Chair backrest structure and foldable chair

Abstract

A chair backrest structure and a backrest chair having the chair backrest structure. The chair backrest structure includes a backrest plate and a fixed frame for supporting the backrest plate. At least an upper edge of the backrest plate is folded backward to form a fixed flange, and the fixed frame comprises an installation slot corresponding to the fixed flange. The backrest plate is a vacuum-formed plastic plate, and a surface of the fixed flange comprises one or more inverted protruding teeth formed by vacuum-forming or by molding. The fixed flange is disposed in the installation slot, and the one or more inverted protruding teeth are buckled to an edge of the installation slot to limit the fixed flange from being separated from the installation slot.

What is claimed is: 
     
         1 . A chair backrest structure, comprising:
 a backrest plate, and   a fixed frame for supporting the backrest plate, wherein:
 the backrest plate is a plastic element, 
 the fixed frame is a metal element, 
 at least an upper edge of the backrest plate is folded backward to form a fixed flange, 
 the fixed frame comprises an installation slot corresponding to the fixed flange, 
 the backrest plate is a vacuum-formed plastic plate, 
 a surface of the fixed flange comprises one or more inverted protruding teeth formed by vacuum-forming or by molding, 
 the fixed flange is disposed in the installation slot, and 
 the one or more inverted protruding teeth are buckled to an edge of the installation slot to limit the fixed flange from being separated from the installation slot. 
   
     
     
         2 . The chair backrest structure according to  claim 1 , wherein:
 the upper edge and left and right edges of the backrest plate are all folded backward to form the fixed flange,   the one or more inverted protruding teeth are a plurality of inverted protruding teeth, and   the plurality of inverted protruding teeth are arranged on the fixed flange at even intervals from beginning to end.   
     
     
         3 . The chair backrest structure according to  claim 2 , wherein:
 the fixed frame comprises two supporting sections with left-right symmetry and a mounting section connected to top ends of the two supporting sections,   the upper edge of the backrest plate is arc-shaped,   a shape of the mounting section of the fixed frame cooperates with a shape of the upper edge of the backrest plate, and   the installation slot extends from a top of a first one of the two supporting sections to a top of a second one of the two supporting sections after passing through the mounting section.   
     
     
         4 . The chair backrest structure according to  claim 3 , wherein:
 the fixed frame further comprises a lateral rod connected between lower parts of the two supporting sections.   
     
     
         5 . A foldable chair, comprising:
 the chair backrest structure according to  claim 1 ,   a chair leg, and   a seat plate, wherein:
 a structure between the chair leg and the seat plate of the foldable chair comprises a sliding seat and a connecting shaft, 
 the sliding seat is slidably connected to a side edge of the seat plate, 
 the connecting shaft is disposed on the chair leg, 
 the sliding seat is rotatably connected to the connecting shaft, 
 the sliding seat is U-shaped, 
 a plastic lining shaped as a U is disposed in the sliding seat, 
 the plastic lining is attached to an inner surface of the sliding seat, 
 the sliding seat is sleeved on the side edge of the seat plate from bottom to top, 
 the plastic lining comprises a pressing edge, 
 the side edge of the seat plate comprises a positioning step, and 
 the pressing edge abuts an upper side of the positioning step to limit movement of the sliding seat in a vertical direction to prevent the sliding seat from being separated from the side edge of the seat plate in the vertical direction. 
   
     
     
         6 . The foldable chair according to  claim 5 , wherein:
 a bottom surface of the plastic lining comprises a supporting rib protruding upward, and   the supporting rib abuts a lower side of the positioning step.   
     
     
         7 . The foldable chair according to  claim 5 , wherein:
 the seat plate comprises a vacuum-formed panel and a supporting frame,   an outer side of the vacuum-formed panel comprises a surrounding edge vertically extending downward,   the supporting frame is disposed along an inner surface of the surrounding edge, and   the positioning step is disposed on an inner surface of the supporting frame.   
     
     
         8 . The foldable chair according to  claim 7 , wherein:
 a bottom of the supporting frame is folded outward to form a C-shaped hook, and   a bottom end of the surrounding edge is disposed in the C-shaped hook to be pressed and secured by the C-shaped hook.   
     
     
         9 . The foldable chair according to  claim 8 , wherein:
 a bottom surface of the plastic lining comprises a sliding groove corresponding to the C-shaped hook, and   the C-shaped hook is matched with and installed in the sliding groove.   
     
     
         10 . The foldable chair according to  claim 5 , wherein:
 a first side edge of the plastic lining opposite to the pressing edge comprises a positioning flange,   a second side edge of the plastic lining where the pressing edge is located laterally blocks the positioning step from an inner side of the seat plate, and   the positioning flange laterally blocks an outer edge of the seat plate from an outer side of the seat plate.   
     
     
         11 . The foldable chair according to  claim 5 , wherein:
 the plastic lining is buckled to the sliding seat.   
     
     
         12 . The foldable chair according to  claim 5 , wherein:
 the connecting shaft is fixedly hinged to the chair leg.