Metal fusion bonding – Process – With shaping
Reexamination Certificate
2000-09-06
2001-08-28
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
With shaping
C219S062000
Reexamination Certificate
active
06279813
ABSTRACT:
This invention is in the field of formed metal products and in particular provides a cylindrical helical seamed tube wherein the seam thereof is at an angle of less than 25 degrees, and an apparatus and method for forming same.
BACKGROUND OF THE INVENTION
Metal tubing is commonly made in a conventional tubing mill by feeding a strip of metal into a hollow cylindrical shoe with the longitudinal axis of the metal strip aligned with the axis of the shoe and the finished tubing. The welded seam is straight down the side of the tubing, aligned with the axis of the tubing as well. This requires that the width of the metal strip being formed is substantially equal to Π times the diameter of the tubing being made (ΠD). For example, for 2 inch tubing these conventional tubing mills require a strip of metal 3.14×2 inches=6.28 inches in width. Tubing mills for manufacturing such tubing are complex and costly.
It is also known to manufacture helical seamed tubing wherein a narrow metal strip is fed at an angle into a cylindrical shoe to form a hollow tube with a helical seam which is then welded. An apparatus and method for forming helical seamed tubing with a diameter of 0.5 to 2 inches is disclosed in U.S. Pat. No. 4,501,948 to Yampolsky et al. The Yampolsky patent is directed to controlling the tendency of the seam to separate once it leaves the cylindrical shoe, the control being necessary in order to maintain the seam closed in such a manner that it can be effectively welded.
Cylindrical helical seamed tube wherein the seam thereof is at an angle of less than 25 degrees with respect to the axis of said tube is not known in the prior art.
In prior art helical seamed tubing, the strip of metal used to form the tubing is substantially narrower than that needed to form straight seam tubing and the angle between the longitudinal axis of the tubing being formed and the longitudinal axis of the metal strip being fed into the cylindrical dye is relatively large. In the Yampolsky device this angle is 33 degrees. This angle corresponds to the angle between the welded seam of the tubing and the axis of the tubing. At angles less than this, the edges of the metal strip are not effectively formed and result in flat spots and bulges along the edge which cannot be effectively welded.
Helical seamed tubing with this large angle of 33 degrees between the respective axes requires a much longer seam and therefore substantial welding. For a 10 foot length of tubing, the Yampolsky device requires a weld that is approximately 11.923 feet long, an increase of 19.23% in weld length compared to a straight seam tubing. This increased length of welding is costly and causes high temperatures in the tubing and distortion.
As the seam angle increases the tube has reduced strength as well which is undesirable in most applications. A tube with a seam angle that was less than 25 degrees would be stronger, and a tube with a seam angle approaching one degree would have very similar strength to a conventional straight seam tube.
Metal coil is conventionally manufactured in standard widths and when customers order a particular width there is a left over strip which is available at a much reduced price, since its uses are very limited. In a conventional straight seam 2 inch tubing mill, any strips of material that are less than approximately 6.28 inches in width are not suitable to form the material. These narrower strips can be purchased very cheaply, since there are few uses and therefore little demand for them.
A cylindrical helical seamed tube with a low helix angle and strength approaching that of a conventional straight seam tube would be desirable, as the cost of metal to make same would be reduced.
Such a tube, and a method and apparatus of making same from a strip of metal that is only slightly narrower than ΠD would be advantageous, as the helical seam would be relatively long as opposed to conventional helical seamed tubing, thereby requiring only slightly more welding than the conventional straight seam tube. For example with an angle between the longitudinal axis of the tubing being formed and the longitudinal axis of the metal strip being fed into the cylindrical dye of only 10 degrees, a 10 foot length of tubing requires a weld that is only approximately 10.15 feet long, an increase of only 1.5% in weld length compared to a straight seam tubing.
Such a method an apparatus that allowed for forming a tube of a particular diameter from various widths of material would be particularly advantageous, as it would increase the sources of suitable material, and decrease the cost of the metal strip.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide substantially cylindrical helical seamed tubing wherein the angle between the helical seam and the axis of the tubing made is between 1 and 25 degrees as well as a method of, and apparatus for, making same from a metal strip that is somewhat less than Π times the outside diameter of the tubing made.
It is a further object of the present invention to provide such a method and apparatus wherein tubing with a given outside diameter may, with some adjustment, be made from metal strip of different widths.
The invention accomplishes its objects providing in one aspect a cylindrical helical seamed metal tube wherein the seam thereof is at an angle of between 1 and 25 degrees with respect to the axis of said tube.
In a second aspect the invention provides a method of making 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, said acute angle being between 1 and 25 degrees; after said tube is substantially formed within said tubing former with said leading and trailing edges juxtaposed, 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.
The disclosed method allows for making metal tubing from metal strip that is slightly narrower than ΠD. Prior art helical seamed tubing is not available with these small angles between the seam and tubing axis.
In a third aspect the invention provides an apparatus for making 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, said apparatus comprising: a tubing former operable 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; means for continuously feeding said metal strip into said tubing former, said means for continuously feeding operative to maintain said strip longitudinal axis at a substantially constant acute angle with respect to said tube longitudinal axis, said acute angle between 1 and 25 degrees; first means to apply pressure, after said tube is substantially formed within said tubing former with said leading and trailing edges juxtaposed, on at least said leading edge, leading portion, trailing edge a
Akins Edward A.
Harms George
Akins Edward A.
Dunn Tom
Johnson Jonathan
Lamb Charles G.
Reutlinger Middleton
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