Back extension backrest

Abstract

A backrest for use with a chair that has a seat and a base. The backrest includes a lower member having a proximal end and a distal end, and upper member attached to the chair at the proximal end. A spring-hinge mechanism pivotally connects the lower member in the vicinity of the distal end to the upper member. A lumbar support is attached to the upper member and the lower member and spans the spring-hinge mechanism. In use a user sitting on the seat may, by anterior flexing of the user's upper back cause the upper member to pivot relative to the lower member from an unflexed position to a flexed position.

1 . A backrest for use with a chair having a seat and a base, the backrest comprising:
 a) a lower member having a proximal end and a distal end, and attached to the chair at the proximal end;   b) an upper member;   c) a spring-hinge mechanism pivotally connecting the lower member in the vicinity of the distal end to the upper member; and   d) a lumbar support attached to the upper member and the lower member and spanning the spring-hinge mechanism wherein, in use a user sitting on the seat may, by anterior flexing of the user's upper back cause the upper member to pivot relative to the lower member from an unflexed position to a flexed position.   
     
     
         2 . The backrest as defined in  claim 1 , wherein an upper-back roller is attached to the upper member distal from the spring-hinge mechanism. 
     
     
         3 . A backrest for use with a chair having a seat and a base, the backrest comprising:
 a) a lower member having a proximal end and a distal end, and attached to the chair at the proximal end;   b) an upper member;   c) a spring-hinge mechanism pivotally connecting the lower member in the vicinity of the distal end to the upper member;   d) a lumbar support attached to the upper member and the lower member and spanning the spring-hinge mechanism; and   c) an upper-back roller attached to the upper member distal from the spring-hinge mechanism;   wherein, in use a user sitting on the seat may, by anterior flexing of the user's upper back cause the upper member to pivot relative to the lower member from an unflexed position to a flexed position.