| 摘要 |
PURPOSE:To remove backlash precisely with a small-sized and simple structure by frictionally contacting two pairs of relatively rotatable and coaxial transmission gears having the same modules and pitch circles respectively and the different numbers of teeth in a driving gear system. CONSTITUTION:Two pairs of transmission gears 32, 33 and 34, 35 having the same modules and pitch circles respectively, and the number of teeth of the gears 32, 34 is smaller than that of the gears 33, 35 by only one. Since the number of teeth of the gear 32 is different from that of the ear 33 and both the gears 32, 33 receive friction in the thrust direction by a compression spring 44 inserted between clatch plates 40, 41, their teeth are shifted each other in accordance with the rotation of a pinion 29, so that contact force is applied to both the sides of the teeth of the pinion 29. Consequently, the gear 33 is slipped from the gear 32 and both the gears 32, 33 are rotated while removing backlash against the pinion 29. In addition, backlash is similarly removed between a focus gear 26 and the gears 34, 35, so that the focus can be always correctly held. |
