Butterfly valve and method of manufacturing the same

1. A butterfly valve comprising:

a body in which an inserting space is formed; and

a disk inserted into the inserting space of the body,

wherein fluid flow is opened or closed in response to rotation of the disk,

wherein the disk further includes:

a disk body formed of a metal;

a first plastic layer formed of a first plastic on the disk body;

a second plastic layer formed of a second plastic on the first plastic layer,

wherein a melting point of the first plastic layer is different from a melting point of the second plastic layer,

wherein the disk body is formed of a framework structure having a rim and a plurality of spokes extending from the rim toward a center of the rim, an internal space is formed between the plurality of spokes in a sector shape,

wherein the first plastic layer is formed on the disk body to fill the internal space between the plurality of spokes, and

wherein a strength of the first plastic layer is higher than a strength of the second plastic layer, and

wherein a corrosion resistance of the second plastic layer is higher than a corrosion resistance of the first plastic layer.

2. The butterfly valve of claim 1 , the disk body is not exposed outside as the first plastic layer or the second plastic layer covers whole of the disk body.

3. The butterfly valve of claim 1 ,

wherein the first and second plastic layers are formed through an insert molding, the melting point of the first plastic is higher than the melting point of the second plastic.

4. The butterfly valve of claim 1 , wherein the first plastic layer is formed of an engineering plastic and produces the disk body with precise shape by forming the engineering plastic on the disk body, and

wherein the second plastic layer is formed of a fluorine resin and is formed of constant thickness on the first plastic layer.

5. The butterfly valve of claim 1 ,

wherein the first plastic layer covers the whole of the disk body and the second plastic layer covers the whole of the first plastic layer,

wherein an acid resistance of the second plastic layer is higher than an acid resistance of the first plastic layer, and

wherein a unit weight of each of the first and the second plastic is lighter than a unit weight of the metal.

6. The butterfly valve of claim 5 ,

wherein a surface of the disk body is uneven and a surface of the second plastic layer is flat, and plastic surfaces of the first and the second plastic layer are more precise than a metal surface of the disk body.