Patent Description:
Modern wind turbines are commonly used to supply electricity into the electrical grid. Wind turbines of this kind generally comprise a tower and a rotor arranged on the tower. The rotor, which typically comprises a hub and a plurality of blades, is set into rotation under the influence of the wind on the blades. Said rotation generates a torque that is normally transmitted through a rotor shaft to a generator, either directly ("directly driven") or through the use of a gearbox. This way, the generator produces electricity which can be supplied to the electrical grid.

In order to extract more energy from the wind, the size of the rotor diameter is increased by increasing the dimensions of the wind turbine blades. To reduce the overall weight of the wind turbine blades, these may generally comprise composite materials and are often manufactured with resin-infused glass fiber composites. The manufacturing of wind turbine blade shells using composite materials allows them to meet the requirements with respect to size, geometry, and weight. Further, fibers can be aligned with load paths, generating blades with anisotropic mechanical properties and with enhanced mechanical properties. The possibility of fiber alignment allows placing the fibers at the exact position and direction as needed to provide the component with the required stiffness and strength.

The shells of the wind turbine blades carry part of the load and maintain an aerodynamic shape. The main load bearing structures in wind turbine blades are formed by spars. A spar in a wind turbine blade may comprise a spar cap near the suction side of the blade and a spar cap near the pressure side of the blade, and a shear web between the spar caps. The shear web is generally formed like a plate configured to be subjected to shear loads.

Depending on the length, and configuration of the blades, and depending on the design loads, spars with different configurations may be used. In some examples, a blade may include a main web assembly, including a leading edge main web and a trailing edge main web, i.e. two main webs, the former of which is arranged closer to the leading edge, and the latter being arranged closer to the trailing edge of the blade. The main web assembly may extend from a root of a blade to close to a tip of the blade. The blade may further comprise a third shear web which may extend from a root towards about half or about two thirds of the blade, and may also comprise a C-shaped stiffener in an inboard section of the blade near the trailing edge.

During manufacturing, a shell of the blade may be formed, e.g. two half-shells, particularly a downwind shell (for the suction side of the blade) and an upwind shell (for the pressure side of the blade) may be formed. The webs may be positioned in a mold in one half-shell and the other half-shell may be positioned on top, after which the parts are joined.

It is known for the main web assembly to be assembled before positioning in the mold. The main leading edge web, and the trailing edge web are connected to each other through a plurality of staybolts. The staybolts comprise a shaft with threaded portions on each end. A tubular spacer is arranged around the shaft. Between each end of the tubular spacer and the corresponding web a washer may be arranged. At both ends of the shaft, on the outside of the assembly, an additional washer may be arranged, and nuts are mounted on the ends of the shaft. Each of the webs is thus retained between a washer and tube on an inside of the web assembly, and a washer and nut on the outside of the web assembly.

Since the webs may be arranged close to each other (particularly for portions closer to the tip of the blade), it is a complicated manual process to fix the washers, and tubular spacers of the different staybolts in place. Additionally, after the main web assembly has been joined to the blade shells, the staybolts are to be removed, but this means that an operator needs to enter the space inside the main web assembly to remove the washers, and tubular spacers. This is a cumbersome manual process which poses significant safety and health concerns. In practice not all spacers, and washers on an inside of the main web assembly can be removed.

<CIT>, <CIT>, <CIT> show different known examples of a fastener assembly for connecting a first web to a second web.

The present disclosure provides examples of systems and methods that at least partially overcome some of the drawbacks of existing wind turbine blade manufacturing processes, and in particular facilitate assembling and disassembling main web assemblies.

In a first aspect, a fastener assembly for connecting a first web to a second web is disclosed. An inside is defined between the first and second webs, and an inner surface of the first web faces an inner surface of the second web, an outer surface of the first web being arranged on an outside of the first web, and an outer surface of the second web being arranged on an outside of the second web. The fastener assembly comprises a shaft, a first fastener, and a second fastener.

The shaft has a first end configured to be arranged with the first web, a second end configured to be arranged on the outside of the second web, and a central portion configured to be arranged between the first and second webs. The central portion includes one or more stoppers near the first end, the stoppers having a retracted position wherein the stoppers substantially do not protrude beyond an outer surface of the central portion and a deployed position wherein the stoppers protrude beyond the outer surface of the central portion such that the first web can be fixed between the stoppers and the first fastener when mounted on the first end of the shaft.

The central portion has a cross-sectional area that is larger than the cross-sectional area of the second end such that the second web can be fixed between the second fastener when mounted on the second end of the shaft and the central portion of the shaft, and the stoppers are configured to be deployed from the outside of the first web.

In accordance with this aspect, a fastener assembly is provided which can connect two webs to each other, wherein the assembly of the two webs can be mounted and unmounted from an outside of the assembly. an operator does not have to reach into the space between the webs to mount or unmount the fasteners. The fastener assembly may be used e.g. in the assembly of a main shear web assembly, and in the manufacture of a wind turbine blade, but other implementations are possible as well.

On one end, a web is fixed between a fastener on an outside and a portion of the shaft of the fastener assembly. Due to an increase in dimensions, e.g. diameter, of the central portion of the shaft with respect to the second end of the shaft, the web will inevitably engage and be nested against the portion of the shaft with increased size. At the opposite end, the web is also fixed and retained between a fastener on the outside and stoppers on an inside. The stopper can be deployed to perform their stopper function from an outside of the web assembly.

Throughout the present disclosure, a web may be regarded as any form of plate i.e. any relatively flat and thin piece of material. Thin herein may be understood to mean that length and width of the plate are orders of magnitude larger than the thickness. The webs may be made of any suitable structural material, in particular they may be made of composite or metal material. The webs may form part of an assembly including caps or flanges at the ends of the webs.

In a further aspect, a main web assembly for a wind turbine blade is disclosed. The main web assembly comprises a first shear web and a second shear web. An inside is defined between the first and second shear webs, and an inner surface of the first web faces an inner surface of the second web, an outer surface of the first web being arranged on an outside of the first web, and an outer surface of the second being arranged an on outside of the second web.

The first and second shear webs are connected through a plurality of fastener assemblies comprising a shaft, a first fastener, and a second fastener. The shaft has a first end arranged with the first shear web, a second end arranged on the outside of the second shear web, and a central portion arranged between the first and second shear webs. The central portion includes one or more stoppers near the first end, the stoppers having a retracted position wherein the stoppers substantially do not protrude beyond an outer surface of the central portion and a deployed position wherein the stoppers protrude beyond the outer surface of the central portion such that the first shear web is fixed between the stoppers and the first fastener mounted on the first end of the shaft.

The central portion has a cross-sectional area that is larger than a cross-sectional area of the second end and the second shear web is fixed between the second fastener mounted on the shaft and the central portion of the shaft, and wherein the stoppers are configured to be deployed from an outside of the first shear web.

In yet a further aspect, a method for assembling a main web assembly of a wind turbine blade is disclosed. The method comprises arranging a leading edge shear web with a trailing edge shear web such that an inner surface of the leading edge shear web faces an inner surface of the trailing edge shear web, an inside of the main web assembly being defined between the leading edge shear web and the trailing edge shear web. The method further comprises connecting the leading edge shear web to the trailing edge shear web by mounting a plurality of fastener assemblies.

The mounting of one of the fastener assemblies comprises introducing a shaft from an outside of the main web assembly through a hole in a first shear web selected from the leading and trailing edge shear webs and subsequently through a hole in a second shear web selected from the leading and trailing edge shear webs, until a second end of the shaft extends through the second shear web to an outside of the main web assembly, and a central portion of the shaft engages with the second shear web.

The method further comprises deploying one or more stoppers in the central portion to protrude beyond an outer surface of the central portion of the shaft and mounting a first fastener on the first end of the shaft to retain the first shear web between the stoppers and the first fastener and mounting a second fastener on the second end of the shaft to retain the second shear web between the second fastener and the central portion of the shaft, wherein the stoppers are deployed from an outside of the main web assembly.

Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation only, not as a limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims.

<FIG> illustrates a conventional modern upwind wind turbine <NUM> according to the so-called "Danish concept" with a tower <NUM>, a nacelle <NUM> and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub <NUM> and three blades <NUM> extending radially from the hub <NUM>, each having a blade root <NUM> nearest the hub and a blade tip <NUM> furthest from the hub <NUM>.

The chord length of the transition region <NUM> typically increases with increasing distance from the hub. The width of the chord decreases with increasing distance from the hub.

The wind turbine blade <NUM> comprises a blade shell comprising two blade shell parts or half shells, a first blade shell part <NUM> and a second blade shell part <NUM>, typically made of fiber-reinforced polymer. The wind turbine blade <NUM> may comprise additional shell parts, such as a third shell part and/or a fourth shell part. The first blade shell part <NUM> is typically a pressure side or upwind blade shell part. The second blade shell part <NUM> is typically a suction side or downwind blade shell part. The first blade shell part <NUM> and the second blade shell part <NUM> are fastened together with adhesive, such as glue, along bond lines or glue joints <NUM> extending along the trailing edge <NUM> and the leading edge <NUM> of the blade <NUM>. Typically, the root ends of the blade shell parts <NUM>, <NUM> have a semi-circular or semi-oval outer cross-sectional shape.

<FIG> is a schematic diagram illustrating a cross sectional view of an exemplary wind turbine blade <NUM>, e.g. a cross sectional view of the airfoil region of the wind turbine blade <NUM>. The wind turbine blade <NUM> comprises a leading edge <NUM>, a trailing edge <NUM>, a pressure side <NUM>, a suction side <NUM>, a first spar cap <NUM>, and a second spar cap <NUM>. The wind turbine blade <NUM> comprises a chord line <NUM> between the leading edge <NUM> and the trailing edge <NUM>. The wind turbine blade <NUM> comprises shear webs <NUM>, such as a leading edge shear web and a trailing edge shear web. The shear webs <NUM> could alternatively be a spar box with spar sides, such as a trailing edge spar side and a leading edge spar side. The spar caps <NUM>, <NUM> may comprise carbon fibers while the rest of the shell parts <NUM>, <NUM> may comprise glass fibers.

<FIG> is a schematic diagram illustrating an exemplary mold system for molding a blade shell of a wind turbine blade. The mold system <NUM> comprises a first mold <NUM> and a second mold <NUM>. The first mold <NUM> is configured for manufacturing a first blade shell part of a wind turbine blade, such as an upwind shell part of the wind turbine blade (forming the pressure side). The second mold <NUM> is configured for manufacturing a second blade shell part of the wind turbine blade, such as a downwind shell part of the wind turbine blade (forming the suction surface).

<FIG> schematically illustrates an example of a fastener assembly for connecting a first web <NUM> to a second web <NUM>. Note that in the figures only a small portion of the webs are shown, and only a single fastener assembly. It should be clear that the webs may be significantly wider and longer than what is shown in the schematic figured. Also a plurality of fastener assemblies may typically be used to connect the webs.

An inside is defined between the first and second webs <NUM>, <NUM>, and an inner surface <NUM> of the first web <NUM> faces an inner surface <NUM> of the second web <NUM>, an outer surface <NUM> of the first web <NUM> being arranged on an outside of the first web <NUM>, and an outer surface <NUM> of the second web <NUM> being arranged an on outside of the second web <NUM>.

The fastener assembly comprises a shaft <NUM>, a first fastener <NUM>, and a second fastener (not shown in <FIG>). The shaft has a first end <NUM> configured to be arranged with the first web <NUM>, a second end <NUM> configured to be arranged on the outside of the second web <NUM>, and a central portion <NUM> configured to be arranged between the first and second webs <NUM>, <NUM>.

The central portion <NUM> includes one or more stoppers <NUM> near the first end <NUM>. The stoppers have a retracted position wherein the stoppers substantially do not protrude beyond an outer surface of the central portion <NUM> and a deployed position (such as shown in <FIG>) wherein the stoppers <NUM> protrude beyond the outer surface of the central portion <NUM> such that the first web <NUM> can be fixed between the stoppers <NUM> and the first fastener <NUM> when mounted on the first end <NUM> of the shaft <NUM>.

The central portion <NUM> has a cross-sectional area that is larger than the cross-sectional area of the second end <NUM> such that the second web <NUM> can be fixed between the second fastener (not shown in <FIG>) when mounted on the second end <NUM> of the shaft <NUM> and the central portion <NUM> of the shaft <NUM>.

The stoppers <NUM> are configured to be deployed from the outside of the first web <NUM>.

In examples, the first end <NUM> of the shaft <NUM> may comprise a first thread configured to mate with a thread of the first fastener <NUM>, and the second end <NUM> of the shaft <NUM> may comprise a second thread configured to mate with a thread of the second fastener <NUM>. For example, the second fastener may be a nut <NUM> with an internal thread. The nut <NUM> may be mounted around the second end <NUM> of shaft <NUM>. In other examples, alternative ways of coupling the fasteners on the shaft may be used, e.g. a bayonet coupling.

In the example of <FIG>, the first fastener <NUM> is configured to deploy the stoppers <NUM>. The stoppers <NUM> in this example may be formed by spring biased pins <NUM> arranged inside the central portion <NUM> of the shaft <NUM>. the default position of the pins <NUM> may be a retracted position wherein the pins do not significantly protrude beyond the outer surface of central portion <NUM>. In the retracted position, the pins <NUM> may be substantially inside the shaft and do not impede movement of the shaft <NUM> through a hole in one of the webs.

The first fastener <NUM> may comprise a head portion <NUM>, a threaded portion <NUM>, and a distal tapered portion <NUM>, see the example of <FIG>. The head portion <NUM> is shown to be proximally arranged in this example, and the head portion <NUM> is configured to engage the first web <NUM>. The threaded portion <NUM> may mate with an internal thread inside the first end <NUM> of shaft <NUM>. As the first fastener is threaded onto the shaft <NUM>, the first fastener is displaced laterally, in the shown example, from the left to the right. As the first fastener <NUM> is displaced, the distal tapered portion <NUM> protrudes further into the inside of shaft <NUM> and can engage with the spring biased pins <NUM>. As the tapered portion <NUM> continues to be displaced laterally, the spring biased pins <NUM> are progressively pushed into their deployed position. The first web <NUM> may thus be retained between the head portion <NUM> and the spring biased pins <NUM>.

Although not shown in the example of <FIG>, on one or both outsides of the webs one or more washers may be arranged. the first web may be clamped or retained between the first fastener (in this example, the head portion <NUM> of fastener <NUM>), one or more washers and the stoppers <NUM>. The second web may be clamped or retained between the second fastener (e.g. a threaded nut), one or more washers and the central portion <NUM> of the shaft <NUM>. The washers may be plain washers.

<FIG> schematically illustrate another example of a fastener assembly which may be used in a similar manner. In <FIG>, a web assembly <NUM> is illustrated. The web assembly may be a main web assembly for a wind turbine blade. The main web assembly comprises a first shear web <NUM>, and a second shear web <NUM>. An inside is defined between the first and second shear webs <NUM>, <NUM>, and an inner surface <NUM> of the first web <NUM> faces an inner surface <NUM> of the second web <NUM>, an outer surface <NUM> of the first web <NUM> being arranged on an outside of the first web <NUM>, and an outer surface <NUM> of the second web <NUM> being arranged an on outside of the second web <NUM>, similarly to what was depicted in the example of <FIG>.

The first and second shear webs <NUM>, <NUM> are connected through a plurality of fastener assemblies. Note that only a single fastener assembly is shown in both examples, in reality a plurality of fastener assemblies may be used. The fastener assembly comprises a shaft <NUM>, a first fastener <NUM>, and a second fastener <NUM>. The shaft <NUM> has a first end <NUM> arranged with the first shear web <NUM>, a second end <NUM> arranged on the outside of the second shear web <NUM>, and a central portion <NUM> arranged between the first and second shear webs <NUM> ,<NUM>.

The central portion <NUM> includes one or more stoppers <NUM> near the first end, the stoppers <NUM> having a retracted position wherein the stoppers substantially do not protrude beyond an outer surface of the central portion <NUM> and a deployed position wherein the stoppers <NUM> protrude beyond the outer surface of the central portion <NUM> such that the first shear web is fixed between the stoppers <NUM> and the first fastener <NUM> mounted on the first end <NUM> of the shaft <NUM>.

As in the example of <FIG>, the central portion <NUM> has a cross-sectional area that is larger than a cross-sectional area of the second end <NUM> and the second shear web <NUM> is fixed between the second fastener <NUM> mounted on the shaft <NUM> and the central portion <NUM> of the shaft <NUM>. The stoppers <NUM>, <NUM> are configured to be deployed from an outside of the first shear web <NUM>.

The first end <NUM> in this example extends through the first shear web <NUM> and is arranged on an outside of the first web <NUM>. Both on the outside of the first shear web <NUM> and on the outside of the second shear web <NUM>, washers <NUM> are arranged.

In the example of <FIG>, a fastener assembly includes a split pin <NUM> with resilient tines <NUM>, <NUM>. The tines <NUM>, <NUM> comprise an upstanding portion <NUM>, <NUM> at their distal ends <NUM>. An operator can compress the split pin <NUM>, pushing the resilient tines <NUM>, <NUM> towards each other. The upstanding portions <NUM>,<NUM> in that situation may be regarded to be in a retracted position. The split pin <NUM> has a reduced height in cross-section and may be moved into the shaft <NUM> or be removed from the shaft.

As may be seen in <FIG>, the first end <NUM> of the shaft <NUM> comprises a slit <NUM>. The upstanding portions <NUM>, <NUM> are configured to extend through the slit <NUM> and form the stoppers. In the example, two slits <NUM> (one on the top and another at the bottom) are provided.

The slits <NUM> extend from the first portion <NUM> into the central portion <NUM>. In the shown example, the slits <NUM> have a rounded opening <NUM> at the distal ends, through which the upstanding portions <NUM>, <NUM> protrude outwardly to their deployed position.

One of the first and second shear webs <NUM>, <NUM> may be a leading edge shear web, and the other of the first and second shear webs <NUM>, <NUM> may be a trailing edge shear web. In a further aspect of the present disclosure, a wind turbine blade comprising such a main web assembly <NUM> is provided.

In the example of <FIG>, the second end <NUM> of the shaft <NUM> comprises a thread, and the second fastener <NUM> is a nut configured to mate with this thread.

In a further aspect, a method for assembling a web assembly is provided, particularly for a main web assembly of a wind turbine blade. The method comprises arranging a leading edge shear web with a trailing edge shear web such that an inner surface of the leading edge shear web faces an inner surface of the trailing edge shear web, an inside of the main web assembly being defined between the leading edge shear web and the trailing edge shear web.

The method further comprises connecting the leading edge shear web to the trailing edge shear by mounting a plurality of fastener assemblies. Either of the examples of <FIG> and <FIG> may be used. The mounting of one of the fastener assemblies comprises introducing a shaft <NUM> from an outside of the main web assembly through a hole in a first shear web <NUM> selected from the leading and trailing edge shear webs and subsequently through a hole in a second shear web <NUM> selected from the leading and trailing edge shear webs, until a second end <NUM> of the shaft <NUM> extends through the second shear web <NUM> to an outside of the main web assembly, and a central portion <NUM> of the shaft <NUM> engages with the second shear web <NUM>. The first web may be the leading edge shear web, and in that case, the second web is the trailing edge shear web. The first web may be the trailing edge shear web, and in that case, the second web is the leading edge shear web.

The method further comprises deploying one or more stoppers (pins <NUM>, or upstanding portions <NUM>, <NUM>) in the central portion <NUM> to protrude beyond an outer surface of the central portion <NUM> of the shaft <NUM> and mounting a first fastener <NUM>, <NUM> on the first end <NUM> of the shaft <NUM> to retain the first shear web <NUM> between the stoppers <NUM>, <NUM> and the first fastener <NUM>, <NUM>.

A second fastener <NUM> is mounted on the second end <NUM> of the shaft <NUM> to retain the second shear web <NUM> between the second fastener <NUM> and the central portion <NUM> of the shaft <NUM>, the stoppers <NUM>, <NUM> being deployed from an outside of the main web assembly.

It is noted that the fastener assemblies in the examples of <FIG> and <FIG> can be mounted from outside of the web assembly. No washers or other fasteners are arranged at an inside of the main web assembly. No operators need to access the space inside the web assembly. It should be clear that the order of the several method steps of this method can be changed.

In some examples, deploying of the stoppers comprises introducing a split pin <NUM> from an outside of the main web assembly through the first end <NUM> of the shaft <NUM>, wherein the split pin comprises two tines <NUM>, <NUM> comprising an upstanding portion <NUM>, <NUM> at distal end <NUM> of the tines <NUM>, <NUM> to form the stoppers. An operator may compress the split pin <NUM> to put the stoppers (upstanding portions <NUM>, <NUM>) into a retracted position for their introduction. In the retracted position, the upstanding portions <NUM>, <NUM> do not extend beyond the outer surface of the shaft <NUM>. After introduction, the upstanding portions <NUM>, <NUM> extend through slits <NUM> in the central portion of the shaft.

In other examples, the central portion <NUM> comprises two spring biased pins forming the stoppers, the pins being deployed by mounting the first fastener, as was illustrated with respect to <FIG>, the first fastener comprising a tapered portion which engages the spring biased pins as the first fastener is mounted at the first end of the shaft.

The method may further comprise removing the fastener assemblies after attaching the main web assembly to an upwind blade shell and a downwind blade shell, and particularly removing the fastener assemblies from the outside of the main web assembly.

This written description uses examples to disclose the present teaching, including the preferred embodiments, and also to enable any person skilled in the art to practice it, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims.

Claim 1:
A fastener assembly for connecting a first web (<NUM>) to a second web (<NUM>),
wherein an inside is defined between the first (<NUM>) and second webs (<NUM>), and an inner surface (<NUM>) of the first web (<NUM>) faces an inner surface (<NUM>) of the second web (<NUM>), an outer surface (<NUM>) of the first web (<NUM>) being arranged on an outside of the first web (<NUM>), and an outer surface (<NUM>) of the second web (<NUM>) being arranged an on outside of the second web (<NUM>), the fastener assembly comprising:
a shaft (<NUM>), a first fastener (<NUM>; <NUM>), and a second fastener (<NUM>; <NUM>),
the shaft (<NUM>) having a first end (<NUM>) configured to be arranged with the first web (<NUM>), a second end (<NUM>) configured to be arranged on the outside of the second web (<NUM>), and a central portion (<NUM>) configured to be arranged between the first (<NUM>) and second webs (<NUM>), wherein
the central portion (<NUM>) includes one or more stoppers (<NUM>;<NUM>, <NUM>) near the first end, the stoppers (<NUM>; <NUM>, <NUM>) having a retracted position wherein the stoppers (<NUM>; <NUM>, <NUM>) substantially do not protrude beyond an outer surface of the central portion (<NUM>) and a deployed position wherein the stoppers (<NUM>; <NUM>, <NUM>) protrude beyond the outer surface of the central portion (<NUM>) such that the first web (<NUM>) can be fixed between the stoppers and the first fastener (<NUM>; <NUM>) when mounted on the first end (<NUM>) of the shaft (<NUM>), wherein
the central portion (<NUM>) has a cross-sectional area that is larger than the cross-sectional area of the second end (<NUM>) such that the second web (<NUM>) can be fixed between the second fastener (<NUM>; <NUM>) when mounted on the second end (<NUM>) of the shaft (<NUM>) and the central portion (<NUM>) of the shaft, and
wherein the stoppers (<NUM>; <NUM>, <NUM>) are configured to be deployed from the outside of the first web (<NUM>).