Support structure for wind blades

Abstract

A support structure (1) for wind blades (2), each wind blade (2) having an upper surface (8) and a lower surface (9), said support structure (1) comprising: an enclosure (10) insertable within a wing cavity (11) defined between the upper surface (8) and the lower surface (9), said enclosure (10) extending along a longitudinal direction (X-X) between a first end portion (13) which can be coupled to a rotor hub (3a) for wind blades (2) and an opposite second end portion (14), said enclosure (10) having a side wall (15) connected to the first end portion (13) and the second end portion (14) and configured to be coupled to the upper surface (8) and the lower surface (9); said enclosure (10) having one or more cavities (20) defined between the side wall (15), the first end portion (13) and the second end portion (14); an inflatable frame (30) arranged within at least one cavity (20) and configured to reversibly switch between a first configuration and a second configuration wherein said inflatable frame (30) preloads at least partially the side wall (15) of the enclosure (10).

Description

[0001] “ Support structure for wind blades”

[0002] DESCRIPTION

[0003] Technical Field

[0004] The present invention relates to a support structure for aerogenerator components, in particular wind blades, and is employed in wind turbines used in the field of energy production. A further object of the present invention is a wind blade provided with the support structure.

[0005] State of the Art

[0006] Wind power generation devices, including horizontal axis wind turbines, are known in the state of the art. These devices comprise a rotor provided with blades, for example three. The rotor is connected via a hub to the nacelle placed at the top of a tower. The nacelle is able to rotate with respect to the tower, so as to be aligned with the wind direction. The rotor shaft is arranged to transmit the rotary motion of the blades to a current generator housed in the nacelle. Known wind blades are mainly made of composite materials such as fibreglass and are generally manufactured in one single piece to be then transported to the sites for mounting thereof on the rotor, which is placed at the top of the tower. These wind blades have support structures (also known as SPAR) inside the wing cavity to provide structural support to the blade during use. These support structures, in one piece with the rest of the blade, have, for example, ribs which are internally coupled to the aerodynamic surfaces to support and retain these surfaces. The latter are rigid surfaces made of composite materials and have in the cross-section the typical shape of an airfoil from the rotor to the free end opposite thereto. In accordance with other examples, the support structures may be associated to inflatable wind blades. Specifically, the aerodynamic surface of the wind blade is defined by inflating an enclosure that would otherwise collapse onto the support structure thereof.

[0007] Problems of the Prior Art

[0008] The known support structures and the wind blades thereof have numerous disadvantages, including the problem of transportation and the use of non-recyclable materials. In fact, known wind blades require all the components to be assembled at the factory to be then transported to the site in one piece. Transport, given the size of the wind turbines, represents a handling problem as well as an increase in costs, time and emissions. In addition, as anticipated, the wind blades and the associated support structures are made of non-recyclable materials, representing a serious problem during the production, maintenance and, above all, disposal step. Specifically, in the production step, this type of wind turbine requires long manufacturing times for arranging the material layers, which in any case increases the risk of generating flaws. The latter can obviously cause premature blade failure.

[0009] Object of the Invention

[0010] The object of the invention in question is to realise a support structure for wind turbines capable of overcoming the drawbacks of the aforementioned prior art.

[0011] In particular, it is the object of the present invention to provide a support structure for wind blades capable of improving the structural strength of the wind blades as well as fulfil their mechanical requirements.

[0012] The stated technical task and specified objects are substantially achieved by a support structure for wind blades comprising the technical features set forth in one or more of the appended claims.

[0013] Advantages of the Invention

[0014] Advantageously, the support structure of the present invention allows to reduce the overall weight of the wind blade.

[0015] Advantageously, the support structure of the present invention allows to ease the coupling to the hub or aerogenerator.

[0016] Advantageously, the support structure of the present invention can be made of completely recyclable materials reducing the use of materials that are polluting and difficult to dispose of.

[0017] Advantageously, the support structure of the present invention allows to reduce the overall production costs of a wind blade as well as to facilitate transportation to the wind blade mounting site. In fact, the support structure of the present invention can be assembled on site as it can be realized in multiple modular sectors.

[0018] Advantageously, the support structure of the present invention allows to manage the vibrations induced by the external forces on the wind blade.

[0019] Advantageously, the support structure of the present invention allows to vary and manage the modal response of the structure itself.

[0020] Advantageously, the support structure of the present invention facilitates, during the construction step, the identification of possible flaws and facilitates the correction / restoration in order to guarantee the integrity and durability of the wind blade in view of the chosen material, which is more studied than composite materials.

[0021] Advantageously, the support structure of the present invention allows to improve the overall safety of the wind blades.

[0022] Advantageously, the support structure of the present invention allows to improve the buckling resistance while reducing the thicknesses that are required to construct the wind blade.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further characteristics and advantages of the present invention will become more apparent from the indicative, and therefore non-limiting, description of a preferred but not exclusive embodiment of a support structure for a wind blade, as illustrated in the accompanying drawings wherein:

[0025] - Fig. 1 : shows a schematic view of the wind turbine;

[0026] - Fig. 2: shows a schematic perspective view of a support structure in accordance with an embodiment of the present invention with some parts omitted to better show others;

[0027] - Fig.3: shows a schematic perspective view of the support structure in accordance with an embodiment of the present invention with some parts omitted to better show others;

[0028] - Fig.4: shows a schematic perspective view of the support structure inserted into the wind blade with some parts omitted to better show others;

[0029] - Fig. 5: shows a schematic view of a cross-section of the support structure inserted inside the wind blade in accordance with an embodiment of the present invention with some parts omitted to better show others;

[0030] - Fig. 6: shows a schematic view of a cross-section of the support structure inserted inside the wind turbine blade in accordance with a further embodiment of the present invention with some parts omitted to better show others;

[0031] - Fig.7: shows a schematic view of a butterfly diagram along the thickness of a surface portion of the enclosure of the support structure in accordance with a first configuration;

[0032] - Fig.8: shows a schematic view of a butterfly diagram along the thickness of a surface portion of the enclosure of the support structure in accordance with a second configuration in which the structure is pre-loaded under pressure;

[0033] - Fig. 9: shows a schematic view of a diagram of stresses due to pressure along the thickness of a surface portion of the enclosure of the support structure in accordance with the second configuration in which the structure is pre-loaded under pressure. DETAILED DESCRIPTION

[0034] Even if not explicitly highlighted, the individual features disclosed with reference to the specific embodiments shall be understood as accessory to and / or interchangeable with other features disclosed with reference to other embodiments.

[0035] The present invention relates to a support structure for aerogenerator components, in particular wind blades, globally indicated in the figures with 1.

[0036] This support structure 1 is configured to provide correct structural support to the relative wind blade 2.

[0037] Specifically, this support structure 1 allows to fulfil the mechanical requirements for a support structure of a wind blade.

[0038] It is worth noting that the support structure 1 acts as a resistant core for the wind blade 2, as explained hereinafter, providing structural support to the wind blade both in operation and in a rest condition wherein the wind blade is stationary, i.e. in a non- operational condition.

[0039] It is worth noting that each wind blade 2 can be associated with a rotor hub 3a to define a rotor 3. Specifically, each wind blade 2 has an upper surface 8 and a lower surface 9, i.e. an upper side and a lower side respectively extending along a longitudinal direction X-X.

[0040] The upper surface (or suction side) 8 and lower surface (or pressure side) 9 define a leading edge 6 and a trailing edge 7.

[0041] It should be noted that each wind blade 2 has a wing cavity 11 defined between the upper surface 8 and lower surface 9.

[0042] The support structure 1 comprises an enclosure 10 insertable into a wing cavity 11.

[0043] Specifically, the enclosure 10 extends along a longitudinal extension direction X-X between a first end portion 13 which can be coupled to the rotor hub 3a and an opposite end portion 14. The enclosure 10 also has a side wall 15 connected to the first end portion 13 and the second end portion 14.

[0044] Preferably, the side wall 15 has a thickness that can, for example, be in a range between 0.1 mm and 10 mm, but also 25 mm or 50 mm.

[0045] This side wall 15 is configured to be coupled to the upper surface 8 and the lower surface 9.

[0046] In accordance with a preferred embodiment, the enclosure 10 comprises mechanical connection means 80 configured to couple the side wall 15 with the upper surface 8 and the lower surface 9 of the wind blade. These mechanical connection means 80 may comprise for example ribs configured to be externally coupled to the enclosure 10 in order to mechanically connect the upper surface 8 and the lower surface 9 to the enclosure 10.

[0047] The support structure 1 can thereby fulfil its structural and support function.

[0048] It is worth noting that the side wall 15 has a front portion 16 facing the leading edge 6 and a rear portion 17 opposite thereto and facing the trailing edge 7.

[0049] Preferably, the front portion 16 and the rear portion 17 are spaced along a transverse direction Y-Y perpendicular to the longitudinal direction X-X.

[0050] The side wall 15 has an upper portion 18 facing the upper surface 8 and a lower portion 19 facing the lower surface 9.

[0051] Preferably, the upper portion 18 and the lower portion 19 are mutually spaced along a spacing direction Z-Z perpendicular to the transverse direction Y-Y and to the longitudinal direction X-X.

[0052] In accordance with a preferred embodiment, the enclosure 10 has one or more cavities 20.

[0053] Specifically, these one or more cavities 20 are defined between the side wall 15, the first end portion 13 and the second end portion 14.

[0054] Preferably, the enclosure 10 has a first and a second base 13a, 14a at the first end portion 13 and the second end portion 14 respectively. Specifically, the one or more cavities 20 are defined between the first base 13a, second base 14a and the side wall 15.

[0055] It is worth noting that, the side wall 15 has an inner surface 15a facing the cavity 20 and an outer surface 15b opposite thereto and facing the inside of the wing cavity 11.

[0056] In accordance with a preferred embodiment, the mechanical connection means 80 are associated with the outer surface 15b.

[0057] The support structure 10 comprises an inflatable frame 30 arranged within at least one cavity 20. Preferably, the inflatable frame 30 can be arranged in more cavities 20 if present.

[0058] This inflatable frame 30 is configured to reversibly switch between a first configuration and a second configuration.

[0059] In this second configuration, the inflatable frame 30 is configured to at least partially preload the side wall 15 of the enclosure 10. It should be noted that switching from the first configuration to the second configuration takes place by the inflow and pressurisation of a fluid, such as air, while switching from the second to the first configuration takes place by the outflow of the fluid.

[0060] Specifically, the inflatable frame 30 is configured to generate a force acting internally to the enclosure 10, on the inner surface 15a, adapted to at least partially preload the side wall 15 by switching from the first configuration to the second configuration, inflating at least partially. In detail, the inflatable frame 30 is configured to apply a pressure at least partially on the side wall 15 by pushing it internally by expansion.

[0061] The inflatable frame 30 thereby allows the enclosure 10 to perform a structural and support function for the wind blade 2.

[0062] In accordance with a preferred embodiment, the inflatable frame 30 is configured to at least partially preload axially and / or radially the side wall 15 by contact by switching from the first configuration to the second configuration by means of the inflow and pressurisation of a fluid. Specifically, the second configuration is the configuration in which the inflatable frame 20 allows the preloading of at least a portion of the side wall 15.

[0063] Preferably, the inflatable frame 30, switching from the first configuration to the second configuration, expands and transmits a force inside the enclosure 10. Specifically, the inflatable frame 30 expands and transmits the force on a portion of the side wall 15 and possibly on other elements, as explained below, to at least partially preload the side wall 15.

[0064] Specifically, the inflatable frame 30 is configured to axially and / or radially preload the upper portion 18 and the lower portion 19 of the enclosure by switching from the first to the second configuration. Preferably, the inflatable frame 30 is configured to also axially and / or radially preload the front portion 16 and rear portion 17 of the enclosure by switching from the first configuration to the second configuration.

[0065] It should be noted that the distribution of the stresses on the support structure 1 and in particular on the side wall 15 at a thickness thereof can assume a butterfly distribution as illustrated in Figures 7 and 8 where traction stresses Ft and compressive stresses Fc are visible. Specifically, external forces applied to the wind blade and therefore transmitted to the support structure 1 as known have a distributed shear and a momentum that can be represented by a butterfly diagram along the thickness. Figure 7 shows a schematic butterfly diagram in a configuration wherein the enclosure 10 is not preloaded and where the applied traction stresses Ft and compressive stresses Fc are visible, while Figure 8 shows a schematic butterfly diagram in the configuration in which the enclosure is preloaded and where the preload stresses, due to the pressure exerted by the inflatable frame and illustrated schematically in Figure 9, are added to the traction stresses Ft and compressive stresses Fc reducing and preferably eliminating the compressive stresses Fc.

[0066] Advantageously, the support structure 1 is able to provide the necessary structural support to the wind blade by means of the relative mechanical connection existing between the support structure 1 and the upper surface 8 and the lower surface 9 due to the preload provided to the enclosure 10.

[0067] Preferably, the axially and / or radially preloaded enclosure 10 is configured to compensate for compressive and / or shear stresses generated on the enclosure 10.

[0068] For example, these stresses may be generated by external forces generated on the wind blade and transmitted to the support structure 1. These external forces may be the aerodynamic forces developed on the wind blade for example during operation.

[0069] It is worth noting that the preload applied on the enclosure can also vary the vibration frequencies of the support structure and therefore of the wind blade. This allows to vary the frequency itself of the support structure and therefore of the wind blade, preventing it from resonating with external forces.

[0070] In accordance with a preferred embodiment, the enclosure 10 comprises partition walls 23 mutually spaced along the longitudinal direction X-X between the first and second end portions 13, 14.

[0071] Each cavity 20 is defined between two adjacent partition walls 23 and a portion of side wall 15c between the two consecutive partition walls 23. It is worth noting that the partition walls 23 at the first end portion 14 and second end portion 15 may coincide with the first and second base 13a, 14a.

[0072] In accordance with a preferred embodiment, adjacent cavities 20 may have the relative partition wall 23 in common or have separate and distinct partition walls 23.

[0073] Preferably, the inflatable frame 30 switching between the first and second configuration can also preload the partition walls 23. It is worth noting that the inflatable frame 30 can at least partially preload the side wall 15 by pushing the partition walls 23 associated with the corresponding cavity 20 in opposite directions. Advantageously, switching from the first configuration to the second configuration modifies the distribution of stresses applied along the upper portion 18 and the lower portion 19. Preferably, switching from the first configuration to the second configuration modifies the distribution of the stresses acting also on the front portion 16, on the rear portion 17 as well as on the partition walls 23 by preloading them axially and / or radially.

[0074] In accordance with a preferred embodiment, the inflatable frame 30 comprises one or more inflatable chambers 40 configured to at least partially occupy the one or more cavities 20. Specifically, at least one cavity 20 comprises one or more inflatable chambers 40.

[0075] These inflatable chambers 40 are configured to at least partially preload the side wall 15 when the frame switches between the first configuration and the second configuration.

[0076] Specifically, the inflatable chambers 40 are configured to act inside the enclosure 10 in the relative cavity 20 to apply relative pressure to the enclosure 10 and at least partially preload the side wall 15 and preferably one or more partition walls 23.

[0077] It should be noted that each inflatable chamber 40 is configured to switch between the first and second configurations by the inflow and pressurisation of the fluid inside the inflatable chamber 40 and relative outflow. Specifically, each inflatable chamber 40 switching between the first and second configurations is inflated by expanding so as to apply a pressure internally to the enclosure 10 pushing it in the expansion direction. In detail, the inflatable frame switches from the first to the second configuration when at least one or more inflatable chambers 40 switch from the first to the second configuration by at least partially preloading the side wall 15 and possibly one or more partition walls 23.

[0078] It is worth noting that each inflatable chamber 40 has an inner volume 41 that can be inflated by a fluid. Preferably, by switching from the first to the second configuration, the inner volume 41 may only be partially filled, but sufficiently for the one or more inflatable chambers 40 to at least partially fill the relative cavity 20 and to at least partially preload the side wall 15 and possibly one or more partition walls 23.

[0079] Specifically, in one or more cavities 20, the inflatable chambers 40 are configured to expand only partially with respect to a maximum expansion, but sufficiently to adhere internally to the enclosure 10 and apply a pressure for the relative preloading of a portion of the side wall 15.

[0080] In fact, each cavity 20 has a cavity volume 20a smaller than the sum of the inner volumes 41 of the inflatable chambers 40 contained therein that they could actually occupy if filled completely.

[0081] Specifically, the inner volume 41 of the inflatable chambers 40 may occupy a greater volume than the volume it actually occupies when the inflatable chamber 40 is inserted inside a cavity 20 alone or with other inflatable chambers 40.

[0082] It is thereby possible to compensate for any leaks in one or more inflatable chambers 40 without losing preload, as well as to adjust the preload itself by increasing the pressure inside the chamber without incurring risks.

[0083] It is therefore worth noting that each inflatable chamber 40 expands switching from the first to the second configuration by at least partially filling the relative inner volume 41 as a function of the cavity 20.

[0084] Preferably, the inflatable chambers 40 are arranged adjacent to each other longitudinally along the longitudinal direction X-X. Alternatively, the inflatable chambers 40 are arranged adjacent to each other along the transverse direction Y-Y. Alternatively, the inflatable chambers 40 are arranged adjacent to each other longitudinally along the longitudinal direction X-X and transverse to the longitudinal direction X-X.

[0085] It is worth noting that each cavity 20 may have a different distribution of the one or more inflatable chambers.

[0086] Advantageously, the compartmentalisation of the enclosure 10 allows the preload of the enclosure 10 at different levels along the longitudinal development, preferably due to the lack of watertight cavities 20.

[0087] Advantageously, the compartmentalisation of the energy stored under pressure (pressure multiplied by volume) in the inflatable chambers 40 reduces the likelihood of all energy being released at the same time, improving the safety of the support structure.

[0088] In accordance with a preferred embodiment for example shown in Figure 6, each inflatable chamber 40 comprises a perimeter wall 50 defining the inner volume 41. These one or more perimeter walls 50 are inserted within one or more cavities 20 to at least partially adhere internally to the enclosure 10.

[0089] Specifically, each perimeter wall 50 is configured to at least partially abut against one of side wall 15, one or more partition walls 13, 14, one or more perimeter walls 50 of adjacent inflatable chambers 40, or a combination thereof.

[0090] The one or more of the perimeter walls 50 are thereby configured to push against each other in order to at least partially preload the side wall 15 by switching from the first configuration to the second configuration. In fact, the one or more inflatable chambers 40 expand, switching from the first configuration to the second configuration, and pushing against each other by contact between the perimeter walls 50, the side wall 15 and the one or more partition walls 23 apply pressure on the enclosure to at least partially preload the side wall 15.

[0091] In accordance with a preferred embodiment, the inflatable frame comprises an inflatable chamber 40 in at least one cavity 20. The perimeter wall 50 of the inflatable chamber 40 is configured to adhere internally to the side wall 15 and to one or more partition walls 23 by switching from the first configuration to the second configuration.

[0092] In accordance with a preferred embodiment wherein the frame comprises multiple inflatable chambers 40 in at least one cavity 20, the perimeter walls 50 of the inflatable chambers 40 are configured to at least partially abut against one of the side wall 15, one or more partition walls 23, one or more perimeter walls 50 of adjacent inflatable chambers 40, or a combination thereof, by switching from the first configuration to the second configuration. In accordance with the present embodiment, one or more inflatable chambers 40 expand switching from the first to the second configuration by at least partially filling the respective inner volume 41 depending on the cavity 20 in which the one or more inflatable chambers 40 are inserted and on the presence of other inflatable chambers 40. Specifically, each cavity 20, by means of its relative side wall 15c and partition walls 23, limits the expansion of the one or more inflatable chambers 40 in combination with the mutual limitation of the other inflatable chambers 40 present in the relative cavity 20.

[0093] For example, the perimeter wall 50 may be in contact with portions of perimeter wall 50, or at least partially with one or more portions of perimeter wall 50 and a portion of side wall 15, or at least partially with one or more portions of perimeter walls 50 and a portion of one or more partition wall 23, or at least partially with one or more portions of perimeter walls 50, a portion of side wall 15 and a portion of one or more partition walls 23, and so on.

[0094] Preferably, each cavity 20 having a cavity volume less than the sum of the inner inflatable volumes 41 of the inflatable chambers contained therein, the perimeter walls 50 may have folds 52, in fact, the inner inflatable volume 41 is only partially filled. These folds 52, in case the inflatable chamber 40 needs greater expansion, tend to become increasingly smaller as the inflatable chamber 40 expands and occupies more volume. In this case, the inner volume 41 tends to fill up more than in an earlier condition.

[0095] It is worth noting that perimeter wall 50 has structural and fluid impermeability characteristics. In accordance with a preferred embodiment, the perimeter wall 50 can be made from a polymer or rubber film, coupled with a strong fabric, such as a fabric made from synthetic fibres such as polyester, polyamide, aramid or metal.

[0096] In accordance with a preferred embodiment that is alternative and combinable with the previous one illustrated for example in Figure 3, the inflatable frame 30 comprises one or more containment elements 60 each defining a containment volume 61 configured to contain one or more inflatable chambers 40.

[0097] The containment element 60 may comprise, for example, containment bands, a containment net or a containment wall, etc.

[0098] Preferably, each containment element 60 has an outer containment surface 60a configured to abut at least partially against one of the side wall 15, one or more partition walls 23, one or more adjacent containment elements 60, one or more adjacent inflatable chambers 40, or a combination thereof. It is worth noting that each containment element 60 has an inner containment surface 60b opposite to the outer containment surface 60a and configured to abut at least partially against one or more adjacent inflatable chambers 40 inserted within the containment volume 61.

[0099] Thus, the one or more containment elements 60 together with the relative inflatable chambers 40 push against each other when the one or more inflatable chambers 40 switch from the first configuration to the second configuration to at least partially preload the side wall 15. Specifically, the one or more containment elements 60 together with the relative inflatable chambers 40 apply a relative pressure internally to the enclosure 10 on a relative portion of the side wall 15 and possibly to one or more partition walls 23.

[0100] Preferably, each chamber 40 comprises an inner wall 70 defining the inner volume 41. The inflatable chambers 40 and thus the corresponding inner walls 70 are inserted within the containment volume 61 of the containment element 60.

[0101] Specifically, each inner wall 70 is configured to abut at least partially against one of the containment element 60, one or more partition walls 23, one or more inner walls 70 of adjacent inflatable chambers 40, the side wall 15 or a combination thereof. Thus, as anticipated, the inner walls 70 are configured to push against each other in order to push the one or more containment elements 60 against the side wall 15 in order to preload it at least partially by switching from the first configuration to the second configuration.

[0102] In accordance with a preferred embodiment, the inflatable frame 30 comprises a containment element 60 and an inflatable chamber 40 inserted within the containment volume 61 in at least one cavity 20. In the present embodiment, the inner wall 70 of the inflatable chamber 40 is configured to adhere at least partially to one of the containment element 60, one or more partition walls 23, the side wall 15 or a combination thereof. Instead, the containment element 60 is configured to adhere internally to the relative portion of the side wall 15 and to one or more partition walls 23 by switching from the first configuration to the second configuration.

[0103] In accordance with an alternative preferred embodiment, the inflatable frame 30 comprises a containment element 60 and two or more inflatable chambers 40 inserted within the containment volume 61 in at least one cavity 20. In the present embodiment, each inner wall 70 is configured to adhere at least partially to one of the containment element 60, one or more adjacent inner walls 70, one or more partition walls 23, the side wall 15 or a combination thereof. Instead, the containment element 60 is configured to adhere internally to the side wall 15 and to one or more partition walls 23.

[0104] In accordance with an alternative preferred embodiment, the inflatable frame comprises containment elements 60 and one or more inflatable chambers 40 inserted into each containment element 60. According to the present embodiment, each containment element 60, by means of its outer containment surface 60a, is configured to adhere at least partially to one of adjacent containment elements 60, the side wall 15, one or more partition walls 23, one or more inner walls 70 of adjacent inflatable chambers 40, or a combination thereof. Instead, each inner wall 70 is configured to adhere at least partially to one of the containment elements 60, the side wall 15, one or more partition walls 23, one or more inner walls 70 of adjacent inflatable chambers 40 or a combination thereof.

[0105] In accordance with embodiments wherein the containment element 60 is present, each inflatable chamber 40 expands switching from the first to the second configuration by filling at least partially the relative inner volume 41 depending on i) the cavity 20 in which the one or more inflatable chambers 40 are inserted, ii) the presence of other inflatable chambers 40, and iii) the one or more containment elements 60 containing the one or more inflatable chambers 40. Specifically, each cavity 20 by means of its side wall 15c and partition walls 23 limits the expansion of the one or more inflatable chambers 40. In addition, the other inflatable chambers 40 mutually limit the relative expansion of each of the inflatable chambers 40 inserted into the cavity as well as the relative containment element 60.

[0106] For example, the inner wall 70 may be in contact with portions of inner walls 70, or at least partially with one or more portions of inner walls 70 and a portion of the side wall 15, or at least partially with one or more portions of inner walls 70 and a portion of the one or more partition walls 23, or at least partially with one or more portions of inner walls 70, a portion of the side wall 15 and a portion of the one or more partition walls 23, or one or more portions of inner walls 70 and a portion of the containment element 60, or a portion of the containment element 60, at least partially with one or more portions of inner walls 70 and a portion of the side wall 15 etc.

[0107] In accordance with a preferred embodiment, each cavity 20 having a cavity volume less than the sum of the inner inflatable volumes 41 of the inflatable chambers contained therein, the internal walls 70 may have folds 73 as well as the containment elements 60 may have relative folds 63, in fact, the inner inflatable volume 41 is only partially filled. These folds 73, 63, in case the one or more inflatable chambers 40 need greater expansion, tend to become increasingly smaller as the one or more inflatable chambers 40 expand and occupy larger volume. In this case, each inner volume 41 and containment volume 61 tend to fill up more than in a previous condition.

[0108] It is worth noting that the folds 52, 63, 73, schematically shown in the figures, may have different geometric shapes and may be formed within the relative cavity at random.

[0109] Preferably, the containment element 60 has structural characteristics. In accordance with a preferred embodiment, the containment element 50 can be made in textile form with synthetic fibres, for example polyester, polyamide, aramid and metal and / or a combination thereof.

[0110] Preferably, the inner wall 70 has fluid impermeability characteristics. In accordance with a preferred embodiment, the inner wall 70 can be made from a polymer or rubber film with the possibility self-support fabric.

[0111] In accordance with a preferred embodiment, the inflatable chambers 40 can be inflated and deflated independently of each other. It is worth noting that the inflatable chambers 40 can therefore switch independently of each other between the first and second configurations and in any intermediate filling configurations.

[0112] Specifically, each inflatable chamber 40, as anticipated, is configured to occupy a greater volume than the actual volume occupied by switching from the first configuration to the second configuration when inserted into a relative cavity 20. Thus, should one or more of the inflatable chambers 40 deflate due to a failure and / or malfunction, the other inflatable chambers 40 can make up for the missing volume by expanding more within the relative cavity 20 and preloading at least partially the side wall 15. In fact, the second configuration is the configuration wherein the inflatable chambers 40 provide the preload. Therefore, in the event of voluntary or involuntary switch of one or more inflatable chambers 40 from the second to the first configuration, the remaining inflatable chambers 40 in the second configuration tend to expand more to maintain the preload. If necessary, other inflatable chambers 40 maintained in a first configuration can be activated and switched from the first to the second configuration. It is worth noting that the inflatable frame thereby avoids losing the “improved” mechanical characteristics of the enclosure 10 as a result of a rupture and / or inflation of a single or a percentage of the inflatable chambers 40. It is worth noting that the loss of a single inflatable chamber 40 or a certain percentage thereof can be compensated for by the remaining inflatable chambers, thus generating redundancy.

[0113] In accordance with a preferred embodiment, the inflatable frame 40 comprises one or more inflating devices configured to regulate the inflow and outflow of a fluid within each inflatable chamber 40 to control the preload of the side wall 15 by switching from the first to the second configuration. For example, these inflating devices may comprise pumps, valves and fluid connections to inflow and outflow fluid into each inflatable chamber.

[0114] Advantageously, the inflatable frame 30 makes it possible to maintain and control a state of stress due to the pressure exerted on at least a portion of the side wall 15' and on one or more partition walls of a relative cavity 20 due to the material of the perimeter wall or the combination of the materials of the containment element and of the inner walls combined with the inflating devices.

[0115] For example, the pressure inside the chamber 40 can be in a range between 0.1 and 40 barg, preferably between 0.5 and 20 barg.

[0116] In accordance with a preferred embodiment, the inflatable frame 30 is configured to switch the enclosure 10 between a rest configuration and an operational configuration in which the side wall 15 is at least partially preloaded by switching said inflatable frame 30 between the first configuration and the second configuration. Preferably, in the operational configuration one or more partition walls 23 of the cavities 20, wherein one or more inflatable chambers 40 are arranged in a second configuration, are pre-loaded.

[0117] Specifically, the side wall 15 at least partially axially and / or radially preloaded in the operational configuration is configured to at least partially compensate for compressive and / or shear stresses generated on the enclosure 10.

[0118] In accordance with the preferred embodiment, the enclosure 10 maintains substantially the same predefined shape while switching between the rest configuration and the operational configuration. Preferably, the enclosure 10 maintains a substantially equivalent shape while switching between the rest configuration and the operational configuration and vice versa. More preferably, the enclosure 10 is substantially rigid and while switching between the rest configuration and the operational configuration remains in the elastic field thus avoiding plastic deformations.

[0119] It is worth noting that the enclosure 10, switching from rest configuration to operational configuration, has a deformation of less than 10%, preferably less than 1% even more preferably less than 0.2%.

[0120] In accordance with a preferred embodiment, the enclosure 10 has a predefined shape selected from a cylindroid, a one-sheet hyperboloid, a frustum of one-sheet hyperboloid, quadratic cylinders, a cone, a frustum of a cone or a combination of one or more of said geometrical shapes.

[0121] Advantageously, the inflatable frame 30 with the relative inflatable chambers 40 is configured to transmit the relative force to at least partially preload the enclosure 10. Adherence to the inner surface of the enclosure 10 is possible due to the elastic characteristics of the material of the containment wall 50 or the combination between the material of the containment element 60 and the inner walls 70. These materials allow deformation to adapt to the inner shape of the enclosure 10 to at least partially preload the relative side wall 15.

[0122] Advantageously, the inflatable chambers 40 are configured to autonomously support the inner pressure without incurring in structural damage, i.e., the pressurised fluid is safely confined within the chamber, regardless of the presence of the enclosure.

[0123] In accordance with a preferred embodiment, the enclosure 10 is at least partially made of metal material. Preferably, the enclosure 10 is completely made of metal material.

[0124] It is worth noting that metal material may comprise one of metal alloys, ferrous metal alloys, ferrous material, steel or a combination thereof. Specifically, the enclosure 10 is at least partially, preferably totally, made of metal alloys, ferrous metal alloys, ferrous steel material or a combination thereof.

[0125] In accordance with a preferred embodiment, the enclosure 10 is at least partially made of steel, e.g. S1300, S960, S690.

[0126] Preferably, the enclosure 10 is completely made of steel.

[0127] Advantageously, the metal material used makes it possible to more accurately predict the behaviour of the support structure and of the wind blade due to the stronger knowledge of this material, for example, facilitating the structural calculation and the fatigue life of the structure.

[0128] In accordance with a preferred embodiment alternative to the previous one, the enclosure 10 can be at least partially made of composite material, for example, consisting of glass fibre, carbon fibres, fabrics, aramid fibres, sandwich materials and epoxy resins and of ferrous material and / or at least partially of steel, for example.

[0129] Thanks to the use of metal material, the support structure 1 can be assembled in the factory and / or directly on the site of use. Thanks to the use of metal material such as selected from ferrous material and / or steel, it is possible to use known processing methodologies, for example, processing and construction methodologies typical of light carpentry or automatic manufacturing lines (for example automotive lines), then moulding, calendering, welding, etc.

[0130] In accordance with a preferred embodiment, the support structure is partitioned in one or more sectors 22 that are consecutive and can be coupled along the longitudinal direction X-X. Specifically, the one or more sectors 22 define the predefined shape of the enclosure 15 and the one or more cavities 20.

[0131] It is worth noting that each sector 22 has a respective first sector base 22a and a second sector base 22b opposite thereto along the extension direction X-X. It is worth noting that in the embodiment in which the enclosure 15 has a single sector 22, the first sector base 22a and the second sector base 22b correspond to the first base 13a and the second base 14a of the enclosure 10. Alternatively, in the embodiment in which the enclosure 15 has several consecutive sectors 22, the second sector base 22b of each sector 22 is coupled with the first sector base 22a of the successive sector 22 along the longitudinal direction X-X from the first base 13a to the second base 14a of the enclosure 15. Preferably, the second sector base 22b and the first sector base 22a of two consecutive sectors coincide. It should be noted that the sectors 22 can be assembled to define the enclosure 15 also on the site of use of the wind farm in order to facilitate transportation.

[0132] Preferably, the partition walls 23 may be distributed along each sector 22 into which the enclosure 15 is divided and / or coincide with the relevant sector bases 22a, 22b.

[0133] Preferably, each sector 22 has a geometrical shape selected from a cylindroid, a one-sheet hyperboloid, a frustum of one-sheet hyperboloid, quadratic cylinders, a cone, a frustum of a cone or a combination of one or more of said geometrical shapes. It is worth noting that geometrically it is known that the cone is a particular case of the one- sheet hyperboloid in which the coefficients of the geometric function of the one-sheet hyperboloid assume specific values known to the person skilled in the art. Preferably, the frustum of a cone or the frustum of one-sheet hyperboloid having a geometric shape is given by the portion of the geometric figure extended between two bases which are spaced apart from each other and tapered in a continuous way between the major base and the minor base. It is also worth noting that each frustum of a cone or frustum of one-sheet hyperboloid, as well as the other geometric shapes with which the sectors can be made, have a relative side wall that follows the geometric course of the geometric shape thereof. Advantageously, the use of frustums of a cone makes it possible to simplify the construction of the support structure.

[0134] Advantageously, the surfaces defining the enclosure 10 can be obtained, for example, by means of suitably cut, calendared and welded flat sheets. The one or more cavities that they define allow, once pressurized, to reduce shape tolerances to a minimum. In addition, minimal pressurization within the one or more cavities allows to stiffen and obtain a desired shape of the enclosure and / or the wing cavity itself, avoiding unwanted deformations due to the weight of the structure and / or the blade itself.

[0135] It is worth noting that the support structure 1 may comprise a pressurisation system configured to maintain a certain pressure within each cavity 20 less than 100 barg, preferably less than 10 barg, more preferably less than 0.45 barg.

[0136] A further object of the present invention is a wind blade 2 of a wind turbine 400. Each wind blade 2 has, as anticipated, an upper surface 8 and a lower surface 9 defining a leading edge 6 and a trailing edge 7. Specifically, the upper surface 8 and the lower surface 9 extend along a longitudinal direction X-X between a rotor end portion 4a associable to the rotor hub 3a and a free end portion 4b opposite thereto and define a wing cavity 11. Specifically, the wind blades 2 with the hub 3a define the rotor 3. It is worth noting that the hub is configured to be mechanically connected to a nacelle rotatably connected to the top of the tower.

[0137] Each wind blade comprises a support structure 1, as previously described, inserted into the wing cavity 11 and associated to the upper surface 8 and the lower surface 9.

Claims

CLAIMS1. Support structure (1) for wind blades (2), each wind blade (2) having an upper surface (8) and a lower surface (9), said support structure (1) comprising:- an enclosure (10) insertable into a wing cavity (11) defined between the upper surface (8) and the lower surface (9), said enclosure (10) extending along a longitudinal direction (X-X) between a first end portion (13) which can be coupled to a rotor hub (3a) for wind blades (2) and an opposite second end portion (14), said enclosure (10) having a side wall (15) connected to the first end portion (13) and the second end portion(14) and configured to be coupled to the upper surface (8) and the lower surface (9);- said enclosure (10) having one or more cavities (20) defined between the side wall(15), the first end portion (13) and the second end portion (14); characterised in that it comprises- an inflatable frame (30) arranged within at least one cavity (20) and configured to switch reversibly between a first configuration and a second configuration in which said inflatable frame (30) at least partially preloads the side wall (15) of the enclosure (10).

2. The support structure (1) according to claim 1, wherein said inflatable frame (30) is configured to axially and / or radially preload the side wall (15) by contact, switching from the first configuration to the second configuration by means of injection and pressurisation of a fluid.

3. The support structure (1) according to claim 1 or 2 wherein:- the enclosure (10) comprises partition walls (23) mutually spaced along the longitudinal direction (X-X) between first and second end portions (13, 14) each cavity (20) being defined between two adjacent partition walls (23) and a portion of the side portion (15a) comprised between the two partition walls (13, 14);- the inflatable frame (30) comprises one or more inflatable chambers (40) configured to occupy at least part of the one or more cavities (20) and to at least partially preload the side wall (15) when switching between the first configuration and the second configuration, each inflatable chamber (40) having an inner volume (41) inflatable by a fluid.

4. The support structure (1) according to claim 3, wherein each inflatable chamber (40) comprises a perimeter wall (50) defining the interior volume (41), each perimeter wall (50) being configured to abut at least partially against one of the side wall (15), one or more partition walls (23), one or more perimeter walls (50) of adjacent inflatable chambers (40) or a combination thereof so as to push against each other to preload at least in part the side wall (15) by switching from the first configuration to the second configuration.

5. The support structure (1) according to claim 4, wherein- the inflatable frame (30) comprises an inflatable chamber (40) in at least one cavity (20);- when switching from the first configuration to the second configuration, the perimeter wall (50) of the inflatable chamber (40) is configured to adhere internally to the side wall (15) and to one or more partition walls (23).

6. The support structure (1) according to claim 3, wherein the inflatable frame (30) comprises one or more containment elements (60) each defining a containment volume (61) configured to contain one or more inflatable chambers (40), each containment element (60) having an outer containment surface (60a) configured to abut at least partially against one of the side wall (15), one or more partition walls (23), one or more adjacent containment elements (60), one or more adjacent inflatable chambers (40) ora combination thereof so as to push against each other when said one or more inflatable chambers switch from the first configuration to the second configuration to at least partially preload the side wall (15) .

7. The support structure (1) according to claim 6, wherein each chamber (40) comprises an inner wall (70) defining the inner volume (41), each inner wall (70) being configured to abut at least partially against one of the one or more containment element (60), one or more side walls (23), one or more inner walls (70) of adjacent inflatable chambers (40), the side wall (15) or a combination thereof so as to push the one or more containment elements (60) against the side wall (15) to at least partially preload it when switching from the first configuration to the second configuration.

8. The support structure (1) according to claim 7, wherein- the inflatable frame (30) comprises a containment element (60) and an inflatable chamber (40) inserted into the containment volume (61) in at least one cavity (20);- when switching from the first configuration to the second configuration, said inner wall (70) of said inflatable chamber (40) is configured to adhere at least partially to one of the containment element (60), one or more partition walls (23), the side wall (15) or a combination thereof, and said containment element (60) is configured to adhere internally to the side wall (15) and one or more partition walls (23).

9. The support structure (1) according to claim 8, wherein:- the inflatable frame (30) comprises a containment element (60) and two or more inflatable chambers (40) inserted into the containment volume (61) in at least one cavity (20);- when switching from the first configuration to the second configuration, eachinner wall (70) is configured to adhere at least partially to one of the containment element (60), one or more adjacent inner walls (70), one or more partition walls (23), the side wall (15) or a combination thereof, and said containment element (60) is configured to adhere internally to the side wall (15) and one or more partition walls (23).

10. The support structure (1) according to any one of claims 3 to 9, wherein the inflatable chambers (40) are arranged adjacent to each other longitudinally along the longitudinal direction (X-X) or the inflatable chambers (40) are arranged adjacent to each other along a transverse direction (Y-Y) transverse to the longitudinal direction (X-X).

11. The support structure (1) according to any one of claims 3 to 9, wherein the inflatable chambers (40) are arranged adjacent to each other longitudinally along the longitudinal direction (X-X) and transversely to the longitudinal direction (X-X).

12. The support structure (1) according to any one of claims 3 to 11, wherein the inflatable chambers (40) are independently inflatable and deflatable .

13. The support structure (1) according to any one of claims 3 to 12, wherein- the inflatable frame (40) comprises one or more inflation devices configured to regulate the inflow and outflow of a fluid within each inflatable chamber (40) to control the preload of the side wall (15) when switching from the first to the second configuration.

14. The support structure (1) according to claim 13, wherein said enclosure (10) comprises mechanical connection means (80) configured to couple the side wall (15)with the upper surface (8) and the lower surface (9) of the wind blade.

15. The support system (1) according to any one of claims 1 to 14, wherein- said inflatable frame (30) is configured to make the enclosure (10) switch between a rest configuration and an operational configuration in which the side wall (15) is at least partially preloaded by switching said inflatable frame between the first configuration and the second configuration.

16. The support structure (1) according to claim 16, wherein said side wall (15) at least partially axially and / or radially pre-loaded in the operational configuration is configured to at least partially compensate for compressive and / or shear stresses generated on the enclosure (10).

17. The support structure (1) according to any one of claims 14 to 16, said enclosure (10) has a predefined shape and is configured to maintain substantially the same predefined shape switching between the rest configuration and the operational configuration, having a deformation of less than 10%, preferably less than 1% even more preferably less than 0.2%18. The support structure (1) according to claim 17, wherein the enclosure (10) has a predefined shape chosen from a cylindroid, a single-pitch hyperboloid, a truncated hyperboloid, quadratic cylinders, a cone, a truncated cone, or a combination of one or more of said geometric shapes.

19. The support structure (1) according to any one of claims 1 to 18, wherein the enclosure (10) is at least partly made of metallic material comprising one of metal alloy, ferrous metal alloy, ferrous material, steel or a combination thereof, preferably theenclosure (10) is made entirely of metallic material.

20. The support structure (1) according to any one of claims 1 to 19, wherein , each cavity (20) has an internal pressure of less than 100 barg preferably less than 10 barg, more preferably less than 0.45 barg.

21. Wind blade (2) for wind turbines (400) comprising:- an upper surface (8) and a lower surface (9) defining a leading edge (6) and a trailing edge (7), said upper surface (8) and said lower surface (9) extending along an extension direction (X-X) between a rotor end portion (4a) associated with the rotor hub (3a) and an opposite free end portion (4b) and defining a wing cavity (11);- a support structure (1) according to any one of claims 1 to 20, inserted into the wing cavity (11) and associated with the upper surface (8) and the lower surface (9).

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