Importance

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Abstract

A chair control mechanism is provided for use on a chair having a separate seat 14 and backrest 16 that move with respect to a base 12 of the chair. The mechanism 22 includes a housing 26 supported on the base, and brackets 28, 30 secured to the seat and backrest. The seat bracket 28 is supported on the housing for pivotal movement about a horizontally extending front pivot axis 68 between an upright position and a reclining position, and the front pivot axis is located adjacent the front end of the housing. The backrest bracket 30 is supported on the housing for pivotal movement about a horizontally extending rear pivot axis 80 that is located rearward of the front pivot axis. A mechanical linkage 70, 78 is connected between the brackets at a position spaced rearward of the rear pivot axis relative to the housing for transmitting pivoting movement between the brackets, and a spring assembly 32 is connected between the housing and the backrest bracket for biasing the seat and backrest toward the upright position. A forward travel-stop control assembly 38 is provided on the mechanism for adjusting the forward most position of the seat and backrest, as is a tilt control assembly 36 which permits the seat and backrest to be locked against tilting movement. The tilt control assembly 36 includes a locking plate 102 supported on the housing for relative translational movement between an extended position in which the locking plate is received in an aperture of the backrest bracket to lock the backrest bracket from further pivotal movement, and a retracted position removed from the aperture to allow further pivotal movement of the seat and backrest. A locking pawl 106 is supported on a lever 104 of the tilt assembly and engages the lock plate 102 to retract and extend the plate when the lever is rotated. In addition, a clutch is interposed between the actuating lever and the locking pawl for exerting a rotating force on the locking pawl to move the locking pawl from the second position when the actuating lever is rotated. The rotating force of the clutch is smaller than the friction force that is exerted on the locking plate when the pivoting force of the spring assembly 32 is exerted on the locking plate such that the locking plate can only be retracted when the friction force is reduced to a magnitude less than the rotating force.

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First Claim