Lifting boom transmission mechanism - comprises ram acting directly on driving mechanism

摘要

The transmission mechanism lifts and lowers a boom barring off a passage or railway level-crossing. It comprises a ram (27) acting directly on the driving mechanism of the boom (25), and typically hydraulic. The driving mechanism can comprise a crank (23), turning about the tilt axis (6) of the boom, or alternatively, a plate moved to and fro by the ram in a straight line and containing a transverse notch, in which there engages an eccentric pin on a coupling member on the boom spindle, thus converting a sliding movement into a rotary one.FL.