Joint for double-walled drill pipe

Claim 2

A length of double-walled pipe for a reverse-circulation drill string comprising an outer pipe and an inner pipe concentrically disposed to provide a flow passage of annular cross section between said pipes, the outer pipe having threaded box and pin ends, said box and pin ends being thickened radially inwardly from the ends of said outer pipes, the ends of said inner pipe being spaced axially inwardly of the pin ends of said outer pipe and being also spaced axially inwardly from the innermost ends of said threaded ends, said inner pipe being fixed coaxially in said outer pipe by longitudinal spacing members engaging said inner and outer pipes and bridging said flow passage and a connector tube comprising a central portion having an inner diameter the same as the inner diameter of the inner pipes and having sleeve end portions formed with a coaxial bore having an inner diameter sufficiently larger than the exterior diameter of the inner pipes for engaging said inner pipes as a free sliding fit, and fluid seal means seated in said sleeve end portions and adapted to frictionally engage the ends of inner pipes of adjacent pipe lengths when the pipe lengths are connected together by threaded engagement of said pin and box ends and wherein said longitudinal spacing members extend along the end portions of said inner pipe and terminate in said thickened end portion of the outer pipe, terminal portions of said spacing members being tapered to guide a sleeve end to concentric engagement axially with an inner pipe end and having their radial inward margins relieved to pass said sleeve end portions.

Claim 3

A length of double-walled pipe for a reverse circulation drill string comprising an outer pipe and an inner pipe concentrically disposed to provide a flow passage of annular cross section between said pipes, the outer pipe having threaded box and pin ends, said box and pin ends being thickened radially inwardly from the ends of said outer pipes, the ends of said inner pipe being spaced axially inwardly of the pin ends of said outer pipe and being also spaced axially inwardly from the innermost ends of said threaded ends, said inner pipe being fixed coaxially in said outer pipe by longitudinal spacing members engaging said inner and outer pipes and bridging said flow passage and a connector tube comprising a central portion having an inner diameter the same as the inner diameTer of the inner pipes and having sleeve end portions formed with a coaxial bore having an inner diameter sufficiently larger than the exterior diameter of the inner pipes for engaging said inner pipes as a free sliding fit, and fluid seal means seated in said sleeve end portions and adapted to frictionally engage the ends of inner pipes of adjacent pipe lengths when the pipe lengths are connected together by threaded engagement of said pin and box ends and wherein the walls of said box and pin ends have greater thickness in the area which is inward axially from the said ends and wherein said inner pipe ends are spaced from the thickened wall portion by from about 0.3 to about 0.7 times the outside diameter of said inner pipe and wherein said connector tube has a sleeve end portion fractionally larger than said spacing distance and wherein said sleeve ends are thickened and each has an outside diameter which is only slightly less than in the minimum diameter portion of said pipe ends so to be a guided fit within said portions of said inner pipe ends.

Claim 4

A length of double-walled pipe for a reverse circulation drill string comprising an outer pipe and an inner pipe concentrically disposed to provide a flow passage of annular cross section between said pipes, the outer pipe having threaded box and pin ends, said box and pin ends being thickened radially inwardly from the ends of said outer pipes, the ends of said inner pipe being spaced axially inwardly of the pin ends of said outer pipe and being also spaced axially inwardly from the innermost ends of said threaded ends, said inner pipe being fixed coaxially in said outer pipe by longitudinal spacing members engaging said inner and outer pipes and bridging said flow passage and a connector tube comprising a central portion having an inner diameter the same as the inner diameTer of the inner pipes and having sleeve end portions formed with a coaxial bore having an inner diameter sufficiently larger than the exterior diameter of the inner pipes for engaging said inner pipes as a free sliding fit, and fluid seal means seated in said sleeve end portions and adapted to frictionally engage the ends of inner pipes of adjacent pipe lengths when the pipe lengths are connected together by threaded engagement of said pin and box ends and wherein the walls of said box and pin ends have greater thickness in the area which is inward axially from the said ends and wherein said inner pipe ends are spaced from the thickened wall portion by from about 0.3 to about 0.7 times the outside diameter of said inner pipe and wherein said connector tube has a sleeve end portion fractionally larger than said spacing distance and wherein said sleeve ends are thickened and each has an outside diameter which is only slightly less than in the minimum diameter portion of said pipe ends so to be a guided fit within said portions of said inner pipe ends.

Claim 5

A pipe as set forth in claim 2 wherein the walls of said outer pipe and said connector tube which define said annular passage are flared in the area where said thickened portions terminate within said outer pipes to present smooth transition portions to fluid flow in said passage.

Claim 6

A pipe as set forth in claim 3 wherein said connector tube is formed as a metal body having a smooth inner wall and a smooth outer wall with a gradual change of diameter between a central constant diameter portion and sleeve end portions of larger diameter.

Claim 7

A pipe as set forth in claim 4 wherein said connector tube is formed as a metal or other structural body having constant wall thickness and having internal peripheral grooves in said sleeve end portions adapted to seat O-ring sealing elements.