Apparatus for use in raising or lowering a load in a condition of relative motion

A wave compensated off-shore crane for unloading and loading a vessel which moves relative thereto due to wave motion, said crane including a winch, a reeving system, load supporting means and wave compensating means, said reeving system being connected to said winch and to said wave compensating means for raising and lowering said load supporting means and for compensating for said wave motion, said wave compensating means including:

• an hydraulic ram;
• first and second pulley means, said first pulley means being connected to one end of said ram and said second pulley means being connected to the other end of said ram;
• first and second preloaded hydro-pneumatic accumulators, said preloading being provided by respective first and second sources of low and high pressure compressed gas, low pressure being provided for applying a light tension to said line means equivalent to a minor proportion of the weight of said load and said high pressure being provided for applying a high tension to said line means, which high tension is equivalent to a major proportion of, but does not exceed the weight of said load when unloading, and is greater than the weight of said load when loading;
• an hydraulic selector valve, said selector valve connecting said first and second accumulators to said hydraulic ram;
• and
• unidirectional locking means for preventing retraction of said ram to prevent said line means from lowering said load from the crest of said wave motion.

A wave compensated off-shore crane for unloading and loading a vessel which moves relative thereto due to wave motion, said crane including a line storage drum, with primary drive means, load supporting means, and wave compensating means, said drum being connected to said load supporting means by a line and being connected to said wave compensating means for compensating for said wave motion, said wave compensating means includng:

• an hydraulic motor;
• a differential gear, said motor being connected to said drum by said differential gear;
• first, second and third preloaded hydro-pneumatic accumulators, said motor being connected on one side to said third accumulator and on the other side to said first and second accumulators, said first and second accumulators being preloaded by compressed gas in a closed pneumatic system whereby said first accumulator is preloaded to apply a light tension to said line which is equivalent to a minor proportion of the weight of said load, and said second accumulator is preloaded for applying a high tension to said line equivalent to a major proportion of but not exceeding the weight of said load when unloading and being greater than said load when loading;
• an hydraulic selector valve, said selector valve connecting said first and second accumulators to said other side of said motor whereby said light and high tensions may be selectively applied to said line;
• a fourth preloaded hydro-pneumatic accumulator connected to said other side of said motor for smoothing the operation of said motor when said selector valve is actuated for selectively connecting said first and second accumulators to said motor;
• and
• a pilot operated, non-return valve, said non-return valve being connected between said other side of said motor and said selector valve whereby said line is prevented from being lowered by said drum from the crest of said wave motion.

An improvement in wave compensating apparatus for an off-shore crane, said crane being provided for unloading and loading a vessel which moves relative thereto due to wave motion, said crane including primary drive means, load attachment means and line means connecting said primary drive means to said load attachment means;

• said wave compensating apparatus including hydraulically driven means for taking and paying out said line means, hydro-pneumatic means acting on said hydraulically driven means for tensioning said line means to compensate for said wave motion, said hydro-pneumatic means including first accumulator means for imparting a light tension to said line means, said light tension being equivalent to a minor proportion of the weight of said load, and unidirectional locking means for preventing said line means from lowering said load from the crest of said wave motion, the improvement comprising:
• second accumulator means for imparting a high tension to said line means;
• and
• selector means operatively coupled to said first and second accumulator means for selectively connecting said first and second accumulator means to said hydraulically driven means.