| 摘要 |
PURPOSE:To always impart proper opening force and to safely and lightly enable opening and closing without causing rapid falling or the like by increasing the opening force with an adjustment means when the gravity of an upper frame is increased by mounting an attachable/detachable member and reducing the opening force when the gravity is reduced by detaching the attachable/ detachable member. CONSTITUTION:The pressurizing force of a pressurizing means 8 imparting the opening force to the upper frame 3 is set so as to be adjustable by the adjustment means 12. The adjustment means 12 is actuated according to the member 7 which can be attached/and detached to/from the frame 3 and it switches the pressurizing force to be two-steps, multisteps and stepless. |
