| 摘要 |
A front derailleur (10, 60, 1000, 1100, 1200, 1600, 1700, 2110) including an annular chain guide (90, 236, 236', 900, 1500) for engagement and disengagement of a bicycle chain (42) with multiple chain rings (22, 24, 26) of a crankset. The annular chain guide (90, 236, 236', 900, 1500) may be positioned by linear guide rods (28). The annular chain guide (90, 236, 236', 900, 1500) may have an inside lifting surface (218, 218', 2018) and an outside pulling surface (216, 216', 2016 for engaging diametrically opposed corners of a chain when viewed in cross-section. The annular chain guide (90, 236, 236', 900, 1500) may have an opening defined by a polygon having at least five sides. The motion of the annular chain guide (90, 236, 236', 900, 1500) during a up-shift, i.e., displacement of the chain from a smaller chain ring to a next larger chain ring includes an upward, outward and rearward linear motion relative to a bicycle frame including upward force exerted by the annular chain guide (90, 236, 236', 900, 1500) against the chain (42). The motion of the annular chain guide (90, 236, 236', 900, 1500) during a down-shift is exactly opposite whereby the annular chain guide (90, 236, 236', 900, 1500) exerts a pulling down force against the chain (42). |
