| 摘要 |
PCT No. PCT/GB91/01653 Sec. 371 Date Apr. 22, 1993 Sec. 102(e) Date Apr. 22, 1993 PCT Filed Sep. 25, 1991 PCT Pub. No. WO92/05314 PCT Pub. Date Apr. 2, 1992.A drive mechanism for a pivoted member (1), such as a beam of a traffic barrier, comprises a rotary element (6) coupled to the pivoted member (1). A friction roller (7) for driving the rotary element (6) is supported on a mounting (8) that is pivoted on an axis (9) and biased about the axis (9) to hold the friction roller (7) in pressure contact with the rotary element (6). When the friction roller (7) is driven to rotate the element (6) to raise the pivoted member (1), the frictional force between the roller (7) and the driven element (6) is increased, whereas the frictional driving force is reduced when the roller (7) is rotated in the reverse direction. |
