| 摘要 |
PURPOSE:To enable to move a rack only when a driving gear is driven and to retract the rack when rotation of the driving gear is stopped, by holding a free gear capable of coming into mesh with the driving gear and a rack moving gear simultaneously on a gear retaining plate disposed coaxially with the driving gear. CONSTITUTION:When a gear 1 is rotated, a moment of rotation to turn a free gear 2 around the gear 1 is produced at a retainer plate 3 by the frictional force produced between the gear 1 and the retainer plate 3 and the force acted at the contact face between the gear 1 and the free gear 2, so that the free gear 2 is turned toward a rack moving gear 4 and comes into mesh with the same. On the other hand, when rotation of the gear 1 is stopped, the moment of rotation produced between the gear 1 and the free gear retaining plate 3 and between the free gear 2 and the retainer plate 3 is reduced to zero while leaving only the frictional force acted between the retainer plate 3 and the gear 1. Resultantly, the free gear 2 is retracted in the direction opposite to that in which said moment of rotation is acted, so that the free gear 2 comes out of engagement with the rack moving gear 4. |
