Abstract: The invention is provided with means for detecting a situation of rotating a rotary work lifter at any time, and a determining portion for determining whether operation of the rotary work lifter is to be stopped by a state of rotating the rotary work lifter detected by the means, thereby, operation of the rotary work lifter can be stopped when rotation of the rotary work lifter is interrupted by pinching a work piece or the like between the rotary work lifter and a working table or the like, or when the rotation is interrupted by some other influence. Therefore, the rotary work lifter, the working table or the like can be prevented from being finally destructed by continuing to generate a torque by a drive source even after interrupting rotation of the rotary work lifter as in a background art.

Abstract: The invention is provided with means for detecting a situation of rotating a rotary work lifter at any time, and a determining portion for determining whether operation of the rotary work lifter is to be stopped by a state of rotating the rotary work lifter detected by the means, thereby, operation of the rotary work lifter can be stopped when rotation of the rotary work lifter is interrupted by pinching a work piece or the like between the rotary work lifter and a working table or the like, or when the rotation is interrupted by some other influence. Therefore, the rotary work lifter, the working table or the like can be prevented from being finally destructed by continuing to generate a torque by a drive source even after interrupting rotation of the rotary work lifter as in a background art.

Abstract: A laser beam machining head comprises a first machining head section having a flange in a first end part in a direction along an optical axis direction of laser light and having a laser light emission nozzle in a second end part, a second machining head section having an engaged part engaged with the above-mentioned flange of the first machining head section for detachably holding the above-mentioned first machining head section, and an O ring being engaged in an engagement part placed in an outer peripheral surface of the above-mentioned flange opposed to an inner peripheral surface of the above-mentioned engaged part and pressed against the inner peripheral surface of the above-mentioned engaged part, whereby when the first machining head section collides with an obstacle, a breakage prevention function reliably operates for preventing not only damage to the first machining head section, but also damage to the whole laser beam machining head, and in the normal state, the first machining head section is held