Casing scraper
FIELD OF THE INVENTION 
     The present invention relates to a scraper tool for cleaning the interior of tubular members and more particularly a scraper tool having cutter blade assemblies which provide substantially annular contact with the interior surface of tubular members. 
     BACKGROUND OF THE INVENTION 
     The cleaning of the interior surface of tubular members is desirable and often necessary in the oil and gas industry where tubular members such as casing are positioned in a well bore. Typically, such cleaning is accomplished by lowering a tool into the casing or well bore and moving the tool so as to cut foreign matter such as cement sheaths, mill scale, burrs, bullets stuck in the casing, etc. from the interior of the casing. 
     The scraping of a well casing allows close fitting tools such as packers to be lowered into the well casing and activated so as to attach to the casing without becoming stuck in the casing and without being damaged by foreign objects on the interior wall of the casing. 
     Typical casing scraper tools have required manipulation by rotation or reciprocation in the well bore in order to provide the scraping action to all areas of the interior diameter of the casing. In U.S. Pat. No. 3,032,114, cutter blades on a scraper tool were spaced apart circumferentially about the tool, resulting in potentially incomplete or inadequate scraping of the tubular member due to the open areas between the adjacent cutter blades. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a new and improved scraper tool to clean the interior surface of tubular members and in particular to clean the interior surface of well casing. 
     The present invention provides a casing scraper tool having a substantially 360° contact area to provide for a substantially complete scraping of the casing without the requirement of rotating the scraper or the possibility of missing an area of the casing due to spaces between adjacent scraper blades. 
     The present invention further provides a spring alignment housing to provide alignment and support for the springs employed to bias the scraper cutter blades radially outwardly from a supporting mandrel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view, partially in section, of the scraper tool of the present invention. 
     FIG. 2 is an enlarged sectional view along line 2--2 of FIG. 1. 
     FIG. 3 is an cross-sectional view along line 3--3 of FIG. 2 showing the cutter blades expanded. 
     FIG. 4 is a cross-sectional view along line 3--3 of FIG. 2 showing the cutter blades retracted in a pipe. 
     FIG. 5 is an exploded view of one of the scraper or cutter blades, the springs, and the housing therefor. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The apparatus A of the present invention is adapted for running in a well casing on a conventional tubing string (not shown). As shown in FIG. 1, a mandrel 10 includes an upper section 10a having a threaded pin section P to threadedly connect with a tubing string thereabove (not shown). The mandrel lower section 10b includes a threaded box section B to threadedly receive a lower pipe string (not shown). In use, the apparatus A is normally located in a string of pipe to enable it to be lowered into a well casing for performing scraping or cleaning operations inside a casing. The mandrel upper section 10a and lower section 10b are joined by a threaded connection 12 more fully described hereinbelow. 
     The mandrel upper section 10a includes a reduced diameter longitudinal section 14 which forms a longitudinally and circumferentially extending upper recess 16 on mandrel 10. The upper recess 16 has an undercut portion 18 formed by an annular downwardly extending retaining lip 19. An annular projection or ring 20 forms the lower joint of the recess 16 and separates the upper recess 16 from a lower recess 30. Lip 19 is engaged by fingers 46 of the cutter blades as described below. 
     Lower recess 30 extends from annular projection 20 to a threaded extension 22 of mandrel upper section 10a. Threaded extension 22 is adaptd to receive lower section 10b of mandrel 10. An upwardly extending retaining lip 32 is formed on lower section 10b to thereby form undercut portion 24 when threaded with upper section 10a. Lip 32 is engaged by depending fingers 46 of the cutter blades described below. Surrounding annular section 20 is annular ring 23 which is releasably positioned around annular protection 20, as will be explained. Orientation of annular ring 23 about annular projection 20 forms retaining extensions 25 which engage with adjacent fingers 46 of the cutter blades described below. 
     A plurality of arcuate cutter blades 40 are provided, each of which includes cutter teeth 41 formed by a plurality of spaced grooves 42 which preferably extend at an oblique angle relative to the longitudinal axis of the cutter blade. The cutter teeth 41 are usually tool steel or other suitable material to resist wear. Each end 44 of each cutter blade 40 includes extending fingers 46 to engage with extending lips 19 and 32 and retaining extensions 25, as more fully explained below. 
     The inside of each cutter blade 40 includes a recess 50 adapted to receive a spring housing block 52 (FIG. 5). Spring housing block 52 includes an arcuate surface 54 which generally conforms in shape to the external surface of the recessed portions of mandrel 10. Extending through spring block 52 from arcuate surface 54 are three holes or bores 56 adapted to receive coil biasing springs 57. Coil springs 57 contact mandrel 10 and cutter blade 40 to bias cutter blade 40 radially outwardly. Spring block 52 maintains the relative position of each biasing spring 57. 
     Each cutter blade 40 is an arcuate segment of a circle, such that when a set of cutter blades are oriented upon mandrel 10 a substantially circular cutter assembly C is provided. Each cutter blade includes on each of its longitudinal ends 58 an S-shaped contact surface 59 to overlap and interfit with a corresponding S-shaped contact surface 59 on the adjacent blades (See FIGS. 3 and 4). The interfitting contact surfaces 59 provide for a substantially continuous engagement of each of the sets 60 and 62 of cutter blades in various pipe diameters. 
     The scraper tool is assembled with the mandrel portion 10b removed from the mandrel portion 10a. The first or upper set 60 of three cutter blades 40 are placed on mandrel 10 with their upper fingers 46 positioned beneath undercut 18. When so positioned, each cutter blade 40 has a spring housing 52 and springs 57 located within recess 50, and with the springs 57 compressed enough to maintain sufficient radial outward force on each blade 40 to maintain blades 40 urged into contact with the inside of a casing C even when in the fully extended position (FIGS. 2 and 3) with sufficient force to effect a scraping or cutting action on the inside of the casing. 
     Annular ring 23 is then longitudinally slid onto the mandrel until it is disposed adjacent annular projection 20 with its extensions 25 extending over lower fingers 46 of the cutter blades of set 60, thereby confining upper cutter assembly 60 on mandrel 10 while allowing limited radial movement of the cutter blades 40 biased radially outwardly by springs 57 from the fully retracted position (FIG. 4) to the fully extended position (FIG. 3) depending on the inside diameter of the casing relative to the blades 40. 
     Next, the cutter blades 40 of lower cutter assembly 62 are positioned around mandrel 10 with the spring housings 52 and springs 57, and with the upper fingers 46 of cutter blades 40 in set 62 extending under extensions 25 of annular ring 20. Lower mandrel section 10b is then threaded to upper mandrel section 10a to position retainer lip 32 around the lower fingers 46 of the cutter blades 40 of the set 62, thereby confining both lower cutter assembly 62 and upper cutter assembly 60 on mandrel 10. 
     In use, the scraper tool is lowered within a casing or pipe string to be cleaned. The tool is rotated and/or reciprocated to effect the cleaning of the inside surface of the casing. Each of the radially outwardly biased cutter assemblies 60 and 62 provides substantially 360° of contact between the cutter blades 40 and the interior surface of the casing. Further, the upper set 60 is preferably oriented circumferentially with respect to the lower set 62 (for example, 30 degrees) so that the relatively small spacing between the blades 40 in the upper set 60 is offset circumferentially from the corresponding spacing between the blades 40 in the lower set 62, whereby the blades 40 of the upper set 50 will contact the casing being scraped at the areas of the spacing between the blades 40 of the lower set 62. Similarly, the blades 40 of the lower set 62 will contact the casing of the areas of the spacing of the blades 40 on the upper set 60. 
     In practice, the outer diameter of the cutter blade assemblies 60 and 62 is determined by the interior diameter of the casing to be cleaned. Before insertion of the apparatus A into the casing small spaces exist between adjacent cutter blades 40 which are biased outwardly by springs 57 (FIG. 3). Upon insertion of the apparatus A into the casing, contact between the cutter blades 40 and the casing compresses springs 57 through contact of the cutter blades 50 with the interior of the casing. The intermeshing of adjacent cutter blades 50 as they are forced radially inwardly by contact with the casing essentially eliminates or minimizes the space between adjacent cutter blades 40 (FIG. 4). 
     Although the invention is described as including two adjacent cutter blade assemblies 60 and 62, the invention is readily adaptable to a single cutter blade assembly. In adapting to a single cutter blade assembly, the threaded extension 22 and the upwardly extending retainer lip 32 formed on lower section 10b which forms undercut portion 24 to be engaged by depending fingers 46 of the butter blades would be oriented in place of annular projection 20 and annular ring 23. Such an adaptation to a single cutter blade assembly would provide substantially annular contact with the interior surface of the casing due to the minimization of the space between adjacent cutter blades 40. Further, although the invention is described as including three cutter blades per cutter assembly, the invention is readily adaptable to cutter assemblies comprising two or more cutter blades without departing from the spirit and scope of the invention. Also, although coil springs 57 are preferred, other resilient biasing means may be employed in place of coil springs. 
     It should be understood that the foregoing description and the drawings of the invention are not intended to be limiting, but are only exemplary of the inventive features which are defined in the claims.