Patent Publication Number: US-2017363064-A1

Title: Blade for wind power generator

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2016-0077456 filed on Jun. 21, 2016 in the Korean Patent Office, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a blade, more particularly, to a blade for a wind power generator. 
     2. Description of Related Art 
     Wind power generators that generate electric energy using wind power have been studied as an alternative energy source due to depletion of natural resources such as petroleum and coal natural gas due to industrial development and increase in population. 
     A wind power generator is provided with a nacelle at the top of a tower installed on the ground, and electrical energy is generated as a hub installed in the nacelle is rotated together with the blade by the wind blowing in from the front. 
     Conventional blades of wind power generator have been manufactured by mold-based method wherein synthetic resin and the like are poured into a mold. Therefore, in the case of a blade to be used in a large-sized wind power generator, there have been problems that the manufacturing cost of the mold is high and a new mold must be fabricated every time the shape of the blade is improved. 
     In addition, since the blades are fabricated by the mold-based method, there have been problems of limitations in the length of the blade for fabrication and its weight reduction. 
     In addition, since the blade is integrally formed using a mold, there has been problems of high transportation cost as well as frequent accidents occurring during transportation of the blade. 
     Accordingly, techniques for fabricating blades having a combined structure of ribs and spars have been researched, and such blade for wind power generators is disclosed in U.S. Pat. No. 9,188,102 (hereinafter, referred to as “Patent document 1”) and U.S. Patent Publication No. 2014-0119933 (hereinafter, referred to as “Patent document 2”). 
     In the blade for wind power generators of the Patent document 1, a fabric skin is coupled (bonded) to a span member and a rib of the blade to form an outer skin of the blade. In this case, rivet holes are respectively formed in a gasket, the span member and the rib which are provided in the fabric skin. Thus, the fabric skin is coupled (bonded) to the span member and the rib by inserting rivets into such rivet holes. 
     In the blade for wind power generators of the Patent document 2, a fabric strip is coupled to a rib of the blade to form an outer skin of the blade. In this case, an insertion slot is formed in the rib, and the fabric strip is inserted in the insertion slot. As described above, the fabric strip inserted into the insertion slot is fixed by an insertion member provided with a head to be inserted into the insertion slot, and due to this, the fabric strip is coupled to the rib. 
     For the case of the blade of the Patent document 1, a separate gasket formed with rivet holes must be provided in the fabric skin, and also separate rivet holes must be formed in the span member and the rib. Also, for the case of the blade of the Patent document 2, an insertion slot is formed in the rib, and an insertion member provided with a head must be provided separately. Thus, as described above, for the case of the blades of the Patent documents 1 and 2, there is a problem that a longer time is required for manufacturing the blade because the manufacturing process becomes complicated, and the manufacturing cost is increased as well. 
     For the case of the blades of the Patent documents 1 and 2, even when the fabric skin or the fabric strip is damaged due to the long time operation of the blade, the separation of the fabric skin or the fabric strip from the rib and the like is difficult, therefore, the replacement of the fabric skin or the fabric strip is not easy. Thus, there is a problem that the maintenance of the blade is difficult and the lifetime of the blade is reduced. 
     PRIOR-ART DOCUMENTS 
     Patent Documents 
     Patent document 1: US Pat. No. 9,188,102 
     Patent document 2: US patent Publication No. 2014-0119933 
     SUMMARY 
     An objective of the present invention devised to solve above described problems is to provide a blade for a wind power generator capable of reducing the manufacturing time and the manufacturing cost, and at the same time, facilitating the maintenance of the blade. 
     A blade for a wind power generator according to a first feature of the present invention characterized in that and comprises: a main spar; a front rib and a rear rib respectively located in the front side and the rear side of the main spar; and a skin, installed on the main spar, the front rib and the rear rib, constituting the outer skin of the blade, wherein the skin is coupled by a zipper formed in the skin. 
     In addition, the zipper is characterized in that and comprises an end portion zipper connecting the both end portions of the skin, wherein the end portion zipper comprises: a first end portion zipper teeth and a second end portion zipper teeth respectively formed at the both end portions of the skin; and an end portion zipper slide, slidably installed at least in any one of the end portion zipper teeth among the first end portion zipper teeth and the second end portion zipper teeth, coupling the first end portion zipper teeth and the second end portion zipper teeth to each other, wherein the end portion zipper is located in the rear side of a suction surface of the blade. 
     In addition, it is characterized in that the end portion zipper is covered by the cover portion provided in the skin, wherein the cover portion covers the end portion zipper from the front side of the suction surface of the blade towards the rear side of the suction surface of the blade. 
     In addition, a plurality of the skins is installed on the main spar and the front rib and the rear rib, and forms the outer skin of the blade, wherein the zipper comprises a side portion zipper coupling the adjacent skins among the plurality of the skins, wherein the side portion zipper comprises: a first side portion zipper teeth and a second side portion zipper teeth respectively formed in the both side portions of the plurality of the skins; and a side portion zipper slide, slidably installed at least in any one of the side portion zipper teeth among the first side portion zipper teeth and the second side portion zipper teeth, coupling the first side portion zipper teeth and the second side portion zipper teeth of the adjacent skins among the plurality of the skins to each other, wherein the side portion zipper is located on the airfoil of the blade formed by the main spar, the first rib and the rear rib. 
     According to a blade for a wind power generator of the present invention, as previously described, there are advantageous effects as follows. 
     Since no separate rivets and rivet holes are required for the coupling of the skin to the components of the blade, reduction of the manufacturing time and the manufacturing cost of the blade for a wind power generator can be achieved. 
     Since the skin can be easily separated from the spar and the rib, the replacement of the skin becomes possible so that the maintenance is easy, and due to this, the lifetime of the blade for a wind power generator can be extended. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a wind power generator provided with a blade according to a preferred exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view of a blade according to the preferred exemplary embodiment of the present invention. 
         FIG. 3  is a perspective view illustrating the main spar, the front rib and the rear rib in  FIG. 2 . 
         FIG. 4  is a plan view illustrating the skin of the blade in  FIG. 2 . 
         FIGS. 5 and 6  are the perspective views illustrating the installation of the skin on the main spar, the front rib and the rear rib in  FIG. 3 . 
         FIG. 7  is a perspective view illustrating the skin of the blade in  FIG. 2  provided with a cover portion. 
     
    
    
     DESCRIPTION OF SYMBOLS 
       
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                  10: wind power generator 
                  11: tower 
               
               
                   
                  13: nacelle 
                  15: hub 
               
               
                   
                 100: blade 
                 101: blade root 
               
               
                   
                 102: blade tip 
                 103: leading edge 
               
               
                   
                 104: trailing edge 
                 106: suction surface 
               
               
                   
                 107: pressure surface 
                 110: main spar 
               
               
                   
                 130: front rib 
                 131: front convex portion 
               
               
                   
                 150: rear rib 
                 151: rear protrusion 
               
               
                   
                 200: skin 
                 210: end portion zipper 
               
            
           
           
               
               
            
               
                   
                 211: first end portion zipper teeth 
               
               
                   
                 212: second end portion zipper teeth 
               
               
                   
                 214: end portion zipper slide 
               
               
                   
                 216: first end portion zipper stopper 
               
               
                   
                 217: second end portion zipper stopper 
               
               
                   
                 230: side portion zipper 
               
               
                   
                 231: first side portion zipper teeth 
               
               
                   
                 232: second side portion zipper teeth 
               
               
                   
                 234: side portion zipper slide 
               
               
                   
                 236: first side portion zipper stopper 
               
               
                   
                 237: second side portion zipper stopper 
               
               
                   
                 250: cover portion 
               
               
                   
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the preferred exemplary embodiments of the present invention will be described with reference to the accompanying drawings as follows. 
       FIG. 1  is a side view of a wind power generator provided with a blade according to a preferred exemplary embodiment of the present invention;  FIG. 2  is a perspective view of a blade according to the preferred exemplary embodiment of the present invention;  FIG. 3  is a perspective view illustrating the main spar, the front rib and the rear rib in  FIG. 2 ;  FIG. 4  is a plan view illustrating the skin of the blade in  FIG. 2 ;  FIGS. 5 and 6  are the perspective views illustrating the installation of the skin on the main spar, the front rib and the rear rib in  FIG. 3 ; and  FIG. 7  is a perspective view illustrating the skin of the blade in  FIG. 2  provided with a cover portion. 
     As illustrated in  FIG. 1 , a wind power generator  10  equipped with blades  100  according to the preferred exemplary embodiment of the present invention comprises: a tower  11 , a nacelle  13 , a hub  15  and a plurality of blades  100 . 
     The tower  11  is fixedly installed in the ground surface, and performs supporting function for the nacelle  13 , the hub  15  and the blades  100 . In this case, it is preferred that the tower  11  is installed in a place where the atmospheric interference can be minimized such as a ridge of a mountain, above the sea, or a roof of a building. 
     The hub  15  is installed in the front end portion of the nacelle  13 , and can be coupled to the nacelle  13  so that it can be rotated centered around the axis. Hereinafter, a blade  100  according to the preferred exemplary embodiment of the present invention will be described. 
     As illustrated in  FIGS. 2 and 5 , the blade  100  has an airfoil cross-section, and it may be installed in the hub  15  in multiple numbers in a way that they have a certain angle of attack with respect to the wind blowing from the front of the wind power generator  10 . 
     A blade root  101  is provided at the one end of the blade  100 , and a blade tip  102  is provided at the other end thereof. In this case, the direction from the blade root  101  towards the blade tip  102  is referred to as a spanwise direction. 
     The blade root  101  is the region wherein the blade  100  and the hub  15  are jointed, and the blade tip  102  is the region wherein the cross-sectional area of the blade  100  is getting smaller as it travels along the spanwise direction towards the other end of the blade  100 . 
     In addition, a leading edge  103  is formed in the front side of the blade  100 , and a trailing edge  104  is formed in the rear side of the blade  100 . In this case, the direction from the leading edge  103  towards the flat back  104  is referred to as a chordwise direction. 
     The upper surface of the blade  100  is comprised of a suction surface  106 , and the lower surface of the blade  100  is comprised of a pressure surface  107 . 
     The suction surface  106  is an approximately convex surface, and it is a surface wherein the pressure is reduced because the wind blowing towards the leading edge  103  of the blade  100  is passing through this surface with a relatively higher speed. 
     The pressure surface  107  is an approximately concave surface, and it is a surface wherein the pressure is reduced because the wind blowing towards the leading edge  103  of the blade  100  is passing through this surface with a relatively slower speed. 
     The difference between the wind speeds in the suction surface  106  and the pressure surface  107 , as described above, generates a lifting force directing from the pressure surface  107  towards the suction surface  106  in the blade  100 , and the generated lifting force rotates the blade  100  thereby. 
     In other words, as the wind blowing from the front side of the wind power generator  10  passes through the surface of the blade  100 , a lifting force is generated; the lifting force generated in this way rotates the blade  100  and the hub  15 , and the rotational force of the blade  100  and the hub  15  is transferred to the nacelle  13  and converted into the electrical energy thereby. 
     The blade  100  according to the preferred exemplary embodiment of the present invention comprises: a main spar  110 ; a front rib  130  and a rear rib  150  respectively located in the front side and the rear side of the main spar  110 ; and a skin  200 , installed on the main spar  110  and the front rib  130  and the rear rib  150 , constituting the outer skin. 
     Hereinafter, the main spar  110 , the front rib  130  and the rear rib  150  of the blade  100  according to the preferred exemplary embodiment of the present invention will be described. 
     As illustrated in  FIGS. 3, 5 and 6 , the main spar  110  has a length along the spanwise direction of the blade  100 , and forms a frame along the spanwise direction of the blade  100 . 
     In the front side surface of the main spar  110 , a plurality of front ribs  130  is disposed along the spanwise direction of the blade  100 ; in the rear side surface of the main spar  110 , a plurality of rear ribs  150  is disposed along the spanwise direction of the blade  100 . 
     The front rib  130  has a cross-section similar to an ‘inverted D,’ and the rear side surface is connected to the front side surface of the main spar  110 , and forms a frame along the spanwise direction of the blade  100  thereby. 
     A plurality of front ribs  130  may be connected and disposed in the front side surface of the main spar  110  along the spanwise direction of the blade  100 . 
     In addition, the front surface of each of the plurality of front ribs  130  is formed with a front convex portion  131  forwardly convex, and due to such front convex portion  131 , the shape of the leading edge  103  of the blade  100  is accomplished. 
     The front surface of the rear rib  150  is connected to the rear side surface of the main spar  110 , and forms a frame along the chordwise direction of the blade  100  thereby. 
     A plurality of rear ribs  150  may be connected and disposed in the rear side surface of the main spar  110  along the spanwise direction of the blade  100 . 
     In the rear side of the rear rib  150 , a rear protruded portion  151  where the upper surface and the lower surface of the rear rib  150  are meet. Such rear protruded portion  151 , together with the skin  200 , forms the shape of the trailing edge  104  of the blade  100 . 
     As described above, the plurality of front ribs  130  and the plurality of rear ribs  150  are disposed in multiple numbers respectively in the front side surface and the rear side surface of the main spar  110  along the spanwise direction of the blade  100 . In this case, it is preferred that the plurality of front ribs  130  and the plurality of rear ribs  150  are disposed to have an equal separation distance. In other words, the plurality of front ribs  130  is disposed in the front side surface of the main spar  110  with an equal separation distance, and the plurality of rear ribs  150  is disposed in the front side surface of the main spar  110  with an equal separation distance, and it is preferred that the equal separation distances of the plurality of front ribs  130  and the plurality of rear ribs  150  are formed to be equal. 
     As described above, as the plurality of front ribs  130  and the plurality of rear ribs  150  have an equal separation distance in common, the weight of the blade  100  can be uniformly distributed thereby. In addition, by fabricating the width (length along the spanwise direction) of skin  300  for the blade to be the same as the equal separation distance of the plurality of front ribs  130  and the plurality of rear ribs  150 , the skin  300  for the blade can be easily installed in the blade  100 . 
     The above described main spar  110 , front rib  130  and rear rib  150  form the cross-sectional shape of the blade  100 , and such cross-section of the blade  100  is referred to as an airfoil. 
     The airfoil of the blade  100  has a forwardly convex shape due to the front convex portion  131  of the front rib  130 , and this forms (forms) the leading edge  103  of the blade  100 . 
     In addition, the rear side of the airfoil of the blade  100  has a protruded shape due to the rear protruded portion  151 , and this forms (forms) the trailing edge  104  of the blade  100 . 
     The airfoil of the blade  100  has approximately an upwardly convex shape due to the upper surface of the front rib  130  and the upper surface of the rear rib  150  of the main spar  110 , and this forms the suction space  106  of the blade  100 . 
     The airfoil of the blade  100  has approximately a concave shape due to the lower surface of the front rib  130  and the lower surface of the rear rib  150  of the main spar  110 , and this forms the pressure space  107  of the blade  100 . 
     The airfoil of the blade  100  may be formed in a way that the size thereof is getting smaller as it travels toward the blade tip  102 . 
     In other words, in the spanwise direction of the blade  100 , the size of airfoil of the blade (that is, cross-section of blade  100 ) may be formed in a way that it is getting smaller as it travels from the blade root  101  towards the blade tip  102 , for this configuration, the sizes of the main spar  110 , the front rib  130  and the rear rib  150  may be formed in a way that the sizes thereof are getting smaller as it travels along the direction towards the blade tip  102 . 
     Hereinafter, the skin  200  of the blade  100  according to the preferred exemplary embodiment of the present invention will be described. 
     As illustrated in  FIGS. 2 to 6 , the skin  200  is installed on the main spar  110 , the front rib  130  and the rear rib  150 , and forms the outer skin of the blade  100  thereby. 
     The skin  200  may be comprised of many skins; in this case, a plurality of the skins  200  is installed on the main spar  110 , and the front rib  130  and the rear rib  150 , and may form the outer skin of the blade  100 . In this way, when the plurality of the skins  200  forms the outer skin of the blade  100 , there is an advantage that easiness in manufacturing can be achieved when the blade  100  is to be manufactured in a large size. 
     Each of the plurality of the skins  200  has a length and a width. The length of the skin  200  is corresponding to the length along the chordwise direction of the blade  100 , and hereinafter, the both ends along the lengthwise direction of the skin  200  will be referred to as the both ends of the skin  200 , that is, one end portion and other end portion of the skin. The width of the skin  200  is corresponding to the length along the spanwise direction of the blade  100 , and hereinafter, the both ends along the widthwise direction of the skin  200  will be referred to as the both sides of the skin  200 , that is, one side portion and other side portion of the skin  200 . 
     It is preferred that the above described length of the skin, that is, the length between the both ends, is formed to be the size just enough to cover the main spar  110 , and the front rib  130  and the rear rib  150 , and due to this, the skin  200  can be easily installed on the main spar  110 , and the front rib  130  and the rear rib  150 . 
     In addition, when the skin  200  is comprised of many skins, although the width, that is the distance between the both side portions, of each of the plurality of the skins  200  may be formed in various sizes, it is preferred that the total width of the plurality of the skins  200 , wherein all the multiple numbers of skins are combined, is corresponding to the length of the blade  100  along the spanwise direction, and due to this, the plurality of the skins  200  can be easily installed on the main spar  110 , and the front rib  130  and the rear rib  150 . 
     Each of the plurality of the skins  200  is composed of a composite material including a fabric (fiber) material, and a zipper is formed in each of the plurality of the skins  200 . 
     The zipper formed in each of the plurality of the skins  200  comprises: an end portion zipper  210  coupling the both end portions of the plurality of the skins  200 ; and a side portion zipper  230  coupling the adjacent skins  200  among the plurality of the skins  200 . 
     Hereinafter, the end portion zipper  210  will be described. 
     The end portion zipper  210  comprises: a first end portion zipper teeth  211 ; a second end portion zipper teeth  212 ; an end portion zipper slide  214  slidably installed in the second end portion zipper teeth  212 ; a first end portion zipper stopper  216 ; and a second end portion zipper stopper  217 . The first end portion zipper teeth  211  is formed at the one end portion of the skin  200 , and the second end portion zipper teeth  212  is formed at the other end portion of the skin  200 . In this case, the first end portion zipper teeth  211  and the second end portion zipper teeth  212  are formed not in all but only in the region excluding a part of the region of the both end portions of the skin  200  to facilitate coupling of a first side portion zipper teeth  231  and a second side portion zipper teeth  232  of the side portion zipper  230 , which will be described later. In other words, the first end portion zipper teeth  211  and the second end portion zipper teeth  212  are formed only in the region excluding the corner region where the both end portions and the both side portions meet, and the first end portion zipper teeth  211  and the second end portion zipper teeth  212  are not formed in the corner region. Thus, when teeth coupling between the first side portion zipper teeth  231  and the second side portion zipper teeth  232  are accomplished, the first end portion zipper teeth  211  and the second end portion zipper teeth  212  will not interfere the teeth coupling between the first side portion zipper teeth  231  and the second side portion zipper teeth  232 , and due to this, the coupling of the end portion zipper  210  and the side portion zipper  230  can be accomplished easily. 
     The end portion zipper slide  214  is installed in the second end portion zipper teeth  212  and slidable within the range of the first end portion zipper stopper  216  and the second end portion zipper stopper  217  provided in the second end portion zipper teeth  212 . 
     Thus, after the first end portion zipper teeth  211  is inserted into the first end portion zipper stopper  216 , the end portion zipper slide  214  is slided from the first end portion zipper stopper  216  towards the second end portion zipper stopper  217  so that the first end portion zipper teeth  211  and the second end portion zipper teeth  212  can be coupled. 
     Unlike the above description, the end portion zipper slide  214  may be installed in the first end portion zipper teeth  211 . In this case, the first end portion zipper stopper  216  towards the second end portion zipper stopper  217  is provided in the first end portion zipper teeth  211 , and the end portion zipper slide  214  can be slided within the range of the first end portion zipper stopper  216  towards the second end portion zipper stopper  217  provided in the first end portion zipper teeth  211 . 
     Hereinafter, the side portion zipper  230  will be described. 
     The side portion zipper  230  comprises: a first side portion zipper teeth  231  and a second side portion zipper teeth  232  respectively formed at the both side portions of the skin  200 ; a side portion zipper slide  234  slidably installed in the second side portion zipper teeth  232 ; and a first side portion zipper stopper  236  and a second side portion zipper stopper  237  provided in the second side portion zipper teeth  232 . 
     The first side portion zipper teeth  231  is formed in the one side portion of the skin  200 , and the second side portion zipper teeth  232  is formed in the other side portion of the skin  200 . In this case, the first side portion zipper teeth  231  and the second side portion zipper teeth  232  is formed in the entire region of the both side portions of the skin  200 . 
     The side portion zipper slide  234  is installed in the second side portion zipper teeth  232  and slidable within the range of the first side portion zipper stopper  236  and the second side portion zipper stopper  237  provided in the second side portion zipper teeth  232 . Thus, after the first side portion zipper teeth  231  is inserted into the first side portion zipper stopper  236 , the side portion zipper slide  234  is slided from the first side portion zipper stopper  236  towards the second side portion zipper stopper  237  so that the first side portion zipper teeth  231  and a second side portion zipper teeth  232  can be coupled through teeth. 
     Unlike the above description, the side portion zipper slide  234  may be installed in the first side portion zipper teeth  231 . In this case, the first side portion zipper stopper  236  and the second side portion zipper stopper  237  are provided in the first side portion zipper teeth  231 , and the side portion zipper slide  234  is slidable within the range of the first side portion zipper stopper  236  and the second side portion zipper stopper  237  provided in the first side portion zipper teeth  231 . 
     The above described the first side portion zipper teeth  231  and the second side portion zipper teeth  232  may not be installed in all of the plurality of the skins  200 . 
     To be explained more specifically, in the case of the skin  200  that forms the outer skin of the blade root  101  among the plurality of the skins  200 , the first side portion zipper teeth  231  is not formed in the one side portion thereof since there is no other skin  200  to be coupled towards the one side portion of the skin  200 . In this way, in the case of the skin  200  that forms the outer skin of the blade root  101  among the plurality of the skins  200 , since there is no first side portion zipper teeth  231 , the first end portion zipper teeth  211  and the second end portion zipper teeth  212  can be formed up to the corner along the direction of the one side portion of the skin  200 . 
     In addition, in the case of the skin  200  that forms the outer skin of the blade tip  102  among the plurality of the skins  200 , the second side portion zipper teeth  232  is not formed in the other side portion thereof since there is no other skin  200  to be coupled towards the other side portion of the skin  200 . In this way, in the case of the skin  200  that forms the outer skin of the blade tip  102 , since there is no second side portion zipper teeth  232 , the first end portion zipper teeth  211  and the second end portion zipper teeth  212  can be formed up to the corner along the direction of the other side portion of the skin  200 . 
     Hereinafter, a method wherein the above described plurality of the skins  200  is installed on the main spar  110 , the front rib  130  and the rear rib  150  so as to manufacture the blade  100  according to an exemplary embodiment of the present invention will be described. 
     It is preferred that the plurality of the skins  200  is sequentially installed along the spanwise direction of the blade  100 . 
     Thus, as illustrated in  FIG. 5 , first, a skin  200  (hereinafter, referred to as a first skin  200 ) to form the outer skin of the blade root  101  is wrapped around the main spar  110 , the front rib  130  and the rear rib  150 . In this case, the first skin  200  is positioned in a way that the end portion zipper  210  of the first skin  200 , that is, the first end portion zipper teeth  211  and the second end portion zipper teeth  212 , is located in the rear side of the suction surface  106  of the blade  100 . 
     As described above, after the first skin  200  is positioned, as previously described, the first end portion zipper teeth  211  is inserted into the first end portion zipper stopper  216  provided in the second end portion zipper teeth  212 , and then, the end portion zipper slide  214  is slided from the first end portion zipper stopper  216  up to the second end portion zipper stopper  217 . 
     When the end portion zipper slide  214  is slided completely up to the second end portion zipper stopper  217 , the first end portion zipper teeth  211  and the second end portion zipper teeth  212  are coupled each other through teeth, due to this, the both end portions of the first skin  200 , that is, the one end portion and the other end portion are mutually coupled. Therefore, the first skin  200  is installed on the main spar  110 , the front rib  130  and the rear rib  150  without using a separate adhesive and the like. 
     In this way, after the installation of the first skin  200  forming the outer skin of the blade root  101  completely, a second skin  200  adjacent to the first skin  200  is installed. 
     First, after the first side portion zipper teeth  231  of the second skin  200  is inserted into the first side portion zipper stopper  236  provided in the second side portion zipper teeth  232  of the first skin  200 , the side portion zipper slide  234  is slided from the first side portion zipper stopper  236  up to the second side portion zipper stopper  237 . 
     When the side portion zipper slide  234  is slided up to the second side portion zipper stopper  237  completely, the second side portion zipper teeth  232  of the first skin  200  and the first side portion zipper teeth  231  of the second skin  200  are mutually coupled through teeth, and due to this, the other side portion of the first skin  200  and the one side portion of the second skin  200  are mutually coupled. Therefore, the first skin  200  and the second skin  200  are mutually coupled without using a separate adhesive and the like. 
     In this way, after the first skin  200  and the second skin  200  are mutually coupled, the first end portion zipper teeth  211  and the second end portion zipper teeth  212  of the second skin  200  are mutually coupled using the same method as described in the first skin  200 , and then the installation of the second skin  200  is completed. 
     The above described the installation methods for the first skin  200  and the second skin  200  are repeated up to the skin  200  that forms the outer skin of the blade tip  102  region, the installation of the plurality of the skins  200  is completed, and due to this, the plurality of the skins  200  is installed on the main spar  110 , the front rib  130  and the rear rib  150 , thereby forming the outer skin of the blade  100 . 
     As described above, in the blade  100  according to the preferred exemplary embodiment of the present invention, a plurality of the skins  200  is installed on the main spar  110 , the front rib  130  and the rear rib  150  through zipper-coupling so as to form the outer skin of the blade, therefore, unlike the blade of the prior art, since neither separate rivets nor rivet holes are required for the coupling of the skins, the reduction of the manufacturing time and cost of the blade  100  can be achieved. 
     In addition, the plurality of the skins  200  is coupled through zipper-coupling, that is, the coupling of the end portion zipper  210  and the side portion zipper  230 , the skins  200  can be easily separated from the main spar  110 , the front rib  130  and the rear rib  150  by releasing the teeth coupling of the end portion zipper  210  and/or the side portion zipper  230 , and due to this, the skin  200  can be easily replaced. Thus, the maintenance of the blade  100  of the wind power generator  10  to be used long period of time or more can be facilitated, and due to this, the lifetime of the wind power generator  10  can be extended. 
     As described above, when the plurality of the skins  200  is installed on the main spar  110 , the front rib  130  and the rear rib  150  and forms the outer skin of the blade  100 , the side portion zipper  230  of each of the plurality of the skins  200  is located on the airfoil of the blade  100  formed by the main spar  110 , the front rib  130  and the rear rib  150 . In other words, the side portion zipper  230  is located on the airfoil of the blade  100  forming a kind of strip in the shape like the outer surface of the front rib  130  and the rear rib  150 . 
     It is preferred that the side portion zipper slide  234  of the side portion zipper  230  is not to be exposed towards the outside, that is, the outer surface of the blade  100 , to achieve this, the side portion zipper slide  234  may be installed towards the opposite location (the side portion zipper slide  234  is facing towards the inner surface of the blade  100 ) as illustrated in  FIG. 6 . Thus, the side portion zipper slide  234  is protected from being exposed to the outer surface of the blade  100 ; due to this, the outer surface of the blade  100  of the region, wherein the side portion zipper  230  is formed, can be maintained relatively smooth, so that the generation of the lifting force of the blade  100  can be facilitated. 
     As described above, when the plurality of the skins  200  is installed on the main spar  110 , the front rib  130  and the rear rib  150  and forms the outer skin of the blade  100 , every end portion zipper  210  of each of the plurality of the skins  200  is located in the rear side of the suction surface  106  of the blade  100 . In this way, as the end portion zipper  210  is located in the rear side of the suction surface  106  of the blade  100 , the lifting force of the blade  100  can be facilitated. 
     To be explained more specifically, as the wind is blowing towards the leading edge  103  of the blade  100  in order to rotate the blade  100 , the wind is passing through the suction surface  106  of the blade  100  with a high speed. In this case, the front side of the suction surface  106 , that is, the region, among the suction surface  106 , located close to the leading edge  103 , is the region to where the wind is directly blowing in, therefore, if the end portion zipper  210  is located in the front side of the suction surface  106 , turbulence is formed so that the lifting force of the blade  100  cannot be generated effectively. However, as described above, when the end portion zipper  210  is located in the rear side of the suction surface  106 , turbulence is not produced since the rear side of the suction surface  106  is not the region to where the wind is directly blowing in, and due to this, the generation of lifting force of the blade  100  is not affected, therefore the generation of lifting force of the blade  100  can be facilitated. 
     Furthermore, as described above, since the first end portion zipper teeth  211  and the second end portion zipper teeth  212  are not formed in all the region of the both end portions of the skin  200 ; it is possible that there may be a non-zipper-coupled region (as a corner portion where the both end portions of the skin  200  meet, and where the first end portion zipper teeth  211  and the second end portion zipper teeth  212  are not formed), however, since this is also located in the rear side of the suction surface  106 , the generation of lifting force of the blade  100  is not affected significantly. 
     As illustrated in  FIG. 7 , in each of the plurality of the skins  200  of the blade  100  according to the preferred exemplary embodiment of the present invention may further comprise a cover portion  250 . 
     In this case, the cover portion  250  is provided in the skin  200  in a way that the one end portion of the cover portion  250  and the both side portions of the cover  250  are connected to the skin  200 . Thus, the cover portion  250  covers the end portion zipper  210  from the front side direction of the suction surface  106  of the blade  100  toward the rear side direction of the suction surface  106  of the blade  100 . The cover portion  250  is provided in the way described above, so that the end portion zipper slide  214  of the end portion zipper  210  is not exposed to the outer surface of the blade  100 , therefore the generation of the lifting force of the blade  100  can be facilitated. In addition, the region where the above described zipper-coupling is not accomplished is also covered by the cover portion  250 , therefore, the seam portion of the region where the zipper-coupling is not accomplished is not exposed towards outside. 
     Furthermore, the cover portion  250  and the skin  200  can cover the end portion zipper  210  more certainly since the regions except the other end portion of the cover portion  250 , in other words, the one end portion and the both side portions, are connected to one another. 
     To be explained more specifically, when the wind is blowing towards the leading edge  103  of the blade  100  and passing through the surface of the suction surface  106 , the space formed between the cover portion  250  and the skin  200  is getting smaller due to the force of the wind so that the cover portion  250  and the skin  200  are more closely contacted, and due to this, the cover portion  250  can cover the end portion zipper  210  more certainly. Thus, the rear side of the suction surface  106  of the blade  100  can be maintained to be relatively smooth, and due to this, the generation of the lifting force of the blade  100  can be facilitated. 
     As described above, although the present invention has been described with reference to the preferred exemplary embodiments, various changes and alterations of the present invention can be made by those skilled in the art without departing from the spirit and the scope of the present invention written in the claims described herein below.