Patent ID: 7013766

Claim:
An extension structure, comprising: a main body, the main body having a receiving chamber formed therein and a circular shaft hole formed though a peripheral wall thereof in open communication with the receiving chamber; a drive rod movably mounted in the receiving chamber of the main body and having an operation slot formed in an end portion thereof and disposed in aligned relation with the shaft hole of the main body, the drive rod having an oblique guide edge formed on a distal end of the operation slot; an elastic member mounted in the main body and urged between the main body and the drive rod; and a rotation control member rotatably mounted in the shaft hole of the main body and rested on the drive rod, so that the drive rod is moved in the main body responsive to rotation of the rotation control member; said rotation control member including: a rotation body rotatably mounted in the shaft hole of the main body, the rotation body being formed with a recessed oblique guide face on one portion thereof disposed contiguous the oblique guide edge in a first position of the rotation control member and an arcuate peripheral wall on a remaining portion thereof, the rotation body being rotatable between the first position and a second position where the peripheral wall of the rotation body rests on the guide edge of the drive rod and thereby cams the drive rod to move distally, a knob coupled to a top side of the rotation body and extending outwardly from the main body, a circular drive section formed on a bottom side of the rotation body and received in the operation slot of the drive rod, and a circular enlarged head formed on a distal end of the drive section and extending outwardly from a peripheral wall of the drive rod and having a portion thereof in contact with the drive rod.