Blade root embedded part, blade root assembly with embedded connecting structure and blade

Abstract

The invention provides a blade root embedded part, a blade root assembly with an embedded connecting structure and a blade. The blade root embedded part comprises a sleeve body, and a first cambered surface area and a second cambered surface area are arranged around the peripheral face of the sleeve body. And the grabbing and pulling part is arranged in the first cambered surface area of the sleeve body, and the grabbing and pulling part is formed by extending the peripheral surface of the sleeve body back to the axis direction of the sleeve body. When the blade root embedded part is used, the blade root embedded part is embedded in the embedded position in the blade root, the grabbing and pulling part in the first cambered surface area can increase the contact area of the sleeve body and the blade root, the connection strength of the blade root embedded part and the blade root is improved, and then the drawing performance of the blade root embedded part is improved. And moreover, the second cambered surface area is not provided with a grabbing and pulling part, so that a corresponding area in the blade root can be avoided, and the blade root embedded part is convenient to mount and use.

Description

Technical Field

[0001] The present application relates to the technical field of wind power generation, and in particular to a blade root embedded part, a blade root assembly with an embedded connection structure, and a blade. Background Art

[0002] With the development of the wind power industry, the size, length and weight of wind turbine blades are getting bigger and bigger, which makes the blade root connection load also increase accordingly, which puts higher requirements on the connection strength between the wind turbine blade root and the hub. At present, there are two main forms of blade root connection: drilling connection and embedded connection. Compared with the two, embedded connection is more widely used.

[0003] The failure of the embedded connection structure is mainly due to bolt breakage and pull-out damage of the embedded bolt sleeve. In order to deal with the pull-out damage of the embedded bolt sleeve, the relevant technology also provides some solutions. For example, in the patent application document with publication number CN115111249A, publication date September 27, 2022, and invention name A kind of embedded bolt sleeve and wind turbine, the outer surface of the embedded bolt sleeve is modified, and multiple groove areas of different depths are designed. The embedded bolts are wrapped with a glass fiber layer when in use; in the patent application document with publication number CN114770984A, publication date July 22, 2022, and invention name Bolt sleeve for root connection of wind turbine blades and method for improving its embedded strength, the external thread of the bolt sleeve is also modified, and a micro-groove structure is processed, and the groove is filled with wire harness winding material when in use.

[0004] Although the above solution strengthens the connection between the bolt sleeve and the winding harness, the bolt sleeve and the winding harness can still be pulled out as a whole, and the connection strength is not ideal. Summary of the invention

[0005] In view of the above problems, the present application provides a blade root embedded part, a blade root assembly and a blade with an embedded connection structure, wherein the blade root embedded part is conducive to improving the connection strength.

[0006] In the first aspect, some embodiments of the present application provide a blade root embedded part including a sleeve body and a grabbing portion; the sleeve body is provided with a first arc surface area and a second arc surface area around the outer peripheral surface of the sleeve body; the grabbing portion is arranged in the first arc surface area of ​​the sleeve body, and the grabbing portion is formed by extending from the outer peripheral surface of the sleeve body in the direction away from the axis of the sleeve body.

[0007] According to the blade root embedded parts provided in some embodiments of the present application, on the side of the sleeve body through which the bolt is inserted, the angle between the extension direction of the grabbing portion and the axis of the sleeve body is R; the value range of R is 30° to 90°.

[0008] According to the blade root embedded parts provided in some embodiments of the present application, the value of R is 90°.

[0009] According to the blade root embedded parts provided in some embodiments of the present application, the number of the first arc surface areas is two, which are symmetrically distributed on the sleeve body; the number of the second arc surface areas is two, which are symmetrically distributed on the sleeve body; the first arc surface area is located between the second arc surface areas, and the area of ​​the first arc surface area is smaller than the area of ​​the second arc surface area.

[0010] According to the blade root embedded part provided in some embodiments of the present application, the straight line in which the grabbing portion extends intersects with the axis of the sleeve body.

[0011] According to the blade root embedded part provided in some embodiments of the present application, the straight line where the grabbing portion extends is not in the same plane as the axis of the sleeve body.

[0012] According to the blade root embedded parts provided in some embodiments of the present application, a part of the straight line where the grabbing portion extends intersects with the axis of the sleeve body, and another part of the straight line where the grabbing portion extends is not in the same plane as the axis of the sleeve body.

[0013] According to the blade root embedded part provided in some embodiments of the present application, the angle between the multiple grabbing parts in the same first arc surface area is 0°; the angle between the grabbing parts in two first arc surface areas is 180°.

[0014] According to the blade root embedded parts provided in some embodiments of the present application, along the axial direction of the sleeve body, the outer peripheral surface of the sleeve body includes alternatingly distributed concave portions and convex portions; in the first arc surface area, the grabbing portion is located on the concave portion and / or the convex portion.

[0015] According to the blade root embedded part provided in some embodiments of the present application, in the first curved surface area, the grabbing portion is located on the convex portion.

[0016] According to the blade root embedded parts provided in some embodiments of the present application, the distance between the free end of the grabbing portion located on the concave portion and the axis of the sleeve body is a; the distance between the free end of the grabbing portion located on the convex portion and the axis of the sleeve body is b; the value of a is not greater than the value of b.

[0017] According to the blade root embedded parts provided in some embodiments of the present application, the value of a is equal to the value of b.

[0018] According to the blade root embedded part provided in some embodiments of the present application, the grabbing portion is columnar and is integrally formed with the sleeve body and / or detachably connected.

[0019] According to the blade root embedded part provided in some embodiments of the present application, the cross-sectional area of ​​the grabbing portion gradually decreases along the extension direction of the grabbing portion.

[0020] According to the blade root embedded part provided in some embodiments of the present application, the cross-sectional area of ​​the grabbing portion remains unchanged along the extension direction of the grabbing portion.

[0021] According to the blade root embedded part provided in some embodiments of the present application, along the extension direction of the grabbing portion, the cross-sectional area of ​​a part of the grabbing portion gradually decreases, while the cross-sectional area of ​​another part of the grabbing portion remains unchanged.

[0022] According to the blade root embedded part provided in some embodiments of the present application, the sleeve body is detachably connected to the grabbing portion via a threaded connection.

[0023] According to the blade root embedded part provided in some embodiments of the present application, the grabbing portion is provided with an outward convex section at an end away from the sleeve body, and the outward convex section is hook-shaped.

[0024] According to the blade root embedded part provided in some embodiments of the present application, the cross-sectional area of ​​the outward convex section is larger than the cross-sectional area of ​​the adjacent portion on the grabbing portion.

[0025] According to the blade root embedded parts provided in some embodiments of the present application, the grabbing portion is provided with an outward convex section at the end away from the sleeve body, the outward convex section is hook-shaped, and the cross-sectional area of ​​the outward convex section is larger than the cross-sectional area of ​​the adjacent part on the grabbing portion.

[0026] According to the blade root embedded part provided in some embodiments of the present application, the hook shape of the outward convex section is any one of L-shape, T-shape and J-shape.

[0027] In the second aspect, some embodiments of the present application provide a blade root assembly with a pre-embedded connection structure, comprising a blade root body and a pre-embedded connection structure; the blade root body comprises an outer wall, an inner wall and a filler layer, the filler layer is filled between the outer wall and the inner wall; the pre-embedded connection structure comprises the blade root embedded part embedded in the filler layer; the sleeve body of the blade root embedded part is pre-embedded in the filler layer, and the grabbing portion of the blade root embedded part is inserted into the outer wall and / or the inner wall.

[0028] According to the blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application, the thickness of the outer wall is greater than the depth of the grabbing portion inserted into the outer wall, and the difference between the two values ​​ranges from 0.5 mm to 3.5 mm; the thickness of the inner wall is greater than the depth of the grabbing portion inserted into the inner wall, and the difference between the two values ​​ranges from 0.5 mm to 3.5 mm.

[0029] According to the blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application, the difference between the thickness of the outer wall and the depth of the gripping portion inserted into the outer wall is 2 mm; the difference between the thickness of the inner wall and the depth of the gripping portion inserted into the inner wall is 2 mm.

[0030] According to some embodiments of the present application, the blade root assembly with a pre-embedded connection structure further comprises a winding layer, which is wound around the outer circumference of the sleeve body, and the thickness of the winding layer is smaller than the protrusion height of the grabbing portion on the sleeve body.

[0031] According to the blade root assembly with a pre-embedded connection structure provided by some embodiments of the present application, the winding layer is a fiber bundle winding layer.

[0032] According to the blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application, the blade root body is in a circular ring shape, and there are multiple sleeve bodies, and the multiple sleeve bodies are distributed along the circumference of the packing layer.

[0033] According to some embodiments of the present application, the blade root assembly with the embedded connection structure further comprises a filling block, wherein the filling blocks are multiple and the multiple filling blocks are distributed along the circumference of the packing layer, and each of the filling blocks is located between the two sleeve bodies and fits with the sleeve bodies.

[0034] According to some embodiments of the present application, the blade root assembly with a pre-embedded connection structure further comprises a wedge block, one end of which is inserted into the wedge-shaped area of ​​the packing layer and the other end of which is abutted against one end of the sleeve body.

[0035] According to the blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application, a seal is installed on the sleeve body at the place where the wedge block abuts the sleeve body. The seal includes a sealing plug and a sealing ring, and the sealing ring is located between the sealing plug and the sleeve body.

[0036] In a third aspect, some embodiments of the present application provide a blade, comprising a blade root assembly with a pre-embedded connection structure provided by any of the above-mentioned technical solutions.

[0037] The technical solution provided by the embodiments of the present disclosure brings at least the following beneficial effects:

[0038] Some embodiments of the present application provide a blade root embedded part, a blade root assembly and a blade with an embedded connection structure. The blade root embedded part includes a sleeve body and a grabbing portion, the grabbing portion is located in a first arc surface area on the outer peripheral surface of the sleeve body, and extends in the axial direction away from the sleeve body. When in use, the blade root embedded part is embedded in the embedded position in the blade root, and the grabbing portion in the first arc surface area can increase the contact area between the sleeve body and the blade root, improve the connection strength between the blade root embedded part and the blade root, and further improve the pulling performance of the blade root embedded part. In addition, the grabbing portion is not provided in the second arc surface area, so that the corresponding area in the blade root can be avoided, which is convenient for the installation and use of the blade root embedded part.

[0039] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limitations of the present application. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings.

[0041] Figure 1 A schematic diagram of the three-dimensional structure of a blade root embedded part provided in some embodiments of the present application;

[0042] Figure 2 A schematic diagram of the front structure of a blade root embedded part provided in some embodiments of the present application;

[0043] Figure 3 For this application Figure 2 A local enlarged schematic diagram at point A;

[0044] Figure 4 A schematic diagram of the front structure of a blade root embedded part provided in some other embodiments of the present application;

[0045] Figure 5 For this application Figure 4 A local enlarged schematic diagram at B;

[0046] Figure 6 A front structural schematic diagram of a blade root embedded part provided in some other embodiments of the present application;

[0047] Figure 7 For this application Figure 6 A local enlarged schematic diagram at C;

[0048] Figure 8 A schematic diagram of the side structure of a blade root embedded part provided in some embodiments of the present application;

[0049] Fig. 9 A schematic diagram of the side structure of a blade root embedded part provided in some other embodiments of the present application;

[0050] Fig.10 A longitudinal cross-sectional view of a blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application;

[0051] Fig.11 For this application Fig.10 A partial enlarged schematic diagram at D;

[0052] Fig.12 A transverse cross-sectional view of a blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application.

[0053] In the attached picture:

[0054] 1-sleeve body; 11-second arc surface area; 12-first arc surface area; 13-convex portion; 14-concave portion; 2-grasping portion; 3-inner wall; 4-outer wall; 5-wedge block; 6-winding layer; 7-filling block. DETAILED DESCRIPTION

[0055] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0056] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the embodiments of the present application should have the common meanings understood by technicians in the field to which the embodiments of the present application belong.

[0057] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0058] In addition, the technical terms "first", "second", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0059] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0060] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0061] The technical terms are explained as follows:

[0062] Drilling connection: After the composite wind turbine blade is manufactured, holes are drilled vertically and evenly on the end face of the blade root, so that one end of the stud can be embedded into the blade root shell along the radial direction of the blade root through the drilling hole and fixed with the transverse nut, and the other end is embedded in the wind turbine hub to complete the connection between the blade root shell and the wind turbine hub.

[0063] Embedded connection: The embedded parts (generally including bolt sleeves, fiberglass wedge blocks, and round foam wedge blocks) are pre-embedded in the blade root composite material layer and cast together with the blade skin. After the blade is prepared and formed, the stud bolts are directly screwed into the bolt sleeve to complete the connection between the blade and the fan hub.

[0064] Bolt sleeve pull-out force: The combined force of the metal deformation resistance of the bolt sleeve and the friction between the bolt sleeve and the composite material contact surface overcome during the pulling process.

[0065] As the size, length and weight of wind turbine blades increase, the blade root connection load also increases accordingly, and higher requirements are placed on the connection strength between the root of the wind turbine blade and the hub. Currently, blade root connections mainly include two forms: drilling connection and embedded connection. Among them, the failure mode of the embedded connection structure is mainly bolt breakage and embedded bolt sleeve pull-out damage. In order to cope with the pull-out damage of the embedded bolt sleeve, some technologies have processed the outer peripheral surface of the embedded bolt sleeve (such as increasing the roughness, improving the cleanliness, processing grooves), and wrapped it with fiber bundles. However, the results are not ideal, and the bolt sleeve and the fiber bundle will still be pulled out as a whole.

[0066] Some embodiments of the present application provide a blade root embedded part, a blade root assembly with an embedded connection structure, and a blade, which can improve the connection strength between the blade root embedded part and the blade root.

[0067] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the three-dimensional structure of the blade root embedded part provided in some embodiments of the present application, wherein the dotted line is only used to better distinguish the first curved surface area 12 from the second curved surface area 11, and is not a physical structure.

[0068] The blade root embedded part provided in some embodiments of the present application includes a sleeve body 1 and a grabbing portion 2. On the sleeve body 1, a first arc surface area 12 and a second arc surface area 11 are provided around the outer peripheral surface of the sleeve body 1, and the grabbing portion 2 is arranged in the first arc surface area 12 of the sleeve body 1. The grabbing portion 2 is formed by the outer peripheral surface of the sleeve body 1 extending in the direction opposite to the axis of the sleeve body 1.

[0069] On the outer circumference of the sleeve body 1, the first arc surface area 12 and the second arc surface area 11 are set to clearly distinguish the distribution area of ​​the grabbing portion 2. There is no actual structure to define the junction of the first arc surface area 12 and the second arc surface area 11. The sleeve body 1 is cut along a plane perpendicular to the axis of the sleeve body 1. The outer contour of the sleeve body 1 can be any of a circle, an ellipse, a polygon, etc. The sleeve is processed with an internal thread for threaded connection with bolts, studs, etc.

[0070] The grabbing portion 2 protrudes from the outer circumferential surface of the sleeve body 1, and one end of the grabbing portion 2 is connected to the sleeve body 1, and the other end is a free end. Compared with the end connected to the sleeve body 1, the free end of the grabbing portion 2 is farther away from the axis of the sleeve body 1. When the grabbing portion 2 extends in the direction away from the axis of the sleeve body 1, the extension direction of the grabbing portion 2 can have any angle with the axis of the sleeve body 1, and the extension direction of the grabbing portion 2 can intersect with the axis of the sleeve body 1 or be out of plane.

[0071] In the above structure, the grabbing portion 2 is located in the first arc surface area 12 of the outer peripheral surface of the sleeve body 1, and extends in the direction opposite to the axis of the sleeve body 1. When the blade root embedded part is used, it is embedded in the embedded position in the blade root. The grabbing portion 2 in the first arc surface area 12 can increase the contact area between the sleeve body 1 and the blade root, especially in the thickness direction of the blade root (radial direction of the blade root). The grabbing portion 2 can penetrate into the blade root and connect with the inner wall 3 and / or outer wall 4 of the blade root, thereby improving the connection strength between the blade root embedded part and the blade root, and improving the pulling performance of the blade root embedded part. In addition, the grabbing portion 2 is not provided in the second arc surface area 11 of the sleeve body 1, so that the corresponding area in the blade root (such as the area where the UD block is located) can be avoided, which is convenient for the installation and use of the blade root embedded part.

[0072] Please refer to Figure 2 , Figure 3 , Figures 6 to 9 ,in, Figure 2 A schematic diagram of the front structure of a blade root embedded part provided in some embodiments of the present application; Figure 3 For this application Figure 2 A local enlarged schematic diagram at point A; Figure 6 A front structural schematic diagram of a blade root embedded part provided in some other embodiments of the present application; Figure 7 For this application Figure 6 A local enlarged schematic diagram at C; Figure 8 A schematic diagram of the side structure of a blade root embedded part provided in some embodiments of the present application; Fig. 9 The side structure diagram of the blade root embedded part provided in some other embodiments of the present application, wherein the dotted lines correspond to the axis of the sleeve body 1, the center line of the sleeve body 1, and the extension direction of the grabbing portion 2, and the left side of the figure is the side where the bolt (or stud) is inserted.

[0073] In some embodiments of the present application, on the side of the sleeve body 1 where the bolt is inserted, the angle between the extension direction of the grabbing portion 2 and the axis of the sleeve body 1 is R, and the value range of R is 30° to 90°. For example, the value of R can be 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°, or any intermediate value between any two adjacent endpoints mentioned above.

[0074] In the above structure, the angle R is not an obtuse angle, so the grabbing portion 2 can be better inserted into the blade root when being pulled, and is not easy to slide out from the original position. The angle R is not an acute angle less than 30°, so the grabbing portion 2 can be extended from the outer peripheral surface of the sleeve body 1 as much as possible, increasing the contact between the blade root embedded part and the blade root in its own radial direction, and preventing the blade root embedded part from being pulled out with the nearby blade root structure when being pulled. Figure 6 and Figure 7 As shown, when the included angle R is an acute angle of not less than 30°, it can be more tightly embedded in the blade root after being pulled.

[0075] like Figure 2 , Figure 3 , Figure 8 and Fig. 9 As shown, in some embodiments of the present application, the value of R is 90°.

[0076] When R is 90°, the axis of the sleeve body 1 is perpendicular to the extension direction of the grabbing portion 2. At this time, the axis of the sleeve body 1 and the extension direction of the grabbing portion 2 may intersect or be out of plane, or the extension direction of a portion of the grabbing portion 2 may intersect with the axis of the sleeve body 1, and the extension direction of another portion of the grabbing portion 2 may be out of plane with the axis of the sleeve body 1.

[0077] When the blade root embedded part is used, the wire harness can be wound around the outer circumference of the sleeve body 1. When R takes a value of 90°, the wound wire harness will not be hindered by the grabbing portion 2, and the operation is more convenient.

[0078] like Figure 1 , Figure 8 and Fig. 9 As shown, in some embodiments of the present application, the number of the first arc surface areas 12 is two, which are symmetrically distributed on the sleeve body 1; the number of the second arc surface areas 11 is two, which are symmetrically distributed on the sleeve body 1; the first arc surface area 12 is located between the second arc surface areas 11, and the area of ​​the first arc surface area 12 is smaller than the area of ​​the second arc surface area 11.

[0079] In the above structure, the angle between the two first curved surface areas 12 is 180°, and the angle between the two second curved surface areas 11 is 180°. The grabbing portion 2 is distributed in the two first curved surface areas 12. The two first curved surface areas 12 correspond to the outer wall 4 and the inside of the blade root respectively when pre-embedded, and the two second curved surface areas 11 correspond to the filling blocks 7 (UD blocks) in the blade root respectively. The area of ​​the first curved surface area 12 is smaller than the area of ​​the second curved surface area 11, which can avoid interference between the grabbing portion 2 and the UD block, and facilitate the installation of the embedded parts of the blade root during the pre-embedded operation.

[0080] like Figure 3 , Figure 7 and Figure 8 As shown, in some embodiments of the present application, the straight line in which the grabbing portion 2 extends intersects with the axis of the sleeve body 1 .

[0081] When the straight line where the grabbing portion 2 extends intersects the axis of the sleeve body 1, along the axis of the sleeve body 1, the straight line where the grabbing portion 2 extends and the axis of the sleeve body 1 can be perpendicular (e.g. Figure 3As shown), the straight line where the grabbing portion 2 extends and the axis of the sleeve body 1 may be at an acute angle of not less than 30° (as shown Figure 7 shown).

[0082] When the straight line in which the grabbing portion 2 extends intersects the axis of the sleeve body 1 , the grabbing portion 2 can be distributed along the radial direction of the sleeve body 1 , which facilitates the molding and installation of the grabbing portion 2 .

[0083] like Fig. 9 As shown, in some embodiments of the present application, the straight line where the grabbing portion 2 extends is not in the same plane as the axis of the sleeve body 1 .

[0084] exist Fig. 9 In the side structural diagram of the blade root embedded part shown, the straight line where the extension direction of the left and right two of the three grabbing parts 2 above the sleeve body 1 is located is not in the same plane as the axis of the sleeve body 1, and the straight line where the extension direction of the left and right two of the three grabbing parts 2 below the sleeve body 1 is located is also not in the same plane as the axis of the sleeve body 1, which can provide a variety of schemes for the design of the grabbing parts 2 on the sleeve body 1.

[0085] like Fig. 9 As shown, in some embodiments of the present application, a straight line where a portion of the grabbing portion 2 extends intersects with the axis of the sleeve body 1 , and a straight line where another portion of the grabbing portion 2 extends is not in the same plane as the axis of the sleeve body 1 .

[0086] exist Fig. 9 In the side structural diagram of the blade root embedded part shown, among the three grabbing parts 2 above the sleeve body 1, the straight line where the middle grabbing part 2 extends intersects with the axis of the sleeve body 1; among the three grabbing parts 2 below the sleeve body 1, the straight line where the middle grabbing part 2 extends intersects with the axis of the sleeve body 1. The straight lines where the remaining grabbing parts 2 extend are all out of plane with the axis of the sleeve body 1.

[0087] In the above structure, a solution is provided in which the straight line where the grabbing part 2 extends is not in the same plane as the axis of the sleeve body 1 and the straight line where the grabbing part 2 extends intersects the axis of the sleeve body 1, further expanding the design concept of the grabbing part 2.

[0088] like Fig. 9 As shown, in some embodiments of the present application, the angle between the multiple grabbing portions 2 in the same first arc surface area 12 is 0°; the angle between the grabbing portions 2 in two first arc surface areas 12 is 180°.

[0089] In the same first arc surface area 12 , all the grabbing portions 2 are arranged in parallel, and the free ends of any two different grabbing portions 2 in different first arc surface areas 12 extend in opposite directions, with an included angle of 180°.

[0090] In the above structure, multiple grabbing parts 2 in one first curved surface area 12 are arranged in parallel, which is convenient for placing on the lower paving material during pre-embedding, and multiple grabbing parts 2 in another first curved surface area 12 are arranged in parallel, which is convenient for laying the upper paving material thereon (the upper paving material and the lower paving material correspond to the inner wall 3 and the outer wall 4 of the blade root after forming). Since the straight lines where all the grabbing parts 2 extend are parallel, during operation, the blade root embedded parts and the upper paving material can be placed on the lower paving material in turn, and there is no need to adjust the blade root embedded parts to ensure that each grabbing part 2 is inserted into the corresponding auxiliary material, which can greatly facilitate the operation of workers and save on-site operation time.

[0091] Please refer to Figure 4 and Figure 5 , Figure 4 A schematic diagram of the front structure of a blade root embedded part provided in some other embodiments of the present application; Figure 5 For this application Figure 4 A partial enlarged schematic diagram at B. Wherein L represents the distance between the free end of the grabbing portion 2 and the axis of the sleeve body 1.

[0092] In some embodiments of the present application, along the axial direction of the sleeve body 1 , the outer circumferential surface of the sleeve body 1 includes alternatingly distributed concave portions 14 and convex portions 13 ; in the first arc surface area 12 , the grabbing portion 2 is located on the concave portion 14 and / or the convex portion 13 .

[0093] like Figure 4 and Figure 5 As shown, the grabbing portion 2 is distributed on both the concave portion 14 and the convex portion 13; Figure 2 and Figure 3 As shown, the grabbing portion 2 is only distributed on the convex portion 13 .

[0094] It is worth noting that the outer circumference of the sleeve body 1 is a concave-convex surface with alternating concave and convex along the axial direction, and the concave-convex surface includes a concave portion 14 and a convex portion 13. The first arc surface area 12 and the second arc surface area 11 on the outer circumference of the sleeve body 1 are specific area divisions of the concave-convex surface. That is, the first arc surface area 12 is a concave-convex surface along the axial direction of the sleeve body 1, and the second arc surface area 11 is also a concave-convex surface along the axial direction of the sleeve body 1.

[0095] Regarding the design of the concave-convex surface, along the axis of the sleeve body 1, the concave-convex surface may be wavy, serrated, etc., or the concave-convex surface may be a threaded shape formed on the outer circumference of the sleeve body 1 around the axis of the sleeve body 1. The concave-convex surface may be subjected to surface sandblasting to improve the roughness and cleanliness, thereby improving the connection strength during connection.

[0096] In the above structure, the outer peripheral surface of the sleeve body 1 is simultaneously provided with a concave-convex surface and a grabbing portion 2, which can not only increase the contact area between the blade root embedded part and the blade root when in use, but also enable the grabbing portion 2 to be inserted into the gap position of the blade root paving material (the paving material can be a woven structure, and there are gaps between the criss-crossing woven wires), thereby improving the connection strength between the blade root embedded part and the blade root without destroying the paving structure, and improving the anti-pull-out bearing capacity of the blade root embedded part.

[0097] like Figure 2 and Figure 3 As shown, in some embodiments of the present application, in the first curved surface area 12 , the grabbing portion 2 is located on the convex portion 13 .

[0098] In the above structure, within the two first arc surface areas 12, the grabbing portion 2 is only provided on the convex portion 13, and no grabbing portion 2 is provided on the concave portion 14, which is beneficial to the subsequent fiber bundle winding step of the subsequent sleeve body 1, reduces the influence of the grabbing portion 2 on the wound fiber bundle, and avoids defects such as the infusion cavity.

[0099] like Figure 5 As shown, in some embodiments of the present application, the distance between the free end of the grabbing portion 2 located on the concave portion 14 and the axis of the sleeve body 1 is a; the distance between the free end of the grabbing portion 2 located on the convex portion 13 and the axis of the sleeve body 1 is b; the value of a is not greater than the value of b.

[0100] When the grabbing portion 2 is provided on both the concave portion 14 and the convex portion 13, the value of the distance b between the free end of the grabbing portion 2 on the convex portion 13 and the axis of the sleeve body 1 is greater than or equal to the value of the distance a between the free end of the grabbing portion 2 on the concave portion 14 and the axis of the sleeve body 1.

[0101] When the value of a is smaller than the value of b, the grabbing portion 2 on the convex portion 13 and the grabbing portion 2 on the concave portion 14 can have the same specifications (completely the same appearance) to improve interchangeability.

[0102] When the value of a is equal to the value of b, that is, Figure 5 As shown, when the values ​​of a and b are both the length of L in the figure, the length of the grabbing portion 2 located on the concave portion 14 is greater than the length of the grabbing portion 2 located on the convex portion 13. At this time, the risk of filling the cavity due to the different values ​​of a and b can be avoided.

[0103] like Figure 5 As shown, in some embodiments of the present application, in order to ensure the injection quality at the root of the blade, the corresponding grabbing portions 2 on the concave portion 14 and the convex portion 13 are designed so that the value of a is equal to the value of b.

[0104] like Figure 1As shown, in some embodiments of the present application, the grabbing portion 2 is columnar, and the grabbing portion 2 is located on the outer circumferential surface of the sleeve body 1. It can be formed as one piece with the sleeve body 1, or it can be detachably connected to the sleeve body 1. It is also possible that a part of the grabbing portion 2 is formed as one piece with the sleeve body 1, and the other part of the grabbing portion 2 is detachably connected to the sleeve body 1.

[0105] When the grabbing part 2 and the sleeve body 1 are formed as one body, the grabbing part 2 and the sleeve body 1 can be designed to be bonded, welded, or integrally formed using 3D printing technology. When the grabbing part 2 and the sleeve body 1 are detachably connected, the grabbing part 2 and the sleeve body 1 can be designed to be snap-fitted, or threaded.

[0106] The grabbing portion 2 is in a columnar shape, for example, a cylindrical shape, an elliptical cylindrical shape, or a polygonal cylindrical shape. When the grabbing portion 2 is in a polygonal cylindrical shape, its cross section may be a regular polygon, for example, a regular pentagon, a regular hexagon, or the like.

[0107] In some embodiments of the present application, in order to facilitate the installation of the grabbing part 2 on the sleeve body 1, a hole is drilled on the outer circumferential surface of the sleeve body 1 and an internal thread is processed (the hole drilled cannot be connected to the threaded hole in the sleeve body 1), and an external thread is processed on the end portion where the grabbing part 2 is connected to the sleeve body 1. The grabbing part 2 is fastened to the sleeve body 1 through the cooperation of the external thread and the internal thread, thereby realizing a detachable connection between the sleeve body 1 and the grabbing part 2.

[0108] In the above structure, the sleeve body 1 and the grabbing portion 2 are detachably connected by threaded connection, which facilitates the installation and adjustment of the grabbing portion 2 on the sleeve body 1. In particular, when the radial direction of the sleeve body 1 coincides with the straight line in which the grabbing portion 2 extends, it is only necessary to machine the threaded hole along the radial direction of the sleeve body 1, which facilitates the machining of the threaded hole.

[0109] like Figure 8 and Fig. 9 As shown, in some embodiments of the present application, along the extension direction of the grasping portion 2, the cross-sectional area of ​​the grasping portion 2 gradually decreases.

[0110] The cross-sectional area of ​​the grasping portion 2 refers to the area of ​​the cross section obtained by cutting the grasping portion 2 along a plane perpendicular to the extending direction of the grasping portion 2.

[0111] Along the extension direction of the grabbing portion 2, the cross-sectional area of ​​the end (free end) of the grabbing portion 2 far from the sleeve body 1 is small, and the cross-sectional area of ​​the end of the grabbing portion 2 close to the sleeve body 1 is large. The cross-sectional area changes evenly and continuously.

[0112] In the above structure, the end of the grabbing portion 2 close to the sleeve body 1 is relatively thick, which can effectively improve the connection strength between the grabbing portion 2 and the sleeve body 1; the end of the grabbing portion 2 away from the sleeve body 1 is relatively thin, which can be more easily inserted into the outer wall 4 and / or inner wall 3 of the blade root.

[0113] In some embodiments of the present application, for the convenience of processing the grabbing portion 2, the cross-sectional area of ​​the grabbing portion 2 remains unchanged along the extension direction of the grabbing portion 2. When processing the grabbing portion 2, the rod material can be cut into several sections to directly obtain the grabbing portion 2.

[0114] In some embodiments of the present application, the convenience of processing the grabbing portion 2 and the convenience of pre-embedding the embedded parts of the blade root can also be taken into account. Specifically, the grabbing portion 2 can be designed as a combination of two forms. Along the extension direction of the grabbing portion 2, the cross-sectional area of ​​a part of the grabbing portion 2 gradually decreases, while the cross-sectional area of ​​the other part of the grabbing portion 2 remains unchanged.

[0115] In some embodiments of the present application, the grabbing portion 2 is provided with an outwardly protruding section at the end away from the sleeve body 1 , and the outwardly protruding section may be hook-shaped.

[0116] In the extension direction of the grabbing portion 2, the grabbing portion 2 may be designed with a hook-shaped convex section at the end where the free end is located, and the hook shape may be a J-shaped hook, an L-shaped hook, or a T-shaped hook. For example, an arc-shaped bend may be provided, and a J-shaped arc-shaped bend may form a convex section; a vertical beam may be added to one side of the free end to form an L-shaped convex section; vertical beams may also be added to both sides of the free end to form a T-shaped convex section.

[0117] In the above structure, by providing the hook-shaped convex section, the peeling resistance of the grabbing portion 2 and the connection strength with the blade root can be increased.

[0118] In some embodiments of the present application, the cross-sectional area of ​​the outer convex section is larger than the cross-sectional area of ​​the adjacent portion on the grasping portion 2 .

[0119] In the extension direction of the grabbing portion 2 , the grabbing portion 2 may be designed in a spherical, ellipsoidal or other shape with a larger cross-sectional area at one end where the free end is located, forming an outward convex section.

[0120] In the above structure, due to the increase in cross-sectional area, the structural strength of the grabbing portion 2 itself is increased, and the connection strength between the grabbing portion 2 and the blade root is also increased.

[0121] In some embodiments of the present application, a portion of the convex section of the grasping portion 2 may be designed to be hook-shaped, and during the design, the cross-sectional area of ​​the convex section is increased so that the cross-sectional area of ​​the convex section is larger than the cross-sectional area of ​​the adjacent portion on the grasping portion 2 .

[0122] Please refer to Figures 10 to 12 , Fig.10A longitudinal cross-sectional view of a blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application; Fig.11 For this application Fig.10 A partial enlarged schematic diagram at D; Fig.12 A transverse cross-sectional view of a blade root assembly with a pre-embedded connection structure provided in some embodiments of the present application.

[0123] Some embodiments of the present application provide a blade root assembly with a pre-embedded connection structure. The blade root assembly with the pre-embedded connection structure includes a blade root body and a pre-embedded connection structure. The blade root body includes an outer wall 4, an inner wall 3 and a filler layer, and the filler layer is filled between the outer wall 4 and the inner wall 3. The pre-embedded connection structure includes a blade root pre-embedded part embedded in the filler layer; a sleeve body 1 of the blade root pre-embedded part is pre-embedded in the filler layer, and a grabbing portion 2 of the blade root pre-embedded part is inserted into the outer wall 4 and / or the inner wall 3.

[0124] The blade root body is made of resin infusion, and the pre-embedded connection structure is pre-embedded between the outer wall 4 and the inner wall 3 before infusion. After infusion, a filler layer is infused between the outer wall 4 and the inner wall 3, and the outer wall 4, the filler layer, the inner wall 3 and the pre-embedded connection structure are formed as a whole. When the pre-embedded connection structure is pre-embedded, the free end of the grabbing portion 2 of the blade root pre-embedded part is inserted into the outer wall 4 and / or the inner wall 3, so as to realize the connection between the blade root pre-embedded part and the outer wall 4 and / or the inner wall 3 after forming.

[0125] In the above structure, the grabbing portion 2 is inserted into the weaving gap position of the outer wall 4 and / or the inner wall 3. During the insertion process, only the fiber bundles of the fiber cloth are partially squeezed away from the original position. After resin infusion and heating and curing, the grabbing portion 2 is tightly combined with the outer wall 4 and / or the inner wall 3, and then the blade root embedded parts can directly interact with the outer wall 4 and / or the inner wall 3, which can improve the pull-out resistance of the blade root embedded parts, enhance the overall connection strength of the blade root assembly, and meet higher blade root connection load requirements.

[0126] like Fig.10 and Fig.12 As shown, in some embodiments of the present application, the thickness of the outer wall 4 is greater than the depth of the grasping portion 2 inserted into the outer wall 4, and the difference (H) between the two ranges from 0.5 mm to 3.5 mm, for example, the difference can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or any intermediate value between any two adjacent endpoint values ​​mentioned above; the thickness of the inner wall 3 is greater than the depth of the grasping portion 2 inserted into the inner wall 3, and the difference between the two ranges from 0.5 mm to 3.5 mm, for example, the difference can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, or any intermediate value between any two adjacent endpoint values ​​mentioned above.

[0127] In the above structure, by setting the thickness of the outer wall 4 to be greater than the insertion depth of the grabbing portion 2 and the thickness of the inner wall 3 to be greater than the insertion depth of the grabbing portion 2, the grabbing portion 2 can be inserted into the inner wall 3 and / or the outer wall 4 without protruding from the surface of the inner wall 3 and / or the outer wall 4.

[0128] like Fig.12 As shown, in some embodiments of the present application, the difference between the thickness of the outer wall 4 and the depth of the grasping portion 2 inserted into the outer wall 4 is 2 mm; the difference between the thickness of the inner wall 3 and the depth of the grasping portion 2 inserted into the inner wall 3 is 2 mm.

[0129] In the above structure, by further limiting the difference, not only the reliability of the connection between the blade root embedded part and the outer wall 4 and the inner wall 3 can be ensured, but also the manufacturer can be easily controlled to avoid the generation of defective products.

[0130] like Fig.11 As shown, in some embodiments of the present application, the embedded connection structure further includes a winding layer 6, which is wound on the outer circumference of the sleeve body 1, and the thickness of the winding layer 6 is less than the protrusion height of the grabbing portion 2 on the sleeve body 1.

[0131] In the above structure, the winding layer 6 can be a fiber bundle winding layer. When the outer peripheral surface of the sleeve body 1 is a concave-convex surface, by winding the winding layer 6 and then pouring resin, the contact area between the sleeve body 1 and the filler layer of the blade root body can be increased, thereby improving the anti-pullout bearing capacity of the sleeve body 1.

[0132] like Fig.12 As shown, in some embodiments of the present application, the blade root body is in a circular ring shape, and there are multiple sleeve bodies 1. The multiple sleeve bodies 1 are distributed along the circumference of the packing layer, and multiple connection positions for the external hub can be provided on the circumference of the blade root body, so that the blade root body is evenly stressed when connected to the hub.

[0133] like Fig.12 As shown, in some embodiments of the present application, the pre-embedded connection structure further includes a filling block 7, and there are multiple filling blocks 7, and the multiple filling blocks 7 are distributed along the circumference of the packing layer, and each filling block 7 is located between two sleeve bodies 1 and fits with the sleeve body 1. When pre-embedded, the sleeve body 1 can use the filling block 7 to fix the position to ensure the accuracy of the pre-embedded position and ensure the connection strength after molding. Among them, the filling block 7 can be a UD block.

[0134] like Fig.12As shown, when the filling block 7 is fitted with the sleeve body 1, there is a filling block 7 on each side of a sleeve body 1, and the upper side of the sleeve body 1 is the inner wall 3, and the lower side of the sleeve body 1 is the outer wall 4. The area where the sleeve body 1 fits with the left filling block 7 is a second curved surface area 11, and the area where the sleeve body 1 fits with the right filling block 7 is another second curved surface area 11. Between the two filling blocks 7, the sleeve body 1 faces the inner wall 3 is a first curved surface area 12, and between the two filling blocks 7, the sleeve body 1 faces the outer wall 4 is another first curved surface area 12.

[0135] like Fig.10 As shown, in some embodiments of the present application, the embedded connection structure further includes a wedge block 5, one end of which is inserted into the wedge-shaped area of ​​the packing layer and the other end is abutted against one end of the sleeve body 1, so as to provide positioning for the sleeve body 1 in the axial direction of the sleeve body 1. The wedge block 5 can be a foam wedge block 5.

[0136] like Fig.10 As shown, in some embodiments of the present application, a seal is installed on the sleeve body 1 at the point where the wedge block 5 abuts against the sleeve body 1. The seal includes a sealing plug and a sealing ring, and the sealing ring is located between the sealing plug and the sleeve body 1.

[0137] In the above structure, a sealing plug is arranged between the wedge block 5 and the sleeve body 1, and the sealing plug can be threadedly connected with the sleeve body 1. A sealing ring is installed on the sealing plug, and the sealing ring can seal the gap between the sealing plug and the sleeve body 1, thereby preventing the inner cavity of the sleeve body 1 from being immersed and contaminated by resin when the resin is poured.

[0138] Some embodiments of the present application also provide a method for producing a blade root assembly with a pre-embedded connection structure, comprising:

[0139] Assemble the sleeve body 1, the sealing ring, and the sealing plug to prevent the threaded part inside the sleeve body 1 from being infiltrated with resin during vacuum resin infusion;

[0140] The surface of the sleeve body 1 is sandblasted to improve the roughness and cleanliness of the outer peripheral surface;

[0141] Winding the fiber bundle on the outer circumference of the sleeve body 1 so that the fiber bundle winding layer is closely fitted with the grabbing portion 2;

[0142] Laying down the lower composite fiber cloth layer of the blade root assembly;

[0143] A filling block 7 is placed on the lower composite fiber cloth layer, and a sleeve body 1 is placed between the two filling blocks 7. The first arc surface area 12 on the sleeve body 1 needs to be adjusted to the gap position between the filling blocks 7 on both sides, and the grabbing portion 2 is inserted into the lower composite fiber cloth layer. During the insertion process, only the fiber bundles in the lower composite fiber cloth layer are partially squeezed away from the original position.

[0144] A wedge block 5 is placed at the end of the sleeve body 1 to complete the arrangement of the embedded connection structure;

[0145] The upper composite fiber cloth layer of the blade root assembly is laid on the embedded connection structure, and the grabbing and pulling part 2 is also inserted into the upper composite fiber cloth layer. During the insertion process, only the fiber bundles in the upper composite fiber cloth layer are partially squeezed away from the original position;

[0146] The resin and curing agent are injected by vacuum infusion, and heated and cured to obtain an integrated blade root component with a pre-embedded connection structure.

[0147] Some embodiments of the present application further provide a blade, which comprises a blade root assembly with a pre-embedded connection structure according to any of the above embodiments.

[0148] The blade provided in the embodiment of the present application has all the beneficial effects of the blade root assembly with a pre-embedded connection structure provided in the above embodiments of the present application. For details, please refer to the specific description of the blade root assembly with a pre-embedded connection structure in the above embodiments, and this embodiment will not be repeated here.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A blade root embedded part, characterized in that: include: A sleeve body, wherein a first arc surface area and a second arc surface area are provided around the outer circumference of the sleeve body; The grabbing portion is arranged in the first arc surface area of ​​the sleeve body, and the grabbing portion is formed by extending from the outer peripheral surface of the sleeve body in the direction opposite to the axial line of the sleeve body.

2. The blade root embedded part according to claim 1, characterized in that: On the side of the sleeve body that penetrates the bolt, the angle between the extension direction of the grabbing portion and the axis of the sleeve body is R; The value range of R is 30° to 90°; Preferably, the value of R is 90°.

3. The blade root embedded part according to claim 1, characterized in that: The number of the first arc surface areas is two, which are symmetrically distributed on the sleeve body; The number of the second arc surface areas is two, which are symmetrically distributed on the sleeve body; The first arc surface area is located between the second arc surface areas, and the area of ​​the first arc surface area is smaller than the area of ​​the second arc surface area.

4. The blade root embedded part according to claim 3, characterized in that: The straight line in which the grabbing portion extends intersects with the axis of the sleeve body; and / or The straight line where the grabbing portion extends is not in the same plane as the axis of the sleeve body; Preferably, the angle between the plurality of the grabbing portions in the same first arc surface area is 0°; The included angle between the grabbing portions in the two first arc surface areas is 180°.

5. The blade root embedded part according to claim 1, characterized in that: Along the axial direction of the sleeve body, the outer peripheral surface of the sleeve body includes concave portions and convex portions that are alternately distributed; In the first curved surface area, the grabbing portion is located on the concave portion and / or the convex portion; Preferably, in the first curved surface area, the grabbing portion is located on the convex portion.

6. The blade root embedded part according to claim 5, characterized in that: The distance between the free end of the grabbing portion located on the concave portion and the axis of the sleeve body is a; The distance between the free end of the grabbing portion located on the convex portion and the axis of the sleeve body is b; The value of a is not greater than the value of b; Preferably, the value of a is equal to the value of b.

7. The blade root embedded part according to claim 1, characterized in that: The grabbing portion is columnar and is integrally formed with the sleeve body and / or detachably connected; Along the extension direction of the grabbing portion, the cross-sectional area of ​​the grabbing portion gradually decreases; and / or Along the extension direction of the grabbing portion, the cross-sectional area of ​​the grabbing portion remains unchanged; Preferably, the sleeve body and the grabbing portion are detachably connected via a threaded connection.

8. The blade root embedded part according to claim 1, characterized in that: The grabbing portion is provided with an outer convex section at an end away from the sleeve body; The outer protrusion section is hook-shaped; and / or The cross-sectional area of ​​the convex section is larger than the cross-sectional area of ​​the adjacent portion on the grabbing portion; Preferably, the hook shape of the outer convex section is any one of L-shape, T-shape and J-shape.

9. A blade root assembly with a pre-embedded connection structure, characterized in that: include: The blade root body comprises an outer wall, an inner wall and a filler layer, wherein the filler layer is filled between the outer wall and the inner wall; The embedded connection structure comprises a blade root embedded part according to any one of claims 1 to 8 embedded in the filler layer; The sleeve body of the blade root embedded part is embedded in the filler layer, and the grabbing portion of the blade root embedded part is inserted into the outer wall and / or the inner wall.

10. The blade root assembly with a pre-embedded connection structure according to claim 9, characterized in that: The thickness of the outer wall is greater than the depth of the grabbing portion inserted into the outer wall, and the difference between the thickness and the depth is in the range of 0.5 mm to 3.5 mm. The thickness of the inner wall is greater than the depth of the grabbing portion inserted into the inner wall, and the difference between the thickness and the inner wall is in the range of 0.5 mm to 3.5 mm. Preferably, the difference between the thickness of the outer wall and the depth of the grabbing portion inserted into the outer wall is 2 mm; the difference between the thickness of the inner wall and the depth of the grabbing portion inserted into the inner wall is 2 mm.

11. A blade, characterized in that: It comprises a blade root assembly with a pre-embedded connection structure as claimed in claim 9 or 10.

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