A seat device is provided, comprising: a frame, a seat platform which is hinged to the frame so as to be pivotable between a completely folded position and a completely unfolded position, in which a user is allowed to seat thereon, and a spring mechanism with a variable overall spring constant, via which the seat platform is connected to the frame in a manner so as to be biased towards its folded position, thereby reducing an effort required by the user, who seats on the seat platform, for standing up therefrom, wherein the spring mechanism comprises a plurality of spring devices, each of which has an at least substantially constant spring characteristic which is at least substantially defined by a corresponding spring constant, and which are connected to each other in series, wherein the spring mechanism is provided such that, when the seat platform is at least substantially in its completely folded position, the variable overall spring constant is lower than in the case when the seat platform is at least substantially in its completely unfolded position, and wherein, when the seat platform is in its completely unfolded position, the overall spring constant is defined by the spring constants of only a fraction of the plurality of spring devices.
