Abstract:
A mechanical inspection sled which can be pushed through a pipeline using a series of connecting rigid rods. Mechanical measuring devices are mounted on the sled. These devices deflect when the pipe&#39;s internal diameter decreases. The deflection is visually observable by the user through a series of reflective indicators. The measuring devices are sufficiently pliable to allow the sled to pass beyond distorted areas and complete a full inspection of the pipeline. The measurement devices are adjustable to allow the sled to be used in many different pipe sizes. Because the device is purely mechanical, it is quite rugged and able to withstand harsh environments.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   This application is a CONTINUATION of U.S. application Ser. No. 10/021,790, filed on Dec. 19, 2001. The Applicants hereby expressly claim the benefit of the earlier application under 35 U.S.C. §120 and 37 CFR §1.53(b). The parent application Ser. No. (10/021,790) is now abandoned. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable 
   MICROFICHE APPENDIX 
   Not Applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to the field of piping inspection. More specifically, the invention comprises an adjustable sled which detects and measures vertical and horizontal deflection in the interior diameter of a flexible pipe as it is advanced through the pipe. The device transmits its deflection measurements to the user by simple visual means, eliminating the need for electronic devices. 
   2. Description of the Related Art 
   Piping is commonly used as a means to convey drainage water and other liquids. Buried pipe has traditionally been made of concrete. Concrete&#39;s widespread use is attributable to the fact that it is readily available, durable, and quite strong. Concrete piping may be buried deep within the soil without concern for structural failure. Recently, however, more flexible piping has come into widespread use. Flexible piping is often made from thin-gage metals, or polymers such as polyvinyl chloride and polyethylene. Such flexible piping is subject to circumferential deflection when exposed to soil loading. 
   Proper installation and soil compacting is critical for flexible piping. If the soil surrounding the flexible piping is correctly compacted in layers, a “soil arch” develops over the top of the piping which prevents excessive deflection. If, however, the soil is added around the piping without properly compacting it layer by layer, then the deflection may become excessive. While one would intuitively expect vertical deflection, horizontal deflection also occurs. Excessive deflection can lead to localized or generalized failure of the pipe wall, resulting in a catastrophic leak. 
   These concerns are heightened when the flexible piping is made of a polymer, since distorting loads tend to produce buckling and cracking in such polymers. Although the cracks may start small, they tend to propagate through the polymer—eventually weakening it to the point of failure. The distorting forces can also produce failures in the joints between two sections of pipe, which must carry the load when one pipe shifts relative to its neighbor. 
   It is possible to visually monitor the soil compaction process and ensure that it is carried out correctly. However, it is difficult or impossible to determine if the soil compaction has resulted in excessive pipe deflection after the fact. Examination of these deflections is often used as the criterion to determine the acceptability of flexible piping installations. Accordingly, a device for easily measuring such deflections would be useful. 
   The prior art approach to measuring the deflections has generally been to create a mandrel having an outside diameter equal to the minimum acceptable inside diameter of the piping. A cable is passed through the piping and this cable is used to drag the test mandrel back through. The shortcomings of this approach are as follows: 
   1. A new mandrel must be made for each pipe size that is to be inspected; 
   2. A cable must be passed completely through the piping before the mandrel is introduced—often a difficult process in itself; 
   3. An additional cable must be attached to the trailing end of the mandrel to pull it free if it gets stuck; 
   4. The mandrel can be lodged by debris in the piping, giving a false impression of excessive deflection; and 
   5. Once the mandrel reaches a point of excessive deflection it can proceed no further, meaning that the remainder of the piping system cannot be inspected. 
   Other more sophisticated approaches are found in the prior art. As an example, U.S. Pat. No. 6,170,344 to Ignagni (2001) reveals an inspection “pig” equipped with an inertial measurement system (presumably gyroscopes and accelerometers). Another approach employs projected laser beams and video cameras, along with computers running software which can translate the laser projections into distance measurements on the inner wall of the pipeline. 
   The reader should appreciate that buried piping which is used to convey drainage water—as opposed to oil or natural gas piping—is often filled with water puddles and other contamination. The use of electronic devices is therefore difficult, owing to the rugged nature of the application. An electronics-intensive approach is also inherently expensive. All these limitations are significant. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is a mechanical inspection sled which can be pushed through a pipeline using a series of connecting rigid rods. Mechanical measuring devices are mounted on the sled. These devices deflect when the pipe&#39;s internal diameter decreases. The deflection is visually observable by the user through a series of reflective indicators. The measuring devices are sufficiently pliable to allow the sled to pass beyond distorted areas and complete a full inspection of the pipeline. 
   The measurement devices are adjustable to allow the sled to be used in many different pipe sizes. Because the device is purely mechanical, it is quite rugged and able to withstand harsh environments. In addition, very little training is required to use the device. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is an isometric view, showing the inspection sled. 
       FIG. 2  is an isometric view, showing details of the rear portion of the sled. 
       FIG. 3  is an isometric view with a cutaway, showing the inspection sled in a pipe. 
       FIG. 4  is an isometric view with a cutaway, showing how the inspection sled is advanced through a pipe. 
       FIG. 5  is an isometric view, showing the deflection of the lateral test arm. 
       FIG. 5B  is an elevation view, showing the operation of the lateral visual indicators. 
       FIG. 5C  is an elevation view, showing the operation of the lateral visual indicators. 
       FIG. 6  is an isometric view, showing the deflection of the vertical test arm. 
       FIG. 6B  is an isometric view, showing the operation of the vertical visual indicators. 
       FIG. 6C  is an elevation view, showing the operation of the vertical visual indicators. 
       FIG. 7  is a perspective view, showing the operation of the plumb in keeping the inspection sled level. 
       FIG. 7B  is a perspective view, illustrating the horizontal and vertical diameters of a pipe. 
       FIG. 8  is an isometric view, showing how the inspection sled can be adjusted to inspect larger pipes. 
       FIG. 9  is a perspective view, showing two inspection sleds in two pipes having different diameters. 
       FIG. 10  is an isometric view, showing a gage used for calibration. 
       FIG. 11  is an isometric view, showing the application of a gage. 
       FIG. 12  is an isometric view, showing a refined version which represents the preferred embodiment. 
       FIG. 13  is a detail view of the preferred embodiment. 
       FIG. 14  is an isometric view, showing the preferred embodiment with its vertical deflection bar translated downward. 
       FIG. 15  is a detail view of the preferred embodiment. 
       FIG. 16  is a detail view, illustrating portions of the visual indicator system. 
       FIG. 17  is a detail view, illustrating portions of the visual indicator system. 
       FIG. 17B  is an isometric view, illustrating details of the visual indicator system. 
       FIG. 18  is a detail view, illustrating the operation of the visual indicator system. 
       FIG. 19  is an isometric view, showing another simplified embodiment. 
       FIG. 20  is a detail view, showing some details of the simplified embodiment. 
       FIG. 21  is an elevation view, illustrating details of the visual indicator system. 
       FIG. 22  is an elevation view, illustrating details of the visual indicator system. 
       FIG. 23  is an elevation view, illustrating details of the visual indicator system. 
   

   REFERENCE NUMERALS IN THE DRAWINGS 
     10  inspection sled  12  runner 
     14  front tube boss  16  rear tube boss 
     18  middle tube boss  20  front tube clamp 
     22  rear tube clamp  24  middle tube clamp 
     26  forward mast  28  rear mast 
     30  plumb mast  32  plumb boss 
     34  plumb clamp  36  plumb bracket 
     38  plumb  40  pipe 
     42  forward bracket  44  rear bracket 
     46  lateral test arm  48  lateral fixed arm 
     50  vertical test arm  52  plumb pivot 
     54  plumb weight  56  plumb reflector 
     58  18″-diameter pipe  60  extension rod 
     62  rod receiver  64  rod coupler 
     66  lateral flag  68  lateral indicator 
     70  vertical flag  72  vertical indicator 
     74  24″ inspection sled  76  24″ lateral fixed arm 
     78  24″ lateral test arm  80  24″ vertical test arm 
     82  24″-diameter pipe  84  gage 
     86  vertical zero  88  horizontal zero 
     90  calibration steps  92  horizontal diameter 
     94  vertical diameter  96  bottom region 
     98  first side region  100  top region 
     102  second side region  104  vertical deflection bar 
     106  forward spring bracket  108  rear spring bracket 
     110  guide rod  112  guide rod hole 
     114  compression spring  116  stop collar 
     118  point reflector  120  flex mast 
     122  contact point  124  tube 
     126  tube mount  128  orifice 
     130  reflector  132  reflector card 
     134  window card  136  first window 
     138  first reflector  140  second reflector 
     142  card mount  144  guide slot 
     146  second window  148  third window 
     150  fourth window  152  fifth window 
     154  sixth window  156  seventh window 
     158  eighth window  160  third reflector 
     162  fourth reflector  164  fifth reflector 
     166  sixth reflector  168  seventh reflector 
     170  eighth reflector  174  ninth reflector 
     176  tenth reflector  178  eleventh reflector 
     180  twelfth reflector 
   DESCRIPTION OF THE INVENTION 
   The principal objective of the present invention is to measure deformations in the horizontal and vertical diameters of a pipe. The “horizontal diameter” is defined as a measurement of the pipe&#39;s internal diameter taken through its centerline in a direction which is parallel to the earth&#39;s surface. The “vertical diameter” is defined as a measurement of the pipe&#39;s internal diameter taken through its centerline in a direction which is perpendicular to the earth&#39;s surface 
     FIG. 1  illustrates the major components of inspection sled  10 . All the components are mounted on a base element, designated in the view as runner  12 . Runner  12  is a ski-like structure, having upturned ends. It is intended to slide along the inside lower surface of a pipe. Although a wheeled carriage could be employed, runner  12  is simpler and has been found to be satisfactory. 
   Mounted directly to runner  12  are front tube boss  14 , middle tube boss  18 , rear tube boss  16 , and plumb boss  32 . In the embodiment shown, runner  12  is made from sheet aluminum. The bosses are machined from aluminum blocks. However, those skilled in the art will appreciate that the material selection is simply one of manufacturing expedience. As an example, runner  12  and the attached bosses could be manufactured as an integral piece of glass reinforced polymer—using the reaction injection molding method. As illustrated, the bosses are simply bolted to runner  12 . 
   Each tube boss has a cylindrical cavity running transversely through it. Pipe  40  is laid into these cavities. Front tube clamp  20 , middle tube clamp  24 , rear tube clamp  22 , and plumb clamp  34  are then placed over the top of pipe  40 . These tube clamps also have transverse cylindrical cavities corresponding to those found in the tube bosses. The tube clamps are bolted to the tube bosses using conventional fasteners, with the result that pipe  40  is mechanically affixed to runner  12 . 
   Forward mast  26  rises vertically from front tube clamp  20 . Forward bracket  42  is mounted to forward mast  26  by conventional means. Forward bracket  42  is vertically adjustable, so that a user can move it up and down forward mast  26 , locking it in place in a desired position. Rear mast  28  rises vertically from rear tube clamp  22 . Rear bracket  44  is mounted to rear mast  28  in a vertically adjustable manner. The vertical height of forward bracket  42  and rear bracket  44  must be adjusted in unison, as will be explained subsequently. 
   Lateral fixed arm  48  is attached to forward bracket  42  and rear bracket  44 . It is substantially rigid. It lies in a horizontal plane, which will ideally rest on the horizontal diameter  92  of a pipe being inspected. Opposite lateral fixed arm  48  is lateral test arm  46 . The forward portion of lateral test arm  46  is fixed to forward bracket  42 . The rear portion, however, is free to move. Lateral test arm  46  is made of a resilient and flexible material. Solid aluminum rod is a good choice, as it is able to bend in and out substantially without suffering a plastic deformation. As test sled  10  is advanced through a pipe and encounters a reduction in the horizontal diameter  92  of the pipe, lateral test arm  46  will deflect, with its rearward portion moving inward. 
   Vertical test harm  50  is the vertical counterpart to lateral test arm  46 . Its forward portion is secured to forward mast  26 , but its rear portion is free to move. If test sled  10  encounters a reduction in a pipe&#39;s vertical diameter  94 , vertical test arm  50  will deflect, with its rearward portion moving downward. 
   It is important that inspection sled  10  remain level during its progress through a pipe. Otherwise, it will not be measuring the true horizontal  92  and vertical  94  diameters of the pipe. Plumb  38  is provided as a leveling aid. Plumb mast  30  rises vertically from plumb clamp  34 . Plumb  38  is pivotally mounted to plumb mast  30 . Plumb bracket  36  restricts the angular travel of plumb  38 . 
   FIG.  2 —which is a partial view—shows the rear features of inspection sled  10  in more detail. Plumb  38  is attached to plumb mast  30  by plumb pivot  52 . Plumb  38  is free to rotate as indicated by the arrows. Plumb weight  54  ensures that plumb  38  is oriented vertically when inspection sled  10  is level. In that state, plumb reflector  56  is completely obscured by plumb weight  54  (when the device is viewed from the rear). 
   The reader should appreciate that inspection sled  10  will be introduced into an open end of a pipe and advanced away from the user. The user will customarily shine a light into the pipe to observe the progress of the device. Provided that inspection sled  10  is level, the user will not see any reflection from plumb reflector  56 . However, if inspection sled  10  rotates, plumb  38  will pivot and plumb reflector  56  will be exposed. This informs the user that the device is no longer level and should therefore be adjusted. 
     FIG. 2  also shows the hollow end of pipe  40 , designated as rod receiver  62 . The user customarily advances the device by sticking another length of pipe into rod receiver  62  and pushing the device forward. Rod receiver  62  is typically equipped with a transverse hole, into which a locking pin from the pushing rod will lock. 
     FIG. 3  shows inspection sled  10  placed within 18″-diameter pipe  58  (shown with a cutaway).  FIG. 4  shows how inspection sled  10  is advanced. Extension rod  60  is placed into rod receiver  62  and the user pushes the device forward, as indicated by the arrow. A number of rigid extension rods  60  are used to advance the device. Each one contains rod coupler  64 , which is a necked-down cylinder which fits within the hollow extension rod  60  before it. Extension rods  60  contain transverse locking pins which automatically lock successive rods together and prevent one from turning relative to its neighbor. Owing to these features, the user can push inspection sled  10  forward and rotate it to keep it level. 
     FIG. 5  illustrates the operation of lateral test arm  46 . As explained previously, when test sled  10  encounters a reduction in the horizontal diameter  92  of a pipe, lateral test arm  46  deflects inward, as shown by the arrow. Lateral flag  66  is attached to the rearward end of lateral test arm  46 . As lateral test arm  46  deflects inward, lateral flag  66  moves inward across the rearward face of rear bracket  44 . 
     FIG. 5B  shows a view of the rear of test sled  10  with lateral test arm  46  in its undeflected state. When a force is applied to lateral test arm  46 , lateral flag  66  moves inward in the direction indicated. As it does so, it begins to occlude a series of lateral indicators  68 , which are affixed to the rearward face of rear bracket  44 . This view approximates the user&#39;s view of the device, as the user looks down a pipe.  FIG. 5C  shows lateral test arm  46  in a deflected state. The reader will observe that two of the three lateral indicators  68  have been occluded, thus indicating to the user the state of the deflection. These lateral indicators  68  are typically color-coded strips or dots of highly reflective material. The use of color coding allows the user to discern the degree of deflection of lateral test arm  46  at great distances. It is important to note that test sled  10  conveys all of its information through the use of reflectors. It has no electrical power source whatsoever. 
     FIG. 6  illustrates the presence of vertical flag  70  on the rear extremity of vertical test arm  50 . As vertical test arm  50  is deflected downward via a reduction in the vertical pipe diameter, vertical flag  70  moves downward across the rearward face of rear bracket  44 .  FIG. 6B  shows a rear view of vertical test arm  50  in its undeflected state. In this position, vertical flag  70  has not occluded vertical indicators  72 .  FIG. 6C  shows vertical test arm  50  deflected downward. The reader will observe that vertical flag  70  has occluded two of the three vertical indicators  72 . Again, through the use of color coding in the vertical indicators  72 , the degree of deflection can be observed by the user over considerable distance. 
     FIG. 7  is a perspective view illustrating test sled  10  traveling through 18″-diameter pipe  58  (pipe  58  is shown with a cutaway). In this illustration, test sled  10  has become canted in a clockwise direction. The reader will observe that plumb  38  has remained vertical, with the result that plumb reflector  56  is now visible. The user is thereby informed that the device is not level and a correction is made. 
     FIG. 7B  illustrates the measurement objectives of the device. 18″-diameter pipe  58  is roughly divided into top region  100 , right side region  98 , left side region  102 , and bottom region  96 . There is, of course, no clear demarcation between these regions since the pipe is ideally cylindrical. The objective is to measure values for horizontal diameter  92  and vertical diameter  94 . In order to measure these values, the device must be level. Returning to  FIG. 7 , the reader will observe that the non-level state of the device means that lateral fixed arm  48  and lateral test arm  46  are not lying in the plane of horizontal diameter  92 . Likewise, vertical test arm  50  is not lying in the plane of vertical diameter  94 . A correction is therefore needed and the user can supply this by twisting the push rods as he or she advances the device. 
     FIG. 7  also illustrates well the device&#39;s operation. Lateral fixed arm  48  maintains contact with right side region  98 . Lateral test arm  46  maintains contact with left side region  102 . If a reduction in horizontal diameter  92  is encountered, lateral test arm  46  will deflect. Lateral test arm  46  is sufficiently flexible to allow the device to pass through a substantial constriction and continue onward. 
   Runner  12  maintains contact with bottom region  96 . Vertical test arm  50  maintains contact with top region  100 . If a reduction in the vertical diameter  94  is encountered, vertical test arm  50  will deflect. It is also sufficiently pliable to allow the device to pass through a constricted area and continue. 
   Those skilled in the art will appreciate that the width of runner  12  prevents the device from sitting on the lowest point of the pipe&#39;s interior. The width of runner  12  must be accounted for in determining the appropriate height of vertical test arm  50 . This is especially true since the device contemplates that many different pipe diameters may have to be inspected. 
   One inspection sled  10  may be used to inspect a wide range of pipe diameters by incorporating adjustment features. Inspection sled  10  is adapted to inspect an 18″-diameter pipe.  FIG. 8  depicts inspection sled  10  next to 24″ inspection sled  74 , which is adapted to inspect a 24″-diameter pipe. 
   24″ inspection sled  74  is simply inspection sled  10  adjusted to fit a larger pipe. The reader will observe that forward bracket  42  has been moved up its mast and locked into a higher position. Likewise, rear bracket  44  has been moved upward. Larger test arms are also needed. 24″ inspection sled  74  is equipped with 24″ lateral fixed arm  76 , 24″ lateral test arm  78 , and 24″ vertical test arm  80 . All these arms are easily removed and replaced. 24″ inspection sled  74  is identical to inspection sled  10  in every respect, other than the vertical and horizontal adjustments and the different arms. In fact, in actual practice, the user will typically use only inspection sled with sets of different arms to accommodate the different pipe diameters. 
     FIG. 9  shows the two variants side by side. Inspection sled  10  fits tightly within 18″-diameter pipe  58 . 24″ inspection sled  74  fits tightly within 24″-diameter pipe  82 . The reader will thus observe how the use of adjustments and the different arm sets allow a single inspection sled to be adapted to fit many different pipe diameters. 
   It is important to calibrate the inspection sled  10  for the particular diameter of pipe that will be inspected. This goal could be accomplished in many different ways, such as by providing markings on the masts and arms to indicate the correct adjusted positions.  FIG. 10  illustrates another approach using a gage. Gage  84  has horizontal zero  88 , vertical zero  86 , and a series of calibration steps  90 . 
     FIG. 11  illustrates the use of gage  84 . Inspection sled  10  is placed on flat surface  86 . Gage  84  is then placed against inspection sled  10 , with vertical zero  86  being placed on flat surface  86  and horizontal zero  88  being placed against the side of runner  12 . A particular calibration step  90  (depending on the pipe diameter involved) is use to set the correct position or lateral fixed arm  48 , and likewise for lateral test arm  46 . The calibration steps  90  are marked to indicate which one should be used. A similar gage can be fabricated and employed for vertical test arm  50 . 
   The device disclosed in  FIGS. 1–11  is capable of measuring deflections in a pipe&#39;s vertical  94  and horizontal  92  diameters. Practical experience illustrates that a reduction in the pipe&#39;s vertical diameter  94  is the more significant measurement, since this indicates settling of the soil around the pipe. A variation only measuring the pipe&#39;s vertical diameter  94  can therefore provide the most needed information and also reduce complexity. 
   In addition, the device disclosed in  FIGS. 1–11  has been found to have certain limitations in its visual indicating system. It is common for the user to advance the device up to 100 feet into a pipe. At that distance, it is difficult for the user to discern the degree of occlusion of lateral indicators  68  and vertical indicators  72 . This is true even though different colors are used for successive indicators. At ranges approaching 100 feet, human vision simply blurs the two colors together and makes it difficult to observe the degree of occlusion. Thus, a more sophisticated visual indicating system is desirable. 
     FIGS. 12–18  illustrate a second embodiment addressing these concerns. Because this version remedies the problems just discussed, it is the preferred embodiment. As seen in  FIG. 12 , the structure of inspection sled  10  is the same with only a few exceptions. Because the preferred embodiment is not designed to measure deflections in a pipe&#39;s horizontal diameter  92 , it has two lateral fixed arms  48 . Vertical deflection bar  104  is designed to measure reductions in a pipe&#39;s vertical diameter  94 , using a refined system. The user will observe that forward spring bracket  106  is attached to forward bracket  42 . Likewise, rear spring bracket  108  is attached to rear bracket  46 . 
   Both forward spring bracket  106  and rear spring bracket  108  have a guide rod  110  passing through them. Guide rods  110  are free to move up and down relative to the two spring brackets. Vertical deflection bar  104  is attached to the upper end of each guide rod  110 . Springs are employed to bias vertical deflection bar  104  toward its upper position—as shown. 
     FIG. 13  is a detail view. The reader will observe that the two horizontal portions of forward spring bracket  106  are each pierced by a guide rod hole  112 . Guide rod  110  slides up and down within guide rod holes  112 . Stop collar  116  is adjustably attached to guide rod  110 . Compression spring  114  fits closely around guide rod  110 . Its lower end bears against forward spring bracket  106 . Its upper end bears against the lower surface of stop collar  116 . 
   Identical components are located proximate rear spring bracket  108 . The result is that the two guide rods  110  are naturally biased upward, resulting in vertical deflection bar  104  being naturally biased upward. 
     FIG. 14  shows the device as it would appear upon encountering a reduction in a pipe&#39;s vertical diameter  94 . Vertical deflection bar  104  has been forced downward as indicated by the arrow, resulting in guide rods  110  moving downward.  FIG. 15  shows a detail view of forward spring bracket  106  as vertical deflection bar  104  is forced downward. The reader will observe that guide rod  110  has moved downward as indicated. Stop collar  116  has also moved downward, resulting in the compression of compression spring  114 . Once the region of reduced vertical diameter  94  within the pipe is passed, compression springs  114  will restore the device to its undeflected state. 
   The use of this revised system for measuring vertical deflection is quite effective. However, an improved means of visually communicating the degree of deflection to the user is also needed.  FIGS. 16–18  and  21 – 23  illustrate the improved indicating system. In  FIG. 16 , reflector card  132  has been attached to the rear face of rear bracket  44 . The reader will also observe that card mount  142  has been attached to the rear guide rod  110 . Card mount  142  will also move up and down with guide rod  110 . Accordingly, reflector card  132  is provided with a vertical slot allowing for clearance as card mount  142  moves downward. 
   In  FIG. 17 , the reader will note that window card  134  is positioned to be attached to card mount  142  so that it slides up and down with guide rod  110 . Window card  134  has eight windows  136 , which allow the display of reflectors placed on reflector card  132 . Window card  134  is configured to slide up and down over the rear surface of reflector card  132 . 
     FIG. 17B  shows reflector card  132  and window card  134  placed side by side for comparison. Ordinarily, of course, window card  134  would be placed over the front of reflector card  132 . As deflection in the internal diameter for the pipe is encountered, window card  134  slides up and down relative to reflector card  132 . Various reflectors are thereby exposed through the eight windows in window card  134 . 
   The following is a listing of the reflectors found on reflector card  132  in the preferred embodiment: (1) First reflector  138 , fourth reflector  162 , fifth reflector  164 , and ninth reflector  174  are green; (2) Second reflector  140 , third reflector  160 , seventh reflector  168 , and tenth reflector  176  are yellow; and (3) Sixth reflector  166 , eighth reflector  170 , eleventh reflector  178 , and twelfth reflector  180  are red. The eight windows on window card  134  are configured to interact with these reflectors in order to convey information to the user. 
     FIG. 18  shows window card  134  mounted in place. In the view shown, the device has encountered a reduction in the pipe&#39;s vertical diameter  94 , resulting in the downward movement of vertical deflection bar  104 . Guide rod  110  has moved downward as indicated. Window card  134 , being connected to guide rod  110 , has moved downward relative to reflector card  132 . The windows on window card  134  are exposing certain reflectors, thereby indicating the degree of deflection to the user. 
   The arrangement of reflectors on reflector card  132  and windows on window card  134  can be configured to convey a great deal of information. A series of examples is provided in  FIGS. 21 through 23 . 
     FIG. 21  shows window card  134  in front of reflector card  132 . The features of reflector card  132  can be seen as hidden lines. In this view, window card  134  has traveled downward with respect to reflector card  132 . A portion of third reflector  160  (yellow) is visible through seventh window  156 . 
     FIG. 22  shows window card  134  after it has traveled further downward. The reader will observe that a portion of first reflector  138  (green) is visible through first window  136 . Likewise, a portion of fourth reflector  162  (green) is visible through fourth window  150 . 
     FIG. 23  shows window card  134  after it has traveled still further downward. In addition to the reflectors visible in  FIG. 22 , the reader will observe that a portion of fifth reflector  164  (green) is visible through fifth window  152 . Thus, through the use of the reflectors, the device can communicate very fine readings on the degree of deflection encountered. 
   It is obviously important to keep window card  134  aligned with reflector card  132 . Returning now to  FIG. 18 , guide slot  144  is provided through window card  134 . This slot engages guide bushings mounted on reflector card  132  to prevent skew. For purposes of visual clarity, these guide bushings have not been shown. Those skilled in the art will appreciate that additional windows and reflectors could be provided to convey even more detailed information. The concept for such additional indicators would be identical to that for the ones described. 
   The preferred embodiment encompasses adjustments allowing it to be used for different pipe diameters. Returning to  FIGS. 12 and 13 , those skilled in the art will appreciate that the position of the two stop collars  116  on the two guide rods  110  will determine the vertical position of vertical deflection bar  104  in the undeflected state. Thus, adjustment means (such as a set screw and a corresponding series of detents in guide rods  110 ) can be provided to allow the user to set the vertical position of vertical deflection bar  104  for a variety of different pipe diameters. Of course, different sets of lateral fixed arms  48  must still be employed. 
   Some users have expressed a desire for a very simply “pass-fail” version of the device. This embodiment would provide a single indication of a failing condition in a pipe&#39;s vertical diameter  94 .  FIGS. 19 and 20  illustrate such a device. This is a quick test method that could be followed by more precise methods using other features of the device. 
   In  FIG. 19 , inspection sled  10  has two lateral fixed arms  48 . Rising from middle tube clamp  24  is flex mast  120 . Flex mast  120  is typically made from a resilient material and has the general characteristics of an automotive radio antenna. Flex mast  120  is topped by contact point  122 . Point reflector  118  is attached to flex mast  120  just below contact point  122 . 
     FIG. 20  shows point reflector  118  in more detail. Tube mount  126  attaches tube  124  to flex mast  120 . Tube  124  is hollow (shown with a cutaway). Its forward portion contains reflector  130 . Its rearward portion tapers to orifice  128 . As a user shines a flashlight toward the device in a pipe, light enters through orifice  128 , strikes reflector  130 , and bounces back to the user as a single bright point of light. 
   The height of contact point  122  is set equal to the minimum acceptable vertical diameter  94  for the pipe being inspected. Likewise, lateral fixed arms corresponding to the minimum acceptable horizontal diameter for pipe the pipe are employed. If contact point  122  encounters a smaller vertical diameter  94 , flex mast  120  will bend backward, angling tube  124  downward. The geometry of the device then prevents the reflection of the user&#39;s flashlight beam. From the user&#39;s vantage point, the single bright point of light disappears. When this happens, the user knows that a failing condition is present. The user may then wish to reconfigure the device using the window card and reflector card to obtain more information. 
   Accordingly, the reader will appreciate that the proposed invention provides a simple device for measuring constrictions in the diameter of buried piping. The invention has additional advantages in that:
         1. It can be adjusted to inspect different sizes of pipe;   2. It does not require a cable to be passed through the pipe before introducing the inspection device;   3. It is not easily obstructed by puddles or debris within the pipe;   4. It can pass beyond an obstructed diameter to inspect the entire pipe; and   5. It provides a simple visual indication system requiring no internal electrical devices.       

   Although the preceding description contains significant detail, it should not be construed as limiting the scope of the invention but rather as providing illustrations of the various embodiments of the invention. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.