Patent Publication Number: US-2023135767-A1

Title: Method for manufacturing wind turbine tower structure with embedded reinforcement elements

Description:
FIELD 
     The present disclosure relates in general to wind turbine towers, and more particularly to methods of manufacturing wind turbine tower structures with embedded reinforcement elements. 
     BACKGROUND 
     Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known foil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid. 
     The wind turbine tower is generally constructed of steel tubes, pre-fabricated concrete sections, or combinations thereof. Further, the tubes and/or concrete sections are typically formed off-site, shipped on-site, and then arranged together to erect the tower. For example, one manufacturing method includes forming pre-cast concrete rings, shipping the rings to the site, arranging the rings atop one another, and then securing the rings together. As wind turbines continue to grow in size, however, conventional manufacturing methods are limited by transportation regulations that prohibit shipping of tower sections having a diameter greater than about 4 to 5 meters. Thus, certain tower manufacturing methods include forming a plurality of arc segments and securing the segments together on site to form the diameter of the tower, e.g. via bolting. Such methods, however, require extensive labor and can be time-consuming. 
     In view of the foregoing, the art is continually seeking improved methods for manufacturing wind turbine towers. Accordingly, the present disclosure is directed to methods for manufacturing wind turbine tower structures that address the aforementioned issues. In particular, the present disclosure is directed to methods for manufacturing wind turbine tower structures with embedded reinforcement elements. 
     BRIEF DESCRIPTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one aspect, the present disclosure is directed to a system for manufacturing a structure, such as a tower structure of a wind turbine. The system includes a supporting frame assembly moveable in a vertical direction of the structure. Further, the system includes an additive printing assembly secured to the supporting frame assembly. The additive printing assembly includes at least one printer head configured to dispense a first cementitious material. The system also includes a reinforcement dispensing assembly supported by the supporting frame assembly. Thus, the reinforcement dispensing assembly is configured to automatically and continuously dispense a plurality of reinforcing members as the structure is printed and built up via the at least one printer head and as the supporting frame assembly moves in the vertical direction. 
     In an embodiment, the printer head(s) of the additive printing assembly may include, at least, an outer printer head for printing an outer wall of the structure and an inner printer header for printing an inner wall of the structure. Further, in another embodiment, the additive printing assembly may include an intermediate printer head secured between the outer and inner printer heads for filling an area between the outer and inner tower walls with a second cementitious material. 
     In certain embodiments, the second cementitious material may be different than the first cementitious material. In particular, in one embodiment, the second cementitious material may be a self-compacting cementitious material. 
     In further embodiments, the supporting frame assembly may include at least one ring-shaped platform assembly supported by a plurality of rod members. More specifically, in an embodiment, the ring-shaped platform assembly may include a platform supporting an outer ring support member and an inner ring support member arranged concentrically with each other with the plurality of rod members extending therebetween. In particular embodiments, the outer and inner ring support members may each have an adjustable diameter. 
     In additional embodiments, the system may include a lifting jack that is moveable along each of the plurality of rod members so as to move the supporting frame assembly in the vertical direction by raising the outer and inner ring support members. In certain embodiments, the lifting jacks may be hydraulically-driven, pneumatically-driven, or mechanically-driven, such as via a screw, and/or combinations thereof 
     In another embodiment, the reinforcement dispensing assembly may also include a plurality of roller devices and the plurality of reinforcing members may be reinforcing cables. In such embodiments, the reinforcing cables may be dispensed from the plurality of roller devices by automatically and continuously rolling the reinforcing cables therefrom under tension. Further, in an embodiment, the roller devices may be arranged atop the outer ring support member or the inner ring support member. 
     Alternatively, the reinforcement dispensing assembly may include a plurality of pulley blocks with one of the plurality of pulley blocks being arranged with each of the plurality of roller devices, the plurality of pulley blocks arranged atop the at least one ring-shaped platform assembly, the plurality of roller devices being arranged lower than the plurality of pulley blocks. 
     In yet another embodiment, the reinforcement dispensing assembly may include a plurality of feeder devices arranged atop at least one of the outer ring support member or the inner ring support member. In such embodiments, the reinforcing members may be reinforcing bars. Accordingly, the reinforcing bars may be dispensed from the plurality of feeder devices by automatically and continuously pushing the reinforcing bars therefrom. 
     In another aspect, the present disclosure may be directed to a method for manufacturing a structure. The method includes (a) providing a supporting frame assembly having at least one ring-shaped platform assembly supported by a plurality of rod members. Further, the method includes (b) arranging an additive printing assembly and a reinforcement dispensing assembly with the at least one ring-shaped platform assembly. Moreover, the method includes (c) raising the at least one ring-shaped platform assembly a certain distance in a vertical direction by moving the at least one ring-shaped platform assembly along the plurality of rod members. In addition, the method includes (d) dispensing a plurality of reinforcing members from the reinforcement dispensing assembly under tension. The method also includes (e) printing, via at least one printer head of the additive printing assembly, at least a portion of the structure via at least one cementitious material so as to embed the dispensed plurality of reinforcing members therein. 
     In an embodiment, the method may include repeating steps (c) through (d) to complete the structure. 
     In another embodiment, moving the at least one ring-shaped platform assembly along the plurality of rod members in the vertical direction may include hydraulically driving the at least one ring-shaped platform assembly along the plurality of rod members via a plurality of lifting jacks. 
     In further embodiments, printing, via the at least one printer head of the additive printing assembly, at least the portion of the structure via the at least one cementitious material may include printing, via outer and inner printer heads of the additive printing assembly, outer and inner walls of the structure of a first cementitious material and filling, via an intermediate printer head secured between the outer and inner printer heads, an area between the outer and inner walls of the structure with a second cementitious material. It should be understood that the method may further include any of the additional features and/or steps as described herein. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG.  1    illustrates a perspective view of one embodiment of a wind turbine according to the present disclosure; 
         FIG.  2    illustrates a cross-sectional view of one embodiment of a tower structure of a wind turbine according to the present disclosure; 
         FIG.  3    illustrates a partial, perspective view of one embodiment of a system for manufacturing a tower structure according to the present disclosure; 
         FIG.  4    illustrates a cross-sectional view of one embodiment of a system for manufacturing a tower structure according to the present disclosure; 
         FIG.  5    illustrates a schematic diagram of one embodiment of a reinforcement dispensing assembly of a system for manufacturing a tower structure according to the present disclosure; 
         FIG.  6    illustrates a schematic diagram of another embodiment of a reinforcement dispensing assembly of a system for manufacturing a tower structure according to the present disclosure; 
         FIG.  7    illustrates a schematic diagram of yet another embodiment of a reinforcement dispensing assembly of a system for manufacturing a tower structure according to the present disclosure; 
         FIG.  8    illustrates a top view of one of the outer and inner ring support members of a system for manufacturing a tower structure according to the present disclosure; 
         FIG.  9    illustrates a flow diagram of one embodiment of a method for manufacturing a tower structure according to the present disclosure; and 
         FIG.  10    illustrates a block diagram of one embodiment of a controller of an additive printing device according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Generally, the present disclosure is directed to systems and methods for manufacturing structures, such as tower structures, using automated deposition of cementitious materials via technologies such as additive manufacturing, 3-D Printing, spray deposition, extrusion additive manufacturing, concrete printing, automated fiber deposition, as well as other techniques that utilize computer numeric control and multiple degrees of freedom to deposit material. More specifically, the systems and methods of the present disclosure include an automated reinforcement integration module to gradually feed reinforcing members into the tower structure during the construction process, which allows for incorporation of continuous vertical reinforcing members into the completed concrete structure. 
     Thus, the methods described herein provide many advantages not present in the prior art. For example, the systems and methods of the present disclosure allow for automation of integrating both vertical and horizontal reinforcing members into a tower structure during construction, enable full automation of concrete structure construction, simplify the construction process with faster speeds, accommodates both steel cable and conventional steel rebar as reinforcement, and directly forms the conduits for post-tension bars or cables, which are necessary for concrete towers. 
     Referring now to the drawings,  FIG.  1    illustrates one embodiment of a wind turbine  10  according to the present disclosure. As shown, the wind turbine  10  includes a tower  12  extending from a foundation  15  or support surface with a nacelle  14  mounted atop the tower  12 . A plurality of rotor blades  16  are mounted to a rotor hub  18 , which is in turn connected to a main flange that turns a main rotor shaft. The wind turbine power generation and control components are housed within the nacelle  14 . The view of  FIG.  1    is provided for illustrative purposes only to place the present invention in an exemplary field of use. It should be appreciated that the invention is not limited to any particular type of wind turbine configuration. In addition, the present invention is not limited to use with wind turbine towers but may be utilized in any application having concrete constructions and/or tall towers in addition to wind towers, including for example homes, bridges, tall towers and other aspects of the concrete industry. Further, the methods described herein may also apply to manufacturing any similar structure that benefits from the advantages described herein. 
     Referring now to  FIG.  2   , a cross-sectional view of a tower structure  12  of a wind turbine  10  manufactured according to the present disclosure is illustrated. As shown in the illustrated embodiment, the tower structure  12  defines a circumferential tower wall  20  having an outer surface  22  and an inner surface  24 . Further, as shown, the circumferential tower wall  20  generally defines a hollow interior  26  that is commonly used to house various turbine components (e.g. a power converter, transformer, etc.). In addition, as will be described in more detail below, the tower structure  12  is formed using additive manufacturing. Moreover, as shown, the tower structure  12  is formed of a cementitious material  28  that is reinforced with one or more reinforcement elements  30 . In particular embodiments, the reinforcement element(s)  30  may include, for example, elongated reinforcing cables or wires, reinforcing bars (also referred to as rebar), (hollow or solid), fibers (such as metal, glass, or carbon fibers) and/or any such structures or materials as may be known in the art to reinforce concrete structures. For example, as shown in  FIG.  2   , the tower structure  12  may include a plurality of pre-tensioned linear cables  32  embedded in the cementitious material  28 . 
     In addition, the cementitious material  28  described herein may include any suitable workable paste that is configured to bind together after curing to form a structure. As examples, a cementitious material may include lime or calcium silicate based hydraulically setting materials such as Portland cement, fly ash, blast furnace slag, pozzolan, limestone fines, gypsum, or silica fume, as well as combinations of these. In some embodiments, the cementitious material  28  may additionally or alternatively include non-hydraulic setting material, such as slaked lime and/or other materials that harden through carbonation. Cementitious materials may be combined with fine aggregate (e.g., sand) to form mortar, or with rough aggregate (sand and gravel) to form concrete, including both cement-based and non-cement based concretes. For example, in certain embodiments, the cementitious material may include geopolymer concrete, biopolymer concrete, or any other suitable concrete. A cementitious material may be provided in the form of a slurry, which may be formed by combining any one or more cementitious materials with water, as well as other known additives, including accelerators, retarders, extenders, weighting agents, dispersants, fluid-loss control agents, lost-circulation agents, strength-retrogression prevention agents, free-water/free-fluid control agents, expansion agents, plasticizers (e.g., superplasticizers such as polycarboxylate superplasticizer or polynaphthalene sulfonate superplasticizer), and so forth. The relative amounts of respective materials to be provided in a cementitious material may be varied in any manner to obtain a desired effect. 
     Referring now to  FIGS.  3 - 9   , the present disclosure is directed to systems and methods for manufacturing tower structures, such as wind turbine towers, via additive manufacturing. Additive manufacturing, as used herein, is generally understood to encompass processes used to synthesize three-dimensional objects in which successive layers of material are formed under computer control to create the objects. As such, objects of almost any size and/or shape can be produced from digital model data. It should further be understood that the additive manufacturing methods of the present disclosure may encompass three degrees of freedom, as well as more than three degrees of freedom such that the printing techniques are not limited to printing stacked two-dimensional layers but are also capable of printing curved and/or irregular shapes. 
     Referring particularly to  FIG.  3   , a perspective view of one embodiment of a system  100  for manufacturing a tower structure  102  according to the present disclosure is illustrated. As shown, the system  100  includes a supporting frame assembly  104  moveable in a vertical direction of the tower structure  102 . More specifically, as shown in  FIGS.  3  and  4   , the supporting frame assembly  104  may include a ring-shaped platform assembly  106  supported by a plurality of rod members  108 . For example, as shown in the illustrated embodiment, the ring-shaped platform assembly  106  may include a platform  110  supporting an outer ring support member  112  and an inner ring support member  114  arranged concentrically with each other with the plurality of rod members extending therebetween  108 . 
     In particular embodiments, the outer and inner ring support members  112 ,  114  may each have an adjustable diameter. For example, as shown in  FIG.  8   , the outer and inner ring support members  112 ,  114  may be segmented, with the segments  115  joined together via slidable, hollow sleeves  117 . Thus, as shown, the slidable, hollow sleeves  117  are configured to receive varying lengths of the segments  115  so as to adjust the diameter of the outer and inner ring support members  112 ,  114 . In certain embodiments, the hollow sleeves  117  and/or the segments  115  may be sufficiently flexible to enable the radius of curvature to change over the range of tower diameters. Accordingly, the outer and inner ring support members  112 ,  114  can be adjusted to accommodate tower structures of varying sizes. 
     Referring now particularly to  FIGS.  3  and  4   , the system  100  may include a lifting jack  116  that is moveable along each of the plurality of rod members  108  so as to move the supporting frame assembly  104  in the vertical direction V, i.e. by raising the outer and inner ring support members  112 ,  114  continuously or incrementally. In certain embodiments, the lifting jacks  116  may be hydraulically-driven screw jack. In further embodiments, the lifting jacks  116  may be driven using any suitable means, such as pneumatic, mechanical, etc. Thus, by lifting the lifting jack(s)  116 , the supporting frame assembly  104  can be lifted to any desired height. 
     Referring particularly to  FIG.  3   , the system  100  also includes an additive printing assembly  118  secured to the supporting frame assembly  104 . It should be understood that the additive printing assembly  118  described herein generally refers to any suitable additive printing device having one or more nozzles or printer heads for depositing material (such as the cementitious material described herein) onto a surface that is automatically controlled by a controller to form an object programmed within the computer (such as a CAD file). More specifically, as shown, the additive printing assembly  118  may include at least one printer head  120 ,  122  configured to dispense a first cementitious material  124 . For example, in an embodiment, as shown in  FIG.  3   , the printer head(s)  120 ,  122  of the additive printing assembly  118  may include, at least, an outer printer head  120  for printing an outer wall  126  of the tower structure  102  and an inner printer header  122  for printing an inner wall  128  of the tower structure  102 . 
     In addition, as shown, the additive printing assembly  118  may also include an intermediate printer head  130  secured between the outer and inner printer heads  120 ,  122 . As such, in certain embodiments, the intermediate printer head  130  may be a pump for filling an area  132  between the outer and inner tower walls  126 ,  128  with a second cementitious material  134  may be different than the first cementitious material  124 . In particular, in one embodiment, the first cementitious material  124  may be a fast-setting concrete. Therefore, the printed outer and inner walls can harden very quickly and can thus hold hydrostatic pressure of poured concrete. Accordingly, the second cementitious material  134  may be a self-compacting cementitious material. In further embodiments, the additive printing assembly  118  may include any suitable number of printer heads including more than three printer heads or less than three printer heads. 
     Referring now to  FIGS.  3 - 7   , the system  100  also includes a reinforcement dispensing assembly  136  supported by the supporting frame assembly  104 . Thus, the reinforcement dispensing assembly  136  is configured to automatically and continuously dispense a plurality of reinforcing members  138  as the tower structure  102  is printed and built up via the printer head(s)  120 ,  122 ,  130  and as the supporting frame assembly  104  moves in the vertical direction V. For example, as shown in  FIGS.  3 - 5  and  7   , the reinforcement dispensing assembly  136  may include a plurality of roller devices  140 . In such embodiments, the reinforcing members  138  may be reinforcing cables  142  or wires. In such embodiments, the reinforcing cables  40  may be dispensed from the roller devices  140 , e.g. by automatically and continuously rolling the reinforcing cables  142  therefrom under tension. Further, in an embodiment, as shown in  FIGS.  3 - 5   , the roller devices  140  may be arranged atop the outer or inner ring support members  112 ,  114 . 
     Alternatively, as shown in  FIG.  7   , the reinforcement dispensing assembly  136  may include a plurality of pulley blocks  144  with one of the plurality of pulley blocks  144  being arranged with each of the plurality of roller devices  140 . Accordingly, as show, the pulley blocks  144  may be arranged atop the outer or inner ring support members  112 ,  114  and the roller devices  140  may be arranged lower than the pulley blocks  144 , such as on the ground. 
     Referring to  FIG.  6   , in alternative embodiments, the reinforcement dispensing assembly  136  may include a plurality of feeder devices  146  arranged atop the outer or inner ring support members  112 ,  114 . In such embodiments, the reinforcing members  138  may be reinforcing bars  148 . Accordingly, as shown, the reinforcing bars  148  may be dispensed from the feeder devices  146  by automatically and continuously pushing the reinforcing bars  148  therefrom. 
     Referring particularly to  FIG.  9   , a flow diagram of one embodiment of a method  200  for manufacturing a tower structure  102  according to the present disclosure is illustrated is illustrated. In general, the method  200  will be described herein with reference to the tower structure  102 , such as a wind turbine tower, formed using the system  100  shown in  FIGS.  3 - 8   . However, it should be appreciated that the disclosed method  200  may be implemented to form other similar tower structures having any other suitable configurations. In addition, although  FIG.  9    depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and/or adapted in various ways without deviating from the scope of the present disclosure. 
     As shown at ( 202 ), the method  200  may include providing the supporting frame assembly  104  described herein. As shown at ( 204 ), the method  200  may include arranging the additive printing assembly  118  and the reinforcement dispensing assembly  136  with the ring-shaped platform assembly  106  of the supporting frame assembly  104 . As shown at ( 206 ), the method  200  may include raising the ring-shaped platform assembly  106  to a certain distance in the vertical direction V by moving the ring-shaped platform assembly  106  along the plurality of rod members  108 , e.g. via a plurality of lifting jacks  116 . 
     While the ring-shaped platform assembly  106  is being lifted or after, as shown at ( 208 ), the method  200  may include dispensing a plurality of reinforcing members  138  from the reinforcement dispensing assembly  136 . For example, as mentioned, in an embodiment, the reinforcing member(s)  138  may be reinforcing cable  142  that is unwound from a rolling device  140  under tension. Alternatively, as mentioned, the reinforcing member(s)  138  may be reinforcing bards  148  that are pushed down and into a space that will ultimately be filled or printed with cementitious material. 
     It should be understood that the reinforcing member(s)  138  may extend along the entire height of the tower structure  102  or along only a portion of the tower height. In addition, in such embodiments, the additive printing assembly  118  is configured to print the cementitious material around the reinforcing member(s)  138 . In alternative embodiments, the reinforcement dispensing assembly  136  may be configured to provide tension to the reinforcing member(s)  138 , such as when the member(s) are cables, during printing of the tower structure  102  and/or during lifting of the supporting frame assembly  104 . In such embodiments, the method  200  may also include varying a tension of the one or more reinforcing member(s)  138  as a function of a cross-section of the tower structure  102  during the printing process. Thus, such reinforcing member(s)  138  are configured to manage tensile stresses of the tower structure  102 . 
     Referring still to  FIG.  9   , as shown at ( 210 ), the method  200  may include printing, via at least one printer head of the additive printing assembly  118 , at least a portion of the tower structure  102  via at least one cementitious material so as to embed the dispensed plurality of reinforcing members  138  therein. For example, in an embodiment, as shown in  FIG.  4   , the method  200  may include printing, via the outer and inner printer heads  120 ,  122  of the additive printing assembly  118 , the outer and inner walls  126 ,  128  of the tower structure  102  of the first cementitious material  124 . Such walls  126 ,  128  may be printed simultaneously to save time or separately, if needed. Then, the method  200  may include filling, via the intermediate printer head  130  secured between the outer and inner printer heads  120 ,  122 , the area  132  between the outer and inner walls  126 ,  128  with the second cementitious material  134  so as to completely cast the tower structure  102 . This process (i.e. steps  206 ,  208  and  210 ) can be repeated to complete the tower structure  102  up to any suitable height. Moreover, in certain embodiments, the rod members  108  of the supporting frame assembly  104  may be removed after construction of the tower structure  102 , thereby creating holes or channels that can be used as conduits for post-tension bars or cables. 
     In addition, in certain embodiments, the additive printing assembly  118  is configured to print the cementitious material in a manner that accounts for the cure rate thereof such that the tower structure  102 , as it is being formed, can bond to itself. In addition, the additive printing assembly  118  is configured to print the tower structure  102  in a manner such that it can withstand the weight of the walls  126 ,  128  as the additively-formed cementitious material can be weak during printing. Thus, the reinforcement element(s)  138  of the tower structure  12  are provided to enable the tower to withstand wind loads that can cause the tower  12  to be susceptible to cracking. 
     Referring now to  FIG.  10   , a block diagram of one embodiment of a controller  300  configured to control the additive printing assembly  118  described herein is illustrated. As shown, the controller  300  may include one or more processor(s)  302  and associated memory device(s)  304  configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). Additionally, the controller  300  may also include a communications module  306  to facilitate communications between the controller  300  and the various components of the additive printing assembly  118 . Further, the communications module  306  may include a sensor interface  308  (e.g., one or more analog-to-digital converters) to permit signals transmitted from one or more sensors  310 ,  312  to be converted into signals that can be understood and processed by the processor(s)  302 . It should be appreciated that the sensors may be communicatively coupled to the communications module  306  using any suitable means. For example, as shown in  FIG.  10   , the sensors  310 ,  312  may be coupled to the sensor interface  308  via a wired connection. However, in other embodiments, the sensors  310 ,  312  may be coupled to the sensor interface  308  via a wireless connection, such as by using any suitable wireless communications protocol known in the art. As such, the processor(s)  302  may be configured to receive one or more signals from the sensors. 
     As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. The processor(s)  302  is also configured to compute advanced control algorithms and communicate to a variety of Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). Additionally, the memory device(s)  304  may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s)  304  may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s)  302 , configure the controller  300  to perform the various functions as described herein. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.