Main shaft locking mechanism

A main shaft locking mechanism, comprising:

• a fixing ring having a circular inner wall;
• a driving plate coupled to a power supply unit, wherein the driving plate comprises a central hole and a plurality of operation pins, and a plurality of sector protrusions are distributed at a circumferential edge of the central hole;
• a main shaft comprising a portion whose cross section is an equilateral polygon, wherein the equilateral portion has a plurality of sides and a plurality of corners, a number of the sides of the equilateral portion is equal to that of the sector protrusions, and the equilateral portion of the main shaft is disposed through the central hole of the driving plate;
• a plurality of detents, wherein a number of the detents is equal to that of the corners of the equilateral portion of the main shaft, each of the detents comprises an exterior side and an interior side opposite to the exterior side, the exterior side is arcuate shaped, the interior side is configured with two corner protrusions protruded out from two ends of the interior side, the interior side is further configured with a concave portion defined between the two corner protrusions, each of the detents is disposed between the main shaft and the inner wall of the fixing ring, such that each of the corners of the main shaft is received in the concave portion of the corresponding detents, and each of the operation pins is disposed between the two adjacent detents.