EP3794229A1

EP3794229A1 - Connection joint for a sectional wind turbine blade and associated methods

Info

Publication number: EP3794229A1
Application number: EP19724738.0A
Authority: EP
Inventors: Anton Bech
Original assignee: Vestas Wind Systems AS
Current assignee: Vestas Wind Systems AS
Priority date: 2018-05-16
Filing date: 2019-05-13
Publication date: 2021-03-24
Also published as: WO2019219139A1

Abstract

A wind turbine rotor blade includes a first blade section and a second blade section which engage each other across a joint interface. A connection joint couples the first and second blade sections together across the joint interface. The connection joint includes a plurality of eyes provided at the first and second blade sections and a clamp assembly coupled to the eyes across the joint interface. The clamp assembly includes a plurality of clamp supports, at least one retention head on each side of the joint interface, and a plurality of fasteners. Each of the retention heads is formed from a plurality of discrete bridge elements arranged to collectively form the retention head. The modular nature of the retention heads accommodates various misalignments in the elements of the connection joint. A method of assembling a wind turbine blade is also disclosed.

Description

CONNECTION JOINT FOR A SECTIONAL WIND TURBINE BLADE AND ASSOCIATED METHODS

Technical Field

The invention relates generally to wind turbines, and more particularly to an improved connection joint for connecting adjacent sections of a sectional wind turbine rotor blade, and a method of forming a sectional wind turbine rotor blade having an improved connection joint for connecting the sections of the rotor blade together.

Background

Wind turbines are used to produce electrical energy using a renewable resource and without combusting a fossil fuel. Generally, a wind turbine converts kinetic energy from the wind into electrical power. A horizontal-axis wind turbine includes a tower, a nacelle located at the apex of the tower, and a rotor having a central hub and a plurality of blades coupled to the hub and extending outwardly therefrom. The rotor is supported on a shaft extending from the nacelle, which shaft is either directly or indirectly operatively coupled with a generator which is housed inside the nacelle. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator.

Traditional wind turbine blades include an outer shell positioned about an inner structural support. The outer shell typically includes upper and lower shell halves that mate together at corresponding edges to define an aerodynamic cross-sectional profile. The outer shell may be appropriately shaped so as to provide the aerodynamic aspects of the wind turbine blade. In a conventional process, the upper and lower shell halves are provided as one-piece structures which may be formed in a moulding process, for example. The inner structural support, which may include one or more spars, is typically positioned in a cavity between the upper and lower shell halves and extends in a longitudinal direction of the blade. The spar provides strength and stiffness to the blade such that the blades may withstand the loads imposed during operation of the wind turbine. The spar generally includes spar caps associated with the upper and lower shells and one or more spar webs that span between the spar caps associated with the upper and lower shells. By way of example, the spar may include a box-shaped tubular element having spar caps engaged with the upper and lower shells and two spar webs extending therebetween. More recently, spar caps are being integrated into the formation of the upper and lower shells, such that the spar caps form part of the outer surface of the blades. One or more spar webs then extend between the integrated spar caps to provide structural support to the blade.

In recent years, wind power has become a more attractive alternative energy source and the number of wind turbines, wind farms, etc., has significantly increased, both on land and off shore. Additionally, the size of wind turbines has also significantly increased, with modern wind turbine blades extending between 50 to 80 meters in length and is expected to further increase in the future. The increased length in the wind turbine blades has introduced a number of interesting design considerations for wind turbine designers and manufacturers. For example, production facilities, including the physical space as well as the equipment for manufacturing the blades (e.g., moulds, cranes and other handling equipment) must accommodate the increased size of the blades. Additionally, the logistics and transportation of such large blades becomes increasingly difficult as the length of the blades continues to increase. In the end, the production, handling and transportation of large scale wind turbine blades is associated with significant challenges and high costs that may present a practical limit to the length of wind turbine blades which may be manufactured.

One approach for addressing these issues is to provide a wind turbine blade having two or more sections which are subsequently coupled together to form the complete wind turbine blade. In this approach, each blade section may include an outer shell and an inner spar. The blade sections are then brought together at a joint interface and secured together to form the complete blade. The joint interface, however, must be designed so as to have the necessary strength to be able to transfer safely the loads and moments across the joint from one blade section to the next. One design provides one or more spar extensions from one or both of the blade section interfaces which are insertable into respective spar receivers at the other blade section interface. These elements may then be bonded or otherwise coupled together to form the connection joint between the blade sections. Another design includes a plurality of connectors at the joint interface to provide a positive coupling between the blade sections. To withstand the loads acting, for example, along a mid-span of the blade, however, the connectors may be numerous and sizeable, such that the amount of blade material at the joint interface (and through which the loads must be transferred to the connectors) significantly decreases and raises the possibility of compromising the structural integrity of the blade.

While current connection joints for sectional blade designs are sufficient to achieve their intended purpose, manufacturers continually strive to provide a connection joint for coupling wind turbine blade sections that accommodates increased loading across the joint interface in a cost-effective manner and without sacrificing the structural integrity of the blade in the region of the joint.

Summary

To these and other ends, aspects of the invention are directed to a wind turbine rotor blade including a first blade section having a first blade interface and a second blade section having a second blade interface. The first blade interface engages with the second blade interface across a joint interface. A connection joint couples the first and second blade sections together across the joint interface. The connection joint includes a plurality of eyes provided at the first and second blade sections adjacent the first and second blade interfaces. A clamp assembly is coupled to the plurality of eyes across the joint interface to join the blade sections together. The clamp assembly includes a plurality of clamp supports, each clamp support received in one or more eyes of the first and second blade sections. The clamp assembly also includes a retention head on each side of the joint interface, each retention head being engaged with a plurality of clamp supports on each side of the joint interface, and a plurality of fasteners, wherein each fastener is coupled to the retention heads on opposite sides of the joint interface. Each of the retention heads is formed from a plurality of discrete bridge elements arranged to collectively form the retention head.

Each bridge element may be configured to engage with at least two clamp supports of the clamp assembly. Preferably, each bridge element may engage with only two clamp supports of the clamp assembly. This modularity allows the retention heads to accommodate misalignments and/or deformations in the elements of the connection joint.

Each of the clamp supports, or both the bridge elements and clamp supports may include a feature for enhancing the contact between the bridge element and the clamp support. The contact-enhancing feature may have a spherical profile, a cylindrical profile, or a compound convex-concave profile. In one embodiment, the clamp supports include a contact-enhancing feature having a pair of end contact-enhancing features with a cylindrical profile and an intermediate contact-enhancing feature having a compound convex-concave profile. In an exemplary embodiment, each bridge element has a first leg extending from a first end of the bridge element and a pair of legs extending from a second, opposite end of the bridge element and defining a cavity therebetween. The first leg may include a contact-enhancing feature having a spherical profile, and the pair of legs may each include a contact-enhancing feature having a cylindrical profile. As a result of this configuration, two adjacent bridge elements of a retention head are configured to interlace or nest with each other along an overlap region. In this regard, the first leg of one bridge element may be received in the cavity of an adjacent bridge element to define the interlace along the overlap region. Each bridge element may include a bore configured to receive one of the fasteners, each bore having a radiused inlet and the fastener may be configured to have a radiused aspect that engages the inlet. The radiused aspects of the bridge elements and fasteners are configured to accommodate potential misalignments and deformations in the connection joint.

The clamp assembly may include a first end clamp support, a second end clamp support, and a plurality of intermediate clamp supports between the first and second end clamp supports, wherein each end clamp support is engaged by a single bridge element on each side of the joint interface, and wherein each intermediate clamp support is engaged by two bridge elements on each side of the joint interface. Each fastener may be positioned between two adjacent clamp supports. When the two adjacent clamp supports are intermediate clamp supports, the fastener may be centrally located between the two adjacent clamp supports and the clamping force from the fastener may be distributed about equally to the two adjacent clamp supports. Alternatively, when the two adjacent clamp supports include an end clamp support, the fastener may be located closer to the end clamp support than the other clamp support. In this way, more of the clamping force from the fastener may be attributed to the end clamp support. In a further alternative, when the two adjacent clamp supports include an end clamp support, a stud bolt of the fastener may have a size or strength that is greater than a size or strength of a stud bolt when the two adjacent clamp supports are intermediate clamp supports. In this way, the tension force in the fastener may be increased to provide an increased clamping force in the end clamp support.

The plurality of clamp supports may be configured as a plurality of brackets or a plurality of cross pins. For example, the plurality of brackets may include a plurality of U-shaped brackets having a base and two legs extending from opposed ends of the base. The legs of the U- shaped brackets are configured to engage eyes on opposed sides of the joint interface. Alternatively, the clamp supports may be configured as cross pins that extend through one or more surfaces of the wind turbine blade, but do not extend across the joint interface. When the plurality of clamp supports includes cross pins, the clamp assembly may further include a plurality of retention heads on each side of the joint interface, wherein at least one retention head is positioned on an exterior side of the wind turbine blade and at least one retention head is positioned on an interior side of the wind turbine blade. There may be instances where there is insufficient room internal to the wind turbine blade to accommodate a retention head. In such an instance, each retention head may be positioned on an exterior side of the wind turbine blade. The eyes provided at the blade interface of the blade sections may be defined by connecting elements provided with the blade sections. The connecting elements may, for example, be embedded within the material that forms the blade sections. The eyes may extend in a thickness (i.e. flapwise direction) of the wind turbine blade and may provide a passage way from an exterior side of the wind turbine blade to an interior side of the wind turbine blade.

In one embodiment, a wind turbine includes a tower, a nacelle positioned on the tower and a rotor coupled to the nacelle having at least one wind turbine blade in accordance with the invention and as described above.

In another embodiment, a method of assembling a wind turbine blade includes providing a first blade section with a first blade interface and a second blade section with a second blade interface, wherein the first and second blade interfaces include a plurality of eyes; positioning the first blade interface relative to the second blade interface across a joint interface; engaging a plurality of clamp supports with the eyes on the first and second blade sections; forming a retention head on each side of the joint interface by arranging a plurality of discrete bridge elements relative to each other; engaging the retention heads with a plurality of clamp supports on each side of the joint interface; and engaging fasteners between the retention heads on opposite sides of the joint interface to couple the first and second blade sections together.

Brief Description of the Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

Fig. 1 is a diagrammatic perspective view of a wind turbine in which embodiments of the invention may be used;

Fig. 2 is a perspective view of a sectional wind turbine blade in accordance with an embodiment of the invention;

Fig. 3 is a partial perspective view of a sectional wind turbine blade in accordance with an embodiment of the invention;

Fig. 3A is a cross-sectional view of the blade shown in Fig. 3;

Fig. 3B is another cross-sectional view of the blade shown in Fig. 3; Fig. 4 is a disassembled view of a connection joint in accordance with one embodiment of the invention;

Fig. 5 is a partially assembled view of a connection joint in accordance with one embodiment of the invention;

Fig. 6 is an assembled view of a connection joint in accordance with one embodiment of the invention;

Fig. 7 is a top view of a connection joint in accordance with one embodiment of the invention; Fig. 8 is a cross-sectional view of a connection joint in accordance with one embodiment of the invention;

Fig. 9 is an end view of a connection joint in accordance with one embodiment of the invention; Fig. 10 is a perspective view of a bracket of a clamp assembly in accordance with one embodiment of the invention;

Fig. 1 1 is a top perspective view of a bridge element in accordance with one embodiment of the invention;

Fig. 12 is a bottom perspective view of a bridge element in accordance with one embodiment of the invention;

Fig. 13 is a side view of a bridge element in accordance with one embodiment of the invention; Fig. 14 is a perspective view of another clamp assembly in accordance with one embodiment of the invention;

Fig. 15 is an assembled view of a connection joint in accordance with one embodiment of the invention;

Fig. 16 is a cross-sectional view of a connection joint in accordance with one embodiment of the invention;

Fig. 17 is a cross-sectional view of a connection joint in accordance with one embodiment of the invention;

Fig. 18 is a partial perspective view of a bracket of a clamp assembly in accordance with one embodiment of the invention; and

Fig. 19 is a bottom perspective view of a bridge element in accordance with one embodiment of the invention.

Detailed Description

With reference to Fig. 1 , a wind turbine 10 includes a tower 12, a nacelle 14 disposed at the apex of the tower 12, and a rotor 16 operatively coupled to a generator (not shown) housed inside the nacelle 14. In addition to the generator, the nacelle 14 houses miscellaneous components required for converting wind energy into electrical energy and various components needed to operate, control, and optimize the performance of the wind turbine 10. The tower 12 supports the load presented by the nacelle 14, the rotor 16, and other components of the wind turbine 10 that are housed inside the nacelle 14 and also operates to elevate the nacelle 14 and rotor 16 to a height above ground level or sea level, as may be the case, at which faster moving air currents of lower turbulence are typically found.

The rotor 16 of the wind turbine 10, which is represented as a horizontal-axis wind turbine, serves as the prime mover for the electromechanical system. Wind exceeding a minimum level will activate the rotor 16 and cause rotation in a plane substantially perpendicular to the wind direction. The rotor 16 of wind turbine 10 includes a central hub 18 and at least one rotor blade 20 that projects outwardly from the central hub 18 at locations circumferentially distributed thereabout. In the representative embodiment, the rotor 16 includes three blades 20, but the number may vary. The blades 20 are configured to interact with the passing air flow to produce lift that causes the central hub 18 to spin about a central longitudinal axis.

The wind turbine 10 may be included among a collection of similar wind turbines belonging to a wind farm or wind park that serves as a power generating plant connected by transmission lines with a power grid, such as a three-phase alternating current (AC) power grid. The power grid generally consists of a network of power stations, transmission circuits, and substations coupled by a network of transmission lines that transmit the power to loads in the form of end users and other customers of electrical utilities. Under normal circumstances, the electrical power is supplied from the generator to the power grid as known to a person having ordinary skill in the art.

Figs. 2 and 3 illustrate a sectional wind turbine blade 20. The wind turbine blade 20 includes a first blade section 22 and a second blade section 24 which are connected to each other at a joint interface 26 to form an assembled blade 20. In an exemplary embodiment, the joint interface 26 may be located at approximately the mid-span of the wind turbine blade 20; however, other positions for a joint interface along the span of the blade 20 are also possible. The first blade section 22 includes a root end 28, a leading edge 30a, a trailing edge 32a, a suction side 34a and a pressure side 36a. The first blade section 22 terminates at a first blade interface 38 opposite to the root end 28. Similarly, and using similar reference numbers, the second blade section 24 includes a tip end 40, a leading edge 30b, a trailing edge 32b, a suction side 34b and a pressure side 36b. The second blade section 24 begins at a second blade interface 42 opposite to the tip end 40. The first blade interface 38 and the second blade interface 42 may be brought together to form the joint interface 26. While Fig. 2 is shown and described as having two blade sections 22, 24 joined at one joint interface 26, it should be recognized that the sectional wind turbine blade 20 may be formed by more than two blade sections with multiple joint interfaces which are connected together in a manner described more fully below to form an assembled blade 20. Accordingly, the invention should not be limited to the specific embodiment shown in Fig. 2.

Forming wind turbine blades in sections does provide certain advantages. For example, since the blade sections are smaller, the production facilities and handling equipment do not have to be as large. In this regard, existing facilities and equipment are most likely sufficient to manufacture large wind turbine blades in multiple sections. Thus, special facilities and equipment do not have to be developed or dedicated to provide blades of increased length. Moreover, the transportation aspects of segmented blades are more manageable and less costly. More particularly, as the blade segments have a manageable size (as compared to the blade as a whole), the transportation of blade segments may be accomplished using current equipment and techniques (e.g., semi-trucks, etc.). Thus, new ways, regulations, etc. of transporting wind turbine blades do not have to be developed to accommodate blades of increased length. Furthermore, segmented blades allow maintenance and repairs to be made by replacing damaged blade sections, as opposed to the entire blade. While the segmented nature of the blades provides certain benefits and addresses many issues, the issue around the strength of the connection joint across the joint interface remains a concern for making a segmented approach viable for blades of increasing length. Further aspects are directed to providing a connection joint having increased strength and making a segmented blade design viable.

Fig. 3A illustrates a cross section of the blade 20 (wherein the webs have been removed for clarity purposes) through the first blade section 22. As illustrated in this figure, the first blade section 22 includes spar caps 50a, 52a associated with an upper shell half that defines the suction side 34a and a lower shell half that defines the pressure side 36a of the blade 20, respectively. Additionally, the blade 20 may include additional support elements adjacent the trailing edge 32 in the form of trailing edge stringers 54a, 56a also associated with the shell halves that define the suction and pressure sides 34a, 36a of the blade 20. Fig. 3B shows a similar cross section through the second blade section 24, which includes spar caps 50b, 52b and trailing edge stringers 54b, 56b associated with the upper and lower shell halves that define the suction and pressure sides 34b, 36b of the blade 20. In one example, the spar caps 50, 52 and trailing edge stringers 54, 56 may be incorporated into the blade so as to form part of the outer shell of the blade sections 22, 24. In this regard, the spar caps 50, 52 and/or the trailing edge stringers 54, 56 may be formed from pre-cured, solid pultrusion strips for reinforcement or strengthening purposes. These pultrusions are often long, flat strips formed of straight carbon filaments embedded in cured resin matrix. Pultrusions may extend along a significant portion of a blade’s spanwise extension. In the instant case, the pultrusions may extend for a substantial length of the first and second blade sections 22, 24. The flat pultruded strips are typically laid up in longitudinal stacks during moulding of the blade sections, as discussed below. While the present embodiment illustrates the spar caps 50, 52 and trailing edge stringers 54, 56 being incorporated into the outer shell of the blade sections, the invention is not limited to such an arrangement. For example, it should be recognized that aspects of the invention may be used in alternative embodiments wherein the spar caps and possibly the training edge stringers do not form part of the outer shell of the blade sections, but engage with an interior surface of the outer shell. In such an embodiment, the spar caps may be formed from pultrusions or be formed from fibres and resin materials made through other processes generally known in the art. Thus, the invention is not limited to that shown in Figs. 3A and 3B.

As illustrated in Figs. 3 and 4-8, a connection joint 60 between the first and second blade sections 22, 24 of the blade 20 at a joint interface 26 includes a plurality of connecting elements 62 integrated into the blade sections 22, 24 adjacent their respective blade interfaces 38, 42. More particularly, the connecting elements 62 may be integrated into the spar caps 50, 52, and preferably also the trailing end stringers 54, 56, adjacent their respective blade interfaces 38, 42. As illustrated in the figures, the connecting elements 62 may be distributed along a width of the spar caps 50, 52 and trailing edge stringers 54, 56 (e.g., in a chordwise direction of the blade) and be substantially embedded within the material that forms spar caps 50, 52 and trailing edge stringers 54, 56. One or more connecting elements 62, for example two connecting elements, may also span a thickness of the spar caps 50, 52 and trailing edge stringers 54, 56 (e.g., in a flapwise direction of the blade) and be substantially embedded in the material that forms these elements. The number of connecting elements 62 along the width of the spar caps 50, 52 and trailing edge stringers 54, 56 depends on the size of the blade 20, among other potential factors, but may be anywhere from 10 to 40 connecting elements for blades between 50 m-80 m in length. It should be realized, however, that more or less connecting elements may be used depending on the specific application.

The connecting elements 62 may be formed from a composite material comprising fibres, such as glass or carbon fibres, and a suitable resin material, such as epoxy. More particularly, the connecting elements 62 may be configured as elongate wedge-shaped members 64 having a through hole or eye 66. As illustrated in Fig. 3, the connecting elements 62 are oriented such that the eyes 66 extend in a thickness or flapwise direction of the wind turbine blade 20 so as to provide an opening between an exterior side of the blade to an interior side of the blade. Additional details of the exemplary connecting elements 62, including how the connecting elements are made and integrated into a wind turbine blade are provided in commonly-owned International Application No. PCT/DK2017/050441 . Accordingly, further details of the connecting elements 62 will not be provided herein. While the exemplary embodiment has the eyes 66 defined by the connecting elements 62, the invention is not so limited. In this regard, the eyes 66 may be formed through other means. By way of example, the eyes 66 may be formed in the blade sections 22, 24 through various post-processing techniques such a drilling, boring, etc. Thus it should be realized that other techniques may also be available to form the eyes 66 in blade sections 22, 24.

In an exemplary embodiment, the first and second blade interfaces 38, 42 at least along the spar caps 50, 52 and the trailing edge stringers 54, 56 may be defined by a mounting plate 68. The mounting plate 68 includes a first end face 70 having generally arcuate recesses 72 configured to abut the arcuate ends of the connecting elements 62 and a second end face 74 having a generally planar or flat profile. The second end faces 74 of respective mounting plates 68 are configured to engage each other when the blade sections 22, 24 are coupled together across the joint interface 26. The mounting plates 68 may be adhesively bonded to the blade sections 22, 24 during, for example, the manufacture of the blade sections 22, 24. Additionally, in an exemplary embodiment, the mounting plates 68 may be formed from a suitable metal, such as steel. Other materials, however, may also be possible within the scope of the invention. The mounting plates 68 facilitate good abutting contact between the two blade interfaces 38, 42 and facilitate a more uniform load distribution across the joint interface 26.

With the blade sections 22, 24 and blade interfaces 38, 42 as described above, an exemplary embodiment of the coupling of the blade sections 22, 24 to form an assembled blade 20 using the eyes 66 of the connecting elements 62 will now be described. In this regard and in further reference to the figures, in addition to the connecting elements 62, the connection joint 60 further includes a clamp assembly 76 for essentially clamping the two blade sections 22, 24 together at the joint interface 26. Figs. 4-9 illustrate an exemplary clamp assembly 76a along the trailing edge stringers 54, 56 of the blade sections 22, 24The clamp assembly 76a includes a plurality of clamp supports, which in this example includes a plurality of U-shaped clamps or brackets 80, a pair of retention heads 82, and a plurality of fasteners 84. The clamp assembly 76a cooperates with the connecting elements 62 embedded within the blade sections 22, 24 to securely couple the blade sections 22, 24 together across the joint interface 26 to form the assembled blade 20. In an exemplary embodiment, as best illustrated for example in Fig. 10, each of the U-shaped brackets 80 include a plate-like body 86 having an elongate base 88 with a first leg 90 extending from a first end of the base 88 and a second leg 92 extending from an opposed second end of the base 88, which collectively provide the U-shaped profile of the bracket 80. The base 88 may have a generally rectangular profile including a generally planar inner surface 94, a generally planar outer surface 96, and opposed side surfaces 98, 100 extending between the inner and outer surfaces 94, 96. Each of the legs 90, 92 includes a body having first and second generally planar first and second side surfaces 102, 104, a generally planar outer end surface 106, and an inner end surface 108. Each leg 90, 92 extends from the base 88 and terminates at a tip end 1 10. In an exemplary embodiment, the U-shaped brackets 80 may be formed from metal, such as steel. However, other suitable materials may also be possible.

As will be explained in more detail below, the legs 90, 92 of the brackets 80 are configured to be received in and extend through eyes 66 of respective connecting elements 62 on first and second blade sections 22, 24 across the joint interface 26. In this regard, the inner end surface 108 of the legs 90, 92 may be configured to engage the connecting elements 62 in a manner that more uniformly distributes the applied loads at the joint interface 26 to the spar caps 50, 52 and trailing edge stringers 54, 56 of the blade sections 22, 24. In one embodiment (not shown), the inner end surface 108 of the legs 90, 92 may have a profile (e.g., a generally arcuate profile) that generally matches the arcuate profile of the eyes 66 of the connecting elements 62. In other words, a contacting interface for matching the generally arcuate end of the eyes 66 of the connecting elements 62 may be fixedly and monolithically integrated into the brackets 80 themselves.

In an alternative embodiment, however, and as illustrated in the figures, each of the brackets 80 of the clamp assembly 76a may include a pair of saddles 1 16 coupled to each bracket 80 for interfacing with the eyes 66 of the connecting elements 62 in an advantageous manner. More particularly, the saddles 1 16 may be coupled to the brackets 80 so as to be adjacent the inner end surface 108 of the legs 90, 92, as illustrated in Fig. 10. Additionally, the saddles 1 16 may be movably coupled to the brackets 80. More specifically, in an exemplary embodiment, the saddles 1 16 may be pivotally coupled to the body 86 of the brackets 80, and more particularly pivotally coupled to the inner end surface 108 of the brackets 80. The ability of the saddles 1 16 to move relative to the brackets 80 allows the clamp assembly 76a to accommodate certain misalignments and deformations (e.g., in the brackets) in the components of the connection joint 60 at the joint interface 26, and thereby maintain good contact between the clamp assembly 76a and the eyes 66 of the connecting elements 62. Each of the saddles 1 16 includes a generally triangular-shaped body having generally planar upper and lower surfaces 1 18, 120, generally planar first and second side surfaces 122, 124, a generally arcuate inner end surface 126, and an outer end surface 128. The inner end surface 126 may be shaped (e.g., curved) to generally correspond to the curvature of the arcuate end of the eyes 66 of the connecting elements 62, and thereby distribute loads in an efficient manner (see Figs. 5, 7 and 8). The outer end face 128 includes an upper portion 128a and a lower portion 128b that meet at an apex 130 approximately at a mid-height of the saddles 1 16. A generally arcuate recess 132 may be formed at the apex 130 in the outer end surface 128 of the saddles 1 16. The upper and lower portions 128a, 128b of the outer end surface 128 slope away from the recess 132 toward the arcuate inner end surface 126, as illustrated in the figures.

The saddles 1 16 are configured to engage with the legs 90, 92 along the inner end surfaces 108 thereof. To this end, and in an exemplary embodiment, the legs 90, 92 may have a generally triangular shape such that the inner end surface 108 includes an upper portion 108a and a lower portion 108b that meet at an apex 134 disposed intermediate the base 88 and the tip 1 10 of the legs 90, 92. The upper and lower portions 108a, 108b of the inner end surface 108 slope away from the apex 134 toward the outer end surface 106, as illustrated in the figures. The apex 134 on the inner end surface 108 of the legs 90, 92 has a shape that generally corresponds to the shape of the recess 132 in the saddles 1 16. In this way, the saddles 1 16 may be movably seated on the inner end surface 108 of the apex 134 on the legs 90, 92. The triangular shape of the legs 90, 92 and saddles 1 16 (and the sloping of the relevant surfaces) provide gaps 136 (Fig. 8) between the legs 90, 92 and saddles 1 16 above and below the apex 134 that allow the saddles 1 16 to pivot relative to the brackets 80 and within the plane of the brackets 80, as illustrated by arrow A. Accordingly, should there be misalignments associated with the brackets 80 and/or deformation of the brackets 80 during assembly or use, the saddles 1 16 are configured to accommodate such misalignments/deformations to maintain substantially full contact with the connecting elements 62 in the blade sections 22, 24.

Because, in the exemplary embodiment, the saddles 1 16 are separate and discrete elements which are coupled to the brackets 80, it may be advantageous to include a fastener of some sort to maintain the coupling between the saddles 1 16 and brackets 80. Such a fastener simply operates as an assembly aid that allows the clamp assembly 76a to be more efficiently assembled. In this way, the bracket and saddles become an assembly that may be more easily transported and handled by a technician during the process for coupling the first and second blade sections 22, 24 together. In one embodiment, the assembly aid fastener may take the form of one or more spring clips 138. For example, each saddle 1 16 may be coupled to a corresponding leg 90, 92 of a bracket 80 by a pair of V-shaped spring clips 138. Each spring clip includes a nearly closed circular head 140 and two legs 142 extending therefrom in a V-shaped configuration. Each leg includes a plurality of connected segments, the last segment of which is received in a bore in the bracket 80. In an exemplary embodiment, the bracket 80 may include raised bosses 144 having a bore for receiving a segment of the legs 142. The head 140 of the clips 138 may be coupled to the upper or lower surfaces 1 18, 120 of the saddle 1 16 as best illustrated in Fig. 10. The spring clips 138 are configured to couple the saddles 1 16 to the brackets 80, but yet still allow the saddles 1 16 some range of pivotal movement relative to the brackets 80.

As illustrated in Figs. 3, 6 and 7, the retention heads 82 of the clamp assembly 76a extend from a first end bracket 80a, across one or more intermediate brackets 80b to a second end bracket 80c. Unlike the retention heads in commonly-owned International Application No. PCT/DK2017/050441 , the retention heads 82 are formed by a plurality of discrete bridge elements 150 arranged relative to each other to form the collective retention heads 82. Forming the retention heads 82 from a plurality of bridge elements 150 provides a number of advantages over more rigid, monolithic retention head designs. In this regard, the plurality of brackets across the joint interface 26 may not always be in perfect alignment due to various tolerance stack ups that occur during manufacture of the blade sections. For example, one or more connecting elements 62 may have slight variations in position along the first and second blade interfaces 38, 42. Moreover, the various fasteners used to clamp the two blade sections together may be subject to different loads, which may cause the legs of associated brackets to slightly deflect or deform more than other brackets in the clamp assembly. Due to the several possibilities for variations that may occur when clamping of the two blade sections together, the ability of the retention heads to accommodate various misalignments, deformations, etc. in elements of the connection joint is desirable, and provides an improvement over the more rigid, monolithic retention head designs. Through this aspect, it is believed that the clamp assembly provides a stronger, more robust connection joint for the wind turbine blade sections. Aspects of the inventive bridge elements will now be discussed in more detail.

Figs. 1 1 -13 illustrate a bridge element 150. The bridge element 150 includes a body having an upper surface 152, a lower surface 154, side surfaces 156, 158, a first end 160, and a second end 162. In an exemplary embodiment, the bridge elements 150 may be formed from a suitable metal, such as steel. Flowever, other materials may also be possible. The upper and lower surfaces 152, 154 may be generally planar in one embodiment. A through bore 164 extends through the bridge element 150 from the upper surface 152 to the lower surface 154 and is configured to receive a part of the fastener 84 (e.g., a stud bolt) therethrough. The bridge element 150 may further include a radiused inlet 166 immediately adjacent the bore 164 on the upper surface 152. The radiused inlet 166 is configured to receive a portion of the fastener 84 (e.g., nut) having a corresponding radiused portion to seat in the inlet 166 in a manner that allows slight misalignments. In an exemplary embodiment, the inlet 166 may have a radius of curvature between about 30mm and about 70mm. Other valves, however, may also be possible.

The first end 160 of the bridge element 150 includes a single extending projection or leg 168 that terminates at a rounded tip 170 that generally lies along a centreline 172 of the bridge element 150 that extends through the centre of the bore 164 (see Figs. 9 and 12). The side surfaces 156, 158 of the bridge element 150 along the leg 168 converge in a direction toward the rounded tip 170 (see Fig. 9) and the upper surface of the leg 168 includes a downwardly- sloping faceted surface 174. The second end 162 of the bridge element 150 includes a pair of extending projections or legs 176, 178 in a V-shaped configuration to define a central V- shaped recess or cavity 180 disposed therebetween. Each of the legs 176, 178 terminates in a rounded tip 182. Moreover, the apex 184 of the recess 180 may be positioned along the centreline 172 of the bridge element 150. In an exemplary embodiment, the side surfaces 156, 158 of the bridge element 150 along the outside of the legs 176, 178 may not converge toward the tips 182 of their respective legs 176, 178, but remain straight (see Fig. 9). Additionally, the upper surface of each of the legs 176, 178 may include downwardly-sloping faceted surfaces 186a, 186b separated by a spine 188.

The lower surface 154 of the bridge element 150 is configured to cooperate with brackets 80 in an improved manner. In this regard, the lower surface 154 includes features that facilitate good contact between the bridge elements 150 and the brackets 80 even under conditions of misalignments and variations in the clamp assembly 76a. For example, purely planar lower surfaces of the bridge elements may produce point loads on the brackets 80 when the clamp assembly 76a is subject to misalignments and variations in fit. The point loading of the brackets 80 may result in high stress concentrations that may ultimately create fatigue and failure of a bracket 80 or bridge element 150. To help avoid point loading between the brackets 80 and bridge elements 150 under misaligned and/or deformed conditions, the lower surface 154 of the bridge element 150 may include one or more contact-enhancing features 190. By way of example and without limitation, the portion of the lower surface 154 associated with leg 168 may include a first contact-enhancing feature 190a. In an exemplary embodiment, the first contact-enhancing feature 190a may be generally spherical, i.e., having a finite radius of curvature in two mutually perpendicular directions which are approximately equal to each other. In an exemplary embodiment, the radius of curvature of the first contact-enhancing feature 190a may be between about 50 mm and about 200 mm. Other values, however, may also be possible depending on the specific application. The spherical shape of the first contact-enhancing feature 190a is configured to provide improved contact for misalignments in multiple directions. For example, the spherical shape may be configured to accommodate slight misalignments and deformations in elements of the clamp assembly 76a in a chordwise direction, flap direction and/or longitudinal direction of the blade 20.

Additionally, or alternatively, the portion of the lower surface 154 associated with the legs 176, 178 may include a second contact-enhancing feature 190b. In one embodiment, the second contact-enhancing feature 190b may be generally cylindrical, i.e., having a finite radius of curvature in one direction (that direction being in the chord direction in the reference frame illustrated in Fig. 9, for example). The radius of curvature of the second contact-enhancing feature 190b may similarly be between about 50 mm and about 200 mm. In an exemplary embodiment, other values, however, may also be possible depending on the specific application. The cylindrical shape may likewise be configured to accommodate misalignment in elements of the clamp assembly 76a. In an alternative embodiment, the second contact enhancing feature 190b may be similar to the first contact-enhancing feature 190a and have a generally spherical configuration in order to accommodate misalignments in multiple directions. In any event, the contact-enhancing features 190 associated with the lower surface 154 of the bridge elements 150 are configured to provide good contact between the bridge elements 150 and brackets 80 under misaligned and/or deformed conditions associated with components of the connection joint 60. In this way, improved load transfer across the joint interface 26 may be achieved under such non-ideal conditions.

Fig. 12 illustrates further features associated with the lower surface 154 of the bridge elements 150. In this regard, the bridge elements 150 may include an assembly aid that facilitates the placement of the plurality of bridge elements 150 relative to the plurality of brackets 80 when forming the retention heads 82. In an exemplary embodiment, the assembly aid may include a plurality of dowel pins 192 received within corresponding bores 194 formed in the lower surface 154 and which extend from the lower surface 154, as illustrated in Figs. 12 and 13. The purpose of the dowel pins 192 will be explained in more detail below. The use of the clamp assembly 76a to couple the first and second blade portions 22, 24 will now be described in more detail. As an initial step, the first and second blade sections 22, 24 may be brought together such that the first and second blade interfaces 38, 42 are in contact with each other at the joint interface 26. In this way, the connecting elements 62 at the spar caps 50, 52 and/or trailing edge stringers 54, 56 are generally aligned across the joint interface 26. To facilitate a coupling between the blade sections 22, 24, the saddles 1 16 may be coupled to the U-shaped brackets 80 using, for example, the spring clips 138. As noted above, the saddles 1 16 may be pre-assembled to the brackets 80 prior to shipping the brackets 80 to the assembly site of the segmented wind turbine blade 20 (e.g., the installation site of the wind turbine). Also, as noted above, the saddles 1 16 are capable of pivoting relative to the brackets 80 as illustrated by arrow A (Fig. 8) to accommodate slight misalignments, yet still provide a good distribution of loads during use.

In any event, a plurality of those assemblies may then be inserted into the aligned eyes 66 of the connecting elements 62 at the spar caps 50, 52 (clamp assembly 76b) and/or the trailing edge stringers 54, 56 (clamp assembly 76a) and across joint interface 26 until the base 88 of the brackets 80 engages or is in near contact with a surface of the blade sections 22, 24. In an exemplary embodiment, and as illustrated in Figs. 3 and 8, the base 88 of the brackets 80 may be on the interior of the wind turbine blade 20 and confronting an interior surface 196 of the blade 20. The saddles 1 16 have a length to essentially fit within the height of the one or more connecting elements 62 (e.g., two stacked connecting elements 62) at the blade interfaces 38, 42. In this way, and as illustrated in Fig. 8, the saddles 1 16 generally do not extend beyond or significantly extend beyond the eyes 66 of the connecting elements 62 (e.g., very little to no exposed portions). In contrast, the legs 90, 92 have a length so that an exposed portion of the legs 90, 92 adjacent the tips 1 10 extends beyond a surface of the blade sections 22, 24. As illustrated in Figs. 3 and 8, this surface may be an exterior surface 198 of the wind turbine blade 20. In one embodiment, the legs 90, 92 extend from the base 88 at an angle slightly greater than ninety degrees (e.g., between ninety-two and ninety-five degrees) such that the legs 90, 92 have to be slightly flexed toward each other during insertion of the legs 90, 92 through the eyes 66 of the connecting elements 62. In this way, the brackets 80 (and associated saddles 1 16) may essentially remain in place across the joint interface 26 with no or very little temporary tooling to maintain their positions relative to the blade sections 22, 24.

With the plurality of brackets 80 and saddles 1 16 so positioned relative to the eyes 66 of the connecting elements 62, retention heads 82 may be assembled from a plurality of bridge elements 150. In one embodiment and starting at the end bracket 80a on the side of blade section 22 (i.e., legs 92 as seen in Figs. 5 and 6), a bridge element 150 may be positioned so as to engage the end bracket 80a and an adjacent intermediate bracket 80b. More particularly, the bridge element 150 may be positioned such that the single leg 168 engages the end bracket 80a and the two legs 176, 178 engage the intermediate bracket 80b. The bridge element 150 may be oriented such that the lower surface 154 of the bridge element 150 engages with the outer end surface 106 of the legs 92 of the brackets 80. In this regard, the outer end surfaces 106, may include a groove 200 that provides an abutment surface for the bridge elements 150; in this embodiment the abutment surface is generally planar. In an exemplary embodiment, the legs 168, 176, 178 may engage with at least a majority of the width of the brackets 80 (e.g., over 50% to about 95% of the full width). In one embodiment, the legs 168, 176, 178 may engage with substantially the full width of the brackets 80. This aspect is best shown in Fig. 9, for example. The increased contact area between the bridge element 150 and the brackets 80 more evenly distributes the loads to the brackets 80. To aid in positioning the bridge element 150 relative to the brackets 80, the dowel pins 192 may be configured to engage with the side surfaces 104, 102, and more particularly the confronting side surfaces 104, 102 of adjacent brackets 80 (see Figs. 6 and 8). When the bridge element 150 is so positioned, the bore 164 in the bridge element is disposed between the two adjacent brackets 80a, 80b and is configured to receive a fastener 84, as explained in more detail below.

The next series of bridge elements 150 may be positioned in a similar manner, wherein the single leg 168 of the subsequent bridge element 150 is positioned in the cavity 180 formed by the prior positioned bridge element 150 and the two legs 176, 178 engage the next intermediate bracket 80b. With the placement of the last bridge element 150 of the retention head 82, the end bracket 80c is engaged by the two legs 176, 178 of the last bridge element 150. It should be appreciated that each bridge element 150 in the retention head 82 contacts at least two brackets 80 without contacting all of the brackets 80 in the clamp assembly. For example, each bridge element 150 may be configured to contact only two brackets 80, and more particularly two adjacent brackets 80. The plurality of bridge elements 150 that form a retention head 82 are not fixedly secured to adjacent bridge elements. This allows a certain amount of play in the retention head 82 to accommodate various misalignments, deformations, etc. It should further be appreciated that the one leg/two-leg design of bridge elements 150 provides an overlap region R (Fig. 9) between adjacent bridge elements. Thus, adjacent bridge elements 150 interlace (i.e., nest) with each other along the retention head. This interlacing allows the bridge element 150 to overlie substantially a full width of the brackets 80 (Fig. 9). Such an arrangement enhances load transfer and reduces the likelihood of high stress concentrations that may weaken the connection joint 60. This process of assembling the retention head 82 from a plurality of bridge elements 150 may then be repeated for the legs 90 associated with the other blade section 24 on the other side of the joint interface 26 (see Fig. 6). In an exemplary embodiment, the orientation of the bridge elements 150 on the legs 90 may be the opposite to that of legs 92. In this regard, for the end bracket 80a, the first bridge element 150 may be oriented such that the two legs 176, 178 of the bridge element 150 engage with the outer end surface 106 of the legs 90, as illustrated in Fig. 6. In an alternative embodiment, however, the orientation of the bridge elements 150 may be generally the same as for legs 92 (not shown). As noted above, the dowel pins 192 helps hold the retention heads 82/brackets 80 assembly together during the formation of the two retention heads 82.

With the retention heads 82 on both sides of the joint interface 26 assembled and supported by a plurality of brackets 80, and the bores 164 in the retention heads 82 located between the legs 90, 92 of adjacent brackets 80, the fasteners 84 may be assembled. In an exemplary embodiment, the fasteners 84 may include a stud bolt 202 having threaded ends and a pair of nuts 204 for engaging the threaded ends of the stud bolts 202. In this regard, one end of a stud bolt 202 may be inserted through a bore 164 of a bridge element 150 on one side of the joint interface 26 and inserted through the bore 164 of a corresponding bridge element 150 on the other side of the joint interface 26. The bores 164 in the bridge elements 150 may be slightly larger than the stud bolts 202 to allows for misalignments. The nuts 204 may then be applied to the threaded ends of the stud bolt 202 and tightened. As alluded to above, the nuts 204 may include a radiused protrusion extending from the nut face that confronts the bridge elements 150. The radiused protrusion is sized and shaped to generally correspond to the size and shape of the radiused inlet 166 of the bridge elements 150. When the nuts 204 are tightened, the radiused protrusion is seated within the radiused inlet 166. Due to the slight oversizing of the bores 164 and the radiused nature of the nuts 204 and inlet 166, such misalignments in the stud bolds 202 across the joint interface 26 may be generally accommodated. This process of inserting fasteners 84 may be repeated until fasteners 84 are associated with each of the bridge elements 150 of the retention heads 82. In a preferred embodiment, the nuts 204 of the fasteners 84 may be preliminarily tightened until all of the fasteners 84 of the clamp assembly 76 are in position. Then, the nuts 204 may be finally tightened in a progressive pattern until the stud bolts 202 are sufficiently tensioned and the blade sections 22, 24 are sufficiently coupled together across the joint interface 26. It should be appreciated, however, that alternative methods for tightening the nuts 204 and tensioning the stud bolts 202 are possible. As discussed above, and perhaps as can be better understood at this point, the connection joint 60 may be subject to variations that may result in misalignments and/or deformations associated with elements of the connection joint 60. For example, the connecting elements 62 may not be properly positioned due to various manufacturing variations or there may be a variation in position of the legs 90, 92 of the brackets 80 such that the legs 90, 92 on either side of the connection joint are not ideally aligned. Furthermore, during tightening of the nuts 204 of the fasteners 84, the legs 90, 92 of the brackets 80 may elastically or plastically deform toward each other under increased tensioning of the stud bolts 202. These deformations may not be uniform across the plurality of brackets 80 of the clamp assembly 76 which may result in certain misalignments. Due to these potential variations, it is considered advantageous to have a retention head design that accommodates these potential variations. The inventor has discovered that by forming the retention heads from a plurality of discrete, interlaced bridge elements, there is sufficient play in the retention heads that allows for these variations, but yet results in a strong and robust connection joint. In other words, despite the variations in the connection joint, there remains excellent contact between the brackets 80 and the connecting elements 62 (e.g., via the pivotable saddles), excellent contact between the bridge elements 150 and the brackets 80 (e.g., via the contact-enhancing features associated with the legs of the bridge elements) and excellent contact between the nuts 204 of the fasteners 84 and the bridge elements 150 (e.g., via the radiused inlet 166 and the radiused protrusion of the nuts 204).

It should be recognized that there may be a different order of the assembly steps to achieve a coupling of the blade sections 22, 24. By way of example, in the embodiment described above, all of the brackets 80 of the clamp assembly 76a were first inserted through the respective eyes 66 of the connecting elements 62 associated with the blade sections 22, 24; then all of the bridge elements 150 were assembled together to form both of the retention heads 82; then the fasteners 84 were inserted through the bores 164 of the bridge elements 150. In an alternative embodiment, once two adjacent brackets 80 are positioned through eyes 66 of the connecting elements 62 across the joint interface 26 (i.e., without further brackets being inserted), a bridge element 150 may be positioned on the adjacent legs 90, 92 on both sides of the joint interface 26. Then a stud bolt 202 may be inserted through the bores 164 and the nuts 204 engaged with the threaded ends of the stud bolt 202. Subsequently, another bracket 80 may be inserted adjacent the prior bracket, followed by positioning a subsequent bridge element 150 on both sides of the joint interface 26, and followed by inserting another fastener 84. This pattern may be repeated until the clamp assembly 76a is completed. Accordingly, there may be a wide variety of ways to assemble the clamp assembly 76a and the invention should not be limited to the particular order of steps described above. As best illustrated in Fig. 9, along the intermediate brackets 80b, each bridge element 150 engages with two adjacent brackets 80. Due to the symmetry, it may be desirable to locate the fastener 84 substantially in the centre between the two adjacent brackets 80b. In this way, each bracket 80b takes approximately half the clamping force produced by the intermediate fastener 84. For the end brackets 80a, 80c, however, the symmetry is broken, as only one bridge element 150 engages with the respective end brackets 80a, 80c. Should the fastener 84 be positioned in the centre between the end brackets 80a, 80c and their adjacent intermediate brackets 80b, then the end brackets 80a, 80b would only be subject to about half of the clamping force from the adjacent fastener. As there is no other fastener on the opposite side of the end brackets 80a, 80c, the clamping force in the end brackets 80a, 80c may not be as high as desired. One approach for remedying this deficiency is to move the position of the bore 164 through the last bridge elements 150 such that the fasteners 84 are closer to the end brackets 80a, 80c. In this way, a greater percentage of the clamping force generated by the adjacent fastener will be felt by the end brackets 80a, 80c. Of course, this means that the adjacent intermediate bracket 80b will receive a lower percentage of the clamping force from the fastener 84. Flowever, since the intermediate bracket 80b also receives a contribution from the clamping force from the next closest fastener, it may be possible to strike a balance of increasing the clamping force in the end brackets 80a, 80c without reducing the clamping force on the adjacent intermediate bracket 80b below an acceptable level. In an alternative embodiment, the tension in the fastener 84 immediately adjacent the end brackets 80a, 80c may be increased to provide an acceptable clamping force in the end brackets 80a, 80c. In this regard, the fastener 84 immediately adjacent the end brackets 80a, 80c may be configured to have a strength greater than the fasteners between two intermediate brackets 80b. By way of example, the size of the stud bolts 202 (e.g., the diameter) adjacent the end brackets 80a, 80c may be larger compared to that between the intermediate brackets 80b. Alternatively, the material properties (shear strength, tensile strength, etc.) of the stud bolts 202 adjacent the end brackets 80a, 80c may be selected so as to provide increased strength (e.g., with or without an increase in bolt size) relative to the stud bolts 202 between adjacent intermediate brackets 80b.

Details above were primarily described relative to a clamp assembly 76a associated with the trailing edge stringers 54, 56 for purposes of discussion and understanding. It should be recognized that all of the details above also apply to a clamp assembly 76b associated with the spar caps 50, 52. In this regard, Fig. 14 illustrates a connection joint having a clamp assembly 76b associated with the spar caps 50, 52 and associated with a portion of the blade 20 where, for example, the curvature of the blade surface is more pronounced relative to the blade surface at the trailing edge stringers 54, 56. Moreover, in the exemplary embodiment described above, the base 88 of the U-shaped brackets 80 were positioned on the interior side of the blade sections 22, 24 while retention heads 82, stud bolts 202 and nuts 204 were positioned on the exterior side of the blade sections 22, 24. It may also be possible, however, to have the base 88 of the U-shaped brackets 80 on the exterior side of the blade sections 22, 24 while retention heads 82, stud bolts 202 and nuts 204 are on the interior side of the blade sections 22, 24. Furthermore, in one embodiment, the configuration shown in the figures may be used only on the trailing edge stringers 54, 56 at the joint interface 26, while the opposite arrangement may be used for the spar caps 50, 52. This may be due to, for example, a lack of sufficient space in the region of the trailing edge stringers 54, 56 on the interior of the blade 20. In any event, once the blade sections 22, 24 are joined together in the manner described above, a fairing 206 may be applied to the exterior side of the connection joint 60 in order to minimize the aerodynamic disruptions due to the presence of the connection joint 60. In this regard, the fairing 206 may include selectively movable and lockable closures 208 for gaining access to the spar caps 50, 52 and trailing edge stringers 54, 56 at the connection joint 60.

Figs. 15 and 16 illustrate another embodiment of a clamp assembly 76c along the trailing edge stringers 54, 56 for essentially clamping the two blade sections 22, 24 together at the joint interface 26. The clamp assembly 76c includes a plurality of clamp supports, a plurality of retention heads 82, and a plurality of fasteners. In contrast to the previous embodiments, in this embodiment the clamp supports include a plurality of cross pins 210. The clamp assembly 76c cooperates with the connecting elements 62 embedded within the blade sections, 22, 24 to securely couple the blade sections 22, 24 together across the joint interface 26 to form the assembled blade 20. This clamp assembly can also be used to join the spar caps 50, 52.

In this embodiment, each cross pin 210 includes a body having generally planar upper and lower surfaces 212, 214, generally planar first and second side surfaces 216, 218, a generally arcuate inner end surface 220, and a generally planar outer end surface 222. The inner end surface 220 may be shaped (e.g., curved) to generally correspond to the curvature of the arcuate end of the eyes 66 of the connecting elements 62, and thereby distribute loads in an efficient manner. The cross pins 210 may be inserted into the aligned eyes 66 of the connecting elements 62 at the spar caps 50, 52 and/or the trailing edge stringers 54, 56. Similar to the above, the clamp assembly 76c includes first and second end cross pins 210a, 210c and a plurality of intermediate cross pins 210b. When so positioned in the eyes 66 of the connecting elements 62, the cross pins 210 have a length such that a portion of the cross pins 210 extends beyond the exterior surface 198 of the wind turbine blade 20 and a portion of the cross pins 210 extends beyond the interior surface 196 of the wind turbine blade 20. As illustrated in Figs. 15 and 16, the clamp assembly 76c includes a plurality of retention heads 82 engaged with the cross pins 210 on each side of the joint interface 26. Accordingly, in this embodiment, the clamp assembly 76c includes a retention head 82 adjacent the exterior surface 198 and the interior surface 196 on both sides of the joint interface 26. The retention heads 82 are assembled from a plurality of bridge elements 150 as described above and therefore provide the plethora of benefits that are described above. The bridge elements 150 interact with the cross pins 210 in much that same way that the bridge elements 150 interact with the legs 90, 92 of the brackets 80 described above. In any event, with the retention heads 82 on both sides of joint interface 26 assembled and supported by a plurality of cross pins 210, and the bores 164 in the retention heads 82 located between adjacent cross pins 210, the fasteners 84 may be assembled, such as in the manner described above.

The embodiment shown in Figs. 15 and 16 illustrates retention heads 82 adjacent both the interior surface 196 and the exterior surface 198 of the wind turbine blade 20. There may be circumstances, however, that warrant the elimination of the retention heads 82 adjacent the interior surface 196 of the wind turbine blade 20. For example, in some applications, it may be difficult to provide retention heads 82 adjacent the interior surface 196 for the trailing edge stringers 54, 56. In this regard, there may not be enough space to allow a technician to assemble the interior retention heads 82. Fig. 17 illustrates another clamp assembly 76d where the retention heads on the interior of the wind turbine blade may be omitted such that the connection joint 60 includes retention heads 82 only adjacent the exterior surfaces 198 of the wind turbine blade 20. In this regard, the length of the cross pins 210 may be configured such that there is a portion of the cross pin 210 exposed beyond an upper exterior surface 198 of the wind turbine blade and a portion of the cross pin 210 (i.e., the same cross pin) exposed beyond a lower exterior surface 198 of the wind turbine blade 20. The retention heads 82 and fasteners 84 may then be assembled so as to engage the exposed portions of the cross pins 210 and thereby join the two blade sections 22, 24 together similar to that described above.

In the embodiments described above, the contact-enhancing features 190 were provided on the bridge elements 150 and those features engaged with generally planar surfaces of the brackets 80 or the cross pins 210. In a further alternative embodiment, the contact-enhancing features may be provided on the clamp supports (e.g., the brackets/cross pins) or on both the bridge elements 150 and the clamp supports 80, 210. In this regard, Fig. 18 illustrates an alternative embodiment of a bracket 230 that is similar in many respects to bracket 80 described above and includes reference numbers which refer to like features as described above. The primary difference between bracket 80 and bracket 230 is the configuration of the grooves 200, 200a. In bracket 80, the groove 200, which is configured to engage with the bridge elements 150, were generally planar. Groove 200a of bracket 230 includes a contact enhancing feature 190. More particularly, and as illustrated in Fig. 18, the groove 200a includes a pair of end contact-enhancing features 190b and an intermediate contact enhancing feature 190c. In an exemplary embodiment, the two end contact-enhancing features 190b may have a generally cylindrical profile while the intermediate contact enhancing feature 190c may have a compound convex-concave profile. The two end contact enhancing features 190b are configured to be engaged by the legs 176, 178 of one bridge element while the intermediate contact-enhancing feature 190c is configured to be engaged by the leg 168 from an adjacent bridge element, similar to that shown in Fig. 9.

To this end, a bridge element 232 may be configured to engage with the bracket 230, and more particularly groove 200a, in an improved manner when under misaligned or deformed conditions. In this regard, a portion of the lower surface 154 associated with leg 168 may include a contacting-enhancing feature 190d. In an exemplary embodiment, the contact enhancing feature 190d may have a compound convex-concave profile. Moreover, since the bracket 230 includes generally cylindrical end contact-enhancing features 190b, the lower surface 154 of the legs 176, 178 may be generally planar, i.e., lack any contact-enhancing features, as illustrated in Fig. 19. Alternatively, the lower surface 154 of the legs 176, 178 may have a concave profile. In any event, the contact-enhancing features 190 on the brackets 230, bridge elements 232, or on both the brackets 23 and bridge elements 232 allows the system to accommodate slight misalignments and deformations in the elements of the clamp assemblies. Although the alternative arrangement of the contact-enhancing features 190 were illustrated for U-shaped brackets 232 and bridge elements 150, it will be appreciated that the cross pins 210 shown in Figs. 15-17, may alternatively include a groove 200a on outer end surface 222 having contact-enhancing features 190b, 190c similar to that shown in Fig. 18. Bridge elements 232 may then be used with such cross pins to facilitate good contact between the cross pins and bridge elements.

While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the various features of the invention may be used alone or in any combination depending on the needs and preferences of the user.

Claims

1 . A wind turbine rotor blade (20), comprising:

a first blade section (22) having a first blade interface (38);

a second blade section (24) having a second blade interface (40), wherein the first blade interface (38) engages with the second blade interface (40) across a joint interface (26); and

a connection joint (60) for coupling the first and second blade sections (22, 24) together across the joint interface (26), the connection joint comprising:

a plurality of eyes (66) provided at the first and second blade sections (22, 24) adjacent the first and second blade interfaces (38, 40); and

a clamp assembly (76) coupled to the plurality of eyes (66) across the joint interface (26), wherein the clamp assembly comprises:

a plurality of clamp supports (80, 210, 230), each clamp support received in one or more eyes (66) of the first and second blade sections (22, 24);

a retention head (82) on each side of the joint interface (26), each retention head (82) engaged with a plurality of clamp supports (80, 210, 230) on each side of the joint interface (26); and

a plurality of fasteners (84), each fastener coupled to the retention heads (82) on opposite sides of the joint interface (26),

wherein each of the retention heads (82) is formed from a plurality of discrete bridge elements (150, 232) arranged to collectively form the retention head (82).

2. The wind turbine blade according to claim 1 , wherein each bridge element (150, 232) engages with at least two clamp supports (80, 210, 230) of the clamp assembly (76).

3. The wind turbine blade according to claim 2, wherein each bridge element (150, 232) engages with only two clamp supports (80, 210, 230) of the clamp assembly (76).

4. The wind turbine blade according to any of the preceding claims, wherein each of the bridge elements (150, 232), each of the clamp supports (80, 210, 230), or both include a feature (190) for enhancing the contact between the bridge elements (150, 232) and the clamp supports (80, 210, 230).

5. The wind turbine blade according to claim 4, wherein each of the clamp supports includes a contact-enhancing feature (190) having a pair of end contact-enhancing surfaces (190b) with a cylindrical profile and an intermediate contact-enhancing surface having a compound convex-concave profile.

6. The wind turbine blade according to claim 4, wherein each of the bridge elements includes a contact-enhancing feature (190), wherein the contact-enhancing feature (190) has a spherical profile, a cylindrical profile, or a compound convex-concave profile.

7. The wind turbine blade according to any of the preceding claims, wherein each bridge element (150, 232) has a first leg (168) extending from a first end of the bridge element and a pair of legs (176, 178) extending from a second, opposite end of the bridge element (150, 232) and defining a cavity (180) therebetween.

8. The wind turbine blade according to claim 7 when dependent from claim 5, wherein the first leg (168) includes a contact-enhancing feature (190d) having a compound convex- concave profile.

9. The wind turbine blade according to claim 7 when dependent from claim 6, wherein the first leg (168) includes a contact-enhancing feature (190a) having a spherical profile, and wherein the pair of legs (176, 178) each include a contact-enhancing feature (190b) having a cylindrical profile.

10. The wind turbine blade according to any of the preceding claims, wherein two adjacent bridge elements (150, 232) of a retention head interlace with each other along an overlap region.

1 1 . The wind turbine blade according to claim 10 when dependent from claim 7, wherein the first leg (168) of one bridge element is received in the cavity (180) of another bridge element to define the interlace along the overlap region.

12. The wind turbine blade according to any of the preceding claims, wherein each bridge element (150, 232) includes a bore (164) configured to receive one of the fasteners (84), each bore having a radiused inlet (166), the fastener (84) configured to have a radiused aspect that engages the inlet.

13. The wind turbine blade according to any of the preceding claims, wherein the clamp assembly (76) includes a first end clamp support (80a, 210a), a second end clamp support (80c, 210c), and a plurality of intermediate clamp supports (80b, 210b) between the first and second end clamp supports, wherein each end clamp support is engaged by a single bridge element (150, 232) on each side of the joint interface (26), and wherein each intermediate clamp support is engaged by two bridge elements (150, 232) on each side of the joint interface (26).

14. The wind turbine blade according to any of the preceding claims, wherein each fastener (84) is positioned between two adjacent clamp supports (80, 210, 230).

15. The wind turbine blade according to claim 14 when dependent from claim 13, wherein when the two adjacent clamp supports are intermediate clamp supports (80b, 210b), the fastener (84) is centrally located between the two adjacent clamp supports, or when the two adjacent clamp supports include an end clamp support (80a, 80c, 210a, 210c), the fastener (84) is located closer to the end clamp support than the other clamp support.

16. The wind turbine blade according to claim 14 when dependent from claim 13, wherein the fasteners (84) include a stud bolt (202), and wherein when the two adjacent clamp supports include an end clamp support (80a, 80c, 210a, 210c), the stud bolt (202) has a size or strength that is greater than a size or strength of a stud bolt when the two adjacent clamp supports are intermediate clamp supports (80b, 210b).

17. The wind turbine blade according to any of the preceding claims, wherein the plurality of clamp supports includes a plurality of brackets (80, 232) or a plurality of cross pins (210).

18. The wind turbine blade according to claim 17, wherein the plurality of brackets (80, 232) includes a plurality of U-shaped brackets.

19. The wind turbine blade according to claim 17, wherein the plurality of clamp supports includes a plurality of cross pins (210), the clamp assembly (76c) further comprising a plurality of retention heads (82) on each side of the joint interface (26), wherein at least one retention head (82) is positioned on an exterior side (198) of the wind turbine blade (20) and at least one retention head (82) is positioned on an interior side (196) of the wind turbine blade (20).

20. The wind turbine blade according to claim 17, wherein the plurality of clamp supports includes a plurality of cross pins (210), the clamp assembly (76d) further comprising a plurality of retention heads (82) on each side of the joint interface (26), wherein each retention head (82) is positioned on an exterior side (198) of the wind turbine blade (20).

21 . The wind turbine blade according to any of the preceding claims, wherein the plurality of eyes (66) extends in a thickness or flapwise direction of the wind turbine blade (20).

22. The wind turbine according to any of the preceding claims, wherein the first and second blade sections (22, 24) include a plurality of connecting elements (62) adjacent the first and second blade interfaces (38, 40), wherein the connecting elements define the eyes.

23. A wind turbine, comprising:

a tower (12);

a nacelle (14) positioned on the tower (12); and

a rotor (16) coupled to the nacelle (14) having at least one wind turbine blade (20) according to any of the preceding claims.

24. A method of assembling a wind turbine blade, comprising:

providing a first blade section (22) with a first blade interface (38) and a second blade section (24) with a second blade interface (40), the first and second blade interfaces (38, 40) including a plurality of eyes (66);

positioning the first blade interface (38) relative to the second blade interface (40) across a joint interface (26);

engaging a plurality of clamp supports (80, 210, 230) with the eyes (66) on the first and second blade sections (22, 24);

forming a retention head (82) on each side of the joint interface (26) by arranging a plurality of discrete bridge elements (150, 232) relative to each other;

engaging the retention heads (82) with a plurality of clamp supports (80, 210) on each side of the joint interface (26); and

engaging fasteners (84) between the retention heads (82) on opposite sides of the joint interface (26) to couple the first and second blade sections (22, 24) together.

25. The method according to claim 24, wherein engaging the retention heads (82) with a plurality of clamp supports (80, 210, 230) further comprises engaging each bridge element (150, 232) with only two clamp supports (80, 210, 230).

26. The method according to claim 24 or 25, wherein forming the retention head (82) on each side of the joint interface (26) further comprises arranging the plurality of discrete bridge elements (150, 232) relative to each other so that adjacent bridge elements interlace with each other along an overlap region.

27. The method according to any of claims 24-26, wherein the clamp assembly (76) includes a first end clamp support (80a, 210a), a second end clamp support (80c, 210c), and a plurality of intermediate clamp supports (80b, 210b) between the first and second end clamp supports, and wherein engaging the retention heads (82) with a plurality of clamp supports on each side of the joint interface (26) further comprises:

engaging each intermediate clamp support (80b, 210b) with two bridge elements (150, 232); and

engaging each end clamp support (80a, 80c, 210a, 210c) with one bridge element (150, 232).