Chair with seat and backrest that oscillate in a synchronized way

Abstract

A chair with seat and backrest that oscillate in a synchronized way, comprising: a base structure ( 14 ); a backrest-supporting structure ( 26 ) articulated to the base structure ( 14 ) about a first transverse axis (A); a seat-supporting structure ( 44 ) which is mobile with respect to the base structure ( 14 ) in a way synchronized with the movement of oscillation of the backrest-supporting structure ( 26 ); and elastic means ( 24 ) tending to counteract the oscillation backwards of the seat and backrest. One rear part of the seat-supporting structure ( 44 ) is articulated to the backrest-supporting structure ( 26 ) about a second axis of oscillation (B) parallel to the aforesaid first axis (A), and one front part of the seat-supporting structure ( 44 ) is connected to the base structure ( 44 ) by means of at least one articulation element ( 50 ).

1 . A chair with seat and backrest that oscillate in a synchronized way, comprising: 
 a base structure;    a backrest-supporting structure articulated to the base structure about a first transverse axis;    a seat-supporting structure which is mobile with respect to the base structure in a way synchronized with the movement of oscillation of the backrest-supporting structure; and    elastic means tending to counteract the oscillation backwards of the seat and backrest,    wherein one rear part of the seat-supporting structure is articulated to the backrest-supporting structure about a second oscillation axis parallel to the aforesaid first axis, and one front part of the seat-supporting structure is connected to the base structure by means of at least one articulation element.    
     
     
         2 . The chair according to    claim 1   , wherein the backrest-supporting structure is mounted in an oscillating way about a transverse tubular element carried by the base structure and is fixed to the outer ends of a torsion bar set inside said transverse tubular element.  
     
     
         3 . The chair according to    claim 2   , wherein the backrest-supporting structure comprises a pair of side tubular elements set at the opposite ends of said transverse tubular element.  
     
     
         4 . The chair according to    claim 3   , wherein the aforesaid side tubular elements are connected together by a transverse rod defining the aforesaid second articulation axis.  
     
     
         5 . The chair according to    claim 1   , wherein the seat-supporting structure is connected to the base structure by means of an articulated-quadrilateral mechanism.  
     
     
         6 . The chair according to    claim 5   , wherein the aforesaid front part of the seat-supporting structure is articulated to the base structure by means of a pair of connecting rods.  
     
     
         7 . The chair according to    claim 5   , wherein the aforesaid torsion bar co-operates with an adjusting device including a lever fixed to a central portion of the torsion bar and a screw mechanism designed to adjust the position of said lever with respect to the base structure.  
     
     
         8 . The chair according to    claim 1   , comprising a blocking device for blocking the seat and backrest in at least one selected position.  
     
     
         9 . The chair according to    claim 8   , wherein the aforesaid blocking device comprises a lever articulated to the base structure about the aforesaid first transverse axis and articulated to the backrest-supporting structure about the aforesaid second transverse axis, the blocking lever co-operating with a control device including at least one blocking element movable between an inoperative, releasing, position and an operative, blocking, position.  
     
     
         10 . The chair according to    claim 9   , wherein the aforesaid control device comprises a pair of blocking pins slidable in a direction orthogonal to the plane of oscillation of the blocking lever and co-operating with respective arrays of holes provided on the blocking lever.  
     
     
         11 . The chair according to    claim 10   , wherein the aforesaid control device comprises an oscillating shaft carrying a transverse pin which controls sliding of the aforesaid blocking pins by means of a pair of pin springs.  
     
     
         12 . The chair according to    claim 11   , wherein the aforesaid control device comprises a retention device designed to withhold said oscillating shaft respectively in a blocking position and in a releasing position.