Abstract:
A metal-debris magnetic scavenging tool useable inside a buried, horizontal metallic pipeline through an access opening which has been cut into the upper wall portion of the pipeline overhead where the resulting debris has collected. A raiseable/lowerable and rotatable array of magnets, surface exposed, and operating moveably as a unit, agitate and collect debris principally within an area-footprint which allows for clearance lifting and removal of collected debris through the access opening.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention pertains to management of underground metal pipelines, such as underground gas pipelines. Very specifically, it relates to a method and apparatus for scavenging for removal metal debris of the kind which collects at the base of such a pipeline during and as a consequence of cutting into the pipeline for the purpose of installing various kinds of fittings. A preferred embodiment of the invention is described herein in the setting of a procedure known in the gas utility industry as a “tap a line stopper” procedure. 
     In a procedure of the type just generally identified above, when certain kinds of work needs to be performed on and with respect to a previously installed underground metal gas pipeline, a large, generally “circular” overhead access hole is appropriately cut into such a pipeline at a selected location for the purpose of installing a maintenance-related fitting. During such a procedure, metal debris falls down into and collects near the base of the pipeline immediately under where such an access hole is created. The debris which typically results includes a large chunk of metal referred to as a coupon which generally has the size and shape of the hole which has been cut, as well as smaller shavings and other shards of metal. 
     There are many reasons why it is important to remove, as effectively as possible, all such debris. Prior art approaches directed toward accomplishing debris scavenging and collecting have not been entirely and regularly successful. An unsuccessful removal procedure, often dictates the need to implement a significantly more expensive “clean-up” operation involving more cutting, and pipeline exposure digging. Today, where as in the past it was occasionally acceptable to leave debris in such a pipeline, a new kind of requirement exists which mandates that pipelines be clear for the passage of inspection devices. Such a mandate requires that, in substantially all instances where such metallic debris is created, it must essentially be thoroughly removed from a pipeline. Accordingly, it is very important today that there be a reliable and relatively inexpensive procedure for debris removal, and the present invention uniquely and very successfully addresses this issue. 
     According to a preferred embodiment of the invention, a novel scavenging tool is proposed which, fundamentally, employs magnetism for debris collection and removal. Included in this tool are (a) a somewhat pancake-shaped cylindrical tool body which is formed around a central axis as a body of revolution out of a soft-magnetic material, (b) an elongate tool stem which extends coaxially from one side, or face, of the tool body, (c) plural, angularly distributed, generally cylindrical sockets formed in the opposite face of the tool body, and disposed generally symmetrically about the central axis of the tool, and (d) plural, generally cylindrical, button-like, permanent magnets which fit snuggly within these sockets with their outwardly facing faces fully exposed, and somewhat recessed below the face level into which the sockets extend. A chamfered rim region which circumsurrounds the outsides of the magnet-receiving sockets is formed on the tool body. 
     The tool body and tool stem may be joined to one another in any suitable fashion, such as by bolt-joining, and the magnets are held in place in the sockets in a manner which causes them to operate completely as fixed units along with the tool body. Preferably, these magnets are held in place principally by the force of magnetic attraction which exists between them and the soft-magnetic material, typically steel, out of which the tool body is formed. Other manners of securement for the these magnets may be employed, such as adhesive bonding and/or screw attachment, but in most instances, magnetic attraction is entirely sufficient to stabilize the magnets securely within the sockets. 
     The fact that the outwardly facing faces of the installed magnets are exposed for viewing, so-to-speak, on that face of the tool body into which the receiving sockets are formed results in magnetic field lines existing in an outwardly bulging fashion into the air space immediately adjacent the exposed openings of the sockets. As a consequence, distributed generally angularly and somewhat circumferentially about the long axis of the tool, and adjacent the open ends of the sockets, there exists a kind of spatially undulating-strength, composite magnetic field which, with rotation of the tool about its long axis, and with respect to a magnetically attractable object which is nearby the exposed facial side of the magnets, produces what is referred to herein as a time-variant (in apparent strength) magnetic field. 
     Preferably, the largest outside diameter in the tool of this invention, and namely the largest outside diameter which characterizes the cylindrical tool body, is just somewhat less than the nominal diameter of a cut access opening (mentioned earlier) which is formed in a metal gas pipeline that is to be addressed by scavenging operation of the tool. With the mentioned chamfered rim region in existence on the tool body, according to the invention, the actual outer facial extremity of the tool body which exposes the magnets in the sockets has a diameter which is considerably less than that of the largest outside diameter in the tool body. 
     The various features and operating advantages of this tool will become very fully apparent, as will its capability of meeting the need expressed earlier herein, as the description which now follows is read in conjunction with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary isometric view illustrating a preferred embodiment of a metal debris scavenging tool made in accordance with the present invention. 
         FIG. 2  is a simplified schematic diagram illustrating the relative positional (anglar and linear) locations in the tool of  FIG. 1  that exist between certain generally parallel axes. These axes include the long central axis of the tool per se, as well as the respective axes of symmetry of several button-like (four) permanent magnets which are employed in this tool. 
         FIG. 3  is an enlarged, fragmentary, partly cross-sectioned view of the tool in  FIG. 1 , taken generally along the line  3 — 3  in FIG.  1 . 
         FIG. 4  is a somewhat smaller scale fragmentary side elevation, with portions of certain structures broken away to illustrate details of construction, showing the tool of  FIG. 1  in use with respect to scavenging metallic debris from inside the base of a metallic gas pipeline which has been cut with an overhead access opening in the process of performing a procedure like that discussed earlier herein. 
         FIG. 5  is a view, on a slightly smaller scale than that which is employed in  FIG. 4 , and which is fragmentary in nature, illustrating, from a point of view which is taken along the long axis of the pipeline of  FIG. 4 , showing how the chamfered rim region of the tool body in the tool of this invention disposes itself within the cross-sectional area of that pipeline. 
         FIG. 6  is a graphical illustration picturing, very generally, what was referred to herein earlier as a kind of undulating magnetic field distribution which extends somewhat circumferentially about the tool&#39;s long axis, and exposed on that end of the tool which generally faces the viewer in FIG.  1 . 
         FIG. 7  is a much enlarged fragmentary diagram illustrating how debris collected by the tool of this invention is generally acquired and retained for withdrawal from within a pipeline. Specifically, this figure suggests how, generally speaking, the “perimetral outline” of collected debris normally lies within what can be though of herein as the generally circular footprint of the cross-sectional area of an access opening which has been cut into a pipeline, such as into the pipeline shown in  FIGS. 4 and 5 . 
         FIG. 8  aids  FIG. 7  in picturing a gathered-debris perimetral outline. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning attention now to the drawings, and referring first of all to  FIGS. 1-3  inclusive, indicated generally at  10  is a magnetic metal-debris scavenging tool constructed in accordance with the present invention. In general terms, tool  10  includes a somewhat pancake-shaped cylindrical tool body  12 . Body  12  is a body of revolution that is centered on an axis of revolution shown by dash-dot line  14 . It is made preferably of a soft-magnetic material such as steel. Suitably joined, as by a screw, such as the one shown at  16 , coaxially with and to tool body  12  is an elongate tool stem  18 . 
     Tool body  12 , includes a generally fixed-diameter cylindrical interior-region portion  12   a  which joins with an inwardly tapering, chamfered, frustro-conical rim region  12   b  which generally faces toward the viewer in  FIG. 1 , and which is shown facing to the left generally in FIG.  3 . As will become apparent, tool body  12  is constructed with dimensions that are especially suited for use of tool  10  for scavenging metal debris within a buried metal gas pipeline having a nominal inside diameter of about 4-inches. To this end, the large diameter, truly cylindrical portion,  12   a , in tool body  12  has an outside diameter with a radius of curvature, shown at R 1  in  FIG. 3 , of about 1.75-inches, with this diameter shrinking in size, progressing to the left along axis  14  in  FIGS. 1 and 3 , to a somewhat smaller overall outside diameter with a radius indicated at R 2  in FIG.  3 . The tool body has an axial thickness, shown at d 3  in  FIG. 3 , herein of about 0.75-inches, and of this d 3  dimension, the axial thickness of portion  12   a  (not specifically designated in the drawing figures) is about 0.25-inches, with the frustro-conical rim region  12   b  having an axial dimension (also not specifically designated in the drawings) herein of about 0.5-inches. As viewed in  FIG. 3 , the acute angle which the surface of frustro conical region  12   b  appears to make with axis  14 , shown at α 1 , is about 30-degrees. 
     The side, or face,  12   c  in the end region in tool body  12  which generally faces the viewer in  FIG. 1 , and which faces to the left in  FIG. 3 , is referred to herein as a generally planar end face which lies in a plane that is substantially normal to axis  14 . 
     From the tool description which has been given so far herein, it will be seen that rim portion  12   b  intersects interior region  12   a  along a circular line having the radius R 1 , and intersects face  12   c  along another circular line having the radius R 2 . 
     Extending axially into, and opening to, face  12   c  herein, are four generally cylindrical sockets, such as those shown at  20 , which are distributed angularly equally about axis  14  at the locations generally shown in the figures. Each of these sockets has a central long axis of symmetry, such as the axes shown at  22 , which generally parallels previously mentioned axis  14 . Each axis  22  lies at substantially the same radial distance from axis  14 . Each of these sockets has a diameter herein of about 0.5-inches, and a depth (see d 1  in  FIG. 3 ) of about 0.375-inches.  FIG. 2  schematically illustrates the relative spatial dispositions of axes  14  and  22 . As can be seen in  FIG. 2 , and as was suggested earlier, from an angular disposition point of view, and as viewed in the plane of  FIG. 2  which is normal to all of these axes, adjacent axes  22  lie, relative to axis  14 , at angles with respect to one another which are less than 180-degrees, and very specifically herein, about 90-degrees. This angle is shown at α 2  in FIG.  2 . 
     Placed and held by magnetic force within sockets  20  in tool body  12 , are form-fitting, cylindrical-button magnets, such as those shown at  24  (an array). These magnets, which are of the “permanent type” are commercially available, and typically are made of robust magnetic material capable of exhibiting a relatively powerful magnetic field. The cylindrical central axes of magnets  24  are substantially co-aligned with socket axes  22 . Each magnet has an axial dimension (see d 2  in  FIG. 3 ) of about 0.25-inches with a result that the outwardly facing ends, or sides, of the magnets are recessed slightly within those ends of sockets  20  which open to tool body face  12   c . This condition of recess is clearly pictured in  FIGS. 1 and 3 . 
     Tool stem  18  herein has a generally hexagonal cross section, and may typically, with respect to tool  10  as such is now being described, have a length generally of about 8-inches. This is not a critical length. 
     As was mentioned above, tool  10 , as pictured and dimensioned herein, is designed for use with respect to a buried pipeline having a nominal inside diameter of about 4-inches. Turning attention to  FIGS. 4-8 , inclusive, now along with  FIGS. 1-3 , inclusive, such a metal gas pipeline is shown generally at  28  in  FIGS. 4 and 5 . Especially with attention focussed on  FIGS. 4 ,  5 ,  7  and  8 , what is here being pictured with respect to pipeline  28  is a portion of a pipeline maintenance procedure referred to earlier herein as a “tap a line stopper” procedure. In particular, these several figures illustrate how tool  10  is employed to remove (scavenge) metal debris which has resulted from the cutting into the overhead portion of the wall in pipe  28  of an access opening, such as the access opening shown at  30  in  FIGS. 4 ,  5 , and  8 . 
     Access opening  30  has been prepared in a conventional cutting process employed by gas line maintenance people, after and before which cutting various additional fittings, such as the one shown very fragmentarily at  32  in  FIG. 4 , are (or may be) appropriately attached to pipe  28 , as by welding. A weld joint which exists between pipeline  28  and fitting  32  is shown herein generally and fragmentarily at  34  in FIG.  4 . Fitting  32  is generally cylindrical in nature, and matchingly circumsurrounds circular cut  30  which has the generally circular cross-sectional area footprint shown by dash-double-dot line  30  in FIG.  8 . In pipeline  28 , which nominally has an inside diameter of about 4-inches, access opening  30 , as such is pictured in  FIG. 8 , has a nominal diameter of about 3.75-inches. 
     The cutting procedure by way of which access opening  30  was produced has resulted in the creation of a collection of metal debris  36  adjacent the base of pipeline  28 , directly beneath access opening  30 . As illustrated in  FIG. 4 , debris  36  includes one singular large chunk  36   a , referred to as a coupon, and a collection of smaller shavings/shards such as those pointed to in  FIG. 4  at  36   b . Coupon  36   a , generally speaking, takes the form of the major piece of metallic pipeline which once substantially filled access opening  30 . 
     It is to enable easy and substantially complete removal of debris  36  herein that tool  10  has been designed. 
     In any suitable manner not especially relevant to the present invention, tool  10 , through its tool stem  18 , is appropriately joined to a power-driven rotary machine (not shown), and is securely positioned so as to be diametrally lowerable into pipeline  28  via access opening  30  with the axis of revolution of tool  10  being substantially coincident with this opening&#39;s central axis shown by a dash-double-dot line  30   a  in FIG.  4 . Very specifically, pre-use positioning of tool  10  is such that vertical movement of the tool, during its use, along axis  14 , will result in the large diameter portion of body portion  12   a  freely clearing the inside of fitting  32 , as well as also clearing the side margins of circular access opening  30 . This is the condition in which tool  10  is shown in  FIG. 4  prior to this tool&#39;s being introduced downwardly into the interior of pipeline  28 . 
     With respect to, now, to the scavenging of debris  36  by tool  10 , the tool is appropriately lowered downwardly through opening  30  to a region immediately above debris  36 , as is indicated generally by arrow  38  in FIG.  4 . As can be seen especially well in  FIG. 5 , the chamfered rim region  12   b  of tool body  12  allows this tool body to be lowered quite deeply toward and into the base region of pipe  28 . 
     With tool  10  thus lowered, the power-drive mechanism attached to it, mentioned above, is operated, bidirectionally if desired, to produce rotation of tool  10  about its axis of revolution  14 . Such bidirectional rotation is indicated in  FIGS. 4 and 5  by double-ended curved arrow  40 . 
     By virtue of the fact that the four magnets,  24 , which are included in tool  10 , are outwardly exposed through the recessed regions in sockets  20  which open to face  12   c , a kind of angularly undulating, spatial magnetic field distribution exists, which, with rotation of the tool as indicated by arrow  40 , causes beneath the tool, and at each stationary region within pipeline  28  which is faced by downwardly facing face  12   c , the experience of a time-variant magnetic field strength. Field strength distribution is suggested generally by the graphical image presented in FIG.  6 . Peaks and valleys in this undulating field strength relate to the relative quadrature dispositions of exposed magnets  24 , distributed, as was previously described, generally at angular positions around axis  14  which are about 90-degrees apart. 
     As a consequence, now, of lowering of tool  10  downwardly toward debris  36 , and as is aided by modest rotation of the tool about its axis of revolution, a significant debris gathering activity takes place, whereby the metallic debris pictured at  36  is effectively moved and gathered to become magnetically caught on the underside of tool body  12 , closely adjacent one or more of magnets  24 . Because of the presence of chamfered region  12   b  in tool body  12 , metallic debris is generally gathered in such a fashion that its outside gathered perimetral outline will, under most circumstances, lie generally within the axially viewable footprint (see  FIG. 8 ) of opening  30 . In  FIG. 8 , a stylized perimeter outline for such collected debris is shown generally by dashed line  42 .  FIG. 7  also generally illustrates this situation where pieces of collected debris, magnetically held beneath tool face  12   c , are shown generally at  44 . 
     It should be understood that not in all circumstances will tool rotation be required for proper collecting and removal of all debris. 
     The invention thus proposes a novel and very capable, simple to construct and use metal-debris-scavenging tool. The distributed spread of facially exposed magnets, enabled to be rotated as described above, to operate as a unit (non-relatively-moveable) with the tool body and stem, and to be capable of introducing a time-variant magnetic field in the zone of debris collection, offers a highly successful apparatus and procedure for removing metallic debris from metal pipelines. 
     While a preferred embodiment of and manner of practicing the invention have been described herein, variations and modification which come within the scope of the invention are certainly possible.