Abstract: A dockleveller installation is provided having a dockboard hinged for pivotal movement and a composite pneumatic-hydraulic system for pivoting the dockboard. The composite system includes a fluid-filled cylinder attached to the dockboard, a pressurized air supply, and a multiplier connected therebetween. The multiplier is a closed cylindrical member comprising an air cylinder segment connected to the air supply and a fluid cylinder segment connected to the hydraulic cylinder. The interior cross-sectional area of the air segment is greater than that of the fluid segment. The multiplier also includes a double headed piston, one end of which reciprocates and seals in the air segment, the other end of which reciprocates and seals in the fluid segment. This composite system enables pressure to be transferred through the multiplier from the air supply to the hydraulic cylinder, causing the cylinder to open and the dockboard to pivot.

Abstract: A releasable hold-down device is provided for use in a dockleveller wherein dock-raising springs are used to raise the dockboard. The hold-down device comprises a hydraulic cylinder assembly having the piston connected to the dockboard and the cylinder connected to the dockleveller frame. The cylinder assembly must thus expand and contract to permit the dockboard to be raised by the spring and lowered by the weight of a man standing on the dockboard. The cylinder assembly has fluid-filled stem and base chambers. A connecting conduit permits fluid movement between the chambers. A valve means in the conduit controls this fluid movement. There is provided means for mechanically opening the valve means to permit the dockboard to be raised by the spring with concomitant expansion of the cylinder assembly.