Chair control mechanism utilizing plane spiral spring

Abstract From the Canadian patent

A low profile chair iron for controlling biased tilting between a seat or backrest and a support uses a substantially flat coil spring of increasingly smaller diameter coils between pivotably connected support bracket and a chair part bracket. Tension adjusting means for the spring are pivotably mounted with respect to the central coils of the spring and/or support bracket for minimizing nonuniform loading of the spring during the pivotable movement of the chair part bracket with respect to the support bracket.