Joint for Double-Walled Drill Pipe (Patent No: 755976)

Inventor: Becker, Floyd W.

Location: Calgary

Comments: N/A

Description:
Claims:

1. A double-walled drill pipe comprising inner and outer pipes coaxially disposed to form an annular chamber, said outer pipe having respective tapered ends formed as a male connector and a female coupling for disconnectably joining with mating connectors and couplings of other lengths of said outer pipe, the male connector having a threaded tapering portion and a progressively stepped bore including a first bore formed in the narrow end having a diameter substantially equal to the inner diameter of said inner pipe, a second bore being substantially a free fit for said inner pipe, and a third larger bore having a diameter intermediate the inner diameter of said outer pipe and the outer diameter of said inner pipe, a peripheral groove and transverse apertures formed in said threaded portion communicating with said third bore and the exterior of said male connector, the female coupling having an interior thread reducing in diameter in the axial inward direction and a fourth bore formed in said female coupling spaced axially inwardly from said interior threading having an inner diameter which is a free fit for said inner pipe, said inner pipe extending from a seating in said second bore upwardly into said female coupling beyond said fourth bore, and said female coupling having an internal groove communicating with axially formed passages registering with said peripheral groove and said transverse apertures to connect annular chambers of joined lengths of said drill pipe.

2. A double wall drill pipe having inner and outer pipes defining central and annular passages and having joint means for joining lengths of drill pipe in end-to-end relation whereby to provide continuous separate passageways between said central passages and between said annular passages along a drill string, said joint means comprising a tubular end fitting secured to the lower end of said outer pipe and having a shoulder, a conic outer face tapering away from said end to a diameter less than the internal diameter of said outer pipe, the end of the fitting remote from said outer pipe having a radially inturned flange and a cylindrical bore, said bore being a free fit for said inner cylindrical pipe and said flange having an inner diameter substantially equal to the inner diameter of said inner pipe, and said fitting having a second bore disposed intermediate said cylindrical bore and an end of said outer pipe which is intermediate the inner diameter of said outer pipe and the outer diameter of said inner pipe, and peripherally spaced apertures piercing said end fitting wall and opening into said second bore to communicate with said annular passage; and a second fitting on the other end of said tubular body having an internal thread complementary with said outer thread for receiving an end fitting of another length of drill pipe, said other fitting having apertures extending axially between said annular passage and a plurality of connecting radial apertures opening inwardly, said other fitting having an internal bore adjacent said tubular body which is a clearance fit for said second pipe, said inner pipe having a length greater than that of the outer pipe whereby when one end of said inner pipe is supported on said flange, the other end extends within said second fitting.


3. A double wall drill pipe as set forth in Claim 2 wherein said first and second fittings have their threaded portions grooved respectively externally and internally in the planes of their associated radial apertures.