of the present invention to provide a structural platform for a variety of light sources, light detectors, signal conditioners, and other electrical and electro-mechanical devices.  
           [0013]    Accordingly, the present invention provides for an optical soil sensor for mobilized measurements of in-situ soil characteristics. The sensor has a shank assembly, which creates a furrow in which a soil sample is exposed, and a window plate assembly including a window through which emitted and reflected light pass. The sensor window, formed of a hard and durable material, is positioned in intimate contact with the soil sample as the sensor moves across the ground or field and is therefore continually cleaned and scoured by the soil to greatly reduce or eliminate window buildup and contamination. The intimate contact between the window and the soil also eliminates a sample distance or gap through which light must pass, thereby reducing measurement distortion or error. Finally, the soil sensor of the present invention provides a structural platform compatible with a wide variety of light sources, light detectors, signal conditioners, and other devices.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith, and in which like reference numerals are used to indicate like parts in the various views:  
         [0015]    [0015]FIG. 1 is an elevation view showing the soil sensor, coulter, and gauge wheels coupled with and traveling behind a tractor.  
         [0016]    [0016]FIG. 2 is a fragmentary side elevation view of the soil sensor with portions broken away showing the shank assembly coupled with the window plate assembly and the bottom surfaces of the window plate and shank tip in intimate contact with the soil sample.  
         [0017]    [0017]FIG. 3 is a detailed fragmentary cutaway view showing generally the light source, light detector, mounting block, window plate, and window.  
         [0018]    [0018]FIG. 4 is an exploded fragmentary perspective view showing the shank assembly and the window plate assembly.  
         [0019]    [0019]FIG. 5 is a fragmentary perspective view showing the window plate assembly, shown in phantom lines, coupled with the shank assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Referring to the drawings in greater detail, and initially to FIG. 1, an optical soil sensor for mobilized measurements of in-situ soil characteristics is designated generally by the numeral  10 . The soil sensor  10  is coupled with a vehicle  12  such as a tractor and travels behind vehicle  12  as the vehicle  12  moves across the surface  16  of ground such as a farm field. The position of soil sensor  10  relative to the surface  16  of the ground is adjustable using a hydraulic piston  18  and a mechanical linkage  20 , or by other means well known to those skilled in the art. Gauge wheels  22  are coupled with vehicle  12  and travel on the surface  16  of the ground and behind the vehicle  12 . The gauge wheels  22  serve to support, and provide a height reference for, soil sensor  10 . For the sake of clarity, only one gauge wheel  22  is shown in FIG. 1, but it will be understood that at least one wheel  22  is positioned on each side of soil sensor  10  to provide adequate support for sensor  10 . As shown in FIG. 1, a coulter  24  may be coupled with vehicle  12  ahead and in the path of soil sensor  10 . Coulter  24  makes a vertical cut in the surface  16  of the ground and, in doing so, cuts stalks and other debris lying in the path of soil sensor  10  that might otherwise wrap around, damage, or affect the performance of sensor  10 .  
         [0021]    As best seen in FIGS. 4 and 5, soil sensor  10  includes a shank assembly  30 , a window plate assembly  32 , and a mounting block  34  that, when coupled with each other, provide a structural platform  36  that carries the light source, light detector, cables, and other electrical and electro-mechanical components of sensor  10 . As best seen in FIGS. 1 and 4, shank assembly  30  includes a shank extension  38  coupled at its upper end with vehicle  12  through mechanical linkage  20  and coupled at its lower end with shank plate  40 . As shown in FIG. 4, shank plate  40  is a single structural member formed or bent into a generally “U” or “V” shape, with a leading edge  42  and an interior edge  43  at the closed end of plate  40 . Shank extension  38  is coupled with shank plate  40  by welding the lower end of shank extension  38  to the interior edge  43  of plate  40 . It will be understood to one skilled in the art that shank extension  38  may be rigidly coupled with shank plate  40  by bolts, rivets, or other suitable mechanical fastening means.  
         [0022]    As best seen in FIG. 4, A shank tip  44  is coupled with the shank plate  40  adjacent the lower edge of plate  40  and at the leading edge  42 . Shank tip  44  has a first beveled edge  45  and is preferably coupled with shank plate  40  by spot welding, bolts, rivets, or other means well known to those skilled in the art. Shank tip  44  will wear during use and, therefore, the method of coupling shank tip  44  with shank plate  40  should preferably allow shank tip  44  to be removed from plate  40  and replaced relatively easily. Shank plate  40  has mounting holes  46  formed therein for use in coupling shank plate  40  with window plate assembly  32 , as described below.  
         [0023]    Window plate assembly  32  generally includes connector brackets  48  and a window plate  50 , as best seen in FIG. 4. Brackets  48  are generally “U” or “C” shaped channel members rigidly coupled at one end with window plate  50  by welding or other suitable mechanical means. Brackets  48  extend obliquely from plate  50  at an angle corresponding to the contours of shank plate  40 , as depicted in FIGS. 2 and 4. Brackets  48  have bolt holes  52  formed therein for use in coupling brackets  48  with shank plate  40 , as described below. As best seen in FIG. 3, window plate  50  has an aperture  54  therein. A window  56  is mounted within aperture  54  and is coupled with window plate  50  by adhesive, shrink fit, beveled edges, or other suitable mechanical fastening means. It will be understood that, due to the abrasive nature of soil, window  56  will wear during use and should therefore be coupled with plate  50  by means that allow a worn window  56  to be removed from plate  50  and a new window  56  to be replaced with relative ease. Window  56  is preferably formed of a synthetic sapphire material. It will be understood, however, that window  56  may be formed of any sufficiently transparent and wear-resistant material. Window plate  50  has a second beveled edge  58 , as best seen in FIG. 4. Edge  58  is beveled at an angle determined by the angle of the first beveled edge  45  of shank tip  44 , such that first beveled edge  45  is in intimate and continuous contact with second beveled edge  58  when shank assembly  30  is coupled with window plate assembly  32 , as described below.  
         [0024]    Referring now to FIGS. 3 and 4, mounting block  34  is coupled with and above window plate  50  by bolts  60  or other suitable mechanical fastening means. As best seen in FIG. 3, a recessed cavity  62  is formed in the bottom surface of block  34 , and first and second angled passages  64   a  and  64   b  extend from the upper surface  65  of block  34  to the recessed cavity  62 . A light source mounting assembly  68  and a light detector mounting assembly  70  are coupled with block  34 . Mounting assemblies  68  and  70  have first and second brackets  72  and first and second clips  74 . A light source  76  is coupled with mounting block  34  by inserting light source  76  downward and at an angle through first clip  74  and into and through angled passage  64   a  such that the tip of light source  76  extends into recessed cavity  62 . Light detector  78  is similarly coupled with mounting block  34  by inserting detector  78  downward and at an angle through second clip  74  and into and through angled passage  64   b  such that the tip of light detector  78  extends into recessed cavity  62 . It will be understood by one skilled in the art that light source  76  and light detector  78  are disposed at angles such that light emitted from light source  76  will pass downward through window  54 , reflect from soil sample  88 , pass upward through window  54 , and impinge on light detector  78 .  
         [0025]    It will also be understood by one skilled in the art that many light source and light detector configurations may be used with the soil sensor  10  of the present invention. Detectors are available that provide a single reading within a given band of wavelengths, while others are available that provide a simultaneous reading for each of several different wavelengths. The soil sensor  10  of the present invention provides a platform for the particular source and detector selected for a specific application, measurement, or soil type.  
         [0026]    As best seen in FIGS. 2, 4 and  5 , shank assembly  30 , window plate assembly  32 , and mounting block  34  are coupled with each other to present a structural platform  36  on which light source  76 , light detector  78 , window  56 , and other components are carried. Mounting block  34  is coupled with window plate assembly  32  as described above. Shank assembly  30  is coupled with window plate assembly by inserting window plate assembly  32  into the area defined by generally U-shaped or V-shaped shank plate  40 . Mounting holes  46  are aligned with bolt holes  52 , and first and second beveled edges  45  and  58  are positioned in intimate contact with each other. Bolts  84  are then inserted into and through mounting holes  46  and bolt holes  52 , thereby rigidly coupling shank assembly  30  with window plate assembly  32  and forming a substantially rigid structural platform  36 . As best seen in FIG. 2, the bottom surfaces of shank tip  44 , window plate  50 , and window  56  present a substantially smooth, continuous, planar surface when shank assembly  30  is coupled with window plate assembly  32 .  
         [0027]    In operation, soil sensor  10  is coupled with vehicle  12 , as depicted in FIG. 1. The operator driving vehicle  12  manipulates hydraulic piston  18  and mechanical linkage  20  to embed the shank tip  44  and window plate  50  into the ground, preferably such that the bottom surfaces of shank tip  44 , window plate  50 , and window  56  are at a depth of 3 to 6 inches below the surface  16  of the ground. It will be understood that sensor  10  may be used at other depths, as soil and ground conditions dictate. As vehicle  12  moves across the surface  16  of ground such as a farm field, the soil sensor  10  travels behind and in the path of vehicle  12 , and shank tip  44  and the leading edge  42  of shank plate  40  form a furrow  86  in the ground, thereby exposing a soil sample  88  in the substantially smooth, horizontal plane formed in the bottom of the furrow  86 .  
         [0028]    As the bottom surfaces of shank tip  44 , window plate  50 , and window  56  move along the furrow  86  and slide over the exposed soil samples  88 , the bottom surface of window  56  is in intimate contact with soil sample  88 . There is no air space or gap between the bottom surface of window  56  and soil sample  88  during operation of the sensor. Accordingly, window  56  is inherently self-cleaning in operation as the sensor  10  moves across the ground or field, in that window  56  is continuously scoured of soil, moisture, dust, debris, and other residue that might otherwise collect on the bottom surface of window  56  and adversely affect the measurement integrity of sensor  10  by scattering or impeding light passing through window  56 . If a coulter  24  is used, as shown in FIG. 1, the coulter  24  should be positioned at a depth shallower than that of the bottom surfaces of shank tip  44 , window plate  50 , and window  56  so that the soil sample  88  lies in a substantially smooth, horizontal plane undisturbed by grooves or other marks made by the coulter  24 .  
         [0029]    To measure the in-situ soil characteristics of the soil samples  88  exposed within furrow  86  as the sensor  10  and vehicle  12  travel across the ground, light is first emitted from light source  76 , as best seen in FIG. 3. The emitted light  90  travels downward and at an angle from source  76 , through recessed cavity  62 , aperture  54 , and window  56 , and strikes and reflects off soil sample  88 . The reflected light  92  then travels upwards and at an angle through window  56 , aperture  54 , and recessed cavity  62 , and is detected by light detector  78 .  
         [0030]    In the embodiment shown in FIG. 3, light source  76  and light detector  78  are mounted directly above and adjacent to mounting plate  34  and window  56 . In this configuration, electrical cables  94  connect light source  76  and light detector  78  to a power source, signal conditioner  96  (as seen in FIG. 1), computer, data logger, and/or global positioning device mounted remotely above soil sensor  10  and near vehicle  12 . Alternatively, fiber optic cables or other means could be used to transmit emitted light  90  from a remotely mounted light source  76  and reflected light  92  to a remotely mounted light detector  78  and signal conditioner  96 . Remote mounting of the light source  76  and light detector  78  above the soil sensor  10  and away from dirt, dust, and moisture would reduce damage to and deterioration of these components.  
         [0031]    It will be seen from the foregoing that this invention is one well adapted to attain the ends and objects set forth above, and to attain other advantages which are obvious and inherent in the device. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and within the scope of the claims. It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, all matter shown in the accompanying drawings or described hereinabove is to be interpreted as illustrative and not limiting.