Abstract: A clamp holds two members together. The first member includes a recess into which a fastener is located. A bore is provided to the recess to allow a tool to be used to operate the fastener. The second member is arranged to accept the fastener and so join the members. The recess and bore are sized to prevent release of the fastener through the bore. In this way, the fastener cannot easily be removed or lost when the clamp is in use and is tamperproof. The clamp is used to hold portions of a sleeve around a body of the tool, and to hold scraper blades and/or brushes to the body.

Abstract: A clamp (10) for holding two members together. The first member includes a recess into which a fastener is located. A bore is provided to the recess to allow a tool to be used to operate the fastener. The second member is arranged to accept the fastener and so join the members. The recess and bore are sized to prevent release of the fastener through the bore. In this way, the fastener cannot easily be removed or lost when the clamp is in use and is tamperproof. Embodiments of a downhole tool are described where the clamp is used to hold portions of a sleeve around a body of the tool, and to hold scraper blades and/or brushes to the body.

Abstract: A turbine drive system (10) for a downhole tool comprises a stator (12) and a rotor (14). The rotor (14) is mounted externally of the stator (12) and, in use, the rotor (14) is rotated relative to the stator (12) to drive the downhole tool. The stator (12) is provided with a through bore (15) for providing access through the drive system (10).

Abstract: A bearing (10) for use in a downhole motor assembly having an inner race (12) formed as a unitary construction. The inner race (12) has an inner surface (14) defining a first diameter (D1) and an outer surface (16) defining an second diameter (D2) and a number of race-ways (18). The bearing (10) also has an outer race (20) having an inner surface (22) defining a first diameter (D3), an outer surface (26) defining a second diameter (D4) and a number of race-ways (28). Bearing elements (30) are provided in the raceways (18, 28) to couple the inner race (12) and the outer race (20) such that, in use, the inner race (12) and the outer race (20) can rotate relative to each other. The inner race (12) of the bearing (10) is configured so that an inner diameter of the inner race is outside a drill through of a downhole motor assembly.

Abstract: A ball valve seat (10) is disclosed which provides a temporary seal for a plug (40). The valve seat comprises a substantially cylindrical body (30) of a first volume, which defines a seating surface (34). A pressure differential is developed across the valve seat when the plug sealingly engages the seating surface. The body is formed of an elastic material which compresses from a first volume to a smaller second volume by application of a force on the plug, to provide a clearance which is greater than a plugging dimension of the plug, thus allowing passage of the plug downstream. After passage of the plug, the body returns to the first volume.

Abstract: A downhole tool which can perform a task in a well bore, such as circulating fluid radially from the tool. The function is selectively performed by virtue of a sleeve moving within a central bore of the tool. Movement of the sleeve is effected by dropping a ball through a ball seat on the sleeve. Movement of the sleeve is controlled by an index sleeve such that the tool can be cycled back to the first operating position by dropping identical balls through the sleeve. Embodiments are described wherein the balls are deformable, the seat is deformable and the seat provides a helical channel through which the ball passes.

Abstract: A clamp (10) for holding two members (12, 14) together. The first member includes a recess (30) into which a fastener (38) is located. A further access port (42) is provided to the recess to allow a tool (44) to be used to operate the fastener. The second member is arranged to accept the fastener and so join the members. The recess and port are sized to prevent release of the fastener through the port. In this way, the fastener cannot easily be removed or lost when the clamp is in use and is tamperproof. Embodiments of a downhole tool are described where the clamp is used to hold portions of a sleeve around a body of the tool, and to hold scraper blades (384) and/or brushes (394) to the body.

Abstract: A downhole tool including a selectively releasable joint, a downhole drilling assembly including the downhole tool, and a corresponding method. In one embodiment of the invention, a downhole drilling assembly includes a downhole tool having a first body and a second body mounted for relative rotation; a joint part for use in forming a selectively releasable joint between the second body and a part of the assembly coupled to the second body; and one or more locking member(s) for locking the first and second bodies relative to one another against relative rotation so as to allow a release force to be applied through the first body to release the releasable joint and allow the tool to be separated from the part of the assembly.

Abstract: A turbine is disclosed which includes a turbine blade housing having an inner facing portion of a first material having a first coefficient of expansion, and a turbine blade body having an outer facing portion of a second coefficient of expansion greater than said first coefficient. In a preferred embodiment, the blade housing comprises a number of steel shroud rings and the turbine blade body comprises a number of stators and rotors of a thermoplastic material. An interference fit between stator blades and the shroud rings is enhanced in use due to the difference in thermal and/or hydrophilic coefficients of expansion of the first and second materials.

Abstract: The invention relates to a downhole tool including a selectively releasable joint, a downhole drilling assembly including the downhole tool, and to a corresponding method. In one embodiment of the invention, a downhole drilling assembly includes a downhole tool having a first body and a second body mounted for relative rotation; a joint part for use in forming a selectively releasable joint between the second body and a part of the assembly coupled to the second body; and one or more locking member(s) for locking the first and second bodies relative to one another against relative rotation so as to allow a release force to be applied through the first body to release the releasable joint and allow the tool to be separated from the part of the assembly.

Abstract: A turbine is disclosed which includes a turbine blade housing having an inner facing portion of a first material having a first coefficient of expansion, and a turbine blade body having an outer facing portion of a second coefficient of expansion greater than said first coefficient. In a preferred embodiment, the blade housing comprises a number of steel shroud rings and the turbine blade body comprises a number of stators and rotors of a thermoplastic material. An interference fit between stator blades and the shroud rings is enhanced in use due to the difference in thermal and/or hydrophilic coefficients of expansion of the first and second materials.