Patent ID: 7516681

Claim:
An external circulation type ball screw, comprising: a screw defined with a helical groove; a nut being a hollow structure defined with a rolling groove, the rolling groove being opposite the helical groove, the nut being mounted on and reciprocates along the screw, in a periphery of the nut being formed a plane defined with a plurality of fixing holes, each fixing hole having a stopping surface; a plurality of rolling elements mounted between the rolling groove and the helical groove; a return device including a guiding member and a cover; the guiding member defined with two guiding portions and a first half pipe; each guiding portion fixed in the fixing hole of the nut and disposed with a nail and a guiding passage, the nail protruded toward and inserted in the rolling groove of the nut, one end of the guiding passage being connected to the helical groove and the rolling groove, the other end of the guiding passage being connected to the first half pipe, the first half pipe being mounted between the guiding portions and being defined with a first half passage; the cover including a second half pipe and two fixing portions, the second half pipe being connected to the fixing portions and covering the first half pipe, the second half pipe being defined with a second half passage, and the fixing portion covering the guiding portion.