Ocean floor dredge system having a pneumohydraulic means suitable for providing tripping and heave compensation modes

Pneumohydraulic means designed to provide lifting capability and heave compensation capability, and to provide damping with both capabilities, for a surface vessel, the system comprising:

• a closed cylinder having upper and lower end caps;
• a piston head slidably sealably movable within the cylinder;
• a piston rod secured to one end of the piston head and extending sealably through one end cap;
• a slender, elongated spear portions extending outwardly from a second end of the piston head towards the second end cap;
• each of the piston spear, piston head and piston rod defining a piston conduit opening into the cylinder at a first end and extending from its first end at the end of the piston spear nearest the second end cap, through the piston head and part way along the piston rod;
• a hollow drain conduit extending from the second end cap into and in fluid flow connection with the piston conduit, the hollow drain conduit extending substantially concentric with the piston conduit;
• vent means through the second end cap in sequential fluid flow connection with the hollow drain conduit and piston conduit;
• damping means acting in cooperation with the piston spear;
• an accumulator vent through the cylinder relatively closer to the first end cap;
• first pressure vent through the cylinder relatively closer to the first end cap;
• and a second pressure vent through the cylinder relatively closer to the second end cap;
• the piston having a stroke between the accumulator vent and first pressure vent and the second pressure vent;
• a source of hydraulic fluid pressure connected between the first pressure vent and the second pressure vent;
• a pneumohydraulic accumulator means connected to the accumulator vent;
• a valve intermediate the pneumohydraulic accumulator means and the accumulator vent;
• whereby the cylinder can be operated to provide a heavy lifting capability and can be operated in a second mode to provide a heave compensation capability when the accumulator vent is opened to the pneumohydraulic accumulator means, and an oil cap can thus be maintained above the piston head to a height substantially equal to the length of the spear to provide a damping capability during the heavy lift mode.