Abstract:
The inner surface of an underground tunnel defining structure, such as a culvert or pipe, is measured by apparatus including a portable hand held battery powered laser unit releasably attached to a rotor disk supported within the tunnel by an adjustable stand or tripod for rotation on a generally horizontal axis. The disk has peripherally spaced notches which receive a spring-biased latch member for positioning the disk and laser unit at predetermined angular positions about the axis. The laser unit emits a laser beam to a target on the inner surface of the structure and displays on the unit a precision distance reading from the laser unit to the target. The distance reading for each target is entered in a chart for comparison with a prior measurement reading to indicate changes in the shape or profile of the inner surface.

Description:
BACKGROUND OF THE INVENTION 
     Throughout the United States, there are many underpass structures that define a tunnel extending under a roadway, such as, for example, a culvert or pipe arch formed of corrugated sheet metal or other material which can change in shape or cross-sectional configuration over a period of time. Frequently, it is desirable to determine the degree of change in configuration or shape by comparing a current actual cross-sectional shape with the original or a prior cross-sectional shape to insure that the structure continues to have sufficient strength to support the load above the structure. While horizontal and vertical measurements are sometimes manually made of the structure at intervals along the length of the tunnel, such measurements require substantial time and effort, resulting in significant cost. There are also various forms or types of complex laser equipment for measuring and/or detecting the inner surfaces of a bore or pipe, such as disclosed, for example, in U.S. Pat. Nos. 7,164,476, 7,345,757, 7,349,083,7,557,914 and 7,567,350. However, none of the equipment is suitable for quickly, economically and efficiently measuring and determining the cross-sectional shape or configuration of a tunnel defining structure. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to apparatus for measuring the inner surface of a structure embedded in the ground and defining a tunnel, such as a corrugated metal culvert or arch. The apparatus is economical in construction and provides for quickly and efficiently measuring and determining the shape or cross-sectional configuration of the structure. The apparatus is also portable and may be easily and quickly shifted to different positions along the length of the tunnel. In general, the apparatus includes a portable stand which is supported by a bottom portion of the structure or the tunnel and projects upwardly into the tunnel. The top of the stand supports a rotor for rotation on a generally horizontal axis, and a portable hand held type battery powered laser unit is supported by the rotor for rotation with the rotor on its axis. The laser unit emits a beam of coherent light to a target on the inner surface of the structure and automatically and precisely measures and displays the distance from the laser unit to the target. The rotor and laser unit rotate together on the axis to predetermined angular positions around the axis to provide for obtaining a distance measurement to a target on the inner surface at each of the angular positions. A chart may be used to record the displayed measured distance to each target, and the recorded data may be used to generate a two dimensional shape of the inner surface for comparison with the original shape or a previously measured shape. 
     Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical section through a corrugated metal culvert defining a tunnel and in which is positioned portable measuring apparatus constructed in accordance with the invention; 
         FIG. 2  is an enlarged fragmentary perspective view of the measuring apparatus shown in  FIG. 1 ; 
         FIG. 3  is an elevational front view of the measuring apparatus shown in  FIG. 2 ; 
         FIG. 4  is an exploded perspective view of the laser measuring unit shown in  FIG. 3  and its supporting panel; and 
         FIG. 5  is a fragmentary perspective rear view of the apparatus shown in  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , a tunnel defining structure in the form of corrugated sheet metal tubular culvert  10  extends within the earth or ground  12  and defines a tunnel  14  which commonly serves as a water underpass below a roadway. As an example, the culvert  10  may have a span of 17 feet and a rise of 16 feet. As a result of the loading on the culvert  10  by the earth or ground  12  pressing against the sides and top portion of the culvert and/or a roadway above the culvert, it is not uncommon for the culvert to be distorted after a period of time with the distortion creating stresses in the culvert and changing the cross-sectional shape or profile or configuration of the culvert. Thus it is sometimes desirable to measure the cross-sectional shape or configuration of the inner surface of the culvert  10  at longitudinal spaced intervals along the length of the tunnel  14  so that the current actual shape may be compared with the original shape or a previous measured shape of the culvert and to determine if there are any bulges or flat areas or tears in the culvert. 
     In accordance with the present invention, measuring apparatus  20  includes a support stand in the form of a collapsible tripod  24  of the type commonly used by surveyors and which has three elongated and adjustable telescopic legs  26  each pivotally connected to a top support plate or platform  28  having a flat top surface  31 . Each of the foldable and adjustable telescopic legs  26  has a clamping mechanism  34  which provides for infinite longitudinal adjustment of each leg. The apparatus  20  also includes a measuring system  40  mounted on the top surface  31  of the adjustable stand or tripod  24 . The measuring system includes an adjustable angle bracket  44  ( FIG. 5 ) having an elongated horizontal member or leg  46  with a longitudinal extending slot  47  for receiving a threaded stud (not shown) connected to a knob  49 . The stud is threaded into a nut (not shown) adjacent the bottom surface of the top plate  28  so that when the knob  49  is tightened with the member or leg  46  in a selected horizontal position, the leg  46  is clamped against a spacer plate  53  and the top surface  31  of the support platform  28 . A circular bubble-type level  54  is mounted on the leg  46  and provides for conveniently leveling the top surface  31  of the support platform of the tripod  24  by simply adjusting one or more of the legs  26 . 
     The adjustable angle bracket  44  also includes an upwardly projecting or generally vertical member or leg  57  which is pivotally connected to the leg  46  and may be angularly positioned relative to the leg  46  after releasing a knob  59  having a threaded stud (not shown) extending through a slot within an ear or flange  61  secured or welded to the leg  57 . The threaded stud extends into a threaded hole within a vertical flange  63  secured or welded to the leg  46  so that when the knob  59  is tightened, the leg  57  is held in a selected angular position relative to the leg  46 . 
     The vertical leg  57  has an upper end portion  66  which supports a bearing  68  in which a shaft  70  is supported for rotation on a substantially horizontal axis. The rearward end portion of the shaft  70  is secured by a screw  72 , and a forward end portion of the shaft  70  is secured to a hub  73  which supports a circular rotor or disk  75  for rotation with the shaft on a horizontal axis. The disk  75  has peripherally spaced semi-circular recesses or notches  76  which are spaced every ten degrees to provide thirty-six notches around the perimeter of the disk  75 . A horizontal plate or arm  78  projects laterally from the front end of the leg  46  and supports a stop or latch lever  80  ( FIG. 3 ) for pivotal movement on a stud  82  threaded into a flange  84  projecting upwardly from the arm  78 . The lever  80  has a square stud  86  on its inner end, and the stud  86  projects into one of the notches  76  to prevent or lock the disk  75  from rotating at a selected position of the disk. The lever  80  is spring biased by a compression spring  88  which is compressed when the outer end of the lever  80  is pressed upwardly to retract the stud  86  from a notch  76  so that the disk  75  is free to rotate. 
     As shown in  FIGS. 3 &amp; 4 , a vertical rectangular panel  90  is spaced from and connected to the disk  75  for rotation with the disk by a set of posts  94  ( FIGS. 2 &amp; 5 ) which project into and are adhesively attached to the disk  75  and panel  90 . As shown in  FIGS. 2-4 , a portable battery powered laser unit  100  is removably attached to the panel  90  by strips  102  and  104  of hook and loop fasteners, commonly referred to by the trademark VELCRO. A set of four locating pins  106  project forwardly from the panel  90  ( FIGS. 3 &amp; 4 ) and precisely position the laser unit  100  on the disk  75  so that the center of the unit  100  is on the axis of rotation. One form of hand held type laser unit which has provided satisfactory results is produced by The Stanley Works and sold as a laser measuring tool under the trademarks FatMax and IntelliMeasure. The tool or unit allows one person to measure the distance from the unit to a target located up to 40 feet and has an accuracy of plus or minus 0.5 percent. The unit emits a coherent laser beam and has an LCD display screen showing the distance from the center or bottom end of the laser unit to the target. 
     In operation of the measuring apparatus  20  within the corrugated metal culvert  10 , the unit  20  is positioned generally within a center portion of the tunnel  14  defined by the culvert with the support stand or tripod  24  supported by the floor of the culvert. If the tunnel defining structure does not have a floor, the apparatus  20  is placed on the ground or whatever forms the bottom surface for the tunnel. After the apparatus is positioned and the laser unit  100  is energized, the unit emits a laser beam on a target or spot on the inner surface of the culvert. The unit  100  then displays on a screen  110  the measured distance between the center of the unit  100  and the spot or target on the inner surface of the culvert. The distance is recorded on a chart, after which the latch member or lever  80  is released, and the disk  75  is manually rotated ten degrees or to another selected angle where the disk  75  is retained by the latch lever  80 . Then another distance reading is made and displayed by the unit  100  and recorded on the chart. 
     If it is desired to have an actual cross-sectional profile or shape of the entire inner surface of the culvert at a selected location, a measurement may be taken every ten degrees by indexing the disk  75  and laser unit  100  in angular increments of ten degrees through 360 degrees by using the stop lever  80  successively within each of the notches  76 . If the actual profile or shape of only an upper portion of the culvert or of any other portion of the culvert is desired, the disk  75  may be indexed through only the desired angle of measurements. 
     From the drawings and the above description, it is apparent that measuring apparatus constructed in accordance with the invention provides desirable features and advantages. For example, the portable apparatus  20  is simple to use at any longitudinally spaced intervals along the length of the tunnel  14  defined by the underground structure. The legs  26  may be quickly adjusted to position the measuring system  40  at the desired elevation and location within the tunnel. The rotation of the disk  75  on its axis assures that the laser measuring beam emitted by the laser unit  100  is always in a vertical or substantially vertical plane within the tunnel. In addition, after the support stand or tripod  24  is positioned within the tunnel and the top surface  31  is leveled using the bubble level  54 , a more precise position of the laser beam emitted from the unit  100  may be obtained by using the adjustment knobs  49  and  59 , for example, to assure that the plane of measurement by the unit  100  is always in only one corrugation of the culvert  10 . The portable hand held laser unit  100  may also be easily removed from the panel  90  and disk  75  for storage or when it is desired to service the laser unit  100 , for example, to replace the battery or change the mode of display between English and Metric measurements. 
     While the form of measuring apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of the invention, and that changes made therein without departing from the scope and spirit of the invention as defined in the appended claims.