PURPOSE: To improve the performance of operation without hindering facilitation of getting on and off a driver seat by incorporating linkage in a control box that doubles as a universal rise and fall armrest.

CONSTITUTION: Linkage 25 that transmits the operating force of an operating lever 6 to an operating valve 1 is incorporated in a universal rise and fall control rise and fall control box 4. Besides, when a driver gets off from his or her seat, the release lever 14 on the operating lever 6 side is revolved downward and the operating lever 6 is stopped to the central position by an operating lever stop piece 10. Since the release lever 16 on the box 4 side is unlocked, the driver can get on and off his or her seat without being interrupted by the box 4 by revolving this release lever 16 upward, removing a hooking lever 24 from a hooking plate 23, and revolving the box 4 upward in this condition.