Internal machining apparatus for hollow workpiece

1. An internal machining apparatus for machining an internal surface of a hollow workpiece, the apparatus comprising:

a work head rotatably supporting a work spindle for rotationally driving the hollow workpiece;

a foot stock provided to face the work head;

a machining unit holding a cutting blade and configured to be inserted into the hollow workpiece;

a pair of unit holding arbors respectively supported by the work head and the foot stock to advance and retract in an axial direction thereof and being capable of non-rotatably holding the machining unit inserted in the hollow workpiece at both sides thereof; and

a turning mechanism configured to be supplied with a drive power transmitted through the interior of one of the unit holding arbors for turning the cutting blade held on the machining unit about an axis orthogonal to an axis of the unit holding arbors.

2. The internal machining apparatus as set forth in claim 1 , further comprising:

a unit supply device configured to insert the machining unit gripped thereby into the hollow workpiece and to be evacuated with the machining unit remaining left in the hollow workpiece prior to a machining of the hollow workpiece.

3. The internal machining apparatus as set forth in claim 1 , wherein:

the turning mechanism includes a rotational drive member rotatably received in the one of the unit holding arbors for supplying the drive power to the turning mechanism; and

the machining unit comprises:

a unit body configured to be non-rotatably held by the pair of unit holding arbors;

a turn center shaft supported in the unit body to be rotatable about the axis orthogonal to the axis of the unit holding arbors and holding the cutting blade; and

a driven member rotatably supported in the machining unit and being drivingly connectable with the rotational drive member for transmitting rotation of the rotational drive member to the turn center shaft.

4. The internal machining apparatus as set forth in claim 3 , further comprising:

a unit supply device configured to insert the machining unit gripped thereby into the hollow workpiece and to be evacuated with the machining unit remaining left in the hollow workpiece prior to a machining of the hollow workpiece.

5. The internal machining apparatus as set forth in claim 1 , wherein two machining units one of which is the machining unit defined in claim 1 and the other of which holds a different cutting blade are used and are inserted successively one at a time into the hollow workpiece to be used for the machining of the hollow workpiece.

6. The internal machining apparatus as set forth in claim 5 , wherein the other machining unit holds the different cutting blade movably in a radial direction, the apparatus further comprising:

an axial moving mechanism for moving the other machining unit in the axial direction of the pair of unit holding arbors by the cooperation of the pair of unit holding arbors; and

a radial moving mechanism for moving the cutting blade held by the other machining unit in the radial direction of the pair of unit holding arbors when a drive power is supplied through a rotational drive member passing through the one of the unit holding arbors.

7. The internal machining apparatus as set forth in claim 6 , further comprising:

a unit supply device configured to insert the two machining units gripped thereby successively one at a time into the hollow workpiece and to be evacuated with the inserted machining unit remaining left in the hollow workpiece prior to a machining of the hollow workpiece.