Backrest of height-adjustable chair

Abstract

A backrest of a height-adjustable chair includes a height-adjustable seat including a seat cushion frame, a seat cushion thereon, and a backrest connection unit including a first mounting portion and a second mounting portion on the seat cushion frame; and a backrest body including a backrest frame body, a backrest plate, and an S-shaped frame body therebetween. A clearance for adjustment is defined between the backrest frame body and the backrest plate, and an S-shaped portion of the S-shaped frame body is located therein. An end of the backrest frame body close to the height-adjustable seat is mounted at the first mounting portion, a lower end of the S-shaped frame body is mounted at the second mounting portion, when the backrest body is raised, the S-shaped frame body is extended, and when the backrest body is lowered, the S-shaped frame body is compressed.

What is claimed is: 
     
         1 . A backrest of a height-adjustable chair, comprising:
 a height-adjustable seat comprising a seat cushion frame, a seat cushion on the seat cushion frame, and a backrest connection unit on the seat cushion frame, wherein the backrest connection unit comprises a first mounting portion and a second mounting portion; and   a backrest body comprising a backrest frame body, a backrest plate connected to a part of the backrest frame body, and an S-shaped frame body between the backrest frame body and the backrest plate, wherein a clearance for adjustment is defined between the backrest frame body and the backrest plate, and an S-shaped portion of the S-shaped frame body is located in the clearance for adjustment;   wherein an end of the backrest frame body close to the height-adjustable seat is mounted at the first mounting portion, a lower end of the S-shaped frame body close to the height-adjustable seat is mounted at the second mounting portion, when the backrest body is raised, the S-shaped frame body is extended, and when the backrest body is lowered, the S-shaped frame body is compressed.   
     
     
         2 . The backrest of the height-adjustable chair according to  claim 1 , wherein the backrest frame body is a frame body with a space in a middle of the backrest frame body, a cam is provided between the backrest frame body and the S-shaped frame body, and a connecting lug for mounting the cam is provided on the backrest frame body;
 wherein an end of the backrest plate close to the height-adjustable seat is provided with a mounting lug, a cam hole is defined in the mounting lug, and when the backrest plate is assembled with the backrest frame body, the cam is located in the cam hole.   
     
     
         3 . The backrest of the height-adjustable chair according to  claim 2 , wherein the S-shaped frame body comprises a first curved portion and a second curved portion, the second curved portion is located close to the height-adjustable seat, the first curved portion is connected to the second curved portion and the first curved portion is located above the second curved portion, the first curved portion and the second curved portion are curved away from each other, and a lower half of the backrest plate aligns flush with the first curved portion. 
     
     
         4 . The backrest of the height-adjustable chair according to  claim 3 , wherein textures are uniformly provided on the backrest plate, the textures are configured to ensure comfort after the backrest plate is bent, an upper half of the backrest plate is defined as a first backrest plate while the lower half of the backrest plate is defined as a second backrest plate, and a thickness of the first backrest plate is smaller than a thickness of the second backrest plate. 
     
     
         5 . The backrest of the height-adjustable chair according to  claim 3 , wherein the first curved portion has a curvature, and the second curved portion is uniformly configured with a plurality of cushioning grooves on a surface facing the height-adjustable seat. 
     
     
         6 . The backrest of the height-adjustable chair according to  claim 5 , wherein the plurality of cushioning grooves are L-shaped. 
     
     
         7 . The backrest of the height-adjustable chair according to  claim 6 , wherein the backrest connection unit is L-shaped, the first mounting portion extends horizontally while the second mounting portion extends vertically, the first mounting portion is connected to the seat cushion frame, and a chamber around the second mounting portion is defined at a bottom of the backrest frame body, so that the backrest frame body is adjustable in a vertical direction. 
     
     
         8 . The backrest of the height-adjustable chair according to  claim 7 , wherein a height positioning structure is provided between the backrest frame body and the backrest connection unit, and the height positioning structure is configured to lock a height position of the backrest. 
     
     
         9 . The backrest of the height-adjustable chair according to  claim 7 , wherein a lug plate is provided at the lower end of the S-shaped frame body, the lug plate is configured with a connecting hole, and the S-shaped frame body is rotatably connected to the first mounting portion via the connecting hole. 
     
     
         10 . The backrest of the height-adjustable chair according to  claim 9 , wherein the S-shaped frame body is rotatably connected to a rear end of the seat cushion frame via the connecting hole.