Multi-oil-cylinder movable-boom lifting structure for excavator

A multi-oil-cylinder movable-boom lifting structure for an excavator comprises a movable boom body, a left oil cylinder, a right oil cylinder, a middle oil cylinder and a rotary table body, wherein one end part of the movable boom body is hinged to a point A of the rotary table body; one end of the middle oil cylinder is hinged to a point E of the movable boom body, and the other end of the middle oil cylinder is hinged to a point C of the rotary table body; the left oil cylinder and the right oil cylinder are symmetrically arranged at two sides of the middle oil cylinder; one end of the left oil cylinder and one end of the right oil cylinder are coaxially hinged to a point D of the movable boom body, and the other end of the left oil cylinder and the other end of the right oil cylinder are coaxially hinged to a point B of the rotary table body; and the angles of and the distances between all the hinge points simultaneously meet the following formulae: AD:AE=AB:AC=(0.8-1.2), and DAE angle=BAC angle +/- 10 degrees. The multi-oil-cylinder movable-boom lifting structure is simple, facilitates control of a hydraulic system, simple in movable boom structure, easy in processing of all holes and convenient in hinge pin assembly and disassembly.