Patent ID: 8443685

Claim:
A safety mechanism for a linear actuator having a guide screw and a telescopic tube, the safety mechanism comprising: a nut for connecting the guide screw, having a larger diameter cylinder and a smaller diameter cylinder extending from one end of the larger diameter cylinder; a nut sheath fixed on the smaller diameter cylinder of the nut to form an integer, wherein an outside of the nut sheath is provided with a plurality of bumps; a sleeve, one end of which is put around outside of the nut sheath and the other end of which is connected to the telescopic tube from outside, wherein an outside of the sleeve is provided with a plurality of rabbets corresponding to the bumps; and a torsion spring disposed around outside of the nut sheath and the sleeve; wherein when the guide screw is rotated, the nut sheath is engaged with the sleeve by embedding the bumps into the rabbets, respectively; when the sleeve stops, the bumps and the rabbets depart from engagement to make the nut sheath and the nut freely rotate against the sleeve, wherein the nut sheath further comprises a first ring section and a second ring section extending from the first ring section, and the sleeve is put around the second ring section.