Main spindle apparatus and tool holder clamp unit used therefor

1. A main spindle apparatus, comprising:

a main spindle having a through hole in an axial direction thereof;

a main spindle head rotatably supporting the main spindle therein;

a tool holder clamp unit including:

a unit main body having a tool mounting hole to which a tool holder is mounted;

a clamp mechanism for clamping the tool holder; and

a bias mechanism for biasing the clamp mechanism in a clamping state; and

a clamp release mechanism provided on the main spindle head side, the clamp release mechanism releasing the clamping state of the clamp mechanism by operating the bias mechanism,

wherein the tool holder clamp unit is mounted in the through hole of the main spindle so that the tool holder clamp unit is removable from a front side of the through hole of the main spindle,

wherein a single step is provided inside the main spindle so as to define a small diameter portion positioned on a rear side of the main spindle and a large diameter portion positioned the front side of the main spindle,

wherein the bias mechanism is positioned at the small diameter portion when the tool holder clamp unit is mounted in the through hole of the main spindle, and

wherein the large diameter portion houses the unit main body and the clamp mechanism.

2. The main spindle apparatus according to claim 1 , wherein the unit main body of the tool holder clamp unit is substantially tube shaped,

the clamp mechanism is provided interior of the unit main body, and

the biasing mechanism is provided at a rear end of the unit main body.

3. The main spindle apparatus according to claim 2 , wherein the clamp mechanism comprises:

a slider provided in the unit main body, the slider reciprocally slides within a predetermined stroke range in an axial direction; and

a plurality of clamp members connected on a front end portion of the slider,

wherein the bias mechanism comprises:

a drawing bar connected to a rear end portion of the slider;

a first spring receiving member provided at a rear end portion of the drawing bar;

a second spring receiving member provided at a rear end portion of the unit main body, and

a bias member provided between the first spring receiving member and the second spring receiving member, the bias member biasing the drawing bar to a clamp position.

4. The main spindle apparatus according to claim 3 , wherein radially center portions of the clamp mechanism and the drawing bar are formed with coolant paths for supplying a coolant to a center portion of the tool holder.

5. The main spindle apparatus according to claim 3 , wherein the clamp release mechanism comprises:

an operating member provided in the through hole of the main spindle so as to contact with a rear end portion of the first spring receiving member and so as to reciprocate in the axial direction, the operating member having protrusion which protrudes in a radial direction; and

a piston reciprocating in the axial direction so as to contact with the protrusion of the operating member,

wherein the piston presses the protrusion forwardly in order to release the clamp state of the tool holder.

6. The main spindle apparatus according to claim 3 , wherein the bias mechanism biases the drawing bar rearwardly in order to set the clamp mechanism in the clamp state.

7. The main spindle apparatus according to claim 1 , wherein the front end portion of the unit main body is integrally formed with a flange portion, and

the flange portion is attached to a front end face of the main spindle by a bolt.

8. The main spindle apparatus according to claim 1 , wherein the bias mechanism includes a disc spring or a coil spring.

9. The main spindle apparatus according to claim 1 , wherein the through hole of the main spindle is formed such that diameter of the through hole is stepwisely reduced from a front end of the main spindle apparatus to a rear end of the spindle apparatus.

10. The main spindle apparatus according to claim 1 , wherein the apparatus is operable to remove the total of the tool holder clamp unit from the front side of the main spindle without removing any mechanism from a rear portion of the tool holder clamp unit, and

wherein the clamp mechanism and the bias mechanism are also be taken out integrally.

11. The main spindle apparatus according to claim 1 , wherein the tool holder is disposed on the front side of main spindle.

12. The main spindle apparatus according to claim 1 , wherein the bias mechanism is provided so as to be exposed outside after the tool holder clamp unit is removed.

13. A main spindle apparatus, comprising:

a main spindle having a through hole in an axial direction thereof;

a main spindle head rotatably supporting the main spindle within the main spindle head;

a tool holder clamp unit within the main spindle and comprising:

a unit main body having a tool mounting hole to which a tool holder is mounted;

a clamp mechanism for clamping the tool holder; and

a force actuator that biases the clamp mechanism in a clamping state; and

a clamp release mechanism provided in the main spindle and that releases the clamping state of the clamp mechanism by operating the force actuator,

wherein the tool holder clamp unit is mounted in the through hole of the main spindle so that the tool holder clamp unit is removable from a front side of the through hole of the main spindle,

wherein a single step is provided inside the main spindle so as to define a small diameter portion positioned on a rear side of the main spindle and a large diameter portion positioned on a front side of the main spindle,

wherein the bias mechanism is positioned at the small diameter portion when the tool holder clamp unit is mounted in the through hole of the main spindle, and

wherein the large diameter portion houses the unit main body and the clamp mechanism.

14. The main spindle apparatus according to claim 13 , wherein the force actuator comprises a spring.

15. The main spindle apparatus according to claim 13 , wherein the tool holder is disposed on the front side of main spindle.

16. The main spindle apparatus according to claim 13 , wherein the tool holder clamp unit is mounted in the through hole of the main spindle so that the tool holder clamp unit is removable from a front side of the through hole of the main spindle without accessing the tool holder clamp unit from the rear side of the main spindle.

17. The main spindle apparatus according to claim 13 , wherein the force actuator is provided so as to be exposed outside after the tool holder clamp unit is removed.