Barrel and bolt connecting device, wind turbine and connecting method

Abstract

The invention relates to an improved barrel and bolt connecting device, the purpose of which is to reduce the bending moment generated in the T-bolt connection by means of both components, with the structure of the two parts combining to enhance the connection under high bending loading and, in this way, the durability and performance of the connection are increased.

Description

[0001] BARREL AND BOLT JOINING DEVICE, WIND TURBINE AND JOINING PROCEDURE

[0002] DESCRIPTION

[0003] TECHNICAL SECTOR

[0004] The invention falls within the sector of wind turbine components, in particular the joints or fixings at the root of the blade to the hub (with or without pitch change bearing) of a wind turbine, which use the T-Bolt joint that is regularly made with the combination of a bolt and a barrel, and in which the transmission of motion and torque to the generator shaft occurs through said device.

[0005] The present invention consists of an improved barrel and bolt joining device, which aims to reduce the Fleeter moment that occurs in the T-Bolt joint by means of both components with a structure of both pieces that in combination favor the joint with the high bending stress they withstand and thereby increase their lifespan and performance.

[0006] BACKGROUND OF THE INVENTION

[0007] Currently, we find that the rotor of a wind turbine typically consists of three blades (airfoil blades), made of composite material, rigidly attached or through bearings to a steel or cast iron hub, which is responsible for transmitting the movement and torque to the generator shaft.

[0008] It is vitally important that the connection between the blade and the hub is made properly and efficiently, as this will determine the correct operation of the wind turbine and the integrity of the blades themselves, as well as the durability of the assembly and its maximum performance. Consequently, one of the essential requirements for this connection is to withstand the loads acting on the blade and transmitting them to the hub as efficiently as possible.

[0009] As the wind turbine industry has developed, various solutions for blade-hub connections have been designed. Blades are manufactured from composite materials such as fiberglass in a polymer matrix (polyester or epoxy). It is well known that one of the critical aspects of structures made from such composite materials is the design of the connections, whether between different composite elements or between composite and metal parts. Especially critical in the field of wind turbines is the anchoring system for each blade to the turbine hub. This connection must meet, among other requirements, high reliability, safety, and a long service life, all while being simple to manufacture and assemble. One of the most successful solutions for this connection is the one that has been widely used: the T-bolt connection.This connection involves placing a series of metal cylinders or bolts perpendicular to the laminate near the blade root edge. These bolts have a threaded hole perpendicular to their axis in their center and act as nuts. These nuts, in combination with threaded bolts inserted into the laminate parallel to the blade axis, create the connection. These bolts are subjected to high prestress and are responsible for transmitting the blade loads to the hub.

[0010] This solution and use of a bolt and pin combination has been employed in numerous inventions. For example, patent WO01 / 42647 described this type of connection as early as 2001. However, over time it has been observed that in these connections using bolts and pins to join the roots of certain blades to the hub, the bolts are breaking due to the high bending stress they endure. Consequently, solutions or alternatives to this connection are being sought. For instance, variations such as those in patent US2019 / 0264650 combine two bolts with a pin that has two parallel threads instead of one. The use of a U-shaped bolt has also been observed in patent ES2875018.

[0011] The object of the present invention is an improved barrel and bolt joining device, which solves the problem of breakage due to the bending stress it suffers when transmitting the load, thereby obtaining a longer lifespan and better performance of the blade-to-rotor hub joining of the wind turbine.

[0012] EXPLANATION OF THE INVENTION

[0013] The present invention is an improved barrel and bolt connection device for the blade, by its root, to the hub (with or without pitch change bearing) of the rotor of a wind turbine, in which said connection is constituted by a threaded bolt, which will be inserted into a barrel which, in turn, is made up of two pieces, one being inserted or housed inside the other, but maintaining between them a clearance that allows some movement in order to reduce the Fleeter moment that the barrel transmits to the bolt.

[0014] The barrel consists of two pieces, one acts as a nut and the other as a receiver.

[0015] The nut has the thread in its central inner part where it will receive the threaded bolt, and is arranged as follows: - On its outer face, it is curved with the same arc continued by the wall of the receiving piece that gives rise to the barrel itself or any other shape that does not extend beyond the perimeter of the barrel; - The inner face, being hemispherical, is also curved, with a convex curvature that contacts the inner conical surface of the receiving piece; - On its side walls, it will have a shape that, on the one hand, allows movement due to the clearance with the receiving piece, and on the other hand, prevents it from rotating so that the bolt can be threaded onto it without any other support than the fit provided by the housing of the receiving piece.

[0016] The receiving piece, which is basically cylindrical, has the following features: - A central through-hole, perpendicular to its axis, through which the bolt will be inserted. The depth of this hole will not exceed the radius of the receiving piece; - On the other side, a larger, opposite-facing hole to receive the nut onto which the bolt will be screwed. The depth of this hole will be as deep as the hole that receives the bolt; - At the point where both holes for the bolt and the nut meet, a concave circular chamfer will be machined around its entire inner perimeter to receive the convex, curved inner face of the nut.

[0017] Once the connecting device of the invention is assembled, combining the bolt and barrel components (the barrel consisting of two parts: a nut and a receiver), the slight Fleeter movement that occurs at the joint is neutralized by the clearance provided by the nut inside the barrel with its receiver. This allows the load to be transmitted from the blade to the rotor hub of the wind turbine much more effectively, resulting in greater durability and improved performance of the connection.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following drawings explain the different parts and arrangements of the elements that make up the improved barrel and pin coupling device of the present invention. These drawings complement the descriptive text, illustrating the preferred, but in no way limiting, example of the invention.

[0020] Figure 1 shows a schematic of a three-bladed wind turbine consisting of a tower (1) which, at its top, mounts a nacelle (2), coupled to this nacelle (2) is mounted a rotor (3), which serves as a structural base to mount the wind blades (4) on the hubs (5).

[0021] Figure 2 shows a front view of the joint (8) of the blade (4) with the bushing (5) on the rotor (3), with the holes (6) perpendicular to the laminate near the root edge (7).

[0022] Figure 3 shows a view of a conventional joint with a T-Bolt between a blade (4) having a laminate (10), which by its root (7) is joined to the bushing (5) through the bolt (11) and a pin (9).

[0023] Figure 4 is a cross-section view of a conventional joint showing only a bolt (9) with the screw (11) threaded onto it.

[0024] Figure 5 is a view of the nut (12) in which you can see the central hole (13) which has the thread (14), the curved side wall (16), the flat side wall (17), the curved outer face (24) and the inner semi-spherical face (15) which is convex curved.

[0025] Figure 6 shows a view of the receiving piece (18) where the through hole (19) for the bolt (11) and the recess (20) for the nut (12) can be seen. The concave, circular chamfer (21) between the through hole (19) and the recess (20) is also visible on the inside. Figure 7.- It is a cross-section view of the assembly of the joint with the improved barrel (22) and bolt (11) joining device of the invention, representing the bolt (11) that is inserted into the receiving piece (18) through the through hole (19) to be joined to the nut (12), by the thread (14) and how the nut (12) is inserted into the receiving piece (18) through the housing hole (20) and supported on the chamfer (21), representing in turn the clearance (23, 23') that occurs both between the receiving piece (18) and the nut (12) on one side and the receiving piece (18) and the bolt (11) on the other, namely, a first clearance (23) between the receiving piece (18) and the nut (12), and a second clearance (23') between the receiving piece (18) and the bolt (11).

[0026] Figure 8.- Is a view of the assembly of the improved barrel (22) and bolt (11) joining device of the invention, in which the barrel (22) is observed, which is made up of the two pieces, the nut (12) and the receiving piece (18), in which the nut (12) has the bolt (11) threaded through the central hole (13), all with the first clearance (23) and the second clearance (23') (not shown).

[0027] Figure 9 shows a view of the nut (12), opposite to the view in Figure 5, in which you can see the inner convex curved face (15) which is semi-spherical, the curved side wall (16), the flat side wall (17) and the through hole (19).

[0028] Figure 10 shows another embodiment of the nut (12) in which the central hole (13) is not through the curved lateral outer face (24) of the nut (12).

[0029] The following is a list of the various elements represented in the figures that make up the invention.

[0030] (1) Tower.

[0031] (2) Gondola. (3) Rotor.

[0032] (4) Wind blade.

[0033] (5) Bushing.

[0034] (6) Holes.

[0035] (7) Root of the shovel (4).

[0036] (8) Union between the Blade (4) and the Bushing (5).

[0037] (9) Bolt.

[0038] (10) Internal lamination of the blade (4)

[0039] (11) Threaded bolt.

[0040] (12) Nut.

[0041] (13) Center hole of the nut (12).

[0042] (14) Thread that carries the central hole (13) of the nut (12).

[0043] (15) Inner curved convex semi-spherical face of the nut (12).

[0044] (16) Curved side outer wall of the nut (12).

[0045] (17) Straight outer side wall of the nut (12).

[0046] (18) Receiving piece or support of the barrel (22).

[0047] (19) Through hole of the receiving piece (18).

[0048] (20) Receiving piece housing hole (18).

[0049] (21) Concave circular chamfer.

[0050] (22) Barrel consisting of the receiving piece (18) and the nut (12).

[0051] (23) First clearance between the receiving piece (18) and the nut (12).

[0052] (23') Second clearance between the receiving piece (18) and the bolt (11).

[0053] (24) Curved outer face of the nut (12).

[0054] PREFERRED EMBODIMENT OF THE INVENTION

[0055] In view of the above, the present invention relates to an improved barrel and bolt joining device, of the wind turbine blade (4), by its root (7) to the hub (5) of the rotor (3) of a nacelle (2) of the tower (1) of a wind turbine, joining (8) constituted by the combination of a threaded bolt (11) that is inserted into a barrel (22), which in turn is made up of two pieces, one of which is a nut (12) that is housed in the other receiving piece (18).

[0056] Preferably, the nut (12) is arranged so that its outer face (24) has the same curvature as the outer cylindrical receiving piece (18). Its inner hemispherical face (15) has a convex curvature to seat against the conical inner face of the supporting piece (18). Furthermore, preferably, the nut (12) has two parallel, flat outer lateral walls (17) and two opposing curved outer lateral walls (18), such that these shapes stabilize the nut (12) for threading the bolt (11) once the nut is inserted into the housing hole (20) in the receiving piece (18) designed to accommodate the nut (12).

[0057] In a similarly preferred embodiment, the support piece (18) is arranged so that it has a central through hole (19) perpendicular to its axis through which it will receive the bolt (11). It also has another housing hole (20) machined in the opposite direction from the outer face (24), extending to the same depth, diameter, and diameter until it meets the through hole (19), which houses the nut (12). For this preferred embodiment, the housing hole (20) has an inner wall that corresponds to the flat (17) and curved (16) side walls of the nut (12). At the intersection of the through hole (19) and the housing hole (20), along its entire inner perimeter, it has a circular chamfer or concave conical surface (21) on which the nut (12) rests with its convex inner hemispherical face (15).

[0058] The parts forming the barrel (22), once assembled with the bolt (11), will have a first clearance (23) between the side walls of the nut (12) and the housing hole (20), and a second clearance (23') between the through hole (19) and the bolt (11). This, combined with the seating of the convex inner hemispherical wall (15) of the nut (12) and the concave chamfer (21) inside the receiving piece (18), allows these clearances to neutralize the slight Fleeter movement that occurs at the joint (8) due to the continuous movement of the blade (4) and the transmission of the load through the barrel (22) and the bolt (11). This arrangement of the joint (8) by barrel (22) and bolt (11), which is the subject of the present invention, provides greater durability and improved performance.

Claims

CLAIMS 1.- Device for joining a wind turbine blade (4), by its root (7), to the hub (5) of the rotor (3) of a nacelle (2) of the tower (1) of a wind turbine comprising a threaded bolt (11) and a barrel (22); characterized in that the barrel (22) comprises: - a nut (12); and - a receiving piece (18) which in turn comprises a through hole (19); wherein the nut (12) is configured, in use, to be housed in the receiving piece (18) and the through hole (19) is configured to allow passage of the threaded bolt (11) which in turn is configured to be threaded onto the nut (12); wherein a first clearance (23) is established between the nut (12) and the receiving piece (18). 2.- Joining device according to claim 1, characterized in that a second clearance (23') is established between the threaded bolt (11) and the through hole (19) of the receiving piece (18). 3.- Joining device according to any of the preceding claims, characterized in that the nut (12) comprises a central hole (13) where a thread (14) is arranged. 4.- Joining device according to any of the preceding claims, characterized in that the nut (12) comprises a convex circular wall (15) configured to rest on a concave circular chamfer (21) arranged inside the receiving piece (18). 5.- Joining device according to claim 4, because the convex circular wall (15) of the nut (12) is hemispherical. 6.- Joining device according to any of the preceding claims, characterized in that the nut (12) comprises side walls (16, 17) configured to prevent rotation inside the receiving piece (18) once housed in the receiving piece (18). 7.- Joining device according to claim 6, characterized in that the nut (12) comprises two flat and parallel outer lateral walls (17), in addition to two other curved outer lateral walls (16) facing each other, wherein the receiving piece (18) comprises a shape configured to accommodate the nut (12). 8.- Joining device according to any of the preceding claims, characterized in that the nut (12) comprises a curved outer face (24) with the same curvature as an outer wall of the receiving piece (18). 9.- Joining device according to any of the preceding claims, characterized in that the barrel (22) comprises a radius, where the through hole (19) of the receiving piece (18) is smaller than the radius of the barrel (22). 10- Joining device according to any of the preceding claims, characterized in that the receiving piece (18) comprises an additional hole (20) configured to accommodate the nut (12) which is larger than the through hole (19). 11.- Joining device according to claim 6, characterized in that the through hole (19) reaches the additional hole (20).

12. A wind turbine comprising at least one wind blade (4) comprising a root (7), a nacelle (2) comprising a rotor (3) which in turn comprises a hub (5), and a tower (1), wherein the root of the at least one wind blade (4) is joined to the hub (5) by means of a joining device of any of the preceding claims, wherein the threaded bolt (11) It is attached to the hub (5) and the barrel (22) is located at the root (7) of the blade (4). 13.- Procedure for joining a wind turbine blade (4), by its root (7), to the hub (5) of the rotor (3) of a nacelle (2) of the tower (1) of a wind turbine comprising the following steps: - a step of inserting a threaded bolt (11) attached to the hub (5) through a through hole (19) of a receiving piece (18) of a barrel (22) disposed in the root (7) of the wind turbine blade (4); - a step of seating a nut (12) of the barrel (22) in the receiving piece (18) establishing a first clearance (23) between the nut (12) and the receiving piece (18); and - a threading stage of the threaded bolt (11) into the nut (12).

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