Perfusion assembly

Abstract

The invention describes an infusion assembly (1) for forming a joint for resin infusion between two hollow elongate preform sections (21, 22), comprising an outer vacuum arrangement comprising an outer vacuum bag (11) adapted to be attached to an outer surface of the preform sections (21, 22); an inner vacuum arrangement comprising an inner vacuum bag (12) adapted to be attached to an inner surface of the preformed section (21, 22); and an overpressure arrangement comprising a source of pressurized air (15) and one or more inflatable bags (14, 141, 142) configured to apply an overpressure (Pover) against the inner vacuum bag (12) during a resin infusion procedure. The invention further describes a method of joining prefabricated sections (21, 22) of a wind turbine rotor blade using such a cast-in-place assembly (1).

Description

TECHNICAL FIELD

[0001] Large components, such as wind turbine rotor blades having a length of 80 m or more, can be difficult to transport due to their length and weight. For example, the rotor blades of today’s wind turbines can be too long for ground transportation to be essentially possible, and such rotor blades can therefore be assembled from two or more pre-fabricated components. Thus, such large components can be manufactured in a modular fashion, e.g. by manufacturing two or more sections separately, and then afterwards assembling the sections at or close to the installation site. Long wind turbine rotor blades can be assembled from two or more pre-fabricated rotor blade sections, each of which can be manufactured using a suitable mould in a VARTM (Vacuum Assisted Resin Transfer Moulding) process. BACKGROUND

[0002] When joining pre-fabricated inner and outer rotor blade sections, it is important to ensure that the mechanical properties of the resulting assembly correspond to the mechanical properties of an equivalent one-piece assembly, i.e. the performance of the modular wind turbine rotor blade should not be worse than that of an equivalent one-piece rotor blade manufactured as a single component.

[0003] The pre-fabricated rotor blade sections can be mechanically joined, e.g. by the arrangement of fasteners extending through bushings formed in the joint region. Such mechanical joints can significantly increase the mass in the joint region. Furthermore, any metallic components of the joint need special consideration in view of lightning protection. It is also known to use glued joints to join the pre-fabricated elements. However, glued joints can have insufficient mechanical strength.

[0004] It can be preferred to use resin infused joints to join two pre-fabricated sections. To this end, the pre-fabricated sections can be manufactured to include complementary joint features which contact when the rotor blade sections are pushed together; alternatively, the pre-fabricated sections can be shaped to fit on either side of a joint insert. During joining of the pre-fabricated elements, the joining surfaces of the pre-fabricated elements form a mould for the lay-up to be infused, i.e. these joining surfaces define an infusion space. The joint is made by arranging a vacuum bag assembly around the interface between the rotor blade sections and performing vacuum assisted resin transfer to infuse resin into the infusion space and through any dry lay-up material, e.g. through the material layers of the joint insert between the two pre-fabricated sections. After curing, the resin bond holds the pre-fabricated rotor blade sections together.

[0005] However, the layup of prefabricated rotor blade segments can include various types of materials, any of which may initially contain some amount of moisture. This also applies to the bonding features at the interface ends of the prefabricated segments. During VARTM of the prefabricated segments, the reduced pressure throughout the layup has the effect of lowering the boiling point of any evaporated retained moisture, thus leaving empty (air-filled) pores in the material. Therefore, the cured prefabricated component may exhibit some degree of porosity within its laminated structure. This unavoidable porosity in the prefabricated laminate does not substantially affect the structural performance of the prefabricated segment, but it presents a problem when forming joints between two or more such prefabricated segments in subsequent VARTM processes.

[0006] This is because the bonding surfaces of the precast sections now exhibit a porous surface feature, resulting in small openings at the bonding surfaces. The problematic feature is the tunnel-like holes extending from the bonding surfaces into the body of the precast sections. Blind tunnel holes may terminate some distance into the laminate, while end-open tunnel holes may terminate some distance beyond the joint. Therefore, air can enter the filling space through these tunnel holes, making it difficult or even impossible to establish and maintain the required low vacuum pressure for subsequent VARTM processes, where the precast sections will form the joint portion.

[0007] Therefore, the object of the present invention is to provide an improved method for connecting prefabricated rotor blade sections.

[0008] This objective is achieved by the claimed injection assembly and the claimed method of connecting two hollow, slender prefabricated sections. Summary of the Invention

[0009] According to the present invention, the infusion assembly can be used during the formation of a resin-infused joint between two hollow, elongated prefabricated sections (e.g., an inner prefabricated section and an outer prefabricated section of a wind turbine rotor blade). The infusion assembly of the present invention includes an external vacuum arrangement having an external vacuum bag attached to the outer surface of the prefabricated section on either side of the intended joint; an internal vacuum arrangement having an internal vacuum bag attached to the inner surface of the prefabricated section on either side of the intended joint; and an overpressure arrangement including a pressurized air source and one or more inflatable bags arranged to apply a uniformly distributed overpressure against the internal vacuum bag when the inflatable bags(s) are filled to a predetermined overpressure.

[0010] The advantage of the infusion assembly of the present invention is that when inflated above ambient pressure, the inflatable bag applies a gentle force against the internal vacuum bag. As the resin is being infused into the infusion space under vacuum, the slight overpressure is sufficient to ensure that the resin is pushed into any pores on the bonding surface, and in particular, that the resin is pushed into any tunnel holes at least some distance, thereby sealing the holes and effectively preventing air from entering the infusion space from the outside.

[0011] Therefore, the infusion assembly of the present invention eliminates the problems associated with air leakage through tunnel-like pores during the infusion process, as described in the introduction. Instead, using the method of the present invention, any such pores become entirely advantageous because they make a valuable contribution to the mechanical strength of the joint when filled with resin.

[0012] According to the present invention, a method for joining two hollow, elongated prefabricated sections includes the following steps: aligning the prefabricated sections to contact at a joint; and providing an embodiment of the infusion assembly of the present invention. The method includes the following subsequent steps: attaching an outer vacuum bag to the outer surface of the prefabricated section on either side of the intended joint; attaching an inner vacuum bag to the inner surface of the prefabricated section on either side of the intended joint; establishing a vacuum in the infusion space defined by the vacuum bag; and deploying an overpressure arrangement to apply overpressure against the inner vacuum bag while infusing resin into the infusion space.

[0013] Particularly advantageous embodiments and features of the invention are given by the dependent claims, as disclosed in the description below. Features of different claim types may be suitably combined to give further embodiments not described herein.

[0014] Although the internal vacuum arrangement comprises multiple sheets of thin polymer material secured along their long edges to the inner surface of the mating area with butyl seals, these sheets are generally referred to as “bags”. In the following text, the sheets of the internal vacuum arrangement may be referred to as bags, layers, or foils.

[0015] Instead of attempting to address air leakage from the tunnel bore into the filling space while establishing and maintaining a vacuum before and during resin filling, the method of the present invention provides a way to perform resin filling unaffected by such air leakage by applying overpressure against a sheet arranged in an internal vacuum. Therefore, the method of the present invention may hereinafter be referred to as the "Vacuum Assisted and Pressurized Resin Transfer Molding" (VAPRTM) process.

[0016] In the following text, it may be assumed that the prefabricated sections are sections of a modular wind turbine rotor blade. In the case of a two-piece modular rotor blade, these include an inner prefabricated section having a root tip, a transition region, and a portion of the airfoil, while the outer prefabricated section includes the remainder of the airfoil and terminates at the tip. Of course, a modular wind turbine rotor blade can be assembled from three or more such prefabricated sections, and any two adjacent sections can be joined using the infusion assembly of the present invention.

[0017] The external vacuum arrangement preferably includes an external fastener or "mold sleeve" that extends around the prefabricated sections and surrounds the external vacuum bag (i.e., the fastener is wider than the external vacuum bag), and is configured to hold the prefabricated sections in their intended configuration until the joint is formed. The external fastener is constructed to resist pressure applied to the prefabricated sections from the inside, i.e., pressure exerted by the inflatable pressure bag when it is filled with air at a pressure higher than ambient or atmospheric pressure, so that the prefabricated sections retain their shape throughout the VARTM process. Thus, the external fastener can be considered as an external mold for the joint used for resin infusion, while the inflatable pressure bag can be considered as an internal mold for the joint used for resin infusion.

[0018] In addition to the internal vacuum bag, the internal vacuum arrangement may include multiple layers, as well as one or more resin inlet ports, one or more outlet ports, and one or more overflow suction ports. For example, the internal vacuum arrangement may include an internal vacuum bag, one or more safety bags with overflow suction devices, passive bags without overflow suction devices, etc. Any vacuum bag, safety bag, passive bag, etc., is securely attached to the inner surface of the prefabricated section by a suitable sealant, such as a butyl seal. In the following, without limiting the invention in any way, the seal between the bag and the surface of the prefabricated section may be assumed to be a butyl seal, although other devices forming such a seal may exist as known to those skilled in the art.

[0019] The overpressure arrangement can include any number of pressure bags, and the appropriate number can be determined by the geometry of the prefabricated section. For example, a rotor blade prefabricated section can include a shear web extending in the spanwise direction. Therefore, in a preferred embodiment of the invention, the overpressure arrangement includes a first inflatable bag for placement on one side of the shear web extending through the prefabricated section and a second inflatable bag for placement on the other side of the shear web. Since the inflatable bags apply pressure to the internal vacuum assembly, the terms "inflatable bag" and "pressure bag" can be used interchangeably herein.

[0020] The pressure bag can be any suitable inflatable component, such as a balloon, bladder, hose, etc. In a particularly preferred embodiment of the invention, the pressure bag is made from a flat tube of a certain length. The flat tube can be rolled up to a desired width and can be made of polypropylene, polyamide, polyethylene, or any other suitable material or combination of materials. The length of the cut sections is chosen such that the inflatable pressure bag preferably extends beyond the edge of the widest bag of the internal vacuum arrangement with a large margin. For example, for a 100m rotor blade, the pressure bag can be formed from a flat tube 630cm wide; the widest bag of the internal vacuum arrangement can have a spanwise extension of 12m, such that the flat tube is preferably cut to a length of 20m or longer to include sufficient length to form a seal at each end, thereby forming a closed inflatable bag.

[0021] During the consolidation and curing of the joint, it can be advantageous to provide physical support to the insert and the internal vacuum arrangement. This can be accomplished by providing one or more shafts shaped to match the interior of the rotor blades in the joint region. Thus, in another preferred embodiment of the invention, any such shaft is arranged inside the inflatable pouch of the infusion assembly. If the shear web extends through the joint region, the infusion assembly can deploy two shafts, with the leading-edge shaft arranged in one pressure pouch to be positioned on one side of the shear web, and the trailing-edge shaft arranged in another pressure pouch to be positioned on the other side of the shear web.

[0022] The method of the present invention preferably includes a preparatory step of forming an airtight seal at each end of the cut length of the flat tube. The airtight seal can be formed in any suitable manner, as long as it prevents air from escaping when the bag is inflated. In a preferred embodiment of the invention, the seal is formed as a cold-shrink seal. For example, at one end of the tube, the outer edge is bundled, and the bundle is pushed into the cold-shrink tube. Then, according to the manufacturer's instructions, contraction is performed, for example, by pulling a very stiff plastic auger from inside the pre-tensioned tube, thereby allowing the rubber shrink tube to retract until the bundle is airtight.

[0023] Preferably, the airtight seal at the rear end or "outer" end of the inflatable bag is formed facing inwards, meaning the airtight seal can be formed from inside the bag, since it is typically only possible to access the outer end of the arrangement from the inner end of the rotor blade assembly. This allows a technician to form the seal after the flat-lay fitting is placed inside the prefabricated assembly.

[0024] An airtight seal can be formed around the hoses, such as an air inlet hose and / or an overflow suction hose. An air inlet hose is required at the front end or "inside" end of the inflatable bag, while the overflow suction hose can pass through the seals at both ends, allowing the overflow suction hose to extend from the interior of the outer prefabricated section through the bag to the interior of the inner prefabricated section. A pressurized air source is connected to the air inlet hose to inflate the pressure bag.

[0025] The material used to make the pressure bag can exhibit a degree of elasticity, such that overpressure can only be achieved by inflating the bag to its expansion limit. In the infusion assembly of the present invention, overpressure is desired once the pressure bag is inflated to fill the space inside the mating region. Therefore, in one approach, the expansion limit of the inflatable bag (determined by its material composition and its initial dimensions) is adapted to the volume to be filled in the mating region. This can be achieved by using a bag made of a very thick material, possibly also made of reinforcing material.

[0026] In a preferred embodiment of the invention, any further expansion of the pressure bag (after inflation to fill the space in the joint area) is prevented by a suitable expansion containment device, thereby allowing for greater freedom in selecting the initial size of the pressure bag. The expansion containment device can be a mesh sleeve, industrial mesh, etc., closed at both ends to limit the longitudinal (i.e., spanwise) expansion of the inflatable bag. For example, the mesh sleeve is placed around a flat tube before forming an airtight seal at each end to complete the inflatable bag. The length of the mesh sleeve is chosen to limit the spanwise expansion of the pressure bag, thus preventing over-inflation of the elastic material of the pressure bag. For this purpose, the mesh sleeve can be closed at both ends in any suitable manner.

[0027] An exemplary sequence of steps may be as follows: Push two prefabricated rotor blade segments together on either side of the engagement insert; attach an external vacuum bag to the outer surface of either side of the engagement; place an external fastener or external mold housing in place to hold the prefabricated segments and engagement insert in this configuration; attach an internal vacuum bag and any additional (multiple) safety bags to the inner surface of either side of the engagement; cut the flat tube length from the roll; place the shaft inside the cut length; place a mesh sleeve around the cut length; place these components on either side of the shear web in the engagement area; arrange the hoses as desired; form an airtight seal at each end of each inflatable bag, and tighten the open end of the mesh sleeve to define the spanwise length of the inflatable pressure bag. The infusion assembly is now ready to assist the VARTM procedure. This can be performed as follows: a vacuum is established in the filling space defined by internal and external vacuum bags; resin is filled into the filling space through one or more resin inlet ports; a pressure bag is inflated to a slight overpressure (e.g., 100 mbar above ambient pressure) to apply pressure against the internal vacuum bag during the resin filling step and force the resin to fill any tunnel holes in the precast section; resin overflow is discharged through one or more overflow suction hoses.

[0028] Arranging the overflow suction hose through the interior of the pressure bag (rather than placing it between the pressure bag and the internal vacuum assembly) ensures that pressure is applied evenly by the pressure bag against the internal vacuum assembly, and also ensures that the hose will not leave an imprint along the inner surface of the cured joint. If the overflow suction hose can be placed without leaving an imprint in the cured joint, the overflow suction hose can be arranged to be placed along the vertical plane of the shear web before inflating the pressure bag.

[0029] After the resin is uniformly poured through the filling space, it cures in a subsequent curing step. This can be aided by applying heat. For example, external fasteners may include heating elements to heat the filling space from the outside. However, most of the resin-filled material is directed toward the interior of the rotor blades. Therefore, in another preferred embodiment of the invention, the internal vacuum arrangement and / or overpressure arrangement include heating devices to heat the filling space from the interior of the rotor blades. For example, any bag in the internal vacuum arrangement may be manufactured to include thin heating elements or wires that can be connected to a voltage source. Alternatively or additionally, the overpressure arrangement may be configured to heat the air inside the inflated pressure bag. For example, the overpressure arrangement may utilize a blower and an electric heater to enhance the pressurized air source, the blower and electric heater being arranged such that once the pressure bag has been inflated to press against the internal vacuum bag to aid the consolidation of the composite layers in the joint, the heated air can circulate in the inflated pressure bag to aid the curing stage by heating the joint area from the interior of the rotor blades. Attached Figure Description

[0030] Other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. However, it should be understood that the drawings are for illustrative purposes only and are not intended to be limiting of the invention.

[0031] Figure 1 An exploded view of a modular wind turbine rotor blade is shown; Figure 2 The cross-section at the interface between prefabricated sections of a modular wind turbine rotor blade is shown. Figure 3 shows a cross-section through the joint between the prefabricated rotor blade sections; Figure 4 An embodiment of the infusion assembly of the present invention is shown in cross-section; Figure 5 The effects of the infusion assembly of the present invention are demonstrated; Figures 6-10 The formation of an inflatable bag is shown in an embodiment of the infusion assembly of the present invention; Figure 11 Elements of the infusion assembly of the present invention are shown inside a prefabricated section; Figure 12 The solidified joint between two prefabricated rotor blade sections is shown.

[0032] Throughout the drawing, similar reference numerals refer to similar objects. The objects in the drawing do not necessarily need to be drawn to scale. Detailed Implementation

[0033] Figure 1 An exploded view of a modular wind turbine rotor blade 2 is shown. Here, the modular rotor blade includes a prefabricated inner section 21 and a prefabricated outer section 22, as well as an insert 23, which is attached to the prefabricated sections 21 and 22 by resin injection to form a joint between the two prefabricated sections.

[0034] Figure 2 The modular wind turbine rotor blades (e.g., before steps 21 and 22 of the joining sections are shown) are illustrated. Figure 1 The cross-section at the interface between rotor blade segments 21 and 22 of rotor blade 2). Here, the "open end" of each segment 21 and 22 is tapered. The outer end of the insert 23 is also tapered to match the shape of the tapered open ends of the prefabricated segments 21 and 22. The insert 23 comprises a layer of dried layup material.

[0035] Figure 3 illustrates the passage through some stages during the VARTM procedure in the prior art method for joining rotor blade sections 21 and 22. Figure 2The figure shows a cross-section of the joint. The outer vacuum bag 31 of the infusion assembly is tapered to the outer surfaces of sections 21, 22 by means of a sealant (such as butyl tape 4). The figure also shows an inner vacuum bag 32 tapered to the inner surfaces of rotor blade sections 21, 22. The inner vacuum bag 32 can be positioned around a support structure (such as a shaft). In the first step of a conventional VARTM procedure, a negative pressure is established in the infusion space defined by the vacuum bags 31, 32 and their butyl seals 4, and resin is infused through the material layer of the insert 23. As explained above, problems arise if the lamination of the preform is not diffusion-sealed due to tunnel holes 21P, 22P extending from the joint surfaces to the outside. Two exemplary holes are shown, but typically many such holes can exist, extending between an opening at the joint surfaces 210, 220 and another opening on the outside of the bag-like joint area (as defined by the butyl seal 4). These holes can be very small, even microscopic, and exemplary tunnel holes are shown in great exaggerated form in the accompanying drawings. As indicated by the arrows, these tunnel holes allow air to escape into the filling space. This continuous inward leakage of air makes it difficult, or even impossible, to achieve and maintain the required low pressure throughout the resin filling process. This significantly degrades the quality of the resin filling process, and the mechanical properties of the joints may be compromised. However, as explained above, it is critical for wind turbine rotor blades to withstand very high loads during operation, and the joints between rotor blade sections must reliably meet these requirements. Any defects in the resin bonding between rotor blade sections can lead to serious or even catastrophic damage during the life of the rotor blade.

[0036] This invention overcomes these problems by ensuring that the vacuum bag seal is not damaged by residual air during the resin infusion stage, as explained in the accompanying drawings below: Figure 4 A plan view of an embodiment of the infusion assembly of the present invention is shown in cross-section. This figure illustrates the following as described above. Figure 1 The rotor blade sections 21, 22 and insert 23 are described in the text.

[0037] In this exemplary embodiment, the outer end of insert 23 is tapered to match the shape of the tapered open ends of segments 21, 22 as described above; however, it should be understood that the complementary surfaces of these portions 21, 22, 23 may have any suitable shape. Insert 23 comprises a layer of dried layup material as explained above. During the VAPR™ process of this invention, insert 23 is infused with resin to bond all portions 21, 22, 23 together. The shapes of these portions 21, 22, 23 and the material composition of the dried layup 23 are selected based on the desired mechanical properties at the formed joint. While the rotor blade assembly may be held in any suitable orientation during resin infusion, it can be assumed below that the rotor blades are held such that their chord plane is substantially horizontal. Shear web 24 extends substantially vertically between the suction and pressure sides of the rotor blade assembly.

[0038] The figure also shows an external fastener 10, which is implemented, for example, as a rigid sleeve extending around the joint area of ​​the assembled rotor blades. This external fastener 10 serves to hold the two prefabricated sections 21, 22 together until the joint cures. An external vacuum bag 11 is attached to the outer surface, for example, by means of one or more butyl seals 4, as shown here. Alternatively, the vacuum bag 11 can be secured by means of an internal cavity between one or more flexible rubber profiles to seal against environmental pressure.

[0039] Inside the rotor blades, an inner vacuum bag 12 is attached to the inner surface, for example, by means of a butyl seal 4. As those skilled in the art will know, during the VARTM process, a vacuum pump draws air from the cavity defined by the inner vacuum bag 11 and the outer vacuum bag 12 to establish a vacuum, and resin is infused through the resin inlet port. For clarity, these components (vacuum pump, resin supply, inlet and outlet ports, etc.) are not shown in the figures.

[0040] Instead of relying on butyl seals and ambient pressure to maintain the vacuum between the inner vacuum bag 11 and the outer vacuum bag 12 during resin infusion, the method of the present invention establishes a slight overpressure P against the inner vacuum bag 12. over In this exemplary embodiment, the infusion assembly 1 of the present invention deploys a pair of pressure bags 141, 142, one of which extends longitudinally through the interior of the rotor blade on either side of the shear web 24. The first pressure bag 141 is arranged between the leading edge LE and the web 24, and the second pressure bag 142 is arranged between the web 24 and the trailing edge TE. In this exemplary embodiment, the pressure bags 141, 142 are formed from flat bags of a given length, cut to a certain size, and then closed at each end to form seals 143, 144. Although not shown in the figures, a support shaft may be arranged inside each pressure bag 141, 142.

[0041] In preparation for the resin infusion step, pressure bags 141 and 142 are inflated to a slight overpressure, for example, 50-650 mbar above ambient pressure. Inflating pressure bags 141 and 142 to the desired overpressure can be done after the step of establishing a vacuum or negative pressure between the inner vacuum bag 11 and the outer vacuum bag 12 and before the resin infusion step begins.

[0042] The outer vacuum bag 11 is held in place by the outer fastener 10, and the inflation pressure bags 141 and 142 ensure that the inner vacuum bag 12 is also held in place. A slight overpressure acting on both sides of each butyl seal 4 ensures that the seal 4 is not damaged.

[0043] The low pressure and elevated temperature within the infusion space during VARTM, combined with the higher pressure of the inflatable pressure bag, have the combined effect of forcing air out of any tunnel holes (i.e., in the direction away from the bonding surface), thereby allowing resin to be infused into these spaces. The resin effectively seals these holes. Therefore, the infusion assembly 1 of the present invention eliminates the problems associated with air leakage from the pores in the precast sections 21, 22. Instead, any such pores become entirely advantageous because they make a valuable contribution to the mechanical strength of the joint when filled with resin. The VAPRTM method of the present invention is substantially unaffected by air leakage into the infusion space through the tunnel holes in the precast sections.

[0044] During the VAPR™ process of the present invention described above, there may be an increased possibility of liquid resin overflow. However, this is a relatively minor problem and is far outweighed by the benefits of preventing air intrusion into the filling space and ensuring high-pressure quality at the joints between prefabricated rotor blade sections.

[0045] Even so, it is generally desirable to minimize resin overflow during the VARTM process. With this in mind, the filling assembly 1 of the present invention can be equipped with additional measures. The figure shows a first safety bag 131 attached to the inner surface to completely surround the inner vacuum bag 12. An overflow suction hose 171 or sieving hose can be arranged between layers 12, 131, 132, extending circumferentially around the inner cavity and connecting to an overflow suction pump.

[0046] For additional protection, a second safety bag 132 can be attached to the inner surface to completely surround the first safety bag 131. A passive stop layer 133, i.e., another layer without any suction device, can be arranged to extend beyond the outer edge of the second safety bag 132, thereby surrounding all the preceding layers 132, 131, 12. This passive stop layer 133 effectively separates the pressurized area from the vacuum area.

[0047] This combination of multiple bags 131, 132, 133 (e.g., layers or sheets of thin polymer material) (with active suction between them) serves as a single, completely airtight and thick membrane that ultimately prevents air from diffusing into the filling space through the pores in the prefabricated element.

[0048] Any resin not collected by the overflow suction hose will collect at the lowest point, below pressure bags 141 and 142, and in the space between layers 12, 131, 132, and 133. Additional overflow suction hoses can be provided to drain this resin. A foam labyrinth can be placed to ensure that resin does not escape into the rotor blades.

[0049] Figure 5 The principles of the invention are illustrated in the diagram, which shows an enlarged view of the area near the outer edge of the bags 12, 131, 132, and 133 within the rotor blades. Here, a single pressure bag 14 is shown in its inflated state. For clarity, layers 12, 131, 132, and 133 are shown as being spaced some distance apart; however, it should be understood that the inflated pressure bag 14 is used to press all layers tightly against each other to function as a single, thicker layer. A slight overpressure (e.g., 100 mbar above ambient) in the pressure bag 14 acts on both sides of each butyl seal 4 and ensures that any resin in the filling space will have to "work harder" to break through the butyl seal. The overpressure from the inflated pressure bag 14 is sufficient to hold any components (such as circumferential screening hoses, overflow suction hoses, foam labyrinths, etc.) in place, which can be connected to an external vacuum pump via an overflow container.

[0050] Pressure bags 141 and 142 can be used as follows Figures 6-10 Prepare as shown, starting with a flat roll of tube 14R made of a suitable material, such as bulk polyethylene, polypropylene, polyamide, or any combination thereof. Cut tubes of suitable length from roll 14R as indicated. Figure 7 The following step is illustrated, in which shaft 26 is inserted into the cut length 14C of the tube. Here, shaft 26 has a flat side corresponding to the vertical shear web to be placed in the joining region, and a shaped component that matches the shape of the leading edge in the joining region. Similar assemblies are prepared with shafts shaped to fit on the other side of the shear web to match the trailing edge shape.

[0051] The radial expansion of the pressure bag is limited by the inner surface of the mating area. To protect the pressure bag from over-inflation along its length, a suitable structure, such as a mesh sleeve 18 (e.g., a tubular industrial mesh cut to a specified length), can be placed on the pressure bag 14. Figure 8As indicated in the diagram, a further step is shown in which the mesh sleeve 18 is placed around the bag-shaped shaft prior to the step of inserting the bag-shaped shaft into the engagement area. The mesh sleeve 18 will be used to accommodate the longitudinal expansion of the inflatable pressure bag. The mesh sleeve 18 allows the pressure bag 14 to inflate to the desired overpressure by accommodating the longitudinal expansion of the pressure bag 14 and preventing excessive stretching of the elastic material of the pressure bag 14. The mesh sleeve 18 can be closed at both ends in any suitable manner.

[0052] Once the shaft has been placed in fitting 14C (and the mesh sleeve), these components can be inserted into the mating area. In the preceding steps, the workers have attached the internal vacuum arrangements 12, 131, 132 to the inner surfaces of the prefabricated sections 21, 22 using butyl seals, and have connected the overflow suction hoses to the internal vacuum arrangements 12, 131, 132.

[0053] Once the bag-shaped shaft has been placed in place, pressure bags 141 and 142 are formed. For this purpose, the open ends of the cut pieces 14C are bundled together to form airtight seals 143 and 144 at each end, such as... Figure 9 As indicated herein. Here, a seal 143 is formed inside the tube 14C to form the “outer” end of the bag. Another “inner” seal 144 is formed by binding the other open end of the cutter 14C to complete the bag 14. The airtight seals 143, 144 are preferably implemented as cold-shrink seals. One or more hoses may be arranged as needed before forming the airtight seals 143, 144. For example, air inlet hoses 151, 152 are arranged in the inner seal 144 of the pressure bags 141, 142 for subsequent connection to the inflation assembly 15, such as the pressurized air source 15, as indicated herein. A plurality of overflow suction hoses 171 may be arranged to extend through one or both pressure bags 141, 142 via the outer seal 143 and the inner seal 144 for subsequent connection to the vacuum pump 17, as indicated herein. Subsequently, during the VAPRTM process of the present invention, devices such as the inflation assembly 15, the air heater 16, the vacuum pump 17, etc., can be arranged in the accessible inner end inside the rotor blades.

[0054] Figure 11This is a schematic diagram of the arrangement of bags 12, 131, 132 and pressure bags 141, 142 relative to the joints between the rotor blade sections (indicated by dashed lines extending from the inner bag 12, which is arranged around the airfoil shape of the internal vacuum arrangement). This figure only shows the components arranged inside the rotor blades during the VARTM process: for clarity, rotor blade sections 21, 22 and the joining insert 23 are not shown, but it should be understood that the layers 12, 131, 132 of the internal vacuum arrangement are attached to the inner surfaces of rotor blade sections 21, 22 on either side of the joining insert 23. As described above, it can be assumed that the expansion of the inflation pressure bags 141, 142 in the longitudinal direction is limited either by selecting a suitable material for the pressure bags or by placing a mesh sleeve around the pressure bags and securing the ends of the mesh sleeve to limit the maximum length of the inflation pressure bags.

[0055] The figure illustrates: an inner vacuum bag 12, secured to the inner surface of the rotor blade section by butyl seals 4 along each of its side edges; a first safety bag 131, wider than the inner vacuum bag 12, also secured to the inner surface of the rotor blade section by butyl seals 4 along each of its side edges; and a second safety bag 132, wider than the first safety bag 131, also secured to the inner surface of the rotor blade section by butyl seals 4 along each of its side edges. The width of the inner vacuum bag 12 can be assumed to exceed the width of the associated engagement area by a suitable margin; for example, the inner vacuum bag 12 can be significantly wider than the insert 23 shown in the previous figures. The spanwise length of each pressure bag exceeds the spanwise extension of the inner vacuum arrangement.

[0056] The figure also shows an exemplary overflow suction hose 171 that passes through a seal at the outer end of the pressure bag 141 and another seal at the inner end of the pressure bag 141 from the gap between layers 12, 131, 132 to the suction assembly 17.

[0057] The figure also indicates the location of the shear web 24 extending through the interior of the rotor blades in the spanwise direction. This shear web 24 effectively divides the interior space into leading and trailing edge regions. To ensure that the overpressure of the inflation pressure bags 141, 142 is applied uniformly against the internal vacuum arrangement, the two pressure bags 141, 142 are inflated using a common air source 15 via hose arrangements 151, 152, as shown here.

[0058] After the joint has solidified and cured, the pressure bags 141 and 142 are depressurized; devices 15, 16, and 17 are disconnected, the inner seal 144 is opened, the shaft is pulled out from inside the rotor blades, the outer seal 143 is opened, the pressure bags 141 and 142 are removed, and any overflow suction hoses 171 and all layers of the internal vacuum arrangements 12, 132, 132, and 133 are detached from the inner surface of the joint area. At the outside of the rotor blades, the outer fastener 10 and the outer vacuum bag 11 are removed.

[0059] Figure 12 The diagram schematically illustrates the cured joint 28 between two prefabricated rotor blade sections 21, 22 after joining using the infusion assembly and VAPRTM method of the present invention. The cured resin (indicated by the dotted pattern) has filled the infusion spaces, thereby penetrating the layers of the insert 23. Resin has also been pushed into any tunnel holes, such as those indicated by resin-filled holes 21F, 22F in the prefabricated sections (again, these are shown in exaggerated proportions), to fill or at least partially fill these spaces, thus effectively sealing any air leaks. In addition to promoting negative pressure during the VARTM process, these resin-filled holes contribute to the strength of the cured joint 28 and rotor blade 2.

[0060] While the invention has been disclosed by way of preferred embodiments and variations thereof, it will be understood that many additional modifications and variations can be made therein without departing from the scope of the invention. For example, a circular pad or foam sleeve can be placed around the pressure bag to ensure uniform pressure distribution when the pressure bag is inflated. Such a foam sleeve can also reduce the rate of temperature loss during the curing stage. The foam sleeve or pad can be held in place by a structure such as the mesh sleeve described above.

[0061] For clarity, it should be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “including” does not exclude other steps or elements.

Claims

1. A filling assembly (1) for forming a resin filling joint between two hollow, elongated prefabricated sections (21, 22), comprising: - An external vacuum arrangement comprising an external vacuum bag (11) adapted to be attached to the outer surface of the prefabricated sections (21, 22). - An internal vacuum arrangement comprising an internal vacuum bag (12) adapted to be attached to the inner surface of the prefabricated sections (21, 22); and - An overpressure arrangement comprising a pressurized air source (15) and one or more inflatable bags (14, 141, 142), the inflatable bags (14, 141, 142) being configured to apply overpressure (P) against the inner vacuum bag (12) during the resin infusion procedure. over ).

2. The infusion assembly according to the preceding claim, wherein, The overpressure arrangement includes a first inflatable bag (141) for placement on one side of the shear web (24) extending through the prefabricated sections (21, 22) and a second inflatable bag (142) for placement on the other side of the shear web (24).

3. The infusion assembly according to any one of the preceding claims includes an air inlet hose (151, 152) disposed between the pressurized air source (15) and the interior of the inflatable bag (141, 142).

4. The infusion assembly according to any one of the preceding claims, wherein, The length of the inflatable bags (14, 141, 142) exceeds the span of the internal vacuum arrangement (12, 131, 132, 133).

5. The infusion assembly according to any one of the preceding claims, comprising a shaft (26) disposed inside an inflatable bag (14, 141, 142).

6. The infusion assembly according to any one of the preceding claims, comprising a receiving device (18) arranged around the inflatable bag (14, 141, 142) to limit the expansion of the inflatable bag (14, 141, 142) in the spanwise direction.

7. The infusion assembly according to any one of the preceding claims, wherein, The inflatable bags (14, 141, 142) are made of a flat tube of a certain length.

8. The infusion assembly according to the preceding claim, wherein, The inflatable bags (14, 141, 142) are formed by airtight seals (143, 144) at each end of the length of the flat tube.

9. The infusion assembly according to any one of the preceding claims, wherein, The internal vacuum arrangement further includes at least one safety bag (131, 132) arranged to surround the internal vacuum bag (12).

10. A method for connecting prefabricated sections (21, 22) of a wind turbine rotor blade, the method comprising the following steps: - Align the prefabricated sections (21, 22) to make contact at the joint; - Provide an infusion assembly (1) according to any one of claims 1 to 9; And subsequently - Attach the external vacuum bag (11) to the outer surface of the prefabricated sections (21, 22); - Attach the internal vacuum bag (12) to the inner surface of the prefabricated sections (21, 22); - A vacuum is established in the filling space defined by the vacuum bags (11, 12); and - Deploy the overpressure arrangement to apply overpressure (P) against the internal vacuum bag (12). over ),at the same time - The resin is poured into the filling space defined by the vacuum bags (11, 12).

11. The method according to the preceding claim includes a preparation step of forming an inflatable bag (14, 141, 142) from a tube (14C) of a certain length cut from a flat tube roll (14R).

12. The method according to the preceding claim, comprising the step of forming an airtight seal (143) at each end of the cut length (14C).

13. The method according to the preceding claim, wherein, The airtight seal (143) is formed as a cold-shrink seal.

14. The method according to any one of the preceding claims, comprising a preparation step of arranging an overflow suction hose (171) to extend from the interior of one prefabricated section (22) through an inflatable bag (14, 141, 142) to the interior of another prefabricated section (21).

15. A wind turbine rotor blade (2), comprising at least: - A hollow, elongated inner prefabricated section (21) with a bonding surface (210). - A hollow, elongated, prefabricated outer section (22) with a bonding surface (220); and - The joint between the prefabricated sections (21, 22) is formed in a resin infusion process performed by the infusion assembly according to any one of claims 1 to 10; The feature is that the tunnel holes (21F, 22F) at the bonding surfaces (210, 220) of the prefabricated sections (21, 22) are at least partially filled with resin.

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