is not the vertical sliding type but a rotationally opening closing type the configuration of the damper body 1 and other parts is the same as that in the first embodiment the rack member 9 is composed of fan shaped portions 9 a and 9 b having different diameters on the outer circumferences of the fan shaped portions 9 a and 9 b a first rack 7 and a second rack 8 are provided respectively the first rack 7 and the second rack 8 are respectively situated at the different positions offset along the axis direction of the rotative shaft 3 to engage with a small diameter pinion 4 and a large diameter pinion 5 provided on the damper body 1 incidentally the alternating short and long dash line in the drawing represents a vertical line in the second embodiment the movement of the door 2 can be adjusted in two steps in the entire process from the state when the door 2 is moved up for opening to the state when the door closes after the hand is moved away from the door 2 in the fully opening state of the door as shown in fig5 the first rack 7 engages with the small diameter pinion 4 here when the weight of the door 2 itself acts as the rotational torque on the rotative shaft 3 through the first rack 7 and the small diameter pinion 4 the rotative shaft 3 rotates at a very low speed to slowly move down the door 2 the first rack 7 moves engaging with the small diameter.