| 摘要 |
PROBLEM TO BE SOLVED: To further reduce manufacturing cost, by manufacturing a mast by extrusion, by extremely simplifying a structure of the mast. SOLUTION: Substantially "V"-shaped groove parts 1b and 1b in cross-sectional view are formed in the vertical direction in a front part 1c and a rear part 1d in a recessed part 1a of the mast 1. A lift roller 2 fitted to the recessed part 1a formed on the mast 1 is formed into a substantially rhombus shape in cross-section. COPYRIGHT: (C)2006,JPO&NCIPI
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