Patent ID: 7080884

Claim:
A working chair with adjustable backrest support pre-set tension, comprising: a seat comprising a seat support and a seat plate supported above the seat support, the seat support and seat plate each having a forward edge; a first pivot at the forward edge of the seat support and a second pivot at the forward edge of the seat plate; a backrest support having an end part pivotally connected to the seat support; an energy storing device for biasing the backrest support against the back of a seated user; a manually operable adjustment mechanism for adjusting a pre-set tension of the energy storing device; a guide bar pivotally mounted between the first and second pivots; the energy storing device having a front end and a rear end, the front end of the energy storing device being positioned on the guide bar and rotatably mounted on the second pivot and the rear end of the energy storing device adjustably engaging the end part of the backrest support at a contact point; the contact point between the rear end of the energy storing device and the end part of the backrest support being adjustable; the adjustment mechanism comprising an interlocking element positioned on the end part of the backrest support, the interlocking element being adapted to be forced into engagement with the energy storing device.