Prestressed stretch-draw device

The utility model relates to a prestressed tensioner which is composed of a screw thread draw rod, a connection hinge, a pin shaft, a nut, wire cables and a pulley wheel. A cable head casting opening, the inner chamber of which is in a rectangular conical shape is fixed to the connection hinge which can slide in the box body, an anti-loosing sleeve plate is sleeved on the nut and fixedly connected with a bearing positioning seat sleeve, and six wire cables penetrate through a safe hanging clamp which is fixed to the soleplate of the main beam of the crane. The utility model improves on the former patent CN2061930U to the applicant, the stretching force can be increased from primary 85-170 tons to 120-240 tons, and the utility model can be used for repairing the main beam of the crane, the elevating capacity of which reaches to hundred tons.