Locking mechanism for a rotary working member

Locking mechanism for a rotary working member wherein a working member (D) and a locking flange (3) are loosely fitted to the small-diameter threaded part of a rotary drive shaft (1) equipped with a large-diameter part and a small-diameter threaded part, which mechanism is of a type wherein a locking nut (5)—which comprises a main unit and a flange and is screwed to the small-diameter threaded part presses the working member against the end surface of the large-diameter part of the rotary drive shaft via the locking flange, thereby locking the working member to the rotary drive shaft, characterized in that:

• an operating ring (7) is externally fitted, with the ability to rotate, to the main body of the locking nut in between the locking flange and the flange of the locking nut;
• a ball bearing is inserted between the operating ring and the locking flange;
• three or more arc-shaped grooves are formed—facing toward each other and extending in concentric shapes in the circumferential direction—in the mating surfaces of the flange of the locking nut and the operating ring;
• locking balls (9) are accommodated inside the arc-shaped grooves of the flange of the locking nut and the operating ring which face toward each other;
• each pair of arc-shaped grooves which accommodate the locking balls has a total dimension—in the axial direction of the rotary drive shaft—which is less than the diameter of a locking ball;
• and a localized indentation is formed at the bottom surfaces on at least one side of the said pairs of arc-shaped grooves.