主权项 |
1. An apparatus comprising:
a cylindrical cassette with a cylindrical inner sleeve and an cylindrical outer sleeve, the inner sleeve fitting inside the outer sleeve and configured so that when the outer sleeve is rotated in a first direction, the inner sleeve is also rotated, and when the outer sleeve is rotated in a second direction opposite to the first direction, the inner sleeve is not rotated; said cassette having a bevel gear at each axial end; and said outer sleeve having teeth oriented along the axis of the cassette. |