FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2003
[See section 10, Rule 13]
COMPLETE SPECIFICATION
TITLE :- "SPIRAL WELDED TOWERS AND METHODS OF MAKING SAME"
Name :- WELSPUN STEEL LTD. [APPLICANT]
[ A company organized , incorporated & existing under the laws of India ]
Address :- WELSPUN HOUSE, 6TH FLOOR, KAMALA CITY, SENAPATI BAPAT MARG, LOWER PAREL, MUMBAI-400013.MAHARASHTRA-INDIA
Preamble of the Description:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED:

SPIRAL WELDED TOWERS AND METHODS OF MAKING SAME
TECHNICAL FIELD
[0002] The present disclosure relates to a spiral welded towers and methods of making such towers.
BACKGROUND
[0001] Clean energy is becoming increasingly important. Wind turbines, in particular, have the potential to reduce fossil fuel consumption and minimize the effects of globaJ warming. Wind turbines, however, require significant capital investment. Recent efforts to improve wind turbine output has increased in the annual plant load factor (PLF). For instance, the PLF for on¬shore wind turbines has increased from 13 to 16 % to 28 to 32% (average). In general, higher altitudes have the more favorable wind conditions for wind power and wind turbines positioned at heights above 60 meters benefit from more favorable wind conditions and generate more annual power. The potential is to increase PLF to 45 to 55 % (average) if the turbines are placed at a height of 160 to 200 meters above ground or sea level. Thus, the current trend is to place wind turbines at a height of 100 to 200 meters above ground for on-shore uses in order to increase wind power per turbine. Adding height to wind towers adds weight and cost. Increasing weight must result in a return on the capital employed if wind power will be widely adopted. A lighter, high tower is the requirement of the day. But "higher" towers will be exposed to higher stresses during construction and use. Stringent quality control of materials and the fabrication process is required given the significant safety factors designed into higher tower. Most current tower designs target a diameter to thickness ratio (the "D/T ratio") around 100 or less. In general, the higher the D/T ratio, the lower the collapse strength of the tower structure. However larger diameters with lower wall thickness may be stronger in bending than lesser diameter with larger wall thickness. In recent years, the objective has been to increase the diameter. However, as noted above, there is limit for using highway transportation for wind towers, 4 to 4.5 meters maximum diameter, depending on the country and specific locality. Spiral welded towers, however, are strong stable structures that are rigid and less prone to buckling. A D/T up to 150 may be used for high towers constructed using spiral welding techniques. This, in turn, creates the potential for higher'tower heights at lower weights than what might be possible otherwise.
[0002] Constructing spiral welded towers of 100 meters are more in height is complex and time consuming. The process involves fabricating individual substructures, such as tubes or

cones, of a given size made from feedstock plates. The individual substructures may have a height of 2 to 3 meters and joined together by welding to create a sub-tower of 16 to 28 meters height. Multiple sub-towers may be connected end-to-end at the tower site to create the completed tower. For example, a tower with a 100 meter height will have 30 to 40 sub-structures. Final assembly may include welding the internals, shot blasting, primer coats, final coats etc. Between the manufacturing of sub-structures and the assembly process at the tower site, the tower is subjected to some sort of off-line inspection of welds, joints, etc. The entire scope of tower production is essentially a fabrication process used over last 50 to 100 years. The process is very labor-intensive and subject to workmanship of the workers. Because of the possibility of human error, such as welding disconnects, etc, tower design is very conservative.
[0003] Constructing tapered towers has additional complexities. Typical tapered towers have a base diameter of 4 to 4.5m, depending on the transport restrictions in a specific country. For off-shore applications, the base diameter may go up to 12 m. Fabricating sub-cones is done in shops located near ports for easy transport to the offshore location. In some applications, such as for wind towers located on-shore, tower height is between 60 to 110 meters, with wall thickness for individual sub-cones of 12 mm to 45 mm. For offshore applications, the tower height is between 80 to 140 meters with wall thickness for individual sub-cones of 14 mm to 80 mm (or more). Creating such large structures with the required base diameters is challenging. For example, in tapered tower production, the substructures are conical structures made by bending a feedstock plate into a conical shape. To create the desired taper, however, the feedstock plate must have a curvature so that when the feedstock is bent into the conical shape, the edges of the feedstock plate more or less align. In one example, the feedstock plates are cut into a trapezoidal shape and ends of the trapezoid plates are welded together to create a "curved" feedstock plate. Because a trapezoid shape is used for the individual plates, edges of the feedstock are not curvilinear but have straight portions that interest at the weld joints. Such a process is described in U.S. Patent No. 9,302,303 (the "303 patent") (attached) assigned to Keystone Tower Systems Inc. The result is gaps between the wraps and defects when the feedstock plate is bent to into the conical shape.
SUMMARY

[0004] An embodiment of the present disclosure is a method for forming a spiral wound tapered structure. The method comprises moving a feedstock plate on a conveyor. The elongated plate has a first lateral edge and a second lateral edge spaced from the first lateral edge along a lateral direction, wherein a plane extends through the first lateral edge and the second lateral edge. The method includes bending the elongated plate in the lateral direction along the plane so that the first lateral edge curves to form a curved plate, wherein the first lateral edge of the curved plate has at least one radius of curvature. The method includes feeding the curved plate into a spiral-winding device in an in-feed direction. The method also includes bending the curved plate around a first axis into a spiral wound tapered structure with the spiral winding device so that portions of the first lateral edge and the second lateral edge are adjacent. While bending the curved plate, the method also includes adjusting the in-feed direction of lie curved plate according to the at least one radius of curvature of the first lateral edge of the curved plate. The method includes advancing the spiral wound tapered structure in a direction along the first axis to form a cone shaped structure.
Another embodiment of the present disclosure is a spiral wound structure. The spiral wound structure includes a tapered body having a base and a top spaced above the base along a central longitudinal axis that is centered with respect to the base and the top. A spirally wound plate wraps around the central longitudinal axis from the base to the top so that tapered body tapers toward the central longitudinal axis. The spirally wound plate has a first inner surface that faces the central longitudinal axis, a second outer surface opposite from the first inner surface, and a plate thickness that is perpendicular to the first inner surface and that extends from the first inner surface to the second outer surface. The plate has a first lateral edge that extends between the first inner surface and the second outer surface and a second lateral edge opposite to the first lateral edge and that extends between the first inner surface and the second outer surface. Portions of the first and second lateral edges adjacent to each other are joined. The plate thickness varies along a direction the spirally wound plate wraps around the central longitudinal axis from the base to the top.
BRIEF DESCRIPTION OF THE DRAWINGS
[0001] The foregoing summary, as well as the following detailed description of illustrative embodiments of the present application, will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the present application. there is shown in the drawings illustrative embodiments of the disclosure. It should be

understood, however, that the application is not limited to the precise arrangements and instrumentalities shown.
[0005] Figure 1A is a schematic side view of a spiral welded tower constructed in accordance with an embodiment of the present disclosure;
[0006] Figure IB is a schematic view of the spiral welded tower illustrated in Figure 1A, shown cut along a straight line and un-rolled to illustrate various features of the spiral welded tower;
[0007] Figure 2 is a sectional view of a portion of the wall of the spiral welded tower shown in Figures 1A and IB;
[0008] Figure 3 is a curved plate used to construct the spiral welded tower illustrated in Figures 1A and IB;
[0009] Figure 4 is a siole view of the curved plate shown in Figure 3;
[0010] Figure 5 is a cross-sectional view of the curved plate taken along line 5-5 in Figure 4;
[0011] Figure 6 is a process flow diagram illustrating a method of manufacturing a spiral welded tower illustrated in Figures 1A and IB;
[0012] Figure 7 is a schematic view of a coiler used to coil a feedstock plate according to an embodiment of the present disclosure;
[0013] Figure 8A is a schematic top view of equipment used to laterally curve a feedstock plate into the curved plate used to form a diverging cone shaped tower structure;
[0014] Figure 8B is a schematic top view of equipment used to laterally curve a feedstock plate into the curved plate used to form a converging cone shaped tower structure;
[0015] Figure 8C is a schematic of a control system for the equipment used to laterally curve a feedstock plate into the curved plate;
[0016] Figure 9A illustrates a transition portion used to couple an end of a curved plate for forming a bottom portion of a diverging cone shape to an end of a curved plate for forming a bottom portion of a converging cone shape;
[0017] Figure 9B illustrates a transition piece used to couple an end of a curved plate for forming a top portion of diverging cone shape to an end of a curved plate for forming a top portion of a converging cone shape:
[0018] Figure 10A is a top schematic view of in-feed table for a curved plate used to form a diverging cone shape;

[0019] Figure 1 OB is a top schematic view of in-feed table for a curved plate used to form a converging cone shape;
[0020] Figure 11A is a side schematic view of a system used to form a diverging cone shaped spiral welded tower;
[0021] Figure 1 IB is a side schematic view of the system shown in Figure 10A showing formation of a converging cone continuous with formation of the diverging cone spiral welded tower;
[0022] Figure 11C is a schematic of a control system for the spiral winding device shown in Figures 11A and 1 IB;
[0023] Figure 12A is a top schematic view illustrating how the curved plate is used to form the diverging cone shaped spiral welded tower illustrated in Figure 11 A;
[0024] Figure 12B is a top schematic view illustrating how the curved plate is used to
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form the converging cone shaped spiral welded tower illustrated in Figure 1 IB; and
[0025] Figure 13 is a top schematic view illustrating how the in feed table and/or spiral wending device pivot during formation of the spiral welded tower;
[0026] Figure 14 is a top schematic view illustrating how in feed table and/or spiral wending device pivot during formation of the spiral welded tower;
[0027] Figure 15 is a top schematic view illustrating how the in feed table and/or spiral wending device pivot during formation of the spiral welded tower;
[0028] Figure 16 is a top schematic view illustrating how in feed table and/or spiral wending device pivot during formation of the spiral welded tower;
[0029] Figure 17 is a top schematic view illustrating how the feed-table and/or forming table pivot during formation of the spiral welded tower;
[0030] Figure 18 is a side view of a hybrid tower including a spiral welded structure according to an embodiment of the present disclosure;
[0031] Figure 19 is a side view of the base portion of the hybrid tower shown in Figure 18;
[0032] Figure 20 is a top plan view of the base portion of the hybrid tower shown in Figure 18; and
[0033] Figure 21 illustrates a device used to connect pipes together to form the base portion of the hybrid tower shown in Figure 18.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0034] Embodiments of the present disclosure include spiral welded structures, towers made from such spiral welded structures, and related systems and methods for manufacturing such spiral welded structures and towers. The spiral welded structures as described herein are particularly suitable for use as wind towers in wind turbines. According, embodiments of the present disclosure include wind turbines that include a nacelle and motors attached to blades, and towers that support the nacelles. The spiral welded structures are not limited to use as. wind towers. For example, the spiral welded structures may be used as mobile telephone towers, power transmission towers, or other applications where towers are constructed by fastening or welding multiple sections on top of one another to achieve the desired height. The inventive concepts described herein yield towers with less complex manufacturing requirements, decreased welding requirements, and reduced final tower weight while yielding generally more stable structures compared to conventional methods of tower production. The reduction in weight alone can provide significant cost savings and make high height tower production more economically viable, in particular for wind tower production.
[0035] Referring to Figures 1A and IB, an exemplary spiral welded tower structure 10 is illustrated. The spiral welded structure 10 includes tower body 20 having a base 12, a top 14 spaced above the base 12 along a central axis A, and a wall 16 that extends from the base 12 to the top 14. The wall 16 is formed from a spirally wound plate 30 wrapped in a helical pattern around the central axis A. As shown, the wall 16 may comprise N wraps of the plate 30 to form the full height of the spiral welded structure 10. The plate was a width W. The spiral welded structure 10 has a tower height H that extends from the base 12 to the top 14 in direction parallel to the central axis A. The base can define a base diameter D2 and the top defines a top diameter Dl. In the embodiment shown, the towered is tapered such that the top diameter Dl is less than the based diameter D2. In alternative embodiments, the tower may be a straight tower such that the base diameter D2 and the top diameter are substantially similar.
[0036] In accordance with the illustrated embodiment shown in Figures 1A and IB, the spiral welded spiral welded structure 10 may be in the form of a truncated cone. A truncated cone has a base plane PI, a top plane P2 above and parallel to the base plane PI, and a vertex (not shown) that is spaced above the top plane P2. As shown, the base 12 extends along the base plane PI and the central axis A passes through the vertex and a geometric center (not shown) of the base 12 that lies on the base plane P2. The central axis A may be perpendicular to the base plane PI. For convenience, the tapered towers and structures disclosed herein are described as a truncated cone formed by a top plane PI intersecting a right circular cone at a predetermined

height H from the base plane P2 along the central axis A. However, one of skill in the art will appreciate that the tapered towers and structures are not limited to shapes defined by a right circular truncated cone.
[0037] The height of spiral welded towers varies based on the application and location of installation. So-called on-shore towers may have a height H of approximately 80 to 150 meters (m) with a base diameter D2 of 4.0 to 7.0 m. It is generally not feasible to transport towers (or tower segments) with diameters greater than 4.5 m over land. For manufacturing facilities that are able to access a port without land transport obstructions, spiral towers may be made with a height H of approximately 190.0 to 200.0 and a base diameter D2 of approximately 7.0 to 12.0 m. In one example, the spiral welded spiral welded structure 10 is a wind tower with a height H between 50 to 200 m. An on-shore wind tower may have height H between 50 and 150 m. Off-shore wind towers may have height of up to 200 m. In certain examples, spiral welded structures can be formed with smaller diameters than those describe above. For instance, a tower with a base dimeter as low as 0.75 meters is within the scope of the present disclosure.
[0038] Turning to Figures 3 and 4, the spiral welded structure 10 is formed by winding a curved plate 30 into a spirally welded structure shown in figure 1A. The curved plate 30 includes a first end 32, a second end 34 opposite the first end 32, an intermediate portion 36 that extends between the first end 32 and second end 34. The curved plate 30 also includes a first lateral edge 40 and a second lateral edge 42 spaced from the first lateral edge 40. The curved plate 30 can extend along a central plate axis C that extends between the first and second lateral edges 40 and 42. The first and second lateral edges 40 and 42 converge at the first end 32 and the second end 34. The curved plate proximate to the first end 32 is configured to form the top 14 of the spiral welded structure 10 and the curved plate proximate to the second end 34 is configured to form the base 12 of the spiral welded structure 10. The curved plate 30 is wrapped around the central axis A so that portions of the first lateral edge 40 and second lateral edge 42 are adjacent to each other. Furthermore, in the finished spiral welded structure 10, the curve plate axis C extends around the central axis A in a helical pattern. As illustrated, both of the first lateral edge 40 and the second lateral edge 42 are curved.
[0039] The curved plate 30 has a defined lateral curvature to facilitate forming a spirally wound tower structure. A "lateral curvature" refers to a plate that has curved first and second lateral edges that curve in a common plane. This is opposed to bending or curving plate to form a spirally wound tower. As illustrated, both of the first lateral edge 40and the second lateral edge 42 are curved along a plane P3 that extends through the first and second lateral edges 40 and 42. In one embodiment, the first lateral edge 40 has a radius of curvature that varies as it

extends from the first end 32 of the curved plate 30 to the second end 34 of the curved plate 30. For example, the curved plate 30 has a first radius of curvature Rl at the first end 32, which forms the top 14 of the spiral welded structure 10, and a second radius of curvature R2 at the second end 34, which forms the base 12 of the spiral welded structure 10. The second radius of curvature R2 is greater than the first radius of curvature. Depending on the specific manufacturing technique or phase of production as during tower formation as explained below, the first lateral edge 40 has a concave profile and the second lateral edge 42 has a convex profile (see Figures 3 and 11 A). However, the first lateral edge 40 can have a convex profile and the second lateral edge 42 may have a concave profile (see Figure 1 IB). Whether the first lateral edge 40 and the second lateral edge 42 have a convex or concave profiles based on whether a particular curved plate is being used to form a diverging cone portion or a converging cone portion of the tower structure during manufacturing. See for examples Figures 10A and 10B which are explained further below.
[0040] The curve plate 30 can also define a predetermined width W. The width W extends from the first lateral edge 40 to the second lateral edge 42. The width W is perpendicular the first lateral edge 40 and/or the second lateral edge 42. The width W of the intermediate portion 36 may be substantially constant. The term "substantially constant" is used to denote that the dimensions are maintained relative to theoretical design parameters within industry accepted manufacturing tolerances. As shown, the first end 32 of the curved plate has width W that tapers to a point. This tapering of the first end 32 facilitates forming the top 14 of the spiral welded structure 10. Likewise, the second end 34 of the curve plate has width W that tapers to a point. The tapering of the second end 34 facilitates forming the base 12 of the spiral welded structure 10. In one embodiment according to an aspect of the disclosure, the width W of curved plate 30 between ends 32 and 34 may vary between 1.0 to 2.0 meters, preferable between about 1.6 to 2.0 m.
[0041] Referring to Figures 4 and 5, the curve plate 30 also has thickness T selected for the application. As best shown in Figures 4 and 5, the curved plate has a first surface 50 and a second surface 52 that is opposite the first surface 50.- The curve plate 30 defines a thickness T that extends from the first surface 50 to the second surface 52. The thickness T is a dimension that is perpendicular to the first surface 50 and/or the second surface 52. When formed into the wall 16 of the spiral welded structure 10, the first surface 50 forms the interior: "surface of the spiral welded structure 10 and the second surface 52 forms an exterior surface of the spiral welded structure 10. As used herein, the thickness T can is referred to as the tower wall thickness. The thickness T of the curved plate 30 can vary as it extends from the first end 32 to

the second end 34. As illustrated in Figure 4, the thickness at the first end 32 is less than the thickness at the second end 34. The thickness T of the intermediate portion 36 of the plate varies continuously from the first end 32 to the second end 34. This varying thickness creates a narrower wall thickness proximate the top 14 of the spiral welded structure 10 compared to the wall thickness T proximate the base 12. In one example, the wall thickness varies along the curved plate axis C as the plate 30 extends around the central axis A. Because the curved plate 30 is spirally wrapped to form the tower wall 16, adjacent portions of the lateral the curved plate 30 have a slight thickness differential, as best shown in Figure 3. For exemplary wind tower applications, the thickness T at the first end 32 (near top 14) may be as low as 12 mm, and the second end thickness at the second end 34 (or near the base 12) may be between 25 mm and 90 mm, depending on turbine installed on the tower, dynamic loads incurred, and the height of the tower.
[0042] Generally, the spiral welded tower is manufactured as a single unit. In some examples, the spiral wound structure can be cut into tower segments to accommodate transportation constraints. The tower segments are then reconnected on-site to form the full height of the spiral welded tower as illustrated in Figure 1A. In such an example, the total number of segments that are welded together to form a completed tower is between 4 segments and 10 segments. The number of segments welded together to fewer than the number of segment required to form conventional towers today. The result is less welds, lower weight, and faster production rates. These factors result in a favorable return on investments compared to typical tower construction used today.
[0043] Another embodiment of disclosure is a hybrid tower 110 as illustrated in Figures 18-21. As shown in Figure 18, the hybrid tower 110 includes a base structure 112 and an upper tower structure 130 that is coupled to a top end 116 of the base structure 112. The base structure 112 has a bottom end 114, a top end 116 above the bottom end 114, and a pipe cluster 120 that extends from the bottom end 114 of the base structure 112 and the top end 116 of the base ■structure 112. The pipe cluster 120 is made of plurality of pipes that form structural supports for the upper tower structure 130. The pipes may be tapered pipes or straight pipes made using the techniques described herein. For example, the pipes are spiral welded structures with a ^:- continuously variable wall thickness. In another example, the pipes the pipe cluster 120 are spiral welded structures with a relative constant wall thickness. The hybrid tower will have reduced weight due to use of the pipe cluster 120. The pipe cluster 120 can be pre-fabricated at the plant and then dismantled into transportable sections. After disassembly, each section will be

under 3.5 to 4.5 meters in width and 16 to 25 meters in length. Then, the sections of the pipe
cluster 120 may be re-assembled at the tower site and then built up to create a tower (with the
upper tower structure 130) having a height of 100 meters or more. In situations where the pipe
cluster 120 is preassembled at the plant, a base structure 112 with a finished base diameter of 10
meters can constructed.
[0044] The upper tower structure 130 is positioned on top and is coupled to the top end
116 of the base structure 112.^ The upper tower structure 130 is substantially similar to the spiral
weld tower structure 10 shown in Figure 1A and may be made according to method 200
described below and illustrated in figures 6-17. The upper tower structure 130 has a bottom end
132 and a top 134 that is adapted to receive a nacelle of a wind turbine. The pipe cluster 120 as
shown in the Fig. 18 can be covered with sheets by simply riveting or other mechanical means to
achieve the look a full conical tower.
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[0045] As illustrated in Figure 21, two adjacent pipes in the pipe cluster 120 are coupled together with a coupling device 140. The coupling device 140 may be a torpedo. The coupling device 140 fits with a first pipe 152 and a second pipe 154 of the pipe cluster 120. The torpedo 140 will fit loosely along the inside of the first pipe 152 and the second pipe 154. The torpedo 140 can be pressurized beyond the yield point so that it expands and locks on to the second pipe 154. When the pressure is released, the second pipe 154 will lock on to the torpedo 140 giving a locked tight fit. In some cases, the connection with a torpedo may be stronger than welding. The process described may be referred to a shrink fitting. However, other attachment mechanism may be used as well.
[0046] Another embodiment of disclosure is a method 200 for forming a spiral wound tapered structure with a variable wall thickness, as shown in Figure 6. Figure 6 is a process flow diagram illustrating the basic steps in manufacturing a spirally welded structure 10 as described above. Method 200 may include tower design 210, plate formation 220, plate coiling 230, plate bending 240, spiral welding 250, and tower construction 260. Various aspects of the method 200 are illustrated with reference to Figures 7-18 and each basic step is further described below.
[0047] Continuing with Figure 6, the method may 200 may include designing 210 a tower, including the development of tower specifications, such as height, top dimension, base dimension, cone angle (if applicable), width of feedstock plate, load capacities, and other aspects associated with tower design. In addition, it a model of the curvature of the feedstock plate used to create the conical tower may be generated using computer aided design tools as is known in the art.

[0048] After tower design, method 200 includes plate formation 220 whereby a feedstock plate F is manufactured according to required specifications. The feedstock plate F, for example, may have a length of 20. to 150 meters and weigh between 5 tons and 60 tons. Plate formation 220 may involve selection of slab size and development of the rolling program for creating a variable wall thickness T in the feedstock plate F. Therefore, in one example, the varying thickness T of the feedstock plate F is accomplished during plate formation 220. Any .particular plate formation process may be used to create the feedstock plate F.
[0049] With reference to Figures 6 and 7, plate coiling 230 follows plate formation 220. Plate coiling 230 involves winding the feedstock plate F into a coiled plate for transport and later processing. In plate coiling 230, the feedstock plate F is coiled using a coiler 300 as shown in Figure 7. The coiler 300 is an open coiler with inside diameter of 4.0 to 6.0 meters, depending upon the end use for the thickness of input plate. The coiler 300 has a first set of pinch rolls 320, a 3-roll bending device 330, a second set of pinch rolls 348, and a coil box 340. The coil box 340 has driven outside rollers 342 and curve aprons 344. A top portion 346 of the coil box 340 holds the driven rollers 342 and the aprons 344. An attachment 360 can be opened when coiling is complete to release the completed coiled plate.
[0050] During plate coiling 230, the feedstock plate F, which may be as long as 150 meters, enters the pinch roll assembly 320 and is fed to bending device 330. The full length of the feedstock plate F, as much as 150 meter long, is lying on the roller table in a flat condition and without creating any obstruction for plate coiling 230. The 3-roll bending device 330 will bend the feedstock plate F so that it enters a coil box 340 with driven outside rollers 342 and curved aprons 344 to guide the feedstock plate F. The second pinch roll set 348 forces the bent coil plate around in the coil box 340. The driven rollers 342 guide the coil plate inside the coil box 340. When the full coil plate, at the desire weight, is inside the coil box 340, the attachment will swing open so that the coiled plate can be removed from the coil box 340. As the coil plate will have continuous variation in wall, the 3-roll bending device 330 will adjust itself so that a roundness as required is maintained. The first pinch rolls 320 and the second pinch rolls 348 may have a hydraulic force control to* grip the plate to move it forward in synchronization with the 3-roll bending device 330. In one example, the coiler 300 is a heavy down coiler and plates up to 30 mm thick may coiled. In other examples, feedstock plate up 70 mm or more may be coiled into coiled plate. However, a range of plate thicknesses may be used. Plate coiling 230 may yield coiled plates of 1.6 to 2 meters.wide. In one example, the completed coil weight may be between 5 tons to 60 tons.

[0051] Referring to Figures 6, 8A and 8B, following plate coiling 230, the coiled plate F is subjected to plate bending 240 whereby lateral curvature is imparted into the feedstock plate F to create the curved plate 30 as described above.
[0052] In plate bending 240, the feedstock plate F is bent via a bending apparatus 400 as shown in Figure 8A. The bending apparatus 400 includes an un-coiler 402, a coil opener 404, a first pinch roll set 406, a conveyer 408, guide rolls 410 disposed on either side of the conveyer 408, an optional heater 412.(e.g. an induction heater) and a second set of pinch rolls 414 that are hydraulically controlled and have variable drives. A lateral bending zone 420 includes first set of tapered rolls 422 and a second set tapered rolls 424 positioned on a stand 426. Guide rollers 430 and 432 are located at the exit of the lateral curving zone 420. The pinch rolls 441, tapered rolls 422, and tapered rolls 424 may be operated via a hydraulics system 480 (Figure 8C). The bending apparatus 400 may be equipped to mark the curve plate 30 during plate bending 240. For instance, the method may include marking the curved plate 30 at predetermined intervals with an indication of one or more design parameters of the spiral wound tapered structure. The design parameters/dimensions may include a wall thickness, a radius of curvature, a diameter, and a position from the top of the spiral wound tapered structure.
[0053] In plate bending operation 240, the un-coiler 402 and coil opener 404 unwind the coiled feedstock plate F onto the conveyer 408 for gripping by pinch rollers 406. Guide rolls 410 direct the feedstock plate F, via the conveyer 408, into the lateral bending zone 420. Several methods that may be used to impart lateral curvature into feedstock plate F in the lateral bending zone 420. In one example, a heater 412, such as an induction heater, is adjacent to the later bending zone 420 and exposes the feedstock plate F to elevate temperatures e.g. about 800 degrees C. In one example, this may require an estimated that 180 KWH to heat 1 ton of feedstock plate F per hour of processing. The feedstock plate F is fed into the tapered rolls 422 and the tapered rolls 424 via conveyer 408. Pressure applied to tapered rolls 422 and 424 will impart stretch to feedstock plate F unevenly between pinch rollers 414 and the tapered rollers 424 such that portion of the plate proximate the first lateral edge 40 is stretched to a greater degree than a portion of the plate proximate the second lateral edge 42. The result is a controlled, uneven stretch to generate the required curvature in the plate. The guide rolls 430 can also act as leveling rolls for the plate. Detection units, such as lasers or other optical devices may be positioned at guide rolls 430 to measure the curvature of the edges 40 and 42 of the plate 30.
[0054] Fig. 8B illustrates a bending apparatus 400' used to illustrate how curvature in plate 30' used for form a converging shaped cone. The bending apparatus 400' shown in Figure

8B is the substantially the same as the bending apparatus 400 shown in Figure 8A. Similar reference numbers are used to illustrated features common to each apparatus. However, in figure 8B. the apparatus 400' is used to form a curve plate 30' where the first lateral edge 40 is concave the second lateral edge 42 has convex for forming a converging cone as further described below. According, the lateral bending zone 420' has tapered rolls 422' and tapered rolls 422' that are oriented in a different direction. Furthermore," the conveyer 408' may be designed to accommodate the different curvature direction created by apparatus 400'.
[0055] As shown in Figure 8C, the bending apparatus 400, 400' may include a control system 450. The control system 450 includes one or more controllers 460, detection units 470, a hydraulic system 480. The hydraulic system 480 operates the pinch rolls 441, tapered rolls 422, and tapered rolls 424. The control system 450 is used to control operation of the lateral bending zone 420 and control formation of the plate curvature. The controllers 460 may be electrically
■
coupled to the detection unit 470 and to the hydraulic system 480. The control system 450 processes the curve data obtained from the detection unit 470. The controller 460, via a feed-back loop, adjusts operation of the hydraulics that operates the pinch roles 414, tapered rolls 422, and tapered rolls 424. The controller 460, in response to receiving the curve data, adjusts the extent of stretch on the incoming feedstock plate to maintain the curvature within the desired threshold. In any event, the bending apparatus 400 (or 400') shown in Figure 8A produces a curved plate 30 with a first lateral edge 40 having a convex curve and the second lateral edge 42 having a concave curve for forming a diverging cone as further described below.
[0056] In an embodiment of the present disclosure, the method may include recoiling the curved plate 30 into a coiled curved plate. In such an embodiment, the curved plate 30 can be recoiled into coiled plate using a coiler 300 similar to that shown in Figure 7. However, the laterally curved plate can be stored flat on a large table as needed.
[0057] Referring to Figures 9A and 9B, the plate bending 240 may include coupling
two curved plates 30 and 30' together with a transition portion 70, 170 to form an "S-curved"
plate 31. As shown in Figure 9A, the transition portion 70 couples a first curved plate 30 having
a curvature in a first direction to a second curved plate 30' having a curvature in a second
direction that is opposite the first direction. Several transition portions 70,170 are used to
coupled plates 30, 30' together. A first transition portion 70 has a first end 72 with an edge
r'*' adapted to couple to the end 32 of a first plate 30."and a second end 74 with an edge adapted to ?
couple to the end 32' of the second plate 30:. As shown in Figure 9B, a second transition portion 170 has a first end 172 with an edge adapted to couple to an end 34' of the second plate 30', and a second end 174 with an edge adapted to couple to end 34 of the first plate 30. In this manner, a

single strip of material can be fed into the spiral forming system 500 (Figures 10A-11B) to
create a diverging cone spiral welded structure and a converging cone spiral welded structure in
a continuous operation. This avoids the need to stop spiral welding every time one tower section
is completed to restart production. Furthermore, this minimizes waste, which could be up to 17
to 25 meter of 2 meter wide strip being scrapped per tower structure. While this feature is
preferred, embodiments of the present disclosure could use strips that did not have a transitions
portion 70 that creates an "Srcurved" plate.
[0058] Next, a spiral welding operation 250 transforms the curved plate 30 into the
spirally welded structure \0 with a spiral forming system 500 as shown in Figures 10A-1 IB. As
shown in Figure 10A, the spiral forming system 500 includes an infeed table 510 (Figures 10A
and 10B) and a spiral forming device 550 (Figures 11A-1 IB). The infeed table 510 is designed
to hold the curved plate 30 for presentation to the spiral-forming device 550. In infeed table 510
* *
may include a support table 512 set on a movable platform (not shown), a welding unit 514, end edging device 516, a set of pinch rollers 518, and a set of guide rolls 520 that direct the curved plate 30 into the spiral forming device 550. The infeed table 510 is movable, or pivotable, about a swivel point 502 according to the curvature of the curved plate 30. The entire infeed table 510 is adjustable using position transducers and servo hydraulics and controlled via feedback loop based on data concerning the structure of the curved plate 30. The swivel point 502 is coaxial with a vertical axis Yl and is proximate to a welding point 504 where adjacent edges of the curved plate 30 are welded together with the spiral welding device 550. The welding device 514 attaches two plates end together while the edging device 516 creates a chamfered ends and defines the plate width W. The edge device can create width within an error of 0.5 mm in some cases. The pinch rolls 518 are hydraulically powered and feeds the curved plate 30 into spiral forming device 550 (Figures 11A and 11B). The guide rolls 520, pinch feed rolls 518, edging device 516 and welding unit 514, swing around the pivot point 520 but also are individually side adjustable. Thus, an imaginary center line of the curved plate is equidistant from all mechanical equipment performing their functions. This way the curved plate may ride centered to guide rolls 520, pinch rolls 518, edging machine 516 and welding table 514. The balance of curved plats behind the weld unit 514. with a large spread, may be free floating on the ball rollers located on the table. The ball rollers allow multi-direction movement of the curved plate
[0059] Fig.-'lOB shows an infeed table 510' that is substantially similar to the infeed table 510. However, the infeed table 510' is configured to for curved plate 30' for forming a converging shaped cone. The infeed table 510' shown in Figure 10B is the substantially the same as the infeed table 510 shown in Figure 10A. Similar reference numbers are used to

illustrated features common to each table. However, in figure 10B, the infeed table 510' is used
to form a curve plate where the first lateral edge 40 is concave the second lateral edge 42 has
convex for forming a converging cone. :.-.
[0060] As shown in Figures 11A and 1 IB, the spiral forming device 550 has a bending section 552 that includes a 3-roll bending device. The bending section 552 bends the curved plate about the first axis XL The bending device has a bending beam with multiple rollers and is operated using hydraulics. The angle of the multiple rollers may be changed in accordance to the feeding angle of the curved plate, again using servo hydraulics. The rollers are operated to match the linear movement of the curved plate into the spiral welding device 550. The bending section 552 may accommodate tapered angle configurations. Furthermore, the bending section 552 may have angle adjustable rolls and width adjustment capability to handle a range of tower structure diameters and configurations. A welding unit 554 joins two edges 40, 42 of the curved plate 30 at the welding point 504. The welding unit 554 may be a multiple wire welding device or single wire tack welding device. It is noted that the swivel point 502 as shown rests very close to the welding point 504. A welding unit is shown, however the in alternative embodiments, the two edges may be joined together using alternative means. For example, portions of the first lateral edge and the second lateral edge may be joined together by welding, either continuously or via tack welding. Alternatively, portions of the first lateral edge and the second lateral edge may be joined together by chemically bonding through application of adhesives and the like. In yet another embodiment, portions of the first lateral edge and the second lateral edge may joined by mechanically fasteners. In still other embodiments, portions of the first and second lateral edges may be joined together through any combination of welding, chemical bonding, and mechanical fasteners.
[0061] A pressure device 560 is used for controlling the diameter based on the feedback
of the curved plate thickness. As the thickness varies, the pressure device 560 operates to react
to changes in the plate thickness. A forming roll cluster 570 adjusts itself with changing angle
for diameter control. The forming roll cluster 570 may be 3-roll set cluster. A center roll cluster
is used to press the plate against adjacent roll cluster on the left and right side. The central roll
cluster helps form the diameter of the tower structure. The spacing between the left and right side
roll clusters is changed with respect to center roll cluster to control the diameter. Furthermore,
the inclination of the rolls with respect to plate is kept substantially parallel. As the diameter of ?
the tower structure changes, the angle at-the pivot point 502 changes. The roll clusters 570 allows the curved plate to move in a parallel direction as the angle at the pivot point 502 changes.

[0062] An outside cage 572 surrounds the spiral welded structure 10 and is used to" help control diameter. The cage 572 has rollers placed along the top and two sets of rollers at 75 degrees with respect to the top relative to the vertical axis V. An additional welding unit 574 may be used to in circumstances where the formed tower structure is finished on line. An inspection unit 576, such as an ultrasonic inspection unit, is used for checking the weld quality.
[0063] A runout table 578 includes multiple guide arms 580 to holding the formed spiral welded structure 10 in position as the tower is advanced. The guide arms 580 change position with changes in the structure diameter. The guide arms 580 will be hydraulically loaded with position control transducers and will open up gradually as the tapered structures moves forward. A hydraulic cylinder 582 is used for automatic gap control at the welding unit 554. The movement of hydraulic cylinder 582 causes the run out table on which the formed tower structure to provide continuous a rotational movement and longitudinal movement. The movement initiated by this hydraulic cylinder 582 insures that portions of the curved plate at the weld point 504 are always touching (or proximate) each other. The position transducers 594 (Figure 11C, discussed below) at predetermined time intervals (e.g. every 1/4 second or less) compare the position of the curved plate at weld point 504 and give the correct command via the control system 590 (Figure 11C). A readout device 584 is device scanner to for reading bar code information during production.
[0064] As shown in Figure 11C, the spiral welding device 550 may have a control system 590 for controlling operation of the spiral welding device 550. The control system 590 may include one or more controllers 592, position transducers 594 and a hydraulic system 596. The position transducers 592 to determine the position of the formed tower structure throughout the tower processing. The position transducers 592 can generate position data for an outside surface of spiral tapered structure. The transducers also control the bending pressure/load on the multiple rolls as per the cone angle. The position data is fed to the controller 592 The controller 592 responsive to the position data, generates one or more control signals that cause the hydraulic system 596 to alter the positions of the one or more of the components of the spiral welding device 550. For instance, the controller 592 can cause the pressure device 560 to move based on differences in plate thickness. Furthermore, the position transducers 594 can determine how the diameter of the cone shape is changing as the tower structure is formed and advanced along the run-out table. This, in turn, can cause the guide arms 580 to .move in manner to maintain the relative position of the towered structure during spiral welding. Furthermore several position transducers 594 may be located on the welding device 550 for identifying the curved plate position and the tower diameter. At least one position transducer 594 is located close to the

weld point 504 to sense the position of the curved plate with respect to the weld point 504. Correction, if any is required, is given to the guide rolls 520, via the controller 592, which can move laterally to direct the curved plate towards the weld point 520. Another set of position transducers, e.g. two or three or more, are used to follow diameter of the tower structure. This addition set of position transducers give commands, via the controller 592, to: 1) the pressure * cylinder 560 to decrease or increase the load for bending the curved plate as needed; and/or 2) the roll cluster 570 to change the in-feed direction, as per pre-calculated angle for specific diameters. It should be appreciated that additional position transducers and controllers may be used. In addition, the spiral welding device 550 may have other components that are with any modern spiral welding device 550.
[0065] In spiral welding 250, the curved plate 30 is fed into a spiral winding device 550 using the infeed table 510 so that the plate 30 travels in an "in-feed" direction I. The entire infeed table 510 can move in an arc R about the swivel point 502 according to the curvature of the curved plate 30. As the curved plate is fed into the spiral forming device 550, the spiral forming device bends the curved plate around the first axis XI to form a cone shape so that portions of the first lateral edge 40 and the second lateral edge 42 are adjacent. As shown, initially a diverging cone shape structure 10D is produced as illustrated in Figure 11A and 12A.
10066] While bending the curved plate 30, the in-feed direction I of the curved plate 30 is adjusted according to the curvature of the first lateral edge 40 of the curved plate 30. The spiral forming device 550 further advances the spiral wound tapered structure 10 in a direction along the first axis XI to form the diverging cone shaped structure 10D as shown in Figures 11A and 12A. As can be seen in Figure 11A and 12A, the curve plate 30 is fed to the spiral welding device 550 so that adjacent portion of the edges 40 and 42 are joined at the weld point 504. As the curved plate 30 is wound around the first axis XI to form the structure 10 the infeed table 510 pivots about the swivel point 502 based on the curvature of the curved plate 30. As shown Figure 12A, the lateral edge 42 is concave and in this orientation, a diverging cone shaped structure 10D is made during tower production. When the desired length of the diverging cone shaped structure 10D shown in Figures 11A and 12A is completed, the method transitions into the making the converging cone shaped structure 10C shown in Figures 1 IB and 12B.
[0067] After the spiral forming device 550 forms the diverging cone shape structure 10D, the process transitions into forming a converging shape that is adjacent to the diverging cone shaped structure 10D in a continuous operation, as shown in Figure 1 IB. Transitioning the .■ spiral wound tapered structure from the diverging cone shaped structure 10D into the converging cone shaped structure 10C includes bending the transition portion 70 where the direction of

curvature of the curved plate 30 changes. As shown in Figures 1 IB and 12B, the curvepiate 30' is fed into the spiral welding device 550 to form a converging cone shaped structure IOC. As can .;;be seen in Figure 12A. the lateral edge 42 is now .convex and in this orientation, a converging cone shaped structure IOC is made during tower production. The transition portion 70 allows un-interrupted production of towers with the spiral welding device 550 and reduces waste.
[0068] Figures 13-18 illustrate how in-feed table 510 and/or spiral forming device 550 may be used to align edges of the curvate plate during cone formation. In one example, for the curved plates that are, for example 125 meters long and a transition portion 70 is used to coupled plates 30 and 30' together, the spread required for pivoting the infeed table 510 may be as much as 100 meters. Accordingly, to maintain in-feed table 510 within reasonable limits, it is advantageous to pivot both the infeed table 510 and the spiral forming device 550 about a
* *
common point 502. Figure 13 illustrates pivoting of the in-feed table 510 relative to a fixed spiral forming device 550. In Figure 14, production of the diverging cone shape structure 10D is completed and the transition portion 70 approaches the weld point 504 of the spiral forming device. At this stage, the spiral forming device 550 pivots about 12 degrees counter clockwise about the swivel point 502. Note that the 12 degrees is exemplary. As shown in Figure 15, to form the converging cone shaped structure IOC. the infeed table 510 pivots and the spiral forming device 550 pivots to form the changing angle of the cone shape as the plate is wrapped around the first axis XI. In Figure 16, the converging cone shaped structure 10C is nearing completion with the in-feed table 510 stationary and the spiral forming device 550 pivots back in a clockwise direction. In Figure 17, the infeed table 510 and spiral forming device 550 are back in the original configuration shown in Figure 13. For higher outputs, at the welding unit, instead of multi wire inside and outside welding, tack welding may be used at speeds of 2 to 4 meters/min. After cutting the tower sections, off-line inside and outside diameter welding can be used, followed by ultrasonic testing and radiography.
[0069] After spiral welding 250, completed towers may be constructed tower construction operation 260. In tower construction operation 260, the spiral welded structures 10 ■ are formed into the completed tower based on the specific application. The formed towers may be shipped to production site where appropriate. For large sized towers, the formed tower structures may bercut into multiple tower segments, shipped to the tower site, and welded together end-to-end to create the completed tower. For instance, the system may include a roller table of a length from 100 meters to 160 meters, where the tower structure can be cut in sub-

sections. In one example, the tower sections are cut using water plasma arc systems for further processing as is usual for wind towers.
[0070] Advantages of the present production method is reduction in the total welding length. This due, in part, to welding at the spiral welding device 550 because the curved plate when formed into the spiral wound structure has far lesser disconnects in wall to wall. Welding can be continuous in accordance to the present disclosure. The results are towers suitable for wind towers/turbines with lower weights at heights 100 meters or higher. Less weight results in more economically viable model for wind power. Conventional wind tower production requires that use of individual plates, large man power, and lot of material wastage. The present disclosure will create lighter towers with better on line quality control and lesser dependence on human power and their errors.

What is Claimed:
1. A method of forming a spiral wound tapered structure, the method comprising:
moving a feedstock plate on a conveyor, the elongated plate having a first lateral edge
and a second lateral edge spaced from the first lateral edge along a lateral direction, wherein a plane extends through the first lateral edge and the second lateral edge;
bending the elongated plate in the lateral direction along the plane so that the first lateral edge curves to form a curved plate, wherein the first lateral edge of the curved plate has at least one radius of curvature;
feeding the curved plate into a spiral winding device in an in-feed direction;
bending the curved plate around a first axis into a spiral wound tapered structure with the spiral winding device so that portions of the first lateral edge and the second lateral edge are adjacent:
while bending the curved plate, adjusting the in-feed direction of the curved plate according to the at least one radius of curvature of the first lateral edge of the curved plate; and
advancing the spiral wound tapered structure in a direction along the first axis to form a cone shaped structure.
2. The method of claim 1, wherein feeding the curved plate into the spiral winding device comprises advancing the spiral wound tapered structure in a direction along the first axis to form at least one of a diverging cone shape and a converging shape in a continuous operation.
3. The method of claim 1, wherein feeding the curved plate into the spiral winding device comprises advancing the spiral wound tapered structure in a direction along the first axis to form a diverging cone shape and a converging shape adjacent to the diverging cone shape.
4. The method of claim 1. wherein advancing the spiral wound tapered structure in a direction along the first axis comprising transitioning the spiral wound tapered structure from a diverging cone shape into a converging cone shape in a continuous operation.
5. The method of claim 4. wherein transitioning the spiral wound tapered structure from the diverging cone shape into the converging cone shape comprises bending a transition portion of curved plate, wherein the transition portion is where the direction of curvature of the curved plate changes.

6. The method of claim 1. wherein the elongated plate has a first end. a second end, a length that extends from the first end to the second end, wherein the length of the elongated plate is between 20 meters and 150 meters prior to bending. <-..
7. The method of claim 1. wherein the elongated plate weights between 5 tons and 60 tons.
8. The method of claim 1. wherein the elongated plate has a first end, a second end, a length that extends from the first end to the second end, a first surface, a second surface spaced from the first surface, and a thickness that extends from the first surface to the second surface, wherein the thickness is perpendicular to the length, wherein the thickness varies along the length of the elongated plate.
9. The method of claim 1, wherein bending the elongated plate in the lateral direction along the plane includes one of a) heating the elongated plate or b) cold bending the elongated plate.
10. The method of claim 1, wherein the step of adjusting the in-feed direction comprises pivoting the conveyer about a second axis that is perpendicular to the first axis, wherein the second axis intersects a point that at or proximate where the first and second lateral edges meet during bending.
11. The method of claim 1, wherein the step of adjusting the in-feed direction comprises at pivoting at least one of the conveyer and the spiral forming device.
12. The method of claim 1, further comprising measuring the radius of curvature of the first lateral edge, and wherein adjusting the in-feed direction of the curved plate is based on the measured radius of curvature.
13. The method of claim 1, further comprising:
marking the curved plate at predetermined intervals with an indication of one or more design parameters of the spiral wound tapered structure.
-1 -i
14. The method of claim 13, wherein the indication of one or more design parameters is a computer readable code.
15. The method of claim 1, further comprising:
adjusting a width of the curved plate, wherein the width extends from the first lateral edge to the second lateral edge along the plane.

16. The method of claim 15, wherein adjusting the width of the curved plate comprises milling at least one of the first lateral edge'and the second lateral edge.
17. The method of claim 1. while bending the curved plate around the axis into the spiral wound tapered structure, controlling a gap between the portions of the first lateral edge and the second lateral edge that are adjacent.
18. The method of claim 1, further comprising:
joining the portions of the first lateral edge and the second lateral edge that are adjacent.
19. The method of claim 18, wherein joining the portions of the first lateral edge and the
second lateral edge together includes one of:
a. welding the portions of the first and second lateral edges together;
b. * chemically bonding the portions of the first and second lateral edges together; or
c. mechanically fastening the portions of the first and second lateral edges together.
20. The method of claim 1, further comprising coiling the curved plate into a coil.
21. The method of claim 20, after coiling the curved plate, unwinding the coil for feeding into the spiral winding device.
22. The method of claim 1, wherein a length of a completed spiral wound structure is between 50.0 meters and 200.0 meters.
23. The method of claim 1, further comprising cutting the spiral wound structure into a plurality of cone segments.
24. The method of claim 23, further comprising constructing a spiral welded tower comprising the plurality of cone segments
25. The method of claim 24, wherein constructing the spiral welded tower comprises attaching the plurality of the cone segments to each other.
26. The method of claim-25, wherein the number of cone segments is between 4 and 10.
27. A spiral wound tapered structure, comprising:
a tapered body having a base, a top spaced above the base along a central longitudinal axis that is centered with respect to the base and the top, and a spirally wound plate that wraps around'sthe central longitudinal axis from the base to the top so that tapered body tapers toward the central longitudinal axis,

the spirally wound plate having:
a first inner surface that faces the central longitudinal axis;
a second outer surface opposite from the first inner surface:
a plate thickness that is perpendicular to the first inner surface and that extends from the first inner surface to the second outer surface:
a first lateral edge that extends between the first inner surface and the second outer surface; and
a second lateral edge opposite to the first lateral edge and that extends between the first inner surface and the second outer surface, and portions of the first and second lateral edges are joined adjacent to each other,
wherein the plate thickness varies along a direction the spirally wound plate wraps around the central longitudinal axis from the base to the top.
28. The tapered structure of claim 74, wherein the spirally wound plate defines a plate width
that extends from the first lateral edge to the second lateral edge and that is perpendicular to the
plate thickness, a plate length that is perpendicular to the plate width and the plate thickness,
wherein the plate thickness varies along the plate length.
29. The tapered structure of claim 27, wherein the portions of the first lateral edge and the
second lateral edges that are joined adjacent to each other have different plate thicknesses.
30. A tower comprising a plurality of spiral wound tapered structures according to claim 27.
31. A hybrid tower, comprising:
a base structure having a bottom end, a top end above the bottom end. and a cluster of pipes that extend from the bottom end of the base structure and the top end of the base structure;
an upper tower structure comprising a plurality of spiral wound tapered structures according to claim 27 connected to each other, wherein the upper tower structure is coupled to the top end of the base structure.