Multi-stage combined spring

The invention is suitable for the technical field of springs, and provides a multi-stage combined spring which comprises an inner sleeve, a supporting disc and an outer sleeve, a buffer cavity is formed between the inner sleeve and the outer sleeve, a fixed end cover is fixed to one end of the outer sleeve, an inner spring is arranged in the buffer cavity, an exhaust hole is formed in one end of the outer sleeve, and a guide pipe penetrates through the fixed end cover. A piston ring is fixed at one end of the conduit. The inner spring is installed in the buffer cavity, the outer spring is installed outside the outer sleeve, the spring rigidity of the outer spring is larger than that of the inner spring, and impact force borne by the guide pipe firstly acts on the inner spring; excessive impact force is transferred to the outer spring, the situation that a single spring bears impact is avoided, the load capacity of the combined spring is improved, meanwhile, fatigue damage to the single spring caused by excess