Patent Description:
Many applications for large-scale support structures have thick, tubular walls. For example, off-shore wind turbines require large, thick-walled support towers and pilings because such wind turbines are large in size and experience high loading. Processes for producing these support structures are expensive and time-consuming, requiring rolling and welding of thick steel plate (e.g., <NUM>-<NUM>). Rolling plate of such thickness requires the use of expensive specialty equipment to produce high forces. Also, welding thick plate requires a large number of weld passes, making the process lengthy and, therefore, adding to the cost of fabrication.

Accordingly, there is a need for forming support structures capable of withstanding high loading while being amenable to rapid and cost-effective fabrication.

<CIT> describes an apparatus for and method of manufacturing helically wound tubular structures including a rotating faceplate upon which are mounted a plurality of diameter defining rollers which, in operation, cause a strip material to be plastically deformed into a helical winding which may be lain down in abutting or self-overlapping relationship to form said tubular structure.

<CIT> describes an apparatus for fabricating multi-layer spiral tubes including first drive means for performing rotation of an inner cylinder around which a web is to be wrapped spirally, a slide base moveable along the longitudinal direction of the inner cylinder, the slide base being disposed on a bed so as to be slidable along the longitudinal direction of the inner cylinder, a plurality of pairs of cradles mounted on the slide base for placing the inner cylinder thereon, first depressing rolls for wrapping the web, second depressing rolls for constraining a weld portion of the web, an automatic gap detector for detecting a gap between adjacent edge portions of the wrapped web, an automatic welding machine for welding edge portions of the wrapped web, an automatic grinding machine for grinding excess metal of welding, an automatic defect hunter for detecting defects in the weld portion, a web feed table for feeding the web, second drive means for moving the web feed table, and a central control unit is provided and coupled to the first drive means, the cradles, the first depressing rolls, the second depressing rolls, the automatic gap detector, the automatic welding machine, the automatic grinding machine, the automatic defect hunter, the web feed table and the second drive means, for controlling the operations of these component means in a concentrated manner.

Tubular structures, systems, and methods are generally directed to support structures having structural properties similar to thick-walled structures while being formed using materials having thickness amendable to rolling and welding and, thus, useful for rapid and cost-effective fabrication.

According to one aspect, a tubular structure according to appended claim <NUM> is provided.

In some implementations, a collective thickness of the wrap and the base may vary in a direction parallel to the longitudinal axis of the base. For example, a thickness of the wrap varies in a direction parallel to the longitudinal axis of the base. Additionally, or alternatively, a thickness of the base is substantially constant in a direction parallel to the longitudinal axis of the base. Further, or instead, the thickness of the wrap may vary monotonically in a direction parallel to the longitudinal axis of the base. As an example, the tubular shape of the base may include a frustocone tapered in a direction parallel to the longitudinal axis and the thickness of the wrap decreases monotonically in a direction of a taper of the frustocone.

In certain implementations, the plurality of layers are at least partially stacked on one another in a radial direction. For example, each layer of the plurality of layers may circumscribe the base at least once. Additionally, or alternatively, a number of layers of the plurality of layers may vary in a direction parallel to the longitudinal axis of the base. Each layer of the plurality of layers is welded to the base, to another layer of the plurality of layers, or a combination thereof. In some cases, the respective spiral seam of a given layer may be longitudinally offset from the respective spiral seam of each layer adjacent to the given layer.

In some implementations, the base may include a seam extending about the longitudinal axis of the base. For example, the respective spiral seam of the at least one layer of the wrap may be longitudinally spaced from the seam of the base along the longitudinal axis. Additionally, or alternatively, the seam of the base may be parallel to the respective spiral seam of the at least one layer of the wrap.

According to another aspect, a system for forming a tubular structure may include a drive system including drive rolls actuatable to move a planar form of stock material in a feed direction, a curving device positioned to receive the planar form of the stock material moving in the feed direction, the curving device controllable to bend the planar form of the stock material to produce a curved form of the stock material, a plurality of support rollers operable to rotatably support a curved surface of a material, and one or more pressure rolls positioned to receive the curved form of the stock material from the curving device, and the one or more pressure rolls movable to press the curved form of the stock material from the curving device onto the curved surface of the material rotatably supported on the plurality of support rollers. In some implementations, the system may further include a joiner positioned to join the curved form of the stock material to itself, to the curved surface rotatably supported on the plurality of support rollers, or to a combination thereof. Additionally, or alternatively, the system may further include a guidance system positioned to receive the curved form of the stock material from the curving device, the guidance system including an actuator controllable to wind the curved form of the stock material along a respective spiral seam of a given layer of a tubular structure being formed. The actuator may include, for example, one or more edge guides, one or more edge rollers, one or more pinch rolls, or a combination thereof. In some instances, the guidance system may further include a sensor configured to sense a parameter indicative of a position of the curved form of the stock material along the respective spiral seam, wherein the actuator is in electrical communication with the sensor, and the actuator is adjustable based on a signal from the sensor to adjust a position of the curved form of the stock material along the respective spiral seam of the given layer of the tubular structure being formed.

According to another aspect, a method of forming a tubular structure may include bending a portion of a planar form of a strip of a stock material into a curved form of the stock material, wrapping the curved form of the stock material onto a curved surface of a base to form a spiral seam about a longitudinal axis defined by the base, and joining the curved form of the stock material at least to itself along the spiral seam.

In certain implementations, wrapping the curved form of the stock material onto the curved surface of the base may include pressing the curved form of the stock material onto the curved surface of the base.

In some implementations, joining the curved form of the stock material at least to itself along the spiral seam may include joining the curved form of the stock material to the curved surface of the base.

In certain implementations, joining the curved form of the stock material at least to itself may include welding the curved form of the stock material to itself along the spiral seam.

According to another aspect, a system for forming a tubular structure may include a tensioning roller positionable in contact with a planar form of a stock material as the planar form of the stock material moves in a feed direction, a rotator actuatable to rotate a curved surface of a base about a longitudinal axis defined by the base, a guidance system including an actuator controllable to wind the planar form of the stock material along a spiral seam about the longitudinal axis of the base, and a joiner positioned to join the stock material at least to itself along the spiral seam as the tubular structure is being formed.

In some implementations, the actuator may include one or more edge guides, one or more edge rollers, one or more pinch rolls, or a combination thereof.

In certain implementations, the guidance system may further include a sensor configured to sense a parameter indicative of a position of the stock material along the spiral seam, wherein the actuator is in electrical communication with the sensor, and the actuator is adjustable based on a signal from the sensor to adjust a position of the planar form of the stock material along the spiral seam as the tubular structure is being formed.

According to yet another aspect, a method of forming a tubular structure may include coupling a plurality of sheets in a nonlinear end-to-end engagement with one another to produce a planar form of a stock material, securing the stock material to a curved surface of a base defining a longitudinal axis, and with the stock material secured to the base, rotating the curved surface of the base about the longitudinal axis of the base, the rotation of the curved surface of the base curving the planar form of the stock material about the curved surface of the base with a first longitudinal edge and a second longitudinal edge of the stock material forming at least one spiral seam about the longitudinal axis of the base. In some implementations, the method may further include, with the stock material secured to the base and the curved surface of the base rotating about the longitudinal axis, moving the planar form of the stock material through one or more tensioning rollers. Additionally, or alternatively, the method may further include joining the stock material to itself at least along the at least one spiral seam. In some instances, joining the stock material to itself at least along the at least one spiral seam may further include joining a layer of the stock material to the curved surface of the base, to a previous layer of the stock material, or a combination thereof.

According to still another aspect, a tubular structure may include a first shell, a second shell having a frustoconical shape, the first shell nested within the second shell with the first shell and the second shell defining a gap therebetween, and a stabilizer disposed in the gap, the stabilizer maintaining a position of the first shell and the second shell relative to one another.

In some implementations, the first shell may be substantially parallel to the second shell along a longitudinal axis defined by the first shell.

In certain implementations, the stabilizer may include a filler material bonded to the first shell, the second shell, or a combination thereof.

In some implementations, the stabilizer may include a plurality of structural elements extending through the gap and coupled to each of the first shell and the second shell. For example, the first shell may define a plurality of first holes, the second shell may define a plurality of second holes aligned with the plurality of first holes, and each one of the plurality of structural elements may extend though one of the plurality of the first holes and a corresponding one of the plurality of the second holes.

According to still another aspect, a tubular structure may include a shell having a first surface and a second surface, the first surface defining an elongate cavity, the first surface opposite the second surface, the shell having a tubular shape defining a longitudinal axis extending along the elongate cavity, and the shell having a spiral seam extending about the longitudinal axis, and a plurality of elongate ribs coupled to the shell with a longitudinal dimension of each elongate rib substantially parallel to the longitudinal axis defined by the tubular shape of the shell.

In some implementations, the tubular shape of the shell may be frustoconical.

In certain implementations, at least one of the plurality of elongate ribs may be secured along the first surface of the shell.

In some implementations, at least one of the plurality of elongate ribs may be secured along the second surface of the shell.

In certain implementations, the plurality of elongate ribs may be coupled to one another along a plurality of longitudinal seams substantially coplanar the longitudinal axis defined by the tubular shape of the shell.

In some implementations, each one of the plurality of elongate ribs may be V-shaped with a first leg and a second leg coupled to one another at an apex, and the first leg and the second leg are coupled to the shell.

The embodiments will now be described more fully hereinafter with reference to the accompanying figures, in which exemplary embodiments are shown. The foregoing may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein.

Recitation of ranges of values herein are not intended to be limiting, referring instead individually to any and all values falling within the range, unless otherwise indicated herein, and each separate value within such a range is incorporated into the specification as if it were individually recited herein. The words "about," "approximately," or the like, when accompanying a numerical value, are to be construed as including any deviation as would be appreciated by one of ordinary skill in the art to operate satisfactorily for an intended purpose. Ranges of values and/or numeric values are provided herein as examples only, and do not constitute a limitation on the scope of the described embodiments. The use of any and all examples or exemplary language ("e.g.," "such as," or the like) is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of those embodiments. No language in the specification should be construed as indicating any unclaimed element as essential to the practice of the disclosed embodiments.

As used herein, the term "tubular structure" shall be understood to include any manner and form of structure defining an elongate cavity and having a substantially curvilinear two-dimensional profile about a longitudinal axis extending along the elongate cavity. Thus, unless otherwise specified or made clear from the context, some examples of tubular structures include frustocones and cylinders (e.g., right circular cylinders). Unless otherwise indicated, it shall be understood that tubular shapes described herein may include shapes approximating geometric ideals such as curvilinear, frustoconical, conical, or cylindrical. Such approximations of geometric ideals may include approximation of a frustocone using stacks of layers of material and/or deviations from a geometric ideal resulting from typical manufacturing tolerances.

Further, as used herein, the term "thickness" and variations thereof shall be understood to refer generally to a wall thickness of a given material and shall be understood in context. For example, with respect to a single layer, thickness shall be generally understood to refer to wall thickness of the single layer, unless otherwise specified or made clear from the context. Additionally, or alternatively, with respect to a plurality of layers, thickness shall be understood to refer to the overall thickness of the plurality of layers wrapped on top of one another, unless a contrary use is indicated. Further, or instead, with respect to tubular structures described herein, thickness shall be understood to refer to the overall thickness of the tubular structure at a given point along a longitudinal axis and, thus, may refer to a wall thickness of a base alone or to the combined thickness of a base supporting a wrap, as the case may be at the given point along the longitudinal axis.

Still further, as used herein, the terms "longitudinal" and "radial" shall be understood to refer to directions in a cylindrical coordinate system unless a contrary intent is clear from the context. Thus, in particular, references to a radial direction shall be understood to refer to a direction perpendicular to a longitudinal axis. Further, or instead, a longitudinal direction associated with such a cylindrical coordinate system shall be understood to be parallel to a longitudinal axis associated with the structure being described. While the longitudinal axis may correspond to a center axis of any given structure, it shall be appreciated that this does not necessarily have to be the case in certain implementations.

The devices, systems, and methods of the present disclosure are described in the context of tubular structures useful as towers for large wind turbines (e.g., off-shore wind turbines) capable of withstanding high loads. More specifically, in the interest of clear and efficient description, aspects of the present disclosure are generally described in the context of frustocones, but shall be understood to be equally applicable to cylinders unless a contrary intent is indicated. Further, for the sake of clear illustration, tubular structures are shown as unitary constructions. However, unless a contrary intent is indicated, any one or more of the various different frustocones described herein shall be understood to be manufacturable in sections according to the dimensional requirements of a given end-use. Still further, unless otherwise specified or made clear from the context, such tubular structures described herein may be used in any one or more of various different applications requiring high strength and/or high stiffness, such as tubular structures useful in pilings or other support structures for wind turbines or, more generally, for large civil structures, pipelines, pressure vessels, etc..

Referring now to <FIG>, a wind turbine assembly <NUM> may include a wind turbine <NUM> and a tubular structure <NUM>. The wind turbine <NUM> may be supported by the tubular structure <NUM>, with the tubular structure <NUM> withstanding loading conditions associated with movement of the wind turbine <NUM> and an installation environment. In certain instances, the tubular structure <NUM> may have a diameter decreasing along the length of the tubular structure <NUM> such that the top, where the wind turbine <NUM> is attached, has a smaller diameter than the bottom, where the tubular structure <NUM> is fixedly secured to the ground or other rigid surface. The longitudinally tapering diameter of the tubular structure <NUM> can be useful, for example, for addressing competing considerations of efficient use of material while providing structural strength to support the loads exerted on the tubular structure <NUM> in the field. However, the strength profiles achievable using longitudinal tapering may be subject to certain limits (e.g., dimensional constraints associated with transport and/or installation). Thus, as described in greater detail below, the thickness of material of the tubular structure <NUM> may be additionally, or alternatively, varied to facilitate achieving a predetermined strength profile of the tubular structure <NUM> while navigating practical considerations, such as installation time and cost.

The tubular structure <NUM> may include a base <NUM> and a wrap <NUM>. The base <NUM> may have a first surface <NUM> and a second surface <NUM> opposite one another, with a distance between the first surface <NUM> and the second surface <NUM> defining a thickness of the base <NUM>. The first surface <NUM> of the base <NUM> may define an elongate cavity <NUM>, and the base <NUM> may have a tubular shape defining a longitudinal axis "L" extending along the elongate cavity <NUM>. The wrap <NUM> may include a plurality of layers 116a,b,c,d (referred to collectively as the plurality of layers 116a,b,c,d and individually as a first layer 116a, a second layer 116b, a third layer 116c, and a fourth layer 116d) and the wrap <NUM> may be supported on the second surface <NUM> of the base <NUM>. That is, as described in greater detail below, the first layer 116a may be supported on the second surface <NUM> of the base <NUM>, the second layer 116b may be supported on the first layer 116a, the third layer 116c may be supported on the second layer 116b, and the fourth layer 116d may be supported on the third layer 116c. While the tubular structure <NUM> is described below as including the plurality of layers 116a,b,c,d, it shall be appreciated that this is for the sake of clear and efficient description of certain aspects associated with the wrap <NUM> including multiple layers. However, unless otherwise specified, any description associated with the plurality of layers 116a,b,c,d below shall be understood to be applicable to implementations including only a single instance of a layer and/or to implementations including more than four layers. Further, or instead, for the sake of clear and efficient description, each one of the plurality of layers 116a,b,c,d shall be understood to have the same nominal composition as one another and may have any one or more of varying different nominal thicknesses relative to one another, as may be useful for achieving a given thickness profile of the tubular structure <NUM> in a direction parallel to the longitudinal axis "L.

With the wrap <NUM> supported on the base <NUM>, the tubular structure <NUM> may have strength similar to an otherwise identically dimensioned structure formed using a thick-walled material of the same material thickness as the combined material thickness of the plurality of layers 116a,b,c,d and the base <NUM>. However, as compared to working with the thick-walled material to achieve a target thickness profile (e.g., strength profile) in a longitudinal direction, the wrap <NUM> supported on the base <NUM> offers significant advantages. For example, because each one of the plurality of layers 116a,b,c,d is individually thinner than the thick-walled material, each one of the plurality of layers 116a,b,c,d may be rolled, welded, or otherwise manipulated relatively easily as compared to the thick-walled material. That is, as compared to achieving a target overall thickness using the thick-walled material, achieving the target overall thickness using the wrap <NUM> positioned on the base <NUM> may reduce production time and/or production costs. Similarly, each one of the plurality of layers 116a,b,c,d may be sized to reduce or eliminate the need for specialty equipment that may otherwise be required for working with thick-walled material of comparable thickness to the plurality of layers 116a,b,c,d.

In general, the base <NUM> may be any one or more of various different tubular shapes useful for supporting the plurality of layers 116a,b,c,d such that the combined tubular structure <NUM> may have predetermined thickness profile in a direction parallel to the longitudinal axis "L. " For example, the base <NUM> may include a frustocone, which itself has a strength profile that makes efficient use of material for supporting the wind turbine <NUM> and about which the wrap <NUM> may be positioned to reinforce the wider end of the frustocone - thus, adding to the strength difference achievable between the wide end of the frustocone and the narrow end of the frustocone of given dimensions. Stated differently, the wrap <NUM> supported on the base <NUM> may advantageously decouple certain design constraints (e.g., strength-to-size) associated with forming a support structure using only a single layer of material.

In certain implementations, the base <NUM> may have a substantially constant thickness (e.g., allowing for normal manufacturing tolerances associated with commercially available metal sheet stock) in a direction parallel to the longitudinal axis "L. " Such a substantially constant thickness may be useful, for example, for forming the base <NUM> using any one or more of various different stock materials that may be readily and cost-effectively sourced. Additionally, or alternatively, forming the base <NUM> with a constant thickness may be useful for forming the base <NUM> quickly using any one or more of various different techniques and with little or no need for special equipment.

In general, the plurality of layers 116a,b,c,d of the wrap <NUM> may be dimensioned relative to one another and relative to the base <NUM> to achieve a predetermined thickness profile of the tubular structure <NUM> in a direction parallel to the longitudinal axis "L. " Significantly, one or more of the plurality of layers 116a,b,c,d may extend along only a portion of a longitudinal dimension of the base <NUM> such that a thickness of the wrap <NUM> in the radial direction varies in a direction parallel to the longitudinal axis "L" to facilitate varying a thickness profile of the tubular structure <NUM> in a direction parallel to the longitudinal axis "L. " For example, the number of the plurality of layers 116a,b,c,d may decrease in a direction parallel to the longitudinal axis "L" such that the wrap <NUM> has a monotonically decreasing thickness in the direction parallel to the longitudinal axis "L. " That is, according to this example, the tubular structure <NUM> may have a first overall thickness t<NUM> along a first end portion <NUM> and a second overall thickness t<NUM> along a second end portion <NUM>, with the first overall thickness t<NUM> greater than the second overall thickness t<NUM>. While one or more of the plurality of layers 116a,b,c,d may have a constant wall thickness in a direction parallel to the axis "L," it shall be appreciated that one or more of the plurality of layers 116a,b,c,d may have a wall thickness that varies at least along a portion of a longitudinal dimension of the given layer. Further, or instead, while each one of the plurality of layers 116a,b,c,d may have the same thickness profile as one another, it shall be appreciated that one or more of the plurality of layers 116a,b,c,d may have thickness profiles that differ from at least another one of the plurality of layers 116a,b,c,d. Thus, more generally, unless otherwise specified or made clear from the context, the plurality of layers 116a,b,c,d may have any one or more of various different thickness profiles in a direction parallel to the longitudinal axis "L," as may be necessary or useful to achieve an overall thickness profile of the wrap <NUM> in a direction parallel to the longitudinal axis "L.

In the particular example shown in <FIG>, the plurality of layers 116a,b,c,d of the wrap <NUM> are supported on the base <NUM> with a wrapped configuration in which the plurality of layers 116a,b,c,d of the wrap are at least partially stacked on one another in the radial direction, resulting a thickness profile of the tubular structure <NUM> having five different thicknesses in a direction parallel to the longitudinal axis "L" - with the first thickness t<NUM> along the first end portion <NUM> of the tubular structure <NUM> corresponding to the combined thickness of the base <NUM> and all of the plurality of layers 116a,b,c,d, while the second thickness t<NUM> along the second end portion <NUM> of the tubular structure <NUM> corresponds to the wall thickness between the first surface <NUM> and the second surface <NUM> of the base <NUM>.

Each one of the plurality of layers 116a,b,c,d may have a first longitudinal edge <NUM> and a second longitudinal edge <NUM> coupled to one another such that each one of the plurality of layers 116a,b,c,d circumscribes the base <NUM> at least once. For example, the first longitudinal edge <NUM> and the second longitudinal edge <NUM> of each one of the plurality of layers 116a,b,c,d may be coupled to one another along a respective plurality of spiral seams 118a,b,c,d (referred to collectively as the plurality of spiral seams 118a,b,c,d and individually as the first spiral seam 118a, the second spiral seam 118b, the third spiral seam 118c, and the fourth spiral seam 118d). That is, the first layer 116a may form the first spiral seam 118a, the second layer 116b may form the second spiral seam 118b, the third layer 116c may form the third spiral seam 118c, and the fourth layer 116d may form the fourth spiral seam 118d. Each one of the plurality of spiral seams 118a,b,c,d may extend about the longitudinal axis "L" of the base <NUM>, such as may be useful for forming each one of the plurality of spiral seams 118a,b,c,d in a continuous or substantially continuous joining process as the base <NUM> is rotated about the longitudinal axis "L," according to any one or more of the various different techniques described herein.

In certain implementations, the plurality of layers 116a,b,c,d may be joined to the base <NUM> and/or to one another, as is useful for efficiently distributing external loads through the tubular structure <NUM>. For example, the plurality of layers 116a,b,c,d may be joined to the base <NUM> and/or to one another with a plurality of welds 120a,b,c,d, e (collectively referred to as the plurality of welds 120a,b,c,d and individually referred to herein as the first weld 120a, the second weld 120b, the third weld 120c, the fourth weld 120d, and the fifth weld 120e). As used in this context, the term "weld" shall be understood to refer to a joint formed between at least two adjacent pieces of material.

For example, the first weld 120a may be a double-sided weld used to join the base <NUM> to itself along a seam <NUM> such that the base <NUM> may be a stable structure upon which the plurality of layers 116a,b,c,d of the wrap <NUM> may be positioned and to which the plurality of layers 116a,b,c,d may be directly or indirectly secured to form the tubular structure <NUM>. In certain instances, the seam <NUM> of the base <NUM> may be a spiral seam, such as may be useful for producing the base <NUM> using any one or more of various different automated techniques, such as those described in <CIT>.

Additionally, or alternatively, the first weld 120a may be formed as part of a different process than the process used to secure the plurality of layers 116a,b,c,d to the base <NUM>. Thus, while the first weld 120a may correspond to a spiral seam of the base <NUM>, it shall be appreciated that such a spiral seam may not necessarily be used on the base <NUM>, given that the base <NUM> may not be formed as part of a continuous or substantially continuous process in which spiral seams are useful. Additionally, or alternatively, the second weld 120b may penetrate into the base <NUM> as well as into the first spiral seam 118a formed by the first longitudinal edge <NUM> and the second longitudinal edge <NUM> of the first layer 116a such that the second weld 120b may be substantially coextensive with the first spiral seam 118a. Similarly, the third weld 120c may be coextensive along the second spiral seam 118b to join the first layer 116a and the second layer 116b to one another. In an analogous manner, the second layer 116b, the third layer 116c, and the fourth layer 116d may be joined to one another via the fourth weld 120d and the fifth weld 120e.

The first longitudinal edge <NUM> and the second longitudinal edge <NUM> of each one of the plurality of layers 116a,b,c,d may each include one or more features useful for facilitating alignment and/or coupling of these edges with respect to one another. For example, the first longitudinal edge <NUM> and the second longitudinal edge <NUM> may each include a single bevel such that, when aligned the first longitudinal edge <NUM> and the second longitudinal edge <NUM> of a given layer form a "V" shape into which a respective one of the second weld 120b, the third weld 120c, the fourth weld 120d, or the fifth weld 120e may be formed using a single-sided welding process. In the first layer 116a, such "V" edge preparation may, for example, facilitate joining the first longitudinal edge <NUM> and the second longitudinal edge <NUM> to one another and to the base <NUM> simultaneously, resulting a better weld quality. Similarly, for each one of the subsequent layers (the second layer 116b, the third layer 116c, and the fourth layer 116d), the "V" edge preparation may facilitate joining the first longitudinal edge <NUM> and the second longitudinal edge <NUM> to one another and to a preceding layer simultaneously, with a corresponding improvement in weld quality.

In some instances, the plurality of spiral seams 118a,b,c,d may be longitudinally offset from one another in a direction parallel to the longitudinal axis "L" of the base <NUM>. With such an offset, the plurality of seams 118a,b,c,d do not line up on top of each other in a radial direction extending from the longitudinal axis "L. " This type of spacing may facilitate distributing weld-induced stresses along the tubular structure <NUM>, as the tubular structure <NUM> is being formed, thus facilitating control over quality of the tubular structure <NUM>.

Referring now to <FIG> and <FIG>, a system <NUM> may include a drive system <NUM>, a curving device <NUM>, a plurality of support rollers <NUM>, and one or more instances of a pressure roll <NUM>. Unless otherwise specified or made clear from the context, the system <NUM> may be operable to form the tubular structure <NUM> (<FIG>). For example, the drive system <NUM> may be actuatable to move a planar form of stock material <NUM> (e.g., from a stock source <NUM>) in a feed direction "F" and into the curving device <NUM>, where the planar form of the stock material <NUM> may be pre-curved into a curved form of the stock material <NUM>. The curved form of the stock material <NUM> may be moved between the one or more instances of the pressure roll <NUM> and a curved surface <NUM> of a material supported on the plurality of support rollers <NUM> to, ultimately, form the wrap <NUM> (<FIG>) of the tubular structure <NUM> (<FIG>). That is, depending on the stage of fabrication and the thickness profile of the tubular structure <NUM> (<FIG>) being formed using the system <NUM>, the curved surface <NUM> receiving the curved form of the stock material <NUM> may be the second surface <NUM> of the base <NUM> (<FIG>) or a surface of a preceding layer of the wrap <NUM> (<FIG>). Pre-rolling the stock material <NUM> in the curving device <NUM> to form the curved form of the stock material <NUM> may increase the degree to which the stock material <NUM> conforms to the curved surface <NUM> (e.g., to the base <NUM> and/or to the previous one of the plurality of layers 116a,b,c,d in <FIG>) to increase strength, stiffness, and/or other desirable properties of the tubular structure (e.g., the tubular structure <NUM> in <FIG>) being formed.

In general, the drive system <NUM> may include drive rolls <NUM> actuatable to move the planar form of the stock material <NUM> in the feed direction "F. " For example, the drive rolls <NUM> may pinch the planar form of the stock material such that rotation of the drive rolls <NUM> can move the planar form of the stock material <NUM> along the feed direction "F. " In certain implementations, the feed direction "F" can be substantially constant (e.g., with the drive rolls <NUM> in a substantially stationary position as the rotation of the drive rolls <NUM> moves the planar form of the stock material <NUM> to and/or through the curving device <NUM>). Additionally, or alternatively, the feed direction "F" can change such that the planar form of the stock material <NUM> undergoes rotational motion and/or substantially rotational motion as the planar form for the stock material <NUM> is moved to and through the curving device <NUM>. Such changes in the feed direction "F" can be useful for aligning edges of the stock material <NUM> to form any one or more of the spiral seams described herein. Examples of such changes in the feed direction "F" to produce rotational and/or substantially rotational motion as part of the fabrication process of tubular structures are described in <CIT>, and <CIT>. More generally, any equipment suitable for moving planar material according to any of various different techniques known in the art can be used to move the planar form of the stock material <NUM> from the stock source <NUM> to, and in some instances through, the curving device <NUM>. Such equipment can include, for example, robotic arms, pistons, servo motors, screws, actuators, rollers, drivers, electromagnets, or combinations thereof.

The curving device <NUM> may be positioned to receive the planar form of the stock material <NUM> moving in the feed direction "F," and the curving device <NUM> may bend the planar form of the stock material <NUM> fed into it to produce the curved form of the stock material <NUM>. As an example, the curving device <NUM> may bend the planar form of the stock material <NUM> without imparting in-plane deformation to the stock material <NUM>. Additionally, or alternatively, the curving device <NUM> may impart a controlled amount of curvature to the stock material <NUM> such that the stock material <NUM> in the curved form may approximately match curvature of the curved surface <NUM> onto which the curved form of the stock material <NUM> is moved.

The curving device <NUM> may, for example, include roll banks 242a, 242b, 242c positioned relative to one another and to the planar form of the stock material <NUM> to impart curvature to the planar form of the stock material <NUM> fed through the roll banks 242a, 242b, 242c. In certain instances, the roll banks 242a, 242b, 242c may be arranged as a triple-roll and, further or instead, the roll banks 242a, 242b, 242c may be movable relative to one another to vary a bending moment applied to the stock material <NUM> moving through the curving device <NUM>. Each one of the roll banks 242a, 242b, 242c may include, for example, a plurality of individual rollers independently rotatable relative to one another and arranged along a respective axis defined by the respective one of the roll bank 242a, 242b, 242c. Further, or instead, the individual rollers of the roll banks 242a, 242b, 242c may be positionable relative to a respective axis defined by the one of the roll banks 242a, 242b, 242c (e.g., through an actuation signal received by a control system).

In general, the support rollers <NUM> may allow the curved surface <NUM> of the tubular structure being formed to rotate relative to the curved form of the stock material <NUM> moving from the curving device <NUM> onto the curved surface <NUM>. In some implementations, one or more of the support rollers <NUM> may be actively controlled to rotate the curved surface <NUM> at a predetermined rate, such as may be useful for providing tension to the curved form of the stock material <NUM> to facilitate locating the curved form of the stock material <NUM> tightly onto the curved surface <NUM>. In some instances, one or more of the support rollers <NUM> may be passive such that the force of the curved form of the stock material <NUM> moving onto the curved surface <NUM> may rotate the curved surface <NUM> as the tubular structure is being formed.

Each of the one or more instances of the pressure roll <NUM> may include one or more rollers movable to press the curved form of the stock material <NUM> onto the curved surface <NUM> rotatably supported on the plurality of support rollers <NUM>. For example, at least one instance of the pressure roll <NUM> may be rotatable about an axis parallel to the curved surface <NUM> of the base <NUM> to move the curved form of the stock material <NUM> onto the curved surface <NUM> from the curving device <NUM>. Additionally, or alternatively, at least one instance of the pressure roll <NUM> may be movable in a radial direction relative to the tubular structure being formed, with such radial movement of the at least one instance of the pressure roll <NUM> useful for controlling a degree of conformity between the curved form of the stock material <NUM> and the curved surface <NUM>. Stated differently, radial movement of the at least one instance of the pressure roll <NUM> may reduce the likelihood of unintended gaps between layers of material of a wrap and/or between the wrap and a base, with the reduced likelihood of such gaps including improved load bearing performance.

In certain implementations, the system <NUM> may include a joiner <NUM> positioned or positionable to join (e.g., mechanically couple) the curved form of the stock material <NUM> to itself (e.g., along any one or more of the spiral seams described above with respect to <FIG>). Further, or instead, the joiner <NUM> may be positioned or positionable to join the curved form of the stock material <NUM> to the curved surface <NUM> rotatably supported on the plurality of support rollers <NUM>. As an example, the joiner <NUM> may be positioned between two instances of the pressure roll <NUM> to increase the likelihood of a tight fit between the curved form of the stock material <NUM> to the curved surface <NUM> as a joining operation is carried out. In some instances, the joiner <NUM> may mechanically couple material together on a continuous basis as the curved form of the stock material <NUM> moves onto the curved surface <NUM> rotating on the support rollers <NUM>. Such continuous mechanical coupling may be useful for, among other things, achieving target structural performance of the tubular structure being formed. Additionally, or alternatively, the joiner <NUM> may be operable to intermittently couple (e.g., at fixed distances) material along any one or more of the various different spiral seams described herein, with such intermittent coupling being useful for faster throughput.

The joiner <NUM> may include, for example, a welder operable to form any one or more of the various different welds described herein. A variety of techniques for welding are known in the art and may be adapted for joining any one or more edges together as contemplated herein. This may, for example, include any welding technique that melts a base metal or other material along any one or more of the various different seams described herein, optionally along with a filler added to the joint to improve strength of the bond. Conventional welding techniques suitable for structurally joining metal include, by way of example and not limitation: gas metal arc welding (GMAW), including inert gas (MIG) and/or metal active gas (MAG); submerged arc welding (SAW); laser welding; and gas tungsten arc welding (also known as tungsten, inert gas or "TIG" welding); and many others.

In certain implementations, the system <NUM> may include a guidance system <NUM> positioned to receive the curved form of the stock material <NUM> from the curving device <NUM>. The guidance system <NUM> may include, for example, an actuator <NUM> controllable (e.g., in a direction substantially parallel to a longitudinal axis of the tubular structure being formed) to wind the curved form of the stock material <NUM> along a respective spiral seam of a given layer of a wrap being coupled to the base of the tubular structure being formed. Some examples of the actuator <NUM> include, but are not limited to, one or more edge guides, one or more edge rollers, one or more pinch rolls, or a combination thereof. In some cases, the guidance system <NUM> may further include a sensor <NUM> operable to sense a parameter indicative of a position of the curved form of the stock material <NUM> along the spiral seam being formed by the curved form of the stock material <NUM> moving onto the curved surface <NUM>. Examples of the sensor <NUM> may include an optical sensor, one or more cameras of a machine vision system, a contact sensor, or a combination thereof. The actuator <NUM> may, for example, be adjustable based on a signal from the sensor <NUM> to implement a corresponding adjustment of a position of the curved form of the stock material <NUM> along the spiral seam being formed as the curved form of the stock material <NUM> moves onto the curved surface <NUM>.

While one or more aspects of operation of the system <NUM> may be carried out through manual operation by an operator, the system <NUM> may include a control system <NUM> to facilitate accurate and repeatable control of certain aspects of operation of the system <NUM> in some implementations. The control system <NUM> may include, for example, a processing unit <NUM> and a storage medium <NUM> in communication with the processing unit <NUM>. The processing unit <NUM> may include one or more processors, and the storage medium <NUM> may include a non-transitory, computer-readable storage medium. The storage medium <NUM> may store computer-executable instructions that, when executed by the processing unit <NUM>, cause the system <NUM> to perform one or more of the various different aspects of fabrication of a tubular structure using the system <NUM>. Optionally, the control system <NUM> may include an input device (e.g., a keyboard, a mouse, and/or a graphical user interface) in communication with the processing unit <NUM> and the storage medium <NUM> such that the processing unit <NUM> is additionally, or alternatively, responsive to input received through the input device as the processing unit <NUM> executes one or more of the fabrication methods described herein.

<FIG> is a flowchart of an exemplary method <NUM> of forming a tubular structure. Unless otherwise specified or made clear from the context, any one or more aspects of the exemplary method <NUM> may be implemented as computer-readable instructions stored on the storage medium <NUM> (<FIG>) and executable by the processing unit <NUM> (<FIG>) of the control system <NUM> (<FIG>) to operate the system <NUM> (<FIG>) to form the tubular structure <NUM> described with respect to <FIG>. In certain implementations, the exemplary method <NUM> may include certain preparatory steps that may include coupling a plurality of sheets to one another in a nonlinear end-to-end engagement with one another to produce a planar form of the stock material having straight, longitudinal edges, while being wrappable to form a spiral seam. Further, or instead, the exemplary method <NUM> may include securing the stock material to a curved surface of the base or to a preceding layer, as the case may be, at the start of the process of wrapping a given layer. For the sake of clear and efficient explanation, these preparatory steps are described in detail below with respect to the discussion of <FIG>, given that such steps are more easily understood with respect to the illustration of the hardware in <FIG> and <FIG> used to carry out the method represented in <FIG>. However, unless otherwise indicated or made clear from the context, any one or more of the preparatory steps described below with respect to <FIG> shall be understood to be includable in the exemplary method <NUM> without departing from the scope of the present disclosure.

As shown in step <NUM>, the exemplary method <NUM> may include bending a portion of a planar form of a strip of a stock material into a curved form of the stock material. Such bending may be carried out, for example, by moving the planar form of the stock material to and through a curving device, such as the curving device <NUM> (<FIG> and <FIG>). Through such bending, the stock material may approximate a curvature of the curved surface onto which the stock material may be guided. For example, in instances in which the tubular structure being formed is frustoconical, the planar form of the strip of stock material may be curved to progressively changing diameters in accordance with corresponding changes in diameter of the frustoconical shape of the tubular structure being formed. In this context, it shall be appreciated that, while a plurality of layers wrapped on a frustoconical base may deviate from a geometric frustocone, the resulting shape of the tubular structure with these features is nevertheless referred to herein as a frustocone.

As shown in step <NUM>, the exemplary method <NUM> may include wrapping the curved form of the stock material onto a curved surface of a base (e.g., the base <NUM> in <FIG> and <FIG>) to form a spiral seam about a longitudinal axis defined by the base. The base may be formed separately (e.g., via can-rolling or spiral welding processes) and, further or instead, may be a single layer of material (e.g., having a constant thickness) having a tubular shape. In general, wrapping the curved form of the stock material onto the curved surface of the base may include any manner and form of physical positioning of the curved form of the stock material to fit the stock material onto the curved surface while also positioning the stock material in abutment with itself (e.g., two longitudinal edges) to form a spiral seam extending about the longitudinal axis of the base. Thus, for example, wrapping the curved form of the stock material onto the curved surface may include moving the curved form of the stock material using any one or more of the various different guidance systems described herein. Further, or instead, wrapping the curved form of the stock material onto the curved surface may include pressing the stock material onto the curved surface via pressure exerted by one or more pressure rolls described herein.

As shown in step <NUM>, the exemplary method <NUM> may include joining the curved form of the stock material at least to itself along the spiral seam. Further, or instead, the stock material may be joined to the curved surface of the base along the spiral seam. Unless otherwise specified or made clear from the context, joining the curved form of the stock material to itself along the spiral seam may include any one or more of various different welding techniques described herein. As a specific example, joining the curved form of the stock material to itself may include welding the curved form of the stock material to itself and to the curved surface of the base along the spiral seam. In certain instances, the weld process may include inspection, such as visual, ultrasonic, magnetic particle, or other techniques, performed manually or automatically, after one layer has been applied and before a next layer is applied to cover or otherwise obscure inspection of the weld. Additionally, or alternatively, a cap of the weld may be removed (e.g., by grinding away the cap material until the weld is flush with the surface of the layer being welded) using any one or more of various different manual and/or automated techniques before the next layer is applied. For example, weld cap removal may be carried out in-line with the weld and, further or instead, may be performed continuously as the tubular structure is formed, reducing the time and cost required for weld cap removal. As compared to instances in which the weld cap is not removed, removing the weld cap may facilitate conforming subsequent layers more tightly to the base or to a previous layer, as the case may be.

While steps of the exemplary method <NUM> have been described with respect to securing a first layer of a wrap onto a base, it shall be appreciated that any one or more of the various different steps of the exemplary method <NUM> may be repeated as necessary for adding additional layers of a wrap to the base. It shall be appreciated, however, that with repetition of steps for placement of layers after the first layer, each subsequent layer is wrapped upon a preceding layer in the stack of layers and each layer may form a different spiral seam than the spiral seam formed by the preceding layer.

Having described certain systems and methods for forming the tubular structure <NUM> (<FIG>) based on pre-curving layers of a wrap prior to positioning such layers on a base and methods of operating such a system, attention is now directed to the description of systems and methods of forming the tubular structure <NUM> (<FIG>) using tension to fit a curved form of stock material onto a curved surface.

Referring now to <FIG> and <FIG>, a system <NUM> may include one or more instances of a tensioning rollers <NUM>, a rotator <NUM>, a guidance system <NUM>, and a joiner <NUM>. Each instance of the tensioning roller <NUM> may be positionable in contact with a planar form of a stock material <NUM> as the planar form of the stock material <NUM> is moved in the feed direction "F" to impart tension to the planar form of the stock material <NUM>. The rotator <NUM> may be actuatable to rotate a curved surface, such as the second surface <NUM>, of the base <NUM> about the longitudinal axis "L. " The stock material <NUM> may be directly or indirectly attached to the curved surface of the base <NUM> such that, as the rotator <NUM> rotates the curved surface of the base <NUM> in a direction away from the one or more instances of the tensioning roller <NUM>, the rotation of the base <NUM> may pull the planar form of the stock material <NUM> from a stock source <NUM> toward the base <NUM> in a feed direction "F. " As the curved surface of the base <NUM> continues to rotate, the planar form of the stock material <NUM> may be pulled onto the curved surface of the base <NUM> to bend the stock material <NUM> along a first spiral seam 118a to form the first layer 116a.

Accurate positioning of the stock material <NUM> along the first spiral seam <NUM> for formation of the first layer 116a (and for positioning along spiral seams associated with subsequent layers) may be advantageously achieved through a combination of a shape of the planar form of the stock material <NUM> and operation of the guidance system <NUM>. That is, the planar form of the stock material <NUM> from the stock source <NUM> may include a plurality of sheets in a non-linear end-to-end engagement with one another according to any one or more of various different techniques. In particular, unless otherwise specified or made clear from the context, the planar form of the stock material <NUM> and any other stock material described herein (e.g., the stock material <NUM> in <FIG>) may include a plurality of sheets in a non-linear end-to-end-engagement with another according to the techniques for arranging straight-edged sheets of material relative to one another to form a spiral seam, as described in in <CIT>. Further, between the one or more instances of the tensioning roller <NUM> and the base <NUM>, the guidance system <NUM> may make adjustments to the position of the stock material <NUM> such that the stock material <NUM> winds along the first spiral seam 118a.

Following rotation of the curved surface of the base <NUM> to form the first layer 116a it shall be appreciated that analogous rotation of the curved surface of the base <NUM> about the longitudinal axis "L" may form a subsequent layer by pulling the planar form of the stock material <NUM> onto the first layer 116a. This process may be repeated as necessary to form a wrap including a predetermined number and position of layers to achieve a thickness profile according to design specifications. Among other things, the resulting tight fit from pulling the planar form of the stock material <NUM> onto a curved surface of the base <NUM> or onto a preceding layer of material may be useful for increasing structural quality in the tubular structure being formed.

In general, the one or more instances of the tensioning roller <NUM> may be actuatable to move perpendicular to the major surfaces of the planar form of the stock material <NUM> to increase or decrease tension in the planar form of the stock material <NUM>, as may be useful for controlling positioning of the stock material <NUM> along a spiral seam. Additionally, or alternatively, tension in the planar form of the stock material <NUM> moving in the feed direction "F" may be adjusted by controlling resistance of the rotation of the tensioning roller <NUM>. The one or more instances of the tensioning roller <NUM> may define a gap through which the planar form of the stock material <NUM> may pass, and the position of the one or more instances of the tensioning roller <NUM> may be controllable to move the gap in a direction perpendicular to the feed direction "F. " Additionally, or alternatively, each instance of the tensioning roller <NUM> may be rotatable at least about an axis transverse to the feed direction "F.

The rotator <NUM> may include, for example, one or more rollers drivable to rotate the base <NUM> about the longitudinal axis "L" at a controlled speed. Further, or instead, at least a portion of the rotator <NUM> may support the base <NUM> as the base <NUM> rotates to wrap the stock material <NUM> along a spiral seam. For example, the rotator <NUM> may at least support each end of the base <NUM>.

The guidance system <NUM> may include an actuator <NUM> controllable to wind the planar form of the stock material <NUM> along a spiral seam extending about the longitudinal axis "L" of the base <NUM>. The actuator <NUM> may, for example, control a position of the planar form of the stock material <NUM> in a direction transverse to the feed direction "F," as may be useful for achieving fine adjustments of the stock material <NUM> to position longitudinal edges of the stock material <NUM> adjacent to one another to form the spiral seam as the stock material <NUM> is wound onto the base <NUM> through rotation of the base <NUM>. The actuator <NUM> may include, for example, one or more edge guides, one or more edge rollers, one or more pinch rolls, or a combination thereof.

Additionally, or alternatively, the guidance system <NUM> may include a sensor <NUM> operable to sense a parameter indicative of a position of the planar form of the stock material <NUM>. The actuator <NUM> may be adjustable based on a signal from the sensor <NUM> to adjust a position of the planar form of the stock material <NUM> as the tubular structure is being formed. For example, the sensor <NUM> may sense a position of the planar form of the stock material <NUM> at a point just before the stock material <NUM> is wound along a spiral seam. Additionally, or alternatively, the sensor <NUM> may sense a position of the stock material <NUM> (e.g., longitudinal edges of the stock material <NUM>) along the spiral seam being formed by the stock material <NUM>. The sensor <NUM> may include, for example, an optical sensor, a camera as part of a machine vision system, a contact sensor, or a combination thereof.

In general, the joiner <NUM> may mechanically couple the stock material <NUM> to itself and/or to the base <NUM> according to any one or more of various different techniques described herein. Thus, the joiner <NUM> may include a welder operable to form any one or more of the various different welds described herein. For example, with respect to securing the stock material <NUM> to the base <NUM>, the joiner <NUM> may form the weld 120b (<FIG>). It shall be appreciated that the joiner <NUM> may similarly form other welds associated with the addition of subsequent layers as necessary to form a wrap on the base <NUM> to achieve a tubular structure having a predetermined strength profile.

<FIG> is a flowchart of an exemplary method <NUM> of forming a tubular structure. Unless otherwise specified or made clear from the context, any one or more aspects of the exemplary method <NUM> may be implemented as computer-readable instructions stored on the storage medium <NUM> (<FIG>) and executable by the processing unit <NUM> (<FIG>) of the control system <NUM> (<FIG>) to operate the system <NUM> (<FIG>) to form the tubular structure <NUM> described with respect to <FIG>.

As shown in step <NUM>, the exemplary method <NUM> may include coupling (e.g., welding) a plurality of sheets (e.g., metal sheets in the shape of trapezoids) in end-to-end engagement with one another produce a planar form of the stock material. In this context, end-to-end coupling shall be understood to include coupling together a short edge of one sheet to a short edge of another sheet to form a seam transverse to parallel long edges of each sheet. Such coupling may include, for example, welding sheets together according to any one or more of the various different welding techniques described herein. As indicated above, the nonlinear end-to-end engagement of the plurality of sheets may include an orientation in which with straight edges (e.g., parallel straight edges) may be curved to form spiral seams. In certain implementations, the plurality of sheets may be coupled in a nonlinear end-to-end engagement with one another such that the longitudinal edges of each sheet are transvers to the longitudinal edges of at least one other sheet. Further, or instead, the plurality of sheets may be coupled in a linear end-to-end engagement with one another such that the longitudinal edges of each sheet are colinear to the longitudinal edges of each of the other sheets. Further, or instead, in instances in which the tubular structure being formed is a right-circular cylinder, a single sheet may be used as the planar form of the stock material.

As shown in step <NUM>, the exemplary method <NUM> may include securing the stock material to a curved surface of a base defining a longitudinal axis. It may be generally desirable to use one or more techniques for permanently securing the stock material to the curved surface to reduce the likelihood of unintended decoupling of the stock material from the curved surface as tension is imparted to the stock material. For example, the stock material may be secured to the curved surface of the base using one or more welding techniques described herein.

As shown in step <NUM>, the exemplary method <NUM> may include rotating the curved surface of the base about the longitudinal axis of the base. With the stock material secured to the base (e.g., directly or indirectly secured to the curved surface of the base), it shall be appreciated that rotation of the curved surface of the base may curve the planar form of the stock material about the curved surface of the base. That is, the stock material may be curved about the curved surface of the base such that the stock material and the base collectively form at least a portion of the tubular structure being formed. In the case of a first layer, the planar form of the stock material curving about the curved surface of the base may fit the stock material directly onto the curved surface of the base. Additionally, or alternatively, for subsequent layers, the planar form of the stock material curving about the curved surface of the base may fit the stock material directly onto a preceding layer of stock material secured to the base. In certain implementations, by controlling a position of the stock material as the stock material is curved about the curved surface of the base, a first longitudinal edge and a second longitudinal edge of the stock material may form a spiral seam about the longitudinal axis of the base such that the stock material and the base collectively form at least a portion of the tubular structure being formed.

As shown in step <NUM>, the exemplary method <NUM> may include, with the stock material secured to the base, moving the planar from of the stock material through one or more tensioning rollers as the curved surface of the base rotates about the longitudinal axis. The one or more tensioning rollers may be adjustable, for example, to adjust an amount of tension in the planar form of the stock material to facilitate achieving a tight fit of the stock material moving onto the curved surface of the base.

As shown in step <NUM>, the exemplary method <NUM> may include joining the stock material to itself along the at least one spiral seam. For example, joining the stock material to itself at least along the at least one spiral seam may include welding the stock material to itself to form a weld coextensive with the spiral seam. Additionally, or alternatively, joining the stock material to itself along the at least one spiral seam may include joining the stock material to the curved surface of the base, to a preceding layer of the stock material, or a combination thereof.

In general, unless otherwise specified or made clear from the context, it shall be appreciated that any one or more of the various different steps of the exemplary method <NUM> may be repeated as necessary to wrap a plurality of layers onto one another in any number and orientation of layers useful for forming a tubular structure having a predetermined strength profile.

While certain implementations have been described, other implementations are additionally or alternatively possible.

For example, while a planar form of a stock material has been described as being wound onto a base to form a tubular structure, it shall be appreciated that the planar form of stock material may be additionally, or alternatively, wrapped onto a reusable mandrel, rather than a base forming a portion of the final tubular structure. Continuing with this example, the process of adding material may be repeated, using the first layer (formed on the mandrel) as a base, until a tubular structure is formed with a wrap including a number and position of layers, as necessary to achieve a predetermined strength profile of the tubular structure.

As another example, reinforced tubular structures have been described as including a base and one or more layers wrapped about the base to impart increased thickness - and therefore strength - to the base, other approaches to reinforcing tubular structures are additionally or alternatively possible. For example, as described in examples that follow, a tubular structure may include a stabilizer disposed between a plurality of shells to impart overall strength to the tubular structure.

Referring now to <FIG>, a tubular structure <NUM> may include a first shell <NUM>, a second shell <NUM>, and a filler material <NUM>. The second shell <NUM> may have a frustoconical shape, and the first shell <NUM> may be nested within the second shell <NUM> such that the first shell <NUM> and the second shell <NUM> define a gap therebetween. The filler material <NUM> may be disposed in the gap defined between the first shell <NUM> and the second shell <NUM>. For example, the filler material <NUM> may fill the gap, as may be useful for achieving uniform strength characteristics in the tubular structure <NUM>. In particular, the filler material <NUM> may facilitate transferring stresses (e.g., shear stress) between the first shell <NUM> and the second shell <NUM>. Additionally, or alternatively, the filler material <NUM> disposed in the gap defined by the first shell <NUM> and the second shell <NUM> may reduce the likelihood of buckling of the first shell <NUM> and the second shell <NUM> under a given load, as compared to the likelihood of buckling the first shell <NUM> and the second shell <NUM>, under the same load, without the filler material <NUM> between the first shell <NUM> and the second shell <NUM>. That is, the tubular structure <NUM> may achieve strength and stiffness comparable to strength and stiffness of a tubular structure formed with thick, solid metal walls. However, because the first shell <NUM> and the second shell <NUM> may have thin metal walls compared to the tubular structure formed with thick, solid metal walls, the strength performance of the tubular structure <NUM> may be generally achievable at significantly less cost and with significantly faster production time, as compared to forming the tubular structure that achieves the same strength performance using thick, solid metal walls.

In general, one or both of the first shell <NUM> or the second shell <NUM> may be formed using spiral formation of a strip of a stock material. In certain instances, the first shell <NUM> and the second shell <NUM> may be concentrically aligned with one another such that the gap defined between the first shell <NUM> and the second shell <NUM> is substantially symmetric about a center axis "C" defined by the first shell <NUM> and the second shell <NUM>. Among other things, such symmetry may be generally useful for forming the tubular structure <NUM> with substantially uniform strength in a circumferential direction about the frustoconical shape of the second shell <NUM>. In some cases, the second shell <NUM> may circumscribe the first shell <NUM> such that the gap formed by the first shell <NUM> and the second shell <NUM> is annular, with such an annulus being useful for containing the filler material <NUM> between the first shell <NUM> and the second shell <NUM> and away from external conditions. As a more specific example, the first shell <NUM> may be substantially parallel to the second shell <NUM> along a longitudinal axis (e.g., the center axis "C") defined by the first shell <NUM>. That is, the first shell <NUM> may have a frustoconical shape parallel to the frustoconical shape of the second shell <NUM> such that the gap between the first shell <NUM> and the second shell <NUM> is also frustoconical. As with other frustoconical shapes described herein, a frustoconical shape of a gap between the first shell <NUM> and the second shell <NUM> may be useful for achieving strength performance using less material and, thus, ultimately at less cost.

The filler material <NUM> may, for example, include a material bonded to the first shell <NUM>, the second shell <NUM>, or a combination thereof. The filler material may include any one or more of various different types of material that may bond to metal while having desirable strength characteristics for a given end-use application. As an example, the filler material may include a material having consistent strength characteristics throughout a volume of the filler material. Some examples of materials useful in the filler material include cement, filled epoxy, grout, high density foam, sand, or combinations thereof. In some instances, the filler material may include a plurality of constituent components spatially separated from one another, with such spatial separation of constituent components useful for achieving a targeted strength profile in a longitudinal direction parallel to the center axis "C. " Continuing with this example, constituent components of such a filler material may include different concrete formulations arranged in strata in a direction parallel to the center axis "C.

Referring now to <FIG>, a tubular structure <NUM> may include a first shell <NUM>, a second shell <NUM>, and a plurality of structural elements <NUM> (e.g., steel rods, ribs, tubes, or a combination thereof). Unless otherwise specified or made clear from the context, the first shell <NUM> and the second shell <NUM> may be arranged relative to one another in a manner analogous to any one or more of the arrangements of the first shell <NUM> and the second shell <NUM> described above with respect to <FIG>. Thus, for example, the second shell <NUM> may have a frustoconical shape, and the first shell <NUM> may be nested in the second shell <NUM> such that a gap <NUM> is defined between the first shell <NUM> and the second shell <NUM>. The plurality of structural elements <NUM> may be coupled to each of the first shell <NUM> and the second shell <NUM> and extend through the gap <NUM>. Through such coupling, each one of the plurality of structural elements <NUM> may facilitate transferring shear loading and/or reducing the likelihood of buckling of each shell. More specifically, with the plurality of structural elements <NUM> coupling the first shell <NUM> and the second shell <NUM>, the tubular structure <NUM> may achieve structural performance similar to structural performance of tubular structures formed with thick, solid metal walls. Thus, as with other examples describe herein, the tubular structure <NUM> may facilitate achieving structural performance comparable to tubular structures formed with thick, solid metal walls, while being significantly less expensive to produce.

In certain instances, the first shell <NUM> may define a plurality of first holes <NUM> and the second shell <NUM> may define a plurality of second holes <NUM> aligned with the plurality of first holes <NUM>. Continuing with this example, each one of the plurality of structural elements <NUM> may extend through one of the plurality of first holes <NUM> and a corresponding one of the plurality of the second holes <NUM>, as may be useful for installing and/or replacing the structural elements <NUM> in the gap <NUM> without requiring access to the gap <NUM>. For example, each one of the plurality of structural elements <NUM> may be passed through the plurality of first holes <NUM> to the plurality of second holes <NUM> to couple the first shell <NUM> and the second shell <NUM> to one another. Additionally, or alternatively, each one of the plurality of structural elements <NUM> may be welded or otherwise joined to each of the first shell <NUM> and the second shell <NUM> to stiffen the tubular structure <NUM>, as compared to the stiffness of the first shell <NUM> and the second shell <NUM> alone.

While certain implementations of reinforced tubular structures have been described as including stabilizers disposed between shells, it shall be appreciated that stabilizers may additionally or alternatively be disposed along an outer surface of a shell to form a tubular structure with structural performance comparable to structural performance of tubular structures formed of thick, solid metal walls, while being less expensive and faster to produce than such tubular structures formed of thick, solid metal walls.

For example, referring now to <FIG>, a tubular structure <NUM> may include a shell <NUM> and a plurality of elongate ribs <NUM>. The shell <NUM> may have a first surface <NUM> and a second surface <NUM> opposite one another, and the first surface <NUM> may define a cavity <NUM>. The shell <NUM> may have a tubular shape (e.g., a frustoconical shape) defining a longitudinal axis "L. " The shell <NUM> may have a spiral seam <NUM> extending about the longitudinal axis "L," and each one of the plurality of elongate ribs <NUM> may be coupled to the shell <NUM> (e.g., along one or both of the first surface <NUM> or the second surface <NUM>) with a longitudinal dimension of each elongate rib <NUM> substantially coplanar with the longitudinal axis "L" such that the longitudinal dimension of each one of the elongate ribs <NUM> extends across the spiral seam <NUM> of the shell <NUM> to provide structural support across the spiral seam <NUM>. In certain implementations, each one of the elongate ribs <NUM> may be notched to facilitate passing the spiral seam <NUM> of the shell <NUM> underneath the plurality of elongate ribs <NUM> with reduced likelihood of interfering with the tight fit between each one of the plurality of elongate ribs <NUM> and the shell <NUM>.

The plurality of elongate ribs <NUM> may be spaced relative to one another along the shell <NUM> according to any spacing as may be useful for achieving a target structural performance. For example, the plurality of elongate ribs <NUM> may be coupled to one another along a plurality of longitudinal seams <NUM> substantially coplanar with the longitudinal axis "L" defined by the tubular shape of the shell. As a more specific example, the plurality of elongate ribs <NUM> may be coupled to one another to circumscribe the shell <NUM>, as may be useful for achieving substantially uniform strength about a circumference of the shell <NUM>. While any one or more of various different techniques may be used to couple the plurality of elongate ribs <NUM> to the shell <NUM>, the longitudinal seams <NUM> may be formed by welding the plurality of elongate ribs <NUM> to the shell <NUM> using a full or skip weld in some implementations.

In certain implementations, each one of the elongate ribs <NUM> may be V-shaped with a first leg <NUM> and a second leg <NUM> coupled to one another at an apex <NUM>, and the first leg <NUM> and the second leg <NUM> coupled to the shell <NUM> such that the apex <NUM> points in a radial direction away from the shell <NUM>. Continuing with this example, the elongate ribs <NUM> may be formed into the V shape using a press brake. Additionally, or alternatively, the elongate ribs <NUM> may be roll formed, or formed of pairs of flat strips of material joined (e.g., welded) together at the apex <NUM>.

The above systems, devices, methods, processes, and the like may be realized in hardware, software, or any combination of these suitable for the control, data acquisition, and data processing described herein. This includes realization in one or more microprocessors, microcontrollers, embedded microcontrollers, programmable digital signal processors or other programmable devices or processing circuitry, along with internal and/or external memory. This may also, or instead, include one or more application specific integrated circuits, programmable gate arrays, programmable array logic components, or any other device or devices that may be configured to process electronic signals. It will further be appreciated that a realization of the processes or devices described above may include computer-executable code created using a structured programming language such as C, an object oriented programming language such as C++, or any other high-level or low-level programming language (including assembly languages, hardware description languages, and database programming languages and technologies) that may be stored, compiled or interpreted to run on one of the above devices, as well as heterogeneous combinations of processors, processor architectures, or combinations of different hardware and software. At the same time, processing may be distributed across devices such as the various systems described above, or all of the functionality may be integrated into a dedicated, standalone device. All such permutations and combinations are intended to fall within the scope of the present disclosure.

Embodiments disclosed herein may include computer program products comprising computer-executable code or computer-usable code that, when executing on one or more computing devices, performs any and/or all of the steps of the control systems described above. The code may be stored in a non-transitory fashion in a computer memory, which may be a memory from which the program executes (such as random access memory associated with a processor), or a storage device such as a disk drive, flash memory or any other optical, electromagnetic, magnetic, infrared or other device or combination of devices. In another aspect, any of the control systems described above may be embodied in any suitable transmission or propagation medium carrying computer-executable code and/or any inputs or outputs from same.

The method steps of the implementations described herein are intended to include any suitable method of causing such method steps to be performed, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. So, for example performing the step of X includes any suitable method for causing another party such as a remote user, a remote processing resource (e.g., a server or cloud computer) or a machine to perform the step of X. Similarly, performing steps X, Y and Z may include any method of directing or controlling any combination of such other individuals or resources to perform steps X, Y and Z to obtain the benefit of such steps. Thus, method steps of the implementations described herein are intended to include any suitable method of causing one or more other parties or entities to perform the steps, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. Such parties or entities need not be under the direction or control of any other party or entity, and need not be located within a particular jurisdiction.

Claim 1:
A tubular structure (<NUM>) comprising:
a base (<NUM>) having a first surface (<NUM>) and a second surface (<NUM>) opposite one another, the first surface defining an elongate cavity (<NUM>), and the base having a tubular shape defining a longitudinal axis (L) extending along the elongate cavity; and
a wrap (<NUM>) supported on the second surface of the base, the wrap including a plurality of layers (116a,b,c,d), each layer having a first longitudinal edge (<NUM>) and a second longitudinal edge (<NUM>) welded to one another along a respective spiral seam (118a,b,c,d) associated with the given layer and extending about the longitudinal axis of the base; and
wherein each layer of the plurality of layers is welded to the base, to at least one other layer of the plurality of layers, or to a combination thereof.