Undercut stator for a positive displacment motor
AssigneeSmith International, Inc.
InventorsLance D. Underwood, William D. Murray, Thomas K. Washburn
Life of this patent
Estimating the term…
Abstract
A Moineau style stator includes a stator tube having a plurality of rigid helical lobes formed on an inner surface thereof. The helical lobes define a major internal tube diameter that is greater than a pass through diameter of the tube such that the major diameter undercuts the pass through diameter of the tube. A major liner diameter may also be less than the pass through diameter so as to provide a suitable interference fit between rotor and stator.
Claims16
A Moineau style stator comprising:
- an integral stator tube including a longitudinal end having an internal pass through diameter;
- the stator tube defining an internal helical cavity and further including a plurality of internal rigid helical lobes formed on an inner surface of the tube, the helical cavity having a major internal tube diameter that is greater than the pass through diameter of the longitudinal end.
A subterranean drilling motor comprising:
- a rotor having a plurality of rotor lobes on a helical outer surface of the rotor;
- a stator including an integral stator tube, the stator tube including a longitudinal end having an internal pass through diameter, the stator tube defining an internal helical cavity and further including a plurality of rigid helical lobes formed on an inner surface of the tube, the helical cavity having a major internal tube diameter that is greater than the pass through diameter of the longitudinal end, the stator further including a resilient liner deployed on an inner surface of the stator tube and presented to the internal helical cavity, the resilient liner defining a major internal liner diameter that is less than the pass through diameter of the longitudinal end.
- the rotor deployable in the helical cavity of the stator tube such that an outer surface of the rotor is in a rotational interference fit with the resilient liner.
A method of fabricating a Moineau style stator, the method comprising:
- (a) providing a stator tube including at least one longitudinal end having a first pass through diameter;
- (b) forming a helical profile on an inner surface of the tube, the helical profile including a plurality of rigid internal helical lobes and a major internal tube diameter that is less than the first pass through diameter;
- and
- (c) mechanically working the at least one longitudinal end of the stator tube so as to reduce outer and inner diameters of the end such that the end has a second pass through diameter, the second pass through diameter being less than the major internal tube diameter formed in (b).
A method of fabricating a Moineau style stator, the method comprising:
- (a) providing a stator tube including at least one longitudinal end having a pass through diameter, the stator tube further including an internal relief groove wherein an inner diameter of the relief groove is greater than the pass through diameter;
- (b) assembling an electrochemical machining electrode in the relief groove, the electrode including a plurality of distinct work pieces, each of the work pieces having an outer diameter less than the pass through diameter, said assembled electrode defining a major helical diameter greater than the pass through diameter;
- (c) electrochemically machining an internal helical profile in the stator tube using the electrodes assembled in (b), the internal helical profile including a plurality of rigid helical lobes and a major internal tube diameter that is greater than the pass through diameter of the longitudinal end;
- and
- (d) disassembling and removing the electrochemical machining electrode from the stator tube.
Dependencies are inferred from the claim text.