Abstract: A support for tilting or synchronized chair is provided. The device includes a supporting frame, a mobile frame, an elastic member, a stiffness adjustment mechanism coupled with the elastic member, a locking mechanism for engaging the mobile frame with the supporting frame, and an actuation device for engaging and disengaging the locking mechanism. The actuation device includes a rocker arm and a return arm. The return arm is connected to the end of the rocker arm that the locking mechanism is attached. The rocker arm has at least two positions of stable equilibrium that are determined by the engagement or disengagement of the locking mechanism. An alternative embodiment includes an outer shell having first and second pins that are coupled with the backrest frame. The second pin may be positioned within a slot formed in the shell so that the backrest frame may move between upright and reclined positions.

Abstract: A support for tilting or synchronized chair is provided. The device includes a supporting frame, a mobile frame, an elastic member, a stiffness adjustment mechanism coupled with the elastic member, a locking mechanism for engaging the mobile frame with the supporting frame, and an actuation device for engaging and disengaging the locking mechanism. The actuation device includes a rocker arm and a return arm. The return arm is connected to the end of the rocker arm that the locking mechanism is attached. The rocker arm has at least two positions of stable equilibrium that are determined by the engagement or disengagement of the locking mechanism. An alternative embodiment includes an outer shell having first and second pins that are coupled with the backrest frame. The second pin may be positioned within a slot formed in the shell so that the backrest frame may move between upright and reclined positions.