Casing thread protector
This invention pertains to thread protectors for threads at the ends of tubular goods. More specifically, but not in a limiting sense, the thread protector is intended for short term installation on male threads on well pipe joints being handled between horizontal racks and a well derrick. Elastomeric housings and metal securing features with quick release capability characterize protectors of the class disclosed. 
     BACKGROUND 
     Tubular goods for installation in wells experience considerable handling and storage between steel mill and well and a cylindrical thread protector normally stays on every male thread until it reaches the well site. These are screw on protectors and have a full complement of threads. It takes a number of turns to remove the original protector and that expenditure of time cannot be tolerated during installation of tubular strings in wells. The original protector is removed at the well site and a quick releasing one is installed. It rides from rack to rig and is removed when the joint is to be threadedly attached to the downwardly continuing string. During the interval that the protector is on threads, a last bore drift test is usually done and it is desirable that the protector does not interfere with the drift passage. 
     A considerable amount of development work has been done in efforts to improve the bands and related tensioning gear to keep the casing protectors from being knocked off the thread during the rack to well trip. 
     The body of protectors in rig site use are currently made of elastomer, usually polyurethane, but sometimes black rubber. The elastomer is formulated and cured to serve the skid and bash protection function and does not always favor thread gripping. The elastomer would grip threads if enough hoop force were applied by the securing bands. The securing bands that are closed by hand have limited energy available and do not drive the elastomer into the thread grooves sufficiently to prevent occasional slipping of the protector. 
     It is therefore an object of this invention to provide an elastomeric thread protector with higher unit loading to more effectively urge the elastomer into the thread grooves yet allow drift testing of the pipe bore. 
     It is another object of this invention to provide replaceable elements subject to the higher unit loading to reduce the frequency of total body losses due to thread load induced damage. 
     It is yet another object of this invention to provide a tensioning hoop band for closing thread protectors on pipe threads that is readily replaceable when damaged to preserve the elastomeric body. 
     These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached claims and appended drawings. 
     SUMMARY OF THE INVENTION 
     The protector has an elastomer body of generally toroidal shape common to a doughnut. The toroid is cut by a plane containing the axis of symmetry and extending from the axis outward. This allows the body bore to expand to accept the pipe to be protected. A circumferential tensioning band of metal is carried in a peripheral groove about the body. The band is closed across the cut gap by a toggle clamp. The closed body has a generally cylindrical bore approximating the size of the pipe outside dimension. A salient feature of this protector is a complement of pads extending radially inward from the bore to engage the threads of the pipe. This reduces contact area and increases unit load. Additionally, the pads do not necessarily have the physical characteristics of the general body and can be devised to optimize the extrusion of elastomer into thread grooves, and can be provided of soft metal or plastic with grooves to engage threads. 
     The pads are replaceable and are attached to the body by releasable means optionally including grooves for a composite pad set, dovetails for each pad, and enlarged adhesive junctures. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     In the drawings wherein like symbols refer to similar features, FIG. 1A is an elevation viewed along the axis of pipe to be protected. 
     FIG. 1B is an unsectioned view similar to FIG. 1A in the alternate position, open to release pipe. 
     FIG. 2 is a right side view, partly sectioned, of the protector of FIG. 1A. 
     FIG. 3 is a sectional view of a selected area of FIGS. 1A and 2. 
     FIG. 4 is a sectional view taken along line 4--4 of FIG. 3. 
     FIG. 5 is a sectional view similar to that of FIG. 3 but showing an alternate form of one feature of the invention. 
     FIG. 6 is a sectional view taken along line 6--6 of FIG. 5. 
     FIG. 7 is a sectional view, similar to that of FIG. 5, of an alternate form of the invention. 
     FIG. 8 is a sectional view taken along line 8--8 of FIG. 7. 
     FIG. 9 is an elevation of component common to FIGS. 1A through 12. 
     FIG. 10 is a sectional view taken along line 10--10 of FIG. 9. 
     FIG. 11 is a right end view of the component of FIG. 10. 
     FIG. 12 is an elevated view of an alternate body configuration. 
     FIG. 13 is a sectional view taken along line 13--13 of FIG. 12. 
    
    
     DETAILED DESCRIPTION OF DRAWINGS 
     In FIG. 1A, doughnut shaped body 1 has cut C to allow the body to gape open to release pipe threads gripped by pads 1c in bore 1a. The cut is closed and held on pipe by toggle clamp 2 which applies tension to band 3 to apply radial force between pads 1c and the threads to be protected. Bore 1b is about the same diameter as the casing bore and provides plane 1h to stop and position pipe entering the bore 1a. 
     In FIG. 1B clamp 2 has been actuated to open the cut C and increase the periphery of the cylinder defined by surfaces on pads 1c to release threads when gripped and for installation on threads to be protected. 
     In FIG. 2, an orthogonal projection of FIG. 1A, the toggle clamp 2 is shown with cams 2b bearing upon band plate, or terminal, 3b. Clamp lever 2a is attached to the cam structure 2d and pivots about pin 2h to allow links 2g to relax thrust on pin 2c and bolt 2b. Clamp bolt 2b extends through adjusting nut 2f which loads optional spring (or spring washer) 2e which bears upon band plate 3b. The band and clamp arrangement is old art using the toggle or over-center self locking feature. Band 3a is carried in recess 1e which extends around most of the body periphery. The band can, optionally, be imbedded in the body elastomer. Band plates 3b are peripherally captured in grooves 1f. If bolt 2d is removed, plates 3b can be slid radially outward along the grooves to free the band 3. On most protector sizes the resilience of the pads 1c, flexed more by higher unit loading than would occur by engaging pipe with the full periphery, eliminates the need for the spring 2e and it is replaced by a flat washer. 
     In FIG. 1A the bore 1a is achieved by radial cutouts (either cut or molded) to relieve the original bore which produced cylindrical surfaces on pads 1c. This arrangement is suitable when pad elastomer can be identical to that of the general body. 
     FIGS. 3 through 8 represent alternate constructions of thread engagement pads represented by the lower portion of FIG. 2 and the related section on FIG. 1A. 
     In FIGS. 3 and 4, pad insert 4c, confined in recess 4b of body 4, projects inwardly from bore 4a. Bore 4a does not need to touch the pipe being protected. Flange 4d locates the pipe end but has no further purpose in the gripping of pads 4c. Flange 4d does prevent a pipe end impact from forcing the pad to slip on threads. 
     FIGS. 5 and 6 show alternate means for securing pads 6b to body 5. The pads 6b are formed on a circular band 6a from which they extend radially inward. The formed band 6, with pads 6b, is then secured to the surface of bore 5a and cut at the location of the body cut C (FIG. 1). Mechanical fastening, adhesive, or a combination of the two is used to secure the band in the bore. Shoulder 5d serves to position pipe. 
     FIGS. 7 and 8 show a sectioned body 7 without grooves or slots for pad inserts. Pad 7b is shaped to increase the surface area available for adhesive to join pad and body. Surface 7a can be the cylindrical form produced by the bore 1a (FIG. 1) or it can be shaped to define the location of the pads for their distribution about the periphery of pipe to be gripped. Flange 7c does the usual pipe locating. 
     The general construction and alternate operational positions having been shown for the preferred embodiment of the invention, FIGS. 12 and 13 are shown without alternate positions and without some of the clamping details. 
     FIGS. 12 and 13 represent an alternate body construction, preferred on larger size protectors, in which the peripheral band is partially enclosed within a body tunnel and rapid opening is assured by an independent opening spring. On larger protectors, the peripheral groove that accepts the peripheral band is eliminated to attain greater rigidity. 
     Body 10 has recess 10b for the usual toggle clamp handle and the shorter recess 10b for one band terminal 3b. Recess 10b is long enough to permit attachment of one 3b terminal after the band is inserted through the tunnel 10d. The riveting or fixture brazing method is preferred for attaching the final terminal. The band is still removable by cutting it in the recess 10b after the bolt 2b is removed to allow the band to swing outward. 
     Spring 11, an optional feature, is inserted into openings 10c before the bolt is installed. Cut 10a is shown almost closed in preparation for installation of the clamp handle and related links connectable to bolt 2b. 
     Spring 11 is shown to act against terminals 3b. This spring can be replaced by two springs in separate openings, one on each side of the bolt in axially separated openings. 
     The body bore 10e is shown without the grip enhancing features of FIGS. 1a and FIGS. 3 through 8. These features have been disclosed herein and can be used as desired for this optional body configuration. 
     From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the protector. 
     It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims. 
     As many possible embodiments may be made of the protector of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.