Chair adjustment mechanism

An adjustable chair, comprising a stationary portion and an adjustable portion that is adjustable relative to the stationary portion, wherein the stationary portion comprises a frame portion and the adjustable portion comprises a backrest portion and an armrest portion, the chair further comprising an adjustment mechanism that permits adjustment of the adjustable portion into a selected one of at least two adjustment positions defined by respective cam surfaces, the adjustment mechanism having:

• a housing attached beneath the armrest portion, the housing having a forward wall, a rearward wall and a pair of opposing side walls extending between the forward and rear walls and a bottom wall which collectively define, in conjunction with the armrest portion, an interior closed space;
• the bottom wall having a single guide slot therein extending longitudinally in the housing and having a predetermined lateral slot width;
• said housing, defining in said interior closed space, a longitudinal continuous serpentine adjustment surface defining the at least two adjustment positions longitudinally spaced apart as adjustment surface segments, the serpentine adjustment surface defines a cam surface for a cam follower on an adjustment plate which adjustment plate movably extends through said guide slot;
• said adjustment plate having an upper plate region extending into said interior closed space and a lower plate region extending below the bottom wall of said housing, the upper and lower adjustment plate regions being planar with a thickness complementary to said guide slot lateral width such that the adjustment plate substantially closes the guide slot thereat;
• said cam follower formed in the upper plate region which moves over the serpentine cam surface as the adjustment plate moves longitudinally within the interior closed space;
• said lower plate region extends outward from said guide slot and is configured to be attachable to the stationary portion of the chair;
• wherein the adjustment plate is movable between a first vertical position and a second vertical position relative to the housing, in the first vertical position the adjustment plate is able to move in the longitudinal direction from one side of the serpentine cam surface to the other side of the serpentine cam surface, in the second vertical position the cam follower on the adjustment plate is able to engage either one of the first and second adjustment surface segments to selectively adjust a longitudinal position of the adjustment plate relative to the housing to the at least two adjustment positions.