Abstract: The invention relates to a drive system, in particular a downhole drilling assembly (10). In the preferred embodiment, a bearing mechanism (14,24) of the assembly (10) is isolated from a gear mechanism (20) of the assembly (10), to prevent failure of the bearing mechanism (14, 24) due to vibration and heat generated by the gear mechanism (20) in use. A lower bearing unit (24) of the bearing mechanism (24) is coupled to the gear mechanism (20) by a shock eliminating coupling assembly (22), which prevents the transmission of shock loads to the gear mechanism (20). Also, the gear mechanism (20) is coupled through a shock eliminating coupling assembly (18) to a turbine (16) and thus to an upper bearing unit (14). Sealing assemblies (60, 116) are provided for the gear mechanism (20) and the upper bearing unit (14) to prevent drilling fluid ingress and consequent damage. The assembly (10) may also carry a torsionally flexible drive shaft (46).

Abstract: The invention relates to a drive system, in particular a downhole drilling assembly (10). In the preferred embodiment, a bearing mechanism (14,24) of the assembly (10) is isolated from a gear mechanism (20) of the assembly (10), to prevent failure of the bearing mechanism (14, 24) due to vibration and heat generated by the gear mechanism (20) in use. A lower bearing unit (24) of the bearing mechanism (24) is coupled to the gear mechanism (20) by a shock eliminating coupling assembly (22), which prevents the transmission of shock loads to the gear mechanism (20). Also, the gear mechanism (20) is coupled through a shock eliminating coupling assembly (18) to a turbine (16) and thus to an upper bearing unit (14). Sealing assemblies (60, 116) are provided for the gear mechanism (20) and the upper bearing unit (14) to prevent drilling fluid ingress and consequent damage. The assembly (10) may also carry a torsionally flexible drive shaft (46).

Abstract: The invention relates to a drive system, in particular a downhole drilling assembly (10). In the preferred embodiment, a bearing mechanism (14, 24) of the assembly (10) is isolated from a gear mechanism (20) of the assembly (10), to prevent failure of the bearing mechanism (14, 24) due to vibration and heat generated by the gear mechanism (20) in use. A lower bearing unit (24) of the bearing mechanism (24) is coupled to the gear mechanism (20) by a shock eliminating coupling assembly (22), which prevents the transmission of shock loads to the gear mechanism (20). Also, the gear mechanism (20) is coupled through a shock eliminating coupling assembly (18) to a turbine (16) and thus to an upper bearing unit (14). Sealing assemblies (60, 116) are provided for the gear mechanism (20) and the upper bearing unit (14) to prevent drilling fluid ingress and consequent damage. The assembly (10) may also carry a torsionally flexible drive shaft (46).

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: 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 drive system, in particular a downhole drilling assembly (10). In the preferred embodiment, a bearing mechanism (14, 24) of the assembly (10) is isolated from a gear mechanism (20) of the assembly (10), to prevent failure of the bearing mechanism (14, 24) due to vibration and heat generated by the gear mechanism (20) in use. A lower bearing unit (24) of the bearing mechanism (24) is coupled to the gear mechanism (20) by a shock eliminating coupling assembly (22), which prevents the transmission of shock loads to the gear mechanism (20). Also, the gear mechanism (20) is coupled through a shock eliminating coupling assembly (18) to a turbine (16) and thus to an upper bearing unit (14). Sealing assemblies (60, 116) are provided for the gear mechanism (20) and the upper bearing unit (14) to prevent drilling fluid ingress and consequent damage. The assembly (10) may also carry a torsionally flexible drive shaft (46).