Special-shaped ratchet wheel, length adjusting device and head-mounted equipment

The utility model discloses a special-shaped ratchet wheel, a length adjusting device and head-mounted equipment. The head-mounted equipment comprises a length adjusting device, the length adjusting device comprises a special-shaped ratchet wheel, the special-shaped ratchet wheel comprises an inner wheel and an outer wheel, the outer wheel comprises an arc-shaped main body, two extension arms, two bending arms and two ratchet wheel teeth, the two extension arms and the arc-shaped main body jointly form a sector-ring-shaped piece, and the two bending arms and the two ratchet wheel teeth are arranged in the sector-ring-shaped piece. The two ends of each bent arm are correspondingly connected to the two ends of one extension arm respectively, and the middle of each bent arm is bent towards the inner wheel; a limiting groove is defined by each bending arm and the corresponding extension arm; and each ratchet tooth protrudes out of the surface of one side, far away from the inner wheel, of the extension arm and is