PURPOSE: To dispense with a special space for an air pump by utilizing a strut pipe for piston-cylinder to hold a folded control lever on the outer surface of the strut pipe.

CONSTITUTION: When a second lever 5 is pushed forward together with a first lever 3 until a support lever 8 bears against the outer wall portion 16a of a bracket 16, the first and second levers 3, 5 and the support lever 8 occupy a certain relative position. Both levers function as a single lever and cannot swing laterally with respect to a strut pipe C. Thus, this gets ready for pumping operation so that a special space for an air pump is not needed.