Abstract: A stepless luffing mechanism for the super-lifting counterweight of a crawler crane, and an operating method thereof. The luffing mechanism includes a main luffing mast, a lifting oil cylinder, a luffing structure and a pulling board for the counterweight, and a super-lifting mast. The cylinder's lower end is connected with the counterweight, and its upper end is connected with a lower end of a front part of the luffing structure. The upper end of the luffing structure's front part is connected with the pulling board's lower end. A lifting rope connects the pulling board's upper end with the super-lifting mast's upper end. The super-lifting mast's lower end is connected with a platform's back end. An angle measuring sensor for the main luffing mast is provided on the super-lifting mast. A lower end of a back part of the luffing structure is connected with a pin shaft of the platform.

Abstract: The present invention provides a crane boom with multi main chord consisting of an underpart boom sections, an insert jib section and a boom head connected in turn. Said underpart boom sections and insert jib section are multi-main-chord boom sections, there is a main-chord on each of the angle part of the cross-section of the multi-main-chord boom section. Said main-chords are connected one another by several belly bars. Add at least one main-chord on the angle part of the cross section along the width or the height of said multi-main-chord boom, and the added main-chord parallels to the original main-chord. The crane boom with multi main chord of the present invention, without changing the size of the boom sections during transporting, the cross-sectional area of the main-chord is increased and the integral stiffness of the boom is strengthened by increasing main-chord number of boom, thus fold increasing the structural carrying capacity of the boom which is suitable for large crane.