Hoisting mechanism

A hoisting mechanism comprising:

• a. a frame;
• b. a jib connected to the frame about a substantially horizontal pivot shaft;
• c. topping means for raising and lowering the jib;
• d. a hoisting cable and a hoisting-cable drive;
• e. hoisting-cable guide means that define a path for the hoisting cable between the hoisting-cable drive and a hoisting-cable guide arranged on the jib, from which the hoisting cable hangs downwards;
• and
• f. a device for limiting the loading on the hoisting mechanism, comprising:
• i. a hoisting-cable guide for the hoisting cable, wherein the hoisting-cable guide is displaceable with respect to the frame or the jib, wherein the displacement of the hoisting-cable guide changes the length of the path;
• ii. a first hydraulic component arranged between the frame or jib and the displaceable hoisting-cable guide, wherein the first hydraulic component comprises a first chamber of a first variable volume;
• iii. a second hydraulic component comprising a second chamber with a second variable volume;
• iv. a pressure source connected to the second hydraulic component in order to maintain a substantially constant hydraulic pressure in the second chamber;
• and
• v. a connection between the first chamber and the second chamber, wherein the connection comprises a pressure-limiting valve assembly and actuating means, wherein the actuating means detects pressure in the first chamber.