| 摘要 |
<p>PURPOSE:To absorb a shock when a projection provided to a rotation inhibiting means engages with a tooth, by forming the rotation inhibiting means, constituting a back tension unit, of an elastic material. CONSTITUTION:Rotation inhibiting means 96 equipped with a pair of the 1st and 2nd projections 92 and 94 provided symmetrically on the right and left is fixed, being oscillatable, in the center of the upper edge part of traveling part 88. The oscillating tracks of projections 92 and 94, when traveling part 8 is moved to the vertical upper part, can cross rotating tracks of teeth 70 and 170 of the 1st and 2nd ratchets 66 and 166 and when traveling part 88 is moved vertically downward, they never cross them. Since rotation inhibiting means 96 is made of an elastic material such as plastics, a shock when projections 92 and 94 engages with teeth 70 and 170 of ratchets 66 and 166 can be absorbed by shock absorption part 97.</p> |
