GB2327458A - Locking arrangement - Google Patents

Abstract

Relative rotation between tubular members (101, 102), which may be part of a downhole tool, is alternatively permitted and prevented by a locking arrangement comprising a rotary cam (105) with associated cam followers (103) carried in apertures in one (102) of the tubular members. In one position of the cam (105), the cam followers (103) are engaged in recesses (106) in the other (101) tubular member, while in a second position of the cam (105) the cam followers (103) are released from the recesses (106). The cam (105) is rotated by axial movement of a sleeve (114) which is biased in one direction by a spring (115) and can be driven in the opposite direction by fluid pressure produced by a dart (110) seating on a leading edge (113) of the sleeve (114) to obturate fluid flow through the tubular members.

Description

Locking Arranaement This invention relates to a locking arrangement for locking rotation of one member relative to another member. The invention has particular, although not exclusive, utility for alternatively connecting and disconnecting two relatively rotatable members of a down hole tool.

The present invention provides a locking arrangement for alternatively preventing and permitting relative rotat-ion between first and second members arranged on and rotatable about a common axis; the arrangement comprising a cam rotatable within a portion of the first member between first and second positions; at least one cam follower which, in a first position of the cam, engages in a formation in the second member to lock the first and second members together rotationally, and which cam follower, in a second position of the cam, disengages from said formation to permit relative rotation between the first and second members; and means operable by a pressurised fluid to produce rotation of the cam.

Preferably, the or each cam follower is a roller which is engageable in a recess acting as said formation, and the or each roller is located in an aperture formed in the first member.

The cam is preferably rotatable by means of axial movement of a co-operating member, produced by said application of pressurised fluid.

The co-operating member may extend through an aperture passing substantially axially through the cam.

The co-operating member and the cam may suitably cooperate by means of an auger screw thread.

Preferably, at least one resilient member biases the co-operating member to a position in which the cam is arranged at an unlocked orientation, and application of the pressurised fluid moves the cam to a locking position.

The pressurised fluid may be arranged to act upon an actuator which, in turn, acts upon the co-operating member. The actuator may be removable from the apparatus.

In a particularly preferred form of the invention, the first and second members are tubular and form a downhole tool adapted to form part of a drill string having a continuous bore for circulation of drilling fluid; and said cooperating member is shaped to provide an apertured seat in the bore, and said actuator is an object which can be passed through the bore in the flow of drilling fluid to engage said seat to obturate fluid flow.

An embodiment of the invention will be described, by way of example, with reference to the drawing, the single figure of which is a cross-section of part of a downhole tool incorporating a locking arrangement.

The locking arrangement shown is used in association with a down hole tool 100 (illustrated in cross-section about centre line 200) which has a first drill pipe 101 connected to a second drill pipe 102.

The locking arrangement comprises a plurality of cam followers in the form of rollers 103 carried in apertures in a circumferential wall 104 of an end of the second drill pipe 102 which is arranged within an end of the first drill pipe 101. Rotation of the cam 105 to a locking position causes outward movement of the rollers 103 to co-operate with associated annular grooves 106 at a wall of the first drill pipe 101 to lock the pipes 101,102 together for rotation.

The cam 105 is rotated to its locking position in the following way: a. an actuator in the form of a dart 110 is fed down an internal bore of the drill pipe; b. a pressurised fluid P is caused to act at the rear 111 of the dart 110 to force a tapered leading edge 112 of the dart to act against a co-operating activating edge 113 of a sleeve 114; c. the sleeve 114 is thus forced to slide downwardly; d. a portion of the sleeve 114 passes through and co operates with a central aperture of the cam 105 by means of an auger thread. Downward movement of the sleeve 114 thus causes rotation of the cam 105 to its locking position.

The sleeve 114 is biased to its unlocking position by means of a plurality of compression springs 115.

When the fluid pressure P acting on the dart 110 is released, relative rotation between the first and second pipes 101,102 will tend to push the rollers 103 inwardly to their unlocked position. This biasing, and the biasing of springs 115, causes the cam 105 to rotate to its unlocked position to release the locking arrangement.

A plurality of locking arrangements may be arranged at spaced positions along a string of drill pipes. Each locking arrangement may have an associated dart. The dart for the lowermost locking arrangement may be dimensioned or arranged so that it can pass through the uppermost locking arrangements.

In an alternative arrangement, the dart 110 causes radial expansion of the sleeve 114 to rotate the cam 105 to its locking position.

Attention is drawn to my copending Application No 9605006.7 (serial No 2298676) from which this Application is divided, and which described and claims a locking arrangement having similarities to the foregoing but making use of a double cam arrangement and particularly adapted for use in bicycles.

Claims (12)

1. Claims

   1A locking arrangement for alternatively preventing and permitting relative rotation between first and second members arranged on and rotatable about a common axis; the arrangement comprising a cam rotatable within a portion of the first member between first and second positions; at least one cam follower which, in a first position of the cam, engages in a formation in the second member to lock the first and second members together rotationally, and which cam follower, in a second position of the cam, disengages from said formation to permit relative rotation between the first and second members; and means operable by a pressurised fluid to produce rotation of the cam.
2. 2 An arrangement according to Claim 1, in which the or each cam follower is a roller which is engageable in a recess acting as said formation.
3. 3 An arrangement according to Claim 2, in which the or each roller is located in an aperture formed in the first member.
4. 4 A locking arrangement in accordance with any preceding Claim in which the cam is rotatable by means of axial movement of a co-operating member, produced by said application of pressurised fluid.
5. 5 A locking arrangement in accordance with Claim 4 in which the co-operating member extends through an aperture passing substantially axially through the cam.
6. 6 A locking arrangement in accordance with Claim 5 in which the co-operating member and the cam co operate by means of an auger screw thread.
7. 7 A locking arrangement in accordance with any preceding Claims in which at least one resilient member biases the co-operating member to a position in which the cam is arranged at an unlocked orientation.
8. 8 A locking arrangement in accordance with any one of Claims 4 to 7, in which application of the pressurised fluid moves the cam to a locking position.
9. 9 A locking apparatus in accordance with Claim 8 in which the pressurised fluid is arranged to act upon an actuator which, in turn, acts upon the co operating member.
10. 10 A locking apparatus in accordance with Claim 9 in which the actuator is removable from the apparatus.
11. 11 A locking arrangement according to Claim 10, in which the first and second members are tubular and form a downhole tool adapted to form part of a drill string having a continuous bore for circulation of drilling fluid; and in which said cooperating member is shaped to provide an apertured seat in the bore, and said actuator is an object which can be passed through the bore in the flow of drilling fluid to engage said seat to obturate fluid flow.
12. 12 A locking arrangement substantially as herein described with reference to the accompanying drawing.