Patent ID: 8056441

Claim:
A control knob device, comprising: a main body of cylindrical shape defining a top surface and a lateral surface, the top surface having a stopping wall of ring shape, with two inserting openings formed thereon and apart from each other, the lateral surface having a plurality of guiding recesses extending upwards and downwards and a plurality of sliding slots, each of the sliding slots running circumferentially and communicating with the corresponding guiding recess, with the depth thereof greater than that of the guiding recess; a shell coupled to the main body comprising a covering plate and a lateral plate enclosing the lateral surface, the covering plate having two blocking portions located at an outer surface of the stopping wall and adjacent to the inserting openings, the lateral plate having portions extending inwards to form a plurality of inserting slices corresponding to the sliding slots; and a spring element located within the stopping wall having two elastic ends, wherein the shell is coupled to the main body by the inserting slices passing through the guiding recesses and inserted into the sliding slots, the elastic ends are inserted into the inserting openings and abut against the blocking portions for making the rotated shell return automatically.