Patent Publication Number: US-11662028-B2

Title: Butterfly valve and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 16/659,489, which was filed on Oct. 21, 2019, and which is a continuation application of U.S. application Ser. No. 16/659,489, which was filed on Oct. 21, 2019, and which is a continuation application of PCT application filed on Jan. 23, 2019 and assigned Serial No. PCT/KR2019/000975, and which claims priority from Korean Patent Application No. 10-2018-0048160 filed with the Korean Intellectual Property Office on Apr. 25, 2018, Korean Patent Application No. 10-2018-0167205 filed with the Korean Intellectual Property Office on Dec. 21, 2018, Korean Patent Application No. 10-2018-0167458 filed with the Korean Intellectual Property Office on Dec. 21, 2018, Korean Patent Application No. 10-2018-0167460 filed with the Korean Intellectual Property Office on Dec. 21, 2018, Korean Patent Application No. 10-2018-0167461 filed with the Korean Intellectual Property Office on Dec. 21, 2018, and Korean Patent Application No. 10-2018-0167459 filed with the Korean Intellectual Property Office on Dec. 21, 2018. The entire disclosures of above patent applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a butterfly valve and method of manufacturing the same. 
     BACKGROUND 
     Conventional butterfly valve is formed of only steel, and thus its strength is high, but it is easy to be corroded, its weight is heavy and its manufacture cost has increased. Specially, the butterfly valve should be precisely processed, but it is difficult to process precisely the butterfly valve because the butterfly valve is formed of the steel. Accordingly, it is impossible to achieve mass production. 
     SUMMARY 
     To solve problem of the convention technique, the present disclosure is to provide a butterfly valve which may enhance corrosion resistance or acid resistance with keeping its strength, have light weight and realize mass production, and method of manufacturing the same. 
     A butterfly valve according to an embodiment of the present disclosure comprises a body in which an inserting space is formed; and a disk inserted into the inserting space of the body. Here, fluid flow is opened or closed in response to rotation of the disk. The disk includes: a disk body formed of a metal; a first plastic layer formed of a first plastic on the disk body; and a second plastic layer formed of a second plastic on the first plastic layer, wherein a melting point of the first plastic layer is higher than a melting point of the second plastic layer. 
     A disk used in a butterfly valve according to an embodiment of the present disclosure comprises a disk body formed of a metal; a first plastic layer formed on the disk body and formed of a first plastic; and a second plastic layer formed on the first plastic layer and formed of a second plastic. Here, wherein a melting point of the first plastic is different from a melting point of the second plastic. 
     A body covering a disk in a butterfly valve according to an embodiment of the present disclosure comprises: an upper body; and a lower body. Here, an inserting space is formed by combining the upper body with the lower body, the disk is inserted into the inserting space, and at least one of the upper body and the lower body includes a framework formed of a metal and a plastic layer formed on the framework. 
     A fluid contacting member contacted with a fluid in a valve according to an embodiment of the present disclosure comprises: a body formed of a metal and manufactured by using a mechanical processing; a first plastic layer formed on the body and formed of a first plastic; and a second plastic layer formed on the first plastic layer and formed of a second plastic. Here, the plastic layers are formed through an insert molding, and a melting point of the first plastic is different from a melting point of the second plastic. 
     A method of manufacturing a disk used in a butterfly valve according to an embodiment of the present disclosure comprises: forming a first plastic layer on a disk body formed of a metal through an insert molding; and forming a second plastic layer on the first plastic layer through an insert molding. Here, a melting point of a first plastic of the first plastic layer is different from a melting point of a second plastic of the second plastic layer. 
     Butterfly valve and method of manufacturing the same according to the present disclosure use a disk including a disk body formed of a metal and plastic layers formed on the disk body through an insert molding, thus the butterfly valve may have enhanced corrosion resistance or acid resistance with keeping similar strength to a butterfly valve formed of only steel. 
     Additionally, a weight of the butterfly valve has reduced, it is easy to mold the butterfly valve and so it is possible to achieve mass production. Of course, it is possible to manufacture precisely the butterfly valve. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Example embodiments of the present disclosure will become more apparent by describing in detail example embodiments of the present disclosure with reference to the accompanying drawings, in which: 
         FIG.  1    is a perspective view illustrating a butterfly valve according to an embodiment of the present disclosure; 
         FIG.  2    is a view illustrating a disassemble structure of the butterfly valve according to an embodiment of the present disclosure; 
         FIG.  3    is a view illustrating a disk according to an embodiment of the present disclosure; 
         FIG.  4    is a view illustrating partial section of the disk according to an embodiment of the present disclosure; 
         FIG.  5    is a view illustrating an upper body and a lower body according to an embodiment of the present disclosure; and 
         FIG.  6    is a view illustrating a disk body according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the present specification, an expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present specification, terms such as “comprising” or “including,” etc., should not be interpreted as meaning that all of the elements or operations are necessarily included. That is, some of the elements or operations may not be included, while other additional elements or operations may be further included. Also, terms such as “unit,” “module,” etc., as used in the present specification may refer to a part for processing at least one function or action and may be implemented as hardware, software, or a combination of hardware and software. 
     Embodiments of the present disclosure relate to a valve, particularly a butterfly valve. The butterfly valve may have enhanced lifetime and corrosion resistance, etc. with keeping similar strength and precision to a butterfly valve formed of only steel. Furthermore, manufacture cost of the butterfly may be considerably reduced, productivity of the butterfly valve may be highly enhanced and it is possible to realize mass production. 
     Conventional butterfly valve is formed of only steel, and thus its strength is high, but it is difficult to process precisely the butterfly valve and so productivity of the butterfly valve has lowered and manufacturing cost of the butterfly valve is high. Moreover, the butterfly valve has been easily corroded when it is used in a ship, a water treatment apparatus (a seawater desalination apparatus, a wastewater treatment apparatus) and so on, and thus it can&#39;t use the butterfly valve more than one year. 
     The butterfly valve of the present disclosure may enhance corrosion resistance, lifetime (more than 10 years), reduce manufacturing cost and reduce weight by molding plastic on a metal, e.g. a light metal such as aluminum. 
     Of course, the present technique is not limited to the butterfly valve, and it is applicable to any valves as described below. 
     Hereinafter, various embodiments of the disclosure will be described in detail with reference to accompanying drawings. 
       FIG.  1    is a perspective view illustrating a butterfly valve according to an embodiment of the disclosure,  FIG.  2    is a view illustrating a disassemble structure of the butterfly valve according to an embodiment of the disclosure, and  FIG.  3    is a view illustrating a disk according to an embodiment of the disclosure.  FIG.  4    is a view illustrating partial section of the disk according to an embodiment of the disclosure,  FIG.  5    is a view illustrating an upper body and a lower body according to an embodiment of the disclosure, and  FIG.  6    is a view illustrating a disk body according to an embodiment of the disclosure. 
     In  FIG.  1   , the butterfly valve of the present embodiment includes a disk  100 , a disk supporting member  102  and a body  104 . In another embodiment, the butterfly valve may include only the disk  100  and the body  104  without the disk supporting member  102 . 
     The disk  100  may be manufactured by forming plastics on a metal, e.g. a light metal such as aluminum through two consecutive molding as described below, and opens or closes flow of a fluid. The disk  100  is opened according as it rotates by for example 90° when the fluid flows through the butterfly valve, and the disk  100  is closed as shown in  FIG.  1    when the flowing of the fluid is blocked. 
     The disk supporting member  102  supports stably the disk  100 , and it may be formed of a fluorine resin, for example a Polytetrafluoroethylene, PTFE, a Perfluoroalkoxy alkane PFA or a Polyvinylidene fluoride PVDF, etc. The fluorine resin means every resin including fluorine in a molecule, and has excellent heat resistance, excellent chemical resistance, excellent electric insulation, small friction coefficient, and does not have adhesion. 
     The body  104  covers the disk supporting member  102 , and may be formed by mixing a glass fiber with for example a Polyvinyl Chloride PVC, a polypropylene PP, a Poly Phenylene sulfide PPS, a Polyphthalamide PPA, a Polyamide PA6, a Polyamide PA66, a Polyketone POK or a Polyethylene PE. As a result, strength, impact resistance and mechanical feature of the body  104  may be enhanced. This will be described in detail below. 
     In another embodiment, the body  104  may be formed by mixing a glass fiber and a carbon fiber with for example, a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. Accordingly, strength, impact resistance and mechanical feature of the body  104  may be enhanced. 
     In still another embodiment, the body  104  may be formed by mixing a glass fiber, a carbon fiber and a graphite fiber with for example, a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. As a result, strength, impact resistance and mechanical feature of the body  104  may be enhanced. 
     Hereinafter, structure and combination of elements in the butterfly valve of the disclosure will be described in detail. 
     In  FIG.  2    to  FIG.  5   , a disk  100  may include an opening-closing member  100   a , a manipulation member  100   b  and a fixing member  100   c.    
     The opening-closing member  100   a  opens or closes flow of a fluid, and may have for example a circular shape. A structure of the opening-closing member  100   a  will be described below. 
     The manipulation member  100   b  is connected to an upper part of the opening-closing member  100   a , and it is projected in an upward direction. The manipulation member  100   b  is projected in an upward direction of an upper body  104   a  through a hole  510  formed at a central part of the upper body  104   a , as shown in  FIG.  1   . The manipulation member  100   b  is combined with a control unit (not shown), and rotates in response to control of the control unit. As a result, the opening-closing member  100   a  is rotated, and thus an opening-closing operation is performed. 
     The fixing member  100   c  is inserted into a hole  540  formed at a central part of a lower body  104   b , and so the disk  100  may be stably fixed to the body  104 . The fixing member  100   c  is not projected outside when it is inserted, and it may have smaller length than the manipulation member  100   b.    
     The disk supporting member  102  may include a first supporting member  102   a  and a second supporting member  102   b.    
     The first supporting member  102   a  may have the same shape as the opening-closing member  100   a , e.g. circular shape, and it may have a size higher than the opening-closing member  100   a.    
     In an embodiment, a space (hole)  208  may be formed through a front surface and a rear surface of the first supporting member  102   a , and a home  209  may be formed along general circumference of the first supporting member  102   a.    
     In an embodiment, the hole  200  into which the manipulation member  100   b  is inserted is formed at a top central part of the first supporting member  102   a , and a hole  202  into which the fixing member  100   c  is inserted may be formed at a lower central part of the first supporting member  102   a.    
     The second supporting member  102   b  may have the same shape, e.g. circular shape as the opening-closing member  100   a , an opening member  204  may be formed at a top central part of the second supporting member  102   b , an opening member may be formed at a lower central part of the second supporting member  102   b , and holes may be respectively formed on the opening member  204  and the opening member. Here, a hole of the opening member  204  corresponds to the hole  200  formed on the top of the first supporting member  102   a , and a hole of the opening member formed at the lower central part corresponds to the hole  202  formed on the lower part of the first supporting member  102   a.    
     In an embodiment, the second supporting member  102   b  may be formed of an Ethylene Propylene Diene Monomer EPDM, a Fluoro Elastomers FKM or a silicon, etc. 
     The opening-closing member  100   a  of the disk  100  may be inserted into the space  208  of the first supporting member  102   a , and the second supporting member  102   b  may be combined on a home  209  formed at the top of the first supporting member  102   a . That is, the second supporting member  102   b  fixes stably the opening-closing member  100   a  by applying a pressure to the opening-closing member  100   a  of the disk  100  inserted in the space  208  of the first supporting member  102   a.    
     In an embodiment, the opening-closing member  100   a  of the disk  100  has a little higher size than the space  208  of the first supporting member  102   a . An outermost part of the opening-closing member  100   a  is made up of a plastic to have elasticity, and thus the opening-closing member  100   a  may be inserted into the space  208  of the first supporting member  102   a.    
     The manipulation member  100   b  may be exposed outside through a hole  510  formed to a top central part of the upper body  104   a , and the fixing member  100   c  may be inserted into a hole  540  formed to a lower central part of the lower body  104   b.    
     Here, the manipulation member  100   b  may be stably fixed to the supporting members  102   a  and  102   b  and the upper body  104   a  by using fastening members  242  and  246 , and the fixing member  100   c  may be stably fixed to the lower body  104   b  by using a fastening member  240 . 
     A structure for fixing the disk  100  and controlling rotation for opening/closing is not limited to the above structure and may be variously modified. 
     Referring to  FIG.  5   , the upper body  104   a  may include an upper base formed of a metal, e.g. a light metal such as an aluminum, etc. and an upper plastic layer  560  formed by mixing a glass fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE, etc. 
     The upper base may include an upper framework  500 , a reception member  502 , a head  504 , pipe combination members  506  and bottom members  508   a  and  508   b  in both sides. 
     Top and bottom of the upper framework  500  may have semi-circular shape, and the upper framework  500  may be formed of a metal, especially a light metal. Here, the upper framework  500  and a lower framework  530  may form a space into which the disk supporting member  102  for supporting the disk  100  can be inserted. To fix stably the disk supporting member  102 , a home  520  may be formed at a lower outer surface of the upper framework  500 , and a home  550  may be formed at an inner surface of the lower framework  530 . 
     The reception member  502  may be longitudinal-extended at a central part of the upper framework  500  in a direction crossing over the upper framework  500 , preferably a direction vertical to the upper framework  500 , and it may be formed of a metal. 
     A hole  510  may be formed at the reception member  502 , and the manipulation member  100   b  of the disk  100  may be exposed outside via the hole  510 . 
     The head  504  may be connected to an end part of the reception member  502 , be made up of a metal, and have a size higher than the reception member  502 . Here, the manipulation member  100   b  may be projected over the head  504 . 
     The pipe combination member  506  is used for connecting pipes, for example may be a rib projected from the upper framework  500 , and may be formed of a metal. 
     In an embodiment, a hole  512  may be formed on the pipe combination member  506 . The butterfly valve may be combined with pipes by passing a fixing member such as a bolt, etc. through the pipes and the butterfly valve after the pipes locate at both sides of the butterfly valve. Here, the bolt may pass through the pipe combination member  506  of the butterfly valve. That is, the pipe combination member  506  may be used for combining the butterfly valve with the pipes. 
     The bottom members  508   a  and  508   b  are formed at both ends of the upper framework  500 , respectively. These bottom members  508   a  and  508   b  may be used for combination with the lower body  104   b , and it may be formed of a metal. For example, a bolt inserting members  230   a  and  232   a  may be formed on each of the bottom members  508   a  and  508   b.    
     The upper plastic layer  560  is formed on the upper base, for example may be formed on the upper base through an insert molding. 
     In an embodiment, the upper plastic layer  560  may be formed by mixing a glass fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. 
     In another embodiment, the upper plastic layer  560  may be formed by mixing a glass fiber and a carbon fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE, or by mixing a glass fiber, a carbon fiber and a graphite fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. 
     In still another embodiment, the upper plastic layer  560  may be formed by mixing a carbon fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE, or by mixing a carbon fiber and a graphite fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. As a result, strength, impact resistance or mechanical feature of the upper base may be enhanced. 
     That is, the upper body  104   a  may have similar strength to an upper body formed of only steel with including thin thickness of the upper framework  500  made up of a steel by forming the upper plastic layer  560  in which the glass fiber, etc. is mixed. As a result, the upper body  104   a  may maintain the strength with light weight. 
     Referring to  FIG.  5   , the lower body  104   b  may include a lower base and a lower plastic layer  562 . Here, the lower base may have a lower framework  530 , a reception member  532 , a pipe combination member  534  and bottom members  536   a  and  536   b.    
     The lower framework  530  may have a shape corresponding to the upper framework  500 , for example a semi-circular shape, and it may be made up of a light metal such as an aluminum, etc. 
     The reception member  532  receives the fixing member  100   c  of the disk  100  and may be formed of a metal. A hole  540  in which the fixing member  100   c  is inserted is formed on the reception member  532 . 
     The pipe combination member  534  may perform the same function as the pipe combination member  506 , be projected from the lower framework  530  and be formed of a metal. A hole  542  may be formed on the pipe combination member  534 . 
     The bottom members  536   a  and  536   b  are formed at both ends of the lower framework  530 , respectively. These bottom members  536   a  and  536   b  may be used for combination with the upper  104   a , and it may be formed of a metal. For example, a bolt inserting members  234   a  and  236   a  may be formed on each of the bottom members  536   a  and  536   b . The upper body  104   a  and the lower body  104   b  may be combined according as the bolts  220  are inserted into the bolt inserting members  230   a ,  232   a ,  234   a  and  236   a  as shown in  FIG.  2   . 
     The lower plastic layer  562  is formed on the lower base, for example may be formed on the lower base through an insert molding. 
     In an embodiment, the lower plastic layer  562  may be formed by mixing a glass fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. 
     In another embodiment, the lower plastic layer  562  may be formed by mixing a glass fiber and a carbon fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE, or by mixing a glass fiber, a carbon fiber and a graphite fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. 
     In still another embodiment, the lower plastic layer  562  may be formed by mixing a carbon fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE, or by mixing a carbon fiber and a graphite fiber with a PVC, a PP, a PPS, a PPA, a PA6, a PA66, a POK or a PE. 
     As a result, strength, impact resistance or mechanical feature of the lower body  104   b  may be enhanced. 
     That is, the lower body  104   b  may have similar strength to a lower body formed of only steel with including thin thickness of the lower framework  530  made up of a steel by forming the lower plastic layer  562  in which the glass fiber, etc. is mixed. As a result, the lower body  104   b  may maintain the strength with light weight. 
     Hereinafter, structure of the disk  100  will be described in detail. 
     In  FIG.  3    and  FIG.  4   , the opening-closing member  100   a  of the disk  100  may include a disk body  300 , a first plastic layer  302  and a second plastic layer  304 . Two plastic layers  302  and  304  are shown in drawings, but the opening-closing member  100   a  may include three or more plastic layers. 
     The disk body  300  is a base framework of the disk  100 , and it may be formed of a metal, for example a light metal such as an aluminum, etc. 
     In an embodiment, the disk body  300  may have a circular shape as shown in  FIG.  3   , and at least one hole  310  may be formed thereon. On the other hand, the disk body  300  is not limited as a structure in  FIG.  3   , and it may have a framework structure  300   a  which has a circular shape and many spaces in the circular shape as shown in  FIG.  6   . 
     The first plastic layer  302  may be formed on the disk body  300  through an insert molding. Here, the first plastic layer  302  may cover the whole of the disk body  300 . 
     In an embodiment, the first plastic layer  302  may be formed of high strength plastic, e.g. an engineering plastic or a super engineering plastic. For example, the first plastic layer  302  may be made up of a polyphenylene ethers resin composition including a polyphenylene ethers resin and a polystyrene resin, or a polyimide, a polysulfone, a poly phenylene sulfide, a polyamide imide, a polyacrylate, a polyether sulfone, a polyether ether ketone, a polyether imide, a liquid crystal polyester, a polyether ketone, etc. and their combination. 
     The second plastic layer  304  may be formed on the first plastic layer  302  through an insert molding. Here, the second plastic layer  304  may cover the whole of the first plastic layer  302  and fill holes on the disk body  300  and the first plastic layer  302 . 
     In an embodiment, the second plastic layer  304  may be formed of a fluorine resin, e.g. a polytetrafluoroethylene PTFE, a Perfluoroalkoxy alkane PFA or a polyvinylidene fluoride PVDF, etc. 
     In another embodiment, the second plastic layer  304  may be formed of a plastic having a melting point smaller than the first plastic layer  302 . For example, the second plastic layer  304  may be formed of the PTFE. 
     The first plastic layer  302  and the second plastic layer  304  may be formed of plastics having different melting point. 
     In an embodiment, corrosion resistance or acid resistance of a second plastic of the second plastic layer  304  is excellent than that of a first plastic of the first plastic layer  302 , and strength of the first plastic may be better than that of the second plastic. That is, the first plastic may increase the strength of the disk  100 , and the second plastic may prevent corrosion or oxidation due to fluid. 
     Briefly, the opening-closing member  100   a  of the disk  100  may include the disk body  300 , the first plastic layer  302  and the second plastic layer  304  disposed in sequence. 
     The whole of conventional disk is formed of a steel, and thus it should be manufactured by using a mechanical processing. However, it is difficult to process precisely the steel to have desire shape, and so productivity of the disk gets much lower. As a result, it is impossible to achieve mass production. Of course, since the whole of the disk is formed of steel, the strength of the disk is high, but weight and manufacture cost of the disk are great and the disk is easy to be corroded. 
     In the disk  100  of the present disclosure, only the disk body  300  as the base framework is formed of the metal, and the plastic layers  302  and  304  are formed on the disk body  300  through two insert moldings. 
     The disk body  300  is considerably thin compared with the conventional disk, and thus it is easy to process precisely the disk body  300  to have desired shape though mechanical processing is performed. Specially, since precise shape of the disk  100  may be realized through the first plastic layer  302 , it is not necessary to process precisely the disk body  300 . Hence, it is possible to produce the disk  100  in large quantities. 
     Corrosion resistance and acid resistance of the disk  100  may be considerably enhanced and the disk  100  may have excellent strength characteristics, due to the plastic layers  302  and  304 . Particularly, since the first plastic layer  302  is formed of the engineering plastic or the super engineering plastic, the disk  100  may have very small weight with keeping the strength similar to the conventional disk. For example, when the conventional butterfly valve formed of only steel has weight lkg, the butterfly valve of the present disclosure may have weight  350   g  with keeping the strength similar to the conventional butterfly valve. That is, super lightweight may be achieved. 
     On the other hand, the second plastic layer  304  formed of PTFE is directly formed on the disk body  300  formed of the steel without the first plastic layer  302 . In this case, the problem exists in that thickness of the PTFE formed on the steel is not constant or uniform (flat). That is, it is difficult to process the disk to have precise shape. 
     Accordingly, the method of manufacturing the valve of the present disclosure uses high strength plastic (for example, engineering plastic or super engineering plastic) which is practicable easily precise-processing on the metal. That is, the method may produce the disk  100  with precise shape by forming the first plastic layer  302  formed of high strength plastic on the disk body  300  formed of the metal. 
     Subsequently, the method may form the second plastic layer  304  formed of the PTFE on the first plastic layer  302  formed of the high strength plastic. Here, the PTFE may be formed of constant thickness on the high strength plastic. 
     Shortly, the opening-closing member  100   a  of the disk  100  may have enhanced productivity and reduced weight and manufacture cost with maintaining the same precise shape and processing as the conventional disk. Additionally, it is possible to achieve mass production of the butterfly valve. 
     Only the disk  100  is mentioned in above description. However, the structure of the disk  100  is applicable to every fluid contacting member of valves other than the butterfly valve, wherein the fluid contacting member should have excellent corrosion resistance because it contacts with fluid. That is, the fluid contacting member may include a body formed of a metal, a first plastic layer formed of high strength plastic on the body, and a second plastic layer formed of fluorine resin on the first plastic layer. 
     Hereinafter, plastic layers  560  and  562  of the body  104  will be described in detail. Since the plastic layers  560  and  562  have the same component, only the plastic layer  560  will be described. 
     In an embodiment, the plastic layer  560  may be formed by mixing a PP with a glass fiber. Preferably, the glass fiber has 0 weight percent to 40 weight percent, and the PP has a weight percent higher than 60 weight percent. Experimental result is shown in following table 1. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 glass fiber  
                 Tensile strength  
               
               
                 embodiment 
                 weight percent 
                 (Mpa@23° C.) [ASTM D638] 
               
               
                   
               
             
            
               
                 comparison 
                  0 
                 25 
               
               
                 1 
                 10 
                 54 
               
               
                 2 
                 15 
                 59 
               
               
                 3 
                 20 
                 78 
               
               
                 4 
                 30 
                 83 
               
               
                 5 
                 40 
                 94 
               
               
                   
               
            
           
         
       
     
     It is verified through the above table 1 that tensile strength of the plastic layer  560  when the plastic layer  560  is formed by mixing the PP with the glass fiber is very greater than that of a plastic layer formed of only the PP. That is, mechanical property and chemical property may be enhanced. However, it is difficult to manufacture the plastic layer  560  to have desired shape because an insert molding feature for manufacturing the plastic layer  560  is deteriorated when the glass fiber has a weight percent higher than 40 weight percent. 
     In another embodiment, the plastic layer  560  may be formed by mixing a PPS with a glass fiber. Preferably, the glass fiber has 0 weight percent to 40 weight percent, and the PPS has a weight percent higher than 60 weight percent. Experimental result is shown in following table 2. 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 glass fiber  
                 Tensile strength  
               
               
                 embodiment 
                 weight percent 
                 (Mpa@23° C.) [ASTM D638] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 comparison 
                 0 
                 70 
               
               
                 1 
                 30 
                 140 
               
               
                 2 
                 40 
                 200 
               
               
                   
               
            
           
         
       
     
     It is verified through the above table 2 that tensile strength of the plastic layer  560  when the plastic layer  560  is formed by mixing the PPS with the glass fiber is greater than that of a plastic layer formed of only the PPS. That is, mechanical property and chemical property may be enhanced, and thus light and strong plastic layer  560  may be formed. However, it is difficult to manufacture the plastic layer  560  to have desired shape because an insert molding feature for manufacturing the plastic layer  560  is deteriorated when the glass fiber has a weight percent higher than 40 weight percent. 
     In still another embodiment, the plastic layer  560  may be formed by mixing a PPA with a glass fiber. Preferably, the glass fiber has 0 weight percent to 55 weight percent, and the PPA has a weight percent higher than 45 weight percent. Experimental result is shown in following table 3. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 glass fiber  
                 Tensile strength  
               
               
                 embodiment 
                 weight percent 
                 (Mpa@23° C.) [ASTM D638] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 comparison 
                 0 
                 105 
               
               
                 1 
                 25 
                 170 
               
               
                 2 
                 35 
                 210 
               
               
                 3 
                 45 
                 250 
               
               
                 4 
                 55 
                 270 
               
               
                   
               
            
           
         
       
     
     It is verified through the above table 3 that tensile strength of the plastic layer  560  when the plastic layer  560  is formed by mixing the PPA with the glass fiber is greater than that of a plastic layer formed of only the PPA. That is, mechanical property and chemical property may be enhanced, and thus light and strong plastic layer  560  may be formed. However, it is difficult to manufacture the plastic layer  560  to have desired shape because an insert molding feature for manufacturing the plastic layer  560  is deteriorated when the glass fiber has a weight percent higher than 55 weight percent. 
     In still another embodiment, the plastic layer  560  may be formed by mixing a PA6 with a glass fiber. Preferably, the glass fiber has 0 weight percent to 50 weight percent, and the PA6 has a weight percent higher than 50 weight percent. Experimental result is shown in following table 4. 
     
       
         
           
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                 glass fiber  
                 Tensile strength  
               
               
                 embodiment 
                 weight percent 
                 (Mpa@23° C.) [ASTM D638] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 comparison 
                 0 
                 70 
               
               
                 1 
                 15 
                 125 
               
               
                 2 
                 20 
                 145 
               
               
                 3 
                 30 
                 170 
               
               
                 4 
                 33 
                 180 
               
               
                 5 
                 35 
                 185 
               
               
                 6 
                 40 
                 192 
               
               
                 7 
                 45 
                 200 
               
               
                 8 
                 50 
                 220 
               
               
                   
               
            
           
         
       
     
     It is verified through the above table 4 that tensile strength of the plastic layer  560  when the plastic layer  560  is formed by mixing the PA6 with the glass fiber is very greater than that of a plastic layer formed of only the PA6. That is, mechanical property and chemical property may be enhanced, and thus light and strong plastic layer  560  may be formed. However, it is difficult to manufacture the plastic layer  560  to have desired shape because an insert molding feature for manufacturing the plastic layer  560  is deteriorated when the glass fiber has a weight percent higher than 50 weight percent. 
     In still another embodiment, the plastic layer  560  may be formed by mixing a PA66 with a glass fiber. Preferably, the glass fiber has 0 weight percent to 50 weight percent, and the PA66 has a weight percent higher than 50 weight percent. Experimental result is shown in following table 5. 
     
       
         
           
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                 glass fiber  
                 Tensile strength  
               
               
                 embodiment 
                 weight percent 
                 (Mpa@23° C.) [ASTM D638] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 comparison 
                 0 
                 80 
               
               
                 1 
                 25 
                 165 
               
               
                 2 
                 30 
                 186 
               
               
                 3 
                 33 
                 196 
               
               
                 4 
                 35 
                 200 
               
               
                 5 
                 50 
                 245 
               
               
                   
               
            
           
         
       
     
     It is verified through the above table 5 that tensile strength of the plastic layer  560  when the plastic layer  560  is formed by mixing the PA66 with the glass fiber is very greater than that of a plastic layer formed of only the PA66. That is, mechanical property and chemical property may be enhanced, and thus light and strong plastic layer  560  may be formed. However, it is difficult to manufacture the plastic layer  560  to have desired shape because an insert molding feature for manufacturing the plastic layer  560  is deteriorated when the glass fiber has a weight percent higher than 50 weight percent. 
     In still another embodiment, the plastic layer  560  may be formed by mixing a POK with a glass fiber. Preferably, the glass fiber has 0 weight percent to 40 weight percent, and the POK has a weight percent higher than 60 weight percent. Experimental result is shown in following table 6. 
     
       
         
           
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                   
                 glass fiber  
                 Tensile strength  
               
               
                 embodiment 
                 weight percent 
                 (Mpa@23° C.) [ASTM D638] 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 comparison 
                 0 
                 60 
               
               
                 1 
                 15 
                 100 
               
               
                 2 
                 20 
                 125 
               
               
                 3 
                 30 
                 140 
               
               
                 4 
                 40 
                 165 
               
               
                   
               
            
           
         
       
     
     It is verified through the above table 6 that tensile strength of the plastic layer  560  when the plastic layer  560  is formed by mixing the POK with the glass fiber is very greater than that of a plastic layer formed of only the POK. That is, mechanical property and chemical property may be enhanced, and thus light and strong plastic layer  560  may be formed. However, it is difficult to manufacture the plastic layer  560  to have desired shape because an insert molding feature for manufacturing the plastic layer  560  is deteriorated when the glass fiber has a weight percent higher than 40 weight percent. 
     The embodiments of the present disclosure described above are disclosed only for illustrative purposes. A person having ordinary skill in the art would be able to make various modifications, alterations, and additions without departing from the spirit and scope of the disclosure, but it is to be appreciated that such modifications, alterations, and additions are encompassed by the scope of claims set forth below.