Chair

1. A chair comprising a support, a seat element, a back element, a foot element, a spring mechanism, and a weight-control-operated adjustment installation for the spring mechanism, wherein the spring mechanism comprises at least one leaf spring that on one side is clamped in the support, and at least one bearing that is displaceable on a raceway between at least one of the leaf springs and the support, wherein the back element and/or the seat element are/is supported on a free end region of the at least one leaf spring, wherein the adjustment installation comprises an actuator, a transmission means, and a weighing mechanism that guides the actuator, characterized in that:

the actuator comprises a gear wheel, and the actuator in the stressing and the de-stressing of the seat element is displaced by the mechanical weighing action on a rack that is disposed in a locationally fixed manner on the foot element and herein rolls on said rack,

wherein the transmission means comprises a knuckle joint lever,

wherein the knuckle joint lever comprises a first leg and a second leg,

wherein the first leg is connected in a rotationally fixed manner to the gear wheel,

wherein the first leg and the second leg an articulation point are interconnected so as to be rotated in an articulated manner about an articulation axis,

wherein the second leg is connected to the bearing,

wherein the bearing, depending on a rotary position of the first gear wheel between a forward position and a rearward position, is positioned below the at least one leaf spring such that said leaf spring, depending on the respective position of the bearing, supports the back element to a variable degree.

2. The chair as claimed in claim 1 , characterized in that the leaf spring in the case of a completely tilted-back back element by way of a force slides the bearing from the rearward position thereof in the direction of the forward position of said bearing such that by way of the first and of the second leg a torque acts on the first gear wheel of the actuator, wherein said torque, by way of a position of the legs assumed by the latter in the rearward position of the bearing, is kept low in such a manner that any rotation of the first gear wheel is prevented on account of the weight-controlled weighing mechanism.

3. The chair as claimed in claim 1 , characterized in that the two legs in the rearward position of the bearing conjointly are at an angle α<30°.

4. The chair as claimed in claim 1 , characterized in that the first leg in the rearward position of the bearing is at an angle β of at least 130° in relation to a movement direction of the bearing.

5. The chair as claimed in claim 1 , characterized in that the first leg is shorter than the second leg, and in that the first leg has a length which is at most half a length of the second leg.

6. The chair as claimed in claim 1 , characterized in that the transmission means comprises a second gear wheel and a rack that is configured so as to be locationally fixed on the support,

wherein the second gear wheel is connected to a free end of the second leg so as to be rotatable about a rotation axis,

wherein the second gear wheel in a rotating movement of the first gear wheel rolls on the rack that is configured on the support, and

wherein the second gear wheel is connected to the bearing in such a manner that said second gear wheel engages in a denticulation that is configured on the bearing such that the bearing in the rolling of the second gear wheel is displaced with the second gear wheel on the rack that is configured on the support displaced relative to the second gear wheel.

7. The chair as claimed in claim 1 , characterized in that the chair comprises an articulation means and a weighing spring, wherein the foot element and the support are connected by the articulation means, and wherein the support is supported on the foot element by way of the weighing spring.

8. The chair as claimed in claim 1 , characterized in that the back element and the seat element form a seat shell.

9. The chair as claimed in claim 8 , characterized in that the chair comprises a front swing arm and a rear swing arm, wherein the front swing arm is pivotably articulated on the support and is connected to the seat element, wherein the rear swing arm is pivotably articulated on the support and is connected to the seat shell.

10. The chair as claimed in claim 8 , characterized in that the leaf spring is fixed to the support by a first end region, bearing on the bearing outside the first end region, and supporting the seat shell outside the first end region.