Locking mechanisms for downhole and wireline tools

Abstract

A locking mechanism 12 for a tool 10, the locking mechanism comprising an inner locking mandril 14 and at least one outer locking sleeve 16, the inner locking mandril and the at least one outer sleeve having inner and outer co-operable shoulders 18, 20, with the inner shoulder provided on an outer surface 22 of the inner locking mandril and the outer shoulder provided on an inner surface 24 of the outer sleeve, wherein a ring element 26 may be placed between the co-operable shoulders to abut both the inner mandril and outer sleeve. A tool comprising one or more of the locking mechanisms is also claimed. The shoulders may be a continuous raised portion or ridge or may be one or more circumferential slots. The ring may be formed from one or more segments and may be three to six segments. The outer locking sleeve may be provided with a ring segment access slot. There may be a guide cover covering the ring segment access slot, which may be cruciform shaped and may comprise a cover portion and a guide portion.

Description

Description Field of the Invention The present invention relates to locking mechanisms, especially such locking mechanisms that may be used for such downhole and wireline tools such as well plugs and barriers. These may be for both oil and gas production and wireline applications, but may also be usable in other borehole applications, such as fracking, water wells, etc. Background to the Invention Locking mechanisms for downhole tools and wireline applications are typically threaded connectors. Whilst simple and reliable, they are not without their flaws, particularly as any applied toque may overtighten or loosed the threaded connectors. Summary of the Invention According to a first aspect of the present invention there is provided a locking mechanism for a tool, the locking mechanism comprising an inner locking mandril and at least one outer locking sleeve, the inner locking mandril and the at least one outer sleeve having inner and outer co-operable shoulders, with the inner shoulder provided on an outer surface of the inner locking mandril and the outer shoulder provided on an inner surface of the outer sleeve, wherein a ring element may be placed between the co-operable shoulders to abut both the inner mandril and outer sleeve. The shoulders may be provided by a continuous raised portion or ridge surrounding the surfaces. Alternatively the shoulders may be provided by one or more circumferential slots provided around the inner and / or outer surfaces of the respective sleeve / mandril. The ring element may be formed from one or more part-circular ring segments. There may be three to six ring segments. There may be at least four ring segments. There may be six ring segments. The outer locking sleeve may be provided with a ring segment access slot. There may be a guide cover provided to cover the ring segment access slot. The guide cover may be generally cruciform shaped. The guide cover may comprise a cover portion and a guide portion. An outer sleeve may extend from an inner mandril to form a locking body. In this way, multiple locking bodies may be joined to form one or more locking mechanisms. According to a second aspect of the present invention there is provided a tool with a locking mechanism according to a first aspect of the present invention. Brief Description of the Drawings Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings, in which: Fig. 1 is a part-sectional perspective view of a first embodiment tool with locking mechanism according to the present invention; Fig. 2 is a partially exploded perspective view of the tool of Fig. 1; Fig. 3 is a partially transparent / partially exploded perspective view of the tool of Fig. 1; Fig. 4 is a perspective view of a guide cover of the tool of Fig. 1; Fig. 5 is a perspective view of a split ring segment of the tool of Fig. 1; Fig. 6 is a perspective view of the outer sleeve of the tool of Fig. 1; Fig. 7 is a further perspective view of the outer sleeve of the tool of Fig. 1; Fig. 8 is a detail perspective view of a second embodiment tool with locking mechanism according to the present invention; Fig. 9 is a perspective view of a guide cover of the tool of Fig. 8; Fig. 10 is a partially transparent perspective view of a third embodiment tool with locking mechanism according to the present invention; Fig. 11 is a further partially transparent perspective view of the tool of Fig. 10; Fig. 12 is a further partially transparent perspective view of the tool of Fig. 10; and Fig. 13 is a perspective view of the inner locking mandril of the tool of Fig. 10. Referring to the drawings and initially to Fig. 1, a downhole tool 10 with a locking mechanism 12 is depicted. The locking mechanism 12 comprises an inner locking mandril 14 and an outer locking sleeve 16, the inner locking mandril 14 and the outer sleeve 16 having inner and outer co-operable shoulders 18, 20, with the inner shoulder 18 provided on an outer surface 22 of the inner locking mandril 14 and the outer shoulder 20 provided on an inner surface 24 of the outer sleeve, wherein a ring element 26 is placed within the co-operable shoulders to engage both the inner locking mandril 14 and outer sleeve 16. In the present embodiment, the inner locking mandril 14 is positioned within the outer locking sleeve 16 to form a locking assembly 28 (see Figs 6 and 7) with the inner locking mandril 14 extending from the outer locking sleeve 16. An outer mandril flange 30 is provided on the distal edge of the inner locking mandril 14 (located distally from the outer locking sleeve 16). A seal ring groove 32 is located adjacent to the outer mandril flange 30 which receives a rubber o-ring seal 31. An inner mandril flange 34 is located adjacent the seal ring groove 32, the two flanges 30, 34 defining the groove 32 on an outer surface 36 of the inner locking mandril 14. A guide slot 38 is formed along the outer surface 36 of the inner locking mandril 14. The guide slot 38 runs longitudinally along the mandril 14. The outer locking sleeve 16 is provided with a first end outer flange 40 and a second end outer flange 42. The second end outer flange 42 is provided with six bores 44 to enable mechanical attachment. A ring access aperture 46 is formed in the outer surface 48 of the outer locking sleeve 16. The ring access aperture 46 is a cruciform shape comprising generally an elongate ring segment access slot 47 running circumferentially and a slightly shorter elongate slot 49 running longitudinally. A guide cover 50 is provided which fits into the ring access aperture 46 and has a corresponding cruciform shape. The guide cover 50 comprises a cover portion 52 and a guide portion 54. A guide cover lobe 56 extends from the cover portion 52 and is provided with a lobe bore 58. A grub screw 60 and washer 62 are provided to enable mechanical attachment of the guide cover 50 onto the outer locking sleeve 16. A guide cover lip 53 extends from the underside portion of the guide portion 54. The guide cover lip 53 extends beyond the locus of the ring access aperture 46 to prevent the guide cover 50 coming loose. The guide portion 54 is thicker than the cover portion 52. The guide portion 54 seats within the guide slot 38 of the inner locking mandril 14 and allows the guide cover 50 and the outer locking sleeve 16 to selectively move along the guide slot 38 in a telescoping fashion. A ring element 26 is provided for the locking mechanism 12. The ring element 64 comprises one or more ring segments 66. In the present embodiment there are six ring segments 66 each accounting for approximately 60° of the overall ring element 26. The ring segments 66 are provided with chamfered longitudinal edges 68. A ring segment tapped bore 70 is provided at the approximate centre point of the ring segment 66. This may be used to manipulate the ring segments 66 into and out of the locking mechanism. The ring segments 66 are dimensioned such that they may pass through the outer sleeve 16 via the circumferential ring segment access slot 47. Six ring segments 66 may be passed through the circumferential ring segment access slot 47 to form the ring element 26. As each ring segment 66 is fed through the circumferential elongate slot 47 it may be moved around the mandril 14 to allow the next ring segment 66 to be fed in. Once the ring element 26 is completed, the guide cover 50 may be attached which holds the ring element 26 in place. A second embodiment tool 110 and locking mechanism 112 are depicted in Figs 8 and 9. The second embodiment is largely identical to the first embodiment and a similar numbering scheme is used to identify technical elements albeit with a prefixing “1”. The second embodiment’s main difference is in the guide cover 150 and the ring access aperture 146. The guide cover 150 has a much longer guide portion 154 than in the first embodiment with ring access aperture 146 being modified to suit with an accordingly longer longitudinal elongate slot 149. Furthermore, in the second embodiment, the locking ring segments (not shown) are stationary to the outer sleeve 116 at all times allowing the inner mandril 114 to slide whereas in the first embodiment the ring segments 66 are tied to the inner mandril 14 allowing the outer sleeve 16 to slide. A third embodiment tool 210 and locking mechanism 212 are depicted in Figs 10 to 13. The third embodiment is largely similar to the first and second embodiments and a similar numbering scheme is used to identify technical elements albeit with a prefixing “2”. The third embodiment tool 210 has a modified inner locking mandril 214. Instead of being a simple sleeve, the inner locking mandril 214 is provided with a crenelated first end 215 which fits inside the outer locking sleeve 216. Four elongate fingers 217 comprise the crenelated first end 215. The elongate fingers 217 follow the same general outer shape of the inner mandril sleeve 214. The inherent resilience of the material used to form the mandril 214 means that the elongate fingers 217 display some resilience and may be elastically deformed such that the effective diameter of the crenelated first end 215 may be reduced to fit inside the outer sleeve 216. The leading edges 219 of the elongate fingers are provided with a three-stage stepped profile 221. This both allows the fingers 217 to deflect inwardly when being presented to the outer sleeve 216, but also allows them to abut a corresponding stepped profile 223 provided on the inner surface of the outer sleeve 216. Furthermore, the inner shoulder 220 has been replaced with a series of circumferential slots 225 provided on the inner mandril 214; however this maintains in effect a series of discontinuous shoulders provided into which the ring elements 266 may be placed and retained. In the present embodiment there are four circumferential slots 225 for four ring elements 266, with each of the slots 225 spanning the gaps between the elongate fingers 217. It will be appreciated that the number of slots may be increased or decreased to suit. In addition, the number of elongate fingers may also be varied to suit the application. This arrangement allows the inner locking mandril 214 to be readily slid into place and be removable in a similar fashion. Thus, the inner locking 5 mandril 214 performs a telescopic type movement.

Claims

1. A locking mechanism for a tool, the locking mechanism comprising an inner locking mandril and at least one outer locking sleeve, the inner locking mandril and the at least one outer sleeve having inner and outer co-operable shoulders, with the inner shoulder provided on an outer surface of the inner locking mandril and the outer shoulder provided on an inner surface of the outer sleeve, wherein a ring element may be placed between the co-operable shoulders to abut both the inner mandril and outer sleeve.

2. The locking mechanism of claim 1 wherein the shoulders are provided by a continuous raised portion or ridge surrounding the surfaces.

3. The locking mechanism of claim 1 wherein the shoulders may be provided by one or more circumferential slots provided around the inner and / or outer surfaces of the respective sleeve / mandril.

4. The locking mechanism of any preceding claim wherein the ring element is formed from one or more part-circular ring segments.

5. The locking mechanism of claim 4 wherein there are three to six ring segments.

6. The locking mechanism claims 4 or 5 wherein there are at least four ring segments.

7. The locking mechanism of claims 4 to 6 wherein there are six ringsegments.

8. The locking mechanism of any preceding claim wherein the outer locking sleeve is provided with a ring segment access slot.

9. The locking mechanism of claim 8 wherein there is a guide cover provided to cover the ring segment access slot.

10. The locking mechanism of claim 9 wherein the guide cover is a generally cruciform shaped.

11. The locking mechanism of claims 9 or 10 wherein the guide cover comprises a cover portion and a guide portion.

12. The locking mechanism of any preceding claim wherein an outer sleeve extends from an inner mandril to form a locking body.

13. A tool including one or more locking mechanisms according to any preceding claim.

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