| 摘要 |
A cylindrical ink roller sleeve is mounted on a fixed shaft for sliding axially on and rotating on the shaft. First and second helical elements are fixed internally of the sleeve coaxially with each other and concentric to the shaft. The convolutions of the helixes have different pitches and twist in opposite directions. A device having helix followers at opposite ends is supported from the shaft. Rotation of the sleeve while one helix is engaged by a follower drives the sleeve axially in one direction at one speed until a limit is reached whereupon the one follower is disengaged from one helix and the other follower is engaged with the other helix to drive the ink roller sleeve in the opposite direction at a different axial speed.
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