PURPOSE: To change the effective length of both sleeves and to enable rotational movement operation of different sizes by cooperating inclined faces provided on a connecting sleeve and an adjusting sleeve with each other.

CONSTITUTION: An adjusting sleeve 14 under the action of a second spring 13 is provided and a connecting sleeve 10 and the adjusting sleeve 14 are cooperated in inclined faces 15, 16. The adjusting sleeve 14 is non-rotatably arranged on a rotational spindle 5 at a selectable angle position. The second spring 13 has a spring force large than the spring force of a first spring 9 so as to thrust the adjusting sleeve 14 toward a stopper 17 on the rotational spindle 5. The effective length of the both sleeves is changed by the inclined faces 15, 16 and connecting members between the connecting sleeve 10 and the spindle are brought in contact with each other by threading of the rotational spindle 5 so as to restrict the rotational movement of the rotational spindle 5.