Patent ID: 7128199

Claim:
A hooked dust scraper attached to each end of a contact surface between a nut and a screw bolt of a ball screw unit with a lead L, therein at least one retaining slot being formed in said nut at said contact surfaces, the hooked dust scraper comprising: a tooth portion with a plurality of teeth formed in an inner circumference thereof in mesh with said screw bolt; and a hook portion with a plurality pawls formed in an outer circumference and protruded outwardly from an outer edge thereof; wherein a fissure is formed between said tooth portion and said hook portion so that said pawls can be squeezed beneath said nut to engage with said retaining slot, and said pawls are arrayed along said outer edge keeping a pitch P, and a clearance δ is reserved between the teeth and the thread of said screw bolt with a relationship P≦720°·(δ/L).