TRANSSHIPPING BRIDGE FOR LOADING AND UNLOADING FREIGHT

摘要

1. Dockboard for loading ramps having a bridging plate (1), which is mounted at its rear end on the ramp so as to be pivotable about a horizontal axis (2) and is upwardly displaceable by means of a litting cylinder (11), and an extension portion (4), which is pivotally hinged to the free end of the bridging plate (1) and is displaceable into its operative position by means of a pivotal cylinder (9), the extension portion being supported in its operative position on a platform (5) to be loaded or unloaded and being pivotable into a substantially vertical position to assume its position of rest, whereby the pressure line (20) of the pivotal cylinder (9) is connected, via a pressure limiting valve (21), to the pressure line (19) of the lifting cylinder (11) in such a manner that the extension portion (4) only swivels-out into its operative position when the brigding plate (1) assumes its upper end position and, when the pressure generator (15) is switched-off and the extension portion (4) is in its operative position, the bridging plate (1) is lowered as a result of its own weight, characterized in that the lifting cylinder (11) and the pivotal cylinder (9) are adapted to be single-acting, and the return line (22) of the single-acting lifting cylinder (11) is connected to the pressure line (20) of the single-acting pivotal cylinder (9) by means of a relief valve (25), whereby the dynamic pressure, which is being produced in the return line (22) by the specific weight of the lowering bridging plate (1), is greater than the pressure in the pressure line (20) so that the relief valve (25) prevents the pressure medium overflowing from the return line (22) onto the pressure line (20) of the single-acting pivotal cylinder (9).