Caster

1. A caster comprising a shaft, a first elastic ring, a C-shaped ring, and a second elastic ring;

wherein the shaft has one end inserted and secured in a wheel, and a first rod is extended from the other end of the shaft, and a second rod protrudes from an end of the first rod; the diameter of the first rod is larger than that of the second rod, and an end of the second rod comprises a flexible portion;

wherein the first elastic ring has a first outer periphery and a central hole, and the first elastic ring is disposed on the second rod of the shaft through the central hole so as to align the first outer periphery with an outer periphery of the first rod; an open end of the central hole has a first collar axially extended from an edge thereof, and the radial distance between a center of the central hole and the first outer periphery is two to four times greater than the radial distance between the center of the central hole and the first collar, and the first collar is positioned at a middle portion of the second rod;

wherein the C-shaped ring disposed on the second rod through the flexible portion is disposed on the first collar of the first elastic ring, and the outer diameter of the C-shaped ring is larger than the diameter of the first rod; and

wherein the second elastic ring has a second outer periphery and an axle hole, and the second elastic ring is disposed on the second rod of the shaft through the axle hole, and the second outer periphery is aligned with the outer periphery of the first rod; a second collar is axially extended from an edge of an open end of the axle hole, and the diameter of the second collar and the diameter of the first collar are the same so as to connect together to prevent the C-shaped ring from coupling with the shaft; the flexible portion of the shaft is adapted to abut against the first elastic ring, the C-shaped ring, and the second elastic ring so as to secure the positions thereof,

wherein an open end of the first collar and an open end of the second collar respectively have a first wavy edge and a second wavy edge which are adapted to fit together, and

wherein each of the axial height of the first collar and the axial height of the second collar is the same as the axial height of the C-shaped ring.

2. The caster of claim 1 , wherein an open end of the first collar and an open end of the second collar respectively have a first zigzag edge and a second zigzag edge which are adapted to fit together.

3. The caster of claim 2 , wherein each of the axial height of the first collar and the axial height of the second collar is the same as the axial height of the C-shaped ring.

4. The caster of claim 1 , wherein each of the first elastic ring and the second elastic ring is made of nylon integrally, and the shaft and the C-shaped ring are made of metal.

5. The caster of claim 1 , wherein a tapered ring is formed on an outer surface of the shaft between the wheel and the first rod, and the diameter of the tapered ring is gradually smaller toward the first rod.

6. The caster of claim 1 , wherein an open end of the second elastic ring other than the end having the second collar comprises a second annular recess portion at an inner periphery thereof, and the second annular recess portion is adapted to provide deformation space for the flexible portion.

7. The caster of claim 5 , wherein an open end of the first elastic ring other than the end comprising the first collar has a first annular recess portion at an inner periphery thereof, and the first annular recess portion is adapted to reduce the thickness of the first elastic ring, so as to enhance the elasticity of the first elastic ring against the first rod.

8. The caster of claim 1 , wherein the first elastic ring and the second elastic ring have the same structure which is formed by the same mold.