| 摘要 |
A telescoping support such as a mast or boom employs a number of separate telescoping sections which fit one inside the other, with the outermost section being secured to a base. A double acting piston is situated completely inside the innermost section, with the piston rod being secured to the base and the piston cylinder arranged to reciprocate up and down within that section. On the upstroke of the cylinder, a hook mounted thereon engages a fixture located near the bottom of the innermost section. The cylinder hitches up the mast section, whereupon the fixture latches onto a retainer near the top of the next outer mast section. The cylinder then returns to its lowermost position and commences a second upstroke. Another hook engages a similar fixture near the bottom of the next outer mast section so that that section is lifted up until the fixture thereon latches onto the top of the third outer mast section. Again, the cylinder returns to its lowermost position and the process is repeated with the cylinder reciprocating up and down and each time hitching up the next outer mast section as well as all those supported by it until the mast is fully extended with all its movable sections being supported by the outermost section of the mast.
|
