Patent Description:
The document <CIT> discloses a high pressure tube and a method of manufacturing it.

Pipes are long, hollow tubular structures used for a variety of purposes. They are now generally produced by two distinct methods that result in either a welded or seamless pipe. In both methods, raw steel is first cast into a more workable starting form. It is then made into a pipe by stretching the steel out into a seamless tube or forcing the edges together and sealing them with a weld.

As mentioned, tubular structures such as pipe come in generally two configurations - seamless and welded. Both generally have different uses. Seamless tubes are typically lighter-weight and have thinner walls and are generally used for transporting liquids. Welded tubes are heavier, more rigid, have a better consistency, are typically straighter, and generally used for gas transportation, electrical conduit, and plumbing. Typically, they are used in instances when the pipe is not put under a high degree of stress.

The primary raw material in pipe production is steel. Steel is made up of primarily iron. Other metals that may be present in the alloy include aluminum, manganese, titanium, tungsten, vanadium, and zirconium. Some finishing materials are sometimes used during production.

Steel pipes can generally be made by two different processes. The overall production method for both processes involves three steps. First, raw steel is converted into a more workable form (e.g., ingots, blooms, slabs). Next, the pipe is formed on a continuous or semi-continuous production line. Finally, the pipe is cut and modified to meet the customer's needs.

Molten steel is made by melting iron ore and coke (a carbon-rich substance that results when coal is heated in the absence of air) in a furnace. Most of the carbon is removed by blasting oxygen into the liquid. The molten steel is then poured into large, thick-walled iron molds, where it cools into ingots.

To produce a bloom, the ingot is passed through a pair of grooved steel rollers that are stacked. These types of rollers are called "two-high mills. " In some cases, three rollers are used. The rollers are mounted so that their grooves coincide, and they move in opposite directions. This action causes the steel to be squeezed and stretched into thinner, longer pieces. When the rollers are reversed by the human operator, the steel is pulled back through making it thinner and longer. This process is repeated until the steel achieves the desired shape. During this process, machines called manipulators flip the steel so that each side is processed evenly.

Blooms are typically processed further before they are made into pipes. Blooms are converted into billets by putting them through more rolling devices which make them longer and narrower. The billets are cut by devices known as flying shears. These are a pair of synchronized shears that race along with the moving billet and cut it. This allows efficient cuts without stopping the manufacturing process. These billets are stacked and will eventually become seamless pipe.

Slabs are also reworked. To make them malleable, they are first heated to <NUM>,<NUM>° F (<NUM>,<NUM>° C). This causes an oxide coating to form on the surface of the slab. This coating is broken off with a scale breaker and high pressure water spray. The slabs are then sent through a series of rollers on a hot mill and made into thin, narrow strips of steel called skelp. This mill can be as long as a half mile. As the slabs pass through the rollers, they become thinner and longer. In the course of about three minutes a single slab can be converted from a <NUM> in (<NUM>) thick piece of steel to a thin steel ribbon that can be a quarter mile long.

After stretching, the steel is pickled. This process involves running it through a series of tanks that contain sulfuric acid to clean the metal. To finish, it is rinsed with cold and hot water, dried, and then rolled up on large spools and packaged for transport to a pipe making facility.

Both skelp and billets are used to make pipes. Skelp is made into welded pipe. It is first placed on an unwinding machine. As the spool of steel is unwound, it is heated. The steel is then passed through a series of grooved rollers. As it passes by, the rollers cause the edges of the skelp to curl together. This forms an unwelded pipe.

The steel next passes by welding electrodes. These devices seal the two ends of the pipe together. The welded seam is then passed through a high pressure roller which helps create a tight weld. The pipe is then cut to a desired length and stacked for further processing. Welded steel pipe is a continuous process and depending on the size of the pipe, it can be made as fast as <NUM>,<NUM> ft (<NUM>) per minute.

When seamless pipe is needed, square billets are used for production. They are heated and molded to form a cylinder shape, also called a round. The round is then put in a furnace where it is heated white-hot. The heated round is then rolled with great pressure. This high pressure rolling causes the billet to stretch out and a hole to form in the center. Since this hole is irregularly shaped, a bullet shaped piercer point is pushed through the middle of the billet as it is being rolled. After the piercing stage, the pipe may still be of irregular thickness and shape. To correct this, it is passed through another series of rolling mills.

After either type of pipe is made, they may be put through a straightening machine. They may also be fitted with joints so two or more pieces of pipe can be connected. The most common type of joint for pipes with smaller diameters is threading-tight grooves that are cut into the end of the pipe. The pipes are also sent through a measuring machine. This information along with other quality control data is automatically stenciled on the pipe. The pipe is then sprayed with a light coating of protective oil. Most pipe is typically treated to prevent it from rusting. This is done by galvanizing it or giving it a coating of zinc. Depending on the use of the pipe, other paints or coatings may be used.

The characteristics of tubular structures such as pipe can be controlled during production. For example, the diameter of the pipe is often modified depending on how it will be used. The diameter can range from small pipes to large pipes used to transport gas throughout a city. The wall thickness of the pipe can also be controlled with very limited accuracy. Often, the type of steel will also have an impact on the pipe's strength and flexibility. Other controllable characteristics include length, coating material, and end finish. In any regard, it is understood by one of skill in the art that the tubular structures such as pipe made according to the generally understood processes will typically comprise a single homogenous metal, are exceptionally heavy, have limited dimensional accuracy, and are difficult to modify or integrate components therein.

Thus, one of skill in the art understands that there is a clear need to provide a method to manufacture tubular structures, such as pipes, that are lightweight and easy to modify. Further, there is a clear need to provide a layered manufacturing process for tubular structures that can produce exceptionally high quality tubular structures where the starting inside dimension, wall thickness, and exterior dimension can be precisely defined and controlled. Further, there is a need for a layered manufacturing process that can produce unique tubular structures that feature options such as combining different materials, high strength-to-weight properties, enclosed insulation zones, secondary fluid passageways, and integrated couplings or other useful components such as sensors.

The present disclosure provides for an elongate tubular structure according to claim <NUM>.

Further embodiments are disclosed in the appended claims.

As used herein, a "tubular structure" refers to a product that is generally symmetrically formed about a longitudinal axis and often has a high aspect ratio (length is much longer than the maximum cross-sectional dimension). A tubular structure may have a cross section that is circular, rectangular, square, or any other desired shape.

The terms machine direction, cross-machine direction, and Z-direction are generally relative to the direction of sheet metal <NUM> travel through a manufacturing process. The "machine direction" is known to those of skill in the art as the direction of travel of sheet metal <NUM> through the process. The "cross-machine direction" is orthogonal and coplanar thereto. The "Z-direction" is orthogonal to both the machine- and cross-machine directions.

Although any re-coilable material can be used (i.e., metal or non-metal), the preferred raw material for the convolutely wound tubular structures <NUM> (also referred to herein as tubular structures <NUM>) of the present disclosure can be generally provided as a coil of relatively thin sheet metal. A sheet metal is typically provided in a relatively thin form where the Z-direction dimension is substantially less than the machine- and cross-machine direction dimensions. A sheet metal is convolutely wound about a mandrel having a longitudinal axis. The thickness of the sheet metal may be selected from a wide range of available gauges. In one non-limiting example, the sheet metal has a thickness of <NUM> inches to <NUM> inches (<NUM> - <NUM>). The width of the supply coils may also be selected from a wide range of available slit widths. In one non-limiting example, supply coils are used which have a width of <NUM> inches to <NUM> inches (<NUM> meters - <NUM> meters). The sheet metal may be selected to provide the desired properties of the resulting tubular structure. Many metals are suitable and include, but are not limited to, carbon steel, stainless steel, metal alloys, titanium, cobalt, aluminum, brass, and copper. The sheet metal may be prepared using various manufacturing methods known in the art to provide sheet metal with the desired physical properties prior to being wound into supply coils. For example, carbon steel may be provided as cold rolled sheet metal coils, hot rolled sheet metal coils, or galvanized sheet metal coils.

As shown in <FIG>, a process <NUM> for making tubular structures <NUM> (also referred to herein as manufacturing process <NUM> and/or process <NUM>) provides for the sheet metal supply coils <NUM> to be loaded onto a mandrel <NUM> of an uncoiler apparatus <NUM> that supports the sheet metal supply coils <NUM> (also referred to herein as supply coils <NUM>) while rotating them in the direction, R, that unwinds the sheet metal <NUM> disposed convolutely about the supply coil <NUM> and feeds the sheet metal <NUM> to downstream processing operations. The exterior circumferential surface of the supply coil <NUM> can be supported by rollers <NUM> positioned underneath the supply coil <NUM> where the longitudinal axis of each support roller <NUM> is parallel to the longitudinal axis <NUM> of the supply coil <NUM>. Each support roller <NUM> may be driven to rotate and unwind the supply coil <NUM>.

A support mandrel <NUM> may be inserted through the core of the supply coil <NUM>. The support mandrel(s) <NUM> can be inserted into a respective supply coil <NUM> and affixed to the uncoiler apparatus <NUM> core via mounting arms <NUM> sized to engage both ends of the core of the supply coil <NUM>. Both ends of the support mandrel <NUM> may be supported within the uncoiler apparatus <NUM> and the mandrel may be connected to a motor to rotate the supply coil <NUM> and unwind the sheet metal <NUM>. Both support rollers <NUM> and a support mandrel <NUM> may be used to support the supply coil <NUM>. Other uncoiling or unwinding apparatus configurations known to those of skill in the art may also be used to perform the supply coil <NUM> unwinding operation.

After the sheet metal <NUM> is unwound from the supply coil <NUM>, it is conveyed through downstream operations until it is wound in the recoiler <NUM> to create the desired tubular structure <NUM>. Driven or non-driven rollers <NUM> and stationary supports <NUM> may be used to support and convey the sheet metal <NUM> while defining the web path throughout the manufacturing process <NUM>. In a preferred embodiment, the sheet metal <NUM> processing components are mounted such that their longitudinal axes are level within relatively close tolerances (e.g., level across the entire length +/- <NUM> inches or +/- <NUM>) to ensure consistent tracking of the sheet metal <NUM> throughout the manufacturing process <NUM>.

In a preferred embodiment, all sheet metal <NUM> processing components used in the manufacturing process <NUM> are mounted with their longitudinal axes parallel to one another within relatively close tolerances (e.g. +/- <NUM> inches or +/- <NUM>) to provide consistent tracking of the sheet metal <NUM> throughout the manufacturing process <NUM>. Tension of the sheet metal <NUM> can be controlled to provide uniform processing operations. Suitable tension control methods known in the art include, but are not limited to, sheet metal accumulation zones (e.g., a single accumulation loop within a pit between unit operations), sheet metal festoon accumulators, dancers, and load cells which may be used to regulate relative speeds between consecutive unit operations. Other sheet metal tension control techniques known to those of skill in the art may also be used.

In a preferred embodiment, the sheet metal <NUM> tension can be controlled with load cells <NUM> that detect the tension and force within the sheet metal <NUM> at desired location(s) within the process <NUM>, comparing the force to a target, and adjusting the relative speed of any adjacent sheet metal <NUM> conveying devices used in the manufacturing process <NUM> to maintain the target force and tension within the sheet metal <NUM>. In this regard, one of skill in the art can provide a suitable tension control algorithm that compares an actual tension in the sheet metal <NUM> with a desired target tension to determine a tension adjustment factor. The tension adjustment factor can then be applied to the manufacturing process <NUM> equipment to provide for an adjustment of the speed of the sheet metal <NUM> by process control equipment to provide for a corrected sheet metal <NUM> speed and thereby adjust the sheet metal <NUM> tension. Such a process can be accomplished in-situ or by any off-line process suitable for one of skill in the art.

The process <NUM> for making tubular structures <NUM> provides for a sheet metal <NUM> to be attached to a winding mandrel <NUM> (mandrel <NUM>). The winding mandrel <NUM> is a replaceable support that defines the interior cross sectional shape and size of the desired tubular structure <NUM>. The mandrel <NUM> may be fabricated to provide the desired length, cross-sectional shape, and cross-sectional dimensions of the tubular structure <NUM> to be produced. The mandrel <NUM> can be slightly longer than the width of the sheet metal <NUM> used to form the tubular structure <NUM>. The mandrel <NUM> shape may be selected to provide the desired cross-sectional shape (geometry) of the interior of a tubular structure <NUM>, the elongate tubular structure, and or the ultimate exterior geometry of the resulting tubular structure <NUM>, and/or elongate tubular structure. The elongate tubular structure can have a cross-sectional geometry selected from the group consisting of circular, polygonal (e.g., rectangular, square, triangular, hexagonal, etc.), elliptical, and combinations thereof.

The cross-sectional dimensions of the mandrel <NUM> may be selected to provide the desired interior cross-sectional dimensions of the tubular structure <NUM>. For example, the mandrel <NUM> may be circular and have an outside diameter equal to <NUM> inch. Alternatively, the mandrel <NUM> may be circular and have an outside diameter equal to <NUM> inches. Yet still, the mandrel <NUM> may be rectangular and comprise outside dimensions equal to <NUM> inches by <NUM> inches. The mandrel <NUM> design is very flexible and can provide a very wide range of tubular structure <NUM> interior cross sectional shapes and sizes, thereby eliminating a major constraint in prior art fabrication processes for tubular structures <NUM>.

Mandrel <NUM> is preferably designed to provide for the leading edge <NUM> of the sheet metal <NUM> forming tubular structure <NUM> to be disposed thereupon and/or attached thereto. Any adherence force should be sufficient to maintain the desired sheet handling tension and prevent slippage between the sheet metal <NUM> and the mandrel <NUM> surface as the sheet metal <NUM> is convolutely disposed about the mandrel <NUM> in the first revolution as the winding process <NUM> begins.

Vacuum ports can be provided within the surface of the mandrel <NUM>. The force exerted by the vacuum level may be sufficient to provide the desired holding force between the sheet metal <NUM> and the mandrel <NUM>. The vacuum force may be maintained for the initial portion of the process <NUM> and then turned off when no longer needed. After the winding process <NUM> is complete, positive air pressure may be provided through the ports to enable removal of the convolutely wound tubular structure <NUM> from the winding mandrel <NUM>.

A first end of the mandrel <NUM> can be coupled to a motor to provide the rotation force for the winding process <NUM>. The second end distal from the first end of the mandrel <NUM> can be supported throughout the winding process <NUM>. The second end support can be disengaged and repositioned a sufficient distance to remove the convolutely wound tubular structure <NUM> from the mandrel <NUM> after the winding process <NUM> is complete.

Mandrels <NUM> can be fabricated from a wide range of materials and by using methods known in the art. Using fabrication capabilities known in the art, mandrels <NUM> may be produced to provide the desired tubular structure interior dimension to a very accurate level. For example, the mandrel <NUM> length and cross sectional dimensions can be +/- <NUM> inches from the target. Mandrels <NUM> can be made for each desired cross sectional shape and size combination and re-used during production of tubular structures <NUM> to have the desired interior cross-sectional shape and size.

Adjustable geometry mandrels 160A comprising similar interior cross-sectional shapes but with different sizes throughout a significant range may be used to produce tubular structures <NUM>. For example, an adjustable circular arbor mandrel 160A, known to one of skill in the art, may be used during the production of round tubular structures <NUM> having an interior diameter ranging from <NUM> inches to <NUM> inches.

As shown in <FIG>, one embodiment of the process <NUM> for making tubular structures <NUM> provides for a tubular structure <NUM> to be formed by convolutely winding a sheet metal <NUM> about the longitudinal axis of the tubular structure <NUM> while the winding force is transmitted from a motor to a winding mandrel <NUM>. In this configuration, known in the art as center winding, the rotating speed of the mandrel <NUM> is controlled to provide a uniform surface speed at the point where the incoming sheet metal <NUM> first contacts the winding tubular structure <NUM>, from the beginning of the winding cycle through the completion of the winding cycle.

Recoiler 150A can provide for a plurality of mandrels <NUM> to be disposed upon a turret <NUM> that is rotatable about a rotational axis. In this manner, a sheet metal <NUM> supplied from supply coil <NUM> from uncoiler <NUM> can be convolutely wound about a first mandrel <NUM> while a second mandrel <NUM> is disposed in a position to receive sheet metal <NUM> after the tubular structure <NUM> disposed upon the first mandrel <NUM> is complete and rotated away from a defined winding position. In other words, when the tubular structure <NUM> being formed from sheet metal <NUM> about a first mandrel <NUM> disposed upon the turret <NUM> is completed (e.g., has attained a desired thickness), the sheet metal <NUM> can be severed forming a first tail portion, the first tail portion can be attached to the previous convolution of tubular structure <NUM> (i.e., the tail portion formed in sheet metal <NUM> bonded to an immediately subjacent convolution of the first sheet metal to form a tubular structure <NUM>), the mandrel <NUM> having the tubular structure <NUM> disposed thereabout can be rotated away from a winding position, turret <NUM> can be rotated about its rotational axis to position a new mandrel <NUM> into the winding position, and the leading edge of the severed sheet metal <NUM> can be fixably disposed upon, or attached to, the new mandrel <NUM>. This can provide a nearly continuous production of tubular structures <NUM>.

The desired speed profile can be pre-calculated for a given tubular structure <NUM> geometry. The variables that define the speed profile include the sheet metal <NUM> incoming speed, the tubular structure <NUM> interior cross-sectional dimension, the tubular structure <NUM> exterior cross-sectional dimension, and the thickness of the sheet metal <NUM> being wound. In embodiments where the sheet metal <NUM> is deformed out-of-plane for portions of the tubular structure <NUM> wall, the average in-wound thickness of the deformed sheet metal <NUM> (which may include some compression) is used for the thickness value for that portion of the speed profile.

A laser measurement system <NUM> (or any measurement system) can be used to measure the outer diameter of the tubular structure <NUM> as it is being wound. A controller <NUM> can be operatively and/or communicatively coupled to the laser measurement system <NUM> as well as the equipment associated with the formation of tubular structure <NUM> to control when each discrete unit operation is activated or deactivated during the tubular structure <NUM> formation process.

For example, a tubular structure <NUM> can be a circular pipe having an inside diameter of <NUM> inches and an outside diameter of <NUM> inches. The incoming sheet metal <NUM> is undeformed, has a uniform thickness of <NUM> inches, and has a speed at the recoiler <NUM> of <NUM> feet per minute. The wall thickness of the pipe (i.e., tubular structure <NUM>) may be calculated using the formula:<MAT>.

In this example: (<NUM> inches - <NUM> inches) / <NUM> = <NUM> inches
The number of mandrel <NUM> revolutions required to form the pipe may be calculated using the formula:<MAT>.

In this example: <NUM> inches / <NUM> inches = <NUM> revolutions
The outside diameter of the winding pipe after "Y" revolutions may be calculated using the formula: <MAT>.

In this example after <NUM> revolutions: <NUM> inches + (<NUM> x <NUM> inches x <NUM>) = <NUM> inches.

In this example after <NUM> revolutions: <NUM> inches + (<NUM> x <NUM> inches x <NUM>) = <NUM> inches
The required rotational speed of the mandrel <NUM> to maintain a uniform surface speed at the point where the incoming sheet metal first contacts the winding tubular structure <NUM> may be calculated using the formula: <MAT>.

One of skill in the art may use such calculations to create a target speed profile for all points in the process <NUM> for the tubular structure <NUM>. Motor controllers known in the art may use such speed profiles to regulate the motor and mandrel <NUM> rotational speeds at all points throughout the winding cycle, thereby providing a reliable means for winding the desired tubular structure <NUM>.

A similar approach may be used to control the winding speed of a non-circular tubular structure <NUM>, such as one comprising a rectangular or square interior cross-section. The calculations are similar, although the formulae for determining the instantaneous outside diameter or perimeter must be altered to account for the difference in geometry between the desired interior cross-section and the circular cross-sectional example described above.

A key advantage of the current invention relative to prior art is the unprecedented flexibility to produce tubular structures <NUM> with a very wide range of interior dimension, wall thickness, and exterior dimension combinations. As described supra, nearly any desired tubular structure <NUM> interior cross sectional shape and size can be provided by an appropriately designed winding mandrel <NUM>. Once the winding process <NUM> is initiated by wrapping the incoming sheet metal <NUM> around the winding mandrel <NUM>, the winding process <NUM> continues until the desired wall thickness and exterior dimensions are produced, at which point the winding process is terminated, and the sheet metal <NUM> is cut off. The winding process <NUM> can be easily terminated only a few winding revolutions after the start of the winding process, thereby producing a relatively thin wall. If desired, the winding process <NUM> may also continue for a relatively extended period after the winding process <NUM> is initiated before the process <NUM> is terminated, and the sheet metal <NUM> is cut off. In this latter method, a very thick wall tubular structure <NUM> may be produced.

In one embodiment, the outer dimensions of the winding tubular structure <NUM> can be measured throughout the entire winding process <NUM>. Measurement systems are known in the art to continuously measure the outer dimensions of the winding tubular structure <NUM>. For example, a digital micrometer can contact the winding structure and provide an accurate measurement (+/- <NUM> inches) of the wound wall thickness. Further, non-contact laser triangulation measurement systems can be used to scan the winding tubular structure <NUM> and provide an accurate measurement (within <NUM> inches) of the wound wall thickness. Measurement systems may be used to monitor the winding process <NUM> and provide a winding termination signal when a target wall thickness and corresponding outer dimensions of a tubular structure <NUM> have been produced.

The process <NUM> can provide both unprecedented flexibility for the cross-sectional shape and size of tubular structures <NUM> and very accurate production of the desired interior cross sectional dimensions, wall thickness, and cross sectional exterior dimensions. All three parameters may be controlled within very tight tolerances over a wide size range. Presume a round pipe having a target <NUM> inch inside diameter, a <NUM> outside diameter, and a corresponding wall thickness of <NUM> inches is desired. A sheet metal <NUM> with a uniform thickness of <NUM> inches is used to form the pipe. A mandrel <NUM> with an outside diameter of <NUM> inches is used for producing the pipe. The sheet metal <NUM> is wound around the mandrel <NUM> using a hybrid winding process. A laser triangulation system can monitor the wall thickness from the start of the process <NUM> until the target of <NUM> inches is produced, at which point the process <NUM> is terminated, and the sheet metal <NUM> is cut off. Here, the pipe will have approximately <NUM> revolutions of sheet metal to form the wall (<NUM> inch wall/<NUM> inch thick sheet metal). The final pipe will be at or very close to the target dimensions for inside diameter, wall thickness, and outside diameter. Expected dimensional variations in these parameters is less than +/- <NUM>% of the target dimension.

A source of minor variation for the inside diameter, wall thickness, and outside diameter is the leading and trailing edge of the sheet metal <NUM> used to form the pipe. The inside diameter of the pipe measured just downstream of the leading edge of sheet metal <NUM> may measure <NUM> inches. The same measurement taken just upstream of the leading edge <NUM> may be approximately <NUM> inches due to the thickness of the sheet metal <NUM> leading edge <NUM>. A similar effect may be found on the exterior of the pipe at the trailing edge of the sheet metal <NUM>. This variation in dimensional accuracy may be mitigated by using a thinner sheet metal <NUM> for the inner and outer portions of the tubular structure <NUM>. For example, the first few layers and last few layers of the pipe may be formed using a sheet metal <NUM> comprising a relatively small thickness of <NUM> inches, thus reducing approximately <NUM>% of the minor dimensional variation. In a second embodiment, the leading edge <NUM> of the sheet metal <NUM> may be bevel ground or machined by means known in the art to eliminate the step and provide a very thin, blended-in edge prior to wrapping the sheet metal <NUM> around the mandrel <NUM> and initiating the winding process <NUM>. The trailing edge <NUM> of the sheet metal <NUM> may be similarly ground or machined after the process <NUM> is completed. A grinding or machining operation can also eliminate approximately <NUM>% of a minor dimensional variation. Using one, or both, of these methods can further improve the accuracy of the produced tubular structure <NUM>. It is preferable that any minor variations associated with the sheet metal <NUM> ends in wound tubular structures <NUM> be mitigated so that, for example, the actual inside diameter, wall thickness, and outside diameter variances from their respective targets are all less than +/- <NUM>% of target. It can be preferable that the actual inside diameter, wall thickness, and outside diameter variances from their respective targets are all less than +/-<NUM>% of target. One of skill in the art would clearly understand that the resulting inside diameter, a wall thickness, and an outside diameter of the elongate tubular structure can have a standard deviation of less of than about <NUM>% of a respective average measurement for said inside diameter, said wall thickness, and said outside diameter as determined by a Pipe Dimension Measurement system.

Additionally, the structure of the produced tubular structure <NUM> can be further enhanced by providing a secondary convolute winding. Such a process can increase wall thickness of the tubular structure <NUM>, provide a change in the outer material comprising the tubular structure <NUM>, as well as improve the appearance of the produced tubular structure <NUM>. By way of example, a secondary convolute winding can be provided to the tubular structure <NUM> by first attaching the leading edge <NUM> of the second sheet metal <NUM> to the tubular structure <NUM> at a position proximate to but not overlapping the trailing edge <NUM> of the first sheet metal <NUM>. Appropriate bonding may be provided between the respective layers of the first sheet metal <NUM> and second sheet metal <NUM> to provide the necessary structural integrity as a desired number of additional layers of second sheet metal <NUM> are wound onto tubular structure <NUM>. In other words, an additional wind to the convolutely wound structure is provided after the fact.

Tubular structures having improved strength-to-weight properties may be desired and/or required. Here, at least a portion of the convolutely wound tubular structure is formed with a net structural density that is substantially less than the density of the constituent sheet metal material used to form the tubular structure. The reduced density portion of the tubular structure wall may be designed to optimize any desired mechanical property or combination of mechanical properties of the tubular structure. This includes, but is not limited to, mass, weight, shear strength, axial tensile strength, axial compression strength, torsional strength, modulus of elasticity in a desired plane or orientation, internal pressure rating, and external pressure rating.

<FIG> provide an exemplary tubular structure 180D with improved strength-to-weight properties. The tubular structure 180D may be produced by convolutely winding a sheet metal comprising pre-formed voids <NUM> to form at least a portion of the tubular structure 180D. For example, a first inner region <NUM> of the tubular structure <NUM> can be formed by convolutely winding a homogenous sheet metal around the longitudinal axis <NUM> of the tubular structure <NUM>. A second region <NUM> of the tubular structure 180D is then formed by winding a second sheet metal having pre-formed voids <NUM>, such as circles, around the first inner region <NUM> about the longitudinal axis <NUM> of the tubular structure 180D by overlying the first sheet metal. A perforated sheet metal having a total void area of <NUM>% to <NUM>% can be used to form at least a portion of the second region <NUM> of the tubular structure 180D. A third region <NUM> of the tubular structure 180D is then formed by winding the first homogenous sheet metal around second region <NUM> about the longitudinal axis <NUM> of the tubular structure 180D and overlying the second sheet metal until the desired wall thickness and the desired outer dimensions of the tubular structure 180D are attained. The tubular structure 180D formed in this manner can have a surprisingly substantially lower total mass with a relatively minor decrease in strength, modulus of elasticity, and pressure rating. This type of improved strength-to-weight tubular structure 180D may be especially useful in aeronautical, space, and inter-stellar applications.

As shown in <FIG>, a tubular structure 180E with improved strength-to-weight properties may be produced by unwinding a homogenous sheet metal <NUM>, forming voids in situ in selected portions of the sheet metal <NUM> with a void generation system <NUM> to form a sheet metal 120E portion having voids disposed therein, and then winding the sheet metal 120E into tubular structure 180E. In a non-limiting example, the voids 230A can be registered in the cross-machine direction but unregistered in the machine direction. A first sheet metal <NUM> supplied in a first sheet metal supply coil <NUM> is unwound in an uncoiler apparatus <NUM> and fed into a downstream recoiler <NUM> where it is convolutely wound to form the first inner region <NUM> of the tubular structure 180E. After the first inner region <NUM> of the tubular structure 180E is formed, voids 230A are generated in the sheet metal <NUM> to form a sheet metal 120E having voids disposed therein prior to winding the sheet metal 120E to form the second region <NUM> of tubular structure 180E.

Voids 230A can be generated to form sheet metal 120E portion by mechanical contact operations such as punching or cutting. The punching or cutting operations may remove discrete portions of sheet metal 120E to reduce mass while still maintaining substantial material continuity in both the machine- and cross-machine directions. Alternatively, voids 230A can be generated to form sheet metal 120E by non-mechanical cutting operations such as water jet cutting or laser cutting. Water jet and laser cutting systems are known in the art and can be effective in cutting sheet metal. Both water jet and laser cutting systems also have advantages for quickly and easily changing the void size, shape, or spacing. Since no mechanical tooling is used in these systems, they are more flexible and can quickly make changes via programming to control the position of the device that cuts the sheet metal. Other metal cutting techniques known in the art may also be used to generate voids 230A. The position, size, shape, and spacing of the discrete voids 230A can be selected to provide a reduced mass and preservation of mechanical properties such as strength, modulus of elasticity, and pressure rating. After the second region <NUM> of the tubular structure is formed with the sheet metal 120E, the void generation system <NUM> can be de-activated. The homogenous first sheet metal <NUM> can then be wound to form the third region <NUM> of the tubular structure 180E. It may be preferable to bond at least a portion of the adjacent layers within the inner <NUM>, second <NUM>, and third <NUM> regions of the tubular structure 180E as discussed supra. The tubular structure 180E can have substantially lower total mass with a relatively minor decrease in strength, modulus of elasticity, and pressure rating. This type of improved strength-to-weight tubular structure 180E may be especially useful in aeronautical and space applications.

Alternatively, as shown in <FIG>, a tubular structure 180F with improved strength-to-weight properties may be produced by unwinding a homogenous sheet metal <NUM>, forming voids 230B in the sheet metal <NUM> to form a sheet metal 120F, and winding the first sheet metal 120E into a tubular structure 180F as discussed supra. The voids 230B can be registered in both the cross-machine direction and the machine direction. A laser cutting system may be controlled to create any desired void 230B position, size, and shape. The machine direction void 230B spacing and cross machine void spacing may also be controlled. Voids 230B can be generated in the sheet metal <NUM> to form relatively high aspect ratio rectangles with their minimum dimension generally parallel to the longitudinal axis <NUM> of the tubular structure 180F. The machine direction spacing D<NUM>, D<NUM> of the voids 230B can be increased for succeeding voids 230B so that a void 230B overlays a preceding void 230B when wound into the tubular structure 180F. The machine direction void 230B spacing increase (i.e., D<NUM> > D<NUM>) can be proportional to the thickness of the first metal material <NUM> forming sheet metal <NUM> and may be pre-determined and programmed into the laser cutting system by means known in the art. The machine direction length L<NUM>, L<NUM> of the voids 230B can be increased for succeeding voids 230B so that a void 230B overlays a preceding void 230B when wound into the tubular structure 180F. Additionally, the machine direction void length increase (i.e., L<NUM> > L<NUM>) can be proportional to the thickness of the first metal material <NUM> forming sheet metal <NUM> and may be pre-determined and programmed into the laser cutting system by means known in the art. Further, voids 230B can be axially aligned and circumferentially aligned, thus creating continuous structural regions in the axial direction which provide a tubular structure 180F with a relatively high cross-sectional moment of inertia and correspondingly low axial deflection.

After the second region <NUM> of tubular structure 180F is formed with sheet metal 120F comprising the desired voids, the void generation system <NUM> is de-activated and the remainder of tubular structure <NUM> formed with the homogenous sheet metal <NUM> as discussed supra. The tubular structure 180F formed in this manner has substantially lower total mass with a relatively minor decrease in strength, modulus of elasticity, and pressure rating. This type of improved strength-to-weight tubular structure 180F may be especially useful in aeronautical and space applications.

In some applications, it may be desired to use tubular structures <NUM> having enhanced surface properties on the interior and/or exterior of the tubular structure <NUM>. For example, a food processing operation may require a smooth pipe interior that is resistant to buildup and microbial contamination. In prior art pipe fabrication processes, such as the production of seamless pipe, this is difficult to achieve. The original formed surface is, by nature, rough. Secondary smoothing processes may mitigate the roughness. But these are expensive, time consuming, and limited in effectiveness. A layered fabrication process, combined with the low temperature processing capability, can provide the desired pipe interior comprising enhanced surface properties.

For example, <NUM> grade cold rolled stainless steel is supplied in sheet metal form. The sheet metal may be produced with an ASTM No. <NUM> finish that is exceptionally smooth and mirror-like in its appearance. This mirror-like surface may be used to form the first inner region of the desired tubular structure. A standard <NUM> stainless steel with a relatively rougher ASTM No. 2B finish may be used to form the succeeding second region and third region of the pipe. This fabrication process provides the desired enhanced surface for the pipe's interior while maintaining the use of standard, cost effective materials for the overwhelming majority of the pipe's total material. The pipe's exceptionally smooth interior surface may effectively mitigate buildup and contamination as particles cannot easily stick to it. Cleaning and flushing operations can also easily remove any small areas of buildup that may occur.

In another non-limiting example, a low surface energy coating, microbial resistant coating, or anti-microbial coating may be applied to the <NUM> grade stainless steel sheet metal with an ASTM No. <NUM> finish prior to winding the sheet metal into the first inner region of the pipe. This selective coating may further enhance the surface properties of the pipe's interior and further mitigate buildup, contamination, and microbial growth. Any combination of coatings and finishing operations may be used to selectively improve the sheet metal <NUM> surface which subsequently forms the interior surface of a wound tubular structure <NUM>.

Similar techniques may be used to provide enhanced surface properties for the exterior surface of the tubular structure <NUM>. These improvements may mitigate environmental damage by providing corrosion resistance, mitigating algae growth in subsea applications, and the like. Any combination of coatings and finishing operations may be used to selectively improve the exterior surface of a wound tubular structure <NUM>.

It may be necessary to constrain the respective layers from unwinding or unraveling during transportation and end usage in some layered tubular structure <NUM> applications. In the invention, the layers are adhesively bonded <NUM> during the manufacturing process using a class of adhesives known as structural adhesives. These adhesives are typically based on epoxy, acrylic, urethane, or cyanoacrylate chemistries and are known in the art to provide very strong bonds between adjoining metal surfaces.

In a preferred embodiment, adhesive is applied to one side of the sheet metal <NUM> after other processes such as splicing, void generation, and out-of-plane deformation are complete, and before the winding process. Adhesive application processes <NUM> known in the art are suitable for applying the liquid adhesive in this application. These fluid application processes include spray, extrusion through nozzles, extrusion through slot dies, gravure, offset gravure, flexographic, permeable rolls, jetting, and spray systems. In one non-limiting example, a permeable roll is used to apply adhesive to sheet metal <NUM> just prior to sheet metal <NUM> being wound to form tubular structure <NUM>. Adhesive is applied in a desired pattern (defined by the aperture pattern in the surface of the permeable roll) to the top face of sheet metal <NUM> as sheet metal <NUM> travels in a near-horizontal plane just prior to entering recoiler <NUM> and the winding process. The application pattern may be optimized for the particular tubular structure <NUM> application. For example, adhesive can be applied in a continuous line at the transverse leading edge of the sheet metal <NUM>, continuous lines along both edges of the sheet metal <NUM>, and in discrete dots spaced apart in regular intervals in both the machine direction and cross machine direction.

As sheet metal <NUM> enters the recoiler <NUM>, it is attached to winding mandrel <NUM> via vacuum ports in the surface of mandrel <NUM>. The bottom face of sheet metal <NUM>, without adhesive, is brought into contact with the surface of mandrel <NUM>. As mandrel <NUM> rotates, sheet metal <NUM> is guided around the longitudinal axis of mandrel <NUM> to form first layer <NUM> of tubular structure <NUM>. After approximately one revolution, the leading edge <NUM> of the top face of sheet metal <NUM> is brought into contact with the bottom face of sheet metal <NUM> entering the winding process and layer-to-layer bonding occurs. Continued rotation of mandrel <NUM> conveys additional sheet metal <NUM> into the winding process <NUM>, with adhesive previously applied in a pattern on the top face continuing to contact and bond with the bottom face of the sheet metal <NUM> entering the winding process. This process continues until the tubular structure <NUM> wall thickness and desired outer dimensions are attained. In a preferred embodiment, adhesive application is discontinued for the last length of sheet metal <NUM> corresponding to the final perimeter of tubular structure <NUM>. This ensures no adhesive is present on the exterior of the tubular structure <NUM>. In another embodiment, a supplemental line of adhesive can be applied at the transverse trailing edge of sheet metal <NUM> to effectively seal the exterior edge layer.

Once adhesive has been applied to at least one face of sheet metal <NUM> entering the winding process, the winding tension and the force exerted by an adjustable pressure roll <NUM>, which presses in a generally perpendicular direction to sheet metal <NUM> to compress sheet metal <NUM> against the winding tubular structure <NUM>, provide sufficient pressure to effectively bond the layers of tubular structure <NUM> together during the winding process. Some adhesives can require curing at elevated temperatures. If these adhesives are selected, the finished tubular structure <NUM> may be placed inside an oven known to provide the required curing environment. Some adhesives also require two parts, with one fluid acting as a catalyst to activate the bonding in the other fluid. If these adhesives are used, a secondary permeable roll may be used to apply the second adhesive to the bottom face of sheet metal <NUM> prior to the winding process. The bottom face adhesive pattern may match the top face adhesive pattern and be registered in both the machine direction and cross machine direction by means known in the art to ensure the two adhesives are brought into face to face contact in the winding process.

The continuous lines of adhesive at the transverse leading edge <NUM>, transverse trailing edge, and both sides of sheet metal <NUM> ensure uninterrupted sealing at all edges of tubular structure <NUM>. This can ensure no inter-layer migration of the interior fluid or gas conveyed within tubular structure <NUM> and can prevent exterior inter-layer migration of environmental liquids or gas. In other words, a tail portion formed in sheet metal <NUM> can be adhesively bonded to an immediately subjacent convolution of said first sheet metal to form a tubular structure <NUM>.

The adhesive bonding process provides an effective means for creating a rigid structure from multiple layers of a relatively flexible sheet metal <NUM>. The strength, modulus of elasticity, and pressure ratings of such tubular structures are theoretically equivalent to homogenous material structures comprising similar materials and dimensions.

Welding <NUM> can be used to constrain the layers from unwinding or unraveling during transportation and end usage. In one embodiment, the layers are welded during the fabrication process using a fiber laser system.

The welding operation <NUM> can be applied to one side of sheet metal <NUM> after other processes such as splicing, void generation, and out-of-plane deformation are complete, and before or during the winding process. Many welding processes are known in the art and several are suitable for permanently joining adjacent layers of sheet metal <NUM> in a wound tubular structure <NUM>. These welding processes include shielded metal arc welding, gas metal arc welding, flux-cored arc welding, gas tungsten arc welding, submerged arc welding, electron beam welding, and laser welding. Several types of laser welding are known in the art and may be used, including gas lasers (which use a gas such as helium, nitrogen, or carbon dioxide as the medium), solid state lasers (which use solid media such as neodymium in yttrium aluminum garnet, or Nd:YAG), and fiber lasers (in which the medium is the optical cable itself). Fiber laser welding can be used to permanently attach adjacent layers of sheet metal <NUM> in a wound tubular structure <NUM>. Fiber laser welding may permanently join as few as two adjacent layers or, if more power is applied, permanently join three or more adjacent layers of sheet metal <NUM>. Fiber laser welding may be done in continuous lines or in discrete zones. The laser head may be positioned near the sheet metal to be welded and moved quickly and accurately in the x, y, and z planes by means known in the art to weld in any desired pattern. To improve operating rate and efficiency, multiple laser heads may be used to simultaneously weld multiple locations of sheet metal <NUM>. In short, a tail portion formed in sheet metal <NUM> can be welded to an immediately subjacent convolution of said first sheet metal to form a tubular structure <NUM>.

In a non-limiting example, three fiber lasers are mounted on the downstream side of the recoiler <NUM> and pointed in a generally horizontal plane toward the rewinding tubular structure <NUM>. The first laser is mounted at a first machine direction edge of the winding sheet metal <NUM> and provides a continuous machine direction edge weld for a first end of the winding tubular structure <NUM>. The second laser is mounted at a second opposite machine direction edge of the sheet metal <NUM> and provides a continuous machine direction edge weld for the second opposite end of the winding tubular structure <NUM>. The third laser is movably mounted and provides continuous cross machine direction edge welds for the leading and trailing ends of the sheet metal <NUM> for each tubular structure <NUM>. The third laser can also provide discrete spot welds across the face of the winding tubular structure <NUM>. Discrete spot welds may be made in any desired position, any desired pattern, may have any desired spacing interval in the machine direction, and may have any desired spacing interval in the cross machine direction. A wound tubular structure <NUM> can be permanently welded together in a continuous area along both machine direction ends, both the leading and trailing transverse edges of the sheet metal <NUM>, and at a sufficient number of interior locations to provide a rigid structure.

The welding process <NUM> can provide an effective means for creating a rigid structure from multiple layers of a relatively flexible sheet metal <NUM>. The strength, modulus of elasticity, and pressure ratings of such tubular structures <NUM> are theoretically equivalent to homogenous tubular structures comprising similar materials and dimensions.

The elongate tubular structures of the present disclosure comprise a first tubular structure and a second tubular structure wherein a first end of the first tubular structure is matingly and fasteningly engaged to a first end of the second tubular structure in order to produce the longer elongate structure. The two structures may be matingly and fasteningly engaged by welding the two ends of the structures together or by using engagement couplings.

The respective ends of the two structures can be welded together in a mated fashion using any typical pipe welding process known in the industry including, but not limited to shielded metal arc welding, laser beam welding, electron beam welding, magnetic pulse welding, and friction stir welding.

The respective ends of the two structure can alternatively coupled using typical pipe connecting devices know in the industry.

Prior art tubular structures require substantial secondary operations after the production of the tubular structures to add required ancillary components. The ancillary components include, but are not limited to, couplings for joining tubular structures in end-to-end configurations, flow sensors, pressure sensors, vibration sensors, and temperature sensors. The layered winding method <NUM> of the present disclosure provides the opportunity to integrate such components into the production of tubular structures <NUM>, eliminating altogether the need for costly and less efficient secondary integration operations, or to minimize the secondary integration operations.

As shown in <FIG>, one embodiment provides for a coupling <NUM> to be integrated into the production of a tubular structure <NUM> to enable the mating and fastening engagement of tubular structures <NUM> in an end-to-end configuration to provide a desired length of connected tubular structures <NUM>. The couplings <NUM> may comprise any form known in the art, including but not limited to flange, threaded, and right angle turns. The couplings <NUM> can comprise a flange configuration that enables subsequent connections using nuts and bolts. Flange couplings can be integrated into a wound pipe by winding a first sheet metal <NUM> comprising a first width to form a first inner region <NUM> of the pipe. In a preferred embodiment, adjacent layers of first sheet metal <NUM> are welded together during winding of first inner region <NUM>.

The winding process <NUM> continues until the outside diameter of first inner region <NUM> of tubular structure <NUM> is slightly less than the inside diameter of an appropriately selected flange coupling <NUM>. The winding process is paused, first sheet metal <NUM> is cut off in the cross-machine direction, and two flange couplings <NUM> are prepared for installation on opposed ends of tubular structure <NUM>. In a non-limiting example, the inside surfaces and the outside surfaces of the coupling <NUM> hubs are coated with structural adhesive prior to integration into tubular structure <NUM>. A first flange coupling <NUM> is then placed over a first end of tubular structure <NUM> and a second flange coupling <NUM> is placed over the opposed end of tubular structure <NUM>. The outer end face of the first coupling <NUM> can be aligned in the cross-machine direction with the outer end face of first inner region <NUM> of tubular structure <NUM> and the outer end face of the second coupling <NUM> is aligned in the cross-machine direction with the outer end face of the tubular structure <NUM> first inner region <NUM>. The first flange coupling <NUM> can be adhesively bonded to the first end of tubular structure <NUM> and the second flange coupling <NUM> is adhesively bonded to the second end of tubular structure <NUM> to provide the requisite mating and fastening engagement of the respective tubular structures <NUM>.

In a non-limiting example, the flange couplings <NUM> comprise a hub, wherein the hub comprises an inner diameter that is approximately equal over the entire length of the hub. The hub also comprises an outside diameter that is approximately equal from the inner end face of the hub to the end of the hub that transitions to the integral flange portion of the coupling <NUM>. The flange portion of the coupling <NUM> comprises a flange thickness and an outside diameter. In a preferred embodiment, the coupling <NUM> flange outside diameter is greater than the hub outside diameter and the hub outside diameter is greater than the hub inside diameter. After the two couplings <NUM> are placed on the opposite ends of the tubular structure <NUM>, the first sheet metal <NUM> width is reduced to a second sheet metal 120J width by laser cutting or other suitable means, wherein the difference between the first sheet metal <NUM> width and the second sheet metal 120J width is approximately equal to the combined hub lengths of the first and second flange couplings <NUM>. The leading edge of the second sheet metal 120J is then welded to the outer layer of the first inner region <NUM> of the tubular structure <NUM>. Winding is then resumed to form the second region <NUM> of the tubular structure <NUM>. In a preferred embodiment, the adjacent layers of the second sheet metal 120J are welded together during the winding of the second region <NUM> of the tubular structure <NUM>.

In another preferred embodiment, both edges of second sheet metal 120J in each layer of second region <NUM> of tubular structure <NUM> are adjacent to the hub inner end faces of the first and second flange couplings <NUM>. The winding process continues until the diameter of the second region <NUM> is approximately equal to the hub outside diameter of the two flange couplings <NUM>. The winding process is then paused and second sheet metal 120J is cut off in the cross-machine direction. The sheet metal <NUM> width is then increased to a third sheet metal width <NUM> by laser cutting or other suitable means, wherein the difference between the first sheet metal <NUM> width and the third sheet metal <NUM> width is approximately equal to the combined thicknesses of the flange portions of the two couplings <NUM> installed on opposed ends of tubular structure <NUM>. The leading edge <NUM> of sheet metal <NUM> is then welded to the outer layer of second region <NUM> of tubular structure <NUM>. Winding is then resumed to form third region <NUM> of tubular structure <NUM>. The first layer of the third region <NUM> overlies the outer surface of both the first and second flange coupling <NUM> hubs, which comprise adhesive previously applied, and the outer layer of second region <NUM>. The third region <NUM> of the tubular structure <NUM> is thus adhesively bonded to the first flange coupling <NUM> and second flange coupling <NUM>. In a preferred embodiment, adjacent layers of third sheet metal <NUM> can be welded together during the winding of third region <NUM> of tubular structure <NUM>.

In another embodiment, both edges of third sheet metal <NUM> in each layer of third region <NUM> of tubular structure <NUM> are adjacent to the flange inner end faces of first and second flange couplings <NUM>. The winding process continues until the diameter of third region <NUM> is approximately equal to the desired target tubular structure <NUM> outside diameter, at which point the winding process is terminated and third sheet metal <NUM> is cut off in the cross-machine direction.

The diameter of the flange bolt holes is sufficiently greater than the outside diameter of the tubular structure <NUM> to allow easy installation of nuts and bolts through the coupling <NUM> flanges to join adjacent tubular structures <NUM> and form a desired length of connected tubular structures <NUM>. Other types of couplings <NUM> may be similarly integrated into wound tubular structures <NUM> or other tubular structures <NUM> by making manufacturing modifications as known by one of skill in the art. Other couplings <NUM> may provide connections for adjacent tubular structures <NUM> wherein the longitudinal axes <NUM> of the two tubular structures <NUM> are aligned. Alternatively, other couplings <NUM> may provide connections for adjacent tubular structures <NUM> wherein the longitudinal axis of a first tubular structure <NUM> is orthogonal to the longitudinal axis of a second connected tubular structure <NUM>. This manufacturing method reduces or eliminates secondary fabrication processes related to the integration of couplings <NUM>, such as separate welding operations, which are often effort intensive and costly.

Referring to <FIG>, a desired length of connected tubular structures <NUM> may be produced by sequentially winding tubular structures <NUM> onto opposite ends of couplings <NUM>, wherein the first end of a first coupling <NUM> is integrated into a first wound tubular structure <NUM> and the second end of the first coupling <NUM> is integrated into a second wound tubular structure <NUM> to matingly and fasteningly engage a first wound tubular structure <NUM> and a second wound tubular structure <NUM>. In other words, the mating and fastening engagement of the first end of the first tubular structure <NUM> and the first end of the second tubular structure <NUM> can provide for the first longitudinal axis of a first wound tubular structure <NUM> and the second longitudinal axis of a second wound tubular structure <NUM> to be collectively elongate. This method eliminates much of the effort required to connect tubular structures <NUM> after manufacturing is complete, such as the previous example of flange couplings <NUM> comprising nut and bolt fasteners. The first coupling <NUM> can be fixably and matingly attached to a first end of the a first wound tubular structure <NUM> and a first end of a second wound tubular structure <NUM> by bonding the first coupling to the first end of the a first wound tubular structure <NUM> and a first end of a second wound tubular structure <NUM> or to the sheet meal <NUM> forming first wound tubular structure <NUM> and second wound tubular structure <NUM>. Such bonding to provide sufficient mating and fastening engagement can be selected from the group consisting of friction bonding, compressive bonding, adhesive bonding, welding, combinations thereof or by any other technique known to one of skill in the art of bonding metals and other materials.

Further, the first coupling <NUM> disposed between the first end of said first wound tubular structure <NUM> and said first end of the second tubular structure <NUM> can be provided with a desired bend modulus. Providing the first coupling <NUM> with a suitable bend modulus can provide sufficient flexure to facilitate the mating and fastening engagement of the first end of the first tubular structure <NUM> and the first end of the second tubular structure <NUM> when the first longitudinal axis and the second longitudinal axis are not collectively elongate. Such flexure can be incorporated into first coupling <NUM> as strict flexure (i.e., first coupling <NUM> bends) or by rotation (i.e., first coupling <NUM> is provided with an axis of rotation - either linear or off-set), combinations thereof, and the like.

In one embodiment, common couplings <NUM> can be integrated into the production of tubular structures <NUM> to enable joining the structures in an end-to-end configuration mating and fastening engagement within the manufacturing environment. Common couplings <NUM> may comprise a center flange portion and hubs that extend outward from both sides of the center flange. Common couplings <NUM> comprise a center flange outer first diameter, a hub outer middle diameter, a hub inner third diameter, and a center flange inner fourth diameter.

In a preferred embodiment, the center flange outer first diameter is greater than the hub outer middle diameter, the hub outer diameter is greater than the hub inner third diameter, and the hub inner third diameter is greater than the center flange inside fourth diameter. For example, the center flange thickness of the center flange annular region disposed radially inside the hub portion of the coupling <NUM> is approximately equal to the center flange thickness of the center flange annular region disposed radially outside the hub portion of the coupling <NUM>. To produce a first tubular structure <NUM>, a first common coupling <NUM> may be integrated into a wound tubular structure <NUM> by winding a first sheet metal <NUM> comprising a first width to form a first inner region <NUM> of the first tubular structure <NUM>. In a preferred embodiment, the adjacent layers of first sheet metal <NUM> are welded together during the winding of the first inner region of the first tubular structure <NUM>. The winding process continues until the outside diameter of first inner region <NUM> of the first pipe is slightly less than the common coupling <NUM> hub inner third diameter. The winding process <NUM> is paused, first sheet metal <NUM> is cut off in the cross machine direction, and first common coupling <NUM> is prepared for installation on a first end of first tubular structure <NUM>.

In a non-limiting example, the inside surfaces and the outside surfaces of a first end of the first common coupling <NUM> hub are coated with structural adhesive prior to integration into the first tubular structure <NUM>. The first common coupling is then placed over a first end of the first tubular structure <NUM> where it becomes adhesively bonded to the first inner region of the first tubular structure <NUM>. In a preferred embodiment, the innermost face of the center flange is positioned adjacent the end face of the wound first inner region <NUM> of the first tubular structure <NUM>. After the common coupling <NUM> is placed on the first end of the first inner region <NUM> of the first tubular structure <NUM>, first sheet metal <NUM> width is reduced to a second sheet metal 120J width by laser cutting or other suitable means, wherein the difference between the first sheet metal <NUM> width and the second sheet metal 120J width is approximately equal to the length of the first common coupling <NUM> hub portion that overlies first inner region <NUM> of wound first tubular structure <NUM>. The leading edge of sheet metal 120J is then welded to the outer layer of first inner region <NUM> of first tubular structure <NUM>. Winding is then resumed to form second region <NUM> of first tubular structure <NUM>. In a preferred embodiment, adjacent layers of second sheet metal 120J are welded together during the winding of second region <NUM> of first tubular structure <NUM>.

In another preferred embodiment, the edge of sheet metal 120J in each layer of second region <NUM> of first tubular structure <NUM> closest to common coupling <NUM> are adjacent to the common coupling <NUM> hub inner end face. The winding process <NUM> continues until the diameter of second region <NUM> is approximately equal to the hub outside second diameter. The winding process <NUM> is then paused and sheet metal 120J is cut off in the cross machine direction. The sheet metal 120J width is then increased to first sheet metal <NUM> width. The leading edge <NUM> of sheet metal <NUM> is then welded to the outer layer of second region <NUM> of tubular structure <NUM>. Winding is then resumed to form third region <NUM> of tubular structure <NUM>. The first layer of third region <NUM> overlies the outer surface of the common coupling <NUM> hub, which comprises adhesive previously applied, and the outer layer of second region <NUM>. The third region <NUM> of tubular structure <NUM> is adhesively bonded to common coupling <NUM>.

In another embodiment, adjacent layers of first sheet metal <NUM> are welded together during the winding of third region <NUM> of tubular structure <NUM>. The edges of sheet metal <NUM> in each layer of third region <NUM> of tubular structure <NUM> closest to common coupling <NUM> are adjacent to the center flange's inner end face. The winding process continues until the diameter of outer third region <NUM> is approximately equal to the desired target first tubular structure <NUM> outside diameter, at which point the winding process <NUM> is terminated and sheet metal <NUM> is cut off in the cross machine direction. The outer diameter of the first tubular structure <NUM> third region <NUM> can be approximately equal to the center flange outer first diameter. This method provides means to integrate the first end of a common coupling <NUM> within a first wound tubular structure <NUM>.

After the above common coupling <NUM> integration process is completed, the wound first tubular structure <NUM> may be removed from mandrel <NUM> and moved to a suitable cross machine position to not interfere with succeeding winding operations <NUM>. In a preferred embodiment, first tubular structure <NUM> is supported by two rollers spaced apart underneath first tubular structure <NUM> and positioned to maintain alignment between the winding mandrel <NUM> longitudinal axis and the first tubular structure <NUM> longitudinal axis <NUM>. In a preferred embodiment, the rollers are connected to a motor and may be driven at the same rotational speed as winding mandrel <NUM>. A second tubular structure <NUM> is subsequently wound with first sheet metal <NUM> comprising the first width to form a first inner region <NUM> of the second pipe like the process to form the first tubular structure <NUM> described supra. When the first inner region <NUM> of the second tubular structure <NUM> section is slightly less than the common coupling <NUM> hub inner third diameter, the winding process is paused, and the first common coupling integrated within the first tubular structure <NUM> is prepared for installation on a first end of the second tubular structure <NUM>. In a non-limiting example, the inside surfaces and the outside surfaces of the second end of the first common coupling <NUM> hub are coated with structural adhesive prior to integration into the second tubular structure <NUM>. The first tubular structure <NUM>, comprising the common coupling <NUM>, is moved in the cross machine to place the second end of the common coupling <NUM> hub over the first end of the first inner region <NUM> of second tubular structure <NUM>. The second end of the common coupling <NUM> hub becomes adhesively bonded to first inner region <NUM> of the second tubular structure <NUM>.

In a preferred embodiment, the innermost face of the common coupling <NUM> center flange is positioned adjacent the end face of the wound first inner region <NUM> of the second tubular structure <NUM>. After the common coupling <NUM> is placed on the first end of the first inner region <NUM> of the second tubular structure <NUM>, the first sheet metal <NUM> width is reduced to a second sheet metal 120J and winding is then resumed to form second region <NUM> of the second tubular structure <NUM>. The winding process <NUM> continues until the diameter of the second region <NUM> of the second tubular structure <NUM> is approximately equal to the hub outside second diameter. The winding process is then paused, sheet metal 120J width is then increased to the first sheet metal <NUM> width and welded to the outer layer of second region <NUM> of the second tubular structure <NUM>. Winding is then resumed to form the third region <NUM> of the second tubular structure <NUM>.

The winding process <NUM> continues until the diameter of the third region <NUM> of the second tubular structure <NUM> is approximately equal to the desired target second tubular structure <NUM> outside diameter, typically equal to the desired target first tubular structure <NUM> outside diameter. The winding process is stopped and sheet metal <NUM> is cut off in the cross machine direction.

This method provides means to integrate the second end of the common coupling <NUM> within a second tubular structure <NUM>, thereby joining the first tubular structure <NUM>, comprising the first end of the common coupling <NUM>, to a second tubular structure <NUM>, within the manufacturing environment. This method may be repeated as many times as desired to join two or more tubular structures <NUM> together within the manufacturing environment and produce a desired length of connected tubular structures <NUM>.

Further, a desired length of angularly related and connected tubular structures <NUM> may be produced by sequentially winding tubular structures <NUM> onto opposite ends of couplings <NUM>, wherein the first end of a first coupling <NUM> is integrated into a first wound tubular structure <NUM> and the second end of the first coupling <NUM> is integrated into a second wound tubular structure <NUM> to matingly and fasteningly engage a first wound tubular structure <NUM> and a second wound tubular structure <NUM> where the first longitudinal axis of a first tubular structure <NUM> is angularly disposed relative to the first longitudinal axis of a first tubular structure <NUM>. In other words, the mating and fastening engagement of the first end of the first tubular structure <NUM> and the first end of the second tubular structure <NUM> can provide for the first longitudinal axis of a first wound tubular structure <NUM> and the second longitudinal axis of a second wound tubular structure <NUM> are angularly disposed relative to each other. For example, it may be desirable to provide a matingly and fasteningly engaged first wound tubular structure <NUM> disposed orthogonal from a second wound tubular structure <NUM>.

Other types of couplings <NUM> may be similarly integrated into tubular structures <NUM> by making manufacturing modifications as known by one of skill in the art. This manufacturing method may reduce or eliminate secondary fabrication processes related to the integration of couplings <NUM>, such as a separate welding operation, which are often effort intensive and costly.

As shown in <FIG>, for example, a coupling 335A having a disk-like shape (e.g., wafer or washer shaped) can be integrated into a tubular structure <NUM>. In one embodiment, coupling 335A can be matingly and fastenably attached at attachment abutments <NUM> after the formation of first wound tubular structure <NUM> and second wound tubular structure <NUM>. Attachment abutments <NUM> can comprise a weld seam or adhesive connection between a respective tubular structure <NUM> and coupling 335A.

Alternatively, a disk-like shaped coupling 335A can be integrated directly into the manufacturing process for the formation of a tubular structure <NUM>. For example, as tubular structure <NUM> is being wound about a mandrel <NUM>, an attachment abutment <NUM> can be formed between an edge of the sheet material <NUM> forming tubular structure <NUM> and the coupling 335A. The attachment abutment <NUM> can be formed by welding or adhesively connecting the edge of sheet metal <NUM> forming tubular structure <NUM> and coupling 335A as sheet metal <NUM> is being disposed about mandrel <NUM> rotating about its longitudinal axis. Without desiring to be bound by theory, it is believed that such in situ formation of the attachment abutment <NUM> between the edge of sheet metal <NUM> forming tubular structure <NUM> and coupling 335A can accommodate any material inconsistencies in the edge of sheet metal <NUM> that could cause anything but a complete end of tubular structure that is completely orthogonal to the longitudinal axis of mandrel <NUM>. In other words, any deviation in the distance between the sheet metal forming the end of tubular structure <NUM> and coupling 335A can be accounted for by the mating and fixable attachment of the edge of the sheet metal <NUM> forming the end of tubular structure <NUM> and coupling 335A by the presentation of a welded or adhesive attachment therebetween. Such mating and fastening attachment using coupling 335A can form an elongate tubular structure.

Alternatively still, as shown in <FIG>, an elongate tubular structure can be formed from a pair of tubular structures <NUM> disposed end-to-end and formed from the parallel infeed of sheet metal <NUM> toward mandrel <NUM>. Here, opposed ends of the respective sheet metal <NUM> can be matingly and fixedly attached by attachment abutments <NUM>. As shown, attachment abutments <NUM> can be provided during the winding process for the formation of each respective tubular structure <NUM> to directly attach the respective end of sheet metal <NUM> disposed adjacent the end of second sheet metal <NUM> (i.e., directly conjoining respective ends of respective sheet metals <NUM> to form an elongate tubular structure during the winding process). Alternatively, one of skill in the art may find it useful to provide an attachment abutment 400A to respective ends of respective sheet metals <NUM> prior to the formation of an elongate wound tubular structure. In this instance, the tubular structure wound will be necessarily the product of two conjoined ends of respective sheet metals <NUM> prior to entry into the winding process.

As shown in <FIG>, a wandering seam (i.e., abutment line <NUM>) can be provided to an elongate tubular structure that is the result of a direct mating and fastening engagement between the respective ends of two tubular structures <NUM> each formed from a respective sheet metal <NUM>. Here, a portion of each sheet metal <NUM> can be superimposed upon the other to form an overlap between the adjacently disposed sheet metals <NUM>. A pair of position-adjustable slitters <NUM> can slit the respective end of each respective sheet metal <NUM> as each respective sheet metal proceeds toward the winding process to form each respective tubular structure <NUM> and the resulting matingly and fasteningly engaged elongate tubular structure. As each sheet meal <NUM> approaches the winding process, each slitter <NUM> can remove an end portion of the sheet metal <NUM> cooperatively associated thereto. Ideally, the combination of removed portions of each respective sheet metal <NUM> provides for a side-by-side placement of an edge of each respective sheet metal that would facilitate the placement of an attachment abutment <NUM> thereby fasteningly and matingly joining the respective sheet metals <NUM> and forming an elongate tubular structure.

It can be preferred to provide each slitter <NUM> with cooperative movement one to the other to facilitate the creating of the mutual side-by-side placement of each edge of the respective sheet metals <NUM>. Without desiring to be bound by theory, it can also be beneficial to affix the position of each slitter <NUM> relative to each other and to cooperatively move the slitter <NUM> combination relative to the cross-machine direction relative to the sheet metals <NUM> to cause the formed side-by-side edge to continuously move in the cross-machine direction. It is believed that this 'wandering' (or 'oscillating') side-by-side edge of each sheet metal <NUM> and the ensuing development of the attachment abutment <NUM> to form a 'wandering' abutment line <NUM> thereto can shift the location of the attachment abutment <NUM> in each subsequent convolution forming the respective tubular structures <NUM> and the ensuing elongate tubular structure so that the abutment line <NUM> is not radially disposed about a single point of the longitudinal axis <NUM> of the resulting elongate tubular structure. Rather, structural integrity of the attachment abutment <NUM> and an increase in the bend modulus of the resulting elongate tubular structure can be realized if the cross-machine direction placement of the attachment abutments <NUM> are all decentralized from a single point on the longitudinal axis <NUM> of the elongate tubular structure. In other words, the attachment abutments <NUM> from each respective conjoined ends of a first convolution of each tubular structure <NUM> can each have a cross-machine direction position on the longitudinal axis <NUM> of the elongate tubular structure that is different from the cross-machine direction position of a succeeding attachment abutment(s) for a succeeding convolution of each tubular structure <NUM> that forms the elongate tubular structure. This can form the 'wandering' abutment line <NUM> shown in <FIG>.

In the embodiment shown in <FIG>, an extended length tubular structure <NUM> may be produced by overlapping sheet metals in the cross machine direction prior to winding into tubular structures <NUM>. This method can eliminate the effort required to connect tubular structures <NUM> after manufacturing is complete, such as welding tubular structures <NUM> together in an end-to-end configuration.

For example, five supply coils of sheet metal <NUM>, 105N are provided to manufacture a tubular structure <NUM>, wherein all five supply coils <NUM>, 105N comprise the same material and grade of sheet metal. The first supply coil <NUM> comprises <NUM> grade stainless steel sheet metal <NUM> which is <NUM> inches wide, the second supply coil <NUM> comprises <NUM> grade stainless steel sheet metal <NUM> which is <NUM> inches wide, the third supply coil 105N comprises <NUM> grade stainless steel sheet metal 120N which is <NUM> inches wide, the fourth supply coil <NUM> comprises <NUM> grade stainless steel sheet metal <NUM> which is <NUM> inches wide, and the fifth supply coil 105N comprises <NUM> grade stainless steel sheet metal 120N which is <NUM> inches wide.

The first sheet metal <NUM> and the second sheet metal <NUM> are unwound and conveyed in a side-by-side orientation to provide a total cross machine width of manufactured sheet metal approximately equal to their combined widths, or <NUM> inches. The third 105N, fourth <NUM>, and fifth 105N sheet metals are also unwound and conveyed in a side-by-side orientation, with the fourth sheet metal <NUM> disposed intermediate the third sheet metal 105N and the fifth sheet metal 105N, such that it is in the center position of the three-sheet-metal group. The total cross machine width of manufactured sheet metal for this three-sheet-metal group is also approximately equal to their combined widths, or <NUM> inches. After unwinding and prior to being rewound to form a tubular structure <NUM>, adhesive is applied to one side of the first sheet metal <NUM> and to one side of the second sheet metal <NUM>. For example, a permeable roll can be used to apply the adhesive in a desired pattern (defined by the aperture pattern in the surface of the permeable roll) to the top face of the first sheet metal <NUM> and the top face of the second sheet metal <NUM> as both the sheet metals travel in a near-horizontal plane. The application pattern may be optimized for the desired tubular structure <NUM> application. Adhesive can be applied in a continuous line at the transverse leading edge of the first and second sheet metals <NUM>, in continuous lines along both machine direction edges of the first and second sheet metals <NUM>, in discrete dots spaced apart in regular intervals in both the machine direction and cross machine directions of the first and second sheet metals <NUM>, and/or in a continuous line at the transverse trailing edge of the first and second sheet metals <NUM>.

After the adhesive has been applied to first and second sheet metals <NUM>, the three-sheet-metal group is brought into face-to-face contact with first and second sheet metals <NUM> such that the adhesive is disposed intermediate first layer <NUM> of sheet metal <NUM>, comprising the first and second sheet metals, and the second layer <NUM> of sheet metal, comprising the third, fourth, and fifth sheet metals, to create a <NUM>-ply laminate. The <NUM>-ply laminate is then attached to the winding mandrel <NUM>, the winding process <NUM> is initiated, and the winding process <NUM> continues until the desired wall thickness and exterior dimensions of the tubular structure <NUM> are attained, at which point the winding process is terminated and all five sheet metals <NUM>, 120N are cut off in the cross-machine direction. The winding tension and the force exerted by an adjustable pressure roll <NUM> can provide sufficient pressure to effectively bond the first <NUM> and second <NUM> layers via adhesive bonding. For example, each <NUM>-ply laminate layer can comprise two plies of adhesively bonded sheet metal, and each <NUM>-ply laminate layer within tubular structure <NUM> can be joined to the underlying <NUM>-ply laminate layer within wound tubular structure <NUM> by laser welding.

In a preferred embodiment, the widths and relative orientation of the constituent sheet metals for tubular structure <NUM> are selected to ensure the machine direction sheet metal edges within the first ply of a <NUM>-ply laminate layer do not overlie, nor are the machine direction edges in proximity to, the machine direction sheet metal edges within the second ply of the <NUM>-ply laminate. Such alignment of, or proximity of, machine direction edges in adjacent layers may produce overlying areas of reduced strength, thereby weakening the wound tubular structure <NUM> or providing a path for leakage from the interior of the tubular structure <NUM>. In the non-limiting example above, the machine direction edges in first layer <NUM> of sheet metal in the <NUM>-ply laminate are approximately <NUM> inches from a first end of tubular structure <NUM> and the machine direction edges in second layer <NUM> of the <NUM>-ply laminate are approximately <NUM> inches and <NUM> inches from the first end of tubular structure <NUM>. This significant difference in the cross-machine positions of the machine direction edges of the first <NUM> and second <NUM> layers within the <NUM>-ply laminate can provide the desired structural integrity and leak-proof construction targets for tubular structure <NUM>.

This method can provide the capability to produce a wide range of tubular structure <NUM> lengths, including tubular structure <NUM> lengths substantially greater than the individual widths of constituent sheet metals <NUM>, 120N.

Any dimensions and/or values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension and/or value is intended to mean both the recited dimension and/or value and a functionally equivalent range surrounding that dimension and/or value.

Claim 1:
An elongate tubular structure comprising:
a) a first tubular structure (<NUM>) comprising: of
<NUM>) a first sheet metal (<NUM>) having a machine direction and a width, said first sheet metal (<NUM>) being continuously and convolutely wound about a first longitudinal axis forming a plurality of convolution layers, wherein the convolution layers are adhesively bonded using structural adhesives; and wherein said first tubular structure (<NUM>) comprises a net structural density substantially less than the density of said first sheet metal (<NUM>); and said first sheet metal (<NUM>) having a tail portion; and,
<NUM>) wherein said tail portion of said first sheet metal (<NUM>) is disposed upon and bonded by a structural adhesive to an immediately subjacent convolution of said first sheet metal (<NUM>) along said width to form said first tubular structure (<NUM>);
b) a second tubular structure (<NUM>) comprising:
<NUM>) a second sheet metal (<NUM>) being convolutely wound about a second longitudinal axis, said second sheet metal (<NUM>) having a tail portion; and,
<NUM>) wherein said tail portion of said second sheet metal (<NUM>) is disposed upon and adhesively bonded using structural adhesive to an immediately subjacent convolution of said second sheet metal (<NUM>) to form said second tubular structure (<NUM>); and,
e) wherein a first end of said first tubular structure (<NUM>) is matingly and fasteningly engaged to a first end of said second tubular structure (<NUM>).