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

Abstract

An extension yoke, a self-hoisting wind turbine crane with such a yoke, and a method of using such a yoke are disclosed. The yoke comprises a frame structure comprising a lifting portion and a load transfer portion, forming an obtuse angle with each other, and at least one crane attachment element positioned between the load transfer portion and the lifting portion, said at least one crane attachment element being configured for establishing a pivot connection to a crane. The lifting portion comprised a load attachment element and the load transfer portion comprise at least one load transfer element, said load transfer element being configured for transferring compressive force by pressing against a reception surface of the crane and for moving in relation to the reception surface. The frame structure may comprise at least two substantially parallel longitudinal beams, at least one cross-beam, and/or at least one stabilisation element.