Drilling tool with retractable pilot drilling unit
First Claim
1. A drilling tool for pilot drilling a subterranean formation, comprising:
- a tubular outer housing having means at the upper end thereof for connection to a drill pipe string and containing a stator of a fluid operated drilling motor;
a tubular inner housing axially supported in said outer housing and rotationally free with respect thereto carrying a rotor of a fluid operated drilling motor on the exterior thereof; and
a pilot drilling unit axially disposable in and retractable from the interior of said inner housing and including a reaction surface at the top thereof for producing an axially forwardly directed force on said pilot drilling unit in response to flow of drilling fluid to said motor and a drill bit at the bottom thereof, said pilot drilling unit and said inner housing including mutually engageable means for preventing rotation of said pilot drilling unit within said inner housing while permitting axial movement of said pilot drilling unit therewithin.
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Accused Products
Abstract
The present invention comprises a drilling tool including a retractable pilot drilling unit driven by a fluid operated motor, the motor comprising a stator mounted on the interior of a tubular outer housing and a rotor mounted on the exterior of a tubular inner housing axially supported in said outer housing and rotationally free with respect thereto. The pilot drilling unit is rotationally fixed within the inner housing, but axially moveable therewithin so that pressure of drilling fluid used to drive the motor will also act on reaction surfaces of the pilot drilling unit to urge it axially forward. The top of the pilot drilling unit includes a fishing head for retracting the pilot drilling unit from the drilling tool, and reinserting it therein.
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Citations
8 Claims
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1. A drilling tool for pilot drilling a subterranean formation, comprising:
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a tubular outer housing having means at the upper end thereof for connection to a drill pipe string and containing a stator of a fluid operated drilling motor; a tubular inner housing axially supported in said outer housing and rotationally free with respect thereto carrying a rotor of a fluid operated drilling motor on the exterior thereof; and a pilot drilling unit axially disposable in and retractable from the interior of said inner housing and including a reaction surface at the top thereof for producing an axially forwardly directed force on said pilot drilling unit in response to flow of drilling fluid to said motor and a drill bit at the bottom thereof, said pilot drilling unit and said inner housing including mutually engageable means for preventing rotation of said pilot drilling unit within said inner housing while permitting axial movement of said pilot drilling unit therewithin. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification