Abstract:
A pipe crawler apparatus particularly useful for 3-inch and 4-inch diameter pipes is provided. The pipe crawler apparatus uses a gripping apparatus in which a free end of a piston rod is modified with a bearing retaining groove. Bearings, placed within the groove, are directed against a camming surface of three respective pivoting support members. The non-pivoting ends of the support members carry a foot-like gripping member that, upon pivoting of the support member, engages the interior wall of the pipe.

Description:
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     The United States Government has rights in this invention pursuant to contract no. DE-AC09-96SR18500 between the U.S. Department of Energy and Westinghouse Savannah River Company L.L.C. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to inspection apparatuses known in the industry as pipe crawlers. Pipe crawlers are used to inspect the interior of pipes and similar passageways associated with water and sewage systems, industrial piping such as chemical or gas conduits, and piping used within nuclear reactors or related caustic or high stress environments. Pipe crawlers are frequently used to deploy monitoring equipment including sensors and/or cameras, to monitor the pipe integrity, and to help diagnose needed repairs or maintenance. 
     BACKGROUND OF THE INVENTION 
     Pipe crawlers, pipe inspection “rabbits” and similar vehicles are widely used for inspecting the interior surfaces of piping systems, storage tanks, and process vessels for damaged or flawed structural features. Typically, such devices include a testing probe, sensor, or camera carried by a support structure that travels through the piping system being inspected. 
     Many of the remote inspection devices have been designed for pipes having a six-inch or greater inner diameter. However, there remains a need for the inspection of smaller diameter pipes. While current advances in miniaturization technology have made cameras and sensors small enough to fit within a small diameter pipe, there have been few advances in the design of a delivery vehicle having adequate motive forces to deploy a small diameter inspection vehicle through a pipe system. For example, miniature electric motors do not provide enough motive force to pull extensive length tethers behind the crawler. Similarly, miniature air cylinders do not have the capacity to generate enough pushing force directly against the inner-walled pipe as is required for inch-worm motion. 
     The art teaches a variety of pipe inspection apparatuses. Two such apparatuses are taught in U.S. Pat. Nos. 5,770,800 and 5,398,560, assigned to the U.S. Department of Energy and incorporated herein by reference. These pipe inspection apparatuses move through the use of differential hydraulic pressure or the use of a pipe pig to carry the apparatus. 
     U.S. Pat. No. 4,460,920 to Weber describes a remote controlled pipe crawler having front and rear stepping bodies interconnected by a gimbal joint. U.S. Pat. No. 4,601,204 Fournot et al teaches a duct crawler having pneumatically or hydraulically operated pivot arms and rubber gripping feet used in a pull-pusher combination mode. However, there are limitations to the size and motive force capable of being exerted by the prior art devices as set forth above. 
     In particular, there is a need for a pipe inspection apparatus delivery vehicle that will provide the necessary motive force for small diameter pipes. The apparatus should be dimensioned to pass through various sizes of piping and be able to readily negotiate bends in the piping. In addition, the pipe crawler should be able to generate a sufficient motive force that can propel inspection equipment and the resulting physical and electronic tether through extended lengths of piping. 
     Accordingly, there remains room for variation and improvement within the art. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is to provide a flexible pipe crawler having sufficient motive force to successfully traverse small diameter pipes while attached to remote monitoring equipment and sensors. 
     It is yet another aspect of the present invention to provide a pipe crawler apparatus in which a pneumatic piston is used to actuate a plurality of pivoting grip members, each grip member being used to engage the interior of a pipe. 
     It is an additional aspect of the present invention to provide a pipe crawler capable of negotiating 3 inch and 4 inch inner diameter pipe using the selective, intermittent pushing and pulling action of an air cylinder. The air cylinder is operatively connected on opposite ends to a respective first gripping unit and a second gripping unit. The first and the second gripping units are used to selectively engage and disengage the pipe crawler with respect to the interior of the pipe while the intervening air cylinder proceeds to move the non-engaged gripping unit within the pipe. 
     It is yet another aspect of the present invention to provide an improved gripping unit for use in a pipe crawler apparatus. The gripping unit translates the linear motion of a piston rod to bring about the pivoting action of multiple support posts. Each post carries on a non-pivoting end a gripping member adapted for engaging an inner pipe surface. 
     The gripping pneumatic unit provides a stronger interengagement with the pipe interior than the direct application of a piston rod against the interior surface of a pipe. Accordingly, the gripping unit of the present invention enables a pipe crawler apparatus that can operate carrying a greater weight load than a conventionally constructed pipe crawler. 
     Further, the present invention allows a compact design having sufficient motive force capability such that small diameter pipes may be accessed and surveyed using the pipe crawler constructed according to the present invention. 
     These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification including reference to the accompanying drawings. 
     FIG. 1 is a perspective view of a pipe crawler apparatus as depicted within a cut-away portion of a pipe. 
     FIG. 2 is a schematic view of a single gripping unit showing additional details of the construction and operation of the gripping unit. 
     FIGS. 3A through 3E illustrate the intermittent pushing and pulling action of the pipe crawler apparatus. 
     FIG. 4 is an exploded perspective view of the cam-actuated pivoting gripping members of the pipe crawler apparatus. 
     FIG. 5 is a perspective end view of the camera and lighting system used in association with the pipe crawler apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference now will be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present invention are disclosed in the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary constructions. 
     In describing the various figures herein, the same reference numbers are used throughout to describe the same material, apparatus or process pathway. To avoid redundancy, detailed descriptions of much of the apparatus once described in relation to a figure is not repeated in the descriptions of subsequent figures, although such apparatus or process is labeled with the same reference numbers. 
     As seen in reference to FIGS. 1 and 2, a preferred embodiment for a pipe crawler apparatus  10  is provided by a series of joined piston units seen as units  10 A through  10 C. The right side of the pipe crawler drive apparatus  10  is designated as the front “F” and is associated with unit  10 A. Unit  10 A has a housing  12 A that defines a first air cylinder  14 A, a piston rod  16 A having a first end in communication with a pressure plate  18 A and gasket  19 A carried within the air cylinder  12 A, and a second free end. The front end of unit  10 A supports a frame  20  that defines a central cavity adapted for passing through the free end of piston rod  16 A. 
     As best seen in FIG. 4, frame  20 A defines a plurality of posts  30  that are pivotally connected to the frame and that are secured to side plates  24  of frame  20  through respective pins  22 . Side plates  24  further define apertures  26 . Pins  22  are received through apertures  26  along with apertures  32  defined by post  30 . Adjacent the pin receiving apertures  32 , a camming surface, seen here in the form of an arcuate notch  34 , is defined by each post  30 . 
     Post  30  is secured to the frame  20  via pins  22  thereby placing camming surface  32  opposite the piston rod  16 A. Piston rod  16 A defines a circumferential groove  17 A opposite cam surface  34 . A cylindrical bearing  40  is positioned between the notch  34  and the oppositely spaced groove  17 A, bearing  40  thereby operatively engaging both notch  34  and groove  17 A. Bearing  40  is held in position by opposing side plates  24  opposite the end walls of bearing  40 . 
     As piston rod  16 A is extended outwardly toward the front of pipe crawler apparatus  10 , the piston movement directs bearing  40  in further engagement with the cam surface defined by notch  34 , thereby causing post  30  to pivot outwardly as seen by the directional arrows in FIG.  2 . The pivoting motion, in turn, directs an outer edge  52  of gripping member  50  to extend away from an axis of the pipe crawler apparatus  10  and thereby engage an interior surface of the surrounding pipe. 
     The plurality of springs  60  provides sufficient tension such that the respective drive and gripping units are maintained in a substantially axial alignment when the pipe crawler apparatus is in a horizontal orientation. Preferably, when one set of grippers are engaged into the interior pipe wall, the pipe crawler apparatus is sufficiently rigid that the apparatus does not otherwise sag or touch the adjacent pipe walls. Further, the springs  60  are sufficiently pliant that the pipe crawler apparatus may negotiate sharp bends and turns. Following a turn, the spring  60  will provide sufficient tension to bring about an axial alignment of the pipe crawler when in a horizontal portion of pipe. This arrangement prevents damage from occurring to the pipe interior walls or to the pipe crawler apparatus that could otherwise be created by friction between the components of the pipe crawler apparatus and the pipe interior walls. 
     Gripping unit  10 C operates in an identical fashion and has the corresponding construction and operation of gripper unit  10 A. Accordingly, similar reference numerals are used on the figures with the letter “C” being used to designate certain structures associated with gripping unit  10 C. As best seen in reference to FIG. 1, unit  10 C has a reverse orientation with respect to unit  10 A. 
     When placed within the operative environment of a pipe interior, cylinder  14 A extends rod  16 A, causing the bearings  40  to engage cam  34 . The pressure exerted by the three respective bearings  40  onto the corresponding three cams  34  pivots each cam post  30  to thereby engage the inner pipe wall by the respective edges  52  of attached gripping members  50 . As best seen in reference to FIG. 4, gripping members  50 , seen here in the form of a foot-shaped unit, may be secured to post  30  through threaded fasteners such as screws or bolts. The reversible nature of the attachment allows grippers  50  to be replaced as needed. It also allows various sizes, textures, and shapes of grippers  50  to be used in the pipe crawler apparatus  10 . 
     Opposite the base portion of gripper unit  10 A, a piston drive unit  10 B is provided. Drive unit  10 B has a housing  12 B that defines a first air cylinder  14 B, a piston rod  16 B having a first end in communication with a pressure plate  18 B that is carried within the housing  12 B, and a second free end. The front end of drive unit  10 B extends axially in a rearward direction seen in reference to apparatus  10  of FIG.  1 . An inner connecting member  80  connects unit  10 A to unit  10 B. As best seen in reference to FIG. 1, connecting member  80  may be in the form of respective interconnected rods, the interconnection being in the form of a universal joint  82 . The respective end portions of connecting member  80  may be threadedly attached to a cover plate  54  attached at the base of each respective unit  10 A and  10 B. 
     A coiled spring  60  may be placed between the units  10 A and  10 B with the connecting member  80  traversing through the interior of the spring  60 . Spring  60  is held under tension between the respective unit  10 A and  10 B. Preferably, the exterior surface of each cover plate  54  defines a circular flange region upon which terminal portions of spring  60  may be seated. A free end of piston  16 B is threadedly attached to a circular disc member  56 . A portion of the piston rod  16 B may traverse and extend past the disc member  56 . The extended portion is used to threadedly attach a second attachment member  80  that is in turn connected to a base of a second piston gripper unit  10 C. A second spring  60  is positioned between units  10 B and  10 C similar to the arrangement seen between units  10 A and  10 B. 
     As best seen in reference to FIGS. 3A through 3E, the operation of the pipe crawler apparatus  10  makes use of the intermittent gripping action of gripping units  10 A and  10 C. As seen in FIG. 3A, when the gripping portions of unit  10 A are engaged to the interior wall of the pipe, drive unit  10 B has piston rod  16 B fully extended. As seen in reference to FIG. 3B, piston rod  16 B is retracted inside housing  12 B, thereby pulling disengaged gripper unit  10 C in an axial direction toward unit  10 A. Next, as seen in reference to FIG. 3C, gripping unit  10 C is used to engage the interior walls of the pipe. Upon engagement, drive unit  10 B is used to extend piston rod  16 B (FIG. 3D) and thereby extends in a forward direction the disengaged gripping unit  10 A along with the housing portion  12 B of drive unit  10 B. Once drive unit  10 B is fully extended, the gripping members of unit  10 A again engage the interior walls of the pipe wherein the inch-worm type motion may be repeated. The sequence of motions may be readily repeated to bring about a reverse direction of travel for the pipe crawler apparatus  10 . Alternatively, for removal from a conduit, it is possible to use the accompanying tethers to physically pull the disengaged pipe crawler apparatus  10  from the pipe. 
     Each piston,  10 A,  10 B, and  10 C makes use of air pressure changes within the respective cylinder to bring about movement of the pressure plate and attached piston rod. As seen in reference to FIG. 1, a plurality of pneumatic air lines  100  is supplied to the pipe crawler apparatus  10 . Each cylinder is in communication with a pair of individual air lines  100 . Each cylinder defines a pair of ports “P” through which an individual air line  100  is in communication. As best seen in references to FIGS. 3A through 3B, the flow pathway of pressurized air or other fluid into and from each cylinder is illustrated by diagrammatic arrows and that depict the standard operation of a cylinder as is conventional and well known within the art. 
     For instance, pressure plate  18 A divides the interior of air cylinder  14 A into two discrete chambers. Pressure applied along air line  100  into one portion of a cylinder interior will force the pressure plate and associated rod  16 A to move. During the movement, the air pressure supplied along line  100  to the second part of the cylinder is released, allowing air on the opposite side of the pressure plate to exit the cylinder as the plate advances. Upon reversing of the air pressure and air flow pathways, the reverse movement of the cylinder is carried out. 
     As further seen in reference to FIG. 1, an additional supply line  110  is provided, which is used to provide electric power to the lights and camera and also to provide a video line for transmitting the camera image to the remote operator. The control of the lights, camera, and various pneumatic lines may be fully automated using a series of control switches and valves in communication with the respective individual air lines  100 . Properly synchronized, a rapid movement of the pipe crawler apparatus through a pipe or similar conduit is obtained. 
     Accordingly, the movement of the pipe crawler is in a step-wise fashion as the engagement and disengagement of the cam feet is used to hold alternating ends of the pipe crawler stationary. The air cylinder of unit  10 B is used to alternately push the front unit  10 A in a forward direction then pull the rear section  10 C of the pipe crawler. The use of the pneumatically actuated cam-driven feet provides a surprisingly strong motive force, which has been found capable of pulling significant loads while traversing a vertical pipe. The pipe crawler also has a series of flexible universal joints  82  that permit turns and bends to be negotiated. The components can be assembled so that the pipe crawler is able to negotiate a 4 inch schedule  160  pipe (inner diameter 3.44 inches). In such a narrow confine, miniature electric motors and air cylinders lack the strength to perform adequately using prior art motive techniques. The mechanical advantages offered by the cam driven feet affords capabilities for pipe inspection heretofore unavailable. 
     The length of the piston rod  16 B of the drive unit  10 B may be varied. By selecting a drive unit having a longer length piston rod, the drive unit is capable of a greater “throw” distance with each stroke of the piston. However, a smaller length piston is preferred in applications where the pipe crawler apparatus  10  must negotiate right-angle bends or other sharp curves in the piping system. Otherwise, the extended length of drive unit  10 B would be unable to traverse sharp bends. 
     As seen in reference to FIG. 5, an upper portion of drive unit  10 A, corresponding to the front of the pipe crawler apparatus  10 , may be equipped with a camera  70  along with a series of lights, seen here in the form of light-emitting diodes (LEDs)  72 . Lights  72  and camera  70  are mounted on a support plate  74 . Support plate  74  is, in turn, supported along legs  76 , which attaches to frame  20 A. As illustrated, the light and camera assembly seen in FIG. 5 is carried in an elevated position with respect to the underlying frame  20 . This positioning allows the previously described operation of the piston, post, and gripping members to proceed without interruption. While not separately illustrated, a similar light and camera assembly could also be attached to the rear portion of the pipe crawler apparatus  10  corresponding to gripper unit  10 C. 
     As seen in reference to FIG. 1, a preferred embodiment of the pipe crawler uses three cam operated feet, each foot positioned approximately 120 degrees apart with respect to the pipe crawler circumference. If four spaced cams and grippers (90 degrees apart) were to be used, surface irregularities in the pipe interior would at times permit only two opposite grippers to engage the wall, the other opposing pair failing to contact the inner wall surface The use of only three cams allows a single piston rod to provide an engaging force via three cams and three grippers to provide tight engagement with the pipe wall. 
     The preferred embodiment described above sets forth a pipe crawler apparatus in which a single drive unit  10 B is used to move oppositely positioned gripper units  10 A and  10 C. It is readily understood by one having ordinary skill in the art that additional tools and segments may be added within the body portion of the pipe crawler apparatus. Such segments may include various sensors and diagnostic arrays that are deployed by the pipe crawler apparatus. Further, any number of additional gripping units and/or drive units may be added as needed to provide sufficient motive power to a pipe crawler apparatus. For instance, multiple gripper units  10 A could be coupled in series along with multiple gripper units  10 C. Units  10 A may be operated in tandem and clustered along the front of the pipe crawler apparatus  10 . In turn, gripper units  10 C may be positioned along the rear of the pipe crawler apparatus and also designed to operate in tandem with each other. One or more drive units  10 B may then be used to provide the inch-worm motion to the pipe crawler apparatus. 
     Many variations, changes, and substitutions will be apparent to one having ordinary skill in the art. Such changes and substitutions can be made to the preferred embodiment herein described without departing from the spirit and scope of the present invention as defined by the following claims. 
     Although preferred embodiments of the invention have been described using specific terms, devices, and methods, such description is for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or the scope of the present invention, which is set forth in the following claims. In addition, it should be understood that aspects of the various embodiments may be interchanged, both in whole or in part. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein.