| 摘要 |
A pair of triangular prisms (1, 3) are joined together by a twin-action band hinge (4, 10, 11) so that the prisms can roll over each other between two end positions. The band hinge has a first band (4) with the same length as the peripheral surface (2) of a first prism (1), the first band being joined to the first prism at one end (5) and to the second prism at the other end (7). Two further bands (10, 11) on either side of the first band have the same length as the peripheral surface (9) of the second prism. These two bands are joined to the second prism at one end and to the first prism at the other end. In one of the prism end positions the first band is contact with the peripheral surface of the first prism and extends around it between two ends in a first peripheral direction, whilst the two other bands are in contact with the peripheral surface of the second prism and extending between its two ends in a second peripheral direction opposite to the first direction. |
