Extension yoke for self-hoisting crane, a self-hoisting wind turbine crane with an extension yoke, and use of an extension yoke

An extension yoke for a self-hoisting wind turbine crane, the extension yoke comprising:

• a frame structure comprising:
• a lifting portion,
• a load transfer portion,
• at least one crane attachment element between the load transfer portion and the lifting portion, the at least one crane attachment element being configured to establish a pivot connection to a crane,
• wherein the lifting portion has a proximal end at the at least one crane attachment element, a distal end opposite the proximal end of the lifting portion, and a load attachment element at the distal end of the lifting portion,
• wherein the load transfer portion has a proximal end at the at least one crane attachment element, a distal end opposite the proximal end of the load transfer portion, and at least one load transfer element at the distal end of the load transfer portion, wherein the load transfer element is configured to be displaced in relation to a reception surface of the self-hoisting wind turbine crane prior to a lifting operation and the load transfer element is configured for being displaced in relation to the reception surface while being in contact therewith during the lifting operation, and wherein the load transfer element is further configured to transfer compressive force by pressing against the reception surface of the self-hoisting wind turbine crane and to move in relation to the reception surface, and
• wherein the load transfer portion and the lifting portion form an obtuse angle with each other;
• and
• at least one stabilisation element interconnecting portions of the frame structure, the at least one stabilisation element forming an acute angle with at least one portion of the interconnecting portions of the frame structure.