Flexible support device for chair back tilting

A flexible support device for chair back tilting comprising:

• a supporting frame including a back portion formed on a rear end of the supporting frame, two peripheral extensions extending from two sides of a bottom of the back portion, two rotatable tabs oppositely extending from the two peripheral extensions, two through orifices defined on the two rotatable tabs, two rotatable edges formed on two distal ends of the two peripheral extensions, two first coupling orifices defined on the two rotatable edges, and two second coupling orifices formed proximate to the two first coupling orifices;
• a seat mounting including a first fixing portion and a second fixing portion opposite to the first fixing portion, two connecting fences connected with two sides of the first fixing portion and the second fixing portion, two rotatable locating portions formed on the two sides of the second fixing portion, two defining orifices defined on the two rotatable locating portions and corresponding to the two through orifices of the supporting frame, two joining elements configured to connect with the two through orifices of the supporting frame via the two defining orifices of the seat mounting, two slide orifices defined on two inner walls of the two connecting fences adjacent to the first fixing portion, and a drive protrusion extending to the second fixing portion from a center of an inner wall of the first fixing portion;
• and
• a base including two locating fringes with two first positioning orifices corresponding to the two first coupling orifices of the supporting frame, two second positioning orifices corresponding to the two second coupling orifices of the supporting frame, such that the two first coupling orifices and the two second coupling orifices of the supporting frame are connected with the two first positioning orifices and the two second positioning orifices by using two first screw bolts and two second screw bolts;
• the base further includes a holder extending from a center of a front end thereof and connected with a first end of a spring, and a second end of the spring being connected with a center of a first side of a flexible sheet;
• wherein the flexible sheet has two peripheral sections formed on two sides thereof and accommodated in two receiving grooves of two connectors, the base further includes two connection segments corresponding to the two connectors, wherein the two connection segments have two openings, and the two connectors have two pegs extending therefrom and corresponding to the two openings so that the two pegs of the two connectors are connected with the two openings of the two connection segments, and the two peripheral sections of the flexible sheet are fixed on the two connection segments, thus fixing the flexible sheet;
• wherein the two connection segments have two shafts extending from two outer walls thereof and slidably received in the two slide orifices of the seat mounting, and a center of a second side of the flexible sheet opposite to the spring is biased against the drive protrusion of the seat mounting.