Patent ID: 7497515

Claim:
A backrest structure for a chair having: a curved track in a fixed relation to a seat of the chair; a carriage slidably mounted on the curved track; a backrest mounted on the carriage; a resilient support mechanism provided for resiliently supporting the carriage and backrest with respect to the seat so that the carriage is biased uppermost to support the backrest in an erect position, and adapted to slide down along the curved track and tilt the backrest rearwards and downwardly in response to a rearward shift of the weight of a person sitting on the chair and leaning against the backrest, the resilient support mechanism including a pair of compressible spring rods positioned at sides of the chair; adjustment means provided for adjusting the resilient support mechanism such that the backrest is enabled to be maintained in the erect position in response to different body loads of persons utilizing the chair, wherein the resilient support mechanism is anchored at a first end to the carriage and at a second end to the adjustment means.