Patent ID: 7810414

Claim:
A depth adjustment device mounted to a front end of a power tool, said power tool having a drive bit mounted to the front end thereof, said drive bit being driven by said power tool via a clutch, said drive bit being adapted for screwing a screw onto a workpiece, said depth adjustment device comprising: a coupling member having a through hole and being fixed to the front end of said power tool so as to have said drive bit pass through said through hole, said coupling member having a limit recess and a lock recess at each of two opposite positions of an external periphery of said coupling member, and each said limit recess extending along an imaginary longitudinal axis of said coupling member, each said lock recess extending from said limit recess at the same position of the external peripher of said coupling member and extending along the external periphery of said coupling member and communicating with said limit recess; a hollow stationary sleeve sleeved onto said coupling member for said drive bit to pass therethrough, said stationary sleeve having: two first lock portions, each of which is formed at one of two opposite positions of an underside thereof and close to a rear opening thereof, said two first lock portions being respectively stopped against sidewalls of said lock recesses of said coupling member to stop said stationary sleeve from rotation with respect to said coupling member, said stationary sleeve having two spring parts formed at a rear end thereof, each of said spring parts having a second lock portion formed at a distal end thereof, said second lock portions being respectively locked to said lock recesses to prevent said stationary sleeve from disengaging from said coupling member, and said stationary sleeve having an external thread formed at an external periphery thereof; and a hollow adjustment sleeve sleeved onto said stationary sleeve, said adjustment sleeve having: a lip portion formed at a front end of the adjustment sleeve for lying against said workpiece so as to have said drive bit pass through said adjustment sleeve and protruding beyond said lip portion, and said adjustment sleeve having an internal thread formed therein and engaged with said external thread of said stationary sleeve in such a way that said adjustment sleeve is capable of being movably mounted to said stationary sleeve, whereby a depth for which said screw is screwed onto said workpiece is capable of being adjusted when a length for which said drive bit protrudes beyond said lip portion is changed.