Backrest device

Abstract

A backrest device comprises at least one backrest and at least one connecting unit having two springs, two jointing members and a connecting member. Each spring comprises a first end and a second end. Each jointing member is provided with at least one first engaging block for engaging with the first end of the spring. The connecting member is provided with at least one second engaging block for engaging with the second end of the spring and is fixed to a chair stably. When the user sits in the chair with his back leaning against the backrest, since the springs are flexible, which can enable the backrest to be freely adjusted and moved in response to the movement of the back of the user, producing a buffering effect and providing a comfortable support to the back of the user, so the user will feel comfortable.

1 . A backrest device, comprising:
 at least one backrest; and   at least one connecting unit having two springs, two jointing members and a connecting member, each spring being provided with a first end and a second end arranged in a reverse direction to the first end, the jointing members being fixed to the backrest and the first ends of the springs, respectively, the connecting member being provided with two connecting portions for fixing to the second ends of the springs, respectively.   
     
     
         2 . The backrest device as claimed in  claim 1 , wherein each jointing member is provided with at least one first engaging block for engaging with the first end of each spring, and each connecting portion of the connecting member is provided with at least one second engaging block for engaging with the second end of each spring. 
     
     
         3 . The backrest device as claimed in  claim 1 , wherein the backrest device further comprises two mounting members for receiving the springs. 
     
     
         4 . The backrest device as claimed in  claim 1 , wherein two positioning blocks are provided on a rear surface of the backrest, each positioning block is provided with a threaded sleeve having an inner threaded portion, and each jointing member is defined with a through hole through which a threaded member is threaded in the inner threaded portion of the threaded sleeve of the positioning block, so that the jointing members are fixed to the positioning blocks of the backrest stably. 
     
     
         5 . The backrest device as claimed in  claim 1 , wherein the backrest device is assembled to a chair whose frame is provided with a built-in nut, the connecting member is defined with a penetrating hole, and a bolt is threaded through the penetrating hole of the connecting member into the built-in nut of the frame to fix the connecting member to the frame. 
     
     
         6 . The backrest device as claimed in  claim 3 , wherein the mounting members are made of flexible material.