Patent ID: 7770979

Claim:
An adjusting mechanism for adjusting arm rest of a chair, comprising: an inner tube having a connection portion at a lower end thereof and the connection portion adapted to be connected with the chair, an axial groove defined in an outside thereof and multiple positioning holes defined through a wall defining the axial groove; an outer tube mounted to the inner tube and an arm rest connected to a top end thereof, an engaging portion protruding inward from an inside of the outer tube and movably engaged with the axial groove of the inner tube, a through hole defined through a wall defining the engaging portion and located at a lower end of the engaging portion, a support protruding from an outside of the engaging portion and located at a mediate portion of the engaging portion, the through hole being in alignment with one of the positioning holes, a part extending from the outside of the engaging portion and defining a guide slot which is located above the through hole, and an operation member having a mediate portion thereof pivotably connected to the support of the engaging portion so that the operation member is pivotable about the support, a hook extending from a lower end thereof and a guide plate located above the hook, the guide plate movably accommodated in the guide slot and the hook extending through the through hole and engaged with one of the positioning holes, a spring biased between the engaging portion and an inside of a top end of the operation member, wherein a first stop extends from the inner end of the axial groove and is located beneath the positioning holes, a sliding member is movably engaged with the axial groove and has a second stop, an opening is defined through a wall of the outer tube and the sliding member is engaged with the opening, the second stop is stopped by the first stop when the outer tube is moved relative to the inner tube to prevent the outer tube from disengaging from the inner tube.