Structure for chair backrest

Abstract

A structure for chair backrest is disclosed. The chair includes a first support frame, a second support frame coupled to the first support frame, a seat section arranged between the first support frame and the second support frame. The first support frame includes a backrest mounted thereon. The first support frame includes a lower frame section and an upper frame section. The lower frame section and the upper frame section include, mounted therebetween, a supine inclination assembly that upon receiving a force acting thereon takes a movement for achieving an predetermined angle of supine inclination. In this way, easy adjustment of the angular position of the backrest may be achieved for comfortableness of the user, and excessive inclination that causes potential risk can be avoided so as to improve the utilization of the backrest of the chair.

I claim: 
     
         1 . A chair backrest structure, wherein the chair comprises a first support frame, a second support frame coupled to the first support frame, a seat section arranged between the first support frame and the second support frame, the first support frame comprising a backrest mounted thereon, wherein the first support frame comprises a lower frame section and an upper frame section, the lower frame section and the upper frame section comprising, mounted therebetween, a supine inclination assembly that upon receiving a force acting thereon takes a movement for achieving an predetermined angle of supine inclination. 
     
     
         2 . The chair backrest structure according to  claim 1 , wherein the backrest is mounted to the upper frame section. 
     
     
         3 . The chair backrest structure according to  claim 1 , wherein the supine inclination assembly comprises an upper insertion piece, a lower insertion piece, and a return spring; the upper insertion piece comprises an upper insertion section, the upper insertion piece being provided, on an end thereof opposite to the upper insertion section, with an upper connection section, the upper connection section comprising an upper accommodation section formed therein, the upper insertion piece comprising an upper fitting section formed therein and extending in a direction from the upper connection section toward the upper insertion section, the upper fitting section being provided, at one side of a lower end thereof, with a constraint recess; the upper accommodation section comprises an upper through hole formed therein and extending through the upper insertion piece; the lower insertion piece comprises a lower insertion section, the lower insertion section comprising a locking hole formed therein, the lower insertion piece being provided, on an end thereof opposite to the lower insertion section, with a lower connection section, the lower connection section comprising a lower accommodation section formed therein, the lower insertion piece comprising a lower fitting section formed therein and extending in a direction from the lower connection section toward the lower insertion section, the lower insertion piece comprising a constraint peg formed thereon and projecting in a direction opposite to the lower insertion section; the lower accommodation section comprises a lower through hole formed therein and extending through the lower insertion piece; the return spring is arranged between the upper accommodation section and the lower accommodation section and the return spring has an end fit into and mounted in the upper fitting section and an opposite end fit into and mounted in the lower fitting section; and the upper insertion section of the upper insertion piece is inserted into a lower end of the upper frame section of the first support frame and the lower insertion section of the lower insertion piece is inserted into an upper end of the lower frame section of the first support frame. 
     
     
         4 . The chair backrest structure according to  claim 3 , wherein the lower insertion section of the lower insertion piece is provided with a locking hole formed therein, the lower frame section comprising a through aperture formed therein, a fastening element being screwed to the through aperture and the locking hole to fix the lower insertion piece to the lower frame section. 
     
     
         5 . The chair backrest structure according to  claim 3 , wherein the upper connection section and the lower connection section are opposite to each other and the constraint peg and the constraint recess correspond to each other, the constraint peg having an outside diameter smaller than the constraint recess, the constraint peg being received in the constraint recess. 
     
     
         6 . The chair backrest structure according to  claim 3 , wherein the constraint peg is engageable with an inside surface of the constraint recess to stop a movement of the upper insertion piece to take an angle of supine inclination with respect to the lower insertion piece so as to limit a maximum angle of supine inclination of the backrest. 
     
     
         7 . The chair backrest structure according to  claim 1 , wherein the first support frame and the second support frame are coupled to each other with a coupling member; and lower ends of the first support frame and the second support frame are provided with casters, the second support frame having an upper end to which armrests are mounted. 
     
     
         8 . The chair backrest structure according to  claim 1 , wherein the seat section comprises a cushion and a seat frame, the seat section being coupled through the seat frame between the first support frame and the second support frame.