Chair having synchronously coupled tiltable seat and back rest

Claim 1

A chair comprising a seat support, a seat pivotally connected to said seat support at a first hinge point located adjacent the forward edge of said seat, a back rest support pivotably connected to said seat support at a second hinge point spaced from said first hinge point, linkage means between said seat and said back rest support operative to cause pivotal motion of said back rest support about said second hinge point to effect related pivotal motion of said seat about said first hinge point, a third hinge point adjacent the rear end of said seat support, said linkage means comprising a generally vertical connecting element having its upper end pivotally connected to said seat adjacent the rear edge of said seat and having its lower end pivotally connected to said back rest support at a location between said second and third hinge points, a fourth hinge point located on said back rest support above said third hinge point, said back rest support being substantially L-shaped and comprising a generally horizontal leg and a generally vertical leg, the free end of said generally horizontal leg being pivotally attached to said second hinge point at a location rearward of said first hinge point and forward of said third hinge point, said fourth hinge point being located near the free end of said generally vertical leg, an elongated stored power element extending in a generally vertical direction and having a pair of opposing ends which are connected to said third and fourth hinge points respectively, and a back rest mounted on said back rest support, said back rest including a rear cover, said stored power element being concealed within said back rest between its forwardmost surface and said rear cover.