Importance

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Abstract

There is provided a hoist as for an ocean floor dredging operation, which is capable of providing hydraulic heavy lifting capacity, for raising or lowering the dredging means between a surface ship and the ocean floor, and further can routinely provide the ship heave compensation when lifting capacity is not required, for example during dredging operation, or if the raising or lowering of pipe during pipe deployment and retrieval operations is discontinued for any other reasons, such as extremely high seas. The pneumohydraulic system comprises a piston slidably sealably movable within a cylinder and dividing the cylinder into upper and lower portions; a pneumohydraulic accumulator for providing hydraulic fluid to each of the cylinder portions and the necessary valve means to open and close the necessary connections for filling and evacuating one of the cylinder portions with hydraulic fluid without rendering hydraulically inoperative the second portion of the cylinder. A hollow spear extending above the piston head maintains an oil cap sufficient to provide damping capability with the damping means provided.

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First Claim