Apparatus for Preventing Separation of Downhole Motor from Drillstring

Abstract

A downhole motor for a drillstring has a housing with upper and lower portions coupled to one another. A rotor in the lower portion has an outward tapered receptacle at one end. An extension is coupled to the rotor and is disposed relative to a seat in the housing. An outer body of the extension has an external shoulder to engage the seat with separation of the upper and lower housing portions. An end of this outer body is disposed in the outward tapered receptacle of the rotor and defines an internal taper tapering inward in an internal passage of the body. An inner body is inserted into the internal passage of the outer body. An end of the inner body wedges the internal inward taper at the end of the outer body into the outward tapered receptacle on the rotor to hold the extension on the rotor. Should the lower housing portion separate from the upper housing portion, the shoulder on the extension can engage the seat so that the motor does not fully separate.

What is claimed is: 
     
         1 . A downhole motor for a drillstring, the motor comprising:
 a housing having upper and lower portions coupled to one another and having a seat;   a rotor disposed in the lower portion and having an outward tapered receptacle at a distal end; and   an extension having a lower end coupled to the rotor and having an upper end disposed in the upper portion beyond the seat, the extension at least including:
 an outer body defining a first internal passage from a first end to a second end, the first end having an external shoulder disposed thereabout to engage the seat with separation of the upper and lower portions of the housing from one another, the second end disposed in the outward tapered receptacle of the rotor and defining an internal taper tapering inward in the first internal passage; and 
 an inner body having a third end and a fourth end, the inner body inserted into the first internal passage of the outer body, the fourth end wedging the internal inward taper at the second end of the outer body into the outward tapered receptacle on the rotor. 
   
     
     
         2 . The motor of  claim 1 , wherein the rotor defines a through-bore communicating with the outward tapered receptacle; and wherein the inner body defines a second internal passage from the third end to the fourth end, the second internal passage communicating with the through-bore of the rotor. 
     
     
         3 . The motor of  claim 1 , wherein the third end of the inner body comprises external thread threading to internal thread of the first internal passage at the first end of the outer body. 
     
     
         4 . The motor of  claim 1 , wherein the inner and outer bodies are tubular. 
     
     
         5 . The motor of  claim 1 , wherein the internal inward taper of the second end of the outer body comprises a conical wedge formed on the second end of the outer body, the conical wedge expandable outward, by the inner body, into the outward tapered receptacle on the rotor. 
     
     
         6 . The motor of  claim 5 , wherein the conical wedge defines a plurality of axial scores thereabout facilitating the expansion outward. 
     
     
         7 . The motor of  claim 5 , wherein the conical wedge defines a plurality of axial cuts thereabout forming a plurality of tabs. 
     
     
         8 . The motor of  claim 1 , wherein the external shoulder disposed about the first end of the outer body comprises:
 a tapered head on the first end having a ledge disposed thereabout;   an expandable shoulder disposed on the tapered head against the ledge; and   a nut tightened on the first end and expanding the expandable shoulder outward on the tapered head.   
     
     
         9 . The motor of  claim 1 , wherein the seat comprises a landing shoulder fixedly installed in the upper portion or integrally formed in the upper portion. 
     
     
         10 . An extension affixing to a receptacle on a distal end of a rotor for a downhole motor, the motor having a seat disposed in a housing between upper and lower portions coupled together, the extension comprising:
 an outer body defining a first internal passage from a first end to a second end, the first end having an external shoulder disposed thereabout to engage the seat with separation of the upper and lower portions of the housing from one another, the second end disposed in the receptacle of the rotor and defining an internal taper tapering inward in the first internal passage; and   an inner body defining a second internal passage from a third end to a fourth end, the inner body inserted into the first internal passage of the outer body, the fourth end wedging the internal inward taper at the second end of the outer body into the receptacle of the rotor.   
     
     
         11 . The motor of  claim 10 , wherein the inner body defines a second internal passage therethrough from the third end to the fourth end. 
     
     
         12 . The motor of  claim 10 , wherein the third end of the inner body comprises external thread affixing to internal thread of the first internal passage at the first end of the outer body. 
     
     
         13 . The motor of  claim 10 , wherein the inner and outer bodies are tubular. 
     
     
         14 . The motor of  claim 10 , wherein the internal inward taper of the second end of the outer body comprises a conical wedge formed on the second end of the outer body, the conical wedge expandable outward by the inner body into the receptacle on the rotor. 
     
     
         15 . The motor of  claim 14 , wherein the conical wedge defines a plurality of axial scores thereabout facilitating the expansion outward. 
     
     
         16 . The motor of  claim 14 , wherein the conical wedge defines a plurality of axial cuts thereabout forming a plurality of tabs. 
     
     
         17 . The motor of  claim 10 , wherein the external shoulder disposed about the first end of the outer body comprises:
 a tapered head disposed on the first end and having a ledge disposed about the first end;   an expandable shoulder disposed on the tapered head of the first end against the ledge; and   a nut tightened on the first end and expanding the expandable shoulder outward on the tapered head.   
     
     
         18 . A method of assembling a downhole motor for a drillstring, the method comprising, not necessarily in sequence:
 coupling an upper portion of a motor housing to a lower portion of the motor housing;   affixing a lower end of an extension to a receptacle on a distal end of a rotor disposed in the lower portion of the motor housing by—
 inserting a proximal end of an outer body of the extension into the receptacle of the rotor, 
 inserting an inner body into the outer body toward an internal inward taper in a first internal passage of the outer body, and 
 wedging the internal inward taper at the proximal end of the outer body into the receptacle of the rotor with the inserted inner body; and 
   arranging the upper end of the extension to engage relative to a seat in the motor housing with separation of the upper and lower portions from one another.   
     
     
         19 . The method of  claim 18 , wherein inserting the inner body into the outer body comprises threading external thread on the inner body to internal thread in the first internal passage of the outer body. 
     
     
         20 . The method of  claim 18 , wherein wedging the internal inward taper at the proximal end of the outer body into the receptacle of the rotor with the inserted inner body comprises expanding a conical wedge, formed on the internal inward taper of the second end of the outer body, outward, by the inner body, into an outward taper of the receptacle on the rotor.