Spindle motor and clamping apparatus

1. A clamping apparatus comprising:

a case having a side surface on which a plurality of arm holes are formed;

an arm, which moves inside and outside the case through one of the arm holes while being restricted by the case and has an upper part and a lower part that are guided by the case; and

an elastic member installed inside the case to elastically support the arm,

wherein the arm comprises:

a body, which has a first end disposed at an outside of the case and a second end disposed at an inside of the case,

a guide rail, which is formed at both sides of the body such that a motion of a lower part of the guide rail is guided by the case, and

an anti-separation rail, which is formed at the both sides of the body such that a motion of an upper part of the anti-separation rail is guided by the case.

2. The clamping apparatus according to claim 1 , wherein the body, the guide rail and the anti-separation rail are integrally formed.

3. The clamping apparatus according to claim 1 , wherein the case has a contact protrusion, which protrudes downward from the inside of the case to guide a motion of the anti-separation rail.

4. The clamping apparatus according to claim 3 , wherein the contact protrusion comes into a line contact with the anti-separation rail.

5. The clamping apparatus according to claim 3 , wherein the contact protrusion has a hemispherical cross section and extends in a direction perpendicular to a direction of motion of the anti-separation rail.

6. The clamping apparatus according to claim 1 , wherein the anti-separation rail has an upper surface, which is inclined in such a manner that the upper surface is lowered as the upper surface goes to the outside of the case.

7. The clamping apparatus according to claim 1 , wherein the anti-separation rail has a lower surface, which is inclined in such a manner that the lower surface rises as the lower surface goes to the outside of the case.

8. The clamping apparatus according to claim 1 , wherein a motion of the anti-separation rail is restricted by the case when the anti-separation rail moves out of the case.

9. The clamping apparatus according to claim 1 , further comprising a plurality of claws that are formed at the side surface of the case while being alternately disposed with the arm holes.

10. A clamping apparatus comprising:

a case having a side surface on which a plurality of arm holes are formed;

an arm, which moves inside and outside the case through one of the arm holes while being restricted by the case; and

an elastic member installed inside the case to elastically support the arm,

wherein, when the arm moves, an upper surface of the arm is slid while making contact with the case at a first distance from a center of the case and a lower surface of the arm is slid while making contact with the case at a second distance longer than the first distance,

wherein the arm comprises:

a body, which has a first end disposed at an outside of the case and a second end disposed at an inside of the case,

a guide rail, which is formed at both sides of the body such that a motion of a lower part of the guide rail is guided by the case at the second distance, and

an anti-separation rail, which is formed at the both sides of the body such that a motion of an upper part of the anti-separation rail is guided by the case at the first distance.

11. The clamping apparatus according to claim 10 , wherein the body, the guide rail and the anti-separation rail are integrally formed.

12. The clamping apparatus according to claim 10 , wherein the case has a contact protrusion, which protrudes downward from the inside of the case to guide a motion of the anti-separation rail.

13. The clamping apparatus according to claim 12 , wherein the contact protrusion has a curved surface.

14. The clamping apparatus according to claim 10 , wherein a thickness of the anti-separation rail is inversely-proportional to a distance thereof relative to a center of the case.

15. The clamping apparatus according to claim 10 , further comprising a plurality of claws that are formed at the side surface of the case while being alternately disposed with the arm holes.

16. A spindle motor comprising:

a base;

a bearing housing installed on the base;

a bearing press-fitted into an inner circumference of the bearing housing;

a rotary shaft, which is supported by the bearing and rotatably installed on the bearing;

a stator including a core disposed around the bearing housing and a coil wound around the core;

a rotor including a rotor yoke which is coupled to the rotary shaft and a magnet which is coupled to the rotor yoke to face the coil; and

a clamping apparatus installed on the rotor yoke,

wherein the clamping apparatus comprises:

a case having a side surface on which a plurality of arm holes are formed;

an arm which moves inside and outside the case through one of the arm holes by being restricted by the case and has an upper part and a lower part that are guided by the case; and

an elastic member installed inside the case to elastically support the arm.

17. The spindle motor according to claim 16 , further comprising a fastening member, which comes into contact with an upper surface of the rotor yoke and is inserted into the rotary shaft such that the rotor yoke is coupled to the rotary shaft.

18. The spindle motor according to claim 16 , wherein the arm comprises:

a body, which has a first end disposed at an outside of the case and a second end disposed at an inside of the case,

a guide rail, which is formed at both sides of the body such that a motion of a lower part of the guide rail is guided by the case, and

an anti-separation rail, which is formed at the both sides of the body such that a motion of an upper part of the anti-separation rail is guided by the case.