FRICTION REDUCING TOOL

Abstract: A friction reducing tool for drilling applications having a plurality of rollers for about the periphery of the tool (3). The rollers (4) have extensions (7) which locate within cavities (8) to prevent the rollers from passing from cavity (10) to the exterior of the tool. The tool is formed in multiple parts (3a and 3b) having interengaging tongues (5 and 6) which are joined together by passing a rod (15) through bore (13). A groove (14) is provided in outer component (2) to enable rod (15) to be inserted in bore (13).

Description: FRICTION REDUCING TOOL Technical Field The present invention relates to a friction reducing tool suitable for use in drilling applications. In one aspect the present invention relates to a tool having a multipart rotatable outer component wherein the parts may be secured together by rods insertable through a groove in the main body part of the drill string component and a tool incorporating rollers having positive roller containment. Background of the invention It is known in the industry to provide a tool in which an outer rotatable portion is formed in multiple parts, which are secured together about the tool. Typically, a recess is provided in the main body portion of the tool and the multiple parts are secured about the main body portion within the recess so as to be rotatable thereabout. Typically, the multiple portions are fastened together by bolts or other similar fastening means. Often this requires projecting flanges which may cause obstruction. Further, under extreme loads the multiple portions could separate, leaving parts of the tool obstructing a well. It is also known to provide rollers about the periphery of a tool to minimise friction. Typically, such rollers are inserted into a cavity in the tool from the exterior and a pin is inserted to secure the roller in place. Under severe load conditions the pin can shear and the roller and pin may drop out of the tool and obstruct the well. Disclosure of the invention It is an object of the present invention to overcome these problems or at least to provide the public with a useful choice. According to a first aspect of the invention there is provided a friction reducing tool for drilling applications comprising a generally tubular body portion having a cavity in a side wall thereof which accommodates a roller, wherein the cavity is dimensioned so that the roller can be introduced into the cavity from the interior of the body portion but cannot pass out of the cavity to the exterior of the body portion According to a further aspect of the invention there is provided a friction reducing tool having an inner component securable to or about a drill string and an outer component rotatable about the inner component, wherein the outer component is formed in multiple parts secured together by rods and is located within an annular recess in the inner component and wherein a groove is provided in the inner component adjacent the recess to enable a rod to be inserted when the parts of the outer component are assembled about the recess. The groove is preferably angled downwardly towards the recess so that the rod deflects as it is inserted into apertures in the parts and, when in place, abuts against thrust faces of the drill string component. According to a further aspect there is provided a friction reducing tool comprising a plastic sleeve for securement about a drill pipe, first and second collars to secure the plastic sleeve to a drill pipe at either end thereof and an outer component for securement about the plastic sleeve between the collars, wherein the outer component is provided with a plurality of friction reducing rollers about the periphery thereof. Brief Description of the drawings The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 : shows a partial perspective view of an outer component of a friction reducing tool. Figure 2: shows a partial cross-sectional view of the outer component shown in figure 1 . Figure 3: shows a partial cross-sectional view along the axis of the tool. Figure 4: shows a partial cross-sectional view of the outer component. Figure 5: shows an exploded view of a roller and roller cavity. Figure 6: shows insertion of a rod to secure the parts of an outer component together. Figure 7: shows a perspective view of the groove which guides the rod during the insertion operation shown in figure 6. Figure 8: shows an embodiment incorporating a plastics bearing having longitudinal channels. Figure 9: shows a further embodiment incorporating a plastics sleeve. Best mode for carrying out the invention Referring firstly to figures 1 to 5 there is shown a friction reducing tool 1 comprising an inner component 2 and a rotatable outer component 3. Outer component 3 includes a plastic bearing 3c and is rotatable with respect to inner component 2 to reduce rotational friction. A plurality of rollers 4 are provided in three banks about the periphery of rotatable component 3 within cavities 10 to reduce axial drag. Outer rotatable component 3 is divided into two parts 3a and 3b which, during assembly, are inter-engaged about inner component 2 within recess 1 6 (see figure 7) and secured in place by rods 1 5 passing through apertures in inter-engaging tongue portions 5 and 6. Each roller 4 is provided with extensions 7 at each end, which, in use, are located within a respective cavity 8. Overhangs 9 prevent roller 4 from leaving cavity 10 should axle 1 1 shear under high load conditions. As shown in figure 2 the diameter of the bore through roller 4 increases towards the ends of the roller to reduce sheer forces on axle 1 1 at the ends of the roller. To assemble the banks of rollers each roller must be inserted from the interior of outer section 3 and when extensions 7 are located within cavity 8, pin 1 1 is inserted to secure each roller in place. Pin 1 1 may be secured in place by welding 1 2 or other suitable means. From figure 1 it will be seen that outer part 3a includes tongues 5 which inter-engage with tongues 6 of outer part 3b. A rod is first passed through apertures in interengaged tongues of outer parts 3a and 3b to join the halves together in a hinged manner. The hinged assembly is then placed within recess 1 6 and tongues 5 and 6 brought into engagement (as shown in figure 1 ). Outer parts 3a and 3b are secured together by placing a rod through aperture 13. It is important that no part of the drill string component is released to obstruct a well. There is thus provided a groove 14 to facilitate insertion of rod 1 5 to secure parts 3a and 3b together (see figure 7). As shown diagrammatically in figure 7 parts 3a and 3b are interengaged within recess 1 6 of body portion 2 with aperture 1 3 aligned with groove 14. Rod 1 5 is then guided by groove 14 into aperture 1 3 to secure parts 3a and 3b together. Once the rod 1 5 is inserted a grub screw 17 may be inserted to retain pin 1 5 in place. As is shown diagrammatically in figure 7 rod 1 5 is deflected as it is inserted within aperture 13 so that it would be extremely difficult for rod 1 5 to dislodge. Further, as it would be rare for rod 1 5 to be aligned with groove 14, the chance of rod 1 5 separating is further minimised. Preferably groove 14 is provided in the top end of body portion 2 so that rod 1 5 will not be forced against groove 14 by the force of gravity. The drill string component is preferably formed of steel although the rollers 4 could be formed of suitable plastics materials. Referring to figure 8 an embodiment incorporating a thermoplastics bearing 21 between an outer section 20 and a main body portion 22 is shown conceptually in cross section. The thermoplastics bearing 21 incorporates rectangular channels 23 to facilitate lubrication. Referring now to figure 9 there is shown an alternative embodiment in which a plastics sleeve 30 is secured directly to drill string 31 by stop collars 32 and 33. Outer section 34 is of the same construction as outer section 3 described above and is secured about plastics sleeve 30. The interior surface of outer component 34 is preferably hard faced and precision ground to reduce friction between outer component 34 and plastics sleeve 30. In use plastics sleeve 30 may be slid over one end of drill pipe 31 . Alternatively, where a hinged or multi-part sleeve is employed, the sleeve may be placed about drill pipe 31 . A first collar 32 may then be secured about sleeve 30 at one end thereof. The collars may be of single or multipart construction. Outer component 34 may then be placed about plastics sleeve 30 and a rod inserted within bore 35 to secure the parts together (as previously described). Stop collar 33 may then be secured about the other end of plastics sleeve 30 to secure plastics sleeve 30 to drill pipe 31 and retain outer component 34 between stop collars 32 and 33. Although this invention has been described in relation to a component for use with a drill string it will be appreciated that the principles of the invention may be applied to a component for installing casing or in other drilling applications. It will be appreciated that the present invention provides an arrangement for mounting rollers which minimises the likelihood of parts of a drill string component obstructing a well. Further, the invention provides a means of reliably securing together multipart outer components which provides strength and minimises the risk of components obstructing a well. Where in the foregoing description reference has been made to integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth. Although this invention has been described by way of example it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope of the invention as defined in the appended claims.

Claims: CLAIMS: 1 . A friction reducing tool for drilling applications comprising a generally tubular body portion having a cavity in a side wall thereof which accommodates a roller, wherein the cavity is dimensioned so that the roller can be introduced into the cavity from the interior of the body portion but cannot pass out of the cavity to the exterior of the body portion. 2. A tool as claimed in claim 1 wherein the roller is provided with projections at either end thereof which locate within overhang portions of the body portion. 3. A tool as claimed in claim 2 wherein the projections are in the form of tubular extensions at either end of the roller. 4. A tool as claimed in claim 2 or claim 3 wherein the overhang portions are substantially complementary to the shape of the projections. 5. A tool as claimed in any one of the preceding claims wherein the roller has a bore therethrough to accommodate an axle, the diameter of the bore increasing towards the outer ends thereof to reduce sheer forces on the axle. 6. A tool as claimed in any one of the preceding claims wherein a plurality of cavities are provided about the periphery of the tool. 7. A tool as claimed in any one of the preceding claims wherein a plurality of rollers are provided in each cavity. 8. A friction reducing tool having an inner component securable to or about a drill string and an outer component rotatable about the inner component, wherein the outer component is formed in multiple parts secured together by rods and is located within an annular recess in the inner component, and wherein a groove is provided in the inner component adjacent the recess to enable a rod to be inserted whilst parts of the outer component are assembled about the recess. 9. A tool as claimed in claim 8 wherein the groove is inclined downwardly from one end of the inner component to the recess. 10. A tool as claimed in claim 8 or claim 9 wherein each part of the outer component is provided with interengaging tongues so that the parts may be joined in a hinged manner. 1 1 . A tool as claimed in any one of claims 8 to 10 wherein the outer component is formed in two parts. 1 2. A tool as claimed in any one of claims 8 to 1 1 wherein a plastics sleeve is provided between the inner and outer components. 1 3. A tool as claimed in any one of claims 8 to 1 2 wherein the inner component is a sub-assembly having couplings for engagement to sections of a drill pipe. 1 4. A friction reducing tool comprising a plastics sleeve for securement about a drill pipe, first and second collars to secure the plastics sleeve to a drill pipe at either end thereof and an outer component for securement about the plastics sleeve between the collars wherein the outer component is provided with a plurality of friction reducing rollers about the periphery thereof. 1 5. A tool as claimed in claim 14 wherein the outer component is formed in a plurality of parts which is secured together by rods passing through apertures in interengaging faces of the parts. 1 6. A tool as claimed in claim 14 or claim 1 5 wherein the interior faces of the parts are hard faced and ground. 1 7. A method of assembling a friction reducing tool as claimed in claim 14 about a drill pipe comprising: i/ placing a plastics sleeve about the drill pipe; ii/ securing a collar about one end of the plastics sleeve; iii/ positioning the outer component about the plastics sleeve; and iv/ securing a collar about the other end of the plastics sleeve to retain the outer component about the plastics sleeve between the collars. 1 8. A method as claimed in claim 1 7 wherein the outer component is formed in a plurality of parts which are secured together by inserting a rod through apertures in interengaging faces of the parts when the parts are bought together in step iii.

Inventors: MURRAY GEOFFREY NEIL, MURRAY, GEOFFREY, NEIL
Applicants: AUSTOIL TECHNOLOGY LIMITED, MURRAY GEOFFREY NEIL, MURRAY, GEOFFREY, NEIL
Application year: 1998
Main classification: E21B17
IPC codes: E21B17