Chair back

Abstract

A chair back, belonging to the field of office furniture, comprises a stretching mechanism, and a supporting mechanism including a supporting frame, an adjusting lever and a rotor disposed on the supporting frame, a spring disposed on the adjusting lever, and a rope wound across the rotor and having an end connected to the spring and an end connected to the stretching mechanism. A sliding slot is formed in the supporting frame. An adjusting block sliding along the sliding slot is disposed in the sliding slot and connected to the adjusting lever in a threaded manner, and has a side abutting against one end of the spring. The stretching mechanism can elastically change to some extent in the stretching direction thereof, so that when moving in this direction, the back of a user will always cling to the backrest, and thus, the user feels more comfortably

What is claimed is: 
     
         1 . A chair back, comprising a stretching mechanism ( 30 ) and a supporting mechanism ( 20 ), the supporting mechanism ( 20 ) comprising a supporting frame ( 21 ), an adjusting lever ( 22 ) and a rotor ( 23 ) disposed on the supporting frame ( 21 ), a spring ( 24 ) disposed on the adjusting lever ( 22 ), and a rope ( 25 ) wound across the rotor ( 23 ) and having an end connected to the spring ( 24 ) and an end connected to the stretching mechanism ( 30 ), wherein:
 a sliding slot ( 211 ) is formed in the supporting frame ( 21 ), and an adjusting block ( 212 ) sliding along the sliding slot ( 211 ) is disposed in the sliding slot ( 211 ) and connected to the adjusting lever ( 22 ) in a threaded manner, and has a side abutting against one end of the spring ( 24 ).   
     
     
         2 . The chair back according to  claim 1 , wherein the stretching mechanism ( 30 ) comprises a stretchable shroud ( 31 ) disposed on the supporting frame ( 21 ) and at least one load-supporting block ( 32 ) disposed on an inner wall of the stretchable shroud ( 31 );
 the load-supporting block ( 32 ) is connected to one end of the rope ( 25 ).   
     
     
         3 . The chair back according to  claim 2 , wherein a guide block ( 321 ) is disposed on an outer side of the outermost load-supporting block ( 32 ) and slides along a guide groove ( 50 ). 
     
     
         4 . The chair back according to  claim 3 , wherein the guide groove ( 50 ) comprises a side limiting part ( 51 ), and top limiting parts ( 52 ) are disposed at an upper end and a lower end of the side limiting part ( 51 ). 
     
     
         5 . The chair back according to  claim 3 , further comprising a limiting mechanism ( 4 ), wherein:
 the limiting mechanism ( 4 ) comprises:   at least one guide roller ( 41 ) which is located on one side of the load-supporting block ( 32 ) and rotates in a direction tangent to a stretching direction of the stretching mechanism ( 30 ); and   at least one guide face ( 42 ) which is located on another side of the load-supporting block ( 32 ) and is parallel to the stretching direction of the stretching mechanism ( 30 ).   
     
     
         6 . The chair back according to  claim 5 , wherein under the condition of at least two load-supporting blocks ( 32 ), the guide rollers ( 41 ) or guide faces ( 42 ) on inner sides of the adjacent load-supporting blocks ( 32 ) are connected by means of an inner connecting frame ( 43 ). 
     
     
         7 . The chair back according to  claim 2 , further comprising a lock handle ( 60 ) provided with a clamping column ( 601 ), wherein:
 a plurality of clamping grooves ( 320 ) are formed in the load-supporting block ( 32 );   the clamping column ( 601 ) is to be embedded in one of the clamping grooves ( 320 ).   
     
     
         8 . The chair back according to  claim 7 , wherein the lock handle ( 60 ) comprises a pull rod ( 602 ), and the clamping column ( 601 ) is hinged to a lower end of the pull rod ( 602 ). 
     
     
         9 . The chair back according to  claim 8 , wherein a flexible part ( 603 ) for elastically pressing the clamping column ( 601 ) is disposed over the clamping column ( 601 );
 the flexible part ( 603 ) is a press spring, the pull rod ( 602 ) penetrates through an extension port ( 210 ), and the press spring is disposed around the pull rod ( 602 ) below the extension port ( 210 ).   
     
     
         10 . The chair back according to  claim 7 , wherein when the clamping column ( 601 ) is clamped in one of the clamping grooves ( 320 ), a free end of the clamping column ( 601 ) is higher than a hinged end of the clamping column ( 601 ) and the pull rod ( 602 ).