Claims
- 1. A method of making a cylindrical helical seamed tube having a tube longitudinal axis from a metal strip having a strip longitudinal axis and parallel longitudinal edges being a leading edge adjacent a leading portion of said metal strip, and a trailing edge, adjacent a trailing portion of said metal strip, comprising the following steps:continuously feeding said metal strip into a tubing former to form said metal strip into a helical tube with said leading and trailing edges juxtaposed, said tubing former defining an aperture with a cylindrical wall, said feeding such that said strip longitudinal axis is at a substantially constant acute angle with respect to said tube longitudinal axis until said tube is substantially formed within said tubing former with said leading and trailing edges juxtaposed until said acute angle between 1 and 25 degrees; applying pressure on at least said leading edge, leading portion, trailing edge and trailing portion in the direction of said cylindrical wall such that said leading edge, trailing edge and trailing portion substantially conform to said cylindrical wall; fusing said juxtaposed leading and trailing edges together to form a fused seam; and maintaining said leading and trailing edges in a juxtaposed position until said seam cools sufficiently to maintain said juxtaposed position.
- 2. The method of claim 1 wherein said substantially constant acute angle between said strip longitudinal axis and said tube longitudinal axis is between 3 and 25 degrees.
- 3. The method of claim 1 wherein said substantially constant acute angle between said strip longitudinal axis and said tube longitudinal axis is adjustable.
- 4. The method of claim 1 including the step of applying pressure on said leading edge and leading portion of the metal strip in the direction of said cylindrical wall after said leading edge enters said tubing former so that said leading edge and leading portion substantially conform with said cylindrical wall.
- 5. The method of claim 1 wherein said step of feeding said metal strip includes applying a force on said metal strip in the direction of said strip longitudinal axis and into said tubing former after said leading edge and leading portion have entered said tubing former and been partially formed.
- 6. The method of claim 4 wherein said step of feeding said metal strip includes applying a force on said metal strip in the direction of said strip longitudinal axis after said leading edge and leading portion have entered said tubing former and been partially formed.
- 7. The method of claim 1 including the further step, after said tube is substantially formed within said tubing former with said leading and trailing edges juxtaposed, of applying pressure on a substantial portion of the inner wall of said tube in the direction of said cylindrical wall such that same substantially conforms to said cylindrical wall.
- 8. The method of claim 1 wherein said pressure is applied by rollers.
- 9. The method of claim 1 wherein said fusing is accomplished by welding.
- 10. The method of claim 9 wherein said welding is performed on a top portion of said tube, such that said tube is generally below a welding head.
- 11. The method of claim 10 comprising the step, immediately prior to welding, of passing said tube through a spacer defining a tapered aperture having an entrance end with a diameter slightly larger than the outside diameter of said tube and having an exit end with substantially the same diameter as the outside diameter of said tube, said spacer movable along said tube longitudinal axis.
- 12. The method of claim 1 wherein said step of maintaining said leading and trailing edges in a juxtaposed position until said seam cools comprises passing said tube through a cooling aperture with a diameter substantially equal to the outside diameter of said tube, said cooling aperture further comprising a groove to accommodate said seam.
- 13. The method of claim 1 further comprising the step of passing said tube through a set of forming rollers to remove irregularities in the cylindrical shape of said tube.
CROSS REFERENCE TO RELATED APPLICATION
This application is a divisional application of patent application Ser. No. 09/421, 684 filed Oct. 20, 1999, now U.S. Pat. No. 6,145,732.
US Referenced Citations (13)