Mechanical device for use particularly for the synchronous movement of the seat and backrest of a chair

Claim 1

A mechanical device connectable to an upper end of a central column extending from a chair base for use particularly for synchronous movement of a seat and backrest of a chair, including a first support bracket connectable to the upper end of the central column, said first support bracket including an enclosed lower flat surface and a pair of vertical walls extending upwardly from opposite sides of said lower surface, a second fastening bracket including an upper flat surface and a pair of vertical walls extending downwardly from opposite sides of said upper surface, said downwardly extending walls of said second bracket being located outwardly from and overlapping the entire length of said upwardly extending walls of said first bracket, said second bracket adapted to be connected to the seat, a first axis extending through said upwardly extending walls of said first bracket and through said downwardly extending walls of said second bracket, said first axis pivotally connecting said second bracket to said first bracket for pivotal rotation of said second bracket about said first axis, said first axis being transversely spaced with respect to the central column, a third bracket having a first end adapted to be secured to the backrest and a second end including a pair of slotted apertures, said third bracket being located between said upwardly extending walls of said first bracket, a second axis extending through said downwardly extending walls of said second bracket and through said third bracket, said second axis pivotally connecting said third bracket to said second bracket for pivotal rotation of said third bracket with respect to said second bracket about said second axis, means connected between said first and third brackets for limiting pivotal movement of said third bracket with respect to said first bracket including a third axis extending through said upwardly extending walls of said first bracket and through said slotted apertures of said third bracket, means for the selective locking of said second bracket and said third bracket in a stationary position relative to said first bracket including a plurality of adjacent lamellae covers located between said upwardly extending walls of said first bracket, each cover including an aperture at a first end and a slotted aperture at a second end, and a fourth axis extending through said downwardly extending walls of said second bracket and through said apertures in said first end of said covers, said third axis extending through said slotted apertures in said covers, said third axis being operative to selectively lock said second and third brackets in said stationary position relative to said first bracket, and means for resiliently exerting force against said first and second brackets, said means for exerting force extending between said first and second brackets and located between said second axis and said fourth axis, whereby pivotal movement of said third bracket with respect to said second bracket causes synchronous pivotal movement of said second bracket with respect to said first bracket.