Sea swell compensation

Claim 2

A sea swell and shock load compensator comprising a hydraulically-operated means for heaving in and paying out a hoist rope, a high pressure hydraulic system for supplying hydraulic fluid to the means so as to enable the means to heave in the hoist rope when carrying a load under a given maximum load, and a low pressure hydraulic system for supplying hydraulic fluid to the means so as to enable the means to heave in the hoist rope when carrying a load under a given lesser load, the hydraulic systems being pressurised by gas-loaded accumulators, and selection means for selectively connecting the hydraulic systems with the hydraulically-operated means.

Claim 3

A compensator according to claim 1, also including an intermediate pressure hydraulic system.

Claim 4

A compensator according to claim 1, wherein the hydraulically operated means is a ram having sheaves for reeving the hoist rope into a looped configuration and the ram is operative to heave in the hoist rope by lengthening the looped configuration.

Claim 5

A compensator according to claim 1, wherein the hydraulically-operated means comprises a pump-motor in driving relation with a winch, the pump-motor being operative as a hydraulic motor to drive the winch in the sense to heave in the hoist rope and as a hydraulic pump to be driven by the winch in the sense to pay out the hoist rope.

Claim 6

A hoist for use in transferring or supporting a load either between two stations at least on of which is floating in water subject to a swell or between a single station, which is either floating in the water or fixed, and the water itself, and for installation at either of the two stations or at the single station, the hoist comprising a hoist rope, means for attaching a load to the hoist rope, a hydraulically-operated means to heave in and pay out the hoist rope, two hydraulic systems connected to the hydraulically-operated means, and selection means for selectively putting one of said systems into communication with the hydraulically-operated means and isolating the other from the hydraulically-operated means, each one of the hydraulic systems including a gas-loaded accumulator, the hydraulically-operated means being biassed towards heaving in the hoist rope by the gas pressure in the accumulator in the hydraulic system with which the hydraulically-operated means is in communication, and the accumulators being gas-loaded to different predetermined pressures, one of which pressures is lower than that required to enable the hydraulically-operated means to support the weight of a load but high enough to maintain tension in the hoist rope when the load-attaching means is attached to a load substantially supported by means other than the hoist rope and thereby to compensate for relative motion between the two stations or between the single station and the water, and the other of which pressures is at least sufficient to enable the hydraulically-operated means to heave in the hoist rope when the hoist rope is tensioned and the load is entirely supported by the hoist rope.

Claim 7

A hoist for use in transferring or supporting a load either between two stations at least on of which is floating in water subject to a swell or between a single station, which is either floating in the water or fixed, and the water itself, and for installation at either of the two stations or at the single station, the hoist comprising a hoist rope, means for attaching a load to the hoist rope, a hydraulically-operated means to heave in and pay out the hoist rope, two hydraulic systems connected to the hydraulically-operated means, and selection means for selectively putting one of said systems into communication with the hydraulically-operated means and isolating the other from the hydraulically-operated means, each one of the hydraulic systems including a gas-loaded accumulator, the hydraulically-operated means being biassed towards heaving in the hoist rope by the gas pressure in the accumulator in the hydraulic system with which the hydraulically-operated means is in communication, and the accumulators being gas-loaded to different predetermined pressures, one of which pressures is lower than that required to enable the hydraulically-operated means to support the weight of a load but high enough to maintain tension in the hoist rope when the load-attaching means is attached to a load substantially supported by means other than the hoist rope and thereby to compensate for relative motion between the two stations or between the single station and the water, and the other of which pressures is at least sufficient to enable the hydraulically-operated means to heave in the hoist rope when the hoist rope is tensioned and the load is entirely supported by the hoist rope.

Claim 8

A hoist according to claim 5, also including an intermediate pressure hydraulic system with its own gas-loaded accumulator.

Claim 9

A hoist according to claim 5, wherein the hydraulically-operated means is a ram having sheaves for reeving the hoist rope into a looped configuration and the ram is operative to heave in the hoist rope by lengthening the looped configuration.

Claim 10

A hoist according to claim 7, including a winch and means whereby the winch can be operated automatically to augment the heaving-in or paying-out of hoist rope by the compensator when the ram is nearing its limit of travel.

Claim 11

A hoist according to claim 5, wherein the hydraulically-operating means comprises a pump-motor in driving relation with a winch, the pump-motor being operative as a hydraulic motor to drive the winch in the sense to heave in the hoist rope and as a hydraulic pump to be driven by the winch in the sense to pay out the hoist rope.

Claim 12

A hoist according to claim 5, including a winch and means thereon to enable the hoist rope to part company with the winch in the event of the winch having fully paid-out the hoist rope.