| 摘要 |
<p>A support column for a pivotal chair. The support column may be fully enclosed and yet permit selective adjustability in the height of the seat section above a base portion merely by rotation of the seat section. A threaded spindle is nonrotatably secured to, and extends downwardly from, a seat section and is received within a hub tube that extends upwardly from the base portion. An adjusting nut is threaded onto the spindle to control the axial extent to which the spindle is received within the hub tube and thereby regulates the height of the seat section above the base portion. The adjusting nut is normally rotatable with the spindle, and an arm is secured to the adjusting nut which will engage a lost motion device after the seat section has been rotated through no more than a predetermined angular range. After the seat section has been further rotated through no more than an additionally predetermined angular range, the lost motion device - which is mounted to be freely rotatable with respect to the spindle - contacts a stop so that continued rotation of the seat section in the same direction effects relative movement between the spindle and the adjusting nut to adjust the height of the seat section. The angular range through which the seat section is rotated before the stop restrains both the lost motion device and the arm on the adjusting nut from rotating with the spindle constitutes the free pivotal range through which the seat section can be rotated without effecting any adjustment in the height thereof.</p> |
